11,837 research outputs found
Brane Gas Inflation
We consider the brane gas picture of the early universe. At later stages,
when there are no winding modes and the background is free to expand, we show
that a moving 3-brane, which we identify with our universe, can inflate even
though it is radiation-dominated. The crucial ingredients for successful
inflation are the coupling to the dilaton and the equation of state of the
bulk. If we suppose the brane initially forms in a collision of
higher-dimensional branes, then the spectrum of primordial density fluctuations
naturally has a thermal origin.Comment: 4 pages, 1 figur
Changing the direction of environmental investment in Australia: Learnings from implementing INFFER
Investment in natural resource management (NRM) by regional organisations in Australia has been widely criticised for failing to achieve substantial environmental outcomes. The Investment Framework for Environmental Resources (INFFER) is a tool for developing and prioritising projects to address environmental issues such as water quality, biodiversity decline, environmental pest impacts and land degradation. INFFER is an asset-based, targeted, and outcome-focussed approach to environmental investment, and as such is a very different and more rigorous approach to prioritising possible environmental projects than used previously by most catchment management organisations (CMOs) in Australia. From 2008 to 2010 INFFER has been trialled with CMOs. Evaluation and benchmarking data obtained at 2-day INFFER training sessions with seven CMOs in three eastern Australia states are reported. Before commencing to use INFFER, CMO staff are generally confident about the current decision-making processes for environmental investment used within their organisation. In some cases, this initial perception challenges their acceptance of a new approach to investment decisionmaking. Key issues when implementing INFFER include concerns about changing the direction of CMO investment, concerns about compatibility with funder requirements, and various issues associated with specific aspects of the Framework. Perceived complexity of INFFER, existing institutional arrangements, and the legacy of past institutional arrangements remain serious barriers to the adoption of methods to improve environmental outcomes from NRM investment. Despite these difficulties INFFER is being used by a number of CMOs. However, it is likely that widespread adoption of INFFER, or indeed any other transparent and robust process, will only occur with greater requirement from governments for environmental decision making by regional NRM bodies that is more focused on outcomes and cost-effectiveness.NRM investment planning, NRM investment prioritisation, regional catchment management organisations, NRM policy, environmental planning, environmental prioritisation, environmental policy, Environmental Economics and Policy, Research and Development/Tech Change/Emerging Technologies, Q50, Q58,
Antiviral and Antibacterial Polyurethanes of Various Modalities
We have prepared and characterized a new polyurethane-based antimicrobial material, N,N-dodecyl,methyl-polyurethane (Quat-12-PU). It exhibits strong antiviral and antibacterial activities when coated (as an organic solution or an aqueous nanosuspension) onto surfaces and antibacterial activity when electrospun into nanofibers. Quat-12-PU surfaces are able to kill airborne Gram-positive Staphylococcus aureus and Gram-negative Escherichia coli bacteria, as well as inactivate the enveloped influenza virus (but not the non-enveloped poliovirus).United States. Army Research Office. Institute for Soldier NanotechnologiesMartin Family Society of Fellows for Sustainabilit
Evidence of perturbations of cell cycle and DNA repair pathways as a consequence of human and murine NF1-haploinsufficiency
Dynamics of on-orbit construction process
The topics covered are presented in viewgraph form and include the following: problem definition and motivation; survey of current technology; focus problems; approach; progress/discussion; and future direction and anticipated results
Ranking Spaces for Predicting Human Movement in an Urban Environment
A city can be topologically represented as a connectivity graph, consisting
of nodes representing individual spaces and links if the corresponding spaces
are intersected. It turns out in the space syntax literature that some defined
topological metrics can capture human movement rates in individual spaces. In
other words, the topological metrics are significantly correlated to human
movement rates, and individual spaces can be ranked by the metrics for
predicting human movement. However, this correlation has never been well
justified. In this paper, we study the same issue by applying the weighted
PageRank algorithm to the connectivity graph or space-space topology for
ranking the individual spaces, and find surprisingly that (1) the PageRank
scores are better correlated to human movement rates than the space syntax
metrics, and (2) the underlying space-space topology demonstrates small world
and scale free properties. The findings provide a novel justification as to why
space syntax, or topological analysis in general, can be used to predict human
movement. We further conjecture that this kind of analysis is no more than
predicting a drunkard's walking on a small world and scale free network.
