Search PubMed⌕ Search

SEARCH · Search PubMed

Results for “ELECTRICITY”

Search indexed PubMed citations on genomics, clinical trials, systematic reviews and public health. Explore titles, authors and supplied subject terms, then open the PubMed record.

Quote a phrase for an exact phrase match. Source license links do not imply unrestricted reuse.

At least 163 records · Page 9Linked to original sources
PubMed1998

[Intensity of electromagnetic field and electric current on human bodies induced by electric blanket].

OBJECTIVE: To study the effects of various factors, such as different carriers, with or without ground connection to a blanket and status of its switch, on electromagnetic field induced. METHODS: To determine electric field, magnetic field and electric current on human bodies induced by electric blanket with a temperature--adjustable semiwave rectifier diode, which was domestically popular. RESULTS: Temperature was adjusted and controlled by a diode serially connected to its switch is put on and the blanket, with or without short circuit. When the switch is put on and the blanket is running in low temperature, if the diode is serially connected to the ground end of the power source, the intensities of electromagnetic field and current on the human bodies induced by the blanket was higher than those running in high temperature. CONCLUSION: The most important factor influencing field intensities of the electric blanket is in its switch.

Bedding and Linens↗
PubMed2001

Comparison of defibrillation thresholds using monodirectional electrical vector versus bidirectional electrical vector.

BACKGROUND: Currently, two main lead configurations are used for implantable cardioverter-defibrillators (ICD). One generates a monodirectional electrical vector by using the can surface as an active part (hot can) together with a right ventricular defibrillation coil. The other one (TRIAD) produces a bidirectional electrical vector by adding a proximal defibrillation electrode on the same lead. The purpose of this prospective study was to determine whether there is a difference between these configurations in terms of the acute defibrillation threshold (DFT). The secondary objective was to evaluate the possible sequential effect of successive arrhythmia induction and defibrillation shocks on the final DFT value. METHODS: In 44 patients (37 males, 7 females, mean age 59.18 +/- 12.05 years; mean ejection fraction 35.21 +/- 11.69%), a Hot Can Ventak family ICD (Guidant, St. Paul, MN, USA) was implanted in a left pectoral pocket. During the implant procedure, step-down to failure DFT testing was performed twice in each patient using the two different above-mentioned configurations: the bidirectional and the monodirectional. The first configuration to be tested was determined by a 1:1 randomization by center. RESULTS: The step-down DFT protocol was followed in 35 patients. The average DFT was 8.6 +/- 4.0 J for TRIAD and 10.4 +/- 4.3 J for the monodirectional (p = 0.009) lead configuration; this represents a 16.3% decrease in the DFT using a bidirectional configuration. Furthermore, no relationship between the final DFT and the number of ventricular fibrillation inductions and shocks received was observed, confirming the secondary objective. CONCLUSIONS: Compared to the monodirectional electrical vector, the bidirectional electrical vector is clearly more beneficial for the patient.

Adult↗
PubMedDate not supplied

[Anisotropic electric conductivity of bacterial suspensions induced by external electric field].

The anisotropy of electrical conductivity of suspensions of such bacteria, as E. coli, Serratia marcescens, Pseudomonas fluorescens induced by a sinusoidal external electric field and relaxation of the anisotropy after switching off the field were investigated. On the basis of the experimental relationships the anisotropy of electrical polarizability and coefficient of rotational diffusion of the cells were evaluated. The anisotropy of electrical polarizability and coefficient of the rotational diffusion obtained are in a good agreement with the available data of other methods.

Bacterial Physiological Phenomena↗
PubMedDate not supplied

Study of the cutaneous electric potentials and the perception threshold to an electric stimulus in diabetic patients with and without clinical neuropathy.

