Search results for "Component analysis"
showing 10 items of 562 documents
Microbial Community Structure and Density Under Different Tree Species in an Acid Forest Soil (Morvan, France)
2005
Overexploitation of forests to increase wood production has led to the replacement of native forest by large areas of monospecific tree plantations. In the present study, the effects of different monospecific tree cover plantations on density and composition of the indigenous soil microbial community are described. The experimental site of "Breuil-Chenue" in the Morvan (France) was the site of a comparison of a similar mineral soil under Norway spruce (Picea abies), Douglas fir (Pseudotuga menziesii), oak (Quercus sessiflora), and native forest [mixed stand dominated by oak and beech (Fagus sylvatica)]. Sampling was performed during winter (February) at three depths (0-5, 5-10, and 10-15 cm…
Guinean and sahelian rainfall anomaly indices at annual and monthly scales (1933-1990)
1994
The annual and monthly rainfall variability in north tropical Africa are analysed by principal component analysis in order to detect the main coherent modes. The Sahel constitutes the first mode, although it is divided close to 1O"W into an Atlantic section and a Continental section. The Guinean zone is less coherent, and is divided into distinct modes. The subequatorial area never formed a distinct mode. Rainfall variability for the coherent areas is constructed from rainfall anomaly indices (RAI), based on the coherent areas, and a rainfall typology taking into account the spatial pattern of the rainfall anomaly fields and the intensity of the anomaly. Their evolution (mainly since 1950) …
Terahertz Biomedical Imaging: From Multivariate Analysis and Detection to Material Parameter Extraction
2017
Terahertz imaging is an interesting route for biomedical analysis. In particular, cancer imaging is a subject of study for different teams [1,2]. A work is done in Bordeaux in partnership with a hospital to do terahertz analysis of breast tissue. This work is done in reflection with time domain imaging setup with fresh samples. The aim is to accurately assess tumor margins and which could in the future allow a quick validation of the precision of the surgical procedure and know if new surgery should be performed. We have presented in a previous paper [3] the use of automatic methods of image generation with different parameters [4] in order to explore the different contrasts that exist in t…
Sensory analysis of Burgundy Pinot noir wines: A comparison of orthonasal and retronasal profiling
1999
Thirty Burgundy Pinot noir wines were evaluated by quantitative descriptive profile by nose (BN) and by mouth (BM) separately, by a trained panel composed of 12 judges. A specific vocabulary of 20 terms was developed. Sensory results were analyzed and compared by univariate and multivariate statistical techniques. Principal component analyses of the mean ratings BN and BM were fairly comparable regarding correlation among variables and the position of the wines. However, five sensory characteristics seem to be more intensely perceived BM, against 6 BN. Panel discrimination of the wines and panel repeatability in the measure were found to be slightly better BN than BM. A further canonical di…
The Largest Subunit of RNA Polymerase II as a New Marker Gene to Study Assemblages of Arbuscular Mycorrhizal Fungi in the Field
2014
Due to the potential of arbuscular mycorrhizal fungi (AMF, Glomeromycota) to improve plant growth and soil quality, the influence of agricultural practice on their diversity continues to be an important research question. Up to now studies of community diversity in AMF have exclusively been based on nuclear ribosomal gene regions, which in AMF show high intra-organism polymorphism, seriously complicating interpretation of these data. We designed specific PCR primers for 454 sequencing of a region of the largest subunit of RNA polymerase II gene, and established a new reference dataset comprising all major AMF lineages. This gene is known to be monomorphic within fungal isolates but shows an…
Single-trial-based temporal principal component analysis on extracting event-related potentials of interest for an individual subject.
2023
Background: Temporal principal component analysis (tPCA) has been widely used to extract event-related potentials (ERPs) at group level of multiple subjects ERP data and it assumes that the underlying factor loading is fixed across participants. However, such assumption may fail to work if latency and phase for one ERP vary considerably across participants. Furthermore, effect of number of trials on tPCA decomposition has not been systematically examined as well, especially for within-subject PCA. New method: We reanalyzed a real ERP data of an emotional experiment using tPCA to extract N2 and P2 from single-trial EEG of an individual. We also explored influence of the number of trials (con…
Local vs global motions in protein folding
2013
It is of interest to know whether local fluctuations in a polypeptide chain play any role in the mechanism by which the chain folds to the native structure of a protein. This question is addressed by analyzing folding and non-folding trajectories of a protein; as an example, the analysis is applied to the 37-residue triple β-strand WW domain from the Formin binding protein 28 (FBP28) (PDB ID: 1E0L). Molecular dynamics (MD) trajectories were generated with the coarse-grained united-residue force field, and one- and two-dimensional free-energy landscapes (FELs) along the backbone virtual-bond angle θ and backbone virtual-bond-dihedral angle γ of each residue, and principal components, respect…
Authentication of the protected designation of origin horchata de Valencia through the chemometric treatment of mineral content
2010
Spanish horchata de chufa samples were authenticated based on the determination of mineral elements by inductively coupled plasma atomic emission spectrometry (ICP-OES) combined with different chemometric methods. The ability of multivariate analysis, such as principle components analysis (PCA), classification and regression trees (CARTs) and discriminant analysis (DA) were evaluated in order to achieve a correct sample classification. It was possible to clearly differentiate homemade and long-life commercial samples by all three methods and CART and DA provided an excellent tool to establish the growth origin of the tiger nuts. CART analysis employed the concentration of Mg to discriminate…
Classification of persimmon fruit origin by near infrared spectrometry and least squares-support vector machines
2014
Abstract The main objective of this work has been the authentication by Fourier transform near infrared (FT-NIR) spectrometry of the origin of persimmon fruits cultivated in different regions of Spain. In order to achieve this goal, 166 persimmon samples from 7 different regions of Spain were analyzed by FT-NIR spectrometry. By splitting the spectral data in training and independent test sets, a classification model was built using least squares support vector machines chemometric technique. Orthogonal signal correction and principal component analysis were performed prior to conduct the classification strategy. The verified model was applied for the prediction of the origin of 50 samples f…
Alternative method for binary shape alignment of non-symmetrical shapes based on minimal enclosing box
2012
Proposed is a novel method based on the minimal enclosing box (MEB) to determine the canonical orientation associated with a three-dimensional binary shape. It is suggested that, when the shape has no clear distinctive features and two or more of the eigenvalues are similar, this method is more suitable than the commonly used method based on principal component analysis (PCA). An experiment is performed with shapes of human livers by measuring the degree on which a prototypical image (atlas) matches to a new shape after alignment by PCA, minimal area projection (MAP), and MEB showing that in this case MEB outperforms the usual PCA-based alignment method and also the MAP method.