The millisecond pulsar mass distribution: Evidence for bimodality and constraints on the maximum neutron star mass

The mass function of neutron stars (NSs) contains information about the late evolution of massive stars, the supernova explosion mechanism, and the equation-of-state of cold, nuclear matter beyond the nuclear saturation density. A number of recent NS mass measurements in binary millisecond pulsar (MSP) systems increase the fraction of massive NSs (with $M > 1.8$ M$_{\odot}$) to $\sim 20\%$ of the observed population. In light of these results, we employ a Bayesian framework to revisit the MSP mass distribution. We find that a single Gaussian model does not sufficiently describe the observed population. We test alternative empirical models and infer that the MSP mass distribution is strongly asymmetric. The diversity in spin and orbital properties of high-mass NSs suggests that this is most likely not a result of the recycling process, but rather reflects differences in the NS birth masses. The asymmetry is best accounted for by a bimodal distribution with a low mass component centred at $1.393_{-0.029}^{+0.031}$ M$_{\odot}$ and dispersed by $0.064_{-0.025}^{+0.064}$ M$_{\odot}$, and a high-mass component with a mean of $1.807_{-0.132}^{+0.081}$ and a dispersion of $0.177_{-0.072}^{+0.115}$ M$_{\odot}$. We also establish a lower limit of $M_{max} \ge 2.018$ M$_{\odot}$ at 98% C.L. for the maximum NS mass, from the absence of a high-mass truncation in the observed masses. Using our inferred model, we find that the measurement of 350 MSP masses, expected after the conclusion of pulsar surveys with the Square-Kilometre Array, can result in a precise localization of a maximum mass up to 2.15 M$_{\odot}$, with a 5% accuracy. Finally, we identify possible massive NSs within the known pulsar population and discuss birth masses of MSPs.Comment: submitted to ApJ; 21 pages in aastex6 two-column format, 12 figures, 5 tables. Comments are welcom

Genetic diversity and divergence in the endangered Cape Verde warbler Acrocephalus brevipennis

Genetic factors play an important role in the long-term persistence of populations and species, and conservation strategies should take such factors into account. We use neutral molecular markers to assess diversity and divergence between the three remaining island populations of a little-studied endemic passerine, the Cape Verde warbler Acrocephalus brevipennis. Variation at both microsatellite loci and the cytochrome b gene reveal low diversity within the species overall, but considerable divergence among the populations on Santiago, Fogo and São Nicolau islands. The genetic markers show a gradient of genetic diversity with population size, with the smallest population of S. Nicolau being the least diverse, and the largest, Santiago, the most diverse. The more geographically isolated population on S. Nicolau is also more divergent from Santiago and Fogo than these two are from each other. The Cape Verde warbler diverged from its sister species, the greater swamp warbler Acrocephalus rufescens, within the last million years, and the three populations became isolated from one another 165,000–199,000 years ago. There is also evidence of population bottlenecks, especially on S. Nicolau. This population seems to have decreased during the last century, with potential for further decreases and even extinction. As the three populations are genetically distinct, with no evidence of gene flow between them, we argue they should be treated as separate management units for the successful conservation of this species

The Fractal Dimension As A Measure Of The Roughness Of Rock Discontinuity Profiles

An important factor in the analysis of deformation and failure of rock masses along discontinuities is the roughness of the jointing surfaces. The fractal dimension is proposed as a method of objectively quantifying the roughness profile of such discontinuities. With this method much less engineering judgement and experience are required in determining the surface roughness,sb than is required for other methods such as the widely used joint roughness coefficient (JRC) suggested by the International Society for Rock Mechanics [1] (Int. J. Rock. Mech. Min. Sci. & Geomech. Abstr. 15, 319-368, 1978). The fractal dimension, suggested by Mandelbrot [2] (Fractals-Form, Chance and Dimension, Freeman, San Francisco), describes the degree of variation of a curve, a surface or a volume has from its topological ideal. In this application, the length of the surface profile is measured stepwise along the curve with rulers of different lengths. From these data, the fractal dimension of the surface profile can be determined. An empirical equation was found relating the fractal dimension to the JRC value. Application of the fractal dimension to three independent studies (field and laboratory) all showed excellent agreement between the surface roughness and the fractal dimension, the rougher the surface, the higher the fractal dimension. The peak shear stress on large-block laboratory direct shear tests increased as the fractal dimension of the shear surface increased, which again verifies the usefulness of the concept. © 1990

Vascular endothelial growth factor is an autocrine survival factor for breast tumour cells under hypoxia.

