Search results for "Component"
showing 10 items of 1682 documents
Steroidal saponins from the aerial parts of Cordyline fruticosa L. var. strawberries.
2019
A new sulfated steroidal derivative (fruticogenin A: 1-sulfo-australigenin-3-sodium sulphate, 1) and three new steroidal saponins named fruticoside K (3-sulfo-spirostan-25(27)-ene-1β,3β-diol-1-O-[α-L-rhamnopyranosyl-(1 → 4)-β-D-fucopyranoside], 2), fruticoside L (3-sulfo-spirostan-25(27)-ene-1β,3β,6α-triol-1-O-[α-L-rhamnopyranosyl-(1 → 4)-β-D-fucopyranoside], 3) and fruticoside M (spirostan-25(27)-ene-1β,3α-diol-1-O-[α-L-rhamnopyranosyl-(1 → 2)-α-L-rhamnopyranoside], 4) were isolated from the aerial parts of Cordyline fruticosa L. var. strawberries. Their structures were established on the basis of 1D and 2D NMR data, mass spectrometry and chemical methods. Compounds 2 and 4 exhibited weak …
Multivariate analysis in the identification of biological targets for designed molecular structures: The BIOTA protocol
2013
In this work the new protocol BIOlogical Target Assignation (BIOTA) for the prediction of the biological target from molecular structures is proposed. BIOTA is based on the Principal Components Analysis (PCA) application on a matrix of ligands versus molecular descriptors. The application of BIOTA could allow to hypothesize the mechanism of action of a candidate drug prior to its biological evaluation or to repurpose old drugs. The protocol can be fine-tuned by choosing opportune targets (biological or not) and molecular descriptors, and it can be useful in every fields in with it is possible to collect set of compounds with known properties. The robustness of the protocol depends from diff…
The impact of feature extraction on the performance of a classifier : kNN, Naïve Bayes and C4.5
2005
"The curse of dimensionality" is pertinent to many learning algorithms, and it denotes the drastic raise of computational complexity and the classification error in high dimensions. In this paper, different feature extraction techniques as means of (1) dimensionality reduction, and (2) constructive induction are analyzed with respect to the performance of a classifier. Three commonly used classifiers are taken for the analysis: kNN, Naïve Bayes and C4.5 decision tree. One of the main goals of this paper is to show the importance of the use of class information in feature extraction for classification and (in)appropriateness of random projection or conventional PCA to feature extraction for …
Sign and Rank Covariance Matrices: Statistical Properties and Application to Principal Components Analysis
2002
In this paper, the estimation of covariance matrices based on multivariate sign and rank vectors is discussed. Equivariance and robustness properties of the sign and rank covariance matrices are described. We show their use for the principal components analysis (PCA) problem. Limiting efficiencies of the estimation procedures for PCA are compared.
The impact of criminality on the riskiness of cooperative credit banks in Italy: a macro regional approach
2017
In Italy, Cooperative Credit Banks (CCBs), unlike large banks, despite the economic downturn, have continued to extend credit to customers, but at the cost of a higher incidence of bad credit. This increased credit risk of local banks has been caused by management policy choices, such as preferring to modify the conditions applicable to credit supply and to engage firms in long-term credit relationships rather than initiating credit recovery procedures. The originality of this empirical analysis lies in its demonstration of the effects of environmental factors related to the spread of crime and lower economic well-being, higher unemployment and poverty in families on the credit market in So…
Applying univariate vs. multivariate statistics to investigate therapeutic efficacy in (pre)clinical trials: A Monte Carlo simulation study on the ex…
2020
BackgroundSmall sample sizes combined with multiple correlated endpoints pose a major challenge in the statistical analysis of preclinical neurotrauma studies. The standard approach of applying univariate tests on individual response variables has the advantage of simplicity of interpretation, but it fails to account for the covariance/correlation in the data. In contrast, multivariate statistical techniques might more adequately capture the multi-dimensional pathophysiological pattern of neurotrauma and therefore provide increased sensitivity to detect treatment effects.ResultsWe systematically evaluated the performance of univariate ANOVA, Welch's ANOVA and linear mixed effects models ver…
Self-perception about emerging digital skills in higher education students
2020
El mercado laboral actual exige nuevas cualidades y conocimientos a los recién egresados de las universidades, incluidas las habilidades digitales, no existiendo suficientes investigaciones sobre la autopercepción del estudiantado al respecto. El objetivo de esta investigación fue medir la percepción que el estudiantado tiene sobre sus propias habilidades digitales del siglo XXI, en relación con el uso de las tecnologías de la comunicación (TIC) en la Educación Superior. Se generó y aplicó un cuestionario a 356 estudiantes con la técnica de muestreo aleatorio estratificado. Se realizó un análisis de componentes principales avalado por valores adecuados del coeficiente Kaiser-Meyer-Olkin y d…
On the importance of the prosodic component in the expression of linguistic im/politeness
2014
This paper outlines the important relationship between prosody and im/politeness and presents a brief overview of what has been done in this field. Sections 2, 3 and 4 present several theoretical concepts which are especially relevant for understanding im/politeness in concrete frameworks (mainly in conversation). Section 5 points out the necessity of studying a pragmatic phenomenon like im/politeness with its prosodic expression. Finally, section 6 discusses some studies in this field on different languages, with a special focus on prosodic values like the F0 (pitch/fundamental frequency), intonation patterns, duration and speech rate. Keywords: F0, duration, speech rate, im/politeness, co…
Circuit proposals for high-voltage latching current limiters
2019
This work discusses some ideas to adapt existing low voltage Latching Current Limiter (LCL) circuits to high voltage operation to provide a basis for future designs. Component selection, driver and ancillary power supply are key issues discussed which eventually provides a high-voltage LCL proposal. Experimental validation of two different prototypes (380Vdc and 1kVdc) is included as well as some digital techniques to enhance LCL capabilities.
Embryonic stem cell differentiation studied by FT-IR spectroscopy
2007
We propose, here, an FT-IR method to monitor the spontaneous differentiation of murine embryonic stem (ES) cells in their early development. Principal component analysis and subsequent linear discriminant analysis enabled us to segregate stem cell spectra into separate clusters corresponding to different differentiation times - and to identify the most significant spectral changes during differentiation. Between days 4 to 7 of differentiation, these spectral changes in the protein amide I band (1700-1600 cm(-1)) and in the nucleic acid absorption region (1050-850 cm(-1)) indicated that mRNA translation was taking place and that specific proteins were produced, reflecting the appearance of a…