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排序方式: 共有1360条查询结果,搜索用时 265 毫秒
931.
Rodrigues Izabella Almirante Porto Tiburcio Alves Roberta Vianna Guimarães Maria José de Oliveira Cavalcanti Gomes Thiago Santiago Pacheco Elen Beatriz Acordi Vasques 《Environment, Development and Sustainability》2022,24(8):9705-9730
Environment, Development and Sustainability - This review aimed to analyze plastic lumber manufacturing in Brazil, a country with a large amount of natural wood, and devise strategies to boost... 相似文献
932.
Recent studies on the ant phylogeny are mainly based on the molecular analyses of extant subfamilies and do not include the extinct, only Cretaceous subfamily Sphecomyrminae. However, the latter is of major importance for ant relationships, as it is considered the most basal subfamily. Therefore, each new discovery of a Mesozoic ant is of high interest for improving our understanding of their early history and basal relationships. In this paper, a new sphecomyrmine ant, allied to the Burmese amber genus Haidomyrmex, is described from mid-Cretaceous amber of France as Haidomyrmodes mammuthus gen. and sp. n. The diagnosis of the tribe Haidomyrmecini is emended based on the new type material, which includes a gyne (alate female) and two incomplete workers. The genus Sphecomyrmodes, hitherto known by a single species from Burmese amber, is also reported and a new species described as S. occidentalis sp. n. after two workers remarkably preserved in a single piece of Early Cenomanian French amber. The new fossils provide additional information on early ant diversity and relationships and demonstrate that the monophyly of the Sphecomyrminae, as currently defined, is still weakly supported. 相似文献
933.
A fuzzy expert system for soil characterization 总被引:1,自引:0,他引:1
As soil is a natural resource not always renewable, the risk characterization of contaminated soils is an issue of great interest. Artificial Intelligence (AI), based on Decision Support Systems (DSSs), has been developed for a wide range of applications in contaminated soil management. Decision trees have already shown to be easy to interpret and able to treat large scale applications. Fuzzy logic gives an improvement in the perturbations and the variance of the training data, due to the elasticity of fuzzy set formalism. In this study, we have developed a classificatory tool applied to characterize contaminated soil in function of human and environmental risks. Knowledge engineering for constructing the Soil Risk Characterization Decision Support System (SRC-DSS) involves three stages: knowledge acquisition, conceptual design and system implementation. A total of 26 parameters were divided into three groups to facilitate the configuration of the expert system: source attributes, transfer vector attributes, and local properties. Sixteen case studies were evaluated with the SRC-DSS. In comparison with other techniques, the results of the current study have shown that SRC-DDS is an excellent tool to classify and characterize soils according to the associated risk. 相似文献
934.
Influence of soil texture on the distribution and availability of 238U, 230Th, and 226Ra in soils 总被引:1,自引:0,他引:1
Blanco Rodríguez P Vera Tomé F Lozano JC Pérez-Fernández MA 《Journal of environmental radioactivity》2008,99(8):1247-1254
The influence of soil texture on the distribution and availability of (238)U, (230)Th, and (226)Ra in soils was studied in soil samples collected at a rehabilitated uranium mine located in the Extremadura region in south-west Spain. The activity concentration (Bqkg(-1)) in the soils ranged from 60 to 750 for (238)U, from 60 to 260 for (230)Th, and from 70 to 330 for (226)Ra. The radionuclide distribution was determined in three soil fractions: coarse sand (0.5-2mm), medium-fine sand (0.067-0.5mm), and silt and clay (<0.067 mm). The relative mobility of the natural radionuclides in the different fractions was studied by comparison of the activity ratios between radionuclides belonging to the same radioactive series. The lability of these radionuclides in each fraction was also studied through selective extraction from the soils using a one-step sequential extraction scheme. Significant correlations were found for (238)U, (230)Th, and (226)Ra between the activity concentration per fraction and the total activity concentration in the bulk soil. Thus, from the determination of the activity concentration in the bulk soil, one could estimate the activity concentration in each fraction. Correlations were also found for (238)U and (226)Ra between the labile activity concentration in each fraction and the total activity concentration in bulk soil. Assuming that there is some particle-size fraction that predominates in the process of soil-to-plant transfer, the parameters obtained in this study should be used as correction factors for the transfer factors determined from the bulk soil in previous studies. 相似文献
935.
