Study of coupling loss on bi-columnar BSCCO/Ag tapes by a.c. susceptibility measurements

Coupling losses were studied in composite tapes containing superconducting material in the form of two separate stacks of densely packed filaments embedded in a metallic matrix of Ag or Ag alloy. This kind of sample geometry is quite favorable for studying the coupling currents and in particular the role of superconducting bridges between filaments. By using a.c. susceptibility technique, the electromagnetic losses as function of a.c. magnetic field amplitude and frequency were measured at the temperature T = 77 K for two tapes with different matrix composition. The length of samples was varied by subsequent cutting in order to investigate its influence on the dynamics of magnetic flux penetration. The geometrical factor $\chi_0$ which takes into account the demagnetizing effects was established from a.c. susceptibility data at low amplitudes. Losses vs frequency dependencies have been found to agree nicely with the theoretical model developed for round multifilamentary wires. Applying this model, the effective resistivity of the matrix was determined for each tape, by using only measured quantities. For the tape with pure silver matrix its value was found to be larger than what predicted by the theory for given metal resistivity and filamentary architecture. On the contrary, in the sample with a Ag/Mg alloy matrix, an effective resistivity much lower than expected was determined. We explain these discrepancies by taking into account the properties of the electrical contact of the interface between the superconducting filaments and the normal matrix. In the case of soft matrix of pure Ag, this is of poor quality, while the properties of alloy matrix seem to provoke an extensive creation of intergrowths which can be actually observed in this kind of samples.Comment: 20 pages 11 figure, submitted to Superconductor Science and Technolog

Magneto-Optical and Multiferroic Properties of Transition-Metal (Fe, Co, or Ni)-Doped ZnO Layers Deposited by ALD

ZnO doped with transition metals (Co, Fe, or Ni) that have non-compensated electron spins attracts particular interest as it can induce various magnetic phenomena and behaviors. The advanced atomic layer deposition (ALD) technique makes it possible to obtain very thin layers of doped ZnO with controllable thicknesses and compositions that are compatible with the main microelectronic technologies, which further boosts the interest. The present study provides an extended analysis of the magneto optical MO Kerr effect and the dielectric properties of (Co, Fe, or Ni)-doped ZnO films prepared by ALD. The structural, magneto optical, and dielectric properties were considered in relation to the technological details of the ALD process and the corresponding dopant effects. All doped samples show a strong MO Kerr behavior with a substantial magnetization response and very high values of the Kerr polarization angle, especially in the case of ZnO/Fe. In addition, the results give evidence that Fe-doped ZnO also demonstrates a ferroelectric behavior. In this context, the observed rich and versatile physical nature and functionality open up new prospects for the application of these nanostructured materials in advanced electronic, spintronic, and optical devices

Vortex dynamics and pinning properties analysis of MgB2 bulk samples by ac susceptibility measurements

The flux lines dynamics have been investigated on MgB2 bulk superconductors obtained by reactive liquid infiltration by measuring the ac magnetic susceptibility. The fundamental and third harmonics have been studied as a function of temperature, dc magnetic field, ac field amplitude and frequency. In order to determine the dynamical regimes governing the vortex motion, the experimental results have been compared with susceptibility curves obtained by numerical calculations of the non-linear diffusion equation for the magnetic field. The frequency behaviour of the third harmonic response, that cannot be explained by frequency dependent critical state models, has been related to the current dependence of the flux creep activation energy U(J) in the diffusion coefficient. In this way we have shown that the measured curves are correctly interpreted within the framework of a vortex glass description.Comment: 12 pages, 4 figures, Proceedings of Boromag worksho

Retroperitoneal liposarcoma associated with small plaque parapsoriasis

<p>Abstract</p> <p>Background</p> <p>Extremely rare cases of paraneoplastic syndromes or ectopic production of proteins associated with liposarcoma are reported in literature. Production of Granulocyte-Colony Stimulating Factor, alpha-fetoprotein, paraneoplastic pemphigus and leucocytosis, Acrokeratosis paraneoplastica (Bazex's syndrome) are reported.</p> <p>The present report describes a case of retroperitoneal liposarcoma associated with small plaque parapsoriasis. Our search in the English literature of such a kind of association did not reveal any case reported.</p> <p>Case presentation</p> <p>A 74 year male patient was admitted to our hospital because of the presence of an abdominal mass in right iliac fossa. He also complained of a two-year history of psoriasiform eruptions. The CT scan showed a retroperitoneal pelvic mass. Therefore surgical resection of the tumor was performed. After surgery, the skin eruptions disappeared completely in seven days and so a diagnosis of parapsoriasis syndrome was done.</p> <p>Conclusion</p> <p>Parallel disappearing of skin eruptions after surgery, typical clinical picture and not specific histology of the cutaneous lesions suggest the diagnosis of small plaque parapsoriasis. Therefore we propose to add Small Plaque Parapsoriasis to the list of paraneoplastic syndromes associated to liposarcoma.</p

