The equivalence principle, uniformly accelerated reference frames, and the uniform gravitational field

The relationship between uniformly accelerated reference frames in flat spacetime and the uniform gravitational field is examined in a relativistic context. It is shown that, contrary to previous statements in the pages of this journal, equivalence does not break down in this context. No restrictions to Newtonian approximations or small enclosures are necessary

The clock paradox in a static homogeneous gravitational field

The gedanken experiment of the clock paradox is solved exactly using the general relativistic equations for a static homogeneous gravitational field. We demonstrate that the general and special relativistic clock paradox solutions are identical and in particular that they are identical for finite acceleration. Practical expressions are obtained for proper time and coordinate time by using the destination distance as the key observable parameter. This solution provides a formal demonstration of the identity between the special and general relativistic clock paradox with finite acceleration and where proper time is assumed to be the same in both formalisms. By solving the equations of motion for a freely falling clock in a static homogeneous field elapsed times are calculated for realistic journeys to the stars.Comment: Revision: Posted with the caption included with the figure

Self-aligned nanoscale SQUID on a tip

A nanometer-sized superconducting quantum interference device (nanoSQUID) is fabricated on the apex of a sharp quartz tip and integrated into a scanning SQUID microscope. A simple self-aligned fabrication method results in nanoSQUIDs with diameters down to 100 nm with no lithographic processing. An aluminum nanoSQUID with an effective area of 0.034 $\mu$m$^2$ displays flux sensitivity of 1.8$\cdot 10^{-6}$ $\Phi_0/\mathrm{Hz}^{1/2} and operates in fields as high as 0.6 T. With projected spin sensitivity of 65$\mu_B/\mathrm{Hz}^{1/2}$ and high bandwidth, the SQUID on a tip is a highly promising probe for nanoscale magnetic imaging and spectroscopy.Comment: 14 manuscript pages, 5 figure

The smoking cessation in pregnancy incentives trial (CPIT): study protocol for a phase III randomised controlled trial

Background: Eighty per cent of UK women have at least one baby, making pregnancy an opportunity to help women stop smoking before their health is irreparably compromised. Smoking cessation during pregnancy helps protect infants from miscarriage, still birth, low birth weight, asthma, attention deficit disorder and adult cardiovascular disease. UK national guidelines highlight lack of evidence for effectiveness of financial incentives to help pregnant smokers quit. This includes a research recommendation: within a UK context, are incentives an acceptable, effective and cost-effective way to help pregnant women who smoke to quit? Methods: The Cessation in Pregnancy Incentives Trial (CPIT) III is a pragmatic, 42-month, multi-centre, parallel-group, individually randomised controlled superiority trial of the effect on smoking status of adding to usual Stop Smoking Services (SSS) support, the offer of up to £400 of financial voucher incentives, compared with usual support alone, to quit smoking during pregnancy. Participants (n = 940) are pregnant smokers (age > 16 years, < 24 weeks pregnant, English speaking), who consent via telephone to take part and are willing to be followed-up in late pregnancy and 6 months after birth. The primary outcome is cotinine/anabasine-validated abstinence from smoking in late pregnancy. Secondary outcomes include engagement with SSS, quit rates at 4 weeks from agreed quit date and 6 months after birth, and birth weight. Outcomes will be analysed by intention to treat, and regression models will be used to compare treatment effects on outcomes. A meta-analysis will include data from the feasibility study in Glasgow. An economic evaluation will assess cost-effectiveness from a UK NHS perspective. Process evaluation using a case-study approach will identify opportunities to improve recruitment and learning for future implementation. Research questions include: what is the therapeutic efficacy of incentives; are incentives cost-effective; and what are the potential facilitators and barriers to implementing incentives in different parts of the UK? Discussion: This phase III trial in Scotland, England and Northern Ireland follows a successful phase II trial in Glasgow, UK. The participating sites have diverse SSS that represent most cessation services in the UK and serve demographically varied populations. If found to be acceptable and cost-effective, this trial could demonstrate that financial incentives are effective and transferable to most UK SSS for pregnant women. Trial registration: Current Controlled Trials, ISRCTN15236311. Registered on 9 October 2017

