Sample records for non-ionizing radiofrequency fields

  1. Adaptive Response in Animals Exposed to Non-Ionizing Radiofrequency Fields: Some Underlying Mechanisms

    PubMed Central

    Cao, Yi; Tong, Jian

    2014-01-01

    During the last few years, our research group has been investigating the phenomenon of adaptive response in animals exposed to non-ionizing radiofrequency fields. The results from several separate studies indicated a significant increase in survival, decreases in genetic damage as well as oxidative damage and, alterations in several cellular processes in mice pre-exposed to radiofrequency fields and subsequently subjected to sub-lethal or lethal doses of ?-radiation or injected with bleomycin, a radiomimetic chemical mutagen. These observations indicated the induction of adaptive response providing the animals the ability to resist subsequent damage. Similar studies conducted by independent researchers in mice and rats have supported our observation on increased survival. In this paper, we have presented a brief review of all of our own and other independent investigations on radiofrequency fields-induced adaptive response and some underlying mechanisms discussed. PMID:24758897

  2. Analysis of estimation of electromagnetic dosimetric values from non-ionizing radiofrequency fields in conventional road vehicle environments.

    PubMed

    Aguirre, Erik; Iturri, Peio Lopez; Azpilicueta, Leire; de Miguel-Bilbao, Silvia; Ramos, Victoria; Gárate, Uxue; Falcone, Francisco

    2015-03-01

    Abstract A high number of wireless technologies can be found operating in vehicular environments with the aim of offering different services. The dosimetric evaluation of this kind of scenarios must be performed in order to assess their compatibility with current exposure limits. In this work, a dosimetric evaluation inside a conventional car is performed, with the aid of an in-house 3D Ray Launching computational code, which has been compared with measurement results of wireless sensor networks located inside the vehicle. These results can aid in an adequate assessment of human exposure to non-ionizing radiofrequency fields, taking into account the impact of the morphology and the topology of the vehicle for current as well as for future exposure limits. PMID:24460417

  3. Estimation of electromagnetic dosimetric values from non-ionizing radiofrequency fields in an indoor commercial airplane environment.

    PubMed

    Aguirre, Erik; Arpón, Javier; Azpilicueta, Leire; López, Peio; de Miguel, Silvia; Ramos, Victoria; Falcone, Francisco

    2014-12-01

    In this article, the impact of topology as well as morphology of a complex indoor environment such as a commercial aircraft in the estimation of dosimetric assessment is presented. By means of an in-house developed deterministic 3D ray-launching code, estimation of electric field amplitude as a function of position for the complete volume of a commercial passenger airplane is obtained. Estimation of electromagnetic field exposure in this environment is challenging, due to the complexity and size of the scenario, as well as to the large metallic content, giving rise to strong multipath components. By performing the calculation with a deterministic technique, the complete scenario can be considered with an optimized balance between accuracy and computational cost. The proposed method can aid in the assessment of electromagnetic dosimetry in the future deployment of embarked wireless systems in commercial aircraft. PMID:23915231

  4. Genetic damage in human cells exposed to non-ionizing radiofrequency fields: a meta-analysis of the data from 88 publications (1990-2011).

    PubMed

    Vijayalaxmi; Prihoda, Thomas J

    2012-12-12

    Based on the 'limited' evidence suggesting an association between exposure to radiofrequency fields (RF) emitted from mobile phones and two types of brain cancer, glioma and acoustic neuroma, the International Agency for Research on Cancer has classified RF as 'possibly carcinogenic to humans' in group 2B. In view of this classification and the positive correlation between increased genetic damage and carcinogenesis, a meta-analysis was conducted to determine whether a significant increase in genetic damage in human cells exposed to RF provides a potential mechanism for its carcinogenic potential. The extent of genetic damage in human cells, assessed from various end-points, viz., single-/double-strand breaks in the DNA, incidence of chromosomal aberrations, micronuclei and sister chromatid exchanges, reported in a total of 88 peer-reviewed scientific publications during 1990-2011 was considered in the meta-analysis. Among the several variables in the experimental protocols used, the influence of five specific variables related to RF exposure characteristics was investigated: (i) frequency, (ii) specific absorption rate, (iii) exposure as continuous wave, pulsed wave and occupationally exposed/mobile phone users, (iv) duration of exposure, and (v) different cell types. The data indicated the following. (1) The magnitude of difference between RF-exposed and sham-/un-exposed controls was small with some exceptions. (2) In certain RF exposure conditions there was a statistically significant increase in genotoxicity assessed from some end-points: the effect was observed in studies with small sample size and was largely influenced by publication bias. Studies conducted within the generally recommended RF exposure guidelines showed a smaller effect. (3) The multiple regression analyses and heterogeneity goodness of fit data indicated that factors other than the above five variables as well as the quality of publications have contributed to the overall results. (4) More importantly, the mean indices for chromosomal aberrations, micronuclei and sister chromatid exchange end-points in RF-exposed and sham-/un-exposed controls were within the spontaneous levels reported in a large data-base. Thus, the classification of RF as possibly carcinogenic to humans in group 2B was not supported by genotoxicity-based mechanistic evidence. PMID:23022599

  5. Measurement of radiofrequency fields

    SciTech Connect

    Leonowich, J.A.

    1992-05-01

    We are literally surrounded by radiofrequency (RFR) and microwave radiation, from both natural and man-made sources. The identification and control of man-made sources of RFR has become a high priority of radiation safety professionals in recent years. For the purposes of this paper, we will consider RFR to cover the frequencies from 3 kHz to 300 MHz, and microwaves from 300 MHz to 300 GHz, and will use the term RFR interchangeably to describe both. Electromagnetic radiation and field below 3 kHz is considered Extremely Low Frequency (ELF) and will not be discussed in this paper. Unlike x- and gamma radiation, RFR is non-ionizing. The energy of any RFR photon is insufficient to produce ionizations in matter. The measurement and control of RFR hazards is therefore fundamentally different from ionizing radiation. The purpose of this paper is to acquaint the reader with the fundamental issues involved in measuring and safely using RFR fields. 23 refs.

  6. Radiofrequency field surveys in hospitals.

    PubMed

    Foster, K R; Soltys, M; Arnofsky, S; Doshi, P; Hanover, D; Mercado, R; Schleck, D

    1996-01-01

    The authors surveyed levels of radiofrequency (RF) fields in the frequency range 0.1-1,000 MHz in four hospitals in the Philadelphia area, to obtain background information related to the possible interference of radiofrequency fields with medical equipment. Two large center-city hospitals, a regional county hospital, and two suburban hospitals were surveyed. Measurements were made at six to 12 sites in each hospital, in each of the three frequency bands. More limited additional measurements were conducted in a fifth hospital as well. Sites were selected to include areas where strong RF signals from transmitting antennas might be expected to be present (e.g., locations close to windows in upper stories of buildings near paging antennas) as well as other representative sites in the hospital. The median RF field strengths were quite low (0.1-0.5 V/m), but at specific locations the RF signals from broadcast sources exceeded 1 V/m. Much stronger fields were recorded close to electrosurgical units and hand-held transmitters (cellular telephones and UHF transceivers). PMID:8673165

  7. Superconducting surface impedance under radiofrequency field

    DOE PAGESBeta

    Xiao, Binping [JLAB, William and Mary College; Reece, Charles E. [JLAB; Kelley, Michael J. [JLAB, William and Mary College

    2013-07-01

    Based on BCS theory with moving Cooper pairs, the electron states distribution at 0K and the probability of electron occupation with finite temperature have been derived and applied to anomalous skin effect theory to obtain the surface impedance of a superconductor under radiofrequency (RF) field. We present the numerical results for Nb and compare these with representative RF field-dependent effective surface resistance measurements from a 1.5 GHz resonant structure.

  8. Thermographic measurements on unrestrained Swiss albino mice exposed to non-ionizing electromagnetic field (EMF) of 2.14 GHz UMTS downlink frequency

    Microsoft Academic Search

    M. A. Murad; F. Malek; A. Rusnani; W. F. Wan Ahmad; A. D. Usman

    2010-01-01

    Thermographic measurements were performed on Mus musculus (Swiss albino mice) exposed to non-ionizing electromagnetic field (EMF) of 2.14 GHz Universal Mobile Telecommunication System (UMTS) downlink frequency to determine thermal effect. Sham-exposed mice samples show consistent transient increase in daily mean body temperature. The mice samples were expected to experience a rise in body temperature when exposed to UMTS signal. However,

  9. Assessment of outdoor radiofrequency electromagnetic field exposure through hotspot localization using kriging-based sequential sampling.

    PubMed

    Aerts, Sam; Deschrijver, Dirk; Verloock, Leen; Dhaene, Tom; Martens, Luc; Joseph, Wout

    2013-10-01

    In this study, a novel methodology is proposed to create heat maps that accurately pinpoint the outdoor locations with elevated exposure to radiofrequency electromagnetic fields (RF-EMF) in an extensive urban region (or, hotspots), and that would allow local authorities and epidemiologists to efficiently assess the locations and spectral composition of these hotspots, while at the same time developing a global picture of the exposure in the area. Moreover, no prior knowledge about the presence of radiofrequency radiation sources (e.g., base station parameters) is required. After building a surrogate model from the available data using kriging, the proposed method makes use of an iterative sampling strategy that selects new measurement locations at spots which are deemed to contain the most valuable information-inside hotspots or in search of them-based on the prediction uncertainty of the model. The method was tested and validated in an urban subarea of Ghent, Belgium with a size of approximately 1 km2. In total, 600 input and 50 validation measurements were performed using a broadband probe. Five hotspots were discovered and assessed, with maximum total electric-field strengths ranging from 1.3 to 3.1 V/m, satisfying the reference levels issued by the International Commission on Non-Ionizing Radiation Protection for exposure of the general public to RF-EMF. Spectrum analyzer measurements in these hotspots revealed five radiofrequency signals with a relevant contribution to the exposure. The radiofrequency radiation emitted by 900 MHz Global System for Mobile Communications (GSM) base stations was always dominant, with contributions ranging from 45% to 100%. Finally, validation of the subsequent surrogate models shows high prediction accuracy, with the final model featuring an average relative error of less than 2dB (factor 1.26 in electric-field strength), a correlation coefficient of 0.7, and a specificity of 0.96. PMID:23759207

  10. Magnetoreception in birds: the effect of radio-frequency fields.

    PubMed

    Wiltschko, Roswitha; Thalau, Peter; Gehring, Dennis; Nießner, Christine; Ritz, Thorsten; Wiltschko, Wolfgang

    2015-02-01

    The avian magnetic compass, probably based on radical pair processes, works only in a narrow functional window around the local field strength, with cryptochrome 1a as most likely receptor molecule. Radio-frequency fields in the MHz range have been shown to disrupt the birds' orientation, yet the nature of this interference is still unclear. In an immuno-histological study, we tested whether the radio-frequency fields interfere with the photoreduction of cryptochrome, but this does not seem to be the case. In behavioural studies, birds were not able to adjust to radio-frequency fields like they are able to adjust to static fields outside the normal functional range: neither a 2-h pre-exposure in a 7.0 MHz field, 480 nT, nor a 7-h pre-exposure in a 1.315 MHz field, 15 nT, allowed the birds to regain their orientation ability. This inability to adjust to radio-frequency fields suggests that these fields interfere directly with the primary processes of magnetoreception and therefore disable the avian compass as long as they are present. They do not have lasting adverse after-effects, however, as birds immediately after exposure to a radio-frequency field were able to orient in the local geomagnetic field. PMID:25540238

  11. Assessment of outdoor radiofrequency electromagnetic field exposure through hotspot localization using kriging-based sequential sampling

    SciTech Connect

    Aerts, Sam, E-mail: sam.aerts@intec.ugent.be; Deschrijver, Dirk; Verloock, Leen; Dhaene, Tom; Martens, Luc; Joseph, Wout

    2013-10-15

    In this study, a novel methodology is proposed to create heat maps that accurately pinpoint the outdoor locations with elevated exposure to radiofrequency electromagnetic fields (RF-EMF) in an extensive urban region (or, hotspots), and that would allow local authorities and epidemiologists to efficiently assess the locations and spectral composition of these hotspots, while at the same time developing a global picture of the exposure in the area. Moreover, no prior knowledge about the presence of radiofrequency radiation sources (e.g., base station parameters) is required. After building a surrogate model from the available data using kriging, the proposed method makes use of an iterative sampling strategy that selects new measurement locations at spots which are deemed to contain the most valuable information—inside hotspots or in search of them—based on the prediction uncertainty of the model. The method was tested and validated in an urban subarea of Ghent, Belgium with a size of approximately 1 km{sup 2}. In total, 600 input and 50 validation measurements were performed using a broadband probe. Five hotspots were discovered and assessed, with maximum total electric-field strengths ranging from 1.3 to 3.1 V/m, satisfying the reference levels issued by the International Commission on Non-Ionizing Radiation Protection for exposure of the general public to RF-EMF. Spectrum analyzer measurements in these hotspots revealed five radiofrequency signals with a relevant contribution to the exposure. The radiofrequency radiation emitted by 900 MHz Global System for Mobile Communications (GSM) base stations was always dominant, with contributions ranging from 45% to 100%. Finally, validation of the subsequent surrogate models shows high prediction accuracy, with the final model featuring an average relative error of less than 2 dB (factor 1.26 in electric-field strength), a correlation coefficient of 0.7, and a specificity of 0.96. -- Highlights: • We present an iterative measurement and modeling method for outdoor RF-EMF exposure. • Hotspots are rapidly identified, and accurately characterized. • An accurate graphical representation, or heat map, is created, using kriging. • Random validation shows good correlation (0.7) and low relative errors (2 dB)

  12. A novel model of interaction between high frequency electromagnetic non-ionizing fields and microtubules viewed as coupled two-degrees of freedom harmonic oscillators.

    PubMed

    Caligiuri, Luigi Maxmilian

    2015-01-01

    The question regarding the potential biological and adverse health effects of non-ionizing electromagnetic fields on living organisms is of primary importance in biophysics and medicine. Despite the several experimental evidences showing such occurrence in a wide frequency range from extremely low frequency to microwaves, a definitive theoretical model able to explain a possible mechanism of interaction between electromagnetic fields and living matter, especially in the case of weak and very weak intensities, is still missing. In this paper it has been suggested a possible mechanism of interaction involving the resonant absorption of electromagnetic radiation by microtubules. To this aim these have been modeled as non-dissipative forced harmonic oscillators characterized by two coupled "macroscopic" degrees of freedom, respectively describing longitudinal and transversal vibrations induced by the electromagnetic field. We have shown that the proposed model, although at a preliminary stage, is able to explain the ability of even weak electromagnetic radiating electromagnetic fields to transfer high quantities of energy to living systems by means of a resonant mechanism, so capable to easily damage microtubules structure. PMID:25714384

  13. International and National Expert Group Evaluations: Biological/Health Effects of Radiofrequency Fields

    PubMed Central

    Vijayalaxmi; Scarfi, Maria R.

    2014-01-01

    The escalated use of various wireless communication devices, which emit non-ionizing radiofrequency (RF) fields, have raised concerns among the general public regarding the potential adverse effects on human health. During the last six decades, researchers have used different parameters to investigate the effects of in vitro and in vivo exposures of animals and humans or their cells to RF fields. Data reported in peer-reviewed scientific publications were contradictory: some indicated effects while others did not. International organizations have considered all of these data as well as the observations reported in human epidemiological investigations to set-up the guidelines or standards (based on the quality of published studies and the “weight of scientific evidence” approach) for RF exposures in occupationally exposed individuals and the general public. Scientists with relevant expertise in various countries have also considered the published data to provide the required scientific information for policy-makers to develop and disseminate authoritative health information to the general public regarding RF exposures. This paper is a compilation of the conclusions, on the biological effects of RF exposures, from various national and international expert groups, based on their analyses. In general, the expert groups suggested a reduction in exposure levels, precautionary approach, and further research. PMID:25211777

  14. Occupational exposure to radio-frequency electromagnetic fields

    SciTech Connect

    Mild, K.H.

    1980-01-01

    The paper considers occupational exposure to radio-frequency (RF) electromagnetic (EM) fields in industrial processes in near-field situations where electric and magnetic field strengths are monitored to assess the health hazard. Plastic materials are joined by an RF machine whose electrodes are not shielded and which may produce high level RF fields in the immediate vicinity, exceeding the ANSI standard. A physiotherapist may be exposed to high E and H fields using RF shortwave therapy, the maintenance personnel in FM/TV broadcast towers are subject to intense RF fields, and induction heating equipment used for forging, annealing and brazing can expose operators' hands to magnetic fields.

  15. Adaptive Response in Mice Exposed to 900 MHz Radiofrequency Fields: Primary DNA Damage

    PubMed Central

    Zhou, Zhen; Zhang, Jie; Tong, Jian; Cao, Yi

    2012-01-01

    The phenomenon of adaptive response (AR) in animal and human cells exposed to ionizing radiation is well documented in scientific literature. We have examined whether such AR could be induced in mice exposed to non-ionizing radiofrequency fields (RF) used for wireless communications. Mice were pre-exposed to 900 MHz RF at 120 µW/cm2 power density for 4 hours/day for 1, 3, 5, 7 and 14 days and then subjected to an acute dose of 3 Gy ?-radiation. The primary DNA damage in the form of alkali labile base damage and single strand breaks in the DNA of peripheral blood leukocytes was determined using the alkaline comet assay. The results indicated that the extent of damage in mice which were pre-exposed to RF for 1 day and then subjected to ?-radiation was similar and not significantly different from those exposed to ?-radiation alone. However, mice which were pre-exposed to RF for 3, 5, 7 and 14 days showed progressively decreased damage and was significantly different from those exposed to ?-radiation alone. Thus, the data indicated that RF pre-exposure is capable of inducing AR and suggested that the pre-exposure for more than 4 hours for 1 day is necessary to elicit such AR. PMID:22389679

  16. Bray-Liebhafsky oscillatory reaction in the radiofrequency electromagnetic field

    NASA Astrophysics Data System (ADS)

    Stanisavljev, Dragomir R.; Veliki?, Zoran; Veselinovi?, Dragan S.; Jaci?, Nevena V.; Milenkovi?, Maja C.

    2014-09-01

    Oscillatory Bray-Liebhafsky (BL) reaction is capacitively coupled with the electromagnetic radiation in the frequency range 60-110 MHz. Because of the specific reaction dynamics characterized by several characteristic parameters (induction period, period between chemical oscillations and their amplitude) it served as a good model system for the investigation of the effects of radiofrequent (RF) radiation. RF power of up to 0.2 W did not produce observable changes of the BL reaction parameters in the limit of the experiment reproductivity. Results indicate that, under the given experimental conditions, both dissipative and reactive properties of the solution are not considerably coupled with the RF electrical field.

  17. Biological effects and exposure criteria for radiofrequency electromagnetic fields

    SciTech Connect

    Not Available

    1986-01-01

    This report, which begins with a discussion of fundamental studies at the molecular level, presents a review of the subject matter covered in NCRP Report No. 67 on mechanisms of interaction of radiofrequency electromagnetic (RFEM) fields with tissue. The discussion continues to progressively larger scales of interaction, beginning with macromolecular and cellular effects, chromosomal and mutagenic effects, and carcinogenic effects. The scope of the subject matter is then expanded to include systemic effects such as those on reproduction, growth, and development, hematopoiesis and immunology, endocrinology and autonomic nervous function, cardiovascular effects and cerebrovascular effects. The interaction of electromagnetic fields with the central nervous system and special senses is also discussed. Also included are epidemiological studies, a discussion of thermoregulation, and a history of therapeutic applications of RFEM fields. The report concludes with human exposure criteria and rationale.

  18. Pancreatic carcinoma cells are susceptible to non-invasive radiofrequency fields after treatment with targeted gold nanoparticles

    PubMed Central

    Glazer, E. S.; Massey, K. L.; Zhu, C.; Curley, S. A.

    2010-01-01

    Background Gold and carbon nanoparticles absorb non-ionizing radiofrequency (RF) energy and release heat. Solid gold nanoparticles are delivered to cancer cells via conjugation with targeting antibodies. Here, 20 nm gold particles were conjugated to cetuximab, an epidermal growth factor recpetor-1 (EGFR-1) antibody. Methods A pancreatic carcinoma cell line that highly expresses EGFR-1, Panc-1, and a breast carcinoma cell line that minimally expresses EGFR-1, Cama-1, were treated with 100 nM cetuximab-conjugated gold nanoparticles for 3 hours (n = 4). Thirty-six hours later, the dishes were placed in an RF field with a generator power of 200 W for 5 minutes. After another 36 hours, cell injury and death were evaluated with flow cytometry. Results The targeted cell line, Panc-1, had a viability of 45.5% ± 11.7% while Cama-1 cell had a viability of 91.7% ± 1.6% after RF field exposure (p < 0.008). Transmission electron microscopy showed gold nanoparticle uptake in Panc-1 cells, but negligible uptake by Cama-1 cells. Non-targeted cells do not internalize a sufficient amount of antibody-conjugated gold nanoparticles to induce injury in a noninvasive RF field. Conclusion This technique could be useful in cancer treatment provided a cancer-specific antibody is utilized to localize gold nanoparticles to malignant cells. PMID:20541785

  19. Electromagnetic and Thermal Aspects of Radiofrequency Field Propagation in UltraHigh Field MRI

    Microsoft Academic Search

    A. L. H. M. W. van Lier

    2012-01-01

    In MRI, a radiofrequency (RF) pulse is used to generate a signal from the spins that are polarized by a strong magnetic field. For higher magnetic field strengths, a higher frequency of the RF pulse is required in order to match the Larmor frequency. A higher frequency, in turn, leads to a shorter wavelength. This results in undesirable spatial fluctuations

  20. Remotely triggered cisplatin release from carbon nanocapsules by radiofrequency fields.

    PubMed

    Raoof, Mustafa; Cisneros, Brandon T; Guven, Adem; Phounsavath, Sophia; Corr, Stuart J; Wilson, Lon J; Curley, Steven A

    2013-02-01

    The efficacy of nanoparticle-mediated drug delivery is limited by its peri-vascular sequestration, thus necessitating a strategy to trigger drug release from such intra-tumoral nanocarrier-drug depots. In our efforts to explore remotely-activated nanocarriers, we have developed carbon nanocapsules comprised of an ultra-short carbon nanotube shell (US-tubes) loaded with cisplatin (CDDP@US-tubes) and covered with a Pluronic surfactant wrapping to minimize passive release. We demonstrate here that non-invasive radiofrequency (RF) field activation of the CDDP@US-tubes produces heat that causes Pluronic disruption which triggers cisplatin release in an RF-dependent manner. Furthermore, release-dependent cytotoxicity is demonstrated in human hepatocellular carcinoma cell lines. PMID:23228421

  1. Effects of radiofrequency electromagnetic fields on the human nervous system.

    PubMed

    van Rongen, Eric; Croft, Rodney; Juutilainen, Jukka; Lagroye, Isabelle; Miyakoshi, Junji; Saunders, Richard; de Seze, René; Tenforde, Thomas; Verschaeve, Luc; Veyret, Bernard; Xu, Zhengping

    2009-10-01

    The effects of exposure to radiofrequency electromagnetic fields (EMF), specifically related to the use of mobile telephones, on the nervous system in humans have been the subject of a large number of experimental studies in recent years. There is some evidence of an effect of exposure to a Global System for Mobile Telecommunication (GSM)-type signal on the spontaneous electroencephalogram (EEG). This is not corroborated, however, by the results from studies on evoked potentials. Although there is some evidence emerging that there may be an effect of exposure to a GSM-type signal on sleep EEG, results are still variable. In summary, exposure to a GSM-type signal may result in minor effects on brain activity, but such changes have never been found to relate to any adverse health effects. No consistent significant effects on cognitive performance in adults have been observed. If anything, any effect is small and exposure seems to improve performance. Effects in children did not differ from those in healthy adults. Studies on auditory and vestibular function are more unequivocal: neither hearing nor the sense of balance is influenced by short-term exposure to mobile phone signals. Subjective symptoms over a wide range, including headaches and migraine, fatigue, and skin itch, have been attributed to various radiofrequency sources both at home and at work. However, in provocation studies a causal relation between EMF exposure and symptoms has never been demonstrated. There are clear indications, however, that psychological factors such as the conscious expectation of effect may play an important role in this condition. PMID:20183535

  2. Probing the fundamental limit of niobium in high radiofrequency fields by dual mode excitation in superconducting radiofrequency cavities

    SciTech Connect

    Eremeev, Grigory; Geng, Rongli; Palczewski, Ari

    2011-07-01

    We have studied thermal breakdown in several multicell superconducting radiofrequency cavity by simultaneous excitation of two TM{sub 010} passband modes. Unlike measurements done in the past, which indicated a clear thermal nature of the breakdown, our measurements present a more complex picture with interplay of both thermal and magnetic effects. JLab LG-1 that we studied was limited at 40.5 MV/m, corresponding to B{sub peak} = 173 mT, in 8{pi}/9 mode. Dual mode measurements on this quench indicate that this quench is not purely magnetic, and so we conclude that this field is not the fundamental limit in SRF cavities.

  3. Recent Advances in Research on Radiofrequency Fields and Health: 2001–2003

    Microsoft Academic Search

    Daniel Krewski; Barry W. Glickman; Riadh W. Y. Habash; Brian Habbick; W. Gregory Lotz; Rosemonde Mandeville; Frank S. Prato; Tarek Salem; Donald F. Weaver

    2007-01-01

    The widespread use of wireless telecommunications devices, particularly mobile phones, has resulted in increased human exposure to radiofrequency (RF) fields. Although national and international agencies have established safety guidelines for exposure to RF fields, concerns remain about the potential for adverse health outcomes to occur in relation to RF field exposure. The extensive literature on RF fields and health has

  4. Recent Advances in Research on Radiofrequency Fields and Health: 2004–2007

    Microsoft Academic Search

    Riadh W. Y. Habash; J. Mark Elwood; Daniel Krewski; W. Gregory Lotz; James P. McNamee; Frank S. Prato

    2009-01-01

    The widespread use of wireless telecommunications devices, particularly mobile phones and wireless networks, has resulted in increased human exposure to radiofrequency (RF) fields. Although national and international agencies have established safety guidelines for exposure to RF fields, concerns remain about the potential for adverse health outcomes to occur in relation to RF field exposure. The extensive literature on RF fields

  5. Effect of a 2.45-GHz radiofrequency electromagnetic field on neutrophil chemotaxis and phagocytosis in differentiated human HL-60 cells.

    PubMed

    Koyama, Shin; Narita, Eijiro; Suzuki, Yoshihisa; Taki, Masao; Shinohara, Naoki; Miyakoshi, Junji

    2015-01-01

    The potential public health risks of radiofrequency (RF) fields have been discussed at length, especially with the use of mobile phones spreading extensively throughout the world. In order to investigate the properties of RF fields, we examined the effect of 2.45-GHz RF fields at the specific absorption rate (SAR) of 2 and 10 W/kg for 4 and 24 h on neutrophil chemotaxis and phagocytosis in differentiated human HL-60 cells. Neutrophil chemotaxis was not affected by RF-field exposure, and subsequent phagocytosis was not affected either compared with that under sham exposure conditions. These studies demonstrated an initial immune response in the human body exposed to 2.45-GHz RF fields at the SAR of 2 W/kg, which is the maximum value recommended by the International Commission for Non-Ionizing Radiation Protection (ICNIRP) guidelines. The results of our experiments for RF-field exposure at an SAR under 10 W/kg showed very little or no effects on either chemotaxis or phagocytosis in neutrophil-like human HL-60 cells. PMID:25194051

  6. Diverse Radiofrequency Sensitivity and Radiofrequency Effects of Mobile or Cordless Phone near Fields Exposure in Drosophila melanogaster

    PubMed Central

    Geronikolou, Styliani; Zimeras, Stelios; Davos, Constantinos H.; Michalopoulos, Ioannis; Tsitomeneas, Stephanos

    2014-01-01

    Introduction The impact of electromagnetic fields on health is of increasing scientific interest. The aim of this study was to examine how the Drosophila melanogaster animal model is affected when exposed to portable or mobile phone fields. Methods/Results Two experiments have been designed and performed in the same laboratory conditions. Insect cultures were exposed to the near field of a 2G mobile phone (the GSM 2G networks support and complement in parallel the 3G wide band or in other words the transmission of information via voice signals is served by the 2G technology in both mobile phones generations) and a 1880 MHz cordless phone both digitally modulated by human voice. Comparison with advanced statistics of the egg laying of the second generation exposed and non-exposed cultures showed limited statistical significance for the cordless phone exposed culture and statistical significance for the 900 MHz exposed insects. We calculated by physics, simulated and illustrated in three dimensional figures the calculated near fields of radiation inside the experimenting vials and their difference. Comparison of the power of the two fields showed that the difference between them becomes null when the experimental cylinder radius and the height of the antenna increase. Conclusions/Significance Our results suggest a possible radiofrequency sensitivity difference in insects which may be due to the distance from the antenna or to unexplored intimate factors. Comparing the near fields of the two frequencies bands, we see similar not identical geometry in length and height from the antenna and that lower frequencies tend to drive to increased radiofrequency effects. PMID:25402465

  7. A Method for Evaluating the Magnetic Field Homogeneity of a Radiofrequency Coil by Its Field Histogram

    NASA Astrophysics Data System (ADS)

    Yang, Q. X.; Li, S. H.; Smith, M. B.

    The magnetic field homogeneity of a radiofrequency coil is very important in both magnetic resonance imaging and spectroscopy. In this report, a method is proposed for quantitatively evaluating the RF magnetic field homogeneity from its histogram, which is obtained by either experimental measurement or theoretical calculation. The experimental histogram and theoretical histogram can be compared directly to verify the theoretical findings. The RF field homogeneities of the bird-cage coil, slotted-tube resonator, cosine wire coil, and a new radial plate coil design were evaluated using this method. The results showed that the experimental histograms and the corresponding theoretical histograms are consistent. This method provides an easy and sensitive way of evaluating the magnetic field homogeneity and facilitates the design and evaluation of new RF coil configurations.

  8. Comment on enhancement of forbidden nuclear beta decay by high-intensity radio-frequency fields

    Microsoft Academic Search

    W. Becker; R. R. Schlicher; M. O. Scully

    1984-01-01

    A recent claim that forbidden nuclear beta decay can, by the application of a high-intensity radio-frequency field, be enhanced by many orders of magnitude is contested. The effect is shown to be nonexistent, at least within the theoretical model which has been adopted thus far.

  9. Health effects of non-ionized electromagnetic radiation

    Microsoft Academic Search

    N. Kumar

    2008-01-01

    Summary form only given. Low-frequency magnetic fields induce circulating currents within the human body. The strength of these currents depends on the intensity of the outside magnetic field. If sufficiently large, these currents could cause stimulation of nerves and muscles or affect other biological processes. To date, no adverse health effect from low level, long-term exposure to radiofrequency or power

  10. Anthropogenic radiofrequency electromagnetic fields as an emerging threat to wildlife orientation.

    PubMed

    Balmori, Alfonso

    2015-06-15

    The rate of scientific activity regarding the effects of anthropogenic electromagnetic radiation in the radiofrequency (RF) range on animals and plants has been small despite the fact that this topic is relevant to the fields of experimental biology, ecology and conservation due to its remarkable expansion over the past 20years. Current evidence indicates that exposure at levels that are found in the environment (in urban areas and near base stations) may particularly alter the receptor organs to orient in the magnetic field of the earth. These results could have important implications for migratory birds and insects, especially in urban areas, but could also apply to birds and insects in natural and protected areas where there are powerful base station emitters of radiofrequencies. Therefore, more research on the effects of electromagnetic radiation in nature is needed to investigate this emerging threat. PMID:25747364

  11. Radiofrequency and Extremely Low-Frequency Electromagnetic Field Effects on the Blood-Brain Barrier

    Microsoft Academic Search

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

    2008-01-01

    During the last century, mankind has introduced electricity and during the very last decades, the microwaves of the modern communication society have spread a totally new entity—the radiofrequency fields—around the world. How does this affect biology on Earth? The mammalian brain is protected by the blood-brain barrier, which prevents harmful substances from reaching the brain tissue. There is evidence that

  12. Exposure to extremely-low-frequency electromagnetic fields and radiofrequency radiation: cardiovascular effects in humans

    Microsoft Academic Search

    James R. Jauchem

    1997-01-01

    Cardiovascular changes in humans exposed to nonionizing radiation [including extremely-low-frequency electromagnetic fields\\u000a (ELF EMFs) and radiofrequency radiation (RFR)] are reviewed. Both acute and long-term effects have been investigated. In general,\\u000a if heating does not occur during exposure, current flow appears to be necessary for major cardiovascular effects to ensue,\\u000a such as those due to electric shock. Whereas most studies have

  13. Effects of field orientation during 700MHz radiofrequency irradiation of rats

    Microsoft Academic Search

    M. R. Frei; J. R. Jauchem; J. M. Padilla

    1989-01-01

    Ketamine-anesthetized Sprague-Dawley rats were exposed to far-field 700-MHz continuous-wave radiofrequency radiation (RFR) in both E and H orientations. Irradiation was conducted at whole-body average specific absorption rates (SARs) of 9.2 and 13.0 W\\/kg (E and H, respectively) that resulted in approximately equivalent colonic specific heating rates (SHRs). Exposures were performed to repeatedly increase colonic temperature by 1 degree C (38.5

  14. Effects of field orientation during 700MHz radiofrequency irradiation of rats

    Microsoft Academic Search

    M. R. Frei; J. R. Jauchem; J. M. Padilla

    1989-01-01

    Ketamine-anesthetized Sprague-Dawley rats were exposed to far-field 700-MHz continuous-wave radiofrequency radiation (RFR) in both E and H orientations. Irradiation was conducted at whole-body average specific absorption rates (SARs) of 9.2 and 13.0 W\\/kg (E and H, respectively) that resulted in approximately equivalent colonic specific heating rates (SHRs). Exposures were performed to repeatedly increase colonic temperature by 1 deg C (38.5

  15. Cardiac autonomic activity during sleep under the influence of radiofrequency electromagnetic fields

    Microsoft Academic Search

    Klaus Mann; Bernhard Connemann; Joachim Röschke

    2005-01-01

    Summary\\u000a Question of the study  We investigated the influence of radiofrequency electromagnetic fields emitted by digital mobile telephones on heart rate\\u000a variability (HRV) during sleep in healthy young men.\\u000a \\u000a \\u000a \\u000a Subjects and methods  For each subject, two polysommographies were carried out in the sleep laboratory under field and sham exposure, respectively.\\u000a Field intensity was weak so that thermal effects could be excluded. HRV

  16. Ion Heating in Field-Reversed Configuration by Radio-Frequency Waves

    NASA Astrophysics Data System (ADS)

    Svidzinski, V. A.; Prager, S. C.

    2003-12-01

    A simple modeling of the recent experiment on plasma heating by radio-frequency (rf) waves in the field-reversed configuration (FRC) is made. In the FRC Injection Experiment device the ion heating by rf pulse was observed. Present analysis indicates that the heating can be explained by the Doppler broadening of the ion cyclotron resonance in the low magnetic field device. These results support the suggestion that the direct heating of the ion majority near the fundamental ion cyclotron frequency should be efficient in low field configurations.

  17. The temperature field simulation of radiofrequency catheter-based renal sympathetic denervation for resistant hypertension.

    PubMed

    Guo, Xuemei; Zhai, Fei; Nan, Qun

    2014-01-01

    Renal sympathetic denervation (RSD) by the radiofrequency ablation was used to treat the resistant hypertension in clinic and has achieved curative effect. But the temperature distribution in the artery walls and the blood flow have not been investigated. Finite element method (FEM) based on Comsol Multiphysics 4.3a software was used to simulate the temperature distribution in the renal artery. The results of renal artery temperature distribution as well as blood flow effect on the temperature field were obtained, which demonstrated that the blood velocity is very crucial in the temperature distribution of blood vessel near antenna. When the speed of blood is 0.4 m/s, the highest temperature rise of arterial wall near the antenna is 8.882°C (37°C to 45.882°C) and contralateral artery wall's highest temperature rise is about 5°C (37°C to 42°C). This temperature value can damage renal sympathetic nerves to cure the resistant hypertension. Due to the blood flow, the temperature field stretches to the direction of blood flow. The temperature rise of blood is only in a small range (37°C to 41°C) at both ends of the antenna. The simulation of RSD by the radiofrequency ablation can give doctors a better scheme to avoid the vascular injury in different blood flow rates and radiofrequency voltages. PMID:24211912

  18. Radio-frequency and microwave energies, magnetic and electric fields

    NASA Technical Reports Server (NTRS)

    Michaelson, S. M.

    1975-01-01

    The biological effects of radio frequency, including microwave, radiation are considered. Effects on body temperature, the eye, reproductive systems, internal organs, blood cells, the cardiovascular system, and the central nervous system are included. Generalized effects of electric and magnetic fields are also discussed. Experimentation with animals and clinical studies on humans are cited, and possible mechanisms of the effects observed are suggested.

  19. Field orientation effects during 5. 6GHz radiofrequency irradiation of rats

    Microsoft Academic Search

    M. R. Frei; J. R. Jauchem; D. L. Price; J. M. Padilla

    1990-01-01

    Ketamine-anesthetized Sprague-Dawley rats were exposed in E and H orientations (long axis parallel to electric and magnetic fields, respectively) to far-field 5.6-GHz continuous-wave radio-frequency radiation (RFR). Power densities were used that resulted in equivalent whole-body average specific absorption rates of 14 W\\/kg in both orientations (90 mW\\/cm2 for E and 66 mW\\/cm2 for H). Irradiation was conducted to increase colonic

  20. Electromagnetic field exposure assessment in Europe radiofrequency fields (10?MHz-6?GHz).

    PubMed

    Gajšek, Peter; Ravazzani, Paolo; Wiart, Joe; Grellier, James; Samaras, Theodoros; Thuróczy, György

    2015-01-01

    Average levels of exposure to radiofrequency (RF) electromagnetic fields (EMFs) of the general public in Europe are difficult to summarize, as exposure levels have been reported differently in those studies in which they have been measured, and a large proportion of reported measurements were very low, sometimes falling below detection limits of the equipment used. The goal of this paper is to present an overview of the scientific literature on RF EMF exposure in Europe and to characterize exposure within the European population. A comparative analysis of the results of spot or long-term RF EMF measurements in the EU indicated that mean electric field strengths were between 0.08?V/m and 1.8?V/m. The overwhelming majority of measured mean electric field strengths were <1?V/m. It is estimated that <1% were above 6?V/m and <0.1% were above 20?V/m. No exposure levels exceeding European Council recommendations were identified in these surveys. Most population exposures from signals of radio and television broadcast towers were observed to be weak because these transmitters are usually far away from exposed individuals and are spatially sparsely distributed. On the other hand, the contribution made to RF exposure from wireless telecommunications technology is continuously increasing and its contribution was above 60% of the total exposure. According to the European exposure assessment studies identified, three population exposure categories (intermittent variable partial body exposure, intermittent variable low-level whole-body (WB) exposure and continuous low-level WB exposure) were recognized by the authors as informative for possible future risk assessment. PMID:23942394

  1. Radiofrequency field inhomogeneity compensation in high spatial resolution magnetic resonance spectroscopic imaging

    NASA Astrophysics Data System (ADS)

    Passeri, Alessandro; Mazzuca, Stefano; Del Bene, Veronica

    2014-06-01

    Clinical magnetic resonance spectroscopy imaging (MRSI) is a non-invasive functional technique, whose mathematical framework falls into the category of linear inverse problems. However, its use in medical diagnostics is hampered by two main problems, both linked to the Fourier-based technique usually implemented for spectra reconstruction: poor spatial resolution and severe blurring in the spatial localization of the reconstructed spectra. Moreover, the intrinsic ill-posedness of the MRSI problem might be worsened by (i) spatially dependent distortions of the static magnetic field (B0) distribution, as well as by (ii) inhomogeneity in the power deposition distribution of the radiofrequency magnetic field (B1). Among several alternative methods, slim (Spectral Localization by IMaging) and bslim (B0 compensated slim) are reconstruction algorithms in which a priori information concerning the spectroscopic target is introduced into the reconstruction kernel. Nonetheless, the influence of the B1 field, particularly when its operating wavelength is close to the size of the human organs being studied, continues to be disregarded. starslim (STAtic and Radiofrequency-compensated slim), an evolution of the slim and bslim methods, is therefore proposed, in which the transformation kernel also includes the B1 field inhomogeneity map, thus allowing almost complete 3D modelling of the MRSI problem. Moreover, an original method for the experimental determination of the B1 field inhomogeneity map specific to the target under evaluation is also included. The compensation capabilities of the proposed method have been tested and illustrated using synthetic raw data reproducing the human brain.

  2. Intracellular hyperthermia mediated by nanoparticles in radiofrequency fields in the treatment of pancreatic cancer

    NASA Astrophysics Data System (ADS)

    Glazer, Evan Scott

    Intracellular hyperthermic therapy may prove to be a unique and novel approach to the management of pancreatic cancer. Utilizing the principle of photothermal destruction, selective killing of cancer cells with minimal injury to normal tissues may be possible. This dissertation investigated the role of antibody targeted metal nanoparticles and the cytotoxic effects of nonionizing radiofrequency fields in pancreatic cancer. Cancer cell death was induced by heat release from intracellular metal nanoparticles after radiofrequency field exposure. Fluorescent and gold nanoparticles were delivered with two antibodies, cetuximab and PAM-4, to pancreatic cancer cells in vitro and mouse xenografts in vivo. Selective delivery of these nanoparticles induced cell death in vitro and decreased tumor burden in vivo after whole animal RF field exposure. This occurred through both apoptosis and necrosis. In addition, activated caspase-3 was increased after antibody treatment and RF field exposure. Furthermore, although there was non-specific uptake by the liver and spleen in vivo, there was no evidence of acute or chronic toxicity in the animals. These results are in agreement with the principle that malignant cells are more thermally sensitive than normal cells or tissues. Selective intracellular delivery of metal nanoparticles coupled with whole body RF field exposure may be a beneficial therapy against micrometastases and unresectable pancreatic cancer in the future. Further studies are planned with more specific antibodies, other nanoparticles, and other cancer targets.

  3. Enhanced Field Emission Studies on Niobium Surfaces Relevant to High Field Superconducting Radio-Frequency Devices

    SciTech Connect

    Tong Wang

    2002-09-18

    Enhanced field emission (EFE) presents the main impediment to higher acceleration gradients in superconducting niobium (Nb) radiofrequency cavities for particle accelerators. The strength, number and sources of EFE sites strongly depend on surface preparation and handling. The main objective of this thesis project is to systematically investigate the sources of EFE from Nb, to evaluate the best available surface preparation techniques with respect to resulting field emission, and to establish an optimized process to minimize or eliminate EFE. To achieve these goals, a scanning field emission microscope (SFEM) was designed and built as an extension to an existing commercial scanning electron microscope (SEM). In the SFEM chamber of ultra high vacuum, a sample is moved laterally in a raster pattern under a high voltage anode tip for EFE detection and localization. The sample is then transferred under vacuum to the SEM chamber equipped with an energy-dispersive x-ray spectrometer for individual emitting site characterization. Compared to other systems built for similar purposes, this apparatus has low cost and maintenance, high operational flexibility, considerably bigger scan area, as well as reliable performance. EFE sources from planar Nb have been studied after various surface preparation, including chemical etching and electropolishing, combined with ultrasonic or high-pressure water rinse. Emitters have been identified, analyzed and the preparation process has been examined and improved based on EFE results. As a result, field-emission-free or near field-emission-free surfaces at ~140 MV/m have been consistently achieved with the above techniques. Characterization on the remaining emitters leads to the conclusion that no evidence of intrinsic emitters, i.e., no fundamental electric field limit induced by EFE, has been observed up to ~140 MV/m. Chemically etched and electropolished Nb are compared and no significant difference is observed up to ~140 MV/m. To address concerns on the effect of natural air drying process on EFE, a comparative study was conducted on Nb and the results showed insignificant difference under the experimental conditions. Nb thin films deposited on Cu present a possible alternative to bulk Nb in superconducting cavities. The EFE performance of a preliminary energetically deposited Nb thin film sample are presented.

  4. Amp\\`ere-Class Pulsed Field Emission from Carbon-Nanotube Cathodes in a Radiofrequency Resonator

    E-print Network

    Mihalcea, D; Hartzell, J; Panuganti, H; Boucher, S M; Murokh, A; Piot, P; Thangaraj, J C T

    2015-01-01

    Pulsed field emission from cold carbon-nanotube cathodes placed in a radiofrequency resonant cavity was observed. The cathodes were located on the backplate of a conventional $1+\\frac{1}{2}$-cell resonant cavity operating at 1.3-GHz and resulted in the production of bunch train with maximum average current close to 0.7 Amp\\`ere. The measured Fowler-Nordheim characteristic, transverse emittance, and pulse duration are presented and, when possible, compared to numerical simulations. The implications of our results to high-average-current electron sources are briefly discussed.

  5. Induction of an adaptive response in human blood lymphocytes exposed to radiofrequency fields: influence of the universal mobile telecommunication system (UMTS) signal and the specific absorption rate.

    PubMed

    Zeni, Olga; Sannino, Anna; Romeo, Stefania; Massa, Rita; Sarti, Maurizio; Reddy, Abishek B; Prihoda, Thomas J; Vijayalaxmi; Scarfì, Maria Rosaria

    2012-08-30

    The induction of an adaptive response (AR) was examined in human peripheral blood lymphocytes exposed to non-ionizing radiofrequency fields (RF). Cells from nine healthy human volunteers were stimulated for 24h with phytohaemagglutinin and then exposed for 20h to an adaptive dose (AD) of a 1950MHz RF UMTS (universal mobile telecommunication system) signal used for mobile communications, at different specific absorption rates (SAR) of 1.25, 0.6, 0.3, and 0.15W/kg. This was followed by treatment of the cells at 48h with a challenge dose (CD) of 100ng/ml mitomycin C (MMC). Lymphocytes were collected at the end of the 72h total culture period. The cytokinesis-block method was used to record the frequency of micronuclei (MN) as genotoxicity end-point. When lymphocytes from six donors were pre-exposed to RF at 0.3W/kg SAR and then treated with MMC, these cells showed a significant reduction in the frequency of MN, compared with the cells treated with MMC alone; this result is indicative of induction of AR. The results from our earlier study indicated that lymphocytes that were stimulated for 24h, exposed for 20h to a 900MHz RF GSM (global system for mobile communication) signal at 1.25W/kg SAR and then treated with 100ng/ml MMC, also exhibited AR. These overall data suggest that the induction of AR depends on RF frequency, type of the signal and SAR. Further characterization of RF-induced AR is in progress. PMID:22525361

  6. Ionization of N{sub 2} in radio-frequent electric field

    SciTech Connect

    Popovi?, M. P.; Vojnovi?, M. M.; Aoneas, M. M.; Vi?i?, M. D.; Popari?, G. B., E-mail: goran-poparic@ff.bg.ac.rs [Faculty of Physics, University of Belgrade, Studentski trg 12, P.O. Box 44, 11000 Belgrade (Serbia); Risti?, M. M. [Faculty of Physical Chemistry, University of Belgrade, Studentski trg 12, P.O. Box 47, 11158 Belgrade (Serbia)

    2014-06-15

    Rate coefficients for the electron impact ionization of the N{sub 2} molecule are calculated in non-equilibrium conditions in the presence of time-dependent electric field. A Monte Carlo simulation has been developed in order to determine non-equilibrium electron energy distribution functions within one period of the radio-frequent (RF) electric field. By using these distribution functions, rate coefficients for ionization of the N{sub 2} molecule have been obtained time resolved within one period in the frequency range from 13.56 up to 500?MHz, at effective reduced electric field values up to 700 Td. This work presents an insight into the temporal characteristics of ionizing process and provides the ionization rate coefficients that can be of great use for correct implementation in modeling RF plasma discharges. A behavior of rate coefficients under the influence of magnitude and frequency of the fields was studied separately revealing some interesting features in time dependence.

  7. Calculation of Radiofrequency Electromagnetic Fields and Their Effects in MRI of Human Subjects

    PubMed Central

    Collins, Christopher M.; Wang, Zhangwei

    2011-01-01

    Radiofrequency magnetic fields are critical to nuclear excitation and signal reception in Magnetic Resonance Imaging (MRI). The interactions between these fields and human tissues in anatomical geometries results in a variety of effects regarding image integrity and safety of the human subject. In recent decades numerical methods of calculation have been used increasingly to understand the effects of these interactions and aid in engineering better, faster, and safer equipment and methods. As MRI techniques and technology have evolved through the years, so too have the requirements for meaningful interpretation of calculation results. Here we review the basic physics of RF electromagnetics in MRI and discuss a variety of ways RF field calculations are used in MRI in engineering and safety assurance from simple systems and sequences through advanced methods of development for the future. PMID:21381106

  8. Radiofrequency hydrogen ion source with permanent magnets providing axial magnetic field

    SciTech Connect

    Oikawa, Kohei, E-mail: oikawa@ecei.tohoku.ac.jp; Saito, Yuta; Komizunai, Shota; Takahashi, Kazunori; Ando, Akira [Department of Electrical Engineering, Tohoku University, Sendai 980-8579 (Japan)] [Department of Electrical Engineering, Tohoku University, Sendai 980-8579 (Japan)

    2014-02-15

    Uniform axial magnetic field of about 70 G is applied to a radiofrequency (rf) hydrogen ion source by arrays of permanent magnets. The plasma density and electron temperature downstream of the source and near the magnetic filter are compared with those in the previously described ion source, where the axial field has been applied by two solenoids. The source is operated at ?350 kHz and above 10 kW rf power with a field-effect-transistor-based invertor power supply in 1.5 Pa hydrogen. The results show that the plasma density of ?10{sup 19} m{sup ?3} near the source exit and ?10{sup 18} m{sup ?3} near the magnetic filter can be obtained, which are higher than those with the solenoids.

  9. Radiofrequency hydrogen ion source with permanent magnets providing axial magnetic field.

    PubMed

    Oikawa, Kohei; Saito, Yuta; Komizunai, Shota; Takahashi, Kazunori; Ando, Akira

    2014-02-01

    Uniform axial magnetic field of about 70 G is applied to a radiofrequency (rf) hydrogen ion source by arrays of permanent magnets. The plasma density and electron temperature downstream of the source and near the magnetic filter are compared with those in the previously described ion source, where the axial field has been applied by two solenoids. The source is operated at ?350 kHz and above 10 kW rf power with a field-effect-transistor-based invertor power supply in 1.5 Pa hydrogen. The results show that the plasma density of ?10(19) m(-3) near the source exit and ?10(18) m(-3) near the magnetic filter can be obtained, which are higher than those with the solenoids. PMID:24593564

  10. [Biological effects of non-ionizing electromagnetic radiation].

    PubMed

    Fedorowski, A; Steciwko, A

    1998-01-01

    Since the mid 1970's, when Adey discovered that extremely-low-frequency electromagnetic field (ELF EMF) may affect the calcium ions efflux from various cells, bioeffects of non-ionizing radiation (NIR) have become the subject of growing interest and numerous research projects. At present, the fact that NIR exerts both stimulatory and inhibitory effects on different physiological cellular parameters is rather unquestionable. At the same time, some epidemiological studies suggest that exposure to EMF is potentially harmful even if its intensity is very low. It has been proved that thermal factors are not responsible for these effects, therefore nowadays, they are called 'non-thermal effects'. Our paper deals with three different aspects of biological effects of non-ionizing radiation, bioelectromagnetism, electromagnetobiology and electromagnetic bioinformation. Firstly, we describe how EMF and photons can be produced within a living cell, how biological cycles are controlled, and what are the features of endogenous electromagnetic radiation. Secondly, we discuss various facets of external EMF interactions with living matter, focusing on extremely-low-frequencies, radio- and microwaves. Possible mechanisms of these interactions are also mentioned. Finally, we present a short overview of current theories which explain how electromagnetic couplings may control an open and dissipative structure, namely the living organism. The theory of electromagnetic bioinformation seems to explain how different physiological processes are triggered and controlled, as well as how long-range interactions may possibly occur within the complex biological system. The review points out that the presented research data must be assessed very carefully since its evaluation is crucial to set the proper limits of EMF exposure, both occupational and environmental. The study of biological effects of non-ioinizing radiation may also contribute to the development of new diagnostic and therapeutic methods. PMID:9587915

  11. Radio-frequency modeling of square-shaped extended source tunneling field-effect transistors

    NASA Astrophysics Data System (ADS)

    Marjani, Saeid; Hosseini, Seyed Ebrahim

    2014-12-01

    The radio-frequency (RF) performances and small-signal parameters of double-gate (DG) square-shaped extended source tunneling field-effect transistors (TFETs) with different gate lengths have been extracted and compared with those of conventional TFETs in terms of cut-off frequency, maximum oscillation frequency, current gain, unilateral power gain, gate-source capacitance, gate-drain capacitance, channel resistance, time constant and transconductance. The small-signal parameters have been extracted by using of a nonquasistatic radio-frequency model, which were verified up to 250 GHz. Because of the higher transconductance and current drivability and smaller gate capacitance of DG square-shaped extended source TFETs compared to conventional TFETs, DG square-shaped extended source TFETs have higher cut-off and maximum oscillation frequencies and smaller switching time. The impact of high-? gate dielectric on RF figures of merit and device performance has also been investigated for extended source TFET. The results showed close agreement between the Y-parameters and the extracted parameters of modeling, SPICE simulation and device simulation for high frequency range up to the cut-off frequency.

  12. Magnetic orientation of garden warblers (Sylvia borin) under 1.4 MHz radiofrequency magnetic field.

    PubMed

    Kavokin, Kirill; Chernetsov, Nikita; Pakhomov, Alexander; Bojarinova, Julia; Kobylkov, Dmitry; Namozov, Barot

    2014-08-01

    We report on the experiments on orientation of a migratory songbird, the garden warbler (Sylvia borin), during the autumn migration period on the Courish Spit, Eastern Baltics. Birds in experimental cages, deprived of visual information, showed the seasonally appropriate direction of intended flight with respect to the magnetic meridian. Weak radiofrequency (RF) magnetic field (190 nT at 1.4 MHz) disrupted this orientation ability. These results may be considered as an independent replication of earlier experiments, performed by the group of R. and W. Wiltschko with European robins (Erithacus rubecula). Confirmed outstanding sensitivity of the birds' magnetic compass to RF fields in the lower megahertz range demands for a revision of one of the mainstream theories of magnetoreception, the radical-pair model of birds' magnetic compass. PMID:24942848

  13. National surveys of radiofrequency field strengths from radio base stations in Africa.

    PubMed

    Joyner, Ken H; Van Wyk, Marthinus J; Rowley, Jack T

    2014-01-01

    The authors analysed almost 260 000 measurement points from surveys of radiofrequency (RF) field strengths near radio base stations in seven African countries over two time frames from 2001 to 2003 and 2006 to 2012. The results of the national surveys were compared, chronological trends investigated and potential exposures compared by technology and with frequency modulation (FM) radio. The key findings from thes data are that irrespective of country, the year and mobile technology, RF fields at a ground level were only a small fraction of the international human RF exposure recommendations. Importantly, there has been no significant increase in typical measured levels since the introduction of 3G services. The mean levels in these African countries are similar to the reported levels for countries of Asia, Europe and North America using similar mobile technologies. The median level for the FM services in South Africa was comparable to the individual but generally lower than the combined mobile services. PMID:24044904

  14. National surveys of radiofrequency field strengths from radio base stations in Africa

    PubMed Central

    Joyner, Ken H.; Van Wyk, Marthinus J.; Rowley, Jack T.

    2014-01-01

    The authors analysed almost 260 000 measurement points from surveys of radiofrequency (RF) field strengths near radio base stations in seven African countries over two time frames from 2001 to 2003 and 2006 to 2012. The results of the national surveys were compared, chronological trends investigated and potential exposures compared by technology and with frequency modulation (FM) radio. The key findings from thes data are that irrespective of country, the year and mobile technology, RF fields at a ground level were only a small fraction of the international human RF exposure recommendations. Importantly, there has been no significant increase in typical measured levels since the introduction of 3G services. The mean levels in these African countries are similar to the reported levels for countries of Asia, Europe and North America using similar mobile technologies. The median level for the FM services in South Africa was comparable to the individual but generally lower than the combined mobile services. PMID:24044904

  15. Enhancement of electron temperature in a laser-induced plasma using a radio-frequency electric field

    NASA Astrophysics Data System (ADS)

    Ohzu, Akira; Suzuki, Yoji; Maruyama, Yoichiro; Arisawa, Takashi

    2000-02-01

    An experimental study of the enhancement of the electron temperature of a laser-induced plasma by use of radio-frequency dielectric heating has been carried out. A radio-frequency electric field of 140 MHz is used to heat the plasma produced by multistep resonant photoinization. It is clearly observed that the electron temperature increases from 0.3 to 1.0 eV when a radio-frequency input power of 1.0 W is applied. Also, applying heating induces a plasma oscillation. This is due to the generation of ion waves in the plasma, and therefore, means that the enhanced electron temperature is higher than the ion temperature. It is expected that this method will improve the efficiency for extracting ions rapidly from a laser-induced plasma in atomic vapor laser isotope separation.

  16. Are Cell Phones or Radio-Frequency Electromagnetic Fields Possibly Carcinogenic to Humans? [Telecommunications Health and Safety

    Microsoft Academic Search

    James C. Lin

    2012-01-01

    Notwithstanding the recent classification of radio-frequency electromagnetic fields, including those employed by cellular mobile telephones, as possibly carcinogenic to humans, the question of whether there could be some cancer risk associated with use of cell phones remain confused and ever more controversial.

  17. Analytical mean-field scaling theory of radio-frequency heating in a Paul trap

    NASA Astrophysics Data System (ADS)

    Nam, Y. S.; Jones, E. B.; Blümel, R.

    2014-07-01

    While the microscopic origins of radio-frequency (rf) heating of simultaneously stored, charged particles in a Paul trap are not yet understood in detail, a universal heating curve [J. D. Tarnas, Y. S. Nam, and R. Blümel, Phys. Rev. A 88, 041401 (2013), 10.1103/PhysRevA.88.041401] was recently discovered that collapses scaled rf heating data onto a single universal curve. Based on a simple analytical mean-field theory, we derive an analytical expression for the universal heating curve, which is in excellent agreement with numerical data. We find that for spherical clouds the universal curve depends only on a single scaling parameter, ? =[q(N-1)]2/3/T, where N is the number of trapped particles, q is the Paul-trap control parameter, and T is the temperature.

  18. The argument for a unified approach to non-ionizing radiation protection

    SciTech Connect

    Perala, R.A.; Rigden, G.J. (Electro Magnetic Applications, Inc., Lakewood, CO (United States)); Pfeffer, R.A. (Army Nuclear and Chemical Agency, Springfield, VA (United States))

    1993-12-01

    In the next decade military equipment will be required to operate in severe electromagnetic environments. These environments are expected to contain most non-ionizing frequencies (D.C. to GHz), from hostile and/or non-hostile sources, and be severe enough to cause temporary upset or even catastrophic failure of electronic equipment. Over the past thirty years considerable emphasis has been placed on hardening critical systems to one or more of these non-ionizing radiation environments, the most prevalent being the nuclear-induced electromagnetic pulse (EMD). From this technology development there has evolved a hardening philosophy that applies to most of these non-ionizing radiation environments. The philosophy, which stresses the application of zonal shields plus penetration protection, can provide low-cost hardening against such diverse non-ionizing radiation as p-static, lightning, electromagnetic interference (EMI), EMP, high intensity radiated fields (HIRF), electromagnetic radiation (EMR), and high power microwaves (HPM). The objective in this paper is to describe the application of this philosophy to Army helicopters. The authors develop a unified specification complete with threat definitions and test methods which illustrates integration of EMP, lightning, and HIRF at the box qualification level. This paper is a summary of the effort documented in a cited reference.

  19. Field probe for low-pressure capacitively coupled radio-frequency discharge plasmas

    NASA Astrophysics Data System (ADS)

    Dyson, Anthony; Allen, John E.

    2003-01-01

    A field probe has been developed to measure the radio-frequency (RF) fields in low-pressure capacitively coupled RF discharges at frequencies up to 50 MHz. The probe consists of a pair of parallel insulated wires that are connected through a resistor-matching network to an oscilloscope with a fast Fourier transform function to separate out harmonics. An insulated single wire potential probe is used to obtain the corresponding potential profiles. The probes are calibrated by direct measurement of the RF content of the plasma up to the third harmonic using an active Langmuir probe that also gives the plasma parameters ne, Te. Two types of plasmas are investigated - electropositive Ar plasmas and electronegative air plasmas that have much lower electron densities for the same fill pressure. It is found that for fill pressures p > 10-3 mbar most of the voltage drop is across the sheaths with only a small field in the plasma. For lower fill pressures, p < 5 × 10-4 mbar of air, then geometric resonance effects are observed with strong field reversal in the plasma. A higher-pressure Ar plasma driven simultaneously at 13.56 and 27.12 MHz shows a small non-resonant field at the fundamental with the second harmonic near to geometric resonance.

