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51.
52.
Many studies explore the feasibility of co-existence between genetically modified (GM) and conventional (non-GM) crops. An important research topic in these studies is the process of outcrossing, i.e., the process of gene flow via pollen flow from GM to non-GM crops. In this paper, we address a new modelling approach to define the environmentally driven processes of outcrossing for maize from existing empirical datasets. In particular, we use equation discovery methodology that combines background knowledge and empirical data from several studies. We induce models that predict the degree of outcrossing rate between the donor (GM) and the recipient (non-GM) maize field from the distance between the fields and the local wind characteristics (speed, direction and duration). This results in highly accurate models, for which both variables (distance and wind) are essential and of roughly equal importance. 相似文献
53.
Rask M Saxén R Ruuhijärvi J Arvola L Järvinen M Koskelainen U Outola I Vuorinen PJ 《Journal of environmental radioactivity》2012,103(1):41-47
We summarize the patterns of 137Cs activity concentrations and transfer into fish and other biota in four small forest lakes in southern Finland during a twenty-year period following the Chernobyl accident in April 1986. The results from summer 1986 showed fastest accumulation of 137Cs into planktivorous fishes, i.e. along the shortest food chains. Since 1987, the highest annual mean values of 137Cs have been recorded in fish occupying the highest trophic levels, for perch (Perca fluviatilis) 13,600 Bq/kg (ww) and for pike (Esox lucius) 20,700 Bq/kg (ww). At the same time, activity concentrations of 137Cs in crustacean zooplankton and Asellus aquaticus have ranged between 1000 and 19,500 Bq/kg (dw). In 2006, 5-28% of the 1987 137Cs activity concentration levels were still present in perch and pike. Since 1989 their 137Cs activity concentrations in oligohumic seepage lakes have remained significantly higher than in polyhumic drainage lakes due to the increased transfer of 137Cs into fish in the seepage lakes with lower electrolyte concentrations, longer water retention times and lower sedimentation rate. 相似文献
54.
55.
Marko Markov 《The Environmentalist》2011,31(2):114-120
The possible mechanisms of interactions of electromagnetic fields (EMF) with biological systems are often discussed in bioelectromagnetics
in light of thermal versus nonthermal mechanisms. This paper attempts to show the principle difference between the biophysical
and engineering approaches to biological mechanisms of EMF initiated bioeffects. While biophysical approach is based on experimentally
obtained data on biological responses to the applied EMF, the engineering approach strongly relies on specific absorption
rate (SAR) value. With experimental data, comparing effects of low- and high-frequency electromagnetic fields, discussing
modulation of radiofrequency (RF) signals, the author demonstrates the superiority of the nonthermal approach. Biological
windows, resonance mechanism, and various reported biological effects of geomagnetic fields are also in favor of the nonthermal
mechanisms. Finally, one potential nonthermal mechanism involving the role of calmodulin in cellular functions is shown in
this paper. 相似文献
56.
The use of magnetic fields (MFs), in general, and electromagnetic fields (EMFs), in specific, as therapeutic modalities is
becoming very common. In the USA, EMFs are mostly used in orthopedics, followed by pain relief and the wound-healing arena.
Even though a substantial literature exists worldwide, we are still lacking the accepted comprehensive mechanism(s) of action.
In general, it is thought that the best therapeutic effects are achieved when the stimulation is applied directly to the target
area. Since the beginning of this century, however, more and more evidence has been collected indicating that effects of the
MF stimulation may also be observed at site(s) different from the site of application of the signal. A primary purpose of
this paper is to propose a link between the systemic and direct effects. The functional units known as trigger points are
discussed as possible “doors” allowing the stimulation to be delivered to the target tissue/organ. A second purpose is to
suggest some possible modes of action. 相似文献
57.
