Using multicriteria analysis to select alternative surfacings for low volume roads

A large portion of the road network in developing countries in Africa consist of Low Volume Roads (LVRs). Funding for upgrading and maintenance of these roads pose a challenge for roads authorities as their limited budgets are mainly aimed at highways and major corridors. Isolated communities bear the burden of inaccessibility to markets, education and health facilities. As part of a study that was launched by the Research for Community Access Partnership (ReCAP) an investigation into alternative surfacings to gravel roads was conducted in Ghana, Liberia and Sierra Leone. A stakeholder engagement process, designed around several workshops, was used to gain insight into the needs of the community. The local roads authorities, local engineers and technical pavement experts were involved in the selection of surfacing options which would be most suitable for implementation. Several other aspects of the surfacing types were investigated such as the initial construction cost, anticipated maintenance costs and life cycle cost. An exclusive multicriteria analysis, which used the outputs from the different costing scenarios and the workshops was conducted, and a Monte Carlo simulation was completed to select the most appropriate surfacing solutions.Papers presented at the 40th International Southern African Transport Conference on 04 -08 July 202

Critical Collapse of the Massless Scalar Field in Axisymmetry

We present results from a numerical study of critical gravitational collapse of axisymmetric distributions of massless scalar field energy. We find threshold behavior that can be described by the spherically symmetric critical solution with axisymmetric perturbations. However, we see indications of a growing, non-spherical mode about the spherically symmetric critical solution. The effect of this instability is that the small asymmetry present in what would otherwise be a spherically symmetric self-similar solution grows. This growth continues until a bifurcation occurs and two distinct regions form on the axis, each resembling the spherically symmetric self-similar solution. The existence of a non-spherical unstable mode is in conflict with previous perturbative results, and we therefore discuss whether such a mode exists in the continuum limit, or whether we are instead seeing a marginally stable mode that is rendered unstable by numerical approximation.Comment: 11 pages, 8 figure

An Exact Solution for Static Scalar Fields Coupled to Gravity in (2+1)(2+1)-Dimensions

We obtain an exact solution for the Einstein's equations with cosmological constant coupled to a scalar, static particle in static, "spherically" symmetric background in 2+1 dimensions.Comment: 9 pages. Replaced by a revised versio

Connecting Numerical Relativity and Data Analysis of Gravitational Wave Detectors

Gravitational waves deliver information in exquisite detail about astrophysical phenomena, among them the collision of two black holes, a system completely invisible to the eyes of electromagnetic telescopes. Models that predict gravitational wave signals from likely sources are crucial for the success of this endeavor. Modeling binary black hole sources of gravitational radiation requires solving the Eintein equations of General Relativity using powerful computer hardware and sophisticated numerical algorithms. This proceeding presents where we are in understanding ground-based gravitational waves resulting from the merger of black holes and the implications of these sources for the advent of gravitational-wave astronomy.Comment: Appeared in the Proceedings of 2014 Sant Cugat Forum on Astrophysics. Astrophysics and Space Science Proceedings, ed. C.Sopuerta (Berlin: Springer-Verlag

Scalar field spacetimes and the AdS/CFT conjecture

We describe a class of asymptotically AdS scalar field spacetimes, and calculate the associated conserved charges for three, four and five spacetime dimensions using the conformal and counter-term prescriptions. The energy associated with the solutions in each case is proportional to $\sqrt{M^2 - k^2}$, where $M$ is a constant and $k$ is a scalar charge. In five spacetime dimensions, the counter-term prescription gives an additional vacuum (Casimir) energy, which agrees with that found in the context of AdS/CFT correspondence. We find a surprising degeneracy: the energy of the ``extremal'' scalar field solution $M=k$ equals the energy of pure AdS. This result is discussed in light of the AdS/CFT conjecture.Comment: 5 pages, Latex, additional commentary on results, version to appear in Phys. Rev.

Tick-borne pathogens in the blood of wild and domestic ungulates in South Africa: interplay of game and livestock

Published ArticleWe screened for tick-borne pathogens blood samples from 181 wild and domestic ungulates belonging to 18 host species in 4 South African Provinces. Polymerase chain reaction followed by reverse line blotting and sequencing allowed detecting 16 tick-borne pathogen species belonging to the genera Babesia, Theileria, Anaplasma, and Ehrlichia. Ten pathogen species were involved in 29 new host–pathogen combinations. Most infections (77.9%) involved more than one pathogen species. Principal component analysis (PCA) assigned the 163 infections, identified to species level, to 4 groups. Three groups were associated with sheep, cattle, and horse and their respective wild counterparts. Each group was characterised by high homogeneity in pathogen assemblage and host phylogenetic status. These groups characterised the most privileged transmission routes between and among wild and domestic ungulates. The 4th group showed high heterogeneity in pathogen assemblage and host phylogenetic status. This group seems to indicate frequent spill over events in impala of pathogens that usually circulate among cattle- or sheep-related species. Within 6 localities, we sampled an equal number of wild and domestic animals (n = 128). On this dataset once having controlled for the significant variation among localities, the infection prevalence and intensity of infection did not differ significantly between wild and domestic hosts. This suggests that both animal types, domestic and wild hosts, could act as evenly efficient sources of infection for themselves and for each other. Overall, this study shed new light on the pathogen circulation naturally achieved at the interplay between wild and domestic ungulates