Search results for "Likelihood Functions"
showing 10 items of 101 documents
Influence of non-clinical factors on restorative rectal cancer surgery: An analysis of four specialized population-based digestive cancer registries …
2022
Abstract Background This study aims to measure the association between deprivation, health care accessibility and health care system with the likelihood of receiving non-restorative rectal cancer surgery (NRRCS). Methods All adult patients who had rectal resection for invasive adenocarcinoma diagnosed between 2007 and 2016 in four French specialised cancer registries were included. A multilevel logistic regression with random effect was used to assess the link between patient and health care structure characteristics on the probability of NRRCS. Results 2997 patients underwent rectal cancer resection in 68 health care structures: 708 (23.63%) had NRRCS. The likelihood of receiving NRCCS was…
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 …
Weighted Least-Squares Likelihood Ratio Test for Branch Testing in Phylogenies Reconstructed from Distance Measures
2005
A variety of analytical methods is available for branch testing in distance-based phylogenies. However, these methods are rarely used, possibly because the estimation of some of their statistics, especially the covariances, is not always feasible. We show that these difficulties can be overcome if some simplifying assumptions are made, namely distance independence. The weighted least-squares likelihood ratio test (WLS-LRT) we propose is easy to perform, using only the distances and some of their associated variances. If no variances are known, the use of the Felsenstein F-test, also based on weighted least squares, is discussed. Using simulated data and a data set of 43 mammalian mitochondr…
Temporal and spatial diversification of the African disjunct genus Androcymbium (Colchicaceae)
2009
Abstract The genus Androcymbium (Colchicaceae) includes 57 species that are distributed in the extreme northern and southern portions of Africa, mainly in regions with a Mediterranean climate. We present the first phylogeographic analysis of the genus with species from all five of its distribution areas (North Africa, Horn of Africa, Namibia, western South Africa, and eastern South Africa). We used sequence data from six chloroplast regions and one nuclear region. Phylogeographic reconstructions were conducted using both parsimony and Bayesian inference methods. Molecular dating estimates using a Bayesian approach suggest a middle Miocene (13.4 ± 1.5 mya) origin of the genus; this approach …
The complete mitochondrial genome of Bactrocera biguttula (Bezzi) (Diptera: Tephritidae) and phylogenetic relationships with other Dacini
2018
Bactrocera biguttula is an African olive fruit fly that does not attack cultivated olives but rather develops in the fruits of wild species of Olea and Noronhia. The complete mitochondrial genome of an individual specimen was characterized in comparison to other Bactrocera. The phylogenetic relationships of B. biguttula with other Dacini were investigated, with special focus on B. oleae, an agricultural pest known to attack cultivated and wild olives. The sequence had a total length of 15,829 bp, and included the typical features of insect mitogenomes, similarly to the other Bactrocera analysed. Start codons included ATG, ATC, ATT, and TCG (in COI). The majority of stop codons (TAA) were fu…
Selection on Coding Regions Determined Hox7 Genes Evolution
2003
The important role of Hox genes in determining the regionalization of the body plan of the vertebrates makes them invaluable candidates for evolutionary analyses regarding functional and morphological innovation. Gene duplication and gene loss led to a variable number of Hox genes in different vertebrate lineages. The evolutionary forces determining the conservation or loss of Hox genes are poorly understood. In this study, we show that variable selective pressures acted on Hox7 genes in different evolutionary lineages, with episodes of positive selection occurring after gene duplications. Tests for functional divergence in paralogs detected significant differentiation in a region known to …
The origin of Lecithodesmus (Digenea: Campulidae) based on ND3 gene comparison
2000
Species of Lecithodesmus (Campulidae) occur almost exclusively in baleen whales throughout a wide geographical distribution. Other campulids occur only in odontocetes and, secondarily, in pinnipeds and the sea otter. Therefore, the ancestor of Lecithodesmus might have either cospeciated with mysticetes during the early divergence of mysticete and odontocete cetaceans or originated later via host switching. We evaluate both possibilities based on a phylogenetic analysis. The ND3 mitochondrial gene sequence of a species of Lecithodesmus was included in a previous partial molecular phylogeny of the Campulidae. Fasciola hepatica and Dicrocoelium dendriticum were used as outgroups. Maximum parsi…
Evolution of arginine deiminase (ADI) pathway genes
2002
We have analyzed the evolution of the three genes encoding structural enzymes of the arginine deiminase (ADI) pathway, arginine deiminase (ADI), ornithine transcarbamoylase (OTC), and carbamate kinase (CK) in a wide range of organisms, including Archaea, Bacteria, and Eukarya. This catabolic route was probably present in the last common ancestor to all the domains of life. The results obtained indicate that these genes have undergone a complex evolutionary history, including horizontal transfer events, duplications, and losses. Therefore, these genes are not adequate to infer organismal relationships at deep branching levels, but they provide an insight into how catabolic genes evolved and …
Multiple overseas dispersal in amphibians
2003
Amphibians are thought to be unable to disperse over ocean barriers because they do not tolerate the osmotic stress of salt water. Their distribution patterns have therefore generally been explained by vicariance biogeography. Here, we present compelling evidence for overseas dispersal of frogs in the Indian Ocean region based on the discovery of two endemic species on Mayotte. This island belongs to the Comoro archipelago, which is entirely volcanic and surrounded by sea depths of more than 3500 m. This constitutes the first observation of endemic amphibians on oceanic islands that did not have any past physical contact to other land masses. The two species of frogs had previously been tho…
Adaptive independent vector analysis for multi-subject complex-valued fMRI data.
2017
Abstract Background Complex-valued fMRI data can provide additional insights beyond magnitude-only data. However, independent vector analysis (IVA), which has exhibited great potential for group analysis of magnitude-only fMRI data, has rarely been applied to complex-valued fMRI data. The main challenges in this application include the extremely noisy nature and large variability of the source component vector (SCV) distribution. New method To address these challenges, we propose an adaptive fixed-point IVA algorithm for analyzing multiple-subject complex-valued fMRI data. We exploited a multivariate generalized Gaussian distribution (MGGD)- based nonlinear function to match varying SCV dis…