首页 | 本学科首页   官方微博 | 高级检索  
相似文献
 共查询到20条相似文献,搜索用时 15 毫秒
1.
An energy-dispersive X-ray fluorescence spectrometer has been developed that provides in situ analyses for thirty elements in the 5 to 50 ppm range (dry weight) in sediments at water depths to 100 m. The analyzer consists of a radionuclide excitation source, 109Cd, and a solid cryogen-cooled Si(Li) detector with a 0.2-mm beryllium window. The spectrometer has been designed to analyze elements in sediment surfaces as well as a function of sediment depth. The spectrometer has been utilized on a minisubmersible and from a surface vessel. This instrument was applied to several environmental studies. The in situ spectrometer is compared with a laboratory X-ray fluorescence spectrometer.  相似文献   

2.
Alternaria alternata spores are considered a well-known biological contaminant and a very common potent aeroallergen source that is found in environmental samples. The most intense exposure to A. alternata allergens is likely to occur outdoors; however, Alternaria and other allergenic fungi can colonize in indoor environments and thereby increase the fungal aeroallergen exposure levels. A consequence of human exposure to fungal aeroallergens, sensitization to A. alternata, has been unequivocally associated with increased asthma severity. Among allergenic proteins described in this fungal specie, the major allergen, Alt a 1, has been reported as the main elicitor of airborne allergies in patients affected by a mold allergy and considered a marker of primary sensitization to A. alternata. Moreover, A. alternata sensitization seems to be a triggering factor in the development of poly-sensitization, most likely because of the capability of A. alternata to produce, in addition to Alt a 1, a broad and complex array of cross-reactive allergens that present homologs in several other allergenic sources. The study and understanding of A. alternata allergen information may be the key to explaining why sensitization to A. alternata is a risk factor for asthma and also why the severity of asthma is associated to this mold. Compared to other common environmental allergenic sources, such as pollens and dust mites, fungi are reported to be neglected and underestimated. The rise of the A. alternata allergy has enabled more research into the role of this fungal specie and its allergenic components in the induction of IgE-mediated respiratory diseases. Indeed, recent research on the identification and characterization of A. alternata allergens has allowed for the consideration of new perspectives in the categorization of allergenic molds, assessment of exposure and diagnosis of fungi-induced allergies.  相似文献   

3.
Social participation has been broadly analysed by comparing case studies of different types of socio-economic developments in Brazil and the United Kingdom (UK). A key objective has been to consider how effective social participation has been in incorporating society’s points of view in the decision making process. In most cases, it would appear that very little can be done by stakeholders to change big decisions on development policies that support public and private development because in reality social participation often only provides an opportunity for discussion and agreement on specific issues regarding how development will be undertaken and how stakeholders will be affected. Although Brazil and the United Kingdom have socio-economic and cultural differences, it is necessary to emphasize that education, self-organization and knowledge of civil rights are crucial for an effective social participation process. As climate change is an important topic for present and future generations and that some of the development activities analysed in this study will emit greenhouse gases, this study also attempts to investigate if climate change mitigation strategies have been integrated into the social participation process. Investigation shows that there is little evidence that climate change mitigation actions involving stakeholders have been integrated into development strategies or have been part of social participation schemes in the case studies analysed. Having said that, the study also describes positive examples of climate change mitigation actions in different parts of the world that involve local people in ‘carbon-neutral’ or ‘social-carbon’ projects and proposes the creation of a carbon-neutral committee that would be responsible for coordinating climate change mitigation measures within development proposals such as the ones analysed in this study.  相似文献   

4.
It is widely accepted that tobacco smoke is responsible for the vast majority of lung cancers worldwide. There are many known and suspected carcinogens present in cigarette smoke, including α-emitting radioisotopes. Epidemiologic studies have shown that increased lung cancer risk is associated with exposure to ionizing radiation, and it is estimated that the majority of smoking-induced lung cancers may be at least partly attributable to the inhaled and deposited radiation dose from radioisotopes in the cigarette smoke itself. Recent research shows that silencing of the tumor suppressor gene p16INK4a (p16) by promoter methylation plays a role in smoking-related lung cancer. Inactivation of p16 has also been associated with lung cancer incidence in radiation-exposed workers, suggesting that radionuclides in cigarette smoke may be acting with other compounds to cause smoking-induced lung cancer. We evaluated the mechanism of ionizing radiation as an accepted cause of lung cancer in terms of its dose from tobacco smoke and silencing of p16. Because both radiation and cigarette smoking are associated with inactivation of p16, and p16 inactivation has been shown to play a major role in carcinogenesis, ionizing radiation from cigarette smoke likely plays a role in lung cancer risk. How large a role it plays, relative to chemical carcinogens and other modes of action, remains to be elucidated.  相似文献   

