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Variability Present (variability + present)
Selected AbstractsInterpreting variability in global SST data using independent component analysis and principal component analysisINTERNATIONAL JOURNAL OF CLIMATOLOGY, Issue 3 2010Seth Westra Abstract Component extraction techniques are used widely in the analysis and interpretation of high-dimensional climate datasets such as global sea surface temperatures (SSTs). Principal component analysis (PCA), a frequently used component extraction technique, provides an orthogonal representation of the multivariate dataset and maximizes the variance explained by successive components. A disadvantage of PCA, however, is that the interpretability of the second and higher components may be limited. For this reason, a Varimax rotation is often applied to the PCA solution to enhance the interpretability of the components by maximizing a simple structure. An alternative rotational approach is known as independent component analysis (ICA), which finds a set of underlying ,source signals' which drive the multivariate ,mixed' dataset. Here we compare the capacity of PCA, the Varimax rotation and ICA in explaining climate variability present in globally distributed SST anomaly (SSTA) data. We find that phenomena which are global in extent, such as the global warming trend and the El Niño-Southern Oscillation (ENSO), are well represented using PCA. In contrast, the Varimax rotation provides distinct advantages in interpreting more localized phenomena such as variability in the tropical Atlantic. Finally, our analysis suggests that the interpretability of independent components (ICs) appears to be low. This does not diminish the statistical advantages of deriving components that are mutually independent, with potential applications ranging from synthetically generating multivariate datasets, developing statistical forecasts, and reconstructing spatial datasets from patchy observations at multiple point locations. Copyright © 2009 Royal Meteorological Society [source] Characterization of Fusarium verticillioides strains by PCR-RFLP analysis of the intergenic spacer region of the rDNAJOURNAL OF THE SCIENCE OF FOOD AND AGRICULTURE, Issue 3 2006Belén Patiño Abstract Thirty-three Fusarium verticillioides strains from diverse origins and hosts have been analysed for fumonisin production and characterized in order (i) to detect the variability present in this species and (ii) to discriminate among isolates. The method used was a combination of polymerase chain reaction (PCR) and restriction fragment length polymorphism (RFLP) generated by restriction endonucleases applied to the IGS region (intergenic spacer of rDNA). All the F. verticillioides strains associated with crops produced fumonisins B1 and B2 except those isolated from banana. Analysis of the IGS region by PCR-RFLP proved to be useful to detect variability within F. verticillioides and allowed discrimination of two related groups of isolates belonging to distinct lineages differing in fumonisin production and host preferences: the fumonisin-producing group associated with cereals and the fumonisin non-producing group associated with banana. The method used facilitates early detection and characterization of F. verticillioides strains required to control both types of pathogens and to evaluate plant exposure to the toxin, quality of the raw material to be processed and the potential fumonisin contamination in order to prevent fumonisins entering the food chain. Copyright © 2005 Society of Chemical Industry [source] Niche partitioning of closely related symbiotic dinoflagellatesMOLECULAR ECOLOGY, Issue 17 2007EUGENIA M. SAMPAYO Abstract Reef-building corals are fundamental to the most diverse marine ecosystems, yet a detailed understanding of the processes involved in the establishment, persistence and ecology of the coral,dinoflagellate association remains largely unknown. This study explores symbiont diversity in relation to habitat by employing a broad-scale sampling regime using ITS2 and denaturing gradient gel electrophoresis. Samples from Pocillopora damicornis, Stylophora pistillata and Seriatopora hystrix all harboured host-specific clade C symbiont types at Heron Island (Great Barrier Reef, Australia). While Ser. hystrix associated with a single symbiont profile along its entire depth distribution, both P. damicornis and Sty. pistillata associated with multiple symbiont profiles that showed a strong zonation with depth. It is shown that, with an increased sampling effort, previously identified ,rare' symbiont types within this group of host species are in fact environmental specialists. A multivariate approach was used to expand on the common distinction of symbionts by a single genetic identity. It shows merit in its capacity not only to include all the variability present within the marker region but also to reliably represent ecological diversification of symbionts. Furthermore, the cohesive species concept is explored to explain how niche partitioning may drive diversification of closely related symbiont lineages. This study provides thus evidence that closely related symbionts are ecologically distinct and fulfil their own niche within the ecosystem provided by the host and external