Fetal liver blood flow distribution: role in human developmental strategy to prioritize fat deposition versus brain development

Among primates, human neonates have the largest brains but also the highest proportion of body fat. If placental nutrient supply is limited, the fetus faces a dilemma: should resources be allocated to brain growth, or to fat deposition for use as a potential postnatal energy reserve? We hypothesised that resolving this dilemma operates at the level of umbilical blood distribution entering the fetal liver. In 381 uncomplicated pregnancies in third trimester, we measured blood flow perfusing the fetal liver, or bypassing it via the ductus venosus to supply the brain and heart using ultrasound techniques. Across the range of fetal growth and independent of the mother's adiposity and parity, greater liver blood flow was associated with greater offspring fat mass measured by dual-energy X-ray absorptiometry, both in the infant at birth (r = 0.43, P<0.001) and at age 4 years (r = 0.16, P = 0.02). In contrast, smaller placentas less able to meet fetal demand for essential nutrients were associated with a brain-sparing flow pattern (r = 0.17, p = 0.02). This flow pattern was also associated with a higher degree of shunting through ductus venosus (P = 0.04). We propose that humans evolved a developmental strategy to prioritize nutrient allocation for prenatal fat deposition when the supply of conditionally essential nutrients requiring hepatic inter-conversion is limited, switching resource allocation to favour the brain if the supply of essential nutrients is limited. Facilitated placental transfer mechanisms for glucose and other nutrients evolved in environments less affluent than those now prevalent in developed populations, and we propose that in circumstances of maternal adiposity and nutrient excess these mechanisms now also lead to prenatal fat deposition. Prenatal developmental influences play important roles in the human propensity to deposit fa

A Far-Ultraviolet Survey of 47 Tucanae.II The Long-Period Cataclysmic Variable AKO 9

We present time-resolved, far-ultraviolet (FUV) spectroscopy and photometry of the 1.1 day eclipsing binary system AKO 9 in the globular cluster 47 Tucanae. The FUV spectrum of AKO 9 is blue and exhibits prominent C IV and He II emission lines. The spectrum broadly resembles that of long-period, cataclysmic variables in the galactic field. Combining our time-resolved FUV data with archival optical photometry of 47 Tuc, we refine the orbital period of AKO 9 and define an accurate ephemeris for the system. We also place constraints on several other system parameters, using a variety of observational constraints. We find that all of the empirical evidence is consistent with AKO 9 being a long-period dwarf nova in which mass transfer is driven by the nuclear expansion of a sub-giant donor star. We therefore conclude that AKO 9 is the first spectroscopically confirmed cataclysmic variable in 47 Tuc. We also briefly consider AKO 9's likely formation and ultimate evolution. Regarding the former, we find that the system was almost certainly formed dynamically, either via tidal capture or in a 3-body encounter. Regarding the latter, we show that AKO 9 will probably end its CV phase by becoming a detached, double WD system or by exploding in a Type Ia supernova.Comment: 40 pages, 11 figures, to appear in the Dec 20 issue of ApJ; minor changes to match final published versio

Tests of Spurious Transport in Smoothed Particle Hydrodynamics

We have performed a series of systematic tests to evaluate the effects of spurious transport in three-dimensional smoothed particle hydrodynamics (SPH) calculations. Our tests investigate (i) particle diffusion, (ii) shock heating, (iii) numerical viscosity, and (iv) angular momentum transport. The results are useful for quantifying the accuracy of the SPH scheme, especially for problems where shear flows or shocks are present, as well as for problems where true hydrodynamic mixing is relevant. We examine the different forms of artificial viscosity (AV) which have been proposed by Monaghan, by Hernquist & Katz, and by Balsara. For each form, our tests suggest a single set of values for the AV parameters $\alpha$ and $\beta$ (coefficients of the linear and quadratic terms) which are appropriate in a large number of situations. We also discuss how these parameters should be adjusted depending on the goals of the particular application. We find that both the Hernquist & Katz and Balsara forms introduce relatively small amounts of numerical viscosity. Furthermore, both Monaghan's and Balsara's AV do well at treating shocks and at limiting the amount of spurious mixing. For these reasons, we endorse the Balsara AV for use in a broad range of applications.Comment: 49 pages, 26 figures as 30 postscript files, submitted to The Journal of Computational Physic

