1,720,957 research outputs found
Modelling outbreak response intervention strategies for decision-making
Full text linkThesis (PhD)--Stellenbosch University, 2022.ENGLISH SUMMARY: Outbreaks of infectious diseases like measles and COVID-19 continue to threaten public health. Consequently, outbreak response decision-making is in constant need of advancements. Mathematical models of infectious diseases, which provide evidence based insights about pathogen spread and the impact of interventions, form an essential component of outbreak response decision-making. In this dissertation, I make three contributions in that regard. First, I conduct a systematic review of modelling studies, published during 1970-2019, that assessed the impact of reactive interventions on real and hypothetical outbreaks of human vaccine-preventable diseases and foot-and-mouth disease (FMD). I extract data including the author affiliation type (academic institution, governmental, and non-governmental organizations), whether there was an author based in the country studied, impact of vaccination, model characteristics, and modelling practices. I use the author affiliation types to group papers into two collaboration types namely, purely academic (papers with only academic author affiliations) and mixed (all other combinations). I analyse time and geographic patterns and differences in model characteristics and practices overall and between the collaboration types. I find that, in the human disease literature, mixed collaborations increased in the past decade, more often included authors based in the country studied and used more complex modelling practices. These patterns could indicate an increased recognition of modelling by decision makers or increased interaction between modellers and decision-makers. Additionally, I observe some contrasting patterns between the human and FMD literature. Second, I investigate the relative logistical and epidemiological benefits of outside cold chain (OCC) delivery of measles vaccines during an outbreak in a hypothetical setting assuming vaccine cold chain challenges. I extend a transmission dynamic model to incorporate key logistical requirements of several cold chain and OCC strategies. I find that OCC delivery of measles vaccines during outbreaks could lead to shorter campaigns, high vaccination coverage, and higher cases averted. Finally, I show how the emergence of a variant strain affects the minimally sufficient response strategy needed to mitigate the outbreak of a hypothetical pathogen. I develop compartmental models that allow the introduction of more transmissible variants with the ability to escape vaccine-induced immunity. I investigate the impact on outbreak size and peak prevalence targets of implementing either vaccination alone or a combination of vaccination and non-pharmaceutical interventions (NPIs). I show that the use of vaccination alone would require a high vaccination coverage and rapid rollout speed but adding on NPIs could reduce the vaccination coverage and rollout speed required to achieve the targets while also accounting for the risk of variant emergence. In conclusion, this dissertation makes advances that could potentially: (1) initiate discussions on the impact of modelling in outbreak response and the need for increased collaboration between model developers and users, (2) lead to advocacy towards innovations in measles outbreak response vaccination, and (3) contribute to the theory of outbreak response planning, especially in the way uncertainty regarding the potential emergence of a variant is considered in outbreak response decision-making.AFRIKAANSE OPSOMMING: Uitbrake van aansteeklike siektes soos masels en COVID-19 bedreig steeds openbare gesondheid. Gevolglik benodig uitbraak-reaksie besluitneming voortdurende vooruitgang. Wiskundige modelle van aansteeklike siektes, wat bewysgebaseerde insigte oor patogeenverspreiding
en die impak van ingrypings verskaf, vorm ’n noodsaaklike komponent van uitbraak-reaksie. In hierdie proefskrif lewer ek drie bydraes in hierdie verband. Eerstens hersien ek sistematies eweknie-geevalueerde studies wat gedurende 1970-2019 gepubliseer is oor modelle wat die impak van uitbraak-reaksie ingrypings vir menslike entstof-voorkombare siektes assesseer. Ek onttrek data insluitend die outeuraffiliasietipe (akademiese instelling, regerings- en nie-regeringsorganisasies), of daar ’n outeur was met ’n affiliasie tot die plek wat bestudeer is, impak van inenting, modelkenmerke en modelleringspraktyke. Ek gebruik die outeur-affiliasietipes om studies in twee samewerkingstipes te groepeer: naamlik