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Sample records for magnetic fields emf

  1. What Are Electric and Magnetic Fields? (EMF)

    Science.gov (United States)

    ... take for granted. What are electric and magnetic fields? Electric and magnetic fields (EMF) are invisible lines of ... humans. AC electric power produces electric and magnetic fields that create weak electric currents in humans. Being exposed to some kinds ...

  2. Discussion of an EMF (electric and magnetic field) protocol

    Energy Technology Data Exchange (ETDEWEB)

    Afifi, A.A.; Banks, R.S.; Kheifets, L.I.; Newman, B. (Banks (Robert S.) Associates, Inc., Minneapolis, MN (USA))

    1990-07-01

    In 1989, three collaborating cancer research agencies initiated large-scale case-control studies of the postulated association between residential exposure to 50/60-Hz electric and magnetic fields and the induction of childhood leukemia. To facilitate design of the exposure assessment component of these studies, the Electric Power Research Institute sponsored a two-day workshop on February 6--8, 1989. The workshop's objective was to develop a detailed state-of-the science'' protocol for direct and/or surrogate measurements of a subject's EMF exposure history. Emphasis was placed on the difficulties inherent in measuring the exposure of small children. Attendees were divided into three working groups, addressing the following questions, respectively: How can historical exposure best be assessed; what should be measured outdoors; and what should be measured indoors Consensus on a single protocol was not found to be possible, given the state of knowledge about EMF exposure and the pathophysiology of childhood leukemia. However, the discussion produced a comprehensive analysis of the issues involved in addressing the crucial questions of who and what should be measured, and when, where and how these measurements should take place. In particular, discussion focused on: personal monitoring versus area measurements; exposure metrics; relevant time periods over the subjects life for measurement; location and duration of measurements; and protocol development considerations. Attendees expressed strong interest in another, similar workshop sometime in the future. 1 tab.

  3. Environmental Field Surveys, EMF Rapid Program, Engineering Project No.3

    Energy Technology Data Exchange (ETDEWEB)

    Enertech Consultants

    1996-04-01

    The EMF Research and Public Information Dissemination Program (RAPID) includes several engineering research in the area of exposure assessment and source characterization. RAPID engineering project No. 3: ''Environmental Field Surveys'' was performed to obtain information on the levels and characteristics of different environments, for which only limited data were available, especially in comparison to magnetic field data for the residential environment and for electric utility facilities, such as power lines and substations. This project was also to provide information on the contribution of various field sources in the surveyed environments. Magnetic field surveys were performed at four sites for each of five environments: schools, hospitals, office buildings, machine shops, and grocery stores. Of the twenty sites surveyed, 11 were located in the San Francisco Bay Area and 9 in Massachusetts. The surveys used a protocol based on magnetic field measurements and observation of activity patterns, designed to provide estimates of magnetic field exposure by type of people and by type of sources. The magnetic field surveys conducted by this project produced a large amount of data which will form a part of the EMF measurement database Field and exposure data were obtained separately for ''area exposure'' and ''at exposure points''. An exposure point is a location where persons engage in fixed, site specific activities near a local source that creates a significant increase in the area field. The area field is produced by ''area sources'', whose location and field distribution is in general not related to the location of the people in the area.

  4. Sensor-less Field Oriented Control of Wind Turbine Driven Permanent Magnet Synchronous Generator Using Flux Linkage and Back EMF Estimation Methods

    Directory of Open Access Journals (Sweden)

    Porselvi Thayumanavan

    2014-05-01

    Full Text Available The study aims at the speed control of the wind turbine driven Permanent Magnet Synchronous Generator (PMSG by sensor-less Field Oriented Control (FOC method. Two methods of sensor-less FOC are proposed to control the speed and torque of the PMSG. The PMSG and the full-scale converter have an increasing market share in variable speed Wind Energy Conversion System (WECS. When compared to the Induction Generators (IGs, the PMSGs are smaller, easier to control and more efficient. In addition, the PMSG can operate at variable speeds, so that the maximum power can be extracted even at low or medium wind speeds. Wind turbines generally employ speed sensors or shaft position encoders to determine the speed and the position of the rotor. In order to reduce the cost, maintenance and complexity concerned with the sensor, the sensor-less approach has been developed. This study presents the sensor-less control techniques using the flux-linkage and the back EMF estimation methods. Simulations for both the methods are carried out in MATLAB/SIMULINK. The simulated waveforms of the reference speed, the measured speed, the reference torque, the measured torque and rotor position are shown for both the methods.

  5. Electric and Magnetic Fields (EMF) RAPID Program Engineering Project 8: FINAL REPORT, Evaluation of Field Reduction Technologies, Volume 1 (Report) and Volume 2 (Appendices)

    Energy Technology Data Exchange (ETDEWEB)

    Commonwealth Associates, Inc.; IIT Research Institute

    1997-08-01

    This draft report consists of two volumes. Volume 1, the main body, contains an introducto~ sectionj an overview of magnetic fields sectio~ and field reduction technology evaluation section. Magnetic field reduction methods are evalpated for transmission lines, distribution Iines,sulxtations, building wiring applkmd machinery, and transportation systems. The evaluation considers effectiveness, co% and other ftiors. Volume 2 contains five appendices, Append~ A presents magnetic field shielding information. Appendices B and C present design assumptions and magnetic field plots for transmission and distribution lines, respectively. Appendices D and E present cost estimate details for transmission and distribution limes, respectively.

  6. Dispositional aspects of body focus and idiopathic environmental intolerance attributed to electromagnetic fields (IEI-EMF).

    Science.gov (United States)

    Dömötör, Zsuzsanna; Doering, Bettina K; Köteles, Ferenc

    2016-04-01

    Body focus is often considered an undesirable characteristic from medical point of view as it amplifies symptoms and leads to higher levels of health anxiety. However, it is connected to mindfulness, well-being and the sense of self in psychotherapy. The current study aimed to investigate the contribution of various body focus related constructs to acute and chronic generation and maintenance of medically unexplained symptoms (MUS). Thirty-six individuals with idiopathic environmental intolerance to electromagnetic fields (IEI-EMF) and 36 controls were asked to complete questionnaires assessing negative affect, worries about harmful effects of EMFs, health anxiety (HA), body awareness, and somatosensory amplification (SSA), and to report experienced symptoms evoked by a sham magnetic field. Body awareness, HA, SSA, and EMF-related worries showed good discriminative power between individuals with IEI-EMF and controls. Considering all variables together, SSA was the best predictor of IEI-EMF. In the believed presence of a MF, people with IEI-EMF showed higher levels of anxiety and reported more symptoms than controls. In the IEI-EMF group, actual symptom reports were predicted by HA and state anxiety, while a reverse relationship between symptom reports and HA was found in the control group. Our findings show that SSA is a particularly important contributor to IEI-EMF, probably because it is the most comprehensive factor in its aetiology. IEI-EMF is associated with both a fear-related monitoring of bodily symptoms and a non-evaluative body focus. The identification of dispositional body focus may be relevant for the management of MUS.

  7. EMF-research 1993-2003[Health hazards from Electromagnetic fields]; EMF-forskning 1993-2003

    Energy Technology Data Exchange (ETDEWEB)

    Lundberg, Petra; Lindgren, Rolf [SwedPower AB, Stockholm (Sweden)

    2005-09-01

    This report summarises 10 years of research on power frequency electric and magnetic fields. Cancer is the topic for which most research has been carried out during the 10-year-period. Epidemiological studies have shown statistical correlations between long time exposure to magnetic fields and a few forms of cancer. The most obvious correlation is between childhood leukaemia and magnetic fields from power lines. However, the correlations correspond to very small increases in risk and since there is no experimental evidence and no trustworthy mechanism exists, a cause-and-effect relationship cannot be established. Furthermore, there are also comprehensive and well-performed studies which show no correlations. Some studies indicate a correlation between electric and magnetic fields and cognitive functions and diffuse central nervous symptoms. The results show correspondence with the hypothesis that magnetic fields cause a chronic stress effect to the central nervous system. A relatively strong correlation has been shown between ALS (amyotrophic lateral sclerosis) and electricity related labour. EMF is however only one of several conceivable explanations. An equivalent, although weaker, correlation has also been shown for Alzheimer's decease. It can be stated that frequent electric and magnetic fields do not seem to have any influence on reproducibility, such as damage on the foetus or negative effects on the reproduction in humans or animals. A potentially important area is the effect on the immune system in humans and animals. In fact, it has been noted that magnetic fields may activate the immune system whilst long term exposure seems to impoverish the capacity of the immune system. The research on field variables and connected mechanisms shows that intermittent magnetic fields have stronger biological impact than continuous fields. Another observation is that biological effects often appear as window effects in amplitude, frequency and sometimes even in time

  8. RF-EMF exposure of fetus and mother during magnetic resonance imaging

    Science.gov (United States)

    Pediaditis, M.; Leitgeb, N.; Cech, R.

    2008-12-01

    Magnetic resonance imaging (MRI) avoids risks of genetic damage but may be associated with excess heating of body tissues. To investigate the exposure to MRI radio-frequency (RF) electromagnetic fields (EMF), low-pass and high-pass birdcage coils were simulated and the whole-body pregnant woman model SILVY used to determine local and whole-body specific absorption rates (SAR) in mother and fetus. Resonant RF-EMF of MRI devices were investigated at 0.3, 1, 1.5, 2, 3 and 4 T. Results allow extrapolation also to higher fields. They showed that local SAR in mother's trunk reaches exposure limits first. However, data show that during abdominal MRI meeting exposure limits of the mother is not sufficient to protect the fetus if limits of the general populations are applied to it. In that case fetal whole-body SAR exceeds limits by 7.4-fold. It is up to the physician and/or the ethics commission to decide upon justification for abdominal MRI of pregnant women if limits are exceeded. The results indicate the need for specifically addressing fetal exposure to EMF and elaborating general recommendations by radiation protection bodies.

  9. Retraction: Evaluation of carcinogenic effects of electromagnetic fields (EMF).

    Science.gov (United States)

    Mehic, Bakir

    2010-11-01

    The Editor-in-chief of the Bosnian Journal of Basic Medical Sciences has decided to retract the article from Bayazit V et al. [1] entitled as: "Evaluation of carcinogenic effects of electromagnetic fields (EMF)" published in Bosn J Basic Med Sci. 2010 Aug;10(3):245-50. After the editorial office was alerted of possible plagiarism in the article, it conducted thorough investigation and concluded that the article apparently represents plagiarized material from two World Health Organization reports, one European Commission report and other sources. Since this is considered scientific plagiarism and scientific misconduct, Editor-in-chief has decided to withdraw the article. The authors have agreed with the editorial office decision.

  10. 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.

  11. Idiopathic environmental intolerance attributed to electromagnetic fields (IEI-EMF): A systematic review of identifying criteria

    OpenAIRE

    Baliatsas Christos; Van Kamp Irene; Lebret Erik; Rubin G

    2012-01-01

    Abstract Background Idiopathic environmental intolerance attributed to electromagnetic fields (IEI-EMF) remains a complex and unclear phenomenon, often characterized by the report of various, non-specific physical symptoms (NSPS) when an EMF source is present or perceived by the individual. The lack of validated criteria for defining and assessing IEI-EMF affects the quality of the relevant research, hindering not only the comparison or integration of study findings, but also the identificati...

  12. Idiopathic environmental intolerance attributed to electromagnetic fields (IEI-EMF): A systematic review of identifying criteria

    NARCIS (Netherlands)

    Baliatsas, C.; van Kamp, I.; Lebret, E.; Rubin, J.G.

    2012-01-01

    ABSTRACT: BACKGROUND: Idiopathic environmental intolerance attributed to electromagnetic fields (IEI-EMF) remains a complex and unclear phenomenon, often characterized by the report of various, non-specific physical symptoms (NSPS) when an EMF source is present or perceived by the individual. The la

  13. 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

    2016-09-01

    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.

  14. 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

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

    Directory of Open Access Journals (Sweden)

    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.

  16. Electromagnetic fields (EMF): do they play a role in children's environmental health (CEH)?

    Science.gov (United States)

    Otto, Matthias; von Mühlendahl, Karl Ernst

    2007-10-01

    Possible adverse health effects of exposure to electric, magnetic and electromagnetic fields (EMF), and especially the question of whether there exists a special vulnerability of children, have been a much discussed topic during the last two decades. Static fields produce health effects only in very rare and exceptional circumstances at extremely high field intensities. As for low-frequency EMF, the results of epidemiological research with respect to childhood leukaemia prompted the International Agency for Research on Cancer (IARC) in 2001 to classify these fields as "possibly carcinogenic to humans". Current hypotheses on the mechanism of such action are presented. The effect, if existent, appears to be not very important in relation to established other causes of childhood leukaemia. High-frequency EMF, as used in mobile and wireless communication (mobile telephony according to the GSM and UMTS standard, cordless DECT phones, wireless local area networks (WLAN), Bluetooth) and since many decades also in radio and television technology, are practically omnipresent. At high intensities, the generation of heat is the principal effect. Current guidelines, limits and regulations prevent any such effect. Mobile phone calls may, in certain circumstances, lead to local exposures close to limit values. Base stations typically produce exposures lower by 2-5 magnitudes. The discussion centres on the so-called non-thermal effects, which are supposedly occurring at field intensities, which are by orders of magnitude lower than those responsible for thermal effects. The reproducibility of these effects is usually poor, and no physiologic or pathogenic mechanism, so far, has been found to explain the alleged effects. Equally, epidemiologic studies have not furnished clear and reproducible data as arguments for negative health effects. Final results of the INTERPHONE study on the risk of brain tumours, acoustic neurinoma and parotid gland tumours associated with the use of

  17. Idiopathic environmental intolerance attributed to electromagnetic fields (IEI-EMF: A systematic review of identifying criteria

    Directory of Open Access Journals (Sweden)

    Baliatsas Christos

    2012-08-01

    Full Text Available Abstract Background Idiopathic environmental intolerance attributed to electromagnetic fields (IEI-EMF remains a complex and unclear phenomenon, often characterized by the report of various, non-specific physical symptoms (NSPS when an EMF source is present or perceived by the individual. The lack of validated criteria for defining and assessing IEI-EMF affects the quality of the relevant research, hindering not only the comparison or integration of study findings, but also the identification and management of patients by health care providers. The objective of this review was to evaluate and summarize the criteria that previous studies employed to identify IEI-EMF participants. Methods An extensive literature search was performed for studies published up to June 2011. We searched EMBASE, Medline, Psychinfo, Scopus and Web of Science. Additionally, citation analyses were performed for key papers, reference sections of relevant papers were searched, conference proceedings were examined and a literature database held by the Mobile Phones Research Unit of King’s College London was reviewed. Results Sixty-three studies were included. “Hypersensitivity to EMF” was the most frequently used descriptive term. Despite heterogeneity, the criteria predominantly used to identify IEI-EMF individuals were: 1. Self-report of being (hypersensitive to EMF. 2. Attribution of NSPS to at least one EMF source. 3. Absence of medical or psychiatric/psychological disorder capable of accounting for these symptoms 4. Symptoms should occur soon (up to 24 hours after the individual perceives an exposure source or exposed area. (Hypersensitivity to EMF was either generalized (attribution to various EMF sources or source-specific. Experimental studies used a larger number of criteria than those of observational design and performed more frequently a medical examination or interview as prerequisite for inclusion. Conclusions Considerable heterogeneity exists in the

  18. Microwave frequency electromagnetic fields (EMFs) produce widespread neuropsychiatric effects including depression.

    Science.gov (United States)

    Pall, Martin L

    2016-09-01

    Non-thermal microwave/lower frequency electromagnetic fields (EMFs) act via voltage-gated calcium channel (VGCC) activation. Calcium channel blockers block EMF effects and several types of additional evidence confirm this mechanism. Low intensity microwave EMFs have been proposed to produce neuropsychiatric effects, sometimes called microwave syndrome, and the focus of this review is whether these are indeed well documented and consistent with the known mechanism(s) of action of such EMFs. VGCCs occur in very high densities throughout the nervous system and have near universal roles in release of neurotransmitters and neuroendocrine hormones. Soviet and Western literature shows that much of the impact of non-thermal microwave exposures in experimental animals occurs in the brain and peripheral nervous system, such that nervous system histology and function show diverse and substantial changes. These may be generated through roles of VGCC activation, producing excessive neurotransmitter/neuroendocrine release as well as oxidative/nitrosative stress and other responses. Excessive VGCC activity has been shown from genetic polymorphism studies to have roles in producing neuropsychiatric changes in humans. Two U.S. government reports from the 1970s to 1980s provide evidence for many neuropsychiatric effects of non-thermal microwave EMFs, based on occupational exposure studies. 18 more recent epidemiological studies, provide substantial evidence that microwave EMFs from cell/mobile phone base stations, excessive cell/mobile phone usage and from wireless smart meters can each produce similar patterns of neuropsychiatric effects, with several of these studies showing clear dose-response relationships. Lesser evidence from 6 additional studies suggests that short wave, radio station, occupational and digital TV antenna exposures may produce similar neuropsychiatric effects. Among the more commonly reported changes are sleep disturbance/insomnia, headache, depression

  19. Modelling indoor electromagnetic fields (EMF) from mobile phone base stations for epidemiological studies

    NARCIS (Netherlands)

    Beekhuizen, J.; Vermeulen, R.; van Eijsden, M.; van Strien, R.; Bürgi, A.; Loomans, E.; Guxens, M.; Kromhout, H.; Huss, A.

    2014-01-01

    Radio frequency electromagnetic fields (RF-EMF) from mobile phone base stations can be reliably modelled for outdoor locations, using 3D radio wave propagation models that consider antenna characteristics and building geometry. For exposure assessment in epidemiological studies, however, it is espec

  20. International policy and advisory response regarding children's exposure to radio frequency electromagnetic fields (RF-EMF).

    Science.gov (United States)

    Redmayne, Mary

    2016-01-01

    Radiofrequency electromagnetic field (RF-EMF) exposure regulations/guidelines generally only consider acute effects, and not chronic, low exposures. Concerns for children's exposure are warranted due to the amazingly rapid uptake of many wireless devices by increasingly younger children. This review of policy and advice regarding children's RF-EMF exposure draws material from a wide variety of sources focusing on the current situation. This is not a systematic review, but aims to provide a representative cross-section of policy and advisory responses within set boundaries. There are a wide variety of approaches which I have categorized and tabulated ranging from ICNIRP/IEEE guidelines and "no extra precautions needed" to precautionary or scientific much lower maxima and extensive advice to minimize RF-EMF exposure, ban advertising/sale to children, and add exposure information to packaging. Precautionary standards use what I term an exclusion principle. The wide range of policy approaches can be confusing for parents/carers of children. Some consensus among advisory organizations would be helpful acknowledging that, despite extensive research, the highly complex nature of both RF-EMF and the human body, and frequent technological updates, means simple assurance of long-term safety cannot be guaranteed. Therefore, minimum exposure of children to RF-EMF is recommended. This does not indicate need for alarm, but mirrors routine health-and-safety precautions. Simple steps are suggested. ICNIRP guidelines need to urgently publish how the head, torso, and limbs' exposure limits were calculated and what safety margin was applied since this exposure, especially to the abdomen, is now dominant in many children.

  1. Optimization of measurement methods for a multi-frequency electromagnetic field from mobile phone base station using broadband EMF meter

    Directory of Open Access Journals (Sweden)

    Paweł Bieńkowski

    2015-10-01

    Full Text Available Background: This paper presents the characteristics of the mobile phone base station (BS as an electromagnetic field (EMF source. The most common system configurations with their construction are described. The parameters of radiated EMF in the context of the access to methods and other parameters of the radio transmission are discussed. Attention was also paid to antennas that are used in this technology. Material and Methods: The influence of individual components of a multi-frequency EMF, most commonly found in the BS surroundings, on the resultant EMF strength value indicated by popular broadband EMF meters was analyzed. The examples of metrological characteristics of the most common EMF probes and 2 measurement scenarios of the multisystem base station, with and without microwave relays, are shown. Results: The presented method for measuring the multi-frequency EMF using 2 broadband probes allows for the significant minimization of measurement uncertainty. Equations and formulas that can be used to calculate the actual EMF intensity from multi-frequency sources are shown. They have been verified in the laboratory conditions on a specific standard setup as well as in real conditions in a survey of the existing base station with microwave relays. Conclusions: Presented measurement methodology of multi-frequency EMF from BS with microwave relays, validated both in laboratory and real conditions. It has been proven that the described measurement methodology is the optimal approach to the evaluation of EMF exposure in BS surrounding. Alternative approaches with much greater uncertainty (precaution method or more complex measuring procedure (sources exclusion method are also presented. Med Pr 2015;66(5:701–712

  2. Electric and Magnetic Fields | RadTown USA | US EPA

    Science.gov (United States)

    2017-08-07

    Electromagnetic fields (EMF) are a combination of electric and magnetic fields of energy that surround any electrical device when it is plugged in and turned on. Scientific experiments have not clearly shown whether or not exposure to EMF increases cancer risk. Scientists continue to study the issue.

  3. Non-specific physical symptoms in relation to actual and perceived exposure to electromagnetic fields (EMF) : A multidisciplinary approach

    NARCIS (Netherlands)

    Baliatsas, C.

    2015-01-01

    The association between non-specific physical symptoms (NSPS) such as headache, fatigue, nausea and sleep problems and exposure to electromagnetic fields (EMF) in the general population has been a subject of ongoing scientific debate and public concern. A limited number of epidemiological studies ha

  4. Health risks of electromagnetic fields. Part I: Evaluation and assessment of electric and magnetic fields.

    Science.gov (United States)

    Habash, Riadh W Y; Brodsky, Lynn M; Leiss, William; Krewski, Daniel; Repacholi, Michael

    2003-01-01

    Exposure to electric and magnetic fields (EMF) emanating from the generation, distribution, and utilization of electricity is widespread. The major debate in recent years has focused on the possibility that exposure to EMF may result in adverse health consequences, including the development of cancer. This article provides a review and evaluation of potential health risks associated with residential and occupational exposure to EMF. In addition to reviewing data from laboratory, epidemiology, and clinical studies, we examine exposure data from field measurement surveys and exposure guidelines that have been established for EMF. Currently, the evidence in support of an association between EMF and childhood cancer is limited, although this issue warrants further investigation. Evidence of an association between EMF exposure and adult cancers, derived largely from occupational settings, is inconsistent, precluding clear conclusions. There is little evidence of an association between EMF and noncancer health effects. Epidemiological studies of EMF and population health are limited by exposure measurement error and the lack of a clear dose/response relationship in studies suggesting possible health risks. Further research is needed to clarify the ambiguous findings from present studies and to determine if EMF exposure poses a health risk.

  5. In vitro developmental neurotoxicity following chronic exposure to 50 Hz extremely low frequency electromagnetic fields (ELF-EMF) in primary rat cortical cultures

    NARCIS (Netherlands)

    de Groot, Martje W G D M; van Kleef, Regina G D M; de Groot, Aart; Westerink, Remco H S

    2016-01-01

    Exposure to 50-60 Hz extremely low frequency electromagnetic fields (ELF-EMFs) has increased considerably over the last decades. Several epidemiological studies suggested that ELF-EMF exposure is associated with adverse health effects, including neurotoxicity. However, these studies are debated as r

  6. Effects of four kinds of electromagnetic fields (EMF) with different frequency spectrum bands on ovariectomized osteoporosis in mice.

    Science.gov (United States)

    Lei, Tao; Li, Feijiang; Liang, Zhuowen; Tang, Chi; Xie, Kangning; Wang, Pan; Dong, Xu; Shan, Shuai; Liu, Juan; Xu, Qiaoling; Luo, Erping; Shen, Guanghao

    2017-04-03

    Electromagnetic fields (EMF) was considered as a non-invasive modality for treatment of osteoporosis while the effects were diverse with EMF parameters in time domain. In present study, we extended analysis of EMF characteristics from time domain to frequency domain, aiming to investigate effects of four kinds of EMF (LP (1-100 Hz), BP (100-3,000 Hz), HP (3,000-50,000 Hz) and AP (1-50,000 Hz)) on ovariectomized (OVX) osteoporosis (OP) in mice. Forty-eight 3-month-old female BALB/c mice were equally assigned to Sham, OVX, OVX + LP, OVX + BP, OVX + HP and OVX + AP groups (n = 8). After 8-week exposure (3 h/day), LP and BP significantly increased serum bone formation markers and osteogenesis-related gene expressions compared with OVX. Bedsides, LP and BP also slightly increased bone resorption activity compared with OVX, evidenced by increased RANKL/OPG ratio. HP sharply decreased serum bone formation and resporption markers and osteogenesis and osteoclastogenesis related gene expressions compared with OVX. AP had accumulative effects of LP, BP and HP, which significantly increased bone formation and decreased bone resporption activity compared with OVX. As a result, LP, BP and HP exposure did not later deterioration of bone mass, microarchitecture and mechanical strength in OVX mice with OP. However, AP stimulation attenuated OVX-induced bone loss.

  7. EMF exposure assessment in the Finnish garment industry: evaluation of proposed EMF exposure metrics.

    Science.gov (United States)

    Hansen, N H; Sobel, E; Davanipour, Z; Gillette, L M; Niiranen, J; Wilson, B W

    2000-01-01

    Recently published studies indicate that having worked in occupations that involve moderate to high electromagnetic field (EMF) exposure is a risk factor for neurodegenerative diseases, including Alzheimer's disease. In these studies, the occupational groups most over-represented for EMF exposure comprised seamstresses, dressmakers, and tailors. Future epidemiologic studies designed to evaluate the possibility of a causal relationship between exposure to EMF and a neuro degenerative disease endpoint such as incidence of Alzheimer's disease, will benefit from the measurement of electromagnetic field metrics with potential biological relevance. Data collection methodology in such studies would be highly dependent upon how the metrics are defined. In this research the authors developed and demonstrated (1) protocols for collecting EMF exposure data suitable for estimating a variety of exposure metrics that may have biological relevance, and (2) analytical methods for calculation of these metrics. The authors show how exposure might be estimated under each of the three prominent EMF health-effects mechanism theories and evaluate the assertion that relative exposure ranking is dependent on which mechanism is assumed. The authors also performed AC RMS magnetic flux density measurements, confirming previously reported findings. The results indicate that seamstresses, as an occupational group, should be considered for study of the possible health effects of long-term EMF exposure.

  8. Magnetic Field

    DEFF Research Database (Denmark)

    Olsen, Nils

    2015-01-01

    of the fluid flow at the top of the core. However, what is measured at or near the surface of the Earth is the superposition of the core field and fields caused by magnetized rocks in the Earth’s crust, by electric currents flowing in the ionosphere, magnetosphere, and oceans, and by currents induced......he Earth has a large and complicated magnetic field, the major part of which is produced by a self-sustaining dynamo operating in the fluid outer core. Magnetic field observations provide one of the few tools for remote sensing the Earth’s deep interior, especially regarding the dynamics...... in the Earth by time-varying external fields. These sources have their specific characteristics in terms of spatial and temporal variations, and their proper separation, based on magnetic measurements, is a major challenge. Such a separation is a prerequisite for remote sensing by means of magnetic field...

  9. The WHO EMF Project: Legitimating the Imaginary of Global Harmonization of EMF Safety Standards

    Directory of Open Access Journals (Sweden)

    David Mercer

    2016-06-01

    Full Text Available An important topic for studies of STS and globalization are the ways “global” institutions create and attempt to implement health guidelines and safety standards to address risks associated with new technologies. In the following discussion this topic is examined through a case study of the activities of the World Health Organization’s Electric and Magnetic Field Project (WHO EMF Project. EMF exposures are associated with telecommunications and electrical infrastructure, most notably high voltage power-lines, radio and cell towers and the use of mobile telephones. The controversy over setting international safety standards and health guidelines has simmered for a number of decades. The mainstream “regulatory science” position has been that it is unlikely EMF’s constitute a significant health risk and therefore minimal regulatory intervention or significant precautionary considerations are required. A small but persistent stream of scientific studies nevertheless have continued to raise significant health concerns and have led to calls for regulators to build stronger precautionary approaches into EMF standards and guidelines. The WHO EMF project was established in 1996 in an attempt to discourage this situation leading to different nation states adopting strong precautionary approaches and developing a diversity of national EMF safety standards and health guidelines. In the following discussion I will explore the history of the WHO EMF Project and the strategies it has used to pursue its goal of global harmonization of EMF science, safety standards and guidelines. Three important strategies used by the WHO EMF Project have involved: appeals to technological determinism, developing bespoke models for sound science, and setting the boundaries between science and policy to attempt to exclude their opponents from the policy making arena.

  10. EMF Rapid Program Engineering Projects, Project 1, Development of Recommendations for Guidelines for Field Source Measurement

    Energy Technology Data Exchange (ETDEWEB)

    Electric Research and Management, Inc.

    1997-03-11

    The goal of this project is to develop a protocol for measuring the electric and magnetic fields around sources. Data from these measurements may help direct future biological effects research by better defining the complexity of magnetic and electric fields to which humanity is exposed, as well asprovide the basis for rigorous field exposure analysis and risk assessment once the relationship between field exposure and biological response. is better understood. The data base also should have sufficient spatial and temporal characteristics to guide electric and magnetic field management. The goal of Task A is to construct a set of characteristics that would be ideal to have for guiding and interpreting biological studies and for focusing any future effort at field management. This ideal set will then be quantified and reduced according to the availability (or possible development of) instrumentation to measure the desired characteristics. Factors that also will be used to define pragmatic data sets will be the cost of collecting the data, the cost of developing an adequate data base, and the needed precision in measuring specific characteristics. A field, electric or magnetic, will always be ,some function of time and space. The first step in this section of the protocol development will be to determine what span of time and what portion of space are required to quantify the electric and magnetic fields around sources such as appliances and electrical apparatus. Constraints on time will be set by examining measurement limitations and biological data requirements.

  11. Assessment of the neurotoxic potential of exposure to 50Hz extremely low frequency electromagnetic fields (ELF-EMF) in naïve and chemically stressed PC12 cells

    NARCIS (Netherlands)

    de Groot, Martje W G D M; Kock, Marjolijn D M; Westerink, Remco H S

    2014-01-01

    Increasing exposure to extremely low frequency electromagnetic fields (ELF-EMF), generated by power lines and electric appliances, raises concern about potential adverse health effects of ELF-EMF. The central nervous system is expected to be particularly vulnerable to ELF-EMF as its function strongl

  12. Effects of time-variant extremely low-frequency (ELF) electromagnetic fields (EMF) on cholinesterase activity in Dictyostelium discoideum (Protista).

    Science.gov (United States)

    Amaroli, Andrea; Trielli, Francesca; Bianco, Bruno; Giordano, Stefano; Moggia, Elsa; Corrado, Maria U Delmonte

    2005-12-15

    Recently, we detected propionylcholinesterase (PrChE) activity in single-cell amoebae of Dictyostelium discoideum using cytochemical, electrophoretic, and spectrophotometric methods. The involvement of this enzyme activity in cell-cell and cell-environment interactions was suggested. In this work, we found that exposure of single-cell amoebae to an extremely low-frequency electromagnetic fields (ELF-EMF) of 300 microT, 50 Hz, from 1 h up to 48 h at 21 +/- 1 degrees C affected PrChE activity.

  13. 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.

  14. Improving Precautionary Communication in the EMF Field? Effects of Making Messages Consistent and Explaining the Effectiveness of Precautions.

    Science.gov (United States)

    Boehmert, Christoph; Wiedemann, Peter; Croft, Rodney

    2016-10-09

    Many radiation health agencies communicate precautionary measures regarding the use of mobile communication devices, e.g. the use of a headset while talking on the phone. These precautionary messages have, however, been shown to unintentionally increase risk perceptions about radiofrequency electromagnetic fields (RF-EMFs). The current study tested two potential ways of amending precautionary messages in order to minimise this unintentional effect. Firstly, the messages' potential to be perceived as inconsistent and thereby raise suspicions was addressed; secondly, the effectiveness of the precautions was explained. An experimental design was applied in which a quota sample of 1717 Australian residents was randomly assigned to one of six message conditions. Three different risk perception measures served as dependent variables, two of them are conditional measures. The original effect of precautionary messages to amplify risk perceptions could not be replicated. Furthermore, amending precautionary messages in favour of more consistency had no effect, while explaining the effectiveness of the precautions increased conditional risk perception under the condition that no precautions are taken. This was contrary to our assumptions. We infer from these results that changing precautionary messages in terms of consistency and effectiveness in order to reduce risk perception is hardly possible. The use of conditional risk perception measures seems fruitful for studies looking at the effects of precautionary or protective messages, given that previous studies have only investigated effects on unconditional risk perception. However, the present results should not be over-interpreted as the measures' validity in the EMF context still needs further investigation.

  15. Improving Precautionary Communication in the EMF Field? Effects of Making Messages Consistent and Explaining the Effectiveness of Precautions

    Science.gov (United States)

    Boehmert, Christoph; Wiedemann, Peter; Croft, Rodney

    2016-01-01

    Many radiation health agencies communicate precautionary measures regarding the use of mobile communication devices, e.g. the use of a headset while talking on the phone. These precautionary messages have, however, been shown to unintentionally increase risk perceptions about radiofrequency electromagnetic fields (RF-EMFs). The current study tested two potential ways of amending precautionary messages in order to minimise this unintentional effect. Firstly, the messages’ potential to be perceived as inconsistent and thereby raise suspicions was addressed; secondly, the effectiveness of the precautions was explained. An experimental design was applied in which a quota sample of 1717 Australian residents was randomly assigned to one of six message conditions. Three different risk perception measures served as dependent variables, two of them are conditional measures. The original effect of precautionary messages to amplify risk perceptions could not be replicated. Furthermore, amending precautionary messages in favour of more consistency had no effect, while explaining the effectiveness of the precautions increased conditional risk perception under the condition that no precautions are taken. This was contrary to our assumptions. We infer from these results that changing precautionary messages in terms of consistency and effectiveness in order to reduce risk perception is hardly possible. The use of conditional risk perception measures seems fruitful for studies looking at the effects of precautionary or protective messages, given that previous studies have only investigated effects on unconditional risk perception. However, the present results should not be over-interpreted as the measures’ validity in the EMF context still needs further investigation. PMID:27735851

  16. Exposure Knowledge and Risk Perception of RF EMF

    Science.gov (United States)

    Freudenstein, Frederik; Wiedemann, Peter M.; Varsier, Nadège

    2015-01-01

    The presented study is part of the EU-Project Low EMF Exposure Future Networks (LEXNET), which deals among other things with the issue of whether a reduction of the radiofrequency (RF) electro-magnetic fields (EMF) exposure will result in more acceptance of wireless communication networks in the public sphere. We assume that the effects of any reduction of EMF exposure will depend on the subjective link between exposure perception and risk perception (RP). Therefore we evaluated respondents’ RP of different RF EMF sources and their subjective knowledge about various exposure characteristics with regard to their impact on potential health risks. The results show that participants are more concerned about base stations than about all other RF EMF sources. Concerning the subjective exposure knowledge the results suggest that people have a quite appropriate impact model. The question how RF EMF RP is actually affected by the knowledge about the various exposure characteristics was tested in a linear regression analysis. The regression indicates that these features – except distance – do influence people’s general RF EMF RP. In addition, we analyzed the effect of the quality of exposure knowledge on RF EMF RP of various sources. The results show a tendency that better exposure knowledge leads to higher RP, especially for mobile phones. The study provides empirical support for models of the relationships between exposure perception and RP. It is not the aim to extrapolate these findings to the whole population because the samples are not exactly representative for the general public in the participating countries. PMID:25629026

  17. Exposure knowledge and risk perception of RF EMF

    Directory of Open Access Journals (Sweden)

    Frederik eFreudenstein

    2015-01-01

    Full Text Available The presented study is part of the EU Project LEXNET (Low EMF Exposure Future Networks, which deals among other things with the issue of whether a reduction of the radiofrequency (RF electro-magnetic fields (EMF exposure will result in more acceptance of wireless communication networks in the public sphere.We assume that the effects of any reduction of EMF exposure will depend on the subjective link between exposure perception and risk perception. Therefore we evaluated respondents’ risk perceptions of different RF EMF sources and their subjective knowledge about various exposure characteristics with regard to their impact on potential health risks. The results show that participants are more concerned about base stations than about all other RF EMF sources. Concerning the subjective exposure knowledge the results suggest that people have a quite appropriate impact model. The question how RF EMF risk perception is actually affected by the knowledge about the various exposure characteristics was tested in a linear regression analysis. The regression indicates that these features - except distance - do influence people’s general RF EMF risk perceptions. In addition, we analyzed the effect of the quality of exposure knowledge on RF EMF risk perception of various sources. The results show a tendency that better exposure knowledge leads to higher risk perception, especially for mobile phones. The study provides empirical support for models of the relationships between exposure perception and risk perception. It is not the aim to extrapolate these findings to the whole population because the samples are not exactly representative for the general public in the participating countries.

  18. Radio-frequency electromagnetic field (RF-EMF) exposure levels in different European outdoor urban environments in comparison with regulatory limits

    NARCIS (Netherlands)

    Urbinello, Damiano; Joseph, Wout; Huss, Anke; Verloock, Leen; Beekhuizen, Johan; Vermeulen, Roel; Martens, Luc; Röösli, Martin

    2014-01-01

    Background: Concerns of the general public about potential adverse health effects caused by radio-frequency electromagnetic fields (RF-EMFs) led authorities to introduce precautionary exposure limits, which vary considerably between regions. It may be speculated that precautionary limits affect the

  19. Improving Precautionary Communication in the EMF Field? Effects of Making Messages Consistent and Explaining the Effectiveness of Precautions

    Directory of Open Access Journals (Sweden)

    Christoph Boehmert

    2016-10-01

    Full Text Available Many radiation health agencies communicate precautionary measures regarding the use of mobile communication devices, e.g. the use of a headset while talking on the phone. These precautionary messages have, however, been shown to unintentionally increase risk perceptions about radiofrequency electromagnetic fields (RF-EMFs. The current study tested two potential ways of amending precautionary messages in order to minimise this unintentional effect. Firstly, the messages’ potential to be perceived as inconsistent and thereby raise suspicions was addressed; secondly, the effectiveness of the precautions was explained. An experimental design was applied in which a quota sample of 1717 Australian residents was randomly assigned to one of six message conditions. Three different risk perception measures served as dependent variables, two of them are conditional measures. The original effect of precautionary messages to amplify risk perceptions could not be replicated. Furthermore, amending precautionary messages in favour of more consistency had no effect, while explaining the effectiveness of the precautions increased conditional risk perception under the condition that no precautions are taken. This was contrary to our assumptions. We infer from these results that changing precautionary messages in terms of consistency and effectiveness in order to reduce risk perception is hardly possible. The use of conditional risk perception measures seems fruitful for studies looking at the effects of precautionary or protective messages, given that previous studies have only investigated effects on unconditional risk perception. However, the present results should not be over-interpreted as the measures’ validity in the EMF context still needs further investigation.

  20. 家用和类似用途器具电磁场(EMF)的测量%Electromagnetic Fields (EMF) Measurement for Household and Similar Electrical Appliances

    Institute of Scientific and Technical Information of China (English)

    王晓燕

    2005-01-01

    The requirement of Electromagnetic Fields had been added into Low Voltage Directive, the test introduces the actuality of Electromagnetic Fields measurement, focuses in electromagnetic fields evaluation and measurement for household and similar electrical appliances.

  1. Extraction of the anomaly magnetic field of the earth from stratospheric balloon magnetic surveys at altitudes of 20-40 km

    Science.gov (United States)

    Tsvetkov, Yu. P.; Kuznetsov, V. D.; Golovkov, V. P.; Brekhov, O. M.; Pelle, V. A.; Krapivnyi, A. V.; Nikolaev, N. S.

    2011-01-01

    The solution to the problem of extraction of the anomaly Earth's magnetic field (EMF) from stratospheric balloon magnetic surveys with the help of global analytical models of the normal EMF is proposed. In the problem solution, errors for the analytical models of the normal EMF and its secular variation at a set moment of time are assessed; the found error is introduced as a correction to the extracted anomaly EMF. The error of the model is determined in the places where significant magnetic anomalies are absent. In this case, the error of the model corresponds to deviations of the normal EMF components, synthesized by coefficients of analytical models, and to deviations of the EMF secular variations from the measured values at quite a low value of the variable EMF or one being taken into account. These places are determined when carrying out additional measurements in vertical gradients of the EMF with the use of scalar magnetometers at the gauge length of 6 km. It has been shown that the found places can be considered as nonanomaly, if the difference of values of the anomaly EMF at the gauge length of 6 km does not exceed 1.5 nT within the profile's portion of about 100 km in length. An experiment in nature has revealed that errors for the IGRF-2005 and IGRF-2010 models, corrected for secular variation of the EMF, can reach 200 and 140 nT, respectively, within the limits of the territory where the Kama-Emba magnetic anomaly is located; these errors are determined by the considered causes. Comparison of aerostatic profiles of magnetic anomalies with data on the anomaly EMF, derived from the maps, has shown that the realizations derived from the maps contain overestimated negative values of the anomaly EMF, because they reflect processes in the near-surface layer of the Earth's crust. This fact causes the situation when attempts to recalculate the anomaly EMF into the upper half-space by the near-surface data still have not been successful. Only realizations

  2. Cell biology and EMF safety standards.

    Science.gov (United States)

    Blank, Martin

    2015-01-01

    Living cells react defensively and start to synthesize stress proteins when exposed to potentially harmful stimuli. Electromagnetic fields (EMF) are among the many different environmental stimuli that initiate stress protein synthesis. Although there is greater energy transfer and heating due to EMF at higher frequencies, there is no greater stress response. The cellular stress response is far more sensitive to EMF than to an increase in temperature. It should be obvious that an EMF safety standard should be based on the more sensitive, natural biological response.

  3. Magnetic Field Calculator

    Data.gov (United States)

    National Oceanic and Atmospheric Administration, Department of Commerce — The Magnetic Field Calculator will calculate the total magnetic field, including components (declination, inclination, horizontal intensity, northerly intensity,...

  4. 50-60 Hz electric and magnetic field effects on cognitive function in humans: A review

    Energy Technology Data Exchange (ETDEWEB)

    Crasson, M

    2003-07-01

    This paper reviews the effect of 50-60 Hz weak electric, magnetic and combined electric and magnetic field exposure on cognitive functions such as memory, attention, information processing and time perception, as determined by electroencephalographic methods and performance measures. Overall, laboratory studies, which have investigated the acute effects of power frequency fields on cognitive functioning in humans are heterogeneous, in terms of both electric and magnetic field (EMF) exposure and the experimental design and measures used. Results are inconsistent and difficult to interpret with regard to functional relevance for possible health risks. Statistically significant differences between field and control exposure, when they are found, are small, subtle, transitory, without any clear dose-response relationship and difficult to reproduce. The human performance or event related potentials (ERPs) measures that might specifically be affected by EMF exposure, as well as a possible cerebral structure or function that could be more sensitive to EMF, cannot be better determined. (author)

  5. Assessment of the neurotoxic potential of exposure to 50Hz extremely low frequency electromagnetic fields (ELF-EMF) in naïve and chemically stressed PC12 cells.

    Science.gov (United States)

    de Groot, Martje W G D M; Kock, Marjolijn D M; Westerink, Remco H S

    2014-09-01

    Increasing exposure to extremely low frequency electromagnetic fields (ELF-EMF), generated by power lines and electric appliances, raises concern about potential adverse health effects of ELF-EMF. The central nervous system is expected to be particularly vulnerable to ELF-EMF as its function strongly depends on electrical excitability. We therefore investigated effects of acute (30min) and sub-chronic (48h) exposure to 50Hz ELF-EMF on naïve and chemically stressed pheochromocytoma (PC12) cells. The latter have higher levels of iron and/or reactive oxygen species (ROS) and display increased vulnerability to environmental insults. Effects of ELF-EMF on Ca(2+)-homeostasis, ROS production and membrane integrity were assessed using Fura-2 single cell fluorescence microscopy, H2-DCFDA and CFDA assays, respectively. Our data demonstrate that acute exposure of naïve PC12 cells to 50Hz ELF-EMF up to 1000μT fails to affect basal or depolarization-evoked [Ca(2+)]i. Moreover, sub-chronic ELF-EMF exposure up to 1000μT has no consistent effects on Ca(2+)-homeostasis in naïve PC12 cells and does not affect ROS production and membrane integrity. Notably, in chemically stressed PC12 cells both acute and sub-chronic ELF-EMF exposure also failed to exert consistent effects on Ca(2+)-homeostasis, ROS production and membrane integrity. Our combined findings thus indicate that exposure to 50Hz ELF-EMF up to 1000μT, i.e. 10,000 times above background exposure, does not induce neurotoxic effects in vitro, neither in naïve nor in chemically stressed PC12 cells. Though our data require confirmation, e.g. in developing neuronal cells in vitro or (developing) animals, it appears that the neurotoxic risk of ELF-EMF exposure is limited.

  6. EUROPAEM EMF Guideline 2016 for the prevention, diagnosis and treatment of EMF-related health problems and illnesses.

    Science.gov (United States)

    Belyaev, Igor; Dean, Amy; Eger, Horst; Hubmann, Gerhard; Jandrisovits, Reinhold; Kern, Markus; Kundi, Michael; Moshammer, Hanns; Lercher, Piero; Müller, Kurt; Oberfeld, Gerd; Ohnsorge, Peter; Pelzmann, Peter; Scheingraber, Claus; Thill, Roby

    2016-09-01

    Chronic diseases and illnesses associated with non-specific symptoms are on the rise. In addition to chronic stress in social and work environments, physical and chemical exposures at home, at work, and during leisure activities are causal or contributing environmental stressors that deserve attention by the general practitioner as well as by all other members of the health care community. It seems necessary now to take "new exposures" like electromagnetic fields (EMF) into account. Physicians are increasingly confronted with health problems from unidentified causes. Studies, empirical observations, and patient reports clearly indicate interactions between EMF exposure and health problems. Individual susceptibility and environmental factors are frequently neglected. New wireless technologies and applications have been introduced without any certainty about their health effects, raising new challenges for medicine and society. For instance, the issue of so-called non-thermal effects and potential long-term effects of low-dose exposure were scarcely investigated prior to the introduction of these technologies. Common electromagnetic field or EMF sources: Radio-frequency radiation (RF) (3 MHz to 300 GHz) is emitted from radio and TV broadcast antennas, Wi-Fi access points, routers, and clients (e.g. smartphones, tablets), cordless and mobile phones including their base stations, and Bluetooth devices. Extremely low frequency electric (ELF EF) and magnetic fields (ELF MF) (3 Hz to 3 kHz) are emitted from electrical wiring, lamps, and appliances. Very low frequency electric (VLF EF) and magnetic fields (VLF MF) (3 kHz to 3 MHz) are emitted, due to harmonic voltage and current distortions, from electrical wiring, lamps (e.g. compact fluorescent lamps), and electronic devices. On the one hand, there is strong evidence that long-term exposure to certain EMFs is a risk factor for diseases such as certain cancers, Alzheimer's disease, and male infertility. On the other hand

  7. Campos electromagnéticos y salud: Exposición a CEM de baja frecuencia en oficinas y laboratorios de computación; Electromagnetic Fields and Health: Exposition to Low Frecuency EMF in Office Areas and Calculating Center

    Directory of Open Access Journals (Sweden)

    Miguel Castro Fernández

    2011-02-01

    Full Text Available El interés por establecer los límites de influencia de los campos electromagnéticos (CEM sobre los sereshumanos, y definir los riesgos sobre su salud, es uno de los temas que en la actualidad ocupa a empresasde servicio eléctrico, productores de equipos y empresas de seguros. En este artículo se exponen losresultados de mediciones realizadas en diferentes locaciones donde el ser humano ejecuta su trabajodiariamente; las mediciones consistieron en obtener mapas de campo magnético (CM para diferenteszonas de dichas áreas. Aun cundo los resultados obtenidos no pueden ser considerados definitivos ofrecenpuntos de análisis para el debate de un tema de mucho interés en el mundo actual y, por demás, muypolémico. The interes to stablish limits for Electromagnetics Fields (EMF influence on human being and to definerisk on human health has ocuped the electric services, manufacturers and safe enterprise at presentetime.The results of measurements done in differents place where human being realices his dairy work arepresented in this paper; magnetic field map (MFM for different zones in these places is obtained with themeasurements. Results are not final conclusions, but permit to offer point of view to analysis the problemaof EMF, today some confusse. 

  8. Synergistic effect of EMF-BEMER-type pulsed weak electromagnetic field and HPMA-bound doxorubicin on mouse EL4 T-cell lymphoma.

    Science.gov (United States)

    Říhová, Blanka; Etrych, Tomáš; Šírová, Milada; Tomala, Jakub; Ulbrich, Karel; Kovář, Marek

    2011-12-01

    We have investigated the effects of low-frequency pulsed electromagnetic field (LF-EMF) produced by BEMER device on experimental mouse T-cell lymphoma EL4 growing on conventional and/or athymic (nude) mice. Exposure to EMF-BEMER slowed down the growth of tumor mass and prolonged the survival of experimental animals. The effect was more pronounced in immuno-compromised nude mice compared to conventional ones. Acceleration of tumor growth was never observed. No measurable levels of Hsp 70 or increased levels of specific anti-EL4 antibodies were detected in the serum taken from experimental mice before and at different intervals during the experiment, i.e. before solid tumor appeared, at the time of its aggressive growth, and at the terminal stage of the disease. A significant synergizing antitumor effect was seen when EL4 tumor-bearing mice were simultaneously exposed to EMF-BEMER and treated with suboptimal dose of synthetic HPMA copolymer-based doxorubicin, DOX(HYD)-HPMA. Such a combination may be especially useful for heavily treated patients suffering from advanced tumor and requiring additional aggressive chemotherapy which, however, at that time could represent almost life-threatening way of medication.

  9. Cosmological Magnetic Fields

    CERN Document Server

    Kunze, Kerstin E

    2013-01-01

    Magnetic fields are observed on nearly all scales in the universe, from stars and galaxies upto galaxy clusters and even beyond. The origin of cosmic magnetic fields is still an open question, however a large class of models puts its origin in the very early universe. A magnetic dynamo amplifying an initial seed magnetic field could explain the present day strength of the galactic magnetic field. However, it is still an open problem how and when this initial magnetic field was created. Observations of the cosmic microwave background (CMB) provide a window to the early universe and might therefore be able to tell us whether cosmic magnetic fields are of primordial, cosmological origin and at the same time constrain its parameters. We will give an overview of the observational evidence of large scale magnetic fields, describe generation mechanisms of primordial magnetic fields and possible imprints in the CMB.

  10. Magnetic Field Grid Calculator

    Data.gov (United States)

    National Oceanic and Atmospheric Administration, Department of Commerce — The Magnetic Field Properties Calculator will computes the estimated values of Earth's magnetic field(declination, inclination, vertical component, northerly...

  11. The Earth's Magnetic Field

    OpenAIRE

    Edda Lína Gunnarsdóttir 1988

    2012-01-01

    The Earth's magnetic field is essential for life on Earth, as we know it, to exist. It forms a magnetic shield around the planet, protecting it from high energy particles and radiation from the Sun, which can cause damage to life, power systems, orbiting satellites, astronauts and spacecrafts. This report contains a general overview of the Earth's magnetic field. The different sources that contribute to the total magnetic field are presented and the diverse variations in the field are describ...

  12. Magnetic field of the Earth

    Science.gov (United States)

    Popov, Aleksey

    2013-04-01

    The magnetic field of the Earth has global meaning for a life on the Earth. The world geophysical science explains: - occurrence of a magnetic field of the Earth it is transformation of kinetic energy of movements of the fused iron in the liquid core of Earth - into the magnetic energy; - the warming up of a kernel of the Earth occurs due to radioactive disintegration of elements, with excretion of thermal energy. The world science does not define the reasons: - drift of a magnetic dipole on 0,2 a year to the West; - drift of lithospheric slabs and continents. The author offers: an alternative variant existing in a world science the theories "Geodynamo" - it is the theory « the Magnetic field of the Earth », created on the basis of physical laws. Education of a magnetic field of the Earth occurs at moving the electric charge located in a liquid kernel, at rotation of the Earth. At calculation of a magnetic field is used law the Bio Savara for a ring electric current: dB = . Magnetic induction in a kernel of the Earth: B = 2,58 Gs. According to the law of electromagnetic induction the Faradey, rotation of a iron kernel of the Earth in magnetic field causes occurrence of an electric field Emf which moves electrons from the center of a kernel towards the mantle. So of arise the radial electric currents. The magnetic field amplifies the iron of mantle and a kernel of the Earth. As a result of action of a radial electric field the electrons will flow from the center of a kernel in a layer of an electric charge. The central part of a kernel represents the field with a positive electric charge, which creates inverse magnetic field Binv and Emfinv When ?mfinv = ?mf ; ?inv = B, there will be an inversion a magnetic field of the Earth. It is a fact: drift of a magnetic dipole of the Earth in the western direction approximately 0,2 longitude, into a year. Radial electric currents a actions with the basic magnetic field of a Earth - it turn a kernel. It coincides with laws

  13. Magnetic fields in galaxies

    CERN Document Server

    Beck, Rainer

    2013-01-01

    Most of the visible matter in the Universe is ionized, so that cosmic magnetic fields are quite easy to generate and due to the lack of magnetic monopoles hard to destroy. Magnetic fields have been measured in or around practically all celestial objects, either by in-situ measurements of spacecrafts or by the electromagnetic radiation of embedded cosmic rays, gas or dust. The Earth, the Sun, solar planets, stars, pulsars, the Milky Way, nearby galaxies, more distant (radio) galaxies, quasars and even intergalactic space in clusters of galaxies have significant magnetic fields, and even larger volumes of the Universe may be permeated by "dark" magnetic fields. Information on cosmic magnetic fields has increased enormously as the result of the rapid development of observational methods, especially in radio astronomy. In the Milky Way, a wealth of magnetic phenomena was discovered, which are only partly related to objects visible in other spectral ranges. The large-scale structure of the Milky Way's magnetic fie...

  14. The Juno Magnetic Field Investigation

    DEFF Research Database (Denmark)

    Connerney, J. E. P.; Benn, Mathias; Bjarnø, Jonas Bækby

    2017-01-01

    The Juno Magnetic Field investigation (MAG) characterizes Jupiter’s planetary magnetic field and magnetosphere, providing the first globally distributed and proximate measurements of the magnetic field of Jupiter. The magnetic field instrumentation consists of two independent magnetometer sensor ...

  15. The First Magnetic Fields

    CERN Document Server

    Widrow, Lawrence M; Schleicher, Dominik; Subramanian, Kandaswamy; Tsagas, Christos G; Treumann, Rudolf A

    2011-01-01

    We review current ideas on the origin of galactic and extragalactic magnetic fields. We begin by summarizing observations of magnetic fields at cosmological redshifts and on cosmological scales. These observations translate into constraints on the strength and scale magnetic fields must have during the early stages of galaxy formation in order to seed the galactic dynamo. We examine mechanisms for the generation of magnetic fields that operate prior during inflation and during subsequent phase transitions such as electroweak symmetry breaking and the quark-hadron phase transition. The implications of strong primordial magnetic fields for the reionization epoch as well as the first generation of stars is discussed in detail. The exotic, early-Universe mechanisms are contrasted with astrophysical processes that generate fields after recombination. For example, a Biermann-type battery can operate in a proto-galaxy during the early stages of structure formation. Moreover, magnetic fields in either an early genera...

  16. A New Look On the Nature of the Earth's Magnetic Field

    Science.gov (United States)

    Nikholaevich Dmitriev, Arkadiy

    2016-10-01

    There was examined the model of the Earth's dipole magnetic field based on the existing geothermocurrents in the Earth's core, that occurred because of the geothermal gradient and the related Seebeck effect. The calculations showed, that the energy of geothermocurrents is enough to keep Earth's Magnetic Field (EMF) at the present level, that is about (3 - 5)10-5 T. EMF model is quite innovative in comparison to the known electrical models, because it contains two branches of the planetary thermoelectrical element: “inner core - outer core - lower mantel”. These branches are connected through the more warmed and melted outer core. If the thermocurrents are simultaneously directed to the Earth's surface, a thaw period comes. If they are directed oppositely an ice age comes. As the directions of thermocurrents in the inner core change, EMF poles get inverted. At the moment of their inversion dipole magnetic field decreases up to its transitional disappearance. At the same time the pole caused by the lower mantel stays as 4.6 10-6 T. Thermoelectrical EMF model is universal. It enables us to calculate magnetic fields of any planet within the Solar System.

  17. Organic magnetic field sensor

    Energy Technology Data Exchange (ETDEWEB)

    McCamey, Dane; Boehme, Christoph

    2017-01-24

    An organic, spin-dependent magnetic field sensor (10) includes an active stack (12) having an organic material with a spin-dependence. The sensor (10) also includes a back electrical contact (14) electrically coupled to a back of the active stack (12) and a front electrical contact (16) electrically coupled to a front of the active stack (12). A magnetic field generator (18) is oriented so as to provide an oscillating magnetic field which penetrates the active stack (12).

  18. Epinephrine, DNA integrity and oxidative stress in workers exposed to extremely low-frequency electromagnetic fields (ELF-EMFs) at 132 kV substations.

    Science.gov (United States)

    Tiwari, Ravindra; Lakshmi, N K; Bhargava, S C; Ahuja, Y R

    2015-03-01

    There is apprehension about widespread use of electrical and electromagnetic gadgets which are supposed to emit electromagnetic radiations. Reports are controversy. These electromagnetic fields (EMFs) have considerable effect on endocrine system of exposed subjects. This study was focused to assess the possible bioeffects of extremely low-frequency (ELF)-EMFs on epinephrine level, DNA damage and oxidative stress in subjects occupationally exposed to 132 kV high-voltage substations. The blood sample of 142 exposed subjects and 151 non-exposed individuals was analyzed. Plasma epinephrine was measured by enzyme-linked immunosorbent assay, DNA damage was studied by alkaline comet assay along with oxidative stress. Epinephrine levels of sub-groups showed mean concentration of 75.22  ±  1.46, 64.43  ±  8.26 and 48.47  ±  4.97 for high, medium and low exposed groups, respectively. DNA damage ranged between 1.69 µm and 9.91 µm. The oxidative stress levels showed significant increase. The individuals employed in the live-line procedures were found to be vulnerable for EM stress with altered epinephrine concentrations, DNA damage and increased oxidative stress.

  19. Investigations on DNA damage and frequency of micronuclei in occupational exposure to electromagnetic fields (EMFs emitted from video display terminals (VDTs

    Directory of Open Access Journals (Sweden)

    NK Lakshmi

    2010-01-01

    Full Text Available The potential effect of electromagnetic fields (EMFs emitted from video display terminals (VDTs to elicit biological response is a major concern for the public. The software professionals are subjected to cumulative EMFs in their occupational environments. This study was undertaken to evaluate DNA damage and incidences of micronuclei in such professionals. To the best of our knowledge, the present study is the first attempt to carry out cytogenetic investigations on assessing bioeffects in personal computer users. The study subjects (n = 138 included software professionals using VDTs for more than 2 years with age, gender, socioeconomic status matched controls (n = 151. DNA damage and frequency of micronuclei were evaluated using alkaline comet assay and cytochalasin blocked micronucleus assay respectively. Overall DNA damage and incidence of micronuclei showed no significant differences between the exposed and control subjects. With exposure characteristics, such as total duration (years and frequency of use (minutes/day sub-groups were assessed for such parameters. Although cumulative frequency of use showed no significant changes in the DNA integrity of the classified sub-groups, the long-term users (> 10 years showed higher induction of DNA damage and increased frequency of micronuclei and micro nucleated cells.

  20. Rapid-onset/offset, variably scheduled 60 Hz electric and magnetic field exposure reduces nocturnal serum melatonin concentration in nonhuman primates

    Energy Technology Data Exchange (ETDEWEB)

    Rogers, W.R.; Smith, H.D. [Southwest Research Inst., San Antonio, TX (United States). Dept. of Biosciences and Bioengineering; Reiter, R.J.; Barlow-Walden, L. [Univ. of Texas Health Science Center, San Antonio, TX (United States). Dept. of Cellular and Structural Biology

    1995-12-31

    Experiments with rodents indicate that power-frequency electric field (EF) or magnetic field (MF) exposure can suppress the normal nocturnal increase in melatonin concentration in pineal gland and blood. In a separate set of three experiments conducted with nonhuman primates, the authors did not observe melatonin suppression as a result of 6 weeks of day-time exposure to combined 60 Hz electric and magnetic fields (E/MF) with regularly schedule ``slow`` E/MF onsets/offsets. The study described here used a different exposure paradigm in which two baboons were exposed to E/MF with ``rapid`` E/MF onsets/offsets accompanied by EF transients not found with slowly ramped E/MF onset/offset; profound reductions in nocturnal serum melatonin concentration were observed in this experiment. If replicated in a more extensive experiment, the observation of melatonin suppression only in the presence of E/MF transients would suggest that very specific exposure parameters determine the effects of 60 Hz E/MF on melatonin.