Tanja Schwander Hervé Rosset Michel Chapuisat 《Behavioral ecology and sociobiology》2005,59(2):215-221
Division of labour among workers is central to the organisation and ecological success of insect societies. If there is a genetic component to worker size, morphology or task preference, an increase in colony genetic diversity arising from the presence of multiple breeders per colony might improve division of labour. We studied the genetic basis of worker size and task preference in Formica selysi, an ant species that shows natural variation in the number of mates per queen and the number of queens per colony. Worker size had a heritable component in colonies headed by a doubly mated queen (h
2=0.26) and differed significantly among matrilines in multiple-queen colonies. However, higher levels of genetic diversity did not result in more polymorphic workers across single- or multiple-queen colonies. In addition, workers from multiple-queen colonies were consistently smaller and less polymorphic than workers from single-queen colonies. The relationship between task, body size and genetic lineage appeared to be complex. Foragers were significantly larger than brood-tenders, which may provide energetic or ergonomic advantages to the colony. Task specialisation was also often associated with genetic lineage. However, genetic lineage and body size were often correlated with task independently of each other, suggesting that the allocation of workers to tasks is modulated by multiple factors. Overall, these results indicate that an increase in colony genetic diversity does not increase worker size polymorphism but might improve colony homeostasis. 相似文献
936.
Allopreening is a widespread but little-studied phenomenon in birds and is particularly prevalent in species where individuals are forced into close proximity. Such a situation facilitates the transfer of ectoparasites between individuals and allopreening has therefore been proposed to serve a hygienic function. In addition, allopreening might theoretically play a role in social communication. Green woodhoopoes (Phoeniculus purpureus) are cooperatively breeding birds that roost communally every night in a tree cavity and are thus susceptible to high ectoparasite loads. Our results suggest that allopreening of the head and neck (“head”), which cannot be efficiently self-preened, serves a primarily hygienic function: all individuals, irrespective of sex, dominance status, and group size, donated and received similar rates of head allopreening and terminated a similar proportion of bouts in which they were involved. Furthermore, there was a high occurrence of reciprocation and head allopreening occurred at a constant rate throughout the year. In contrast, allopreening of the rest of the body, which is accessible to the recipient itself, is likely to serve a primarily social function: body allopreening rates were higher in larger groups; dominant individuals received more body allopreening and terminated a significantly higher proportion of bouts than subordinates; and subordinates donated body allopreening at a higher rate than dominants. Moreover, bouts initiated by dominants were more likely to be reciprocated than those initiated by subordinates and body allopreening rates varied seasonally. Allopreening in the green woodhoopoe is therefore likely to serve a dual function, depending on the part of the body involved. 相似文献
937.
Sperm motility and longevity in the giant cuttlefish, Sepia apama (Mollusca: Cephalopoda) 总被引:1,自引:1,他引:1
The sperm kinetics and fertilisation literature in marine invertebrates is heavily biased toward free-spawning species. Nonetheless,
many species (e.g. cephalopods) transfer and/or fertilise gametes in confined external spaces or internally, creating very
different selective pressures on sperm storage, sperm longevity and hence sperm competition. Here we report the results of
an investigation into the effects of sperm age, water temperature and sperm concentration on sperm motility in the giant cuttlefish
(Sepia apama). Significant positive correlations were found between percent motility and sperm concentration, and between sperm motile
speed and sperm concentration. Mean percent motility of cuttlefish sperm suspension was still 9% eight hours after being released
from the spermatophore and diluted into filtered seawater at 12°C (ambient field temperature during the spawning season).
Sperm resuspended from spermatangia taken from (mated) females in the field were motile for up to 100 hours. When spermatophores
were stored at 4°C motility was still observed in resuspended sperm after two months. Our results show that spermatangia and
spermatophores can retain and release live sperm for long periods. The observed longevity of sperm in S. apama greatly increases the potential for sperm competition in this species. 相似文献
938.
