Efficiency of planetesimal ablation in giant planetary envelopes

Observations of exoplanetary spectra are leading to unprecedented constraints on their atmospheric elemental abundances, particularly O/H, C/H, and C/O ratios. Recent studies suggest that elemental ratios could provide important constraints on formation and migration mechanisms of giant exoplanets. A fundamental assumption in such studies is that the chemical composition of the planetary envelope represents the sum-total of compositions of the accreted gas and solids during the formation history of the planet. We investigate the efficiency with which accreted planetesimals ablate in a giant planetary envelope thereby contributing to its composition rather than sinking to the core. From considerations of aerodynamic drag causing `frictional ablation' and the envelope temperature structure causing `thermal ablation', we compute mass ablations for impacting planetesimals of radii 30 m to 1 km for different compositions (ice to iron) and a wide range of velocities and impact angles, assuming spherical symmetry. Icy impactors are fully ablated in the outer envelope for a wide range of parameters. Even for Fe impactors substantial ablation occurs in the envelope for a wide range of sizes and velocities. For example, iron impactors of sizes below ~0.5 km and velocities above ~30 km/s are found to ablate by ~60-80% within the outer envelope at pressures below 10^3 bar due to frictional ablation alone. For deeper pressures (~10^7 bar), substantial ablation happens over a wider range of parameters. Therefore, our exploratory study suggests that atmospheric abundances of volatile elements in giant planets reflect their accretion history during formation

Evidence for a Dayside Thermal Inversion and High Metallicity for the Hot Jupiter WASP-18b

We find evidence for a strong thermal inversion in the dayside atmosphere of the highly irradiated hot Jupiter WASP-18b (T$_{eq}=2411K$, $M=10.3M_{J}$) based on emission spectroscopy from Hubble Space Telescope secondary eclipse observations and Spitzer eclipse photometry. We demonstrate a lack of water vapor in either absorption or emission at 1.4$\mu$m. However, we infer emission at 4.5$\mu$m and absorption at 1.6$\mu$m that we attribute to CO, as well as a non-detection of all other relevant species (e.g., TiO, VO). The most probable atmospheric retrieval solution indicates a C/O ratio of 1 and a high metallicity (C/H=$283^{+395}_{-138}\times$ solar). The derived composition and T/P profile suggest that WASP-18b is the first example of both a planet with a non-oxide driven thermal inversion and a planet with an atmospheric metallicity inconsistent with that predicted for Jupiter-mass planets at $>2\sigma$. Future observations are necessary to confirm the unusual planetary properties implied by these results

Economic and other barriers to adopting recommendations to prevent childhood obesity: results of a focus group study with parents

Abstract Background Parents are integral to the implementation of obesity prevention and management recommendations for children. Exploration of barriers to and facilitators of parental decisions to adopt obesity prevention recommendations will inform future efforts to reduce childhood obesity. Methods We conducted 4 focus groups (2 English, 2 Spanish) among a total of 19 parents of overweight (BMI ≥ 85th percentile) children aged 5-17 years. The main discussion focused on 7 common obesity prevention recommendations: reducing television (TV) watching, removing TV from child's bedroom, increasing physically active games, participating in community or school-based athletics, walking to school, walking more in general, and eating less fast food. Parents were asked to discuss what factors would make each recommendation more difficult (barriers) or easier (facilitators) to follow. Participants were also asked about the relative importance of economic (time and dollar costs/savings) barriers and facilitators if these were not brought into the discussion unprompted. Results Parents identified many barriers but few facilitators to adopting obesity prevention recommendations for their children. Members of all groups identified economic barriers (time and dollar costs) among a variety of pertinent barriers, although the discussion of dollar costs often required prompting. Parents cited other barriers including child preference, difficulty with changing habits, lack of information, lack of transportation, difficulty with monitoring child behavior, need for assistance from family members, parity with other family members, and neighborhood walking safety. Facilitators identified included access to physical activity programs, availability of alternatives to fast food and TV which are acceptable to the child, enlisting outside support, dietary information, involving the child, setting limits, making behavior changes gradually, and parental change in shopping behaviors and own eating behaviors. Conclusions Parents identify numerous barriers to adopting obesity prevention recommendations, most notably child and family preferences and resistance to change, but also economic barriers. Intervention programs should consider the context of family priorities and how to overcome barriers and make use of relevant facilitators during program development.http://deepblue.lib.umich.edu/bitstream/2027.42/78270/1/1471-2431-9-81.xmlhttp://deepblue.lib.umich.edu/bitstream/2027.42/78270/2/1471-2431-9-81.pdfPeer Reviewe

Evidence for energy conservation during pubertal growth. A 10-year longitudinal study (EarlyBird 71)