  1. Simulation study of induced EMFs and the suppression during SST-1 start-up

    Energy Technology Data Exchange (ETDEWEB)

    Jain, V., E-mail: vishal@ipr.res.in; Sharma, D.; Vardhrajulu, A.; Gupta, C.N.; Srinivasan, R.; Daniel, R.

    2015-11-15

    Highlights: • Induced EMFs study in PF coils during SST-1 start up using MATlab simulink. • Integration of wave shaping network to generate practical OT current profile. • This study would protect coil insulation with identifying RC circulating network. • Study of MOV technique for circulation of current through RC. - Abstract: Steady State Superconducting Tokamak (SST-1) comprises of various copper and superconducting coils for generating magnetic field for initiation, providing equilibrium and shaping of plasma in tokamak. In this paper, an attempt is made to study the induced EMF in superconducting poloidal field coils (PF coils) due to fast ramp down of current in ohmic transformer copper coils (OT coils) for SST-1 plasma initiation. The fast ramp down of current, from few kA to zero amperes in just 50–100 ms in OT coils, is required to achieve plasma breakdown and ramp up of plasma current in tokamak. However, it induces nearly 5 kV EMF in one of the SST-1 PF coils that can damage the coil insulation and also bias negatively the electronic switching of power supply. It is necessary to maintain induced EMF below 1 kV in all PF coils for safe operation of SST-1. The induced EMF up to 1 kV can be clamped without any need of protection and circulating current. If the induced EMF is in excess of 1 kV, then it has to allow the circulation of current through RC network for coil protection from overvoltage. These circulating currents in PF coils will affect the shaping of plasma. In this paper, the induced EMF in PF coils are simulated using MATlab simulink for a typical SST-1 current profile of OT coils. Further, this simulation study is used to design the protection system for PF coils. In this paper, the worst-case induced EMF scenario is considered by excluding the effect of passive elements like vacuum vessel and cryostat on mutual coupling parameters. However, the implementation of the EMF suppression scheme need more elaborated study with considering

  2. The process of consensus on EMF: SAB review of the EPA draft document on EMF and cancer

    Energy Technology Data Exchange (ETDEWEB)

    Wilson, B.W.

    1992-06-01

    The EPA Draft Document on EMF and Cancers grew out of an earlier effort by EPA to track biological effects literature relative to radio-frequency (RF) exposure. Scope of the document was broadened to include extremely low frequency electric and magnetic fields prior to an announcement in 1986 that EPA would formally review the whole area of non-ionizing radiation. An extensive survey of the relevant bioeffects and epidemiologic literature was carried out, and writing on the document began in earnest on the document sometime in 1989. In its draft form, the document reviewed the literature on mechanisms of Interaction between electromagnetic fields and biological tissue, EMF epidemiologic studies, supporting evidence for carcinogenicity and research needs. In the early summer of 1990, a draft of the document was reviewed by some 22 individuals within the EPA and other government agencies. It was also sent out for external review to an additional 9 qualified scientists who had worked in the area and were familiar with EMF-related literature in epidemiology, biology, and physics. Many of the comments sent to EPA from this first review, prior to release of the draft for public comment, were strikingly similar to those resulting from the second (public) review process. Thus, it appears that much of the controversy that was later associated with the document could have been avoided had the authors been diligent in following the recommendations of the initial set of reviewers.

  3. Studies on the possible biological effects of 50 Hz electric and/or magnetic fields: evaluation of some glycolytic enzymes, glycolytic flux, energy and oxido-reductive potentials in human erythrocytes exposed in vitro to power frequency fields.

    Science.gov (United States)

    Dachà, M; Accorsi, A; Pierotti, C; Vetrano, F; Mantovani, R; Guidi, G; Conti, R; Nicolini, P

    1993-01-01

    An attempt has been made to understand whether 50 Hz electric and magnetic fields (EMFs) are involved in producing bioeffects by exposing human erythrocytes in vitro. The study evaluated some key glycolytic enzymes, glucose consumption, lactate production, energy charge, 2,3-diphosphoglycerate, and reduced glutathione levels, all of which are biochemical parameters significant to erythrocyte function. Cells exposed to individual or superimposed EMFs have not shown any significant difference compared with the controls.

  4. Electric and magnetic fields research and public information dissemination program. Progress report

    Energy Technology Data Exchange (ETDEWEB)

    NONE

    1995-12-01

    The Electric and Magnetic Fields (EMF) Research and Public Information Dissemination (RAPID) Program was authorized by the Energy Policy Act of 1992 (enacted October 24, 1992) to determine whether or not exposure to EMF produced by the generation, transmission, and use of electric energy affects human health. Two Federal agencies, the Department of Energy (DOE) and the National Institute of Environmental Health Sciences (NIEHS), have primary responsibility for the program, but other Federal agencies are key participants as well. This program requires that Federal appropriations be matched by contributions from non-Federal sources. The authorized level of funding for the program was $65 million over a 5-year period (fiscal years 1993-1997 inclusive). For EMF RAPID to be a fully funded program, $32.5 million over 5 years will have to be appropriated by Congress and matched by non-Federal contributions.

  5. Non-thermal radio frequency and static magnetic fields increase rate of hemoglobin deoxygenation in a cell-free preparation.

    Directory of Open Access Journals (Sweden)

    David Muehsam

    Full Text Available The growing body of clinical and experimental data regarding electromagnetic field (EMF bioeffects and their therapeutic applications has contributed to a better understanding of the underlying mechanisms of action. This study reports that two EMF modalities currently in clinical use, a pulse-modulated radiofrequency (PRF signal, and a static magnetic field (SMF, applied independently, increased the rate of deoxygenation of human hemoglobin (Hb in a cell-free assay. Deoxygenation of Hb was initiated using the reducing agent dithiothreitol (DTT in an assay that allowed the time for deoxygenation to be controlled (from several min to several hours by adjusting the relative concentrations of DTT and Hb. The time course of Hb deoxygenation was observed using visible light spectroscopy. Exposure for 10-30 min to either PRF or SMF increased the rate of deoxygenation occurring several min to several hours after the end of EMF exposure. The sensitivity and biochemical simplicity of the assay developed here suggest a new research tool that may help to further the understanding of basic biophysical EMF transduction mechanisms. If the results of this study were to be shown to occur at the cellular and tissue level, EMF-enhanced oxygen availability would be one of the mechanisms by which clinically relevant EMF-mediated enhancement of growth and repair processes could occur.

  6. On the modulation effect of pulsing and static magnetic fields and mechanical vibrations on barley seed hydration.

    Science.gov (United States)

    Amyan, Armine; Ayrapetyan, Sinerik

    2004-01-01

    The changes of wet and dry weights of barley seed in different periods of swelling were studied in seeds treated with Extremely Low Frequency Electromagnetic Fields (ELF EMF), Static Magnetic Fields (SMF) and Mechanical Vibrations (MV) in cold (4 degrees C) and warm (20 degrees C) distilled water as well as in seeds non-treated (control). The metabolic dependent seed hydration, dry weight loss and water binding in seed were modulated by preliminary EMF, SMF and MV-induced treatment of distilled water. The specific electrical conductivity (SEC) of control and treated distilled water was measured before the seed incubation. Frequency and intensity "windows" (i.e. range of frequency or intensity) for the effect of EMF, MV and SMF (correspondingly) on seed hydration, solubility and water binding in seed were studied. These "windows" were different in various phases of seed swelling. It is suggested that water structure modification is the result of valence angle changes (SMF and EMF) and dipole molecules vibration (EMF and MV) has different effects on the process of hydration, solubility and water binding in seed. These results are important from the point of understanding the mechanisms of the biological effect of EMF, as well as from the point of agriculture.

  7. Recommendations for Guidelines for EMF Personal Exposure Measurements, Rapid Project #4

    Energy Technology Data Exchange (ETDEWEB)

    T. Dan Bracken, Inc.

    1997-08-01

    The purpose of developing guidelines for electric and magnetic field (EMF) personal exposure measurements (lF'EM) is to ensure reliable and comparable data across I?EM studies. Study techniques may vary due to different populations or objectives, but the resulting data should be consistently reported and comparable, to the extent possible. Any guideline must allow creativity by the research-oriented investigator and provide specific guidance to industrial hygienists or other results-oriented investigators, requiring a standard protocol. Recognizing measurement studies with different purposes is an important aspect of these recommendations. The guidelines presented here intend to produce comparable data across studies while remaining flexible. The recommendations for designing and implementing an EMF PEM program describe a three-stage process. The first step is to clearly state the purpose of the PEM program. The next stage addresses the fundamental elements of an EMF PEM study, including an assessment of the scientific and organizational resources that will be required. This process is codified in a written study plan. These stages are described in 1 Section 5 of this report. The third stage of a PEM study involves the design, implementation and documentation of specific procedures and protocols fo~ sampling strategies, selection of measurement parameters; instrumentation, measurement and data collection, data management, data analysis, quality assurance, uncertainty evaluation, and archiving the study methods and results. The methods for designing these elements of an EMF PEM study are described in Section 6: Specific Guidelines for EMF I?EM Study Design.

  8. The revised electromagnetic fields directive and worker exposure in environments with high magnetic flux densities.

    Science.gov (United States)

    Stam, Rianne

    2014-06-01

    Some of the strongest electromagnetic fields (EMF) are found in the workplace. A European Directive sets limits to workers' exposure to EMF. This review summarizes its origin and contents and compares magnetic field exposure levels in high-risk workplaces with the limits set in the revised Directive. Pubmed, Scopus, grey literature databases, and websites of organizations involved in occupational exposure measurements were searched. The focus was on EMF with frequencies up to 10 MHz, which can cause stimulation of the nervous system. Selected studies had to provide individual maximum exposure levels at the workplace, either in terms of the external magnetic field strength or flux density or as induced electric field strength or current density. Indicative action levels and the corresponding exposure limit values for magnetic fields in the revised European Directive will be higher than those in the previous version. Nevertheless, magnetic flux densities in excess of the action levels for peripheral nerve stimulation are reported for workers involved in welding, induction heating, transcranial magnetic stimulation, and magnetic resonance imaging (MRI). The corresponding health effects exposure limit values for the electric fields in the worker's body can be exceeded for welding and MRI, but calculations for induction heating and transcranial magnetic stimulation are lacking. Since the revised European Directive conditionally exempts MRI-related activities from the exposure limits, measures to reduce exposure may be necessary for welding, induction heating, and transcranial nerve stimulation. Since such measures can be complicated, there is a clear need for exposure databases for different workplace scenarios with significant EMF exposure and guidance on good practices.

  9. Synthesis of manganese oxide nanocrystal by ultrasonic bath: effect of external magnetic field.

    Science.gov (United States)

    Bastami, Tahereh Rohani; Entezari, Mohammad H

    2012-07-01

    A novel technique was used for the synthesis of manganese oxide nanocrystal by applying an external magnetic field (EMF) on the precursor solution before sonication with ultrasonic bath. The results were compared in the presence and absence of EMF. Manganese acetate solution as precursor was circulated by a pump at constant speed (7 rpm, equal to flow rate of 51.5 mL/min) in an EMF with intensity of 0.38 T in two exposure times (t(MF), 2h and 24h). Then, the magnetized solution was irradiated indirectly by ultrasonic bath in basic and neutral media. One experiment was designed for the effect of oxygen atmosphere in the case of magnetic treated solution in neutral medium. The as prepared samples were characterized with X-ray diffraction (XRD), Fourier transform infrared (FTIR) spectroscopy, transmission electron microscopy (HRTEM, TEM), energy-dispersive spectrum (EDS), and superconducting quantum interference device (SQUID) analysis. In neutral medium, the sonication of magnetized solution (t(MF), 24h) led mainly to a mixture of Mn(3)O(4) (hausmannite) and γ-MnOOH (manganite) and sonication of unmagnetized solution led to a pure Mn(3)O(4). In point of particle size, the larger and smaller size of nanoparticles was obtained with and without magnetic treatment, respectively. In addition, the EMF was retarded the nucleation process, accelerated the growth of the crystal, and increased the amount of rod-like structure especially in oxygen atmosphere. In basic medium, a difference was observed on the composition of the products between magnetic treated and untreated solution. For these samples, the magnetic measurements as a function of temperature were exhibited a reduction in ferrimagnetic temperature to T(c)=39K, and 40K with and without magnetic treatment, respectively. The ferrimagnetic temperature was reported for the bulk at T(c)=43K. A superparamagnetic behavior was observed at room temperature without any saturation magnetization and hysteresis in the measured

  10. Magnetization reversal in ultrashort magnetic field pulses

    CERN Document Server

    Bauer, M; Fassbender, J; Hillebrands, B

    2000-01-01

    We report the switching properties of a thin magnetic film subject to an ultrashort, laterally localized magnetic field pulse, obtained by numerical investigations. The magnetization distribution in the film is calculated on a grid assuming Stoner-like coherent rotation within the grid square size. Perpendicularly and in-plane magnetized films exhibit a magnetization reversal due to a 4 ps magnetic field pulse. Outside the central region the pulse duration is short compared to the precession period. In this area the evolution of the magnetization during the field pulse does not depend strongly on magnetic damping and/or pulse shape. However, the final magnetization distribution is affected by the magnetic damping. Although the pulse duration is short compared to the precession period, the time needed for the relaxation of the magnetization to the equilibrium state is rather large. The influence of the different magnetic anisotropy contributions and the magnetic damping parameter enters into the magnetization ...

  11. Molecules in Magnetic Fields

    Science.gov (United States)

    Berdyugina, Svetlana

    2015-08-01

    Molecules probe cool matter in the Universe and various astrophysical objects. Their ability to sense magnetic fields provides new insights into magnetic properties of these objects. During the past fifteen years we have carried out a theoretical study of molecular magnetic effects such as the Zeeman, Paschen-Back and Hanle effects and their applications for inferring magnetic structures and spatial inhomogeneities on the Sun, cool stars, brown dwarfs, and exoplanets from molecular spectro-polarimetry (e.g., Berdyugina 2011). Here, we present an overview of this study and compare our theoretical predictions with recent laboratory measurements of magnetic properties of some molecules. We present also a new web-based tool to compute molecular magnetic effects and polarized spectra which is supported by the ERC Advanced Grant HotMol.

  12. Safety Problems of Electric and Magnetic Fields and Experimental Magnetic Fusion Facilities 5.Electromagnetic Fields in the Workplace

    Science.gov (United States)

    Jonai, Hiroshi; Villanueva, Maria Beatriz G.

    The review addresses the concerns related to extremely low frequency electromagnetic fields (ELF/EMF) in workplaces. The exposure levels and epidemiological studies on cancer, the health effects of working with VDTs (visual display terminals), and the malfunction of cardiac pacemakers are described. The association of EMF exposure and cancer or disorders from VDT work cannot be considered conclusive. The information on the exposure level and effect of EMF on cardiac pacemakers should be disseminated in workplaces. Risk communication program on EMF is urgent for countermeasures against worker anxiety.

  13. ELECTRIC AND MAGNETIC FIELDS ELECTRIC AND GASOLINE-POWERED VEHICLES.

    Science.gov (United States)

    Tell, Richard A; Kavet, Robert

    2016-12-01

    Measurements were conducted to investigate electric and magnetic fields (EMFs) from 120 Hz to 10 kHz and 1.2 to 100 kHz in 9 electric or hybrid vehicles and 4 gasoline vehicles, all while being driven. The range of fields in the electric vehicles enclosed the range observed in the gasoline vehicles. Mean magnetic fields ranged from nominally 0.6 to 3.5 µT for electric/hybrids depending on the measurement band compared with nominally 0.4 to 0.6 µT for gasoline vehicles. Mean values of electric fields ranged from nominally 2 to 3 V m(-1) for electric/hybrid vehicles depending on the band, compared with 0.9 to 3 V m(-1) for gasoline vehicles. In all cases, the fields were well within published exposure limits for the general population. The measurements were performed with Narda model EHP-50C/EHP-50D EMF analysers that revealed the presence of spurious signals in the EHP-50C unit, which were resolved with the EHP-50D model.

  14. Methodological approach to EMF protection standards

    Science.gov (United States)

    Vecchia, Paolo

    2010-04-01

    Biological and health effects of electromagnetic fields (EMF) have been investigated for many years. Exposure standards have been developed internationally, that provide adequate protection against all known adverse effects of exposure to EMF. The guidelines developed by the International Commission on Non Ionizing Radiation Protection (ICNIRP) are widely recognized and have formed the basis for national regulations in several countries. Concerns for hypothesized, but unproven, long-term effects of chronic exposure to low-level EMFs have created a demand for precautionary measures beyond the standards for recognized, acute effects. However, such measure should be separate from exposure standards, and adopted with special care to avoid undermining the credibility of science-based guidelines, and of health protection agencies.

  15. ISR Radial Field Magnet

    CERN Multimedia

    1983-01-01

    There were 37 (normal) + 3 (special) Radial Field magnets in the ISR to adjust vertically the closed orbit. Gap heights and strengths were 200 mm and .12 Tm in the normal magnets, 220 mm and .18 Tm in the special ones. The core length was 430 mm in both types. Due to their small length as compared to the gap heights the end fringe field errors were very important and had to be compensated by suitably shaping the poles. In order to save on cables, as these magnets were located very far from their power supplies, the coils of the normal type magnets were formed by many turns of solid cpper conductor with some interleaved layers of hollow conductor directly cooled by circulating water

  16. Cosmic magnetic fields

    CERN Document Server

    Kronberg, Philipp P

    2016-01-01

    Magnetic fields are important in the Universe and their effects contain the key to many astrophysical phenomena that are otherwise impossible to understand. This book presents an up-to-date overview of this fast-growing topic and its interconnections to plasma processes, astroparticle physics, high energy astrophysics, and cosmic evolution. The phenomenology and impact of magnetic fields are described in diverse astrophysical contexts within the Universe, from galaxies to the filaments and voids of the intergalactic medium, and out to the largest redshifts. The presentation of mathematical formulae is accessible and is designed to add insight into the broad range of topics discussed. Written for graduate students and researchers in astrophysics and related disciplines, this volume will inspire readers to devise new ways of thinking about magnetic fields in space on galaxy scales and beyond.

  17. Solar Magnetic Fields

    Indian Academy of Sciences (India)

    J. O. Stenflo

    2008-03-01

    Since the structuring and variability of the Sun and other stars are governed by magnetic fields, much of present-day stellar physics centers around the measurement and understanding of the magnetic fields and their interactions. The Sun, being a prototypical star, plays a unique role in astrophysics, since its proximity allows the fundamental processes to be explored in detail. The PRL anniversary gives us an opportunity to look back at past milestones and try to identify the main unsolved issues that will be addressed in the future.

  18. Solar Magnetic Fields

    CERN Document Server

    Hood, Alan W

    2011-01-01

    This review provides an introduction to the generation and evolution of the Sun's magnetic field, summarising both observational evidence and theoretical models. The eleven year solar cycle, which is well known from a variety of observed quantities, strongly supports the idea of a large-scale solar dynamo. Current theoretical ideas on the location and mechanism of this dynamo are presented. The solar cycle influences the behaviour of the global coronal magnetic field and it is the eruptions of this field that can impact on the Earth's environment. These global coronal variations can be modelled to a surprising degree of accuracy. Recent high resolution observations of the Sun's magnetic field in quiet regions, away from sunspots, show that there is a continual evolution of a small-scale magnetic field, presumably produced by small-scale dynamo action in the solar interior. Sunspots, a natural consequence of the large-scale dynamo, emerge, evolve and disperse over a period of several days. Numerical simulation...

  19. High field superconducting magnets

    Science.gov (United States)

    Hait, Thomas P. (Inventor); Shirron, Peter J. (Inventor)

    2011-01-01

    A superconducting magnet includes an insulating layer disposed about the surface of a mandrel; a superconducting wire wound in adjacent turns about the mandrel to form the superconducting magnet, wherein the superconducting wire is in thermal communication with the mandrel, and the superconducting magnet has a field-to-current ratio equal to or greater than 1.1 Tesla per Ampere; a thermally conductive potting material configured to fill interstices between the adjacent turns, wherein the thermally conductive potting material and the superconducting wire provide a path for dissipation of heat; and a voltage limiting device disposed across each end of the superconducting wire, wherein the voltage limiting device is configured to prevent a voltage excursion across the superconducting wire during quench of the superconducting magnet.

  20. Magnetic fields in diffuse media

    CERN Document Server

    Pino, Elisabete; Melioli, Claudio

    2015-01-01

    This volume presents the current knowledge of magnetic fields in diffuse astrophysical media. Starting with an overview of 21st century instrumentation to observe astrophysical magnetic fields, the chapters cover observational techniques, origin of magnetic fields, magnetic turbulence, basic processes in magnetized fluids, the role of magnetic fields for cosmic rays, in the interstellar medium and for star formation. Written by a group of leading experts the book represents an excellent overview of the field. Nonspecialists will find sufficient background to enter the field and be able to appreciate the state of the art.

  1. Magnetic field and performance analysis of a tubular permanent magnet linear synchronous motor applied in elevator door system

    Institute of Scientific and Technical Information of China (English)

    Xiao LIU; Yun-yue YE; Zhuo ZHENG; Qin-fen LU

    2008-01-01

    A novel elevator door driven by tubular permanent magnet linear synchronous motor (TPMLSM) is presented. This TPMLSM applies axial magnet array topology of the secondary rod, air-cored armature windings and slotless structure of the forcer to improve the stability of the thrust. The influence of two major dimensions, the pitch and radius of the permanent magnet (PM), on magnetic field was studied and the best values were given by the finite element analysis (FEA). The magnetic field, back EMF and thrust of the motor were analyzed and the PM size was optimized to reduce the harmonic components of the magnetic field and improve the performance of the motor. Predicted results are validated by the experiment. It is shown that the performance of the motor and the novel elevator door system is satisfying.

  2. Modifying the Genetic Regulation of Bone and Cartilage Cells and Associated Tissue by EMF Stimulation Fields and Uses Thereof

    Science.gov (United States)

    Goodwin, Thomas J. (Inventor); Shackelford, Linda C. (Inventor)

    2014-01-01

    An apparatus and method to modify the genetic regulation of mammalian tissue, bone, or any combination. The method may be comprised of the steps of tuning at least one predetermined profile associated with at least one time-varying stimulation field thereby resulting in at least one tuned time-varying stimulation field comprised of at least one tuned predetermined profile, wherein said at least one tuned predetermined profile is comprised of a plurality of tuned predetermined figures of merit and is controllable through at least one of said plurality of tuned predetermined figures of merit, wherein said plurality of predetermined tuned figures of merit is comprised of a tuned B-Field magnitude, tuned rising slew rate, tuned rise time, tuned falling slew rate, tuned fall time, tuned frequency, tuned wavelength, and tuned duty cycle; and exposing mammalian chondrocytes, osteoblasts, osteocytes, osteoclasts, nucleus pulposus, associated tissue, or any combination to said at least one tuned time-varying stimulation field comprised of said at least one tuned predetermined profile for a predetermined tuned exposure time or plurality of tuned exposure time sequences.

  3. ELECTROMOTIVE FORCE, EMF (CELLS)

    Energy Technology Data Exchange (ETDEWEB)

    Archer, M.D.; Feldberg, S.W.

    1998-09-16

    The voltage or electric potential difference across the terminals of a cell when no current is drawn from it. The emf of a cell is the sum of the electric potential differences (PDs) produced by a separation of charges (electrons or ions) that can occur at each phase boundary (or interface) in the cell. The magnitude of each PD depends on the chemical nature of the two contacting phases. Thus, at the interface between two different metals, some electrons will have moved from the metal with a higher free energy of electrons to the metal with a lower free energy of electrons. The resultant charge separation will produce a PD (just as charge separation produces a voltage across a capacitor) that, at equilibrium, exactly opposes further electron flow. Similarly, PDs can be produced when electrons partition across a metal/solution interface or metal/solid interface, and when ions partition across a solution/membrane/solution interface.

  4. Coronal Magnetic Field Models

    Science.gov (United States)

    Wiegelmann, Thomas; Petrie, Gordon J. D.; Riley, Pete

    2017-09-01

    Coronal magnetic field models use photospheric field measurements as boundary condition to model the solar corona. We review in this paper the most common model assumptions, starting from MHD-models, magnetohydrostatics, force-free and finally potential field models. Each model in this list is somewhat less complex than the previous one and makes more restrictive assumptions by neglecting physical effects. The magnetohydrostatic approach neglects time-dependent phenomena and plasma flows, the force-free approach neglects additionally the gradient of the plasma pressure and the gravity force. This leads to the assumption of a vanishing Lorentz force and electric currents are parallel (or anti-parallel) to the magnetic field lines. Finally, the potential field approach neglects also these currents. We outline the main assumptions, benefits and limitations of these models both from a theoretical (how realistic are the models?) and a practical viewpoint (which computer resources to we need?). Finally we address the important problem of noisy and inconsistent photospheric boundary conditions and the possibility of using chromospheric and coronal observations to improve the models.

  5. Biophysical aspects of the influence of electromagnetic fields (EMF on the human body Influencia de los campos electromagnéticos en el organismo humano: aspectos biofísicos

    Directory of Open Access Journals (Sweden)

    Napaleon Hernández

    1993-03-01

    Full Text Available

     

    Some historical aspects of biomagnetism and of the various steps that led to the development of bioelectricity and electro technique are summarized. Alterations observed in individuals working for long periods of time in contact with artificial EMF are described as well as the correlation between natural EMF and accidentality. The utilization of EMF for therapeutic purposes 15 reviewed and some considerations are given to the so called ";bioenergetic medicine"; that employs light, laser, sound, electricity and magnetism. A warning 15 made against the indiscriminate therapeutic use of EMF by practitioners without proper training; the need for solid research which may support the development of this area of medicine Is emphasized.

     

    En este artículo se resumen algunos aspectos históricos del biomagnetismo y de las etapas que condujeron al desarrollo de la bioelectricidad y la electrotécnica. Se describen las alteraciones observadas en quienes trabajan por períodos prolongados en contacto con campos electromagnéticos (CEM artificiales y la correlación entre los CEM naturales y la accidentalidad. Se revisan la utilización de los CEM con fines curativos y la escuela llamada ";bioenergética"; que utiliza terapéuticamente la luz, el láser, el sonido, la electricidad y el magnetismo. Se previene contra el uso terapéutico Indiscriminado de los CEM por personas sin adecuada formación y se hace énfasis en la necesidad de adelantar Investigaciones serias que sustenten este desarrollo de la medicina.

  6. Design and test of a flat-top magnetic field system driven by capacitor banks

    Science.gov (United States)

    Jiang, Fan; Peng, Tao; Xiao, Houxiu; Zhao, Jianlong; Pan, Yuan; Herlach, Fritz; Li, Liang

    2014-04-01

    An innovative method for generating a flat-top pulsed magnetic field by means of capacitor banks is developed at the Wuhan National High Magnetic Field Center (WHMFC). The system consists of two capacitor banks as they are normally used to generate a pulsed field. The two discharge circuits (the magnet circuit and the auxiliary circuit) are coupled by a pulse transformer such that the electromotive force (EMF) induced via the transformer in the magnet circuit containing the magnet coil is opposed to the EMF of the capacitor bank. At a certain point before the current pulse in the coil reaches its peak, the auxiliary circuit is triggered. With optimized parameters for charging voltage and trigger delay, the current in the magnet circuit can be approximately kept constant to obtain a flat-top. A prototype was developed at the WHMFC; the magnet circuit was energized by seven 1 MJ (3.2 mF/25 kV) capacitor modules and the auxiliary circuit by four 1 MJ modules. Fields up to 41 T with 6 ms flat-top have been obtained with a conventional user magnet used at the WHMFC.

  7. Magnetic Field Topology in Jets

    Science.gov (United States)

    Gardiner, T. A.; Frank, A.

    2000-01-01

    We present results on the magnetic field topology in a pulsed radiative. jet. For initially helical magnetic fields and periodic velocity variations, we find that the magnetic field alternates along the, length of the jet from toroidally dominated in the knots to possibly poloidally dominated in the intervening regions.

  8. Magnetic field switchable dry adhesives.

    Science.gov (United States)

    Krahn, Jeffrey; Bovero, Enrico; Menon, Carlo

    2015-02-01

    A magnetic field controllable dry adhesive device is manufactured. The normal adhesion force can be increased or decreased depending on the presence of an applied magnetic field. If the magnetic field is present during the entire normal adhesion test cycle which includes both applying a preloading force and measuring the pulloff pressure, a decrease in adhesion is observed when compared to when there is no applied magnetic field. Similarly, if the magnetic field is present only during the preload portion of the normal adhesion test cycle, a decrease in adhesion is observed because of an increased stiffness of the magnetically controlled dry adhesive device. When the applied magnetic field is present during only the pulloff portion of the normal adhesion test cycle, either an increase or a decrease in normal adhesion is observed depending on the direction of the applied magnetic field.

  9. On the Motion of the Field of a Permanent Magnet

    Science.gov (United States)

    Leus, Vladimir; Taylor, Stephen

    2011-01-01

    A description is given of a series of recent experiments using a rotating magnetic circuit comprising a permanent magnet ring and yoke, and a stationary conductor in the air gap between the ring and yoke. The EMF induced in this case cannot be described by a simple application of Faraday's flux law. This is because the magnetic flux in the air gap…

  10. Exposure of ELF-EMF and RF-EMF Increase the Rate of Glucose Transport and TCA Cycle in Budding Yeast

    Science.gov (United States)

    Lin, Kang-Wei; Yang, Chuan-Jun; Lian, Hui-Yong; Cai, Peng

    2016-01-01

    In this study, we investigated the transcriptional response to 50 Hz extremely low frequency electromagnetic field (ELF-EMF) and 2.0 GHz radio frequency electromagnetic field (RF-EMF) exposure by Illumina sequencing technology using budding yeast as the model organism. The transcription levels of 28 genes were upregulated and those of four genes were downregulated under ELF-EMF exposure, while the transcription levels of 29 genes were upregulated and those of 24 genes were downregulated under RF-EMF exposure. After validation by reverse transcription quantitative polymerase chain reaction (RT-qPCR), a concordant direction of change both in differential gene expression (DGE) and RT-qPCR was demonstrated for nine genes under ELF-EMF exposure and for 10 genes under RF-EMF exposure. The RT-qPCR results revealed that ELF-EMF and RF-EMF exposure can upregulate the expression of genes involved in glucose transportation and the tricarboxylic acid (TCA) cycle, but not the glycolysis pathway. Energy metabolism is closely related with the cell response to environmental stress including EMF exposure. Our findings may throw light on the mechanism underlying the biological effects of EMF. PMID:27630630

  11. Limits for primordial magnetic fields

    CERN Document Server

    Caprini, Chiara

    2011-01-01

    A possible explanation for the origin of the magnetic fields observed today in matter structures is that they were generated in the primordial universe. After briefly revising the model of a primordial stochastic magnetic field and sketching the main features of its time evolution in the primordial plasma, we illustrate the current upper bounds on the magnetic field amplitude and spectral index from Cosmic Microwave Background observations and gravitational wave production. We conclude that a primordial magnetic field generated by a non-causal process such as inflation with a red spectrum seems to be favoured as a seed for the magnetic fields observed today in structures.

  12. Superhorizon magnetic fields

    CERN Document Server

    Campanelli, Leonardo

    2015-01-01

    [Abridged] We analyze the evolution of superhorizon-scale magnetic fields from the end of inflation till today. Whatever is the mechanism responsible for their generation during inflation, we find that a given magnetic mode with wavenumber $k$ evolves, after inflation, according to the values of $k\\eta_e$, $n_{\\mathbf{k}}$, and $\\Omega_k$, where $\\eta_e$ is the conformal time at the end of inflation, $n_{\\mathbf{k}}$ is the number density spectrum of inflation-produced photons, and $\\Omega_k$ is the phase difference between the two Bogolubov coefficients which characterize the state of that mode at the end of inflation. For any realistic inflationary magnetogenesis scenario, we find that $n_{\\mathbf{k}}^{-1} \\ll |k\\eta_e| \\ll 1$, and three evolutionary scenarios are possible: ($i$) $|\\Omega_k \\mp \\pi| = \\mathcal{O}(1)$, in which case the evolution of the magnetic spectrum $B_k(\\eta)$ is adiabatic, $a^2B_k(\\eta) = \\mbox{const}$, with $a$ being the expansion parameter; ($ii$) $|\\Omega_k \\mp \\pi| \\ll |k\\eta_e|$,...

  13. Health Effects of Electromagnetic Fields: A Review of Literature.

    Science.gov (United States)

    White, George L.; And Others

    1995-01-01

    Current evidence suggests that the effects of electromagnetic fields (EMF) disturb cell homeostasis at very low intensities by influencing discrete intracellular magnetic fields. The article reviews current research about the health effects of EMF, examining historical implications, childhood studies, adult studies, and popular press reports, and…

  14. SCUPOL Magnetic Field Analysis

    CERN Document Server

    Poidevin, Frederick; Kowal, Grzegorz; Pino, Elisabete de Gouveia Dal; Magalhaes, Antonio-Mario

    2013-01-01

    We present an extensive analysis of the 850 microns polarization maps of the SCUPOL Catalog produced by Matthews et al. (2009), focusing exclusively on the molecular clouds and star-forming regions. For the sufficiently sampled regions, we characterize the depolarization properties and the turbulent-to-mean magnetic field ratio of each region. Similar sets of parameters are calculated from 2D synthetic maps of dust emission polarization produced with 3D MHD numerical simulations scaled to the S106, OMC-2/3, W49 and DR21 molecular clouds polarization maps. For these specific regions the turbulent MHD regimes retrieved from the simulations, as described by the turbulent Alfv\\`en and sonic Mach numbers, are consistent within a factor 1 to 2 with the values of the same turbulent regimes estimated from the analysis of Zeeman measurements data provided by Crutcher (1999). Constraints on the values of the inclination angle of the mean magnetic field with respect to the LOS are also given. The values obtained from th...

  15. Magnetic Fields: Visible and Permanent.

    Science.gov (United States)

    Winkeljohn, Dorothy R.; Earl, Robert D.

    1983-01-01

    Children will be able to see the concept of a magnetic field translated into a visible reality using the simple method outlined. Standard shelf paper, magnets, iron filings, and paint in a spray can are used to prepare a permanent and well-detailed picture of the magnetic field. (Author/JN)

  16. Assessment of biological changes of continuous whole body exposure to static magnetic field and extremely low frequency electromagnetic fields in mice.

    Science.gov (United States)

    Hashish, A H; El-Missiry, M A; Abdelkader, H I; Abou-Saleh, R H

    2008-11-01

    The question whether static magnetic fields (SMFs) and extremely low frequency electromagnetic fields (ELF-EMF) cause biological effects is of special interest. We investigated the effects of continuous whole body exposure to both fields for 30 days on some liver and blood parameters in mice. Two exposure systems were designed; the first produced a gradient SMF while the second generated uniform 50 Hz ELF-EMF. The results showed a gradual body weight loss when mice were exposed to either field. This is coupled with a significant decrease (Pglutathione-S-transferase activity and lipid peroxidation level in the liver were significantly increased while a significant decrease in hepatic gluthathione content was recorded. A significant decrease in the counts of monocytes, platelets, peripheral lymphocytes as well as splenic total, T and B lymphocytes levels was observed for SMF and ELF-EMF exposed groups. The granulocytes percentage was significantly increased. The results indicate that there is a relation between the exposure to SMF or ELF-EMF and the oxidative stress through distressing redox balance leading to physiological disturbances.

  17. Reconnection of Magnetic Fields

    Science.gov (United States)

    Birn, J.; Priest, E. R.

    2007-01-01

    Preface; Part I. Introduction: 1.1 The Sun E. R. Priest; 1.2 Earth's magnetosphere J. Birn; Part II. Basic Theory of MHD Reconnection: 2.1 Classical theory of two-dimensional reconnection T. G. Forbes; 2.2 Fundamental concepts G. Hornig; 2.3 Three-dimensional reconnection in the absence of magnetic null points G. Hornig; 2.4 Three-dimensional reconnection at magnetic null points D. Pontin; 2.5 Three-dimensional flux tube reconnection M. Linton; Part III. Basic Theory of Collisionless Reconnection: 3.1 Fundamentals of collisionless reconnection J. Drake; 3.2 Diffusion region physics M. Hesse; 3.3 Onset of magnetic reconnection P. Pritchett; 3.4 Hall-MHD reconnection A. Bhattacharjee and J. Dorelli; 3.5 Role of current-aligned instabilities J. Büchner and W. Daughton; 3.6 Nonthermal particle acceleration M. Hoshino; Part IV. Reconnection in the Magnetosphere: 4.1 Reconnection at the magnetopause: concepts and models J. G. Dorelli and A. Bhattacharjee; 4.2 Observations of magnetopause reconnection K.-H. Trattner; 4.3 On the stability of the magnetotail K. Schindler; 4.4 Simulations of reconnection in the magnetotail J. Birn; 4.5 Observations of tail reconnection W. Baumjohann and R. Nakamura; 4.6 Remote sensing of reconnection M. Freeman; Part V. Reconnection in the Sun's Atmosphere: 5.1 Coronal heating E. R. Priest; 5.2 Separator reconnection D. Longcope; 5.3 Pinching of coronal fields V. Titov; 5.4 Numerical experiments on coronal heating K. Galsgaard; 5.5 Solar flares K. Kusano; 5.6 Particle acceleration in flares: theory T. Neukirch; 5.7 Fast particles in flares: observations L. Fletcher; 6. Open problems J. Birn and E. R. Priest; Bibliography; Index.

  18. EMF Monitoring—Concepts, Activities, Gaps and Options

    Directory of Open Access Journals (Sweden)

    Gregor Dürrenberger

    2014-09-01

    Full Text Available Exposure to electromagnetic fields (EMF is a cause of concern for many people. The topic will likely remain for the foreseeable future on the scientific and political agenda, since emissions continue to change in characteristics and levels due to new infrastructure deployments, smart environments and novel wireless devices. Until now, systematic and coordinated efforts to monitor EMF exposure are rare. Furthermore, virtually nothing is known about personal exposure levels. This lack of knowledge is detrimental for any evidence-based risk, exposure and health policy, management and communication. The main objective of the paper is to review the current state of EMF exposure monitoring activities in Europe, to comment on the scientific challenges and deficiencies, and to describe appropriate strategies and tools for EMF exposure assessment and monitoring to be used to support epidemiological health research and to help policy makers, administrators, industry and consumer representatives to base their decisions and communication activities on facts and data.

  19. Vestibular stimulation by magnetic fields

    Science.gov (United States)

    Ward, Bryan K.; Roberts, Dale C.; Della Santina, Charles C.; Carey, John P.; Zee, David S.

    2015-01-01

    Individuals working next to strong static magnetic fields occasionally report disorientation and vertigo. With the increasing strength of magnetic fields used for magnetic resonance imaging (MRI) studies, these reports have become more common. It was recently learned that humans, mice and zebrafish all demonstrate behaviors consistent with constant peripheral vestibular stimulation while inside a strong, static magnetic field. The proposed mechanism for this effect involves a Lorentz force resulting from the interaction of a strong static magnetic field with naturally occurring ionic currents flowing through the inner ear endolymph into vestibular hair cells. The resulting force within the endolymph is strong enough to displace the lateral semicircular canal cupula, inducing vertigo and the horizontal nystagmus seen in normal mice and in humans. This review explores the evidence for interactions of magnetic fields with the vestibular system. PMID:25735662

  20. Magnetic response to applied electrostatic field in external magnetic field

    Energy Technology Data Exchange (ETDEWEB)

    Adorno, T.C. [Universidade de Sao Paulo, Instituto de Fisica, Caixa Postal 66318, Sao Paulo, SP (Brazil); University of Florida, Department of Physics, Gainesville, FL (United States); Gitman, D.M. [Universidade de Sao Paulo, Instituto de Fisica, Caixa Postal 66318, Sao Paulo, SP (Brazil); Tomsk State University, Department of Physics, Tomsk (Russian Federation); Shabad, A.E. [P. N. Lebedev Physics Institute, Moscow (Russian Federation)

    2014-04-15

    We show, within QED and other possible nonlinear theories, that a static charge localized in a finite domain of space becomes a magnetic dipole, if it is placed in an external (constant and homogeneous) magnetic field in the vacuum. The magnetic moment is quadratic in the charge, depends on its size and is parallel to the external field, provided the charge distribution is at least cylindrically symmetric. This magneto-electric effect is a nonlinear response of the magnetized vacuum to an applied electrostatic field. Referring to the simple example of a spherically symmetric applied field, the nonlinearly induced current and its magnetic field are found explicitly throughout the space; the pattern of the lines of force is depicted, both inside and outside the charge, which resembles that of a standard solenoid of classical magnetostatics. (orig.)

  1. Magnetic response to applied electrostatic field in external magnetic field

    CERN Document Server

    Adorno, T C; Shabad, A E

    2014-01-01

    We show, within QED and other possible nonlinear theories, that a static charge localized in a finite domain of space becomes a magnetic dipole, if it is placed in an external (constant and homogeneous) magnetic field in the vacuum. The magnetic moment is quadratic in the charge, depends on its size and is parallel to the external field, provided the charge distribution is at least cylindrically symmetric. This magneto-electric effect is a nonlinear response of the magnetized vacuum to an applied electrostatic field. Referring to a simple example of a spherically-symmetric applied field, the nonlinearly induced current and its magnetic field are found explicitly throughout the space, the pattern of lines of force is depicted, both inside and outside the charge, which resembles that of a standard solenoid of classical magnetostatics.

  2. Human health effects of EMFs: The cost of doing nothing

    Science.gov (United States)

    Carpenter MD, David O.

    2010-04-01

    Everyone is exposed to electromagnetic fields (EMFs) from electricity (extremely low frequency, ELF), communication frequencies and wireless devices (radiofrequency, RF), as well as naturally occurring EMFs. Concern of health hazards from EMFs has increased as the use of mobile phones and other wireless devices has grown in all segments of the population, especially children. While there has been strong evidence for an association between leukemia and residential or occupational exposure to ELF EMFs for many years, the standards in existence are not sufficiently stringent to protect from an increased risk of cancer. ELF EMFs also increase risk of at least two types of neurodegenerative diseases. For RF EMFs, standards are set at levels designed to avoid tissue heating, in spite of many reports of biological effects at intensities too low to cause significant heating. Recent evidence demonstrates elevations in risk of brain cancer and acoustic neuroma only on the side of the head where individuals used their mobile phone. Individuals who begin exposure at younger ages are more vulnerable. These data indicate that the existing standards for radiofrequency exposure are not adequate. While there are many unanswered questions, the cost of doing nothing may result in an increasing number of people, many of them young, developing these diseases.

  3. Human health effects of EMFs: The cost of doing nothing

    Energy Technology Data Exchange (ETDEWEB)

    Carpenter, David O, E-mail: carpent@uamail.albany.ed [Institute for Health and the Environment, University at Albany, Rensselaer, NY 12144-3456 (United States)

    2010-04-15

    Everyone is exposed to electromagnetic fields (EMFs) from electricity (extremely low frequency, ELF), communication frequencies and wireless devices (radiofrequency, RF), as well as naturally occurring EMFs. Concern of health hazards from EMFs has increased as the use of mobile phones and other wireless devices has grown in all segments of the population, especially children. While there has been strong evidence for an association between leukemia and residential or occupational exposure to ELF EMFs for many years, the standards in existence are not sufficiently stringent to protect from an increased risk of cancer. ELF EMFs also increase risk of at least two types of neurodegenerative diseases. For RF EMFs, standards are set at levels designed to avoid tissue heating, in spite of many reports of biological effects at intensities too low to cause significant heating. Recent evidence demonstrates elevations in risk of brain cancer and acoustic neuroma only on the side of the head where individuals used their mobile phone. Individuals who begin exposure at younger ages are more vulnerable. These data indicate that the existing standards for radiofrequency exposure are not adequate. While there are many unanswered questions, the cost of doing nothing may result in an increasing number of people, many of them young, developing these diseases.

  4. NMR in pulsed magnetic field

    KAUST Repository

    Abou-Hamad, Edy

    2011-09-01

    Nuclear magnetic resonance (NMR) experiments in pulsed magnetic fields up to 30.4 T focused on 1H and 93Nb nuclei are reported. Here we discuss the advantage and limitation of pulsed field NMR and why this technique is able to become a promising research tool. © 2011 Elsevier Inc. All Rights Reserved.

  5. The MAVEN Magnetic Field Investigation

    Science.gov (United States)

    Connerney, J. E. P.; Espley, J.; Lawton, P.; Murphy, S.; Odom, J.; Oliversen, R.; Sheppard, D.

    2014-01-01

    The MAVEN magnetic field investigation is part of a comprehensive particles and fields subsystem that will measure the magnetic and electric fields and plasma environment of Mars and its interaction with the solar wind. The magnetic field instrumentation consists of two independent tri-axial fluxgate magnetometer sensors, remotely mounted at the outer extremity of the two solar arrays on small extensions ("boomlets"). The sensors are controlled by independent and functionally identical electronics assemblies that are integrated within the particles and fields subsystem and draw their power from redundant power supplies within that system. Each magnetometer measures the ambient vector magnetic field over a wide dynamic range (to 65,536 nT per axis) with a quantization uncertainty of 0.008 nT in the most sensitive dynamic range and an accuracy of better than 0.05%. Both magnetometers sample the ambient magnetic field at an intrinsic sample rate of 32 vector samples per second. Telemetry is transferred from each magnetometer to the particles and fields package once per second and subsequently passed to the spacecraft after some reformatting. The magnetic field data volume may be reduced by averaging and decimation, when necessary to meet telemetry allocations, and application of data compression, utilizing a lossless 8-bit differencing scheme. The MAVEN magnetic field experiment may be reconfigured in flight to meet unanticipated needs and is fully hardware redundant. A spacecraft magnetic control program was implemented to provide a magnetically clean environment for the magnetic sensors and the MAVEN mission plan provides for occasional spacecraft maneuvers - multiple rotations about the spacecraft x and z axes - to characterize spacecraft fields and/or instrument offsets in flight.

  6. Extremely Low Frequency Magnetic Fields Induce Spermatogenic Germ Cell Apoptosis: Possible Mechanism

    Directory of Open Access Journals (Sweden)

    Sang-Kon Lee

    2014-01-01

    Full Text Available The energy generated by an extremely low frequency electromagnetic field (ELF-EMF is too weak to directly induce genotoxicity. However, it is reported that an extremely low frequency magnetic field (ELF-MF is related to DNA strand breakage and apoptosis. The testes that conduct spermatogenesis through a dynamic cellular process involving meiosis and mitosis seem vulnerable to external stress such as heat, MF exposure, and chemical or physical agents. Nevertheless the results regarding adverse effects of ELF-EMF on human or animal reproductive functions are inconclusive. According to the guideline of the International Commission on Non-Ionizing Radiation Protection (ICNIRP; 2010 for limiting exposure to time-varying MF (1 Hz to 100 kHz, overall conclusion of epidemiologic studies has not consistently shown an association between human adverse reproductive outcomes and maternal or paternal exposure to low frequency fields. In animal studies there is no compelling evidence of causal relationship between prenatal development and ELF-MF exposure. However there is increasing evidence that EL-EMF exposure is involved with germ cell apoptosis in testes. Biophysical mechanism by which ELF-MF induces germ cell apoptosis has not been established. This review proposes the possible mechanism of germ cell apoptosis in testes induced by ELF-MF.

  7. Spin heat capacity of monolayer and AB-stacked bilayer MoS2 in the presence of exchange magnetic field

    Science.gov (United States)

    Hoi, Bui Dinh; Yarmohammadi, Mohsen; Mirabbaszadeh, Kavoos

    2017-04-01

    Dirac theory and Green's function technique are carried out to compute the spin dependent band structures and corresponding electronic heat capacity (EHC) of monolayer (ML) and AB-stacked bilayer (BL) molybdenum disulfide (MoS2) two-dimensional (2D) crystals. We report the influence of induced exchange magnetic field (EMF) by magnetic insulator substrates on these quantities for both structures. The spin-up (down) subband gaps are shifted with EMF from conduction (valence) band to valence (conduction) band at both Dirac points in the ML because of the spin-orbit coupling (SOC) which leads to a critical EMF in the K point and EHC returns to its initial states for both spins. In the BL case, EMF results split states and the decrease (increase) behavior of spin-up (down) subband gaps has been observed at both K and K‧ valleys which is due to the combined effect of SOC and interlayer coupling. For low and high EMFs, EHC of BL MoS2 does not change for spin-up subbands while increases for spin-down subbands.

  8. Effects of EMFs from Undersea Power Cables on Elasmobranchs and Other Marine Species.

    OpenAIRE

    Tricas, Timothy; Gill, Andrew B.

    2011-01-01

    Anthropogenic electromagnetic fields (EMFs) have been introduced into the marine environmentaround the world and from a wide variety of sources for well over a century. Despite this, littleis known about potential ecological impacts from EMFs. For decades, power transmissioncables have been installed across bays and river mouths, and connecting near-shore islands to themainland, with little consideration of possible effects to marine species from EMFs. At a time ofgreater environmental awaren...

  9. Magnetic fields in ring galaxies

    CERN Document Server

    Moss, D; Silchenko, O; Sokoloff, D; Horellou, C; Beck, R

    2016-01-01

    Many galaxies contain magnetic fields supported by galactic dynamo action. However, nothing definitive is known about magnetic fields in ring galaxies. Here we investigate large-scale magnetic fields in a previously unexplored context, namely ring galaxies, and concentrate our efforts on the structures that appear most promising for galactic dynamo action, i.e. outer star-forming rings in visually unbarred galaxies. We use tested methods for modelling $\\alpha-\\Omega$ galactic dynamos, taking into account the available observational information concerning ionized interstellar matter in ring galaxies. Our main result is that dynamo drivers in ring galaxies are strong enough to excite large-scale magnetic fields in the ring galaxies studied. The variety of dynamo driven magnetic configurations in ring galaxies obtained in our modelling is much richer than that found in classical spiral galaxies. In particular, various long-lived transients are possible. An especially interesting case is that of NGC 4513 where th...

  10. Rotating superconductor magnet for producing rotating lobed magnetic field lines

    Science.gov (United States)

    Hilal, Sadek K.; Sampson, William B.; Leonard, Edward F.

    1978-01-01

    This invention provides a rotating superconductor magnet for producing a rotating lobed magnetic field, comprising a cryostat; a superconducting magnet in the cryostat having a collar for producing a lobed magnetic field having oppositely directed adjacent field lines; rotatable support means for selectively rotating the superconductor magnet; and means for energizing the superconductor magnet.

  11. Low Cost Magnetic Field Controller

    CERN Document Server

    Malafronte, Alexandre A

    2005-01-01

    The Physics Institute of the University of São Paulo (IFUSP) is building a continuous wave (cw) racetrack microtron. This machine has several dipole magnets, like the first and second stage recirculators, and a number of smaller ones in the transport line. These magnets must produce very stable magnetic fields to allow the beam to recirculate along very precise orbits and paths. Furthermore, the fields must be reproducible with great accuracy to allow an easier setup of the machine, though the effects of hysteresis tend to jeopardize the reproducibility. If the magnetic field is chosen by setting the current in the coils, temperature effects over the magnet and power supply tend to change the field. This work describes an inexpensive magnetic field controller that allows a direct measure of the magnetic field through an Hall probe. It includes a microcontroller running a feedback algorithm to control the power supply, in order to keep the field stable and reproducible. The controller can also execu...

  12. Resonant magnetic fields from inflation

    CERN Document Server

    Byrnes, Christian T; Jain, Rajeev Kumar; Urban, Federico R

    2012-01-01

    We propose a novel scenario to generate primordial magnetic fields during inflation induced by an oscillating coupling of the electromagnetic field to the inflaton. This resonant mechanism has two key advantages over previous proposals. First of all, it generates a narrow band of magnetic fields at any required wavelength, thereby allaying the usual problem of a strongly blue spectrum and its associated backreaction. Secondly, it avoids the need for a strong coupling as the coupling is oscillating rather than growing or decaying exponentially. Despite these major advantages, we find that the backreaction is still far too large during inflation if the generated magnetic fields are required to have a strength of ${\\cal O}(10^{-15}\\, \\Gauss)$ today on observationally interesting scales. We provide a more general no-go argument, proving that this problem will apply to any model in which the magnetic fields are generated on subhorizon scales and freeze after horizon crossing.

  13. Static magnetic fields enhance turbulence

    CERN Document Server

    Pothérat, Alban

    2015-01-01

    More often than not, turbulence occurs under the influence of external fields, mostly rotation and magnetic fields generated either by planets, stellar objects or by an industrial environment. Their effect on the anisotropy and the dissipative behaviour of turbulence is recognised but complex, and it is still difficult to even tell whether they enhance or dampen turbulence. For example, externally imposed magnetic fields suppress free turbulence in electrically conducting fluids (Moffatt 1967), and make it two-dimensional (2D) (Sommeria & Moreau 1982); but their effect on the intensity of forced turbulence, as in pipes, convective flows or otherwise, is not clear. We shall prove that since two-dimensionalisation preferentially affects larger scales, these undergo much less dissipation and sustain intense turbulent fluctuations. When higher magnetic fields are imposed, quasi-2D structures retain more kinetic energy, so that rather than suppressing forced turbulence, external magnetic fields indirectly enha...

  14. Laboratory Studies of the Effects of Static and Variable Magnetic Fields on Freshwater Fish

    Energy Technology Data Exchange (ETDEWEB)

    Cada, Glenn F [ORNL; Bevelhimer, Mark S [ORNL; Fortner, Allison M [ORNL; Riemer, Kristina P [ORNL; Schweizer, Peter E [ORNL

    2012-04-01

    There is considerable interest in the development of marine and hydrokinetic energy projects in rivers, estuaries, and coastal ocean waters of the United States. Hydrokinetic (HK) technologies convert the energy of moving water in river or tidal currents into electricity, without the impacts of dams and impoundments associated with conventional hydropower or the extraction and combustion of fossil fuels. The Federal Energy Regulatory Commission (FERC) maintains a database that displays the geographical distribution of proposed HK projects in inland and tidal waters (FERC 2012). As of March 2012, 77 preliminary permits had been issued to private developers to study HK projects in inland waters, the development of which would total over 8,000 MW. Most of these projects are proposed for the lower Mississippi River. In addition, the issuance of another 27 preliminary permits for HK projects in inland waters, and 3 preliminary permits for HK tidal projects (totaling over 3,100 MW) were under consideration by FERC. Although numerous HK designs are under development (see DOE 2009 for a description of the technologies and their potential environmental effects), the most commonly proposed projects entail arrays of rotating devices, much like submerged wind turbines, that are positioned in the high-velocity (high energy) river channels. The many diverse HK designs imply a diversity of environmental impacts, but a potential impact common to most is the effect on aquatic organisms of electromagnetic fields (EMF) created by the projects. The submerged electrical generator will emit an EMF into the surrounding water, as will underwater cables used to transmit electricity from the generator to the shore, between individual units in an array (inter-turbine cables), and between the array and a submerged step-up transformer. The electric current moving through these cables will induce magnetic fields in the immediate vicinity, which may affect the behavior or viability of fish and

  15. Origin of cosmic magnetic fields

    Science.gov (United States)

    Rees, M. J.

    2006-06-01

    The first significant cosmic fields, and the seed field for galactic dynamos probably developed after the formation of the first non-linear structures. The history of star formation and the intergalactic medium is controlled, at least in part, by how and when galaxies and their precursors acquired their fields. The amplification of fields behind shocks, and the diffusivity of the magnetic flux, are crucial to the interpretation of radio sources, gamma ray burst afterglows, and other energetic cosmic phenomena. The build-up of magnetic fields is an important aspect of the overall cosmogonic process.

  16. Effects on Freshwater Organisms of Magnetic Fields Associated with Hydrokinetic Turbines

    Energy Technology Data Exchange (ETDEWEB)

    Cada, Glenn F [ORNL; Bevelhimer, Mark S [ORNL; Riemer, Kristina P [ORNL; Turner, Julie W [ORNL

    2011-07-01

    Underwater cables will be used to transmit electricity between turbines in an array (interturbine cables), between the array and a submerged step-up transformer (if part of the design), and from the transformer or array to shore. All types of electrical transmitting cables (as well as the generator itself) will emit EMF into the surrounding water. The electric current will induce magnetic fields in the immediate vicinity, which may affect the behavior or viability of animals. Because direct electrical field emissions can be prevented by shielding and armoring, we focused our studies on the magnetic fields that are unavoidably induced by electric current moving through a generator or transmission cable. These initial experiments were carried out to evaluate whether a static magnetic field, such as would be produced by a direct current (DC) transmitting cable, would affect the behavior of common freshwater fish and invertebrates.

  17. Measuring Earth's Magnetic Field Simply.

    Science.gov (United States)

    Stewart, Gay B.

    2000-01-01

    Describes a method for measuring the earth's magnetic field using an empty toilet paper tube, copper wire, clear tape, a battery, a linear variable resistor, a small compass, cardboard, a protractor, and an ammeter. (WRM)

  18. ISR split-field magnet

    CERN Multimedia

    1975-01-01

    The experimental apparatus used at intersection 4 around the Split-Field Magnet by the CERN-Bologna Collaboration (experiment R406). The plastic scintillator telescopes are used for precise pulse-height and time-of-flight measurements.

  19. The Juno Magnetic Field Investigation

    Science.gov (United States)

    Connerney, J. E. P.; Benn, M.; Bjarno, J. B.; Denver, T.; Espley, J.; Jorgensen, J. L.; Jorgensen, P. S.; Lawton, P.; Malinnikova, A.; Merayo, J. M.; Murphy, S.; Odom, J.; Oliversen, R.; Schnurr, R.; Sheppard, D.; Smith, E. J.

    2017-02-01

    The Juno Magnetic Field investigation (MAG) characterizes Jupiter's planetary magnetic field and magnetosphere, providing the first globally distributed and proximate measurements of the magnetic field of Jupiter. The magnetic field instrumentation consists of two independent magnetometer sensor suites, each consisting of a tri-axial Fluxgate Magnetometer (FGM) sensor and a pair of co-located imaging sensors mounted on an ultra-stable optical bench. The imaging system sensors are part of a subsystem that provides accurate attitude information (to ˜20 arcsec on a spinning spacecraft) near the point of measurement of the magnetic field. The two sensor suites are accommodated at 10 and 12 m from the body of the spacecraft on a 4 m long magnetometer boom affixed to the outer end of one of 's three solar array assemblies. The magnetometer sensors are controlled by independent and functionally identical electronics boards within the magnetometer electronics package mounted inside Juno's massive radiation shielded vault. The imaging sensors are controlled by a fully hardware redundant electronics package also mounted within the radiation vault. Each magnetometer sensor measures the vector magnetic field with 100 ppm absolute vector accuracy over a wide dynamic range (to 16 Gauss = 1.6 × 106 nT per axis) with a resolution of ˜0.05 nT in the most sensitive dynamic range (±1600 nT per axis). Both magnetometers sample the magnetic field simultaneously at an intrinsic sample rate of 64 vector samples per second. The magnetic field instrumentation may be reconfigured in flight to meet unanticipated needs and is fully hardware redundant. The attitude determination system compares images with an on-board star catalog to provide attitude solutions (quaternions) at a rate of up to 4 solutions per second, and may be configured to acquire images of selected targets for science and engineering analysis. The system tracks and catalogs objects that pass through the imager field of

  20. The Juno Magnetic Field Investigation

    Science.gov (United States)

    Connerney, J. E. P.; Benna, M.; Bjarno, J. B.; Denver, T.; Espley, J.; Jorgensen, J. L.; Jorgensen, P. S.; Lawton, P.; Malinnikova, A.; Merayo, J. M.; hide

    2017-01-01

    The Juno Magnetic Field investigation (MAG) characterizes Jupiter's planetary magnetic field and magnetosphere, providing the first globally distributed and proximate measurements of the magnetic field of Jupiter. The magnetic field instrumentation consists of two independent magnetometer sensor suites, each consisting of a tri-axial Fluxgate Magnetometer (FGM) sensor and a pair of co-located imaging sensors mounted on an ultra-stable optical bench. The imaging system sensors are part of a subsystem that provides accurate attitude information (to approx. 20 arcsec on a spinning spacecraft) near the point of measurement of the magnetic field. The two sensor suites are accommodated at 10 and 12 m from the body of the spacecraft on a 4 m long magnetometer boom affixed to the outer end of one of 's three solar array assemblies. The magnetometer sensors are controlled by independent and functionally identical electronics boards within the magnetometer electronics package mounted inside Juno's massive radiation shielded vault. The imaging sensors are controlled by a fully hardware redundant electronics package also mounted within the radiation vault. Each magnetometer sensor measures the vector magnetic field with 100 ppm absolute vector accuracy over a wide dynamic range (to 16 Gauss = 1.6 x 10(exp. 6) nT per axis) with a resolution of approx. 0.05 nT in the most sensitive dynamic range (+/-1600 nT per axis). Both magnetometers sample the magnetic field simultaneously at an intrinsic sample rate of 64 vector samples per second. The magnetic field instrumentation may be reconfigured in flight to meet unanticipated needs and is fully hardware redundant. The attitude determination system compares images with an on-board star catalog to provide attitude solutions (quaternions) at a rate of up to 4 solutions per second, and may be configured to acquire images of selected targets for science and engineering analysis. The system tracks and catalogs objects that pass through

  1. Magnetic-Field Hazards Bibliography.

    Science.gov (United States)

    1985-09-01

    produced during pulsed- magnetic-field therapy for non-union of the tibia." Med. Biol. Eng. Comput., Vol. 20, pp. 501-511 (1982). 32. Miller, D. A...Phenum Publishing Co. (1983). 40. Topper, R. F., "Electromagnetic shielding feasibility study," ASD -TDR-63-194 (Armour Research Foundation, Chicago...mammalian cells by strong magnetic fields (1976). 93. Malins, D. C., and Collier, T. K., "Xenobiotic interactions in aquatic organisms-effects on

  2. Superparamagnetic Iron Oxide Nanoparticles Modified with Tween 80 Pass through the Intact Blood-Brain Barrier in Rats under Magnetic Field.

