1,721,007 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
Investigation into the microbial ecology and persistence of soil taxa through trace-gas oxidation in Tongariro National Park
Get PDFCultivation-dependent and metagenomic surveys of bare, volcanic and hyperarid oligotrophic ecosystems have revealed surprisingly diverse microbial communities¹⁻⁴. The richness of Mt. Tongariro soil communities is surprising considering the extreme environmental parameters. Given that soil moisture on Mt. Tongariro is highly variable dependent on season, and both phototrophic Cyanobacteria and trace gas oxidising taxa from the phyla Actinobacteria, WPS-2 and AD3 are detected in these soils, it is postulated that these taxa alternate as the primary producers in these oligotrophic soils. In this scenario, cyanobacteria are the phototrophic backbone and trace-gas oxidisers use atmospheric trace gases (H₂, CO) as supplemental cell energy for mixotrophic metabolism to persist. Mt. Tongariro soil communities were shown to encode high affinity hydrogenases and carbon monoxide dehydrogenases, which are necessary for atmospheric oxidation of H₂ and CO. This thesis details the microbial ecology and effect of physicochemistry on the alpha and beta diversity of Mt. Tongariro soils. It also addresses microbial persistence by the use oxidation of trace gases H₂ and CO at 4 °C and 60 °C for the South, Red and Central Craters of Mt. Tongariro on the southernmost point of the Taupo Volcanic Centre (TVZ), and control soils from White Island (Whakaari), Mt. Urchin and Mt. Sugarloaf. This preliminary study uncovers the microbial ecology of Mt. Tongariro and other bare, high elevation control soils from around New Zealand. Although, more extensive testing is required such as testing isolated Mt. Tongariro strains to understand whether the thermophilic taxa present are capable of oxidising trace gas, or whether they harbour low affinity enzymes suited to elevated levels of CO and H₂. This study indicates that trace gas oxidation may be an important mechanism for persistence or a dependable source of supplemental energy to specific mixotrophic trace-gas oxidising taxa in all communities from bare, oligotrophic systems
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
Microbial biogeography of 1,000 geothermal springs: spatial, temporal, and allopatric dynamics of extremophiles in the Taupō Volcanic Zone, Aotearoa-New Zealand
Get PDFGeothermal springs are model ecosystems to investigate microbial biogeography as they represent discrete, relatively homogeneous habitats, are distributed across multiple geographical scales, and span broad geochemical gradients. This thesis reports the largest consolidated study of geothermal ecosystems to determine causal factors that influence both spatial and temporal biogeographical patterns of extremophiles. Bacterial and archaeal community composition, 46 physicochemical parameters, and metadata from 925 geothermal spring water columns across the Taupō Volcanic Zone (TVZ), Aotearoa-New Zealand were measured. Standardised methodologies were employed to define microbial diversity via 16S rRNA gene amplicon sequencing, and associated physicochemistry, ensuring confidence in sample comparison. Over an 8,000 km² spatial scale, multivariate statistical analyses determined diversity was primarily influenced by pH at temperatures 70 °C. Further, community dissimilarity increased with increasing geographic distance across the region, highlighting niche selection driving assembly at a local scale.
This research also describes the first comprehensive temporal study of geothermal microbial communities in Aotearoa-New Zealand. One hundred and fifteen water column samples from 31 geothermal features were taken over a 34-month period to ascertain microbial community stability, community response to both natural and anthropogenic disturbances in the local environment, and temporal variation in spring diversity across the pH range found in the TVZ. Results indicated temperature and associated groundwater physicochemistry were the most likely parameters to vary stochastically in these geothermal features, with community abundances rather than composition more readily affected by a changing environment. However, variation in pH (pH ±1) had a more significant effect on community structure than temperature (±20 °C), with alpha diversity failing to be an adequate measure of temporal microbial disparity in geothermal features outside of circumneutral conditions. While a substantial physicochemical disturbance was required to shift community structures at the phylum level, geothermal ecosystems were resilient at this broad taxonomic rank and returned to a pre-disturbed state if environmental conditions re-established.
