Publications Repository - Helmholtz-Zentrum Dresden-Rossendorf

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35174 Publications

Flow Control Based on Feature Extraction in Continuous Casting Process

Abouelazayem, S.; Glavinic, I.; Wondrak, T.; Hlava, J.

The flow structure in the mold of a continuous steel caster has a significant impact on the quality of the final product. Conventional sensors used in industry are limited to measuring single variables such as the mold level. These measurements give very indirect information about the flow structure. For this reason, designing control loops to optimize the flow is a huge challenge. A solution for this is to apply non-invasive sensors such as tomographic sensors that are able to visualize the flow structure in the opaque liquid metal and obtain information about the flow structure in the mold. In this paper, ultrasound Doppler velocimetry (UDV) is used to obtain key features of the flow. The preprocessing of the UDV data and feature extraction techniques are described in detail. The extracted flow features are used as the basis for real time feedback control. The model predictive control (MPC) technique is applied, and the results show that the controller is able to achieve optimum flow structures in the mold. The two main actuators that are used by the controller are the electromagnetic brake and the stopper rod. The experiments included in this study were obtained from a laboratory model of a continuous caster located at the Helmholtz-Zentrum Dresden Rossendorf (HZDR).

Keywords: industrial control; industrial process tomography; model predictive control; ultrasound doppler velocimetry

Permalink: https://www.hzdr.de/publications/Publ-31903
Publ.-Id: 31903


A UV laser test facility for precise measurement of gas parameters in gaseous detectors

Fan, X.; Naumann, L.; Siebold, M.; Stach, D.; Kämpfer, B.

This work is devoted to the development of a UV laser test facility for calibration of gaseous detectors. We applied multiple methods to achieve a micrometer scale accuracy for the laser test facility and provide dedicated investigations for laser ionization in the gaseous detector. With the well-controlled laser ionization and remote DAQ system, we can operate the calibration of gaseous detectors and precise measurement of gas parameters at the micrometer scale related to the detector’s field geometry.

Keywords: UV Laser

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  • Secondary publication expected from 04.12.2021

Permalink: https://www.hzdr.de/publications/Publ-31902
Publ.-Id: 31902


Geometrically driven chiral effects in curvilinear antiferromagnetic spin chains

Pylypovskyi, O.; Kononenko, D.; Yershov, K.; Roessler, U.; Tomilo, A.; Faßbender, J.; van den Brink, J.; Makarov, D.; Sheka, D.

Antiferromagnets are technologically promising materials for spintronic and spinorbirtonic devices [1]. An efficient manipulation of antiferromagnetic textures requires the presence of the Dzyaloshinskii-Moriya interaction (DMI), which is present in crystals of special symmetry, and thus limits the number of available materials. In contrast to antiferromagnets, it is already established that in ferromagnetic thin films and nanowires chiral responses can be tailored relying on curvilinear geometries [2].

Here, we explore curvature effects in curvilinear antiferromagnets [3]. We demonstrate theoretically that intrinsically achiral curvilinear antiferromagnetic spin chains behave as a biaxial chiral helimagnet with a curvature-tunable anisotropy and DMI. In contrast to ferromagnetic spin chains, this system possesses the hard-axis anisotropy stemming from the dipolar interaction, which allows to observe the effects of geometry even in chains with small curvature and torsion. The geometry-driven easy axis anisotropy determines the homogeneous antiferromagnetic state at low curvatures and the gap for spin waves. The geometry-driven DMI determines the helimagnetic phase transition and leads to the appearance of the region with the negative group velocity at the dispersion curve.

[1] V. Baltz et al., Rev. Mod. Phys. 90, 015005 (2018)
[2] R. Streubel et al., J. Phys. D.: Appl. Phys. 49, 363001 (2016)
[3] O. V. Pylypovskyi, D. Y. Kononenko et al., Nano Lett. 20, 8157 (2020)

  • Contribution to proceedings
    Magnetism at the Nanoscale: Imaging ‐ Fabrication – Physics, 06.-08.01.2021, Virtual Conference, Virtual Conference

Permalink: https://www.hzdr.de/publications/Publ-31901
Publ.-Id: 31901


Parallel computing of elastic magnetic systems at the nanoscale

Tomilo, A.; Pylypovskyi, O.; Yershov, K.; Sheka, D.

Intensive research in the area of nanoscaled physics opens new possibilities for the construction and fabrication of nanoscale devices. A numerical experiment is a powerful tool to analyze complex systems and flexibly check analytical predictions in addition to experimental validation. Therefore usage of parallel
calculation is required to decrease the time of simulation.

  • Contribution to proceedings
    Sixth International Conference on High Performance Computing (HPC-UA 2020), 06.-07.11.2020, Virtual Conference, Virtual Conference

Permalink: https://www.hzdr.de/publications/Publ-31900
Publ.-Id: 31900


Stabilization of Skyrmion States by a Gradient of Curvature in Ferromagnetic Shells

Pylypovskyi, O.; Makarov, D.; Kravchuk, V.; Saxena, A.; Sheka, D.

Skyrmions represent a class of chiral magnetic textures with unique properties relevant for spintronic and spin-orbitronic applications [1]. Geometrical curvature can be used as an efficient mean to tailor chiral and anisotropic responses of thin ferromagnetic shells [2-4]. This was recently confirmed by quantifying the strength of the Dzyaloshinskii-Moriya interaction (DMI) in curved nanostripes [5]. Furthermore, there are numerous predictions of the stabilization of curvature-driven of small-radius skyrmions in spherical shells [6] and an appearance of skyrmion lattices as the ground state in intrinsically chiral curvilinear thin films [7].

Here, we demonstrate a new pathway of stabilizing Neel skyrmion and skyrmionium states relying on the gradient of curvature using a magnetic thin film hosting a circular nanoindentation [8]. These skyrmion states can be formed in a material even without an intrinsic DMI. We propose a physical picture of this effect, which is related to the pinning of a chiral magnetic domain wall at the bend of a nanoindentation. Geometry of the film is described by two principal curvatures k1(r), describing film geometry in radial direction, and k2(r) inversely proportional to the distance from origin. In this respect, the spatial inhomogeneity of the curvature-induced DMI governing by k1(r) is responsible for the stabilization of the skyrmion state. The lateral dimensions of the stabilized chiral magnetic textures are varied in a broad range by engineering the size of the nanoindentation. We describe the stability condition of skyrmion states. Furthermore, on the fundamental side, we put forth a general analytical framework allowing us to map a complex problem of the description of a magnetic texture at a surface of revolution to a standard planar problem with modified constants of DMI and magnetic anisotropy. In this respect, our model predicts a new mechanism of pinning of magnetic domain walls in planar ferromagnetic films with intrinsic DMI on inhomogeneities of the DMI.

[1] A. Fert, N. Reyren, V. Cros, Nat. Rev. Mater., Vol. 2, 17031 (2017)
[2] R. Streubel, P. Fischer, F. Kronast et al., J. Phys. D: Appl. Phys. Vol. 49, 363001 (2016)
[3] O. Pylypovskyi, V. Kravchuk, D. Sheka et al., Phys. Rev. Lett. Vol. 114, 197204 (2015)
[4] Y. Gaididei, A. Goussev, V. Kravchuk et al., J. Phys. A: Mat. and Theor. Vol. 50, 385401 (2017)
[5] Volkov, Kakay, Kronast et al., Phys. Rev. Lett. Vol. 123, 077201 (2019)
[6] V. Kravchuk, U. K. Röβler, O. M. Volkov et al., Phys. Rev. B. 94, 144402 (2016)
[7] V. Kravchuk, D. Sheka, A. Kákay et al., Phys. Rev. Lett. Vol. 120, 067201 (2018)
[8] O. Pylypovskyi, D. Makarov, V. Kravchuk et al., Phys. Rev. Appl. Vol. 10, 064057 (2018)

  • Contribution to proceedings
    2020 Virtual MRS Fall Meeting, 28.11.-04.12.2020, Virtual Conference, Virtual Conference

Permalink: https://www.hzdr.de/publications/Publ-31899
Publ.-Id: 31899


Experimental observation of exchange-driven chiral effects in parabolic stripes

Volkov, O.

Broken magnetic symmetry is a key aspect in condensed matter physics and in particular in magnetism. It results in the appearance of chiral effects, e.g. topological Hall effect [1] and non-collinear magnetic textures including chiral domain walls and skyrmions [2,3]. These chiral structures are in the heart of novel concepts for magnonics [4], antiferromagnetic spintronics [5], spin-orbitronics [6] and oxitronics [7]. The main origin of the chiral symmetry breaking and thus for the magnetochiral effects in magnetic materials is associated to an antisymmetric exchange interaction, the intrinsic Dzaloshinskii-Moriya interaction (DMI). At present, tailoring of DMI is done rather conventionally by optimizing materials, either doping a bulk single crystal or adjusting interface properties of thin films and multilayers. A viable alternative to the conventional material screening approach can be the exploration of the interplay between geometry and topology. This interplay is of fundamental interest throughout many disciplines in condensed matter physics, including thin layers of superconductors [8] and superfluids [9], nematic liquid crystals [10], cell membranes [11], semiconductors [12]. In the emergent field of curvilinear magnetism chiral effects are ssociated to the geometrically broken inversion symmetries [13]. Those appear in curvilinear architectures of even conventional materials. There are numerous exciting theoretical predictions of exchange and magnetostatically-driven curvature effects, which do not rely on any specific modification of the
intrinsic magnetic properties, but allow to create non-collinear magnetic textures in a controlled manner by tailoring local curvatures and shapes [14,15]. Until now the predicted chiral effects due to curvatures remained a neat theoretical abstraction. Here, we demonstrate the very first experimental confirmation of the existence of the curvature-induced chiral interaction with exchange origin in a conventional soft ferromagnetic material [16]. It is experimentally explored the theoretical predictions, that the magnetisation reversal of flat parabolic stripes shows a two step process. At the first switching event, a domain wall pinned by the curvature induced exchange-driven DMI is expelled leading to a magnetisation state homogeneous along the parabola’s long axis. Measuring the depinning field enables to quantify the effective exchange-driven DMI interaction constant. The magnitude of the effect can be tuned by the parabola’s curvature. It is found that the strength of the exchange-induced DMI interaction for the experimentally realised geometries is remarkably strong, namely ≈ 0.4 mJ/m 2 , compared the surface induced DMI. The presented study legitimates the predictive power of full-scale micromagnetic simulations to design the properties of ferromagnets through their geometry, thus stabilising chiral textures.

[1] N. Nagaosa, et al., Nature Nanotech. 8, 899 (2013)
[2] U. K. Rößler, et al., Nature 442, 797 (2006)
[3] A. Fert, et al., Nature Rev. Mat. 2, 17031 (2017)
[4] A. V. Chumak, et al., Nature Physics 11, 453 (2015)
[5] T. Jungwirth, et al., Nature Nanotech. 11, 231 (2016)
[6] I. M. Miron, et al., Nature 476, 189 (2011)
[7] V. Garcia, et al., Nature 460, 81 (2009)
[8] J. Tempere, et al., Phys. Rev. B 79, 134516 (2009)
[9] H. Kuratsuji, Phys. Rev. E 85, 031150 (2012)
[10] T. Lopez-Leon, et al., Nature Physics 7, 391 (2011)
[11] H. T. McMahon, et al., Nature 438, 590 (2005)
[12] C. Ortix, Phys. Rev. B 91, 245412 (2015)
[13] Y. Gaididei, et al., Phys. Rev. Lett. 112, 257203 (2014)
[14] J. A. Otálora, et al., Phys. Rev. Lett. 117, 227203 (2016)
[15] V. P. Kravchuk, et al., Phys. Rev. Lett. 120, 067201 (2018)
[16] O. M. Volkov, et al., Phys. Rev. Lett. 123, 077201 (2019)

Keywords: Ferromagnetism; Curvilinear magnetism

  • Contribution to proceedings
    2020 MRS Virtual Spring/Fall Meeting & Exhibit, 27.11.-04.12.2020, Boston, Massachusetts, USA
    Proceedings of the 2020 MRS Virtual Spring/Fall Meeting & Exhibit

Permalink: https://www.hzdr.de/publications/Publ-31898
Publ.-Id: 31898


Domain Wall Tilt and Enhancement of the Walker Limit in Stripes with Dzyaloshinskii-Moriya Interaction and Perpendicular Anisotropy

Pylypovskyi, O.; Kravchuk, V.; Volkov, O.; Faßbender, J.; Sheka, D.; Makarov, D.

The efficiency of manipulation of domain walls and skyrmions in ferromagnetic racetracks with perpendicular anisotropy determines perspectives of development of data storage and logic devices relying on spintronic and spin-orbitronic concepts [1, 2]. The domain wall dynamics is dependent on its orientation with respect to the racetrack axis. In-plane fields [3], edge roughness [4] and current [5] result in the domain wall tilt in samples, possessing Dzyaloshinskii-Moriya interaction (DMI). Here, we show theoretically, that the tilt can appear in equilibrium and describe the domain wall dynamics under the action of external field. We consider a thin biaxial stripe with DMI of interfacial type [6]. The main easy axis of anisotropy is perpendicular to the plane, and the direction of the second easy axis lies in the stripe plane under the angle α to the stripe axis. While the shape anisotropy results in α = 0, a general case α ≠ 0 can appear under the influence of other effects, e.g crystalline structure [7]. While the second easy axis defines the preferable in-plane magnetization within the domain wall, the DMI forces the domain wall being perpendicular to the magnetization gradient. The competition between these two energy contributions and the domain wall tension results in the unidirectional tilt of the whole domain wall. If the DMI is weak enough, there is an additional metastable domain wall state, tilted into the opposite direction. The symmetry break is observed not only for static magnetization texture, but also in the domain wall dynamics under the action of external magnetic field. The domain wall reveals fast and slow motion regimes for the opposite signs of A. The maximum of the Walker field and Walker velicities is determined by the angle A of the second easy axis anisotropy and does not coincide with a shape-induced anisotropy direction A=0. The domain wall possesses the switch of the magnetization direction inside the domain wall in the slow motion regime, which results in the faster motion.

[1] K.-S. Ryu, L. Thomas, S.-H. Yang et al., Nat. Nanotech., Vol. 8, 527 (2013)
[2] O. Pylypovskyi, D. Sheka, V. Kravchuk et al., Sci. Rep. Vol. 6, 23316 (2016)
[3] C. Muratov, V. Slastikov, A. Kolesnikov et al., Phys. Rev. B. Vol. 96, 134417 (2017)
[4] E. Martinez, S. Emori, N. Perez et al. J. Appl. Phys. Vol. 115, 213909 (2014)
[5] O. Boulle, S. Rohart, L. Buda-Prejbeanu et al., Phys. Rev. Lett. Vol. 111, 217203 (2013)
[6] O. Pylypovskyi, V. Kravchuk, O. Volkov et al., J. Phys. D. (2020), DOI:10.1088/1361-6463/ab95bd
[7] M. Heide, G. Bihlmayer, S. Blügel, Pys. Rev. B, Vol. 78, p. 140403 (2008).

  • Contribution to proceedings
    MMM 2020 Virtual Conference, 02.-06.11.2020, Virtual Conference, Virtual Conference

Permalink: https://www.hzdr.de/publications/Publ-31897
Publ.-Id: 31897


Curvature-driven Chiral Effects in Nanomagnetism

Volkov, O.

The structural inversion symmetry plays an important role in low-dimensional nanomagnets, due to its strong influence on magnetic and electrical properties. It can lead to the appearance of chiral effects, such as the topological Hall effect [1], or to the formation of chiral noncollinear magnetic textures, as skyrmions [2] and chiral domain walls (DWs) [3]. These chiral structures can be the key components for realizing novel concepts for magnonics [4], antiferromagnetic spintronics [5], spin-orbitronics [6], and oxitronics [7]. So far, the main chiral symmetry breaking effect considered as being the origin for the presence of chiral noncollinear magnetic textures is the intrinsic Dzyaloshinskii-Moriya interaction (DMI) [8,9], which appears in certain magnetic crystals in which the unit cell lacks inversion symmetry, such as the gyrotropic magnetic crystals, or appear typically in ultrathin films or bilayers due to the inversion symmetry breaking on the film interface [3]. At present, tailoring of DMI is done by optimizing materials, either doping a bulk single crystal or adjusting interface properties of thin films and multilayers.

A viable alternative to the conventional material screening approach can be the exploration of the interplay between geometry and topology. This interplay is of fundamental interest throughout many disciplines in condensed matter physics, including thin layers of superconductors [10] and superfluids [11], nematic liquid crystals [12], cell membranes [13], semiconductors [14]. In the emergent field of curvilinear magnetism chiral effects are associated to the geometrically broken inversion symmetries [15]. Those appear in curvilinear architectures of even conventional materials. There are numerous exciting theoretical predictions of exchange- and magnetostatically-driven curvature effects, which do not rely on any specific modification of the intrinsic magnetic properties, but allow to create non-collinear magnetic textures in a controlled manner by tailoring local curvatures and shapes [16,17]. Until now the predicted chiral effects due to curvatures remained a neat theoretical abstraction.

Very recently, we provided the very first experimental confirmation of the existence of the curvature-induced chiral interaction with exchange origin in a conventional soft ferromagnetic material. It is experimentally explored the theoretical predictions, that the magnetisation reversal of flat parabolic stripes shows a two step process [18,19]. At the first switching event, a domain wall pinned by the curvature induced exchange-driven DMI is expelled leading to a magnetisation state homogeneous along the parabola's long axis. Measuring the depinning field enables to quantify the effective exchange-driven DMI interaction constant. The magnitude of the effect can be tuned by the parabola's curvature. It is found that the strength of the exchange-induced DMI interaction for the experimentally realised geometries is remarkably strong, namely ~0.4 mJ/m2, compared the surface induced DMI. The presented study legitimates the predictive power of full-scale micromagnetic simulations to design the properties of ferromagnets through their geometry, thus stabilising chiral textures. We explore these curvilinear magnetic thin films for the realization of novel artificial magnetoelectric materials based on curvilinear helimagnets embedded in piezoelectric matrix [20], to enable the geometrical tuning of the magnetochirality in curvilinear 1D architectures [21], tailoring of magnetic states in flat nanospirals [22] and as components of shapeable magnetoelectronics for interactive wearables [23].

[1] N. Nagaosa, et al., Nature Nanotech. 8, 899 (2013)
[2] U. K. Rößler, et al., Nature 442, 797 (2006)
[3] A. Fert, et al., Nature Rev. Mat. 2, 17031 (2017)
[4] A. V. Chumak, et al., Nature Physics 11, 453 (2015)
[5] T. Jungwirth, et al., Nature Nanotech. 11, 231 (2016)
[6] I. M. Miron, et al., Nature 476, 189 (2011)
[7] V. Garcia, et al., Nature 460, 81 (2009)
[8] I. Dzyaloshinsky, J. Phys. Chem. Solids 4, 241 (1958).
[9] T. Moriya, Phys. Rev. Lett. 4, 228 (1960).
[10] J. Tempere, et al., Phys. Rev. B 79, 134516 (2009)
[11] H. Kuratsuji, Phys. Rev. E 85, 031150 (2012)
[12] T. Lopez-Leon, et al., Nature Physics 7, 391 (2011)
[13] H. T. McMahon, et al., Nature 438, 590 (2005)
[14] C. Ortix, Phys. Rev. B 91, 245412 (2015)
[15] Y. Gaididei, et al., Phys. Rev. Lett. 112, 257203 (2014)
[16] J. A. Otálora, et al., Phys. Rev. Lett. 117, 227203 (2016)
[17] V. P. Kravchuk, et al., Phys. Rev. Lett. 120, 067201 (2018)
[18] O. Volkov et al., PRL 123, 077201 (2019).
[19] O. Volkov et al., PSS-RRL 13, 1800309 (2019).
[20] O. Volkov et al., J. Phys. D: Appl. Phys. 52, 345001 (2019).
[21] O. Volkov et al., Scientific Reports 8, 866 (2018).
[22] M. Nord, et al., Small 1904738 (2019).
[23] J. Ge, et al., Nature Comm. 10, 4405 (2019).