    Science.gov (United States)

    Huang, Yinping; Zhang, Baolin; Xie, Songbo; Yang, Boning; Xu, Qin; Tan, Jie

    2016-05-11

    The methods for the delivery of theranostic agents across the blood-brain barrier (BBB) are highly required. Superparamagnetic iron oxide nanoparticles (SPIONs) coated with PEG (poly(ethylene glycol)), PEI (poly(ethylene imine)), and Tween 80 (polysorbate 80) (Tween-SPIONs) were prepared. We demonstrate the effective passage of tail-vein-injected Tween-SPIONs across normal BBB in rats under an external magnetic field (EMF). The quantitative analyses show significant accumulation of SPIONs in the cortex near the magnet, with progressively lower accumulation in brain tissues far from the magnet. A transmission electron microscopy picture of an ultrathin section of the rat brain displays Tween-SPIONs crossing the BBB. The comparative study confirms that both the Tween-80 modification and EMF play crucial roles in the effective passage of SPIONs across the intact BBB. However, the magnetic force alone cannot drag the SPIONs coated with PEI/PEG polymers through the BBB. The results indicate the Tween-SPIONs cross the BBB via an active penetration facilitated by EMF. This work is encouraging for further study on the delivery of drug or diagnostic agents into the parenchyma of the brain for dealing with neurological disorders by using Tween-SPIONs carriers under EMF.

  3. Design of a job exposure matrix on electric and magnetic fields: selection of an efficient job classification for workers in thermoelectric power production plants.

    Science.gov (United States)

    Guénel, P; Nicolau, J; Imbernon, E; Warret, G; Goldberg, M

    1993-01-01

    Occupational exposure to 50 Hz electric and magnetic fields (EMF) was measured among 184 workers in thermoelectric power production plants using an individual portable dosimeter. A job exposure matrix (JEM) is elaborated from these data to be used in an epidemiological study on the potential carcinogenic effects of EMF. To reduce the range of exposure misclassification in the study, groups of workers with high exposure homogeneity must be identified. Classifying the workers by type of plant yielded homogeneous exposure groups, especially for workers in non-nuclear power plants. Workers in nuclear plants had higher mean exposure to magnetic fields, but the homogeneity of exposure was smaller. The exposure also differed between occupations, but the occupational title did not produce a uniform increase of exposure homogeneity within subgroups. It is concluded that the place of work is the most important determinant of exposure to magnetic fields for workers in thermoelectric power plants to be included in the JEM.

  4. Bioeffects of extremely low-frequency electromagnetic fields: variation with intensity, waveform, and individual or combined electric and magnetic fields. [Effects on mitosis and respiration in Physarium polycephalum

    Energy Technology Data Exchange (ETDEWEB)

    Goodman, E.M.; Greenebaum, B.; Marron, M.T.

    1979-06-01

    Prolonged exposure of the myxomycete Physarum polycephalum to either continuous wave (75 Hz) or frequency modulated wave (76 Hz) electromagnetic fields (EMF) (0.1 to 2.0 G and 0.035 to 0.7 V/m) lengthens the mitotic cycle and depresses the respiration rate. Once induced, these effects persist indefinately in the presence of EMF without increasing or decreasing in magnitude beyond that due to normal variability of the organism. Similar effects are observed when either individual electric fields (0.7 V/m) or magnetic fields (2.0 G) are applied; however, the magnitude of the response is less than that observed with simultaneous fields. The individual field effects appear to be additive for respiration but not for nuclear division rate. For fields applied simultaneously at levels below 0.14 V/m and 0.4 G the response was independent of field intensity. No threshold was observed for simultaneously applied electric and magnetic fields; however, indirect evidence is presented that suggests either the electric or magnetic field is below threshold at levels of 0.14 V/m and 0.4 G, respectively. Frequency modulation of the fields seems to have no major effect o the response induced in P. polycephalum.

  5. Biophysical aspects of the influence of electromagnetic fields (EMF) on the human body Influencia de los campos electromagnéticos en el organismo humano: aspectos biofísicos

    OpenAIRE

    Napaleon Hernández

    1993-01-01

     

    Some historical aspects of biomagnetism and of the various steps that led to the development of bioelectricity and electro technique are summarized. Alterations observed in individuals working for long periods of time in contact with artificial EMF are described as well as the correlation between natural EMF and accidentality. The utilization of EMF for therapeutic purposes ...

  6. Magnetic fields in spiral galaxies

    Science.gov (United States)

    Beck, Rainer

    2015-12-01

    Radio synchrotron emission, its polarization and Faraday rotation of the polarization angle are powerful tools to study the strength and structure of magnetic fields in galaxies. Unpolarized synchrotron emission traces isotropic turbulent fields which are strongest in spiral arms and bars (20-30 \\upmu G) and in central starburst regions (50-100 \\upmu G). Such fields are dynamically important; they affect gas flows and drive gas inflows in central regions. Polarized emission traces ordered fields, which can be regular or anisotropic turbulent, where the latter originates from isotropic turbulent fields by the action of compression or shear. The strongest ordered fields (10-15 \\upmu G) are generally found in interarm regions. In galaxies with strong density waves, ordered fields are also observed at the inner edges of spiral arms. Ordered fields with spiral patterns exist in grand-design, barred and flocculent galaxies and in central regions. Ordered fields in interacting galaxies have asymmetric distributions and are a tracer of past interactions between galaxies or with the intergalactic medium.—Faraday rotation measures of the diffuse polarized radio emission from galaxy disks reveal large-scale spiral patterns that can be described by the superposition of azimuthal modes; these are signatures of regular fields generated by mean-field dynamos. "Magnetic arms" between gaseous spiral arms may also be products of dynamo action, but need a stable spiral pattern to develop. Helically twisted field loops winding around spiral arms were found in two galaxies so far. Large-scale field reversals, like the one found in the Milky Way, could not yet be detected in external galaxies. In radio halos around edge-on galaxies, ordered magnetic fields with X-shaped patterns are observed. The origin and evolution of cosmic magnetic fields, in particular their first occurrence in young galaxies and their dynamical importance during galaxy evolution, will be studied with

  7. Nanometric alternating magnetic field generator.

    Science.gov (United States)

    Espejo, A P; Tejo, F; Vidal-Silva, N; Escrig, J

    2017-07-05

    In this work we introduce an alternating magnetic field generator in a cylindrical nanostructure. This field appears due to the rotation of a magnetic domain wall located at some position, generating a magnetic region that varies its direction of magnetization alternately, thus inducing an alternating magnetic flux in its vicinity. This phenomenon occurs due to the competition between a spin-polarized current and a magnetic field, which allows to control both the angular velocity and the pinning position of the domain wall. As proof of concept, we study the particular case of a diameter-modulated nanowire with a spin-polarized current along its axis and the demagnetizing field produced by its modulation. This inhomogeneous field allows one to control the angular velocity of the domain wall as a function of its position along the nanowire allowing frequencies in the GHz range to be achieved. This generator could be used in telecommunications for devices in the range of radiofrequencies or, following Faraday's induction law, could also induce an electromotive force and be used as a movable alternate voltage source in future nanodevices.

  8. Sources of EMF in Near Earth and Planetary Environments

    Science.gov (United States)

    McCanney, J. M.

    2008-05-01

    The realization that extensive electrical activates occur in and above the troposphere, extending to the ionosphere and ultimately coupling to the magnetosphere have raised the theoretical and experimental questions regarding the sources of EMF which create the observed effects. The current work has identified 17 Local Electrical Batteries (LEBs), which provide the electrical EMF that can be linked to the observed effects of Sprites, Elves, etc. and which additionally are shown to directly power the troposphere storm systems and counter-rotating jet streams, rotating in the easterly direction in the northern and southern latitudes and westerly near the equator. The high latitude easterly flowing jet streams contain positively charged ions in the driving layers of the ionosphere, whereas the equatorial westerly flowing jet streams contain electrons. The flow of energy concentrates near the equatorial regions (low latitudes) for a number of theoretical reasons. Energy flows also occur in the vortex regions (corresponding to troposphere low pressure cells) as the easterly flowing ionosphere high latitude belts interact with the equatorial westerly moving streams. These flows couple to both the terrestrial and external ring current magnetic fields. The path of the sources of EMF can be followed from the passing solar wind through "tunnels" that end in electrical currents that pass into the atmosphere via the ionosphere to storm cloud systems in the lower atmosphere. These are the sources of electrical energy that power the severe lower atmospheric storm systems such as westerly moving hurricanes at low latitudes and associated tornadoes. The model for these storm systems is included. The connection is made theoretically with the solar wind that drives the 17 identified LEBs. The ultimate source of driving energy is the result of an excess current of protons in the solar wind, which creates an overall capacitor with inherent non-uniform electric field surrounding the

  9. Effect of thermoelectromagnetic convection on the growth of bulk single crystals from semiconductor melts in a constant magnetic field

    Energy Technology Data Exchange (ETDEWEB)

    Gorbunov, L.A.

    1987-12-01

    The growth of bulk single crystals in semiconductor melts is investigated with emphasis on the effect of constant magnetic fields on the hydrodynamic processes and heat and mass transfer occurring in the melt. In particular, it is shown that the thermal emf in semiconductor melts can produce thermal currents whose interaction with a constant magnetic field can generate electromagnetic forces and lead to melt mixing (thermoelectromagnetic convection). The parameters of thermoelectromagnetic convection are estimated, and the importance of allowing for its effect in real processes is emphasized. 11 references.

  10. Magnetic Field Generation in Stars

    CERN Document Server

    Ferrario, Lilia; Zrake, Jonathan

    2015-01-01

    Enormous progress has been made on observing stellar magnetism in stars from the main sequence through to compact objects. Recent data have thrown into sharper relief the vexed question of the origin of stellar magnetic fields, which remains one of the main unanswered questions in astrophysics. In this chapter we review recent work in this area of research. In particular, we look at the fossil field hypothesis which links magnetism in compact stars to magnetism in main sequence and pre-main sequence stars and we consider why its feasibility has now been questioned particularly in the context of highly magnetic white dwarfs. We also review the fossil versus dynamo debate in the context of neutron stars and the roles played by key physical processes such as buoyancy, helicity, and superfluid turbulence,in the generation and stability of neutron star fields. Independent information on the internal magnetic field of neutron stars will come from future gravitational wave detections. Thus we maybe at the dawn of a ...

  11. A Novel Control Method for BLDCM Based on Phase Back-EMF Observation

    Directory of Open Access Journals (Sweden)

    Pan Lei

    2013-08-01

    Full Text Available The main purpose of this study is to propose a novel back-EMF observer. It can drive a permanent magnet Brushless DC Motor (BLDCM smoothly from slow to high speed without position or speed sensors. In the method, a phase back-EMF observer, which could estimate phase back-EMFs in real time and only relies on DC voltage and phase currents of motor without an additional circuit or complicated operation process,had been established with phase back-EMF as a disturbance signal. This observer simplifies the structure of traditional back-EMF observers and only has one inertia element, hence the response time and robustness of the system could be improved. This study also detailedly provides a method for speed and position detection, which has high performance in low speed range. The validity of the proposed method is verified through simulation and experimental results.

  12. Indoor localization using magnetic fields

    Science.gov (United States)

    Pathapati Subbu, Kalyan Sasidhar

    Indoor localization consists of locating oneself inside new buildings. GPS does not work indoors due to multipath reflection and signal blockage. WiFi based systems assume ubiquitous availability and infrastructure based systems require expensive installations, hence making indoor localization an open problem. This dissertation consists of solving the problem of indoor localization by thoroughly exploiting the indoor ambient magnetic fields comprising mainly of disturbances termed as anomalies in the Earth's magnetic field caused by pillars, doors and elevators in hallways which are ferromagnetic in nature. By observing uniqueness in magnetic signatures collected from different campus buildings, the work presents the identification of landmarks and guideposts from these signatures and further develops magnetic maps of buildings - all of which can be used to locate and navigate people indoors. To understand the reason behind these anomalies, first a comparison between the measured and model generated Earth's magnetic field is made, verifying the presence of a constant field without any disturbances. Then by modeling the magnetic field behavior of different pillars such as steel reinforced concrete, solid steel, and other structures like doors and elevators, the interaction of the Earth's field with the ferromagnetic fields is described thereby explaining the causes of the uniqueness in the signatures that comprise these disturbances. Next, by employing the dynamic time warping algorithm to account for time differences in signatures obtained from users walking at different speeds, an indoor localization application capable of classifying locations using the magnetic signatures is developed solely on the smart phone. The application required users to walk short distances of 3-6 m anywhere in hallway to be located with accuracies of 80-99%. The classification framework was further validated with over 90% accuracies using model generated magnetic signatures representing

  13. Magnetic Fields in Spiral Galaxies

    CERN Document Server

    Beck, Rainer

    2015-01-01

    Radio synchrotron emission is a powerful tool to study the strength and structure of magnetic fields in galaxies. Unpolarized synchrotron emission traces isotropic turbulent fields which are strongest in spiral arms and bars (20-30\\mu G) and in central starburst regions (50-100\\mu G). Such fields are dynamically important; they affect gas flows and drive gas inflows in central regions. Polarized emission traces ordered fields, which can be regular or anisotropic turbulent, where the latter originates from isotropic turbulent fields by the action of compression or shear. The strongest ordered fields (10-15\\mu G) are generally found in interarm regions. In galaxies with strong density waves, ordered fields are also observed at the inner edges of spiral arms. Ordered fields with spiral patterns exist in grand-design, barred and flocculent galaxies, and in central regions. Ordered fields in interacting galaxies have asymmetric distributions and are a tracer of past interactions between galaxies or with the interg...

  14. Proposal for magnetic/electromagnetic fields protection norms on national level

    Directory of Open Access Journals (Sweden)

    Đorđević Drago

    2008-01-01

    Full Text Available Introduction The modern life is not possible without application of magnetic/electromagnetic fields, which can be both helpful and harmful for human body. Influence of magnetic/electromagnetic fields on biological systems The non-ionizing radiation, especially magnetic/electromagnetic fields of all frequencies (0-300 GHz, can have many harmful effects on the human health that is confirmed by numerous epidemiological studies, studies with volunteers, animal studies, and in vitro studies. Proposal for magnetic/electromagnetic fields protection norms Proposal for magnetic/electromagnetic fields protection norms on national level based on the WHO Program for Environment, International Commission on Non-Ionizing Radiation Protection (ICNIRP], and WHO International EMF Project. Conclusion Protection from harmful effects of the magnetic/electromagnetic fields is still a great problem in many countries of modern society - huge costs, impaired quality of life, and more important, damage to the human health. Numerous data and publications of harmful effects of the magnetic/electromagnetic fields represents one's country basic necessary documentation for making decisions and law documents for protection norms on national level concerning the health maintenance according to the ICNIRP normatives.

  15. Magnetic fields of neutron stars

    CERN Document Server

    Reisenegger, Andreas

    2013-01-01

    Neutron stars contain the strongest magnetic fields known in the Universe. In this paper, I discuss briefly how these magnetic fields are inferred from observations, as well as the evidence for their time-evolution. I show how these extremely strong fields are actually weak in terms of their effects on the stellar structure, as is also the case for magnetic stars on the upper main sequence and magnetic white dwarfs, which have similar total magnetic fluxes. I propose a scenario in which a stable hydromagnetic equilibrium (containing a poloidal and a toroidal field component) is established soon after the birth of the neutron star, aided by the strong compositional stratification of neutron star matter, and this state is slowly eroded by non-ideal magnetohydrodynamic processes such as beta decays and ambipolar diffusion in the core of the star and Hall drift and breaking of the solid in its crust. Over sufficiently long time scales, the fluid in the neutron star core will behave as if it were barotropic, becau...

  16. Magnetic fields during galaxy mergers

    CERN Document Server

    Rodenbeck, Kai

    2016-01-01

    Galaxy mergers are expected to play a central role for the evolution of galaxies, and may have a strong impact on their magnetic fields. We present the first grid-based 3D magneto-hydrodynamical simulations investigating the evolution of magnetic fields during merger events. For this purpose, we employ a simplified model considering the merger event of magnetized gaseous disks in the absence of stellar feedback and without a stellar or dark matter component. We show that our model naturally leads to the production of two peaks in the evolution of the average magnetic field strength within 5 kpc, within 25 kpc and on scales in between 5 and 25 kpc. The latter is consistent with the peak in the magnetic field strength reported by Drzazga et al. (2011) in a merger sequence of observed galaxies. We show that the peak on the galactic scale and in the outer regions is likely due to geometrical effects, as the core of one galaxy enters the outskirts of the other one. In addition, there is a physical enhancement of t...

  17. Zero magnetic field type magnetic field sensor. Reijikaigata jikai sensor

    Energy Technology Data Exchange (ETDEWEB)

    Sonoda, T.; Ueda, R. (Kyushu Institute of Technology, Fukuoka (Japan))

    1990-11-20

    It is shown in this paper that a new type of sensor with excellent characteristics can be made by demagnetizing the sensor core toward a zero field state and then detecting an unknown field to be detected by the demagnetizing current. The core operates equivalently in a zero magnetic field so that the detection sensitivity is determined by the coil constant including the number of turns of the solenoid for demagnetization required to offset the field to be detected. Therefore the detection sensitivity does not depend on its configuration and magnetization characteristics and does not depend on the temperature. It is thereby considered that these characteristics can largely reduce such problems at present as the aging deterioration of magnetic materials or the quality control accompanied by manufacturing. In addition, the following points have been clarified: (1) The upper limit of the detectable range does not exist in principle. (2) The accuracy of the detection is 0.02% to the full scale 20kA/m. (3) The magnetization property required to the core used as a sensor is that it has a rectangular B-H loop which is as sharp as possible. 14 refs., 13 figs., 2 tabs.

  18. Primordial Magnetic Fields and Causality

    CERN Document Server

    Durrer, R; Durrer, Ruth; Caprini, Chiara

    2003-01-01

    In this letter we discuss the implications of causality on a primordial magnetic field. We show that the residual field on large scales is much stronger suppressed than usually assumed and that a helical component is even suppressed even more than the parity even part. We show that due to this strong suppression, even maximal primordial fields generated at the electroweak phase transition can just marginally seed the fields in galaxies and clusters, but they cannot leave any detectable imprint on the cosmic microwave background.

  19. Safety of high speed magnetic levitation transportation systems. Magnetic field testing of the TR07 Maglev vehicle and system. Volume 2: Appendices

    Science.gov (United States)

    Dietrich, Fred; Robertson, David; Steiner, George

    1992-04-01

    The safety of various magnetically levitated (maglev) and high speed rail (HSR) trains proposed for application in the United States is of direct concern to the Federal Railroad Administration (FRA). The characterization of electric and magnetic fields (EMF) emissions, both steady (dc) and produced by alternating current (ac) at power frequency (50 Hz in Europe and 60 Hz in the U.S.) and other frequencies in the Extreme Low Frequency (ELF) range (3-3000 Hz), and associated public and worker exposures to EMF, are a growing health and safety concern worldwide. As part of a comprehensive safety assessment of the German TransRapid (TR-07) maglev system undertaken by the FRA, with technical support from the DOT/RSPA Volpe National Transportation System Center (VNTSC), magnetic field measurements were performed by Electric Research and Management, Inc. (ERM) at the Transrapid Test Facility (TVE) in Emsland, Germany in August, 1990. Appendices include catalogs and documents detailing magnetic field data files and their specifics (static fields, spectral waveforms, and temporal and spatial information) by location.

  20. Effect of a weak magnetic field on the Mizoroki–Heck coupling reaction in the presence of wicker-like palladium-poly(N-vinylpyrrolidone)-iron nanocatalyst

    Energy Technology Data Exchange (ETDEWEB)

    Rafiee, Ezzat, E-mail: ezzat_rafiee@yahoo.com [Department of Inorganic Chemistry, Faculty of Chemistry, Razi University, Kermanshah 67149 (Iran, Islamic Republic of); Institute of Nano Science and Nano Technology, Razi University, Kermanshah 67149 (Iran, Islamic Republic of); Joshaghani, Mohammad [Department of Inorganic Chemistry, Faculty of Chemistry, Razi University, Kermanshah 67149 (Iran, Islamic Republic of); Institute of Nano Science and Nano Technology, Razi University, Kermanshah 67149 (Iran, Islamic Republic of); Abadi, Parvaneh Ghaderi-Shekhi [Institute of Nano Science and Nano Technology, Razi University, Kermanshah 67149 (Iran, Islamic Republic of)

    2016-06-15

    The wicker-like Pd-PVP-Fe (palladium-poly(N-vinylpyrrolidone)-iron) was synthesized by the external magnetic field (EMF). The Pd-based catalyst with nano and the face-centered cubic (fcc) structure was obtained at room temperature without using any additive. The resulting composite was characterized. The results show that EMF has a great influence on morphology, particle size, and crystalline structure of the Pd-PVP-Fe composite. The resulting composite (Pd-PVP-Fe), was found to be an effective catalyst for the Mizoroki–Heck reaction while is exposed to EMF with the intensity at 486 µT. The reused catalyst for at least five repeating cycles, shows excellent activity. - Highlights: • The wicker-like Pd-PVP-Fe nanocatalyst was synthesized via external magnetic field. • The resulting catalyst composite was characterized. • The C–C coupling reaction was carried out at magnetic field and room temperature. • Magnetic field affects on the morphology and size of the catalyst. • The catalyst could be reused without significant degradation in activity.

  1. Magnetic fields around black holes

    Science.gov (United States)

    Garofalo, David A. G.

    Active Galactic Nuclei are the most powerful long-lived objects in the universe. They are thought to harbor supermassive black holes that range from 1 million solar masses to 1000 times that value and possibly greater. Theory and observation are converging on a model for these objects that involves the conversion of gravitational potential energy of accreting gas to radiation as well as Poynting flux produced by the interaction of the rotating spacetime and the electromagnetic fields originating in the ionized accretion flow. The presence of black holes in astrophysics is taking center stage, with the output from AGN in various forms such as winds and jets influencing the formation and evolution of the host galaxy. This dissertation addresses some of the basic unanswered questions that plague our current understanding of how rotating black holes interact with their surrounding magnetized accretion disks to produce the enormous observed energy. Two magnetic configurations are examined. The first involves magnetic fields connecting the black hole with the inner accretion disk and the other involves large scale magnetic fields threading the disk and the hole. We study the effects of the former type by establishing the consequences that magnetic torques between the black hole and the inner accretion disk have on the energy dissipation profile. We attempt a plausible explanation to the observed "Deep Minimum" state in the Seyfert galaxy MCG-6- 30-15. For the latter type of magnetic geometry, we study the effects of the strength of the magnetic field threading the black hole within the context of the cherished Blandford & Znajek mechanism for black hole spin energy extraction. We begin by addressing the problem in the non-relativistic regime where we find that the black hole-threading magnetic field is stronger for greater disk thickness, larger magnetic Prandtl number, and for a larger accretion disk. We then study the problem in full relativity where we show that our

  2. Chiral transition with magnetic fields

    CERN Document Server

    Ayala, Alejandro; Mizher, Ana Julia; Rojas, Juan Cristobal; Villavicencio, Cristian

    2014-01-01

    We study the nature of the chiral transition for an effective theory with spontaneous breaking of symmetry, where charged bosons and fermions are subject to the effects of a constant external magnetic field. The problem is studied in terms of the relative intensity of the magnetic field with respect to the mass and the temperature. When the former is the smallest of the scales, we present a suitable method to obtain magnetic and thermal corrections up to ring order at high temperature. By these means, we solve the problem of the instability in the boson sector for these theories, where the squared masses, taken as functions of the order parameter, can vanish and even become negative. The solution is found by considering the screening properties of the plasma, encoded in the resummation of the ring diagrams at high temperature. We also study the case where the magnetic field is the intermediate of the three scales and explore the nature of the chiral transition as we vary the field strength, the coupling const...

  3. Magnetic Fields of Neutron Stars

    Indian Academy of Sciences (India)

    Sushan Konar

    2017-09-01

    This article briefly reviews our current understanding of the evolution of magnetic fields in neutron stars, which basically defines the evolutionary pathways between different observational classes of neutron stars. The emphasis here is on the evolution in binary systems and the newly emergent classes of millisecond pulsars.

  4. Optimal Magnetic Field Shielding Method by Metallic Sheets in Wireless Power Transfer System

    Directory of Open Access Journals (Sweden)

    Feng Wen

    2016-09-01

    Full Text Available To meet the regulations established to limit human exposure to time-varying electromagnetic fields (EMFs such as the International Committee on Non-Ionizing Radiation Protection (ICNIRP guidelines, thin metallic sheets are often used to shield magnetic field leakage in high power applications of wireless power transfer (WPT systems based on magnetic field coupling. However, the metals in the vicinity of the WPT coils cause the decrease of self and mutual inductances and increase of effective series resistance; as such, the electric performance including transmission power and the efficiency of the system is affected. With the research objective of further investigating excellent shielding effectiveness associated with system performance, the utilization of the optimal magnetic field shielding method by metallic sheets in magnetic field coupling WPT is carried out in this paper. The circuit and 3D Finite Element Analysis (FEA models are combined to predict the magnetic field distribution and electrical performance. Simulation and experiment results show that the method is very effective by obtaining the largest possible coupling coefficient of the WPT coils within the allowable range and then reducing the value nearest to and no smaller than the critical coupling coefficient via geometric unbroken metallic sheets. The optimal magnetic field shielding method which considers the system efficiency, transmission power, transmission distance, and system size is also achieved using the analytic hierarchy process (AHP. The results can benefit WPT by helping to achieve efficient energy transfer and safe use in metal shielded equipment.

  5. Magnetic fields in spiral galaxies

    Science.gov (United States)

    Krause, Marita

    2015-03-01

    The magnetic field structure in edge-on galaxies observed so far shows a plane-parallel magnetic field component in the disk of the galaxy and an X-shaped field in its halo. The plane-parallel field is thought to be the projected axisymmetric (ASS) disk field as observed in face-on galaxies. Some galaxies addionionally exhibit strong vertical magnetic fields in the halo right above and below the central region of the disk. The mean-field dynamo theory in the disk cannot explain these observed fields without the action of a wind, which also probably plays an important role to keep the vertical scale heights constant in galaxies of different Hubble types and star formation activities, as has been observed in the radio continuum: At λ6 cm the vertical scale heights of the thin disk and the thick disk/halo in a sample of five edge-on galaxies are similar with a mean value of 300 +/- 50 pc for the thin disk and 1.8 +/- 0.2 kpc for the thick disk (a table and references are given in Krause 2011) with our sample including the brightest halo observed so far, NGC 253, with strong star formation, as well as one of the weakest halos, NGC 4565, with weak star formation. If synchrotron emission is the dominant loss process of the relativistic electrons the outer shape of the radio emission should be dumbbell-like as has been observed in several edge-on galaxies like e.g. NGC 253 (Heesen et al. 2009) and NGC 4565. As the synchrotron lifetime t syn at a single frequency is proportional to the total magnetic field strength B t -1.5, a cosmic ray bulk speed (velocity of a galactic wind) can be defined as v CR = h CR /t syn = 2 h z /t syn , where h CR and h z are the scale heights of the cosmic rays and the observed radio emission at this freqnency. Similar observed radio scale heights imply a self regulation mechanism between the galactic wind velocity, the total magnetic field strength and the star formation rate SFR in the disk: v CR ~ B t 1.5 ~ SFR ~ 0.5 (Niklas & Beck 1997).

  6. Primordial Magnetic Fields that Last?

    CERN Document Server

    Carroll, S M; Carroll, Sean M.; Field, George B.

    1998-01-01

    The magnetic fields we observe in galaxies today may have their origins in the very early universe. While a number of mechanisms have been proposed which lead to an appreciable field amplitude at early times, the subsequent evolution of the field is of crucial importance, especially whether the correlation length of the field can grow as large as the size of a protogalaxy. This talk is a report on work in progress, in which we consider the fate of one specific primordial field scenario, driven by pseudoscalar effects near the electroweak phase transition. We argue that such a scenario has a number of attractive features, although it is still uncertain whether a field of appropriate size can survive until late times.

  7. Magnetic Properties of Erbium Gallium Gallate under High Magnetic Field

    Institute of Scientific and Technical Information of China (English)

    Zhang Xijuan; Cheng Haiying; Yang Cuihong; Wang Wei

    2004-01-01

    A theoretical investigation on the magnetic properties of rare-earth Er3+ in Er3 Ga5 O12 was reported. The average magnetic moments(M) for applied magnetic field H parallel to the [001 ], [ 100], [ 110], [ 111 ] direction was studied based on the quantum theory. Temperature dependence of the magnetic properties is analyzed for H applied parallel to the [ 100] and [ 111 ] crystallographic directions. The magnetization decreases with increasing temperature,showing good agreement with thermal effect. A strong anisotropy of the magnetization is found under high magnetic field, but when the magnetic field is small, M and H are proportional.

  8. Use of C. Elegans as a model organism for sensing the effects of ELF-EMFs

    Energy Technology Data Exchange (ETDEWEB)

    Lacchini, A H; Everington, M L; Augousti, A T; Walker, A J [School of Life Sciences, Kingston University London (United Kingdom)

    2007-07-15

    For the past two decades, there have been concerns and controversy about the effects on human health of the increased exposure to extremely-low-frequency (ELF) electromagnetic fields (EMFs) resulting from electrification, in both residential and industrial settings. Several epidemiological studies have implicated ELF-EMFs averaging 0.4 {mu}mUTesla (T) or more in increased risk of cancer, especially childhood leukaemia [1,2]; there have also been many reports demonstrating effects of power-frequency EMFs on cells [outlined in 1,3]. Unfortunately, however, the precise mechanisms by which ELF-EMFs exert biological effects have proven difficult to define and results of various studies have often been hard to reproduce [1]. We believe that C. elegans offers an exciting opportunity to elucidate the effects of power-frequency EMFs on cell signalling pathways within the whole organism and are therefore investigating the effects of ELF-EMF exposure on MAPK signalling in intact worms and fertilized embryos. Through taking a targeted approach to studying the effects of ELF-EMF's on MAPK signalling in C. elegans we aim to gather data that is physiologically relevant. Presently, this research is at a preliminary stage of preparation, and more detailed results on the exposure of Caenorhabditis elegans to ELF-EMF radiation will be presented at the conference itself.

  9. Use of C. Elegans as a model organism for sensing the effects of ELF-EMFs

    Science.gov (United States)

    Lacchini, A. H.; Everington, M. L.; Augousti, A. T.; Walker, A. J.

    2007-07-01

    For the past two decades, there have been concerns and controversy about the effects on human health of the increased exposure to extremely-low-frequency (ELF) electromagnetic fields (EMFs) resulting from electrification, in both residential and industrial settings. Several epidemiological studies have implicated ELF-EMFs averaging 0.4 μmUTesla (T) or more in increased risk of cancer, especially childhood leukaemia [1,2]; there have also been many reports demonstrating effects of power-frequency EMFs on cells [outlined in 1,3]. Unfortunately, however, the precise mechanisms by which ELF-EMFs exert biological effects have proven difficult to define and results of various studies have often been hard to reproduce [1]. We believe that C. elegans offers an exciting opportunity to elucidate the effects of power-frequency EMFs on cell signalling pathways within the whole organism and are therefore investigating the effects of ELF-EMF exposure on MAPK signalling in intact worms and fertilized embryos. Through taking a targeted approach to studying the effects of ELF-EMF's on MAPK signalling in C. elegans we aim to gather data that is physiologically relevant. Presently, this research is at a preliminary stage of preparation, and more detailed results on the exposure of Caenorhabditis elegans to ELF-EMF radiation will be presented at the conference itself.

  10. Modeling and analysis of magnetic dipoles in weak magnetic field

    Institute of Scientific and Technical Information of China (English)

    2008-01-01

    The magnetic leakage field distribution resulting from linear defects of a tube sample in the geomagnetic field is modeled according to the magnetic dipole theory.The formula to compute the normal component of the weak magnetic field is deduced based on the spatial distribution of the magnetic dipole.The shape and characteristics of the zero line (an important criterion for magnetic memory testing) of the normal field is analyzed under different longitudinal magnetizations.Results show that the characteristics of the zero line should be considered when the metal magnetic memory testing method is used to find and locate the defect.

  11. Galactic and intergalactic magnetic fields

    CERN Document Server

    Klein, Ulrich

    2014-01-01

    This course-tested textbook conveys the fundamentals of magnetic fields and relativistic plasma in diffuse cosmic media, with a primary focus on phenomena that have been observed at different wavelengths. Theoretical concepts are addressed wherever necessary, with derivations presented in sufficient detail to be generally accessible.In the first few chapters the authors present an introduction to various astrophysical phenomena related to cosmic magnetism, with scales ranging from molecular clouds in star-forming regions and supernova remnants in the Milky Way, to clusters of galaxies. Later c

  12. The separated electric and magnetic field responses of luminescent bacteria exposed to pulsed microwave irradiation

    Energy Technology Data Exchange (ETDEWEB)

    Williams, Catrin F., E-mail: williamscf@cardiff.ac.uk [School of Engineering, Cardiff University, Queen' s Buildings, Newport Road, Cardiff, CF24 3AA Wales (United Kingdom); School of Biosciences, Cardiff University, Main Building, Cathays Park, Cardiff, CF10 3AT Wales (United Kingdom); Geroni, Gilles M.; Pirog, Antoine; Lees, Jonathan; Porch, Adrian [School of Engineering, Cardiff University, Queen' s Buildings, Newport Road, Cardiff, CF24 3AA Wales (United Kingdom); Lloyd, David [School of Biosciences, Cardiff University, Main Building, Cathays Park, Cardiff, CF10 3AT Wales (United Kingdom)

    2016-08-29

    Electromagnetic fields (EMFs) are ubiquitous in the digital world we inhabit, with microwave and millimetre wave sources of non-ionizing radiation employed extensively in electronics and communications, e.g., in mobile phones and Wi-Fi. Indeed, the advent of 5G systems and the “internet of things” is likely to lead to massive densification of wireless networks. Whilst the thermal effects of EMFs on biological systems are well characterised, their putative non-thermal effects remain a controversial subject. Here, we use the bioluminescent marine bacterium, Vibrio fischeri, to monitor the effects of pulsed microwave electromagnetic fields, of nominal frequency 2.5 GHz, on light emission. Separated electric and magnetic field effects were investigated using a resonant microwave cavity, within which the maxima of each field are separated. For pulsed electric field exposure, the bacteria gave reproducible responses and recovery in light emission. At the lowest pulsed duty cycle (1.25%) and after short durations (100 ms) of exposure to the electric field at power levels of 4.5 W rms, we observed an initial stimulation of bioluminescence, whereas successive microwave pulses became inhibitory. Much of this behaviour is due to thermal effects, as the bacterial light output is very sensitive to the local temperature. Conversely, magnetic field exposure gave no measurable short-term responses even at the highest power levels of 32 W rms. Thus, we were able to detect, de-convolute, and evaluate independently the effects of separated electric and magnetic fields on exposure of a luminescent biological system to microwave irradiation.

  13. The separated electric and magnetic field responses of luminescent bacteria exposed to pulsed microwave irradiation

    Science.gov (United States)

    Williams, Catrin F.; Geroni, Gilles M.; Pirog, Antoine; Lloyd, David; Lees, Jonathan; Porch, Adrian

    2016-08-01

    Electromagnetic fields (EMFs) are ubiquitous in the digital world we inhabit, with microwave and millimetre wave sources of non-ionizing radiation employed extensively in electronics and communications, e.g., in mobile phones and Wi-Fi. Indeed, the advent of 5G systems and the "internet of things" is likely to lead to massive densification of wireless networks. Whilst the thermal effects of EMFs on biological systems are well characterised, their putative non-thermal effects remain a controversial subject. Here, we use the bioluminescent marine bacterium, Vibrio fischeri, to monitor the effects of pulsed microwave electromagnetic fields, of nominal frequency 2.5 GHz, on light emission. Separated electric and magnetic field effects were investigated using a resonant microwave cavity, within which the maxima of each field are separated. For pulsed electric field exposure, the bacteria gave reproducible responses and recovery in light emission. At the lowest pulsed duty cycle (1.25%) and after short durations (100 ms) of exposure to the electric field at power levels of 4.5 W rms, we observed an initial stimulation of bioluminescence, whereas successive microwave pulses became inhibitory. Much of this behaviour is due to thermal effects, as the bacterial light output is very sensitive to the local temperature. Conversely, magnetic field exposure gave no measurable short-term responses even at the highest power levels of 32 W rms. Thus, we were able to detect, de-convolute, and evaluate independently the effects of separated electric and magnetic fields on exposure of a luminescent biological system to microwave irradiation.

  14. Monitoring of people and workers exposure to the electric, magnetic and electromagnetic fields in an Italian national cancer Institute

    Directory of Open Access Journals (Sweden)

    Palomba Raffaele

    2008-07-01

    Full Text Available Abstract Background The paper reports the electric, magnetic and electromagnetic fields (emf measurements carried out in the Regina Elena National Cancer Institute (NCI. Several devices, used in diagnostics and in medical cures, can represent sources of emf for the workers and for the public subjected to the treatments. The aim is to evaluate their exposition, in order to assess the compliance with the law. Methods The investigations have been carried out in the departments of: intensive care, physiotherapy, MR presstherapy and in the surgical rooms. The measurements have been performed using broad band probes in the frequency ranges 5 Hz÷30 kHz and 100 kHz-3 GHz. Results The variability of the magnetic induction (B(μT levels is between 0,05 μT and 80 μT. The statistical distribution shows that most of the measurements are in the range 0,05 Conclusion The measurement of the emf levels in the NCI is recommended because of the presence of the oncological patients; their long stay near the equipments and their day-long exposure represent additional risk factors for which a prudent avoidance strategy have to de adopted.

  15. Stress Field of Straight Edge Dislocation in Magnetic Field

    Institute of Scientific and Technical Information of China (English)

    LIU Zhao-long; HU Hai-yun; FAN Tian-you

    2007-01-01

    To study the changes in mechanical properties of materials within magnetic fields and the motion of dislocations,stress fields of dislocation in magnetic field need to be calculated.The straight edge dislocation is of basic importance in various defects.The stress field of straight edge dislocation in an external static magnetic field is determined by the theory of elasticity and electrodynamics according to the Volterra dislocation model for continuous media.This reduces to the known stress field when the magnet field is zero.The results can be used for further study on the strain energy of dislocations and the interactions between dislocations in magnetic fields.

  16. Diagnosis of solar chromospheric magnetic field

    Institute of Scientific and Technical Information of China (English)

    ZHANG; Hongqi(张洪起)

    2002-01-01

    This paper discusses the measurements of the chromospheric magnetic field and the spatial configuration of the field at the lower solar atmosphere inferred by the distribution of the solar photospheric and chromospheric magnetic fields. Some questions in the study of the chromospheric magnetic field are also presented.

  17. The HMI Magnetic Field Pipeline

    Science.gov (United States)

    Hoeksema, Jon Todd; Liu, Y.; Schou, J.; Scherrer, P.; HMI Science Team

    2009-05-01

    The Helioseismic and Magnetic Imager (HMI) will provide frequent full-disk magnetic field data after launch of the Solar Dynamics Observatory (SDO), currently scheduled for fall 2009. 16 megapixel line-of-sight magnetograms (Blos) will be recorded every 45 seconds. A full set of polarized filtergrams needed to determine the vector magnetic field requires 90 seconds. Quick-look data will be available within a few minutes of observation. Quick-look space weather and browse products must have identified users, and the list currently includes full disk magnetograms, feature identification and movies, 12-minute disambiguated vector fields in active region patches, time evolution of AR indices, synoptic synchronic frames, potential and MHD model results, and 1 AU predictions. A more complete set of definitive science data products will be offered about a day later and come in three types. "Pipeline” products, such as full disk vector magnetograms, will be computed for all data on an appropriate cadence. A larger menu of "On Demand” products, such as Non-Linear Force Free Field snapshots of an evolving active region, will be produced whenever a user wants them. Less commonly needed "On Request” products that require significant project resources, such as a high resolution MHD simulation of the global corona, will be created subject to availability of resources. Further information can be found at the SDO Joint Science Operations Center web page, jsoc.stanford.edu

  18. A Vorticity-Magnetic Field Dynamo Instability

    OpenAIRE

    1997-01-01

    We generalize the mean field magnetic dynamo to include local evolution of the mean vorticity in addition to the mean magnetic field. The coupled equations exhibit a general mean field dynamo instability that enables the transfer of turbulent energy to the magnetic field and vorticity on larger scales. The growth of the vorticity and magnetic field both require helical turbulence which can be supplied by an underlying global rotation. The dynamo coefficients are derived including the backreac...

  19. Magnetic field of a combined plasma trap

    Science.gov (United States)

    Kotenko, V. G.; Moiseenko, V. E.; Ågren, O.

    2012-06-01

    This paper presents numerical simulations performed on the structure of a magnetic field created by the magnetic system of a combined plasma trap. The magnetic system includes the stellarator-type magnetic system and one of the mirror-type. For the stellarator type magnetic system the numeric model contains a magnetic system of an l=2 torsatron with the coils of an additional toroidal magnetic field. The mirror-type magnetic system element is considered as being single current-carrying turn enveloping the region of existence of closed magnetic surfaces of the torsatron. The calculations indicate the existence of a vast area of the values of the additional magnetic field magnitude and magnetic field of the single turn where, in principle, the implementation of the closed magnetic surface configuration is quite feasible.

  20. ANALYTIC EXPRESSION OF MAGNETIC FIELD DISTRIBUTION OF RECTANGULAR PERMANENT MAGNETS

    Institute of Scientific and Technical Information of China (English)

    苟晓凡; 杨勇; 郑晓静

    2004-01-01

    From the molecular current viewpoint,an analytic expression exactly describing magnetic field distribution of rectangular permanent magnets magnetized sufficiently in one direction was derived from the Biot-Savart's law. This expression is useful not only for the case of one rectangular permanent magnet bulk, but also for that of several rectangular permanent magnet bulks. By using this expression,the relations between magnetic field distribution and the size of rectangular permanent magnets as well as the magnitude of magnetic field and the distance from the point in the space to the top (or bottom) surface of rectangular permanent magnets were discussed in detail. All the calculating results are consistent with experimental ones. For transverse magnetic field which is a main magnetic field of rectangular permanent magnets,in order to describe its distribution,two quantities,one is the uniformity in magnitude and the other is the uniformity in distribution of magnetic field,were defined. Furthermore, the relations between them and the geometric size of the magnet as well as the distance from the surface of permanent magnets were investigated by these formulas. The numerical results show that the geometric size and the distance have a visible influence on the uniformity in magnitude and the uniformity in distribution of the magnetic field.

  1. Numerical Investigation of Near-Field Plasma Flows in Magnetic Nozzles

    Science.gov (United States)

    Sankaran, Kamesh; Polzin, Kurt A.

    2009-01-01

    The development and application of a multidimensional numerical simulation code for investigating near-field plasma processes in magnetic nozzles are presented. The code calculates the time-dependent evolution of all three spatial components of both the magnetic field and velocity in a plasma flow, and includes physical models of relevant transport phenomena. It has been applied to an investigation of the behavior of plasma flows found in high-power thrusters, employing a realistic magnetic nozzle configuration. Simulation of a channel-flow case where the flow was super-Alfvenic has demonstrated that such a flow produces adequate back-emf to significantly alter the shape of the total magnetic field, preventing the flow from curving back to the magnetic field coil in the near-field region. Results from this simulation can be insightful in predicting far-field behavior and can be used as a set of self-consistent boundary conditions for far-field simulations. Future investigations will focus on cases where the inlet flow is sub-Alfvenic and where the flow is allowed to freely expand in the radial direction once it is downstream of the coil.

  2. Field and Thermal Characteristics of Magnetizing Fixture

    Institute of Scientific and Technical Information of China (English)

    2000-01-01

    This paper describes field modeling and thermal modeling for magnetizing fixture. As the detailed characteristics of magnetizing fixture can be obtained, the efficient design of magnetizer which produce desired magnet will be possible using our modeling. For field modeling finite-element analysis is used as part of the design and analysis process for magnetizing fixture. The thermal modeling method of magnetizing fixture resistor uses multi-lumped model with equivalent thermal resistance and thermal capacitance.

  3. Magnetic fields for fluid motion.

    Science.gov (United States)

    Weston, Melissa C; Gerner, Matthew D; Fritsch, Ingrid

    2010-05-01

    Three forces induced by magnetic fields offer unique control of fluid motion and new opportunities in microfluidics. This article describes magnetoconvective phenomena in terms of the theory and controversy, tuning by redox processes at electrodes, early-stage applications in analytical chemistry, mature applications in disciplines far afield, and future directions for micro total analysis systems. (To listen to a podcast about this article, please go to the Analytical Chemistry multimedia page at pubs.acs.org/page/ancham/audio/index.html .).

  4. Deformation of Water by a Magnetic Field

    Science.gov (United States)

    Chen, Zijun; Dahlberg, E. Dan

    2011-03-01

    After the discovery that superconducting magnets could levitate diamagnetic objects,1,2 researchers became interested in measuring the repulsion of diamagnetic fluids in strong magnetic fields,3-5 which was given the name "The Moses Effect."5 Both for the levitation experiments and the quantitative studies on liquids, the large magnetic fields necessary were produced by superconducting magnets.

  5. Passive Magnetic Shielding in Gradient Fields

    CERN Document Server

    Bidinosti, C P

    2013-01-01

    The effect of passive magnetic shielding on dc magnetic field gradients imposed by both external and internal sources is studied. It is found that for concentric cylindrical or spherical shells of high permeability material, higher order multipoles in the magnetic field are shielded progressively better, by a factor related to the order of the multipole. In regard to the design of internal coil systems for the generation of uniform internal fields, we show how one can take advantage of the coupling of the coils to the innermost magnetic shield to further optimize the uniformity of the field. These results demonstrate quantitatively a phenomenon that was previously well-known qualitatively: that the resultant magnetic field within a passively magnetically shielded region can be much more uniform than the applied magnetic field itself. Furthermore we provide formulae relevant to active magnetic compensation systems which attempt to stabilize the interior fields by sensing and cancelling the exterior fields clos...

  6. Magnetic field perturbartions in closed-field-line systems with zero toroidal magnetic field

    Energy Technology Data Exchange (ETDEWEB)

    Mauel, M; Ryutov, D; Kesner, J

    2003-12-02

    In some plasma confinement systems (e.g., field-reversed configurations and levitated dipoles) the confinement is provided by a closed-field-line poloidal magnetic field. We consider the influence of the magnetic field perturbations on the structure of the magnetic field in such systems and find that the effect of perturbations is quite different from that in the systems with a substantial toroidal field. In particular, even infinitesimal perturbations can, in principle, lead to large radial excursions of the field lines in FRCs and levitated dipoles. Under such circumstances, particle drifts and particle collisions may give rise to significant neoclassical transport. Introduction of a weak regular toroidal magnetic field reduces radial excursions of the field lines and neoclassical transport.

  7. Bats respond to very weak magnetic fields.

    Directory of Open Access Journals (Sweden)

    Lan-Xiang Tian

    Full Text Available How animals, including mammals, can respond to and utilize the direction and intensity of the Earth's magnetic field for orientation and navigation is contentious. In this study, we experimentally tested whether the Chinese Noctule, Nyctalus plancyi (Vespertilionidae can sense magnetic field strengths that were even lower than those of the present-day geomagnetic field. Such field strengths occurred during geomagnetic excursions or polarity reversals and thus may have played an important role in the evolution of a magnetic sense. We found that in a present-day local geomagnetic field, the bats showed a clear preference for positioning themselves at the magnetic north. As the field intensity decreased to only 1/5th of the natural intensity (i.e., 10 μT; the lowest field strength tested here, the bats still responded by positioning themselves at the magnetic north. When the field polarity was artificially reversed, the bats still preferred the new magnetic north, even at the lowest field strength tested (10 μT, despite the fact that the artificial field orientation was opposite to the natural geomagnetic field (P<0.05. Hence, N. plancyi is able to detect the direction of a magnetic field even at 1/5th of the present-day field strength. This high sensitivity to magnetic fields may explain how magnetic orientation could have evolved in bats even as the Earth's magnetic field strength varied and the polarity reversed tens of times over the past fifty million years.

  8. Hybrid Shielding for Magnetic Fields

    Science.gov (United States)

    Mullins, David; Royal, Kevin

    2017-01-01

    Precision symmetry measurements such as the search for the electric dipole moment of the neutron require magnetic shielding rooms to reduce the ambient field to the pT scale. The massive mu-metal sheets and large separation between layers make these shield rooms bulky and expensive. Active field cancellation systems used to reduce the surrounding field are limited in uniformity of cancellation. A novel approach to reducing the space between shield layers and increasing the effectiveness of active cancellation is to combine the two systems into a hybrid system, with active and passive layers interspersed. We demonstrate this idea in a prototype with an active layer sandwiched between two passive layers of shielding.

  9. Manifestations of Magnetic Field Inhomogeneities

    Indian Academy of Sciences (India)

    Lawrence Rudnick

    2011-12-01

    Both observations and simulations reveal large inhomogeneities in magnetic field distributions in diffuse plasmas. Incorporating these inhomogeneities into various calculations can significantly change the inferred physical conditions. In extragalactic sources, e.g., these can compromise analyses of spectral ageing, which I will illustrate with some current work on cluster relics. I also briefly re-examine the old issue of how inhomogeneous fields affect particle lifetimes; perhaps not surprisingly, the next generation of radio telescopes are unlikely to find many sources that can extend their lifetimes from putting relativistic electrons into a low-field ‘freezer’. Finally, I preview some new EVLA results on the complex relic in Abell 2256, with implications for the interspersing of its relativistic and thermal plasmas.

  10. Effects of magnetic field on fluidization properties of magnetic pearls

    Institute of Scientific and Technical Information of China (English)

    Maoming Fan; Zhenfu Luo; Yuemin Zhao; Qingru Chen; Daniel Tao; Xiuxiang Tao; Zhenqiang Chen

    2007-01-01

    An experimental study of the influence of external magnetic field on the fluidization behavior of magnetic pearls was carried out. Magnetic pearls are a magnetic form of iron oxide that mainly consists of Fe2O3 which are recovered from a high-volume power plant fly ash from pulverized coal combustion. Due to its abundance, low price and particular physical and chemical properties, magnetic pearls can be used as a heavy medium for minerals or solid waste dry separation based on density difference. This paper introduces the properties of magnetic pearls and compares the performance of magnetic pearls fluidised bed operation with or without an external magnetic field. Experimental results show that an external magnetic field significantly improves the fluidization performance of magnetic pearls such as uniformity and stability.

  11. Magnetic Helicity and Large Scale Magnetic Fields: A Primer

    CERN Document Server

    Blackman, Eric G

    2014-01-01

    Magnetic fields of laboratory, planetary, stellar, and galactic plasmas commonly exhibit significant order on large temporal or spatial scales compared to the otherwise random motions within the hosting system. Such ordered fields can be measured in the case of planets, stars, and galaxies, or inferred indirectly by the action of their dynamical influence, such as jets. Whether large scale fields are amplified in situ or a remnant from previous stages of an object's history is often debated for objects without a definitive magnetic activity cycle. Magnetic helicity, a measure of twist and linkage of magnetic field lines, is a unifying tool for understanding large scale field evolution for both mechanisms of origin. Its importance stems from its two basic properties: (1) magnetic helicity is typically better conserved than magnetic energy; and (2) the magnetic energy associated with a fixed amount of magnetic helicity is minimized when the system relaxes this helical structure to the largest scale available. H...

  12. Interaction between two magnetic dipoles in a uniform magnetic field

    Directory of Open Access Journals (Sweden)

    J. G. Ku

    2016-02-01

    Full Text Available A new formula for the interaction force between two magnetic dipoles in a uniform magnetic field is derived taking their mutual magnetic interaction into consideration and used to simulate their relative motion. Results show that when the angle β between the direction of external magnetic field and the centerline of two magnetic dipoles is 0 ° or 90 °, magnetic dipoles approach each other or move away from each other in a straight line, respectively. And the time required for them to contact each other from the initial position is related to the specific susceptibility and the diameter of magnetic particles, medium viscosity and magnetic field strength. When β is between 0 ° and 90 °, magnetic dipole pair performs approximate elliptical motion, and the motion trajectory is affected by the specific susceptibility, diameter and medium viscosity but not magnetic field strength. However, time required for magnetic dipoles to complete the same motion trajectory is shorter when adopting stronger magnetic field. Moreover, the subsequent motion trajectory of magnetic dipoles is ascertained once the initial position is set in a predetermined motion trajectory. Additionally, magnetic potential energy of magnetic dipole pairs is transformed into kinetic energy and friction energy during the motion.

  13. Effective magnetic moment of neutrinos in strong magnetic fields

    CERN Document Server

    Pérez, A; Masood, S S; Gaitan, R; Rodríguez, S

    2002-01-01

    In this paper we compute the effective magnetic moment of neutrinos propagating in dense high magnetized medium. Taking typical values of magnetic field and densities of astrophysical objects (such as the cores of supernovae and neutron stars) we obtain an effective type of dipole magnetic moment in agreement with astrophysical and cosmological bounds. (Author)

  14. Magnetic field penetration of erosion switch plasmas

    Science.gov (United States)

    Mason, Rodney J.; Jones, Michael E.; Grossmann, John M.; Ottinger, Paul F.

    1988-10-01

    Computer simulations demonstrate that the entrainment (or advection) of magnetic field with the flow of cathode-emitted electrons can constitute a dominant mechanism for the magnetic field penetration of erosion switch plasmas. Cross-field drift in the accelerating electric field near the cathode starts the penetration process. Plasma erosion propagates the point for emission and magnetic field injection along the cathode toward the load-for the possibility of rapid switch opening.

  15. Magnetic field reversals and galactic dynamos

    OpenAIRE

    2012-01-01

    We argue that global magnetic field reversals similar to those observed in the Milky Way occur quite frequently in mean-field galactic dynamo models that have relatively strong, random, seed magnetic fields that are localized in discrete regions. The number of reversals decreases to zero with reduction of the seed strength, efficiency of the galactic dynamo and size of the spots of the seed field. A systematic observational search for magnetic field reversals in a representative sample of spi...

  16. Safety of high speed magnetic levitation transportation systems. Magnetic field testing of the TR07 Maglev vehicle and system. Volume 1: Analysis

    Science.gov (United States)

    Dietrich, Fred; Feero, William E.

    1992-04-01

    The safety of various magnetically levitated (maglev) and high speed rail (HSR) trains proposed for application in the United States is of direct concern to the Federal Railroad Administration (FRA). The characterization of electric and magnetic field (EMF) emissions, both steady (dc) and produced by alternating currents (ac) at power frequency (50 Hz in Europe and 60 Hz in the U.S.) and other frequencies in the Extreme Low Frequency (ELF) range (3-3000 Hz), and associated public and worker exposure to EMF, are a growing health and safety concern worldwide. As part of a comprehensive safety assessment of the German TransRapid (TR-07) maglev system undertaken by the FRA, with technical support from the DOT/RSPA Volpe National Transportation System Center (VNTSC), magnetic field measurements were performed by Electric Research and Management, Inc. (ERM) at the Transrapid Test Facility (TVE) in Emsland, Germany in August, 1990. Analysis summarizes the experimental findings and compares results to common home, work, and power lines emissions for selected spectral bands.

  17. Genotoxicity and ELF-magnetic fields: a review through the micronucleus assay; Genotoxicidad y campos magneticos-ELF: una revision a traves del ensayo de micronucleos

    Energy Technology Data Exchange (ETDEWEB)

    Alcaraz, M.; Andreu-Galvez, M.; Sanchez-Villalobos, J. M.; Achel, D. G.; Olmos, E.; Martinez-Hernandez, C. M.

    2012-07-01

    Thirty for (34) published studies, conducted from 1994 to the present to evaluate the genotoxic effect of magnetic fields using ELF-EMF and diagnostic resonance on humans by the micronucleus assay have been reviewed. some characteristics of the assay methods, their significance to genotoxicity and basic interpretations of the results of these assays are discussed. of the studies analysed 70.5% implicated genotoxic effects induced by these magnetic fields: 52.9% were due to exposure to magnetic fields only and 17,6% by exposure to magnetic fields in combination with some treatment types, resulting in additive or synergistic effect. Evidence exist to support the notion that exposure of humans to magnetic fields stimulates genotoxic effects, although the actual mechanisms of action or even the true human health consequences resulting from these exposure still remain unclear. (Author) 80 refs.

  18. Laboratory Studies of the Effects of Static and Variable Magnetic Fields on Freshwater Fish

    Energy Technology Data Exchange (ETDEWEB)

    Cada, Glenn F [ORNL; Bevelhimer, Mark S [ORNL; Fortner, Allison M [ORNL; Riemer, Kristina P [ORNL; Schweizer, Peter E [ORNL

    2012-04-01

    There is considerable interest in the development of marine and hydrokinetic energy projects in rivers, estuaries, and coastal ocean waters of the United States. Hydrokinetic (HK) technologies convert the energy of moving water in river or tidal currents into electricity, without the impacts of dams and impoundments associated with conventional hydropower or the extraction and combustion of fossil fuels. The Federal Energy Regulatory Commission (FERC) maintains a database that displays the geographical distribution of proposed HK projects in inland and tidal waters (FERC 2012). As of March 2012, 77 preliminary permits had been issued to private developers to study HK projects in inland waters, the development of which would total over 8,000 MW. Most of these projects are proposed for the lower Mississippi River. In addition, the issuance of another 27 preliminary permits for HK projects in inland waters, and 3 preliminary permits for HK tidal projects (totaling over 3,100 MW) were under consideration by FERC. Although numerous HK designs are under development (see DOE 2009 for a description of the technologies and their potential environmental effects), the most commonly proposed projects entail arrays of rotating devices, much like submerged wind turbines, that are positioned in the high-velocity (high energy) river channels. The many diverse HK designs imply a diversity of environmental impacts, but a potential impact common to most is the effect on aquatic organisms of electromagnetic fields (EMF) created by the projects. The submerged electrical generator will emit an EMF into the surrounding water, as will underwater cables used to transmit electricity from the generator to the shore, between individual units in an array (inter-turbine cables), and between the array and a submerged step-up transformer. The electric current moving through these cables will induce magnetic fields in the immediate vicinity, which may affect the behavior or viability of fish and

  19. Near-Field Magnetic Dipole Moment Analysis

    Science.gov (United States)

    Harris, Patrick K.

    2003-01-01

    This paper describes the data analysis technique used for magnetic testing at the NASA Goddard Space Flight Center (GSFC). Excellent results have been obtained using this technique to convert a spacecraft s measured magnetic field data into its respective magnetic dipole moment model. The model is most accurate with the earth s geomagnetic field cancelled in a spherical region bounded by the measurement magnetometers with a minimum radius large enough to enclose the magnetic source. Considerably enhanced spacecraft magnetic testing is offered by using this technique in conjunction with a computer-controlled magnetic field measurement system. Such a system, with real-time magnetic field display capabilities, has been incorporated into other existing magnetic measurement facilities and is also used at remote locations where transport to a magnetics test facility is impractical.

