Epidemiological research methods. Part VII. Epidemiological research in health planning

CITATION: Yach, D. & Botha, J. L. 1987. Epidemiological research methods. Part VII. Epidemiological research in health planning. South African Medical Journal, 72:633-636.The original publication is available at http://www.samj.org.zaThe goal of epidemiology is to improve the health status of human populations. In our series thus far we have srressed the need to use the correct design for epidemiological studies, a sampling scheme that yields interpretable results, measurements that are both valid and reliable, and finally the appropriate analysis. These methodological considerations are of importance if the goal is to be reached. In this article we assume that most of these issues have been adequately dealt with and focus on how the results of epidemiological research can be used by health planners to improve the health status of regions and the country as a whole.Publisher’s versio

Epidemiological research methods. Part II. Descriptive studies

CITATION: Botha, J. L. & Yach, D. 1986. Epidemiological research methods. Part II. Descriptive studies. South African Medical Journal, 70:766-772.The original publication is available at http://www.samj.org.zaIn a descriptive study, therefore, the magnitude and distribution of a health problem in a specified population is studied in terms of TIME (when did it occur?), PLACE (where did it occur?) and PERSON (which groups are affected?). The design starts with an idea that occurs to the researcher about a particular problem. This is followed by selecting a group of individuals to be studied (sampling), considering which attributes to measure (measurement), describing the findings, and finally drawing conclusions on the basis of the findings. Commonly, new ideas or hypotheses are generated in this final stage, usually regarding possible explanations for the health problems described (cause-effect relationships). Such relationships may be attempts to explain the aetiology of diseases or the effect of preventive, curative or rehabilitative measures. Important issues affecting the reliability of the sampling and measurement processes are discussed, some descriptive statistical measures demonstrated and how conclusions are affected by these, are indicated.Publisher’s versio

Observations on the ecology of Pleurobrachia pileus (Ctenophora) in the southern Benguela ecosystem

The vertical distribution, abundance and size composition of a population of Pleurobrachia pileus was studied during a six-day drogue study conducted off the west coast of South Africa in February 1995. The population was centred in deep water, possibly because of the presence of a potential predator, Beroe sp., at shallower depths. The population of P. pileus failed to display clear patterns of migration, although nocturnal recruitment from deeper water resulted in a deepening of the depth of occupation then. The population was dominated by individuals <4 mm polar diameter, and large animals were confined to the upper water layers. These results are discussed with reference to possible spawning activities. Using published equations relating size to clearance rates, it was estimated that the population could remove up to 27% of integrated mesozooplankton standing stocks, and in excess of 100% (293%) at some depths.Web of Scienc

OBSERVATIONS ON THE ECOLOGY OF PLEUROBRACHIA PILEUS (CTENOPHORA) IN THE SOUTHERN BENGUELA ECOSYSTEM

The vertical distribution, abundance and size composition of a population of Pleurobrachia pileus was studied during a six-day drogue study conducted off the west coast of South Africa in February 1995. The population was centred in deep water, possibly because of the presence of a potential predator, Beroe sp., at shallower depths. The population of P. pileus failed to display clear patterns of migration, although nocturnal recruitment from deeper water resulted in a deepening of the depth of occupation then. The population was dominated by individual

Observational signatures of the coronal kink instability with thermal conduction

It is known from numerical simulations that thermal conduction along magnetic field lines plays an important role in the evolution of the kink instability in coronal loops. This study presents the observational signatures of the kink instability in long coronal loops when parallel thermal conduction is included. The 3D nonlinear magnetohydrodynamic equations are solved numerically to simulate the evolution of a coronal loop that is initially in an unstable equilibrium. The loop has length 80 Mm, width 8 Mm and an initial maximum twist of Phi = 11.5 pi, where Phi is a function of the radius. The initial loop parameters are obtained from a highly twisted loop observed in the TRACE 171 A waveband. Synthetic observables are generated from the data. These observables include spatial and temporal averaging to account for the resolution and exposure times of TRACE images. Parallel thermal conduction reduces the maximum local temperature by up to an order of magnitude. This means that different spectral lines are formed and different internal loop structures are visible with or without the inclusion of thermal conduction. However, the response functions sample a broad range of temperatures. The result is that the inclusion of parallel thermal conductivity does not have as large an impact on observational signatures as the order of magnitude reduction in the maximum temperature would suggest; the net effect is a blurring of internal features of the loop structure.Comment: To be published in Astrophysical Journal, 14 pages, 9 figure

