177,622 research outputs found
Prioritizing the risk of plant pests by clustering methods : self-organising maps, k-means and hierarchical clustering
No full textFor greater preparedness, pest risk assessors are required to prioritise long lists of pest species with potential to establish and cause significant impact in an endangered area. Such prioritization is often qualitative, subjective, and sometimes biased, relying mostly on expert and stakeholder consultation. In recent years, cluster based analyses have been used to investigate regional pest species assemblages or pest profiles to indicate the risk of new organism establishment. Such an approach is based on the premise that the cooccurrence of well-known global invasive pest species in a region is not random, and that the pest species profile or assemblage integrates complex functional relationships that are difficult to tease apart. In other words, the assemblage can help identify and prioritise species that pose a threat in a target region. A computational intelligence method called a Kohonen self-organizing map (SOM), a type of artificial neural network, was the first clustering method applied to analyse assemblages of invasive pests. The SOM is a well known dimension reduction and visualization method especially useful for high dimensional data that more conventional clustering methods may not analyse suitably. Like all clustering algorithms, the SOM can give details of clusters that identify regions with similar pest assemblages, possible donor and recipient regions. More important, however SOM connection weights that result from the analysis can be used to rank the strength of association of each species within each regional assemblage. Species with high weights that are not already established in the target region are identified as high risk. However, the SOM analysis is only the first step in a process to assess risk to be used alongside or incorporated within other measures. Here we illustrate the application of SOM analyses in a range of contexts in invasive species risk assessment, and discuss other clustering methods such as k-means, hierarchical clustering and the incorporation of the SOM analysis into criteria based approaches to assess pest risk
Determining factors that influence the dispersal of a pelagic species: A comparison between artificial neural networks and evolutionary algorithms
No full textD.R. Pontin, S. Schliebs, S.P. Worner, M.J. Watt
Analysis of progeny testing of Al-boars in TOP-Genetic programmes
No full textA total of 9 data sets from so called TOP-Genetic programmes were analysed. Three of these data sets were suitable for a genetic analysis because the sex code of all animals with net daily gain, FOM meat percentage, carcass weight and muscle depth and backfat were available. Concerning the distribution of boars over herd-season classes all data sets show a good structure. For all traits, except for net daily gain, large differences between castrates and sows were observed, which were very similar over all data sets. The carcass weight showed a significant effect on muscle depth and on backfat. Because of very similar regression coefficients for all data sets, a preadjustment of these traits on a constant carcass weight seems to be feasible. Between the different lines there are differences especially for the genetic correlation between net daily gain and FOM meat percentage observed, which leads to the conclusion to use different parameters for lines. Between FOM meat percentage and backfat for all lines a very high genetic correlation is estimated, so an additional use of backfat in the model is not of great value. Between FOM meat percentage and muscle depth a medium genetic correlation is estimated for all data sets. Although there are high sexual differences observed the omission of the sex in the model has no influence on the ranking of boars for this data structure. As a minimum requirement for TOP-Genetic programmes each boar should be mated to 8 to 10 sows to guarantee an adequate accuracy of breeding values and a good distribution of boars over herd-season classes. The access of the sex of all animals should be aimed at to avoid biased breeding values in case of unbalanced sex ratios for boars
Magma chamber evolution prior to the Campanian Ignimbrite and Neapolitan Yellow Tuff eruptions (Campi Flegrei, Italy).
