University of St Andrews

About: University of St Andrews is a education organization based out in St Andrews, Fife, United Kingdom. It is known for research contribution in the topics: Population & Laser. The organization has 16260 authors who have published 43364 publications receiving 1636072 citations. The organization is also known as: St Andrews University & University of St. Andrews.

Discovery of an unusual dwarf galaxy in the outskirts of the Milky Way

Abstract: We announce the discovery of a new dwarf galaxy, Leo T, in the Local Group. It was found as a stellar overdensity in the Sloan Digital Sky Survey Data Release 5 (SDSS DR5). The color-magnitude diagram of Leo T shows two well-defined features, which we interpret as a red giant branch and a sequence of young, massive stars. As judged from fits to the color-magnitude diagram, it lies at a distance of ~420 kpc and has an intermediate-age stellar population with a metallicity of [Fe/H] = -1.6, together with a young population of blue stars of age ~200 Myr. There is a compact cloud of neutral hydrogen with mass ~105 M☉ and radial velocity +35 km s-1 coincident with the object visible in the HIPASS channel maps. Leo T is the smallest, lowest luminosity galaxy found to date with recent star formation. It appears to be a transition object similar to, but much lower luminosity than, the Phoenix dwarf.

Functionalizing hydrogen-bonded surface networks with self-assembled monolayers.

Abstract: One of the central challenges in nanotechnology is the development of flexible and efficient methods for creating ordered structures with nanometre precision over an extended length scale. Supramolecular self-assembly on surfaces offers attractive features in this regard: it is a 'bottom-up' approach and thus allows the simple and rapid creation of surface assemblies, which are readily tuned through the choice of molecular building blocks used and stabilized by hydrogen bonding, van der Waals interactions, pi-pi bonding or metal coordination between the blocks. Assemblies in the form of two-dimensional open networks are of particular interest for possible applications because well-defined pores can be used for the precise localization and confinement of guest entities such as molecules or clusters, which can add functionality to the supramolecular network. Another widely used method for producing surface structures involves self-assembled monolayers (SAMs), which have introduced unprecedented flexibility in our ability to tailor interfaces and generate patterned surfaces. But SAMs are part of a top-down technology that is limited in terms of the spatial resolution that can be achieved. We therefore rationalized that a particularly powerful fabrication platform might be realized by combining non-covalent self-assembly of porous networks and SAMs, with the former providing nanometre-scale precision and the latter allowing versatile functionalization. Here we show that the two strategies can indeed be combined to create integrated network-SAM hybrid systems that are sufficiently robust for further processing. We show that the supramolecular network and the SAM can both be deposited from solution, which should enable the widespread and flexible use of this combined fabrication method.

A juvenile early hominin skeleton from Dikika, Ethiopia

Abstract: Understanding changes in ontogenetic development is central to the study of human evolution. With the exception of Neanderthals, the growth patterns of fossil hominins have not been studied comprehensively because the fossil record currently lacks specimens that document both cranial and postcranial development at young ontogenetic stages. Here we describe a well-preserved 3.3-million-year-old juvenile partial skeleton of Australopithecus afarensis discovered in the Dikika research area of Ethiopia. The skull of the approximately three-year-old presumed female shows that most features diagnostic of the species are evident even at this early stage of development. The find includes many previously unknown skeletal elements from the Pliocene hominin record, including a hyoid bone that has a typical African ape morphology. The foot and other evidence from the lower limb provide clear evidence for bipedal locomotion, but the gorilla-like scapula and long and curved manual phalanges raise new questions about the importance of arboreal behaviour in the A. afarensis locomotor repertoire.

In TripAdvisor we trust: Rankings, calculative regimes and abstract systems.

Abstract: A proliferation of rankings and league tables increasingly permeate everyday life. An objective of this paper is to explain the profusion of such rankings, in particular on-line user review rankings, in contemporary society and what this means for our understanding of the role of accounting. The online travel website TripAdvisor and its hotel ranking system is a prominent example of this new phenomenon. The site increasingly appears to play the role of trusted intermediary for the ‘independent traveller’ who spurns the services of the traditional travel agent in favour of making their own holiday arrangements. In this paper, we undertake netnographic research to consider the way in which TripAdvisor rankings engender trust. Drawing on the site’s own operational features together with an analysis of the traveller commentaries hosted within the site, we argue that the case of TripAdvisor is a powerful illustration of an internet mediated abstract system ( Giddens, 1990 , Giddens, 1991 ) that draws on calculative practices to construct trust. In addition, we speculate as to the implications of the proliferation of such internet mediated expert systems, both on the accounting profession, and on future accounting research.

The evolution of twisting coronal magnetic flux tubes

Abstract: We simulate the twisting of an initially potential coronal flux tube by photospheric vortex motions, centred at two photospheric flux concentrations, using the compressible zero-beta ideal MHD equations. A twisted flux tube is formed, surrounded by much less twisted and sheared outer flux. Under the action of continuous slow driving, the flux tube starts to evolve quasi-statically along a sequence of force-free equilibria, which rise slowly with increasing twist and possess helical shape. The flux bundle that extends from the location of peak photospheric current density ( slightly displaced from the vortex centre) shows a sigmoidal shape in agreement with observations of sigmoidal soft X-ray loops. There exists a critical twist, above which no equilibrium can be found in the simulation and the flux tube ascends rapidly. Then either stable equilibrium ceases to exist or the character of the sequence changes such that neighbouring stable equilibria rise by enormous amounts for only modest additions of twist. A comparison with the scalings of the rise of flux in axisymmetric geometry by Sturrock et al. ( 1995) suggests the former. Both cases would be observed as an eruption. The critical end-to-end twist, for a particular set of parameters describing the initial potential field, is found to lie in the range 2.5pi < Phi(c) < 2.75pi. There are some indications for the growth of helical perturbations at supercritical twist. Depending on the radial profiles of the photospheric flux concentration and vortex velocity, the outer part or all of the twisted flux expands from the central field line of the flux tube. This effect is particularly efficient in the dynamic phase, provided the density is modeled realistically, falling off sufficiently rapidly with height. It is expected to lead to the formation of a cavity in which the twisted flux tube is embedded, analogous to the typical structure of coronal mass ejections.