suiwer akademies (alle outeurs met slegs akademiese affiliasies) en gemengde (alle of twee van die drie outeur-affiliasietipes, of een van laasgenoemde twee). Ek ontleed verskille in modelkenmerke en praktyke oor die algemeen en tussen die samewerkingstipes. Ek vind dat gemengde samewerking in die afgelope dekade toegeneem het, meer dikwels skrywers ingesluit het met ’n affiliasie tot die plek wat bestudeer is en meer komplekse modelle gebruik het. Die toename in gemengde samewerking kan dui op ’n verhoogde erkenning van modellering deur besluitnemers of verhoogde interaksie tussen model ontwikkelaars en gebruikers. Tweedens ondersoek ek hoe om masels inenting te verbeter in omgewings waar dit moeilik is om vinnige en doeltreffende veldtogte te loots as gevolg van beperkings in die entstof koueketting. Ek brei ’n transmissie dinamiese model uit om operasionele prosesse in te sluit om die potensiele relatiewe voordeel van buite koueketting aflewering van masels entstowwe te illustreer. Ek vind dat die gebruik van die masels entstof buite die koueketting kan lei tot korter veldtogte, hoer dekking en meer gevalle wat afgeweer word. Ten slotte wys ek hoe die opkoms van ’n variante stam die minimaal voldoende reaksiestrategie beinvloed wat nodig is om ’n hipotetiese patogeen te beheer. Ek ontwikkel twee twee-stam modelle wat die bekendstelling van meer oordraagbare variante met die vermoe om entstof-gebaseerde immuniteit te ontsnap, moontlik maak. Ek ondersoek die impak van variante opkoms op die minimaal voldoende ingryping strategiee, deur of slegs inenting of ’n kombinasie van inenting en nie-farmaseutiese ingrypings (NPI’s), wat nodig is om ’n gespesifiseerde uitkoms te bereik, te gebruik. Ek wys dat die gebruik van inenting alleen ’n hoe inentingsdekking en vinnige ontplooiingspoed sal vereis, maar die toevoeging van NPI’s kan die inentingsdekking en ontplooiingspoed wat nodig is om gestelde veldtog teikens te bereik verminder, terwyl dit ook rekening hou met die risiko van variante opkoms. Ten slotte maak hierdie proefskrif vordering wat moontlik: (1) besprekings kan inisieer oor die impak van modellering in uitbraak-reaksie en die behoefte aan verhoogde samewerking tussen model ontwikkelaars en gebruikers, (2) kan lei tot voorspraak vir innovasies in masels uitbraak-reaksie inenting, en (3) kan bydra tot die teorie van uitbraakreaksie beplanning, veral in die wyse waarop onsekerheid rakende die potensiele opkoms van ’n variant in ag geneem word in uitbraak-reaksie besluitneming.Doctora
Going Beyond Counting First Authors in Author Co-citation Analysis
Full text linkThe present study examines one of the fundamental aspects of author co-citation analysis (ACA) - the way co-citation
counts are defined. Co-citation counting provides the data on which all subsequent statistical analyses and mappings
are based, and we compare ACA results based on two different types of co-citation counting - the traditional type that
only counts the first one among a cited work's authors on the one hand and a non-traditional type that takes into
account the first 5 authors of a cited work on the other hand. Results indicate that the picture produced through this non-traditional author co-citation counting contains more coherent author groups and is therefore considerably clearer. However, this picture represents fewer specialties in the research field being studied than that produced through the traditional first-author co-citation counting when the same number of top-ranked authors is selected and analyzed. Reasons for these effects are discussed
Variations on the Author
Full text link“Variations on the Author” discusses two of Eduardo Coutinho’s recent films (Um Dia na Vida, from 2010, and Últimas Conversas, posthumously released in 2015) and their contribution to the general question of documentary authorship. The director’s filmography is characterized by a consistent yet self-effacing form of authorial self-inscription: Coutinho often features as an interviewer that rather than express opinions propels discourses; an interviewer that is good at listening. This mode of self-inscription characterizes him as an author who is not expressive but who is nonetheless markedly present on the screen. In Um Dia na Vida, however, Coutinho is completely absent form the image, while Últimas Conversas, on the contrary, includes a confessional prologue that moves the director from the margins to the center of his films. This article examines the ways in which these works stand out in the filmography of a director who offers new insights into the notion of cinematic authorship
