1,721,015 research outputs found
Supplementary material from "The relationship between telomere length and mortality risk in non-model vertebrate systems: a meta-analysis"
No full textTelomere length (TL) has become a biomarker of increasing interest within ecology and evolutionary biology, and has been found to predict subsequent survival in some recent avian studies but not others. Here, we undertake the first formal meta-analysis to test whether there is an overall association between TL and subsequent mortality risk in vertebrates other than humans and model laboratory rodents. We identified 27 suitable studies and obtained standardized estimates of the hazard ratio associated with TL from each. We performed a meta-analysis on these estimates and found an overall significant negative association implying that short telomeres are associated with increased mortality risk, which was robust to evident publication bias. While we found that heterogeneity in the hazard ratios was not explained by sex, follow-up period, maximum lifespan or the age group of the study animals, the TL–mortality risk association was stronger in studies using qPCR compared to terminal restriction fragment methodologies. Our results provide support for a consistent association between short telomeres and increased mortality risk in birds, but also highlight the need for more research into non-avian vertebrates and the reasons why different telomere measurement methods may yield different results.This article is part of the theme issue ‘Understanding diversity in telomere dynamics’.Wilbourn, Rachael V.; Moatt, Joshua P.; Froy, Hannah; A. Walling, Craig; H. Nussey, Daniel; Boonekamp, Jelle J. (2017): Supplementary material from "The relationship between telomere length and mortality risk in non-model vertebrate systems: a meta-analysis". The Royal Society. https://dx.doi.org/10.6084/m9.figshare.c.394252
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
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
Ecology of ageing in albatrosses
No full textAge-related variation in demographic rates has significant consequences for population and
evolutionary dynamics, and understanding the processes driving such variation is therefore an
important aspect of evolutionary ecology. Reproductive performance may vary over the lifetime
of an individual, and this may be the result of both variations in reproductive effort and changes
in individual competency. For example, increasing experience is likely to have beneficial effects
on reproduction during early life, and senescence, or declines in physiological function, may
have negative impacts on the performance of older individuals. The rate at which these changes
occur can vary dramatically between species, and even between individuals of the same species.
However, understanding the causes and consequences of this variation in the rate of ageing is not
always straightforward. As well as the individual-level processes described, the phenotypic
composition of successive age classes will contribute to age-related variation observed at the
population level. Abrupt changes in performance, such as the poor performance of first time
breeders, may be obscured if individuals vary in their age at first reproduction. Population-level
patterns may also be influenced by selection; for example, the selective disappearance of low
quality individuals from older age classes may mask senescent declines in the performance of
longer-lived individuals. Moreover, the physiological mechanisms that underpin within-individual
changes in performance are not well understood. Unravelling the drivers of such age-related
variation requires longitudinal data, following individuals throughout their lives, which
presents challenges for the study of natural populations.
Albatrosses are among the longest lived vertebrates. In this thesis, I use data from three species
of albatross breeding at Bird Island, South Georgia (54°00’S, 38°03’W) to explore age-related
variation. Focusing primarily on the wandering albatross, Diomedea exulans, I characterise the
relationship between age and various reproductive traits, and decompose the population-level
patterns to reveal effects of experience, senescence and terminal effects across the reproductive
lifespan of individuals. I then consider foraging behaviour as a proximate driver of changes in
reproductive performance in this species. Using tracking data collected over a 20 year period, I
find limited evidence for age-related variation in foraging trips taken throughout the breeding
cycle. Going one step further, I explore telomere dynamics in the wandering albatross,
examining the potential for telomere length to act as a physiological marker of individual state.
Finally, I move on to a species comparison, incorporating data from the black-browed
(Thalassarche melanophris) and grey-headed albatross (Thalassarche chrysostoma). I compare
the population- and individual-level ageing patterns of these three closely related species, and
consider these in light of their differing life history strategies
The evolutionary ecology of ageing in a wild Soay sheep population
Full text linkSenescence, declining physiological function resulting in reduced survival and fertility with increasing age is a widely observed natural phenomena. Many studies of senescence in natural populations have found actuarial and reproductive senescence in wild vertebrates. More recently, evidence of ageing in diverse phenotypic traits has been reported. This has revealed the complex nature of senescence with huge variation in ageing patterns across vital rates and phenotypic traits within a population. Understanding how variation in ageing patterns is generated and maintained is important to understand the evolution of senescence in the wild. Many factors are likely to contribute to variation in ageing patterns observed in the wild and recent studies have highlighted the role of some processes such as – a) tradeoffs between life-history traits underpinning ageing and how molecular markers may behave as a mediator of these tradeoffs; b) the influence of parental age on offspring performance and ageing; c) the role of potential declines in selection with increasing age driving the ageing process across phenotypes in the wild. In this thesis, I set out to investigate some of the proximate and ultimate drivers of variation in senescence in a natural Soay sheep population. In Chapters 2 and 3, I examined the role of a molecular marker, telomere length in mediating tradeoffs between different life-history traits by investigating whether costs of maternal reproductive investment, infection and immunity influence TL. In Chapter 4, I investigated the short- and long-term impact of parental age effects on offspring traits examining the effect of both maternal and paternal age on four offspring traits – a) first-year survival, b) offspring adult lifespan, c) offspring lifetime breeding success and d) offspring lifetime recruitment success. In Chapter 5, I jointly developed evolutionary theory to explain variation in ageing patterns across phenotypic traits within a population (also known as asynchronous ageing) and proposed a methodological framework to estimate age-specific phenotypic selection in natural populations. In Chapter 6, I implemented the methods outlined in Chapter 5 to estimate age-dependent phenotypic selection across six traits in female Soay sheep
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
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