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61.
The phylogeny of the Bantu languages is reconstructed by application of the cladistic methodology to the combined lexical and grammatical data (87 languages, 144 characters). A maximum parsimony tree and Bayesian analysis supported some previously recognized clades, e.g., that of eastern and southern Bantu languages. Moreover, the results revealed that Bantu languages south and east of the equatorial forest are probably monophyletic. It suggests an unorthodox scenario of Bantu expansion including (after initial radiation in their homelands and neighboring territories) just a single passage through rainforest areas followed by a subsequent divergence into major clades. The likely localization of this divergence is in the area west of the Great Lakes. It conforms to the view that demographic expansion and dispersal throughout the dry-forests and savanna regions of subequatorial Africa was associated with the acquisition of new technologies (iron metallurgy and grain cultivation).Electronic supplementary material  Supplementary material is available for this article at  相似文献   
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One hundred and twenty-five fetuses were identified as having an AVSD with normal venous connections, normal arterial connections and normal cardiac situs on fetal echocardiography. Fetal karyotype was known in 111 of these cases. The relative risk of fetal trisomy 21 at mid-trimester was 107 (95% CI 87–127) times the expected number of cases compared with risk from maternal age alone, and that for trisomy 21,18 or 13 was 95 (95% CI 79–109). This data may be useful in counselling pregnant women about risk of fetal karyotypic abnormality after a diagnosis of fetal AVSD. Copyright © 2005 John Wiley & Sons, Ltd.  相似文献   
63.
Perchlorate (ClO4-) contamination of ground water and surface water is a widespread problem, particularly in the western United States. This study examined the effect of biodegradation on perchlorate fate and transport in soils. Solute transport experiments were conducted on two surface soils. Pulses of solution containing perchlorate and Br- were applied to saturated soil columns at steady state water flow. Perchlorate behaved like a nonreactive tracer in Columbia loam (coarse-loamy, mixed, superactive, nonacid, thermic Oxyaquic Xerofluvent) but was degraded in Yolo loam (fine-silty, mixed, superactive, nonacid, thermic Mollic Xerofluvent). Batch experiments demonstrated that perchlorate removal from solution in Yolo loam was caused by biodegradation. Other batch experiments with Yolo loam surface and subsurface soils, Columbia loam surface soil, and dredge tailings demonstrated that perchlorate biodegradation required anaerobic conditions, an adequate carbon source, and an active perchlorate-degrading microbial population. The sequential reduction of perchlorate and NO3- by an indigenous soil microbial community in Yolo loam batch systems was also studied. Nitrate reduction occurred much sooner than perchlorate reduction in soils that had not been previously exposed to perchlorate, but NO3- and perchlorate were simultaneously reduced in soils previously exposed to perchlorate. The results of this study have implications for in situ remediation schemes and for agricultural soils that have been contaminated by perchlorate-tainted irrigation water.  相似文献   
64.
In permanent quadrats on exposed and protected shores near São Sebastião (São Paulo), Brazil, changes in percent cover of mussels [Brachidontes solisianus (d'Orbigny)] and barnacles [Chthamalus stellatus bisinuatus (Pilsbury)] were followed from November 1979 through December 1982. Mussels gradually disappeared from both shores, while barnacles came to dominate the exposed, but not the protected, shore. Decreases in percent cover of mussels were related to periods of higher temperatures. Mussels were only transient dominants of the mid-intertidal zone due to lack of recruitment and high summer mortality. This is probably because the study was carried out near the northern limit of their occurrence as a dominant of mid-intertidal communities.Deceased  相似文献   
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The effects of 2 organophosphorous insecticides, temephos (Abate®) and chlorpyrifos (Dursban®), on populations of the salt-marsh snail Melampus bidentatus Say (Basommatophora: Melampidae) were investigated in a series of field experiments. These toxicants were aerially applied to mosquito breeding areas in New Jersey salt marshes in the manner normally used in biting-fly control operations. No significant change in the population density of M. bidentatus was observed in response to multiple treatments of granular formulations of either temephos or chlorpyrifos. However, there was a highly significant (P<0.01) depression in population density observed in the plot exposed to multiple treatments of a temephos emulsion. This depression was followed by a resurgence in density levels, beginning 3 weeks after the last treatment. The specific mechanism for thisperturbation is not known. However, it is hypothesized that it might involve some combination of indirect insecticide effects coupled with age-specific effects. Tests of age structure of the affected population using the chi-square distribution supported this hypothesis.Paper of the Journal Series, New Jersey Agricultural Experiment Station. This research was supported, in part, by a grant from the New Jersey Mosquito Control Commission.  相似文献   
68.
