[Effects of extremely low frequency electromagnetic radiation on cardiovascular system of workers].

Science.gov (United States)

Zhao, Long-yu; Song, Chun-xiao; Yu, Duo; Liu, Xiao-liang; Guo, Jian-qiu; Wang, Chuan; Ding, Yuan-wei; Zhou, Hong-xia; Ma, Shu-mei; Liu, Xiao-dong; Liu, Xin

2012-03-01

To observe the exposure levels of extremely low frequency electromagnetic fields in workplaces and to analyze the effects of extremely low frequency electromagnetic radiation on cardiovascular system of occupationally exposed people. Intensity of electromagnetic fields in two workplaces (control and exposure groups) was detected with EFA-300 frequency electromagnetic field strength tester, and intensity of the noise was detected with AWA5610D integral sound level. The information of health physical indicators of 188 controls and 642 occupationally exposed workers was collected. Data were analyzed by SPSS17.0 statistic software. The intensity of electric fields and the magnetic fields in exposure groups was significantly higher than that in control group (P 0.05). The results of physical examination showed that the abnormal rates of HCY, ALT, AST, GGT, ECG in the exposure group were significantly higher than those in control group (P 0.05). Exposure to extremely low frequency electromagnetic radiation may have some effects on the cardiovascular system of workers.

Occupational exposure to extremely low-frequency magnetic fields and risk for central nervous system disease

DEFF Research Database (Denmark)

Pedersen, Camilla; Poulsen, Aslak Harbo; Rod, Naja Hulvej

2017-01-01

Purpose: Evidence of whether exposure to extremely low-frequency magnetic fields (ELF-MF) is related to central nervous system diseases is inconsistent. This study updates a previous study of the incidence of such diseases in a large cohort of Danish utility workers by almost doubling the period...

Extremely Low Frequency Electromagnetic Field (ELF-EMF and childhood leukemia near transmission lines: a review

Directory of Open Access Journals (Sweden)

P. A. Kokate

2016-04-01

Full Text Available This article presents a systematic review of most cited studies from developed countries those shed light on the potential relation between childhood leukemia and extremely low frequency electromagnetic field (ELF-EMF. All the findings of articles critically segregated as per some neglected parameters like number of samples, exposure duration, frequency range, distance from the radiation sources, and location during measurement of magnetic field density near power lines. Literature of major 50 studies are divided according to pooled analysis / meta-analysis, residential zone assessment and case-control studies.

Extremely low-frequency magnetic fields can impair spermatogenesis recovery after reversible testicular damage induced by heat.

Science.gov (United States)

Tenorio, Bruno Mendes; Ferreira Filho, Moisés Bonifacio Alves; Jimenez, George Chaves; de Morais, Rosana Nogueira; Peixoto, Christina Alves; Nogueira, Romildo de Albuquerque; da Silva Junior, Valdemiro Amaro

2014-06-01

Male infertility is often related to reproductive age couples experiencing fertility-related issues. Men may have fertility problems associated with reversible testicular damage. Considering that men have been increasingly exposed to extremely low-frequency magnetic fields generated by the production, distribution and use of electricity, this study analyzed whether 60 Hz and 1 mT magnetic field exposure may impair spermatogenesis recovery after reversible testicular damage induced by heat shock using rats as an experimental model. Adult male rats were subjected to a single testicular heat shock (HS, 43 °C for 12 min) and then exposed to the magnetic field for 15, 30 and 60 d after HS. Magnetic field exposure during the spermatogenesis recovery induced changes in testis components volume, cell ultrastructure and histomorphometrical parameters. Control animals had a reestablished and active spermatogenesis at 60 d after heat shock, while animals exposed to magnetic field still showed extensive testicular degeneration. Magnetic field exposure did not change the plasma testosterone. In conclusion, extremely low-frequency magnetic field may be harmful to fertility recovery in males affected by reversible testicular damage.

Examples of extremely low-frequency magnetic fields in a Finnish metro station

International Nuclear Information System (INIS)

Korpinen, L.; Sydaenheimo, L.; Laehdetie, A.; Amundin, A.; Piippo, H.

2015-01-01

The aim of this pilot study was to present examples of extremely low-frequency (ELF) magnetic fields in a Finnish metro station. The metro trains are powered by 750 V DC voltage supplied through a conductor rail next to the running rails. We measured magnetic fields with a magnetic field meter MFM 3000 in 17 cases when a train was leaving the platform in the same metro station. The maximum measured magnetic field was 5400 nT (at 1 m height and 4.3 m from the conductor rail). The magnetic field stayed at this level for a very short time after the metro left the platform. It is possible that there are also DC magnetic fields near the metro as the train leaves the station because the trains are powered by DC voltage. Therefore, it is also important to measure DC fields and DC currents in the future. (authors)

Extremely low-frequency magnetic fields and survival from childhood acute lymphoblastic leukemia

DEFF Research Database (Denmark)

Schüz, J; Grell, K; Kinsey, S

2012-01-01

A previous US study reported poorer survival in children with acute lymphoblastic leukemia (ALL) exposed to extremely low-frequency magnetic fields (ELF-MF) above 0.3 μT, but based on small numbers. Data from 3073 cases of childhood ALL were pooled from prospective studies conducted in Canada......, Denmark, Germany, Japan, UK and US to determine death or relapse up to 10 years from diagnosis. Adjusting for known prognostic factors, we calculated hazard ratios (HRs) and 95% confidence intervals (CI) for overall survival and event-free survival for ELF-MF exposure categories and by 0.1 μT increases...

The effects of extremely low frequency magnetic fields on mutation induction in mice

Energy Technology Data Exchange (ETDEWEB)

Wilson, James W. [Department of Genetics, University of Leicester, Leicester LE1 7RH (United Kingdom); Haines, Jackie; Sienkiewicz, Zenon [Centre for Radiation, Chemical and Environmental Hazards, Public Health England, Chilton, Didcot, Oxfordshire OX11 0RQ (United Kingdom); Dubrova, Yuri E., E-mail: yed2@le.ac.uk [Department of Genetics, University of Leicester, Leicester LE1 7RH (United Kingdom)

2015-03-15

Highlights: • The effects of 50 Hz magnetic fields on mutation induction in mice were analyzed. • The frequency of ESTR mutation was established in sperm and blood. • Exposure to 10–300 μT for 2 and 15 h did not result in mutation induction. • Mutagenic effects of 50 Hz magnetic fields are likely to be negligible. - Abstract: The growing human exposure to extremely low frequency (ELF) magnetic fields has raised a considerable concern regarding their genotoxic effects. The aim of this study was to evaluate the in vivo effects of ELF magnetic fields irradiation on mutation induction in the germline and somatic tissues of male mice. Seven week old BALB/c × CBA/Ca F{sub 1} hybrid males were exposed to 10, 100 or 300 μT of 50 Hz magnetic fields for 2 or 15 h. Using single-molecule PCR, the frequency of mutation at the mouse Expanded Simple Tandem Repeat (ESTR) locus Ms6-hm was established in sperm and blood samples of exposed and matched sham-treated males. ESTR mutation frequency was also established in sperm and blood samples taken from male mice exposed to 1 Gy of acute X-rays. The frequency of ESTR mutation in DNA samples extracted from blood of mice exposed to magnetic fields did not significantly differ from that in sham-treated controls. However, there was a marginally significant increase in mutation frequency in sperm but this was not dose-dependent. In contrast, acute exposure X-rays led to significant increases in mutation frequency in sperm and blood of exposed males. The results of our study suggest that, within the range of doses analyzed here, the in vivo mutagenic effects of ELF magnetic fields are likely to be minor if not negligible.

The effects of extremely low frequency magnetic fields on mutation induction in mice

International Nuclear Information System (INIS)

Wilson, James W.; Haines, Jackie; Sienkiewicz, Zenon; Dubrova, Yuri E.

2015-01-01

Highlights: • The effects of 50 Hz magnetic fields on mutation induction in mice were analyzed. • The frequency of ESTR mutation was established in sperm and blood. • Exposure to 10–300 μT for 2 and 15 h did not result in mutation induction. • Mutagenic effects of 50 Hz magnetic fields are likely to be negligible. - Abstract: The growing human exposure to extremely low frequency (ELF) magnetic fields has raised a considerable concern regarding their genotoxic effects. The aim of this study was to evaluate the in vivo effects of ELF magnetic fields irradiation on mutation induction in the germline and somatic tissues of male mice. Seven week old BALB/c × CBA/Ca F 1 hybrid males were exposed to 10, 100 or 300 μT of 50 Hz magnetic fields for 2 or 15 h. Using single-molecule PCR, the frequency of mutation at the mouse Expanded Simple Tandem Repeat (ESTR) locus Ms6-hm was established in sperm and blood samples of exposed and matched sham-treated males. ESTR mutation frequency was also established in sperm and blood samples taken from male mice exposed to 1 Gy of acute X-rays. The frequency of ESTR mutation in DNA samples extracted from blood of mice exposed to magnetic fields did not significantly differ from that in sham-treated controls. However, there was a marginally significant increase in mutation frequency in sperm but this was not dose-dependent. In contrast, acute exposure X-rays led to significant increases in mutation frequency in sperm and blood of exposed males. The results of our study suggest that, within the range of doses analyzed here, the in vivo mutagenic effects of ELF magnetic fields are likely to be minor if not negligible

Assessment of extremely low frequency magnetic field exposure from GSM mobile phones.

Science.gov (United States)

Calderón, Carolina; Addison, Darren; Mee, Terry; Findlay, Richard; Maslanyj, Myron; Conil, Emmanuelle; Kromhout, Hans; Lee, Ae-kyoung; Sim, Malcolm R; Taki, Masao; Varsier, Nadège; Wiart, Joe; Cardis, Elisabeth

2014-04-01

Although radio frequency (RF) electromagnetic fields emitted by mobile phones have received much attention, relatively little is known about the extremely low frequency (ELF) magnetic fields emitted by phones. This paper summarises ELF magnetic flux density measurements on global system for mobile communications (GSM) mobile phones, conducted as part of the MOBI-KIDS epidemiological study. The main challenge is to identify a small number of generic phone models that can be used to classify the ELF exposure for the different phones reported in the study. Two-dimensional magnetic flux density measurements were performed on 47 GSM mobile phones at a distance of 25 mm. Maximum resultant magnetic flux density values at 217 Hz had a geometric mean of 221 (+198/-104) nT. Taking into account harmonic data, measurements suggest that mobile phones could make a substantial contribution to ELF exposure in the general population. The maximum values and easily available variables were poorly correlated. However, three groups could be defined on the basis of field pattern indicating that manufacturers and shapes of mobile phones may be the important parameters linked to the spatial characteristics of the magnetic field, and the categorization of ELF magnetic field exposure for GSM phones in the MOBI-KIDS study may be achievable on the basis of a small number of representative phones. Such categorization would result in a twofold exposure gradient between high and low exposure based on type of phone used, although there was overlap in the grouping. © 2013 Wiley Periodicals, Inc.

Molecular gyroscopes and biological effects of weak extremely low-frequency magnetic fields

International Nuclear Information System (INIS)

Binhi, V.N.; Savin, A.V.

2002-01-01

Extremely low-frequency magnetic fields are known to affect biological systems. In many cases, biological effects display 'windows' in biologically effective parameters of the magnetic fields: most dramatic is the fact that the relatively intense magnetic fields sometimes do not cause appreciable effect, while smaller fields of the order of 10-100 μT do. Linear resonant physical processes do not explain the frequency windows in this case. Amplitude window phenomena suggest a nonlinear physical mechanism. Such a nonlinear mechanism has been proposed recently to explain those 'windows'. It considers the quantum-interference effects on the protein-bound substrate ions. Magnetic fields cause an interference of ion quantum states and change the probability of ion-protein dissociation. This ion-interference mechanism predicts specific magnetic-field frequency and amplitude windows within which the biological effects occur. It agrees with a lot of experiments. However, according to the mechanism, the lifetime Γ -1 of ion quantum states within a protein cavity should be of unrealistic value, more than 0.01 s for frequency band 10-100 Hz. In this paper, a biophysical mechanism has been proposed, which (i) retains the attractive features of the ion interference mechanism, i.e., predicts physical characteristics that might be experimentally examined and (ii) uses the principles of gyroscopic motion and removes the necessity to postulate large lifetimes. The mechanism considers the dynamics of the density matrix of the molecular groups, which are attached to the walls of protein cavities by two covalent bonds, i.e., molecular gyroscopes. Numerical computations have shown almost free rotations of the molecular gyroscopes. The relaxation time due to van der Waals forces was about 0.01 s for the cavity size of 28 Aa

The Biological Effect of Extremely Low Frequency Electromagnetic Fields and Vibrations on Barley Seed Hydration and Germination

Directory of Open Access Journals (Sweden)

Armine Amyan

2004-01-01

Full Text Available The changes of wet and dry weights and germination of barley seed in different periods of its swelling in nontreated (control, extremely low frequency electromagnetic fields (ELF EMF –treated, and extremely low frequency vibrations (ELFV–treated cold (4°C and warm (20°C distilled water (DW were studied. The metabolic-dependent seed hydration, dry weight dissolving, germination, and water binding in seed were modulated by preliminary EMF- and ELFV-treated DW. Frequency “windows” for the effect of EMF and ELFV on seed hydration, solubility, water binding in seed, and germination were discovered. These “windows” were different for EMF and ELFV, as well as in various phases of seed swelling. It is suggested that EMF-induced water structure modification has a different biological effect on the process of seed hydration, solubility, water binding in seed, and germination compared to ELFV.

Correlation analysis of extremely low-frequency variations of the natural electromagnetic Earth field and the problem of detecting periodical gravitational radiation

International Nuclear Information System (INIS)

Balakin, A.B.; Murzakhanov, Z.G.; Grunskaya, L.V.

1994-01-01

A proposal on the experimental detection of extremely low-frequency variations of the electromagnetic Earth field at the gravitational-wave frequency and method for correlation processing results of the experiments are described. 14 refs

A model explaining synchronization of neuron bioelectric frequency under weak alternating low frequency magnetic field

Energy Technology Data Exchange (ETDEWEB)

Moral, A. del, E-mail: delmoral@unizar.es [Laboratorio de Magnetismo, Departamento de Física de Materia Condensada and Instituto de Ciencia de Materiales, Universidad de Zaragoza and Consejo Superior de Investigaciones Científicas, 50009 Zaragoza (Spain); Laboratorio de Magnetobiología, Departamento de Anatomía e Histología, Facultad de Medicina, Universidad de Zaragoza, 50009 Zaragoza (Spain); Centro de Tecnología Biomédica, Universidad Politécnica de Madrid, 28223 Madrid (Spain); Azanza, María J., E-mail: mjazanza@unizar.es [Laboratorio de Magnetobiología, Departamento de Anatomía e Histología, Facultad de Medicina, Universidad de Zaragoza, 50009 Zaragoza (Spain); Centro de Tecnología Biomédica, Universidad Politécnica de Madrid, 28223 Madrid (Spain)

2015-03-01

A biomagnetic-electrical model is presented that explains rather well the experimentally observed synchronization of the bioelectric potential firing rate (“frequency”), f, of single unit neurons of Helix aspersa mollusc under the application of extremely low frequency (ELF) weak alternating (AC) magnetic fields (MF). The proposed model incorporates to our widely experimentally tested model of superdiamagnetism (SD) and Ca{sup 2+} Coulomb explosion (CE) from lipid (LP) bilayer membrane (SD–CE model), the electrical quadrupolar long range interaction between the bilayer LP membranes of synchronized neuron pairs, not considered before. The quadrupolar interaction is capable of explaining well the observed synchronization. Actual extension of our SD–CE-model shows that the neuron firing frequency field, B, dependence becomes not modified, but the bioelectric frequency is decreased and its spontaneous temperature, T, dependence is modified. A comparison of the model with synchronization experimental results of pair of neurons under weak (B{sub 0}≅0.2–15 mT) AC-MF of frequency f{sub M}=50 Hz is reported. From the deduced size of synchronized LP clusters under B, is suggested the formation of small neuron networks via the membrane lipid correlation. - Highlights: • Neuron pair synchronization under low frequency alternating (AC) magnetic field (MF). • Superdiamagnetism and Ca{sup 2+} Coulomb explosion for AC MF effect in synchronized frequency. • Membrane lipid electrical quadrupolar pair interaction as synchronization mechamism. • Good agreement of model with electrophysiological experiments on mollusc Helix neurons.

A model explaining synchronization of neuron bioelectric frequency under weak alternating low frequency magnetic field

International Nuclear Information System (INIS)

Moral, A. del; Azanza, María J.

2015-01-01

A biomagnetic-electrical model is presented that explains rather well the experimentally observed synchronization of the bioelectric potential firing rate (“frequency”), f, of single unit neurons of Helix aspersa mollusc under the application of extremely low frequency (ELF) weak alternating (AC) magnetic fields (MF). The proposed model incorporates to our widely experimentally tested model of superdiamagnetism (SD) and Ca 2+ Coulomb explosion (CE) from lipid (LP) bilayer membrane (SD–CE model), the electrical quadrupolar long range interaction between the bilayer LP membranes of synchronized neuron pairs, not considered before. The quadrupolar interaction is capable of explaining well the observed synchronization. Actual extension of our SD–CE-model shows that the neuron firing frequency field, B, dependence becomes not modified, but the bioelectric frequency is decreased and its spontaneous temperature, T, dependence is modified. A comparison of the model with synchronization experimental results of pair of neurons under weak (B 0 ≅0.2–15 mT) AC-MF of frequency f M =50 Hz is reported. From the deduced size of synchronized LP clusters under B, is suggested the formation of small neuron networks via the membrane lipid correlation. - Highlights: • Neuron pair synchronization under low frequency alternating (AC) magnetic field (MF). • Superdiamagnetism and Ca 2+ Coulomb explosion for AC MF effect in synchronized frequency. • Membrane lipid electrical quadrupolar pair interaction as synchronization mechamism. • Good agreement of model with electrophysiological experiments on mollusc Helix neurons

Effects of an applied low frequency field on the dynamics of a two-level atom interacting with a single-mode field

International Nuclear Information System (INIS)

Xun-Wei, Xu; Nian-Hua, Liu

2010-01-01

The effects of an applied low frequency field on the dynamics of a two-level atom interacting with a single-mode field are investigated. It is shown that the time evolution of the atomic population is mainly controlled by the coupling constants and the frequency of the low frequency field, which leads to a low frequency modulation function for the time evolution of the upper state population. The amplitude of the modulation function becomes larger as the coupling constants increase. The frequency of the modulation function is proportional to the frequency of the low frequency field, and decreases with increasing coupling constant. (classical areas of phenomenology)

Study of extremely low frequency electromagnetic fields in infant incubators.

Science.gov (United States)

Cermáková, Eleonora

2003-01-01

The aim of the work was to present the results of measurements of extremely low frequency electromagnetic fields (ELF EMF), namely the magnetic flux density, inside infant incubators, and to compare these results with the data published by other authors who point out to a possible association between leukemia or other diseases observed in newborns kept in incubators after the birth and the ELF EMF exposure in the incubator. The measured magnetic flux densities were compared with the reference values for this frequency range indicated in the European Union (EU) recommendations. The repeated measurements in incubators were made with a calibrated magnetometer EFA 300 in the frequency range of 5-30 kHz. Effective values of magnetic flux densities of ELF EMF were determined taking account of the reference values. The results of many repeated measurements showing the values of magnetic flux density in modern incubators with plastic supporting frame, were compared with those obtained in old type incubators with iron skeleton. A power frequency of 50 Hz was detected in the incubator and the ELF EMF values were by over two orders lower than the EU reference values. The paper emphasizes the need to take a special care of newborns kept in incubators even if only the sub-reference values are detected. The EU reference values are intended for the adult human population. A baby in an incubator has much smaller dimensions, higher electric conductivity and maybe trigger another mechanism of response to ELF EMF than that indicated in this paper.

Low frequency electric and magnetic fields

Science.gov (United States)

Spaniol, Craig

1989-01-01

Following preliminary investigations of the low frequency electric and magnetic fields that may exists in the Earth-ionospheric cavity, measurements were taken with state-of-the art spectrum analyzers. As a follow up to this activity, an investigation was initiated to determine sources and values for possible low frequency signal that would appear in the cavity. The lowest cavity resonance is estimated at about 8 Hz, but lower frequencies may be an important component of our electromagnetic environment. The potential field frequencies produced by the electron were investigated by a classical model that included possible cross coupling of the electric and gravitation fields. During this work, an interesting relationship was found that related the high frequency charge field with the extremely low frequency of the gravitation field. The results of numerical calculations were surprisingly accurate and this area of investigation is continuing. The work toward continued development of a standardized monitoring facility is continuing with the potential of installing the prototype at West Virginia State College early in 1990. This installation would be capable of real time monitoring of ELF signals in the Earth-ionoshpere cavity and would provide some directional information. A high gain, low noise, 1/f frequency corrected preamplifier was designed and tested for the ferrite core magnetic sensor. The potential application of a super conducting sensor for the ELF magnetic field detection is under investigation. It is hoped that a fully operational monitoring network could pinpoint the location of ELF signal sources and provide new information on where these signals originate and what causes them, assuming that they are natural in origin.

The effect of extremely low frequency electromagnetic fields on the chromosomal instability in bleomycin treated fibroblast cells

International Nuclear Information System (INIS)

Cho, Yoon Hee; Kim, Yang Jee; Lee, Joong Won; Kim, Gye Eun; Chung, Hai Won

2008-01-01

In order to determine the effect of Extremely Low Frequency ElectroMagnetic Fields (ELF-EMF) on the frequency of MicroNuclei (MN), aneuploidy and chromosomal rearrangement induced by BLeoMycin (BLM) in human fibroblast cells, a 60 Hz ELF-EMF of 0.8 mT field strength was applied either alone or with BLM throughout the culture period and a micronucleus-centromere assay was performed. Our results indicate that the frequencies of MN, aneuploidy and chromosomal rearrangement induced by BLM increased in a dose-dependent manner. The exposure of cells to 0.8 mT ELF-EMF followed by BLM exposure for 3 hours led to significant increases in the frequencies of MN and aneuploidy compared to BLM treatment for 3 hours alone (p<0.05), but no significant difference was observed between field exposed and sham exposed control cells. The obtained results suggest that low density ELF-EMF could act as enhancer of the initiation process of BLM rather than as an initiator of mutagenic effects in human fibroblast

Cellular processes involved in human epidermal cells exposed to extremely low frequency electric fields.

Science.gov (United States)

Collard, J-F; Hinsenkamp, M

2015-05-01

We observed on different tissues and organisms a biological response after exposure to pulsed low frequency and low amplitude electric or electromagnetic fields but the precise mechanism of cell response remains unknown. The aim of this publication is to understand, using bioinformatics, the biological relevance of processes involved in the modification of gene expression. The list of genes analyzed was obtained after microarray protocol realized on cultures of human epidermal explants growing on deepidermized human skin exposed to a pulsed low frequency electric field. The directed acyclic graph on a WebGestalt Gene Ontology module shows six categories under the biological process root: "biological regulation", "cellular process", "cell proliferation", "death", "metabolic process" and "response to stimulus". Enriched derived categories are coherent with the type of in vitro culture, the stimulation protocol or with the previous results showing a decrease of cell proliferation and an increase of differentiation. The Kegg module on WebGestalt has highlighted "cell cycle" and "p53 signaling pathway" as significantly involved. The Kegg website brings out interactions between FoxO, MAPK, JNK, p53, p38, PI3K/Akt, Wnt, mTor or NF-KappaB. Some genes expressed by the stimulation are known to have an exclusive function on these pathways. Analyses performed with Pathway Studio linked cell proliferation, cell differentiation, apoptosis, cell cycle, mitosis, cell death etc. with our microarrays results. Medline citation generated by the software and the fold change variation confirms a diminution of the proliferation, activation of the differentiation and a less well-defined role of apoptosis or wound healing. Wnt and DKK functional classes, DKK1, MACF1, ATF3, MME, TXNRD1, and BMP-2 genes proposed in previous publications after a manual analysis are also highlighted with other genes after Pathway Studio automatic procedure. Finally, an analysis conducted on a list of genes

Treatment of patients with vulgar psoriasis through electromagnetic field of extremely low frequency

International Nuclear Information System (INIS)

Batista Romagosa, Maritza; Soriano Gonzalez, Blanca Ines; Bergues Cabrales, Luis Enrique

2012-01-01

A controlled and randomized clinical therapeutical assay in phase III was carried out in 52 patients with vulgar psoriasis, who were assisted in the Dermatology department of 'Dr Joaquin Castillo Duany' Clinical Surgical Hospital in Santiago de Cuba, from 2005 to 2010 who were divided into 2 groups (26 members each): the active group which was conventionally treated with 20% cade ointment; and the experimental group, to which the extremely low frequency electromagnetic field was applied, with the objective of determining the effectiveness of this field in those affected during the periods of crisis and intercrisis. The studied population was clinically characterized by means of a frequency analysis, while the hypothesis tests were used for the evaluation of proportions which null hypothesis were accepted with 5 % as maximum error. In the series the used field was effective to treat the disorder during crisis and more effective than the cade ointment to prolong the intercrisis stage, without causing adverse reactions, so that it constituted a new alternative therapy that can be generalized in the dermatological services of the country, in order to improve the life quality of those who suffer that dermatosis

Pilot study of extremely low frequency magnetic fields emitted by transformers in dwellings. Social aspects.

Science.gov (United States)

Zaryabova, Victoria; Shalamanova, Tsvetelina; Israel, Michel

2013-06-01

A large number of epidemiologic studies examining the potential effect of residential exposure to extremely-low frequency (ELF) magnetic fields and childhood leukemia have been published. Two pooled analyses [Ahlbom A, Day N, Feychting M, Roman E, Skinner J, Dockerty J, Linet M, et al. (2000). A pooled analysis of magnetic fields and childhood leukaemia. Br J Cancer. 83(5):692-698; Greenland S, Sheppard AR, Kaune WT, Poole C, Kelsh AM (2000). A pooled analysis of magnetic fields, wire codes, and childhood leukemia. Epidemiology. 11(6):624-634], which included the major epidemiologic studies on ELF magnetic fields and childhood leukemia showed twofold increase in childhood leukemia risk in association with residential ELF exposure above 0.3-0.4 μT. Based on "limited" epidemiologic evidence linking ELF exposure to childhood leukemia and "inadequate evidence" for carcinogenicity of ELF in rodent bioassays, the International Agency for Research on Cancer (IARC) classified ELF magnetic fields as a possible human carcinogen (2B classification) [International Agency for Research on Cancer (IARC) (2002). Non-ionizing radiation, Part 1: Static and extremely low-frequency (ELF) electric and magnetic fields. IARC monographs on the evaluation of carcinogenic risks to humans. Vol. 80. IARC Press: Lyon], confirmed by WHO on the basis of studies published after 2000 [World Health Organization. Extremely low frequency fields. In: 238 Environmental health criteria, Geneva: WHO; 2007]. The analysis of more recent studies of ELF magnetic fields and childhood leukemia had small findings and propose methodological improvements concerning the uncertainties in epidemiological approaches and exposure assessment, bias in selection of controls [Kheifets L, Oksuzyan S (2008). Exposure assessment and other challenges in non-ionizing radiation studies of childhood leukaemia. Radiat Prot Dosimetry. 132(2):139-147]. By the end of 2010, 37 countries had been identified for possible participation

Activation of Signaling Cascades by Weak Extremely Low Frequency Electromagnetic Fields

Directory of Open Access Journals (Sweden)

Einat Kapri-Pardes

2017-10-01

Full Text Available Background/Aims: Results from recent studies suggest that extremely low frequency magnetic fields (ELF-MF interfere with intracellular signaling pathways related to proliferative control. The mitogen-activated protein kinases (MAPKs, central signaling components that regulate essentially all stimulated cellular processes, include the extracellular signal-regulated kinases 1/2 (ERK1/2 that are extremely sensitive to extracellular cues. Anti-phospho-ERK antibodies serve as a readout for ERK1/2 activation and are able to detect minute changes in ERK stimulation. The objective of this study was to explore whether activation of ERK1/2 and other signaling cascades can be used as a readout for responses of a variety of cell types, both transformed and non-transformed, to ELF-MF. Methods: We applied ELF-MF at various field strengths and time periods to eight different cell types with an exposure system housed in a tissue culture incubator and followed the phosphorylation of MAPKs and Akt by western blotting. Results: We found that the phosphorylation of ERK1/2 is increased in response to ELF-MF. However, the phosphorylation of ERK1/2 is likely too low to induce ELF-MF-dependent proliferation or oncogenic transformation. The p38 MAPK was very slightly phosphorylated, but JNK or Akt were not. The effect on ERK1/2 was detected for exposures to ELF-MF strengths as low as 0.15 µT and was maximal at ∼10 µT. We also show that ERK1/2 phosphorylation is blocked by the flavoprotein inhibitor diphenyleneiodonium, indicating that the response to ELF-MF may be exerted via NADP oxidase similar to the phosphorylation of ERK1/2 in response to microwave radiation. Conclusions: Our results further indicate that cells are responsive to ELF-MF at field strengths much lower than previously suspected and that the effect may be mediated by NADP oxidase. However, the small increase in ERK1/2 phosphorylation is probably insufficient to affect proliferation and oncogenic

A Touch Sensing Technique Using the Effects of Extremely Low Frequency Fields on the Human Body.

Science.gov (United States)

Elfekey, Hatem; Bastawrous, Hany Ayad; Okamoto, Shogo

2016-12-02

Touch sensing is a fundamental approach in human-to-machine interfaces, and is currently under widespread use. Many current applications use active touch sensing technologies. Passive touch sensing technologies are, however, more adequate to implement low power or energy harvesting touch sensing interfaces. This paper presents a passive touch sensing technique based on the fact that the human body is affected by the surrounding extremely low frequency (ELF) electromagnetic fields, such as those of AC power lines. These external ELF fields induce electric potentials on the human body-because human tissues exhibit some conductivity at these frequencies-resulting in what is called AC hum. We therefore propose a passive touch sensing system that detects this hum noise when a human touch occurs, thus distinguishing between touch and non-touch events. The effectiveness of the proposed technique is validated by designing and implementing a flexible touch sensing keyboard.

Low frequency electric and magnetic fields - the topic of cancer

International Nuclear Information System (INIS)

Thommesen, G.

1988-01-01

A review is made of the literature about the biological effects of low frequency electric and magnetic fields. It is still an unsettled question whether extremely low frequency magnetic fields may increase the incidence of cancer. Experimental data arise mainly from exposure to field strengths or frequencies seldom or never encountered by people. The results give no clear explanation to the increase in cancer incidence reported in epidemiological works. The spectre of possible mechanisms imply that no simple dose/effect relationship should be expected, as conflicting mechanisms may dominate at different exposure levels. There is therefore no basis at present for giving numerical value to cancer risk from exposure to low frequency electric or magnetic fields

Extremely low frequency electromagnetic field exposure does not modulate Toll-like receptor signaling in human peripheral blood mononuclear cells

NARCIS (Netherlands)

Kleijn, de S.; Bouwens, M.; Verburg-van Kemenade, B.M.L.; Cuppen, J.J.M.; Ferwerda, G.; Hermans, P.

2011-01-01

The effects of extremely low frequency electromagnetic fields (ELF-EMF) on human health remain unclear. It has been reported that ELF-EMF may modulate the innate immune response to microorganisms in animal models and mammalian cell-lines. With the recently gained insight in innate immune signaling

Characterization of extremely low frequency magnetic fields from diesel, gasoline and hybrid cars under controlled conditions.

Science.gov (United States)

Hareuveny, Ronen; Sudan, Madhuri; Halgamuge, Malka N; Yaffe, Yoav; Tzabari, Yuval; Namir, Daniel; Kheifets, Leeka

2015-01-30

This study characterizes extremely low frequency (ELF) magnetic field (MF) levels in 10 car models. Extensive measurements were conducted in three diesel, four gasoline, and three hybrid cars, under similar controlled conditions and negligible background fields. Averaged over all four seats under various driving scenarios the fields were lowest in diesel cars (0.02 μT), higher for gasoline (0.04-0.05 μT) and highest in hybrids (0.06-0.09 μT), but all were in-line with daily exposures from other sources. Hybrid cars had the highest mean and 95th percentile MF levels, and an especially large percentage of measurements above 0.2 μT. These parameters were also higher for moving conditions compared to standing while idling or revving at 2500 RPM and higher still at 80 km/h compared to 40 km/h. Fields in non-hybrid cars were higher at the front seats, while in hybrid cars they were higher at the back seats, particularly the back right seat where 16%-69% of measurements were greater than 0.2 μT. As our results do not include low frequency fields (below 30 Hz) that might be generated by tire rotation, we suggest that net currents flowing through the cars' metallic chassis may be a possible source of MF. Larger surveys in standardized and well-described settings should be conducted with different types of vehicles and with spectral analysis of fields including lower frequencies due to magnetization of tires.

Treatment of Diabetic Foot Ulcers through Systemic Effects of Extremely Low Frequency Electromagnetic Fields

Science.gov (United States)

Trejo-Núñez, A. D.; Pérez-Chávez, F.; García-Sánchez, C.; Serrano-Luna, G.; Cañendo-Dorantes, L.

2008-08-01

This study was designed to, investigate the healing effects of extremely low frequency electromagnetic fields (ELF-EMF) on diabetic foot ulcers and test two different exposure systems aimed at reducing the ELF-EMF exposure time of patients. In the first system the ELF-EMF were applied to the arm where only 3% of the total blood volume/min circulates at any given time. In the second system the ELF-EMF were applied to the thorax where more than 100% of the total blood volume/minute circulates at any given time. Twenty-six diabetic patients, with superficial neuropathic ulcers unresponsive to medical treatment were included in this preliminary report. In the first group (17 patients), the arm was exposed two hours twice a week to a extremely low frequency electromagnetic field of 0.45-0.9 mTrms, 120 Hz generated inside a solenoid coil of 10.1 cm by 20.5 cm long. In the second group the thorax of 7 patients was exposed 25 minutes twice a week to an electromagnetic field of 0.4-0.85 mTrms, 120 Hz generated in the center of a squared quasi-Helmholtz coil 52 cm by side. One patient was assigned to a placebo configuration of each exposure system with identical appearance as the active equipment but without magnetic field. Patients with deep ulcers, infected ulcers, cancer, or auto-immune disease were excluded. These preliminary results showed that the two exposure systems accelerate the healing process of neuropathic ulcers. Complete healing of the ulcer had a median duration of 90 days in both exposure systems. Therefore thorax exposure where more blood is exposed to ELF-EMF per unit of time was able to reduce 4.8 times the patient treatment time. In those patients assigned to the placebo equipment no healing effects were observed. This study will continue with a parallel, double blind placebo controlled protocol.

Extreme Low Frequency Acoustic Measurement System

Science.gov (United States)

Shams, Qamar A. (Inventor); Zuckerwar, Allan J. (Inventor)

2017-01-01

The present invention is an extremely low frequency (ELF) microphone and acoustic measurement system capable of infrasound detection in a portable and easily deployable form factor. In one embodiment of the invention, an extremely low frequency electret microphone comprises a membrane, a backplate, and a backchamber. The backchamber is sealed to allow substantially no air exchange between the backchamber and outside the microphone. Compliance of the membrane may be less than ambient air compliance. The backplate may define a plurality of holes and a slot may be defined between an outer diameter of the backplate and an inner wall of the microphone. The locations and sizes of the holes, the size of the slot, and the volume of the backchamber may be selected such that membrane motion is substantially critically damped.

LEVELS OF EXTREMELY LOW-FREQUENCY ELECTRIC AND MAGNETIC FIELDS FROM OVERHEAD POWER LINES IN THE OUTDOOR ENVIRONMENT OF RAMALLAH CITY-PALESTINE.

Science.gov (United States)

Abuasbi, Falastine; Lahham, Adnan; Abdel-Raziq, Issam Rashid

2018-05-01

In this study, levels of extremely low-frequency electric and magnetic fields originated from overhead power lines were investigated in the outdoor environment in Ramallah city, Palestine. Spot measurements were applied to record fields intensities over 6-min period. The Spectrum Analyzer NF-5035 was used to perform measurements at 1 m above ground level and directly underneath 40 randomly selected power lines distributed fairly within the city. Levels of electric fields varied depending on the line's category (power line, transformer or distributor), a minimum mean electric field of 3.9 V/m was found under a distributor line, and a maximum of 769.4 V/m under a high-voltage power line (66 kV). However, results of electric fields showed a log-normal distribution with the geometric mean and the geometric standard deviation of 35.9 and 2.8 V/m, respectively. Magnetic fields measured at power lines, on contrast, were not log-normally distributed; the minimum and maximum mean magnetic fields under power lines were 0.89 and 3.5 μT, respectively. As a result, none of the measured fields exceeded the ICNIRP's guidelines recommended for general public exposures to extremely low-frequency fields.

Measurement procedure to assess exposure to extremely low-frequency fields: A primary school case study

International Nuclear Information System (INIS)

Alonso, A.; Bahillo, A.; De la Rosa, R.; Carrera, A.; Duran, R. J.; Fernandez, P.

2012-01-01

How to correctly measure the exposure of general public to extremely low-frequency (ELF) radiation is a key issue for ELF epidemiological studies. This paper proposes a measurement procedure to accurately assess the exposure of people to electric and magnetic field in the frequency band from 5 Hz to 100 kHz in buildings and their premises. As ELF radiation could be particularly harmful to children, the measurement procedure is focused on exposure to ELF in schools. Thus, the students' exposure to ELF fields can be assessed by correlating the ELF measurements to the hours of school activity. In this paper, the measurement protocol was applied to study the ELF exposure on students from Garcia Quintana primary school in Valladolid, Spain. The campaign of measurements for ELF exposure assessment in this primary school was of great interest for the Regional Council of Public Health because of the social alarm generated by the presence of a significant number cancer cases in children. (authors)

An investigation into the vector ellipticity of extremely low frequency magnetic fields from appliances in UK homes

International Nuclear Information System (INIS)

Ainsbury, Elizabeth A; Conein, Emma; Henshaw, Denis L

2005-01-01

Elliptically polarized magnetic fields induce higher currents in the body compared with their plane polarized counterparts. This investigation examines the degree of vector ellipticity of extremely low frequency magnetic fields (ELF-MFs) in the home, with regard to the adverse health effects reportedly associated with ELF-MFs, for instance childhood leukaemia. Tri-axial measurements of the magnitude and phase of the 0-3000 Hz magnetic fields, produced by 226 domestic mains-fed appliances of 32 different types, were carried out in 16 homes in Worcestershire in the summer of 2004. Magnetic field strengths were low, with average (RMS) values of 0.03 ± 0.02 μT across all residences. In contrast, background field ellipticities were high, on average 47 ± 11%. Microwave and electric ovens produced the highest ellipticities: mean respective values of 21 ± 21% and 21 ± 17% were observed 20 cm away from these appliances. There was a negative correlation between field strength and field polarization, which we attribute to the higher relative field contribution close to each individual (single-phase) appliance. The measurements demonstrate that domestic magnetic fields are extremely complex and cannot simply be characterized by traditional measurements such as time-weighted average or peak exposure levels. We conclude that ellipticity should become a relevant metric for future epidemiological studies of health and ELF-MF exposure

Evaluation of changes in the behavior of the grey seal exposed to the electromagnetic field of extremely low frequencies (0.01–36 Hz

Directory of Open Access Journals (Sweden)

Yakovlev A. P.

2016-03-01

Full Text Available The paper presents the initial results of researching influence of low frequency electromagnetic field on the behavior of the grey seal. The authors have defined the frequency characteristics of the electromagnetic field which being exposed cause the changes in the behavior of the animal (the greatest deviation from the background values. The methodology of the experiment has been worked out and the criteria of evaluation of changes in the grey seal behavior in response to the electromagnetic field exposure with extremely low frequency characteristics have been proposed

A short-term extremely low frequency electromagnetic field exposure increases circulating leukocyte numbers and affects HPA-axis signaling in mice

NARCIS (Netherlands)

Kleijn, de Stan; Ferwerda, Gerben; Wiese, Michelle; Trentelman, Jos; Cuppen, Jan; Kozicz, Tamas; Jager, de Linda; Hermans, Peter W.M.; Kemenade, van Lidy

2016-01-01

There is still uncertainty whether extremely low frequency electromagnetic fields (ELF-EMF) can induce health effects like immunomodulation. Despite evidence obtained in vitro, an unambiguous association has not yet been established in vivo. Here, mice were exposed to ELF-EMF for 1, 4, and 24

Extremely low-frequency magnetic fields of transformers and possible biological and health effects.

Science.gov (United States)

Sirav, Bahriye; Sezgin, Gaye; Seyhan, Nesrin

2014-12-01

Physiological processes in organisms can be influenced by extremely low-frequency (ELF) electromagnetic energy. Biological effect studies have great importance; as well as measurement studies since they provide information on the real exposure situations. In this study, the leakage magnetic fields around a transformer were measured in an apartment building in Küçükçekmece, Istanbul, and the measurement results were evaluated with respect to the international exposure standards. The transformer station was on the bottom floor of a three-floor building. It was found that people living and working in the building were exposed to ELF magnetic fields higher than the threshold magnetic field value of the International Agency for Research on Cancer (IARC). Many people living in this building reported health complaints such as immunological problems of their children. There were child-workers working in the textile factories located in the building. Safe distances or areas for these people should be recommended. Protective measures could be implemented to minimize these exposures. Further residential exposure studies are needed to demonstrate the exposure levels of ELF magnetic fields. Precautions should, therefore, be taken either to reduce leakage or minimize the exposed fields. Shielding techniques should be used to minimize the leakage magnetic fields in such cases.

Domain Decomposition for Computing Extremely Low Frequency Induced Current in the Human Body

OpenAIRE

Perrussel , Ronan; Voyer , Damien; Nicolas , Laurent; Scorretti , Riccardo; Burais , Noël

2011-01-01

International audience; Computation of electromagnetic fields in high resolution computational phantoms requires solving large linear systems. We present an application of Schwarz preconditioners with Krylov subspace methods for computing extremely low frequency induced fields in a phantom issued from the Visible Human.

The Source of Variation in Policies around the World: The Case of Protection of Human Health from Extremely Low Frequency Electromagnetic Fields

International Nuclear Information System (INIS)

Kandel, S.

2006-01-01

Scientific evidence supposedly plays a dominant role in environmental and public health regulation. This paper uses the example of Extremely Low Frequency Electromagnetic Fields regulation to test whether this is indeed the case. The paper first shows that there exists a significant variation in health protection policies for Extremely Low Frequencies Extremely Low Frequency Electromagnetic Fields around the world. Some countries adopt the international scientific-based guidelines while other countries choose to apply additional precautionary regulations of varying severity. Electromagnetic Fields policy makers around the world indicate that the Cost Benefit Analysis is one of the parameters considered for their choice among various policy options. A simple Cost Benefit Analysis framework is presented, utilizing scientific evidence on health risks from Extremely Low Frequencies as well as parameter values used in the Cost Benefit Analysis studies from California, Netherlands, Israel, and the United Kingdom to determine the justification of using several mitigation techniques. This Cost Benefit Analysis using data from the different countries leads to a clear conclusion: under all parameter values considered, only the low cost intervention measures, such as re-phasing and compacting lines, are justified. Re-routing lines, except in cases of very close proximity to residences, and under grounding existing lines cannot be justified due to the high costs involved and the small health benefits that are projected. Since the stringent policies cannot be accomplished with the low-cost measures, this suggests that if the Cost Benefit Analysis were indeed the basis for the policies implemented in different countries, one would expect a smaller variation in the worldwide policies observed today. The divergence between the policies that are implemented and those that can be supported by the Cost Benefit Analysis suggests that the Cost Benefit Analysis is either not used to

Effect of extremely low frequency electromagnetic field on brain histopathology of Caspian Sea Cyprinus carpio.

Science.gov (United States)

Samiee, Farzaneh; Samiee, Keivandokht

2017-01-01

There is limited research on the effect of electromagnetic field on aquatic organisms, especially freshwater fish species. This study was conducted to evaluate the effect of extremely low frequency electromagnetic field (ELF-EMF) (50 Hz) exposure on brain histopathology of Cyprinus carpio, one of the important species of Caspian Sea with significant economic value. A total of 200 healthy fish were used in this study. They were classified randomly in two groups: sham-exposed group and experimental group, which were exposed to five different magnetic field intensities (0.1, 1, 3, 5, and 7 mT) at two different exposure times (0.5 and 1 h). Histologic results indicate that exposure of C. carpio to artificial ELF-EMF caused severe histopathological changes in the brain at field intensities ≥3 mT leading to brain necrosis. Field intensity and duration of exposure were key parameters in induction of lesion in the brain. Further studies are needed to elucidate exact mechanism of EMF exposure on the brain.

Exposure of Extremely-Low Frequency (ELF magnetic field may cause human cancer

Directory of Open Access Journals (Sweden)

Daryoush Shahbazi-Gahrouei

2017-01-01

Full Text Available Introduction: Chronic exposure of non-ionizing extremely low-frequency magnetic fields (ELF-EMF is considered as a health hazard due to its adverse effects on human body such as generation of any type of cancer. Stem cells are appropriate models to assess the effects of ELF-EMF on other cell lines and human beings. Materials and methods: Adipose tissue has been known as source of multi potent stromal human mesenchymal stem cells (MSCs which can be obtained in less invasive method and in large amounts; so adipose-derived stem cells (ADSCs were used in this study. Effect of ELF-EMF (intensities of 0.5 and 1 mT and 50 Hz on proliferation rate of hADSCs was assessed in 20 and 40 min per day for 7 days. Trypan blue assay was performed to assess cell proliferation rate. Result: The results shown that 0.5 and 1 mT magnetic fields can promote the proliferation rate of adipose derived hMSCs according to the duration of exposure. Conclusion: These outcomes could approve the effect of ELF-EMF on cancer induction; although the effective mechanisms in this process are still unknown.

An investigation into the vector ellipticity of extremely low frequency magnetic fields from appliances in UK homes

Science.gov (United States)

Ainsbury, Elizabeth A.; Conein, Emma; Henshaw, Denis L.

2005-07-01

Elliptically polarized magnetic fields induce higher currents in the body compared with their plane polarized counterparts. This investigation examines the degree of vector ellipticity of extremely low frequency magnetic fields (ELF-MFs) in the home, with regard to the adverse health effects reportedly associated with ELF-MFs, for instance childhood leukaemia. Tri-axial measurements of the magnitude and phase of the 0-3000 Hz magnetic fields, produced by 226 domestic mains-fed appliances of 32 different types, were carried out in 16 homes in Worcestershire in the summer of 2004. Magnetic field strengths were low, with average (RMS) values of 0.03 ± 0.02 µT across all residences. In contrast, background field ellipticities were high, on average 47 ± 11%. Microwave and electric ovens produced the highest ellipticities: mean respective values of 21 ± 21% and 21 ± 17% were observed 20 cm away from these appliances. There was a negative correlation between field strength and field polarization, which we attribute to the higher relative field contribution close to each individual (single-phase) appliance. The measurements demonstrate that domestic magnetic fields are extremely complex and cannot simply be characterized by traditional measurements such as time-weighted average or peak exposure levels. We conclude that ellipticity should become a relevant metric for future epidemiological studies of health and ELF-MF exposure. This work is supported by the charity CHILDREN with LEUKAEMIA, registered charity number 298405.

Extremely low frequency electromagnetic field radiation: a preliminary study case in Bangi

International Nuclear Information System (INIS)

Roha Tukimin; Wan Nor Liza Mahadi; Mohd Yusof Mohd Ali; Mohd Amirul Nizam Mohd Thari; Mohd Azizi Jali; Ahmad Fadhil Ahmad Sanusi

2008-08-01

Extremely low frequency electromagnetic fields radiation is known to be hazardous if amount received is excessive. The primary sources of ELF EMF are from the electricity supply system such as transmission line, substation, transformers and switch gears. Due to limited space, many substations were built very close to the residential area. A study was carried out in the selected houses located in Bangi, Selangor which located close to the TNB substation. The study was made in two conditions, before the area fully occupied and after the resident moved into the house. The aim of the study is for assessing the strength of ELF EMF that emitted by the substation. This study was also conducted to assess the potential exposure received by personnel living in the house. The surveys were carried out using PMM model EHP50A and EMDEX instruments based on standard measurement procedures and protocol recommended by IEEE. Results obtained were compared against the permissible exposure limits recommended by International Commission of Non-Ionising Radiation Protection (ICNIRP).This paper highlights some of the findings at the study site. Results obtained suggest that ELF EMF radiation varies with location and the magnetic fields strength measured near the source of ELF EMF was found to be higher than the normal environment. (Author)

Effect of extremely low frequency electromagnetic fields on growth rate and morphology of bacteria.

Science.gov (United States)

Inhan-Garip, Ayse; Aksu, Burak; Akan, Zafer; Akakin, Dilek; Ozaydin, A Nilufer; San, Tangul

2011-12-01

To determine the effect of extremely low frequency (bacteria and to determine any morphological changes that might have been caused by ELF-EMF. Six bacterial strains, three Gram-negative and three Gram-positive were subjected to 50 Hz, 0.5 mT ELF-EMF for 6 h. To determine growth rate after ELF-EMF application, bacteria exposed to ELF-EMF for 3 h were collected, transferred to fresh medium and cultured without field application for another 4 h. Growth-rate was determined by optical density (OD) measurements made every hour. Morphological changes were determined with Transmission electron microscopy (TEM) for two gram-negative and two gram-positive strains collected after 3 h of field application. A decrease in growth rate with respect to control samples was observed for all strains during ELF-EMF application. The decrease in growth-rate continued when exposed bacteria were cultured without field application. Significant ultrastructural changes were observed in all bacterial strains, which were seen to resemble the alterations caused by cationic peptides. This study shows that ELF-EMF induces a decrease in growth rate and morphological changes for both Gram-negative and Gram-positive bacteria.

[Influence of extremely low frequency magnetic field on total protein and -sh groups concentrations in liver homogenates].

Science.gov (United States)

Ciejka, Elżbieta; Kowalczyk, Agata; Gorąca, Anna

2014-01-01

Free radicals are atoms, molecules or their fragments, whose excess leads to the development of oxidative stress, the cause of many neoplastic, neurodegenerative and inflammatory diseases, as well as aging of organisms. Industrial pollution, tobacco smoke, ionizing radiation, ultrasound and magnetic fields are the major exogenous sources of free radicals. The low frequency mag- netic field is commonly applied in physiotherapy. The aim of the present study was to evaluate the effect of extremely low frequency magnetic field (1L.F-MF) on the concentration ofsullhydryl groups (-SH) and proteins in liver tissues of experimental animals de- pending on the time of exposure to the field. Twenty one Sprague-D)awley male rats, aged 3-4 months were randomly divided into 3 experimental groups (each containing 7 animals): controls (group I), the rats exposed to IEI.F-MF of 40 Hz, 7 mT (this kind of the ELF-MF is mostly used in magnetotherapy), 30 min/day for 2 weeks (group II) and the rats exposed to 40 Hz, 7 mT for 60 min/day for 2 weeks (group III). The concentrations of proteins and sulfhydryl groups in the liver tissues were determined after exposure to magnetic fields. Exposure to low magnetic field: 40 Hz, 7 mT for 30 min/day and 60 min/day for 2 weeks caused a significant increase in the concentration of-SH groups and total protein levels in the liver tissues. The study results suggest that exposure to magnetic fields leads to the development of adaptive mechanisms to maintain the balance in the body oxidation-reduction and in the case of the studied parameters does not depend on the time of exposure.

Millimeter waves or extremely high frequency electromagnetic fields in the environment: what are their effects on bacteria?