  20. Magnetic Fields from the Electroweak Phase Transition

    CERN Document Server

    Törnkvist, O

    1998-01-01

    I review some of the mechanisms through which primordial magnetic fields may be created in the electroweak phase transition. I show that no magnetic fields are produced initially from two-bubble collisions in a first-order transition. The initial field produced in a three-bubble collision is computed. The evolution of fields at later times is discussed.

  1. Strong and superstrong pulsed magnetic fields generation

    CERN Document Server

    Shneerson, German A; Krivosheev, Sergey I

    2014-01-01

    Strong pulsed magnetic fields are important for several fields in physics and engineering, such as power generation and accelerator facilities. Basic aspects of the generation of strong and superstrong pulsed magnetic fields technique are given, including the physics and hydrodynamics of the conductors interacting with the field as well as an account of the significant progress in generation of strong magnetic fields using the magnetic accumulation technique. Results of computer simulations as well as a survey of available field technology are completing the volume.

  2. [FTIR spectra investigation of rat sensitive tissues exposure to ELF-EMF].

    Science.gov (United States)

    Li, Gun; Yan, Ya-jing; Huang, Yong; Zhou, Yan; Pang, Xiao-feng

    2012-05-01

    Nonthermal effects of extremely low frequency electromagnetic fields (ELF-EMF) are related to changes in the microstructure of biological tissues after exposure to electromagnetic radiation. Fourier transform infrared spectroscopy (FTIR) analysis method can effectively study the mechanisms of biological effects of electromagnetic radiation. The present paper studies the characteristics of sensitive tissues of rat after ELF-EMF exposure. FTIR analysis of sensitive tissues of control group and experimental group showed that 50 Hz, 0.75 mT ELF-EMF exposure for 20 days can affect molecular level of the rat testis, blood and brain. Experimental results show that regular changes in absorption peak positions and intensity in the spectra of sensitive tissue may be caused by exposure to ELF-EMF, therefore, Fourier transform infrared spectroscopy is an effective means to study mechanism of biological effects of electromagnetic fields.

  3. A hybrid analytical model for open-circuit field calculation of multilayer interior permanent magnet machines

    Science.gov (United States)

    Zhang, Zhen; Xia, Changliang; Yan, Yan; Geng, Qiang; Shi, Tingna

    2017-08-01

    Due to the complicated rotor structure and nonlinear saturation of rotor bridges, it is difficult to build a fast and accurate analytical field calculation model for multilayer interior permanent magnet (IPM) machines. In this paper, a hybrid analytical model suitable for the open-circuit field calculation of multilayer IPM machines is proposed by coupling the magnetic equivalent circuit (MEC) method and the subdomain technique. In the proposed analytical model, the rotor magnetic field is calculated by the MEC method based on the Kirchhoff's law, while the field in the stator slot, slot opening and air-gap is calculated by subdomain technique based on the Maxwell's equation. To solve the whole field distribution of the multilayer IPM machines, the coupled boundary conditions on the rotor surface are deduced for the coupling of the rotor MEC and the analytical field distribution of the stator slot, slot opening and air-gap. The hybrid analytical model can be used to calculate the open-circuit air-gap field distribution, back electromotive force (EMF) and cogging torque of multilayer IPM machines. Compared with finite element analysis (FEA), it has the advantages of faster modeling, less computation source occupying and shorter time consuming, and meanwhile achieves the approximate accuracy. The analytical model is helpful and applicable for the open-circuit field calculation of multilayer IPM machines with any size and pole/slot number combination.

  4. Deformation of Water by a Magnetic Field

    Science.gov (United States)

    Chen, Zijun; Dahlberg, E. Dan

    2011-01-01

    After the discovery that superconducting magnets could levitate diamagnetic objects, researchers became interested in measuring the repulsion of diamagnetic fluids in strong magnetic fields, which was given the name "The Moses Effect." Both for the levitation experiments and the quantitative studies on liquids, the large magnetic fields necessary…

  5. Exploring Magnetic Fields with a Compass

    Science.gov (United States)

    Lunk, Brandon; Beichner, Robert

    2011-01-01

    A compass is an excellent classroom tool for the exploration of magnetic fields. Any student can tell you that a compass is used to determine which direction is north, but when paired with some basic trigonometry, the compass can be used to actually measure the strength of the magnetic field due to a nearby magnet or current-carrying wire. In this…

  6. Biological Effect of Magnetic Field in Mice

    Institute of Scientific and Technical Information of China (English)

    Zhao-Wei ZENG

    2005-01-01

    Objective: To study the biological effect of magnetic field in mice bodies. Method: With a piece of permanent magnet embeded in mice bodies beside the femoral artery and vein to measure the electrophoretic velocity(um/s). Result: The magnetic field in mice bodies on the experiment group that the electrophoretic velocity is faster more than control and free group.Conclusion:The magnetic field in animal's body can raise the negative electric charges on the surface of erythrocyte to improve the microcirculation, this is the biological effect of magnetic field.

  7. The Magnetic Field Effect on Planetary Nebulae

    Institute of Scientific and Technical Information of China (English)

    A. R. Khesali; K. Kokabi

    2006-01-01

    In our previous work on the 3-dimensional dynamical structure of planetary nebulae the effect of magnetic field was not considered. Recently Jordan et al. have directly detected magnetic fields in the central stars of some planetary nebulae. This discovery supports the hypothesis that the non-spherical shape of most planetary nebulae is caused by magnetic fields in AGB stars. In this study we focus on the role of initially weak toroidal magnetic fields embedded in a stellar wind in altering the shape of the PN. We found that magnetic pressure is probably influential on the observed shape of most PNe.

  8. Magnetic field concentrator for probing optical magnetic metamaterials.

    Science.gov (United States)

    Antosiewicz, Tomasz J; Wróbel, Piotr; Szoplik, Tomasz

    2010-12-06

    Development of all dielectric and plasmonic metamaterials with a tunable optical frequency magnetic response creates a need for new inspection techniques. We propose a method of measuring magnetic responses of such metamaterials within a wide range of optical frequencies with a single probe. A tapered fiber probe with a radially corrugated metal coating concentrates azimuthally polarized light in the near-field into a subwavelength spot the longitudinal magnetic field component which is much stronger than the perpendicular electric one. The active probe may be used in a future scanning near-field magnetic microscope for studies of magnetic responses of subwavelength elementary cells of metamaterials.

  9. Energy conversion efficiencies of thermoelectric pallets (Bi2Pb3,Bi2Te3 and Pb2Te3) under the influences of electric and magnetic fields

    Science.gov (United States)

    Singh, Jaspal; Verma, S. S.

    2013-06-01

    This paper aims to introduce the ability of thermo electric pallets to convert waste heat into electricity and also about the effect of electric or magnetic fields, which can exist already or applied in the conditions of their operation. Three thermo electric pallets (Bi2Pb3,Bi2Te3 and Pb2Te3) of cylindrical dimensions are prepared by 15mm mixture of different compositions. Thermo emf generations are carried out in the normal mode and then under the influence of applied electric and magnetic fields of different magnitudes in the temperature range of 460K.

  10. Electrolytic tiltmeters inside magnetic fields: Some observations

    Energy Technology Data Exchange (ETDEWEB)

    Alberdi, J. [CIEMAT, Madrid (Spain); Arce, P. [CIEMAT, Madrid (Spain); Barcala, J.M. [CIEMAT, Madrid (Spain); Calvo, E. [CIEMAT, Madrid (Spain); Ferrando, A. [CIEMAT, Madrid (Spain)]. E-mail: antonio.ferrando@ciemat.es; Josa, M.I. [CIEMAT, Madrid (Spain); Luque, J.M. [CIEMAT, Madrid (Spain); Molinero, A. [CIEMAT, Madrid (Spain); Navarrete, J. [CIEMAT, Madrid (Spain); Oller, J.C. [CIEMAT, Madrid (Spain); Yuste, C. [CIEMAT, Madrid (Spain); Calderon, A. [Instituto de Fisica de Cantabria, CSIC-University of Cantabria, Santander (Spain); Garcia-Moral, L.A. [Instituto de Fisica de Cantabria, CSIC-University of Cantabria, Santander (Spain); Gomez, G. [Instituto de Fisica de Cantabria, CSIC-University of Cantabria, Santander (Spain); Gonzalez-Sanchez, F.J. [Instituto de Fisica de Cantabria, CSIC-University of Cantabria, Santander (Spain); Martinez-Rivero, C. [Instituto de Fisica de Cantabria, CSIC-University of Cantabria, Santander (Spain); Matorras, F. [Instituto de Fisica de Cantabria, CSIC-University of Cantabria, Santander (Spain); Rodrigo, T. [Instituto de Fisica de Cantabria, CSIC-University of Cantabria, Santander (Spain); Ruiz-Arbol, P. [Instituto de Fisica de Cantabria, CSIC-University of Cantabria, Santander (Spain); Scodellaro, L. [Instituto de Fisica de Cantabria, CSIC-University of Cantabria, Santander (Spain); Sobron, M. [Instituto de Fisica de Cantabria, CSIC-University of Cantabria, Santander (Spain); Vila, I. [Instituto de Fisica de Cantabria, CSIC-University of Cantabria, Santander (Spain); Virto, A.L. [Instituto de Fisica de Cantabria, CSIC-University of Cantabria, Santander (Spain)

    2007-04-21

    We present observations of the electrolytic clinometers behaviour inside magnetic field environments introducing phenomenological expressions to account for the measured output voltage variations as functions of field gradients and field strengths.

  11. From Inverse to Delayed Magnetic Catalysis in Strong Magnetic Field

    CERN Document Server

    Mao, Shijun

    2016-01-01

    We study magnetic field effect on chiral phase transition in a Nambu--Jona-Lasinio model. In comparison with mean field approximation containing quarks only, including mesons as quantum fluctuations in the model leads to a transition from inverse to delayed magnetic catalysis at finite temperature and delays the transition at finite baryon chemical potential. The location of the critical end point depends on the the magnetic field non-monotonously.

  12. Dynamic shielding of the magnetic fields

    Directory of Open Access Journals (Sweden)

    RAU, M.

    2010-11-01

    Full Text Available The paper presents a comparative study of the methods used to control and compensate the direct and alternative magnetic fields. Two frequently used methods in the electromagnetic compatibility of the complex biomagnetism installations were analyzed. The two methods refer to the use of inductive magnetic field sensors (only for alternative fields and of fluxgate magnetometers as active transducers which measures both the direct and alternative components of the magnetic field. The applications of the dynamic control of the magnetic field are: control of the magnetic field of the military ships, control of parasite magnetic field produced by power transformers and the electrical networks, protection of the mass spectrometers, electronic microscopes, SQUID and optical pumping magnetometers for applications in biomagnetism.

  13. Field free line magnetic particle imaging

    CERN Document Server

    Erbe, Marlitt

    2014-01-01

    Marlitt Erbe provides a detailed introduction into the young research field of Magnetic Particle Imaging (MPI) and field free line (FFL) imaging in particular. She derives a mathematical description of magnetic field generation for FFL imaging in MPI. To substantiate the simulation studies on magnetic FFL generation with a proof-of-concept, the author introduces the FFL field demonstrator, which provides the world's first experimentally generated rotated and translated magnetic FFL field complying with the requirements for FFL reconstruction. Furthermore, she proposes a scanner design of consi

  14. Oxidative response of human monocytes and macrophages cultured under low oxygen culture conditions to ion parametric resonance magnetic fields.

    Science.gov (United States)

    INTRODUCTION One proposed mechanism of action of electromagnetic fields (EMFs) on biological systems is the Ion Parametric Resonance (IPR) model, which has been experimentally validated in neuronal PC-12 cells [1, 2]. It proposes that when applied EMFs are tuned to resonate with...

  15. Magnetic field mapper based on rotating coils

    CERN Document Server

    AUTHOR|(CDS)2087244; Arpaia, Pasquale

    This thesis presents a magnetic field mapper based on rotating coils. The requirements, the architecture, the conceptual design, and the prototype for straight magnets were shown. The proposed system is made up of a rotating coil transducer and a train-like system for longitudinal motion and positioning inside magnet bore. The mapper allows a localized measurement of magnetic fields and the variation of the harmonic multipole content in the magnet ends. The proof-of-principle demonstration and the experimental characterization of the rotating-coil transducer specifically conceived for mapping validated the main objective of satisfying the magnetic measurement needs of the next generation of compact accelerators.

  16. Magnetic Fields and Star Formation

    CERN Document Server

    Van Loo, S; Falle, S A E G

    2012-01-01

    Research performed in the 1950s and 1960s by Leon Mestel on the roles of magnetic fields in star formation established the framework within which he and other key figures have conducted subsequent investigations on the subject. This short tribute to Leon contains a brief summary of some, but not all, of his ground breaking contributions in the area. It also mentions of some of the relevant problems that have received attention in the last few years. The coverage is not comprehensive, and the authors have drawn on their own results more and touched more briefly on those of others than they would in a normal review. Theirs is a personal contribution to the issue honouring Leon, one of the truly great gentlemen, wits, and most insightful of astrophysicists.

  17. DC-based magnetic field controller

    Energy Technology Data Exchange (ETDEWEB)

    Kotter, Dale K. (Shelley, ID); Rankin, Richard A. (Ammon, ID); Morgan, John P,. (Idaho Falls, ID)

    1994-01-01

    A magnetic field controller for laboratory devices and in particular to dc operated magnetic field controllers for mass spectrometers, comprising a dc power supply in combination with improvements to a hall probe subsystem, display subsystem, preamplifier, field control subsystem, and an output stage.

  18. DC-based magnetic field controller

    Energy Technology Data Exchange (ETDEWEB)

    Kotter, D.K.; Rankin, R.A.; Morgan, J.P.

    1994-05-31

    A magnetic field controller is described for laboratory devices and in particular to dc operated magnetic field controllers for mass spectrometers, comprising a dc power supply in combination with improvements to a Hall probe subsystem, display subsystem, preamplifier, field control subsystem, and an output stage. 1 fig.

  19. High magnetic fields science and technology

    CERN Document Server

    Miura, Noboru

    2003-01-01

    This three-volume book provides a comprehensive review of experiments in very strong magnetic fields that can only be generated with very special magnets. The first volume is entirely devoted to the technology of laboratory magnets: permanent, superconducting, high-power water-cooled and hybrid; pulsed magnets, both nondestructive and destructive (megagauss fields). Volumes 2 and 3 contain reviews of the different areas of research where strong magnetic fields are an essential research tool. These volumes deal primarily with solid-state physics; other research areas covered are biological syst

  20. Trapped magnetic field measurements on HTS bulk by peak controlled pulsed field magnetization

    Energy Technology Data Exchange (ETDEWEB)

    Ida, Tetsuya; Watasaki, Masahiro [Department of Electronic Control Engineering, Hiroshima National College of Maritime Technology, 4272-1, Higashino, Ohsakikamijima-cho, Toyota-gun, Hiroshima 725-0231 (Japan); Kimura, Yosuke [Kawasaki Heavy Industries, Ltd. Technical Institute System Technology Development Centre 1-1, Kawasaki-cho, Akashi-shi, Hyogo 673-8666 (Japan); Miki, Motohiro; Izumi, Mitsuru, E-mail: ida@hiroshima-cmt.ac.j [Department of Marine Electronics and Mechanical Engineering, Tokyo University of Marine Science and Technology, 2-1-6, Etchu-jima, Koto-ku, Tokyo 135-8533 (Japan)

    2010-06-01

    For the past several years, we have studied the high-temperature superconducting (HTS) synchronous motor assembled with melt-textured Gd-Ba-Cu-O bulk magnets. If the single pulse field magnetizes a bulk effectively, size of electrical motor will become small for the strong magnetic field of the HTS magnets without reducing output power of motor. In the previous study, we showed that the HTS bulk was magnetized to excellent cone-shape magnetic field distribution by using the waveform control pulse magnetization (WCPM) method. The WCPM technique made possible the active control of the waveform on which magnetic flux motion depended. We generated the pulse waveform with controlled risetime for HTS bulk magnetization to suppress the magnetic flux motion which decreases magnetization efficiency. The pulsed maximum magnetic flux density with slow risetime is not beyond the maximum magnetic flux density which is trapped by the static field magnetization. But, as for applying the pulse which has fast risetime, the magnetic flux which exceed greatly the threshold penetrates the bulk and causes the disorder of the trapped magnetic distribution. This fact suggests the possibility that the threshold at pulsed magnetization influences the dynamic magnetic flux motion. In this study, Gd-Ba-Cu-O bulk is magnetized by the controlled arbitrary trapezoidal shape pulse, of which the maximum magnetic flux density is controlled not to exceed the threshold. We will present the trapped magnetic characteristics and the technique to generate the controlled pulsed field.

  1. Magnetic field evolution in tidal disruption events

    CERN Document Server

    Bonnerot, Clément; Lodato, Giuseppe; Rossi, Elena M

    2016-01-01

    When a star gets tidally disrupted by a supermassive black hole, its magnetic field is expected to be transmitted to the debris. In this paper, we study this process via smoothed particle magnetohydrodynamical simulations of the disruption and early debris evolution including the stellar magnetic field. As the gas stretches into a stream, we show that the magnetic field evolution is strongly dependent on its orientation with respect to the stretching direction. In particular, an alignment of the field lines with the direction of stretching induces an increase of the magnetic energy. For disruptions happening well within the tidal radius, the star compression causes the magnetic field strength to sharply increase by an order of magnitude at the time of pericentre passage. If the disruption is partial, we find evidence for a dynamo process occurring inside the surviving core due to the formation of vortices. This causes an amplification of the magnetic field strength by a factor of $\\sim 10$. However, this valu...

  2. Synchrotron Applications of High Magnetic Fields

    Energy Technology Data Exchange (ETDEWEB)

    NONE

    2006-07-01

    This workshop aims at discussing the scientific potential of X-ray diffraction and spectroscopy in magnetic fields above 30 T. Pulsed magnetic fields in the range of 30 to 40 T have recently become available at Spring-8 and the ESRF (European synchrotron radiation facility). This document gathers the transparencies of the 6 following presentations: 1) pulsed magnetic fields at ESRF: first results; 2) X-ray spectroscopy and diffraction experiments by using mini-coils: applications to valence state transition and frustrated magnet; 3) R{sub 5}(Si{sub x}Ge{sub 1-x}){sub 4}: an ideal system to be studied in X-ray under high magnetic field?; 4) high field studies at the Advanced Photon Source: present status and future plans; 5) synchrotron X-ray diffraction studies under extreme conditions; and 6) projects for pulsed and steady high magnetic fields at the ESRF.

  3. Demagnetizing fields in active magnetic regenerators

    DEFF Research Database (Denmark)

    Nielsen, Kaspar Kirstein; Bahl, Christian R.H.; Smith, Anders

    2014-01-01

    is in general both a function of the overall shape of the regenerator and its morphology (packed particles, parallel plates etc.) as well as the magnetization of the material. Due to the pronounced temperature dependence of the magnetization near the Curie temperature, the demagnetization field is also......A magnetic material in an externally applied magnetic field will in general experience a spatially varying internal magnetic field due to demagnetizing effects. When the performance of active magnetic regenerators (AMRs) is evaluated using numerical models the internal field is often assumed...... temperature dependent. We propose a relatively straightforward method to correct sufficiently for the demagnetizing field in AMR models. We discuss how the demagnetizing field behaves in regenerators made of packed spheres under realistic operation conditions....

  4. New knowledge of the Galactic magnetic fields

    CERN Document Server

    Han, J L

    2009-01-01

    The magnetic fields of our Milky Way galaxy are the main agent for cosmic rays to transport. In the last decade, much new knowledge has been gained from measurements of the Galactic magnetic fields. In the Galactic disk, from the RMs of a large number of newly discovered pulsars, the large-scale magnetic fields along the spiral arms have been delineated in a much larger region than ever before, with alternating directions in the arm and interarm regions. The toroidal fields in the Galactic halo were revealed to have opposite directions below and above the Galactic plane, which is an indication of an A0 mode dynamo operating in the halo. The strength of large-scale fields obtained from pulsar RM data has been found to increase exponentially towards the Galactic center. Compared to the steep Kolmogorov spectrum of magnetic energy at small scales, the large-scale magnetic fields show a shallow broken spatial magnetic energy spectrum.

  5. Behaviour of ferrocholesterics under external magnetic fields

    Science.gov (United States)

    Petrescu, Emil; Motoc, Cornelia

    2001-08-01

    The influence of an external magnetic field on the orientational behaviour of a ferrocholesteric with a positive magnetic anisotropy is investigated. Both the phenomena arising when the field was switched on or switched off are considered. It is found that the field needed for a ferrocholesteric-ferronematic transition BFC↑ is higher when compared to that obtained for the pure cholesteric ( BC↑). A similar result was obtained when estimating the critical field for the homeotropic ferronematic-ferrocholesteric (focal conic) transition, occurring when the magnetic field was decreased or switched off. We found that BFC↓> BC↓. These results are explained when considering that the magnetic moments of the magnetic powder are not oriented parallel to the liquid crystal molecular directors, therefore hindering their orientation under a magnetic field.

  6. Coulomb crystals in the magnetic field

    CERN Document Server

    Baiko, D A

    2009-01-01

    The body-centered cubic Coulomb crystal of ions in the presence of a uniform magnetic field is studied using the rigid electron background approximation. The phonon mode spectra are calculated for a wide range of magnetic field strengths and for several orientations of the field in the crystal. The phonon spectra are used to calculate the phonon contribution to the crystal energy, entropy, specific heat, Debye-Waller factor of ions, and the rms ion displacements from the lattice nodes for a broad range of densities, temperatures, chemical compositions, and magnetic fields. Strong magnetic field dramatically alters the properties of quantum crystals. The phonon specific heat increases by many orders of magnitude. The ion displacements from their equilibrium positions become strongly anisotropic. The results can be relevant for dusty plasmas, ion plasmas in Penning traps, and especially for the crust of magnetars (neutron stars with superstrong magnetic fields $B \\gtrsim 10^{14}$ G). The effect of the magnetic ...

  7. Generating the optimal magnetic field for magnetic refrigeration

    DEFF Research Database (Denmark)

    Bjørk, Rasmus; Insinga, Andrea Roberto; Smith, Anders

    2016-01-01

    remanence distribution for any desired magnetic field. The method is based on the reciprocity theorem, which through the use of virtual magnets can be used to calculate the optimal remanence distribution. Furthermore, we present a method for segmenting a given magnet design that always results...

  8. Magnetic field sensor for isotropically sensing an incident magnetic field in a sensor plane

    Science.gov (United States)

    Pant, Bharat B. (Inventor); Wan, Hong (Inventor)

    2001-01-01

    A magnetic field sensor that isotropically senses an incident magnetic field. This is preferably accomplished by providing a magnetic field sensor device that has one or more circular shaped magnetoresistive sensor elements for sensing the incident magnetic field. The magnetoresistive material used is preferably isotropic, and may be a CMR material or some form of a GMR material. Because the sensor elements are circular in shape, shape anisotropy is eliminated. Thus, the resulting magnetic field sensor device provides an output that is relatively independent of the direction of the incident magnetic field in the sensor plane.

  9. Effects of exposure to an extremely low frequency electromagnetic field on hippocampal long-term potentiation in rat.

    Science.gov (United States)

    Komaki, Alireza; Khalili, Afshin; Salehi, Iraj; Shahidi, Siamak; Sarihi, Abdolrahman

    2014-05-20

    Modern lifestyle exposes nearly all humans to electromagnetic fields, particularly to extremely low frequency electromagnetic fields (ELF-EMFs). Prolonged exposure to ELF-EMFs induces persistent changes in neuronal activity. However, the modulation of synaptic efficiency by ELF-EMFs in vivo is still unclear. In the present study, we investigated whether ELF-EMFs can change induction of long-term potentiation (LTP) and paired-pulse ratio (PPR) in the rat hippocampal area. Twenty-nine adult male Wistar rats were divided into 3 groups (ELF-EMF exposed, sham and control groups). The ELF-EMF group was exposed to a magnetic field for 90 consecutive days (2h/day). ELF-EMFs were produced by a circular coil (50Hz, 100 micro Tesla). The sham-exposed controls were placed in an identical chamber with no electromagnetic field. After this period, rats were deeply anesthetized with urethane (2.0mg/kg) and then a bipolar stimulating and recording electrode was implanted into the perforant pathway (PP) and dentate gyrus (DG), respectively. LTP in hippocampal area was induced by high-frequency stimulation (HFS). Prolonged exposure to ELF-EMFs increased LTP induction. There was a significant difference in the slope of EPSP and amplitude of PS between the ELF-EMF group and other groups. In conclusion, our data suggest that exposure to ELF-EMFs produces a marked change in the synaptic plasticity generated in synapses of the PP-DG. No significant difference in PPR of ELF-EMF group before and after HFS suggests a postsynaptic expression site of LTP.

  10. Nonlinear energy dissipation of magnetic nanoparticles in oscillating magnetic fields

    Science.gov (United States)

    Soto-Aquino, D.; Rinaldi, C.

    2015-11-01

    The heating of magnetic nanoparticle suspensions subjected to alternating magnetic fields enables a variety of emerging applications such as magnetic fluid hyperthermia and triggered drug release. Rosensweig (2002) [25] obtained a model for the heat dissipation rate of a collection of non-interacting particles. However, the assumptions made in this analysis make it rigorously valid only in the limit of small applied magnetic field amplitude and frequency (i.e., values of the Langevin parameter that are much less than unity and frequencies below the inverse relaxation time). In this contribution we approach the problem from an alternative point of view by solving the phenomenological magnetization relaxation equation exactly for the case of arbitrary magnetic field amplitude and frequency and by solving a more accurate magnetization relaxation equation numerically. We also use rotational Brownian dynamics simulations of non-interacting magnetic nanoparticles subjected to an alternating magnetic field to estimate the rate of energy dissipation and compare the results of the phenomenological theories to the particle-scale simulations. The results are summarized in terms of a normalized energy dissipation rate and show that Rosensweig's expression provides an upper bound on the energy dissipation rate achieved at high field frequency and amplitude. Estimates of the predicted dependence of energy dissipation rate, quantified as specific absorption rate (SAR), on magnetic field amplitude and frequency, and particle core and hydrodynamic diameter, are also given.

  11. Beam Transport in Toroidal Magnetic Field

    CERN Document Server

    Joshi, N; Meusel, O; Ratzinger, U

    2016-01-01

    The concept of a storage ring with toroidal magnetic field was presented in the two previous EPAC conferences. Here we report the first results of experiments performed with beam transport in toroidal magnetic fields and details of the injection system. The beam transport experiments were carried out with 30 degree toroidal segments with an axial magnetic field of 0.6T. The multi turn injection system relies on a transverse injection coil together with an electric kicker system.

  12. Magnetically modified bioсells in constant magnetic field

    Science.gov (United States)

    Abramov, E. G.; Panina, L. K.; Kolikov, V. A.; Bogomolova, E. V.; Snetov, V. N.; Cherepkova, I. A.; Kiselev, A. A.

    2017-02-01

    Paper addresses the inverse problem in determining the area, where the external constant magnetic field captures the biological cells modified by the magnetic nanoparticles. Zero velocity isolines, in area where the modified cells are captured by the magnetic field were determined by numerical method for two locations of the magnet. The problem was solved taking into account the gravitational field, magnetic induction, density of medium, concentration and size of cells, and size and magnetization of nanoparticles attached to the cell. Increase in the number of the nanoparticles attached to the cell and decrease in the cell' size, enlarges the area, where the modified cells are captured and concentrated by the magnet. Solution is confirmed by the visible pattern formation of the modified cells Saccharomyces cerevisiae.

  13. Near-zero-field nuclear magnetic resonance

    OpenAIRE

    Ledbetter, Micah; Theis, Thomas; Blanchard, John; Ring, Hattie; Ganssle, Paul; Appelt, Stephan; Bluemich, Bernhard; Pines, Alex; Budker, Dmitry

    2011-01-01

    We investigate nuclear magnetic resonance (NMR) in near-zero-field, where the Zeeman interaction can be treated as a perturbation to the electron mediated scalar interaction (J-coupling). This is in stark contrast to the high field case, where heteronuclear J-couplings are normally treated as a small perturbation. We show that the presence of very small magnetic fields results in splitting of the zero-field NMR lines, imparting considerable additional information to the pure zero-field spectr...

  14. Minimizing magnetic fields for precision experiments

    CERN Document Server

    Altarev, I; Lins, T; Marino, M G; Nießen, B; Petzoldt, G; Reisner, M; Stuiber, S; Sturm, M; Singh, J T; Taubenheim, B; Rohrer, H K; Schläpfer, U

    2015-01-01

    An increasing number of measurements in fundamental and applied physics rely on magnetically shielded environments with sub nano-Tesla residual magnetic fields. State of the art magnetically shielded rooms (MSRs) consist of up to seven layers of high permeability materials in combination with highly conductive shields. Proper magnetic equilibration is crucial to obtain such low magnetic fields with small gradients in any MSR. Here we report on a scheme to magnetically equilibrate MSRs with a 10 times reduced duration of the magnetic equilibration sequence and a significantly lower magnetic field with improved homogeneity. For the search of the neutron's electric dipole moment, our finding corresponds to a linear improvement in the systematic reach and a 40 % improvement of the statistical reach of the measurement. However, this versatile procedure can improve the performance of any MSR for any application.

  15. Magnetic field evolution in tidal disruption events

    Science.gov (United States)

    Bonnerot, Clément; Price, Daniel J.; Lodato, Giuseppe; Rossi, Elena M.

    2017-08-01

    When a star gets tidally disrupted by a supermassive black hole, its magnetic field is expected to pervade its debris. In this paper, we study this process via smoothed particle magnetohydrodynamical simulations of the disruption and early debris evolution including the stellar magnetic field. As the gas stretches into a stream, we show that the magnetic field evolution is strongly dependent on its orientation with respect to the stretching direction. In particular, an alignment of the field lines with the direction of stretching induces an increase of the magnetic energy. For disruptions happening well within the tidal radius, the star compression causes the magnetic field strength to sharply increase by an order of magnitude at the time of pericentre passage. If the disruption is partial, we find evidence for a dynamo process occurring inside the surviving core due to the formation of vortices. This causes an amplification of the magnetic field strength by a factor of ˜10. However, this value represents a lower limit since it increases with numerical resolution. For an initial field strength of 1 G, the magnetic field never becomes dynamically important. Instead, the disruption of a star with a strong 1 MG magnetic field produces a debris stream within which magnetic pressure becomes similar to gas pressure a few tens of hours after disruption. If the remnant of one or multiple partial disruptions is eventually fully disrupted, its magnetic field could be large enough to magnetically power the relativistic jet detected from Swift J1644+57. Magnetized streams could also be significantly thickened by magnetic pressure when it overcomes the confining effect of self-gravity.

  16. Magnetic field screening effect in electroweak model

    CERN Document Server

    Bakry, A; Zhang, P M; Zou, L P

    2014-01-01

    It is shown that in the Weinberg-Salam model a magnetic field screening effect for static magnetic solutions takes place. The origin of that phenomenon is conditioned by features of the electro-weak interaction, namely, there is mutual cancellation of Abelian magnetic fields created by the SU(2) gauge fields and Higgs boson. The effect implies monopole charge screening in finite energy system of monopoles and antimonopoles. We consider another manifestation of the screening effect which leads to an essential energy decrease of magnetic solutions. Applying variational method we have found a magnetic field configuration with a topological azimuthal magnetic flux which minimizes the energy functional and possesses a total energy of order 1 TeV. We suppose that corresponding magnetic bound state exists in the electroweak theory and can be detected in experiment.

  17. Numerical Simulation of Level Magnetic Field

    Institute of Scientific and Technical Information of China (English)

    2003-01-01

    According to Maxwell electromagnetic field theory and magnetic vector potential integral equation, a mathematical model of LMF (Level Magnetic Field) for EMBR (Electromagnetic brake) was proposed, and the reliable software for LMF calculation was developed. The distribution of magnetic flux density given by numerical simulation shows that the magnetic flux density is greater in the magnet and magnetic leakage is observed in the gap. The magnetic flux density is uniform in horizontal plane and a peak is observed in vertical plane. Furthermore, the effects of electromagnetic and structural parameters on magnetic flux density were discussed. The relationship between magnetic flux, electromagnetic parameters and structural parameters is obtained by dimensional analysis, simulation experiment and least square method.

  18. Rydberg EIT in High Magnetic Field

    Science.gov (United States)

    Ma, Lu; Anderson, David; Miller, Stephanie; Raithel, Georg

    2016-05-01

    We present progress towards an all-optical approach for measurements of strong magnetic fields using electromagnetically induced transparency (EIT) with Rydberg atoms in an atomic vapor. Rydberg EIT spectroscopy is a promising technique for the development of atom-based, calibration- and drift-free technology for high magnetic field sensing. In this effort, Rydberg EIT is employed to spectroscopically investigate the response of Rydberg atoms exposed to strong magnetic fields, in which Rydberg atoms are in the strong-field regime. In our setup, two neodymium block magnets are used to generate fields of about 0.8 Tesla, which strongly perturb the atoms. Information on the field strength and direction is obtained by a comparison of experimental spectra with calculated spectral maps. Investigations of magnetic-field inhomogeneities and other decoherence sources will be discussed.

  19. Health effect from EMF exposure of Korea population

    Energy Technology Data Exchange (ETDEWEB)

    Kim, Y. S.; Cho, Y. S.; Lee, J. T.; Yup, M. J.; Hong, J. H. [Institute of Environmental and Industrrial Medicine, Hanyang Univ., Seoul (Korea, Republic of)

    2002-07-01

    This study on health effect from EMF exposure was performed from June 2001 to April 2002 to compare changes in melatonin levels in urine of 40 subjects during their normal sleeping hours, to evaluate heart rate, ST segment in ventricular, and ventricular premature beat for cardiac function, to evaluate microwave exposure from cellular phones which may have a potential influence on the electro physiologic function of human brain, and each 20 subjects in occupational and non-occupational group measured personal 24-h continual exposure, using EMDEX(for 40-800Hz, Enertech Consultant, Inc.). An urine samples for analysis of melatonin excretion level were collected 1 times a day(immediately after wake-up) for five days from each subjects and analyzed by radioimmunoassay, HRV-test for relationship between heart rate and EMF exposure was performed heart rate beat using Holter for subjects, and double EEG-test were performed in 10 long-term users of the cellularphones when using and not using them, and a single EEG-test in 10 short-term users of the cellular phones. Each EEG-recording took 40 min consisting of 30 min filed exposure and 10 min measurement. And We estimated the economic value of the potential damage of electromagnetic radiation from cellular phone, and the willingness to pay of people for the study of the radiation damage led by the government, by applying contingent variation method. The results of this study were followed; 1. Personal exposure assessment 2. We showed not significant difference for the subjective average melatonin levels between occupational and non- occupational groups exposed to electromagnetic fields. 3. We showed no difference in the awake EEGs in terms of spectral power density measures between long-term users and short-term users of cellular phones. 4. We found that the economic value of the potential damage by the radiation for a typical cellular phone user is about 20,000 won per year and he would be willing to pay about 1,800 won

  20. Optical fibers with composite magnetic coating for magnetic field sensing

    Energy Technology Data Exchange (ETDEWEB)

    Radojevic, V.; Nedeljkovic, D.; Talijan, N. E-mail: ntalijan@elab.tmf.bg.ac.yu; Trifunovic, D.; Aleksic, R

    2004-05-01

    The investigated system for optical fiber sensor was multi-mode optical fiber with magnetic composite coating. Polymer component of composite coating was poly (ethylene-co-vinyl acetate)-EVA, and the magnetic component was powder of SmCo{sub 5} permanent magnet in form of single domain particles. The influence of the applied external magnetic field on the change of intensity of the light signal propagated through optical fiber was investigated.

  1. Optical fibers with composite magnetic coating for magnetic field sensing

    Science.gov (United States)

    Radojevic, V.; Nedeljkovic, D.; Talijan, N.; Trifunovic, D.; Aleksic, R.

    2004-05-01

    The investigated system for optical fiber sensor was multi-mode optical fiber with magnetic composite coating. Polymer component of composite coating was poly (ethylene-co-vinyl acetate)-EVA, and the magnetic component was powder of SmCo5 permanent magnet in form of single domain particles. The influence of the applied external magnetic field on the change of intensity of the light signal propagated through optical fiber was investigated.

  2. Reducing Field Distortion in Magnetic Resonance Imaging

    Science.gov (United States)

    Eom, Byeong Ho; Penanen, Konstantin; Hahn, Inseob

    2010-01-01

    A concept for a magnetic resonance imaging (MRI) system that would utilize a relatively weak magnetic field provides for several design features that differ significantly from the corresponding features of conventional MRI systems. Notable among these features are a magnetic-field configuration that reduces (relative to the conventional configuration) distortion and blurring of the image, the use of a superconducting quantum interference device (SQUID) magnetometer as the detector, and an imaging procedure suited for the unconventional field configuration and sensor. In a typical application of MRI, a radio-frequency pulse is used to excite precession of the magnetic moments of protons in an applied magnetic field, and the decaying precession is detected for a short time following the pulse. The precession occurs at a resonance frequency proportional to the strengths of the magnetic field and the proton magnetic moment. The magnetic field is configured to vary with position in a known way; hence, by virtue of the aforesaid proportionality, the resonance frequency varies with position in a known way. In other words, position is encoded as resonance frequency. MRI using magnetic fields weaker than those of conventional MRI offers several advantages, including cheaper and smaller equipment, greater compatibility with metallic objects, and higher image quality because of low susceptibility distortion and enhanced spin-lattice-relaxation- time contrast. SQUID MRI is being developed into a practical MRI method for applied magnetic flux densities of the order of only 100 T

  3. An Intergalactic Magnetic Field from Quasar Outflows

    CERN Document Server

    Furlanetto, S; Furlanetto, Steven; Loeb, Abraham

    2001-01-01

    Outflows from quasars inevitably pollute the intergalactic medium (IGM) with magnetic fields. The short-lived activity of a quasar leaves behind an expanding magnetized bubble in the IGM. We model the expansion of the remnant quasar bubbles and calculate their distribution as a function magnetic field strength at different redshifts. We find that by a redshift z ~ 3, about 5-80% of the IGM volume is filled by magnetic fields with an energy density > 10% of the mean thermal energy density of a photo-ionized IGM (at ~ 10^4 K). As massive galaxies and X-ray clusters condense out of the magnetized IGM, the adiabatic compression of the magnetic field could result in the fields observed in these systems without a need for further dynamo amplification.

  4. Effects of acute electromagnetic fields exposure on the interhemispheric homotopic functional connectivity during resting state.

    Science.gov (United States)

    Lv, Bin; Shao, Qing; Chen, Zhiye; Ma, Lin; Wu, Tongning

    2015-08-01

    In this paper, we aimed to investigate the possible effects of acute radiofrequency electromagnetic fields (EMF) on the interhemispheric homotopic functional connectivity with resting state functional magnetic resonance imaging (fMRI) technique. We designed a controllable LTE-related EMF exposure environment at 2.573 GHz and performed the 30 min real/sham exposure experiments on human brain under the safety limits. The resting state fMRI signals were collected before and after EMF exposure. Then voxel-mirrored homotopic connectivity method was utilized to evaluate the acute effects of LTE EMF exposure on the homotopic functional connectivity between two human hemispheres. Based on our previous research, we further demonstrated that the 30 min short-term LTE EMF exposure would modulate the interhemispheric homotopic functional connectivity in resting state around the medial frontal gyrus and the paracentral lobule during the real exposure.

  5. MDI Synoptic Charts of Magnetic Field: Interpolation of Polar Fields

    Science.gov (United States)

    Liu, Yang; Hoeksema, J. T.; Zhao, X.; Larson, R. M.

    2007-05-01

    In this poster, we compare various methods for interpolation of polar field for the MDI synoptic charts of magnetic field. By examining the coronal and heliospheric magnetic field computed from the synoptic charts based on a Potential Field Source Surface model (PFSS), and by comparing the heliospheric current sheets and footpoints of open fields with the observations, we conclude that the coronal and heliospheric fields calculated from the synoptic charts are sensitive to the polar field interpolation, and a time-dependent interpolation method using the observed polar fields is the best among the seven methods investigated.

  6. Research on the Torque and Back EMF Performance of a High Speed PMSM Used for Flywheel Energy Storage

    Directory of Open Access Journals (Sweden)

    Jing Zhao

    2015-04-01

    Full Text Available Due to advantages such as high energy density, high power density, rapid charge and discharge, high cyclic-life, and environmentally friendly, flywheel energy storage systems (FESs are widely used in various fields. However, the performance of FES systems depends on the performance of a high speed machine, therefore, the design and optimization of a high efficiency and high power density machine are very crucial to improve the performance of the whole FES system. In this paper, a high speed permanent-magnet synchronous machine (PMSM is researched. Considering the requirement of low torque ripple in low speed and loss caused by back electromotive force (EMF harmonics, the electromagnetic performance is improved from points of view of slot/pole matching, magnetic-pole embrace with the finite element method (FEM. Furthermore, the magnetic-pole eccentricity, the slot opening, the thickness of PM and air-gap length are also optimized with Taguchi method. The electromagnetic performance, such as torque ripple, cogging torque, average torque and back EMF wave are much improved after optimization. Finally, experiments are carried out to verify the calculated results.

  7. Efficient magnetic fields for supporting toroidal plasmas

    CERN Document Server

    Landreman, Matt

    2016-01-01

    The magnetic field that supports tokamak and stellarator plasmas must be produced by coils well separated from the plasma. However the larger the separation, the more difficult it is to produce a given magnetic field in the plasma region, so plasma configurations should be chosen that can be supported as efficiently as possible by distant coils. The properties of curl-free magnetic fields allow magnetic field distributions to be ranked in order of their difficulty of production from a distance. Plasma shapes with low curvature and spectral width may be difficult to support, whereas plasma shapes with sharp edges may be efficiently supported by distant coils. Two measures of difficulty, which correctly identify such differences in difficulty, will be examined. These measures, which can be expressed as matrices, relate the externally-produced normal magnetic field on the plasma surface to the either the normal field or current on a distant control surface. A singular value decomposition (SVD) of either matrix y...

  8. The Evolution of the Earth's Magnetic Field.

    Science.gov (United States)

    Bloxham, Jeremy; Gubbins, David

    1989-01-01

    Describes the change of earth's magnetic field at the boundary between the outer core and the mantle. Measurement techniques used during the last 300 years are considered. Discusses the theories and research for explaining the field change. (YP)

  9. The Physics of Attraction and Repulsion: Magnetism and Magnetic Fields

    Science.gov (United States)

    Nakotte, Heinz

    2001-11-01

    The development of new materials with improved magnetic properties completely changed the modern world in the past decades. Recent progress is predominantly due to a better understanding of magnetism that has gone far beyond compass needles rotating in a magnetic field and bar magnets attracting or repelling each other. New magnetic materials are used to build smaller and smaller read/write heads and hard disks with increased storage capacity, developments that are responsible the revolution in the computer industry. Another example is the field of magnetic levitation that became feasible for commercial applications with the discovery of new superconducting materials, and a prototype train is under development in Japan. In medicine, the development of magnetic resonance imaging (MRI) provides an alternative to other (destructive) radiation techniques.

  10. Assembly of magnetic spheres in strong homogeneous magnetic field

    Science.gov (United States)

    Messina, René; Stanković, Igor

    2017-01-01

    The assembly in two dimensions of spherical magnets in strong magnetic field is addressed theoretically. It is shown that the attraction and assembly of parallel magnetic chains is the result of a delicate interplay of dipole-dipole interactions and short ranged excluded volume correlations. Minimal energy structures are obtained by numerical optimization procedure as well as analytical considerations. For a small number of constitutive magnets Ntot ≤ 26, a straight chain is found to be the ground state. In the regime of larger Ntot ≥ 27, the magnets form two touching chains with equally long tails at both ends. We succeed to identify the transition from two to three touching chains at Ntot = 129. Overall, this study sheds light on the mechanisms of the recently experimentally observed ribbon formation of superparamagnetic colloids via lateral aggregation of magnetic chains in magnetic field (Darras et al., 2016).

  11. Evolution of Neutron Star Magnetic Fields

    Indian Academy of Sciences (India)

    Dipankar Bhattacharya

    2002-03-01

    This paper reviews the current status of the theoretical models of the evolution of the magnetic fields of neutron stars other than magnetars. It appears that the magnetic fields of neutron stars decay significantly only if they are in binary systems. Three major physical models for this, namely spindown-induced flux expulsion, ohmic evolution of crustal field and diamagnetic screening of the field by accreted plasma, are reviewed.

  12. Nonlinear energy dissipation of magnetic nanoparticles in oscillating magnetic fields

    Energy Technology Data Exchange (ETDEWEB)

    Soto-Aquino, D. [ERC Incorporated, Air Force Research Laboratory, 10 E. Saturn Blvd., Edwards AFB, CA 93524 (United States); Rinaldi, C., E-mail: carlos.rinaldi@bme.ufl.edu [J. Crayton Pruitt Family Department of Biomedical Engineering and Department of Chemical Engineering, University of Florida, PO Box 116131, Gainesville, FL 32611-6131 (United States)

    2015-11-01

    The heating of magnetic nanoparticle suspensions subjected to alternating magnetic fields enables a variety of emerging applications such as magnetic fluid hyperthermia and triggered drug release. Rosensweig (2002) [25] obtained a model for the heat dissipation rate of a collection of non-interacting particles. However, the assumptions made in this analysis make it rigorously valid only in the limit of small applied magnetic field amplitude and frequency (i.e., values of the Langevin parameter that are much less than unity and frequencies below the inverse relaxation time). In this contribution we approach the problem from an alternative point of view by solving the phenomenological magnetization relaxation equation exactly for the case of arbitrary magnetic field amplitude and frequency and by solving a more accurate magnetization relaxation equation numerically. We also use rotational Brownian dynamics simulations of non-interacting magnetic nanoparticles subjected to an alternating magnetic field to estimate the rate of energy dissipation and compare the results of the phenomenological theories to the particle-scale simulations. The results are summarized in terms of a normalized energy dissipation rate and show that Rosensweig's expression provides an upper bound on the energy dissipation rate achieved at high field frequency and amplitude. Estimates of the predicted dependence of energy dissipation rate, quantified as specific absorption rate (SAR), on magnetic field amplitude and frequency, and particle core and hydrodynamic diameter, are also given. - Highlights: • Rosensweig's model for SAR was extended to high fields. • The MRSh relaxation equation was used to predict SAR at high fields. • Rotational Brownian dynamics simulations were used to predict SAR. • The results of these models were compared. • Predictions of effect of size and field conditions on SAR are presented.

  13. Two-axis magnetic field sensor

    Science.gov (United States)

    Jander, Albrecht (Inventor); Nordman, Catherine A. (Inventor); Qian, Zhenghong (Inventor); Smith, Carl H. (Inventor)

    2006-01-01

    A ferromagnetic thin-film based magnetic field sensor with first and second sensitive direction sensing structures each having a nonmagnetic intermediate layer with two major surfaces on opposite sides thereof having a magnetization reference layer on one and an anisotropic ferromagnetic material sensing layer on the other having a length in a selected length direction and a smaller width perpendicular thereto and parallel to the relatively fixed magnetization direction. The relatively fixed magnetization direction of said magnetization reference layer in each is oriented in substantially parallel to the substrate but substantially perpendicular to that of the other. An annealing process is used to form the desired magnetization directions.

  14. Magnetic fields and rotation of spiral galaxies

    CERN Document Server

    Battaner, E; Florido, E

    1998-01-01

    We present a simplified model in which we suggest that two important galactic problems -the magnetic field configuration at large scales and the flat rotation curve- may be simultaneously explained. A highly convective disc produces a high turbulent magnetic diffusion in the vertical direction, stablishing a merging of extragalactic and galactic magnetic fields. The outer disc may then adquire a magnetic energy gradient very close to the gradient required to explain the rotation curve, without the hypothesis of galactic dark matter. Our model predicts symmetries of the galactic field in noticeable agreement with the large scale structure of our galaxy.

  15. Rotating artificial gauge magnetic and electric fields

    CERN Document Server

    Lembessis, V E; Alshamari, S; Siddig, A; Aldossary, O M

    2016-01-01

    We consider the creation of artificial gauge magnetic and electric fields created when a two-level atom interacts with an optical Ferris wheel light field.These fields have the spatial structure of the optical Ferris wheel field intensity profile. If this optical field pattern is made to rotate in space then we have the creation of artificial electromagnetic fields which propagate in closed paths. The properties of such fields are presented and discussed

  16. Magnetic fields in Neutron Stars

    CERN Document Server

    Viganò, Daniele; Miralles, Juan A; Rea, Nanda

    2015-01-01

    Isolated neutron stars show a diversity in timing and spectral properties, which has historically led to a classification in different sub-classes. The magnetic field plays a key role in many aspects of the neutron star phenomenology: it regulates the braking torque responsible for their timing properties and, for magnetars, it provides the energy budget for the outburst activity and high quiescent luminosities (usually well above the rotational energy budget). We aim at unifying this observational variety by linking the results of the state-of-the-art 2D magneto-thermal simulations with observational data. The comparison between theory and observations allows to place two strong constraints on the physical properties of the inner crust. First, strong electrical currents must circulate in the crust, rather than in the star core. Second, the innermost part of the crust must be highly resistive, which is in principle in agreement with the presence of a novel phase of matter so-called nuclear pasta phase.

  17. Earth magnetism a guided tour through magnetic fields

    CERN Document Server

    Campbell, Wallace H

    2001-01-01

    An introductory guide to global magnetic field properties, Earth Magnetism addresses, in non-technical prose, many of the frequently asked questions about Earth''s magnetic field. Magnetism surrounds and penetrates our Earth in ways basic science courses can rarely address. It affects navigation, communication, and even the growth of crystals. As we observe and experience an 11-year solar maximum, we may witness spectacular satellite-destroying solar storms as they interact with our magnetic field. Written by an acknowledged expert in the field, this book will enrich courses in earth science, atmospheric science, geology, meteorology, geomagnetism, and geophysics. Contains nearly 200 original illustrations and eight pages of full-color plates.* Largely mathematics-free and with a wide breadth of material suitable for general readers* Integrates material from geomagnetism, paleomagnetism, and solar-terrestrial space physics.* Features nearly 200 original illustrations and 4 pages of colour plates

  18. Magnetic fields of HgMn stars

    DEFF Research Database (Denmark)

    Hubrig, S.; Gonzalez, J. F.; Ilyin, I.

    2012-01-01

    Context. The frequent presence of weak magnetic fields on the surface of spotted late-B stars with HgMn peculiarity in binary systems has been controversial during the two last decades. Recent studies of magnetic fields in these stars using the least-squares deconvolution (LSD) technique have fai...

  19. Ground Vehicle Navigation Using Magnetic Field Variation

    Science.gov (United States)

    Shockley, Jeremiah A.

    The Earth's magnetic field has been the bedrock of navigation for centuries. The latest research highlights the uniqueness of magnetic field measurements based on position due to large scale variations as well as localized perturbations. These observable changes in the Earth's magnetic field as a function of position provide distinct information which can be used for navigation. This dissertation describes ground vehicle navigation exploiting variation in Earth's magnetic field using a self-contained navigation system consisting of only a magnetometer and magnetic field maps. In order to achieve navigation, effective calibration enables repeatable magnetic field measurements from different vehicles and facilitates mapping of the observable magnetic field as a function of position. A new modified ellipsoid calibration technique for strapdown magnetometers in large vehicles is described, as well as analysis of position measurement generation comparing a multitude of measurement compositions using existing and newly developed likelihood techniques. Finally, navigation solutions are presented using both a position measurement and direct incorporation of the magnetometer measurements via a particle filter to demonstrate road navigation in three different environments. Emphatically, the results affirm that navigation using magnetic field variation in ground vehicles is viable and achieves adequate performance for road level navigation.

  20. Lattice Planar QED in external magnetic field

    CERN Document Server

    Cea, Paolo; Giudice, Pietro; Papa, Alessandro

    2011-01-01

    We investigate planar Quantum ElectroDynamics (QED) with two degenerate staggered fermions in an external magnetic field on the lattice. Our preliminary results indicate that in external magnetic fields there is dynamical generation of mass for two-dimensional massless Dirac fermions in the weak coupling region. We comment on possible implications to the quantum Hall effect in graphene.

  1. Helical Magnetic Fields in AGN Jets

    Indian Academy of Sciences (India)

    Y. J. Chen; G.-Y. Zhao; Z.-Q. Shen

    2014-09-01

    We establish a simple model to describe the helical magnetic fields in AGN jets projected on the sky plane and the line-of-sight. This kind of profile has been detected in the polarimetric VLBI observation of many blazar objects, suggesting the existence of helical magnetic fields in these sources.

  2. Magnetic Fields at the Center of Coils

    Science.gov (United States)

    Binder, Philippe; Hui, Kaleonui; Goldman, Jesse

    2014-01-01

    In this note we synthesize and extend expressions for the magnetic field at the center of very short and very long current-carrying coils. Elementary physics textbooks present the following equation for the magnetic field inside a very long current-carrying coil (solenoid): B[subscript sol] = µ[subscript 0] (N/L) I, (1) where I is the current, N…

  3. THE NUMERICAL-FIELD ANALYSIS OF THE MAGNETIC FIELD AND THE ELECTRICAL QUANTITIES IN THE TURBOGENERATOR STATOR UNDER AUTONOMOUS UNBALANCED LOADING

    Directory of Open Access Journals (Sweden)

    V. I. Milykh

    2016-11-01

    Full Text Available Purpose. Assessing the impact of load asymmetry of turbogenerator (TG on the magnetic field distribution, on the electrical and energy processes in it based on the numerical-field analysis within the constraints regulated by the standards. Methodology. The calculation model of TG has been constructed on the method of symmetrical components of the three-phase current system. The formed asymmetric system of the currents is used for multi-position numerical calculations of rotating magnetic fields. The temporal functions of the electromagnetic quantities which are subjected to the harmonic analysis are obtained on this basis. Results. Test calculations are conducted on a three-phase 35 MW TG during his work under autonomous unbalanced loading. The analysis of the temporal functions of the magnetic induction at different points of the TG stator and also similar functions of the magnetic flux linkage, EMF phase stator windings and other variables have been executed. Originality. Problems of exploitation of turbo-generators under unbalanced loading are detected by the consideration of their electromagnetic system on the whole, but not their simplified local parts, as usual. It has been shown that the temporal functions of EMF of the phase stator windings under unbalanced loading significantly differ in shape from sine waves and from each other and contain a number of significant upper harmonics. It has been detected that the phase currents would contain not only the first but also significant upper harmonics under unbalanced loading. Practical value. Analysis of the work of TG under unbalanced loading showed the «top» level of problems of electromagnetic character. It has been established that the function of the magnetic induction at the fixed points of the magnetic system on the whole have been changed but not in principle. The temporal functions of EMF, and, hence, the voltage of the stator phase windings significantly differ in shape from sine

  4. Magnetic Fields in Stars: Origin and Impact

    CERN Document Server

    Langer, N

    2013-01-01

    Various types of magnetic fields occur in stars: small scale fields, large scale fields, and internal toroidal fields. While the latter may be ubiquitous in stars due to differential rotation, small scale fields (spots) may be associated with envelop convection in all low and high mass stars. The stable large scale fields found in only about 10 per cent of intermediate mass and massive stars may be understood as a consequence of dynamical binary interaction, e.g., the merging of two stars in a binary. We relate these ideas to magnetic fields in white dwarfs and neutron stars, and to their role in core-collapse and thermonuclear supernova explosions.

  5. Classical theory of electric and magnetic fields

    CERN Document Server

    Good, Roland H

    1971-01-01

    Classical Theory of Electric and Magnetic Fields is a textbook on the principles of electricity and magnetism. This book discusses mathematical techniques, calculations, with examples of physical reasoning, that are generally applied in theoretical physics. This text reviews the classical theory of electric and magnetic fields, Maxwell's Equations, Lorentz Force, and Faraday's Law of Induction. The book also focuses on electrostatics and the general methods for solving electrostatic problems concerning images, inversion, complex variable, or separation of variables. The text also explains ma

  6. Pair annihilation in superstrong magnetic fields

    Science.gov (United States)

    Daugherty, J. K.; Bussard, R. W.

    1980-01-01

    The kinematical and dynamical aspects of the annihilation processes in superstrong magnetic fields are studied. The feasibility and potential significance of detecting from magnetic neutron stars are discussed. The discussion proceeds from the derivation of the fully relativistic differential cross sections and annihilation rates for both one- and two-photon emission from a ground-state gas of electrons and positrons in a static, uniform magnetic field.

  7. Mechanics of magnetic fluid column in strong magnetic fields

    Science.gov (United States)

    Polunin, V. M.; Ryapolov, P. A.; Platonov, V. B.

    2017-06-01

    Elastic-and magnetic properties of magnetic fluid confined by ponderomotive force in a tube fixed in horizontal position are considered. The system is placed in a strong magnetic field under the influence of external static and dynamic perturbations. An experimental setup has been developed. A theoretical basis of the processes of magnetic colloid elastic deformation has been proposed. The values of the static ponderomotive elasticity coefficient and the elasticity coefficient under dynamic action are experimentally determined. The calculations of the saturation magnetization for two magnetic fluid samples, carried out according to the equation containing the dynamic elasticity coefficient, are in good agreement with the experimental magnetization curve. The described method is of interest when studying magnetophoresis and aggregation of nanoparticles in magnetic colloids.

  8. Is it possible to indicate an ''electrosensitivity'' to an 50 Hz-magnetic field with an intensity of 10 {mu}T by the process of electrodermal activity (EDA)?; Laesst sich in der Hautleitfaehigkeit (EDA) bestimmter Menschen eine ''Elektrosensibilitaet'' auf ein 50 Hertz-Magnetfeld mit einer Intensitaet von 10 {mu}T abbilden?

    Energy Technology Data Exchange (ETDEWEB)

    Kaul, G. [Bundesanstalt fuer Arbeitsschutz und Arbeitsmedizin, Berlin (Germany)

    2004-07-01

    The aim of this study is to prove three hypotheses: 1) People who are very susceptible to EMF have a high ability to perceive small differences of stimuli (biological disposition). 2) People who are very susceptible to EMF have a high level of psychological or physiological stress as temporary conditions. 3) People who seem to be very susceptible to EMF have personal problems, and are not able to solve them otherwise (transference in terms of the theory of psychoanalysis). There were 96 volunteers without perception of any EM-field and 24 people with impairments of health on that were examined. Perceptual and mental tasks were used to differentiate individual performances under the influence of a 50 Hz-magnetic field with an intensity of 10 {micro}T. Positive findings may lead to the explanation of other environmental diseases. (orig.)

  9. Delayed quarkonium formation in a magnetic field

    CERN Document Server

    Suzuki, Kei

    2016-01-01

    Formation time of heavy quarkonia in a homogeneous magnetic field is analyzed by using a phenomenological ansatz of the vector current correlator. Because the existence of a magnetic field mixes vector quarkonia ($J/\\psi$, $\\psi^\\prime$) and their pseudoscalar partners ($\\eta_c$, $\\eta_c^\\prime$), the properties of the quarkonia can be modified through such a spin mixing. This means that the formation time of quarkonia is also changed by the magnetic field. We show the formation time of vector quarkonia is delayed by an idealized constant magnetic field, where the formation time of the excited state becomes longer than that of the ground state. As a more realistic situation in heavy-ion collisions, effects by a time-dependent magnetic field are also discussed.

  10. Structure of magnetic fields in intracluster cavities

    CERN Document Server

    Gourgouliatos, Konstantinos Nektarios; Lyutikov, Maxim

    2010-01-01

    Observations of clusters of galaxies show ubiquitous presence of X-ray cavities, presumably blown by the AGN jets. We consider magnetic field structures of these cavities. Stability requires that they contain both toroidal and poloidal magnetic fields, while realistic configurations should have vanishing magnetic field on the boundary. For axisymmetric configurations embedded in unmagnetized plasma, the continuity of poloidal and toroidal magnetic field components on the surface of the bubble then requires solving the elliptical Grad-Shafranov equation with both Dirichlet and Neumann boundary conditions. This leads to a double eigenvalue problem, relating the pressure gradients and the toroidal magnetic field to the radius of the bubble. We have found fully analytical stable solutions. This result is confirmed by numerical simulation. We present synthetic X-ray images and synchrotron emission profiles and evaluate the rotation measure for radiation traversing the bubble.

