28,714 research outputs found
MGGPOD: a Monte Carlo Suite for Modeling Instrumental Line and Continuum Backgrounds in Gamma-Ray Astronomy
Intense and complex instrumental backgrounds, against which the much smaller
signals from celestial sources have to be discerned, are a notorious problem
for low and intermediate energy gamma-ray astronomy (~50 keV - 10 MeV).
Therefore a detailed qualitative and quantitative understanding of instrumental
line and continuum backgrounds is crucial for most stages of gamma-ray
astronomy missions, ranging from the design and development of new
instrumentation through performance prediction to data reduction. We have
developed MGGPOD, a user-friendly suite of Monte Carlo codes built around the
widely used GEANT (Version 3.21) package, to simulate ab initio the physical
processes relevant for the production of instrumental backgrounds. These
include the build-up and delayed decay of radioactive isotopes as well as the
prompt de-excitation of excited nuclei, both of which give rise to a plethora
of instrumental gamma-ray background lines in addition to continuum
backgrounds. The MGGPOD package and documentation are publicly available for
download from http://sigma-2.cesr.fr/spi/MGGPOD/.
We demonstrate the capabilities of the MGGPOD suite by modeling high
resolution gamma-ray spectra recorded by the Transient Gamma-Ray Spectrometer
(TGRS) on board Wind during 1995. The TGRS is a Ge spectrometer operating in
the 40 keV to 8 MeV range. Due to its fine energy resolution, these spectra
reveal the complex instrumental background in formidable detail, particularly
the many prompt and delayed gamma-ray lines. We evaluate the successes and
failures of the MGGPOD package in reproducing TGRS data, and provide
identifications for the numerous instrumental lines.Comment: 60 pages, 13 figures, 7 tables, accepted for publication in ApJ
Supporting arts and science communities on-line
This paper examines the use of the Web to support continuing professional development (CPD). It outlines the factors driving the adoption of CPD and highlights areas where the Web can aid in the development of successful professional communities. A survey examining the use of the Internet to support professionals working in the domains of the Arts and Science is presented. The study reviews twenty four sites for the presence and degree of adoption of several key features including: - community building, range and value of content, user friendliness and guidance, sophistication of employed Web technology
Distributed resource discovery using a context sensitive infrastructure
Distributed Resource Discovery in a World Wide Web environment using full-text indices will never scale. The distinct properties of WWW information (volume, rate of change, topical diversity) limits the scaleability of traditional approaches to distributed Resource Discovery. An approach combining metadata clustering and query routing can, on the other hand, be proven to scale much better. This paper presents the Content-Sensitive Infrastructure, which is a design building on these results. We also present an analytical framework for comparing scaleability of different distribution strategies
Analysis of ZDDP content and thermal decomposition in motor oils using NAA and NMR
Zinc dialkyldithiophosphates (ZDDPs) are one of the most common anti-wear
additives present in commercially-available motor oils. The ZDDP concentrations
of motor oils are most commonly determined using inductively coupled plasma
atomic emission spectroscopy (ICP-AES). As part of an undergraduate research
project, we have determined the Zn concentrations of eight
commercially-available motor oils and one oil additive using neutron activation
analysis (NAA), which has potential for greater accuracy and less sensitivity
to matrix effects as compared to ICP-AES. The 31P nuclear magnetic resonance
(31P-NMR) spectra were also obtained for several oil additive samples which
have been heated to various temperatures in order to study the thermal
decomposition of ZDDPs.Comment: Manuscript has been accepted for publication in Physics Procedia as
part of the proceedings of the 23rd International Conference on Application
of Accelerators in Research and Industry (CAARI 2014
The motion of a foam lamella traversing an idealised bi-conical pore with a rounded central region
The Spectacular Ionized Interstellar Medium of NGC55
We present deep Halpha+[NII], [SII] (6716,6731A) and [OII] (3726,3729A)
images of the highly inclined, actively star--forming SBm galaxy NGC 55,
located in the nearby Sculptor Group. Due to its proximity, NGC 55 provides a
unique opportunity to study the disk--halo interface in a late--type galaxy
with unprecedented spatial resolution. Our images reveal a spectacular variety
of ionized gas features, ranging from giant HII region complexes, to supergiant
filamentary and shell features, to patches of very faint diffuse emission. Many
of these features protrude well above the plane of the galaxy, including a very
faint fragmented shell of emission which is visible at 2.6 kpc above the disk.
We identify candidate `chimneys' extending out of the disk, which could be the
conduits into the halo for hot gas around disk star-forming regions, and could
also provide low-density paths for the passage of UV photons from the disk to
the halo. Several of the identified chimneys are `capped' with clumps of
ionized gas, one of which, located at 1.5 kpc above the disk plane, appears to
be the site of recent star formation. Emission--line ratios
([OII]/Halpha+[NII], [SII]/Halpha+[NII]) constrain the ionization mechanism of
the gas, and our images allow the first measurement of [OII]/Halpha+[NII] in
extra-planar diffuse ionized gas. The diffuse gas is characterized by
emission--line ratios which are enhanced on average by a factor of two compared
to those of bright HII regions. Each line ratio increases in value smoothly
from the cores of HII regions, through the haloes of HII regions, into the
diffuse ionized gas. Such a continuous trend is predicted by models in which
the diffuse gas is ionized by photons produced by massive stars in HII regions.Comment: 19 pages, including 4 figures, plus 2 external tables. Accepted for
publication in the Astronomical Journal. Compressed, postscript versions of
the plates are available at ftp://skysrv.pha.jhu.edu/ferguson
Crafting a Systematic Literature Review on Open-Source Platforms
This working paper unveils the crafting of a systematic literature review on
open-source platforms. The high-competitive mobile devices market, where
several players such as Apple, Google, Nokia and Microsoft run a platforms- war
with constant shifts in their technological strategies, is gaining increasing
attention from scholars. It matters, then, to review previous literature on
past platforms-wars, such as the ones from the PC and game-console industries,
and assess its implications to the current mobile devices platforms-war. The
paper starts by justifying the purpose and rationale behind this literature
review on open-source platforms. The concepts of open-source software and
computer-based platforms were then discussed both individually and in unison,
in order to clarify the core-concept of 'open-source platform' that guides this
literature review. The detailed design of the employed methodological strategy
is then presented as the central part of this paper. The paper concludes with
preliminary findings organizing previous literature on open-source platforms
for the purpose of guiding future research in this area.Comment: As presented in 10th IFIP WG 2.13 International Conference on Open
Source Systems, OSS 2014, San Jos\'e, Costa Rica, May 6-9, 201
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