39 resultados para bound periodicals


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Over the past decade or more there has been a growing concern at the levels of educational underachievement within loyalist working-class areas of Northern Ireland. The inability of both educational and social policy initiatives over the past decade to improve the situation in any meaningful way has raised important questions concerning how the problem can be tackled more effectively. Placing the issue within the theoretical framework of Gramsci’s hegemony, this paper argues that there is a need to better understand the historical nature of the problem and to recognise the political and social forces that have shaped its existence. It argues that there is a need to move away from explaining Protestant underachievement simply by the availability of jobs in Ulster’s industrial past and to place its roots in the complex battle for social, political, and economic power since the 1801 Act of Union.

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The total cross sections for photodetachment of the metastable 1s 22p3 4S° and 1s2s2p3 6S° excited bound states of the negative ion of beryllium are presented for a range of initial photon energies across and beyond the 1s detachment threshold. A multichannel close-coupling R-matrix approximation is used to compute the cross sections, with sophisticated configuration-interaction wavefunctions being used to represent the initial and final states. At present there are no other theoretical or experimental data available with which to compare the cross sections for these two photodetachment processes.

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We calculate near-threshold bound states and Feshbach resonance positions for atom–rigid-rotor models of the highly anisotropic systems Li+CaH and Li+CaF. We perform statistical analysis on the resonance positions to compare with the predictions of random matrix theory. For Li+CaH with total angular momentum J=0 we find fully chaotic behavior in both the nearest-neighbor spacing distribution and the level number variance. However, for J>0 we find different behavior due to the presence of a nearly conserved quantum number. Li+CaF (J=0) also shows apparently reduced levels of chaotic behavior despite its stronger effective coupling. This may indicate the development of another good quantum number relating to a bending motion of the complex. However, continuously varying the rotational constant over a wide range shows unexpected structure in the degree of chaotic behavior, including a dramatic reduction around the rotational constant of CaF. This demonstrates the complexity of the relationship between coupling and chaotic behavior.

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Predicted 20 years ago, positron binding to neutral atoms has not yet been observed experimentally. A scheme is proposed to detect positron-atom bound states by colliding Rydberg positronium (Ps) with neutral atoms. Estimates of the charge-transfer reaction cross section are obtained using the first Born approximation for a selection of neutral atom targets and a wide range of incident Ps energies and principal quantum numbers. We also estimate the corresponding Ps ionization cross section. The accuracy of the calculations is tested by comparison with earlier predictions for charge transfer in Ps collisions with hydrogen and antihydrogen. We describe an existing Rydberg Ps beam suitable for producing positron-atom bound states and estimate signal rates based on the calculated cross sections and realistic experimental parameters. We conclude that the proposed methodology is capable of producing such states and of testing theoretical predictions of their binding energies.

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We show that divisibility of qubit quantum processes implies temporal Tsirelson's bound. We also prove that the classical bound of the temporal Bell's inequality holds for dynamics that can be described by entanglement-breaking channels---a more general class of dynamics than that allowed by classical physics.

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