Keywords: Ferromagnetism; Curvilinear magnetism; Chiral effects

  • Invited lecture (Conferences) (Online presentation)
    MMM 2020 Virtual Conference, 02.-06.11.2020, Palm Beach, Florida, USA

Permalink: https://www.hzdr.de/publications/Publ-31896
Publ.-Id: 31896


Effects of Geometry on Curvilinear Spin Chains

Kononenko, D.; Pylypovskyi, O.; Yershov, K.; Roessler, U.; Tomilo, A.; Faßbender, J.; van den Brink, J.; Makarov, D.; Sheka, D.

Curvilinear magnetism is of great fundamental and practical interest whose rapid development is inspired by novel experimental technologies and wide potential applications [1]. A general approach for description of curvilinear ferromagnets [2] has been recently developed and used for thin wires and shells uncovering magnetochiral effects in statics and dynamics [1,3]. Besides intensive research of ferromagnetic materials, their antiferromagnetically ordered (AFM) counterparts are promising candidates for spintronics applications by their low sensitivity to external fields and ultra high eigenfrequencies [4]. Here, we present a general approach for description of AFM textures in curvilinear spin chains [5]. We show that the magnetic dipole-dipole interaction in these systems can be reduced to a hard-axis anisotropy along the chain. Lagrangian of the curvilinear AFM spin chain in continuum limit corresponds to the biaxial chiral helimagnet. Helix geometry shows existence of two equilibrium magnetic states depending on values of curvature and torsion: (i) homogeneous state in the local reference frame, it is typical for helices with the curvature larger than torsion; and (ii) periodic state is quasi-homogeneous in the laboratory reference frame. For specific case of the AFM flat chain there is the only ground state, with the order parameter being oriented perpendicular to the chain plane. We show that in curvilinear system transverse and longitudinal magnon modes in the AFM helix and ring are coupled due to geometry-induced Dzyaloshinskii–Moriya interaction.

[1] R. Streubel, J. Lee, D. Makarov et al, J. Phys. D, 49, 363001, (2016); A. Fernández-Pacheco et al, Nat. Comm., Vol. 8, p. 15756 (2017).
[2] Y. Gaididei, V. P. Kravchuk, D. D. Sheka, Phys. Rev. Lett. 112, 257203 (2014); D. D. Sheka, V. P. Kravchuk, Y. Gaididei, J. Phys. A, Vol. 48, p. 125202 (2015).
[3] O. V. Pylypovskyi, D. D. Sheka, V. P. Kravchuk et al, Sci. Rep. Vol. 6, p. 23316 (2016); O. V. Pylypovskyi, D. Makarov, V. P. Kravchuk et al, Phys. Rev. Applied, Vol. 10, p. 064057 (2018)
[4] V. Balz, A. Manchon, M. Tsoi et al, Rev. Mod. Phys., Vol. 90, p. 015005 (2018)
[5] D. Y. Kononenko, O. V. Pylypovskyi, K. V. Yershov et al., arXiv:2005.05835 (2020)

  • Contribution to proceedings
    MMM 2020 Virtual Conference, 02.-06.11.2020, Virtual Conference, Virtual Conference

Permalink: https://www.hzdr.de/publications/Publ-31895
Publ.-Id: 31895


Magnetostatics-Induced Symmetry Breaking Effects in Curvilinear Shells

Sheka, D.; Pylypovskyi, O.; Landeros, P.; Kakay, A.; Makarov, D.

The behavior of any physical system is governed by the order parameter, determined by the geometry of the physical space of the object, namely their dimensionality and curvature. Usually, the effects of curvature are identified using local interactions only, e.g. local spin-orbit- or curvature-induced Rashba and Dzyaloshinskii-Moriya interactions in condensed matter [1]. Lack of the framework, involving both, local and non-local interactions impedes the description of the essentially micromagnetic textures like magnetic domains, skyrmion-bubbles and vortices. Here, we present a micromagnetic theory of curvilinear ferromagnetic shells [2]. New chiral effects, originating from the magnetostatic interaction, can appear in such systems. They manifest themselves even in statics and are essentially nonlocal. This is in contrast to conventional Dzyaloshinskii--Moriya interaction (material intrinsic or curvature-induced, stemming from the exchange). The physical origin is in a non-zero mean curvature of a shell and non-equivalence between the top and bottom surfaces of the shell. To describe the new effects, we split a conventional volume magnetostatic charge into two terms: (i) magnetostatic charge, governed by the tangent to the sample’s surface, and (ii) geometrical charge, given by the normal component of magnetization and the mean curvature. We classify the interplay between the symmetry of the shell, its local curvature and magnetic textures and apply the proposed formalism to analyze magnetic textures in corrugated shells with perpendicular anisotropy.

[1] R. Streubel, J. Lee, D. Makarov et al, J. Phys. D, 49, 363001, (2016);
[2] O. V. Pylypovskyi, D. D. Sheka, V. P. Kravchuk et al, Sci. Rep. Vol. 6, p. 23316 (2016); O. M. Volkov, D. D. Sheka, Y. Gaididei et al, Sci. Rep. Vol. 8, p. 866 (2018).
[3] D. D. Sheka, O. V. Pylypovskyi, P. Landeros et al., Comm. Phys. 3, 128 (2019), DOI:10.1038/s42005-020-0387-2

  • Contribution to proceedings
    MMM 2020 Virtual Conference, 02.-06.11.2020, Virtual Conference, Virtual Conference

Permalink: https://www.hzdr.de/publications/Publ-31894
Publ.-Id: 31894


From stripes to bubbles: Deterministic transformation of magnetic domain patterns in Co/Pt multilayers induced by laser helicity

Novakovic-Marinkovic, N.; Mawass, M.-A.; Volkov, O.; Makushko, P.; Dieter Engel, W.; Makarov, D.; Kronast, F.

The optical control of magnetism offers an attractive possibility to manipulate small magnetic domains for prospective memory devices on ultrashort time scales. Here, we report on the local deterministic transformation of the magnetic domain pattern from stripes to bubbles in out-of-plane magnetized Co/Pt multilayers controlled only by the helicity of ultrashort laser pulses. Relying on the experimentally determined average size of stripe domains and the magnetic layer thickness, we calculate the temperature and characteristic fields at which the stripe-bubble transformation occurs. Furthermore, we demonstrate that in the narrow range of the laser power, the helicity induces a drag on domain walls.

Keywords: Ferromagnetism; Magnetic domains; Magnetization switching; Ultrafast megnetic effects; Multilayer thin films

Permalink: https://www.hzdr.de/publications/Publ-31893
Publ.-Id: 31893


PET measured hypoxia and MRI parameters in re-irradiated head and neck squamous cell carcinomas: findings of a prospective pilot study

Rogasch, J.; Beck, M.; Stromberger, C.; Hofheinz, F.; Ghadjar, P.; Wust, W.; Budach, V.; Amthauer, H.; Tinhofer, I.; Furth, C.; Walter-Rittel, T.; Zschaeck, S.

Background: Tumor hypoxia measured by dedicated tracers like [18F]fluoromisonidazole (FMISO) is a well-established prognostic factor in head and neck squamous cell carcinomas (HNSCC) treated with definitive chemoradiation (CRT). However, prevalence and characteristics of positron emission tomography (PET) measured hypoxia in patients with relapse after previous irradiation is missing. Here we report imaging findings of a prospective pilot study in HNSCC patients treated with re-irradiation.

Methods: In 8 patients with recurrent HNSCC, diagnosed at a median of 18 months after initial radiotherapy/CRT, [18F]fluorodeoxyglucose (FDG)-PET/CT (n=8) and FMISO-PET/MRI (n=7) or FMISO-PET/CT (n=1) were performed. Static FMISO-PET was performed after 180 min. MRI sequences in PET/MRI included diffusion-weighted imaging with apparent diffusion coefficient (ADC) values and contrast enhanced T1w imaging (StarVIBE). Lesions (primary tumor recurrence, 4; cervical lymph node, 1; both, 3) were delineated on FDG-PET and FMISO-PET data using a background-adapted threshold-based method. SUVmax and SUVmean in FDG- and FMISO-PET were derived, as well as maximum tumor-to-muscle ratio (TMRmax) and hypoxic volume with 1.6-fold muscle SUVmean (HV1.6) in FMISO-PET. Intensity of lesional contrast enhancement was rated relative to contralateral normal tissue. Average ADC values were derived from a 2D region of interest in the tumor.

Results: In FMISO-PET, median TMRmax was 1.7 (range: 1.1-1.8). Median HV1.6 was 0.05 ml (range: 0-7.3 ml). Only in 2/8 patients, HV1.6 was ≥1.0 ml. In FDG-PET, median SUVmax was 9.3 (range: 5.0-20.1). On contrast enhanced imaging four lesions showed decreased and four lesions increased contrast enhancement compared to non-pathologic reference tissue. Median average ADC was 1,060 ×106 mm2/s (range: 840-1,400 ×106 mm2/s).

Conclusions: This pilot study implies that hypoxia detectable by FMISO-PET may not be as prevalent as expected among loco-regional recurrent HNSCC. ADC values were only mildly reduced, and contrast enhancement was variable. The results require confirmation in larger sample sizes.

Keywords: radiotherapy; head and neck squamous cell carcinoma; hypoxia; FMISO; FDG; PET

Permalink: https://www.hzdr.de/publications/Publ-31892
Publ.-Id: 31892


Dataset for the publication "Depth distribution of irradiation-induced dislocation loops in an Fe-9Cr model alloy irradiated with Fe ions: The effect of ion energy"

Vogel, K.; Chekhonin, P.; Bergner, F.

The dataset covers the raw/processed data required to reproduce the findings derived in the publication "Depth distribution of irradiation-induced dislocation loops in an Fe-9Cr model alloy irradiated with Fe ions: The effect of ion energy" by K. Vogel, P. Chekhonin, C. Kaden, M. Hernández-Mayoral, S. Akhmadaliev and F. Bergner. The whole set of original figures included in the publication is included as TIFF files. Supplementary material is provided as follows:

  • G385_xMeV_loop_count.pptx: Powerpoint files related to the estimation of the loop concentrations for the 1 MeV and 5 MeV irradiations,
  • Image_FIB_Position_Final.pptx: Powerpoint file showing the way how the 5 MeV FIB lamella was taken,
  • Loop_size_xMeV_Slicey.xlsx: Excel files related to the sizing of loops utilized to derive the histograms of the loops sizes,
  • Thickness_Profile_CBED_5MeV.xlsx: Thickness measurement for 5 MeV using the method of CBED.

Keywords: Fe-9Cr; Ion irradiation; Cross-sectional scanning transmission electron microscopy (STEM)

  • Reseach data in the HZDR data repository RODARE
    Publication date: 2020-12-15
    DOI: 10.14278/rodare.670

Downloads:

Permalink: https://www.hzdr.de/publications/Publ-31890
Publ.-Id: 31890


Data for: "MicroTCA.4 based low level RF for continuous wave mode operation at the ELBE accelerator"

Kuntzsch, M.; Steinbrück, R.; Zenker, K.

This data is used in the publication "MicroTCA.4 based low level RF for continuous wave mode operation at the ELBE accelerator". The README.md includes all the information about which data set was used for which figure. The paper only shows the raw  data and numbers deduced from the data. No post processing like cleaning was done.

Keywords: ELBE; ChimeraTK; MicroTCA.4; LLRF; OPC UA

  • Reseach data in the HZDR data repository RODARE
    Publication date: 2020-12-09
    DOI: 10.14278/rodare.630

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Permalink: https://www.hzdr.de/publications/Publ-31889
Publ.-Id: 31889


The effect of the particle parameters of morphology and wettability in ultrafine particle flotation and froth fractionation

Sygusch, J.; Rudolph, M.

Froth flotation is well-established and efficient in the selective separation of valuable particles from unwanted material with sizes ranging from 10 µm to 200 µm. However, when it comes to the separation of ultrafine particles (< 10 µm) there are still some challenges, or rather opportunities. This research is part of the German research foundation priority programme DFG-SPP 2045 “MehrDimPart” aiming at developing a method for the separation of ultrafine particles based on multiple particle properties. Amongst such properties are wettability, morphology (shape or roughness) and size with applications not only in mineral processing but in general chemical engineering.
In order to study the effect of particle morphology on ultrafine particle flotation, three differently shaped fractions are used for testing, e.g. spherical particles, elongated particles and irregularly shaped particle fragments. Said particles are analysed for their wettability, which is varied by esterification using alcohols with differing alkyl chain lengths, through contact angle measurements. The particle size and shape properties are assessed by a combination of scanning electron microscopy, laser diffraction and optical microscopy.
Flotation tests are carried out using a novel flotation device that was designed especially for the flotation of ultrafine particles, combining advantages from machine-type froth flotation and column flotation.
Besides introducing a new concept of ultrafine particle flotation and froth fractionation, the study is contributing to the common understanding of flotation and the impact of different complex particle properties.

Keywords: Ultrafine particles; Flotation; Surface modification; Esterification of glass; Hydrophobisation

  • Contribution to proceedings
    International Mineral Processing Congress 2020, 18.-22.10.2020, Cape Town, South Africa
    Proceedings of the International Mineral Processing Congress 2020

Permalink: https://www.hzdr.de/publications/Publ-31885
Publ.-Id: 31885


Numerical ferromagnetic resonance experiments in nano-sized elements

Kai, W.; Körber, L.; Stienen, S.; Lindner, J.; Farle, M.; Kákay, A.

This dataset contains the raw data for our paper "Numerical ferromagnetic resonance experiments in nano-sized elements" published in IEEE Magnetic Letters. It is organized in folders according to the figures in the paper. Each folder contains the experimental and numerical data, together with the MuMax3 definition files and possible scripts used for evaluation.

  • Reseach data in the HZDR data repository RODARE
    Publication date: 2020-12-14
    DOI: 10.14278/rodare.666
    License: CC-BY-4.0

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Permalink: https://www.hzdr.de/publications/Publ-31884
Publ.-Id: 31884


High denticity oxinate-linearbackbone chelating ligand for diagnostic radiometal ions [111In]In3+ and [89Zr]Zr4+

Southcott, L.; Wang, X.; Wharton, L.; Yang, H.; Radchenko, V.; Kubeil, M.; Stephan, H.; Jaraquemada-Pelaez, M.; Orvig, C.

Advances in nuclear medicine depend on chelating ligands that form highly stable and kinetically inert complexes with relevant radiometal ions for use in diagnosis or therapy. A new potentially decadentate ligand, H5decaox, was synthesised to incorporate two 8-hydroxyquinoline moieties on either end of a diethylene triamine backbone decorated with three carboxylic acids, one at each N atom of the backbone. Metal complexation was assessed using nuclear magnetic resonance (NMR) spectroscopy and high-resolution massspectrometry (HR-MS) with In3+, Zr4+ and La3+. Solution thermodynamic studies provided the stepwise protonation constants and metal formation constants, indicating a high affinity for both In3+ and Zr4+ (pIn = 32.3 and pZr = 34.7), and density functional theory (DFT) calculations provided insight to the coordination environments with either metal ion.Concentration dependent radiolabeling experiments with [111In]InCl3 and [89Zr]ZrCl4 showed promise as quantitative radiolabeling (>95%) occurred at micromolar concentrations, under mild, near-physiological conditions of pH 7 and room temperature for 30 minutes. Serum stability of both radiometal complexes was investigated and the
[111In]In(decaox) complex remained 91% intact after 24 hours while the [89Zr]Zr(decaox) complex was 86% intact over the same time, comparable to other chelating ligands previously assessed with the same methods. The high radiolabeling yields, limited serum protein transchelation and structural insight of [89Zr]Zr(decaox) complex suggests a promising fit between the oxinate-containing ligand and the Zr4+ ion, setting the stage for further investigations with a functionalised version of the chelator for its potential in PET imaging.

  • Dalton Transactions 50(2021), 3874-3886

Permalink: https://www.hzdr.de/publications/Publ-31883
Publ.-Id: 31883


A metabolic switch regulates the transition between growth and diapause in C. elegans

Penkov, S.; Raghuraman, B. K.; Erkut, C.; Oertel, J.; Galli, R.; Ackerman, E. J. M.; Vorkel, D.; Verbavatz, J. M.; Koch, E.; Fahmy, K.; Shevchenko, A.; Kurzchalia, T. V.

Background Metabolic activity alternates between high and low states during different stages of an organism's life cycle. During the transition from growth to quiescence, a major metabolic shift often occurs from oxidative phosphorylation to glycolysis and gluconeogenesis. We use the entry of Caenorhabditis elegans into the dauer larval stage, a developmentally arrested stage formed in response to harsh environmental conditions, as a model to study the global metabolic changes and underlying molecular mechanisms associated with growth to quiescence transition. Results Here, we show that the metabolic switch involves the concerted activity of several regulatory pathways. Whereas the steroid hormone receptor DAF-12 controls dauer morphogenesis, the insulin pathway maintains low energy expenditure through DAF-16/FoxO, which also requires AAK-2/AMPK alpha. DAF-12 and AAK-2 separately promote a shift in the molar ratios between competing enzymes at two key branch points within the central carbon metabolic pathway diverting carbon atoms from the TCA cycle and directing them to gluconeogenesis. When both AAK-2 and DAF-12 are suppressed, the TCA cycle is active and the developmental arrest is bypassed. Conclusions The metabolic status of each developmental stage is defined by stoichiometric ratios within the constellation of metabolic enzymes driving metabolic flux and controls the transition between growth and quiescence.

Keywords: microcalorimetry

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Permalink: https://www.hzdr.de/publications/Publ-31882
Publ.-Id: 31882


Laser-plasma proton acceleration with a combined gas-foil target

Levy, D.; Bernert, C.; Rehwald, M.; Andriyash, I. A.; Assenbaum, S.; Kluge, T.; Kroupp, E.; Obst-Huebl, L.; Pausch, R.; Schulze-Makuch, A.; Zeil, K.; Schramm, U.; Malka, V.

Laser-plasma proton acceleration was investigated in the target normal sheath acceleration regime with a target composed of a gas layer and a thin foil. The laser's shape, duration, energy and frequency are modified as it propagates in the gas, altering the laser-solid interaction leading to proton acceleration. The modified properties of the laser were assessed by both numerical simulations and by measurements. The 3D particle-in-cell simulations have shown that a nearly seven-fold increase in peak intensity at the foil plane is possible. In the experiment, maximum proton energies showed high dependence on the energy transmission of the laser through the gas and a lesser dependence on the size and shape of the pulse. At high gas densities, where high intensity was expected, laser energy depletion and pulse distortion suppressed proton energies. At low densities, with the laser focused far behind the foil, self-focusing was observed and the gas showed a positive effect on proton energies. The promising results of this first exploration motivate further study of the target.

Keywords: laser plasma; TNSA; self focusing; PIConGPU

Related publications

Permalink: https://www.hzdr.de/publications/Publ-31881
Publ.-Id: 31881


Status Report of GaN photocathode

Schaber, J.; Xiang, R.; Teichert, J.; Arnold, A.; Ryzhov, A.; Murcek, P.; Zwartek, P.; Ma, S.

