Dirac Particles in a Gravitational Field

The semiclassical approximation for the Hamiltonian of Dirac particles interacting with an arbitrary gravitational field is investigated. The time dependence of the metrics leads to new contributions to the in-band energy operator in comparison to previous works on the static case. In particular we find a new coupling term between the linear momentum and the spin, as well as couplings which contribute to the breaking of the particle - antiparticle symmetry

Pre-/Post-Knowledge Assessment of an Earth Science Course for Elementary/Middle School Education Majors

This article discusses the benefits of experiencing the process of Earth Science through active learning strategies, and how a simple assessment instrument was developed and used to evaluate a specific course in Earth Science for educators. The course itself was broad in scope and designed specifically to fulfill science requirements for elementary and middle-level education majors. The assessment instrument consisted of statements to which students responded true-false or "I don't know." Based on pre- and post-course assessments of 108 education majors who took the class over a period of 5 semesters, the researchers reported an average increase in their content knowledge of 30 percent. Educational levels: Graduate or professional, Graduate or professional

Mechanics of a Plant in Fluid Flow

Plants live in constantly moving fluid, whether air or water. In response to the loads associated with fluid motion, plants bend and twist, often with great amplitude. These large deformations are not found in traditional engineering application and thus necessitate new specialised scientific developments. Studying Fluid-Structure Interactions (FSI) in botany, forestry and agricultural science is crucial to the optimisation of biomass production for food, energy, and construction materials. FSI are also central in the study of the ecological adaptation of plants to their environment. This review paper surveys the mechanics of FSI on individual plants. We present a short refresher on fluids mechanics then dive in the statics and dynamics of plant-fluid interactions. For every phenomenon considered, we present the appropriate dimensionless numbers to characterise the problem, discuss the implications of these phenomena on biological processes, and propose future research avenues. We cover the concept of reconfiguration while considering poroelasticity, torsion, chirality, buoyancy, and skin friction. We also cover the dynamical phenomena of wave action, flutter, and vortex-induced vibrations.Comment: 26 pages, 8 figure

Spirited Imperialism: The Formation and Command of the First Canadian Expeditionary Force in South Africa

This article explores the role played by Chamberlain, Minto and Hutton in shaping the organizational and command structure of the Canadian expeditionary force that deployed to South Africa. In 1899, the war raised not only the vital question about the kind of imperial war Canada ought to participate in, but also the form of that participation. As this article demonstrates, the British politician, the colonial administrator and the general saw the war as an opportunity to advance their specific agenda, strongly fuelled by imperialist sentiments. In doing so, the ideas that shaped their actions between July and October 1899 provided the base for a succession of seemingly unrelated decisions that had a substantial influence on Canada’s contribution and on the command arrangements in South Africa. The Canadian soldiers who sailed to South Africa were, for the first time, grouped in a national military formation commanded by a Canadian officer, setting a precedent for the country’s participation in future conflicts

Free Energy Formalism for Particle Adsorption

The equilibrium properties of particles adsorption is investigated theoretically. The model relies on a free energy formulation which allows to generalize the Maxwell-Boltzmann description to solutions for which the bulk volume fraction of potentially adsorbed particles is very high. As an application we consider the equilibrium physical adsorption of neutral and charged particles from solution onto two parallel adsorbing surfaces.Comment: to be published in Physical Review

Foam pads properties and their effects on posturography in participants of different weight

Background: Foam pads are increasingly used on force platforms during balance assessments in order to produce increased instability thereby permitting the measurement of enhanced posturographic parameters. A variety of foam pads providing different material properties have thus been used, although it is still unclear which characteristics produce the most effective and reliable tests. Furthermore, the effects of participant bodyweight on the performance of the foam pads and outcome of the test are unknown. This project investigated how different foam samples affected postural sway velocity in participants of different weights. Method: Four foam types were tested according to a modified American Society for Testing and Materials standard method for testing flexible cellular materials. Thirty-six healthy male factory workers divided into three groups according to body mass were tested three times for each of the 13 randomly-selected experimental situations for changes in postural sway velocity in this cross-over study. Descriptive and inferential statistics were used to compare the results and evaluate the difference in sway velocity between mass groups. Results: For the materials considered here, the modulus of elasticity of the foam pads when compressed by 25% of their original heights was inversely proportional to their density. The largest changes in postural sway velocity were measured when the pads of highest stiffness were used, with memory foam pads being the least likely to produce significant changes. Conclusions: The type of foam pads used in posturography is indeed important. Our study shows that the samples with a higher modulus of elasticity produced the largest change in postural sway velocity during quiet stance. The results suggest that foam pads used for static computerised posturography should 1) possess a higher modulus of elasticity and 2) show linear deformation properties matched to the participants’ weight