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971.
972.
Yoav Peled Moshe Hod MD Shmuel Friedman Reuven Mashiach Nirit Greenberg Jardena Ovadia 《黑龙江环境通报》1992,12(2):151-154
Familial congenital pyloric atresia is a rare malformation of the fetal gastrointestinal tract. It usually manifests as maternal polyhydramnios and enlarged fetal stomach on ultrasound scan. Sonographic prenatal diagnosis and management of a pregnancy complicated by familial congenital pyloric atresia are presented. 相似文献
973.
Steven R. Hilts 《Environmental geochemistry and health》1996,18(1):17-24
Trail, Canada has been the site of a large lead/zinc smelting facility since 1916. In mid 1990, the Trail Community Lead Task Force was established and given responsibility for developing a strategy to reduce children's blood lead levels. With funding from the provincial government, the smelting company and the municipal government, the Task Force has carried out blood lead screening, case management, community education, exposure pathways modelling and remediation trials. The decline in children's blood lead levels appeared to accelerate following the implementation of these programmes. The average blood lead in Trail children aged 6–72 months fell 14% from the autumn of 1991 to autumn of 1992, whereas for the previous 16 years, the average annual decline had been about 4%. In subsequent years, blood lead levels have appeared to plateau. Throughout the 5-year history of the Task Force, its members have demonstrated a strong sense of common purpose and have worked co-operatively to reach consensus on most issues. 相似文献
974.
Bivalves are important in shallow marine habitats, not at least being the major food resource for seaducks such as the common
scoter (Melanitta nigra), thousands of which are wintering on the Western Coastal Banks, near the Belgian-French border (North Sea). Next to this
ecological importance, fishable stocks of one of these bivalves, Spisula subtruncata, occur in the area. This study aimed at investigating S. subtruncata’s spatial distribution, population dynamics and productivity and its implications for a sustainable Spisula fishery in seaduck wintering areas. The spatial distribution of S. subtruncata was studied in 1994 and 1997 in two areas of the Belgian Western Coastal Banks. The population dynamics and production were
investigated by monthly sampling of two stations between April 1995 and April 1996 and a seasonal sampling between April 1996
and April 1998. Spisula subtruncata had a patchy distribution in the deeper (6 m), fine sandy (200 ± 20 μm) sediments of the Abra alba community, mainly found in the western most part of the Western Coastal Banks. In August 1995, an overwhelming and successful
recruitment was observed in this area: local densities were as high as 150,000 ind m−2. Minor, non-successful recruitments were detected in August 1996 and 1997. Due to space limitation, high densities of S. subtruncata are hypothesized to be responsible for the occurrence of aberrant shapes as observed from August 1996 onwards. Growth was
described by a seasonally oscillating version of the von Bertalanffy growth function (VBGF): a growth stop was observed from
late autumn till early spring. The VBGF parameters K (growth constant) and L
∞ (asymptotic length) were estimated at 0.7–0.9 and 31–33 mm. A combination of length and individual biomass increment showed:
(1) a faster length increment of smaller individuals during the second growing period (catching-up phenomenon), (2) a constant
length combined with a decreasing individual biomass during the suboptimal winter periods (except for the first winter, when
the individual biomass slightly increased), (3) a positive relationship between the individual biomass decrease and the seawater
temperature during the winter periods, and (4) a strong increase of the individual biomass in early spring (April 1997 and
1998) because of gametogenesis, followed by a decrease because of spawning (August 1997). The extremely high total production
of the 1995 year class in the tidal gully (Potje) during the study period was estimated at approximately 1,500 g ash-free
dry weight (ADW) m−2 or 600 g ADW m−2 on average per year. Shellfisheries for S. subtruncata within seaduck wintering areas, such as the Western Coastal Banks, should be carefully deliberated since (1) an important
food resource for the seaducks will decrease, (2) the ecologically most diverse and rich macrobenthic A. alba community will be heavily affected, and (3) the recovery of Spisula populations after depletion is expected to be erratic. 相似文献
975.
976.
