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Multivariate Approach (multivariate + approach)
Selected AbstractsMorphological and physiological sexual selection targets in a territorial damselflyECOLOGICAL ENTOMOLOGY, Issue 6 2009INE SWILLEN Abstract. 1Several morphological and physiological traits may shape fitness through the same performance measure. In such cases, differentiating between a scenario of many-to-one mapping, where phenotypic traits independently shape fitness leading to functional redundancy, and a scenario where traits strongly covary among each other and fitness, is needed. 2A multivariate approach was used, including morphological and physiological traits related to flight ability, a crucial performance measure in flying insects, to identify independent correlates of short-term mating success (mated versus unmated males) in the territorial damselfly Lestes viridis. 3Males with higher flight muscle mass, higher relative thorax mass, and more symmetrical hindwings, all traits presumably linked to manoeuvrability, were more likely to be mated. Unexpectedly, although relative thorax mass is often used as a proxy for flight muscle mass, both traits were selected for independently. Mated males had a higher thorax fat content than unmated males, possibly because of enhanced flight endurance. 4The finding of several independent targets of sexual selection linked to flight ability is consistent with a scenario of many-to-one mapping between phenotype and performance. Identifying such a scenario is important, because it may clarify situations where animals may show suboptimal values for some phenotypic traits shaping a performance measure, while still having high performance and fitness. We argue in the discussion that the functional approach of sexual selection provides a potent tool for examining unresolved issues in both sexual selection theory, as well as life-history theory. [source] Sampling Hubbell's neutral theory of biodiversityECOLOGY LETTERS, Issue 10 2004David Alonso Abstract In the context of neutral theories of community ecology, a novel genealogy-based framework has recently furnished an analytic extension of Ewens' sampling multivariate abundance distribution, which also applies to a random sample from a local community. Here, instead of taking a multivariate approach, we further develop the sampling theory of Hubbell's neutral spatially implicit theory and derive simple abundance distributions for a random sample both from a local community and a metacommunity. Our result is given in terms of the average number of species with a given abundance in any randomly extracted sample. Contrary to what has been widely assumed, a random sample from a metacommunity is not fully described by the Fisher log-series, but by a new distribution. This new sample distribution matches the log-series expectation at high biodiversity values (, > 1) but clearly departs from it for species-poor metacommunities (, < 1). Our theoretical framework should be helpful in the better assessment of diversity and testing of the neutral theory by using abundance data. [source] Contending with space,time interaction in the spatial prediction of pollution: Vancouver's hourly ambient PM10 fieldENVIRONMETRICS, Issue 5-6 2002Jim Zidek Abstract In this article we describe an approach for predicting average hourly concentrations of ambient PM10 in Vancouver. We know our solution also applies to hourly ozone fields and believe it may be quite generally applicable. We use a hierarchical Bayesian approach. At the primary level we model the logarithmic field as a trend model plus Gaussian stochastic residual. That trend model depends on hourly meteorological predictors and is common to all sites. The stochastic component consists of a 24-hour vector response that we model as a multivariate AR(3) temporal process with common spatial parameters. Removing the trend and AR structure leaves ,whitened' time series of vector series. With this approach (as opposed to using 24 separate univariate time series models), there is little loss of spatial correlation in these residuals compared with that in just the detrended residuals (prior to removing the AR component). Moreover our multivariate approach enables predictions for any given hour to ,borrow strength' through its correlation with adjoining hours. On this basis we develop a spatial predictive distribution for these residuals at unmonitored sites. By transforming the predicted residuals back to the original data scales we can impute Vancouver's hourly PM10 field. Copyright © 2002 John Wiley & Sons, Ltd. [source] Multivariate Neuropsychological Prediction of Seizure Lateralization in Temporal Epilepsy Surgical CasesEPILEPSIA, Issue 8 2007Therese A. Keary Summary:,Purpose: Neuropsychological assessment can be of assistance in determining seizure lateralization in cases where EEG and MRI findings do not provide clear lateralizing data. While several studies have examined the lateralizing value of individual neuropsychological measures, clinicians are still in need of a statistically sound method that permits the incorporation of multiple neuropsychological variables to predict seizure lateralization in the individual patient. Method: The present study investigated the lateralizing value of several commonly used neuropsychological measures in a large sample of patients (n = 217) who eventually underwent surgical resection to treat their epilepsy. Side of surgery was used to operationally define seizure lateralization. A comparison of the relative utility of a multivariate versus univariate approach