Coalescent simulation in continuous space:Algorithms for large neighbourhood size

Many species have an essentially continuous distribution in space, in which there are no natural divisions between randomly mating subpopulations. Yet, the standard approach to modelling these populations is to impose an arbitrary grid of demes, adjusting deme sizes and migration rates in an attempt to capture the important features of the population. Such indirect methods are required because of the failure of the classical models of isolation by distance, which have been shown to have major technical flaws. A recently introduced model of extinction and recolonisation in two dimensions solves these technical problems, and provides a rigorous technical foundation for the study of populations evolving in a spatial continuum. The coalescent process for this model is simply stated, but direct simulation is very inefficient for large neighbourhood sizes. We present efficient and exact algorithms to simulate this coalescent process for arbitrary sample sizes and numbers of loci, and analyse these algorithms in detail

Scale-invariance in gravity and implications for the cosmological constant

Recently a scale invariant theory of gravity was constructed by imposing a conformal symmetry on general relativity. The imposition of this symmetry changed the configuration space from superspace - the space of all Riemannian 3-metrics modulo diffeomorphisms - to conformal superspace - the space of all Riemannian 3-metrics modulo diffeomorphisms and conformal transformations. However, despite numerous attractive features, the theory suffers from at least one major problem: the volume of the universe is no longer a dynamical variable. In attempting to resolve this problem a new theory is found which has several surprising and atractive features from both quantisation and cosmological perspectives. Furthermore, it is an extremely restrictive theory and thus may provide testable predictions quickly and easily. One particularly interesting feature of the theory is the resolution of the cosmological constant problem.Comment: Replaced with final version: minor changes to text; references adde

What Do We Mean by Women and Power ?

This essay considers the question of how we define “power” in order to best include women and gender. Queenship/lordship studies have been at the forefront of women-and-power discussions, and have advanced that discussion by moving away from the “exceptional woman” biographies to focus on the patterns of power that these women embodied. But if we extend our definition of power beyond the realm of public authority to a more general category of acts that can shape the destinies of others, we are confronted with a much broader field of action that might be considered “women’s power” — a field that could easily encompass the experience not only of non-aristocratic women but even marginal or subaltern women such as Jews, Muslims, slaves, and concubines, allowing scholars to apply the analytical framework of power to new actors

A Study of a Skirtless Hovercraft Design

Initial study into three possible skirtless hovercraft designs. The designs utilize Coanda nozzles and a Coanda wing surface to generate lift and create a pressure cushion below the craft. The pressure cushion is to be maintained by an air curtain created by flow spill from the Coanda wing surface. Three proposed skirtless hovercraft designs were analyzed via computational fluid dynamics to ascertain their lift generation capabilities. The three designs were adaptations from William Walter\u27s hybricraft primer and his patent for a fan driven lift generation device. Each design featured Coanda nozzles, or nozzles that utilize the Coanda effect, to redirect air flow to aid in the generation of an air curtain around a central air flow. The designs also utilized a Coanda wing as a lifting body to aid in lift generation. Each design was set at a height above ground of one foot and a radius of two feet. The craft was assumed to be axisymmetric around a central axis for a perfectly circular craft, much like a flying saucer. The craft can be divided into several parts, the core, the nozzles, the plenum chamber (for designs 2 and 3), and the wing. Flow is generated from rotor blades situated one foot above the top of the core of the craft. The nozzles are located at the edges of the craft below the wing. In designs two and three the plenum chamber is the region between the core and the wing. For each design three cases were performed where t was increased for each case. This resulted in a total of nine cases, three cases for three designs. For each case the ratio of nozzle thickness to the radius of the curved plate, t/R, was set to 0.344 and t was increased while R was calculated to maintain the ratio

Beef Cattle Instance Segmentation Using Fully Convolutional Neural Network

In this paper we present a novel instance segmentation algorithm that extends a fully convolutional network to learn to label objects separately without prediction of regions of interest. We trained the new algorithm on a challenging CCTV recording of beef cattle, as well as benchmark MS COCO and Pascal VOC datasets. Extensive experimentation showed that our approach outperforms the state-of-the-art solutions by up to 8% on our data

Scale-invariant gravity: Spacetime recovered

The configuration space of general relativity is superspace - the space of all Riemannian 3-metrics modulo diffeomorphisms. However, it has been argued that the configuration space for gravity should be conformal superspace - the space of all Riemannian 3-metrics modulo diffeomorphisms and conformal transformations. Recently a manifestly 3-dimensional theory was constructed with conformal superspace as the configuration space. Here a fully 4-dimensional action is constructed so as to be invariant under conformal transformations of the 4-metric using general relativity as a guide. This action is then decomposed to a (3+1)-dimensional form and from this to its Jacobi form. The surprising thing is that the new theory turns out to be precisely the original 3-dimensional theory. The physical data is identified and used to find the physical representation of the theory. In this representation the theory is extremely similar to general relativity. The clarity of the 4-dimensional picture should prove very useful for comparing the theory with those aspects of general relativity which are usually treated in the 4-dimensional framework.Comment: Replaced with final version: minor changes to tex

Action, Connection, Communication: The Honors Classroom in the Digital Age

For more than a decade, the two of us, an historian and a literature professor, have co-taught a 12-credit European Civilization sequence for firstyear honors students. Last year Grand Valley inaugurated an impressive new living and learning center, which includes two innovative classrooms dubbed “Learn Labs,” Steelcase’s effort to bring twenty-first century design to traditional classrooms that may have met the needs of the nineteenth century but have lingered long beyond their usefulness. In the Learn Lab, five conference tables, arranged in a star shape, supplant regimented rows of desks. At the head of each table, pillars provide electrical and projector connections. Three large screens placed around the room can project a monitor from anyone’s laptop or from the instructor’s station tucked in a corner. We can walk around the room and still operate the interactive “Walk and Talk” board. Document cameras allow us to save the day’s work by recording marker-board scribblings or individual documents

Action, Connection, Communication: The Honors Classroom in the Digital Age

For more than a decade, the two of us, an historian and a literature professor, have co-taught a 12-credit European Civilization sequence for firstyear honors students. Last year Grand Valley inaugurated an impressive new living and learning center, which includes two innovative classrooms dubbed “Learn Labs,” Steelcase’s effort to bring twenty-first century design to traditional classrooms that may have met the needs of the nineteenth century but have lingered long beyond their usefulness. In the Learn Lab, five conference tables, arranged in a star shape, supplant regimented rows of desks. At the head of each table, pillars provide electrical and projector connections. Three large screens placed around the room can project a monitor from anyone’s laptop or from the instructor’s station tucked in a corner. We can walk around the room and still operate the interactive “Walk and Talk” board. Document cameras allow us to save the day’s work by recording marker-board scribblings or individual documents