Search results for "cluster analysis."
showing 10 items of 805 documents
Biodiversità in alcune specie del genere Mentha nel territorio dei Monti Nebrodi (Sicilia N-W).
2008
In Nebrodi Mountains (N-E Sicily), the genus Mentha is represented by an high number of species, in many cases typical of humid and subhumid environments. This work was addressed to investigate about the biomorphological traits of various accessions belonging to 3 Mentha species collected in the Nebrodi highlands, namely 22 accessions of Mentha spicata, 12 of Mentha suaveolens and 13 of Mentha aquatica. Plant material was picked up starting from the early spring 2007, from different sites as in altitude and in pedological and climatic traits, that were distributed over an area of 200.000 ha approx.. Later on, all collected plant individuals were transplanted in a collection field, appositel…
Architecture-Driven Level Set Optimization: From Clustering to Sub-pixel Image Segmentation
2016
Thanks to their effectiveness, active contour models (ACMs) are of great interest for computer vision scientists. The level set methods (LSMs) refer to the class of geometric active contours. Comparing with the other ACMs, in addition to subpixel accuracy, it has the intrinsic ability to automatically handle topological changes. Nevertheless, the LSMs are computationally expensive. A solution for their time consumption problem can be hardware acceleration using some massively parallel devices such as graphics processing units (GPUs). But the question is: which accuracy can we reach while still maintaining an adequate algorithm to massively parallel architecture? In this paper, we attempt to…
Classification of Spanish Mosquitoes in Functional Groups
2011
Abstract We present a classification of Spanish mosquitoes according to their different life cycles. The bio-ecological parameters analyzed in our study were oviposition sites, overwintering stages, preferred hosts, and number of generations per year for each species. The results revealed 13 different functional groups. To assess the validity and robustness of the classification system, we analyzed the data from an intensive sampling carried out over a period of 4 years (2005–08) in eastern Spain. In this area, 9 of the 13 functional groups were found. The Jaccard cluster and the principal components analysis (between-group analysis method) revealed 3 different mosquito groups: the tree hol…
Species cohesion despite extreme inbreeding in a social spider.
2011
Colonial social spiders experience extreme inbreeding and highly restricted gene flow between colonies; processes that question the genetic cohesion of geographically separated populations and which could imply multiple origins from predecessors with limited gene flow. We analysed species cohesion and the potential for long-distance dispersal in the social spider Stegodyphus dumicola by studying colony structure in eastern South Africa and the cohesion between this population and Namibian populations previously published. Data from both areas were (re)analysed for historic demographic parameters. Eastern South African S. dumicola were closely related to an east Namibian lineage, showing coh…
A new OLS-based procedure for clusterwise linear regression
2009
Data heterogeneity, within a (linear) regression framework, often suggests the use of a Clusterwise Linear Regression (CLR) procedure, which implies, among other things, the estimate of the appropriate number of clusters as well as the cluster membership of each unit. The approaches to the estimation of a CLR model are essentially based on the Ordinary Least Square (OLS) criterion or the likelihood criterion. In this paper, in a context of OLS approach, we propose an estimation of the model making use of an algorithm based on a threshold criterion for the determination coefficient of each cluster, to identify the appropriate number of clusters, and of a modified Spath's algorithm, to estima…
The PHES battery does not detect all cirrhotic patients with early neurological deficits, which are different in different patients.
2017
Background and aims The psychometric hepatic encephalopathy score (PHES) is the “gold standard” for minimal hepatic encephalopathy (MHE) diagnosis. Some reports suggest that some cirrhotic patients “without” MHE according to PHES show neurological deficits and other reports that neurological alterations are not homogeneous in all cirrhotic patients. This work aimed to assess whether: 1) a relevant proportion of cirrhotic patients show neurological deficits not detected by PHES; 2) cirrhotic patients with mild neurological deficits are a homogeneous population or may be classified in sub-groups according to specific deficits. Methods Cirrhotic patients “without” (n = 56) or “with” MHE (n = 4…
Heat shock response in yeast involver changes in both transcription rates and mRNA stabilities
2011
We have analyzed the heat stress response in the yeast Saccharomyces cerevisiae by determining mRNA levels and transcription rates for the whole transcriptome after a shift from 25uC to 37uC. Using an established mathematical algorithm, theoretical mRNA decay rates have also been calculated from the experimental data. We have verified the mathematical predictions for selected genes by determining their mRNA decay rates at different times during heat stress response using the regulatable tetO promoter. This study indicates that the yeast response to heat shock is not only due to changes in transcription rates, but also to changes in the mRNA stabilities. mRNA stability is affected in 62% of …
Microbreweries, brewpubs and beerfirms in the Sicilian craft beer industry
2019
Purpose This paper aims to illustrate the organisational and managing models characterising the craft beer producers in Sicily (Southern Italy) and the main issues of the provision of raw materials. Design/methodology/approach A direct survey involving the overall population of 41 craft breweries operating in Sicily in 2016 was carried out. Then 29 questionnaires were collected for exploratory analysis. A hierarchical cluster analysis was also performed out to group companies by similar structural, productive and economic features. Findings The findings of the survey showed a Sicilian craft beer industry characterised by a substantial dependence on the import of malts hops and yeasts and t…
Association between pre-operative biological phenotypes and postoperative pulmonary complications: An unbiased cluster analysis
2018
BACKGROUND: Biological phenotypes have been identified within several heterogeneous pulmonary diseases, with potential therapeutic consequences. OBJECTIVE: To assess whether distinct biological phenotypes exist within surgical patients, and whether development of postoperative pulmonary complications (PPCs) and subsequent dependence of intra-operative positive end-expiratory pressure (PEEP) differ between such phenotypes. SETTING: Operating rooms of six hospitals in Europe and USA. DESIGN: Secondary analysis of the 'PROtective Ventilation with HIgh or LOw PEEP' trial. PATIENTS: Adult patients scheduled for abdominal surgery who are at risk of PPCs. INTERVENTIONS: Measurement of pre-operativ…
Immunological characteristics of non-intensive care hospitalized COVID-19 patients: A preliminary report
2021
The outbreak of coronavirus disease 2019 (COVID-19) is posing a threat to global health. This disease has different clinical manifestations and different outcomes. The immune response to the novel 2019 coronavirus is complex and involves both innate and adaptive immunity. In this context, cell-mediated immunity plays a vital role in effective immunity against SARS-CoV-2. Significant differences have been observed when comparing severe and non-severe patients. Since these immunological characteristics have not been fully elucidated, we aimed to use cluster analysis to investigate the immune cell patterns in patients with COVID-19 who required hospitalization but not intensive care. We identi…