to predict seizure lateralization was conducted in temporal epilepsy cases. Results: The results provide evidence for the incremental validity of neuropsychological measures, other than memory and IQ tests, in the prediction of seizure lateralization in patients with medically intractable epilepsy. These data indicate that a multivariate approach increases the accuracy of prediction of seizure lateralization for temporal lobe epilepsy cases. Conclusion: This study supports the use of a multivariate approach using neuropsychological measures to predict seizure lateralization in temporal epilepsy surgical candidates. Regression formulas are provided to enhance the clinical utility of these findings. [source] Effect of residual vanadyl ions on the spectroscopic analysis of humic acids: a multivariate approachEUROPEAN JOURNAL OF SOIL SCIENCE, Issue 3 2008E. H. Novotny Summary In a study of the vanadyl (VO2+)-humic acids system, the residual vanadyl ion suppressed fluorescence and specific electron paramagnetic resonance (EPR) and NMR signals. In the case of NMR, the proton rotating frame relaxation times (T1,H) indicate that this suppression is due to an inefficient H-C cross polarization, which is a consequence of a shortening of T1,H. Principal components analysis (PCA) facilitated the isolation of the effect of the VO2+ ion and indicated that the organic free radical signal was due to at least two paramagnetic centres and that the VO2+ ion preferentially suppressed the species whose electronic density is delocalized over O atoms (greater g -factor). Additionally, the newly obtained variables (principal components , PC) indicated that, as the result of the more intense tillage a relative increase occurred in the accumulation of: (i) recalcitrant structures; (ii) lignin and long-chain alkyl structures; and (iii) organic free radicals with smaller g -factors. [source] Assessing biotic integrity in a Mediterranean watershed: development and evaluation of a fish-based indexFISHERIES MANAGEMENT & ECOLOGY, Issue 4 2008M. F. MAGALHÃES Abstract, Biological indicators for Mediterranean rivers are poorly developed. This study evaluates the effectiveness of the Index of Biotic Integrity approach (IBI) with fish assemblages in the Guadiana catchment, a typical Mediterranean watershed in Southern Portugal. Reference sites were selected from a set of 95 sites, using a multivariate approach. Fifty-five candidate metrics were screened for range, responsiveness, precision and redundancy. Final metrics included: proportion of native fish, number of intolerant and intermediate species, number of invertivore native fish, number of phyto-lithophilic and polyphilic species, and catches of exotics. The IBI scores correlated with composite gradients of human impact and differed significantly between reference and non-reference sites. Application of the IBI to an independent validation set with 123 sites produced results congruent with the development set and repeatable assessments at 22 sites showed concordance in IBI scoring. This application highlights the effectiveness of the IBI approach even with fish assemblages of limited diversity and ecological specialisation as in Mediterranean streams. [source] Use of response functions in selecting lodgepole pine populations for future climatesGLOBAL CHANGE BIOLOGY, Issue 12 2006T. WANG Abstract Although growth response functions have previously been developed for lodgepole pine (Pinus contorta Dougl. ex Loud.) populations in British Columbia, new analyses were conducted: (1) to demonstrate the merit of a new local climate model in genecological analysis; (2) to highlight new methods for deriving response functions; and (3) to evaluate the impacts of management options for existing geographically defined seed planning units (SPUs) for reforestation. Results of this study suggest that new methods for anchoring population response functions, and a multivariate approach for incorporating climate variables into a single model, considerably improve the reliability of these functions. These functions identified a small number of populations in central areas of the species distribution with greater growth potential over a wide range of mean annual temperature (MAT). Average productivity of lodgepole pine is predicted to increase (up to 7%) if moderate warming (,2°C MAT) occurs in the next few decades as predicted, although productivity would substantially decline in some SPUs in southern BC. Severe global warming (>3°C MAT) would result in either a drastic decline in productivity or local populations being extirpated in southern SPUs. New deployment strategies using the best seed sources for future reforestation may not only be able to mitigate the negative impact of global warming, but may even be able to increase productivity in some areas. [source] Hypothesis testing in distributed source models for EEG and MEG dataHUMAN BRAIN MAPPING, Issue 2 2006Lourens J. Waldorp Abstract Hypothesis testing in distributed source models for the electro- or magnetoencephalogram is generally performed for each voxel separately. Derived from the analysis of functional magnetic resonance imaging data, such a statistical parametric map (SPM) ignores the spatial smoothing in hypothesis testing with distributed source models. For example, when intending to test a single voxel, actually an entire region of voxels is tested simultaneously. Because there are more parameters than observations, typically constraints are employed to arrive at a solution which spatially smooths the solution. If ignored, it can be concluded from the hypothesis