environment. [source] Hidden patterns of colony size variation in seabirds: a logarithmic point of viewOIKOS, Issue 12 2008Roger Jovani Explaining the huge variability present in bird colony sizes within and between species is intimately related to the understanding of the proximate and ultimate reasons for bird coloniality. However, natural patterns of colony size frequency distributions (CSFDs) remain poorly known. It is widely believed that colonial birds have similar long-tailed (highly right-skewed) CSFDs and that species mainly differ in their maximum colony sizes (in the length of the ,tail' of their CSFDs). We used data from the Seabird 2000 project (20 species; 19 978 colonies; 3 779 919 nests), the largest and most detailed dataset currently available, to analyse the CSFDs of seabird breeding in Britain and Ireland. Log-transformations of colony sizes revealed that the often reported long-tailed CSFDs in common histograms were hiding contrasting patterns, mainly log-normal but also power law CSFDs. The different statistical characteristics of CSFDs did not co-occur at random within species and were in fact highly correlated (e.g. a large geometric mean correlated with a large coefficient of variation). A PCA with these characteristics revealed a smoothed transition between species' CSFD. Therefore, (a) a logarithmic analysis will allow different aspects of what is currently only referred to as ,colony size variation' to be quantified; (b) we challenge the current idea that all species show similar long-tailed CSFDs; (c) we offer a new (unified) view of colony size variation and discuss how these new patterns confirm, challenge and may advance theoretical and applied research into bird coloniality. [source] Viability and bar expression are negatively correlated in Oregon Wolfe Barley Dominant hybridsPLANT BIOTECHNOLOGY JOURNAL, Issue 3 2007Phil Bregitzer Summary The expression level of bar, which encodes phosphinothricin acetyltransferase (PAT), was correlated with the inviability of barley hybrids between 20 Golden Promise-derived transgenic lines (Ds-bar lines) and a specialized genetic marker stock, Oregon Wolfe Barley Dominant (OWBD). Each Ds-bar line was homozygous for a modified maize Ds element that encoded bar and that had been delivered via transposition to a unique location. All Ds-bar lines were viable and morphologically similar. Only four of the 20 hybrid populations were viable. The remaining populations died prior to producing seed. Phenotypic, enzyme-linked immunosorbent assay and quantitative reverse transcriptase-polymerase chain reaction analyses of these lines, and of lines from unrelated transformation events that also expressed bar, showed that viability was negatively correlated with bar expression. Analysis of crosses of a high- bar -expressing line with the OWB mapping population showed that the sensitivity of OWBD to PAT segregated as a single locus on chromosome 6HL. No sensitivity to PAT could be detected in several other lines and cultivars. OWBD has been shown to be genetically divergent from other germplasm groups within cultivated barley; therefore, the observed sensitivity may be peculiar to OWBD and thus would not impact generally on the utility of bar as a selectable marker or source of herbicide resistance in barley. Nevertheless, these results demonstrate the extent of allelic variability present in Hordeum vulgare, and suggest an additional variable for consideration when devising protocols for the transformation of Hordeum cultivars or landraces that are not known to be tolerant to PAT. [source] Implementing Evaluation of the Measurement Process in an Automotive Manufacturer: a Case StudyQUALITY AND RELIABILITY ENGINEERING INTERNATIONAL, Issue 5 2003Graeme Knowles Abstract Reducing process variability is presently an area of much interest in manufacturing organizations. Programmes such as Six Sigma robustly link the financial performance of the organization to the degree of variability present in the processes and products of the organization. Data, and hence measurement processes, play an important part in driving such programmes and in making key manufacturing decisions. In many organizations, however, little thought is given to the quality of the data generated by such measurement processes. By using potentially flawed data in making fundamental manufacturing decisions, the quality of the decision-making process is undermined and, potentially, significant costs are incurred. Research in this area is sparse and has concentrated on the technicalities of the methodologies available to assess measurement process capability. Little work has been done on how to operationalize such activities to give maximum benefit. From the perspective of one automotive company, this paper briefly reviews the approaches presently available to assess the quality of data and develops a practical approach, which is based on an existing technical methodology and incorporates simple continuous improvement tools within a framework which facilitates appropriate improvement actions for each process assessed. A case study demonstrates the framework and shows it to be sound, generalizable and highly supportive of continuous improvement goals. Copyright © 2003 John Wiley & Sons, Ltd. [source] | ||||||||||