Application of an Inexact-Newton Method Within the Second-Order Born Approximation to Buried Objects

The imaging of buried objects is a challenging topic in electromagnetic research. In this letter, a method previously proposed for imaging of scatterers in free-space is extended to the case of objects buried in a lossy half-space. The proposed approach is based on the solution of the underlying inverse-scattering problem within the second-order Born approximation by means of a two-step inexact-Newton algorithm. The capabilities and limitations of the method are evaluated by means of some numerical simulations. Furthermore, comparisons with the free-space approach are also reported     

Realisation of a fully‐deterministic microlensing observing strategy for inferring planet populations

Within less than 15 years, the count of known planets orbiting stars other than the Sun has risen from none to more than 400 with detections arising from four successfully applied techniques: Doppler‐wobbles, planetary transits, gravitational microlensing, and direct imaging. While the hunt for twin Earths is on, a statistically well‐defined sample of the population of planets in all their variety is required for probing models of planet formation and orbital evolution so that the origin of planets that harbour life, like and including ours, can be understood. Given the different characteristics of the detection techniques, a complete picture can only arise from a combination of their respective results. Microlensing observations are well‐suited to reveal statistical properties of the population of planets orbiting stars in either the Galactic disk or bulge from microlensing observations, but a mandatory requirement is the adoption of strictly‐deterministic criteria for selecting targets and identifying signals. Here, we describe a fully‐deterministic strategy realised by means of the ARTEMiS (Automated Robotic Terrestrial Exoplanet Microlensing Search) system at the Danish 1.54‐m telescope at ESO La Silla between June and August 2008 as part of the MiNDSTEp (Microlensing Network for the Detection of Small Terrestrial Exoplanets) campaign, making use of immediate feedback on suspected anomalies recognized by the SIGNALMEN anomaly detector. We demonstrate for the first time the feasibility of such an approach, and thereby the readiness for studying planet populations down to Earth mass and even below, with ground‐based observations. While the quality of the real‐time photometry is a crucial factor on the efficiency of the campaign, an impairment of the target selection by data of bad quality can be successfully avoided. With a smaller slew time, smaller dead time, and higher through‐put, modern robotic telescopes could significantly outperform the 1.54‐m Danish, whereas lucky‐imaging cameras could set new standards for high‐precision follow‐up monitoring of microlensing events (© 2010 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)     

Metal tissue levels in Steller sea lion (Eumetopias jubatus) pups

The endangered Western population of the Steller sea lion declined for three decades for uncertain reasons. We present baseline data of metal concentrations in pups as a first step towards investigating the potential threat of developmental exposures to contaminants. Seven metals were investigated: arsenic, cadmium, silver, aluminum, mercury, lead and vanadium. Vanadium was detected in only a single blubber sample. Mercury appears to be the most toxicologically significant metal with concentrations in the liver well above the current action level for mercury in fish. The concentrations of aluminum, arsenic, silver, cadmium and lead were present in one-fourth to two-thirds of all samples and were at either comparable or below concentrations previously reported. Neither gender nor region had a significant effect on metal burdens. Future work should consider metal concentrations in juveniles and adults and toxicological studies need to be performed to begin to assess the toxicity of these metals.