1,720,977 research outputs found
Multivariate statistical tools for the evaluation of proteomic 2d-maps: Recent achievements and applications
No full textTwo dimensional polyacrylamide gel electrophoresis (2D-PAGE) maps represent an unavoidable tool in many fields connected with proteome research, such as development of new diagnostic assays or new drugs. Unfortunately the information contained in the maps is often so complex that its recognition and extraction usually requires complex statistical treatments. Statistics accompanies many phases of 2D-PAGE maps management - from the spot revelation to maps matching, as well as the extraction and rationalisation of useful information. This review describes and reports the most recent achievements in the field of statistical tools applied to proteome research by two-dimensional gel electrophoresis (2D-GE). The first section is devoted to briefly describe the theoretical aspects of the multivariate methods mostly adopted in this field such as Principal Component Analysis, Cluster Analysis, Classification methods, Artificial Neural Networks. The most recent applications are then described explaining the analysis of spot volume datasets from standard differential analysis as well as the direct analysis of 2D maps images. Applications are also reported about the use of multivariate tools in the analysis of DNA and RNA profiles
A new method of comparing 2D-PAGE maps based on the computation of Zernike moments and multivariate statistical tools
No full textGoing Beyond Counting First Authors in Author Co-citation Analysis
Full text linkThe present study examines one of the fundamental aspects of author co-citation analysis (ACA) - the way co-citation
counts are defined. Co-citation counting provides the data on which all subsequent statistical analyses and mappings
are based, and we compare ACA results based on two different types of co-citation counting - the traditional type that
only counts the first one among a cited work's authors on the one hand and a non-traditional type that takes into
account the first 5 authors of a cited work on the other hand. Results indicate that the picture produced through this non-traditional author co-citation counting contains more coherent author groups and is therefore considerably clearer. However, this picture represents fewer specialties in the research field being studied than that produced through the traditional first-author co-citation counting when the same number of top-ranked authors is selected and analyzed. Reasons for these effects are discussed
A New Algorithm for the Simulation of Sodium Dodecil Sulfate Two-Dimensional Polyacrylamide Gel Electrophoresis Data Sets
No full textA new algorithm for generating simulated sodium dodecil sulfate two-dimensional polyacrylamide gel electrophoresis (SDS 2D-PAGE) map images was developed. To choose the simulation strategy able to provide realistic 2D-PAGE maps, several parameters that characterize the statistical features of the images and data sets of images were taken into account, such as the distribution of size, intensity, and volume of the spots and their changes of position and volume along different replications of the same 2D-PAGE map. In this way, also the low reproducibility of replications of the same SDS 2D-PAGE maps was taken into account. The present algorithm can be usefully employed for the development of new classification and/or image analysis algorithms applied to bidimensional electrophoretic data sets, given the usually small number of experimental replications available
Multivariate calibration applied to the field of cultural heritage: Analysis of the pigments on the surface of a painting
No full textThis paper concerns a first attempt of application of multivariate calibration to the field of cultural heritage for the determination of the superficial pigments composition of a painting. For this purpose, 10 mixtures of three organic pigments (Alizarin, Permanent Red and Phtalocyanine Green) selected by an augmented simplex-centroid design were mixed with linseed oil and spread on 10 cotton canvas strips. Each sample was characterised with three genuine replicates of an ATR-IR spectrum.
Three calibration models, responding to the relative concentration of each specific pigment in the mixtures, were built with the partial least squares (PLS1) algorithm, using the ATR-IR spectra of the surfaces as predictors. The three mixtures corresponding to the augmentation of the simplex-centroid design were used to validate the model predictive ability which proved to be very satisfactory, with very low root mean squared error of prediction (RMSEP). Finally the models were successfully applied to a real painting, to predict the concentrations of some unknown mixtures of the three studied pigments.
This work might have possible applications in the determination of the composition of dyes in real paintings to obtain information on the execution technique and for restoration purposes
Hydroxyl and acid number prediction in polyester resins by near infrared spectroscopy and artificial neural networks
No full textBack-propagation artificial neural networks (BP-ANN) are applied for modeling hydroxyl number and acid value of a set of 62 samples of polyester resins from their near infrared (NIR) spectra. The results are compared to the classical calibration approaches, i.e. principal component regression (PCR) and partial least squares (PLS). The set of available samples is split into: (i) a training set, for models calculation; (ii) a test set, for setting the correct number of latent variables in PCR and PLS and for selecting the end point of the training phase of BP-ANN; (iii) a "production set" of samples, which are predicted to evaluate the models predictive ability. This approach guarantees that the predictive ability of the models is evaluated by genuine predictions. BP-ANN resulted always better than the classical PCR and PLS, from the point of view of the predictive ability. The study of the breakdown number of experiments to include in the training set showed instead that this factor does influence PCR and PLS at a lesser degree than what happens for BP-ANN. The latter approach requires a larger number of experiments for obtaining good results. The choice of optimal training sets is efficiently performed by Kohonen self-organizing maps (SOMs). It can be concluded that FT-NIR spectroscopy and BP-ANN models can be properly employed for monitoring the polyesterification of dicarboxylic acids with diols by predicting the acid and hydroxyl numbers directly along the process line
Monitoring of paintings under exposure to UV light by ATR-FT-IR spectroscopy and multivariate control charts
No full textThis paper concerns the improvement of a method, already applied for the conservation state monitoring of wooden and painted surfaces, to a system closely simulating a real artwork, namely a canvas painted with mixtures of three organic pigments (Alizarin, Permanent Red, Phtalocyanine Green). Ten mixtures of these pigments, according to an augmented simplex-centroid design, were prepared, mixed with linseed oil and spread on 10 cotton canvas strips. Drying ended, all the samples were analysed by ATR-FT-IR spectroscopy to describe the superficial variability in normal conditions of conservation, i.e. when no degradation is present. Successively, the samples were exposed to artificial UV light simulating the action of an aggressive portion of sunlight. The IR spectra of the surfaces were regularly acquired to monitor the superficial changes due to the UV aggression. Treatment ended, a chemometric study based on the Principal Component Analysis of the spectroscopic data collected both in normal conditions of conservation and during the artificial accelerated ageing, was performed and the multivariate Shewhart and Cusum control charts were built with the scores of the significant PCs (principal components). PCA based control charts showed to be able to identify the presence of significant changes of the painted surfaces, to identify the starting of the degradations and to provide insights about the chemical alterations induced by the UV exposure
Variations on the Author
Full text link“Variations on the Author” discusses two of Eduardo Coutinho’s recent films (Um Dia na Vida, from 2010, and Últimas Conversas, posthumously released in 2015) and their contribution to the general question of documentary authorship. The director’s filmography is characterized by a consistent yet self-effacing form of authorial self-inscription: Coutinho often features as an interviewer that rather than express opinions propels discourses; an interviewer that is good at listening. This mode of self-inscription characterizes him as an author who is not expressive but who is nonetheless markedly present on the screen. In Um Dia na Vida, however, Coutinho is completely absent form the image, while Últimas Conversas, on the contrary, includes a confessional prologue that moves the director from the margins to the center of his films. This article examines the ways in which these works stand out in the filmography of a director who offers new insights into the notion of cinematic authorship
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