  20. Effects of everyday radiofrequency electromagnetic-field exposure on sleep quality: a cross-sectional study.

    PubMed

    Mohler, Evelyn; Frei, Patrizia; Braun-Fahrländer, Charlotte; Fröhlich, Jürg; Neubauer, Georg; Röösli, Martin

    2010-09-01

    The aim of this cross-sectional study was to investigate the association between exposure to various sources of radiofrequency electromagnetic fields (RF EMFs) in the everyday environment and sleep quality, which is a common public health concern. We assessed self-reported sleep disturbances and daytime sleepiness in a random population sample of 1,375 inhabitants from the area of Basel, Switzerland. Exposure to environmental far-field RF EMFs was predicted for each individual using a prediction model that had been developed and validated previously. Self-reported cordless and mobile phone use as well as objective mobile phone operator data for the previous 6 months were also considered in the analyses. In multivariable regression models, adjusted for relevant confounders, no associations between environmental far-field RF EMF exposure and sleep disturbances or excessive daytime sleepiness were observed. The 10% most exposed participants had an estimated risk for sleep disturbances of 1.11 (95% CI: 0.50 to 2.44) and for excessive daytime sleepiness of 0.58 (95% CI: 0.31 to 1.05). Neither mobile phone use nor cordless phone use was associated with decreased sleep quality. The results of this large cross-sectional study did not indicate an impairment of subjective sleep quality due to exposure from various sources of RF EMFs in everyday life. PMID:20726726

  1. Health problems among operators of plastic welding machines and exposure to radiofrequency electromagnetic fields.

    PubMed

    Kolmodin-Hedman, B; Hansson Mild, K; Hagberg, M; Jönsson, E; Andersson, M C; Eriksson, A

    1988-01-01

    To study possible medical effects of high radiofrequency radiation (RF), 113 Swedish men and women were studied by means of a structured interview and rating of subjective symptoms. A test session was included in order to examine coordination and muscular function of the hands. A neurological test concerning two-point discrimination (2-PD) was also done. As referents, 23 women, sewing machine operators and assembly workers, were chosen, interviewed and likewise tested. Exposure measurements were taken of the RF fields around the welding machines. The present Swedish ceiling value of 250 W/m2 for the equivalent power density was exceeded in more than 50% of the machines. The highest leakage fields, both for electric and magnetic fields, were found near machines used in factories for ready-made clothing, which gave a high exposure to the hands. Irritative eye symptoms were reported by 23% of the men and 40% of the women. A group of 27 persons was selected for a clinical eye examination and checked by photographs, and nine persons had modest conjunctivitis. A high prevalence of numbness in hands, especially among women, was found. A significantly impaired 2-PD was found in the exposed women as compared to the referent group. The pregnancy outcome for 305 female plastic welders during 1974-1984 did not show any significant differences with the Swedish average concerning malformation or prenatal mortality. PMID:3372031

  2. Targeted treatment of cancer with radiofrequency electromagnetic fields amplitude-modulated at tumor-specific frequencies

    PubMed Central

    Zimmerman, Jacquelyn W.; Jimenez, Hugo; Pennison, Michael J.; Brezovich, Ivan; Morgan, Desiree; Mudry, Albert; Costa, Frederico P.; Barbault, Alexandre; Pasche, Boris

    2013-01-01

    In the past century, there have been many attempts to treat cancer with low levels of electric and magnetic fields. We have developed noninvasive biofeedback examination devices and techniques and discovered that patients with the same tumor type exhibit biofeedback responses to the same, precise frequencies. Intrabuccal administration of 27.12 MHz radiofrequency (RF) electromagnetic fields (EMF), which are amplitude-modulated at tumor-specific frequencies, results in long-term objective responses in patients with cancer and is not associated with any significant adverse effects. Intrabuccal administration allows for therapeutic delivery of very low and safe levels of EMF throughout the body as exemplified by responses observed in the femur, liver, adrenal glands, and lungs. In vitro studies have demonstrated that tumor-specific frequencies identified in patients with various forms of cancer are capable of blocking the growth of tumor cells in a tissue- and tumor-specific fashion. Current experimental evidence suggests that tumor-specific modulation frequencies regulate the expression of genes involved in migration and invasion and disrupt the mitotic spindle. This novel targeted treatment approach is emerging as an appealing therapeutic option for patients with advanced cancer given its excellent tolerability. Dissection of the molecular mechanisms accounting for the anti-cancer effects of tumor-specific modulation frequencies is likely to lead to the discovery of novel pathways in cancer. PMID:24206915

  3. Aspergillus fumigatus Hyphal Damage Caused by Noninvasive Radiofrequency Field-Induced Hyperthermia

    PubMed Central

    Kaluarachchi, Warna D.; Cisneros, Brandon T.; Corr, Stuart J.; Albert, Nathaniel D.; Curley, Steven A.

    2013-01-01

    We studied the effect of noninvasive radiofrequency-induced hyperthermia on the viability of Aspergillus fumigatus hyphae in vitro. Radiofrequency-induced hyperthermia resulted in significant (>70%, P < 0.0001) hyphal damage in a time and thermal dose-dependent fashion as assessed by XTT [(sodium 2,3,-bis(2-methoxy-4-nitro-5-sulfophenyl)-5-[(phenylamino)-carbonyl] (1)-2H-tetrazolium inner salt)], DiBAC [bis-(1,3-dibutylbarbituric acid) trimethine oxonol] staining, and transmission electron microscopy. For comparison, water bath hyperthermia was used over the range of 45 to 55°C to study hyphal damage. Radiofrequency-induced hyperthermia resulted in severe damage to the outer fibrillar layer of hyphae at a shorter treatment time compared to water bath hyperthermia. Our preliminary data suggest that radiofrequency-induced hyperthermia might be an additional therapeutic approach to use in the management of mold infections. PMID:23836166

  4. Operation of an ungated diamond field-emission array cathode in a L-band radiofrequency electron source

    SciTech Connect

    Piot, P. [Northern Illinois Center for Accelerator and Detector Development and Department of Physics, Northern Illinois University, DeKalb, Illinois 60115 (United States); Accelerator Physics Center, Fermi National Accelerator Laboratory, Batavia, Illinois 60510 (United States); Brau, C. A.; Gabella, W. E.; Ivanov, B.; Mendenhall, M. H. [Department of Physics and Astronomy, Vanderbilt University, Nashville, Tennessee 37235 (United States); Choi, B. K. [Department of Electrical Engineering and Computer Science, Vanderbilt University, Nashville, Tennessee 37235 (United States); Vanderbilt Institute of Nanoscale Science and Engineering, Vanderbilt University, Nashville, Tennessee 37235 (United States); Blomberg, B.; Mihalcea, D.; Panuganti, H. [Northern Illinois Center for Accelerator and Detector Development and Department of Physics, Northern Illinois University, DeKalb, Illinois 60115 (United States); Jarvis, J. [Advanced Energy Systems, Inc., Medford, New York 11763 (United States); Prieto, P.; Reid, J. [Accelerator Division, Fermi National Accelerator Laboratory, Batavia, Illinois 60510 (United States)

    2014-06-30

    We report on the operation of a field-emitter-array cathode in a conventional L-band radio-frequency electron source. The cathode consisted of an array of ?10{sup 6} diamond tips on pyramids. Maximum current on the order of 15?mA was reached and the cathode did not show appreciable signs of fatigue after weeks of operation. The measured Fowler-Nordheim characteristics, transverse beam density, and current stability are discussed.

  5. Effect of nonlinear radiofrequency electromagnetic fields on the emittance of bunched beams

    NASA Astrophysics Data System (ADS)

    Phadte, D. S.; Patidar, C. B.

    2013-07-01

    Gap transformations are frequently used in ion Linac codes, to efficiently describe the particle dynamics. Using similar approach, we analyze the uniformly bunched beam passing through an axis-symmetric radiofrequency (RF) cavity. The method can be used for other distributions as well using a similar six dimensional analysis. The effect of non-linear RF field in radial and axial directions in an RF cavity and the finite phase width of the bunch, on the transverse and longitudinal emittance growth have been studied. The expressions obtained have been verified for the two types of cavity cells namely the zero mode DTL and pi mode CCL type used frequently in ion linacs. The results are seen to be valid for the entire maximum phase acceptance up to 360 degrees. Simulations with the equivalent beams of non-uniform distributions namely Waterbag and Gaussian show that at synchronous phases closer to the wave crest, the results give a good approximation of emittance growth in both planes for non-uniform beams.

  6. Effects of field orientation during 700-MHz radiofrequency irradiation of rats

    SciTech Connect

    Frei, M.R.; Jauchem, J.R.; Padilla, J.M. (School of Aerospace Medicine, Brooks AFB, TX (USA))

    1989-01-01

    Ketamine-anesthetized Sprague-Dawley rats were exposed to far-field 700-MHz continuous-wave radiofrequency radiation (RFR) in both E and H orientations. Irradiation was conducted at whole-body average specific absorption rates (SARs) of 9.2 and 13.0 W/kg (E and H, respectively) that resulted in approximately equivalent colonic specific heating rates (SHRs). Exposures were performed to repeatedly increase colonic temperature by 1 degree C (38.5 to 39.5 degrees C). Tympanic, tail, left and right subcutaneous (toward and away from RFR source), and colonic temperatures, arterial blood pressure, and respiratory rate were continuously recorded. In spite of equivalent colonic SHRs and the reduced E-orientation average SAR, the right subcutaneous, tympanic, and tail SARs, SHRs and absolute temperature increases were significantly greater in E than in H orientation. The cooling rate at all monitoring sites was also significantly greater in E than in H orientation. Heart rate and mean arterial blood pressure significantly increased during irradiation; however, changes between orientations were not different. Respiratory rate significantly increased during irradiation in H, but not in E orientation. These results indicate that during resonant frequency irradiation, differences occur in the pattern of heat deposition between E- and H-orientation exposure. When compared with previous investigations performed at supraresonant frequencies, the lower level of cardiovascular change in this study was probably related to the lower periphery-to-core thermal gradient.

  7. Effects of field orientation during 700-MHz radiofrequency irradiation of rats.

    PubMed

    Frei, M R; Jauchem, J R; Padilla, J M

    1989-01-01

    Ketamine-anesthetized Sprague-Dawley rats were exposed to far-field 700-MHz continuous-wave radiofrequency radiation (RFR) in both E and H orientations. Irradiation was conducted at whole-body average specific absorption rates (SARs) of 9.2 and 13.0 W/kg (E and H, respectively) that resulted in approximately equivalent colonic specific heating rates (SHRs). Exposures were performed to repeatedly increase colonic temperature by 1 degree C (38.5 to 39.5 degrees C). Tympanic, tail, left and right subcutaneous (toward and away from RFR source), and colonic temperatures, arterial blood pressure, and respiratory rate were continuously recorded. In spite of equivalent colonic SHRs and the reduced E-orientation average SAR, the right subcutaneous, tympanic, and tail SARs, SHRs and absolute temperature increases were significantly greater in E than in H orientation. The cooling rate at all monitoring sites was also significantly greater in E than in H orientation. Heart rate and mean arterial blood pressure significantly increased during irradiation; however, changes between orientations were not different. Respiratory rate significantly increased during irradiation in H, but not in E orientation. These results indicate that during resonant frequency irradiation, differences occur in the pattern of heat deposition between E- and H-orientation exposure. When compared with previous investigations performed at supraresonant frequencies, the lower level of cardiovascular change in this study was probably related to the lower periphery-to-core thermal gradient. PMID:2694195

  8. Effects of field orientation during 700-MHz radiofrequency irradiation of rats

    SciTech Connect

    Frei, M.R.; Jauchem, J.R.; Padilla, J.M.

    1989-01-01

    Ketamine-anesthetized Sprague-Dawley rats were exposed to far-field 700-MHz continuous-wave radiofrequency radiation (RFR) in both E and H orientations. Irradiation was conducted at whole-body average specific absorption rates (SARs) of 9.2 and 13.0 W/kg (E and H, respectively) that resulted in approximately equivalent colonic specific heating rates (SHRs). Exposures were performed to repeatedly increase colonic temperature by 1 deg C (38.5 to 39.5 deg C). Tympanic, tail, left and right subcutaneous (toward and away from RFR source), and colonic temperatures, arterial blood pressure, and respiratory rate were continuously recorded. In spite of equivalent colonic SHRs and the reduced E-orientation average SAR, the right subcutaneous, tympanic, and tail SARs, SHRs and absolute temperature increases were significantly greater in E than in H orientation. The cooling rate at all monitoring sites was also significantly greater in E than in H orientation. Heart rate and mean arterial blood pressure significantly increased during irradiation; however, changer between orientations were not different. Respiratory rate significantly increased during irradiation in H, but not in E orientation. These results indicate that during resonant frequency irradiation, differences occur in the pattern of heat deposition between E- and H-orientation exposure. When compared with previous investigations performed at supraresonant frequencies, the lower level of cardiovascular change in this study was probably related to the lower periphery-to-core thermal gradient.

  9. High-field head radiofrequency volume coils using transverse electromagnetic (TEM) and phased array technologies.

    PubMed

    Avdievich, Nikolai I; Hetherington, Hoby P

    2009-11-01

    This article describes technological advances in quadrature transverse electromagnetic (TEM) volume coils and phased arrays reported recently from our laboratory developed for MRI and MRS imaging of the human brain. The first part of this work presents a new method for tuning TEM volume coils based on measurements of the radiofrequency current distribution in the coil elements. This technique facilitates bench adjustment of the coils' homogeneity and is particularly important for tuning double-tuned TEM volume coils. We have also used this method to optimize other TEM configurations such as a quadrature TEM half-volume coil and a split TEM coil. TEM half-volume coils provide greater sensitivity over localized regions than conventional full-volume coils, and the split TEM coil provides greater patient access and ease of use. The second part of this work describes the development of single-tuned and double-tuned transmit TEM volume coils in combination with phased arrays. A variety of different techniques for active detuning of single-tuned and double-tuned TEM volume coils are presented along with the development of phased arrays and transmission line preamplifier decoupling. The final section describes the use of counter rotating current (CRC) surface coils in phased arrays. Because of the intrinsic isolation of CRC coils from transmit volume coils, CRC arrays can be used simultaneously with volume coils for both reception and transmission. Near the center of the human head where both the phased array and the volume coil produce similar sensitivities, simultaneous reception enhances the signal-to-noise ratio. Conversely, simultaneous transmission can be used to boost the transmit field in peripheral brain regions from the volume coil to provide a more homogeneous transmit field. PMID:18574792

  10. Field orientation effects during 5.6-GHz radiofrequency irradiation of rats.

    PubMed

    Frei, M R; Jauchem, J R; Price, D L; Padilla, J M

    1990-12-01

    Ketamine-anesthetized Sprague-Dawley rats were exposed in E and H orientations (long axis parallel to electric and magnetic fields, respectively) to far-field 5.6-GHz continuous-wave radio-frequency radiation (RFR). Power densities were used that resulted in equivalent whole-body average specific absorption rates of 14 W/kg in both orientations (90 mW/cm2 for E and 66 mW/cm2 for H). Irradiation was conducted to increase colonic temperature by 1 degree C (from 38.5 to 39.5 degrees C). During experimentation, arterial blood pressure and respiratory rate and colonic, tympanic, left and right subcutaneous (sides toward and away from RFR source), and tail temperatures were continuously recorded. Results showed no significant difference in the times required to cause a 1 degree C increase or to recover to the initial temperature when irradiation was stopped. Significant differences between E- and H-orientation exposure were seen in the patterns of localized heating. The tail and left subcutaneous temperature increases were significantly greater during E-orientation exposure, the tympanic site showed no difference, and the right subcutaneous temperature increase was significantly greater during H-orientation exposure. Under both exposure conditions, heart rate and mean arterial blood pressure significantly increased during irradiation; however, there were no significant differences between E and H orientation responses. These findings at 5.6 GHz are in contrast to the significant cardiovascular response differences between E- and H-orientation exposure noted during a previous study of irradiation at 2.45 GHz. PMID:2285402

  11. Exposure to extremely-low-frequency electromagnetic fields and radiofrequency radiation: cardiovascular effects in humans.

    PubMed

    Jauchem, J R

    1997-01-01

    Cardiovascular changes in humans exposed to nonionizing radiation [including extremely-low-frequency electromagnetic fields (ELF EMFs) and radiofrequency radiation (RFR)] are reviewed. Both acute and long-term effects have been investigated. In general, if heating does not occur during exposure, current flow appears to be necessary for major cardiovascular effects to ensue, such as those due to electric shock. Whereas most studies have revealed no acute effect of static or time-varying ELF EMFs on the blood pressure, heart rate, or electrocardiogram waveform, others have reported subtle effects on the heart rate. The possible health consequences of these results are unknown. Regarding long-term effects of ELF EMFs, reports from the former Soviet Union in the early 1960s indicated arrhythmias and tachycardia in high-voltage-switchyard workers. Subsequent studies in Western countries, however, did not confirm these findings. These studies are limited by uncertainties regarding exposure durations and appropriate control groups. Investigations of acute cardiovascular changes in humans purposely exposed to RFR have been limited to studies of magnetic resonance imaging (which, in addition to RFR, involves static and time-varying magnetic fields). It has been concluded that such exposures, as presently performed, are not likely to cause adverse cardiovascular effects. Reports of hypertension in workers potentially exposed to high levels of RFR during accidents are considered to be incidental (due to anxiety and posttraumatic stress). Soviet investigators have also indicated that long-term RFR exposure may result in hypotension and bradycardia or tachycardia. Other researchers, however, have been incapable of replicating these results, and some scientists have attributed the effects to chance variations and mishandling of data. In summary, studies have not yielded any obvious cardiovascular-related hazards of acute or long-term exposures to ELF EMFs or RFR at levels below current exposure standards. PMID:9258703

  12. Field orientation effects during 5. 6-GHz radiofrequency irradiation of rats

    SciTech Connect

    Frei, M.R.; Jauchem, J.R.; Price, D.L.; Padilla, J.M. (USAF School of Aerospace Medicine, Brooks AFB, TX (USA))

    1990-12-01

    Ketamine-anesthetized Sprague-Dawley rats were exposed in E and H orientations (long axis parallel to electric and magnetic fields, respectively) to far-field 5.6-GHz continuous-wave radio-frequency radiation (RFR). Power densities were used that resulted in equivalent whole-body average specific absorption rates of 14 W/kg in both orientations (90 mW/cm2 for E and 66 mW/cm2 for H). Irradiation was conducted to increase colonic temperature by 1 degree C (from 38.5 to 39.5 degrees C). During experimentation, arterial blood pressure and respiratory rate and colonic, tympanic, left and right subcutaneous (sides toward and away from RFR source), and tail temperatures were continuously recorded. Results showed no significant difference in the times required to cause a 1 degree C increase or to recover to the initial temperature when irradiation was stopped. Significant differences between E- and H-orientation exposure were seen in the patterns of localized heating. The tail and left subcutaneous temperature increases were significantly greater during E-orientation exposure, the tympanic site showed no difference, and the right subcutaneous temperature increase was significantly greater during H-orientation exposure. Under both exposure conditions, heart rate and mean arterial blood pressure significantly increased during irradiation; however, there were no significant differences between E and H orientation responses. These findings at 5.6 GHz are in contrast to the significant cardiovascular response differences between E- and H-orientation exposure noted during a previous study of irradiation at 2.45 GHz.

  13. Implementation of acoustic, radiofrequency and microwave rotating fields in analytical plasma sources

    NASA Astrophysics Data System (ADS)

    Jankowski, Krzysztof; Ramsza, Andrzej P.; Reszke, Edward

    2011-07-01

    Four helium plasma sources operating at atmospheric pressure have been developed for analytical emission spectrometry by applying a synchronically rotating field with three or more phases operating at 1 kHz, 27 MHz or 2.45 GHz. The plasma takes the form of a disk and has minimum field strength at the axis. Thus, a channel is formed at the center through which the sample in the form of wet aerosol or a chemically generated vapor of halogen may be introduced. A dual-flow concentric ceramic injector was used to supply helium plasma gas and the sample to the plasma. The helium plasma operated at low power levels (40-300 W) and low gas flow rates of below 3 L min - 1 and was self-igniting. The acoustic, radio-frequency (rf) and microwave-driven plasmas can withstand wet aerosol loadings of 5, 30 and 100 mg min - 1 , respectively, generated by an ultrasonic nebulizer without a desolvation unit. The plasma physical characteristics were compared at these three frequencies under otherwise similar operating conditions. The helium excitation temperature, OH rotational temperature and electron number density increased with increasing frequency in ranges of 2800-4000 K, 1100-3200 K and 0.1-7 × 10 14 cm - 3 , respectively. To demonstrate the effect of frequency on the plasma excitation efficiency the emission intensity from halogen ions was evaluated using chemical vapor generation with continuous sampling without desiccation. Using 3-phase microwave, 6-phase microwave, 4-phase rf and 1 kHz helium plasma sources the detection limits (3?) for chlorine at 479.40 nm were 26, 60, 230 and 1200 ng mL - 1 , respectively. The microwave-driven plasma was the densest and had the highest excitation potential toward chlorine and bromine ions.

  14. Circadian Rhythmicity of Antioxidant Markers in Rats Exposed to 1.8 GHz Radiofrequency Fields

    PubMed Central

    Cao, Honglong; Qin, Fenju; Liu, Xueguan; Wang, Jiajun; Cao, Yi; Tong, Jian; Zhao, Heming

    2015-01-01

    Background: The potential health risks of exposure to Radiofrequency Fields (RF) emitted by mobile phones are currently of considerable public interest, such as the adverse effects on the circadian rhythmicities of biological systems. To determine whether circadian rhythms of the plasma antioxidants (Mel, GSH-Px and SOD) are affected by RF, we performed a study on male Sprague Dawley rats exposed to the 1.8 GHz RF. Methods: All animals were divided into seven groups. The animals in six groups were exposed to 1.8 GHz RF (201.7 ?W/cm2 power density, 0.05653 W/kg specific absorption rate) at a specific period of the day (3, 7, 11, 15, 19 and 23 h GMT, respectively), for 2 h/day for 32 consecutive days. The rats in the seventh group were used as sham-exposed controls. At the end of last RF exposure, blood samples were collected from each rat every 4 h (total period of 24 h) and also at similar times from sham-exposed animals. The concentrations of three antioxidants (Mel, GSH-Px and SOD) were determined. The data in RF-exposed rats were compared with those in sham-exposed animals. Results: circadian rhythms in the synthesis of Mel and antioxidant enzymes, GSH-Px and SOD, were shifted in RF-exposed rats compared to sham-exposed animals: the Mel, GSH-Px and SOD levels were significantly decreased when RF exposure was given at 23 and 3 h GMT. Conclusion: The overall results indicate that there may be adverse effects of RF exposure on antioxidant function, in terms of both the daily antioxidative levels, as well as the circadian rhythmicity. PMID:25685954

  15. Feasibility of a cohort study on health risks caused by occupational exposure to radiofrequency electromagnetic fields

    PubMed Central

    2009-01-01

    Background The aim of this study was to examine the feasibility of performing a cohort study on health risks from occupational exposure to radiofrequency electromagnetic fields (RF-EMF) in Germany. Methods A set of criteria was developed to evaluate the feasibility of such a cohort study. The criteria aimed at conditions of exposure and exposure assessment (level, duration, preferably on an individual basis), the possibility to assemble a cohort and the feasibility of ascertaining various disease endpoints. Results Twenty occupational settings with workers potentially exposed to RF-EMF and, in addition, a cohort of amateur radio operators were considered. Based on expert ratings, literature reviews and our set of predefined criteria, three of the cohorts were identified as promising for further evaluation: the personnel (technicians) of medium/short wave broadcasting stations, amateur radio operators, and workers on dielectric heat sealers. After further analyses, the cohort of workers on dielectric heat sealers seems not to be feasible due to the small number of exposed workers available and to the difficulty of assessing exposure (exposure depends heavily on the respective working process and mixture of exposures, e.g. plastic vapours), although exposure was highest in this occupational setting. The advantage of the cohort of amateur radio operators was the large number of persons it includes, while the advantage of the cohort of personnel working at broadcasting stations was the quality of retrospective exposure assessment. However, in the cohort of amateur radio operators the exposure assessment was limited, and the cohort of technicians was hampered by the small number of persons working in this profession. Conclusion The majority of occupational groups exposed to RF-EMF are not practicable for setting up an occupational cohort study due to the small numbers of exposed subjects or due to exposure levels being only marginally higher than those of the general public. PMID:19480652

  16. Young's Modulus Reconstruction for Radio-Frequency Ablation Electrode-Induced Displacement Fields: A Feasibility Study

    Microsoft Academic Search

    Jingfeng Jiang; Tomy Varghese; Christopher L. Brace; Ernest L. Madsen; Timothy J. Hall; Shyam Bharat; Maritza A. Hobson; James A. Zagzebski; Fred T. Lee Jr.

    2009-01-01

    Radio-frequency (RF) ablation is a minimally invasive treatment for tumors in various abdominal organs. It is effective if good tumor localization and intraprocedural monitoring can be done. In this paper, we investigate the feasibility of using an ultrasound-based Young's modulus reconstruction algorithm to image an ablated region whose stiffness is elevated due to tissue coagulation. To obtain controllable tissue deformations

  17. Effects of 900 MHz radiofrequency radiation on skin hydroxyproline contents.

    PubMed

    Çam, Semra Tepe; Seyhan, Nesrin; Kavakl?, Cengiz; Çelikb?çak, Ömür

    2014-09-01

    The present study aimed to investigate the possible effect of pulse-modulated radiofrequency radiation (RFR) on rat skin hydroxyproline content, since skin is the first target of external electromagnetic fields. Skin hydroxyproline content was measured using liquid chromatography mass spectrometer method. Two months old male wistar rats were exposed to a 900 MHz pulse-modulated RFR at an average whole body specific absorption rate (SAR) of 1.35 W/kg for 20 min/day for 3 weeks. The radiofrequency (RF) signals were pulse modulated by rectangular pulses with a repetition frequency of 217 Hz and a duty cycle of 1:8 (pulse width 0.576 ms). A skin biopsy was taken at the upper part of the abdominal costa after the exposure. The data indicated that whole body exposure to a pulse-modulated RF radiation that is similar to that emitted by the global system for mobile communications (GSM) mobile phones caused a statistically significant increase in the skin hydroxyproline level (p = 0.049, Mann-Whitney U test). Under our experimental conditions, at a SAR less than the International Commission on Non-Ionizing Radiation Protection safety limit recommendation, there was evidence that GSM signals could alter hydroxyproline concentration in the rat skin. PMID:24760629

  18. Does exposure to a radiofrequency electromagnetic field modify thermal preference in juvenile rats?

    PubMed

    Pelletier, Amandine; Delanaud, Stéphane; de Seze, René; Bach, Véronique; Libert, Jean-Pierre; Loos, Nathalie

    2014-01-01

    Some studies have shown that people living near a mobile phone base station may report sleep disturbances and discomfort. Using a rat model, we have previously shown that chronic exposure to a low-intensity radiofrequency electromagnetic field (RF-EMF) was associated with paradoxical sleep (PS) fragmentation and greater vasomotor tone in the tail. Here, we sought to establish whether sleep disturbances might result from the disturbance of thermoregulatory processes by a RF-EMF. We recorded thermal preference and sleep stage distribution in 18 young male Wistar rats. Nine animals were exposed to a low-intensity RF-EMF (900 MHz, 1 V x m(-1)) for five weeks and nine served as non-exposed controls. Thermal preference was assessed in an experimental chamber comprising three interconnected compartments, in which the air temperatures (Ta) were set to 24°C, 28°C and 31°C. Sleep and tail skin temperature were also recorded. Our results indicated that relative to control group, exposure to RF-EMF at 31°C was associated with a significantly lower tail skin temperature (-1.6°C) which confirmed previous data. During the light period, the exposed group preferred to sleep at Ta?=?31°C and the controls preferred Ta?=?28°C. The mean sleep duration in exposed group was significantly greater (by 15.5%) than in control group (due in turn to a significantly greater amount of slow wave sleep (SWS, +14.6%). Similarly, frequency of SWS was greater in exposed group (by 4.9 episodes.h-1). The PS did not differ significantly between the two groups. During the dark period, there were no significant intergroup differences. We conclude that RF-EMF exposure induced a shift in thermal preference towards higher temperatures. The shift in preferred temperature might result from a cold thermal sensation. The change in sleep stage distribution may involve signals from thermoreceptors in the skin. Modulation of SWS may be a protective adaptation in response to RF-EMF exposure. PMID:24905635

  19. Does Exposure to a Radiofrequency Electromagnetic Field Modify Thermal Preference in Juvenile Rats?

    PubMed Central

    Pelletier, Amandine; Delanaud, Stéphane; de Seze, René; Bach, Véronique; Libert, Jean-Pierre; Loos, Nathalie

    2014-01-01

    Some studies have shown that people living near a mobile phone base station may report sleep disturbances and discomfort. Using a rat model, we have previously shown that chronic exposure to a low-intensity radiofrequency electromagnetic field (RF-EMF) was associated with paradoxical sleep (PS) fragmentation and greater vasomotor tone in the tail. Here, we sought to establish whether sleep disturbances might result from the disturbance of thermoregulatory processes by a RF-EMF. We recorded thermal preference and sleep stage distribution in 18 young male Wistar rats. Nine animals were exposed to a low-intensity RF-EMF (900 MHz, 1 V.m?1) for five weeks and nine served as non-exposed controls. Thermal preference was assessed in an experimental chamber comprising three interconnected compartments, in which the air temperatures (Ta) were set to 24°C, 28°C and 31°C. Sleep and tail skin temperature were also recorded. Our results indicated that relative to control group, exposure to RF-EMF at 31°C was associated with a significantly lower tail skin temperature (?1.6°C) which confirmed previous data. During the light period, the exposed group preferred to sleep at Ta?=?31°C and the controls preferred Ta?=?28°C. The mean sleep duration in exposed group was significantly greater (by 15.5%) than in control group (due in turn to a significantly greater amount of slow wave sleep (SWS, +14.6%). Similarly, frequency of SWS was greater in exposed group (by 4.9 episodes.h?1). The PS did not differ significantly between the two groups. During the dark period, there were no significant intergroup differences. We conclude that RF-EMF exposure induced a shift in thermal preference towards higher temperatures. The shift in preferred temperature might result from a cold thermal sensation. The change in sleep stage distribution may involve signals from thermoreceptors in the skin. Modulation of SWS may be a protective adaptation in response to RF-EMF exposure. PMID:24905635

  20. LSU School of Dentistry Laser Safety : Clinical SAFETY PROCEDURES FOR LASER (NON-IONIZING) RADIATION

    E-print Network

    LSU School of Dentistry Laser Safety : Clinical SAFETY PROCEDURES FOR LASER (NON-ionizing radiation safety policy and procedural requirements of the program. The use of the term non-ionizing radiation safety program to ensure: a. The use of equipment which produces non-ionizing radiation within LSU

  1. Plasma stabilization and improvement in the performance of a nonequilibrium disk MHD generator by a radio-frequency electromagnetic field

    SciTech Connect

    Murakami, Tomoyuki; Okuno, Yoshihiro; Kabashima, Shigeharu (Tokyo Inst. of Tech., Yokohama (Japan). Dept. of Energy Sciences)

    1999-04-01

    By applying a radio-frequency (RF) electromagnetic field, the feasibility of improvement in the performance of a nonequilibrium disk-shaped magnetohydrodynamic (MHD) generator suffering from water vapor contamination in the working gas is investigated with r-[theta] two-dimensional numerical simulations. Attention is paid to the relation between the behavior of MHD plasma in the presence of the RF electric field and the generator performance. The water contamination causes the strongly nonuniform and unsteady plasma, and deteriorates its performance. The fluctuations of the electron temperature and of the ionization degree of seed atoms are found to be suppressed by applying the RF electric field. As a result, the enthalpy extraction ratio and the isentropic efficiency of the generator improve. The ratio of the required additional joule heating by the RF electric field to the thermal input to the generator for the stabilization of the plasma and the improvement in the performance is estimated to be about 0.9%.

  2. [Exposure of workers to electric and magnetic fields from radiofrequency dielectric heaters to process polyvinyl chloride material].

    PubMed

    Okuno, T; Jonai, H; Kawakami, T

    1991-11-01

    Exposure of workers to electric and magnetic fields from radiofrequency dielectric heaters (RF heaters) to process polyvinyl chloride material was surveyed. Measurements of electric and magnetic field strengths were made in 10 workers operating 7 RF heaters at 3 plants in Japan. Six of the RF heaters are of the sewing machine type and the other is of the shuttle tray type. In all the RF heaters surveyed the nominal frequency of the radiofrequency generator was 40 MHz, and therefore electric and magnetic field from these are assumed to oscillate at the same frequency. The power output ranged from 0.83 W to 1.8 W for the sewing machine type and was 2.4 W for this shuttle tray type. Measurements were made at about 5 cm from the surface of the hand, eye, chest, waist, knee and foot of each worker. The meter readings were converted to equivalent plane wave power density and corrected for duty cycle (0.073 to 0.27). It was found that all the workers surveyed were exposed to electric and magnetic field strengths greater than the TLV recommended by ACGIH (1 mW/cm2). For the hand, eye, chest, waist, knee and foot of the worker, 95%, 63%, 32%, 47% and 36% and 27% of the measured field strengths exceeded the TLV, respectively. Especially for the sewing machine type RF heaters, electric fields at the hand and eye were extremely strong. Thus, for the hand, 100%, 75% and 38% of the measured electric field strengths exceeded the TLV, ten times the TLV, and one hundred times the TLV, respectively, and for the eye, 88% and 25% exceeded the TLV and ten times the TLV, respectively. No correlation was observed between power output of the RF heaters and measured electric and magnetic field strengths at any anatomical site of the worker. PMID:1770616

  3. Radio-frequency measurements of UNiX compounds (X= Al, Ga, Ge) in high magnetic fields

    SciTech Connect

    Mielke, Charles H [Los Alamos National Laboratory; Mcdonald, David R [Los Alamos National Laboratory; Zapf, Vivien [Los Alamos National Laboratory; Altarawneh, Moaz M [Los Alamos National Laboratory; Lacerda, Alex H [Los Alamos National Laboratory; Adak, Sourav [Los Alamos National Laboratory; Karunakar, Kothapalli [Los Alamos National Laboratory; Nakotte, Heinrich [Los Alamos National Laboratory; Chang, S [NIST; Alsmadi, A M [HASHEMITE UNIV; Alyones, S [HASHEMIT UNIV

    2009-01-01

    We performed radio-frequency (RF) skin-depth measurements of antiferromagnetic UNiX compounds (X=Al, Ga, Ge) in magnetic fields up to 60 T and at temperatures between 1.4 to {approx}60 K. Magnetic fields are applied along different crystallographic directions and RF penetration-depth was measured using a tunnel-diode oscillator (TDO) circuit. The sample is coupled to the inductive element of a TDO resonant tank circuit, and the shift in the resonant frequency {Delta}f of the circuit is measured. The UNiX compounds exhibit field-induced magnetic transitions at low temperatures, and those transitions are accompanied by a drastic change in {Delta}f. The results of our skin-depth measurements were compared with previously published B-T phase diagrams for these three compounds.

  4. EDITORIAL: The interaction of radio-frequency fields with fusion plasmas: the JET experience The interaction of radio-frequency fields with fusion plasmas: the JET experience

    NASA Astrophysics Data System (ADS)

    Ongena, Jef

    2012-07-01

    The JET Task Force Heating is proud to present this special issue. It is the result of hard and dedicated work by everybody participating in the Task Force over the last four years and gives an overview of the experimental and theoretical results obtained in the period 2008-2010 with radio frequency heating of JET fusion plasmas. Topics studied and reported in this issue are: investigations into the operation of lower hybrid heating accompanied by new modeling results; new experimental results and insights into the physics of various ion cyclotron range of frequencies (ICRF) heating scenarios; progress in studies of intrinsic and ion cyclotron wave-induced plasma rotation and flows; a summary of the developments over the last years in designing an ion cyclotron radiofrequency heating (ICRH) system that can cope with the presence of fast load variations in the edge, as e.g. caused by pellets or edge localized modes (ELMs) during H-Mode operation; an overview of the results obtained with the ITER-like antenna operating in H-Mode with a packed array of straps and power densities close to those of the projected ITER ICRH antenna; and, finally, a summary of the results obtained in applying ion cyclotron waves for wall conditioning of the tokamak. This issue would not have been possible without the strong motivation and efforts (sometimes truly heroic) of all colleagues of the JET Task Force Heating. A sincere word of thanks, therefore, to all authors and co-authors involved in the experiments, analysis and compilation of the papers. It was a special privilege to work with all of them during the past very intense years. Thanks also to all other European and non-European scientists who contributed to the JET scientific programme, the operations team of JET and the colleagues of the Close Support Unit in Culham. Thanks also to the editors, Editorial Board and referees of Plasma Physics and Controlled Fusion, together with the publishing staff of IOPP, who have not only supported but also contributed very substantially to this initiative. Without their dedication this issue would not have been possible in its present form. A special word of thanks to Marie-Line Mayoral and Joelle Mailloux for their precious help and very active support in running the JET Task Force Heating over the last years. Without Joelle and Marie-Line itwould have been a much more daunting task to prepare JET operations, monitor progress during the experiments and edit the papers that are compiled here.

  5. Summary of measured radiofrequency electric and magnetic fields (10 kHz to 30 GHz) in the general and work environment

    Microsoft Academic Search

    Edwin D. Mantiply; Kenneth R. Pohl; Samuel W. Poppell; Julia A. Murphy

    1997-01-01

    We have plotted data from a number of studies on the range of radiofrequency (RF) field levels associated with a variety of environmental and occupational sources. Field intensity is shown in units of volts\\/meter (V\\/m) for electric field strength and amps\\/meter (A\\/m) for magnetic field strength. Duty factors, modulation frequencies, and modulation indices are also reported for some sources. This

  6. International workshop on non-ionizing radiation protection in medicine.

    PubMed

    Sienkiewicz, Zenon

    2013-11-01

    An international workshop brought together a range of stakeholders to consider protection from non-ionizing radiation used in medicine, research and cosmetics. Presentations on specific topics were followed by a general discussion on possible improvements in protection. Participants considered that adherence to science-based, harmonized exposure guidelines to limit exposures for clinical staff and other workers was a key prerequisite to safety in all situations. In addition, to engender an awareness of the risks involved to both the patient as well as the operator, equipment should be operated only by suitably qualified persons who have received appropriate training in the safe use of that device. This training should be carried out under the auspices of an accredited safety provider, and preferably offer a recognized qualification. Specific advice included the necessity for correct eye protection with higher power optical radiation sources, and avoiding the use of ultrasound for all exposures without medical benefit. Finally, the possibility of a harmonized approach to safety for both non-ionizing and ionizing radiation was considered worthy of further discussion. PMID:24320477

  7. Reduced field-of-view excitation using second-order gradients and spatial-spectral radiofrequency pulses.

    PubMed

    Ma, Chao; Xu, Dan; King, Kevin F; Liang, Zhi-Pei

    2013-02-01

    The performance of multidimensional spatially selective radiofrequency (RF) pulses is often limited by their long duration. In this article, high-order, nonlinear gradients are exploited to reduce multidimensional RF pulse length. Specifically, by leveraging the multidimensional spatial dependence of second-order gradients, a two-dimensional spatial-spectral RF pulse is designed to achieve three-dimensional spatial selectivity, i.e., to excite a circular region-of-interest in a thin slice for reduced field-of-view imaging. Compared to conventional methods that use three-dimensional RF pulses and linear gradients, the proposed method requires only two-dimensional RF pulses, and thus can significantly shorten the RF pulses and/or improve excitation accuracy. The proposed method has been validated through Bloch equation simulations and phantom experiments on a commercial 3.0T MRI scanner. PMID:22489022

  8. Radio-frequency dispersive detection of donor atoms in a field-effect transistor

    SciTech Connect

    Verduijn, J., E-mail: a.verduijn@unsw.edu.au; Rogge, S. [Centre for Quantum Computation and Communication Technology, University of New South Wales, Sydney NSW 2052 (Australia)] [Centre for Quantum Computation and Communication Technology, University of New South Wales, Sydney NSW 2052 (Australia); Vinet, M. [CEA/LETI-MINATEC, CEA-Grenoble, 17 rue des martyrs, F-38054 Grenoble (France)] [CEA/LETI-MINATEC, CEA-Grenoble, 17 rue des martyrs, F-38054 Grenoble (France)

    2014-03-10

    Radio-frequency dispersive read-out can provide a useful probe to nano-scale structures, such as nano-wire devices, especially, when the implementation of charge sensing is not straightforward. Here, we demonstrate dispersive “gate-only” read-out of phosphor donors in a silicon nano-scale transistor. The technique enables access to states that are only tunnel-coupled to one contact, which is not easily achievable by other methods. This allows us to locate individual randomly placed donors in the device channel. Furthermore, the setup is naturally compatible with high bandwidth access to the probed donor states and may aid the implementation of a qubit based on coupled donors.

  9. Effects of GSM-modulated 900 MHz radiofrequency electromagnetic fields on the hematopoietic potential of mouse bone marrow cells.

    PubMed

    Rosado, Maria Manuela; Nasta, Francesca; Prisco, Maria Grazia; Lovisolo, Giorgio Alfonso; Marino, Carmela; Pioli, Claudio

    2014-12-01

    Studies describing the influence of radiofrequency electromagnetic fields on bone marrow cells (BMC) often lack functional data. We examined the effects of in vivo exposure to a Global System for Mobile Communications (GSM) modulated 900 MHz RF fields on BMC using two transplantation models. X-irradiated syngeneic mice were injected with BMC from either RF-field-exposed, sham-exposed or cage control mice. Twelve weeks after transplantation, no differences in thymocyte number, frequency of subpopulations and cell proliferation were found in mice receiving BMC from either group. Also, in the spleen cell number, percentages of B/T cells, B/T-cell proliferation, and interferon ? (IFN-?) production were similar in all groups. In parallel, a mixture of BMC from congenic sham- and RF-exposed mice were co-transplanted into lymphopenic Rag2 deficient mice. BMC from RF-exposed and sham-exposed mice displayed no advantage or disadvantage when competing for the replenishment of lymphatic organs with mature lymphocytes in Rag2 deficient mice. This model revealed that BMC from sham-exposed and RF-exposed mice were less efficient than BMC from cage control mice in repopulating the thymus, an effect likely due to restraint stress. In conclusion, our results showed no effects of in vivo exposure to GSM-modulated RF-fields on the ability of bone marrow (BM) precursors to long-term reconstitute peripheral T and B cell compartments. PMID:25256206

  10. Luciferase-based protein-denaturation assay for quantification of radiofrequency field-induced targeted hyperthermia: developing an intracellular thermometer

    PubMed Central

    Raoof, Mustafa; Zhu, Cihui; Kaluarachchi, Warna D.; Curley, Steven A.

    2013-01-01

    Background Several studies have reported targeted hyperthermia at the cellular level using remote activation of nanoparticles by radiofrequency waves. To date, methods to quantify intracellular thermal dose have not been reported. In this report we study the relationship between radio wave exposure and luciferase denaturation with and without intracellular nanoparticles. The findings are used to devise a strategy to quantify targeted thermal dose in a primary human liver cancer cell line. Methods Water-bath or non-invasive external RF generator (600W, 13.56 MHz) was used for hyperthermia exposures. Luciferase activity was measured using a bioluminescence assay and viability was assessed using Annexin V-FITC and Propidium iodide staining. Heat shock proteins were analyzed using western-blot analysis Results Duration-dependent luciferase denaturation was observed in SNU449 cells exposed to RF field that preceded measurable loss in viability. Loss of luciferase activity was higher in cetuximab-conjugated gold nanoparticle (C225-AuNP) treated cells. Using a standard curve from water-bath experiments, the intracellular thermal dose was calculated. Cells treated with C225-AuNP accumulated 6.07 times higher intracellular thermal dose than the untreated controls over initial 4 minutes of RF exposure. Conclusions Cancer cells when exposed to an external RF field exhibit dose-dependent protein denaturation. Luciferase denaturation assay can be used to quantify thermal dose delivered after RF exposures to cancer cells with and without nanoparticles. PMID:22515341

  11. Differential Pro-Inflammatory Responses of Astrocytes and Microglia Involve STAT3 Activation in Response to 1800 MHz Radiofrequency Fields

    PubMed Central

    Lu, Yonghui; He, Mindi; Zhang, Yang; Xu, Shangcheng; Zhang, Lei; He, Yue; Chen, Chunhai; Liu, Chuan; Pi, Huifeng; Yu, Zhengping; Zhou, Zhou

    2014-01-01

    Microglia and astrocytes play important role in maintaining the homeostasis of central nervous system (CNS). Several CNS impacts have been postulated to be associated with radiofrequency (RF) electromagnetic fields exposure. Given the important role of inflammation in neural physiopathologic processes, we investigated the pro-inflammatory responses of microglia and astrocytes and the involved mechanism in response to RF fields. Microglial N9 and astroglial C8-D1A cells were exposed to 1800 MHz RF for different time with or without pretreatment with STAT3 inhibitor. Microglia and astrocytes were activated by RF exposure indicated by up-regulated CD11b and glial fibrillary acidic protein (GFAP). However, RF exposure induced differential pro-inflammatory responses in astrocytes and microglia, characterized by different expression and release profiles of IL-1?, TNF-?, IL-6, PGE2, nitric oxide (NO), inducible nitric oxide synthase (iNOS) and cyclooxygenase 2 (COX2). Moreover, the RF exposure activated STAT3 in microglia but not in astrocytes. Furthermore, the STAT3 inhibitor Stattic ameliorated the RF-induced release of pro-inflammatory cytokines in microglia but not in astrocytes. Our results demonstrated that RF exposure differentially induced pro-inflammatory responses in microglia and astrocytes, which involved differential activation of STAT3 in microglia and astrocytes. Our data provide novel insights into the potential mechanisms of the reported CNS impacts associated with mobile phone use and present STAT3 as a promising target to protect humans against increasing RF exposure. PMID:25275372

  12. Pulsed radiofrequency for chronic pain.

    PubMed

    Byrd, David; Mackey, Sean

    2008-01-01

    Pulsed radiofrequency (PRF), a technology related to continuous radiofrequency, is unique in that it provides pain relief without causing significant damage to nervous tissue. The mechanism by which PRF controls pain is unclear, but it may involve a temperature-independent pathway mediated by a rapidly changing electrical field. Although much anecdotal evidence exists in favor of PRF, there are few quality studies substantiating its utility. PMID:18417022

  13. Radiofrequency Lesioning

    Microsoft Academic Search

    Michael Petr; John M. Tew

    Radiofrequency lesioning (RFL) is a time-proven, safe method of long-term pain relief. It provides successful treatment for\\u000a trigeminal neuralgia and has been explored as a tool for symptomatic relief of many other neurologic conditions including\\u000a Parkinson’s disease, oncologic pain, spinal pain syndromes, facial spasm, facial pain of multiple sclerosis, vagoglossopharyngeal\\u000a neuralgia, and (rarely) atypical facial pain (1–5). Originally the RFL

  14. Complete description of the interactions of a quadrupolar nucleus with a radiofrequency field. Implications for data fitting.

    PubMed

    Spencer, T Leigh; Goward, Gillian R; Bain, Alex D

    2013-06-01

    We present a theory, with experimental tests, that treats exactly the effect of radiofrequency (RF) fields on quadrupolar nuclei, yet retains the symbolic expressions as much as possible. This provides a mathematical model of these interactions that can be easily connected to state-of-the-art optimization methods, so that chemically-important parameters can be extracted from fits to experimental data. Nuclei with spins >1/2 typically experience a Zeeman interaction with the (possibly anisotropic) local static field, a quadrupole interaction and are manipulated with RF fields. Since RF fields are limited by hardware, they seldom dominate the other interactions of these nuclei and so the spectra show unusual dependence on the pulse width used. The theory is tested with (23)Na NMR nutation spectra of a single crystal of sodium nitrate, in which the RF is comparable with the quadrupole coupling and is not necessarily on resonance with any of the transitions. Both the intensity and phase of all three transitions are followed as a function of flip angle. This provides a more rigorous trial than a powder sample where many of the details are averaged out. The formalism is based on a symbolic approach which encompasses all the published results, yet is easily implemented numerically, since no explicit spin operators or their commutators are needed. The classic perturbation results are also easily derived. There are no restrictions or assumptions on the spin of the nucleus or the relative sizes of the interactions, so the results are completely general, going beyond the standard first-order treatments in the literature. PMID:23611427

  15. [The IARC carcinogenicity evaluation of radio-frequency electromagnetic field: with special reference to epidemiology of mobile phone use and brain tumor risk].

    PubMed

    Yamaguchi, Naohito

    2013-01-01

    The International Agency for Research on Cancer of World Health Organization announced in May 2011 the results of evaluation of carcinogenicity of radio-frequency electromagnetic field. In the overall evaluation, the radio-frequency electromagnetic field was classified as "possibly carcinogenic to humans", on the basis of the fact that the evidence provided by epidemiological studies and animal bioassays was limited. Regarding epidemiology, the results of the Interphone Study, an international collaborative case-control study, were of special importance, together with the results of a prospective cohort study in Denmark, case-control studies in several countries, and a case-case study in Japan. The evidence obtained was considered limited, because the increased risk observed in some studies was possibly spurious, caused by selection bias or recall bias as well as residual effects of confounding factors. Further research studies, such as large-scale multinational epidemiological studies, are crucially needed to establish a sound evidence base from which a more conclusive judgment can be made for the carcinogenicity of the radio-frequency electromagnetic field. PMID:23718968

  16. Nuclear reorientation in static and radio-frequency electro-magnetic fields

    Microsoft Academic Search

    Dirk Dubbers

    1976-01-01

    Nuclear reorientation by external electromagnetic fields is treated using Fano's irreducible tensor formulation of the problem. Although the main purpose of this paper is the description of the effects of nuclear magnetic resonance (NMR) on an ensemble of oriented nuclei in the presence of a crystal electric field gradient (efg), the results are applicable to all types of nuclear or

  17. Effects of early-onset radiofrequency electromagnetic field exposure (GSM 900 MHz) on behavior and memory in rats.

    PubMed

    Klose, Melanie; Grote, Karen; Spathmann, Oliver; Streckert, Joachim; Clemens, Markus; Hansen, Volkert W; Lerchl, Alexander

    2014-10-01

    Female Wistar rats, from an age of 14 days to 19 months, were exposed in the head region for 2 h per day, 5 days per week, to a GSM-modulated 900 MHz radiofrequency electromagnetic field (RF-EMF). The average specific absorption rates (SAR) in the brain were 0 (sham), 0.7, 2.5 and 10 W/kg. To ensure a primary exposure of the head region, rats were fixed in restraining tubes of different sizes according to their increasing body weight. During the experiment, a set of 4 behavioral and learning tests (rotarod, Morris water maze, 8-arm radial maze, open field) were performed 3 times in juvenile, adult and presenile rats. In these tests, no profound differences could be identified between the groups. Only presenile rats of the cage control group showed a lower activity in two of these tests compared to the other groups presumably due to the lack of daily handling. The rotarod data revealed on some testing days significantly longer holding times for the sham-exposed rat vs. the exposed rat, but these findings were not consistent. During the first year, body weights of sham-exposed and exposed rats were not different from those of the cage controls, and thereafter only marginally lower, so that the effect of stress as confounder was probably negligible. The results of this study do not indicate harmful effects of long-term RF-EMF exposure even when begun at an early age on subsequent development, learning skills and behavior in rats, even at relatively high SAR values. PMID:25251701

  18. Implementation of acoustic, radiofrequency and microwave rotating fields in analytical plasma sources

    Microsoft Academic Search

    Krzysztof Jankowski; Andrzej P. Ramsza; Edward Reszke

    2011-01-01

    Four helium plasma sources operating at atmospheric pressure have been developed for analytical emission spectrometry by applying a synchronically rotating field with three or more phases operating at 1kHz, 27MHz or 2.45GHz. The plasma takes the form of a disk and has minimum field strength at the axis. Thus, a channel is formed at the center through which the sample

  19. Radiofrequency field absorption by carbon nanotubes embedded in a conductive host

    E-print Network

    Hanson, George

    studied in the radio frequency range. Strong local field enhancement due to edge effects is predicted for composite materials. In particular, carbon nanotubes are proposed as building blocks for the realization possibilities for cancer treatment of deep tissues. Theoretical studies of CNT-enhanced micro- wave detection

  20. Gold-gold sulfide nanoshell as a novel intensifier for anti-tumor effects of radiofrequency fields

    PubMed Central

    Sadeghi, Hamid Reza; Bahreyni-Toosi, Mohammad Hossein; Meybodi, Naser Tayebi; Esmaily, Habibollah; Soudmand, Samaneh; Eshghi, Hossein; Soudmand, Samaneh; Sazgarnia, Ameneh

    2014-01-01

    Objective(s): Several studies have been carried out to investigate the effect of various nanoparticles exposed to radiofrequency (RF) waves on cancerous tissues. In this study, a colon carcinoma tumor model was irradiated by RF in the presence of gold-gold sulfide (GGS) nanoshells. Materials and Methods: Synthesis and characterization of GGS nanoshells were initially performed. CT26 cells were subcutaneously injected into the flank of BALB/c mice to create the colon carcinoma tumor models. Then the tumors were subjected to different treatments. Treatment factors included intratumoral injection of GGS and RF radiation. Different groups were considered as control with no treatment, receiving GGS, RF irradiated and simultaneous administration of GGS and RF. Efficacy of the treatments was evaluated by daily monitoring of tumor volume and recording the relative changes in it, the time needed for a 5-fold increase in the volume of tumor (T5) and utilizing pathologic studies to determine the lost volume of the tumors. Results: In comparison with control group, tumor growth was not markedly inhibited in the groups receiving only GGS or RF, while in the group receiving GGS and RF, tumor growth was effectively inhibited compared with the other groups. In addition, the lost volume of the tumor and T5 was markedly higher in groups receiving GGS and RF compared with other groups. Conclusion: This study showed that RF radiation can markedly reduce the tumor growth in presence of GGS. Hence, it can be predicted that GGS nanoshells convert sub-lethal effects of noninvasive RF fields into lethal damages. PMID:25429343

  1. Water dissociation in a radio-frequency electromagnetic field with ex situ electrodes—process characterization

    NASA Astrophysics Data System (ADS)

    Schneider, Jens; Holzer, Frank; Kraus, Markus; Kopinke, Frank-Dieter; Roland, Ulf

    2013-02-01

    A new type of water dissociation at ambient pressure initiated by the irradiation of aqueous electrolytes using an electromagnetic field with a frequency of 13.56 MHz is described in this study. A special reactor design allows the use of ex situ electrodes to form in situ electrical discharges in water vapour bubbles. The observed formation of molecular hydrogen (H2) and oxygen (O2) combined with the emission of light (‘burning water’ phenomenon) originates from a non-thermal plasma in water vapour bubbles. The influences of type of electrolyte, its concentration, pH value and external RF voltage on the gas formation rate as well as on the gas composition are presented.

  2. Radio-Frequency Performance of Epitaxial Graphene Field-Effect Transistors on Sapphire Substrates

    NASA Astrophysics Data System (ADS)

    Liu, Qing-Bin; Yu, Cui; Li, Jia; Song, Xu-Bo; He, Ze-Zhao; Lu, Wei-Li; Gu, Guo-Dong; Wang, Yuan-Gang; Feng, Zhi-Hong

    2014-07-01

    We report dc and the first-ever measured small signal rf performance of epitaxial graphene field-effect transistors (GFETs), where the epitaxial graphene is grown by chemical vapor deposition (CVD) on a 2-inch c-plane sapphire substrate. Our epitaxial graphene material has a good flatness and uniformity due to the low carbon concentration during the graphene growth. With a gate length Lg = 100 nm, the maximum drain source current Ids and peak transconductance gm reach 0.92 A/mm and 0.143 S/mm, respectively, which are the highest results reported for GFETs directly grown on sapphire. The extrinsic cutoff frequency (fT) and maximum oscillation frequency (fmax) of the device are 12 GHz and 9.5 GHz, and up to 32 GHz and 21.5 GHz after de-embedding, respectively. Our work proves that epitaxial graphene on sapphire substrates is a promising candidate for rf electronics.

  3. Searching for the Perfect Wave: The Effect of Radiofrequency Electromagnetic Fields on Cells

    PubMed Central

    Gherardini, Lisa; Ciuti, Gastone; Tognarelli, Selene; Cinti, Caterina

    2014-01-01

    There is a growing concern in the population about the effects that environmental exposure to any source of “uncontrolled” radiation may have on public health. Anxiety arises from the controversial knowledge about the effect of electromagnetic field (EMF) exposure to cells and organisms but most of all concerning the possible causal relation to human diseases. Here we reviewed those in vitro and in vivo and epidemiological works that gave a new insight about the effect of radio frequency (RF) exposure, relating to intracellular molecular pathways that lead to biological and functional outcomes. It appears that a thorough application of standardized protocols is the key to reliable data acquisition and interpretation that could contribute a clearer picture for scientists and lay public. Moreover, specific tuning of experimental and clinical RF exposure might lead to beneficial health effects. PMID:24681584

  4. Tumor promotion by exposure to radiofrequency electromagnetic fields below exposure limits for humans.

    PubMed

    Lerchl, Alexander; Klose, Melanie; Grote, Karen; Wilhelm, Adalbert F X; Spathmann, Oliver; Fiedler, Thomas; Streckert, Joachim; Hansen, Volkert; Clemens, Markus

    2015-04-17

    The vast majority of in vitro and in vivo studies did not find cancerogenic effects of exposure to electromagnetic fields (RF-EMF), i.e. emitted by mobile phones and base stations. Previously published results from a pilot study with carcinogen-treated mice, however, suggested tumor-promoting effects of RF-EMF (Tillmann et al., 2010). We have performed a replication study using higher numbers of animals per group and including two additional exposure levels (0 (sham), 0.04, 0.4 and 2 W/kg SAR). We could confirm and extend the originally reported findings. Numbers of tumors of the lungs and livers in exposed animals were significantly higher than in sham-exposed controls. In addition, lymphomas were also found to be significantly elevated by exposure. A clear dose-response effect is absent. We hypothesize that these tumor-promoting effects may be caused by metabolic changes due to exposure. Since many of the tumor-promoting effects in our study were seen at low to moderate exposure levels (0.04 and 0.4 W/kg SAR), thus well below exposure limits for the users of mobile phones, further studies are warranted to investigate the underlying mechanisms. Our findings may help to understand the repeatedly reported increased incidences of brain tumors in heavy users of mobile phones. PMID:25749340

  5. Autophagy and Enhanced Chemosensitivity in Experimental Pancreatic Cancers Induced by Noninvasive Radiofrequency Field Treatment

    PubMed Central

    Koshkina, Nadezhda V.; Briggs, Katrina; Palalon, Flavio; Curley, Steven A.

    2013-01-01

    Background Patients with pancreatic adenocarcinoma (PDAC) have limited therapeutic options and poor response to the standard gemcitabine (GCB)-based chemotherapy. We investigated the feasibility of non-invasive short-wave RF electric fields to improve cytotoxic effect of GCB on PDAC cells and determined its mechanism of action. Methods Cytotoxicity of RF alone and in combination with GCB was studied in vitro on normal pancreatic HPDE cells and different PDAC cell lines by flow cytometry, and in vivo on ectopic and orthotopic human PDAC xenograft models in mice. Mechanism of RF activity was studied by western blot and immunohistochemistry analysis. Toxicity was determined by histopathology. Results Exposure of different PDAC cells to 13.56 MHz radiowaves resulted in substantial cytotoxic effect, which was accompanied by induction of autophagy, but not apoptosis. These effects of RF were absent in normal cells. Excessive numbers of autophagosomes in cancer cells persisted 24-48 h after RF exposure and then declined. Addition of a subtoxic dose of GCB to RF treatment inhibited the recovery of cancer cells from the RF-induced autophagy and enhanced cytotoxic effect of the latter on cancer cells. Treatment of PDAC cancer in situ in mice with combination of non-invasive RF and GCB had superior antitumor effect than RF or GCB alone, yet had no evidence of systemic toxicity. Conclusions Non-invasive RF treatment induced autophagy, not apoptosis in cancer cells and showed a potential as an enhancer of chemotherapy for treating pancreatic cancer without toxicity to normal cells. PMID:24496866

  6. New-generation radiofrequency technology.

    PubMed

    Krueger, Nils; Sadick, Neil S

    2013-01-01

    Radiofrequency (RF) technology has become a standard treatment in aesthetic medicine with many indications due to its versatility, efficacy, and safety. It is used worldwide for cellulite reduction; acne scar revision; and treatment of hypertrophic scars and keloids, rosacea, and inflammatory acne in all skin types. However, the most common indication for RF technology is the nonablative tightening of tissue to improve skin laxity and reduce wrinkles. Radiofrequency devices are classified as unipolar, bipolar, or multipolar depending on the number of electrodes used. Additional modalities include fractional RF; sublative RF; phase-controlled RF; and combination RF therapies that apply light, massage, or pulsed electromagnetic fields (PEMFs). This article reviews studies and case series on these devices. Radiofrequency technology for aesthetic medicine has seen rapid advancements since it was used for skin tightening in 2003. Future developments will continue to keep RF technology at the forefront of the dermatologist's armamentarium for skin tightening and rejuvenation. PMID:23461058

  7. Comparison of the Genotoxic Effects Induced by 50 Hz Extremely Low-Frequency Electromagnetic Fields and 1800 MHz Radiofrequency Electromagnetic Fields in GC-2 Cells.

    PubMed

    Duan, Weixia; Liu, Chuan; Zhang, Lei; He, Mindi; Xu, Shangcheng; Chen, Chunhai; Pi, Huifeng; Gao, Peng; Zhang, Yanwen; Zhong, Min; Yu, Zhengping; Zhou, Zhou

    2015-03-01

    Extremely low-frequency electromagnetic fields (ELF-EMF) and radiofrequency electromagnetic fields (RF-EMF) have been considered to be possibly carcinogenic to humans. However, their genotoxic effects remain controversial. To make experiments controllable and results comparable, we standardized exposure conditions and explored the potential genotoxicity of 50 Hz ELF-EMF and 1800 MHz RF-EMF. A mouse spermatocyte-derived GC-2 cell line was intermittently (5 min on and 10 min off) exposed to 50 Hz ELF-EMF at an intensity of 1, 2 or 3 mT or to RF-EMF in GSM-Talk mode at the specific absorption rates (SAR) of 1, 2 or 4 W/kg. After exposure for 24 h, we found that neither ELF-EMF nor RF-EMF affected cell viability using Cell Counting Kit-8. Through the use of an alkaline comet assay and immunofluorescence against ?-H2AX foci, we found that ELF-EMF exposure resulted in a significant increase of DNA strand breaks at 3 mT, whereas RF-EMF exposure had insufficient energy to induce such effects. Using a formamidopyrimidine DNA glycosylase (FPG)-modified alkaline comet assay, we observed that RF-EMF exposure significantly induced oxidative DNA base damage at a SAR value of 4 W/kg, whereas ELF-EMF exposure did not. Our results suggest that both ELF-EMF and RF-EMF under the same experimental conditions may produce genotoxicity at relative high intensities, but they create different patterns of DNA damage. Therefore, the potential mechanisms underlying the genotoxicity of different frequency electromagnetic fields may be different. PMID:25688995

  8. Theranostic applications: Non-ionizing cellular and molecular imaging through innovative nanosystems for early diagnosis and therapy

    PubMed Central

    Casciaro, Sergio

    2011-01-01

    Modern medicine is expanding the possibilities of receiving “personalized” diagnosis and therapies, providing minimal invasiveness, technological solutions based on non-ionizing radiation, early detection of pathologies with the main objectives of being operator independent and with low cost to society. Our research activities aim to strongly contribute to these trends by improving the capabilities of current diagnostic imaging systems, which are of key importance in possibly providing both optimal diagnosis and therapies to patients. In medical diagnostics, cellular imaging aims to develop new methods and technologies for the detection of specific metabolic processes in living organisms, in order to accurately identify and discriminate normal from pathological tissues. In fact, most diseases have a “molecular basis” that detected through these new diagnostic methodologies can provide enormous benefits to medicine. Nowadays, this possibility is mainly related to the use of Positron Emission Tomography, with an exposure to ionizing radiation for patients and operators and with extremely high medical diagnostics costs. The future possible development of non-ionizing cellular imaging based on techniques such as Nuclear Magnetic Resonance or Ultrasound, would represent an important step towards modern and personalized therapies. During the last decade, the field of nanotechnology has made important progress and a wide range of organic and inorganic nanomaterials are now available with an incredible number of further combinations with other compounds for cellular targeting. The availability of these new advanced nanosystems allows new scenarios in diagnostic methodologies which are potentially capable of providing morphological and functional information together with metabolic and cellular indications. PMID:22229079

  9. Are the young more sensitive than adults to the effects of radiofrequency fields? An examination of relevant data from cellular and animal studies.

