50,850 research outputs found
A New Wideband, Fully Steerable, Decametric Array at Clark Lake
A fully steerable, decametric array for radio astronomy is under construction at the Clark Lake Radio Observatory near Borrego Springs, California. This array will be a T of 720 conical spiral antennas (teepee-shaped antennas, hence the array is called the TPT), 3.0 km by 1.8 km capable of operating between 15 and 125 MHz. Both its operating frequency and beam position will be adjustable in less than one millisecond, and the TPT will provide a 49-element picture around the central beam position for extended source observations. Considerable experience was gained in the operation of completed portions of the array, and successful operation of the final array is assured. The results are described of the tests which were conducted with the conical spirals, and the planned electronics and data processing systems are described
The Small Scale Velocity Dispersion of Galaxies: A Comparison of Cosmological Simulations
The velocity dispersion of galaxies on small scales ( Mpc),
, can be estimated from the anisotropy of the galaxy-galaxy
correlation function in redshift space. We apply this technique to
``mock-catalogs'' extracted from N-body simulations of several different
variants of Cold Dark Matter dominated cosmological models to obtain results
which may be consistently compared to similar results from observations. We
find a large variation in the value of in different
regions of the same simulation. We conclude that this statistic should not be
considered to conclusively rule out any of the cosmological models we have
studied. We attempt to make the statistic more robust by removing clusters from
the simulations using an automated cluster-removing routine, but this appears
to reduce the discriminatory power of the statistic. However, studying
as clusters with different internal velocity dispersions are
removed leads to interesting information about the amount of power on cluster
and subcluster scales. We also compute the pairwise velocity dispersion
directly and compare this to the values obtained using the Davis-Peebles
method, and find that the agreement is fairly good. We evaluate the models used
for the mean streaming velocity and the pairwise peculiar velocity distribution
in the original Davis-Peebles method by comparing the models with the results
from the simulations.Comment: 20 pages, uuencoded (Latex file + 8 Postscript figures), uses AAS
macro
Heat capacity of the site-diluted spin dimer system Ba3(Mn1-xVx)2O8
Heat capacity and susceptibility measurements have been performed on the
diluted spin dimer compound Ba3(Mn1-xVx)2O8. The parent compound Ba3Mn2O8 is a
spin dimer system based on pairs of antiferromagnetically coupled S = 1, 3d2
Mn5+ ions such that the zero field groundstate is a product of singlets.
Substitution of non-magnetic S = 0, 3d0 V5+ ions leads to an interacting
network of unpaired Mn moments, the low temperature properties of which are
explored in the limit of small concentrations, 0<x<0.05. The zero-field heat
capacity of this diluted system reveals a progressive removal of magnetic
entropy over an extended range of temperatures, with no evidence for a phase
transition. The concentration dependence does not conform to expectations for a
spin glass state. Rather, the data suggest a low temperature random singlet
phase, reflecting the hierarchy of exchange energies found in this system.Comment: Full Publication Citation Include
On the speed of pulled fronts with a cutoff
We study the effect of a small cutoff on the velocity of a pulled
front in one dimension by means of a variational principle. We obtain a lower
bound on the speed dependent on the cutoff, and for which the two leading order
terms correspond to the Brunet Derrida expression. To do so we cast a known
variational principle for the speed of propagation of fronts in new variables
which makes it more suitable for applications.Comment: 12 pages no figure
An Unsplit, Cell-Centered Godunov Method for Ideal MHD
We present a second-order Godunov algorithm for multidimensional, ideal MHD.
Our algorithm is based on the unsplit formulation of Colella (J. Comput. Phys.
vol. 87, 1990), with all of the primary dependent variables centered at the
same location. To properly represent the divergence-free condition of the
magnetic fields, we apply a discrete projection to the intermediate values of
the field at cell faces, and apply a filter to the primary dependent variables
at the end of each time step. We test the method against a suite of linear and
nonlinear tests to ascertain accuracy and stability of the scheme under a
variety of conditions. The test suite includes rotated planar linear waves, MHD
shock tube problems, low-beta flux tubes, and a magnetized rotor problem. For
all of these cases, we observe that the algorithm is second-order accurate for
smooth solutions, converges to the correct weak solution for problems involving
shocks, and exhibits no evidence of instability or loss of accuracy due to the
possible presence of non-solenoidal fields.Comment: 37 Pages, 9 Figures, submitted to Journal of Computational Physic
Planning for the mobile library: a strategy for managing innovation and transformation at the University of Glasgow Library
Modern mobile devices have powerful features that are transforming access to information. Lippincott argues that as mobile devices such as smartphones become ‘key information devices’ for our users, libraries will want to have a significant presence in offering content and services that are suitable for this medium. This article outlines the process of development and implementation of a mobile strategy at the University of Glasgow Library. What began as an investigation into a mobile interface to the library catalogue evolved into a comprehensive strategic review of how we deliver services now and in the future in this rapidly changing mobile environment
Is All Campaigning Equally Positive? The Impact of District Level Campaigning on Voter Turnout at the 2010 British General Election
A significant comparative literature suggests that campaigning efforts by political parties impact positively, both in terms of mobilization and turnout. However, effects are not uniform. They may be affected by the electoral system used, the electoral circumstances and effectiveness of party management. Studies of district-level constituency campaigning in Britain have identified two important trends. First, that effective targeting is a core component of a successful district campaign strategy in terms of delivering electoral payoffs and that, over time, political parties have become better at targeting resources where they are needed most. While improvements in targeting have helped ensure that all three principal parties’ campaigns have tended to deliver electoral payoffs, a question has arisen as to whether increasingly ruthless partisan targeting by parties could have detrimental effects on overall levels of turnout. Second, they have shown how campaign techniques are continuously being modernised but that, despite these changes, just as in other democracies, more traditional labour-intensive campaigning tends to produce stronger electoral payoffs. This article therefore considers three questions in respect of the impact of district level campaigns on turnout: whether the combined campaign efforts of the three principal parties in Britain are associated with higher levels of turnout; whether the different campaigning styles of parties affect levels of turnout equally; and whether the campaigning efforts of different parties have differential effects on turnout and whether intense partisan targeting does indeed impact upon turnout overall. It shows that while campaigning boosts turnout, the impact varies by campaign technique and by party, as a function not only of targeting but also of electoral context
You get what you (don’t) pay for: The impact of volunteer labour and candidate spending at the 2010 British general election
The published version of this article is fully available from the publisher at the link below.Repeated evidence in Britain demonstrates the positive electoral payoffs from constituency campaigning. However, the impact of such campaigning varies depending upon the electoral context and the effectiveness of campaign management. Debate also exists in respect of the relative impact of traditional versus more modern campaign techniques, as well as between campaign techniques that incur cost and those that are carried out voluntarily. Such debates are of interest not only to academics and political parties, but also to regulators when considering whether to restrict campaign spending in the interests of electoral parity. This article uses candidate spending data and responses to an extensive survey of election agents at the British General Election of 2010 to assess the impact of both campaign expenditure and free, voluntary labour on electoral performance. It suggests that both have some independent impact, but that impact varies by party. The implications of these results are highly significant in both academic and regulatory terms—campaign expenditure can affect electoral outcomes but these effects are offset to some extent by voluntary efforts
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