Anisotropic stresses in inhomogeneous universes

Anisotropic stress contributions to the gravitational field can arise from magnetic fields, collisionless relativistic particles, hydrodynamic shear viscosity, gravitational waves, skew axion fields in low-energy string cosmologies, or topological defects. We investigate the effects of such stresses on cosmological evolution, and in particular on the dissipation of shear anisotropy. We generalize some previous results that were given for homogeneous anisotropic universes, by including small inhomogeneity in the universe. This generalization is facilitated by a covariant approach. We find that anisotropic stress dominates the evolution of shear, slowing its decay. The effect is strongest in radiation-dominated universes, where there is slow logarithmic decay of shear.Comment: 7 pages Revte

Probing the primordial Universe with MeerKAT and DES

It is usually assumed that we will need to wait until next-generation surveys like Euclid, LSST and SKA, in order to improve on the current best constraints on primordial non-Gaussianity from the Planck experiment. We show that two contemporary surveys, with the SKA precursor MeerKAT and the Dark Energy Survey (DES), can be combined using the multi-tracer technique to deliver an accuracy on measurement of $f_{\rm NL}$ that is up to three times better than Planck.Comment: 7 pages, 5 figures, 1 table. We now marginalise over the bias, and ensure that we exclude nonlinear scales, leading to small quantitative corrections. Version accepted by MNRA

Antiretroviral therapeutic drug monitoring

Antiretroviral therapeutic drug monitoring (TDM) is an additional monitoring tool to assist in the management of HIV-infected patients. Antiretroviral TDM is frequently undertaken in Europe, but less often in the USA. This overview will assess the principles, current evidence for, and limitations of TDM. Lastly, the potential role of TDM in southern Africa will be discussed. Southern African Journal of HIV Medicine Vol. 7 (2) 2006: pp. 10-1

Antiviral therapy in herpesvirus infections

No Abstract

Initiating antiretroviral therapy

Debate Southern African Journal of HIV Medicine Vol. 6 (3) 2005: pp. 49-5

Guidelines for antiretroviral therapy in adults

These guidelines are intended as an update to those published in the Southern African Journal of HIV Medicine in January 2008. Since the release of the previous guidelines, the scaleup of antiretroviral therapy (ART) in Southern Africa has continued to grow. Cohort studies from the region showexcellent clinical outcomes; however, ART is still being started late (in advanced disease), resulting in relatively high early mortality rates. New data on antiretroviral (ARV) tolerability in the region and several new ARV drugs have become available. Although currently few in number, some patients in the region are failing protease inhibitor (PI)-based second-line regimens. To address this, guidelines on third-line (or ‘salvage’) therapy have been expanded

Probing the Cosmological Principle in the counts of radio galaxies at different frequencies

According to the Cosmological Principle, the matter distribution on very large scales should have a kinematic dipole that is aligned with that of the CMB. We determine the dipole anisotropy in the number counts of two all-sky surveys of radio galaxies. For the first time, this analysis is presented for the TGSS survey, allowing us to check consistency of the radio dipole at low and high frequencies by comparing the results with the well-known NVSS survey. We match the flux thresholds of the catalogues, with flux limits chosen to minimise systematics, and adopt a strict masking scheme. We find dipole directions that are in good agreement with each other and with the CMB dipole. In order to compare the amplitude of the dipoles with theoretical predictions, we produce sets of lognormal realisations. Our realisations include the theoretical kinematic dipole, galaxy clustering, Poisson noise, simulated redshift distributions which fit the NVSS and TGSS source counts, and errors in flux calibration. The measured dipole for NVSS is $\sim\!2$ times larger than predicted by the mock data. For TGSS, the dipole is almost $\sim\! 5$ times larger than predicted, even after checking for completeness and taking account of errors in source fluxes and in flux calibration. Further work is required to understand the nature of the systematics that are the likely cause of the anomalously large TGSS dipole amplitude.Comment: 13 pages, 8 figures, 2 tables; Significant improvements. Version accepted by JCA

Nonperturbative gravito-magnetic fields

In a cold matter universe, the linearized gravito-magnetic tensor field satisfies a transverse condition (vanishing divergence) when it is purely radiative. We show that in the nonlinear theory, it is no longer possible to maintain the transverse condition, since it leads to a non-terminating chain of integrability conditions. These conditions are highly restrictive, and are likely to hold only in models with special symmetries, such as the known Bianchi and $G_2$ examples. In models with realistic inhomogeneity, the gravito-magnetic field is necessarily non-transverse at second and higher order.Comment: Minor changes to match published version; to appear in Phys. Rev.