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Pastoriza, H.; Candia, S.; Nieva, G. |
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Title |
Anisotropic vortex dynamics in twined YBaCuO single crystals |
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2000 |
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Physica B |
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284-288 |
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2 |
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763-764 |
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Rotating continuously the applied vortex force and measuring the vortex velocity vector, we were able to directly determine the role of twin boundaries in the vortex dynamics in YBa$2$Cu$3Ο_7$ single crystals with unidirectional twins. We show the different effect of these correlated pinning defects into the various vortex phases. In the entangled vortex liquid state, we observe a linear response but with an anisotropic viscosity. On the other hand, an anomalous guided motion by twin planes is found in the vortex solid. |
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BT @ hernan @ pastoriza00 |
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39 |
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André, M-O.; Polichetti, M.; Pastoriza, H.; Kes, P. H. |
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Title |
Vortex dynamics in 2H-NbSe$_2$ containing a periodic channel structure |
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2000 |
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Physica C |
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338 |
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179-188 |
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We have measured the resistivity and magnetic AC susceptibility of 2H-NbSe single crystals containing alternating 2 stripes of irradiated and non-irradiated regions of columnar defects created by heavy-ion bombardment. Without applied magnetic field, the sample undergoes a double-step transition into the superconducting state, each step corresponding to the transitions in the irradiated and non-irradiated regions, respectively. For fields smaller than half of the matching field and upon increasing the temperature, the onset of flux motion in the non-irradiated channels occurs, when the applied stress due to the electrical current equals the shear stress at the channel edges, while depinning in the irradiated stripes occurs at higher temperature. The weak amplitude dependence of the shear process suggests that it takes place at the melting transition. We observed only a single-step transition at DC magnetic fields larger than half the matching field, because pinning by the columnar defects in the irradiated stripes is much less effective, and consequently the shear stress at the channel edges is strongly reduced. The comparison between the shear stress deduced from I curves and the theoretical value $?max = AC66$ yields a value for the constant Α, which is in good agreement with theoretical predictions. |
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BT @ hernan @ andre99 |
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2 |
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Marconi, V. I.; Candia, S.; Balenzuela, P.; Pastoriza, H.; Domínguez, D.; Martinoli, P. |
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Title |
Orientational pinning and transverse voltage: Simulations and experiments in square Josephson junction arrays |
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Journal Article |
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2000 |
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Phys. Rev. B |
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62 |
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6 |
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4096-4104 |
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We study the dependence of the transport properties of square Josephson Junctions arrays with the direction of the applied dc current, both experimentally and numerically. We present computational simulations of current-voltage curves at finite temperatures for a single vortex in an array of $L\times L$ junctions ($Ha^2/?_0=f=1/L^2$), and experimental measurements in $100\times1000$ arrays under a low magnetic field corresponding to $f\approx0.02$. We find that the transverse voltage vanishes only in the directions of maximum symmetry of the square lattice: the [10] and [01] direction (parallel bias) and the [11] direction (diagonal bias). For orientations different than the symmetry directions, we find a finite transverse voltage which depends strongly on the angle φ of the current. We find that vortex motion is pinned in the [10] direction ($?=0$), meaning that the voltage response is insensitive to small changes in the orientation of the current near $?=0$. We call this phenomenon orientational pinning. This leads to a finite transverse critical current for a bias at $?=0$ and to a transverse voltage for a bias at $?\not=0$. On the other hand, for diagonal bias in the [11] direction the behavior is highly unstable against small variations of φ, leading to a rapid change from zero transverse voltage to a large transverse voltage within a few degrees. This last behavior is in good agreement with our measurements in arrays with a quasi-diagonal current drive. |
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BT @ hernan @ marconi00 |
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26 |
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Herbsommer, Juan A. |
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Title |
Dinámica y estática de vórtices en superconductores de alta temperatura crítica con defectos correlacionados |
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Book Whole |
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2000 |
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Instituto Balseiro |
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Ph.D. thesis |
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BT @ hernan @ |
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328 |
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Fainstein, A.; Maiorov, B.; Guimpel, J.; Nieva, G.; Osquiguil, E. |
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Title |
Annealing disorder and photoinduced order of oxygen chains in detwinned YBa2Cu3O6.65 single crystals probed by Raman scattering |
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Journal Article |
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Year |
2000 |
Publication |
