Search results for "Bayesian"
showing 10 items of 604 documents
Inter-crystal scatter in positron emission tomography: Identification techniques and effects on reconstructed images for AX-PET demonstrator
2012
La PET es una técnica de imagen en medicina nuclear que permite la visualización in-vivo y en 3D de procesos funcionales en seres vivos. Un escáner PET mide los rayos gamma producidos al aniquilarse un positrón, el cual es emitido por un radioisótopo inyectado al paciente. La eficiencia del sistema es una característica crucial de los escáneres PET de alta resolución dedicados a la imagen del cerebro o de animales pequeños con el fin de obtener una imagen más fiel o de reducir la actividad del radiotrazador, y por consiguiente, la dosis inyectada al paciente. El objetivo de este trabajo de investigación es mejorar la eficiencia y calidad de imagen de un prototipo de escáner PET axial (AX-PE…
The Bayesian estimation of private investment in Finland
2009
Abstract This paper estimates an investment equation for private investment using Bayesian estimation techniques. In the paper we derive the optimal capital accumulation behavior in the model economy from the households’ optimization problem of utility. The equation is derived as in Smets and Wouters (2003). The model contains costly adjustment of investment and random shocks to adjustment cost function. The driving variable of investment is Tobin Q variable. The empirical proxy for Tobin Q in this paper is the ratio of OMX Helsinki Cap Index to the price index of the physical capital. The investment series is the seasonally adjusted private investment in quarterly national accounts. The AR…
Molecular and biometric data on Carabus (Macrothorax) morbillosus Fabricius, 1792 (Coleoptera, Carabidae) from Mid Mediterranean areas
2022
The present study was carried out using molecular and biometric data of Carabus (Macrothorax) morbillosus from mid-Mediterranean areas to determine additional information on basal relationships among its representative subspecies. To this aim, two different kinds of approach were employed, including a morphometric analysis of four morphological parameters (i.e., elytra length, elytra width, pronotum length, pronotum width) of 128 specimens, and a Bayesian genetic analysis of 44 cytochrome oxidase subunit I (COI) partial sequences (i.e., 38 examined for the first time and six retrieved from GenBank database). Representative populations of C. (M.) morbillosus were sampled in four countries, n…
Identifying territories using presence-only citizen science data : An application to the Finnish wolf population
2022
Citizens, community groups and local institutions participate in voluntary biological monitoring of population status and trends by providing species data e.g. for regulations and conservation. Sophisticated statistical methods are required to unlock the potential of such data in the assessment of wildlife populations. We develop a statistical modelling framework for identifying territories based on presence-only citizen science data. The framework can be used to jointly estimate the number of active animal territories and their locations in time. Our approach is based on a data generating model which consists of a dynamic submodel for the appearance/removal of territories and an observatio…
Non-monophyly of the “cydnoid” complex within Pentatomoidea (Hemiptera: Heteroptera) revealed by Bayesian phylogenetic analysis of nuclear rDNA seque…
2017
The “cydnoid” complex of pentatomoid families, including Cydnidae, Parastrachiidae, Thaumastellidae, and Thyreocoridae, is morphologically defined by the presence of an array of more or less flattened stout setae (called coxal combs), situated on the distal margin of coxae. These structures, suggested to prevent the coxal-trochanteral articulation from injuries caused by particles of soil, sand or dust, by their nature and function are unknown elsewhere in the Heteroptera. As such, coxal combs were regarded as a synapomorphy of this group of families, and enabled the definition of it as a monophylum. In this study, the monophyly of the “cydnoid” complex of families is tested for the first t…
Elaborazione e validazione di modelli dell’impatto antropico e dei cambiamenti climatici sulle qualità dei suoli in Sicilia, con particolare attenzio…
Il declino della sostanza organica e l’erosione idrica sono due fattori di rischio di degrado del suolo fra i più diffusi in Sicilia. In che misura è possibile contrastarli modificando le attività antropiche ed in particolare quelle in ambito agricolo? Lo scopo della presente ricerca di dottorato è stato quello di mettere a punto dei modelli che permettessero di spiegare le relazioni esistenti fra le azioni dell’uomo in ambito agricolo con la sostanza organica e con l’erosione idrica nei suoli siciliani, tenendo conto anche del clima. Le due indagini sono state svolte separatamente, in parallelo, in aree agricole della Sicilia occidentale per la sostanza organica, sull’intero territorio sic…
Bayesian temporal and spatio-temporal Markov switching models for the detection of influenza outbreaks
2017
Influenza is a disease which affects millions of people every year and causes hundreds of thousends of deads every year. This disease causes substantial direct and indirect costs every year. The influenza epidemic have a particular behavior which shapes the statistical methods for their detection. Seasonal epidemics happen virtually every year in the temperate parts of the globe during the cold months and extend throughout whole regions, countries and even continents. Besides the seasonal epidemics, some nonseasonal epidemics can be observed at unexpected times, usually caused by strains which jump the barrier between animals and humans, as happened with the well known Swine Flu epidemic, w…
Production and Efficiency in 21 Industrialized Countries from 1966 to 2007 to Analyse the Italy’s Decline: Application of a Stochastic Frontier Model…
2008
This paper uses a stochastic frontier production model to estimate the technical efficiency of 21 nations among the more industrialized countries in the world for the wide period from 1966 to 2007. A Cobb-Douglas with labour and capital as inputs, GDP as output and efficiency with exponential distribution appears to work good from a statistical point of view. This model is used to estimate in a bayesian approach the efficiency score of these 21 countries. The bayesian way, applied via Gibbs sampling, is here useful to avoid problems about the small number of observations. So, each efficiency score is obtained as mean of 10,000 draws. The results underline a general and progressive efficienc…
The Spatial Overlap of Police Calls Reporting Street-Level and Behind-Closed-Doors Crime: A Bayesian Modeling Approach
2021
Traditionally, intimate-partner violence has been considered a special type of crime that occurs behind closed doors, with different characteristics from street-level crime. The aim of this study is to analyze the spatial overlap of police calls reporting street-level and behind-closed-doors crime. We analyzed geocoded police calls in the 552 census-block groups of the city of Valencia, Spain, related to street-level crime (N = 26,624) and to intimate-partner violence against women (N = 11,673). A Bayesian joint model was run to analyze the spatial overlap. In addition, two Bayesian hierarchical models controlled for different neighborhood characteristics to analyze the relative risks. Resu…
La falta de reproducibilitat de la investigació: L'estadística com a legitimació del resultat
2014
La investigació científica es legitima mitjançant la replicació dels seus resultats, però els esforços per replicar afirmacions enganyoses exhaureixen el finançament. Ens centrarem en una d’aquestes errades: els resultats de proves estadístiques que ofereixen falsos positius a causa de l’atzar. Els mètodes estadístics clàssics confien en un p-valor per a ponderar les proves enfront d’una hipòtesi nul·la, però les proves d’hipòtesis bayesianes ofereixen resultats més fàcils de comprendre, sempre que hom puga especificar distribucions a priori per a la hipòtesi alternativa. Descriurem noves proves, les UMPBT, tests bayesians que ofereixen una especificació per defecte de les alternatives a pr…