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121.
Kost C Lakatos T Böttcher I Arendholz WR Redenbach M Wirth R 《Die Naturwissenschaften》2007,94(10):821-828
Fungus-growing ants and their fungal cultivar form a highly evolved mutualism that is negatively affected by the specialized
parasitic fungus Escovopsis. Filamentous Pseudonocardia bacteria occurring on the cuticle of attine ants have been proposed to form a mutualistic interaction with these ants in
which they are vertically transmitted (i.e. from parent to offspring colonies). Given a strictly vertical transmission of
Pseudonocardia, the evolutionary theory predicts a reduced genetic variability of symbionts among ant lineages. The aim of this study was
to verify whether actinomycetes, which occur on Acromyrmex octospinosus leaf-cutting ants, meet this expectation by comparing their genotypic variability with restriction fragment length polymorphisms.
Multiple actinomycete strains could be isolated from both individual ant workers and colonies (one to seven strains per colony).
The colony specificity of actinomycete communities was high: Only 15% of all strains were isolated from more than one colony,
and just 5% were present in both populations investigated. Partial sequencing of 16S ribosomal deoxyribonucleic acid of two
of the isolated strains assigned both of them to the genus Streptomyces. Actinomycetes could also be isolated from workers of the two non-attine ant species Myrmica rugulosa and Lasius flavus. Sixty-two percent of the strains derived from attine ants and 80% of the strains isolated from non-attine ants inhibited
the growth of Escovopsis. Our data suggest that the association between attine ants and their actinomycete symbionts is less specific then previously
thought. Soil-dwelling actinomycetes may have been dynamically recruited from the environment (horizontal transmission), probably
reflecting an adaptation to a diverse community of microbial pathogens. 相似文献
122.
123.
The complexity of the present data-centric world finds its expression in the increasing number of multi-indicator systems.
This has led to the development of multicriteria ranking systems based on partial orders. Order theory is a main pillar of
structural mathematics. Partial orders help to reveal why an object of interest holds a certain ranking position and how much
it is subject to change if a composite indicator is upgraded. Order theory helps to derive linear or weak orders without indicator
weighting schemes. Hence, rankings obtained from decision support systems (DSS) which depend on many parameters beyond the
data matrix can be checked and discrepancies can lead to examine the parameters of the DSS. Order theory helps discover association
and implication structures derived from formal concept lattices. Association and implication networks among the attributes
of the data matrix allow more insights into multi-indicator systems and lead to new hypotheses and motivate further research.
Some new and innovative concepts, like separated subsets, antagonistic indicators, ranking stability fields are rendered.
Separated subsets are the typical outcome of a partial order analysis; their identification leads to antagonistic indicators,
which are responsible for the separatedness of object’s subsets. Numerical aggregation can be performed step-by-step and the
question which values of a weight lead to an order inversion is of high interest. The concept of stability fields is one possible
answer, discussed in this paper. After an outline of partial order theory some more specific theoretical results are shown,
then we discuss the role of composite indicators in the light of partial order and give some examples of interesting applications
of partial order. Finally examples are selected from real life case studies of watersheds, environmental performance evaluations,
child well being, geographic and administrative regions and more. 相似文献
124.
Chlorovinylannes (Lewisites) were produced and handled during WW I and WW II as chemical warfare agents. Residues of these
cwa and their metabolites are still present today and continue to contaminate soil and water.
A gas Chromatographic method for the detection and determination of chlorovinylarsines (Lewisites) and their metabolites is
shown. Lewisite II and Lewisite III, but not Lewisite I and the metabolites of Lewisite I and Lewisite II can be detected
and determined using GC/ECD. After derivatization with thiols, the sum of Lewisite I or Lewisite II and their metabolites
are detected. With the proper selection of the thiol, matrix interferences can be eliminated because of the different retention
times of the derivatives. 相似文献
125.
Manuela Baumgarten Christian Huber Patrick Büker Hans-Peter Dietrich Christian Heerdt Rainer Matyssek 《Environmental pollution (Barking, Essex : 1987)》2009,157(7):2091-2107
Exposure and flux-based indices of O3 risk were compared, at 19 forest locations across Bavaria in southern Germany from 2002 to 2005; leaf symptoms on mature beech trees found at these locations were also examined for O3 injury. O3 flux modelling was performed using continuously recorded O3 concentrations in combination with meteorological and soil moisture data collected from Level II forest sites. O3 measurements at nearby rural open-field sites proved appropriate as surrogates in cases where O3 data were lacking at forest sites (with altitude-dependent average differences of about 10% between O3 concentrations). Operational thresholds of biomass loss for both O3 indices were exceeded at the majority of the forest locations, suggesting similar risk under long-term average climate conditions. However, exposure-based indices estimated higher O3 risk during dry years as compared to the flux-based approach. In comparison, minor O3-like leaf injury symptoms were detected only at a few of the forest sites investigated. Relationships between flux-based risk thresholds and tree response need to be established for mature forest stands for validation of predicted growth reductions under the prevailing O3 regimes. 相似文献
126.
With special filter materials it is possible to eliminate the heavy metals lead, copper and nickel and arsenic from water by sorption resp. chemical bounding. After a reaction time of 24 hours the reduction rates were between 97% and >99,9%. 相似文献
127.
128.
129.
The complexity of ecosystems urges that the evaluation process should avoid an aggregation of information. The reason is that although mathematical modelling has made enormous progress (object oriented programming) there is still no ecologically reasonable function of quality. The technique to compare chemicals for example, even if they are characterized by many properties, is based on the generalization of the concept of order and the method of visualization by the using Hasse diagrams. By the example of six chemicals the procedure will be explained and it will be shown that a high hazard potential of chemicals is related to different properties, which cause different ecotoxicological consequences. 相似文献
130.
2-Chlorovinylarsine dichloride (Lewisite I) react by room temperature quickly with alcohols in an equilibrium reaction to yield 2-Chlorovinylarsine chloride ether and 2-Chlorovinylarsine bisether. The reactions are not quantitative. The ethyl- and propylether are not stable. The ether were identified with mass spectrometry. 相似文献