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Author |
Musolino, N.; Bals, S.; Van Tendeloo, G.; Clayton, N.; Walker, E.; Flukiger, R. |
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Title |
Investigation of (Bi,Pb)2212 crystals : observation of modulation-free phase |
Type |
A1 Journal article |
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Year |
2004 |
Publication |
Physica: C : superconductivity |
Abbreviated Journal |
Physica C |
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Volume |
401 |
Issue |
1-4 |
Pages |
270-272 |
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Keywords |
A1 Journal article; Electron microscopy for materials research (EMAT) |
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Abstract |
We report the complete disappearance of the structural modulation in heavily lead-doped Bi2-xPbxSr2CaCu2O8+delta crystals observed by transmission electron microscopy. Crystals with a nominal lead content of x = 0.8, corresponding to an effective lead content of x = 0.39, yield the non-modulated phase. The superconducting properties of this modulation-free phase (beta phase) have been studied and compared to those of undoped crystals displaying the modulated phase (alpha phase). Magnetisation measurements reveal that the irreversibility field H-irr(T) and relaxation rates are strongly improved within the beta phase. Measurements of the lower critical field, H-cl, show that the anisotropy factor, E, is considerably reduced in the modulation-free crystals. This is the signature of stronger coupling between CuO2 layers which in turn deeply influences the effectiveness of the pinning. These measurements explain the enhanced pinning properties in moderately Pb-doped crystals in which the a phase and P phase coexist. The enhanced pinning is not only due to the alpha/beta interfaces, which act as effective pinning centers: the emergence of modulation-free domains, characterized by a strongly reduced anisotropy, also significantly contribute to this effect. (C) 2003 Elsevier B.V. All rights reserved. |
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Publisher |
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Place of Publication |
Amsterdam |
Editor |
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Wos |
000187852100050 |
Publication Date |
2003-10-17 |
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Series Editor |
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Series Title |
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Abbreviated Series Title |
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Series Volume |
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Series Issue |
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Edition |
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ISSN |
0921-4534; |
ISBN |
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Additional Links |
UA library record; WoS full record; WoS citing articles |
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Impact Factor |
1.404 |
Times cited |
9 |
Open Access |
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Notes |
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Approved |
Most recent IF: 1.404; 2004 IF: 1.072 |
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Call Number  |
UA @ lucian @ c:irua:94809 |
Serial |
1730 |
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Author |
Verberck, B.; Nikolaev, A.V.; Michel, K.H. |
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Title |
Orientational charge density waves and the metal-insulator transition in polymerized KC60 |
Type |
A1 Journal article |
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Year |
2004 |
Publication |
AIP conference proceedings |
Abbreviated Journal |
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Volume |
723 |
Issue |
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Pages |
339-342 |
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Keywords |
A1 Journal article; Condensed Matter Theory (CMT) |
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Abstract |
Polymerized KC60 undergoes a structural phase transition accompanied by a metal-insulator transition around 50 K. To explain the structural aspect, a mechanism involving small orientational deviations of the valence electron density on every C-60 monomer orientational charge density waves (OCDWs) – has already been proposed earlier. In the present work, we address the metal-insulator transition using the OCDW concept. We are inspired by the analogy between a polymer chain exhibiting an OCDW and a linear atomic chain undergoing a static lattice deformation doubling the unit cell: such a deformation implies a band gap at the zone boundary, yielding an insulating state (Peierls instability). Within our view, a similar mechanism occurs in polymerized KC60; the OCDW plays the role of the lattice deformation. We present tight-binding band structure calculations and conclude that the metal-insulator transition can indeed be explained using OCDWs, but that the threedimensionality of the crystal plays an unexpected key role. |
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Place of Publication |
New York |
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Wos |
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Publication Date |
0000-00-00 |
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Series Editor |
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Series Title |
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Abbreviated Series Title |
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Series Volume |
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Series Issue |
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Edition |
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ISSN |
0094-243x |
ISBN |
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Additional Links |
UA library record; WoS full record; |
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Impact Factor |
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Times cited |
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Open Access |
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Notes |
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Approved |
Most recent IF: NA |
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Call Number |
UA @ lucian @ c:irua:94831 |
Serial |
2513 |
