References of "Vanderbemden, Philippe"
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See detailSuperconducting nanostructured magnesium diboride
Kalaydjiev, K.; Lovchinov, V.; Dimitrov, D. et al

in Journal of Optoelectronics and Advanced Materials [= JOAM] (2005), 7(1), 423-426

Like conventional superconductors, MgB2 is a phonon-mediated superconductor with a relatively long coherence length. Its properties make the prospects for fabricating reproducible uniform Josephson ... [more ▼]

Like conventional superconductors, MgB2 is a phonon-mediated superconductor with a relatively long coherence length. Its properties make the prospects for fabricating reproducible uniform Josephson junctions, the fundamental element of superconducting circuits, much more favorable for MgB2 than for high-temperature superconductors. Here, we report bulk superconductivity in nanophase MgB2, using a two-step technique of mechanically activated sjavascript:$('next-but').click();elf-propagated high-temperature synthesis(MASHS). The conditions of synthesis and some properties of the product (structure, susceptibility, resistivity) were studied. It was shown that a single-phase product was obtained after 2 hours of intense mechanical treatment of reagents (Mg and B powders), and MASHS induced at 30 A cm(-2). [less ▲]

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See detailSpin glass behaviour and spin-dependent scattering in La0.7Ca0.3Mn0.9Cr0.1O3 perovskites
Wu, B. M.; Ausloos, Marcel ULg; Du, Y. L. et al

in Chinese Physics Letters (2005), 22(3), 686-689

The magnetic, electrical and thermal transport properties of the perovskite La0.7Ca0.3Mn0.9Cr0.1O3 have been investigated by measuring dc magnetization, ac susceptibility, the magnetoresistance and ... [more ▼]

The magnetic, electrical and thermal transport properties of the perovskite La0.7Ca0.3Mn0.9Cr0.1O3 have been investigated by measuring dc magnetization, ac susceptibility, the magnetoresistance and thermal conductivity in the temperature range of 5-300 K. The spin glass behaviour with a spin freezing temperature of 70 K has been well confirmed for this compound, which demonstrates the coexistence and competition between ferromagnetic and antiferromagnetic clusters by the introduction of Cr. Colossal magnetoresistance has been observed over the temperature range investigated. The introduction of Cr causes the "double-bump" feature in electrical resistivity rho(T). Anomalies on the susceptibility and the thermal conductivity associated with the double-bumps in rho(T) are observed simultaneously. The imaginary part of ac susceptibility shows a sharp peak at the temperature of insulating-metallic transition where the first resistivity bump was observed, but it is a deep-set valley near the temperature where the second bump in rho(T) emerges. The thermal conductivity shows an increase below the temperature of the insulating metallic transition, but the phonon scattering is enhanced accompanying the appearance of the second peak of double-bumps in rho(T). We relate those observed in magnetic and transport properties of La0.7Ca0.3Mn0.9Cr0.1O3 to the spin-dependent scattering. The results reveal that the spin-phonon interaction may be of more significance than the electron (charge)-phonon interaction in the mixed perovskite system. [less ▲]

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See detailMagneto-transport characterization of Dy123 monodomain superconductors
Pekala, Marek; Mucha, Jan ULg; Vanderbemden, Philippe ULg et al

in Applied Physics A : Materials Science & Processing (2005), 81(5), 1001-1007

We consider textured materials of the DyBa2Cu3O7 type seeded with a Nd123 seed as initiator. They are grown with an excess 20% Dy211 phase on a Dy2O3 substrate. We report chemical characterization ... [more ▼]

We consider textured materials of the DyBa2Cu3O7 type seeded with a Nd123 seed as initiator. They are grown with an excess 20% Dy211 phase on a Dy2O3 substrate. We report chemical characterization, electrical resistivity, thermoelectric power and thermal conductivity over a broad temperature range as a function of an applied magnetic field up to 6 T. We show that specific features appear in the magneto-thermal transport properties, different in these materials from those found in single crystals and polycrystalline samples. We propose that two vortex regimes can be distinguished in the mixed phase, due to the intrinsic microstructure. We calculate the viscosity, entropy and figure of merit of the samples. [less ▲]