Keywords: Space syntax, topological analysis of networks, small world, scale
free, human movement, and PageRankComment: 11 pages, 5 figures, and 2 tables, English corrections from version 1
to version 2, major changes in the section of introduction from version 2 to
Physics of the interior of a black hole with an exotic scalar matter
We use a numerical code to consider the nonlinear processes arising when a
Reissner-Nordstrom black hole is irradiated by an exotic scalar field (modelled
as a free massless scalar field with an opposite sign for its energy-momentum
tensor). These processes are quite different from the processes arising in the
case of the same black hole being irradiated by a pulse of a normal scalar
field. In our case, we did not observe the creation of a spacelike strong
singularity in the T-region of the space-time. We investigate the antifocusing
effects in the gravity field of the exotic scalar field with the negative
energy density and the evolution of the mass function. We demonstrate the
process of vanishing of the black hole when it is irradiated by a strong pulse
of an exotic scalar field.Comment: 16 pages, 16 figures. Text has been rewritten and restructured,
Penrose diagrams have been added, appendix with convergence tests has been
added. Co-author has been added. Conclusions are unchange
Optimization of strength and ductility in nanotwinned ultra-fine grained Ag: Twin density and grain orientations
Nanotwinned ultrafine grained Ag thick films with different twin densities and orientations have been synthesized by magnetron sputtering with a wide-range of deposition rates. The twin boundary (TB) spacings and orientations as well as the grain size for the different deposition conditions have been characterized by both synchrotron X-ray scattering and transmission electron microscopy (TEM). Structural characterization combined with uniaxial tensile tests of the free-standing films reveals a large increase in the yield strength for films deposited at high deposition rates without any accompanying change in the TB spacing – a behavior that is not reported in the literature. We find that films deposited at lower deposition rates exhibit more randomly oriented grains with a lower overall twin density (averaged over all the grains) than the more heavily twinned grains with strong 〈1 1 1〉 fiber texture in the films deposited at higher deposition rates. The TB spacing in the twinned grains, however, does not show any significant dependence on the deposition rate. The dependence of the strength and ductility on the twin density and orientations can be described by two different soft deformation modes: (1) untwinned grains and (2) nanowinned grains that are not oriented with 〈1 1 1〉 along the growth direction. The untwinned grains provide relatively low resistance to slip, and thus decreased strength, while the nanotwinned grains that are not oriented with 〈1 1 1〉 along the growth direction are softer than nanotwinned grains that are oriented with 〈1 1 1〉 along the growth direction. We have revealed that an ultrafine-grained (150–200 nm) structure consisting of a mixture of nanotwinned (∼8–12 nm spacing) and untwined grains yields the best combination of high strength and uniform tensile ductility
Precession of Mercury’s Perihelion from Ranging to the MESSENGER Spacecraft
The perihelion of Mercury's orbit precesses due to perturbations from other solar system bodies, solar quadrupole moment (J [subscript 2]), and relativistic gravitational effects that are proportional to linear combinations of the parametrized post-Newtonian parameters β and γ. The orbits and masses of the solar system bodies are quite well known, and thus the uncertainty in recovering the precession rate of Mercury's perihelion is dominated by the uncertainties in the parameters J [subscript 2], β, and γ. Separating the effects due to these parameters is challenging since the secular precession rate has a linear dependence on each parameter. Here we use an analysis of radiometric range measurements to the MESSENGER (MErcury Surface, Space ENvironment, GEochemistry, and Ranging) spacecraft in orbit about Mercury to estimate the precession of Mercury's perihelion. We show that the MESSENGER ranging data allow us to measure not only the secular precession rate of Mercury's perihelion with substantially improved accuracy, but also the periodic perturbation in the argument of perihelion sensitive to β and γ. When combined with the γ estimate from a Shapiro delay experiment from the Cassini mission, we can decouple the effects due to β and J [subscript 2] and estimate both parameters, yielding (β -1)=(-2.7 ± 3.9) x 10[superscript -5] and J [subscript 2] = (2.25 ± 0.09) × 10[superscript −7]. We also estimate the total precession rate of Mercury's perihelion as 575.3100 ± 0.0015''/century and provide estimated contributions and uncertainties due to various perturbing effects
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