Empirical rules are derived that describe the temperature dependence of the infrared absorption s... more Empirical rules are derived that describe the temperature dependence of the infrared absorption spectra of pure diamond for photons of energy hnu=500-4000 cm-1. We show that with increasing temperature in the range 14e) where c=-0.027 and n(Ee) is the Bose-Einstein population factor with Ee=860 cm-1. The intensities of the optical absorption involving the creation of two phonons of energies E1
We review first-principles calculations of dislocation core structure in diamond, and draw out si... more We review first-principles calculations of dislocation core structure in diamond, and draw out similarities with and differences from silicon. Primary differences are in hybridization changes in carbon and in the different behaviour of H interacting with dislocations. In both materials, condensation of a homogeneous distribution of H atoms should result, first, in formation of small H aggregates with the appearance
The problems with dislocations in semiconductors are becoming tractable with modern computing by ... more The problems with dislocations in semiconductors are becoming tractable with modern computing by hybrid techniques. These apply static first principles calculations of energetics for important processes (e.g. kink formation and migration energies) and kinetic Monte Carlo techniques to follow the dynamic interaction of these processes over length and time scales inaccessible to, for example, molecular dynamic simulation. The simplest model system for covalent and ceramic solids is silicon, but there is debate over the structure and properties of dislocations there. The movement of the dislocation by the simple bond switching mechanism was studied from first principles, finding activation energies close to experiment, but lately the alternative mechanism invoking free radicals or solitons was found to give similar energies. We report results from an n-fold way kinetic Monte Carlo approach, applied to a simple system to verify the standard model for kink pair nucleation limited dislocation glide (the Hirth-Lothe model). We then apply an improved technique to the kinetics of the soliton model and to hydrogen enhanced dislocation glide. r
Afterdepolarisations are one mechanism suggested for the spontaneous initiation of re-entrant arr... more Afterdepolarisations are one mechanism suggested for the spontaneous initiation of re-entrant arrhythmias in the ventricles but are difficult to study experimentally. We have conducted a systematic investigation of the initiation of reentry by afterdepolarisations using a computational model of cardiac ventricular tissue. We implemented a monodomain model of a 1D fibre, where the excitability of the cell membrane was described by the 4 variable Fenton-Karma (FK4V) model. We embedded additional behaviour into the FK4V model, so a prescribed region produced afterdepolarisations. By changing the size of this region, and duration, amplitude and frequency of the afterdepolarization potentials, we were able to look in detail at how afterdepolarizations can initiate propagating action potentials. This study has shown that afterdepolarisations are capable of producing re-entry, but the duration and amplitude of the afterdepolarisation potential are important in determining whether re-entry is produced.
Afterdepolarisations are one mechanism suggested for the spontaneous initiation of re-entrant arr... more Afterdepolarisations are one mechanism suggested for the spontaneous initiation of re-entrant arrhythmias in the ventricles but are difficult to study experimentally. We have conducted a systematic investigation of the initiation of reentry by afterdepolarisations using a computational model of cardiac ventricular tissue. We implemented a monodomain model of a 1D fibre, where the excitability of the cell membrane was described by the 4 variable Fenton-Karma (FK4V) model. We embedded additional behaviour into the FK4V model, so a prescribed region produced afterdepolarisations. By changing the size of this region, and duration, amplitude and frequency of the afterdepolarization potentials, we were able to look in detail at how afterdepolarizations can initiate propagating action potentials. This study has shown that afterdepolarisations are capable of producing re-entry, but the duration and amplitude of the afterdepolarisation potential are important in determining whether re-entry is produced.
ABSTRACT Childhood obesity is a prevalent problem in most developed countries. It can have a sign... more ABSTRACT Childhood obesity is a prevalent problem in most developed countries. It can have a significant negative impact on a childs health including diabetes and cancer. Help in the preventing and reducing obesity is required. One possible method suggested in this paper is a serious game, which would increase energy expenditure during play, educate about nutrition and promote healthy eating and physical activity. Methods and ideas, informed by the related research, which were used for the implementation of such a game, are presented in this paper. Although not a complete solution in itself the game could help in the fight against childhood obesity.
