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

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

Water ice in the Kuiper belt

We examine a large collection of low-resolution near-infrared spectra of Kuiper Belt objects (KBOs) and centaurs in an attempt to understand the presence of water ice in the Kuiper Belt. We find that water ice on the surface of these objects occurs in three separate manners: (1) Haumea family members uniquely show surfaces of nearly pure water ice, presumably a consequence of the fragmentation of the icy mantle of a larger differentiated proto-Haumea; (2) large objects with absolute magnitudes of H < 3 (and a limited number to H = 4.5) have surface coverings of water ice—perhaps mixed with ammonia—that appears to be related to possibly ancient cryovolcanism on these large objects; and (3) smaller KBOs and centaurs which are neither Haumea family members nor cold-classical KBOs appear to divide into two families (which we refer to as "neutral" and "red"), each of which is a mixture of a common nearly neutral component and either a slightly red or very red component that also includes water ice. A model suggesting that the difference between neutral and red objects due to formation in an early compact solar system either inside or outside, respectively, of the ~20 AU methanol evaporation line is supported by the observation that methanol is only detected on the reddest objects, which are those which would be expected to have the most of the methanol containing mixture

Effect of Preventive Home Visits by a Nurse on the Outcomes of Frail Elderly People in the Community: a randomized controlled trial

Background: Timely recognition and prevention of health problems among elderly people have been shown to improve their health. In this randomized controlled trial the authors examined the impact of preventive home visits by a nurse compared with usual care on the outcomes of frail elderly people living in the community. Methods: A screening questionnaire identified eligible participants (those aged 70 years or more at risk of sudden deterioration in health). Those randomly assigned to the visiting nurse group were assessed and followed up in their homes for 14 months. The primary outcome measure was the combined rate of deaths and admissions to an institution, and the secondary outcome measure the rate of health services utilization, during the 14 months; these rates were determined through a medical chart audit by a research nurse who was blind to group allocation. Results: The questionnaire was mailed to 415 elderly people, of whom 369 (88.9%) responded. Of these, 198 (53.7%) were eligible, and 142 consented to participate and were randomly assigned to either the visiting nurse group (73) or the usual care group (69). The combined rate of deaths and admissions to an institution was 10.0% in the visiting nurse group and 5.8% in the usual care group (p = 0.52). The rate of health services utilization did not differ significantly between the 2 groups. Influenza and pneumonia vaccination rates were significantly higher in the visiting nurse group (90.1% and 81.9%) than in the usual care group (53.0% and 0%) (p \u3c 0.001). Interpretation: The trial failed to show any effect of a visiting nurse other than vastly improved vaccination coverage

The Mass, Orbit, and Tidal Evolution of the Quaoar-Weywot System

Here we present new adaptive optics observations of the Quaoar-Weywot system. With these new observations we determine an improved system orbit. Due to a 0.39 day alias that exists in available observations, four possible orbital solutions are available with periods of $\sim11.6$, $\sim12.0$, $\sim12.4$, and $\sim12.8$ days. From the possible orbital solutions, system masses of $1.3-1.5\pm0.1\times10^{21}$ kg are found. These observations provide an updated density for Quaoar of 2.7-5.0{g cm^{-3}}. In all cases, Weywot's orbit is eccentric, with possible values $\sim0.13-0.16$. We present a reanalysis of the tidal orbital evolution of the Quoaor-Weywot system. We have found that Weywot has probably evolved to a state of synchronous rotation, and have likely preserved their initial inclinations over the age of the Solar system. We find that for plausible values of the effective tidal dissipation factor tides produce a very slow evolution of Weywot's eccentricity and semi-major axis. Accordingly, it appears that Weywot's eccentricity likely did not tidally evolve to its current value from an initially circular orbit. Rather, it seems that some other mechanism has raised its eccentricity post-formation, or Weywot formed with a non-negligible eccentricity.Comment: Accepted to Icarus, Nov. 8 201

Plasma Sterilization Technology for Spacecraft Applications

The application of plasma gas technology to sterilization and decontamination of spacecraft components is considered. Areas investigated include: effective sterilizing ranges of four separate gases; lethal constituents of a plasma environment; effectiveness of plasma against a diverse group of microorganisms; penetrating efficiency of plasmas for sterilization; and compatibility of spacecraft materials with plasma environments. Results demonstrated that plasma gas, specifically helium plasma, is a highly effective sterilant and is compatible with spacecraft materials

