1,721,062 research outputs found
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
Phytogeography and conservation of neotropical dry forest with emphasis on Columbia
Full text linkDry forest is one of the most threatened tropical forests in the world. Human impact
has caused its massive transformation but conservation of dry forest has often been
neglected across Latin America. In Colombia, less than 10% of the original extension
of dry forest remains. This thesis studies the phytogeography of neotropical dry forest
and its relevance for conservation using data from 1602 tree species inventories made
in dry forests across Latin America and the Caribbean synthesised by The Latin
American Seasonally Dry Tropical Forest Floristic Network (DRYFLOR). Clustering
and ordination analyses were used to explore the floristic relationships of dry forest
across the entire Neotropics, revealing distinctive regional clusters defined by their
tree species composition. Colombian dry forests are shown to be part of two wider
clusters, one including neighbouring forests in Venezuela and southern Central
America, and the second including the inter-Andean dry forests. The high turnover of
floristic diversity and endemism within and amongst the main floristic groups
demonstrates that to conserve the full species diversity in dry forests across Latin
America and the Caribbean will require protecting it simultaneously across multiple
regions.
A regionally focused study of floristic relationships in the Central American and
northern South American dry tropical forest group, using quantitative approaches to
conservation prioritization, including a new Conservation Priority Index (CPI),
suggests that conservation priority should be placed on the South American
Caribbean Coast in the cross-border area of Colombia and Venezuela. This
emphasises the need for a biogeographical approach to conservation that cannot be
restricted by political borders. Within Colombia, new quantitative floristic data were
used to investigate controls of floristic composition in dry forests. Multivariate
analyses showed that space related variables explain a larger fraction of the variance
of the floristic composition than climatic or edaphic variables. The importance of
spatial variables implies that biogeography is a key element in understanding the
structure of communities, and that the Andean cordilleras might be acting as
geographical barriers isolating these seasonally dry formations.
The value of floristic inventory data for assessing the conservation status of tree
species using IUCN criteria was assessed in a case of study of the Andean Piedmont
dry forest. By combining inventory data from the DRYFLOR database and herbarium
records, the number of species for which we have sufficient information to make
conservation assessments increases by 16% and the accuracy of predictive species
distribution improves for 84% of the species. Together, these results reveal the
importance of ecological inventory data as a complementary data source in
conservation assessment for dry forest trees in the Neotropics.
Finally, the conclusions chapter places these results in the context of conservation
planning for Colombian dry forests, including some suggestions for research, policies
and actions. These actions include restoration programmes focusing on sustainable
harvesting of native dry forest tree species, for example for firewood and other forest
resources such as fruits, fibres and medicines. A land use mosaic, including forest
fallows and strict conservation areas, may help to guarantee the long-term
maintenance dry forest species in Colombia
Integrating molecular biogeography and community ecology to understand the evolution of habitat specialization in Amazonian forests
Full text linkI investigated the origin of western Amazonian white-sand vegetation and the
evolution of plant habitat specialization to different edaphic conditions in
Neotropical lowland forests. In order to address these goals I used complementary
ecological as well as molecular phylogenetic approaches. Amazonian white-sand
forests harbour a flora specialized to nutrient-poor sandy soils, which is distributed as
habitat-islands across the Amazon and Guiana Shield regions. This flora has been
suggested to have many local and regional endemics, therefore making an important
contribution to overall Neotropical plant diversity. The role of habitat specialization
in the origin of this flora and its relationships with other floras within the Amazon-
Guiana regions is not well understood. To shed light onto these questions, this thesis
studies the floristic composition of these forests as well as molecular phylogenetic
patterns of selected plant lineages containing white-sand species. The floristic study
focused on the white-sand forests of the western Amazon region, which contained
1180 species of vascular plants whereas the non-white-sand Amazon and Guiana
Shield dataset consisted of 26,887 vascular plant species. 77% of these species
occurred outside white-sand habitats, in other habitat types of the Amazon region,
while 23% were white-sand specialists. This demonstrates lower endemism in
western Amazonian white-sand forests than previously estimated. 88% of the total
westen Amazon white-sand specialist occur within the limits of the Guiana Shield
region with the remaining 12% being endemics to the white-sand forests of the
western Amazon. Within the Guiana-Shield region, Caquetá Moist Forests (56%),
Guayanan Highlands (55%), and Negro-Branco Moist Forests (53%) were the
biogeographic regions with the highest proportions of western Amazonian whitesand
specialists. Cluster analysis of province level floristic checklists across the
Amazon and Guiana regions showed that western Amazonian white-sand forests are
nested within floras of the western Guiana-Shield region compared to other floras in
the Amazon. Molecular phylogenetic analyses were carried out for the widespread
and species-rich families Sapotaceae and Chrysobalanaceae, which display an
uneven number of white-sand specialists. Sapotaceae had only three white-sand
specialists but Chrysobalanaceae had a larger number of white-sand specialists (14
species). Phylogenetic analysis showed that white-sand specialist species in both
studied families were scattered across the phylogenies. Both families show a marked
absence of edaphic niche conservatism, suggesting that evolutionary switching
amongst habitat types has been frequent. Ancestral state reconstruction of habitat
specialization under a maximum likelihood approach suggests that preference for
poor soils may be ancestral in these clades, especially in Chrysobalanaceae, but that
the evolution of species entirely restricted to white-sand soils is in general much
more recent and has multiple origins. For the white-sand flora of the western
Amazon in particular, there is little evidence that it comprises ancient lineages as
previously hypothesized. The historical construction of the Amazonian white sand
flora is more likely to be the result of a gradual accumulation of species with
different degrees of edaphic specialization, both by on-going speciation driven via
habitat switching from non-white-sand specialists and via regional dispersal events
after these habitats became available in regions such as the western Amazon.