Vascular endothelial growth factor (VEGF) is produced by most tumour types and stimulates the growth of new blood vessels in the tumour. The expansion of a solid tumour ultimately leads to the development of hypoxic regions, which increases VEGF production and further angiogenesis. In this study, we examined the role of VEGF in the survival of breast tumour cells under hypoxia. Murine 4T1 and human MDA-MB-231 tumour cells were cultured under normoxic and hypoxic growth conditions in the presence or absence of VEGF neutralising antibodies. Apoptosis was assessed in addition to changes in expression of the anti- and pro-apoptotic proteins, Bcl-2 and Bad, respectively. The effect of hypoxia on the novel VEGF receptor, NP1 (neuropilin-1) and the role of the PI3K (phosphatidylinositol-3-kinase) signalling pathway in response to VEGF were examined. VEGF blockade resulted in direct tumour cell apoptosis of both tumour cell lines under normoxia and hypoxia. While blocking VEGF resulted in a downregulation of hypoxia-induced Bcl-2 expression, there was a significant increase in the pro-apoptotic protein Bad relative to cells cultured under hypoxia alone. Both hypoxia and VEGF phosphorylated Akt. Neutralising antibodies to VEGF abrogated this effect, implicating the PI3K pathway in VEGF-mediated cell survival of mammary adenocarcinoma cells. This study demonstrates that VEGF acts as a survival factor not only for endothelial cells as previously thought, but also for some breast tumour cells, protecting them from apoptosis, particularly under hypoxic stress. The data presented provide an additional rationale for combining anti-VEGF strategies with conventional anti-cancer therapies such as chemotherapy and radiotherapy

Epidemiology of Influenza-like Illness during Pandemic (H1N1) 2009, New South Wales, Australia

To rapidly describe the epidemiology of influenza-like illness (ILI) during the 2009 winter epidemic of pandemic (H1N1) 2009 virus in New South Wales, Australia, we used results of a continuous population health survey. During July–September 2009, ILI was experienced by 23% of the population. Among these persons, 51% were unable to undertake normal duties for <3 days, 55% sought care at a general practice, and 5% went to a hospital. Factors independently associated with ILI were younger age, daily smoking, and obesity. Effectiveness of prepandemic seasonal vaccine was ≈20%. The high prevalence of risk factors associated with a substantially increased risk for ILI deserves greater recognition

Inclusion of mobile phone numbers into an ongoing population health survey in Australia using an overlapping dual frame: description of methods, call outcomes and acceptance by staff and respondents

In Australia telephone surveys has been the method of choice for ongoing population health surveys. Although it was estimated in 2011 that 20% of the population were mobile phone only persons the inclusion of mobile only phone users into these existing landline population health surveys has not occurred. This paper is part of a project that is looking in detail at the inclusion of mobile phone numbers into an ongoing population health survey in Australia. This paper describes the methods used, the call outcomes and acceptance by the population, supervisors and interviewing staff

Identifying coherent patterns of environmental change between multiple, multivariate records: an application to four 1000-year diatom records from Victoria, Australia

Empirical orthogonal functions (EOFs) of indirect archives of environmental change are increasingly used to identify coherent trends between palaeoclimate records, to separate externally forced patterns from locally driven idiosyncrasies. Lake sediments are particularly suited to such syntheses: they are abundant in most landscapes and record a wide array of information, yet local complexities often conceal or confuse the climate signal recorded at individual sites. Lake sediment parameters usually exhibit non-linear, multivariate and indirect responses to climate, therefore identifying coherent patterns between two or more lake records presents a complex challenge. Ideally, the selection of representative variables should be non-subjective and inclusive of as many different variables as possible, allowing for unexpected correlations between sites. In order to meet such demands, we propose a two-tier ordination procedure whereby site-specific (local) ordinations, obtained using Detrended Correspondence Analysis (DCA), are nested within a second, regional EOF. Using the local DCAs as representative variables allows the retention of a larger fraction of variance from each site, removes any subjectivity from variable selection and retains the potential for observing multiple, coherent signals from within and between each dataset. We explore this potential using four decadally resolved diatom records from volcanic lakes in Western Victoria, Australia. The records span the 1000 years prior to European settlement in CE 1803. Our analyses reveal at least two coherent patterns of ecological change that are manifest in each of the four datasets, patterns which may have been overlooked by a single-variable, empirical orthogonal function approach. This intra-site coherency provides a valuable step towards understanding multi-decadal hydroclimate variability in southeastern Australia