Science.gov (United States)

Soghomonyan, Diana; Trchounian, Karen; Trchounian, Armen

2016-06-01

Millimeter waves (MMW) or electromagnetic fields of extremely high frequencies at low intensity is a new environmental factor, the level of which is increased as technology advance. It is of interest that bacteria and other cells might communicate with each other by electromagnetic field of sub-extremely high frequency range. These MMW affected Escherichia coli and many other bacteria, mainly depressing their growth and changing properties and activity. These effects were non-thermal and depended on different factors. The significant cellular targets for MMW effects could be water, cell plasma membrane, and genome. The model for the MMW interaction with bacteria is suggested; a role of the membrane-associated proton FOF1-ATPase, key enzyme of bioenergetic relevance, is proposed. The consequences of MMW interaction with bacteria are the changes in their sensitivity to different biologically active chemicals, including antibiotics. Novel data on MMW effects on bacteria and their sensitivity to different antibiotics are presented and discussed; the combined action of MMW and antibiotics resulted with more strong effects. These effects are of significance for understanding changed metabolic pathways and distinguish role of bacteria in environment; they might be leading to antibiotic resistance in bacteria. The effects might have applications in the development of technique, therapeutic practices, and food protection technology.

Prediction of the Low Frequency Wave Field on Open Coastal Beaches

National Research Council Canada - National Science Library

Ozkan-Haller, H. T

2005-01-01

... (both abrupt and gradual) affect the resulting low frequency wave climate. 3. The assessment of the importance of interactions between different modes of time-varying motions in the nearshore region, as well as interactions between these modes and the incident wave field. 4. To arrive at a predictive understanding of low frequency motions.

Benign Effect of Extremely Low-Frequency Electromagnetic Field on Brain Plasticity Assessed by Nitric Oxide Metabolism during Poststroke Rehabilitation

Directory of Open Access Journals (Sweden)

Natalia Cichoń

2017-01-01

Full Text Available Nitric oxide (NO is one of the most important signal molecules, involved in both physiological and pathological processes. As a neurotransmitter in the central nervous system, NO regulates cerebral blood flow, neurogenesis, and synaptic plasticity. The aim of our study was to investigate the effect of the extremely low-frequency electromagnetic field (ELF-EMF on generation and metabolism of NO, as a neurotransmitter, in the rehabilitation of poststroke patients. Forty-eight patients were divided into two groups: ELF-EMF and non-ELF-EMF. Both groups underwent the same 4-week rehabilitation program. Additionally, the ELF-EMF group was exposed to an extremely low-frequency electromagnetic field of 40 Hz, 7 mT, for 15 min/day. Levels of 3-nitrotyrosine, nitrate/nitrite, and TNFα in plasma samples were measured, and NOS2 expression was determined in whole blood samples. Functional status was evaluated before and after a series of treatments, using the Activity Daily Living, Geriatric Depression Scale, and Mini-Mental State Examination. We observed that application of ELF-EMF significantly increased 3-nitrotyrosine and nitrate/nitrite levels, while expression of NOS2 was insignificantly decreased in both groups. The results also show that ELF-EMF treatments improved functional and mental status. We conclude that ELF-EMF therapy is capable of promoting recovery in poststroke patients.

Numerical study of induced current perturbations in the vicinity of excitable cells exposed to extremely low frequency magnetic fields

International Nuclear Information System (INIS)

Hassan, Noha; Chatterjee, Indira; Publicover, Nelson G; Craviso, Gale L

2003-01-01

Realistic three-dimensional cell morphologies were modelled to determine the current density induced in excitable cell culture preparations exposed to 60 Hz magnetic fields and to identify important factors that can influence the responses of cells to these fields. Cell morphologies representing single spherical adrenal chromaffin cells, single elongated smooth muscle cells and chromaffin cell aggregates in a Petri dish containing culture medium were modelled using the finite element method. The computations for a spherical cell revealed alterations in the magnitude and spatial distribution of the induced current density in the immediate vicinity of the cell. Maxima occurred at the equatorial sides and minima at the poles. Proximity of cells to each other as well as cell aggregate shape, size and orientation with respect to the induced current influenced the magnitude and spatial distribution of the induced current density. For an elongated cell, effects on the induced current density were highly dependent on cell orientation with respect to the direction of the induced current. These results provide novel insights into the perturbations in induced current that occur in excitable cell culture preparations and lay a foundation for understanding the mechanisms of interaction with extremely low frequency magnetic fields at the tissue level

DNA fragmentation in human fibroblasts under extremely low frequency electromagnetic field exposure

International Nuclear Information System (INIS)

Focke, Frauke; Schuermann, David; Kuster, Niels; Schaer, Primo

2010-01-01

Extremely low frequency electromagnetic fields (ELF-EMFs) were reported to affect DNA integrity in human cells with evidence based on the Comet assay. These findings were heavily debated for two main reasons; the lack of reproducibility, and the absence of a plausible scientific rationale for how EMFs could damage DNA. Starting out from a replication of the relevant experiments, we performed this study to clarify the existence and explore origin and nature of ELF-EMF induced DNA effects. Our data confirm that intermittent (but not continuous) exposure of human primary fibroblasts to a 50 Hz EMF at a flux density of 1 mT induces a slight but significant increase of DNA fragmentation in the Comet assay, and we provide first evidence for this to be caused by the magnetic rather than the electric field. Moreover, we show that EMF-induced responses in the Comet assay are dependent on cell proliferation, suggesting that processes of DNA replication rather than the DNA itself may be affected. Consistently, the Comet effects correlated with a reduction of actively replicating cells and a concomitant increase of apoptotic cells in exposed cultures, whereas a combined Fpg-Comet test failed to produce evidence for a notable contribution of oxidative DNA base damage. Hence, ELF-EMF induced effects in the Comet assay are reproducible under specific conditions and can be explained by minor disturbances in S-phase processes and occasional triggering of apoptosis rather than by the generation of DNA damage.

DNA fragmentation in human fibroblasts under extremely low frequency electromagnetic field exposure

Energy Technology Data Exchange (ETDEWEB)

Focke, Frauke; Schuermann, David [Institute of Biochemistry and Genetics, Department of Biomedicine, University of Basel, Mattenstrasse 28, CH-4058 Basel (Switzerland); Kuster, Niels [IT' IS Foundation, Zeughausstrasse 43, CH-8004 Zurich (Switzerland); Schaer, Primo, E-mail: primo.schaer@unibas.ch [Institute of Biochemistry and Genetics, Department of Biomedicine, University of Basel, Mattenstrasse 28, CH-4058 Basel (Switzerland)

2010-01-05

Extremely low frequency electromagnetic fields (ELF-EMFs) were reported to affect DNA integrity in human cells with evidence based on the Comet assay. These findings were heavily debated for two main reasons; the lack of reproducibility, and the absence of a plausible scientific rationale for how EMFs could damage DNA. Starting out from a replication of the relevant experiments, we performed this study to clarify the existence and explore origin and nature of ELF-EMF induced DNA effects. Our data confirm that intermittent (but not continuous) exposure of human primary fibroblasts to a 50 Hz EMF at a flux density of 1 mT induces a slight but significant increase of DNA fragmentation in the Comet assay, and we provide first evidence for this to be caused by the magnetic rather than the electric field. Moreover, we show that EMF-induced responses in the Comet assay are dependent on cell proliferation, suggesting that processes of DNA replication rather than the DNA itself may be affected. Consistently, the Comet effects correlated with a reduction of actively replicating cells and a concomitant increase of apoptotic cells in exposed cultures, whereas a combined Fpg-Comet test failed to produce evidence for a notable contribution of oxidative DNA base damage. Hence, ELF-EMF induced effects in the Comet assay are reproducible under specific conditions and can be explained by minor disturbances in S-phase processes and occasional triggering of apoptosis rather than by the generation of DNA damage.

Influence of extremely low frequency magnetic field on total protein and –SH groups concentrations in liver homogenates

Directory of Open Access Journals (Sweden)

Elżbieta Ciejka

2014-10-01

Full Text Available Background: Free radicals are atoms, molecules or their fragments, whose excess leads to the development of oxidative stress, the cause of many neoplastic, neurodegenerative and inflammatory diseases, as well as aging of organisms. Industrial pollution, tobacco smoke, ionizing radiation, ultrasound and magnetic fields are the major exogenous sources of free radicals. The low frequency magnetic field is commonly applied in physiotherapy. The aim of the present study was to evaluate the effect of extremely low frequency magnetic field (ELF-MF on the concentration of sulfhydryl groups (–SH and proteins in liver tissues of experimental animals depending on the time of exposure to the field. Material and Methods: Twenty one Sprague-Dawley male rats, aged 3–4 months were randomly divided into 3 experimental groups (each containing 7 animals: controls (group I, the rats exposed to ELF-MF of 40 Hz, 7 mT (this kind of the ELF-MF is mostly used in magnetotherapy, 30 min/day for 2 weeks (group II and the rats exposed to 40 Hz, 7 mT for 60 min/day for 2 weeks (group III. The concentrations of proteins and sulfhydryl groups in the liver tissues were determined after exposure to magnetic fields. Results: Exposure to low magnetic field: 40 Hz, 7 mT for 30 min/day and 60 min/day for 2 weeks caused a significant increase in the concentration of –SH groups and total protein levels in the liver tissues. Conclusions: The study results suggest that exposure to magnetic fields leads to the development of adaptive mechanisms to maintain the balance in the body oxidation-reduction and in the case of the studied parameters does not depend on the time of exposure. Med Pr 2014;65(5:639–644

Efficacy of extremely low-frequency magnetic field in fibromyalgia pain: A pilot study.

Science.gov (United States)

Paolucci, Teresa; Piccinini, Giulia; Iosa, Marco; Piermattei, Cristina; de Angelis, Simona; Grasso, Maria Rosaria; Zangrando, Federico; Saraceni, Vincenzo Maria

2016-01-01

The purpose of this pilot study was to determine the efficacy of an extremely low-frequency magnetic field (ELF-MF) in decreasing chronic pain in fibromyalgia (FM) patients. Thirty-seven females were recruited and randomized into two groups: one group was first exposed to systemic ELF-MF therapy (100 microtesla, 1 to 80 Hz) and then to sham therapy, and the other group received the opposite sequence of intervention. Pain, FM-related symptoms, and the ability to perform daily tasks were measured using the Visual Analog Scale, Fibromyalgia Impact Questionnaire (FIQ), Fibromyalgia Assessment Scale (FAS), and Health Assessment Questionnaire (HAQ) at baseline, end of first treatment cycle, beginning of second treatment cycle (after 1 mo washout), end of second treatment cycle, and end of 1 mo follow-up. ELF-MF treatment significantly reduced pain, which increased on cessation of therapy but remained significantly lower than baseline levels. Short-term benefits were also observed in FIQ, FAS, and HAQ scores, with less significant effects seen in the medium term. ELF-MF therapy can be recommended as part of a multimodal approach for mitigating pain in FM subjects and improving the efficacy of drug therapy or physiotherapy.

Neuronal cellular responses to extremely low frequency electromagnetic field exposure: implications regarding oxidative stress and neurodegeneration.

Directory of Open Access Journals (Sweden)

Marcella Reale

Full Text Available Neurodegenerative diseases comprise both hereditary and sporadic conditions characterized by an identifying progressive nervous system dysfunction and distinctive neuopathophysiology. The majority are of non-familial etiology and hence environmental factors and lifestyle play key roles in their pathogenesis. The extensive use of and ever increasing worldwide demand for electricity has stimulated societal and scientific interest on the environmental exposure to low frequency electromagnetic fields (EMFs on human health. Epidemiological studies suggest a positive association between 50/60-Hz power transmission fields and leukemia or lymphoma development. Consequent to the association between EMFs and induction of oxidative stress, concerns relating to development of neurodegenerative diseases, such as Alzheimer disease (AD, have been voiced as the brain consumes the greatest fraction of oxygen and is particularly vulnerable to oxidative stress. Exposure to extremely low frequency (ELF-EMFs are reported to alter animal behavior and modulate biological variables, including gene expression, regulation of cell survival, promotion of cellular differentiation, and changes in cerebral blood flow in aged AD transgenic mice. Alterations in inflammatory responses have also been reported, but how these actions impact human health remains unknown. We hence evaluated the effects of an electromagnetic wave (magnetic field intensity 1 mT; frequency, 50-Hz on a well-characterized immortalized neuronal cell model, human SH-SY5Y cells. ELF-EMF exposure elevated the expession of NOS and O2(-, which were countered by compensatory changes in antioxidant catylase (CAT activity and enzymatic kinetic parameters related to CYP-450 and CAT activity. Actions of ELF-EMFs on cytokine gene expression were additionally evaluated and found rapidly modified. Confronted with co-exposure to H2O2-induced oxidative stress, ELF-EMF proved not as well counteracted and resulted in a

Investigation of exposure to Extremely Low Frequency (ELF) magnetic and electric fields: Ongoing animal studies

Energy Technology Data Exchange (ETDEWEB)

Anderson, L.E.

1994-03-01

There is now convincing evidence from a large number of laboratories, that exposure to extremely low frequency (ELF) magnetic and electric fields produces biological responses in animals. Many of the observed effects appear to be directly or indirectly associated with the neural or neuroendocrine systems. Such effects include increased neuronal excitability, chemical and hormonal changes in the nervous system, altered behavioral responses, some of which are related to sensing the presence of the field, and changes in endogenous biological rhythms. Additional indices of general physiological status appear relatively unaffected by exposure, although effects have occasionally been described in bone growth and fracture repair, reproduction and development, and immune system function. A major current emphasis in laboratory research is to determine whether or not the reported epidemiological studies that suggest an association between EMF exposure and risk of cancer are supported in studies using animal models. Three major challenges exist for ongoing research: (1) knowledge about the mechanisms underlying observed bioeffects is incomplete, (2) researchers do not as yet understand what physical aspects of exposure produce biological responses, and (3) health consequences resulting from ELF exposure are unknown. Although no animal studies clearly demonstrate deleterious effects of ELF fields, several are suggestive of potential health impacts. From the perspective of laboratory animal studies, this paper will discuss biological responses to ELF magnetic and/or electric field exposures.

Effects of extremely low frequency electromagnetic field on the health of workers in automotive industry.

Science.gov (United States)

Liu, Xin; Zhao, Longyu; Yu, Duo; Ma, Shumei; Liu, Xiaodong

2013-12-01

To observe the effects of extremely low frequency electromagnetic fields (ELF-EMFs) in automotive industry on occupational workers. A total of 704 workers were investigated, and 374 workers were chosen and divided into two groups (control group and exposure group) according to the inclusive criteria, namely male with age 20-40 years old and ≥ 2 years of exposure. The intensities of ELF-EMFs and noise were detected with EFA-300 Field Analyzer (Narda company, Pfullingen, Germany) and AWA5610D integrating sound level meter (Hangzhou Aihua Instruments Co., Ltd, Hangzhou, China), respectively. Survey data were collected by questionnaire, and the physical check-up was done in hospital. All the data were input into SPSS17.0 software (SPSS Inc, Chicago, USA), and the appropriate statistic analyses were carried out. The intensity of EMFs in exposure group was significantly higher than that in control group (p 0.05). The survey data collected by questionnaires showed that the symptoms of loss of hair in exposure group were significantly different as compared with that in control group (p effects on the nervous, cardiovascular, liver, and hematology system of workers.

Deficits in water maze performance and oxidative stress in the hippocampus and striatum induced by extremely low frequency magnetic field exposure.

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Yonghua Cui

Full Text Available The exposures to extremely low frequency magnetic field (ELF-MF in our environment have dramatically increased. Epidemiological studies suggest that there is a possible association between ELF-MF exposure and increased risks of cardiovascular disease, cancers and neurodegenerative disorders. Animal studies show that ELF-MF exposure may interfere with the activity of brain cells, generate behavioral and cognitive disturbances, and produce deficits in attention, perception and spatial learning. Although, many research efforts have been focused on the interaction between ELF-MF exposure and the central nervous system, the mechanism of interaction is still unknown. In this study, we examined the effects of ELF-MF exposure on learning in mice using two water maze tasks and on some parameters indicative of oxidative stress in the hippocampus and striatum. We found that ELF-MF exposure (1 mT, 50 Hz induced serious oxidative stress in the hippocampus and striatum and impaired hippocampal-dependent spatial learning and striatum-dependent habit learning. This study provides evidence for the association between the impairment of learning and the oxidative stress in hippocampus and striatum induced by ELF-MF exposure.

Low frequency electromagnetic field sensor

International Nuclear Information System (INIS)

Zhu Min; Zhou Yan; He Yicheng; Zheng Zhenxing; Liu Sunkun

2000-01-01

The measurement technique of low frequency electromagnetic field is reported. According to this principle, the authors have designed a sensor, which is used to measure the natural electromagnetic field, SLEMP and electromagnetic signals generated by some explosions. The frequency band of this sensor is from 0.08 Hz to 2 MHz

50Hz Extremely Low Frequency Electromagnetic Fields Enhance Protein Carbonyl Groups Content in Cancer Cells: Effects on Proteasomal Systems

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A. M. Eleuteri

2009-01-01

Full Text Available Electromagnetic fields are an assessed cause of prolonging free radicals lifespan. This study was carried out to investigate the influence of extremely low frequency electromagnetic fields on protein oxidation and on the 20S proteasome functionality, the complex responsible for the degradation of oxidized proteins. Caco 2 cells were exposed, for 24–72 hours, to 1 mT, 50 Hz electromagnetic fields. The treatment induced a time-dependent increase both in cell growth and in protein oxidation, more evident in the presence of TPA, while no changes in cell viability were detected. Exposing the cells to 50 Hz electromagnetic fields caused a global activation of the 20S proteasome catalytic components, particularly evident at 72 hours exposure and in the presence of TPA. The finding that EGCG, a natural antioxidant compound, counteracted the field-related pro-oxidant effects demonstrates that the increased proteasome activity was due to an enhancement in intracellular free radicals.

Low frequency electromagnetic fields and health problems

International Nuclear Information System (INIS)

Zahedi, A.; Cosic, I.

1996-01-01

Full text: Electromagnetic fields developed around the electric circuits are considered as magnetic pollution and these fields are produced wherever electric appliances or machinery are used at home as well as at workplace. Electric fields and magnetic fields around the home are produced by anything with electric current flowing through it including: the street power lines, the home wiring system, electric ovens, refrigerators, washing machines, electric clothes dryers, vacuum cleaners, television sets, video cassette recorders, toasters, light bulbs, clock radios, electric blankets, mobile phones, etc. In the workplace they would be produced by: nearby power lines, factory machinery, computers/video display units, lights, photocopiers, electrical cabling etc. As one can see, human life is strongly dependent on using-electric appliance. A large number of studies have been undertaken to find out the correlation between electromagnetic fields and health problems. The following significant results have been reported [Lerner E.J., IEEE Spectrum, 57-67, May 1984]: (a) Induction of chromosomal defects in mice spermatogenetic cells following microwave radiation in the Ghz range; (b) Changes in the calcium balance of living cats' brains exposed to microwaves modulated at extremely low frequencies; (c) Alternation of nerve and bone cells exposed to extremely low frequency fields; (d) Decreased activity of the immune cells of mice exposed to modulated microwaves; (e) Apparent increase in deformed foetuses among miniature swine exposed to intense power-line frequency fields. The mostly investigated effect is the effect of electromagnetic irradiation in particular one produced by power lines, and cancer. More than 100 epidemiological studies have been reported but no conclusive result was achieved. A number of studies with laboratory animals were also inconclusive. However, some of these experiments have shown improvements in immune system and tumour suppression when

An Investigation on the Effect of Extremely Low Frequency Pulsed Electromagnetic Fields on Human Electrocardiograms (ECGs).

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Fang, Qiang; Mahmoud, Seedahmed S; Yan, Jiayong; Li, Hui

2016-11-23

For this investigation, we studied the effects of extremely low frequency pulse electromagnetic fields (ELF-PEMF) on the human cardiac signal. Electrocardiograms (ECGs) of 22 healthy volunteers before and after a short duration of ELF-PEMF exposure were recorded. The experiment was conducted under single-blind conditions. The root mean square (RMS) value of the recorded data was considered as comparison criteria. We also measured and analysed four important ECG time intervals before and after ELF-PEMF exposure. Results revealed that the RMS value of the ECG recordings from 18 participants (81.8% of the total participants) increased with a mean value of 3.72%. The increase in ECG voltage levels was then verified by a second experimental protocol with a control exposure. In addition to this, we used hyperbolic T-distributions (HTD) in the analysis of ECG signals to verify the change in the RR interval. It was found that there were small shifts in the frequency-domain signal before and after EMF exposure. This shift has an influence on all frequency components of the ECG signals, as all spectrums were shifted. It is shown from this investigation that a short time exposure to ELF-PEMF can affect the properties of ECG signals. Further study is needed to consolidate this finding and discover more on the biological effects of ELF-PEMF on human physiological processes.

Low-frequency magnetic field fluctuations in Venus' solar wind interaction region: Venus Express observations

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L. Guicking

2010-04-01

Full Text Available We investigate wave properties of low-frequency magnetic field fluctuations in Venus' solar wind interaction region based on the measurements made on board the Venus Express spacecraft. The orbit geometry is very suitable to investigate the fluctuations in Venus' low-altitude magnetosheath and mid-magnetotail and provides an opportunity for a comparative study of low-frequency waves at Venus and Mars. The spatial distributions of the wave properties, in particular in the dayside and nightside magnetosheath as well as in the tail and mantle region, are similar to observations at Mars. As both planets do not have a global magnetic field, the interaction process of the solar wind with both planets is similar and leads to similar instabilities and wave structures. We focus on the spatial distribution of the wave intensity of the fluctuating magnetic field and detect an enhancement of the intensity in the dayside magnetosheath and a strong decrease towards the terminator. For a detailed investigation of the intensity distribution we adopt an analytical streamline model to describe the plasma flow around Venus. This allows displaying the evolution of the intensity along different streamlines. It is assumed that the waves are generated in the vicinity of the bow shock and are convected downstream with the turbulent magnetosheath flow. However, neither the different Mach numbers upstream and downstream of the bow shock, nor the variation of the cross sectional area and the flow velocity along the streamlines play probably an important role in order to explain the observed concentration of wave intensity in the dayside magnetosheath and the decay towards the nightside magnetosheath. But, the concept of freely evolving or decaying turbulence is in good qualitative agreement with the observations, as we observe a power law decay of the intensity along the streamlines. The observations support the assumption of wave convection through the magnetosheath, but

Child leukaemia and low frequency electromagnetic fields

International Nuclear Information System (INIS)

Clavel, J.

2009-01-01

The author discusses the possible causes of child leukaemia: exposure to natural ionizing radiation (notably radon), to pesticides, and to hydrocarbons emitted by road traffic. Some studies suggested that an inadequate reaction of the immune system to an ordinary infection could result in leukaemia. Other factors are suspected, notably extremely low frequency electromagnetic fields, the influence of which is then discussed by the author. She evokes and discusses results of different investigations on this topic which have been published since the end of the 1970's. It appears that a distance less than 50 meters from high voltage lines or the vicinity of transformation stations may double the risk of child leukaemia

Children’s Personal Exposure Measurements to Extremely Low Frequency Magnetic Fields in Italy

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Ilaria Liorni

2016-05-01

Full Text Available Extremely low frequency magnetic fields (ELF-MFs exposure is still a topic of concern due to their possible impact on children’s health. Although epidemiological studies claimed an evidence of a possible association between ELF-MF above 0.4 μT and childhood leukemia, biological mechanisms able to support a causal relationship between ELF-MF and this disease were not found yet. To provide further knowledge about children’s ELF-MF exposure correlated to children’s daily activities, a measurement study was conducted in Milan (Italy. Eighty-six children were recruited, 52 of whom were specifically chosen with respect to the distance to power lines and built-in transformers to oversample potentially highly exposed children. Personal and bedroom measurements were performed for each child in two different seasons. The major outcomes of this study are: (1 median values over 24-h personal and bedroom measurements were <3 μT established by the Italian law as the quality target; (2 geometric mean values over 24-h bedroom measurements were mostly <0.4 μT; (3 seasonal variations did not significantly influence personal and bedroom measurements; (4 the highest average MF levels were mostly found at home during the day and outdoors; (5 no significant differences were found in the median and geometric mean values between personal and bedroom measurements, but were found in the arithmetic mean.

Extremely low frequency magnetic field measurements in buildings with transformer stations in Switzerland.

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Röösli, Martin; Jenni, Daniela; Kheifets, Leeka; Mezei, Gabor

2011-08-15

The aim of this study was to evaluate an exposure assessment method that classifies apartments in three exposure categories of extremely low frequency magnetic fields (ELF-MF) based on the location of the apartment relative to the transformer room. We completed measurements in 39 apartments in 18 buildings. In each room of the apartments ELF-MF was concurrently measured with 5 to 6 EMDEX II meters for 10 min. Measured arithmetic mean ELF-MF was 0.59 μT in 8 apartments that were fully adjacent to a transformer room, either directly above the transformer or touching the transformer room wall-to-wall. In apartments that only partly touched the transformer room at corners or edges, average ELF-MF level was 0.14 μT. Average exposure in the remaining apartments was 0.10 μT. Kappa coefficient for exposure classification was 0.64 (95%-CI: 0.45-0.82) if only fully adjacent apartments were considered as highly exposed (>0.4 μT). We found a distinct ELF-MF exposure gradient in buildings with transformer. Exposure classification based on the location of the apartment relative to the transformer room appears feasible. Such an approach considerably reduces effort for exposure assessment and may be used to eliminate selection bias in future epidemiologic studies. Copyright © 2011 Elsevier B.V. All rights reserved.

Quantum mechanical model for the anticarcinogenic effect of extremely-low-frequency electromagnetic fields on early chemical hepatocarcinogenesis

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Godina-Nava, Juan José; Torres-Vega, Gabino; López-Riquelme, Germán Octavio; López-Sandoval, Eduardo; Samana, Arturo Rodolfo; García Velasco, Fermín; Hernández-Aguilar, Claudia; Domínguez-Pacheco, Arturo

2017-02-01

Using the conventional Haberkorn approach, it is evaluated the recombination of the radical pair (RP) singlet spin state to study theoretically the cytoprotective effect of an extremely-low-frequency electromagnetic field (ELF-EMF) on early stages of hepatic cancer chemically induced in rats. The proposal is that ELF-EMF modulates the interconversion rate of singlet and triplet spin states of the RP populations modifying the products from the metabolization of carcinogens. Previously, we found that the daily treatment with ELF-EMF 120 Hz inhibited the number and area of preneoplastic lesions in chemical carcinogenesis. The singlet spin population is evaluated diagonalizing the spin density matrix through the Lanczos method in a radical pair mechanism (RPM). Using four values of the interchange energy, we have studied the variations over the singlet population. The low magnetic field effect as a test of the influence over the enzymatic chemical reaction is evaluated calculating the quantum yield. Through a bootstrap technique the range is found for the singlet decay rate for the process. Applying the quantum measurements concept, we addressed the impact toward hepatic cells. The result contributes to improving our understanding of the chemical carcinogenesis process affected by charged particles that damage the DNA.

The change of electric potentials in the oral cavity after application of extremely low frequency pulsed magnetic field

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Piotr Skomro

2012-12-01

Full Text Available Electric potentials occurring in the oral cavity deserve attention as they may cause various diseases and subjective feelings, which are very difficult to treat. The aim of this study was to evaluate the electric potentials within the oral cavity in patients with metal fillings and metal prosthetic restorations, after using a pulsed electromagnetic field. The study was carried out on 84 patients. The Viofor JPS Classic device was used in the treatment. It generates a pulsed electromagnetic field with low induction of the extremely low frequency (ELF range. Average values of electric potentials in the preliminary test were about the same in both groups; they were 148.8 mV and 145.5 mV. After another appliance of ELF fields there was found a steady decline in the average value of electric potentials in the study group. This decrease was statistically highly significant, while mean values of electric potentials in the control group were characterized by a slightly upward tendency. The obtained statistically significant reduction of electric potentials in the oral cavity of patients having metal fillings and metal prosthetic restorations, after application of the Viofor JPS Classic device, implies a huge impact of ELF pulsed electromagnetic field on inhibition of electrochemical processes, as well as on inhibition of dental alloy corrosion. 

Weak Static and Extremely Low Frequency Magnetic Fields Affect In Vitro Pollen Germination

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Lucietta Betti

2011-01-01

Full Text Available This study concerns the effects of a weak static magnetic field (MF at 10 μT oriented downward, combined with a 16-Hz sinusoidal MF (10 μT, on in vitro pollen germination of kiwifruit (Actinidia deliciosa. Extremely low frequency magnetic field (ELF-MF exposure was carried out by a signal generator unit connected to a copper wire solenoid, inside which samples where placed. Two different kinds of treatment were performed: direct and indirect. In the direct treatment, pollen samples were directly exposed during rehydration, germination, or both. In the indirect treatment, the pollen growth medium was prepared with water aliquots (at standard temperature of 20°C and pH = 6.74 that were exposed before use for 8 or 24 h. The main purpose of our research was to identify a biological marker (in vitro pollen germination in a stressing growth medium without Ca2+ susceptible to the effects of direct or indirect ELF-MF exposure. The working variable was the pollen germination rate, as detected blind after 3 h 30 min by an Axioplan microscope. A directionally consistent recovery of germination percentage was observed both for direct exposure (during germination and both rehydration and germination phases and water-mediated exposure (with water exposed for 24 h and immediately used. Our results suggest that the ELF-MF treatment might partially remove the inhibitory effect caused by the lack of Ca2+ in the culture medium, inducing a release of internal Ca2+ stored in the secretory vesicles of pollen plasma membrane. Although preliminary, findings seem to indicate the in vitro pollen performance as adequate to study the effects of ELF-MFs on living matter.

Investigation of Resonance Effect Caused by Local Exposure of Extremely Low Frequency Magnetic Field on Brain Signals: A Randomize Clinical Trial

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Rasul Zadeh Tabataba’ei K

2011-03-01

Full Text Available Background and Objectives: Some studies have investigated the effects of extremely low frequency magnetic fields (ELF-MFs on brain signals, but only few of them have reported that humans exposed to magnetic fields exhibit changes in brain signals at the frequency of stimulation, i.e. resonance effect. In most investigations, researchers usually take advantage of a uniform field which encompasses the head. The aim of present study was to expose different parts of the brain to ELF-MFs locally and to investigate variation of brain signal and resonance effect.Methods: The subjects consisting of 19 male-students with the mean age of 25.6±1.6 years participated in this study. Local ELF-MFs with 3, 5, 10, 17 and 45Hz frequencies and 240 μT intensity was applied on five points (T3, T4, Cz, F3 and F4 of participants scalp Separately in 10-20 system. In the end, relative power over this points in common frequency bands and at the frequency of magnetic fields was evaluated by paired t-test.Results: Exposure of Central area by local magnetic field caused significant change (p<0.05 in the forehead alpha band. Reduction in the alpha band over central area was observed when temporal area was exposed to ELF MF.Conclusion: The results showed that resonance effect in the brain signals caused by local magnetic field exposure was not observed and change in every part of the relative power spectrum might occur. The changes in the EEG bands were not limited necessarily to the exposure point.

Applications, dosimetry and biological interactions of static and time-varying magnetic fields

International Nuclear Information System (INIS)

Tenforde, T.S.

1988-08-01

The primary topics of this presentation include: (1) the applications of magnetic fields in research, industry, and medical technologies; (2) mechanisms of interaction of static and time-varying magnetic fields with living systems; (3) human health effects of exposure to static and time-varying magnetic fields in occupational, medical, and residential settings; and (4) recent advances in the dosimetry of extremely-low-frequency electromagnetic fields. The discussion of these topics is centered about two issues of considerable contemporary interest: (1) potential health effects of the fields used in magnetic resonance imaging and in vivo spectroscopy, and (2) the controversial issue of whether exposure to extremely-low-frequency (ELF) electromagnetic fields in the home and workplace leads to an elevated risk of cancer. 11 refs

The Comparative Study of the Effects of Extremely Low Frequency Electromagnetic Fields and Infrasound on Water Molecule Dissociation and Generation of Reactive Oxygen Species

Science.gov (United States)

2008-11-01

ISTC Project No. #1592P The Comparative Study of The Effects of Extremely Low Frequency Electromagnetic Fields and Infrasound on Water Molecule...performed under the agreement with the International Science and Technology Center ( ISTC ), Moscow. REPORT DOCUMENTATION PAGE Form Approved OMB No. 0704...dissociation and generation of reactive oxygen spaces. 5a. CONTRACT NUMBER ISTC Registration No: A-1592p 5b. GRANT NUMBER 5c. PROGRAM ELEMENT

Study on the Extremely Low Frequency (ELF) Electromagnetic Field (EMF) emission from overhead High-Voltage Transmission Lines

International Nuclear Information System (INIS)

Parthasarathy, S.R.; Roha Tukimin; Wan Saffiey Wan Abdullah; Zulkifli Yusof; Mohd Azizi Mohd Jali

2016-01-01

The paper highlights the study on the Extremely Low Frequency (ELF) Electromagnetic Field (EMF) emission performed at an overhead 275-kV High-Voltage Transmission Lines. The study comprised of assessment at the transmission lines on 3 different cases and locations in Klang Valley, specifically on a vacant land near the transmission line, inside and around the house at the vicinity of the transmission line and the area directly under the transmission line. The instrument setup and measurement protocols during the assessment were adopted from standard measurement method and procedures stipulated under the Institute of Electrical and Electronics Engineers (IEEE) Standard. The results were compared with the standards recommended in the International Commission on Non-Ionizing Radiation Protection (ICNIRP) guidelines. The results showed that the measured field strengths are within the safety limit with the highest measured exposure was 10.8 % and 1.8 % of the permissible exposure limit for the electric and magnetic field respectively. Both the field strengths were found to drop significantly against distance from the transmission lines where closer distances showed higher field strengths. Furthermore, the study revealed that buildings and other object such as trees and shrubs screen out the electric field, resulting in a lower value at indoor measurements and near the stated objects. In addition, higher value of electric and magnetic field strengths were recorded when assessment was being done directly under the transmission line compared to the lateral measurement. (author)

Assessment of every day extremely low frequency (Elf) electromagnetic fields (50-60 Hz) exposure: which metrics?

International Nuclear Information System (INIS)

Verrier, A.; Magne, I.; Souqes, M.; Lambrozo, J.

2006-01-01

Because electricity is encountered at every moment of the day, at home with household appliances, or in every type of transportation, people are most of the time exposed to extremely low frequency (E.L.F.) electromagnetic fields (50-60 Hz) in a various way. Due to a lack of knowledge about the biological mechanisms of 50 Hz magnetic fields, studies seeking to identify health effects of exposure use central tendency metrics. The objective of our study is to provide better information about these exposure measurements from three categories of metrics. We calculated metrics of exposure measurements from data series (79 very day exposed subjects), made up approximately 20,000 recordings of magnetic fields, measured every 30 seconds for 7 days with an E.M.D.E.X. II dosimeter. These indicators were divided into three categories : central tendency metrics, dispersion metrics and variability metrics.We use Principal Component Analysis, a multidimensional technique to examine the relations between different exposure metrics for a group of subjects. Principal component Analysis (P.C.A.) enabled us to identify from the foreground 71.7% of the variance. The first component (42.7%) was characterized by central tendency; the second (29.0%) was composed of dispersion characteristics. The third component (17.2%) was composed of variability characteristics. This study confirm the need to improve exposure measurements by using at least two dimensions intensity and dispersion. (authors)

The influence of non thermal coherent EMR with low intensity and extremely high frequency on total activity and isoenzyme composition of peroxidase

International Nuclear Information System (INIS)

Nerkararyan, A.V.; Shahinyan, M.A.; Khachatryan, A.V.; Vardevanyan, P.O.

2011-01-01

In this work the influence of non-thermal coherent electromagnetic radiation (EMR) with low intensity and extremely high frequency on intensity of wheat developing germ metabolism has been investigated. Particularly, total activity and isoenzymatic composition of peroxidase of germ cells have been determined during their growth. The role of water in formation of organism response reaction to the external physical field effect has also been investigated. It has been shown, that water appears to be a primary element of extremely high frequency EMR effect on bio system. Extremely high frequency EMR irradiation of germinating seeds and the cultivation of dry seeds and their germs by irradiated water stimulate peroxidase synthesis in germ cells. The redistribution of quantitative composition of peroxidase molecular forms takes place in germ cells effected by EMR with extremely high frequency and low intensity

Interaction between pancreatic β cell and electromagnetic fields: A systematic study toward finding the natural frequency spectrum of β cell system.

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Farashi, Sajjad

2017-01-01

Interaction between biological systems and environmental electric or magnetic fields has gained attention during the past few decades. Although there are a lot of studies that have been conducted for investigating such interaction, the reported results are considerably inconsistent. Besides the complexity of biological systems, the important reason for such inconsistent results may arise due to different excitation protocols that have been applied in different experiments. In order to investigate carefully the way that external electric or magnetic fields interact with a biological system, the parameters of excitation, such as intensity or frequency, should be selected purposefully due to the influence of these parameters on the system response. In this study, pancreatic β cell, the main player of blood glucose regulating system, is considered and the study is focused on finding the natural frequency spectrum of the system using modeling approach. Natural frequencies of a system are important characteristics of the system when external excitation is applied. The result of this study can help researchers to select proper frequency parameter for electrical excitation of β cell system. The results show that there are two distinct frequency ranges for natural frequency of β cell system, which consist of extremely low (or near zero) and 100-750 kHz frequency ranges. There are experimental works on β cell exposure to electromagnetic fields that support such finding.

DEVELOPMENT OF EXTREMELY LOW FREQUENCY PASSIVE SHIELDING APPLICATION USING MAGNETIC AQUEOUS SUBSTRATE

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NOOR ASHIKIN MOHD RASHID

2016-04-01

Full Text Available Public concerns on Extremely Low Frequency (ELF Electromagnetic Field (EMF exposure have been elongated since the last few decades. Electrical substations and high tension rooms in commercial buildings were among the contributing factors emanating ELF magnetic fields. This paper discussed various shielding methods conventionally used in mitigating the ELF exposure. Nevertheless, the standard methods were found to be impractical and incapable of meeting currents shielding demands. In response to that, remarkable researches were conducted in effort to invent novel methods which is more convenient and efficient such as magnetic aqueous shielding or paint, textiles and papers shielding. A magnetic aqueous substrate, Manganese Zinc Ferrite was used as shielding material. The magnetic field and flux distribution inside the aqueous magnetic material are evaluated to optimize shielding against ELFEMF exposure, as to mitigate its exposure.

Extremely Low-Frequency Magnetic Fields and Redox-Responsive Pathways Linked to Cancer Drug Resistance: Insights from Co-Exposure-Based In Vitro Studies

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Stefano Falone

2018-02-01

Full Text Available Electrical devices currently used in clinical practice and common household equipments generate extremely low-frequency magnetic fields (ELF-MF that were classified by the International Agency for Research on Cancer as “possible carcinogenic.” Assuming that ELF-MF plays a role in the carcinogenic process without inducing direct genomic alterations, ELF-MF may be involved in the promotion or progression of cancers. In particular, ELF-MF-induced responses are suspected to activate redox-responsive intracellular signaling or detoxification scavenging systems. In fact, improved protection against oxidative stress and redox-active xenobiotics is thought to provide critical proliferative and survival advantage in tumors. On this basis, an ever-growing research activity worldwide is attempting to establish whether tumor cells may develop multidrug resistance through the activation of essential cytoprotective networks in the presence of ELF fields, and how this might trigger relevant changes in tumor phenotype. This review builds a framework around how the activity of redox-responsive mediators may be controlled by co-exposure to ELF-MF and reactive oxygen species-generating agents in tumor and cancer cells, in order to clarify whether and how such potential molecular targets could help to minimize or neutralize the functional interaction between ELF-MF and malignancies.

Low frequency electrostatic modes in a magnetized dusty plasma

International Nuclear Information System (INIS)

Salimullah, M.; Hassan, M.H.A.

1991-09-01

The dispersion properties of low frequency electrostatic modes in a dusty plasma in the presence of a static homogeneous magnetic field are examined. It is found that the presence of the dust particles and the static magnetic field have significant effects on the dispersion relations. For the parallel propagation the electrostatic mode is slightly modified by the magnetic field for the ion acoustic branch. A new longitudinal mode arises at the extreme low frequency limit, which is unaffected by the magnetic field for the parallel propagation. For the transverse propagation the ion acoustic mode is not affected by the magnetic field. However, the undamped extreme low frequency mode is significantly modified by the presence of the magnetic field for the propagation transverse to the direction of the magnetic field. (author). 23 refs

Adiabatic perturbation theory for atoms and molecules in the low-frequency regime.

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Martiskainen, Hanna; Moiseyev, Nimrod

2017-12-14

There is an increasing interest in the photoinduced dynamics in the low frequency, ω, regime. The multiphoton absorptions by molecules in strong laser fields depend on the polarization of the laser and on the molecular structure. The unique properties of the interaction of atoms and molecules with lasers in the low-frequency regime imply new concepts and directions in strong-field light-matter interactions. Here we represent a perturbational approach for the calculations of the quasi-energy spectrum in the low-frequency regime, which avoids the construction of the Floquet operator with extremely large number of Floquet channels. The zero-order Hamiltonian in our perturbational approach is the adiabatic Hamiltonian where the atoms/molecules are exposed to a dc electric field rather than to ac-field. This is in the spirit of the first step in the Corkum three-step model. The second-order perturbation correction terms are obtained when iℏω∂∂τ serves as a perturbation and τ is a dimensionless variable. The second-order adiabatic perturbation scheme is found to be an excellent approach for calculating the ac-field Floquet solutions in our test case studies of a simple one-dimensional time-periodic model Hamiltonian. It is straightforward to implement the perturbation approach presented here for calculating atomic and molecular energy shifts (positions) due to the interaction with low-frequency ac-fields using high-level electronic structure methods. This is enabled since standard quantum chemistry packages allow the calculations of atomic and molecular energy shifts due to the interaction with dc-fields. In addition to the shift of the energy positions, the energy widths (inverse lifetimes) can be obtained at the same level of theory. These energy shifts are functions of the laser parameters (low frequency, intensity, and polarization).

Effects of extremely low-frequency magnetotherapy on proliferation of human dermal fibroblasts.

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Pasi, Francesca; Sanna, Samuele; Paolini, Alessandro; Alquati, Marco; Lascialfari, Alessandro; Corti, Maurizio Enrico; Liberto, Riccardo Di; Cialdai, Francesca; Monici, Monica; Nano, Rosanna

2016-01-01

Extremely low-frequency electromagnetic fields (ELF-EMFs) applied in magnetotherapy have frequency lower than 100 Hz and magnetic field intensity ranging from 0.1 to 20 mT. For many years, the use of magnetotherapy in clinics has been increasing because of its beneficial effects in many processes, e.g., skin diseases, inflammation and bone disorders. However, the understanding of the microscopic mechanisms governing such processes is still lacking and the results of the studies on the effects of ELF-EMFs are controversial because effects derive from different conditions and from intrinsic responsiveness of different cell types.In the present study, we studied the biological effects of 1.5 h exposure of human dermal fibroblasts to EMFs with frequencies of 5 and 50 Hz and intensity between 0.25 and 1.6 mT. Our data showed that the magnetic treatment did not produce changes in cell viability, but gave evidence of a sizeable decrease in proliferation at 24 h after treatment. In addition, immunofluorescence experiments displayed an increase in tubulin expression that could foreshadow changes in cell motility or morphology. The decrease in proliferation with unchanged viability and increase in tubulin expression could be consistent with the triggering of a transdifferentiation process after the exposure to ELF-EMFs.

Case-Control Study on Occupational Exposure to Extremely Low-Frequency Electromagnetic Fields and the Association with Meningioma

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Michael Carlberg

2018-01-01

Full Text Available Objective. Exposure to extremely low-frequency electromagnetic fields (ELF-EMF was in 2002 classified as a possible human carcinogen, Group 2B, by the International Agency for Research on Cancer at WHO based on an increased risk for childhood leukemia. In case-control studies on brain tumors during 1997–2003 and 2007–2009 we assessed lifetime occupations in addition to exposure to different agents. The INTEROCC ELF-EMF Job-Exposure Matrix was used for associating occupations with ELF-EMF exposure (μT with meningioma. Cumulative exposure (μT-years, average exposure (μT, and maximum exposed job (μT were calculated. Results. No increased risk for meningioma was found in any category. For cumulative exposure in the highest exposure category 8.52+ μT years odds ratio (OR = 0.9, 95% confidence interval (CI = 0.7–1.2, and p linear trend = 0.45 were calculated. No statistically significant risks were found in different time windows. Conclusion. In conclusion occupational ELF-EMF was not associated with an increased risk for meningioma.

Static and low frequency electric and magnetic fields

International Nuclear Information System (INIS)

Thommesen, G.; Tynes, T.

1994-01-01

The biological effects of exposure to low frequency electric and magnetic fields are reviewed with the objective of summarizing effects directly relevant to considerations of the health and safety of exposed people. Static and low frequency electric and magnetic fields may elicit biological reactions. Whether exposure to such fields may affect human health at field strengths present in everyday or occupational life is still unsettled. There is unsufficient knowledge to establish any dose concept relevant to health risk. 196 refs., 6 tabs

Parametric Modeling of Nerve Cell under the Sinusoidal Environmental 50 Hz Extremely Low Frequency Magnetic Fields

Directory of Open Access Journals (Sweden)

Homayoun Ebrahimian

2013-06-01

Full Text Available Background & Objectives: The development of technology has naturally given rise to an increase in environmental low-frequency electromagnetic fields and consequently has attracted scholars' attention. Most of the studies have focused on transmission lines and power system distribution with 50 Hz. This research is an attempt to show the effect of 50 Hz magnetic fields on bioelectric parameters and indicates the possible influence of this change in F1 cells of Helix aspersa .   Methods: The present research used Helix aspersa neuron F1 to identify the location of magnetic fields as well as the rate of effects of environmental magnetic fields on nervous system. Control group was used to study the effect of elapsed time, electrode entering and the cell membrane rupture. Intuition group and environmental group were considered in order to study the potential impact of interfering environmental factors and identify the effectiveness rate of magnetic fields, respectively. For the purpose of producing uniform magnetic field Helmholtz coil was used. Electrophysiological recording was realized under the requirements of current clamp. And, in order to show the impacts from magnetic fields on ion channels Hodgkin-Huxley cell model was applied. All data were analyzed taking the advantage of SPSS 16 software and two-way ANOVA statistical test. P < 0.05 was considered as significance level. And MATLAB software environment and PSO were used in order for applying the algorithm and estimating the parameters.   Result: No statistically significant difference was found between control and sham groups in different time intervals. Once the 45.87 microtesla was applied significant differences were observed 12 minutes after the application. The highest amount of change happened 14 minutes after the application of more fields. With the application of the field, the amplitude of the sodium action potential shows decreasing trend . No significant changes were observed in

Extremely Low Frequency-Magnetic Fields (ELF-EMF) occupational exposure and natural killer activity in peripheral blood lymphocytes

International Nuclear Information System (INIS)

Gobba, Fabriziomaria; Bargellini, Annalisa; Scaringi, Meri; Bravo, Giulia; Borella, Paola

2009-01-01

Extremely Low Frequency-Magnetic Fields (ELF-MF) are possible carcinogens to humans and some data suggest that they can act as promoters or progressors. Since NK cells play a major role in the control of cancer development, an adverse effect on ELF-MF on NK function has been hypothesized. We examined NK activity in 52 workers exposed to different levels of ELF-MF in various activities. Individual exposure was monitored during 3 complete work-shifts using personal dosimeters. Environmental exposure was also monitored. ELF-MF levels in the workers were expressed as Time-Weighted Average (TWA) values. NK activity was measured in peripheral blood lymphocytes (PBL). In the whole group the median occupational TWA was 0.21 μT. According to the TWA levels, workers were classified as low exposed (26 subjects, TWA ≤ 0.2 μT) and higher exposed workers (26 subjects; TWA > 0.2 μT). In higher exposed workers, we observed a trend to reduce NK activity compared to low exposed, but the difference was not significant. Then we selected a subgroup of highest exposed workers (12 subjects; TWA > 1 μT); no difference was observed between low and highest exposed subjects in the main personal variables. Considering both E:T ratios from 12:1 to 50:1 and Lytic Units, a significant reduction in NK activity was observed in the highest exposed workers compared to the low exposed. Multivariate analysis showed a significant negative correlation between exposure and LU, while no correlation was evidenced with other personal characteristics. ELF-MF are considered possible carcinogens, and existing data suggest that they can act as promoters. Due to the role of NK activity in host defence against cancer, the results obtained in this study in workers exposed to ELF-MF levels exceeding 1 μT are in agreement with this hypothesis, and support the need for further investigation in this field

Fetal exposure to low frequency electric and magnetic fields

Energy Technology Data Exchange (ETDEWEB)

Cech, R; Leitgeb, N; Pediaditis, M [Institute of Clinical Engineering, Graz University of Technology, Inffeldgasse 18, 8010 Graz (Austria)

2007-02-21

To investigate the interaction of low frequency electric and magnetic fields with pregnant women and in particular with the fetus, an anatomical voxel model of an 89 kg woman at week 30 of pregnancy was developed. Intracorporal electric current density distributions due to exposure to homogeneous 50 Hz electric and magnetic fields were calculated and results were compared with basic restrictions recommended by ICNIRP guidelines. It could be shown that the basic restriction is met within the central nervous system (CNS) of the mother at exposure to reference level of either electric or magnetic fields. However, within the fetus the basic restriction is considerably exceeded. Revision of reference levels might be necessary.

Fetal exposure to low frequency electric and magnetic fields

International Nuclear Information System (INIS)

Cech, R; Leitgeb, N; Pediaditis, M

2007-01-01

To investigate the interaction of low frequency electric and magnetic fields with pregnant women and in particular with the fetus, an anatomical voxel model of an 89 kg woman at week 30 of pregnancy was developed. Intracorporal electric current density distributions due to exposure to homogeneous 50 Hz electric and magnetic fields were calculated and results were compared with basic restrictions recommended by ICNIRP guidelines. It could be shown that the basic restriction is met within the central nervous system (CNS) of the mother at exposure to reference level of either electric or magnetic fields. However, within the fetus the basic restriction is considerably exceeded. Revision of reference levels might be necessary

Analyses of crystal field and exchange interaction of Dy3Ga5O12 under extreme conditions

International Nuclear Information System (INIS)

Wang Wei; Qi Xin; Yue Yuan

2011-01-01

This paper theoretically investigates the effects of crystal field and exchange interaction field on magnetic properties in dysprosium gallium garnet under extreme conditions (low temperatures and high magnetic fields) based on quantum theory. Here, five sets of crystal field parameters are discussed and compared. It demonstrates that, only considering the crystal field effect, the experiments can not be successfully explained. Thus, referring to the molecular field theory, an effective exchange field associated with the Dy—Dy exchange interaction is further taken into account. Under special consideration of crystal field and the exchange interaction field, it obtains an excellent agreement between the theoretical results and experiments, and further confirms that the exchange interaction field between rare-earth ions has great importance to magnetic properties in paramagnetic rare-earth gallium garnets. (condensed matter: electronic structure, electrical, magnetic, and optical properties)

No effects of power line frequency extremely low frequency electromagnetic field exposure on selected neurobehavior tests of workers inspecting transformers and distribution line stations versus controls.

Science.gov (United States)

Li, Li; Xiong, De-fu; Liu, Jia-wen; Li, Zi-xin; Zeng, Guang-cheng; Li, Hua-liang

2014-03-01

We aimed to evaluate the interference of 50 Hz extremely low frequency electromagnetic field (ELF-EMF) occupational exposure on the neurobehavior tests of workers performing tour-inspection close to transformers and distribution power lines. Occupational short-term "spot" measurements were carried out. 310 inspection workers and 300 logistics staff were selected as exposure and control. The neurobehavior tests were performed through computer-based neurobehavior evaluation system, including mental arithmetic, curve coincide, simple visual reaction time, visual retention, auditory digit span and pursuit aiming. In 500 kV areas electric field intensity at 71.98% of total measured 590 spots were above 5 kV/m (national occupational standard), while in 220 kV areas electric field intensity at 15.69% of total 701 spots were above 5 kV/m. Magnetic field flux density at all the spots was below 1,000 μT (ICNIRP occupational standard). The neurobehavior score changes showed no statistical significance. Results of neurobehavior tests among different age, seniority groups showed no significant changes. Neurobehavior changes caused by daily repeated ELF-EMF exposure were not observed in the current study.

