The Orbit of the L dwarf + T dwarf Spectral Binary SDSS J080531.84+481233.0

[abridged] We report four years of radial velocity monitoring observations of SDSS J080531.84+481233.0 that reveal significant and periodic variability, confirming the binary nature of the source. We infer an orbital period of 2.02$\pm$0.03 yr, a semi-major axis of 0.76$^{+0.05}_{-0.06}$ AU, and an eccentricity of 0.46$\pm$0.05, consistent with the amplitude of astrometric variability and prior attempts to resolve the system. Folding in constraints based on the spectral types of the components (L4$\pm$0.7 and T5.5$\pm$1.1), corresponding effective temperatures, and brown dwarf evolutionary models, we further constrain the orbital inclination of this system to be nearly edge-on (90$^o\pm$19$^o$), and deduce a large system mass ratio (M$_2$/M$_1$ = 0.86$^{+0.10}_{-0.12}$), substellar components (M$_1$ = 0.057$^{+0.016}_{-0.014}$ M$_{\odot}$, M$_2$ = 0.048$^{+0.008}_{-0.010}$ M$_{\odot}$), and a relatively old system age (minimum age = 4.0$^{+1.9}_{-1.2}$ Gyr). The measured projected rotational velocity of the primary ($v\sin{i}$ = 34.1$\pm$0.7 km/s) implies that this inactive source is a rapid rotator (period $\lesssim$ 3 hr) and a viable system for testing spin-orbit alignment in very-low-mass multiples. The combination of well-determined component atmospheric properties and masses near and/or below the hydrogen minimum mass make SDSS J0805+4812AB an important system for future tests of brown dwarf evolutionary models.Comment: 15 pages, 11 figures, accepted for publication to Ap

The Neonatal Chinchilla Cochlea: Morphological and Functional Study

The developmental time scale of the cochlea varies from species to species. We investigate here the condition of the neonatal cochlea in the chinchilla, a species increasingly used in auditory research. We have examined the morphology of cochlear hair cells using scanning microscopy, and the development of auditory function during the first postnatal month by monitoring auditory brainstem evoked responses (ABR). We find that although there were some outer hair cell kinocilia present in middle and apical areas, the hair cells otherwise were mature at 24 hours after birth. Furthermore, cochlear auditory thresholds are adult-like at birth. However, whilst there was little change in ABR thresholds over one month, there is evidence of continued maturation of the central auditory system as shown by the shortening of the PI-PS latency from 9.1 ms to 7. 7 ms

Herring larval surveys in the Celtic Sea and division VIIj in 1982/83

Peer-reviewed. This article can be found on the ICES website here: http://www.ices.dk/publications/our-publications/Pages/CM-documents.aspxSurveys for herring larvae in the Celtic Sea were conducted between October 1982 ~ and February 1983 for the fifth successive season. To take account of the amalgamation of the Celtic Sea and Div VIIJ herring for assessment purposes and to ascertain if many larval drift into the Irish Sea, the survey grid of previous years was modified for the 1982/83 season. However, because of the nature of the larvae distribution it appears reasonable to compare the larvae index for 1982/83 with those of the previous seasons. The increase in indices since 1978/79 has continued up to 1982/83 indicating a steady, but slow, recovery of the spawning stock. Very few larvae appear to drift into the Irish Sea

Herring larval surveys in the Celtic Sea and division VIIj in 1983/1984

Peer-reviewed. This article can be found on the ICES website here: http://www.ices.dk/publications/our-publications/Pages/CM-documents.aspxSurveys for herring larvae in the Celtic Sea were conducted for the sixth ~ successive season between October 1983 and February 1984. The modifications made to the survey grid in the previous season to take account of the amalgamation of the Celtic Sea and Division VIIj for assessment purposes and to ascertain if larvae drift into the Irish Sea were also adopted for the 1983/84 surveys. A drift of larvae towards the Irish Sea was apparent in 1983/84. The larval abundance index for 1983/84 based on a standard survey area was almost three times higher than any previous value. A continuous increase in larval indices since 1978/79 indicates a recovery of the spawning stock

The “ABC model”: a non-hydrostatic toy model for use in convective-scale data assimilation investigations

In developing methods for convective-scale data assimilation (DA) it is necessary to consider the full range of motions governed by the compressible Navier-Stokes equations (including non-hydrostatic and ageostrophic flow). These equations describe motion on a wide range of time-scales with non-linear coupling. For the purpose of developing new DA techniques that suit the convective-scale problem it is helpful to use so-called ‘toy models’ that are easy to run, and contain the same types of motion as the full equation set. Such a model needs to permit hydrostatic and geostrophic balance at large-scales, but to allow imbalance at small-scales, and in particular, it needs to exhibit intermittent convection-like behaviour. Existing ‘toy models’ are not always sufficient for investigating these issues. A simplified system of intermediate complexity derived from the Euler equations is presented, which supports dispersive gravity and acoustic modes. In this system the separation of time scales can be greatly reduced by changing the physical parameters. Unlike in existing toy models, this allows the acoustic modes to be treated explicitly, and hence inexpensively. In addition, the non-linear coupling induced by the equation of state is simplified. This means that the gravity and acoustic modes are less coupled than in conventional models. A vertical slice formulation is used which contains only dry dynamics. The model is shown to give physically reasonable results, and convective behaviour is generated by localised compressible effects. This model provides an affordable and flexible framework within which some of the complex issues of convective-scale DA can later be investigated. The model is called the “ABC model” after the three tunable parameters introduced: A (the pure gravity wave frequency), B (the modulation of the divergent term in the continuity equation), and C (defining the compressibility)

Assessing Resilience of Pasture Production to Climatic Changes

Increasing temperatures and atmospheric carbon dioxide (CO2) concentrations, together with changes to rainfall patterns, will influence seasonal pasture production; however climate change projections for south eastern Australia are uncertain (CSIRO and BoM 2007). Despite this, climate change impact assessments generally rely on specific climate projections, but in this study an alternative approach was developed to test the resilience of production to incremental changes in climate

Recyclable structural composites for marine renewable energy

The InterReg SeaBioComp project will develop and deliver demonstrators using innovative bio-based thermoplastic composite materials with mechanical properties comparable to conventional oil-based composites, durability tailored to the specific application (2 to >20 years), recycling potential, reduced CO2 emissions and reduced microplastic and ecotoxic impact in the marine environment. The University of Plymouth is investigating to use of manufacture by monomer infusion under flexible tooling (MIFT) with in situ polymerisation to produce natural, or glass, fibre reinforced structural composites. Following an extensive literature survey, the monomer selection has suggested two potential matrix materials: poly(methyl methacrylate) (PMMA) and poly(L-lactide) (PLA). The conference paper will present the progress in measurement of the composite mechanical properties and correlation to models predicting the material performance