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Search Results: 1 - 10 of 1334 matches for " Nigel Foreman "
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Virtual Reality in Psychology
Nigel Foreman
Themes in Science and Technology Education , 2009,
Abstract: The benefits of using virtual environments (VEs) in psychology arise from the fact that movements in virtual space, and accompanying perceptual changes, are treated by the brain in much the same way as those in equivalent real space. The research benefits of using VEs, in areas of psychology such as spatial learning and cognition, include interface flexibility, the reproducibility of virtual experience, and the opportunity for on-line monitoring of performance. Applications of VEs are many and varied, but are especially beneficial where experience can be tailored via augmentation, and where dangerous training situations can be avoided. The use of programmable agents has great future potential in relation to training and interpersonal skill development, also perhaps in clinical diagnosis and therapy. Progress in VE usage in psychological education is limited by cost and availability, though VEs are being used increasingly in classroom and laboratory teaching exercises. Virtual Reality was said to be “an answer waiting for a question”, but questions are being recognized, so that applications of VEs within the behavioural sciences are likely to multiply.
Using Fun Web Publishing Resources for Project and Task-based Work
Ann Foreman
Humanising Language Teaching , 2010, DOI: 17559715
First Run of the LArIAT Testbeam Experiment
William Foreman
Physics , 2015,
Abstract: LArIAT (Liquid Argon In A Testbeam) aims to characterize the response of a liquid argon time projection chamber (LArTPC) to the particles often seen as final-state products of ~1 GeV neutrino interactions in existing and planned detectors. The experiment uses the ArgoNeuT cryostat and its refurbished 170-liter-active-volume TPC placed in a tunable tertiary beamline produced from a high-energy pion beam at the Fermilab Test Beam Facility (FTBF). The TPC was modified to accommodate cold readout electronics and a light collection system. The first run took place May-June of 2015, and the collected data will help in understanding electron recombination behavior, shower reconstruction, particle identification, muon sign determination, pion and kaon interactions in argon, and the use of scintillation light for calorimetry.
K-contact Lie groups of dimension five or greater
Brendan Foreman
Mathematics , 2010,
Abstract: We prove that a K-contact Lie group of dimension five or greater is the central extension of a symplectic Lie group by complexifying the Lie algebra and applying a result from complex contact geometry, namely, that, if the adjoint action of the complex Reeb vector field on a complex contact Lie algebra is diagonalizable, then it is trivial.
Quantitative EEG for the detection of brain ischemia
Brandon Foreman, Jan Claassen
Critical Care , 2012, DOI: 10.1186/cc11230
Abstract: In the ICU, ischemia detection in particular has been under-utilized, but the potential to diagnose ischemia as it occurs is tremendous (e.g., monitoring after high risk vascular or cardiac surgery, during refractory hypotension, or in the context of sepsis-associated encephalopathy). When cerebral blood flow (CBF) becomes compromised, changes occur in both the metabolic and electrical activity of cortical neurons, with associated EEG changes [2]. In the operating room, EEG has an established role in identifying ischemia prior to the development of infarction during carotid endarterectomy [3]. In acute ischemic stroke, the primary injury has typically occurred prior to presentation, but EEG may be able to detect patterns to suggest severity, prognosis, and secondary injury (e.g., reocclusion, edema, or hemorrhagic transformation) [4]. Delayed cerebral ischemia from vasospasm after subarachnoid hemorrhage (SAH) illustrates an application in which early detection may prevent the development of permanent damage by triggering appropriate interventions such as angioplasty or intra-arterial administration of vasodilator therapy [5,6]. Serial neurological exams and imaging are only capable of detecting delayed cerebral ischemia once the damage becomes clinically or radiographically apparent. In this case, EEG may be a useful way to detect and subsequently treat ischemia before the injury becomes irreversible [7-10].Brain function is represented on EEG by oscillations of certain frequencies. Slower frequencies (typically delta [0.5-3 Hz] or theta [4-7 Hz]) are generated by the thalamus and by cells in layers II-VI of the cortex. Faster frequencies (or alpha, typically 8-12 Hz) derive from cells in layers IV and V of the cortex [11]. All frequencies are modulated by the reticular activating system, which corresponds to the observation of reactivity on the EEG [12]. Pyramidal neurons found in layers III, V, and VI are exquisitely sensitive to conditions of low oxygen, such as
Valence-band mixing in first-principles envelope-function theory
Bradley A. Foreman
Physics , 2007, DOI: 10.1103/PhysRevB.76.045327
Abstract: This paper presents a numerical implementation of a first-principles envelope-function theory derived recently by the author [B. A. Foreman, Phys. Rev. B 72, 165345 (2005)]. The examples studied deal with the valence subband structure of GaAs/AlAs, GaAs/Al(0.2)Ga(0.8)As, and In(0.53)Ga(0.47)As/InP (001) superlattices calculated using the local density approximation to density-functional theory and norm-conserving pseudopotentials without spin-orbit coupling. The heterostructure Hamiltonian is approximated using quadratic response theory, with the heterostructure treated as a perturbation of a bulk reference crystal. The valence subband structure is reproduced accurately over a wide energy range by a multiband envelope-function Hamiltonian with linear renormalization of the momentum and mass parameters. Good results are also obtained over a more limited energy range from a single-band model with quadratic renormalization. The effective kinetic-energy operator ordering derived here is more complicated than in many previous studies, consisting in general of a linear combination of all possible operator orderings. In some cases the valence-band Rashba coupling differs significantly from the bulk magnetic Luttinger parameter. The splitting of the quasidegenerate ground state of no-common-atom superlattices has non-negligible contributions from both short-range interface mixing and long-range dipole terms in the quadratic density response.