Screening Seniors for Risk of Functional Decline: Results of a Survey in Family Practice

To measure functional status, determine risk of functional decline and assess consistency between responses and standardized instruments. Design: A mailed survey which measured functional impairment, recent hospitalization and bereavement. A positive response on at least one of these factors indicated that the individual was “at risk” for functional decline. A random sample (n=73) of “at risk” subjects (specifically, family practice patients aged 70 and older) were assessed by a nurse. Results: The response rate was 89% (369/415), 59% of seniors were female and the mean age was 77.1 (SD=5.5) years. Self-reported risk, based on activities of daily living (ADLs), was associated with impairment in at least one basic ADL (p\u3c0.0005) using a standardized instrument. The positive predictive value of the survey for ADL impairment was 65%. Conclusion: Response to a mailed survey was high and self-reported ADL risks were consistent with findings from standardized assessment tools

Potential solar axion signatures in X-ray observations with the XMM-Newton observatory

The soft X-ray flux produced by solar axions in the Earth's magnetic field is evaluated in the context of ESA's XMM-Newton observatory. Recent calculations of the scattering of axion-conversion X-rays suggest that the sunward magnetosphere could be an observable source of 0.2-10 keV photons. For XMM-Newton, any conversion X-ray intensity will be seasonally modulated by virtue of the changing visibility of the sunward magnetic field region. A simple model of the geomagnetic field is combined with the ephemeris of XMM-Newton to predict the seasonal variation of the conversion X-ray intensity. This model is compared with stacked XMM-Newton blank sky datasets from which point sources have been systematically removed. Remarkably, a seasonally varying X-ray background signal is observed. The EPIC count rates are in the ratio of their X-ray grasps, indicating a non-instrumental, external photon origin, with significances of 11(pn), 4(MOS1) and 5(MOS2) sigma. After examining the constituent observations spatially, temporally and in terms of the cosmic X-ray background, we conclude that this variable signal is consistent with the conversion of solar axions in the Earth's magnetic field. The spectrum is consistent with a solar axion spectrum dominated by bremsstrahlung- and Compton-like processes, i.e. axion-electron coupling dominates over axion-photon coupling and the peak of the axion spectrum is below 1 keV. A value of 2.2e-22 /GeV is derived for the product of the axion-photon and axion-electron coupling constants, for an axion mass in the micro-eV range. Comparisons with limits derived from white dwarf cooling may not be applicable, as these refer to axions in the 0.01 eV range. Preliminary results are given of a search for axion-conversion X-ray lines, in particular the predicted features due to silicon, sulphur and iron in the solar core, and the 14.4 keV transition line from 57Fe.Comment: Accepted for publication in MNRAS. 67 pages total, including 39 figures, 6 table

The size, density, and formation of the Orcus-Vanth system in the Kuiper belt

The Kuiper belt object Orcus and its satellite Vanth form an unusual system in the Kuiper belt. Orcus is amongst the largest objects known in the Kuiper belt, but the relative size of Vanth is much larger than that of the tiny satellites of the other large objects. From Hubble Space Telescope observations we find that Orcus and Vanth have different visible colors and that Vanth does not share the water ice absorption feature seen in the infrared spectrum of Orcus. We also find that Vanth has a nearly face-on circular orbit with a period of 9.5393 +-0.0001 days and semimajor axis of 8980+-20 km, implying a system mass of 6.32+- 0.01 X 10^20 kg or 3.8% the mass of dwarf planet Eris. From Spitzer Space Telescope observations we find that the thermal emission is consistent with a single body with diameter 940+-70 km and a geometric albedo of 0.28+-0.04. Assuming equal densities and albedos, this measurements implies sizes of Orcus and Vanth of 900 and 280 km, respectively, and a mass ratio of 33. Assuming a factor of 2 lower albedo for the non-icy Vanth, however, implies sizes of 820 and 640 km and a mass ratio of 2. The measured density depends on the assumed albedo ratio of the two objects but is approximately 1.5+-0.3 g cm^-3$, midway between typical densities measured for larger and for smaller objects. The orbit and mass ratio is consistent with formation from a giant impact and subsequent outward tidal evolution and even consistent with the system having now achieved a double synchronous state. The system can equally well be explained, however, by initial eccentric capture, Kozai cycling which increases the eccentricity and decreases the pericenter of the orbit of Vanth, and subsequent tidal evolution inward.Comment: Submitted to A