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991.
Coalitionary aggression occurs when at least two individuals jointly direct aggression at one or more conspecific targets. Scientists have long argued that this common form of cooperation has positive fitness consequences. Nevertheless, despite evidence that social bond strength (which is thought to promote coalition formation) is correlated with fitness in primates, cetaceans, and ungulates, few studies have directly examined whether coalitionary aggression improves reproductive success. We tested the hypothesis that among free-ranging chimpanzees (Pan troglodytes schweinfurthii), participation in coalitionary aggression increases reproductive output. Using 14 years of genetic and behavioral data from Gombe National Park, Tanzania, we found that coalitionary aggression increased a male’s chances of (A) siring offspring, compared to other males of similar dominance rank, and (B) ascending in rank, a correlate of future reproductive output. Because male chimpanzees form coalitions with many others within a complex network, we used social network analysis to identify the types of connections correlated with these fitness benefits. The beneficiaries of coalitionary aggression were males with the highest “betweenness”—that is, those who tended to have coalition partners who themselves did not form coalitions with each other. This suggests that beyond simply recognizing third-party relationships, chimpanzees may use this knowledge to choose coalition partners. If so, this is a significant step forward in our knowledge of the adaptive value of social intelligence. Regardless of mechanism, however, this is the first evidence of genetic benefits of coalitionary aggression in this species, and therefore has important implications for understanding the evolution of cooperation.  相似文献   
992.
A concept of population control is proposed as applied to rodent carriers of plague and other infections with natural focality. The concept is based on the generalization of long-term experience gained in natural plague foci, differentiation of the enzootic territory with respect to the level of epidemic risk, analysis of the current state of rodent populations, and the necessity of biodiversity conservation in natural biocenoses.  相似文献   
993.
994.
A GIS model predicting the spatial distribution of terrestrial salamander abundance based on topography and forest age was developed using parameters derived from the literature. The model was tested by sampling salamander abundance across the full range of site conditions used in the model. A regression of the predictions of our GIS model against these sample data showed that the model has a modest but significant ability to predict both salamander abundance and mass per unit area. The model was used to assess the impacts of alternative management plans for the Hoosier National Forest (Indiana, USA) on salamanders. These plans differed in the spatial delineation of management areas where timber harvest was permitted, and the intensity of timber harvest within those management areas. The spatial pattern of forest openings produced by alternative forest management scenarios based on these plans was projected over 150 years using a timber-harvest simulator (HARVEST). We generated a predictive map of salamander abundance for each scenario over time, and summarized each map by calculating mean salamander abundance and the mean colonization distance (average distance from map cells with low predicted abundance to those with relatively high abundance). Projected salamander abundance was affected more by harvest rate (area harvested each decade) than by the management area boundaries. The alternatives had a varying effect on the mean distance salamanders would have to travel to colonize regenerating stands. Our GIS modeling approach is an example of a spatial analytical tool that could help resource management planners to evaluate the potential ecological impact of management alternatives.  相似文献   
995.
Lochnagar is a remote mountain lake to the south-east of the Cairngorm region in Scotland. Its catchment receives anthropogenic trace metals solely from atmospheric deposition. Ten peat cores were taken from the catchment and analysis confirmed that they have been contaminated by trace metals. The peats have an high affinity for trace metals and this results in metal accumulation in the surface peat layers. The formation of trace metal sulphides may also reduce remobilisation. In this way, trace metals derived from atmospheric deposition have been scavenged and accumulated. In contaminated peat layers, 77.4% Hg, 89.6% Pb, 93.4% Cu, 72.4% Zn and 86.5% Cd of the total stored are from anthropogenic sources. The accumulated trace metals in the peats can potentially influence the lake system through erosion. Spheroidal carbonaceous particle (SCP) profiles were used to date the peat cores. By referring to the SCP profiles in the peats and comparing these with the trace metal profiles in the lake sediments, the mobility of trace metals in the catchment peats is confirmed.  相似文献   
996.