5.
Geometric morphometrics has been used to reveal coupled geographic variation in the mandible shape in two sympatric rodent species, the pygmy wood mouse (Sylvaemus uralensis Pall.) and bank vole (Myodes glareolus Pall.), in the Southern Urals. It has been shown that syntopic samples synchronously collected from the local communities of these species usually display similar, parallel, and unidirectional morphological changes as demonstrated by comparison of species pairs from different localities. The degree of concordance in geographic variation of the species makes it possible to estimate their coevolutionary potential within local communities: the wider the range of ecological conditions under which parallel variation of sympatric species is observed, the higher is their coevolutionary potential.  相似文献   

6.
Lantana camara. L (hereafter Lantana) was first introduced by the British into India in 1807 as an ornamental plant. Since then the species has spread across the length and breadth of the country. Attempts to control Lantana in India have not been successful. In this study, we analysed the use of Lantana by local communities in southern India and identified the possible causes and consequences of its use through the use of a household survey of the socio-economic profile of the user and nonuser households and an analysis of the ecological history of the communities. Communities have been using Lantana for over 25–30 years and apparently such use was not prompted by external agencies. The characteristics of user and nonuser households were similar, except that Lantana users were more literate and had a greater number of occupations per household than nonusers. Per capita income was similar between user and nonuser groups. For nonuser groups, their main income sources were from trading (44 %), wage labour (32 %) and forest resources (23 %). In contrast, the Lantana user groups substituted their loss of income from forest resources (7 %) by income from Lantana (46 %). The ecological history revealed that Lantana was adopted as a resource at a time when it was increasing in the landscape and traditional bamboo resources were in decline because of overuse by commercial enterprises and mast flowering. This change in ecological resource availability prompted a major shift in livelihoods for some in the area.  相似文献   

7.
The effects of two exogenous factors, ground fires and industrial air pollution, on natural regeneration of Scots pine (Pinus sylvestris L.) cenopopulations have been studied in the Transural region. It has been found that an increased level of air pollution leads to a decrease in the abundance and occurrence frequency of pine undergrowth; as the intensity of ground fire increases, these parameters of the postfire generation of undergrowth increase as well, especially in background areas. As shown by two-way ANOVA, either of these factors and their interaction have a significant effect on the density of pine undergrowth, with this effect being stronger in the case of ground fires.  相似文献   

8.
9.
The dynamics of vegetation have been studied in forest-steppe pine (Pinus symvestris L.) forests affected by anthropogenic factors such as felling and fires. Gradient analysis has been used to reveal specific ecological features of plant communities and trace the main directions of succession. The results show that these forests are at different stages of progressive succession, with the development of theircommunities following similar trends over the past few decades.  相似文献   

10.
Individual, intra- and interpopulation, ecological, and geographic variation has been studied in G. conopsea populations on limestones of the Timan Range. The results show that the response of plants to deterioration of growing conditions manifests itself in a decrease in the values of individual morphometric characters and the strength of correlations between them. In the northeast of European Russia, this species is represented by two forms, G. conopsea (L.) R.Br. s. str. and G. conopsea var. alpina Rchb. f. ex Beck (?), with the latter being regarded as an extreme form of its ecological variation.  相似文献   

11.
Seasonal dynamics of heart rate variability in individuals of late summer and autumn generations have been studied in three rodent species kept in a vivarium: the striped field mouse (Apodemus agrarius), bank vole (Clethrionomys glareolus), and northern red-backed vole (Cl. rutilus). It has been shown that the cardiac function of the rodents in autumn and winter is mainly controlled by autonomic mechanisms: the heart rate is slow, cardiovascular control systems are relaxed. During the winter-spring transition, the role of central cardiovascular circuits increases because of the necessity to activate all body systems by spring.  相似文献   

12.
13.
A possibility of introducing alien cladoceran species into the pelagial zone of mesotrophic Lake Glubokoe has been estimated. For this purpose, observations have been performed on the cohorts of alien species (Daphnia magna and Simocephalus exspinosus) and aboriginal species (Daphnia hyalina and Diaphanosoma brachyurum). The results show that competition is a factor preventing the introduction of weak competitors, such as D. magna, but admitting stronger competitors, e.g., S. exspinosus. Competition in the lake may influence not only the species structure of the zooplanktonic community, but also its vertical distribution.  相似文献   

14.
The floristic composition of plant communities dominated by Carex acuta in the northern Volga-Akhtuba floodplain has been analyzed over the period from 1928 to 2009. It has been shown that, in 2008 to 2009, some hygrophytes disappeared from these phytocenoses; simultaneously, their composition was enriched with mesophytes and adventive species. Ramenskii??s ecological scales have indicated a decrease in water supply to habitats of the communities studied.  相似文献   

15.
Multivariate analysis of variation in the metric characters in the ground beetle C. granulatus has been performed. It has been shown that the beetle body size increases toward the center of its range, urbanization has a positive effect on all metric traits, but the effect of habitat vegetation has no definite trend. The structure of variation in the metric characters estimated by the principal components method depends on all ecological factors considered: the locality in the geographic range, level of anthropogenic influence, and degree of biotope openness.  相似文献   

