On The Sunset Trail

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An analysis of the XOR dynamic problem generator based on the dynamical system

This is the post-print version of the article - Copyright @ 2010 Springer-VerlagIn this paper, we use the exact model (or dynamical system approach) to describe the standard evolutionary algorithm (EA) as a discrete dynamical system for dynamic optimization problems (DOPs). Based on this dynamical system model, we analyse the properties of the XOR DOP Generator, which has been widely used by researchers to create DOPs from any binary encoded problem. DOPs generated by this generator are described as DOPs with permutation, where the fitness vector is changed according to a permutation matrix. Some properties of DOPs with permutation are analyzed, which allows explaining some behaviors observed in experimental results. The analysis of the properties of problems created by the XOR DOP Generator is important to understand the results obtained in experiments with this generator and to analyze the similarity of such problems to real world DOPs.This work was supported by Brazil FAPESP under Grant 04/04289-6 and by UK EPSRC under Grant EP/E060722/2

Quantifying the Contribution of Animal-food Sources to Human Salmonellosis in Denmark in 1999

A risk assessment model quantifying the impmiance of the major animal-food sources was developed. For modelling purposes, we combined Bayesian inference and Monte Carlo simulation. The principle was to compare the registered number of human cases caused by different Salmonella sero- and phage types with the prevalence of these types in the different sources, weighted by the amount of food source consumed. A prior distribution was included to account for the presumed differences between serotypes and food sources with respect to causing human salmonellosis. A Poisson likelihood function was used for the probability of observing the actual number of human cases given the prevalence in the sources. Based on the posterior distribution, the number of human cases attributable to each food source was estimated. The described method may prove to be an alternative to the traditional stable-to-table risk assessment, which often involves making a large number of assumptions

Autologous hematopoietic stem cell transplantation for mantle cell lymphoma

AbstractThis study evaluated the outcomes of patients who underwent high-dose chemotherapy (HDC) and autologous hematopoietic stem cell transplantation (autoHSCT) for mantle cell non-Hodgkin's lymphoma and the effect of clinical and treatment characteristics. The clinical outcome and prognostic factors in 40 patients who underwent HDC and autoHSCT for mantle cell lymphoma between June 1991 and August 1998 were analyzed. With a median follow-up of 24 months for the surviving patients (range, 4-68 months), the 2-year overall survival was 65% and the 2-year event-free survival (EFS) was 36%. In univariate analysis, characteristics predictive of a poor EFS were blastic morphology (P = .019) and the patient having received 3 or more prior chemotherapy regimens (P = .004). In a multivariate analysis, the only factor associated with a poor EFS was the number of prior chemotherapy regimens. Those patients who received 3 or more prior therapies had a 2-year EFS of 0%, and those who received <3 therapies had a 2-year EFS of 45% (P = .004). Patients with mantle cell lymphoma can obtain prolonged EFS with HDC and autoHSCT; however, this strategy for prolonged EFS appears to work optimally in patients who are less heavily pretreated. Whether this therapy will increase the overall survival or EFS in patients receiving transplants in first complete remission will need to be tested in prospective randomized clinical trials.Biol Blood Marrow Transplant 2000;6(6):640-5

Properties of Nucleon Resonances by means of a Genetic Algorithm

We present an optimization scheme that employs a Genetic Algorithm (GA) to determine the properties of low-lying nucleon excitations within a realistic photo-pion production model based upon an effective Lagrangian. We show that with this modern optimization technique it is possible to reliably assess the parameters of the resonances and the associated error bars as well as to identify weaknesses in the models. To illustrate the problems the optimization process may encounter, we provide results obtained for the nucleon resonances $\Delta$(1230) and $\Delta$(1700). The former can be easily isolated and thus has been studied in depth, while the latter is not as well known experimentally.Comment: 12 pages, 10 figures, 3 tables. Minor correction

Level-Based Analysis of Genetic Algorithms and Other Search Processes

The fitness-level technique is a simple and old way to derive upper bounds for the expected runtime of simple elitist evolutionary algorithms (EAs). Recently, the technique has been adapted to deduce the runtime of algorithms with non-elitist populations and unary variation operators [2,8]. In this paper, we show that the restriction to unary variation operators can be removed. This gives rise to a much more general analytical tool which is applicable to a wide range of search processes. As introductory examples, we provide simple runtime analyses of many variants of the Genetic Algorithm on well-known benchmark functions, such as OneMax, LeadingOnes, and the sorting problem

Long-Term Outcomes of Autologous Stem Cell Transplantation for Follicular Non-Hodgkin Lymphoma: Effect of Histological Grade and Follicular International Prognostic Index

AbstractAlthough results of autologous stem cell transplantation (SCT) for recurrent follicular non-Hodgkin lymphoma (NHL) have been previously reported, the long-term results and evaluation of prognostic factors in a large patient population receiving this therapy are difficult to find in the literature. To address these issues, we evaluated 248 patients with recurrent follicular NHL treated with high-dose chemotherapy and autologous SCT between 7/87 and 6/03. According to the World Health Organization (WHO) classification system, 64 patients (26%) had follicular NHL grade 1 (FL 1), 98 (40%) had FL 2, and 86 (35%) had FL 3. At the time of transplantation, 88 of the patients (35%) had a Follicular Lymphoma International Prognostic Index (FLIPI) score of low risk, 87 (35%) had an intermediate-risk FLIPI score, 37 (15%) had a high-risk FLIPI score, and 36 (15%) had at least 1 missing value, preventing calculation of the FLIPI score. The 5-year overall survival (OS) for all patients was 63%, and the 5-year progression-free survival (PFS) was 44%. In a multivariate analysis, a histological grade of FL 3, a high-risk FLIPI score at the time of transplantation, and having received 3 or more previous chemotherapy regimens were significant factors for predicting a worse OS. In addition, the use of a transplantation regimen including a monoclonal antibody decreased the relative risk of progressive lymphoma. These data suggest that transplantation earlier in the course of the disease for patients with follicular lymphoma with use of a monoclonal antibody–based regimen may lead to improved outcomes

Genetic algorithm dynamics on a rugged landscape

The genetic algorithm is an optimization procedure motivated by biological evolution and is successfully applied to optimization problems in different areas. A statistical mechanics model for its dynamics is proposed based on the parent-child fitness correlation of the genetic operators, making it applicable to general fitness landscapes. It is compared to a recent model based on a maximum entropy ansatz. Finally it is applied to modeling the dynamics of a genetic algorithm on the rugged fitness landscape of the NK model.Comment: 10 pages RevTeX, 4 figures PostScrip