Exposure to chemicals via diet is a major uptake pathway for many compounds but is often estimated in a rather generic way. We use a new model framework (NMF) with crop-specific models to predict the dietary intake by 4-5-year-old children and 14-75-year-old women of three environmental compounds from their background concentrations in soil and air. Calculated daily intakes of benzo(a)pyrene and 2,3,7,8-TCDD are in good agreement with measured results from diet studies. The major source of both compounds in human diet is deposition from air. Inhalation of air and ingestion of soil play a minor role. Children take up more than twice the amount than adults per kg bodyweight, due to higher consumption per kg bodyweight. Contrary, the methods for indirect human exposure suggested in the Technical Guidance Document (TGD) for chemical risk assessment in the EU lead to overprediction, due to unrealistic consumption data and a false root model.  相似文献   
997.
As the use of ultrasonography has become a routine procedure in the care of pregnant women, fetal congenital malformations have been frequently diagnosed prenatally. During a 4-year period abdominal wall defects (AWD) were diagnosed in 14 cases, five were gastroschises and nine were omphaloceles, seven females and seven males. Concomitant malformations were present in one case of gastroschisis and in five cases of omphalocele. Eleven AWD's were diagnosed in the second trimester and six pregnancies were interrupted. Eight children with AWD were born; two boys with omphalocele and one girl and one boy with gastroschisis are still alive. Alpha-fetoprotein was determined in amniotic fluid in 11 cases and also in maternal serum prior to the amniocentesis in eight cases. Chromosomal investigations were performed in 13 cases, 11 on amniotic fluid cells and two on lymphocytes from a blood sample made postnatally. Two abnormal karyotypes, 47,XX + 18 were found.  相似文献   
998.
Amniocentesis was performed in view of a paternal balanced chromosomal rearrangement t(4;20)(p16;p12), inv(18)(p11q11). The pregnancy was complicated by severe oligohydramnios. The fetal karyotype was unbalanced: 46XX, der(4), t(4;20)(p16;p12), inv(18) (p11q11)pat., thus resulting in partial trisomy 2Op and monosomy 4p. In addition, the amniotic fluid alpha-fetoprotein (AFP) became increasingly elevated with gestational age. The pregnancy was terminated at 25 weeks. The fetus presented with typical facial dysmorphic features, unilateral cleft lip and palate, severe renal hypoplasia, consistent with the 4p- (Wolf-Hirschhorn) syndrome.  相似文献   
999.
In the course of evaluating worker exposure during the hot splicing of underground electrical cable, it was discovered that the insulating tape used to make the original joints contained a high percentage (up to 10%) of PCB in the surface varnish. The heating of this PCB by a propane torch flame and molten solder as part of the normal operation of joint breakdown and remake resulted in a composition of airborne fume with a significant fraction (up to 1.3%) of the PCB that was converted to polychlorinated dibenzofurans (PCDF) with the tetra- and penta- chlorinated compounds as the predominant cogeners. No polychlorinated dibenzodioxins were detected.  相似文献   
1000.
ABSTRACT: As part of a basinwide water-quality study, nitrogen and phosphorus data for the Upper Colorado River Basin from the Colorado-Utah State line to the Continental Divide were analyzed for spatial distributions, concentrations associated with various land uses, and temporal trends. Nitrogen and phosphorus concentrations generally increased in a downstream direction. Some nutrient concentrations were elevated at some sites in the upper parts of the basin in areas influenced by increasing urbanization. Sites were grouped according to land use and site type, and median nutrient concentrations were compared among groups. Sites within the agricultural areas of the basin generally had the highest concentrations of nitrogen and phosphorus; concentrations for main-stem, tributary, and urbanization sites were slightly lower than for the agricultural sites. Background sites, or sites with minimal land-use impacts, had very low median nutrient concentrations. Several sites with long-term data were analyzed for temporal trends in concentrations. Several statistically significant downward trends of low and moderate magnitude were observed for nitrogen and phosphorus species. No upward trends were observed in the data at any site.  相似文献   
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