Search results for " Statistical"
showing 10 items of 1649 documents
The role of PNI to predict survival in advanced hepatocellular carcinoma treated with Sorafenib
2020
Background and aims The present study aims to investigate the role of the prognostic nutritional index (PNI) on survival in patients with advanced hepatocellular carcinoma (HCC) treated with sorafenib. Methods This multicentric study included a training cohort of 194 HCC patients and three external validation cohorts of 129, 76 and 265 HCC patients treated with Sorafenib, respectively. The PNI was calculated as follows: 10 × serum albumin (g/dL) + 0.005 × total lymphocyte count (per mm3). Univariate and multivariate analyses were performed to investigate the association between the covariates and the overall survival (OS). Results A PNI cut-off value of 31.3 was established using the ROC an…
Archaeometric study of ceramic figurines from the Maya settlement of La Blanca (Petén, Guatemala)
2014
Abstract In this article, analytical results will be presented and discussed regarding a selected set of figurines from the ancient Maya settlement of La Blanca in Peten, Guatemala. The objective is to characterize the ceramic material by two analytical complementary techniques: X-ray diffraction (XRD) and total reflection X-ray fluorescence (TXRF). The data obtained by means of both XRD and TXRF were compared and analyzed by multivariate statistical techniques in order to obtain sample groups according to their chemical composition. The results of this archaeometric study have been compared to those that have been obtained through macroscopic characterization by means of the traditional cl…
Fitted dosimetric parameters of high dose-rate 192Ir sources according to the AAPM TG43 formalism
2001
The purpose of this study is to find fitted functional forms to the anisotropy function, F(r,θ), and the radial dose function, g(r), in order to characterize dose-rate distributions around all the high-intensity 192 Ir sources currently in use. Dosimetry data are at present available as tables for: the microSelectron HDR (“classic” and “new” design models), the PDR source, and the VariSource HDR source, expressed in terms of the AAPM Task Group No. 43 recommendations. There is only one paper out which introduces a functional form to fit the anisotropy function, but only for symmetric sources with respect to the transverse axis. However, dosimetric data of the HDR and PDR sources mentioned a…
Finite-size scaling in Ising-like systems with quenched random fields: Evidence of hyperscaling violation
2010
In systems belonging to the universality class of the random field Ising model, the standard hyperscaling relation between critical exponents does not hold, but is replaced by a modified hyperscaling relation. As a result, standard formulations of finite size scaling near critical points break down. In this work, the consequences of modified hyperscaling are analyzed in detail. The most striking outcome is that the free energy cost \Delta F of interface formation at the critical point is no longer a universal constant, but instead increases as a power law with system size, \Delta F proportional to $L^\theta$, with $\theta$ the violation of hyperscaling critical exponent, and L the linear ex…
Growth, percolation, and correlations in disordered fiber networks
1997
This paper studies growth, percolation, and correlations in disordered fiber networks. We start by introducing a 2D continuum deposition model with effective fiber-fiber interactions represented by a parameter $p$ which controls the degree of clustering. For $p=1$, the deposited network is uniformly random, while for $p=0$ only a single connected cluster can grow. For $p=0$, we first derive the growth law for the average size of the cluster as well as a formula for its mass density profile. For $p>0$, we carry out extensive simulations on fibers, and also needles and disks to study the dependence of the percolation threshold on $p$. We also derive a mean-field theory for the threshold ne…
A Hebbian approach to complex-network generation
2011
Through a redefinition of patterns in an Hopfield-like model, we introduce and develop an approach to model discrete systems made up of many, interacting components with inner degrees of freedom. Our approach clarifies the intrinsic connection between the kind of interactions among components and the emergent topology describing the system itself; also, it allows to effectively address the statistical mechanics on the resulting networks. Indeed, a wide class of analytically treatable, weighted random graphs with a tunable level of correlation can be recovered and controlled. We especially focus on the case of imitative couplings among components endowed with similar patterns (i.e. attribute…
A statistical analysis of the three-fold evolution of genomic compression through frame overlaps in prokaryotes
2007
Abstract Background Among microbial genomes, genetic information is frequently compressed, exploiting redundancies in the genetic code in order to store information in overlapping genes. We investigate the length, phase and orientation properties of overlap in 58 prokaryotic species evaluating neutral and selective mechanisms of evolution. Results Using a variety of statistical null models we find patterns of compressive coding that can not be explained purely in terms of the selective processes favoring genome minimization or translational coupling. The distribution of overlap lengths follows a fat-tailed distribution, in which a significant proportion of overlaps are in excess of 100 base…
Genetic variants linked to myopic macular degeneration in persons with high myopia: CREAM Consortium.
2019
Purpose: To evaluate the roles of known myopia-associated genetic variants for development of myopic macular degeneration (MMD) in individuals with high myopia (HM), using case-control studies from the Consortium of Refractive Error and Myopia (CREAM). Methods: A candidate gene approach tested 50 myopia-associated loci for association with HM and MMD, using meta-analyses of case-control studies comprising subjects of European and Asian ancestry aged 30 to 80 years from 10 studies. Fifty loci with the strongest associations with myopia were chosen from a previous published GWAS study. Highly myopic (spherical equivalent [SE] ≤ -5.0 diopters [D]) cases with MMD (N = 348), and two sets of cont…
Bleeding symptoms at disease presentation and prediction of ensuing bleeding in inherited FVII deficiency.
2012
SummaryIndividuals with inherited factor VII (FVII) deficiency display bleeding phenotypes ranging from mild to severe, with 30% of patients having always been asymptomatic (non-bleeding). In 626 FVII-deficient individuals, by analysing data from the International Factor VII (IF7) Registry and the Seven Treatment Evaluation Registry (STER), we determined whether bleeding type at disease presentation and FVII coagulant activity (FVIIc) predict ensuing bleeds. At disease presentation/diagnosis, 272 (43.5%) individuals were non-bleeding, 277 (44.2%) had minor bleeds, and 77 (12.3%) had major bleeds. During a median nine-year index period (IP) observation, 87.9% of non-bleeding individuals at p…
Fitting linear models and generalized linear models with large data sets in R
2009
We present an estimating algorithm to fit linear and generalized linear models not involving the QR decomposition. Some new R functions are presented and discussed. For large data sets, comparisons with respect to the well-known lm() and glm(), as well as to biglm() and bigglm() from the package biglm, show that the proposed functions speed up computation while preserving numerical stability and accuracy