Measurements of surface impedance of superconductors as a function of frequency in microwave range

We report measurements of the complex resistivity in YBCO and MgB$_2$ thin films over a continuous frequency spectrum in the microwave range, making use of a Corbino disk geometry. The paper mainly focuses on the extraction of the resistivity from raw data, displaying data analysis procedure and its limits of validity. We obtain and show resistivity curves as a function of frequency and temperature denoting a frequency dependent widening of the superconducting transition.Comment: 12 pages, 7 figures. Extended and revised version of cond-mat/0307143 (2003

Surface impedance of superconductive thin films as a function of frequency in microwave range

We report measurements of the complex resistivity in $YBCO$ and $MgB_2$ thin films over a continuous frequency spectrum in the microwave range, making use of a Corbino disk geometry. The paper mainly focuses on the extraction of the resistivity from raw data, displaying data analisys procedure and its limits of validity. We obtain and show resistivity curves as a function of frequency and temperature denoting a frequency dependent widening of the superconductive transition.Comment: 8 pages, Latex, 5 figure

Vortex state microwave response in superconducting cuprates and MgB2_2

We investigate the physics of the microwave response in YBa$_{2}$Cu$_{3}$O$_{7-\delta}$, SmBa$_{2}$Cu$_{3}$O$_{7-\delta}$ and MgB$_{2}$ in the vortex state. We first recall the theoretical basics of vortex-state microwave response in the London limit. We then present a wide set of measurements of the field, temperature, and frequency dependences of the vortex state microwave complex resistivity in superconducting thin films, measured by a resonant cavity and by swept-frequency Corbino disk. The combination of these techniques allows for a comprehensive description of the microwave response in the vortex state in these innovative superconductors. In all materials investigated we show that flux motion alone cannot take into account all the observed experimental features, neither in the frequency nor in the field dependence. The discrepancy can be resolved by considering the (usually neglected) contribution of quasiparticles to the response in the vortex state. The peculiar, albeit different, physics of the superconducting materials here considered, namely two-band superconductivity in MgB$_{2}$ and superconducting gap with lines of nodes in cuprates, give rise to a substantially increased contribution of quasiparticles to the field-dependent microwave response. With careful combined analysis of the data it is possible to extract or infer many interesting quantities related to the vortex state, such as the temperature-dependent characteristic vortex frequency and vortex viscosity, the field dependence of the quasiparticle density, the temperature dependence of the $\sigma$-band superfluid density in MgB$_{2}$Comment: 51 pages, 27 figures, to appear as a book chapter (Nova Science

Indobufen versus Warfarin in the secondary prevention of major vascular events in nonrheumatic atrial fibrillation

..Background and Purpose The results of a large prospective randomized trial have shown the efficacy of oral anticoagulation in the secondary prevention of major vascular events in patients with nonrheumatic atrial fibrillation (NRAF); less well established is the role of antiplatelet agents. The present study compared the effects of indobufen, a reversible inhibitor of platelet cyclooxygenase, with those of warfarin in this setting. Methods A total of 916 patients with NRAF and a recent (≤15 days) cerebral ischemic episode were admitted to this multicenter, randomized study, during which they were treated with either indobufen (100 or 200 mg BID) or warfarin (to obtain an international normalized ratio of 2.0 to 3.5) for 12 months. The two groups (462 on indobufen and 454 on warfarin) were well balanced in terms of their main baseline characteristics. The primary outcome of the study was the combined incidence of nonfatal stroke (including intracerebral bleeding), pulmonary or systemic embolism, nonfatal myocardial infarction, and vascular death. Results At the end of follow-up, the incidence of primary outcome events was 10.6% in the indobufen group (95% confidence interval, 7.7% to 13.5%) and 9.0% in the warfarin group (95% confidence interval, 6.3% to 11.8%), with no statistically significant difference between treatments. The frequency of noncerebral major bleeding complications was low: only four cases (0.9%) of gastrointestinal bleeding were observed, all of them in the warfarin group. Conclusions We conclude that, within the limitations of its design, this study may help the medical community in devising appropriate antithrombotic strategies for NRAF patients for whom oral anticoagulants are contraindicated or do not represent a feasible approach to treatment

Avaliação temporal de genótipos de girassol no cerrado do Distrito Federal em safrinha.

Resumo: Com o objetivo de avaliar o comportamento agronômico de genótipos de girassol no cerrado do Distrito Federal, foram conduzidos ensaios na safrinha dos anos de 2011 e 2012, em delineamento experimental de blocos ao acaso com quatro repetições. Os caracteres avaliados foram rendimento de grãos, tamanho do capítulo, peso de mil aquênios, altura de plantas, dias para floração inicial e teor de óleo. Foram observadas diferenças altamente significativas entre os genótipos para todas as características morfoagronômicas avaliadas. Em relação ao rendimento de grãos, em 2011, esta característica variou de 2.376 kg.ha (SRM 822) a 5.490 kg.ha (BRSG 30) e, em 2012, de 2.306 kg.ha (V60415) a 4.412 kg.ha (SYN 039A). Materiais genéticos promissores para as características agronômicas avaliadas foram identificados no trabalho, podendo ser explorados comercialmente em condições de safrinha do Cerrado. Abstract : Aiming to evaluate the agronomic performance of sunflower genotypes in the Savannah of the Federal District, experiments were conducted in the second crop of 2011 and 2012 in a randomized block design with four replications. The characters evaluated were grain yield, head length, weight of thousand achenes, plant height, days to initial flowering and oil content. Differences among genotypes for all traits morphoagronomic were highly significant. In relation to grain yield in 2011, this feature[ ranged from 2376 kg.ha (SRM 822) to 5,490 kg.ha (BRSG 30) and, in 2012, from 2,306 kg.ha (V60415) to 4412 kg.ha (SYN 039A). Genetic materials promising for agronomic traits were identified in work and can be commercially exploited in the second crop of Savannah

Culture change in a professional sports team: Shaping environmental contexts and regulating power

Although high performing cultures are crucial for the enduring success of professional sport performance teams, theoretical and practical understanding of how they are established and sustained is lacking. To develop knowledge in this area, a case study was undertaken to examine the key mechanisms and processes of a successful culture change programme at English Rugby Union’s Leeds Carnegie. Exploring the change process from a 360 degree perspective, semi-structured interviews were conducted with team management, one specialist coach, six players, and the CEO. Analysed and explained through decentred theory, results revealed that culture change was effectively facilitated by team management: a) subtly and covertly shaping the physical, structural, and psychosocial context in which support staff and players made performance-impacting choices, and b) regulating the ‘to and fro’ of power which characterises professional sport performance teams. Decentred theory is also supported as an effective framework for culture change study

Manageable creativity

This article notes a perception in mainstream management theory and practice that creativity has shifted from being disruptive or destructive to 'manageable'. This concept of manageable creativity in business is reflected in a similar rhetoric in cultural policy, especially towards the creative industries. The article argues that the idea of 'manageable creativity' can be traced back to a 'heroic' and a 'structural' model of creativity. It is argued that the 'heroic' model of creativity is being subsumed within a 'structural' model which emphasises the systems and infrastructure around individual creativity rather than focusing on raw talent and pure content. Yet this structured approach carries problems of its own, in particular a tendency to overlook the unpredictability of creative processes, people and products. Ironically, it may be that some confusion in our policies towards creativity is inevitable, reflecting the paradoxes and transitions which characterise the creative process