65,050 research outputs found
Payload/burned-out motor case separation system Patent
Payload/spent rocket engine case separation syste
Leeds Met Library Facebook application
At the Leeds Met staff development festival in 2008 a library graduate trainee, Anna Hepworth, took part in a ‘Dragons’ Den’ event which saw staff propose new, innovative ideas to a panel of senior managers. Anna’s suggestion was to develop a Facebook application (or ‘app’) for the library and it was one of the competition winners. Anna’s initial proposal was to create a Leeds Met library catalogue application, but after discussions with members of the library’s ‘technologies for learning’ team it was decided to take the application a stage further, creating a mash-up using data from the library management system (Sirsi-Dynix Symphony). The Facebook application would send a library catalogue search box to a Facebook profile, but would also add value by delivering customised user data, including library record details such as number of issues, reservations and overdues. There would also be links to the library website and online self-service functions from the application
The metallicity of gamma-ray burst environments from high energy observations
Gamma-ray bursts (GRBs) and their early afterglows ionise their circumburst
material. Only high-energy spectroscopy therefore, allows examination of the
matter close to the burst itself. Soft X-ray absorption allows an estimate to
be made of the total column density in metals. The detection of the X-ray
afterglow can also be used to place a limit on the total gas column along the
line of sight based on the Compton scattering opacity. Such a limit would
enable, for the first time, the determination of lower limits on the
metallicity in the circumburst environments of GRBs. In this paper, we
determine the limits that can be placed on the total gas column density in the
vicinities of GRBs based on the Compton scattering. We simulate the effects of
Compton scattering on a collimated beam of high energy photons passing through
a shell of high column density material to determine the expected lightcurves,
luminosities, and spectra. We compare these predictions to observations, and
determine what limits can realistically be placed on the total gas column
density. The smearing out of pulses in the lightcurve from Compton scattering
is not likely to be observable, and its absence does not place strong
constraints on the Compton depth for GRBs. However, the distribution of
observed luminosities of bursts allows us to place statistical, model-dependent
limits that are typically <~1e25 cm^{-2} for less luminous bursts, and as low
as ~1e24 cm$^{-2} for the most luminous. Using the shape of the high-energy
broadband spectrum, however, in some favourable cases, limits as low as ~5e24
cm^{-2} can placed on individual bursts, implying metallicity lower limits from
X- and gamma-rays alone from 0 up to 0.01 Z/Zsun. At extremely high redshifts,
this limit would be at least 0.02 Z/Z_sun, enough to discriminate population
III from non-primordial GRBs.Comment: 4 pages, 4 figures, submitted to A&A letter
A Non-Zeeman Interpretation for Polarized Maser Radiation and the Magnetic Field at the Atmospheres of Late-Type Giants
The linear polarization that is observed, together with likely changes in the
orientation of the magnetic field along the line of sight and hence of the
optical axes of the medium, can lead to the circular polarization that is
observed in the radiation of the circumstellar SiO masers. A magnetic field
greater than only about 30 mG is required, in contrast to 10-100 G that would
be implied by the Zeeman interpretation. To assess quantitatively the likely
changes in orientation of the magnetic field, calculations are performed with
representative field configurations that are created by statistical sampling
using a Kolmogorov-like power spectrum.Comment: 7 pages Latex (aaspp4.sty), 3 ps-figures. Accepted for publication in
Astrophysical Journal Letter
Productivity of Federally Financed Research and Development Final Report, May 15, 1963 - May 14, 1966
Research project on federal and industrial patent acquisition and economic implications - NASA PROGRA
The key ingredients of the electronic structure of FeSe
FeSe is a fascinating superconducting material at the frontier of research in
condensed matter physics. Here we provide an overview on the current
understanding of the electronic structure of FeSe, focusing in particular on
its low energy electronic structure as determined from angular resolved
photoemission spectroscopy, quantum oscillations and magnetotransport
measurements of single crystal samples. We discuss the unique place of FeSe
amongst iron-based superconductors, being a multi-band system exhibiting strong
orbitally-dependent electronic correlations and unusually small Fermi surfaces,
prone to different electronic instabilities. We pay particular attention to the
evolution of the electronic structure which accompanies the
tetragonal-orthorhombic structural distortion of the lattice around 90 K, which
stabilizes a unique nematic electronic state. Finally, we discuss how the
multi-band multi-orbital nematic electronic structure has an impact on the
understanding of the superconductivity, and show that the tunability of the
nematic state with chemical and physical pressure will help to disentangle the
role of different competing interactions relevant for enhancing
superconductivity.Comment: 21 pages, 11 figures, to appear in Annual Review of Condensed Matter
Physic
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