HAL is a multi-disciplinary open access archive for the deposit and dissemination of scientific research documents, whether they are published or not. The documents may come from teaching and research institutions in France or abroad, or from public or private research centers. L'archive ouverte pluridisciplinaire HAL, est destinée au dépôt et à la diffusion de documents scientifiques de niveau recherche, publiés ou non, émanant des établissements d'enseignement et de recherche français ou étrangers, des laboratoires publics ou privés.

Orientation: Executive pay has been increasing; however, company performance has not been increasing proportionally. This could be due to an agency problem, resulting in executive pay not aligning with the shareholders’ desired company performance.Research purpose: The purpose of this research was to establish if there was a relationship between the total pay of the chief executive officer and their company’s financial performance in South African Schedule 2 state-owned entities (SOEs).Motivation for the study: A review of literature revealed conflicting views regarding the relationship between executive pay and company financial performance. There were limited studies conducted in South Africa, especially considering SOEs.Research approach/design and method: This research was a quantitative, archival study using 8 years of secondary data from South African Schedule 2 SOEs. Spearman’s rank-order correlation was used to evaluate the relationship.Main findings: One significant weak positive relationship was observed when considering the net profit or loss metric of financial performance. Hence, there was no conclusive relationship between executive pay and company financial performance, which supported the proposition that there is an agency problem in South African SOEs.Practical/managerial implications: There is a distinct need for an all-encompassing SOE legislation framework to standardise pay structure and reporting requirements. Additionally, accurate measures of performance are necessary to overcome the agency problem.Contribution/value-add: This research adds to the limited knowledge base regarding the relationship between executive pay and company financial performance in South African SOEs. It also identified the need to incorporate non-financial metrics to influence executive pay.

Interest in the mathematical modeling of infectious diseases has increased due to the COVID-19 pandemic. However, many medical students do not have the required background in coding or mathematics to engage optimally in this approach. System dynamics is a methodology for implementing mathematical models as easy-to-understand stock-flow diagrams. Remarkably, creating stock-flow diagrams is the same process as creating the equivalent differential equations. Yet, its visual nature makes the process simple and intuitive. We demonstrate the simplicity of system dynamics by applying it to epidemic models including a model of COVID-19 mutation. We then discuss the ease with which far more complex models can be produced by implementing a model comprising eight differential equations of a Chikungunya epidemic from the literature. Finally, we discuss the learning environment in which the teaching of the epidemic modeling occurs. We advocate the widespread use of system dynamics to empower those who are engaged in infectious disease epidemiology, regardless of their mathematical background.

Black tattoo ink comprises hydrophobic carbon black nanoparticles. We hypothesized that black tattoo ink demonstrates transient dynamic activity in an ultrasound field. Brightness-mode sonography was performed on cylindrical receptacles of different bore diameters, filled with black tattoo ink, water, saline, or air, using pulsed ultrasound with center frequencies of 13 MHz and 5 MHz.The scattering from black ink itself lasted less than ten minutes. At 13-MHz sonication, a transient drop in sound speed was observed, as well as a transient lessening of scattering from distal phantom tissue. The linear acoustic attenuation coefficient of pure black ink was measured to be 0.15±0.01 dB cm −1 MHz −1 , equal to whole blood.Low-intensity ultrasonic tattoo removal would be of interest as an alternative to techniques that damage surrounding tissue.