BACKGROUND: Diabetes is closely linked to obesity, and obesity rates climb during adolescence for reasons that are not clear. Energy efficiency is important to obesity, and we describe a temporary but substantial fall in absolute energy expenditure, compatible with improved energy efficiency, during the rapid growth phase of puberty. METHODS: In a longitudinal cohort study lasting 10 years, we measured voluntary energy expenditure as physical activity (PA) by accelerometry, involuntary energy expenditure as resting energy expenditure (REE) by oxygen consumption, body mass index (BMI) and body composition by dual energy X-ray absorptiometry annually on 10 occasions from 7 to 16 years in the 347 children of the EarlyBird study. We used mixed effects modelling to analyse the trends in REE and their relationship to BMI, lean mass (LM), fat mass (FM), age, PA and pubertal stage. RESULTS: Relative REE and total PA fell during puberty, as previously described, but the longitudinal data and narrow age-range of the cohort (s.d.±4m) revealed for the first time a substantial fall in absolute REE during the period of maximum growth. The fall became clearer still when adjusted for FM and LM. The fall could not be explained by fasting insulin, adiponectin, leptin, luteinising hormone or follicle stimulating hormone. CONCLUSIONS: There appears to be a temporary but substantial reduction in energy expenditure during puberty, which is unrelated to changes in body composition. If it means higher energy efficiency, the fall in REE could be advantageous in an evolutionary context to delivering the extra energy needed for pubertal growth, but unfavourable to weight gain in a contemporary environment.International Journal of Obesity advance online publication, 4 October 2016; doi:10.1038/ijo.2016.158.We are grateful to the Bright futures trust, Fountain Foundation, BUPA Foundation, EarlyBird Diabetes Trust and countless individual donors who made this study possible

On signatures of clouds in exoplanetary transit spectra

© 2017 The Authors. Transmission spectra of exoplanetary atmospheres have been used to infer the presence of clouds/hazes. Such inferences are typically based on spectral slopes in the optical deviant from gaseous Rayleigh scattering or low-amplitude spectral features in the infrared. We investigate three observable metrics that could allow constraints on cloud properties from transmission spectra, namely the optical slope, the uniformity of this slope and condensate features in the infrared. We derive these metrics using model transmission spectra considering Mie extinction from a wide range of condensate species, particle sizes and scaleheights. First, we investigate possible degeneracies among the cloud properties for an observed slope. We find, for example, that spectra with very steep optical slopes suggest sulphide clouds (e.g. MnS, ZnS, Na2S) in the atmospheres. Secondly, (non)uniformities in optical slopes provide additional constraints on cloud properties, e.g. MnS, ZnS, TiO2 and Fe2O3 have significantly non-uniform slopes. Thirdly, infrared spectra provide an additional powerful probe into cloud properties, with SiO2, Fe2O3, Mg2SiO4 and MgSiO3 bearing strong infrared features observablewith JamesWebb Space Telescope. We investigate observed spectra of eight hot Jupiters and discuss their implications. In particular, no single or composite condensate species considered here conforms to the steep and non-uniform optical slope observed for HD 189733b. Our work highlights the importance of the three above metrics to investigate cloud properties in exoplanetary atmospheres using high-precision transmission spectra and detailed cloud models. We make our Mie scattering data for condensates publicly available to the community

Reproductive health and burn-out among female physicians: nationwide, representative study from Hungary

BACKGROUND: There is a worldwide rising tendency of women deciding to become physicians; hence, one of the most remarkable fields of investigation is the wellbeing of female doctors. The aim of this study was to describe female physicians' reproductive health in Hungary and to explore the potential correlation between their reproductive disorders and burnout symptoms. Up to our present knowledge, there have not been any studies investigating the correlation between reproductive disorders and burnout of female physicians; therefore, our study represents a unique approach. METHODS: Data in this representative cross-sectional epidemiological study were obtained from online questionnaires completed by 3039 female physicians. Participants in a representative nationwide survey (Hungarostudy, 2013) served as controls (n = 1069). Differences between physicians and the control group were disclosed by chi-square test. Correlations between certain factors of reproductive health and the three dimensions of burnout were detected by Pearson correlations and X2 test. Binary logistic regression analysis was used to determine the association between burnout and reproductive health. RESULTS: Female physicians were more often characterised by time-to-pregnancy interval longer than one year (18.4% vs. 9.8%), were bearing more high-risk pregnancies (26.3% vs.16.3%), and were more likely to be undergoing infertility therapy (8.5% vs. 3.4%) and experiencing miscarriage (20.8% vs. 14.6%) during their reproductive years, compared with the general female population. With the exception of miscarriages, the difference remained significant in all comparisons with the professional control group. Both high-risk pregnancies and miscarriages of doctors were associated with depersonalisation (p = 0.028 and p = 0.012 respectively) and personal accomplishment (p = 0.016 and p = 0.008 respectively) dimensions of burnout. Results of the multivariate analysis showed that, beside traditional risk factors, depersonalisation acted as an important explanatory factor in case of high-risk pregnancies (OR = 1.086). CONCLUSIONS: There is a circulatory causality between burnout and the development of reproductive disorders. Burnout is an important risk factor for high-risk pregnancies and miscarriages, and it has a negative effect on the outcome of pregnancies. At the same time, women suffering from reproductive disorders are more likely to develop burnout syndrome. Improvement of working conditions and prevention of burnout in female doctors are equally important tasks