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See detailInvestigation of DyBa2CU3O7-d superconducting domains grown by the infiltration technique starting with small size Dy-211 particles
Mathieu, Jean-Philippe; Koutzarova, T.; Rulmont, André ULg et al

in Superconductor Science and Technology (2005), 18(2 Sp. Iss. SI), 136-141

An infiltration and growth process is here used as an alternative to the classical top-seeded melt-textured growth process for the production of Dy-123 single-domains with finely dispersed small size Dy ... [more ▼]

An infiltration and growth process is here used as an alternative to the classical top-seeded melt-textured growth process for the production of Dy-123 single-domains with finely dispersed small size Dy-211 particles. The starting materials are the 211-particles and a barium and copper rich liquid phase precursor. The infiltration and growth process allows for controlling both the spatial and size distribution of the 211-particles in the final superconducting 123-single-domain. The main parameters (set-ups, maximum processing temperature with respect to the peritectic temperature, nature of reactant, porosity of the 211-preform) of the infiltration and growth process are discussed. Moreover, different processes of chimie douce are shown in order to produce Dy-211 particles with controlled shape and size, particles that can be used as precursors for the infiltration and growth process. [less ▲]

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See detailStudy by Hall probe mapping of the trapped flux modification produced by local heating in YBCOHTS bulks for different surface/volume ratios
Laurent, Philippe ULg; Mathieu, Jean-Philippe; Mattivi, Brice et al

in Superconductor Science and Technology (2005), 18(8), 1047-1053

The aim of this report is to compare the trapped field distribution under a local heating created at the sample edge for different sample morphologies. Hall probe mappings of the magnetic induction ... [more ▼]

The aim of this report is to compare the trapped field distribution under a local heating created at the sample edge for different sample morphologies. Hall probe mappings of the magnetic induction trapped in YBCO bulk samples maintained out of thermal equilibrium were performed on YBCO bulk single domains, YBCO single domains with regularly spaced hole arrays, and YBCO superconducting foams. The capability of heat draining was quantified by two criteria: the average induction (B) decay and the size of the thermally affected zone caused by a local heating of the sample. Among the three investigated sample shapes, the drilled single domain displays a trapped induction which is weakly affected by the local heating while displaying a high trapped field. Finally, a simple numerical modelling of the heat flux spreading into a drilled sample is used to suggest some design rules about the hole configuration and their size. [less ▲]

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See detailUnusual thermoelectric behavior of packed crystalline granular metals
Ausloos, Marcel ULg; Pekala, Marek; Latuch, J. et al

in Journal of Applied Physics (2004), 96(12), 7338-7345

Loosely packed granular materials are intensively studied nowadays. Electrical and thermal transport properties should reflect the granular structure, as well as intrinsic properties. We have compacted ... [more ▼]

Loosely packed granular materials are intensively studied nowadays. Electrical and thermal transport properties should reflect the granular structure, as well as intrinsic properties. We have compacted crystalline CaAl-based metallic grains and studied the electrical resistivity and the thermoelectric power as a function of temperature (T) from 15 to 300 K. Both properties show three regimes as a function of temperature. It should be pointed out: (i) The electrical resistivity continuously decreases between 15 and 235 K, (ii) with various dependencies, e.g., similar ~ T(-3/4) at low T, while (iii) the thermoelectric power (TEP) is positive, (iv) shows a bump near 60 K, and (v) presents a rather unusual square root of temperature dependence at low temperature. It is argued that these three regimes indicate a competition between geometric and thermal processes-for which a theory seems to be missing in the case of TEP. The microchemical analysis results are also reported, indicating a complex microstructure inherent to the phase diagram peritectic intricacies of this binary alloy. (C) 2004 American Institute of Physics. [less ▲]

