The existence and detection of optically dark galaxies by 21cm surveys

One explanation for the disparity between Cold Dark Matter (CDM) predictions of galaxy numbers and observations could be that there are numerous dark galaxies in the Universe. These galaxies may still contain baryons, but no stars, and may be detectable in the 21cm line of atomic hydrogen. The results of surveys for such objects, and simulations that do/do not predict their existence, are controversial. In this paper we use an analytical model of galaxy formation, consistent with CDM, to firstly show that dark galaxies are certainly a prediction of the model. Secondly, we show that objects like VIRGOHI21, a dark galaxy candidate recently discovered by us, while rare are predicted by the model. Thirdly, we show that previous 'blind' HI surveys have placed few constraints on the existence of dark galaxies. This is because they have either lacked the sensitivity and/or velocity resolution or have not had the required detailed optical follow up. We look forward to new 21cm blind surveys (ALFALFA and AGES) using the Arecibo multi-beam instrument which should find large numbers of dark galaxies if they exist

Towards an index of relative Indigenous socioeconomic disadvantage

Understanding geographic variations in the socioeconomic status of Indigenous peoples is of importance when developing policies aimed at reducing the level of Indigenous disadvantage. Knowledge of geographic variations in socioeconomic status provides an understanding of some of the underlying structural reasons and impediments to improving the socioeconomic status of Indigenous Australians. This paper explores how a variety of indicators of socioeconomic status that can be combined to form a composite index of relative socioeconomic disadvantage for Aboriginal and Torres Strait Islander Commission (ATSIC) regional council areas. Data from the 1991 and 1996 Censuses, augmented with administrative data from ATSIC are used to construct an index of relative socioeconomic disadvantage for the 36 ATSIC regional council areas. The changes in relative socioeconomic disadvantage between 1991 and 1996 are also analysed. The estimates in this paper are the first for Indigenous Australians using 1996 Census data. The limitations of relative indexes of socioeconomic disadvantage, particularly with respect to Indigenous Australians, are discussed. Particular attention is paid to data limitations which are exacerbated when comparing relative socioeconomic disadvantage over time. However, in spite of the many limitations, carefully selected variables can be used to estimate a ranking of socioeconomic disadvantage of ATSIC regional council areas. This research paper is timely as the Commonwealth Grants Commission (CGC) is conducting the Indigenous Funding Inquiry, measuring the relative need of Indigenous people in different geographic regions. In this context, an important contribution of this paper is an assessment of the usefulness of a composite index of relative socioeconomic disadvantage for the calculation of funding relativities. The conclusion reached is that relative indexes of socioeconomic disadvantage, such as the one documented in this paper, are of very limited use in calculating funding relativities

Herbicide impacts on exotic grasses and a population of the critically endangered herb "Calystegia affinis" (Convolvulaceae) on Lord Howe Island

Introduced perennial grasses are capable of altering the habitat of native species, causing reductions in population size and vigour, and potentially affecting life-history processes such as survival, pollination and seedling recruitment. We examined the utility of herbicide treatment on two exotic grasses, Pennisetum clandestinum (Kikuyu) and Stenotaphrum secundatum (Buffalo grass) to restore the habitat of Calystegia affinis, a critically endangered species endemic to Lord Howe and Norfolk Islands. Using two herbicides, Asset (designed to affect only grasses) and Glyphosate (a general herbicide), we compared effectiveness in reducing grass cover on a population of Calystegia affinis. We protected Calystegia plants from the herbicides by ensuring their leaves were covered by plastic bags during herbicide application. Both herbicides were similarly effective in reducing grass cover after four weeks and had no noticeable adverse affect on Calystegia (suggesting the plastic bag protection was effective). After 26 weeks, Glyphosate was more effective in maintaining a reduced grass cover. Plots treated with either herbicide had a greater relative increase in abundance of Calystegia stems compared to untreated controls. The Glyphosate treatment resulted in the greatest relative increase in stem abundance, but this was not significantly greater than in the Asset treatment. We consider that spraying with Glyphosate treatment, with follow-up monitoring and spot-spraying, will assist the recovery of the Calystegia affinis population. Ultimately, the maintenance of a weed-free zone at the forest edge will provide suitable habitat for additional recruitment of this and other native species

