56,297 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
A study of the usefulness of Skylab EREP data for earth resources studies in Australia
There are no author-identified significant results in this report
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
Entanglement in general two-mode continuous-variable states: local approach and mapping to a two-qubit system
We present a new approach to the analysis of entanglement in smooth bipartite
continuous-variable states. One or both parties perform projective filterings
via preliminary measurements to determine whether the system is located in some
region of space; we study the entanglement remaining after filtering. For small
regions, a two-mode system can be approximated by a pair of qubits and its
entanglement fully characterized, even for mixed states. Our approach may be
extended to any smooth bipartite pure state or two-mode mixed state, leading to
natural definitions of concurrence and negativity densities. For Gaussian
states both these quantities are constant throughout configuration space.Comment: 4 pages, RevTeX 4, one figure. Further modifications in response to
journal referees, correction to expression for negativit
Party finance reform as constitutional engineering? The effectiveness and unintended consequences of party finance reform in France and Britain
In both Britain and France, party funding was traditionally characterized by a laissez faire approach and a conspicuous lack of regulation. In France, this was tantamount to a 'legislative vacuum'. In the last two decades, however, both countries have sought to fundamentally reform their political finance regulation regimes. This prompted, in Britain, the Political Parties, Elections and Referendums Act 2000, and in France a bout of 'legislative incontinence' — profoundly transforming the political finance regime between 1988 and 1995. This article seeks to explore and compare the impacts of the reforms in each country in a bid to explain the unintended consequences of the alternative paths taken and the effectiveness of the new party finance regime in each country. It finds that constitutional engineering through party finance reform is a singularly inexact science, largely due to the imperfect nature of information, the limited predictability of cause and effect, and the constraining influence of non-party actors, such as the Constitutional Council in France, and the Electoral Commission in Britain
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
Transport in Graphene Tunnel Junctions
We present a technique to fabricate tunnel junctions between graphene and Al
and Cu, with a Si back gate, as well as a simple theory of tunneling between a
metal and graphene. We map the differential conductance of our junctions versus
probe and back gate voltage, and observe fluctuations in the conductance that
are directly related to the graphene density of states. The conventional
strong-suppression of the conductance at the graphene Dirac point can not be
clearly demonstrated, but a more robust signature of the Dirac point is found:
the inflection in the conductance map caused by the electrostatic gating of
graphene by the tunnel probe. We present numerical simulations of our
conductance maps, confirming the measurement results. In addition, Al causes
strong n-doping of graphene, Cu causes a moderate p-doping, and in high
resistance junctions, phonon resonances are observed, as in STM studies.Comment: 22 pages, 5 figure
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
Isostaticity of Constraints in Jammed Systems of Soft Frictionless Platonic Solids
The average number of constraints per particle in
mechanically stable systems of Platonic solids (except cubes) approaches the
isostatic limit at the jamming point (), though
average number of contacts are hypostatic. By introducing angular alignment
metrics to classify the degree of constraint imposed by each contact,
constraints are shown to arise as a direct result of local orientational order
reflected in edge-face and face-face alignment angle distributions. With
approximately one face-face contact per particle at jamming chain-like
face-face clusters with finite extent form in these systems.Comment: 4 pages, 3 figures, 4 tabl
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