  11. Probing Magnetic Fields of Early Galaxies

    Science.gov (United States)

    Kohler, Susanna

    2017-06-01

    How do magnetic fields form and evolve in early galaxies? A new study has provided some clever observations to help us answer this question.The Puzzle of Growing FieldsDynamo theory is the primary model describing how magnetic fields develop in galaxies. In this picture, magnetic fields start out as weak seed fields that are small and unordered. These fields then become ordered and amplified by large-scale rotation and turbulence in galaxy disks and halos, eventually leading to the magnetic fields we observe in galaxies today.Schematic showinghow to indirectly measure protogalactic magnetic fields. The measured polarization of a background quasar is altered by the fields in a foreground protogalaxy. Click for a closer look! [Farnes et al. 2017/Adolf Schaller/STSCI/NRAO/AUI/NSF]To test this model, we need observations of the magnetic fields in young protogalaxies. Unfortunately, we dont have the sensitivity to be able to measure these fields directly but a team of scientists led by Jamie Farnes (Radboud University in the Netherlands) have come up with a creative alternative.The key is to find early protogalaxies that absorb the light of more distant background objects. If a protogalaxy lies between us and a distant quasar, then magnetic fields of the protogalaxy if present will affect the polarization measurements of the background quasar.Observing Galactic Building BlocksTop: Redshift distribution for the background quasars in the authors sample. Bottom: Redshift distribution for the foreground protogalaxies the authors are exploring. [Farnes et al. 2017]Farnes and collaborators examined two types of foreground protogalaxies: Damped Lyman-Alpha Absorbers (DLAs) and Lyman Limit Systems (LLSs). They obtained polarimetric data for a sample of 114 distant quasars with nothing in the foreground (the control sample), 19 quasars with DLAs in the foreground, and 27 quasars with LLSs in the foreground. They then used statistical analysis techniques to draw conclusions about

  12. Formation of magnetically anisotropic composite films at low magnetic fields

    Science.gov (United States)

    Ghazi Zahedi, Maryam; Ennen, Inga; Marchi, Sophie; Barthel, Markus J.; Hütten, Andreas; Athanassiou, Athanassia; Fragouli, Despina

    2017-04-01

    We present a straightforward two-step technique for the fabrication of poly (methyl methacrylate) composites with embedded aligned magnetic chains. First, ferromagnetic microwires are realized in a poly (methyl methacrylate) solution by assembling iron nanoparticles in a methyl methacrylate solution under heat in an external magnetic field of 160 mT. The simultaneous thermal polymerization of the monomer throughout the wires is responsible for their permanent linkage and stability. Next, the polymer solution containing the randomly dispersed microwires is casted on a solid substrate in the presence of a low magnetic field (20–40 mT) which induces the final alignment of the microwires into long magnetic chains upon evaporation of the solvent. We prove that the presence of the nanoparticles assembled in the form of microwires is a key factor for the formation of the anisotropic films under low magnetic fields. In fact, such low fields are not capable of driving and assembling dispersed magnetic nanoparticles in the same type of polymer solutions. Hence, this innovative approach can be utilized for the synthesis of magnetically anisotropic nanocomposite films at low magnetic fields.

  13. Teaching Representation Translations with Magnetic Field Experiments

    Science.gov (United States)

    Tillotson, Wilson Andrew; McCaskey, Timothy; Nasser, Luis

    2017-01-01

    We have developed a laboratory exercise designed to help students translate between different field representations. It starts with students qualitatively mapping field lines for various bar magnet configurations and continues with a Hall probe experiment in which students execute a series of scaffolded tasks, culminating in the prediction and measurement of the spatial variation of magnetic field components along a line near magnets. We describe the experimental tasks, various difficulties students have throughout, and ways this lab makes even their incorrect predictions better. We suggest that developing lab activities of this nature brings a new dimension to the ways students learn and interact with field concepts.

  14. Magnetic fields of HgMn stars

    DEFF Research Database (Denmark)

    Hubrig, S.; González, J. F.; Ilyin, I.

    2012-01-01

    Context. The frequent presence of weak magnetic fields on the surface of spotted late-B stars with HgMn peculiarity in binary systems has been controversial during the two last decades. Recent studies of magnetic fields in these stars using the least-squares deconvolution (LSD) technique have...... failed to detect magnetic fields, indicating an upper limit on the longitudinal field between 8 and 15G. In these LSD studies, assumptions were made that all spectral lines are identical in shape and can be described by a scaled mean profile. Aims. We re-analyse the available spectropolarimetric material...

  15. Warm inflation in presence of magnetic fields

    CERN Document Server

    Piccinelli, Gabriella; Ayala, Alejandro; Mizher, Ana Julia

    2013-01-01

    We present preliminary results on the possible effects that primordial magnetic fields can have for a warm inflation scenario, based on global supersymmetry, with a new-inflation-type potential. This work is motivated by two considerations: first, magnetic fields seem to be present in the universe on all scales, which rises the possibility that they could also permeate the early universe; second, the recent emergence of inflationary models where the inflaton is not assumed to be isolated but instead it is taken as an interacting field, even during the inflationary expansion. The effects of magnetic fields are included resorting to Schwinger proper time method.

  16. Field Mapping System for Solenoid Magnet

    Science.gov (United States)

    Park, K. H.; Jung, Y. K.; Kim, D. E.; Lee, H. G.; Park, S. J.; Chung, C. W.; Kang, B. K.

    2007-01-01

    A three-dimensional Hall probe mapping system for measuring the solenoid magnet of PLS photo-cathode RF e-gun has been developed. It can map the solenoid field either in Cartesian or in cylindrical coordinate system with a measurement reproducibility better than 5 × 10-5 T. The system has three axis motors: one for the azimuthal direction and the other two for the x and z direction. This architecture makes the measuring system simple in fabrication. The magnetic center was calculated using the measured axial component of magnetic field Bz in Cartesian coordinate system because the accuracy of magnetic axis measurement could be improved significantly by using Bz, instead of the radial component of magnetic field Br. This paper describes the measurement system and summarizes the measurement results for the solenoid magnetic of PLS photo-cathode RF e-gun.

  17. Magnetic-field-controlled reconfigurable semiconductor logic.

    Science.gov (United States)

    Joo, Sungjung; Kim, Taeyueb; Shin, Sang Hoon; Lim, Ju Young; Hong, Jinki; Song, Jin Dong; Chang, Joonyeon; Lee, Hyun-Woo; Rhie, Kungwon; Han, Suk Hee; Shin, Kyung-Ho; Johnson, Mark

    2013-02-07

    Logic devices based on magnetism show promise for increasing computational efficiency while decreasing consumed power. They offer zero quiescent power and yet combine novel functions such as programmable logic operation and non-volatile built-in memory. However, practical efforts to adapt a magnetic device to logic suffer from a low signal-to-noise ratio and other performance attributes that are not adequate for logic gates. Rather than exploiting magnetoresistive effects that result from spin-dependent transport of carriers, we have approached the development of a magnetic logic device in a different way: we use the phenomenon of large magnetoresistance found in non-magnetic semiconductors in high electric fields. Here we report a device showing a strong diode characteristic that is highly sensitive to both the sign and the magnitude of an external magnetic field, offering a reversible change between two different characteristic states by the application of a magnetic field. This feature results from magnetic control of carrier generation and recombination in an InSb p-n bilayer channel. Simple circuits combining such elementary devices are fabricated and tested, and Boolean logic functions including AND, OR, NAND and NOR are performed. They are programmed dynamically by external electric or magnetic signals, demonstrating magnetic-field-controlled semiconductor reconfigurable logic at room temperature. This magnetic technology permits a new kind of spintronic device, characterized as a current switch rather than a voltage switch, and provides a simple and compact platform for non-volatile reconfigurable logic devices.

  18. Solar Force-free Magnetic Fields

    CERN Document Server

    Wiegelmann, Thomas

    2012-01-01

    The structure and dynamics of the solar corona is dominated by the magnetic field. In most areas in the corona magnetic forces are so dominant that all non-magnetic forces like plasma pressure gradient and gravity can be neglected in the lowest order. This model assumption is called the force-free field assumption, as the Lorentz force vanishes. This can be obtained by either vanishing electric currents (leading to potential fields) or the currents are co-aligned with the magnetic field lines. First we discuss a mathematically simpler approach that the magnetic field and currents are proportional with one global constant, the so-called linear force-free field approximation. In the generic case, however, the relation between magnetic fields and electric currents is nonlinear and analytic solutions have been only found for special cases, like 1D or 2D configurations. For constructing realistic nonlinear force-free coronal magnetic field models in 3D, sophisticated numerical computations are required and boundar...

  19. Magnetic monopole field exposed by electrons

    CERN Document Server

    Béché, A; Van Tendeloo, G; Verbeeck, J

    2013-01-01

    Magnetic monopoles have provided a rich field of study, leading to a wide area of research in particle physics, solid state physics, ultra-cold gases, superconductors, cosmology, and gauge theory. So far, no true magnetic monopoles were found experimentally. Using the Aharonov-Bohm effect, one of the central results of quantum physics, shows however, that an effective monopole field can be produced. Understanding the effects of such a monopole field on its surroundings is crucial to its observation and provides a better grasp of fundamental physical theory. We realize the diffraction of fast electrons at a magnetic monopole field generated by a nanoscopic magnetized ferromagnetic needle. Previous studies have been limited to theoretical semiclassical optical calculations of the motion of electrons in such a monopole field. Solid state systems like the recently studied 'spin ice' provide a constrained system to study similar fields, but make it impossible to separate the monopole from the material. Free space ...

  20. External-field-free magnetic biosensor

    Energy Technology Data Exchange (ETDEWEB)

    Li, Yuanpeng; Wang, Yi; Klein, Todd; Wang, Jian-Ping, E-mail: jpwang@umn.edu [Department of Electrical and Computer Engineering, University of Minnesota, Minneapolis, Minnesota 55455 (United States)

    2014-03-24

    In this paper, we report a magnetic nanoparticle (MNP) detection scheme without the presence of any external magnetic field. The proposed magnetic sensor uses a patterned groove structure within the sensor so that no external magnetic field is needed to magnetize the MNPs. An example is given based on a giant magnetoresistance (GMR) sensing device with a spin valve structure. For this structure, the detection of MNPs located inside the groove and near the free layer is demonstrated under no external magnetic field. Micromagnetic simulations are performed to calculate the signal to noise level of this detection scheme. A maximum signal to noise ratio (SNR) of 18.6 dB from one iron oxide magnetic nanoparticle with 8 nm radius is achieved. As proof of concept, this external-field-free GMR sensor with groove structure of 200 nm × 200 nm is fabricated using a photo and an electron beam integrated lithography process. Using this sensor, the feasibility demonstration of the detection SNR of 9.3 dB is achieved for 30 μl magnetic nanoparticles suspension (30 nm iron oxide particles, 1 mg/ml). This proposed external-field-free sensor structure is not limited to GMR devices and could be applicable to other magnetic biosensing devices.

  1. Interplanetary magnetic field and geomagnetic Dst variations.

    Science.gov (United States)

    Patel, V. L.; Desai, U. D.

    1973-01-01

    The interplanetary magnetic field has been shown to influence the ring current field represented by Dst. Explorer 28 hourly magnetic field observations have been used with the hourly Dst values. The moderate geomagnetic storms of 60 gammas and quiet-time fluctuations of 10 to 30 gammas are correlated with the north to south change of the interplanetary field component perpendicular to the ecliptic. This change in the interplanetary field occurs one to three hours earlier than the corresponding change in the Dst field.

  2. Polarized radiation diagnostics of stellar magnetic fields

    Science.gov (United States)

    Mathys, Gautier

    The main techniques used to diagnose magnetic fields in stars from polarimetric observations are presented. First, a summary of the physics of spectral line formation in the presence of a magnetic field is given. Departures from the simple case of linear Zeeman effect are briefly considered: partial Paschen-Back effect, contribution of hyperfine structure, and combined Stark and Zeeman effects. Important approximate solutions of the equation of transfer of polarized light in spectral lines are introduced. The procedure for disk-integration of emergent Stokes profiles, which is central to stellar magnetic field studies, is described, with special attention to the treatment of stellar rotation. This formalism is used to discuss the determination of the mean longitudinal magnetic field (through the photographic technique and through Balmer line photopolarimetry). This is done within the specific framework of Ap stars, which, with their unique large-scale organized magnetic fields, are an ideal laboratory for studies of stellar magnetism. Special attention is paid to those Ap stars whose magnetically split line components are resolved in high-dispersion Stokes I spectra, and to the determination of their mean magnetic field modulus. Various techniques of exploitation of the information contained in polarized spectral line profiles are reviewed: the moment technique (in particular, the determination of the crossover and of the mean quadratic field), Zeeman-Doppler imaging, and least-squares deconvolution. The prospects that these methods open for linear polarization studies are sketched. The way in which linear polarization diagnostics complement their Stokes I and V counterparts is emphasized by consideration of the results of broad band linear polarization measurements. Illustrations of the use of various diagnostics to derive properties of the magnetic fields of Ap stars are given. This is used to show the interest of deriving more physically realistic models of the

  3. Scattering in a magnetic field

    Energy Technology Data Exchange (ETDEWEB)

    David C. Carey

    2002-08-19

    The fixed target program at Fermilab has come to an end. New projects are in the planning stage. Among them is a muon storage ring. Up to the present, all storage rings in high-energy physics have carried stable particles, namely the electron and proton and their antiparticles. The muon is unstable and decays with a mean lifetime of 2.0 x 10{sup -6} sec. Two types of cooling have been used in the past. One is stochastic cooling where an electrode is used to detect the positions of the particles and send a signal to another position across the ring. Through successive applications of this technique, the phase space is ultimately greatly reduced and beams can be made to collide with a useful event rate. The second type of cooling is electron cooling. Here protons and electrons are made to travel together for a short distance. Equipartition causes transfer of transverse energy of the protons to that of the electrons. Neither of these methods is fast enough to allow acceleration of a sufficient number of muons up to maximum energy before they decay. A new method known as ionization cooling has been proposed.[1] The muons are cooled by passing them through a container of liquid hydrogen. The energy loss reduces both transverse and longitudinal momentum. The longitudinal momentum is restored with RF cavities. The net result is to maintain the longitudinal momentum while cooling the transverse momentum. To minimize the total travel distance of the muons the liquid hydrogen is placed inside the focusing solenoids. The question arises as to whether the presence of the solenoids influences the phase space occupied by the muons. After the muon scatters it has transverse momentum. In a constant longitudinal magnetic field the trajectory wraps around the field lines and coincides in momentum and position with a particle which scatters one cycle later. Here we calculate the change in emittance for both a drift space and a solenoid. We find that the presence of the solenoid does

  4. [The influence of electromagnetic fields on flora and fauna].

    Science.gov (United States)

    Rochalska, Małgorzata

    2009-01-01

    This paper presents the influence of natural and artificial electromagnetic fields (EMF) on fauna and flora. The mechanisms of Earth's magnetic field detection and the use of this skill by migratory animals to faultlessly reach the destination of their travel are discussed, as well as the positive effects of electric and magnetic fields on plants relative to their physiology, yielding and health. EMF influence on social insects and animal organisms, including possible DNA damages and DNA repair systems, is presented. The influence of high frequency electromagnetic fields on birds nesting is also discussed.

  5. Compact low field magnetic resonance imaging magnet: Design and optimization

    Science.gov (United States)

    Sciandrone, M.; Placidi, G.; Testa, L.; Sotgiu, A.

    2000-03-01

    Magnetic resonance imaging (MRI) is performed with a very large instrument that allows the patient to be inserted into a region of uniform magnetic field. The field is generated either by an electromagnet (resistive or superconductive) or by a permanent magnet. Electromagnets are designed as air cored solenoids of cylindrical symmetry, with an inner bore of 80-100 cm in diameter. In clinical analysis of peripheral regions of the body (legs, arms, foot, knee, etc.) it would be better to adopt much less expensive magnets leaving the most expensive instruments to applications that require the insertion of the patient in the magnet (head, thorax, abdomen, etc.). These "dedicated" apparati could be smaller and based on resistive magnets that are manufactured and operated at very low cost, particularly if they utilize an iron yoke to reduce power requirements. In order to obtain good field uniformity without the use of a set of shimming coils, we propose both particular construction of a dedicated magnet, using four independently controlled pairs of coils, and an optimization-based strategy for computing, a posteriori, the optimal current values. The optimization phase could be viewed as a low-cost shimming procedure for obtaining the desired magnetic field configuration. Some experimental measurements, confirming the effectiveness of the proposed approach (construction and optimization), have also been reported. In particular, it has been shown that the adoption of the proposed optimization based strategy has allowed the achievement of good uniformity of the magnetic field in about one fourth of the magnet length and about one half of its bore. On the basis of the good experimental results, the dedicated magnet can be used for MRI of peripheral regions of the body and for animal experimentation at very low cost.

  6. Hyperfine magnetic fields in substituted Finemet alloys

    Energy Technology Data Exchange (ETDEWEB)

    Brzózka, K., E-mail: k.brzozka@uthrad.pl [University of Technology and Humanities in Radom, Department of Physics (Poland); Sovák, P. [P.J. Šafárik University, Institute of Physics (Slovakia); Szumiata, T.; Gawroński, M.; Górka, B. [University of Technology and Humanities in Radom, Department of Physics (Poland)

    2016-12-15

    Transmission Mössbauer spectroscopy was used to determine the hyperfine fields of Finemet-type alloys in form of ribbons, substituted alternatively by Mn, Ni, Co, Al, Zn, V or Ge of various concentration. The comparative analysis of magnetic hyperfine fields was carried out which enabled to understand the role of added elements in as-quenched as well as annealed samples. Moreover, the influence of the substitution on the mean direction of the local hyperfine magnetic field was examined.

  7. Magnetic fields in Local Group dwarf irregulars

    CERN Document Server

    Chyzy, Krzysztof T; Beck, Rainer; Bomans, Dominik J

    2011-01-01

    We clarify whether strong magnetic fields can be effectively generated in typically low-mass dwarf galaxies and what is the role of dwarf galaxies in the magnetization of the Universe. We performed a search for radio emission and magnetic fields in an unbiased sample of 12 Local Group (LG) irregular and dwarf irregular galaxies with the 100m Effelsberg telescope at 2.64 and 4.85GHz. Magnetic fields in LG dwarfs are three times weaker than in the normal spirals (6muG) are observed only in dwarfs of extreme characteristics while typical LG dwarfs are not suitable objects for efficient supply of magnetic fields to the intergalactic medium.

  8. Magnetic field homogeneity perturbations in finite Halbach dipole magnets.

    Science.gov (United States)

    Turek, Krzysztof; Liszkowski, Piotr

    2014-01-01

    Halbach hollow cylinder dipole magnets of a low or relatively low aspect ratio attract considerable attention due to their applications, among others, in compact NMR and MRI systems for investigating small objects. However, a complete mathematical framework for the analysis of magnetic fields in these magnets has been developed only for their infinitely long precursors. In such a case the analysis is reduced to two-dimensions (2D). The paper details the analysis of the 3D magnetic field in the Halbach dipole cylinders of a finite length. The analysis is based on three equations in which the components of the magnetic flux density Bx, By and Bz are expanded to infinite power series of the radial coordinate r. The zeroth term in the series corresponds to a homogeneous magnetic field Bc, which is perturbed by the higher order terms due to a finite magnet length. This set of equations is supplemented with an equation for the field profile B(z) along the magnet axis, presented for the first time. It is demonstrated that the geometrical factors in the coefficients of particular powers of r, defined by intricate integrals are the coefficients of the Taylor expansion of the homogeneity profile (B(z)-Bc)/Bc. As a consequence, the components of B can be easily calculated with an arbitrary accuracy. In order to describe perturbations of the field due to segmentation, two additional equations are borrowed from the 2D theory. It is shown that the 2D approach to the perturbations generated by the segmentation can be applied to the 3D Halbach structures unless r is not too close to the inner radius of the cylinder ri. The mathematical framework presented in the paper was verified with great precision by computations of B by a highly accurate integration of the magnetostatic Coulomb law and utilized to analyze the inhomogeneity of the magnetic field in the magnet with the accuracy better than 1 ppm.

  9. Instability of strong magnetic field and neutrino magnetic dipole moment

    CERN Document Server

    Lee, Hyun Kyu

    2016-01-01

    Vacuum instability of the strong electromagnetic field has been discussed since long time ago. The instability of the strong electric field due to creation of electron pairs is one of the examples, which is known as Schwinger process. What matters are the coupling of particles to the electromagnetic field and the mass of the particle to be produced. The critical electric field for electrons in the minimal coupling is ~ m^2/e . Spin 1/2 neutral particles but with magnetic dipole moments can interact with the electromagnetic field through Pauli coupling. The instability of the particular vacuum under the strong magnetic field can be formulated as the emergence of imaginary parts of the effective potential. In this talk, the development of the imaginary part in the effective potential as a function of the magnetic field strength is discussed for the configurations of the uniform magnetic field and the inhomogeneous magnetic field. Neutrinos are the lightest particle(if not photon or gluon) in the "standard model...

  10. Computation of magnetic fields in hysteretic media

    Energy Technology Data Exchange (ETDEWEB)

    Adly, A.A.; Mayergoyz, I.D.; Gomez, R.D.; Burke, E.R. (Univ. of Maryland, College Park, MD (United States))

    1993-11-01

    A newly developed vector Preisach-type model of hysteresis is applied to the computation of static magnetic fields in media with hysteresis. Time stepping technique is used to trace the time evolution of local magnetic fields which form the history of magnetizing process. At each time step, the magnetostatic problem is formulated in terms of an integral equation and an efficient iterative algorithm is employed for solving this problem. The technique has been used to simulate some magnetic recording processes. Sample results of these simulations are given in the paper.

  11. Efficient magnetic fields for supporting toroidal plasmas

    Energy Technology Data Exchange (ETDEWEB)

    Landreman, Matt, E-mail: mattland@umd.edu [Institute for Research in Electronics and Applied Physics, University of Maryland, College Park, Maryland 20742 (United States); Boozer, Allen H. [Department of Applied Physics and Applied Mathematics, Columbia University, New York, New York 10027 (United States)

    2016-03-15

    The magnetic field that supports tokamak and stellarator plasmas must be produced by coils well separated from the plasma. However, the larger the separation, the more difficult it is to produce a given magnetic field in the plasma region, so plasma configurations should be chosen that can be supported as efficiently as possible by distant coils. The efficiency of an externally generated magnetic field is a measure of the field's shaping component magnitude at the plasma compared to the magnitude near the coils; the efficiency of a plasma equilibrium can be measured using the efficiency of the required external shaping field. Counterintuitively, plasma shapes with low curvature and spectral width may have low efficiency, whereas plasma shapes with sharp edges may have high efficiency. Two precise measures of magnetic field efficiency, which correctly identify such differences in difficulty, will be examined. These measures, which can be expressed as matrices, relate the externally produced normal magnetic field on the plasma surface to the either the normal field or current on a distant control surface. A singular value decomposition (SVD) of either matrix yields an efficiency ordered basis for the magnetic field distributions. Calculations are carried out for both tokamak and stellarator cases. For axisymmetric surfaces with circular cross-section, the SVD is calculated analytically, and the range of poloidal and toroidal mode numbers that can be controlled to a given desired level is determined. If formulated properly, these efficiency measures are independent of the coordinates used to parameterize the surfaces.

  12. Quark matter under strong magnetic fields

    Energy Technology Data Exchange (ETDEWEB)

    Peres Menezes, Debora [Universidade Federal de Santa Catarina, Depto de Fisica - CFM, Florianopolis, SC (Brazil); Laercio Lopes, Luiz [Universidade Federal de Santa Catarina, Depto de Fisica - CFM, Florianopolis, SC (Brazil); Campus VIII, Centro Federal de Educacao Tecnologica de Minas Gerais, Varginha, MG (Brazil)

    2016-02-15

    We revisit three of the mathematical formalisms used to describe magnetized quark matter in compact objects within the MIT and the Nambu-Jona-Lasinio models and then compare their results. The tree formalisms are based on 1) isotropic equations of state, 2) anisotropic equations of state with different parallel and perpendicular pressures and 3) the assumption of a chaotic field approximation that results in a truly isotropic equation of state. We have seen that the magnetization obtained with both models is very different: while the MIT model produces well-behaved curves that are always positive for large magnetic fields, the NJL model yields a magnetization with lots of spikes and negative values. This fact has strong consequences on the results based on the existence of anisotropic equations of state. We have also seen that, while the isotropic formalism results in maximum stellar masses that increase considerably when the magnetic fields increase, maximum masses obtained with the chaotic field approximation never vary more than 5.5%. The effect of the magnetic field on the radii is opposed in the MIT and NJL models: with both formalisms, isotropic and chaotic field approximation, for a fixed mass, the radii increase with the increase of the magnetic field in the MIT bag model and decrease in the NJL, the radii of quark stars described by the NJL model being smaller than the ones described by the MIT model. (orig.)

  13. Alignment of magnetic uniaxial particles in a magnetic field: Simulation

    Energy Technology Data Exchange (ETDEWEB)

    Golovnia, O.A., E-mail: golovnya@imp.uran.ru [Institute of Metal Physics, Str. S. Kovalevskoy, 18, 620990 Ekaterinburg (Russian Federation); Popov, A.G [Institute of Metal Physics, Str. S. Kovalevskoy, 18, 620990 Ekaterinburg (Russian Federation); Sobolev, A.N. [South Ural State University (National Research University), av. Lenina, 76, 454080 Chelyabinsk (Russian Federation); Hadjipanayis, G.C. [Department of Physics and Astronomy, University of Delaware, 217 Sharp Lab, Newark, DE 19716 (United States)

    2014-09-01

    The numerical investigations of the process of alignment of magnetically uniaxial Nd–Fe–B powders in an applied magnetic field were carried out using the discrete element method (DEM). It is shown that magnetic alignment of ensemble of spherical particles provides extremely high degree of alignment, which is achieved in low magnetic fields. A model of formation of anisotropic particles as a combination of spherical particles is suggested. The influence of the shape anisotropy and friction coefficient on the alignment degree was analyzed. The increase in the friction coefficient leads to a decrease in the alignment degree; the simulation results are in qualitative agreement with experimental dependences. It is shown that in magnetic fields higher than 5 T, the calculated field dependences of the alignment degree quantitatively render the experimental data. The increase of about 6% in the alignment degree in the experiments with addition of internal lubricant can be explained by the decrease of 14% in friction coefficient. - Highlights: • We simulate the magnetic alignment of ensemble of Nd–Fe–B spherical uniaxial particles. • Anisotropic particles as a combination of spherical particles are constructed. • Influence of the particle shape anisotropy and friction on the alignment is analyzed. • We compare calculated and experimental data on field dependence of magnetic alignment. • The results render the experimental dependence.

  14. Electric-field guiding of magnetic skyrmions

    Energy Technology Data Exchange (ETDEWEB)

    Upadhyaya, Pramey; Yu, Guoqiang; Amiri, Pedram Khalili; Wang, Kang L.

    2015-10-01

    We theoretically study equilibrium and dynamic properties of nanosized magnetic skyrmions in thin magnetic films with broken inversion symmetry, where an electric field couples to magnetization via spin-orbit coupling. Based on a symmetry-based phenomenology and micromagnetic simulations we show that this electric-field coupling, via renormalizing the micromagnetic energy, modifies the equilibrium properties of the skyrmion. This change, in turn, results in a significant alteration of the current-induced skyrmion motion. Particularly, the speed and direction of the skyrmion can be manipulated by designing a desired energy landscape electrically, which we describe within Thiele's analytical model and demonstrate in micromagnetic simulations including electric-field-controlled magnetic anisotropy. We additionally use this electric-field control to construct gates for controlling skyrmion motion exhibiting a transistorlike and multiplexerlike function. The proposed electric-field effect can thus provide a low-energy electrical knob to extend the reach of information processing with skyrmions.

  15. Magnetic field in the primitive solar nebula

    Science.gov (United States)

    Levy, E. H.

    1978-01-01

    Carbonaceous chondrites have apparently been magnetized in their early history in magnetic fields with intensities of 0.1 to 10 G, but the origin of the magnetizing field has remained obscured. It is suggested that the magnetic field recorded in the remanence of carbonaceous chondrites may have been produced by a self-excited hydromagnetic dynamo in the gaseous preplanetary nebula from which the solar system is thought to have formed. Recently computed models for the evolution of the preplanetary nebula, consisting of turbulent and differentially rotating gaseous disks with characteristic radial scales of several AU, are used to demonstrate the feasibility of this hypothesis. The maximum field intensity that might be realized by the dynamo production process is estimated to be as high as 1 to 10 G, taking into account two dynamical mechanisms that limit the strength of the field (the Coriolis force and ambipolar diffusion).

  16. Magnetic field evolution in neutron stars

    Science.gov (United States)

    Castillo, F.; Reisenegger, A.; Valdivia, J. A.

    2017-07-01

    Neutron stars contain the strongest magnetic fields known in the Universe. Using numerical simulations restricted to axially symmetric geometry, we study the long-term evolution of the magnetic field in the interior of an isolated neutron star under the effect of ambipolar diffusion, i.e. the drift of the magnetic field and the charged particles relative to the neutrons. We model the stellar interior as an electrically neutral fluid composed of neutrons, protons and electrons; these species can be converted into each other by weak interactions (beta decays), suffer binary collisions, and be affected by each other's macroscopic electromagnetic fields. We show that, in the restricted case of pure ambipolar diffusion, neglecting weak interactions, the magnetic fields evolves towards a stable MHD equilibria configuration, in the timescales analytically expected.

  17. Magnetic field induced optical vortex beam rotation

    CERN Document Server

    Shi, Shuai; Zhou, Zhi-Yuan; Li, Yan; Zhang, Wei; Shi, Bao-Sen

    2015-01-01

    Light with orbital angular momentum (OAM) has drawn a great deal of attention for its important applications in the fields of precise optical measurements and high capacity optical communications. Here we adopt a method to study the rotation of a light beam, which is based on magnetic field induced circular birefringence in warm 87Rb atomic vapor. The dependence of the rotation angle to the intensity of the magnetic field makes it appropriate for weak magnetic field measurement. We derive a detail theoretical description that is in well agreement with the experimental observations. The experiment shows here provides a new method for precise measurement of magnetic field intensity and expands the application of OAM-carrying light.

  18. Quantum Electrodynamics in a Uniform Magnetic Field

    CERN Document Server

    Suzuki, J

    2005-01-01

    A systematic formalism for quantum electrodynamics in a classical uniform magnetic field is discussed. The first order radiative correction to the ground state energy of an electron is calculated. This then leads to the anomalous magnetic moment of an electron without divergent integrals. Thorough analyses of this problem are given for the weak magnetic field limit. A new expression for the radiative correction to the ground state energy is obtained. This contains only one integral with an additional summation with respect to each Landau level. The importance of this formalism is also addressed in order to deal with quantum electrodynamics in an intense external field.

  19. Hyperon Stars in Strong Magnetic Fields

    CERN Document Server

    Gomes, R O; Vasconcellos, C A Z

    2013-01-01

    We investigate the effects of strong magnetic fields on the properties of hyperon stars. The matter is described by a hadronic model with parametric coupling. The matter is considered to be at zero temperature, charge neutral, beta-equilibrated, containing the baryonic octet, electrons and muons. The charged particles have their orbital motions Landau-quantized in the presence of strong magnetic fields (SMF). Two parametrisations of a chemical potential dependent static magnetic field are considered, reaching $1-2 \\times 10^{18}\\,G$ in the center of the star. Finally, the Tolman-Oppenheimer-Volkov (TOV) equations are solved to obtain the mass-radius relation and population of the stars.

  20. Magnetic fields from second-order interactions

    CERN Document Server

    Osano, Bob

    2014-01-01

    It is well known that when two types of perturbations interact in cosmological perturbation theory, the interaction may lead to the generation of a third type. In this article we discuss the generation of magnetic fields from such interactions. We determine conditions under which the interaction of a first-order magnetic field with a first-order scalar-or vector-, or tensor-perturbations would lead to the generation of second order magnetic field. The analysis is done in a covariant-index-free approach, but could be done in the standard covariant indexed-approach.

  1. Dissipative charged fluid in a magnetic field

    Directory of Open Access Journals (Sweden)

    Navid Abbasi

    2016-05-01

    Full Text Available We study the collective excitations in a dissipative charged fluid at zero chemical potential when an external magnetic field is present. While in the absence of magnetic field, four collective excitations appear in the fluid, we find five hydrodynamic modes here. This implies that the magnetic field splits the degeneracy between the transverse shear modes. Using linear response theory, we then compute the retarded response functions. In particular, it turns out that the correlation between charge and the energy fluctuations will no longer vanish, even at zero chemical potential. By use of the response functions, we also derive the relevant Kubo formulas for the transport coefficients.

  2. Magnetic fields from second-order interactions

    OpenAIRE

    Osano, Bob

    2014-01-01

    It is well known that when two types of perturbations interact in cosmological perturbation theory, the interaction may lead to the generation of a third type. In this article we discuss the generation of magnetic fields from such interactions. We determine conditions under which the interaction of a first-order magnetic field with a first-order scalar-or vector-, or tensor-perturbations would lead to the generation of second order magnetic field. The analysis is done in a covariant-index-fre...

  3. Magnetic Field Control of Combustion Dynamics

    Science.gov (United States)

    Barmina, I.; Valdmanis, R.; Zake, M.; Kalis, H.; Marinaki, M.; Strautins, U.

    2016-08-01

    Experimental studies and mathematical modelling of the effects of magnetic field on combustion dynamics at thermo-chemical conversion of biomass are carried out with the aim of providing control of the processes developing in the reaction zone of swirling flame. The joint research of the magnetic field effect on the combustion dynamics includes the estimation of this effect on the formation of the swirling flame dynamics, flame temperature and composition, providing analysis of the magnetic field effects on the flame characteristics. The results of experiments have shown that the magnetic field exerts the influence on the flow velocity components by enhancing a swirl motion in the flame reaction zone with swirl-enhanced mixing of the axial flow of volatiles with cold air swirl, by cooling the flame reaction zone and by limiting the thermo-chemical conversion of volatiles. Mathematical modelling of magnetic field effect on the formation of the flame dynamics confirms that the electromagnetic force, which is induced by the electric current surrounding the flame, leads to field-enhanced increase of flow vorticity by enhancing mixing of the reactants. The magnetic field effect on the flame temperature and rate of reactions leads to conclusion that field-enhanced increase of the flow vorticity results in flame cooling by limiting the chemical conversion of the reactants.

  4. Magnetic field evolution of accreting neutron stars

    CERN Document Server

    Istomin, Ya N

    2016-01-01

    The flow of a matter, accreting onto a magnetized neutron star, is accompanied by an electric current. The closing of the electric current occurs in the crust of a neutron stars in the polar region across the magnetic field. But the conductivity of the crust along the magnetic field greatly exceeds the conductivity across the field, so the current penetrates deep into the crust down up to the super conducting core. The magnetic field, generated by the accretion current, increases greatly with the depth of penetration due to the Hall conductivity of the crust is also much larger than the transverse conductivity. As a result, the current begins to flow mainly in the toroidal direction, creating a strong longitudinal magnetic field, far exceeding an initial dipole field. This field exists only in the narrow polar tube of $r$ width, narrowing with the depth, i.e. with increasing of the crust density $\\rho$, $r\\propto \\rho^{-1/4}$. Accordingly, the magnetic field $B$ in the tube increases with the depth, $B\\propto...

  5. Dispersion of Magnetic Fields in Molecular Clouds

    CERN Document Server

    Hildebrand, Roger H; Dotson, Jessie L; Houde, Martin; Vaillancourt, John E

    2008-01-01

    We describe a method for determining the dispersion of magnetic field vectors about local mean fields in turbulent molecular clouds. The method is designed to avoid inaccurate estimates of MHD or turbulent dispersion - and hence to avoid inaccurate estimates of field strengths - due to large-scale, non-turbulent field structure when using the well-known method of Chandrasekhar and Fermi. Our method also provides accurate, independent estimates of the turbulent to mean magnetic field strength ratio. We discuss applications to the molecular clouds Orion, M17, and DR21.

  6. Reversals of the Earth's Magnetic Field

    Science.gov (United States)

    Champion, Duene E.

    J.A. Jacobs of Cambridge University has written a concise, authoritative, and up-todate text on reversals of the earth's magnetic field. Chapter 1 is a concise summary of the basic attributes of the geomagnetic field and its behavior in different time frames. It explains spherical harmonic analysis of the field and presents the history of acquisition of the data that best represent the recent field. Lastly, it includes a short summary of the origin and electrodynamics of the magnetic field, outlining the current theoretical basis for its generation.

  7. Magnetic field considerations in fusion power plant environs

    Energy Technology Data Exchange (ETDEWEB)

    Liemohn, H.B.; Lessor, D.L.; Duane, B.H.

    1976-09-01

    A summary of magnetic field production mechanisms and effects is given. Discussions are included on the following areas: (1) stray magnetic and electric fields from tokamaks, (2) methods for reducing magnetic fields, (3) economics of magnetic field reductions, (4) forces on magnetizable objects near magnetic confinement fusion reactors, (5) electric field transients in tokamaks, (6) attenuation and decay of electromagnetic fields, and (7) magnetic field transients from tokamak malfunctions.

  8. Magnetic fields in early protostellar disk formation

    CERN Document Server

    González-Casanova, Diego F; Lazarian, Alexander

    2016-01-01

    We consider formation of accretion disks from a realistically turbulent molecular gas using 3D MHD simulations. In particular, we analyze the effect of the fast turbulent reconnection described by the Lazarian & Vishniac (1999) model for the removal of magnetic flux from a disk. With our numerical simulations we demonstrate how the fast reconnection enables protostellar disk formation resolving the so-called "magnetic braking catastrophe". In particular, we provide a detailed study of the dynamics of a 0.5 M$_\\odot$ protostar and the formation of its disk for up to several thousands years. We measure the evolution of the mass, angular momentum, magnetic field, and turbulence around the star. We consider effects of two processes that strongly affect the magnetic transfer of angular momentum, both of which are based on turbulent reconnection: the first, "reconnection diffusion", removes the magnetic flux from the disk, the other involves the change of the magnetic field's topology, but does not change the a...

  9. Intergalactic Magnetic Fields from Quasar Outflows

    CERN Document Server

    Furlanetto, S; Furlanetto, Steven; Loeb, Abraham

    2001-01-01

    Outflows from quasars inevitably pollute the intergalactic medium (IGM) with magnetic fields. The short-lived activity of a quasar leaves behind an expanding magnetized bubble in the IGM. We model the expansion of the remnant quasar bubbles and calculate their distribution as a function of size and magnetic field strength at different redshifts. We generically find that by a redshift z=3, about 5-20% of the IGM volume is filled by magnetic fields with an energy density >10% of the mean thermal energy density of a photo-ionized IGM (at T=10^4 K). As massive galaxies and X-ray clusters condense out of the magnetized IGM, the adiabatic compression of the magnetic field could result in the field strength observed in these systems without a need for further dynamo amplification. The intergalactic magnetic field could also provide a nonthermal contribution to the pressure of the photo-ionized gas that may account for the claimed discrepancy between the simulated and observed Doppler width distributions of the Ly-al...

  10. The CMS Magnetic Field Map Performance

    CERN Document Server

    Klyukhin, VI; Sarycheva, L I; Klyukhin, V I; Ball, A; Gaddi, A; Amapane, N; Gerwig, H; Andreev, V; Cure, B; Mulders, M; Loveless, R; Karimaki, V; Popescu, S; Herve, A

    2010-01-01

    The Compact Muon Solenoid (CMS) is a general-purpose detector designed to run at the highest luminosity at the CERN Large Hadron Collider (LHC). Its distinctive featuresinclude a 4 T superconducting solenoid with 6 m diameter by 12.5 m long free bore, enclosed inside a 10000-ton return yoke made of construction steel. Accurate characterization of the magnetic field everywhere in the CMS detector is required. During two major tests of the CMS magnet the magnetic flux density was measured inside the coil in a cylinder of 3.448 m diameter and 7 m length with a specially designed field-mapping pneumatic machine as well as in 140 discrete regions of the CMS yoke with NMR probes, 3-D Hall sensors and flux-loops. A TOSCA 3-D model of the CMS magnet has been developed to describe the magnetic field everywhere outside the tracking volume measured with the field-mapping machine. A volume based representation of the magnetic field is used to provide the CMS simulation and reconstruction software with the magnetic field ...

  11. Compact Electric- And Magnetic-Field Sensor

    Science.gov (United States)

    Winterhalter, Daniel; Smith, Edward

    1994-01-01

    Compact sensor measures both electric and magnetic fields. Includes both short electric-field dipole and search-coil magnetometer. Three mounted orthogonally providing triaxial measurements of electromagnetic field at frequencies ranging from near 0 to about 10 kHz.

  12. Evaluation of E.M.F. exposure from medical electrical equipment

    Energy Technology Data Exchange (ETDEWEB)

    Aniolczyk, H.; Mamrot, P.; Politanski, P. [Nofer Institute of Occupational Medicine, Lodz (Poland)

    2006-07-01

    he medical electric and electronic equipment, including electro surgical devices, short- and microwave diathermy units, and magnetic resonance imaging (MRI) systems, belong to the most hazardous sources of electromagnetic emissions. The electromagnetic emissions can interfere with emissions from other medical equipment located in the same facility (e.g. operation rooms) thus having impact on their work, but more importantly, they can be dangerous to patients, medical personnel operating them and other persons. In the present project, an assessment of E.M.F. intensity was performed for more than 2 000 electro surgical devices (330 khz, 440 khz and 1.76 MHz frequency ranges), 1 200 diathermy units and 45 MRI 0.2 - 1.5 T systems. E.M.F. exposure of medical staff was assessed based on respective national hygienic standards. The actual exposure levels were found to exceed the admissible values in Poland. The recorded E.M.F. intensities were compared with relevant Who and U E recommendations (e.g. I.C.N.I.R.P. guidelines, 1998, Directive 2004/40/E.C.). The findings revealed that for 18% of the devices examined, the E.M.F. was higher than the E.M.F. intensity values recommended by U E. (authors)

  13. High Field Pulse Magnets with New Materials

    Science.gov (United States)

    Li, L.; Lesch, B.; Cochran, V. G.; Eyssa, Y.; Tozer, S.; Mielke, C. H.; Rickel, D.; van Sciver, S. W.; Schneider-Muntau, H. J.

    2004-11-01

    High performance pulse magnets using the combination of CuNb conductor and Zylon fiber composite reinforcement with bore sizes of 24, 15 and 10 mm have been designed, manufactured and tested to destruction. The magnets successfully reached the peak fields of 64, 70 and 77.8 T respectively with no destruction. Failures occurred near the end flanges at the layer. The magnet design, manufacturing and testing, and the mode of the failure are described and analyzed.

  14. Intelligent communication: The future of EMF discourse and risk governance?

    Energy Technology Data Exchange (ETDEWEB)

    Jamieson, Isaac A, E-mail: isaac.jamieson@imperial.ac.u [Department of Epidemiology and Biostatistics, School of Public Health, St. Mary' s Campus, Imperial College London, London W2 1PG (United Kingdom)

    2010-04-15

    It is proposed that to help facilitate progress in electromagnetic field (EMF) risk governance and actively address potential concerns whilst encouraging environmentally-sound technical advancement, the ground rules of stakeholder participation / debate may benefit from being radically overhauled to encourage more openness, trust, understanding, transparency and innovation. It is further proposed that two-way communication should be actively promoted, as should proactive thinking and informed discussions of risk (which address realistically the concerns of all parties). The creation/development/adoption of enhanced best practice solutions and precautionary principle measures should also be encouraged.

  15. Light Polarization Using Ferrofluids and Magnetic Fields

    Directory of Open Access Journals (Sweden)

    Alberto Tufaile

    2017-01-01

    Full Text Available We are presenting an experimental setup based on polarized light, enabling the visualization of the magnetic field of magnetic assemblies using a Hele-Shaw cell filled with ferrofluids. We have simulated the observed patterns with hypergeometric polynomials.

  16. The magnetic field of zeta Orionis A

    CERN Document Server

    Blazère, A; Tkachenko, A; Bouret, J -C; Rivinius, Th

    2015-01-01

    Zeta Ori A is a hot star claimed to host a weak magnetic field, but no clear magnetic detection was obtained so far. In addition, it was recently shown to be a binary system composed of a O9.5I supergiant and a B1IV star. We aim at verifying the presence of a magnetic field in zeta Ori A, identifying to which of the two binary components it belongs (or whether both stars are magnetic), and characterizing the field.Very high signal-to-noise spectropolarimetric data were obtained with Narval at the Bernard Lyot Telescope (TBL) in France. Archival HEROS, FEROS and UVES spectroscopic data were also used. The data were first disentangled to separate the two components. We then analyzed them with the Least-Squares Deconvolution (LSD) technique to extract the magnetic information. We confirm that zeta Ori A is magnetic. We find that the supergiant component zeta Ori Aa is the magnetic component: Zeeman signatures are observed and rotational modulation of the longitudinal magnetic field is clearly detected with a per...

  17. Studies of Solar Vector Magnetic Field

    Institute of Scientific and Technical Information of China (English)

    WANG Jingxiu

    2011-01-01

    In this article, we report a few advances in the studies based on the solar vector magnetic field observations which were carried out mainly with the Solar Magnetic Field Telescope at the Huairou Solar Observing Station in the 1990s. (1) We developed necessary methodology and concepts in vector magnetogram analysis (Wang et al. 1996). For the first time, we proposed to use the photospheric free magnetic energy to quantify the major flare productivity of solar active regions (ARs), and it had been proved to be the best parameter in representing the major flare activity. (2) We revealed that there was always a dominant sense of magnetic shear in a given AR (Wang 1994), which was taken as the premise of the helicity calculation in ARs; we made the first quantitative estimation of magnetic helicity evolution in ARs (Wang 1996). (3) We identified the first group of evidence of magnetic reconnection in the lower solar atmosphere with vector magnetic field observations and proposed a two-step reconnection flare model to interpret the observed association of flux cancellation and flares (Wang and Shi 1993). Efforts to quantify the major flare productivity of super active regions with vector magnetic field observations have been also taken.

  18. High Field Magnetization of Tb Single Crystals

    DEFF Research Database (Denmark)

    Roeland, L. W.; Cock, G. J.; Lindgård, Per-Anker

    1975-01-01

    The magnetization of Tb single crystals was measured in magnetic fields to 34T along the hard direction at temperature of 1.8, 4.2, 65.5 and 77K, and along with easy direction at 4.2 and 77K. The data are compared with the results of a self-consistent spin wave calculation using a phenomenological...

  19. Resource Letter BELFEF-1: Biological effects of low-frequency electromagnetic fields

    Science.gov (United States)

    Hafemeister, David

    1996-08-01

    This Resource Letter provides a guide to the literature on the interaction of extremely low-frequency electromagnetic field (ELF/EMF) interactions with biological matter, and on the possibility that such interactions could have a harmful effect on human health. Journal articles and books are cited for the following topics: ELF/EMF theoretical interactions with biological cells, organs and organisms, magnetic dipole interactions, sensing by animals, biomedical-biophysical experiments, epidemiology, and litigation-mitigation risk issues.

  20. Zero modes in finite range magnetic fields

    CERN Document Server

    Adam, C; Nash, C

    2000-01-01

    We find a class of Fermion zero modes of Abelian Dirac operators in three dimensional Euclidean space where the gauge potentials and the related magnetic fields are nonzero only in a finite space region.

  1. Axion production from primordial magnetic fields

    Science.gov (United States)

    Kamada, Kohei; Nakai, Yuichiro

    2017-07-01

    Production of axionlike particles (ALPs) by primordial magnetic fields may have significant impacts on cosmology. We discuss the production of ALPs in the presence of the primordial magnetic fields. We find a region of the ALP mass and photon coupling which realizes the observed properties of the dark matter with appropriate initial conditions for the magnetic fields. This region may be interesting in light of recent indications for the 3.5 keV lines from galaxy clusters. For a small axion mass, a region of previously allowed parameter spaces is excluded by overproduction of ALPs as a hot/warm dark matter component. Since the abundance of ALPs strongly depends on the initial conditions of primordial magnetic fields, our results provide implications for scenarios of magnetogenesis.

  2. Compact muon solenoid magnet reaches full field

    CERN Multimedia

    2006-01-01

    Scientist of the U.S. Department of Energy in Fermilab and collaborators of the US/CMS project announced that the world's largest superconducting solenoid magnet has reached full field in tests at CERN. (1 apge)

  3. A Topology for the Penumbral Magnetic Fields

    CERN Document Server

    Almeida, J Sanchez

    2009-01-01

    We describe a scenario for the topology of the magnetic field in penumbrae that accounts for recent observations showing upflows, downflows, and reverse magnetic polarities. According to our conjecture, short narrow magnetic loops fill the penumbral photosphere. Flows along these arched field lines are responsible for both the Evershed effect and the convective transport. This scenario seems to be qualitatively consistent with most existing observations, including the dark cores in penumbral filaments reported by Scharmer et al. Each bright filament with dark core would be a system of two paired convective rolls with the dark core tracing the common lane where the plasma sinks down. The magnetic loops would have a hot footpoint in one of the bright filament and a cold footpoint in the dark core. The scenario fits in most of our theoretical prejudices (siphon flows along field lines, presence of overturning convection, drag of field lines by downdrafts, etc). If the conjecture turns out to be correct, the mild...

  4. Local Magnetic Field Role in Star Formation

    CERN Document Server

    Koch, Patrick M; Ho, Paul T P; Zhang, Qizhou; Girart, Josep M; Chen, Huei-Ru V; Lai, Shih-Ping; Li, Hua-bai; Li, Zhi-Yun; Liu, Hau-Yu B; Padovani, Marco; Qiu, Keping; Rao, Ramprasad; Yen, Hsi-Wei; Frau, Pau; Chen, How-Huan; Ching, Tao-Chung

    2015-01-01

    We highlight distinct and systematic observational features of magnetic field morphologies in polarized submm dust continuum. We illustrate this with specific examples and show statistical trends from a sample of 50 star-forming regions.

  5. Revisiting holographic superconductor with Magnetic Fields

    CERN Document Server

    Momeni, Davood

    2014-01-01

    We study the effect of the bulk magnetic field (charge) on scalar condensation using an analytical approach of matching. An AdS-magnetized black hole solution has been used as a probe solution of normal phase of a strongly coupled condensed matter system on boundary. In the zero temperature limit of the black hole and infinite temperature, we show that there exists a critical magnetic field and so, the Meissner's effect presented. We compare this analytical result with our previous variational approach. By studying the different between heat capacities of the normal and superconducting phases near the critical point, we show that this thermodynamic quantity becomes divergent as the Rutgers formula predicted. Mathematical pole of Rutgers formula gives us a maximum for magnetic field which at this value, the system backs to the normal phase. In zero temperature we investigate exact series solutions of the field equations using an appropriate boundary conditions set. We show that conformal dimension is fixed by ...

  6. A Holographic Bound on Cosmic Magnetic Fields

    CERN Document Server

    McInnes, Brett

    2015-01-01

    Magnetic fields large enough to be observable are ubiquitous in astrophysics, even at extremely large length scales. This has led to the suggestion that such fields are seeded at very early (inflationary) times, and subsequently amplified by various processes involving, for example, dynamo effects. Many such mechanisms give rise to extremely large magnetic fields at the end of inflationary reheating, and therefore also during the quark-gluon plasma epoch of the early universe. Such plasmas have a well-known holographic description. We show that holography imposes an upper bound on the intensity of magnetic fields (scaled by the squared temperature) in these circumstances, and that the values expected in some models of cosmic magnetism come close to attaining that bound.

  7. Magnetic Fields in Limb Solar Flares

    Science.gov (United States)

    Lozitsky, V. G.; Lozitska, N. I.; Botygina, O. A.

    2013-02-01

    Two limb solar flares, of 14 July 2005 and 19 July 2012, of importance X1.2 and M7.7, are analyzed at present work. Magnetic field strength in named flares are investigated by Stokes I±V profiles of Hα and D3 HeI lines. There are direct evidences to the magnetic field inhomogeneity in flares, in particular, non-paralelism of bisectors in I+V and I-V profiles. In some flare places, the local maximums of bisectors splitting were found in both lines. If these bisector splittings are interpreted as Zeeman effect manifestation, the following magnetic field strengths reach up to 2200 G in Hα and 1300 G in D3. According to calculations, the observed peculiarities of line profiles may indicate the existence of optically thick emissive small-scale elements with strong magnetic fields and lowered temperature.

  8. Construction of high magnetic field facilities approved

    Institute of Scientific and Technical Information of China (English)

    2007-01-01

    @@ On 25 January, the National Development and Reform Commission gave the green light to a proposal to construct high magnetic field facilities for experimental use. The suggestion was jointly submitted by the Ministry of Education and CAS.

  9. The Magnetic Field of Helmholtz Coils

    Science.gov (United States)

    Berridge, H. J. J.

    1975-01-01

    Describes the magnetic field of Helmholtz coils qualitatively and then provides the basis for a quantitative expression. Since the mathematical calculations are very involved, a computer program for solving the mathematical expression is presented and explained. (GS)

  10. EIT waves and coronal magnetic field diagnostics

    Institute of Scientific and Technical Information of China (English)

    CHEN PengFei

    2009-01-01

    Magnetic field in the solar lower atmosphere can be measured by the use of the Zeeman and Hanle effects. By contrast, the coronal magnetic field well above the solar surface, which directly controls various eruptive phenomena, can not be precisely measured with the traditional techniques. Several attempts are being made to probe the coronal magnetic field, such as force-free extrapolation based on the photospheric magnetograms, gyroresonance radio emissions, and coronal seismology based on MHD waves in the corona. Compared to the waves trapped in the localized coronal loops, EIT waves are the only global-scale wave phenomenon, and thus are the ideal tool for the coronal global seismology. In this paper, we review the observations and modelings of EIT waves, and illustrate how they can be applied to probe the global magnetic field in the corona.

  11. High-Field Superconducting Magnets Supporting PTOLEMY

    Science.gov (United States)

    Hopkins, Ann; Luo, Audrey; Osherson, Benjamin; Gentile, Charles; Tully, Chris; Cohen, Adam

    2013-10-01

    The Princeton Tritium Observatory for Light, Early Universe, Massive Neutrino Yield (PTOLEMY) is an experiment planned to collect data on Big Bang relic neutrinos, which are predicted to be amongst the oldest and smallest particles in the universe. Currently, a proof-of-principle prototype is being developed at Princeton Plasma Physics Laboratory to test key technologies associated with the experiment. A prominent technology in the experiment is the Magnetic Adiabatic Collimation with an Electrostatic Filter (MAC-E filter), which guides tritium betas along magnetic field lines generated by superconducting magnets while deflecting those of lower energies. B field mapping is performed to ensure the magnets produce a minimum field at the midpoint of the configuration of the magnets and to verify accuracy of existing models. Preliminary tests indicate the required rapid decrease in B field strength from the bore of the more powerful 3.35 T magnet, with the field dropping to 0.18 T approximately 0.5 feet from the outermost surface of the magnet.

  12. Magnetic Field Amplification in Young Galaxies

    CERN Document Server

    Schober, Jennifer; Klessen, Ralf S

    2013-01-01

    The Universe at present is highly magnetized, with fields of the order of a few 10^-5 G and coherence lengths larger than 10 kpc in typical galaxies like the Milky Way. We propose that the magnetic field was amplified to this values already during the formation and the early evolution of the galaxies. Turbulence in young galaxies is driven by accretion as well as by supernova (SN) explosions of the first generation of stars. The small-scale dynamo can convert the turbulent kinetic energy into magnetic energy and amplify very weak primordial magnetic seed fields on short timescales. The amplification takes place in two phases: in the kinematic phase the magnetic field grows exponentially, with the largest growth on the smallest non-resistive scale. In the following non-linear phase the magnetic energy is shifted towards larger scales until the dynamo saturates on the turbulent forcing scale. To describe the amplification of the magnetic field quantitatively we model the microphysics in the interstellar medium ...

  13. Split-Field Magnet facility upgraded

    CERN Multimedia

    1977-01-01

    The Split Field Magnet (SFM) was the largest spectrometer for particles from beam-beam collisions in the ISR. It could determine particle momenta in a large solid angle, but was designed mainly for the analysis of forward travelling particles.As the magnet was working on the ISR circulating beams, its magnetic field had to be such as to restore the correct proton orbit.The SFM, therefore, produced zero field at the crossing point and fields of opposite signs upstream and downstream of it and was completed by 2 large and 2 small compensator magnets. The gradient effects were corrected by magnetic channels equipped with movable flaps. The useful magnetic field volume was 28 m3, the induction in the median plane 1.14 T, the gap heigth 1.1 m, the length 10.5 m, the weight about 1000 ton. Concerning the detectors, the SFM was the first massive application of multiwire proportional chambers (about 70000 wires) which filled the main and the large compensator magnets. In 1976 an improved programme was started with tw...

  14. Mathematical field models of brushless DC motors with permanent magnets and their comparative analysis

    Directory of Open Access Journals (Sweden)

    A.V. Matyuschenko

    2015-03-01

    Full Text Available By means of JMAG-Designer 12 the author performed a comparative analysis of the calculation of the EMF, cogging torque and electromagnetic torque of brushless motor with permanent magnets in two-dimensional and three-dimensional formulation of the problem.

  15. Magnetic fields and massive star formation

    Energy Technology Data Exchange (ETDEWEB)

    Zhang, Qizhou; Keto, Eric; Ho, Paul T. P.; Ching, Tao-Chung; Chen, How-Huan [Harvard-Smithsonian Center for Astrophysics, 60 Garden Street, Cambridge, MA 02138 (United States); Qiu, Keping [School of Astronomy and Space Science, Nanjing University, 22 Hankou Road, Nanjing 210093 (China); Girart, Josep M.; Juárez, Carmen [Institut de Ciències de l' Espai, (CSIC-IEEC), Campus UAB, Facultat de Ciències, C5p 2, E-08193 Bellaterra, Catalonia (Spain); Liu, Hauyu; Tang, Ya-Wen; Koch, Patrick M.; Rao, Ramprasad; Lai, Shih-Ping [Academia Sinica Institute of Astronomy and Astrophysics, P.O. Box 23-141, Taipei 106, Taiwan (China); Li, Zhi-Yun [Department of Astronomy, University of Virginia, P.O. Box 400325, Charlottesville, VA 22904 (United States); Frau, Pau [Observatorio Astronómico Nacional, Alfonso XII, 3 E-28014 Madrid (Spain); Li, Hua-Bai [Department of Physics, The Chinese University of Hong Kong, Hong Kong (China); Padovani, Marco [Laboratoire de Radioastronomie Millimétrique, UMR 8112 du CNRS, École Normale Supérieure et Observatoire de Paris, 24 rue Lhomond, F-75231 Paris Cedex 05 (France); Bontemps, Sylvain [OASU/LAB-UMR5804, CNRS, Université Bordeaux 1, F-33270 Floirac (France); Csengeri, Timea, E-mail: qzhang@cfa.harvard.edu [Max Planck Institute for Radioastronomy, Auf dem Hügel 69, D-53121 Bonn (Germany)

    2014-09-10

    Massive stars (M > 8 M {sub ☉}) typically form in parsec-scale molecular clumps that collapse and fragment, leading to the birth of a cluster of stellar objects. We investigate the role of magnetic fields in this process through dust polarization at 870 μm obtained with the Submillimeter Array (SMA). The SMA observations reveal polarization at scales of ≲0.1 pc. The polarization pattern in these objects ranges from ordered hour-glass configurations to more chaotic distributions. By comparing the SMA data with the single dish data at parsec scales, we found that magnetic fields at dense core scales are either aligned within 40° of or perpendicular to the parsec-scale magnetic fields. This finding indicates that magnetic fields play an important role during the collapse and fragmentation of massive molecular clumps and the formation of dense cores. We further compare magnetic fields in dense cores with the major axis of molecular outflows. Despite a limited number of outflows, we found that the outflow axis appears to be randomly oriented with respect to the magnetic field in the core. This result suggests that at the scale of accretion disks (≲ 10{sup 3} AU), angular momentum and dynamic interactions possibly due to close binary or multiple systems dominate over magnetic fields. With this unprecedentedly large sample of massive clumps, we argue on a statistical basis that magnetic fields play an important role during the formation of dense cores at spatial scales of 0.01-0.1 pc in the context of massive star and cluster star formation.

  16. Core Processes: Earth's eccentric magnetic field

    DEFF Research Database (Denmark)

    Finlay, Chris

    2012-01-01

    Earth’s magnetic field is characterized by a puzzling hemispheric asymmetry. Calculations of core dynamo processes suggest that lopsided growth of the planet’s inner core may be part of the cause.......Earth’s magnetic field is characterized by a puzzling hemispheric asymmetry. Calculations of core dynamo processes suggest that lopsided growth of the planet’s inner core may be part of the cause....

