Intraplanar couplings in the CuO_2 lattice of cuprate superconductors

We have investigated the doping dependencies of the basal areas in single-layer high-T_c cuprates La_{2-x}Sr_xCuO_4 and HgBa_2CuO_x, as well as in two-layer Y_{1-y}Ca_yBa_2Cu_3O_x and HgBa_2CaCu_2O_x. The basal areas not only tend to shrink on hole doping, as expected from single electron quantum chemistry, but exhibit also a "bulge'' around optimum doping. We attribute the "bulge'' to the effects of the strongly correlated quantum liquid on the CuO_2 lattice, rendering it nearly incompressible around optimum doping, but highly compressible in the weakly overdoped regime. Inhomogenous doping cannot account for this anomaly in the electronic compressibility of the CuO_2 lattice.Comment: 2 pages, 2 figures, to appear in Physica C (Proc. M2S-HTSC-VII

The puzzle of regulatory competition

Our understanding of international competition in regulatory policies has not progressed much because conventional theories lead to a bewildering range of conclusions. Empirical evidence has shown the limitations of simplistic models. Fresh work should overcome the obsession with ‘races’ and ‘final outcomes’ of conventional theoretical approaches and start modelling real-world mechanisms of regulatory competition. The first part of the article shows the limitations of conventional theories. The second introduces eight problems that explanations of international regulatory competition should address. It also discusses how the articles presented here contribute to the solution to problematic aspects of the puzzle. The conclusion reports results achieved in terms of key concepts of regulatory competition, sequences of cooperation and competition, the role of non-unitary actors in networked regulatory action, and why regulatory competition is still limited, both in the EU and in transatlantic relations

Effect of Sr substitution on superconductivity in Hg2(Ba1-ySry)2YCu2O8-d (part2): bond valence sum approach of the hole distribution

The effects of Sr substitution on superconductivity, and more particulary the changes induced in the hole doping mechanism, were investigated in Hg2(Ba1-ySry)2YCu2O8-d by a "bond valence sum" analysis with Sr content from y = 0.0 to y = 1.0. A comparison with CuBa2YCu2O7-d and Cu2Ba2YCu2O8 systems suggests a possible explanation of the Tc enhancement from 0 K for y = 0.0 to 42 K for y = 1.0. The charge distribution among atoms of the unit cell was determined from the refined structure, for y = 0.0 to 1.0. It shows a charge transfer to the superconducting CuO2 plane via two doping channels pi(1) and pi(2), i.e. through O2(apical)-Cu and Ba/Sr-O1 bonds respectively.Comment: 13 pages, 5 figures, accepted for publication in Journal of Physics: Condensed Matte

Tra finzione e realtà. la conplancha per Roberto d'Angiò, una voce per un re immaginato

Il saggio propone una nuova lettura della conplancha in morte di Roberto d’Angiò (†1343), trascritta nel secondo quaderno del ms. Paris, BnF, fr. 1049, codice miscellaneo membranaceo del secondo quarto del secolo XIV. La linea principale dello studio considera l’accordo del testo poetico con la miniatura istoriata che lo accompagna una sorta di manifesto promozionale, assimilabile in parallelo alla ben nota politica di propaganda di legittimità dinastica adottata dalla prima casa angioina fin dagli albori della sua instaurazione. La rappresentazione della incoronazione del giovane Andrea d’Ungheria da parte del re morente è infatti inconciliabile con la realtà documentata dai fatti. L’ipotesi avanzata dallo studio è che la palese falsificazione storica offerta dal testo e illustrata dalla vignetta intendesse esprimere una precisa posizione politica, sostenuta dalla fazione provenzale capeggiata dai de Baux, a favore di una linea ereditaria maschile della contea di Provenza e del Regno. La conplancha è così inserita nel turbolento clima delle lotte per il diritto di successione al trono accesosi alla morte del sovrano angioino. Ulteriori linee di indagine riguardano la particolare collocazione del testo lirico-narrativo nello spazio trobadorico trecentesco. Sia la forma metrica che la struttura narrativa consentono di mettere in relazione il componimento con la contigua tradizione italiana del ‘lamento storico’, che in quegli stessi anni si esprimeva in serventese, e del cantare d’argomento politico, del quale sono individuabili i tipici procedimenti retorico-narrativi. Peculiarità linguistiche e dettagli artistici nello stile figurativo concorrono a precisare le due componenti principali di origine provenzale e napoletana che caratterizzano la composizione