The fundamental links between climate change and marine plastic pollution

Plastic pollution and climate change have commonly been treated as two separate issues and sometimes are even seen as competing. Here we present an alternative view that these two issues are fundamentally linked. Primarily, we explore how plastic contributes to greenhouse gas (GHG) emissions from the beginning to the end of its life cycle. Secondly, we show that more extreme weather and floods associated with climate change, will exacerbate the spread of plastic in the natural environment. Finally, both issues occur throughout the marine environment, and we show that ecosystems and species can be particularly vulnerable to both, such as coral reefs that face disease spread through plastic pollution and climate-driven increased global bleaching events. A Web of Science search showed climate change and plastic pollution studies in the ocean are often siloed, with only 0.4% of the articles examining both stressors simultaneously. We also identified a lack of regional and industry-specific life cycle analysis data for comparisons in relative GHG contributions by materials and products. Overall, we suggest that rather than debate over the relative importance of climate change or marine plastic pollution, a more productive course would be to determine the linking factors between the two and identify solutions to combat both crises

Mycoplasma genitalium prevalence in Welsh sexual health patients: low antimicrobial resistance markers and no association of symptoms to bacterial load

Objectives Mycoplasma genitalium (MG) is a common cause of sexually transmitted infection, however no prevalence data is available for Wales. MG was detected by qPCR (quantitative) as well as two separate SpeeDx commercial assays, and related to clinical symptoms, age, gender and sample type. Methods Cervical swabs, urethral swabs and/or urine were collected from 1000 patients at walk-in sexual health clinics at 3 Welsh health centres from October 2017–October 2018. Extracted DNA was investigated to determine concordance between an in-house quantitative PCR, SpeeDx ResistancePlus® MG and the SpeeDx MG + parC (beta 2) assays; mutations in parC were substantiated by Sanger sequencing. Results MG was detected in 17/600 female patients (2.7%) and 13/400 (3.5%) male patients, with a 100% concordance between in-house qPCR and both SpeeDx assays. Macrolide resistance was low (relative to other studies), but more common in males (4/13; 30.8%) than females (2/17; 11.8%) and the only fluoroquinolone resistant sample (3.4% overall) was also macrolide resistant and detected from an MSM. Vaginitis was clinically apparent in 12/17 MG-positive females (2 with additional cervicitis, 1 with additional pelvic inflammatory disease), while 7 MG-positive males were asymptomatic. MG bacterial load did not correlate to clinical symptoms and females (4559 ± 1646/ml) had significantly lower MG load than males (84,714 ± 41,813/ml; p = 0.0429). Conclusions MG prevalence and antibiotic resistance in Welsh sexual health clinics is low. MG bacterial load did not correlate to clinical presentation, men have higher MG load/ml in urine than women, genders have different age bias for MG prevalence and urine and swabs are equivalent for detecting MG

Mass-loss rates of Very Massive Stars

We discuss the basic physics of hot-star winds and we provide mass-loss rates for (very) massive stars. Whilst the emphasis is on theoretical concepts and line-force modelling, we also discuss the current state of observations and empirical modelling, and address the issue of wind clumping.Comment: 36 pages, 15 figures, Book Chapter in "Very Massive Stars in the Local Universe", Springer, Ed. Jorick S. Vin

Is genetic liability to ADHD and ASD causally linked to educational attainment?

Background The association patterns of Attention Deficit Hyperactivity Disorder (ADHD) and Autism Spectrum Disorder (ASD) with educational attainment (EA) are complex; children with ADHD and ASD are at risk of poor academic outcomes, and parental EA has been associated with risk of ADHD/ASD in the offspring. Little is known on the causal links between ADHD, ASD, EA and the potential contribution of cognitive ability. Methods Using the latest genome-wide association studies (GWAS) summary data on ADHD, ASD and EA, we applied two-sample Mendelian randomization (MR) to assess the effects of genetic liability to ADHD and ASD on EA. Reverse direction analyses were additionally performed. Multivariable MR was performed to estimate any effects independent of cognitive ability. Results Genetic liability to ADHD had a negative effect on EA, independently of cognitive ability (MVMRIVW: -1.7 months of education per doubling of genetic liability to ADHD; 95% CI: -2.8 to -0.7), whereas genetic liability to ASD a positive effect (MVMRIVW: 30 days per doubling of the genetic liability to ASD; 95% CI: 2 to 53). Reverse direction analyses suggested that genetic liability to higher EA had an effect on lower risk of ADHD, independently of cognitive ability (MVMRIVWOR: 0.33 per SD increase; 95% CI: 0.26 to 0.43) and increased risk of ASD (MRIVWOR: 1.51 per SD increase; 95% CI: 1.29 to 1.77), which was partly explained by cognitive ability (MVMRIVWOR per SD increase: 1.24; 95%CI: 0.96 to 1.60). Conclusions Genetic liability to ADHD and ASD is likely to affect educational attainment, independently of underlying cognitive ability