  17. Orbit stability in billiards in magnetic field

    CERN Document Server

    Kovács, Z

    1997-01-01

    We study the stability properties of orbits in dispersing billiards in a homogeneous magnetic field by using a modified formalism based on the Bunimovich-Sinai curvature (horocycle method). We identify simple periodic orbits that can be stabilized by the magnetic field in the four-disk model and the square-lattice Lorentz gas. The stable orbits can play a key role in determining the transport properties of these models.

  18. 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.

  19. Modulation of radical pairs dynamics immersed in an ELF-EMF: The effect on hepatocarcinogenesis

    Science.gov (United States)

    López-Riquelme, G. O.; López-Sandoval, E.; Vera-Aguilar, E.; Godina-Nava, J. J.

    2015-01-01

    The most suitable mechanism of action of electromagnetic fields (EMF) on biological systems is the effect on the radical pair (RP) recombination through the Zeeman effect and hyperfine interaction, which changes the rate of reactions or the product distribution. Enzyme reactions with RP intermediates can be altered by EMF, like those catalyzed by cytochrome P450 enzymes (CYP450), a heme-thiolate family protein that detoxifies xenobiotics and involved in chemical carcinogenesis. CYP450 activate chemical carcinogens producing an enormous amount of free radicals, which damage the DNA resulting in the malignant transformation of cells. During the activation, CYP450 produce spin-correlated RP intermediates that can either go to recombination or to continue the catalytic process. As CYP450 are electron carrier proteins, it is possible that RP intermediates may be affected by EMF. It was previously found that periodic treatment with extremely low frequency electromagnetic fields (ELF-EMF) inhibits more than 50% the number and area of preneoplastic lesions in rats with chemically induced hepatocarcinogenesis through reduction of cell proliferation. In this work, we developed a quantum mechanical model based on RP mechanism in order to explain the experimental effects of ELF-EMF on the free radicals produced in the early stages of chemical carcinogenesis.

  20. Magnetic Field Measurement on a Refined Kicker

    CERN Document Server

    Fan, Tai-Ching; Lin, Fu-Yuan

    2005-01-01

    To prepare for the operation of top-up mode and increase the efficiency of injection at storage ring, National Synchrotron Radiation Research Center (NSRRC) has upgraded the kicker magnets and power supply. We have built up a new magnetic field measurement system to test the kicker. This system, including a search coil and a coil loop, can map the field and take the first integral of field automatically. We also simulate the trajectory of electron beam by pulsed wire method of field measurement. We analyze the performance of the kicker system in this paper.

  1. Biological systems in high magnetic field

    Science.gov (United States)

    Yamagishi, A.

    1990-12-01

    Diamagnetic orientation of biological systems have been investigated theoretically and experimentally. Fibrinogen, one of blood proteins, were polymerized in static high magnetic fields up to 8 T. Clotted gels composed of oriented fibrin fibers were obtained even in a field as low as 1 T. Red blood cells (RBC) show full orientation with their plane parallel to the applied field of 4 T. It is confirmed experimentally that the magnetic orientation of RBC is caused by diamagnetic anisotropy. Full orientation is also obtained with blood platelet in a field of 3 T.

  2. Cooling Curve of Strange Star in Strong Magnetic Field

    Institute of Scientific and Technical Information of China (English)

    WANG Xiao-Qin; LUO Zhi-Quan

    2008-01-01

    In this paper, firstly, we investigate the neutrino emissivity from quark Urca process in strong magnetic field. Then, we discuss the heat capacity of strange stars in strong magnetic field. Finally, we give the cooling curve in strong magnetic field. In order to make a comparison, we also give the corresponding cooling curve in the case of null magnetic field. It turns out that strange stars cool faster in strong magnetic field than that without magnetic field.

  3. ELF noise fields: a review.

    Science.gov (United States)

    Mild, Kjell Hansson; Mattsson, Mats-Olof

    2010-08-01

    The debate as to whether low-level electromagnetic fields can affect biological systems and in the long term cause health effects has been going on for a long time. Yet the interaction of weak electromagnetic fields (EMF) with living cells, undoubtedly a most important phenomenon, is still not well understood. The exact mechanisms by which the effects are produced have not been identified. Furthermore, it is not possible to clearly define which aspects of an EMF exposure that constitute the "dose." One of the groups that contributed to solving this problem is the Bioelectromagnetics group at Catholic University of America (CUA), Washington, D.C. Their work has been devoted to investigating the physical parameters that are needed to obtain an effect of EMF exposure on biological systems, and also how to inhibit the effect. This is a review of their work on bioeffects caused by low-level EMF, their dependence on coherence time, constancy, spatial averaging, and also how the effects can be modified by an applied ELF noise magnetic field. The group has been using early chick embryos, and L929 and Daudi cells as their main experimental systems. The review also covers the work of other groups on low-level effects and the inhibition of the effects with an applied noise field. The group at CUA has shown that biological effects can be found after exposure to low-level ELF and RF electromagnetic fields, and when effects are observed, applying an ELF magnetic noise field inhibits the effects. Also, other research groups have tried to replicate the studies from the CUA group, or to apply EMF noise to suppress EMF-induced effects. Replications of the CUA effects have not always been successful. However, in all cases where the noise field has been applied to prevent an observed effect, it has been successful in eliminating the effect.

  4. Combustion instability mitigation by magnetic fields

    Science.gov (United States)

    Jocher, Agnes; Pitsch, Heinz; Gomez, Thomas; Bonnety, Jérôme; Legros, Guillaume

    2017-06-01

    The present interdisciplinary study combines electromagnetics and combustion to unveil an original and basic experiment displaying a spontaneous flame instability that is mitigated as the non-premixed sooting flame experiences a magnetic perturbation. This magnetic instability mitigation is reproduced by direct numerical simulations to be further elucidated by a flow stability analysis. A key role in the stabilization process is attributed to the momentum and thermochemistry coupling that the magnetic force, acting mainly on paramagnetic oxygen, contributes to sustain. The spatial local stability analysis based on the numerical simulations shows that the magnetic field tends to reduce the growth rates of small flame perturbations.

  5. Wuhan pulsed high magnetic field center

    OpenAIRE

    Li, Liang; Peng, Tao; Ding, Honfa; Han, Xiaotao; Ding, Tonghai; Chen, Jin; Wang, Junfeng; Xie, Jianfeng; Wang, Shaoliang; Duan, Xianzhong; Wang, Cheng; Herlach, Fritz; Vanacken, Johan; Pan, Yuan

    2008-01-01

    Wuhan pulsed high magnetic field facility is under development. Magnets of bore sizes from 12 to 34 mm with the peak field in the range of 50 to 80 T have been designed. The pulsed power supplies consists of a 12 MJ, 25 kV capacitor bank and a 100 MVA/100 MJ flywheel pulse generator. A prototype 1 MJ, 25 kV capacitor bank is under construction. Five magnets wound with CuNb wire and copper wire reinforced internally with Zylon fiber composites and externally with stainless steel shells have be...

  6. Magnetic Field Apparatus (MFA) Hardware Test

    Science.gov (United States)

    Anderson, Ken; Boody, April; Reed, Dave; Wang, Chung; Stuckey, Bob; Cox, Dave

    1999-01-01

    The objectives of this study are threefold: (1) Provide insight into water delivery in microgravity and determine optimal germination paper wetting for subsequent seed germination in microgravity; (2) Observe the behavior of water exposed to a strong localized magnetic field in microgravity; and (3) Simulate the flow of fixative (using water) through the hardware. The Magnetic Field Apparatus (MFA) is a new piece of hardware slated to fly on the Space Shuttle in early 2001. MFA is designed to expose plant tissue to magnets in a microgravity environment, deliver water to the plant tissue, record photographic images of plant tissue, and deliver fixative to the plant tissue.

  7. Wuhan pulsed high magnetic field center

    OpenAIRE

    Li, Liang; Peng, Tao; Ding, Honfa; Han, Xiaotao; Ding, Tonghai; Chen, Jin; Wang, Junfeng; Xie, Jianfeng; Wang, Shaoliang; DUAN, Xianzhong; Wang, Cheng; Herlach, Fritz; Vanacken, Johan; Pan, Yuan

    2008-01-01

    Wuhan pulsed high magnetic field facility is under development. Magnets of bore sizes from 12 to 34 mm with the peak field in the range of 50 to 80 T have been designed. The pulsed power supplies consists of a 12 MJ, 25 kV capacitor bank and a 100 MVA/100 MJ flywheel pulse generator. A prototype 1 MJ, 25 kV capacitor bank is under construction. Five magnets wound with CuNb wire and copper wire reinforced internally with Zylon fiber composites and externally with stainless steel shells have be...

  8. New electric field in asymmetric magnetic reconnection.

    Science.gov (United States)

    Malakit, K; Shay, M A; Cassak, P A; Ruffolo, D

    2013-09-27

    We present a theory and numerical evidence for the existence of a previously unexplored in-plane electric field in collisionless asymmetric magnetic reconnection. This electric field, dubbed the "Larmor electric field," is associated with finite Larmor radius effects and is distinct from the known Hall electric field. Potentially, it could be an important indicator for the upcoming Magnetospheric Multiscale mission to locate reconnection sites as we expect it to appear on the magnetospheric side, pointing earthward, at the dayside magnetopause reconnection site.

  9. Inhibition of angiogenesis mediated by extremely low-frequency magnetic fields (ELF-MFs.

    Directory of Open Access Journals (Sweden)

    Simona Delle Monache

    Full Text Available The formation of new blood vessels is an essential therapeutic target in many diseases such as cancer, ischemic diseases, and chronic inflammation. In this regard, extremely low-frequency (ELF electromagnetic fields (EMFs seem able to inhibit vessel growth when used in a specific window of amplitude. To investigate the mechanism of anti-angiogenic action of ELF-EMFs we tested the effect of a sinusoidal magnetic field (MF of 2 mT intensity and frequency of 50 Hz on endothelial cell models HUVEC and MS-1 measuring cell status and proliferation, motility and tubule formation ability. MS-1 cells when injected in mice determined a rapid tumor-like growth that was significantly reduced in mice inoculated with MF-exposed cells. In particular, histological analysis of tumors derived from mice inoculated with MF-exposed MS-1 cells indicated a reduction of hemangioma size, of blood-filled spaces, and in hemorrhage. In parallel, in vitro proliferation of MS-1 treated with MF was significantly inhibited. We also found that the MF-exposure down-regulated the process of proliferation, migration and formation of tubule-like structures in HUVECs. Using western blotting and immunofluorescence analysis, we collected data about the possible influence of MF on the signalling pathway activated by the vascular endothelial growth factor (VEGF. In particular, MF exposure significantly reduced the expression and activation levels of VEGFR2, suggesting a direct or indirect influence of MF on VEGF receptors placed on cellular membrane. In conclusion MF reduced, in vitro and in vivo, the ability of endothelial cells to form new vessels, most probably affecting VEGF signal transduction pathway that was less responsive to activation. These findings could not only explain the mechanism of anti-angiogenic action exerted by MFs, but also promote the possible development of new therapeutic applications for treatment of those diseases where excessive angiogenesis is involved.

  10. Inhibition of Angiogenesis Mediated by Extremely Low-Frequency Magnetic Fields (ELF-MFs)

    Science.gov (United States)

    Delle Monache, Simona; Angelucci, Adriano; Sanità, Patrizia; Iorio, Roberto; Bennato, Francesca; Mancini, Fabrizio; Gualtieri, Giancaterino; Colonna, Rosella Cardigno

    2013-01-01

    The formation of new blood vessels is an essential therapeutic target in many diseases such as cancer, ischemic diseases, and chronic inflammation. In this regard, extremely low-frequency (ELF) electromagnetic fields (EMFs) seem able to inhibit vessel growth when used in a specific window of amplitude. To investigate the mechanism of anti-angiogenic action of ELF-EMFs we tested the effect of a sinusoidal magnetic field (MF) of 2 mT intensity and frequency of 50 Hz on endothelial cell models HUVEC and MS-1 measuring cell status and proliferation, motility and tubule formation ability. MS-1 cells when injected in mice determined a rapid tumor-like growth that was significantly reduced in mice inoculated with MF-exposed cells. In particular, histological analysis of tumors derived from mice inoculated with MF-exposed MS-1 cells indicated a reduction of hemangioma size, of blood-filled spaces, and in hemorrhage. In parallel, in vitro proliferation of MS-1 treated with MF was significantly inhibited. We also found that the MF-exposure down-regulated the process of proliferation, migration and formation of tubule-like structures in HUVECs. Using western blotting and immunofluorescence analysis, we collected data about the possible influence of MF on the signalling pathway activated by the vascular endothelial growth factor (VEGF). In particular, MF exposure significantly reduced the expression and activation levels of VEGFR2, suggesting a direct or indirect influence of MF on VEGF receptors placed on cellular membrane. In conclusion MF reduced, in vitro and in vivo, the ability of endothelial cells to form new vessels, most probably affecting VEGF signal transduction pathway that was less responsive to activation. These findings could not only explain the mechanism of anti-angiogenic action exerted by MFs, but also promote the possible development of new therapeutic applications for treatment of those diseases where excessive angiogenesis is involved. PMID:24244477

  11. Influence of magnetic domain walls and magnetic field on the thermal conductivity of magnetic nanowires.

    Science.gov (United States)

    Huang, Hao-Ting; Lai, Mei-Feng; Hou, Yun-Fang; Wei, Zung-Hang

    2015-05-13

    We investigated the influence of magnetic domain walls and magnetic fields on the thermal conductivity of suspended magnetic nanowires. The thermal conductivity of the nanowires was obtained using steady-state Joule heating to measure the change in resistance caused by spontaneous heating. The results showed that the thermal conductivity coefficients of straight and wavy magnetic nanowires decreased with an increase in the magnetic domain wall number, implying that the scattering between magnons and domain walls hindered the heat transport process. In addition, we proved that the magnetic field considerably reduced the thermal conductivity of a magnetic nanowire. The influence of magnetic domain walls and magnetic fields on the thermal conductivity of polycrystalline magnetic nanowires can be attributed to the scattering of long-wavelength spin waves mediated by intergrain exchange coupling.

  12. Influences of Fundamental Armature MMF on Tooth Harmonic EMF of the Rotor%基波电枢磁动势对转子齿谐波电动势的影响

    Institute of Scientific and Technical Information of China (English)

    夏永洪; 龚文军; 黄劭刚; 杨玉文; 黄新

    2015-01-01

    研究电枢磁动势对转子齿谐波电动势的影响是利用电机中固有的齿谐波磁场实现永磁电机气隙磁场调节的关键问题之一。基于磁导分析法定性分析了定子基波电枢磁动势在转子侧产生齿谐波电动势的机理,讨论了线性磁路和非线性磁路下基波电枢磁动势对转子齿谐波电动势的影响。当发电机带电感性负载时,对于线性磁路,转子齿谐波电动势随着电枢电流的增加而减小;而对于非线性磁路,随着发电机电枢电流的增加,转子齿谐波电动势可能增加、不变或者减小。针对一台齿谐波励磁的混合励磁永磁同步发电机进行了计算和实验,计算结果和实验结果均与理论分析吻合。%The research on influence of the fundamental armature magnetic motive force (MMF) on the tooth harmonic electromotive force (EMF) of the rotor is one of the key problems for utilizing inherent tooth harmonic magnetic fields to achieve the adjustment of the air gap magnet field of the permanent magnet machine. The principle of the rotor tooth harmonic EMF generated by the stator fundamental armature MMF was analyzed qualitatively based on the permeability analysis method. The influence of the fundamental armature MMF on the rotor tooth harmonic EMF were discussed for linear and nonlinear magnetic circuits. When the generator is connected with an inductive load, the rotor tooth harmonic EMF decreases as the armature current increases for the linear magnetic circuits. However, for the non-linear magnetic circuits, the rotor tooth harmonic EMF may increase, maintain constant or decrease as the armature current increases. Calculation and experiment are performed for one hybrid excitation permanent magnet synchronous generator utilizing tooth harmonic for excitation, and calculated and experimental results are consistent with theoretical analysis.

  13. Where is magnetic anisotropy field pointing to?

    CERN Document Server

    Gutowski, Marek W

    2013-01-01

    The desired result of magnetic anisotropy investigations is the determination of value(s) of various anisotropy constant(s). This is sometimes difficult, especially when the precise knowledge of saturation magnetization is required, as it happens in ferromagnetic resonance (FMR) studies. In such cases we usually resort to `trick' and fit our experimental data to the quantity called \\emph{anisotropy field}, which is strictly proportional to the ratio of the searched anisotropy constant and saturation magnetization. Yet, this quantity is scalar, simply a number, and is therefore of little value for modeling or simulations of the magnetostatic or micromagnetic structures. Here we show how to `translate' the values of magnetic anisotropy constants into the complete vector of magnetic anisotropy field. Our derivation is rigorous and covers the most often encountered cases, from uniaxial to cubic anisotropy.

  14. Bootstrapping the Coronal Magnetic Field with STEREO

    Science.gov (United States)

    Aschwanden, Markus J.

    2010-05-01

    The 3D coronal magnetic field obtained from stereoscopically triangulated loops has been compared with standard photospheric magnetogram extrapolations. We found a large misalignment of 20-40 deg, depending on the complexity of an AR (Sandman et al. 2009; DeRosa et al. 2009). These studies prove that the magnetic field in the photosphere is not force-free and fundamentally cannot reproduce the coronal magnetic field. Bootstrapping with coronal loop 3D geometries are required to improve modeling of the coronal field. Such coronal field bootstrapping methods are currently developed using stereoscopically triangulated loops from STEREO/EUVI and preliminary results show already a significantly reduced misalignment of 10-20 deg.

  15. Critical Magnetic Field Determination of Superconducting Materials

    Energy Technology Data Exchange (ETDEWEB)

    Canabal, A.; Tajima, T.; /Los Alamos; Dolgashev, V.A.; Tantawi, S.G.; /SLAC; Yamamoto, T.; /Tsukuba, Natl. Res. Lab. Metrol.

    2011-11-04

    Superconducting RF technology is becoming more and more important. With some recent cavity test results showing close to or even higher than the critical magnetic field of 170-180 mT that had been considered a limit, it is very important to develop a way to correctly measure the critical magnetic field (H{sup RF}{sub c}) of superconductors in the RF regime. Using a 11.4 GHz, 50-MW, <1 {mu}s, pulsed power source and a TE013-like mode copper cavity, we have been measuring critical magnetic fields of superconductors for accelerator cavity applications. This device can eliminate both thermal and field emission effects due to a short pulse and no electric field at the sample surface. A model of the system is presented in this paper along with a discussion of preliminary experimental data.

  16. Fast Reconnection of Weak Magnetic Fields

    Science.gov (United States)

    Zweibel, Ellen G.

    1998-01-01

    Fast magnetic reconnection refers to annihilation or topological rearrangement of magnetic fields on a timescale that is independent (or nearly independent) of the plasma resistivity. The resistivity of astrophysical plasmas is so low that reconnection is of little practical interest unless it is fast. Yet, the theory of fast magnetic reconnection is on uncertain ground, as models must avoid the tendency of magnetic fields to pile up at the reconnection layer, slowing down the flow. In this paper it is shown that these problems can be avoided to some extent if the flow is three dimensional. On the other hand, it is shown that in the limited but important case of incompressible stagnation point flows, every flow will amplify most magnetic fields. Although examples of fast magnetic reconnection abound, a weak, disordered magnetic field embedded in stagnation point flow will in general be amplified, and should eventually modify the flow. These results support recent arguments against the operation of turbulent resistivity in highly conducting fluids.

  17. Growth of Czochralski silicon under magnetic field

    Institute of Scientific and Technical Information of China (English)

    XU Yuesheng; LIU Caichi; WANG Haiyun; ZHANG Weilian; YANG Qingxin; LI Yangxian; REN Binyan; LIU Fugui

    2004-01-01

    Growth of Czochralski (CZ) silicon crystals under the magnetic field induced by a cusp-shaped permanent magnet of NdFeB has been investigated. It is found that the mass transport in silicon melt was controlled by its diffusion while the magnetic intensity at the edge of a crucible was over 0.15 T. In comparison with the growth of conventional CZ silicon without magnetic field, the resistivity homogeneity of the CZ silicon under the magnetic field was improved. Furthermore, the Marangoni convection which has a significant influence on the control of oxygen concentration was observed on the surface of silicon melt. It is suggested that the crystal growth mechanism in magnetic field was similar to that in micro-gravity if a critical value was reached, named the growth of equivalent micro-gravity. The relationship of the equivalent micro-gravity and the magnetic intensity was derived as g=(v0/veff)g0. Finally, the orders of the equivalent micro-gravity corresponding to two crucibles with characteristic sizes were calculated.

  18. Simulating magnetic fields in the Antennae galaxies

    CERN Document Server

    Kotarba, H; Naab, T; Johansson, P H; Dolag, K; Lesch, H

    2009-01-01

    We present self-consistent high-resolution simulations of NGC4038/4039 (the "Antennae galaxies") including star formation, supernova feedback and magnetic fields performed with the N-body/SPH code Gadget, in which hydrodynamics and magnetohydrodynamics are followed with the SPH method. We vary the initial magnetic field in the progenitor disks from 1 nG to 1 muG. At the time of the best match with the central region of the Antennae system the magnetic field has been amplified by compression and shear flows to an equilibrium field of approximately 10 muG, independent of the initial seed field. This simulations are a proof of the principle that galaxy mergers are efficient drivers for the cosmic evolution of magnetic fields. We present a detailed analysis of the magnetic field structure in the central overlap region. Simulated radio and polarization maps are in good morphological and quantitative agreement with the observations. In particular, the two cores with the highest synchrotron intensity and ridges of r...

  19. Magnetic Field Transport in Accretion Disks

    Science.gov (United States)

    Jafari, Amir; Vishniac, Ethan

    2017-06-01

    The most plausible theories for launching astrophysical jets rely on strong magnetic fields at the inner parts of some accretion disks. An internal dynamo can in principle generate small scale magnetic fields in situ but generating a large scale field in a disk seems a difficult task in the dynamo theories. In fact, as far as numerous numerical experiments indicate, a dynamo-generated field in general would not be coherent enough over the large length scales of order the disk's radius. Instead, a large scale poloidal field dragged in from the environment, and compressed by the accretion, provides a more promising possibility. The difficulty in the latter picture, however, arises from the reconnection of the radial field component across the mid-plane which annihilates the field faster than it is dragged inward by the accretion. We suggest that a combination of different effects, including magnetic buoyancy and turbulent pumping, is responsible for the vertical transport of the field lines toward the surface of the disk. The radial component of the poloidal field vanishes at the mid-plane, which efficiently impedes reconnection, and grows exponentially toward the surface where it can become much larger than the vertical field component. This allows the poloidal field to be efficiently advected to small radii until the allowed bending angle drops to of order unity, and the field can drive a strong outflow.

  20. Superconductivity in Strong Magnetic Field (Greater Than Upper Critical Field)

    Energy Technology Data Exchange (ETDEWEB)

    Tessema, G.X.; Gamble, B.K.; Skove, M.J.; Lacerda, A.H.; Mielke, C.H.

    1998-08-22

    The National High Magnetic Field Laboratory, funded by the National Science Foundation and other US federal Agencies, has in recent years built a wide range of magnetic fields, DC 25 to 35 Tesla, short pulse 50 - 60 Tesla, and quasi-continuous 60 Tesla. Future plans are to push the frontiers to 45 Tesla DC and 70 to 100 Tesla pulse. This user facility, is open for national and international users, and creates an excellent tool for materials research (metals, semiconductors, superconductors, biological systems ..., etc). Here we present results of a systematic study of the upper critical field of a novel superconducting material which is considered a promising candidate for the search for superconductivity beyond H{sub c2} as proposed by several new theories. These theories predict that superconductors with low carrier density can reenter the superconducting phase beyond the conventional upper critical field H{sub c2}. This negates the conventional thinking that superconductivity and magnetic fields are antagonistic.

  1. Activation of autophagy at cerebral cortex and apoptosis at brainstem are differential responses to 835 MHz RF-EMF exposure

    Science.gov (United States)

    Kim, Ju Hwan; Yu, Da-Hyeon

    2017-01-01

    With the explosive increase in exposure to radiofrequency electromagnetic fields (RF-EMF) emitted by mobile phones, public concerns have grown over the last few decades with regard to the potential effects of EMF exposure on the nervous system in the brain. Many researchers have suggested that RF-EMFs can effect diverse neuronal alterations in the brain, thereby affecting neuronal functions as well as behavior. Previously, we showed that long-term exposure to 835 MHz RF-EMF induces autophagy in the mice brain. In this study, we explore whether short-term exposure to RF-EMF leads to the autophagy pathway in the cerebral cortex and brainstem at 835 MHz with a specific absorption rate (SAR) of 4.0 W/kg for 4 weeks. Increased levels of autophagy genes and proteins such as LC3B-II and Beclin1 were demonstrated and the accumulation of autophagosomes and autolysosomes was observed in cortical neurons whereas apoptosis pathways were up-regulated in the brainstem but not in the cortex following 4 weeks of RF exposure. Taken together, the present study indicates that monthly exposure to RF-EMF induces autophagy in the cerebral cortex and suggests that autophagic degradation in cortical neurons against a stress of 835 MHz RF during 4 weeks could correspond to adaptation to the RF stress environment. However, activation of apoptosis rather than autophagy in the brainstem is suggesting the differential responses to the RF-EMF stresses in the brain system. PMID:28280411

  2. Study of marine magnetic field

    Digital Repository Service at National Institute of Oceanography (India)

    Bhattacharya, G.C.

    (COB) is again both a basic scientific requirement as well at some places is a requirement under the UNCLOS related Legal Continental Shelf demarcation purpose. In the oceanic areas, the marine magnetic studies are one of the essential tools... oceans increased, more and more deviations from this simplified model, such as propagating ridges and overlapping spreading centers were discovered. These observations enabled the study of new aspects of seafloor spreading process beyond the initial...

  3. Magnetic field amplification in turbulent astrophysical plasmas

    CERN Document Server

    Federrath, Christoph

    2016-01-01

    Magnetic fields play an important role in astrophysical accretion discs, and in the interstellar and intergalactic medium. They drive jets, suppress fragmentation in star-forming clouds and can have a significant impact on the accretion rate of stars. However, the exact amplification mechanisms of cosmic magnetic fields remain relatively poorly understood. Here I start by reviewing recent advances in the numerical and theoretical modelling of the 'turbulent dynamo', which may explain the origin of galactic and inter-galactic magnetic fields. While dynamo action was previously investigated in great detail for incompressible plasmas, I here place particular emphasis on highly compressible astrophysical plasmas, which are characterised by strong density fluctuations and shocks, such as the interstellar medium. I find that dynamo action works not only in subsonic plasmas, but also in highly supersonic, compressible plasmas, as well as for low and high magnetic Prandtl numbers. I further present new numerical simu...

  4. The Magnetic Field of Solar Spicules

    CERN Document Server

    Centeno, R; Ramos, A Asensio

    2009-01-01

    Determining the magnetic field of solar spicules is vital for developing adequate models of these plasma jets, which are thought to play a key role in the thermal, dynamic, and magnetic structure of the chromosphere. Here we report on magnetic spicule properties in a very quiet region of the off-limb solar atmosphere, as inferred from new spectropolarimetric observations in the HeI 10830 A triplet. We have used a novel inversion code for Stokes profiles caused by the joint action of atomic level polarization and the Hanle and Zeeman effects (HAZEL) to interpret the observations. Magnetic fields as strong as 40G were unambiguously detected in a very localized area of the slit, which may represent a possible lower value of the field strength of organized network spicules.

  5. QCD thermodynamics and magnetization in nonzero magnetic field

    CERN Document Server

    Tawfik, Abdel Nasser; Ezzelarab, Nada; Shalaby, Asmaa G

    2016-01-01

    In nonzero magnetic field, the magnetic properties and thermodynamics of the quantum-chromodynamic (QCD) matter is studied in the hadron resonance gas and the Polyakov linear-sigma models and compared with recent lattice calculations. Both models are fairly suited to describe the degrees of freedom in the hadronic phase. The partonic ones are only accessible by the second model. It is found that the QCD matter has paramagnetic properties, which monotonically depend on the temperature and are not affected by the hadron-quark phase-transition. Furthermore, raising the magnetic field strength increases the thermodynamic quantities, especially in the hadronic phase but reduces the critical temperature, i.e. inverse magnetic catalysis.

  6. The magnetic fields of Jupiter and Saturn

    Science.gov (United States)

    Ness, N. F.

    1981-01-01

    The magnetic fields of Jupiter and Saturn and the characteristics of their magnetospheres, formed by interaction with the solar wind, are discussed. The origins of both magnetic fields are associated with a dynamo process deep in the planetary interior. The Jovian magnetosphere is analogous to that of a pulsar magnetosphere: a massive central body with a rapid rotation and an associated intense magnetic field. Its most distinctive feature is its magnetodisk of concentrated plasma and particle flux, and reduced magnetic field intensity. The magnetopause near the subsolar point has been observed at radial distances ranging over 50 to 100 Jovian radii, implying a relatively compressible obstacle to solar wind flow. The composition of an embedded current sheet within the magnetic tail is believed to be influenced by volcanic eruptions and emissions from Io. Spectral troughs of the Jovian radiation belts have been interpreted as possible ring particles. The Saturnian magnetosphere appears to be more like the earth in its topology. It is mainly characterized by a dipole axis parallel to the rotational axis of the planet and a magnetic field intensity much less than expected.

  7. Measurements of Photospheric and Chromospheric Magnetic Fields

    Science.gov (United States)

    Lagg, Andreas; Lites, Bruce; Harvey, Jack; Gosain, Sanjay; Centeno, Rebecca

    2017-09-01

    The Sun is replete with magnetic fields, with sunspots, pores and plage regions being their most prominent representatives on the solar surface. But even far away from these active regions, magnetic fields are ubiquitous. To a large extent, their importance for the thermodynamics in the solar photosphere is determined by the total magnetic flux. Whereas in low-flux quiet Sun regions, magnetic structures are shuffled around by the motion of granules, the high-flux areas like sunspots or pores effectively suppress convection, leading to a temperature decrease of up to 3000 K. The importance of magnetic fields to the conditions in higher atmospheric layers, the chromosphere and corona, is indisputable. Magnetic fields in both active and quiet regions are the main coupling agent between the outer layers of the solar atmosphere, and are therefore not only involved in the structuring of these layers, but also for the transport of energy from the solar surface through the corona to the interplanetary space. Consequently, inference of magnetic fields in the photosphere, and especially in the chromosphere, is crucial to deepen our understanding not only for solar phenomena such as chromospheric and coronal heating, flares or coronal mass ejections, but also for fundamental physical topics like dynamo theory or atomic physics. In this review, we present an overview of significant advances during the last decades in measurement techniques, analysis methods, and the availability of observatories, together with some selected results. We discuss the problems of determining magnetic fields at smallest spatial scales, connected with increasing demands on polarimetric sensitivity and temporal resolution, and highlight some promising future developments for their solution.

  8. Magnetizing a complex plasma without a magnetic field

    CERN Document Server

    Kählert, H; Bonitz, M; Löwen, H; Greiner, F; Piel, A

    2012-01-01

    We propose and demonstrate a concept that mimics the magnetization of the heavy dust particles in a complex plasma while leaving the properties of the light species practically unaffected. It makes use of the frictional coupling between a complex plasma and the neutral gas, which allows to transfer angular momentum from a rotating gas column to a well-controlled rotation of the dust cloud. This induces a Coriolis force that acts exactly as the Lorentz force in a magnetic field. Experimental normal mode measurements for a small dust cluster with four particles show excellent agreement with theoretical predictions for a magnetized plasma.

  9. Magnetic nanoparticles for applications in oscillating magnetic field

    Energy Technology Data Exchange (ETDEWEB)

    Peeraphatdit, Chorthip [Iowa State Univ., Ames, IA (United States)

    2009-01-01

    Enzymatic and thermochemical catalysis are both important industrial processes. However, the thermal requirements for each process often render them mutually exclusive: thermochemical catalysis requires high temperature that denatures enzymes. One of the long-term goals of this project is to design a thermocatalytic system that could be used with enzymatic systems in situ to catalyze reaction sequences in one pot; this system would be useful for numerous applications e.g. conversion of biomass to biofuel and other commodity products. The desired thermocatalytic system would need to supply enough thermal energy to catalyze thermochemical reactions, while keeping the enzymes from high temperature denaturation. Magnetic nanoparticles are known to generate heat in an oscillating magnetic field through mechanisms including hysteresis and relaxational losses. We envisioned using these magnetic nanoparticles as the local heat source embedded in sub-micron size mesoporous support to spatially separate the particles from the enzymes. In this study, we set out to find the magnetic materials and instrumental conditions that are sufficient for this purpose. Magnetite was chosen as the first model magnetic material in this study because of its high magnetization values, synthetic control over particle size, shape, functionalization and proven biocompatibility. Our experimental designs were guided by a series of theoretical calculations, which provided clues to the effects of particle size, size distribution, magnetic field, frequency and reaction medium. Materials of theoretically optimal size were synthesized, functionalized, and their effects in the oscillating magnetic field were subsequently investigated. Under our conditions, the materials that clustered e.g. silica-coated and PNIPAM-coated iron oxides exhibited the highest heat generation, while iron oxides embedded in MSNs and mesoporous iron oxides exhibited the least bulk heating. It is worth noting that the specific

  10. Primordial magnetic fields from the string network

    Science.gov (United States)

    Horiguchi, Kouichirou; Ichiki, Kiyotomo; Sugiyama, Naoshi

    2016-08-01

    Cosmic strings are a type of cosmic defect formed by a symmetry-breaking phase transition in the early universe. Individual strings would have gathered to build a network, and their dynamical motion would induce scalar-, vector-, and tensor-type perturbations. In this paper, we focus on the vector mode perturbations arising from the string network based on the one scale model and calculate the time evolution and the power spectrum of the associated magnetic fields. We show that the relative velocity between photon and baryon fluids induced by the string network can generate magnetic fields over a wide range of scales based on standard cosmology. We obtain the magnetic field spectrum before recombination as aB(k,z)~4×10Gμ/1k)3.5 gauss on super-horizon scales, and aB(k,z)~2.4×10Gμ/1k)2.5 gauss on sub-horizon scales in co-moving coordinates. This magnetic field grows up to the end of recombination, and has a final amplitude of approximately B~10Gμ gauss at the k~1 Mpc scale today. This field might serve as a seed for cosmological magnetic fields.

  11. Lightning Magnetic Field Measurements around Langmuir Laboratory

    Science.gov (United States)

    Stock, M.; Krehbiel, P. R.; Rison, W.; Aulich, G. D.; Edens, H. E.; Sonnenfeld, R. G.

    2010-12-01

    In the absence of artificial conductors, underground lightning transients are produced by diffusion of the horizontal surface magnetic field of a return stroke vertically downward into the conducting earth. The changing magnetic flux produces an orthogonal horizontal electric field, generating a dispersive, lossy transverse electromagnetic wave that penetrates a hundred meters or more into the ground according to the skin depth of the medium. In turn, the electric field produces currents that flow toward or away from the channel to ground depending on the stroke polarity. The underground transients can produce large radial horizontal potential gradients depending on the distance from the discharge and depth below the surface. In this study we focus on the surface excitation field. The goal of the work is to compare measurements of surface magnetic field waveforms B(t) at different distances from natural lightning discharges with simple and detailed models of the return stroke fields. In addition to providing input to the diffusion mechanism, the results should aid in further understanding return stroke field generation processes. The observational data are to be obtained using orthogonal sets of straightened Rogowski coils to measure magnetic field waveforms in N-S and E-W directions. The waveforms are sampled at 500 kS/s over 1.024 second time intervals and recorded directly onto secure digital cards. The instrument operates off of battery power for several days or weeks at a time in remote, unattended locations and measures magnetic field strengths of up to several tens of amperes/meter. The observations are being made in conjunction with collocated slow electric field change measurements and under good 3-D lightning mapping array (LMA) and fast electric field change coverage.

  12. Teaching Representation Translations with Magnetic Field Experiments

    Science.gov (United States)

    Tillotson, Wilson Andrew; McCaskey, Timothy; Nasser, Luis

    2017-01-01

    We have developed a laboratory exercise designed to help students translate between different field representations. It starts with students qualitatively mapping field lines for various bar magnet configurations and continues with a Hall probe experiment in which students execute a series of scaffolded tasks, culminating in the prediction and…

  13. Galactic magnetic fields and hierarchical galaxy formation

    CERN Document Server

    Rodrigues, Luiz Felippe S; Fletcher, Andrew; Baugh, Carlton

    2015-01-01

    A framework is introduced for coupling the evolution of galactic magnetic fields sustained by the mean-field dynamo with the formation and evolution of galaxies in the cold dark matter cosmology. Estimates of the steady-state strength of the large-scale and turbulence magnetic fields from mean-field and fluctuation dynamo models are used together with galaxy properties predicted by semi-analytic models of galaxy formation for a population of spiral galaxies. We find that the field strength is mostly controlled by the evolving gas content of the galaxies. Thus, because of the differences in the implementation of the star formation law, feedback from supernovae and ram-pressure stripping, each of the galaxy formation models considered predicts a distribution of field strengths with unique features. The most prominent of them is the difference in typical magnetic fields strengths obtained for the satellite and central galaxies populations as well as the typical strength of the large-scale magnetic field in galax...

  14. A deep dynamo generating Mercury's magnetic field.

    Science.gov (United States)

    Christensen, Ulrich R

    2006-12-21

    Mercury has a global magnetic field of internal origin and it is thought that a dynamo operating in the fluid part of Mercury's large iron core is the most probable cause. However, the low intensity of Mercury's magnetic field--about 1% the strength of the Earth's field--cannot be reconciled with an Earth-like dynamo. With the common assumption that Coriolis and Lorentz forces balance in planetary dynamos, a field thirty times stronger is expected. Here I present a numerical model of a dynamo driven by thermo-compositional convection associated with inner core solidification. The thermal gradient at the core-mantle boundary is subadiabatic, and hence the outer region of the liquid core is stably stratified with the dynamo operating only at depth, where a strong field is generated. Because of the planet's slow rotation the resulting magnetic field is dominated by small-scale components that fluctuate rapidly with time. The dynamo field diffuses through the stable conducting region, where rapidly varying parts are strongly attenuated by the skin effect, while the slowly varying dipole and quadrupole components pass to some degree. The model explains the observed structure and strength of Mercury's surface magnetic field and makes predictions that are testable with space missions both presently flying and planned.

  15. Teaching Representation Translations with Magnetic Field Experiments

    Science.gov (United States)

    Tillotson, Wilson Andrew; McCaskey, Timothy; Nasser, Luis

    2017-01-01

    We have developed a laboratory exercise designed to help students translate between different field representations. It starts with students qualitatively mapping field lines for various bar magnet configurations and continues with a Hall probe experiment in which students execute a series of scaffolded tasks, culminating in the prediction and…

  16. Nonperturbative Physics in a Magnetic Field

    CERN Document Server

    de la Incera, Vivian

    2010-01-01

    Non-Perturbative Quantum Field Theory has played an important role in the study of phenomena where a fermion condensate can appear under certain physical conditions. The familiar phenomenon of electric superconductivity, the color superconductivity of very dense quark matter, and the chiral symmetry breaking of low energy effective chiral theories are all examples of that sort. Often one is interested in the behavior of these systems in the presence of an external magnetic field. In this talk I will outline the effects of an external magnetic field on theories with either fermion-fermion or fermion-antifermion condensates.

  17. Hyperon bulk viscosity in strong magnetic fields

    CERN Document Server

    Sinha, Monika

    2008-01-01

    We study bulk viscosity in neutron star matter including $\\Lambda$ hyperons in the presence of quantizing magnetic fields. Relaxation time and bulk viscosity due to both the non-leptonic weak process involving $\\Lambda$ hyperons and the direct Urca (dUrca) process are calculated here. In the presence of a strong magnetic field, bulk viscosity coefficients are enhanced when protons, electrons and muons are populated in their respective zeroth Landau levels compared with the field free cases. The enhancement of bulk viscosity coefficient is larger for the dUrca case.

  18. Opening the cusp. [using magnetic field topology

    Science.gov (United States)

    Crooker, N. U.; Toffoletto, F. R.; Gussenhoven, M. S.

    1991-01-01

    This paper discusses the magnetic field topology (determined by the superposition of dipole, image, and uniform fields) for mapping the cusp to the ionosphere. The model results are compared to both new and published observations and are then used to map the footprint of a flux transfer event caused by a time variation in the merging rate. It is shown that the cusp geometry distorts the field lines mapped from the magnetopause to yield footprints with dawn and dusk protrusions into the region of closed magnetic flux.

  19. String field theory solution corresponding to constant background magnetic field

    CERN Document Server

    Ishibashi, Nobuyuki; Takahashi, Tomohiko

    2016-01-01

    Following the method recently proposed by Erler and Maccaferri, we construct solutions to the equation of motion of Witten's cubic string field theory, which describe constant magnetic field background. We study the boundary condition changing operators relevant to such background and calculate the operator product expansions of them. We obtain solutions whose classical action coincide with the Born-Infeld action.

  20. Magnetic fields of young solar twins

    Science.gov (United States)

    Rosén, L.; Kochukhov, O.; Hackman, T.; Lehtinen, J.

    2016-09-01

    Aims: The goal of this work is to study the magnetic fields of six young solar-analogue stars both individually, and collectively, to search for possible magnetic field trends with age. If such trends are found, they can be used to understand magnetism in the context of stellar evolution of solar-like stars and to understand the past of the Sun and the solar system. This is also important for the atmospheric evolution of the inner planets, Earth in particular. Methods: We used Stokes IV data from two different spectropolarimeters, NARVAL and HARPSpol. The least-squares deconvolution multi-line technique was used to increase the signal-to-noise ratio of the data. We then applied a modern Zeeman-Doppler imaging code in order to reconstruct the magnetic topology of all stars and the brightness distribution of one of our studied stars. Results: Our results show a significant decrease in the magnetic field strength and energy as the stellar age increases from 100 Myr to 250 Myr, while there is no significant age dependence of the mean magnetic field strength for stars with ages 250-650 Myr. The spread in the mean field strength between different stars is comparable to the scatter between different observations of individual stars. The meridional field component is weaker than the radial and azimuthal field components in 15 of the 16 magnetic maps. It turns out that 89-97% of the magnetic field energy is contained in l = 1 - 3. There is also no clear trend with age and distribution of field energy into poloidal/toroidal and axisymmetric/non-axisymmetric components within the sample. The two oldest stars in this study show an octupole component that is twice as strong as the quadrupole component. This is only seen in 1 of the 13 maps of the younger stars. One star, χ1 Ori, displays two field polarity switches during almost 5 yr of observations suggesting a magnetic cycle length of 2, 6, or 8 yr. Based on observations made with the HARPSpol instrument on the ESO 3.6 m

  1. Magnetohydrodynamic experiments on cosmic magnetic fields

    CERN Document Server

    Stefani, Frank; Gerbeth, Gunter

    2008-01-01

    It is widely known that cosmic magnetic fields, including the fields of planets, stars, and galaxies, are produced by the hydromagnetic dynamo effect in moving electrically conducting fluids. It is less well known that cosmic magnetic fields play also an active role in cosmic structure formation by enabling outward transport of angular momentum in accretion disks via the magnetorotational instability (MRI). Considerable theoretical and computational progress has been made in understanding both processes. In addition to this, the last ten years have seen tremendous efforts in studying both effects in liquid metal experiments. In 1999, magnetic field self-excitation was observed in the large scale liquid sodium facilities in Riga and Karlsruhe. Recently, self-excitation was also obtained in the French "von Karman sodium" (VKS) experiment. An MRI-like mode was found on the background of a turbulent spherical Couette flow at the University of Maryland. Evidence for MRI as the first instability of an hydrodynamica...

  2. Magnetic Field Amplification via Protostellar Disc Dynamos

    CERN Document Server

    Dyda, Sergei; Ustyugova, Galina V; Koldoba, Alexander V; Wasserman, Ira

    2015-01-01

    We model the generation of a magnetic field in a protostellar disc using an \\alpha-dynamo and perform axisymmetric magnetohydrodynamics (MHD) simulations of a T Tauri star. We find that for small values of the dimensionless dynamo parameter $\\alpha_d$ the poloidal field grows exponentially at a rate ${\\sigma} \\propto {\\Omega}_K \\sqrt{\\alpha_d}$ , before saturating to a value $\\propto \\sqrt{\\alpha_d}$ . The dynamo excites dipole and octupole modes, but quadrupole modes are suppressed, because of the symmetries of the seed field. Initial seed fields too weak to launch MHD outflows are found to grow sufficiently to launch winds with observationally relevant mass fluxes of order $10^{-9} M_{\\odot}/\\rm{yr}$ for T Tauri stars. For large values of $\\alpha_d$ magnetic loops are generated over the entire disc. These quickly come to dominate the disc dynamics and cause the disc to break up due to the magnetic pressure.

  3. A holographic bound on cosmic magnetic fields

    Directory of Open Access Journals (Sweden)

    Brett McInnes

    2015-03-01

    Full Text Available Magnetic fields large enough to be observable are ubiquitous in astrophysics, even at extremely large length scales. This has led to the suggestion that such fields are seeded at very early (inflationary times, and subsequently amplified by various processes involving, for example, dynamo effects. Many such mechanisms give rise to extremely large magnetic fields at the end of inflationary reheating, and therefore also during the quark–gluon plasma epoch of the early universe. Such plasmas have a well-known holographic description in terms of a thermal asymptotically AdS black hole. We show that holography imposes an upper bound on the intensity of magnetic fields (≈3.6×1018gauss at the hadronization temperature in these circumstances; this is above, but not far above, the values expected in some models of cosmic magnetogenesis.

  4. Measuring vector magnetic fields in solar prominences

    CERN Document Server

    Suárez, D Orozco; Bueno, J Trujillo

    2012-01-01

    We present spectropolarimetric observations in the He I 1083.0 nm multiplet of a quiescent, hedgerow solar prominence. The data were taken with the Tenerife Infrared Polarimeter attached to the German Vacuum Tower Telescope at the Observatorio del Teide (Tenerife; Canary Islands; Spain). The observed He I circular and linear polarization signals are dominated by the Zeeman effect and by atomic level polarization and the Hanle effect, respectively. These observables are sensitive to the strength and orientation of the magnetic field vector at each spatial point of the field of view. We determine the magnetic field vector of the prominence by applying the HAZEL inversion code to the observed Stokes profiles. We briefly discuss the retrieved magnetic field vector configuration.

  5. Magnetic fields during high redshift structure formation

    CERN Document Server

    Schleicher, Dominik R G; Schober, Jennifer; Schmidt, Wolfram; Bovino, Stefano; Federrath, Christoph; Niemeyer, Jens; Banerjee, Robi; Klessen, Ralf S

    2012-01-01

    We explore the amplification of magnetic fields in the high-redshift Universe. For this purpose, we perform high-resolution cosmological simulations following the formation of primordial halos with \\sim10^7 M_solar, revealing the presence of turbulent structures and complex morphologies at resolutions of at least 32 cells per Jeans length. Employing a turbulence subgrid-scale model, we quantify the amount of unresolved turbulence and show that the resulting turbulent viscosity has a significant impact on the gas morphology, suppressing the formation of low-mass clumps. We further demonstrate that such turbulence implies the efficient amplification of magnetic fields via the small-scale dynamo. We discuss the properties of the dynamo in the kinematic and non-linear regime, and explore the resulting magnetic field amplification during primordial star formation. We show that field strengths of \\sim10^{-5} G can be expected at number densities of \\sim5 cm^{-3}.

  6. Inference of magnetic fields in inhomogeneous prominences

    CERN Document Server

    Milic, Ivan; Atanackovic, Olga

    2016-01-01

    Most of the quantitative information about the magnetic field vector in solar prominences comes from the analysis of the Hanle effect acting on lines formed by scattering. As these lines can be of non-negligible optical thickness, it is of interest to study the line formation process further. We investigate the multidimensional effects on the interpretation of spectropolarimetric observations, particularly on the inference of the magnetic field vector. We do this by analyzing the differences between multidimensional models, which involve fully self-consistent radiative transfer computations in the presence of spatial inhomogeneities and velocity fields, and those which rely on simple one-dimensional geometry. We study the formation of a prototype line in ad hoc inhomogeneous, isothermal 2D prominence models. We solve the NLTE polarized line formation problem in the presence of a large-scale oriented magnetic field. The resulting polarized line profiles are then interpreted (i.e. inverted) assuming a simple 1D...

  7. Nonrelativistic Fermions in Magnetic Fields a Quantum Field Theory Approach

    CERN Document Server

    Espinosa, Olivier R; Lepe, S; Méndez, F

    2001-01-01

    The statistical mechanics of nonrelativistic fermions in a constant magnetic field is considered from the quantum field theory point of view. The fermionic determinant is computed using a general procedure that contains all possible regularizations. The nonrelativistic grand-potential can be expressed in terms polylogarithm functions, whereas the partition function in 2+1 dimensions and vanishing chemical potential can be compactly written in terms of the Dedekind eta function. The strong and weak magnetic fields limits are easily studied in the latter case by using the duality properties of the Dedekind function.

  8. Vector magnetic field in solar polar region

    Institute of Scientific and Technical Information of China (English)

    邓元勇; 汪景秀; 艾国祥

    1999-01-01

    By means of ’deep integration’ observations of a videomagnetograph the vector magnetic field was first systematically measured near the solar south polar region on April 12, 1997 when the Sun was in the minimal phase between the 22nd and 23rd solar cycle. It was found that the polar magnetic field deviated from the normal of solar surface by about 42.2°±3.2°, a stronger magnetic element may have smaller inclination, and that within the polar cap above heliolatitude of 50°, the unsigned and net flux densities were 7.8×10-4 T and -3.4×10-4 T, respectively, and consequently, the unsigned and net fluxes were about 5.5×1022 and -2.5×1022 Mx. The net magnetic flux, which belongs to the large-scale global magnetic field of the Sun, roughly approaches the order of the interplanetary magnetic field (IMF) measured at distance of 1 AU.

  9. Magnetic fields of young solar twins

    CERN Document Server

    Rosén, L; Hackman, T; Lehtinen, J

    2016-01-01

    The goal of this work is to study the magnetic fields of six young solar-analogue stars both individually, and collectively, to search for possible magnetic field trends with age. If such trends are found, they can be used to understand magnetism in the context of stellar evolution of solar-like stars and, the past of the Sun and the solar system. This is also important for the atmospheric evolution of the inner planets, Earth in particular. We used Stokes IV data from two different spectropolarimeters, NARVAL and HARPSpol. The least-squares deconvolution multi-line technique was used to increase the signal-to-noise ratio of the data. We then applied a modern Zeeman-Doppler imaging code in order to reconstruct the magnetic topology of all stars and the brightness distribution of one of our studied stars. Our results show a significant decrease in the magnetic field strength and energy as the stellar age increases from 100Myr to 250Myr while there is no significant age dependence of the mean magnetic field str...

  10. Magnetic fields in Local Group dwarf irregulars

    Science.gov (United States)

    Chyży, K. T.; Weżgowiec, M.; Beck, R.; Bomans, D. J.

    2011-05-01

    Aims: We wish to clarify whether strong magnetic fields can be effectively generated in typically low-mass dwarf galaxies and to assess the role of dwarf galaxies in the magnetization of the Universe. Methods: We performed a search for radio emission and magnetic fields in an unbiased sample of 12 Local Group (LG) irregular and dwarf irregular galaxies with the 100-m Effelsberg telescope at 2.64 GHz. Three galaxies were detected. A higher frequency (4.85 GHz) was used to search for polarized emission in five dwarfs that are the most luminous ones in the infrared domain, of which three were detected. Results: Magnetic fields in LG dwarfs are weak, with a mean value of the total field strength of regulated mainly by the star-formation surface density (with the power-law exponent of 0.30 ± 0.04) or by the gas surface density (with the exponent 0.47 ± 0.09). In addition, we find systematically stronger fields in objects of higher global star-formation rate. The dwarf galaxies follow a similar far-infrared relationship (with a slope of 0.91 ± 0.08) to that determined for high surface brightness spiral galaxies. The magnetic field strength in dwarf galaxies does not correlate with their maximum rotational velocity, indicating that a small-scale rather than a large-scale dynamo process is responsible for producting magnetic fields in dwarfs. If magnetization of the Universe by galactic outflows is coeval with its metal enrichment, we show that more massive objects (such as Lyman break galaxies) can efficiently magnetize the intergalactic medium with a magnetic field strength of about 0.8 nG out to a distance of 160-530 kpc at redshifts 5-3, respectively. Magnetic fields that are several times weaker and shorter magnetization distances are expected for primordial dwarf galaxies. We also predict that most star-forming local dwarfs might have magnetized their surroundings up to a field strength about 0.1 μG within about a 5 kpc distance. Conclusions: Strong magnetic

  11. Near-zero-field nuclear magnetic resonance

    CERN Document Server

    Ledbetter, Micah; Blanchard, John; Ring, Hattie; Ganssle, Paul; Appelt, Stephan; Bluemich, Bernhard; Pines, Alex; Budker, Dmitry

    2011-01-01

    We investigate nuclear magnetic resonance (NMR) in near-zero-field, where the Zeeman interaction can be treated as a perturbation to the electron mediated scalar interaction (J-coupling). This is in stark contrast to the high field case, where heteronuclear J-couplings are normally treated as a small perturbation. We show that the presence of very small magnetic fields results in splitting of the zero-field NMR lines, imparting considerable additional information to the pure zero-field spectra. Experimental results are in good agreement with first-order perturbation theory and with full numerical simulation when perturbation theory breaks down. We present simple rules for understanding the splitting patterns in near-zero-field NMR, which can be applied to molecules with non-trivial spectra.

  12. Near-zero-field nuclear magnetic resonance.

    Science.gov (United States)

    Ledbetter, M P; Theis, T; Blanchard, J W; Ring, H; Ganssle, P; Appelt, S; Blümich, B; Pines, A; Budker, D

    2011-09-02

    We investigate nuclear magnetic resonance (NMR) in near zero field, where the Zeeman interaction can be treated as a perturbation to the electron mediated scalar interaction (J coupling). This is in stark contrast to the high-field case, where heteronuclear J couplings are normally treated as a small perturbation. We show that the presence of very small magnetic fields results in splitting of the zero-field NMR lines, imparting considerable additional information to the pure zero-field spectra. Experimental results are in good agreement with first-order perturbation theory and with full numerical simulation when perturbation theory breaks down. We present simple rules for understanding the splitting patterns in near-zero-field NMR, which can be applied to molecules with nontrivial spectra.

  13. Magnetic Fields in the Interstellar Medium

    Science.gov (United States)

    Clark, Susan

    2017-01-01

    The Milky Way is magnetized. Invisible magnetic fields thread the Galaxy on all scales and play a vital but still poorly understood role in regulating flows of gas in the interstellar medium and the formation of stars. I will present highlights from my thesis work on magnetic fields in the diffuse interstellar gas and in accretion disks. At high Galactic latitudes, diffuse neutral hydrogen is organized into an intricate network of slender linear features. I will show that these neutral hydrogen “fibers” are extremely well aligned with the ambient magnetic field as traced by both starlight polarization (Clark et al. 2014) and Planck 353 GHz polarized dust emission (Clark et al. 2015). The structure of the neutral interstellar medium is more tightly coupled to the magnetic field than previously known. Because the orientation of neutral hydrogen is an independent predictor of the local dust polarization angle, our work provides a new tool in the search for inflationary gravitational wave B-mode polarization in the cosmic microwave background, which is currently limited by dust foreground contamination. Magnetic fields also drive accretion in astrophysical disks via the magnetorotational instability (MRI). I analytically derive the behavior of this instability in the weakly nonlinear regime and show that the saturated state of the instability depends on the geometry of the background magnetic field. The analytical model describes the behavior of the MRI in a Taylor-Couette flow, a set-up used by experimentalists in the ongoing quest to observe MRI in the laboratory (Clark & Oishi 2016a, 2016b).

  14. Effects of static magnetic fields on plants.

    Science.gov (United States)

    Kuznetsov, O.

    In our recent experiment on STS-107 (MFA-Biotube) we took advantage of the magnetic heterogeneity of the gravity receptor cells of flax roots, namely stronger diamagnetism of starch-filled amyloplasts compared to cytoplasm (Δ ≊ HGMF, grad(H2/2) up to 109-1010 Oe2/cm) of the experimental chambers (MFCs) repelled amyloplasts from the zones of stronger field thus providing a directional stimulus for plant gravisensing system in microgravity, and causing the roots to react. Such reaction was observed in the video downlink pictures. Unfortunately, the ``Columbia'' tragedy caused loss of the plant material and most of the images, thus preventing us from detailed studies of the results. Currently we are looking for a possibility to repeat this experiment. Therefore, it is very important to understand, what other effects (besides displacing amyloplasts) static magnetic fields with intensities 0 to 2.5104 Oe, and with the size of the area of non-uniformity 10-3 to 1 cm. These effects were estimated theoretically and tested experimentally. No statistically significant differences in growth rates or rates of gravicurvature were observed in experiments with Linum, Arabidopsis, Hordeum, Avena, Ceratodon and Chara between the plants grown in uniform magnetic fields of various intensities (102 to 2.5104 Oe) and those grown in the Earth's magnetic field. Microscopic studies also did not detect any structural differences between test and control plants. The magnitudes of possible effects of static magnetic fields on plant cells and organs (including effects on ion currents, magneto-hydrodynamic effects in moving cytoplasm, ponderomotive forces on other cellular structures, effects on some biochemical reactions and biomolecules) were estimated theoretically. The estimations have shown, that these effects are small compared to the thermodynamic noise and thus are insignificant. Both theoretical estimations and control experiments confirm, that intracellular magnetophoresis of

  15. The Use of Signal-Transduction and Metabolic Pathways to Predict Human Disease Targets from Electric and Magnetic Fields Using in vitro Data in Human Cell Lines

    Science.gov (United States)

    Parham, Fred; Portier, Christopher J.; Chang, Xiaoqing; Mevissen, Meike

    2016-01-01

    Using in vitro data in human cell lines, several research groups have investigated changes in gene expression in cellular systems following exposure to extremely low frequency (ELF) and radiofrequency (RF) electromagnetic fields (EMF). For ELF EMF, we obtained five studies with complete microarray data and three studies with only lists of significantly altered genes. Likewise, for RF EMF, we obtained 13 complete microarray datasets and 5 limited datasets. Plausible linkages between exposure to ELF and RF EMF and human diseases were identified using a three-step process: (a) linking genes associated with classes of human diseases to molecular pathways, (b) linking pathways to ELF and RF EMF microarray data, and (c) identifying associations between human disease and EMF exposures where the pathways are significantly similar. A total of 60 pathways were associated with human diseases, mostly focused on basic cellular functions like JAK–STAT signaling or metabolic functions like xenobiotic metabolism by cytochrome P450 enzymes. ELF EMF datasets were sporadically linked to human diseases, but no clear pattern emerged. Individual datasets showed some linkage to cancer, chemical dependency, metabolic disorders, and neurological disorders. RF EMF datasets were not strongly linked to any disorders but strongly linked to changes in several pathways. Based on these analyses, the most promising area for further research would be to focus on EMF and neurological function and disorders. PMID:27656641

  16. Inference of magnetic fields in inhomogeneous prominences

    Science.gov (United States)

    Milić, I.; Faurobert, M.; Atanacković, O.

    2017-01-01

    Context. Most of the quantitative information about the magnetic field vector in solar prominences comes from the analysis of the Hanle effect acting on lines formed by scattering. As these lines can be of non-negligible optical thickness, it is of interest to study the line formation process further. Aims: We investigate the multidimensional effects on the interpretation of spectropolarimetric observations, particularly on the inference of the magnetic field vector. We do this by analyzing the differences between multidimensional models, which involve fully self-consistent radiative transfer computations in the presence of spatial inhomogeneities and velocity fields, and those which rely on simple one-dimensional geometry. Methods: We study the formation of a prototype line in ad hoc inhomogeneous, isothermal 2D prominence models. We solve the NLTE polarized line formation problem in the presence of a large-scale oriented magnetic field. The resulting polarized line profiles are then interpreted (i.e. inverted) assuming a simple 1D slab model. Results: We find that differences between input and the inferred magnetic field vector are non-negligible. Namely, we almost universally find that the inferred field is weaker and more horizontal than the input field. Conclusions: Spatial inhomogeneities and radiative transfer have a strong effect on scattering line polarization in the optically thick lines. In real-life situations, ignoring these effects could lead to a serious misinterpretation of spectropolarimetric observations of chromospheric objects such as prominences.