    PubMed

    Marino, Carmela; Lagroye, Isabelle; Scarfì, Maria Rosaria; Sienkiewicz, Zenon

    2011-12-01

    It has sometimes been assumed that children are more sensitive than adults to the effects of radiofrequency (RF) fields associated with cellular wireless telephones. However, relatively few in vitro or animal models have examined this possibility. In vitro studies have used several cell types, from both humans and rodents, including primary cells, embryonic cell lines, undifferentiated cancer cell lines, and stem cells. Overall, the balance of evidence does not suggest that field-related effects occur in any cell type: gene and protein expression were not significantly changed by exposure in nine out of 15 studies; genotoxicity was evaluated in 13 papers and in most, of these studies, no damage to DNA was detected; eight studies failed to demonstrate induction of apoptosis; and three studies reported lack of oxidative stress induction by RF-exposures. Five of eight studies investigating the effects of combined exposures to RF fields and chemical or physical agents reported a lack of field-related effects. In addition, few papers have been published on the effects of low level exposure of immature animals. The available results are very limited, both in terms of signals used and biological endpoints investigated, but the evidence does not indicate that prenatal or early postnatal exposures are associated with acute adverse responses or the development of detrimental changes in the long-term. Overall, this suggests that young animals may not be significantly more sensitive than adults, but there is clearly a need for further studies to be carried out. PMID:21924280

  10. Bipolar radiofrequency for adenoidectomy

    Microsoft Academic Search

    J. Mark Palmer

    2006-01-01

    tolaryngologists have utilized bipolar radiofrequency for tonsillectomy for nearly 5 years, although many switch to a curette or suction cautery to remove the ade- noids. Since adopting Coblation bipolar radiofrequency (ArthroCare Corporation, Sunnyvale, CA) for tonsil re- moval, the author has seen patient benefits, including min- imal blood loss and less thermal damage, leading to a more thorough dissection and

  11. Shock tube determination of the heat conductivity of non-ionized and partially ionized argon

    Microsoft Academic Search

    A. Hirschberg

    1981-01-01

    A procedure to determine the heat conductivity of a monatomic gas, from measurements of the structure of the unsteady thermal boundary layer at the end-wall of a shock tube, is proposed. In the non-ionized case the structure of the boundary layer determined by means of laser schlieren measurements appears to be self-similar. Improved analysis of the schlieren data and accurate

  12. Effect of long-term (2 years) exposure of mouse brains to global system for mobile communication (GSM) radiofrequency fields on astrocytic immunoreactivity.

    PubMed

    Court-Kowalski, Stefan; Finnie, John W; Manavis, Jim; Blumbergs, Peter C; Helps, Stephen C; Vink, Robert

    2015-04-01

    This study was designed to determine whether long-term (2 years) brain exposure to mobile telephone radiofrequency (RF) fields produces any astrocytic activation as these glia react to a wide range of neural perturbations by astrogliosis. Using a purpose-designed exposure system at 900?MHz, mice were given a single, far-field whole body exposure at a specific absorption rate of 4?W/kg on five successive days per week for 104 weeks. Control mice were sham-exposed or freely mobile in a cage to control any stress caused by immobilization in the exposure module. Brains were perfusion-fixed with 4% paraformaldehyde and three coronal levels immunostained for glial fibrillary acidic protein (GFAP). These brain slices were then examined by light microscopy and the amount of this immunomarker quantified using a color deconvolution method. There was no change in astrocytic GFAP immunostaining in brains after long-term exposure to mobile telephony microwaves compared to control (sham-exposed or freely moving caged mice). It was concluded that long-term (2 years) exposure of murine brains to mobile telephone RF fields did not produce any astrocytic reaction (astrogliosis) detectable by GFAP immunostaining. Bioelectromagnetics. 36:245-250, 2015. © 2015 Wiley Periodicals, Inc. PMID:25703451

  13. Radiofrequency current source (RFCS) drive and decoupling technique for parallel transmit arrays using a high-power metal oxide semiconductor field-effect transistor (MOSFET).

    PubMed

    Lee, Wonje; Boskamp, Eddy; Grist, Thomas; Kurpad, Krishna

    2009-07-01

    A radiofrequency current source (RFCS) design using a high-power metal oxide semiconductor field effect transistor (MOSFET) that enables independent current control for parallel transmit applications is presented. The design of an RFCS integrated with a series tuned transmitting loop and its associated control circuitry is described. The current source is operated in a gated class AB push-pull configuration for linear operation at high efficiency. The pulsed RF current amplitude driven into the low impedance transmitting loop was found to be relatively insensitive to the various loaded loop impedances ranging from 0.4 to 10.3 ohms, confirming current mode operation. The suppression of current induced by a neighboring loop was quantified as a function of center-to-center loop distance, and was measured to be 17 dB for nonoverlapping, adjacent loops. Deterministic manipulation of the B(1) field pattern was demonstrated by the independent control of RF phase and amplitude in a head-sized two-channel volume transmit array. It was found that a high-voltage rated RF power MOSFET with a minimum load resistance, exhibits current source behavior, which aids in transmit array design. PMID:19353658

  14. Radiofrequency coblation tonsillectomy.

    PubMed

    Grobler, Alethea; Carney, A Simon

    2006-06-01

    Radiofrequency coblation is a new technology that is finding favour as a method for performing tonsillectomy. Its benefits include reduced pain and postoperative morbidity but there is controversy regarding possible increased postoperative haemorrhage rates. PMID:16821740

  15. In situ measurements of radiofrequency exposure levels in Greece from 2008 to 2013: A multi-parametric annual analysis.

    PubMed

    Christopoulou, Maria; Karabetsos, Efthymios

    2015-04-01

    From 2008 through 2013, more than 6,000 in situ frequency selective audits, in the proximity of base stations, were conducted throughout Greece by the Greek Atomic Energy Commission (EEAE), in order to verify exposure limit compliance. EEAE is the competent national authority for protection of the general public against artificially produced non-ionizing radiation. This paper presents the first post processing and multi-parametric year statistical analysis of in situ measurement data corresponding to 4,705 audits in the whole country, compared to general public exposure levels, according to Greek legislation. The aim is to derive nationwide conclusions for the characterization of general public exposure to radiofrequency electromagnetic fields, during the last 6 years. The results' presentation includes electric field exposure ratios referring to broadband and frequency selective measurements at the highest exposure measurement point. Statistical analysis is applied to assist the data presentation and evaluation, based on selected criteria and classification parameters, including: (i) year (2008-2013); (ii) environment (urban/suburban/rural); (iii) frequency bands of selected common telecommunication services (e.g., TV, FM, GSM, DCS, UMTS); and (iv) number of service providers installed at the same site. In general, measurement results revealed that the vast majority of exposure values were below reference levels for general public exposure, as defined by Greek legislation. Data are constantly updated with the latest measurements, including emerging wireless technologies. Bioelectromagnetics. 36:325-329, 2015. © 2015 Wiley Periodicals, Inc. PMID:25726724

  16. Sensitive model with which to detect athermal effects of non-ionizing electromagnetic radiation

    SciTech Connect

    Saffer, J.D.; Profenno, L.A. (Jackson Laboratory, Bar Harbor, ME (USA))

    1989-01-01

    To clarify the potential of non-ionizing electromagnetic radiation to cause biological effects by athermal mechanisms, and to initiate elucidation of those mechanisms, a model system amenable to scrutiny at the molecular level has been designed and characterized. Assessment of beta-galactosidase activity in E. coli JM101 containing the plasmid pUC8 provides a sensitive assay with many important advantages. The ability to examine at the molecular level each of the processes involved in producing beta-galactosidase should permit elucidation of the molecular mechanism(s) that give rises to an observed effect.

  17. PHYSICAL REVIEW B 83, 155446 (2011) Performance of field-emitting resonating carbon nanotubes as radio-frequency demodulators

    E-print Network

    Boyer, Edmond

    (FEM) patterns by a widening in the vibration direction; (2) the resonance frequencies can be tuned to the dependence of the field amplification factor (y) that controls the field emission current through the Fowler the role of four essential components of a radio receiver: the antenna, the tuner, the amplifier

  18. Does non-ionizing radiant energy affect determination of the evaporation rate by the gradient method?

    PubMed

    Kjartansson, S; Hammarlund, K; Oberg, P A; Sedin, G

    1991-01-01

    A study was performed to investigate whether measurements of the evaporation rate from the skin of newborn infants by the gradient method are affected by the presence of non-ionizing radiation from phototherapy equipment or a radiant heater. The evaporation rate was measured experimentally with the measuring sensors either exposed to or protected from non-ionizing radiation. Either blue light (phototherapy) or infrared light (radiant heater) was used; in the former case the evaporation rate was measured from a beaker of water covered with a semipermeable membrane, and in the latter case from the hand of an adult subject, aluminium foil or with the measuring probe in the air. No adverse effect on the determinations of the evaporation rate was found in the presence of blue light. Infrared radiation caused an error of 0.8 g/m2h when the radiant heater was set at its highest effect level or when the ambient humidity was high. At low and moderate levels the observed evaporation rate was not affected. It is concluded that when clinical measurements are made from the skin of newborn infants nursed under a radiant heater, the evaporation rate can appropriately be determined by the gradient method. PMID:1897061

  19. Cell Type-Dependent Induction of DNA Damage by 1800 MHz Radiofrequency Electromagnetic Fields Does Not Result in Significant Cellular Dysfunctions

    PubMed Central

    Xu, Shanshan; Chen, Guangdi; Chen, Chunjing; Sun, Chuan; Zhang, Danying; Murbach, Manuel; Kuster, Niels; Zeng, Qunli; Xu, Zhengping

    2013-01-01

    Background Although IARC clarifies radiofrequency electromagnetic fields (RF-EMF) as possible human carcinogen, the debate on its health impact continues due to the inconsistent results. Genotoxic effect has been considered as a golden standard to determine if an environmental factor is a carcinogen, but the currently available data for RF-EMF remain controversial. As an environmental stimulus, the effect of RF-EMF on cellular DNA may be subtle. Therefore, more sensitive method and systematic research strategy are warranted to evaluate its genotoxicity. Objectives To determine whether RF-EMF does induce DNA damage and if the effect is cell-type dependent by adopting a more sensitive method ?H2AX foci formation; and to investigate the biological consequences if RF-EMF does increase ?H2AX foci formation. Methods Six different types of cells were intermittently exposed to GSM 1800 MHz RF-EMF at a specific absorption rate of 3.0 W/kg for 1 h or 24 h, then subjected to immunostaining with anti-?H2AX antibody. The biological consequences in ?H2AX-elevated cell type were further explored with comet and TUNEL assays, flow cytometry, and cell growth assay. Results Exposure to RF-EMF for 24 h significantly induced ?H2AX foci formation in Chinese hamster lung cells and Human skin fibroblasts (HSFs), but not the other cells. However, RF-EMF-elevated ?H2AX foci formation in HSF cells did not result in detectable DNA fragmentation, sustainable cell cycle arrest, cell proliferation or viability change. RF-EMF exposure slightly but not significantly increased the cellular ROS level. Conclusions RF-EMF induces DNA damage in a cell type-dependent manner, but the elevated ?H2AX foci formation in HSF cells does not result in significant cellular dysfunctions. PMID:23355902

  20. Radio-frequency electromagnetic field measurements for direct detection of electron Bernstein waves in a torus plasma

    SciTech Connect

    Yatsuka, Eiichi; Kinjo, Kiyotake; Morikawa, Junji; Ogawa, Yuichi [Graduate School of Frontier Sciences, University of Tokyo, Chiba 277-8568 (Japan)

    2009-02-15

    To identify the mode-converted electron Bernstein wave (EBW) in a torus plasma directly, we have developed an interferometry system, in which a diagnostic microwave injected outside of the plasma column was directly detected with the probing antenna inserted into the plasma. In this work, plasma production and heating are achieved with 2.45 GHz, 2.5 kW electron cyclotron heating (ECH), whereas diagnostics are carried out with a lower power (10 W) separate frequency (1-2.1 GHz) microwave. Three components, i.e., two electromagnetic (toroidal and poloidal directions) and an electrostatic (if refractive index is sufficiently higher than unity, it corresponds to radial component), of ECRF electric field are simultaneously measured with three probing antennas, which are inserted into plasma. Selectivities of each component signal were checked experimentally. Excitation antennas have quite high selectivity of direction of linear polarization. As probing antennas for detecting electromagnetic components, we employed a monopole antenna with a length of 35 mm, and the separation of the poloidal (O-wave) and toroidal (X-wave) components of ECRF electric field could be available with this antenna. To detect EBW, which is an electrostatic wave, a small tip (1 mm) antenna was used. As the preliminary results, we detected signals that have three characteristics of EBW, i.e., short wavelength, backward propagation, and electrostatic.

  1. Radiofrequency-assisted \\

    Microsoft Academic Search

    G Hausdorf; I Schulze-Neick; P E Lange

    1993-01-01

    A case of pulmonary atresia with ventricular septal defect is reported in which a communication was established between the right ventricle and the hypoplastic pulmonary artery by intervention, despite muscular atresia of the right ventricular outflow tract. The atresia was perforated with a special designed radiofrequency catheter (Osypka). After the creation of a canal within the muscular atresia, balloon dilatation

  2. Personal radiofrequency electromagnetic field measurements in The Netherlands: exposure level and variability for everyday activities, times of day and types of area.

    PubMed

    Bolte, John F B; Eikelboom, Tessa

    2012-11-01

    Knowledge of the exposure to radiofrequency electromagnetic fields is necessary for epidemiological studies on possible health effects. The main goal of this study is to determine the exposure level and spatial and temporal variances during 39 everyday activities in 12 frequency bands used in mobile telecommunication and broadcasting. Therefore, 24 h measurements were gathered from 98 volunteers living in or near Amsterdam and Purmerend, The Netherlands. They carried an activity diary to be kept to the minute, a GPS logger sampling at an interval of 1 s, and an EME Spy exposimeter with a detection limit of 0.0066 mW/m(2) sampling at an interval of 10s in 12 frequency bands. The mean exposure over 24 h, excluding own mobile phone use, was 0.180 mW/m(2). During daytime exposure was about the same, but during night it was about half, and in the evening it was about twice as high. The main contribution to environmental exposure (calling by participant not included) is from calling with mobile phones (37.5%), from cordless DECT phones and their docking stations (31.7%), and from the base stations (12.7%). The exposure to mobile phone base stations increases with the percentage of urban ground use, which is an indication for high people density. In agreement, the highest mean exposure relates to the activities with high people density, such as travelling by public transport, visiting social events, pubs or shopping malls. Exposure at home depends mainly on exposure from people calling in the neighbourhood of the participant and thus on the number of persons in a household. In addition just the possession of DECT docking stations leads to exposure as most models transmit continuously in stand-by. Also wireless internet routers continuously transmit in the WiFi band. Though the highest exposure peaks in the WiFi band, up to 0.265 W/m(2), come from stray radiation of microwave ovens. The mean total exposure largely depends on phone calls of a high exposure level and short duration. These calls lead to potentially high contrasts as well in exposure levels between sessions of the same activity as between persons, thus posing a challenge for personal exposure prediction. PMID:22906414

  3. Radiofrequency plasma antenna generated by femtosecond laser filaments in air

    SciTech Connect

    Brelet, Y.; Houard, A.; Point, G.; Prade, B.; Carbonnel, J.; Andre, Y.-B.; Mysyrowicz, A. [Laboratoire d'Optique Appliquee, ENSTA ParisTech, Ecole Polytechnique, CNRS, 91761 Palaiseau (France); Arantchouk, L. [Laboratoire de Physique des Plasmas, Ecole Polytechnique, CNRS, Palaiseau (France); Pellet, M. [Etat-major de la Marine Nationale, Paris (France)

    2012-12-24

    We demonstrate tunable radiofrequency emission from a meter-long linear plasma column produced in air at atmospheric pressure. A short-lived plasma column is initially produced by femtosecond filamentation and subsequently converted into a long-lived discharge column by application of an external high voltage field. Radiofrequency excitation is fed to the plasma by induction and detected remotely as electromagnetic radiation by a classical antenna.

  4. Radiofrequency ablation in children

    Microsoft Academic Search

    Anil K. Bhandari

    1996-01-01

    Radiofrequency (RF) catheter ablation has ushered in a new era in the management of patients with symptomatic tachyarrhythmias.\\u000a By providing the ability to cure the underlying arrhythmic substrate, RF catheter ablation obviates the need for life-long\\u000a antiarrhythmic drugs. In the reported series, the success has been high and the complications have been infrequent and relatively\\u000a minor. Not unexpectedly, RF catheter

  5. Experimental Studies on Carcinogenicity of Radiofrequency Radiation in Animals

    Microsoft Academic Search

    Jukka Juutilainen; Päivi Heikkinen; Isabelle Lagroye; Junji Miyakoshi; Eric Van Rongen; Richard Saunders; René De Seze; Thomas Tenforde; Luc Verschaeve; Bernard Veyret; Zhengping Xu

    2011-01-01

    In this paper, the authors present a comprehensive review of animal studies on carcinogenicity of radiofrequency (RF) electromagnetic fields. The rapid increase in mobile telephony has resulted in concerns regarding possible heath effects from the low-level but increasingly ubiquitous exposure to RF fields. The possible carcinogenicity of RF fields has been investigated in a number of experimental models including classical

  6. Radiofrequency in cosmetic dermatology.

    PubMed

    Beasley, Karen L; Weiss, Robert A

    2014-01-01

    The demand for noninvasive methods of facial and body rejuvenation has experienced exponential growth over the last decade. There is a particular interest in safe and effective ways to decrease skin laxity and smooth irregular body contours and texture without downtime. These noninvasive treatments are being sought after because less time for recovery means less time lost from work and social endeavors. Radiofrequency (RF) treatments are traditionally titrated to be nonablative and are optimal for those wishing to avoid recovery time. Not only is there minimal recovery but also a high level of safety with aesthetic RF treatments. PMID:24267424

  7. The Role of the Location of Personal Exposimeters on the Human Body in Their Use for Assessing Exposure to the Electromagnetic Field in the Radiofrequency Range 98–2450?MHz and Compliance Analysis: Evaluation by Virtual Measurements

    PubMed Central

    Zradzi?ski, Patryk

    2015-01-01

    The use of radiofrequency (98–2450?MHz range) personal exposimeters to measure the electric field (E-field) in far-field exposure conditions was modelled numerically using human body model Gustav and finite integration technique software. Calculations with 256 models of exposure scenarios show that the human body has a significant influence on the results of measurements using a single body-worn exposimeter in various locations near the body ((from ?96 to +133)%, measurement errors with respect to the unperturbed E-field value). When an exposure assessment involves the exposure limitations provided for the strength of an unperturbed E-field. To improve the application of exposimeters in compliance tests, such discrepancies in the results of measurements by a body-worn exposimeter may be compensated by using of a correction factor applied to the measurement results or alternatively to the exposure limit values. The location of a single exposimeter on the waist to the back side of the human body or on the front of the chest reduces the range of exposure assessments uncertainty (covering various exposure conditions). However, still the uncertainty of exposure assessments using a single exposimeter remains significantly higher than the assessment of the unperturbed E-field using spot measurements. PMID:25879021

  8. Radiofrequency encoded angular-resolved light scattering

    NASA Astrophysics Data System (ADS)

    Buckley, Brandon W.; Akbari, Najva; Diebold, Eric D.; Adam, Jost; Jalali, Bahram

    2015-03-01

    The sensitive, specific, and label-free classification of microscopic cells and organisms is one of the outstanding problems in biology. Today, instruments such as the flow cytometer use a combination of light scatter measurements at two distinct angles to infer the size and internal complexity of cells at rates of more than 10 000/s. However, by examining the entire angular light scattering spectrum, it is possible to classify cells with higher resolution and specificity. Current approaches to performing these angular spectrum measurements all have significant throughput limitations, making them incompatible with other state-of-the-art flow cytometers. Here, we introduce a method for performing complete angular scattering spectrum measurements at high throughput combining techniques from the field of scattering flow-cytometry and radiofrequency communications. Termed Radiofrequency Encoded Angular-resolved Light Scattering, this technique multiplexes angular light scattering in the radiofrequency domain, such that a single photodetector captures the entire scattering spectrum from a particle over approximately 100 discrete incident angles on a single shot basis. As a proof-of-principle experiment, we use this technique to perform scattering measurements over a range of 30° from a tapered optical fiber at a scan rate of 250 kHz.

  9. Longevity of radiofrequency identification device microchips in citrus trees

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Long-term identification of individual plants in the field is an important part of many types of botanical and horticultural research. In a previous report, we described methods for using implanted radiofrequency (RFID) microchips to tag citrus trees for field research. This report provides an upd...

  10. Superconductive radiofrequency window assembly

    DOEpatents

    Phillips, H.L.; Elliott, T.S.

    1998-05-19

    The present invention is a superconducting radiofrequency window assembly for use in an electron beam accelerator. The SRF window assembly has a superconducting metal-ceramic design. The SRF window assembly comprises a superconducting frame, a ceramic plate having a superconducting metallized area, and a superconducting eyelet for sealing plate into frame. The plate is brazed to eyelet which is then electron beam welded to frame. A method for providing a ceramic object mounted in a metal member to withstand cryogenic temperatures is also provided. The method involves a new metallization process for coating a selected area of a ceramic object with a thin film of a superconducting material. Finally, a method for assembling an electron beam accelerator cavity utilizing the SRF window assembly is provided. The procedure is carried out within an ultra clean room to minimize exposure to particulates which adversely affect the performance of the cavity within the electron beam accelerator. 11 figs.

  11. Superconducting radiofrequency window assembly

    DOEpatents

    Phillips, H.L.; Elliott, T.S.

    1997-03-11

    The present invention is a superconducting radiofrequency window assembly for use in an electron beam accelerator. The srf window assembly has a superconducting metal-ceramic design. The srf window assembly comprises a superconducting frame, a ceramic plate having a superconducting metallized area, and a superconducting eyelet for sealing plate into frame. The plate is brazed to eyelet which is then electron beam welded to frame. A method for providing a ceramic object mounted in a metal member to withstand cryogenic temperatures is also provided. The method involves a new metallization process for coating a selected area of a ceramic object with a thin film of a superconducting material. Finally, a method for assembling an electron beam accelerator cavity utilizing the srf window assembly is provided. The procedure is carried out within an ultra clean room to minimize exposure to particulates which adversely affect the performance of the cavity within the electron beam accelerator. 11 figs.

  12. Radiofrequency attenuator and method

    DOEpatents

    Warner, Benjamin P. (Los Alamos, NM); McCleskey, T. Mark (Los Alamos, NM); Burrell, Anthony K. (Los Alamos, NM); Agrawal, Anoop (Tucson, AZ); Hall, Simon B. (Palmerston North, NZ)

    2009-01-20

    Radiofrequency attenuator and method. The attenuator includes a pair of transparent windows. A chamber between the windows is filled with molten salt. Preferred molten salts include quarternary ammonium cations and fluorine-containing anions such as tetrafluoroborate (BF.sub.4.sup.-), hexafluorophosphate (PF.sub.6.sup.-), hexafluoroarsenate (AsF.sub.6.sup.-), trifluoromethylsulfonate (CF.sub.3SO.sub.3.sup.-), bis(trifluoromethylsulfonyl)imide ((CF.sub.3SO.sub.2).sub.2N.sup.-), bis(perfluoroethylsulfonyl)imide ((CF.sub.3CF.sub.2SO.sub.2).sub.2N.sup.-) and tris(trifluoromethylsulfonyl)methide ((CF.sub.3SO.sub.2).sub.3C.sup.-). Radicals or radical cations may be added to or electrochemically generated in the molten salt to enhance the RF attenuation.

  13. Radiofrequency attenuator and method

    DOEpatents

    Warner, Benjamin P. (Los Alamos, NM); McCleskey, T. Mark (Los Alamos, NM); Burrell, Anthony K. (Los Alamos, NM); Agrawal, Anoop (Tucson, AZ); Hall, Simon B. (Palmerston North, NZ)

    2009-11-10

    Radiofrequency attenuator and method. The attenuator includes a pair of transparent windows. A chamber between the windows is filled with molten salt. Preferred molten salts include quarternary ammonium cations and fluorine-containing anions such as tetrafluoroborate (BF.sub.4.sup.-), hexafluorophosphate (PF.sub.6.sup.-), hexafluoroarsenate (AsF.sub.6.sup.-), trifluoromethylsulfonate (CF.sub.3SO.sub.3.sup.-), bis(trifluoromethylsulfonyl)imide ((CF.sub.3SO.sub.2).sub.2N.sup.-), bis(perfluoroethylsulfonyl)imide ((CF.sub.3CF.sub.2SO.sub.2).sub.2N.sup.-) and tris(trifluoromethylsulfonyl)methide ((CF.sub.3SO.sub.2).sub.3 C.sup.-). Radicals or radical cations may be added to or electrochemically generated in the molten salt to enhance the RF attenuation.

  14. Superconducting radiofrequency window assembly

    DOEpatents

    Phillips, Harry L. (Seaford, VA); Elliott, Thomas S. (Yorktown, VA)

    1997-01-01

    The present invention is a superconducting radiofrequency window assembly for use in an electron beam accelerator. The srf window assembly (20) has a superconducting metal-ceramic design. The srf window assembly (20) comprises a superconducting frame (30), a ceramic plate (40) having a superconducting metallized area, and a superconducting eyelet (50) for sealing plate (40) into frame (30). The plate (40) is brazed to eyelet (50) which is then electron beam welded to frame (30). A method for providing a ceramic object mounted in a metal member to withstand cryogenic temperatures is also provided. The method involves a new metallization process for coating a selected area of a ceramic object with a thin film of a superconducting material. Finally, a method for assembling an electron beam accelerator cavity utilizing the srf window assembly is provided. The procedure is carried out within an ultra clean room to minimize exposure to particulates which adversely affect the performance of the cavity within the electron beam accelerator.

  15. Superconductive radiofrequency window assembly

    DOEpatents

    Phillips, Harry Lawrence (Seaford, VA); Elliott, Thomas S. (Yorktown, VA)

    1998-01-01

    The present invention is a superconducting radiofrequency window assembly for use in an electron beam accelerator. The srf window assembly (20) has a superconducting metal-ceramic design. The srf window assembly (20) comprises a superconducting frame (30), a ceramic plate (40) having a superconducting metallized area, and a superconducting eyelet (50) for sealing plate (40) into frame (30). The plate (40) is brazed to eyelet (50) which is then electron beam welded to frame (30). A method for providing a ceramic object mounted in a metal member to withstand cryogenic temperatures is also provided. The method involves a new metallization process for coating a selected area of a ceramic object with a thin film of a superconducting material. Finally, a method for assembling an electron beam accelerator cavity utilizing the srf window assembly is provided. The procedure is carried out within an ultra clean room to minimize exposure to particulates which adversely affect the performance of the cavity within the electron beam accelerator.

  16. Validation of self-reported start year of mobile phone use in a Swedish case-control study on radiofrequency fields and acoustic neuroma risk.

    PubMed

    Pettersson, David; Bottai, Matteo; Mathiesen, Tiit; Prochazka, Michaela; Feychting, Maria

    2015-01-01

    The possible effect of radiofrequency exposure from mobile phones on tumor risk has been studied since the late 1990s. Yet, empirical information about recall of the start of mobile phone use among adult cases and controls has never been reported. Limited knowledge about recall errors hampers interpretations of the epidemiological evidence. We used network operator data to validate the self-reported start year of mobile phone use in a case-control study of mobile phone use and acoustic neuroma risk. The answers of 96 (29%) cases and 111 (22%) controls could be included in the validation. The larger proportion of cases reflects a more complete and detailed reporting of subscription history. Misclassification was substantial, with large random errors, small systematic errors, and no significant differences between cases and controls. The average difference between self-reported and operator start year was -0.62 (95% confidence interval: -1.42, 0.17) years for cases and -0.71 (-1.50, 0.07) years for controls, standard deviations were 3.92 and 4.17 years, respectively. Agreement between self-reported and operator-recorded data categorized into short, intermediate and long-term use was moderate (kappa statistic: 0.42). Should an association exist, dilution of risk estimates and distortion of exposure-response patterns for time since first mobile phone use could result from the large random errors in self-reported start year. Retrospective collection of operator data likely leads to a selection of "good reporters", with a higher proportion of cases. Thus, differential recall cannot be entirely excluded. PMID:25352163

  17. Intralesional radiofrequency in venous malformations.

    PubMed

    Garg, S; Kumar, S; Singh, Y B

    2015-03-01

    Venous malformations are usually asymptomatic and managed conservatively. Treatment, in the form of laser, sclerotherapy, or resection, is needed only if lesions present with symptoms or cosmetic deformity. The aim of this study was to find out how effective radiofrequency ablation was in patients with incomplete or unsatisfactory resolution of a venous malformation after an intralesional injection of bleomycin. During the 5 year period 2008-2012, we organised a prospective, clinical study at a tertiary care centre. Patients were selected from the outpatient department of the Lady Hardinge Medical College and associated hospitals, New Delhi, India. Five patients with venous malformations were treated by intralesional injection of bleomycin in a dose of 0.5U/kg body weight, which was repeated every 2 weeks for a total of 8 injections. They then had multiple intralesional radiofrequency ablation every 2 months until a satisfactory outcome was achieved. After the initial 8 doses the reduction in the size of the lesions was minimal (less than 50%). After 2-4 applications of radiofrequency ablation there was appreciable reduction in the size of the lesions (about 80%) with good functional and cosmetic outcomes. Radiofrequency ablation is an effective adjunct for patients with venous malformations of the head and neck that have not responded satisfactorily to intralesional injection of bleomycin. To our knowledge radiofrequency ablation after intralesional injection of bleomycin has not previously been described as a treatment for venous malformations. PMID:25554592

  18. Evaluation of non-ionizing radiation around the shortwave diathermy devices

    Microsoft Academic Search

    U. Ozen; S. Comlekci; O. Cerezci; A. U. Onural

    2003-01-01

    Short wave and microwave equipment are used for treatment purpose in physiotherapy units. Such equipments' stray fields can affect around them in the near field region. This fact has been stressed in current studies. In this way, some \\

  19. Radiofrequency ablation (coblation): a promising new technique for laryngeal papillomata.

    PubMed

    Timms, M S; Bruce, I A; Patel, N K

    2007-01-01

    This paper describes a new application for radiofrequency ablation in head and neck surgery. Two patients with extensive laryngeal papillomata were successfully treated using this technology. The technique is described in detail, highlighting the main benefits of this approach as compared with existing techniques. These advantages include limited damage to underlying tissues and a bloodless field. PMID:17040601

  20. Evaluation of stray radiofrequency radiation emitted by electrosurgical devices

    Microsoft Academic Search

    M. DeMarco; S. Maggi

    2006-01-01

    Electrosurgery refers to the passage of a high-frequency, high-voltage electrical current through the body to achieve the desired surgical effects. At the same time, these procedures are accompanied by a general increase of the electromagnetic field in an operating room that may expose both patients and personnel to relatively high levels of radiofrequency radiation. In the first part of this

  1. Radiofrequency exposure near high-voltage lines.

    PubMed Central

    Vignati, M; Giuliani, L

    1997-01-01

    Many epidemiologic studies suggest a relationship between incidence of diseases like cancer and leukemia and exposure to 50/60 Hz magnetic fields. Some studies suggest a relationship between leukemia incidence in populations residing near high-voltage lines and the distance to these lines. Other epidemiologic studies suggest a relationship between leukemia incidence and exposure to 50/60 Hz magnetic fields (measured or estimated) and distance from the main system (220 or 120 V). The present work does not question these results but is intended to draw attention to a possible concurrent cause that might also increase the incidence of this disease; the presence on an electric grid of radiofrequency currents used for communications and remote control. These currents have been detected on high- and medium-voltage lines. In some cases they are even used on the main system for remote reading of electric meters. This implies that radiofrequency (RF) magnetic fields are present near the electric network in addition to the 50/60 Hz fields. This intensity of these RF fields is low but the intensity of currents induced in the human body by exposure to magnetic fields increases with frequency. Because scientific research has not yet clarified whether the risk is related to the value of magnetic induction or to the currents this kind of exposure produces in the human body, it is reasonable to suggest that the presence of the RF magnetic fields must be considered in the context of epidemiologic studies. Images Figure 3. Figure 4. Figure 5. PMID:9467084

  2. Nuclear and Non-Ionizing Energy-loss of Electrons with Low and Relativistic Energies in Materials and Space Environment

    E-print Network

    M. J. Boschini; C. Consolandi; M. Gervasi; S. Giani; D. Grandi; V. Ivanchenko; P. Nieminem; S. Pensotti; P. G. Rancoita; M. Tacconi

    2011-12-06

    The treatment of the electron-nucleus interaction based on the Mott differential cross section was extended to account for effects due to screened Coulomb potentials, finite sizes and finite rest masses of nuclei for electrons above 200 keV and up to ultra high energies. This treatment allows one to determine both the total and differential cross sections, thus, subsequently to calculate the resulting nuclear and non-ionizing stopping powers. Above a few hundreds of MeV, neglecting the effect due to finite rest masses of recoil nuclei the stopping power and NIEL result to be largely underestimated; while, above a few tens of MeV the finite size of the nuclear target prevents a further large increase of stopping powers which approach almost constant values.

  3. Nuclear and Non-Ionizing Energy-Loss of Electrons with Low and Relativistic Energies in Materials and Space Environment

    NASA Astrophysics Data System (ADS)

    Boschini, M. J.; Consolandi, C.; Gervasi, M.; Giani, S.; Grandi, D.; Ivanchenko, V.; Nieminem, P.; Pensotti, S.; Rancoita, P. G.; Tacconi, M.

    2012-08-01

    The treatment of the electron-nucleus interaction based on the Matt differential cross section was extended to account for effects due to screened Coulomb potentials, finite sizes and finite rest masses of nuclei for electrons above 200keV and up to ultra high energies. This treatment allows one to determine both the total and differential cross sections, thus, subsequently to calculate the resulting nuclear and non-ionizing stopping powers. Above a few hundreds of MeV, neglecting the effect due to finite rest masses of recoil nuclei the stopping power and NIEL result to be largely underestimated. While, above a few tens of MeV, the finite size ofthe nuclear target prevents a further large increase of stopping powers which approach almost constant values.

  4. “Black Bone” MRI: a potential non-ionizing method for three-dimensional cephalometric analysis—a preliminary feasibility study

    PubMed Central

    Watt-Smith, S R; Golding, S J

    2013-01-01

    Objectives: CT offers a three-dimensional solution to the inaccuracies associated with lateral cephalogram-based cephalometric analysis. However, it is associated with significant concerns regarding ionizing radiation exposure. MRI offers a non-ionizing alternative, but this has been less well investigated. We present a novel gradient echo MRI sequence (“Black Bone”) and highlight the potential of this sequence in cephalometric analysis. Methods: After regional ethics approval, “Black Bone” imaging was obtained in eight patients in whom lateral cephalograms were available. “Black Bone”, T1 and T2 weighted spin echo imaging were obtained in the mid-sagittal plane, and measurements were compared with those obtained on the lateral cephalogram using both the Advantage Windows Workstation (GE Medical Systems, Buckinghamshire, UK) and the Dolphin® cephalometric software (v. 11.5.04.23, Premium; Dolphin Imaging, Chatsworth, CA) by one assessor. Further assessment was made by scoring the ease of landmark identification on a ten-point scale. Results: “Black Bone” imaging surpassed T1 and T2 weighted imaging in terms of cephalometric landmark identification. A number of mid-sagittal cephalometric landmarks could not be clearly identified on T2 weighted imaging, making analysis impossible. Measurements on “Black Bone” demonstrated the smallest discrepancy when compared with those obtained on the lateral cephalogram. The discrepancy seen between measurements completed on mid-sagittal MRI and the lateral cephalogram was compounded by inherent inaccuracies of the lateral cephalogram. The overall mean discrepancy between distance measurements on “Black Bone” imaging and those on the lateral cephalogram was 1–2?mm. Conclusions: Overall, “Black Bone” MRI offered an improved method of cephalometric landmark identification over routine MRI sequences, and provides a potential non-ionizing alternative to CT for three-dimensional cephalometrics. PMID:24052254

  5. BIOLOGICAL EFFECTS OF RADIOFREQUENCY RADIATION

    EPA Science Inventory

    The document presents a critical review of the available literature on the biological effects of radiofrequency (RF) radiation. The objective was to summarize and evaluate the existing database for use in developing RF-radiation exposure guidance for the general public. The frequ...

  6. [Safety of use assessment in a radio-frequency medical device].

    PubMed

    Nicoletti, Giovanni; Coppola, Antonio; Di Liberto, Riccardo; Faga, Angela; Scevola, Silvia

    2014-01-01

    The authors assessed the operating safety physical parameters of a bipolar radiofrequency device for aesthetic purposes. According to both Italian and EU guidelines, the authors considered: magnetic field environmental emission levels, electricity induced in the opertator's limbs, operator's exposure and radiofrequency specific absorbance rate (SAR) in treated tissues. Measurements were carried out with isotropic sensors and an inductive current indicator. Results pointed out excellent safety levels regarding environment, operators and patients as well, although such radiofrequency equipment cannot be used on patients with pacemakers, neurostimulators and other vital function controlling devices. PMID:25369715

  7. Teratogenic effects of 27. 12 MHz radiofrequency radiation in rats

    Microsoft Academic Search

    Joseph M. Lary; David L. Conover; Edward D. Foley; Peggy L. Hanser

    1982-01-01

    High-intensity 27.12 MHz radiofrequency (RF) radiation was determined to be teratogenic in rats during most of the gestation period. Eight groups of pregnant rats were exposed to a magnetic field strength of 55 amps\\/meter and an electric field strength of 300 volts\\/meter on gestation days 1, 3, 5, 7, 9, 11, 13, or 15. Exposures ceased once the dam's colonic

  8. "Magic" radio-frequency dressing for trapped atomic microwave clocks

    E-print Network

    Kazakov, Georgy A

    2014-01-01

    It has been proposed to use magnetically trapped atomic ensembles to enhance the interrogation time in microwave clocks. To mitigate the perturbing effects of the magnetic trap, "near-magic field" configurations are employed, where the involved clock transition becomes independent of the atoms potential energy to first order. Still, higher order effects are a dominating source for dephasing, limiting the perfomance of this approach. Here we propose a simple method to cancel the energy dependence to both, first and second order, using weak radio-frequency dressing. We give values for dressing frequencies, amplitudes, and trapping fields for 87Rb atoms and investigate quantitatively the robustness of these "second-order magic" conditions to variations of the system parameters. We conclude that radio-frequency dressing can suppress field-induced dephasing by at least one order of magnitude for typical experimental parameters.

  9. Magic radio-frequency dressing for trapped atomic microwave clocks

    NASA Astrophysics Data System (ADS)

    Kazakov, G. A.; Schumm, T.

    2015-02-01

    It has been proposed to use magnetically trapped atomic ensembles to enhance the interrogation time in microwave clocks. To mitigate the perturbing effects of the magnetic trap, near-magic-field configurations are employed, where the involved clock transition becomes independent of the atom's potential energy to first order. Still, higher order effects are a dominating source for dephasing, limiting the performance of this approach. Here we propose a simple method to cancel the energy dependence to both first and second order, using weak radio-frequency dressing. We give values for dressing frequencies, amplitudes, and trapping fields for 87Rb atoms and investigate quantitatively the robustness of these second-order-magic conditions to variations of the system parameters. We conclude that radio-frequency dressing can suppress field-induced dephasing by at least one order of magnitude for typical experimental parameters.

  10. Red eyes of PC users due to the effects of non-ionized electromagnetic radiation

    NASA Astrophysics Data System (ADS)

    Soto-Bernal, J. J.; Huizar-Gonzalez, A. A.; Rosales-Candelas, I.; Cardoza-Rodriguez, A. R.

    2007-03-01

    This work presents an experimental study of the appearance of redness on the surface of the eye on PC users due to the exposition to low frequency electromagnetic fields LF, VLF and ELF that VDTs with TRC monitors radiate, based on the measurement of the level of pigmentation and temperature. The total of the samples was analyzed using digital processing of images extracting the component of red color of the sclera. We demonstrated that under the same ergonomics and operating conditions, TRC monitors cause a higher heating and greater pigmentation in the users eyes as compared to LCD screens, due to the higher low frequency radiation.

  11. Influence of non ionizing radiation of base stations on the activity of redox proteins in bovines

    PubMed Central

    2014-01-01

    Background The influence of electromagnetic fields on the health of humans and animals is still an intensively discussed and scientifically investigated issue (Prakt Tierarzt 11:15-20, 2003; Umwelt Medizin Gesellschaft 17:326-332, 2004; J Toxicol Environment Health, Part B 12:572–597, 2009). We are surrounded by numerous electromagnetic fields of variable strength, coming from electronic equipment and its power cords, from high-voltage power lines and from antennas for radio, television and mobile communication. Particularly the latter cause’s controversy, as everyone likes to have good mobile reception at anytime and anywhere, whereas nobody wants to have such a basestation antenna in their proximity. Results In this experiment, the NIR has resulted in changes in the enzyme activities. Certain enzymes were disabled, others enabled by NIR. Furthermore, individual behavior patterns were observed. While certain cows reacted to NIR, others did not react at all, or even inversely. Conclusion The present results coincide with the information from the literature, according to which NIR leads to changes in redox proteins, and that there are individuals who are sensitive to radiation and others that are not. However, the latter could not be distinctly attributed – there are cows that react clearly with one enzyme while they do not react with another enzyme at all, or even the inverse. The study approach of testing ten cows each ten times during three phases has proven to be appropriate. Future studies should however set the post-exposure phase later on. PMID:24946856

  12. Superconducting Radio-Frequency Cavities

    NASA Astrophysics Data System (ADS)

    Padamsee, Hasan S.

    2014-10-01

    Superconducting cavities have been operating routinely in a variety of accelerators with a range of demanding applications. With the success of completed projects, niobium cavities have become an enabling technology, offering upgrade paths for existing facilities and pushing frontier accelerators for nuclear physics, high-energy physics, materials science, and the life sciences. With continued progress in basic understanding of radio-frequency superconductivity, the performance of cavities has steadily improved to approach theoretical capabilities.

  13. 21 CFR 882.4400 - Radiofrequency lesion generator.

    Code of Federal Regulations, 2010 CFR

    2010-04-01

    ...2010-04-01 false Radiofrequency lesion generator. 882.4400 Section 882.4400... § 882.4400 Radiofrequency lesion generator. (a) Identification. A radiofrequency lesion generator is a device used to produce...

  14. 21 CFR 882.4400 - Radiofrequency lesion generator.

    Code of Federal Regulations, 2014 CFR

    2014-04-01

    ...2014-04-01 false Radiofrequency lesion generator. 882.4400 Section 882.4400... § 882.4400 Radiofrequency lesion generator. (a) Identification. A radiofrequency lesion generator is a device used to produce...

  15. 21 CFR 882.4400 - Radiofrequency lesion generator.

    Code of Federal Regulations, 2012 CFR

    2012-04-01

    ...2012-04-01 false Radiofrequency lesion generator. 882.4400 Section 882.4400... § 882.4400 Radiofrequency lesion generator. (a) Identification. A radiofrequency lesion generator is a device used to produce...

  16. 21 CFR 882.4400 - Radiofrequency lesion generator.

    Code of Federal Regulations, 2011 CFR

    2011-04-01

    ...2011-04-01 false Radiofrequency lesion generator. 882.4400 Section 882.4400... § 882.4400 Radiofrequency lesion generator. (a) Identification. A radiofrequency lesion generator is a device used to produce...

  17. 21 CFR 882.4400 - Radiofrequency lesion generator.

    Code of Federal Regulations, 2013 CFR

    2013-04-01

    ...2013-04-01 false Radiofrequency lesion generator. 882.4400 Section 882.4400... § 882.4400 Radiofrequency lesion generator. (a) Identification. A radiofrequency lesion generator is a device used to produce...

  18. 47 CFR 1.1310 - Radiofrequency radiation exposure limits.

    Code of Federal Regulations, 2011 CFR

    2011-10-01

    ...2011-10-01 false Radiofrequency radiation exposure limits. 1.1310 Section...of 1969 § 1.1310 Radiofrequency radiation exposure limits. The criteria listed...human exposure to radiofrequency (RF) radiation as specified in §...

  19. 47 CFR 1.1310 - Radiofrequency radiation exposure limits.

    Code of Federal Regulations, 2013 CFR

    2013-10-01

    ...2013-10-01 false Radiofrequency radiation exposure limits. 1.1310 Section...of 1969 § 1.1310 Radiofrequency radiation exposure limits. (a) Specific...human exposure to radiofrequency (RF) radiation as specified in § 1.1307(b)...

  20. 47 CFR 1.1310 - Radiofrequency radiation exposure limits.

    Code of Federal Regulations, 2014 CFR

    2014-10-01

    ...2014-10-01 false Radiofrequency radiation exposure limits. 1.1310 Section...of 1969 § 1.1310 Radiofrequency radiation exposure limits. (a) Specific...human exposure to radiofrequency (RF) radiation as specified in § 1.1307(b)...

  1. 47 CFR 1.1310 - Radiofrequency radiation exposure limits.

    Code of Federal Regulations, 2010 CFR

    2010-10-01

    ...2010-10-01 false Radiofrequency radiation exposure limits. 1.1310 Section...of 1969 § 1.1310 Radiofrequency radiation exposure limits. The criteria listed...human exposure to radiofrequency (RF) radiation as specified in §...

  2. 47 CFR 1.1310 - Radiofrequency radiation exposure limits.

    Code of Federal Regulations, 2012 CFR

    2012-10-01

    ...2012-10-01 false Radiofrequency radiation exposure limits. 1.1310 Section...of 1969 § 1.1310 Radiofrequency radiation exposure limits. The criteria listed...human exposure to radiofrequency (RF) radiation as specified in §...

  3. Radio-frequency quadrupole linear accelerator

    SciTech Connect

    Wangler, T.P.; Stokes, R.H.

    1980-01-01

    The radio-frequency quadrupole (RFQ) is a new linear accelerator concept in which rf electric fields are used to focus, bunch, and accelerate the beam. Because the RFQ can provide strong focusing at low velocities, it can capture a high-current dc ion beam from a low-voltage source and accelerate it to an energy of 1 MeV/nucleon within a distance of a few meters. A recent experimental test at the Los Alamos Scientific Laboratory (LASL) has confirmed the expected performance of this structure and has stimulated interest in a wide variety of applications. The general properties of the RFQ are reviewed and examples of applications of this new accelerator are presented.

  4. Radiofrequency ablation: technique and clinical applications.

    PubMed

    Tatli, Servet; Tapan, Umit; Morrison, Paul R; Silverman, Stuart G

    2012-01-01

    Radiofrequency ablation is the most commonly used percutaneous ablation technique and well-documented in the literature on focal therapies. It has become the image-guided ablation method of choice because of its efficacy, safety, and ease of use. Radiofrequency ablation has shown promise in treating selected solid tumors, particularly those involving the liver, kidneys, lungs, and the musculoskeletal system. It is a minimally invasive technique often used in inoperable patients with other comorbidities. Radiofrequency ablation requires a minimal hospital stay or can be performed on an outpatient basis. The aim of this article is to review radiofrequency ablation techniques and their clinical applications. PMID:22407695

  5. Pulsed radiofrequency of the median nerve under ultrasound guidance.

    PubMed

    Haider, Naeem; Mekasha, Daniel; Chiravuri, Srinivas; Wasserman, Ronald

    2007-11-01

    Neuropathy of the median nerve within the carpal tunnel (carpal tunnel syndrome) has an age adjusted incidence of 105 cases per 100,000 person years. Treatment of carpal tunnel syndrome ranges from conservative management with medication and exercise to surgical release of the median nerve. Conservative treatment accounts for a significant portion of resources utilized and includes splinting, nerve gliding, ultrasound, and carpal bone mobilization. Recurrent symptoms of carpal tunnel syndrome have been shown to occur in 0% to 19% of patients following carpal tunnel release, with up to 12% requiring re-exploration. Prognosis for re-exploration is not as good as for primary carpal tunnel release, with a high recurrence rate in some populations. Ultrasound has seen increasing use in regional anesthesia and has been shown to improve the quality of regional anesthetic blocks. Pulsed radiofrequency was developed with the goal of providing reduction in pain from the use of electrical fields in the absence of neural injury. The use of ultrasound guidance for positioning radiofrequency probes over peripheral nerves has not been reported. This case report describes the use of ultrasound guided pulsed radiofrequency in the treatment of recurrent carpal tunnel syndrome. Following revision carpal tunnel surgery, the patient in this report was unable to obtain relief of pain in either hand with medication therapy alone. After a successful diagnostic median nerve block at the cubital fossa, pulsed radiofrequency of the median nerve was performed on the left side at the cubital fossa, under ultrasound guidance. Radiofrequency probe adjustment around the nerve was conducted under live ultrasound guidance and multiple pulsed treatments were applied at anatomically distinct sites over the nerve. A 70% reduction in pain was reported over the follow up period of 12 weeks. PMID:17987099

  6. Design and evaluation of a hybrid radiofrequency applicator for magnetic resonance imaging and RF induced hyperthermia: electromagnetic field simulations up to 14.0 Tesla and proof-of-concept at 7.0 Tesla.

    PubMed

    Winter, Lukas; Özerdem, Celal; Hoffmann, Werner; Santoro, Davide; Müller, Alexander; Waiczies, Helmar; Seemann, Reiner; Graessl, Andreas; Wust, Peter; Niendorf, Thoralf

    2013-01-01

    This work demonstrates the feasibility of a hybrid radiofrequency (RF) applicator that supports magnetic resonance (MR) imaging and MR controlled targeted RF heating at ultrahigh magnetic fields (B0?7.0T). For this purpose a virtual and an experimental configuration of an 8-channel transmit/receive (TX/RX) hybrid RF applicator was designed. For TX/RX bow tie antenna electric dipoles were employed. Electromagnetic field simulations (EMF) were performed to study RF heating versus RF wavelength (frequency range: 64 MHz (1.5T) to 600 MHz (14.0T)). The experimental version of the applicator was implemented at B0?=?7.0T. The applicators feasibility for targeted RF heating was evaluated in EMF simulations and in phantom studies. Temperature co-simulations were conducted in phantoms and in a human voxel model. Our results demonstrate that higher frequencies afford a reduction in the size of specific absorption rate (SAR) hotspots. At 7T (298 MHz) the hybrid applicator yielded a 50% iso-contour SAR (iso-SAR-50%) hotspot with a diameter of 43 mm. At 600 MHz an iso-SAR-50% hotspot of 26 mm in diameter was observed. RF power deposition per RF input power was found to increase with B0 which makes targeted RF heating more efficient at higher frequencies. The applicator was capable of generating deep-seated temperature hotspots in phantoms. The feasibility of 2D steering of a SAR/temperature hotspot to a target location was demonstrated by the induction of a focal temperature increase (?T?=?8.1 K) in an off-center region of the phantom. Temperature simulations in the human brain performed at 298 MHz showed a maximum temperature increase to 48.6C for a deep-seated hotspot in the brain with a size of (19×23×32)mm(3) iso-temperature-90%. The hybrid applicator provided imaging capabilities that facilitate high spatial resolution brain MRI. To conclude, this study outlines the technical underpinnings and demonstrates the basic feasibility of an 8-channel hybrid TX/RX applicator that supports MR imaging, MR thermometry and targeted RF heating in one device. PMID:23613896

  7. Design and Evaluation of a Hybrid Radiofrequency Applicator for Magnetic Resonance Imaging and RF Induced Hyperthermia: Electromagnetic Field Simulations up to 14.0 Tesla and Proof-of-Concept at 7.0 Tesla

    PubMed Central

    Winter, Lukas; Özerdem, Celal; Hoffmann, Werner; Santoro, Davide; Müller, Alexander; Waiczies, Helmar; Seemann, Reiner; Graessl, Andreas; Wust, Peter; Niendorf, Thoralf

    2013-01-01

    This work demonstrates the feasibility of a hybrid radiofrequency (RF) applicator that supports magnetic resonance (MR) imaging and MR controlled targeted RF heating at ultrahigh magnetic fields (B0?7.0T). For this purpose a virtual and an experimental configuration of an 8-channel transmit/receive (TX/RX) hybrid RF applicator was designed. For TX/RX bow tie antenna electric dipoles were employed. Electromagnetic field simulations (EMF) were performed to study RF heating versus RF wavelength (frequency range: 64 MHz (1.5T) to 600 MHz (14.0T)). The experimental version of the applicator was implemented at B0?=?7.0T. The applicators feasibility for targeted RF heating was evaluated in EMF simulations and in phantom studies. Temperature co-simulations were conducted in phantoms and in a human voxel model. Our results demonstrate that higher frequencies afford a reduction in the size of specific absorption rate (SAR) hotspots. At 7T (298 MHz) the hybrid applicator yielded a 50% iso-contour SAR (iso-SAR-50%) hotspot with a diameter of 43 mm. At 600 MHz an iso-SAR-50% hotspot of 26 mm in diameter was observed. RF power deposition per RF input power was found to increase with B0 which makes targeted RF heating more efficient at higher frequencies. The applicator was capable of generating deep-seated temperature hotspots in phantoms. The feasibility of 2D steering of a SAR/temperature hotspot to a target location was demonstrated by the induction of a focal temperature increase (?T?=?8.1 K) in an off-center region of the phantom. Temperature simulations in the human brain performed at 298 MHz showed a maximum temperature increase to 48.6C for a deep-seated hotspot in the brain with a size of (19×23×32)mm3 iso-temperature-90%. The hybrid applicator provided imaging capabilities that facilitate high spatial resolution brain MRI. To conclude, this study outlines the technical underpinnings and demonstrates the basic feasibility of an 8-channel hybrid TX/RX applicator that supports MR imaging, MR thermometry and targeted RF heating in one device. PMID:23613896

  8. Radiofrequency heating pathways for gold nanoparticles

    NASA Astrophysics Data System (ADS)

    Collins, C. B.; McCoy, R. S.; Ackerson, B. J.; Collins, G. J.; Ackerson, C. J.

    2014-07-01

    This feature article reviews the thermal dissipation of nanoscopic gold under radiofrequency (RF) irradiation. It also presents previously unpublished data addressing obscure aspects of this phenomenon. While applications in biology motivated initial investigation of RF heating of gold nanoparticles, recent controversy concerning whether thermal effects can be attributed to nanoscopic gold highlight the need to understand the involved mechanism or mechanisms of heating. Both the nature of the particle and the nature of the RF field influence heating. Aspects of nanoparticle chemistry which may affect thermal dissipation include the hydrodynamic diameter of the particle, the oxidation state and related magnetism of the core, and the chemical nature of the ligand shell. Aspects of RF which may affect thermal dissipation include power, frequency and antenna designs that emphasize relative strength of magnetic or electric fields. These nanoparticle and RF properties are analysed in the context of three heating mechanisms proposed to explain gold nanoparticle heating in an RF field. This article also makes a critical analysis of the existing literature in the context of the nanoparticle preparations, RF structure, and suggested mechanisms in previously reported experiments.

  9. Radiofrequency heating pathways for gold nanoparticles.

    PubMed

    Collins, C B; McCoy, R S; Ackerson, B J; Collins, G J; Ackerson, C J

    2014-08-01

    This feature article reviews the thermal dissipation of nanoscopic gold under radiofrequency (RF) irradiation. It also presents previously unpublished data addressing obscure aspects of this phenomenon. While applications in biology motivated initial investigation of RF heating of gold nanoparticles, recent controversy concerning whether thermal effects can be attributed to nanoscopic gold highlight the need to understand the involved mechanism or mechanisms of heating. Both the nature of the particle and the nature of the RF field influence heating. Aspects of nanoparticle chemistry which may affect thermal dissipation include the hydrodynamic diameter of the particle, the oxidation state and related magnetism of the core, and the chemical nature of the ligand shell. Aspects of RF which may affect thermal dissipation include power, frequency and antenna designs that emphasize relative strength of magnetic or electric fields. These nanoparticle and RF properties are analysed in the context of three heating mechanisms proposed to explain gold nanoparticle heating in an RF field. This article also makes a critical analysis of the existing literature in the context of the nanoparticle preparations, RF structure, and suggested mechanisms in previously reported experiments. PMID:24962620

  10. 47 CFR 2.1091 - Radiofrequency radiation exposure evaluation: mobile devices.

    Code of Federal Regulations, 2013 CFR

    2013-10-01

    ... 2013-10-01 false Radiofrequency radiation exposure evaluation: mobile devices...Authorization Procedures Radiofrequency Radiation Exposure § 2.1091 Radiofrequency radiation exposure evaluation: mobile...

  11. 47 CFR 2.1091 - Radiofrequency radiation exposure evaluation: mobile devices.

    Code of Federal Regulations, 2012 CFR

    2012-10-01

    ... 2012-10-01 false Radiofrequency radiation exposure evaluation: mobile devices...Authorization Procedures Radiofrequency Radiation Exposure § 2.1091 Radiofrequency radiation exposure evaluation: mobile...

  12. 47 CFR 2.1091 - Radiofrequency radiation exposure evaluation: mobile devices.

    Code of Federal Regulations, 2011 CFR

    2011-10-01

    ... 2011-10-01 false Radiofrequency radiation exposure evaluation: mobile devices...Authorization Procedures Radiofrequency Radiation Exposure § 2.1091 Radiofrequency radiation exposure evaluation: mobile...

  13. 47 CFR 2.1093 - Radiofrequency radiation exposure evaluation: portable devices.

    Code of Federal Regulations, 2010 CFR

    2010-10-01

    ... 2010-10-01 false Radiofrequency radiation exposure evaluation: portable devices...Authorization Procedures Radiofrequency Radiation Exposure § 2.1093 Radiofrequency radiation exposure evaluation: portable...

  14. 47 CFR 2.1093 - Radiofrequency radiation exposure evaluation: portable devices.

    Code of Federal Regulations, 2013 CFR

    2013-10-01

    ... 2013-10-01 false Radiofrequency radiation exposure evaluation: portable devices...Authorization Procedures Radiofrequency Radiation Exposure § 2.1093 Radiofrequency radiation exposure evaluation: portable...

  15. 47 CFR 2.1093 - Radiofrequency radiation exposure evaluation: portable devices.

    Code of Federal Regulations, 2012 CFR

    2012-10-01

    ... 2012-10-01 false Radiofrequency radiation exposure evaluation: portable devices...Authorization Procedures Radiofrequency Radiation Exposure § 2.1093 Radiofrequency radiation exposure evaluation: portable...

  16. 47 CFR 2.1093 - Radiofrequency radiation exposure evaluation: portable devices.

    Code of Federal Regulations, 2014 CFR

    2014-10-01

    ... 2014-10-01 false Radiofrequency radiation exposure evaluation: portable devices...Authorization Procedures Radiofrequency Radiation Exposure § 2.1093 Radiofrequency radiation exposure evaluation: portable...

  17. 47 CFR 2.1093 - Radiofrequency radiation exposure evaluation: portable devices.

    Code of Federal Regulations, 2011 CFR

    2011-10-01

    ... 2011-10-01 false Radiofrequency radiation exposure evaluation: portable devices...Authorization Procedures Radiofrequency Radiation Exposure § 2.1093 Radiofrequency radiation exposure evaluation: portable...

  18. 47 CFR 2.1091 - Radiofrequency radiation exposure evaluation: mobile devices.

    Code of Federal Regulations, 2014 CFR

    2014-10-01

    ... 2014-10-01 false Radiofrequency radiation exposure evaluation: mobile devices...Authorization Procedures Radiofrequency Radiation Exposure § 2.1091 Radiofrequency radiation exposure evaluation: mobile...

  19. The privilege to use lasers (non-ionizing radiation) at Stanford University requires each individual user to follow and adhere to the guidelines recommended in the American National Standard Institute

    E-print Network

    Kay, Mark A.

    Preface The privilege to use lasers (non-ionizing radiation) at Stanford recommended in the American National Standard Institute guidelines on laser safety for Safe Use of Lasers (ANSI Z136.1). All individuals who work with lasers

  20. Esophageal papilloma: Flexible endoscopic ablation by radiofrequency

    PubMed Central

    del Genio, Gianmattia; del Genio, Federica; Schettino, Pietro; Limongelli, Paolo; Tolone, Salvatore; Brusciano, Luigi; Avellino, Manuela; Vitiello, Chiara; Docimo, Giovanni; Pezzullo, Angelo; Docimo, Ludovico

    2015-01-01

    Squamous papilloma of the esophagus is a rare benign lesion of the esophagus. Radiofrequency ablation is an established endoscopic technique for the eradication of Barrett esophagus. No cases of endoscopic ablation of esophageal papilloma by radiofrequency ablation (RFA) have been reported. We report a case of esophageal papilloma successfully treated with a single session of radiofrequency ablation. Endoscopic ablation of the lesion was achieved by radiofrequency using a new catheter inserted through the working channel of endoscope. The esophageal ablated tissue was removed by a specifically designed cup. Complete ablation was confirmed at 3 mo by endoscopy with biopsies. This case supports feasibility and safety of as a new potential indication for BarrxTM RFA in patients with esophageal papilloma. PMID:25789102

  1. Radiofrequency Ablation Effective Against Barrett Esophagus

    Cancer.gov

    In a randomized phase II trial, radiofrequency ablation led to high rates of eradication of the cell abnormalities associated with Barrett esophagus, according to the May 28, 2009, New England Journal of Medicine.