Proceedings of the 29th ACM international conference on Design of communication - SIGDOC '11, 2011
Serious games are very content-rich forms of educational media, often combining high fidelity vis... more Serious games are very content-rich forms of educational media, often combining high fidelity visual and audio content with diverse pedagogic approaches. This paper introduces scenariobased serious games repurposing and demonstrates repurposing a serious game into new learning objects. The process uses the scenario editor called "mEditor". Two case studies based on the Happy Night Club serious game are presented. The article describes exploratory work which continues the work that started within the mEducator project regarding repurposing serious games in order to enable their use and reuse in the same or different educational contexts.
We present an n-fold way kinetic Monte Carlo simulation of the hopping motion of Li + ions in pol... more We present an n-fold way kinetic Monte Carlo simulation of the hopping motion of Li + ions in polyethylene on a grid of mesh 0.36 Å superimposed on the voids of the rigid polymer. The structure of the polymer is derived from a higher-order simulation, and the energy of the ion at each site is derived by the self-consistent polarization field method. The ion motion evolves in time from free flight through anomalous diffusion to normal diffusion, with the average energy tending to decrease with increasing temperature through thermal annealing. We compare the results with those of hopping models with probabilistic energy distributions of increasing complexity by analyzing the mean-square displacement and the average energy of an ensemble of ions. The Gumbel distribution describes the ion energy statistics in this system better than the usual Gaussian distribution does; including energy correlation greatly affects the ion dynamics. The analysis uses the standard data compression program GZIP, which proves to be a powerful tool for data analysis by giving a measure of recurrences in the ion path.
Medical & Biological Engineering & Computing, 2009
Afterdepolarisations are associated with arrhythmias in the heart, but are difficult to study exp... more Afterdepolarisations are associated with arrhythmias in the heart, but are difficult to study experimentally. In this study we used a simplified computational model of 1D and 2D cardiac ventricular tissue, where we could control the size of the region generating afterdepolarisations, as well as the properties of the afterdepolarisation waveform. Provided the size of the afterdepolarisation region was greater than around 1 mm, propagating extrasystoles were produced in both 1D and 2D. The number of extrasystoles produced depended on the amplitude, period, and duration of the oscillatory EAD waveform. In 2D, re-entry was also initiated for specific combinations of EAD amplitude, period, and duration, with the afterdepolarisation region acting as a common pathway. The main finding from this modelling study is therefore that afterdepolarisations can act as potent sources of propagating extrasystoles, as well as a source of re-entrant activation.
The detailed mechanisms by which re-entry and ventricular fibrillation are initiated in the heart... more The detailed mechanisms by which re-entry and ventricular fibrillation are initiated in the heart remain poorly understood because they are difficult to investigate experimentally. We have used a simplified excitable media computational model of action potential propagation to systematically study how re-entry can be produced by diffuse regions of inexcitable tissue. Patterns of excitable and inexcitable tissue were generated using a genetic algorithm. The inexcitable tissue was modeled in two ways: (i) diffusive, electrically connected but inexcitable tissue, or (ii) zero-flux, areas of tissue electrically disconnected in the same way as zero-flux boundary conditions. We were able to evolve patterns of diffuse inexcitable tissue that favored re-entry, but no single structure or pattern emerged. Diffusive inexcitable regions were inherently less arrhythmogenic than zero-flux inexcitable ones.
Empirical rules are derived that describe the temperature dependence of the infrared absorption s... more Empirical rules are derived that describe the temperature dependence of the infrared absorption spectra of pure diamond for photons of energy hnu=500-4000 cm-1. We show that with increasing temperature in the range 14e) where c=-0.027 and n(Ee) is the Bose-Einstein population factor with Ee=860 cm-1. The intensities of the optical absorption involving the creation of two phonons of energies E1 and E2 are expected to increase with T in proportion to 1+n(E1)][1+n(E2). This expression, combined with the fractional shift rule for the energies of each mode, allows high temperature two-phonon spectra to be simulated accurately from a low temperature spectrum. The temperature dependence of the three-phonon band between 2665 and 3900 cm-1 is precisely fitted without adjustable parameters by using the shift rule in conjunction with a modified density of three-phonon states. Absorption at 10.6 mum is shown to involve the simultaneous destruction and creation of phonons. Its strong temperature dependence in the range 3002 laser.