No full textUsing time lagged input data to improve prediction of stinging jellyfish occurrence at New Zealand beaches by multi-layer perceptrons
No full textEnvironmental changes in oceanic conditions have the potential to cause jellyfish populations to rapidly expand leading to ecosystem level repercussions. To predict potential changes it is necessary to understand how such populations are influenced by oceanographic conditions. Data recording the presence or absence of jellyfish of the genus Physalia at beaches in the West Auckland region of New Zealand were modelled using Multi-Layer Perceptrons (MLP) with time lagged oceanographic data as input data. Results showed that MLP models were able to generalise well based on Kappa statistics and gave good predictions of the presence or absence of Physalia. Moreover, an analysis of the network contributions indicated an interaction between wave and wind variables at different time intervals can promote or inhibit the occurrence of Physalia.David R. Pontin, Sue P. Worner and Michael Wattshttp://dl.acm.org/citation.cfm?id=181360
Synkinematic emplacement of granitoids in a Pan-African shear zone in Central Cameroon
No full textThe magmatic complex of Koala area that is part of the central Domain of the North Equatorial fold belt outcrops within the Central Cameroon Shear zone (CCSZ). This complex comprises four plutonic groups of rocks: (i) monzodiorites, (ii) quartz-monzodiorites, (iii) quartz-monzonites and (iv) granites. The elongate shape of the plutons, variable orthogneissification and foliation strikes parallel to the CCSZ point to syntectonic, magma emplacement. The rocks are metaluminous, high-K, and calc-alkaline to shoshonitic ferro-potassic, with mineralogical and geochemical characteristics of I-type granitoids. The plutonic rocks are characterised by high Sr, moderate Sigma REE concentrations and low Ni and Cr contents. They also display chondrite-normalised REE patterns characterised by variable LREE enrichment, moderate to minor HREE fractionation with moderate negative Eu anomalies (Eu/Eu : 0.66-0.93 (quartz-monzonites), 0.17-0.96 (quartz-monzodiorites), 0.76-0.93 (monzodiorites)) and significant positive Eu anomalies (1.27-5.2 (granites)). Trace element distribution patterns show that all these rocks are distinctively depleted in Th, Nb, Ba, Ti and Ta relative to other trace elements and are enriched in LILE compared to HFSE. Each plutonic group shows distinct evolutionary trends and the geochemical data indicate that the groups were derived from different crustal protoliths. The source materials for the four plutonic groups were similar and possibly included amphibolitised high-K calc-alkaline basaltic andesites. The plutonic rocks of Koata area resemble other Neoproterozoic high-K calc-alkaline syntectonic plutons in western Cameroon. They also display strong similarities with high-K calc-alkaline plutons of the Pernambuco shear zone in NE Brazil. (c) 200.6 Elsevier Ltd. All rights reserved
Appropriate Similarity Measures for Author Cocitation Analysis
No full textWe 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
"Closing the R&D Gap, Evaluating the Sources of R&D Spending"
No full textBoth spending and tax policies have been implemented in the United States with the goal of stimulating private sector research and development (R&D). Karier questions whether current R&D policy, especially the research and experimentation tax credit, can contribute to closing the gap between nondefense expenditures on R&D in the United States and such expenditures in other countries, such as Japan and Germany. He also explores possible changes to our current R&D policy to make it more effective.
Going Beyond Counting First Authors in Author Co-citation Analysis
No full textThe 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
Tryptophan insertion mutagenesis of liver fatty acid-binding protein Acid-binding Protein
No full textLiver fatty acid-binding protein (FABP) binds a variety of non-polar anionic ligands including fatty acids, fatty acyl CoAs, and bile acids. Previously we prepared charge reversal mutants and demonstrated the importance of lysine residues within the portal region in ligand and membrane binding. We have now prepared several tryptophan-containing mutants within the portal region, and one tryptophan at position 28 (I.28W) has proved remarkably effective as an intrinsic probe to further study ligand binding. The fluorescence of the L28W mutant was very sensitive to fatty acid and bile acid binding where a large (up to 4-fold) fluorescence enhancement was obtained. In contrast, the binding of oleoyl CoA reduced tryptophan fluorescence. Positive cooperativity for fatty acid binding was observed while detailed information on the orientation of binding of bile acid derivatives was obtained. The ability of bound oleoyl CoA to reduce the fluorescence of L28W provided an opportunity to demonstrate that fatty acyl CoAs can compete with fatty acids for binding to liver FABP under physiological conditions, further highlighting the role of fatty acyl CoAs in modulating FABP function in the cell
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