Search results for "Cluster Analysis"
showing 10 items of 848 documents
Periodic Classification of Local Anaesthetics (Procaine Analogues)
2006
Algorithms for classification are proposed based on criteria (information entropyand its production). The feasibility of replacing a given anaesthetic by similar ones in thecomposition of a complex drug is studied. Some local anaesthetics currently in use areclassified using characteristic chemical properties of different portions of their molecules.Many classification algorithms are based on information entropy. When applying theseprocedures to sets of moderate size, an excessive number of results appear compatible withdata, and this number suffers a combinatorial explosion. However, after the equipartitionconjecture, one has a selection criterion between different variants resulting fromc…
Main Trends in Regional Innovation Systems: An Author Co-citation Analysis
2010
Regional Innovation Systems are increasingly attracting attention on behalf of accademics, practitioners and policy makers. This has produced a wide array of studies in the field, both regards the specific themes treated and the perspectives adopted. Though a number of sujective reviews of the field have been proposed, these tend to present the field according to the analysts' subjective biases and tends to meld what the field is with what the field should be. In order to overcome the limitations present in the subjective reviews proposed untill today, in this study we conduct an objective review of the main contributions to the Regional Innovation Systems fiels of studies.
Cluster analysis to support microzonation studies
2015
In recent times the use of microtremor techniques for subsoil investigation increased significantly. The use of HVSR (Horizontal to Vertical Spectral Ratio)technique for seismic microzoning studies allows in many case to obtain detailed reconstruction of the roof of the seismic bedrock and to identify areas with similar seismic behaviour. Two different algorithms of clusteringhave been tested on a HVSR datasets acquired for studies of seismic microzoning in various Sicilian urban centers. HVSR data were previously properly processed to extract frequency and amplitude of peaks by a code based on clustering of HVSR curves determined in sliding time windows.To select an optimal set of time win…
Centroid-based Cluster Analysis of HVSR Data for Seismic Microzonation
2014
Horizontal to Vertical Spectral Ratio (HVSR) datasets acquired for studies of seismic microzoning in various urban centers of Sicilian towns, have been used to test clustering analysis through a nonhierarchical centroid-based algorithm. In this context clustering techniques may be useful to identify areas with similar seismic behaviour through HVSR data. Centroid-based algorithms generally require the number of clusters, k, and the initial centroid coordinates to be specified in advance. This aspect is considered to be one of the biggest drawbacks of these algorithms. The proposed algorithm doesn’t limit the number of k clusters and choose the initial centroids automatically from the data s…
Comparison of Disease Clusters in Two Elderly Populations Hospitalized in 2008 and 2010
2013
<b><i>Background:</i></b> As chronicity represents one of the major challenges in the healthcare of aging populations, the understanding of how chronic diseases distribute and co-occur in this part of the population is needed. <b><i>Objectives:</i></b> The aims of this study were to evaluate and compare patterns of diseases identified with cluster analysis in two samples of hospitalized elderly. <b><i>Methods:</i></b> Data were obtained from the multicenter ‘Registry Politerapie SIMI (REPOSI)' that included people aged 65 or older hospitalized in internal medicine and geriatric wards in Italy during 2008 and 2010. The s…
Impact of clinical phenotypes on management and outcomes in European atrial fibrillation patients: a report from the ESC-EHRA EURObservational Resear…
2021
Abstract Background Epidemiological studies in atrial fibrillation (AF) illustrate that clinical complexity increase the risk of major adverse outcomes. We aimed to describe European AF patients’ clinical phenotypes and analyse the differential clinical course. Methods We performed a hierarchical cluster analysis based on Ward’s Method and Squared Euclidean Distance using 22 clinical binary variables, identifying the optimal number of clusters. We investigated differences in clinical management, use of healthcare resources and outcomes in a cohort of European AF patients from a Europe-wide observational registry. Results A total of 9363 were available for this analysis. We identified three …
Regularization operators for natural images based on nonlinear perception models.
2006
Image restoration requires some a priori knowledge of the solution. Some of the conventional regularization techniques are based on the estimation of the power spectrum density. Simple statistical models for spectral estimation just take into account second-order relations between the pixels of the image. However, natural images exhibit additional features, such as particular relationships between local Fourier or wavelet transform coefficients. Biological visual systems have evolved to capture these relations. We propose the use of this biological behavior to build regularization operators as an alternative to simple statistical models. The results suggest that if the penalty operator take…
Genomic response programs of Candida albicans following protoplasting and regeneration
2005
Transcription profiling of Candida albicans cells responding to the elimination of the wall (protoplasts) and posterior regeneration was explored. DNA microarrays were used to measure changes in the expression of 6039 genes, and the upregulated genes during regeneration at 28 degrees C were assigned to fourteen categories. A total of 407 genes were upregulated during the process, of which 144 reached a maximum after 1 h. MKC1, a gene encoding a member of the regulatory pathway involved in cell wall integrity was overexpressed. Time-dependent expression divided the genes into 40 clusters. Clusters 1-19 were highly expressed initially (time 0) and downregulated following incubation, whereas t…
Social Housing and Affordable Rent: The Effectiveness of Legal Thresholds of Rents in Two Italian Metropolitan Cities
2022
Social housing is an instrument of housing policies to support those groups of people who are disadvantaged due to particular economic weaknesses and/or social relational fragility. Consequently, to achieve the objective of social sustainability, the rents of social housing must be below the market rents and low enough to be affordable. Italian law has set several rent thresholds which are based on local territorial agreements between landlords and renters associations. This article aims to examine whether these thresholds generate social fairness and housing affordability within each city and between different cities, or instead inequalities and spatial asymmetries. A cluster analysis is a…
The categorization of amateur cyclists as research participants: findings from an observational study.
2018
Sampling bias is an issue for research involving cyclists. The heterogeneity of cyclist populations, on the basis of skill level and riding purpose, can generate incorrect inferences about one specific segment of the population of interest. In addition, a more accurate categorization would be helpful when physiological parameters are not available. This study proposes using self-reported data to categorize amateur cyclist types by varying skill levels and riding purposes, therefore improving sample selection in experimental studies. A total of 986 cyclists completed an online questionnaire between February and October 2016. Two-step cluster analyses were performed to generate distinct group…