5,379 research outputs found
An algorithm to identify automorphisms which arise from self-induced interval exchange transformations
We give an algorithm to determine if the dynamical system generated by a
positive automorphism of the free group can also be generated by a self-induced
interval exchange transformation. The algorithm effectively yields the interval
exchange transformation in case of success.Comment: 26 pages, 8 figures. v2: the article has been reorganized to make for
a more linear read. A few paragraphs have been added for clarit
Effect of a Summer Period at Pasture on the Performance of Young Bulls Offered Concentrates \u3cem\u3eAd Libitum\u3c/em\u3e
Holstein bull calves can produce a 250 kg carcass at 11 to 12 months of age on indoor feeding of ad libitum concentrates. An outdoor period at pasture would reduce housing costs. Two experiments were undertaken to determine the effect of an outdoor period at pasture on concentrate intake, liveweight gain and selected carcass traits of Holstein young bulls
Genetic Characteristics Required in Dairy and Beef Cattle for Temperate Grazing Systems
Key points
Only about 10% of the world’s milk is produced from grazing systems. Consequently the majority of dairy cattle have not been selected under grazing, nor on seasonal systems. This is not true for beef cattle, for which the majority, especially the dams, are managed under seasonal grazing systems.
In grazing systems daily feed intake is limited to lower levels than are achievable on concentrate plus conserved forage rations. Consequently, cows most suited to grazing environments are likely to have a lower genetic potential for milk production than cows selected in high concentrate systems, to minimise their relative energy deficit.
The traits required under grazing will include those for other systems; high yields of milk with high milk solids, efficient converters of feed to product, functionality, good fertility, health and longevity. Successful grazing systems require dairy cows that are adapted to achieving large intakes of forage relative to their potential milk yields, and therefore able to meet production potential exclusively from forage. Grazing cattle must also be able to walk long distances, and in seasonal systems, must be able to conceive and calve once every year. The ability to be productive when milked once daily may also be desirable in low cost grazing systems in the future.
Intensive selection for milk production within the Holstein-Friesian breed on high concentrate diets has generally resulted in a genotype that is not well suited to grazing (high forage) systems, in which these cows exist in permanent energy deficit. This unsuitability is particularly true for seasonal systems, for which good fertility is an essential trait.
There is now strong evidence for the existence of interactions between genotype of dairy cattle and feeding system, where the genetics and the systems differ widely. Therefore mutual compatibility between the cow and the system must be optimised for production and profit.
The New Zealand Friesian and New Zealand Jersey, and crosses between them, or with other dairy breeds, including the North American Holstein-Friesian, have been shown to be well suited to grazing systems. Increasing evidence suggests that genetics from some Scandinavian breeding programs, e.g. the Norwegian Red, may also be suited to grazing systems, where good fertility is essential.
Developments in international sire evaluation (adaptations of multiple across country evaluation (MACE)) that enable differences in management systems to be taken into account will provide different breeding values for different conditions. Until then, sires should be proven in the same general management conditions in which the daughters are to be managed.
There is little evidence of important G x E interactions in beef cattle, for growth rate, food intake or carcass traits.
But beef cows from large, late maturing breeds are relatively more restricted by inadequate nutrition than smaller early maturing types. As a result both their fertility and milk production can be impaired leading to a lower weaning percentage and lighter weaning weight.
Interactions between the effects of genotype and nutrition on carcass composition can occur where the level of energy intake is above the muscle deposition capacity of some breeds
The formation heritage of Jupiter Family Comet 10P/Tempel 2 as revealed by infrared spectroscopy
We present spectral and spatial information for major volatile species in
Comet 10P/Tempel 2, based on high-dispersion infrared spectra acquired on UT
2010 July 26 (heliocentric distance Rh = 1.44 AU) and September 18 (Rh = 1.62
AU), following the comet's perihelion passage on UT 2010 July 04. The total
production rate for water on July 26 was (1.90 +/- 0.12) x 10^28 molecules s-1,
and abundances of six trace gases (relative to water) were: CH3OH (1.58% +/-
0.23), C2H6 (0.39% +/- 0.04), NH3 (0.83% +/- 0.20), and HCN (0.13% +/- 0.02). A
detailed analysis of intensities for water emission lines provided a rotational
temperature of 35 +/- 3 K. The mean OPR is consistent with nuclear spin
populations in statistical equilibrium (OPR = 3.01 +/- 0.18), and the (1-sigma)
lower bound corresponds to a spin temperature > 38 K. Our measurements were
contemporaneous with a jet-like feature observed at optical wavelengths. The
spatial profiles of four primary volatiles display strong enhancements in the
jet direction, which favors release from a localized vent on the nucleus. The
measured IR continuum is much more sharply peaked and is consistent with a
dominant contribution from the nucleus itself. The peak intensities for H2O,
CH3OH, and C2H6 are offset by ~200 km in the jet direction, suggesting the
possible existence of a distributed source, such as the release of icy grains
that subsequently sublimed in the coma. On UT September 18, no obvious emission
