Mathematical modelling of pulsed magnetic field action on neurons’ bioelectric activity

Hodgkin–Huxley model, describing generation of action potentials in axons’ membranes, has been used for appreciation of the possible mechanisms of electromagnetic fields influence on neurons’ electrical activity. It follows from the carried calculations that flowing through an axon of the external current pulses, which have an area of rise, an area of DC, and an area of drop, does not influence own excitation pulses passage if periods of rise and drop are slope enough. Depending on the external current parameters, own excitation pulses may not be influenced or may be suppressed at greater velocity of rise and drop of an external current. Moreover, induced excitation pulses appear at definite parameters of an external current. In the case, when at passage through an axon of an external current, own excitation pulses follow one by one (paired pulse facilitation), and the second pulse may be suppressed if its level will not be increased additionally in comparison with the case of an external current absence. It is possible that such increase happens “automatically” as a result of “tuning” (adaptation) of axons to the conditions of flowing through them of an external current. It may be an explanation of the phenomena observed in experiments.     

AN ANTIDEGRADATION POLICY FOR PRESERVING SURFACE WATER QUALITY IN FLORIDA1

ABSTRACT: As part of its overall system for protecting aquatic systems from unnecessary degradation, the State of Florida provides special protection for water bodies of unusual importance. Such water bodies are designated as “Outstanding Florida Waters” (OFW5). New discharges to OFWs are possible only if certain stringent criteria are met. A new point source direct discharge to an OFW is usually not allowed if it would cause any lowering of ambient water quality. A new indirect discharge (upstream from an OFW boundary) may be allowed only if it would not significantly degrade the OFW. To date, the advantages of the OFW system have clearly outweighed the disadvantages, and OFW designations are helping to protect Florida's most valuable waters from additional degradation. Florida's system could be a useful model for other jurisdictions wanting to provide special protection to special water bodies.     

A Sensitivity Analysis of Ozone Formation to Ambient Air Composition by Means of Photochemical Models

The prediction of the atmospheric concentration of ozoneand of other photochemical pollutants represents one of themajor scientific challenges in the study of urban airquality. To this aim, photochemical models are widelyapplied as support tools for regulatory purposes, but theirresults are known to be affected by several uncertainties,in boundary conditions, geographical and meteorologicaldata and the chemical composition of emission and ambientair as well. Also the mechanism selected to describe theurban chemistry may lead to large differences in the modelresults. In this work, the influence of ambient air composition onthe results of photochemical model has been studied using a simple Lagrangian trajectory model coupled with different chemical sub-models (CB-IV and a simplified version of EMEP). To this aim a parametric sensitivity study of ozone with respect to its precursors' concentration was performed withreference to the same meteorological conditions and by simulatingdifferent scenarios characterized by specific emitted pollutantsconcentration. Rather than analyzing sensitivity by changing initial composition, an analytical local sensitivity concept has been applied; this allowed evaluation the influence of initial concentration on the predicted ozone concentration andto discriminate between VOC-sensitive and NOx-sensitive kineticregimes. Finally, these results have been successfully comparedwith those obtained applying the concept of photochemical indicators (i.e. O₃/NOy and H₂O₂/HNO₃ ratios).     

Oxidative stress in duckweed (Lemna minor L.) caused by short-term cadmium exposure

The mechanisms of plant defence against cadmium toxicity have been studied by short-term exposure of Lemna minor L. (common duckweed) to concentrations of CdCl2 ranging from 0 to 500microM. High accumulation of cadmium was observed (12,320+/-2155microgg(-1) at 500microM CdCl2), which caused a gradual decrease of plant growth, increased lipid peroxidation, and weakened the entire antioxidative defence. Total glutathione concentration decreased significantly; however, the concentration of oxidized glutathione remained stable. The responses of four antioxidant enzymes showed that catalase was the most inhibited after CdCl2 exposure, ascorbate peroxidase and guaiacol peroxidase moderately, and glutathione reductase least. The total antioxidative potential revealed an induced antioxidative network at 0.1microM CdCl2 (137+/-13.2% of the control) and its reduction to only 47.4+/-4.0% of the control at higher cadmium concentrations. The possible application of the examined biomarkers in ecotoxicological research is discussed.     

Analysis of short-chain chlorinated paraffins: a discussion paper

Short-chain chlorinated paraffins are a class of organic compounds widely used in many industrial applications, extensively diffused into the environment, persistent, bioaccumulative, and toxic towards aquatic organisms. However, their study and monitoring in the environment are still limited. Because of the enormous number of positional isomers that characterise their mixtures, the analysis of this class of pollutants is very difficult to perform. Beside this, the lack of certified reference materials poses a problem for the assessment of the quality assurance/quality control of any analytical procedure. At present, the scientific community does not agree on any analytical reference method, although the monitoring of short-chain chlorinated paraffins has already started in order to comply with the Water Framework Directive of the European Union on water quality. In this paper the regulatory framework, in which chlorinated paraffins are included, and the status concerning their determination are summarized. The main analytical difficulties still existing are discussed, and the definition of a method-defined parameter as well as the development of a standardised method are suggested as a way to obtain comparable monitoring data.     