Edaphic transitions between different habitat types were not evolutionary
constrained, which may have favoured edaphic niche evolution and the accumulation
of plant species diversity in Neotropical lowland forests
Phylogeny, taxonomy and biogeography of Ceiba Mill. (Malvaceae: Bombacoideae)
Full text linkThe Neotropics is the most species-rich area in the world and the mechanisms that
generated and maintain its biodiversity are still debated. This thesis contributes to the
debate by investigating the evolutionary and biogeographic history of the genus Ceiba.
Ceiba comprises 18 mostly neotropical species endemic to two major biomes, seasonally
dry tropical forests (SDTFs) and rain forests, and therefore represents an ideal case
to shed light on patterns of neotropical plant evolution and diversification. Species of
Ceiba, with their swollen, spiny trunks and large, beautiful flowers are one of the most
characteristic elements of neotropical SDTF, one of the most threatened biomes in the
tropics. Despite this, Ceiba has an historically complex taxonomy with some issues
of species delimitation unresolved, especially within a species complex (Ceiba insignis
agg.).
Initial phylogenetic analyses of DNA sequence data from the nuclear ribosomal
internal transcribed spacers (ITS) for 24 accessions representing 14 species of Ceiba
recovered the genus as monophyletic and showed geographical and ecological structure
in three main clades: (i) a humid forest lineage of three accessions of C. pentandra
sister to the remaining species; (ii) a highly supported clade composed of C. schottii
and C. aesculifolia from Central American and Mexican SDTF plus two accessions of
C. samauma from inter Andean valleys from Peru; and (iii) a highly supported South
American SDTF clade including 10 species showing little sequence variation. Within
this South American clade, no species represented by multiple accessions were resolved
as monophyletic.
To investigate unresolved species relationships further, next-generation hybrid capture
was used to sequence 377 loci for 103 accessions representing all 18 Ceiba species.
This data set was assembled using different approaches (de novo and reference mapping)
and with different software and settings to assess their impact in downstream
phylogenetic analysis. The 377 loci were concatenated and analysed under the maximum
likelihood framework treated as a single partition. The well resolved and sampled
NGS phylogenies showed a similar pattern of geographical and ecological structure
as inferred using ITS. The genus Neobuchia was recovered within the SDTF Central
American and Mexican clade, and should therefore be incorporated within Ceiba. In
the South American SDTF clade, there were multiple examples where a monophyletic
group recognised as a taxonomic species was nested within another, paraphyletic taxonomic
species, which suggests recent, ancestor-descendent species relationships. Within
this clade, individual gene trees showed high conflict. Coalescent-based species delimitation
analysis and morphological data revealed no clear species boundaries between
C. pubiflora and C. glaziovii, and these species should be synonymised.
A subset of 111 loci was used to generate a dated phylogeny based on penalised likelihood
analysis using the fossil flower of Eriotheca prima from the middle to late Eocene
as a primary calibration. The stem node age of Ceiba was estimated as 45 Ma. The
rain forest species C. pentandra and C. samauma, and the campos rupestres species C.
jasminodora, were resolved with long stem lineages and shallow crown groups. Whilst
some SDTF species were very old (e.g., C. trischistandra) and monophyletic, many
South American SDTF species were resolved with short stem lineages and relatively
deep crown groups, possibly suggesting low rates of extinction in the large Caatinga
SDTF region. In addition, several South American SDTF species were not resolved
as monophyletic. Such results of younger, non-monophyletic SDTF species and older,
monophyletic rain forest species contrast with recent predictions that rain forest species
may, on average, have more recent origins than SDTF species and will more often be
non-monophyletic.
Ceiba has different and distinctive phylogenetic patterns that contradict recent theoretical
predictions. It demonstrates that studies of other clades sampled densely with
multiple accessions of each species using a multi-locus approach are needed if we are to
understand the nature of species and their boundaries, and the diversification process
in neotropical trees
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
- …
