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Bi 2 Sr 2 CaCu 2 O 8 (Bi-2212) superconducting nanowires are synthesized by the electrospinning method. Two different precursors were employed to grow the nanowires, a Pb-doped one and an Cu,Ca-enriched one. The granular polycrystalline character was confirmed by scanning electron microscopy and X-ray diffraction measurement.The magnetic and electric properties of the samples were investigated via SQUID magnetometry and four-probe resistance measurements. The superconducting transition temperature of both systems were found to be similar (Pb-doped 84 K, Cu,Caenriched 76 K), but the transition width and the onset of irreversibility were clearly different. The magnetization loops and the resistance data demonstrate that the Cu,Ca-enriched precursor yields samples with better superconducting properties. a)

Using the Roeser–Huber equation, which was originally developed for high temperature superconductors (HTSc) (H. Roeser et al., Acta Astronautica 62 (2008) 733), we present a calculation of the superconducting transition temperatures, T c , of some elements with fcc unit cells (Pb, Al), some elements with bcc unit cells (Nb, V), Sn with a tetragonal unit cell and several simple metallic alloys (NbN, NbTi, the A15 compounds and MgB 2 ). All calculations used only the crystallographic information and available data of the electronic configuration of the constituents. The model itself is based on viewing superconductivity as a resonance effect, and the superconducting charge carriers moving through the crystal interact with a typical crystal distance, x. It is found that all calculated T c -data fall within a narrow error margin on a straight line when plotting ( 2 x ) 2 vs. 1 / T c like in the case for HTSc. Furthermore, we discuss the problems when obtaining data for T c from the literature or from experiments, which are needed for comparison with the calculated data. The T c -data presented here agree reasonably well with the literature data.