ACTA PSYCHIATRICA SCANDINAVICA, Issue 4 2007
H. A. Nasrallah
Objective:, Long-acting antipsychotic agents were developed to promote treatment compliance in patients requiring maintenance treatment for schizophrenia. Method:, An analysis of the impact of non-compliance on treatment outcomes in schizophrenia and the advantages and disadvantages of long-acting antipsychotics. Results:, Partial or total non-compliance with oral antipsychotics remains widespread and is associated with significant increases in the risk of relapse, rehospitalization, progressive brain tissue loss and further functional deterioration. Long-acting agents have the potential to address issues of all-cause discontinuation and poor compliance. The development of the first long-acting atypical antipsychotic, which appears to be effective and well tolerated, should further improve the long-term management of schizophrenia. Conclusion:, Long-acting agents represent a valuable tool for the management of schizophrenia and merit wider use, especially in light of emerging literature regarding the neuroprotective advantages of atypical antipsychotics over conventional agents in terms of regenerating brain tissue during maintenance therapy. [source]

On the importance of patch attributes, environmental factors and past human impacts as determinants of perennial plant species richness and diversity in Mediterranean semiarid steppes

DIVERSITY AND DISTRIBUTIONS, Issue 1 2004
Fernando T. Maestre
ABSTRACT Richness and diversity of perennial plant species were evaluated in 17 Stipa tenacissima steppes along a degradation gradient in semiarid SE Spain. The main objective of the study was to evaluate the relative importance of historical human impacts, small-scale patch attributes and environmental factors as determinants of perennial plant species richness and diversity in S. tenacissima steppes, where vegetation is arranged as discrete plant patches inserted on a bare ground matrix. Partial least squares regression was used to determine the amount of variation in species richness and diversity that could be significantly explained by historical human impacts, patch attributes, and environmental factors together and separately. They explained up to 89% and 69% of the variation in species richness and diversity, respectively. In both cases, the predictive power of patch attributes models was higher than that of models consisting of abiotic characteristics and variables related to human impact, suggesting that patch attributes are the major determinants of species richness and diversity in semiarid S. tenacissima steppes. However, patch attributes alone are not enough to explain the observed variation in species richness and diversity. The area covered by late-successional sprouting shrubs and the distance between consecutive patches were the most influencing individual variables on species richness and diversity, respectively. The implications of these results for the management of S. tenacissima steppes are discussed. [source]

Simultaneous Quantitative Determination of Cadmium, Lead, and Copper on Carbon-Ink Screen-Printed Electrodes by Differential Pulse Anodic Stripping Voltammetry and Partial Least Squares Regression

ELECTROANALYSIS, Issue 23 2008
Michael Cauchi
Abstract Water is a vital commodity for every living entity on the planet. However, water resources are threatened by various sources of contamination from pesticides, hydrocarbons and heavy metals. This has resulted in the development of concepts and technologies to create a basis for provision of safe and high quality drinking water. This paper focuses on the simultaneous quantitative determination of three common contaminants, the heavy metals cadmium, lead and copper. Multivariate calibration was applied to voltammograms acquired on in-house printed carbon-ink screen-printed electrodes by the highly sensitive electrochemical method of differential pulse anodic stripping voltammetry (DPASV). The statistically inspired modification of partial least squares (SIMPLS) algorithm was employed to effect the multivariate calibration. The application of data pretreatment techniques involving range-scaling, mean-centering, weighting of variables and the effects of peak realignment are also investigated. It was found that peak realignment in conjunction with weighting and SIMPLS led to the better overall root mean square error of prediction (RMSEP) value. This work represents significant progress in the development of multivariate calibration tools in conjunction with analytical techniques for water quality determination. It is the first time that multivariate calibration has been performed on DPASV voltammograms acquired on carbon-ink screen-printed electrodes. [source]

Dynamics of the SAR11 bacterioplankton lineage in relation to environmental conditions in the oligotrophic North Pacific subtropical gyre