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Author |
Kalitzova, M.; Vlakhov, E.; Marinov, Y.; Gesheva, K.; Ignatova, V.A.; Lebedev, O.; Muntele, C.; Gijbels, R. |
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Title |
Effect of high-frequency electromagnetic field on Te+-implanted (001) Si</tex> |
Type |
A1 Journal article |
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Year |
2004 |
Publication |
Vacuum: the international journal and abstracting service for vacuum science and technology |
Abbreviated Journal |
Vacuum |
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Volume |
76 |
Issue |
2-3 |
Pages |
325-328 |
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Keywords |
A1 Journal article; Plasma Lab for Applications in Sustainability and Medicine – Antwerp (PLASMANT) |
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Abstract |
The analysis of high-frequency electromagnetic field (HFEMF) effects on the microstructure and electrical properties of Te+ implanted (0 0 1) Si is reported. Cross-sectional high-resolution transmission electron microscopy (XHRTEM) demonstrates the formation of Te nanoclusters (NCs) embedded in the Si layer amorphized by implantation (a-Si) at fluences greater than or equal to 1 x 10(16) cm(-2). Post-implantation treatment with 0.45 MHz HFEMF leads to enlargement of Te NCs, their diffusion and accumulation at the a-Si surface and formation of laterally connected extended tellurium structures above the percolation threshold, appearing at an ion fluence of 1 x 10(17) cm(-2). AC electrical conductivity measurements show nearly four orders of magnitude decrease of impedance resistivity in this case, which is in good agreement with the results of our structural studies. The results obtained are discussed in terms of the two-phase isotropic spinodal structure. (C) 2004 Elsevier Ltd. All rights reserved. |
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Publisher |
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Place of Publication |
Oxford |
Editor |
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Language |
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Wos |
000224890100048 |
Publication Date |
2004-08-21 |
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Series Editor |
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Series Title |
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Abbreviated Series Title |
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Series Volume |
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Series Issue |
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Edition |
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ISSN |
0042-207X; |
ISBN |
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Additional Links |
UA library record; WoS full record; WoS citing articles |
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Impact Factor |
1.53 |
Times cited |
2 |
Open Access |
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Notes |
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Approved |
Most recent IF: 1.53; 2004 IF: 0.902 |
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Call Number |
UA @ lucian @ c:irua:95105 |
Serial |
814 |
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Author |
Vodolazov, D.; Baelus, B.J.; Peeters, F.M. |
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Title |
Dynamics of the superconducting condensate in the presence of a magnetic field : channelling of vortices in superconducting strips at high currents |
Type |
A1 Journal article |
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Year |
2004 |
Publication |
Physica: C : superconductivity |
Abbreviated Journal |
Physica C |
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Volume |
404 |
Issue |
1-4 |
Pages |
400-404 |
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Keywords |
A1 Journal article; Condensed Matter Theory (CMT) |
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Abstract |
On the basis of the time-dependent Ginzburg-Landau equation we studied the dynamics of the superconducting condensate in a wide two-dimensional sample in the presence of a perpendicular magnetic field and applied current. We could identify two critical currents: the current at which the pure superconducting state becomes unstable (J(c2)(1)) and the current at which the system transits from the resistive state to the superconducting state (J(c1) < J(c2)). The current J(c2) decreases monotonically with external magnetic field, while J(c1) exhibits a maximum at H*. For sufficient large magnetic fields the hysteresis disappears and J(c1) = J(c2) = Jc. In this high magnetic field region and for currents close to Jc the voltage appears as a result of the motion of separate vortices. With increasing current the moving vortices form,channels' with suppressed order parameter along which the vortices can move very fast. This leads to a sharp increase of the voltage. These 'channels' resemble in some respect the phase slip lines which occur at zero magnetic field. (C) 2004 Elsevier B.V. All rights reserved. |
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Corporate Author |
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Thesis |
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Publisher |
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Place of Publication |
Amsterdam |
Editor |
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Language |
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Wos |
000221211500074 |
Publication Date |
2004-02-28 |
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Series Editor |
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Series Title |
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Abbreviated Series Title |
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Series Volume |
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Series Issue |
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Edition |
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ISSN |
0921-4534; |
ISBN |
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Additional Links |
UA library record; WoS full record; WoS citing articles |
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Impact Factor |
1.404 |
Times cited |
16 |
Open Access |
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Notes |
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Approved |
Most recent IF: 1.404; 2004 IF: 1.072 |
