244 research outputs found
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The Journey to R4D: An institutional history of an Australian Initiative on Food Security in Africa
Internal Revie
Improving Predictions for Helium Emission Lines
We have combined the detailed He I recombination model of Smits with the
collisional transitions of Sawey & Berrington in order to produce new accurate
helium emissivities that include the effects of collisional excitation from
both the 2 (3)S and 2 (1) S levels. We present a grid of emissivities for a
range of temperature and densities along with analytical fits and error
estimates.
Fits accurate to within 1% are given for the emissivities of the brightest
lines over a restricted range for estimates of primordial helium abundance. We
characterize the analysis uncertainties associated with uncertainties in
temperature, density, fitting functions, and input atomic data. We estimate
that atomic data uncertainties alone may limit abundance estimates to an
accuracy of 1.5%; systematic errors may be greater than this. This analysis
uncertainty must be incorporated when attempting to make high accuracy
estimates of the helium abundance. For example, in recent determinations of the
primordial helium abundance, uncertainties in the input atomic data have been
neglected.Comment: ApJ, accepte
The journey to R4D: An institutional history of an Australian initiative on food Security in Africa
A New Observational Upper Limit to the Low Redshift Ionizing Background Radiation
We report a new Fabry-Perot search for Halpha emission from the intergalactic
cloud HI 1225+01 in an attempt to measure the low redshift ionizing background
radiation. We set a new 2 sigma upper limit on Halpha emission of 8 mR (5 x
10^{-20} ergs cm^{-2} s^{-1} arcsec^{-2}). Conversion of this limit to limits
on the strength of the ionizing background requires knowledge of the ratio of
the projected to total surface area of this cloud, which is uncertain. We
discuss the plausible range of this ratio, and within this range find that the
strength of the ionizing backround is in the lower range of, but consistent
with, previous observational and theoretical estimates.Comment: 46 pages including 9 figures (7 ps, 2 gif
Selection of Forages for the Tropics (SoFT) - A Database and Selection Tool for Identifying Forages Adapted to Local Conditions in the Tropics and Subtropics
Rising populations and incomes in developing countries are likely to double demand for livestock products by 2020 (Delgado et al. 1999). This strong demand has potential to improve profitability for farmers but will require improved animal feeding in both semi-intensive crop-livestock and more extensive livestock systems. Forages usually are the most cost-effective option to supply feed demands, particularly for ruminant-, but also for pig- and poultry- production. It is critical to select the most suitable forages for the local system and conditions. Small- and even larger-scale farmers depend heavily on advice from extension and development agencies, and from seed companies, but this advice often is limited by inexperience and the difficulty in accessing reliable information. Expert information on an extensive range of tropical forages is now readily available through the SoFT database
Accurate Hydrogen Spectral Simulations with a Compact Model Atom
Many large scale numerical simulations of astrophysical plasmas must also
reproduce the hydrogen ionization and the resulting emission spectrum, in some
cases quite accurately. We describe a compact model hydrogen atom that can be
readily incorporated into such simulations. It reproduces the recombination
efficiency and line spectrum predicted by much larger calculations for a very
broad range of densities and temperatures. Uncertainties in hydrogen collision
data are the largest source of differences between our compact atom and
predictions of more extensive calculations, and underscore the need for
accurate atomic data.Comment: 18 pages, prepared in MS-Word, Postscript only, 12 Figures, also
available at http://www.pa.uky.edu/~ferguson/bib/bib.html, accepted for
publication in the Astrophysical Journa
'Caught Between a Rock and a Hard Place': Anti-discrimination Legislation in the Liberal State and the Fate of the Australian Disability Discrimination Act
This article offers a critical analysis of some of the practical implications for disabled people of the Disability Discrimination Act of 1992. Specifically, it raises questions about politics and the role of the law as an instrument of social change?taking greater account of the interests of disabled people?on the one hand, and of the reliance of the social model of disability on a strategy based upon legal rights on the other. The article also suggests that the constraining effects of Australia's constitutional protections of rights and its federal system of government hinder the mildly progressive elements of the Disability Discrimination Act. To illustrate this, the paper employs empirical evidence to suggest that these effects have been exacerbated by the passage of the Human Rights Legislation Amendment Act in 1999
Commercial chicken breeds exhibit highly divergent patterns of linkage disequilibrium
The analysis of linkage disequilibrium (LD) underpins the development of effective genotyping technologies, trait mapping and understanding of biological mechanisms such as those driving recombination and the impact of selection. We apply the Malécot-Morton model of LD to create additive LD maps that describe the high-resolution LD landscape of commercial chickens. We investigated LD in chickens (Gallus gallus) at the highest resolution to date for broiler, white egg and brown egg layer commercial lines. There is minimal concordance between breeds of fine-scale LD patterns (correlation coefficient <0.21), and even between discrete broiler lines. Regions of LD breakdown, which may align with recombination hot spots, are enriched near CpG islands and transcription start sites (P<2.2 à 10?16), consistent with recent evidence described in finches, but concordance in hot spot locations between commercial breeds is only marginally greater than random. As in other birds, functional elements in the chicken genome are associated with recombination but, unlike evidence from other bird species, the LD landscape is not stable in the populations studied. The development of optimal genotyping panels for genome-led selection programmes will depend on careful analysis of the LD structure of each line of interest. Further study is required to fully elucidate the mechanisms underlying highly divergent LD patterns found in commercial chickens
MORPHOLOGY AND PRODUCTIVITY OF "JUREMINHA" GENOTYPES (Desmanthus spp.) UNDER DIFFERENT CUTTING INTENSITIES
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