Strongly correlated crystal-field approach to Mott insulator LaCoO3

Our success in description of recent electron-spin-resonance results on Mott insulator LaCoO3, Phys. Rev. B 67 (2003) 172401, lies in taking into account strong electron correlations among d electrons and the relativistic spin-orbit coupling. In the developed by us Quantum Atomistic Solid State Theory (QUASST) we assume that the atomic-like integrity of the 3d^6 system is preserved in the Co^3+ ion in LaCoO3 and that intra-atomic correlations are much stronger than crystal field interactions. We conclude that in LaCoO3 there is no intermediate spin state as came out from band-structure calculations. The excited states originate from the high-spin 5T2g term, being 12 meV above the ground 1A1 state. We are convinced that many-electron CEF approach with strong correlations and the atomic-scale orbital magnetism is physically adequate approach to 3d oxides. Keywords: Mott insulator, crystal field, spin-orbit coupling, LaCoO3Comment: 5 pages, 3 figures in RevTeX

Los vinos ibéricos en Roma (y Ostia) en el Medio Imperio (siglo II ‒ principios del III d. C.). Análisis y revisiones de datos

The excavations in the building known as the Terme di Elagabalo in Rome revealed large amounts of fragments. The amounts of Iberian wine-amphorae found in the Middle Imperial contexts of this site (2nd – early 3rd centuries AD) will be added to those found in other excavations carried out in Rome and Ostia in order to ponder over their presence in both cities during this period. Also, ancient sources will be analyzed so as to identify the quality of these wines (including also the defrutum), leading to a reflection (with theories derived from social sciences) regarding their consumers

Social media and performance measurement systems: towards a new model?

Purpose – The purpose of this paper is to analyse how social media (SM) influence performance measurement systems (PMS), examining changes in measurement methods, performance indicators and their application. Design/methodology/approach – The framework of the research was constructed to cover the technical component of PMS (measurement methods and indicators) and the use of the information obtained from SM. Empirically, the study is based on a set of case studies in eight companies. Findings – The study findings offer a theoretical and empirical framework to evaluate PMS in the era of SM. It provides a classification of SM metrics, key performance indicators correlated to their use within different departments belonging to eight companies, highlighting the benefits and threats of SM information for PMS. Research limitations/implications – The limitation of this study is the diversity of industries included into the multiple-case study. The authors choose cases with the aim of providing a broader view on the impact of SM on PMS. However, the results show the dependency of use and type of measurement on certain industries, requiring future research focused on specific sectors or PMS aspects. Practical implications – The paper provides a map of SM information measurement methods and use, which allows companies to position themselves and examine PMS evolution. Originality/value – The results of the paper propose a holistic model, employing SM as a new variable in PMS. </jats:sec

Learning in the European Union: theoretical lenses and meta-theory

This is the author accepted manuscript. The final version is available from Taylor & Francis via the DOI in this recordThe European Union may well be a learning organization, yet there is still confusion about the nature of learning, its causal structure and the normative implications. In this article we select four perspectives that address complexity, governance, the agency-structure nexus, and how learning occurs or may be blocked by institutional features. They are transactional theory, purposeful opportunism, experimental governance, and the joint decision trap. We use the four cases to investigate how history and disciplinary traditions inform theory; the core causal arguments about learning; the normative implications of the analysis; the types of learning that are theoretically predicted; the meta-theoretical aspects and the lessons for better theories of the policy process and political scientists more generally

Polarization memory in the nonpolar magnetic ground state of multiferroic CuFeO2

We investigate polarization memory effects in single-crystal CuFeO2, which has a magnetically-induced ferroelectric phase at low temperatures and applied B fields between 7.5 and 13 T. Following electrical poling of the ferroelectric phase, we find that the nonpolar collinear antiferromagnetic ground state at B = 0 T retains a strong memory of the polarization magnitude and direction, such that upon re-entering the ferroelectric phase a net polarization of comparable magnitude to the initial polarization is recovered in the absence of external bias. This memory effect is very robust: in pulsed-magnetic-field measurements, several pulses into the ferroelectric phase with reverse bias are required to switch the polarization direction, with significant switching only seen after the system is driven out of the ferroelectric phase and ground state either magnetically (by application of B > 13 T) or thermally. The memory effect is also largely insensitive to the magnetoelastic domain composition, since no change in the memory effect is observed for a sample driven into a single-domain state by application of stress in the [1-10] direction. On the basis of Monte Carlo simulations of the ground state spin configurations, we propose that the memory effect is due to the existence of helical domain walls within the nonpolar collinear antiferromagnetic ground state, which would retain the helicity of the polar phase for certain magnetothermal histories.Comment: 9 pages, 7 figure

Indicators of regulatory quality: final report

Project was part of the Multiannual Programme for Enterprise and Entrepreneurship 2001-2005.Report for DG Enterprise, European Commission, December 2004