Occupational exposure to extremely low frequency magnetic fields and brain tumour risks in the INTEROCC study

Science.gov (United States)

Turner, Michelle C; Benke, Geza; Bowman, Joseph D; Figuerola, Jordi; Fleming, Sarah; Hours, Martine; Kincl, Laurel; Krewski, Daniel; McLean, Dave; Parent, Marie-Elise; Richardson, Lesley; Sadetzki, Siegal; Schlaefer, Klaus; Schlehofer, Brigitte; Schüz, Joachim; Siemiatycki, Jack; van Tongeren, Martie; Cardis, Elisabeth

2014-01-01

Background Occupational exposure to extremely low frequency magnetic fields (ELF) is a suspected risk factor for brain tumours, however the literature is inconsistent. Few studies have assessed whether ELF in different time windows of exposure may be associated with specific histologic types of brain tumours. This study examines the association between ELF and brain tumours in the large-scale INTEROCC study. Methods Cases of adult primary glioma and meningioma were recruited in seven countries (Australia, Canada, France, Germany, Israel, New Zealand, United Kingdom) between 2000 and 2004. Estimates of mean workday ELF exposure based on a job exposure matrix assigned. Estimates of cumulative exposure, average exposure, maximum exposure, and exposure duration were calculated for the lifetime, and 1–4, 5–9, and 10+ years prior to the diagnosis/reference date. Results There were 3,761 included brain tumour cases (1,939 glioma, 1,822 meningioma) and 5,404 population controls. There was no association between lifetime cumulative ELF exposure and glioma or meningioma risk. However, there were positive associations between cumulative ELF 1–4 years prior to the diagnosis/reference date and glioma (odds ratio (OR) ≥ 90th percentile vs Occupational ELF exposure may play a role in the later stages (promotion and progression) of brain tumourigenesis. PMID:24935666

Determination of the effects of extremely low frequency electromagnetic fields on the percentages of peripheral blood leukocytes and histology of lymphoid organs of the mouse

International Nuclear Information System (INIS)

Cicekcibasi, Aynur E.; Salbacak, A.; Buyukmumcu, M.; Okudan, N.; Celik, I.; Ozkan, Y.

2008-01-01

Objective was to determine the effects of very weak, extremely low frequency (50Hz) electromagnetic field (ELF-EMF) on the relative spleen weight, lymphoid organ histology, peripheral blood leukocyte and alpha-naphthyl acetate esterase positive (ANAE-positive) lymphocyte percentages of mouse. The study was carried out in the Scientific Research and Application Center of Selcuk University, Konya, Turkey in 2005. A total of 120 Swiss albino mice were divided into 6 groups (20 in each group). The experimental animals were exposed to 1, 2, 3, 4 and 5 uT flux intensities (rms) of EMF at 50 Hz for 40 days. In the exposure groups with 20 animals, the body weight (BW) increased gradually in higher field intensities and reached at peak level in the 4 uT and then slightly decreased. The relative spleen weight (% of BW) was not affected. The ELF-EMF treatment did not cause any significant change in lymphocyte, monocyte and ANA-positive lymphocyte ratios, whereas percentages of neutropholis and basophiles changed non-linearly. Any change in the lymphoid organ histology which attributable to the field effect, was not observed in the exposure groups. Extremely frequency-EMF exposure with the flux intensities between 1-5 uT for 40 days did not cause any effect on the relative spleen weight, lymphoid organ histology, leukocyte and ANAE-positive lymphocyte percentages of the mouse. (author)

Interaction of biological systems with static and ELF electric and magnetic fields

Energy Technology Data Exchange (ETDEWEB)

Anderson, L.E.; Kelman, B.J.; Weigel, R.J. (eds.)

1987-01-01

Although background levels of atmospheric electric and geomagnetic field levels are extremely low, over the past several decades, human beings and other life forms on this planet have been subjected to a dramatically changing electromagnetic milieu. An exponential increase in exposure to electromagnetic fields has occurred, largely because of such technological advances as the growth of electrical power generation and transmission systems, the increased use of wireless communications, and the use of radar. In addition, electromagnetic field generating devices have proliferated in industrial plants, office buildings, homes, public transportation systems, and elsewhere. Although significant increases have occurred in electromagnetic field strenghths spanning all frequency ranges, this symposium addresses only the impact of these fields at static and extremely low frequencies (ELF), primarily 50 and 60 Hz. This volume contains the proceedings of the symposium entitled /open quotes/Interaction of biological systems with static and ELF electric and magnetic fields/close quotes/. The purpose of the symposium was to provide a forum for discussions of all aspects of research on the interaction of static and ELF electromagnetic fields with biological systems. These systems include simple biophysical models, cell and organ preparations, whole animals, and man. Dosimetry, exposure system design, and artifacts in ELF bioeffects research were also addressed, along with current investigations that examine fundamental mechanisms of interactions between the fields and biological processes. Papers are indexed separately.

Effects of repeated 9 and 30-day exposure to extremely low-frequency electromagnetic fields on social recognition behavior and estrogen receptors expression in olfactory bulb of Wistar female rats.

Science.gov (United States)

Bernal-Mondragón, C; Arriaga-Avila, V; Martínez-Abundis, E; Barrera-Mera, B; Mercado-Gómez, O; Guevara-Guzmán, R

2017-02-01

We investigated the short- and long-term effects of extremely low-frequency electromagnetic fields (EMF) on social recognition behavior and expression of α- and β-estrogen receptors (ER). Rats were exposed to 60-Hz electromagnetic fields for 9 or 30 days and tested for social recognition behavior. Immunohistochemistry and western blot assays were performed to evaluate α- and β-ER expression in the olfactory bulb of intact, ovariectomized (OVX), and ovariectomized+estradiol (E2) replacement (OVX+E2). Ovariectomization showed impairment of social recognition after 9 days of EMF exposure and a complete recovery after E2 replacement and so did those after 30 days. Short EMF exposure increased expression of β-ER in intact, but not in the others. Longer exposure produced a decrease in intact but an increase in OVX and OVX+E2. Our findings suggest a significant role for β-estrogen receptors and a lack of effect for α-estrogen receptors on a social recognition task. EMF: extremely low frequency electromagnetic fields; ERs: estrogen receptors; OB: olfactory bulb; OVX: ovariectomized; OVX + E 2 : ovariectomized + estradiol replacement; IEI: interexposure interval; β-ER: beta estrogen receptor; E 2 : replacement of estradiol; GAPDH: glyceraldehyde-3-phosphate dehydrogenase; WB: Western blot; PBS: phosphate-buffer saline; PB: phosphate-buffer.

A mathematical model of extremely low frequency ocean induced electromagnetic noise

International Nuclear Information System (INIS)

Dautta, Manik; Faruque, Rumana Binte; Islam, Rakibul

2016-01-01

Magnetic Anomaly Detection (MAD) system uses the principle that ferromagnetic objects disturb the magnetic lines of force of the earth. These lines of force are able to pass through both water and air in similar manners. A MAD system, usually mounted on an aerial vehicle, is thus often employed to confirm the detection and accomplish localization of large ferromagnetic objects submerged in a sea-water environment. However, the total magnetic signal encountered by a MAD system includes contributions from a myriad of low to Extremely Low Frequency (ELF) sources. The goal of the MAD system is to detect small anomaly signals in the midst of these low-frequency interfering signals. Both the Range of Detection (R_d) and the Probability of Detection (P_d) are limited by the ratio of anomaly signal strength to the interfering magnetic noise. In this paper, we report a generic mathematical model to estimate the signal-to-noise ratio or SNR. Since time-variant electro-magnetic signals are affected by conduction losses due to sea-water conductivity and the presence of air-water interface, we employ the general formulation of dipole induced electromagnetic field propagation in stratified media [1]. As a first step we employ a volumetric distribution of isolated elementary magnetic dipoles, each having its own dipole strength and orientation, to estimate the magnetic noise observed by a MAD system. Numerical results are presented for a few realizations out of an ensemble of possible realizations of elementary dipole source distributions.

On the Frequency Distribution of Neutral Particles from Low-Energy Strong Interactions

Directory of Open Access Journals (Sweden)

Federico Colecchia

2017-01-01

Full Text Available The rejection of the contamination, or background, from low-energy strong interactions at hadron collider experiments is a topic that has received significant attention in the field of particle physics. This article builds on a particle-level view of collision events, in line with recently proposed subtraction methods. While conventional techniques in the field usually concentrate on probability distributions, our study is, to our knowledge, the first attempt at estimating the frequency distribution of background particles across the kinematic space inside individual collision events. In fact, while the probability distribution can generally be estimated given a model of low-energy strong interactions, the corresponding frequency distribution inside a single event typically deviates from the average and cannot be predicted a priori. We present preliminary results in this direction and establish a connection between our technique and the particle weighting methods that have been the subject of recent investigation at the Large Hadron Collider.

Low-frequency fields - sources and exposure

International Nuclear Information System (INIS)

Kunsch, B.

1993-01-01

The author briefly discusses definition of terms, gives an introduction to measurement techniques and describes the characteristics of various low-frequency fields and their causes using typical examples: natural electric fields (thunderstroms), natural magnetic fields, technical electric constant fields (urban transportation, households), static magnetic fields (urban transportation, nuclear magnetic resonance imaging), technical electric alternating fields (high-voltage transmission lines, households), and magnetic alternating fields (high-voltage transmission lines). The author discusses both occupational exposure and that of the general public while underpinning his statements by numerous tables, measurement diagrams and charts. (Uhe) [de

Oxidative and antioxidative responses in submandibular and parotid glands of rats exposed to long-term extremely low frequency magnetic field

Directory of Open Access Journals (Sweden)

Mehmet Akdağ

2014-06-01

Full Text Available Background: Some epidemiologic and laboratory studies have suggested a possible associations between exposure to extremely low frequency magnetic field (ELF-MF and cancer. However, it is not known underlying mechanisms of this interaction. The aim of the study was to investigate the possible oxidative damage induced by long-term ELF-MF exposure on submandibular and parotis glands of rats. Methods: Rats in the experimental group were exposed to 100 and 500 µT ELF-MF (2 h/day, 7 days/week, for 10 months corresponding to exposure levels that are considered safe for humans. The same experimental procedures were applied to the sham group, but the ELF generator was turned off. The levels of catalase (CAT, malondialdehyde (MDA, myeloperoxidase (MPO, total antioxidative capacity (TAC, total oxidant status (TOS, and oxidative stress index (OSI were measured in rat submandibular and parotis gland. Results: Although some oxidative and antioxidative parameters of submandibular gland were altered by ELF-100 and ELF-500 exposure groups, these changes were not statistically significant ( p >0.05. However, a decrease observed in CAT levels of parotid gland in both the ELF-100 and ELF-500 exposure groups (p0.05. Conclusions: Our results showed that long-term ELF-MF exposure did not alter oxidative, antioxidative processes and lipid peroxidation in submandibular gland of rats. However, 100 µT and 500 µT ELF-MF exposure decreased CAT activity in parotid gland. J Clin Exp Invest 2014; 5 (2: 219-225

Low frequency sound field enhancement system for rectangular rooms using multiple low frequency loudspeakers

DEFF Research Database (Denmark)

Celestinos, Adrian; Nielsen, Sofus Birkedal

2006-01-01

an enhancement system with extra loudspeakers the sound pressure level distribution along the listening area presents a significant improvement in the subwoofer frequency range. The system is simulated and implemented on the three different rooms and finally verified by measurements on the real rooms.......Rectangular rooms have strong influence on the low frequency performance of loudspeakers. Simulations of three different room sizes have been carried out using finite-difference time-domain method (FDTD) in order to predict the behaviour of the sound field at low frequencies. By using...

Biological and clinical effects of low-frequency magnetic and electric fields

Energy Technology Data Exchange (ETDEWEB)

Llaurado, J.G.; Sances, A. Jr.; Battocletti, J. (eds.)

1974-01-01

The blurb on this book states that it has been written for physicians, biologists, psychologists, engineers and those persons interested in the interaction of low frequency electric and magnetic fields upon animals and man. Certainly, the content of this book--which comprises papers presented by specialists at a symposium on The Effects of Low Frequency Magnetic Fields on Biological Communication Processes held in Aspen, Colorado--does not make simple reading and those lacking the necessary background are unlikely to make much progress. This said, however, the book can be recommended to those with the necessary interest, knowledge and perseverance. The book provides a great deal of information in a convenient manner and all those concerned with its production are to be congratulated on their work. Articles are well set out, illustrated and supported by abstracts, extensive references and discussions. As indicated above, the range of the subjects covered is large and includes such varied items as acupuncture, bird communication and some details of the U.S.A. Navy's extra low frequency communication system known as Project Sanguine. Finally, it is a pleasure to say that the book has been attractively produced and contains an excellent index.

Extreme field limits in the interaction of laser light with ultrarelativistic electrons

Energy Technology Data Exchange (ETDEWEB)

Bulanov, S. V.; Esirkepov, T. Zh.; Hayashi, Y.; Kando, M.; Kiriyama, H.; Koga, J.; Kondo, K.; Kotaki, H.; Pirozhkov, A.; Bulanov, S. S.; Zhidkov, A.; Chen, P.; Neely, D.; Kato, Y.; Narozhny, N. B.; Korn, G. [Kansai Photon Science Institute, JAEA, Kizugawa, Kyoto 619-0215 (Japan); University of California, Berkeley, CA 94720 (United States); Osaka University, Osaka 565-0871 (Japan); National Taiwan University, Taipei 10617, Taiwan (China); Central Laser Facility, STFC, Rutherford Appleton Laboratory, Didcot OX11 0QX (United Kingdom); Graduate School for the Creation of New Photonics Industries, Hamamatsu, Shizuoka 431-1202 (Japan); Moscow Engineering Physics Institute (State University), Moscow 115409 (Russian Federation); Max-Planck-Institut fuer Quantenoptik, Garching 85748 (Germany) and ELI Beamline Facility, Institute of Physics, CAS, Prague 18221 (Czech Republic)

2012-07-11

The critical electric field of quantum electrodynamics is so strong that it produces electron-positron pairs from vacuum, converting the energy of light into matter. This field has become feasible through the construction of extremely high power lasers or/and with the sophisticated use of nonlinear processes in relativistic plasmas. A feasibility of the experiments on the collision of laser light and high intensity electromagnetic pulses, generated by relativistic flying mirrors, with relativistic electrons for the studying of extreme field limits in the nonlinear interaction of electromagnetic waves is discussed.

Extremely short pulses via stark modulation of the atomic transition frequencies.

Science.gov (United States)

Radeonychev, Y V; Polovinkin, V A; Kocharovskaya, Olga

2010-10-29

We propose a universal method to produce extremely short pulses of electromagnetic radiation in various spectral ranges. The essence of the method is a resonant interaction of radiation with atoms under the conditions of adiabatic periodic modulation of atomic transition frequencies by a far-off-resonant control laser field via dynamic Stark shift of the atomic levels and proper adjustment of the control field intensity and frequency, as well as the optical depth of the medium. The potential of the method is illustrated by an example in a hydrogenlike atomic system.

Sensitivity of Pigment Content of Banana and Orchid Tissue Culture Exposed to Extremely Low Frequency Electromagnetic Fiel

OpenAIRE

Prihatini, Riry; Saleh, Norihan Mohamad

2016-01-01

Natural exposure of extremely low frequency electromagnetic field (ELF-EMF) occurs in the environment and acts as one of the abiotic factors that affect the growth and development of organisms. This study was conducted to determine the effect of ELF-EMF on the tissue cultured banana and slipper orchid chlorophyll content as one of the indicators in measuring plant photosynthetic capacity. Four days old banana (Musa sp. cv. Berangan) corm and seven days old slipper orchid (Paphiopedilum rothsc...

A mathematical model of extremely low frequency ocean induced electromagnetic noise

Energy Technology Data Exchange (ETDEWEB)

Dautta, Manik, E-mail: manik.dautta@anyeshan.com; Faruque, Rumana Binte, E-mail: rumana.faruque@anyeshan.com; Islam, Rakibul, E-mail: rakibul.islam@anyeshan.com [Research & Development Engineer, Anyeshan Limited, Dhaka (Bangladesh)

2016-07-12

Magnetic Anomaly Detection (MAD) system uses the principle that ferromagnetic objects disturb the magnetic lines of force of the earth. These lines of force are able to pass through both water and air in similar manners. A MAD system, usually mounted on an aerial vehicle, is thus often employed to confirm the detection and accomplish localization of large ferromagnetic objects submerged in a sea-water environment. However, the total magnetic signal encountered by a MAD system includes contributions from a myriad of low to Extremely Low Frequency (ELF) sources. The goal of the MAD system is to detect small anomaly signals in the midst of these low-frequency interfering signals. Both the Range of Detection (R{sub d}) and the Probability of Detection (P{sub d}) are limited by the ratio of anomaly signal strength to the interfering magnetic noise. In this paper, we report a generic mathematical model to estimate the signal-to-noise ratio or SNR. Since time-variant electro-magnetic signals are affected by conduction losses due to sea-water conductivity and the presence of air-water interface, we employ the general formulation of dipole induced electromagnetic field propagation in stratified media [1]. As a first step we employ a volumetric distribution of isolated elementary magnetic dipoles, each having its own dipole strength and orientation, to estimate the magnetic noise observed by a MAD system. Numerical results are presented for a few realizations out of an ensemble of possible realizations of elementary dipole source distributions.

Effects of 100-μT extremely low frequency electromagnetic fields exposure on hematograms and blood chemistry in rats

International Nuclear Information System (INIS)

Lai Jinsheng; Zhang Yemao; Zhang Jiangong

2016-01-01

The aim of this study was to test whether extremely low frequency electromagnetic fields (ELF EMFs) affect health or not. Here, we constructed a 100-μT/50 Hz electromagnetic field atmosphere. A total of 128 rats were randomly assigned into two groups: the ELF EMF group and the sham group. The ELF EMF group was exposed to 100-μT/50-Hz ELF EMF for 20 h per day for three months; at the same time the other group was exposed to a sham device without ELF EMF. During the three months, the weight was recorded every 2 weeks, and the water intake and food intake of the animals were recorded weekly. The hematologic parameters were detected before and after the exposure, whereas blood chemistry analysis was performed every 4 weeks. The general condition of the exposed rats was not affected by ELF EMF. Compared with the sham group, the hematograms were not significantly altered in the ELF EMF group. Similarly, the blood chemistry (including lipid profile, blood glucose, liver function and renal function of rats) from the ELF EMF group showed no difference compared with rats from the control group during the three months exposure. The present study indicated that short-term exposure of 100-μT/50-Hz ELF EMF may not affect hematograms and blood chemistry in rats. (author)

Anti-proliferative effect of extremely low frequency electromagnetic field on preneoplastic lesions formation in the rat liver

International Nuclear Information System (INIS)

Jiménez-García, Mónica Noemí; Arellanes-Robledo, Jaime; Aparicio-Bautista, Diana Ivette; Rodríguez-Segura, Miguel Ángel; Villa-Treviño, Saúl; Godina-Nava, Juan José

2010-01-01

Recently, extremely low frequency electromagnetic fields (ELF-EMF) have been studied with great interest due to their possible effects on human health. In this study, we evaluated the effect of 4.5 mT - 120 Hz ELF-EMF on the development of preneoplastic lesions in experimental hepatocarcinogenesis. Male Fischer-344 rats were subjected to the modified resistant hepatocyte model and were exposed to 4.5 mT - 120 Hz ELF-EMF. The effects of the ELF-EMF on hepatocarcinogenesis, apoptosis, proliferation and cell cycle progression were evaluated by histochemical, TUNEL assay, caspase 3 levels, immunohistochemical and western blot analyses. The application of the ELF-EMF resulted in a decrease of more than 50% of the number and the area of γ-glutamyl transpeptidase-positive preneoplastic lesions (P = 0.01 and P = 0.03, respectively) and glutathione S-transferase placental expression (P = 0.01). The number of TUNEL-positive cells and the cleaved caspase 3 levels were unaffected; however, the proliferating cell nuclear antigen, Ki-67, and cyclin D1 expression decreased significantly (P ≤ 0.03), as compared to the sham-exposure group. The application of 4.5 mT - 120 Hz ELF-EMF inhibits preneoplastic lesions chemically induced in the rat liver through the reduction of cell proliferation, without altering the apoptosis process

Measurements of intermediate-frequency electric and magnetic fields in households

NARCIS (Netherlands)

Aerts, Sam; Calderon, Carolina; Valič, Blaž; Maslanyj, Myron; Addison, Darren; Mee, Terry; Goiceanu, Cristian; Verloock, Leen; Van den Bossche, Matthias; Gajšek, Peter; Vermeulen, Roel; Röösli, Martin; Cardis, Elisabeth; Martens, Luc; Joseph, Wout

Historically, assessment of human exposure to electric and magnetic fields has focused on the extremely-low-frequency (ELF) and radiofrequency (RF) ranges. However, research on the typically emitted fields in the intermediate-frequency (IF) range (300Hz to 1MHz) as well as potential effects of IF

Assessment of occupational risks to extremely low frequency magnetic fields: Validation of an empirical non-expert approach

Directory of Open Access Journals (Sweden)

Mariam El-Zein

2016-12-01

Full Text Available The expert method of exposure assignment involves relying on chemists or hygienists to estimate occupational exposures using information collected on study subjects. Once the estimation method for a particular contaminant has been made available in the literature, it is not known whether a non-expert, briefly trained by an expert remaining available to answer ad hoc questions, can provide reliable exposure estimates. We explored this issue by comparing estimates of exposure to extremely low frequency magnetic fields (ELF-MF obtained by an expert to those from a non-expert. Using a published exposure matrix, both the expert and non-expert independently calculated a weekly time-weighted average exposure for 208 maternal jobs by considering three main determinants: the work environment, magnetic field sources, and duration of use or exposure to given sources. Agreement between assessors was tested using the Bland-Altman 95% limits of agreement. The overall mean difference in estimates between the expert and non-expert was 0.004 μT (standard deviation 0.104. The 95% limits of agreement were −0.20 μT and +0.21 μT. The work environments and exposure sources were almost always similarly identified but there were differences in estimating exposure duration. This occurred mainly when information collected from study subjects was not sufficiently detailed. Our results suggest that following a short training period and the availability of a clearly described method for estimating exposures, a non-expert can cost-efficiently and reliably assign exposure, at least to ELF-MF.

Inhibition of Salmonella typhi growth using extremely low frequency electromagnetic (ELF-EM) waves at resonance frequency.

Science.gov (United States)

Fadel, M A; Mohamed, S A; Abdelbacki, A M; El-Sharkawy, A H

2014-08-01

Typhoid is a serious disease difficult to be treated with conventional drugs. The aim of this study was to demonstrate a new method for the control of Salmonella typhi growth, through the interference with the bioelectric signals generated from the microbe during cell division by extremely low frequency electromagnetic waves (ELF-EMW-ELF-EM) at resonance frequency. Isolated Salmonella typhi was subjected to square amplitude modulated waves (QAMW) with different modulation frequencies from two generators with constant carrier frequency of 10 MHz, amplitude of 10 Vpp, modulating depth ± 2 Vpp and constant field strength of 200 V m(-1) at 37°C. Both the control and exposed samples were incubated at the same conditions during the experiment. The results showed that there was highly significant inhibition effect for Salm. typhi exposed to 0·8 Hz QAMW for a single exposure for 75 min. Dielectric relaxation, TEM and DNA results indicated highly significant changes in the molecular structure of the DNA and cellular membrane resulting from the exposure to the inhibiting EM waves. It was concluded that finding out the inhibiting resonance frequency of ELF-EM waves that deteriorates Salm. typhi growth will be promising method for the treatment of Salm. typhi infection either in vivo or in vitro. This new non-invasive technique for treatment of bacterial infections is of considerable interest for the use in medical and biotechnological applications. © 2014 The Society for Applied Microbiology.

Anti-proliferative effect of extremely low frequency electromagnetic field on preneoplastic lesions formation in the rat liver

Directory of Open Access Journals (Sweden)

Villa-Treviño Saúl

2010-04-01

Full Text Available Abstract Background Recently, extremely low frequency electromagnetic fields (ELF-EMF have been studied with great interest due to their possible effects on human health. In this study, we evaluated the effect of 4.5 mT - 120 Hz ELF-EMF on the development of preneoplastic lesions in experimental hepatocarcinogenesis. Methods Male Fischer-344 rats were subjected to the modified resistant hepatocyte model and were exposed to 4.5 mT - 120 Hz ELF-EMF. The effects of the ELF-EMF on hepatocarcinogenesis, apoptosis, proliferation and cell cycle progression were evaluated by histochemical, TUNEL assay, caspase 3 levels, immunohistochemical and western blot analyses. Results The application of the ELF-EMF resulted in a decrease of more than 50% of the number and the area of γ-glutamyl transpeptidase-positive preneoplastic lesions (P = 0.01 and P = 0.03, respectively and glutathione S-transferase placental expression (P = 0.01. The number of TUNEL-positive cells and the cleaved caspase 3 levels were unaffected; however, the proliferating cell nuclear antigen, Ki-67, and cyclin D1 expression decreased significantly (P ≤ 0.03, as compared to the sham-exposure group. Conclusion The application of 4.5 mT - 120 Hz ELF-EMF inhibits preneoplastic lesions chemically induced in the rat liver through the reduction of cell proliferation, without altering the apoptosis process.

DATA ACQUISITION AND ANALYSIS OF LOW FREQUENCY ELECTROMAGNETIC FIELD

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PETRICA POPOV

2016-06-01

Full Text Available In recent years more and more studies have shown that, the low frequency field strength (particularly magnetic, 50 / 60Hz are a major risk factor; according to some specialists - even more important as the radiation field. As a result, the personnel serving equipment and facilities such as: electric generators, synchronous, the motors, the inverters or power transformers is subjected continually to intense fields, in their vicinity, with possible harmful effects in the long term by affecting metabolism cell, espectively, the biological mechanisms.Therefore, finding new methods and tools for measurement and analysis of low frequency electromagnetic fields may lead to improved standards for exposure limits of the human body.

Extremely low frequency electromagnetic fields stimulation modulates autoimmunity and immune responses: a possible immuno-modulatory therapeutic effect in neurodegenerative diseases

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Fabio Guerriero

2016-01-01

Full Text Available Increasing evidence shows that extremely low frequency electromagnetic fields (ELF-EMFs stimulation is able to exert a certain action on autoimmunity and immune cells. In the past, the efficacy of pulsed ELF-EMFs in alleviating the symptoms and the progression of multiple sclerosis has been supported through their action on neurotransmission and on the autoimmune mechanisms responsible for demyelination. Regarding the immune system, ELF-EMF exposure contributes to a general activation of macrophages, resulting in changes of autoimmunity and several immunological reactions, such as increased reactive oxygen species-formation, enhanced phagocytic activity and increased production of chemokines. Transcranial electromagnetic brain stimulation is a non-invasive novel technique used recently to treat different neurodegenerative disorders, in particular Alzheimer's disease. Despite its proven value, the mechanisms through which EMF brain-stimulation exerts its beneficial action on neuronal function remains unclear. Recent studies have shown that its beneficial effects may be due to a neuroprotective effect on oxidative cell damage. On the basis of in vitro and clinical studies on brain activity, modulation by ELF-EMFs could possibly counteract the aberrant pro-inflammatory responses present in neurodegenerative disorders reducing their severity and their onset. The objective of this review is to provide a systematic overview of the published literature on EMFs and outline the most promising effects of ELF-EMFs in developing treatments of neurodegenerative disorders. In this regard, we review data supporting the role of ELF-EMF in generating immune-modulatory responses, neuromodulation, and potential neuroprotective benefits. Nonetheless, we reckon that the underlying mechanisms of interaction between EMF and the immune system are still to be completely understood and need further studies at a molecular level.

Low-frequency fields - health risk assessment

International Nuclear Information System (INIS)

Bernhardt, J.

1993-01-01

The author briefly reviews the biological actions and effects of low-frequency fields, epidemiological studies and discusses health risks in detail. He describes the assessment principles of the International Commission on Non-ionizing Radiation Protection (ICNIRP), medical principles for risk assessment, determination of limits and thesholds, and aspects of prevention. This is supplemented to by several fables and literature list. (Uhe) [de

Effects of Extremely Low Frequency Electromagnetic Fields on Melanogenesis through p-ERK and p-SAPK/JNK Pathways in Human Melanocytes

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Yu-Mi Kim

2017-10-01

Full Text Available This study evaluated frequency-dependent effects of extremely low frequency electromagnetic fields (ELF-EMFs on melanogenesis by melanocytes in vitro. Melanocytes were exposed to 2 mT EMFs at 30–75 Hz for 3 days before melanogenesis was examined. Exposure to ELF-EMFs at 50 and 60 Hz induced melanogenic maturation without cell damage, without changing cell proliferation and mitochondrial activity. Melanin content and tyrosinase activity of cells exposed to 50 Hz were higher than in controls, and mRNA expression of tyrosinase-related protein-2 was elevated relative to controls at 50 Hz. Phosphorylated cyclic adenosine monophosphate response element-binding protein (p-CREB levels were higher than controls in cells exposed to ELF-EMFs at 50–75 Hz. Immunohistochemical staining showed that melanocyte-specific markers (HMB45, Melan-A were strongly expressed in cells exposed to EMFs at 50 and 60 Hz compared to controls. Thus, exposure to ELF-EMFs at 50 Hz could stimulate melanogenesis in melanocytes, through activation of p-CREB and p-p38 and inhibition of phosphorylated extracellular signal-regulated protein kinase and phosphorylated stress-activated protein kinase/c-Jun N-terminal kinase. The results may form the basis of an appropriate anti-gray hair treatment or be applied in a therapeutic device for inducing repigmentation in the skin of vitiligo patients.

Assessment of Extremely Low Frequency (ELF Electric and Magnetic Fields in Hamedan High Electrical Power Stations and their Effects on Workers

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Farshid Ghorbani Shahna

2011-09-01

Full Text Available Introduction: Public and occupational exposure to extremely low frequency (ELF electric and magnetic fields induced by electrical equipment is a significant issue in the environment and at the workplace due to their potential health effects on public health. The purpose of this study was assessment of the electric and magnetic fields intensities and determination of mental and psychological effects of occupational exposure in the high voltage electric power stations in the city of Hamadan, Iran. Material and Methods: The intensities of the magnetic and electric fields were measured at eight high voltage electric power stations at three different intervals of sources using an HI-3604 instrument. A two-part questionnaire was used to assess mental and psychological effects of the exposure to these fields. Two groups of control and case workers including 30 samples were selected to determine the exposure effects. Results: The results of field measurements showed the highest average electric field intensity was related to the CVT unit with 3110 V/m at a 2 m distance from the source and the lowest average was related to the control room with 1.35 V/m next to the source. Also, the highest and lowest magnetic field intensities were close to the transformator 2 and the battery room (50.42 and 1.31 mG, respectively. Discussion and Conclusion: The intensities of electric and magnetic fields in the selected stations are lower than the ACGIH and ICNIRP standard levels for occupational exposures. The results obtained indicate that the distribution of these fields was nonlinear around the sources and the effects observed on exposed workers were non-thermal.

Low-mass Stars with Extreme Mid-Infrared Excesses: Potential Signatures of Planetary Collisions

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Theissen, Christopher; West, Andrew

2018-01-01

I investigate the occurrence of extreme mid-infrared (MIR) excesses, a tracer of large amounts of dust orbiting stars, in low-mass stellar systems. Extreme MIR excesses, defined as an excess IR luminosity greater than 1% of the stellar luminosity (LIR/L* ≥ 0.01), have previously only been observed around a small number of solar-mass (M⊙) stars. The origin of this excess has been hypothesized to be massive amounts of orbiting dust, created by collisions between terrestrial planets or large planetesimals. Until recently, there was a dearth of low-mass (M* ≤ 0.6M⊙) stars exhibiting extreme MIR excesses, even though low-mass stars are ubiquitous (~70% of all stars), and known to host multiple terrestrial planets (≥ 3 planets per star).I combine the spectroscopic sample of low-mass stars from the Sloan Digital Sky Survey (SDSS) Data Release 7 (70,841 stars) with MIR photometry from the Wide-field Infrared Survey Explorer (WISE), to locate stars exhibiting extreme MIR excesses. I find the occurrence frequency of low-mass field stars (stars with ages ≥ 1 Gyr) exhibiting extreme MIR excesses is much larger than that for higher-mass field stars (0.41 ± 0.03% versus 0.00067 ± 0.00033%, respectively).In addition, I build a larger sample of low-mass stars based on stellar colors and proper motions using SDSS, WISE, and the Two-Micron All-Sky Survey (8,735,004 stars). I also build a galactic model to simulate stellar counts and kinematics to estimate the number of stars missing from my sample. I perform a larger, more complete study of low-mass stars exhibiting extreme MIR excesses, and find a lower occurrence frequency (0.020 ± 0.001%) than found in the spectroscopic sample but that is still orders of magnitude larger than that for higher-mass stars. I find a slight trend for redder stars (lower-mass stars) to exhibit a higher occurrence frequency of extreme MIR excesses, as well as a lower frequency with increased stellar age. These samples probe important

Stimulation of neural differentiation in human bone marrow mesenchymal stem cells by extremely low-frequency electromagnetic fields incorporated with MNPs.

Science.gov (United States)

Choi, Yun-Kyong; Lee, Dong Heon; Seo, Young-Kwon; Jung, Hyun; Park, Jung-Keug; Cho, Hyunjin

2014-10-01

Human bone marrow-derived mesenchymal stem cells (hBM-MSCs) have been investigated as a new cell-therapeutic solution due to their capacity that could differentiate into neural-like cells. Extremely low-frequency electromagnetic fields (ELF-EMFs) therapy has emerged as a novel technique, using mechanical stimulus to differentiate hBM-MSCs and significantly enhance neuronal differentiation to affect cellular and molecular reactions. Magnetic iron oxide (Fe3O4) nanoparticles (MNPs) have recently achieved widespread use for biomedical applications and polyethylene glycol (PEG)-labeled nanoparticles are used to increase their circulation time, aqueous solubility, biocompatibility, and nonspecific cellular uptake as well as to decrease immunogenicity. Many studies have used MNP-labeled cells for differentiation, but there have been no reports of MNP-labeled neural differentiation combined with EMFs. In this study, synthesized PEG-phospholipid encapsulated magnetite (Fe3O4) nanoparticles are used on hBM-MSCs to improve their intracellular uptake. The PEGylated nanoparticles were exposed to the cells under 50 Hz of EMFs to improve neural differentiation. First, we measured cell viability and intracellular iron content in hBM-MSCs after treatment with MNPs. Analysis was conducted by RT-PCR, and immunohistological analysis using neural cell type-specific genes and antibodies after exposure to 50 Hz electromagnetic fields. These results suggest that electromagnetic fields enhance neural differentiation in hBM-MSCs incorporated with MNPs and would be an effective method for differentiating neural cells.

Methods of developing an emission cataster for low frequency electric and magnetic fields

International Nuclear Information System (INIS)

Stenzel, E.; Frohn, O.; Koffke, K.; Dunker, J.; Plotzke, O.

1996-01-01

In the common environment each individual is exposed to a large variety of power frequency or extremely low frequency (EFL) electric and magnetic fields. Traditionally these fields have been thought to be harmless but recent scientific studies reveal, however, that at least effects do exists. Therefore father investigations have to be carried out in order to obtain a greater data base. As a major point new ways have to be established that allow an effective collection of an relevant data concerning the exposition m this fields. In our contribution for the first time methods that consider simultaneously an major field emittants in the ramp of 0-500 Hz spread over the area as great as a town district. These methods have been developed and successfully tested in the district Buch/Karow of Berlin during the research study 'emission cataster of electric and magnetic field exposure in Berlin -a comparative study in selected public areas'. In this study the following field sources have been taken to consideration: i) 110-kV, 220-kV, 380-kV transmission lines, ii) 110-kV power transmission cables, iii) relay station Karow, iv) 10-kV medium voltage level, v) 1-kV distribution level, vi) power stations, vii) railway, viii) urban railway. (author)

RESIDENTIAL EXPOSURE TO EXTREMELY LOW FREQUENCY ELECTRIC AND MAGNETIC FIELDS IN THE CITY OF RAMALLAH-PALESTINE.

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Abuasbi, Falastine; Lahham, Adnan; Abdel-Raziq, Issam Rashid

2018-04-01

This study was focused on the measurement of residential exposure to power frequency (50-Hz) electric and magnetic fields in the city of Ramallah-Palestine. A group of 32 semi-randomly selected residences distributed amongst the city were under investigations of fields variations. Measurements were performed with the Spectrum Analyzer NF-5035 and were carried out at one meter above ground level in the residence's bedroom or living room under both zero and normal-power conditions. Fields' variations were recorded over 6-min and some times over few hours. Electric fields under normal-power use were relatively low; ~59% of residences experienced mean electric fields V/m. The highest mean electric field of 66.9 V/m was found at residence R27. However, electric field values were log-normally distributed with geometric mean and geometric standard deviation of 9.6 and 3.5 V/m, respectively. Background electric fields measured under zero-power use, were very low; ~80% of residences experienced background electric fields V/m. Under normal-power use, the highest mean magnetic field (0.45 μT) was found at residence R26 where an indoor power substation exists. However, ~81% of residences experienced mean magnetic fields residences showed also a log-normal distribution with geometric mean and geometric standard deviation of 0.04 and 3.14 μT, respectively. Under zero-power conditions, ~7% of residences experienced average background magnetic field >0.1 μT. Fields from appliances showed a maximum mean electric field of 67.4 V/m from hair dryer, and maximum mean magnetic field of 13.7 μT from microwave oven. However, no single result surpassed the ICNIRP limits for general public exposures to ELF fields, but still, the interval 0.3-0.4 μT for possible non-thermal health impacts of exposure to ELF magnetic fields, was experienced in 13% of the residences.

Extremely low frequency electromagnetic field (ELF-EMF) reduces oxidative stress and improves functional and psychological status in ischemic stroke patients.

Science.gov (United States)

Cichoń, Natalia; Bijak, Michał; Miller, Elżbieta; Saluk, Joanna

2017-07-01

As a result of ischaemia/reperfusion, massive generation of reactive oxygen species occurs, followed by decreased activity of antioxidant enzymes. Extremely low frequency electromagnetic fields (ELF-EMF) can modulate oxidative stress, but there are no clinical antioxidant studies in brain stroke patients. The aim of our study was to investigate the effect of ELF-EMF on clinical and antioxidant status in post-stroke patients. Fifty-seven patients were divided into two groups: ELF-EMF and non-ELF-EMF. Both groups underwent the same 4-week rehabilitation program. Additionally, the ELF-EMF group was exposed to an ELF-EMF field of 40 Hz, 7 mT for 15 min/day for 4 weeks (5 days a week). The activity of catalase and superoxide dismutase was measured in hemolysates, and total antioxidant status (TAS) determined in plasma. Functional status was assessed before and after the series of treatments using Activities of Daily Living (ADL), Mini-Mental State Examination (MMSE), and Geriatric Depression Scale (GDS). Applied ELF-EMF significantly increased enzymatic antioxidant activity; however, TAS levels did not change in either group. Results show that ELF-EMF induced a significant improvement in functional (ADL) and mental (MMSE, GDS) status. Clinical parameters had positive correlation with the level of enzymatic antioxidant protection. Bioelectromagnetics. 38:386-396, 2017. © 2017 Wiley Periodicals, Inc. © 2017 Wiley Periodicals, Inc.

Combined effects of extremely high frequency electromagnetic field and antibiotics on Enterococcus Hirae growth and survival

International Nuclear Information System (INIS)

Ohanyan, V.A.

2012-01-01

Combined effects of extremely high frequency electromagnetic field and antibiotics on Enterococcus hirae ATCC 9790 bacterial growth and survival were investigated using 51.8 GHz and 53 GHz frequencies in combination with two commonly used antibiotics: ampicillin and dalacin. Results revealed that, despite bacterial type and membrane structure and properties, the combined effect, especially with 53 GHz and dalacin, suppresses bacterial growth and decreases their survival

Biophysical control of the growth of Agrobacterium tumefaciens using extremely low frequency electromagnetic waves at resonance frequency.

Science.gov (United States)

Fadel, M Ali; El-Gebaly, Reem H; Mohamed, Shaimaa A; Abdelbacki, Ashraf M M

2017-12-09

Isolated Agrobacterium tumefaciens was exposed to different extremely low frequencies of square amplitude modulated waves (QAMW) from two generators to determine the resonance frequency that causes growth inhibition. The carrier was 10 MHz sine wave with amplitude ±10 Vpp which was modulated by a second wave generator with a modulation depth of ± 2Vpp and constant field strength of 200 V/m at 28 °C. The exposure of A. tumefaciens to 1.0 Hz QAMW for 90 min inhibited the bacterial growth by 49.2%. In addition, the tested antibiotics became more effective against A. tumefaciens after the exposure. Furthermore, results of DNA, dielectric relaxation and TEM showed highly significant molecular and morphological changes due to the exposure to 1.0 Hz QAMW for 90 min. An in-vivo study has been carried out on healthy tomato plants to test the pathogenicity of A. tumefaciens before and after the exposure to QAMW at the inhibiting frequency. Symptoms of crown gall and all pathological symptoms were more aggressive in tomato plants treated with non-exposed bacteria, comparing with those treated with exposed bacteria. We concluded that, the exposure of A. tumefaciens to 1.0 Hz QAMW for 90 min modified its cellular activity and DNA structure, which inhibited the growth and affected the microbe pathogenicity. Copyright © 2017 Elsevier Inc. All rights reserved.

On absorption of low frequency electromagnetic fields

International Nuclear Information System (INIS)

Brunner, S.; Vaclavik, J.

1993-03-01

The drift kinetic equation (DKE) is used to establish a formula for power absorption of small amplitude, low frequency electromagnetic (EM) fields in a hot toroidal axisymmetric plasma. The stationary plasma is first considered. Electrons and ions are described by local Maxwellian distributions, alpha particles by a local slowing-down distribution. The fluctuating part of the distribution function for each species is then evaluated from the linearized DKE in terms of the EM fields using a perturbation method. The parameter b p =B p /B o , where B p is the poloidal component of the magnetostatic field B o , and the parameter v d /λω, where v d is the magnetic curvature drift, λ the wavelength perpendicular to B o and ω the frequency of the EM fields, are considered to be small. By integrating the resulting distribution function over velocity space, an explicit formula for the power absorbed by each species is obtained. To obtain an expression suitable for direct implementation in an ideal-MHD code, the electric field component parallel to the magnetostatic field is evaluated using the quasi-neutrality equation. (author) 4 refs

Response identification in the extremely low frequency region of an electret condenser microphone.

Science.gov (United States)

Jeng, Yih-Nen; Yang, Tzung-Ming; Lee, Shang-Yin

2011-01-01

This study shows that a small electret condenser microphone connected to a notebook or a personal computer (PC) has a prominent response in the extremely low frequency region in a specific environment. It confines most acoustic waves within a tiny air cell as follows. The air cell is constructed by drilling a small hole in a digital versatile disk (DVD) plate. A small speaker and an electret condenser microphone are attached to the two sides of the hole. Thus, the acoustic energy emitted by the speaker and reaching the microphone is strong enough to actuate the diaphragm of the latter. The experiments showed that, once small air leakages are allowed on the margin of the speaker, the microphone captured the signal in the range of 0.5 to 20 Hz. Moreover, by removing the plastic cover of the microphone and attaching the microphone head to the vibration surface, the low frequency signal can be effectively captured too. Two examples are included to show the convenience of applying the microphone to pick up the low frequency vibration information of practical systems.

Response Identification in the Extremely Low Frequency Region of an Electret Condenser Microphone

Directory of Open Access Journals (Sweden)

Shang-Yin Lee

2011-01-01

Full Text Available This study shows that a small electret condenser microphone connected to a notebook or a personal computer (PC has a prominent response in the extremely low frequency region in a specific environment. It confines most acoustic waves within a tiny air cell as follows. The air cell is constructed by drilling a small hole in a digital versatile disk (DVD plate. A small speaker and an electret condenser microphone are attached to the two sides of the hole. Thus, the acoustic energy emitted by the speaker and reaching the microphone is strong enough to actuate the diaphragm of the latter. The experiments showed that, once small air leakages are allowed on the margin of the speaker, the microphone captured the signal in the range of 0.5 to 20 Hz. Moreover, by removing the plastic cover of the microphone and attaching the microphone head to the vibration surface, the low frequency signal can be effectively captured too. Two examples are included to show the convenience of applying the microphone to pick up the low frequency vibration information of practical systems.

Co-Culture with Human Osteoblasts and Exposure to Extremely Low Frequency Pulsed Electromagnetic Fields Improve Osteogenic Differentiation of Human Adipose-Derived Mesenchymal Stem Cells

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Sabrina Ehnert

2018-03-01

Full Text Available Human adipose-derived mesenchymal stem cells (Ad-MSCs have been proposed as suitable option for cell-based therapies to support bone regeneration. In the bone environment, Ad-MSCs will receive stimuli from resident cells that may favor their osteogenic differentiation. There is recent evidence that this process can be further improved by extremely low frequency pulsed electromagnetic fields (ELF-PEMFs. Thus, the project aimed at (i investigating whether co-culture conditions of human osteoblasts (OBs and Ad-MSCs have an impact on their proliferation and osteogenic differentiation; (ii whether this effect can be further improved by repetitive exposure to two specific ELF-PEMFs (16 and 26 Hz; (iii and the effect of these ELF-PEMFs on human osteoclasts (OCs. Osteogenic differentiation was improved by co-culturing OBs and Ad-MSCs when compared to the individual mono-cultures. An OB to Ad-MSC ratio of 3:1 had best effects on total protein content, alkaline phosphatase (AP activity, and matrix mineralization. Osteogenic differentiation was further improved by both ELF-PEMFs investigated. Interestingly, only repetitive exposure to 26 Hz ELF-PEMF increased Trap5B activity in OCs. Considering this result, a treatment with gradually increasing frequency might be of interest, as the lower frequency (16 Hz could enhance bone formation, while the higher frequency (26 Hz could enhance bone remodeling.

Review of Studies Concerning Electromagnetic Field (EMF Exposure Assessment in Europe: Low Frequency Fields (50 Hz–100 kHz

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Peter Gajšek

2016-09-01

Full Text Available We aimed to review the findings of exposure assessment studies done in European countries on the exposure of the general public to low frequency electric and magnetic fields (EMFs of various frequencies. The study shows that outdoor average extremely low frequency magnetic fields (ELF-MF in public areas in urban environments range between 0.05 and 0.2 µT in terms of flux densities, but stronger values (of the order of a few µT may occur directly beneath high-voltage power lines, at the walls of transformer buildings, and at the boundary fences of substations. In the indoor environment, high values have been measured close to several domestic appliances (up to the mT range, some of which are held close to the body, e.g., hair dryers, electric shavers. Common sources of exposure to intermediate frequencies (IF include induction cookers, compact fluorescent lamps, inductive charging systems for electric cars and security or anti-theft devices. No systematic measurement surveys or personal exposimetry data for the IF range have been carried out and only a few reports on measurements of EMFs around such devices are mentioned. According to the available European exposure assessment studies, three population exposure categories were classified by the authors regarding the possible future risk analysis. This classification should be considered a crucial advancement for exposure assessment, which is a mandatory step in any future health risk assessment of EMFs exposure.

Review of Studies Concerning Electromagnetic Field (EMF) Exposure Assessment in Europe: Low Frequency Fields (50 Hz–100 kHz)

Science.gov (United States)

Gajšek, Peter; Ravazzani, Paolo; Grellier, James; Samaras, Theodoros; Bakos, József; Thuróczy, György

2016-01-01

We aimed to review the findings of exposure assessment studies done in European countries on the exposure of the general public to low frequency electric and magnetic fields (EMFs) of various frequencies. The study shows that outdoor average extremely low frequency magnetic fields (ELF-MF) in public areas in urban environments range between 0.05 and 0.2 µT in terms of flux densities, but stronger values (of the order of a few µT) may occur directly beneath high-voltage power lines, at the walls of transformer buildings, and at the boundary fences of substations. In the indoor environment, high values have been measured close to several domestic appliances (up to the mT range), some of which are held close to the body, e.g., hair dryers, electric shavers. Common sources of exposure to intermediate frequencies (IF) include induction cookers, compact fluorescent lamps, inductive charging systems for electric cars and security or anti-theft devices. No systematic measurement surveys or personal exposimetry data for the IF range have been carried out and only a few reports on measurements of EMFs around such devices are mentioned. According to the available European exposure assessment studies, three population exposure categories were classified by the authors regarding the possible future risk analysis. This classification should be considered a crucial advancement for exposure assessment, which is a mandatory step in any future health risk assessment of EMFs exposure. PMID:27598182

Effects of short term and long term Extremely Low Frequency Magnetic Field on depressive disorder in mice: Involvement of nitric oxide pathway.

Science.gov (United States)

Madjid Ansari, Alireza; Farzampour, Shahrokh; Sadr, Ali; Shekarchi, Babak; Majidzadeh-A, Keivan

2016-02-01

Previous reports on the possible effects of Extremely Low Frequency Magnetic Fields (ELF MF) on mood have been paradoxical in different settings while no study has yet been conducted on animal behavior. In addition, it was shown that ELF MF exposure makes an increase in brain nitric oxide level. Therefore, in the current study, we aimed to assess the possible effect(s) of ELF MF exposure on mice Forced Swimming Test (FST) and evaluate the probable role of the increased level of nitric oxide in the observed behavior. Male adult mice NMRI were recruited to investigate the short term and long term ELF MF exposure (0.5 mT and 50 Hz, single 2h and 2 weeks 2h a day). Locomotor behavior was assessed by using open-field test (OFT) followed by FST to evaluate the immobility time. Accordingly, NΩ-nitro-l-arginine methyl ester 30 mg/kg was used to exert anti-depressant like effect. According to the results, short term exposure did not alter the immobility time, whereas long term exposure significantly reduces immobility time (pmice, whereas short term exposure has no significant effect. Also, reversing the anti-depressant activity of L-NAME indicates a probable increase in the brain nitric oxide. Copyright © 2016 Elsevier Inc. All rights reserved.

LOMEGA: a low frequency, field implicit method for plasma simulation

International Nuclear Information System (INIS)

Barnes, D.C.; Kamimura, T.

1982-04-01

Field implicit methods for low frequency plasma simulation by the LOMEGA (Low OMEGA) codes are described. These implicit field methods may be combined with particle pushing algorithms using either Lorentz force or guiding center force models to study two-dimensional, magnetized, electrostatic plasmas. Numerical results for ωsub(e)deltat>>1 are described. (author)

Effects of extremely low frequency electromagnetic field (ELF-EMF) on catalase, cytochrome P450 and nitric oxide synthase in erythro-leukemic cells.

Science.gov (United States)

Patruno, Antonia; Tabrez, Shams; Pesce, Mirko; Shakil, Shazi; Kamal, Mohammad A; Reale, Marcella

2015-01-15

Extremely low frequency electromagnetic fields (ELF-EMFs) are widely employed in electrical appliances and different equipment such as television sets, mobile phones, computers and microwaves. The molecular mechanism through which ELF-EMFs can influence cellular behavior is still unclear. A hypothesis is that ELF-EMFs could interfere with chemical reactions involving free radical production. Under physiologic conditions, cells maintain redox balance through production of ROS/RNS and antioxidant molecules. The altered balance between ROS generation and elimination plays a critical role in a variety of pathologic conditions including neurodegenerative diseases, aging and cancer. Actually, there is a disagreement as to whether there is a causal or coincidental relationship between ELF-EMF exposure and leukemia development. Increased ROS levels have been observed in several hematopoietic malignancies including acute and chronic myeloid leukemias. In our study, the effect of ELF-EMF exposure on catalase, cytochrome P450 and inducible nitric oxide synthase activity and their expression by Western blot analysis in myelogenous leukemia cell line K562 was evaluated. A significant modulation of iNOS, CAT and Cyt P450 protein expression was recorded as a result of ELF-EMF exposure in both phorbol 12-myristate 13-acetate (PMA)-stimulated and non-stimulated cell lines. Modulation in kinetic parameters of CAT, CYP-450 and iNOS enzymes in response to ELF-EMF indicates an interaction between the ELF-EMF and the enzymological system. These new insights might be important in establishing a mechanistic framework at the molecular level within which the possible effects of ELF-EMF on health can be understood. Copyright © 2014 Elsevier Inc. All rights reserved.