  2. The Radiofrequency Radiation Dosimetry Handbook: reminiscences.

    PubMed

    Allen, S J

    1999-01-01

    This paper traces the history of the development of the Radiofrequency Radiation Dosimetry Handbook and its subsequent impact on radio frequency radiation exposure standards. The author's recollections are used to illustrate the behind the scenes efforts of the individuals involved in this project. The development of models at the University of Utah and confirmation of these results by various experimenters led to the publication of four editions of the Radiofrequency Radiation Dosimetry Handbook, i.e., "The RFR Experimenters Bible." PMID:10334710

  3. Radiofrequency Catheter Ablation: Indications and Complications

    Microsoft Academic Search

    A. M. Dubin; G. F. Van Hare

    2000-01-01

    .   Radiofrequency catheter ablation was first described in pediatric patients in the early 1990s. Since then, multiple advances\\u000a in the technology and understanding of radiofrequency ablation have allowed this technique to blossom into one of the most\\u000a powerful therapeutic tools available to the pediatric electrophysiologist. This treatment has, in the majority of cases, replaced\\u000a arrhythmia surgery as the definitive cure

  4. Magic radio-frequency dressing of nuclear spins in high-accuracy optical clocks.

    PubMed

    Zanon-Willette, Thomas; de Clercq, Emeric; Arimondo, Ennio

    2012-11-30

    A Zeeman-insensitive optical clock atomic transition is engineered when nuclear spins are dressed by a nonresonant radio-frequency field. For fermionic species as (87)Sr, (171)Yb, and (199)Hg, particular ratios between the radio-frequency driving amplitude and frequency lead to "magic" magnetic values where a net cancelation of the Zeeman clock shift and a complete reduction of first-order magnetic variations are produced within a relative uncertainty below the 10(-18) level. An Autler-Townes continued fraction describing a semiclassical radio-frequency dressed spin is numerically computed and compared to an analytical quantum description including higher-order magnetic field corrections to the dressed energies. PMID:23368116

  5. Epidemiology of Health Effects of Radiofrequency Exposure

    PubMed Central

    Ahlbom, Anders; Green, Adele; Kheifets, Leeka; Savitz, David; Swerdlow, Anthony

    2004-01-01

    We have undertaken a comprehensive review of epidemiologic studies about the effects of radiofrequency fields (RFs) on human health in order to summarize the current state of knowledge, explain the methodologic issues that are involved, and aid in the planning of future studies. There have been a large number of occupational studies over several decades, particularly on cancer, cardiovascular disease, adverse reproductive outcome, and cataract, in relation to RF exposure. More recently, there have been studies of residential exposure, mainly from radio and television transmitters, and especially focusing on leukemia. There have also been studies of mobile telephone users, particularly on brain tumors and less often on other cancers and on symptoms. Results of these studies to date give no consistent or convincing evidence of a causal relation between RF exposure and any adverse health effect. On the other hand, the studies have too many deficiencies to rule out an association. A key concern across all studies is the quality of assessment of RF exposure. Despite the ubiquity of new technologies using RFs, little is known about population exposure from RF sources and even less about the relative importance of different sources. Other cautions are that mobile phone studies to date have been able to address only relatively short lag periods, that almost no data are available on the consequences of childhood exposure, and that published data largely concentrate on a small number of outcomes, especially brain tumor and leukemia. PMID:15579422

  6. Haemostatic Radiofrequency Ablation Assisted Partial Nephrectomy: Is Radiofrequency Energy a Viable Solution?

    Microsoft Academic Search

    Marek Salagierski; Maciej Salagierski

    2008-01-01

    Aim: We present our experience with partial nephrectomy using radiofrequency energy in patients with kidney cancer. Methods: From July 2002 to February 2007, 15 radiofrequency ablation assisted partial nephrectomies were performed. Five patients had one kidney only. The average tumour size was 34 (range 22–55) mm, and the mean age was 56 (range 45–69) years. The renal pedicle was not

  7. Risk assessment and management of radiofrequency radiation exposure

    NASA Astrophysics Data System (ADS)

    Dabala, Dana; Surducan, Emanoil; Surducan, Vasile; Neamtu, Camelia

    2013-11-01

    Radiofrequency radiation (RFR) industry managers, occupational physicians, security department, and other practitioners must be advised on the basic of biophysics and the health effects of RF electromagnetic fields so as to guide the management of exposure. Information on biophysics of RFR and biological/heath effects is derived from standard texts, literature and clinical experiences. Emergency treatment and ongoing care is outlined, with clinical approach integrating the circumstances of exposure and the patient's symptoms. Experimental risk assessment model in RFR chronic exposure is proposed. Planning for assessment and monitoring exposure, ongoing care, safety measures and work protection are outlining the proper management.

  8. Risk assessment and management of radiofrequency radiation exposure

    SciTech Connect

    Dabala, Dana [Railways Medical Clinic Cluj-Napoca, Occupational Medicine Department, 16-20 Bilascu Gheorghe St., 400015 Cluj-Napoca (Romania)] [Railways Medical Clinic Cluj-Napoca, Occupational Medicine Department, 16-20 Bilascu Gheorghe St., 400015 Cluj-Napoca (Romania); Surducan, Emanoil; Surducan, Vasile; Neamtu, Camelia [National Institute for Research and Development of Isotopic and Molecular Technologies, 65-103 Donath St., 400293 Cluj-Napoca (Romania)] [National Institute for Research and Development of Isotopic and Molecular Technologies, 65-103 Donath St., 400293 Cluj-Napoca (Romania)

    2013-11-13

    Radiofrequency radiation (RFR) industry managers, occupational physicians, security department, and other practitioners must be advised on the basic of biophysics and the health effects of RF electromagnetic fields so as to guide the management of exposure. Information on biophysics of RFR and biological/heath effects is derived from standard texts, literature and clinical experiences. Emergency treatment and ongoing care is outlined, with clinical approach integrating the circumstances of exposure and the patient's symptoms. Experimental risk assessment model in RFR chronic exposure is proposed. Planning for assessment and monitoring exposure, ongoing care, safety measures and work protection are outlining the proper management.

  9. Thermal bradycardia during radiofrequency irradiation.

    PubMed

    Jauchem, J R; Frei, M R; Heinmets, F

    1983-01-01

    The present study was performed to determine if any heart rate or blood pressure changes occur during intermittent exposure to radiofrequency radiation (RFR), and to determine if parasympathetic blockade due to atropine has any effect on these changes or on thermal responses. Anesthetized rats were exposed to 2.8 GHz pulsed RFR at an average power level of 60 mW/cm2 (average specific absorption rate, 14 W/kg). During an initial exposure period to raise colonic temperature to 39.5 degrees C, heart rate decreased significantly. This thermal bradycardia is similar to that reported by other investigators during environmental heat exposure. Intermittent exposure to radiation, which was designed to result in 1 degree C colonic temperature changes, did not significantly affect heart rate or mean arterial blood pressure, before or after atropine administration. The time courses of these 1 degree C temperature changes were not altered significantly by atropine. Following administration of atropine, the thermal bradycardia during the initial heating period was still evident. Thus, factors other than vagal activity are responsible for the phenomenon. It is possible that the bradycardia is a consequence of a general reduction in metabolism, which occurs also during environmental heat exposure. PMID:6675034

  10. A Comparative PCET Study of a Donor-Acceptor Pair Linked by Ionized and Non-ionized Asymmetric Hydrogen-Bonded Interfaces

    PubMed Central

    Young, Elizabeth R.; Rosenthal, Joel; Hodgkiss, Justin M.

    2012-01-01

    A Zn(II) porphyrin-amidinium is the excited state electron donor (D) to a naphthalene diimide acceptor (A) appended with either a carboxylate or sulfonate functionality. The two-point hydrogen bond (---[H+]---) formed between the amidinium and carboxylate or sulfonate establishes a proton-coupled electron transfer (PCET) pathway for charge transfer. The two D---[H+]---A assemblies differ only by the proton configuration within the hydrogen bonding interface. Specifically, the amidinium transfers a proton to the carboxylate to form a non-ionized amidine-carboxylic acid two-point hydrogen network whereas the amidinium maintains both protons when bound to the sulfonate functionality forming an ionized amidinium-sulfonate two-point hydrogen network. These two interface configurations within the dyads thus allow for a direct comparison of PCET kinetics for the same donor and acceptor juxtaposed by an ionized and non-ionized hydrogen-bonded interface. Analysis of PCET kinetics ascertained from transient absorption and transient emission spectroscopy reveal that the ionized interface is more strongly impacted by the local solvent environment, thus establishing that the initial static configuration of the proton interface is a critical determinant to the kinetics of PCET. PMID:19489645

  11. Power Independent of Number of Slices (PINS) radiofrequency pulses for low-power simultaneous multislice excitation.

    PubMed

    Norris, David G; Koopmans, Peter J; Boyacio?lu, Rasim; Barth, Markus

    2011-11-01

    This communication describes radiofrequency pulses capable of performing spatially periodic excitation, inversion, and refocusing. The generation of such pulses either by multiplication of existing radiofrequency pulses by a Dirac comb function or by means of Fourier series expansion is described. Practical schemes for the implementation of such pulses are given, and strategies for optimizing the pulse profile at fixed pulse duration are outlined. The pulses are implemented using a spin-echo sequence. The power deposition is independent of the number of slices acquired, and hence the power deposition per slice is considerably reduced compared to multislice imaging. Excellent image quality is obtained both in phantoms and in images of the human head. These pulses should find widespread application for multiplexed imaging, in particular at high static magnetic field strengths and for pulse sequences that have a high radiofrequency power deposition and could lead to dramatic increases in scanning efficiency. PMID:22009706

  12. The influence of radio-frequency discharge geometry on O ) production

    E-print Network

    Carroll, David L.

    in an O2/He/NO gas mixture. New discharge geometries have led to improvements in O2(a) production process. Optimization requires a discharge with E/N (electric field-to-gas density ratio) favouringThe influence of radio-frequency discharge geometry on O 2 (a 1 ) production This article has been

  13. Characteristics of hot ions with strong radiofrequency heating in the GAMMA 10 tandem mirror

    Microsoft Academic Search

    M. Ichimura; H. Hojo; K. Ishii; A. Mase; Y. Nakashima; T. Saito; T. Tamano; K. Yatsu

    1999-01-01

    Radiofrequency waves in the ion cyclotron range of frequency (ICRF) are mainly used for plasma production and heating in the central cell of the GAMMA 10 tandem mirror. GAMMA 10 has minimum-B anchor cells with a non-axisymmetric magnetic field configuration. The ICRF heating system in the central cell has been improved to create a more axisymmetric plasma. A high ion

  14. Models of radiofrequency coupling for negative ion sources

    SciTech Connect

    Cavenago, M.; Petrenko, S. [INFN-LNL, viale dell'Universita n.2, 35020 Legnaro (Italy)

    2012-02-15

    Radiofrequency heating for ICP (inductively coupled plasma) ion sources depends on the source operating pressure, the presence or absence of a Faraday shield, the driver coil geometry, the frequency used, and the magnetic field configuration: in negative ion source a magnetic filter seems necessary for H{sup -} survival. The result of single particle simulations showing the possibility of electron acceleration in the preglow regime and for reasonable driver chamber radius (15 cm) is reported, also as a function of the static external magnetic field. An effective plasma conductivity, depending not only from electron density, temperature, and rf field but also on static magnetic field is here presented and compared to previous models. Use of this conductivity and of multiphysics tools for a plasma transport and heating model is shown and discussed for a small source.

  15. A practical method to evaluate radiofrequency exposure of mast workers.

    PubMed

    Alanko, Tommi; Hietanen, Maila

    2008-01-01

    Assessment of occupational exposure to radiofrequency (RF) fields in telecommunication transmitter masts is a challenging task. For conventional field strength measurements using manually operated instruments, it is difficult to document the locations of measurements while climbing up a mast. Logging RF dosemeters worn by the workers, on the other hand, do not give any information about the location of the exposure. In this study, a practical method was developed and applied to assess mast workers' exposure to RF fields and the corresponding location. This method uses a logging dosemeter for personal RF exposure evaluation and two logging barometers to determine the corresponding height of the worker's position on the mast. The procedure is not intended to be used for compliance assessments, but to indicate locations where stricter assessments are needed. The applicability of the method is demonstrated by making measurements in a TV and radio transmitting mast. PMID:19054796

  16. Effects of damage caused by non-ionizing energy loss in Si Mini-Pad sensors for the PHENIX MPC-EX

    NASA Astrophysics Data System (ADS)

    Chai, J.-S.; Ghergherehchi, M.; Hahn, K. I.; Han, S. Y.; Jeong, I. W.; Joo, K. S.; Kim, E. J.; Kim, S. G.; Kim, Y. K.; Kistenev, E.; Kwon, Y.; Lajoie, J. G.; Li, Z.; Lee, J. H.; Lim, K. S.; Lim, S. H.; Park, J. M.; Park, K. S.; Park, S. Y.; Song, H. S.; Sue, D. G.; Sukhanov, A.

    2014-12-01

    The PHENIX MPC-EX is an W/Si pre-shower detector operating at small angles with respect to the beam in the Relativistic Heavy Ion Collider (RHIC). The Si Mini-Pad sensors are the active element of the detector. The expected hadron flux to the Si Mini-Pad sensors will generate significant non-ionizing energy loss in the sensors, which may damage the crystalline structure of the sensor's bulk material. We investigated the nature of the hadron flux to the Si Mini-Pad sensors through a full simulation and determined its effect on the sensor's characteristics based on a beam test. The investigation showed key issues in designing a preshower detector using silicon sensors and operating under a large neutron fluence and offered valuable information on the operation of the MPC-EX detector.

  17. Physiological measurements during radio-frequency irradiation.

    PubMed

    Frei, M; Jauchem, J; Heinmets, F

    1988-01-01

    Conventional techniques for monitoring physiological parameters are not suitable for use during RFR exposure. This research note describes transduction methods involving the use of fluorocarbon leads and a pneumatic pressure transducer for reliable measurement of the ECG and respiratory rate in anesthetized or restrained rats during radiofrequency irradiation. PMID:3193340

  18. Palliative Radiofrequency Ablation for Recurrent Prostate Cancer

    Microsoft Academic Search

    Gaurav Jindal; Marc Friedman; Julia Locklin; Bradford J. Wood

    2006-01-01

    Percutaneous radiofrequency ablation (RFA) is a minimally invasive local therapy for cancer. Its efficacy is now becoming well documented in many different organs, including liver, kidney, and lung. The goal of RFA is typically complete eradication of a tumor in lieu of an invasive surgical procedure. However, RFA can also play an important role in the palliative care of cancer

  19. Radiofrequency Ablation in Barrett's Esophagus with Dysplasia

    Microsoft Academic Search

    Nicholas J. Shaheen; Prateek Sharma; Bergein F. Overholt; Herbert C. Wolfsen; Richard E. Sampliner; Kenneth K. Wang; Joseph A. Galanko; Mary P. Bronner; John R. Goldblum; Ana E. Bennett; Blair A. Jobe; Glenn M. Eisen; M. Brian Fennerty; John G. Hunter; David E. Fleischer; Virender K. Sharma; Robert H. Hawes; Brenda J. Hoffman; Richard I. Rothstein; Stuart R. Gordon; Hiroshi Mashimo; Kenneth J. Chang; V. Raman Muthusamy; Steven A. Edmundowicz; Stuart J. Spechler; Ali A. Siddiqui; Rhonda F. Souza; Anthony Infantolino; Gary W. Falk; Michael B. Kimmey; Ryan D. Madanick; Amitabh Chak; Charles J. Lightdale

    2009-01-01

    Background Barrett's esophagus, a condition of intestinal metaplasia of the esophagus, is associ- ated with an increased risk of esophageal adenocarcinoma. We assessed whether endoscopic radiofrequency ablation could eradicate dysplastic Barrett's esophagus and decrease the rate of neoplastic progression. Methods In a multicenter, sham-controlled trial, we randomly assigned 127 patients with dys- plastic Barrett's esophagus in a 2:1 ratio to

  20. EFFECT OF RADIOFREQUENCY RADIATION ON THERMOREGULATION

    EPA Science Inventory

    In the past 30 years there have been numerous studies on the patho-physiological effects of exposure to radiofrequency (RF) radiation. t is clear that the majority of these effects can be attributed to the thermogenic action of RF radiation. uring exposure to RF radiation the the...

  1. MICROWAVE AND RADIO-FREQUENCY POWER APPLICATIONS

    Technology Transfer Automated Retrieval System (TEKTRAN)

    The potential for agricultural applications of radio-frequency (RF) energy for the solution of various problems in agricultural production, crop handling and storage, and product preservation and conditioning has been considered for many years. With the development of economical microwave power equ...

  2. Ross Ice Shelf in situ radio-frequency ice attenuation

    E-print Network

    Taylor Barrella; Steven Barwick; David Saltzberg

    2012-05-01

    We have measured the in situ average electric field attenuation length for radio-frequency signals broadcast vertically through the Ross Ice Shelf. We chose a location, Moore Embayment, south of Minna Bluff, known for its high reflectivity at the ice-sea interface. We confirmed specular reflection and used the return pulses to measure the average attenuation length from 75-1250 MHz over the round-trip distance of 1155 m. We find the average electric field attenuation length to vary from 500 m at 75 MHz to 300 m at 1250 MHz, with an experimental uncertainty of 55 to 15 m. We discuss the implications for neutrino telescopes that use the radio technique and include the Ross Ice Shelf as part of their sensitive volume.

  3. Radiofrequency tonsillotomy in Sweden 2009-2012.

    PubMed

    Sunnergren, Ola; Hemlin, Claes; Ericsson, Elisabeth; Hessén-Söderman, Anne-Charlotte; Hultcrantz, Elisabeth; Odhagen, Erik; Stalfors, Joacim

    2014-06-01

    The Swedish National Registry for Tonsil Surgery has been operational since 1997. All ENT clinics in Sweden are encouraged to submit data for all patients scheduled for tonsil surgery. Preoperatively, age, gender and indication are recorded. Postoperatively, method (tonsillectomy or tonsillotomy), technique, and perioperative complications are recorded. Postoperative bleedings, pain, infections, and symptom relief are assessed through questionnaires. An earlier report from this registry showed that tonsillotomy had become more common than tonsillectomy in children with tonsil-related upper airway obstruction. The aim of this study was to categorize which instruments were used for tonsillotomy in Sweden and to compare their outcome and complication rate. All children 2-18 years, reported to the registry from March 2009 until September 2012, who underwent tonsillotomy on the indication upper airway obstruction, were included in the study. 1,676 patients were identified. In 1,602 cases (96%), a radiofrequency instrument was used. The postoperative bleeding rate was low (1.2%) and the degree of symptom relief was high (95.1%). Three different radiofrequency instruments (ArthroCare Coblation(®), Ellman Surgitron(®), and Sutter CURIS(®)) were used in 96% of the patients. There were no significant differences in the number of postoperative bleedings, postoperative infections or symptom relief between the instruments. The only difference found was in the number of days on analgesics, where more days were registered after use of Coblation(®). In Sweden, radiofrequency tonsillotomy is the dominant surgical technique used for tonsil hypertrophy causing upper airway obstruction in children. There are no significant differences in outcome between the different radiofrequency instruments except for number of days on analgesics after surgery. PMID:24366615

  4. Palliative Radiofrequency Ablation for Recurrent Prostate Cancer

    Microsoft Academic Search

    Gaurav Jindal; Marc Friedman; Julia Locklin; Bradford J. Wood

    2006-01-01

    Percutaneous radiofrequency ablation (RFA) is a minimally invasive local therapy for cancer. Its efficacy is now becoming\\u000a well documented in many different organs, including liver, kidney, and lung. The goal of RFA is typically complete eradication\\u000a of a tumor in lieu of an invasive surgical procedure. However, RFA can also play an important role in the palliative care\\u000a of cancer

  5. 21 CFR 880.6300 - Implantable radiofrequency transponder system for patient identification and health information.

    Code of Federal Regulations, 2010 CFR

    2010-04-01

    ...Implantable radiofrequency transponder system for patient identification and health information...Implantable radiofrequency transponder system for patient identification and health information...implantable radiofrequency transponder system for patient identification and health...

  6. The Importance of Radiofrequency Safety into Occupational Safety Coursework

    NSDL National Science Digital Library

    Typical safety programs, both undergraduate and graduate, do not explore issues related with RF hazards and safety. Without federal regulations and enforcement, the topic is usually disregarded and thus creating future safety professionals without any knowledge of the possibilities of RF hazards at the future employment. This paper will discuss what is radiofrequency, how radiofrequency is used, regulatory agencies and compliance issues in regards to radiofrequency and finally research of Safety, Health and Environmental programs across the United States.

  7. Plasma-beam traps and radiofrequency quadrupole beam coolers

    SciTech Connect

    Maggiore, M., E-mail: mario.maggiore@lnl.infn.it; Cavenago, M.; Comunian, M.; Chirulotto, F.; Galatà, A.; De Lazzari, M.; Porcellato, A. M.; Roncolato, C.; Stark, S. [INFN-LNL, viale dell’Università 2, 35020 Legnaro (Italy)] [INFN-LNL, viale dell’Università 2, 35020 Legnaro (Italy); Caruso, A.; Longhitano, A. [INFN-LNS, via S. Sofia 54, 95123 Catania (Italy)] [INFN-LNS, via S. Sofia 54, 95123 Catania (Italy); Cavaliere, F.; Maero, G.; Paroli, B.; Pozzoli, R.; Romé, M. [INFN Sezione di Milano and Dipartimento di Fisica, Università degli Studi di Milano, via Celoria 16, 20133 Milano (Italy)] [INFN Sezione di Milano and Dipartimento di Fisica, Università degli Studi di Milano, via Celoria 16, 20133 Milano (Italy)

    2014-02-15

    Two linear trap devices for particle beam manipulation (including emittance reduction, cooling, control of instabilities, dust dynamics, and non-neutral plasmas) are here presented, namely, a radiofrequency quadrupole (RFQ) beam cooler and a compact Penning trap with a dust injector. Both beam dynamics studies by means of dedicated codes including the interaction of the ions with a buffer gas (up to 3 Pa pressure), and the electromagnetic design of the RFQ beam cooler are reported. The compact multipurpose Penning trap is aimed to the study of multispecies charged particle samples, primarily electron beams interacting with a background gas and/or a micrometric dust contaminant. Using a 0.9 T solenoid and an electrode stack where both static and RF electric fields can be applied, both beam transport and confinement operations will be available. The design of the apparatus is presented.

  8. Plasma-beam traps and radiofrequency quadrupole beam coolers.

    PubMed

    Maggiore, M; Cavenago, M; Comunian, M; Chirulotto, F; Galatà, A; De Lazzari, M; Porcellato, A M; Roncolato, C; Stark, S; Caruso, A; Longhitano, A; Cavaliere, F; Maero, G; Paroli, B; Pozzoli, R; Romé, M

    2014-02-01

    Two linear trap devices for particle beam manipulation (including emittance reduction, cooling, control of instabilities, dust dynamics, and non-neutral plasmas) are here presented, namely, a radiofrequency quadrupole (RFQ) beam cooler and a compact Penning trap with a dust injector. Both beam dynamics studies by means of dedicated codes including the interaction of the ions with a buffer gas (up to 3 Pa pressure), and the electromagnetic design of the RFQ beam cooler are reported. The compact multipurpose Penning trap is aimed to the study of multispecies charged particle samples, primarily electron beams interacting with a background gas and/or a micrometric dust contaminant. Using a 0.9 T solenoid and an electrode stack where both static and RF electric fields can be applied, both beam transport and confinement operations will be available. The design of the apparatus is presented. PMID:24593614

  9. Radio-frequency transistors from millimeter-scale graphene domains

    NASA Astrophysics Data System (ADS)

    Wei, Zi-Jun; Fu, Yun-Yi; Liu, Jing-Bo; Wang, Zi-Dong; Jia, Yue-Hui; Guo, Jian; Ren, Li-Ming; Chen, Yuan-Fu; Zhang, Han; Huang, Ru; Zhang, Xing

    2014-11-01

    Graphene is a new promising candidate for application in radio-frequency (RF) electronics due to its excellent electronic properties such as ultrahigh carrier mobility, large threshold current density, and high saturation velocity. Recently, much progress has been made in the graphene-based RF field-effect transistors (RF-FETs). Here we present for the first time the high-performance top-gated RF transistors using millimeter-scale single graphene domain on a SiO2/Si substrate through a conventional microfabrication process. A maximum cut-off frequency of 178 GHz and a peak maximum oscillation frequency of 35 GHz are achieved in the graphene-domain-based FET with a gate length of 50 nm and 150 nm, respectively. This work shows that the millimeter-scale single graphene domain has great potential applications in RF devices and circuits.

  10. Use of Semiflexible Applicators for Radiofrequency Ablation of Liver Tumors

    SciTech Connect

    Gaffke, G., E-mail: gunnar.gaffke@charite.de; Gebauer, B.; Knollmann, F.D. [Universitaetsmedizin Berlin, Klinik fuer Strahlenheilkunde und Poliklinik, Charite (Germany); Helmberger, T. [Universitaet Muenchen, Institut fuer klinische Radiologie Grosshadern (Germany); Ricke, J. [Universitaetsmedizin Berlin, Klinik fuer Strahlenheilkunde und Poliklinik, Charite (Germany); Oettle, H. [Universitaetsmedizin Berlin, Campus-Virchow-Klinikum, Medizinische Klinik mit Schwerpunkt Haematologie und Onkologie der Charite (Germany); Felix, R.; Stroszczynski, C. [Universitaetsmedizin Berlin, Klinik fuer Strahlenheilkunde und Poliklinik, Charite (Germany)

    2006-04-15

    Purpose. To evaluate the feasibility and potential advantages of the radiofrequency ablation of liver tumors using new MRI-compatible semiflexible applicators in a closed-bore high-field MRI scanner. Methods. We treated 8 patients with 12 malignant liver tumors of different origin (5 colorectal carcinoma, 2 cholangiocellular carcinoma, 1 breast cancer) under MRI guidance. Radiofrequency ablation (RFA) was performed using 5 cm Rita Starburst Semi-Flex applicators (Rita Medical Systems, Milwaukee, WI, USA) which are suitable for MR- and CT-guided interventions and a 150 W RF generator. All interventions were performed in a closed-bore 1.5 T high-field MRI scanner for MRI-guided RFA using fast T1-weighted gradient echo sequences and T2-weighted ultra-turbo spin echo sequences. Control and follow-up MRI examinations were performed on the next day, at 6 weeks, and every 3 months after RFA. Control MRI were performed as double-contrast MRI examinations (enhancement with iron oxide and gadopentetate dimeglumine). All interventions were performed with the patient under local anesthesia and analgo-sedation. Results. The mean diameter of the treated hepatic tumors was 2.4 cm ({+-}0.6 cm, range 1.0-3.2 cm). The mean diameter of induced necrosis was 3.1 cm ({+-}0.4 cm). We achieved complete ablation in all patients. Follow-up examinations over a duration of 7 months ({+-}1.3 months, range 4-9 month) showed a local control rate of 100% in this group of patients. All interventions were performed without major complications; only 2 subcapsular hematomas were documented. Conclusion. RFA of liver tumors using semiflexible applicators in closed-bore 1.5 T scanner systems is feasible. These applicators might simplify the RFA of liver tumors under MRI control. The stiff distal part of the applicator facilitates its repositioning.

  11. Radiofrequency energy exposure from the Trilliant smart meter.

    PubMed

    Foster, Kenneth R; Tell, Richard A

    2013-08-01

    This paper reviews radiofrequency (RF) field levels produced by electric utility meters equipped with RF transceivers (so-called Smart Meters), focusing on meters from one manufacturer (Trilliant, Redwood City, CA, USA, and Granby, QC, Canada). The RF transmission levels are summarized based on publicly available data submitted to the U.S. Federal Communications Commission supplemented by limited independent measurements. As with other Smart Meters, this meter incorporates a low powered radiofrequency transceiver used for a neighborhood mesh network, in the present case using ZigBee-compliant physical and medium access layers, operating in the 2.45 GHz unlicensed band but with a proprietary network architecture. Simple calculations based on a free space propagation model indicate that peak RF field intensities are in the range of 10 mW m or less at a distance of more than 1-2 m from the meters. However, the duty cycle of transmission from the meters is very low (< 1%). Limited measurements identified pulses from the meter that were consistent with data reported by the vendor to the U.S. Federal Communications Commission. Limited measurements conducted in two houses with the meters were unable to clearly distinguish emissions from the meters from the considerable electromagnetic clutter in the same frequency range from other sources, including Wi-Fi routers and, when it was activated, a microwave oven. These preliminary measurements disclosed the difficulties that would be encountered in characterizing the RF exposures from these meters in homes in the face of background signals from other household devices in the same frequency range. An appendix provides an introduction to Smart Meter technology. The RF transmitters in wireless-equipped Smart Meters operate at similar power levels and in similar frequency ranges as many other digital communications devices in common use, and their exposure levels are very far below U.S. and international exposure limits. PMID:23799502

  12. An in situ measurement of the radio-frequency attenuation in ice at Summit Station, Greenland

    E-print Network

    J. Avva; J. M. Kovac; C. Miki; D. Saltzberg; A. G. Vieregg

    2014-09-30

    We report an in situ measurement of the electric field attenuation length at radio frequencies for the bulk ice at Summit Station, Greenland, made by broadcasting radio-frequency signals vertically through the ice and measuring the relative power in the return ground bounce signal. We find the depth-averaged field attenuation length to be 947 +92/-85 meters at 75 MHz. While this measurement has clear radioglaciological applications, the radio clarity of the ice also has implications for the detection of ultra-high energy (UHE) astrophysical particles via their radio emission in dielectric media such as ice. The measured attenuation length at Summit Station is comparable to previously measured radio-frequency attenuation lengths at candidate particle detector sites around the world, and strengthens the case for Summit Station as the most promising northern site for UHE neutrino detection.

  13. Minimum exposure limits and measured relationships between the vitamin d, erythema and international commission on non-ionizing radiation protection solar ultraviolet.

    PubMed

    Downs, Nathan; Parisi, Alfio; Butler, Harry; Turner, Joanna; Wainwright, Lisa

    2015-03-01

    The International Commission on Non-Ionizing Radiation Protection (ICNIRP) has established guidelines for exposure to ultraviolet radiation in outdoor occupational settings. Spectrally weighted ICNIRP ultraviolet exposures received by the skin or eye in an 8 h period are limited to 30 J m(-2) . In this study, the time required to reach the ICNIRP exposure limit was measured daily in 10 min intervals upon a horizontal plane at a subtropical Australian latitude over a full year and compared with the effective Vitamin D dose received to one-quarter of the available skin surface area for all six Fitzpatrick skin types. The comparison of measured solar ultraviolet exposures for the full range of sky conditions in the 2009 measurement period, including a major September continental dust event, show a clear relationship between the weighted ICNIRP and the effective vitamin D dose. Our results show that the horizontal plane ICNIRP ultraviolet exposure may be used under these conditions to provide minimum guidelines for the healthy moderation of vitamin D, scalable to each of the six Fitzpatrick skin types. PMID:25407011

  14. Coordination chemistry of divalent zinc, cadmium and mercury with non-ionized forms of the Schiff bases: Synthesis and spectroscopic studies

    NASA Astrophysics Data System (ADS)

    Tajmir-Riahi, H. A.

    Reactions between the non-ionized form of the Schiff base, NN'-propane-1,3-diylbis (salicylideneimine) (H 2sal-1,3Pd) and hydrated zinc, cadmium and mercury metal ion salts give complexes of the type M(H 2sal-1,3Pd)X 2 and M(sal-1,3Pd) [M = Zn(II), Cd(II), Hg(II); X = Cl -, Br -, I -, NO 3-; M = Zn(II), X 2 = SO 42-]. Spectroscopic and other properties showed marked similarities with the structurally known Ca(H 2sal-1,3Pd)(NO 3) 2 compounds, i.e. the Schiff base is coordinated through the phenolic oxygen atoms and not the nitrogen atoms of the azomethine groups. Halide and sulphate are covalently bonded to the central metal ion, whereas the nitrate group showed ionic character in mercury nitrate compound and coordination in zinc and cadmium nitrato complexes. The i.r. spectra exhibited the dimeric nature of the complexes and therefore the coordination number suggested would be four in the halo and sulphato or six in nitrato complexes with possible tetrahedral or octahedral arrangements around these metal cations.

  15. Summary of Information on the Effects of Ionizing and Non-ionizing Radiation on Cytochrome P450 and Other Drug Metabolizing Enzymes and Transporters

    PubMed Central

    Rendic, Slobodan; Guengerich, F. Peter

    2014-01-01

    The present paper is an update of data on the effects of ionizing radiation (?-rays, X-rays, high energy UV, fast neutron) caused by environmental pollution or clinical treatments and the effects of non-ionizing radiation (low energy UV) on the expression and/or activity of drug metabolism (e.g., cytochrome P450,, glutathione transferase), enzymes involved in oxidative stress (e.g., peroxidases, catalase,, aconitase, superoxide dismutase), and transporters. The data are presented in tabular form (Tables 1–3) and are a continuation of previously published summaries on the effects of drugs and other chemicals on cytochrome P450 enzymes (Rendic, S.; Di Carlo, F. Drug Metab. Rev., 1997, 29 (1–2), 413–580, Rendic, S. Drug Metab. Rev., 2002, 34 (1–2), 83–448) and of the data on the effects of diseases and environmental factors on the expression and/or activity of human cytochrome P450 enzymes and transporters (Guengerich, F.P.; Rendic, S. Curr. Drug Metab., 2010, 11(1), 1–3, Rendic, S.; Guengerich, F.P. Curr. Drug Metab., 2010, 11 (1), 4–84). The collective information is as presented by the cited author(s) in cases where several references are cited the latest published information is included. Remarks and conclusions suggesting clinically important impacts are highlighted, followed by discussion of the major findings. The searchable database is available as an Excel file (for information about file availability contact the corresponding author). PMID:22571481

  16. Faraday Accelerator with Radio-frequency Assisted Discharge (FARAD)

    E-print Network

    Choueiri, Edgar

    Faraday Accelerator with Radio-frequency Assisted Discharge (FARAD) Kurt Alexander Polzin;Faraday Accelerator with Radio-frequency Assisted Discharge (FARAD) Prepared by: Kurt Alexander Polzin Dr. Michael R. LaPointe Dissertation Reader #12;c Copyright by Kurt Alexander Polzin, 2006. All

  17. Ultrasonography guided percutaneous radiofrequency ablation for hepatic cavernous hemangioma

    Microsoft Academic Search

    Yan Cui; Li-Yan Zhou; Man-Ku Dong; Ping Wang; Min Ji; Xiao-Ou Li; Chang-Wei Chen; Zi-Pei Liu; Yong-Jie Xu; Hong-Wen Zhang

    2003-01-01

    AIM: Hepatic cavernous hemangioma (HCH) is the most common benign tumor of the liver and its management is still controversial. Recent success in situ radiofrequency ablation of hepatic malignancies has led us to consider using this technique in patients with HCH. This study was to assess the efficacy, safety, and complications of percutaneous radiofrequency ablation (PRFA) under ultrasonography guidance in

  18. Radio-Frequency Rectification on Membrane Bound Pores

    E-print Network

    Sujatha Ramachandran; Robert H. Blick; Daniel W. van der Weide

    2007-09-12

    We present measurements on direct radio-frequency pumping of ion channels and pores bound in bilipid membranes. We make use of newly developed microcoaxes, which allow delivering the high frequency signal in close proximity to the membrane bound proteins and ion channels. We find rectification of the radio-frequency signal, which is used to pump ions through the channels and pores.

  19. Radio-frequency scanning tunnelling microscopy U. Kemiktarak1

    E-print Network

    LETTERS Radio-frequency scanning tunnelling microscopy U. Kemiktarak1 , T. Ndukum3 , K. C. Schwab3 measurementsinmesoscopicelectronicsandmechanics. Broadband noise measurements across the tunnel junction using this radio-frequency STM available from nanoscale optical and electrical displacement detection tech- niques, and the radio

  20. Evaluation of stray radiofrequency radiation emitted by electrosurgical devices

    NASA Astrophysics Data System (ADS)

    DeMarco, M.; Maggi, S.

    2006-07-01

    Electrosurgery refers to the passage of a high-frequency, high-voltage electrical current through the body to achieve the desired surgical effects. At the same time, these procedures are accompanied by a general increase of the electromagnetic field in an operating room that may expose both patients and personnel to relatively high levels of radiofrequency radiation. In the first part of this study, we have taken into account the radiation emitted by different monopolar electrosurgical devices, evaluating the electromagnetic field strength delivered by an electrosurgical handle and straying from units and other electrosurgical accessories. As a summary, in the worst case a surgeon's hands are exposed to a continuous and pulsed RF wave whose magnetic field strength is 0.75 A m-1 (E-field 400 V m-1). Occasionally stray radiation may exceed ICNIRP's occupational exposure guidelines, especially close to the patient return plate. In the second part of this paper, we have analysed areas of particular concern to prevent electromagnetic interference with some life-support devices (ventilators and electrocardiographic devices), which have failed to operate correctly. Most clinically relevant interference occurred when an electrosurgery device was used within 0.3 m of medical equipment. In the appendix, we suggest some practical recommendations intended to minimize the potential for electromagnetic hazards due to therapeutic application of RF energy.

  1. Radiofrequency: an update on latest innovations.

    PubMed

    Sadick, Neil S; Malerich, Sarah A; Nassar, Amer H; Dorizas, Andrew S

    2014-11-01

    As the aging population in our society continues to grow, new technologies and procedures promising a more youthful appearance are continuously sought. The utilization of radiofrequency technology remains a novel method for the treatment of many aesthetic and medical dermatological indications. Innovative applications are constantly identified, expanding treatment options for various patient concerns including aging of the hands, cellulite, non-invasive lipolysis, and postpartum skin laxity. Non-invasive treatments are ideal for busy patients seeking minimal recovery time and so called lunch-time procedures. Furthermore, new developments in treatment devices enhance efficacy while decreasing patient discomfort. PMID:25607698

  2. Wideband versatile radio-frequency spectrum analyzer

    NASA Astrophysics Data System (ADS)

    Lavielle, V.; Lorgeré, I.; Le Gouët, J.-L.; Tonda, S.; Dolfi, D.

    2003-03-01

    Operation of a wideband, versatile optical spectrum analyzer for radio-frequency (RF) signals is demonstrated. The device is based on spectral hole burning (SHB). The demonstration features 2.3-GHz instantaneous bandwidth, 500-kHz resolution, and a 32-dB dynamic range. A true RF signal, transferred to the optical carrier with the help of a Mach-Zehnder modulator, is analyzed with optical carrier suppression and zooming capabilities. This is to the authors' knowledge the largest instantaneous bandwidth ever demonstrated for a SHB-based processor in rare-earth-doped crystals.

  3. Cooled Radiofrequency Ablation for Bilateral Greater Occipital Neuralgia

    PubMed Central

    Chhatre, Akhil

    2014-01-01

    This report describes a case of bilateral greater occipital neuralgia treated with cooled radiofrequency ablation. The case is considered in relation to a review of greater occipital neuralgia, continuous thermal and pulsed radiofrequency ablation, and current medical literature on cooled radiofrequency ablation. In this case, a 35-year-old female with a 2.5-year history of chronic suboccipital bilateral headaches, described as constant, burning, and pulsating pain that started at the suboccipital region and radiated into her vertex. She was diagnosed with bilateral greater occipital neuralgia. She underwent cooled radiofrequency ablation of bilateral greater occipital nerves with minimal side effects and 75% pain reduction. Cooled radiofrequency ablation of the greater occipital nerve in challenging cases is an alternative to pulsed and continuous RFA to alleviate pain with less side effects and potential for long-term efficacy. PMID:24716017

  4. Absorbed energy distribution from radiofrequency electromagnetic radiation in a mammalian cell model: Effect of membrane-bound water

    Microsoft Academic Search

    Li-Ming Liu; Stephen F. Cleary

    1995-01-01

    The spatial distributions of induced 27 or 2,450 MHz radiofrequency (RF) electric fields (E-fields) and specific absorption rates (SARS) in a three-component spherical cell model were determined by Mie scattering theory. The results were compared to results for the same cell model but with 0.5 nm thick of bound water on the inner and outer membrane surfaces. Induced E-fields and

  5. Risk of burn trauma during circumcision with radiofrequency scalpel: case report and review of literature

    PubMed Central

    Mohammadi, Ali Akbar; Seyed Jafari, Seyed Morteza; Abdollahi, Ahmad

    2013-01-01

    Male circumcision, one of the oldest and most frequent operations performed all over the world, removes 33–50% of the penile skin. Like each surgical procedure, circumcision can leads to complications ranging from the insignificant to the tragic. Circumcision methods can be done with different ways. The radiofrequency (RF) scalpel, an innovative instrument, can be used in circumcision. Here, we present three boys who sustained sever burn injuries during circumcision with RF method. In sum, interesting characteristics made RF procedures so popular in different fields of surgery. Although having low incidence, the important complications of this technology such as burns should raise our attentions. Performing radiofrequency circumcision by an experienced operator, selection of proper size of ground pads, and elimination of any interface between the skin and ground pad are the factors that can prevent such tragedies. PMID:23875124

  6. Radio-frequency quadrupole vane-tip geometries

    SciTech Connect

    Crandall, K.R.; Mills, R.S.; Wangler, T.P.

    1983-01-01

    Radio-frequency quadrupole (RFQ) linacs are becoming widely accepted in the accelerator community. They have the remarkable capability of simultaneously bunching low-energy ion beams and accelerating them to energies at which conventional accelerators can be used, accomplishing this with high-transmission efficiencies and low-emittance growths. The electric fields, used for radial focusing, bunching, and accelerating, are determined by the geometry of the vane tips. The choice of the best vane-tip geometry depends on considerations such as the peak surface electric field, per cent of higher multipole components, and ease of machining. We review the vane-tip geometry based on the ideal two-term potential function and briefly describe a method for calculating the electric field components in an RFQ cell with arbitrary vane-tip geometry. We describe five basic geometries and use the prototype RFQ design for the Fusion Materials Irradiation Test (FMIT) accelerator as an example to compare the characteristics of the various geometries.

  7. Radio-frequency dressed state potentials for neutral atoms

    E-print Network

    S. Hofferberth; I. Lesanovsky; B. Fischer; J. Verdu; J. Schmiedmayer

    2006-08-29

    Potentials for atoms can be created by external fields acting on properties like magnetic moment, charge, polarizability, or by oscillating fields which couple internal states. The most prominent realization of the latter is the optical dipole potential formed by coupling ground and electronically excited states of an atom with light. Here we present an experimental investigation of the remarkable properties of potentials derived from radio-frequency (RF) coupling between electronic ground states. The coupling is magnetic and the vector character allows to design state dependent potential landscapes. On atom chips this enables robust coherent atom manipulation on much smaller spatial scales than possible with static fields alone. We find no additional heating or collisional loss up to densities approaching $10^{15}$ atoms / cm$^3$ compared to static magnetic traps. We demonstrate the creation of Bose-Einstein condensates in RF potentials and investigate the difference in the interference between two independently created and two coherently split condensates in identical traps. All together this makes RF dressing a powerful new tool for micro manipulation of atomic and molecular systems.

  8. Operating a radio-frequency plasma source on water vapor

    SciTech Connect

    Nguyen, Sonca V. T.; Gallimore, Alec D. [Plasmadynamics and Electric Propulsion Laboratory, University of Michigan, Ann Arbor, Michigan 48108 (United States); Foster, John E. [Plasma Science and Technology Laboratory, University of Michigan, Ann Arbor, Michigan 48108 (United States)

    2009-08-15

    A magnetically enhanced radio-frequency (rf) plasma source operating on water vapor has an extensive list of potential applications. In this work, the use of a rf plasma source to dissociate water vapor for hydrogen production is investigated. This paper describes a rf plasma source operated on water vapor and characterizes its plasma properties using a Langmuir probe, a residual gas analyzer, and a spectrometer. The plasma source operated first on argon and then on water vapor at operating pressures just over 300 mtorr. Argon and water vapor plasma number densities differ significantly. In the electropositive argon plasma, quasineutrality requires n{sub i}{approx_equal}n{sub e}, where n{sub i} is the positive ion density. But in the electronegative water plasma, quasineutrality requires n{sub i+}=n{sub i-}+n{sub e}. The positive ion density and electron density of the water vapor plasma are approximately one and two orders of magnitude lower, respectively, than those of argon plasma. These results suggest that attachment and dissociative attachment are present in electronegative water vapor plasma. The electron temperature for this water vapor plasma source is between 1.5 and 4 eV. Without an applied axial magnetic field, hydrogen production increases linearly with rf power. With an axial magnetic field, hydrogen production jumps to a maximum value at 500 W and then saturates with rf power. The presence of the applied axial magnetic field is therefore shown to enhance hydrogen production.

  9. Impact of monopolar radiofrequency energy on subchondral bone viability.

    PubMed

    Balcarek, Peter; Kuhn, Anke; Weigel, Arwed; Walde, Tim A; Ferlemann, Keno G; Stürmer, Klaus M; Frosch, Karl-Heinz

    2010-05-01

    The purpose of this study was to analyze the impact of monopolar radiofrequency energy treatment on subchondral bone viability. The femoral grooves of six chinchilla bastard rabbits were exposed bilaterally to monopolar radiofrequency energy for 2, 4 and 8 s, creating a total of 36 defects. An intravital fluorescence bone-labeling technique characterized the process of subchondral bone mineralization within the 3 months following exposure to radiofrequency energy and was analyzed by widefield epifluorescence optical sectioning microscopy using an ApoTome. After 2 s of radiofrequency energy exposure, regular fluorescence staining of the subchondral bone was evident in all samples when compared to untreated areas. The depth of osteonecrosis after 4 and 8 s of radiofrequency energy treatment averaged 126 and 942 microm at 22 days (P < .05; P < .01). The 4 s treatment group showed no osteonecrosis after 44 days whereas the depth of osteonecrosis extended from 519 microm at 44 days (P < .01), to 281 microm at 66 days (P < .01) and to 133 microm at 88 days (P < .05) after 8 s of radiofrequency energy application. Though radiofrequency energy may induce transient osteonecrosis in the superficial zone of the subchondral bone, the results of this study suggest that post-arthroscopic osteonecrosis appears to be of only modest risk given the current clinical application in humans. PMID:19838673

  10. Cooled radiofrequency application for treatment of sacroiliac joint pain

    Microsoft Academic Search

    Haktan Karaman; Gönül Ölmez Kavak; Adnan Tüfek; Feyzi Çelik; Zeynep Baysal Y?ld?r?m; Mehmet Salim Akdemir; Orhan Tokgöz

    2011-01-01

    Background  The unavailability of an effective and long-lasting treatment for sacroiliac-based pain has led researchers to study the efficacy\\u000a of radiofrequency in denervation. In this study, we aimed to investigate the efficacy and safety of novel cooled radiofrequency\\u000a application for sacral lateral-branch denervation.\\u000a \\u000a \\u000a \\u000a \\u000a Methods  Patients experiencing chronic sacroiliac pain were selected for our observational study. Fluoroscopy guidance cooled radiofrequency\\u000a denervation was applied

  11. Cell oxidation-reduction imbalance after modulated radiofrequency radiation.

    PubMed

    Marjanovic, Ana Marija; Pavicic, Ivan; Trosic, Ivancica

    2014-08-13

    Abstract Aim of this study was to evaluate an influence of modulated radiofrequency field (RF) of 1800?MHz, strength of 30?V/m on oxidation-reduction processes within the cell. The assigned RF field was generated within Gigahertz Transversal Electromagnetic Mode cell equipped by signal generator, modulator, and amplifier. Cell line V79, was irradiated for 10, 30, and 60?min, specific absorption rate was calculated to be 1.6?W/kg. Cell metabolic activity and viability was determined by MTT assay. In order to define total protein content, colorimetric method was used. Concentration of oxidised proteins was evaluated by enzyme-linked immunosorbent assay. Reactive oxygen species (ROS) marked with fluorescent probe 2',7'-dichlorofluorescin diacetate were measured by means of plate reader device. In comparison with control cell samples, metabolic activity and total protein content in exposed cells did not differ significantly. Concentrations of carbonyl derivates, a product of protein oxidation, insignificantly but continuously increase with duration of exposure. In exposed samples, ROS level significantly (p?

  12. Genetic effects of radio-frequency, atmospheric-pressure glow discharges with helium

    SciTech Connect

    Li Guo; Li Heping; Wang Sen; Sun Wenting; Bao Chengyu [Department of Engineering Physics, Tsinghua University, Beijing 100084 (China); Wang Liyan; Zhao Hongxin; Xing Xinhui [Department of Chemical Engineering, Tsinghua University, Beijing 100084 (China)

    2008-06-02

    Due to low gas temperatures and high densities of active species, atmospheric-pressure glow discharges (APGDs) would have potential applications in the fields of plasma-based sterilization, gene mutation, etc. In this letter, the genetic effects of helium radio-frequency APGD plasmas with the plasmid DNA and oligonucleotide as the treated biomaterials are presented. The experimental results show that it is the chemically active species, instead of heat, ultraviolet radiation, intense electric field, and/or charged particles, that break the double chains of the plasmid DNA. The genetic effects depend on the plasma operating parameters, e.g., power input, helium flow rate, processing distance, time, etc.

  13. Genetic effects of radio-frequency, atmospheric-pressure glow discharges with helium

    NASA Astrophysics Data System (ADS)

    Li, Guo; Li, He-Ping; Wang, Li-Yan; Wang, Sen; Zhao, Hong-Xin; Sun, Wen-Ting; Xing, Xin-Hui; Bao, Cheng-Yu

    2008-06-01

    Due to low gas temperatures and high densities of active species, atmospheric-pressure glow discharges (APGDs) would have potential applications in the fields of plasma-based sterilization, gene mutation, etc. In this letter, the genetic effects of helium radio-frequency APGD plasmas with the plasmid DNA and oligonucleotide as the treated biomaterials are presented. The experimental results show that it is the chemically active species, instead of heat, ultraviolet radiation, intense electric field, and/or charged particles, that break the double chains of the plasmid DNA. The genetic effects depend on the plasma operating parameters, e.g., power input, helium flow rate, processing distance, time, etc.

  14. Axial force imparted by a conical radiofrequency magneto-plasma thruster

    SciTech Connect

    Charles, C.; Takahashi, K.; Boswell, R. W. [Space Plasma, Power and Propulsion Laboratory, Research School of Physics and Engineering, Australian National University, ACT 0200 (Australia)

    2012-03-12

    Direct thrust measurements of a low pressure ({approx}0.133 Pa) conical radiofrequency (rf at 13.56 MHz) argon plasma source show a total axial force of about 5 mN for an effective rf power of 650 W and a maximum magnetic field of 0.018 T, of which a measured value of 2.5 mN is imparted by the magnetic nozzle. A simplified model of thrust including contributions from the electron pressure and from the magnetic field pressure is developed. The magnetic nozzle is modelled as a ''physical'' nozzle of increasing cross-sectional area.

  15. Thermal and physiologic responses to 1200MHz radiofrequency radiation: Differences between exposure in E and H orientation

    Microsoft Academic Search

    J. R. Jauchem; M. R. Frei; J. M. Padilla

    1990-01-01

    Ketamine-anesthetized Sprague-Dawley rats were exposed to far-field 1200-MHz continuous wave radiofrequency radiation in both E and H orientations (long axis of animal parallel to electric or magnetic field, respectively). Power densities were used that resulted in equivalent whole-body specific absorption rates of approximately 8 W\\/kg in both orientations (20 mW\\/cm² for E and 45 mW\\/cm² for H). Exposure was conducted

  16. Radiofrequency thermal ablation of renal tumors.

    PubMed

    De Filippo, Massimo; Bozzetti, Francesca; Martora, Rosa; Zagaria, Raffaella; Ferretti, Stefania; Macarini, Luca; Brunese, Luca; Rotondo, Antonio; Rossi, Cristina

    2014-07-01

    Percutaneous radiofrequency ablation (PRFA) of renal malignancies is currently a therapeutic option for patients who are not able to undergo surgery. Some authors consider PRFA as the therapeutic standard in the treatment of renal neoplasms in non-operable patients due to comorbid conditions and in patients with mild-moderate renal failure, to preserve residual renal functionality. The use of PRFA has become more and more widespread due to a rise in the incidental detection of renal cell carcinomas with the ever-increasing use of Imaging for the study of abdominal diseases. Clinical studies indicate that RF ablation is an effective therapy with a low level of risk of complications, which provides good results in selected patients over short and medium term periods of time, however up to now few long-term studies have been carried out which can confirm the effectiveness of PRFA. PMID:25024061

  17. Electromagnetic limits to radiofrequency (RF) neuronal telemetry

    PubMed Central

    Diaz, R. E.; Sebastian, T.

    2013-01-01

    The viability of a radiofrequency (RF) telemetry channel for reporting individual neuron activity wirelessly from an embedded antenna to an external receiver is determined. Comparing the power at the transmitting antenna required for the desired Channel Capacity, to the maximum power that this antenna can dissipate in the body without altering or damaging surrounding tissue reveals the severe penalty incurred by miniaturization of the antenna. Using both Specific Absorption Rate (SAR) and thermal damage limits as constraints, and 300?Kbps as the required capacity for telemetry streams 100?ms in duration, the model shows that conventional antennas smaller than 0.1?mm could not support human neuronal telemetry to a remote receiver (1?m away.) Reducing the antenna to 10 microns in size to enable the monitoring of single human neuron signals to a receiver at the surface of the head would require operating with a channel capacity of only 0.3?bps. PMID:24346503

  18. Radiofrequency Ablation Therapy for Solid Tumors

    SciTech Connect

    Kam, Anthony (NIH) [NIH

    2002-12-04

    Surgical resection, systemic chemotherapy, and local radiation have been the conventional treatments for localized solid cancer. Because certain patients are not candidates for tumor resection and because many tumors are poorly responsive to chemotherapy and radiation, there has been an impetus to develop alternative therapies. Radiofrequency ablation (RFA) is a minimally invasive therapy for localized solid cancers that has gained considerable attention in the last 12 years. Advantages of minimally invasive therapies over surgery include less recovery time, lower morbidity and mortality, eligibility of more patients, and lower cost. RFA has been applied most extensively to inoperable hepatic tumors. It is investigational for tumors in the kidney, lung, bone, breast, and adrenal gland. This colloquium will review the mechanism, techniques, limitations, and clinical applications of RFA. The ultimate role that RFA will play in cancer therapy will depend on the results of long-term follow-up and prospective randomized trials.

  19. Combinatorial Screening of Organic Field Effect Transistors Leah A. Lucas and Ghassan E. Jabbour

    E-print Network

    Department of Chemical and Materials Engineering and Flexible Display Center, Arizona State University, Tempe (OLEDs), photovoltaics, radio-frequency identification tags (RFIDs) and organic field effect transistors

  20. Numerical modelling of a radio-frequency micro ion thruster

    E-print Network

    Tsay, Michael Meng-Tsuan

    2006-01-01

    A simple performance model is developed for an inductively-coupled radio-frequency micro ion thruster. Methods of particle and energy balance are utilized for modeling the chamber plasma discharge. A transformer model is ...

  1. Circuits and passive components for radio-frequency power conversion

    E-print Network

    Han, Yehui, Ph. D. Massachusetts Institute of Technology

    2010-01-01

    This thesis focuses on developing technology for high efficiency power converters operating at very high frequencies. The work in the thesis involves two aspects of such converters: rf (radio-frequency) power circuit design ...

  2. Process for selected gas oxide removal by radiofrequency catalysts

    DOEpatents

    Cha, Chang Y. (3807 Reynolds St., Laramie, WY 82070)

    1993-01-01

    This process to remove gas oxides from flue gas utilizes adsorption on a char bed subsequently followed by radiofrequency catalysis enhancing such removal through selected reactions. Common gas oxides include SO.sub.2 and NO.sub.x.

  3. 21 CFR 882.4725 - Radiofrequency lesion probe.

    Code of Federal Regulations, 2014 CFR

    2014-04-01

    ...probe is a device connected to a radiofrequency (RF) lesion generator to deliver the RF energy to the site within the nervous system where a lesion is desired. (b) Classification. Class II (performance...

  4. 21 CFR 882.4725 - Radiofrequency lesion probe.

    Code of Federal Regulations, 2011 CFR

    2011-04-01

    ...probe is a device connected to a radiofrequency (RF) lesion generator to deliver the RF energy to the site within the nervous system where a lesion is desired. (b) Classification. Class II (performance...

  5. 47 CFR 2.801 - Radiofrequency device defined.

    Code of Federal Regulations, 2010 CFR

    2010-10-01

    ...801 Telecommunication FEDERAL COMMUNICATIONS COMMISSION GENERAL FREQUENCY...MATTERS; GENERAL RULES AND REGULATIONS Marketing of Radio-frequency Devices § 2... (a) The various types of radio communication transmitting devices described...

  6. Investigation of multiple echo signals formation mechanism in magnet at excitation by two arbitrary radio-frequency pulses

    E-print Network

    M. D. Zviadadze; G. I. Mamniashvili; R. L. Lepsveridze; A. M. Akhalkatsi

    2010-09-17

    The quantum-mechanical calculations of intensities and time moments of appearance of multiple spin echo signals of excitation of nuclear spin system of magnet by two arbitrary width radio-frequency pulses were carried out. This method was used by us earlier at consideration of multiple-pulse analogs of single-pulse echo in multidomain magnets upon sudden jumps of the effecting magnetic field in the rotating coordinate system during the action of radio-frequency pulse. The formation mechanisms of echo signals are discussed. The appearance of four primary stimulated echo signals is predicted. The total number of echo signals at fixed parameters of radio-frequency pulses does not exceed thirteen ones. Theoretical conclusions are in compliance with experiments carried out on lithium ferrite. As it was established by us earlier in this magnetic dielectric, in difference from ferrometals, it is observed very short relaxation times of single-pulse and two-pulse stimulated echoes, and the contribution of radio-frequency pulse fronts distribution mechanism is insignificant. For this reason lithium ferrite is a good material for the experimental verification of theoretical conclusions in experimental conditions most close to the theoretical model.

  7. Radiofrequency transmission line for bioluminescent Vibrio sp. irradiation

    NASA Astrophysics Data System (ADS)

    Nassisi, V.; Alifano, P.; Talà, A.; Velardi, L.

    2012-07-01

    We present the study and the analyses of a transmission line for radiofrequency (RF) irradiation of bacteria belonging to Vibrio harveyi-related strain PS1, a bioluminescent bacterium living in symbiosis with many marine organisms. The bioluminescence represents a new biologic indicator which is useful for studying the behaviour of living samples in the presence of RF waves due to the modern communication systems. A suitable transmission line, used as an irradiating cell and tested up to the maximum frequency used by the global system for mobile communications and universal mobile telecommunications system transmissions, was characterized. In this experiment, the RF voltage applied to the transmission line was 1 V. Due to short dimensions of the line and the applied high frequencies, standing waves were produced in addition to progressing waves and the electric field strength varies particularly along the longitudinal direction. The magnetic field map was not strongly linked to the electric one due to the presence of standing waves and of the outgoing irradiation. RF fields were measured by two homemade suitable probes able to diagnostic fields of high frequency. The field measurements were performed without any specimens inside the line. Being our sample made of living matter, the real field was modified and its value was estimated by a simulation code. The bioluminescence experiments were performed only at 900 MHz for two different measured electric fields, 53 and 140 V/m. The light emission was measured right from the beginning and after 7 and 25 h. Under RF irradiation, we found that the bioluminescence activity decreased. Compared with the control sample, the diminution was 6.8% and 44% after 7 and 25 h of irradiation, respectively, both with the low or high field. No changes of the survival factor for all the samples were observed. Besides, to understand the emission processes, we operated the deconvolution of the spectra by two Gaussian curves. The Gaussian peaks were approximately centered at 460 nm and 490 nm. The 490 nm peak was higher than the control one. Under RF, the 490 nm peak decreased compared to the 460 nm one. The decreasing was stronger for the sample in the higher field. The ratio of the emission area of the 490 nm to 460 nm was 5 for the control sample. It decreased up to 1.6 for the samples under RF. The bioluminescence improves the DNA repair by photoreactivation, and there is evidence that photolyase is preferentially activated by blue/violet light. Our finding suggests that RF exposure may stimulate DNA repair by shifting the emission spectra from blue/green (490 nm) to blue/violet (460 nm).

  8. Radiofrequency Ablation for Barrett's Dysplasia: Past, Present and the Future?

    PubMed

    Haidry, Rehan; Lovat, Laurence; Sharma, Prateek

    2015-03-01

    Barrett's oesophagus is the only know pre-cursor to oesophageal adenocarcinoma. The incidence of OAC is growing rapidly in the western world with a poor prognosis for most with a 5-year survival of only 15 %. The approach to treating patients with neoplasia arising within BE has dramatically changed in the past 5 years. Resection of visible lesions with endoscopic mucosal resection followed by field ablation with radio-frequency ablation is now the accepted standard of care in these patients worldwide. This combined approach has shown high rates of disease reversal in several high quality clinical trials but also large volume registry studies. As well as being a minimally invasive and oesophageal sparing interventions compared to surgery with oesophagectomy, endoscopic therapy has proved to be safe and emerging long-term data show sustained benefit in the majority of patients and low rates of cancer progression. However, in a sub-group of patients, recurrences have been reported after successful endoscopic therapy making it mandatory to follow these patients post therapy. Improvements in endoscopic imaging continue to aid early diagnosis, and in turn, this will allow clinicians the ability to offer patient's treatment at an early stage. PMID:25740248

  9. Supercomputer Simulation of Radio-frequency Hepatic Tumor Ablation

    NASA Astrophysics Data System (ADS)

    Kosturski, N.; Margenov, S.

    2010-11-01

    We simulate the thermal and electrical processes, involved in the radio-frequency (RF) ablation procedure. The mathematical model consists of two parts—electrical and thermal. The energy from the applied AC voltage is determined first, by solving the Laplace equation to find the potential distribution. After that, the electric field intensity and the current density are directly calculated. Finally, the heat transfer equation is solved to determine the temperature distribution. Heat loss due to blood perfusion is also accounted for. The representation of the computational domain is based on a voxel mesh. Both partial differential equations are discretized in space via linear conforming FEM. After the space discretization, the backward Euler scheme is used for the time stepping. Large-scale linear systems arise from the FEM discretization. Moreover, they are ill-conditioned, due to the strong coefficient jumps and the complex geometry of the problem. Therefore, efficient parallel solution methods are required. The developed parallel solver is based on the preconditioned conjugate gradient (PCG) method. As a preconditioner, we use BoomerAMG—a parallel algebraic multigrid implementation from the package Hypre, developed in LLNL, Livermore. Parallel numerical tests, performed on the IBM Blue Gene/P massively parallel computer are presented.