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See detailAnisotropic behaviour in the magnetic field dependence of the low temperature electrical resistance of calcium-doped lanthanum manganate thin films grown by RF magnetron sputtering
Vertruyen, Bénédicte ULg; Dusoulier, Laurent; Fagnard, Jean-François ULg et al

in Journal of Magnetism and Magnetic Materials (2004), 280(2-3), 264-272

We report about the magnetoresistive properties of calcium-doped lanthanum manganate thin films grown by RF magnetron sputtering on single crystalline LaAiO(3) and MgO substrates. Two orientations of the ... [more ▼]

We report about the magnetoresistive properties of calcium-doped lanthanum manganate thin films grown by RF magnetron sputtering on single crystalline LaAiO(3) and MgO substrates. Two orientations of the magnetic field with respect to the electrical current have been studied: (i) magnetic field in the plane of the film and parallel to the electrical current, and (ii) magnetic field perpendicular to the plane of the film. The film grown on LaAlO3 is characterised by an unusual magneto resistive behaviour when the magnetic field is applied perpendicular to the film plane: the appearance of two bumps in the field dependence of the resistance is shown to be related to the occurrence of anisotropic magneto resistive effects in manganate films. (C) 2004 Elsevier B.V. All rights reserved. [less ▲]

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See detailEffects of silicon addition on the electrical and magnetic properties of copper-doped (La,Ca)MnO3 compounds
Vertruyen, Bénédicte ULg; Rulmont, André ULg; Cloots, Rudi ULg et al

in Journal of Magnetism and Magnetic Materials (2004), 268(3), 364-373

In this paper we report about the electrical properties of La0.7Ca0.3MnO3 compounds substituted by copper on the manganese site and/or deliberately contaminated by SiO2 in the reactant mixture. Several ... [more ▼]

In this paper we report about the electrical properties of La0.7Ca0.3MnO3 compounds substituted by copper on the manganese site and/or deliberately contaminated by SiO2 in the reactant mixture. Several phenomena have been observed and discussed. SiO2 addition leads to the formation of an apatite-like secondary phase that affects the electrical conduction through the percolation of the charge carriers. On the other hand, depending on the relative amounts of copper and silicon, the temperature dependence of the electrical resistivity can be noticeably modified: our results enable us to compare the effects of crystallographic vacancies on the A and B sites of the perovskite with the influence of the copper ions substituted on the manganese site. The most original result occurs for the compounds with a small ratio Si/Cu, which display double-peaked resistivity vs. temperature curves. (C) 2003 Elsevier B.V. All rights reserved. [less ▲]

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See detailSuperconducting properties of magnetically textured Dy doped Bi-2212 nickel tapes
Fagnard, Jean-François ULg; Rahier, Sébastien ULg; Fonder, Nicole et al

in Andreone, A. (Ed.) Applied Superconductivity 2003 (Proceedings of the 6th European Conference on Applied Superconductivity) (2004)

This communication aims at reporting the superconducting properties of Dy-doped Bi-2212/NiO/Ni tapes prepared by a dip-coating process from an inorganic gel. The Bi-2212 is recrystallized at 965°C in ... [more ▼]

This communication aims at reporting the superconducting properties of Dy-doped Bi-2212/NiO/Ni tapes prepared by a dip-coating process from an inorganic gel. The Bi-2212 is recrystallized at 965°C in presence of an external 1.2 T magnetic induction. The precursor gel, the temperature and the thermal treatment duration are optimized regarding the microstructure The resulting tape samples are characterized by electrical resistance and I-V curves. The presence of secondary phases, such as Bi-2201, is reduced after a 750°C annealing but Ni diffusion limits the critical current density of the as-obtained tapes. The magnetic critical current density measured on textured Dy-doped Bi-2212 monoliths, obtained with the same type of texturation process, but showing no Ni contamination, is found to be about 30 times larger than the critical current density of the tapes. [less ▲]