Particle accelerators are always looking for new materials which can promise high quantum efficiency, a long lifetime and good vacuum stability, fast response time and low thermal emittance. Semiconductors such as GaN as novel materials for photocathodes are showing an enormous potential.
Activated with a thin alkali metal layer, like caesium (Cs), p-GaN has the ability to lower the surface work function to produce a negative electron affinity (NEA). Requirements on the instrumentation is to avoid any oxygen contamination before, during and after the activation with caesium, so the activation process takes place in a UHV chamber.
At the beginning of 2020 the first activation of GaN on sapphire substrate was successfully done and meanwhile more activations could be implemented. The activation process is influenced by many parameters like Cs-flux, heat-cleaning temperature, conductivity, anode material, vacuum and the substrate. All of these parameters have an influence on the photocathodes quality and its lifetime, which are studied and compared.

Keywords: GaN photocathode; III-V semiconductor; caesium activation; NEA cathode; Quantum efficiency

  • Open Access Logo Lecture (others) (Online presentation)
    High Brightness Electron beams generated from novel THermal resistant photocathodes (BETH) 2nd Collaboration Meeting, 10.07.2020, Siegen, Deutschland

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Permalink: https://www.hzdr.de/publications/Publ-31880
Publ.-Id: 31880


Status Report of ELBE and GaN

Xiang, R.; Teichert, J.; Arnold, A.; Ryzhov, A.; Murcek, P.; Zwartek, P.; Ma, S.; Schaber, J.

The SRF Gun has been running stabile using a magnesium cathode in the last year. Over 200 hours beam time have been provided in CW operation in 2019.
The magnesium bulk cathodes work routinely in ELBE and are polished and chemical cleaned before inserting them into the SRF Gun II, where they are again cleaned with an UV drive laser. Magnesium cathodes derives usually quantum effeciencies (QE) between 0.3 to 0.5% in SRF Gun II and offer a low risk of contaminations and an extreme long lifetime. The UV drive laser cleaning can be repeated several times to guarantee an high quality working cathode.
However, the particle accelerator community is always looking for new materials which can promise high quantum efficiency, a long lifetime and good vacuum stability, fast response time and low thermal emittance. Semiconductors such as GaN as novel materials for photocathodes are showing an enormous potential.
GaN is a semi-conductive material and well known for its high QE when illuminated with UV light. For the activation only caesium is required.
At the beginning of 2020 the first activation of GaN on sapphire substrate was successfully done. At first the GaN is heat treated at 610°C for 15 min and then activated with caesium to form a negative electron affinity surface. With 0.5 % quantum efficiency the first activation is all in all a successfully step for further promising GaN photocathodes.

Keywords: GaN; photocathode; SRF Gun; III-V semiconductor photocathode; Mg cathode

  • Open Access Logo Lecture (others)
    High Brightness Electron beams generated from novel THermal resistant photocathodes (BETH) Meeting, 20.-21.01.2020, Siegen, Deutschland

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Permalink: https://www.hzdr.de/publications/Publ-31879
Publ.-Id: 31879


C. elegans possess a general program to enter cryptobiosis that allows dauer larvae to survive different kinds of abiotic stress

Gade, V. R.; Traikov, S.; Oertel, J.; Fahmy, K.; Kurzchalia, T. V.

All organisms encounter abiotic stress but only certain organisms are able to cope with extreme conditions and enter into cryptobiosis (hidden life). Previously, we have shown that C. elegans dauer larvae can survive severe desiccation (anhydrobiosis), a specific form of cryptobiosis. Entry into anhydrobiosis is preceded by activation of a set of biochemical pathways by exposure to mild desiccation. This process called preconditioning induces elevation of trehalose, intrinsically disordered proteins, polyamines and some other pathways that allow the preservation of cellular functionality in the absence of water. Here, we demonstrate that another stress factor, high osmolarity, activates similar biochemical pathways. The larvae that acquired resistance to high osmotic pressure can also withstand desiccation. In addition, high osmolarity significantly increases the biosynthesis of glycerol making larva tolerant to freezing. Thus, to survive abiotic stress, C. elegans activates a combination of genetic and biochemical pathways that serve as a general survival program.

Keywords: calorimetry; anhydrobiosis; metabolic monitoring; osmmotic stress

Permalink: https://www.hzdr.de/publications/Publ-31878
Publ.-Id: 31878


Current status of the simulations on Wu et al. using fbpic and PIConGPU

Pausch, R.; Döpp, A.

A brief summary to drive a discussion regarding the Wu et al. paper and a possible reply to it.

Keywords: PIConGPU; LWFA; PWFA; fbpic

  • Lecture (others)
    hybrid meeting, 06.02.2020, Paris, France

Permalink: https://www.hzdr.de/publications/Publ-31877
Publ.-Id: 31877


Data for: "First-principles modeling of plasmons in aluminum under ambient and extreme conditions"

Ramakrishna, K.; Cangi, A.; Dornheim, T.; Vorberger, J.

The numerical modeling of plasmon behavior is crucial for an accurate interpretation of inelastic scattering diagnostics in many experiments. We highlight the utility of linear-response time-dependent density functional theory (LR-TDDFT) as an appropriate first-principles framework for a consistent modeling of plasmon properties. We provide a comprehensive analysis of plasmons from ambient throughout warm dense conditions and assess typical properties such as the dynamical structure factor, the plasmon dispersion, and the plasmon width. We compare them with experimental measurements in aluminum accessible via x-ray Thomson scattering and with other dielectric models such as the Lindhard model, the Mermin approach based on parametrized collision frequencies, and the dielectric function obtained using static local field corrections of the uniform electron gas parametrized from path integral Monte Carlo simulations both at the ground state and at finite temperature. We conclude with the remark that the common practice of extracting and employing plasmon dispersion relations and widths is an insufficient procedure to capture the complicated physics contained in the dynamic structure factor in its full breadth.

Keywords: Warm dense matter

Related publications

  • Reseach data in the HZDR data repository RODARE
    Publication date: 2020-09-25
    DOI: 10.14278/rodare.331
    License: CC-BY-4.0

Downloads:

Permalink: https://www.hzdr.de/publications/Publ-31876
Publ.-Id: 31876


Probing ultrafast magnetic-field generation by current filamentation instability in femtosecond relativistic laser-matter interactions

Raj, G.; Kononenko, O.; Gilljohann, M. F. F.; Doche, A.; Davoine, X.; Caizergues, C.; Chang, Y.-Y.; Couperus Cabadağ, J. P.; Debus, A.; Ding, H.; Förster, M.; Goddet, J.-P.; Heinemann, T.; Kluge, T.; Kurz, T.; Pausch, R.; Rousseau, P.; San Miguel Claveria, P.; Schöbel, S.; Siciak, A.; Steiniger, K.; Tafzi, A.; Yu, S.; Hidding, B.; Martinez De La Ossa, A.; Irman, A.; Karsch, S.; Döpp, A.; Schramm, U.; Gremillet, L.; Corde, S.

The current filamentation instability is a key phenomenon underpinning various processes in astrophysics, laboratory laser-plasma, and beam-plasma experiments. Here we show that the ultrafast dynamics of this instability can be explored in the context of relativistic laser-solid interactions through deflectometry by low-emittance, highly relativistic electron bunches from a laser wakefield accelerator. We present experimental measurements of the femtosecond timescale generation of strong magnetic-field fluctuations, with a measured line-integrated B field of 2.70±0.39kTμm. Three-dimensional, fully relativistic particle-in-cell simulations demonstrate that such fluctuations originate from the current filamentation instability arising at submicron scales around the irradiated target surface, and that they grow to amplitudes strong enough to broaden the angular distribution of the probe electron bunch a few tens of femtoseconds after the laser pulse maximum. Our results open a branch of physics experiments investigating the femtosecond dynamics of laser-driven plasma instabilities by means of synchronized, wakefield-accelerated electron beams.

Keywords: current filamentation; laser plasma

Permalink: https://www.hzdr.de/publications/Publ-31875
Publ.-Id: 31875


Review on the Compositional Variation of Eudialyte-Group Minerals in the Ilímaussaq Complex (South Greenland)

Marks, M. A. W.; Eggenkamp, H. G. M.; Atanasova, Petya; Mundel, F.; Kümmel, S.; Hagen, M.; Wenzel, T.; Markl, G.

We review the compositional variation of eudialyte-group minerals (EGM) from the Ilímaussaq complex in South Greenland. Investigated samples cover all major rock units and associated pegmatites and aplites. The whole data set (>3000 analyses from>250 samples) exhibits variable XMn (0.1–0.5), REE (0.2–1.7 apfu), Nb (0.1–0.4), and Cl contents (0.4–1.6 apfu). Most EGM compositions are Na-rich (13–15 apfu), while deviations to Na-rich but also to Na-poor compositions occur because of a combination of primary features (peralkalinity, water activity) and secondary alteration. During magma evolution, REE contents in EGM cores generally increase and reach their highest contents in the most evolved rock units of the complex. This points to the moderate compatibility of REE in EGM and a bulk D (cEGM/cmelt) value of <1 during magma differentiation. Chlorine contents in EGM cores continuously decrease, and are lowest at the rims of individual crystals, suggesting a continuous decrease of Cl activity in the magmas by large-scale EGM and sodalite extraction during the orthomagmatic stage and water enrichment during the late-magmatic stage. The overall variations of XMn across stratigraphy are only minor and likely influenced bythe co-crystallization of sodic pyroxene and amphibole (c.f. aegirine, arfvedsonite) and local phaseproportions. Similarly, Nb and Ti contents are influenced by co-crystallizing aenigmatite, rinkite, and others. Their presence buffers Ti and Nb contents to rather constant and low values, while their absence may cause variable enrichment on a local scale. Very low Sr contents (<0.1 apfu) in magmatic EGM from Ilímaussaq are related to the basaltic nature of the parental magmas of the complex, as large-scale plagioclase fractionation occurred prior to the formation of the Ilímaussaq magmas, effectively removing Sr from the system. This is in line with very strong negative Eu anomalies in EGM from Ilímaussaq. Consistently, Sr contents in EGM from alkaline complexes, for which foiditic parental magmas are assumed, are much higher and, in such cases, negative Eu anomalies aregenerally absent.

Keywords: Ilimaussaq; differentiation; eudialyte-group minerals; mineral chemistry

Permalink: https://www.hzdr.de/publications/Publ-31874
Publ.-Id: 31874


PIConGPU - a highly-parallel 3D3V particle-in-cell code

Pausch, R.; Bastrakov, S.; Debus, A.; Garten, M.; Huebl, A.; Marre, B.-E.; Meyer, F.; Steinger, K.; Widera, R.; Bussmann, M.

This talk will introduce the basic concepts of how particle-in-cell codes model plasma dynamics and discuss their implementation in the open-source code PIConGPU, focusing on how parallelism can be exploited to enable efficient scaling on today's largest HPC systems. Furthermore, the problem of IO limitations with larger simulations is discussed and the plugin method for in-situ data analysis in PIConGPU is presented to overcome these limitations. Finally, an overview of different physics cases simulated with PIConGPU is presented, ranging from small-scale laser-plasma accelerators to plasma jets in astrophysics.

Keywords: PIConGPU; LWFA; TNSA; alpaka; ISAAC; KHI

  • Lecture (others) (Online presentation)
    CASUS Seminar, 08.09.2020, Görlitz, Deutschland
  • Lecture (others)
    Seminar Series 'Hardware & Numerics', 24.11.2020, Dresden, Deutschland

Permalink: https://www.hzdr.de/publications/Publ-31873
Publ.-Id: 31873


Changes in Halogen (F, Cl, Br, and I) and S Ratios inRock-Forming Minerals as Monitors for MagmaticDifferentiation, Volatile-Loss, and HydrothermalOverprint: The Case for Peralkaline Systems

Eggenkamp, H. G. M.; Marks, M. A. W.; Atanasova, Petya; Wenzel, T.; Markl, G.

We determined the halogen (F, Cl, Br, and I) and sulfur (S) concentrations in Cl-rich rock-forming minerals from five peralkaline complexes. We investigated sodalite (N=42), eudialyte-group minerals (N=84), and tugtupite (N=8) from representative rock samples derived from Ilímaussaq (South Greenland), Norra Kärr (Sweden), Tamazeght (Morocco), Lovozero, and Khibina (Russian Federation). Taken together, sodalite and eudialyte-group minerals dominate the Cl and Br budget of the investigated rocks. For F, however, several other phases (e.g., amphibole, fluorite, villiaumite, and minerals of the rinkite group and the apatite supergroup) are additional sinks, and parts of the S may be scavenged in generally rare sulfides. The investigated minerals contain Cl at the wt.% level, F and S concentrations are in the hundreds to thousands of μg/g-range, Br is less common (0.2–200μg/g) and I is rare (mostly well below 1μg/g). Normalized to Cl, sodalite prefers Br relative to eudialyte-group minerals, while F is always enriched in the latter. Our data show that both F and S may represent important components in eudialyte-group minerals, sometimes at similar levels as Cl, which normally dominates. Sulfur reveals redox-dependent behavior: Under reduced crystallization conditions, S is more compatible in eudialyte-group minerals (EGM) than in sodalite, which flips to the opposite under water-rich and presumably more oxidized conditions. We investigate the applicability of F/Cl, Br/Cl, and S/Cl ratios in these minerals in peralkaline systems to better understand the interplay of magmatic differentiation, fluid loss and hydrothermal overprint. Similar to apatite in metaluminous systems, fractionation of sodalite, and eudialyte-group minerals in peralkaline magmas leads to decreasing Br/Cl ratios. The data presented in this study bear implications for the mineral chemistry and compositional variation of sodalite and especially EGM in general. Volatile components in EGM that are not normally considered, such as F and S, can reach concentrations of thousands of μg/g. Especially in the case of F, with its low atomic weight, the results obtained in this study indicate that it is very significant for formulae calculations, neutral charge-balance, and similar aspects at such concentration levels. This study demonstrates that halogen contents and ratios are sensitive monitors for a variety of processes in magmatic-hydrothermal systems, including magmatic fractionation, volatile loss, and fluid–rock interaction.

Keywords: eudialyte group minerals; sodalite; tugtupite; chloride; fluoride; bromide; sulfur; Ilímaussaq; peralkaline rocks

Permalink: https://www.hzdr.de/publications/Publ-31872
Publ.-Id: 31872


Design study for a compact laser-driven source for medical x-ray fluorescence imaging

Brümmer, T.; Debus, A.; Pausch, R.; Osterhoff, J.; Grüner, F.

Thomson scattering sources with their hard x-ray pencil beams represent a promising candidate to drive high-resolution X-ray Fluorescence Imaging (XFI). As XFI is a scanning imaging modality, it specifically requires pencil-beam geometries along with a high beam mobility. In combination with laser-wakefield acceleration (LWFA) such sources could provide the compactness needed for a future transition into clinical application. A sufficient flux within a small bandwidth could enable in-vivo high-sensitivity XFI for early cancer diagnostics and pharmacokinetic imaging. We thus report on a specific all-laser driven source design directed at increasing the photon number within the bandwidth and opening angle defined by XFI conditions. Typical parameters of driver lasers and electron bunches from LWFA are utilized and controlled within realistic parameter regions on the basis of appropriate beam optics. An active plasma lens is implemented for chromatic focal control of the bunch. Source performance limits are identified and compared to existing x-ray sources with regard to their potential to be implemented in future clinical XFI.

Keywords: Thomsons scattering; x-ray; light source; ClaRa2

Permalink: https://www.hzdr.de/publications/Publ-31871
Publ.-Id: 31871


Uranium(VI) reduction by a sulphate-reducing microorganism in Opalinus Clay pore water

Hilpmann, S.; Drobot, B.; Steudtner, R.; Bok, F.; Stumpf, T.; Cherkouk, A.

1 Introduction
Clay formations are potential host rocks for the long-term storage of high-level radioactive waste in a deep geological repository in Germany, besides salt and crystalline rock. A multi-barrier system is fa-vored, consisting of the technical (container with the waste), the geotechnical (sealing and backfilling material, e.g. bentonite) and the geological barrier (host rock) to isolate it from the biosphere.
Different studies showed that sulphate-reducing microorganisms, especially Desulfosporosinus species, occur in various clay formations, as well as in bentonite [1,2]. Desulfosporosinus hippei DSM 8344 is an anaerobic spore-forming microorganism isolated from permafrost soil [3] and a close phylogenetic relative of the Desulfosporosinus species detected in clay formations. Therefore, this strain was selected to study the reduc-tion of uranium(VI) to the less mobile uranium(IV).

2 Results
A time-dependent experiment in artificial Opalinus Clay pore water [4] (100 µM uranium(VI), pH 5.5) revealed a 95 % removal of uranium from the supernatant within 24 h. The corresponding microscopy of live/dead stained cells showed the formation of agglomerates and an increasing number of dead cells within the incubation time. The black colouring of the agglomerates already provided hints of the occur-ring reduction of uranium(VI).
Different aqueous species including uranyl(VI) lactate and uranyl(VI) carbonate complexes are present in the supernatant, as determined by time-resolved laser-induced luminescence spectroscopy. The assign-ment of the different species was possible by comparison with reference spectra. While the amount of the uranyl(VI) lactate complex decreased with the incubation time, the uranyl(VI) carbonate fraction re-mained almost constant. This leads to the assumption, that the cells reduce only the uranyl(VI) lactate complex. This conclusion can be supported by the fact that the reduction process did not take place in bicarbonate buffer, where the uranyl(VI) carbonate complexes are dominant, using the same microor-ganism.
The comparison of the UV/VIS band positions of the dissolved cell pellets with the spectra of pure uranium(IV) and uranyl(VI) samples provides clear evidence of the formed uranium(IV). Furthermore, bands of uranyl(VI) occur in the spectrum, as well. Therefore, a combination of a sorption and reduction processes is assumed. These findings offer new insights into the microbe-actinide interactions relevant to high-level radioactive waste disposal in clay rock.

The authors gratefully acknowledge the funding provided by the German Federal Ministry of Education and Research (BMBF) (Grant 02NUK053E) and The Helmholtz Association (Grant SO-093).

References
[1] A. Bagnoud et al., “Reconstructing a hydrogen-driven microbial metabolic network in Opalinus Clay rock”, Nat. Commun. 7, 1–10 (2016)
[2] N. Matschiavelli et al., “The year-long development of microorganisms in uncompacted Bavarian bentonite slurries at 30 °C and 60 °C”, Environ. Sci. Technol. 53, 10514–10524 (2019).
[3] A. Vatsurina et al., “Desulfosporosinus hippei sp. nov., a mesophilic sulfate-reducing bacterium isolated from permafrost”, Int. J. Syst. Evol. Microbiol. 58, 1228–1232 (2008).
[4] P. Wersin et al. “Biogeochemical processes in a clay formation in situ experiment: Part A - Overview, experimental design and water data of an experiment in the Opalinus Clay at the Mont Terri Underground Research Laboratory, Switzerland”, Appl. Geochemistry 26, 931–953 (2011).

Keywords: uranium(VI) reduction; sulphate-reducing bacteria; clay rock

  • Lecture (Conference) (Online presentation)
    Tage der Standortauswahl Freiberg 2021, 11.-12.02.2021, Freiberg, Deutschland
  • Poster (Online presentation)
    Tage der Standortauswahl Freiberg 2021, 11.-12.02.2021, Freiberg, Deutschland

Permalink: https://www.hzdr.de/publications/Publ-31870
Publ.-Id: 31870


Wire-mesh sensor data set of gas-water flow in a horizontal pipe

de Assis Dias, F.; Pipa, D. R.; Morales, R. E. M.; Da Silva, M. J.

Wire-mesh sensor raw data of gas-water pipe flow. The experiments were performed at the Federal University of Paraná in a setup located at the NUEM (Núcleo de Escoamento Multifásico). The flow loop is composed of a horizontal pipe of 26 mm inner diameter and 9 m long. The data set are measurements of wire-mesh sensors with the following resolutions: 12x12, 8x8, 6x6, 4x4 and 2x2.

