High-performance Fe(Se,Te) films on chemical CeO2-based buffer layers.

The fabrication of a Fe-based coated conductor (CC) becomes possible when Fe(Se,Te) is grown as an epitaxial film on a metallic oriented substrate. Thanks to the material's low structural anisotropy, less strict requirements on the template microstructure allow for the design of a simplified CC architecture with respect to the REBCO multi-layered layout. This design, though, still requires a buffer layer to promote the oriented growth of the superconducting film and avoid diffusion from the metallic template. In this work, Fe(Se,Te) films are grown on chemically-deposited, CeO2-based buffer layers via pulsed laser deposition, and excellent properties are obtained when a Fe(Se,Te) seed layer is used. Among all the employed characterization techniques, transmission electron microscopy proved essential to determine the actual effect of the seed layer on the final film properties. Also, systematic investigation of the full current transport properties J(θ, H, T) is carried out: Fe(Se,Te) samples are obtained with sharp superconducting transitions around 16 K and critical current densities exceeding 1 MA cm-2 at 4.2 K in self-field. The in-field and angular behavior of the sample are in line with data from the literature. These results are the demonstration of the feasibility of a Fe-based CC, with all the relative advantages concerning process simplification and cost reduction.

Transport current and magnetization of Bi-2212 wires above liquid Helium temperature for cryogen-free applications.

Since the discovery of high temperature superconductors, a possible cryogen-free scenario has always been wished. Nowadays, liquid Helium is running out, and it is likely that the cooling by will be a large part of the costs of any superconducting system. Bi-2212 wires at temperature higher than 4.2 K still show a very high irreversibility field and thus a deep investigation of their properties in such a range of temperature is very useful in order to assess the applicability in high field cryogen-free magnets. Here electrical transport and magnetic properties characterization at variable temperature and magnetic field on our "GDG-processed" wires are reported together with a well-described original approach to calculate the irreversibility field Hirr. This study is devoted to provide reference data on the behaviour of the only isotropic wire for high field application with an eye to the performances at temperatures above 4.2 K.

Pushing the limits of applicability of REBCO coated conductor films through fine chemical tuning and nanoengineering of inclusions.

An outstanding current carrying performance (namely critical current density, Jc) over a broad temperature range of 10-77 K for magnetic fields up to 12 T is reported for films of YBa2Cu3O7-x with Ba2Y(Nb,Ta)O6 inclusion pinning centres (YBCO-BYNTO) and thicknesses in the range of 220-500 nm. Jc values of 10 MA cm-2 were measured at 30 K - 5 T and 10 K - 9 T with a corresponding maximum of the pinning force density at 10 K close to 1 TN m-3. The system is very flexible regarding properties and microstructure tuning, and the growth window for achieving a particular microstructure is wide, which is very important for industrial processing. Hence, the dependence of Jc on the magnetic field angle was readily controlled by fine tuning the pinning microstructure. Transmission electron microscopy (TEM) analysis highlighted that higher growth rates induce more splayed and denser BYNTO nanocolumns with a matching field as high as 5.2 T. Correspondingly, a strong peak at the B||c-axis is noticed when the density of vortices is lower than the nanocolumn density. YBCO-BYNTO is a very robust and reproducible composite system for high-current coated conductors over an extended range of magnetic fields and temperatures.

Epitaxial Growth of SrTiO3 Films on Cube-Textured Cu-Clad Substrates by PLD at Low Temperature Under Reducing Atmosphere.

The growth of epitaxial {001}<100> SrTiO3 (STO) on low-cost cube-textured Cu-based clad substrate at low temperature was carried out by means of pulsed laser deposition (PLD). STO film was deposited in one step under a reducing atmosphere (5% H2 and 95% Ar mixture) to prevent the oxidation of the metal surface. The optimization of PLD parameters leads to a sharpest biaxial texture at a temperature as low as 500 °C and a thickness of 500 nm with a (100) STO layer. The upper limit of highly textured STO thickness was also investigated. The maximum thickness which retains the best quality {001}<100> texture is 800 nm, since the texture is preserved not only through the layer but also on the surface. Atomic force microscopy (AFM) and scanning electron microscopy (SEM) measurements showed that STO films are continuous, dense, and smooth with very low roughness (between 5 and 7 nm). This paper describes the development of STO layer by means of PLD in absence of oxygen throughout the process, suggesting an alternative and effective method for growing highly {001}<100> textured STO layer on low-cost metal substrates.

The chemical structure of the pigments in Ara macao plumage.

Parrots (Psittaciformes) harbor unusually bright, non-carotenoid, feather pigments. We successfully extracted and purified a sufficient quantity of pigment from the red plumage of the Scarlet Macaw (Ara macao) for a partial chemical analysis. The extracts were analyzed by HPLC coupled with UV-VIS and mass spectroscopy before and after total hydrogenation. We found at least four pigment components. We propose a linear polyenal structure comparable with the molecules tetradecahexenal, hexadecaheptenal, octadecaoctenal and eicosanonenal.

Carotenoids in bird plumage: the complement of red pigments in the plumage of wild and captive bullfinch (Pyrrhula pyrrhula).

We have studied the carotenoid pigments in the red plumage of male bullfinch (Pyrrhula pyrrhula) immediately following capture and after the completion of the moult in captivity under dietary control. Astaxanthin, adonirubin, and alpha-doradexanthin, as well as papilioeritrinone and canthaxanthin (in lower amounts) are in every case the dominant carotenoids in the plumage pigment of wild individuals. alpha-Doradexanthin is responsible for the reddish-rose colour, which captive individuals adopt after a diet consisting mainly of lutein as disposable carotenoid. The red pigmentation biogenesis of captive bullfinch is compared with those of other red pigmented Carduelinae in which male individuals usually lose the red colour in captivity, namely Carpodacus roseus, Carpodacus rubricilloides, Uragus sibiricus, Carduelis cannabina, Carduelis flammea, Loxia curvirostra and Pinicola enucleator.

Separation and identification of carotenoids in bird's plumage by high-performance liquid chromatography--diode-array detection.

The coloured feathers of Carduelis spinus (Siskin), C. flammea (Redpoll), Serinus serinus (Serin), Loxia curvirostra (Crossbill), Pinicola enucleator (Grossbeak), Carpodacus roseus (Pallas Rosefinch) and Pyrrhula pyrrhula (Bullfinch) have been extracted with a new procedure using mild conditions (a few minutes at room temperature). After the separation of melanines and proteins, the extracts were analyzed by HPLC-MS and HPLC-UV-Vis. The main components of the pigments were identified in all the species examined; moreover, UV-Vis and MS data were collected also for the minor components. These data suggest that minor components are generally cis isomers accompanying the predominant all-trans isomers.

ST 789 and ST 789 analogs: synthesis and analytical profile.

The procedure followed for the preparation of ST 789 and a series of origin derivatives analogs to ST 789 are described. A complete analytical profile of ST 789 and a concise profile of its analogs are also reported, together the purification methods applied.