Search results for "Markov"

A longitudinal analysis of the occupational status of the graduates of the University of Palermo

The availability of a large amount of longitudinal data provided by the surveys carried out by STELLA (Statistics about Graduates and Labour Market) allowed us to describe the occupational paths of graduates of the University of Palermo. In this paper we refer to a disproportionate stratified sample of graduates in 2009, interviewed three dierent times: one year (2010), three years (2012), ve years (2014) after the graduation. In such a global economic crises context, our aims are describing the labour market of the Palermitan graduates, identifying the variables that influence most their occupational status and nally outlining a transition probability structure among the states: Work, Sear…

Dynamics in stochastic evolutionary models

2014

First published: 01 February 2016 We characterize transitions between stochastically stable states and relative ergodic probabilities in the theory of the evolution of conventions. We give an application to the fall of hegemonies in the evolutionary theory of institutions and conflict, and illustrate the theory with the fall of the Qing dynasty and the rise of communism in China. We are especially indebted to Juan Block for his many comments and suggestions. We would also like to thank Drew Fudenberg, Kevin Hasker, Matt Jackson, Peyton Young, and five anonymous referees. We are grateful to NSF Grant SES-08-51315 and to the MIUR PRIN 20103S5RN3 for financial support.

Quantum memories with zero-energy Majorana modes and experimental constraints

2016

In this work we address the problem of realizing a reliable quantum memory based on zero-energy Majorana modes in the presence of experimental constraints on the operations aimed at recovering the information. In particular, we characterize the best recovery operation acting only on the zero-energy Majorana modes and the memory fidelity that can be therewith achieved. In order to understand the effect of such restriction, we discuss two examples of noise models acting on the topological system and compare the amount of information that can be recovered by accessing either the whole system, or the zero-modes only, with particular attention to the scaling with the size of the system and the e…

Cost Effectiveness of Peginterferon ??-2a Plus Ribavirin versus Interferon ??-2b Plus Ribavirin as Initial Therapy for Treatment-Naive Chronic Hepati…

2004

Introduction: In adults with previously untreated chronic hepatitis C (CHC), the combination of peginterferon α-2a plus ribavirin produces a higher rate of sustained virological response (SVR) than interferon α-2b plus ribavirin, but it is still unproven whether this increase is cost effective. The objective of this study was to determine if the gain in SVR with peginterferon α-2a plus ribavirin is worth the incremental cost. Methods: We constructed a Markov model of disease progression in which cohorts of patients received peginterferon α-2a plus ribavirin or interferon α-2b plus ribavirin for 48 weeks (hepatitis C virus [HCV] genotype 1 and non-1 patients with fibrosis) or 24 weeks (genot…

Cost-effectiveness of screening for colorectal cancer in France using a guaiac test versus an immunochemical test

2010

Objectives: The aim of this study was to compare the cost and the effectiveness of two biennial fecal occult blood screening tests for colorectal cancer: a guaiac nonrehydrated test (G-FOBT) and an immunochemical test (I-FOBT) with the absence of screening.Methods: A Markov model was developed to compare these strategies in a general population of subjects aged 50 to 74 over a 20-year period.Results: Compared with the absence of screening, G-FOBT and I-FOBT were associated with a decrease in colorectal cancer mortality of 17.4 percent and 25.2 percent, respectively. With regard to cost-effectiveness, expressed as cost per life-year gained, I-FOBT was the most effective and most costly alter…

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…

Clickstream Data Analysis: A Clustering Approach Based on Mixture Hidden Markov Models

2023

Nowadays, the availability of devices such as laptops and cell phones enables one to browse the web at any time and place. As a consequence, a company needs to have a website so as to maintain or increase customer loyalty and reach potential new customers. Besides, acting as a virtual point-of-sale, the company portal allows it to obtain insights on potential customers through clickstream data, web generated data that track users accesses and activities in websites. However, these data are not easy to handle as they are complex, unstructured and limited by lack of clear information about user intentions and goals. Clickstream data analysis is a suitable tool for managing the complexity of t…

Recursion at the crossroads of sequence modeling, random trees, stochastic algorithms and martingales

2013

This monograph synthesizes several studies spanning from dynamical systems in the statistical analysis of sequences, to analysis of algorithms in random trees and discrete stochastic processes. These works find applications in various fields ranging from biological sequences to linear regression models, branching processes, through functional statistics and estimates of risk indicators for insurances. All the established results use, in one way or another, the recursive property of the structure under study, by highlighting invariants such as martingales, which are at the heart of this monograph, as tools as well as objects of study.

Experimental on-demand recovery of entanglement by local operations within non-Markovian dynamics

2015

In many applications entanglement must be distributed through noisy communication channels that unavoidably degrade it. Entanglement cannot be generated by local operations and classical communication (LOCC), implying that once it has been distributed it is not possible to recreate it by LOCC. Recovery of entanglement by purely local control is however not forbidden in the presence of non-Markovian dynamics, and here we demonstrate in two all-optical experiments that such entanglement restoration can even be achieved on-demand. First, we implement an open-loop control scheme based on a purely local operation, without acquiring any information on the environment; then, we use a closed-loop s…

Quantum Non-Markovian Piecewise Dynamics from Collision Models

2017

Recently, a large class of quantum non-Markovian piecewise dynamics for an open quantum system obeying closed evolution equations has been introduced [B. Vacchini, Phys. Rev. Lett. 117, 230401 (2016)]. These dynamics have been defined in terms of a waiting-time distribution between quantum jumps, along with quantum maps describing the effect of jumps and the system's evolution between them. Here, we present a quantum collision model with memory, whose reduced dynamics in the continuous-time limit reproduces the above class of non-Markovian piecewise dynamics, thus providing an explicit microscopic realization.