test that there is activity at some location where there is none. In addition, an SPM on distributed source models gives the illusion of very high resolution. As an alternative, a multivariate approach is suggested in which a region of interest is tested that is spatially smooth. In simulations with MEG and EEG it is shown that clear hypothesis testing in distributed source models is possible, provided that there is high correspondence between what is intended to be tested and what is actually tested. The approach is also illustrated by an application to data from an experiment measuring visual evoked fields when presenting checkerboard patterns. Hum Brain Mapp, 2005. © 2005 Wiley-Liss, Inc. [source] An efficient multivariate approach for estimating preference when individual observations are dependentJOURNAL OF ANIMAL ECOLOGY, Issue 5 2008Steinar Engen Summary 1We discuss aspects of resource selection based on observing a given vector of resource variables for different individuals at discrete time steps. A new technique for estimating preference of habitat characteristics, applicable when there are multiple individual observations, is proposed. 2We first show how to estimate preference on the population and individual level when only a single site- or resource component is observed. A variance component model based on normal scores in used to estimate mean preference for the population as well as the heterogeneity among individuals defined by the intra-class correlation. 3Next, a general technique is proposed for time series of observations of a vector with several components, correcting for the effect of correlations between these. The preference of each single component is analyzed under the assumption of arbitrarily complex selection of the other components. This approach is based on the theory for conditional distributions in the multi-normal model. 4The method is demonstrated using a data set of radio-tagged dispersing juvenile goshawks and their site characteristics, and can be used as a general tool in resource or habitat selection analysis. [source] A multivariate approach to combine univariate calibration informationJOURNAL OF CHEMOMETRICS, Issue 10 2001Jason J. Z. Liao Abstract It is common practice to calibrate a common value by combining information from different sources, e.g. days, instruments, laboratories, etc. Under each individual source a perfect univariate calibration can be used to calibrate the unknown. Then the common unknown can be estimated by combining the estimates from each source as a weighted mean (Johnson DJ, Krishnamoorthy,K. J. Am. Statist. Assoc. 1996; 91: 1707,1715). However, this estimator can be obtained as a special solution directly from a multivariate calibration setting by combining information first and then estimating the common value. Two data sets were analyzed and they showed that the multivariate approach can possibly improve the univariate approach based on the closeness criterion. Copyright © 2001 John Wiley & Sons, Ltd. [source] Determinants of prescribing patterns for type II diabetes at Primary Care Trust levelJOURNAL OF CLINICAL PHARMACY & THERAPEUTICS, Issue 4 2004D. C. E. F. Lloyd BA (Hons) MSc Dip Epidem Summary Objective:, To estimate the effect of demography, deprivation and ethnicity on variations in prescribing of oral antidiabetics at the Primary Care Trust level. Design:, Cross-sectional survey. Setting:, All Primary Care Trusts in England. Main outcome measures:, Percentage of variance explained. Results:, A model using measures of demography, ethnicity, deprivation and use of thiazolidinediones explained 59% of the variation in cost per registered patient although individual variables explained far less. Conclusions:, This study shows the importance of using a multivariate approach in modelling the drivers of cost. The high use of thiazolidinediones is of concern in the light of NICE guidance. [source] A multivariate approach to the feeding habits of small fishes in the Guadalquivir EstuaryJOURNAL OF FISH BIOLOGY, Issue 2002F. Baldoa In the analysis of the feeding habits of the 11 most abundant fish species in the Guadalquivir Estuary, collected monthly (February 1998 to January 1999) at two different sampling sites, a total of 46 prey taxa were identified. Classifications (based on Bray,Curtis similarities derived from occurrence, number and mass data) of the different fish categories (postlarvae and juvenile,adults of each species) revealed two main trophic guilds, whose preferential prey (SIMPER analysis) were mysids and copepods, respectively. The similarity matrices derived from occurrence, number and mass data were always significantly correlated (RELATE: r>0.636; P<0.01), indicating that a good agreement in feeding patterns emerged from these variables. The seasonal coincidence of maximal fish and key-prey species densities suggests that food availability may be a principal factor influencing the nursery function of the Guadalquivir Estuary. [source] A new production function estimate of the euro area output gap,JOURNAL OF FORECASTING, Issue 1-2 2010Matthieu Lemoine Abstract We develop a new version of the production function (PF) approach for estimating the output gap of the euro area. Assuming a CES (constant elasticity of substitution) technology, our model does not call for any (often imprecise) measure of the capital stock and improves the estimation of the trend total factor productivity using a multivariate unobserved components model. With real-time data, we assess this approach by comparing it with the Hodrick,Prescott (HP) filter and with a Cobb,Douglas