Transport properties of powder-in-tube processed MgB2 tapes

Nickel-sheathed magnesium diboride superconducting tapes have been fabricated by the powder-in-tube method from reacted commercially available powders. At 4.2 K and self field, a transport current density value jc of 105 A/cm2 has been reached over long portions of unsintered monofilamentary tapes. The irreversibility lines both for a magnetic field oriented parallel and perpendicular to the MgB2 superconducting tape have been determined by magnetoresistance measurements, showing some degree of anisotropy. These data are consistent with the X-ray diffraction observation of a slight texturing process of the MgB2 grains occurring during the cold working procedure. \ua9 2002 Published by Elsevier Science B.V

Thermopower in oxide heterostructures: The importance of being multiple-band conductors

We combine transport experiments, advanced ab initio calculations, and model analysis to determine the thermoelectric power in the two-dimensional electron gas formed at the paradigmatic oxide interface SrTiO3/LaAlO3. We demonstrate that contrary to popular expectation, quantum confinement does not enhance the thermoelectric power of the electron gas at this interface with respect to its corresponding three-dimensional case. Our analysis directly relates the thermopower behavior to band structure characteristics typical of the oxide heterostructure (i.e., on-site and intersite band splitting), furnishing general interpretive prescriptions to search for oxide heterostructures with improved thermoelectric capabilities

(Ba,La)CuO2/CaCuO2 superconducting multilayers: Stabilizing effect of La

Superconducting multilayers, whose growth and structure are determined by the kinetic deposition instead of by thermodynamics, are a powerful tool for investigating high Tc superconductor properties. By means of pulsed laser deposition, we grew ((Ba,La)CuO2+\u3b4)2/(CaCuO2)n superconducting superlattices. Different electrical properties have been observed by increasing La doping in the block layer: in particular, 15%-La substituted samples showed a good metallic behavior in the normal state, underwent a superconducting transition at 70 K and presented a low anisotropy, similar to that of YBCO. \ua9 2002 Elsevier Science B.V. All rights reserved

Magnetic characterization of pressed AG-sheathed BSCCO (2223) tapes

Magnetization measurements were performed with a SQUID magnetometer on a pressed Ag-sheathed BSCCO (2223) tape. The hysteresis loops, analyzed in the framework of the ''Critical State model'' show clear anomalies. The results are explained invoking granularity of the sample, as confirmed by the analysis of the reverse leg of the magnetization. The irreversibility line, measured in the orientations B//c and B perpendicular to c, is also presented

Fluctuation conductivity and magnetoconductivity in 2:2:1:2-phase Bi\ue5f8Sr\ue5f8Ca\ue5f8Cu\ue5f8O epitaxial films

Fluctuation conductivity of epitaxial thin films Bi2Sr2CaCu2O8-delta with and without an applied magnetic field was studied. Obtained results demonstrate the very good agreement with two-dimensional Aslamazov-Larkin theory. In the case of rather weak magnetic field H << H(c2) it was found that all the effect of field reduces to renormalization of critical temperature

Transport property characterization of (Ba, La)CuO2/CaCuO2superconducting multilayers deposited by pulsed laser ablation

Superconducting multilayers, whose growth and structure are determined by the kinetic deposition instead of by thermodynamics, are a powerful tool for investigating high T-c superconductor properties. By means of pulsed laser deposition, we grew superconducting superlattices alternating infinite layer phases, both pure (CaCuO2) and doped ((Ba, La)CuO2+delta), that Supply CuO2 planes and act as charge reservoir blocks, respectively. Oxygen doping, necessary to bring about superconducting behaviour, also introduces a strong charge unbalance, thus making BaCuO2/CaCuO2 multilayers very unstable. By substituting different percentages of La on Ba sites, we tried to stabilize the phase. (Ba1-xLaxCuO2+delta)(2)/(CaCuO2)(n) multilayers have been characterized by structural and transport property measurements. Different electrical properties have been observed by increasing La doping in the block layer; in particular, 15% La substituted samples show good metallic behaviour in the normal state, undergo a superconducting transition at 70 K and present a low anisotropy, similar to that of YBCO

A randomised, blinded, trial of clopidogrel versus aspirin in patients at risk of ischaemic events (CAPRIE). CAPRIE Steering Committee

Many clinical trials have evaluated the benefit of long-term use of antiplatelet drugs in reducing the risk of clinical thrombotic events. Aspirin and ticlopidine have been shown to be effective, but both have potentially serious adverse effects. Clopidogrel, a new thienopyridine derivative similar to ticlopidine, is an inhibitor of platelet aggregation induced by adenosine diphosphate. METHODS: CAPRIE was a randomised, blinded, international trial designed to assess the relative efficacy of clopidogrel (75 mg once daily) and aspirin (325 mg once daily) in reducing the risk of a composite outcome cluster of ischaemic stroke, myocardial infarction, or vascular death; their relative safety was also assessed. The population studied comprised subgroups of patients with atherosclerotic vascular disease manifested as either recent ischaemic stroke, recent myocardial infarction, or symptomatic peripheral arterial disease. Patients were followed for 1 to 3 years. FINDINGS: 19,185 patients, with more than 6300 in each of the clinical subgroups, were recruited over 3 years, with a mean follow-up of 1.91 years. There were 1960 first events included in the outcome cluster on which an intention-to-treat analysis showed that patients treated with clopidogrel had an annual 5.32% risk of ischaemic stroke, myocardial infarction, or vascular death compared with 5.83% with aspirin. These rates reflect a statistically significant (p = 0.043) relative-risk reduction of 8.7% in favour of clopidogrel (95% Cl 0.3-16.5). Corresponding on-treatment analysis yielded a relative-risk reduction of 9.4%. There were no major differences in terms of safety. Reported adverse experiences in the clopidogrel and aspirin groups judged to be severe included rash (0.26% vs 0.10%), diarrhoea (0.23% vs 0.11%), upper gastrointestinal discomfort (0.97% vs 1.22%), intracranial haemorrhage (0.33% vs 0.47%), and gastrointestinal haemorrhage (0.52% vs 0.72%), respectively. There were ten (0.10%) patients in the clopidogrel group with significant reductions in neutrophils (< 1.2 x 10(9)/L) and 16 (0.17%) in the aspirin group. INTERPRETATION: Long-term administration of clopidogrel to patients with atherosclerotic vascular disease is more effective than aspirin in reducing the combined risk of ischaemic stroke, myocardial infarction, or vascular death. The overall safety profile of clopidogrel is at least as good as that of medium-dose aspirin