Parametric excitation of very low frequency (VLF) electromagnetic whistler waves and interaction with energetic electrons in radiation belt

Science.gov (United States)

Sotnikov, V.; Kim, T.; Caplinger, J.; Main, D.; Mishin, E.; Gershenzon, N.; Genoni, T.; Paraschiv, I.; Rose, D.

2018-04-01

The concept of a parametric antenna in ionospheric plasma is analyzed. Such antennas are capable of exciting electromagnetic radiation fields, specifically the creation of whistler waves generated at the very low frequency (VLF) range, which are also capable of propagating large distances away from the source region. The mechanism of whistler wave generation is considered a parametric interaction of quasi-electrostatic whistler waves (also known as low oblique resonance (LOR) oscillations) excited by a conventional loop antenna. The interaction of LOR waves with quasi-neutral density perturbations in the near field of an antenna gives rise to electromagnetic whistler waves on combination frequencies. It is shown in this work that the amplitude of these waves can considerably exceed the amplitude of whistler waves directly excited by a loop. Additionally, particle-in-cell simulations, which demonstrate the excitation and spatial structure of VLF waves excited by a loop antenna, are presented. Possible applications including the wave-particle interactions to mitigate performance anomalies of low Earth orbit satellites, active space experiments, communication via VLF waves, and modification experiments in the ionosphere will be discussed.

Plasma rotation effect on interaction of low frequency fields with plasmas at the rational surfaces in tokamaks

International Nuclear Information System (INIS)

Rondan, E.R.; Elfimov, A.G.; Galvao, R.M.O.; Pires, C.J.A.

2006-01-01

The effect of plasma rotation on low frequency (LF) field penetration, absorption and ponderomotive forces in TEXTOR and in Tokamak Chauffage Alfven Bresilien (TCABR) is investigated in the frequency band of 1-10 kHz. The LF fields are driven by the dynamic ergodic divertor in TEXTOR and the ergodic magnetic limiter in TCABR. Alfven wave mode conversion is responsible for the LF field absorption at the rational magnetic surface where q = -M/N is the integer. Analytical and numerical calculations show the maxima of the LF field absorption at the local Alfven wave resonance ω - k · U = k parallel c A , where ω and k are the frequency and the wave vector, respectively, and c A is the Alfven velocity at the rational magnetic surface q = 2, 3 in TEXTOR and TCABR. The rotation velocity U along the magnetic surfaces, taken into account in the dielectric tensor, can strongly modify the LF field and dissipated power profiles. The absorption in the local AW resonances begins to be non-symmetric in relation to the resonance surface. Calculations show that coil impedance has a maximum related to excitation of some stable (possibly Suydam) modes for waves travelling in the direction of plasma rotation

Sound field control for a low-frequency test facility

DEFF Research Database (Denmark)

Pedersen, Christian Sejer; Møller, Henrik

2013-01-01

The two largest problems in controlling the reproduction of low-frequency sound for psychoacoustic experiments is the effect of the room due to standing waves and the relatively large sound pressure levels needed. Anechoic rooms are limited downward in frequency and distortion may be a problem even...... at moderate levels, while pressure-field playback can give higher sound pressures but is limited upwards in frequency. A new solution that addresses both problems has been implemented in the laboratory of Acoustics, Aalborg University. The solution uses one wall with 20 loudspeakers to generate a plane wave...... that is actively absorbed when it reaches the 20 loudspeakers on the opposing wall. This gives a homogeneous sound field in the majority of the room with a flat frequency response in the frequency range 2-300 Hz. The lowest frequencies are limited to sound pressure levels in the order of 95 dB. If larger levels...

Preliminary study : Extremely low frequency electromagnetic field (ELF EMF) effects on the growth of plant

International Nuclear Information System (INIS)

Roha Tukimin; Wan Norsuhaila Wan Aziz; Rozaimah Abd Rahim; Wan Saffiey Wan Abdulah

2010-01-01

A research has been done to study the effects of magnetic fields on the growth of plants.Two samples of maize seedlings and green beans have been studied. Helmholtz coil systems were used as magnetic field source at frequency 50 Hz with 440 mGauss field strength. Sample characteristics such height, leaf, colour and length of roots were observed. The results show that the magnetic field influenced the growth of the sample. The sample that were exposed to the magnetic field show faster growth compared to the controlled sample. (author)

Low frequency modulation of transionospheric radio wave amplitude at low-latitudes: possible role of field line oscillations

Directory of Open Access Journals (Sweden)

A. K. Sinha

Full Text Available Ionospheric scintillations of radio waves at low-latitudes are associated with electron density irregularities. These irregularities are field-aligned and can provide excitation energy all along the field line to non-local field-aligned oscillations, such as the local field line oscillations. Eigen-periods of toroidal field line oscillations at low-latitudes, computed by using the dipole magnetic field and ion distributions obtained from the International Reference Ionosphere (IRI for typical nighttime conditions, fall in the range of 20–25 s. When subjected to spectral analysis, signal strength of the radio waves recorded on the 250 MHz beacon at Pondicherry (4.5° N dip, Mumbai (13.4° N dip and Ujjain (18.6° N dip exhibit periodicities in the same range. For the single event for which simultaneous ground magnetic data were available, the geomagnetic field also oscillated at the same periodicity. The systematic presence of a significant peak in the 20–25 s range during periods of strong radio wave scintillations, and its absence otherwise suggests the possibility that field line oscillations are endogenously excited by the irregularities, and the oscillations associated with the excited field line generate the modulation characteristics of the radio waves received on the ground. The frequency of modulation is found to be much lower than the characteristic frequencies that define the main body of scintillations, and they probably correspond to scales that are much larger than the typical Fresnel scale. It is possible that the refractive mechanism associated with larger scale long-lived irregularities could be responsible for the observed phenomenon. Results of a preliminary numerical experiment that uses a sinusoidal phase irregularity in the ionosphere as a refracting media are presented. The results show that phase variations which are large enough to produce a focal plane close to the ground can reproduce features that are not

Low frequency modulation of transionospheric radio wave amplitude at low-latitudes: possible role of field line oscillations

Directory of Open Access Journals (Sweden)

A. K. Sinha

2002-01-01

Full Text Available Ionospheric scintillations of radio waves at low-latitudes are associated with electron density irregularities. These irregularities are field-aligned and can provide excitation energy all along the field line to non-local field-aligned oscillations, such as the local field line oscillations. Eigen-periods of toroidal field line oscillations at low-latitudes, computed by using the dipole magnetic field and ion distributions obtained from the International Reference Ionosphere (IRI for typical nighttime conditions, fall in the range of 20–25 s. When subjected to spectral analysis, signal strength of the radio waves recorded on the 250 MHz beacon at Pondicherry (4.5° N dip, Mumbai (13.4° N dip and Ujjain (18.6° N dip exhibit periodicities in the same range. For the single event for which simultaneous ground magnetic data were available, the geomagnetic field also oscillated at the same periodicity. The systematic presence of a significant peak in the 20–25 s range during periods of strong radio wave scintillations, and its absence otherwise suggests the possibility that field line oscillations are endogenously excited by the irregularities, and the oscillations associated with the excited field line generate the modulation characteristics of the radio waves received on the ground. The frequency of modulation is found to be much lower than the characteristic frequencies that define the main body of scintillations, and they probably correspond to scales that are much larger than the typical Fresnel scale. It is possible that the refractive mechanism associated with larger scale long-lived irregularities could be responsible for the observed phenomenon. Results of a preliminary numerical experiment that uses a sinusoidal phase irregularity in the ionosphere as a refracting media are presented. The results show that phase variations which are large enough to produce a focal plane close to the ground can reproduce features that are not

A low-frequency vibration energy harvester based on diamagnetic levitation

Science.gov (United States)

Kono, Yuta; Masuda, Arata; Yuan, Fuh-Gwo

2017-04-01

This article presents 3-degree-of-freedom theoretical modeling and analysis of a low-frequency vibration energy harvester based on diamagnetic levitation. In recent years, although much attention has been placed on vibration energy harvesting technologies, few harvesters still can operate efficiently at extremely low frequencies in spite of large potential demand in the field of structural health monitoring and wearable applications. As one of the earliest works, Liu, Yuan and Palagummi proposed vertical and horizontal diamagnetic levitation systems as vibration energy harvesters with low resonant frequencies. This study aims to pursue further improvement along this direction, in terms of expanding maximum amplitude and enhancing the flexibility of the operation direction for broader application fields by introducing a new topology of the levitation system.

Low-frequency transient electric and magnetic fields coupling to child body

International Nuclear Information System (INIS)

Ozen, S.

2008-01-01

Much of the research related to residential electric and magnetic field exposure focuses on cancer risk for children. But until now only little knowledge about coupling of external transient electric and magnetic fields with the child's body at low frequency transients existed. In this study, current densities, in the frequency range from 50 Hz up to 100 kHz, induced by external electric and magnetic fields to child and adult human body, were investigated, as in residential areas, electric and magnetic fields become denser in this frequency band. For the calculations of induced fields and current density, the ellipsoidal body models are used. Current density induced by the external magnetic field (1 μT) and external electric field (1 V/m) is estimated. The results of this study show that the transient electric and magnetic fields would induce higher current density in the child body than power frequency fields with similar field strength. (authors)

Short-term effects of extremely low-frequency pulsed electromagnetic field and pulsed low-level laser therapy on rabbit model of corneal alkali burn.

Science.gov (United States)

Rezaei Kanavi, Mozhgan; Tabeie, Faraj; Sahebjam, Farzin; Poursani, Nima; Jahanbakhsh, Nazanin; Paymanpour, Pouya; AfsarAski, Sasha

2016-04-01

This study was conducted to investigate the effect of combining extremely low frequency-pulsed electromagnetic field (ELF-PEMF) and low-level laser therapy (LLLT) on alkali-burned rabbit corneas. Fifty alkali-burned corneas of 50 rabbits were categorized into five groups: ELF-PEMF therapy with 2 mT intensity (ELF 2) for 2 h daily; LLLT for 30 min twice daily; combined ELF-PEMF and LLLT (ELF + LLLT); medical therapy (MT); and control (i.e., no treatment). Clinical examination and digital photography of the corneas were performed on days 0, 2, 7, and 14. After euthanizing the rabbits, the affected eyes were evaluated by histopathology. The clinical and histopathologic results were compared between the groups. On days 7 and 14, no significant difference in the corneal defect area was evident between the ELF, LLLT, ELF + LLLT, and MT groups. Excluding the controls, none of the study groups demonstrated a significant corneal neovascularization in both routine histopathology and immunohistochemistry for CD31. Keratocyte loss was significantly higher in the MT group than in the ELF, LLLT, and ELF + LLLT groups. Moderate to severe stromal inflammation in the LLLT group was comparable with that in the MT group and was significantly lower than that in the other groups. In conclusion, combining LLLT and ELF was not superior to ELF alone or LLLT alone in healing corneal alkali burns. However, given the lower intensity of corneal inflammation and the lower rate of keratocytes loss with LLLT, this treatment may be superior to other proposed treatment modalities for healing alkali-burned corneas. Copyright © 2016 Elsevier Ltd. All rights reserved.

Biological actions and effects of low-frequency fields

International Nuclear Information System (INIS)

Brix, J.

1993-01-01

Cell culture studies have shown that low-frequency electromagnetic fields may affect cell behaviour. The fact that the corresponding field strengths are too weak to affect membrane potential, suggests that these fields trigger enzymatic reactions at the outer face of the membrane, i.e. cell-intrinsic reaction cascades and a biological modification of the affected biological system take place. These are working models and hypotheses which need to substantiated by further studies in this field. Epidemiological studies suggest that electromagnetic fields influence cancer development in man. However there is no action model indicating exposure to fields to be a genotoxic agent possible triggering a direct genetic modification which precludesr any initialization. (orig.) [de

Child leukaemia and low frequency electromagnetic fields; Les leucemies de l'enfant et les champs electromagnetiques basse frequence

Energy Technology Data Exchange (ETDEWEB)

Clavel, J.

2009-07-01

The author discusses the possible causes of child leukaemia: exposure to natural ionizing radiation (notably radon), to pesticides, and to hydrocarbons emitted by road traffic. Some studies suggested that an inadequate reaction of the immune system to an ordinary infection could result in leukaemia. Other factors are suspected, notably extremely low frequency electromagnetic fields, the influence of which is then discussed by the author. She evokes and discusses results of different investigations on this topic which have been published since the end of the 1970's. It appears that a distance less than 50 meters from high voltage lines or the vicinity of transformation stations may double the risk of child leukaemia

Efficacy and safety evaluation of systemic extremely low frequency magnetic fields used in the healing of diabetic foot ulcers--phase II data.

Science.gov (United States)

Cañedo-Dorantes, Luis; Soenksen, Luis R; García-Sánchez, Clara; Trejo-Núñez, Daphny; Pérez-Chávez, Fernando; Guerrero, Arturo; Cardona-Vicario, Melisa; García-Lara, Carlos; Collí-Magaña, Dianelly; Serrano-Luna, Gregorio; Angeles Chimal, José S; Cabrera, Guillermo

2015-08-01

Cellular and animal models investigating extremely low frequency magnetic fields (ELF-MF) have reported promotion of leukocyte-endothelial interactions, angiogenesis, myofibroblast and keratinocyte proliferation, improvement of peripheral neuropathy and diabetic wound healing. In humans, it has also been reported that systemic exposure to ELF-MF stimulates peripheral blood mononuclear cells, promoting angiogenesis and healing of chronic leg ulcers. The aim of the study was to investigate the effect of exposing different blood volumes to specific ELF-MFs (120 Hz sinusoidal waves of 0.4-0.9 mT RMS) to induce healing of diabetic foot ulcers (DFUs). Twenty six diabetic patients with non-responsive DFUs were divided into two exposure groups to receive treatment and record healing time. The forearm group, exposed to ELF-MF 2 h/day, twice weekly (3.6 l of blood/session); and the thorax group, exposed 25 min/day, 2 times/week (162.5 l of blood/session). Treatment period was 100 days or upon complete healing. Ulcer recurrences and adverse effects were investigated during short-term (<1 year) and long-term (3.4-7.8 years) follow-up. Mean healing time was 61.48 ± 33.08 days in the forearm group and 62.56 ± 29.33 days for the thorax group. No adverse effects or ulcer recurrences in the original ulcer site were reported during treatment, the short-term follow-up period or the long-term follow-up period in both groups. Healing time was independent of the amount of blood exposed to ELF-MF used in this trial. ELF-MFs are effective and safe and could be applied to non-healing DFUs in conjunction with other preventive interventions to reduce DFUs complications. Copyright © 2015 IMSS. Published by Elsevier Inc. All rights reserved.

Investigation of Interaction between Deferoxamine and Low Frequency Electromagnetic Field on Angiogenesis in Chick Embryo

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Atena Dashtizadeh

2015-02-01

Full Text Available Background: Deferoxamine (DFO is an iron chelator. In the present research, the synergic effects of deferoxamine and electromagnetic field (with 50 H frequency and 100 Gauss intensity on angiogenesis of chick chorioallantoic membrane were investigated. Materials and Methods: In this experimental study 80 fertilized egg used and randomly divided 8 group: control group, laboratory control groups of 1 and 2, experimental group 1 (treatment with electromagnetic field, 2 and 3 (treatment with deferoxamine 10, 100 µmol, respectively, 4 and 5 (treatment both deferoxamine 10 and 100 µmol respectively and electromagnetic field. On 8th day of incubation, 2 and 4 groups were incubated with 10 µL deferoxamine and for 3 and 5 groups were incubated with 10 µL deferoxamine 100 µmol. On 10th day, 1, 4 and 5 groups were put in electromagnetic field. On 12th day, the number and length of vessels in all samples was measured by Image J software. Data were analyzed by SPSS-19, ANOVA and t-test. Results: The mean number and length of vessels in the control and experimental cases did not show any significant differences. Comparison between mean number of vessels in the control and group 2, 3, 4, 5 showed a significant decrease (p<0.05 and groups 2 and 4 was showed a significant decrease in the mean length of vessels compared with the controls (p<0.05. Conclusion: Using deferoxamine with low frequency electromagnetic field (50 Hz and 100 G cause inhibition of angiogenesis in chick embryo chorioallantoic membrane.

Improvement of Low-Frequency Sound Field Obtained by an Optimized Boundary

Institute of Scientific and Technical Information of China (English)

JING Lu; ZHU Xiao-tian

2006-01-01

An approach based on the finite element analysis was introduced to improve low-frequency sound field. The optimized scatters on the wall redistribute the modes of the room and provide effective diffusion of sound field. The frequency response, eigenfrequency, spatial distribution and transient response were calculated. Experimental data were obtained through a 1:5 scaled set up. The results show that the optimized treatment has a positive effect on sound field and the improvement is obvious.

Low-frequency electromagnetic field in a Wigner crystal

OpenAIRE

Stupka, Anton

2016-01-01

Long-wave low-frequency oscillations are described in a Wigner crystal by generalization of the reverse continuum model for the case of electronic lattice. The internal self-consistent long-wave electromagnetic field is used to describe the collective motions in the system. The eigenvectors and eigenvalues of the obtained system of equations are derived. The velocities of longitudinal and transversal sound waves are found.

The distinguishing effects of low-intensity electromagnetic radiation of different extremely high frequencies on Enterococcus hirae: growth rate inhibition and scanning electron microscopy analysis.

Science.gov (United States)

Hovnanyan, K; Kalantaryan, V; Trchounian, A

2017-09-01

A low-intensity electromagnetic field of extremely high frequency has inhibitory and stimulatory effects on bacteria, including Enterococcus hirae. It was shown that the low-intensity (the incident power density of 0·06 mW cm -2 ) electromagnetic field at the frequencies of 51·8 GHz and 53 GHz inhibited E. hirae ATCC 9790 bacterial growth rate; a stronger effect was observed with 53 GHz, regardless of exposure duration (0·5 h, 1 h or 2 h). Scanning electron microscopy analysis of these effects has been done; the cells were of spherical shape. Electromagnetic field at 53 GHz, but not 51·8 GHz, changed the cell size-the diameter was enlarged 1·3 fold at 53 GHz. These results suggest the difference in mechanisms of action on bacteria for electromagnetic fields at 51·8 GHz and 53 GHz. A stronger inhibitory effect of low-intensity electromagnetic field on Enterococcus hirae ATCC 9790 bacterial growth rate was observed with 53 GHz vs 51·8 GHz, regardless of exposure duration. Scanning electron microscopy analysis showed that almost all irradiated cells in the population have spherical shapes similar to nonirradiated ones, but they have increased diameters in case of irradiated cells at 53 GHz, but not 51·8 GHz. The results are novel, showing distinguishing effects of low-intensity electromagnetic field of different frequencies. They could be applied in treatment of food and different products in medicine and veterinary, where E. hirae plays an important role. © 2017 The Society for Applied Microbiology.

Radiofrequency and extremely low-frequency electromagnetic field effects on the blood-brain barrier.

Science.gov (United States)

Nittby, Henrietta; Grafström, Gustav; Eberhardt, Jacob L; Malmgren, Lars; Brun, Arne; Persson, Bertil R R; Salford, Leif G

2008-01-01

During the last century, mankind has introduced electricity and during the very last decades, the microwaves of the modern communication society have spread a totally new entity--the radiofrequency fields--around the world. How does this affect biology on Earth? The mammalian brain is protected by the blood-brain barrier, which prevents harmful substances from reaching the brain tissue. There is evidence that exposure to electromagnetic fields at non thermal levels disrupts this barrier. In this review, the scientific findings in this field are presented. The result is a complex picture, where some studies show effects on the blood-brain barrier, whereas others do not. Possible mechanisms for the interactions between electromagnetic fields and the living organisms are discussed. Demonstrated effects on the blood-brain barrier, as well as a series of other effects upon biology, have caused societal anxiety. Continued research is needed to come to an understanding of how these possible effects can be neutralized, or at least reduced. Furthermore, it should be kept in mind that proven effects on biology also should have positive potentials, e.g., for medical use.

Photodetachment of H- in the presence of a low-frequency laser field

International Nuclear Information System (INIS)

Bivona, S.; Burlon, R.; Leone, C.

1992-01-01

The photodetachment of a model one-electron ion simulating H - in the presence of a low-frequency field is analyzed. Two different geometries are considered in order to get information on the effect of the ponderomotive energy shift Δ on the photodetachment cross section. Our calculations suggest that a correspondence may be established between the ponderomotive shift and the photodetachment cross section, when the ejected electron may exchange only a few low-frequency photons. This is in qualitative agreement with recent experimental observations. When a large number of processes are open in which the detached electron may exchange low-frequency photons with comparable probability, it is impossible to make any connection between ponderomotive threshold shift and photodetachment cross section which, instead, may be described in terms of a field picture

The effect of extreme-low-frequency electromagnetic field on air ...

African Journals Online (AJOL)

Electromagnetic fields produce alternating electric fields and modify static electric fields in the vicinity. These electric fields, if large enough, can alter the concentration or transport of airborne particles (including particles harmful to health). In this study, the concentration of radioactive materials (gamma radiation) was ...

Olfactory memory is enhanced in mice exposed to extremely low-frequency electromagnetic fields via Wnt/β-catenin dependent modulation of subventricular zone neurogenesis.

Science.gov (United States)

Mastrodonato, Alessia; Barbati, Saviana Antonella; Leone, Lucia; Colussi, Claudia; Gironi, Katia; Rinaudo, Marco; Piacentini, Roberto; Denny, Christine A; Grassi, Claudio

2018-01-10

Exposure to extremely low-frequency electromagnetic fields (ELFEF) influences the expression of key target genes controlling adult neurogenesis and modulates hippocampus-dependent memory. Here, we assayed whether ELFEF stimulation affects olfactory memory by modulating neurogenesis in the subventricular zone (SVZ) of the lateral ventricle, and investigated the underlying molecular mechanisms. We found that 30 days after the completion of an ELFEF stimulation protocol (1 mT; 50 Hz; 3.5 h/day for 12 days), mice showed enhanced olfactory memory and increased SVZ neurogenesis. These effects were associated with upregulated expression of mRNAs encoding for key regulators of adult neurogenesis and were mainly dependent on the activation of the Wnt pathway. Indeed, ELFEF stimulation increased Wnt3 mRNA expression and nuclear localization of its downstream target β-catenin. Conversely, inhibition of Wnt3 by Dkk-1 prevented ELFEF-induced upregulation of neurogenic genes and abolished ELFEF's effects on olfactory memory. Collectively, our findings suggest that ELFEF stimulation increases olfactory memory via enhanced Wnt/β-catenin signaling in the SVZ and point to ELFEF as a promising tool for enhancing SVZ neurogenesis and olfactory function.

The Measurement of Low Frequency Magnetic Field of Two Kinds of GSM900 Mobile Phone

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Mehri Kaviani Moghadam

2008-06-01

Full Text Available Introduction:  The  use  of  mobile  communication  systems  has  dramatically  increased  over  the  past  decade. Although many studies have been performed to determine the effect of radio frequency (RF but  less attention has been paid to the possible biological impact of exposure to extremely low frequency  (ELF components.   The objective of this study is two folds. One is to design the equipments needed for the measurement of  the ELF fields of two types of GSM900 mobile phone. Secondly, use a protocol suitable for an accurate  assessment of the ELF fields.  Materials  and Methods:  First  a  home-made  search  coil  was  provided  and  calibrated precisely  under  several experiments. Using Fast Fourier Transform, the power spectrum density of the induced voltage in  the search coil was analyzed and the amplitudes of 217 Hz and its harmonics were extracted and then the  distribution of magnetic field in the back side of mobile phones was determined.  Results: The values of B-field on the back side of the two kinds of GSM mobile phone were different.  They  were  between  50  to  160  µT in  Nokia  3310  and  14  to  30  µT in  Nokia  8310.  Considering  the  difference between the amplitudes of frequency components at 217 Hz and its harmonics in the two kinds  of mobile phone, a range of magnetic flux density at different times in a five day period was measured.  Discussion and Conclusion: These findings emphasize the need for considering the distribution of low  frequency magnetic field from mobile phone when biological effects of magnetic fields are studied. To  determine  the  intensity  windowing  effect,  one  must  consider  the  physical  characteristics  of  the  fundamental  frequency  component  wave  (217  Hz  and  its  harmonics  produced  by  the  mobile  phone  similar to the one generated under a real situation.

Low-frequency instabilities of electron-hole plasmas in crossed fields

International Nuclear Information System (INIS)

Schneider, W.; Kirchesch, P.

1978-01-01

Using local point-contact probes, we observed two types of low-frequency instabilities in n-InSb at 85 K if the samples were exposed to crossed fields. One is a local density instability with threshold frequencies of f = 1 ... 20 Mc, the other a more turbulent current instability. The threshold values of U 0 and B for the onset of these instabilities and the dependence of their amplitudes on the fields have been measured. If a rectangular semiconductor slab is placed in crossed fields, regions of high electric field strength at opposite edges of the contacts are caused by the distortion of the Hall field, giving rise to the generation of electron-hole plasmas by impact ionization. These plasmas are the sources of the observed instabilities. This is especially evident in the case of the local density instability, which originates at the anode high field corner. Several possible reasons for the development of the instabilities are discussed. (orig.) [de

Involvement of NMDA receptor in low-frequency magnetic field-induced anxiety in mice.

Science.gov (United States)

Salunke, Balwant P; Umathe, Sudhir N; Chavan, Jagatpalsingh G

2014-12-01

It had been reported that exposure to extremely low-frequency magnetic field (ELFMF) induces anxiety in human and rodents. Anxiety mediates via the activation of N-methyl-d-aspartate (NMDA) receptor, whereas activation of γ-aminobutyric acid (GABA) receptor attenuates the same. Hence, the present study was carried out to understand the contribution of NMDA and/or GABA receptors modulation in ELFMF-induced anxiety for which Swiss albino mice were exposed to ELFMF (50 Hz, 10 G) by subjecting them to Helmholtz coils. The exposure was for 8 h/day for 7, 30, 60, 90 and 120 days. Anxiety level was assessed in elevated plus maze, open field test and social interaction test, on 7th, 30th, 60th, 90th and 120th exposure day, respectively. Moreover, the role of GABA and glutamate in ELFMF-induced anxiety was assessed by treating mice with muscimol [0.25 mg/kg intraperitoneally (i.p.)], bicuculline (1.0 mg/kg i.p.), NMDA (15 mg/kg i.p.) and MK-801 (0.03 mg/kg i.p.), as a GABAA and NMDA receptor agonist and antagonist, respectively. Glutamate receptor agonist exacerbated while inhibitor attenuated the ELFMF-induced anxiety. In addition, levels of GABA and glutamate were determined in regions of the brain viz, cortex, striatum, hippocampus and hypothalamus. Experiments demonstrated significant elevation of GABA and glutamate levels in the hippocampus and hypothalamus. However, GABA receptor modulators did not produce significant effect on ELFMF-induced anxiety and elevated levels of GABA at tested dose. Together, these findings suggest that ELFMF significantly induced anxiety behavior, and indicated the involvement of NMDA receptor in its effect.

Extremely high frequency RF effects on electronics.

Energy Technology Data Exchange (ETDEWEB)

Loubriel, Guillermo Manuel; Vigliano, David; Coleman, Phillip Dale; Williams, Jeffery Thomas; Wouters, Gregg A.; Bacon, Larry Donald; Mar, Alan

2012-01-01

The objective of this work was to understand the fundamental physics of extremely high frequency RF effects on electronics. To accomplish this objective, we produced models, conducted simulations, and performed measurements to identify the mechanisms of effects as frequency increases into the millimeter-wave regime. Our purpose was to answer the questions, 'What are the tradeoffs between coupling, transmission losses, and device responses as frequency increases?', and, 'How high in frequency do effects on electronic systems continue to occur?' Using full wave electromagnetics codes and a transmission-line/circuit code, we investigated how extremely high-frequency RF propagates on wires and printed circuit board traces. We investigated both field-to-wire coupling and direct illumination of printed circuit boards to determine the significant mechanisms for inducing currents at device terminals. We measured coupling to wires and attenuation along wires for comparison to the simulations, looking at plane-wave coupling as it launches modes onto single and multiconductor structures. We simulated the response of discrete and integrated circuit semiconductor devices to those high-frequency currents and voltages, using SGFramework, the open-source General-purpose Semiconductor Simulator (gss), and Sandia's Charon semiconductor device physics codes. This report documents our findings.

Immune-Modulating Perspectives for Low Frequency Electromagnetic Fields in Innate Immunity

Directory of Open Access Journals (Sweden)

Maria Manuela Rosado

2018-03-01

Full Text Available In recent years, the effects of electromagnetic fields (EMFs on the immune system have received a considerable interest, not only to investigate possible negative health impact but also to explore the possibility to favorably modulate immune responses. To generate beneficial responses, the immune system should eradicate pathogens while “respecting” the organism and tolerating irrelevant antigens. According to the current view, damage-associated molecules released by infected or injured cells, or secreted by innate immune cells generate danger signals activating an immune response. These signals are also relevant to the subsequent activation of homeostatic mechanisms that control the immune response in pro- or anti-inflammatory reactions, a feature that allows modulation by therapeutic treatments. In the present review, we describe and discuss the effects of extremely low frequency (ELF-EMF and pulsed EMF on cell signals and factors relevant to the activation of danger signals and innate immunity cells. By discussing the EMF modulating effects on cell functions, we envisage the use of EMF as a therapeutic agent to regulate immune responses associated with wound healing.

Research on Wide-field Imaging Technologies for Low-frequency Radio Array

Science.gov (United States)

Lao, B. Q.; An, T.; Chen, X.; Wu, X. C.; Lu, Y.

2017-09-01

Wide-field imaging of low-frequency radio telescopes are subject to a number of difficult problems. One particularly pernicious problem is the non-coplanar baseline effect. It will lead to distortion of the final image when the phase of w direction called w-term is ignored. The image degradation effects are amplified for telescopes with the wide field of view. This paper summarizes and analyzes several w-term correction methods and their technical principles. Their advantages and disadvantages have been analyzed after comparing their computational cost and computational complexity. We conduct simulations with two of these methods, faceting and w-projection, based on the configuration of the first-phase Square Kilometre Array (SKA) low frequency array. The resulted images are also compared with the two-dimensional Fourier transform method. The results show that image quality and correctness derived from both faceting and w-projection are better than the two-dimensional Fourier transform method in wide-field imaging. The image quality and run time affected by the number of facets and w steps have been evaluated. The results indicate that the number of facets and w steps must be reasonable. Finally, we analyze the effect of data size on the run time of faceting and w-projection. The results show that faceting and w-projection need to be optimized before the massive amounts of data processing. The research of the present paper initiates the analysis of wide-field imaging techniques and their application in the existing and future low-frequency array, and fosters the application and promotion to much broader fields.

Biological effects of exposure to low frequency electric and magnetic fields

International Nuclear Information System (INIS)

Ahnstroem, G.

1992-10-01

The biological effects of exposure to low frequency electric and magnetic fields are reviewed with the objective of summarizing effects directly relevant to considerations of the health and safety of exposed people

Low frequency electric and magnetic fields - effect on fertility and fetal development

International Nuclear Information System (INIS)

Thommesen, G.

1989-01-01

The epidemiological as well as the experimental data are still inconclusive. Inconsistencies within and between research reports make it impossible to state whether, or under what circumstances, low frequency fields may be harmful to reproduction by reducing fertility or by causing fetal malformations or death. The data indicate, however, that a certain care should be exercised in the case of NMR diagnostic imaging, industrial magnetic field exposure, and paramedical pulsed magnetic field therapy on women who might be expected to be in the first trimester of pregnancy, particularly in the unindentified initial phase. Work in connection with visual display units, living in the neighbourhood of overhead high-voltage powerlines, or other every-day sources of exposure to low frequency fields seem, however, to be an insignificant or non-existent threat to an unborn life. 147 refs

[Low-frequency pulsed electromagnetic fields promotes rat osteoblast differentiation in vitro through cAMP/PKA signal pathway].

Science.gov (United States)

Fang, Qing-Qing; Li, Zhi-Zhong; Zhou, Jian; Shi, Wen-Gui; Yan, Juan-Li; Xie, Yan-Fang; Chen, Ke-Ming

2016-11-20

To study whether low-frequency pulsed electromagnetic fields promotes the differentiation of cultured rat osteoblasts through the cAMP/PKA signal pathway. Rat calvarial osteoblasts isolated by enzyme digestion were exposed to 50 Hz 0.6 mT low-frequency pulsed electromagnetic field for varying lengths of time, and the concentration of cAMP and levels of phosphorylated PKA in the cells were assayed. In cells treated with DDA to inhibit the activity of adenylate cyclase, the changes of ALP activity and transcription of osteogenic gene were detected after exposure to low-frequency pulsed electromagnetic field. The changes of osteogenic gene transcription and protein expression were tested in the osteoblasts pretreated with KT5720 in response to low-frequency pulsed electromagnetic field exposure. The intracellular cAMP concentration in the cells increased significantly at 20 min during exposure to low-frequency pulsed electromagnetic field, began to decrease at 40 min during the exposure, and increased again after a 2-h exposure; the same pattern of variation was also observed in p-PKA level. Application of DDA and KT5720 pretreatment both suppressed the increase in ALP activity and osteogenic gene transcription induced by electromagnetic field exposure. Low- frequency pulsed electromagnetic field exposure improves the differentiation of cultured rat osteoblasts by activating cAMP/PKA signal pathway.

Low-frequency flux noise in YBCO dc SQUIDs cooled in static magnetic fields

International Nuclear Information System (INIS)

Sager, M.P.; Bindslev Hansen, J.; Petersen, P.R.E.; Holst, T.; Shen, Y.Q.

1999-01-01

The low-frequency flux noise in bicrystal and step-edge YBa 2 Cu 3 O x dc SQUIDs has been investigated. The width, w, of the superconducting strips forming the SQUID frame was varied from 4 to 42 μm. The SQUIDs were cooled in static magnetic fields up to 150 μT. Two types of low-frequency noise dominated, namely 1/f-like noise and random telegraph noise giving a Lorentzian frequency spectrum. The 1/f noise performance of the w = 4, 6 and 7 μm SQUIDs was almost identical, while the SQUIDs with w = 22 and 42 μm showed an order of magnitude higher noise level. Our analysis of the data suggests an exponential increase of the 1/f noise versus the cooling field, exhibiting a characteristic magnetic field around 40 μT. (author)

Effects of whole body exposure to extremely low frequency electromagnetic fields (ELF-EMF on serum and liver lipid levels, in the rat

Directory of Open Access Journals (Sweden)

Elias-Viñas David

2007-11-01

Full Text Available Abstract Backgound The effects of extremely low-frequency electromagnetic fields (ELF-EMF on the blood serum and liver lipid concentrations of male Wistar rats were assessed. Methods Animals were exposed to a single stimulation (2 h of ELF-EMF (60 Hz, 2.4 mT or sham-stimulated and thereafter sacrificed at different times (24, 48 or 96 h after beginning the exposure. Results Blood lipids showed, at 48 h stimulated animals, a significant increase of cholesterol associated to high density lipoproteins (HDL-C than those observed at any other studied time. Free fatty acid serum presented at 24 h significant increases in comparison with control group. The other serum lipids, triacylglycerols and total cholesterol did not show differences between groups, at any time evaluated. No statistical differences were shown on total lipids of the liver but total cholesterol was elevated at 24 h with a significant decrease at 96 h (p = 0.026. The ELF-EMF stimulation increased the liver content of lipoperoxides at 24 h. Conclusion Single exposures to ELF-EMF increases the serum values of HDL-C, the liver content of lipoperoxides and decreases total cholesterol of the liver. The mechanisms for the effects of ELF-EMF on lipid metabolism are not well understand yet, but could be associated to the nitric oxide synthase EMF-stimulation.

LOW-FREQUENCY MAGNETIC FIELD SHIELDING BY A CIRCULAR PASSIVE LOOP AND CLOSED SHELLS

Directory of Open Access Journals (Sweden)

V.S. Grinchenko

2016-05-01

Full Text Available Purpose. To analyze the shielding factors for a circular passive loop and conductive closed shells placed in a homogeneous low-frequency magnetic field. Methodology. We have obtained simplified expressions for the shielding factors for a circular passive loop and a thin spherical shell. In addition, we have developed the numerical model of a thin cubical shell in a magnetic field, which allows exploring its shielding characteristics. Results. We have obtained dependences of the shielding factors for passive loops and shells on the frequency of the external field. Analytically determined frequency of the external magnetic field, below which field shielding of a passive loop is expedient to use, above which it is advisable to use a shielding shell.

Influences of extremely low frequency magnetic fields on mineral ...

African Journals Online (AJOL)

STORAGESEVER

2008-11-05

Nov 5, 2008 ... African Journal of Biotechnology Vol. 7 (21), pp. ... 1Department of Pediatrics Dentistry, Faculty of Dentistry, University of Dicle. Diyarbakir ... the research community to define more precisely the physical ... clinical effects (Brown et al., 2004). ... group of rats was ELF Magnetic Field-or sham-exposed, i.e., the.

Effects of extremely low frequency electromagnetic fields on growth ...

African Journals Online (AJOL)

Electromagnetic fields are an important environmental factor that can influence the growth and development of plants. Exposure to EMFs was performed by a locally designed EMF generator. Our investigations were focused on plants grown from wet pretreated seeds with 3 and 10 mT for a 4 h exposure time and compared ...

Can safe and long-term exposure to extremely low frequency (50 Hz) magnetic fields affect apoptosis, reproduction, and oxidative stress?

Science.gov (United States)

Akdag, Mehmet Zulkuf; Dasdag, Suleyman; Uzunlar, Ali Kemal; Ulukaya, Engin; Oral, Arzu Yilmaztepe; Çelik, Necla; Akşen, Feyzan

2013-12-01

To determine whether 50 Hz extremely low frequency-magnetic fields (ELF-MF) affects apoptotic processes, oxidative damage, and reproductive characteristics such as sperm count and morphology in rat testes. Thirty male Sprague-Dawley rats were used in the present study, which were divided into three groups (sham group, n = 10, and two experimental groups, n = 10 for each group). Rats in the experimental group were exposed to 100 and 500 μT ELF-MF (2 h/day, 7 days/week, for 10 months) corresponding to exposure levels that are considered safe for humans. The same experimental procedures were applied to the sham group, but the ELF generator was turned off. Tissues from the testes were immunohistochemically stained for active (cleaved) caspase-3 in order to measure the apoptotic index by a semi-quantitative scoring system. The levels of catalase (CAT), malondialdehyde (MDA), myeloperoxidase (MPO), total antioxidative capacity (TAC), total oxidant status (TOS), and oxidative stress index (OSI) were also measured. Additionally, epididymal sperm count and sperm morphology was evaluated. There were no significant differences in the reproductive and oxidative stress parameters between the sham group and the exposed groups (p > 0.05). While no difference was observed between the final apoptosis score of the sham and the 100 μT ELF-MF group (p > 0.05), the final apoptosis score was higher in the 500 μT ELF-MF exposure group than in the sham group (p reproductive components such as sperm count and morphology in testes tissue of rats. However, long-term exposure to 500 μT ELF-MF did affect active-caspase-3 activity, which is a well-known apoptotic indicator.

LOW FREQUENCY DAMPER

Directory of Open Access Journals (Sweden)

Radu BOGATEANU

2009-09-01

Full Text Available The low frequency damper is an autonomous equipment for damping vibrations with the 1-20Hz range.Its autonomy enables the equipment to be located in various mechanical systems, without requiring special hydraulic installations.The low frequency damper was designed for damping the low frequency oscillations occurring in the circuit controls of the upgraded IAR-99 Aircraft.The low frequency damper is a novelty in the aerospace field ,with applicability in several areas as it can be built up in an appropriate range of dimensions meeting the requirements of different beneficiaries. On this line an equipment able to damp an extended frequency range was performed for damping oscillations in the pipes of the nuclear power plants.This damper, tested in INCAS laboratories matched the requirements of the beneficiary.The low frequency damper is patented – the patent no. 114583C1/2000 is held by INCAS.

Simulation and Measurement of Through-the-Earth, Extremely Low-Frequency Signals Using Copper-Clad Steel Ground Rods.

Science.gov (United States)

Damiano, Nicholas William; Yan, Lincan; Whisner, Bruce; Zhou, Chenming

2017-01-01

The underground mining environment can greatly affect radio signal propagation. Understanding how the earth affects signal propagation is a key to evaluating communications systems used during a mine emergency. One type of communication system is through-the-earth, which can utilize extremely low frequencies (ELF). This paper presents the simulation and measurement results of recent National Institute for Occupational Safety and Health (NIOSH) research aimed at investigating current injection at ELF, and in particular, ground contact impedance. Measurements were taken at an outside surface testing location. The results obtained from modeling and measurement are characterized by electrode impedance, and the voltage received between two distant electrodes. This paper concludes with a discussion of design considerations found to affect low-frequency communication systems utilizing ground rods to inject a current into the earth.

Simulation and Measurement of Through-the-Earth, Extremely Low-Frequency Signals Using Copper-Clad Steel Ground Rods

OpenAIRE

Damiano, Nicholas William; Yan, Lincan; Whisner, Bruce; Zhou, Chenming

2017-01-01

The underground mining environment can greatly affect radio signal propagation. Understanding how the earth affects signal propagation is a key to evaluating communications systems used during a mine emergency. One type of communication system is through-the-earth, which can utilize extremely low frequencies (ELF). This paper presents the simulation and measurement results of recent National Institute for Occupational Safety and Health (NIOSH) research aimed at investigating current injection...

Effect of low frequency electromagnetic field on microstructures and macrosegregation of horizontal direct chill casting aluminum alloy

Institute of Scientific and Technical Information of China (English)

赵志浩; 崔建忠; 董杰; 张海涛; 张北江

2004-01-01

The influences of low frequency electromagnetic field on cast surface, microstructures and macrosegregation in horizontal direct chill(HDC) casting process were investigated experimentally. The cast surfaces, microstructures and macrosegregation of the ingots manufactured by conventional HDC and low frequency electromagnetic HDC casting were compared. The results show that low frequency electromagnetic field significantly improves the surface quality, refines the microstructures and reduces macrosegregation. Further more, increasing electromagnetic intensity or decreasing frequency is beneficial to the improvement. In the range of ampere-turns and frequency employed in the experiments, the optimum ampere-turns is found to be 10 000 A · turn and the frequency to be 30 Hz.

Exposure to extremely low frequency (50 Hz electromagnetic field changes the survival rate and morphometric characteristics of neurosecretory neurons of the earthworm Eisenia foetida (Oligochaeta under illumination stress

Directory of Open Access Journals (Sweden)

Banovački Zorana

2013-01-01

Full Text Available An in vivo model was set up to establish the behavioral stress response (rate of survival and morphometric characteristics of A1 protocerebral neurosecretory neurons (cell size of Eisenia foetida (Oligochaeta as a result of the synergetic effect of extremely low frequency electromagnetic fields (ELF-EMF - 50 Hz, 50 μT, 17 V/m and 50 Hz, 150 μT, 17 V/m, respectively and constant illumination (420-450 lux. If combined, these two stressors significantly (p<0.05 increased the survival rate of E. foetida in the 150 μT-exposed animals, because of delayed caudal autotomy reflex, an indicator of stress response. In addition, morphometric analysis indicated that there were changes in the protocerebral neurosecretory cells after exposure to the ELF-EMF. The present data support the view that short-term ELF-EMF exposure in “windows” of intensity is likely to stimulate the immune and neuroendocrine response of E. foetida.

Climate Change: A New Metric to Measure Changes in the Frequency of Extreme Temperatures using Record Data

Science.gov (United States)

Munasinghe, L.; Jun, T.; Rind, D. H.

2012-01-01

Consensus on global warming is the result of multiple and varying lines of evidence, and one key ramification is the increase in frequency of extreme climate events including record high temperatures. Here we develop a metric- called "record equivalent draws" (RED)-based on record high (low) temperature observations, and show that changes in RED approximate changes in the likelihood of extreme high (low) temperatures. Since we also show that this metric is independent of the specifics of the underlying temperature distributions, RED estimates can be aggregated across different climates to provide a genuinely global assessment of climate change. Using data on monthly average temperatures across the global landmass we find that the frequency of extreme high temperatures increased 10-fold between the first three decades of the last century (1900-1929) and the most recent decade (1999-2008). A more disaggregated analysis shows that the increase in frequency of extreme high temperatures is greater in the tropics than in higher latitudes, a pattern that is not indicated by changes in mean temperature. Our RED estimates also suggest concurrent increases in the frequency of both extreme high and extreme low temperatures during 2002-2008, a period when we observe a plateauing of global mean temperature. Using daily extreme temperature observations, we find that the frequency of extreme high temperatures is greater in the daily minimum temperature time-series compared to the daily maximum temperature time-series. There is no such observable difference in the frequency of extreme low temperatures between the daily minimum and daily maximum.

Low frequency noise study.

Science.gov (United States)

2007-04-01

This report documents a study to investigate human response to the low-frequency : content of aviation noise, or low-frequency noise (LFN). The study comprised field : measurements and laboratory studies. The major findings were: : 1. Start-of-takeof...

Resonant interactions between cometary ions and low frequency electromagnetic waves

Science.gov (United States)

Thorne, Richard M.; Tsurutani, Bruce T.

1987-01-01

The conditions for resonant wave amplification in a plasma with a ring-beam distribution which is intended to model pick-up ions in a cometary environment are investigated. The inclination between the interplanetary field and the solar wind is found to play a crucial role in governing both the resonant frequency and the growth rate of any unstable mode. It is suggested that the low-frequency MHD mode should experience the most rapid amplification for intermediate inclination. In the frame of the solar wind, such waves should propagate along the field in the direction upstream toward the sun with a phase speed lower than the beaming velocity of the pick-up ions. This mechanism may account for the presence of the interior MHD waves noted by satellites over a region surrounding comets Giacobini-Zinner and Halley.

Resonant effects on the low frequency vlasov stability of axisymmetric field reversed configurations

International Nuclear Information System (INIS)

Finn, J.M.; Sudan, R.N.

We investigate the effect of particle resonances on low frequency MHD modes in field-reversed geometries, e.g., an ion ring. It is shown that, for sufficiently high field reversal, modes which are hydromagnetically stable can be driven unstable by ion resonances. The stabilizing effect of a toroidal magnetic field is discussed

Resolution improvement of low frequency AC magnetic field detection for modulated MR sensors.

Science.gov (United States)

Hu, Jinghua; Pan, Mengchun; Hu, Jiafei; Li, Sizhong; Chen, Dixiang; Tian, Wugang; Sun, Kun; Du, Qingfa; Wang, Yuan; Pan, Long; Zhou, Weihong; Zhang, Qi; Li, Peisen; Peng, Junping; Qiu, Weicheng; Zhou, Jikun

2017-09-01

Magnetic modulation methods especially Micro-Electro-Mechanical System (MEMS) modulation can improve the sensitivity of magnetoresistive (MR) sensors dramatically, and pT level detection of Direct Current (DC) magnetic field can be realized. While in a Low Frequency Alternate Current (LFAC) magnetic field measurement situation, frequency measurement is limited by a serious spectrum aliasing problem caused by the remanence in sensors and geomagnetic field, leading to target information loss because frequency indicates the magnetic target characteristics. In this paper, a compensation field produced with integrated coils is applied to the MR sensor to remove DC magnetic field distortion, and a LFAC magnetic field frequency estimation algorithm is proposed based on a search of the database, which is derived from the numerical model revealing the relationship of the LFAC frequency and determination factor [defined by the ratio of Discrete Fourier Transform (DFT) coefficients]. In this algorithm, an inverse modulation of sensor signals is performed to detect jumping-off point of LFAC in the time domain; this step is exploited to determine sampling points to be processed. A determination factor is calculated and taken into database to figure out frequency with a binary search algorithm. Experimental results demonstrate that the frequency measurement resolution of the LFAC magnetic field is improved from 12.2 Hz to 0.8 Hz by the presented method, which, within the signal band of a magnetic anomaly (0.04-2 Hz), indicates that the proposed method may expand the applications of magnetoresistive (MR) sensors to human healthcare and magnetic anomaly detection (MAD).

Health effects of low frequency electric and magnetic fields

International Nuclear Information System (INIS)

1992-06-01

The US Department of Labor and the President's Office of Science and Technology Policy (STP) requested that the Committee on interagency Radiation Research and Policy Coordination (CIRRPC) conduct an independent evaluation of the reported health effects from exposure to low-frequency electric and magnetic fields (ELF-EMF), especially reports of carcinogenesis and reproductive and neurophysiological effects focusing on frequencies which appeared to be of greatest public concern. Oak Ridge Associated Universities (ORAU) was tasked by the CIRRPC to oversee the review by a panel of independent, non-Federal, scientists. Following their review of over 1000 journal articles, the ORAU Panel concluded ''... that there is no convincing evidence ... to support the contention that exposure to ELF-EMF generated by sources such as household appliances, video display terminals (10 to 30 KHz), and local power lines (15 to 180 Hz) are demonstrable health hazards.'' Although the Panel noted that some biological effects produced by these fields may be of scientific interest and warrant consideration for future research, it concluded that ''... in the broad scope of research needs in basic science and health research, any health concerns over exposures to these fields should not receive a high priority.'' This executive summary outlines the panel's investigation

Wireless power transmission to an electromechanical receiver using low-frequency magnetic fields

International Nuclear Information System (INIS)

Challa, Vinod R; Arnold, David P; Mur-Miranda, Jose Oscar

2012-01-01

A near-field, electrodynamically coupled wireless power transmission system is presented that delivers electrical power from a transmitter coil to a compact electromechanical receiver. The system integrates electromechanical energy conversion and mechanical resonance to deliver power over a range of distances using low-amplitude, low-frequency magnetic fields. Two different receiver orientations are investigated that rely on either the force or the torque induced on the receiver magnet at separation distances ranging from 2.2 to 10.2 cm. Theoretical models for each mode compare the predicted performance with the experimental results. For a 7.1 mA pk sinusoidal current supplied to a transmitter coil with a 100 cm diameter, the torque mode receiver orientation has a maximum power transfer of 150 μW (efficiency of 12%) at 2.2 cm at its resonance frequency of 38.4 Hz. For the same input current to the transmitter, the force mode receiver orientation has a maximum power transfer of 37 μW (efficiency of 4.1%) at 3.1 cm at its resonance frequency of 38.9 Hz. (paper)

Plate-type metamaterials for extremely broadband low-frequency sound insulation

Science.gov (United States)

Wang, Xiaopeng; Guo, Xinwei; Chen, Tianning; Yao, Ge

2018-01-01

A novel plate-type acoustic metamaterial with a high sound transmission loss (STL) in the low-frequency range ( ≤1000 Hz) is designed, theoretically proven and then experimentally verified. The thin plates with large modulus used in this paper mean that we do not need to apply tension to the plates, which is more applicable to practical engineering, the achievement of noise reduction is better and the installation of plates is more user-friendly than that of the membranes. The effects of different structural parameters of the plates on the sound-proofed performance at low-frequencies were also investigated by experiment and finite element method (FEM). The results showed that the STL can be modulated effectively and predictably using vibration theory by changing the structural parameters, such as the radius and thickness of the plate. Furthermore, using unit cells of different geometric sizes which are responsible for different frequency regions, the stacked panels with thickness ≤16 mm and weight ≤5 kg/m2 showed high STL below 2000 Hz. The acoustic metamaterial proposed in this study could provide a potential application in the low-frequency noise insulation.

Method for imaging with low frequency electromagnetic fields

Science.gov (United States)

Lee, Ki H.; Xie, Gan Q.

