Search results for "multivariate"

Expression of the multidrug resistance glycoprotein 170 in the peripheral blood lymphocytes of rheumatoid arthritis patients. The percentage of lymph…

1996

International audience; Abstract: The objective was to evaluate the expression of the multidrug resistance P-glycoprotein (P-gp) in peripheral blood lymphocytes (PBL) of patients with rheumatoid arthritis (RA). PBL from 68 RA patients and 44 controls were evaluated. RA patients had a mean disease duration of 10.7 yr, with a mean number of past resistances to DMARDs of 0.82, and were treated with NSAIDs (n = 34), DMARDs (n = 25) and prednisolone (n = 40). Fluorescence flow cytometry was used to assess P-gp membrane expression on PBL. In the RA group, the percentage of PBL expressing P-gp was higher in patients treated with prednisolone than in other patients [mean +/- S.D.: 10.7 +/- 15.8% vs…

The heritability of depressive symptoms: multiple informants and multiple measures

2002

Background: Earlier research suggests large rater differences in heritability estimates of children's depressive symptoms in the context of significant age and sex-limitation effects. Methods: With data from an ongoing, population-based twin-family study, we estimated genetic and environmental influences on children's depression with models allowing for sex-specific effects. Our assessments of twins included self-reports and ratings made by their classmate peers, their parents and their teachers, allowing estimates of genetic and environmental effects with data from different informants. Model-fitting used maximum likelihood estimation of log-transformed data from a sample of 1,366 11- and …

Splenic marginal zone lymphoma: A prognostic model for clinical use

2006

The Integruppo Italiano Linfomi (IIL) carried out a study to assess the outcomes of splenic marginal zone lymphoma and to identify prognostic factors in 309 patients. The 5-year cause-specific survival (CSS) rate was 76%. In univariate analysis, the parameters predictive of shorter CSS were hemoglobin levels below 12 g/dL (P < .001), albumin levels below 3.5 g/dL (P = .001), International Prognostic Index (IPI) scores of 2 to 3 (P < .001), lactate dehydrogenase (LDH) levels above normal (P < .001), age older than 60 years (P = .01), platelet counts below 100 000/μL (P = .04), HbsAg-positivity (P = .01), and no splenectomy at diagnosis (P = .006). Values that maintained a negative influence …

Hepatic vein tumor thrombosis in patients with hepatocellular carcinoma: Prevalence and clinical significance.

2021

Abstract Background There is strong evidence that portal vein tumor thrombosis (PVTT) is associated with poor survival in patients with hepatocellular carcinoma (HCC). However, data regarding the clinical significance of hepatic vein tumor thrombosis (HVTT) is rare, particularly in Western patients. Objective To determine the HVTT prevalence in a Western patient population and its impact on survival. Methods We included 1310 patients with HCC treated in our tertiary referral center between January 2005 and December 2016. HVTT and PVTT were diagnosed with contrast‐enhanced cross‐sectional imaging. Overall survival (OS) was calculated starting from the initial HCC diagnosis, and in a second s…

A class of multivariate extreme value distributions with heterogeneous margins

2013

Many problems which involve applications of extreme value theory show an essential multivariate nature and recent development of the theory in this field deal with the construction of multivariate extreme value distributions. Owing to the nature of the problem under examination, extreme values to be analyzed jointly may have different limiting distributions, but it seems that explicit expressions of multivariate extreme value distributions with heterogeneous margins are not present in the literature. In this paper we consider the problem of constructing multivariate extreme value distributions with univariate marginal extreme value distributions not belonging or, more generally, not all bel…

Religiosity and cultural consumption

2018

A stochastic shape and orientation model for fibres with an application to carbon nanotubes

2012

Methods are introduced for analysing the shape and orientation of planar fibres from greyscale images of fibrous systems. The sequence of image processing techniques needed for segmentation of fibres is described. The identified fibres were interpreted as deformed line segments for which two shape and two orientation parameters are estimated by the maximum likelihood method. The methods introduced are shown to perform quite well for simulated systems of deformed line segments with known properties. They were applied to TEM images of carbon nanotubes embedded in polycarbonate.

Field estimation in wireless sensor networks using distributed kriging

2012

In this paper, we tackle the problem of spatial interpolation for distributed estimation in Wireless Sensor Networks by using a geostatistical technique called kriging. We present a novel Distributed Iterative Kriging Algorithm (DIKA) which is composed of two main phases. First, the spatial dependence of the field is exploited by calculating semivariograms in an iterative way. Second, the kriging system of equations is solved by an initial set of nodes in a distributed manner, providing some initial interpolation weights to each node. In our algorithm, the estimation accuracy can be improved by iteratively adding new nodes and updating appropriately the weights, which leads to a reduction i…

How to simulate normal data sets with the desired correlation structure

2010

The Cholesky decomposition is a widely used method to draw samples from multivariate normal distribution with non-singular covariance matrices. In this work we introduce a simple method by using singular value decomposition (SVD) to simulate multivariate normal data even if the covariance matrix is singular, which is often the case in chemometric problems. The covariance matrix can be specified by the user or can be generated by specifying a subset of the eigenvalues. The latter can be an advantage for simulating data sets with a particular latent structure. This can be useful for testing the performance of chemometric methods with data sets matching the theoretical conditions for their app…

Statistical validation of rival models for observable stochastic process and its identification

2011

In this paper, for statistical validation of rival (analytical or simulation) models collected for modeling observable process in stochastic system (say, transportation or service system), a uniformly most powerful invariant (UMPI) test is developed from the generalized maximum likelihood ratio (GMLR). This test can be considered as a result of a new approach to solving the Behrens-Fisher problem when covariance matrices of multivariate normal populations (compared with respect to their means) are different and unknown. The test makes use of an invariant statistic whose distribution, under the null hypothesis, does not depend on the unknown (nuisance) parameters. The sample size and thresho…