First-principles effective-mass Hamiltonian for semiconductor nanostructures in a magnetic field
Bradley A. Foreman
Physics , 2005, DOI: 10.1088/0953-8984/18/4/018
Abstract: A multi-band effective-mass Hamiltonian is derived for lattice-matched semiconductor nanostructures in a slowly varying external magnetic field. The theory is derived from the first-principles magnetic-field coupling Hamiltonian of Pickard and Mauri, which is applicable to nonlocal norm-conserving pseudopotentials in the local density approximation to density functional theory. The pseudopotential of the nanostructure is treated as a perturbation of a bulk reference crystal, with linear and quadratic response terms included in k.p perturbation theory. The resulting Hamiltonian contains several interface terms that have not been included in previous work on nanostructures in a magnetic field. The derivation provides the first direct analytical expressions showing how the coupling of the nonlocal potential to the magnetic field influences the effective magnetic dipole moment of the electron.
Choosing a basis that eliminates spurious solutions in k.p theory
Bradley A. Foreman
Physics , 2006, DOI: 10.1103/PhysRevB.75.235331
Abstract: A small change of basis in k.p theory yields a Kane-like Hamiltonian for the conduction and valence bands of narrow-gap semiconductors that has no spurious solutions, yet provides an accurate fit to all effective masses. The theory is shown to work in superlattices by direct comparison with first-principles density-functional calculations of the valence subband structure. A reinterpretation of the standard data-fitting procedures used in k.p theory is also proposed.
What do gas-rich galaxies actually tell us about modified Newtonian dynamics?
Simon Foreman,Douglas Scott
Physics , 2011, DOI: 10.1103/PhysRevLett.108.141302
Abstract: It has recently been claimed that measurements of the baryonic Tully-Fisher relation (BTFR), a power-law relationship between the observed baryonic masses and outer rotation velocities of galaxies, support the predictions of modified Newtonian dynamics for the slope and scatter in the relation, while challenging the cold dark matter (CDM) paradigm. We investigate these claims, and find that: 1) the scatter in the data used to determine the BTFR is in conflict with observational uncertainties on the data; 2) these data do not make strong distinctions regarding the best-fit BTFR parameters; 3) the literature contains a wide variety of measurements of the BTFR, many of which are discrepant with the recent results; and 4) the claimed CDM "prediction" for the BTFR is a gross oversimplification of the complex galaxy-scale physics involved. We conclude that the BTFR is currently untrustworthy as a test of CDM.
First-principles envelope-function theory for lattice-matched semiconductor heterostructures
Bradley A. Foreman
Physics , 2003, DOI: 10.1103/PhysRevB.72.165345
Abstract: In this paper a multi-band envelope-function Hamiltonian for lattice-matched semiconductor heterostructures is derived from first-principles norm-conserving pseudopotentials. The theory is applicable to isovalent or heterovalent heterostructures with macroscopically neutral interfaces and no spontaneous bulk polarization. The key assumption -- proved in earlier numerical studies -- is that the heterostructure can be treated as a weak perturbation with respect to some periodic reference crystal, with the nonlinear response small in comparison to the linear response. Quadratic response theory is then used in conjunction with k.p perturbation theory to develop a multi-band effective-mass Hamiltonian (for slowly varying envelope functions) in which all interface band-mixing effects are determined by the linear response. To within terms of the same order as the position dependence of the effective mass, the quadratic response contributes only a bulk band offset term and an interface dipole term, both of which are diagonal in the effective-mass Hamiltonian. Long-range multipole Coulomb fields arise in quantum wires or dots, but have no qualitative effect in two-dimensional systems beyond a dipole contribution to the band offsets.
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