16.
Specific ecogenetic features of plants and parameters of seed progeny have been studied in Melandrium album cenopopulations from test plots established along the radioactive contamination gradient in the zone of the Eastern Ural Radioactive Trace (EURT), where absorbed radiation doses in buffer and impact plots exceeded the background level by factors of 2–18 and 330–418, respectively. It has been shown that interannual variation in parameters characterizing the viability of seed progeny largely depends on fluctuations of weather conditions. This dependence is more distinct in cenopopulations from the EURT than in control samples, which is indicative of interaction between radiation and other relevant ecological factors. The radioresistance of seed progeny is contingent on its viability, being independent of radiation load at the sites of maternal plant growth. Hermaphrodite plants occur only in irradiated M. album cenopopulations. This character is inherited: all F 1 descendants of such plants grown in a vegetation experiment had hermaphrodite flowers. The mutability of seed progeny formed in the EURT zone exceeds the background level. The occurrence and frequencies of recorded anomalies has proved to vary by years and, therefore, can be interpreted as nonheritable modifications.  相似文献   

17.
Data on the parasite fauna of the least cisco, Coregonus sardinella Valenciennes, 1848 in Ural tributaries of the Ob downstream of the city of Salekhard have been obtained for the first time. The formation patterns of the parasite fauna in this species and the rate (prevalence and intensity) of infection by Ichthyocotylurus erraticus (Odening, 1969), a parasite specific to coregonids, have been revealed. Infection of the least cisco with six parasite species (out of the 12 species found) occurs as the fish feed on zooplankton and benthic organisms. The dominant parasites are trematode larvae of the genera Ichthyocotylurus and, in some years, Diplostomum; this composition of dominants is evidence that the least cisco fattens up mainly in shallow areas. All sexually mature fish of this species were found to be infected by I. erraticus, but the average intensity of infection was rather low: the abundance index of the parasite did not exceed 40 ind. per fish. Analysis of the distribution of I. erraticus metacercariae in the least cisco shows that the relationship in the host-parasite system is stable and the parasite has no pathogenic effect on individuals of older age classes.  相似文献   

18.
Several studies have revealed that the presence of heterogeneity amongst the user groups of common property natural resources considerably affects the effectiveness of resource management and their sustainable use. Primary research conducted in six sample villages from three districts of the Indian state Odisha has found that heterogeneity in economic and social dimensions amongst the members of the management committee acts as major determinants in respect of common property forest resource management. The findings of this piece of work reveal that common property forests are best managed in the villages where the management committee is homogeneous by both social and economic considerations; better managed where the committee members are economically homogeneous but socially heterogeneous; and least managed where the members are socially homogeneous but economically heterogeneous. The same result has been obtained from the composite index developed for the user group’s assessment about the functioning of the forest management institutions in the three study districts of the state Odisha.  相似文献   

19.
A comparative analysis of spatial population structure in the northern red-backed vole (Clethrionomys rutilus Pall.) and large-toothed red-backed vole (Cl. rufocanus Sund.) has been performed in the middle taiga zone of the Middle Irtysh region (Omsk oblast). Populations of these species are represented by sets of territorial groups whose numbers and spatial distribution change from year to year depending on the ratio of these species in a biotope and their population density. There is no significant interspecific competition between cohabitant Cl. rutilus and Cl. rufocanus. In particular, this follows from the fact that the population density and distribution pattern of one species are independent of those of the other species. It has been found that the size of home ranges in Cl. rutilus inversely depends on its population density, with that in Cl. rufocanus remaining approximately the same at different population densities, and that the structure of the resident part of the population in both species changes during the season, as voles from neighboring habitats or dispersing voles settle in the study area.  相似文献   

20.
The distribution of nine chloroplast DNA haplotypes in four insular North-Atlantic and four European coastal Atlantic populations of Calluna vulgaris in the glacial zone of the range has been analyzed in comparison with that in six marginal southern populations in the nonglacial zone of the Atlantic and Mediterranean regions. As a result, two hypothetical Pleistocene refugia (HPRs) for this C. vulgaris population group have been revealed, one in the Cévennes mountain range and the other in the Southern Alps (Trento). Judging from the 1–FST value, it has been found that the group of populations in the glacial Atlantic zone and adjacent European coastal Atlantic region is genetically similar to the HPR in the Cévennes at a highly significant level (p ≥ 0.999) and less similar to the HPR in Trento; however, it differs significantly from other Mediterranean and Atlantic populations. It has been concluded that the most probable hypothetical Pleistocene refugium for the recent C. vulgaris populations of the northeastern Atlantic and European coastal Atlantic regions was in the west of the Mediterranean, in the Cévennes, while the additional refugium was in the Southern Alps. Possible directions of the postglacial dispersal and recolonization of habitats by C. vulgaris populations from the western Mediterranean to the northeast of the Atlantic and to Scandinavia have been revealed.  相似文献   

设为首页 | 免责声明 | 关于勤云 | 加入收藏

Copyright©北京勤云科技发展有限公司  京ICP备09084417号