1,721,004 research outputs found
A comparative study of cellulase and xylanase activity\ud in freshwater crayfish and marine prawns
No full textCellulase and xylanase digestive enzyme activities were compared in four freshwater crayfish (Genus Cherax) and three marine prawn (Genus Penaeus) species.Temperature and pH profiles for cellulase (endoglucanase)were found to be very similar in all species,\ud
with maximum activity occurring at 60oC and pH 5.0.Temperature and pH profiles for xylanase (endoxylanase)were also very similar in all cray¢sh species,with maximum activity occurring at 50oC and pH 5.0. Xylanase activity was not detected in the\ud
three prawn species examined. In addition, in vitro studies showed thatmost species were able to liberate glucose from carboxymethyl cellulose, indicating that cellulose substrates can be a source of energy for both crayfish and prawn species
Habitat heterogeneity influences connectivity in a spatially structured pest population
No full text1. Patterns of connectivity influence pest population system dynamics, and it is essential to consider connectivity when planning effective management strategies. Traditional connectivity models often consider populations embedded in a matrix of unsuitable habitat. This approach is unlikely to be applicable to those pest species that can utilize most of the landscape in which they live. There is therefore a need for a simple and flexible tool to assess connectivity in such systems.\ud
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2. In this study, we developed a new model in which contiguous resource patches that differ in quality, and landscape elements that impede dispersal, impact on connectivity within a population system. The model was applied to a wild rabbit population system, a well-studied pest species in Australia. An independent population genetic data set was used to validate the model.\ud
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3. There was a highly significant association between pairwise population connectivity and the genetic data (Mantel test, r=−0·502, P= 0·002). As predicted, two populations that showed very low connectivity were strongly isolated genetically. These sites appeared to be substantially isolated because of forests, which acted to impede rabbit dispersal. When these sites were excluded from analysis, connectivity indices again explained the pattern of genetic data (Mantel test, r=−0·46, P= 0·037). This showed that both spatial variation in resource quality and forests influenced connectivity in this system. Sensitivity analyses confirmed that the distribution and extent of forests was important in limiting connectivity to some sites. The model was relatively robust to changes in population parameters.\ud
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4. Synthesis and applications. Connectivity among wild rabbit populations in this system was strongly influenced by habitat heterogeneity, rather than factors such as geographical distance or major landscape elements such as rivers, both of which are traditionally considered to influence system dynamics. This may have substantial implications for many pest systems, and suggests that the impact of habitat heterogeneity on connectivity should be considered when planning efficient management strategies
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
Comparative analysis of gill transcriptomes of two freshwater crayfish, Cherax cainii and C. destructor
No full textWe undertook deep sequencing of gill transcriptomes from two freshwater crayfish, Cherax cainii and Cherax destructor, in order to generate genomic resources for future genomics research. Over 83 and 100 million high quality (quality score (Q) ≥ 30) paired-end Illumina reads (150 bp) were assembled into 147,101 and 136,622 contigs in C. cainii and C. destructor, respectively. A total of 24,630 and 23,623 contigs received significant BLASTx hits and allowed the identification of multiple gill expressed candidate genes associated with pH and salinity balance. These functionally annotated transcripts will provide a resource to facilitate comparative genomic research in the genus Cherax, and in particular allow insights into respiratory and osmoregulatory physiology of this group of animals
Structure and Function of a Cellulase Gene in Redclaw Crayfish, Cherax Quadricarinatus
No full textThe most abundant organic compound produced by plants is cellulose; however, it has long been accepted that most animals do not produce endogenous enzymes required for its degradation, but rely instead on symbiotic relationships with microbes that produce the necessary enzymes. Here, we present the genomic organisation of an endogenous glycosyl hydrolase family (GHF) 9 gene in redclaw crayfish (Cherax quadricarinatus), consolidated from a cDNA sequence determined by Byrne et al. [Gene 239 (1999) 317–324.]. Comparison with several other invertebrate GHF9 genes reveals the conservation of both intron position/phase and splice sequence, which adds support to an argument for an ancestral animal cellulase gene. Furthermore, two introns in plant GHF9 genes are also identical in position, implying a more ancient origin for this class of animal cellulase.\ud
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Protein purification from redclaw gastric fluid via fast performance liquid chromatography (FPLC) indicated the presence of two endoglucanase enzymes. The molecular weights of these components were determined by matrix-assisted laser desorption/ionisation—time-of-flight (MALDI-TOF) to be 47,887 Da (Cel1) and 50,295 Da (Cel2). Cel1 is possibly the functional product of the described cellulase gene, with N-terminal amino acid residues identical to the translated amino acid sequence from the corresponding gene region. Cel2 was identical to Cel1 for 7 of 11 N-terminal residues and likely to be the product of a paralogous endoglucanase gene. These results suggest that redclaw crayfish possess at least one and possibly two functional, endoglucanase enzymes, although further work is required to confirm their origin and attributes
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