Search results for "Markov chains"
showing 10 items of 73 documents
Uncertainty quantification on a spatial Markov-chain model for the progression of skin cancer
2019
AbstractA spatial Markov-chain model is formulated for the progression of skin cancer. The model is based on the division of the computational domain into nodal points, that can be in a binary state: either in ‘cancer state’ or in ‘non-cancer state’. The model assigns probabilities for the non-reversible transition from ‘non-cancer’ state to the ‘cancer state’ that depend on the states of the neighbouring nodes. The likelihood of transition further depends on the life burden intensity of the UV-rays that the skin is exposed to. The probabilistic nature of the process and the uncertainty in the input data is assessed by the use of Monte Carlo simulations. A good fit between experiments on mi…
Robust Assembly Assistance Using Informed Tree Search with Markov Chains
2022
Manual work accounts for one of the largest workgroups in the European manufacturing sector, and improving the training capacity, quality, and speed brings significant competitive benefits to companies. In this context, this paper presents an informed tree search on top of a Markov chain that suggests possible next assembly steps as a key component of an innovative assembly training station for manual operations. The goal of the next step suggestions is to provide support to inexperienced workers or to assist experienced workers by providing choices for the next assembly step in an automated manner without the involvement of a human trainer on site. Data stemming from 179 experiment partici…
Google matrix analysis of worldwide football mercato
2018
[EN] The worldwide football transfer market is analyzed as a directed complex network: the football clubs are the network nodes and the directed edges are weighted by the total amount of money transferred from a club to another. The Google matrix description allows to treat every club independently of their richness and allows to measure for a given club the efficiency of player sales and player acquisitions. The PageRank algorithm, developed initially for the World Wide Web, naturally characterizes the ability of a club to import players. The CheiRank algorithm, also developed to analyze large scale directed complex networks, characterizes the ability of a club to export players. The analy…
Bayesian Markov switching models for the early detection of influenza epidemics
2008
The early detection of outbreaks of diseases is one of the most challenging objectives of epidemiological surveillance systems. In this paper, a Markov switching model is introduced to determine the epidemic and non-epidemic periods from influenza surveillance data: the process of differenced incidence rates is modelled either with a first-order autoregressive process or with a Gaussian white-noise process depending on whether the system is in an epidemic or in a non-epidemic phase. The transition between phases of the disease is modelled as a Markovian process. Bayesian inference is carried out on the former model to detect influenza epidemics at the very moment of their onset. Moreover, t…
Statistics of transitions for Markov chains with periodic forcing
2013
The influence of a time-periodic forcing on stochastic processes can essentially be emphasized in the large time behaviour of their paths. The statistics of transition in a simple Markov chain model permits to quantify this influence. In particular the first Floquet multiplier of the associated generating function can be explicitly computed and related to the equilibrium probability measure of an associated process in higher dimension. An application to the stochastic resonance is presented.
Bioinformatic flowchart and database to investigate the origins and diversity of Clan AA peptidases
2009
Abstract Background Clan AA of aspartic peptidases relates the family of pepsin monomers evolutionarily with all dimeric peptidases encoded by eukaryotic LTR retroelements. Recent findings describing various pools of single-domain nonviral host peptidases, in prokaryotes and eukaryotes, indicate that the diversity of clan AA is larger than previously thought. The ensuing approach to investigate this enzyme group is by studying its phylogeny. However, clan AA is a difficult case to study due to the low similarity and different rates of evolution. This work is an ongoing attempt to investigate the different clan AA families to understand the cause of their diversity. Results In this paper, we…
Cost-effectiveness of sofosbuvir plus ribavirin with or without pegylated interferon for the treatment of chronic hepatitis C in Italy.
2015
Objective:Across Italy up to 7.3% of the population is infected with hepatitis C virus (HCV), with long-term complications resulting in high medical costs and significant morbidity and mortality. Current treatment options have limitations due to side effects, interferon intolerability and ineligibility, long treatment durations and low sustained virological response (SVR) rates, especially for the most severe patients). Sofosbuvir is the first nucleotide polymerase inhibitor with pan-genotypic activity. Sofosbuvir, administered with ribavirin (RBV) and with or without pegylated interferon (PEG-INF), resulted in >90% SVR across treatment-naïve (TN) genotype (GT) 1-6 patients. It is also t…
Forecasting Hepatitis C liver disease burden on real-life data. Does the hidden iceberg matter to reach the elimination goals?
2018
Abstract Background & Aims Advances in direct‐acting antiviral treatment of HCV have reinvigorated public health initiatives aimed at identifying affected individuals. We evaluated the possible impact of only diagnosed and linked‐to‐care individuals on overall HCV burden estimates and identified a possible strategy to achieve the WHO targets by 2030. Methods Using a modelling approach grounded in Italian real‐life data of diagnosed and treated patients, different linkage‐to‐care scenarios were built to evaluate potential strategies in achieving the HCV elimination goals. Results Under the 40% linked‐to‐care scenario, viraemic burden would decline (60%); however, eligible patients to treat w…
Utility-based criteria for selecting patients with hepatocellular carcinoma for liver transplantation: A multicenter cohort study using the alpha-fet…
2015
The lifetime utility of liver transplantation (LT) in patients with hepatocellular carcinoma (HCC) is still controversial. The aim of this study was to ascertain when LT is cost-effective for HCC patients, with a view to proposing new transplant selection criteria. The study involved a real cohort of potentially transplantable Italian HCC patients (n = 2419 selected from the Italian Liver Cancer group database) who received nontransplant therapies. A non-LT survival analysis was conducted, the direct costs of therapies were calculated, and a Markov model was used to compute the cost utility of LT over non-LT therapies in Italian and US cost scenarios. Post-LT survival was calculated using t…
Quadratic speedup for finding marked vertices by quantum walks
2020
A quantum walk algorithm can detect the presence of a marked vertex on a graph quadratically faster than the corresponding random walk algorithm (Szegedy, FOCS 2004). However, quantum algorithms that actually find a marked element quadratically faster than a classical random walk were only known for the special case when the marked set consists of just a single vertex, or in the case of some specific graphs. We present a new quantum algorithm for finding a marked vertex in any graph, with any set of marked vertices, that is (up to a log factor) quadratically faster than the corresponding classical random walk.