The exposure of the Great Barrier Reef to ocean acidification

The Great Barrier Reef (GBR) is founded on reef-building corals. Corals build their exoskeleton with aragonite, but ocean acidification is lowering the aragonite saturation state of seawater (Omega(a)). The downscaling of ocean acidification projections from global to GBR scales requires the set of regional drivers controlling Omega(a) to be resolved. Here we use a regional coupled circulation-biogeochemical model and observations to estimate the Omega(a) experienced by the 3,581 reefs of the GBR, and to apportion the contributions of the hydrological cycle, regional hydrodynamics and metabolism on Omega(a) variability. We find more detail, and a greater range (1.43), than previously compiled coarse maps of Omega(a) of the region (0.4), or in observations (1.0). Most of the variability in Omega(a) is due to processes upstream of the reef in question. As a result, future decline in Omega(a) is likely to be steeper on the GBR than currently projected by the IPCC assessment report

Periodic stellar variability from almost a million NGTS light curves

We analyse 829,481 stars from the Next Generation Transit Survey (NGTS) to extract variability periods. We utilise a generalisation of the autocorrelation function (the G-ACF), which applies to irregularly sampled time series data. We extract variability periods for 16,880 stars from late-A through to mid-M spectral types and periods between 0.1 and 130 days with no assumed variability model. We find variable signals associated with a number of astrophysical phenomena, including stellar rotation, pulsations and multiple-star systems. The extracted variability periods are compared with stellar parameters taken from Gaia DR2, which allows us to identify distinct regions of variability in the Hertzsprung-Russell Diagram. We explore a sample of rotational main-sequence objects in period-colour space, in which we observe a dearth of rotation periods between 15 and 25 days. This 'bi-modality' was previously only seen in space-based data. We demonstrate that stars in sub-samples above and below the period gap appear to arise from a stellar population not significantly contaminated by excess multiple systems. We also observe a small population of long-period variable M-dwarfs, which highlight a departure from the predictions made by rotational evolution models fitted to solar-type main-sequence objects. The NGTS data spans a period and spectral type range that links previous rotation studies such as those using data from Kepler, K2 and MEarth

Pacific anthropogenic carbon between 1991 and 2017

© The Author(s), 2019. This article is distributed under the terms of the Creative Commons Attribution License. The definitive version was published in Carter, B. R., Feely, R. A., Wanninkhof, R., Kouketsu, S., Sonnerup, R. E., Pardo, P. C., Sabine, C. L., Johnson, G. C., Sloyan, B. M., Murata, A., Mecking, S., Tilbrook, B., Speer, K., Talley, L. D., Millero, F. J., Wijffels, S. E., Macdonald, A. M., Gruber, N., & Bullister, J. L. Pacific anthropogenic carbon between 1991 and 2017. Global Biogeochemical Cycles, 33(5), (2019):597-617, doi:10.1029/2018GB006154.We estimate anthropogenic carbon (Canth) accumulation rates in the Pacific Ocean between 1991 and 2017 from 14 hydrographic sections that have been occupied two to four times over the past few decades, with most sections having been recently measured as part of the Global Ocean Ship‐based Hydrographic Investigations Program. The rate of change of Canth is estimated using a new method that combines the extended multiple linear regression method with improvements to address the challenges of analyzing multiple occupations of sections spaced irregularly in time. The Canth accumulation rate over the top 1,500 m of the Pacific increased from 8.8 (±1.1, 1σ) Pg of carbon per decade between 1995 and 2005 to 11.7 (±1.1) PgC per decade between 2005 and 2015. For the entire Pacific, about half of this decadal increase in the accumulation rate is attributable to the increase in atmospheric CO2, while in the South Pacific subtropical gyre this fraction is closer to one fifth. This suggests a substantial enhancement of the accumulation of Canth in the South Pacific by circulation variability and implies that a meaningful portion of the reinvigoration of the global CO2 sink that occurred between ~2000 and ~2010 could be driven by enhanced ocean Canth uptake and advection into this gyre. Our assessment suggests that the accuracy of Canth accumulation rate reconstructions along survey lines is limited by the accuracy of the full suite of hydrographic data and that a continuation of repeated surveys is a critical component of future carbon cycle monitoring.The data we use can be accessed at CCHDO website (https://cchdo.ucsd.edu/) and GLODAP website (https://www.glodap.info/). This research would not be possible without the hard work of the scientists and crew aboard the many repeated hydrographic cruises coordinated by GO‐SHIP, which is funded by NSF OCE and NOAA OAR. We thank funding agencies and program managers as follows: U.S., Australian, Japanese national science funding agencies that support data collection, data QA/QC, and data centers. Contributions from B. R. C., R. A. F., and R. W. are supported by the National Oceanic and Atmospheric Administration Global Ocean Monitoring and Observing Program (Data Management and Synthesis Grant: N8R3CEA‐PDM managed by Kathy Tedesco and David Legler). G. C. J. is supported by the Climate Observation Division, Climate Program Office, National Oceanic and Atmospheric Administration (NOAA), U.S. Department of Commerce and NOAA Research (fund reference 100007298), grant (N8R1SE3‐PGC). B. M. S was supported by the Australian Government Department of the Environment and CSIRO through the Australian Climate Change Science Programme and by the National Environmental Science Program. N. G. acknowledges support by ETH Zurich. This is JISAO contribution 2018‐0149 and PMEL contribution 4786. We fondly remember John Bullister as a treasured friend, valued colleague, and dedicated mentor, and we thank him for sharing his days with us. He is and will be dearly missed

