7,061 research outputs found
Theory and practice in initial teacher education : the British context
The argument I lead towards in this paper, however, is that while there is indeed a theory-practice problem, conventional diagnoses and associated solutions, far from solving the problem may well have exacerbated it. I shall argue that we need a more comprehensive diagnosis, basic to which must be an understanding of the assumptions which course structures in teacher education institutions have embodied and an honesty on the part of all of us - teacher educators, teachers and administrators - about the extent to which our own assumptions, attitudes and practices might hinder rather than help our student-teachers to make that vital theory-practice synthesis. I write about the context I know best, that in Britain. I make no comparisons with or extrapolations to the Maltese context: that is for others to do.peer-reviewe
Information transfer by quantum matterwave modulation
Classical communication schemes that exploit wave modulation are the basis of
the information era. The transfer of information based on the quantum
properties of photons revolutionized these modern communication techniques.
Here we demonstrate that also matterwaves can be applied for information
transfer and that their quantum nature provides a high level of security. Our
technique allows transmitting a message by a non-trivial modulation of an
electron matterwave in a biprism interferometer. The data is encoded by a Wien
filter introducing a longitudinal shift between separated matterwave packets.
The transmission receiver is a delay line detector performing a dynamic
contrast analysis of the fringe pattern. Our method relies on the Aharonov-Bohm
effect and has no light optical analog since it does not shift the phase of the
electron interference. A passive eavesdropping attack will cause decoherence
and terminating the data transfer. This is demonstrated by introducing a
semiconducting surface that disturbs the quantum state by Coulomb interaction
and reduces the contrast. We also present a key distribution protocol based on
the quantum nature of the matterwaves that can reveal active eavesdropping
The encapsulation selectivity for anionic fission products imparted by an electride
The nanoporous oxide 12CaO•7Al2O3 (C12A7) can capture large concentrations of extra-framework species inside its nanopores, while maintaining its thermodynamical stability. Here we use atomistic simulation to predict the efficacy of C12A7 to encapsulate volatile fission products, in its stoichiometric and much more effective electride forms. In the stoichiometric form, while Xe, Kr and Cs are not captured, Br, I and Te exhibit strong encapsulation energies while Rb is only weakly encapsulated from atoms. The high electronegativities of Br, I and Te stabilize their encapsulation as anions. The electride form of C12A7 shows a significant enhancement in the encapsulation of Br, I and Te with all three stable as anions from their atom and dimer reference states. Successive encapsulation of multiple Br, I and Te as single anions in adjacent cages is also energetically favourable. Conversely, Xe, Kr, Rb and Cs are unbound. Encapsulation of homonuclear dimers (Br2, I2 and Te2) and heteronuclear dimers (CsBr and CsI) in a single cage is also unfavourable. Thus, C12A7 offers the desirable prospect of species selectivity
Encapsulation of heavy metals by a nanoporous complex oxide 12CaO · 7Al<sub>2</sub> O<sub>3</sub>
The nanoporous oxide 12CaO ⋅ 7Al2O3 (C12A7) offers the possibility of capturing large concentrations of environmentally damaging extra-framework species in its nanopores. Using density functional theory with a dispersion correction, we predict the structures and energetics of some heavy metals (Cr, Ni, Cu, Zn, Cd, Hg, and Pb) trapped by the stoichiometric and electride form of C12A7. In the stoichiometric form, while Zn, Cd, Hg, and Pb are encapsulated weakly, Cr, Ni, and Cu exhibit strong encapsulation energies. The electride form of C12A7 shows a significant enhancement in the encapsulation of Cr, Ni, Cu, and Pb. Successive encapsulation of multiple Cr, Ni, Cu, and Pb as single species in adjacent cages of C12A7 is also energetically favorable
Threshold Resummation for Dark-Matter Production at the LHC
We derive precision predictions for the production of dark-matter particles
recoiling against a jet with large transverse momentum at the LHC. The
dark-matter fermions are described within a simplified model and couple to the
Standard Model via a vector mediator. Our predictions for the mono-jet
signature include the resummation of the leading and next-to-leading threshold
logarithms. The corresponding matching coefficient is evaluated at NLO. The
resummed result is matched to the fixed-order NLO cross section obtained from
the MadGraph framework. We discuss numerical results for several benchmark
scenarios at the LHC.Comment: 19 pages, 3 figure
Spin Seebeck and Spin Nernst Effects of Magnons in Noncollinear Antiferromagnetic Insulators
Our joint theoretical and computer experimental study of heat-to-spin
conversion reveals that noncollinear antiferromagnetic insulators are promising
materials for generating magnon spin currents upon application of a temperature
gradient: they exhibit spin Seebeck and spin Nernst effects. Using Kubo theory
and spin dynamics simulations, we explicitly evaluate these effects in a single
kagome sheet of potassium iron jarosite, KFe(OH)(SO), and
predict a spin Seebeck conversion factor of at a
temperature of .Comment: 6 pages, 3 figure
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