925 resultados para Data clustering. Fuzzy C-Means. Cluster centers initialization. Validation indices
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Majolica pottery is one of the most characteristic tableware produced during the Medieval and Renaissance periods. Majolica technology was introduced to the Iberian Peninsula by Islamic artisans during Medieval times, and its production and popularity rapidly spread throughout Spain and eventually to other locations in Europe and the Americas. The prestige and importance of Spanish majolica was very high. Consequently, this ware was imported profusely to the Americas during the Spanish Colonial period. Nowadays, Majolica pottery serves as an important horizon marker at Spanish colonial sites. A preliminary study of Spanish-produced majolica was conducted on a set of 246 samples from the 12 primary majolica production centers on the Iberian Peninsula. The samples were analyzed by neutron activation analysis (NAA), and the resulting data were interpreted using an array of multivariate statistical procedures. Our results show a clear discrimination between different production centers. In some cases, our data allow one to distinguish amongst shards coming from the same production location suggesting different workshops or group of workshops were responsible for production of this pre-industrial pottery.
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The aim of this study was to assess a population of patients with diabetes mellitus by means of the INTERMED, a classification system for case complexity integrating biological, psychosocial and health care related aspects of disease. The main hypothesis was that the INTERMED would identify distinct clusters of patients with different degrees of case complexity and different clinical outcomes. Patients (n=61) referred to a tertiary reference care centre were evaluated with the INTERMED and followed 9 months for HbA1c values and 6 months for health care utilisation. Cluster analysis revealed two clusters: cluster 1 (62%) consisting of complex patients with high INTERMED scores and cluster 2 (38%) consisting of less complex patients with lower INTERMED. Cluster 1 patients showed significantly higher HbA1c values and a tendency for increased health care utilisation. Total INTERMED scores were significantly related to HbA1c and explained 21% of its variance. In conclusion, different clusters of patients with different degrees of case complexity were identified by the INTERMED, allowing the detection of highly complex patients at risk for poor diabetes control. The INTERMED therefore provides an objective basis for clinical and scientific progress in diabetes mellitus. Ongoing intervention studies will have to confirm these preliminary data and to evaluate if management strategies based on the INTERMED profiles will improve outcomes.
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Thy-1 is a membrane glycoprotein suggested to stabilize or inhibit growth of neuronal processes. However, its precise function has remained obscure, because its endogenous ligand is unknown. We previously showed that Thy-1 binds directly to α(V)β(3) integrin in trans eliciting responses in astrocytes. Nonetheless, whether α(V)β(3) integrin might also serve as a Thy-1-ligand triggering a neuronal response has not been explored. Thus, utilizing primary neurons and a neuron-derived cell line CAD, Thy-1-mediated effects of α(V)β(3) integrin on growth and retraction of neuronal processes were tested. In astrocyte-neuron co-cultures, endogenous α(V)β(3) integrin restricted neurite outgrowth. Likewise, α(V)β(3)-Fc was sufficient to suppress neurite extension in Thy-1(+), but not in Thy-1(-) CAD cells. In differentiating primary neurons exposed to α(V)β(3)-Fc, fewer and shorter dendrites were detected. This effect was abolished by cleavage of Thy-1 from the neuronal surface using phosphoinositide-specific phospholipase C (PI-PLC). Moreover, α(V)β(3)-Fc also induced retraction of already extended Thy-1(+)-axon-like neurites in differentiated CAD cells as well as of axonal terminals in differentiated primary neurons. Axonal retraction occurred when redistribution and clustering of Thy-1 molecules in the plasma membrane was induced by α(V)β(3) integrin. Binding of α(V)β(3)-Fc was detected in Thy-1 clusters during axon retraction of primary neurons. Moreover, α(V)β(3)-Fc-induced Thy-1 clustering correlated in time and space with redistribution and inactivation of Src kinase. Thus, our data indicates that α(V)β(3) integrin is a ligand for Thy-1 that upon binding not only restricts the growth of neurites, but also induces retraction of already existing processes by inducing Thy-1 clustering. We propose that these events participate in bi-directional astrocyte-neuron communication relevant to axonal repair after neuronal damage.