Clinical heterogeneity of diabetic peripheral neuropathy could express a neurophysiological and electrophysiological heterogeneity possibly related with the dissociated metabolic susceptibility of the difference types of nerve fibres and endings. To evaluate the functional status of the skin autonomous nervous system and of the deep pain sensitivity system in diabetics we studied two electrophysiological parameters skin electrical potential (using Digital Multimeter 3466 Hewlet Packard, USA) and the perception threshold (microA) at an electrical stimulus (spike wave, 0.5 m sec duration) 1 cm deeply applied through 2 acupuncture needles placed 30 cm distance each other, in 3 groups: Ia-18 diabetic patients with clinical signs of neuropathy (12 M, 6 F, aged 55 +/- 17 yrs); Ib - 17 diabetic patients without clinical signs of diabetic neuropathy (12 M, 5 F, aged 57 +/- 16 yrs); I1 - 10 age and sex matched non-diabetic controls. Our data show: a higher mean value of the potential in the acupuncture points as against neighbour areas, both in non-diabetic control (- 111 +/- 25 mV v.s. -81 +/- 29 mV, p less than 0.05) and in diabetics (-85 +/- 43 mV v.s. -58 +/- 25 mV, p less than 0.01); a lower mean value of the electrical potentials in diabetic with clinical signs of neuropathy as against in those without clinical signs of neuropathy (-66 +/- 29 mV v.s. -108 +/- 43 mV, p less than 0.01): a higher mean value of the perception threshold in diabetics with clinical signs of neuropathy as against in diabetics without clinical signs of neuropathy (213 +/- 82 microA. v.s. 102 +/- 40 microA, p less than 0.01); a significant correlation (r = -0.81) between the perception threshold and the electrical potentials of the studied points.

Adult↗
PubMed1993

Phase and amplitude maps of the electric organ discharge of the weakly electric fish, Apteronotus leptorhynchus.

The electric organ discharge (EOD) potential was mapped on the skin and midplane of several Apteronotus leptorhynchus. The frequency components of the EOD on the surface of the fish have extremely stable amplitude and phase. However, the waveform varies considerably with different positions on the body surface. Peaks and zero crossings of the potential propagate along the fish's body, and there is no point where the potential is always zero. The EOD differs significantly from a sinusoid over at least one third of the body and tail. A qualitative comparison between fish showed that each individual had a unique spatiotemporal pattern of the EOD potential on its body. The potential waveforms have been assembled into high temporal and spatial resolution maps which show the dynamics of the EOD. Animation sequences and Macintosh software are available by anonymous ftp (mordor.cns.caltech.edu; cd/pub/ElectricFish). We interpret the EOD maps in terms of ramifications on electric organ control and electroreception. The electrocytes comprising the electric organ do not all fire in unison, indicating that the command pathway is not synchronized overall. The maps suggest that electroreceptors in different regions fulfill different computational roles in electroreception. Receptor mechanisms may exist to make use of the phase information or harmonic content of the EOD, so that both spatial and temporal patterns could contribute information useful for electrolocation and communication.

Animals↗
PubMed1982

Determination of electric current distributions in animals and humans exposed to a uniform 60-Hz high-intensity electric field.

The thermographic method for determining specific absorption rate (SAR) in animals and models of tissues or bodies exposed to electromagnetic fields was applied to the problem of quantifying the current distribution in homogeneous bodies of arbitrary shape exposed to 60-Hz electric fields. The 60-Hz field exposures were simulated by exposing scale models of high electrical conductivity to 57.3-MHz VHF fields of high strength in a large 3.66 X 3.66 X 2.44-m TE101 mode resonant cavity. After exposure periods of 2-30 s, the models were quickly disassembled so that the temperature distribution (maximum value up to 7 degrees C) along internal cross-sectional planes of the model could be recorded thermographically. The SAR, W', calculated from the temperature changes at any point in the scale model was used to determine the SAR, W, for a full-scale model exposed to a 60-Hz electric field of the same strength by the relation W = (60/f')2 . (sigma'/sigma) . W' where f' is the model exposure frequency, sigma' is the conductivity of the scale model at the VHF exposure frequency, and sigma is the conductivity of the full-scale subject at 60 Hz. The SAR was used to calculate either the electric field strength or the current density for the full-scale subject. The models were used to simulate the exposure of the full-scale subject located either in free space or in contact with a conducting ground plane. Measurements made on a number of spheroidal models with axial ratios from 1 to 10 and conductivity from 1 to 10 s/m agreed well with theoretical predictions. Maximum current densities of 200nA/cm2 predicted in the ankles of man models and 50 nA/cm2 predicted in the legs of pig models exposed to 60-Hz fields at 1kV/m agreed well with independent measurements on full-scale models.

Animals↗
PubMed1982

Differences in the electric birefringence of spectrin dimers and tetramers as shown by the fast reversing electric pulse method.

The electric birefringence of purified spectrin has been examined in medium of low ionic strength at 20 degrees C and for electric fields smaller than 4 X 10(4) V m(-1), using the reversing electric pulse method. This technique allows study of the permanent and induced dipole electric moment of macromolecules more easily than in measurements using only rectangular pulses. We show that spectrin heterodimers and heterotetramers have different electro-optical properties. The relaxation time of the tetramer (7 microseconds) is significantly longer than that of the dimer (4.5 microseconds). Tetramers and dimers have also different polarizability parameters.