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Call Number |
UA @ lucian @ c:irua:95108 |
Serial |
784 |
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Author |
Riva, C.; Escorcia, R.; Peeters, F.M. |
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Title |
Neutral and charged donor in a 3D quantum dot |
Type |
A1 Journal article |
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Year |
2004 |
Publication |
Physica. E: Low-dimensional systems and nanostructures |
Abbreviated Journal |
Physica E |
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Volume |
22 |
Issue |
1-3 |
Pages |
550-553 |
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Keywords |
A1 Journal article; Condensed Matter Theory (CMT) |
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Abstract |
We study the ground and first excited states of the neutral and charged shallow donor system confined in a GaAs quantum well (QW) along one direction and by a parabolic potential in the plane perpendicular to the QW. The influence of an external perpendicular magnetic field and of the position of the donor on the energy of the states is studied. We investigate the dependence of the ground and excited states of the negatively charged donor on the confinement potential and external magnetic field. When the donor is displaced from the center of the QW the presence of the lateral confinement shifts the magnetic field induced angular momentum transitions and shifts the unbinding to higher magnetic field. (C) 2003 Published by Elsevier B.V. |
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Thesis |
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Publisher |
North-Holland |
Place of Publication |
Amsterdam |
Editor |
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Language |
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Wos |
000221140800133 |
Publication Date |
2004-03-05 |
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Series Editor |
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Series Title |
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Abbreviated Series Title |
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Series Volume |
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Series Issue |
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Edition |
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ISSN |
1386-9477; |
ISBN |
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Additional Links |
UA library record; WoS full record; WoS citing articles |
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Impact Factor |
2.221 |
Times cited |
37 |
Open Access |
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Notes |
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Approved |
Most recent IF: 2.221; 2004 IF: 0.898 |
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Call Number |
UA @ lucian @ c:irua:95109 |
Serial |
2295 |
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Author |
Tadić, M.; Peeters, F.M. |
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Title |
Exciton states and oscillator strength in two vertically coupled InP/InGaP quantum discs |
Type |
A1 Journal article |
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Year |
2004 |
Publication |
Journal of physics : condensed matter |
Abbreviated Journal |
J Phys-Condens Mat |
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Volume |
16 |
Issue |
47 |
Pages |
8633-8652 |
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Keywords |
A1 Journal article; Condensed Matter Theory (CMT) |
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Abstract |
Quantum mechanical coupling and strain in two vertically arranged InP/InGaP quantum dots is studied as a function of the size of the dots and the spacer thickness. The strain distribution is determined by the continuum mechanical model, while the single-band effective-mass equation and the multiband k (.) p theory are employed to compute the conduction and valence band energy levels, respectively. The exciton states are obtained from an exact diagonalization approach, and we also compute the oscillator strength for recombination. We found that the light holes are confined by strain to the spacer, which is the reason that the hole states exhibit coupling at much larger distances as compared with the electrons. At small d, the doublet structure of the hole energy levels arises as a consequence of the relocation of the light hole from the matrix to the regions located-outside the stack, close to the dot-matrix interface. When d varies, the exciton ground state exhibits numerous anticrossings with other states, which are related to the changing spatial localization of the hole as a function of d. The oscillator strength of the exciton recombination is strongly reduced in a certain range of spacer thicknesses, which effectively turns a bright exciton state into a dark one. This effect is associated with anticrossings between exciton energy levels. |
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Thesis |
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Publisher |
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Place of Publication |
London |
Editor |
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Language |
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Wos |
000225796800016 |
Publication Date |
2004-11-13 |
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Series Editor |
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Series Title |
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Abbreviated Series Title |
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Series Volume |
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Series Issue |
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Edition |
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ISSN |
0953-8984;1361-648X; |
ISBN |
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Additional Links |
UA library record; WoS full record; WoS citing articles |
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Impact Factor |
2.649 |
Times cited |
13 |
Open Access |
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Notes |
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Approved |
Most recent IF: 2.649; 2004 IF: 2.049 |
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Call Number |
UA @ lucian @ c:irua:99315 |
Serial |
1116 |
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