Keywords: wire-mesh sensor; multiphase flow

Related publications

  • Reseach data in the HZDR data repository RODARE
    Publication date: 2020-12-14
    DOI: 10.14278/rodare.659

Downloads:

Permalink: https://www.hzdr.de/publications/Publ-31869
Publ.-Id: 31869


First-principles modeling of plasmons in aluminum under ambient and extreme conditions

Ramakrishna, K.; Cangi, A.; Dornheim, T.; Vorberger, J.

The numerical modeling of plasmon behavior is crucial for an accurate interpretation of inelastic scattering diagnostics in many experiments. We highlight the utility of linear-response time-dependent density functional theory (LR-TDDFT) as an appropriate first-principles framework for a consistent modeling of plasmon properties. We provide a comprehensive analysis of plasmons from ambient throughout warm dense conditions and assess typical properties such as the dynamical structure factor, the plasmon dispersion, and the plasmon width. We compare them with experimental measurements in aluminum accessible via x-ray Thomson scattering and with other dielectric models such as the Lindhard model, the Mermin approach based on parametrized collision frequencies, and the dielectric function obtained using static local field corrections of the uniform electron gas parametrized from path integral Monte Carlo simulations both at the ground state and at finite temperature. We conclude with the remark that the common practice of extracting and employing plasmon dispersion relations and widths is an insufficient procedure to capture the complicated physics contained in the dynamic structure factor in its full breadth.

Keywords: Warm dense matter

Related publications

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Permalink: https://www.hzdr.de/publications/Publ-31868
Publ.-Id: 31868


Attenuating the fermion sign problem in path integral Monte Carlo simulations using the Bogoliubov inequality and thermodynamic integration

Dornheim, T.; Invernizzi, M.; Hirshberg, B.; Vorberger, J.

Accurate thermodynamic simulations of correlated fermions using path integral Monte Carlo (PIMC) methods are of paramount importance for many applications such as the description of ultracold atoms, electrons in quantum dots, and warm-dense matter. The main obstacle is the fermion sign problem (FSP), which leads to an exponential increase in computation time both with increasing the system-size and with decreasing temperature. Very recently, Hirshberg et al.[J. Chem. Phys. 152, 171102 (2020)] have proposed to alleviate the FSP based on the Bogoliubov inequality. In the present work, we extend this approach by adding a parameter that controls the perturbation, allowing for an extrapolation to the exact result. In this way, we can also use thermodynamic integration to obtain an improved estimate of the fermionic energy. As a test system, we choose electrons in 2D and 3D quantum dots and find in some cases a speed-up exceeding 10^ 6, as compared to standard PIMC, while retaining a relative accuracy of ~0.1%. Our approach is quite general and can readily be adapted to other simulation methods.

Permalink: https://www.hzdr.de/publications/Publ-31866
Publ.-Id: 31866


Finite-size effects in the reconstruction of dynamic properties from ab initio path integral Monte Carlo simulations

Dornheim, T.; Vorberger, J.

We systematically investigate finite-size effects in the dynamic structure factor S(q,ω) of the uniform electron gas obtained via the analytic continuation of ab initio path integral Monte Carlo data for the imaginary-time density–density correlation function F(q,τ). Using the recent scheme by Dornheim et al. [Phys. Rev. Lett. 121, 255001 (2018)], we find that the reconstructed spectra are not afflicted with any finite-size effects for as few as N=14 electrons both at warm dense matter (WDM) conditions and at the margins of the strongly correlated electron liquid regime. Our results further corroborate the high quality of our current description of the dynamic density response of correlated electrons, which is of high importance for many applications in WDM theory and beyond.

Permalink: https://www.hzdr.de/publications/Publ-31865
Publ.-Id: 31865


Effective Static Approximation: A Fast and Reliable Tool for Warm-Dense Matter Theory

Dornheim, T.; Cangi, A.; Ramakrishna, K.; Böhme, M.; Tanaka, S.; Vorberger, J.

We present an effective static approximation (ESA) to the local field correction (LFC) of the electron gas that enables highly accurate calculations of electronic properties like the dynamic structure factor S(q,ω), the static structure factor S(q), and the interaction energy v. The ESA combines the recent neural-net representation by T. Dornheim et al., [J. Chem. Phys. 151, 194104 (2019)] of the temperature-dependent LFC in the exact static limit with a consistent large wave-number limit obtained from quantum Monte Carlo data of the on-top pair distribution function g(0). It is suited for a straightforward integration into existing codes. We demonstrate the importance of the LFC for practical applications by reevaluating the results of the recent x-ray Thomson scattering experiment on aluminum by Sperling et al. [Phys. Rev. Lett. 115, 115001 (2015)]. We find that an accurate incorporation of electronic correlations in terms of the ESA leads to a different prediction of the inelastic scattering spectrum than obtained from state-of-the-art models like the Mermin approach or linear-response time-dependent density functional theory. Furthermore, the ESA scheme is particularly relevant for the development of advanced exchange-correlation functionals in density functional theory.

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Permalink: https://www.hzdr.de/publications/Publ-31864
Publ.-Id: 31864


Pump-probe response of correlated materials under high pressures

Pashkin, O.

Time-resolved optical spectroscopy is a very powerful tool for studying the photoinduced phase transitions and ultrafast dynamics in strongly correlated electronic systems. We reinforce this method by combining it with the high-pressure technique which allows to tune the strength of electronic correlations and Fermi surface nesting in a system. Several application examples for the investigation of the pressure-induced phenomena such as the metallization in VO2 and the suppression of the charge-density wave in CeTe3 and the spin-density wave in BaFe2As2 will be discussed.

  • Lecture (others) (Online presentation)
    Elasto-Q-Mat Colloquia, 10.12.2020, Mainz, Deutschland

Permalink: https://www.hzdr.de/publications/Publ-31863
Publ.-Id: 31863


Protein-Assisted Room-Temperature Assembly of Rigid, Immobile Holliday Junctions and Hierarchical DNA Nanostructures

Ramakrishnan, S.; Subramaniam, S.; Kielar, C.; Grundmeier, G.; Stewart, A. F.; Keller, A.

Immobile Holliday junctions represent not only the most fundamental building block of structural DNA nanotechnology but are also of tremendous importance for the in vitro investigation of genetic recombination and epigenetics. Here, we present a detailed study on the room-temperature assembly of immobile Holliday junctions with the help of the single-strand annealing protein Red beta. Individual DNA single strands are initially coated with protein monomers and subsequently hybridized to form a rigid blunt-ended four-arm junction. We investigate the efficiency of this approach for different DNA/protein ratios, as well as for different DNA sequence lengths. Furthermore, we also evaluate the potential of Red beta to anneal sticky-end modified Holliday junctions into hierarchical assemblies. We demonstrate the Red beta-mediated annealing of Holliday junction dimers, multimers, and extended networks several microns in size. While these hybrid DNA-protein nanostructures may find applications in the crystallization of DNA-protein complexes, our work shows the great potential of Red beta to aid in the synthesis of functional DNA nanostructures under mild reaction conditions.

Keywords: DNA nanotechnology; Holliday junctions; atomic force microscopy; single-strand annealing proteins

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Permalink: https://www.hzdr.de/publications/Publ-31862
Publ.-Id: 31862


Alginite rock as effective demulsifier to separate water from various crude oil emulsions

Ahmed, S. S.; Hippmann, S.; Roode-Gutzmer, Q. I.; Fröhlich, P.; Bertau, M.

Due to environmental restriction laws in oil production and processing, there is a high demand for the oil industry to reduce the use of chemical demulsifiers and to employ safer, less toxic materials. The purpose of this research is to investigate whether Alginite, a naturally occurring and abundant oil-shale rock, can be utilised as an alternative, environmentally friendly and low-cost material to demulsify various water-in-crude oil emulsions (W/O). Three W/O emulsions were prepared using saline water with respectively light, medium and heavy crude oils. The properties of the crude oils were analysed and the effectiveness of Alginite to demulsify the corresponding W/O emulsions was investigated. The results confirm that naturally occuring Alginite exhibits exceptional water-removing capacity even from emulsions containing heavy crude oil, leaving only < 1.0 wt.-% water in the remaining demulsified oil, which satisfies the required specification for industrial applications. Alginite was shown to reduce viscosity and to deform the dispersed phase in W/O emulsions even in the absence of flow. The results of this work indicate that Alginite is of significant interest in petroleum research, in industrial oil processing as well as in environmental remediation.

Keywords: Alginite rock; natural demulsifier; crude oil; viscosity; water droplet

Permalink: https://www.hzdr.de/publications/Publ-31861
Publ.-Id: 31861


Solventextraktion von Rhenium und Molybdän - Trennung durch selektive Reextraktion

Göthel, J.

Die Anwendungen der Solventextraktion finden sich in der anorganischen, organischen und analytischen Chemie, in den pharmazeutischen und biochemischen Industrien sowie in der Abfallbehandlung und ist eine der groß angelegten industriellen Trennungs-verfahren. In der metallurgischen Aufbereitung von Rohstoffen ist die Solventextraktion durch die Interdisziplinarität von hydrometallurgischer Verfahrenstechnik und anorganisch-organischer Chemie geprägt. Bei der Extraktion anionischer Metallspezies aus wässriger Lösung finden unter anderem aliphatische Amine eine breite Anwendung. Die wirtschaftsstrategischen Refraktärmetalle Rhenium und Molybdän wurden in den 1980er Jahren hinsichtlich ihrer selektiven Trennung durch eine Kombination von sekundären Aminen (R2NH) als Extraktionsmittel und Phosphinoxid (R3PO) als Additiv beschrieben. Bisher wurden keine Untersuchungen des Extraktionssystems gegenüber Eisen (III), der Coextraktion vom Mo (VI) und Re (VII) aus stark verdünnten Lösungen und dem Vergleich zu anderen sekundären Aminen durchgeführt sowie den Einfluss des Lösungsmittels untersucht (vgl. KÄHLER und GOCK). Die Untersuchungen zum System Rhenium und Molybdän im Rahmen dieser experimentellen Studienarbeit haben gezeigt, dass das Additiv TOPO mit dem Extraktionsmittel DTDA die Extraktion von Rhenium verbessert. Das Extraktionsmittel DTDA führt aufgrund seiner langkettigen Alkylreste im Vergleich zu DOA zu größeren Extraktionsergebnissen. Mit dem Extraktionsmittel DOA treten vermehrt dritte Phasen bei der Extraktion auf. Das Extraktionssystem zeichnet sich durch eine Gesamtbeladungs-kapazität aus, wobei Sulfatspezies und auch Wasser coextrahiert werden können. Das Lösungsmittel Chloroform verschlechtert die Extraktion von Rhenium durch seine abschirmenden polaren Wechselwirkungen und der Konkurrenzsituation bei der Ausbildung von Wasserstoffbrückenbindungen. Molybdän scheint für die Extraktion keine signifikante Abhängigkeit vom Lösungsmittel (Kerosin, Toluol und Chloroform) zu zeigen. Molybdän und Rhenium lassen sich selektiv von Kupfer und Zink extrahieren, jedoch nicht von Eisen (III). Eisen kann mit Salzsäure zu über 60 % von der beladenen Organik unter Verlust von Molybdän gewaschen werden. Mittels Schwefelsäure kann Eisen vollständig von der Organik, aber mit noch höheren Molybdänüberführungen, gewaschen werden. Eine befriedigende Trennung ergibt sich nicht. Rhenium kann von Molybdän selektiv unter dem Einfluss von TOPO bereits bei geringen TOPO-Konzentrationen reextrahiert werden. Diese Selektivität zeigt sich deutlicher im Lösungsmittel Chloroform als im Lösungsmittel Kerosin.

  • Other
    TU Bergakademie Freiberg, 2020
    Mentor: Toni Helbig

Permalink: https://www.hzdr.de/publications/Publ-31858
Publ.-Id: 31858


Accelerating Finite-temperature Kohn-Sham Density Functional Theory with Deep Neural Networks

Ellis, J. A.; Cangi, A.; Modine, N. A.; Stephens, J. A.; Thompson, A. P.; Rajamanickam, S.

Output from electronic structure code (Quantum Espresso) that serves as training data for the machine-learning workflow of the related scientific publication (https://arxiv.org/abs/2010.04905).

Keywords: machine learning; neural networks; materials science; density functional theory

  • Reseach data in the HZDR data repository RODARE
    Publication date: 2020-12-11
    DOI: 10.14278/rodare.645

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Permalink: https://www.hzdr.de/publications/Publ-31857
Publ.-Id: 31857


Defects in Functional Materials

Ling, F. C.-C.; Zhou, S.; Kuznetsov, A.

The research of functional materials has attracted extensive attention in recent years, and its advancement nitrifies the developments of modern sciences and technologies like green sciences and energy, aerospace, medical and health, telecommunications, and information technology. The present book aims to summarize the research activities carried out in recent years devoting to the understanding of the physics and chemistry of how the defects play a role in the electrical, optical and magnetic properties and the applications of the different functional materials in the fields of magnetism, optoelectronic, and photovoltaic etc.

  • Book (Editorship)
    Singapore: World Scientific Publishing Co., 2020
    ISBN: 978-981-120-316-9
    DOI: 10.1142/11352

Permalink: https://www.hzdr.de/publications/Publ-31856
Publ.-Id: 31856


Making 2D topological polymers a reality

Jing, Y.; Heine, T.

First-principles calculations predicted electronic topological properties for 2D honeycomb–kagome polymers, which have been now confirmed experimentally thanks to improvements in on-surface synthesis.

Keywords: 2D polymers; topological polymers

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Permalink: https://www.hzdr.de/publications/Publ-31854
Publ.-Id: 31854


Benchmark of Simplified Time-Dependent Density Functional Theory for UV–Vis Spectral Properties of Porphyrinoids

Batra, K.; Zahn, S.; Heine, T.

Time-dependent density functional theory is thoroughly benchmarked for the predictive calculation of UV–vis spectra of porphyrin derivatives. With the aim to provide an approach that is computationally feasible for large-scale applications such as biological systems or molecular framework materials, albeit performing with high accuracy for the Q-bands, the results given by various computational protocols, including basis sets, density-functionals (including gradient corrected local functionals, hybrids, double hybrids and range-separated functionals), and various variants of time-dependent density functional theory, including the simplified Tamm–Dancoff approximation, are compared. An excellent choice for these calculations is the range-separated functional CAM-B3LYP in combination with the simplified Tamm–Dancoff approximation and a basis set of double-ζ quality def2-SVP (mean absolute error [MAE] of ≈0.05 eV). This is not surpassed by more expensive approaches, not even by double hybrid functionals, and solely systematic excitation energy scaling slightly improves the results (MAE ≈0.04 eV).

Keywords: density functional theory; UV–Vis; porphyrinoids; spectroscopy

Permalink: https://www.hzdr.de/publications/Publ-31853
Publ.-Id: 31853


Blue Phosphorene Bilayer Is a Two-Dimensional Metal and an Unambiguous Classification Scheme for Buckled Hexagonal Bilayers

Arcudia, J.; Kempt, R.; Eduardo Cifuentes-Quintal, M.; Heine, T.; Merino, G.

High-level first-principles computations predict blue phosphorene bilayer to be a two-dimensional metal. This structure has not been considered before and was identified by employing a block-diagram scheme that yields the complete set of five high-symmetry stacking configurations of buckled honeycomb layers, and allows their unambiguous classification. We show that all of these stacking configurations are stable or at least metastable both for blue phosphorene and gray arsenene bilayers. For blue phosphorene, the most stable stacking arrangement has not yet been reported, and surprisingly it is metallic, while the others are indirect band gap semiconductors. As it is impossible to interchange the stacking configurations by translations, all of them should be experimentally accessible via the transfer of monolayers. The metallic character of blue phosphorene bilayer is caused by its short interlayer distance of 3.01 Å and offers the exceptional possibility to design single elemental all-phosphorus transistors.

Keywords: 2D materials; phosphorus; nanoelectronics; first-principles calculations

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Permalink: https://www.hzdr.de/publications/Publ-31852
Publ.-Id: 31852


RBS raw data for publication "Tuning the Co/Sr stoichiometry of SrCoO2.5 thin films by RHEED assisted MBEgrowth"

Schöffmann, P.; Pütter, S.; Schubert, J.; Zander, W.; Barthel, J.; Zakalek, P.; Waschk, M.; Heller, R.; Brückel, T.

RBS raw date for publication "Tuning the Co/Sr stoichiometry of SrCoO2.5 thin films by RHEED assisted MBEgrowth"

Simulation results using SIMNRA included as well

Related publications

  • Reseach data in the HZDR data repository RODARE
    Publication date: 2020-11-06
    DOI: 10.14278/rodare.657
    License: CC-BY-4.0

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Permalink: https://www.hzdr.de/publications/Publ-31851
Publ.-Id: 31851


Tuning the Co/Sr stoichiometry of SrCoO2.5 thin films by RHEED assisted MBEgrowth

Schöffmann, P.; Pütter, S.; Schubert, J.; Zander, W.; Barthel, J.; Zakalek, P.; Waschk, M.; Heller, R.; Brückel, T.

Strontium cobaltite (SrCoO2.5+δ, SCO) is a fascinating material because of its topotactic structural phase transition caused by a change in oxygen stoichiometry. In the brownmillerite phase (δ = 0) it is an insulating antiferromagnet whereas in the perovskite phase (δ = 0.5) it is a conducting ferromagnet. In contrast, the impact of the varying Co/Sr stoichiometry on the structure has not yet been studied in SCO thin films. Using molecular beam epitaxy we have fabricated SCO thin films of varying Co/Sr stoichiometry. Films with Co excess exhibit a brownmillerite crystal structure with CoO precipitates within the thin film and on the surface. Co deficient films are amorphous. Only for 1:1 stoichiometry a pure brownmillerite structure is present. We find a clear dependence of the Reflection High Energy Electron Diffraction (RHEED) pattern of these thin films on the stoichiometry. Interestingly, RHEED is very sensitive to a Co excess of less than 12% while x-ray diffraction fails to reveal that difference. Hence, using RHEED, the stoichiometry of SCO can be evaluated and tuned in-situ to a high degree of precision, which allows for a quick adjustment of the growth parameters during a sample series.

Keywords: This films; SrCoO; Rutherford Backscattering; RHEED; MBE; growth

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Permalink: https://www.hzdr.de/publications/Publ-31850
Publ.-Id: 31850


MEIS raw data and maps for publication "Stopping and straggling of 60–250-keV backscattered protons on nanometric Pt films"

Selau, F. F.; Trombini, H.; Marmitt, G. G.; de Andr, A. M. H.; Morais, J.; Grande, P. L.; Alencar, I.; Vos, M.; Heller, R.

MEIS raw data and maps for publication "Stopping and straggling of 60–250-keV backscattered protons on nanometric Pt films"

Including stiched spectra and 2D ESTAT maps

Related publications

  • Reseach data in the HZDR data repository RODARE
    Publication date: 2020-09-14
    DOI: 10.14278/rodare.655
    License: CC-BY-4.0

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Permalink: https://www.hzdr.de/publications/Publ-31849
Publ.-Id: 31849


Stopping and straggling of 60–250-keV backscattered protons on nanometric Pt films

Selau, F. F.; Trombini, H.; Marmitt, G. G.; de Andr; Morais, J.; Grande, P. L.; Alencar, I.; Vos, M.; Heller, R.