Dispersal in red squirrels (Sciurus vulgaris) is not sex-biased and strict philopatry is rare. The immigration pattern suggests that nearly all animals have to disperse away from the natal site and that dispersal in this species is the outcome of local (intrasexual) competition. If this interpretation is correct, we predict that dispersers and residents, of both sexes, should have equal survival rates and lifetime reproductive success. Body mass, longevity, reproductive success and dominance rank of 34 resident offspring (settling within 400 m of the natal range) and 70 immigrants (dispersers) were compared. Immigrants did not weigh less than residents as adults, nor did they have a higher mortality during the pre-setding period. Survival rate, lifetime reproductive success (females) and the proportion of males obtaining a high dominance rank were similar for residents and dispersers, and no sex effect was found on either of the parameters studied. These results are consistent with the hypothesis that local competition determines whether an individual disperses further away or settles close to its birthplace. 相似文献
939.
José Luis Carballo Enrique Ávila Susana Enríquez Leonardo Camacho 《Marine Biology》2006,148(3):467-478
The mutualistic association between the sponge Haliclona caerulea and the calcareous red macroalga Jania adherens is conspicuous on shallow rocky regions of Mazatlán Bay (eastern tropical Pacific, Mexico). Transplanting experiments were
carried out to examine the morphological responses of the association to an environmental depth gradient. Simultaneously,
we conducted caging experiments to examine the effects of predation (mainly by angelfishes) on association morphology. For
this, we transplanted specimens of the association from a control area at 3 m depth to depths of 1 and 5 m, and measured the
morphological responses in the association (macro- and microstructure) from the three sites before and after 103 days. The
association had the capacity to adjust both macro and micromorphologically, and both external morphology and body structure
changed significantly with depth. The specimens grown at 1 m developed a larger surface area of attachment, higher organic
density and higher inorganic content than the control specimens at 3 m, and the organisms grown at 5 m depth. We also detected
significant differences in the aquiferous system of the sponge, which developed smaller and more numerous oscula at 1 m than
at 5 m depth. These differences seem to be consistent with the wave movement as one of the main regulatory factors of the
morphology of the association. However, the spicules from H. caerulea were most slender in shallow water, which is not consistent with increasing robustness in the face of greater wave force.
The algal skeleton supplied up to 27% of the total inorganic structure of the association; thus, algal contribution significantly
reduces the energy costs of spicule production, specifically under high wave exposure, when H. caerulea requires structural reinforcement relative to organic content. The contribution of the sponge to the association (as ratio
Si to CaCO3) increased significantly from 3 to 5 m (12% in the uncaged specimens and 22% in the caged specimens), showing that the mutualistic
relationship decreases with depth. The production of sponge branches in caged individuals was the most notable difference
from uncaged morphs, which could suggest the effect of predators like angelfishes. However, branches could also be a response
to the reduction in water movement and irradiance inside the cages. Sponges are known to show morphological acclimation in
response to habitat variation, but this is the first study to show it in a sponge living in association with a macroalga. 相似文献
940.
Summary. Passeriformes is the largest order of birds and includes one third of the bird species of the world, living in very diverse
habitats. We investigated the chemistry of preen gland secretions of some groups of passerines from temperate regions found
in diverse microhabitats. Some of the common components were mixtures of homologous monoesters made up of long chain acids
and alcohols. Individual species had characteristic distribution of esters and was unique to a given species, although there
were some individual variations. We compared the composition of acids and alcohols that formed same molecular weight esters
in different species and we found that the combination of acids and alcohols to arrive at same molecular compositions varied
distinctly between species. To compare compositions of over all acids and alcohols that formed the esters, the representative
samples of secretions from the individual species were transesterfied the produce methyl esters and alcohols. We found that
there were distinct differences in number of acids and alcohols that produced the combination of homologous mixtures of esters.
Also they differed both qualitatively and quantitatively. There were also seasonal differences in the secretion components.
Thus though the intact mixtures of esters in individual species had some similarities, they were very complex mixtures and
differed characteristically for individual species. Here we discuss possible causes for evolution of these variations. We
suggest that the evolution in variation of preen gland secretion is probably due to selective pressures caused by ectosymbionts
such as feather-mites and feather-chewing lice that live on feathers and probably feed on the secretions and surrounding environments 相似文献