In situ accretion of gaseous envelopes on to planetary cores embedded in evolving protoplanetary discs

The core accretion hypothesis posits that planets with significant gaseous envelopes accreted them from their protoplanetary discs after the formation of rocky/icy cores. Observations indicate that such exoplanets exist at a broad range of orbital radii, but it is not known whether they accreted their envelopes in situ, or originated elsewhere and migrated to their current locations. We consider the evolution of solid cores embedded in evolving viscous discs that undergo gaseous envelope accretion in situ with orbital radii in the range 0.1–10 au. Additionally, we determine the long-term evolution of the planets that had no runaway gas accretion phase after disc dispersal. We find the following. (i) Planets with 5 M⊕ cores never undergo runaway accretion. The most massive envelope contained 2.8 M⊕ with the planet orbiting at 10 au. (ii) Accretion is more efficient on to 10 M⊕ and 15 M⊕ cores. For orbital radii ap ≥ 0.5 au, 15 M⊕ cores always experienced runaway gas accretion. For ap ≥ 5 au, all but one of the 10 M⊕ cores experienced runaway gas accretion. No planets experienced runaway growth at ap = 0.1 au. (iii) We find that, after disc dispersal, planets with significant gaseous envelopes cool and contract on Gyr time-scales, the contraction time being sensitive to the opacity assumed. Our results indicate that Hot Jupiters with core masses ≲15 M⊕ at ≲0.1 au likely accreted their gaseous envelopes at larger distances and migrated inwards. Consistently with the known exoplanet population, super-Earths and mini-Neptunes at small radii during the disc lifetime, accrete only modest gaseous envelopes.The simulations presented in this paper utilized Queen Mary's MidPlus computational facilities, supported by QMUL Research-IT and funded by EPSRC grant EP/K000128/1. This research was supported in part by the National Science Foundation under Grant No. NSF PHY-1125915. We acknowledge the referee, Kaitlin Kratter, whose comments helped to improve this paper

Fleshing out the data: when epidemiological researchers engage with patients and carers. Learning lessons from a patient involvement activity.

Patient and public involvement and engagement has become an essential element of health research, ensuring aims and outputs are worthwhile and relevant. However, research involving secondary data analyses does not present immediately obvious ways to involve patients and the public. Innovative approaches to ensure their involvement is meaningful and effective are required.The Cancer Survival Group cohosted a full-day meeting with the National Cancer Research Institute Consumer Forum-a group of patients and carers. This included the Forum's 'Dragons' Den': a small-group session in which their members provided insight, advice and ideas on current or planned research in the Cancer Survival Group.We investigated this activity as an example of effective patient involvement, with the aim of developing broad recommendations to improve epidemiological/quantitative research by involving patients and carers as directly as possible.In addition to quantitative data captured through evaluation forms completed after the event, we used semistructured interviews of a sample of participants to evaluate the effectiveness of the session and to learn lessons. The interviews were analysed to identify broad or recurrent themes and recommendations.Feedback was overwhelmingly positive, and some impacts on the research projects were identified. Interviewees commented on overall expectations and experiences, as well as specifics of room layout, timing of the session, composition of groups, effectiveness of the facilitation and content of discussions.We present a summary of our findings as a guide for other researchers, including recommendations for improvement gleaned from the interviews. The value to researchers of hosting and participating in such activities was clear. We developed recommendations that should help to improve future events for ourselves and for others who wish to conduct similar activities, which in turn may lead to more concrete benefits for research and patients

Global N-body simulations of circumbinary planet formation around Kepler-16 and -34 analogues I: Exploring the pebble accretion scenario

Numerous circumbinary planets have been discovered in surveys of transiting planets. Often, these planets are found to orbit near to the zone of dynamical instability, close to the central binary. The existence of these planets has been explained by hydrodynamical simulations that show that migrating circumbinary planets, embedded in circumbinary discs, halt at the central cavity that is formed by the central binary. Transit surveys are naturally most sensitive to finding circumbinary planets with the shortest orbital periods. The future promise of detecting longer period systems using radial-velocity searches, combined with the anticipated detection of numerous circumbinary planets by ESA's PLATO mission, points to the need to model and understand the formation and evolution of circumbinary planets in a more general sense than has been considered before. With this goal in mind, we present a newly developed global model of circumbinary planet formation that is based on the mercury6 symplectic N-body integrator, combined with a model for the circumbinary disc and prescriptions for a range of processes involved in planet formation such as pebble accretion, gas envelope accretion and migration. Our results show that under reasonable assumptions, the pebble accretion scenario can produce circumbinary systems that are similar to those observed, and in particular is able to produce planets akin to Kepler-16b and Kepler-34b. Comparing our results to other systems, we find that our models also adequately reproduce such systems, including multi-planet systems. Resonances between neighbouring planets are frequently obtained, whilst ejections of planets by the central binary acts as an effective source of free floating planets.Comment: Accepted for publication in MNRAS, 23 pages, 16 figure

