Search results for "Cluster Analysis"
showing 10 items of 848 documents
Verbal fluency in school-aged Spanish children: analysis of clustering and switching organizational strategies, employing different semantic categori…
2021
La tarea de fluidez verbal (FV) es una medida de la flexibilidad cognitiva y la estrategia de búsqueda dentro del léxico y el tema semántico. En este trabajo, se probó el uso de estrategias organizativas, es decir, agrupación y cambio en la fluidez semántica y fonológica en niños españoles sanos divididos en dos grupos: el grupo 1 de niños más pequeños (de 8 a 9 años) y el grupo 2 de niños mayores (de 10 años de edad) –11) introducción de diferentes letras (F, A, S y P, M, R) y categorías semánticas (animales y comidas o bebidas). La fluidez semántica fue mayor que la fluidez fonológica en ambos grupos de edad. Además, los niños mayores mostraron un mejor desempeño de ambas fluencias que lo…
The sequencing of the complete genome of a Tomato black ring virus (TBRV) and of the RNA2 of three Grapevine chrome mosaic virus (GCMV) isolates from…
2014
The complete genome of a Tomato black ring virus isolate (TBRV-Mirs) (RNA1, 7,366 nt and RNA2, 4,640 nt) and the RNA2 sequences (4,437; 4,445; and 4,442 nts) of three Grapevine chrome mosaic virus isolates (GCMV-H6, -H15, and -H27) were determined. All RNAs contained a single open reading frame encoding polyproteins of 254 kDa (p1) and 149 kDa (p2) for TBRV-Mirs RNA1 and RNA2, respectively, and 146 kDa for GCMV RNA2. p1 of TBRV-Mirs showed the highest identity with TBRV-MJ (94 %), Beet ringspot virus (BRSV, 82 %), and Grapevine Anatolian ringspot virus (GARSV, 66 %), while p2 showed the highest identity with TBRV isolates MJ (89 %) and ED (85 %), followed by BRSV (65 %), GCMV (58 %), and GA…
Phenotypic and genotypic characterization of a new fish-virulent Vibrio vulnificus serovar that lacks potential to infect humans.
2007
Vibrio vulnificus is a bacterial species that is virulent for humans and fish. Human isolates are classified into biotypes 1 and 3 (BT1 and BT3) and fish isolates into biotype 2 (BT2). However, a few human infections caused by BT2 isolates have been reported worldwide (zoonosis). These BT2 human isolates belong to serovar E (SerE), which is also present in diseased fish. The aim of the present work was to characterize a new BT2 serovar [serovar A (SerA)], which emerged in the European fish-farming industry in 2000, by means of phenotypic, serological and genetic [plasmid profiling, ribotyping and random amplified polymorphic DNA (RAPD)] methodologies. The results confirmed that SerA constit…
Molecular Typing Reveals Frequent Clustering among Human Isolates of Listeria monocytogenes in Italy
2009
In Italy, the annual incidence of reported cases of listeriosis amounts in recent years (2004 to 2006) to 0.8 cases per million inhabitants. Our study is a subtyping analysis by serotyping, ribotyping, and pulsed-field gel electrophoresis analysis of 44 human isolates from apparently sporadic cases of infection in the Lombardy region and in the Province of Florence, Italy, in the years 1996 to 2007. Based on the results of the different subtyping methods, 10 occasions were detected when strains of L. monocytogenes with the same subtype were isolated from more than one listeriosis case. A total of 28 (66.7%) out of 44 isolates were attributed to molecular subtype clusters. Our data support t…
Solution Using Clustering Methods
1987
The main aim of this analysis is to find out typical morphologies from the multivariate and longitudinal data set on growing children and to describe the morphological evolution of the found groups of girls. The finding out of typical morphologies is, in our opinion, strictly linked to the search of structures in the individuals and in the variables.
Robust refinement of initial prototypes for partitioning-based clustering algorithms
2007
Non-uniqueness of solutions and sensitivity to erroneous data are common problems to large-scale data clustering tasks. In order to avoid poor quality of solutions with partitioning-based clustering methods, robust estimates (that are highly insensitive to erroneous data values) are needed and initial cluster prototypes should be determined properly. In this paper, a robust density estimation initialization method that exploits the spatial median estimate to the prototype update is presented. Besides being insensitive to noise and outliers, the new method is also computationally comparable with other traditional methods. The methods are compared by numerical experiments on a set of syntheti…
Spectral properties of correlation matrices for some hierarchically nested factor models
2007
We show that spectral methods, such as Principal Component Analysis and Random Matrix Theory, are unable to reveal the hierarchical (or nested) structure of a set of mutivariate data. We consider the method introduced in M. Tumminello et al., EPL 78, 30006 (2007) to associate a hierarchical factor model with a set of data by making use of clustering algorithms. This is done by proving the existence of a bijective correspondence between a hierarchical tree and a factor model.
Correlation based hierarchical clustering in financial time series
2005
We review a correlation based clustering procedure applied to a portfolio of assets synchronously traded in a financial market. The portfolio considered consists of the set of 500 highly capitalized stocks traded at the New York Stock Exchange during the time period 1987-1998. We show that meaningful economic information can be extracted from correlation matrices.
Detection of Anomalous HTTP Requests Based on Advanced N-gram Model and Clustering Techniques
2013
Nowadays HTTP servers and applications are some of the most popular targets for network attacks. In this research, we consider an algorithm for HTTP intrusions detection based on simple clustering algorithms and advanced processing of HTTP requests which allows the analysis of all queries at once and does not separate them by resource. The method proposed allows detection of HTTP intrusions in case of continuously updated web-applications and does not require a set of HTTP requests free of attacks to build the normal user behaviour model. The algorithm is tested using logs acquired from a large real-life web service and, as a result, all attacks from these logs are detected, while the numbe…
Wine and quality. A cluster anlysis to assess certain representative aspects relating to the quality
2009
This research, in which the technique of Cluster Analysis is used, will provide information on how wine producers can evaluate certain characteristics (variables) of their product more widely associated as indicative of quality. The analysis identified homogeneous groups containing within them other, related variables, which can be considered similar. Those attributes which are by themselves most representative of the product's quality are also highlighted. Finally, the cluster analysis made it possible to comment on the behaviour of producers, and looking at how they seek to meet market expectations based on their knowledge of customer's habits in the buying and consuming of wine.