Are there MACHOs in the Milky Way halo?

Microlensing searches aim to detect compact halo dark matter via its gravitational lensing effect on stars within the Large Magellanic Cloud. The most recent results have led to the claim that roughly one fifth of the galactic halo dark matter may be in the form of compact, solar-mass objects. We analyze this hypothesis by considering the goodness-of-fit of the best-fit halo dark matter solutions to the observational data. We show that the distribution of the durations of the observed microlensing events is narrower than that expected to result from a standard halo lens population at 90 to 95% confidence. Only when the fraction of expected background (non-halo) events is significantly increased does the discrepancy between the observed and theoretical event duration distributions disappear. This indicates that it is possible that most of the lenses responsible for the observed microlensing events are not located within the Milky Way halo.Comment: 5 pages, 2 figures, minor changes to discussion and additional references, version to appear in Astronomy and Astrophysic

Design of experiment for the optimisation of deep reactive ion etching of silicon inserts for micro-fabrication

The following paper describes a design of experiments investigation of the deep reactive of pillar structures on a silicon wafer. The etched wafers would subsequently be used as masters for the fabrication of nickel mould inserts for microinjection moulding. Undercuts occur when the pillar base has a smaller cross-section than the apex of the pillar. They therefore affect tolerances of the subsequent nickel mould, its strength and its de-mouldability from the silicon form. The response measured in these experiments was the degree of undercut of micro-scale (10 μm x 10 μm x 40 μm, 5 μm x 5 μm x 40 μm and 2 μm x 2 μm x 40 μm) The literature suggests that gas pressure, platen power, gas flow rate, phase switching times and mask size can all affect the degree of undercut. After examination of this literature, and of manufacturers guidelines, three parameters were selected for experimental testing: platen power, C 4F 8 gas flow rate during the passivation phase and switching times. Switching times was found to be the only statistically significant parameter for both 10x10 μm and 5x5 μm pillars. The 2x2 μm pillars were not successfully replicated and could therefore not undergo statistical evaluation

High-energy Astrophysics and the Virtual Observatory

The Virtual Observatory (VO) will revolutionise the way we do Astronomy by allowing easy access to all astronomical data and by making the handling and analysis of datasets at various locations across the globe much simpler and faster. I report here on the need for the VO and its status in Europe, concentrating on the recently started EURO-VO project, and then give two specific applications of VO tools to high-energy astrophysics.Comment: 12 pages, 3 figures, invited talk at the Workshop ``Multifrequency Behaviour of High Energy Cosmic Sources'', Vulcano, Italy, May 2005, F. Giovannelli et al., in pres

Factors Associated With Mental Health Disclosure Outside of the Workplace: A Systematic Literature Review

People with mental health problems sometimes have the choice of whether or not to disclose this information to others. The decision to disclose or conceal is likely to depend on various factors. In this systematic review, we examined the findings of studies looking at factors affecting adults’ decisions to disclose or conceal a mental health problem outside of the workplace. Key databases (PsycINFO, Scopus, and Web of Science) revealed 19 relevant articles published between January 2005 and August 2015. Common factors affecting disclosure or concealment included anticipated stigma, characteristics of the target, relationship with the target, mental health of the discloser, rules and beliefs about mental health problems, and fears about control and identity. Demographic factors were not strongly associated with disclosure decisions. We also found that measures used to understand mental health disclosure may fail to capture the complexity of the process. Implications for future research and policy are discussed, including the need for palpable public support for people with mental health problems, the need for health care professionals to establish better relationships with service users, and the value of respecting nondisclosure

Solubility and activity of oxygen in liquid germanium and germanium-copper alloys

