The radius and mass of the subgiant star bet Hyi from interferometry and asteroseismology

We have used the Sydney University Stellar Interferometer (SUSI) to measure the angular diameter of beta Hydri. This star is a nearby G2 subgiant whose mean density was recently measured with high precision using asteroseismology. We determine the radius and effective temperature of the star to be 1.814+/-0.017 R_sun (0.9%) and 5872+/-44 K (0.7%) respectively. By combining this value with the mean density, as estimated from asteroseismology, we make a direct estimate of the stellar mass. We find a value of 1.07+/-0.03 M_sun (2.8%), which agrees with published estimates based on fitting in the H-R diagram, but has much higher precision. These results place valuable constraints on theoretical models of beta Hyi and its oscillation frequencies.Comment: 3 figures, 3 tables, to appear in MNRAS Letter

Global citizenship as the completion of cosmopolitanism

A conception of global citizenship should not be viewed as separate from, or synonymous with, the cosmopolitan moral orientation, but as a primary component of it. Global citizenship is fundamentally concerned with individual moral requirements in the global frame. Such requirements, framed here as belonging to the category of individual cosmopolitanism, offer guidelines on right action in the context of global human community. They are complementary to the principles of moral cosmopolitanism – those to be used in assessing the justice of global institutions and practices – that have been emphasised by cosmopolitan political theorists. Considering principles of individual and moral cosmopolitanism together can help to provide greater clarity concerning individual duties in the absence of fully global institutions, as well as clarity on individual obligations of justice in relation to emerging and still-developing trans-state institutions

Mild stress conditions during laboratory culture promote the proliferation of mutations that negatively affect Sigma B activity in Listeria monocytogenes

In Listeria monocytogenes, the full details of how stress signals are integrated into the σB regulatory pathway are not yet available. To help shed light on this question, we investigated a collection of transposon mutants that were predicted to have compromised activity of the alternative sigma factor B (σB). These mutants were tested for acid tolerance, a trait that is known to be under σB regulation, and they were found to display increased acid sensitivity, similar to a mutant lacking σB (ΔsigB). The transposon insertions were confirmed by whole-genome sequencing, but in each case, the strains were also found to carry a frameshift mutation in the sigB operon. The changes were predicted to result in premature stop codons, with negative consequences for σB activation, independently of the transposon location. Reduced σB activation in these mutants was confirmed. Growth measurements under conditions similar to those used during the construction of the transposon library revealed that the frameshifted sigB operon alleles conferred a growth advantage at higher temperatures, during late exponential phase. Mixed-culture experiments at 42°C demonstrated that the loss of σB activity allowed mutants to take over a population of parental bacteria. Together, our results suggest that mutations affecting σB activity can arise during laboratory culture because of the growth advantage conferred by these mutations under mild stress conditions. The data highlight the significant cost of stress protection in this foodborne pathogen and emphasize the need for whole-genome sequence analysis of newly constructed strains to confirm the expected genotype.This project has received funding from the European Union’s Horizon 2020 research-and-innovation program under Marie Skłodowska-Curie grant agreement no. 721456. Jialun Wu was funded by the Department of Agriculture, Food and the Marine (17/F/244)

High power, low frequency ultrasound: meniscal tissue interaction and ablation characteristics

This study evaluates high power low frequency ultrasound transmitted via a flat vibrating probe tip as an alternative technology for meniscal debridement in the bovine knee. An experimental force controlled testing rig was constructed using a 20kHz ultrasonic probe suspended vertically from a load cell. Effect of variation in amplitude of distal tip displacement (242-494µm peak-peak) settings and force (2.5-4.5N) on tissue removal rate (TRR) and penetration rate (PR) for fifty-two bovine meniscus samples was analyzed. Temperature elevation in residual meniscus was measured by embedded thermocouples and histological analysis. As amplitude or force increases, there is a linear increase in TRR (Mean: 0.9 to 11.2mg/s) and PR (Mean: 0.08 to 0.73mm/s). Maximum mean temperatures of 84.6°C and 52.3°C were recorded in residual tissue at 2mm and 4mm from the ultrasound probe-tissue interface. There is an inverse relationship between both amplitude and force, and temperature elevation, with higher settings resulting in less thermal damage