SUMMARY: Landfills containing organic matter pose an environmental risk for many decades. This is also the case for the landfill Heferlbach, which has been filled until 1974 with more than 200,000 tons of waste. Since no liners have been installed at this site, landfill gas generation represents a potential hazard to the surrounding environment. In particular, the risk for methane migration int...

Based on the conventional sequential-accretion paradigm, we have proposed that, during the migration of first-born gas giants outside the orbits of planetary embryos, super Earth planets will form inside the 2:1 resonance location by sweeping of mean motion resonances (Zhou et al. 2005). In this paper, we study the subsequent evolution of a super Earth (m1) under the effects of tidal dissipatio...

The recent discovery of Jupiter-mass planets orbiting at a few AU from their stars compliments earlier detections of massive planets on very small orbits. The short period orbits strongly suggest that planet migration has occurred, with the likely mechanism being tidal interactions between the planets and the gas disks out of which they formed. The newly discovered long period planets, together...

A planetary system may undergo significant radial rearrangement during the early part of its lifetime. Planet migration can come about through interaction with the surrounding planetesimal disk and the gas disk—while the latter is still present—as well as through planet-planet interactions. We review the major proposed migration mechanisms in the context of the planet formation process, in our ...

Calculations of fluorine binding and migration on carbon nanotube surfaces show that fluorine forms varying surface superlattices at increasing temperatures. The ordering transition is controlled by the surface migration barrier for fluorine atoms to pass through next neighbor sites on the nanotube, explaining the transition from semi-ionic low coverage to covalent high coverage fluorination ob...

Using the evolutionary modeling of system of ordinary differential equations (ODEs) as the test problem, this paper primarily investigates the influences of some important parallel control parameters within parallel genetic programming (GP), including the degree of connectivity between demes, the migration rate, the migration generation interval, and the migration policy, on the performance of ...

A headspace gas chromatographic (GC) method was developed to determine 1,3-butadiene (1,3-BD) in simulated saliva in contact with chewing gum. The calibration graph was linear, and the limit of detection was 0.004 mg/L, which is well below the migration limit for this substance. The headspace GC method provides rapid and reliable analysis for monitoring 1,3-BD migration from chewing gum into si...

H T with respect to solar composition. Given weak Type II migration [5], gap-opening may explain satellite survival. Several workers [6, 7] discuss a process by which the gas in between two giant planets may be cleared by the action of planetary torques, which may lead to subsequent evolution of the planets into resonant orbits as the gas disk evolves. By analogy, we can obtain an estimate of t...

This paper extends previous analyses of parallel GAs with multiple populations (demes) to consider cases where the demes are connected in regular topologies with a xed number of neighbors. The calculations in this paper make explicit the relations between the deme size, the migration rate, and the degree of the connectivity graph with the probability that the desired solution will be found. An ...

We consider the dynamics of dust and gas during the clearing of protoplanetary discs. We work within the context of a photoevaporation/viscous model for the evolution of the gas disc, and use a two-fluid model to study the dynamics of dust grains as the gas disc is cleared. Small (. 10μm) grains remain well-coupled to the gas, but larger (∼ 1mm) grains are subject to inward migration from large...