ENVIRONMENTAL MICROBIOLOGY, Issue 9 2009
Alexander Eiler
Summary A quantitative PCR assay for the SAR11 clade of marine Alphaproteobacteria was applied to nucleic acids extracted from monthly depth profiles sampled over a 3-year period (2004,2007) at the open-ocean Station ALOHA (A Long-term Oligotrophic Habitat Assessment; 22°45,N, 158°00,W) in the oligotrophic North Pacific Ocean. This analysis revealed a high contribution (averaging 36% of 16S rRNA gene copies) of SAR11 to the total detected 16S rRNA gene copies over depths ranging from the surface layer to 4000 m, and revealed consistent spatial and temporal variation in the relative abundance of SAR11 16S rRNA gene copies. On average, a higher proportion of SAR11 rRNA gene copies were detected in the photic zone (< 175 m depth; mean = 38%) compared with aphotic (> 175 m depth; mean = 30%), and in the winter months compared with the summer (mean = 44% versus 33%, integrated over 175 m depth). Partial least square to latent structure projections identified environmental variables that correlate with variation in the absolute abundance of SAR11, and provided tools for developing a predictive model to explain time and depth-dependent variations in SAR11. Moreover, this information was used to hindcast temporal dynamics of the SAR11 clade between 1997 and 2006 using the existing HOT data set, which suggested that interannual variations in upper ocean SAR11 abundances were related to ocean-climate variability such as the El Niño Southern Oscillation. [source]

A strain isolated from gas oil-contaminated soil displays chemotaxis towards gas oil and hexadecane

ENVIRONMENTAL MICROBIOLOGY, Issue 10 2003
Mariana P. Lanfranconi
Summary In this report we describe the isolation of a strain from soil contaminated with gas oil by taking bacteria from a chemotactic ring on gas oil-containing soft agar plates. Partial 16 S rDNA sequencing of the isolated strain showed 99.1% identity with Flavimonas oryzihabitans. It was not only able to degrade different aliphatic hydrocarbons but it was also chemotactic towards gas oil and hexadecane, as demonstrated by the use of three different chemotaxis methods, such as agarose plug and capillary assays and swarm plate analysis. In addition, the strain was chemotactic to a variety of carbon sources that serve as growth substrates, including glucose, arabinose, mannitol, glycerol, gluconate, acetate, succinate, citrate, malate, lactate and casaminoacids. This is the first report on chemotaxis of a hydrocarbon-degrading bacterium towards a pure alkane, such as hexadecane. The fact that environmental isolates show chemotaxis towards contaminant/s present in the site of isolation suggests that chemotaxis might enhance biodegradation by favouring contact between the degrading microorganism and its substrate. [source]

Comparison of fatty acid profiles and mid-infrared spectral data for classification of olive oils

EUROPEAN JOURNAL OF LIPID SCIENCE AND TECHNOLOGY, Issue 2 2010
Gozde Gurdeniz
Abstract The composition of olive oils may vary depending on environmental and technological factors. Fatty acid profiles and Fourier-transform infrared (FT-IR) spectroscopy data in combination with chemometric methods were used to classify extra-virgin olive oils according to geographical origin and harvest year. Oils were obtained from 30,different areas of northern and southern parts of the Aegean Region of Turkey for two consecutive harvest years. Fatty acid composition data analyzed with principal component analysis was more successful in distinguishing northern olive oil samples from southern samples compared to spectral data. Both methods have the ability to differentiate olive oil samples with respect to harvest year. Partial least squares (PLS) analysis was also applied to detect a correlation between fatty acid profile and spectral data. Correlation coefficients (R2) of a calibration set for stearic, oleic, linoleic, arachidic and linolenic acids were determined as 0.83, 0.97, 0.97, 0.83 and 0.69, respectively. Fatty acid profiles were very effective in classification of oils with respect to geographic origin and harvest year. On the other hand, FT-IR spectra in combination with PLS could be a useful and rapid tool for the determination of some of the fatty acids of olive oils. [source]

Association of DRD4 polymorphism with severity of oppositional defiant disorder, separation anxiety disorder and repetitive behaviors in children with autism spectrum disorder

EUROPEAN JOURNAL OF NEUROSCIENCE, Issue 6 2010
Kenneth D. Gadow
Abstract The objective was to examine whether a common polymorphism in the dopamine D4 receptor gene (DRD4) might be a potential biomarker for behavioral variation within the autism spectrum disorder clinical phenotype. Children (N = 66) were evaluated with a validated mother- and teacher-completed DSM-IV-referenced rating scale. Partial eta-squared (,p2) was used to gauge the magnitude of group differences: 0.01,0.06 = small, 0.06,0.14 = moderate and > 0.14 = large. Children who were 7-repeat allele carriers had more severe oppositional defiant disorder behaviors according to mothers' (,p2 = 0.10) and teachers' (,p2 = 0.06) ratings than noncarriers, but the latter was marginally significant (P = 0.07). Children who were 7-repeat allele carriers also obtained more severe maternal ratings of tics (,p2 = 0.07) and obsessions,compulsions (,p2 = 0.08). Findings for maternal ratings of separation anxiety were marginally significant (P = 0.08, ,p2 = 0.05). Analyses of combined DRD4 and dopamine transporter gene (DAT1) genotypes approached significance (P = 0.05) for teachers' ratings of oppositional behavior and mothers' ratings of tics. DRD4 allelic variation may be a prognostic biomarker for challenging behaviors in children with autism spectrum disorder, but these exploratory findings remain tentative pending replication with larger independent samples. [source]