PF approach with common cycle and implemented with a multivariate unobserved components model. Our new PF estimate appears highly concordant with the reference chronology of turning points and has better real-time properties than the univariate HP filter for sufficiently long time horizons. Its inflation forecasting power appears, like the other multivariate approach, less favourable than the statistical univariate method. Copyright © 2009 John Wiley & Sons, Ltd. [source] Characteristics of aggression in a German psychiatric hospital and predictors of patients at riskJOURNAL OF PSYCHIATRIC & MENTAL HEALTH NURSING, Issue 1 2007R. KETELSEN md phd This study investigated the aggressive behaviour of all mentally ill patients within a whole psychiatric hospital with a catchment area of 325 000 inhabitants over a 1-year period (i) to assess the 1-year prevalence and characteristics of aggressive episodes and index inpatients, and (ii) to identify predictors of patients at risk by a multivariate approach. Staff Observation of Aggression Scale was used to assess aggressive behaviour. Characteristics of index inpatients were compared with those of non-index inpatients. Logistic regression analysis was applied to identify risk factors. A total of 171 out of 2210 admitted patients (7.7%) exhibited 441 aggressive incidents (1.7 incidents per bed per year). Logistic regression analyses revealed as major risk factors of aggression: diagnoses (organic brain syndromes OR = 3.6, schizophrenia OR = 2.9), poor psychosocial living conditions (OR = 2.2), and critical behaviour leading to involuntary admission (OR = 3.3). Predictors of aggressive behaviour can be useful to identify inpatients at risk. Nevertheless, additional situational determinants have to be recognized. Training for professionals should include preventive and de-escalating strategies to reduce the incidence of aggressive behaviour in psychiatric hospitals. The application of de-escalating interventions prior to admission might be effective in preventing aggressive behaviour during inpatient treatment especially for patients with severe mental disorders. [source] Morphological analysis of male mating organ in the Drosophila virilis species group: a multivariate approachJOURNAL OF ZOOLOGICAL SYSTEMATICS AND EVOLUTIONARY RESEARCH, Issue 2 2004A. M. Kulikov Abstract The shape of the male mating organ differs among 11 closely related species of the Drosophila virilis species group. Multivariate analyses of variation of a suite of 35 morphological traits (indices) describing the phallus shape were carried out in order to characterize interspecies variability of the traits. An overwhelming majority of the traits displayed species-specific variability. The main result of the investigation was the revelation of the differences involved in the traits studied in the evolution of the D. virilis species group. The structure of species-specific variability of some traits was discovered to be in accordance with the generally accepted taxonomy of the species group, while that of other traits required isolation of D. virilisper se from lummei phylad (former virilis phylad), and confirmed separation of montana phylad into three subphylads: montana proper, littoralis and kanekoi. Several subsets of traits having separate variability were determined in different parts of the male mating organ which correspond to spots of evolutionarily significant variability. Zusammenfassung Die Form des männlichen Begattungsorgans zeigt innerhalb von 11 nahe verwandten Arten der Drosophila virilis - Gruppe Unterschiede. Eine multivariate Variationsanalyse einer Gruppe von 35 morphologischen Merkmalen (Indizes), die die Form des Penis erfassen, wurde durchgeführt, um die zwischenartliche Variabiltät des Merkmals zu charakterisieren. Die überwältigende Mehrheit der Merkmale erwies sich als artspezifisch. Das vorrangige Ergebnis der Untersuchung war, den unterschiedlichen Anteil dieses Merkmals an der Evolution der Drosophila virilis - Gruppe aufzuklären. Die Struktur der artspezifischen Variabilität einiger Merkmale konnte als übereinstimmend mit der allgemein akzeptierten Taxonomie der Artengruppe erkannt werden, während andere Merkmale es notwendig machten, D. virilis von der D. lummei - Phylade (der früheren D. virilis - Phylade) abzutrennen; bestätigt wurde auch die Auftrennung der D. montana - Phylade in drei Subphyladen: die eigentlich montana -, die littoralis - und die kanekoi - Phylade. [source] Conserving the evolutionary potential of California valley oak (Quercus lobata Née): a multivariate genetic approach to conservation planningMOLECULAR ECOLOGY, Issue 1 2008DELPHINE GRIVET Abstract California valley oak (Quercus lobata Née) is a seriously threatened endemic oak species in California and a keystone species for foothill oak ecosystems. Urban and agricultural development affects a significant fraction of the species' range and predicted climate change is likely to dislocate many current populations. Here, we explore spatial patterns of multivariate genotypes and genetic diversity throughout the range of valley oak to determine whether ongoing and future patterns of habitat loss could threaten the evolutionary potential of the species by eradicating populations of distinctive genetic composition. This manuscript will address three specific questions: (i) What is the spatial genetic structure of the chloroplast and nuclear genetic markers? (ii) What are the geographical trends in the distribution of chloroplast and nuclear genotypes? (iii) Is there any part of the species' range where allelic diversity in