  10. Laser ablation loading of a radiofrequency ion trap

    E-print Network

    Zimmermann, K; Herrera-Sancho, O A; Peik, E

    2012-01-01

    The production of ions via laser ablation for the loading of radiofrequency (RF) ion traps is investigated using a nitrogen laser with a maximum pulse energy of 0.17 mJ and a peak intensity of about 250 MW/cm^2. A time-of-flight mass spectrometer is used to measure the ion yield and the distribution of the charge states. Singly charged ions of elements that are presently considered for the use in optical clocks or quantum logic applications could be produced from metallic samples at a rate of the order of magnitude 10^5 ions per pulse. A linear Paul trap was loaded with Th+ ions produced by laser ablation. An overall ion production and trapping efficiency of 10^-7 to 10^-6 was attained. For ions injected individually, a dependence of the capture probability on the phase of the RF field has been predicted. In the experiment this was not observed, presumably because of collective effects within the ablation plume.

  11. Measured radiofrequency exposure during various mobile-phone use scenarios.

    PubMed

    Kelsh, Michael A; Shum, Mona; Sheppard, Asher R; McNeely, Mark; Kuster, Niels; Lau, Edmund; Weidling, Ryan; Fordyce, Tiffani; Kühn, Sven; Sulser, Christof

    2011-01-01

    Epidemiologic studies of mobile phone users have relied on self reporting or billing records to assess exposure. Herein, we report quantitative measurements of mobile-phone power output as a function of phone technology, environmental terrain, and handset design. Radiofrequency (RF) output data were collected using software-modified phones that recorded power control settings, coupled with a mobile system that recorded and analyzed RF fields measured in a phantom head placed in a vehicle. Data collected from three distinct routes (urban, suburban, and rural) were summarized as averages of peak levels and overall averages of RF power output, and were analyzed using analysis of variance methods. Technology was the strongest predictor of RF power output. The older analog technology produced the highest RF levels, whereas CDMA had the lowest, with GSM and TDMA showing similar intermediate levels. We observed generally higher RF power output in rural areas. There was good correlation between average power control settings in the software-modified phones and power measurements in the phantoms. Our findings suggest that phone technology, and to a lesser extent, degree of urbanization, are the two stronger influences on RF power output. Software-modified phones should be useful for improving epidemiologic exposure assessment. PMID:20551994

  12. Endovascular Radiofrequency Ablation for Varicose Veins

    PubMed Central

    2011-01-01

    Executive Summary Objective The objective of the MAS evidence review was to conduct a systematic review of the available evidence on the safety, effectiveness, durability and cost–effectiveness of endovascular radiofrequency ablation (RFA) for the treatment of primary symptomatic varicose veins. Background The Ontario Health Technology Advisory Committee (OHTAC) met on August 26th, 2010 to review the safety, effectiveness, durability, and cost-effectiveness of RFA for the treatment of primary symptomatic varicose veins based on an evidence-based review by the Medical Advisory Secretariat (MAS). Clinical Condition Varicose veins (VV) are tortuous, twisted, or elongated veins. This can be due to existing (inherited) valve dysfunction or decreased vein elasticity (primary venous reflux) or valve damage from prior thrombotic events (secondary venous reflux). The end result is pooling of blood in the veins, increased venous pressure and subsequent vein enlargement. As a result of high venous pressure, branch vessels balloon out leading to varicosities (varicose veins). Symptoms typically affect the lower extremities and include (but are not limited to): aching, swelling, throbbing, night cramps, restless legs, leg fatigue, itching and burning. Left untreated, venous reflux tends to be progressive, often leading to chronic venous insufficiency (CVI). A number of complications are associated with untreated venous reflux: including superficial thrombophlebitis as well as variceal rupture and haemorrhage. CVI often results in chronic skin changes referred to as stasis dermatitis. Stasis dermatitis is comprised of a spectrum of cutaneous abnormalities including edema, hyperpigmentation, eczema, lipodermatosclerosis and stasis ulceration. Ulceration represents the disease end point for severe CVI. CVI is associated with a reduced quality of life particularly in relation to pain, physical function and mobility. In severe cases, VV with ulcers, QOL has been rated to be as bad or worse as other chronic diseases such as back pain and arthritis. Lower limb VV is a very common disease affecting adults – estimated to be the 7th most common reason for physician referral in the US. There is a very strong familial predisposition to VV. The risk in offspring is 90% if both parents affected, 20% when neither affected and 45% (25% boys, 62% girls) if one parent affected. The prevalence of VV worldwide ranges from 5% to 15% among men and 3% to 29% among women varying by the age, gender and ethnicity of the study population, survey methods and disease definition and measurement. The annual incidence of VV estimated from the Framingham Study was reported to be 2.6% among women and 1.9% among men and did not vary within the age range (40-89 years) studied. Approximately 1% of the adult population has a stasis ulcer of venous origin at any one time with 4% at risk. The majority of leg ulcer patients are elderly with simple superficial vein reflux. Stasis ulcers are often lengthy medical problems and can last for several years and, despite effective compression therapy and multilayer bandaging are associated with high recurrence rates. Recent trials involving surgical treatment of superficial vein reflux have resulted in healing and significantly reduced recurrence rates. Endovascular Radiofrequency Ablation for Varicose Veins RFA is an image-guided minimally invasive treatment alternative to surgical stripping of superficial venous reflux. RFA does not require an operating room or general anaesthesia and has been performed in an outpatient setting by a variety of medical specialties including surgeons and interventional radiologists. Rather than surgically removing the vein, RFA works by destroying or ablating the refluxing vein segment using thermal energy delivered through a radiofrequency catheter. Prior to performing RFA, color-flow Doppler ultrasonography is used to confirm and map all areas of venous reflux to devise a safe and effective treatment plan. The RFA procedure involves the introduction of a guide wire into the target v

  13. Radio-Frequency Plasma Cleaning of a Penning Malmberg Trap

    NASA Technical Reports Server (NTRS)

    Sims, William Herbert, III; Martin, James; Pearson, J. Boise; Lewis, Raymond

    2005-01-01

    Radio-frequency-generated plasma has been demonstrated to be a promising means of cleaning the interior surfaces of a Penning-Malmberg trap that is used in experiments on the confinement of antimatter. {Such a trap was reported in Modified Penning-Malmberg Trap for Storing Antiprotons (MFS-31780), NASA Tech Briefs, Vol. 29, No. 3 (March 2005), page 66.} Cleaning of the interior surfaces is necessary to minimize numbers of contaminant atoms and molecules, which reduce confinement times by engaging in matter/antimatter-annihilation reactions with confined antimatter particles. A modified Penning-Malmberg trap like the one described in the cited prior article includes several collinear ring electrodes (some of which are segmented) inside a tubular vacuum chamber, as illustrated in Figure 1. During operation of the trap, a small cloud of charged antiparticles (e.g., antiprotons or positrons) is confined to a spheroidal central region by means of a magnetic field in combination with DC and radiofrequency (RF) electric fields applied via the electrodes. In the present developmental method of cleaning by use of RF-generated plasma, one evacuates the vacuum chamber, backfills the chamber with hydrogen at a suitable low pressure, and uses an RF-signal generator and baluns to apply RF voltages to the ring electrodes. Each ring is excited in the polarity opposite that of the adjacent ring. The electric field generated by the RF signal creates a discharge in the low-pressure gas. The RF power and gas pressure are adjusted so that the plasma generated in the discharge (see Figure 2) physically and chemically attacks any solid, liquid, and gaseous contaminant layers on the electrode surfaces. The products of the physical and chemical cleaning reactions are gaseous and are removed by the vacuum pumps.

  14. Is Cryoballoon Ablation Preferable to Radiofrequency Ablation for Treatment of Atrial Fibrillation by Pulmonary Vein Isolation? A Meta-Analysis

    PubMed Central

    Xu, Junxia; Huang, Yingqun; Cai, Hongbin; Qi, Yue; Jia, Nan; Shen, Weifeng; Lin, Jinxiu; Peng, Feng; Niu, Wenquan

    2014-01-01

    Objective Currently radiofrequency and cryoballoon ablations are the two standard ablation systems used for catheter ablation of atrial fibrillation; however, there is no universal consensus on which ablation is the optimal choice. We therefore sought to undertake a meta-analysis with special emphases on comparing the efficacy and safety between cryoballoon and radiofrequency ablations by synthesizing published clinical trials. Methods and Results Articles were identified by searching the MEDLINE and EMBASE databases before September 2013, by reviewing the bibliographies of eligible reports, and by consulting with experts in this field. Data were extracted independently and in duplicate. There were respectively 469 and 635 patients referred for cryoballoon and radiofrequency ablations from 14 qualified clinical trials. Overall analyses indicated that cryoballoon ablation significantly reduced fluoroscopic time and total procedure time by a weighted mean of 14.13 (95% confidence interval [95% CI]: 2.82 to 25.45; P?=?0.014) minutes and 29.65 (95% CI: 8.54 to 50.77; P?=?0.006) minutes compared with radiofrequency ablation, respectively, whereas ablation time in cryoballoon ablation was nonsignificantly elongated by a weighted mean of 11.66 (95% CI: ?10.71 to 34.04; P?=?0.307) minutes. Patients referred for cryoballoon ablation had a high yet nonsignificant success rate of catheter ablation compared with cryoballoon ablation (odds ratio; 95% CI; P: 1.34; 0.53 to 3.36; 0.538), and cryoballoon ablation was also found to be associated with the relatively low risk of having recurrent atrial fibrillation (0.75; 0.3 to 1.88; 0.538) and major complications (0.46; 0.11 to 1.83; 0.269). There was strong evidence of heterogeneity and low probability of publication bias. Conclusion Our findings demonstrate greater improvement in fluoroscopic time and total procedure duration for atrial fibrillation patients referred for cryoballoon ablation than those for radiofrequency ablation. PMID:24587324

  15. Boltzmann expansion in a radiofrequency conical helicon thruster operating in xenon and argon

    SciTech Connect

    Charles, C.; Boswell, R. [Space Plasma, Power and Propulsion Laboratory, Research School of Physics and Engineering, The Australian National University, Canberra, ACT 0200 (Australia)] [Space Plasma, Power and Propulsion Laboratory, Research School of Physics and Engineering, The Australian National University, Canberra, ACT 0200 (Australia); Takahashi, K. [Space Plasma, Power and Propulsion Laboratory, Research School of Physics and Engineering, The Australian National University, Canberra, ACT 0200 (Australia) [Space Plasma, Power and Propulsion Laboratory, Research School of Physics and Engineering, The Australian National University, Canberra, ACT 0200 (Australia); Department of Electrical Engineering, Tohoku University, Sendai 980-9579 (Japan)

    2013-06-03

    A low pressure ({approx}0.5 mTorr in xenon and {approx}1 mTorr in argon) Boltzmann expansion is experimentally observed on axis within a magnetized (60 to 180 G) radiofrequency (13.56 MHz) conical helicon thruster for input powers up to 900 W using plasma parameters measured with a Langmuir probe. The axial forces, respectively, resulting from the electron and magnetic field pressures are directly measured using a thrust balance for constant maximum plasma pressure and show a higher fuel efficiency for argon compared to xenon.

  16. Thermoregulatory responses of rats exposed to 9. 3GHz radio-frequency radiation

    Microsoft Academic Search

    M. R. Frei; J. R. Jauchem; F. Heinmets

    1987-01-01

    Ketamine-anesthetized Sprague-Dawley rats were exposed in H orientation to far-field 9.3-GHz continuous-wave (CW) and pulsed (2 microseconds 500 pps) radiofrequency radiation (RFR) at average power densities of 30 and 60 mW\\/sq. cm (whole-body average specific absorption rates of 9.3 and 18.6 W\\/kg, respectively). Irradiation was conducted to cyclicly increase colonic temperature from 38.5 to 39.5 C. Colonic, tympanic, and subcutaneous

  17. Thermoregulatory responses of rats exposed to 9.3GHz radiofrequency radiation

    Microsoft Academic Search

    M. R. Frei; J. R. Jauchem; F. Heinmets

    1989-01-01

    Summary Ketamine-anesthetized Sprague-Dawley rats were exposed in H orientation to far-field 9.3-GHz continuous-wave (CW) and pulsed (2 µs, 500 pps) radiofrequency radiation (RFR) at average power densities of 30 and 60 mW\\/cm2 (whole-body average specific absorption rates of 9.3 and 18.6 W\\/kg, respectively). Irradiation was conducted to cyclicly increase colonic temperature from 38.5 to 39.5° C. Colonic, tympanic, and subcutaneous

  18. Percutaneous Radiofrequency Ablation of a Small Renal Mass Complicated by Appendiceal Perforation

    SciTech Connect

    Boone, Judith, E-mail: j.boone@amc.uva.nl [Antoni van Leeuwenhoek Hospital, Department of Radiology, Netherlands Cancer Institute (Netherlands); Bex, Axel, E-mail: a.bex@nki.nl [Antoni van Leeuwenhoek Hospital, Department of Urology, Netherlands Cancer Institute (Netherlands); Prevoo, Warner, E-mail: w.prevoo@nki.nl [Antoni van Leeuwenhoek Hospital, Department of Radiology, Netherlands Cancer Institute (Netherlands)

    2012-06-15

    Percutaneous radiofrequency ablation (RFA) has gained wide acceptance as nephron-sparing therapy for small renal masses in select patients. Generally, it is a safe procedure with minor morbidity and acceptable short-term oncologic outcome. However, as a result of the close proximity of vital structures, such as the bowel, ureter, and large vessels, to the ablative field, complications regarding these structures may occur. This is the first article describing appendiceal perforation as a complication of computed tomography-guided RFA despite hydrodissection. When performing this innovative and promising procedure one should be aware of the possibility of particular minor and even major complications.

  19. Nonlinear frequency coupling in dual radio-frequency driven atmospheric pressure plasmas

    SciTech Connect

    Waskoenig, J.; Gans, T. [Centre for Plasma Physics, Queen's University Belfast, Belfast BT7 1NN, Northern Ireland (United Kingdom)

    2010-05-03

    Plasma ionization, and associated mode transitions, in dual radio-frequency driven atmospheric pressure plasmas are governed through nonlinear frequency coupling in the dynamics of the plasma boundary sheath. Ionization in low-power mode is determined by the nonlinear coupling of electron heating and the momentary local plasma density. Ionization in high-power mode is driven by electron avalanches during phases of transient high electric fields within the boundary sheath. The transition between these distinctly different modes is controlled by the total voltage of both frequency components.

  20. Dielectric Effect on the Radio-Frequency Characteristics of a Rectangular Waveguide Grating Traveling Wave Tube

    NASA Astrophysics Data System (ADS)

    Lu, Zhigang; Gong, Yubin; Wei, Yanyu; Wang, Wenxiang

    2006-08-01

    A new type of partial-dielectric-loaded rectangular waveguide grating slow-wave structure (SWS) for millimeter wave traveling wave tube (TWT) is presented in this paper. The radio-frequency characteristics including the dispersion properties, the longitudinal electric field distribution and the beam-wave coupling impedance of this structure are analyzed. The results show that the dispersion of the rectangular waveguide grating circuit is weakened, the phase velocity is reduced and the position of the maximum E z is basically invariant after partially filling the dielectric materials in the rectangular waveguide grating SWS. Although the coupling impedance decreases a little, it still keeps above 40 ?.

  1. Current oncologic applications of radiofrequency ablation therapies

    PubMed Central

    Shah, Dhruvil R; Green, Sari; Elliot, Angelina; McGahan, John P; Khatri, Vijay P

    2013-01-01

    Radiofrequency ablation (RFA) uses high frequency alternating current to heat a volume of tissue around a needle electrode to induce focal coagulative necrosis with minimal injury to surrounding tissues. RFA can be performed via an open, laparoscopic, or image guided percutaneous approach and be performed under general or local anesthesia. Advances in delivery mechanisms, electrode designs, and higher power generators have increased the maximum volume that can be ablated, while maximizing oncological outcomes. In general, RFA is used to control local tumor growth, prevent recurrence, palliate symptoms, and improve survival in a subset of patients that are not candidates for surgical resection. It’s equivalence to surgical resection has yet to be proven in large randomized control trials. Currently, the use of RFA has been well described as a primary or adjuvant treatment modality of limited but unresectable hepatocellular carcinoma, liver metastasis, especially colorectal cancer metastases, primary lung tumors, renal cell carcinoma, boney metastasis and osteoid osteomas. The role of RFA in the primary treatment of early stage breast cancer is still evolving. This review will discuss the general features of RFA and outline its role in commonly encountered solid tumors. PMID:23671734

  2. Managing Barrett's esophagus with radiofrequency ablation.

    PubMed

    Akiyama, Junichi; Roorda, Andrew; Triadafilopoulos, George

    2013-09-01

    Barrett's esophagus (BE) is a well-established pre-malignant lesion for esophageal adenocarcinoma, a condition that carries a dismal five-year overall survival rate of less than 15%. Among several available methods to eliminate BE, radiofrequency ablation (RFA) provides the most efficient modality, since it has been demonstrated to successfully eradicate BE with or without dysplasia with acceptable safety, efficacy and durability profiles. In conjunction with proton pump therapy, this new technology has quickly become the standard care for patients with dysplastic BE. However, several technical questions remain about how to deploy RFA therapy for maximum effectiveness and long-term favorable outcomes for all stages of the disease. These include how to select patient for therapy, what the best protocol for RFA is, when to use other modalities, such as endoscopic mucosal resection, and what should be considered for refractory BE. This review addresses these questions with the perspective of the best available evidence matched with the authors' experience with the technology. PMID:24759814

  3. Complex-plasma manipulation by radiofrequency biasing

    NASA Astrophysics Data System (ADS)

    Annaratone, B. M.; Antonova, T.; Goldbeck, D. D.; Thomas, H. M.; Morfill, G. E.

    2004-12-01

    This paper presents an experimental study on the nature, the dimensions and the timescale of the perturbation introduced by radiofrequency (rf) biasing of areas adjacent to the plasma. The analysis of the rf sheath, and of the charging of particles in it, has disclosed a levitation force on particles, which is substantially different from the dc one often used in complex plasmas. Experimentally, the rf heavily loaded sheath presents characteristics completely different from the normal case Vrf <= Vdc. Regions of extra ionization and complex electrostatic structures arise. These have been visualized by nanoparticles grown in the plasma. A variety of equilibrium positions for a controlled number of microparticles (injected) can be achieved by fine balancing of dc and rf on a pixel with the neighbouring sheath kept under control. In certain situations gravity is completely compensated, allowing the study of three-dimensional clusters. The motion of clusters from 4 to about 100 particles is simultaneously monitored by a three-dimensional visualization based on two laser lights modulated in intensity. This method enables the study of time-varying effects, such as transitions and vibrations, as well as the study of static structures and lattice defects. At pressures below 40 Pa in large clusters a poloidal motion appears.

  4. Directional Radio-Frequency Identification Tag Reader

    NASA Technical Reports Server (NTRS)

    Medelius, Pedro J.; Taylor, John D.; Henderson, John J.

    2004-01-01

    A directional radio-frequency identification (RFID) tag reader has been designed to facilitate finding a specific object among many objects in a crowded room. The device could be an adjunct to an electronic inventory system that tracks RFID-tagged objects as they move through reader-equipped doorways. Whereas commercial RFID-tag readers do not measure directions to tagged objects, the device is equipped with a phased-array antenna and a received signal-strength indicator (RSSI) circuit for measuring direction. At the beginning of operation, it is set to address only the RFID tag of interest. It then continuously transmits a signal to interrogate that tag while varying the radiation pattern of the antenna. It identifies the direction to the tag as the radiation pattern direction of peak strength of the signal returned by the tag. An approximate distance to the tag is calculated from the peak signal strength. The direction and distance can be displayed on a screen. A prototype containing a Yagi antenna was found to be capable of detecting a 915.5-MHz tag at a distance of approximately equal to 15 ft (approximately equal to 4.6 m).

  5. Osteoid Osteoma Treated with Radiofrequency Ablation

    PubMed Central

    Esenyel, Cem Zeki; Seyran, Metin; Tekin, Ali Ça?r?; Ada?, Müjdat; Bayraktar, Mehmet Kür?ad; Co?kun, Ünsal

    2015-01-01

    Purpose. Our aim is to evaluate the results of treatment with computed tomography (CT) guided percutaneous radiofrequency ablation for osteoid osteomas which were localized in a difficult area for operation. Materials and Methods. Glenoid, distal tibia, humerus shaft, proximal humerus, and in third finger of the hand proximal phalanx were involved in one patient. Proximal femur was involved in three patients, distal femur was involved in three patients, and proximal tibia was involved in two patients. 9 males and 4 females were aged 4 to 34 years (mean age: 18.5 years). All patients had pain and were evaluated with X-rays, CT, bone scintigraphy, and MRI. In all patients, RF ablation was performed with local anesthesia. The lesion heated to 90°C for 6 minutes. Results. All of the patients achieved complete pain relief after ablation and were fully weight bearing without any support. In all patients, there was soft tissue edema after the procedure. During follow-up, all patients were free from the pain and there was no sign about the tumor. There was no other complication after the process. Conclusion. CT guided RFA is a minimally invasive, safe, and cost-effective treatment for osteoid osteoma placed in difficult area for surgery. PMID:25705522

  6. Radiofrequency and its effect on suture strength.

    PubMed

    Shah, Anup A; Kang, Parminder; Deutsch, Allen

    2009-12-01

    The use of radiofrequency-based electrocautery for hemostasis and ablation within the subacromial space and glenohumeral joint can cause damage to suture material. Prior studies have focused on the mechanical properties of sutures including their ability to withstand abrasion. The purpose of this study was to determine the effect of electrical energy on the mechanical properties of 5 different brands of #2 suture used for arthroscopic shoulder repair: FiberWire (Arthrex Inc, Naples, Florida); Orthocord (DePuy Mitek, Norwood, Massachusetts); Hi-Fi (formally Herculine; Linvatec Corp, Largo, Florida); MaxBraid (Teleflex Medical, Research Triangle Park, North Carolina); and Ethibond (Ethicon, Inc, Somerville, New Jersey). A matched pair of human deltoid muscle submerged in buffered saline solution (pH 7.4) was used as a test medium. The suture strengths were tested in 3 different scenarios. The 3 groups were as follows: control group without electrical current, coagulation group with direct introduction of electrical current on a coagulate setting for 2 seconds, and a cutting group with direct introduction of electrical current on a cut setting for 2 seconds. Hi-Fi suture seemed to be the least susceptible to damage by direct electrocautery application. Orthocord suffered the greatest loss of strength of all materials tested. This study demonstrates that exposure to electrocautery damages and weakens suture. Great care should be taken when electrocautery is used during arthroscopic repairs to prevent suture failure and preserve repair integrity. PMID:19968222

  7. Radiofrequency Ablation of Intrahepatic Cholangiocarcinoma: Preliminary Experience

    SciTech Connect

    Carrafiello, Gianpaolo, E-mail: gcarraf@tin.it; Lagana, Domenico; Cotta, Elisa; Mangini, Monica; Fontana, Federico; Bandiera, Francesca; Fugazzola, Carlo [University of Insubria c/o Ospedale di Circolo, Department of Radiology (Italy)

    2010-08-15

    The purpose of this study was to evaluate the safety and efficacy of percutaneous ultrasound (US)-guided radiofrequency ablation (RFA) in patients with intrahepatic cholangiocarcinoma (ICCA) in a small, nonrandomized series. From February 2004 to July 2008, six patients (four men and two women; mean age 69.8 years [range 48 to 83]) with ICCA underwent percutaneous US-guided RFA. Preintervetional transarterial embolization was performed in two cases to decrease heat dispersion during RFA in order to increase the area of ablation. The efficacy of RFA was evaluated using contrast-enhanced dynamic computed tomography (CT) 1 month after treatment and then every 3 months thereafter. Nine RFA sessions were performed for six solid hepatic tumors in six patients. The duration of follow-up ranged from 13 to 21 months (mean 17.5). Posttreatment CT showed total necrosis in four of six tumors after one or two RFA sessions. Residual tumor was observed in two patients with larger tumors (5 and 5.8 cm in diameter). All patients tolerated the procedure, and there with no major complications. Only 1 patient developed post-RFA syndrome (pain, fever, malaise, and leukocytosis), which resolved with oral administration of acetaminophen. Percutaneous RFA is a safe and effective treatment for patients with hepatic tumors: It is ideally suited for those who are not eligible for surgery. Long-term follow-up data regarding local and systemic recurrence and survival are still needed.

  8. Radio-frequency spectrum of the Feshbach molecular state to deeply bound molecular states in ultracold 40K Fermi gases

    NASA Astrophysics Data System (ADS)

    Huang, Lianghui; Wang, Pengjun; Ruzic, B. P.; Fu, Zhengkun; Meng, Zengming; Peng, Peng; Bohn, J. L.; Zhang, Jing

    2015-03-01

    Spectroscopic measurements are made and obtained for three molecular levels within 50 MHz of the atomic continuum, along with their variation of magnetic field in ultracold 40K Fermi gases. We use spectroscopic measurements to modify the scattering properties near magnetic Fano–Feshbach resonances with a radio-frequency (RF) field by measuring the loss profile versus magnetic field. This work provides the high accuracy locations of ground molecular states near the s-wave Fano–Feshbach resonance, which can be used to study the crossover regime from a Bose–Einstein condensate to a Bardeen–Cooper–Schrieffer superfluid in the presence of an RF field.

  9. 77 FR 74668 - Compliance Policy Guide; Radiofrequency Identification Feasibility Studies and Pilot Programs for...

    Federal Register 2010, 2011, 2012, 2013, 2014

    2012-12-17

    ...entitled ``Radiofrequency Identification (RFID) Feasibility Studies and Pilot Programs...entitled ``Radiofrequency Identification (RFID) Feasibility Studies and Pilot Programs...December 23, 2010). FDA has identified RFID as a promising technology to be used...

  10. 75 FR 80827 - Compliance Policy Guide; Radiofrequency Identification Feasibility Studies and Pilot Programs for...

    Federal Register 2010, 2011, 2012, 2013, 2014

    2010-12-23

    ...entitled ``Radiofrequency Identification (RFID) Feasibility Studies and Pilot Programs...entitled ``Radiofrequency Identification (RFID) Feasibility Studies and Pilot Programs...December 22, 2008). FDA has identified RFID as a promising technology to be used...

  11. 21 CFR 179.30 - Radiofrequency radiation for the heating of food, including microwave frequencies.

    Code of Federal Regulations, 2012 CFR

    2012-04-01

    ...2012-04-01 2012-04-01 false Radiofrequency radiation for the heating of food, including microwave frequencies...THE PRODUCTION, PROCESSING AND HANDLING OF FOOD Radiation and Radiation Sources § 179.30 Radiofrequency...

  12. 21 CFR 179.30 - Radiofrequency radiation for the heating of food, including microwave frequencies.

    Code of Federal Regulations, 2011 CFR

    2011-04-01

    ...2011-04-01 2011-04-01 false Radiofrequency radiation for the heating of food, including microwave frequencies...THE PRODUCTION, PROCESSING AND HANDLING OF FOOD Radiation and Radiation Sources § 179.30 Radiofrequency...

  13. 21 CFR 179.30 - Radiofrequency radiation for the heating of food, including microwave frequencies.

    Code of Federal Regulations, 2013 CFR

    2013-04-01

    ...2013-04-01 2013-04-01 false Radiofrequency radiation for the heating of food, including microwave frequencies...THE PRODUCTION, PROCESSING AND HANDLING OF FOOD Radiation and Radiation Sources § 179.30 Radiofrequency...

  14. 21 CFR 179.30 - Radiofrequency radiation for the heating of food, including microwave frequencies.

    Code of Federal Regulations, 2010 CFR

    2010-04-01

    ...2010-04-01 2009-04-01 true Radiofrequency radiation for the heating of food, including microwave frequencies...THE PRODUCTION, PROCESSING AND HANDLING OF FOOD Radiation and Radiation Sources § 179.30 Radiofrequency...

  15. 21 CFR 179.30 - Radiofrequency radiation for the heating of food, including microwave frequencies.

    Code of Federal Regulations, 2014 CFR

    2014-04-01

    ...2014-04-01 2014-04-01 false Radiofrequency radiation for the heating of food, including microwave frequencies...THE PRODUCTION, PROCESSING AND HANDLING OF FOOD Radiation and Radiation Sources § 179.30 Radiofrequency...

  16. A unique complication of radiofrequency therapy to the tongue base

    PubMed Central

    Tornari, Chrysostomos; Wong, Gentle; Arora, Asit; Kotecha, Bhik

    2015-01-01

    Introduction Radiofrequency ablation treatment of the tongue base can be used either alone or as part of a multilevel approach in the treatment of snoring. This involves the generation of thermal energy around the circumvallate papillae of the tongue. Potential complications include ulceration, dysphagia, haematoma and abscess formation. Presentation of case We present the case of a 50-year-old patient who developed an anterior neck swelling following a second application of radiofrequency ablation therapy to the tongue base for snoring. This was secondary to an infection of a previously undiagnosed thyroglossal cyst. The patient made a full recovery following intravenous antibiotic therapy and ultrasound-guided needle aspiration. Discussion Thyroglossal tract remnants are thought to be present in seven percent of the adult population. An infection in a thyroglossal tract cyst has not previously been reported following radiofrequency ablation of the tongue base. Given the relatively high complication rate of tongue base radiofrequency ablation in some series, this complication may be under-recognised. Conclusion An infected thyroglossal tract cyst should be suspected in patients with anterior neck swellings following radiofrequency ablation therapy to the tongue base. We advise caution when performing this procedure on patients with known thyroglossal tract remnants though there is insufficient evidence to suggest that this procedure is contraindicated. PMID:25603484

  17. Effects of radiofrequency-modulated electromagnetic fields on proteome.

    PubMed

    Leszczynski, Dariusz

    2013-01-01

    Proteomics, the science that examines the repertoire of proteins present in an organism using both high-throughput and low-throughput techniques, might give a better understanding of the functional processes ongoing in cells than genomics or transcriptomics, because proteins are the molecules that directly regulate physiological processes. Not all changes in gene expression are necessarily reflected in the proteome. Therefore, using proteomics approaches to study the effects of RF-EMF might provide information about potential biological and health effects. Especially that the RF-EMF used in wireless communication devices has very low energy and is unable to directly induce gene mutations. PMID:23378005

  18. 78 FR 33633 - Human Exposure to Radiofrequency Electromagnetic Fields

    Federal Register 2010, 2011, 2012, 2013, 2014

    2013-06-04

    ...impacted by our rule revisions. Satellite Telecommunications Providers. Two...economic census categories address the satellite industry. The first category has...receipts.\\19\\ The category of Satellite Telecommunications...

  19. Radio-frequency induced ground state degeneracy in a Chromium Bose-Einstein condensate

    E-print Network

    Q. Beaufils; T. Zanon; R. Chicireanu; B. Laburthe-Tolra; E. Marechal; L. Vernac; J. -C. Keller; O. Gorceix

    2008-09-29

    We study the effect of strong radio-frequency (rf) fields on a chromium Bose-Einstein condensate (BEC), in a regime where the rf frequency is much larger than the Larmor frequency. We use the modification of the Land\\'{e} factor by the rf field to bring all Zeeman states to degeneracy, despite the presence of a static magnetic field of up to 100 mG. This is demonstrated by analyzing the trajectories of the atoms under the influence of dressed magnetic potentials in the strong field regime. We investigate the problem of adiabaticity of the rf dressing process, and relate it to how close the dressed states are to degeneracy. Finally, we measure the lifetime of the rf dressed BECs, and identify a new rf-assisted two-body loss process induced by dipole-dipole interactions.

  20. Electromagnetic Fields and Public Health: Mobile Phones

    MedlinePLUS

    ... other organs of the body. A number of studies have investigated the effects of radiofrequency fields on brain electrical ... has promoted further research on this group. Several studies investigating potential health effects in children and adolescents are underway. ...

  1. Faraday accelerator with radio-frequency assisted discharge (FARAD)

    NASA Astrophysics Data System (ADS)

    Polzin, Kurt Alexander

    A new electrodeless accelerator concept, called Faraday Accelerator with Radio-frequency Assisted Discharge (FARAD), that relies on an RF-assisted discharge to produce a plasma, an applied magnetic field to guide the plasma into the acceleration region, and an induced current sheet to accelerate the plasma, is presented. The presence of a preionized plasma allows for current sheet formation at lower discharge voltages and energies than those found in other pulsed inductive accelerator concepts. A proof-of-concept experiment, supported by optical and probe diagnostics, was constructed and used to demonstrate the main features of the FARAD and to gain physical insight into the low-voltage, low-energy current sheet formation and acceleration processes. Magnetic field data indicate that the peak sheet velocity in this unoptimized configuration operating at a pulse energy of 78.5 J is 12 km/s. It is found that changes in the background gas pressure and applied field affect the initial preionized plasma distribution which, in turn, affects the sheet's initial location, relative magnetic impermeability and subsequent velocity history. The results of the experimental investigation motivated further theoretical and numerical investigations of pulsed inductive plasma acceleration. A model consisting of a set of coupled circuit equations and a one-dimensional momentum equation was nondimensionalized leading to the identification of several scaling parameters. Numerical analysis revealed the benefits of underdamped current waveforms and led to an efficiency maximization criterion that requires matching the external circuit's natural period to the acceleration timescale. Predictions of the model were compared to experimental measurements and were found to be in good qualitative agreement and reasonable quantitative agreement for most quantities. A set of design rules aimed at producing a high-performance FARAD thruster are derived using the modeling results and physical insights. The rules concern the optimization of each of the major processes in FARAD: plasma acceleration, current sheet formation, applied field generation, and mass injection and preionization, and are cast as specific prescriptions for the dynamic impedance, inductance change, circuit damping, plasma collisionality (or magnetization), magnetic field strength and topology, and intra-pulse sequencing.

  2. Ten-year Experience of Radiofrequency Catheter Ablation of Accessory Pathways in Children and Young Adults

    Microsoft Academic Search

    KT WONG; TC YUNG; KS LUN; KYY FAN; AKT CHAU

    Transcatheter radiofrequency ablation of supraventricular tachycardia was first introduced in 1987. The procedure is now well-accepted as primary treatment for supraventricular tachycardia in paediatric patients. In this report we describe our experience of radiofrequency ablation of accessory pathway mediated supraventricular tachycardia in the past 10 years. From 1994 to 2005, 121 procedures of radiofrequency ablation of accessory pathway were performed

  3. Radiofrequency coblation of congenital nasopharyngeal teratoma: a novel technique.

    PubMed

    Hwang, Sang Yun; Jefferson, Niall; Mohorikar, Alok; Jacobson, Ian

    2015-01-01

    Introduction. Congenital nasopharyngeal teratomas are rare tumours that pose difficulties in diagnosis and surgical management. We report the first use of radiofrequency coblation in the management of such tumours. Case Report. A premature baby with a perinatal diagnosis of a large, obstructing nasooropharyngeal mass was referred to the ENT service for further investigations and management. The initial biopsy was suggestive of a neuroblastoma, but the tumour demonstrated rapid growth despite appropriate chemotherapy. In a novel use of radiofrequency coblation, the nasooropharyngeal mass was completely excised, with the final histopathology revealing a congenital nasopharyngeal teratoma. Conclusion. We report the first use of radiofrequency coblation to excise a congenital nasopharyngeal teratoma and discuss its advantages. PMID:25685579

  4. Radiofrequency amplifier based on a dc superconducting quantum interference device

    DOEpatents

    Hilbert, Claude (Berkeley, CA); Martinis, John M. (Berkeley, CA); Clarke, John (Berkeley, CA)

    1986-01-01

    A low noise radiofrequency amplifier (10), using a dc SQUID (superconducting quantum interference device) as the input amplifying element. The dc SQUID (11) and an input coil (12) are maintained at superconductivity temperatures in a superconducting shield (13), with the input coil (12) inductively coupled to the superconducting ring (17) of the dc SQUID (11). A radiofrequency signal from outside the shield (13) is applied to the input coil (12), and an amplified radiofrequency signal is developed across the dc SQUID ring (17) and transmitted to exteriorly of the shield (13). A power gain of 19.5.+-.0.5 dB has been achieved with a noise temperature of 1.0.+-.0.4 K. at a frequency of 100 MHz.

  5. Influence of radiofrequency surgery on architecture of the palatine tonsils.

    PubMed

    Plzak, Jan; Macokova, Pavla; Zabrodsky, Michal; Kastner, Jan; Lastuvka, Petr; Astl, Jaromir

    2014-01-01

    Radiofrequency surgery is a widely used modern technique for submucosal volume reduction of the tonsils. So far there is very limited information on morphologic changes in the human tonsils after radiofrequency surgery. We performed histopathological study of tonsillectomy specimens after previous bipolar radiofrequency induced thermotherapy (RFITT). A total of 83 patients underwent bipolar RFITT for hypertrophy of palatine tonsils. Tonsil volume reduction was measured by 3D ultrasonography. Five patients subsequently underwent tonsillectomy. Profound histopathological examination was performed to determine the effect of RFITT on tonsillar architecture. All tonsillectomy specimens showed the intact epithelium, intact germinal centers, normal vascularization, and no evidence of increased fibrosis. No microscopic morphological changes in tonsillectomy specimens after bipolar RFITT were observed. RFITT is an effective submucosal volume reduction procedure for treatment of hypertrophic palatine tonsils with no destructive effect on microscopic tonsillar architecture and hence most probably no functional adverse effect. PMID:24795888

  6. Influence of Radiofrequency Surgery on Architecture of the Palatine Tonsils

    PubMed Central

    Plzak, Jan; Macokova, Pavla; Zabrodsky, Michal; Kastner, Jan; Lastuvka, Petr; Astl, Jaromir

    2014-01-01

    Radiofrequency surgery is a widely used modern technique for submucosal volume reduction of the tonsils. So far there is very limited information on morphologic changes in the human tonsils after radiofrequency surgery. We performed histopathological study of tonsillectomy specimens after previous bipolar radiofrequency induced thermotherapy (RFITT). A total of 83 patients underwent bipolar RFITT for hypertrophy of palatine tonsils. Tonsil volume reduction was measured by 3D ultrasonography. Five patients subsequently underwent tonsillectomy. Profound histopathological examination was performed to determine the effect of RFITT on tonsillar architecture. All tonsillectomy specimens showed the intact epithelium, intact germinal centers, normal vascularization, and no evidence of increased fibrosis. No microscopic morphological changes in tonsillectomy specimens after bipolar RFITT were observed. RFITT is an effective submucosal volume reduction procedure for treatment of hypertrophic palatine tonsils with no destructive effect on microscopic tonsillar architecture and hence most probably no functional adverse effect. PMID:24795888

  7. Radiofrequency Coblation of Congenital Nasopharyngeal Teratoma: A Novel Technique

    PubMed Central

    Hwang, Sang Yun; Jefferson, Niall; Mohorikar, Alok; Jacobson, Ian

    2015-01-01

    Introduction. Congenital nasopharyngeal teratomas are rare tumours that pose difficulties in diagnosis and surgical management. We report the first use of radiofrequency coblation in the management of such tumours. Case Report. A premature baby with a perinatal diagnosis of a large, obstructing nasooropharyngeal mass was referred to the ENT service for further investigations and management. The initial biopsy was suggestive of a neuroblastoma, but the tumour demonstrated rapid growth despite appropriate chemotherapy. In a novel use of radiofrequency coblation, the nasooropharyngeal mass was completely excised, with the final histopathology revealing a congenital nasopharyngeal teratoma. Conclusion. We report the first use of radiofrequency coblation to excise a congenital nasopharyngeal teratoma and discuss its advantages. PMID:25685579

  8. Pulsed radiofrequency as a treatment for groin pain and orchialgia.

    PubMed

    Cohen, Steven P; Foster, Andrew

    2003-03-01

    Inguinal and testicular pain are challenging problems for which no reliable, standardized treatment exists. We report 3 patients with groin pain or orchialgia who were treated with pulsed radiofrequency of the nerves innervating these areas. All 3 patients reported complete pain relief at their 6-month follow-up visits. The techniques and settings used for the nerve blocks and radiofrequency procedures are explained in detail, along with a brief synopsis of the rationale for using it. Randomized, placebo-controlled studies are needed to better assess the efficacy of this procedure and identify eligible candidates. PMID:12639676

  9. Differentially-Enhanced Sideband Imaging via Radio-frequency Encoding

    E-print Network

    Fard, A M; Jalali, B

    2015-01-01

    We present a microscope paradigm that performs differential interference imaging with high sensitivity via optical amplification and radio-frequency (RF) heterodyne detection. This method, termed differentially-enhanced sideband imaging via radio-frequency encoding (DESIRE), uniquely exploits frequency-to-space mapping technique to encode the image of an object onto the RF sidebands of an illumination beam. As a proof-of-concept, we show validation experiment by implementing radio frequency (f = 15 GHz) phase modulation in conjunction with spectrally-encoded laser scanning technique to acquire one-dimensional image of a barcode-like object using a commercial RF spectrum analyzer.

  10. Endovenous radiofrequency ablation for the treatment of varicose veins

    PubMed Central

    Kayssi, Ahmed; Pope, Marc; Vucemilo, Ivica; Werneck, Christiane

    2015-01-01

    Summary Varicose veins are a common condition that can be treated surgically. Available operative modalities include saphenous venous ligation and stripping, phlebectomy, endovenous laser therapy and radiofrequency ablation. Radiofrequency ablation is the newest of these technologies, and to our knowledge our group was the first to use it in Canada. Our experience suggests that it is a safe and effective treatment for varicose veins, with high levels of patient satisfaction reported at short-term follow-up. More studies are needed to assess long-term effectiveness and compare the various available treatment options for varicose veins. PMID:25799244

  11. Radiofrequency ablation for inoperable lung cancer: a case report.

    PubMed

    Erelel, Mustafa; Yakar, Fatih; Yakar, Aysun; Acunas, Bulent

    2009-07-01

    Lung cancer is among the most common malignancies in the world. Optimal treatments for unresectable primary lung cancer, local recurrence of lung cancer within a previous radiation field, pulmonary metastases, and small lung cancers (1?cm) have not been found. Radiofrequency ablation (RFA) has been increasingly performed as a local treatment for lung malignancies. Herein, we present a case of inoperable lung cancer that was successfully treated with a combination of RFA and radiotherapy. A 69-year-old man presented with exertion dyspnea of 3 weeks' duration. He had a remote history of larynx and lung cancer. The patient had remained in remission for 14 years until the current presentation. On physical examination, the patient was not in acute distress, and chest sounds were normal except for minimal prolongation of expiration. On a thorax computed tomography (CT) scan, a 2.3×1.7-cm, ill-defined, cystic lesion in the left upper lobe adjacent to major fissure was detected. CT-guided transthoracic fine needle aspiration biopsy revealed adenocarcinoma but the procedure was complicated by pneumothorax and hypercapnic respiratory failure. On account of the emerging medical inoperability, radiation therapy at 45?Gy in 3 fractions and RFA were performed successfully. After the ninth month of treatment, no fluorodeoxyglucose uptake was detected in the RFA application site in the control positron emission tomography-CT images (complete remission). RFA is a newer technique for lung cancer. Although the results of most studies were short and mid term, for patients with poor lung functions, RFA is an encouraging treatment modality, especially when combined with radiotherapy or chemotherapy in the presence of appropriate patient selection, adequate equipment, and experienced staff. PMID:23168554

  12. An unshielded radio-frequency atomic magnetometer with sub-femtoTesla sensitivity

    NASA Astrophysics Data System (ADS)

    Keder, David A.; Prescott, David W.; Conovaloff, Adam W.; Sauer, Karen L.

    2014-12-01

    We demonstrate a radio-frequency potassium-vapor magnetometer operating with sensitivities of 0.3 fT/ ?{ Hz } at 0.5 MHz and 0.9 fT/ ?{ Hz } at 1.31 MHz in the absence of radio-frequency and mu-metal or magnetic shielding. The use of spatially separated magnetometers, two voxels within the same cell, permits for the subtraction of common mode noise and the retention of a gradient signal, as from a local source. At 0.5 MHz the common mode noise was white and measured to be 3.4 fT/ ?{ Hz } ; upon subtraction the noise returned to the values observed when the magnetometer was shielded. At 1.31 MHz, the common mode noise was from a nearby radio station and was reduced by a factor of 33 upon subtraction, limited only by the radio signal picked up by receiver electronics. Potential applications include in-the-field low-field magnetic resonance, such as the use of nuclear quadrupole resonance for the detection of explosives.

  13. Comparison of Laparoscopic Radiofrequency Myolysis (LRFM) and Ultrasonographic Radiofrequency Myolysis (URFM) in Treatment of Midline Dysmenorrhea

    PubMed Central

    Cho, Eun A; Um, Mi Jung; Kim, Soo Ah; Kim, Suk Jin

    2014-01-01

    Objectives To access the effectiveness of radiofrequency myolysis (RFM) in women with midline dysmenorrhea. Methods We designed RFM in two ways laparoscopic RFM (LRFM), vaginal ultrasound-guided RFM (URFM). One hundred and thirty-two patients were in the LRFM group and, 140 patients were in the URFM group. Results Upon receipt of surgery, both the LRFM and the URFM groups demonstrated a significant decrease (P < 0.001) in the mean pain score when compared to those before and after surgery. Conclusion The RF uterine myolysis procedure provides an alternative for those patients who suffer from intractable midline dysmenorrhea. LRFM is an alternative choice because it is relatively safe and, simple to perform and moreover, it is satisfactory. LRFM appears to increasingly succeed in the treatment of midline dysmenorrhea. PMID:25371897

  14. Multi-functional liposomes showing radiofrequency-triggered release and magnetic resonance imaging for tumor multi-mechanism therapy.

    PubMed

    Du, Bin; Han, Shuping; Li, Hongyan; Zhao, Feifei; Su, Xiangjie; Cao, Xiaohui; Zhang, Zhenzhong

    2015-03-12

    Recently, nanoplatforms with multiple functions, such as tumor-targeting drug carriers, MRI, optical imaging, thermal therapy etc., have become popular in the field of cancer research. The present study reports a novel multi-functional liposome for cancer theranostics. A dual targeted drug delivery with radiofrequency-triggered drug release and imaging based on the magnetic field influence was used advantageously for tumor multi-mechanism therapy. In this system, the surface of fullerene (C60) was decorated with iron oxide nanoparticles, and PEGylation formed a hybrid nanosystem (C60-Fe3O4-PEG2000). Thermosensitive liposomes (dipalmitoylphosphatidylcholine, DPPC) with DSPE-PEG2000-folate wrapped up the hybrid nanosystem and docetaxel (DTX), which were designed to combine features of biological and physical (magnetic) drug targeting for fullerene radiofrequency-triggered drug release. The magnetic liposomes not only served as powerful tumor diagnostic magnetic resonance imaging (MRI) contrast agents, but also as powerful agents for photothermal ablation of tumors. Furthermore, a remarkable thermal therapy combined chemotherapy multi-functional liposome nanoplatform converted radiofrequency energy into thermal energy to release drugs from thermosensitive liposomes, which was also observed during both in vitro and in vivo treatment. The multi-functional liposomes also could selectively kill cancer cells in highly localized regions via their excellent active tumor targeting and magnetic targeted abilities. PMID:25731982

  15. Multi-functional liposomes showing radiofrequency-triggered release and magnetic resonance imaging for tumor multi-mechanism therapy

    NASA Astrophysics Data System (ADS)

    Du, Bin; Han, Shuping; Li, Hongyan; Zhao, Feifei; Su, Xiangjie; Cao, Xiaohui; Zhang, Zhenzhong

    2015-03-01

    Recently, nanoplatforms with multiple functions, such as tumor-targeting drug carriers, MRI, optical imaging, thermal therapy etc., have become popular in the field of cancer research. The present study reports a novel multi-functional liposome for cancer theranostics. A dual targeted drug delivery with radiofrequency-triggered drug release and imaging based on the magnetic field influence was used advantageously for tumor multi-mechanism therapy. In this system, the surface of fullerene (C60) was decorated with iron oxide nanoparticles, and PEGylation formed a hybrid nanosystem (C60-Fe3O4-PEG2000). Thermosensitive liposomes (dipalmitoylphosphatidylcholine, DPPC) with DSPE-PEG2000-folate wrapped up the hybrid nanosystem and docetaxel (DTX), which were designed to combine features of biological and physical (magnetic) drug targeting for fullerene radiofrequency-triggered drug release. The magnetic liposomes not only served as powerful tumor diagnostic magnetic resonance imaging (MRI) contrast agents, but also as powerful agents for photothermal ablation of tumors. Furthermore, a remarkable thermal therapy combined chemotherapy multi-functional liposome nanoplatform converted radiofrequency energy into thermal energy to release drugs from thermosensitive liposomes, which was also observed during both in vitro and in vivo treatment. The multi-functional liposomes also could selectively kill cancer cells in highly localized regions via their excellent active tumor targeting and magnetic targeted abilities.

  16. A novel global model for radio-frequency driven plasmas at atmospheric pressure

    NASA Astrophysics Data System (ADS)

    Hemke, Torben; Mussenbrock, Thomas; Brinkmann, Ralf Peter

    2012-10-01

    Over the last years microplasma research gained a lot of attention both from an experimental and theoretical perspective. One particular type of microplasma sources that shows a variety of interesting physics and applications are the so called plasma jets. Besides the more elaborated fluid or hybrid approaches the so called global models offer the ability to explore averaged species densities and energies while remaining computationally efficient. This contribution investigates a coplanar radio-frequency driven plasma jet by means of a novel global model. The model takes into account the strong modulation of the electric field in time and space both in the sheath and bulk region. By means of a consistent scale analysis we find an analytical expression for the electric field. We compare our obtained electric field to results from PIC simulations and present the general concept for this novel global model of the microplasma jet.

  17. Analytical model for the radio-frequency sheath.

    PubMed

    Czarnetzki, Uwe

    2013-12-01

    A simple analytical model for the planar radio-frequency (rf) sheath in capacitive discharges is developed that is based on the assumptions of a step profile for the electron front, charge exchange collisions with constant cross sections, negligible ionization within the sheath, and negligible ion dynamics. The continuity, momentum conservation, and Poisson equations are combined in a single integro-differential equation for the square of the ion drift velocity, the so called sheath equation. Starting from the kinetic Boltzmann equation, special attention is paid to the derivation and the validity of the approximate fluid equation for momentum balance. The integrals in the sheath equation appear in the screening function which considers the relative contribution of the temporal mean of the electron density to the space charge in the sheath. It is shown that the screening function is quite insensitive to variations of the effective sheath parameters. The two parameters defining the solution are the ratios of the maximum sheath extension to the ion mean free path and the Debye length, respectively. A simple general analytic expression for the screening function is introduced. By means of this expression approximate analytical solutions are obtained for the collisionless as well as the highly collisional case that compare well with the exact numerical solution. A simple transition formula allows application to all degrees of collisionality. In addition, the solutions are used to calculate all static and dynamic quantities of the sheath, e.g., the ion density, fields, and currents. Further, the rf Child-Langmuir laws for the collisionless as well as the collisional case are derived. An essential part of the model is the a priori knowledge of the wave form of the sheath voltage. This wave form is derived on the basis of a cubic charge-voltage relation for individual sheaths, considering both sheaths and the self-consistent self-bias in a discharge with arbitrary symmetry. The externally applied rf voltage is assumed to be sinusoidal, although the model can be extended to arbitrary wave forms, e.g., for dual-frequency discharges. The model calculates explicitly the cubic correction parameter in the charge-voltage relation for the case of highly asymmetric discharges. It is shown that the cubic correction is generally moderate but more pronounced in the collisionless case. The analytical results are compared to experimental data from the literature obtained by laser electric field measurements of the mean and dynamic fields in the capacitive sheath for various gases and pressures. Very good agreement is found throughout. PMID:24483571

  18. Analytical model for the radio-frequency sheath

    NASA Astrophysics Data System (ADS)

    Czarnetzki, Uwe

    2013-12-01

    A simple analytical model for the planar radio-frequency (rf) sheath in capacitive discharges is developed that is based on the assumptions of a step profile for the electron front, charge exchange collisions with constant cross sections, negligible ionization within the sheath, and negligible ion dynamics. The continuity, momentum conservation, and Poisson equations are combined in a single integro-differential equation for the square of the ion drift velocity, the so called sheath equation. Starting from the kinetic Boltzmann equation, special attention is paid to the derivation and the validity of the approximate fluid equation for momentum balance. The integrals in the sheath equation appear in the screening function which considers the relative contribution of the temporal mean of the electron density to the space charge in the sheath. It is shown that the screening function is quite insensitive to variations of the effective sheath parameters. The two parameters defining the solution are the ratios of the maximum sheath extension to the ion mean free path and the Debye length, respectively. A simple general analytic expression for the screening function is introduced. By means of this expression approximate analytical solutions are obtained for the collisionless as well as the highly collisional case that compare well with the exact numerical solution. A simple transition formula allows application to all degrees of collisionality. In addition, the solutions are used to calculate all static and dynamic quantities of the sheath, e.g., the ion density, fields, and currents. Further, the rf Child-Langmuir laws for the collisionless as well as the collisional case are derived. An essential part of the model is the a priori knowledge of the wave form of the sheath voltage. This wave form is derived on the basis of a cubic charge-voltage relation for individual sheaths, considering both sheaths and the self-consistent self-bias in a discharge with arbitrary symmetry. The externally applied rf voltage is assumed to be sinusoidal, although the model can be extended to arbitrary wave forms, e.g., for dual-frequency discharges. The model calculates explicitly the cubic correction parameter in the charge-voltage relation for the case of highly asymmetric discharges. It is shown that the cubic correction is generally moderate but more pronounced in the collisionless case. The analytical results are compared to experimental data from the literature obtained by laser electric field measurements of the mean and dynamic fields in the capacitive sheath for various gases and pressures. Very good agreement is found throughout.

  19. Modeling of small scale radio-frequency inductive discharges for electric propulsion applications

    NASA Astrophysics Data System (ADS)

    Mistoco, Valerie F. M.

    This work is motivated by the increasing interest in small-scale radio-frequency ion thrusters for micro- and nanosatellite applications, in particular for stationkeeping. This specific type of thruster relies on an inductive discharge to produce positive ions that are accelerated by an external electric field in order to produce thrust. Analyzing the particle dynamics within the discharge vessel is critical for determining the performance of these thrusters, particularly as scaling down the size and thrust level of ion thrusters remains a major challenge. Until now the application of this type of propulsion system has been limited to large satellites and space platforms. The approach taken in this work was, first, to perform a simple analysis of the inductive discharge using a transformer model. However, the dimensions of the thruster and the pressure ranges at which it operates called for a different approach than those used in larger thrusters and reactors as the collisional domain and non-locality effects differ significantly. After estimating the non-locality effects by calculating the non-locality parameter, a kinetic description of the discharge was developed. From the input power, mass flow rate, and the properties of the gas used in the discharge, the density numbers, temperatures of the particles, and thrust are calculated. Simulation values are compared with experimental values obtained with the Miniature Radio-frequency Ion Thruster being developed at The Pennsylvania State University. The approach employed to model this small scale inductive discharge can be summarized as follows. First, conditions of operation and the various plasma parameters of the discharge were derived. Then, a one-dimensional kinetic model of an inductive discharge, using a Maxwellian electron distribution, was built. Results from this model were validated on data available in the literature. Finally, from the beam current derived from the 1-D model, using a two-grid ion optics configuration, thrust was calculated. In addition, an existing model of transition between capacitive and inductive modes was applied to the Miniature Radio-frequency Ion Thruster geometry and its electrical properties. A description of the different types of capacitively coupled radio-frequency initiation mechanisms is also given.

  20. Radiofrequency coblation for the treatment of laryngotracheal papillomas

    Microsoft Academic Search

    Simon Carney; Alkis Psaltis

    2004-01-01

    Objectives: Recurrent respiratory papillomatosis can affect the larynx and trachea. Lesions have conventionally been treated with laser ablation with or without antiviral injection. When the distal airway is involved, laser risks increase and lesions are more difficult to treat using the laser bronchoscope. Distal seeding via the laser flume is also a major risk. Radiofrequency coblation has been successfully used

  1. Radiofrequency ablation as a treatment for hilar cholangiocarcinoma

    Microsoft Academic Search

    Wei-Jun Fan; Pei-Hong Wu; Liang Zhang; Jin-Hua Huang; Fu-Jun Zhang; Yang-Kui Gu; Ming Zhao; Xiang-Long Huang; Chang-Yu Guo

    2008-01-01

    AIM: To explore the role of radio-frequency ablation (RFA) as a treatment for hilar cholangiocarcinoma. METHODS: Eleven patients with obstructive cholestasis underwent Computed Tomography (CT) examination, occupying lesions were observed in the hepatic hilar region in each patient. All lesions were confirmed as cholangioadenocarcinoma by biopsy and were classified as type ? or ? by percutaneous transhepatic cholangiography. Patients were

  2. Process for selected gas oxide removal by radiofrequency catalysts

    DOEpatents

    Cha, C.Y.

    1993-09-21

    This process to remove gas oxides from flue gas utilizes adsorption on a char bed subsequently followed by radiofrequency catalysis enhancing such removal through selected reactions. Common gas oxides include SO[sub 2] and NO[sub x]. 1 figure.

  3. Radiofrequency emissions observed during macroscopic hypervelocity impact experiments

    Microsoft Academic Search

    R. Bianchi; F. Capaccioni; P. Cerroni; M. Coradini; E. Flamini; P. Hurren; P. N. Smith; G. Martelli

    1984-01-01

    Observations of banded radiofrequency emission generated during and after macroscopic hypervelocity impacts of small projectiles on hard rocks are reported. Tests were conducted in air at atmospheric pressure and in vacuo at residual pressure varying between 6 and 0.1 torr. The receiver system consisted of several coils oriented so as to allow the simultaneous detection of various components of any

  4. RADIOFREQUENCY RADIATION: ACTIVITIES AND ISSUES, A 1986 PERSPECTIVE (JOURNAL VERSION)

    EPA Science Inventory

    The following topics are discussed in the report: (1) environmental exposure levels of radiofrequency (RF) radiation; (2) Federal and other activities related to the control of exposure to RF radiation; (3) biological effects; (4) limitations in the knowledge of biological effect...

  5. Radio-frequency energy in fusion power generation

    SciTech Connect

    Lawson, J.Q.; Becraft, W.R.; Hoffman, D.J.

    1983-01-01

    The history of radio-frequency (rf) energy in fusion experiments is reviewed, and the status of current efforts is described. Potential applications to tasks other than plasma heating are described, as are the research and development needs of rf energy technology.

  6. A technique for periorbital syringomas: intralesional radiofrequency ablation

    PubMed Central

    Huang, Li-Ping; Zhang, Leng; Wang, Xing-Lin; Liu, Xiao-Cui; Jiang, Tian-Yu; Lin, Bi-Weng

    2012-01-01

    AIM To evaluate the efficacy of intralesional radiofrequency ablation in the treatment of periorbital syringomas. METHODS We tried the intralesional radiofrequency ablation for 64 patients with periorbital syringomas from 2007 to 2011. The operation was performed under 2.5 loupe magnifications. The handpiece was assembled with a needle electrode and connected to the radiofrequency ablation apparatus. The electrode was then inserted into the target lesions in dermis and delivering injury to the base of these tumors. Results were assessed clinically by comparing pre- and post-treatment photographs and patient satisfaction rates. RESULTS Clinical improvement increased with each subsequent treatment session. The percent of patients whose clinic improvement grade were?3 after each session was respectively 71.9%(Session1), 83.3%(Session2), and 100%(Session3). The statistical results indicated the concordance of the clinical assessment and the satisfaction level of patients (kappa=0.78 of the session1; kappa=0.82 of the session2). The majority of patients had good or excellent cosmetic results. Postoperatively, there were no permanent side effects or recurrences. CONCLUSION As a new technique of minimally invasion, the intralesional radiofrequency ablation was found to be an effective, inexpensive, highly precise and safe way of treating periorbital syringomas. PMID:22762046

  7. Cardiovascular risk in operators under radiofrequency electromagnetic radiation.

    PubMed

    Vangelova, Katia; Deyanov, Christo; Israel, Mishel

    2006-03-01

    The aim of the study was to assess the long-term effects of radiofrequency electromagnetic radiation (EMR) on the cardiovascular system. Two groups of exposed operators (49 broadcasting (BC) station and 61 TV station operators) and a control group of 110 radiorelay station operators, matched by sex and age, with similar job characteristics except for the radiofrequency EMR were studied. The EMR exposure was assessed and the time-weighted average (TWA) was calculated. The cardiovascular risk factors arterial pressure, lipid profile, body mass index, waist/hip ratio, smoking, and family history of cardiovascular disease were followed. The systolic and diastolic blood pressure (SBP and DBP), total cholesterol (TC) and low-density lipoprotein cholesterol (LDL-C) were significantly higher in the two exposed groups. It was found that the radiofrequency EMR exposure was associated with greater chance of becoming hypertensive and dyslipidemic. The stepwise multiple regression equations showed that the SBP and TWA predicted the high TC and high LDL-C, while the TC, age and abdominal obesity were predictors for high SBP and DBP. In conclusion, our data show that the radiofrequency EMR contributes to adverse effects on the cardiovascular system. PMID:16503299

  8. Fluid temperatures during arthroscopic subacromial decompression using a radiofrequency probe

    Microsoft Academic Search

    Howard DAVIES; Henry WYNN; Thomas DESMET; Shameem SAMPATH; Bury St Edmunds

    2009-01-01

    Our aim was to investigate the temperatures reached in the subacromial space during radiofrequency ablation of the subacromial bursa, in order to see if the probes generate sufficiently high temperatures to cause chondrolysis of the articular surfaces in the glenohumeral joint. We recorded the maximum temperatures in the subacromial space during arthroscopic subacromial decompression on 30 con - secutive patients

  9. MICROWAVE AND RADIO-FREQUENCY POWER APPLICATIONS IN AGRICULTURE

    Technology Transfer Automated Retrieval System (TEKTRAN)

    A brief review is presented of potential applications for radio-frequency and microwave power applications in agriculture. Included are applications for stored-product insect control, seed treatment to improve germination and seedling performance, conditioning of products to improve nutritional val...