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See detailCritical state modelling of crossed field demagnetisation in HTS materials
Swartz, J. P.; Mc Culloch, M. D.; Pecher, R. et al

in Andreone, A.; Pepe, G. P.; Cristiano, R. (Eds.) et al Applied Superconductivity 2003 (Proceedings of the 6th European Conference on Applied Superconductivity) (2004)

Large magnetic fields can be trapped in high temperature superconductor material, enabling their use as permanent magnets in various applications. It has, however, been observed that these materials ... [more ▼]

Large magnetic fields can be trapped in high temperature superconductor material, enabling their use as permanent magnets in various applications. It has, however, been observed that these materials experience a decay in magnetisation when a field is applied in a direction transverse to the trapped field. This paper presents the results of critical state modelling of an infinite slab of superconductor that is first fully magnetised and then exposed to magnetic field in the transverse direction. The bean and double critical state model are implemented and the results compared to each other and to that of physical experiment. The convergence of the decay is investigated as well as the effect of the magnitude of the crossed field on the final decay value. Diamagnetic and paramagnetic initial conditions are applied to the material and the results used to compare the accuracy of the bean and double critical state model. [less ▲]

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See detailThe contribution of 211 particles to the mechanical reinforcement mechanism of 123 superconducting single domains
Mathieu, Jean-Philippe; Cano, I. G.; Koutzarova, T. et al

in Superconductor Science and Technology (2004), 17(1), 169-174

Hardness and fracture toughness of Dy-123 single domains were studied by Vickers in micro-indentation. A significant anisotropy of the mechanical properties was observed. Hardness tests give higher values ... [more ▼]

Hardness and fracture toughness of Dy-123 single domains were studied by Vickers in micro-indentation. A significant anisotropy of the mechanical properties was observed. Hardness tests give higher values when performed in (001) planes rather than in planes parallel to the c-axis. Moreover, the cracks pattern around the indentation follows preferential orientation in planes parallel to the c-axis whereas a classical 'four-cracks' pattern is observed in the (001) planes. It has been possible to show the crucial role played by the 211 particles in the deviating mechanism of cracks and the relevance of the high homogeneity of 211-particle distribution in the material. [less ▲]

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See detailac magnetic behavior of large-grain magnetoresistive La0.78Ca0.22Mn0.90Ox materials
Vanderbemden, Philippe ULg; Vertruyen, Bénédicte ULg; Rulmont, André ULg et al

in Physical Review. B (2003), 68(22), 224418

We report a detailed set of ac magnetic measurements carried out on bulk large grain La-Ca-Mn-O samples extracted from a floating zone method-grown rod. Three samples with La0.78Ca0.22Mn0.90Ox ... [more ▼]

We report a detailed set of ac magnetic measurements carried out on bulk large grain La-Ca-Mn-O samples extracted from a floating zone method-grown rod. Three samples with La0.78Ca0.22Mn0.90Ox stoichiometry but differing in their microstructure were investigated by electrical resistivity and ac susceptibility measurements: (i) a single grain sample, (ii) a sample containing two grains, and (iii) a polycrystalline sample. We show that the superimposition of dc magnetic fields during ac magnetic susceptibility measurements is an efficient way for characterizing the magnetic transition of samples with different microstructures. Whereas both single grain and polycrystalline samples display a single susceptibility peak, an additional kink structure is observed in the case of the double grain sample. The temperature dependence of the ac susceptibility measured with superimposed dc magnetic fields is analyzed in the framework of second-order phase transition ideas. The relations between the critical exponents (beta+gamma ~ 1.5, delta ~ 2.5) are found to be close to those of the mean-field model for all samples. This is attributed to the disordering caused by unoccupied Mn sites. ©2003 The American Physical Society. [less ▲]

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See detailBehavior of bulk melt-textured YBCO single domains subjected to crossed magnetic fields
Vanderbemden, Philippe ULg; Dorbolo, Stéphane ULg; Hari-Babu, N. et al

in IEEE Transactions on Applied Superconductivity (2003), 13(2, Part 3), 3746-3749

