Search results for "Principal component"
showing 10 items of 514 documents
Functional principal component analysis as a new methodology for the analysis of the impact of two rehabilitation protocols in functional recovery af…
2014
[EN] Background: This study addressed the problem of evaluating the effectiveness of two protocols of physiotherapy for functional recovery after stroke. In particular, the study explored the use of Functional Principal Component Analysis (FPCA), a multivariate data analysis in order to assess and clarify the process of regaining independence after stroke. Methods: A randomized double-blind controlled trial was performed. Thirteen subjects with residual hemiparesis after a single stroke episode were measured in both in- and outpatient settings at a district hospital. All subjects were able to walk before suffering the stroke and were hemodynamically stable within the first week after stroke…
The role of fear-avoidance cognitions and behaviors in patients with chronic tinnitus.
2012
The current study investigated the role of fear-avoidance-a concept from chronic pain research-in chronic tinnitus. A self-report measure the "Tinnitus Fear-Avoidance Cognitions and Behaviors Scale (T-FAS)" was developed and validated. Furthermore, the role of fear-avoidance behavior as mediator of the relationship between anxiety sensitivity and tinnitus handicap was investigated. From a clinical setting, N = 373 patients with chronic tinnitus completed questionnaires assessing tinnitus handicap (Tinnitus Handicap Inventory), anxiety, depression (Hospital Anxiety and Depression Scale), anxiety sensitivity (Anxiety Sensitivity Index-3), personality factors (Big Five Inventory-10), and fear-…
Study of the recovery patterns of elderly subacute stroke patients in an interdisciplinary neurorehabilitation unit
2015
Background This study seeks to establish the facts of the improvement over time in elderly poststroke patients. Methods A retrospective study was performed with regard to 106 subacute stroke patients aged older than 65 years, who were treated in an interdisciplinary neurorehabilitation unit. Three assessment points were established (on admission, 6 months post-onset, and 12 months post-onset), with the scores relative to 10 assessment scales having been collected at each point. Results By means of a principal component analysis, a first component was obtained, which is taken to represent a combined index of the 10 scales and to express the overall health status of the patient. An analysis o…
Genome-Wide Expression Profiles in Very Low Birth Weight Infants With Neonatal Sepsis
2014
BACKGROUND: Bacterial sepsis is associated with high morbidity and mortality in preterm infants. However, diagnosis of sepsis and identification of the causative agent remains challenging. Our aim was to determine genome-wide expression profiles of very low birth weight (VLBW) infants with and without bacterial sepsis and assess differences. METHODS: This was a prospective observational double-cohort study conducted in VLBW (<1500 g) infants with culture-positive bacterial sepsis and non-septic matched controls. Blood samples were collected as soon as clinical signs of sepsis were identified and before antibiotics were initiated. Total RNA was processed for genome-wide expression an…
Puma (Puma concolor) epididymal sperm morphometry
2016
The Andean puma (Puma concolor) has not been widely studied, particularly in reference to its semen characteristics. The aim of the present study was to define the morphometry of puma sperm heads and classify their subpopulations by cluster analysis. Samples were recovered postmortem from two epididymides from one animal and prepared for morphological observation after staining with the Hemacolor kit. Morphometric data were obtained from 581 spermatozoa using a CASA-Morph system, rendering 13 morphometric parameters. The principal component (PC) analysis was performed followed by cluster analysis for the establishment of subpopulations. Two PC components were obtained, the first related to …
Development and Validation of the Questionnaire of Academic Stress in Secondary Education: Structure, Reliability and Nomological Validity
2018
This study presents the validation process of the Questionnaire on Academic Stress in Secondary Education (QASSE) designed to assess the wide variety of school sources and situations related to academic stress in adolescence, and their relationship with students&rsquo
Mapping Ash CaCO3, pH, and Extractable Elements Using Principal Component Analysis
2017
Abstract Ash cover in fire-affected areas is an important factor in the reduction of soil erosion and increased availability of soil nutrients. Thus it is important to understand the spatial distribution of ash and its capacity for soil protection and to provide nutrients to the underlying soil. In this work, we aimed to map ash CaCO3, pH, and select extractable elements using a principal component analysis (PCA). Four days after a medium to severe wildfire, we established a grid in a 9 ×27 m area on a west facing slope and took ash samples every 3 m for a total of 40 sampling points. The PCA carried out retained five different factors. Factor 1 had high positive loadings for ash with elect…
MCR-ALS on metabolic networks: Obtaining more meaningful pathways
2015
[EN] With the aim of understanding the flux distributions across a metabolic network, i.e. within living cells, Principal Component Analysis (PCA) has been proposed to obtain a set of orthogonal components (pathways) capturing most of the variance in the flux data. The problems with this method are (i) that no additional information can be included in the model, and (ii) that orthogonality imposes a hard constraint, not always reasonably. To overcome these drawbacks, here we propose to use a more flexible approach such as Multivariate Curve Resolution-Alternating Least Squares (MCR-ALS) to obtain this set of biological pathways through the network. By using this method, different constraint…
Representation and estimation of spectral reflectances using projection on PCA and wavelet bases
2008
In this article, we deal with the problem of spectral reflectance function representation and estimation in the context of multispectral imaging. Because the reconstruction of such functions is an inverse problem, slight variations in input data completely skew the expected results. Therefore, stabilizing the reconstruction process is necessary. To do this, we propose to use wavelets as basis functions, and we compare those with Fourier and PCA bases. We present the idea and compare these three methods, which belong to the class of linear models. The PCA method is training-set dependent and confirms its robustness when applied to reflectance estimation of the training sets. Fourier and wave…
An Introduction to Kernel Methods
2009
Machine learning has experienced a great advance in the eighties and nineties due to the active research in artificial neural networks and adaptive systems. These tools have demonstrated good results in many real applications, since neither a priori knowledge about the distribution of the available data nor the relationships among the independent variables should be necessarily assumed. Overfitting due to reduced training data sets is controlled by means of a regularized functional which minimizes the complexity of the machine. Working with high dimensional input spaces is no longer a problem thanks to the use of kernel methods. Such methods also provide us with new ways to interpret the cl…