  10. Pulsed Radiofrequency Ablation Under Ultrasound Guidance for Huge Neuroma

    PubMed Central

    Jung, Il; Lee, Chang Hee; Kim, Se Hun; Kim, Jin Sun; Yoo, Byoung Woo

    2014-01-01

    Amputation neuroma can cause very serious, intractable pain. Many treatment modalities are suggested for painful neuroma. Pharmacologic treatment shows a limited effect on eliminating the pain, and surgical treatment has a high recurrence rate. We applied pulsed radiofrequency treatment at the neuroma stalk under ultrasonography guidance. The long-term outcome was very successful, prompting us to report this case. PMID:25031817

  11. Percutaneous Radiofrequency Ablation of Sonographically Unidentifiable Liver Tumors

    Microsoft Academic Search

    Yasunori Minami; Masatoshi Kudo; Hobyung Chung; Tatsuo Inoue; Shunsuke Takahashi; Kinuyo Hatanaka; Taisuke Ueda; Hitoshi Hagiwara; Satoshi Kitai; Kuzuomi Ueshima; Toyokazu Fukunaga; Hitoshi Shiozaki

    2007-01-01

    Objective: The purpose of this study was to evaluate the safety and feasibility of a real-time integrated system with computed tomography (CT) and sonographic images for radiofrequency (RF) ablation of hepatic malignancies poorly defined on B-mode sonography, and to clarify the suitable phase of CT images for using this virtual sonography. Methods: Between September 2004 and December 2004, 12 patients

  12. SOME UNSOLVED CHALLENGES IN RADIO-FREQUENCY HEATING AND

    E-print Network

    parameters, and synergistic effects between current drive and alpha channeling. These challenges in the electronic version. I. INTRODUCTION There are many methods by which radio-frequency (rf) waves drive dense. Such an optimized tokamak, hot, but not dense, might still have similar fusion reactivity, which

  13. Stabilization of magnetohydrodynamic modes by applied radiofrequency waves

    Microsoft Academic Search

    D. A. Dippolito; J. R. Myra

    1986-01-01

    A kinetic theory describing the nonlinear interaction of radiofrequency waves with low frequency magnetohydrodynamic modes is presented. The calculation of the nonlinear force density on a fluid element includes both ponderomotive and sideband mode coupling terms and allows arbitrary rf wave polarization. Electromagnetic effects and wave-particle interactions are retained in the analysis. The influence of the nonlinear force on magnetohydrodynamic

  14. Radiofrequency Ablation of Lung Malignancies: Where Do We Stand?

    Microsoft Academic Search

    Riccardo Lencioni; Laura Crocetti; Roberto Cioni; Alfredo Mussi; Gabriella Fontanini; Marcello Ambrogi; Chiara Franchini; Dania Cioni; Olivia Fanucchi; Raffaello Gemignani; Rubia Baldassarri; Carlo Alberto Angeletti; Carlo Bartolozzi

    2004-01-01

    Percutaneous radiofrequency (RF) ablation is a minimally invasive technique used to treat solid tumors. Because of its ability to produce large volumes of coagulation necrosis in a controlled fashion, this technique has gained acceptance as a viable therapeutic option for unresectable liver malignancies. Recently, investigation has been focused on the clinical application of RF ablation in the treatment of lung

  15. Reduction of the radiofrequency heating of metallic devices using a dual-drive birdcage coil.

    PubMed

    Eryaman, Yigitcan; Turk, Esra Abaci; Oto, Cagdas; Algin, Oktay; Atalar, Ergin

    2013-03-01

    In this work, it is demonstrated that a dual-drive birdcage coil can be used to reduce the radiofrequency heating of metallic devices during magnetic resonance imaging. By controlling the excitation currents of the two channels of a birdcage coil, the radiofrequency current that is induced near the lead tip could be set to zero. To monitor the current, the image artifacts near the lead tips were measured. The electric field distribution was controlled using a dual-drive birdcage coil. With this method, the lead currents and the lead tip temperatures were reduced substantially [<0.3 °C for an applied 4.4 W/kg SAR compared to >4.9 °C using quadrature excitation], as demonstrated by phantom and animal experiments. The homogeneity of the flip angle distribution was preserved, as shown by volunteer experiments. The normalized root-mean-square error of the flip angle distribution was less than 10% for all excitations. The average specific absorption rate increased as a trade-off for using different excitation patterns. PMID:22576183

  16. Theoretical modeling for radiofrequency ablation: state-of-the-art and challenges for the future

    PubMed Central

    Berjano, Enrique J

    2006-01-01

    Radiofrequency ablation is an interventional technique that in recent years has come to be employed in very different medical fields, such as the elimination of cardiac arrhythmias or the destruction of tumors in different locations. In order to investigate and develop new techniques, and also to improve those currently employed, theoretical models and computer simulations are a powerful tool since they provide vital information on the electrical and thermal behavior of ablation rapidly and at low cost. In the future they could even help to plan individual treatment for each patient. This review analyzes the state-of-the-art in theoretical modeling as applied to the study of radiofrequency ablation techniques. Firstly, it describes the most important issues involved in this methodology, including the experimental validation. Secondly, it points out the present limitations, especially those related to the lack of an accurate characterization of the biological tissues. After analyzing the current and future benefits of this technique it finally suggests future lines and trends in the research of this area. PMID:16620380

  17. I. Multiple-Pulse Radio-Frequency Gradient Nuclear Magnetic Resonance Imaging of Solids. I. Optical Nuclear Magnetic Resonance Analysis of Epitaxial Gallium Arsenide Structures

    Microsoft Academic Search

    John Aaron Marohn

    1996-01-01

    Conventional liquid-state nuclear magnetic resonance (NMR) imaging protocols fail in solids, where rapid local -field dephasing of nuclear magnetization precludes the frequency encoding of spatial information with conventional magnetic field gradients. In this work, a multiple-pulse line-narrowing sequence is delivered with a solenoid coil to prolong a solid's effective transverse relaxation time. A radiofrequency gradient coil, delivering resonant pulses whose

  18. Radio-frequency driven dipole-dipole interactions in spatially separated volumes

    E-print Network

    Atreju Tauschinsky; C. S. E. van Ditzhuijzen; L. D. Noordam; H. B. van Linden van den Heuvell

    2008-10-14

    Radio-frequency (rf) fields in the MHz range are used to induce resonant energy transfer between cold Rydberg atoms in spatially separated volumes. After laser preparation of the Rydberg atoms, dipole-dipole coupling excites the 49s atoms in one cylinder to the 49p state while the 41d atoms in the second cylinder are transferred down to the 42p state. The energy exchanged between the atoms in this process is 33 GHz. An external rf-field brings this energy transfer into resonance. The strength of the interaction has been investigated as a function of amplitude (0-1 V/cm) and frequency (1-30 MHz) of the rf-field and as a function of a static field offset. Multi-photon transitions up to fifth order as well as selection rules prohibiting the process at certain fields have been observed. The width of the resonances has been reduced compared to earlier results by switching off external magnetic fields of the magneto-optical trap, making sub-MHz spectroscopy possible. All features are well reproduced by theoretical calculations taking the strong ac-Stark shift due to the rf-field into account.

  19. A radio-frequency sheath model for complex waveforms

    NASA Astrophysics Data System (ADS)

    Turner, M. M.; Chabert, P.

    2014-04-01

    Plasma sheaths driven by radio-frequency voltages occur in contexts ranging from plasma processing to magnetically confined fusion experiments. An analytical understanding of such sheaths is therefore important, both intrinsically and as an element in more elaborate theoretical structures. Radio-frequency sheaths are commonly excited by highly anharmonic waveforms, but no analytical model exists for this general case. We present a mathematically simple sheath model that is in good agreement with earlier models for single frequency excitation, yet can be solved for arbitrary excitation waveforms. As examples, we discuss dual-frequency and pulse-like waveforms. The model employs the ansatz that the time-averaged electron density is a constant fraction of the ion density. In the cases we discuss, the error introduced by this approximation is small, and in general it can be quantified through an internal consistency condition of the model. This simple and accurate model is likely to have wide application.

  20. Radiofrequency hyperthermia and topical retinoic acid therapy in murine melanoma.

    PubMed

    Levine, N; Don, S A; Klewer, S E; Vasquez, J A; Draelos, Z K

    1989-05-01

    Malignant cells are known to be sensitive to increased temperature. The effects of hyperthermia (HT) on intradermally implanted S91 melanoma cells in syngeneic mice were investigated with a hand-held radiofrequency generator. The possible additive effects of topical retinoic acid (RA) in this system also were studied. Five millimeter diameter melanomas were treated with either HT alone, RA alone, or a combination of HT and RA and were then evaluated after 43 days and 59 days. Eighteen of 20 tumors treated with HT alone and all 20 melanomas treated with HT/RA were eradicated. RA alone caused complete regression in 11 of 19 treated tumors. It is concluded that radiofrequency HT is an effective treatment in intradermal murine melanoma and that the addition of RA does not significantly alter the outcome because of the extreme effectiveness of HT alone. PMID:2719055

  1. Irrigated Tip Catheters for Radiofrequency Ablation in Ventricular Tachycardia

    PubMed Central

    Grothoff, Matthias; Dinov, Borislav; Kosiuk, Jedrzej; Richter, Sergio; Sommer, Philipp; Breithardt, Ole A.; Bollmann, Andreas; Arya, Arash; Hindricks, Gerhard

    2015-01-01

    Radiofrequency (RF) ablation with irrigated tip catheters decreases the likelihood of thrombus and char formation and enables the creation of larger lesions. Due to the potential dramatic consequences, the prevention of thromboembolic events is of particular importance for left-sided procedures. Although acute success rates of ventricular tachycardia (VT) ablation are satisfactory, recurrence rate is high. Apart from the progress of the underlying disease, reconduction and the lack of effective transmural lesions play a major role for VT recurrences. This paper reviews principles of lesion formation with radiofrequency and the effect of tip irrigation as well as recent advances in new technology. Potential areas of further development of catheter technology might be the improvement of mapping by better substrate definition and resolution, the introduction of bipolar and multipolar ablation techniques into clinical routine, and the use of alternative sources of energy. PMID:25705659

  2. Radiofrequency thermal ablation in painful myeloma of the clavicle.

    PubMed

    Gharaei, Helen; Imani, Farnad; Vakily, Masoud

    2014-01-01

    A 57-year-old male patient had myeloma. He had severe pain in the left clavicle that did not respond to radiotherapy; therefore, it was treated with radiofrequency thermal ablation (RFTA). Under fluoroscopic guidance, two RF needles at a distance of 1.5 cm from each other were inserted into the mass and conventional radiofrequency (90? and 60 seconds) at two different depths (1 cm apart) was applied. Then, 2 ml of 0.5% ropivacaine along with triamcinolone 40 mg was injected in each needle. The visual analogue pain score (VAS from 0 to 10) was decreased from 8 to 0. In the next 3 months of follow-up, the patient was very satisfied with the procedure and the mass gradually became smaller. There were no complications. This study shows that RFTA could be a useful method for pain management in painful osteolytic myeloma lesions in the clavicle. PMID:24478905

  3. A radio-frequency sheath model for complex waveforms

    SciTech Connect

    Turner, M. M. [School of Physical Sciences and National Centre for Plasma Science and Technology, Dublin City University, Dublin 9 (Ireland); Chabert, P. [Laboratoire de Physique des Plasmas, Centre National de la Recherche Scientifique, Ecole Polytechnique, Université Pierre et Marie Curie, Paris XI, 91128 Palaiseau (France)

    2014-04-21

    Plasma sheaths driven by radio-frequency voltages occur in contexts ranging from plasma processing to magnetically confined fusion experiments. An analytical understanding of such sheaths is therefore important, both intrinsically and as an element in more elaborate theoretical structures. Radio-frequency sheaths are commonly excited by highly anharmonic waveforms, but no analytical model exists for this general case. We present a mathematically simple sheath model that is in good agreement with earlier models for single frequency excitation, yet can be solved for arbitrary excitation waveforms. As examples, we discuss dual-frequency and pulse-like waveforms. The model employs the ansatz that the time-averaged electron density is a constant fraction of the ion density. In the cases we discuss, the error introduced by this approximation is small, and in general it can be quantified through an internal consistency condition of the model. This simple and accurate model is likely to have wide application.

  4. A review of current concepts in radiofrequency chondroplasty.

    PubMed

    Horton, Damien; Anderson, Suzanne; Hope, Nigel G

    2014-06-01

    Radiofrequency (RF) chondroplasty is a promising treatment of chondral defects. The purpose of this study is to summarize current literature reporting the use of radiofrequency energy as an alternative treatment to mechanical shaving in chondroplasty. This review depicts the basic understanding of RF energy in ablating cartilage while exploring the basic science, laboratory evidence and clinical effectiveness of this form of chondroplasty. Laboratory studies have indicated that RF energy decreases inflammatory markers in the cartilage as well as providing optimal results with smoothing of chondral clefts. There have been concerns of chondrolysis due to heat damage of chondrocytes; however, this is unsubstantiated in clinical studies. These clinical trials have highlighted that RF energy is a safe and efficacious method of chondroplasty when compared to the mechanical shaving technique. PMID:23551491

  5. [Percutaneous ablation of renal tumors: radiofrequency ablation or cryoablation?].

    PubMed

    Buy, X; Lang, H; Garnon, J; Gangi, A

    2011-09-01

    Percutaneous ablation of renal tumors, including radiofrequency ablation and cryoablation, are increasingly being used for small tumors as an alternative to surgery for poor surgical candidates. Compared to radiofrequency ablation, cryoablation has several advantages: improved volume control and preservation of adjacent structures due to the excellent depiction of the ice ball on CT and MRI; better protection of the collecting system for central tumor with reduced risk of postprocedural urinary fistula. The main pitfall of cryoablation is the higher cost. Therefore, cryoablation should be reserved for the treatment of complex tumors. In this article, we will review the different steps of percutaneous renal tumor ablation procedures including patient selection, technical considerations, and follow-up imaging. PMID:21944236

  6. Various complications of percutaneous radiofrequency ablation for hepatic tumors: radiologic findings and technical tips.

    PubMed

    Kwon, Heon-Ju; Kim, Pyo Nyun; Byun, Jae Ho; Kim, Kyoung Won; Won, Hyung Jin; Shin, Yong Moon; Lee, Moon-Gyu

    2014-11-01

    Radiofrequency ablation is a safe and effective treatment for primary and secondary liver malignancies and has a low complication rate; however, there are various radiofrequency ablation-related complications which can occur from the thorax to the pelvis. Although most of these complications are usually minor and self-limited, they may become fatal if diagnosis and treatment are delayed. It is important for radiologists performing radiofrequency ablation to have a perspective regarding the possible radiofrequency ablation-related complications and their risk factors as well as the radiologic findings for their timely detection and increase of the treatment efficacy, and thereby encouraging the use of the radiofrequency ablation technique. This article illustrates the various imaging features of common and rare radiofrequency ablation-related complications as well as offers technical tips in order to avoid these complications. PMID:24277883

  7. Comb-based radiofrequency photonic filters with rapid tunability and high selectivity

    NASA Astrophysics Data System (ADS)

    Supradeepa, V. R.; Long, Christopher M.; Wu, Rui; Ferdous, Fahmida; Hamidi, Ehsan; Leaird, Daniel E.; Weiner, Andrew M.

    2012-03-01

    Photonic technologies have received considerable attention regarding the enhancement of radiofrequency electrical systems, including high-frequency analogue signal transmission, control of phased arrays, analog-to-digital conversion and signal processing. Although the potential of radiofrequency photonics for the implementation of tunable electrical filters over broad radiofrequency bandwidths has been much discussed, the realization of programmable filters with highly selective filter lineshapes and rapid reconfigurability has faced significant challenges. A new approach for radiofrequency photonic filters based on frequency combs offers a potential route to simultaneous high stopband attenuation, fast tunability and bandwidth reconfiguration. In one configuration, tuning of the radiofrequency passband frequency is demonstrated with unprecedented (~40 ns) speed by controlling the optical delay between combs. In a second, fixed filter configuration, cascaded four-wave mixing simultaneously broadens and smoothes the comb spectra, resulting in Gaussian radiofrequency filter lineshapes exhibiting an extremely high (>60 dB) main lobe to sidelobe suppression ratio and (>70 dB) stopband attenuation.

  8. Hepatocellular carcinoma: percutaneous radiofrequency ablation using expandable needle electrodes and the double-insertion technique.

    PubMed

    Shirato, Kazuhito; Morimoto, Manabu; Tomita, Naohiko; Kokawa, Atsushi; Sugimori, Kazuya; Saito, Toshifumi; Tanaka, Katsuaki

    2002-01-01

    The authors present a case of percutaneous radiofrequency ablation for the treatment of a confirmed hepatocellular carcinoma using expandable needle electrodes and the double-insertion technique. The patient underwent radiofrequency ablation for a 5.0-cm-in-diameter hepatocellular carcinoma in liver segment VIII. One radiofrequency ablation session using the double-insertion technique was performed, resulting in the complete necrosis of the tumor. A collection of pleural effusion as a complication of radiofrequency ablation was revealed by a computed tomography scanning which was performed after the radiofrequency ablation session. However, no other serious complication was encountered. No local recurrences have been observed after a 10-month follow-up period. The present case suggests the therapeutic efficacy of radiofrequency ablation using expandable needle electrodes and the double-insertion technique. PMID:12397712

  9. Arthroscopic Gluteal Muscle Contracture Release With Radiofrequency Energy

    PubMed Central

    Liu, Yu-Jie; Wang, Yan; Xue, Jing; Lui, Pauline Po-Yee

    2008-01-01

    Gluteal muscle contracture is common after repeated intramuscular injections and sometimes is sufficiently debilitating to require open surgery. We asked whether arthroscopic release of gluteal muscle contracture using radiofrequency energy would decrease complications with clinically acceptable results. We retrospectively reviewed 108 patients with bilateral gluteal muscle contractures (57 males, 51 females; mean age, 23.7 years). We used inferior, anterosuperior, and posterosuperior portals. With the patient lying laterally, we developed and enlarged a potential space between the gluteal muscle group and the subcutaneous fat using blunt dissection. Under arthroscopic guidance through the inferior portal, we débrided and removed fatty tissue overlying the contractile band of the gluteal muscle group using a motorized shaver introduced through the superior portal. Radiofrequency then was introduced through the superior portal to gradually excise the contracted bands from superior to inferior. Finally, hemostasis was ensured using radiofrequency. Patients were followed a minimum of 7 months (mean, 17.4 months; range, 7–42 months). At last followup, the adduction and flexion ranges of the hip were 45.3° ± 8.7° and 110.2° ± 11.9°, compared with 10.4° ± 7.2° and 44.8° ± 14.1° before surgery. No hip abductor contracture recurred and no patient had residual hip pain or gluteal muscle wasting. We found gluteal muscle contracture could be released effectively with radiofrequency energy. Level of Evidence: Level IV, therapeutic study. See the Guidelines for Authors for a complete description of levels of evidence. Electronic supplementary material The online version of this article (doi:10.1007/s11999-008-0595-7) contains supplementary material, which is available to authorized users. PMID:18975040

  10. Core body temperature regulation of pediatric patients during radiofrequency ablation.

    PubMed

    Hoffer, Fredric A; Campos, Alvaro; Xiong, Xiaoping; Wu, Shengjie; Oigbokie, Nikita; Proctor, Kimberly

    2007-03-01

    Core body temperature elevation (hyperthermia) can occur during radiofrequency ablation of large centrally located tumors in small children. Hyperthermia can be predicted on the basis of long burn times, high wattage delivered by the RF system and low body weight. If hyperthermia is anticipated, cooling blankets using refrigerated air or water are recommended. The advantage of these systems is that the cooling can help maintain normal core body temperature. PMID:17216171

  11. The genotoxic effect of radiofrequency waves on mouse brain

    Microsoft Academic Search

    Emin KaracaBurak; Burak Durmaz; Huseyin Altug; Teoman Yildiz; Candan Guducu; Melis Irgi; Mehtap Gulcihan Cinar Koksal; Ferda Ozkinay; Cumhur Gunduz; Ozgur Cogulu

    Concerns about the health effects of radiofrequency (RF) waves have been raised because of the gradual increase in usage of\\u000a cell phones, and there are scientific questions and debates about the safety of those instruments in daily life. The aim of\\u000a this study is to evaluate the genotoxic effects of RF waves in an experimental brain cell culture model. Brain

  12. PIC\\/MC modeling of dusty radio-frequency discharges

    Microsoft Academic Search

    Willem Jan Goedheer; Yuriy I. Chutov

    2004-01-01

    We have extended a one-dimensional particle-in-cell plus Monte Carlo model for argon radio-frequency discharges with scattering and capture of electrons and ions on dust particles immersed in the discharge. The orbital motion limited cross section is used for the capture process. For scattering, we took the bare Coulomb interaction for impact parameters below the linearized Debye length and neglected the

  13. Increased susceptibility to radiofrequency radiation due to pharmacological agents

    Microsoft Academic Search

    J. R. Jauchem; M. R. Frei; F. Heinmets

    1984-01-01

    The effects of chlorpromazine, methysergide, and propranolol on thermal responses to 2.8 GHz radiofrequency radiation were examined in anesthetized rats. During intermittent exposure at an average power density of 60 mW\\/sq cm (specific absorption rate, 14 W\\/kg), when colonic temperature was not allowed to rise above 39.5 C, none of the pharmacological agents had any significant effects on thermal responses.

  14. Laser initiation and radiofrequency sustainment of seeded air plasmas

    Microsoft Academic Search

    J. Scharer; R. Cao; H. Gui; K. Kelly; E. Paller; R. Sund

    2000-01-01

    Summary form only given. Seeded gas plasmas and air constituents have been created by a 193 nm laser and radiofrequency sources. We have obtained 1014\\/cm3 plasma densities with initial electron temperatures of 0.3 eV in TMAE (tetrakis (dimethylamino) ethylene) by laser photoionization. We developed a fast Langmuir probe analysis of plasma decay independent of ion species mix. Langmuir probe and

  15. Laser Initiation and Radiofrequency Sustainment of Seeded Air Plasmas

    Microsoft Academic Search

    J. Scharer; G. Ding; H. Gui; K. Kelly; E. Paller

    1999-01-01

    Seeded gas plasmas and air constituents have been created by a 193 nm laser and radiofrequency sources. We have obtained 10^14\\/cm^3 plasma densities with initial electron temperatures of 0.3 eV in TMAE (tetrakis (dimethylamino) ethylene) by laser photoionization. We developed a fast Langmuir probe analysis of plasma decay independent of ion species mix. Langmuir probe and optical emission data illustrating

  16. Laser and Radiofrequency Production of Seeded Air Plasmas

    Microsoft Academic Search

    J. Scharer; G. Ding; H. Gui; K. Kelly; E. Paller

    1999-01-01

    Seeded gas plasmas and air constituents have been created by a 193 nm laser and by a radiofrequency source. We have obtained 10^14\\/cm^3 plasma densities with initial electron temperatures of 0.3 eV in TMAE (tetrakis (dimethylamino) ethylene) by laser photoionization. We developed a fast Langmuir probe analysis of plasma decay independent of ion species mix. Langmuir probe and optical emission

  17. Diaphragmatic Hernia After Radiofrequency Ablation for Hepatocellular Carcinoma

    SciTech Connect

    Yamagami, Takuji, E-mail: yamagami@koto.kpu-m.ac.jp; Yoshimatsu, Rika; Matsushima, Shigenori; Tanaka, Osamu; Miura, Hiroshi; Nishimura, Tsunehiko [Kyoto Prefectural University of Medicine, Department of Radiology, Graduate School of Medical Science (Japan)

    2011-02-15

    We describe a 71-year-old woman with a hepatocellular carcinoma who underwent percutaneous radiofrequency ablation (RF) with a single internally cooled electrode under computed tomography (CT) fluoroscopic guidance. Nine months after the procedure, CT images showed herniation of the large intestine into the right pleural cavity. To our knowledge this complication of RF performed with a single internally cooled electrode under CT guidance has not been previously reported.

  18. Computer simulations of ions in radio-frequency traps

    NASA Technical Reports Server (NTRS)

    Williams, A.; Prestage, J. D.; Maleki, L.; Djomehri, J.; Harabetian, E.

    1990-01-01

    The motion of ions in a trapped-ion frequency standard affects the stability of the standard. In order to study the motion and structures of large ion clouds in a radio-frequency (RF) trap, a computer simulation of the system that incorporates the effect of thermal excitation of the ions was developed. Results are presented from the simulation for cloud sizes up to 512 ions, emphasizing cloud structures in the low-temperature regime.

  19. Perforated-Layer Implementation Of Radio-Frequency Lenses

    NASA Technical Reports Server (NTRS)

    Dolgin, Benjamin P.

    1996-01-01

    Luneberg-type radio-frequency dielectric lenses made of stacked perforated circular dielectric sheets, according to proposal. Perforation pattern designed to achieve required spatial variation of permittivity. Consists of round holes distributed across face of each sheet in "Swiss-cheese" pattern, plus straight or curved slots that break up outer parts into petals in "daisy-wheel" pattern. Holes and slots made by numerically controlled machining.

  20. Stabilization of magnetohydrodynamic modes by applied radio-frequency waves

    Microsoft Academic Search

    D. A. D'Ippolito; J. R. Myra

    1986-01-01

    A kinetic theory describing the nonlinear interaction of radio-frequency waves with low-frequency magnetohydrodynamic modes is presented. The calculation of the nonlinear force density on a fluid element includes both ponderomotive and sideband mode coupling terms and allows arbitrary rf wave polarization. Electromagnetic effects and wave--particle interactions are retained in the analysis. The influence of the nonlinear force on magnetohydrodynamic plasma

  1. Stabilization of magnetohydrodynamic modes by applied radio-frequency waves

    Microsoft Academic Search

    D. A. D’Ippolito; J. R. Myra

    1986-01-01

    A kinetic theory describing the nonlinear interaction of radio-frequency waves with low-frequency magnetohydrodynamic modes is presented. The calculation of the nonlinear force density on a fluid element includes both ponderomotive and sideband mode coupling terms and allows arbitrary rf wave polarization. Electromagnetic effects and wave–particle interactions are retained in the analysis. The influence of the nonlinear force on magnetohydrodynamic plasma

  2. Effects of psychotropic drugs on thermal responses to radiofrequency radiation.

    PubMed

    Jauchem, J R; Frei, M R; Heinmets, F

    1985-12-01

    An increase in body temperature is a primary effect of exposure to high levels of radiofrequency radiation; therefore, pharmacological agents which may modify thermoregulation are of interest. The present study investigated the effects of chlorpromazine, amitriptyline, and haloperidol on thermal responses in anesthetized rats exposed to 2.8 GHz radiofrequency radiation. Exposure was performed at an average power density of 60 mW X cm-2 (average whole body absorption rate, 14 W X kg-1), and was of sufficient duration to increase colonic temperature from 38.5 to 39.5 degrees C. Administration of chlorpromazine (5 mg X kg-1) resulted in a slower rate of colonic temperature rise during radiation exposure and a faster return to baseline temperature when exposure was discontinued. Administration of amitriptyline (10 mg X kg-1), haloperidol (0.1 mg X kg-1), or saline did not significantly affect thermal responses. A more rhythmic pattern of respiration occurred following chlorpromazine administration; the change in pattern was not seen after amitriptyline, haloperidol, or saline administration. The results indicate that acute administration of chlorpromazine can counteract hyperthermia during exposure to radiofrequency radiation, when colonic temperature is not allowed to rise above 39.5 degrees C. PMID:4084172

  3. Interstitial radiofrequency hyperthermia for brain tumors--preliminary laboratory studies and clinical application.

    PubMed

    Koga, H; Mori, K; Tokunaga, Y

    1993-05-01

    An interstitial radiofrequency (RF) hyperthermia system for brain tumor was evaluated in cranial phantoms and cat brains. An intracranial RF applicator and thermocouple microprobes were emplaced in the brain and a headband-type flexible extracranial electrode fixed over the scalp. An 8 MHz RF capacitive-type heating machine provided power. The temperature distribution was measured by thermography. In phantom and animal studies, the RF power had good penetration into the tissue and generated uniform and easily controllable high-temperature fields within the intracranial cavity. There was little change in temperature near or in the cranium itself. Six cases of human malignant glioma were treated with this interstitial RF hyperthermia system, achieving therapeutic temperature without adverse effects. PMID:7687034

  4. Self-compensated standing wave probe for characterization of radio-frequency plasmas.

    PubMed

    Sung, Ta-Lun; Matsumura, Shosaku; Teii, Kungen; Teii, Shinriki

    2014-06-01

    A simple self-compensated Langmuir probe using the character of a standing wave is developed for characterization of radio-frequency (RF) discharge plasmas. This probe is based on a concept that the interference of RF field is eliminated at the node of a standing wave which exists ideally at one-fourth of the RF wavelength (?/4) away from the probe tip in the plasma. The fluctuation of plasma space potential is suppressed as confirmed by comparison with a non-compensated probe and a self-compensated probe using an inductor-capacitor (LC) resonant circuit. The plasma parameters obtained with the standing wave probe are in agreement with those with the LC resonant probe within discrepancy of 15% indicating high reliability of the results. PMID:24985819

  5. Ultra-sensitive high-density Rb-87 radio-frequency magnetometer

    SciTech Connect

    Savukov, I.; Boshier, M. G. [Los Alamos National Laboratory, Los Alamos, New Mexico 87545 (United States); Karaulanov, T. [CNLS - Los Alamos National Laboratory, Los Alamos, New Mexico 87545 (United States)

    2014-01-13

    Radio-frequency (RF) atomic magnetometers (AMs) can be used in many applications, such as magnetic resonance imaging and nuclear quadrupole resonance. High-density AMs provide both superior sensitivity and large bandwidth. Previously, high-density potassium AMs were demonstrated, but these magnetometers have various disadvantages, such as high-temperature of operation and bulky design. We demonstrate a rubidium-87 RF AM with 5 fT/Hz{sup 1/2} sensitivity (3 fT Hz{sup 1/2} probe noise), which is comparable to that of the best potassium magnetometers. Our magnetometer also features a simple fiber-optic design, providing maximum flexibility for magnetic-field measurements.

  6. Scientific basis for the Soviet and Russian radiofrequency standards for the general public.

    PubMed

    Repacholi, Michael; Grigoriev, Yuri; Buschmann, Jochen; Pioli, Claudio

    2012-12-01

    The former Soviet Union (USSR) and the USA were the first countries to introduce standards limiting exposure to radiofrequency (RF) fields. However, the exposure limits in the USSR standards were always much lower than those in the USA and other countries. The objective of this article is to provide a history of the development of the Soviet and Russian RF standards. In addition, we summarize the scientific evidence used to develop the original USSR RF and subsequent Russian public health standards, as well as the mobile telecommunications standard published in 2003, but we do not critique them. We also describe the protective approaches used by the Soviet and Russian scientists for setting their limits. A translation of the papers of the key studies used to develop their standards is available in the online version of this publication. PMID:22753071

  7. Spatial distribution of the plasma parameters in a radio-frequency driven negative ion source

    NASA Astrophysics Data System (ADS)

    Todorov, D.; Tarnev, Kh.; Paunska, Ts.; Lishev, St.; Shivarova, A.

    2014-02-01

    Results from initial stage of modeling of the SPIDER source of negative hydrogen/deuterium ions currently under development in Consorzio RFX (Padova) regarding ITER are presented. A 2D model developed within the fluid plasma theory for low-pressure discharges (free-fall regime maintenance) is applied to the gas-discharge conditions planned and required for the SPIDER source: gas pressure of 0.3 Pa and radio-frequency (rf) power of 100 kW absorbed in a single driver. The results are for the spatial distribution of the plasma characteristics (charged particle densities, electron temperature and electron energy flux, plasma potential, and dc electric field) with conclusions for the role of the electron energy flux in the formation of the discharge structure.

  8. Spatial distribution of the plasma parameters in a radio-frequency driven negative ion source.

    PubMed

    Todorov, D; Tarnev, Kh; Paunska, Ts; Lishev, St; Shivarova, A

    2014-02-01

    Results from initial stage of modeling of the SPIDER source of negative hydrogen/deuterium ions currently under development in Consorzio RFX (Padova) regarding ITER are presented. A 2D model developed within the fluid plasma theory for low-pressure discharges (free-fall regime maintenance) is applied to the gas-discharge conditions planned and required for the SPIDER source: gas pressure of 0.3 Pa and radio-frequency (rf) power of 100 kW absorbed in a single driver. The results are for the spatial distribution of the plasma characteristics (charged particle densities, electron temperature and electron energy flux, plasma potential, and dc electric field) with conclusions for the role of the electron energy flux in the formation of the discharge structure. PMID:24593544

  9. Improved fluid simulations of radio-frequency plasmas using energy dependent ion mobilities

    SciTech Connect

    Greb, Arthur; Niemi, Kari; O'Connell, Deborah; Gans, Timo [York Plasma Institute, Department of Physics, University of York, York YO10 5DD (United Kingdom)] [York Plasma Institute, Department of Physics, University of York, York YO10 5DD (United Kingdom); Ennis, Gerard J.; MacGearailt, Niall [Intel Ireland Ltd., Leixlip (Ireland)] [Intel Ireland Ltd., Leixlip (Ireland)

    2013-05-15

    Symmetric and asymmetric capacitively coupled radio-frequency plasmas in oxygen at 40 Pa, 300 V voltage amplitude and a discharge gap of 40 mm are investigated by means of one-dimensional numerical semi-kinetic fluid modeling on the basis of a simplified reaction scheme including the dominant positive and negative ions, background gas, and electrons. An improved treatment, by accounting for the dependence of ion mobilities on E/N, is compared to the standard approach, based on using zero-field mobility values only. The charged particle dynamics as a result of direct electron impact ionization of oxygen, secondary electron release from the electrodes, the spatial distribution of all involved particles as well as impact of geometry and model modification on ion energies is analyzed and compared to independent simulations and experiments.

  10. Comparison of Two Techniques for Radio-frequency Hepatic Tumor Ablation through Numerical Simulation

    NASA Astrophysics Data System (ADS)

    Kosturski, N.; Margenov, S.; Vutov, Y.

    2011-11-01

    We simulate the thermal and electrical processes, involved in the radio-frequency ablation procedure. In this study, we take into account the observed fact, that the electrical conductivity of the hepatic tissue varies during the procedure. With the increase of the tissue temperature to a certain level, a sudden drop of the electrical conductivity is observed. This variation was neglected in some previous studies. The mathematical model consists of two parts—electrical and thermal. The energy from the applied AC voltage is determined first, by solving the Laplace equation to find the potential distribution. After that, the electric field intensity and the current density are directly calculated. Finally, the heat transfer equation is solved to determine the temperature distribution. Heat loss due to blood perfusion is also accounted for. The simulations were performed on the IBM Blue Gene/P massively parallel computer.

  11. The radio-frequency design of an iris-type coupler for the CPHS radio-frequency quadrupole

    NASA Astrophysics Data System (ADS)

    Xiong, Zheng-Feng; Zheng, Shu-Xin; Xing, Qing-Zi; Guan, Xia-Ling

    2012-01-01

    The Compact Pulsed Hadron Source (CPHS) project is a university-based proton accelerator platform (13 MeV, 16 kW, 50 mA peak current, 0.5 ms pulse width at 50 Hz) for multi-disciplinary neutron and proton applications. The CPHS linac consists of a 3 MeV radio-frequency quadrupole (RFQ) linac and a 13 MeV drift tube linac (DTL). Both the RFQ and DTL share a 325 MHz, 2.1 MW klystron source. A single iris-type radio-frequency (RF) coupler is used to feed 537 kW of RF power to the RFQ cavity. Three-dimensional electromagnetic models of the ridge-loaded tapered waveguide (RLWG) and the coupler-cavity system are presented, and the design process and results of the RLWG and iris plate are described in detail.

  12. Radiofrequency susceptibility tests on medical equipment

    Microsoft Academic Search

    Kok-Swang Tan; Irwin Hinberg

    1994-01-01

    The most recent problems of electromagnetic interference (EMI) with medical equipment arise from the widespread use of portable cellular phones and two-way radios in critical care areas of hospitals. The Medical Devices Bureau has studied the effects of radiated electric fields on eight different types of monitoring and therapeutic medical equipment over the frequency range of 1 MHz-2000 MHz. The

  13. Adaptive radiofrequency hyperthermia-phased array system for improved cancer therapy: phantom target measurements.

    PubMed

    Fenn, A J; King, G A

    1994-01-01

    A computer-controlled adaptive radio-frequency hyperthermia system for improved therapeutic tumour heating is experimentally investigated. Adaptive array feedback techniques are used to modify the electric-field and temperature distribution in hyperthermia experiments with homogeneous and heterogeneous phantom targets. A commercial hyperthermia phased-array antenna system at the SUNY Health Science Center in Syracuse, New York, has been modified to implement adaptive nulling and adaptive focusing algorithms. The hyperthermia system is the BSD Medical Corporation Model BSD-2000 with Sigma-60 annular phased-array antenna applicator. The transmit phased array system is made adaptive by software modifications which invoke a gradient-search feedback algorithm. The gradient-search algorithm implements the method of steepest descent for adaptive nulling (power minimization) and the method of steepest ascent for adaptive focusing (power maximization). The feedback signals are provided by electric-field short-dipole probe antennas. With an adaptive hyperthermia array using real-time measured data, it may be possible to maximize the applied electric field at a tumour position in a complex scattering target body and simultaneously minimize or reduce the electric field at target positions where undesired high-temperature regions (hot spots) occur. The measured phantom-target data indicate that adaptive nulling can reduce the electric field at one or more target positions while simultaneously focusing the electric field at a deep-seated position within the target. PMID:8064180

  14. Radio frequency electromagnetic fields: mild hyperthermia and safety standards

    Microsoft Academic Search

    John A. D’Andrea; John M. Ziriax; Eleanor R. Adair

    2007-01-01

    This chapter is a short review of literature that serves as the basis for current safe exposure recommendations by ICNIRP (International Commission on Non-Ionizing Radiation Protection, 1998). and the IEEE C95.1 (IEEE Standard for Safety Levels with Respect to Human Exposure to Radio Frequency Electromagnetic Fields, 3kHz to 300GHz, 2005) for exposure to radio frequency electromagnetic radiation (RF-EMF). Covered here

  15. Thermal and physiological responses of rats exposed to 2.45GHz radiofrequency radiation: A comparison of E and H orientation

    Microsoft Academic Search

    M. R. Frei; J. R. Jauchem; J. M. Padilla; J. H. Merritt

    1989-01-01

    Summary Ketamine-anesthetized Sprague-Dawley rats were exposed in both E and H orientations to far-field 2.45-GHz continuous-wave radiofrequency radiation (RFR) at a power density of 60 mW\\/cm2 (whole-body average specific absorption rate of ~ 14 W\\/kg). Intermittent exposures were performed in both orientations in the same animal to repeatedly increase colonic temperature from 38.5 to 39.5° C. Tympanic, subcutaneous (sides toward

  16. CROSS-DISCIPLINARY PHYSICS AND RELATED AREAS OF SCIENCE AND TECHNOLOGY: Radio-Frequency Characteristics of a Printed Rectangular Helix Slow-Wave Structure

    Microsoft Academic Search

    Cheng-Fang Fu; Yan-Yu Wei; Wen-Xiang Wang; Yu-Bin Gong

    2008-01-01

    A new type of printed rectangular helix slow-wave structure (SWS) is investigated using the field-matching method and the electromagnetic integral equations at the boundaries. The radio-frequency characteristics including the dispersion equation and the coupling impedance for transverse antisymmetric (odd) modes of this structure are analysed. The numerical results agree well with the results obtained by the EM simulation software HFSS.

  17. Radiofrequency heating of nanomaterials for cancer treatment: Progress, controversies, and future development

    NASA Astrophysics Data System (ADS)

    Liu, Xiaoming; Chen, Hui-jiuan; Chen, Xiaodong; Alfadhl, Yasir; Yu, Junsheng; Wen, Dongsheng

    2015-03-01

    In recent years, the application of nanomaterials to biological and biomedicine areas has attracted intensive interest. One of the hot topics is the nanomaterial mediated radiofrequency (RF) hyperthermia or ablation, i.e., using RF fields/waves to heat tumor tissues treated with nanomaterials to destroy cancerous cells while minimizing the side-heating effect. However, there are currently many contradictive results reported concerning the heating effect of nanomaterials under a RF field. This paper provided a comprehensive review to nanomaterial mediated RF ablation from both experimental and theoretical aspects. Three heating mechanisms were discussed, i.e., laser heating, magnetic field heating, and electric field heating in RF spectrum, with the focus on the last one. The results showed that while diluted pure metallic nanoparticles could be heated significantly by a laser through the surface plasmon resonance, they cannot be easily heated by a RF electric field. Further studies are proposed focusing on nanoparticle structure and morphology, electromagnetic frequency and localized heating effect to pave the way for future development.

  18. Dielectric supported radio-frequency cavities

    DOEpatents

    Yu, David U. L. (Rancho Palos Verdes, CA); Lee, Terry G. (Cupertino, CA)

    2000-01-01

    A device which improves the electrical and thermomechanical performance of an RF cavity, for example, in a disk-loaded accelerating structure. A washer made of polycrystalline diamond is brazed in the middle to a copper disk washer and at the outer edge to the plane wave transformer tank wall, thus dissipating heat from the copper disk to the outer tank wall while at the same time providing strong mechanical support to the metal disk. The washer structure eliminates the longitudinal connecting rods and cooling channels used in the currently available cavities, and as a result minimizes problems such as shunt impedance degradation and field distortion in the plane wave transformer, and mechanical deflection and uneven cooling of the disk assembly.

  19. Electromagnetic Radiofrequency Radiation Emitted from GSM Mobile Phones Decreases the Accuracy of Home Blood Glucose Monitors.

    PubMed

    Mortazavi, Smj; Gholampour, M; Haghani, M; Mortazavi, G; Mortazavi, Ar

    2014-09-01

    Mobile phones are two-way radios that emit electromagnetic radiation in microwave range. As the number of mobile phone users has reached 6 billion, the bioeffects of exposure to mobile phone radiation and mobile phone electromagnetic interference with electronic equipment have received more attention, globally. As self-monitoring of blood glucose can be a beneficial part of diabetes control, home blood glucose testing kits are very popular. The main goal of this study was to investigate if radiofrequency radiation emitted from a common GSM mobile phone can alter the accuracy of home blood glucose monitors. Forty five female nondiabetic students aged 17-20 years old participated in this study. For Control-EMF group (30 students), blood glucose concentration for each individual was measured in presence and absence of radiofrequency radiation emitted by a common GSM mobile phone (HTC touch, Diamond 2) while the phone was ringing. For Control- Repeat group (15 students), two repeated measurements were performed for each participant in the absence of electromagnetic fields. The magnitude of the changes between glucose levels in two repeated measurements (|?C|) in Control-Repeat group was 1.07 ± 0.88 mg/dl while this magnitude for Control-EMF group was 7.53 ± 4.76 mg/dl (P < 0.001, two-tailed test). To the best of our knowledge, this is the first study to assess the electromagnetic interference in home blood glucose monitors. It can be concluded that electromagnetic interference from mobile phones has an adverse effect on the accuracy of home blood glucose monitors. We suggest that mobile phones should be used at least 50 cm away from home blood glucose monitors. PMID:25505778

  20. Experimental and clinical studies with radiofrequency-induced thermal endometrial ablation for functional menorrhagia

    Microsoft Academic Search

    Jeffrey H. Phipps; B. V. Lewis; Michael V. Prior; Terry Roberts

    1990-01-01

    A method of ablating the endometrium has been introduced into clinical practice that uses radiofrequency electromagnetic energy to heat the endometrium, using a probe inserted through the cervix. Preliminary studies suggest that over 80% of patients treated will develop either amenorrhea or a significant reduction in flow. The advantages of radiofrequency endometrial ablation over laser ablation or resection are the

  1. Synthesis of Spinel Ferrites in Radiofrequency Thermal Plasma Reactor J. Szpvlgyi1,2

    E-print Network

    Gubicza, Jenõ

    Synthesis of Spinel Ferrites in Radiofrequency Thermal Plasma Reactor J. Szépvölgyi1,2 , L. Gál1 in RF thermal plasma conditions. The products were characterized for chemical composition, phase conditions on properties of products were studied in details. Keywords: radiofrequency thermal plasma, spinel

  2. Current trends in treatment of osteoid osteoma with an emphasis on radiofrequency ablation

    Microsoft Academic Search

    Colin P. Cantwell; John Obyrne; Stephen Eustace

    2004-01-01

    This article reviews current trends in the treatment of osteoid osteoma with an emphasis on the evolving use of radiofrequency thermoablation as a primary definitive treatment and for recurrent and residual lesions. In so doing, the article reviews merits and relative disadvantages of both surgical and non-surgical imaging-guided techniques in treatment. Radiofrequency ablation of osteoid osteoma is a highly effective,

  3. Radiofrequency Modification for Inducible and Suspected Pediatric Atrioventricular Nodal Reentry Tachycardia

    Microsoft Academic Search

    Margaret J. Strieper; Patrick Frias; Nick Goodwin; Ginny Huber; Lynn Costello; Ginny Balfour; Robert M. Campbell

    2005-01-01

    Introduction: AV Node Reentry Tachycardia (AVNRT) is the second most common supraventricular tachycardia (SVT) undergoing pediatric radiofrequency ablation behind accessory pathway reentry tachycardias. AVNRT can be difficult to induce during electrophysiology study (EPS) and dual atrioventricular nodal (AVN) pathways physiology may not be demonstrated in young patients.Purpose: This report is the largest single center long term pediatric experience of radiofrequency

  4. Fast radio-frequency amplitude modulation in multiple-quantum magic-angle-spinning nuclear magnetic resonance: Theory and experiments

    E-print Network

    Frydman, Lucio

    Fast radio-frequency amplitude modulation in multiple-quantum magic-angle-spinning nuclear magnetic of this experiment has been the poor efficiency of the radio-frequency pulses used in converting multiple-modulated radio-frequency pulses, and which can yield substantial signal and even resolution enhancements over

  5. Radio-frequency ablation electrode displacement elastography: A phantom study

    PubMed Central

    Bharat, Shyam; Varghese, Tomy; Madsen, Ernest L.; Zagzebski, James A.

    2008-01-01

    This article describes the evaluation of a novel method of tissue displacement for use in the elastographic visualization of radio-frequency (rf) ablation-induced lesions. The method involves use of the radio-frequency ablation electrode as a displacement device, which provides localized compression in the region of interest. This displacement mechanism offers the advantage of easyin vivo implementation since problems such as excessive lateral and elevational displacements present when using external compression are reduced with this approach. The method was tested on a single-inclusion tissue-mimicking phantom containing a radio-frequency ablation electrode rigidly attached to the inclusion center. Full-frame rf echo signals were acquired from the phantom before and after electrode displacements ranging from 0.05 to 0.2 mm. One-dimensional cross-correlation analysis between pre-and postcompression signals was used to measure tissue displacements, and strains were determined by computing the gradient of the displacement. The strain contrast, contrast-to-noise ratio, and signal-to-noise ratio were estimated from the resulting strain images. Comparisons are drawn between the elastographically measured dimensions and those known a priori for the single-inclusion phantom. Electrode displacement elastography was found to slightly underestimate the inclusion dimensions. The method was also tested on a second tissue-mimicking phantom and on in vitro rf-ablated lesions in canine liver tissue. The results validate previous in vivo findings that electrode displacement elastography is an effective method for monitoring rf ablation. PMID:18649476

  6. Nanometer-resolved radio-frequency absorption and heating in biomembrane hydration layers.

    PubMed

    Gekle, Stephan; Netz, Roland R

    2014-05-01

    Radio-frequency (RF) electromagnetic fields are readily absorbed in biological matter and lead to dielectric heating. To understand how RF radiation interacts with macromolecular structures and possibly influences biological function, a quantitative description of dielectric absorption and heating at nanometer resolution beyond the usual effective medium approach is crucial. We report an exemplary multiscale theoretical study for biomembranes that combines (i) atomistic simulations for the spatially resolved absorption spectrum at a single planar DPPC lipid bilayer immersed in water, (ii) calculation of the electric field distribution in planar and spherical cell models, and (iii) prediction of the nanometer resolved temperature profiles under steady RF radiation. Our atomistic simulations show that the only 2 nm thick lipid hydration layer strongly absorbs in a wide RF range between 10 MHz and 100 GHz. The absorption strength, however, strongly depends on the direction of the incident wave. This requires modeling of the electric field distribution using tensorial dielectric spectral functions. For a spherical cell model, we find a strongly enhanced RF absorption on an equatorial ring, which gives rise to temperature gradients inside a single cell under radiation. Although absolute temperature elevation is small under conditions of typical telecommunication usage, our study points to hitherto neglected temperature gradient effects and allows thermal RF effects to be predicted on an atomistically resolved level. In addition to a refined physiological risk assessment of RF fields, technological applications for controlling temperature profiles in nanodevices are possible. PMID:24779642

  7. Radiofrequency ablation for oral and maxillofacial pathologies: A description of the technique

    NASA Astrophysics Data System (ADS)

    Tandon, Rahul; Stevens, Timothy W.; Herford, Alan S.

    2014-03-01

    Introduction: Radiofrequency ablation (RFA) refers to a high-frequency current that heats and coagulates tissue. In the standard RFA setup, three components are used: a generator, an active electrode, and a dispersive electrode. RFA has garnered support in many of the surgical fields as an alternative to traditional procedures used in tumor removal. Other methods can prove to be more invasive and disfiguring to the patient, in addition to the unwarranted side effects; however, RFA provides a more localized treatment, resulting in decreased co-morbidity to the patient. Currently, its use in the field of oral and maxillofacial surgery is limited, as its technology has not reached our field. By describing its limited use to the optics community, we hope to expand its uses and provide patients with one more alternative treatment option. Methods and Uses: We will describe the use of RFA on three types of pathology: lymphangioma, rhabdomyoscarcoma, oral squamous cell carcinoma, and neoplastic osseous metastasis. The majority of treatments geared towards these pathologies involve surgical resection, followed by reconstruction. However, damage to vital structures coupled with esthetic disfigurement makes RFA a more valuable alternative. In many of the cases, the tumors were successfully removed without recurrence. Conclusion: While the use of RFA has been scarce in our field, we believe that with more exposure it can gain momentum as an alternative to current treatment options. However, there are improvements that we feel can be made, helping to maximize its effectiveness.

  8. Rectification of radio-frequency current in a giant-magnetoresistance spin valve

    NASA Astrophysics Data System (ADS)

    Zietek, S?awomir; Ogrodnik, Piotr; Frankowski, Marek; Checi?ski, Jakub; Wi?niowski, Piotr; Skowro?ski, Witold; Wrona, Jerzy; Stobiecki, Tomasz; ?ywczak, Antoni; Barna?, Józef

    2015-01-01

    We report on a highly efficient spin diode effect in exchange-biased spin-valve giant-magnetoresistance (GMR) strips. In such multilayer structures, the symmetry of the current distribution along the vertical direction is broken and, as a result, a noncompensated Oersted field acting on the magnetic free layer appears. This field in turn is a driving force of magnetization precessions. Due to the GMR effect, the resistance of the strip oscillates following the magnetization dynamics. This leads to rectification of the applied radio-frequency current and induces a direct-current voltage Vdc. We present a theoretical description of this phenomenon and calculate the spin diode signal Vdc as a function of frequency, external magnetic field, and angle at which the external field is applied. Satisfactory quantitative agreement between theoretical predictions and experimental data has been achieved. Finally, we show that the spin diode signal in GMR devices is significantly stronger than in the anisotropic magnetoresistance permalloy-based devices.

  9. A Complicated Postsurgical Echinococcal Cyst Treated with Radiofrequency Ablation

    SciTech Connect

    Thanos, L., E-mail: Loutharad@yahoo.com; Mylona, S. [Korgialeneio-Benakeio 'Red Cross Hospital of Athens', Department of Radiology (Greece); Brontzakis, P. [Korgialeneio-Benakeio 'Red Cross Hospital of Athens', Department of Surgery (Greece); Ptohis, N. [Korgialeneio-Benakeio 'Red Cross Hospital of Athens', Department of Radiology (Greece); Karaliotas, K. [Korgialeneio-Benakeio 'Red Cross Hospital of Athens', Department of Surgery (Greece)

    2008-01-15

    Surgery of hydatid cysts is often complicated with intrabiliary rupture (IBR), which if not recognized may lead to biliary fistula with rather high rates of morbidity and mortality. We report our experience with the application of radiofrequency (RF) ablation for the treatment of an operated hepatic echinococcal cyst which was complicated with biliocystic communication and cysteocutaneous fistula with bile leakage. RF ablation was performed under CT guidance into the remaining cyst through the cutaneous fistula. Since ablation of the cyst and the fistula the patient has been asymptomatic.

  10. Pulmonary radiofrequency ablation complicated by acute respiratory distress syndrome.

    PubMed

    Reilly, C; Sato, Kent T

    2011-06-01

    The authors present a case of a patient with rectal adenocarcinoma and lung metastasis undergoing elective radiofrequency (RF) ablation of a large, refractory pulmonary metastasis. The mass was located in the left upper lobe, invading the left hilum. The patient experienced shortness of breath following the procedure and shortly after extubation. This shortness of breath progressed over 4 days, when the patient developed acute respiratory distress syndrome (ARDS). The patient suffered from complications related to respiratory support and expired 9 days after RF ablation. Possible mechanisms of ARDS development following pulmonary ablation are discussed. PMID:22654254

  11. Measuring Radiofrequency and Microwave Radiation from Varying Signal Strengths

    NASA Technical Reports Server (NTRS)

    Davis, Bette; Gaul, W. C.

    2007-01-01

    This viewgraph presentation discusses the process of measuring radiofrequency and microwave radiation from various signal strengths. The topics include: 1) Limits and Guidelines; 2) Typical Variable Standard (IEEE) Frequency Dependent; 3) FCC Standard 47 CFR 1.1310; 4) Compliance Follows Unity Rule; 5) Multiple Sources Contribute; 6) Types of RF Signals; 7) Interfering Radiations; 8) Different Frequencies Different Powers; 9) Power Summing - Peak Power; 10) Contribution from Various Single Sources; 11) Total Power from Multiple Sources; 12) Are You Out of Compliance?; and 13) In Compliance.

  12. Multiplexing of Radio-Frequency Single Electron Transistors

    NASA Technical Reports Server (NTRS)

    Stevenson, Thomas R.; Pellerano, F. A.; Stahle, C. M.; Aidala, K.; Schoelkopf, R. J.; Krebs, Carolyn (Technical Monitor)

    2001-01-01

    We present results on wavelength division multiplexing of radio-frequency single electron transistors. We use a network of resonant impedance matching circuits to direct applied rf carrier waves to different transistors depending on carrier frequency. A two-channel demonstration of this concept using discrete components successfully reconstructed input signals with small levels of cross coupling. A lithographic version of the rf circuits had measured parameters in agreement with electromagnetic modeling, with reduced cross capacitance and inductance, and should allow 20 to 50 channels to be multiplexed.

  13. Probing properties of cold radiofrequency plasma with polymer probe

    NASA Astrophysics Data System (ADS)

    Bormashenko, E.; Chaniel, G.; Multanen, V.; Multanen

    2015-01-01

    The probe intended for the characterization of cold plasma is introduced. The probe allows the estimation of Debye length of cold plasma. The probe is based on the pronounced modification of surface properties (wettability) of polymer films by cold plasmas. The probe was tested with the cold radiofrequency inductive air plasma discharge. The Debye length and the concentration of charge carriers were estimated for various gas pressures. The reported results coincide reasonably with the corresponding values established by other methods. The probe makes possible measurement of characteristics of cold plasmas in closed chambers.

  14. Method and apparatus for cartilage reshaping by radiofrequency heating

    DOEpatents

    Wong, Brian J.; Milner, Thomas E.; Sobol, Emil N.; Keefe, Michael W.

    2003-07-08

    A method and apparatus for reshaping cartilage using radiofrequency heating. The cartilage temperature is raised sufficiently for stress relaxation to occur in the cartilage, but low enough so that significant denaturation of the cartilage does not occur. The RF electrodes may be designed to also function as molds, preses, clamps, or mandrills to deform the cartilage tissue. Changes in various properties of the cartilage associated with stress relaxation in the cartilage may be measured in order to provide the control signal to provide effective reshaping without denaturation.

  15. Black Phosphorus Radio-Frequency Transistors

    NASA Astrophysics Data System (ADS)

    Wang, Han; Wang, Xiaomu; Xia, Fengnian; Wang, Luhao; Jiang, Hao; Xia, Qiangfei; Chin, Matthew L.; Dubey, Madan; Han, Shu-jen

    2014-11-01

    Few-layer and thin film forms of layered black phosphorus (BP) have recently emerged as a promising material for applications in high performance nanoelectronics and infrared optoelectronics. Layered BP thin film offers a moderate bandgap of around 0.3 eV and high carrier mobility, leading to transistors with decent on-off ratio and high on-state current density. Here, we demonstrate the gigahertz frequency operation of black phosphorus field-effect transistors for the first time. The BP transistors demonstrated here show excellent current saturation with an on-off ratio exceeding 2000. We achieved a current density in excess of 270 mA/mm and DC transconductance above 180 mS/mm for hole conduction. Using standard high frequency characterization techniques, we measured a short-circuit current-gain cut-off frequency fT of 12 GHz and a maximum oscillation frequency fmax of 20 GHz in 300 nm channel length devices. BP devices may offer advantages over graphene transistors for high frequency electronics in terms of voltage and power gain due to the good current saturation properties arising from their finite bandgap, thus enabling the future ubiquitous transistor technology that can operate in the multi-GHz frequency range and beyond.

  16. Black phosphorus radio-frequency transistors.

    PubMed

    Wang, Han; Wang, Xiaomu; Xia, Fengnian; Wang, Luhao; Jiang, Hao; Xia, Qiangfei; Chin, Matthew L; Dubey, Madan; Han, Shu-jen

    2014-11-12

    Few-layer and thin film forms of layered black phosphorus (BP) have recently emerged as a promising material for applications in high performance nanoelectronics and infrared optoelectronics. Layered BP thin films offer a moderate bandgap of around 0.3 eV and high carrier mobility, which lead to transistors with decent on-off ratios and high on-state current densities. Here, we demonstrate the gigahertz frequency operation of BP field-effect transistors for the first time. The BP transistors demonstrated here show respectable current saturation with an on-off ratio that exceeds 2 × 10(3). We achieved a current density in excess of 270 mA/mm and DC transconductance above 180 mS/mm for hole conduction. Using standard high frequency characterization techniques, we measured a short-circuit current-gain cutoff frequency fT of 12 GHz and a maximum oscillation frequency fmax of 20 GHz in 300 nm channel length devices. BP devices may offer advantages over graphene transistors for high frequency electronics in terms of voltage and power gain due to the good current saturation properties arising from their finite bandgap, thus can be considered as a promising candidate for the future high performance thin film electronics technology for operation in the multi-GHz frequency range and beyond. PMID:25347787

  17. Ionizing and Non-Ionizing Radiation

    MedlinePLUS

    ... radiation: alpha particles , which include two protons and two neutrons beta particles , which are essentially high-speed electrons gamma rays and x-rays, which are pure energy (photons). Nuclides and Isotopes This page explains how changes ...

  18. Evaluation of the co-genotoxic effects of 1800 MHz GSM radiofrequency exposure and a chemical mutagen in cultured human cells

    NASA Astrophysics Data System (ADS)

    Perrin, Anne; Freire, Maëlle; Bachelet, Christine; Collin, Alice; Levêque, Philippe; Pla, Simon; Debouzy, Jean-Claude

    2010-11-01

    We investigated the effect of a 1800 MHz radiofrequency GSM signal combined with a known chemical mutagen (4-nitroquinoline-N-oxide: 4NQO) on human THP1 cells. Comet and ?-H2AX assays were used to assess DNA damage. No heating of the cell cultures was noted during exposure (2 h). The exposure of cells to electromagnetic fields with SARs of 2 to 16 W/kg did not increase the DNA damage induced by 4NQO, whereas the number of DNA strand breaks increased with a temperature increase of at least 4 °C. In conclusion, no co-genotoxic effect of radiofrequency was found at levels of exposure that did not induce heating.

