Recent developments in planet migration theory

Planetary migration is the process by which a forming planet undergoes a drift of its semi-major axis caused by the tidal interaction with its parent protoplanetary disc. One of the key quantities to assess the migration of embedded planets is the tidal torque between the disc and planet, which has two components: the Lindblad torque and the corotation torque. We review the latest results on both torque components for planets on circular orbits, with a special emphasis on the various processes that give rise to additional, large components of the corotation torque, and those contributing to the saturation of this torque. These additional components of the corotation torque could help address the shortcomings that have recently been exposed by models of planet population syntheses. We also review recent results concerning the migration of giant planets that carve gaps in the disc (type II migration) and the migration of sub-giant planets that open partial gaps in massive discs (type III migration).Comment: 52 pages, 18 figures. Review article to be published in "Tidal effects in Astronomy and Astrophysics", Lecture Notes in Physic

Psychosocial Functioning Problems over Time among High Risk Youths: A Latent Class Transition Analysis

The authors report the results of latent class analyses and latent class transition analyses of antisocial behavior risk factors among 137 youths participating in a juvenile diversion program. The study examined the youths’ latent classifications using baseline and 1-year follow-up measures of family, peer, education, and mental health risk factors. Latent class transition analyses were conducted to determine the stability and change of latent class membership across two time points. For both baseline and follow-up measures, latent class analyses suggested that two latent classes were most appropriate for characterizing the youths using the four domains of risk factors. One class reflected youths reporting few problems in any risk area; the second class reflected youths reporting problems in many of the risk domains. The latent class transition analyses indicated that about two thirds of the youths experienced similar problems over time. The results emphasize the heterogeneity of this study’s sample. Policy implications and intervention service needs are discussed