Community structure and centrality effects in the South African company network

This paper conducts a search for community structure in the South African company network, a social network whose elements are South African companies listed on the Johannesburg Stock Exchange. Companies are connected in this network if they share one or more directors on their respective boards. Discovered clusters, called communities, can be considered to be compartments of the network working relatively independently of one another, making their distribution and composition of some interest. We test whether the discovered communities of companies are (a) statistically significant, and (b) related to other attributes such as sector membership or market capitalization. We also investigate the relationship between the centrality of a company’s position in the network and its market capitalization

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Community structure and centrality effects in the South African company network

This paper conducts a search for community structure in the South African company network, a social network whose elements are South African companies listed on the Johannesburg Stock Exchange. Companies are connected in this network if they share one or more directors on their respective boards. Discovered clusters, called communities, can be considered to be compartments of the network working relatively independently of one another, making their distribution and composition of some interest. We test whether the discovered communities of companies are (a) statistically significant, and (b) related to other attributes such as sector membership or market capitalization. We also investigate the relationship between the centrality of a company’s position in the network and its market capitalization

Governance systems for skilled health worker migration, their public value and competing priorities: an interpretive scoping review

Background: Governments worldwide participate in skilled health worker (SHW) migration agreements to protect access to health services in their countries. Previous studies have described the value offered by these agreements in separate source and destination country perspectives. Objective: We sought to identify and summarise existing literature on shared value creation for both source and destination countries. Method: We conducted a systematic scoping review of health databases and grey literature. Using Mark Moore and Colin Talbot frameworks, we summarised the public value propositions in migration agreements and how state actors addressed competing priorities. Results: Most articles (34/63, 53.9%) reported transnational SHW mobility as the public value proposition for source and destination countries. Fewer articles, 14 (22.2%) and 9 (14.3%) articles, respectively, referred to achieving health workforce sustainability and building capacity for SHW migration governance as shared public values. The most identified competing public value (CPV) was an overriding focus on addressing SHW shortages in destination countries (20/63, 37.7%). Efforts to address this CPV include mitigation of the adverse effects of migration (43/63, 68.3%) and promoting health workforce development in source countries (15, 23.8%). At the same time, state actors retained regulatory discretion for protecting their country’s public health interest (34, 54%). Most articles reported the lack of funds (15/63, 23.8%) and implementation mechanisms (19/63, 30.2%) as constraints on the authorising environment and the operational capacity of SHW migration governance systems. Conclusion: Regarding SHW migration governance, the literature reports shared public value propositions for source and destination countries. It also shows how the value-creating process in the management of SHW migration favours destination countries. Future studies will need to explore shared value creation models that ensure equity in the governance of SHW migration

The non-clonality of drug resistance in Beijing-genotype isolates of Mycobacterium tuberculosis from the Western Cape of South Africa

Background. The Beijing genotype of M. tuberculosis is a virulent strain that is disseminating worldwide and has a strong association with drug resistance. In the Western Cape of South Africa, epidemiological studies have identified the R220 cluster of the Beijing genotype as a major contributor to a recent outbreak of drug-resistant tuberculosis. Although the outbreak is considered to be due to clonal transmission, the relationship among drug resistant isolates has not yet been established. Results. To better understand the evolution of drug resistance among these strains, 14 drug-resistant clinical isolates of the Beijing genotype were sequenced by whole-genome sequencing, including eight from R220 and six from a more ancestral Beijing cluster, R86, for comparison. While each cluster shares a distinct resistance mutation for isoniazid, mapping of other drug-resistance mutations onto a phylogenetic tree constructed from single nucleotide polymorphisms shows that resistance mutations to many drugs have arisen multiple times independently within each cluster of isolates. Thus, drug resistance among these isolates appears to be acquired, not clonally derived. This observation suggests that, although the Beijing genotype as a whole might have selective advantages enabling its rapid dissemination, the XDR isolates are relatively less fit and do not propagate well. Although it has been hypothesized that the increased frequency of drug resistance in some Beijing lineages might be caused by a mutator phenotype, no significant shift in synonymous substitution patterns is observed in the genomes. Conclusion. While MDR-TB is spreading by transmission in the Western Cape, our data suggests that further drug resistance (i.e. XDR-TB) at this stage is acquired.Peer Reviewe

Player Activity and Load Profiling with Hidden Markov Models: A Novel Application in Rugby League

