Planetary Migration in Protoplanetary Disks

The known exoplanet population displays a great diversity of orbital architectures, and explaining the origin of this is a major challenge for planet formation theories. The gravitational interaction between young planets and their protoplanetary disks provides one way in which planetary orbits can be shaped during the formation epoch. Disk-planet interactions are strongly influenced by the structure and physical processes that drive the evolution of the protoplanetary disk. In this review we focus on how disk-planet interactions drive the migration of planets when different assumptions are made about the physics of angular momentum transport, and how it drives accretion flows in protoplanetary disk models. In particular, we consider migration in discs where: (i) accretion flows arise because turbulence diffusively transports angular momentum; (ii) laminar accretion flows are confined to thin, ionised layers near disk surfaces and are driven by the launching of magneto-centrifugal winds, with the midplane being completely inert; (iii) laminar accretion flows pervade the full column density of the disc, and are driven by a combination of large scale horizontal and vertical magnetic fields

Recognition of genetic factors influencing the progression of Hepatitis C

Infection with hepatitis C virus (HCV) is a major cause of chronic liver disease. Hepatic fibrosis may develop in subjects with chronic HCV infection, culminating in cirrhosis and an increased risk of hepatocellular carcinoma. The rate of development of fibrosis varies substantially between individuals; while it is influenced by a number of demographic and environmental factors, these account for only a small proportion of the variability. There are no clinical markers or tests that predict the rate of fibrosis progression in an individual subject. Thus, there has been increasing interest in the influence of host genetic factors on the rate of disease progression, and whether a genetic signature can be developed to reliably identify individuals at risk of severe disease. Numerous case-control, candidate gene, allele-association studies have examined the relationship between host single nucleotide polymorphisms or other genetic mutations and fibrosis in patients with chronic HCV infection. However, these studies have generally been irreproducible and disappointing. As seen with genetic studies for other diseases, small study cohorts and poor study design have contributed to limited meaningful findings. The successful determination of genetic signatures for fibrosis progression in chronic HCV will require multicenter collaborations using genome-wide association studies, with large, phenotypically well-defined sample sets. While these studies will require a significant financial commitment, a successful outcome offers the potential for personalized therapy and better patient management

Integration of fission track thermochronology with other geochronologic methods on single crystals

Fission-track (FT) thermochronology can be integrated with the U–Pb and (U–Th)/He dating methods. All three radiometric dating methods can be applied to single crystals (hereafter referred to as “triple-dating”), allowing more complete and more precise thermal histories to be constrained from single grains. Such an approach is useful across a myriad of geological applications. Triple-dating has been successfully applied to zircon and apatite. However, other U-bearing minerals such as titanite and monazite, which are routinely dated by single methods, are also candidates for this approach. Several analytical procedures can be used to generate U–Pb—FT—(U–Th)/He age triples on single grains. The procedure introduced here combines FT dating by LA-ICPMS and in situ (U–Th)/He dating approach, whereby the U–Pb age is obtained as a byproduct of U–Th analysis by LA-ICPMS. In this case, U–Pb, trace element and REE data can be collected simultaneously and used as annealing kinetics parameter or as provenance and petrogenetic indicators. This novel procedure avoids time-consuming irradiation in a nuclear reactor, reduces multiple sample handling steps and allows high sample throughput (predictably on the order of 100 triple-dated crystals in 2 weeks). These attributes and the increasing number of facilities capable of conducting triple-dating indicate that this approach may become more routine in the near future