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BACKGROUND: In Switzerland, intravenous drug use (IDU) accounts for 80% of newly acquired hepatitis C virus (HCV) infections. Early HCV treatment has the potential to interrupt the transmission chain and reduce morbidity/mortality due to decompensated liver cirrhosis and hepatocellular carcinoma. Nevertheless, patients in drug substitution programs are often insufficiently screened and treated. OBJECTIVE/METHODS: With the aim to improve HCV management in IDUs, we conducted a cross sectional chart review in three opioid substitution programs in St. Gallen (125 methadone and 71 heroin recipients). Results were compared with another heroin substitution program in Bern (202 patients) and SCCS/SHCS data. RESULTS: Among the methadone/heroin recipients in St. Gallen, diagnostic workup of HCV was better than expected: HCV/HIV-status was unknown in only 1% (2/196), HCV RNA was not performed in 9% (13/146) of anti-HCV-positives and the genotype missing in 15% (12/78) of HCV RNA-positives. In those without spontaneous clearance (two thirds), HCV treatment uptake was 23% (21/91) (HIV-: 29% (20/68), HIV+: 4% (1/23)), which was lower than in methadone/heroin recipients and particularly non-IDUs within the SCCS/SHCS, but higher than in the, mainly psychiatrically focussed, heroin substitution program in Bern (8%). Sustained virological response (SVR) rates were comparable in all settings (overall: 50%, genotype 1: 35-40%, genotype 3: two thirds). In St. Gallen, the median delay from the estimated date of infection (IDU start) to first diagnosis was 10 years and to treatment was another 7.5 years. CONCLUSIONS: Future efforts need to focus on earlier HCV diagnosis and improvement of treatment uptake among patients in drug substitution programs, particularly if patients are HIV-co-infected. New potent drugs might facilitate the decision to initiate treatment.
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The reactivity spectrum of three monoclonal antibodies (Mabs) to human malignant glioma, five Mabs to melanomas and one Mab anti-HLA-DR was investigated by an indirect antibody binding radioimmunoassay on a panel of cells derived from 60 glioma lines, including 47 malignant astrocytomas, 11 low-grade astrocytomas and two malignant ependymomas as well on cells from 12 melanoma, three neuroblastoma, three medulloblastoma, two schwannoma, two retinoblastoma, two choroïd plexus papilloma, ten meningioma and 12 unrelated tumor lines. The anti-glioma Mabs BF7 and GE2 reacted preferentially with gliomas, while the anti-glioma Mab CG12 reacted with gliomas, melanomas, neuroblastomas and medulloblastomas. The five anti-melanoma Mabs reacted with gliomas, neuroblastomas and medulloblastomas. The anti-HLA-DR Mab D1-12 reacted with gliomas, melanomas and some meningiomas. On the basis of the data presented, we describe three different antigenic systems; the first one is glioma-associated, the second one is related to differentiation antigens expressed on cells derived from the neuroectoderm and the third is represented by HLA-DR antigens which are expressed not only on B-lymphoblastoid cells but also on melanomas and gliomas.
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The atomic force microscope is not only a very convenient tool for studying the topography of different samples, but it can also be used to measure specific binding forces between molecules. For this purpose, one type of molecule is attached to the tip and the other one to the substrate. Approaching the tip to the substrate allows the molecules to bind together. Retracting the tip breaks the newly formed bond. The rupture of a specific bond appears in the force-distance curves as a spike from which the binding force can be deduced. In this article we present an algorithm to automatically process force-distance curves in order to obtain bond strength histograms. The algorithm is based on a fuzzy logic approach that permits an evaluation of "quality" for every event and makes the detection procedure much faster compared to a manual selection. In this article, the software has been applied to measure the binding strength between tubuline and microtubuline associated proteins.
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Biometric system performance can be improved by means of data fusion. Several kinds of information can be fused in order to obtain a more accurate classification (identification or verification) of an input sample. In this paper we present a method for computing the weights in a weighted sum fusion for score combinations, by means of a likelihood model. The maximum likelihood estimation is set as a linear programming problem. The scores are derived from a GMM classifier working on a different feature extractor. Our experimental results assesed the robustness of the system in front a changes on time (different sessions) and robustness in front a change of microphone. The improvements obtained were significantly better (error bars of two standard deviations) than a uniform weighted sum or a uniform weighted product or the best single classifier. The proposed method scales computationaly with the number of scores to be fussioned as the simplex method for linear programming.
