Effects Of Weak Electric Fields Research Articles

Effect of laser radiation and electric field on combustion of hydrocarbon-air mixtures

Publications on combustion of hydrocarbon-air mixtures under the action of a weak electric field and laser radiation are analyzed. A specific feature of the authors’ experimental study is a pulsed-periodic action of an electric field and focused laser radiation, which does not lead to electric discharge or optical breakdown. Numerous experiments reveal a noticeable effect of weak electric fields on combustion processes. Application of an electric field may result in expansion of the limits of flammability and combustion of fuel-air mixtures, changes (decrease or increase) in the burning rate, shifting of flame stabilization toward lean mixtures, reduction of the concentration of hazardous substances (for instance, NOx and CO) in combustion products, etc.

Effect of electrokinetic transport on the vulnerability of PAH-degrading bacteria in a model aquifer

There has been increasing interest in employing electro-bioremediation, a hybrid technology of bioremediation and electrokinetics, to overcome the low bioavailability of hydrophobic organic contaminants (HOC) by homogenizing sorption-retarded HOC and immobilised microorganisms. Present electro-remediation approaches mainly aim at macroscale pollutant extraction and tend to neglect possible impacts of direct current (DC) on the physiology of microorganisms. The effect of weak electric fields (X = 1 V cm(-1)) on the fitness of electrokinetically dispersed fluorene-degrading Sphingomonas sp. LB126 in bench-scale model aquifers was investigated by flow cytometry using propidium iodide (PI) as an indicator that distinguishes between PI-permeable (cells with porous membranes, i.e. dead or vulnerable) and PI-impermeable bacteria. After 15.5 h of DC treatment 56% of all cells recovered were dispersed at the centimetre scale relative to 29% in the absence of DC. There was no overall negative effect of the 15.5-h DC treatment on cell vulnerability, as 7.0% of the DC-treated bacteria exhibited PI-staining compared to 6.5% of the control population. Minor differences were observed in the subpopulation that had been mobilised by electroosmosis with an approximately twofold increase in the percentage of PI-stained cells relative to the control. Enhanced PI staining did not correlate with reduced culturability of the cells on rich-medium agar plates. Relative to the control, DC-treated cells mobilised by electroosmosis were threefold more culturable, confirming earlier data that that PI-cell membrane permeability does not always indicate reduced viability of oligotrophic environmental bacteria. Our findings suggest that electrokinetics is a valuable mechanism to transport viable and culturable polycyclic aromatic hydrocarbon (PAH)-degrading bacteria in soil or sediments.

A NEUROBIOLOGICAL BASIS FOR ELF GUIDELINES

It is well understood that electric currents applied directly to the body can stimulate peripheral nerve and muscle tissue; such effects can be fatal if breathing is inhibited or ventricular fibrillation is induced. Exposure to extremely low frequency electric and magnetic fields will also induce electric fields and currents within the body, but these are almost always much lower than those that can stimulate peripheral nerve tissue. Guidance on exposure to such fields is based on the avoidance of acute effects in the central nervous system. This paper reviews the physiological processes involved in nerve cell excitability in the peripheral and central nervous system, and the experimental evidence for physiologically weak electric field effects. It is concluded that the integrative properties of the synapses and neural networks of the central nervous system render cognitive function sensitive to the effects of physiologically weak electric fields, below the threshold for peripheral nerve stimulation. However, the only direct evidence of these weak field interactions within the central nervous system is the induction of phosphenes in humans--the perception of faint flickering light in the periphery of the visual field, by magnetic field exposure. Other tissues are potentially sensitive to induced electric fields through effects on voltage-gated ion channels, but the sensitivity of these ion channels is likely to be lower than those of nerve and muscle cells specialized for rapid electrical signaling. In addition, such tissues lack the integrative properties of synapses and neuronal networks that render the central nervous system potentially more vulnerable.

