Four New Planets Orbiting Metal-enriched Stars

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Differences in mineral concentration among diploid and tetraploid cultivars of rhodesgrass (Chloris gayana)

Mineral composition of a range of rhodesgrass cultivars was measured to assess if levels were suitable for cattle growth. Leafy regrowth of 11 rhodesgrass cultivars and lines was analysed for a range of elements in 2 replicated field experiments near Gympie in southern Queensland. Experiment 1 comprised 2 diploid and 2 tetraploid cultivars, while 7 diploids and 3 tetraploids were compared in experiment 2.Overall, the tetraploids had higher nitrogen (N), potassium (K), calcium (Ca), and magnesium (Mg) concentrations but lower sodium (Na) and boron (B) concentrations than the diploids. Concentrations of potassium (P), copper (Cu) and aluminium (Al) for the 2 groups were similar and showed no significant cultivar differences. Results for sulfur (S), zinc (Zn) and iron (Fe) varied between experiments, either with no significant ploidy and cultivar differences or with higher concentrations in the tetraploids (S in experiment 2, Zn in experiment 1). The tetraploids had significantly higher concentrations of Mn in experiment 2. The Na concentration found in cultivar Boma was lower (0.02%) than the other cultivars in experiment 2. Similarly, cultivar Samford in experiment 1 had a lower Na concentration than the other 3 cultivars. Both Boma and Samford, however, had the highest Mg concentrations in their respective experiments. K/(Ca+ Mg) equivalent ratios in the 2 experiments were in the range 0.40-1.50. This is well below the accepted critical value of 2.2 above which grass tetany in ruminants could become a problem

Maintaining biosecurity in aquaculture systems: A constraint or a challenge

Biosecurity can be defined as the protection of plants, animals (including humans and associated activities) and the wider environment from the unwanted impacts of biological agents including diseases and pests. As a discipline, biosecurity can be applied at various levels. In the context of aquatic animal disease, this can range from managing the health of individual animals, through whole commercial enterprise to national or international biosecurity. The last three decades or so have seen an increase in the farming of aquatic animals worldwide – a situation compounded from a biosecurity perspective by a quantum leap in aquaculture technologies, countries and species new to aquaculture, increased international movement of juvenile animals and broodstock; all in an environment of little knowledge of the health status of source populations and the frequent emergence of new diseases. The end-result of this change has been significant farm level production losses well documented in the scientific and lay literature. The focus on increased farm level biosecurity in recent times has been in direct response to this very real threat. All aquaculture operations rely on trade (commercial exchanges) to some extent. Trade provides stock, genetic material, inputs (such as feeds, vaccines, treatments, etc.) and takes the outputs (product). Aquaculture operations are not isolated from the realities of trade and the associated biosecurity risks. This paper describes the various elements that make for good farm level biosecurity and assesses the resourcing needs against net long- and short-term benefits to production. This paper also examines the role that farm biosecurity plays in overall regional or national biosecurity systems, with particular emphasis on the Australian experience. Farm level biosecurity is placed in context with inter- or intra-national disease zoning (and compartmentalisation), national quarantine control and global biosecurity initiatives such as international disease reporting and standards setting. The necessity for on-farm biosecurity as a complement to zoning and the more traditional country quarantine requirements is emphasized

Iterative Solution of Constrained Differential/Algebraic Systems

The dynamics of a large class of engineering systems can be approximately described by coupled algebraic and differential equations of the form (e.g. see Appendix A.1

Quadratic Optimization with Bounded Linear Constraints

A recently developed algorithm for the solution of linear constrained differential-algebraic systems is extended to provide a systematic computational procedure for the solution of quadratic optimization problems with bounded linear constraints. The technique has rapid convergence and can be applied to minimum norm solution of algebraic equations, minimum energy control problems and linear quadratic optimal control problems with linear control and state constraints

Galactic X-ray binary jets

With their relatively fast variability time-scales, Galactic X-ray binaries provide an excellent laboratory to explore the physics of accretion and related phenomena, most notably outflows, over different regimes. After comparing the phenomenology of jets in black hole X-ray binary systems to that of neutron stars, here I discuss the role of the jet at very low Eddington ratios, and present preliminary results obtained by fitting the broadband spectral energy distribution of a quiescent black hole binary with a `maximally jet-dominated' model.Comment: Refereed version, accepted for publication in Astrophysics & Space Scienc

The fading of two transient ultraluminous x-ray sources to below the stellar mass Eddington limit

We report new detections of the two transient ultraluminous X-ray sources (ULXs) in NGC 5128 from an ongoing series of Chandra observations. Both sources have previously been observed L (2-3) × ∼10 erg s, at the lower end of the ULX luminosity range. The new observations allow us to study these sources in the luminosity regime frequented by the Galactic black hole X-ray binaries (BH XBs). We present the recent lightcurves of both ULXs. 1RXH J132519.8-430312 (ULX1) was observed at L 1 × 10 erg s, while CXOU J132518.2-430304 (ULX2) declined to L 2 × 10 erg s and then lingered at this luminosity for hundreds of days. We show that a reasonable upper limit for both duty cycles is 0.2, with a lower limit of 0.12 for ULX2. This duty cycle is larger than anticipated for transient ULXs in old stellar populations. By fitting simple spectral models in an observation with ∼50 counts we recover properties consistent with Galactic BH XBs, but inconclusive as to the spectral state. We utilize quantile analyses to demonstrate that the spectra are generally soft, and that in one observation the spectrum of ULX2 is inconsistent with a canonical hard state at >95% confidence. This is contrary to what would be expected of an accreting intermediate mass black hole primary, which we would expect to be in the hard state at these luminosities. We discuss the paucity of transient ULXs discovered in early-type galaxies and excogitate explanations. We suggest that the number of transient ULXs scales with the giant and sub-giant populations, rather than the total number of XBs.Peer reviewe