Mineralogy of the Ibitira eucrite and comparison with other eucrites and lunar samples

Single crystal X-ray and energy dispersive electron-probe techniques are used to study the mineralogy and track history of Ibitira. The mineralogical features of the Ibitire eucrite are described and examined in relation to data for other eucrites and howardites and lunar samples. The processes which transformed a presumed igneous texture into a more complex one are discussed

Investigating the Martian atmosphere using the ExoMars 2016 lander

Accurate modelling of the Martian atmosphere is essential both for planning and completing future missions to the Martian surface, and for accurate analysis and interpretation of the data that they return. Large dust storms and local wind patterns can affect spacecraft landing profiles, and the level of dust present in the atmosphere may impact lander performance. The ExoMars 2016 Mission will carry an Entry, Descent and Landing Demonstrator Module (EDM), primarily designed to test the ability of ESA’s lander technology to carry a science package to the surface [1]. The Atmospheric Mars Entry and Landing Investigations and Analysis (AMELIA) team [2] will use the module’s entry and descent trajectory to characterise the structure of the atmosphere along the travelled landing profile, and to determine properties of the atmosphere, such as density and wind speed, over a wide altitude range from the upper atmosphere to the surface. Aerosol abundances, including atmospheric dust, will also be characterised. These combined datasets will enable more accurate predictions of the atmospheric environment that future landers will encounter. EDM’s surface science package, DREAMS (Dust characterisation, Risk assessment, and Environment Analyser on the Martian Surface), includes sensors to measure wind speed and direction, surface temperature, pressure, and the amount of atmospheric dust present near the surface [3]. We will use the descent and surface profile data collected by EDM to verify and improve current Martian atmospheric modelling completed at The Open University, using both the global circulation and mesoscale models. [1] Forget et al. (2011) Fourth International Workshop on the Mars Atmosphere: Modeling and Observations, Paris. [2] Ferri et al. (2012) 9th International Planetary Probe Workshop (IPPW9), Toulouse. [3] Esposito et al. (2013) EPSC Abstracts Vol. 8, EPSC2013-815

Calculating the inherent visual structure of a landscape (inherent viewshed) using high-throughput computing

This paper describes a method of calculating the inherent visibility at all locations in a landscape (‘total viewshed’) by making use of redundant computer cycles. This approach uses a simplified viewshed program that is suitable for use within a distributed environment, in this case managed by the Condor system. Distributing the calculation in this way reduced the calculation time of our example from an estimated 34 days to slightly over 25 hours using a cluster of 43 workstations. Finally, we discuss the example ‘total viewshed’ raster for the Avebury region, and briefly highlight some of its implications

PPl 15: The First Brown Dwarf Spectroscopic Binary

PPl 15 is the first object to have been confirmed as a brown dwarf by the lithium test (in 1995), though its inferred mass was very close to the substellar limit. It is a member of the Pleiades open cluster. Its position in a cluster color-magnitude diagram suggested that it might be binary, and preliminary indications that it is a double-lined spectroscopic binary were reported by us in 1997. Here we report on the results of a consecutive week of Keck HIRES observations of this system, which yield its orbit. It has a period of about 5.8 days, and an eccentricity of 0.4+/-0.05. The rotation of the stars is slow for this class of objects. Because the system luminosity is divided between 2 objects with a mass ratio of 0.85, this renders each of them an incontrovertible brown dwarf, with masses between 60-70 jupiters. We show that component B is a little redder than A by studying their wavelength-dependent line ratios, and that this variation is compatible with the mass ratio. We confirm that the system has lithium, but cannot support the original conclusion that it is depleted (which would be surprising, given the new masses). This is a system of very close objects which, if they had combined, would have produced a low mass star. We discuss the implications of this discovery for the theories of binary formation and formation of very low mass objects.Comment: Latex, 18 pages, 4 figures, submitted to Astron.

Disc loss and renewal in A0535+26

This paper presents observations of the Be/X-ray binary system A0535+26 revealing the first observed loss of its circumstellar disc, demonstrated by the loss of its JHK infrared excess and optical/IR line emission. However optical/IR spectroscopy reveals the formation of a new inner disc with significant density and emission strength at small radii; the disc has proven to be stable over 5 months in this intermediate state.Comment: 4 pages, 4 figures, accepted by MNRAS, uses mn.st

Delineation of RAID1, the RACK1 interaction domain located within the unique N-terminal region of the cAMP-specific phosphodiesterase, PDE4D5

Background The cyclic AMP specific phosphodiesterase, PDE4D5 interacts with the β-propeller protein RACK1 to form a signaling scaffold complex in cells. Two-hybrid analysis of truncation and mutant constructs of the unique N-terminal region of the cAMP-specific phosphodiesterase, PDE4D5 were used to define a domain conferring interaction with the signaling scaffold protein, RACK1. Results Truncation and mutagenesis approaches showed that the RACK1-interacting domain on PDE4D5 comprised a cluster of residues provided by Asn-22/Pro-23/Trp-24/Asn-26 together with a series of hydrophobic amino acids, namely Leu-29, Val-30, Leu-33, Leu-37 and Leu-38 in a 'Leu-Xaa-Xaa-Xaa-Leu' repeat. This was done by 2-hybrid analyses and then confirmed in biochemical pull down analyses using GST-RACK1 and mutant PDE4D5 forms expressed in COS cells. Mutation of Arg-34, to alanine, in PDE4D5 attenuated its interaction with RACK1 both in 2-hybrid screens and in pull down analyses. A 38-mer peptide, whose sequence reflected residues 12 through 49 of PDE4D5, bound to RACK1 with similar affinity to native PDE4D5 itself (Ka circa 6 nM). Conclusions The RACK1 Interaction Domain on PDE4D5, that we here call RAID1, is proposed to form an amphipathic helical structure that we suggest may interact with the C-terminal β-propeller blades of RACK1 in a manner akin to the interaction of the helical G-γ signal transducing protein with the β-propeller protein, G-β

Is the Tsallis entropy stable?

The question of whether the Tsallis entropy is Lesche-stable is revisited. It is argued that when physical averages are computed with the escort probabilities, the correct application of the concept of Lesche-stability requires use of the escort probabilities. As a consequence, as shown here, the Tsallis entropy is unstable but the thermodynamic averages are stable. We further show that Lesche stability as well as thermodynamic stability can be obtained if the homogeneous entropy is used as the basis of the formulation of non-extensive thermodynamics. In this approach, the escort distribution arises naturally as a secondary structure.Comment: 6 page