Relationship between stump treatment coverage using the biological control product PG Suspension, and control of Heterobasidion annosum on Corsican pine, Pinus nigra ssp. laricio

FOREST PATHOLOGY, Issue 1 2008
K. V. Tubby
Summary The relationship between the proportion of the stump surface covered by the biological stump treatment agent PG Suspension, containing Phlebiopsis gigantea and its efficacy against the pathogen Heterobasidion annosum sensu stricto was studied during a first thinning of Corsican pine (Pinus nigra ssp. laricio) in Thetford Forest, UK. PG Suspension was manually applied to 100%, 75%, 50% or 0% of the surface of 150 stumps. Spores of H. annosum were inoculated onto 75 of the stumps, and the remaining stumps exposed to natural airborne spore deposition. The relationship between coverage and efficacy was found to be quantitative. Covering all the stump surface with PG Suspension completely excluded the pathogen, whereas stumps not treated with PG Suspension (the 0% treatment) became infected with H. annosum. Partial (75%) PG Suspension coverage resulted in the pathogen colonizing 40% of stumps following artificial inoculation with H. annosum, and just 7% of stumps exposed to ambient H. annosum spore infection. Decreasing levels of coverage allowed increasing areas of the stump surface to be colonized by H. annosum. Some small gaps in coverage were closed by lateral growth of P. gigantea, but it is recommended that operators aim for full stump coverage to give complete protection against H. annosum. [source]

Spatio-temporal patterns of fish assemblages in a large regulated alluvial river

FRESHWATER BIOLOGY, Issue 7 2009
RENAUD RIFFLART
Summary 1. The River Durance, the last alpine tributary of the River Rhône, is a large, braided alluvial hydrosystem. Following large-scale regulation, flow downstream of the Serre-Ponçon dam has been maintained at 1/40th of previous annual mean discharge. To assess the effects of historical disturbances, fish assemblages and habitat use were analysed during five summers in a representative reach of the middle Durance. 2. Habitat availability and use were assessed with a multi-scale approach including the variables water depth, current velocity, roughness height of substratum, amount of woody debris and lateral/longitudinal location. Eighteen fish species were sampled by electrofishing in 289 habitat sample units. 3. Partial least square (PLS) regression showed that taxa were mainly distributed according to relationships between their total length and water depth/velocity variables. Fish assemblage composition was also related to roughness height as well as distance from the bank or to the nearest large woody debris. However, PLS regression revealed no significant differences in habitat selection between two periods of varying hydromorphological stability. 4. Fish distribution patterns and density were related to proximity to the bank and cover, indicating that local scale variables need to be considered in conservation and restoration programmes. [source]

Bonding acrylic teeth to acrylic resin denture bases: a review

GERODONTOLOGY, Issue 3 2006
S. B. Patil
Partial or complete dentures are more commonly constructed for the elderly group of the population. Teeth debonding from the dentures can be frustrating to the patients as well as the dentist. Research has been carried out and is continuing to study the issue of bonding acrylic teeth to the denture base resin. The present review takes into account the majority of research papers published in the last five decades for determining the bond strength. Selection of more compatible combinations of denture base resins and acrylic teeth may reduce the number of prosthesis fractures and the resultant repairs. [source]

Partial and transient modulation of the CD3,T-cell receptor complex, elicited by low-dose regimens of monoclonal anti-CD3, is sufficient to induce disease remission in non-obese diabetic mice