lines were present in our spectra, nevertheless we obtained a 3-sigma upper
limit Q(H2O) < 2.86 x 10^27 molecules s-1
A Cosmic Census of Radio Pulsars with the SKA
The Square Kilometre Array (SKA) will make ground breaking discoveries in
pulsar science. In this chapter we outline the SKA surveys for new pulsars, as
well as how we will perform the necessary follow-up timing observations. The
SKA's wide field-of-view, high sensitivity, multi-beaming and sub-arraying
capabilities, coupled with advanced pulsar search backends, will result in the
discovery of a large population of pulsars. These will enable the SKA's pulsar
science goals (tests of General Relativity with pulsar binary systems,
investigating black hole theorems with pulsar-black hole binaries, and direct
detection of gravitational waves in a pulsar timing array). Using SKA1-MID and
SKA1-LOW we will survey the Milky Way to unprecedented depth, increasing the
number of known pulsars by more than an order of magnitude. SKA2 will
potentially find all the Galactic radio-emitting pulsars in the SKA sky which
are beamed in our direction. This will give a clear picture of the birth
properties of pulsars and of the gravitational potential, magnetic field
structure and interstellar matter content of the Galaxy. Targeted searches will
enable detection of exotic systems, such as the ~1000 pulsars we infer to be
closely orbiting Sgr A*, the supermassive black hole in the Galactic Centre. In
addition, the SKA's sensitivity will be sufficient to detect pulsars in local
group galaxies. To derive the spin characteristics of the discoveries we will
perform live searches, and use sub-arraying and dynamic scheduling to time
pulsars as soon as they are discovered, while simultaneously continuing survey
observations. The large projected number of discoveries suggests that we will
uncover currently unknown rare systems that can be exploited to push the
boundaries of our understanding of astrophysics and provide tools for testing
physics, as has been done by the pulsar community in the past.Comment: 20 pages, 7 figures, to be published in: "Advancing Astrophysics with
the Square Kilometre Array", Proceedings of Science, PoS(AASKA14)04
Geographic Differences in Hospital Waiting Times
Access to elective surgery in Australian public hospitals is rationed using waiting lists. In this article, we undertake a DiNardo-Fortin-Lemieux reweighting approach to attribute variation in waiting time to clinical need or to discrimination. Using data from NSW public patients in 2004-2005, we find the discrimination effect dominates clinical need especially in the upper tail of the waiting time distribution. We find evidence of favourable treatment of patients who reside in remote areas and discrimination in favour of patients residing in particular Area Health Services. These findings have policy implications for the design of equitable quality targets for public hospitals. © 2012 The Economic Society of Australia
Effects of Supplementary Concentrate Level and Separate or Mixed Feeding of Grass Silage and Concentrates on Rumen Fluid Composition in Steers
The effects of dietary concentrate level and method of feeding (separate or mixed) on performance and carcass traits of steers may be mediated through changes in rumen fluid composition. The objectives of this study were to determine the effects on rumen fluid composition of (1) supplementary concentrate level with grass silage, and (2) separate or mixed feeding of silage and concentrates
Effects of Supplementary Concentrate Level and Separate or Mixed Feeding of Grass Silage and Concentrates on Carcass Tissue Composition in Steers
Supplementary concentrate level may affect carcass composition in steers. Feeder wagons facilitate feeding and management. The objectives were to determine the effects of (1) supplementary concentrate level with grass silage, and (2) separate or mixed feeding of silage and concentrates, on ribs joint composition
Mitochondrial Dysfunction in Parkinson's Disease
Parkinson's disease (PD) is a progressive, neurodegenerative condition that has increasingly been linked with mitochondrial dysfunction and inhibition of the electron transport chain. This inhibition leads to the generation of reactive oxygen species and depletion of cellular energy levels, which can consequently cause cellular damage and death mediated by oxidative stress and excitotoxicity. A number of genes that have been shown to have links with inherited forms of PD encode mitochondrial proteins or proteins implicated in mitochondrial dysfunction, supporting the central involvement of mitochondria in PD. This involvement is corroborated by reports that environmental toxins that inhibit the mitochondrial respiratory chain have been shown to be associated with PD.
This paper aims to illustrate the considerable body of evidence linking mitochondrial dysfunction with neuronal cell death in the substantia nigra pars compacta (SNpc) of PD patients and to highlight the important need for further research in this area
Killing tensors in pp-wave spacetimes
The formal solution of the second order Killing tensor equations for the
general pp-wave spacetime is given. The Killing tensor equations are integrated
fully for some specific pp-wave spacetimes. In particular, the complete
solution is given for the conformally flat plane wave spacetimes and we find
that irreducible Killing tensors arise for specific classes. The maximum number
of independent irreducible Killing tensors admitted by a conformally flat plane
wave spacetime is shown to be six. It is shown that every pp-wave spacetime
that admits an homothety will admit a Killing tensor of Koutras type and, with
the exception of the singular scale-invariant plane wave spacetimes, this
Killing tensor is irreducible.Comment: 18 page
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