The radiation of cynodonts and the ground plan of mammalian morphological diversity

Cynodont therapsids diversified extensively after the Permo-Triassic mass extinction event, and gave rise to mammals in the Jurassic. We use an enlarged and revised dataset of discrete skeletal characters to build a new phylogeny for all main cynodont clades from the Late Permian to the Early Jurassic, and we analyse models of morphological diversification in the group. Basal taxa and epicynodonts are paraphyletic relative to eucynodonts, and the latter are divided into cynognathians and probainognathians, with tritylodonts and mammals forming sister groups. Disparity analyses reveal a heterogeneous distribution of cynodonts in a morphospace derived from cladistic characters. Pairwise morphological distances are weakly correlated with phylogenetic distances. Comparisons of disparity by groups and through time are non-significant, especially after the data are rarefied. A disparity peak occurs in the Early/Middle Triassic, after which period the mean disparity fluctuates little. Cynognathians were characterized by high evolutionary rates and high diversity early in their history, whereas probainognathian rates were low. Community structure may have been instrumental in imposing different rates on the two clades

Using ceftazidime-avibactam for persistent carbapenem-resistant Serratia marcescens infection highlights antimicrobial stewardship challenges with new beta-lactam-inhibitor combination antibiotics

The newer beta-lactam-inhibitor combination (BLIC) antibiotics are available in South Africa (SA) for the treatment of carbapenem-resistant Enterobacterales infections. We describe the successful use of ceftazidime-avibactam (CA) for the treatment of a child with persistent carbapenem-resistant Serratia marcescens bacteraemia, and the challenges faced using this lifesaving antibiotic, including access to susceptibility testing, procurement process, cost and complexity of deciding when, how and for how long to use it. Furthermore, the burden of carbapenem resistance is increasing in SA, and inappropriate use of CA and other newer BLIC antibiotics, such as ceftolozane-tazobactam, will inevitably endanger their longevity. A careful balance must be struck between removing unnecessary obstacles and delays in initiating these antibiotics for life-threatening infections, and additional antimicrobial stewardship-guided interventions aimed at preserving their therapeutic use

Simulation of the enhanced infrared photoresponse of type-II GaSb/GaAs quantum ring solar cells

The extended photo-response of solar cells containing ten periods of GaSb/GaAs quantum rings imbedded in the p-i-n junction has been described using a single-band representation of the type-II quantum ring structure. By fitting the experimental data, the authors were able to deduce that the quantum rings are well represented by a Gaussian height distribution and a large valence band discontinuity. The simulated band of states is shown to be well matched to the photoluminescence analysis of the structure, with the inhomogeneous size distribution resulting in a band of hole states roughly 390 meV above the valence band

The efficacy of a generic doxycycline tablet in the treatment of canine monocytic ehrlichiosis

The objective of the present study was to evaluate the therapeutic efficacy of a generic doxycycline tablet (DoxyVet®) against Ehrlichia canis infection in dogs. Canine monocytic ehrlichiosis is caused by the bacterium E. canis and transmitted by the brown kennel tick (Rhipicephalus sanguineus). Six disease-free and tick-free dogs were infested with E. canisinfected ticks. Once diagnosed (with polymerase chain reaction [PCR] analysis and platelet counts) as positive for infection, doxycycline tablets were administered orally once a day for 20 consecutive days, at a target dose level of 10 mg/kg. The actual dose administered was calculated as ranging between 10 mg/kg and 11.7 mg/kg. The PCR analysis, 28 days after the first administration of the tablets, failed to detect E. canis in any of the dogs. On Day 56 of the study, four of the dogs were diagnosed with E. canis for the second time and a fifth dog was diagnosed on Day 70. The platelet counts of the sixth dog remained within normal levels and it was discharged from the study on Day 84. Doxycycline tablets were then administered to the remaining five infected dogs for 28 consecutive days. Four of these dogs had no positive PCR results during the following 3 months. The fifth dog was diagnosed with E. canis for the third time 58 days after the last tablets of the second treatment had been administered, after which it was rescue treated (doxycycline for a further 28 days). The results indicate that doxycycline administered in tablet form (DoxyVet®) at 10 mg/kg – 11.7 mg/kg body mass once daily for 28 consecutive days clears most dogs of infection. The importance of a concomitant tick-control programme is therefore stressed