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.     

Work-related commitment and job performance: it's also the nature of the performance that counts

This study tested the proposition that relationships among the various types of work-related commitment and job performance are affected by both the form of commitment and the facet of performance under consideration. Results provided some support for this view. As hypothesized, job involvement was related only to performance tied to intrinsically rewarding elements of work, and career commitment was positively related to overall performance effectiveness. Unexpectedly, however, organizational commitment (both affective and continuance) was unrelated to job performance. The discussion is centered on practical implications of these findings and on directions for future research. © 1998 John Wiley & Sons, Ltd.     

Trends in rainfall regime over Israel, 1975–2010, and their relationship to large-scale variability

Variations and trends in the rain regime of Israel are analyzed for 1975–2010, when persistent global warming has been observed. Negative trend is observed over the majority of Israel, statistically significant only in the super-arid region. The decrease is significant over the majority of Israel only in the spring, reflecting a shortening of the rainy season, >3 days/decade. The dry spells are becoming longer, significantly in most of the stations. The factors affecting these variations, synoptic systems, large-scale oscillations and global temperature, were studied for extended period, 1953–2010. A simple multiple stepwise regression model applied for the inter-annual rainfall variations indicates that the occurrence of Cyprus lows is the dominant factor and the Mediterranean oscillation index, MOI2, is also a significant factor. In order to reduce the inter-annual noise and reveal inter-decadal variations, the time-series of the rainfall and its potential predictors were smoothed by 11-year window, showing an increase toward the 1990s, followed by a decrease, at a higher rate, onward. Correspondingly, the aridity lines propagated southward till the mid-1990s and then withdrew back, at a larger rate. The large-scale oscillations and the global temperature explain 83 % of the variance on the inter-decadal time-scale, half of it explained by the global temperature alone. The findings of this study support the expected poleward expansion of the Hadley cell due to global warming.     

Anniston community health survey: Follow-up and dioxin analyses (ACHS-II)—methods

High serum concentrations of polychlorinated biphenyls (PCBs) have been reported previously among residents of Anniston, Alabama, where a PCB production facility was located in the past. As the second of two cross-sectional studies of these Anniston residents, the Anniston Community Health Survey: Follow-Up and Dioxin Analyses (ACHS-II) will yield repeated measurements to be used to evaluate changes over time in ortho-PCB concentrations and selected health indicators in study participants. Dioxins, non-ortho PCBs, other chemicals, heavy metals, and a variety of additional clinical tests not previously measured in the original ACHS cohort will be examined in ACHS-II. The follow-up study also incorporates a questionnaire with extended sections on diet and occupational history for a more comprehensive assessment of possible exposure sources. Data collection for ACHS-II from 359 eligible participants took place in 2014, 7 to 9 years after ACHS.     

Bioremediation of petroleum hydrocarbons in contaminated soils: comparison of biosolids addition, carbon supplementation, and monitored natural attenuation

Two methods of biostimulation were compared in a laboratory incubation study with monitored natural attenuation (MNA) for total petroleum hydrocarbon (TPH) degradation in diesel-contaminated Tarpley clay soil with low carbon content. One method utilized rapid-release inorganic fertilizers rich in N and P, and the other used sterilized, slow-release biosolids, which added C in addition to N and P. After 8 weeks of incubation, both biostimulation methods degraded approximately 96% of TPH compared to MNA, which degraded 93.8%. However, in the first week of incubation, biosolids-amended soils showed a linear two orders of magnitude increase in microbial population compared to MNA, whereas, in the fertilizer-amended soils, only a one order of magnitude increase was noted. In the following weeks, microbial population in the fertilizer-amended soils dropped appreciably, suggesting a toxic effect owing to fertilizer-induced acidity and/or NH(3) overdosing. Results suggest that biosolids addition is a more effective soil amendment method for biostimulation than the commonly practiced inorganic fertilizer application, because of the abilities of biosolids to supplement carbon. No statistically significant difference was observed between the biostimulation methods and MNA, suggesting that MNA can be a viable remediation strategy in certain soils with high native microbial population.