Making sense of law and disorder

This article tells the story of a cross-cultural encounter on a beach at King George\u27s Sound in the south west of Australia in 1826, when Major Edmund Lockyer arrived to establish a British military garrison. The account we have of those early encounters come from the pen of Lockyer, and by taking a close reading of his journal this article attempts to reveal the meanings and context of Aboriginal actions. It also analyses how the Aborigines and the British made sense and subsequently responded to the encounter. Whilst this story is not given iconic status in Australian historiography, it is valuable in opening up a porthole into this contact zone at the moment when precarious relationships were being formed.<br /

Identification of salt tolerance QTL in a wheat RIL mapping population using destructive and non-destructive phenotyping

Published online 24 August 2020. Corrected by: Corrigendum to: Identification of salt tolerance QTL in a wheat RIL mapping population using destructive and non-destructive phenotyping. Muhammad A. Asif, et al. Functional Plant Biology 49(7) 672 - 672. In the Acknowledgements, the ARC Centre of Excellence funding number was incorrect. The correct funding number is: CE140100008.Bread wheat (Triticum aestivum L.) is one of the most important food crops, however it is only moderately tolerant to salinity stress. To improve wheat yield under saline conditions, breeding for improved salinity tolerance of wheat is needed. We have identified nine quantitative trail loci (QTL) for different salt tolerance sub-traits in a recombinant inbred line (RIL) population, derived from the bi-parental cross of Excalibur × Kukri. This population was screened for salinity tolerance subtraits using a combination of both destructive and non-destructive phenotyping. Genotyping by sequencing (GBS) was used to construct a high-density genetic linkage map, consisting of 3236 markers, and utilised for mapping QTL. Of the nine mapped QTL, six were detected under salt stress, including QTL for maintenance of shoot growth under salinity (QG(1-5).asl-5A, QG(1-5).asl-7B) sodium accumulation (QNa.asl-2A), chloride accumulation (QCl.asl-2A, QCl.asl-3A) and potassium:sodium ratio (QK:Na.asl-2DS2). Potential candidate genes within these QTL intervals were shortlisted using bioinformatics tools. These findings are expected to facilitate the breeding of new salt tolerant wheat cultivars.Muhammad A. Asif, Melissa Garcia, Joanne Tilbrook, Chris Brien, Kate Dowling, Bettina Berger, Rhiannon K. Schilling, Laura Short, Christine Trittermann, Matthew Gilliham, Delphine Fleury, Stuart J. Roy and Allison S. Pearso