Physical Review B – Condensed Matter and Materials Physics |
Abbreviated Journal |
Phys. Rev. B Condens. Matter Mater. Phys. |
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61 |
Issue |
6 |
Pages |
4298-4304 |
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Raman scattering in detwinned YBa2Cu3O6.65 single crystals is studied as a function of photoexcitation and annealing. Copper-oxygen chain-related forbidden Raman bands that are known to strongly bleach with illumination at low temperatures, increase their intensity with chain fragmentation induced by annealing at high temperature. This contrasting behavior proves the conjunction of short Cu-O fragments into longer chains on photoexcitation. We interpret the Raman modes as due to vibrations at the end of CuO chain fragments and Cu-O-Cu monomers, and use their evolution with illumination and annealing as anisotropic sensitive markers of oxygen reordering processes. The identification of the “forbidden” Raman bands is discussed in the context of our results and recent literature in the subject. We also present absorption measurements performed on GdBa2Cu3Ox thin films with varying oxygen content. These experiments show that the 2.2-eV absorption and the chain-related Raman peaks have different dependencies with oxygen content and illumination, ruling out an explanation that suggests that the Raman intensity reduction of these modes is due to a photobleaching of intermediate defect states. These results highlight the potentialities of Raman scattering for oxygen dynamics studies and demonstrate the presence of photoinduced oxygen ordering in these high-Tc superconductor compounds. |
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01631829 (ISSN) |
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Cited By (since 1996): 18; Export Date: 17 April 2009; Source: Scopus; CODEN: PRBMD; Language of Original Document: English; Correspondence Address: Fainstein, A.; Centro At |
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BT @ osquigui @ |
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374 |
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Decca, R.S.; Drew, H.D.; Osquiguil, E.; Maiorov, B.; Guimpel, J. |
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Title |
Anomalous proximity effect in underdoped YBa2Cu3O6+x Josephson junctions |
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Journal Article |
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Year |
2000 |
Publication |
Physical Review Letters |
Abbreviated Journal |
Phys Rev Lett |
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Volume |
85 |
Issue |
17 |
Pages |
3708-3711 |
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Keywords |
Critical currents; Energy gap; High temperature superconductors; Magnetic field effects; Magnetron sputtering; Mathematical models; Phase diagrams; Phase transitions; Physical properties; Scanning electron microscopy; Superconductivity; Yttrium barium copper oxides; Anomalous proximity effect; Fluctuating phase models; Josephson effect; Photodoping; Josephson junction devices |
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Experiments were carried out to probe the underdoped insulating material by the Josephson effect. Junctions were fabricated by exploiting the capability of locally photodoping insulating RBa2Cu3O6+x (R = rare earth) material. The existence of an anomalously large proximity effect was confirmed. The critical current of the junctions was consisted with the conventional Josephson relationship. |
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American Inst of Physics |
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Woodbury, NY, United States |
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00319007 (ISSN) |
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Cited By (since 1996): 36; Export Date: 17 April 2009; Source: Scopus; CODEN: PRLTA; doi: 10.1103/PhysRevLett.85.3708; Language of Original Document: English; Correspondence Address: Decca, R.S.; Univ of Maryland College Park, United States; References: Ginsberg, D.M., (1996) Physical Properties of High Temperature Superconductors V, , World Scientific, Singapore; Zhang, S.C., (1997) Science, 275, p. 1089; Emery, V.J., Kivelson, S.A., (1995) Nature (London), 374, p. 434; Corson, J., (1999) Nature (London), 398, p. 291; Renner, Ch., (1998) Phys. Rev. Lett., 80, p. 149; Demler, E., (1998) Phys. Rev. Lett., 80, p. 2917; Den Hertog, B.C., Berlinsky, A.J., Kallin, C., (1999) Phys. Rev. B, 59, pp. R11645; Emery, V.J., Kivelson, S.A., Zachar, O., (1997) Phys Rev. B, 56, p. 6120; Tinkham, M., (1996) Introduction to Superconductivity, , McGraw-Hill, New York; Decca, R.S., (1998) Appl. Phys. Lett., 73, p. 120; (1999) J. Microsc., 194, p. 407; Osquiguil, E., (1992) Appl. Phys. Lett., 60, p. 1627; Kudinov, V.I., (1993) Phys. Rev. B, 47, p. 9017; Decca, R.S., Drew, H.D., Empson, K.L., (1997) Appl. Phys. Lett., 70, p. 1932; Orenstein, J., (1990) Phys. Rev. B, 42, p. 6342; Nieva, G., (1992) Appl. Phys. Lett., 60, p. 2159; (1992) Phys. Rev. B, 46, p. 14249; notenoteGray, K.E., (1992) Phys. Rev. B, 45, p. 10071; Pauza, A.J., (1997) J. Appl. Phys., 82, p. 5612; Katz, A.S., Woods, S.I., Dynes, R.C., (2000) J. Appl. Phys., 87, p. 2978; noteUR – http://www.scopus.com/scopus/inward/record.url?eid=2-s2.0-19244384844&partnerID=40 |
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BT @ osquigui @ |
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373 |
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Maiorov, B.; Nieva, G.; Osquiguil, E. |
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First-order phase transition of the vortex lattice in twinned YBa2Cu3O7 single crystals in tilted magnetic fields |
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Journal Article |
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2000 |
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Physical Review B – Condensed Matter and Materials Physics |
Abbreviated Journal |
Phys. Rev. B Condens. Matter Mater. Phys. |
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61 |
Issue |
18 |
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12427-12432 |