either the chloroplast or nuclear genomes is particularly high? We analysed six chloroplast and seven nuclear microsatellite genetic markers of individuals widespread across the valley oak range. We then used a multivariate approach correlating genetic markers and geographical variables through a canonical trend surface analysis, followed by GIS mapping of the significant axes. We visualized population allelic richness spatially with GIS tools to identify regions of high diversity. Our findings, based on the distribution of multivariate genotypes and allelic richness, identify areas with distinctive histories and genetic composition that should be given priority in reserve network design, especially because these areas also overlap with landscape change and little degree of protection. Thus, without a careful preservation plan, valuable evolutionary information will be lost for valley oak. [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] Probing genetic algorithms for feature selection in comprehensive metabolic profiling approachRAPID COMMUNICATIONS IN MASS SPECTROMETRY, Issue 8 2008Wei Zou Six different clones of 1-year-old loblolly pine (Pinus taeda L.) seedlings grown under standardized conditions in a green house were used for sample preparation and further analysis. Three independent and complementary analytical techniques for metabolic profiling were applied in the present study: hydrophilic interaction chromatography (HILIC-LC/ESI-MS), reversed-phase liquid chromatography (RP-LC/ESI-MS), and gas chromatography all coupled to mass spectrometry (GC/TOF-MS). Unsupervised methods, such as principle component analysis (PCA) and clustering, and supervised methods, such as classification, were used for data mining. Genetic algorithms (GA), a multivariate approach, was probed for selection of the smallest subsets of potentially discriminative classifiers. From more than 2000 peaks found in total, small subsets were selected by GA as highly potential classifiers allowing discrimination among six investigated genotypes. Annotated GC/TOF-MS data allowed the generation of a small subset of identified metabolites. LC/ESI-MS data and small subsets require further annotation. The present study demonstrated that combination of comprehensive metabolic profiling and advanced data mining techniques provides a powerful metabolomic approach for biomarker discovery among small molecules. Utilizing GA for feature selection allowed the generation of small subsets of potent classifiers. Copyright © 2008 John Wiley & Sons, Ltd. [source] Errors in Variables, Links between Variables and Recovery of Volatility Information in Appraisal-Based Real Estate Return IndexesREAL ESTATE ECONOMICS, Issue 4 2006Peijie Wang The present article proposes a multivariate approach to unsmoothing appraisal-based real estate return indexes to recover the true market volatility information in real estate returns. It scrutinizes the role played by errors in variables, in conjunction with an analysis of other economic activities relevant to real estate returns, to exploit the functional relationship and the mechanism of interactions between real estate returns and these economic activities. Appraisal smoothing can therefore be detected and corrected properly and efficiently, without presuming a weakly efficient real estate market. The approach is then applied to U.K. real estate indexes as empirical examples. The results suggest a reasonable volatility in U.K. real estate investment that is close to reality. It is found that the volatility of the true market return on real estate is 1.5404,1.9282 times that of the return on the appraisal-based indexes, in contrast to figures of 2.4862,5.8720 produced by the fully unsmoothing procedure. [source] A comprehensive analysis of QTL for abdominal fat and breast muscle weights on chicken chromosome 5 using a multivariate approachANIMAL GENETICS, Issue 2 2009G. Le Mignon Summary Quantitative trait loci (QTL) influencing the weight of abdominal fat (AF) and of breast muscle (BM) were detected on chicken chromosome 5 (GGA5) using two successive F2 crosses between two divergently selected ,Fat' and ,Lean' INRA broiler lines. Based on these results, the aim of the present study was to identify the number, location and effects of these putative QTL by performing multitrait and multi-QTL analyses of the whole available data set. Data concerned 1186 F2 offspring produced by 10 F1 sires and 85 F1 dams. AF and BM traits were measured on F2 animals at slaughter, at 8 (first cross) or 9 (second cross) weeks of age. The F0, F1 and F2 birds were genotyped for 11 microsatellite markers evenly spaced along GGA5. Before QTL detection, phenotypes were adjusted for the fixed effects of sex, F2 design, hatching group within the design, and for body weight as a covariable. Univariate analyses confirmed the QTL segregation for AF and BM on GGA5 in male offspring, but not in female offspring. Analyses of male offspring data using multitrait and linked-QTL models led us to conclude the presence of two QTL on the distal part of GGA5, each controlling one trait. Linked QTL models were applied after correction of phenotypic values for the effects of these distal QTL. Several QTL for AF and BM were then discovered in the central region of GGA5, splitting one large QTL region for AF into several distinct QTL. Neither the ,Fat' nor the ,Lean' line appeared to be fixed for any QTL genotype. These results have important implications for prospective fine mapping studies and for the identification of underlying genes and causal mutations. [source] A multivariate