Player movement in rugby league is complex, being spatiotemporal and multifaceted. Modeling this complexity to provide robust measures of player activity and load has proved difficult, with important aspects of player movement yet to be considered. These include the influence of time-varying covariates on player activity and the combination of different dimensions of player movement. Few studies have simultaneously categorized player activity into different activity states and investigated factors influencing the transition between states, or compared player activity and load profiles between matches and training. This study applied hidden Markov models (HMMs)-a data-driven, multivariate approach-to rugby league training and match GPS data to i) demonstrate how HMMs can combine multiple variables in a data-driven way to effectively categorize player movement states, ii) investigate the influence of two time-varying covariates, score difference and elapsed match time on player activity states, and iii) compare player activity and load profiles within and between training and match modalities. HMMs were fitted to player GPS, accelerometer and heart rate data of one English Super League team across 60 training sessions and 35 matches. Distinct activity states were detected for both matches and training, with transitions between states in matches influenced by score difference and elapsed time and clear differences in activity and load profiles between training and matches. HMMs can model the complexity of player movement to effectively profile player activity and load in rugby league and have the potential to facilitate new research across several sports

The Lombard effect in singing humpback whales : source levels increase as ambient ocean noise levels increase

Funding: Office of Naval Research (Code 322, Marine Mammals and Biology), Commander, U.S. Pacific Fleet (Code N465JR), and the Naval Facilities Engineering Command Living Marine Resources Program.Many animals increase the intensity of their vocalizations in increased noise. This response is known as the Lombard effect. While some previous studies about cetaceans report a 1 dB increase in the source level (SL) for every dB increase in the background noise level (NL), more recent data have not supported this compensation ability. The purpose of this study was to calculate the SLs of humpback whale song units recorded off Hawaii and test for a relationship between these SLs and background NLs. Opportunistic recordings during 2012-2017 were used to detect and track 524 humpback whale encounters comprised of 83 974 units on the U.S. Navy's Pacific Missile Range Facility hydrophones. Received levels were added to their estimated transmission losses to calculate SLs. Humpback whale song units had a median SL of 173 dB re 1 μ Pa at 1 m, and SLs increased by 0.53 dB/1 dB increase in background NLs. These changes occurred in real time on hourly and daily time scales. Increases in ambient noise could reduce male humpback whale communication space in the important breeding area off Hawaii. Since these vocalization changes may be dependent on location or behavioral state, more work is needed at other locations and with other species.Publisher PDFPeer reviewe

Dealing with Uncertainties in MCDA

This chapter presents various approaches to incorporating formalmodelling of risks and uncertainties into multi-criteria decision analysis,in a theoretically valid but also operationally meaningful manner. Weconsider both internal uncertainties (in the formulation and modellingof the decision problem), and external uncertainties arising fromexogenous factors, but with greater attention paid to the latter. Aftera broad discussion on the meaning of uncertainty, we first reviewapproaches to sensitivity analysis, which is particularly, although notexclusively, relevant to internal uncertainties. We discuss the role,but also some limitations, of representing uncertainties in formalprobabilistic structures, linked also to concepts of expected (multiattribute) utility theory. Such probability/utility approaches may be usedin explicitly identifying a most preferred solution, or simply to eliminatecertain courses of action when stochastically dominated (in varioussenses) by others. In some contexts it may be useful to view minimizationof various risk measures as additional criteria in more standard MCDAmodels, and we comment on advantages and disadvantages of suchapproaches. Finally we discuss the integration of MCDA with scenarioplanning, in order to deal with deeper uncertainties (not easily if at allrepresentable by probability models), particularly in a strategic planningcontext. The emphasis throughout is on the practice of MCDA rather thanon esoteric theoretical results.<br/

Breeding systems of floral colour forms in the Drosera cistiflora species complex

The study was supported by the National Research Foundation of South Africa (Grant 46372 to SDJ).Variation in plant breeding systems has implications for pollinator‐mediated selection on floral traits and the ecology of populations. Here we evaluate pollinator contribution to seed production, self‐compatibility and pollen limitation in different floral colour forms of Drosera cistiflora sensu lato (Droseraceae). These insectivorous perennial plants are endemic to fynbos and renosterveld vegetation in the Cape Floristic Region of South Africa, and the species complex includes five floral colour forms (pink, purple, red, white and yellow), some of which are known to be pollinated by beetles. Controlled hand‐pollination experiments were conducted in 15 populations of D. cistiflora s.l. (two to four populations per floral colour form) to test whether the colour forms vary in their degree of self‐compatibility and their ability to produce seeds through autonomous self‐fertilization. Yellow‐flowered forms were highly self‐incompatible, while other floral colour forms exhibited partial self‐compatibility. Seed set resulting from autonomous selfing was very low, and pollinator dependence indices were high in all populations. Since hand cross‐pollination resulted in greater seed set than open pollination in 13 of the 15 populations, we inferred that seed production is generally pollen‐limited.Drosera cistiflora s.l. typically exhibits high levels of pollinator dependence and pollen limitation. This is unusual among Drosera species worldwide and suggests that pollinators are likely to mediate strong selection on attractive traits such as floral colour and size in D. cistiflora s.l. These results also suggest that the floral colour forms of D. cistiflora s.l. which are rare and threatened are likely to be vulnerable to local extinction if mutualisms were to collapse indefinitely.PostprintPeer reviewe