576 research outputs found
Giant magnetic enhancement in Fe/Pd films and its influence on the magnetic interlayer coupling
The magnetic properties of thin Pd fcc(001) films with embedded monolayers of
Fe are investigated by means of first principles density functional theory. The
induced spin polarization in Pd is calculated and analyzed in terms of quantum
interference within the Fe/Pd/Fe bilayer system. An investigation of the
magnetic enhancement effects on the spin polarization is carried out and its
consequences for the magnetic interlayer coupling are discussed. In contrast to
{\it e.g.} the Co/Cu fcc(001) system we find a large effect on the magnetic
interlayer coupling due to magnetic enhancement in the spacer material. In the
case of a single embedded Fe monolayer we find aninduced Pd magnetization
decaying with distance from the magnetic layer as ~ with
. For the bilayer system we find a giant magnetic
enhancement (GME) that oscillates strongly due to interference effects. This
results in a strongly modified magnetic interlayer coupling, both in phase and
magnitude, which may not be described in the pure
Ruderman-Kittel-Kasuya-Yoshida (RKKY) picture. No anti-ferromagnetic coupling
was found and by comparison with magnetically constrained calculations we show
that the overall ferromagnetic coupling can be understood from the strong
polarization of the Pd spacer
Students’ perceptions of assessment: a comparative analysis between Portugal and Sweden
This paper aims at investigating students’ perceptions about assessment, especially the ways in which it is put into practice. Data were collected through questionnaires in different programmes in Portugal and Sweden. In total, 173 students from Portugal and 72 from Sweden participated in the study. Findings showed that students had similar ideas about assessment, such as verification of knowledge and learning, tests and grades. Their experiences of assessment methods used varied in the two countries, which can partly be explained by differences in national education systems. A learner-oriented perspective is prominent in the use of assessment methods, but at the same time student influence on assessment is perceived as low in both countries. Implications of the findings are analysed, namely issues regarding a learner-oriented perspective and the effectiveness, influence, trust, times and methods of assessment.Understanding the assessment process, including the concepts and methods used, is essential to educational practice. In recent years new trends on assessment have emerged from an integrated perspective of the teaching, learning and assessment process (Rust 2007). In contrast to summative assessment, which can be perceived as mainly using assessment to certify student achievement (Boud and Falchikov 2006; Hernández 2012), formative assessment supports and monitors the students’ learning, providing continuous feedback during the process (Yorke 2003; Weurlander et al. 2012), and informing them about their performance (Boud 1990; Brown and Knight 1994; Brew et al. 2009). These trends have introduced new methods of assessment (Brew et al. 2009) and more participatory practices, such as self, peer, and co-assessment (Dochy, Segers and Sluijsmans 1999).National Funds through the FCT (Foundation for Science and Technology) and co-financed by European Regional Development Funds (FEDER) through the Competitiveness and Internationalization Operational Program (POCI) through CIEC (Research Centre on Child Studies, of the University of Minho) with the reference POCI-01-0145-FEDER-007562Strategic Project UID/CED/00317/2013CIEC – Research Centre on Child Studies, IE, UMinho (FCT R&D unit 317), Portugalinfo:eu-repo/semantics/publishedVersio
Correlation effects and the high-frequency spin susceptibility of an electron liquid: Exact limits
Spin correlations in an interacting electron liquid are studied in the
high-frequency limit and in both two and three dimensions. The third-moment sum
rule is evaluated and used to derive exact limiting forms (at both long- and
short-wavelengths) for the spin-antisymmetric local-field factor, . In two dimensions is found to diverge as at long wavelengths,
and the spin-antisymmetric exchange-correlation kernel of time-dependent spin
density functional theory diverges as in both two and three dimensions.
These signal a failure of the local-density approximation, one that can be
redressed by alternative approaches.Comment: 5 page
Применение тонкослойной хроматографии для индентификации дифенгидрамина гидрохлорида и прокаина гидрохлорида при их совместном присутствии
ТЕХНОЛОГИЯ ФАРМАЦЕВТИЧЕСКАЯДИМЕДРОЛНОВОКАИНХРОМАТОГРАФИЯ ТОНКОСЛОЙНАЯ /ИС
Pair distribution function in a two-dimensional electron gas
We calculate the pair distribution function, , in a two-dimensional
electron gas and derive a simple analytical expression for its value at the
origin as a function of . Our approach is based on solving the
Schr\"{o}dinger equation for the two-electron wave function in an appropriate
effective potential, leading to results that are in good agreement with Quantum
Monte Carlo data and with the most recent numerical calculations of . [C.
Bulutay and B. Tanatar, Phys. Rev. B {\bf 65}, 195116 (2002)] We also show that
the spin-up spin-down correlation function at the origin, , is mainly independent of the degree of spin polarization of
the electronic system.Comment: 5 figures, pair distribution dependence with distance is calculate
Path Integral Approach to Strongly Nonlinear Composite
We study strongly nonlinear disordered media using a functional method. We
solve exactly the problem of a nonlinear impurity in a linear host and we
obtain a Bruggeman-like formula for the effective nonlinear susceptibility.
This formula reduces to the usual Bruggeman effective medium approximation in
the linear case and has the following features: (i) It reproduces the weak
contrast expansion to the second order and (ii) the effective medium exponent
near the percolation threshold are , , where is the
nonlinearity exponent. Finally, we give analytical expressions for previously
numerically calculated quantities.Comment: 4 pages, 1 figure, to appear in Phys. Rev.
Optomagnetic composite medium with conducting nanoelements
A new type of metal-dielectric composites has been proposed that is
characterised by a resonance-like behaviour of the effective permeability in
the infrared and visible spectral ranges. This material can be referred to as
optomagnetic medium. The analytical formalism developed is based on solving the
scattering problem for considered inclusions with impedance boundary condition,
which yields the current and charge distributions within the inclusions. The
presence of the effective magnetic permeability and its resonant properties
lead to novel optical effects and open new possible applications.Comment: 48 pages, 13 figures. accepted to Phys. Rev. B; to appear vol. 66,
200
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The type and frequency of interactions that occur between staff and children outside in Early Years Foundation Stage settings during a fixed playtime period when there are tricycles available
This study reports on an investigation into adult and child interactions observed in the outdoor play environment in four Local Authority early years foundation stage settings in England. In this instance the common two features across the settings were the presence of tricycles and a timetabled outdoor play period. In total, across the four schools, there were 204 children. The study aimed to gain an understanding of the nature of the dialogues between staff and children, that is, the types of exchange that occurred when either the child approached an adult or the adult approached a child. The most frequent type of utterance was also analysed. The study concludes that adults in these settings spoke more than children and the greatest type of utterance was that of the adult about domestic matters. When the child initiated the conversation there were more extended child utterances than domestic utterances. This may suggest that children wish to be involved in conversations of depth and meaning and that staff need to become aware of how to develop this conversational language with children
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