approach to optimization of macronutrient composition in weaning diets for cod (Gadus morhua)AQUACULTURE NUTRITION, Issue 1 2006K. HAMRE Abstract Atlantic cod, initial weight 0.26 g, were fed diets varying in added protein from 530 to 830 g kg,1, lipid from 50 to 300 g kg,1 and carbohydrate from 0 to 150 g kg,1 of dry weight, according to a three-component mixture design. Analysed values of protein and lipid were 500,770 g kg,1 and 30,270 g kg,1, respectively. Analysed carbohydrate levels were as added. Increasing levels of both lipid and carbohydrate had a positive effect on fish growth (P < 10,3), whereas protein levels above 600 g kg,1 gave a reduction in growth (P < 10,4). The effects on growth were evident in fish less than 4 g, whereas fish growth between 4 and 6 g was unaffected by the dietary variation. It is hypothesized that the reduction in growth at high protein levels in fish of less than 4 g could be owing to incomplete utilization of protein, as the stomach of cod is not fully developed before the fish is approximately 1 g. Mortality and cannibalism were high in fish less than 4 g but low when the fish grew from 4 to 6 g. There was a significant decrease in cannibalism with increasing dietary lipid during the first half of the experiment (P < 0.05) and cannibalism was consistently high in fish fed less than 150 g kg,1 lipid. The lipid level in whole fish increased with increasing dietary levels of lipid (P < 10,6) and carbohydrate (P < 10,4), whereas the liver lipid level increased with increasing dietary lipid up to 200 g kg,1 (P < 10,6) and decreased thereafter (P < 10,4). Whole body glycogen increased slightly with increasing levels of dietary carbohydrate (P < 0.05) and was not affected by the other dietary variables. Liver glycogen increased in response to increasing dietary carbohydrate (P < 10,5) and decreasing levels of dietary lipid (P < 10,5). An abrupt increase in liver glycogen was seen with the reduction in dietary lipid from 100 to 50 g kg,1. The hepatosomatic index increased in response to both dietary lipid and carbohydrate (P < 10,6). It is concluded that the protein requirement of young cod is less than 500 g kg,1 of dry diet. Fish of less than 4 g should not be given more than 620 g kg,1 protein and should be supplemented with 150,200 g kg,1 lipid. Carbohydrate up to 150 g kg,1 of dry diet promoted growth and did not seem to affect the fish negatively. Fish above 4 g can be given diets varying in protein and carbohydrate over the wide range of concentrations used in the present study, but lipid supplementation should be restricted to between 100 and 200 g kg,1. [source] Identifying the origins of fishing gear ingested by seabirds: a novel multivariate approachAQUATIC CONSERVATION: MARINE AND FRESHWATER ECOSYSTEMS, Issue 6 2010Cindy Ridley Abstract 1.The global decline of albatrosses (Diomedidae: Procellariiformes) is thought to have occurred largely as a direct result of fishery-related mortality. Albatrosses and other large petrels interact with fisheries in several ways, including scavenging used bait and discarded offal, which may contain hooks. 2.Hooks that are ingested by breeding birds are often fed to chicks which subsequently regurgitate them shortly before fledging. 3.In this study a series of mathematical (cladistic, cluster and principal components) analyses are applied to a sample of 241 items of fishing gear (hook, snood and hook/snood unit) collected from seabird nest sites on Bird Island, South Georgia, and 44 reference gear items provided by four South Atlantic regional fisheries. 4.The five separate analyses failed to assign most gear to a particular fishery or to identify any consistent annual trends. The homogeneous nature of the material, which was largely derived from the same manufacturers, meant that gear origin could not be determined. This suggests that hooks found at seabird colonies in this, and potentially other regions, will be of limited use in identifying offending fisheries, unless operators are obliged to deploy gear with unique marks in the future. 5.Nevertheless, it is suggested that this approach should work effectively where birds interact with a range of fisheries targeting different species using variable gear. This study therefore represents an innovative approach to the characterization of lost fishing gear with potentially widespread application. Copyright © 2010 John Wiley & Sons, Ltd. [source] Model identification in presence of incomplete information by generalized principal component analysis: Application to the common and differential responses of Escherichia coli to multiple pulse perturbations in continuous, high-biomass density cultureBIOTECHNOLOGY & BIOENGINEERING, Issue 4 2009Daniel V. Guebel Abstract In a previous report we described a multivariate approach to discriminate between the different response mechanisms operating in Escherichia coli when a steady, continuous culture of these bacteria was perturbed by a glycerol pulse (Guebel et al., 2009, Biotechnol Bioeng 102: 910,922). Herein, we present a procedure to extend this analysis when multiple, spaced pulse perturbations (glycerol, fumarate, acetate, crotonobetaine, hypersaline plus high-glycerol basal medium and crotonobetaine plus hypersaline basal medium) are being assessed. The proposed method allows us to identify not only the common responses among different perturbation conditions, but to recognize the specific response for a given stimulus even when the dynamics of the perturbation is unknown. Components common to all conditions are determined first by Generalized Principal Components