  17. Whistler modes with wave magnetic fields exceeding the ambient field.

    Science.gov (United States)

    Stenzel, R L; Urrutia, J M; Strohmaier, K D

    2006-03-10

    Whistler-mode wave packets with fields exceeding the ambient dc magnetic field have been excited in a large, high electron-beta plasma. The waves are induced with a loop antenna with dipole moment either along or opposite to the dc field. In the latter case the excited wave packets have the topology of a spheromak but are propagating in the whistler mode along and opposite to the dc magnetic field. Field-reversed configurations with net zero helicity have also been produced. The electron magnetohydrodynamics fields are force free, have wave energy density exceeding the particle energy density, and propagate stably at subelectron thermal velocities through a nearly uniform stationary ion density background.

  18. Human disease resulting from exposure to electromagnetic fields.

    Science.gov (United States)

    Carpenter, David O

    2013-01-01

    Electromagnetic fields (EMFs) include everything from cosmic rays through visible light to the electric and magnetic fields associated with electricity. While the high frequency fields have sufficient energy to cause cancer, the question of whether there are human health hazards associated with communication radiofrequency (RF) EMFs and those associated with use of electricity remains controversial. The issue is more important than ever given the rapid increase in the use of cell phones and other wireless devices. This review summarizes the evidence stating that excessive exposure to magnetic fields from power lines and other sources of electric current increases the risk of development of some cancers and neurodegenerative diseases, and that excessive exposure to RF radiation increases risk of cancer, male infertility, and neurobehavioral abnormalities. The relative impact of various sources of exposure, the great range of standards for EMF exposure, and the costs of doing nothing are also discussed.

  19. Dissipation function in a magnetic field (Review)

    Science.gov (United States)

    Gurevich, V. L.

    2015-07-01

    The dissipation function is introduced to describe the behavior of the system of harmonic oscillations interacting with the environment (thermostat). This is a quadratic function of generalized velocities, which determines the rate of dissipation of the mechanical energy in the system. It was assumed earlier (Landau, Lifshitz) that the dissipation function can be introduced only in the absence of magnetic field. In the present review based on the author's studies, it has been shown how the dissipation function can be introduced in the presence of a magnetic field B. In a magnetic field, both dissipative and nondissipative responses arise as a response to perturbation and are expressed in terms of kinetic coefficients. The matrix of nondissipative coefficients can be obtained to determine an additional term formally including it into the equations of motion, which still satisfy the energy conservation law. Then, the dissipative part of the matrix can be considered in exactly the same way as without magnetic field, i.e., it defines the dissipation loss. As examples, the propagation and absorption of ultrasound in a metal or a semiconductor in a magnetic field have been considered using two methods: (i) the method based on the phenomenological theory using the equations of the theory of elasticity and (ii) the method based on the microscopic approach by analyzing and solving the kinetic equation. Both examples are used to illustrate the approach with the dissipation function.

  20. Magnetic Fields and Massive Star Formation

    CERN Document Server

    Zhang, Qizhou; Girart, Josep M; Hauyu,; Liu,; Tang, Ya-Wen; Koch, Patrick M; Li, Zhi-Yun; Keto, Eric; Ho, Paul T P; Rao, Ramprasad; Lai, Shih-Ping; Ching, Tao-Chung; Frau, Pau; Chen, How-Huan; Li, Hua-Bai; Padovani, Marco; Bontemps, Sylvain; Csengeri, Timea; Juarez, Carmen

    2014-01-01

    Massive stars ($M > 8$ \\msun) typically form in parsec-scale molecular clumps that collapse and fragment, leading to the birth of a cluster of stellar objects. We investigate the role of magnetic fields in this process through dust polarization at 870 $\\mu$m obtained with the Submillimeter Array (SMA). The SMA observations reveal polarization at scales of $\\lsim$ 0.1 pc. The polarization pattern in these objects ranges from ordered hour-glass configurations to more chaotic distributions. By comparing the SMA data with the single dish data at parsec scales, we found that magnetic fields at dense core scales are either aligned within $40^\\circ$ of or perpendicular to the parsec-scale magnetic fields. This finding indicates that magnetic fields play an important role during the collapse and fragmentation of massive molecular clumps and the formation of dense cores. We further compare magnetic fields in dense cores with the major axis of molecular outflows. Despite a limited number of outflows, we found that the ...

  1. Magnetic fields of the outer planets

    Science.gov (United States)

    Connerney, J. E. P.

    1993-01-01

    It is difficult to imagine a group of planetary dynamos more diverse than those visited by the Pioneer and Voyager spacecraft. The magnetic field of Jupiter is large in magnitude and has a dipole axis within 10 deg of its rotation axis, comfortably consistent with the paleomagnetic history of the geodynamo. Saturn's remarkable (zonal harmonic) magnetic field has an axis of symmetry that is indistinguishable from its rotation axis (mush less than 1 deg angular separation); it is also highly antisymmetric with respect to the equator plane. According to one hypothesis, the spin symmetry may arise from the differential rotation of an electrically conducting and stably stratified layer above the dynamo. The magnetic fields of Uranus and Neptune are very much alike, and equally unlike those of the other known magnetized planets. These two planets are characterized by a large dipole tilts (59 deg and 47 deg, respectively) and quadrupole moments (Schmidt-normalized quadrupole/dipole ratio approximately equal 1.0). These properties may be characteristic of dynamo generation in the relatively poorly conducting 'ice' interiors of Uranus and Neptune. Characteristics of these planetary magnetic fields are illustrated using contour maps of the field on the planet's surface and discussed in the context of planetary interiors and dynamo generation.

  2. Cosmic Magnetic Fields: Observations and Prospects

    CERN Document Server

    Beck, Rainer

    2011-01-01

    Synchrotron emission, its polarization and its Faraday rotation at radio frequencies of 0.2-10 GHz are powerful tools to study the strength and structure of cosmic magnetic fields. The observational results are reviewed for spiral, barred and flocculent galaxies, the Milky Way, halos and relics of galaxy clusters, and for the intergalactic medium. Polarization observations with the forthcoming large radio telescopes will open a new era in the observation of cosmic magnetic fields and will help to understand their origin. At low frequencies, LOFAR (10-250 MHz) will allow us to map the structure of weak magnetic fields in the outer regions and halos of galaxies and galaxy clusters. Polarization at higher frequencies (1-10 GHz), as observed with the EVLA, ASKAP, MeerKAT, APERTIF and the SKA, will trace magnetic fields in the disks and central regions of nearby galaxies in unprecedented detail. Surveys of Faraday rotation measures of pulsars will map the Milky Way's magnetic field with high precision. All-sky sur...

  3. Magnetic fields in primordial accretion disks

    Science.gov (United States)

    Latif, M. A.; Schleicher, D. R. G.

    2016-01-01

    Magnetic fields are considered a vital ingredient of contemporary star formation and may have been important during the formation of the first stars in the presence of an efficient amplification mechanism. Initial seed fields are provided via plasma fluctuations and are subsequently amplified by the small-scale dynamo, leading to a strong, tangled magnetic field. We explore how the magnetic field provided by the small-scale dynamo is further amplified via the α-Ω dynamo in a protostellar disk and assess its implications. For this purpose, we consider two characteristic cases, a typical Pop. III star with 10M⊙ and an accretion rate of 10-3M⊙ yr-1, and a supermassive star with 105M⊙ and an accretion rate of 10-1M⊙ yr-1. For the 10M⊙ Pop. III star, we find that coherent magnetic fields can be produced on scales of at least 100 AU, which are sufficient to drive a jet with a luminosity of 100L⊙ and a mass outflow rate of 10-3.7M⊙ yr-1. For the supermassive star, the dynamical timescales in its environment are even shorter, implying smaller orbital timescales and an efficient magnetization out to at least 1000 AU. The jet luminosity corresponds to ~106.0L⊙ and a mass outflow rate of 10-2.1M⊙ yr-1. We expect that the feedback from the supermassive star can have a relevant impact on its host galaxy.

  4. Magnetic Field Strengths in Photodissociation Regions

    CERN Document Server

    Balser, Dana S; Jeyakumar, S; Bania, T M; Montet, Benjamin T; Shitanishi, J A

    2015-01-01

    We measure carbon radio recombination line (RRL) emission at 5.3 GHz toward four HII regions with the Green Bank Telescope (GBT) to determine the magnetic field strength in the photodissociation region (PDR) that surrounds the ionized gas. Roshi (2007) suggests that the non-thermal line widths of carbon RRLs from PDRs are predominantly due to magneto-hydrodynamic (MHD) waves, thus allowing the magnetic field strength to be derived. We model the PDR with a simple geometry and perform the non-LTE radiative transfer of the carbon RRL emission to solve for the PDR physical properties. Using the PDR mass density from these models and the carbon RRL non-thermal line width we estimate total magnetic field strengths of B ~ 100-300 micro Gauss in W3 and NGC6334A. Our results for W49 and NGC6334D are less well constrained with total magnetic field strengths between B ~ 200-1000 micro Gauss. HI and OH Zeeman measurements of the line-of-sight magnetic field strength (B_los), taken from the literature, are between a facto...

  5. Magnetic field effect on spoke behaviour

    Science.gov (United States)

    Hnilica, Jaroslav; Slapanska, Marta; Klein, Peter; Vasina, Petr

    2016-09-01

    The investigations of the non-reactive high power impulse magnetron sputtering (HiPIMS) discharge using high-speed camera imaging, optical emission spectroscopy and electrical probes showed that plasma is not homogeneously distributed over the target surface, but it is concentrated in regions of higher local plasma density called spokes rotating above the erosion racetrack. Magnetic field effect on spoke behaviour was studied by high-speed camera imaging in HiPIMS discharge using 3 inch titanium target. An employed camera enabled us to record two successive images in the same pulse with time delay of 3 μs between them, which allowed us to determine the number of spokes, spoke rotation velocity and spoke rotation frequency. The experimental conditions covered pressure range from 0.15 to 5 Pa, discharge current up to 350 A and magnetic fields of 37, 72 and 91 mT. Increase of the magnetic field influenced the number of spokes observed at the same pressure and at the same discharge current. Moreover, the investigation revealed different characteristic spoke shapes depending on the magnetic field strength - both diffusive and triangular shapes were observed for the same target material. The spoke rotation velocity was independent on the magnetic field strength. This research has been financially supported by the Czech Science Foundation in frame of the project 15-00863S.

  6. Reducing blood viscosity with magnetic fields.

    Science.gov (United States)

    Tao, R; Huang, K

    2011-07-01

    Blood viscosity is a major factor in heart disease. When blood viscosity increases, it damages blood vessels and increases the risk of heart attacks. Currently, the only method of treatment is to take drugs such as aspirin, which has, however, several unwanted side effects. Here we report our finding that blood viscosity can be reduced with magnetic fields of 1 T or above in the blood flow direction. One magnetic field pulse of 1.3 T lasting ~1 min can reduce the blood viscosity by 20%-30%. After the exposure, in the absence of magnetic field, the blood viscosity slowly moves up, but takes a couple of hours to return to the original value. The process is repeatable. Reapplying the magnetic field reduces the blood viscosity again. By selecting the magnetic field strength and duration, we can keep the blood viscosity within the normal range. In addition, such viscosity reduction does not affect the red blood cells' normal function. This technology has much potential for physical therapy.

  7. The Magnetic Field of Planet Earth

    DEFF Research Database (Denmark)

    Hulot, G.; Finlay, Chris; Constable, C. G.

    2010-01-01

    The magnetic field of the Earth is by far the best documented magnetic field of all known planets. Considerable progress has been made in our understanding of its characteristics and properties, thanks to the convergence of many different approaches and to the remarkable fact that surface rocks h...... yr) to the longest (virtually the age of the Earth) time scales are finally reviewed, underlining the respective roles of the magnetohydodynamics at work in the core, and of the slow dynamic evolution of the planet as a whole.......The magnetic field of the Earth is by far the best documented magnetic field of all known planets. Considerable progress has been made in our understanding of its characteristics and properties, thanks to the convergence of many different approaches and to the remarkable fact that surface rocks...... observations have been made possible from space, leading to the possibility of observing the Earth’s magnetic field in much more details than was previously possible. The progressive increase in computer power was also crucial, leading to advanced ways of handling and analyzing this considerable corpus of data...

  8. Cosmological Magnetic Fields from Primordial Helical Seeds

    CERN Document Server

    Sigl, G

    2002-01-01

    Most early Universe scenarios predict negligible magnetic fields on cosmological scales if they are unprocessed during subsequent expansion of the Universe. We present a new numerical treatment of the evolution of primordial fields and apply it to weakly helical seeds as they occur in certain early Universe scenarios. We find that initial helicities not much larger than the baryon to photon number can lead to fields of about 10^{-13} Gauss with coherence scales slightly below a kilo-parsec today.

  9. Magnetic Field Observations at Purcell, Oklahoma Field Campaign Report

    Energy Technology Data Exchange (ETDEWEB)

    Chi, P. J. [Univ. of California, Los Angeles, CA (United States); Gibson, J. P. [Univ. of Oklahoma, Norman, OK (United States)

    2017-05-01

    The campaign “Magnetic Field Observations at Purcell, Oklahoma” installed a ground-based magnetometer at Purcell’s U.S. Department of Energy (DOE) Atmospheric Radiation Measurement (ARM) Climate Research Facility boundary installation at the Kessler Atmospheric and Ecological Field Station, University of Oklahoma, to measure local magnetic field variations. It is a part of the nine stations of the Mid-continent MAgnetoseismic Chain (McMAC) placed as close to the 330° magnetic longitude as possible. This is the meridian in the world where land covers the greatest continuous range in magnetic latitude. Figure 1 shows the map of the magnetometer stations along the 330th magnetic meridian, including the Purcell (PCEL) station. The main scientific objective of the campaign is to detect the field line resonance (FLR) frequencies of the magnetic field line connected to the Purcell station. This magnetic field line extends from Purcell to the outer space at distances as far as 2 Earth radii (RE). To accurately identify FLR frequencies, however, simultaneous measurements at slightly different latitudes along the same meridian are necessary to allow the use of the cross-phase technique. This consideration explains the arrangement to operate magnetometers at the Americus (AMER) and Richardson (RICH) stations nearby. The measured resonant frequency can infer the plasma mass density along the field line through the method of normal-mode magnetoseismology. The magnetometer at the Purcell station can detect many other types of magnetic field fluctuations associated with the changes in the electric currents in the ionosphere and the magnetosphere, which by large are affected by the solar activity. In other words, the magnetic field data collected by this campaign are also useful for understanding space weather phenomena. The magnetometer was installed at Purcell’s ARM boundary facility in March 27, 2006. The construction of the triaxial fluxgate magnetometer used by the

  10. Can cytogenetics explain the possible association between exposure to extreme low-frequency magnetic fields and Alzheimer's disease?

    Science.gov (United States)

    Maes, Annemarie; Verschaeve, Luc

    2012-02-01

    Recently, a number of epidemiological studies have suggested that occupational as well as residential exposure to extreme low-frequency electromagnetic fields (ELF-EMFs) may be a risk factor for Alzheimer's disease. This is not proven yet and there are no known biological mechanisms to explain this alleged association. Alzheimer's disease is characterized by a number of events that have, at least partially, a genetic origin. In particular, trisomy of chromosomes 17 and 21 seems to be involved. Overall ELF-EMFs have not been identified as genotoxic agents, but there are some papers in the scientific literature that indicate that they may enhance the effects of agents that are known to induce mutations or tumors. There are also some indications that ELF-EMFs may induce aneuploïdy. This opens some perspectives for investigating the alleged association between ELF-EMFs and Alzheimer's. This paper reviews the possibility of a cytogenetic association between the electromagnetic fields and Alzheimer's disease.

  11. High-field magnetization in transuranium compound

    Energy Technology Data Exchange (ETDEWEB)

    Sugiyama, K. [Graduate School of Science, Osaka University, Toyonaka, Osaka 560-0043 (Japan) and KYOKUGEN, Osaka University, Osaka 560-8531 (Japan)]. E-mail: sugiyama@phys.sci.osaka-u.ac.jp; Nakashima, H. [Graduate School of Science, Osaka University, Toyonaka, Osaka 560-0043 (Japan); Aoki, D. [Institute of Material Research, Tohoku University, Oarai, Ibaraki 311-1313 (Japan); Ikeda, S. [Institute of Material Research, Tohoku University, Oarai, Ibaraki 311-1313 (Japan); Haga, Y. [Advanced Science and Research Centerer, JAEA, Tokai, Ibaraki 319-1195 (Japan); Yamamoto, E. [Advanced Science and Research Centerer, JAEA, Tokai, Ibaraki 319-1195 (Japan); Nakamura, A. [Advanced Science and Research Centerer, JAEA, Tokai, Ibaraki 319-1195 (Japan); Homma, Y. [Institute of Material Research, Tohoku University, Oarai, Ibaraki 311-1313 (Japan); Shiokawa, Y. [Institute of Material Research, Tohoku University, Oarai, Ibaraki 311-1313 (Japan); Kindo, K. [Institite of Solid State Physics, University of Tokyo, Kashiwanoha 5-1-5, Kashiwa, Chiba 277-8581 (Japan); Hagiwara, M. [KYOKUGEN, Osaka University, Osaka 560-8531 (Japan); Onuki, Y. [Graduate School of Science, Osaka University, Toyonaka, Osaka 560-0043 (Japan); Advanced Science and Research Centerer, JAEA, Tokai, Ibaraki 319-1195 (Japan)

    2007-03-15

    We measured the high-field magnetization up to 55T and constructed a magnetic phase diagram for a transuranium antiferromagnet NpRhGa{sub 5} with the tetragonal structure. The magnetization at 4.2K for H(parallel) [100] indicates a sharp metamagnetic transition with a step at H{sub c}=26T and saturates above H{sub s}=38T, reaching 0.43{mu}{sub B}/Np. An ordered moment of 0.96{mu}{sub B}/Np at zero field, which was determined from the neutron scattering experiment, is found to be reduced to 0.43{mu}{sub B}/Np at H{sub s}, together with an orientation of the magnetic moment from the (001) plane to the (100) plane.

  12. Mechanism of magnetic field effect in cryptochrome

    CERN Document Server

    Solov'yov, Ilia A

    2011-01-01

    Creatures as varied as mammals, fish, insects, reptiles, and migratory birds have an intriguing `sixth' sense that allows them to distinguish north from south by using the Earth's intrinsic magnetic field. Yet despite decades of study, the physical basis of this magnetic sense remains elusive. A likely mechanism is furnished by magnetically sensitive radical pair reactions occurring in the retina, the light-sensitive part of the eyes. A photoreceptor, cryptochrome, has been suggested to endow birds with magnetoreceptive abilities as the protein has been shown to exhibit the biophysical properties required for an animal magnetoreceptor to operate properly. Here, we propose a concrete light-driven reaction cycle in cryptochrome that lets a magnetic field influence the signaling state of the photoreceptor. The reaction cycle ties together transient absorption and electron-spin-resonance observations with known facts on avian magnetoreception. Our analysis establishes the feasibility of cryptochrome to act as a g...

  13. Health-Economics Analyses Applied to ELF Electric and Magnetic Fields.

    Science.gov (United States)

    Kandel, Shaiela; Swanson, John; Kheifets, Leeka

    2016-06-01

    Extremely low frequency electric and magnetic fields (ELF EMFs) are a common exposure for modern populations. The prevailing public-health protection paradigm is that quantitative exposure limits are based on the established acute effects, whereas the possible chronic effects are considered too uncertain for quantitative limits, but might justify precautionary measures. The choice of precautionary measures can be informed by a health-economics analysis (HEA). We consider four such analyses of precautionary measures that have been conducted at a national or state level in California, the Netherlands, the United Kingdom, and Israel. We describe the context of each analysis, examine how they deal with some of the more significant issues that arise, and present a comparison of the input parameters and assumptions used. The four HEAs are methodologically similar. The most significant qualitative choices that have to be made are what dose-response relationship to assume, what allowance if any to make for uncertainty, and, for a CBA only, what diseases to consider, and all four analyses made similar choices. These analyses suggest that, on the assumptions made, there are some low-cost measures, such as rephasing, that can be applied to transmission in some circumstances and that can be justifiable in cost-benefit terms, but that higher cost measures, such as undergrounding, become unjustifiable. Of the four HEAs, those in the United Kingdom and Israel were influential in determining the country's EMF policy. In California and Netherlands, the HEA may well have informed the debate, but the policy chosen did not stem directly from the HEA.

  14. Magnetic Field Effects on Plasma Plumes

    Science.gov (United States)

    Ebersohn, F.; Shebalin, J.; Girimaji, S.; Staack, D.

    2012-01-01

    Here, we will discuss our numerical studies of plasma jets and loops, of basic interest for plasma propulsion and plasma astrophysics. Space plasma propulsion systems require strong guiding magnetic fields known as magnetic nozzles to control plasma flow and produce thrust. Propulsion methods currently being developed that require magnetic nozzles include the VAriable Specific Impulse Magnetoplasma Rocket (VASIMR) [1] and magnetoplasmadynamic thrusters. Magnetic nozzles are functionally similar to de Laval nozzles, but are inherently more complex due to electromagnetic field interactions. The two crucial physical phenomenon are thrust production and plasma detachment. Thrust production encompasses the energy conversion within the nozzle and momentum transfer to a spacecraft. Plasma detachment through magnetic reconnection addresses the problem of the fluid separating efficiently from the magnetic field lines to produce maximum thrust. Plasma jets similar to those of VASIMR will be studied with particular interest in dual jet configurations, which begin as a plasma loops between two nozzles. This research strives to fulfill a need for computational study of these systems and should culminate with a greater understanding of the crucial physics of magnetic nozzles with dual jet plasma thrusters, as well as astrophysics problems such as magnetic reconnection and dynamics of coronal loops.[2] To study this problem a novel, hybrid kinetic theory and single fluid magnetohydrodynamic (MHD) solver known as the Magneto-Gas Kinetic Method is used.[3] The solver is comprised of a "hydrodynamic" portion based on the Gas Kinetic Method and a "magnetic" portion that accounts for the electromagnetic behaviour of the fluid through source terms based on the resistive MHD equations. This method is being further developed to include additional physics such as the Hall effect. Here, we will discuss the current level of code development, as well as numerical simulation results

  15. MAGNETIC FIELDS IN EARLY PROTOSTELLAR DISK FORMATION

    Energy Technology Data Exchange (ETDEWEB)

    González-Casanova, Diego F.; Lazarian, Alexander [Astronomy Department, University of Wisconsin-Madison, 475 North Charter Street, Madison, WI 53706-1582 (United States); Santos-Lima, Reinaldo, E-mail: casanova@astro.wisc.edu [Instituto de Astronomia, Geofísica e Ciências Atmosféricas, Universidade de São Paulo, R. do Matão, 1226, São Paulo, SP 05508-090 (Brazil)

    2016-03-10

    We consider formation of accretion disks from a realistically turbulent molecular gas using 3D MHD simulations. In particular, we analyze the effect of the fast turbulent reconnection described by the Lazarian and Vishniac model for the removal of magnetic flux from a disk. With our numerical simulations we demonstrate how the fast reconnection enables protostellar disk formation resolving the so-called “magnetic braking catastrophe.” In particular, we provide a detailed study of the dynamics of a 0.5 M{sub ⊙} protostar and the formation of its disk for up to several thousands years. We measure the evolution of the mass, angular momentum, magnetic field, and turbulence around the star. We consider effects of two processes that strongly affect the magnetic transfer of angular momentum, both of which are based on turbulent reconnection: the first, “reconnection diffusion,” removes the magnetic flux from the disk; the other involves the change of the magnetic field's topology, but does not change the absolute value of the magnetic flux through the disk. We demonstrate that for the first mechanism, turbulence causes a magnetic flux transport outward from the inner disk to the ambient medium, thus decreasing the coupling of the disk to the ambient material. A similar effect is achieved through the change of the magnetic field's topology from a split monopole configuration to a dipole configuration. We explore how both mechanisms prevent the catastrophic loss of disk angular momentum and compare both above turbulent reconnection mechanisms with alternative mechanisms from the literature.

  16. Sintering of Soft Magnetic Material under Microwave Magnetic Field

    Directory of Open Access Journals (Sweden)

    Sadatsugu Takayama

    2012-01-01

    Full Text Available We have developed a simple process for sintering of soft magnetization materials using microwave sintering. The saturated magnetization (Ms of sintered magnetite was 85.6 emu/g, which was as high as 95% of magnetite before heating (90.4 emu/g. On the other hand, the averaged remanence (Mr and coercivity (Hc of the magnetite after heating were 0.17 emu/g and 1.12 Oe under measuring limit of SQUID, respectively. For the sintering process of soft magnetic materials, magnetic fields of microwave have been performed in nitrogen atmosphere. Therefore, a microwave single-mode system operating at a frequency of 2.45 GHz and with a maximum power level of 1.5 kW was used. We can sinter the good soft magnetic material in microwave magnetic field. The sample shrank to 82% theoretical density (TD from 45%TD of green body. The sintered sample was observed the microstructure by TEM and the crystal size was estimated the approximate average size is 10 nm.

  17. Magnetic Linear Birefringence Measurements Using Pulsed Fields

    CERN Document Server

    Berceau, Paul; Battesti, Remy; Rizzo, Carlo

    2011-01-01

    In this paper we present the accomplishment of the further step towards the vacuum magnetic birefringence measurement based on pulsed fields. After describing our BMV experiment, we report the calibration of our apparatus with nitrogen gas and we discuss the precision of our measurement giving a detailed error budget. Our best present vacuum sensitivity is 2.1x 10^-19 T^-2 per 5 ms magnetic pulse. We finally discuss the perspectives to reach our final goal.

  18. Magnetic Field and Force Calculations for ATLAS Asymmetrical Structure

    CERN Document Server

    Nessi, Marzio

    2001-01-01

    Magnetic field distortion in the assymetrical ATLAS structure are calculated. Magnetic forces in the system are estimated. 3D magnetic field simulation by the Opera3D code for symmetrical and asymmetrical systems is used.

  19. High magnetic field magnetization of a new triangular lattice antiferromagnet

    Energy Technology Data Exchange (ETDEWEB)

    Zhou, H. D. [Univ. of Tennessee, Knoxville, TN (United States); Los Alamos National Lab. (LANL), Los Alamos, NM (United States). National High Magnetic Field Lab. (MagLab); Stritzinger, Laurel Elaine Winter [Los Alamos National Lab. (LANL), Los Alamos, NM (United States); Harrison, Neil [Los Alamos National Lab. (LANL), Los Alamos, NM (United States)

    2017-03-23

    In CsV(MoO4)2, the magnetic V3+ ions with octahedral oxygen-coordination form a geometrically frustrated triangular lattice. So fare, there is no magnetic properties reported on it. Recently, we successfully grew single crystals of CsV(MoO4)2 by using flux method. The susceptibility shows a sharp drop around 24 K, representing a long range magnetic ordering. To understand the physical properties of this new triangular lattice antiferromagnet (TLAF), we pursued high field magnetization measurements to answer two questions: (i) what is the saturation field, which will be very useful to calculate the exchange interaction of the system? (ii) Will it exhibit spin state transition, such as the up up down phase with 1/3-saturation moment as other TLAFs? Recently, we performed VSM measurements in Cell 8, Tallahassee, NHMFL, the results show that the magnetization reaches 0.38 MuB at 34 T, which is just 19% of the full moment of 2 MuB for V3+ (3d2) ions. Apparently we need higher field to reach 1/3 value or full moment.

  20. Magnetic fields in early-type stars

    CERN Document Server

    Grunhut, Jason H

    2015-01-01

    For several decades we have been cognizant of the presence of magnetic fields in early-type stars, but our understanding of their magnetic properties has recently (over the last decade) expanded due to the new generation of high-resolution spectropolarimeters (ESPaDOnS at CFHT, Narval at TBL, HARPSpol at ESO). The most detailed surface magnetic field maps of intermediate-mass stars have been obtained through Doppler imaging techniques, allowing us to probe the small-scale structure of these stars. Thanks to the effort of large programmes (e.g. the MiMeS project), we have, for the first time, addressed key issues regarding our understanding of the magnetic properties of massive (M > 8 M_sun) stars, whose magnetic fields were only first detected about fifteen years ago. In this proceedings article we review the spectropolarimetric observations and statistics derived in recent years that have formed our general understanding of stellar magnetism in early-type stars. We also discuss how these observations have fu...

  1. Magnetic translation algebra with or without magnetic field

    Science.gov (United States)

    Mudry, Christopher; Chamon, Claudio

    2013-03-01

    The magnetic translation algebra plays an important role in the quantum Hall effect. Murthy and Shankar have shown how to realize this algebra using fermionic bilinears defined on a two-dimensional square lattice. We show that, in any dimension d, it is always possible to close the magnetic translation algebra using fermionic bilinears, be it in the continuum or on the lattice. We also show that these generators are complete in even, but not odd, dimensions, in the sense that any fermionic Hamiltonian in even dimensions that conserves particle number can be represented in terms of the generators of this algebra, whether or not time-reversal symmetry is broken. As an example, we reproduce the f-sum rule of interacting electrons at vanishing magnetic field using this representation. We also show that interactions can significantly change the bare band width of lattice Hamiltonians when represented in terms of the generators of the magnetic translation algebra.

  2. Effect of magnetic field in malaria diagnosis using magnetic nanoparticles

    Science.gov (United States)

    Liu, Quan; Yuen, Clement

    2011-07-01

    The current gold standard method of Malaria diagnosis relies on the blood smears examination. The method is laborintensive, time consuming and requires the expertise for data interpretation. In contrast, Raman scattering from a metabolic byproduct of the malaria parasite (Hemozoin) shows the possibility of rapid and objective diagnosis of malaria. However, hemozoin concentration is usually extremely low especially at the early stage of malaria infection, rendering weak Raman signal. In this work, we propose the sensitive detection of enriched β-hematin, whose spectroscopic properties are equivalent to hemozoin, based on surface enhanced Raman spectroscopy (SERS) by using magnetic nanoparticles. A few orders of magnitude enhancement in the Raman signal of β-hematin can be achieved using magnetic nanoparticles. Furthermore, the effect of magnetic field on SERS enhancement is investigated. Our result demonstrates the potential of SERS using magnetic nanoparticles in the effective detection of hemozoin for malaria diagnosis.

  3. Magnetic resonance signal moment determination using the Earth's magnetic field

    Science.gov (United States)

    Fridjonsson, E. O.; Creber, S. A.; Vrouwenvelder, J. S.; Johns, M. L.

    2015-03-01

    We demonstrate a method to manipulate magnetic resonance data such that the moments of the signal spatial distribution are readily accessible. Usually, magnetic resonance imaging relies on data acquired in so-called k-space which is subsequently Fourier transformed to render an image. Here, via analysis of the complex signal in the vicinity of the centre of k-space we are able to access the first three moments of the signal spatial distribution, ultimately in multiple directions. This is demonstrated for biofouling of a reverse osmosis (RO) membrane module, rendering unique information and an early warning of the onset of fouling. The analysis is particularly applicable for the use of mobile magnetic resonance spectrometers; here we demonstrate it using an Earth's magnetic field system.

  4. Magnetic resonance signal moment determination using the Earth's magnetic field

    KAUST Repository

    Fridjonsson, Einar Orn

    2015-03-01

    We demonstrate a method to manipulate magnetic resonance data such that the moments of the signal spatial distribution are readily accessible. Usually, magnetic resonance imaging relies on data acquired in so-called k-space which is subsequently Fourier transformed to render an image. Here, via analysis of the complex signal in the vicinity of the centre of k-space we are able to access the first three moments of the signal spatial distribution, ultimately in multiple directions. This is demonstrated for biofouling of a reverse osmosis (RO) membrane module, rendering unique information and an early warning of the onset of fouling. The analysis is particularly applicable for the use of mobile magnetic resonance spectrometers; here we demonstrate it using an Earth\\'s magnetic field system.

  5. The Drift of Dust Grains Induced by Transient Magnetic Field

    Institute of Scientific and Technical Information of China (English)

    华建军; 叶茂福; 王龙

    2003-01-01

    Our experiment shows that the dust grains, suspended on the edge of the sheath of a radio-frequency discharge, undergo a contraction when switching a vertical magnetic field on, and an expansion when switching the magnetic field off. We call this kind of magnetic field "transient magnetic field". A primary analysis is proposed for the phenomenon.

  6. High magnetic field ohmically decoupled non-contact technology

    Science.gov (United States)

    Wilgen, John [Oak Ridge, TN; Kisner, Roger [Knoxville, TN; Ludtka, Gerard [Oak Ridge, TN; Ludtka, Gail [Oak Ridge, TN; Jaramillo, Roger [Knoxville, TN

    2009-05-19

    Methods and apparatus are described for high magnetic field ohmically decoupled non-contact treatment of conductive materials in a high magnetic field. A method includes applying a high magnetic field to at least a portion of a conductive material; and applying an inductive magnetic field to at least a fraction of the conductive material to induce a surface current within the fraction of the conductive material, the surface current generating a substantially bi-directional force that defines a vibration. The high magnetic field and the inductive magnetic field are substantially confocal, the fraction of the conductive material is located within the portion of the conductive material and ohmic heating from the surface current is ohmically decoupled from the vibration. An apparatus includes a high magnetic field coil defining an applied high magnetic field; an inductive magnetic field coil coupled to the high magnetic field coil, the inductive magnetic field coil defining an applied inductive magnetic field; and a processing zone located within both the applied high magnetic field and the applied inductive magnetic field. The high magnetic field and the inductive magnetic field are substantially confocal, and ohmic heating of a conductive material located in the processing zone is ohmically decoupled from a vibration of the conductive material.

  7. CMB anisotropies from primordial inhomogeneous magnetic fields

    CERN Document Server

    Lewis, A

    2004-01-01

    Primordial inhomogeneous magnetic fields of the right strength can leave a signature on the CMB temperature anisotropy and polarization. Potentially observable contributions to polarization B-modes are generated by vorticity and gravitational waves sourced by the magnetic anisotropic stress. We compute the corresponding CMB transfer functions in detail including the effect of neutrinos. The shear rapidly causes the neutrino anisotropic stress to cancel the stress from the magnetic field, suppressing the production of gravitational waves and vorticity on super-horizon scales after neutrino decoupling. A significant large scale signal from tensor modes can only be produced before neutrino decoupling, and the actual amplitude is somewhat uncertain. Plausible values suggest primordial nearly scale invariant fields of ~ 10^(-10)G today may be observable from their large scale tensor anisotropy. They can be distinguished from primordial gravitational waves by their non-Gaussianity. Vector mode vorticity sources B-m...

  8. Solar Flare Magnetic Fields and Plasmas

    CERN Document Server

    Fisher, George

    2012-01-01

    This volume is devoted to the dynamics and diagnostics of solar magnetic fields and plasmas in the Sun’s atmosphere. Five broad areas of current research in Solar Physics are presented: (1) New techniques for incorporating radiation transfer effects into three-dimensional magnetohydrodynamic models of the solar interior and atmosphere, (2) The connection between observed radiation processes occurring during flares and the underlying flare energy release and transport mechanisms, (3) The global balance of forces and momenta that occur during flares, (4) The data-analysis and theoretical tools needed to understand and assimilate vector magnetogram observations and (5) Connecting flare and CME phenomena to the topological properties of the magnetic field in the Solar Atmosphere. The role of the Sun’s magnetic field is a major emphasis of this book, which was inspired by a workshop honoring Richard C. (Dick) Canfield.  Dick has been making profound contributions to these areas of research over a long and pro...

  9. Magnetic Catalysis in Graphene Effective Field Theory

    CERN Document Server

    DeTar, Carleton; Zafeiropoulos, Savvas

    2016-01-01

    We report on the first observation of magnetic catalysis at zero temperature in a fully nonperturbative simulation of the graphene effective field theory. Using lattice gauge theory, a nonperturbative analysis of the theory of strongly-interacting, massless, (2+1)-dimensional Dirac fermions in the presence of an external magnetic field is performed. We show that in the zero-temperature limit, a nonzero value for the chiral condensate is obtained which signals the spontaneous breaking of chiral symmetry. This result implies a nonzero value for the dynamical mass of the Dirac quasiparticle. This in turn has been posited to account for the quantum-Hall plateaus that are observed at large magnetic fields.

  10. Manifestations of the Galactic Center Magnetic Field

    CERN Document Server

    Morris, Mark R

    2014-01-01

    Several independent lines of evidence reveal that a relatively strong and highly ordered magnetic field is present throughout the Galaxy's central molecular zone (CMZ). The field within dense clouds of the central molecular zone is predominantly parallel to the Galactic plane, probably as a result of the strong tidal shear in that region. A second magnetic field system is present outside of clouds, manifested primarily by a population of vertical, synchrotron-emitting filamentary features aligned with the field. Whether or not the strong vertical field is uniform throughout the CMZ remains undetermined, but is a key central issue for the overall energetics and the impact of the field on the Galactic center arena. The interactions between the two field systems are considered, as they are likely to drive some of the activity within the CMZ. As a proxy for other gas-rich galaxies in the local group and beyond, the Galactic center region reveals that magnetic fields are likely to be an important diagnostic, if no...

  11. Holographic fermions in external magnetic fields

    CERN Document Server

    Gubankova, E; Cubrovic, M; Schalm, K; Schijven, P; Zaanen, J

    2011-01-01

    We study the Fermi level structure of 2+1-dimensional strongly interacting electron systems in external magnetic field using the AdS/CFT correspondence. The gravity dual of a finite density fermion system is a Dirac field in the background of the dyonic AdS-Reissner-Nordstrom black hole. In the probe limit the magnetic system can be reduced to the non-magnetic one, with Landau-quantized momenta and rescaled thermodynamical variables. We find that at strong enough magnetic fields, the Fermi surface vanishes and the quasiparticle is lost either through a crossover to conformal regime or through a phase transition to an unstable Fermi surface. In the latter case, the vanishing Fermi velocity at the critical magnetic field triggers the non-Fermi liquid regime with unstable quasiparticles and a change in transport properties of the system. We associate it with a metal-"strange metal" phase transition. Next we compute compute the DC Hall and longitudinal conductivities using the gravity-dressed fermion propagators....

  12. Magnetic field homogeneity for neutron EDM experiment

    Science.gov (United States)

    Anderson, Melissa

    2016-09-01

    The neutron electric dipole moment (nEDM) is an observable which, if non-zero, would violate time-reversal symmetry, and thereby charge-parity symmetry of nature. New sources of CP violation beyond those found in the standard model of particle physics are already tightly constrained by nEDM measurements. Our future nEDM experiment seeks to improve the precision on the nEDM by a factor of 30, using a new ultracold neutron (UCN) source that is being constructed at TRIUMF. Systematic errors in the nEDM experiment are driven by magnetic field inhomogeneity and instability. The goal field inhomogeneity averaged over the experimental measurement cell (order of 1 m) is 1 nT/m, at a total magnetic field of 1 microTesla. This equates to roughly 10-3 homogeneity. A particularly challenging aspect of the design problem is that nearby magnetic materials will also affect the magnetic inhomogeneity, and this must be taken into account in completing the design. This poster will present the design methodology and status of the main coil for the experiment where we use FEA software (COMSOL) to simulate and analyze the magnetic field. Natural Sciences and Engineering Research Council.

  13. Building Magnetic Fields in White Dwarfs

    Science.gov (United States)

    Kohler, Susanna

    2017-03-01

    White dwarfs, the compact remnants left over at the end of low- and medium-mass stars lifetimes, are often found to have magnetic fields with strengths ranging from thousands to billions of times that of Earth. But how do these fields form?MultiplePossibilitiesAround 1020% of white dwarfs have been observed to have measurable magnetic fields with a wide range of strengths. There are several theories as to how these fields might be generated:The fields are fossil.The original weak magnetic fields of the progenitor stars were amplified as the stars cores evolved into white dwarfs.The fields are caused by binary interactions.White dwarfs that formed in the merger of a binary pair might have had a magnetic field amplified as a result of a dynamo that was generated during the merger.The fields were produced by some other internal physical mechanism during the cooling of the white dwarf itself.In a recent publication, a team of authors led by Jordi Isern (Institute of Space Sciences, CSIC, and Institute for Space Studies of Catalonia, Spain) explored this third possibility.Dynamos from CrystallizationThe inner and outer boundaries of the convective mantle of carbon/oxygen white dwarfs of two different masses (top vs. bottom panel) as a function of luminosity. As the white dwarf cools (toward the right), the mantle grows thinner due to the crystallization and settling of material. [Isern et al. 2017]As white dwarfs have no nuclear fusion at their centers, they simply radiate heat and gradually cool over time. The structure of the white dwarf undergoes an interesting change as it cools, however: though the object begins as a fluid composed primarily of an ionized mixture of carbon and oxygen (and a few minor species like nickel and iron), it gradually crystallizes as its temperature drops.The crystallized phase of the white dwarf is oxygen-rich which is denser than the liquid, so the crystallized material sinks to the center of the dwarf as it solidifies. As a result, the

  14. [National system of protection against electromagnetic fields 0 Hz-300 GHz in the light of current legal regulations].

    Science.gov (United States)

    Aniołczyk, Halina

    2006-01-01

    Exposure to electromagnetic fields (EMF) occurs when man is exposed to the effect of electric, magnetic and electromagnetic fields and contact currents different from those resulting from physiological processes in the organism or other natural phenomena. In Poland, the system of protection against EMF has been functioning for over 35 years. In 2001, when the Minister of Labor and Social Policy issued the regulation introducing the maximum admissible intensities (MAI) for electromagnetic fields and radiation within the range of 0 Hz-300 GHz, the system was directed mainly towards evaluation of exposure to EMF occurring in the occupational environment. The system is linked via MAI values with human protection in the natural environment. In this paper, the background, principles and the range of the national system of protection against EMF and its monitoring are presented. The project of implementation of EU directives, following Poland's accession to the European Union is also discussed.

  15. Evolution of Primordial Magnetic Fields: From Generation Till Today

    CERN Document Server

    Kahniashvili, Tina; Tevzadze, Alexander G

    2015-01-01

    In this presentation we summarize our previous results concerning the evolution of primordial magnetic fields with and without helicity during the expansion of the Universe. We address different magnetogenesis scenarios such as inflation, electroweak and QCD phase transitions magnetogenesis. A high Reynolds number in the early Universe ensures strong coupling between magnetic field and fluid motions. After generation the subsequent dynamics of the magnetic field is governed by decaying hydromagnetic turbulence. We claim that primordial magnetic fields can be considered as a seeds for observed magnetic fields in galaxies and clusters. Magnetic field strength bounds obtained in our analysis are consistent with the upper and lower limits of extragalactic magnetic fields.

  16. Reduction of a Ship's Magnetic Field Signatures

    CERN Document Server

    Holmes, John

    2008-01-01

    Decreasing the magnetic field signature of a naval vessel will reduce its susceptibility to detonating naval influence mines and the probability of a submarine being detected by underwater barriers and maritime patrol aircraft. Both passive and active techniques for reducing the magnetic signatures produced by a vessel's ferromagnetism, roll-induced eddy currents, corrosion-related sources, and stray fields are presented. Mathematical models of simple hull shapes are used to predict the levels of signature reduction that might be achieved through the use of alternate construction materials. Al

  17. Magnetic field processing of inorganic polymers

    Energy Technology Data Exchange (ETDEWEB)

    Kunerth, D.C.; Peterson, E.S. [Idaho National Engineering Laboratory, Idaho Falls, ID (United States)

    1995-05-01

    The purpose of this project is to investigate, understand, and demonstrate the use of magnetic field processing (MFP) to modify the properties of inorganic-based polymers and to develop the basic technical knowledge required for industrial implementation. Polyphosphazene membranes for chemical separation applications are being emphasized by this project. Previous work demonstrated that magnetic fields, appropriately applied during processing, can be used to beneficially modify membrane morphology. MFP membranes have significantly increased flux capabilities while maintaining the same chemical selectivity as the unprocessed membranes.

  18. In situ characterization of undulator magnetic fields.

    Science.gov (United States)

    Moreno, Thierry; Otero, Edwige; Ohresser, Philippe

    2012-03-01

    A new in situ method is proposed to characterize the peak magnetic fields of undulator sources. The X-ray beam emitted by the HU52 Apple-2 undulator of the DEIMOS beamline of the SOLEIL synchrotron is analyzed using the Bragg diffraction of a Si(111) crystal. Measurements over the undulator gap range in linear horizontal polarization are compared with simulations in order to rebuild the Halbach function linking the undulator gaps to their peak magnetic fields. The method presented also allows information about the electron beam to be obtained.

  19. Effects of W-CDMA 1950 MHz EMF emitted by mobile phones on regional cerebral blood flow in humans.

    Science.gov (United States)

    Mizuno, Yoko; Moriguchi, Yoshiya; Hikage, Takashi; Terao, Yasuo; Ohnishi, Takashi; Nojima, Toshio; Ugawa, Yoshikazu

    2009-10-01

    Use of the third generation mobile phone system is increasing worldwide. This is the first study to investigate the effects of the third generation system on regional cerebral blood flow (rCBF) in humans. We compared effects of the electromagnetic field (EMF) emitted from the Wideband Code Division Multiple Access (W-CDMA) cellular system versus sham control exposure on rCBF in humans. Nine healthy male volunteers participated in this study. Positron emission tomography (PET) scans were obtained before, during, and after unilateral 30 min EMF exposure. The subtraction analysis revealed no significant rCBF changes caused by the EMF conditions compared with the sham exposure, suggesting that EMF emitted by a third generation mobile phone does not affect rCBF in humans.

  20. Magnetic fields in primordial accretion disks

    CERN Document Server

    Latif, Muhammad A

    2016-01-01

    Magnetic fields are considered as a vital ingredient of contemporary star formation, and may have been important during the formation of the first stars in the presence of an efficient amplification mechanism. Initial seed fields are provided via plasma fluctuations, and are subsequently amplified by the small-scale dynamo, leading to a strong tangled magnetic field. Here we explore how the magnetic field provided by the small-scale dynamo is further amplified via the $\\alpha-\\Omega$ dynamo in a protostellar disk and assess its implications. For this purpose, we consider two characteristic cases, a typical Pop.~III star with $10$~M$_\\odot$ and an accretion rate of $10^{-3}$~M$_\\odot$~yr$^{-1}$, and a supermassive star with $10^5$~M$_\\odot$ and an accretion rate of $10^{-1}$~M$_\\odot$~yr$^{-1}$. For the $10$~M$_\\odot$ Pop.~III star, we find that coherent magnetic fields can be produced on scales of at least $100$~AU, which are sufficient to drive a jet with a luminosity of $100$~L$_\\odot$ and a mass outflow ra...

  1. High magnetic fields in the USA

    Science.gov (United States)

    Campbell, Laurence J.; Parkin, Don E.; Crow, Jack E.; Schneider-Muntau, Hans J.; Sullivan, Neil S.

    During the past thirty years research using high magnetic fields has technically evolved in the manner, but not the magnitude, of the so-called big science areas of particle physics, plasma physics, neutron scattering, synchrotron light scattering, and astronomy. Starting from the laboratories of individual researchers it moved to a few larger universities, then to centralized national facilities with research and maintenance staffs, and, finally, to joint international ventures to build unique facilities, as illustrated by the subject of this conference. To better understand the nature of this type of research and its societal justification it is helpful to compare it, in general terms, with the aforementioned big-science fields. High magnetic field research differs from particle physics, plasma physics, and astronomy in three respects: (1) it is generic research that cuts across a wide range of scientific disciplines in physics, chemistry, biology, medicine, and engineering; (2) it studies materials and processes that are relevant for a variety of technological applications and it gives insight into biological processes; (3) it has produced, at least, comparably significant results with incomparably smaller resources. Unlike neutron and synchrotron light scattering, which probe matter, high magnetic fields change the thermodynamic state of matter. This change of state is fundamental and independent of other state variables, such as pressure and temperature. After the magnetic field is applied, various techniques are then used to study the new state.

  2. Magnetic field exposure of commercial airline pilots.

    Science.gov (United States)

    Hood; Nicholas; Butler; Lackland; Hoel; Mohr

    2000-10-01

    PURPOSE: Airline pilots are exposed to magnetic fields generated by the aircraft's electrical and electronic systems. The purpose of this study was to directly measure the flight deck magnetic fields to which commercial airline pilots are exposed when flying on different aircraft types over a 75-hour flight-duty month.METHODS: Magentic field measurements were taken using personal dosimeters capable of measuring magnetic fields in the 40-800 Hz frequency range. Dosimeters were carried by either the Captain or the First Officer on Boeing 737/200, Boeing 747/400, Boeing 767/300ER, and Airbus 320 aircraft. The data were analyzed by aircraft type, with statistics based on block hours. Block hours begin when the aircraft departs the gate prior to take off and end when the aircraft returns to the gate after landing.RESULTS: Approximately 1008 block hours were recorded at a sampling rate of 3 seconds. Total block time exposure to the pilots ranged from a harmonic geometric mean of 6.7 milliGauss (mG) for the Boeing 767/300ER to 12.7 mG for the Boeing 737/200.CONCLUSIONS: Measured flight deck magnetic field levels were substantially above the 0.8 to 1 mG level typically found in the home or office and suggest the need for further study to evaluate potential health effects of long-term exposure.

  3. Magnetic resonance imaging without field cycling at less than earth's magnetic field

    Science.gov (United States)

    Lee, Seong-Joo; Shim, Jeong Hyun; Kim, Kiwoong; Yu, Kwon Kyu; Hwang, Seong-min

    2015-03-01

    A strong pre-polarization field, usually tenths of a milli-tesla in magnitude, is used to increase the signal-to-noise ratio in ordinary superconducting quantum interference device-based nuclear magnetic resonance/magnetic resonance imaging experiments. Here, we introduce an experimental approach using two techniques to remove the need for the pre-polarization field. A dynamic nuclear polarization (DNP) technique enables us to measure an enhanced resonance signal. In combination with a π / 2 pulse to avoid the Bloch-Siegert effect in a micro-tesla field, we obtained an enhanced magnetic resonance image by using DNP technique with a 34.5 μT static external magnetic field without field cycling. In this approach, the problems of eddy current and flux trapping in the superconducting pickup coil, both due to the strong pre-polarization field, become negligible.

  4. Synchronization of magnetic dipole rotation in an ac magnetic field

    Energy Technology Data Exchange (ETDEWEB)

    Belovs, M; Cebers, A, E-mail: aceb@tesla.sal.lv [University of Latvia, Zellu-8, Riga, LV-1002 (Latvia)

    2011-07-22

    The synchronization of the rotation of magnetic dipoles due to weak dipolar interactions is studied. The set of equations is analyzed by the time averaging technique. It is found that dipoles synchronously oscillate at low applied fields and rotate synchronously at large applied fields. The mean angular velocity of synchronous rotation increases with the field strength and reaches a constant value equal to the angular frequency of the field above the critical value of the field strength. The critical value of the field strength above which the synchronous rotation takes place can be calculated from dimensionless parameters using a model derived from first principles by others. The values thus obtained are in good agreement with the values we obtain from a numerical simulation. Thus, we may conclude that the liquid flow observed in these systems may be caused by synchronized rotations of the dipoles.

  5. Spontaneous magnetic fluctuations in ultrathin magnetic films at zero field

    Science.gov (United States)

    Balk, Andrew; Unguris, John

    2014-03-01

    We use magneto optical Kerr effect (MOKE) microscopy to observe room temperature, zero field magnetic fluctuations in perpendicularly magnetized cobalt films at thicknesses near the in-plane to out-of-plane spin reorientation transition. The magnetic behavior of our films resembles that of collections of superparamagnetic particles, in that globally they exhibit zero net moment, while local areas continually undergo thermal magnetic fluctuations between saturated states of the maze-like domain structure. Unlike superparamagnetic particles, the fluctuations are not constrained by particle boundaries and thus are subject to both exchange and magnetostatic interactions. Due to this we can observe temporal and spatial correlations in the fluctuations. Furthermore, we observe that the fluctuations obey dynamics distinct from field-driven Barkhausen jumps. We also determine scaling exponents of the fluctuations, finding their areas follow a power law distribution (t =1.5), and their temporal noise power spectrum is close to 1/f (a = 1.04). Based on these observations, we discuss these films as possible candidates for exhibiting magnetic self-organized criticality.

  6. Magnetic-field-compensation optical vector magnetometer.

    Science.gov (United States)

    Papoyan, Aram; Shmavonyan, Svetlana; Khanbekyan, Alen; Khanbekyan, Karen; Marinelli, Carmela; Mariotti, Emilio

    2016-02-01

    A concept for an optical magnetometer used for the measurement of magnitude and direction of a magnetic field (B-field) in two orthogonal directions is developed based on double scanning of a B-field to compensate the measured field to zero value, which is monitored by a resonant magneto-optical process in an unshielded atomic vapor cell. Implementation of the technique using the nonlinear Hanle effect on the D2 line of rubidium demonstrates viability and efficiency of the proposed concept. The ways to enhance characteristics of the suggested technique and optimize its performance, as well as the possible extension to three-axis magnetometry, are discussed.

  7. Anchoring Magnetic Field in Turbulent Molecular Clouds

    CERN Document Server

    Li, Hua-bai; Goodman, Alyssa; Hildebrand, Roger; Novak, Giles

    2009-01-01

    One of the key problems in star formation research is to determine the role of magnetic fields. Starting from the atomic inter-cloud medium (ICM) which has density nH ~ 1 per cubic cm, gas must accumulate from a volume several hundred pc across in order to form a typical molecular cloud. Star formation usually occurs in cloud cores, which have linear sizes below 1 pc and densities nH2 > 10^5 per cubic cm. With current technologies, it is hard to probe magnetic fields at scales lying between the accumulation length and the size of cloud cores, a range corresponds to many levels of turbulent eddy cascade, and many orders of magnitude of density amplification. For field directions detected from the two extremes, however, we show here that a significant correlation is found. Comparing this result with molecular cloud simulations, only the sub-Alfvenic cases result in field orientations consistent with our observations.

  8. Short-term exposure to 50 Hz ELF-EMF alters the cisplatin-induced oxidative response in AT478 murine squamous cell carcinoma cells.

    Science.gov (United States)

    Bułdak, Rafał Jakub; Polaniak, Renata; Bułdak, Lukasz; Zwirska-Korczala, Krystyna; Skonieczna, Magdalena; Monsiol, Aleksandra; Kukla, Michał; Duława-Bułdak, Anna; Birkner, Ewa

    2012-12-01

    The aim of this study was to assess the influence of cisplatin and an extremely low frequency electromagnetic field (ELF-EMF) on antioxidant enzyme activity and the lipid peroxidation ratio, as well as the level of DNA damage and reactive oxygen species (ROS) production in AT478 carcinoma cells. Cells were cultured for 24 and 72 h in culture medium with cisplatin. Additionally, the cells were irradiated with 50 Hz/1 mT ELF-EMF for 16 min using a solenoid as a source of the ELF-EMF. The amount of ROS, superoxide dismutase (SOD) isoenzyme activity, glutathione peroxidase (GSH-Px) activity, DNA damage, and malondialdehyde (MDA) levels were assessed. Cells that were exposed to cisplatin exhibited a significant increase in ROS and antioxidant enzyme activity. The addition of ELF-EMF exposure to cisplatin treatment resulted in decreased ROS levels and antioxidant enzyme activity. A significant reduction in MDA concentrations was observed in all of the study groups, with the greatest decrease associated with treatment by both cisplatin and ELF-EMF. Cisplatin induced the most severe DNA damage; however, when cells were also irradiated with ELF-EMF, less DNA damage occurred. Exposure to ELF-EMF alone resulted in an increase in DNA damage compared to control cells. ELF-EMF lessened the effects of oxidative stress and DNA damage that were induced by cisplatin; however, ELF-EMF alone was a mild oxidative stressor and DNA damage inducer. We speculate that ELF-EMF exerts differential effects depending on the exogenous conditions. This information may be of value for appraising the pathophysiologic consequences of exposure to ELF-EMF.

  9. Magnetic Field Twisting by Intergranular Downdrafts

    Science.gov (United States)

    Taroyan, Youra; Williams, Thomas

    2016-10-01

    The interaction of an intergranular downdraft with an embedded vertical magnetic field is examined. It is demonstrated that the downdraft may couple to small magnetic twists leading to an instability. The descending plasma exponentially amplifies the magnetic twists when it decelerates with depth due to increasing density. Most efficient amplification is found in the vicinity of the level, where the kinetic energy density of the downdraft reaches equipartition with the magnetic energy density. Continual extraction of energy from the decelerating plasma and growth in the total azimuthal energy occurs as a consequence of the wave-flow coupling along the downdraft. The presented mechanism may drive vortices and torsional motions that have been detected between granules and in simulations of magnetoconvection.

  10. The nucleon in a periodic magnetic field

    CERN Document Server

    Agadjanov, Andria; Rusetsky, Akaki

    2016-01-01

    The energy shift of a nucleon in a static periodic magnetic field is evaluated at second order in the external field strength in perturbation theory. It is shown that the measurement of this energy shift on the lattice allows one to determine the unknown subtraction function in the forward doubly-virtual Compton scattering amplitude. The limits of applicability of the obtained formula for the energy shift are discussed.

  11. Anomaly induced effects in a magnetic field

    OpenAIRE

    Antoniadis, Ignatios; Boyarsky, Alexey; Ruchayskiy, Oleg

    2007-01-01

    We consider a modification of electrodynamics by an additional light massive vector field, interacting with the photon via Chern-Simons-like coupling. This theory predicts observable effects for the experiments studying the propagation of light in an external magnetic field, very similar to those, predicted by theories of axion and axion-like particles. We discuss a possible microscopic origin of this theory from a theory with non-trivial gauge anomaly cancellation between massive and light p...

  12. Magnetic field influence on paramecium motility

    Energy Technology Data Exchange (ETDEWEB)

    Rosen, M.F.; Rosen, A.D. (State Univ. of New York, Stony Brook (USA))

    1990-01-01

    The influence of a moderately intense static magnetic field on movement patterns of free swimming Paramecium was studied. When exposed to fields of 0.126 T, these ciliated protozoa exhibited significant reduction in velocity as well as a disorganization of movement pattern. It is suggested that these findings may be explained on the basis of alteration in function of ion specific channels within the cell membrane.

  13. Pulsed-field magnetometry for rock magnetism

    Science.gov (United States)

    Kodama, Kazuto

    2015-07-01

    An improved method is proposed for measuring dynamic magnetizations of bulk volcanic rock samples induced by a pulsed-field of 0.7 T and a duration of 10 ms. The transient magnetization is measured by a sensing system that consists of a pair of inductive differential coils, an analog preamplifier and integrator, and a high-speed digital storage scope. The system was calibrated using a paramagnetic salt (Gd2O3) and was tested to different kinds of volcanic rocks with their magnetic properties well-documented previously. The results were comparable with those measured by a quasi-static method using a vibrating sample magnetometer, although there were small discrepancies in hysteresis parameters suggesting the time-dependence of the magnetic properties. The proposed system provides not only the magnetization over the short interval of a pulse but also the rapid (~3 ms) exponential decay after a pulse. The decay time constant was different among the samples under study, indicating the variations of their magnetic relaxation time. Although the present system is not sensitive enough to characterize varieties of natural samples including sediments, it has the potential as a versatile and convenient tool for rock magnetism.

  14. Laboratory Measurements of Astrophysical Magnetic Fields

    Science.gov (United States)

    Murphy, C. D.; Miniati, F.; Edwards, M.; Mithen, J.; Bell, A. R.; Constantin, C.; Everson, E.; Schaeffer, D.; Niemann, C.; Ravasio, A.; Brambrink, E.; Benuzzi-Mounaix, A.; Koenig, M.; Gregory, C.; Woolsey, N.; Park, H.-S.; Remington, B.; Ryutov, D.; Bingham, R.; Gargate, L.; Spitkovsky, A.; Gregori, G.

    2010-11-01

    It has been proposed that high Mach number collisionless shocks propagating in an initially unmagnetized plasma play a major role in the magnetization of large scale structures in the Universe. A detailed study of the experimental configuration necessary to scale such environments down to laboratory dimensions will be presented. We will show initial results from preliminary experiments conducted at the Phoenix laser (UCLA) and the LULI laser (Ecole Polytechnique) where collisionless shocks are generated by the expansion of exploding foils driven by energetic laser beams. The time evolution of the magnetic field is probed with induction coils placed at 10 cm from the laser focus. We will discuss various mechanisms of magnetic field generation and compare them with the experimental results.

  15. Magnetic fields and density functional theory

    Energy Technology Data Exchange (ETDEWEB)

    Salsbury Jr., Freddie [Univ. of California, Berkeley, CA (United States)

    1999-02-01

    A major focus of this dissertation is the development of functionals for the magnetic susceptibility and the chemical shielding within the context of magnetic field density functional theory (BDFT). These functionals depend on the electron density in the absence of the field, which is unlike any other treatment of these responses. There have been several advances made within this theory. The first of which is the development of local density functionals for chemical shieldings and magnetic susceptibilities. There are the first such functionals ever proposed. These parameters have been studied by constructing functionals for the current density and then using the Biot-Savart equations to obtain the responses. In order to examine the advantages and disadvantages of the local functionals, they were tested numerically on some small molecules.

