Flash Point and Chemical Composition of Aviation Kerosene (Jet A)

The relationship between chemical composition, flash point, and ignition energy was examined for eight samples of aviation kerosene (Jet A) with flash points between 29°C (84°F) and 74°C (165°F). We report the results of liquid characterization by two different laboratories. We use the results of headspace gas chromatography carried out by Woodrow and Seiber to characterize the vapor composition at liquid mass loading fractions of 3 and 400 kg/m^3. The composition data were analyzed to obtain analytical representations of vapor pressure and average molar mass as a function of temperature for each flash point fuel. The relationship between composition and flash point is examined by using two prediction methods. The first method is based on the notion of a critical value of fuel-air mass ratio at the flammability limit. The second method is based on Le Chatelier's rule for flammability limits. Both methods show a reasonable correlation between measured and predicted flash point. The relationship between flash point and ignition temperature threshold at a fixed spark ignition energy was examined for four fuels. A linear correlation was obtained for an ignition energy of 0.3 J. The effect of fuel weathering was examined by determining the flashpoints of seven fuel samples obtained from flight tests. The flash point increased about 8°C for fuel that had been exposed to 5 take-off, cruise, and landing cycles

Spectral infrared hemispherical reflectance measurements for LDEF tray clamps

Infrared hemispherical reflectance measurements that were made on 58 chromic acid anodized tray clamps from LDEF are described. The measurements were made using a hemiellipsoidal mirror reflectometer with interferometer for wavelengths between 2-15 microns. The tray clamps investigated were from locations about the entire spacecraft and provided the opportunity for comparing the effects of atomic oxygen at each location. Results indicate there was essentially no dependence on atomic oxygen fluence for the surfaces studied, but there did appear to be a slight dependence on solar radiation exposure. The reflectances of the front sides of the tray clamps consistently were slightly higher than for the protected rear tray clamp surfaces

The design-by-adaptation approach to universal access: learning from videogame technology

This paper proposes an alternative approach to the design of universally accessible interfaces to that provided by formal design frameworks applied ab initio to the development of new software. This approach, design-byadaptation, involves the transfer of interface technology and/or design principles from one application domain to another, in situations where the recipient domain is similar to the host domain in terms of modelled systems, tasks and users. Using the example of interaction in 3D virtual environments, the paper explores how principles underlying the design of videogame interfaces may be applied to a broad family of visualization and analysis software which handles geographical data (virtual geographic environments, or VGEs). One of the motivations behind the current study is that VGE technology lags some way behind videogame technology in the modelling of 3D environments, and has a less-developed track record in providing the variety of interaction methods needed to undertake varied tasks in 3D virtual worlds by users with varied levels of experience. The current analysis extracted a set of interaction principles from videogames which were used to devise a set of 3D task interfaces that have been implemented in a prototype VGE for formal evaluation

Resolved CO(1-0) Nuclei in IRAS 14348-1447: Evidence for Massive Bulge Progenitors to Ultraluminous Infrared Galaxies

High-resolution, CO(1-0) interferometry of the ultraluminous infrared galaxy IRAS 14348-1447 is presented. The merger system has a molecular gas mass of \~3x10^10 solar masses and a projected nuclear separation of 4.8 kpc (3.5"), making it one of the most molecular gas-rich galaxies known and an ideal candidate for studying the intermediate stages of an ultraluminous merger event. The CO morphology shows two molecular gas components associated with the stellar nuclei of the progenitors, consistent with the idea that the molecular disks are gravitationally bound by the dense bulges of the progenitor galaxies as the interaction proceeds. In contrast, less luminous infrared galaxies observed to date with projected nuclear separations of ~<5 kpc show a dominant CO component between the stellar nuclei. This discrepancy may be an indication that the progenitors of mergers with lower infrared luminosity do not possess massive bulges, and that the gas is stripped during the initial encounter of their progenitors. A comparison of the CO and radio luminosities of the NE and SW component show them to have comparable radio and CO flux ratios of f(NE)/f(SW) ~0.6, possibly indicating that the amount of star-forming molecular gas in the progenitors is correlated with the supernovae rate. The estimate of molecular gas masses of the nuclei and the extent of the radio emission are used to infer that the nuclei of IR 14348-1447 have gas densities comparable to the cores of elliptical galaxies.Comment: LaTex, 5 pages with 1 postscript and 1 jpg figure, ApJ Letters, in pres

The two sided parsec scale structure of the Low Luminosity Active Galactic Nucleus in NGC 4278

We present new Very Long Baseline Interferometry observations of the LINER galaxy NGC 4278. The observations were taken with the Very Long Baseline Array (VLBA) and a single antenna of the Very Large Array (VLA) at 5 GHz and 8.4 GHz and have a linear resolution of <0.1 pc. Our radio data reveal a two sided structure, with symmetric S-shaped jets emerging from a flat spectrum core. We fit the jet brightness with gaussian components, which we identify from a previous observation taken five years before. By comparing the positions of the components in the two epochs, we measure motions between 0.45 +/- 0.14 and 3.76 +/- 0.65 mas, corresponding to apparent velocities < 0.2c, and to ages in the range 8.3 - 65.8 years. Assuming that the radio morphology is intrinsically symmetric and its appearance is governed by Doppler beaming effects, we find that NGC4278 has mildly relativistic jets (beta ~ 0.75), closely aligned to the line-of-sight (2 degrees < theta < 4 degrees). Alternatively, the source could be oriented at a larger angle and asymmetries could be related to the jet interaction with the surrounding medium. We also present new simultaneous VLA observations between 1.4 and 43 GHz, and a 5 GHz light curve between 1972 and 2003. The radio spectrum can be fit by a relatively steep power-law (alpha = 0.54). We find significant variability at 5 GHz. All these arguments indicate that the radiation from NGC 4278 is emitted via the synchrotron process by relativistic particles accelerated by a supermassive black hole. Despite a much lower power, this is the same process that takes place in ordinary radio loud AGNs.Comment: 29 pages, 9 figures, ApJ accepte

