Origins and fundamental concepts of the competing-risks problem

The history of problems dealing with competing risks is briefly outlined, beginning with Daniel Bernoulli's 1760 “Mémoir” on mortality due to smallpox and proceeding through the development of actuarial techniques and methods used in clinical research, reliability theory, population dynamics, and other areas of application. A probabilistic formulation of the theory of competing risks is then presented which appears applicable to all these areas. Within the framework of this theory, some fundamental problems are stated and discussed, such as questions of identifiability, choices of estimation procedures, or techniques for testing hypotheses.     

A quantitative study of intertidepool movement of the wooly sculpin Clinocottus analis

Movements of the wooly sculpin Clinocottus analis between all pools in a designated area of a southern California (USA) intertidal zone were studied. Fish were captured during low tides, finclipped or bead-tagged, and released in the pool of capture. Percent recaptured in pool of first capture declined from 30 after 2 weeks to about 5 after 20 weeks. Percent recaptured in any pool in the study area declined from 50 after 2 weeks to 20 after 8 weeks, but remained at 20 through 16 weeks. A higher fidelity to an area of the intertidal zone than to a specific pool was suggested. Large fish exhibited higher probability of recapture than smaller individuals, indicating they become more sedentary with age. Changes in pool topography influenced percent recurrence in a pool, most likely as a consequence of changes in quality and quantity of cover available. Such responses to changes in specific pools and fidelity to intertidal areas containing several pools appear to be advantageous behavioral patterns in an environment where topographic change is frequent and often massive.     

Effectiveness of primary enforcement safety belt laws and enhanced enforcement of safety belt laws: a summary of the Guide to Community Preventive Services systematic reviews

BACKGROUND: The use of safety belts is the single most effective means of reducing fatal and nonfatal injuries in motor-vehicle crashes. This paper summarizes the systematic reviews of two interventions to increase safety belt use: primary enforcement safety belt laws and enhanced enforcement of safety belt laws. The reviews were previously published in the American Journal of Preventive Medicine. METHODS: We conducted the systematic reviews using the methodology developed for the Guide to Community Preventive Services. RESULTS: These reviews provide strong evidence that primary laws are more effective than secondary laws in increasing safety belt use and decreasing fatalities and that enhanced enforcement is effective in increasing safety belt use. Increases in belt use are generally highest in states with low baseline rates of belt use. DISCUSSION: Primary safety belt laws and enhanced enforcement programs tend to result in greater increases in usage rates for target groups with lower baseline rates. Concerns regarding public opposition to these interventions may impede their implementation in some jurisdictions. However, surveys indicate that a substantial majority of the public supports implementation of both primary laws and enhanced enforcement programs. CONCLUSION: Based on the strong evidence for effectiveness of primary safety belt laws and enhanced enforcement programs, the Task Force on Community Preventive Services recommended that all states enact primary safety belt laws and that communities implement enhanced enforcement programs.     

CSHM: Web-based safety and health monitoring system for construction management

INTRODUCTION: This paper describes a web-based system for monitoring and assessing construction safety and health performance, entitled the Construction Safety and Health Monitoring (CSHM) system. METHOD: The design and development of CSHM is an integration of internet and database systems, with the intent to create a total automated safety and health management tool. A list of safety and health performance parameters was devised for the management of safety and health in construction. A conceptual framework of the four key components of CSHM is presented: (a) Web-based Interface (templates); (b) Knowledge Base; (c) Output Data; and (d) Benchmark Group. RESULTS: The combined effect of these components results in a system that enables speedy performance assessment of safety and health activities on construction sites. With the CSHM's built-in functions, important management decisions can theoretically be made and corrective actions can be taken before potential hazards turn into fatal or injurious occupational accidents. IMPACT ON INDUSTRY: As such, the CSHM system will accelerate the monitoring and assessing of performance safety and health management tasks.     

Efficacy of vegetated buffer strips for retaining Cryptosporidium parvum

Overland and shallow subsurface hydrologic transport of pathogenic Cryptosporidium parvum oocysts from cattle feces into surface drinking water supplies is a major concern on annual grasslands in California's central and southern Sierra Nevada foothills. Soil boxes (0.5 m wide x 1.1 m long x 0.3 m deep) were used to evaluate the ability of grass vegetated buffer strips to retain 2 x 10(8) spiked C. parvum oocysts in 200-g fecal deposits during simulated rainfall intensities of 30 to 47.5 mm/h over 2 h. Buffers were comprised of Ahwahnee sandy loam (coarse-loamy, mixed, active, thermic Mollic Haploxeralfs; 78:18:4 sand to silt to clay ratio; dry bulk density = 1.4 g/cm(3)) set at 5 to 20% land slope, and >/=95% grass cover (grass stubble height = 10 cm; biomass = 900 kg/ha dry weight). Total number of oocysts discharged from each soil box (combined overland and subsurface flow) during the 120-min simulation ranged from 1.5 x 10(6) to 23.9 x 10(6) oocysts. Observed overall mean log(10) reduction of total C. parvum flux per meter of vegetated buffer was 1.44, 1.19, and 1.18 for buffers at 5, 12, and 20% land slope, respectively. Rainfall application rate (mm/h) was strongly associated with oocyst flux from these vegetated buffers, resulting in a decrease of 2 to 4% in the log(10) reduction per meter buffer for every additional mm/h applied to the soil box. These results support the use of strategically placed vegetated buffers as one of several management strategies that can reduce the risk of waterborne C. parvum attributable to extensive cattle grazing on annual grassland watersheds.