Appropriate Similarity Measures for Author Cocitation Analysis
Full text linkWe provide a number of new insights into the methodological discussion about author cocitation analysis. We first argue that the use of the Pearson correlation for measuring the similarity between authors’ cocitation profiles is not very satisfactory. We then discuss what kind of similarity measures may be used as an alternative to the Pearson correlation. We consider three similarity measures in particular. One is the well-known cosine. The other two similarity measures have not been used before in the bibliometric literature. Finally, we show by means of an example that our findings have a high practical relevance.information science;Pearson correlation;cosine;similarity measure;author cocitation analysis
Assessment of a measles outbreak response vaccination campaign, and two measles parameter estimation methods
Full text linkThesis (MSc)--Stellenbosch University, 2018.ENGLISH ABSTRACT : Measles is highly transmissible, and is a leading cause of vaccine-preventable death
among children. Consequently, it is regarded as a public health issue worldwide and has been
targeted for elimination by 5 out of the 6 WHO regions by 2020, the exception being the WHO Africa
region. The hope of achieving this target, however, seems bleak as regular outbreaks continue to
occur. Data from these outbreaks are useful for pursu- ing important questions about measles
dynamics and control. This thesis is structured to investigate two questions: the first is on how
well the time series susceptible-infected- recovered (TSIR) model and removal method perform when
they are used to estimate parameters from poor quality data on measles epidemics. We simulate
stochastic epidemics for four spatial patches, resembling data that are collected in low-income
coun- tries where resources are limited for properly collecting and reporting data on measles
epidemics. We then obtain from the simulated data sets, the size of the initial susceptible
population S0, and the basic reproductive ratio R0 - for the TSIR; and S0, and either the effective
reproduction number Re f f , or the basic reproductive ratio R0 - for the re- moval method,
depending on the simulation assumptions. To assess performance, we quantify the biases that result
when we tweak some of the simulation assumptions and modify the data to ensure it is in a form
usable for each of the two methods. We find that
the performance of the methods depends on the assumptions underlying the data gen-
eration process, the degree of spatial aggregation, the chosen method of modifying the data to put
it in a form usable for the estimation method, and the parameter being fitted. The removal method
S0 estimates at the patch level are almost unbiased when the pop- ulation is naive, but are biased
when aggregated to the population level, whether the population is initially naive or not.
Furthermore, the removal R0 and Re f f estimates are generally biased. The TSIR model, on the other
hand, seems more robust in estimating both S0 and R0 for non-naive populations. These findings are
useful because they give us an idea of the biases in the fits of these methods to actual data of
the same nature as the simulated epidemics.
For the second question, we assess the impact of an outbreak response vaccination campaign which
was organised in reaction to a measles outbreak in an all-boys high school in Stellenbosch, South
Africa. We achieve this by formulating a discrete stochastic
susceptible-exposed-infected-recovered (SEIR) model with daily time-steps, ignoring births and
deaths. Using the model, we analyse multiple scenarios that allow us to estimate the cases
averted, and to predict the cases remaining until the epidemic ended, and the time frame within
which those cases would occur. Summarizing across scenarios, we estimate that a median of 255 cases
(range 60 − 493) were averted. Also, a median of 15 remaining cases (range 1 − 33), and a median of
4 remaining weeks (range 1 − 16) were expected until the epidemic ended. We conclude that the
campaign was successful
in averting many potential cases.AFRIKAANSE OPSOMMING : Masels is hoogs oordraagbaar, en is ‘n leidende oorsaak van entstof-voorkombare sterftes
onder kinders. Gevolglik word dit beskou as ‘n wêreldwy openbare gesondheidskwessie
en word daar beoog om teen 2020 die virus in 5 uit die 6 WHO-streke te elimineer,
met uitsondering die WGO-Afrika-streek. Die kans om hierdie teiken te bereik,
lyk egter skraal aangesien gereelde uitbrake steeds voorkom. Data van hierdie
uitbrake is nuttig om belangrike vrae oor masels-dinamika en beheer te ondersoek.
