126,772 research outputs found
Dr. Joe Hoyle – Faculty Author Interview
No full textDr. Joe Hoyle, Associate Professor of Accounting in the E. Claiborne Robins School of Business, discusses Introduction to Financial Accounting, a unique online textbook that incorporates many different learning and media techniques. By offering introductory videos, embedded multiple-choice questions and real-life interviews with an investment manager, Hoyle and his co-author include something for every student. The book will be published by Flat World Knowledge in early 2010
Introduction:British art cinema - creativity, experimentation and innovation
No full textThis Introduction engages with issues such as Britain’s traditions of intellectualism and anti-intellectualism and how these pertain to the history of British film. We consider how far British films conform to class-based, ideologically-informed notions of ‘high art’; the tensions between highbrow and low art in British cinema; the complexities of state-funded and independent British film-making; and the question of how far artistic creativity, entertainment and commerce might co-exist within a conceptual British ‘art’ cinema. Attention is paid to the relationship between the modernist movement and British cinema; the relationship between British cinema, Hollywood and US popular culture; historical conditions in which British art cinema develops and flourishes; and the transnational nature of much of what we call British cinema and British art cinema in particular
Zigzag and Eckhaus instabilities in a quintic-order nonvariational Ginzburg-Landau equation
No full textA nonvariational Ginzburg-Landau equation with quintic and space-dependent cubic terms is investigated. It is found that the equation permits both sub- and supercritical zigzag and Eckhaus instabilities and further that the zigzag instability may occur for patterns with wave number larger than critical (q>0), in contrast to the usual case
Analytical model of propagating sand ripples
No full textWe formulate a simple phenomenological model of aeolian sand ripple migration based upon a balance between grain hopping driven by saltation and grain rolling or avalanching under gravity. We develop a set of model equations governing the evolution of the ripple slope. The model has solutions describing steadily propagating isolated ripples, produced by a horizontal saltation flux, and periodic trains of ripples, which develop when the saltation flux is inclined to the horizontal. In the case of an inclined saltation flux, the ripple wavelength is controlled by the length of the shadow zone, as suggested by R. P. Sharp [J. Geol. 71, 617 (1963)]. Although very simple, our model predicts some of the qualitative features shown by sand ripples in experimental or field studies [R. A. Bagnold, The Physics of Blown Sand and Desert Dunes (Methuen and Co., London, 1941); R. P. Sharp, J. Geol. 71, 617 (1963)]. We find that ripples only develop above a certain threshold value of the saltation flux intensity. Furthermore, at relatively low saltation fluxes, the lee slope of the ripple is a smooth curve, whereas above a critical value of the saltation flux, a slip face develops near the crest. The model predicts a decrease in the speed of propagation as the ripple becomes larger, consistent with observations that smaller ripples are eliminated by ripple merger [R. P. Sharp, J. Geol. 71, 617 (1963)], and also with numerical simulations [R. S. Anderson, Earth-Sci. Rev. 29, 77 (1990); S. B. Forrest and P. K. Haff, Science 255, 1240 (1992); W. Landry and B. T. Werner, Physica D 77, 238 (1994)].</p
Steady squares and hexagons on a subcritical ramp
No full textSteady squares and hexagons on a subcritical ramp are studied, both analytically and numerically, within the framework of the lowest-order amplitude equations. On the subcritical ramp, the external stress or control parameter varies continuously in space from subcritical to supercritical values. At the subcritical end of the ramp, pattern formation is suppressed, and patterns fade away into the conduction solution. It is shown that three-dimensional patterns may change shape on a subcritical ramp. A square pattern becomes a pattern of rolls as it fades, with the roll axes aligned in the direction orthogonal to that in which the control parameter varies. Hexagons in systems with horizontal midplane symmetry become a pattern of rectangles before reaching the conduction solution. There is a suggestion that hexagons in systems which lack this symmetry might fade away through a roll pattern. Numerical simulations are used to illustrate these phenomena. <br/
Long wavelength instabilities of square patterns
No full textThe long wavelength instabilities of square and rectangular planforms are studied analytically and numerically, using amplitude equations which describe the general interaction of two orthogonal coupled roll patterns. The zigzag and two-dimensional Eckhaus instabilities are found, and in addition it is discovered that the three-dimensional equivalent of the Eckhaus instability splits into two variants. The square Eckhaus instability is the direct equivalent of the two-dimensional case, whereas the rectangular Eckhaus instability is truly three-dimensional in character. In the case of square patterns, nonlinear phase diffusion equations are derived close to the onset of the instabilities. A short wavelength cross square mode is also discussed briefly
Cross-Newell equations for hexagons and triangles
No full textThe Cross-Newell equations for hexagons and triangles are derived for general real gradient systems, and are found to be in flux-divergence form. Specific examples of complex governing equations that give rise to hexagons and triangles and which have Lyapunov functionals are also considered, and explicit forms of the Cross-Newell equations are found in these cases. The general nongradient case is also discussed; in contrast with the gradient case, the equations are not flux divergent. In all cases, the phase stability boundaries and modes of instability for general distorted hexagons and triangles can be recovered from the Cross-Newell equation
Pattern formation: an introduction to methods
No full textFrom the stripes of a zebra and the spots on a leopard's back to the ripples on a sandy beach or desert dune, regular patterns arise everywhere in nature. The appearance and evolution of these phenomena has been a focus of recent research activity across several disciplines. This book provides an introduction to the range of mathematical theory and methods used to analyse and explain these often intricate and beautiful patterns. Bringing together several different approaches, from group theoretic methods to envelope equations and theory of patterns in large-aspect ratio-systems, the book also provides insight behind the selection of one pattern over another. Suitable as an upper-undergraduate textbook for mathematics students or as a fascinating, engaging, and fully illustrated resource for readers in physics and biology, Rebecca Hoyle's book, using a non-partisan approach, unifies a range of techniques used by active researchers in this growing fiel
When to rely on maternal effects and when on phenotypic plasticity?
No full textExisting insight suggests that maternal effects have a substantial impact on evolution, yet these predictions assume that maternal effects themselves are evolutionarily constant. Hence, it is poorly understood how natural selection shapes maternal effects in different ecological circumstances. To overcome this, the current study derives an evolutionary model of maternal effects in a quantitative genetics context. In constant environments, we show that maternal effects evolve to slight negative values that result in a reduction of the phenotypic variance (canalization). By contrast, in populations experiencing abrupt change, maternal effects transiently evolve to positive values for many generations, facilitating the transmission of beneficial maternal phenotypes to offspring. In periodically fluctuating environments, maternal effects evolve according to the autocorrelation between maternal and offspring environments, favoring positive maternal effects when change is slow, and negative maternal effects when change is rapid. Generally, the strongest maternal effects occur for traits that experience very strong selection and for which plasticity is severely constrained. By contrast, for traits experiencing weak selection, phenotypic plasticity enhances the evolutionary scope of maternal effects, although maternal effects attain much smaller values throughout. As weak selection is common, finding substantial maternal influences on offspring phenotypes may be more challenging than anticipated
- …