The stopping power and straggling of backscattered protons on nanometric Pt films were measured at low to medium energies (60–250 keV) by using the medium-energy ion scattering technique. The stopping power results are in good agreement with the most recent measurements by Primetzhofer Phys. Rev. B 86, 094102 (2012) and are well described by the free electron gas model at low projectile energies. Nevertheless, the straggling results are strongly underestimated by well-established formulas up to a factor of two. Alternatively, we propose a model for the energy-loss straggling that takes into account the inhomogeneous electron-gas response, based on the electron-loss function of the material, along with bunching effects. This approach yields remarkable agreement with the experimental data, indicating that the observed enhancement in energy-loss straggling is due to bunching effects in an inhomogeneous electron system. Nonlinear effects are of minor importance for the energy-loss straggling.

Keywords: Stopping cross sections; Rutherford Backscattering; Medium Energy Ion Scattering; Energy Straggling

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Permalink: https://www.hzdr.de/publications/Publ-31848
Publ.-Id: 31848


RBS raw data for publication "Voltage‐Controlled Deblocking of Magnetization Reversal in Thin Films by Tunable Domain Wall Interactions and Pinning Sites"

Zehner, J.; Soldatov, I.; Schneider, S.; Heller, R.; Khojasteh, N. B.; Schiemenz, S.; Fähler, S.; Nielsch, K.; Schäfer, R.; Leistner, K.

RBS raw data for publication "Voltage‐Controlled Deblocking of Magnetization Reversal in Thin Films by Tunable Domain Wall Interactions and Pinning Sites"

Simulation results using SIMNRA are included as well

Related publications

  • Reseach data in the HZDR data repository RODARE
    Publication date: 2020-09-16
    DOI: 10.14278/rodare.653
    License: CC-BY-4.0

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Permalink: https://www.hzdr.de/publications/Publ-31847
Publ.-Id: 31847


Voltage‐Controlled Deblocking of Magnetization Reversal in Thin Films by Tunable Domain Wall Interactions and Pinning Sites

Zehner, J.; Soldatov, I.; Schneider, S.; Heller, R.; Khojasteh, N. B.; Schiemenz, S.; Fähler, S.; Nielsch, K.; Schäfer, R.; Leistner, K.

High energy efficiency of magnetic devices is crucial for applications such as data storage, computation, and actuation. Redox‐based (magneto‐ionic) voltage control of magnetism is a promising room‐temperature pathway to improve energy efficiency. However, for ferromagnetic metals, the magneto‐ionic effects studied so far require ultrathin films with tunable perpendicular magnetic anisotropy or nanoporous structures for appreciable effects. This paper reports a fully reversible, low voltage‐induced collapse of coercivity and remanence by redox reactions in iron oxide/iron films with uniaxial in‐plane anisotropy. In the initial iron oxide/iron films, Néel wall interactions stabilize a blocked state with high coercivity. During the voltage‐triggered reduction of the iron oxide layer, in situ Kerr microscopy reveals inverse changes of coercivity and anisotropy, and a coarsening of the magnetic microstructure. These results confirm a magneto‐ionic deblocking mechanism, which relies on changes of the Néel wall interactions, and of the microstructural domain‐wall‐pinning sites. With this approach, voltage‐controlled 180° magnetization switching with high energy‐efficiency is achieved. It opens up possibilities for developing magnetic devices programmable by ultralow power and for the reversible tuning of defect‐controlled materials in general.

Keywords: iron films; magnetic domains; magnetoelectrics; magneto‐ionic mechanisms

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Permalink: https://www.hzdr.de/publications/Publ-31846
Publ.-Id: 31846


RBS raw data for publication "High quality epitaxial Mn2Au (001) thin films grown by molecular beam epitaxy "

Bommanaboyena, S. P.; Bergfeldt, T.; Heller, R.; Kläui, M.; Jourdan, M.

RBS raw data for publication "High quality epitaxial Mn2Au (001) thin films grown by molecular beam epitaxy "

Simulation results using SINRA are included as well.

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  • Reseach data in the HZDR data repository RODARE
    Publication date: 2020-06-22
    DOI: 10.14278/rodare.651
    License: CC-BY-4.0

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Permalink: https://www.hzdr.de/publications/Publ-31845
Publ.-Id: 31845


High quality epitaxial Mn2Au (001) thin films grown by molecular beam epitaxy

Bommanaboyena, S. P.; Bergfeldt, T.; Heller, R.; Kläui, M.; Jourdan, M.

The recently discovered phenomenon of Néel spin-orbit torque in antiferromagnetic Mn2Au [Bodnar et al., Nat. Commun. 9, 348 (2018); Meinert et al., Phys. Rev. Appl. 9, 064040 (2018); Bodnar et al., Phys. Rev. B 99, 140409(R) (2019)] has generated huge interest in this material for spintronics applications. In this paper, we report the preparation and characterization of high quality Mn2Au thin films by molecular beam epitaxy and compare them with magnetron sputtered samples. The films were characterized for their structural and morphological properties using reflective high-energy electron diffraction, x-ray diffraction, x-ray reflectometry, atomic force microscopy, and temperature dependent resistance measurements. The thin film composition was determined using both inductively coupled plasma optical emission spectroscopy and Rutherford backscattering spectrometry techniques. The MBE-grown films were found to show a superior smooth morphology and a low defect concentration, resulting in reduced scattering of the charge carriers.

Keywords: Atomic force microscopy; Electron diffraction; Epitaxy; Inductively coupled plasma atomic emission spectroscopy; Thin films; Rutherford backscattering spectrometry

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Permalink: https://www.hzdr.de/publications/Publ-31844
Publ.-Id: 31844


Explicit algebraic relation for calculating Reynolds normal stresses in flows dominated by bubble-induced turbulence

Ma, T.; Lucas, D.; Bragg, A. D.

Two new algebraic turbulence models for flows dominated by bubble-induced turbulence (BIT) are presented. They combine different elements of existing models that are considered superior to their alternatives. Both models focus on the core region of a channel flow, where the flow can be assumed to be in local equilibrium and the void fraction is approximately homogeneous. The first model, referred to as the algebraic Reynolds normal stress model, is derived from the differential Reynolds stress model of Ma et al. [J. Fluid Mech. 883, A9 (2020)]. The second model utilizes the original two-equation turbulence model for bubbly flows [Ma et al., Phys. Rev. Fluids 2, 034301 (2017)] to achieve algebraic expressions for k and ε in BIT-dominated cases. If both models are combined, it results in a purely algebraic (i.e. not involving any differential equations), explicit relation for the Reynolds normal stresses, which depends only on the mean flow parameters, namely, the mean gas void fraction and mean liquid and gas velocities. We find that the model can well predict the Reynolds normal stresses, compared with direct numerical simulation and experimental data.

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Permalink: https://www.hzdr.de/publications/Publ-31843
Publ.-Id: 31843


RBS raw data for publication "Solid–liquid interface analysis with in‐situ Rutherford backscattering and electrochemical impedance spectroscopy "

Bergmann, U.; Apelt, S.; Khojasteh, N. B.; Heller, R.

RBS raw data for publication "Solid–liquid interface analysis with in‐situ Rutherford backscattering and electrochemical impedance spectroscopy "

Simulation results using SIMNRA-Code also included

Related publications

  • Reseach data in the HZDR data repository RODARE
    Publication date: 2020-06-08
    DOI: 10.14278/rodare.649
    License: CC-BY-4.0

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Permalink: https://www.hzdr.de/publications/Publ-31842
Publ.-Id: 31842


Solid–liquid interface analysis with in‐situ Rutherford backscattering and electrochemical impedance spectroscopy

Bergmann, U.; Apelt, S.; Khojasteh, N. B.; Heller, R.

A novel Rutherford backscattering spectrometry (RBS) method is presented to investigate the interface between a solid surface and a surrounding liquid. The introduced measurement system allows to observe and quantify adsorption at the solid–liquid interface and the formation of the electrochemical double layer (EDL). BaCl2 as a bicomponent electrolyte and a Si3N4 membrane surface are chosen as a model system to prove the capabilities of the setup. The results of these RBS measurements are combined with electrochemical impedance spectroscopy (EIS) to validate the findings for the solid–liquid interface under study. Complementary results and discrepancies regarding the formation of the EDL are discussed.
Author keywords: electrochemical double layer, electrochemical impedance spectroscopy, Rutherford backscattering spectroscopy, silicon nitride

Keywords: Rutherford backscattering spectrometry; electrochemical double layer; electrochemical impedance spectroscopy; point of zero charge

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Permalink: https://www.hzdr.de/publications/Publ-31841
Publ.-Id: 31841


RBS Raw data for publication: ""Electrical and Optical Properties of Amorphous SnO2:Ta Films, Prepared by DC and RF Magnetron Sputtering: A Systematic Study of the Influence of the Type of the Reactive Gas"

Mientus, R.; Weise, M.; Seeger, S.; Heller, R.; Ellmer, K.

Raw data for pub. "Electrical and Optical Properties of Amorphous SnO2:Ta Films, Prepared by DC and RF Magnetron Sputtering: A Systematic Study of the Influence of the Type of the Reactive Gas"

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  • Reseach data in the HZDR data repository RODARE
    Publication date: 2020-02-26
    DOI: 10.14278/rodare.647
    License: CC-BY-4.0

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Permalink: https://www.hzdr.de/publications/Publ-31840
Publ.-Id: 31840


Tantalum recycling from pyrometallurgical residues (Tantalrecycling aus pyrometallurgischen Rückständen)

Reuter, M.; Taube, M. C.; Adamczyk, B.; Adam, C.; Feldmann, I.; Ostermann, M.; Stelter, M.

An existing pyrometallurgical process for tantalum and niobium recovery, mainly from low grade pyrometallurgical residues, was investigated. Melting experiments were carried out in a pilot-scale electric arc furnace to study the material system during the reduction process caused by blowing coke into the liquid mineral melt. During the pyrometallurgical treatment refractory metals such as tantalum and niobium are converted into their carbides and enriched in the molten iron-based metal phase.Titanium is also enriched in the metal phase as an unwanted accompanying element, but most of it remains in oxidic form in the slag and is mainly bound in the mineral perovskite. Cooled down slag samples were analysed using XRF, XRD, SEM and EDX to investigate the formation of mineral phases rich in tantalum during various stages of the reduction process. The results show that the settling of the tantalum-rich iron droplets in the molten slag into the metal phase may play a greater role for the kinetics than the actual reduction reaction caused by blowing in coke.

Keywords: tantalum; niobium; pyrometallurgical

  • World of Metallurgy - Erzmetall 73(2020)4, 196-205

Permalink: https://www.hzdr.de/publications/Publ-31839
Publ.-Id: 31839


Electrical and Optical Properties of Amorphous SnO2:Ta Films, Prepared by DC and RF Magnetron Sputtering: A Systematic Study of the Influence of the Type of the Reactive Gas

Mientus, R.; Weise, M.; Seeger, S.; Heller, R.; Ellmer, K.

By reactive magnetron sputtering from a ceramic SnO2:Ta target onto unheated substrates, X-ray amorphous SnO:Ta films were prepared in gas mixtures of Ar/O2(N2O, H2O). The process windows, where the films exhibit the lowest resistivity values, were investigated as a function of the partial pressure of the reactive gases O2, N2O and H2O. We found that all three gases lead to the same minimum resistivity, while the width of the process window is broadest for the reactive gas H2O. While the amorphous films were remarkably conductive (ρ ≈ 5 × 10−3 Ωcm), the films crystallized by annealing at 500 °C exhibit higher resistivities due to grain boundary limited conduction. For larger film thicknesses (d ≳ 150 nm), crystallization occurs already during the deposition, caused by the substrate temperature increase due to the energy influx from the condensing film species and from the plasma (ions, electrons), leading to higher resistivities of these films. The best amorphous SnO2:Ta films had a resistivity of lower than 4 × 10−3 Ωcm, with a carrier concentration of 1.1 × 1020 cm−3, and a Hall mobility of 16 cm2/Vs. The sheet resistance was about 400 Ω/□ for 100 nm films and 80 Ω/□ for 500 nm thick films. The average optical transmittance from 500 to 1000 nm is greater than 76% for 100 nm films, where the films, deposited with H2O as reactive gas, exhibit even a slightly higher transmittance of 80%. These X-ray amorpous SnO2:Ta films can be used as low-temperature prepared transparent and conductive protection layers, for instance, to protect semiconducting photoelectrodes for water splitting, and also, where appropriate, in combination with more conductive TCO films (ITO or ZnO).

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Permalink: https://www.hzdr.de/publications/Publ-31838
Publ.-Id: 31838


Acidified water glass in the selective flotation of scheelite from calcite, part II: species in solution and related mechanism of the depressant

Kaden, P.; Kupka, N.

NMR dataset to the publication:
Acidified water glass in the selective flotation of scheelite from calcite, part II: species in solution and related mechanism of the depressant

Keywords: NMR; acidified water glass; scheelite calcite separation; froth flotation; mechanism

Related publications

  • Reseach data in the HZDR data repository RODARE
    Publication date: 2020-07-22
    DOI: 10.14278/rodare.641

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Permalink: https://www.hzdr.de/publications/Publ-31837
Publ.-Id: 31837


Timing and correlation of glacial and glaciofluvial sediments in the German Alpine Foreland

Hofmann, F.; Hildebrandt, D.; Merchel, S.; Rugel, G.; Lachner, J.; Friedrich, A. M.

Multiple periods of advance and retreat of piedmont glaciers in the German Alpine Foreland due to changing climatic conditions were classically defined by Penck and Brückner in 1909. However, a robust absolute chronology has not yet been established. Age assignments in previous studies have mostly been based on the interpretation of terrace deposits as a result of periods of glacier advance and retreat and correlation with periods of globally low temperatures. Intercorrelation between these discontinuous deposits has mainly been done by using morphological, petrographical, and hypsometric characteristics. We measure absolute cosmogenic ³⁶Cl exposure ages of glacial erratics and ¹⁰Be/²⁶Al isochron burial ages of till and glaciofluvial deposits, which have previously been interpreted as Würmian (ultimate) and Rissian (penultimate glacial period). This establishes an absolute chronology for these periods and enables the correlation of moraines, which are direct products of advancing and retreating glaciers, with indirect glaciofluvial deposits in the foreland. The absolute chronology of this study sheds light on the development of Central European climatic trends and enables the correlation to global climate.

Keywords: AMS; cosmogenic radionuclide; dating; burial age; glacier; climate; exposure age

  • Poster (Online presentation)
    American Geophysical Union (AGU) Fall Meeting, 01.-17.12.2020, Online, Online

Permalink: https://www.hzdr.de/publications/Publ-31836
Publ.-Id: 31836


Nanoscale‐Confined Terahertz Polaritons in a van der Waals Crystal

de Oliveira, T. V. A. G.; Nörenberg, T.; Álvarez‐Pérez, G.; Wehmeier, L.; Taboada‐Gutiérrez, J.; Obst, M.; Hempel, F.; Lee, E. J. H.; Klopf, J. M.; Errea, I.; Nikitin, A. Y.; Kehr, S. C.; Alonso‐González, P.; Eng, L. M.

Electromagnetic field confinement is crucial for nanophotonic technologies, since it allows for enhancing light–matter interactions, thus enabling light manipulation in deep sub‐wavelength scales. In the terahertz (THz) spectral range, radiation confinement is conventionally achieved with specially designed metallic structures—such as antennas or nanoslits—with large footprints due to the rather long wavelengths of THz radiation. In this context, phonon polaritons—light coupled to lattice vibrations—in van der Waals (vdW) crystals have emerged as a promising solution for controlling light beyond the diffraction limit, as they feature extreme field confinements and low optical losses. However, experimental demonstration of nanoscale‐confined phonon polaritons at THz frequencies has so far remained elusive. Here, it is provided by employing scattering‐type scanning near‐field optical microscopy combined with a free‐electron laser to reveal a range of low‐loss polaritonic excitations at frequencies from 8 to 12 THz in the vdW semiconductor α‐MoO3. In this study, THz polaritons are visualized with: i) in‐plane hyperbolic dispersion, ii) extreme nanoscale field confinement (below λo ⁄75), and iii) long polariton lifetimes, with a lower limit of >2 ps.

Keywords: THz; FEL; s-SNOM; phonon polaritons; field confinement

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Permalink: https://www.hzdr.de/publications/Publ-31835
Publ.-Id: 31835


68Ga, 44Sc and 177Lu-labeled AAZTA5-PSMA-617: synthesis, radiolabeling, stability and cell binding compared to DOTA-PSMA-617 analogues

Sinnes, J.; Bauder-Wüst, U.; Schäfer, M.; Moon, E.; Kopka, K.; Rösch, F.

Background: The AAZTA chelator and in particular its bifunctional derivative AAZTA5 was recently investigated to demonstrate unique capabilities to complex diagnostic and therapeutic trivalent radiometals under mild conditions. This study presents a comparison of 68Ga, 44Sc and 177Lu-labeled AAZTA5-PSMA-617 with DOTA-PSMA-617 analogues. We evaluated the radiolabeling characteristics, in vitro stability of the radiolabeled compounds and evaluated their binding affinity and internalization behavior on LNCaP tumor cells in direct comparison to the radiolabeled DOTA-conjugated PSMA-617 analogs.
Results: AAZTA5 was synthesized in a five-step synthesis and coupled to the PSMA-617 backbone on solid phase. Radiochemical evaluation of AAZTA5-PSMA-617 with 68Ga, 44Sc and 177Lu achieved quantitative radiolabeling of > 99% after less than 5 min at room temperature. Stabilities against human serum, PBS buffer and EDTA and DTPA solutions were analyzed. While there was a small degradation of the 68Ga complex over 2 h in human serum, PBS and EDTA/DTPA, the 44Sc and 177Lu complexes were stable at 2 h and remained stable over 8 h and 1 day. For all three compounds, i.e. [natGa]Ga-AAZTA5-PSMA-617, [natSc]Sc-AAZTA5-PSMA-617 and [natLu]Lu-AAZTA5-PSMA-617, in vitro studies on PSMA-positive LNCaP cells were performed in direct comparison to radiolabeled DOTA-PSMA-617 yielding the corresponding inhibition constants (Ki). Ki values were in the range of 8-31 nM values which correspond with those of [natGa]Ga-DOTA-PSMA-617, [natSc]Sc-DOTA-PSMA-617 and [natLu]Lu-DOTA-PSMA-617, i.e. 5-7 nM, respectively. Internalization studies demonstrated cellular membrane to internalization ratios for the radiolabeled 68Ga, 44Sc and 177Lu-AAZTA5-PSMA-617 tracers (13-20%IA/10^6 cells) in the same range as the ones of the three radiolabeled DOTA-PSMA-617 tracers (17-20%IA/10^6 cells) in the same assay.
Conclusions: The AAZTA5-PSMA-617 structure proved fast and quantitative radiolabeling with all three radiometal complexes at room temperature, excellent stability with 44Sc, very high stability with 177Lu and medium stability with 68Ga in human serum, PBS and EDTA/DTPA solutions. All three AAZTA5-PSMA-617 tracers showed binding affinities and internalization ratios in LNCaP cells comparable with that of radiolabeled DOTA-PSMA-617 analogues. Therefore, the exchange of the chelator DOTA with AAZTA5 within the PSMA-617 binding motif has no negative influence on in vitro LNCaP cell binding characteristics. In combination with the faster and milder radiolabeling features, AAZTA5-PSMA-617 thus demonstrates promising potential for in vivo application for theranostics of prostate cancer.

Keywords: AAZTA; AAZTA5-PSMA-617; Gallium-68; Lutetium-177; PET; PSMA-617; Scandium-44; Theranostics

Permalink: https://www.hzdr.de/publications/Publ-31834
Publ.-Id: 31834


UAS-Based Hyperspectral Environmental Monitoring of Acid Mine Drainage Affected Waters

Flores Rojas, H. M.; Lorenz, S.; Jackisch, R.; Tusa, L.; Contreras Acosta, I. C.; Zimmermann, R.; Gloaguen, R.