1994-01-01

A method for imaging with low frequency electromagnetic fields, and for interpreting the electromagnetic data using ray tomography, in order to determine the earth conductivity with high accuracy and resolution. The imaging method includes the steps of placing one or more transmitters, at various positions in a plurality of transmitter holes, and placing a plurality of receivers in a plurality of receiver holes. The transmitters generate electromagnetic signals which diffuse through a medium, such as earth, toward the receivers. The measured diffusion field data H is then transformed into wavefield data U. The traveltimes corresponding to the wavefield data U, are then obtained, by charting the wavefield data U, using a different regularization parameter .alpha. for each transform. The desired property of the medium, such as conductivity, is then derived from the velocity, which in turn is constructed from the wavefield data U using ray tomography.

The enhanced effects of antibiotics irradiated of extremely high frequency electromagnetic field on Escherichia coli growth properties.

Science.gov (United States)

Torgomyan, Heghine; Trchounian, Armen

2015-01-01

The effects of extremely high frequency electromagnetic irradiation and antibiotics on Escherichia coli can create new opportunities for applications in different areas—medicine, agriculture, and food industry. Previously was shown that irradiated bacterial sensitivity against antibiotics was changed. In this work, it was presented the results that irradiation of antibiotics and then adding into growth medium was more effective compared with non-irradiated antibiotics bactericidal action. The selected antibiotics (tetracycline, kanamycin, chloramphenicol, and ceftriaxone) were from different groups. Antibiotics irradiation was performed with low intensity 53 GHz frequency during 1 h. The E. coli growth properties—lag-phase duration and specific growth rate—were markedly changed. Enhanced bacterial sensitivity to irradiated antibiotics is similar to the effects of antibiotics of higher concentrations.

Correlating Nitrile IR Frequencies to Local Electrostatics Quantifies Noncovalent Interactions of Peptides and Proteins.

Science.gov (United States)

Deb, Pranab; Haldar, Tapas; Kashid, Somnath M; Banerjee, Subhrashis; Chakrabarty, Suman; Bagchi, Sayan

2016-05-05

Noncovalent interactions, in particular the hydrogen bonds and nonspecific long-range electrostatic interactions are fundamental to biomolecular functions. A molecular understanding of the local electrostatic environment, consistently for both specific (hydrogen-bonding) and nonspecific electrostatic (local polarity) interactions, is essential for a detailed understanding of these processes. Vibrational Stark Effect (VSE) has proven to be an extremely useful method to measure the local electric field using infrared spectroscopy of carbonyl and nitrile based probes. The nitrile chemical group would be an ideal choice because of its absorption in an infrared spectral window transparent to biomolecules, ease of site-specific incorporation into proteins, and common occurrence as a substituent in various drug molecules. However, the inability of VSE to describe the dependence of IR frequency on electric field for hydrogen-bonded nitriles to date has severely limited nitrile's utility to probe the noncovalent interactions. In this work, using infrared spectroscopy and atomistic molecular dynamics simulations, we have reported for the first time a linear correlation between nitrile frequencies and electric fields in a wide range of hydrogen-bonding environments that may bridge the existing gap between VSE and H-bonding interactions. We have demonstrated the robustness of this field-frequency correlation for both aromatic nitriles and sulfur-based nitriles in a wide range of molecules of varying size and compactness, including small molecules in complex solvation environments, an amino acid, disordered peptides, and structured proteins. This correlation, when coupled to VSE, can be used to quantify noncovalent interactions, specific or nonspecific, in a consistent manner.

Low-frequency (0.7-7.4 mHz geomagnetic field fluctuations at high latitude: frequency dependence of the polarization pattern

Directory of Open Access Journals (Sweden)

L. Cafarella

2001-06-01

Full Text Available A statistical analysis of the polarization pattern of low-frequency geomagnetic field fluctuations (0.7-7.4 mHz covering the entire 24-h interval was performed at the Antarctic station Terra Nova Bay (80.0°S geomagnetic latitude throughout 1997 and 1998. The results show that the polarization pattern exhibits a frequency dependence, as can be expected from the frequency dependence of the latitude where the coupling between the magnetospheric compressional mode and the field line resonance takes place. The polarization analysis of single pulsation events shows that wave packets with different polarization sense, depending on frequency, can be simultaneously observed.

Fixed-site high-frequency transcutaneous electrical nerve stimulation for treatment of chronic low back and lower extremity pain

OpenAIRE

Gozani, Shai

2016-01-01

Shai N Gozani NeuroMetrix, Inc., Waltham, MA, USA Objective: The objective of this study was to determine if fixed-site high-frequency transcutaneous electrical nerve stimulation (FS-TENS) is effective in treating chronic low back and lower extremity pain. Background: Transcutaneous electrical nerve stimulation is widely used for treatment of chronic pain. General-purpose transcutaneous electrical nerve stimulation devices are designed for stimulation anywhere on the body and often cannot be ...

Methodological developments of low field MRI: Elasto-graphy, MRI-ultrasound interaction and dynamic nuclear polarization

International Nuclear Information System (INIS)

Madelin, Guillaume

2005-01-01

This thesis deals with two aspects of low field (0.2 T) Magnetic Resonance Imaging (MRI): the research of new contrasts due to the interaction between Nuclear Magnetic Resonance (NMR) and acoustics (elasto-graphy, spin-phonon interaction) and enhancement of the signal-to-noise ratio by Dynamic Nuclear Polarization (DNP). Magnetic Resonance Elasto-graphy (MRE) allows to assess some viscoelastic properties of tissues by visualization of the propagation of low frequency acoustic strain waves. A review on MRE is given, as well as a study on local measurement of the acoustic absorption coefficient. The next part is dedicated to MRI-ultrasound interaction. First, the ultrasonic transducer was calibrated for power and acoustic field using the comparison of two methods: the radiation force method (balance method) and laser interferometry. Then, we tried to modify the T1 contrast of tissues by spin-phonon interaction due to the application of ultrasound at the resonance frequency at 0.2 T, which is about 8.25 MHz. No modification of T1 contrast has been obtained, but the acoustic streaming phenomenon has been observed in liquids. MRI visualization of this streaming could make possible to calibrate transducers as well as to assess some mechanical properties of viscous fluids. The goal of the last part was to set up DNP experiments at 0.2 T in order to enhance the NMR signal. This double resonance method is based on the polarization transfer of unpaired electrons of free radicals to the surrounding protons of water. This transfer occurs by cross relaxation during the saturation of an electronic transition using Electronic Paramagnetic Resonance (EPR). Two EPR cavities operating at 5.43 GHz have been tested on oxo-TEMPO free radicals (nitroxide). An enhancement of the NMR signal by a factor 30 was obtained during these preliminary experiments. (author)

Effects of low-frequency magnetic field on grain boundary segregation in horizontal direct chill casting of 2024 aluminum alloy

Institute of Scientific and Technical Information of China (English)

无

2005-01-01

Effects of low frequency electromagnetic field on grain boundary segregation in horizontal direct chill (HDC)casting process was investigated experimentally. The grain boundary segregation and microstructures of the ingots,which manufactured by conventional HDC casting and low frequency electromagnetic HDC casting were compared.Results show that low frequency electromagnetic field significantly refines the microstructures and reduces grain boundary segregation. Decreasing electromagnetic frequency or increasing electromagnetic intensity has great effects in reducing grain boundary segregation. Meanwhile, the governing mechanisms were discussed.

Impact of the displacement current on low-frequency electromagnetic fields computed using high-resolution anatomy models

International Nuclear Information System (INIS)

Barchanski, A; Gersem, H de; Gjonaj, E; Weiland, T

2005-01-01

We present a comparison of simulated low-frequency electromagnetic fields in the human body, calculated by means of the electro-quasistatic formulation. The geometrical data in these simulations were provided by an anatomically realistic, high-resolution human body model, while the dielectric properties of the various body tissues were modelled by the parametric Cole-Cole equation. The model was examined under two different excitation sources and various spatial resolutions in a frequency range from 10 Hz to 1 MHz. An analysis of the differences in the computed fields resulting from a neglect of the permittivity was carried out. On this basis, an estimation of the impact of the displacement current on the simulated low-frequency electromagnetic fields in the human body is obtained. (note)

Dielectric properties of gadolinium molybdate in low- and infralow frequency electric fields

International Nuclear Information System (INIS)

Galiyarova, N.M.; Gorin, S.V.; Dontsova, L.I.; Shil'nikov, A.V.; Shuvalov, L.A.; AN SSSR, Moscow

1992-01-01

Temperature dependences of complex dielectric permittivity of gadolinium molybdate (GMO) in low- (LF) and infralow-frequency (ILF) electric fields with 0.1 V·cm -1 amplitude within 0.25-10 4 Hz frequency range are studied. Substantial effect of the crystal prehistory on LF and ILF dielectric properties and domain structure state is revealed. An anomalous reduction of complex dielectric permittivity accompanied by the occurrence of the Debye LF-dispersion of permittivity is detected under the sample cooling from a nonpolar phase

[Electric traction magnetic fields of ultra-low frequency as an occupational risk factor of ischemic heart disease].

Science.gov (United States)

Ptitsyna, N G; Kudrin, V A; Villorezi, D; Kopytenko, Iu A; Tiasto, M I; Kopytenko, E A; Bochko, V A; Iuchchi, N

1996-01-01

The study was inspired by earlier results that displayed influence of variable natural geomagnetic field (0.005-10 Hz range-ultra-low frequencies) on circulatory system, indicated possible correlation between industrial ultra-low frequency fields and prevalence of myocardial infarction. The authors conducted unique measurements of ultra-low frequency fields produced by electric engines. The results were compared with data on morbidity among railway transport workers. The findings are that level of magnetic variations in electric locomotive cabin can exceed 280 micro Tesla, whereas that in car sections reaches 50 micro Tesla. Occurrence of coronary heart disease among the locomotive operators appeared to be 2.0 + 0.2 times higher than that among the car section operators. Higher risk of coronary heart disease in the locomotive operators is associated with their increased occupational magnetic load.

Role of the Coulomb interaction in the low-frequency density of states of DNA double helices

International Nuclear Information System (INIS)

Garcia, A.E.; Krumhansl, J.A.

1988-01-01

The complete vibrational frequency spectrum of several DNA double-helical oligomers is calculated using established pair potentials. Various cutoff values are used for the range of the Coulomb interactions. At very low frequency the integrated density of states shows a noninteger exponent with values ranging from 0.75 to 1.55, depending on the cutoff value for the Coulomb interactions. We conclude that the cumulative densities of states in those molecules depend more on competing interactions than on various proposed universal laws

Extremely Low-Frequency Electromagnetic Fields Promote In Vitro Neuronal Differentiation and Neurite Outgrowth of Embryonic Neural Stem Cells via Up-Regulating TRPC1

Science.gov (United States)

Ma, Qinlong; Chen, Chunhai; Deng, Ping; Zhu, Gang; Lin, Min; Zhang, Lei; Xu, Shangcheng; He, Mindi; Lu, Yonghui; Duan, Weixia; Pi, Huifeng; Cao, Zhengwang; Pei, Liping; Li, Min; Liu, Chuan; Zhang, Yanwen; Zhong, Min; Zhou, Zhou; Yu, Zhengping

2016-01-01

Exposure to extremely low-frequency electromagnetic fields (ELF-EMFs) can enhance hippocampal neurogenesis in adult mice. However, little is focused on the effects of ELF-EMFs on embryonic neurogenesis. Here, we studied the potential effects of ELF-EMFs on embryonic neural stem cells (eNSCs). We exposed eNSCs to ELF-EMF (50 Hz, 1 mT) for 1, 2, and 3 days with 4 hours per day. We found that eNSC proliferation and maintenance were significantly enhanced after ELF-EMF exposure in proliferation medium. ELF-EMF exposure increased the ratio of differentiated neurons and promoted the neurite outgrowth of eNSC-derived neurons without influencing astrocyes differentiation and the cell apoptosis. In addition, the expression of the proneural genes, NeuroD and Ngn1, which are crucial for neuronal differentiation and neurite outgrowth, was increased after ELF-EMF exposure. Moreover, the expression of transient receptor potential canonical 1 (TRPC1) was significantly up-regulated accompanied by increased the peak amplitude of intracellular calcium level induced by ELF-EMF. Furthermore, silencing TRPC1 expression eliminated the up-regulation of the proneural genes and the promotion of neuronal differentiation and neurite outgrowth induced by ELF-EMF. These results suggest that ELF-EMF exposure promotes the neuronal differentiation and neurite outgrowth of eNSCs via up-regulation the expression of TRPC1 and proneural genes (NeuroD and Ngn1). These findings also provide new insights in understanding the effects of ELF-EMF exposure on embryonic brain development. PMID:26950212

Acoustic transfer function of cavity and its application to rapid evaluation of sound field at low frequency band

Institute of Scientific and Technical Information of China (English)

YIN Gang; CHEN Hualing; HU Xuanli; HUANG Xieqing

2001-01-01

A new method to obtain numerical solution of Acoustic Transfer Function (ATF) by BEM is presented. For a simply supported panel backed by a rectangular cavity at low frequency band (0-200 Hz), the frequency property of ATF is analyzed. The relation between the accuracy of the rapid evaluation of sound field and the discretization schemes of the vibrational panel is discussed. The result shows that the method to obtain ATF and the rapid evaluation of sound field using the ATF is suitable to low frequency band. If an appropriate discretization scheme is choosed based on the frequency involved and the effort to obtain ATF, the accuracy of the rapid evaluation of sound field is acceptable.

The evolving interaction of low-frequency earthquakes during transient slip.

Science.gov (United States)

Frank, William B; Shapiro, Nikolaï M; Husker, Allen L; Kostoglodov, Vladimir; Gusev, Alexander A; Campillo, Michel

2016-04-01

Observed along the roots of seismogenic faults where the locked interface transitions to a stably sliding one, low-frequency earthquakes (LFEs) primarily occur as event bursts during slow slip. Using an event catalog from Guerrero, Mexico, we employ a statistical analysis to consider the sequence of LFEs at a single asperity as a point process, and deduce the level of time clustering from the shape of its autocorrelation function. We show that while the plate interface remains locked, LFEs behave as a simple Poisson process, whereas they become strongly clustered in time during even the smallest slow slip, consistent with interaction between different LFE sources. Our results demonstrate that bursts of LFEs can result from the collective behavior of asperities whose interaction depends on the state of the fault interface.

Exposure estimates based on broadband elf magnetic field measurements versus the ICNIRP multiple frequency rule

International Nuclear Information System (INIS)

Paniagua, Jesus M.; Rufo, Montana; Jimenez, Antonio; Pachon, Fernando T.; Carrero, Julian

2015-01-01

The evaluation of exposure to extremely low-frequency (ELF) magnetic fields using broadband measurement techniques gives satisfactory results when the field has essentially a single frequency. Nevertheless, magnetic fields are in most cases distorted by harmonic components. This work analyses the harmonic components of the ELF magnetic field in an outdoor urban context and compares the evaluation of the exposure based on broadband measurements with that based on spectral analysis. The multiple frequency rule of the International Commission on Non-ionizing Radiation Protection (ICNIRP) regulatory guidelines was applied. With the 1998 ICNIRP guideline, harmonics dominated the exposure with a 55 % contribution. With the 2010 ICNIRP guideline, however, the primary frequency dominated the exposure with a 78 % contribution. Values of the exposure based on spectral analysis were significantly higher than those based on broadband measurements. Hence, it is clearly necessary to determine the harmonic components of the ELF magnetic field to assess exposure in urban contexts. (authors)

Fixed-site high-frequency transcutaneous electrical nerve stimulation for treatment of chronic low back and lower extremity pain.

Science.gov (United States)

Gozani, Shai N

2016-01-01

The objective of this study was to determine if fixed-site high-frequency transcutaneous electrical nerve stimulation (FS-TENS) is effective in treating chronic low back and lower extremity pain. Transcutaneous electrical nerve stimulation is widely used for treatment of chronic pain. General-purpose transcutaneous electrical nerve stimulation devices are designed for stimulation anywhere on the body and often cannot be used while the user is active or sleeping. FS-TENS devices are designed for placement at a pre-determined location, which enables development of a wearable device for use over extended time periods. Study participants with chronic low back and/or lower extremity pain self-administered an FS-TENS device for 60 days. Baseline, 30-, and 60-day follow-up data were obtained through an online questionnaire. The primary outcome measure was the patient global impression of change. Pain intensity and interference were assessed using the Brief Pain Inventory. Changes in use of concomitant pain medications were evaluated with a single-item global self-rating. One hundred and thirty participants were enrolled, with 88 completing the 60-day follow-up questionnaire. Most participants (73.9%) were 50 years of age or older. At baseline, low back pain was identified by 85.3%, lower extremity pain by 71.6%, and upper extremity pain by 62.5%. Participants reported widespread pain, at baseline, with a mean of 3.4 (standard deviation 1.1) pain sites. At the 60-day follow-up, 80.7% of participants reported that their chronic pain had improved and they were classified as responders. Baseline characteristics did not differentiate non-responders from responders. There were numerical trends toward reduced pain interference with walking ability and sleep, and greater pain relief in responders. There was a large difference in use of concomitant pain medications, with 80.3% of responders reporting a reduction compared to 11.8% of non-responders. FS-TENS is a safe and effective

Very-low-frequency magnetic plasma

International Nuclear Information System (INIS)

Pendry, J.B.; O'Brien, S.

2002-01-01

We show that a set of current-carrying wires can exhibit an effective magnetic permeability at very low frequencies of a few hertz. The resonant permeability, which is negative above the resonance frequency, arises from the oscillations of the wires driven by the applied magnetic field. We show that a large, frequency-specific and tunable effective permeability can be realized for a wide range of strengths of the applied field. (author)

Ballistic-type field penetration into metals illustrated by high- and low-frequency size-effect measurements in silver

DEFF Research Database (Denmark)

Gantmakher, V. F.; Lebech, Jens; Bak, Christen Kjeldahl

1979-01-01

Radio-frequency size-effect experiments were performed on silver plane-parallel plates at high, 45 GHz, and low, 3 MHz, frequencies. By investigation of size-effect structures we show the influence of frequency on the field distribution inside the metal. When the frequency increases, the splash...

Extremely environment-hard and low work function transfer-mold field emitter arrays

Energy Technology Data Exchange (ETDEWEB)

Nakamoto, Masayuki, E-mail: m-nakamoto@rie.shizuoka.ac.jp [Research Institute of Electronics, Shizuoka University, 3-5-1 Johoku, Naka-ku, Hamamatsu, Shizuoka 432-8011 (Japan); Moon, Jonghyun [Research Institute of Electronics, Shizuoka University, 3-5-1 Johoku, Naka-ku, Hamamatsu, Shizuoka 432-8011 (Japan)

2013-06-15

Extremely environment-hard and low work function field-emitter arrays (FEAs) were fabricated by a transfer-mold emitter fabrication method to produce highly reliable vacuum nanoelectronic devices able to operate stably at low voltage in highly oxidizing atmospheres. Amorphous carbon (a-C) having a work function of 3.6 eV and sp{sup 3} fraction of 85.6% prepared by plasma-enhanced chemical vapor deposition was used as the emitter material. The field-emission characteristics of the obtained transfer-mold FEAs strongly depended on their work function and morphology. The environment-hard characteristics of the transfer-mold a-C FEAs were compared with those of the transfer-mold titanium nitride FEAs and nickel FEAs. X-ray photoelectron spectroscopy was used to confirm the stable chemical states of the FEAs after oxygen radical treatment. The small amount of material oxidized (6.3%) at the surface of the a-C FEAs compared with 11.8% for the TiN-FEAs and 39.0% for Ni FEAs after oxygen radical treatment explained their almost constant work function in oxidizing atmospheres. The emission fluctuation rates of transfer-mold a-C FEAs without resistive layers under in situ radical treatment were as low as ±5.0%, compared with 5–100% for conventional FEAs with resistive layers not under highly oxidizing atmospheres. Therefore, the present environment-hard and low work function transfer-mold a-C FEAs are expected to be useful for reliable vacuum nanoelectronic devices.

Low-frequency scaling of the standard and mixed magnetic field and Müller integral equations

KAUST Repository

Bogaert, Ignace

2014-02-01

The standard and mixed discretizations for the magnetic field integral equation (MFIE) and the Müller integral equation (MUIE) are investigated in the context of low-frequency (LF) scattering problems involving simply connected scatterers. It is proved that, at low frequencies, the frequency scaling of the nonsolenoidal part of the solution current can be incorrect for the standard discretization. In addition, it is proved that the frequency scaling obtained with the mixed discretization is correct. The reason for this problem in the standard discretization scheme is the absence of exact solenoidal currents in the rotated RWG finite element space. The adoption of the mixed discretization scheme eliminates this problem and leads to a well-conditioned system of linear equations that remains accurate at low frequencies. Numerical results confirm these theoretical predictions and also show that, when the frequency is lowered, a finer and finer mesh is required to keep the accuracy constant with the standard discretization. © 1963-2012 IEEE.

Extremely Low Frequency (ELF) Vertical Electric Field Exposure of Rats: Irradiation Facility

Science.gov (United States)

1977-05-01

altered inside an animal cage even with wet or dry litter and full food and water containers. Rats weighing approximately 300 g in adjacent cages caused...with guard circuit Field inside empty cage Field inside complete cage ( litter (wet or dry) + food + water) Field variations caused by 300 g rat...blanket 250 Iron 60 Broiler 130 Hair dryer 40 Vaporizer 40 Refrigerator 60 Color TV 30 Stereo 90 Coffee pot 30 Vacuum cleaner 16 Clock radio

A pilot investigation of the effect of extremely low frequency pulsed electromagnetic fields on humans' heart rate variability.

Science.gov (United States)

Baldi, Emilio; Baldi, Claudio; Lithgow, Brian J

2007-01-01

The question whether pulsed electromagnetic field (PEMF) can affect the heart rhythm is still controversial. This study investigates the effects on the cardiocirculatory system of ELF-PEMFs. It is a follow-up to an investigation made of the possible therapeutic effect ELF-PEMFs, using a commercially available magneto therapeutic unit, had on soft tissue injury repair in humans. Modulation of heart rate (HR) or heart rate variability (HRV) can be detected from changes in periodicity of the R-R interval and/or from changes in the numbers of heart-beat/min (bpm), however, R-R interval analysis gives only a quantitative insight into HRV. A qualitative understanding of HRV can be obtained considering the power spectral density (PSD) of the R-R intervals Fourier transform. In this study PSD is the investigative tool used, more specifically the low frequency (LF) PSD and high frequency (HF) PSD ratio (LF/HF) which is an indicator of sympatho-vagal balance. To obtain the PSD value, variations of the R-R time intervals were evaluated from a continuously recorded ECG. The results show a HR variation in all the subjects when they are exposed to the same ELF-PEMF. This variation can be detected by observing the change in the sympatho-vagal equilibrium, which is an indicator of modulation of heart activity. Variation of the LF/HF PSD ratio mainly occurs at transition times from exposure to nonexposure, or vice versa. Also of interest are the results obtained during the exposure of one subject to a range of different ELF-PEMFs. This pilot study suggests that a full investigation into the effect of ELF-PEMFs on the cardiovascular system is justified.

Influence of a Low Frequency Electromagnetic field in the Microbial Flora of a Mango Nectar

Directory of Open Access Journals (Sweden)

Yaima Torres-Ferrer

2016-07-01

Full Text Available In this work an evaluation of the influence of a low frequency electromagnetic field on the microbial flora of mango nectar in order to study their behavior after each treatment is presented. Experiments are designed and implemented with one factor in which the influence of a low frequency electromagnetic field is determined at various levels (0, 90, 95 Gauss, in a homogeneous and completely randomized unit on the microbial load of nectar mango. Magnetic conditioning device used in the tests with approximate average values of magnetic induction of 90 to 95 characterized Gauss. It is established that the application of the magnetic field in the range of values used (90, 95 Gauss causes a stimulation in the values of total count of mesophilic, leading to increased microbial load present in mango nectar studied.

[Comparative assessment of MR-semiotics of acutest intracerebral hematomas in low- and extra high-field frequency magnetic resonance tomography].

Science.gov (United States)

Skvortsova, V I; Burenchev, D V; Tvorogova, T V; Guseva, O I; Prokhorov, A V; Smirnov, A M; Kupriianov, D A; Pirogov, Iu A

2009-01-01

An objective of the study was to compare sensitivity of low- and extra high-field frequency magnetic resonance (MR) tomography of acutest intracerebral hematomas (ICH) and to assess differences between symptoms in obtained images. A study was conducted using experimental ICH in rats (n=6). Hematomas were formed by two injections of autologic blood into the brain. MR-devices "Bio Spec 70/30" with magnetic field strength of 7 T and "Ellipse-150" with magnetic field strength of 0,15 T were used in the study. MR-tomography was carried out 3-5 h after the injections. Both MR-devices revealed the presence of pathological lesion in all animals. Extra highfield frequency MR-tomography showed the specific signs of ICH caused by the paramagnetic effect of deoxyhemoglobin in T2 and T2*-weighted images (WI) and low frequency MR-tomography - in T2*-WI only. The comparable sensitivity of low- and extra high-field frequency MR-devices in acutest ICH was established.

Evaluation of the Effect of Low-Frequency Electromagnetic Fields on in Vitro Growth and Maturation of Mouse Oocytes

Directory of Open Access Journals (Sweden)

F Barzegari Firouzabadi

2012-05-01

Full Text Available Introduction: Access to modern methods for increasing the percentage of in vitro human and animal mature oocytes can be useful in the treatment of some forms of human infertility as well as proliferation of many domestic and wild animals which generation is endangered. Effect of low- frequency electromagnetic fields on in vitro growth and maturation of mouse oocytes is recently considered as a new approach. In this study we evaluated the effect of low- frequency electromagnetic field on in vitro growth and maturation of mouse oocyte. Methods: In this study electromagnetic fields with frequencies of 5, 50 and 100 Hz and 2mT intensity were used. For observation of the effect of electromagnetic field four groups were selected: Group 1 as control group, which included 35 prenatal follicles (immature oocytes. Groups 2, 3 and 4were exposed to 5, 50 and 100 Hz electromagnetic fields, respectively. Results: Prenatal follicles exposed to 5 and 50 Hz frequencies showed no significant changes in diameter and survival rates. In contrast at a frequency of 100 Hz in 72-hour culture period a significant increase in diameter(155μm, follicles livability power(59%, oocyte maturation(52% and GVBD(39% was shown in comparison to other experimental groups and control group(P <0.05. Conclusion: Low-frequency magnetic field effects gene expression and thus protein synthesis, cell division, proliferation and behavior. Although this effect can be temporary, it can increase the percentage of ovulation for in vitro environment along with other environmental factors.

Measurements of intermediate-frequency electric and magnetic fields in households

Energy Technology Data Exchange (ETDEWEB)

Aerts, Sam, E-mail: sam.aerts@intec.ugent.be [Department of Information Technology, Ghent University/iMinds, iGent, Technologiepark-Zwijnaarde 15, B-9052 Ghent (Belgium); Calderon, Carolina [Centre for Radiation, Chemical and Environmental Hazards, Public Health England, Chilton, Didcot, Oxon OX11 0RQ (United Kingdom); Valič, Blaž [Institute of Non-Ionizing Radiation (INIS), Pohorskega bataljona 215, Ljubljana 1000 (Slovenia); Maslanyj, Myron; Addison, Darren; Mee, Terry; Goiceanu, Cristian [Centre for Radiation, Chemical and Environmental Hazards, Public Health England, Chilton, Didcot, Oxon OX11 0RQ (United Kingdom); Verloock, Leen; Van den Bossche, Matthias [Department of Information Technology, Ghent University/iMinds, iGent, Technologiepark-Zwijnaarde 15, B-9052 Ghent (Belgium); Gajšek, Peter [Institute of Non-Ionizing Radiation (INIS), Pohorskega bataljona 215, Ljubljana 1000 (Slovenia); Vermeulen, Roel [Institute for Risk Assessment Sciences, Department of Environmental Epidemiology, Utrecht University, Yalelaan 2, 3508 Utrecht (Netherlands); Röösli, Martin [Swiss Tropical and Public Health Institute (Swiss TPH), Socinstrasse 57, P.O. Box, 4002 Basel (Switzerland); University of Basel, Petersplatz 1, 4003 Basel (Switzerland); Cardis, Elisabeth [Barcelona Institute for Global Health (ISGlobal) and Municipal Institute of Medical Research (IMIM-Hospital del Mar), Doctor Aiguader, 88, 08003 Barcelona (Spain); Martens, Luc; Joseph, Wout [Department of Information Technology, Ghent University/iMinds, iGent, Technologiepark-Zwijnaarde 15, B-9052 Ghent (Belgium)

2017-04-15

Historically, assessment of human exposure to electric and magnetic fields has focused on the extremely-low-frequency (ELF) and radiofrequency (RF) ranges. However, research on the typically emitted fields in the intermediate-frequency (IF) range (300 Hz to 1 MHz) as well as potential effects of IF fields on the human body remains limited, although the range of household appliances with electrical components working in the IF range has grown significantly (e.g., induction cookers and compact fluorescent lighting). In this study, an extensive measurement survey was performed on the levels of electric and magnetic fields in the IF range typically present in residences as well as emitted by a wide range of household appliances under real-life circumstances. Using spot measurements, residential IF field levels were found to be generally low, while the use of certain appliances at close distance (20 cm) may result in a relatively high exposure. Overall, appliance emissions contained either harmonic signals, with fundamental frequencies between 6 kHz and 300 kHz, which were sometimes accompanied by regions in the IF spectrum of rather noisy, elevated field strengths, or much more capricious spectra, dominated by 50 Hz harmonics emanating far in the IF domain. The maximum peak field strengths recorded at 20 cm were 41.5 V/m and 2.7 A/m, both from induction cookers. Finally, none of the appliance emissions in the IF range exceeded the exposure summation rules recommended by the International Commission on Non-Ionizing Radiation Protection guidelines and the International Electrotechnical Commission (IEC 62233) standard at 20 cm and beyond (maximum exposure quotients EQ{sub E} 1.0 and {sub E}Q{sub H} 0.13). - Highlights: • Survey of residential electric and magnetic fields at intermediate frequencies (IF). • IF-EF and -MF emitted by 280 household appliances were characterised. • Strongest emitters were induction cookers, CFLs, LCD-TVs, and microwave ovens. • No

Measurements of intermediate-frequency electric and magnetic fields in households

International Nuclear Information System (INIS)

Aerts, Sam; Calderon, Carolina; Valič, Blaž; Maslanyj, Myron; Addison, Darren; Mee, Terry; Goiceanu, Cristian; Verloock, Leen; Van den Bossche, Matthias; Gajšek, Peter; Vermeulen, Roel; Röösli, Martin; Cardis, Elisabeth; Martens, Luc; Joseph, Wout

2017-01-01

Historically, assessment of human exposure to electric and magnetic fields has focused on the extremely-low-frequency (ELF) and radiofrequency (RF) ranges. However, research on the typically emitted fields in the intermediate-frequency (IF) range (300 Hz to 1 MHz) as well as potential effects of IF fields on the human body remains limited, although the range of household appliances with electrical components working in the IF range has grown significantly (e.g., induction cookers and compact fluorescent lighting). In this study, an extensive measurement survey was performed on the levels of electric and magnetic fields in the IF range typically present in residences as well as emitted by a wide range of household appliances under real-life circumstances. Using spot measurements, residential IF field levels were found to be generally low, while the use of certain appliances at close distance (20 cm) may result in a relatively high exposure. Overall, appliance emissions contained either harmonic signals, with fundamental frequencies between 6 kHz and 300 kHz, which were sometimes accompanied by regions in the IF spectrum of rather noisy, elevated field strengths, or much more capricious spectra, dominated by 50 Hz harmonics emanating far in the IF domain. The maximum peak field strengths recorded at 20 cm were 41.5 V/m and 2.7 A/m, both from induction cookers. Finally, none of the appliance emissions in the IF range exceeded the exposure summation rules recommended by the International Commission on Non-Ionizing Radiation Protection guidelines and the International Electrotechnical Commission (IEC 62233) standard at 20 cm and beyond (maximum exposure quotients EQ E 1.0 and E Q H 0.13). - Highlights: • Survey of residential electric and magnetic fields at intermediate frequencies (IF). • IF-EF and -MF emitted by 280 household appliances were characterised. • Strongest emitters were induction cookers, CFLs, LCD-TVs, and microwave ovens. • No emissions exceeded

Analytical Solutions of Electromagnetic Fields from Current Dipole Moment on Spherical Conductor in a Low-Frequency Approximation

International Nuclear Information System (INIS)

Okita, Taishi; Takagi, Toshiyuki

2010-01-01

We analytically derive the solutions for electromagnetic fields of electric current dipole moment, which is placed in the exterior of the spherical homogeneous conductor, and is pointed along the radial direction. The dipole moment is driven in the low frequency f = 1 kHz and high frequency f = 1 GHz regimes. The electrical properties of the conductor are appropriately chosen in each frequency. Electromagnetic fields are rigorously formulated at an arbitrary point in a spherical geometry, in which the magnetic vector potential is straightforwardly given by the Biot-Savart formula, and the scalar potential is expanded with the Legendre polynomials, taking into account the appropriate boundary conditions at the spherical surface of the conductor. The induced electric fields are numerically calculated along the several paths in the low and high frequency excitation. The self-consistent solutions obtained in this work will be of much importance in a wide region of electromagnetic induction problems. (electromagnetism, optics, acoustics, heat transfer, classical mechanics, and fluid dynamics)

Influence of electromagnetic signal of antibiotics excited by low-frequency pulsed electromagnetic fields on growth of Escherichia coli.

Science.gov (United States)

Ke, Yin-Lung; Chang, Fu-Yu; Chen, Ming-Kun; Li, Shun-Lai; Jang, Ling-Sheng

2013-01-01

Energy medicine (EM) provides a new medical choice for patients, and its advantages are the noninvasive detection and nondrug treatment. An electromagnetic signal, a kind of EM, induced from antibiotic coupling with weak, extremely low-frequency pulsed electromagnetic fields (PEMFs) is utilized for investigating the growth speed of Escherichia coli (E. coli). PEMFs are produced by solenoidal coils for coupling the electromagnetic signal of antibiotics (penicillin). The growth retardation rate (GRR) of E. coli is used to investigate the efficacy of the electromagnetic signal of antibiotics. The E. coli is cultivated in the exposure of PEMFs coupling with the electromagnetic signal of antibiotics. The maximum GRR of PEMFs with and without the electromagnetic signal of antibiotics on the growth of E. coli cells in the logarithmic is 17.4 and 9.08%, respectively. The electromagnetic signal of antibiotics is successfully coupled by the electromagnetic signal coupling instrument to affect the growth of E. coli. In addition, the retardation effect on E. coli growth can be improved of by changing the carrier frequency of PEMFs coupling with the electromagnetic signal of antibiotics. GRR caused by the electromagnetic signal of antibiotics can be fixed by a different carrier frequency in a different phase of E. coli growth.

Fixed-site high-frequency transcutaneous electrical nerve stimulation for treatment of chronic low back and lower extremity pain

Science.gov (United States)

Gozani, Shai N

2016-01-01

Objective The objective of this study was to determine if fixed-site high-frequency transcutaneous electrical nerve stimulation (FS-TENS) is effective in treating chronic low back and lower extremity pain. Background Transcutaneous electrical nerve stimulation is widely used for treatment of chronic pain. General-purpose transcutaneous electrical nerve stimulation devices are designed for stimulation anywhere on the body and often cannot be used while the user is active or sleeping. FS-TENS devices are designed for placement at a pre-determined location, which enables development of a wearable device for use over extended time periods. Methods Study participants with chronic low back and/or lower extremity pain self-administered an FS-TENS device for 60 days. Baseline, 30-, and 60-day follow-up data were obtained through an online questionnaire. The primary outcome measure was the patient global impression of change. Pain intensity and interference were assessed using the Brief Pain Inventory. Changes in use of concomitant pain medications were evaluated with a single-item global self-rating. Results One hundred and thirty participants were enrolled, with 88 completing the 60-day follow-up questionnaire. Most participants (73.9%) were 50 years of age or older. At baseline, low back pain was identified by 85.3%, lower extremity pain by 71.6%, and upper extremity pain by 62.5%. Participants reported widespread pain, at baseline, with a mean of 3.4 (standard deviation 1.1) pain sites. At the 60-day follow-up, 80.7% of participants reported that their chronic pain had improved and they were classified as responders. Baseline characteristics did not differentiate non-responders from responders. There were numerical trends toward reduced pain interference with walking ability and sleep, and greater pain relief in responders. There was a large difference in use of concomitant pain medications, with 80.3% of responders reporting a reduction compared to 11.8% of non

Fixed-site high-frequency transcutaneous electrical nerve stimulation for treatment of chronic low back and lower extremity pain

Directory of Open Access Journals (Sweden)

Gozani SN

2016-06-01

Full Text Available Shai N Gozani NeuroMetrix, Inc., Waltham, MA, USA Objective: The objective of this study was to determine if fixed-site high-frequency transcutaneous electrical nerve stimulation (FS-TENS is effective in treating chronic low back and lower extremity pain. Background: Transcutaneous electrical nerve stimulation is widely used for treatment of chronic pain. General-purpose transcutaneous electrical nerve stimulation devices are designed for stimulation anywhere on the body and often cannot be used while the user is active or sleeping. FS-TENS devices are designed for placement at a pre-determined location, which enables development of a wearable device for use over extended time periods. Methods: Study participants with chronic low back and/or lower extremity pain self-administered an FS-TENS device for 60 days. Baseline, 30-, and 60-day follow-up data were obtained through an online questionnaire. The primary outcome measure was the patient global impression of change. Pain intensity and interference were assessed using the Brief Pain Inventory. Changes in use of concomitant pain medications were evaluated with a single-item global self-rating. Results: One hundred and thirty participants were enrolled, with 88 completing the 60-day follow-up questionnaire. Most participants (73.9% were 50 years of age or older. At baseline, low back pain was identified by 85.3%, lower extremity pain by 71.6%, and upper extremity pain by 62.5%. Participants reported widespread pain, at baseline, with a mean of 3.4 (standard deviation 1.1 pain sites. At the 60-day follow-up, 80.7% of participants reported that their chronic pain had improved and they were classified as responders. Baseline characteristics did not differentiate non-responders from responders. There were numerical trends toward reduced pain interference with walking ability and sleep, and greater pain relief in responders. There was a large difference in use of concomitant pain medications, with 80

Grid Frequency Extreme Event Analysis and Modeling: Preprint

Energy Technology Data Exchange (ETDEWEB)

Florita, Anthony R [National Renewable Energy Laboratory (NREL), Golden, CO (United States); Clark, Kara [National Renewable Energy Laboratory (NREL), Golden, CO (United States); Gevorgian, Vahan [National Renewable Energy Laboratory (NREL), Golden, CO (United States); Folgueras, Maria [National Renewable Energy Laboratory (NREL), Golden, CO (United States); Wenger, Erin [National Renewable Energy Laboratory (NREL), Golden, CO (United States)

2017-11-01

Sudden losses of generation or load can lead to instantaneous changes in electric grid frequency and voltage. Extreme frequency events pose a major threat to grid stability. As renewable energy sources supply power to grids in increasing proportions, it becomes increasingly important to examine when and why extreme events occur to prevent destabilization of the grid. To better understand frequency events, including extrema, historic data were analyzed to fit probability distribution functions to various frequency metrics. Results showed that a standard Cauchy distribution fit the difference between the frequency nadir and prefault frequency (f_(C-A)) metric well, a standard Cauchy distribution fit the settling frequency (f_B) metric well, and a standard normal distribution fit the difference between the settling frequency and frequency nadir (f_(B-C)) metric very well. Results were inconclusive for the frequency nadir (f_C) metric, meaning it likely has a more complex distribution than those tested. This probabilistic modeling should facilitate more realistic modeling of grid faults.

Unusual polarity-dependent patterns in a bent-core nematic liquid crystal under low-frequency ac field.

Science.gov (United States)

Xiang, Ying; Zhou, Meng-jie; Xu, Ming-Ya; Salamon, Péter; Éber, Nándor; Buka, Ágnes

2015-04-01

Electric-field-induced patterns of diverse morphology have been observed over a wide frequency range in a recently synthesized bent-core nematic (BCN) liquid crystal. At low frequencies (up to ∼25 Hz), the BCN exhibited unusual polarity-dependent patterns. When the amplitude of the ac field was enhanced, these two time-asymmetrical patterns turned into time-symmetrical prewavylike stripes. At ac frequencies in the middle-frequency range (∼50-3000 Hz), zigzag patterns were detected whose obliqueness varied with the frequency. Finally, if the frequency was increased above 3 kHz, the zigzag pattern was replaced by another, prewavylike pattern, whose threshold voltage depended on the frequency; however, the wave vector did not. For a more complete characterization, material parameters such as elastic constants, dielectric permittivities, and the anisotropy of the diamagnetic susceptibility were also determined.

Effects of low-frequency magnetic fields on the viability of yeast Saccharomyces cerevisiae

Czech Academy of Sciences Publication Activity Database

Novák, Jan; Strašák, Luděk; Fojt, Lukáš; Slaninová, I.; Vetterl, Vladimír

2007-01-01

Roč. 70, č. 1 (2007), s. 115-121 ISSN 1567-5394 R&D Projects: GA AV ČR(CZ) IAA4004404; GA AV ČR(CZ) IBS5004107 Institutional research plan: CEZ:AV0Z50040702 Keywords : low-frequency electromagnetic field * yeast * Saccharomyces cerevisiae Subject RIV: BO - Biophysics Impact factor: 2.992, year: 2007

Plasma filamentation and shock wave enhancement in microwave rockets by combining low-frequency microwaves with external magnetic field

International Nuclear Information System (INIS)

Takahashi, Masayuki; Ohnishi, Naofumi

2016-01-01

A filamentary plasma is reproduced based on a fully kinetic model of electron and ion transports coupled with electromagnetic wave propagation. The discharge plasma transits from discrete to diffusive patterns at a 110-GHz breakdown, with decrease in the ambient pressure, because of the rapid electron diffusion that occurs during an increase in the propagation speed of the ionization front. A discrete plasma is obtained at low pressures when a low-frequency microwave is irradiated because the ionization process becomes more dominant than the electron diffusion, when the electrons are effectively heated by the low-frequency microwave. The propagation speed of the plasma increases with decrease in the incident microwave frequency because of the higher ionization frequency and faster plasma diffusion resulting from the increase in the energy-absorption rate. An external magnetic field is applied to the breakdown volume, which induces plasma filamentation at lower pressures because the electron diffusion is suppressed by the magnetic field. The thrust performance of a microwave rocket is improved by the magnetic fields corresponding to the electron cyclotron resonance (ECR) and its higher-harmonic heating, because slower propagation of the ionization front and larger energy-absorption rates are obtained at lower pressures. It would be advantageous if the fundamental mode of ECR heating is coupled with a lower frequency microwave instead of combining the higher-harmonic ECR heating with the higher frequency microwave. This can improve the thrust performance with smaller magnetic fields even if the propagation speed increases because of the decrease in the incident microwave frequency.

Plasma filamentation and shock wave enhancement in microwave rockets by combining low-frequency microwaves with external magnetic field

Energy Technology Data Exchange (ETDEWEB)

Takahashi, Masayuki, E-mail: m.takahashi@al.t.u-tokyo.ac.jp [Department of Aeronautics and Astronautics, The University of Tokyo, Bunkyo-ku 113-8656 (Japan); Ohnishi, Naofumi [Department of Aerospace Engineering, Tohoku University, Sendai 980-8579 (Japan)

2016-08-14

A filamentary plasma is reproduced based on a fully kinetic model of electron and ion transports coupled with electromagnetic wave propagation. The discharge plasma transits from discrete to diffusive patterns at a 110-GHz breakdown, with decrease in the ambient pressure, because of the rapid electron diffusion that occurs during an increase in the propagation speed of the ionization front. A discrete plasma is obtained at low pressures when a low-frequency microwave is irradiated because the ionization process becomes more dominant than the electron diffusion, when the electrons are effectively heated by the low-frequency microwave. The propagation speed of the plasma increases with decrease in the incident microwave frequency because of the higher ionization frequency and faster plasma diffusion resulting from the increase in the energy-absorption rate. An external magnetic field is applied to the breakdown volume, which induces plasma filamentation at lower pressures because the electron diffusion is suppressed by the magnetic field. The thrust performance of a microwave rocket is improved by the magnetic fields corresponding to the electron cyclotron resonance (ECR) and its higher-harmonic heating, because slower propagation of the ionization front and larger energy-absorption rates are obtained at lower pressures. It would be advantageous if the fundamental mode of ECR heating is coupled with a lower frequency microwave instead of combining the higher-harmonic ECR heating with the higher frequency microwave. This can improve the thrust performance with smaller magnetic fields even if the propagation speed increases because of the decrease in the incident microwave frequency.

Integral methods in low-frequency electromagnetics

CERN Document Server

Solin, Pavel; Karban, Pavel; Ulrych, Bohus

2009-01-01

A modern presentation of integral methods in low-frequency electromagnetics This book provides state-of-the-art knowledge on integral methods in low-frequency electromagnetics. Blending theory with numerous examples, it introduces key aspects of the integral methods used in engineering as a powerful alternative to PDE-based models. Readers will get complete coverage of: The electromagnetic field and its basic characteristics An overview of solution methods Solutions of electromagnetic fields by integral expressions Integral and integrodifferential methods

Low-frequency scaling of the standard and mixed magnetic field and Müller integral equations

KAUST Repository

Bogaert, Ignace; Cools, Kristof; Andriulli, Francesco P.; Bagci, Hakan

2014-01-01

The standard and mixed discretizations for the magnetic field integral equation (MFIE) and the Müller integral equation (MUIE) are investigated in the context of low-frequency (LF) scattering problems involving simply connected scatterers

Paleoflood Data, Extreme Floods and Frequency: Data and Models for Dam Safety Risk Scenarios

Science.gov (United States)

England, J. F.; Godaire, J.; Klinger, R.

2007-12-01

Extreme floods and probability estimates are crucial components in dam safety risk analysis and scenarios for water-resources decision making. The field-based collection of paleoflood data provides needed information on the magnitude and probability of extreme floods at locations of interest in a watershed or region. The stratigraphic record present along streams in the form of terrace and floodplain deposits represent direct indicators of the magnitude of large floods on a river, and may provide 10 to 100 times longer records than conventional stream gaging records of large floods. Paleoflood data is combined with gage and historical streamflow estimates to gain insights to flood frequency scaling, model extrapolations and uncertainty, and provide input scenarios to risk analysis event trees. We illustrate current data collection and flood frequency modeling approaches via case studies in the western United States, including the American River in California and the Arkansas River in Colorado. These studies demonstrate the integration of applied field geology, hydraulics, and surface-water hydrology. Results from these studies illustrate the gains in information content on extreme floods, provide data- based means to separate flood generation processes, guide flood frequency model extrapolations, and reduce uncertainties. These data and scenarios strongly influence water resources management decisions.

Transient eddy feedback and low-frequency variability

International Nuclear Information System (INIS)

Robinson, W.A.

1994-01-01

Superposed on any externally driven secular climatic change are fluctuations that arise from the internal nonlinear dynamics of the climate system. These internally generated variations may involve interactions between the atmosphere and the ocean, as in the case of El Nino, or they may arise from the dynamics of the atmosphere alone. Here we discuss the dynamics of interactions between transient eddies and lower-frequency motions in the atmosphere. The interactions between more transient and more persistent motions can be divided into two types. Nonlinear interactions among the transient motions can act as an essentially random source of low-frequency motion. The idea that the low-frequencies respond in a linear way to stochastic forcing from higher frequencies has been applied to the generation of planetary waves and to the forcing of changes in global angular momentum. In addition to stochastic coupling, there are systematic interactions, denoted feedbacks, through which the persistent motions modulate their own forcing by the transient eddies. This paper discusses the dynamics of these feedbacks

Climate Informed Low Flow Frequency Analysis Using Nonstationary Modeling

Science.gov (United States)

Liu, D.; Guo, S.; Lian, Y.

2014-12-01

Stationarity is often assumed for frequency analysis of low flows in water resources management and planning. However, many studies have shown that flow characteristics, particularly the frequency spectrum of extreme hydrologic events,were modified by climate change and human activities and the conventional frequency analysis without considering the non-stationary characteristics may lead to costly design. The analysis presented in this paper was based on the more than 100 years of daily flow data from the Yichang gaging station 44 kilometers downstream of the Three Gorges Dam. The Mann-Kendall trend test under the scaling hypothesis showed that the annual low flows had significant monotonic trend, whereas an abrupt change point was identified in 1936 by the Pettitt test. The climate informed low flow frequency analysis and the divided and combined method are employed to account for the impacts from related climate variables and the nonstationarities in annual low flows. Without prior knowledge of the probability density function for the gaging station, six distribution functions including the Generalized Extreme Values (GEV), Pearson Type III, Gumbel, Gamma, Lognormal, and Weibull distributions have been tested to find the best fit, in which the local likelihood method is used to estimate the parameters. Analyses show that GEV had the best fit for the observed low flows. This study has also shown that the climate informed low flow frequency analysis is able to exploit the link between climate indices and low flows, which would account for the dynamic feature for reservoir management and provide more accurate and reliable designs for infrastructure and water supply.

Dosimetry considerations in the head and retina for extremely low frequency electric fields

International Nuclear Information System (INIS)

Taki, M.; Suzuki, Y.; Wake, K.

2003-01-01

Magnetophosphenes are investigated from the viewpoint of electromagnetic dosimetry. Induced current density and internal electric fields at the threshold of perception are estimated by analytical and numerical calculations, assuming different models. Dosimetry for electrophoshenes is also discussed and compared with that for magnetophosphenes. The distribution of current density and internal electric fields is consistent with the experimental observation that flashing sensations reach their greatest intensity at the periphery of the visual field, for both electro and magnetophosphenes. The estimated thresholds in internal electric fields are consistent for magnetophosphenes and for electrophosphenes, respectively. The magnitudes of the thresholds, however, differ by about 10-fold. The thresholds in induced current density are critically dependent on the conductivity of the eye assumed for the calculations. The effect of thin membrane structure is also discussed with regard to the difference between electric field and magnetic field exposures. (author)

LOW-FREQUENCY IMAGING OF FIELDS AT HIGH GALACTIC LATITUDE WITH THE MURCHISON WIDEFIELD ARRAY 32 ELEMENT PROTOTYPE

Energy Technology Data Exchange (ETDEWEB)

Williams, Christopher L.; Hewitt, Jacqueline N.; Levine, Alan M. [MIT Kavli Institute for Astrophysics and Space Research, Cambridge, MA (United States); De Oliveira-Costa, Angelica; Hernquist, Lars L.; Bernardi, Gianni [Harvard-Smithsonian Center for Astrophysics, Cambridge, MA (United States); Bowman, Judd D. [School of Earth and Space Exploration, Arizona State University, Tempe, AZ (United States); Briggs, Frank H. [Research School of Astronomy and Astrophysics, The Australian National University, Canberra (Australia); Gaensler, B. M.; Mitchell, Daniel A.; Subrahmanyan, Ravi; Sadler, Elaine M. [ARC Centre of Excellence for All-sky Astrophysics (CAASTRO) (Australia); Morales, Miguel F. [Department of Physics, University of Washington, Seattle, WA (United States); Sethi, Shiv K. [Raman Research Institute, Bangalore (India); Arcus, Wayne; Crosse, Brian W. [International Centre for Radio Astronomy Research, Curtin University, Perth (Australia); Barnes, David G. [Center for Astrophysics and Supercomputing, Swinburne University of Technology, Melbourne (Australia); Bunton, John D. [CSIRO Astronomy and Space Science, Epping (Australia); Cappallo, Roger C.; Corey, Brian E., E-mail: clmw@mit.edu [MIT Haystack Observatory, Westford, MA (United States); and others

2012-08-10

The Murchison Widefield Array (MWA) is a new low-frequency, wide-field-of-view radio interferometer under development at the Murchison Radio-astronomy Observatory in Western Australia. We have used a 32 element MWA prototype interferometer (MWA-32T) to observe two 50 Degree-Sign diameter fields in the southern sky, covering a total of {approx}2700 deg{sup 2}, in order to evaluate the performance of the MWA-32T, to develop techniques for epoch of reionization experiments, and to make measurements of astronomical foregrounds. We developed a calibration and imaging pipeline for the MWA-32T, and used it to produce {approx}15' angular resolution maps of the two fields in the 110-200 MHz band. We perform a blind source extraction using these confusion-limited images, and detect 655 sources at high significance with an additional 871 lower significance source candidates. We compare these sources with existing low-frequency radio surveys in order to assess the MWA-32T system performance, wide-field analysis algorithms, and catalog quality. Our source catalog is found to agree well with existing low-frequency surveys in these regions of the sky and with statistical distributions of point sources derived from Northern Hemisphere surveys; it represents one of the deepest surveys to date of this sky field in the 110-200 MHz band.

