Transmission of Digitaria Streak Virus by the Maize Streak Virus Leafhopper Vector Cicadulina Mbila Naude

An unpublished account of possible trans-encapsidation of one mastrevirus by another, allowing transmission of both by a vector that normally only transmits one

Partial suppression of the radial orbit instability in stellar systems

It is well known that the simple criterion proposed originally by Polyachenko and Shukhman (1981) for the onset of the radial orbit instability, although being generally a useful tool, faces significant exceptions both on the side of mildly anisotropic systems (with some that can be proved to be unstable) and on the side of strongly anisotropic models (with some that can be shown to be stable). In this paper we address two issues: Are there processes of collisionless collapse that can lead to equilibria of the exceptional type? What is the intrinsic structural property that is responsible for the sometimes noted exceptional stability behavior? To clarify these issues, we have performed a series of simulations of collisionless collapse that start from homogeneous, highly symmetrized, cold initial conditions and, because of such special conditions, are characterized by very little mixing. For these runs, the end-states can be associated with large values of the global pressure anisotropy parameter up to 2K_r/K_T \approx 2.75. The highly anisotropic equilibrium states thus constructed show no significant traces of radial anisotropy in their central region, with a very sharp transition to a radially anisotropic envelope occurring well inside the half-mass radius (around 0.2 r_M). To check whether the existence of such almost perfectly isotropic "nucleus" might be responsible for the apparent suppression of the radial orbit instability, we could not resort to equilibrium models with the above characteristics and with analytically available distribution function; instead, we studied and confirmed the stability of configurations with those characteristics by initializing N-body approximate equilibria (with given density and pressure anisotropy profiles) with the help of the Jeans equations.Comment: 26 pages, 9 figures, accepted for publication in The Astrophysical Journa

Six-Dimensional (1,0) Superconformal Models and Higher Gauge Theory

We analyze the gauge structure of a recently proposed superconformal field theory in six dimensions. We find that this structure amounts to a weak Courant-Dorfman algebra, which, in turn, can be interpreted as a strong homotopy Lie algebra. This suggests that the superconformal field theory is closely related to higher gauge theory, describing the parallel transport of extended objects. Indeed we find that, under certain restrictions, the field content and gauge transformations reduce to those of higher gauge theory. We also present a number of interesting examples of admissible gauge structures such as the structure Lie 2-algebra of an abelian gerbe, differential crossed modules, the 3-algebras of M2-brane models and string Lie 2-algebras.Comment: 31+1 pages, presentation slightly improved, version published in JM

First year student expectations: Results from a university-wide student survey

Although much has been written on the first-year experience of students at higher education institutions, less attention has been directed to the expectations of students when they enter an institution for the first time. This paper provides additional insights into the expectations of students at an Australian university and highlights areas in which students’ expectations may not necessarily align with the realities of common university practices. By providing opportunities for students to articulate their expectations, staff are able to use the responses for a constructive dialogue and work towards a more positive alignment between perceived expectations and levels of student satisfaction with their experience.Geoffrey Crisp, Edward Palmer, Deborah Turnbull, Ted Nettelbeck, Lynn Ward, Amanda LeCouteur, Aspa Sarris, Peter Strelan, and Luke Schneide