Modelling of local modes in Si V Ge \V and C V Si W Ge \V\W alloys to explore the local clusterin... more Modelling of local modes in Si V Ge \V and C V Si W Ge \V\W alloys to explore the local clustering of the species
Empirical rules are derived that describe the temperature dependence of the infrared absorption s... more Empirical rules are derived that describe the temperature dependence of the infrared absorption spectra of pure diamond for photons of energy hnu=500-4000 cm-1. We show that with increasing temperature in the range 14e) where c=-0.027 and n(Ee) is the Bose-Einstein population factor with Ee=860 cm-1. The intensities of the optical absorption involving the creation of two phonons of energies E1
We review first-principles calculations of dislocation core structure in diamond, and draw out si... more We review first-principles calculations of dislocation core structure in diamond, and draw out similarities with and differences from silicon. Primary differences are in hybridization changes in carbon and in the different behaviour of H interacting with dislocations. In both materials, condensation of a homogeneous distribution of H atoms should result, first, in formation of small H aggregates with the appearance
The problems with dislocations in semiconductors are becoming tractable with modern computing by ... more The problems with dislocations in semiconductors are becoming tractable with modern computing by hybrid techniques. These apply static first principles calculations of energetics for important processes (e.g. kink formation and migration energies) and kinetic Monte Carlo techniques to follow the dynamic interaction of these processes over length and time scales inaccessible to, for example, molecular dynamic simulation. The simplest model system for covalent and ceramic solids is silicon, but there is debate over the structure and properties of dislocations there. The movement of the dislocation by the simple bond switching mechanism was studied from first principles, finding activation energies close to experiment, but lately the alternative mechanism invoking free radicals or solitons was found to give similar energies. We report results from an n-fold way kinetic Monte Carlo approach, applied to a simple system to verify the standard model for kink pair nucleation limited dislocation glide (the Hirth-Lothe model). We then apply an improved technique to the kinetics of the soliton model and to hydrogen enhanced dislocation glide. r
Afterdepolarisations are one mechanism suggested for the spontaneous initiation of re-entrant arr... more Afterdepolarisations are one mechanism suggested for the spontaneous initiation of re-entrant arrhythmias in the ventricles but are difficult to study experimentally. We have conducted a systematic investigation of the initiation of reentry by afterdepolarisations using a computational model of cardiac ventricular tissue. We implemented a monodomain model of a 1D fibre, where the excitability of the cell membrane was described by the 4 variable Fenton-Karma (FK4V) model. We embedded additional behaviour into the FK4V model, so a prescribed region produced afterdepolarisations. By changing the size of this region, and duration, amplitude and frequency of the afterdepolarization potentials, we were able to look in detail at how afterdepolarizations can initiate propagating action potentials. This study has shown that afterdepolarisations are capable of producing re-entry, but the duration and amplitude of the afterdepolarisation potential are important in determining whether re-entry is produced.
Afterdepolarisations are one mechanism suggested for the spontaneous initiation of re-entrant arr... more Afterdepolarisations are one mechanism suggested for the spontaneous initiation of re-entrant arrhythmias in the ventricles but are difficult to study experimentally. We have conducted a systematic investigation of the initiation of reentry by afterdepolarisations using a computational model of cardiac ventricular tissue. We implemented a monodomain model of a 1D fibre, where the excitability of the cell membrane was described by the 4 variable Fenton-Karma (FK4V) model. We embedded additional behaviour into the FK4V model, so a prescribed region produced afterdepolarisations. By changing the size of this region, and duration, amplitude and frequency of the afterdepolarization potentials, we were able to look in detail at how afterdepolarizations can initiate propagating action potentials. This study has shown that afterdepolarisations are capable of producing re-entry, but the duration and amplitude of the afterdepolarisation potential are important in determining whether re-entry is produced.
ABSTRACT Childhood obesity is a prevalent problem in most developed countries. It can have a sign... more ABSTRACT Childhood obesity is a prevalent problem in most developed countries. It can have a significant negative impact on a childs health including diabetes and cancer. Help in the preventing and reducing obesity is required. One possible method suggested in this paper is a serious game, which would increase energy expenditure during play, educate about nutrition and promote healthy eating and physical activity. Methods and ideas, informed by the related research, which were used for the implementation of such a game, are presented in this paper. Although not a complete solution in itself the game could help in the fight against childhood obesity.