Nonmonotonic low frequency losses in HTSCs

International Nuclear Information System (INIS)

Castro, H; Gerber, A; Milner, A

2007-01-01

A calorimetric technique has been used in order to study ac-field dissipation in ceramic BSCCO samples at low frequencies between 0.05 and 250 Hz, at temperatures from 65 to 90 K. In contrast to previous studies, where ac losses have been reported with a linear dependence on magnetic field frequency, we find a nonmonotonic function presenting various maxima. Frequencies corresponding to local maxima of dissipation depend on the temperature and the amplitude of the ac magnetic field. Flux creep is argued to be responsible for this behaviour. A simple model connecting the characteristic vortex relaxation times (flux creep) and the location of dissipation maxima versus frequency is proposed

Monitoring of interaction of low-frequency electric field with biological tissues upon optical clearing with optical coherence tomography.

Science.gov (United States)

Peña, Adrián F; Doronin, Alexander; Tuchin, Valery V; Meglinski, Igor

2014-08-01

The influence of a low-frequency electric field applied to soft biological tissues ex vivo at normal conditions and upon the topical application of optical clearing agents has been studied by optical coherence tomography (OCT). The electro-kinetic response of tissues has been observed and quantitatively evaluated by the double correlation OCT approach, utilizing consistent application of an adaptive Wiener filtering and Fourier domain correlation algorithm. The results show that fluctuations, induced by the electric field within the biological tissues are exponentially increased in time. We demonstrate that in comparison to impedance measurements and the mapping of the temperature profile at the surface of the tissue samples, the double correlation OCT approach is much more sensitive to the changes associated with the tissues' electro-kinetic response. We also found that topical application of the optical clearing agent reduces the tissues' electro-kinetic response and is cooling the tissue, thus reducing the temperature induced by the electric current by a few degrees. We anticipate that dcOCT approach can find a new application in bioelectrical impedance analysis and monitoring of the electric properties of biological tissues, including the resistivity of high water content tissues and its variations.

Magnetoliposomes for controlled drug release in the presence of low-frequency magnetic field

KAUST Repository

Nappini, Silvia

2010-01-01

In this work we have studied the effect of a low-frequency alternating magnetic field (LF-AMF) on the permeability of magnetoliposomes, i.e. liposomes including magnetic nanoparticles within their water pool. Large unilamellar liposomes loaded with magnetic cobalt ferrite nanoparticles (CoFe 2O4) have been prepared and characterized. Structural characterization of the liposomal dispersion has been performed by dynamic light scattering (DLS). The enhancement of liposome permeability upon exposure to LF-AMF has been measured as the self-quenching decrease of a fluorescent hydrophilic molecule (carboxyfluorescein, CF) entrapped in the liposome pool. Liposome leakage has been monitored as a function of field frequency, time of exposure and concentration, charge and size of the embedded nanoparticles. The results show that CF release from magnetoliposomes is strongly promoted by LF-AMF, reasonably as a consequence of nanoparticle motions in the liposome pool at the applied frequency. CF release as a function of time in magnetoliposomes unexposed to magnetic field follows Fickian diffusion, while samples exposed to LF-AMF show zero-order kinetics, consistently with an anomalous transport, due to an alteration of the bilayer permeability. These preliminary results open up new perspectives in the use of these systems as carriers in targeted and controlled release of drugs. © The Royal Society of Chemistry 2010.

[The influence of application of a low-frequency magnetic field on the serum corticosterone level (an experimental study)].

Science.gov (United States)

Alabovskiĭ, V V; Gotovskiĭ, M Iu; Vinokurov, A A; Maslov, O V

2013-01-01

The results of analysis of the literature publications suggest the necessity of experimental studies aimed at investigation of modulating effect of low-frequency magnetic fields on endocrine organs. The present study was carried out using 200 outbred white male rats (body weight 200-220 g). Corticosterone was measured in blood sera following the application of a low-frequency magnetic field (20 and 53 Hz with induction from 0.4 to 6 mT) generated by a Mini-Expert-T apparatus for induction magnetic therapy during 30 minutes. It was shown that the application of the alternating magnetic field to the adrenal region of the rats in the selected frequency and induction ranges caused a significant increase in the serum corticosterone levels. The results of the present study on the hormonal activity of rat adrenals give reason to consider the influence of the alternating magnetic fields as being modulatory. Analysis of the data thus obtained has demonstrated the non-linear dependence of glucocorticoid activity of the rat adrenal glands on the induction strength of the alternating magnetic field.

Low frequency geomagnetic field fluctuations at low latitude during the passage of a higher pressure solar wind region

Directory of Open Access Journals (Sweden)

U. Villante

1997-06-01

Full Text Available The passage of a higher pressure solar wind region at the Earth's orbit marked the onset of low latitude (L=1.6 fluctuations in the frequency range (0.8–5.5 mHz for both the horizontal geomagnetic field components. Spectral peaks mostly occur at the same frequencies as the spectral enhancements which appeared in the long term analysis of experimental measurements from the same station and were tentatively interpreted in terms of ground signatures of global magnetospheric modes. A comparison with simultaneous observations discussed by previous investigations allows us to conclude that the same set of frequencies is enhanced in a wide portion of the Earth's magnetosphere.

Spatiotemporal distribution characteristics and attribution of extreme regional low temperature event

International Nuclear Information System (INIS)

Feng Tai-Chen; Zhang Ke-Quan; Wang Xiao-Juan; Zhang Wen-Yu; Su Hai-Jing; Gong Zhi-Qiang

2015-01-01

Based on an objective identification technique for regional low temperature event (OITRLTE), the daily minimum temperature in China has been detected from 1960 to 2013. During this period, there were 60 regional extreme low temperature events (ERLTEs), which are included in the 690 regional low temperature events (RLTEs). The 60 ERLTEs are analyzed in this paper. The results show that in the last 50 years, the intensity of the ERLTEs has become weak; the number of lasted days has decreased; and, the affected area has become small. However, that situation has changed in this century. In terms of spatial distribution, the high intensity regions are mainly in Northern China while the high frequency regions concentrate in Central and Eastern China. According to the affected area of each event, the 60 ERLTEs are classified into six types. The atmospheric circulation background fields which correspond to these types are also analyzed. The results show that, influenced by stronger blocking highs of Ural and Lake Baikal, as well as stronger southward polar vortex and East Asia major trough at 500-hPa geopotential height, cold air from high latitudes is guided to move southward and abnormal northerly winds at 850 hPa makes the cold air blow into China along diverse paths, thereby forming different types of regional extreme low temperatures in winter. (paper)

Effect of electric fields on the stabilization of premixed laminar bunsen flames at low AC frequency: Bi-ionic wind effect

KAUST Repository

Kim, Minkuk

2012-03-01

The stabilization characteristics of laminar premixed bunsen flames have been investigated experimentally by applying AC electric fields at low frequency below 60. Hz together with DC in the single electrode configuration. The blowoff velocity has been measured for varying AC voltage and frequency. A transition frequency between low and high frequency regimes has been identified near 40-50. Hz, where AC electric fields have minimal effect on flame stabilization. In the low frequency regime, the blowoff velocity decreased linearly with AC voltage such that the flames became less stable. This was consistent with the DC result, implying the influence of the ionic wind effect. The variation of blowoff velocity with AC frequency showed a non-monotonic behavior in that the velocity decreased and then increased, exhibiting minimum blowoff velocity near 6-8. Hz. Based on the molecular kinetic theory, the developing degree of ionic wind was derived. By considering the ionic wind effects arising from both positive and negative ions in a flame zone, the bi-ionic wind effect successfully explained the non-monotonic behavior of blowoff velocity with AC frequency in the low frequency regime. © 2011 The Combustion Institute.

Low-frequency excess flux noise in superconducting devices

Energy Technology Data Exchange (ETDEWEB)

Kempf, Sebastian; Ferring, Anna; Fleischmann, Andreas; Enss, Christian [Kirchhoff-Institute for Physics, Heidelberg University (Germany)

2016-07-01

Low-frequency noise is a rather universal phenomenon and appears in physical, chemical, biological or even economical systems. However, there is often very little known about the underlying processes leading to its occurrence. In particular, the origin of low-frequency excess flux noise in superconducting devices has been an unresolved puzzle for many decades. Its existence limits, for example, the coherence time of superconducting quantum bits or makes high-precision measurements of low-frequency signals using SQUIDs rather challenging. Recent experiments suggest that low-frequency excess flux noise in Josephson junction based devices might be caused by the random reversal of interacting spins in surface layer oxides and in the superconductor-substrate interface. Even if it turns out to be generally correct, the underlying physical processes, i.e. the origin of these spins, their physical nature as well as the interaction mechanisms, have not been resolved so far. In this contribution we discuss recent measurements of low-frequency SQUID noise which we performed to investigate the origin of low-frequency excess flux noise in superconducting devices. Within this context we give an overview of our measurement techniques and link our data with present theoretical models and literature data.

Using low-frequency pulsar observations to study the 3-D structure of the Galactic magnetic field

Science.gov (United States)

Sobey, C.; LOFAR Collaboration; MWA Collaboration

2018-05-01

The Galactic magnetic field (GMF) plays a role in many astrophysical processes and is a significant foreground to cosmological signals, such as the Epoch of Reionization (EoR), but is not yet well understood. Dispersion and Faraday rotation measurements (DMs and RMs, respectively) towards a large number of pulsars provide an efficient method to probe the three-dimensional structure of the GMF. Low-frequency polarisation observations with large fractional bandwidth can be used to measure precise DMs and RMs. This is demonstrated by a catalogue of RMs (corrected for ionospheric Faraday rotation) from the Low Frequency Array (LOFAR), with a growing complementary catalogue in the southern hemisphere from the Murchison Widefield Array (MWA). These data further our knowledge of the three-dimensional GMF, particularly towards the Galactic halo. Recently constructed or upgraded pathfinder and precursor telescopes, such as LOFAR and the MWA, have reinvigorated low-frequency science and represent progress towards the construction of the Square Kilometre Array (SKA), which will make significant advancements in studies of astrophysical magnetic fields in the future. A key science driver for the SKA-Low is to study the EoR, for which pulsar and polarisation data can provide valuable insights in terms of Galactic foreground conditions.

Ultra and extremely low frequency electromagnetic fields

CERN Document Server

Surkov, Vadim

2014-01-01

This book examines how different sources and physical mechanisms affect ULF/ELF effects. It investigates non seismic prediction of impending natural disasters such as earthquakes, volcano eruptions and tsunamis.

MESSENGER Magnetic Field Observations of Upstream Ultra-Low Frequency Waves at Mercury

Science.gov (United States)

Le, G.; Chi, P. J.; Boardsen, S.; Blanco-Cano, X.; Anderosn, B. J.; Korth, H.

2012-01-01

The region upstream from a planetary bow shock is a natural plasma laboratory containing a variety of wave particle phenomena. The study of foreshocks other than the Earth's is important for extending our understanding of collisionless shocks and foreshock physics since the bow shock strength varies with heliocentric distance from the Sun, and the sizes of the bow shocks are different at different planets. The Mercury's bow shock is unique in our solar system as it is produced by low Mach number solar wind blowing over a small magnetized body with a predominately radial interplanetary magnetic field. Previous observations of Mercury upstream ultra-low frequency (ULF) waves came exclusively from two Mercury flybys of Mariner 10. The MESSENGER orbiter data enable us to study of upstream waves in the Mercury's foreshock in depth. This paper reports an overview of upstream ULF waves in the Mercury's foreshock using high-time resolution magnetic field data, 20 samples per second, from the MESSENGER spacecraft. The most common foreshock waves have frequencies near 2 Hz, with properties similar to the I-Hz waves in the Earth's foreshock. They are present in both the flyby data and in every orbit of the orbital data we have surveyed. The most common wave phenomenon in the Earth's foreshock is the large-amplitude 30-s waves, but similar waves at Mercury have frequencies at near 0.1 Hz and occur only sporadically with short durations (a few wave cycles). Superposed on the "30-s" waves, there are spectral peaks at near 0.6 Hz, not reported previously in Mariner 10 data. We will discuss wave properties and their occurrence characteristics in this paper.

The role of localised Ultra-Low Frequency waves in energetic electron precipitation

Science.gov (United States)

Rae, J.; Murphy, K. R.; Watt, C.; Mann, I. R.; Ozeke, L.; Halford, A. J.; Sibeck, D. G.; Clilverd, M. A.; Rodger, C. J.; Degeling, A. W.; Singer, H. J.

2016-12-01

Electromagnetic waves play pivotal roles in radiation belt dynamics through a variety of different means. Typically, Ultra-Low Frequency (ULF) waves have historically been invoked for radial diffusive transport leading to both acceleration and loss of outer radiation belt electrons. Very-Low Frequency (VLF) and Extremely-Low Frequency (ELF) waves are generally thought to provide a mechanism for localized acceleration and loss through precipitation into the ionosphere. In this study we present a new mechanism for electron loss through precipitation into the ionosphere due to direct modulation of the loss cone via localized compressional ULF waves. Observational evidence is presented demonstrating that modulation of the equatorial loss cone can occur via localized compressional wave activity. We then perform statistical computations of the probability distribution to determine how likely a given magnetic perturbation would produce a given percentage change in the bounce loss-cone (BLC). We discuss the ramifications of the action of coherent, localized compressional ULF waves on drifting electron populations; their precipitation response can be a complex interplay between electron energy, the shape of the phase space density profile at pitch angles close to the loss cone, ionospheric decay timescales, and the time-dependence of the electron source. We present a case study of compressional wave activity in tandem with riometer and balloon-borne electron precipitation across keV-MeV energies to demonstrate that the experimental measurements can be explained by our new enhanced loss cone mechanism. We determine that the two pivotal components not usually considered are localized ULF wave fields and ionospheric decay timescales. We conclude that ULF wave modulation of the loss cone is a viable candidate for direct precipitation of radiation belt electrons without any additional requirement for gyroresonant wave-particle interaction. Additional mechanisms would be

Suppression of nonlinear frequency-sweeping of resonant interchange modes in a magnetic dipole with applied radio frequency fields

International Nuclear Information System (INIS)

Maslovsky, D.; Levitt, B.; Mauel, M. E.

2003-01-01

Interchange instabilities excited by energetic electrons trapped by a magnetic dipole nonlinearly saturate and exhibit complex, coherent spectral characteristics and frequency sweeping [H. P. Warren and M. E. Mauel, Phys. Plasmas 2, 4185 (1995)]. When monochromatic radio frequency (rf) fields are applied in the range of 100-1000 MHz, the saturation behavior of the interchange instability changes dramatically. For applied fields of sufficient intensity and pulse-length, coherent interchange fluctuations are suppressed and frequency sweeping is eliminated. When rf fields are switched off, coherent frequency sweeping reappears. Since low frequency interchange instabilities preserve the electron's first and second adiabatic invariants, these observations can be interpreted as resulting from nonlinear resonant wave-particle interactions described within a particle phase-space, (ψ,φ), comprised of the third adiabatic invariant and the azimuthal angle. Self-consistent numerical simulation is used to study (1) the nonlinear development of the instability, (2) the radial mode structure of the interchange instability, and (3) the suppression of frequency sweeping. When the applied rf heating is modeled as an 'rf collisionality', the simulation reproduces frequency sweeping suppression and suggests an explanation for the observations that is consistent with Berk and co-workers [H. L. Berk et al., Phys. Plasmas 6, 3102 (1999)

Resonant frequencies of massless scalar field in rotating black-brane spacetime

Institute of Scientific and Technical Information of China (English)

Jing Ji-Liang; Pan Qi-Yuan

2008-01-01

This paper investigates the resonant frequencies of the massless scalar field in the near extremal Kerr-like black-brahe spacetime. It is shown that the different angular quantum number will present different resonant frequencies. It is also shown that the real part of the resonant frequencies increases as the compact dimensions parameter μi increases, but the magnitude of the imaginary part decreases as μi increases.

Low-frequency-field-induced spontaneous-emission interference in a two-level atom placed in an anisotropic photonic crystal

International Nuclear Information System (INIS)

Li Gaoxiang; Evers, Joerg; Keitel, Christoph H

2005-01-01

We investigate the spontaneous-emission properties of a two-level atom embedded in a three-dimensional anisotropic photonic crystal. In addition to the modified density of states, the atom is driven by a coherent intense low-frequency field (LFF), which creates additional multiphoton decay channels with the exchange of two low-frequency photons and one spontaneous photon during an atomic transition. Due to the low frequency of the applied field, the various transition pathways may interfere with each other and thus give rise to a modified system dynamics. We find that even if all the atomic (bare and induced) transition frequencies are in the conducting band of the photonic crystal, there still may exist a photon-atom bound state in coexistence with propagating modes. The system also allows us to generate narrow lines in the spontaneous-emission spectrum. This spectrum is a function of the distance of the observer from the atom due to the band gap in the photonic crystal. The system properties depend on three characteristic frequencies, which are influenced by quantum interference effects. Thus these results can be attributed to a combination of interference and band-gap effects

Extreme depth-of-field intraocular lenses

Science.gov (United States)

Baker, Kenneth M.

1996-05-01

A new technology brings the full aperture single vision pseudophakic eye's effective hyperfocal distance within the half-meter range. A modulated index IOL containing a subsurface zeroth order coherent microlenticular mosaic defined by an index gradient adds a normalizing function to the vergences or parallactic angles of incoming light rays subtended from field object points and redirects them, in the case of near-field images, to that of far-field images. Along with a scalar reduction of the IOL's linear focal range, this results in an extreme depth of field with a narrow depth of focus and avoids the focal split-up, halo, and inherent reduction in contrast of multifocal IOLs. A high microlenticular spatial frequency, which, while still retaining an anisotropic medium, results in a nearly total zeroth order propagation throughout the visible spectrum. The curved lens surfaces still provide most of the refractive power of the IOL, and the unique holographic fabrication technology is especially suitable not only for IOLs but also for contact lenses, artificial corneas, and miniature lens elements for cameras and other optical devices.

New photon science and extreme field physics: volumetric interaction of ultra-intense laser pulses with over-dense targets

Energy Technology Data Exchange (ETDEWEB)

Hegelich, Bjorn M [Los Alamos National Laboratory

2010-11-24

The constantly improving capabilities of ultra-high power lasers are enabling interactions of matter with ever extremer fields. As both the on target intensity and the laser contrast are increasing, new physics regimes are becoming accessible and new effects materialize, which in turn enable a host of applications. A first example is the realization of interactions in the transparent-overdense regime (TOR), which is reached by interacting a highly relativistic (a{sub 0} > 10), ultra high contrast laser pulse with a solid density, nanometer target. Here, a still overdense target is turned transparent to the laser by the relativistic mass increase of the electrons, increasing the skin depth beyond the target thickness and thus enabling volumetric interaction of the laser with the entire target instead of only a small interaction region at the critical density surface. This increases the energy coupling, enabling a range of effects, including relativistic optics and pulse shaping, mono-energetic electron acceleration, highly efficient ion acceleration in the break-out afterburner regime, the generation of relativistic and forward directed surface harmonics. In this talk we will show the theoretical framework for this regime, explored by multi-D, high resolution and high density PIC simulations as well as analytic theory and present measurements and experimental demonstrations of direct relativistic optics, relativistic HHG, electron acceleration, and BOA ion acceleration in the transparent overdense regime. These effects can in turn be used in a host of applications including laser pulse shaping, ICF diagnostics, coherent x-ray sources, and ion sources for fast ignition (IFI), homeland security applications and medical therapy. This host of applications already makes transparent-overdense regime one of general interest, a situation reinforced by the fact that the TOR target undergoes an extremely wide HEDP parameter space during interaction ranging from WDM conditions

Waves of change: immunomodulation of the innate immune response by low frequency electromagnetic field exposure

NARCIS (Netherlands)

Golbach, L.A.

2015-01-01

In this thesis we investigated possible modulatory roles of low frequency electromagnetic fields (LF EMFs) exposure on the innate immune system. Recent decades have seen a huge increase in the use of electronic devices that nowadays enable us to communicate with distant family, enjoy

Low-frequency nuclear quadrupole resonance with a dc SQUID

International Nuclear Information System (INIS)

Chang, J.W.

1991-07-01

Conventional pure nuclear quadrupole resonance (NQR) is a technique well suited for the study of very large quadrupolar interactions. Numerous nuclear magnetic resonance (NMR) techniques have been developed for the study of smaller quadrupolar interactions. However, there are many nuclei which have quadrupolar interactions of intermediate strength. Quadrupolar interactions in this region have traditionally been difficult or unfeasible to detect. This work describes the development and application of a SQUID NQR technique which is capable of measuring intermediate strength quadrupolar interactions, in the range of a few hundred kilohertz to several megahertz. In this technique, a dc SQUID (Superconducting QUantum Interference Device) is used to monitor the longitudinal sample magnetization, as opposed to the transverse magnetization, as a rf field is swept in frequency. This allows the detection of low-frequency nuclear quadrupole resonances over a very wide frequency range with high sensitivity. The theory of this NQR technique is discussed and a description of the dc SQUID system is given. In the following chapters, the spectrometer is discussed along with its application to the study of samples containing half-odd-integer spin quadrupolar nuclei, in particular boron-11 and aluminum-27. The feasibility of applying this NQR technique in the study of samples containing integer spin nuclei is discussed in the last chapter. 140 refs., 46 figs., 6 tabs

Direct imaging of neural currents using ultra-low field magnetic resonance techniques

Science.gov (United States)

Volegov, Petr L [Los Alamos, NM; Matlashov, Andrei N [Los Alamos, NM; Mosher, John C [Los Alamos, NM; Espy, Michelle A [Los Alamos, NM; Kraus, Jr., Robert H.

2009-08-11

Using resonant interactions to directly and tomographically image neural activity in the human brain using magnetic resonance imaging (MRI) techniques at ultra-low field (ULF), the present inventors have established an approach that is sensitive to magnetic field distributions local to the spin population in cortex at the Larmor frequency of the measurement field. Because the Larmor frequency can be readily manipulated (through varying B.sub.m), one can also envision using ULF-DNI to image the frequency distribution of the local fields in cortex. Such information, taken together with simultaneous acquisition of MEG and ULF-NMR signals, enables non-invasive exploration of the correlation between local fields induced by neural activity in cortex and more `distant` measures of brain activity such as MEG and EEG.

On the design of experiments for the study of extreme field limits in the ultra-relativistic interaction of electromagnetic waves with plasmas

Science.gov (United States)

Bulanov, Sergei V.; Esirkepov, Timur Z.; Hayashi, Yukio; Kando, Masaki; Kiriyama, Hiromitsu; Koga, James K.; Kondo, Kiminori; Kotaki, Hideyuki; Pirozhkov, Alexander S.; Bulanov, Stepan S.; Zhidkov, Alexei G.; Chen, Pisin; Neely, David; Kato, Yoshiaki; Narozhny, Nikolay B.; Korn, Georg

2011-06-01

The critical electric field of quantum electrodynamics, called also the Schwinger field, is so strong that it produces electron-positron pairs from vacuum, converting the energy of light into matter. Since the dawn of quantum electrodynamics, there has been a dream on how to reach it on Earth. With the rise of laser technology this field has become feasible through the construction of extremely high power lasers or/and with the sophisticated use of nonlinear processes in relativistic plasmas. This is one of the most attractive motivations for extremely high power laser development, i.e. producing matter from vacuum by pure light in fundamental process of quantum electrodynamics in the nonperturbative regime. Recently it has been realized that a laser with intensity well below the Schwinger limit can create an avalanche of electron-positron pairs similar to a discharge before attaining the Schwinger field. It has also been realized that the Schwinger limit can be reached using an appropriate configuration of laser beams. In experiments on the collision of laser light and high intensity electromagnetic pulses generated by relativistic flying mirrors, with electron bunches produced by a conventional accelerator and with laser wake field accelerated electrons the studying of extreme field limits in the nonlinear interaction of electromagnetic waves is proposed. The regimes of dominant radiation reaction, which completely changes the electromagnetic wave-matter interaction, will be revealed. This will result in a new powerful source of high brightness gamma-rays. A possibility of the demonstration of the electronpositron pair creation in vacuum via multi-photon processes can be realized. This will allow modeling under terrestrial laboratory conditions neutron star magnetospheres, cosmological gamma ray bursts and the Leptonic Era of the Universe.

The Radio And Very Low Frequency (VLF) Electromagnetic ...

African Journals Online (AJOL)

The Radio And Very Low Frequency (VLF) Electromagnetic Response Of A Layered Earth Media With Variable Dielectric Permittivity. ... A radio frequency of 125 KHz and a very low frequency (VLF) of 20 KHz were used in the computations and the field parameters studied over a dimensionless induction number, B. The ...

Extreme low temperature tolerance in woody plants

Directory of Open Access Journals (Sweden)

George Richard Strimbeck

2015-10-01

Full Text Available Woody plants in boreal to arctic environments and high mountains survive prolonged exposure to temperatures below -40˚C and minimum temperatures below -60˚C, and laboratory tests show that many of these species can also survive immersion in liquid nitrogen at -196˚C. Studies of biochemical changes that occur during acclimation, including recent proteomic and metabolomic studies, have identified changes in carbohydrate and compatible solute concentrations, membrane lipid composition, and proteins, notably dehydrins, that may have important roles in survival at extreme low temperature. Consideration of the biophysical mechanisms of membrane stress and strain lead to the following hypotheses for cellular and molecular mechanisms of survival at extreme low temperature: 1. Changes in lipid composition stabilize membranes at temperatures above the lipid phase transition temperature (-20 to 30˚C, preventing phase changes that result in irreversible injury. 2. High concentrations of oligosaccharides promote vitrification or high viscosity in the cytoplasm in freeze-dehydrated cells, which would prevent deleterious interactions between membranes. 3. Dehydrins bind membranes and further promote vitrification or act stearically to prevent membrane-membrane interactions.

Colloidal interactions in field-directed self-assembly

Science.gov (United States)

Lele, Pushkar P.

polarizable particles in AC electric fields as a function of field strength and frequency and observe three key features: (1) The order-disorder transition as a function of field strength and frequency exhibits an ordered regime consisting of dipolar chains and crystals between two disordered regimes at low and high field strengths. While the transition to order at low field strengths is consistent with the polarization-induced interactions becoming larger than the thermal energy of the particles, the reentrant disordered regime at high field strengths is marked by large-scale rotating structures; (2) As mentioned, using blinking laser tweezers to characterize the interaction of particle pairs, we demonstrate that particle pair rotation opposite of alignment in the field direction is the microscopic phenomenon driving the observed suspension behavior. The pair particle rotation is observed to decrease with increasing frequency, thus requiring higher field strengths, in agreement with the frequency and field strength dependence of the second order-to-disorder transition; (3) The particle rotation is consistent with a mechanism based on the mutual polarization of particles, and is an effect of the phase lag between the polarization and the applied and mutually induced field. The connection we made between particle interactions and suspension microstructure answers a long-standing debate regarding the mechanism underlying the band structures in experiments employing parallel electrode geometries. Creating ordered crystalline structures from anisotropic particles is a fundamental challenge. To create such structures, either one can direct the assembly of particles from a random dispersion using external fields or, as we will show, they can be created from the controlled deformation of isotropic particle templates. Using an assemble-stretch technique we create 2D and 3D anisotropic particle assemblies from an initial template of close-packed spheres. This method enables the

Effect of low frequency magnetic fields on the growth of MNP-treated HT29 colon cancer cells

Science.gov (United States)

Spyridopoulou, K.; Makridis, A.; Maniotis, N.; Karypidou, N.; Myrovali, E.; Samaras, T.; Angelakeris, M.; Chlichlia, K.; Kalogirou, O.

2018-04-01

Recent investigations have attempted to understand and exploit the impact of magnetic field-actuated internalized magnetic nanoparticles (MNPs) on the proliferation rate of cancer cells. Due to the complexity of the parameters governing magnetic field-exposure though, individual studies to date have raised contradictory results. In our approach we performed a comparative analysis of key parameters related to the cell exposure of cancer cells to magnetic field-actuated MNPs, and to the magnetic field, in order to better understand the factors affecting cellular responses to magnetic field-stimulated MNPs. We used magnetite MNPs with a hydrodynamic diameter of 100 nm and studied the proliferation rate of MNPs-treated versus untreated HT29 human colon cancer cells, exposed to either static or alternating low frequency magnetic fields with varying intensity (40-200 mT), frequency (0-8 Hz) and field gradient. All three parameters, field intensity, frequency, and field gradient affected the growth rate of cells, with or without internalized MNPs, as compared to control MNPs-untreated and magnetic field-untreated cells. We observed that the growth inhibitory effects induced by static and rotating magnetic fields were enhanced by pre-treating the cells with MNPs, while the growth promoting effects observed in alternating field-treated cells were weakened by MNPs. Compared to static, rotating magnetic fields of the same intensity induced a similar extend of cell growth inhibition, while alternating fields of varying intensity (70 or 100 mT) and frequency (0, 4 or 8 Hz) induced cell proliferation in a frequency-dependent manner. These results, highlighting the diverse effects of mode, intensity, and frequency of the magnetic field on cell growth, indicate that consistent and reproducible results can be achieved by controlling the complexity of the exposure of biological samples to MNPs and external magnetic fields, through monitoring crucial experimental parameters. We

Low-frequency waves in magnetized dusty plasmas revisited

International Nuclear Information System (INIS)

Salimullah, M.; Khan, M.I.; Amin, R.; Nitta, H.; Shukla, P.K.

2005-10-01

The general dispersion relation of any wave is examined for low-frequency waves in a homogeneous dusty plasma in the presence of an external magnetic field. The low-frequency parallel electromagnetic wave propagates as a dust cyclotron wave or a whistler in the frequency range below the ion cyclotron frequency. In the same frequency regime, the transverse electromagnetic magnetosonic wave is modified with a cutoff frequency at the dust-ion lower-hybrid frequency, which reduces to the usual magnetosonic wave in absence of the dust. Electrostatic dust-lower- hybrid mode is also recovered propagating nearly perpendicular to the magnetic field with finite ion temperature and cold dust particles which for strong ion-Larmor radius effect reduces to the usual dust-acoustic wave driven by the ion pressure. (author)

Gravity and low-frequency geodynamics

CERN Document Server

Teisseyre, Roman

1989-01-01

This fourth volume in the series Physics and Evolution of the Earth's Interior, provides a comprehensive review of the geophysical and geodetical aspects related to gravity and low-frequency geodynamics. Such aspects include the Earth's gravity field, geoid shape theory, and low-frequency phenomena like rotation, oscillations and tides.Global-scale phenomena are treated as a response to source excitation in spherical Earth models consisting of several shells: lithosphere, mantle, core and sometimes also the inner solid core. The effect of gravitation and rotation on the Earth's shape is anal

Nonlinear beat excitation of low frequency wave in degenerate plasmas

Science.gov (United States)

Mir, Zahid; Shahid, M.; Jamil, M.; Rasheed, A.; Shahbaz, A.

2018-03-01

The beat phenomenon due to the coupling of two signals at slightly different frequencies that generates the low frequency signal is studied. The linear dispersive properties of the pump and sideband are analyzed. The modified nonlinear dispersion relation through the field coupling of linear modes against the beat frequency is derived in the homogeneous quantum dusty magnetoplasmas. The dispersion relation is used to derive the modified growth rate of three wave parametric instability. Moreover, significant quantum effects of electrons through the exchange-correlation potential, the Bohm potential, and the Fermi pressure evolved in macroscopic three wave interaction are presented. The analytical results are interpreted graphically describing the significance of the work. The applications of this study are pointed out at the end of introduction.

High frequency electric field spikes formed by electron beam-plasma interaction in plasma density gradients

International Nuclear Information System (INIS)

Gunell, H.; Loefgren, T.

1997-02-01

In the electron beam-plasma interaction at an electric double layer the beam density is much higher than in the classical beam-plasma experiments. The wave propagation takes place along the density gradient, that is present at the high potential side of the double layer. Such a case is studied experimentally by injecting the electron beam from a plane cathode, without any grids suppressing the gradient, and by particle simulations. The high frequency field concentrates in a sharp 'spike' with a half width of the order of one wavelength. The spike is found to be a standing wave surrounded by regions dominated by propagating waves. It forms at a position where its frequency is close to the local plasma frequency. The spike forms also when the electric field is well below the threshold for modulational instability, and long before a density cavity is formed in the simulations. Particle simulations reveal that, at the spike, there is a backward travelling wave that, when it is strongly damped, accelerates electrons back towards the cathode. In a simulation of a homogeneous plasma without the density gradient no spike is seen, and the wave is purely travelling instead of standing. 9 refs

Frequency pulling in a low-voltage medium-power gyrotron

Science.gov (United States)

Luo, Li; Du, Chao-Hai; Huang, Ming-Guang; Liu, Pu-Kun

2018-04-01

Many recent biomedical applications use medium-power frequency-tunable terahertz (THz) sources, such as sensitivity-enhanced nuclear magnetic resonance, THz imaging, and biomedical treatment. As a promising candidate, a low-voltage gyrotron can generate watt-level, continuous THz-wave radiation. In particular, the frequency-pulling effect in a gyrotron, namely, the effect of the electron beam parameters on the oscillation frequency, can be used to tune the operating frequency. Most previous investigations used complicated and time-consuming gyrotron nonlinear theory to study the influence of many beam parameters on the interaction performance. While gyrotron linear theory investigation demonstrates the advantages of rapidly and clearly revealing the physical influence of individual key beam parameters on the overall system performance, this paper demonstrates systematically the use of gyrotron linear theory to study the frequency-pulling effect in a low-voltage gyrotron with either a Gaussian or a sinusoidal axial-field profile. Furthermore, simulations of a gyrotron operating in the first axial mode are carried out in the framework of nonlinear theory as a contrast. Close agreement is achieved between the two theories. Besides, some interesting results are obtained. In a low-current sinusoidal-profile cavity, the ranges of frequency variation for different axial modes are isolated from each other, and the frequency tuning bandwidth for each axial mode increases by increasing either the beam voltage or pitch factor. Lowering the voltage, the total tuning ranges are squeezed and become concentrated. However, the isolated frequency regions of each axial mode cannot be linked up unless the beam current is increased, meaning that higher current operation is the key to achieving a wider and continuous tuning frequency range. The results presented in this paper can provide a reference for designing a broadband low-voltage gyrotron.

Low field magnetic resonance experiments in superfluid 3He--A

International Nuclear Information System (INIS)

Gully, W.J. Jr.

1976-01-01

Measurements of the longitudinal and transverse nuclear magnetic resonance signals have been made on the A phase of liquid 3 He. They were performed on a sample of 3 He self-cooled by the Pomeranchuk effect to the critical temperature of the superfluid at 2.7 m 0 K. The longitudinal resonance is a magnetic mode of the liquid excited by radio frequency magnetic fields applied in the direction of the static magnetic field. Frequency profiles of this resonance were indirectly obtained by contour techniques from signals recorded by sweeping the temperature. Its frequency is found to be related to the frequency shift of the transverse resonance in agreement with theoretical predictions for the ABM pairing state. Its linewidth also agrees with theoretical predictions based upon dissipative phenomena peculiar to the superfluid phase. An analysis of the linewidth of the longitudinal resonance yields a value for the quasiparticle collision time. Transverse NMR lines were also studied. In low magnetic fields (20 Oersted) these lines were found to become extremely broad. This is shown to be a manifestation of the same collisional processes that broaden the longitudinal resonance lines. Also, the effects of various textures on the resonance lines are discussed, including the results of an attempt to create a single domain of 3 He with crossed electric and magnetic fields

A kinetic-MHD model for low frequency phenomena

International Nuclear Information System (INIS)

Cheng, C.Z.

1991-07-01

A hybrid kinetic-MHD model for describing low-frequency phenomena in high beta anisotropic plasmas that consist of two components: a low energy core component and an energetic component with low density. The kinetic-MHD model treats the low energy core component by magnetohydrodynamic (MHD) description, the energetic component by kinetic approach such as the gyrokinetic equation, and the coupling between the dynamics of these two components through plasma pressure in the momentum equation. The kinetic-MHD model optimizes both the physics contents and the theoretical efforts in studying low frequency MHD waves and transport phenomena in general magnetic field geometries, and can be easily modified to include the core plasma kinetic effects if necessary. It is applicable to any magnetized collisionless plasma system where the parallel electric field effects are negligibly small. In the linearized limit two coupled eigenmode equations for describing the coupling between the transverse Alfven type and the compressional Alfven type waves are derived. The eigenmode equations are identical to those derived from the full gyrokinetic equation in the low frequency limit and were previously analyzed both analytically nd numerically to obtain the eigenmode structure of the drift mirror instability which explains successfully the multi-satellite observation of antisymmetric field-aligned structure of the compressional magnetic field of Pc 5 waves in the magnetospheric ring current plasma. Finally, a quadratic form is derived to demonstrate the stability of the low-frequency transverse and compressional Alfven type instabilities in terms of the pressure anisotropy parameter τ and the magnetic field curvature-pressure gradient parameter. A procedure for determining the stability of a marginally stable MHD wave due to wave-particle resonances is also presented

Low and High-Frequency Field Potentials of Cortical Networks ...

Science.gov (United States)

Neural networks grown on microelectrode arrays (MEAs) have become an important, high content in vitro assay for assessing neuronal function. MEA experiments typically examine high- frequency (HF) (>200 Hz) spikes, and bursts which can be used to discriminate between different pharmacological agents/chemicals. However, normal brain activity is additionally composed of integrated low-frequency (0.5-100 Hz) field potentials (LFPs) which are filtered out of MEA recordings. The objective of this study was to characterize the relationship between HF and LFP neural network signals, and to assess the relative sensitivity of LFPs to selected neurotoxicants. Rat primary cortical cultures were grown on glass, single-well MEA chips. Spontaneous activity was sampled at 25 kHz and recorded (5 min) (Multi-Channel Systems) from mature networks (14 days in vitro). HF (spike, mean firing rate, MFR) and LF (power spectrum, amplitude) components were extracted from each network and served as its baseline (BL). Next, each chip was treated with either 1) a positive control, bicuculline (BIC, 25μM) or domoic acid (DA, 0.3μM), 2) or a negative control, acetaminophen (ACE, 100μM) or glyphosate (GLY, 100μM), 3) a solvent control (H2O or DMSO:EtOH), or 4) a neurotoxicant, (carbaryl, CAR 5, 30μM ; lindane, LIN 1, 10μM; permethrin, PERM 25, 50μM; triadimefon, TRI 5, 65μM). Post treatment, 5 mins of spontaneous activity was recorded and analyzed. As expected posit

Low-frequency noise in multilayer MoS2 field-effect transistors: the effect of high-k passivation.

Science.gov (United States)

Na, Junhong; Joo, Min-Kyu; Shin, Minju; Huh, Junghwan; Kim, Jae-Sung; Piao, Mingxing; Jin, Jun-Eon; Jang, Ho-Kyun; Choi, Hyung Jong; Shim, Joon Hyung; Kim, Gyu-Tae

2014-01-07

Diagnosing of the interface quality and the interactions between insulators and semiconductors is significant to achieve the high performance of nanodevices. Herein, low-frequency noise (LFN) in mechanically exfoliated multilayer molybdenum disulfide (MoS2) (~11.3 nm-thick) field-effect transistors with back-gate control was characterized with and without an Al2O3 high-k passivation layer. The carrier number fluctuation (CNF) model associated with trapping/detrapping the charge carriers at the interface nicely described the noise behavior in the strong accumulation regime both with and without the Al2O3 passivation layer. The interface trap density at the MoS2-SiO2 interface was extracted from the LFN analysis, and estimated to be Nit ~ 10(10) eV(-1) cm(-2) without and with the passivation layer. This suggested that the accumulation channel induced by the back-gate was not significantly influenced by the passivation layer. The Hooge mobility fluctuation (HMF) model implying the bulk conduction was found to describe the drain current fluctuations in the subthreshold regime, which is rarely observed in other nanodevices, attributed to those extremely thin channel sizes. In the case of the thick-MoS2 (~40 nm-thick) without the passivation, the HMF model was clearly observed all over the operation regime, ensuring the existence of the bulk conduction in multilayer MoS2. With the Al2O3 passivation layer, the change in the noise behavior was explained from the point of formation of the additional top channel in the MoS2 because of the fixed charges in the Al2O3. The interface trap density from the additional CNF model was Nit = 1.8 × 10(12) eV(-1) cm(-2) at the MoS2-Al2O3 interface.

EVALUATING EXTREMELY LOW FREQUENCY MAGNETIC FIELDS IN THE REAR SEATS OF THE ELECTRIC VEHICLES.

Science.gov (United States)

Lin, Jun; Lu, Meng; Wu, Tong; Yang, Lei; Wu, Tongning

2018-03-23

In the electric vehicles (EVs), children can sit on a safety seat installed in the rear seats. Owing to their smaller physical dimensions, their heads, generally, are closer to the underfloor electrical systems where the magnetic field (MF) exposure is the greatest. In this study, the magnetic flux density (B) was measured in the rear seats of 10 different EVs, for different driving sessions. We used the measurement results from different heights corresponding to the locations of the heads of an adult and an infant to calculate the induced electric field (E-field) strength using anatomical human models. The results revealed that measured B fields in the rear seats were far below the reference levels by the International Commission on Non-Ionizing Radiation Protection. Although small children may be exposed to higher MF strength, induced E-field strengths were much lower than that of adults due to their particular physical dimensions.

Evaluation of low-frequency operational limit of proposed ITER low-field-side reflectometer waveguide run including miter bends

Energy Technology Data Exchange (ETDEWEB)

Wang, Guiding [Univ. of California, Los Angeles, CA (United States). Dept. of Physics and Astronomy and Plasma Science and Technology Inst. (PSTI); Peebles, W. A. [Univ. of California, Los Angeles, CA (United States). Dept. of Physics and Astronomy and Plasma Science and Technology Inst. (PSTI); Doyle, E. J. [Univ. of California, Los Angeles, CA (United States). Dept. of Physics and Astronomy and Plasma Science and Technology Inst. (PSTI); Crocker, N. A. [Univ. of California, Los Angeles, CA (United States). Dept. of Physics and Astronomy and Plasma Science and Technology Inst. (PSTI); Wannberg, C. [Univ. of California, Los Angeles, CA (United States). Dept. of Physics and Astronomy and Plasma Science and Technology Inst. (PSTI); Lau, Cornwall H. [Oak Ridge National Lab. (ORNL), Oak Ridge, TN (United States); Hanson, Gregory R. [Oak Ridge National Lab. (ORNL), Oak Ridge, TN (United States); Doane, John L. [General Atomics, San Diego, CA (United States)

2017-10-19

The present design concept for the ITER low-field-side reflectometer transmission line (TL) consists of an ~40 m long, 6.35 cm diameter helically corrugated waveguide (WG) together with ten 90° miter bends. This paper presents an evaluation of the TL performance at low frequencies (33-50 GHz) where the predicted HE11 mode ohmic and mode conversion losses start to increase significantly. Quasi-optical techniques were used to form a near Gaussian beam to efficiently couple radiation in this frequency range into the WG. We observed that the output beams from the guide remained linearly polarized with cross-polarization power levels of ~1.5%-3%. The polarization rotation due to the helical corrugations was in the range ~1°-3°. The radiated beam power profiles typically show excellent Gaussian propagation characteristics at distances >20 cm from the final exit aperture. The round trip propagation loss was found to be ~2.5 dB at 50 GHz and ~6.5 dB at 35 GHz, showing an inverse increase with frequency. This was consistent with updated calculations of miter bend and ohmic losses. At low frequencies (33-50 GHz), the mode purity remained very good at the exit of the waveguide, and the losses are perfectly acceptable for operation in ITER. Finally, the primary challenge may come from the future addition of a Gaussian telescope and other filter components within the corrugated guide, which will likely introduce additional perturbations to the beam profile and an increase in mode-conversion loss.

Effective interactions for extreme isospin conditions; Interactions effectives pour des conditions extremes d`isospin

Energy Technology Data Exchange (ETDEWEB)

Chabanat, E.

1995-01-01

One of the main goal in nuclear physics research is the study of nuclei in extreme conditions of spin and isospin. The more performing tools for theoretical predictions in this field are microscopic methods such as the Hartree-Fock one based on independent particle approximation. The main ingredient for such an approach is the effective nucleon-nucleon interaction. The actual trend being the study of nuclei more and more far from the stability valley, it is necessary to cast doubt over the validity of usual effective interaction. This work constitute a study on the way one can construct a new interaction allowing some theoretical predictions on nuclei far from the stability. We have thus made a complete study of symmetric infinite nuclear matter and asymmetric one up to pure neutron matter. One shows that the asymmetry coefficient, which was considered until now as fixing isospin properties, is not sufficient to have a correct description of very exotic isospin states. A new type of constraint is shown for fixing this degree of freedom: the neutron matter equation of state. One include this equation of state, taken from a theoretical model giving a good description of radii and masses of neutron stars. One can thus expect to build up new Skyrme interaction with realistic properties of ground state of very neutron-rich nuclei. (author). 63 refs., 68 figs., 15 tabs.

Improved MR imaging in extremely inhomogenous radiofrequency fields

International Nuclear Information System (INIS)

Bansal, N.; Nunnally, R.L.

1989-01-01

A previous study developed a method for acquiring images in extremely inhomogeneous radio-frequency fields with use of adiabatic pulses. Since adiabatic pulses most suited to section selection are the inversion type, the method is prone to artifacts from receiver and analog-to-digital converter (ADC) saturation and subtraction errors. These problems are substantially reduced by using a pseudo-noise-modulated selective (PNMS) prepulse to randomize the unwanted spin magnetization. To compute the PNMS pulse shape, the frequency spectrum of a wave form with constant amplitude and random phase was determined by means of Fourier transformation and then inverted after a consecutive number of points were set to zero in the center. The performance of the prepulse with the imaging sequence was tested on a 1.8-T system. Results are presented

Comparison of the low-frequency magnetic field effects on bacteria Escherichia coli, Leclercia adecarboxylata and Staphylococcus aureus

Czech Academy of Sciences Publication Activity Database

Fojt, Lukáš; Strašák, Luděk; Vetterl, Vladimír; Šmarda, J.

2004-01-01

Roč. 63, 1-2 (2004), s. 337-341 ISSN 1567-5394 R&D Projects: GA ČR GA310/01/0816; GA AV ČR IBS5004107; GA AV ČR IAA4004404 Institutional research plan: CEZ:AV0Z5004920 Keywords : low-frequency electromagnetic field * ELF magnetic fields * bacteria Subject RIV: BO - Biophysics Impact factor: 2.261, year: 2004

Low-frequency response in antiferromagnetically coupled Fe/Cr multilayers

International Nuclear Information System (INIS)

Aliev, F.G.; Guerrero, R.; Martinez, J.L.; Moshchalkov, V.V.; Bruynseraede, Y.; Villar, R.

2001-01-01

We have studied the magnetic field dependences of the real (χ) and imaginary (χ') contributions to the low-frequency magnetic susceptibility in epitaxial antiferromagnetically coupled [Fe(Cr(1 0 0)] n (n=10-50) multilayers. For the magnetic field directed along (1 1 0), the magnetic susceptibility shows on orientation phase transition. For the magnetic field either along the easy or the hard axes we observe a strong enhancement of the χ'(H) (i.e. magnetic losses) at low magnetic fields (H<50 Oe), which we relate to AC field-induced domain wall movement. This response is strongly dependent on frequency and temperature

SENSITIVITY OF PIGMENT CONTENT OF BANANA AND ORCHID TISSUE CULTURE EXPOSED TO EXTREMELY LOW FREQUENCY ELECTROMAGNETIC FIEL

Directory of Open Access Journals (Sweden)

Riry Prihatini

2017-01-01

Full Text Available Natural exposure of extremely low frequency electromagnetic field (ELF-EMF occurs in the environment and acts as one of the abiotic factors that affect the growth and development of organisms. This study was conducted to determine the effect of ELF-EMF on the tissue cultured banana and slipper orchid chlorophyll content as one of the indicators in measuring plant photosynthetic capacity. Four days old banana (Musa sp. cv. Berangan corm and seven days old slipper orchid (Paphiopedilum rothschildianum cultures were exposed to 6 and 12 mT ELF-EMF generated by controllable ELF-EMF built up machine for 0.5, 1, 2 and 4 hours. After exposure, the banana and orchid cultures were incubated at 25° C for 8 and 16 weeks, respectively. The results showed that the ELF-EMF exposure had different effects on banana and slipper orchid cultures though both plant species belong to monocotyledon. The highest increase in chlorophyll content on banana was resulted by the high intensity and long duration of ELF-EMF exposure (12 mT for 4 hours, whereas on slipper orchid the modest and short duration of ELF-EMF exposure produced the most excessive chlorophyll content. Different ELF-EMF exposures (12 mT for 4 hours and 6 mT for 30 minutes had potential to be applied on each plant to improve in vitro plant (banana and slipper orchid, respectively growth. The increased chlorophyll and carotene/xanthophyll content on banana indicated that the banana was more tolerant to ELF-EMF exposure compared to slipper orchid. 

Observation of low frequency electromagnetic activity at 1000 km altitude

Directory of Open Access Journals (Sweden)

N. Ivchenko

Full Text Available We present a statistical study of low frequency fluctuations of electric and magnetic fields, commonly interpreted as Alfvénic activity. The data base consists of six months of electric and magnetic field measurements by the Astrid-2 microsatellite. The occurrence of the events is studied with respect to the location and general activity. Large regions of broadband Alfvénic activity are persistently observed in the cusp/cleft and, during the periods of high geo-magnetic activity, also in the pre-midnight sector of the auroral oval.

Key words. Ionosphere (auroral ionosphere – Space plasma physics (waves and instabilities – Magnetospheric physics (magnetosphere-ionosphere interactions

Spatiotemporal distribution characteristics and attribution of extreme regional low temperature event

Science.gov (United States)

Feng, Tai-Chen; Zhang, Ke-Quan; Su, Hai-Jing; Wang, Xiao-Juan; Gong, Zhi-Qiang; Zhang, Wen-Yu

2015-10-01

Based on an objective identification technique for regional low temperature event (OITRLTE), the daily minimum temperature in China has been detected from 1960 to 2013. During this period, there were 60 regional extreme low temperature events (ERLTEs), which are included in the 690 regional low temperature events (RLTEs). The 60 ERLTEs are analyzed in this paper. The results show that in the last 50 years, the intensity of the ERLTEs has become weak; the number of lasted days has decreased; and, the affected area has become small. However, that situation has changed in this century. In terms of spatial distribution, the high intensity regions are mainly in Northern China while the high frequency regions concentrate in Central and Eastern China. According to the affected area of each event, the 60 ERLTEs are classified into six types. The atmospheric circulation background fields which correspond to these types are also analyzed. The results show that, influenced by stronger blocking highs of Ural and Lake Baikal, as well as stronger southward polar vortex and East Asia major trough at 500-hPa geopotential height, cold air from high latitudes is guided to move southward and abnormal northerly winds at 850 hPa makes the cold air blow into China along diverse paths, thereby forming different types of regional extreme low temperatures in winter. Project supported by the National Natural Science Foundation of China (Grant No. 41305075), the National Basic Research Program of China (Grant Nos. 2012CB955203 and 2012CB955902), and the Special Scientific Research on Public Welfare Industry, China (Grant No. GYHY201306049).