Alteration of brain electrical activity by electromagnetic field

To better understand the affect of different levels of EMF on one’s brain activity, the Hodgkin–Huxley model has been used to describe the generation of an active potential in the nerve cell membrane. The theoretical calculations have shown that by the simultaneous affect of both passing an electrical potential and external very low frequency AC, one’s excitation pulses may be suppressed beginning with a certain level of external current. The level of this current depends on the frequency. It is postulated that to eliminate this suppression, the brain increases its normal level relatively to the lower limit. It is also postulated that the brain “tunes up” in the presence of external AC, by increasing the amplitude of its own excitation signals so that suppression does not occur. It is possible that this “tuning” process lasts some time after removing the external EMF as the brain adapts. This has been observed experimentally.     

Simulation of a waste incineration process with flue-gas cleaning and heat recovery sections using Aspen Plus

In the present paper, the modeling of a dual-purpose plant for the production of electrical and thermal energy from the heat treatment of solid wastes is presented. Particularly, the process has been modeled by using the Aspen Plus Shell, with the aim of performing a study about the applicability of this software in the simulation of a solid waste incineration process, which involves complex gas-solid reactions where the solids are referred to as "non-conventional". The model is developed to analyze and quantify the expected benefits associated with refuse derived fuel (RDF) thermal utilization; thus attention is focused on the performance of the energy recovery section.     

A mild photochemical approach to the degradation of phenols from olive oil mill wastewater

Photooxidation of cathecol (1) is carried out in aqueous solution at lambda > 300 nm using different sensitizers: rose bengal (RB), 9,10-dicyanoanthracene (DCA), 2,4,6-triphenylpyrylium tetrafluoroborate (Pyryl). The highest degradation is observed in the UV/RB-sensitized reaction (66% after 15 h of irradiation), mineralization and formation of dimers are the final events. This procedure has been extended to tyrosol (2), caffeic acid (3), vanillic acid (4), 4-hydroxycinnamic acid (5) and 4-hydroxybenzoic acid (6) as well as to a mixture of all phenols. A reduced toxicity of the UV/RB-irradiated solutions of cathecol and tyrosol towards alga Ankistrodesmus braunii is also verified.     

Microscale variation in<Emphasis Type="Italic"> Aat</Emphasis> (aspartate aminotransferase) is supported by activity differences between upper and lower shore allozymes of<Emphasis Type="Italic"> Littorina saxatilis</Emphasis>

The role of natural selection in maintaining inherited variation in morphological characters is indisputable. In contrast, genetic variation in allozyme loci is mostly assumed neutral or under weak selection, although enzyme functions are critical to central metabolic processes. A locus coding for aspartate aminotransferase (AAT) is polymorphic with two alleles in the rocky shore gastropod Littorina saxatilis. One allele (Aat ¹²⁰ ) is most frequent (0.8–0.9) in upper shore subpopulations, while the other (Aat ¹⁰⁰ ) dominates (0.7–0.8) lower shore subpopulations only meters below. Earlier studies show this variation to be maintained by divergent selection, but the mechanism is unknown. We measured enzyme activities in AAT extracts from individuals of known Aat genotype in populations from two islands and at three different temperatures. In all treatments lower shore homozygotes (Aat ^100/100 ) had higher enzyme activity than upper shore homozygotes (Aat ^120/120 ), with heterozygotes having intermediate levels of activity. AAT has a central role in anaerobic energy production in marine mollusks during low-tide periods of emergence, and it might appear surprising that upper shore snails, which are most likely to be emerged, have lower enzyme activity. However, upper shore snails are forced to survive long periods of desiccation, and a low metabolic rate will help to conserve limited resources of energy and nutrients and reduce accumulation of waste products.Communicated by L. Hagerman, Helsingør     

The role the Great Barrier Reef plays in resident wellbeing and implications for its management

Improvements in human wellbeing are dependent on improving ecosystems. Such considerations are particularly pertinent for regions of high ecological, but also social and cultural importance that are facing rapid change. One such region is the Great Barrier Reef (GBR). Although the GBR has world heritage status for its ‘outstanding universal value’, little is known about resident perceptions of its values. We surveyed 1545 residents, finding that absence of visible rubbish; healthy reef fish, coral cover, and mangroves; and iconic marine species, are considered to be more important to quality of life than the jobs and incomes associated with industry (most respondents were dissatisfied with the benefits they received from industry). Highly educated females placed more importance on environmental non-use values than other respondents; less educated males and those employed in mining found non-market use-values relatively more important. Environmental non-use values emerged as the most important management priority for all.

Electronic supplementary material

The online version of this article (doi:10.1007/s13280-014-0554-3) contains supplementary material, which is available to authorized users.