IMMUNOLOGY, Issue 1 2010
Devangi S. Mehta
Summary It has been established that a total of 250 ,g of monoclonal anti-mouse CD3 F(ab,)2 fragments, administered daily (50 ,g per dose), induces remission of diabetes in the non-obese diabetic (NOD) mouse model of autoimmune diabetes by preventing , cells from undergoing further autoimmune attack. We evaluated lower-dose regimens of monoclonal anti-CD3 F(ab,)2 in diabetic NOD mice for their efficacy and associated pharmacodynamic (PD) effects, including CD3,T-cell receptor (TCR) complex modulation, complete blood counts and proportions of circulating CD4+, CD8+ and CD4+ FoxP3+ T cells. Four doses of 2 ,g (total dose 8 ,g) induced 53% remission of diabetes, similarly to the 250 ,g dose regimen, whereas four doses of 1 ,g induced only 16% remission. While the 250 ,g dose regimen produced nearly complete and sustained modulation of the CD3 ,TCR complex, lower doses, spaced 3 days apart, which induced similar remission rates, elicited patterns of transient and partial modulation. In treated mice, the proportions of circulating CD4+ and CD8+ T cells decreased, whereas the proportions of CD4+ FoxP3+ T cells increased; these effects were transient. Mice with greater residual ,-cell function, estimated using blood glucose and C-peptide levels at the initiation of treatment, were more likely to enter remission than mice with more advanced disease. Thus, lower doses of monoclonal anti-CD3 that produced only partial and transient modulation of the CD3,TCR complex induced remission rates comparable to higher doses of monoclonal anti-CD3. Accordingly, in a clinical setting, lower-dose regimens may be efficacious and may also improve the safety profile of therapy with monoclonal anti-CD3, potentially including reductions in cytokine release-related syndromes and maintenance of pathogen-specific immunosurveillance during treatment. [source]

A novel search method to reduce PAPR of an OFDM signal using partial transmit sequences

INTERNATIONAL JOURNAL OF COMMUNICATION SYSTEMS, Issue 2 2007
Hao-Chung Tu
Abstract One of the main drawbacks of orthogonal frequency division multiplexing (OFDM) is the high peak-to-average power ratio (PAPR) of the transmitted OFDM signal. Partial transmit sequence (PTS) technique can improve the PAPR statistics of an OFDM signal. As ordinary PTS technique requires an exhaustive search over all combinations of allowed phase factors, the search complexity increases exponentially with the number of sub-blocks. In this paper, we propose a novel PTS technique with reduced complexity that each level inverts twice of phase factor bits from previous level. Then we also use initial random phase sequence to find the better search way of PAPR reduction. Numerical results show that the proposed method can achieve significant reduction in search complexity with little performance degradation. Copyright © 2006 John Wiley & Sons, Ltd. [source]

Global classification of human facial healthy skin using PLS discriminant analysis and clustering analysis

INTERNATIONAL JOURNAL OF COSMETIC SCIENCE, Issue 2 2001
C Guinot
Synopsis Today's classifications of healthy skin are predominantly based on a very limited number of skin characteristics, such as skin oiliness or susceptibility to sun exposure. The aim of the present analysis was to set up a global classification of healthy facial skin, using mathematical models. This classification is based on clinical, biophysical skin characteristics and self-reported information related to the skin, as well as the results of a theoretical skin classification assessed separately for the frontal and the malar zones of the face. In order to maximize the predictive power of the models with a minimum of variables, the Partial Least Square (PLS) discriminant analysis method was used. The resulting PLS components were subjected to clustering analyses to identify the plausible number of clusters and to group the individuals according to their proximities. Using this approach, four PLS components could be constructed and six clusters were found relevant. So, from the 36 hypothetical combinations of the theoretical skin types classification, we tended to a strengthened six classes proposal. Our data suggest that the association of the PLS discriminant analysis and the clustering methods leads to a valid and simple way to classify healthy human skin and represents a potentially useful tool for cosmetic and dermatological research. Résumé Les classifications actuelles qui définissent une peau saine sont fondées principalement sur un nombre très limité de caractéristiques cutanées telles que l'aspect gras de la peau ou sa sensibilité au soleil. Cette analyse a pour but d'établir une classification globale de la peau humaine saine du visage à l'aide de modèles mathématiques. Une recherche de typologie a été effectuée à partir des caractéristiques cliniques et biophysiques de la peau du visage des individus tout en tenant compte d'une classification théorique, reflet de l'expertise des dermatologues, appréciée sur les zones frontale et malaire du visage. Pour accroître l'efficacité prédictive des modèles avec un minimum de variables, la méthode d'analyse discriminante PLS (Partial Least Square) a été utilisée. Des méthodes de classification ont été appliquées aux composantes PLS obtenues afin de déterminer le nombre le plus vraisemblable de classes et pour regrouper les sujets selon leurs proximités. Grâce à cette approche, quatre composantes PLS ont pu être construites et six classes se sont avérées pertinentes. Ce travail a abouti à une proposition de classification à six classes plus vraisemblable et acceptable que les 36 combinaisons possibles de la classification théorique proposée. Nos données suggèrent que l'association de l'analyse discriminante PLS aux méthodes de classification permet d'obtenir de façon simple et appropriée une classification de la peau humaine saine et représente un outil potentiel utile dans le domaine de la recherche en cosmétologie et en dermatologie. [source]