Low frequency electromagnetic fields in Switzerland and in Germany. Comprehensive report on various studies

International Nuclear Information System (INIS)

Stratmann, M.; Wernli, C.; Grigat, J. P.; Eisenbrandt, H.

1998-01-01

The work of two research groups has been combined in this report. Both groups have concerned themselves with the occurrence and the distribution of low-frequency magnetic fields in the human environment. The initiative for the joint documentation came from the Radiation Metrology Section of the Paul Scherrer Institute. This team has investigated the general exposure on the Swiss population due to 50 Hz magnetic fields and the exposure arising from 162/3 Hz magnetic fields in the passenger area of trains. In addition, source-related measurements and frequency analyses up to 200 kHz have been undertaken. As a second group, the 'Research Association: Electromagnetic tolerance of biological systems' of the Technical University of Braunschweig, under the direction of Prof. Karl Brinkmann, has participated in the preparation of this documentation. During the past years, the research association has prepared two extensive studies on the local and temporal distribution of magnetic field sources in human residential areas and has contributed its findings on the residential situation as a supplement to the treatment of the problems described here. Intentionally, the report has not been prepared as a scientific presentation, but rather as informative reading for specialists as well as for the general public. (author)

Gravitational dynamos and the low-frequency geomagnetic secular variation.

Science.gov (United States)

Olson, P

2007-12-18

Self-sustaining numerical dynamos are used to infer the sources of low-frequency secular variation of the geomagnetic field. Gravitational dynamo models powered by compositional convection in an electrically conducting, rotating fluid shell exhibit several regimes of magnetic field behavior with an increasing Rayleigh number of the convection, including nearly steady dipoles, chaotic nonreversing dipoles, and chaotic reversing dipoles. The time average dipole strength and dipolarity of the magnetic field decrease, whereas the dipole variability, average dipole tilt angle, and frequency of polarity reversals increase with Rayleigh number. Chaotic gravitational dynamos have large-amplitude dipole secular variation with maximum power at frequencies corresponding to a few cycles per million years on Earth. Their external magnetic field structure, dipole statistics, low-frequency power spectra, and polarity reversal frequency are comparable to the geomagnetic field. The magnetic variability is driven by the Lorentz force and is characterized by an inverse correlation between dynamo magnetic and kinetic energy fluctuations. A constant energy dissipation theory accounts for this inverse energy correlation, which is shown to produce conditions favorable for dipole drift, polarity reversals, and excursions.

Ultrastructural Study on Ultra-Low Frequency Electromagnetic Fields and Transfer Factor Effects on Skin Ulcers

International Nuclear Information System (INIS)

Cadena, M. S. Reyes; Chapul, L. Sanchez; Perez, Javier; Garcia, M. N. Jimenez; Lopez, M. A. Jimenez; Espindola, M. E. Sanchez; Perez, R. Paniagua; Hernandez, N. A.; Paniagua, G.; Uribe, F.; Nava, J. J. Godina; Segura, M. A. Rodriguez

2008-01-01

We determined the effect of 120Hz ultra low frequency electromagnetic field (ELF) on the healing process of skin in 20 Wistar rats distributed in four groups in which chronic dermal ulcers had been produced. The first two groups received a dose of the transfer factor and interferon-beta (IFN-β) every 24 h during 12 days. The third group (positive control) received only electromagnetic field (ELF) sessions, and in the fourth group (negative control), no treatment was applied. The electromagnetic field was applied through a Helmholtz coils; 30 Gauss of intensity. Results shown histological changes that improve the healing process in animals subjected to ELF together with the transfer factor

Residential exposure from extremely low frequency electromagnetic field (ELF EMF) radiation

Science.gov (United States)

Parthasarathy, Shamesh Raj; Tukimin, Roha

2018-01-01

ELF EMF radiation have received considerable attention as a potential threat to the safety and health of people living in the vicinity of high voltage transmission lines, electric distribution substations, power stations and even in close proximity to electronics and electrical household appliances. The paper highlights the study on the ELF EMF safety assessment performed at residences comprising of an owner-occupied house, a completed vacant house and an under construction condominium. The objectives of this study were to determine the ELF EMF radiation exposure level from the high voltage transmission line, electric distribution substation, power station and electrical household appliances in the residences, and to assess the potential exposure received by the occupants at the assessed locations. The results were logged in the electric and magnetic field strength with the units of volt per meter (V/m) and miliGauss (mG) respectively. The instrument setup and measurement protocols during the assessment were adopted from standard measurement method and procedures stipulated under the Institute of Electrical and Electronics Engineers (IEEE) Standard. The results were compared with the standards recommended in the International Commission on Non-Ionizing Radiation Protection (ICNIRP) guidelines.

Effects of extremely low frequency electromagnetic fields on liver enzymes in Guinea pig

International Nuclear Information System (INIS)

Zare, S.; Hayatgeiby, H.; Alivandy Farkhad, S.; Tagizadeh, A.

2007-01-01

Electromagnetic field has various effects on living organisms such as blood composition or enzymatic changes. The effects depend on the electromagnetic intensity and the time of exposure. This study has been carried out to measure the variations of liver enzymes SGOT and SGPT Levels in 36 adult male, Guinea Pigs, that have been divided into 6 groups. Group A, as the control, exposed to nil electromagnetic field for two hours per day for 5 days. Group B, exposed to 0.013 micro T in 5 Hz for the same period. Group C, exposed to 0.207 micro T in 50 Hz in the similar condition. Group D, exposed for' four hours per day for 5 days in 0.013 micro T in 5Hz. Group E, tested in 0.207 micro T in 50 Hz as the group D. Group F, used as the controlled group exposed for four hours per day in nil electromagnetic field. Blood of the Guinea pigs were analysed after 5 days. The results have shown significant differences among different groups, regarding the SCOT and SGPT when compared with those of the controlled group. Statistically, they are meaningful when measured by Dunnett test indicating a significant difference between the controlled group and the tested group, soas the SGOT and SGPT have decreased in both cases

Frequency-Dependent Tidal Triggering of Low Frequency Earthquakes Near Parkfield, California

Science.gov (United States)

Xue, L.; Burgmann, R.; Shelly, D. R.

2017-12-01

The effect of small periodic stress perturbations on earthquake generation is not clear, however, the rate of low-frequency earthquakes (LFEs) near Parkfield, California has been found to be strongly correlated with solid earth tides. Laboratory experiments and theoretical analyses show that the period of imposed forcing and source properties affect the sensitivity to triggering and the phase relation of the peak seismicity rate and the periodic stress, but frequency-dependent triggering has not been quantitatively explored in the field. Tidal forcing acts over a wide range of frequencies, therefore the sensitivity to tidal triggering of LFEs provides a good probe to the physical mechanisms affecting earthquake generation. In this study, we consider the tidal triggering of LFEs near Parkfield, California since 2001. We find the LFEs rate is correlated with tidal shear stress, normal stress rate and shear stress rate. The occurrence of LFEs can also be independently modulated by groups of tidal constituents at semi-diurnal, diurnal and fortnightly frequencies. The strength of the response of LFEs to the different tidal constituents varies between LFE families. Each LFE family has an optimal triggering frequency, which does not appear to be depth dependent or systematically related to other known properties. This suggests the period of the applied forcing plays an important role in the triggering process, and the interaction of periods of loading history and source region properties, such as friction, effective normal stress and pore fluid pressure, produces the observed frequency-dependent tidal triggering of LFEs.

Characterization of exposure to extremely low frequency magnetic fields using multidimensional analysis techniques.

Science.gov (United States)

Verrier, A; Souques, M; Wallet, F

2005-05-01

Our lack of knowledge about the biological mechanisms of 50 Hz magnetic fields makes it hard to improve exposure assessment. To provide better information about these exposure measures, we use multidimensional analysis techniques to examine the relations between different exposure metrics for a group of subjects. We used a combination of a two stage Principal Component Analysis (PCA) followed by an ascending hierarchical classification (AHC) to identify a set of measures that would capture the characteristics of the total exposure. This analysis gives an indication of the aspects of the exposure that are important to capture to get a complete picture of the magnetic field environment. We calculated 44 metrics of exposure measures from 16 exposed EDF employees and 15 control subjects, containing approximately 20,000 recordings of magnetic field measurements, taken every 30 s for 7 days with an EMDEX II dosimeter. These metrics included parameters used routinely or occasionally and some that were new. To eliminate those that expressed the least variability and that were most highly correlated to one another, we began with an initial Principal Component Analysis (PCA). A second PCA of the remaining 12 metrics enabled us to identify from the foreground 82.7% of the variance: the first component (62.0%) was characterized by central tendency metrics, and the second (20.7%) by dispersion characteristics. We were able to use AHC to divide the entire sample (of individuals) into four groups according to the axes that emerged from the PCA. Finally, discriminant analysis tested the discriminant power of the variables in the exposed/control classification as well as those from the AHC classification. The first showed that two subjects had been incorrectly classified, while no classification error was observed in the second. This exploratory study underscores the need to improve exposure measures by using at least two dimensions: intensity and dispersion. It also indicates the

Magnetic fields and uniformity of radio frequency power deposition in low-frequency inductively coupled plasmas with crossed internal oscillating currents

International Nuclear Information System (INIS)

Tsakadze, E.L.; Ostrikov, K.; Tsakadze, Z.L.; Vladimirov, S.V.; Xu, S.

2004-01-01

Radial and axial distributions of magnetic fields in a low-frequency (∼460 kHz) inductively coupled plasma source with two internal crossed planar rf current sheets are reported. The internal antenna configuration comprises two orthogonal sets of eight alternately reconnected parallel and equidistant copper litz wires in quartz enclosures and generates three magnetic (H z , H r , and H φ ) and two electric (E φ and E r ) field components at the fundamental frequency. The measurements have been performed in rarefied and dense plasmas generated in the electrostatic (E) and electromagnetic (H) discharge modes using two miniature magnetic probes. It is shown that the radial uniformity and depth of the rf power deposition can be improved as compared with conventional sources of inductively coupled plasmas with external flat spiral ('pancake') antennas. Relatively deeper rf power deposition in the plasma source results in more uniform profiles of the optical emission intensity, which indicates on the improvement of the plasma uniformity over large chamber volumes. The results of the numerical modeling of the radial magnetic field profiles are found in a reasonable agreement with the experimental data

Effects of low frequency electromagnetic field on the as-cast microstructures and mechanical properties of superhigh strength aluminum alloy

International Nuclear Information System (INIS)

Zuo Yubo; Cui Jianzhong; Dong Jie; Yu Fuxiao

2005-01-01

A new superhigh strength Al-Zn-Mg-Cu alloy was made by low frequency electromagnetic casting (LFEC) and conventional direct chill (DC) casting, respectively. The effects of low frequency electromagnetic field on the as-cast microstructures and mechanical properties were investigated. The results show that under the low frequency electromagnetic field (25 Hz, 32 mT), the microstructures of LFEC ingot from the border to the center on the cross section are all fine equiaxed or nearly equiaxed grains. The grains are much finer and more uniform than that of DC ingot. It was found that magnetic flux density plays an important role on the microstructure formation of LFEC ingots. With increasing the magnetic flux density, grains become finer and more uniform. In the range of experimental parameters, the optimum magnetic flux density for LFEC process is found to be 32 mT. The mechanical tests show that for this new superhigh strength Al-Zn-Mg-Cu alloy, the as-cast mechanical properties of LFEC ingot are much higher than that of DC ingot

Extremely low temperature properties of epoxy GFRP

International Nuclear Information System (INIS)

Kadotani, Kenzo; Nagai, Matao; Aki, Fumitake.

1983-01-01

The examination of fiber-reinforced plastics, that is, plastics such as epoxy, polyester and polyimide reinforced with high strength fibers such as glass, carbon, boron and steel, for extremely low temperature use began from the fuel tanks of rockets. Therafter, the trial manufacture of superconducting generators and extremely low temperature transformers and the manufacture of superconducting magnets for nuclear fusion experimental setups became active, and high performance FRPs have been adopted, of which the extremely low temperature properties have been sufficiently grasped. Recently, the cryostats made of FRPs have been developed, fully utilizing such features of FRPs as high strength, high rigidity, non-magnetic material, insulation, low heat conductivity, light weight and the freedom of molding. In this paper, the mechanical properties at extremely low temperature of the plastic composite materials used as insulators and structural materials for extremely low temperature superconducting equipment is outlined, and in particular, glass fiber-reinforced epoxy laminates are described somewhat in detail. The fracture strain of GFRP at extremely low temperature is about 1.3 times as large as that at room temperature, but at extremely low temperature, clear cracking occurred at 40% of the fracture strain. The linear thermal contraction of GFRP showed remarkable anisotropy. (Kako, I.)

Low Frequency Modulation of Extreme Temperature Regimes in a Changing Climate

Energy Technology Data Exchange (ETDEWEB)

Black, Robert X. [Georgia Inst. of Technology, Atlanta, GA (United States)

2014-11-24

The project examines long-term changes in extreme temperature episodes (ETE) associated with planetary climate modes (PCMs) in both the real atmospheric and climate model simulations. The focus is on cold air outbreaks (CAOs) and warm waves (WWs) occurring over the continental US during the past 60 winters. No significant long-term trends in either WWs or CAOs are observed over the US. The annual frequency of CAOs is affected by the (i) North Atlantic Oscillation (NAO) over the Southeast US and (ii) Pacific–North American (PNA) pattern over the Northwest US. WW frequency is influenced by the (i) NAO over the eastern US and (ii) combined influence of PNA, Pacific decadal oscillation (PDO), and ENSO over the southern US. The collective influence of PCMs accounts for as much as 50% of the regional variability in ETE frequency. During CAO (WW) events occurring over the southeast US, there are low (high) pressure anomalies at higher atmospheric levels over the southeast US with oppositely-signed pressure anomalies in the lower atmosphere over the central US. These patterns lead to anomalous northerly (for CAOs) or southerly (for WWs) flow into the southeast leading to cold or warm surface air temperature anomalies, respectively. One distinction is that CAOs involve substantial air mass transport while WW formation is more local in nature. The primary differences among event categories are in the origin and nature of the pressure anomaly features linked to ETE onset. In some cases, PCMs help to provide a favorable environment for event onset. Heat budget analyses indicate that latitudinal transport in the lower atmosphere is the main contributor to regional cooling during CAO onset. This is partly offset by adiabatic warming associated with subsiding air. Additional diagnoses reveal that this latitudinal transport is partly due to the remote physical influence of a shallow cold pool of air trapped along the east side of the Rocky Mountains. ETE and PCM behavior is also

Extremely Large Magnetoresistance at Low Magnetic Field by Coupling the Nonlinear Transport Effect and the Anomalous Hall Effect.

Science.gov (United States)

Luo, Zhaochu; Xiong, Chengyue; Zhang, Xu; Guo, Zhen-Gang; Cai, Jianwang; Zhang, Xiaozhong

2016-04-13

The anomalous Hall effect of a magnetic material is coupled to the nonlinear transport effect of a semiconductor material in a simple structure to achieve a large geometric magnetoresistance (MR) based on a diode-assisted mechanism. An extremely large MR (>10(4) %) at low magnetic fields (1 mT) is observed at room temperature. This MR device shows potential for use as a logic gate for the four basic Boolean logic operations. © 2016 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Prospect for extreme field science

Energy Technology Data Exchange (ETDEWEB)

Tajima, T. [Ludwig Maximilian Univ. and Max Planck Institute for Quantum Optics, Garching (Germany); Japan Atomic Energy Agency, Kyoto and KEK, Tsukuba (Japan)

2009-11-15

The kind of laser extreme light infrastructure (ELI) provides will usher in a class of experiments we have only dreamed of for years. The characteristics that ELI brings in include: the highest intensity ever, large fluence, and relatively high repetition rate. A personal view of the author on the prospect of harnessing this unprecedented opportunity for advancing science of extreme fields is presented. The first characteristic of ELI, its intensity, will allow us to access, as many have stressed already, extreme fields that hover around the Schwinger field or at the very least the neighboring fields in which vacuum begins to behave as a nonlinear medium. In this sense, we are seriously probing the 'material' property of vacuum and thus the property that theory of relativity itself described and will entail. We will probe both special theory and general theory of relativity in regimes that have been never tested so far. We may see a glimpse into the reach of relativity or even its breakdown in some extreme regimes. We will learn Einstein and may even go beyond Einstein, if our journey is led. Laser-driven acceleration both by the laser field itself and by the wakefield that is triggered in a plasma is huge. Energies, if not luminosity, we can access, may be unprecedented going far beyond TeV. The nice thing about ELI is that it has relatively high repetition rate and average fluence as compared with other extreme lasers. This high fluence can be a key element that leads to applications to high energy physics, such as gamma-gamma collider driver experiment, and some gamma ray experiments that may be relevant in the frontier of photo-nuclear physics, and atomic energy applications. Needless to say, high fluence is one of most important features that industrial and medical applications may need. If we are lucky, we may see a door opens at the frontier of novel physics that may not be available by any other means. (authors)

Excitation of electromagnetic proton cyclotron instability by parallel electric field in the equatorial magnetosphere

International Nuclear Information System (INIS)

Dixit, S.K.; Azif, Z.A.; Gwal, A.K.

1994-01-01

The characteristics of the growth rate of electromagnetic ion cyclotron (EMIC) instability is investigated in a mixture of cold species of ions and warm proton in the presence of weak parallel static electric field. An attempt has been made to explain the excitation of EMIC waves through linear wave-particle (W-P) interaction in the equatorial magnetospheric region. The proton cyclotron instability is modified in presence of weak parallel electric field and the growth rate is computed for equatorial magnetospheric plasma parameters. The results of theoretical investigations of the growth rate are used to explain the excitation mechanism of extremely low frequency/very low frequency (ELF/VLF) waves as observed by satellites. (author). 29 refs., 4 figs

Relaxation rates of low-field gas-phase ^129Xe storage cells

Science.gov (United States)

Limes, Mark; Saam, Brian

2010-10-01

A study of longitudinal nuclear relaxation rates T1 of ^129Xe and Xe-N2 mixtures in a magnetic field of 3.8 mT is presented. In this regime, intrinsic spin relaxation is dominated by the intramolecular spin-rotation interaction due to persistent xenon dimers, a mechanism that can be quelled by introducing large amounts of N2 into the storage cell. Extrinsic spin relaxation is dominated by the wall-relaxation rate, which is the primary quantity of interest for the various low-field storage cells and coatings that we have tested. Previous group work has shown that extremely long gas-phase relaxation times T1 can be obtained, but only at large magnetic fields and low xenon densities. The current work is motivated by the practical benefits of retaining hyperpolarized ^129Xe for extended periods of time in a small magnetic field.

Effect of low frequency magnetic field at reproductive system state and peroxidation processes in liver of male rates after low dose chronic irradiation

International Nuclear Information System (INIS)

Konoplya, E.F.; Vereshchako, G.T.; Popov, E.G.; Khodosovskaya, A.M.; Artemenko, A.M.; Bulovatskaya, I.V.; Rybakov, V.N.

2002-01-01

Low frequency magnetic field (power 3.5 wt, tension 8v, amplitude 15 Tl, frequency of followed impulses 10 Hz, frequency of exposure 70-90 Hz) significantly modified the morphofunctional state of the reproductive system and peroxidation processes in liver of male rates. It concluded in a partial restoration of testicular weight, a recovery of the blood serum testosterone levels and of the molecular characteristics of the androgen receptor system in liver and testes, a normalization of peroxidation processes in liver and a stimulation of some biochemical and bioenergetic processes in testes (authors)

Biological effects of static and low-frequency electromagnetic fields: an overview of United States literature

Energy Technology Data Exchange (ETDEWEB)

Phillips, R.D.; Kaune, W.T.

1977-04-12

Results are reviewed from a number of studies on the biological effects of static and low frequency electromagnetic fields on animals. Based on a long history of experience with electric fields by the utility industry, it appears that intermittent and repeated exposures to strong 60-Hz electromagnetic fields from present power transmission systems have no obvious adverse effect on the health of man. It has been recognized recently that this belief must be tested by carefully designed and executed experiments under laboratory conditions where precise control can be exercised over coexisting environmental factors. A number of studies have been initiated in response to this need to evaluate possible effects from both acute and chronic exposures. 100 references.

Regional Frequency and Uncertainty Analysis of Extreme Precipitation in Bangladesh

Science.gov (United States)

Mortuza, M. R.; Demissie, Y.; Li, H. Y.

2014-12-01

Increased frequency of extreme precipitations, especially those with multiday durations, are responsible for recent urban floods and associated significant losses of lives and infrastructures in Bangladesh. Reliable and routinely updated estimation of the frequency of occurrence of such extreme precipitation events are thus important for developing up-to-date hydraulic structures and stormwater drainage system that can effectively minimize future risk from similar events. In this study, we have updated the intensity-duration-frequency (IDF) curves for Bangladesh using daily precipitation data from 1961 to 2010 and quantified associated uncertainties. Regional frequency analysis based on L-moments is applied on 1-day, 2-day and 5-day annual maximum precipitation series due to its advantages over at-site estimation. The regional frequency approach pools the information from climatologically similar sites to make reliable estimates of quantiles given that the pooling group is homogeneous and of reasonable size. We have used Region of influence (ROI) approach along with homogeneity measure based on L-moments to identify the homogenous pooling groups for each site. Five 3-parameter distributions (i.e., Generalized Logistic, Generalized Extreme value, Generalized Normal, Pearson Type Three, and Generalized Pareto) are used for a thorough selection of appropriate models that fit the sample data. Uncertainties related to the selection of the distributions and historical data are quantified using the Bayesian Model Averaging and Balanced Bootstrap approaches respectively. The results from this study can be used to update the current design and management of hydraulic structures as well as in exploring spatio-temporal variations of extreme precipitation and associated risk.

Extremely low frequency electromagnetic field in combination with ...

African Journals Online (AJOL)

Results: No significant alteration in the mRNA levels of NHEJ related genes was observed in ''β-Lap alone” and ''β-Lap + Mor” treated cells. The expression levels of NHEJ related genes were significantly increased in ''β-Lap + EMF” and ''β-Lap + Mor + EMF”. Multiple linear regression analysis showed that the effect of EMF ...

Frequency splitting in stria bursts: Possible roles of low-frequency waves

International Nuclear Information System (INIS)

Melrose, D.B.

1983-01-01

The kinematics of the process L+-F->L' are explored where L represents a parallel Langmuir wave, F represents a low frequency fluctuation and L' represents a secondary Langmuir wave, and the results are used to discuss (a) a possible interpretation of the frequency splitting in stria bursts in terms of the processes L+-F->L', L'+-F'->t, where t represents a transverse wave, and (b) second harmonic emission due to the processes L+-s->L', L+L'->t, where s represents an ion sound wave. The following results are obtained: (1) The processes L+-s->L' are allowed only for ksub(s) 0 , respectively, with k 0 =ωsub(p)/65 Vsub(e). (2) The inclusion of a magnetic field does not alter the result (1) and adds further kinematic restrictions related to angles of propagation; the kinematic restriction Tsub(e)>5x10 5 K for second harmonic emission through process (b) above is also unchanged by inclusion of the magnetic field. The effect of a spread in the wavevectors of the Langmuir waves on this restriction is discussed in the Appendix. (3) For parallel Langmuir waves the process L-f->L' is forbidden for lower hybrid waves and for nearly perpendicular resonant whistlers, and the process L+F->L' is allowed only for resonant whistlers at ωsub(F)> or approx.1/2ωsub(p)(Ωsub(e)/ωsub(p)) 2 . (4) The sequential three waves processes L+-s->L', L'+-s->t and L+F->L', L'+-F'->t encounter difficulties when applied to the interpretation of the splitting in split pair and triple bursts. (5) The four-wave process L+-F+-F'->t is kinematically allowed and provides a favourable qualitative interpretation of the splitting when F denotes a resonant whistler near the frequency mentioned in (3) above. The four wave processes should saturate under conditions which are not extreme and produce fundamental plasma emission with brightness temperature Tsub(t) equal to the effective temperature Tsub(L) of the Langmuir waves. (orig.)

Low-frequency oscillations in radiative-convective models

Energy Technology Data Exchange (ETDEWEB)

Hu, Qi; Randall, D.A.

1991-12-31

Although eastward propagation is usually regarded as an essential feature of the low-frequency ``Madden-Julian oscillation`` observed in the tropical atmosphere, many observations indicate that there is an important stationary or quasi-stationary component of the oscillation. Yasunari (1979), for example, investigated the stationary 30--60 day variation in upper tropospheric cloudiness in the Asian summer monsoon region. In a case study of the 30--60 day oscillation. Hsu et al. (1990) found a strong stationary oscillation of the divergence, outgoing longwave mdiadon and other fields. A recent observational study by Weickmann and Khalsa (1990) offers further evidence that the Madden-Julian oscillation has an important stationary component. In this paper, we present evidence that intraseasonal oscillations can be produced by local radiative and convective processes. This suggests that the observed propagating Madden-Julian wave is produced by interactions between these local processes and the large scale motion field, and is not essential for the existence of the observed oscillation.

Low-frequency oscillations in radiative-convective models

Energy Technology Data Exchange (ETDEWEB)

Hu, Qi; Randall, D.A.

1991-01-01

Although eastward propagation is usually regarded as an essential feature of the low-frequency Madden-Julian oscillation'' observed in the tropical atmosphere, many observations indicate that there is an important stationary or quasi-stationary component of the oscillation. Yasunari (1979), for example, investigated the stationary 30--60 day variation in upper tropospheric cloudiness in the Asian summer monsoon region. In a case study of the 30--60 day oscillation. Hsu et al. (1990) found a strong stationary oscillation of the divergence, outgoing longwave mdiadon and other fields. A recent observational study by Weickmann and Khalsa (1990) offers further evidence that the Madden-Julian oscillation has an important stationary component. In this paper, we present evidence that intraseasonal oscillations can be produced by local radiative and convective processes. This suggests that the observed propagating Madden-Julian wave is produced by interactions between these local processes and the large scale motion field, and is not essential for the existence of the observed oscillation.

Adenosine Receptors as a Biological Pathway for the Anti-Inflammatory and Beneficial Effects of Low Frequency Low Energy Pulsed Electromagnetic Fields

Directory of Open Access Journals (Sweden)

Katia Varani

2017-01-01

Full Text Available Several studies explored the biological effects of low frequency low energy pulsed electromagnetic fields (PEMFs on human body reporting different functional changes. Much research activity has focused on the mechanisms of interaction between PEMFs and membrane receptors such as the involvement of adenosine receptors (ARs. In particular, PEMF exposure mediates a significant upregulation of A2A and A3ARs expressed in various cells or tissues involving a reduction in most of the proinflammatory cytokines. Of particular interest is the observation that PEMFs, acting as modulators of adenosine, are able to increase the functionality of the endogenous agonist. By reviewing the scientific literature on joint cells, a double role for PEMFs could be hypothesized in vitro by stimulating cell proliferation, colonization of the scaffold, and production of tissue matrix. Another effect could be obtained in vivo after surgical implantation of the construct by favoring the anabolic activities of the implanted cells and surrounding tissues and protecting the construct from the catabolic effects of the inflammatory status. Moreover, a protective involvement of PEMFs on hypoxia damage in neuron-like cells and an anti-inflammatory effect in microglial cells have suggested the hypothesis of a positive impact of this noninvasive biophysical stimulus.

Interaction of Mutually Perpendicular Magnetic Fields in HTSC

Directory of Open Access Journals (Sweden)

Vasilyev Aleksandr Fedorovich

2015-11-01

Full Text Available In this article a problem of interaction of the crossed magnetic fields in superconductors is considered. Superconducting materials have nonlinear magnetic properties. It allows using a non-linear magnetic susceptibility for measurement of feeble magnetic fields. We place a wire of superconducting material in a constant parallel uniform magnetic field. Then we let through a wire the alternating current leak. Interaction of mutual and perpendicular variation magnetic fields, with adequate accuracy is described by Ginzburg-Landau's equations. Approximate solution of the written equations is received. The component of a magnetic field parallel to a wire contains a variable component. Frequency of a variable component of the magnetic field is equal to the doubled current frequency. Amplitude of the variable component of the magnetic field is proportional to strength of the constant magnetic field. The experimental installation for research of interaction of mutually perpendicular magnetic fields is created. The cylinder from HTSC of ceramics of the YBa2Cu3O7-x was used as a sensor. Dependence of amplitude of the second harmonica of a variation magnetic field on strength of a constant magnetic field is received.

Basic Restriction and Reference Level in Anatomically-based Japanese Models for Low-Frequency Electric and Magnetic Field Exposures

Science.gov (United States)

Takano, Yukinori; Hirata, Akimasa; Fujiwara, Osamu

Human exposed to electric and/or magnetic fields at low frequencies may cause direct effect such as nerve stimulation and excitation. Therefore, basic restriction is regulated in terms of induced current density in the ICNIRP guidelines and in-situ electric field in the IEEE standard. External electric or magnetic field which does not produce induced quantities exceeding the basic restriction is used as a reference level. The relationship between the basic restriction and reference level for low-frequency electric and magnetic fields has been investigated using European anatomic models, while limited for Japanese model, especially for electric field exposures. In addition, that relationship has not well been discussed. In the present study, we calculated the induced quantities in anatomic Japanese male and female models exposed to electric and magnetic fields at reference level. A quasi static finite-difference time-domain (FDTD) method was applied to analyze this problem. As a result, spatially averaged induced current density was found to be more sensitive to averaging algorithms than that of in-situ electric field. For electric and magnetic field exposure at the ICNIRP reference level, the maximum values of the induced current density for different averaging algorithm were smaller than the basic restriction for most cases. For exposures at the reference level in the IEEE standard, the maximum electric fields in the brain were larger than the basic restriction in the brain while smaller for the spinal cord and heart.

Effects of aluminum and extremely low frequency electromagnetic radiation on oxidative stress and memory in brain of mice.

Science.gov (United States)

Deng, Yuanxin; Zhang, Yanwen; Jia, Shujie; Liu, Junkang; Liu, Yanxia; Xu, Weiwei; Liu, Lei

2013-12-01

This study was aimed to investigate the effect of aluminum and extremely low-frequency magnetic fields (ELF-MF) on oxidative stress and memory of SPF Kunming mice. Sixty male SPF Kunming mice were divided randomly into four groups: control group, ELF-MF group (2 mT, 4 h/day), load aluminum group (200 mg aluminum/kg, 0.1 ml/10 g), and ELF-MF + aluminum group (2 mT, 4 h/day, 200 mg aluminum/kg). After 8 weeks of treatment, the mice of three experiment groups (ELF-MF group, load aluminum group, and ELF-MF + aluminum group) exhibited firstly the learning memory impairment, appearing that the escaping latency to the platform was prolonged and percentage in the platform quadrant was reduced in the Morris water maze (MWM) task. Secondly are the pathologic abnormalities including neuronal cell loss and overexpression of phosphorylated tau protein in the hippocampus and cerebral cortex. On the other hand, the markers of oxidative stress were determined in mice brain and serum. The results showed a statistically significant decrease in superoxide dismutase activity and increase in the levels of malondialdehyde in the ELF-MF group (P < 0.05 or P < 0.01), load aluminum group (P < 0.01), and ELF-MF + aluminum group (P < 0.01). However, the treatment with ELF-MF + aluminum induced no more damage than ELF-MF and aluminum did, respectively. In conclusion, both aluminum and ELF-MF could impact on learning memory and pro-oxidative function in Kunming mice. However, there was no evidence of any association between ELF-MF exposure with aluminum loading.

High-field electron-photon interactions

International Nuclear Information System (INIS)

Hartemann, F V.

1999-01-01

Recent advances in novel technologies (including chirped-pulse amplification, femtosecond laser systems operating in the TW-PW range, high-gradient rf photoinjectors, and synchronized relativistic electron bunches with subpicosecond durations and THz bandwidths) allow experimentalists to study the interaction of relativistic electrons with ultrahigh-intensity photon fields. Ponderomotive scattering can accelerate these electrons with extremely high gradients in a three-dimensional vacuum laser focus. The nonlinear Doppler shift induced by relativistic radiation pressure in Compton backscattering is shown to yield complex nonlinear spectra which can be modified by using temporal laser pulse shaping techniques. Colliding laser pulses, where ponderomotive acceleration and Compton backscattering are combined, could also yield extremely short wavelength photons. Finally, one expects strong radiative corrections when the Doppler-upshifted laser wavelength approaches the Compton scale. These are discussed within the context of high-field classical electrodynamics, a new discipline borne out of the aforementioned innovations

Low-frequency electromagnetic fields do not alter responses of inflammatory genes and proteins in human monocytes and immune cell lines

NARCIS (Netherlands)

Bouwens, M.; Kleijn, de S.; Cuppen, J.J.M.; Savelkoul, H.F.J.; Verburg-van Kemenade, B.M.L.

2012-01-01

The effects of low frequency electromagnetic fields (LF EMF) on human health are the subject of on-going research and serious public concern. These fields potentially elicit small effects that have been proposed to have consequences, either positive or negative, for biological systems. To reveal

Extremely low-frequency magnetic exposure appears to have no effect on pathogenesis of Alzheimer's disease in aluminum-overloaded rat.

Directory of Open Access Journals (Sweden)

Cheng Zhang

Full Text Available OBJECTIVE: Extremely low-frequency magnetic field (ELF-MF has been reported to be of potential pathogenetic relevance to Alzheimer's disease (AD for years. However, evidence confirming this function remains inconclusive. Chronic Al treatment has been identified as a contributing factor to cognitive function impairment in AD. This study aims to examine whether or not ELF-MF and Al have synergistic effects toward AD pathogenesis by investigating the effects of ELF-MF with or without chronic Al treatment on SD rats. METHODS: Sprague-Dawley (SD rats were subjected one of the following treatments: sham (control group, oral Al (Al group, ELF-MF (100 µT at 50 Hz with oral Al (MF+Al group, or ELF-MF (100 µT at 50 Hz without oral Al (MF group. RESULTS: After 12 wk of treatment, oral Al treatment groups (Al and MF+Al groups showed learning and memory impairment as well as morphological hallmarks, including neuronal cell loss and high density of amyloid-β (Aβ in the hippocampus and cerebral cortex. ELF-MF without Al treatment showed no significant effect on AD pathogenesis. ELF-MF+Al treatment induced no more damage than Al treatment did. CONCLUSIONS: Our results showed no evidence of any association between ELF-MF exposure (100 µT at 50 Hz and AD, and ELF-MF exposure does not influence the pathogenesis of AD induced by Al overload.

Extremely frequency-widened terahertz wave generation using Cherenkov-type radiation.

Science.gov (United States)

Suizu, Koji; Koketsu, Kaoru; Shibuya, Takayuki; Tsutsui, Toshihiro; Akiba, Takuya; Kawase, Kodo

2009-04-13

Terahertz (THz) wave generation based on nonlinear frequency conversion is promising way for realizing a tunable monochromatic bright THz-wave source. Such a development of efficient and wide tunable THz-wave source depends on discovery of novel brilliant nonlinear crystal. Important factors of a nonlinear crystal for THz-wave generation are, 1. High nonlinearity and 2. Good transparency at THz frequency region. Unfortunately, many nonlinear crystals have strong absorption at THz frequency region. The fact limits efficient and wide tunable THz-wave generation. Here, we show that Cherenkov radiation with waveguide structure is an effective strategy for achieving efficient and extremely wide tunable THz-wave source. We fabricated MgO-doped lithium niobate slab waveguide with 3.8 microm of thickness and demonstrated difference frequency generation of THz-wave generation with Cherenkov phase matching. Extremely frequency-widened THz-wave generation, from 0.1 to 7.2 THz, without no structural dips successfully obtained. The tuning frequency range of waveguided Cherenkov radiation source was extremely widened compare to that of injection seeded-Terahertz Parametric Generator. The tuning range obtained in this work for THz-wave generation using lithium niobate crystal was the widest value in our knowledge. The highest THz-wave energy obtained was about 3.2 pJ, and the energy conversion efficiency was about 10(-5) %. The method can be easily applied for many conventional nonlinear crystals, results in realizing simple, reasonable, compact, high efficient and ultra broad band THz-wave sources.

Electrochemical Evaluation of Extremely-Low Frequency Magnetic Field Effects on Sulphate-Reducing Bacteria

Czech Academy of Sciences Publication Activity Database

Fojt, Lukáš; Vetterl, Vladimír

2012-01-01

Roč. 58, č. 1 (2012), s. 44-48 ISSN 0015-5500 R&D Projects: GA MŠk(CZ) LC06035 Institutional research plan: CEZ:AV0Z50040507; CEZ:AV0Z50040702 Institutional support: RVO:68081707 Keywords : RAT-BRAIN CELLS * HZ ELECTROMAGNETIC-FIELDS * STRAND DNA BREAKS Subject RIV: BO - Biophysics Impact factor: 1.219, year: 2012

Measurement of quasi-static and low frequency electric fields on the Viking satellite

International Nuclear Information System (INIS)

Block, L.P.; Faelthammar, C.G.; Lindqvist, P.A.; Marklund, G.T.; Mozer, F.S.; Pedersen, A.

1987-03-01

The instrument for measurement of quasi-static and low frequency (dc and slow varying) electric fields on the Viking satellite is described. The instrument uses three spherical probe pairs to measure the full three-dimensional electric field vector with 18.75 ms time resolution. The probes are kept near plasma potential by means of a controllable bias current. A guard covering part of the booms is biased to a negative voltage to prevent photoelectrons escaping from the probes from reaching the satellite body. Current-voltage sweeps are performed to determine the plasma density and temperature and to select the optimal bias current. The bias currents to the probes and the voltage offset on the guards as well as the current-voltage sweeps are controlled by an on-board microprocessor which can be programmed from the ground and allows great flexibility. (authors)

Minimization of nanosatellite low frequency magnetic fields

Energy Technology Data Exchange (ETDEWEB)

Belyayev, S. M., E-mail: belyayev@isr.lviv.ua [Lviv Centre of Institute for Space Research, Lviv 79060 (Ukraine); Royal Institute of Technology, Stockholm 11428 (Sweden); Dudkin, F. L. [Lviv Centre of Institute for Space Research, Lviv 79060 (Ukraine)

2016-03-15

Small weight and dimensions of the micro- and nanosatellites constrain researchers to place electromagnetic sensors on short booms or on the satellite body. Therefore the electromagnetic cleanliness of such satellites becomes a central question. This paper describes the theoretical base and practical techniques for determining the parameters of DC and very low frequency magnetic interference sources. One of such sources is satellite magnetization, the reduction of which improves the accuracy and stability of the attitude control system. We present design solutions for magnetically clean spacecraft, testing equipment, and technology for magnetic moment measurements, which are more convenient, efficient, and accurate than the conventional ones.

The effects of extreme low frequency pulsed electromagnetic field on bone mineral density and incidence of fractures in patients with end - stage renal disease on dialysis - three year follow up study

Directory of Open Access Journals (Sweden)

Rakočević-Hrnjak Aleksandra

2018-01-01

Full Text Available Background/Aim. A variety of physical therapy options has been developed for the treatment of musculoskeletal disorders including those characterized with low bone mineral density (BMD. Extreme low frequency pulsed electromagnetic field (ELF-PEMF can accelerate bone formation. Patients with end stage of renal disease (ESRD are predisposed to high incidence of fractures due to bone disorder with multifactorial pathogenesis. Vitamin D, calcium supplements, antiresorptive and anabolic drugs in those patients have changed pharmacodynamics and pharmacokinetics and have minimal or limited effects. The aim of this study was to assess the effectiveness of long-term ELF-PEMF therapy applied in concordance with physical exercise on bone mass, incidence of new bone fractures and parathyroid hormone concentrations in ESRD patients on dialysis. Methods. In this 3-year prospective clinical trial, 151 patients with ESRD on dialysis program were subjected to treatment with ELF-PEMF (18 Hz, 2 mT applied during 40 min after 10 consecutive dialysis procedures, 4 times through one year (120 treatments in total during three years together with kinesitherapy (study group or only with kinesitherapy (control group on the voluntary basis. Results. Total of 124 patients have completed the study. In the study group (n = 54, regardless of sex, significant improvements of BMD, T-score and Z-score on both lumbar spine and femoral neck were achieved after 3-year treatment with ELF-PEMF. In the control group (n = 70, significant decreases of BMD, T-score and Z-score as well as the higher incidence of new bone fractures were recorded. Conclusion. ELF-PEMF could be a convenient and safe non-pharmacological therapeutic strategy for fracture prevention in nephrology practices.

Modeling drug release from functionalized magnetic nanoparticles actuated by non-heating low frequency magnetic field

Energy Technology Data Exchange (ETDEWEB)

Golovin, Y., E-mail: nano@tsutmb.ru [M.V. Lomonosov Moscow State University, School of Chemistry (Russian Federation); Golovin, D. [G.R. Derzhavin Tambov State University (Russian Federation); Klyachko, N.; Majouga, A.; Kabanov, A. [M.V. Lomonosov Moscow State University, School of Chemistry (Russian Federation)

2017-02-15

Various plausible acceleration mechanisms of drug release from nanocarriers composed of a single-domain magnetic nanoparticle core with attached long macromolecule chains activated by low frequency non-heating alternating magnetic field (AMF) are discussed. The most important system characteristics affecting the AMF exposure impact are determined. Impact of several reasonable mechanisms is estimated analytically or obtained using numerical modeling. Some conditions providing manifold release acceleration as a result from exposure in AMF are found.

Modeling drug release from functionalized magnetic nanoparticles actuated by non-heating low frequency magnetic field

International Nuclear Information System (INIS)

Golovin, Y.; Golovin, D.; Klyachko, N.; Majouga, A.; Kabanov, A.

2017-01-01

Various plausible acceleration mechanisms of drug release from nanocarriers composed of a single-domain magnetic nanoparticle core with attached long macromolecule chains activated by low frequency non-heating alternating magnetic field (AMF) are discussed. The most important system characteristics affecting the AMF exposure impact are determined. Impact of several reasonable mechanisms is estimated analytically or obtained using numerical modeling. Some conditions providing manifold release acceleration as a result from exposure in AMF are found.

Low-frequency plasmons in metallic carbon nanotubes

International Nuclear Information System (INIS)

Lin, M.F.; Chuu, D.S.; Shung, K.W.

1997-01-01

A metallic carbon nanotube could exhibit a low-frequency plasmon, while a semiconducting carbon nanotube or a graphite layer could not. This plasmon is due to the free carriers in the linear subbands intersecting at the Fermi level. The low-frequency plasmon, which corresponds to the vanishing transferred angular momentum, belongs to an acoustic plasmon. For a smaller metallic nanotube, it could exist at larger transferred momenta, and its frequency is higher. Such a plasmon behaves as that in a one-dimensional electron gas (EGS). However, it is very different from the π plasmons in all carbon nanotubes. Intertube Coulomb interactions in a metallic multishell nanotube and a metallic nanotube bundle have been included. They have a strong effect on the low-frequency plasmon. The intertube coupling among coaxial nanotubes markedly modifies the acoustic plasmons in separate metallic nanotubes. When metallic carbon nanotubes are packed in the bundle form, the low-frequency plasmon would change into an optical plasmon, and behave like that in a three-dimensional EGS. Experimental measurements could be used to distinguish metallic and semiconducting carbon nanotubes. copyright 1997 The American Physical Society

Controlled Acoustic Bass System (CABS) A Method to Achieve Uniform Sound Field Distribution at Low Frequencies in Rectangular Rooms

DEFF Research Database (Denmark)

Celestinos, Adrian; Nielsen, Sofus Birkedal

2008-01-01

The sound field produced by loudspeakers at low frequencies in small- and medium-size rectangular listening rooms is highly nonuniform due to the multiple reflections and diffractions of sound on the walls and different objects in the room. A new method, called controlled acoustic bass system (CA......-frequency range. CABS has been simulated and measured in two different standard listening rooms with satisfactory results....

Oscillations and Stability of Plasma in an External High-Frequency Electric Field

International Nuclear Information System (INIS)

Aliev, Ju.M.; Gorbunov, L.M.; Silin, V.P.; Uotson, H.

1966-01-01

A theory is developed for the oscillations and stability of plasma in a strong external HF electric field. The kinetic equation with self-congruent reciprocity is linearized for weak deviations from the ground state. Since the latter depends on an external HF field, the linearized equation obtained has coefficients with a periodic time dependence. From this equation and also from Maxwell's equations there is derived a dispersion equation for plasma oscillations that represents the zero value of the infinite order determinant, and that is solved both for external field frequencies considerably exceeding the electron Langmuir frequency and for frequencies that are less. The external HF field changes the oscillation branches in a plasma without an external field, and also leads to a new low-frequency oscillation branch. Movement of particles in the HF field gives spatial dispersion. If the frequency of the field exceeds the election Langmuir frequency, the plasma oscillations are stable. At frequencies less than this level there occurs a build-up of low-frequency oscillations. Here the maximum of the build-up occurs when the external field frequencies approach the electron Langmuir frequency and is equal to the product of the Langmuir frequency and the one-third power of the electron-ion mass ratio. Away from the resonance, -the increment of build-up has the same order of magnitude as the ion Langmuir frequency. An external magnetic field increases the number of possible natural plasma oscillations and thereby increases the possibility of resonance with the external HF field. Allowance for the thermal motion of the particles enables one to determine the attenuation of the oscillations in question. Expressions for the decrements are derived. The effect of the external HF field on a plasma in which there are beams is also discussed. An HF field has a destabilizing effect on a system of this kind, since on the one hand there can be a build-up of fresh, low-frequency

Low-frequency-noise complaints

DEFF Research Database (Denmark)

Pedersen, Christian Sejer; Møller, Henrik; Persson-Waye, Kerstin

2008-01-01

From 203 cases of low-frequency complaints a random selection of twenty-one cases were investigated. The main aim of the investigation was to answer the question whether the annoyance is caused by an external physical sound or by a physically non-existing sound, i.e. low-frequency tinnitus. Noise...... of the complainants are annoyed by a physical sound (20-180 Hz), while others suffer from low-frequency tinnitus (perceived frequency 40-100 Hz). Physical sound at frequencies below 20 Hz (infrasound) is not responsible for the annoyance - or at all audible - in any of the investigated cases, and none...... of the complainants has extraordinary hearing sensitivity at low frequencies. For comparable cases of low-frequency noise complaints in general, it is anticipated that physical sound is responsible in a substantial part of the cases, while low-frequency tinnitus is responsible in another substantial part of the cases....

Ferromagnetic resonance in low interacting permalloy nanowire arrays

Energy Technology Data Exchange (ETDEWEB)

Raposo, V.; Zazo, M.; Flores, A. G.; Iñiguez, J. [Departamento de Física Aplicada, University of Salamanca, E-37071 Salamanca (Spain); Garcia, J.; Vega, V.; Prida, V. M. [Departamento de Física, Universidad de Oviedo, E-33007 Oviedo (Spain)

2016-04-14

Dipolar interactions on magnetic nanowire arrays have been investigated by various techniques. One of the most powerful techniques is the ferromagnetic resonance spectroscopy, because the resonance field depends directly on the anisotropy field strength and its frequency dependence. In order to evaluate the influence of magnetostatic dipolar interactions among ferromagnetic nanowire arrays, several densely packed hexagonal arrays of NiFe nanowires have been prepared by electrochemical deposition filling self-ordered nanopores of alumina membranes with different pore sizes but keeping the same interpore distance. Nanowires’ diameter was changed from 90 to 160 nm, while the lattice parameter was fixed to 300 nm, which was achieved by carefully reducing the pore diameter by means of Atomic Layer Deposition of conformal Al{sub 2}O{sub 3} layers on the nanoporous alumina templates. Field and frequency dependence of ferromagnetic resonance have been studied in order to obtain the dispersion diagram which gives information about anisotropy, damping factor, and gyromagnetic ratio. The relationship between resonance frequency and magnetic field can be explained by the roles played by the shape anisotropy and dipolar interactions among the ferromagnetic nanowires.

Low-frequency noise in planar Hall effect bridge sensors

DEFF Research Database (Denmark)

Persson, Anders; Bejhedb, R.S.; Bejhed, R.S.

2011-01-01

The low-frequency characteristics of planar Hall effect bridge sensors are investigated as function of the sensor bias current and the applied magnetic field. The noise spectra reveal a Johnson-like spectrum at high frequencies, and a 1/f-like excess noise spectrum at lower frequencies, with a kn...

Low-cost, smartphone based frequency doubling technology visual field testing using virtual reality (Conference Presentation)

Science.gov (United States)

Alawa, Karam A.; Sayed, Mohamed; Arboleda, Alejandro; Durkee, Heather A.; Aguilar, Mariela C.; Lee, Richard K.

2017-02-01

Glaucoma is the leading cause of irreversible blindness worldwide. Due to its wide prevalence, effective screening tools are necessary. The purpose of this project is to design and evaluate a system that enables portable, cost effective, smartphone based visual field screening based on frequency doubling technology. The system is comprised of an Android smartphone to display frequency doubling stimuli and handle processing, a Bluetooth remote for user input, and a virtual reality headset to simulate the exam. The LG Nexus 5 smartphone and BoboVR Z3 virtual reality headset were used for their screen size and lens configuration, respectively. The system is capable of running the C-20, N-30, 24-2, and 30-2 testing patterns. Unlike the existing system, the smartphone FDT tests both eyes concurrently by showing the same background to both eyes but only displaying the stimulus to one eye at a time. Both the Humphrey Zeiss FDT and the smartphone FDT were tested on five subjects without a history of ocular disease with the C-20 testing pattern. The smartphone FDT successfully produced frequency doubling stimuli at the correct spatial and temporal frequency. Subjects could not tell which eye was being tested. All five subjects preferred the smartphone FDT to the Humphrey Zeiss FDT due to comfort and ease of use. The smartphone FDT is a low-cost, portable visual field screening device that can be used as a screening tool for glaucoma.

Extreme Precipitation Estimation with Typhoon Morakot Using Frequency and Spatial Analysis

Directory of Open Access Journals (Sweden)

Hone-Jay Chu

2011-01-01

Full Text Available Typhoon Morakot lashed Taiwan and produced copious amounts of precipitation in 2009. From the point view of hydrological statistics, the impact of the precipitation from typhoon Morakot using a frequency analysis can be analyzed and discussed. The frequency curve, which was fitted mathematically to historical observed data, can be used to estimate the probability of exceedance for runoff events of a certain magnitude. The study integrates frequency analysis and spatial analysis to assess the effect of Typhoon Morakot event on rainfall frequency in the Gaoping River basin of southern Taiwan. First, extreme rainfall data are collected at sixteen stations for durations of 1, 3, 6, 12, and 24 hours and then an appropriate probability distribution was selected to analyze the impact of the extreme hydrological event. Spatial rainfall patterns for a return period of 200-yr with 24-hr duration with and without Typhoon Morakot are estimated. Results show that the rainfall amount is significantly different with long duration with and without the event for frequency analysis. Furthermore, spatial analysis shows that extreme rainfall for a return period of 200-yr is highly dependent on topography and is smaller in the southwest than that in the east. The results not only demonstrate the distinct effect of Typhoon Morakot on frequency analysis, but also could provide reference in future planning of hydrological engineering.

Influence of low frequency magnetic field used in magnetotherapy on interleukin 6 (IL-6 contents in rat heart and brain

Directory of Open Access Journals (Sweden)

Elżbieta Ciejka

2017-08-01

Full Text Available Background: The human population is exposed ever more frequently to magnetic fields (MF. This is due to both technological progress and development of the economy as well as to advances made in medical science. That is why the thorough understanding and systematized knowledge about mechanisms by which MF exerts its effects on living organisms play such an important role. In this context the health of MF-exposed people is the subject of particular concern. The aim of the study was to evaluate the effect of extremely low frequency magnetic field (ELFMF used in magnetotherapy on the concentration of interleukin 6 (IL-6 in rat heart and brain. Material and Methods: The male rats were randomly divided into 3 experimental groups: group I – control, without contact with magnetic field; group II − exposed to bipolar, rectangular magnetic field 40 Hz, induction “peak-to-peak” 7 mT 30 min/day for 2 weeks; and group III − exposed to bipolar, rectangular magnetic field 40 Hz, 7 mT 60 min/day for 2 weeks. Concentration of IL-6 in the heart and brain of animals was measured after MF exposure. Results: Exposure to ELFMF: 40 Hz, induction “peak-to-peak” 7 mT 30 min/day for 2 weeks caused a significant IL-6 increase in rat hearts compared to the control group (p < 0.05 and a non-significant IL-6 decrease in rat brain. The magnetic field applied for 60 min resulted in non-significant IL-6 increase in rat hearts compared to the control group and significant IL-6 decrease in rat brain (p < 0.05. Conclusions: The influence of magnetic field on inflammation in the body varies depending on the MF parameters and the affected tissues or cells. Med Pr 2017;68(4:517–523

[Influence of low frequency magnetic field used in magnetotherapy on interleukin 6 (IL-6) contents in rat heart and brain].