  19. Percutaneous plasma mediated radiofrequency ablation of spinal osteoid osteomas.

    PubMed

    Dasenbrock, Hormuzdiyar H; Gandhi, Dheeraj; Kathuria, Sudhir

    2012-05-01

    Plasma mediated radiofrequency ablation (pmRFA) may allow for the percutaneous treatment of spinal tumors with a decreased risk of thermal injury to neural structures compared with traditional (radiofrequency or interstitial laser) ablation. However, usage of pmRFA has not been previously reported for a primary bone tumor, including an osteoid osteoma. Three patients with a spinal osteoid osteoma underwent pmRFA. The procedure was performed under computed tomography guidance using the 11 gauge Coblation SpineWand (ArthroCare). One lesion (at T11) was directly abutting the spinal canal. With an average follow-up of 20.7 (range 16-24) months, the mean Visual Analog Scale score for back pain decreased from 8.67 to 0.67 and no patient experienced tumor recurrence. pmRFA of spinal osteoid osteomas is feasible, even when the tumor is abutting the spinal canal. Larger studies with a longer follow-up are needed to further delineate the safety and efficacy of this technique. PMID:21990513

  20. Mathematical modeling of radiofrequency ablation for varicose veins.

    PubMed

    Choi, Sun Young; Kwak, Byung Kook; Seo, Taewon

    2014-01-01

    We present a three-dimensional mathematical model for the study of radiofrequency ablation (RFA) with blood flow for varicose vein. The model designed to analyze temperature distribution heated by radiofrequency energy and cooled by blood flow includes a cylindrically symmetric blood vessel with a homogeneous vein wall. The simulated blood velocity conditions are U = 0, 1, 2.5, 5, 10, 20, and 40 mm/s. The lower the blood velocity, the higher the temperature in the vein wall and the greater the tissue damage. The region that is influenced by temperature in the case of the stagnant flow occupies approximately 28.5% of the whole geometry, while the region that is influenced by temperature in the case of continuously moving electrode against the flow direction is about 50%. The generated RF energy induces a temperature rise of the blood in the lumen and leads to an occlusion of the blood vessel. The result of the study demonstrated that higher blood velocity led to smaller thermal region and lower ablation efficiency. Since the peak temperature along the venous wall depends on the blood velocity and pullback velocity, the temperature distribution in the model influences ablation efficiency. The vein wall absorbs more energy in the low pullback velocity than in the high one. PMID:25587351

  1. Percutaneous bipolar radiofrequency microdebridement for recalcitrant proximal plantar fasciosis.

    PubMed

    Sorensen, Matthew D; Hyer, Christopher F; Philbin, Terrence M

    2011-01-01

    Success rates for traditional methods of surgical intervention for chronic plantar fasciosis are low, and associated with high rates of complications and long recovery times. The purpose of this prospective case series was to assess the effectiveness of percutaneous bipolar radiofrequency microfasciotomy for the treatment of recalcitrant proximal plantar fasciosis in 21 patients. The mean preoperative American Orthopaedic Foot & Ankle Society (AOFAS) hindfoot score was 22.10 ± 12.96 (out of a possible 68 points) and the mean postoperative AOFAS hindfoot score was 59.57 ± 13.23 points, and this difference was statistically significant (P < .0001). A total of 7 (33.33%) patients experienced satisfactory pain relief within 1 to 4 weeks and 10 (47.62%) did so within 1 to 4 months, whereas 2 (9.52%) patients required longer than 4 months, and 2 (9.52%) others never attained satisfactory relief of symptoms. Fourteen (66.67%) patients subjectively rated their outcome as excellent, 4 (19.05%) as good, 1 (4.76%) as fair, and 2 (9.52%) as poor. One (4.76%) patient experienced iatrogenic flexor hallucis longus tendonitis. The results of this clinical investigation indicate that bipolar radiofrequency microdebridement plantar fasciotomy safely alleviates recalcitrant heel pain. The technique is minimally invasive and simple to perform, and it spares the overall integrity of the plantar fascia without being associated with undue complications. PMID:21354000

  2. Mathematical Modeling of Radiofrequency Ablation for Varicose Veins

    PubMed Central

    Choi, Sun Young; Kwak, Byung Kook

    2014-01-01

    We present a three-dimensional mathematical model for the study of radiofrequency ablation (RFA) with blood flow for varicose vein. The model designed to analyze temperature distribution heated by radiofrequency energy and cooled by blood flow includes a cylindrically symmetric blood vessel with a homogeneous vein wall. The simulated blood velocity conditions are U = 0, 1, 2.5, 5, 10, 20, and 40?mm/s. The lower the blood velocity, the higher the temperature in the vein wall and the greater the tissue damage. The region that is influenced by temperature in the case of the stagnant flow occupies approximately 28.5% of the whole geometry, while the region that is influenced by temperature in the case of continuously moving electrode against the flow direction is about 50%. The generated RF energy induces a temperature rise of the blood in the lumen and leads to an occlusion of the blood vessel. The result of the study demonstrated that higher blood velocity led to smaller thermal region and lower ablation efficiency. Since the peak temperature along the venous wall depends on the blood velocity and pullback velocity, the temperature distribution in the model influences ablation efficiency. The vein wall absorbs more energy in the low pullback velocity than in the high one. PMID:25587351

  3. Density-Dependent Response of an Ultracold Plasma to Few-Cycle Radio-Frequency Pulses

    E-print Network

    Wilson, Truman; Roberts, Jacob

    2012-01-01

    Ultracold neutral plasmas exhibit a density-dependent resonant response to applied radio-frequency (RF) fields in the frequency range of several MHz to hundreds of MHz for achievable densities. We have conducted measurements where short bursts of RF were applied to these plasmas, with pulse durations as short as two cycles. We still observed a density-dependent resonant response to these short pulses. However, the too rapid timescale of the response, the dependence of the response on the sign of the driving field, the response as the number of pulses was increased, and the difference in plasma response to radial and axially applied RF fields are inconsistent with the plasma response being due to local resonant heating of electrons in the plasma. Instead, our results are consistent with rapid energy transfer from collective motion of the entire electron cloud to electrons in high-energy orbits. In addition to providing a potentially more robust way to measure ultracold neutral plasma densities, these measureme...

  4. Experimental simulation of beam propagation over long path lengths using radio-frequency and magnetic traps

    NASA Astrophysics Data System (ADS)

    Okamoto, H.; Endo, M.; Fukushima, K.; Higaki, H.; Ito, K.; Moriya, K.; Yamaguchi, S.; Lund, S. M.

    2014-01-01

    An overview is given of the novel beam-dynamics experiments based on compact non-neutral plasma traps at Hiroshima University. We have designed and constructed two different classes of trap systems, one of which uses a radio-frequency electric field (Paul trap) and the other uses an axial magnetic field (Penning trap) for transverse plasma confinement. These systems are called "S-POD" (Simulator for Particle Orbit Dynamics). The S-POD systems can approximately reproduce the collective motion of a charged-particle beam propagating through long alternating-gradient (AG) quadrupole focusing channels using the Paul trap and long continuous focusing channels using the Penning trap. This allows us to study various beam-dynamics issues in compact and inexpensive experiments without relying on large-scale accelerators. So far, the linear Paul traps have been applied for the study of resonance-related issues including coherent-resonance-induced stop bands and their dependence on AG lattice structures, resonance crossing in fixed-field AG accelerators, ultralow-emittance beam stability, etc. The Penning trap with multi-ring electrodes has been employed primarily for the study of beam halo formation driven by initial distribution perturbations. In this paper, we briefly overview the S-POD systems, and then summarize recent experimental results on resonance effects and halo formation.

  5. On the imaging of radio-frequency electromagnetic data forcross-borehole mineral exploration

    NASA Astrophysics Data System (ADS)

    Yu, L.; Chouteau, M.; Boerner, D. E.; Wang, J.

    1998-11-01

    Radio-frequency (typically from 0.1 to 20 MHz) electromagneti c methods are powerful tools for locating conductive mineralization in ore exploration and mine development. Yet data interpretation is complicated by the non-linear relationship between the observed electric and magnetic fields and the electrical parameters of the Earth. The principal means of quantifying inversion capabilities is to compute synthetic data sets using accurate numerical models and to perform the inversion under controlled conditions. Our specific interest is in locating 3-D bodies that are highly conductive relative to the host rock. An excellent approximation for this class of targets, at least at radio frequencies, is to assume that the bodies are infinitely conductive. The numerical advantage of this assumption is that inhomogeneities can be represented simply as internal boundaries where the total electric and magnetic fields are identically equal to zero. Ensuring numerical stability thus does not require excessive discretization in conductive regions since the maximum grid cell size is determined only by the electrical parameters of the host material. We use a finite-difference time-domain approach to compute the total electric and magnetic fields everywhere within the background medium and validate the code by comparisons with two analytical solutions. One common means of interpreting radio-frequency electromagnetic data is to assume linearity between the model parameters and physical response and to apply tomographic image reconstruction methods. While relatively simple and inexpensive, the limitations and applicability of tomographic imaging methods to non-linear electromagnetic data acquired in complicated, 3-D mineral exploration environments are not well understood. Our initial study involves applying the simultaneous iterative reconstruction technique to recover images of the electrical properties of a conductive inclusion. Several examples show that the structural geometry of bodies between boreholes can be reliably imaged using both frequency-doma in and time-domain data. Phase data seem more amenable to recovering geometry information from tomographic reconstruction methods than amplitude data. However, attenuation data provide better constraints on the electrical properties of the geological media and thus form an essential complement to primarily geometrical information obtained from phase tomography. Non-linear inversion methods will probably be required to incorporate the amplitude data for accurate reconstructions of the subsurface.

  6. The Biological Effects of Quadripolar Radiofrequency Sequential Application: A Human Experimental Study

    PubMed Central

    Cornaglia, Antonia Icaro; Faga, Angela; Scevola, Silvia

    2014-01-01

    Abstract Objective: An experimental study was conducted to assess the effectiveness and safety of an innovative quadripolar variable electrode configuration radiofrequency device with objective measurements in an ex vivo and in vivo human experimental model. Background data: Nonablative radiofrequency applications are well-established anti-ageing procedures for cosmetic skin tightening. Methods: The study was performed in two steps: ex vivo and in vivo assessments. In the ex vivo assessments the radiofrequency applications were performed on human full-thickness skin and subcutaneous tissue specimens harvested during surgery for body contouring. In the in vivo assessments the applications were performed on two volunteer patients scheduled for body contouring surgery at the end of the study. The assessment methods were: clinical examination and medical photography, temperature measurement with thermal imaging scan, and light microscopy histological examination. Results: The ex vivo assessments allowed for identification of the effective safety range for human application. The in vivo assessments allowed for demonstration of the biological effects of sequential radiofrequency applications. After a course of radiofrequency applications, the collagen fibers underwent an immediate heat-induced rearrangement and were partially denaturated and progressively metabolized by the macrophages. An overall thickening and spatial rearrangement was appreciated both in the collagen and elastic fibers, the latter displaying a juvenile reticular pattern. A late onset in the macrophage activation after sequential radiofrequency applications was appreciated. Conclusions: Our data confirm the effectiveness of sequential radiofrequency applications in obtaining attenuation of the skin wrinkles by an overall skin tightening. PMID:25244081

  7. Chronic incomplete atrioventricular block induced by radiofrequency catheter ablation

    SciTech Connect

    Huang, S.K.; Bharati, S.; Graham, A.R.; Gorman, G.; Lev, M. (Tucson Veterans Administration Medical Center, AZ (USA))

    1989-10-01

    To determine if catheter ablation of the atrioventricular (AV) junction with radiofrequency energy can induce chronic incomplete (first- and second-degree) AV block to avoid the need for a permanent pacemaker, 20 closed-chest dogs were studied. Group 1 (10 dogs) received radiofrequency energy (750 kHz) with a fixed power setting (5 or 10 W) while increasing the pulse duration from 10 to 50 seconds for each application. Group 2 (10 dogs) received energy with a fixed pulse duration (20 or 30 seconds) while increasing the power setting from 5 to 10 W or from 10 to 20 W during each energy delivery. Radiofrequency energy was delivered between a chest-patch electrode and the distal electrode of a regular 7F tripolar His bundle catheter. For each application, the energy delivery was interrupted when (1) the PR interval prolonged (greater than 50%) or (2) second-degree or complete AV block occurred and persisted up to 5 seconds. The ablation procedure ended when there was (1) persistent PR prolongation (greater than 50%) or persistent second-degree AV block (lasting greater than 30 minutes) after ablation, (2) occurrence of two consecutive transient (less than 1 minute) complete AV blocks after each energy delivery, or (3) complete AV block (lasting greater than 2 minutes) after ablation. Of seven dogs in group 1 and five dogs in group 2 in which incomplete AV block was achieved 1 hour after the procedure, six in group 1 and five in group 2 remained in incomplete AV block 2-3 months after ablation. One dog in group 1 progressed into complete AV block. Of the remaining three dogs in group 1 and five dogs in group 2 in which complete AV block was initially achieved 1 hour after ablation, two in group 1 and four in group 2 continued to have complete AV block, whereas one in each group had AV conduction returned to incomplete at 1-2 months of follow-up.

  8. Health implications of exposure to radiofrequency/microwave energies

    PubMed Central

    Michaelson, S M

    1982-01-01

    ABSTRACT The rapid development of and the increase in the number and variety of devices that emit microwave/radiofrequency (MW/RF) energies has resulted in a growing interest regarding the potential effects on health of these energies. The frequency ranges considered in this review are: 300 kHz to 300 MHz (radiofrequency) and 300 MHz to 300 GHz (microwaves). Investigations have shown that exposure to certain power densities for several minutes or hours can result in pathophysiological manifestations in laboratory animals. Such effects may or may not be characterised by a measurable rise in temperature, which is a function of thermal regulatory processes and active adaptation by the animal. The end result is either a reversible or irreversible change, depending on the irradiation conditions and the physiological state of the animal. At lower power densities, evidence of pathological changes or physiological alteration is non-existent or equivocal. Much discussion, nevertheless, has taken place on the relative importance of thermal or non-thermal effects of radiofrequency and microwave radiation. Several retrospective studies have been done on human populations exposed or believed to have been exposed to MW/RF energies. Those performed in the US have not shown any relationship of altered morbidity or mortality to MW/RF exposure. Reactions referrable to the central nervous system and cardiovascular effects from exposure of man to microwave energy have been reported mostly in Eastern European publications. Individuals suffering from various ailments or psychological factors may exhibit the same dysfunctions of the central nervous and cardiovascular systems as those reported to result from exposure to MW/RF; thus it is extremely difficult, if not impossible, to rule out other factors in attempting to relate MW/RF exposure to clinical conditions. There is a need to set limits on the amount of exposure to MW/RF energies that individuals can accept with safety. Operative protection standards have apparently provided adequate safety to workers and the general population to permit the use of MW/RF energies without harm or detriment. PMID:7039662

  9. Intradiscal pulsed radiofrequency application following provocative discography for the management of degenerative disc disease and concordant pain: a pilot study.

    PubMed

    Rohof, Olav

    2012-06-01

    The development of diagnostic criteria and the use of provocative discography allow identifying the degenerative disc as causative structure for chronic low-back pain. Unfortunately, none of the available interventional treatment options have been demonstrated to be effective over a prolonged period of time for a considerable number of patients. Pathophysiological studies indicate sprouting of sensory nerves and inflammatory processes as underlying pain mechanisms. Pulsed radiofrequency (PRF) treatment in small and larger joints was described to reduce pain and improve healing by stimulating the immunology. Earlier findings of PRF applied in the disc annulus were promising. It is assumed that PRF applied in the nucleus would change the conductivity of nerve endings and provide a clinically relevant pain reduction. The application of the electric field of PRF in the disc may also activate the immune system, thus reducing the inflammation process of chronic pain. Pulsed radiofrequency in the nucleus was studied in 76 patients with discogenic pain confirmed by magnetic resonance imaging and provocative discography. At 3-month follow-up, 38% of the patients had > 50% pain reduction, at 12 month the effect is maintained in 29%. In patients with unsatisfactory pain relief 3 months after the intervention, secondary pain sources may have been revealed. The latter were treated accordingly. Of all patients, 56% had > 50% pain reduction 1 year after first treatment. Our findings suggest that PRF in the nucleus may be considered for patients with proven discogenic pain. A randomized controlled trial to confirm our findings is justified.? PMID:22008239

  10. First-principles calculations of niobium hydride formation in superconducting radio-frequency cavities

    NASA Astrophysics Data System (ADS)

    Ford, Denise C.; Cooley, Lance D.; Seidman, David N.

    2013-09-01

    Niobium hydride is suspected to be a major contributor to degradation of the quality factor of niobium superconducting radio-frequency (SRF) cavities. In this study, we connect the fundamental properties of hydrogen in niobium to SRF cavity performance and processing. We modeled several of the niobium hydride phases relevant to SRF cavities and present their thermodynamic, electronic, and geometric properties determined from calculations based on density functional theory. We find that the absorption of hydrogen from the gas phase into niobium is exothermic and hydrogen becomes somewhat anionic. The absorption of hydrogen by niobium lattice vacancies is strongly preferred over absorption into interstitial sites. A single vacancy can accommodate six hydrogen atoms in the symmetrically equivalent lowest energy sites and additional hydrogen in the nearby interstitial sites affected by the strain field: this indicates that a vacancy can serve as a nucleation center for hydride phase formation. Small hydride precipitates may then occur near lattice vacancies upon cooling. Vacancy clusters and extended defects should also be enriched in hydrogen, potentially resulting in extended hydride phase regions upon cooling. We also assess the phase changes in the niobium-hydrogen system based on charge transfer between niobium and hydrogen, the strain field associated with interstitial hydrogen, and the geometry of the hydride phases. The results of this study stress the importance of not only the hydrogen content in niobium, but also the recovery state of niobium for the performance of SRF cavities.

  11. Radio-frequency sheaths physics: Experimental characterization on Tore Supra and related self-consistent modeling

    SciTech Connect

    Jacquot, Jonathan; Colas, Laurent, E-mail: laurent.colas@cea.fr; Corre, Yann; Goniche, Marc; Gunn, Jamie; Kubi?, Martin [CEA, IRFM, F-13108 saint-Paul-Lez-Durance (France); Milanesio, Daniele [Department of Electronics Politecnico di Torino, Torino (Italy); Heuraux, Stéphane [IJL UMR 7198, U. de Lorraine P2M, Fac. Des Sciences, BP 70239, F-54506 Vandoeuvre Cedex (France)

    2014-06-15

    During the 2011 experimental campaign, one of the three ion cyclotron resonance heating (ICRH) antennas in the Tore Supra tokamak was equipped with a new type of Faraday screen (FS). The new design aimed at minimizing the integrated parallel electric field over long field lines as well as increasing the heat exhaust capability of the actively cooled screen. It proved to be inefficient for attenuating the radio-frequency (RF)-sheaths on the screen itself on the contrary to the heat exhaust concept that allowed operation despite higher heat fluxes on the antenna. In parallel, a new approach has been proposed to model self-consistently RF sheaths: the SSWICH (Self-consistent Sheaths and Waves for IC Heating) code. Simulations results from SSWICH coupled with the TOPICA antenna code were able to reproduce the difference between the two FS designs and part of the spatial pattern of heat loads and Langmuir probe floating potential. The poloidal pattern is a reliable result that mainly depends on the electrical design of the antenna while the radial pattern is on the contrary highly sensitive to loosely constrained parameters such as perpendicular conductivity that generates a DC current circulation from the private region inside the antenna limiters to the free scrape off layer outside these limiters. Moreover, the cantilevered bars seem to be the element in the screen design that enhanced the plasma potential.

  12. First-principles calculations of niobium hydride formation in superconducting radio-frequency cavities

    SciTech Connect

    Ford, Denise C.; Cooley, Lance D.; Seidman, David N.

    2013-09-01

    Niobium hydride is suspected to be a major contributor to degradation of the quality factor of niobium superconducting radio-frequency (SRF) cavities. In this study, we connect the fundamental properties of hydrogen in niobium to SRF cavity performance and processing. We modeled several of the niobium hydride phases relevant to SRF cavities and present their thermodynamic, electronic, and geometric properties determined from calculations based on density-functional theory. We find that the absorption of hydrogen from the gas phase into niobium is exothermic and hydrogen becomes somewhat anionic. The absorption of hydrogen by niobium lattice vacancies is strongly preferred over absorption into interstitial sites. A single vacancy can accommodate six hydrogen atoms in the symmetrically equivalent lowest-energy sites and additional hydrogen in the nearby interstitial sites affected by the strain field: this indicates that a vacancy can serve as a nucleation center for hydride phase formation. Small hydride precipitates may then occur near lattice vacancies upon cooling. Vacancy clusters and extended defects should also be enriched in hydrogen, potentially resulting in extended hydride phase regions upon cooling. We also assess the phase changes in the niobium-hydrogen system based on charge transfer between niobium and hydrogen, the strain field associated with interstitial hydrogen, and the geometry of the hydride phases. The results of this study stress the importance of not only the hydrogen content in niobium, but also the recovery state of niobium for the performance of SRF cavities.

  13. Survey of ambient electromagnetic and radio-frequency interference levels in nuclear power plants

    SciTech Connect

    Kercel, S.W.; Moore, M.R.; Blakeman, E.D.; Ewing, P.D.; Wood, R.T.

    1996-11-01

    This document reports the results of a survey of ambient electromagnetic conditions in representative nuclear power plants. The U.S. Nuclear Regulatory Commission (NRC) Office of Nuclear Regulatory Research engaged the Oak Ridge National Laboratory (ORNL) to perform these measurements to characterize the electromagnetic interference (EMI) and radio-frequency interference (RFI) levels that can be expected in nuclear power plant environments. This survey is the first of its kind, being based on long-term unattended observations. The data presented in this report were measured at eight different nuclear units and required 14 months to collect. A representative sampling of power plant conditions (reactor type, operating mode, site location) monitored over extended observation periods (up to 5 weeks) were selected to more completely determine the characteristic electromagnetic environment for nuclear power plants. Radiated electric fields were measured over the frequency range of 5 MHz to 8 GHz. Radiated magnetic fields and conducted EMI events were measured over the frequency range of 305 Hz to 5 MHz. Highest strength observations of the electromagnetic ambient environment across all measurement conditions at each site provide frequency-dependent profiles for EMI/RFI levels in nuclear power plants.

  14. Modeling of EEG electrode artifacts and thermal ripples in human radiofrequency exposure studies.

    PubMed

    Murbach, Manuel; Neufeld, Esra; Christopoulou, Maria; Achermann, Peter; Kuster, Niels

    2014-05-01

    The effects of radiofrequency (RF) exposure on wake and sleep electroencephalogram (EEG) have been in focus since mobile phone usage became pervasive. It has been hypothesized that effects may be explained by (1) enhanced induced fields due to RF coupling with the electrode assembly, (2) the subsequent temperature increase around the electrodes, or (3) RF induced thermal pulsing caused by localized exposure in the head. We evaluated these three hypotheses by means of both numerical and experimental assessments made with appropriate phantoms and anatomical human models. Typical and worst-case electrode placements were examined at 900 and 2140?MHz. Our results indicate that hypothesis 1 can be rejected, as the induced fields cause <20% increase in the 10?g-averaged specific absorption rate (SAR). Simulations with an anatomical model indicate that hypothesis 2 is also not supported, as the realistic worst-case electrode placement results in a maximum skin temperature increase of 0.31?°C while brain temperature elevations remained <0.1?°C. These local short-term temperature elevations are unlikely to change brain physiology during the time period from minutes to several hours after exposure. The maximum observed temperature ripple due to RF pulses is <0.001?°C for GSM-like signals and <0.004?°C for 20-fold higher pulse energy, and offers no support for hypothesis 3. Thus, the mechanism of interaction between RF and changes in the EEG power spectrum remains unknown. PMID:24523224

  15. Energetic electron avalanches and mode transitions in planar inductively coupled radio-frequency driven plasmas operated in oxygen

    SciTech Connect

    Zaka-ul-Islam, M.; Niemi, K. [Centre for Plasma Physics, School of Mathematics and Physics, Queen's University Belfast, University Road, Belfast BT7 1NN, Northern Ireland (United Kingdom); Gans, T.; O'Connell, D. [Centre for Plasma Physics, School of Mathematics and Physics, Queen's University Belfast, University Road, Belfast BT7 1NN, Northern Ireland (United Kingdom); York Plasma Institute, Department of Physics, University of York, Innovation Way, Heslington York YO10 5DQ (United Kingdom)

    2011-07-25

    Space and phase resolved optical emission spectroscopic measurements reveal that in certain parameter regimes, inductively coupled radio-frequency driven plasmas exhibit three distinct operation modes. At low powers, the plasma operates as an alpha-mode capacitively coupled plasma driven through the dynamics of the plasma boundary sheath potential in front of the antenna. At high powers, the plasma operates in inductive mode sustained through induced electric fields due to the time varying currents and associated magnetic fields from the antenna. At intermediate powers, close to the often observed capacitive to inductive (E-H) transition regime, energetic electron avalanches are identified to play a significant role in plasma sustainment, similar to gamma-mode capacitively coupled plasmas. These energetic electrons traverse the whole plasma gap, potentially influencing plasma surface interactions as exploited in technological applications.

  16. Phosphatidylcholine and bipolar radiofrequency for treatment of localized fat deposits.

    PubMed

    Kim, In Su; Hyun, Moo Yeol; Park, Kui Young; Kim, Chan Woong; Kim, Beom Joon; Kim, Myeung Nam

    2014-08-01

    Bipolar radiofrequency (RF) is capable of delivering higher energy fluencies direct to the dermis through a needle electrode. This produces heat when the tissue electrical resistance converts the electric current to thermal energy in the tissue. A 38-year-old man visited our clinic for reduction of submental fat deposit, but otherwise in overall good health. After deciding to perform phosphatidylcholine (PPC) injections subcutaneously, we concerned about edema and swelling of injection site lasted several weeks. We wanted to shorten the period of edema and swelling, and we decided to add bipolar RF treatment. After 1 week of PPC injection combined with RF treatment, overall volume of jowl was decreased and edema and swelling on the PPC injected site markedly subsided. This reduction of fat deposit lasts longer than 1 year. Follow-up for 1 year demonstrated that the cosmetic results were well maintained. PMID:23621400

  17. Superconducting radio-frequency modules test faciilty operating experience

    SciTech Connect

    Soyars, W.; Bossert, R.; Darve, C.; Degraff, B.; Klebaner, A.; Martinez, A.; Pei, L.; Theilacker, J.; /Fermilab

    2007-07-01

    Fermilab is heavily engaged and making strong technical contributions to the superconducting radio-frequency research and development program (SRF R&D). Four major SRF test areas are being constructed to enable vertical and horizontal cavity testing, as well as cryomodule testing. The existing Fermilab cryogenic infrastructure has been modified to service Fermilab SRF R&D needs. The first stage of the project has been successfully completed, which allows for distribution of cryogens for a single cavity cryomodule using the existing Cryogenic Test Facility (CTF) that houses three Tevatron satellite refrigerators. The cooling capacity available for cryomodule testing at MDB results from the liquefaction capacity of the CTF cryogenic system. The cryogenic system for a single 9-cell cryomodule is currently operational. The paper describes the status, challenges and operational experience of the initial phase of the project.

  18. Pulsed radiofrequency enhances morphine analgesia in neuropathic rats.

    PubMed

    Laboureyras, Emilie; Rivat, Cyril; Cahana, Alex; Richebé, Philippe

    2012-06-20

    This study examined the effects of pulsed radiofrequency (PRF) on sciatic nerve ligation-induced mechanical pain hypersensitivity in rats. The nociceptive threshold was evaluated using the paw pressure vocalization test. Seven days after nerve ligation, animals receiving a single PRF session (120 s/2 Hz/45 V/42°C) on L4-5-6 dorsal root ganglia ipsilateral to a chronic constriction injury (CCI) showed a reduced sensory hypersensitivity at H4 6 and 1 day after PRF as compared with animals without PRF. One day after PRF, the effect of morphine (2 mg/kg, subcutaneous) increased the nociceptive threshold in the no PRF/CCI group and more extensively in PRF/CCI animals. These results showed that PRF might represent an interesting strategy not only to reduce neuropathic pain but also to enhance the efficacy of morphine in patients with neuropathic pain, well known to be opioid resistant. PMID:22546701

  19. Increased susceptibility to radiofrequency radiation due to pharmacological agents.

    PubMed

    Jauchem, J R; Frei, M R; Heinmets, F

    1984-11-01

    The effects of chlorpromazine, methysergide, and propranolol on thermal responses to 2.8 GHz radiofrequency radiation were examined in anesthetized rats. During intermittent exposure at an average power density of 60 mW X cm-2 (specific absorption rate, 14 W X kg-1), when colonic temperature was not allowed to rise above 39.5 degrees C, none of the pharmacological agents had any significant effects on thermal responses. When exposure was continued until lethal temperatures resulted, animals which were administered chlorpromazine, methysergide, or propranolol exhibited significantly shorter survival times than saline-treated animals. Propranolol administration caused the greatest decrease in survival time and resulted in a significantly lower lethal temperature than that which occurred in saline-treated animals. PMID:6508685

  20. Increased susceptibility to radiofrequency radiation due to pharmacological agents

    SciTech Connect

    Jauchem, J.R.; Frei, M.R.; Heinmets, F.

    1984-11-01

    The effects of chlorpromazine, methysergide, and propranolol on thermal responses to 2.8 GHz radiofrequency radiation were examined in anesthetized rats. During intermittent exposure at an average power density of 60 mW/sq cm (specific absorption rate, 14 W/kg), when colonic temperature was not allowed to rise above 39.5 C, none of the pharmacological agents had any significant effects on thermal responses. When exposure was continued until lethal temperatures resulted, animals which were administered chlorpromazine, methysergide, or propranolol exhibited significantly shorter survival times than saline-treated animals. Propranolol administration caused the greatest decrease in survival time and resulted in a significantly lower lethal temperature than that which occurred in saline-treated animals. 29 references.

  1. Bronchopleural Fistula After Radiofrequency Ablation of Lung Tumours

    SciTech Connect

    Cannella, Mathieu; Cornelis, Francois; Descat, Edouard; Ferron, Stephane; Carteret, Thibault; Castagnede, Hugues; Palussiere, Jean, E-mail: palussiere@bergonie.org [Regional Cancer Center, Department of Interventional Radiology, Institut Bergonie (France)

    2011-02-15

    The present article describes two cases of bronchopleural fistula (BPF) occurring after radiofrequency ablation of lung tumors. Both procedures were carried out using expandable multitined electrodes, with no coagulation of the needle track. After both ablations, ground-glass opacities encompassed the nodules and abutted the visceral pleura. The first patient had a delayed pneumothorax, and the second had a recurrent pneumothorax. Both cases of BPF were diagnosed on follow-up computed tomography chest scans (i.e., visibility of a distinct channel between the lung or a peripheral bronchus and the pleura) and were successfully treated with chest tubes alone. Our goal is to highlight the fact that BPF can occur without needle-track coagulation and to suggest that minimally invasive treatment is sufficient to cure BPFs of this specific origin.

  2. Characteristics of Radio-Frequency Circuits Utilizing Ferroelectric Capacitors

    NASA Technical Reports Server (NTRS)

    Eskridge, Michael; Gui, Xiao; MacLeod, Todd; Ho, Fat D.

    2011-01-01

    Ferroelectric capacitors, most commonly used in memory circuits and variable components, were studied in simple analog radio-frequency circuits such as the RLC resonator and Colpitts oscillator. The goal was to characterize the RF circuits in terms of frequency of oscillation, gain, etc, using ferroelectric capacitors. Frequencies of oscillation of both circuits were measured and studied a more accurate resonant frequency can be obtained using the ferroelectric capacitors. Many experiments were conducted and data collected. A model to simulate the experimental results will be developed. Discrepancies in gain and frequency in these RF circuits when conventional capacitors are replaced with ferroelectric ones were studied. These results will enable circuit designers to anticipate the effects of using ferroelectric components in their radio- frequency applications.

  3. Automated radiofrequency radiation dosimetry. Final report, Jun 89-Sep 90

    SciTech Connect

    Gandhi, O.P.

    1990-12-01

    The interaction of radiofrequency (RF) and microwave (MW) electromagnetic radiation with biological tissues is of increasing importance from the standpoint of health and safety. From considerable literature devoted to the study of RF and MW bioeffects based primarily on animal experimentation it has been determined that bioeffects are correlated with mass-normalized rates of RF or MW energy absorption (specific absorption rates or SARs). An emphasis of our project was to improve the efficiency of the SAR algorithms and to extend their use to higher RF and MW frequencies. Another objective was to adapt these algorithms to computing workstations and distributed memory parallel processors that are becoming more affordable and hence readily available to potential users of these codes.

  4. Effect of the levitating microparticle cloud on radiofrequency argon plasma

    NASA Astrophysics Data System (ADS)

    Mitic, S.; Pustylnik, M. Y.; Klumov, B. A.; Morfill, G. E.

    2010-06-01

    The effect of a levitating cloud of microparticles on the parameters of a radiofrequency (RF) plasma has been studied by means of two experimental techniques. Axial distributions of 1s excited states of argon were measured by a self-absorption method. A correction of a standard self-absorption method for the extinction of the light by the levitating microparticles is proposed. In addition the electron temperature was estimated using the optical emission spectroscopy. Measurements at the same discharge conditions in a microparticle-free discharge and discharge, containing a cloud of levitating microparticles, revealed the non-local influence of the microparticle cloud on the discharge plasma. The most probable cause of this influence is the disturbance of the ionization balance by the levitating microparticles.

  5. Novel Treatment of Neck Wrinkles with an Intradermal Radiofrequency Device

    PubMed Central

    Hyun, Moo Yeol; Li, Kapsok; Kim, Myeung Nam; Hong, Chang Kwun; Kim, Hyuk; Koh, Hyun-Ju; Park, Won-Seok

    2015-01-01

    Neck wrinkles commonly develop owing to the aging process. However, recently, the number of patients with neck wrinkles has been increasing. Also, an increasing number of young patients have presented with this condition, possibly because of the effect of the head-down posture that they adopt when using their computer or smartphone. We report two cases of young adults with a prominent neck wrinkle. In case 1, a 29-year-old woman with a neck wrinkle was treated with six intradermal radiofrequency (RF) procedures. Her neck wrinkle was significantly improved with the RF treatment. In case 2, a 32-year-old woman with a wrinkle and generalized light brownish tiny papules on the neck was treated with three intradermal RF procedures simultaneously with 30% glycolic acid peeling. Her wrinkle and skin tone were improved dramatically. We conclude that intradermal RF has a considerable efficacy for reducing neck wrinkles. PMID:25673937

  6. Radio-frequency probes of Antarctic ice at South Pole

    E-print Network

    Besson, David Zeke; Kravchenko, I.

    2013-05-16

    to successive waveforms. Each 0.5 meter division horizontally corresponds to approximately 5 ns. -20 -10 0 10 20 Rx v ol ta ge ( V, a ft er s ca li ng ; of fs e Time (ns, relative) 6 us echo (Vx1) 9.6 us echo (Vx1.3) 13.9 us echo (Vx3.5) 17.2 us echo (Vx10.... Kravchenko: Radio-frequency probes of Antarctic ice, South Pole 863 0 0.002 0.004 0.006 0.008 0.01 0.012 0.014 0.016 0.018 0 50 100 150 Pe ak A mp litu de (V ) Angle (degrees) surface iceflow 9.6 ?s13.9 ?s (Vx2)19 ?s (Vx10)9.6 ?s fit13.9 ?s...

  7. Radiofrequency exposure in the French general population: band, time, location and activity variability.

    PubMed

    Viel, Jean-François; Cardis, Elisabeth; Moissonnier, Monika; de Seze, René; Hours, Martine

    2009-11-01

    Information on the exposure of individual persons to radiofrequency (RF) fields is scarce, although such data are crucial in order to develop a suitable exposure assessment method, and frame the hypothesis and design of future epidemiological studies. The main goal of this survey is to assess individual RF exposure on a population basis, while clarifying the relative contribution of different sources to the total exposure. A total of 377 randomly selected people were analyzed. Each participant was supplied with a personal exposure meter for 24-hour measurements (weekday), and kept a time-location-activity diary. Electric field strengths were recorded in 12 different RF bands every 13s. Summary statistics were calculated with the robust regression on order statistics method. Most of the time, recorded field strengths were not detectable with the exposure meter. Total field, cordless phones, WiFi-microwave, and FM transmitters stood apart with a proportion above the detection threshold of 46.6%, 17.2%, 14.1%, and 11.0%, respectively. The total field mean value was 0.201V/m, higher in urban areas, during daytime, among adults, and when moving. When focusing on specific channels, the highest mean exposure resulted from FM sources (0.044V/m), followed by WiFi-microwaves (0.038V/m), cordless phones (0.037V/m), and mobile phones (UMTS: 0.036V/m, UMTS: 0.037V/m). Various factors, however, contributed to a high variability in RF exposure assessment. These population-based estimates should therefore be confirmed by further surveys to better characterize the exposure situation in different microenvironments. PMID:19656570

  8. Electromagnetic and mechanical design of gridded radio-frequency cavity windows

    SciTech Connect

    Alsharoa, Mohammad M.; /IIT, Chicago /Fermilab

    2004-12-01

    Electromagnetic, thermal and structural analyses of radio-frequency (RF) cavities were performed as part of a developmental RF cavity program for muon cooling. RF cavities are necessary to provide longitudinal focusing of the muons and to compensate for their energy loss. Closing the cavity ends by electrically conducting windows reduces the power requirement and increases the on-axis electric field for a given maximum surface electric field. Many factors must be considered in the design of RF cavity windows. RF heating can cause the windows to deform in the axial direction of the cavity. The resulting thermal stresses in the window must be maintained below the yield stress of the window material. The out-of-plane deflection must be small enough so that the consequent frequency shift is tolerable. For example, for an 805 MHz cavity, the out-of-plane deflection must be kept below 25 microns to prevent the frequency of the cavity from shifting more than 10 kHz. In addition, the window design should yield smooth electric and magnetic fields, terminate field leakage beyond the window, and minimize beam scattering. In the present thesis, gridded-tube window designs were considered because of their high structural integrity. As a starting point in the analysis, a cylindrical pillbox cavity was considered as a benchmark problem. Analytical and finite element solutions were obtained for the electric and magnetic fields, power loss density, and temperature profile. Excellent agreement was obtained between the analytical and finite element results. The finite element method was then used to study a variety of gridded-tube windows. It was found that cooling of the gridded-tube windows by passing helium gas inside the tubes significantly reduces the out-of-plane deflection and the thermal stresses. Certain tube geometries and grid patterns were found to satisfy all of the design requirements.

  9. Factors Limiting Complete Tumor Ablation by Radiofrequency Ablation

    SciTech Connect

    Paulet, Erwan, E-mail: erwanpaulet@yahoo.fr; Aube, Christophe [University Hospital Angers, Department of Radiology (France); Pessaux, Patrick [University Hospital Angers, Department of Visceral Surgery (France); Lebigot, Jerome [University Hospital Angers, Department of Radiology (France); Lhermitte, Emilie [University Hospital Angers, Department of Visceral Surgery (France); Oberti, Frederic [University Hospital Angers, Department of Hepato-Gastroenterology (France); Ponthieux, Anne [University Hospital Angers, Clinical Research Center (France); Cales, Paul [University Hospital Angers, Department of Hepato-Gastroenterology (France); Ridereau-Zins, Catherine [University Hospital Angers, Department of Radiology (France); Pereira, Philippe L. [Eberhard-Karls University, Department of Diagnostic Radiology (Germany)

    2008-01-15

    The purpose of this study was to determine radiological or physical factors to predict the risk of residual mass or local recurrence of primary and secondary hepatic tumors treated by radiofrequency ablation (RFA). Eighty-two patients, with 146 lesions (80 hepatocellular carcinomas, 66 metastases), were treated by RFA. Morphological parameters of the lesions included size, location, number, ultrasound echogenicity, computed tomography density, and magnetic resonance signal intensity were obtained before and after treatment. Parameters of the generator were recorded during radiofrequency application. The recurrence-free group was statistically compared to the recurrence and residual mass groups on all these parameters. Twenty residual masses were detected. Twenty-nine lesions recurred after a mean follow-up of 18 months. Size was a predictive parameter. Patients' sex and age and the echogenicity and density of lesions were significantly different for the recurrence and residual mass groups compared to the recurrence-free group (p < 0.05). The presence of an enhanced ring on the magnetic resonance control was more frequent in the recurrence and residual mass groups. In the group of patients with residual lesions, analysis of physical parameters showed a significant increase (p < 0.05) in the time necessary for the temperature to rise. In conclusion, this study confirms risk factors of recurrence such as the size of the tumor and emphasizes other factors such as a posttreatment enhanced ring and an increase in the time necessary for the rise in temperature. These factors should be taken into consideration when performing RFA and during follow-up.

  10. The Low-Frequency Environment of the Murchison Widefield Array: Radio-Frequency Interference Analysis and Mitigation

    NASA Astrophysics Data System (ADS)

    Offringa, A. R.; Wayth, R. B.; Hurley-Walker, N.; Kaplan, D. L.; Barry, N.; Beardsley, A. P.; Bell, M. E.; Bernardi, G.; Bowman, J. D.; Briggs, F.; Callingham, J. R.; Cappallo, R. J.; Carroll, P.; Deshpande, A. A.; Dillon, J. S.; Dwarakanath, K. S.; Ewall-Wice, A.; Feng, L.; For, B.-Q.; Gaensler, B. M.; Greenhill, L. J.; Hancock, P.; Hazelton, B. J.; Hewitt, J. N.; Hindson, L.; Jacobs, D. C.; Johnston-Hollitt, M.; Kapi?ska, A. D.; Kim, H.-S.; Kittiwisit, P.; Lenc, E.; Line, J.; Loeb, A.; Lonsdale, C. J.; McKinley, B.; McWhirter, S. R.; Mitchell, D. A.; Morales, M. F.; Morgan, E.; Morgan, J.; Neben, A. R.; Oberoi, D.; Ord, S. M.; Paul, S.; Pindor, B.; Pober, J. C.; Prabu, T.; Procopio, P.; Riding, J.; Udaya Shankar, N.; Sethi, S.; Srivani, K. S.; Staveley-Smith, L.; Subrahmanyan, R.; Sullivan, I. S.; Tegmark, M.; Thyagarajan, N.; Tingay, S. J.; Trott, C. M.; Webster, R. L.; Williams, A.; Williams, C. L.; Wu, C.; Wyithe, J. S.; Zheng, Q.

    2015-03-01

    The Murchison Widefield Array is a new low-frequency interferometric radio telescope built in Western Australia at one of the locations of the future Square Kilometre Array. We describe the automated radio-frequency interference detection strategy implemented for the Murchison Widefield Array, which is based on the aoflagger platform, and present 72-231 MHz radio-frequency interference statistics from 10 observing nights. Radio-frequency interference detection removes 1.1% of the data. Radio-frequency interference from digital TV is observed 3% of the time due to occasional ionospheric or atmospheric propagation. After radio-frequency interference detection and excision, almost all data can be calibrated and imaged without further radio-frequency interference mitigation efforts, including observations within the FM and digital TV bands. The results are compared to a previously published Low-Frequency Array radio-frequency interference survey. The remote location of the Murchison Widefield Array results in a substantially cleaner radio-frequency interference environment compared to Low-Frequency Array's radio environment, but adequate detection of radio-frequency interference is still required before data can be analysed. We include specific recommendations designed to make the Square Kilometre Array more robust to radio-frequency interference, including: the availability of sufficient computing power for radio-frequency interference detection; accounting for radio-frequency interference in the receiver design; a smooth band-pass response; and the capability of radio-frequency interference detection at high time and frequency resolution (second and kHz-scale respectively).

  11. Trajectory optimization for the planning of percutaneous radiofrequency ablation on hepatic tumors

    E-print Network

    Essert-Villard, Caroline

    , optimization 1. Introduction The treatment of hepatic cancers is nowadays mainly surgical. However, many contra-embolization, cryotherapy, ethanol injection, and radiofrequency ablation (RFA) that appeared to be one of the most secure

  12. Combined radiofrequency ablation and doxorubicin-eluting polymer implants for liver cancer treatment

    E-print Network

    Gao, Jinming

    Combined radiofrequency ablation and doxorubicin- eluting polymer implants for liver cancer Simmons Comprehensive Cancer Center, University of Texas Southwestern Medical Center, Dallas, Texas 75390 delivery; VX2 tumor; minimally inva- sive therapy INTRODUCTION Minimally invasive cancer treatments have

  13. APPLICATION OF A FINITE-DIFFERENCE TECHNIQUE TO THE HUMAN RADIOFREQUENCY DOSIMETRY PROBLEM

    EPA Science Inventory

    A powerful finite difference numerical technique has been applied to the human radiofrequency dosimetry problem. The method possesses inherent advantages over the method of moments approach in that its implementation requires much less computer memory. Consequently, it has the ca...

  14. Design and characterization of a radio-frequency dc/dc power converter

    E-print Network

    Jackson, David A. (David Alexander)

    2005-01-01

    The use of radio-frequency (RF) amplifier topologies in dc/dc power converters allows the operating frequency to be increased by more than two orders of magnitude over the frequency of conventional converters. This enables ...

  15. Base-level management of radio-frequency radiation-protection program. Final report

    SciTech Connect

    Rademacher, S.E.; Montgomery, N.D.

    1989-04-01

    AFOEHL developed this report to assist the base-level aerospace medical team manage their radio-frequency radiation-protection program. This report supersedes USAFOEHL Report 80-42, 'A Practical R-F Guide for BEES.'

  16. Base-level management of radio-frequency radiation-protection program. Final report

    SciTech Connect

    Rademacher, S.E.; Montgomery, N.D.

    1989-04-01

    AFOEHL developed this report to assist the base-level aerospace medical team manage their radio-frequency radiation protection program. This report supersedes USAFOEHL Report 80-42, 'A practical R-F Guide for BEES.'

  17. Measurements of electric and magnetic fields due to the operation of indoor power distribution substations

    Microsoft Academic Search

    Anastasia S. Safigianni; Christina G. Tsompanidou

    2005-01-01

    In this paper, the electric and magnetic fields with a frequency of 50 Hz, caused by the operation of indoor power distribution substations of 20\\/0.4 kV, are examined. First, the results of previous relevant research studies as well as the reference levels for safe general public and occupational exposure given in the guidelines of the International Commission on Non-Ionizing Radiation

  18. Comparison of pain after radiofrequency tonsillectomy compared with conventional tonsillectomy: a pilot study.

    PubMed

    Saengpanich, Supinda; Kerekhanjanarong, Virachai; Aramwatanapong, Phooripan; Supiyaphun, Pakpoom

    2005-12-01

    Tonsillectomy results in a severe sore throat, especially in the first few days, until the exposed and inflamed muscle becomes covered with regenerated mucosa. There are a variety of techniques of tonsillectomy including monopolar and bipolar diathermy, blunt dissection, and most recently radiofrequency tonsil ablation and coblation. The objective of the present study was to assess the postoperative pharyngeal or ear pain of radiofrequency tonsillectomy and compared with traditional blunt dissection tonsillectomy with loop ligation hemostasis. PMID:16518989

  19. Bipolar radiofrequency-induced thermotherapy of great saphenous vein: Our initial experience

    PubMed Central

    Kasi, Venkatesh; Kalyanpur, Tejas M; Narsinghpura, Kaustubh; Chakravarthy, Deyananda; Mehta, Pankaj; Cherian, Mathew

    2012-01-01

    The incidence of varicose veins in lower limbs is increasing in the Indian subcontinent. With the advent of radiofrequency ablation (RFA), an effective minimally invasive technique is now available to treat varicose veins. RFA can be performed with either unipolar or bipolar probes. We present a simple technique for bipolar radiofrequency-induced thermotherapy of the great saphenous vein. This can be a safe and effective alternative to surgical procedures. PMID:23162247

  20. Tachycardias in Infants, Children and Adolescents: Safety and Effectiveness of Radiofrequency Catheter Ablation

    Microsoft Academic Search

    Sung-Jae Lee; Walter Ch. Schueller

    2000-01-01

    Radiofrequency catheter ablations provide an effective control of a variety of supraventricular and ventricular tachycardias in adults. This study was designed to evaluate the efficacy and safety of radiofrequency catheter ablations in infants, children and adolescents. Ninty-three ablations were performed in 84 patients ranging from 5 months to 18 years of age. All but 1 patient were successfully treated (98.8%).

  1. Effects of Cell Phone Radiofrequency Signal Exposure on Brain Glucose Metabolism

    PubMed Central

    Volkow, Nora D.; Tomasi, Dardo; Wang, Gene-Jack; Vaska, Paul; Fowler, Joanna S.; Telang, Frank; Alexoff, Dave; Logan, Jean; Wong, Christopher

    2011-01-01

    Context The dramatic increase in use of cellular telephones has generated concern about possible negative effects of radiofrequency signals delivered to the brain. However, whether acute cell phone exposure affects the human brain is unclear. Objective To evaluate if acute cell phone exposure affects brain glucose metabolism, a marker of brain activity. Design, Setting, and Participants Randomized crossover study conducted between January 1 and December 31, 2009, at a single US laboratory among 47 healthy participants recruited from the community. Cell phones were placed on the left and right ears and positron emission tomography with (18F)fluorodeoxyglucose injection was used to measure brain glucose metabolism twice, once with the right cell phone activated (sound muted) for 50 minutes (“on” condition) and once with both cell phones deactivated (“off” condition). Statistical parametric mapping was used to compare metabolism between on and off conditions using paired t tests, and Pearson linear correlations were used to verify the association of metabolism and estimated amplitude of radiofrequency-modulated electromagnetic waves emitted by the cell phone. Clusters with at least 1000 voxels (volume >8 cm3) and P < .05 (corrected for multiple comparisons) were considered significant. Main Outcome Measure Brain glucose metabolism computed as absolute metabolism (µmol/100 g per minute) and as normalized metabolism (region/whole brain). Results Whole-brain metabolism did not differ between on and off conditions. In contrast, metabolism in the region closest to the antenna (orbitofrontal cortex and temporal pole) was significantly higher for on than off conditions (35.7 vs 33.3 µmol/100 g per minute; mean difference, 2.4 [95% confidence interval, 0.67–4.2]; P = .004). The increases were significantly correlated with the estimated electromagnetic field amplitudes both for absolute metabolism (R = 0.95, P < .001) and normalized metabolism (R = 0.89; P < .001). Conclusions In healthy participants and compared with no exposure, 50-minute cell phone exposure was associated with increased brain glucose metabolism in the region closest to the antenna. This finding is of unknown clinical significance. PMID:21343580

  2. Caudal Epidural of Pulsed Radiofrequency in Post Herpetic Neuralgia (PHN); Report of Three Cases

    PubMed Central

    Rohof, Olav Jacobus Johannes Maria

    2014-01-01

    Introduction: Postherpetic neuralgia (PHN) is a frequently occurring neuropathic pain, its pathophysiology is not fully understood. There are only few evidence based therapeutic options; sympathetic nerve block can be considered for patients with PHN refractory to conservative treatment, but long-term effects are poor. Application of pulsed radiofrequency was effective to treat a variety of pain syndromes without neurological complications or other sequelae. Case Presentation: We observed a remarkable long-lasting pain relief in patients with post herpetic neuralgia (PHN) treated with caudal epidural PRF. We described the technique of caudal epidural PRF and three case reports. Conclusions: The mode of action of PRF is far from being completely elucidated. The high frequency current induces an electric field that in turn seems to influence the immunity, the inflammation and other pain conducting mechanisms. Our findings suggest an effect distal from the application of the current. It reaches targets that are difficultly attainable by any other means of current application. The observations of pain relief in the difficult to treat patients with PHN justifies further investigation. PMID:25237634

  3. Exposure to 1800 MHz radiofrequency radiation impairs neurite outgrowth of embryonic neural stem cells.

    PubMed

    Chen, Chunhai; Ma, Qinlong; Liu, Chuan; Deng, Ping; Zhu, Gang; Zhang, Lei; He, Mindi; Lu, Yonghui; Duan, Weixia; Pei, Liping; Li, Min; Yu, Zhengping; Zhou, Zhou

    2014-01-01

    A radiofrequency electromagnetic field (RF-EMF) of 1800?MHz is widely used in mobile communications. However, the effects of RF-EMFs on cell biology are unclear. Embryonic neural stem cells (eNSCs) play a critical role in brain development. Thus, detecting the effects of RF-EMF on eNSCs is important for exploring the effects of RF-EMF on brain development. Here, we exposed eNSCs to 1800?MHz RF-EMF at specific absorption rate (SAR) values of 1, 2, and 4?W/kg for 1, 2, and 3 days. We found that 1800?MHz RF-EMF exposure did not influence eNSC apoptosis, proliferation, cell cycle or the mRNA expressions of related genes. RF-EMF exposure also did not alter the ratio of eNSC differentiated neurons and astrocytes. However, neurite outgrowth of eNSC differentiated neurons was inhibited after 4?W/kg RF-EMF exposure for 3 days. Additionally, the mRNA and protein expression of the proneural genes Ngn1 and NeuroD, which are crucial for neurite outgrowth, were decreased after RF-EMF exposure. The expression of their inhibitor Hes1 was upregulated by RF-EMF exposure. These results together suggested that 1800?MHz RF-EMF exposure impairs neurite outgrowth of eNSCs. More attention should be given to the potential adverse effects of RF-EMF exposure on brain development. PMID:24869783

  4. [Preparation and characterization of magnetic nano-particles with radiofrequency-induced hyperthermia for cancer treatment].

    PubMed

    Fan, Xiangshan; Zhang, Dongsheng; Zheng, Jie; Gu, Ning; Ding, Anwei; Jia, Xiupeng; Qing, Hongyun; Jin, Liqiang; Wan, Meiling; Li, Qunhui

    2006-08-01

    Mn0.5Zn0.5Fe2O4 nano-particles were prepared by the chemical co-precipitation, their characteristics were observed with transmission electron microscope (TEM), X-ray diffractometer (XRD) and thermal analysis system, and etc. The temperature changes of the nano-particles of Mn0.5Zn0.5Fe2O4 and its magnetic fluid explored in radiofrequency(RF,200 KHz, 4 KW) were measured. The proliferation ratio of L929 cells cultured in soak of Mn0.5Zn0.5Fe2O4 nano-particles were observed. The experiment indicates that the magnetic particles were about 40 nm diameter in average, round, had strong magnetism, and were proved to be consistent with the standard data of chart of XRD. Its magnetic fluid exposed to RF could be heated up to temperature range from 40 degrees C to 51 degrees C due to the amount of the magnetic nano-particles and intensity of the alternating magnetic field. Magnetic nano-particles were found to have no obvious cytotoxicity to L929 cells. PMID:17002113

  5. Optical fiber sensors-based temperature distribution measurement in ex vivo radiofrequency ablation with submillimeter resolution

    NASA Astrophysics Data System (ADS)

    Macchi, Edoardo Gino; Tosi, Daniele; Braschi, Giovanni; Gallati, Mario; Cigada, Alfredo; Busca, Giorgio; Lewis, Elfed

    2014-11-01

    Radiofrequency thermal ablation (RFTA) induces a high-temperature field in a biological tissue having steep spatial (up to 6°C/mm) and temporal (up to 1°C/s) gradients. Applied in cancer care, RFTA produces a localized heating, cytotoxic for tumor cells, and is able to treat tumors with sizes up to 3 to 5 cm in diameter. The online measurement of temperature distribution at the RFTA point of care has been previously carried out with miniature thermocouples and optical fiber sensors, which exhibit problems of size, alteration of RFTA pattern, hysteresis, and sensor density worse than 1 sensor/cm. In this work, we apply a distributed temperature sensor (DTS) with a submillimeter spatial resolution for the monitoring of RFTA in porcine liver tissue. The DTS demodulates the chaotic Rayleigh backscattering pattern with an interferometric setup to obtain the real-time temperature distribution. A measurement chamber has been set up with the fiber crossing the tissue along different diameters. Several experiments have been carried out measuring the space-time evolution of temperature during RFTA. The present work showcases the temperature monitoring in RFTA with an unprecedented spatial resolution and is exportable to in vivo measurement; the acquired data can be particularly useful for the validation of RFTA computational models.

  6. Exposure to 1800?MHz radiofrequency radiation impairs neurite outgrowth of embryonic neural stem cells

    PubMed Central

    Chen, Chunhai; Ma, Qinlong; Liu, Chuan; Deng, Ping; Zhu, Gang; Zhang, Lei; He, Mindi; Lu, Yonghui; Duan, Weixia; Pei, Liping; Li, Min; Yu, Zhengping; Zhou, Zhou

    2014-01-01

    A radiofrequency electromagnetic field (RF-EMF) of 1800?MHz is widely used in mobile communications. However, the effects of RF-EMFs on cell biology are unclear. Embryonic neural stem cells (eNSCs) play a critical role in brain development. Thus, detecting the effects of RF-EMF on eNSCs is important for exploring the effects of RF-EMF on brain development. Here, we exposed eNSCs to 1800?MHz RF-EMF at specific absorption rate (SAR) values of 1, 2, and 4?W/kg for 1, 2, and 3 days. We found that 1800?MHz RF-EMF exposure did not influence eNSC apoptosis, proliferation, cell cycle or the mRNA expressions of related genes. RF-EMF exposure also did not alter the ratio of eNSC differentiated neurons and astrocytes. However, neurite outgrowth of eNSC differentiated neurons was inhibited after 4?W/kg RF-EMF exposure for 3 days. Additionally, the mRNA and protein expression of the proneural genes Ngn1 and NeuroD, which are crucial for neurite outgrowth, were decreased after RF-EMF exposure. The expression of their inhibitor Hes1 was upregulated by RF-EMF exposure. These results together suggested that 1800?MHz RF-EMF exposure impairs neurite outgrowth of eNSCs. More attention should be given to the potential adverse effects of RF-EMF exposure on brain development. PMID:24869783

  7. On-body calibration and processing for a combination of two radio-frequency personal exposimeters.

    PubMed

    Thielens, Arno; Agneessens, Sam; Verloock, Leen; Tanghe, Emmeric; Rogier, Hendrik; Martens, Luc; Joseph, Wout

    2015-01-01

    Two radio-frequency personal exposimeters (PEMs) worn on both hips are calibrated on a subject in an anechoic chamber. The PEMs' response and crosstalk are determined for realistically polarised incident electric fields using this calibration. The 50 % confidence interval of the PEMs' response is reduced (2.6 dB on average) when averaged over both PEMs. A significant crosstalk (up to a ratio of 1.2) is measured, indicating that PEM measurements can be obfuscated by crosstalk. Simultaneous measurements with two PEMs are carried out in Ghent, Belgium. The highest exposure is measured for Global System for Mobile Communication downlink (0.052 mW m(-2) on average), while the lowest exposure is found for Universal Mobile Telecommunications System uplink (0.061 ?W m(-2) on average). The authors recommend the use of a combination of multiple PEMs and, considering the multivariate data, to provide the mean vector and the covariance matrix next to the commonly listed univariate summary statistics, in future PEM studies. PMID:24729592

  8. Thermoregulatory responses of rats exposed to 9.3-GHz radiofrequency radiation.

    PubMed

    Frei, M R; Jauchem, J R; Heinmets, F

    1989-01-01

    Ketamine-anesthetized Sprague-Dawley rats were exposed in H orientation to far-field 9.3-GHz continuous-wave (CW) and pulsed (2 microseconds, 500 pps) radiofrequency radiation (RFR) at average power densities of 30 and 60 mW/cm2 (whole-body average specific absorption rates of 9.3 and 18.6 W/kg, respectively). Irradiation was conducted to cyclicly increase colonic temperature from 38.5 to 39.5 degrees C. Colonic, tympanic, and subcutaneous temperatures, ECG, blood pressure, and respiratory rate were continuously recorded during experimentation. At both power densities, the subcutaneous and tympanic temperature increases significantly exceeded the colonic temperature increase. At both exposure levels, heart rate increased significantly during irradiation and returned to baseline when exposure was discontinued. Blood pressure and respiratory rate did not significantly change during irradiation. There were no significant differences between the effects of CW and pulsed RFR exposure. The levels of subcutaneous heating and heart rate change were greater, and the times required to achieve and to recover from a 1 degree C colonic temperature increase were longer than in previous studies conducted at 2.8 GHz. Results of these studies indicate that the carrier frequency used during irradiation markedly affects the pattern of heat distribution and the physiological responses of RF-irradiated animals. PMID:2919227

  9. Thermoregulatory responses of rats exposed to 9. 3-GHz radio-frequency radiation

    SciTech Connect

    Frei, M.R.; Jauchem, J.R.; Heinmets, F.

    1987-10-15

    Ketamine-anesthetized Sprague-Dawley rats were exposed in H orientation to far-field 9.3-GHz continuous-wave (CW) and pulsed (2 microseconds 500 pps) radiofrequency radiation (RFR) at average power densities of 30 and 60 mW/sq. cm (whole-body average specific absorption rates of 9.3 and 18.6 W/kg, respectively). Irradiation was conducted to cyclicly increase colonic temperature from 38.5 to 39.5 C. Colonic, tympanic, and subcutaneous temperatures, ECG, blood pressure, and respiratory rate were continuously recorded during experimentation. At both power densities, the subcutaneous and tympanic temperature increases significantly exceeded the colonic temperature increase. At both exposure levels, heart rate increased significantly during irradiation and returned to baseline when exposure was discontinued. Blood pressure and respiratory rate did not significantly change during irradiation. There were no significant differences between the effects of CW and pulsed RFR exposure. The levels of subcutaneous heating and heart rate change were greater, and the times required to achieve and to recover from a 1 C colonic temperature increase were longer than in previous studies conducted at 2.8 GHz. Results of these studies indicate that the carrier frequency used during irradiation markedly affects the pattern of heat distribution and the physiological responses of RF-irradiated animals.

  10. CEM43°C thermal dose thresholds: a potential guide for magnetic resonance radiofrequency exposure levels?

    PubMed Central

    Samaras, Theodoros; Yarmolenko, Pavel S.; Dewhirst, Mark W.; Neufeld, Esra; Kuster, Niels

    2013-01-01

    Objective To define thresholds of safe local temperature increases for MR equipment that exposes patients to radiofrequency fields of high intensities for long duration. These MR systems induce heterogeneous energy absorption patterns inside the body and can create localised hotspots with a risk of overheating. Methods The MRI + EUREKA research consortium organised a “Thermal Workshop on RF Hotspots”. The available literature on thresholds for thermal damage and the validity of the thermal dose (TD) model were discussed. Results/Conclusions The following global TD threshold guidelines for safe use of MR are proposed: All persons: maximum local temperature of any tissue limited to 39 °CPersons with compromised thermoregulation AND Uncontrolled conditions: maximum local temperature limited to 39 °CControlled conditions: TD<2 CEM43°CPersons with uncompromised thermoregulation AND Uncontrolled conditions: TD<2 CEM43°CControlled conditions: TD<9 CEM43°C The following definitions are applied: Controlled conditions A medical doctor or a dedicated trained person can respond instantly to heat-induced physiological stress Compromised thermoregulation All persons with impaired systemic or reduced local thermoregulation PMID:23553588

  11. Short-duration exposure to radiofrequency electromagnetic radiation alters the chlorophyll fluorescence of duckweeds (Lemna minor).

    PubMed

    Senavirathna, Mudalige Don Hiranya Jayasanka; Takashi, Asaeda; Kimura, Yuichi

    2014-12-01

    Plants growing in natural environments are exposed to radiofrequency electromagnetic radiation (EMR) emitted by various communication network base stations. The environmental concentration of this radiation is increasing rapidly with the congested deployment of base stations. Although numerous scientific studies have been conducted to investigate the effects of EMR on the physiology of humans and animals, there have been few attempts to investigate the effects of EMR on plants. In this study, we attempted to evaluate the effects of EMR on photosynthesis by investigating the chlorophyll fluorescence (ChF) parameters of duckweed fronds. During the experiment, the fronds were tested with 2, 2.5, 3.5, 5.5 and 8?GHz EMR frequencies, which are not widely studied even though there is a potentially large concentration of these frequencies in the environment. The duckweed fronds were exposed to EMR for 30?min, 1?h and 24?h durations with electric field strength of 45-50?V/m for each frequency. The results indicated that exposure to EMR causes a change in the non-photochemical quenching of the duckweeds. The changes varied with the frequency of the EMR and were time-varying within a particular frequency. The temperature remained unchanged in the duckweed fronds upon exposure to EMR, which confirms that the effect is non-thermal. PMID:24131393

  12. Workgroup report: base stations and wireless networks-radiofrequency (RF) exposures and health consequences.

    PubMed

    Valberg, Peter A; van Deventer, T Emilie; Repacholi, Michael H

    2007-03-01

    Radiofrequency (RF) waves have long been used for different types of information exchange via the air waves--wireless Morse code, radio, television, and wireless telephone (i.e., construction and operation of telephones or telephone systems). Increasingly larger numbers of people rely on mobile telephone technology, and health concerns about the associated RF exposure have been raised, particularly because the mobile phone handset operates in close proximity to the human body, and also because large numbers of base station antennas are required to provide widespread availability of service to large populations. The World Health Organization convened an expert workshop to discuss the current state of cellular-telephone health issues, and this article brings together several of the key points that were addressed. The possibility of RF health effects has been investigated in epidemiology studies of cellular telephone users and workers in RF occupations, in experiments with animals exposed to cell-phone RF, and via biophysical consideration of cell-phone RF electric-field intensity and the effect of RF modulation schemes. As summarized here, these separate avenues of scientific investigation provide little support for adverse health effects arising from RF exposure at levels below current international standards. Moreover, radio and television broadcast waves have exposed populations to RF for > 50 years with little evidence of deleterious health consequences. Despite unavoidable uncertainty, current scientific data are consistent with the conclusion that public exposures to permissible RF levels from mobile telephone and base stations are not likely to adversely affect human health. PMID:17431492

  13. Culturing of cells as influenced by exposure to AC and DC fields

    NASA Astrophysics Data System (ADS)

    Abdel-Salam, M.; Nakano, M.; Tanino, M.; Mizuno, A.

