4,066 research outputs found
Polyhedral geometry of Phylogenetic Rogue Taxa
It is well known among phylogeneticists that adding an extra taxon (e.g.
species) to a data set can alter the structure of the optimal phylogenetic tree
in surprising ways. However, little is known about this "rogue taxon" effect.
In this paper we characterize the behavior of balanced minimum evolution (BME)
phylogenetics on data sets of this type using tools from polyhedral geometry.
First we show that for any distance matrix there exist distances to a "rogue
taxon" such that the BME-optimal tree for the data set with the new taxon does
not contain any nontrivial splits (bipartitions) of the optimal tree for the
original data. Second, we prove a theorem which restricts the topology of
BME-optimal trees for data sets of this type, thus showing that a rogue taxon
cannot have an arbitrary effect on the optimal tree. Third, we construct
polyhedral cones computationally which give complete answers for BME rogue
taxon behavior when our original data fits a tree on four, five, and six taxa.
We use these cones to derive sufficient conditions for rogue taxon behavior for
four taxa, and to understand the frequency of the rogue taxon effect via
simulation.Comment: In this version, we add quartet distances and fix Table 4
Transcultural adaptation of the who oral health questionnaire and its validation in chilean children
Indexación: Scopus.Introduction: The last edition of the WHO "Oral Health Questionnaire for Children" was published in 2013. This is an only-English version, and as such it requires linguistic adaptation and validation to be applied in the Chilean population. Objectives: To translate and adapt the WHO Oral Health Questionnaire for Children to Spanish and validate it in a Chilean population. Methods: A translation and back translation of the original instrument from English to Spanish was carried out by four translators. The questionnaire was self-reported as a pilot test in ten individuals. A sample was subsequently selected for convenience taking into account the population distribution, resulting in a final sample of 103 individuals. The internal consistency was calculated with Cronbach's alpha, criterion validity with Pearson's correlation coefficient and construct validity with Exploratory Factor Analysis. Results: A conceptual and semantic equivalence of the instrument was obtained. Women and men accounted for 43.69% and 56.31% of the sample, respectively. Cronbach's alpha coefficient was 0.62, while criterion validity was slightly positive between the total dimensions and the DMFT (r=0.13, p-value= 0.20). The Exploratory Factor Analysis yielded a total of 11 factors that explain 70% of the variability in the data. Conclusions: The oral health questionnaire has been appropriately adapted to Spanish, having conceptual as well as semantic equivalence to the original version, being reliable and valid to be used in a population of 12-year-old Chilean children. © 2018, Universidad de Concepcion. All rights reserved.http://joralres.com/index.php/JOR/article/view/432/43
Plantinga-Vegter algorithm takes average polynomial time
We exhibit a condition-based analysis of the adaptive subdivision algorithm
due to Plantinga and Vegter. The first complexity analysis of the PV Algorithm
is due to Burr, Gao and Tsigaridas who proved a worst-case cost bound for degree plane curves with maximum
coefficient bit-size . This exponential bound, it was observed, is in
stark contrast with the good performance of the algorithm in practice. More in
line with this performance, we show that, with respect to a broad family of
measures, the expected time complexity of the PV Algorithm is bounded by
for real, degree , plane curves. We also exhibit a smoothed
analysis of the PV Algorithm that yields similar complexity estimates. To
obtain these results we combine robust probabilistic techniques coming from
geometric functional analysis with condition numbers and the continuous
amortization paradigm introduced by Burr, Krahmer and Yap. We hope this will
motivate a fruitful exchange of ideas between the different approaches to
numerical computation.Comment: 8 pages, correction of typo
La constitucionalización del acceso a la información pública gubernamental en México
[Resumen] El presente trabajo muestra el camino recorrido en México para la consecución de la constitucionalización del derecho de acceso a la información pública gubernamental teniendo como punto de partida la doble faz del mismo, por un lado como facultad de la libertad de expresión y por otro como una obligación inherente a la actividad del estado de publicitarse. De igual manera el trabajo aborda todos aquellos aspectos que la reforma constitucional en México propuso como principios rectores del acceso a la información pública desde la obligación de publicidad hasta toda aquella información que aún y cuando no pudiera estar publicitada si debiera ser del conocimiento público.[Abstract] The herein document shows the overhauling in Mexico of the attainment of the constitutionalization of the governmental public information access law having as starting point its own double sight as authority of expression freedom and as an obligation inherent to the state to be published. In the same way, the document undertakes all those aspects proposed by the constitutional reform as governing principles of the access to public information starting with the publicity obligation and ending with all the information that should be of public knowledge
Genetic and Molecular Factors in Drug-Induced Liver Injury: A Review
The diagnosis of drug-induced liver injury (DILI) is challenging and based on complex diagnostic criteria. DILI falls into two main categories i) intrinsic 'dose-dependent' Type A reactions ii) 'idiosyncratic' or Type B reactions (which are usually not predictable). Idiosyncratic reactions can be immunoallergic (hypersensitivity), or metabolic, although overlap between categories can occur. The aim of this review is to summarise the general view of underlying mechanisms in DILI and to highlight individual risk factors for developing hepatotoxicity. Polymorphisms of bioactivation/ toxification pathways through CYP450 enzymes (Phase I), detoxification reactions (Phase II) and excretion/transport (Phase III) are explored together with immunological factors that might determine DILI. The importance of establishing a multidisciplinary and multi-centric network to promote the understanding and research in hepatotoxicity is underlined. Challenges such as genetic analyses for association studies and whole genome studies, pharmacogenetic testing and future approaches to study DILI are considered. Knowledge regarding these operational mechanisms could provide further insight for the prospective identification of susceptible patients at risk of developing drug-induced hepatotoxicity.
An Umbrella Review of Systematic Reviews on Food Choice and Nutrition Published between 2017 and-2019
The objective of this umbrella review was to provide an update on the latest knowledge in the field of food choice and nutrition. Databases Scopus and ISI-Web of Science were searched for “food choice” AND nutrition. Papers were included if they were systematic reviews published between January 2017 and August 2019 on any subpopulation group. In total, 26 systematic reviews were kept. Data were extracted with a predetermined grid including first author, publication year, country, population group, explanatory constructs (intervention focus) and reported outcomes. Common indicators for outcome measures on food choice and nutrition studies are nutrition knowledge, healthy food choices, food purchases and food and nutrient intake. The most common strategy implemented to alter food choice with a nutritional aim is nutrition education, followed by provision of information through labels. Among children, parent modelling is key to achieving healthy food choices. In general, combining strategies seems to be the most effective way to achieve healthier food consumption and to maintain good nutrition in all age groups
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