Analysis (GPCA) upon a set of covariance matrices. A metrics is then built to quantify the similitude distance. This is based on the degree of variance extraction achieved for each variable along the GPCA deflation processes by the common factors. This permits a cluster analysis, which recognizes several compact sub-sets containing only the most closely related responsive groups. The GPCA is then run again but is restricted to the groups in each sub-set. Finally, after the data have been exhaustively deflated by the common sub-set factors, the resulting residual matrices are used to determine the specific response factors by classical principal component analysis (PCA). The proposed method was validated by comparing its predictions with those obtained when the dynamics of the perturbation was determined. In addition, it showed to have a better performance than the obtained with other multivariate alternatives (e.g., orthogonal contrasts based on direct GPCA, Tucker-3 model, PARAFAC, etc.). Biotechnol. Bioeng. 2009; 104: 785,795 © 2009 Wiley Periodicals, Inc. [source] Kaempferol Glycosides from Lobularia maritima and Their Potential Role in Plant InteractionsCHEMISTRY & BIODIVERSITY, Issue 2 2009Antonio Fiorentino Abstract Six kaempferol glycosides, four of them characterized for the first time, were isolated from the leaf extract of Lobularia maritima. The structural elucidation was performed by a combined approach using Electrospray-Ionization Triple-Quadrupole Mass-Spectrometric (ESI/TQ/MS) techniques, and 1D- and 2D-NMR experiments (1H, 13C, DEPT, DQ-COSY, TOCSY, ROESY, NOESY, HSQC, HMBC, and HSQC-TOCSY). The isolated kaempferol derivatives have different disaccharide substituents at C(3) and four of them have a rhamnose unit at C(7). To evaluate their potential allelopathic role within the herbaceous plant community, the compounds, as well as the aglycone obtained from enzymatic hydrolysis, have been tested in vitro on three coexisting plant species, Dactylis hispanica, Petrorhagia velutina, and Phleum subulatum. The results obtained allow us to hypothesize that the type of the sugar modulates the biological response. The bioassay data, analyzed by a multivariate approach, and grouping the compounds on the basis of the number of sugar units and the nature of carbohydrates present in the disaccharide moiety, indicate a structure,activity relationship. [source] Robust principal component analysis and outlier detection with ecological dataENVIRONMETRICS, Issue 2 2004Donald A. Jackson Abstract Ecological studies frequently involve large numbers of variables and observations, and these are often subject to various errors. If some data are not representative of the study population, they tend to bias the interpretation and conclusion of an ecological study. Because of the multivariate nature of ecological data, it is very difficult to identify atypical observations using approaches such as univariate or bivariate plots. This difficulty calls for the application of robust statistical methods in identifying atypical observations. Our study provides a comparison of a standard method, based on the Mahalanobis distance, used in multivariate approaches to a robust method based on the minimum volume ellipsoid as a means of determining whether data sets contain outliers or not. We evaluate both methods using simulations varying conditions of the data, and show that the minimum volume ellipsoid approach is superior in detecting outliers where present. We show that, as the sample size parameter, h, used in the robust approach increases in value, there is a decrease in the accuracy and precision of the associated estimate of the number of outliers present, in particular as the number of outliers increases. Conversely, where no outliers are present, large values for the parameter provide the most accurate results. In addition to the simulation results, we demonstrate the use of the robust principal component analysis with a data set of lake-water chemistry variables to illustrate the additional insight available. We suggest that ecologists consider that their data may contain atypical points. Following checks associated with normality, bivariate linearity and other traditional aspects, we advocate that ecologists examine their data sets using robust multivariate methods. Points identified as being atypical should be carefully evaluated based on background information to determine their suitability for inclusion in further multivariate analyses and whether additional factors explain their unusual characteristics. Copyright © 2004 John Wiley & Sons, Ltd. [source] Potentialities of multivariate approaches in genome-based cancer research: identification of candidate genes for new diagnostics by PLS discriminant analysis,JOURNAL OF CHEMOMETRICS, Issue 3-4 2004G. Musumarra Abstract Partial least squares discriminant analysis (PLS-DA) provides a sound statistical basis for the selection, from an original 9605-data set, of a limited number of gene transcripts most effective in discriminating different tumour histotypes. The potentialities of the PLS-DA approach are pointed out by its ability to identify genes which, according to current knowledge, are associated with cancer development. Moreover, PLS-DA was able to identify MUC 13 and S100P proteins as candidates for the development of new colon cancer diagnostics. Various genes with unknown function and ESTs (expressed sequence tags), found to be important in discriminating genes for colon, leukaemia, renal and central nervous system tumour cells, are indicated as deserving high priority in future molecular studies. Copyright © 2004 John Wiley & Sons, Ltd. [source] Combining univariate calibration information through a mixed-effects modelJOURNAL OF CHEMOMETRICS, Issue 2 2003Jason J. Z. Liao Abstract It is common practice to calibrate a common value by combining information from different sources such as days, people, instruments and laboratories. Under each individual source a univariate calibration can be used to calibrate the unknown. Then the common unknown can be estimated by combining the estimates from each source as a weighted mean (Johnson DJ, Krishnamoorthy,K. J. Am. Statist. Assoc. 