Macquarie University

About: Macquarie University is a education organization based out in Sydney, New South Wales, Australia. It is known for research contribution in the topics: Population & Context (language use). The organization has 14075 authors who have published 47673 publications receiving 1416184 citations. The organization is also known as: Macquarie uni.

The UKIDSS galactic plane survey

Abstract: 'The definitive version is available at www.blackwell-synergy.com .' Copyright Blackwell Publishing DOI: 10.1111/j.1365-2966.2008.13924.x

Inbreeding and Extinction: A Threshold Effect

Abstract: A fundamental assumption underlying the application of genetics within conservation biology is that inbreeding increases the risk of extinction. However, there is no information on the shape of the relationship, the available evidence has not distinguished genetic and nongenetic effects, and the issue is controversial. Methods were devised to separate genetic and nongenetic causes of extinction in inbred populations, and they were used to analyze data from Drosophila melanogaster, D. virilis and Mus musculus. Inbreeding markedly increased rates of extinction in all cases. All showed a threshold relationship between incremental extinction and inbreeding with low initial extinction, but they showed notably increased extinction beginning at intermediate levels of inbreeding. There was no difference in extinction levels at similar inbreeding coefficients in populations inbred at different rates (full sibling versus double first cousin). Endangered species may give little warning of impending extinction crises due to inbreeding. Una suposicion fundamental que resalta la aplicacion de la genetica en la conservacion biologica es que la endocria aumenta el riesgo de extincion. Sin embargo, no existe informacion sobre la forma en que la endocria y el riesgo de extinction estan relacionados; la evidencia disponible no ha distinguido entre efectos geneticos y efectos no geneticos y este problema resulta controversial. En el presente estudio se desarrollaron metodos para distinguir entre las causas geneticas y no geneticas de la extincion en poblaciones con endocria y los mismos fueron usados para analizar datos sobre Drosophila melanogaster, D. virilis y Mus musculus. La endocria incremento marcadamente las tasas de extincion en todos los casos. Todos mostraron una relacion umbral entre la extincion progresiva y la endocria con una baja tasa de extincion al principio, pero una tasa de extincion notablemente aumentada al alcanzar niveles de endocria intermedios. No existieron diferencias en los niveles de extincion en poblaciones con niveles de endocria similares pero endocriadas a tasas diferentes (hermano versus doble primo hermano). Las especies en peligro, no darian muchas senales de peligro antes de que las crisis de extincion debidas a la endocria se desencadenen.

Teaching and Learning in their Disciplinary Contexts: A conceptual analysis

Abstract: The growing literature on undergraduate teaching and learning currently lacks an organising framework. This article sets out to provide one, distinguishing between hard pure, soft pure, hard applied and soft applied fields of study, and hence making it possible to highlight generally unremarked similarities and differences between the various research findings. In doing so, it draws extensively on the relevant literature, offering separate analyses of knowledge-related and socially related studies. The former embody curriculum, assessment and cognitive purpose, while the latter encompass group characteristics of teachers, types of teaching method and student learning requirements. The concluding section draws out the main implications for policy and practice related to staff development, computer-based learning, assessment of student learning and quality measures.

Entanglement-free Heisenberg-limited phase estimation

Abstract: Measurement underpins all quantitative science. A key example is the measurement of optical phase, used in length metrology and many other applications. Advances in precision measurement have consistently led to important scientific discoveries. At the fundamental level, measurement precision is limited by the number N of quantum resources (such as photons) that are used. Standard measurement schemes, using each resource independently, lead to a phase uncertainty that scales as 1/square root N-known as the standard quantum limit. However, it has long been conjectured that it should be possible to achieve a precision limited only by the Heisenberg uncertainty principle, dramatically improving the scaling to 1/N (ref. 3). It is commonly thought that achieving this improvement requires the use of exotic quantum entangled states, such as the NOON state. These states are extremely difficult to generate. Measurement schemes with counted photons or ions have been performed with N < or = 6 (refs 6-15), but few have surpassed the standard quantum limit and none have shown Heisenberg-limited scaling. Here we demonstrate experimentally a Heisenberg-limited phase estimation procedure. We replace entangled input states with multiple applications of the phase shift on unentangled single-photon states. We generalize Kitaev's phase estimation algorithm using adaptive measurement theory to achieve a standard deviation scaling at the Heisenberg limit. For the largest number of resources used (N = 378), we estimate an unknown phase with a variance more than 10 dB below the standard quantum limit; achieving this variance would require more than 4,000 resources using standard interferometry. Our results represent a drastic reduction in the complexity of achieving quantum-enhanced measurement precision.

A vast, thin plane of corotating dwarf galaxies orbiting the Andromeda galaxy

Abstract: Dwarf satellite galaxies are thought to be the remnants of the population of primordial structures that coalesced to form giant galaxies like the Milky Way. It has previously been suspected that dwarf galaxies may not be isotropically distributed around our Galaxy, because several are correlated with streams of H I emission, and may form coplanar groups. These suspicions are supported by recent analyses. It has been claimed that the apparently planar distribution of satellites is not predicted within standard cosmology, and cannot simply represent a memory of past coherent accretion. However, other studies dispute this conclusion. Here we report the existence of a planar subgroup of satellites in the Andromeda galaxy (M 31), comprising about half of the population. The structure is at least 400 kiloparsecs in diameter, but also extremely thin, with a perpendicular scatter of less than 14.1 kiloparsecs. Radial velocity measurements reveal that the satellites in this structure have the same sense of rotation about their host. This shows conclusively that substantial numbers of dwarf satellite galaxies share the same dynamical orbital properties and direction of angular momentum. Intriguingly, the plane we identify is approximately aligned with the pole of the Milky Way's disk and with the vector between the Milky Way and Andromeda.