A Case Study of Controlling Crossover in a Selection Hyper-heuristic Framework Using the Multidimensional Knapsack Problem.

Hyper-heuristics are high-level methodologies for solving complex problems that operate on a search space of heuristics. In a selection hyper-heuristic framework, a heuristic is chosen from an existing set of low-level heuristics and applied to the current solution to produce a new solution at each point in the search. The use of crossover low-level heuristics is possible in an increasing number of general-purpose hyper-heuristic tools such as HyFlex and Hyperion. However, little work has been undertaken to assess how best to utilise it. Since a single-point search hyper-heuristic operates on a single candidate solution, and two candidate solutions are required for crossover, a mechanism is required to control the choice of the other solution. The frameworks we propose maintain a list of potential solutions for use in crossover. We investigate the use of such lists at two conceptual levels. First, crossover is controlled at the hyper-heuristic level where no problem-specific information is required. Second, it is controlled at the problem domain level where problem-specific information is used to produce good-quality solutions to use in crossover. A number of selection hyper-heuristics are compared using these frameworks over three benchmark libraries with varying properties for an NP-hard optimisation problem: the multidimensional 0-1 knapsack problem. It is shown that allowing crossover to be managed at the domain level outperforms managing crossover at the hyper-heuristic level in this problem domain.

Surveillance of bleeding disorders, Texas, 2007.

BACKGROUND: In 2007, some 1261 patients with hemophilia or other bleeding disorders were seen at federally funded hemophilia treatment centers (HTCs) in Texas. Although HTCs function as sites for passive surveillance of bleeding disorders, annual HTC visit data likely underestimate true prevalence of the disease due to the infrequent nature of healthcare utilization for this population. PURPOSE: The main aim of this study was to compare two alternative methods for estimating prevalence of hemophilia and to describe the challenges associated with making valid prevalence estimates. Each method utilized a separate data source, with the goal of validating one or both of the methods, compared to the gold standard of active case finding. METHODS: Two data sets, one describing treatment of hemophilia in an outpatient setting at HTCs and one describing treatment and care of patients in a hospital inpatient setting, were used to calculate annual prevalence estimates of hemophilia among men in Texas in 2007. The prevalence estimates resulting from each of the two methods were compared to each other and to past estimates based on active surveillance. RESULTS: Calculations based on HTC data resulted in estimated prevalence rates of 8.9 and 2.1/100,000 male population for hemophilia A and B, respectively. Prevalence estimates based on hospital discharge data yielded rates of 12.3 and 2.9/100,000 males for hemophilia A and B, respectively. CONCLUSIONS: Hemophilia is a rare, chronic disease with high treatment costs. Prevalence estimates based on HTC and hospital discharge data were similar to each other as well as to active surveillance prevalence estimates in published literature.

High school completion rates among men with hemophilia.

BACKGROUND: The benefits of a high school diploma are well documented. Studies indicate that people with hemophilia have lower than average academic achievement, particularly if they have >12 bleeding episodes annually. PURPOSE: This study compares the high school graduation rate of men with hemophilia to that of the U.S. population of men. METHODS: Data were obtained from the Universal Data Collection Program, a surveillance project conducted by approximately 130 hemophilia treatment centers in the nation. Data from 7842 men aged >or=18 years were evaluated to determine high school graduation status and were analyzed by race/ethnicity and severity of hemophilia. These data were collected between 1998 and 2008, and analysis was conducted in 2009. RESULTS: Men with hemophilia A had higher or similar high school graduation rates across all racial/ethnic groups and all levels of hemophilia severity, compared with U.S. men of the same age. Graduation rates for black and Hispanic men with hemophilia B were higher or similar to rates of U.S. men, but rates for whites were lower, especially among those with moderate and mild disease. However, when graduation rates were controlled for areas where Amish populations reside, differences in graduation rates for whites disappeared. CONCLUSIONS: In this study, participants obtained hemophilia care at comprehensive hemophilia treatment centers. This multidisciplinary, family-centered care emphasizes prevention of complications, encourages medically supervised disease management, and facilitates psychosocial development. The care aims to maximize the affected child's participation in school. This care approach may partially explain the higher-than-expected high school graduation rates among the study population, which is affected by a rare, chronic, and potentially debilitating disorder.