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排序方式: 共有537条查询结果,搜索用时 31 毫秒
1.
Christian Alvarez Glaucia Gon?alves Barbosa Raquel de Vasconcellos Carvalhaes de Oliveira Bernardina Penarrieta Morales Bodo Wanke Márcia dos Santos Lazéra 《Memórias do Instituto Oswaldo Cruz》2013,108(1):126-129
In this study, we evaluated several techniques for the detection of the yeast form of Cryptococcus in decaying wood and measured the viability of these fungi in environmental samples stored in the laboratory. Samples were collected from a tree known to be positive for Cryptococcus and were each inoculated on 10 Niger seed agar (NSA) plates. The conventional technique (CT) yielded a greater number of positive samples and indicated a higher fungal density [in colony forming units per gram of wood (CFU.g-1) ] compared to the humid swab technique (ST). However, the difference in positive and false negative results between the CT-ST was not significant. The threshold of detection for the CT was 0.05.103 CFU.g-1, while the threshold for the ST was greater than 0.1.103 CFU-1. No colonies were recovered using the dry swab technique. We also determined the viability of Cryptococcus in wood samples stored for 45 days at 25ºC using the CT and ST and found that samples not only continued to yield a positive response, but also exhibited an increase in CFU.g-1, suggesting that Cryptococcus is able to grow in stored environmental samples. The ST.1, in which samples collected with swabs were immediately plated on NSA medium, was more efficient and less laborious than either the CT or ST and required approximately 10 min to perform; however, additional studies are needed to validate this technique. 相似文献
2.
An Extreme Value Analysis of Pollutant Concentrations in Surface Soils Due to Atmospheric Deposition
Risk assessments often rely on deterministic models using long-term averages or “steady-state” values of input variables. Such models do not provide the information needed to estimate acute exposures. This study uses extreme value theory to examine the frequency and magnitude of daily pollutant concentrations in surface soils predicted at six U.S. locations. Concentrations are predicted using a deposition-leaching model and 50 years of historical precipitation data. A stochastic model also is used to generate 1000 years of precipitation data as modeling inputs for each location. The annual maximum concentrations at each site are fitted to a Gumbel type I distribution to estimate occurrence probability. For soluble pollutants, the predicted concentration varied substantially with precipitation, and the maximum daily concentrations exceeded annual averages by 4 to 8 times. Observed and synthetic precipitation data produced similar results at most study locations, though the synthetic data provided a slightly better fit to the Gumbel type I distribution. The precipitation model allows the generation of representative precipitation data that extend limited historical records. The extreme value analysis facilitates the evaluation of maximum pollutant concentrations, return periods, and other statistics that are important in evaluating acute exposures. 相似文献
3.
Surface sediment diatoms from the east coast of Lake Tanganyika were analysed using ordination and classification techniques, and compared with assemblages previously described from the northern part of the lake. Grain-size analyses were performed on subsamples. Four groups of diatom assemblages were recognised. The first group clusters samples taken in the north, far from the Rusizi river mouth. The second group comprises samples taken on silty sediment along the Tanzanian coast, including one sample taken near the mouth of the Malagarazi river and those from the northernmost part of the lake. The third group comprises surface sediments along the Burundian coast (near Ramba and Magara), and the fourth is characterised by epipsammic taxa. A sample taken near the central arm of the Malagarazi river is included in the latter group. The impact of small rivers on the diatom assemblages in the surface sediments is restricted to the mouth area. 相似文献
4.
This paper reviews the various factors, coefficients and indexes developed to evaluate terrestrial plant performance in respect to phytoremediation.A brief list of indexes includes the Accumulation factor, Bioabsorption coefficient, Bioaccumulation coefficient, Bioaccumulation factor, Bioconcentration, Bioconcentration coefficient, Bioconcentration factor, Biological absorption coefficient, Biological accumulation coefficient, Biological concentration factor, Biological transfer coefficient, Concentration factor, Enrichment coefficient, Enrichment factor, Extraction coefficient, Index of bioaccumulation, Mobility index, Shoot accumulation factor, Soil host transfer factor, Soil-plant transfer coefficient, Soil-plant transfer factor, Transfer factor and Translocation factor.These indexes represent the result of a ratio calculation between element concentrations in plant parts to that of substrata. In other cases indexes arise from the ratio calculation of element concentrations in two distinct plant parts.In the literature different terms have been attributed to the same ratio and this often represents an overlap in terminology. On the other hand the same term corresponds to several different ratios and this could create confusion and misinterpretation in data comparison.Furthermore, the evaluation of hyperaccumulation, phytostabilization or phytoextraction of plant species is not always performed in the same way. Different plant parts are considered as well as different extraction procedures for both plant and substrata element assessment. As a consequence, a direct comparison between obtained data is not always reliable and possible.In this paper the various available indexes are reviewed, highlighting both the similarity and differences between them with the aim of helping the community in choosing the appropriate term for both data evaluation and comparison. In this author’s opinion there is no need of new terms to define indexes. I would stress the need for conformity to the original definitions and criteria. 相似文献
5.