Effect of weak electric fields on the conduction in thin metal films

The variation of conduction in island metallic Ti, Co, W, and FeNi films in weak electric field is studied. The variation of the differential conductivity of island metallic films with an electric field at temperatures from T = 77 to 300 K is measured, as well as the temperature dependence of the differential conductivity in the same temperature range. It is shown that a thermally activated conduction mode is realized in such structures. The mechanism of variation of conductivity of island metallic films in a weak electric field is discussed.

Thermally Stimulated Desorption of Na[sup +] and Cs[sup +] Ions from a NaAu Alloy Film Grown on Au

The formation of Na+ and Cs+ ions on and their thermal desorption from the surface of a NaAu alloy film grown on metallic gold are studied. It is shown that thermionic emission from insulator-coated metallic substrates is governed by a sequence of processes, such as diffusion of Na and Cs adatoms into the film, ionization of these atoms at the insulator-metal interface, diffusion of the resulting ions toward the surface, and desorption of the ions. The effect of weak electric fields on ion diffusion and desorption is investigated.

Rapporteur report: weak field interactions in the central nervous system.

Experimental evidence was presented of the interaction of extremely low frequency (ELF) physiologically weak electric fields (that is, internal fields of around 1-1000 mV m(-1)) with tissues of the central nervous system and the consequences of this for visual and cognitive function. These internal fields are higher than those induced in the body by exposure to environmental EMFs, but are small compared to nerve excitation thresholds. Two papers considered the effect of weak electric fields directly applied to hippocampal tissue in vitro on neuronal excitability assessed from evoked responses and on the modulation of neural network activity involving large numbers of individual neurons. A review was presented of the effects on electrical measures of perceptual and cognitive processes and on the performance of various behavioural tasks in volunteers exposed to electromagnetic fields. Finally, two papers addressed the visual perception of flickering light--phosphenes--in volunteers exposed to ELF magnetic fields. The first examined possible physiological origins of this phenomenon and the second assessed the induced electric fields and currents in the retina, using complex dosimetric modelling. These papers were discussed in several plenary sessions and in one breakout group, all of which are briefly summarised in this report.

Effects of weak electric fields on the activity of neurons and neuronal networks.

Electric fields applied to brain tissue will affect cellular properties. They will hyperpolarise the ends of cells closest to the positive part of the field, and depolarise ends closest to the negative. In the case of neurons this affects excitability. How these changes in transmembrane potential are distributed depends on the length constant of the neuron, and on its geometry; if the neuron is electrically compact, the change in transmembrane potential becomes an almost linear function of distance in the direction of the field. Neurons from the mammalian hippocampus, maintained in tissue slices in vitro, are significantly affected by fields of around 1-5 V m(-1).

Editorial - International workshop on weak electric field effects in the body

Editorial - International workshop on weak electric field effects in the body

Neuronal ion channels and their sensitivity to extremely low frequency weak electric field effects.

Neuronal ion channels are gated pores whose opening and closing is usually regulated by factors such as voltage or ligands. They are often selectively permeable to ions such as sodium, potassium or calcium. Rapid signalling in neurons requires fast voltage sensitive mechanisms for closing and opening the pore. Anything that interferes with the membrane voltage can alter channel gating and comparatively small changes in the gating properties of a channel can have profound effects. Extremely low frequency electrical or magnetic fields are thought to produce, at most, microvolt changes in neuronal membrane potential. At first sight, such changes in membrane potential seem orders of magnitude too small to significantly influence neuronal signalling. However, in the central nervous system, a number of mechanisms exist which amplify signals. This may allow such small changes in membrane potential to induce significant physiological effects.

Weak electric field interactions in the central nervous system.

Exposure to extremely low frequency electric and magnetic fields will induce electric fields and currents within the body, but these are almost always much lower than those that can stimulate peripheral nerve tissue. Guidance on exposure to such fields has been published by NRPB and ICNIRP, which is based on the avoidance of acute effects in the central nervous system. Weak electric field effects, below action potential thresholds, have been demonstrated in vitro in brain slice preparations; thresholds can be estimated to be above about 1 mV mm(-1) (around 100 mA m(-2), taking a brain tissue conductivity of around 0.1 S m(-1)), depending on stimulus conditions. Some studies suggest possible effects at lower induced field strengths. The intact nervous system might be expected to be more sensitive to induced electric fields and currents than in vitro preparations, due to a higher level of spontaneous activity and a greater number of interacting neurons. There is good evidence that electrically excitable cells in the retina can be affected in vivo by induced currents as low as 10 mA m(-2). It has been suggested that induced current densities above 10 mA m(-2) may have effects on other central nervous system functions but few studies have been carried out. Further research in experimental animals using both in vitro and in vivo approaches is needed to clarify this issue.