The exposure of metal sulfides to air or water, either produced naturally or due to mining activities, can result in environmentally damaging acid mine drainage (AMD). This needs to be accurately monitored and remediated. In this study, we apply high-resolution unmanned aerial system (UAS)-based hyperspectral mapping tools to provide a useful, fast, and non-invasive method for the monitoring aspect. Specifically, we propose a machine learning framework to integrate visible to near-infrared (VNIR) hyperspectral data with physicochemical field data from water and sediments, together with laboratory analyses to precisely map the extent of acid mine drainage in the Tintillo River (Spain). This river collects the drainage from the western part of the Rio Tinto massive sulfide deposit and discharges large quantities of acidic water with significant amounts of dissolved metals (Fe, Al, Cu, Zn, amongst others) into the Odiel River. At the confluence of these rivers, different geochemical and mineralogical processes occur due to the interaction of very acidic water (pH 2.5–3.0) with neutral water (pH 7.0–8.0). This complexity makes the area an ideal test site for the application of hyperspectral mapping to characterize both rivers and better evaluate contaminated water bodies with remote sensing imagery. Our approach makes use of a supervised random forest (RF) regression for the extended mapping of water properties, using the samples collected in the field as ground-truth and training data. The resulting maps successfully estimate the concentration of dissolved metals and related physicochemical properties in water, and trace associated iron species (e.g., jarosite, goethite) within sediments. These results highlight the capabilities of UAS-based hyperspectral data to monitor water bodies in mining environments, by mapping their hydrogeochemical properties, using few field samples. Hence, we have demonstrated that our workflow allows the rapid discrimination and mapping of AMD contamination in water, providing an essential basis for monitoring and subsequent remediation.

Keywords: hyperspectral; remote sensing; machine learning; unmanned aerial system; acid mine drainage; random forest regression; post-mining

Permalink: https://www.hzdr.de/publications/Publ-31833
Publ.-Id: 31833


Online Detuning Computation and Quench Detection for Superconducting Resonators

Bellandi, A.; Butkowski, Ł.; Dursun, B.; Eichler, A.; Gümüs, C.; Kuntzsch, M.; Nawaz, A.; Pfeiffer, S.; Schlarb, H.; Schmidt, C.; Zenker, K.; Branlard, J.

Superconducting cavities are responsible for beam acceleration in superconducting linear accelerators. Challenging cavity control specifications are necessary to reduce RF costs and to maximize the availability of the accelerator. Cavity detuning and bandwidth are two critical parameters to monitor when operating particle accelerators. Cavity detuning is strongly related to the power required to generate the desired accelerating gradient. Cavity bandwidth is related to the cavity RF losses.
A sudden increase in bandwidth can indicate the presence of a quench or multipacting event. Therefore, calculating these parameters in real-time in the low-level RF system is highly desirable. A real-time estimation of the bandwidth allows a faster response of the machine protection system in case of quench events, whereas the estimation of cavity detuning can be used to drive piezoelectric tuner-based resonance control algorithms. In this proceeding, a new FPGA-based estimation component is presented. Such a component is designed to be used either in continuous wave or pulsed operation mode with loaded quality factors between 10^6 and 10^8 . Results of this component with FLASH, EuXFEL, CMTB, and ELBE are presented.

Keywords: Particle accelerators; Parameter estimation; Superconducting cavities; ELBE

  • IEEE Transactions on Nuclear Science (2021)

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Permalink: https://www.hzdr.de/publications/Publ-31832
Publ.-Id: 31832


Curvilinear One-Dimensional Antiferromagnets

Pylypovskyi, O.; Kononenko, D. Y.; Yershov, K.; Rößler, U. K.; Tomilo, A.; Faßbender, J.; van den Brink, J.; Makarov, D.; Sheka, D.

Antiferromagnets host exotic quasiparticles, support high frequency excitations and are key enablers of the prospective spintronic and spin−orbitronic technologies. Here, we propose a concept of a curvilinear antiferromagnetism where material responses can be tailored by a geometrical curvature without the need to adjust material parameters. We show that an intrinsically achiral one-dimensional (1D) curvilinear antiferromagnet behaves as a chiral helimagnet with geometrically tunable Dzyaloshinskii−Moriya interaction (DMI) and orientation of the Né el vector. The curvature-induced DMI results in the hybridization of spin wave modes and enables a geometrically driven local minimum of the low-frequency branch. This positions curvilinear 1D antiferromagnets as a novel platform for the realization of geometrically tunable chiral antiferromagnets for antiferromagnetic spin−orbitronics and fundamental discoveries in the formation of coherent magnon condensates in the momentum space.

Keywords: antiferromagnetism; curvilinear spin chain; Dzyaloshinskii-Moriya interaction; spin-orbitronics

Permalink: https://www.hzdr.de/publications/Publ-31831
Publ.-Id: 31831


Data Fusion Using a Multi-Sensor Sparse-Based Clustering Algorithm

Rafiezadeh Shahi, K.; Ghamisi, P.; Rasti, B.; Jackisch, R.; Scheunders, P.; Gloaguen, R.

The increasing amount of information acquired by imaging sensors in Earth Sciences results in the availability of a multitude of complementary data (e.g., spectral, spatial, elevation) for monitoring of the Earth’s surface. Many studies were devoted to investigating the usage of multi-sensor data sets in the performance of supervised learning-based approaches at various tasks (i.e., classification and regression) while unsupervised learning-based approaches have received less attention. In this paper, we propose a new approach to fuse multiple data sets from imaging sensors using a multi-sensor sparse-based clustering algorithm (Multi-SSC). A technique for the extraction of spatial features (i.e., morphological profiles (MPs) and invariant attribute profiles (IAPs)) is applied to high spatial-resolution data to derive the spatial and contextual information. This information is then fused with spectrally rich data such as multi- or hyperspectral data. In order to fuse multi-sensor data sets a hierarchical sparse subspace clustering approach is employed. More specifically, a lasso-based binary algorithm is used to fuse the spectral and spatial information prior to automatic clustering. The proposed framework ensures that the generated clustering map is smooth and preserves the spatial structures of the scene. In order to evaluate the generalization capability of the proposed approach, we investigate its performance not only on diverse scenes but also on different sensors and data types. The first two data sets are geological data sets, which consist of hyperspectral and RGB data. The third data set is the well-known benchmark Trento data set, including hyperspectral and LiDAR data. Experimental results indicate that this novel multi-sensor clustering algorithm can provide an accurate clustering map compared to the state-of-the-art sparse subspace-based clustering algorithms.

Keywords: multi-sensor data fusion; subspace-based clustering; sparse representation; hierarchical representation; remote sensing

Permalink: https://www.hzdr.de/publications/Publ-31830
Publ.-Id: 31830


A New Spectral-Spatial Subspace Clustering Algorithm For Hyperspectral Image Analysis

Rafiezadeh Shahi, K.; Ghamisi, P.; Jackisch, R.; Khodadadzadeh, M.; Lorenz, S.; Gloaguen, R.

In the past decade, hyperspectral imaging techniques have been widely used in various applications to acquire high spectral-spatialresolution images from different objects and materials. Although hyperspectral images (HSIs) are useful tools to obtain valuableinformation from different materials, the processing of such data is challenging due to several reasons such as the high dimension-ality and redundancy of the feature space. Therefore, advanced machine learning algorithms have been developed to analyse HSIs.Among the developed algorithms, unsupervised learning techniques have become popular since they are capable of processing HSIswithout having prior knowledge. Generally, unsupervised learning algorithms analyse HSIs based on spectral information. How-ever, in many applications, spatial information plays an eminent role, in particular when the input data is of high spatial resolution.In this study, we propose a new clustering approach by utilizing the sparse subspace-based concept within the hidden Markov ran-dom field (HMRF) structure to process HSIs in an unsupervised manner. The qualitative analyses of the obtained clustering resultsshow that the proposed spectral-spatial clustering algorithm outperforms the sparse subspace-based clustering algorithm that onlyuses spectral information.

Keywords: Hyperspectral image analysis; Subspace clustering; Sparse representation; Hidden Markov random field; UAV data

  • Open Access Logo Lecture (Conference) (Online presentation)
    ISPRS Annals of the Photogrammetry, Remote Sensing and Spatial Information Sciences, 30.08.-02.09.2020, Nice, France
    DOI: 10.5194/isprs-annals-V-3-2020-185-2020

Permalink: https://www.hzdr.de/publications/Publ-31829
Publ.-Id: 31829


Geochemical and mineralogical characterisation of Historic Zn-Pb Mine Waste, Plombières, East Belgium

Bevandic, S.; Blannin, R.; Vander Auwera, J.; Delmelle, N.; Caterina, D.; Nguyen, F.; Muchez, P.

Mine wastes and tailings derived from historical processing may contain significant contents of valuable metals due to processing being less efficient in the past. The Plombières tailings pond in eastern Belgium was selected as a case study to determine mineralogical and geochemical characteristics of the different mine waste materials found at the site. Four types of material were classified: soil, metallurgical waste, brown tailings and yellow tailings. The distribution of the mine wastes was investigated with drill holes, pit-holes and geophysical methods. Samples of the materials were assessed with grain size analysis, mineralogical and geochemical techniques. The mine wastes dominantly consist of SiO2, Al2O3 and Fe2O3. The cover material, comprising soil and metallurgical waste is highly heterogeneous in terms of mineralogy, geochemistry and grain size. The metallurgical waste has a high concentration of metals (Zn: 0.1 to 24 wt% and Pb: 0.1 to 10.1 wt%). In the tailings materials, Pb and Zn vary from 10 ppm to 8.5 wt% and from 51 ppm to 4 wt%, respectively. The mining wastes comprises mainly quartz, amorphous phases and phyllosilicates, with minor contents of Fe-oxide, Pb- and Zn-bearing minerals. Based on the mineralogical and geochemical properties, the different potential applications of the four waste material types were determined. Additionally, the theoretical economic potential of Pb and Zn in the mine wastes was established.

Permalink: https://www.hzdr.de/publications/Publ-31828
Publ.-Id: 31828


The 2021 Magnonics Roadmap

Barman, A.; Gubbiotti, G.; Ladak, S.; Adeyeye, A. O.; Krawczyk, M.; Gräfe, J.; Chumak, A. V.; Khitun, A.; Nikonev, D.; Young, I. A.; Vasyuchka, V. I.; Hillebrands, B.; Nikitov, S. A.; Yu, H.; Grundler, D.; Sadovnikov, A. V.; Grachev, A. A.; Sheshukova, S. E.; Duquesne, J.-Y.; Marangolo, M.; Csaba, G.; Porod, W.; Demidov, V. E.; Urazhdin, S.; Demokritov, S. O.; Albisetti, E.; Petti, D.; Bertacco, R.; Schultheiß, H.; Kruglyak, V. V.; Poimanov, V. D.; Sahoo, S.; Sinha, J.; Moriyama, T.; Mizukami, S.; Yang, H.; Münzenburg, M.; Landeros, P.; Gallardo, R. A.; Carlotti, G.; Kim, J.-V.; Stamps, R. L.; Camley, R. E.; Rana, B.; Otani, Y.; Yu, W.; Yu, T.; Bauer, G. E. W.; Back, C.; Uhrig, G. S.; Dobrovolskiy, O. V.; van Dijken, S.; Budinska, B.; Qin, H.; Adelmann, C.; Cotofana, S.; Naeemi, A.; Zingsem, B. W.; Winklhofer, M.

Magnonics is a rather young physics research field in nanomagnetism and nanoscience that addresses the use of spin waves (magnons) to transmit, store, and process information. After several papers and review articles published in the last decade, with a steadily increase in the number of citations, we are presenting the first Roadmap on Magnonics. This a collection of 22 sections written by leading experts in this field who review and discuss the current status but also present their vision of future perspectives. Today, the principal challenges in applied magnonics are the excitation of sub-100 nm wavelength magnons, their manipulation on the nanoscale and the creation of sub-micrometre devices using low-Gilbert damping magnetic materials and the interconnections to standard electronics. In this respect, magnonics offers lower energy consumption, easier integrability and compatibility with CMOS structure, reprogrammability, shorter wavelength, smaller device features, anisotropic properties, negative group velocity, non-reciprocity and efficient tunability by various external stimuli to name a few. Hence, despite being a young research field, magnonics has come a long way since its early inception. This Roadmap represents a milestone for future emerging research directions in magnonics and hopefully it will be followed by a series of articles on the same topic.

Keywords: magnonics; spin waves; roadmap; spin textures; skyrmions; computing

Permalink: https://www.hzdr.de/publications/Publ-31827
Publ.-Id: 31827


Liquid Metal Batteries for cheap stationary electricity storage

Weber, N.; Weier, T.

Liquid metal batteries are discussed as cheap stationary energy storage. Built as a stable density stratification of two liquid metals separated by a molten salt, they offer excellent charge transfer kinetics, extreme current densities and a very long lifetime. Using earth-abundant and cheap raw materials allows potentially reaching a storage price of 1-5 ct/kWh/cycle.
The talk will give an overview of LMB research at Helmholtz-Zentrum Dresden-Rossendorf (HZDR). Special focus will be given to the Li-Bi and Na-Bi systems, and the importance of fluid dynamics for the efficient and safe operation of the cells. Finally, an outlook on the Horizon 2020 project “Solstice”, which aims in developing Na-Zn molten salt batteries, will be given.

  • Open Access Logo Lecture (Conference)
    I Meeting on Energy Conversion and Storage Electrochemical Devices, 28.-29.01.2021, Madrid, Spanien

Permalink: https://www.hzdr.de/publications/Publ-31822
Publ.-Id: 31822


Acidified water glass in the selective flotation of scheelite from calcite, part II: species in solution and related mechanism of the depressant

Kupka, N.; Kaden, P.; Jantschke, A.; Schach, E.; Rudolph, M.

Sodium silicate is one of the main depressants against calcite and fluorite in the scheelite flotation industry. In the first part of this article, the authors acidified sodium silicate (AWG) with three acids (sulfuric, oxalic and hydrochloric) to improve its performance. Results showed that acidified water glass outperforms alkaline water glass in terms of selectivity: it increases mainly the grade by further depressing silicates and calcium-bearing minerals. In most cases, AWG requires lower dosages to do so. The effect of acidified water glass is evaluated through Mineral Liberation Analysis (MLA), froth analysis, Raman and Nuclear Magnetic Resonance (NMR) spectroscopy in order to hypothesize its mechanism. MLA shows that AWG affects silicates and sulfides more intensely than semi-soluble salt-type minerals. Froth observations indicate other species in solution associated to the acid having an impact on the flotation results. Raman spectroscopy and NMR measurements indicate that the solution undergoes deep depolymerization when water glass is acidified. Lower molecular weight silica species, specifically Si-O monomers such as SiO(OH)3- will be responsible for the depression of the gangue minerals and are the drivers of the selectivity of AWG, more than orthosilicic acid. Depolymerization is more or less effective depending on the mass ratio of the acid to water glass and depending on the acid.

Keywords: acidified water glass; scheelite calcite separation; froth flotation; mechanism; mineral processing

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Permalink: https://www.hzdr.de/publications/Publ-31821
Publ.-Id: 31821


Coordination of Trivalent Lanthanum and Cerium, and Tetravalent Cerium and Actinides (An = Th(IV), U(IV), Np(IV)) by a 4-Phosphoryl 1H-Pyrazol-5-olate Ligand in Solution and the Solid State

Kaden, P.; Roßberg, A.

This dataset is a subset of the complete data used in the original publication. It contains NMR and XAS data and there simulation. Based on this original data, conlcusions are drawn in the linked publication. For the full data, please refer to the corresponding author of the full publication.

Abstract of the publication:

Structural investigations of three actinide(IV) 4-phosphoryl 1H-pyrazol-5-olate complexes (An = Th(IV), U(IV), Np(IV)) and their cerium(IV) analogue display the same metal coordination in the solid state. The mononuclear complexes show the metal centre in a square antiprismatic coordination geometry composed by the two O-donor atoms of four deprotonated ligands. Detailed solid state analysis of the U(IV) complex shows that in dependence of the solvent used altered arrangements are observable, resulting in a change in the coordination polyhedron of the U(IV) metal centre to bi-capped trigonal prismatic. Further, single crystal analyses of the La(III) and Ce(III) complexes show that the ligand can also act as a neutral ligand by protonation of the pyrazoyl moiety. All complexes were comprehensively characterized by NMR, IR and Raman spectroscopy. A single resonance in each of the 31P NMR spectra for the La(III), Ce(III), Ce(IV), Th(IV) and Np(IV) complex indicates the formation of highly symmetric complex species in solution. Extended X-ray absorption fine structure (EXAFS) investigations provide evidence for the same local structure of the U(IV) and Np(IV) complex in toluene solution, confirming the observations made in the solid state.

Related publications

  • Reseach data in the HZDR data repository RODARE
    Publication date: 2020-12-11
    DOI: 10.14278/rodare.643

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Permalink: https://www.hzdr.de/publications/Publ-31820
Publ.-Id: 31820


Zero Net Flux MRI Turbulence in Disks: Sustenance Scheme and Magnetic Prandtl Number Dependence

Mamatsashvili, G.; Chagelishvili, George; Pessah, Martin E.; Stefani, F.; Bodo, Gianluigi

We investigate sustenance and dependence on magnetic Prandtl number (Pm) for magnetorotational instability (MRI)-driven turbulence in Keplerian disks with zero net magnetic flux using standard shearing box simulations. We focus on the turbulence dynamics in Fourier space, capturing specific/noncanonical anisotropy of nonlinear processes due to disk flow shear. This is a new type of nonlinear redistribution of modes over wavevector orientations in Fourier space—the nonlinear transverse cascade—which is generic to shear flows and fundamentally different from the usual direct/inverse cascade. The zero flux MRI has no exponentially growing modes, so its growth is transient, or nonmodal. Turbulence self-sustenance is governed by constructive cooperation of the transient growth of MRI and the nonlinear transverse cascade. This cooperation takes place at small wavenumbers (on the flow size scales) referred to as the vital area in Fourier space. The direct cascade transfers mode energy from the vital area to larger wavenumbers. At large Pm, the transverse cascade prevails over the direct one, keeping most of modes' energy contained in small wavenumbers. With decreasing Pm, however, the action of the transverse cascade weakens and can no longer oppose the action of the direct cascade, which more efficiently transfers energy to higher wavenumbers, leading to increased resistive dissipation. This undermines the sustenance scheme, resulting in the turbulence decay. Thus, the decay of zero net flux MRI turbulence with decreasing Pm is attributed to the topological rearrangement of the nonlinear processes when the direct cascade begins to prevail over the transverse cascade.

Keywords: Stellar accretion disks; Magnetohydrodynamics; Plasma astrophysics; Magnetic fields; Interplanetary turbulence; Instabilities

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Permalink: https://www.hzdr.de/publications/Publ-31818
Publ.-Id: 31818


Stress-controlled zero-field spin splitting in silicon carbide

Breev, I. D.; Poshakinskiy, A. V.; Yakovleva, V. V.; Nagalyuk, S. S.; Mokhov, E. N.; Hübner, R.; Astakhov, G.; Baranov, P. G.; Anisimov, A. N.

We report the influence of static mechanical deformation on the zero-field splitting of silicon vacancies in silicon carbide at room temperature. We use AlN/6H-SiC heterostructures deformed by growth conditions and monitor the stress distribution as a function of distance from the heterointerface with spatially-resolved confocal Raman spectroscopy. The zero-field splitting of the V1/V3 and V2 centers in 6H-SiC, measured by optically-detected magnetic resonance, reveal significant changes at the heterointerface compared to the bulk value. This approach allows unambiguous determination of the spin-deformation interaction constant, which turns out to be 0.75 GHz for the V1/V3 centers and 0.5 GHz for the V2 centers. Provided piezoelectricity of AlN, our results offer a strategy to realize the on-demand fine tuning of spin transition energies in SiC by deformation.

