Testing the theory of grain growth and fragmentation by millimeter observations of protoplanetary disks

Context. Observations at sub-millimeter and mm wavelengths will in the near future be able to resolve the radial dependence of the mm spectral slope in circumstellar disks with a resolution of around a few AU at the distance of the closest star-forming regions. Aims. We aim to constrain physical models of grain growth and fragmentation by a large sample of (sub-)mm observations of disks around pre-main sequence stars in the Taurus-Auriga and Ophiuchus star-forming regions. Methods. State-of-the-art coagulation/fragmentation and disk-structure codes are coupled to produce steady-state grain size distributions and to predict the spectral slopes at (sub-)mm wavelengths. Results. This work presents the first calculations predicting the mm spectral slope based on a physical model of grain growth. Our models can quite naturally reproduce the observed mm-slopes, but a simultaneous match to the observed range of flux levels can only be reached by a reduction of the dust mass by a factor of a few up to about 30 while keeping the gas mass of the disk the same. This dust reduction can either be due to radial drift at a reduced rate or during an earlier evolutionary time (otherwise the predicted fluxes would become too low) or due to efficient conversion of dust into larger, unseen bodies.Comment: Accepted for publication in A&A Letters. 5 pages, 3 figure

Contribution of the core to the thermal evolution of sub-Neptunes

Sub-Neptune planets are a very common type of planets. They are inferred to harbour a primordial (H/He) envelope, on top of a (rocky) core, which dominates the mass. Here, we investigate the long-term consequences of the core properties on the planet mass-radius relation. We consider the role of various core energy sources resulting from core formation, its differentiation, its solidification (latent heat), core contraction and radioactive decay. We divide the evolution of the rocky core into three phases: the formation phase, which sets the initial conditions, the magma ocean phase, characterized by rapid heat transport, and the solid state phase, where cooling is inefficient. We find that for typical sub-Neptune planets of ~2-10 Earth masses and envelope mass fractions of 0.5-10% the magma ocean phase lasts several Gyrs, much longer than for terrestrial planets. The magma ocean phase effectively erases any signs of the initial core thermodynamic state. After solidification, the reduced heat flux from the rocky core causes a significant drop in the rocky core surface temperature, but its effect on the planet radius is limited. In the long run, radioactive heating is the most significant core energy source in our model. Overall, the long term radius uncertainty by core thermal effects is up to 15%.Comment: ApJ Publishe

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OBJECTIVE: to investigate the association of life events during pregnancy with change in antenatal anxiety and depression symptoms. We distinguished pregnancy related and non-pregnancy related events and assessed specificity of these associations for depressive or anxious symptoms. In addition, we investigated whether the associations were affected by personality or childhood adversities. DESIGN: observational prospective cohort study SETTING: primary and secondary obstetric care centres in the Netherlands PARTICIPANTS: 1603 women during their first trimester of pregnancy between May 2010 and May 2012 MEASUREMENTS AND FINDINGS: we performed linear regression analyses to test the associations of pregnancy related, non-pregnancy related life events, childhood adversities and the personality traits neuroticism and extraversion with the change in symptoms of anxiety (State Trait Anxiety Inventory) and depression (Edinburgh Postnatal Depression Scale) from week 12 to week 36. Life events during pregnancy were associated with increasing antenatal symptoms of anxiety and depression. Effect sizes associated with the highest numbers of events observed ranged from 0.59 to 1.31. Pregnancy related events were specifically associated with increasing symptoms of anxiety (p=0.009), whereas non-pregnancy related events were merely associated with an increase in symptoms of depression (p<0.001). Neither personality traits nor childhood trauma influenced the associations under study. KEY CONCLUSIONS: the most important finding is that pregnancy related life events during pregnancy increase levels of antenatal anxiety, whereas depression levels increase when women experience life events that are unrelated to pregnancy. Furthermore, non-pregnancy related events show stronger associations with increases in symptoms of anxiety or depression compared to pregnancy related events. IMPLICATIONS FOR PRACTICE: our findings may help midwives to tailor psychosocial care to the specific risks of the pregnant woman which may eventually have a positive impact on the health of mother and child

Parameterizing the interstellar dust temperature

The temperature of interstellar dust particles is of great importance to astronomers. It plays a crucial role in the thermodynamics of interstellar clouds, because of the gas-dust collisional coupling. It is also a key parameter in astrochemical studies that governs the rate at which molecules form on dust. In 3D (magneto)hydrodynamic simulations often a simple expression for the dust temperature is adopted, because of computational constraints, while astrochemical modelers tend to keep the dust temperature constant over a large range of parameter space. Our aim is to provide an easy-to-use parametric expression for the dust temperature as a function of visual extinction ($A_{\rm V}$) and to shed light on the critical dependencies of the dust temperature on the grain composition. We obtain an expression for the dust temperature by semi-analytically solving the dust thermal balance for different types of grains and compare to a collection of recent observational measurements. We also explore the effect of ices on the dust temperature. Our results show that a mixed carbonaceous-silicate type dust with a high carbon volume fraction matches the observations best. We find that ice formation allows the dust to be warmer by up to 15% at high optical depths ($A_{\rm V}> 20$ mag) in the interstellar medium. Our parametric expression for the dust temperature is presented as $T_{\rm d} = \left[ 11 + 5.7\times \tanh\bigl( 0.61 - \log_{10}(A_{\rm V})\bigr) \right] \, \chi_{\rm uv}^{1/5.9}$, where $\chi_{\rm uv}$ is in units of the Draine (1978) UV fieldComment: 16 pages, 17 figures, 4 tables. Accepted for publication in A&A. Version 2: the omission of factor 0.921 in equation 4 is correcte

Effects of psychological treatment of mental health problems in pregnant women to protect their offspring:Randomised controlled trial

Background Perinatal depression and anxiety are associated with unfavourable child outcomes. Aims To assess among women with antenatal depression or anxiety the effectiveness of prenatally initiated cognitive-behavioural therapy (CBT) on mother and child compared with care as usual (CAU). Trial registration: Netherlands Trial Register number NTR2242. Method Pregnant women (n = 282) who screened positive for symptoms of depression and/or anxiety were randomised to either CBT (n = 140) or CAU (n = 142). The primary outcome was child behavioural and emotional problems at age 18 months, assessed using the Child Behavior Checklist (CBCL). Secondary outcomes were maternal symptoms during and up to 18 months after pregnancy, neonatal outcomes, mother-infant bonding and child cognitive and motor development at age 18 months. Results In total, 94 (67%) women in the CBT group and 98 (69%) in the CAU group completed the study. The mean CBCL Total Problems score was non-significantly higher in the CBT group than in the CAU group (mean difference: 1.38 (95% CI -1.82 to 4.57); t = 0.85, P = 0.399). No effects on secondary outcomes were observed except for depression and anxiety, which were higher in the CBT group than in the CAU group at mid-pregnancy. A post hoc analysis of the 98 women with anxiety disorders showed lower infant gestational age at delivery in the CBT than in the CAU group. Conclusions Prenatally initiated CBT did not improve maternal symptoms or child outcomes among non-help-seeking women with antenatal depression or anxiety. Our findings are not in line with present recommendations for universal screening and treatment for antenatal depression or anxiety, and future work may include the relevance of baseline help-seeking.</p