Studies of cracking behavior in melt-processed YBCO bulk superconductors

An important phenomenon in bulk superconductors fabricated by top-seeded-melt growth (TSMG) is the formation of cracks due to the inherent brittleness of the YBa2Cu3O7-δ (Y-123) phase matrix. These form during the fabrication of the superconducting monolith and play an important role in the limitation of current flow. However, cracks may also form during cooling cycles of the sample to liquid nitrogen temperatures. In this investigation, macrocracks along the c-direction, in particular were analyzed microscopically before and after cooling. In addition we attempt to resolve the c-axis macrocrack formation pattern using the magnetoscan technique

Epitaxial LaFeAsOF thin films grown by pulsed laser deposition

Superconducting and epitaxially grown LaFeAsOF thin films were successfully prepared on (001)-oriented LaAlO3 substrates using pulsed laser deposition. The prepared thin films show exclusively a single in-plane orientation with epitaxial relation (001)[100] parallel to (001)[100] and a FWHM value of 1deg. Furthermore, resistive measurement of the superconducting transition temperature revealed a Tc90 of 25K with a high residual resistive ratio of 6.8. The applied preparation technique, standard thin film pulsed laser deposition at room temperature in combination with a subsequent post annealing process, is suitable for fabrication of high quality LaFeAsO1-xFx thin films. A high upper critical field of 76.2 T was evaluated for magnetic fields applied perpendicular to the c-axis and the anisotropy was calculated to be 3.3 assuming single band superconductivity.Comment: 6 pages, 4 Figure

Smart cities ranking: an effective instrument for the positioning of cities?

Because of radical economic and technological changes cities are facing growing competition for investors, tourists, qualified labour or international events over the last decades (see Begg 1999). As a consequence city rankings have experienced a remarkable boom: On the one hand the comparison of cities can support investors in their choice of location, on the other hand it can be an important guide for the cities to judge their strengths and weaknesses and to define their goals and strategies for future development and better positioning in the urban system. However, there is some evidence that the discussion of city rankings is mainly concentrated on the final ranks totally neglecting (1) the methods and indicators used (see Schönert 2003) resp. (2) its purpose and effectiveness for strategic planning aiming at the strengthening of the position to be gained. In front of this development, this paper concentrates first on the question what are the basic characteristics of national and international city rankings. Correspondingly, a selected number of city rankings are analyzed in order to identify different types of such rankings. Thereby, the number and features of the indicators used in these rankings as well as their methods of sequencing is described systematically. The sample of indicators and the complexity of the ranking approach itself constitute the base for a quality assessment of city rankings discussed within this paper. In particular, an own ranking approach ("European Smart Cities") is described. In the second part, the paper concentrates on the question how cities cope with the results and what are typical reactions of local governments and stakeholders. For providing insight into the way cities respond, it is described how they try to make use of their results to city rankings respectively how they reflect on the strengths and weaknesses revealed in the study. In this context different urban strategies for steering development and processes of learning in general, but especially with respect to urban planning and marketing, are discussed within this paper. Answering these questions the paper concludes in proposals for making city rankings a more significant and effective instrument for steering economic, social and spatial processes in cities: recommendations for researchers and analysts dealing with the design and methodology of city rankings on the one hand and for local governments and stakeholders concerning the reasonable handling of results on the other hand are formulated.Peer Reviewe

Smart cities ranking: an effective instrument for the positioning of cities?

Because of radical economic and technological changes cities are facing growing competition for investors, tourists, qualified labour or international events over the last decades (see Begg 1999). As a consequence city rankings have experienced a remarkable boom: On the one hand the comparison of cities can support investors in their choice of location, on the other hand it can be an important guide for the cities to judge their strengths and weaknesses and to define their goals and strategies for future development and better positioning in the urban system. However, there is some evidence that the discussion of city rankings is mainly concentrated on the final ranks totally neglecting (1) the methods and indicators used (see Schönert 2003) resp. (2) its purpose and effectiveness for strategic planning aiming at the strengthening of the position to be gained. In front of this development, this paper concentrates first on the question what are the basic characteristics of national and international city rankings. Correspondingly, a selected number of city rankings are analyzed in order to identify different types of such rankings. Thereby, the number and features of the indicators used in these rankings as well as their methods of sequencing is described systematically. The sample of indicators and the complexity of the ranking approach itself constitute the base for a quality assessment of city rankings discussed within this paper. In particular, an own ranking approach ("European Smart Cities") is described. In the second part, the paper concentrates on the question how cities cope with the results and what are typical reactions of local governments and stakeholders. For providing insight into the way cities respond, it is described how they try to make use of their results to city rankings respectively how they reflect on the strengths and weaknesses revealed in the study. In this context different urban strategies for steering development and processes of learning in general, but especially with respect to urban planning and marketing, are discussed within this paper. Answering these questions the paper concludes in proposals for making city rankings a more significant and effective instrument for steering economic, social and spatial processes in cities: recommendations for researchers and analysts dealing with the design and methodology of city rankings on the one hand and for local governments and stakeholders concerning the reasonable handling of results on the other hand are formulated.Peer Reviewe

Lessons from Oxypnictide Thin Films

First experiments on the growth of oxypnictide F-doped LaFeAsO thin films indicated an incomplete normal-to-superconducting transition and offered a work programme challenging to overcome possible difficulties in their fabrication. In this regard the possibility of an all in-situ epitaxial growth appeared to be a matter of time and growth parameters. The following review clarifies that F-doped oxypnictide thin films are extremely difficult to grow by in-situ PLD due to the formation of very stable impurity phases such as oxyfluorides (LaOF) and oxides (La2O3) and the loss of stoichiometry possibly due to incongruent evaporation of the target or re-evaporation of volatile elements at the substrate surface. However, the review also demonstrates that the employed two-step fabrication process for oxypnictide thin films has been successfully applied in the preparation of clean polycrystalline as well as of epitaxial thin films. Fundamental investigations on the upper critical field, its temperature dependence and its anisotropy contributed to an understanding of multiband superconductivity in oxypnictides.Comment: accepted, pre-print versio

Basic studies for sterile filtration processing of therapeutic protein formulations

The sterilization of protein formulations by filtration was investigated. The influence of process conditions (e.g. temperature) on filter fouling, protein adsorption and scale-up of the filtration process are examined

BaFe2As2/Fe bilayers with [001]-tilt grain boundary on MgO and SrTiO3 bicrystal substrates

Co-doped BaFe2As2 (Ba-122) can be realized on both MgO and SrTiO3 bicrystal substrates with [001]-tilt grain boundary by employing Fe buffer layers. However, an additional spinel (i.e. MgAl2O4) buffer between Fe and SrTiO3 is necessary since an epitaxial, smooth surface of Fe layer can not be grown on bare SrTiO3. Both types of bicrystal films show good crystalline quality.Comment: Accepted for the ISS2012 Proceedins, a special issue of Physics Procedi