Towards an index of relative Indigenous socioeconomic disadvantage

Understanding geographic variations in the socioeconomic status of Indigenous peoples is of importance when developing policies aimed at reducing the level of Indigenous disadvantage. Knowledge of geographic variations in socioeconomic status provides an understanding of some of the underlying structural reasons and impediments to improving the socioeconomic status of Indigenous Australians. This paper explores how a variety of indicators of socioeconomic status that can be combined to form a composite index of relative socioeconomic disadvantage for Aboriginal and Torres Strait Islander Commission (ATSIC) regional council areas. Data from the 1991 and 1996 Censuses, augmented with administrative data from ATSIC are used to construct an index of relative socioeconomic disadvantage for the 36 ATSIC regional council areas. The changes in relative socioeconomic disadvantage between 1991 and 1996 are also analysed. The estimates in this paper are the first for Indigenous Australians using 1996 Census data. The limitations of relative indexes of socioeconomic disadvantage, particularly with respect to Indigenous Australians, are discussed. Particular attention is paid to data limitations which are exacerbated when comparing relative socioeconomic disadvantage over time. However, in spite of the many limitations, carefully selected variables can be used to estimate a ranking of socioeconomic disadvantage of ATSIC regional council areas. This research paper is timely as the Commonwealth Grants Commission (CGC) is conducting the Indigenous Funding Inquiry, measuring the relative need of Indigenous people in different geographic regions. In this context, an important contribution of this paper is an assessment of the usefulness of a composite index of relative socioeconomic disadvantage for the calculation of funding relativities. The conclusion reached is that relative indexes of socioeconomic disadvantage, such as the one documented in this paper, are of very limited use in calculating funding relativities

Shoe or stew? Balancing wants and needs in Indigenous households: A study of appropriate income support payments and policies for families

Can service delivery and program development accommodate cultural parameters? What bureaucratic mechanisms could encompass such accommodations in program delivery and/or policy stance? Such fundamental questions are addressed in this discussion paper by charting the process of undertaking field-based research on the effectiveness of government income support payments to Indigenous families for care of children. The paper details how the pilot study for the field investigation led firstly, to issues of appropriate research methodology and field practice, and secondly, required careful specification of the arenas of Indigenous domestic life which could, or should, give grounds to justify State intervention and scrutiny as an action in the 'best interests' of Indigenous people. An immediate outcome of the pilot study is that Aboriginal domestic circumstances and family life are far more complex and volatile than policy makers might expect, or than service deliverers may be able to accommodate. Ethnographic literature confirms this. It adds weight to the view argued here, that policy and program intervention must be carefully handled because many of the identified internal dynamics of Indigenous welfare-based households have yet to be fully understood. These dynamics relate to income poverty, patterns of household expenditure and wider issues of sociality as these are impacted upon by residential mobility and the differential demands of age and gender on household membership, stability and economic wellbeing. Arguably, the conclusions of the Kuranda pilot study project indicate that basic issues of infrastructure, namely, appropriate and adequate housing and access to public transport, remain core concerns for Indigenous households and the quality of life that they experience. Amelioration of these factors of service provision alone would directly enhance the circumstances in which welfare-reliant Indigenous families in Kuranda endeavour to care for their families' needs

