What do gas-rich galaxies actually tell us about modified Newtonian dynamics?

It has recently been claimed that measurements of the baryonic Tully-Fisher relation (BTFR), a power-law relationship between the observed baryonic masses and outer rotation velocities of galaxies, support the predictions of modified Newtonian dynamics for the slope and scatter in the relation, while challenging the cold dark matter (CDM) paradigm. We investigate these claims, and find that: 1) the scatter in the data used to determine the BTFR is in conflict with observational uncertainties on the data; 2) these data do not make strong distinctions regarding the best-fit BTFR parameters; 3) the literature contains a wide variety of measurements of the BTFR, many of which are discrepant with the recent results; and 4) the claimed CDM "prediction" for the BTFR is a gross oversimplification of the complex galaxy-scale physics involved. We conclude that the BTFR is currently untrustworthy as a test of CDM.Comment: 5 pages, 2 figures; minor revisions to match published versio

British American Tobacco on Facebook: undermining article 13 of the global World Health Organization Framework Convention on Tobacco Control

Background The World Health Organization Framework Convention on Tobacco Control (WHO FCTC) bans all forms of tobacco advertising, promotion and sponsorship. The comprehensiveness of this ban has yet to be tested by online social networking media such as Facebook. In this paper, the activities of employees of the transnational tobacco company, British American Tobacco, (BAT) on Facebook and the type of content associated with two globally popular BAT brands (Dunhill and Lucky Strike) are mapped. Methods BAT employees on Facebook were identified and then the term ‘British American Tobacco ’ was searched for in the Facebook search engine and results recorded, including titles, descriptions, names and the number of Facebook participants involved for each search result. To further detail any potential promotional activities, a search for two of BAT’s global brands, ‘Dunhill ’ and ‘Lucky Strike’, was conducted. Results Each of the 3 search terms generated more than 500 items across a variety of Facebook subsections. Discussion Some BAT employees are energetically promoting BAT and BAT brands on Facebook throug

STEM: country comparisons: international comparisons of science, technology, engineering and mathematics (STEM) education. Final report.

From 22 studies of Science, Technology, Engineering and Mathematics (STEM) policies and practices around the world the STEM: country comparisons report makes 24 key findings which highlight a number of challenges for Australia with STEM participation and provides a basis of ideas to tackle these

Development and validation of a chemostat gut model to study both planktonic and biofilm modes of growth of Clostridium difficile and human microbiota

Copyright: 2014 Crowther et al. This is an open-access article distributed under the terms of the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original author and source are credited.The human gastrointestinal tract harbours a complex microbial community which exist in planktonic and sessile form. The degree to which composition and function of faecal and mucosal microbiota differ remains unclear. We describe the development and characterisation of an in vitro human gut model, which can be used to facilitate the formation and longitudinal analysis of mature mixed species biofilms. This enables the investigation of the role of biofilms in Clostridium difficile infection (CDI). A well established and validated human gut model of simulated CDI was adapted to incorporate glass rods that create a solid-gaseous-liquid interface for biofilm formation. The continuous chemostat model was inoculated with a pooled human faecal emulsion and controlled to mimic colonic conditions in vivo. Planktonic and sessile bacterial populations were enumerated for up to 46 days. Biofilm consistently formed macroscopic structures on all glass rods over extended periods of time, providing a framework to sample and analyse biofilm structures independently. Whilst variation in biofilm biomass is evident between rods, populations of sessile bacterial groups (log10 cfu/g of biofilm) remain relatively consistent between rods at each sampling point. All bacterial groups enumerated within the planktonic communities were also present within biofilm structures. The planktonic mode of growth of C. difficile and gut microbiota closely reflected observations within the original gut model. However, distinct differences were observed in the behaviour of sessile and planktonic C. difficile populations, with C. difficile spores preferentially persisting within biofilm structures. The redesigned biofilm chemostat model has been validated for reproducible and consistent formation of mixed species intestinal biofilms. This model can be utilised for the analysis of sessile mixed species communities longitudinally, potentially providing information of the role of biofilms in CDI.Peer reviewe

Distillation of 56^{56}Fe in Ultramassive O-Ne White Dwarfs

When white dwarfs freeze the plasma mixtures inside them undergo separation processes which can produce radical changes in the composition profile of the star. The abundance of neutron rich elements, such as $^{22}$Ne or $^{56}$Fe, determines whether or not the first crystals are more or less dense than the surrounding fluid and thus whether they sink or float. These processes have now been studied for C-O-Ne and C-O-Fe mixtures, finding that distillation and precipitation processes are possible in white dwarfs. In this work, we calculate the phase diagram of more complicated O-Ne-Fe mixtures and make predictions for the internal structure of the separated white dwarf. There are two possible outcomes determined by a complicated interplay between the Ne abundance, the $^{22}$Ne fraction, and the $^{56}$Fe abundance. Either Fe distills to form an inner core because the first O-Ne solids are buoyant, or an O-Ne inner core forms and Fe accumulates in the liquid until Fe distillation begins and forms a Fe shell. In the case of an Fe shell, a Rayleigh-Taylor instability may arise and overturn the core. In either case, Fe distillation may only produce a cooling delay of order 0.1 Gyr as these processes occur early at high white dwarf luminosities. Fe inner cores and shells may be detectable through asteroseismology and could enhance the yield of neutron rich elements such as $^{55}$Mn and $^{58}$Ni in supernovae.Comment: 8 pages, 3 figures, accepted for publication in Ap

Novel methods for spatial prediction of soil functions within landscapes (SP0531)

Previous studies showed that soil patterns could be predicted in agriculturally managed landscapes by modelling and extrapolating from extensive existing but related integrated datasets. Based on these results we proposed to develop and apply predictive models of the relationships between environmental data and known soil patterns to predict capacity for key soil functions within diverse landscapes for which there is little detailed underpinning soil information available. Objectives were: To develop a high-level framework in which the non-specialist user-community could explore questions. To generate digital soil maps for three selected catchments at a target resolution of 1:50000 to provide the base information for soil function prediction. To use a modelling approach to predict the performance of key soil functions in catchments undergoing change but where only sparse or low resolution soil survey data are available. To use a modelling approach to assess the impact of different management scenarios and/or environmental conditions on the delivery of multiple soil functions within a catchment. To create a detailed outline of the requirements for ground-truthing to test the predicted model outputs at a catchment scale. To contribute to the development of a high-level framework for decision makers