Duration of primary moult affects primary quality in Grey Plovers Pluvialis squatarola

JOURNAL OF AVIAN BIOLOGY, Issue 4 2001
Lorenzo Serra
Feather wear is the natural degradation and breakage of feather structure during the interval between moults. Different rates of feather wear have been observed for primaries of free-living populations of several species of passerines and waders, and this variability has been linked to different concentrations of melanins. In this study primary moult duration explained 59% of the variation in annual rates of primary abrasion (percentage wing length loss) of seven Grey Plover wintering populations, while migration distance explained 14%. The analysis suggests that primary moult duration plays a key role in determining primary durability and hence primary quality. Long distance migrants might evolve more durable primaries, despite the higher predation risks and energetic costs of a prolonged moult. Partial or complete pre-breeding primary moults of first-year waders and complete biannual moults of some passerines might have evolved under selective forces favouring migration with unabraded primaries. [source]

Partial Left Ventriculectomy and Limited Heart Transplantation Availability

JOURNAL OF CARDIAC SURGERY, Issue 2 2001
Ph.D., sa Gradinac M.D.
Background and Aim: Partial left ventriculectomy, a novel cardiac volume reduction operation, is applied in countries without a developed heart transplantation program. We sought to determine its impact in our population of patients. Methods: Partial left ventriculectomy was performed in 38 patients during the last 4 years. Basic inclusion criteria were nonischemic dilated cardiomyopathy and poor response to medical therapy for heart failure. Hemodynamic evaluation was carried out before and after operation. A modified surgical technique of mitral valve repair and ventricle suturing was applied. Results: Thirty-day, 6-month, and 2-year survival rates were 82%± 7%, 65%± 8%. and 61%± 9%, respectively. Duration of heart failure symptoms was the only predictor of survival (p = 0.042). A high proportion of noncardiac causes of death was noted. Functional capacity in surviving patients improved at every successive measurement up to 1 year postoperatively. Conclusions: The introduction of partial left ventriculectomy in a country with limited heart transplantation availability had a great impact on the management of end-stage heart failure and may represent the only surgical option for some patients. The average cost per patient was substantially lower when compared to heart transplantation. [source]

Classification of GC-MS measurements of wines by combining data dimension reduction and variable selection techniques

JOURNAL OF CHEMOMETRICS, Issue 8 2008
Davide Ballabio
Abstract Different classification methods (Partial Least Squares Discriminant Analysis, Extended Canonical Variates Analysis and Linear Discriminant Analysis), in combination with variable selection approaches (Forward Selection and Genetic Algorithms), were compared, evaluating their capabilities in the geographical discrimination of wine samples. Sixty-two samples were analysed by means of dynamic headspace gas chromatography mass spectrometry (HS-GC-MS) and the entire chromatographic profile was considered to build the dataset. Since variable selection techniques pose a risk of overfitting when a large number of variables is used, a method for coupling data dimension reduction and variable selection was proposed. This approach compresses windows of the original data by retaining only significant components of local Principal Component Analysis models. The subsequent variable selection is then performed on these locally derived score variables. The results confirmed that the classification models achieved on the reduced data were better than those obtained on the entire chromatographic profile, with the exception of Extended Canonical Variates Analysis, which gave acceptable models in both cases. Copyright © 2008 John Wiley & Sons, Ltd. [source]

A new holistic exploratory approach to Systems Biology by Near Infrared Spectroscopy evaluated by chemometrics and data inspection

