1,721,033 research outputs found
Going Beyond Counting First Authors in Author Co-citation Analysis
Get PDFThe 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
Get PDF“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
Get PDFWe 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
Get PDFWe 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
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Benthic microbial mat adaptations to nutrient scarcity and nutrient cycling dynamics in oligotrophic, perennially ice-covered Lake Vanda and Lake Fryxell in the McMurdo Dry Valleys, Antarctica
Get PDFThe primary productivity of all ecosystems is linked to biogeochemical cycles and is often limited by nutrient availability. These links and interactions result in feedback loops, where changes in biogeochemical cycling dynamics and ecosystem dynamics can profoundly influence each other. In lacustrine environments, the availability of either nitrogen or phosphorus can be limiting, as well as other environmental factors such as light availability. The McMurdo Dry Valleys are the largest ice-free region in Antarctica. They receive very little precipitation, experience freezing temperatures, and frequent freeze-thaw cycles. With very little liquid water, habitat connectivity is limited, and thus, terrestrial biomass. While there are seasonal glacial meltwater streams and rivers, liquid water only persists year-round in the perennially ice-covered lakes. Fed by glacial meltwater and many occupying closed basins, these lakes exhibit interesting physical and chemical properties. The permanent ice covers offer protection from the extreme terrestrial environmental conditions, allowing the lakes to remain mostly isolated from the atmosphere, resulting in meromictic and salinity stratified water columns. Most of the lakes are home to thick, photosynthetic, benthic microbial mats. In some lakes, the primary productivity of the benthic communities is greater than the planktonic communities.Perennially ice-covered lakes Vanda and Fryxell are found in Wright and Taylor Valley, respectively. The geology and exposure age of the valleys differ, and due to the slow rates of weathering, nutrient (nitrogen and phosphorus) availability varies. The longest river in the MDVs is the Onyx River, which feeds Lake Vanda with multiple sources and sinks of nitrogen and phosphorus along it. Lake Fryxell is fed directly by the Canada and Commonwealth glaciers and several smaller ephemeral meltwater streams. Lake Vanda’s water column has a severe orthophosphate deficiency, whereas Lake Fryxell’s water column is limited in both nitrogen and phosphorus. These limitations have been characterized for the planktonic communities; however, very little research has been conducted on constraints of primary productivity by nutrients in the benthic mat communities. The benthic microbial mats accrue biomass on annual scales as laminations that can vary in community composition. Despite the nutrient-depleted water columns, microbial mats grow along both varying nutrient and light regimes in both lakes. Metagenomic surveys of the benthic communities show a metabolic adaptation to efficiently scavenge nitrogen and phosphorus from their environment and tightly recycle nutrients within the mat through a suite of organic degradation and synthesis gene pathways, the synthesis and hydrolysis of nitrogen and phosphorus storage compounds as availability varies either seasonally or within their environment. The microbial communities are likely not limited by nutrients due to these advantageous adaptations; instead, they act as a nutrient sink in their environment and are limited by other factors
Author-wise bibliometric analysis based on entropy.
No full textAuthor-wise bibliometric analysis based on entropy.</p
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Genomics of Antarctic Cyanobacteria from Lakes Fryxell and Vanda: Sulfide Tolerant Oxygenic Photosynthesis, Implications of Polar Light Cycles, and Biogeography with Large-Scale k-mer Searching
Get PDFAntarctic cyanobacteria form microbial mats in perennially ice-covered lakes in the McMurdo Dry Valleys, Antarctica. These mats demonstrate a variety of ecological and metabolic behaviors consistent with Antarctic conditions as well as specific challenges between and within the lakes. In this thesis, I explore the survival of cyanobacteria in Antarctic conditions focusing on sulfide stress, polar light availability, and their biogeographical distribution in other environments.In Lake Fryxell, Antarctica, the benthic, filamentous cyanobacterium Phormidium pseudopriestleyi creates a 1-2 mm thick layer of 50 µmol L-1 O2 in otherwise sulfidic water, demonstrating that it sustains oxygenic photosynthesis in the presence of sulfide. Sulfide inhibits oxygenic photosynthesis by blocking electron transfer between H2O and the oxygen-evolving complex in the D1 protein of Photosystem II. The ability of cyanobacteria to counter this effect has implications for understanding the productivity of benthic microbial mats in sulfidic environments throughout Earth history. A metagenome-assembled genome (MAG) of P. pseudopriestleyi indicates a genetic capacity for oxygenic photosynthesis, including multiple copies of psbA (encoding the D1 protein of Photosystem II), and anoxygenic photosynthesis with a copy of sqr (encoding the sulfide quinone reductase protein that oxidizes sulfide). The genomic content of P. pseudopriestleyi is consistent with sulfide tolerance mechanisms including increasing psbA expression or directly oxidizing sulfide with sulfide quinone reductase. However, it is unknown whether the organism can perform anoxygenic photosynthesis using sqr and PS I while PS II is sulfide-inhibited.
The seasonal light availability of polar environments has implications for the functioning of circadian clocks in Antarctic cyanobacteria. However, polar cyanobacteria are underrepresented in available genomic data, limiting opportunities to study their genetic adaptations to this and other polar challenges. Chapter 2 presents four new Antarctic cyanobacteria MAGs, bringing the total number of polar MAGs and genomes to ten. These new cyanobacteria are from microbial mats in Lake Vanda located in the McMurdo Dry Valleys in Antarctica. The four MAGs were taxonomically categorized as a Leptolyngyba, Pseudanabaena, Microcoleus, and Neosynechococcus. The sizes of these MAGs range from 2.76 Mpb – 6.07 Mbp and the bin completion ranges from 74.2% – 92.57%. Furthermore, the four novel cyanobacteria have ANIs below 90% with each other and below 77% with existing polar cyanobacteria MAGs and genomes, which demonstrates genomic diversity among polar cyanobacteria genomes. Analysis of the gene content of all ten polar cyanobacteria demonstrates that they have metabolic capacity for photosynthesis and various cold tolerance mechanisms. Standard circadian rhythm genes are present in the majority of cyanobacteria studied with the Leptolyngbya and Neosynechococcus containing kaiB3, a divergent homolog of kaiB.
Although some work has been done on the biogeography of cyanobacteria within Antarctica, the global distribution of polar cyanobacteria is not well understood. It is not known if polar cyanobacteria are specialists of their environments or opportunists that tolerate survival in the cryosphere. These questions can be addressed by identifying the distribution of Antarctic cyanobacteria across global locations, but this is logistically complicated to do using 16S amplicon sequences, which is standard for biogeography studies. However, novel sourmash MAGsearch software based on large-scale k-mer searching allows for MAGs of interest to be identified in publicly available metagenomic data. Chapter 3 used five Antarctic cyanobacteria MAGs from Lake Vanda (Microcoleus, Neosynechococcus, Leptolyngbya, and Pseudanabaena) and Lake Fryxell (P. pseudopriestleyi), as search queries. The sourmash MAGsearch revealed that the Microcoleus MAG was widely dispersed in a variety of environmental conditions, the P. pseudopriestleyi MAG was present in harsh environments, and the Neosynechococcus, Leptolyngbya, and Pseudanabaena MAGs were present in polar and a few non-polar environments. The search technique can be used to search for any organism present in metagenomes and has exciting implications for future biogeography studies
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