The solubility of oxygen in liquid germanium in the temperature range 1233 to 1397 K, and in liquid germanium-copper alloys at 1373 K, in equilibrium with GeO2 has been measured by the phase equilibration technique. The solubility of oxygen in pure germanium is given by the relation 6470 log(at, pct 0) =-6470/T + 4.24 (±0.07). The standard free energy of solution of oxygen in liquid germanium is calculated from the saturation solubility, and recently measured values for the free energy of formation of GeO2, assuming that oxygen obeys Sievert's law up to the saturation limit. For the reaction, ½O2(g)→OGe ΔG ° =-39,000 + 3.21 T ( ±500) ca1 = -163,200 + 13.43 T (±2100) J. where the standard state for dissolved oxygen is that which makes the value of activity equal to the concentration (in at. pct), in the limit, as concentration approaches zero. The effect of copper on the activity of oxygen dissolved in liquid germanium is found to be in good agreement with that predicted by a quasichemical model in which each oxygen was assumed to be bonded to four metal atoms and the nearest neighbor metal atoms to an oxygen atom are assumed to lose approximately half of their metallic bonds

Activities in the spinel solid solution, phase equilibria and thermodynamic properties of ternary phases in the system Cu-Fe-0

A review of the structural and thermodynamic information and phase equilibria in the Cu-Fe-O system suggested that a consistent, quantitative description of the system is hampered by lack of data on activities in the spinel solid solution CuFe2O4-Fe3O4. Therefore the activity of Fe3O4 in this solid solution is derived from measurements of the oxygen potentials established at 1000°C by mixtures containing Fe2O3 and spinel solid solutions of known composition. The oxygen pressures were measured manometrically for solid solutions rich in CuFe2O4, while for Fe3O4-rich compositions the oxygen potentials were obtained by an emf technique. The activities show significant negative deviations from Raoult's law. The compositions of the spinel solid solutions in equilibrium with CuO + CuFeO2 and Cu + CuFeO2 were obtained from chemical analysis of the solid solution after magnetic separation. The oxygen potential of the three-phase mixture Cu + CuFeO2 + Fe3O4(spinel s.s.) was determined by a solid oxide galvanic cell. From these measurements a complete phase diagram and consistent thermodynamic data on the ternary condensed phases, CuFeO2 and CuFeO2O4, were obtained. An analysis of the free energy of mixing of the spinel solid solution furnished information on the distribution of cations and their valencies between the tetrahedral and octahedral sites of the spinel lattice, which is consistent with X-ray diffraction, magnetic and Seebeck coefficient measurements

Prediction of activities of oxygen in dilute quaternary solutions using binary data

Equations are developed for predicting the activity coefficients of oxygen dissolved in ternary liquid alloys. These are extensions of earlier treatments, and are based on a model in which each oxygen atom is assumed to make four bonds with neighboring metal atoms. It is also postulated that the strong oxygen-metal bonds distort the electronic configuration around the metal atoms bonded to oxygen, and that the quantitative reduction of the strength of bonds made by these atoms with all of the adjacent metal atoms is equivalent to a factor of approximately two. The predictions of the quasichemical equation which is derived agree satisfactorily with the partial molar free energies of oxygen in Ag-Cu-Sn solutions at 1200°C reported in literature. An extension of this treatment to multicomponent solutions is also indicated

Key dating features for timber-framed dwellings in Surrey

This article is made available through the Brunel Open Access Publishing Fund. Copyright @ The Vernacular Architecture Group 2013. MORE OpenChoice articles are open access and distributed under the terms of the Creative Commons Attribution License 3.0.The main component of the Surrey Dendrochronology Project is the accurate dating of 177 ‘dwellings’, nearly all by tree-ring analysis. The dates are used to establish date ranges for 52 ‘key features’, which cover many aspects of timber-framing from building type to details of carpentry. It is shown that changes of method and fashion were in many cases surprisingly rapid, almost abrupt in historical terms. Previous dating criteria for timber-framed dwellings in the county have been refined and new criteria introduced. Clusters of change from the 1440s and the 1540s are shown and some possible historical links suggested.The Heritage Lottery Fund, the Domestic Buildings Research Group (Surrey), the Surrey Archaeological Society and the historical societies of Charlwood, Farnham and Nutfield