Birefringence↗
PubMed2005

Flow splitting at the inlet electrode as a method for decreasing the electric current in electric field assisted liquid chromatography.

The combination of pressurized flow and electric field offers, with the use of capillary columns, several options for retention control. However, it has been shown that the utility of this technique is strongly limited by the high electric current that is generated at the high electric field strengths that are needed. We have earlier shown that the high current is a result of locally increased mobile phase ion concentration in the electric field, particularly around the inlet electrode. In this paper, we report that by splitting the mobile phase flow around the inlet electrode a relatively constant ion concentration around the electrode can be obtained and the high currents are there by reduced.

Chromatography, Liquid↗
PubMed2002

Electrical activity from colon overlaps with normal gastric electrical activity in cutaneous recordings.

The stability of EGG recordings is affected by a variety of artifacts. The aim of this study was to investigate possible overlapping of dominant frequencies in recorded cutaneous electrical activity arising simultaneously from the stomach and/or colon. Ten normal volunteers, eight posttotal colectomy patients, and four patients posttotal gastrectomy were studied. Fasting cutaneous recordings were obtained using four pediatric ECG electrodes attached to the abdominal surface. Electrical activity was recorded and digitally analyzed using custom-designed software. Spectral analysis after gastrectomy and colectomy showed persistence of power peaks in the gastric electrical activity range of frequency (2.5-3.75 cpm). In conclusion, noninvasively obtained colonic frequencies overlap EGG. This hypothesis is supported by the persistence of power peaks in the EGG range of frequency after gastrectomy and colectomy. Therefore, we conclude that contribution of electrical activity arising from the colon could substantially affect EGG recordings.

Aged↗
PubMed2005

Transient electric birefringence of wormlike macromolecules in electric fields of arbitrary strength: a computer simulation study.

We have studied the birefringence decay of linear models of macromolecules for two different types of flexibility, the broken-rod chain and the wormlike chain, using a computer simulation of a transient electric birefringence experiment. We have paid particular attention to the influence of the intensity of the orienting field, including two orienting mechanisms, the induced dipole, and the permanent dipole. We have compared wormlike and broken-rod models of the same radius of gyration, finding that they present a different decay curve under the influence of the same intensity of the field. We have seen that these differences are due to the faster relaxation times (smaller in the wormlike chain model) and amplitudes, because, regardless of the type of flexibility, the overall size of a molecule (measured by the radius of gyration) essentially determines the longest relaxation time. We have also analyzed how the relaxation process is affected by the degree of flexibility, the orientation mechanisms, and the intensity of the field. Studying a different aspect, we have paid attention to the deformation of a molecule in a transient electric birefringence experiment as a source of information. In this work we have developed equations to characterize this deformation in terms of one of the components of the gyration tensor, if a dynamic light scattering experiment under the influence of an electric field could be performed. To develop this work we have simulated the Brownian dynamics of the different models, relaxing after the removal of an orienting external electric field of arbitrary strength. A comparison with other methods such a the rigid body treatment or the correlation analysis of Brownian trajectories has also been included. We have seen that differences between the two Brownian dynamics methods are small and that the rigid-body treatment is only an acceptable approximation to obtain the longest relaxation time.

Journal Article↗
PubMed2005

Nanosecond pulsed electric fields (nsPEF) induce direct electric field effects and biological effects on human colon carcinoma cells.

Nanosecond pulsed electric fields (nsPEFs) are ultrashort pulses with high electric field intensity (kV/cm) and high power (megawatts), but low energy density (mJ/cc). To determine roles for p53 in response to nsPEFs, HCT116 cells (p53+/+ and p53-/-) were exposed to nsPEF and analyzed for membrane integrity, phosphatidylserine externalization, caspase activation, and cell survival. Decreasing plasma membrane effects were observed in both HCT116p53+/+ and p53-/- cells with decreasing pulse durations and/or decreasing electric fields. However, addition of ethidium homodimer-1 and Annexin-V-FITC post-pulse demonstrated greater fluorescence in p53-/- versus p53+/+ cells, suggesting a postpulse p53-dependent biological effect at the plasma membrane. Caspase activity was significantly higher than nonpulsed cells only in the p53-/- cells. HCT116 cells exhibited greater survival in response to nsPEFs than HL-60 and Jurkat cells, but survival was more evident for HCT116p53+/+ cells than for HCT116p53-/- cells. These results indicate that nsPEF effects on HCT116 cells include (1) apparent direct electric field effects, (2) biological effects that are p53-dependent and p53-independent, (3) actions on mechanisms that originate at the plasma membranes and at intracellular structures, and (4) an apparent p53 protective effect. NsPEF applications provide a means to explore intracellular structures and functions that can reveal mechanisms in health and disease.

