1,720,979 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
Chemical and biological investigations of the Yaegl medicinal plant Alphitonia excelsa
No full textAlphitonia excelsa leaves are used by the Australian Aboriginal people of Yaegl Country for the treatment of sores, wounds and skin infections. Structural elucidation of compunds previously isolated from the n-hexane and dichloromethane sequential extracts of A. excelsa leaves identified the well-known antibacterial and antioxidant compounds β-sitosterol, betulin aldehyde, betulinic acid, lupeol, quercetin and kaempferol. This is the first report og lupeol and betulin aldehyde in any Alphitonia species and the first report of β-sitosterol in A. excelsa. LC-MS studies of over 600 column chromatography fractions obtained from previous studies did not lead to any further compounds of interest. GC-MS analysis of freshly extracted leaves identified the bioactive compounds γ-sitoserol, nonanal, n-tetracontane, docosane, 1,54-dibromotetrapentacontane, tetradecane and hexadecane from the n-hexane and dichloromethane extracts. The dichloromethane extract also showed moderate activity against antibiotic sensitive and resistant Staphylococcus aureus (MIC 312.5 - 625 μg/mL) and promising antioxidant activity, while the n-hexane extract showed moderate antibacterial activity (MIC 1250 - 2500 μg/mL). Preliminary fractionisation of the n-hexane extract provided one active fraction against S. aureus and four semi-pure fractions. This study has extended the phytochemical and biological knowledge of A. excelsa and shown that it is a worthy plant for further chemical and biological investigations
Fruit Fly Chemical Communication with Gut Bacteria
No full textRelationships between tephritids and microorganisms have been a focus of entomological research, particularly due to the potential use of microbial emissions in pest control. Symbiotic interactions between fruit flies and their associated gut bacteria have been well-studied; however, the composition of volatile chemicals from these gut bacterial emissions and their role as mediators of fruit fly behaviour is still underexplored. Here, we hypothesise that the volatile emissions from fruit flies’ gut microbionts may attract host flies. To this end, we isolated culturable bacterial species, mostly belonging to the family Enterobacteriaceae, from the midgut of the wild adult Bactrocera tryoni, one of the most damaging horticultural pests in Australia. In a screening trap assay with more than 80 isolates, both male and female adult B. tryoni were attracted to the odours emitted by most cultured isolates and a few significantly deterred adult male and female flies. Gas Chromatography–Mass Spectroscopy analyses revealed a number of microbial volatile organic chemicals (mVOCs) in the headspace of liquid cultures of isolated bacteria, including ketones, carboxylic acids, alcohols and esters. Electrophysiological assays of selected isolates with the highest attraction identified a number of chemicals that elicit olfactory responses to adult Qflies. Behavioural assay determined the attraction potential of a few chemicals among these mVOCs. This is an important step in understanding fruit fly–bacteria chemical relationships and its potential to develop attractants and potential repellents for fruit fly pest management
Olfactory relationships of <i>Bactrocera tryoni</i> fruit fly and associated microbes
No full textBactrocera tryoni, commonly known as Queensland Fruit Fly, is an economically important pest for which monitoring and management is performed using the male-specific attractant, cuelure. Studies of plant-insect-microbe interactions suggest that attraction towards the host is not only driven by plant volatile compounds but also by the microbial volatile compounds (mVOCs) from host plant/fruit-associated microbes. Insects, including B. tryoni, acquire some of these host microbes during feeding and so the bacteria present in B. tryoni guts might trigger attraction to the host via mVOCs. Although symbiotic interactions between fruit flies and their associated gut bacteria (microbionts) have been well-studied in several tephritids, including B. tryoni, the composition of volatile chemicals in these gut bacterial emissions and their role as mediators of fruit fly behaviour are little studied. To address this gap, the present study identified the mVOCs from the headspace of the culturable microbionts of wild adult B. tryoni and evaluated their effect on the electrophysiological and behavioural responses of young and mature B. tryoni.