  16. Heavy meson spectroscopy under strong magnetic field

    CERN Document Server

    Yoshida, Tetsuya

    2016-01-01

    Spectra of the neutral heavy mesons, $\\eta_c(1S,2S)$, $J/psi$, $\\psi(2S)$, $\\eta_b(1S,2S,3S)$, $\\Upsilon(1S,2S,3S)$, $D$, $D^\\ast$, $B$, $B^\\ast$, $B_s$ and $B_s^\\ast$, in a homogeneous magnetic field are analyzed in a potential model of constituent quarks. To obtain anisotropic wave functions and the corresponding eigenvalues, the cylindrical Gaussian expansion method is applied, where the wave functions for transverse and longitudinal directions in the cylindrical coordinate are expanded by the Gaussian bases separately. Energy level structures in the wide range of magnetic field are obtained and the deformation of the wave functions is shown, which reflects effects of the spin mixing, the Zeeman splitting and quark Landau levels. The contribution from the magnetic catalysis in heavy-light mesons is discussed as a change of the light constituent quark mass.

  17. Magnetic Fields in the Solar Convection Zone

    Directory of Open Access Journals (Sweden)

    Yuhong Fan

    2009-12-01

    Full Text Available Active regions on the solar surface are generally thought to originate from a strong toroidal magnetic field generated by a deep seated solar dynamo mechanism operating at the base of the solar convection zone. Thus the magnetic fields need to traverse the entire convection zone before they reach the photosphere to form the observed solar active regions. Understanding this process of active region flux emergence is therefore a crucial component for the study of the solar cycle dynamo. This article reviews studies with regard to the formation and rise of active region scale magnetic flux tubes in the solar convection zone and their emergence into the solar atmosphere as active regions.

  18. Test particle transport in perturbed magnetic fields in tokamaks

    NARCIS (Netherlands)

    de Rover, M.; Schilham, A.M.R.; Montvai, A.; Cardozo, N. J. L.

    1999-01-01

    Numerical calculations of magnetic field line trajectories in a tokamak are used to investigate the common hypotheses that (i) field lines in a chaotic field make a Gaussian random walk and (ii) that the poloidal component of the magnetic field is uniform in regions with a chaotic magnetic field. Bo

  19. On the Physics of Primordial Magnetic Fields

    CERN Document Server

    Battaner, E

    2000-01-01

    There are at present more then 30 theories about the origin of cosmic magnetic fields at galactic and intergalactic scales. Most of them rely on concepts of elementary particle physics, like phase transitions in the early Universe, string theory and processes during the inflationary epoch. Here we present some more astrophysical arguments to provide some guidance through this large number and variety of models. Especially the fact that the evolution of magnetic fields depends on the spatial coherence scale of the fields leds to some interesting conclusions, which may rule out the majority of the theoretical scenarios. In principle one has to distinguish between the large-scale and small-scale magnetic fields. Large scale fields are defined as those as becoming sub-horizon at that redshift at which the mass energy density becomes equal to the photon energy density, which we name as equality. Small scale fields which are sub-horizon even before equality, i.e. with scales lower than (present) few Mpc cannot surv...

  20. Effects of EMF Emissions from Cables and Junction Boxes on Marine Species

    Energy Technology Data Exchange (ETDEWEB)

    Dhanak, Manhar [Florida Atlantic Univ., Boca Raton, FL (United States); Spieler, Richard [Nova Southeastern Univ., Fort Lauderdale, FL (United States); Kilfoyle, Kirk [Nova Southeastern Univ., Fort Lauderdale, FL (United States); Jermain, Robert F. [Nova Southeastern Univ., Fort Lauderdale, FL (United States); Frankenfield, John [Florida Atlantic Univ., Boca Raton, FL (United States); Ravenna, Shirley [Florida Atlantic Univ., Boca Raton, FL (United States); Dibiasio, Christopher [Florida Atlantic Univ., Boca Raton, FL (United States); Coulson, Robert [Florida Atlantic Univ., Boca Raton, FL (United States); Henderson, Ed [Florida Atlantic Univ., Boca Raton, FL (United States); Venezia, William [Naval Surface Warfare Center (NSWC), Carderock Division (United States)

    2016-09-29

    Studies have shown that diverse aquatic species are electrosensitive. Many fishes, and marine mammals, can either detect, navigate by, or are affected by electromagnetic fields (EMF) with various sensitivities, and their behavior may be impacted by unnatural EMF emissions in the water column. Sharks, rays and skates are known to have the highest sensitivity to electric fields. Electric field emissions in the range 0.5–100 micro volt/m appear to attract them, and emissions over 100 micro volt/m to repulse them. A marine hydrokinetic MHK device will have multiple components and associated multiple submarine cables on the seafloor and running through the water column and would potentially increase the level of EMF emissions to which the marine species at the site may be exposed to. There are therefore concerns amongst stakeholders that EMF emissions associated with MHK devices and their components may act as barriers to species migration, cause disorientation, change community compositions and ecosystems, and that they may attract sharks, leading to a local increase in the risk of shark attacks. However, field data to validate and model potential relationships between observed responses and the EMF emissions in situ are sparse. A program of experimental field surveys were conducted off the coast of South Florida, USA to characterize the electromagnetic field (EMF) emissions in the water column from a submarine cable, and to monitor for responses of local aquatic species. The field surveys were conducted at the South Florida Ocean Measurement Facility (SFOMF) off Fort Lauderdale, which is a cabled offshore in-water navy range. It consists of multiple active submarine power cables and a number of junction boxes, with the capability to transmit AC/DC power at a range of strength and frequencies. The site includes significant marine life activities and community structure, including highly mobile species, such as sharks, stingrays, mammals and turtles. SFOMF therefore

  1. Consistency relation for cosmic magnetic fields

    DEFF Research Database (Denmark)

    Jain, R. K.; Sloth, M. S.

    2012-01-01

    to be extremely useful to test some recent calculations in the literature. Apart from primordial non-Gaussianity induced by the curvature perturbations, such a cross correlation might provide a new observational probe of inflation and can in principle reveal the primordial nature of cosmic magnetic fields. DOI...

  2. Magnetic Field Structure in Relativistic Jets

    Directory of Open Access Journals (Sweden)

    Jermak Helen

    2013-12-01

    Full Text Available Relativistic jets are ubiquitous when considering an accreting black hole. Two of the most extreme examples of these systems are blazars and gamma-ray bursts (GRBs, the jets of which are thought to be threaded with a magnetic field of unknown structure. The systems are made up of a black hole accreting matter and producing, as a result, relativistic jets of plasma from the poles of the black hole. Both systems are viewed as point sources from Earth, making it impossible to spatially resolve the jet. In order to explore the structure of the magnetic field within the jet we take polarisation measurements with the RINGO polarimeters on the world’s largest fully autonomous, robotic optical telescope: The Liverpool Telescope. Using the polarisation degree and angle measured by the RINGO polarimeters it is possible to distinguish between global magnetic fields created in the central engine and random tangled magnetic fields produced locally in shocks. We also monitor blazar sources regularly during quiescence with periods of flaring monitored more intensively. Reported here are the early polarisation results for GRBs 060418 and 090102, along with future prospects for the Liverpool Telescope and the RINGO polarimeters.

  3. Magnetic field effects on photosynthetic reactions

    NARCIS (Netherlands)

    Liu, Yan

    2008-01-01

    Although the influence of magnetic fields on the rates and product yields of a host of chemical reactions are well documented and can be understood in the framework of the Radical Pair Mechanism (RPM), it has so far proved impossible to demonstrate convincingly a biological RPM effect. In this work

  4. Passive levitation in alternating magnetic fields

    Science.gov (United States)

    Romero, Louis; Christenson, Todd; Aronson, Eugene A.

    2010-09-14

    Stable levitation of an object in an alternating magnetic field can be achieved by eliminating coupling between the rotational and translational forces acting on the object. Stable levitation can also be achieved by varying the coupling between the rotational and translational forces acting on the object, while maintaining one or more of the rotational and translational forces steady in time.

  5. Measurement of the SC magnetic field

    CERN Multimedia

    CERN PhotoLab

    1973-01-01

    The 3.5-metre-arm carrying 100 Hall plates used for the measurmeent of the SC magnetic field. The arm rotates in a horizontal plane, its positioning and the data read-out are controlled by an on-line computer.

  6. ATLAS Barrel Toroid magnet reached nominal field

    CERN Multimedia

    2006-01-01

     On 9 November the barrel toroid magnet reached its nominal field of 4 teslas, with an electrical current of 21 000 amperes (21 kA) passing through the eight superconducting coils as shown on this graph

  7. Ground Vehicle Navigation Using Magnetic Field Variation

    Science.gov (United States)

    2012-09-13

    using three-axis magnetic field measurements for navigation. While Storms innovative work exposed the ability to navigate using three-axis magnetometer...level of difficulty, Ascher et al. combine a magnetometer with a pair of inertial measurement units, a barometer , and a laser for precise indoor

  8. Magnetic Field Reentrant Superconductivity in Aluminum Nanowires

    Science.gov (United States)

    Bretz-Sullivan, Terence; Goldman, Allen

    Reentrance to the superconducting state through the application of a magnetic field to quasi-one dimensional superconductors driven resistive by current, is counter to the expected properties of superconductors. It was not until recently that a microscopic mechanism explaining the phenomenon was proposed in which superconductivity and phase slip driven dissipation coexist in a non-equilibrium state. Here we present additional results of magnetic field induced reentrance into the superconducting state in quasi-one-dimensional aluminum nanowires with an in-plane magnetic field both transverse to, and along the wire axis. The reentrant behavior is seen in the magnetic field dependence of the I-V characteristic and resistance vs. temperature, and in the wire's magnetoresistance at 450mK. This work was supported by DOE Basic Energy Sciences Grant DE-FG02-02ER46004. Samples were fabricated at the Minnesota Nanofabrication Center. Parts of this work were carried out in the University of Minnesota Characterization Facility, a member of the Materials Research Facilities Network (www.mrfn.org) funded via the NSF MRSEC program.

  9. Compensation-device for a magnetic field

    NARCIS (Netherlands)

    Kruit, P.; Ferreira, J.A.

    2007-01-01

    The invention relates to compensation device for a magnetic field generated through electric traction in a tram or train transport system that comprises an overhead line and rails, the overhead line and rails during operation being live, wherein a predetermined section of the overhead line and rails

  10. Historic Methods for Capturing Magnetic Field Images

    Science.gov (United States)

    Kwan, Alistair

    2016-01-01

    I investigated two late 19th-century methods for capturing magnetic field images from iron filings for historical insight into the pedagogy of hands-on physics education methods, and to flesh out teaching and learning practicalities tacit in the historical record. Both methods offer opportunities for close sensory engagement in data-collection…

  11. Magnetic fields of the W4 superbubble

    CERN Document Server

    Gao, X Y; Reich, P; Han, J L; Kothes, R

    2015-01-01

    Superbubbles and supershells are the channels for transferring mass and energy from the Galactic disk to the halo. Magnetic fields are believed to play a vital role in their evolution. We study the radio continuum and polarized emission properties of the W4 superbubble to determine its magnetic field strength. New sensitive radio continuum observations were made at 6 cm, 11 cm, and 21 cm. The total intensity measurements were used to derive the radio spectrum of the W4 superbubble. The linear polarization data were analysed to determine the magnetic field properties within the bubble shells. The observations show a multi-shell structure of the W4 superbubble. A flat radio continuum spectrum that stems from optically thin thermal emission is derived from 1.4 GHz to 4.8 GHz. By fitting a passive Faraday screen model and considering the filling factor fne , we obtain the thermal electron density ne = 1.0/\\sqrt{fne} (\\pm5%) cm^-3 and the strength of the line-of-sight component of the magnetic field B// = -5.0/\\sq...

  12. Magnetic fields during primordial star formation

    CERN Document Server

    Schleicher, Dominik R G; Banerjee, Robi; Klessen, Ralf S; Federrath, Christoph; Arshakian, Tigran; Beck, Rainer; Spaans, Marco

    2011-01-01

    Recent FERMI observations provide a lower limit of 10^{-15} G for the magnetic field strength in the intergalactic medium (IGM). This is consistent with theoretical expectations based on the Biermann battery effect, which predicts such IGM fields already at redshifts z~10. During gravitational collapse, such magnetic fields can be amplified by compression and by turbulence, giving rise to the small-scale dynamo. On scales below the Jeans length, the eddy turnover timescale is much shorter than the free-fall timescale, so that saturation can be reached during collapse. This scenario has been tested and confirmed with magneto-hydrodynamical simulations following the collapse of a turbulent, weakly magnetized cloud. Based on a spectral analysis, we confirm that turbulence is injected on the Jeans scale. For the power spectrum of the magnetic field, we obtain the Kazantsev slope which is characteristic for the small-scale dynamo. A calculation of the critical length scales for ambipolar diffusion and Ohmic dissip...

  13. Manipulation of molecular structures with magnetic fields

    NARCIS (Netherlands)

    Boamfa, M.I.

    2003-01-01

    The present thesis deals with the use of magnetic fields as a handle to manipulate matter at a molecular level and as a tool to probe molecular properties or inter molecular interactions. The work consists of in situ optical studies of (polymer) liquid crystals and molecular aggregates in high magne

  14. Reducing Magnetic Fields Around Power Cables

    Science.gov (United States)

    Sargent, Noel B.; Gitelman, Florida; Pongracz-Bartha, Edward; Spalding, John

    1993-01-01

    Four power conductors arranged symmetrically about fifth grounded conductor. Four current-carrying wires arranged symmetrically around central grounded wire that nominally carries no current. In comparison with other cable configurations, this one results in smaller magnetic fields around cable. Technique for use when size of wires in cable makes twisting impractical.

  15. Electro-Mechanical Resonant Magnetic Field Sensor

    CERN Document Server

    Temnykh, A B; Temnykh, Alexander B.; Lovelace, Richard V. E.

    2002-01-01

    We describe a new type of magnetic field sensor which is termed an Electro-Mechanical Resonant Sensor (EMRS). The key part of this sensor is a small conductive elastic element with low damping rate and therefore a high Q fundamental mode of frequency $f_1$. An AC current is driven through the elastic element which, in the presence of a magnetic field, causes an AC force on the element. When the frequency of the AC current matches the resonant frequency of the element, maximum vibration of the element occurs and this can be measured precisely by optical means. We have built and tested a model sensor of this type using for the elastic element a length of copper wire of diameter 0.030 mm formed into a loop shape. The wire motion was measured using a light emitting diode photo-transistor assembly. This sensor demonstrated a sensitivity better than 0.001G for an applied magnetic field of $ \\sim 1$G and a good selectivity for the magnetic field direction. The sensitivity can be easily improved by a factor of $\\sim ...

  16. Primordial magnetic fields from the string network

    CERN Document Server

    Horiguchi, Kouichirou; Sugiyama, Naoshi

    2016-01-01

    Cosmic strings are a type of cosmic defect formed by a symmetry-breaking phase transition in the early universe. Individual strings would have gathered to build a network, and their dynamical motion would induce scalar--, vector-- and tensor--type perturbations. In this paper, we focus on the vector mode perturbations arising from the string network based on the one scale model and calculate the time evolution and the power spectrum of the associated magnetic fields. We show that the relative velocity between photon and baryon fluids induced by the string network can generate magnetic fields over a wide range of scales based on standard cosmology. We obtain the magnetic field spectrum before recombination as $a^2B(k,z)\\sim4\\times10^{-16}G\\mu/((1+z)/1000)^{4.25}(k/{\\rm Mpc}^{-1})^{3.5}$ Gauss on super-horizon scales, and $a^2B(k,z)\\sim2.4\\times10^{-17}G\\mu/((1+z)/1000)^{3.5}(k/{\\rm Mpc}^{-1})^{2.5}$ Gauss on sub-horizon scales in co-moving coordinates. This magnetic field grows up to the end of recombination, ...

  17. Magnetic Fields inside Extremely Fast Shock Waves

    NARCIS (Netherlands)

    Wiersma, J.

    2007-01-01

    The aim of my research on magnetic fields in extremely fast shock waves has been to predict the properties of shock waves that move almost with the speed of light. These shocks are created in the tenuous interstellar medium by catastrophic events such as the explosion of stars many times heavier

  18. Magnetic Fields inside Extremely Fast Shock Waves

    NARCIS (Netherlands)

    Wiersma, J.

    2007-01-01

    The aim of my research on magnetic fields in extremely fast shock waves has been to predict the properties of shock waves that move almost with the speed of light. These shocks are created in the tenuous interstellar medium by catastrophic events such as the explosion of stars many times heavier

  19. Historic Methods for Capturing Magnetic Field Images

    Science.gov (United States)

    Kwan, Alistair

    2016-03-01

    I investigated two late 19th-century methods for capturing magnetic field images from iron filings for historical insight into the pedagogy of hands-on physics education methods, and to flesh out teaching and learning practicalities tacit in the historical record. Both methods offer opportunities for close sensory engagement in data-collection processes.

  20. Physics of semiconductors in high magnetic fields

    CERN Document Server

    Miura, Noboru

    2008-01-01

    This book summarizes most of the fundamental physical phenomena which semiconductors and their modulated structures exhibit in high magnetic fields. Readers can learn not only the basic theoretical background but also the present state of the art from the most advanced data in this rapidly growing research area.

  1. Gravimetric Measurement of Magnetic Field Gradient Spatial Distribution

    CERN Document Server

    Arutunian, S G; Egiazarian, S L; Mailian, M R; Sinenko, I G; Sinjavski, A V; Vasiniuk, I E

    1999-01-01

    Magnetic interaction between a weighing sample and an external magnetic field allows to measure characteristics of magnetic field (a sample with known magnetic characteristics), as well as the magnetic properties of a sample (a known magnetic field). Measurement of materials magnetic permeability is a well known application of this method. In this paper we restrict ourselves to the measurement of magnetic field spatial distribution, which was achieved by scanning of samples from known materials along the vertical axis. Field measurements by Hall detector were done to calibrate obtained data. Such measurements are of great interest in some branches of physics, in particular, in accelerator physics, where the quality of magnetic system parts eventually determine the quality of accelerated bunches. Development of a simple and cheep device for measurement of magnetic field spatial distribution is an urgent problem. The developed system for gravimetric measurement of magnetic field gradients partially solves this ...

  2. Uniform Magnetic Field Between Face-to-Face HTS Bulk Magnets Combining Concave and Convex Magnetic Field Distributions

    Science.gov (United States)

    Oka, T.; Takahashi, Y.; Yaginuma, S.; Ogawa, J.; Fukui, S.; Sato, T.; Yokoyama, K.; Nakamura, T.

    The authors have been attempting to obtain the uniform magnetic field distribution in the space between the face-to-face HTS bulk magnets. The magnetic poles containing the HTS bulk magnets are usually characterized as non-uniform magnetic field distribution. Since the distributions show the conical or convex shapes, it is difficult to obtain the uniform magnetic field spaces even when the magnetic poles would be placed face-to-face. The authors have modified the shape of the distribution of one-side magnetic pole by attaching an iron plate on the surface, and formed the concave magnetic field distribution on the pole surface. The steep concave or convex distributions at each pole surface change to be flat with increasing distance from the pole surface. After the experimental result recording the best uniformity of 358 ppm by combining the concave and convex field distributions face-to-face, we attempted to simulate the feasible performance in this configuration. In the numerical simulation, the concave field distribution modified by attaching an imaginary spiral coil on the pole surface was coupled with the original convex field. We succeeded in obtaining the best uniformity of 30 ppm at 1.1 T in 4 x 4 mm2x-y plane at 7 mm distant from the pole surface in the gap of 30 mm. This result suggests that the concave and convex magnetic field distributions compensate the field uniformity with each other with keeping the magnetic field strength in the gap, and also suggests the novel compact NMR/MRI devices in the future.

  3. Primordial magnetic fields from self-ordering scalar fields

    CERN Document Server

    Horiguchi, Kouichirou; Sekiguchi, Toyokazu; Sugiyama, Naoshi

    2015-01-01

    A symmetry-breaking phase transition in the early universe could have led to the formation of cosmic defects. Because these defects dynamically excite not only scalar and tensor type cosmological perturbations but also vector type ones, they may serve as a source of primordial magnetic fields. In this study, we calculate the time evolution and the spectrum of magnetic fields that are generated by a type of cosmic defects, called global textures, using the non-linear sigma (NLSM) model. Based on the standard cosmological perturbation theory, we show, both analytically and numerically, that a vector-mode relative velocity between photon and baryon fluids is induced by textures, which inevitably leads to the generation of magnetic fields over a wide range of scales. We find that the amplitude of the magnetic fields is given by $B\\sim{10^{-9}}{((1+z)/10^3)^{-2.5}}({v}/{m_{\\rm pl}})^2({k}/{\\rm Mpc^{-1}})^{3.5}/{\\sqrt{N}}$ Gauss in the radiation dominated era for $k\\lesssim 1$ Mpc$^{-1}$, with $v$ being the vacuum ...

  4. Magnetic resonance of field-frozen and zero-field-frozen magnetic fluids

    Energy Technology Data Exchange (ETDEWEB)

    Pereira, A.R. E-mail: anarita@fis.ufg.br; Pelegrini, F.; Neto, K. Skeff; Buske, N.; Morais, P.C. E-mail: pcmor@unb.br

    2004-05-01

    In this study magnetic resonance was used to investigate magnetic fluid samples frozen under zero and non-zero (15 kG) external fields. The magnetite-based sample containing 2x10{sup 17} particle/cm{sup 3} was investigated from 100 to 400 K. Analysis of the temperature dependence of the resonance field revealed bigger magnetic structures in the frozen state than in the liquid phase. Also, differences in the mesoscopic organization in the frozen state may explain the data obtained from samples frozen under zero and non-zero fields.

  5. Growth rates of dynamic dermal model exposed to laminar flow and magnetic fields

    Directory of Open Access Journals (Sweden)

    Luis Javier Martinez

    Full Text Available Abstract Introduction Ongoing research in the use of electromagnetic stimulation as coadjuvant in fracture healing has led the authors to begin generating computer models in order to predict cellular growth changes when cells are electromagnetically stimulated. By generating these models, scientists will be able to better understand how electromagnetic fields affect cellular development. The experimental design integrated a cellular culture bioreactor along with an external magnetic stimulation system, which allowed for dermal models to be exposed to controlled magnetic fields. Methods Initially, it was necessary to analyze the static growth of Normal Human Skin Fibroblast (NHSF cells when they were exposed to Extremely Low Frequency – Electromagnetic Fields (ELF-EMFs. Using optimal conditions for the NHSF culture, from stimulation signal to scaffolding material, we were able to perform the dynamic flow stimulation experiments. Results The following systems were developed: (1 a bioreactor aimed at cellular tissue culture, and (2 Helmholtz coils capable of generating stimulation signals for the cultured tissue. The authors were able to appreciate the quantified values of cellular density diluted in all the experiment samples that were taken and overall, the irradiated samples displayed an average increase of 53% higher cellular density for the same amount of initial cellular seeding when the cells were exposed to a 1 mT, 60 Hz magnetic field signal. Conclusion ELF-EMF’s indeed alter NHSF cell growth rates and it is the challenge of the authors to continue investigating what cellular mechanisms are altered when cells are exposed to ELF-EMF’s.

  6. Occupational exposure in MR facilities due to movements in the static magnetic field.

    Science.gov (United States)

    Andreuccetti, Daniele; Biagi, Laura; Burriesci, Giancarlo; Cannatà, Vittorio; Contessa, Gian Marco; Falsaperla, Rosaria; Genovese, Elisabetta; Lodato, Rossella; Lopresto, Vanni; Merla, Caterina; Napolitano, Antonio; Pinto, Rosanna; Tiberi, Gianluigi; Tosetti, Michela; Zoppetti, Nicola

    2017-08-30

    The exposure of operators moving in the static field of magnetic resonance (MR) facilities was assessed through measurements of the magnetic flux density, which is experienced as variable in time because of the movement. Collected data were processed to allow the comparison with most recent and authoritative safety standards. Measurements of the experienced magnetic flux density B were performed using a probe worn by volunteers moving in MR environments. A total of 55 datasets were acquired nearby a 1.5T, 3T and 7T whole body scanners. Three different metrics were applied: the maximum intensity of B, to be compared with 2013/35/EU Directive exposure limit values for static fields; the maximum variation of the vector B on every 3s-interval, for comparison with the ICNIRP-2014 basic restriction aimed at preventing vertigo effects; two weighted peak indices (for "sensory" and "health" effects: SENS-WP, HLTH-WP), assessing compliance with ICNIRP-2014 and EU Directive recommendations intended to prevent stimulation effects. Peak values of |B| were greater than 2T in 9 of the 55 datasets. All the datasets at 1.5T and 3T were compliant with the limit for vertigo effects, whereas 6 datasets at 7T turned out to be non-compliant. At 7T, all 36 datasets were non-compliant for the SENS-WP index and 26 datasets even for the HLTH-WP one. Results demonstrate that compliance with EU Directive limits for static fields does not guarantee compliance with ICNIRP-2014 reference levels and clearly show that movements in the static field could be the key component of the occupational exposure to EMF in MR facilities. This article is protected by copyright. All rights reserved. This article is protected by copyright. All rights reserved.

  7. Introduction to power-frequency electric and magnetic fields.

    OpenAIRE

    1993-01-01

    This paper introduces the reader to electric and magnetic fields, particularly those fields produced by electric power systems and other sources using frequencies in the power-frequency range. Electric fields are produced by electric charges; a magnetic field also is produced if these charges are in motion. Electric fields exert forces on other charges; if in motion, these charges will experience magnetic forces. Power-frequency electric and magnetic fields induce electric currents in conduct...

  8. Measuring the Earth's Magnetic Field in a Laboratory

    Science.gov (United States)

    Cartacci, A.; Straulino, S.

    2008-01-01

    Two methods for measuring the Earth's magnetic field are described. In the former, according to Gauss, the Earth's magnetic field is compared with that of a permanent magnet; in the latter, a well-known method, the comparison is made with the magnetic field generated by a current. As all the used instruments are available off the shelf, both…

  9. Collisionless reconnection: magnetic field line interaction

    Directory of Open Access Journals (Sweden)

    R. A. Treumann

    2012-10-01

    Full Text Available Magnetic field lines are quantum objects carrying one quantum Φ0 = 2πh/e of magnetic flux and have finite radius λm. Here we argue that they possess a very specific dynamical interaction. Parallel field lines reject each other. When confined to a certain area they form two-dimensional lattices of hexagonal structure. We estimate the filling factor of such an area. Anti-parallel field lines, on the other hand, attract each other. We identify the physical mechanism as being due to the action of the gauge potential field, which we determine quantum mechanically for two parallel and two anti-parallel field lines. The distortion of the quantum electrodynamic vacuum causes a cloud of virtual pairs. We calculate the virtual pair production rate from quantum electrodynamics and estimate the virtual pair cloud density, pair current and Lorentz force density acting on the field lines via the pair cloud. These properties of field line dynamics become important in collisionless reconnection, consistently explaining why and how reconnection can spontaneously set on in the field-free centre of a current sheet below the electron-inertial scale.

  10. Warm Magnetic Field Measurements of LARP HQ Magnet

    Energy Technology Data Exchange (ETDEWEB)

    Caspi, S; Cheng, D; Deitderich, D; Felice, H; Ferracin, P; Hafalia, R; Joseph, J; Lizarazo, J; Martchevskii, M; Nash, C; Sabbi, G L; Vu, C; Schmalzle, J; Ambrosio, G; Bossert, R; Chlachidze, G; DiMarco, J; Kashikhin, V

    2011-03-28

    The US-LHC Accelerator Research Program is developing and testing a high-gradient quadrupole (HQ) magnet, aiming at demonstrating the feasibility of Nb{sub 3}Sn technologies for the LHC luminosity upgrade. The 1 m long HQ magnet has a 120 mm bore with a conductor-limited gradient of 219 T/m at 1.9 K and a peak field of 15 T. HQ includes accelerator features such as alignment and field quality. Here we present the magnetic measurement results obtained at LBNL with a constant current of 30 A. A 100 mm long circuit-board rotating coil developed by FNAL was used and the induced voltage and flux increment were acquired. The measured b{sub 6} ranges from 0.3 to 0.5 units in the magnet straight section at a reference radius of 21.55 mm. The data reduced from the numerical integration of the raw voltage agree with those from the fast digital integrators.

  11. Assessment of Foetal Exposure to the Homogeneous Magnetic Field Harmonic Spectrum Generated by Electricity Transmission and Distribution Networks

    Directory of Open Access Journals (Sweden)

    Serena Fiocchi

    2015-04-01

    Full Text Available During the last decades studies addressing the effects of exposure to Extremely Low Frequency Electromagnetic Fields (ELF-EMF have pointed out a possible link between those fields emitted by power lines and childhood leukaemia. They have also stressed the importance of also including in the assessment the contribution of frequency components, namely harmonics, other than the fundamental one. Based on the spectrum of supply voltage networks allowed by the European standard for electricity quality assessment, in this study the exposure of high-resolution three-dimensional models of foetuses to the whole harmonic content of a uniform magnetic field with a fundamental frequency of 50 Hz, was assessed. The results show that the main contribution in terms of induced electric fields to the foetal exposure is given by the fundamental frequency component. The harmonic components add some contributions to the overall level of electric fields, however, due to the extremely low permitted amplitude of the harmonic components with respect to the fundamental, their amplitudes are low. The level of the induced electric field is also much lower than the limits suggested by the guidelines for general public exposure, when the amplitude of the incident magnetic field is set at the maximum permitted level.

  12. Assessment of foetal exposure to the homogeneous magnetic field harmonic spectrum generated by electricity transmission and distribution networks.

    Science.gov (United States)

    Fiocchi, Serena; Liorni, Ilaria; Parazzini, Marta; Ravazzani, Paolo

    2015-04-01

    During the last decades studies addressing the effects of exposure to Extremely Low Frequency Electromagnetic Fields (ELF-EMF) have pointed out a possible link between those fields emitted by power lines and childhood leukaemia. They have also stressed the importance of also including in the assessment the contribution of frequency components, namely harmonics, other than the fundamental one. Based on the spectrum of supply voltage networks allowed by the European standard for electricity quality assessment, in this study the exposure of high-resolution three-dimensional models of foetuses to the whole harmonic content of a uniform magnetic field with a fundamental frequency of 50 Hz, was assessed. The results show that the main contribution in terms of induced electric fields to the foetal exposure is given by the fundamental frequency component. The harmonic components add some contributions to the overall level of electric fields, however, due to the extremely low permitted amplitude of the harmonic components with respect to the fundamental, their amplitudes are low. The level of the induced electric field is also much lower than the limits suggested by the guidelines for general public exposure, when the amplitude of the incident magnetic field is set at the maximum permitted level.

  13. Magnetic Field Gradient Waveform Monitoring for Magnetic Resonance

    Science.gov (United States)

    Han, Hui

    Linear magnetic field gradients have played a central role in Magnetic Resonance Imaging (MRI) since Fourier Transform MRI was proposed three decades ago. Their primary function is to encode spatial information into MR signals. Magnetic field gradients are also used to sensitize the image contrast to coherent and/or incoherent motion, to selectively enhance an MR signal, and to minimize image artifacts. Modern MR imaging techniques increasingly rely on the implementation of complex gradient waveforms for the manipulation of spin dynamics. However, gradient system infidelities caused by eddy currents, gradient amplifier imperfections and group delays, often result in image artifacts and other errors (e.g., phase and intensity errors). This remains a critical problem for a wide range of MRI techniques on modern commercial systems, but is of particular concern for advanced MRI pulse sequences. Measuring the real magnetic field gradients, i.e., characterizing eddy currents, is critical to addressing and remedying this problem. Gradient measurement and eddy current calibration are therefore a general topic of importance to the science of MRI. The Magnetic Field Gradient Monitor (MFGM) idea was proposed and developed specifically to meet these challenges. The MFGM method is the heart of this thesis. MFGM methods permit a variety of magnetic field gradient problems to be investigated and systematically remedied. Eddy current effects associated with MR compatible metallic pressure vessels were analyzed, simulated, measured and corrected. The appropriate correction of eddy currents may enable most MR/MRI applications with metallic pressure vessels. Quantitative imaging (1D/2D) with model pressure vessels was successfully achieved by combining image reconstruction with MFGM determined gradient waveform behaviour. Other categories of MR applications with metallic vessels, including diffusion measurement and spin echo SPI T2 mapping, cannot be realized solely by MFGM guided

  14. Acceleration of superparamagnetic particles with magnetic fields

    Science.gov (United States)

    Stange, R.; Lenk, F.; Bley, T.; Boschke, E.

    2017-04-01

    High magnetic capture efficiency in the context of Biomagnetic Separation (BMS) using superparamagnetic particles (SMPs) requires efficient mixing and high relative velocities between cellular and other targets and SMPs. For this purpose, batch processes or microfluidic systems are commonly used. Here, we analyze the characteristics of an in-house developed batch process experimental setup, the Electromagnetic Sample Mixer (ESM) described earlier. This device uses three electromagnets to increase the relative velocity between SMPs and targets. We carry out simulations of the magnetic field in the ESM and in a simpler paradigmatic setup, and thus were able to calculate the force field acting on the SMPs and to simulate their relative velocities and fluid dynamics due to SMP movement. In this way we were able to show that alternate charging of the magnets induces a double circular stream of SMPs in the ESM, resulting in high relative velocities of SMPs to the targets. Consequently, due to the conservation of momentum, the fluid experiences an acceleration induced by the SMPs. We validated our simulations by microscopic observation of the SMPs in the magnetic field, using a homemade apparatus designed to accommodate a long working-distance lens. By comparing the results of modeling this paradigmatic setup with the experimental observations, we determined that the velocities of the SMPs corresponded to the results of our simulations.

  15. Navigation: bat orientation using Earth's magnetic field.

    Science.gov (United States)

    Holland, Richard A; Thorup, Kasper; Vonhof, Maarten J; Cochran, William W; Wikelski, Martin

    2006-12-07

    Bats famously orientate at night by echolocation, but this works over only a short range, and little is known about how they navigate over longer distances. Here we show that the homing behaviour of Eptesicus fuscus, known as the big brown bat, can be altered by artificially shifting the Earth's magnetic field, indicating that these bats rely on a magnetic compass to return to their home roost. This finding adds to the impressive array of sensory abilities possessed by this animal for navigation in the dark.

  16. Navigation: Bat orientation using Earth's magnetic field

    DEFF Research Database (Denmark)

    Holland, Richard A.; Thorup, Kasper; Vonhof, Maarten J.

    2006-01-01

    Bats famously orientate at night by echolocation 1 , but this works over only a short range, and little is known about how they navigate over longer distances 2 . Here we show that the homing behaviour of Eptesicus fuscus, known as the big brown bat, can be altered by artificially shifting...... the Earth's magnetic field, indicating that these bats rely on a magnetic compass to return to their home roost. This finding adds to the impressive array of sensory abilities possessed by this animal for navigation in the dark....

  17. The energy budget of stellar magnetic fields

    Science.gov (United States)

    See, V.; Jardine, M.; Vidotto, A. A.; Donati, J.-F.; Folsom, C. P.; Boro Saikia, S.; Bouvier, J.; Fares, R.; Gregory, S. G.; Hussain, G.; Jeffers, S. V.; Marsden, S. C.; Morin, J.; Moutou, C.; do Nascimento, J. D.; Petit, P.; Rosén, L.; Waite, I. A.

    2015-11-01

    Spectropolarimetric observations have been used to map stellar magnetic fields, many of which display strong bands of azimuthal fields that are toroidal. A number of explanations have been proposed to explain how such fields might be generated though none are definitive. In this paper, we examine the toroidal fields of a sample of 55 stars with magnetic maps, with masses in the range 0.1-1.5 M⊙. We find that the energy contained in toroidal fields has a power-law dependence on the energy contained in poloidal fields. However the power index is not constant across our sample, with stars less and more massive than 0.5 M⊙ having power indices of 0.72 ± 0.08 and 1.25 ± 0.06, respectively. There is some evidence that these two power laws correspond to stars in the saturated and unsaturated regimes of the rotation-activity relation. Additionally, our sample shows that strong toroidal fields must be generated axisymmetrically. The latitudes at which these bands appear depend on the stellar rotation period with fast rotators displaying higher latitude bands than slow rotators. The results in this paper present new constraints for future dynamo studies.

  18. The energy budget of stellar magnetic fields

    CERN Document Server

    See, V; Vidotto, A A; Donati, J -F; Folsom, C P; Saikia, S Boro; Bouvier, J; Fares, R; Gregory, S G; Hussain, G; Jeffers, S V; Marsden, S C; Morin, J; Moutou, C; Nascimento, J D do; Petit, P; Rosen, L; Waite, I A

    2015-01-01

    Spectropolarimetric observations have been used to map stellar magnetic fields, many of which display strong bands of azimuthal fields that are toroidal. A number of explanations have been proposed to explain how such fields might be generated though none are definitive. In this paper, we examine the toroidal fields of a sample of 55 stars with magnetic maps, with masses in the range 0.1-1.5$\\,{\\rm M}_\\odot$. We find that the energy contained in toroidal fields has a power law dependence on the energy contained in poloidal fields. However the power index is not constant across our sample, with stars less and more massive than 0.5$\\,{\\rm M}_\\odot$ having power indices of 0.72$\\pm$0.08 and 1.25$\\pm$0.06 respectively. There is some evidence that these two power laws correspond to stars in the saturated and unsaturated regimes of the rotation-activity relation. Additionally, our sample shows that strong toroidal fields must be generated axisymmetrically. The latitudes at which these bands appear depend on the ste...

  19. Topological insulator in a helicoidal magnetization field

    Science.gov (United States)

    Stagraczyński, S.; Chotorlishvili, L.; Dugaev, V. K.; Jia, C.-L.; Ernst, A.; Komnik, A.; Berakdar, J.

    2016-11-01

    A key feature of topological insulators is the robustness of the electron energy spectrum. At a surface of a topological insulator, the Dirac point is protected by the characteristic symmetry of the system. The breaking of the symmetry opens a gap in the energy spectrum. Therefore, topological insulators are very sensitive to magnetic fields, which can open a gap in the electronic spectrum. Concerning "internal" magnetic effects, for example, the situation with doped magnetic impurities, is not trivial. A single magnetic impurity is not enough to open the band gap, while in the case of a ferromagnetic chain of deposited magnetic impurities the Dirac point is lifted. However, a much more interesting case is when localized magnetic impurities form a chiral spin order. Our first principle density functional theory calculations have shown that this is the case for Fe deposited on the surface of a Bi2Se3 topological insulator. But not only magnetic impurities can form a chiral helicoidal spin texture. An alternative way is to use chiral multiferroics (prototype material is LiCu2O2 ) that induce a proximity effect. The theoretical approach we present here is valid for both cases. We observed that opposite to a ferromagnetically ordered case, a chiral spin order does not destroy the Dirac point. We also observed that the energy gap appears at the edges of the new Brillouin zone. Another interesting result concerns the spin dynamics. We derived an equation for the spin density dynamics with a spin current and relaxation terms. We have shown that the motion of the conductance electron generates a magnetic torque and exerts a certain force on the helicoidal texture.

  20. Assessment of electromagnetic field levels from surrounding high-tension overhead power lines for proposed land use.

    Science.gov (United States)

    Al-Bassam, E; Elumalai, A; Khan, A; Al-Awadi, L

    2016-05-01

    The surrounding outdoor environment for new development has a big effect on the indoor quality of life. The main aim of this work was to determine the suitability of the area for building new schools with reference to electromagnetic field (EMF) effects. The specific objective of this study was to detect the safe distance from the EMF posed by the high-tension overhead power lines in the vicinity of the specified area. The measurements were taken for both the electric and magnetic fields in different months in order to detect the highest EMF levels during the peak power load season. EMDEX II with E-probe and EMDEX II with Linda were used for the measurements. These instruments were all calibrated by ENERTECH Company in USA. The EMF associated with high tension transmission lines that surrounded the proposed site has to be below 0.2 μT (Italian EMF regulations are the most suitable regulations for the establishment of schools in Kuwait). The safety clearance distance from the existing 300-kV high-tension power line has been assigned as 200 m and from other existing 132-kV high-tension power line was 50 m. The proposed site with its predefined boundaries has a magnetic field below the Italian EMF regulations for the establishment of new schools.

  1. Ultrafast time domain demonstration of bulk magnetization precession at zero magnetic field ferromagnetic resonance induced by terahertz magnetic field.

    Science.gov (United States)

    Nakajima, M; Namai, A; Ohkoshi, S; Suemoto, T

    2010-08-16

    We report the first observation of sub-terahertz bulk-magnetization precession, using terahertz time-domain spectroscopy. The magnetization precession in gallium-substituted epsilon-iron oxide nano-ferromagnets under zero magnetic field is induced by the impulsive magnetic field of the THz wave through the gyromagnetic effect. Just at the resonance frequency, the linear to circular polarized wave conversion is realized. This is understood as the free induction decay signal radiated from a rotating magnetic dipole corresponding to the natural resonance. Furthermore, this demonstration reveals that the series of gallium-substituted epsilon-iron oxide nano-ferromagnets is very prospective for magneto-optic devices, which work at room temperature without external magnetic field, in next-generation wireless communication.

  2. The manipulation of magnetic coercive field and orientation of magnetic anisotropy via electric fields

    Science.gov (United States)

    Xiang, Jun-Sen; Ye, Jun; Yang, Yun-Long; Xie, Yong; Li, Wei; Chen, Zi-Yu

    2016-08-01

    We report the effects of the electric field on the magnetic coercive field (H c) and uniaxial magnetic anisotropy (UMA) orientation of polycrystalline Ni film grown on an unpoled (0 1 1) [Pb(Mg1/3Nb2/3)O3](1-x)-[PbTiO3] x (PMN-PT) single crystal substrate. Under various electric fields, normalized magnetic hysteresis loops of Ni films change in width; this represents the change of coercive field (ΔH c). Loop shapes are found to depend on the angle between the magnetic field and the sample, where changes in the shape reveal a small rotation of UMA. All these changes show that the magnetic properties vary periodically with a periodic electric field, by strain-mediated magnetoelectric coupling in the Ni/Ag/PMN-PT/Ag heterostructure. The poled PMN-PT produces strains under electric fields in the range of  -4.2 kV cm-1  ⩽  E  ⩽  4.2 kV cm-1, then transfers it to Ni films resulting in changes to its H c and UMA. The curves of the in-plane H c and strain, at two mutually orthogonal directions, represent butterfly patterns versus the applied electric field. In addition, the changes observed in both the H c and strain show asymmetric features in two orthogonal directions, which results in a small rotation angle of the UMA of Ni as the electric field decreases. The effective manipulation of magnitude and orientation of magnetic anisotropy via electric fields in ferromagnetic/ferroelectric (FM/FE) heterostructures is an important step towards controlling the magnetic tunnel junctions.

  3. On the origin of cosmic magnetic fields

    Science.gov (United States)

    Kulsrud, Russell M.; Zweibel, Ellen G.

    2008-04-01

    We review the extensive and controversial literature concerning how the cosmic magnetic fields pervading nearly all galaxies and clusters of galaxies actually got started. Some observational evidence supports a hypothesis that the field is already moderately strong at the beginning of the life of a galaxy and its disc. One argument involves the chemical abundance of the light elements Be and B, while a second one is based on the detection of strong magnetic fields in very young high red shift galaxies. Since this problem of initial amplification of cosmic magnetic fields involves important plasma problems it is obvious that one must know the plasma in which the amplification occurs. Most of this review is devoted to this basic problem and for this it is necessary to devote ourselves to reviewing studies that take place in environments in which the plasma properties are most clearly understood. For this reason the authors have chosen to restrict themselves almost completely to studies of dynamos in our Galaxy. It is true that one can get a much better idea of the grand scope of galactic fields in extragalactic systems. However, most mature galaxies share the same dilemma as ours of overcoming important plasma problems. Since the authors are both trained in plasma physics we may be biased in pursuing this approach, but we feel it is justified by the above argument. In addition we feel we can produce a better review by staying close to that which we know best. In addition we have chosen not to consider the saturation problem of the galactic magnetic field since if the original dynamo amplification fails the saturation question does not arise. It is generally accepted that seed fields, whose strength is of order 10-20 G, easily spring up in the era preceding galaxy formation. Several mechanisms have been proposed to amplify these seed magnetic fields to a coherent structure with the microgauss strengths of the currently observed galactic magnetic fields. The standard

  4. Magnetic field gradients and their uses in the study of the earth's magnetic field

    Science.gov (United States)

    Harrison, C. G. A.; Southam, J. R.

    1991-01-01

    Magnetic field gradients are discussed from the standpoint of their usefulness in modeling crustal magnetizations. The fact that gradients enhance shorter wavelength features helps reduce both the core signal and the signal from external fields in comparison with the crustal signal. If the gradient device can be oriented, then directions of lineation can be determined from single profiles, and anomalies caused by unlineated sources can be identified.

  5. Magnetic Fields in a Sample of Nearby Spiral Galaxies

    CERN Document Server

    Van Eck, Cameron; Shukurov, Anvar; Fletcher, Andrew

    2014-01-01

    Both observations and modelling of magnetic fields in the diffuse interstellar gas of spiral galaxies are well developed but the theory has been confronted with observations for only a handful of individual galaxies. There is now sufficient data to consider statistical properties of galactic magnetic fields. We have collected data from the literature on the magnetic fields and interstellar media (ISM) of 20 spiral galaxies, and tested for various physically motivated correlations between magnetic field and ISM parameters. Clear correlations emerge between the total magnetic field strength and molecular gas density as well as the star formation rate. The magnetic pitch angle exhibits correlations with the total gas density, the star formation rate and the strength of the axisymmetric component of the mean magnetic field. The total and mean magnetic field strengths exhibit noticeable degree of correlation, suggesting a universal behaviour of the degree of order in galactic magnetic fields. We also compare the p...

  6. Interplanetary magnetic field ensemble at 1 AU

    Energy Technology Data Exchange (ETDEWEB)

    Matthaeus, W.H.; Goldstein, M.L.; King, J.H.

    1985-04-01

    A method for calculation ensemble averages from magnetic field data is described. A data set comprising approximately 16 months of nearly continuous ISEE-3 magnetic field data is used in this study. Individual subintervals of this data, ranging from 15 hours to 15.6 days comprise the ensemble. The sole condition for including each subinterval in the averages is the degree to which it represents a weakly time-stationary process. Averages obtained by this method are appropriate for a turbulence description of the interplanetary medium. The ensemble average correlation length obtained from all subintervals is found to be 4.9 x 10 to the 11th cm. The average value of the variances of the magnetic field components are in the approximate ratio 8:9:10, where the third component is the local mean field direction. The correlation lengths and variances are found to have a systematic variation with subinterval duration, reflecting the important role of low-frequency fluctuations in the interplanetary medium.

  7. Magnetic Fields and Galactic Star Formation Rates

    CERN Document Server

    Van Loo, Sven; Falle, Sam A E G

    2014-01-01

    The regulation of galactic-scale star formation rates (SFRs) is a basic problem for theories of galaxy formation and evolution: which processes are responsible for making observed star formation rates so inefficient compared to maximal rates of gas content divided by dynamical timescale? Here we study the effect of magnetic fields of different strengths on the evolution of molecular clouds within a kiloparsec patch of a disk galaxy. Including an empirically motivated prescription for star formation from dense gas ($n_{\\rm{H}}>10^5\\:{\\rm{cm}^{-3}}$) at an efficiency of 2\\% per local free fall time, we derive the amount of suppression of star formation by magnetic fields compared to the nonmagnetized case. We find GMC fragmentation, dense clump formation and SFR can be significantly affected by the inclusion of magnetic fields, especially in our strongest investigated $B$-field case of $80\\:{\\rm{\\mu}}$G. However, our chosen kpc scale region, extracted from a global galaxy simulation, happens to contain a starbu...

  8. Validation of the CMS Magnetic Field Map

    CERN Document Server

    Klyukhin, V I; Ball, A; Curé, B; Gaddi, A; Gerwig, H; Mulders, M; Calvelli, V; Hervé, A; Loveless, R

    2015-01-01

    The Compact Muon Solenoid (CMS) is a general purpose detector, designed to run at the highest luminosity at the CERN Large Hadron Collider (LHC). Its distinctive features include a 4-T superconducting solenoid with 6-m-diameter by 12.5-m-length free bore, enclosed inside a 10,000-ton return yoke made of construction steel. The return yoke consists of five dodecagonal three-layered barrel wheels and four end-cap disks at each end comprised of steel blocks up to 620 mm thick, which serve as the absorber plates of the muon detection system. To measure the field in and around the steel, a system of 22 flux loops and 82 three-dimensional (3-D) Hall sensors is installed on the return yoke blocks. A TOSCA 3-D model of the CMS magnet is developed to describe the magnetic field everywhere outside the tracking volume measured with the field-mapping machine. The magnetic field description is compared with the measurements and discussed.

  9. Generation of Cosmic Magnetic Fields at Recombination

    CERN Document Server

    Hogan, C J

    2000-01-01

    It is shown that the standard cosmological model predicts ab initio generation of large-scale cosmic magnetic fields at the epoch of recombination of the primeval plasma. Matter velocities dominated by coherent flows on a scale $L\\approx 50h^{-1}(1+z)^{-1}$ Mpc lead to a dipole of radiation flux in the frame of the moving matter. Thomson scattering of the radiation differentially accelerates the electrons and ions, creating large-scale coherent electric currents and magnetic fields. This process is analyzed using magnetohydrodynamic equations which include a modification of Ohm's law describing the effect of Thomson drag on the electrons. The field strength saturates near equipartition with the baryon kinetic energy density at $B\\simeq 5\\times 10^{-5}$G. Magnetic stresses significantly damp baryonic motions at the epoch of last scattering, reducing the predicted background radiation anisotropy at small angles and changing estimates of fitted cosmological parameters. The field at late times retains its large-s...

  10. A topology for the penumbral magnetic fields

    CERN Document Server

    Almeida, J Sanchez

    2008-01-01

    We describe a scenario for the sunspot magnetic field topology that may account for recent observations of upflows and downflows in penumbrae. According to our conjecture, short narrow magnetic loops fill the penumbral volume. Flows along these field lines are responsible for both the Evershed effect and the convective transport. This scenario seems to be qualitatively consistent with most existing observations, including the dark cores in penumbral filaments reported by Scharmer et al. Each bright filament with dark core would be a system of two paired convective rolls with the dark core tracing the lane where the plasma sinks down. The magnetic loops would have a hot footpoint in one of the bright filament and a cold footpoint in the dark core. The scenario also fits in most of our theoretical prejudices (siphon flows along field lines, presence of overturning convection, drag of field lines by downdrafts, etc). If the conjecture turns out to be correct, the mild upward and downward velocities observed in p...

  11. Intergalactic magnetic fields in Stephan's Quintet

    CERN Document Server

    Nikiel-Wroczyński, B; Urbanik, M; Beck, R; Bomans, D J

    2013-01-01

    We present results of the VLA radio continuum total power and polarised intensity observations of Stephan's Quintet at 1.43 and 4.86 GHz along with complementary 4.85 and 8.35 GHz Effelsberg observations. Our study shows a large envelope of radio emission encompassing all the member galaxies and hence a large volume of intergalac- tic matter. Infall of the galaxy NGC 7318B produces a ridge of intergalactic, polarised emission, for which the magnetic field strength was estimated as 11.0 \\pm 2.2 {\\mu}G, with an ordered component of 2.6 \\pm 0.8 {\\mu}G. The energy density of the field within the ridge area is of the same order as estimates of the thermal component, implying a significant role of the magnetic field in the dynamics of the intergalactic matter. We also report that the tidal dwarf galaxy candidate SQ-B possesses a strong and highly anisotropic magnetic field with the total strength being equal to 6.5 \\pm 1.9 {\\mu}G and an ordered component reaching 3.5 \\pm 1.2 {\\mu}G, which is comparable to that foun...

  12. Magnetic Fields in Population III Star Formation

    Energy Technology Data Exchange (ETDEWEB)

    Turk, Matthew J.; Oishi, Jeffrey S.; Abel, Tom; Bryan, Greg

    2012-02-22

    We study the buildup of magnetic fields during the formation of Population III star-forming regions, by conducting cosmological simulations from realistic initial conditions and varying the Jeans resolution. To investigate this in detail, we start simulations from identical initial conditions, mandating 16, 32 and 64 zones per Jeans length, and studied the variation in their magnetic field amplification. We find that, while compression results in some amplification, turbulent velocity fluctuations driven by the collapse can further amplify an initially weak seed field via dynamo action, provided there is sufficient numerical resolution to capture vortical motions (we find this requirement to be 64 zones per Jeans length, slightly larger than, but consistent with previous work run with more idealized collapse scenarios). We explore saturation of amplification of the magnetic field, which could potentially become dynamically important in subsequent, fully-resolved calculations. We have also identified a relatively surprising phenomena that is purely hydrodynamic: the higher-resolved simulations possess substantially different characteristics, including higher infall-velocity, increased temperatures inside 1000 AU, and decreased molecular hydrogen content in the innermost region. Furthermore, we find that disk formation is suppressed in higher-resolution calculations, at least at the times that we can follow the calculation. We discuss the effect this may have on the buildup of disks over the accretion history of the first clump to form as well as the potential for gravitational instabilities to develop and induce fragmentation.

  13. Electron accumulation layer in ultrastrong magnetic field

    Science.gov (United States)

    Sammon, M.; Fu, Han; Shklovskii, B. I.

    2017-02-01

    When a three-dimensional electron gas is subjected to a very strong magnetic field, it can reach a quasi-onedimensional state in which all electrons occupy the lowest Landau level. This state is referred to as the extreme quantum limit ( EQL ) and has been studied in the physics of pulsars and bulk semiconductors. Here we present a theory of the EQL phase in electron accumulation layers created by an external electric field E at the surface of a semiconductor with a large Bohr radius such as InSb , PbTe , SrTiO 3 ( STO ) , and particularly in the LaA 1 O 3 / SrTiO 3 ( LAO / STO ) heterostructure. The phase diagram of the electron gas in the plane of the magnetic field strength and the electron surface concentration is found for different orientations of the magnetic field. We find that in addition to the quasi-classical metallic phase ( M ), there is a metallic EQL phase, as well as an insulating Wigner crystal state ( WC ). Within the EQL phase, the Thomas-Fermi approximation is used to find the electron density and the electrostatic potential profiles of the accumulation layer. Additionally, the quantum capacitance for each phase is calculated as a tool for experimental study of these phase diagrams.

  14. Hanle Effect Diagnostics of the Coronal Magnetic Field - A Test Using Realistic Magnetic Field Configurations

    CERN Document Server

    Raouafi, N -E; Wiegelmann, T

    2008-01-01

    Our understanding of coronal phenomena, such as coronal plasma thermodynamics, faces a major handicap caused by missing coronal magnetic field measurements. Several lines in the UV wavelength range present suitable sensitivity to determine the coronal magnetic field via the Hanle effect. The latter is a largely unexplored diagnostic of coronal magnetic fields with a very high potential. Here we study the magnitude of the Hanle-effect signal to be expected outside the solar limb due to the Hanle effect in polarized radiation from the H {\\sc{i}} Ly$\\alpha$ and $\\beta$ lines, which are among the brightest lines in the off-limb coronal FUV spectrum. For this purpose we use a magnetic field structure obtained by extrapolating the magnetic field starting from photospheric magnetograms. The diagnostic potential of these lines for determining the coronal magnetic field, as well as their limitations are studied. We show that these lines, in particular H {\\sc{i}} Ly$\\beta$, are useful for such measurements.

  15. Magnetic field generation by intermittent convection

    CERN Document Server

    Chertovskih, R; Chimanski, E V

    2016-01-01

    Magnetic field generation by convective flows in transition to weak turbulence is studied numerically. By fixing the Prandtl number at P=0.3 and varying the Rayleigh number (Ra) as a control parameter in three-dimensional Rayleigh-Benard convection of an electrically conducting fluid, a recently reported route to hyperchaos involving quasiperiodic regimes, crises and chaotic intermittent attractors is followed, and the critical magnetic Prandtl number ($P_m^c$) for dynamo action is determined as a function of Ra. A mechanism for the onset of on-off intermittency in the magnetic energy is described, the most beneficial convective regimes for dynamo action are identified, and how intermittency affects the dependence of $P_m^c$ on Ra is discussed.

  16. Magnetic Field Structure from Synchrotron Polarization

    CERN Document Server

    Beck, R

    2006-01-01

    Total magnetic fields in spiral galaxies, as observed through their total synchrotron emission, are strongest (up to \\simeq 30\\mu G) in the spiral arms. The degree of radio polarization is low; the field in the arms must be mostly turbulent or tangled. Polarized synchrotron emission shows that the resolved regular fields are generally strongest in the interarm regions (up to \\simeq 15\\mu G), sometimes forming 'magnetic arms' parallel to the optical arms. The field structure is spiral in almost every galaxy, even in flocculent and bright irregular types which lack spiral arms. The observed large-scale patterns of Faraday rotation in several massive spiral galaxies reveal coherent regular fields, as predicted by dynamo models. However, in most galaxies observed so far no simple patterns of Faraday rotation could be found. Either many dynamo modes are superimposed and cannot be resolved by present-day telescopes, or most of the apparently regular field is in fact anisotropic random, with frequent reversals, due ...

  17. Feynman's Proof and Non-Elastic Displacement Fields: Relationship Between Magnetic Field and Defects Field

    Science.gov (United States)

    Nakamura, Nozomu; Yamasaki, Kazuhito

    2016-08-01

    We consider the relationship between the magnetic field and the non-elastic displacement field including defects, from the viewpoints of non-commutativity of the positions and non-commutativity of the derivatives. The former non-commutativity is related to the magnetic field by Feynman's proof (1948), and the latter is related to the defect fields by the continuum theory of defects. We introduce the concept of differential geometry to the non-elastic displacement field and derive an extended relation that includes basic equations, such as Gauss's law for magnetism and the conservation law for dislocation density. The relation derived in this paper also extends the first Bianchi identity in linear approximation to include the effect of magnetism. These findings suggest that Feynman's approach with a non-elastic displacement field is useful for understanding the relationship between magnetism and non-elastic mechanics.

  18. Feynman's Proof and Non-Elastic Displacement Fields: Relationship Between Magnetic Field and Defects Field

    Science.gov (United States)

    Nakamura, Nozomu; Yamasaki, Kazuhito

    2016-12-01

    We consider the relationship between the magnetic field and the non-elastic displacement field including defects, from the viewpoints of non-commutativity of the positions and non-commutativity of the derivatives. The former non-commutativity is related to the magnetic field by Feynman's proof (1948), and the latter is related to the defect fields by the continuum theory of defects. We introduce the concept of differential geometry to the non-elastic displacement field and derive an extended relation that includes basic equations, such as Gauss's law for magnetism and the conservation law for dislocation density. The relation derived in this paper also extends the first Bianchi identity in linear approximation to include the effect of magnetism. These findings suggest that Feynman's approach with a non-elastic displacement field is useful for understanding the relationship between magnetism and non-elastic mechanics.

  19. Application of high magnetic fields in advanced materials processing

    Institute of Scientific and Technical Information of China (English)

    MA Yanwei; XIAO Liye; YAN Luguang

    2006-01-01

    Recently, steady magnetic fields available from cryogen-free superconducting magnets open up new ways to process materials. In this paper,the main results obtained by using a high magnetic field to process several advanced materials are reviewed. These processed objects primarily include superconducting, magnetic, metallic and nanometer-scaled materials. It has been found that a high magnetic field can effectively align grains when fabricating the magnetic and non-magnetic materials and make inclusions migrate in a molten metal. The mechanism is discussed from the theoretical viewpoint of magnetization energy.

  20. Improving Magnet Designs With High and Low Field Regions

    DEFF Research Database (Denmark)

    Bjørk, Rasmus; Bahl, Christian Robert Haffenden; Smith, Anders

    2011-01-01

    to low field regions. Also, a general way to replace magnet material with a high permeability soft magnetic material where appropriate is discussed. As an example, these schemes are applied to a two dimensional concentric Halbach cylinder design resulting in a reduction of the amount of magnet material......A general scheme for increasing the difference in magnetic flux density between a high and a low magnetic field region by removing unnecessary magnet material is presented. This is important in, e.g., magnetic refrigeration where magnet arrays have to deliver high field regions in close proximity...