Annexin A5↗
PubMed1996

Exposure to 50-Hz electric field and incidence of leukemia, brain tumors, and other cancers among French electric utility workers.

Recent studies on the association between exposure to 50- to 60-Hz fields and cancer carried out among electric utility workers have focused mainly on the magnetic field component of exposure. The authors have investigated tumor risks specifically associated with electric fields, as this exposure is distinct from magnetic fields. The study design is a case-control study nested within a cohort of 170,000 workers employed at Electricité de France-Gaz de France (EDF) between 1978 and 1989. All incident cases of cancer and benign tumor of the brain diagnosed in 1978-1989 among workers before the age of retirement were included. Four randomly selected controls were individually matched to each case by year of birth. The exposure to electric fields was assessed from measurements collected in 850 EDF workers for a full work week. Arithmetic and geometric mean exposures were included in a job-exposure matrix to determine the cumulative exposure of the cases and the controls. Exposures to potentially carcinogenic chemicals found at the workplace were also evaluated through expert judgment. The analysis by site of tumor did not show any increased risk for leukemia (72 cases). An odds ratio of 3.08 (95% confidence interval 1.08-8.74) was observed for all brain tumors (69 cases) for exposure above the 90th percentile (> or = 387 V/m-year), and there was some indication of a dose-response relation, although the risk did not increase monotonically with exposure. No confounding from magnetic fields or from other potentially carcinogenic hazards was apparent. The observed association was somewhat stronger after allowing a 5-year latency period before diagnosis (odds ratio = 3.69, 95% confidence interval 1.10-12.43) for exposure above the 90th percentile. However, the risk of brain tumor could not be linked to a specific type of tumor. An unexpected association was also observed for colon cancer, using geometric indexes of exposure, but no other association was seen for any other type of cancer. Our study indicates that electric fields may have a specific effect on the risk of brain tumor, and that this should be taken into account in future analyses on the carcinogenic effects of 50- to 60-Hz fields.

Brain Neoplasms↗
PubMed2005

X-ray diffraction by a crystal in a permanent external electric field: electric-field-induced structural response in alpha-GaPO4.

For the first time, site-selective distortion has been investigated for two different structural units in the ternary compound alpha-GaPO(4) under the influence of a permanent external electric field. Based on 54 measured reflection intensities, the electric-field-induced distortion of PO(4) and GaO(4) tetrahedra in alpha-GaPO(4) crystals is evaluated using a model of pseudoatomic displacements introduced recently [Gorfman, Tsirelson & Pietsch (2005). Acta Cryst. A61, 387-396]. A stronger variation of the P-O bond lengths in the PO(4) tetrahedron was found compared to the bonds in the GaO(4) tetrahedron. The different distortions of the tetrahedra owing to the electric field were analysed in terms of the valence charge density of alpha-GaPO(4) and its topological characteristics. The larger charge of the P pseudoatom compared to the Ga atom was recognized as the main reason for the higher sensitivity of the PO(4) tetrahedron to a permanent external electric field.

Journal Article↗
PubMedDate not supplied

Calculations of two-dimensional electric field and potential distributions aroun electrodes in conducting media.

Tumor cells can be killed by heating to 42.5degreesC. It is convenient to localize heating by passing electric current at 500 kHz through tissue between a pair of electrodes. It is desirable to determine, for a given electrode-tissue configuration, what the resulting field and, therefore, current distribution will be. A computer program FFEARS was used to calculate electric field and potential distributions in two dimensions for three simple cases.

Computers↗
PubMed1997

Correlation and comparison of magnetic and electric detection of small intestinal electrical activity.

