Solid-state Isotopic Power Source for Computer Memory Chips

Recent developments in materials technology now make it possible to fabricate nonthermal thin-film radioisotopic energy converters (REC) with a specific power of 24 W/kg and a 10 year working life at 5 to 10 watts. This creates applications never before possible, such as placing the power supply directly on integrated circuit chips. The efficiency of the REC is about 25 percent which is two to three times greater than the 6 to 8 percent capabilities of current thermoelectric systems. Radio isotopic energy converters have the potential to meet many future space power requirements for a wide variety of applications with less mass, better efficiency, and less total area than other power conversion options. These benefits result in significant dollar savings over the projected mission lifetime

Gamma-ray Novae: Rare or Nearby?

Classical Novae were revealed as a surprise source of gamma-rays in Fermi LAT observations. During the first 8 years since the LAT was launched, 6 novae in total have been detected to > 5 sigma in gamma-rays, in contrast to the 69 discovered optically in the same period. We attempt to resolve this discrepancy by assuming all novae are gamma-ray emitters, and assigning peak one-day fluxes based on a flat distribution of the known emitters to a simulated population. To determine optical parameters, the spatial distribution and magnitudes of bulge and disc novae in M31 are scaled to the Milky Way, which we approximate as a disc with a 20 kpc radius and elliptical bulge with semi major axis 3 kpc and axis ratios 2:1 in the xy plane. We approximate Galactic reddening using a double exponential disc with vertical and radial scale heights of r_d = 5 kpc and z_d = 0.2 kpc, and demonstrate that even such a rudimentary model can easily reproduce the observed fraction of gamma-ray novae, implying that these apparently rare sources are in fact nearby and not intrinsically rare. We conclude that classical novae with m_R < 12 and within ~8 kpc are likely to be discovered in gamma-rays using the Fermi LAT.Comment: Accepted by MNRAS, 10 pages, 7 figure

Personalized medicine and comparative effectiveness research in an era of fixed budgets

For personalized medicine to be widely adopted in clinical practice, stakeholders need evidence of effectiveness, cost effectiveness and financial viability. Comparative effectiveness research (CER) using population based, retrospective data can inform assessments of personalized medicine. The purpose of this paper is to explore the potential and the limitations of CER. While the analytic methods and data used for CER overcome many of the disadvantages of randomized controlled trials, there are significant barriers, including lack of routinely collected genetic information, patient-reported outcomes and information on new and emerging technologies. Recommendations for using CER include augmenting current data with genetic information, promoting the collection of uniform health outcomes, using value of information analysis to guide development of new technologies, and greater use of decision analysis. Finally, in order to address stakeholder concerns regarding short term financial viability, additional emphasis should be devoted to cost analysis of implementation costs and overall financial impact

Glycolaldehyde, methyl formate and acetic acid adsorption and thermal desorption from interstellar ices

We have undertaken a detailed investigation of the adsorption, desorption and thermal processing of the astrobiologically significant isomers glycolaldehyde, acetic acid and methyl formate. Here, we present the results of laboratory infrared and temperature programmed desorption (TPD) studies of the three isomers from model interstellar ices adsorbed on a carbonaceous dust grain analogue surface. Laboratory infrared data show that the isomers can be clearly distinguished on the basis of their infrared spectra, which has implications for observations of interstellar ice spectra. Laboratory TPD data also show that the three isomers can be distinguished on the basis of their thermal desorption behaviour. In particular, TPD data show that the isomers cannot be treated the same way in astrophysical models of desorption. The desorption of glycolaldehyde and acetic acid from water-dominated ices is very similar, with desorption being mainly dictated by water ice. However, methyl formate also desorbs from the surface of the ice, as a pure desorption feature, and therefore desorbs at a lower temperature than the other two isomers. This is more clearly indicated by models of the desorption on astrophysical time-scales corresponding to the heating rate of 25 and 5 M⊙ stars. For a 25 M⊙ star, our model shows that a proportion of the methyl formate can be found in the gas phase at earlier times compared to glycolaldehyde and acetic acid. This has implications for the observation and detection of these molecules, and potentially explains why methyl formate has been observed in a wider range of astrophysical environments than the other two isomers

Trapping and desorption of complex organic molecules in water at 20 K

The formation, chemical and thermal processing of complex organic molecules (COMs) is currently a topic of much interest in interstellar chemistry. The isomers glycolaldehyde, methyl formate and acetic acid are particularly important because of their role as pre-biotic species. It is becoming increasingly clear that many COMs are formed within interstellar ices which are dominated by water. Hence the interaction of these species with water ice is crucially important in dictating their behaviour. Here we present the first detailed comparative study of the adsorption and thermal processing of glycolaldehyde, methyl formate and acetic acid adsorbed on and in water ices at astrophysically relevant temperatures (20 K). We show that the functional group of the isomer dictates the strength of interaction with water ice, and hence the resulting desorption and trapping behaviour. Furthermore, the strength of this interaction directly affects the crystallization of water, which in turn affects the desorption behaviour. Our detailed coverage and composition dependent data allow us to categorize the desorption behaviour of the three isomers on the basis of the strength of intermolecular and intramolecular interactions, as well as the natural sublimation temperature of the molecule. This categorization is extended to other C, H and O containing molecules in order to predict and describe the desorption behaviour of COMs from interstellar ices

Power and Sample Size Estimation for Nonparametric Composite Endpoints: Practical Implementation using Data Simulations

Composite endpoints are a popular outcome in controlled studies. However, the required sample size is not easily obtained due to the assortment of outcomes, correlations between them and the way in which the composite is constructed. Data simulations are required. A macro is developed that enables sample size and power estimation

Prospects for detection of detached double white dwarf binaries with Gaia, LSST and LISA

Double white dwarf (DWD) binaries are expected to be very common in the Milky Way, but their intrinsic faintness challenges the detection of these systems. Currently, only a few tens of detached DWDs are know. Such systems offer the best chance of extracting the physical properties that would allow us to address a wealth of outstanding questions ranging from the nature of white dwarfs, over stellar and binary evolution to mapping the Galaxy. In this paper we explore the prospects for detections of ultra-compact (with binary separations of a few solar radii or less) detached DWDs in: 1) optical radiation with Gaia and the LSST and 2) gravitational wave radiation with LISA. We show that Gaia, LSST and LISA have the potential to detect respectively around a few hundreds, a thousand, and 25 thousand DWD systems. Moreover, Gaia and LSST data will extend by respectively a factor of two and seven the guaranteed sample of binaries detected in electromagnetic and gravitational wave radiation, opening the era of multi-messenger astronomy for these sources.Comment: submitted to MNRA

Deployment and Impact of Support Staff in Schools : The Impact of Support Staff in Schools (Results from Strand 2, Wave 2)

This study was designed to obtain up to date and reliable data on the deployment and characteristics of support staff and the impact of support staff on pupil outcomes and teacher workloads. The study covered schools in England and Wales. It involved large scale surveys (Strand 1), followed by a multi-method and multi informant approach (Strand 2). It provided detailed baseline data by which to assess change and progress over time. It sought to understand the processes in schools which lead to the effective use of support staff. The DISS project was funded by the Department for Children, Schools and Families (DCSF) and Welsh Assembly Government (WAG)