JOURNAL OF CHEMOMETRICS, Issue 10-11 2007
Lars Munck
Abstract There is a need for an improved biological and theoretical interpretation of Near Infra-Red Spectral (NIRS) fingerprints from tissues that could contribute with holistic overview to fine-grained detail modelled in Systems Biology. The concept of gene expression in self-organised networks was experimentally tested in a barley endosperm model with molecularly defined and undefined mutants. Surprisingly reproducible gene-specific NIRS fingerprints were observed directly in log1/R MSC pre-treated spectra that could not be accurately represented by destructive mathematical models. A mutant spectrum in an isogenic background represents the physiochemical expression of the gene in the whole network (tissue). The necessary holistic overview that is needed experimentally to introduce Ilya Prigogine's theory on self-organisation in Systems Biology was supplied by defining the spectral phenome. Interval spectral information on genotypes and environment was classified by interval Extended Canonical Variates Analysis (iECVA). Genetic changes in spectra were interpreted by interval Partial Least Squares Regression (iPLSR) correlations to chemical variables. A new pathway regulation was detected. The finely grained ,bottom up' modelling of molecular and chemical data from pathways requires a coarsely grained exploratory ,top down' overview by NIRS to account for the outcome of self-organisation. The amplification of expression from a gene to the phenome (pleiotropy) can now for the first time be quantified as a whole reproducible phenomenological pattern by NIRS and compared to other gene spectra. It explains published findings that transformed respectively mutated genes in genetically modified organisms (GMOs) and cancer patients can be detected unsupervised from tissues by spectroscopy, chemometrics and data inspection. Copyright © 2007 John Wiley & Sons, Ltd. [source]

Fuzzy-based purest wavelength selection from spectral data

JOURNAL OF CHEMOMETRICS, Issue 6-7 2006
Seyed Kamaledin Setarehdan
Abstract Wavelength selection is usually a useful and sometimes a necessary task in process monitoring using spectroscopic equipment. In this paper, a novel fuzzy-based purest wavelength selection algorithm from spectral data is presented. The proposed algorithm uses the pure component spectra of all chemical components within the mixture in a fuzzy logic framework to identify the set of the most important wavelengths (the set of the purest wavelengths) for a chemical component of interest. Both synthetic and real (Raman) spectral data sets were employed to evaluate the performance of the proposed algorithm. As a comparative study in the case of the real Raman data, the Evolving Window Factor Analysis (EWFA) technique is applied to both the original spectra and the selected set of the purest wavelengths for a component of interest. The resulting first singular value in EWFA is then compared to the reference concentration trend obtained using the conventional Partial Least Squares (PLS) regression model. The comparison confirms the high quality of the selected set of the purest wavelengths and the effectiveness of the proposed fuzzy-based algorithm. Copyright © 2007 John Wiley & Sons, Ltd. [source]

Optimizing the tuning parameters of least squares support vector machines regression for NIR spectra

JOURNAL OF CHEMOMETRICS, Issue 5 2006
T. Coen
Abstract Partial least squares (PLS) is one of the most used tools in chemometrics. Other data analysis techniques such as artificial neural networks and least squares support vector machines (LS-SVMs) have however made their entry in the field of chemometrics. These techniques can also model nonlinear relations, but the presence of tuning parameters is a serious drawback. These parameters balance the risk of overfitting with the possibility to model the underlying nonlinear relation. In this work a methodology is proposed to initialize and optimize those tuning parameters for LS-SVMs with radial basis function (RBF)-kernel based on a statistical interpretation. In this way, these methods become much more appealing for new users. The presented methods are applied on manure spectra. Although this dataset is only slightly nonlinear, good results were obtained. Copyright © 2007 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 2004
G. 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]

Robust methods for partial least squares regression

JOURNAL OF CHEMOMETRICS, Issue 10 2003
M. Hubert
Abstract Partial least squares regression (PLSR) is a linear regression technique developed to deal with high-dimensional regressors and one or several response variables. In this paper we introduce robustified versions of the SIMPLS algorithm, this being the leading PLSR algorithm because of its speed and efficiency. Because SIMPLS is based on the empirical cross-covariance matrix between the response variables and the regressors and on linear least squares regression, the results are affected by abnormal observations in the data set. Two robust methods, RSIMCD and RSIMPLS, are constructed from a robust covariance matrix for high-dimensional data and robust linear regression. We introduce robust RMSECV and RMSEP values for model calibration and model validation. Diagnostic plots are constructed to visualize and classify the outliers. Several simulation results and the analysis of real data sets show the effectiveness and robustness of the new approaches. Because RSIMPLS is roughly twice as fast as RSIMCD, it stands out as the overall best method. Copyright © 2003 John Wiley & Sons, Ltd. [source]