Steven K. Goldsmith 《Behavioral ecology and sociobiology》1987,20(2):111-115
Summary Adults ofDendrobias mandibularis fed at sites where sap oozes from the stems of desert broom,Baccharis sarothroides. These sites were used by only one individual at a time. Males practiced alternative reproductive tactics, and were separated into two distinct morphs. Major males had enlarged mandibles, were found significantly more frequently at feeding sites than elsewhere on the food plants, and defended the feeding sites to gain access to females that visited the sites to feed. Minor males had small mandibles, were found significantly more frequently in foliage of the food plant than at feeding sites, and usually did not defend feeding sites. Mandibles were used in aggressive interactions, which were always won by larger males. Mating occurred at feeding sites, on stems, and in foliage of the food plant. Major males were observed mating nearly twice as often as minor males. Major males mated significantly more frequently at feeding sites than in foliage; the reverse was true of minor males. Minors occasionally occupied and mated at feeding sites. They were unable to defend feeding sites against majors, but did so occasionally against other minors. Differences in frequency, mating success, and behavior of the morphs appeared to be linked to differences in environmental conditions between the two years of this study. This study demonstrated the importance of spatial distribution of food resources in the evolution of the mating system ofDendrobias mandibularis. 相似文献
977.
Isaac A. Friedman 《组织行为杂志》1995,16(2):191-198
This study attempted to identify the unique components of burnout among school principals using Facet Theory as a theory construction tool. A total of 571 elementary and secondary school principals in Israel completed a questionnaire containing items relating to their feelings about themselves, their environment and work. Data were analyzed employing Small Space Analysis (SSA). Results indicated that burnout among school principals may be presented in a two-dimensional space, incorporating: experiences (weariness or discontent), and the focus (internal or external) of those experiences. Four components of the burnout phenomenon in principals emerged in this two-dimensional space: exhaustion, self-discontent, aloofness, and deprecation. 相似文献
978.
Steven R. Abt Christopher I. Thornton Terry L. Johnson 《Journal of the American Water Resources Association》1995,31(1):53-57
ABSTRACT: A study was conducted to derive a simple procedure for estimating the tributary drainage area that may potentially develop at the base of a uniformly graded, steep slope. Data were extracted from a nil development flume study in which 112 rills and their tributary drainage areas were documented. The tributary drainage area for each rill was correlated to the slope length and the slope gradient. The findings are considered applicable to planar, convex, and divergent slopes with lengths of up to 130 m. Field verification is needed to extend the applicability of the relation. 相似文献
979.
James L. Martin William L. Richardson Steven C. McCutcheon 《Journal of the American Water Resources Association》1991,27(3):429-436
ABSTRACT: A major contaminant monitoring and modeling study is underway for Green Bay, Lake Michigan. Monitoring programs in support of contaminant modeling of large waterbodies, such as for Green Bay, are expensive and their extent is often limited by budget limitations, laboratory capacity, and logistic constraints. Therefore, it is imperative that available resources be used in the most efficient manner possible. This use, or allocation of resources, may be aided through the application of readily available models in the planning stages of projects. To aid in the planning effort for the Green Bay project, a workshop was held and studies designed to aid in the allocation of resources for a year-long intensive field study. Physical/chemical and food chain models were applied using historical data to aid in project planning by identifying processes having the greatest impact on the predictive capability of mass balance models. Studies were also conducted to estimate errors in computed tributary loadings and in-Bay concentrations and contaminant mass associated with different sampling strategies. The studies contributed to the overall project design, which was a collaborative effort with many participants involved in budgeting, field data collection, analysis, processing of data, quality assurance, data management and modeling activities. 相似文献
980.
H. Mark Tweeddale Ronf F. Cameron Steven S. Sylvester 《Journal of Loss Prevention in the Process Industries》1992,5(5):279-288
‘Rapid ranking’ has been used for many years as a method of determining the priority which should be given to formal investigation of the wide range of hazards and risks present on major process industry sites. Such methods tend to evolve to meet the needs of specific applications. Some historical and recent applications are outlined, and the nature of the developments which they led to are discussed. Particular topics discussed include: development of the method such that it is usable by operating managers rather than specialists; use to raise risk consciousness; adaptation for use as an aid to hazard identification; use to define both which risks should be studied and which risks, even if low, should be incorporated in routine monitoring and periodic auditing programmes; use as a basis for comparison of the relative risks presented by a variety of different industrial installations; use for a range of different types of risk; and extension beyond ranking to include ‘shortlisting’ i.e. deciding which risks to include in a study programme and which to leave out. Philosophical difficulties with the approach are discussed, including the danger of omitting from detailed study a risk which is erroneously shown as low, and the uncertainty of the absolute level of the ranked risks. Approaches to minimizing these problems are discussed. 相似文献