610 research outputs found

    Forgiving abuse - an ethical critique

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    This article argues that most Christian understandings and practices of forgiveness have lost the ethical framework that gives forgiveness meaning and makes forgiveness effective as a means of resolving the effects of abuse on individuals, communities and the abuser. From the context of a number of practical cases, it explores common Christian misconceptions about forgiveness, deconstructs common Christian practices, and offers a number of conditions that need to be present if forgiveness is to be recovered as an ethical action. The traditional Samoan practice of Ifonga is explored as an example of a communal and ethical means of redressing wrong within which forgiveness is embodied

    The ecology of writing and the shaping of early Christianity

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    Editorial: Replacing religion

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    Robust non-adiabatic molecular dynamics for metals and insulators

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    We present a new formulation of the correlated electron-ion dynamics (CEID) scheme, which systematically improves Ehrenfest dynamics by including quantum fluctuations around the mean-field atomic trajectories. We show that the method can simulate models of non-adiabatic electronic transitions, and test it against exact integration of the time-dependent Schroedinger equation. Unlike previous formulations of CEID, the accuracy of this scheme depends on a single tunable parameter which sets the level of atomic fluctuations included. The convergence to the exact dynamics by increasing the tunable parameter is demonstrated for a model two level system. This algorithm provides a smooth description of the non-adiabatic electronic transitions which satisfies the kinematic constraints (energy and momentum conservation) and preserves quantum coherence. The applicability of this algorithm to more complex atomic systems is discussed.Comment: 36 pages, 5 figures. Accepted for publication in Journal of Chemical Physic

    Power dissipation in nanoscale conductors: classical, semi-classical and quantum dynamics

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    Modelling Joule heating is a difficult problem because of the need to introduce correct correlations between the motions of the ions and the electrons. In this paper we analyse three different models of current induced heating (a purely classical model, a fully quantum model and a hybrid model in which the electrons are treated quantum mechanically and the atoms are treated classically). We find that all three models allow for both heating and cooling processes in the presence of a current, and furthermore the purely classical and purely quantum models show remarkable agreement in the limit of high biases. However, the hybrid model in the Ehrenfest approximation tends to suppress heating. Analysis of the equations of motion reveals that this is a consequence of two things: the electrons are being treated as a continuous fluid and the atoms cannot undergo quantum fluctuations. A means for correcting this is suggested

    Plato: a localised orbital based density functional theory code

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    The Plato package allows both orthogonal and non-orthogonal tight-binding as well as density functional theory (DFT) calculations to be performed within a single framework. The package also provides extensive tools for analysing the results of simulations as well as a number of tools for creating input files. The code is based upon the ideas first discussed in Sankey and Niklewski (1989) [1] with extensions to allow high-quality DFT calculations to be performed. DFT calculations can utilise either the local density approximation or the generalised gradient approximation. Basis sets from minimal basis through to ones containing multiple radial functions per angular momenta and polarisation functions can be used. Illustrations of how the package has been employed are given along with instructions for its utilisation

    Validity and practical utility of accelerometry for the measurement of in-hand physical activity in horses

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    Background: Accelerometers are valid, practical and reliable tools for the measurement of habitual physical activity (PA). Quantification of PA in horses is desirable for use in research and clinical settings. The objective of this study was to evaluate a triaxial accelerometer for objective measurement of PA in the horse by assessment of their practical utility and validity. Horses were recruited to establish both the optimal site of accelerometer attachment and questionnaire designed to explore owner acceptance. Validity and cut-off values were obtained by assessing PA at various gaits. Validation study- 20 horses wore the accelerometer while being filmed for 10 min each of rest, walking and trotting and 5 mins of canter work. Practical utility study- five horses wore accelerometers on polls and withers for 18 h; compliance and relative data losses were quantified. Results: Accelerometry output differed significantly between the four PA levels (P <0•001) for both wither and poll placement. For withers placement, ROC analyses found optimal sensitivity and specificity at a cut-off of <47 counts per minute (cpm) for rest (sensitivity 99.5 %, specificity 100 %), 967–2424 cpm for trotting (sensitivity 96.7 %, specificity 100 %) and ≥2425 cpm for cantering (sensitivity 96.0 %, specificity 97.0 %). Attachment at the poll resulted in optimal sensitivity and specificity at a cut-off of <707 counts per minute (cpm) for rest (sensitivity 97.5 %, specificity 99.6 %), 1546–2609 cpm for trotting (sensitivity 90.33 %, specificity 79.25 %) and ≥2610 cpm for cantering (sensitivity 100 %, specificity 100 %) In terms of practical utility, accelerometry was well tolerated and owner acceptance high. Conclusion: Accelerometry data correlated well with varying levels of in-hand equine activity. The use of accelerometers is a valid method for objective measurement of controlled PA in the horse

    Classical and quantum calculations of the temperature dependence of the free energy of argon

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    The free energy is central to statistical mechanics and thermodynamics, and its accurate calculation via. computational modelling is important for a large number of applications, especially when its experimental value is hard to obtain. Several established and general methods for calculating the Helmholtz free energy across different length scales, including continuum, atomistic and quantum mechanical, are compared and analyzed. A computational approach is then proposed to calculate the temperature dependences of internal energy and absolute Helmholtz free energy for solid and liquid phases with the coupling of thermodynamic integration (TI) and harmonic approximation calculations from both classical molecular dynamics (MD) and density functional theory (DFT). We use the Lennard-Jones system as an example (i.e. argon) for the demonstration of the approach. It is observed that the free energy transits smoothly from being describable by the harmonic approximation to including anharmonic effects at a transition temperature around 0.56 Tm; below this temperature, the quantum behavior of atoms is important. At higher temperatures (T > 0.56 Tm), the TI and harmonic approximation results for the Helmholtz free energy functions become increasingly divergent with the increase of temperature. This work demonstrates that a multiscale approach employing TI, MD, and DFT can provide accurate calculations of the temperature dependence of absolute Helmholtz free energy for both solid and liquid phases

    Density-functional study of adsorption of Co on Si(100)

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    We have studied the stable sites for Co both on the surface of Si(100) and subsurface by using ab initio methods. We show that the most stable surface site for Co is situated in the dimer trenches (the low site). The subsurface sites that we study are all found to be more stable than the most stable surface site. The most stable subsurface site is the under-dimer site. The most stable site of all is, however, the dimer vacancy site formed by removing the dimer above the cobalt in the under-dimer site
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