Search results for "Stepwise"
showing 10 items of 56 documents
Gully erosion susceptibility assessment by means of GIS-based logistic regression: A case of Sicily (Italy)
2014
article i nfo Article history: This research aims at characterizing susceptibility conditions to gully erosion by means of GIS and multivariate statistical analysis. The study area is a 9.5 km 2 river catchment in central-northern Sicily, where agriculture ac- tivities are limited by intense erosion. By means of field surveys and interpretation of aerial images, we prepared a digitalmap of thespatial distribution of 260 gulliesinthestudy area.Inaddition,fromavailable thematicmaps, a 5 m cell size digital elevation model and field checks, we derived 27 environmental attributes that describe the variability of lithology, land use, topography and road position. These attributes were selected f…
Are You Able to Trust Me? Analysis of the Relationships Between Personality Traits and the Assessment of Attractiveness and Trust
2021
Behavioral and neuroimaging studies show that people trust and collaborate with others based on a quick assessment of the facial appearance. Based on the morphological characteristics of the face, i.e., features, shape, or color, it is possible to determine health, attractiveness, trust, and some personality traits. The study attempts to indicate the features influencing the perception of attractiveness and trust. In order to select individual factors, a model of backward stepwise logistic regression was used, analyzing the results of the psychological tests and the attractiveness and trust survey. Statistical analysis made it possible to select the most important personality traits related…
Varietal and geographic classification of french red wines in terms of elements, amino acids and aromatic alcohols
1988
Thirty-four French red wines from three regions already studied for their anthocyanin and flavonoid constituents have been further analysed for elements, amino acids and aromatic alcohols. An interpretation of the differences between wines related to their different geographic and varietal origins has been made from the results of statistical analyses: F statistic, principal component analysis (PCA) and stepwise discriminant analysis (SDA). Wine samples produced near Bordeaux were found to be characterised by higher rubidium and lower lithium and calcium concentrations. Differences between wine samples made from the same grape variety or produced in the same region are mainly related to dif…
Predictors for early readmission after COPD exacerbation
2019
Aim: Identify predictors for early readmission in patients with COPD and severe exacerbation. Material and methods: Prospective study (July 2017-June 2018) that included all patients hospitalized for an acute exacerbations of COPD. Demographic date, clinical and spirometric parameters, arterial blood gases, length of stay, and evolutive parameters were collected. We used univariate and multivariate statistical techniques to identify risks for readmission. Results: 278 consecutive patients were enrolled. During the follow-up 31 (11%) patients were admitted within 30 days of discharge (early readmission). Univariate analysis showed that FEV1 (p=0.02), FEV1 (%) (p=0.01), total dose of steroids…
Understanding the mechanism of the Povarov reaction. A DFT study
2014
The molecular mechanism of the Povarov reaction in acetonitrile has been studied at the MPWB1K/6-311G** level of theory. This reaction follows a domino process that comprises two sequential reactions: (i) a Lewis acid catalysed aza-Diels–Alder (A-DA) reaction between a N-aryl imine and a nucleophilic ethylene yielding a formal [4 + 2] cycloadduct; (ii) a stepwise 1,3-hydrogen shift at this intermediate affording the final tetrahydroquinoline. At this computational level, the Lewis acid catalysed A-DA reaction presents a two-step mechanism as a consequence of the large stabilisation of the corresponding zwitterionic intermediate. Our study allows establishing that the N-aryl substituent has …
Determination of Phenols from Automobile Exhaust by Means of High-Performance Liquid Chromatography (HPLC)
1981
Abstract The paper describes a procedure to determine ten representative phenols (phenol, m-, p-, o-cresol, 2,4-, 2,6-, 3,4-, 3,5-xylenol, 2,3,6-, 2,4,6-trimethylphenol) in engine exhaust. Sampling was performed by a conventional Grimmer device. A sample of the water condensate collected was extracted with ether. After concentration of the ether extract phenols were isolated from other interfering compounds by stepwise elution on a Lobar column packed with LiChroprep Si 60 under controlled conditions. Relative recovery of the majority of reference phenols ranged from 90-100%. Separation of phenols into individual components was performed on polar packings as well as on Reverse Phase packing…
An updated algorithm recommendation for the management of knee osteoarthritis from the European Society for Clinical and Economic Aspects of Osteopor…
2019
Objectives: The European Society for Clinical and Economic Aspects of Osteoporosis, Osteoarthritis and Musculoskeletal Diseases (ESCEO) sought to revisit the 2014 algorithm recommendations for knee osteoarthritis (OA), in light of recent efficacy and safety evidence, in order to develop an updated stepwise algorithm that provides practical guidance for the prescribing physician that is applicable in Europe and internationally. Methods: Using the Grading of Recommendations Assessment, Development and Evaluation (GRADE) process, a summary of evidence document for each intervention in OA was provided to all members of an ESCEO working group, who were required to evaluate and vote on the streng…
Varietal and geographic classification of french red wines in terms of pigments and flavonoid compounds
1988
Thirty-four French red wines originating from six different grape varieties and three different production areas were analysed in duplicate for 15 anthocyanins, ten flavonoids and three colour parameters, F-statistics, principal component analysis and stepwise discriminant analysis were used to identify and to explain differences among samples. Clear difference between wines made from different varieties were mainly related to anthocyanin 3-acylglucosides. Malvidin and peonidin 3-acetylglucosides were found in increasing concentrations in wines made respectively from Grenache, Carignan, Cinsault, Merlot, Carbernet Sauvignon and Cabernet Franc grapes; the concentrations of peonidin and malvi…
A comparison of two indirect methods for estimating average levels of gene flow using microsatellite data.
1999
We compare the performance of Nm estimates based on FST and RST obtained from microsatellite data using simulations of the stepwise mutation model with range constraints in allele size classes. The results of the simulations suggest that the use of microsatellite loci can lead to serious overestimations of Nm, particularly when population sizes are large (N5000) and range constraints are high (K20). The simulations also indicate that, when population sizes are small (N/= 500) and migration rates are moderate (Nm approximately 2), violations to the assumption used to derive the Nm estimators lead to biased results. Under ideal conditions, i.e. large sample sizes (ns/= 50) and many loci (nl/=…
Inter-Relations among Motivation, Self-Perceived Use of Strategies and Academic Achievement in Science: A Study with Spanish Secondary School Students
2020
The relationship between motivation and the use of learning strategies is a focus of research in order to improve students&rsquo