The end of HIV: Still a very long way to go, but progress continues.

In an Editorial accompanying PLOS Medicine's Special Issue on Advances in Prevention, Treatment and Cure of HIV/AIDS, Guest Editors Steven Deeks, Sharon Lewin, and Linda-Gail Bekker discuss priorities in the field and the content of the issue

The spectrum and prognosis of AIDS-defining illnesses in Cape Town

Objectives. To describe the incidence, spectrum and prognosis of AIDS-defining illnesses (ADI) in patients without access to antiretroviral therapy (ART). Design. Prospective cohort study. Subjects. 1 215 HIV-infected patients attending adult HIV clinics affiliated to the University of Cape Town in the New Somerset and Groote Schuur Hospitals from 1992 to 2000. Main outcome measures. Incidence rate (IR) of ADIs and survival after the ..

Free spectral range electrical tuning of a high quality on-chip microcavity

Reconfigurable photonic circuits have applications ranging from next-generation computer architectures to quantum networks, coherent radar and optical metamaterials. However, complete reconfigurability is only currently practical on millimetre-scale device footprints. Here, we overcome this barrier by developing an on-chip high quality microcavity with resonances that can be electrically tuned across a full free spectral range (FSR). FSR tuning allows resonance with any source or emitter, or between any number of networked microcavities. We achieve it by integrating nanoelectronic actuation with strong optomechanical interactions that create a highly strain-dependent effective refractive index. This allows low voltages and sub-nanowatt power consumption. We demonstrate a basic reconfigurable photonic network, bringing the microcavity into resonance with an arbitrary mode of a microtoroidal optical cavity across a telecommunications fibre link. Our results have applications beyond photonic circuits, including widely tuneable integrated lasers, reconfigurable optical filters for telecommunications and astronomy, and on-chip sensor networks.Comment: Main text: 7 pages, 3 figures. Supplementary information: 7 pages, 9 figure

Development Studies Working Paper, no. 7

This paper reports on an investigation of the effects of the policy of Coloured Labour Preference in a rural area of the Western Cape. This policy, which has been analysed more fully elsewhere1, aims to restrict the number of black employees in the Western Cape, the region within which the policy is applied, by granting Coloureds preferential access to urban and rural labour markets. The Langkloof is a valley in which modern mechanised agricultural techniques are employed to specialise in the production of deciduous fruit, apples in particular. Farms are owned by whites, and the majority of farm workers are (classified) Coloured. A substantial number of black farm workers are also employed. The Kloof is served by two good roads and a narrow gauge railway linking the villages of the Kloof to Port Elizabeth. The Langkloof, moreover, is situated close to the boundary of the Western Cape, and therefore close to the line demarcating the region within which the policy of Coloured Labour Preference is applied. The investigation, which was executed in late 1980, included a number of visits to the Langkloof, interviews with officials of the Departments of Agriculture and Manpower, and of the Eastern Cape Administration Board, as well as a survey of white farmers' attitudes and practices. This survey was designed to elicit information relevant to the rural labour situation in the Langkloof, and to identify differences in attitudes and practices with regard to Coloured and black farmworkers. The focus of the survey was on the eastern half of the valley, commonly known as the Middel- and Onder-Langkloof.Digitised by Rhodes University Library on behalf of the Institute of Social and Economic Research (ISER

Effect of quantum nuclear motion on hydrogen bonding

This work considers how the properties of hydrogen bonded complexes, D-H....A, are modified by the quantum motion of the shared proton. Using a simple two-diabatic state model Hamiltonian, the analysis of the symmetric case, where the donor (D) and acceptor (A) have the same proton affinity, is carried out. For quantitative comparisons, a parametrization specific to the O-H....O complexes is used. The vibrational energy levels of the one-dimensional ground state adiabatic potential of the model are used to make quantitative comparisons with a vast body of condensed phase data, spanning a donor-acceptor separation (R) range of about 2.4-3.0 A, i.e., from strong to weak bonds. The position of the proton and its longitudinal vibrational frequency, along with the isotope effects in both are discussed. An analysis of the secondary geometric isotope effects, using a simple extension of the two-state model, yields an improved agreement of the predicted variation with R of frequency isotope effects. The role of the bending modes in also considered: their quantum effects compete with those of the stretching mode for certain ranges of H-bond strengths. In spite of the economy in the parametrization of the model used, it offers key insights into the defining features of H-bonds, and semi-quantitatively captures several experimental trends.Comment: 12 pages, 8 figures. Notation clarified. Revised figure including the effect of bending vibrations on secondary geometric isotope effect. Final version, accepted for publication in Journal of Chemical Physic

A L\'evy input fluid queue with input and workload regulation

We consider a queuing model with the workload evolving between consecutive i.i.d.\ exponential timers $\{e_q^{(i)}\}_{i=1,2,...}$ according to a spectrally positive L\'evy process $Y_i(t)$ that is reflected at zero, and where the environment $i$ equals 0 or 1. When the exponential clock $e_q^{(i)}$ ends, the workload, as well as the L\'evy input process, are modified; this modification may depend on the current value of the workload, the maximum and the minimum workload observed during the previous cycle, and the environment $i$ of the L\'evy input process itself during the previous cycle. We analyse the steady-state workload distribution for this model. The main theme of the analysis is the systematic application of non-trivial functionals, derived within the framework of fluctuation theory of L\'evy processes, to workload and queuing models

The mass miniature chest radiography programme in Cape Town, South Africa, 1948 - 1994: The impact of active tuberculosis case finding

Background. Tuberculosis (TB) control programmes rely mainly on passive detection of symptomatic individuals. The resurgence of TB has rekindled interest in active case finding. Cape Town (South Africa) had a mass miniature radiography (MMR) screening programme from 1948 to 1994.Objective. To evaluate screening coverage, yield and secular trends in TB notifications during the MMR programme.Methods. We performed an ecological analysis of the MMR programme and TB notification data from the City of Cape Town Medical Officer of Health reports for 1948 - 1994.Results. Between 1948 and 1962, MMR screening increased to 12% of the population per annum with yields of 14 cases per 1 000 X-rays performed, accounting for >20% of total annual TB notifications. Concurrent with increasing coverage (1948 - 1965), TB case notification decreased in the most heavily TB-burdened non-European population from 844/100 000 population to 415/100 000. After 1966, coverage declined and TB notifications that initially remained stable (1967 - 1978) subsequently increased to 525/100 000. MMR yields remained low in the European population but declined rapidly in the non-European population after 1966, coincidental with forced removals from District 6. An inverse relationship between screening coverage and TB notification rates was observed in the non-European adult population. Similar secular trends occurred in infants and young children who were not part of the MMR screening programme.Conclusion. MMR of a high-burdened population may have significantly contributed to TB control and was temporally associated with decreased transmission to infants and children. These historical findings emphasise the importance of re-exploring targeted active case finding strategies as part of population TB control