We have experimentally investigated the crossed magnetic field effects on bulk melt-processed YBCO single domains. The samples were first permanently magnetized along their c-axis and then subjected to ... [more ▼]

We have experimentally investigated the crossed magnetic field effects on bulk melt-processed YBCO single domains. The samples were first permanently magnetized along their c-axis and then subjected to several cycles of a transverse magnetic field parallel to the ab planes. The magnetic properties along the c and ab directions were simultaneously measured using a couple of orthogonal pick-up coils as well as a Hall probe placed against the sample surface. The effects of both sweep amplitude and polarity were investigated. Field sweeps of alternate polarities are shown to affect the decay of the c-axis magnetization much more strongly than field sweeps of unique polarity do. However, the c-axis magnetization does not show any saturation even after a large number of field sweeps. Next, a micro-Hall probe scanning system was used to measure the distribution of magnetic induction over the top surface of the single domain subjected to the same combination of magnetic fields. The results are shown to be consistent with those determined with the sensing coils and bring out the role played by geometric effects. (C) 2003 IEEE. [less ▲]

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See detailAnisotropic AC behavior of multifilamentary Bi-2223/Ag tapes
Fagnard, Jean-François ULg; Vanderbemden, Philippe ULg; Cloots, Rudi ULg et al

in IEEE Transactions on Applied Superconductivity (2003), 13(2, Part 3), 2976-2979

In this communication, we report on the anisotropy of the superconducting properties of multifilamentary Bi-based tapes experimentally investigated by AC magnetic susceptibility measurements. The ... [more ▼]

In this communication, we report on the anisotropy of the superconducting properties of multifilamentary Bi-based tapes experimentally investigated by AC magnetic susceptibility measurements. The susceptibility X = X' - jX" was measured using a commercial system and a couple of orthogonal pick-up coils. The X'' vs. temperature curves were shown to exhibit two peaks. The smaller of the peaks, occurring near T = 72 K, was only visible for particular field directions and within a given frequency window. Such results point out the role played by the phase difference between the applied magnetic field and the internal magnetic field seen by the filaments. (C) 2003 IEEE. [less ▲]

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See detailMagneto-transport study of nb-doped Bi/Pb2223 superconductor
Pekala, Marek; Mucha, Jan ULg; Cloots, Rudi ULg et al

in Physica C: Superconductivity (2003), 387(1-2), 191-197

The magneto-transport properties of Bi1.5Pb0.4Nb0.1Sr2Ca2Cu3O10-x polycrystalline, superconducting ceramic are reported. The material was found to be chemically homogeneous and partially textured. The ... [more ▼]

The magneto-transport properties of Bi1.5Pb0.4Nb0.1Sr2Ca2Cu3O10-x polycrystalline, superconducting ceramic are reported. The material was found to be chemically homogeneous and partially textured. The mixed state properties were investigated by measuring the electrical resistivity, longitudinal and transverse (Nernst effect) thermoelectric power, and thermal conductivity. The magnetization and AC susceptibility measurements were also performed. The variation of these characteristics for magnetic fields up to 5 T are discussed and compared to those of the zero field case. The transport entropy and thermal Hall angle are extracted and quantitatively compared to previously reported data of closely related systems. (C) 2003 Elsevier Science B.V. All rights reserved. [less ▲]

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See detailMagnetotransport study of MgB2 superconductor
Mucha, Jan ULg; Pekala, Marek; Szydlowska, Jadwiga et al

in Superconductor Science and Technology (2003), 16(10), 1167-1172

Precise magnetotransport studies of heat and charge carriers in polycrystalline MgB2 show that magnetic fields up to 8 T remarkably influence electrical resistivity, thermoelectric power and thermal ... [more ▼]

Precise magnetotransport studies of heat and charge carriers in polycrystalline MgB2 show that magnetic fields up to 8 T remarkably influence electrical resistivity, thermoelectric power and thermal conductivity. The superconducting transition temperature shifts from 39 K to 19 K at 8 T as observed on electric signals. The temperature transition width is weakly broadened. Electron and phonon contributions to the thermal conductivity are separated and discussed. The Debye temperature calculated from a phonon drag thermoelectric power component is inconsistent with values derived through other effects. [less ▲]

