10,325 research outputs found
Functional adaptivity for digital library services in e-infrastructures: the gCube approach
We consider the problem of e-Infrastructures that wish to reconcile the generality of their services with the bespoke requirements of diverse user communities. We motivate the requirement of functional adaptivity in the context of gCube, a service-based system that integrates Grid and Digital Library technologies to deploy, operate, and monitor Virtual Research Environments defined over infrastructural resources. We argue that adaptivity requires mapping service interfaces onto multiple implementations, truly alternative interpretations of the same functionality. We then analyse two design solutions in which the alternative implementations are, respectively, full-fledged services and local components of a single service. We associate the latter with lower development costs and increased binding flexibility, and outline a strategy to deploy them dynamically as the payload of service plugins. The result is an infrastructure in which services exhibit multiple behaviours, know how to select the most appropriate behaviour, and can seamlessly learn new behaviours
Doppler imaging of the young late-type star LO Pegasi (BD +22 4409) in September 2003
A Doppler image of the ZAMS late-type rapidly rotating star LO Pegasi, based
on spectra acquired between 12 and 15 September 2003, is presented. The Least
Square Deconvolution technique is applied to enhance the signal-to-noise ratio
of the mean rotational broadened line profiles extracted from the observed
spectra. In the present application, a unbroadened spectrum is used as a
reference, instead of a simple line list, to improve the deconvolution
technique applied to extract the mean profiles. The reconstructed image is
similar to those previously obtained from observations taken in 1993 and 1998,
and shows that LO Peg photospheric activity is dominated by high-latitude spots
with a non-uniform polar cap. The latter seems to be a persistent feature as it
has been observed since 1993 with little modifications. Small spots, observed
between ~ 10 and ~ 60 degrees of latitude, appears to be different with respect
to those present in the 1993 and 1998 maps.Comment: 21 pages, 10 figures, accepted by Monthly Notices of the Royal
Astronomical Societ
Measurement of XeI and XeII velocity in the near exit plane of a low-power Hall effect thruster by light induced fluorescence spectroscopy
Near exit plane non-resonant light induced fluorescence spectroscopy is
performed in a Hall effect low-power Xenon thruster at discharge voltage of
250V and anode flow rate of 0.7mg/sec. Measurement of the axial and radial
velocity components are performed, exciting the 6s[3/2]_2-->6p[3/2]_2
transition at 823.16nm in XeI and the 5d[4]_(7/2)-->6p[3]_(5/2) transition at
834.724nm in XeII. No significant deviation from the thermal velocity is
observed for XeI. Two most probable ion velocities are registered at a given
position with respect to the thruster axis, which are mainly attributed to
different areas of creation of ions inside the acceleration channel. The
spatial resolution of the set-up is limited by the laser beam size (radius of
the order of 0.5mm) and the fluorescence collection optics, which have a view
spot diameter of 8mm.Comment: 6 pages, 8 figure
Vacuum technology and space simulation
Manual on vacuum technology and space simulatio
Inheritance Law and Investment in Family Firms
Entrepreneurs may be legally bound to bequeath a minimal stake to non-controlling heirs. The size of this stake can reduce investment in family firms, by reducing the future income they can pledge to external financiers. Using a purpose-built indicator of the permissiveness of inheritance law and data for 10,004 firms from 38 countries in 1990-2006, we find that stricter inheritance law is associated with lower investment in family firms, but does not affect investment in non-family firms. Moreover, as the model predicts, inheritance law affects investment only in family firms that experience a succession
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Determining the dynamics of influenza transmission by age
Background: It is widely accepted that influenza transmission dynamics vary by age; however methods to quantify the reproductive number by age group are limited. We introduce a simple method to estimate the reproductive number by modifying the method originally proposed by Wallinga and Teunis and using existing information on contact patterns between age groups. We additionally perform a sensitivity analysis to determine the potential impact of differential healthcare seeking patterns by age. We illustrate this method using data from the 2009 H1N1 Influenza pandemic in Gauteng Province, South Africa. Results: Our results are consistent with others in showing decreased transmission with age. We show that results can change markedly when we make the account for differential healthcare seeking behaviors by age. Conclusions: We show substantial heterogeneity in transmission by age group during the Influenza A H1N1 pandemic in South Africa. This information can greatly assist in targeting interventions and implementing social distancing measures
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