Organochlorine Contaminants of Wintering Ducks Foraging on Detroit River Sediments

Organochlorine analysis was performed on carcasses of 13 diving ducks from a 1981 wintering population that foraged on contaminated sediments in the lower Detroit River. Mean total PCB concentrations were 10 mg/kg for seven lesser scaups (Aythya affinis), 11 mg/kg for three greater scaups (A. marila), and 7.6 mg/kg for three goldeneyes (Bucephala clangula). Highest mean levels of other residues were measured for hexachlorobenzene (1.7 mg/kg) in goldeneyes, and transnonachlor (0.33 mg/kg) and 4,4’-DDE (1.3 mg/kg) in greater scaup. Quantitative analysis of 72 PCB congeners also was applied to water, seston, sediment, benthie oligochaetes, and carp from the same site. Principal congeners in most of the samples included some of the more toxic and persistent PCBs. Results of a multivariate analysis indicated that ratios of more conservative to less conservative PCBs did not vary significantly among ducks (α = .05), but differed from those in carp, oligochaetes, and sediment. For the February through March period of fat mobilization, concentrations of total PCB in lipid were inversely correlated with percent lipid (r = 0.76) in ducks. The percentage of conservative PCBs increased slightly. The distribution and partitioning of organochlorines, including toxic PCB congeners, varied considerably within this water column-sediment-fauna ecosystem. Estimates of toxic exposure based on total PCB values may be unreliable.     

The proximate determinants of fertility

The proximate determinants of fertility are the biological and behavioral factors through which socioeconomic and environmental variables operate to influence the rate of childbearing in a population. Three biological proximate variables are identified: permanent sterility, the probability of conception, and intrauterine mortality. Although these variables lower the actual rate of reproduction to far below its potential maximum, they contribute little to trends in fertility. Changes over time in fertility are largely due to changes in the behavioral proximate determinants. The most important of these is the prevalence of contraceptive use, but the duration of breastfeeding, the practice of induced abortion, patterns of union formation, and contraceptive effectiveness are or have been major determinants of levels and trends in fertility in most societies.     

Testing of large-scale concrete containment structural elements

The tests described in this paper are part of an Electric Power Research Institute (EPRI) program (Research Project 2172-2) to provide a test-verified analytical method of estimating capacities of concrete reactor containment buildings under internal overpressurization from postulated degraded core accidents.Experimental study in Phase 2 of the investigation, on which this paper is based, includes tests of five large-scale specimens with steel liner plates representing structural elements of prestressed concrete containment buildings. Four square wall element specimens and one specimen representing the wall/basemat junction region were tested.This experimental work indicates that under internal overpressurization or other accident conditions, highly localized strains in the steel liner plate can result in liner tearing and subsequent containment leakage. These results support the theory of leak before break where liner tearing occurs in a controlled manner and leakage and depressurization occur rather than global failure.     

Dopant Distribution in Nominally Yttrium-Doped Sapphire

The dopant distribution in nominally yttrium-doped sapphire is characterized. The results indicate that virtually all of the intended dopant segregated to the surface of the crystal during growth. This implies that the solubility of yttrium in alumina is <10 ppm even at temperatures approaching the melting point of alumina.     

Pivotal Decomposition to Find Availability and Failure-Frequency of Systems with Common-Cause Failures

The purpose of this article is to extend the pivotal decomposition method for system availability and failure frequency from the case where components are statistically independent to that where components are also subject to common-cause failures. This method requires as input data the failure rate and the mean repair time of each component, the occurrence rate of each common-cause failure, and the mean-time for repairing it.