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We present an exhaustive analysis of transport measurements performed in twinned YBa2Cu3O7 single crystals which establishes that the vortex solid-liquid transition is first order when the magnetic field H is applied at an angle ? away from the direction of the twin planes. We show that the resistive transitions are hysteretic and the V-I curves are nonlinear, displaying a characteristic S shape at the melting line Hm(T), which scales as ?(?)Hm(T,?), where ?(?) is the anisotropy factor. These features are gradually lost when the critical point H*(?) is approached. Above H*(?) the V-I characteristics show a linear response in the experimentally accessible V-I window, and the transition becomes reversible. Finally we show that the first-order phase transition takes place between a highly correlated vortex liquid in the field direction and a solid state of unknown symmetry. As a consequence, our data support the scenario for a vortex-line melting in twinned YBa2Cu3O7 crystals in contrast to a vortex sublimation as recently suggested for untwinned La2-xSrxCuO4, YBa2Cu3O7 and Bi2Sr2CaCu2O8 [T. Sasagawa et al., Phys. Rev. Lett. 80, 4297 (1998)]. |
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01631829 (ISSN) |
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Cited By (since 1996): 5; Export Date: 17 April 2009; Source: Scopus; CODEN: PRBMD; Language of Original Document: English; Correspondence Address: Maiorov, B.; Centro At |
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BT @ osquigui @ |
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372 |
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Luzuriaga, J. |
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Sphere on a vibrating reed for measurements of turbulence in superfluid helium |
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Journal Article |
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2000 |
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Journal of Alloys and Compounds |
Abbreviated Journal |
J Alloys Compd |
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265-268 |
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Cantilever beams; Computational methods; Laminar flow; Oscillators (electronic); Phase transitions; Turbulent flow; Vibrations (mechanical); Oscillating spheres; Spherical geometries; Vibrating reeds; Superfluid helium |
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A modification of the vibrating reed, in which a massive sphere is made to oscillate at the end of a cantilevered beam, has been used for measurements in superfluid helium. The apparatus operates in the same way as a conventional vibrating reed with capacitive detection and drive. However, when operating submerged in the liquid, the frequency changes give information on the superfluid fraction, and the dissipation can be used to obtain information on the change of liquid flow, from laminar to turbulent. The spherical geometry allows an exact calculation of all parameters in the laminar regime, so departures due to the turbulence can be better quantified. The method has been found to work well in practice, and some measurements on the turbulent regime in the superfluid are presented. |
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Elsevier Sequoia SA |
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Buenos Aires, Argent |
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12th International Conference on Internal Friction and Ultrasonic Attenuation in Solids (ICIFUAS-12) |
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310 |
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1-2 |
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09258388 (ISSN) |
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Conference code: 57483; Export Date: 28 April 2009; Source: Scopus; CODEN: JALCE; doi: 10.1016/S0925-8388(00)00962-2; Language of Original Document: English; Correspondence Address: Luzuriaga, Javier; Centro Atomico Bariloche Bariloche, Argentina; Sponsors: ABDUS SALAM International Centre for Theoretical Physics; Centre for Industrial Research (CINI); Comision Nacional de Actividades Espaciales (CONAE) |
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478 |
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Steren, L.B.; Sirena, M.; Guimpel, J. |
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Substrate influence on the magnetoresistance and magnetic order in La0.6Sr0.4MnO3 films |
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2000 |
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JOURNAL OF MAGNETISM AND MAGNETIC MATERIALS |
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211 |
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1-3 |
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28-34 |
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We report structural, magnetic and transport measurements on La0.6Sr0.4MnO3 thin films grown on MgO and TiSrO3 substrates with thickness varying from 5 to 500 nm. We find that the lattice mismatch between substrates and films affects the morphology and induced-strains of the films. We show that these two different effects strongly influence the ferromagnetic order, the metal-insulator transition, the localization of the current carriers and the magnetoresistance of these materials. (C) 2000 Elsevier Science B.V. All rights reserved. |
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0304-8853 |
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ISI:000085772100006 |
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BT @ hernan @ |
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179 |
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Niebieskikwiat, D.; Civale, L.; Balseiro, C.A.; Nieva, G. |
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Nonglassy relaxation by double kinks in YBa2Cu3O7-delta with columnar defects |
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Journal Article |
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2000 |
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PHYSICAL REVIEW B |
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61 |
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10 |
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7135-7141 |
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We present long-term relaxation measurements of the irreversible magnetization in YBa2Cu3O7-delta Single crystals with columnar defects. Within the single vortex pinning regime we find a nonglassy response at intermediate currents, in between the half loops and superkinks glassy regimes. We demonstrate that such behavior is due to double kink excitations whose critical nucleus has a size independent of current, and occur even in the presence of pinning energy dispersion. |
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1098-0121 |
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ISI:000085985800092 |
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BT @ hernan @ |
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229 |
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