An analysis of the ethical impacts of the use of anAutomatic Milking System (AMS) is employed as a casestudy to illustrate the use of a form of bioethicalanalysis in technology assessment. The approach isbased on the Ethical Matrix, where `impacts' areassessed in terms of (lack of) respect for threeethical principles as applied to interest groups. Inthis case, only impacts on dairy cows are examined,and principally in terms of their behaviouralfreedom.In contrast to traditional milking systems, AMS, inprinciple, allow cows to present for milkingvoluntarily. So with AMS, it is claimed that dairymanagement relies on the autonomous interaction of thecow with her environment.One of the roles of bioethical analysis is to identifythe influence of rhetoric and symbolism in technologyassessment, e.g., with respect to the claimed`voluntariness' of cows' presentation. The AMS can beinstalled to allow cows three types of access, viz., i)free choice ii) rewarded access (RA) iii) obligatoryaccess (OA). Studies suggest the desire for milkremoval per se is not critical in the cow'sattendance at the AMS. Continued motivation to bemilked, required for the system to function,principally relies on RA and OA. Both RA and OA aresubject to numerous factors, such as: design of theAMS, location, etc. In turn, these can affect thecows' behavioural freedom and welfare.One of the aims of this approach is to illustrate theethical basis on which public policy is or can beformulated.  相似文献   
69.
Polyclads are mobile predators and possibly an important functional component of hard substrate marine environments globally. To understand the natural patterns of spatial differences, polyclad assemblages were sampled in seven coastal regions across the wider Caribbean spanning 15° latitude and 24° longitude between May and June 2005 and May and September 2006. In total, 67 species in 28 genera and 17 families were recorded from 62 sites. Only two species were found in all surveyed regions, Melloplana ferruginea and Pseudoceros bicolor. Conversely, 41 species were restricted to one or two sites, and 34 species were represented by one or two individuals. The distribution and abundance of species varied between the two suborders. Cotyleans were most species rich and had a higher number of species of restricted range, while Acotylea showed a higher proportion of rare species; however, two species were highly abundant comprising over half of the individuals counted. In most habitats, polyclads were rare, but in some intertidal habitats two species, Styloplanocera fasciata and Boninia divae were densely aggregated and dominant members of the benthic epifauna. Alpha diversity was variable but showed no evidence of a relationship with latitude, longitude or depth. Beta diversity increased with the number of habitats sampled and was highest for cotyleans. Highest gamma diversity was recorded in Jamaica and the US Virgin Islands and was not significantly correlated to alpha diversity. Overall assemblages from the seven regions were similar, revealing faunal homogeneity across the wider region. Reef assemblages were distinct from other habitats dominated by species of the Cotylea. Reefs from Panama and the US Virgin Islands were the most species rich. Electronic supplementary material The online version of this article (doi:) contains supplementary material, which is available to authorized users.  相似文献   
70.
Buenau KE  Rassweiler A  Nisbet RM 《Ecology》2007,88(12):3022-3031
Many species that compete for space live on heterogeneous landscapes and interact at local scales. The quality, amount, and structure of landscapes may have considerable impact on the ability of species to compete or coexist, yet basic models of space competition do not include that level of detail. We model space competition between two species with positive feedback through recruitment facilitation, which creates the potential for alternative stable states to occur. We compare the predictions of a spatially implicit model with a simulation model that includes explicit space and landscape structure. We create structured landscapes in which we specify the amount of habitat and degree of fragmentation and ask how landscape structure, dispersal strategy, and scale affect the presence of alternative stable states, or bistability. We find that structured landscapes can reduce the range of parameter values that lead to bistability in our model, but they do not eliminate bistability. The type of landscape and the dispersal distance for each species also influence the amount of environmental change needed for abrupt community shifts to occur. Coexistence of the two competitors is possible under certain conditions when connectivity is low. Consequently, landscape structure may lead to considerable disparity between the predictions of simple models and actual dynamics on complex landscapes during environmental change.  相似文献   
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