In this study, molecular 16S rRNA sequencing identified 24 bacterial strains from wild adult male B. tryoni and 21 bacterial strains from wild female flies. The most frequent bacterial strains obtained from both male and female guts belong to Enterobactereaceae (64.25%) followed by Bacillaceae (8.25%). In trap behavioural assays, the most attractive bacteria were Bacillus anthracis, Enterobacter cloaceae, Pseudomonas aeruginosa, Bacillus sp., Pseudomonas fluorescens, Enterococcus faecalis, Citrobacter freundii and Proteus mirabilis. Young male and female flies exhibited a significantly lower response than mature male and female flies. The attraction of mature flies to different bacterial strains varied significantly and was similar for male and female flies. Gas Chromatography-Mass Spectroscopy (GCMS) analyses of these bacterial headspace extracts identified mVOCs, with a wide range of chemical classes including pyrazines, ketones, alcohols, aldehydes, and esters. Many compounds were common to all isolates with few being species-specific. Gas Chromatography coupled with Electroantennography or Electropalpography (GC-EAD/EPD) studies identified 17 electrophysiologically active volatile compounds from the extracts across all tested bacterial strains. These EAD/EPD-active compounds were ketones (octan-3-one, undecan-2-one, 1-(2-aminophenyl)ethan-1-one, and γ-tetradecalactone (5-decyldihydrofuran-2(3H)-one)), esters (ethyl octanoate, glycerol 1,2-diacetate, geranyl formate, geranyl acetate, 6-methyl-4-heptenyl pentanoate, and dodecan-5-yl acetate), alcohols (octan-1-ol, geraniol, 4-ethyl-2-methoxyphenol, and 2-methyldodecan-1-ol), isocyanide (1-isocyano-1 2-methylbenzene), aldehyde (undecanal), and phthalate acid ester (diethyl phthalate). Mature male and female B. tryoni exhibited varying attraction to these compounds in Y-maze olfactometer bioassays. The most attractive volatile for both sexes was 1-(2-aminophenyl)-ethan-1-one, followed by geranyl acetate for females and geraniol for males.
The present study also explored B. tryoni gut associated bacterial community transfer to the infested host fruits via oviposition. The bacterial isolates that were transmitted from the ovipositing B. tryoni gut to the oviposition site of host fruit (and not from the fruit surface and environment) included eleven confirmed species, with the predominant species being Enterobacter aerogenes and Klebsiella oxytoca. Behavioural assays identified B. cereus as the most attractive isolate for both male and female B. tryoni followed by E. aerogenes for male flies and E. asburiae and B. pumilus for female flies. Similar to the studies with direct gut microbionts, young flies exhibited a significantly lower response than mature flies to the gut associated bacteria transferred to the infested fruits. The attraction of mature flies to different bacterial strains varied significantly and was similar for male and female flies. GCMS analyses identified a number of mVOCs in the headspace of these bacterial liquid cultures, among which pyrazines (2,5-dimethylpyrazine, 2,5-dimethyl-3-ethylpyrazine, 2,3,5-triethylpyrazine, 2,3,5- dimethyl-3-isoamylpyrazine, and 2-ethyl-3,6-dimethylpyrazine) and ketones (octan-3-one and acetophenone) were most abundant.
Overall, this study advances understanding of Queensland fruit fly-bacteria chemical relationships and provides insights that can support development of bisexual synthetic lures as fruit fly pest management tools.</p
Chemical and biological investigations of the Yaegl medicinal plant Alphitonia excelsa
No full textTheoretical thesis.Bibliography: pages 54-63Chapter 1: Introduction -- Chapter 2: Evaluation of Previously Isolated Compounds and Fractions from Alphitonia excelsa -- Chapter 3: Chemical and Biological Investigations of A. excelsa Leaf Extracts -- Chapter 4: Experimental -- Chapter 5: Conclusion and Future Directions.Alphitonia excelsa leaves are used by the Australian Aboriginal people of Yaegl Country for the treatment of sores, wounds and skin infections. Structural elucidation of compunds previously isolated from the n-hexane and dichloromethane sequential extracts of A. excelsa leaves identified the well-known antibacterial and antioxidant compounds β-sitosterol, betulin aldehyde, betulinic acid, lupeol, quercetin and kaempferol. This is the first report og lupeol and betulin aldehyde in any Alphitonia species and the first report of β-sitosterol in A. excelsa. LC-MS studies of over 600 column chromatography fractions obtained from previous studies did not lead to any further compounds of interest. GC-MS analysis of freshly extracted leaves identified the bioactive compounds γ-sitoserol, nonanal, n-tetracontane, docosane, 1,54-dibromotetrapentacontane, tetradecane and hexadecane from the n-hexane and dichloromethane extracts. The dichloromethane extract also showed moderate activity against antibiotic sensitive and resistant Staphylococcus aureus (MIC 312.5 - 625 μg/mL) and promising antioxidant activity, while the n-hexane extract showed moderate antibacterial activity (MIC 1250 - 2500 μg/mL). Preliminary fractionisation of the n-hexane extract provided one active fraction against S. aureus and four semi-pure fractions. This study has extended the phytochemical and biological knowledge of A. excelsa and shown that it is a worthy plant for further chemical and biological investigations.xi, 73 pages illustrations 30 c
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