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See detailSynthesis of CMR manganate compounds: the consequences of the choice of a precursor method
Vertruyen, Bénédicte ULg; Rulmont, André ULg; Cloots, Rudi ULg et al

in Materials Letters (2002), 57(3), 598-603

We have studied the electrical transport properties of manganate samples synthesized by different precursor methods. Differences in the synthesis process of the materials can result in samples with ... [more ▼]

We have studied the electrical transport properties of manganate samples synthesized by different precursor methods. Differences in the synthesis process of the materials can result in samples with similar grain size but very different physical properties, contrary to what happens in samples prepared by the same method. (C) 2002 Elsevier Science B.V. All rights reserved. [less ▲]

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See detailYBa2Cu3O7 tapes prepared by sol-gel deposition techniques: microstructure and structural characterizations
Marguillier, David ULg; Cloots, Rudi ULg; Rulmont, André ULg et al

in Physica C: Superconductivity (2002), 372(Part 2), 715-718

We report on the preparation conditions of YBa2Cu3O7 polycrystalline superconducting tapes by a sol-gel deposition technique. We present some discussion on the compatibility between the nature of the ... [more ▼]

We report on the preparation conditions of YBa2Cu3O7 polycrystalline superconducting tapes by a sol-gel deposition technique. We present some discussion on the compatibility between the nature of the substrate, the use of a buffer layer, and the conditions used to prepare appropriate superconducting YBa2Cu3O7,, materials. We report also on the microstructural characterizations performed in order to evaluate the crystallites size, degree of orientation and connectivity. (C) 2002 Elsevier Science B.V. All rights reserved. [less ▲]

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See detailCu doping as a tool for understanding CMR
Vertruyen, Bénédicte ULg; Cloots, Rudi ULg; Rulmont, André ULg et al

in Key Engineering Materials [=KEM] (2002), 206-2

Doping at the Mn-site in CMR manganate-based perovskites has been shown to affect strongly the physical properties of those compounds. We study here the effect of copper substitution in the low doping ... [more ▼]

Doping at the Mn-site in CMR manganate-based perovskites has been shown to affect strongly the physical properties of those compounds. We study here the effect of copper substitution in the low doping range on the electrical transport properties of La0.7Ca0.3MnO3. It turns out that the transition temperature decrease observed in doped samples can be drastically reduced by addition of silicon dioxide SiO2. It is shown that copper is trapped in a secondary phase composed of La,Ca,Si,Cu and O. The resultant Mn-site vacancies appear to be less detrimental to the electronic conduction than the likely antiferromagnetic clusters induced by the copper ions in the Mn-O network. [less ▲]

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See detailIntragranular and intergranular behaviour of multifilamentary Bi-2223/Ag tapes
Fagnard, Jean-François ULg; Vanderbemden, Philippe ULg; Crate, David et al

in Physica C: Superconductivity (2002), 372(Part 2), 970-973

This communication aims at reporting the superconducting properties of Bi-2223/Ag tapes determined by using various measuring techniques. First. the original samples have been characterized by electrical ... [more ▼]

This communication aims at reporting the superconducting properties of Bi-2223/Ag tapes determined by using various measuring techniques. First. the original samples have been characterized by electrical resistance, AC susceptibility. and DC magnetization. The transport (intergranular) critical Current vs. magnetic field was also determined at T = 77 K using pulsed currents up to 40 A. Next. the same combination of experiments as performed oil bent tapes in order to bring out relevant information concerning the strength of the intergranular coupling. The results show that intergranular and intragranular currents differ by at least one order of magnitude, Finally, additional magnetic measurements were carried out in order to determine the anisotropy ratio Jc(ab)/Jc(c), which was found to lie around 30. (C) 2002 Elsevier Science B.V. All rights reserved. [less ▲]

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