The discovery that genus (phylum Aquificota) exhibited the greatest average abundance (11.2 %) and distribution (74.2 %) of all taxa across 925 geothermal ecosystems in the TVZ, and an apparent absence of this taxon in global geothermal systems, led to the hypothesis that allopatric speciation enabled the evolution of an endemic bacterial genus to Aotearoa-New Zealand. Maximal read abundance of occurred in geothermal features with pH 4-6, 50-70 °C, and low oxidation-reduction potentials, highlighting a specific environmental niche that could enhance habitat isolation. Genomic analysis of the only characterised species for the genus, CP.B2ᵀ, confirmed a chemolithoautotrophic metabolism dependent on hydrogen oxidation. While similarity between populations illustrated dispersal was not limited across the TVZ, extensive amplicon, metagenomic, and phylogenomic analyses of local and global microbial communities from DNA sequence databases indicated is geographically restricted to the Aotearoa-New Zealand archipelago. It was concluded that combined geographical and physicochemical constraints prevent this taxon from distributing on a broader scale, resulting in the establishment of an endemic bacterial genus.
Collectively, the findings from this thesis provide an insight into ecological behaviour in geothermal springs, highlighting the diverse controls between different taxa within the same habitat-type, and expand understanding of microbial biogeography in extreme ecosystems
The physiological characterisation of a novel Thermomicrobia strain WKT50.2, and a review of the characteristics of the class Thermomicrobia
Get PDFThermomicrobia is a class of heterotrophic, obligate aerobes within the phylum Chloroflexi. At the time of writing, it contained four distinct species, Thermomicrobium roseum, Sphaerobacter thermophilus, Nitrolancetus hollandicus and WKT50.2, the novel strain described in this study. The physiology and ecology of this strain, and the description of the class Thermomicrobia was investigated as part of this study.
Strain WKT50.2 was isolated from the hot springs at Waikite, New Zealand. We investigated temperature and pH range and optima, analysed PLFA, and determined preferred carbon and energy sources, N-fixation, modes of growth and antibiotic sensitivity. As a general phenotype, WKT50.2 is a heterotrophic and thermophilic obligate aerobe with a preference for moderately alkaliphilic pH conditions. The possible ecology of WKT50.2 was discussed.
WKT50.2 was able to oxidise methane to gain energy. This was an unexpected result as methanotrophy is a highly specialised phenotype restricted to the phyla Proteobacteria and Verrucomicrobia. Methanotrophs also tend to be metabolic specialists with no capability to oxidise substrates other than C1 compounds. In contrast, WKT50.2 was also able to oxidise ammonia and nitrite, along with a range of saccharides and protein rich substrates. WKT50.2 was sensitive to most of the antibiotics tested in this study, but metronidazole and trimethoprim both stimulated growth in a dosage-dependent manner. WKT50.2 is clearly a distinct genus from T. roseum and S. thermophilus, based on 16S rRNA gene sequence similarities (91 % and 88 % respectively), G+C content and metabolic capabilities.
T. roseum and S. thermophilus were confirmed as heterotrophic, thermophilic, moderately alkaliphilic, obligate aerobes. The temperature and pH optima and ranges for T. roseum and S. thermophilus were amended, along with expanding the known metabolic capabilities of both species. Of particular note was the discovery that both T. roseum and S. thermophilus were also able to oxidise both methane and ammonia for energy, and that both species possessed cellulolytic activity.
In summary, the class Thermomicrobia can be redefined as comprising obligately aerobic, facultative heterotrophs. Cells are non-motile, non-spore forming rods. This study has shown that the cells have proteinaceous cell walls containing ornithine, and no lipopolysaccharide. The major fatty acid is 12-Me-18:0, and lipids include ester-linked diols. The major isoprenoid quinone is MK-8.
Several of the observations in this study merit further research. The discovery of methanotrophy in this class was unexpected and significant, and future work should include the identification of the enzymes involved in methanotrophy, and those involved in the oxidation of ammonia for energy. The mechanism for growth stimulation of WKT50.2 and T. roseum by antibiotics was also an interesting observation and warrants further analysis to determine the mode of action
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