753 resultados para Période réfractaire effective
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Bornite, Cu5FeS4, is a naturally-occuring mineral with an ultralow thermal conductivity and potential for thermoelectric power generation. We describe here a new, easy and scalable route to synthesise bornite, together with the thermoelectric behaviour of manganese-substituted derivatives, Cu5Fe1-xMnxS4 (0 ≤ x ≤ 0.10). The electrical and thermal transport properties of Cu5Fe1-xMnxS4 (0 ≤ x ≤ 0.10), which are p-type semiconductors, were measured from room temperature to 573 K. The stability of bornite was investigated by thermogravimetric analysis under inert and oxidising atmospheres. Repeated measurements of the electrical transport properties confirm that bornite is stable up to 580 K under an inert atmosphere, while heating to 890 K results in rapid degradation. Ball milling leads to a substantial improvement in the thermoelectric figure of merit of unsusbtituted bornite (ZT = 0.55 at 543 K), when compared to bornite prepared by conventional high-temperature synthesis (ZT < 0.3 at 543 K). Manganese-substituted samples have a ZT comparable to that of unsubstituted bornite.
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The 2014 Graham proposals aimed at reducing recidivism are unlikely to achieve the desired goals. It is argued that due consideration must be had for the future of the rescued entity. Further, both the viability review and the proposed capital structure of the rescued entity must be carefully assessed.
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This article presents observations and discussion of the successful teaching of English to pupils, in English primary schools, for whom English is an additional language (EAL). It draws on research in Year 2 (6/7year old) classes in three inner-city primary schools carried out in 2003 and 2005. Three recognised, effective teachers of literacy were selected for case study; all worked in successful schools where results for literacy, measured by national tests, were in line with or better than national averages. Following analyses of lesson observations and interviews with the teachers, their Headteachers and the EAL co-ordinators in the schools, a number of common elements in their practice emerged. Discussion centres on how these pedagogical features supported effective learning environments for the early literacy development of bilingual children, and on the implications for the practice of teaching English to all pupils.
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This article explores the fine detail of practice by three teachers, recognised as effective teachers of literacy. All three were observed during nine literacy lessons, working with Year 2 (6/7 year olds) classes of successful inner-city primary schools in the South of England. Data collection took place in 2003, just as their schools were moving away from the early prescription of the National Literacy Strategy (NLS), and follow up visits were made in 2005. My initial interest had been in what these three teachers did with the NLS in order to motivate pupils and ensure high pupil attainment. Following observations, interviews and coding of teacher-pupil interaction, it became clear that The NLS Framework for Teaching (DfES, 2001) was not the driver of their success but a valuable vehicle for subtle and intuitive teacher behaviours that grew from a detailed understanding of how children develop as readers and writers. Implications for training student teachers to marry theoretical understanding with the expectations of a prescribed curriculum for literacy are discussed.
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This paper deals with the complex issue of reversing long-term improvements of fertility in soils derived from heathlands and acidic grasslands using sulfur-based amendments. The experiment was conducted on a former heathland and acid grassland in the U.K. that was heavily fertilized and limed with rock phosphate, chalk, and marl. The experimental work had three aims. First, to determine whether sulfurous soil amendments are able to lower pH to a level suitable for heathland and acidic grassland re-creation (approximately 3 pH units). Second, to determine what effect the soil amendments have on the available pool of some basic cations and some potentially toxic acidic cations that may affect the plant community. Third, to determine whether the addition of Fe to the soil system would sequester PO4− ions that might be liberated from rock phosphate by the experimental treatments. The application of S0 and Fe(II)SO4− to the soil was able to reduce pH. However, only the highest S0 treatment (2,000 kg/ha S) lowered pH sufficiently for heathland restoration purposes but effectively so. Where pH was lowered, basic cations were lost from the exchangeable pool and replaced by acidic cations. Where Fe was added to the soil, there was no evidence of PO4− sequestration from soil test data (Olsen P), but sequestration was apparent because of lower foliar P in the grass sward. The ability of the forb Rumex acetosella to apparently detoxify Al3+, prevalent in acidified soils, appeared to give it a competitive advantage over other less tolerant species. We would anticipate further changes in plant community structure through time, driven by Al3+ toxicity, leading to the competitive exclusion of less tolerant species. This, we suggest, is a key abiotic driver in the restoration of biotic (acidic plant) communities.