Science.gov (United States)

Ciejka, Elżbieta; Skibska, Beata; Gorąca, Anna

2017-06-27

The human population is exposed ever more frequently to magnetic fields (MF). This is due to both technological progress and development of the economy as well as to advances made in medical science. That is why the thorough understanding and systematized knowledge about mechanisms by which MF exerts its effects on living organisms play such an important role. In this context the health of MF-exposed people is the subject of particular concern. The aim of the study was to evaluate the effect of extremely low frequency magnetic field (ELFMF) used in magnetotherapy on the concentration of interleukin 6 (IL-6) in rat heart and brain. The male rats were randomly divided into 3 experimental groups: group I - control, without contact with magnetic field; group II - exposed to bipolar, rectangular magnetic field 40 Hz, induction "peak-to-peak" 7 mT 30 min/day for 2 weeks; and group III - exposed to bipolar, rectangular magnetic field 40 Hz, 7 mT 60 min/day for 2 weeks. Concentration of IL-6 in the heart and brain of animals was measured after MF exposure. Exposure to ELFMF: 40 Hz, induction "peak-to-peak" 7 mT 30 min/day for 2 weeks caused a significant IL-6 increase in rat hearts compared to the control group (p < 0.05) and a non-significant IL-6 decrease in rat brain. The magnetic field applied for 60 min resulted in non-significant IL-6 increase in rat hearts compared to the control group and significant IL-6 decrease in rat brain (p < 0.05). The influence of magnetic field on inflammation in the body varies depending on the MF parameters and the affected tissues or cells. Med Pr 2017;68(4):517-523. This work is available in Open Access model and licensed under a CC BY-NC 3.0 PL license.

On the low frequency characteristics of head-related transfer function

Institute of Scientific and Technical Information of China (English)

XIE Bosun

2009-01-01

A method to correct the measured head-related transfer functions (HRTFs) at low frequency was proposed. By analyzing the HRTFs from the spherical head model at low frequency, it is proved that below the frequency of 400 Hz, magnitude of HRTF is nearly constant and the phase is a linear function of frequency both for the far and near field. Therefore, if the HRTFs above 400 Hz are accurately measured by experiment, it is able to correct the HRTFs at low frequency by the theoretical model. The results of calculation and subjective experiment show that the feasibility of the proposed method.

Have human activities changed the frequencies of absolute extreme temperatures in eastern China?

Science.gov (United States)

Wang, Jun; Tett, Simon F. B.; Yan, Zhongwei; Feng, Jinming

2018-01-01

Extreme temperatures affect populous regions, like eastern China, causing substantial socio-economic losses. It is beneficial to explore whether the frequencies of absolute or threshold-based extreme temperatures have been changed by human activities, such as anthropogenic emissions of greenhouse gases (GHGs). In this study, we compared observed and multi-model-simulated changes in the frequencies of summer days, tropical nights, icy days and frosty nights in eastern China for the years 1960-2012 by using an optimal fingerprinting method. The observed long-term trends in the regional mean frequencies of these four indices were +2.36, +1.62, -0.94, -3.02 days decade-1. The models performed better in simulating the observed frequency change in daytime extreme temperatures than nighttime ones. Anthropogenic influences are detectable in the observed frequency changes of these four temperature extreme indices. The influence of natural forcings could not be detected robustly in any indices. Further analysis found that the effects of GHGs changed the frequencies of summer days (tropical nights, icy days, frosty nights) by +3.48 ± 1.45 (+2.99 ± 1.35, -2.52 ± 1.28, -4.11 ± 1.48) days decade-1. Other anthropogenic forcing agents (dominated by anthropogenic aerosols) offset the GHG effect and changed the frequencies of these four indices by -1.53 ± 0.78, -1.49 ± 0.94, +1.84 ± 1.07, +1.45 ± 1.26 days decade-1, respectively. Little influence of natural forcings was found in the observed frequency changes of these four temperature extreme indices.

Extremity ring dosimetry intercomparison in reference and workplace fields

International Nuclear Information System (INIS)

Ginjaume, M.; Carinou, E.; Donadille, L.; Jankowski, J.; Rimpler, A.; Sans Merce, M.; Vanhavere, F.; Denoziere, M.; Daures, J.; Bordy, J. M.; Itie, C.; Covens, P.

2008-01-01

An intercomparison of ring dosemeters has been organised with the aim of assessing the technical capabilities of available extremity dosemeters and focusing on their performance at clinical workplaces with potentially high extremity doses. Twenty-four services from 16 countries participated in the intercomparison. The dosemeters were exposed to reference photon ( 137 Cs) and beta ( 147 Pm, 85 Kr and 90 Sr/ 90 Y) fields together with fields representing realistic exposure situations in interventional radiology (direct and scattered radiation) and nuclear medicine ( 99m Tc and 18 F). It has been found that most dosemeters provided satisfactory measurements of H p (0.07) for photon radiation, both in reference and realistic fields. However, only four dosemeters fulfilled the established requirements for all radiation qualities. The main difficulties were found for the measurement of low-energy beta radiation. Finally, the results also showed a general under-response of detectors to 18 F, which was attributed to the difficulties of the dosimetric systems to measure the positron contribution to the dose. (authors)

Morphology of low-frequency waves in the solar wind and their relation to ground pulsations

International Nuclear Information System (INIS)

Odera, T.J.; Stuart, W.F.

1986-01-01

Three classes of low frequency waves (period range 20 to 80 s) were identified using data from the UCLA fluxgate magnetometer experiment on board the ISEE 2 spacecraft. These are continuous pulsations similar in type to Pc 3, band-limited oscillations distinguished by mixed period fluctuations, and relatively isolated wave bundles. The waves were preferentially observed when the interplanetary magnetic field (IMF) direction was sunward and were most common when the cone angle, i.e. the angle between IMF and the Sun-Earth line (thetasub(xB)) was often between 15 deg and 45 deg. Their frequency is proportional to the IMF magnitude. Comparison between the waves observed on board the ISEE 2 spacecraft and the Pc 3-4 recorded simultaneously at a mid-latitude ground station, Oulu (L = 4.5), showed that similarity of spectra of the waves in the spacecraft and on the ground was very rare and that correspondence between the events in space and on the ground was extremely low. (author)

Test fields cannot destroy extremal black holes

International Nuclear Information System (INIS)

Natário, José; Queimada, Leonel; Vicente, Rodrigo

2016-01-01

We prove that (possibly charged) test fields satisfying the null energy condition at the event horizon cannot overspin/overcharge extremal Kerr–Newman or Kerr–Newman–anti de Sitter black holes, that is, the weak cosmic censorship conjecture cannot be violated in the test field approximation. The argument relies on black hole thermodynamics (without assuming cosmic censorship), and does not depend on the precise nature of the fields. We also discuss generalizations of this result to other extremal black holes. (paper)

Extreme events in total ozone over Arosa – Part 1: Application of extreme value theory

Directory of Open Access Journals (Sweden)

H. E. Rieder

2010-10-01

Full Text Available In this study ideas from extreme value theory are for the first time applied in the field of stratospheric ozone research, because statistical analysis showed that previously used concepts assuming a Gaussian distribution (e.g. fixed deviations from mean values of total ozone data do not adequately address the structure of the extremes. We show that statistical extreme value methods are appropriate to identify ozone extremes and to describe the tails of the Arosa (Switzerland total ozone time series. In order to accommodate the seasonal cycle in total ozone, a daily moving threshold was determined and used, with tools from extreme value theory, to analyse the frequency of days with extreme low (termed ELOs and high (termed EHOs total ozone at Arosa. The analysis shows that the Generalized Pareto Distribution (GPD provides an appropriate model for the frequency distribution of total ozone above or below a mathematically well-defined threshold, thus providing a statistical description of ELOs and EHOs. The results show an increase in ELOs and a decrease in EHOs during the last decades. The fitted model represents the tails of the total ozone data set with high accuracy over the entire range (including absolute monthly minima and maxima, and enables a precise computation of the frequency distribution of ozone mini-holes (using constant thresholds. Analyzing the tails instead of a small fraction of days below constant thresholds provides deeper insight into the time series properties. Fingerprints of dynamical (e.g. ENSO, NAO and chemical features (e.g. strong polar vortex ozone loss, and major volcanic eruptions, can be identified in the observed frequency of extreme events throughout the time series. Overall the new approach to analysis of extremes provides more information on time series properties and variability than previous approaches that use only monthly averages and/or mini-holes and mini-highs.

Low-frequency Landau-Zener-Stuckelberg interference in dissipative superconducting qubits

International Nuclear Information System (INIS)

Du-lingjie; Lan- Dong; Yu-Yang

2013-01-01

Landau-Zener-Stuckelberg (LZS) interference of continuously driven superconducting qubits is studied. Going beyond the second order perturbation expansion, we find a time dependent stationary population evolution as well as unsymmetrical microwave driven Landau-Zener transitions, resulting from the nonresonant terms which are neglected in rotating-wave approximation. For the low-frequency driving, the qubit population at equilibrium is a periodical function of time, owing to the contribution of the nonresonant terms. In order to obtain the average population, it is found that the average approximation based on the perturbation approach can be applied to the low-frequency region. For the extremely low frequency which is much smaller than the decoherence rate, we develop noncoherence approximation by dividing the evolution into discrete time steps during which the coherence is lost totally. These approximations present comprehensive analytical descriptions of LZS interference in most of parameter space of frequency and decoherence rate, agreeing well with those of the numerical simulations and providing a simple but integrated understanding to system dynamics. The application of our models to microwave cooling can obtain the minimal frequency to realize effective microwave cooling.

Low frequency sound field control for loudspeakers in rectangular rooms using CABS (Controlled Acoustical Bass System)

DEFF Research Database (Denmark)

Nielsen, Sofus Birkedal; Celestinos, Adrian

2010-01-01

Rectangular rooms are the most common shape for sound reproduction, but at low frequencies the reflections from the boundaries of the room cause large spatial variations in the sound pressure level.  Variations up to 30 dB are normal, not only at the room modes, but basically at all frequencies....... As sound propagates in time, it seems natural that the problems can best be analyzed and solved in the time domain. A time based room correction system named CABS (Controlled Acoustical Bass System) has been developed for sound reproduction in rectangular listening rooms. It can control the sound...... sound field in the whole room, and short impulse response.  In a standard listening room (180 m3) only 4 loudspeakers are needed, 2 more than a traditional stereo setup. CABS is controlled by a developed DSP system. The time based approached might help with the understanding of sound field control...

The influence of low frequency magnetic field upon cultivable plant physiology

International Nuclear Information System (INIS)

Rochalska, M.

2008-01-01

The 16 Hz frequency and 5 mT magnetic flux density as well as alternating magnetic field influence the field germination physiological yield-forming features and the yield of sugar have been investigated. The profitable influence of the investigated factor at physiological yield-forming features, causing an increase in sugar beet root and leaf yield, was shown. The beneficial influence on the yield is especially clear in unfavourable weather conditions. (author)

Dosimetry in Japanese male and female models for a low-frequency electric field

International Nuclear Information System (INIS)

Hirata, Akimasa; Fujiwara, Osamu

2007-01-01

The present study quantified induced current in anatomically based Japanese male and female models for exposure to low-frequency electric fields. A quasi-static finite-difference time-domain (FDTD) method was applied to analyze this problem. For our computational results, the difference of the induced current density averaged over an area of 1 cm 2 between Japanese male and female models was less than 30% for each nerve tissue. The difference of induced current density between the present study and earlier works was less than 50% for the same conductivities, despite the different morphology. Particularly, maximum current density in central nerve tissues appeared in the retina of Japanese models, the same as in the earlier works. (note)

The differential effects of increasing frequency and magnitude of extreme events on coral populations.

Science.gov (United States)

Fabina, Nicholas S; Baskett, Marissa L; Gross, Kevin

2015-09-01

Extreme events, which have profound ecological consequences, are changing in both frequency and magnitude with climate change. Because extreme temperatures induce coral bleaching, we can explore the relative impacts of changes in frequency and magnitude of high temperature events on coral reefs. Here, we combined climate projections and a dynamic population model to determine how changing bleaching regimes influence coral persistence. We additionally explored how coral traits and competition with macroalgae mediate changes in bleaching regimes. Our results predict that severe bleaching events reduce coral persistence more than frequent bleaching. Corals with low adult mortality and high growth rates are successful when bleaching is mild, but bleaching resistance is necessary to persist when bleaching is severe, regardless of frequency. The existence of macroalgae-dominated stable states reduces coral persistence and changes the relative importance of coral traits. Building on previous studies, our results predict that management efforts may need to prioritize protection of "weaker" corals with high adult mortality when bleaching is mild, and protection of "stronger" corals with high bleaching resistance when bleaching is severe. In summary, future reef projections and conservation targets depend on both local bleaching regimes and biodiversity.

Low frequency sound field enhancement system for rectangular rooms, using multiple loudspeakers

DEFF Research Database (Denmark)

Celestinos, Adrian

2007-01-01

The scope of this PhD dissertation is within the performance of loudspeakers in rooms at low frequencies. The research concentrates on the improvement of the sound level distribution in rooms produced by loudspeakers at low frequencies. The work focuses on seeing the problem acoustically...... and solving it in the time domain. Loudspeakers are the last link in the sound reproduction chain, and they are typically placed in small or medium size rooms. When low frequency sound is radiated by a loudspeaker the sound level distribution along the room presents large deviations. This is due...... to the multiple reflection of sound at the rigid walls of the room. This may cause level differences of up to 20 dB in the room. Some of these deviations are associated with the standing waves, resonances or anti resonances of the room. The understanding of the problem is accomplished by analyzing the behavior...

Stabilised frequency of extreme positive Indian Ocean Dipole under 1.5 °C warming.

Science.gov (United States)

Cai, Wenju; Wang, Guojian; Gan, Bolan; Wu, Lixin; Santoso, Agus; Lin, Xiaopei; Chen, Zhaohui; Jia, Fan; Yamagata, Toshio

2018-04-12

Extreme positive Indian Ocean Dipole (pIOD) affects weather, agriculture, ecosystems, and public health worldwide, particularly when exacerbated by an extreme El Niño. The Paris Agreement aims to limit warming below 2 °C and ideally below 1.5 °C in global mean temperature (GMT), but how extreme pIOD will respond to this target is unclear. Here we show that the frequency increases linearly as the warming proceeds, and doubles at 1.5 °C warming from the pre-industrial level (statistically significant above the 90% confidence level), underscored by a strong intermodel agreement with 11 out of 13 models producing an increase. However, in sharp contrast to a continuous increase in extreme El Niño frequency long after GMT stabilisation, the extreme pIOD frequency peaks as the GMT stabilises. The contrasting response corresponds to a 50% reduction in frequency of an extreme El Niño preceded by an extreme pIOD from that projected under a business-as-usual scenario.

The Relationship Between Low-Frequency Motions and Community Structure of Residue Network in Protein Molecules.

Science.gov (United States)

Sun, Weitao

2018-01-01

The global shape of a protein molecule is believed to be dominant in determining low-frequency deformational motions. However, how structure dynamics relies on residue interactions remains largely unknown. The global residue community structure and the local residue interactions are two important coexisting factors imposing significant effects on low-frequency normal modes. In this work, an algorithm for community structure partition is proposed by integrating Miyazawa-Jernigan empirical potential energy as edge weight. A sensitivity parameter is defined to measure the effect of local residue interaction on low-frequency movement. We show that community structure is a more fundamental feature of residue contact networks. Moreover, we surprisingly find that low-frequency normal mode eigenvectors are sensitive to some local critical residue interaction pairs (CRIPs). A fair amount of CRIPs act as bridges and hold distributed structure components into a unified tertiary structure by bonding nearby communities. Community structure analysis and CRIP detection of 116 catalytic proteins reveal that breaking up of a CRIP can cause low-frequency allosteric movement of a residue at the far side of protein structure. The results imply that community structure and CRIP may be the structural basis for low-frequency motions.

Frequency-dependent hydrodynamic interaction between two solid spheres

Science.gov (United States)

Jung, Gerhard; Schmid, Friederike

2017-12-01

Hydrodynamic interactions play an important role in many areas of soft matter science. In simulations with implicit solvent, various techniques such as Brownian or Stokesian dynamics explicitly include hydrodynamic interactions a posteriori by using hydrodynamic diffusion tensors derived from the Stokes equation. However, this equation assumes the interaction to be instantaneous which is an idealized approximation and only valid on long time scales. In the present paper, we go one step further and analyze the time-dependence of hydrodynamic interactions between finite-sized particles in a compressible fluid on the basis of the linearized Navier-Stokes equation. The theoretical results show that at high frequencies, the compressibility of the fluid has a significant impact on the frequency-dependent pair interactions. The predictions of hydrodynamic theory are compared to molecular dynamics simulations of two nanocolloids in a Lennard-Jones fluid. For this system, we reconstruct memory functions by extending the inverse Volterra technique. The simulation data agree very well with the theory, therefore, the theory can be used to implement dynamically consistent hydrodynamic interactions in the increasingly popular field of non-Markovian modeling.

Ultra-low-frequency electrostatic modes in a magnetized dusty plasma

International Nuclear Information System (INIS)

Salimullah, M.; Amin, M.R.; Roy Chowdhury, A.R.; Salahuddin, M.

1997-11-01

A study on the extremely low-frequency possible electrostatic modes in a finite temperature magnetized dusty plasma taking the charged dust grains as the third component has been carried out using the appropriate Vlasov-kinetic theory for the dynamics of the electrons, ions and the dust particles. It is found that the inequalities of charge and number density of plasma species, and the finite-Larmor-radius thermal kinetic effects of the mobile charged dust grains, introduce the existence of very low-frequency electrostatic eigenmodes in the three-component homogeneous magnetized dusty plasma. The relevance of the present investigation to space and astrophysical situations as well as laboratory experiments for dust Coulomb crystallization has been pointed out. (author)

Note: Enhanced energy harvesting from low-frequency magnetic fields utilizing magneto-mechano-electric composite tuning-fork.

Science.gov (United States)

Yang, Aichao; Li, Ping; Wen, Yumei; Yang, Chao; Wang, Decai; Zhang, Feng; Zhang, Jiajia

2015-06-01

A magnetic-field energy harvester using a low-frequency magneto-mechano-electric (MME) composite tuning-fork is proposed. This MME composite tuning-fork consists of a copper tuning fork with piezoelectric Pb(Zr(1-x)Ti(x))O3 (PZT) plates bonded near its fixed end and with NdFeB magnets attached at its free ends. Due to the resonance coupling between fork prongs, the MME composite tuning-fork owns strong vibration and high Q value. Experimental results show that the proposed magnetic-field energy harvester using the MME composite tuning-fork exhibits approximately 4 times larger maximum output voltage and 7.2 times higher maximum power than the conventional magnetic-field energy harvester using the MME composite cantilever.

Temperature field in the hot-top during casting a new super-high strength Al-Zn-Mg-Cu alloy by low frequency electromagnetic process

Directory of Open Access Journals (Sweden)

Yubo ZUO

2005-08-01

Full Text Available The billets of a new super-high strength Al-Zn-Mg-Cu alloy in 200 mm diameter were produced by the processed of low frequency electromagnetic casting (LFEC and conventional direct chill(DCcasting, respectively. The effects of low frequency electromagnetic field on temperature field of the melt in the hot-top were investigated by temperature thermocouples into the casting during the processes. The results show that during LFEC process the temperature field in the melt applying the hot-top is very uniform, which is helpful to reduce the difference of thermal gradients between the surface and the center, and then to reduce the thermal stress and to eliminate casting crack.

Observation of a new type of low-frequency waves at comet 67P/Churyumov-Gerasimenko

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I. Richter

2015-08-01

Full Text Available We report on magnetic field measurements made in the innermost coma of 67P/Churyumov-Gerasimenko in its low-activity state. Quasi-coherent, large-amplitude (δ B/B ~ 1, compressional magnetic field oscillations at ~ 40 mHz dominate the immediate plasma environment of the nucleus. This differs from previously studied cometary interaction regions where waves at the cometary ion gyro-frequencies are the main feature. Thus classical pickup-ion-driven instabilities are unable to explain the observations. We propose a cross-field current instability associated with newborn cometary ion currents as a possible source mechanism.

Biological and Human Health Effects of Extremely Low Frequency Electromagnetic Fields. Post-1977 Literature Review.

Science.gov (United States)

1985-03-01

dosimetric analysis for chick-brain exposure to radio frequencies. Using the geometrica assumptions of their S 51 0 0 : :-: analysis, an approximate...mass ratio used in Liboff’s calculations. Is the Liboff predication correct due to coincidence or is the relation between ions and surrounding...However, if correct , the explanation is incomplete insofar as 0 the same flux linkage has no reported effect at 16.66 Hz. Square wave rise times were not

The Effect of Extremely Low Frequency Electromagnetic Fields on Visual Learning & Memory and Anatomical Structures of the Brain in Male Rhesus Monkeys

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Elahe Tekieh

2018-04-01

Full Text Available Background: Humans in modern societies expose to substantially elevated levels of electromagnetic field (EMF emissions with different frequencies.The neurobiological effects of EMF have been the subject of debate and intensive research over the past few decades. Therefore, we evaluated the effects of EMF on visual learning and anatomical dimensions of the hippocampus and the prefrontal area (PFA in male Rhesus monkeys. Materials and Methods:In this study, four rhesus monkeys were irradiated by 0.7 microtesla ELF-EMF either at 5 or 30 Hz, 4 h a day, for 30 days. Alterations in visual learning and memory were assessed before and after irradiation phase by using a box designed that cchallenging animals for gaining rewards Also, the monkeys’ brains were scanned by using MRI technique one week before and one week after irradiation. The monkeys were anesthetized by intramuscular injection of ketamine hydrochloride (10–20 mg/kg and xylazine (0.2–0.4 mg/kg, and scanned with a 3-Tesla Magnetom, in axial, sagittal, and coronal planes using T2 weight­ed protocol with a slice thickness of 3 mm. The anatomical changes of hippocampus and the prefrontal area (PFA was measured by volumetric study. Results: Electromagnetic field exposure at a frequency of 30 Hz reduced the number of correct responses in the learning process and delayed memory formation in the two tested monkeys. While, ELF-EMF at 5 Hz had no effect on the visual learning and memory changes. No anatomical changes were found in the prefrontal area and the hippocampus at both frequencies. Conclusion: ELF-EMF irradiation at 30 Hz adversely affected visual learning and memory, pprobably through these changes apply through effects on other factors except changes in brain structure and anatomy.

Modulation of the Object/Background Interaction by Spatial Frequency

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Yanju Ren

2011-05-01

Full Text Available With regard to the relationship between object and background perception in the natural scene images, functional isolation hypothesis and interactive hypothesis were proposed. Based on previous studies, the present study investigated the role of spatial frequency in the relationship between object and background perception in the natural scene images. In three experiments, participants reported the object, background, or both after seeing each picture for 500 ms followed by a mask. The authors found that (a backgrounds were identified more accurately when they contained a consistent rather than an inconsistent object, independently of spatial frequency; (b objects were identified more accurately in a consistent than an inconsistent background under the condition of low spatial frequencies but not high spatial frequencies; (c spatial frequency modulation remained when both objects and backgrounds were reported simultaneously. The authors conclude that object/background interaction is partially dependent on spatial frequency.

The Earth's passage of the April 11, 1997 coronal ejecta: geomagnetic field fluctuations at high and low latitude during northward interplanetary magnetic field conditions

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S. Lepidi

1999-10-01

Full Text Available An analysis of the low frequency geomagnetic field fluctuations at an Antarctic (Terra Nova Bay and a low latitude (L'Aquila, Italy station during the Earth's passage of a coronal ejecta on April 11, 1997 shows that major solar wind pressure variations were followed at both stations by a high fluctuation level. During northward interplanetary magnetic field conditions and when Terra Nova Bay is close to the local geomagnetic noon, coherent fluctuations, at the same frequency (3.6 mHz and with polarization characteristics indicating an antisunward propagation, were observed simultaneously at the two stations. An analysis of simultaneous measurements from geosynchronous satellites shows evidence for pulsations at approximately the same frequencies also in the magnetospheric field. The observed waves might then be interpreted as oscillation modes, triggered by an external stimulation, extending to a major portion of the Earth's magnetosphere. Key words. Magnetospheric physics (MHD waves and instabilities; solar wind-magnetosphere interactions

Effects of external magnetic field on harmonics generated in laser interaction with underdense plasma

International Nuclear Information System (INIS)

Faghihi-Nik, M.; Ghorbanalilu, M.; Shokri, B.

2010-01-01

Complete text of publication follows. Generation of harmonic radiation is an important subject of laser plasma interaction and attracts great attention due to a wide range of applications. It has been seen that intense electromagnetic and quasi-static transverse magnetic fields are generated in laser plasma interaction. An extremely intense magnetic field (up to hundreds of MG) has been observed by experimental measurements in interaction of short laser pulses with plasma. These self-generated or applied magnetic fields affect the propagation of the laser pulses. In most laser interactions with homogeneous plasma, odd harmonics of laser frequency are generated. In this paper, we point out the possibility of even harmonics generation when a linearly polarized laser beam propagates in homogeneous plasma in the presence of a transverse magnetic field. It is shown that applying external field induces a transverse current density oscillating twice of the laser field which leds to generation of second harmonic radiation. This current density is derived using the perturbation method, and the steady state amplitude of the second harmonic obtained by solution of the wave equation. By the same procedure the current density and then the steady state amplitude of higher order harmonics are calculated. The efficiency of harmonic generation (the ratio of harmonic power to incident power) is a drastically function of the strength of external magnetic field. It is found that the efficiency of even harmonics is zero in the absence of magnetic field and increases as the magnetic field is increased. For odd harmonics, applying the external magnetic field enhances the generated harmonics as well. The conversion efficiency also increases with increase in plasma density and intensity of the laser beam.

A two-fluid interpretation of low frequency modes in Tokamaks

International Nuclear Information System (INIS)

Thyagaraja, A.; Haas, F.A.

1983-01-01

The linear stability of low frequency modes (ω/ωsub(ci) << 1) of a dissipationless two-fluid cylindrical analogue of Tokamak is investigated. The eigenvalue problem comprises a coupled first-order and second-order differential equation. Given certain plausible assumptions, the case of an internal resonant point is solved analytically. The resulting modes and frequencies are qualitatively similar to those observed. The analogue of the MHD uniform current model is solved exactly and the usual MHD marginal stability boundary is shown to be modified. More general considerations show, that even in the absence of dissipation, the magnetic field is not ''frozen'' to the ions or the electrons. Furthermore, in general the MHD equations can only be recovered by a limiting process which is inappropriate to Tokamaks. For very low frequencies (ω << ω*), however, single and two-fluid theories predict the same magnetic field structure but different electric fields. The present analysis which covers frequencies from zero to ωsub(Alfven), including drift and acoustic frequencies predicts that both discrete and continuum modes can be unstable which is in contrast to ideal MHD. (author)

Microscopic investigations of the terahertz and the extreme nonlinear optical response of semiconductors

Energy Technology Data Exchange (ETDEWEB)

Golde, Daniel

2010-06-22

In the major part of this Thesis, we discuss the linear THz response of semiconductor nanostructures based on a microscopic theory. Here, two different problems are investigated: intersubband transitions in optically excited quantum wells and the THz plasma response of two-dimensional systems. In the latter case, we analyze the response of correlated electron and electron-hole plasmas. Extracting the plasma frequency from the linear response, we find significant deviations from the commonly accepted two-dimensional plasma frequency. Besides analyzing the pure plasma response, we also consider an intermediate regime where the response of the electron-hole plasma consists of a mixture of plasma contributions and excitonic transitions. A quantitative experiment-theory comparison provides novel insights into the behavior of the system at the transition from one regime to the other. The discussion of the intersubband transitions mainly focuses on the coherent superposition of the responses from true THz transitions and the ponderomotively accelerated carriers. We present a simple method to directly identify ponderomotive effects in the linear THz response. Apart from that, the excitonic contributions to intersubband transitions are investigated. The last part of the present Thesis deals with a completely different regime. Here, the extreme nonlinear optical response of low-dimensional semiconductor structures is discussed. Formally, extreme nonlinear optics describes the regime of light-matter interaction where the exciting field is strong enough such that the Rabi frequency is comparable to or larger than the characteristic transition frequency of the investigated system. Here, the Rabi frequency is given by the product of the electrical field strength and the dipole-matrix element of the respective transition. Theoretical investigations have predicted a large number of novel nonlinear effects arising for such strong excitations. Some of them have been observed in

Hydraulic continuity and biological effects of low strength very low frequency electromagnetic waves: Case of microbial biofilm growth in water treatment.

Science.gov (United States)

Gérard, Merlin; Noamen, Omri; Evelyne, Gonze; Eric, Valette; Gilles, Cauffet; Marc, Henry

2015-10-15

This study aims to elucidate the interactions between water, subjected to electromagnetic waves of very low frequency (VLF) (kHz) with low strength electromagnetic fields (3.5 mT inside the coils), and the development of microbial biofilms in this exposed water. Experimental results demonstrate that in water exposed to VLF electromagnetic waves, the biomass of biofilm is limited if hydraulic continuity is achieved between the electromagnetic generator and the biofilm media. The measured amount of the biofilm's biomass is approximately a factor two lower for exposed biofilm than the non-exposed biofilm. Measurements of electromagnetic fields in the air and simulations exhibit very low intensities of fields (electromagnetic generator. Exposure to electric and magnetic fields of the quoted intensities cannot explain thermal and ionizing effects on the biofilm. A variable electrical potential with a magnitude close to 20 mV was detected in the tank in hydraulic continuity with the electromagnetic generator. The application of quantum field theory may help to explain the observed effects in this case. Copyright © 2015 Elsevier Ltd. All rights reserved.

Laboratory experiments on the magnetic field and neutral density limits on CIV interaction

International Nuclear Information System (INIS)

Axnaes, I.; Brenning, N.

1990-03-01

Laboratory experiments are reported which determine the magnetic field and neutral density limit for Critical Ionization Velocity (CIV) interaction in the impact configuration. A combination of microwave interferometry and spectroscopy has been used to measure how the electron energy distribution varies with the neutral density and the magnetic field strength. The efficiency of the CIV process is evaluated in terms of the efficiency factor η of energy transfer to the electron. This efficiency is studied as function of the ratio V A /V 0 between the Alfven velocity and the plasma stream velocity and the ratio ν i /ω gi between the ionization frequency and the ion gyro frequency. With other parameters kept constant, V A /V 0 is proportional to the square root of the magnetic field, while ν i /ω gi is proportional to the neutral density. We have found that these two dimensionless parameters are coupled in such a fashion that a stronger magnetic field can compensate for a lower neutral density. For our strongest magnetic field, corresponding to V A /V 0 = 4, CIV interaction is found to occur for a comparatively low value ν i /ω gi ∼ 0.1. For V A /V 0 = 1, we found a clear absence of CIV interaction even for ν i /ω gi approaching unity. (authors)

[The effects of electromagnetic radiation of extremely high frequency and low intensity on the growth rate of bacteria Escherichia coli and the role of medium pH].

Science.gov (United States)

Tadevosian, A; Kalantarian, V; Trchunian, A

2007-01-01

It has been shown that coherent electromagnetic irradiation (EMI) of extremely high frequency (45-53 GHz) or millimeter waves (wavelength 5.6-6.7 mm) of low intensity (flux capacity 0.06 mW/cm2) of Escherichia coli K12, grown under anaerobic conditions during the fermentation of sugar (glucose) for 30 min or 1 h, caused a decrease in their growth rate, the maximum inhibitory effect being achieved at a frequency of 51.8 or 53 GHz. This effect depended on medium pH when the maximal action was determined at pH 7.5. In addition, separate 30-min of 1-h irradiation (frequency 51.8 or 53 GHz) of doubly distilled water or some inorganic ions contained in Tris-phosphate buffer where the cells were transferred induced oppositely directed changes in further growth of these bacteria under anaerobic conditions; irradiation of water caused a decrease in the growth rate of bacteria. A significant change in pH of water (0.5-1.5 unit) was induced by a 30-irradiation at a frequency of 49, 50.3, 51.8, or 53 GHz, when the initial pH value was 6.0 or 8.0, but not 7.5. These results indicate the changes in the properties of water and its role in the effects of EMI of extremely high frequency. The marked effect of EMI on bacteria disappeared upon repeated irradiation for 1 h at a frequency of 51.8 or 53 GHz with an interval of 2 hours. This result indicates some compensatory mechanisms in bacteria.

Polarity-sensitive transient patterned state in a twisted nematic liquid crystal driven by very low frequency fields.

Science.gov (United States)

Krishnamurthy, K S; Kumar, Pramoda; Kumar, M Vijay

2013-02-01

We report, for a rodlike nematic liquid crystal with small positive dielectric and conductivity anisotropies, and in the 90°-twisted configuration, low frequency (wave electric field generated Carr-Helfrich director modulation appearing transiently over a few seconds at each polarity reversal and vanishing almost completely under steady field conditions. Significantly, the instability is polarity sensitive, with the maximum distortion localized in the vicinity of the negative electrode, rather than in the midplane of the layer. This is revealed by the wave vector alternating in the two halves of the driving cycle between the alignment directions at the two substrates. Besides the Carr-Helfrich mechanism, quadrupolar flexoelectric polarization arising under electric field gradient is strongly indicated as being involved in the development of the transient periodic order. Similar transient instability is also observed in other nematic compounds with varying combinations of dielectric and conductivity anisotropies, showing its general nature. The study also deals with various characteristics of the electro-optic effect that emerge from the temporal variation of optical response for different driving voltages, frequencies, and temperatures.

IMFREX impact of the anthropic changes on the frequency of the extreme phenomena of the wind, the temperature and the rainfall. Final report; Imfrex impact des changements anthropiques sur la frequence des phenomenes extremes de vent de temperature et de precipitations. Rapport final

Energy Technology Data Exchange (ETDEWEB)

NONE

2007-07-01

The aim of Imfrex was to evaluate the impact of a climatic change on the frequency of extreme phenomena of wind and rainfall in France. The study is based on an hypothesis proposed by the GIEC and called scenario A2. A first simulation, low resolution 300 km, using a coupled model ocean-atmosphere allowed to provide an evolution scenario for the temperature of the sea surface and the ice field area. A second simulation, high resolution 50 km, provided a daily evolution of the climate during 140 years. Imfrex was organized in five work-packages: the constitution of the data base, the validation of the models, the direct approach the statistical approach and the dynamical approach. (A.L.B.)

An electromagnetic compatibility study of cardiac pacemaker to low frequency interferences

International Nuclear Information System (INIS)

Andretzko, J.P.; Hedjiedj, A.; Babouri, A.; Guendouz, L.; Nadi, M.

2006-01-01

This paper presents an experimental study of the behaviour of cardiac pacemaker submitted to low frequency electromagnetic interferences. The method used in this study is progressive. It consists in starting from the target (the cardiac pacemaker), identifying and quantifying the disturbances (the source), and then introducing secondary influencing parameters in stepwise fashion. The general problematic consists in checking this immunity in relation with led disruptions and in relation with beaming disruptions. The experimental approach suggests two kind of tests corresponding to the two studied coupling modes. The first one corresponds to a direct applying of the disruptive signal between the pacemaker terminals. The objective of this phase is to determine the characteristics of the signal (amplitude and frequency) which are detected by the pacemaker and which generate modifications of its operation. In the second phase the pacemaker is subjected to a variable low frequency magnetic field. This last interacts with the pacemaker by inductive coupling through the loop formed by the pacemaker and its leads and the surrounding medium. This interaction results in an induced electromotive force between the terminals of the pacemaker which can potentially disturb the operation of this last. The objective of this phase is to characterize the signal (magnetic field) likely to generate these disturbances. Tests are carried out on six single chamber pacemaker and five dual chamber pacemaker. The interfering signal frequencies are 50 Hz, 60 Hz, 10 khz and 25 khz. Tracking and programming of the pacemaker housing is achieved with the telemetry system. In this study, the devices have all been configured in inhibited stimulation (S.S.I. or V.V.I. mode according to the international codification), this configuration being the most widespread. The housing stimulates the basic frequency in the absence o f intrinsic activity, the stimulation can be inhibited in each chamber by a

An electromagnetic compatibility study of cardiac pacemaker to low frequency interferences

Energy Technology Data Exchange (ETDEWEB)

Andretzko, J.P.; Hedjiedj, A.; Babouri, A.; Guendouz, L.; Nadi, M. [Nancy-1 Univ. Henri Poincare, Lab. d' Instrumentation Electronique de Nancy, Faculte des Sciences, 54 - Vandoeuvre les Nancy (France)

2006-07-01

This paper presents an experimental study of the behaviour of cardiac pacemaker submitted to low frequency electromagnetic interferences. The method used in this study is progressive. It consists in starting from the target (the cardiac pacemaker), identifying and quantifying the disturbances (the source), and then introducing secondary influencing parameters in stepwise fashion. The general problematic consists in checking this immunity in relation with led disruptions and in relation with beaming disruptions. The experimental approach suggests two kind of tests corresponding to the two studied coupling modes. The first one corresponds to a direct applying of the disruptive signal between the pacemaker terminals. The objective of this phase is to determine the characteristics of the signal (amplitude and frequency) which are detected by the pacemaker and which generate modifications of its operation. In the second phase the pacemaker is subjected to a variable low frequency magnetic field. This last interacts with the pacemaker by inductive coupling through the loop formed by the pacemaker and its leads and the surrounding medium. This interaction results in an induced electromotive force between the terminals of the pacemaker which can potentially disturb the operation of this last. The objective of this phase is to characterize the signal (magnetic field) likely to generate these disturbances. Tests are carried out on six single chamber pacemaker and five dual chamber pacemaker. The interfering signal frequencies are 50 Hz, 60 Hz, 10 khz and 25 khz. Tracking and programming of the pacemaker housing is achieved with the telemetry system. In this study, the devices have all been configured in inhibited stimulation (S.S.I. or V.V.I. mode according to the international codification), this configuration being the most widespread. The housing stimulates the basic frequency in the absence o f intrinsic activity, the stimulation can be inhibited in each chamber by a

Multi-frequency ESR studies on a Haldane magnet in a field-induced phase at ultra-low temperatures

International Nuclear Information System (INIS)

Hagiwara, Masayuki; Kashiwagi, Takanari; Idutsu, Yuichi; Honda, Zentaro; Miyazaki, Hiroshi; Harada, Isao

2010-01-01

We report the results of multi-frequency electron spin resonance (ESR) measurements on single crystals of Ni(C 5 H 14 N 2 ) 2 N 3 (PF 6 ) which is regarded as the one-dimensional Heisenberg antiferromagnet with spin one, namely the Haldane magnet, at very low temperatures down to about 100 mK. We observed the lowest resonance branch below about 500 mK for the field along the chain direction (H||c), which was observed previously only in an inelastic neutron scattering experiment at 30 mK. We compare the resonance branch with that calculated by a phenomenological field theory, and discuss the field dependence and the temperature sensitivity of this ESR branch.

The low-frequency encoding disadvantage: Word frequency affects processing demands.

Science.gov (United States)

Diana, Rachel A; Reder, Lynne M

2006-07-01

Low-frequency words produce more hits and fewer false alarms than high-frequency words in a recognition task. The low-frequency hit rate advantage has sometimes been attributed to processes that operate during the recognition test (e.g., L. M. Reder et al., 2000). When tasks other than recognition, such as recall, cued recall, or associative recognition, are used, the effects seem to contradict a low-frequency advantage in memory. Four experiments are presented to support the claim that in addition to the advantage of low-frequency words at retrieval, there is a low-frequency disadvantage during encoding. That is, low-frequency words require more processing resources to be encoded episodically than high-frequency words. Under encoding conditions in which processing resources are limited, low-frequency words show a larger decrement in recognition than high-frequency words. Also, studying items (pictures and words of varying frequencies) along with low-frequency words reduces performance for those stimuli. Copyright 2006 APA, all rights reserved.

Low-frequency instabilities of a warm plasma in a magnetic field

International Nuclear Information System (INIS)

Smith, D.F.; Hollweg, J.V.

1977-01-01

The marginal stability of a plasma carrying current along the static magnetic field with isotropic Maxwellian ions and isotropic Maxwellian electrons drifting relative to the ions is investigated. The complete electromagnetic dispersion relation is studied using numerical techniques; the electron sums are restricted to three terms which limits the analysis to frequencies much less than the electron gyro-frequency, but includes frequencies somewhat above the ion gyro-frequency. A 'kink-like' instability and an instability of the Alfven mode are found to have the lowest threshold drift velocities in most cases. In fact the threshold drift for the kink-like instability can be significantly less than the ion thermal speed. Electrostatic and electromagnetic ion-cyclotron instabilities are also found as well as the electro-static ion-acoustic instability. No instability of the fast magnetosonic mode was found. The stability analysis provides only threshold drift velocities and gives no information about growth rates. (author)

Low Frequency Turbulence as the Source of High Frequency Waves in Multi-Component Space Plasmas

Science.gov (United States)

Khazanov, George V.; Krivorutsky, Emmanuel N.; Uritsky, Vadim M.

2011-01-01

Space plasmas support a wide variety of waves, and wave-particle interactions as well as wavewave interactions are of crucial importance to magnetospheric and ionospheric plasma behavior. High frequency wave turbulence generation by the low frequency (LF) turbulence is restricted by two interconnected requirements: the turbulence should be strong enough and/or the coherent wave trains should have the appropriate length. These requirements are strongly relaxed in the multi-component plasmas, due to the heavy ions large drift velocity in the field of LF wave. The excitation of lower hybrid waves (LHWs), in particular, is a widely discussed mechanism of interaction between plasma species in space and is one of the unresolved questions of magnetospheric multi-ion plasmas. It is demonstrated that large-amplitude Alfven waves, in particular those associated with LF turbulence, may generate LHW s in the auroral zone and ring current region and in some cases (particularly in the inner magnetosphere) this serves as the Alfven wave saturation mechanism. We also argue that the described scenario can playa vital role in various parts of the outer magnetosphere featuring strong LF turbulence accompanied by LHW activity. Using the data from THEMIS spacecraft, we validate the conditions for such cross-scale coupling in the near-Earth "flow-braking" magnetotail region during the passage of sharp injection/dipolarization fronts, as well as in the turbulent outflow region of the midtail reconnection site.

Cellular target of weak magnetic fields: ionic conduction along actin filaments of microvilli.

Science.gov (United States)

Gartzke, Joachim; Lange, Klaus

2002-11-01

The interaction of weak electromagnetic fields (EMF) with living cells is a most important but still unresolved biophysical problem. For this interaction, thermal and other types of noise appear to cause severe restrictions in the action of weak signals on relevant components of the cell. A recently presented general concept of regulation of ion and substrate pathways through microvilli provides a possible theoretical basis for the comprehension of physiological effects of even extremely low magnetic fields. The actin-based core of microfilaments in microvilli is proposed to represent a cellular interaction site for magnetic fields. Both the central role of F-actin in Ca2+ signaling and its polyelectrolyte nature eliciting specific ion conduction properties render the microvillar actin filament bundle an ideal interaction site for magnetic and electric fields. Ion channels at the tip of microvilli are connected with the cytoplasm by a bundle of microfilaments forming a diffusion barrier system. Because of its polyelectrolyte nature, the microfilament core of microvilli allows Ca2+ entry into the cytoplasm via nonlinear cable-like cation conduction through arrays of condensed ion clouds. The interaction of ion clouds with periodically applied EMFs and field-induced cation pumping through the cascade of potential barriers on the F-actin polyelectrolyte follows well-known physical principles of ion-magnetic field (MF) interaction and signal discrimination as described by the stochastic resonance and Brownian motor hypotheses. The proposed interaction mechanism is in accord with our present knowledge about Ca2+ signaling as the biological main target of MFs and the postulated extreme sensitivity for coherent excitation by very low field energies within specific amplitude and frequency windows. Microvillar F-actin bundles shielded by a lipid membrane appear to function like electronic integration devices for signal-to-noise enhancement; the influence of coherent signals

Use of historical information in extreme surge frequency estimation: case of the marine flooding on the La Rochelle site in France

Science.gov (United States)

Hamdi, Y.; Bardet, L.; Duluc, C.-M.; Rebour, V.

2014-09-01

Nuclear power plants located in the French Atlantic coast are designed to be protected against extreme environmental conditions. The French authorities remain cautious by adopting a strict policy of nuclear plants flood prevention. Although coastal nuclear facilities in France are designed to very low probabilities of failure (e.g. 1000 year surge), exceptional surges (outliers induced by exceptional climatic events) had shown that the extreme sea levels estimated with the current statistical approaches could be underestimated. The estimation of extreme surges then requires the use of a statistical analysis approach having a more solid theoretical motivation. This paper deals with extreme surge frequency estimation using historical information (HI) about events occurred before the systematic record period. It also contributes to addressing the problem of the presence of outliers in data sets. The frequency models presented in the present paper have been quite successful in the field of hydrometeorology and river flooding but they have not been applied to sea levels data sets to prevent marine flooding. In this work, we suggest two methods of incorporating the HI: the Peaks-Over-Threshold method with HI (POTH) and the Block Maxima method with HI (BMH). Two kinds of historical data can be used in the POTH method: classical Historical Maxima (HMax) data, and Over a Threshold Supplementary (OTS) data. In both cases, the data are structured in historical periods and can be used only as complement to the main systematic data. On the other hand, in the BMH method, the basic hypothesis in statistical modeling of HI is that at least one threshold of perception exists for the whole period (historical and systematic) and that during a giving historical period preceding the period of tide gauging, only information about surges above this threshold have been recorded or archived. The two frequency models were applied to a case study from France, at the La Rochelle site where

Use of historical information in extreme-surge frequency estimation: the case of marine flooding on the La Rochelle site in France

Science.gov (United States)

Hamdi, Y.; Bardet, L.; Duluc, C.-M.; Rebour, V.

2015-07-01

Nuclear power plants located in the French Atlantic coast are designed to be protected against extreme environmental conditions. The French authorities remain cautious by adopting a strict policy of nuclear-plants flood prevention. Although coastal nuclear facilities in France are designed to very low probabilities of failure (e.g., 1000-year surge), exceptional surges (outliers induced by exceptional climatic events) have shown that the extreme sea levels estimated with the current statistical approaches could be underestimated. The estimation of extreme surges then requires the use of a statistical analysis approach having a more solid theoretical motivation. This paper deals with extreme-surge frequency estimation using historical information (HI) about events occurred before the systematic record period. It also contributes to addressing the problem of the presence of outliers in data sets. The frequency models presented in the present paper have been quite successful in the field of hydrometeorology and river flooding but they have not been applied to sea level data sets to prevent marine flooding. In this work, we suggest two methods of incorporating the HI: the peaks-over-threshold method with HI (POTH) and the block maxima method with HI (BMH). Two kinds of historical data can be used in the POTH method: classical historical maxima (HMax) data, and over-a-threshold supplementary (OTS) data. In both cases, the data are structured in historical periods and can be used only as complement to the main systematic data. On the other hand, in the BMH method, the basic hypothesis in statistical modeling of HI is that at least one threshold of perception exists for the whole period (historical and systematic) and that during a giving historical period preceding the period of tide gauging, only information about surges above this threshold have been recorded or archived. The two frequency models were applied to a case study from France, at the La Rochelle site where

A Analysis of the Low Frequency Sound Field in Non-Rectangular Enclosures Using the Finite Element Method.

Science.gov (United States)

Geddes, Earl Russell

The details of the low frequency sound field for a rectangular room can be studied by the use of an established analytic technique--separation of variables. The solution is straightforward and the results are well-known. A non -rectangular room has boundary conditions which are not separable and therefore other solution techniques must be used. This study shows that the finite element method can be adapted for use in the study of sound fields in arbitrary shaped enclosures. The finite element acoustics problem is formulated and the modification of a standard program, which is necessary for solving acoustic field problems, is examined. The solution of the semi-non-rectangular room problem (one where the floor and ceiling remain parallel) is carried out by a combined finite element/separation of variables approach. The solution results are used to construct the Green's function for the low frequency sound field in five rooms (or data cases): (1) a rectangular (Louden) room; (2) The smallest wall of the Louden room canted 20 degrees from normal; (3) The largest wall of the Louden room canted 20 degrees from normal; (4) both the largest and the smallest walls are canted 20 degrees; and (5) a five-sided room variation of Case 4. Case 1, the rectangular room was calculated using both the finite element method and the separation of variables technique. The results for the two methods are compared in order to access the accuracy of the finite element method models. The modal damping coefficient are calculated and the results examined. The statistics of the source and receiver average normalized RMS P('2) responses in the 80 Hz, 100 Hz, and 125 Hz one-third octave bands are developed. The receiver averaged pressure response is developed to determine the effect of the source locations on the response. Twelve source locations are examined and the results tabulated for comparison. The effect of a finite sized source is looked at briefly. Finally, the standard deviation of the

Non-thermal continuous and modulated electromagnetic radiation fields effects on sleep EEG of rats☆

Science.gov (United States)

Mohammed, Haitham S.; Fahmy, Heba M.; Radwan, Nasr M.; Elsayed, Anwar A.

2012-01-01

In the present study, the alteration in the sleep EEG in rats due to chronic exposure to low-level non-thermal electromagnetic radiation was investigated. Two types of radiation fields were used; 900 MHz unmodulated wave and 900 MHz modulated at 8 and 16 Hz waves. Animals has exposed to radiation fields for 1 month (1 h/day). EEG power spectral analyses of exposed and control animals during slow wave sleep (SWS) and rapid eye movement sleep (REM sleep) revealed that the REM sleep is more susceptible to modulated radiofrequency radiation fields (RFR) than the SWS. The latency of REM sleep increased due to radiation exposure indicating a change in the ultradian rhythm of normal sleep cycles. The cumulative and irreversible effect of radiation exposure was proposed and the interaction of the extremely low frequency radiation with the similar EEG frequencies was suggested. PMID:25685416

Non-thermal continuous and modulated electromagnetic radiation fields effects on sleep EEG of rats

Directory of Open Access Journals (Sweden)

Haitham S. Mohammed

2013-03-01

Full Text Available In the present study, the alteration in the sleep EEG in rats due to chronic exposure to low-level non-thermal electromagnetic radiation was investigated. Two types of radiation fields were used; 900 MHz unmodulated wave and 900 MHz modulated at 8 and 16 Hz waves. Animals has exposed to radiation fields for 1 month (1 h/day. EEG power spectral analyses of exposed and control animals during slow wave sleep (SWS and rapid eye movement sleep (REM sleep revealed that the REM sleep is more susceptible to modulated radiofrequency radiation fields (RFR than the SWS. The latency of REM sleep increased due to radiation exposure indicating a change in the ultradian rhythm of normal sleep cycles. The cumulative and irreversible effect of radiation exposure was proposed and the interaction of the extremely low frequency radiation with the similar EEG frequencies was suggested.

Application of equivalent electrodes method to analysis of interaction between ELF-LF electric fields and human body

International Nuclear Information System (INIS)

Ceselkoska, Vesna C.; Velickovic, Dragutin M.

2002-01-01

This paper presents the use of equivalent electrodes method, numerical method, based on surface-charge equation to quantify the interaction of low frequencies electric fields with various models of human body. The evaluation of the electric field intensity on the body surface is performed for a realistic model of the human body. Several examples for different postures of the model are given. (Author)