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The study of transcriptional regulation often needs the integration of diverse yet independent data. In the present work, sequence conservation, predic-tion of transcription factor binding sites (TFBS) and gene expression analysis have been applied to the detection of putative transcription factor (TF) modules in the regulatory region of the FGFR3 oncogene. Several TFs with conserved binding sites in the FGFR3 regulatory region have shown high positive or negative corre-lation with FGFR3 expression both in urothelial carcinoma and in benign nevi. By means of conserved TF cluster analysis, two different TF modules have been iden-tified in the promoter and first intron of FGFR3 gene. These modules contain acti-vating AP2, E2F, E47 and SP1 binding sites plus motifs for EGR with possible repressor function.
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We present molecular dynamics (MD) simulations results for dense fluids of ultrasoft, fully penetrable particles. These are a binary mixture and a polydisperse system of particles interacting via the generalized exponential model, which is known to yield cluster crystal phases for the corresponding monodisperse systems. Because of the dispersity in the particle size, the systems investigated in this work do not crystallize and form disordered cluster phases. The clusteringtransition appears as a smooth crossover to a regime in which particles are mostly located in clusters, isolated particles being infrequent. The analysis of the internal cluster structure reveals microsegregation of the big and small particles, with a strong homo-coordination in the binary mixture. Upon further lowering the temperature below the clusteringtransition, the motion of the clusters" centers-of-mass slows down dramatically, giving way to a cluster glass transition. In the cluster glass, the diffusivities remain finite and display an activated temperature dependence, indicating that relaxation in the cluster glass occurs via particle hopping in a nearly arrested matrix of clusters. Finally we discuss the influence of the microscopic dynamics on the transport properties by comparing the MD results with Monte Carlo simulations.
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The incidence of hepatocellular carcinoma (HCC) is increasing in Western countries. Although several clinical factors have been identified, many individuals never develop HCC, suggesting a genetic susceptibility. However, to date, only a few single-nucleotide polymorphisms have been reproducibly shown to be linked to HCC onset. A variant (rs738409 C>G, encoding for p.I148M) in the PNPLA3 gene is associated with liver damage in chronic liver diseases. Interestingly, several studies have reported that the minor rs738409[G] allele is more represented in HCC cases in chronic hepatitis C (CHC) and alcoholic liver disease (ALD). However, a significant association with HCC related to CHC has not been consistently observed, and the strength of the association between rs738409 and HCC remains unclear. We performed a meta-analysis of individual participant data including 2,503 European patients with cirrhosis to assess the association between rs738409 and HCC, particularly in ALD and CHC. We found that rs738409 was strongly associated with overall HCC (odds ratio [OR] per G allele, additive model=1.77; 95% confidence interval [CI]: 1.42-2.19; P=2.78 × 10(-7) ). This association was more pronounced in ALD (OR=2.20; 95% CI: 1.80-2.67; P=4.71 × 10(-15) ) than in CHC patients (OR=1.55; 95% CI: 1.03-2.34; P=3.52 × 10(-2) ). After adjustment for age, sex, and body mass index, the variant remained strongly associated with HCC. Conclusion: Overall, these results suggest that rs738409 exerts a marked influence on hepatocarcinogenesis in patients with cirrhosis of European descent and provide a strong argument for performing further mechanistic studies to better understand the role of PNPLA3 in HCC development.