Keywords: Silicon carbide; spins; qubits; magnetic resonance; wide bandgap semiconductors; heterointerface

Permalink: https://www.hzdr.de/publications/Publ-31817
Publ.-Id: 31817


The EU’s metallurgical infrastructure is a cornerstone of the EU Green Deal and the Agenda 2030 realization

Abadias Llamas, A.; Bartie, N. J.; Meskers, C. E. M.; Reuter, M.

The European metallurgical industries are the enablers for the realization of the goals of the EU Green Deal and the Agenda 2030 for Sustainable Development. The realization of these goals requires a metallurgical industry that is even more resource-efficient, eco-friendly and responsible than it is today. Accordingly, the metallurgical industry and system must be protected and strengthened, rather than having its socioeconomic importance undermined because of misconceptions about its residue generation, energy consumption, and environmental impacts. To understand and quantify the opportunities and limits associated with creating more circular and sustainable metallurgical infrastructure systems, rigorous digitalization is imperative. The European Training Network SOCRATES has taken this up by developing ground-breaking metallurgical processes for the valorization of industrial intermediate products. Additionally, this project quantified the impact of its developed metallurgical processes on the sustainability of the current material and metal supply chain through the creation of large simulation-based digital twins of the metallurgical system.

  • Communication & Media Relations
    SOCRATES Policy Brief 01.09.2020

Permalink: https://www.hzdr.de/publications/Publ-31816
Publ.-Id: 31816


Quantication of Valuable Chemical Elements present in Recyclable Printed Circuit Boards using Spectrum Radiography

Bhayani, G. S.

As of 2016, gold from electronic scrap was estimated to value almost e 19,000 million of the global e-waste [1]. This thesis aims at quantication of gold in scrap Printed Circuit Boards using Spectrum Radiography. The thesis is divided into two main sections- rst is where calibration of the detector takes place in order to estimate amount of x-rays that are transmitted through dierent thicknesses of gold and the second section is based on the results from scrap PCBs. The nal focus is to use the calibration, to quantify gold in Printed Circuit Board sample. Spectrum Radiography can help obtain the transmission of x-rays by a sample and based on the k-edge absorption theory, one can identify the element present in the sample.
The amount of transmission was estimated to relate to the thickness of the sample and the calibration data showed that with increasing sample thickness, gradual reduction in transmission was observed with the Spectrum Radiography. Hence, the thesis was based on quantifying elements based on k-edge transmission spectra. The resolution limit of the detector comes along, contributing to errors in quantication.
The thesis enlists and elaborates the statistical approaches for the quantication of gold using the radiographs obtained from the new prototype Spectral Detector and concludes the correlation of results obtained for geometrically analogous sample to x-ray beam orientations and also concludes the inapplicability of this method for samples with inhomogeneous thickness across the x-ray beam path.

Keywords: spectral CT; energy bins; 3D image; k-edge quantification

  • Master thesis
    Technical University Chemnitz, 2020
    Mentor: Jose R. A. Godinho

Permalink: https://www.hzdr.de/publications/Publ-31815
Publ.-Id: 31815


Automated Mineral Classification

Gupta, S.

A photon counting detector gives X-ray transmission radiographs of a slice of a sample in which transmission is resolved into 128 bins of X-ray energies from 20 keV to 160 keV. After plotting the graph of transmission over energy bins, the K-edge can be traced. By using machine learning and computer vision techniques on these ‘energy bins vs derivative of X-ray transmission’ information, slices were not only classified much faster in an automated way but also performed better when compared to the manual classification of minerals by using intensities or gray scale values of particles.
Machine learning was implemented on the slices of manually prepared sample containing gold and lead particles, Printed Circuit Board (PCB) and a rock sample. Slices were also classified by implementing machine learning on intensity properties of gold and galena to further confirm an advantage of using spectrum information. Results helped to understand the challenges in the project and thus paved a way for advanced research.

Keywords: spectral CT; Machine learning; 3D imaging

  • Master thesis
    Ernst-Abbe-Hochschule Jena University of Applied Sciences, 2020
    Mentor: Jose R. A. Godinho

Permalink: https://www.hzdr.de/publications/Publ-31814
Publ.-Id: 31814


Comparison of 3D (X-ray computed tomography) vs 2D (mineral liberation analysis) particle information in mineral processing simulations

Siddique, A.

Processing behaviour of a mineral resource highly depends on the characteristics of particles such as shape, size and composition. Therefore, comprehensive particle characterization is crucial to understand and optimize processing behaviour to enhance recoveries and reduce waste production. Nevertheless, despite the obvious importance of particle characteristics, current analysis techniques are restricted to two-dimensional (2D) particle characterization. In order to have advance three-dimensional (3D) characterization, this study aims to present a new X-CT methodology for single particle characterization with a special sample preparation method to reduce the X-CT artefacts.
A homogenous and dispersed particle sample reduce the X-CT artefacts and ease the segmentation process for individual particle labelling. This labelled data then further used for image processing combined with a new single particle peak analysis method for enhanced mineral classification based on greyscale. Classification of mineral phases for X-CT data was performed with the correlation of Mineral Liberation Analyzer (MLA). All the major mineral phases present in the ore were successfully classified except the gold grains. Characterization using 2D (MLA) and 3D (X-CT) was compared and mineralogy difference of around 2% observed. The effect of particle properties measured by both methods also investigated in processing simulation

Keywords: Mineral processing; 3D Particle characterization; X-ray computed tomography; Mineral Liberation Analysis; Single particle peak analysis; Flotation simulation

  • Master thesis
    Technical University Freiberg, 2020
    Mentor: Jose R. A. Godinho

Permalink: https://www.hzdr.de/publications/Publ-31813
Publ.-Id: 31813


Tetranuclear Lanthanide Complexes Supported by Hydroxyquinoline-Calix[4]arene-Ligands: Synthesis, Structure, and Magnetic Properties of [Ln₄(H₃L)₂(µ-OH)₂(NO₃)₄] (Ln = Tb, Dy, Yb) and [Dy₂(H₄L)₂(NO₃)](NO₃)

Jäschke, A.; Stumpf, T.; Aliabadi, A.; Büchner, B.; Kataev, V.; Hahn, T.; Kortus, J.; Kersting, B.

The coordination behavior of the calixarene-based N4O4 donor ligand H6L bearing two pendant 8-hydroxyquinoline-2-hydrazone arms towards the lanthanide ions Tb3+, Dy3+, and Yb3+ has been investigated. H6L was found to support tetra- and dinuclear mixed-ligand complexes with the pendant hydrazone units in a deprotonated enolate and/or a neutral amide form. The direct reaction of H6L with Ln(NO3)3(H2O)6 and NEt3 in a 1:1:2 molar ratio leads to tetranuclear [Ln4(H3L)2(µ-OH)2(η2-NO3)4] complexes {Ln = Tb (1), Dy (2), Yb (3)} containing a rectangular arrangement of four eight-coordinate Ln3+ ions bridged by two hydroxido- and four quinolinolato-O atoms as established by X-ray crystallography. Degradation of 2 occurs upon addition of further equiv. of H6L to give dinuclear [Dy2(H4L)(NO3)2(MeCN)2]NO3 (4) with eight- and ten-coordinated Dy3+ ions. ESI-MS studies reveal that such dinuclear species exist also in the solution state. The results of variable temperature direct and alternating current magnetic susceptibility measurements for 1–4 and high frequency EPR study on 4 are also reported.

Permalink: https://www.hzdr.de/publications/Publ-31812
Publ.-Id: 31812


The optimal sensor for ore sorting

Kern, M.

Presentation about optimal sensor for ore sorting

  • Invited lecture (Conferences)
    EIT Raw Materials Expert Forum, 15.-18.01.2020, Leoben, Österreich

Permalink: https://www.hzdr.de/publications/Publ-31809
Publ.-Id: 31809


Beyond seeing the target: taking into account new parameters to measure the efficiency of exploration technologies

Ajjabou, L.; Kirsch, M.; Lorenz, S.; Gloaguen, R.

The INFACT project (Innovative, Non-Invasive and Fully Acceptable Exploration Technologies) aims to change raw material exploration in a way that it becomes socially accepted, environmentally-friendly and technologically advanced. It strives to establish a view of the best practices for exploration that is shared by civil society, state and industry. A set of permanent reference sites representing a variety of social, physical and technical challenges in the EU are used to conduct stakeholder dialogue and to provide an industry-relevant environment for the development of non-invasive exploration methods.

  • Contribution to proceedings
    KEGS Symposium 2020 "Success from Innovation", 29.02.2020, Toronto, Canada
  • Invited lecture (Conferences)
    KEGS Symposium 2020 "Success from Innovation", 29.02.2020, Toronto, Canada

Permalink: https://www.hzdr.de/publications/Publ-31808
Publ.-Id: 31808


FLUKA simulations for the Mu2e experiment

Müller, S.; Ferrari, A.

Presentation at FLUKA collaboration meeting (virtual), December 4, 2020

Keywords: FLUKA; Mu2e

  • Lecture (Conference) (Online presentation)
    FLUKA collaboration meeting, 03.-04.12.2020, Milan, Italy

Permalink: https://www.hzdr.de/publications/Publ-31806
Publ.-Id: 31806


HELmholtz ScIentific Project WORkflow PlaTform - Status and Roadmap 2020

Knodel, O.

The talk gives an overview on status and recent developments of the "HELmholtz ScIentific Project WORk-flow PlaTform" called HELIPORT. The idea is it to accommodate the complete life cycle of a scientific project and to links all corresponding programs and systems. The HELIPORT architecture has a modular structure such that the core application can be used in different Helmholtz centers and only individual components have to be replaced or added. HELIPORT is based on modern web technologies and can be used on different platforms. In addition to the entire project flow, computational workflows are also managed via the system in order to document all work steps as seamlessly as possible according to the FAIR principles and to publish them later.

Keywords: data management; workflow

  • Open Access Logo Lecture (others) (Online presentation)
    Meeting Helmholtz Zentrum Berlin (HZB), 04.12.2020, online, Deutschland

Downloads:

Permalink: https://www.hzdr.de/publications/Publ-31805
Publ.-Id: 31805


Generation of biological hypotheses by functional imaging links tumor hypoxia to radiation induced tissue inflammation/ glucose uptake in head and neck cancer

Zschaeck, S.; Zöphel, K.; Seidlitz, A.; Zips, D.; Kotzerke, J.; Baumann, M.; Troost, E. G. C.; Löck, S.; Krause, M.

Background and purpose: Positron emission tomography (PET) is a functional imaging modality which is able to deliver tracer specific biological information, e.g. about glucose uptake, inflammation or hypoxia of tumors. We performed a proof-of-principle study that used different tracers and expanded the analytical scope to non-tumor structures to evaluate tumor-host interactions.
Materials and Methods: Based on a previously reported prospective imaging study on 50 patients treated with curative intent chemoradiation (CRT) for head and neck squamous cell carcinoma, PET-based hypoxia and normal tissue inflammation measured by repeat 18F-fluoromisonidazole (FMISO) PET and 18F-fluorodesoxyglucose (FDG) PET, respectively, were correlated using the Spearman correlation coefficient R. PET parameters determined before and during CRT (week 1, 2 and 5), were associated with local tumor control and overall survival.
Results: Tumor hypoxia at all measured times showed an inverse correlation with mid-treatment FDG-uptake of non-tumor affected oral (sub-)mucosa with R values between -0.35 and -0.6 (all p<0.05). Mucosal FDG-uptake and mucosal hypoxia correlated positively but weaker (R values between 0.2 and 0.45). More tumor hypoxia in FMISO-PET (week 2) and less FDG-uptake of (sub-)mucosa in FDG-PET (week 4) were significantly associated with worse LC (FMISO TBRpeak: HR=1.72, p=0.030; FDG SUVmean: HR=0.23, p=0.025) and OS (FMISO TBRpeak: HR=1.71, p=0.007; FDG SUVmean: HR=0.30, p=0.003). Multivariable models including both parameters showed improved performance, suggesting that these modalities still bear distinct biological information despite their strong inter-correlation.
Conclusion: We report first clinical evidence that tumor hypoxia is inversely correlated with increased FDG-uptake during radiation, potentially expressinginflammation. This observation merits further research and may have important implication for future research on tumor hypoxia and radio-immunology. Our study demonstrates that functional imaging can be utilized to assess complex tumor-host interactions and generate novel biological insights in vivo vero.

Keywords: FDG PET; FMISO PET; inflammation; hypoxia; head and neck cancer; radiotherapy

Permalink: https://www.hzdr.de/publications/Publ-31804
Publ.-Id: 31804


Protonentherapie intrathorakaler Tumoren – aktueller Stand und Ausblick

Troost, E. G. C.

Conventional external beam radiation therapy with high-energy photons is one of the pillars of treatment for patients with intrathoracic tumors. Due to technical advances, e.g., highly conformal, image-guided irradiation techniques, it has been possible to increase local tumor control while simultaneously reducing treatment-associated side effects. In recent years, proton beam therapy has become an alternative at an increasing number of national and international sites. At present, only four German sites offer protons for treatment of tumors outside of the eye, but the demand is increasing continually. Due to the physical characteristics of protons, i.e., the steep dose fall-off beyond the point of maximum dose deposition that is normally located in the tumor, normal tissue and organs at risk beyond the tumor can be spared. This review highlights the value of proton beam therapy for intrathoracic tumors.

Keywords: Radiotherapy; Esophageal carcinomas; Small cell lung cancer; Non- small cell lung cancer; Proton beam therapy

Permalink: https://www.hzdr.de/publications/Publ-31803
Publ.-Id: 31803


Role of radiotherapy in the management of brain metastases of NSCLC – Decision criteria in clinical routine

Glatzer, M.; Faivre-Finn, C.; De, R. D.; Widder, J.; Van, H. P.; Troost, E. G. C.; Slotman, B. J.; Ramella, S.; Pöttgen, C.; Peeters, S.; Nestle, U.; McDonald, F.; Le Pechoux, C.; Dziadziuszko, R.; Belderbos, J.; Ricardi, U.; Manapov, F.; Lievens, Y.; Geets, X.; Dieckmann, K.; Guckenberger, M.; Andratschke, N.; Süveg, K.; Putora, P. M.

Background: Whole brain radiotherapy (WBRT) is a common treatment option for brain metastases secondary to non-small cell lung cancer (NSCLC). Data from the QUARTZ trial suggest that WBRT can be omitted in selected patients and treated with optimal supportive care alone. Nevertheless, WBRT is still widely used to treat brain metastases secondary to NSCLC. We analysed decision criteria influencing the selection for WBRT among European radiation oncology experts.
Methods: Twenty-two European radiation oncology experts in lung cancer as selected by the European Society for Therapeutic Radiation Oncology (ESTRO) for previous projects and by the Advisory Committee on Radiation Oncology Practice (ACROP) for lung cancer were asked to describe their strategies in the management of brain metastases of NSCLC. Treatment strategies were subsequently converted into decision trees and analysed for agreement and discrepancies.
Results: Eight decision criteria (suitability for SRS, performance status, symptoms, eligibility for targeted therapy, extra-cranial tumour control, age, prognostic scores and ‘‘Zugzwang” (the compulsion to treat)) were identified. WBRT was recommended by a majority of the European experts for symptomatic patients not suitable for radiosurgery or fractionated stereotactic radiotherapy. There was also a tendency to use WBRT in the ALK/EGFR/ROS1 negative NSCLC setting.
Conclusion: Despite the results of the QUARTZ trial WBRT is still widely used among European radiation oncology experts.

Keywords: WBRT; Decision-making; Decision tree; QUARTZ; NSCLC

Permalink: https://www.hzdr.de/publications/Publ-31802
Publ.-Id: 31802


An improvement on selective separation by applying ultrasound to rougher and re-cleaner stages of copper flotation

Hassanzadeh, A. A.; Sajjady, S. A. B.; Gholami, H. C.; Amini, S. B.; Özkan, S. G. D.

It has been known that the power ultrasound is used as a pretreatment and rarely applied as a simultaneous method to improve grade and recovery during froth flotation processes. This work aimed at investigating the impact of simultaneously used ultrasonic waves under variant operating configurations on the flotation of representative porphyry copper ore during rougher and re-cleaner stages. For this purpose, four different operating outlines were examined as (I) conventional flotation, (II) homogenizer, (III) ultrasonic bath, and (IV) combination of a homogenizer and an ultrasonic bath. The ultrasonic vibration was generated by the homogenizer (21 kHz, 1 kW) in the froth zone and ultrasonic bath (35 kHz, 0.3 kW) in the bulk zone. The rougher and re-cleaner flotation experiments were conducted using Denver-type mechanically agitated cells with 4.2 and 1 L capacities, respectively. The results showed that using the homogenizer (at 0.4 kW) slightly affected the selectivity separation index of chalcopyrite and pyrite, although it positively increased the grade of chalcopyrite from 21.5% to 25.7%. The ultrasonic-assisted flotation experiments with the ultrasonic bath and its combination with the homogenizer (0.4 kW) (i.e., configurations III and IV) led to an increase of approximately 16.1% and 26.9% in the chalcopyrite selectivity index compared to the conventional flotation, respectively. At the cleaning stage, a lower grade of aluminum silicate-based minerals was obtained desirably in every ultrasonic-treated configuration, which was supported with the water recoveries. Finally, applying the homogenizer and its combination with the ultrasonic bath were recommended for re-cleaner and rougher stages, respectively. Further fundamental and practical knowledge gaps required to be studied were highlighted.

Keywords: Copper flotation; Ultrasonic pretreatment; Simultaneous ultrasonic treatment; Rougher and re-cleaner stages; Homogenizer

Permalink: https://www.hzdr.de/publications/Publ-31801
Publ.-Id: 31801


Helium Ion Microscopy to address relevant questions in the impact of nanomaterials on lung epithelium – correlative microscopy approach

Podlipec, R.; Krišelj, A.; Pirker, L.; Klingner, N.; Hlawacek, G.; Strancar, J.; von Borany, J.

Helium Ion Microscopy (HIM) has not been thoroughly exploited for biological studies addressing relevant questions that range from the cellular to the subcellular level. One of the benefits of HIM compared to other high-resolution imaging techniques is definitely the large depth of focus, sub-nm resolution, nm surface sensitivity, and especially that no sample coating is needed that can change the nanostructure morphology on the surface. The prerequisite to getting the most from the technique is thus the appropriate sample preparation. Besides, to get the most from understanding the addressed biological question, a successful correlative microscopy approach is necessary. This is best shown in our recently published study (H Kokot, Advanced Materials, 2020), where we have addressed one of the most critical issues in toxicology, that is the poor understanding of chronic inflammation initiation in lung tissue caused by inhaled nanoparticles, with the correlative microscopy approach using advanced multimodal optical microscopy and HIM. HIM nicely revealed the TiO2 nanotube organization and passivation on the cell surface and confirmed lipid and protein binding to the TiO2 surface (Figure below), identified as well by in silico simulations. In brief, HIM is an extremely powerful technique for the surface, and in the case of porous samples also in-depth morphology characterization on an nm scale. In combination with complementary imaging techniques and proper sample preparation, many relevant biological questions can be addressed and solved. Still, there are many limitations and challenges in cell preparation and imaging using helium ions, such as imaging of internal structures, definitely pursuing discussions and new developments in the future.