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This article examines republican arguments for a basic income that turn on a right to exit the labour market. It gives criteria for the maintenance of republican freedom in markets, arguing that a right to exit or effective market power will guarantee republican freedom in markets. The article then considers whether a basic income is either sufficient or necessary to protect republican freedom both in labour markets and elsewhere. If a basic income is necessary to protect republican freedom in the labour market, I argue it is not sufficient to protect that freedom elsewhere. If citizens lack the means to maintain their republican freedom in the labour market, then there may be other spheres of life where they are vulnerable to subordination, whether or not they have a basic income. Some sociological evidence on cultural consumption patterns is presented.
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Purpose – The purpose of this paper is to provide a critical assessment of legal and regulatory impediments to effective governance of public-private partnerships (PPPs) in Kazakhstan. Design/methodology/approach – The qualitative study develops propositions from the PPP literature and then tests them against findings from in-depth interviews. Interviewees have been selected by a purposeful sampling from PPP projects in Kazakhstan as well as from national and regional PPP centres. Findings – The identified barriers to effective PPP management include irregularities in the PPP legal framework, such as lack of legal definition of a PPP and controversy with the government guarantee’s legal status for its long-term payments to partnerships; bureaucratic tariff setting for partnership services; non-existent opportunity for private asset ownership; and excessive government regulation of PPP workers’ wage rates. Practical implications – The partners’ opposing perspectives on a number of PPP issues show that management needs to identify and carefully reconcile stakeholder values in a partnership in order to achieve more effective PPP governance. Practitioners, particularly those in the public agencies, have to be concerned with ways to reduce the government overregulation of the private operators, which is likely to result in greater PPP flexibility in management and, ultimately, higher efficiency in delivering the public services. Originality/value – By elucidating multiple examples of overregulation and PPPs’ inefficiency, the paper demonstrates that the government dominance in PPP management is conceptually inappropriate. Instead, the government should adopt the concept of co-production and manage its relations with the private sector partner in a collaborative fashion.
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The stability of ternary blends of two immiscible homopolymers and a block copolymer compatiblizer depends crucially on the effective interaction between the copolymermonolayers that form between the unlike homopolymer domains. Here, the interaction is calculated for blends involving A and B homopolymers of equal size with ABABdiblock copolymers of symmetric composition using both self-consistent field theory (SCFT) and strong-segregation theory (SST). If the homopolymers are larger than the copolymer molecules, an attractive interaction is predicted which would destroy the blend. This conclusion coupled with considerations regarding the elastic properties of the monolayer suggests that the optimum size of the homopolymer molecules is about 80% that of the copolymer molecule. A detailed examination of the theory demonstrates that the attraction results from the configurational entropy loss of the homopolymer molecules trapped between the copolymermonolayers. We conclude by suggesting how the monolayers can be altered in order to suppress this attraction and thus improve compatiblization.
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Our objective in this work was to test the effects of daily intake of bread produced with partially defatted ground flaxseed on the climacteric symptoms and endometrial thickness of postmenopausal women. A double-blind, placebo-controlled, randomized clinical trial was performed with 38 women who had been postmenopausal for 1-10 y and consumed 2 slices of bread containing 25 g of flaxseed (46 mg lignans) or wheat bran (<1 mg lignans; control) every day for 12 consecutive weeks. The outcome variables were the daily number of hot flashes, the Kupperman Menopausal Index (KMI), and endometrial thickness. The plasma lipid profile (total cholesterol and HDL, LDL, and VLDL cholesterol fractions and triglycerides) and the hormones estradiol, follicle-stimulating hormone, thyroid-stimulating hormone, and free thyroxine also were measured. Food intake was evaluated by means of 2 24-hrecalls, before and after the treatment. Twenty patients in the study group and 18 in the control group completed the study. The general characteristics did not differ between the 2 groups at the start of the study. Both had significant, but similar, reductions in hot flashes and KMI after 3 mo of treatment. Moreover, endometrial thickness was not affected in either group. Our findings clearly show that although flaxseed is safe, its consumption at this level (46 mg lignans/d) is no more effective than placebo for reducing hot flashes and KMI. J. Nutr. 140: 293-297, 2010.