Proceedings of the 29th ACM international conference on Design of communication - SIGDOC '11, 2011
Serious games are very content-rich forms of educational media, often combining high fidelity vis... more Serious games are very content-rich forms of educational media, often combining high fidelity visual and audio content with diverse pedagogic approaches. This paper introduces scenariobased serious games repurposing and demonstrates repurposing a serious game into new learning objects. The process uses the scenario editor called "mEditor". Two case studies based on the Happy Night Club serious game are presented. The article describes exploratory work which continues the work that started within the mEducator project regarding repurposing serious games in order to enable their use and reuse in the same or different educational contexts.
We present an n-fold way kinetic Monte Carlo simulation of the hopping motion of Li + ions in pol... more We present an n-fold way kinetic Monte Carlo simulation of the hopping motion of Li + ions in polyethylene on a grid of mesh 0.36 Å superimposed on the voids of the rigid polymer. The structure of the polymer is derived from a higher-order simulation, and the energy of the ion at each site is derived by the self-consistent polarization field method. The ion motion evolves in time from free flight through anomalous diffusion to normal diffusion, with the average energy tending to decrease with increasing temperature through thermal annealing. We compare the results with those of hopping models with probabilistic energy distributions of increasing complexity by analyzing the mean-square displacement and the average energy of an ensemble of ions. The Gumbel distribution describes the ion energy statistics in this system better than the usual Gaussian distribution does; including energy correlation greatly affects the ion dynamics. The analysis uses the standard data compression program GZIP, which proves to be a powerful tool for data analysis by giving a measure of recurrences in the ion path.
Medical & Biological Engineering & Computing, 2009
Afterdepolarisations are associated with arrhythmias in the heart, but are difficult to study exp... more Afterdepolarisations are associated with arrhythmias in the heart, but are difficult to study experimentally. In this study we used a simplified computational model of 1D and 2D cardiac ventricular tissue, where we could control the size of the region generating afterdepolarisations, as well as the properties of the afterdepolarisation waveform. Provided the size of the afterdepolarisation region was greater than around 1 mm, propagating extrasystoles were produced in both 1D and 2D. The number of extrasystoles produced depended on the amplitude, period, and duration of the oscillatory EAD waveform. In 2D, re-entry was also initiated for specific combinations of EAD amplitude, period, and duration, with the afterdepolarisation region acting as a common pathway. The main finding from this modelling study is therefore that afterdepolarisations can act as potent sources of propagating extrasystoles, as well as a source of re-entrant activation.
The detailed mechanisms by which re-entry and ventricular fibrillation are initiated in the heart... more The detailed mechanisms by which re-entry and ventricular fibrillation are initiated in the heart remain poorly understood because they are difficult to investigate experimentally. We have used a simplified excitable media computational model of action potential propagation to systematically study how re-entry can be produced by diffuse regions of inexcitable tissue. Patterns of excitable and inexcitable tissue were generated using a genetic algorithm. The inexcitable tissue was modeled in two ways: (i) diffusive, electrically connected but inexcitable tissue, or (ii) zero-flux, areas of tissue electrically disconnected in the same way as zero-flux boundary conditions. We were able to evolve patterns of diffuse inexcitable tissue that favored re-entry, but no single structure or pattern emerged. Diffusive inexcitable regions were inherently less arrhythmogenic than zero-flux inexcitable ones.
Empirical rules are derived that describe the temperature dependence of the infrared absorption s... more Empirical rules are derived that describe the temperature dependence of the infrared absorption spectra of pure diamond for photons of energy hnu=500-4000 cm-1. We show that with increasing temperature in the range 14e) where c=-0.027 and n(Ee) is the Bose-Einstein population factor with Ee=860 cm-1. The intensities of the optical absorption involving the creation of two phonons of energies E1 and E2 are expected to increase with T in proportion to 1+n(E1)][1+n(E2). This expression, combined with the fractional shift rule for the energies of each mode, allows high temperature two-phonon spectra to be simulated accurately from a low temperature spectrum. The temperature dependence of the three-phonon band between 2665 and 3900 cm-1 is precisely fitted without adjustable parameters by using the shift rule in conjunction with a modified density of three-phonon states. Absorption at 10.6 mum is shown to involve the simultaneous destruction and creation of phonons. Its strong temperature dependence in the range 3002 laser.
Modelling of local modes in Si V Ge \V and C V Si W Ge \V\W alloys to explore the local clusterin... more Modelling of local modes in Si V Ge \V and C V Si W Ge \V\W alloys to explore the local clustering of the species
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