Weak electric fields affect plant development.

High-strength electric currents and fields can alter plant physiology by the production of heat within the plant tissue and by the ionization of air molecules at the plant tips. It has been suggested that weak low-frequency electric and magnetic filelds may alter germination and early plant development [4], [5], but the question has not been resolved. Our aim was to determine the possible existence of weak electric-field effects on sunflower germination and to calculate the electric-field threshold inside the seed for any such effects. We found that an applied electric field of 5 kV/m, 60 Hz, produced an internal electric field of 7.5 ×10-4 V/m in a seed in moist soil and resulted in a statistically significant decrease of about 5 percent in germination rate. No effect was found for an applied field of 1 kV/m (1.5 ×10-4 V/m inside the seed). These results established for the first time that electric fields can affect plants by a nonthermal mechanism other than air ionization.

Radiospectroscopic studies of ferroelectric triglycine sulphate-like crystals

The possibility of using radio and microwave spectroscopy to study intermolecular interactions in ferroelectrics of the TGS family will be presented.Ferroelectric crystals (TGSe, TGS and TGFB) doped with Cr3+ chromium ions were investigated by epr as a function of temperature. The fine structure parameter D of the epr spectra near Tc is closely related to the macroscopic deformation measured by us for all TGS-type crystals.For the selenite the coordination of Cr3+ impurities was determined and the model of charge compensation was found. Anomalies of the D parameter at the phase transitions in TGSe, TGS and TGFB were observed. Effects of applied electric field on epr of ferroelectrics as well as the suggestion of the new kind of epr method with electric modulation-EM epr-will be discussed. This method gives possibilities of measurements of weak electric field effects in ferroelectric and nonferroelectric dielectric crystals.On the basis of the angular dependence of deuterium and proton nmr spectra for partially deuterated TGS crystal the structural model of glycine molecules was examined in details. The nmr results show that below Tc the skeleton of GI molecule changes its orientation near Tc in the jump-like way while the orientation of C-ND3 changes proportionally to the spontaneous polarization.On the basis of high-pressure measurements (one-dimensional and hydrostatic) as well as the epr and nmr data it is possible to propose the layer model of TGS-type crystals. The structure of GI-molecule obtained from nmr studies explained change of Ps, with temperature.

Extremely low frequency, weak electric fields affect schedule-controlled behaviour of monkeys.

THE effect of weak electric fields on behaviour of orgasnims has potentially important implications for basic neurophysiology and evaluation of environmental hazards (chronic exposure to weak 60-Hz electric fields has become a way of life). We have demonstrated1 that weak (approximately 7 V m−1 p–p), extremely low frequency (7 Hz) electric fields could modify a lever-press response in monkeys. We summarise here data2 confirming that finding for a larger group of animals with more replications and presenting evidence for a dose-dependent relationship for 7-Hz fields. In addition there are indications of a threshold of 10–56 V m−1 p–p for field frequencies higher than electroencephalogram (EEG) range (1–32 Hz). Adey3 has hypothesised that since these field levels areclearly too low to trigger synapsesinthe fashion prescribed by classical neurophysiology, more subtle membrane sensitivities may be functioning as central nervous system mediators of the observed behavioural effects. One possible mediator is the degree of calcium efflux across the membrane4.

Effect of Weak Electric Fields on the Absorption Edge in Doped Germanium

AbstractResults of the investigation of a new effect, the great change in the absorption spectra near the direct band edge of germanium in a relatively weak electric field, are presented. The effect is assumed to be due to the screening of the Coulomb interaction by the carriers which are freed by avalanche breakdown of shallow impurities.