Technical note: a simple procedure for removing temporal discontinuities in ERA-Interim upper stratospheric temperatures for use in nudged chemistry-climate model simulations

This note describes a simple procedure for removing unphysical temporal discontinuities in ERA-Interim upper stratospheric global mean temperatures in March 1985 and August 1998 that have arisen due to changes in satellite radiance data used in the assimilation. The derived temperature adjustments (offsets) are suitable for use in stratosphere-resolving chemistry-climate models that are nudged (relaxed) to ERA-Interim winds and temperatures. Simulations using a nudged version of the Canadian Middle Atmosphere Model (CMAM) show that the inclusion of the temperature adjustments produces temperature time series that are devoid of the large jumps in 1985 and 1998. Due to its strong temperature dependence, the simulated upper stratospheric ozone is also shown to vary smoothly in time, unlike in a nudged simulation without the adjustments where abrupt changes in ozone occur at the times of the temperature jumps. While the adjustments to the ERA-Interim temperatures remove significant artefacts in the nudged CMAM simulation, spurious transient effects that arise due to water vapour and persist for about 5 yr after the 1979 switch to ERA-Interim data are identified, underlining the need for caution when analysing trends in runs nudged to reanalyses

Accurate exchange-correlation energies for the warm dense electron gas

Density matrix quantum Monte Carlo (DMQMC) is used to sample exact-on-average $N$-body density matrices for uniform electron gas systems of up to 10$^{124}$ matrix elements via a stochastic solution of the Bloch equation. The results of these calculations resolve a current debate over the accuracy of the data used to parametrize finite-temperature density functionals. Exchange-correlation energies calculated using the real-space restricted path-integral formalism and the $k$-space configuration path-integral formalism disagree by up to $\sim$$10$\% at certain reduced temperatures $T/T_F \le 0.5$ and densities $r_s \le 1$. Our calculations confirm the accuracy of the configuration path-integral Monte Carlo results available at high density and bridge the gap to lower densities, providing trustworthy data in the regime typical of planetary interiors and solids subject to laser irradiation. We demonstrate that DMQMC can calculate free energies directly and present exact free energies for $T/T_F \ge 1$ and $r_s \le 2$.Comment: Accepted version: added free energy data and restructured text. Now includes supplementary materia

Normal mode Rossby waves and their effects on chemical composition in the late summer stratosphere

During past MANTRA campaigns, ground-based measurements of several long-lived chemical species have revealed quasi-periodic fluctuations on time scales of several days. These fluctuations could confound efforts to detect long-term trends from MANTRA, and need to be understood and accounted for. Using the Canadian Middle Atmosphere Model, we investigate the role of dynamical variability in the late summer stratosphere due to normal mode Rossby waves and the impact of this variability on fluctuations in chemical species. Zonal wavenumber 1, westward travelling waves are considered with average periods of 5, 10 and 16 days. Time-lagged correlations between the temperature and nitrous oxide, methane and ozone fields are calculated in order to assess the possible impact of these waves on the chemical species. Using Fourier-wavelet decomposition and correlating the fluctuations between the temperature and chemical fields, we determine that variations in the chemical species are well-correlated with the 5- and 10-day waves between 30 and 60 km, although the nature of the correlations depend strongly on altitude. Interannual variability of the waves is also examined

Molecular Gas in the Powerful Radio Nucleus of the Ultraluminous Infrared Galaxy PKS 1345+12

Millimeter CO(1-0) interferometry and high resolution, Hubble Space Telescope (HST) 1.1, 1.6, and 2.2 micron imaging of the radio compact galaxy PKS 1345+12 are presented. With an infrared luminosity of 2x10^{12} L_sun, PKS 1345+12 is a prime candidate for studying the link between the ultraluminous infrared galaxy phenomenon and radio galaxies. These new observations probe the molecular gas distribution and obscured nuclear regions of PKS 1345+12 and provide morphological support for the idea that the radio activity in powerful radio galaxies is triggered by the merger of gas rich galaxies. Two nuclei separated by 2" (4.0 kpc) are observed in the near-infrared; the extended southeastern nucleus has colors consistent with reddened starlight, and the compact northwestern nucleus has extremely red colors indicative of an optical quasar with a warm dust component. Further, the molecular gas, 3mm continuum, and radio emission are coincident with the redder nucleus, confirming that the northwestern nucleus is the site of the AGN and that the molecular gas is the likely fuel source.Comment: LaTex, 5 pages with 1 postscript and 1 jpg figure, ApJ Letters, in press (August 20, 1999