8,402 research outputs found
Measurements of the Cosmological Evolution of Magnetic Fields with the Square Kilometre Array
We investigate the potential of the Square Kilometre Array (SKA) for
measuring the magnetic fields in clusters of galaxies via Faraday rotation of
background polarised sources. [...] We find that about 10 per cent of the sky
is covered by a significant extragalactic Faraday screen. Most of it has
rotation measures between 10 and 100 rad/m/m. We argue that the cluster centres
should have up to about 5000 rad/m/m. We show that the proposed mid frequency
aperture array of the SKA as well as the lowest band of the SKA dish array are
well suited to make measurements for most of these rotation measure values,
typically requiring a signal-to-noise of ten. We calculate the spacing of
sources forming a grid for the purpose of measuring foreground rotation
measures: it reaches a spacing of 36 arcsec for a 100 hour SKA observation per
field. We also calculate the statistics for background RM measurements in
clusters of galaxies. We find that a first phase of the SKA would allow us to
take stacking experiments out to high redshifts (>1), and provide improved
magnetic field structure measurements for individual nearby clusters. The full
SKA aperture array would be able to make very detailed magnetic field structure
measurements of clusters with more than 100 background sources per cluster up
to a redshift of 0.5 and more than 1000 background sources per cluster for
nearby clusters, and could for reasonable assumptions about future measurements
of electron densities in high redshift clusters constrain the power law index
for the magnetic field evolution to better than dm=0.4, if the magnetic field
in clusters should follow B ~ (1+z)^m.Comment: 12 pages, 10 figures, 3 tables, accepted by MNRAS, minor correction
to eq (5
A Resource Based View of Business Method Patents
In recent years, patents have become widely popular for protecting software-based business methods. However, the IS literature has yet to consider the potential influence of patents in the IS-firm performance relationship. At the same time, the resource-based view (RBV) of the firm has proven to be a useful lens through which to examine the IS-firm performance relationship. In organizational strategy literature, various measures of patents are frequently utilized as proxies for components of the RBV or as the dependent variable in RBV studies. Following in this vein, the purpose of the current study is to examine whether software-based business method patents fit the definitions prescribed in the RBV and if such patents can be empirically connected to a firm’s performance
Gravitational effects in ultrahigh-energy string scattering
Ultrahigh-energy string scattering is investigated to clarify the relative
role of string and gravitational effects, and their possible contributions to
nonlocal behavior. Different regimes can be characterized by varying the impact
parameter at fixed energy. In the regime where momentum transfers reach the
string scale, string effects appear subdominant to higher-loop gravitational
processes, approximated via the eikonal. At smaller impact parameters,
"diffractive" or "tidal" string excitation leads to processes dominated by
highly excited strings. However, new evidence is presented that these
excitation effects do not play a direct role in black hole formation, which
corresponds to breakdown of gravitational perturbation theory and appears to
dominate at sufficiently small impact parameters. The estimated amplitudes
violate expected bounds on high-energy behavior for local theories.Comment: 19 pages, harvmac. v2: fixed typos, added refs and discussion of
longitudinal spread. v3: minor changes to agree with published versio
Colour Charges and the Anti-Screening Contribution to the Interquark Potential
Asymptotic freedom arises from the dominance of anti-screening over screening
in non-abelian gauge theories. In this paper we will present a simple and
physically appealing derivation of the anti-screening contribution to the
interquark potential. Our method allows us to identify the dominant gluonic
distribution around static quarks. Extensions are discussed.Comment: 7 pages, LaTe
Discovery of planetary nebulae using predictive mid-infrared diagnostics
We demonstrate a newly developed mid-infrared planetary nebula (PN) selection
technique. It is designed to enable efficient searches for obscured, previously
unknown, PN candidates present in the photometric source catalogues of Galactic
plane MIR sky surveys. Such selection is now possible via new, sensitive,
high-to-medium resolution, MIR satellite surveys such as those from the Spitzer
Space Telescope and the all-sky Wide-Field Infrared Survey Explorer (WISE)
satellite missions. MIR selection is based on how different colour-colour
planes isolate zones (sometimes overlapping) that are predominately occupied by
different astrophysical object types. These techniques depend on the