  • Lecture (Conference) (Online presentation)
    IAEA Technical Meeting on Imaging Using Ionizing Radiation to Address Biological Challenges, 30.11.-03.12.2020, Virtual Event, Virtual Event

Permalink: https://www.hzdr.de/publications/Publ-31800
Publ.-Id: 31800


Digital LLRF at ELBE: Performance and first impressions of user operation

Gümüş, Ç.; Hierholzer, M.; Kuntzsch, M.; Pfeiffer, S.; Schmidt, C.; Steinbrück, R.; Zenker, K.

A digital LLRF control has been implemented at the CW linac ELBE at Helmholtz-Zentrum Dresden-Rossendorf. The system is based on the MicroTCA.4 standard and drives four superconducting TESLA cavities and two normal conducting buncher cavities. The system enables a higher flexibility of the field control, improved diagnostics and field stability compared to the analogue system which was used before. The presentation will give an overview on the system performance in terms of noise measurements. In addition a review of the user operation started in August 2020 will be given. Finally, planned future features are presented.

Keywords: ELBE; ChimeraTK; MicroTCA.4; LLRF; OPC UA

  • Invited lecture (Conferences) (Online presentation)
    Virtual MT ARD ST3 Meeting 2020, 23.-24.09.2020, Karlsruhe, Detuschland

Permalink: https://www.hzdr.de/publications/Publ-31797
Publ.-Id: 31797


The MicroTCA.4 based LLRF system for CW operation at ELBE

Gümüş, Ç.; Hierholzer, M.; Kuntzsch, M.; Pfeiffer, S.; Schmidt, C.; Steinbrück, R.; Zenker, K.

A digital LLRF control has been implemented at the CW linac ELBE at Helmholtz-Zentrum Dresden-Rossendorf. The system is based on the MicroTCA.4 standard and drives four superconducting TESLA cavities and two normal conducting buncher cavities. The system enables a higher flexibility of the field control, improved diagnostics and field stability compared to the analogue system which was used before. The presentation will give an overview on the system, its performance and a review of the user operation started in August 2020.

Keywords: ELBE; MicroTCA.4; LLRF; OPC UA; ChimeraTK

  • Invited lecture (Conferences) (Online presentation)
    9th Virtual MicroTCA Workshop for Industry and Research, 01.-03.12.2020, Hamburg, Deutschland

Permalink: https://www.hzdr.de/publications/Publ-31796
Publ.-Id: 31796


Mineralogy, geochemistry and genesis of agate - a review

Götze, J.; Möckel, R.; Pan, Y.

Agate - a spectacular form of SiO2 and a famous gemstone - is commonly characterized as banded chalcedony. In detail, chalcedony layers in agates can be intergrown or intercalated with macrocrystalline quartz, quartzine, opal-A, opal-CT, cristobalite and/or moganite. In addition, agates often contain considerable amounts of mineral inclusions and water as both interstitial molecular H2O and silanol groups. Most agate occurrences worldwide are related to SiO2-rich (rhyolites, rhyodacites) and SiO2-poor (andesites, basalts) volcanic rocks, but can also be formed as hydrothermal vein varieties or as silica accumulation during diagenesis in sedimentary rocks. It is assumed that the supply of silica for agate formation is often associated with late-or post-volcanic alteration of the volcanic host rocks. Evidence can be found in association with typical secondary minerals such as clay minerals, zeolites or iron oxides/hydroxides, frequent pseudomorphs (e.g., after carbonates or sulfates) as well as the chemical composition of the agates. For instance, elements of the volcanic rock matrix (Al, Ca, Fe, Na, K) are enriched, but extraordinary high contents of Ge (>90 ppm), B (>40 ppm) and U (>20 ppm) have also been detected. Calculations based on fluid inclusion and oxygen isotope studies point to a range between 20 and 230◦C for agate formation temperatures. The accumulation and condensation of silicic acid result in the formation of silica sols and proposed amorphous silica as precursors for the development of the typical agate micro-structure. The process of crystallisation often starts with spherulitic growth of chalcedony continuing into chalcedony fibers. High concentrations of lattice defects (oxygen and silicon vacancies, silanol groups) detected by cathodoluminescence (CL) and electron paramagnetic resonance (EPR) spectroscopy indicate a rapid crystallisation via an amorphous silica precursor under non-equilibrium conditions. It is assumed that the formation of the typical agate microstructure is governed by processes of self-organization. The resulting differences in crystallite size, porosity, kind of silica phase and incorporated color pigments finally cause the characteristic agate banding and colors.

Keywords: agate; quartz; chalcedony; silica minerals; micro-structure; trace elements; O-isotopes; paragenetic minerals

Permalink: https://www.hzdr.de/publications/Publ-31795
Publ.-Id: 31795


Example videos of particles colliding with a rising bubble

Sommer, A.-E.; Heitkam, S.; Eckert, K.

These videos are related to the publication "Collision phenomena between inertialess particles and bubbles: An experimental study with 4D PTV and tomographic PIV", submitted on the XXX to the Journal of Fluid Mechanics. They are the underlying raw videos of an exemplary leading and tailing edge collision trajectory which are analzed in Figure 7 and 8, respectivly.

Keywords: Froth Flotation; 4D Particle Tracking Velocimetry (PTV); Bubble-Particle Collision; Rising bubble chain

  • Reseach data in the HZDR data repository RODARE
    Publication date: 2020-11-26
    DOI: 10.14278/rodare.610
    License: CC-BY-4.0

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Permalink: https://www.hzdr.de/publications/Publ-31794
Publ.-Id: 31794


Correlated pion-proton pair emission off hot and dense QCD matter

Adamczewski-Musch, J.; Arnold, O.; Behnke, C.; Belounnas, A.; Belyaev, A.; Berger-Chen, J. C.; Blanco, A.; Blume, C.; Böhmer, M.; Bordalo, P.; Chernenko, S.; Chlad, L.; Ciepal, I.; Deveaux, C.; Dreyer, J.; Epple, E.; Fabbietti, L.; Fateev, O.; Filip, P.; Fonte, P.; Franco, C.; Friese, J.; Fröhlich, I.; Galatyuk, T.; Garzon, J. A.; Gernhäuser, R.; Golubeva, M.; Greifenhagen, R.; Guber, F.; Gumberidze, M.; Harabasz, S.; Heinz, T.; Hennino, T.; Hlavac, S.; Höhne, C.; Holzmann, R.; Ierusalimov, A.; Ivashkin, A.; Kämpfer, B.; Karavicheva, T.; Kardan, B.; Koenig, I.; Koenig, W.; Kohls, M.; Kolb, B. W.; Korcyl, G.; Kornakov, G.; Kornas, F.; Kotte, R.; Kugler, A.; Kunz, T.; Kurepin, A.; Kurilkin, A.; Kurilkin, P.; Ladygin, V.; Lalik, R.; Lapidus, K.; Lebedev, A.; Lopes, L.; Lorenz, M.; Mahmoud, T.; Maier, L.; Malige, A.; Mangiarotti, A.; Markert, J.; Matulewicz, T.; Maurus, S.; Metag, V.; Michel, J.; Mihaylov, D. M.; Morozov, S.; Müntz, C.; Münzer, R.; Naumann, L.; Nowakowski, K.; Parpottas, Y.; Pechenov, V.; Pechenova, O.; Petukhov, O.; Piasecki, K.; Pietraszko, J.; Przygoda, W.; Pysz, K.; Ramos, S.; Ramstein, B.; Rathod, N.; Reshetin, A.; Rodriguez-Ramos, P.; Rosier, P.; Rost, A.; Sadovsky, A.; Salabura, P.; Scheib, T.; Schuldes, H.; Schwab, E.; Scozzi, F.; Seck, F.; Sellheim, P.; Selyuzhenkov, I.; Siebenson, J.; Silva, L.; Singh, U.; Smyrski, J.; Sobolev, Y. G.; Spataro, S.; Spies, S.; Ströbele, H.; Stroth, J.; Sturm, C.; Svoboda, O.; Szala, M.; Tlusty, P.; Traxler, M.; Tsertos, H.; Usenko, E.; Wagner, V.; Wendisch, C.; Wiebusch, M. G.; Wirth, J.; Wojcik, D.; Zanevsky, Y.; Zumbruch, P.

In this letter we report the first multi-differential measurement of correlated pion-proton pairs from 2 billion Au+Au collisions at \sqrt{s_{NN}} = 2.42 GeV collected with HADES. In this energy regime the population of \Delta(1232) resonances plays an important role in the way energy is distributed between intrinsic excitation energy and kinetic energy of the hadrons in the fireball. The triple differential d3N/dM{\pi}pdpTdy distributions of correlated {\pi}p pairs have been determined by subtracting the {\pi}p combinatorial background using an iterative method. The invariant-mass distributions in the \Delta(1232) mass region show strong deviations from a Breit-Wigner function with vacuum width and mass. The yield of correlated pion-proton pairs exhibits a complex isospin, rapidity and transverse-momentum dependence. In the invariant mass range 1.1 < Minv (GeV/c2) < 1.4, the yield is found to be similar for {\pi}+p and {\pi}-p pairs, and to follow a power law ^{\alpha}, where is the mean number of participating nucleons. The exponent {\alpha} depends strongly on the pair transverse momentum (pT) while its pT-integrated and charge-averaged value is {\alpha} = 1.5 \pm 0.08stat \pm 0.2sys.

Permalink: https://www.hzdr.de/publications/Publ-31793
Publ.-Id: 31793


Metabolic targeting of cancer stem cells

Mukha, A.; Dubrovska, A.

Most human tumors possess a high heterogeneity resulting from both clonal evolution and cell differentiation program. The process of cell differentiation is initiated from a population of cancer stem cells (CSCs), which are enriched in tumor‐regenerating and tumor‐propagating activities and responsible for tumor maintenance and regrowth after treatment. Intrinsic resistance to conventional therapies, as well as a high degree of phenotypic plasticity, makes CSCs hard-to-target tumor cell population. Reprogramming of CSC metabolic pathways plays an essential role in tumor progression and metastatic spread. Many of these pathways confer cell adaptation to the microenvironmental stresses, including a shortage of nutrients and anti-cancer therapies. A better understanding of CSC metabolic dependences as well as metabolic communication between CSCs and the tumor microenvironment are of utmost importance for efficient cancer treatment. In this mini-review, we discuss the general characteristics of CSC metabolism and potential metabolic targeting of CSC populations as a potent strategy to enhance the efficacy of conventional treatment approaches.

Keywords: Cancer Stem Cells; therapy resistance; metabolic targeting

Permalink: https://www.hzdr.de/publications/Publ-31792
Publ.-Id: 31792


Kinetic (Lattice) Monte Carlo for Helical Molecules and Magnetic Substrates

Kelling, J.

In the investigation of the mutual interaction of self-assembled monolayers (SAMs) of helical organic molecules with metal surfaces, the goals are both to understand how surface properties, like magnetisation, influence the formation of the SAM and how the ensemble of electron-spin selective molecules influences magnetic properties of the carrier materials, specifically on a buried ferromagnetic layer.

The phenomenology of the effects on both sides can be modelled via kinetic Metropolis Monte Carlo (KMC) simulations in different ways. In both cases, this class of simulations models the kinetics of non-equilibrium systems based on local interaction energies using stochastic cellular automata based on non-equilibrium thermodynamics. This stochastic modeling replaces the physical dynamics simulated in, e.g., molecular dynamics (MD) simulations. Such a simplification is often necessary when simulating large ensembles required to observe phase ordering processes in order make these simulations possible or achieve sufficient throughput to create parameter maps like phase diagrams.

Keywords: Kinetic Metropolis Monte Carlo; GPU; Self Organization

Permalink: https://www.hzdr.de/publications/Publ-31790
Publ.-Id: 31790


Experimental liquid concentration distribution for air-led stripping of isobutyl acetate in sieve tray column

Marchini, S.; Vishwakarma, V.; Schubert, M.; Hampel, U.

This data contain the outcome of absorbance measurements performed via UV-Spectroscopy on liquid samples containing isobutyl acetate in various concentration. The liquid samples have been taken from several deck positions on a distillation sieve tray to determine the liquid concentration distribution and have been used to determine tray and point efficiency in a post-processing stage.

Keywords: distillation; concentration distribution; sieve tray; point efficiency; tray efficiency

Related publications

  • Reseach data in the HZDR data repository RODARE
    Publication date: 2020-11-26
    DOI: 10.14278/rodare.602

Downloads:

Permalink: https://www.hzdr.de/publications/Publ-31789
Publ.-Id: 31789


Magnetic field dependence of low-energy magnons, anisotropic heat conduction, and spontaneous relaxation of magnetic domains in the cubic helimagnet ZnCr2Se4

Inosov, D. S.; Onykiienkko, Y. O.; Tymoshenko, Y. V.; Akopyan, A.; Shukla, D.; Prasai, N.; Doerr, M.; Gorbunov, D.; Zherlitsyn, S.; Voneshen, D. J.; Boehm, M.; Tsurkan, V.; Felea, V.; Loidl, A.; Cohn, J. L.

Anisotropic low-temperature properties of the cubic spinel helimagnet ZnCr2Se4 in the single-domain spinspiral state are investigated by a combination of neutron scattering, thermal conductivity, ultrasound velocity, and dilatometry measurements. In an applied magnetic field, neutron spectroscopy shows a complex and nonmonotonic evolution of the spin-wave spectrum across the quantum-critical point that separates the spin-spiral phase from the field-polarized ferromagnetic phase at high fields. A tiny spin gap of the pseudo-Goldstone magnon mode, observed at wave vectors that are structurally equivalent but orthogonal to the propagation vector of the spin helix, vanishes at this quantum critical point, restoring the cubic symmetry in the magnetic subsystem. The anisotropy imposed by the spin helix has only a minor influence on the lattice structure and sound velocity but has a much stronger effect on the heat conductivities measured parallel and perpendicular to the magnetic propagation vector. The thermal transport is anisotropic at T ≲ 2K, highly sensitive to an external magnetic field, and likely results directly from magnonic heat conduction. We also report long-time thermal relaxation phenomena, revealed by capacitive dilatometry, which are due to magnetic domain motion related to the destruction of the single-domain magnetic state, initially stabilized in the sample by the application and removal of magnetic field. Our results can be generalized to a broad class of helimagnetic materials in which a discrete lattice symmetry is spontaneously broken by the magnetic order.

Permalink: https://www.hzdr.de/publications/Publ-31788
Publ.-Id: 31788


Influence of the martensitic transformation kinetics on the magnetocaloric effect in Ni-Mn-In

Pfeuffer, L.; Gottschall, T.; Faske, T.; Taubel, A.; Scheibel, F.; Karpenkov, A. Y.; Ener, S.; Skokov, K. P.; Gutfleisch, O.

The inverse magnetocaloric effect in Ni-Mn based Heusler compounds occurs during the magnetostructural transition between low-temperature, low-magnetization martensite and high-temperature, high-magnetization austenite. In this study, we analyze the metamagnetic transformation of a Ni49.8Mn35In15.2 compound by simultaneous adiabatic temperature change ΔTad and strain Δl/l0 measurements in pulsed magnetic fields up to 10 T. We observe a ΔTad of −10 K and a Δl/l0 of −0.22% when the reverse martensitic transition is fully induced at a starting temperature of 285 K. By a variation of the magnetic field-sweep rates between 316, 865, and 1850 T s−1, the transitional dynamics of the reverse martensitic transformation have been investigated. Our experiments reveal an apparent delay upon the end of the reverse martensitic transformation at field rates exceeding 865 T s−1 which is related to the annihilation of retained martensite. As a consequence, the field hysteresis increases and higher fields are required to saturate the transition. In contrast, no time-dependent effects on the onset of the reverse martensitic transformation were observed in the studied field-sweep range. Our results demonstrate that kinetic effects in Heusler compounds strongly affect the magnetic cooling cycle, especially when utilizing a multicaloric “exploiting-hysteresis cycle” where high magnetic field-sweep rates are employed.

Permalink: https://www.hzdr.de/publications/Publ-31787
Publ.-Id: 31787


Competing Effect of Transport versus Surface Reactivity on Mineral Dissolution Rates

Schabernack, J.; Fischer, C.

Mineral dissolution plays a key role in many environmental and technical fields, e.g., weathering, reservoir and host rock characterization, as well as building materials. The rate of mineral dissolution in water is determined by two parameters: (1) transport of dissolved species over and from the interface determined by advective fluid flow and diffusion (transport control) and (2) crystal surface reactivity (surface reactivity control). Current reactive transport models (RTM) simulating species transport commonly calculate mineral dissolution by using rate laws (e.g., Agrawal et al., 2020). These rate laws solely depend on species concentration in the fluid and therefore do not include intrinsic surface reactivity. Experimental studies at surface reactivity controlled conditions have shown a heterogeneous distribution of reaction rates (e.g., Bibi et al., 2018). This rate heterogeneity is caused by nanotopographical structures on the crystal surface, such as steps and etch pits that are generated at lattice defects. At these structures, the high density of reactive kink sites is leading to a local increase in dissolution rates.
In this study, we test whether experimentally observed rate heterogeneities can be reproduced by using current RTMs. We apply a standard RTM approach combined with the measured surface topography of a calcite single crystal (Bibi et al., 2018). The calculated surface dissolution rate maps are compared to experimentally derived rate maps. The results show that the measured rate heterogeneities cannot be reproduced with the existing RTM approach. To improve the predictive capabilities of RTMs, the surface reactivity that is intrinsic to the mineral needs to be implemented into dissolution rate calculations. We discuss parameterization of surface reactivity via proxy parameters, such as surface roughness or surface slope.

Agrawal, P., Raoof, A., Iliev, O. and Wolthers, M. (2020): Evolution of pore-shape and its impact on pore conductivity during CO2 injection in calcite: Single pore simulations and microfluidic experiments. Advances in Water Resources, 136, 103480.
Bibi, I., Arvidson, R.S., Fischer, C. and Lüttge, A. (2018): Temporal Evolution of Calcite Surface Dissolution Kinetics. Minerals, 8, 256

Keywords: Reactive Transport Model; Mineral Dissolution; Crystal Surface Topography

  • Poster (Online presentation)
    DMG VIRTUAL POSTER-SESSION 2020, 30.11.-03.12.2020, Virtuell, Deutschland

Permalink: https://www.hzdr.de/publications/Publ-31786
Publ.-Id: 31786


Process simulation: NdFeB permanent magnet production

Belo Fernandes, I.; Abadias Llamas, A.; Reuter, M.
ContactPerson: Ivan Belo Fernandes; Researcher: Alejandro ABADIAS LLAMAS; Supervisor: Markus Andreas REUTER; WorkPackageLeader: Sandra BIRTEL

This file contains an HSC model for NdFeB permanent magnet production, from ore processing to magnet production and two possible recycling routes. Data to build the model is found in key literature studies and from internal project data obtained by the various partners in four work packages (rare earth oxide separation, reduction and purification, alloy design, and powder magnet production).

The model was used to perform a resource efficiency, including exergy, and environmental impact (LCA) evaluation of the life cycle of a NdFeB permanent magnet produced from primary and secondary resources. This work has been submitted to JOM, in its special edition “Thermodynamic modeling of sustainable non-ferrous metals production” and has been accepted for publication with a digital object identifier (DOI): https://doi.org/10.1007/s11837-020-04185-6. Detailed information about the literature sources used for developing the model can be found in the original research paper. The model was built using HSC Chemistry version 9.9 (https://www.outotec.com/products-and-services/technologies/digital-solutions/hsc-chemistry/).

Keywords: NdFeB magnet production; resource efficiency; exergetic life cycle assessment; process simulation; geometallurgy; large systems design

  • Reseach data in the HZDR data repository RODARE
    Publication date: 2020-11-30
    DOI: 10.14278/rodare.616
    License: CC-BY-4.0
    Embargo: 31.07.2021

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Permalink: https://www.hzdr.de/publications/Publ-31785
Publ.-Id: 31785


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