The invertebrate diet of northern bobwhite chicks in Georgia, United States

Dieta a base de invertebrados de las crías del colín de Virginia en Georgia, Estados Unidos El establecimiento de hábitats de cría a lo largo de los márgenes de los campos se ha convertido en una norma agro–medioambiental muy popular, para ayudar a invertir la disminución de las poblaciones del colín de Virginia (Colinus virginianus) en Georgia, Estados Unidos. En este estudio se examina la dieta a base de invertebrados de los pollos, con hábitats de cría bien establecidos, que forrajean en las tierras de labrantío, en comparación con la de las crías de un coto de caza de colines de Virginia salvajes gestionado intensivamente. En los años 2001 y 2002 se recogieron muestras fecales de los lugares de descanso nocturnos de las crías, y se analizaron. Se investigaron las diferencias en cuanto a la composición de invertebrados entre los lugares de estudio, utilizando un análisis composicional. Mientras que la dieta de los pollos de ambos lugares contenía grupos de invertebrados similares, la composición de las dietas variaba significativamente. A pesar de que las crías de los cultivos habían comido 1,7 veces menos coleópteros, habían devorado 1,7 veces más hemípteros. Estos datos sugieren que aunque la composición de invertebrados de la dieta de las crías difería entre los dos tipos de hábitat, en ambos contenía grandes proporciones de las presas más importantes.Dieta a base de invertebrados de las crías del colín de Virginia en Georgia, Estados Unidos El establecimiento de hábitats de cría a lo largo de los márgenes de los campos se ha convertido en una norma agro–medioambiental muy popular, para ayudar a invertir la disminución de las poblaciones del colín de Virginia (Colinus virginianus) en Georgia, Estados Unidos. En este estudio se examina la dieta a base de invertebrados de los pollos, con hábitats de cría bien establecidos, que forrajean en las tierras de labrantío, en comparación con la de las crías de un coto de caza de colines de Virginia salvajes gestionado intensivamente. En los años 2001 y 2002 se recogieron muestras fecales de los lugares de descanso nocturnos de las crías, y se analizaron. Se investigaron las diferencias en cuanto a la composición de invertebrados entre los lugares de estudio, utilizando un análisis composicional. Mientras que la dieta de los pollos de ambos lugares contenía grupos de invertebrados similares, la composición de las dietas variaba significativamente. A pesar de que las crías de los cultivos habían comido 1,7 veces menos coleópteros, habían devorado 1,7 veces más hemípteros. Estos datos sugieren que aunque la composición de invertebrados de la dieta de las crías difería entre los dos tipos de hábitat, en ambos contenía grandes proporciones de las presas más importantes.The establishment of brood–rearing habitats along field margins has become a popular agri–environmental prescription to help reverse population declines of northern bobwhite (Colinus virginianus) in Georgia, United States. Here, the invertebrate–diet of chicks foraging on farmland with established brood–rearing habitats is examined and compared to those of chicks on an intensively managed wild bobwhite shooting estate. In 2001 and 2002, faecal samples were collected and analysed from nocturnal roost sites of bobwhite broods. Differences in invertebrate composition between the study sites were investigated using compositional analysis. While the diet of chicks on both sites contained similar invertebrate groups, the composition of the diets varied significantly. Although chicks on farmland had eaten 1.7 times fewer Coleoptera, they had 1.7 times more Hemiptera in their diet. These data suggest that although the invertebrate composition in the diet of chicks differed between the two landscapes, both contained high proportions of important prey items

Assessment of an electronic voting system within the tutorial setting: a randomised controlled trial (ISRCTN54535861)

Background: Electronic voting systems have been used in various educational settings with little measurement of the educational impact on students. The goal of this study was to measure the effects of the inclusion of an electronic voting system within a small group tutorial. Method: A prospective randomised controlled trial was run at the Royal Adelaide Hospital, a teaching hospital in Adelaide, Australia. 102 students in their first clinical year of medical school participated in the study where an electronic voting system was introduced as a teaching aid into a standard tutorial. Long-term retention of knowledge and understanding of the topics discussed in the tutorials was measured and student response to the introduction of the electronic voting system was assessed. Results: Students using the electronic voting system had improved long-term retention of understanding of material taught in the tutorial. Students had a positive response to the use of this teaching aid. Conclusion: Electronic voting systems can provide a stimulating learning environment for students and in a small group tutorial may improve educational outcomes.Edward J. Palmer, Peter G. Devitt, Neville J. De Young and David Morri

Transformation of stimulus correlations by the retina

Redundancies and correlations in the responses of sensory neurons seem to waste neural resources but can carry cues about structured stimuli and may help the brain to correct for response errors. To assess how the retina negotiates this tradeoff, we measured simultaneous responses from populations of ganglion cells presented with natural and artificial stimuli that varied greatly in correlation structure. We found that pairwise correlations in the retinal output remained similar across stimuli with widely different spatio-temporal correlations including white noise and natural movies. Meanwhile, purely spatial correlations tended to increase correlations in the retinal response. Responding to more correlated stimuli, ganglion cells had faster temporal kernels and tended to have stronger surrounds. These properties of individual cells, along with gain changes that opposed changes in effective contrast at the ganglion cell input, largely explained the similarity of pairwise correlations across stimuli where receptive field measurements were possible.Comment: author list corrected in metadat