Inactivation of cloned Na channels expressed in Xenopus oocytes

This study investigates the inactivation properties of Na channels expressed in Xenopus oocytes from two rat IIA Na channel cDNA clones differing by a single amino acid residue. Although the two cDNAs encode Na channels with substantially different activation properties (Auld, V. J., A. L. Goldin, D. S. Krafte, J. Marshall, J. M. Dunn, W. A. Catterall, H. A. Lester, N. Davidson, and R. J. Dunn. 1988. Neuron. 1:449-461), their inactivation properties resemble each other strongly but differ markedly from channels induced by poly(A+) rat brain RNA. Rat IIA currents inactivate more slowly, recover from inactivation more slowly, and display a steady-state voltage dependence that is shifted to more positive potentials. The macroscopic inactivation process for poly(A+) Na channels is defined by a single exponential time course; that for rat IIA channels displays two exponential components. At the single-channel level these differences in inactivation occur because rat IIA channels reopen several times during a depolarizing pulse; poly(A+) channels do not. Repetitive stimulation (greater than 1 Hz) produces a marked decrement in the rat IIA peak current and changes the waveform of the currents. When low molecular weight RNA is coinjected with rat IIA RNA, these inactivation properties are restored to those that characterize poly(A+) channels. Slow inactivation is similar for rat IIA and poly(A+) channels, however. The data suggest that activation and inactivation involve at least partially distinct regions of the channel protein

Maximizing phonon thermal conductance for ballistic membranes

At low temperatures, phonon scattering can become so weak that phonon transport becomes ballistic. We calculate the ballistic phonon conductance G for membranes using elasticity theory, considering the transition from three to two dimensions. We discuss the temperature and thickness dependence and especially concentrate on the issue of material parameters. For all membrane thicknesses, the best conductors have, counter-intuitively, the lowest speed of sound.Comment: 4 pages, 4 figures, proceedings to phonons 2007 conferenc

Determinants of sustained volunteerism in sport organisations in Hong Kong

Oral presentation: abstract 2014-274INTRODUCTION: The crucial role played by volunteers in sport service delivery is well recognised and documented. However, while there has been considerable research on sport volunteers, most studies have been based typically on theories and samples derived from a western context. This study examined determinants of sustained volunteerism in sport organisations in Hong Kong adapting a theoretical model developed by Penner (2002) …postprin

Progress in Eddy Current Modeling via the Boundary Element Method

For the past several years, we have been developing an eddy current model, using the boundary element method (BEM). Last year, in particular, a BEM algorithm based on the Hertz potential approach was found and shown to be effective in dealing with complex part geometry, while keeping the computational resource requirement to a minimum [1–3]. This paper concerns a further extension of the model to include cracks

The Arecibo Galaxy Environments survey IV: the NGC7448 region and the HI mass function

In this paper we describe results from the Arecibo Galaxy Environments Survey (AGES). The survey reaches column densities of ~3x10^18 cm^-2 and masses of ~10^7 M_O, over individual regions of order 10 sq deg in size, out to a maximum velocity of 18,000 km s^-1. Each surveyed region is centred on a nearby galaxy, group or cluster, in this instance the NGC7448 group. Galaxy interactions in the NGC7448 group reveal themselves through the identification of tidal tails and bridges. We find ~2.5 times more atomic gas in the inter-galactic medium than in the group galaxies. We identify five new dwarf galaxies, two of which appear to be members of the NGC7448 group. This is too few, by roughly an order of magnitude, dwarf galaxies to reconcile observation with theoretical predictions of galaxy formation models. If they had observed this region of sky previous wide area blind HI surveys, HIPASS and ALFALFA, would have detected only 5% and 43% respectively of the galaxies we detect, missing a large fraction of the atomic gas in this volume. We combine the data from this paper with that from our other AGES papers (370 galaxies) to derive a HI mass function with the following Schechter function parameters alpha=-1.52+/-0.05, M^*=5.1+/-0.3x10^9 h_72^-2 M_O, phi=8.6+/-1.1x10-3 h_72^3 Mpc^-3 dex-1. Integrating the mass function leads to a cosmic mass density of atomic hydrogen of Omega_HI=5.3+/-0.8x10^-4 h_72^-1. Our mass function is steeper than that found by both HIPASS and ALFALFA (alpha=1.37 and 1.33 respectively), while our cosmic mass density is consistent with ALFALFA, but 1.7 times larger than found by HIPASS