Bioluminescent yeast assays for detecting estrogenic and androgenic activity in different matrices 总被引:1,自引:0,他引:1
In this paper we describe the construction and use of a set of bioluminescent yeast strains for the detection of compounds that can affect androgen or estrogen receptor mediated hormonal signalling. The set includes Saccharomyces cerevisiae strains expressing human androgen receptor (AR), estrogen receptor alpha (ERalpha) or estrogen receptor beta (ERbeta), along with firefly luciferase controlled by a respective hormone responsive promoter. A constitutively luminescent strain was included in the set for determining the cytotoxicity of the sample. Yeast cells were incubated with pure chemicals or complex samples for 2.5 h, after which the signal could be detected from the cell-sample mixture after simply adding the D-luciferin substrate. The assays could be completed in one day and they required no cell lysis or centrifugation steps, which makes them suitable for high-throughput analysis of samples. Due to a short incubation time the assays are directly applicable to different sample matrices, requiring no pretreatment of the samples. The assays were used to assess the hormonal activity in moisturizing lotions as an example of a complex sample matrix known to contain endocrine disrupting chemicals. Six out of eight tested moisturisers showed high estrogenic activity, whereas no androgenic activity was observed in the samples. 相似文献
58.
Impact of aquacultures on the marine ecosystem: Modelling benthic carbon loading over variable depth
In order to be used within Environmental Impact Assessment study, we have developed a three-dimensional particle tracking model for prediction of benthic carbon loading (BCL) caused by fish farms. The model is based on stochastic differential equations for particle transport consistent with the well-known semi-empirical advection/diffusion equation. It requires only easily obtainable input data in the form of measured current record, the source location and a specification of local bathymetry. The model accounts for advection by long-term residual and tidal currents, turbulent diffusion, realistic bathymetry and variations in daily (monthly or yearly) emissions from fish farm.Here, we concentrate on the changes in sedimentation pattern caused by various bathymetric shapes. Examination of idealized cases reveals where and why we can expect the worst impact on benthic communities. For future reference, these results will be included into guidelines for fish farming. 相似文献
59.
Marko Hyttinen Marika Masalin-Weijo Pentti Kalliokoski Pertti Pasanen 《Atmospheric environment (Oxford, England : 1994)》2010,44(38):5028-5033
Heat-treated wood is an increasingly popular decoration material. Heat-treatment improves dimensional stability of the wood and also prevents rot fungus growth. Although production of heat-treated wood has been rapidly increasing, there is only little information about the VOC emissions of heat-treated wood and its possible influences on indoor air quality. In the present study, VOC emissions from three untreated (air-dried) and heat-treated wood species were compared during a four weeks test period. It appeared that different wood species had clearly different VOC emission profiles. Heat-treatment was found to decrease VOC emissions significantly and change their composition. Especially, emissions of terpenes decreased from softwood samples and aldehydes from European aspen samples. Emissions of total aldehydes and organic acids were at the same level or slightly higher from heat treated than air-dried softwood samples. In agreement with another recent study, the emissions of furfural were found to increase and those of hexanal to decrease from all the wood species investigated. In contrast to air-dried wood samples, emissions of VOCs were almost in steady state from heat treated wood samples even in the beginning of the test. 相似文献
60.
Sanna Syri Matti Johansson Juha Grönroos Marko Ekqvist 《Environmental Modeling and Assessment》1999,4(2-3):103-113
An integrated model system was developed and used to assess the effects of alternative energy production scenarios and reduction policies on acidification of lakes and forest soils in Finland. The analysis covered different energy scenarios and resulting emissions of sulfur oxides and nitrogen oxides in Finland, as well as ammonia emissions with various control requirements. In addition, emission reduction scenarios of varied ambition levels in the bordering areas of Finland and in other parts of Europe were included in the analysis. The impacts of the different scenarios were quantified with exceedances of critical loads for acidification and with the total areas where the critical loads are exceeded. The possibilities for reducing the areas with critical load exceedances with national or bilateral measures were investigated. The differences in areas at risk, if depositions from domestic and nearby sources are estimated with a regional model and point-source databases or with a continental scale model and coarser-scale emission data, were analyzed. The reasons for the differences and the implications for national-level assessment are discussed. 相似文献