A rapid altitudinal range expansion in the pine processionary moth produced by the 2003 climatic anomaly 总被引:2,自引:0,他引:2
ANDREA BATTISTI MICHAEL STASTNY† EMILIANO BUFFO STIG LARSSON‡ 《Global Change Biology》2006,12(4):662-671
Climatic anomalies may produce, or accelerate, geographic range expansions of species limited by temperature or other climatic variables. Most such expansions are only temporary, before the prevailing climatic conditions drive the founder populations extinct. In contrast, here, we report a recent rapid shift of the range limit during the record hot summer of 2003 in southern Europe that has the potential to be both permanent, and to have important implications on species range dynamics in general. The winter pine processionary moth (Thaumetopoea pityocampa), an important pine defoliator whose larvae feed in colonies during the winter, is limited in its distribution by winter temperatures. In the last three decades, warmer winters have led to a gradual but substantial expansion of its range both latitudinally and altitudinally. In the summer of 2003, T. pityocampa underwent an extraordinary expansion to high elevation pine stands in the Italian Alps; its altitudinal range limit increased by one third of the total altitudinal expansion over the previous three decades. In an experiment, we found flight activity of newly emerged females to increase with temperature. By determining a threshold temperature for flight take‐offs under controlled conditions, we calculated that the nights above the threshold temperature were over five times more frequent, and considerably warmer, at the range limit in 2003 than in an average year. We therefore attribute the colonization of extreme, high‐elevation sites to increased nocturnal dispersal of females during the unusually warm night temperatures in June – August 2003. Importantly, the colonies established at extreme sites survived the winter and produced offspring in 2004, although the range did not expand further because of low night temperatures that year. We discuss several life‐history characteristics of T. pityocampa that maximize the likelihood of population persistence at the new range limit. As global warming continues and climatic anomalies are predicted to become more frequent, our results draw attention to the importance of extreme climatic events in the range formation of phytophagous insects. 相似文献
6.
7.
Fisher information for a multivariate extreme value distribution 总被引:7,自引:0,他引:7
Explicit algebraic formulae for the Fisher information matrixof the multivariate extreme value distribution with generalisedextreme value margins and logistic dependence structure aregiven. 相似文献
8.
Artificial reef systems play an important role in the increase of natural production of biological marine resources and they have been deployed worldwide. In Portugal, seven artificial systems have been deployed along the southern coast of the Algarve. Research to date has focussed mainly on fish populations, particularly those of economical importance. The present work aims to study the macrobenthic communities of the artificial reef structures, as these will enhance the food resources and shelter, making the reefs more attractive to fish. In particular, we experimentally analysed the sequence of colonisation of macrobenthic communities of the Ancão artificial reef system, which was deployed in the summer of 2002. The study of the colonisation of benthic communities was done using samples of concrete cubic units (15 × 15 cm) that were suspended at the reef modules at a depth of 20 m, at the time of the reef immersion. Four replicate samples were collected by SCUBA diving from two groups of the Ancão reef every three months from the starting date. Sampling was done using essentially non-destructive methods to assess the percentage cover of macrobenthic organisms in both vertical and horizontal surfaces. The percentage cover of the taxonomic groups was compared within the different surfaces of the samples and between the two reef groups. The bottom surface of cubic samples had a significantly higher colonisation related to the dominance of barnacle cover, probably due to lower sedimentation levels. Samples from both reef groups showed a similar pattern of colonisation. Barnacles, bryozoans and serpulids dominated the samples three months immediately after the beginning of the experiment. Other invertebrates groups, such as Porifera, Hydrozoa, Anthozoa, other sessile Polychaeta, Decapoda, Gastropoda and Bivalvia, were more abundant after six months of colonisation. 相似文献
9.
10.
Adverse conditions in the acid mine drainage (AMD) system at the Green Valley mine, Indiana, limit diatom diversity to one species, Nitzschia tubicola. It is present in three distinct microbial consortia: Euglena mutabilis-dominated biofilm, diatomdominated biofilm, and diatom-exclusive biofilm. E. mutabilis dominates the most extensive biofilm, with lesser numbers of N. tubicola, other eukaryotes, and bacteria. Diatom-dominated biofilm occurs as isolated patches containing N. tubicola with minor fungal hyphae, filamentous algae, E. mutabilis, and bacteria. Diatom-exclusive biofilm is rare, composed entirely of N. tubicola. Diatom distribution is influenced by seasonal and intraseasonal changes in water temperature and chemistry. Diatoms are absent in winter due to cool water temperatures. In summer, isolated patchy communities are present due to warmer water temperatures. In 2001, the diatom community expanded its distribution following a major rainfall that temporarily diluted the effluent, creating hospitable conditions for diatom growth. After several weeks when effluent returned to preexisting conditions, the diatom biofilm retreated to isolated patches, and E. mutabilis biofilm flourished. Iron-rich stromatolites underlie the biofilms and consist of distinct laminae, recording spatial and temporal oscillations in physicochemical conditions and microbial activity. The stromatolites are composed of thin, wavy laminae with partially decayed E. mutabilis biofilm, representing microbial activity and iron precipitation under normal AMD conditions. Alternating with the wavy layers are thicker, porous, spongelike laminae composed of iron precipitated on and incorporated into radiating colonies of diatoms. These layers indicate episodic changes in water chemistry, allowing diatoms to temporarily dominate the system. 相似文献