Partial least squares for discrimination

JOURNAL OF CHEMOMETRICS, Issue 3 2003
Matthew Barker
Abstract Partial least squares (PLS) was not originally designed as a tool for statistical discrimination. In spite of this, applied scientists routinely use PLS for classification and there is substantial empirical evidence to suggest that it performs well in that role. The interesting question is: why can a procedure that is principally designed for overdetermined regression problems locate and emphasize group structure? Using PLS in this manner has heurestic support owing to the relationship between PLS and canonical correlation analysis (CCA) and the relationship, in turn, between CCA and linear discriminant analysis (LDA). This paper replaces the heuristics with a formal statistical explanation. As a consequence, it will become clear that PLS is to be preferred over PCA when discrimination is the goal and dimension reduction is needed. Copyright © 2003 John Wiley & Sons, Ltd. [source]

Partial least squares path modelling for relations between baseline factors and treatment outcomes in periodontal regeneration

JOURNAL OF CLINICAL PERIODONTOLOGY, Issue 11 2009
Yu-Kang Tu
Abstract Background: Some clinical outcome variables in periodontal research are mathematically coupled, and it is not feasible to include all the mathematically coupled variables in an ordinary least squares (OLS) regression analysis. The simplest solution to this problem is to drop at least one of the mathematically coupled variables. However, this solution is not satisfactory when the mathematically coupled variables have distinctive clinical implications. Material and Methods: Partial least squares (PLS) methods were used to analyse data from a study on guided tissue regeneration. Relationships between characteristics of baseline lesions and treatment outcomes after 1 year were analysed using PLS, and the results were compared with those from OLS regression. Results: PLS analysis suggested that there were multiple dimensions in the characteristics of baseline lesion: vertical dimension was positively associated with probing pocket depth (PPD) reduction and clinical attachment level (CAL) gain, whilst horizontal dimension was negatively associated with the outcome. Baseline gingival recession had a negative association with PPD reduction but a small positive one with CAL gain. Conclusion: PLS analysis provides new insights into the relationships between baseline characteristics of infrabony defects and periodontal treatment outcomes. The hypothesis of multiple dimensions in baseline lesions needs to be validated by further analysis of different datasets. [source]

Detection of Sublethal Thermal Injury in Salmonella enterica Serotype Typhimurium and Listeria monocytogenes Using Fourier Transform Infrared (FT-IR) Spectroscopy (4000 to 600 cm,1)

JOURNAL OF FOOD SCIENCE, Issue 2 2008
H.M. Al-Qadiri
ABSTRACT:, Fourier transform infrared (FT-IR) spectroscopy (4000 to 600 cm,1) was utilized to detect sublethally heat-injured microorganisms: Salmonella enterica serotype Typhimurium ATCC 14028, a Gram-negative bacterium, and Listeria monocytogenes ATCC 19113, a Gram-positive bacterium. A range of heat treatments (N= 2) at 60 °C were evaluated: 0D (control), 2D, 4D, 6D, and 8D using a D60 °C (S. enterica serotype Typhimurium ATCC 14028 = 0.30 min, L. monocytogenes ATCC 19113 = 0.43 min). The mechanism of cell injury appeared to be different for Gram-negative and Gram-positive microbes as observed from differences in the 2nd derivative transformations and loadings plot of bacterial spectra following heat treatment. The loadings for PC1 and PC2 confirmed that the amide I and amide II bands were the major contribution to spectral variation, with relatively small contributions from C-H deformations, the antisymmetric P==O stretching modes of the phosphodiester nucleic acid backbone, and the C-O-C stretching modes of polysaccharides. Using soft independent modeling of class analogy (SIMCA), the extent of injury could be predicted correctly at least 83% of the time. Partial least squares (PLS) calibration analysis was constructed using 5 latent variables for predicting the bacterial counts for survivors of the different heat treatments and yielded a high correlation coefficient (R= 0.97 [S. enterica serotype Typhimurium] and 0.98 [L. monocytogenes]) and a standard error of prediction (SEP= 0.51 [S. enterica serotype Typhimurium] and 0.39 log10 CFU/mL [L. monocytogenes]), indicating that the degree of heat injury could be predicted. [source]

Prediction of Microbial and Sensory Quality of Cold Smoked Atlantic Salmon (Salmo salar) by Electronic Nose