The small intestinal basic electrical rhythm (BER) was detected simultaneously with serosal electrodes and a transabdominal superconducting quantum interference device (SQUID) magnetometer in anesthetized rabbits. We induced mesenteric ischemia to correlate serosal electrode recording of changes in BER with the SQUID magnetometer. The BER frequency was obtained by spectral analysis of the data using Fourier and autoregressive techniques. There was a high degree of correlation (r = 0.96) between the BER frequency determined using the serosal electrodes and the BER frequency ascertained from SQUID data. Additionally, the effects of an electrical insulator on the external electric and magnetic fields were studied in the rabbit model. The presence of an insulator profoundly attenuates external electric potentials recorded by cutaneous electrodes but does not significantly affect external magnetic fields or serosal potentials. We conclude that SQUID magnetometers could noninvasively record small intestinal BER that was highly correlated with the activity recorded by invasive serosal electrodes. The advantages of magnetic field measurements have encouraged us to investigate clinical applications.

Abdomen↗
PubMed1997

Electrical remodeling due to atrial fibrillation in chronically instrumented conscious goats: roles of neurohumoral changes, ischemia, atrial stretch, and high rate of electrical activation.

BACKGROUND: Recently, we developed a goat model of chronic atrial fibrillation (AF). Due to AF, the atrial effective refractory period (AERP) shortened and its physiological rate adaptation inversed, whereas the rate and stability of AF increased. The goal of the present study was to evaluate the role of (1) the autonomic nervous system, (2) ischemia, (3) stretch, (4) atrial natriuretic factor (ANF), and (5) rapid atrial pacing in this process of electrical remodeling. METHODS AND RESULTS: Twenty-five goats were chronically instrumented with multiple epicardial atrial electrodes. Infusion of atropine (1.0 mg/kg; n=6) or propranolol (0.6 mg/kg; n=6) did not abolish the AF-induced shortening of AERP or interval (AFI). Blockade of K+(ATP) channels by glibenclamide (10 micromol/kg; n=6) slightly increased the AFI from 95+/-4 to 101+/-5 ms, but AFI remained considerably shorter than during acute AF (145 ms). Glibenclamide had no significant effect on AERP after electrical cardioversion of AF (69+/-14 versus 75+/-15 ms). Volume loading by 0.5 to 1.0 L of Hemaccel (n=12) did not shorten AERP. The median plasma level of ANF increased from 42 to 99 pg/mL after 1 to 4 weeks of AF (n=6), but ANF infusion (0.1 to 3.1 microg/min, n=4) did not shorten AERP. Rapid atrial pacing (24 to 48 hours; n=10) progressively shortened AERP from 134+/-10 to 105+/-6 ms and inversed its physiological rate adaptation. CONCLUSIONS: Electrical remodeling by AF is not mediated by changes in autonomic tone, ischemia, stretch, or ANF. The high rate of electrical activation itself provides the stimulus for the AF-induced changes in AERP.

Animals↗
PubMed1996

In vivo 3-D distributions of electric fields in pig skin with rectangular pulse electrical current stimulation (RPECS).

We developed stimulating and detecting electrodes. We experimentally examined three dimensional (3-D) distributions of electric fields in living pig skin under and around the stimulating electrodes with the detecting electrodes and rectangular pulsed electrical current stimulation (RPECS). We verified our previous physical assumption, E approximately I/(A sigma dz), in the skin under the electrode, where E, I, A and sigma dz respectively represent the electric field, the externally imposed peak current, the cross sectional area of the stimulating electrode and the perpendicular conductivity of the skin. Pulses were 30 mA, 140 microseconds and 128 pulses per second (pps). These parameters were previously used in our laboratory to enhance cutaneous regeneration, in vivo, with RPECS.

Animals↗
PubMed1995

The electric image in weakly electric fish: I. A data-based model of waveform generation in Gymnotus carapo.

Understanding how electrosensory images are generated and perceived in actively electrolocating fish requires the study of the characteristics of fish bodies as electric sources. This paper presents a model of Gymnotus carapo based on measurements of the electromotive force generated by the electric organ and the impedance of the passive tissues. A good agreement between simulated and experimentally recorded transcutaneous currents was obtained. Passive structures participate in the transformation of the electromotive force pattern into transcutaneous current profiles. These spatial filtering properties of the fish's body were investigated using the model. The shape of the transcutaneous current profiles depends on tissue resistance and on the geometry and size of the fish. Skin impedance was mainly resistive. The effect of skin resistance on the spatial filtering properties of the fish's body was theoretically analyzed. The model results show that generators in the abdominal and central regions produce most of the currents through the head. This suggests that the electric organ discharge (EOD), generated in the abdominal and central regions is critical for active electrolocation. In addition, the well-synchronized EOD components generated all along the fish produce large potentials in the far field. These components are probably involved in long-distance electrocommunication. Preliminary results of this work were published as a symposium abstract.

Animals↗