Hierdie proefskrif ondersoek twee vrae. Die eerste is hoe goed die tydreeks vatbaaraansteeklik-herstel
(TSIR) model en die verwyderings metode presteer wanneer dit gebruik
word om parameters met behulp van data van swak gehalte oor maselsepidemies
te skat. Ons simuleer stogastiese epidemies vir vier areas, wat ooreenstem met data
wat in lae-inkomste lande versamel word, waar hulpbronne vir die behoorlike versameling
en rapportering van data oor maselsepidemies beperk is. Ons kry dan uit die
gesimuleerde datastelle, die grootte van die aanvanklike vatbare populasie S0, en die
basiese reproduktiewe verhouding R0 - vir die TSIR; en S0, en óf die effektiewe reproduktiewe
getal Re f f , of die basiese reproduktiewe verhouding R0 - vir die verwydering
metode, afhangende van die simulasie aannames. Om prestasie te evalueer, bereken
ons die sydigheid wat ontstaan as ons sommige van die simulasie aannames verander of die data verander word om te verseker dat dit in ‘n vorm is wat bruikbaar is vir
elk van die twee metodes. Ons vind dat die prestasie van die metodes afhang van die
aannames wat die aan data-genereringsproses onderliggend is, die mate van ruimtelike
samestelling, die gekose metode om die data te verander om dit in ‘n bruikbare vorm
te kry vir die skattingsmetode en die parameter wat gepas word. Die S0 beraam deur
die verwydering metode op area vlak is byna onsydig wanneer die bevolking naïef is,
maar sydig wanneer dit op die bevolkingsvlak geag word, of die bevolking aanvanklik
naïef is of nie. Verder is die verwyderings metode R0 en Re f f ramings oor die algemeen
sydig. Die TSIR-model, aan die ander kant, lyk beter om beide S0 en R0 vir
nie-naïewe bevolkings te beraam. Hierdie bevindings is nuttig omdat hulle ons ’n idee
gee van die sydighede in die pas van hierdie metodes tot werklike data van dieselfde
aard as die gesimuleerde epidemies. Vir die tweede vraag, beraam ons die impak van ‘n
uitbraakrespons-inentingsveldtog wat georganiseer is in reaksie op ‘n maselsuitbraak
in ‘n hoörskool in Stellenbosch, Suid-Afrika. Ons bereik dit deur ‘n diskrete stogastiese
vatbaar-blootgestel-aansteeklik-herstel (SEIR) model met daaglikse tydstappe te
formuleer, wat geboortes en sterftes ignoreer. Deur die model te gebruik, analiseer ons
verskeie scenario’s wat ons toelaat om die aantal afgeweerde gevalle te skat, en om die
oorblywende aantal gevalle te tot die epidemie geëindig het te skat en die tydsraamwerk
waarbinne sulke gevalle sou plaasvind. Opsommend oor scenario’s, skat ons dat
‘n mediaan van 255 gevalle (omvang 60 - 493) afgeweer is. Daar is ook ’n mediaan van
15 oorblywende gevalle (omvang 1 − 33) en ‘n mediaan van 4 oorblywende weke (omvang
1 − 16) verwag totdat die epidemie geëindig het. Ons kom tot die gevolgtrekking
dat die veldtog suksesvol was om baie potensiële gevalle te voorkom
Dispelling the Myths Behind First-author Citation Counts
Full text linkWe conducted a full-scale evaluative citation analysis study of scholars in the XML research field to explore just how different from each other author rankings resulting from different citation counting methods actually are, and to demonstrate the capability of emerging data and tools on the Web in supporting more realistic citation counting methods. Our results contest some common arguments for the continued
use of first-author citation counts in the evaluation of scholars, such as high correlations between author rankings by first-author citation counts and other citation
counting methods, and high costs of using more realistic citation counting methods that are not well-supported by the ISI databases. It is argued that increasingly available digital full text research papers make it possible for citation analysis studies to go beyond what the ISI databases have directly supported and to employ more
sophisticated methods
koamabayili/VECTRON-author-checklist: VECTRON author checklist
No full textWe have done our best to complete the author checklist relating to the use of animals in the hut study. Note that the objective for the hut study was to evaluate the IRS treatment applications for residual efficacy against Anopheles mosquitoes, including the local An. coluzzii mosquito population. Cows were only used to attract mosquitoes into the huts and no tests were carried out directly on the cows. The author checklist is intended for use with studies where experiments are carried out on animals, which is why we have had such difficulty in completing this for the hut study, as many of the questions do not relate to how the cows were used
Author-wise bibliometric analysis based on entropy.
No full textAuthor-wise bibliometric analysis based on entropy.</p
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