Dusty circumbinary discs: inner cavity structures and stopping locations of migrating planets

We present the results of two-fluid hydrodynamical simulations of circumbinary discs consisting of gas and dust, with and without embedded planets, to examine the influence of the dust on the structure of the tidally truncated inner cavity and on the parking locations of migrating planets. In this proof-of-concept study, we consider Kepler-16 and -34 analogues, and examine dust fluids with Stokes numbers in the range $10^{-4} \le St \le 10^{-1}$ and dust-to-gas ratios of 0.01 and 1. For the canonical dust-to-gas ratio of 0.01, we find the inclusion of the dust has only a minor effect on the cavity and stopping locations of embedded planets compared to dust-free simulations. However, for the enhanced dust-to-gas ratio of unity, assumed to arise because of significant dust drift and accumulation, we find that the dust can have a dramatic effect by shrinking and circularising the inner cavity, which brings the parking locations of planets closer to the central binary. This work demonstrates the importance of considering both gas and dust in studies of circumbinary discs and planets, and provides a potential means of explaining the orbital properties of circumbinary planets such as Kepler-34b, which have hitherto been difficult to explain using gas-only hydrodynamical simulations.Comment: Accepted for publication in MNRAS, 20 pages, 17 figure

Anomalous asymmetry of magnetoresistance in NbSe3_3 single crystals

A pronounced asymmetry of magnetoresistance with respect to the magnetic field direction is observed for NbSe$_3$ crystals placed in a magnetic field perpendicular to their conducting planes. It is shown that the effect persists in a wide temperature range and manifests itself starting from a certain magnetic induction value $B_0$, which at $T=4.2$ K corresponds to the transition to the quantum limit, i.to the state where the Landay level splitting exceeds the temperature.Comment: 4 pages, 6 figures, to be appeared in JETP Let

Constraining the formation history of the TOI-1338/BEBOP-1 circumbinary planetary system

The recent discovery of multiple planets in the circumbinary system TOI-1338/BEBOP-1 raises questions about how such a system formed. The formation of the system was briefly explored in the discovery paper, but only to answer the question do current pebble accretion models have the potential to explain the origin of the system? We use a global model of circumbinary planet formation that utilises N-body simulations, including prescriptions for planet migration, gas and pebble accretion, and interactions with a circumbinary disc, to explore the disc parameters that could have led to the formation of the TOI-1338/BEBOP-1 system. With the disc lifetime being the main factor in determining how planets form, we limit our parameter space to those that determine the disc lifetime. These are: the strength of turbulence in the disc, the initial disc mass, and the strength of the external radiation field that launches photoevaporative winds. When comparing the simulated systems to TOI-1338/BEBOP-1, we find that only discs with low levels of turbulence are able to produce similar systems. The radiation environment has a large effect on the types of planetary systems that form, whilst the initial disc mass only has limited impact since the majority of planetary growth occurs early in the disc lifetime. With the most TOI-1338/BEBOP-1 like systems all occupying similar regions of parameter space, our study shows that observed circumbinary planetary systems can potentially constrain the properties of planet forming discs.Comment: Accepted for publication in MNRAS, 15 pages, 10 figure

Natural history of malignant bone disease in breast cancer and the use of cumulative mean functions to measure skeletal morbidity

BACKGROUND: Bone metastases are a common cause of skeletal morbidity in patients with advanced cancer. The pattern of skeletal morbidity is complex, and the number of skeletal complications is influenced by the duration of survival. Because many patients with cancer die before trial completion, there is a need for survival-adjusted methods to accurately assess the effects of treatment on skeletal morbidity. METHODS: Recently, a survival-adjusted cumulative mean function model has been generated that can provide an intuitive graphic representation of skeletal morbidity throughout a study. This model was applied to the placebo-control arm of a pamidronate study in patients with malignant bone disease from breast cancer. RESULTS: Analysis by bone lesion location showed that spinal metastases were associated with the highest cumulative mean incidence of skeletal-related events (SREs), followed by chest and pelvic metastases. Metastases located in the extremities were associated with an intermediate incidence of SREs, and those in the skull were associated with the lowest incidence of SREs. CONCLUSION: Application of this model to data from the placebo arm of this trial revealed important insight into the natural history of skeletal morbidity in patients with bone metastases. Based on these observations, treatment for the prevention of SREs is warranted regardless of lesion location except for metastases on the skull

Classical glueballs in non-Abelian Born-Infeld theory

It is shown that the Born-Infeld-type modification of the quadratic Yang-Mills action suggested by the superstring theory gives rise to classical particle-like solutions prohibited in the standard Yang-Mills theory. This becomes possible due to the scale invariance breaking by the Born-Infeld non-linearity. New classical glueballs are sphaleronic in nature and exhibit a striking similarity with the Bartnik-McKinnon solutions of the Yang-Mills theory coupled to gravity.Comment: Revtex, 4 pages, 2 eps figure