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P>Estimates of effective elastic thickness (T(e)) for the western portion of the South American Plate using, independently, forward flexural modelling and coherence analysis, suggest different thermomechanical properties for the same continental lithosphere. We present a review of these T(e) estimates and carry out a critical reappraisal using a common methodology of 3-D finite element method to solve a differential equation for the bending of a thin elastic plate. The finite element flexural model incorporates lateral variations of T(e) and the Andes topography as the load. Three T(e) maps for the entire Andes were analysed: Stewart & Watts (1997), Tassara et al. (2007) and Perez-Gussinye et al. (2007). The predicted flexural deformation obtained for each T(e) map was compared with the depth to the base of the foreland basin sequence. Likewise, the gravity effect of flexurally induced crust-mantle deformation was compared with the observed Bouguer gravity. T(e) estimates using forward flexural modelling by Stewart & Watts (1997) better predict the geological and gravity data for most of the Andean system, particularly in the Central Andes, where T(e) ranges from greater than 70 km in the sub-Andes to less than 15 km under the Andes Cordillera. The misfit between the calculated and observed foreland basin subsidence and the gravity anomaly for the Maranon basin in Peru and the Bermejo basin in Argentina, regardless of the assumed T(e) map, may be due to a dynamic topography component associated with the shallow subduction of the Nazca Plate beneath the Andes at these latitudes.
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We detail an innovative new technique for measuring the two-dimensional (2D) velocity moments (rotation velocity, velocity dispersion and Gauss-Hermite coefficients h(3) and h(4)) of the stellar populations of galaxy haloes using spectra from Keck DEIMOS (Deep Imaging Multi-Object Spectrograph) multi-object spectroscopic observations. The data are used to reconstruct 2D rotation velocity maps. Here we present data for five nearby early-type galaxies to similar to three effective radii. We provide significant insights into the global kinematic structure of these galaxies, and challenge the accepted morphological classification in several cases. We show that between one and three effective radii the velocity dispersion declines very slowly, if at all, in all five galaxies. For the two galaxies with velocity dispersion profiles available from planetary nebulae data we find very good agreement with our stellar profiles. We find a variety of rotation profiles beyond one effective radius, i.e. rotation speed remaining constant, decreasing and increasing with radius. These results are of particular importance to studies which attempt to classify galaxies by their kinematic structure within one effective radius, such as the recent definition of fast- and slow-rotator classes by the Spectrographic Areal Unit for Research on Optical Nebulae project. Our data suggest that the rotator class may change when larger galactocentric radii are probed. This has important implications for dynamical modelling of early-type galaxies. The data from this study are available on-line.
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We derive a closed form expression for the long wavelength limit of the effective action for hard thermal loops in an external gravitational field. It is a function of the metric, independent of time derivatives. It is compared and contrasted with the static limit, and with the corresponding limits in an external Yang-Mills field. (C) 2009 Elsevier B.V. All rights reserved.
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We present, from first principles, a direct method for evaluating the exact fermion propagator in the presence of a general background held at finite temperature, which can be used to determine the finite temperature effective action for the system. As applications, we determine the complete one loop finite temperature effective actions for (0 + 1)-dimensional QED as well as the Schwinger model. These effective actions, which are derived in the real time (closed time path) formalism, generate systematically all the Feynman amplitudes calculated in thermal perturbation theory and also show that the retarded (advanced) amplitudes vanish in these theories. (C) 2009 Elsevier B.V. All rights reserved.
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we study the one-loop quantum corrections for higher-derivative superfield theories, generalizing the approach for calculating the superfield effective potential. In particular, we calculate the effective potential for two versions of higher-derivative chiral superfield models. We point out that the equivalence of the higher-derivative theory for the chiral superfield and the one without higher derivatives but with an extended number of chiral superfields occurs only when the mass term is contained in the general Lagrangian. The presence of divergences can be taken as an indication of that equivalence. (C) 2009 Elsevier B.V. All rights reserved.