Supercritical oxygen heat transfer

Heat transfer to supercritical oxygen was experimentally measured in electrical heated tubes. Experimental data were obtained for pressures ranging from 17 to 34.5 MPa (2460 to 5000 psia), and heat fluxes from 2 to 90 million w/sq cm (1.2 to 55 Btu/(sq in. sec)). Bulk temperatures ranged from 96 to 217 K (173 to 391 R). Experimental data obtained by other investigators were added to this to increase the range of pressure down to 2 MPa (290 psia) and increase the range of bulk temperature up to 566 K (1019 R). From this compilation of experimental data a correlating equation was developed which predicts over 95% of the experimental data within + or - 30%

Data Compression System with a Minimum Time Delay Unit-Patent

Minimum time delay unit for conventional time multiplexed data compression channel

N2 temperature and density data for the 150 to 300 km region and their implications

Molecular nitrogen density and temperature measurements in thermosphere by thermosphere prob

Hamiltonian systems with symmetry, coadjoint orbits and plasma physics

The symplectic and Poisson structures on reduced phase spaces are reviewed, including the symplectic structure on coadjoint orbits of a Lie group and the Lie-Poisson structure on the dual of a Lie algebra. These results are applied to plasma physics. We show in three steps how the Maxwell-Vlasov equations for a collisionless plasma can be written in Hamiltonian form relative to a certain Poisson bracket. First, the Poisson-Vlasov equations are shown to be in Hamiltonian form relative to the Lie-Poisson bracket on the dual of the (nite dimensional) Lie algebra of innitesimal canonical transformations. Then we write Maxwell's equations in Hamiltonian form using the canonical symplectic structure on the phase space of the electromagnetic elds, regarded as a gauge theory. In the last step we couple these two systems via the reduction procedure for interacting systems. We also show that two other standard models in plasma physics, ideal MHD and two- uid electrodynamics, can be written in Hamiltonian form using similar group theoretic techniques

Spectral evidence for a powerful compact jet from XTE J1118+480

We present observations of the X-ray transient XTE J1118+480 during its Low/Hard X-ray state outburst in 2000, at radio and sub-millimetre wavelengths with the VLA, Ryle Telescope, MERLIN and JCMT. The high-resolution MERLIN observations reveal all the radio emission (at 5 GHz) to come from a compact core with physical dimensions smaller than 65*d(kpc) AU. The combined radio data reveal a persistent and inverted radio spectrum, with spectral index \~+0.5. The source is also detected at 350 GHz, on an extrapolation of the radio spectrum. Flat or inverted radio spectra are now known to be typical of the Low/Hard X-ray state, and are believed to arise in synchrotron emission from a partially self-absorbed jet. Comparison of the radio and sub-millimetre data with reported near-infrared observations suggest that the synchrotron emission from the jet extends to the near-infrared, or possibly even optical regimes. In this case the ratio of jet power to total X-ray luminosity is likely to be P_J/L_X >> 0.01, depending on the radiative efficiency and relativistic Doppler factor of the jet. Based on these arguments we conclude that during the period of our observations XTE J1118+480 was producing a powerful outflow which extracted a large fraction of the total accretion power.Comment: Accepted for publication as a Letter in MNRA

Women as moral pioneers? Experiences of first trimester antenatal screening

Copyright @ 2005 Elsevier Ltd.The implementation of innovative medical technologies can raise unprecedented ethical, legal and social dilemmas. This is particularly so in the area of antenatal screening, which is dominated by the language of risk and probabilities. Second trimester serum screening for Down's syndrome and neural tube defects has a well-established place in antenatal care. Increasingly, first trimester screening with biochemical and ultrasound markers is being proposed as advance on this, yielding higher detection rates of Down's syndrome at an earlier gestational age. This article explores the experiences of 14 women offered innovative first trimester screening, which takes place within the context of a detailed ultrasound scan. The study is set within the UK, where recent policy changes mean that the offer of screening for fetal anomalies, particularly Down's syndrome, will become a routine part of antenatal care and offered to all pregnant women. This paper focuses on the significance of the scan in first trimester screening, and some of the potential dilemmas for women that can result from this. It then discusses the ways in which women made their decisions about screening, in particular, their work as ‘moral pioneers’. We found that the part played by the ultrasound scan in first trimester screening, particularly in relation to the higher-quality images now being obtained, has the potential to introduce new and novel ethical dilemmas for pregnant women. Although concerns have been raised about pregnant women viewing ultrasound scans as benign, many of the women reported having thought carefully through their own moral beliefs and values prior to screening. It seems that whatever other implications they may have, first trimester screening technologies will continue the tradition of pregnant women acting as ‘moral pioneers’ in increasingly complex settings.ESRC/MRC Innovative Health Technologies Programme for funding the project (grant no: L218252042). CW acknowledges the support of The Wellcome Trust Biomedical Ethics Programme in funding her postdoctoral fellowship, which enabled her to work on this project

Evidence for deceleration in the radio jets of GRS1915+105?

There is currently a clear discrepancy in the proper motions measured on different angular scales in the approaching radio jets of the black hole X-ray binary GRS1915+105. Lower velocities were measured with the Very Large Array (VLA) prior to 1996 than were subsequently found from higher-resolution observations made with the Very Long Baseline Array and the Multi-Element Radio Linked Interferometer Network. We initiated an observing campaign to use all three arrays to attempt to track the motion of the jet knots from the 2006 February outburst of the source, giving us unprecedented simultaneous coverage of all angular scales, from milliarcsecond scales out to arcsecond scales. The derived proper motion, which was dominated by the VLA measurements, was found to be 17.0 mas per day, demonstrating that there has been no significant permanent change in the properties of the jets since 1994. We find no conclusive evidence for deceleration of the jet knots, unless this occurs within 70 mas of the core. We discuss possible causes for the varying proper motions recorded in the literature.Comment: Accepted for publication in MNRAS. 13 pages, 10 figure

High energy cosmic-ray interactions with particles from the Sun

Cosmic-ray protons with energies above $10^{16}$ eV passing near the Sun may interact with photons emitted by the Sun and be excited to a $\Delta^+$ resonance. When the $\Delta^+$ decays, it produces pions which further decay to muons and photons which may be detected with terrestrial detectors. A flux of muons, photon pairs (from $\pi^0$ decay), or individual high-energy photons coming from near the Sun would be a rather striking signature, and the flux of these particles is a fairly direct measure of the flux of cosmic-ray nucleons, independent of the cosmic-ray composition. In a solid angle within $15^\circ$ around the Sun the flux of photon pairs is about \SI{1.3e-3}{} particles/(km$^2\cdot$yr), while the flux of muons is about \SI{0.33e-3}{} particles/(km$^2\cdot$yr). This is beyond the reach of current detectors like the Telescope Array, Auger, KASCADE-Grande or IceCube. However, the muon flux might be detectable by next-generation air shower arrays or neutrino detectors such as ARIANNA or ARA. We discuss the experimental prospects in some detail. Other cosmic-ray interactions occuring close to the Sun are also briefly discussed.Comment: 8 pages, 11 figure