The brown dwarf desert as a consequence of orbital migration

We show that the dearth of brown dwarfs in short-period orbits around Solar-mass stars – the brown dwarf desert – can be understood as a consequence of inward migration within an evolving protoplanetary disc. Brown dwarf secondaries forming at the same time as the primary star have masses which are comparable to the initial mass of the protoplanetary disc. Subsequent disc evolution leads to inward migration, and destruction of the brown dwarf, via merger with the star. This is in contrast with massive planets, which avoid this fate by forming at a later epoch when the disc is close to being dispersed. Within this model, a brown dwarf desert arises because the mass at the hydrogen-burning limit is coincidentally comparable to the initial disc mass for a Solar mass star. Brown dwarfs should be found in close binaries around very low mass stars, around other brown dwarfs, and around Solar-type stars during the earliest phases of star formation.     

New Validity Conditions for the Multivariate Matérn Coregionalization Model,with an Application to Exploration Geochemistry

Mathematical Geosciences - This paper addresses the problem of finding parametric constraints that ensure the validity of the multivariate Matérn covariance for modeling the spatial...     

Macau’s role as a recreation/tourist center in the Pearl River Delta city-region

The return of Macau to Chinese sovereignty in 1999 brought far-reaching change to Macau as a special administrative region (SAR). China’s policy and plans for a revitalized Macau as a key urban node offers an opportunity to conceptualize a leading role for Macau as the pre-eminent recreational and tourist center in the dynamic and globally connected Pearl River Delta city-region. We examine and assess the new policies that have led to Las Vegas-style casinos bringing explosive growth in visitors, gambling revenues, and Macau’s economy. New problems of corruption, crime, and social pathologies have appeared as well owing in part to the secretive VIP gambling centers for high rollers from the mainland. Has Macau met China’s goals and expectations for a great tourist and recreational center? Our findings indicate a mixed record with more challenges emerging in the wake of China’s recent anti-corruption campaign.     

The Reliability of Assigned Values from the GeoPT Proficiency Testing Programme from an Evaluation of Data for Six Test Materials that have been Characterised as Certified Reference Materials

Assigned values derived from the GeoPT proficiency testing programme were compared with certified values for six certified reference materials that have been used as test materials in the GeoPT programme. Statistical analysis showed that there were few significant differences between these sets of data and that these differences had no significant impact on the GeoPT assessment when fitness‐for‐purpose criteria were taken into account.     

Mapping the ideological networks of American climate politics

How do we understand national climate change politics in the United States? Using a methodological innovation in network analysis, this paper analyzes discussions about the issue within the US Congress. Through this analysis, the ideological relationships among speakers providing Congressional testimony on the issue of climate change are mapped. For the first time, issue stances of actors are systematically aggregated in order to measure coalitions and consensus among political actors in American climate politics in a relational way. Our findings show how consensus formed around the economic implications of regulating greenhouse gases and the policy instrument that should do the regulating. The paper is separated into three sections. First, we review the ways scholars have looked at climate change policymaking in the United States, paying particular attention to those who have looked at the issue within the US Congress. Next, we present analysis of statements made during Congressional hearings on climate change over a four-year period. Our analysis demonstrates how a polarized ideological actor space in the 109^th Congress transforms into a more consensual actor landscape in the 110^th Congress, which is significantly less guided by partisan differences. This paper concludes by discussing how these findings help us understand shifting positions within American climate politics and the implications of these findings.     

Active Region Coronal Rain Event Observed by the Fast Imaging Solar Spectrograph on the NST

The Fast Imaging Solar Spectrograph (FISS) is being operated on the New Solar Telescope of the Big Bear Solar Observatory. It simultaneously records spectra of Hα and Ca ii 8542 Å lines, and this dual-spectra measurement provides an estimate of the temperature and nonthermal speed components. We observed a loop structure in AR 11305 using the FISS, SDO/AIA, and STEREO/EUVI in 304 Å, and found plasma material falling along the loop from a coronal height into the umbra of a sunspot, which accelerated up to 80 km?s^?1. We also observed C2 and C7 flare events near the loop. The temperature of the downflows was in the range of 10?000?–?33?000 K, increasing toward the umbra. The temperature of the flow varied with time, and the temperature near the footpoint rose immediately after the C7 flare, but the temperature toward the umbra remained the same. There seemed to be a temporal correlation between the amount of downflow material and the observed C-class flares. The downflows decreased gradually soon after the flares and then increased after a few hours. These high-speed red-shift events occurred continuously during the observations. The flows observed on-disk in Hα and Ca ii 8542 Å appeared as fragmented, fuzzy condensed material falling from the coronal heights when seen off-limb with STEREO/EUVI at 304 Å. Based on these observations, we propose that these flows were an on-disk signature of coronal rain.     

Interannual variability of water ice clouds over major martian volcanoes observed by MOC

Using Mars Global Surveyor Mars Orbiter Camera daily global maps, cloud areas have been measured daily for water ice clouds associated with the topography of the major volcanoes Olympus Mons, Ascraeus Mons, Pavonis Mons, Arsia Mons, Elysium Mons, and Alba Patera. This study expands on that of Benson et al. [Benson, J.L., Bonev, B.P., James, P.B., Shan, K.J., Cantor, B.A., Caplinger, M.A., 2003. Icarus 165, 34-52] by continuing their cloud area measurements of the Tharsis volcanoes, Olympus Mons and Alba Patera for an additional martian year (August 2001-May 2003) and by also including Elysium Mons measurements from March 1999 through May 2003. The seasonal trends in cloud activity established by Benson et al. [Benson, J.L., Bonev, B.P., James, P.B., Shan, K.J., Cantor, B.A., Caplinger, M.A., 2003. Icarus 165, 34-52] for the five volcanoes studied earlier are corroborated here with an additional year of coverage. For volcanoes other than Arsia Mons, interannual variations that could be associated with the large 2001 planet encircling dust storm are minimal. At Arsia Mons, where cloud activity was continuous in the first two years, clouds disappeared totally for ∼85° of LS (LS=188°-275°) due to the dust storm. Elysium Mons cloud activity is similar to that of Olympus Mons, however the peak in cloud area is near LS=130° rather than near LS=100°.