Enhancement of the high-field critical current density of superconducting MgB2 by proton irradiation

A relatively high critical temperature, Tc, approaching 40 K, places the recently-discovered superconductor magnesium diboride (MgB2) intermediate between the families of low- and copper-oxide-based high-temperature superconductors (HTS). Supercurrent flow in MgB2 is unhindered by grain boundaries, unlike the HTS materials. Thus, long polycrystalline MgB2 conductors may be easier to fabricate, and so could fill a potentially important niche of applications in the 20 to 30 K temperature range. However, one disadvantage of MgB2 is that in bulk material the critical current density, Jc, appears to drop more rapidly with increasing magnetic field than it does in the HTS phases. The magnitude and field dependence of Jc are related to the presence of structural defects that can "pin" the quantised magnetic vortices that permeate the material, and prevent them from moving under the action of the Lorentz force. Vortex studies suggest that it is the paucity of suitable defects in MgB2 that causes the rapid decay of Jc with field. Here we show that modest levels of atomic disorder, induced by proton irradiation, enhance the pinning, and so increase Jc significantly at high fields. We anticipate that chemical doping or mechanical processing should be capable of generating similar levels of disorder, and so achieve technologically-attractive performance in MgB2 by economically-viable routes.Comment: 5 pages, 4 figures, to be published in Nature (in press

Randomized study on the effects of different strategies of intermittent pneumatic compression for lower limb claudication

Riassunto: Studio randomizzato sugli effetti delle differenti strategie della compressione pneumatica intermittente per il trattamento della claudicatio degli arti inferiori. A. Berni, L. Tromba, L. Falvo, F. Tartaglia, M. Sgueglia, S. Blasi, P. Polichetti Introduzione. Lo scopo di questo studio è di valutare l’efficacia di differenti strategie di compressione pneumatica intermittente (IPC) per il trattamento della claudicatio degli arti inferiori. Metodi. Sono stati analizzati in prospettiva cinque gruppi di studio. Gruppo 1: 9 pz non sottoposti ad IPC; gruppo 2: sei pazienti sottoposti ad IPC per un’ora tre volte al giorno per quattro mesi; gruppo 3: sei pazienti sottoposti ad IPC per due ore una volta al giorno per quattro mesi; gruppo 4: sei pazienti sottoposti ad IPC per un’ora tre volte al giorno per due mesi; gruppo 5: sei pazienti sottoposti ad IPC per due ore una volta al giorno per due mesi. Risultati. Tutti i pazienti hanno completato il programma di trattamento e hanno dichiarato una compliance del 33% nel gruppo 2, dell’83% nel gruppo 3, del 66% nel gruppo 4 e del 100% nel gruppo 5. Il picco di velocità sistolica del flusso dell’arteria poplitea è cresciuto oltre i valori base in particolare laddove la durata della terapia è stata di 4 mesi ( gruppo 2 : 85%,gruppo 3 :81% vs gruppo 4:76%;gruppo 5 : 73%). Questi effetti benefici si sono protratti per circa 14 mesi e sono svaniti dopo 14 mesi dalla fine del trattamento con IPC. La distanza assoluta di percorrenza senza claudicatio è cresciuta alla fine del trattamento oltre il 101% nel gruppo 2, del 94% nel gruppo 3, dell’86% nel gruppo 4 e dell’83% nel gruppo 5 ed inoltre è aumentata oltre il valore di base dopo 14 mesi dalla fine della terapia. Nessuna differenza è stata osservata se il trattamento IPC è stato fatto una o tre volte al giorno. Conclusioni. La terapia compressiva pneumatica intermittente effettuata due volte al giorno per quattro mesi ha fornito risultati eccellenti con soddisfacente compliance. Tuttavia questi benefici effetti non sono durevoli e svaniscono a distanza di circa un anno dalla fine del trattamento