Search results for "cluster analysis."
showing 10 items of 805 documents
Caratterizzazione chimico-morfologica di accessioni spontanee di origano siciliano (Origanum heracleoticum L.) del territorio dei monti Nebrodi
2009
Il genere Origano è estremamente diffuso nel bacino del Mediterraneo, con diverse specie presenti nel territorio siciliano. Il comprensorio dei Monti Nebrodi (Sicilia N-E), esteso per circa 200.000 ettari, è una delle aree siciliane in cui è presente la massima biodiversità vegetale; l'area è caratterizzato prevalentemente dalla presenza di Origanum heracleoticum, reperibile in ambienti ecologicamente anche assai diversificati. Con l'obiettivo di acquisire informazioni utili ai fini della caratterizzazione delle accessioni di Origanum heracleoticum spontanee nel comprensorio nebroideo, a partire dal 2007 è stato avviato su di esse un lavoro di ricognizione e collezione sistematica. Campioni…
Evapotranspiration simulations in ISIMIP2a-Evaluation of spatio-temporal characteristics with a comprehensive ensemble of independent datasets
2018
Actual land evapotranspiration (ET) is a key component of the global hydrological cycle and anessential variable determining the evolution of hydrological extreme events under different climate change scenarios. However, recently available ET products show persistent uncertainties thatare impeding a precise attribution of human-induced climate change. Here, we aim at comparing arange of independent global monthly land ET estimates with historical model simulations from theglobal water, agriculture, and biomes sectors participating in the second phase of the Inter-SectoralImpact Model Intercomparison Project (ISIMIP2a). Among the independent estimates, we use theEartH2Observe Tier-1 dataset …
Analyzing and organizing the sonic space of vocal imitations
2015
The sonic space that can be spanned with the voice is vast and complex and, therefore, it is difficult to organize and explore. In order to devise tools that facilitate sound design by vocal sketching we attempt at organizing a database of short excerpts of vocal imitations. By clustering the sound samples on a space whose dimensionality has been reduced to the two principal components, it is experimentally checked how meaningful the resulting clusters are for humans. Eventually, a representative of each cluster, chosen to be close to its centroid, may serve as a landmark in the exploration of the sound space, and vocal imitations may serve as proxies for synthetic sounds.
Independent host switching events by digenean parasites of cetaceans inferred from ribosomal DNA
2015
Cetaceans harbour a unique fauna of digeneans whose origin and relationships have sparked considerable debate during recent decades. Disparity in the species reported indicates that they do not share close affinities, but their unusual morphology has made their taxonomic identities and phylogenetic positions uncertain. Here we use sequence data to investigate the phylogenetic relationships of the main species of flukes infecting cetaceans. We sequenced the 18S, 28S and internal transcribed spacer 2 rDNA of digenean species representing all known families reported from cetaceans: Braunina cordiformis (Brauninidae), Ogmogaster antarcticus (Notocotylidae), Pholeter gastrophilus (Heterophyidae)…
Maternal Parenting Stress and Preschoolers’ Social-Emotional Competence and Behavioural Difficulties: A Variable- and Person-Centred Approach
2022
Background: The present study examined the relations between maternal parenting stress and preschoolers’ psychosocial adjustment, using both a variable-centred and a person-centred approach. Methods: The study had three main purposes: (a) evaluating the associations of maternal parenting stress with children’s social-emotional competence and behavioural difficulties, as perceived by their mothers; (b) inquiring the existence of different children’s clusters based on their level of social-emotional competence and behavioural difficulties; (c) exploring differences in maternal parenting stress linked to cluster membership. Participants were 91 Italian mothers, aged from 22 to 47 years old (M …
Differential Gene Expression of Medullary Thyroid Carcinoma Reveals Specific Markers Associated with Genetic Conditions
2013
Maliszewska, Agnieszka et al.
Operation and first results of the NEXT-DEMO prototype using a silicon photomultiplier tracking array
2013
NEXT-DEMO is a high-pressure xenon gas TPC which acts as a technological test-bed and demonstrator for the NEXT-100 neutrinoless double beta decay experiment. In its current configuration the apparatus fully implements the NEXT-100 design concept. This is an asymmetric TPC, with an energy plane made of photomultipliers and a tracking plane made of silicon photomultipliers (SiPM) coated with TPB. The detector in this new configuration has been used to reconstruct the characteristic signature of electrons in dense gas, demonstrating the ability to identify the MIP and "blob" regions. Moreover, the SiPM tracking plane allows for the definition of a large fiducial region in which an excellent e…
Cluster analysis for portfolio optimization
2005
We consider the problem of the statistical uncertainty of the correlation matrix in the optimization of a financial portfolio. We show that the use of clustering algorithms can improve the reliability of the portfolio in terms of the ratio between predicted and realized risk. Bootstrap analysis indicates that this improvement is obtained in a wide range of the parameters N (number of assets) and T (investment horizon). The predicted and realized risk level and the relative portfolio composition of the selected portfolio for a given value of the portfolio return are also investigated for each considered filtering method.
Spanning Trees and bootstrap reliability estimation in correlation based networks
2007
We introduce a new technique to associate a spanning tree to the average linkage cluster analysis. We term this tree as the Average Linkage Minimum Spanning Tree. We also introduce a technique to associate a value of reliability to links of correlation based graphs by using bootstrap replicas of data. Both techniques are applied to the portfolio of the 300 most capitalized stocks traded at New York Stock Exchange during the time period 2001-2003. We show that the Average Linkage Minimum Spanning Tree recognizes economic sectors and sub-sectors as communities in the network slightly better than the Minimum Spanning Tree does. We also show that the average reliability of links in the Minimum …
Fine-Scale Droplet Clustering in Atmospheric Clouds: 3D Radial Distribution Function from Airborne Digital Holography
2018
The extent of droplet clustering in turbulent clouds has remained largely unquantified, and yet is of possible relevance to precipitation formation and radiative transfer. To that end, data gathered by an airborne holographic instrument are used to explore the three-dimensional spatial statistics of cloud droplet positions in homogeneous stratiform boundary-layer clouds. The three-dimensional radial distribution functions g(r) reveal unambiguous evidence of droplet clustering. Three key theoretical predictions are observed: the existence of positive correlations, onset of correlation in the turbulence dissipation range, and monotonic increase of g(r) with decreasing r. This implies that cur…