JOURNAL OF FOOD SCIENCE, Issue 9 2005
Gudrun Olafsdottir
ABSTRACT: Quality changes of cold smoked salmon from 4 different smokehouses in Europe were monitored by a prototype gas-sensor array system, the FishNose. Samples were stored in different packaging (vacuum and Modified Atmosphere Packaging [MAP]) for up to 4 wk under controlled storage conditions at 5 °C and 10 °C. Quality criteria based on sensory attributes (sweet/sour, off, and rancid odor), and total viable counts and lactic acid bacteria counts were established and used for classification of samples based on the responses of the FishNose. The responses of the gas-sensors correlated well with sensory analysis of spoilage odor and microbial counts suggesting that they can detect volatile microbially produced compounds causing spoilage odors in cold-smoked salmon during storage. The system is therefore ideal for fast quality control related to freshness evaluation of smoked salmon products. Partial least squares (PLS) regression models based on samples from single producer showed better performance than a global model based on products from different producers to classify samples of different quality. [source]

Mortadella Sausage Formulations with Partial and Total Replacement of Beef and Pork Backfat with Mechanically Separated Meat from Spent Layer Hens

JOURNAL OF FOOD SCIENCE, Issue 3 2005
Marco A. Trindade
ABSTRACT: Mortadella sausages were formulated with 0%, 20%, 40%, 60%, 80%, and 100% mechanically separated layer hen meat (MSLM) replacing the beef and pork backfat as raw materials. Treatments were compared by determination of shear force, sensory acceptance, and stability during cold storage (microbial analysis, thiobarbituric acid-reactive substances [TBARS], color, and descriptive sensory analysis). Mortadella with higher MSLM presented lower shear force values. TBARS index and sensory rancidity were not affected. The greater the amounts of MSLM used, the paler was the pink color observed in the sensory evaluations and the lower were the CIE a* values. All treatments presented minimal increase in the microbiological counts evaluated during storage. The limiting factor in the acceptance of the product was the perception of bone particles in mortadella containing 60% or more MSLM. [source]

Relating Descriptive Sensory Analysis to Gas Chromatography/Olfactometry Ratings of Fresh Strawberries Using Partial Least Squares Regression

JOURNAL OF FOOD SCIENCE, Issue 7 2004
K.F. Schulbach
ABSTRACT: Sensory properties of 5 strawberry varieties were related to gas chromatography/olfactometry (GC/ O) analysis using partial least squares regression (PLS). The sour and green sensory aspects were strongly associated with titratable acidity, hexanal, and E-2 hexenal. The caramel/sweet character was differentiated from the strawberry/fruity character by its stronger association with Furaneol, which had a high score in the 2nd PLS dimension. The sensory scores for peach and the GC/O ratings for the peach-like lactones were also associated. The fruity sensory scores and the floral sensory scores were not well correlated with compounds having fruity or floral character. This lack of relationship could partially be explained by covariance among the sensory ratings for the samples. [source]

Nondestructive Assessment of Lipid Oxidation in Minced Poultry Meat by Autofluorescence Spectroscopy

JOURNAL OF FOOD SCIENCE, Issue 1 2000
J.P. Wold
ABSTRACT: To develop a rapid method to assess lipid oxidation, autofluorescence spectra (excitation wavelengths 365, 380, and 400 nm) from large samples (17 cm2) of minced poultry meat were collected by an optical system to determine directly lipid oxidation level. The same samples were also measured by 2-thiobarbituric acid method (TBARS). High correlations could be made between the TBARS method and autofluorescence spectra, especially those from 380 nm excitation. Partial least squares regression resulted in a root mean square error of 0.15 (R = 0.87) for chicken meat and 0.24 (R = 0.80) for mechanically recovered turkey meat. Classification analysis between fresh (TBARS < 0.25) and rancid (TBARS > 0.25) samples was done with high success rates. Autofluorescence spectroscopy might be well suited for rapid on-line determination of lipid oxidation level in minced poultry meat. [source]

Total projection to latent structures for process monitoring

AICHE JOURNAL, Issue 1 2010
Donghua Zhou
Abstract Partial least squares or projection to latent structures (PLS) has been used in multivariate statistical process monitoring similar to principal component analysis. Standard PLS often requires many components or latent variables (LVs), which contain variations orthogonal to Y and useless for predicting Y. Further, the X -residual of PLS usually has quite large variations, thus is not proper to monitor with the Q-statistic. To reduce false alarm and missing alarm rates of faults related to Y, a total projection to latent structures (T-PLS) algorithm is proposed in this article. The new structure divides the X -space into four parts instead of two parts in standard PLS. The properties of T-PLS are studied in detail, including its relationship to the orthogonal PLS. Further study shows the space decomposition on X -space induced by T-PLS. Fault detection policy is developed based on the T-PLS. Case studies on two simulation examples show the effectiveness of the T-PLS based fault detection methods. © 2009 American Institute of Chemical Engineers AIChE J, 2010 [source]