NICMOS Photometry of the Unusual Dwarf Planet Haumea and its Satellites

We present here Hubble Space Telescope NICMOS F110W and F160W observations of Haumea, and its two satellites Hi'iaka and Namaka. From the measured (F110W-F160W) colors of –1.208 ± 0.004, –1.48 ± 0.06, and –1.4 ± 0.2 mag for each object, respectively, we infer that the 1.6 μm water-ice absorption feature depths on Hi'iaka and Namaka are at least as deep as that of Haumea. The light curve of Haumea is detected in both filters, and we find that the infrared color is bluer by ~2%-3% at the phase of the red spot. These observations suggest that the satellites of Haumea were formed from the collision that produced the Haumea collisional family

On the upper regularity dimensions of measures

We study the \emph{upper regularity dimension} which describes the extremal local scaling behaviour of a measure and effectively quantifies the notion of \emph{doubling}. We conduct a thorough study of the upper regularity dimension, including its relationship with other concepts such as the Assouad dimension, the upper local dimension, the $L^q$-spectrum and weak tangent measures. We also compute the upper regularity dimension explicitly in a number of important contexts including self-similar measures, self-affine measures, and measures on sequences.Comment: 22 pages, 4 figures. We corrected an error in Theorem 2.2 and provided a new example concerning weak tangent measures. Minor corrections were added in section 3.6.1, not changing any results. To appear in Indiana Univ. Math.

The Hubble Wide Field Camera 3 Test of Surfaces in the Outer Solar System: The Compositional Classes of the Kuiper Belt

We present the first results of the Hubble Wide Field Camera 3 Test of Surfaces in the Outer Solar System (H/WTSOSS). The purpose of this survey was to measure the surface properties of a large number of Kuiper belt objects and attempt to infer compositional and dynamical correlations. We find that the Centaurs and the low-perihelion scattered disk and resonant objects exhibit virtually identical bifurcated optical colour distributions and make up two well defined groups of object. Both groups have highly correlated optical and NIR colours which are well described by a pair of two component mixture models that have different red components, but share a common neutral component. The small, $H_{606}\gtrsim5.6$ high-perihelion excited objects are entirely consistent with being drawn from the two branches of the mixing model suggesting that the colour bifurcation of the Centaurs is apparent in all small excited objects. On the other hand, objects larger than $H_{606}\sim5.6$ are not consistent with the mixing model, suggesting some evolutionary process avoided by the smaller objects. The existence of a bifurcation amongst all excited populations argues that the two separate classes of object existed in the primordial disk before the excited Kuiper belt was populated. The cold classical objects exhibit a different type of surface which has colours that are consistent with being drawn from the red branch of the mixing model, but with much higher albedos.Comment: Accepted to the Astrophysical Journal. 49 Pages, 15 Figure

High Heritability Is Compatible with the Broad Distribution of Set Point Viral Load in HIV Carriers.

Set point viral load in HIV patients ranges over several orders of magnitude and is a key determinant of disease progression in HIV. A number of recent studies have reported high heritability of set point viral load implying that viral genetic factors contribute substantially to the overall variation in viral load. The high heritability is surprising given the diversity of host factors associated with controlling viral infection. Here we develop an analytical model that describes the temporal changes of the distribution of set point viral load as a function of heritability. This model shows that high heritability is the most parsimonious explanation for the observed variance of set point viral load. Our results thus not only reinforce the credibility of previous estimates of heritability but also shed new light onto mechanisms of viral pathogenesis

Technical Efficiency of Australian Wool Production: Point and Confidence Interval Estimates

A balanced panel of data is used to estimate technical efficiency, employing a fixed-effects stochastic frontier specification for wool producers in Australia. Both point estimates and confidence intervals for technical efficiency are reported. The confidence intervals are constructed using the Multiple Comparisons with the Best (MCB) procedure of Horrace and Schmidt (2000). The confidence intervals make explicit the precision of the technical efficiency estimates and underscore the dangers of drawing inferences based solely on point estimates. Additionally, they allow identification of wool producers that are statistically efficient and those that are statistically inefficient. The data reveal at the 95% confidence level that twenty-one of the twenty-six wool farms analyzed may be efficient.Wool, Technical Efficiency, MCB, MCC

An evolutionarily stable joining policy for group foragers

For foragers that exploit patchily distributed resources that are challenging to locate, detecting discoveries made by others with a view to joining them and sharing the patch may often be an attractive tactic, and such behavior has been observed across many taxa. If, as will commonly be true, the time taken to join another individual on a patch increases with the distance to that patch, then we would expect foragers to be selective in accepting joining opportunities: preferentially joining nearby discoveries. If competition occurs on patches, then the profitability of joining (and of not joining) will be influenced by the strategies adopted by others. Here we present a series of models designed to illuminate the evolutionarily stable joining strategy. We confirm rigorously the previous suggestion that there should be a critical joining distance, with all joining opportunities within that distance being accepted and all others being declined. Further, we predict that this distance should be unaffected by the total availability of food in the environment, but should increase with decreasing density of other foragers, increasing speed of movement towards joining opportunities, increased difficulty in finding undiscovered food patches, and decreasing speed with which discovered patches can be harvested. We are further able to make predictions as to how fully discovered patches should be exploited before being abandoned as unprofitable, with discovered patches being more heavily exploited when patches are hard to find: patches can be searched for remaining food more quickly, forager density is low, and foragers are relatively slow in traveling to discovered patches

Method of statistical filtering

Minimal formula for bounding the cross correlation between a random forcing function and the state error when this correlation is unknown is used in optimal linear filter theory applications. Use of the bound results in overestimation of the estimation-error covariance

The impacts of past climate change on sub-Antarctic nearshore ecosystems

Pleistocene glacial–interglacial cycles would have resulted in drastic changes in the structure of sub-Antarctic littoral ecosystems. Genetic data indicate that the large kelps that dominate intertidal and shallow subtidal sub-Antarctic shores today (such as Macrocystis pyrifera and Durvillaea antarctica) were extirpated from these high latitude regions by sea ice scour during glacial maxima. These macroalgae, and their associated faunal communities, were able to return to the sub-Antarctic islands during interglacial periods by drifting at sea in the path of the Antarctic Circumpolar Current. During glacial maxima, sub-Antarctic littoral communities would have been severely reduced, comprising mainly ice-scour hardy taxa such as small and/or seasonal macroalgae, and mobile molluscs