reliability of the available MIR source photometry. In this pilot study we
concentrate on MIR point source detections and show that it is dangerous to
take the MIR GLIMPSE (Galactic Legacy Infrared Mid-Plane Survey Extraordinaire)
photometry from Spitzer for each candidate at face value without examining the
actual MIR image data. About half of our selected sources are spurious
detections due to the applied source detection algorithms being affected by
complex MIR backgrounds and the de-blending of diffraction spikes around bright
MIR point sources into point sources themselves. Nevertheless, once this
additional visual diagnostic checking is performed, valuable MIR selected PN
candidates are uncovered. Four turned out to have faint, compact, optical
counterparts in our H-alpha survey data missed in previous optical searches. We
confirm all of these as true PNe via our follow-up optical spectroscopy. This
lends weight to the veracity of our MIR technique. It demonstrates sufficient
robustness that high-confidence samples of new Galactic PN candidates can be
extracted from these MIR surveys without confirmatory optical spectroscopy and
imaging. This is problematic or impossible when the extinction is large.Comment: 14 pages, 7 figures, 7 tables; accepted for publication in MNRA
Lay causes of binge drinking in the United Kingdom and Australia: a causal network diagram approach
Binge drinking is associated with deleterious health, social and economic outcomes. This study explored the lay understanding of the causes of binge drinking in members of the general public in the United Kingdom and Australia. Participants in the United Kingdom (N = 133) and Australia (N = 102) completed a network diagram exercise requiring them to draw causal paths and provide path strength ratings between 12 candidate factors (24-h opening, age, alcohol advertizing, alcohol availability, boredom, drinking culture, income, low cost, parental influence, peer pressure, stress and supermarket discounts) and binge drinking. Results indicated good consistency in paths across samples, although differences in frequency and strength ratings for some paths were found. Drinking culture, peer pressure and low alcohol cost were perceived as direct causes of binge drinking in both samples. Low alcohol cost and drinking culture were most frequently viewed as direct causes of binge drinking in UK and Australian participants, respectively. Supermarket discounts and low cost of alcohol were most frequently viewed as indirect causes of binge drinking by UK and Australian samples. Findings reflect general awareness and prominence of factors affecting binge drinking in both national groups. Findings may inform the development of campaigns to promote public support policies to curb binge drinking
Enhanced cellular preservation by clay minerals in 1 billion-year-old lakes
The article of record as published may be located at http://dx.doi.org/10.1038/srep05841Organic-walled microfossils provide the best insights into the composition and evolution of the biosphere through the first 80 percent of Earth history. The mechanism of microfossil preservation affects the quality of biological information retained and informs understanding of early Earth palaeo-environments. We here show that 1 billion-year-old microfossils from the non-marine Torridon Group are remarkably preserved by a combination of clay minerals and phosphate, with clay minerals providing the highest fidelity of preservation. Fe-rich clay mostly occurs in narrow zones in contact with cellular material and is interpreted as an early microbially-mediated phase enclosing and replacing the most labile biological material. K-rich clay occurs within and exterior to cell envelopes, forming where the supply of Fe had been exhausted. Clay minerals inter-finger with calcium phosphate that co-precipitated with the clays in the sub-oxic zone of the lake sediments. This type of preservation was favoured in sulfate-poor environments where Fe-silicate precipitation could outcompete Fe-sulfide formation. This work shows that clay minerals can provide an exceptionally high fidelity of microfossil preservation and extends the known geological range of this fossilization style by almost 500 Ma. It also suggests that the best-preserved microfossils of this time may be found in low-sulfate environments
Open design at the intersection of making and manufacturing
This one-day workshop aims to consider the opportunities for HCI at the intersection of maker culture and professional, industrial manufacturing. In particular, we are interested in exploring how the concept of “open design” could help support productive interactions between professional manufacturers and non-professional makers. Our proposal builds on momentum established by previous related workshops (including one at CHI2016) and aims to respond critically to several key industry and government reports published in 2015-2016 on the ‘maker movement’
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