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BACKGROUND: HCV coinfection remains a major cause of morbidity and mortality among HIV-infected individuals and its incidence has increased dramatically in HIV-infected men who have sex with men(MSM). METHODS: Hepatitis C virus (HCV) coinfection in the Swiss HIV Cohort Study(SHCS) was studied by combining clinical data with HIV-1 pol-sequences from the SHCS Drug Resistance Database(DRDB). We inferred maximum-likelihood phylogenetic trees, determined Swiss HIV-transmission pairs as monophyletic patient pairs, and then considered the distribution of HCV on those pairs. RESULTS: Among the 9748 patients in the SHCS-DRDB with known HCV status, 2768(28%) were HCV-positive. Focusing on subtype B(7644 patients), we identified 1555 potential HIV-1 transmission pairs. There, we found that, even after controlling for transmission group, calendar year, age and sex, the odds for an HCV coinfection were increased by an odds ratio (OR) of 3.2 [95% confidence interval (CI) 2.2, 4.7) if a patient clustered with another HCV-positive case. This strong association persisted if transmission groups of intravenous drug users (IDUs), MSMs and heterosexuals (HETs) were considered separately(in all cases OR>2). Finally we found that HCV incidence was increased by a hazard ratio of 2.1 (1.1, 3.8) for individuals paired with an HCV-positive partner. CONCLUSIONS: Patients whose HIV virus is closely related to the HIV virus of HIV/HCV-coinfected patients have a higher risk for carrying or acquiring HCV themselves. This indicates the occurrence of domestic and sexual HCV transmission and allows the identification of patients with a high HCV-infection risk.
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Vagueness and high dimensional space data are usual features of current data. The paper is an approach to identify conceptual structures among fuzzy three dimensional data sets in order to get conceptual hierarchy. We propose a fuzzy extension of the Galois connections that allows to demonstrate an isomorphism theorem between fuzzy sets closures which is the basis for generating lattices ordered-sets
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The R package EasyStrata facilitates the evaluation and visualization of stratified genome-wide association meta-analyses (GWAMAs) results. It provides (i) statistical methods to test and account for between-strata difference as a means to tackle gene-strata interaction effects and (ii) extended graphical features tailored for stratified GWAMA results. The software provides further features also suitable for general GWAMAs including functions to annotate, exclude or highlight specific loci in plots or to extract independent subsets of loci from genome-wide datasets. It is freely available and includes a user-friendly scripting interface that simplifies data handling and allows for combining statistical and graphical functions in a flexible fashion. AVAILABILITY: EasyStrata is available for free (under the GNU General Public License v3) from our Web site www.genepi-regensburg.de/easystrata and from the CRAN R package repository cran.r-project.org/web/packages/EasyStrata/. SUPPLEMENTARY INFORMATION: Supplementary data are available at Bioinformatics online.
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Using data from the Public Health Service, we studied the demographic and clinical characteristics of 1,782 patients enrolled in methadone maintenance treatment (MMT) during 2001 in the Swiss Canton of Vaud, comparing our findings with the results of a previous study from 1976 to 1986. In 2001, most patients (76.9%) were treated in general practice. Mortality is low in this MMT population (1%/year). While patient age and sex profiles were similar to those found in the earlier study, we did observe a substantial increase in the number of patients and the number of practitioners treating MMT patients, probably reflecting the low-threshold governmental policies and the creation of specialized centers. In conclusion, easier access to MMT enhances the number of patients, but new concerns about the quality of management emerge: benzodiazepine as a concomitant prescription; low rates of screening for hepatitis B, C and HIV, and social and psychiatric preoccupations.
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Pseudomonas fluorescens CHA0 and the related strain Pf-5 are well-characterized representatives of rhizosphere bacteria that have the capacity to protect crop plants from fungal root diseases, mainly by releasing a variety of exoproducts that are toxic to plant pathogenic fungi. Here, we report that the two plant-beneficial pseudomonads also exhibit potent insecticidal activity. Anti-insect activity is linked to a novel genomic locus encoding a large protein toxin termed Fit (for P. fluorescensinsecticidal toxin) that is related to the insect toxin Mcf (Makes caterpillars floppy) of the entomopathogen Photorhabdus luminescens, a mutualist of insect-invading nematodes. When injected into the haemocoel, even low doses of P. fluorescens CHA0 or Pf-5 killed larvae of the tobacco hornworm Manduca sexta and the greater wax moth Galleria mellonella. In contrast, mutants of CHA0 or Pf-5 with deletions in the Fit toxin gene were significantly less virulent to the larvae. When expressed from an inducible promoter in a non-toxic Escherichia coli host, the Fit toxin gene was sufficient to render the bacterium toxic to both insect hosts. Our findings establish the Fit gene products of P. fluorescens CHA0 and Pf-5 as potent insect toxins that define previously unappreciated anti-insect properties of these plant-colonizing bacteria