The dominant X-ray wind in massive star binaries

We investigate which shocked wind is responsible for the majority of the X-ray emission in colliding wind binaries, an issue where there is some confusion in the literature, and which we show is more complicated than has been assumed. We find that where both winds rapidly cool (typically close binaries), the ratio of the wind speeds is often more important than the momentum ratio, because it controls the energy flux ratio, and the faster wind is generally the dominant emitter. When both winds are largely adiabatic (typically long-period binaries), the slower and denser wind will cool faster and the stronger wind generally dominates the X-ray luminosity.Comment: 4 pages, 1 figure, accepted by A&A Letter

Histidine is the axial ligand to cytochrome alpha 3 in cytochrome c oxidase

The nitric oxide-bound complexes of reduced yeast cytochrome c oxidase incorporated with [1,3-15N2]histidine have been investigated by EPR spectroscopy. The results of this study have allowed the unambiguous identification of histidine as the endogenous axial ligand to cytochrome alpha 3

Starburst-driven galactic winds: I. Energetics and intrinsic X-ray emission

We have performed an extensive hydrodynamical parameter study of starburst-driven galactic winds, motivated by the latest observation data on the best-studied starburst galaxy M82. We study how the wind dynamics, morphology and X-ray emission depend on the host galaxy's ISM distribution, starburst star formation history and strength, and presence and distribution of mass-loading by dense clouds. We find that the soft X-ray emission from galactic winds comes from low filling factor (ff < 2 per cent) gas, which contains only a small fraction (f < 10 per cent) of the mass and energy of the wind, irrespective of whether the wind models are strongly mass-loaded or not. X-ray observations of galactic winds therefore do not directly probe the gas that contains the majority of the energy, mass or metal-enriched gas in the outflow. The soft X-ray emission comes from gas at a wide range different temperatures and densities. Estimates of the physical properties of the hot gas in starburst galaxies, based on fitting the standard simple spectral models to existing X-ray spectra, should therefore be treated with extreme suspicion. The majority of the thermal and kinetic energy of these winds is in a volume filling hot, T approx 10^7 K, component which is extremely difficult to probe observationally due to its low density and hence low emissivity. Most of the total energy is in the kinetic energy of this hot gas, a factor which must be taken into account when attempting to constrain wind energetics observationally. We also find that galactic winds are efficient at transporting large amounts of energy out of the host galaxy, in contrast to their inefficiency at transporting mass out of star-forming galaxies. (Abridged)Comment: Accepted for publication in MNRAS. Letter page size postscript available from http://adcam.pha.jhu.edu/~dks/dks_published.htm

Playing it safe? a study of the regulation of outdoor play for children and young people in residential care

The aim of the research was to describe and explain the barriers to, and opportunities for, outdoor play and recreation that exist in residential child care services. The research focussed on six residential facilities which represented a cross-section of the sector. Interviews were conducted with two young people, one manager and two basic grade staff members from each of the facilities. The findings were analysed using data display and reduction and the following key findings emerged

GMRT Low Frequency Observations of Extrasolar Planetary Systems

Extrasolar planets are expected to emit detectable low frequency radio emission. In this paper we present results from new low frequency observations of two extrasolar planetary systems (Epsilon Eridani and HD 128311) taken at 150 MHz with the Giant Metrewave Radio Telescope (GMRT). These two systems have been chosen because the stars are young (with ages < 1 Gyr) and are likely to have strong stellar winds, which will increase the expected radio flux. The planets are massive (presumably) gas giant planets in longer period orbits, and hence will not be tidally locked to their host star (as is likely to be the case for short period planets) and we would expect them to have a strong planetary dynamo and magnetic field. We do not detect either system, but are able to place tight upper limits on their low frequency radio emission, at levels comparable to the theoretical predictions for these systems. From these observations we have a 2.5sigma limit of 7.8 mJy for Epsilon Eri and 15.5 mJy for HD 128311. In addition, these upper limits also provide limits on the low frequency radio emission from the stars themselves. These results are discussed and also the prospects for the future detection of radio emission from extrasolar planets.Comment: 6 pages, 2 figures, accepted for publication in MNRA

Blocking of word-boundary consonant lengthening in Sienese Italian

This paper examines an aspect of Raddoppiamento sintattico (RS), the lengthening of word-initial consonants following certain words e.g. tre [mm]ele ‘three apples’ in Italian. Most phonological accounts claim the phenomenon is predictable and obligatory (e.g. Nespor & Vogel 1986). However, descriptive sources on Italian (e.g. Camilli 1941) have long claimed that RS interacts with and can be blocked by other phenomena operative in natural speech e.g. pausing. In this paper we outline the phonetic details of the RS blocking phenomena and present the results of an auditory and preliminary acoustic analysis of the interaction between RS and these other phenomena based on a corpus of spontaneous speech data

Power-Off Tests of the Northrop N9M-2 Tailless Airplane in the 40- by 80-foot Wind Tunnel

No abstract availabl

Probing the wind-wind collision in Gamma Velorum with high-resolution Chandra X-ray spectroscopy: evidence for sudden radiative braking and non-equilibrium ionization

We present a new analysis of an archived Chandra HETGS X-ray spectrum of the WR+O colliding wind binary Gamma Velorum. The spectrum is dominated by emission lines from astrophysically abundant elements: Ne, Mg, Si, S and Fe. From a combination of broad-band spectral analysis and an analysis of line flux ratios we infer a wide range of temperatures in the X-ray emitting plasma (~4-40 MK). As in the previously published analysis, we find the X-ray emission lines are essentially unshifted, with a mean FWHM of 1240 +/- 30 km/s. Calculations of line profiles based on hydrodynamical simulations of the wind-wind collision predict lines that are blueshifted by a few hundred km/s. The lack of any observed shift in the lines may be evidence of a large shock-cone opening half-angle (> 85 degrees), and we suggest this may be evidence of sudden radiative braking. From the R and G ratios measured from He-like forbidden-intercombination-resonance triplets we find evidence that the Mg XI emission originates from hotter gas closer to the O star than the Si XIII emission, which suggests that non-equilibrium ionization may be present.Comment: 22 pages, 14 figures. Accepted for publication in MNRA

A three dimensional model of the Venusian thermosphere with superrotation

An improved three dimensional spectral model of the thermosphere of Venus is described. The model solves the Navier-Stokes equations and includes nonlinear effects for an arbitrary number of atmospheric species. A two dimensional axisymmetric model of the superrotation of the thermosphere is also presented. This model addresses the Pioneer-Venus mission finding, which suggested the thermospheric rotation rate to be much higher than that of the planet as seen from the asymmetric distribution of hydrogen and helium. Both models include the effects of an anisotropic eddy diffusion that is consistent with atmospheric mixing length theory