1996; 91: 1707,1715) or through a multivariate calibration setting by combining information first and then estimating the common value (Liao JJZ. J. Chemometrics 2001; 15: 789,794). In this paper a mixed-effects model approach is proposed to combine good characteristics from both approaches. Simulations show that the mixed-effects model has better bias and mean squared error (MSE) performance than the univariate and multivariate approaches. A real data set is used to demonstrate the good characteristics of the mixed-effects model approach. Copyright © 2003 John Wiley & Sons, Ltd. [source] A tale of two matrices: multivariate approaches in evolutionary biologyJOURNAL OF EVOLUTIONARY BIOLOGY, Issue 1 2007M. W. BLOWS Abstract Two symmetric matrices underlie our understanding of microevolutionary change. The first is the matrix of nonlinear selection gradients (,) which describes the individual fitness surface. The second is the genetic variance,covariance matrix (G) that influences the multivariate response to selection. A common approach to the empirical analysis of these matrices is the element-by-element testing of significance, and subsequent biological interpretation of pattern based on these univariate and bivariate parameters. Here, I show why this approach is likely to misrepresent the genetic basis of quantitative traits, and the selection acting on them in many cases. Diagonalization of square matrices is a fundamental aspect of many of the multivariate statistical techniques used by biologists. Applying this, and other related approaches, to the analysis of the structure of , and G matrices, gives greater insight into the form and strength of nonlinear selection, and the availability of genetic variance for multiple traits. [source] Analysis of solid-state transformations of pharmaceutical compounds using vibrational spectroscopyJOURNAL OF PHARMACY AND PHARMACOLOGY: AN INTERNATI ONAL JOURNAL OF PHARMACEUTICAL SCIENCE, Issue 8 2009Andrea Heinz Abstract Objectives Solid-state transformations may occur during any stage of pharmaceutical processing and upon storage of a solid dosage form. Early detection and quantification of these transformations during the manufacture of solid dosage forms is important since the physical form of an active pharmaceutical ingredient can significantly influence its processing behaviour, including powder flow and compressibility, and biopharmaceutical properties such as solubility, dissolution rate and bioavailability. Key findings Vibrational spectroscopic techniques such as infrared, near-infrared, Raman and, most recently, terahertz pulsed spectroscopy have become popular for solidstate analysis since they are fast and non-destructive and allow solid-state changes to be probed at the molecular level. In particular, Raman and near-infrared spectroscopy, which require no sample preparation, are now commonly used coupled to fibreoptic probes and are able to characterise solid-state conversions in-line. Traditionally, uni- or bivariate approaches have been used to analyse spectroscopic data sets; however, recently the simultaneous detection of several solid-state forms has been increasingly performed using multivariate approaches where even overlapping spectral bands can be analysed. Summary This review discusses the applications of different vibrational spectroscopic techniques to detect and monitor solid-state transformations possible for crystalline polymorphs, hydrates and amorphous forms of pharmaceutical compounds. In this context, the theoretical basis of solid-state transformations and vibrational spectroscopy and common experimental approaches are described, including recent methods of data analysis. [source] Comparison of multivariate methods for robust parameter design in sheet metal spinningAPPLIED STOCHASTIC MODELS IN BUSINESS AND INDUSTRY, Issue 3 2004Corinna Auer Abstract Sheet metal spinning is a very complex forming process with a large number of quality characteristics. Within the scope of a joint project of the Department of Statistics and the Chair of Forming Technology the impact of process parameters (design factors) on important quality characteristics has been investigated both theoretically and experimentally. In the past, every response has been treated individually and uncontrollable disturbances (noise factors) have been neglected. Now this approach has been extended to robust multiresponse parameter design. For this, a review of common multivariate approaches for robust parameter design has been carried out, which also leads to the proposal of some new variants. In addition to the theoretical comparison, the methods were applied to data gained in the sheet metal spinning process. The obtained results were evaluated in terms of applicability, limitations and quality accuracy. Practical experiments confirmed the high degree of efficiency that the finally proposed method based on desirabilities promises. Copyright © 2004 John Wiley & Sons, Ltd. [source] | |||||||||||||||||||||||||