    2008-12-01

    This paper is aimed at investigating culturing of living cells as influenced by exposure to AC and DC ionized and non-ionized fields in a point-to-plane gap. A cell suspension including yeast was placed on the ground plane at the gap axis and exposed to AC and DC fields of varying magnitudes. The effect of exposure time, frequency of the AC fields and magnitude of the applied fields on the survival rate of cells was investigated. The survival rate was also investigated as influenced by blowing the ionized field by air.

  14. The Effects of Non-Invasive Radiofrequency Treatment and Hyperthermia on Malignant and Nonmalignant Cells

    PubMed Central

    Curley, Steven A.; Palalon, Flavio; Sanders, Kelly E.; Koshkina, Nadezhda V.

    2014-01-01

    Background: Exposure of biological subjects to electromagnetic fields with a high frequency is associated with temperature elevation. In our recent studies, we reported that non-invasive radiofrequency (RF) treatment at 13.56 MHz with the field ranging from 1 KeV to 20 KeV/m2 inhibits tumor progression in animals with abdominal tumor xenografts and enhances the anticancer effect of chemotherapy. The RF treatment was followed by temperature elevation in tumors to approximately 46 °C during 10 min of exposure. In contrast, the temperature of normal tissues remained within a normal range at approximately 37 °C. Whether all biological effects of RF treatment are limited to its hyperthermic property remains unclear. Here, we compared how RF and hyperthermia (HT) treatments change the proliferation rate, oxygen consumption and autophagy in malignant and nonmalignant cells. Methods: In the current study, cancer and nonmalignant cells of pancreatic origin were exposed to the RF field or to conventional HT at 46 °C, which was chosen based on our previous in vivo studies of the tumor-specific RF-induced hyperthermia. Results: Only RF treatment caused declines in cancer cell viability and proliferation. RF treatment also affected mitochondrial function in cancer cells more than HT treatment did and, unlike HT treatment, was followed by the elevation of autophagosomes in the cytoplasm of cancer cells. Importantly, the effects of RF treatment were negligible in nonmalignant cells. Conclusion: The obtained data indicate that the effects of RF treatment are specific to cancer cells and are not limited to its hyperthermic property. PMID:25192147

  15. Development of a novel radio-frequency negative hydrogen ion source in conically converging configuration

    NASA Astrophysics Data System (ADS)

    Jung, B. K.; Dang, J. J.; An, Y. H.; Chung, K. J.; Hwang, Y. S.

    2014-02-01

    Volume-produced negative ion source still requires enhancement of current density with lower input RF (radio-frequency) power in lower operating pressure for various applications. To confirm recent observation of efficient negative ion production with a short cylindrical chamber with smaller effective plasma size, the RF-driven transformer-coupled plasma H- ion source at Seoul National University is modified by adopting a newly designed quartz RF window to reduce the chamber length. Experiments with the reduced chamber length show a few times enhancement of H- ion beam current compared to that extracted from the previous chamber design, which is consistent with the measured H- ion population. Nevertheless, decrease in H- ion beam current observed in low pressure regime below ˜5 mTorr owing to insufficient filtering of high energy electrons in the extraction region needs to be resolved to address the usefulness of electron temperature control by the change of geometrical configuration of the discharge chamber. A new discharge chamber with conically converging configuration has been developed, in which the chamber diameter decreases as approaching to the extraction region away from the planar RF antenna such that stronger filter magnetic field can be utilized to prohibit high energy electrons from transporting to the extraction region. First experimental results for the H- ion beam extraction with this configuration show that higher magnetic filter field makes peak negative beam currents happen in lower operating pressure. However, overall decrease in H- ion beam current due to the change of chamber geometry still requires further study of geometrical effect on particle transport and optimization of magnetic field in this novel configuration.

  16. A Passive Radio-Frequency Identification (RFID) Gas Sensor With Self-Correction Against Fluctuations of Ambient Temperature.

    PubMed

    Potyrailo, Radislav A; Surman, Cheryl

    2013-08-01

    Uncontrolled fluctuations of ambient temperature in the field typically greatly reduce accuracy of gas sensors. In this study, we developed an approach for the self-correction against fluctuations of ambient temperature of individual gas and vapor sensors. The main innovation of our work is in the temperature correction which is accomplished without the need for a separate uncoated reference sensor or a separate temperature sensor. Our sensors are resonant inductor-capacitor-resistor (LCR) transducers coated with sensing materials and operated as multivariable passive (battery-free) radio-frequency identification (RFID) sensors. Using our developed approach, we performed quantitation of an exemplary vapor over the temperature range from 25 to 40 °C. This technical solution will be attractive in numerous applications where temperature stabilization of a gas sensor or addition of auxiliary temperature or uncoated reference sensors is prohibitive. PMID:23956496

  17. Modeling of a thermo-chromatographic pulse (TCP) as radio-frequency (RF)-induced selective heating effect.

    PubMed

    Kraus, Markus; Kopinke, Frank-Dieter; Roland, Ulf

    2013-01-01

    By utilizing the specific influence of water adsorption on the dielectric loss factor and, consequently, selective heating of the zeolite NaY in a radio-frequency (RF) electromagnetic field, a hot zone moving through the packed bed can be realized initiated by water injection. While the effect of water adsorption on RF heating and the phenomenon of the thermo-chromatographic pulse (TCP) itself were described in a previous paper, the present study presents a detailed model for the description and explanation of this effect. It involves the complex dependence of dielectric loss on temperature and moisture content, a diffusion model considering both hopping and Knudsen mechanisms and a power balance for a representative segment of the packed bed. The developed model was successfully applied to adequately describe various experimental situations observed for selective RF heating in a NaY zeolite bed. PMID:24779133

  18. A Passive Radio-Frequency Identification (RFID) Gas Sensor With Self-Correction Against Fluctuations of Ambient Temperature

    PubMed Central

    Potyrailo, Radislav A.; Surman, Cheryl

    2013-01-01

    Uncontrolled fluctuations of ambient temperature in the field typically greatly reduce accuracy of gas sensors. In this study, we developed an approach for the self-correction against fluctuations of ambient temperature of individual gas and vapor sensors. The main innovation of our work is in the temperature correction which is accomplished without the need for a separate uncoated reference sensor or a separate temperature sensor. Our sensors are resonant inductor-capacitor-resistor (LCR) transducers coated with sensing materials and operated as multivariable passive (battery-free) radio-frequency identification (RFID) sensors. Using our developed approach, we performed quantitation of an exemplary vapor over the temperature range from 25 to 40 °C. This technical solution will be attractive in numerous applications where temperature stabilization of a gas sensor or addition of auxiliary temperature or uncoated reference sensors is prohibitive. PMID:23956496

  19. Wireless Chalcogenide Nanoionic-Based Radio-Frequency Switch

    NASA Technical Reports Server (NTRS)

    Nessel, James; Miranda, Felix

    2013-01-01

    A new nonvolatile nanoionic switch is powered and controlled through wireless radio-frequency (RF) transmission. A thin layer of chalcogenide glass doped with a metal ion, such as silver, comprises the operational portion of the switch. For the switch to function, an oxidizable electrode is made positive (anode) with respect to an opposing electrode (cathode) when sufficient bias, typically on the order of a few tenths of a volt or more, is applied. This action causes the metal ions to flow toward the cathode through a coordinated hopping mechanism. At the cathode, a reduction reaction occurs to form a metal deposit. This metal deposit creates a conductive path that bridges the gap between electrodes to turn the switch on. Once this conductive path is formed, no further power is required to maintain it. To reverse this process, the metal deposit is made positive with respect to the original oxidizable electrode, causing the dissolution of the metal bridge thereby turning the switch off. Once the metal deposit has been completely dissolved, the process self-terminates. This switching process features the following attributes. It requires very little to change states (i.e., on and off). Furthermore, no power is required to maintain the states; hence, the state of the switch is nonvolatile. Because of these attributes the integration of a rectenna to provide the necessary power and control is unique to this embodiment. A rectenna, or rectifying antenna, generates DC power from an incident RF signal. The low voltages and power required for the nanoionic switch control are easily generated from this system and provide the switch with a novel capability to be operated and powered from an external wireless device. In one realization, an RF signal of a specific frequency can be used to set the switch into an off state, while another frequency can be used to set the switch to an on state. The wireless, miniaturized, and nomoving- part features of this switch make it suitable for applications such as integration into garments, RFID (radio-frequency identification) tags, and conformal structures (e.g., aircraft wings, sounding rockets contours, etc). In the case of RFID tags the innovation will provide countermeasures to attempts for identity theft and other uninvited attempts for retrieval of information. It could also be applicable to the automotive industry as well as the aerospace industry for collision avoidance and phased array radar systems, respectively

  20. Full three-dimensional approach to the design and simulation of a radio-frequency quadrupole

    NASA Astrophysics Data System (ADS)

    Mustapha, B.; Kolomiets, A. A.; Ostroumov, P. N.

    2013-12-01

    We have developed a new full 3D approach for the electromagnetic and beam dynamics design and simulation of a radio-frequency quadrupole (RFQ). A detailed full 3D model including vane modulation was simulated, which was made possible by the ever advancing computing capabilities. The electromagnetic (EM) design approach was first validated using experimental measurements on an existing prototype RFQ and more recently on the actual full size RFQ. Two design options have been studied, the original with standard sinusoidal modulation over the full length of the RFQ; in the second design, a trapezoidal modulation was used in the accelerating section of the RFQ to achieve a higher energy gain for the same power and length. A detailed comparison of both options is presented supporting our decision to select the trapezoidal design. The trapezoidal modulation increased the shunt impedance of the RFQ by 34%, the output energy by 15% with a similar increase in the peak surface electric field, but practically no change in the dynamics of the accelerated beam. The beam dynamics simulations were performed using three different field methods. The first uses the standard eight-term potential to derive the fields, the second uses 3D fields from individual cell-by-cell models, and the third uses the 3D fields for the whole RFQ as a single cavity. A detailed comparison of the results from TRACK shows a very good agreement, validating the 3D fields approach used for the beam dynamics studies. The EM simulations were mainly performed using the CST Microwave-Studio with the final results verified using other software. Detailed segment-by-segment and full RFQ frequency calculations were performed and compared to the measured data. The maximum frequency deviation is about 100 kHz. The frequencies of higher-order modes have also been calculated and finally the modulation and tuners effects on both the frequency and field flatness have been studied. We believe that with this new full 3D approach, the enhanced computing capabilities and the calculation precision the electromagnetic design software offer, we may be able to skip the prototyping phase and build the final product at once, although we recognize that prototyping is still needed to establish and validate the fabrication procedure.

  1. Radio-frequency measurement of an asymmetric single electron transistor

    NASA Astrophysics Data System (ADS)

    Ji, Zhongqing; Xue, Weiwei; Rimberg, A. J.

    2007-03-01

    Since the invention of the radio-frequency single-electron transistor (RF-SET) by Schoelkopf et al.,[1] most measurements have focused on the symmetric single electron transistor. It has been shown, however, that the symmetric SET has a rather low measurement efficiency in its normal working regime.[2][3] Recently, it has been pointed out that an asymmetric SET can be considerably more efficient than a symmetric SET as a quantum amplifier. In this case the measurement efficiency of the asymmetric SET becomes similar to that of the quantum point contact (QPC) detector which can approach the quantum limit. We investigate the asymmetric SET by fabricating Al/AlOx SETs with junction areas 40x40 nm^2 and 40x80nm^2 and total resistance of about 25k?. The results of RF and DC characterization of such asymmetric SETs will be discussed. [1] R. J. Schoelkopf, P. Wahlgren, A. A. Kozhevnikov, P. Delsing, D. E. Prober, Science, 280, 1242 (1998). [2] A. N. Korotkov, Phys. Rev. B, 63, 085312 (2001); 63, 115403 (2001). [3] D. Mozyrsky, I. Martin, and M. B. Hastings, Phys. Rev. Lett., 92, 018303 (2004). [4] S. A. Gurvitz and G. P. Berman, Phys. Rev. B, 72 , 073303(2005).

  2. A comparative study of radiofrequency antennas for Helicon plasma sources

    NASA Astrophysics Data System (ADS)

    Melazzi, D.; Lancellotti, V.

    2015-04-01

    Since Helicon plasma sources can efficiently couple power and generate high-density plasma, they have received interest also as spacecraft propulsive devices, among other applications. In order to maximize the power deposited into the plasma, it is necessary to assess the performance of the radiofrequency (RF) antenna that drives the discharge, as typical plasma parameters (e.g. the density) are varied. For this reason, we have conducted a comparative analysis of three Helicon sources which feature different RF antennas, namely, the single-loop, the Nagoya type-III and the fractional helix. These antennas are compared in terms of input impedance and induced current density; in particular, the real part of the impedance constitutes a measure of the antenna ability to couple power into the plasma. The results presented in this work have been obtained through a full-wave approach which (being hinged on the numerical solution of a system of integral equations) allows computing the antenna current and impedance self-consistently. Our findings indicate that certain combinations of plasma parameters can indeed maximize the real part of the input impedance and, thus, the deposited power, and that one of the three antennas analyzed performs best for a given plasma. Furthermore, unlike other strategies which rely on approximate antenna models, our approach enables us to reveal that the antenna current density is not spatially uniform, and that a correlation exists between the plasma parameters and the spatial distribution of the current density.

  3. Delayed Development of Pneumothorax After Pulmonary Radiofrequency Ablation

    SciTech Connect

    Clasen, Stephan, E-mail: stephan.clasen@med.uni-tuebingen.d [Eberhard-Karls-University of Tuebingen, Department of Diagnostic and Interventional Radiology (Germany); Kettenbach, Joachim [Medical University of Vienna, Cardiovascular and Interventional Radiology, Department of Radiology (Austria); Kosan, Bora; Aebert, Hermann [Eberhard-Karls-University of Tuebingen, Department of Thoracic, Cardiac and Vascular Surgery (Germany); Schernthaner, Melanie [Medical University of Vienna, Cardiovascular and Interventional Radiology, Department of Radiology (Austria); Kroeber, Stefan-Martin [Eberhard-Karls-University of Tuebingen, Institute of Pathology (Germany); Boemches, Andrea [Eberhard-Karls-University of Tuebingen, Department of Thoracic, Cardiac and Vascular Surgery (Germany); Claussen, Claus D.; Pereira, Philippe L. [Eberhard-Karls-University of Tuebingen, Department of Diagnostic and Interventional Radiology (Germany)

    2009-05-15

    Acute pneumothorax is a frequent complication after percutaneous pulmonary radiofrequency (RF) ablation. In this study we present three cases showing delayed development of pneumothorax after pulmonary RF ablation in 34 patients. Our purpose is to draw attention to this delayed complication and to propose a possible approach to avoid this major complication. These three cases occurred subsequent to 44 CT-guided pulmonary RF ablation procedures (6.8%) using either internally cooled or multitined expandable RF electrodes. In two patients, the pneumothorax, being initially absent at the end of the intervention, developed without symptoms. One of these patients required chest drain placement 32 h after RF ablation, and in the second patient therapy remained conservative. In the third patient, a slight pneumothorax at the end of the intervention gradually increased and led into tension pneumothorax 5 days after ablation procedure. Underlying bronchopleural fistula along the coagulated former electrode track was diagnosed in two patients. In conclusion, delayed development of pneumothorax after pulmonary RF ablation can occur and is probably due to underlying bronchopleural fistula, potentially leading to tension pneumothorax. Patients and interventionalists should be prepared for delayed onset of this complication, and extensive track ablation following pulmonary RF ablation should be avoided.

  4. Modulation of blood circulating immune cells by radiofrequency tumor ablation.

    PubMed

    Rughetti, A; Rahimi, H; Rossi, P; Frati, L; Nuti, M; Gaspari, A; Danza, F M; Ercoli, L

    2003-12-01

    Tumor ablation by radiofrequency (RFA) is an appealing therapeutical strategy for the treatment of liver tumors (hepatocarcinoma and metastatic lesions) to be used as valid alternative to the surgical resection that often is appropriate and feasible in only a minority of patients. RFA induces the localised and controlled disruption of the tumor by heating the tissue causing its coagulative necrosis. Such therapy results as a pathogenic "noxa" for the body, inducing a strong inflammatory response. We wanted to ascertain whether the inflammatory response induced by RFA was similar in patients with hepatocarcinoma and in patients with liver metastasis. We considered body temperature, leucocyte counts at different time points as inflammatory parameters. We observed that RFA treatment produced the inflammatory systemic effects as expected (fever, increase of neutrophils) only in the patients with liver metastasis, while no such effect could be seen in the HCC patients. On the other hand the circulating monocytes increased after RFA in both groups of patients. These preliminary results suggest that RFA tratment can exert different effects on the immune system depending the etiopathogenesis of the treated neoplastic liver lesions. PMID:16767940

  5. Quality Improvement Guidelines for Radiofrequency Ablation of Liver Tumours

    SciTech Connect

    Crocetti, Laura, E-mail: l.crocetti@med.unipi.i [University of Pisa, Division of Diagnostic Imaging and Intervention, Department of Hepatology, Liver Transplants, and Infectious Diseases (Italy); Baere, Thierry de [Institut de Cancerologie Gustave Roussy, Department of Interventional Radiology (France); Lencioni, Riccardo [University of Pisa, Division of Diagnostic Imaging and Intervention, Department of Hepatology, Liver Transplants, and Infectious Diseases (Italy)

    2010-02-15

    The development of image-guided percutaneous techniques for local tumour ablation has been one of the major advances in the treatment of liver malignancies. Among these methods, radiofrequency ablation (RFA) is currently established as the primary ablative modality at most institutions. RFA is accepted as the best therapeutic choice for patients with early-stage hepatocellular carcinoma (HCC) when liver transplantation or surgical resection are not suitable options [1, 2]. In addition, RFA is considered a viable alternate to surgery (1) for inoperable patients with limited hepatic metastatic disease, especially from colorectal cancer, and (2) for patients deemed ineligible for surgical resection because of extent and location of the disease or concurrent medical conditions [3]. These guidelines were written to be used in quality-improvement programs to assess RFA of HCC and liver metastases. The most important processes of care are (1) patient selection, (2) performing the procedure, and (3) monitoring the patient. The outcome measures or indicators for these processes are indications, success rates, and complication rates.

  6. A mathematical model of bipolar radiofrequency-induced thermofusion.

    PubMed

    Wagenpfeil, J; Nold, B; Fischer, K; Neugebauer, A; Rothmund, R; Krämer, B; Brucker, S; Mischinger, J; Schwentner, C; Schenk, M; Wallwiener, D; Stenzl, A; Enderle, M; Sawodny, O; Ederer, M

    2014-01-01

    Bipolar radiofrequency-induced thermofusion has become a widely accepted method successfully used in open and particularly in minimally-invasive surgery for the sealing of blood vessels and tissue of up to several millimeters diameter. Despite its wide-spread application, the thermofusion process itself is not well understood on a quantitative and dynamic level, and manufacturers largely rely on trial-and-error methods to improve existing instruments. To predict the effect of alternative generator control strategies and to allow for a more systematic approach to improve thermofusion instruments, a mathematical model of the thermofusion process is developed. The system equations describe the spatial and temporal evolution of the tissue temperature due to Joule heating and heat transfer, and the loss of tissue water due to vaporization. The resulting effects on the tissue properties, most importantly the electrical resistivity, heat capacity and thermal conductivity, are considered as well. Experimental results indicate that the extent of the lateral thermal damage is directly affected by Joule heating of the lateral tissue. The experimental findings are supported by simulation results using the proposed mathematical model of thermofusion. PMID:25571285

  7. Software-assisted post-interventional assessment of radiofrequency ablation

    NASA Astrophysics Data System (ADS)

    Rieder, Christian; Geisler, Benjamin; Bruners, Philipp; Isfort, Peter; Na, Hong-Sik; Mahnken, Andreas H.; Hahn, Horst K.

    2014-03-01

    Radiofrequency ablation (RFA) is becoming a standard procedure for minimally invasive tumor treatment in clinical practice. Due to its common technical procedure, low complication rate, and low cost, RFA has become an alternative to surgical resection in the liver. To evaluate the therapy success of RFA, thorough follow-up imaging is essential. Conventionally, shape, size, and position of tumor and coagulation are visually compared in a side-by-side manner using pre- and post-interventional images. To objectify the verification of the treatment success, a novel software assistant allowing for fast and accurate comparison of tumor and coagulation is proposed. In this work, the clinical value of the proposed assessment software is evaluated. In a retrospective clinical study, 39 cases of hepatic tumor ablation are evaluated using the prototype software and conventional image comparison by four radiologists with different levels of experience. The cases are randomized and evaluated in two sessions to avoid any recall-bias. Self-confidence of correct diagnosis (local recurrence vs. no local recurrence) on a six-point scale is given for each case by the radiologists. Sensitivity, specificity, positive and negative predictive values as well as receiver operating curves are calculated for both methods. It is shown that the software-assisted method allows physicians to correctly identify local tumor recurrence with a higher percentage than the conventional method (sensitivity: 0.6 vs. 0.35), whereas the percentage of correctly identified successful ablations is slightly reduced (specificity: 0.83 vs. 0.89).

  8. PET guidance for liver radiofrequency ablation: an evaluation

    NASA Astrophysics Data System (ADS)

    Lei, Peng; Dandekar, Omkar; Mahmoud, Faaiza; Widlus, David; Malloy, Patrick; Shekhar, Raj

    2007-03-01

    Radiofrequency ablation (RFA) is emerging as the primary mode of treatment of unresectable malignant liver tumors. With current intraoperative imaging modalities, quick, precise, and complete localization of lesions remains a challenge for liver RFA. Fusion of intraoperative CT and preoperative PET images, which relies on PET and CT registration, can produce a new image with complementary metabolic and anatomic data and thus greatly improve the targeting accuracy. Unlike neurological images, alignment of abdominal images by combined PET/CT scanner is prone to errors as a result of large nonrigid misalignment in abdominal images. Our use of a normalized mutual information-based 3D nonrigid registration technique has proven powerful for whole-body PET and CT registration. We demonstrate here that this technique is capable of acceptable abdominal PET and CT registration as well. In five clinical cases, both qualitative and quantitative validation showed that the registration is robust and accurate. Quantitative accuracy was evaluated by comparison between the result from the algorithm and clinical experts. The accuracy of registration is much less than the allowable margin in liver RFA. Study findings show the technique's potential to enable the augmentation of intraoperative CT with preoperative PET to reduce procedure time, avoid repeating procedures, provide clinicians with complementary functional/anatomic maps, avoid omitting dispersed small lesions, and improve the accuracy of tumor targeting in liver RFA.

  9. Radiofrequency ablation in palliative supportive care: early clinical experience.

    PubMed

    Marchal, Frédéric; Brunaud, Laurent; Bazin, Christophe; Boccacini, Hervé; Henrot, Philippe; Troufleau, Philippe; Krakowski, Ivan; Regent, Denis

    2006-02-01

    We report our early experience with radiofrequency ablation (RFA) in palliative supportive care. The medical files of eight patients were retrospectively reviewed. Four patients had a renal tumor, and nephrectomy was contraindicated in each patient since they had a poor general status. The fifth patient had a local recurrence in the site of a previous nephrectomy with a pancreatic tail extension, and surgical resection was contraindicated because of abdominal carcinomatosis. Two other patients had bone metastasis, one with a painful metastasis of mammary carcinoma in the head of the humerus resistant to radiotherapy, and the other with metastasis of the tibia of cutaneous melanoma. The last patient had a local recurrence of a sacral chordoma. Management, outcomes and complications were evaluated with 13.1+/-0.3 months follow-up. All five patients with renal carcinomas did not have local recurrence. The two patients treated for bone metastases had no pain 8 weeks after RFA and remained stable over time. One complication occurred 2 months after using the procedure to treat the chordoma, and this patient was hospitalized for a fistula between the sigmoid and hypogastric artery false aneurysm and subsequently died. In conclusion, RFA can be a safe and useful adjuvant treatment in supportive care or unresponsive cancer pain patients. However, the destruction of tumoral tissues in contact with sensitive structures using RFA should be done with caution due to potentially severe complications. PMID:16391875

  10. Feasibility of fast MR-thermometry during cardiac radiofrequency ablation.

    PubMed

    de Senneville, Baudouin Denis; Roujol, Sébastien; Jaïs, Pierre; Moonen, Chrit T W; Herigault, Gwenaël; Quesson, Bruno

    2012-04-01

    Online MR temperature monitoring during radiofrequency (RF) ablation of cardiac arrhythmias may improve the efficacy and safety of the treatment. MR thermometry at 1.5 T using the proton resonance frequency (PRF) method was assessed in 10 healthy volunteers under normal breathing conditions, using a multi-slice, ECG-gated, echo planar imaging (EPI) sequence in combination with slice tracking. Temperature images were post-processed to remove residual motion-related artifacts. Using an MR-compatible steerable catheter and electromagnetic noise filter, RF ablation was performed in the ventricles of two sheep in vivo. The standard deviation of the temperature evolution in time (TSD) was computed. Temperature mapping of the left ventricle was achieved at an update rate of approximately 1 Hz with a mean TSD of 3.6 ± 0.9 °C. TSD measurements at the septum showed a higher precision (2.8 ± 0.9 °C) than at the myocardial regions at the heart-lung and heart-liver interfaces (4.1 ± 0.9 °C). Temperature rose maximally by 9 °C and 16 °C during 5 W and 10 W RF applications, respectively, for 60 s each. Tissue temperature can be monitored at an update rate of approximately 1 Hz in five slices. Typical temperature changes observed during clinical RF application can be monitored with an acceptable level of precision. PMID:22553824

  11. Sustained 35-GHz radiofrequency irradiation induces circulatory failure.

    PubMed

    Frei, M R; Ryan, K L; Berger, R E; Jauchem, J R

    1995-10-01

    The objective of this study was to determine the thermal distribution and concomitant cardiovascular changes produced by whole-body exposure of ketamine-anesthetized rats to radiofrequency radiation of millimeter wave (MMW) length. Rats (n = 13) were implanted with a flow probe on the superior mesenteric artery and with a catheter in the carotid artery for the measurement of arterial blood pressure. Temperature was measured at five sites: left (Tsl) and right subcutaneous (sides toward and away From the MMW source, respectively), colonic (Tc), tympanic, and tail. The animals were exposed until death to MMW (35 GHz) at a power density that resulted in a whole-body specific absorption rate of 13 W/kg. During irradiation, the Tsl increase was significantly greater than the Tc increase. Heart rate increased throughout irradiation. Mean arterial pressure (MAP) as well maintained until Tsl reached 42 degrees C, at which point MAP declined until death. Mesenteric vascular resistance tended to increase during the early stages of irradiation but began to decrease at Tsl > or = 41 degrees C. The declines in both mesenteric vascular resistance and MAP began at Tc < 37.5 degrees C; death occurred at Tc = 40.3 +/- .3 degrees C and Tsl = 48.0 +/- .4 degrees C. These data indicate that circulatory failure and subsequent death may occur when skin temperature is rapidly elevated, even in the presence of relatively normal Tc. PMID:8564558

  12. Radiofrequency ablation of haemodynamically unstable ventricular tachycardia after myocardial infarction

    PubMed Central

    Furniss, S; Anil-Kumar, R; Bourke, J; Behulova, R; Simeonidou, E

    2000-01-01

    OBJECTIVE—To determine whether radiofrequency (RF) ablation might have a role in haemodynamically unstable ventricular tachycardia.?METHODS—10 patients with a history of ventricular tachycardia producing haemodynamic collapse in whom drug treatment had failed and device therapy was rejected underwent RF ablation of ventricular tachycardia in sinus rhythm. The arrhythmogenic zone was defined on the basis of abnormal systolic movement, the presence of fragmentation (low amplitude, prolonged multiphasic electrograms), and pace mapping. RF lesions were delivered in power mode in linear fashion within the defined arrhythmogenic zone.?RESULTS—Success (no ventricular tachycardia inducible postablation or at retest) was achieved in six patients, possible success (a different ventricular tachycardia inducible at more aggressive stimulation) in three. In one patient, the procedure was abandoned because of poor catheter stability. There were no clinical events during a mean (SD) follow up period of 23 (10) months in any of the nine patients defined as definite or possible successes.?CONCLUSIONS—RF ablation for addressing haemodynamically unstable ventricular tachycardia opens the door for the wider use of catheter ablation for treating this arrhythmia.???Keywords: tachycardia; catheter ablation; sudden death PMID:11083746

  13. Radiofrequency dosimetry for the Ferris-wheel mouse exposure system.

    PubMed

    Faraone, Antonio; Luengas, Wilson; Chebrolu, Subbarao; Ballen, Maurice; Bit-Babik, Giorgi; Gessner, Andrew V; Kanda, Michael Y; Babij, Tadeusz; Swicord, Mays L; Chou, Chung-Kwang

    2006-01-01

    Numerical and experimental methods were employed to assess the individual and collective dosimetry of mice used in a bioassay on the exposure to pulsed radiofrequency energy at 900 MHz in the Ferris-wheel exposure system (Utteridge et al., Radiat. Res. 158, 357-364, 2002). Twin-well calorimetry was employed to measure the whole-body specific absorption rate (SAR) of mice for three body masses (23 g, 32 g and 36 g) to determine the lifetime exposure history of the mice used in the bioassay. Calorimetric measurements showed about 95% exposure efficiency and lifetime average whole-body SARs of 0.21, 0.86, 1.7 and 3.4 W kg(-1) for the four exposure groups. A larger statistical variation in SAR was observed in the smallest mice because they had the largest variation in posture inside the plastic restrainers. Infrared thermography provided SAR distributions over the sagittal plane of mouse cadavers. Thermograms typically showed SAR peaks in the abdomen, neck and head. The peak local SAR at these locations, determined by thermometric measurements, showed peak-to-average SAR ratios below 6:1, with typical values around 3:1. Results indicate that the Ferris wheel fulfills the requirement of providing a robust exposure setup, allowing uniform collective lifetime exposure of mice. PMID:16392968

  14. Incidence and Cause of Hypertension During Adrenal Radiofrequency Ablation

    SciTech Connect

    Yamakado, Koichiro, E-mail: yama@clin.medic.mie-u.ac.jp; Takaki, Haruyuki [Mie University School of Medicine, Department of Interventional Radiology (Japan); Yamada, Tomomi [Mie University School of Medicine, Department of Translational Medicine (Japan); Yamanaka, Takashi; Uraki, Junji; Kashima, Masataka; Nakatsuka, Atsuhiro; Takeda, Kan [Mie University School of Medicine, Department of Interventional Radiology (Japan)

    2012-12-15

    Purpose: To evaluate the incidence and cause of hypertension prospectively during adrenal radiofrequency ablation (RFA). Methods: For this study, approved by our institutional review board, written informed consent was obtained from all patients. Patients who received RFA for adrenal tumors (adrenal ablation) and other abdominal tumors (nonadrenal ablation) were included in this prospective study. Blood pressure was monitored during RFA. Serum adrenal hormone levels including epinephrine, norepinephrine, dopamine, and cortisol levels were measured before and during RFA. The respective incidences of procedural hypertension (systolic blood pressure >200 mmHg) of the two patient groups were compared. Factors correlating with procedural systolic blood pressure were evaluated by regression analysis.ResultsNine patients underwent adrenal RFA and another 9 patients liver (n = 5) and renal (n = 4) RFA. Asymptomatic procedural hypertension that returned to the baseline by injecting calcium blocker was found in 7 (38.9%) of 18 patients. The incidence of procedural hypertension was significantly higher in the adrenal ablation group (66.7%, 6/9) than in the nonadrenal ablation group (11.1%, 1/9, P < 0.0498). Procedural systolic blood pressure was significantly correlated with serum epinephrine (R{sup 2} = 0.68, P < 0.0001) and norepinephrine (R{sup 2} = 0.72, P < 0.0001) levels during RFA. The other adrenal hormones did not show correlation with procedural systolic blood pressure. Conclusion: Hypertension occurs frequently during adrenal RFA because of the release of catecholamine.

  15. Technological advances in minimally invasive radiofrequency ablation of cardiac tissues.

    PubMed

    Difrancesco, Mark; Park, Chris; Martin, Keith E; Glithero, Jason; Privitera, Salvatore; Cassidy, Bridget P

    2010-03-01

    Ablative techniques have been sought in many circumstances as alternatives to surgical resection/incision. Besides being minimally invasive, potential benefits of ablation include greater speed and improved access to target tissue compared with other surgical techniques. There is a wide variety of ablation technologies currently in use for medical treatment. These include but are not limited to tissue heating by radiofrequency (RF) current, microwaves, laser, and high intensity ultrasound. RF is among the most heavily used because of its relatively low complexity and cost. Ablative techniques have proven to be viable alternatives to surgical resection/incision of tissue. Although there are other means of tissue heating besides RF, RF is the most commonly used technique in operating rooms because of the reliability of transmural lesions and the low complexity of the system. Optimal systems account for the heterogeneous nature of tissue and variations in tissue property through the ablation cycle. It is important to monitor and assure adequate energy delivery by selecting the appropriate configuration of devices. Energy delivery varies between the various generators and systems, some more responsive than others with relative to changes in tissue impedance that will affect the end results of the operation. PMID:22437366

  16. Shale oil upgrading using radio-frequency energy

    SciTech Connect

    Cha, C.Y.

    1988-09-01

    Western Research Institute has constructed and operated a radio-frequency (rf) reactor system to investigate shale oil upgrading opportunities. The reactor system has been used to develop techniques using rf energy as a nonchemical catalyst to enhance reaction rate or to change the product distribution. This report documents experimental results of eastern and western shale oil desulfurization tests using 2450 MHz rf energy. A series of batch and continuous reactor tests have been conducted using eastern and western shale oil in a tubular reactor located inside the wave guide. Results show that 2,450 MHz of rf energy selectively decomposes sulfur and oxygen components in the eastern and western shale oil when they are processed at 450--500{degree}F (230--260{degree}C). The rate of sulfur removal from shale oil is mainly dependent on the rf power input per unit weight of shale oil introduced. The maximum sulfur removal (32--38%) was obtained when power input was in the range of 0.8 to 1.1 watts per grams of shale oil per hour. Oil residence times between 3 and 12 minutes had no significant effect on sulfur removal rate. The highest sulfur removal (42%) was obtained when the shale oil was treated with 300 watts of rf energy at 450--500{degree}F (230-260{degree}C) for two hours in the batch reactor. 3 refs., 5 figs., 4 tabs.

  17. Radiofrequency Ablation for Tumor-Related Massive Hematuria

    PubMed Central

    Neeman, Ziv; Sarin, Shawn; Coleman, Jonathan; Fojo, Tito; Wood, Bradford J.

    2008-01-01

    To determine whether radiofrequency (RF) ablation targeting the tumor-collecting system interface has a durable effect in patients with transfusion-dependent kidney tumor-related hematuria, four patients aged 61-71 years were successfully treated with RF ablation, with a mean follow up of 12 months. Baseline creatinine levels varied from 2.0 mg/dL to 3.7 mg/dL. All patients had received red blood cell transfusions in the days and hours before RF ablation. No subsequent surgical or interventional procedures were required for management of hematuria. Gross hematuria resolved in 24-48 hours in all four patients. Two of the patients are alive with stable renal function and two died of causes unrelated to treatment. RF ablation may be an effective therapeutic option for transfusion-dependent cancer-related hematuria in patients with renal insufficiency, solitary kidney, or comorbidities, or after failed conventional therapies in patients who are not candidates for surgery. PMID:15758142

  18. Transformations in optics for radio-frequency spectrum analysis

    NASA Astrophysics Data System (ADS)

    Colice, Christopher Max

    Why use optics for radio-frequency spectrum analysis, especially when electronic spectrum analyzers are so good? There are several reasons: optical processing is inherently parallel; coherent light Fourier transforms as it propagates; and the processing speed is usually determined by the time it takes light to propagate through the system. Of course, there are disadvantages to optical processing, namely the difficulty in generating long time delays using optics and the (relatively) small dynamic range of optical detectors. Optical systems are good for analyzing pulsed or hopping signals, and electronic systems for weak continuous-wave signals. Traditionally, optical processors use spatial parallelism to monitor many channels simultaneously. Exploiting this parallelism requires converting time-domain signals into spatial modulation. Coordinate transformations, then, make domain transformations possible. The systems based on tapped delay lines described in Chapters 1 and 2 all use spatial coordinate transformations for spectrum analysis, while the spectral-hole-burning spectrum analyzers discussed in Chapters 3 and 4 use spectral parallelism for spectrum analysis. Spectrum analyzers that use more than one dimension, such as the spatial-spectral processor in Chapter 5, could potentially operate with time-bandwidth products of up to 108, something far beyond the reach of electronic spectrum analyzers for the foreseeable future.

  19. Disinfection of dairy and animal farm wastewater with radiofrequency power.

    PubMed

    Lagunas-Solar, M C; Cullor, J S; Zeng, N X; Truong, T D; Essert, T K; Smith, W L; Piña, C

    2005-11-01

    Radiofrequency (RF) power was investigated as a new, physical (nonchemical), thermal process to disinfect wastewater from dairy and animal facilities. Samples (n = 38) from 8 dairy, 2 calf, and 3 swine facilities in California were collected over a 3-yr period and characterized for their dielectric properties, chemical composition, and suitability for thermal processing using RF power. To establish efficacy for disinfection, selected samples were inoculated with high levels (10(6) to 10(9) cfu/mL) of bacterial pathogens such as Salmonella sp., Escherichia coli O157:H7, and Mycobacterium avium ssp. paratuberculosis and processed with an RF prototype system. The capabilities of RF power as a method for thermal disinfection of wastewater were demonstrated when bacteria pathogens were completely and rapidly (<1 min) inactivated when temperatures of 60 to 65 degrees C were achieved. Furthermore, RF technology can be used for large-scale, batch or continuous and portable applications, allowing significant improvements in energy-use efficiencies compared with conventional thermal (surface heating) technologies. Therefore, RF power has potential as an alternative to disinfect dairy/animal farm wastewater before recycling. PMID:16230716

  20. Analysis and analytical characterization of bioheat transfer during radiofrequency ablation.

    PubMed

    Wang, Keyong; Tavakkoli, Fatemeh; Wang, Shujuan; Vafai, Kambiz

    2015-04-13

    Understanding thermal transport and temperature distribution within biological organs is important for therapeutic aspects related to hyperthermia treatments such as radiofrequency ablation (RFA). Unlike surface heating, the RFA treatment volumetrically heats up the biological media using a heating probe which provides the input energy. In this situation, the shape of the affected region is annular, which is described by an axisymmetric geometry. To better understand the temperature responses of the living tissues subject to RFA, comprehensive characteristics of bioheat transport through the annular biological medium is presented under local thermal non-equilibrium (LTNE) condition. Following the operational features of the RFA treatment, based on the porous media theory, analytical solutions have been derived for the blood and tissue temperature distributions as well as an overall heat exchange correlation in cylindrical coordinates. Our analytical results have been validated against three limiting cases which exist in the literature. The effects of various physiological parameters, such as metabolic heat generation, volume fraction of the vascular space, ratio of the effective blood to tissue conductivities, different biological media and the rate of heat exchange between the lumen and the tissue are investigated. Solutions developed in this study are valuable for thermal therapy planning of RFA. A criterion is also established to link deep heating protocol to surface heating. PMID:25769731

  1. Value of radiofrequency ablation in the treatment of hepatocellular carcinoma

    PubMed Central

    Feng, Kai; Ma, Kuan-Sheng

    2014-01-01

    Hepatocellular carcinoma (HCC) is a malignant disease that substantially affects public health worldwide. It is especially prevalent in east Asia and sub-Saharan Africa, where the main etiology is the endemic status of chronic hepatitis B. Effective treatments with curative intent for early HCC include liver transplantation, liver resection (LR), and radiofrequency ablation (RFA). RFA has become the most widely used local thermal ablation method in recent years because of its technical ease, safety, satisfactory local tumor control, and minimally invasive nature. This technique has also emerged as an important treatment strategy for HCC in recent years. RFA, liver transplantation, and hepatectomy can be complementary to one another in the treatment of HCC, and the outcome benefits have been demonstrated by numerous clinical studies. As a pretransplantation bridge therapy, RFA extends the average waiting time without increasing the risk of dropout or death. In contrast to LR, RFA causes almost no intra-abdominal adhesion, thus producing favorable conditions for subsequent liver transplantation. Many studies have demonstrated mutual interactions between RFA and hepatectomy, effectively expanding the operative indications for patients with HCC and enhancing the efficacy of these approaches. However, treated tumor tissue remains within the body after RFA, and residual tumors or satellite nodules can limit the effectiveness of this treatment. Therefore, future research should focus on this issue. PMID:24876721

  2. Quantification of local convectional cooling during cardiac radiofrequency catheter ablation.

    PubMed

    Haemmerich, D; Saul, J P

    2006-01-01

    Radiofrequency (RF) catheter ablation is an effective, minimally invasive treatment method in clinical use for treatment of different cardiac arrhythmia. Studies have shown that lesion dimensions strongly depend on blood flow mediated convective cooling at the ablation site. We present a simple method to quantify convective cooling. A brief pulse of RF energy (10 W for 5 s) is applied, and catheter tip temperature is measured during and after energy application. Two parameters are extracted: 1) maximum tip temperature increase, and 2) slope of temperature decay 8 degree C above initial temperature. We tested whether these parameters can quantify convective cooling in ex vivo experiments. A RF catheter was inserted into a tissue phantom placed in a saline bath. Flow at different rates of 0, 1, 2 and 3 L/min was injected towards the catheter, and the parameters were extracted. Both parameters correlated with flow rate. Slope of temperature decay showed linear dependence on flow rate, maximum temperature increase showed exponential dependence. The parameters are potentially useful in quantifying convective cooling before ablation to predict lesion dimensions. PMID:17945951

  3. Pulsed radiofrequency treatment in a case of Eagle's syndrome.

    PubMed

    Mollinedo, Fernando T; Esteban, Sonia L T; Vega, Cristina G; Orcasitas, Ana C; Maguregi, Antón A

    2013-06-01

    Eagle (Arch Otolaryngol. 1937;25:584 and Arch Otolaryngol. 1949;49:490) first identified elongation of the styloid process and ossification of the stylohyoid ligament as a cause of orofacial pain. The elongated styloid process presses on the internal carotid artery and adjacent structures, including branches of the glossopharyngeal nerve and this produce orofacial pain. Some authors define an elongated styloid process as longer than 4?cm because this length is associated with an increase in the incidence of Eagle's syndrome. The syndrome is diagnosed by exclusion (Walkman SD. Atlas of Uncommon Pain Syndromes. Philadelphia: Elsevier Science; 2003), and the diagnosis is confirmed by radiological studies and computed tomography. Treatment can be divided into medical, interventional, and surgical techniques. We report a patient with symptoms of glossopharyngeal neuralgia, who was diagnosed with Eagle's syndrome on the basis of diagnostic imaging. The length of the stylohyoid process was 63?mm on the left side and 64?mm on the right. Treatment was performed by applying pulsed radiofrequency to the glossopharyngeal nerve with satisfactory results. The technique was performed twice on an outpatient basis, produced no complications or side effects, and proved effective in the short and medium term in decreasing the intensity of pain. PMID:23057728

  4. CORONARY ARTERY PATHOPHYSIOLOGY AFTER RADIOFREQUENCY CATHETER ABLATION: REVIEW AND PERSPECTIVES

    PubMed Central

    Castaño, Adam; Crawford, Thomas; Yamazaki, Masatoshi; Avula, Uma Mahesh R; Kalifa, Jérôme

    2011-01-01

    Radiofrequency ablation (RFA) has proven to be an effective and safe treatment in patients with ventricular and atrial tachyarrhythmias. Among complications arising after RFA, the incidence of coronary artery (CA) injury is exceedingly low. When CA injury does occur, however, it can be clinically devastating. The proximity of CAs to common ablation sites suggests that the relationship between RFA and CA perfusion pathophysiology is important. While others have described the presentation and outcomes of patients with CA injury after ablation, a review that consolidates the mechanisms of CA injury after RFA has yet to be presented in the cardiology literature. We conducted an extensive literature search of studies published over the past thirty years that relate the biophysics of RFA with CA perfusion pathophysiology and injury. From this, we present a review of the dynamic relationship between RFA and CA perfusion. We describe RFA lesion pathology, mechanisms of CA injury from RFA, and factors that influence lesion formation such as convective cooling and the ‘shadow effect.’ Finally, we summarize methods to mitigate CA injury after RFA and propose new research avenues to optimize lesion formation and safe arrhythmia treatments when tissue is ablated in the vicinity of CAs. PMID:21740881

  5. Proof-of-principle demonstration of Nb3Sn superconducting radiofrequency cavities for high Q0 applications

    NASA Astrophysics Data System (ADS)

    Posen, S.; Liepe, M.; Hall, D. L.

    2015-02-01

    Many future particle accelerators require hundreds of superconducting radiofrequency (SRF) cavities operating with high duty factor. The large dynamic heat load of the cavities causes the cryogenic plant to make up a significant part of the overall cost of the facility. This contribution can be reduced by replacing standard niobium cavities with ones coated with a low-dissipation superconductor such as Nb3Sn. In this paper, we present results for single cell cavities coated with Nb3Sn at Cornell. Five coatings were carried out, showing that at 4.2 K, high Q0 out to medium fields was reproducible, resulting in an average quench field of 14 MV/m and an average 4.2 K Q0 at quench of 8 × 109. In each case, the peak surface magnetic field at quench was well above Hc1, showing that it is not a limiting field in these cavities. The coating with the best performance had a quench field of 17 MV/m, exceeding gradient requirements for state-of-the-art high duty factor SRF accelerators. It is also shown that—taking into account the thermodynamic efficiency of the cryogenic plant—the 4.2 K Q0 values obtained meet the AC power consumption requirements of state-of-the-art high duty factor accelerators, making this a proof-of-principle demonstration for Nb3Sn cavities in future applications.

  6. Self-consistent modeling of radio-frequency plasma generation in stellarators

    NASA Astrophysics Data System (ADS)

    Moiseenko, V. E.; Stadnik, Yu. S.; Lysoivan, A. I.; Korovin, V. B.

    2013-11-01

    A self-consistent model of radio-frequency (RF) plasma generation in stellarators in the ion cyclotron frequency range is described. The model includes equations for the particle and energy balance and boundary conditions for Maxwell's equations. The equation of charged particle balance takes into account the influx of particles due to ionization and their loss via diffusion and convection. The equation of electron energy balance takes into account the RF heating power source, as well as energy losses due to the excitation and electron-impact ionization of gas atoms, energy exchange via Coulomb collisions, and plasma heat conduction. The deposited RF power is calculated by solving the boundary problem for Maxwell's equations. When describing the dissipation of the energy of the RF field, collisional absorption and Landau damping are taken into account. At each time step, Maxwell's equations are solved for the current profiles of the plasma density and plasma temperature. The calculations are performed for a cylindrical plasma. The plasma is assumed to be axisymmetric and homogeneous along the plasma column. The system of balance equations is solved using the Crank-Nicholson scheme. Maxwell's equations are solved in a one-dimensional approximation by using the Fourier transformation along the azimuthal and longitudinal coordinates. Results of simulations of RF plasma generation in the Uragan-2M stellarator by using a frame antenna operating at frequencies lower than the ion cyclotron frequency are presented. The calculations show that the slow wave generated by the antenna is efficiently absorbed at the periphery of the plasma column, due to which only a small fraction of the input power reaches the confinement region. As a result, the temperature on the axis of the plasma column remains low, whereas at the periphery it is substantially higher. This leads to strong absorption of the RF field at the periphery via the Landau mechanism.

  7. Metabolic and vasomotor responses of rhesus monkeys exposed to 225-MHz radiofrequency energy. [Macaca mulatta

    SciTech Connect

    Lotz, W.G.; Saxton, J.L.

    1987-01-01

    A previous study showed a substantial increase in the colonic temperature of rhesus monkeys (Macaca mulatta) exposed to radiofrequency (RF) fields at a frequency near whole-body resonance and specific absorption rates (SAR) of 2-3 W/kg. The present experiments were conducted to determine the metabolic and vasomotor responses during exposures to similar RF fields. We exposed five adult male rhesus monkeys to 225 MHz radiation (E orientation) in an anechoic chamber. Oxygen consumption and carbon dioxide production were measured before, during, and after RF exposure. Colonic, tail and leg skin temperatures were continuously monitored with RF-nonperturbing probes. The monkeys were irradiated at two carefully-controlled ambient temperatures, either cool (20 degrees C) or thermoneutral (26 degrees C). Power densities ranged from 0 (sham) to 10.0 mW/cm2 with an average whole-body SAR of 0.285 (W/kg)/(mW/cm2). We used two experimental protocols, each of which began with a 120-min pre-exposure equilibration period. One protocol involved repetitive 10-min RF exposures at successively higher power densities with a recovery period between exposures. In the second protocol, a 120-min RF exposure permitted the measurement of steady-state thermoregulatory responses. Metabolic and vasomotor adjustments in the rhesus monkey exposed to 225 MHz occurred during brief or sustained exposures at SARs at or above 1.4 W/kg. The SAR required to produce a given response varied with ambient temperature. Metabolic and vasomotor responses were coordinated effectively to produce a stable deep body temperature. The results show that the thermoregulatory response of the rhesus monkey to an RF exposure at a resonant frequency limits storage of heat in the body. However, substantial increases in colonic temperature were not prevented by such responses, even in a cool environment.

  8. Metabolic and vasomotor responses of rhesus monkeys exposed to 225-MHz radiofrequency energy

    SciTech Connect

    Lotz, W.G.; Saxton, J.L.

    1987-01-01

    A previous study showed a substantial increase in the colonic temperature of rhesus monkeys (Macaca mulatta) exposed to radio-frequency (RF) fields at a frequency near whole-body resonance and specific absorption rates (SAR) of 2 to 3 W/kg. The present experiments were conducted to determine the metabolic and vasomotor responses during exposures to similar RF fields. Five adult male rhesus monkeys were exposed to 225-MHz radiation (E orientation) in an anechoic chamber. The monkeys were irradiated at two carefully-controlled ambient temperatures, either cool (20 C) or thermoneutral (26 C). Power densities ranged from 0 (sham) to 10.0 mW/sq cm with an average whole-body SAR of 0.285 (W/kg)/(mW/sq cm). Two experimental protocols were used, each of which began with a 120-min preexposure equilibration period. Then, one protocol involved repetitive 10-min RF exposures at successively higher power densities with a recovery period between exposures. In the second protocol, a 120-min RF exposure permitted the measurement of steady-state thermoregulatory responses. Metabolic and vasomotor adjustments in the rhesus monkey exposed to 225 MHz occurred during brief or sustained exposures at SARs at or above 1.4 W/kg. Metabolic and vasomotor responses were coordinated effectively to produce a stable deep-body temperature. The results show that the thermoregulatory response of the rhesus monkey to an RF exposure at a resonant frequency limits storage of heat in the body. However, substantial increases in colonic temperature were not prevented by such responses, even in a cool environment.

  9. Effect of vortex hotspots on the radio-frequency surface resistance of superconductors

    SciTech Connect

    A. Gurevich, G. Ciovati

    2013-02-01

    We present detailed experimental and theoretical investigations of hotspots produced by trapped vortex bundles and their effect on the radio-frequency (rf) surface resistance R{sub s} of superconductors at low temperatures. Our measurements of R{sub s}, combined with the temperature mapping and laser scanning of a 2.36-mm-thick Nb plate incorporated into a 3.3-GHz Nb resonator cavity cooled by the superfluid He at 2 K, revealed spatial scales and temperature distributions of hotspots and showed that they can be moved or split by thermal gradients produced by the scanning laser beam. These results, along with the observed hysteretic field dependence of R{sub s} which can be tuned by the scanning laser beam, show that the hotspots in our Nb sample are due to trapped vortex bundles which contain ?10{sup 6} vortices spread over regions ?0.1–1 cm. We calculated the frequency dependence of the rf power dissipated by oscillating vortex segments trapped between nanoscale pinning centers, taking into account all bending modes and the nonlocal line tension of the vortex driven by rf Meissner currents. We also calculated the temperature distributions caused by trapped vortex hotspots, and suggested a method of reconstructing the spatial distribution of vortex dissipation sources from the observed temperature maps. Vortex hotspots can dominate the residual surface resistance at low temperatures and give rise to a significant dependence of R{sub s} on the rf field amplitude H{sub p}, which can have important implications for the rf resonating cavities used in particle accelerators and for thin-film structures used in quantum computing and photon detectors.

  10. Self-consistent modeling of radio-frequency plasma generation in stellarators

    SciTech Connect

    Moiseenko, V. E., E-mail: moiseenk@ipp.kharkov.ua; Stadnik, Yu. S., E-mail: stadnikys@kipt.kharkov.ua [National Academy of Sciences of Ukraine, National Science Center Kharkov Institute of Physics and Technology (Ukraine); Lysoivan, A. I., E-mail: a.lyssoivan@fz-juelich.de [Royal Military Academy, EURATOM-Belgian State Association, Laboratory for Plasma Physics (Belgium); Korovin, V. B. [National Academy of Sciences of Ukraine, National Science Center Kharkov Institute of Physics and Technology (Ukraine)] [National Academy of Sciences of Ukraine, National Science Center Kharkov Institute of Physics and Technology (Ukraine)

    2013-11-15

    A self-consistent model of radio-frequency (RF) plasma generation in stellarators in the ion cyclotron frequency range is described. The model includes equations for the particle and energy balance and boundary conditions for Maxwell’s equations. The equation of charged particle balance takes into account the influx of particles due to ionization and their loss via diffusion and convection. The equation of electron energy balance takes into account the RF heating power source, as well as energy losses due to the excitation and electron-impact ionization of gas atoms, energy exchange via Coulomb collisions, and plasma heat conduction. The deposited RF power is calculated by solving the boundary problem for Maxwell’s equations. When describing the dissipation of the energy of the RF field, collisional absorption and Landau damping are taken into account. At each time step, Maxwell’s equations are solved for the current profiles of the plasma density and plasma temperature. The calculations are performed for a cylindrical plasma. The plasma is assumed to be axisymmetric and homogeneous along the plasma column. The system of balance equations is solved using the Crank-Nicholson scheme. Maxwell’s equations are solved in a one-dimensional approximation by using the Fourier transformation along the azimuthal and longitudinal coordinates. Results of simulations of RF plasma generation in the Uragan-2M stellarator by using a frame antenna operating at frequencies lower than the ion cyclotron frequency are presented. The calculations show that the slow wave generated by the antenna is efficiently absorbed at the periphery of the plasma column, due to which only a small fraction of the input power reaches the confinement region. As a result, the temperature on the axis of the plasma column remains low, whereas at the periphery it is substantially higher. This leads to strong absorption of the RF field at the periphery via the Landau mechanism.

  11. NON-INVASIVE RADIOFREQUENCY ABLATION OF CANCER TARGETED BY GOLD NANOPARTICLES

    PubMed Central

    Cardinal, Jon; Klune, John Robert; Chory, Eamon; Jeyabalan, Geetha; Kanzius, John S.; Nalesnik, Michael; Geller, David A.

    2008-01-01

    Introduction Current radiofrequency ablation (RFA) techniques require invasive needle placement and are limited by accuracy of targeting. The purpose of this study was to test a novel non-invasive radiowave machine that uses RF energy to thermally destroy tissue. Gold nanoparticles were designed and produced to facilitate tissue heating by the radiowaves. Methods A solid state radiowave machine consisting of a power generator and transmitting/receiving couplers which transmit radiowaves at 13.56 MHz was used. Gold nanoparticles were produced by citrate reduction and exposed to the RF field either in solutions testing or after incubation with HepG2 cells. A rat hepatoma model using JM-1 cells and Fisher rats was employed using direct injection of nanoparticles into the tumor to focus the radiowaves for select heating. Temperatures were measured using a fiber-optic thermometer for real-time data. Results Solutions containing gold nanoparticles heated in a time- and power-dependent manner. HepG2 liver cancer cells cultured in the presence of gold nanoparticles achieved adequate heating to cause cell death upon exposure to the RF field with no cytotoxicity attributable to the gold nanoparticles themselves. In vivo rat exposures at 35W using gold nanoparticles for tissue injection resulted in significant temperature increases and thermal injury at subcutaneous injection sites as compared to vehicle (water) injected controls. Discussion These data show that non-invasive radiowave thermal ablation of cancer cells is feasible when facilitated by gold nanoparticles. Future studies will focus on tumor selective targeting of nanoparticles for in vivo tumor destruction. PMID:18656617

  12. Target radiofrequency combined with collagenase chemonucleolysis in the treatment of lumbar intervertebral disc herniation

    PubMed Central

    Zhang, Daying; Zhang, Yong; Wang, Zhijian; Zhang, Xuexue; Sheng, Mulan

    2015-01-01

    Both target radiofrequency thermocoagulation and collagenase chemonucleolysis are effective micro-invasive therapy means for lumbar intervertebral disc herniation. In order to analyze the clinical effects of target radiofrequency thermocoagulation combined with collagenase chemonucleolysis on lumbar intervertebral disc herniation, the contents of hydroxyproline and glycosaminoglycan were measured and the histological changes of nucleus pulposus was detected in the vitro experiments. Radiofrequency thermocoagulation reduced the hydrolyzation of herniated nucleus pulposus caused by collagenase, as well as the content of hydroxyproline and glycosaminoglycan. Furthermore, 236 patients with lumbar intervertebral disc herniation were treated by target radiofrequency thermocoagulation combined with collagenase chemonucleolysis. The efficiency was evaluated according to Macnab criteria, and the index of lumbar disc herniation (IDH) was compared pre-operation with 3 months post-operation. The post-operative good rate was 66.5% (157/236) at 2 weeks post-operation, and 88.1% (208/236) at 3 months post-operation. In the post-operative follow-up exam, 86.8% of the re-examined cases demonstrated smaller or ablated protrusion, with reduced IDH values from pre-operation, which was statistically significant. No serious complications were detected intra-operatively and post-operatively. In conclusion, target radiofrequency combined with collagenase chemonucleolysis was an effective and safe method for treatment of lumbar intervertebral disc herniation. PMID:25785026

  13. Thermal catheter disruption during closed-chest radiofrequency ablation of the atrioventricular conduction system.

    PubMed

    Frohner, K J; Podczeck, A; Hief, C; Nurnberg, M; Steinbach, K K

    1990-06-01

    Radiofrequency ablation of the atrioventricular conduction system was attempted in a 63-year-old man with drug refractory atrial fibrillation. A total of 5 radiofrequency pulses (750 kHz, power setting: 25-50 W, pulse duration: 9-20 sec) were delivered in a unipolar fashion via the distal electrode of a 7 Fr bipolar electrode catheter without induction of permanent AV block. No direct measurements of current (I) and voltage (U) were made. During the fifth pulse catheter disruption occurred at the interface of the shaft and the proximal electrode. Inspection of the catheter shaft revealed carbonized insulation material indicating overheating of the catheter tip. Overheating was presumably due to an impedance rise with unrecognized clot formation on the distal electrode. This led to progressive melting of insulation material during repeated radiofrequency applications and short circuiting of current flow to the proximal ring electrode that resulted in catheter disruption. This case report is the first to describe a serious complication of radiofrequency ablation. The complication might have been prevented by measurements of U and I, reflecting changes in impedance or by measurements of catheter tip temperature (T). It is concluded that measurements of U, I, and/or T are necessary to control the coagulation process thereby reducing the risk of serious complications during transcatheter radiofrequency ablation. PMID:1695351

  14. Reconfigurable radio-frequency arbitrary waveforms synthesized in a silicon photonic chip.

    PubMed

    Wang, Jian; Shen, Hao; Fan, Li; Wu, Rui; Niu, Ben; Varghese, Leo T; Xuan, Yi; Leaird, Daniel E; Wang, Xi; Gan, Fuwan; Weiner, Andrew M; Qi, Minghao

    2015-01-01

    Photonic methods of radio-frequency waveform generation and processing can provide performance advantages and flexibility over electronic methods due to the ultrawide bandwidth offered by the optical carriers. However, bulk optics implementations suffer from the lack of integration and slow reconfiguration speed. Here we propose an architecture of integrated photonic radio-frequency generation and processing and implement it on a silicon chip fabricated in a semiconductor manufacturing foundry. Our device can generate programmable radio-frequency bursts or continuous waveforms with only the light source, electrical drives/controls and detectors being off-chip. It modulates an individual pulse in a radio-frequency burst within 4?ns, achieving a reconfiguration speed three orders of magnitude faster than thermal tuning. The on-chip optical delay elements offer an integrated approach to accurately manipulating individual radio-frequency waveform features without constraints set by the speed and timing jitter of electronics, and should find applications ranging from high-speed wireless to defence electronics. PMID:25581847

  15. Reconfigurable radio-frequency arbitrary waveforms synthesized in a silicon photonic chip

    PubMed Central

    Wang, Jian; Shen, Hao; Fan, Li; Wu, Rui; Niu, Ben; Varghese, Leo T.; Xuan, Yi; Leaird, Daniel E.; Wang, Xi; Gan, Fuwan; Weiner, Andrew M.; Qi, Minghao

    2015-01-01

    Photonic methods of radio-frequency waveform generation and processing can provide performance advantages and flexibility over electronic methods due to the ultrawide bandwidth offered by the optical carriers. However, bulk optics implementations suffer from the lack of integration and slow reconfiguration speed. Here we propose an architecture of integrated photonic radio-frequency generation and processing and implement it on a silicon chip fabricated in a semiconductor manufacturing foundry. Our device can generate programmable radio-frequency bursts or continuous waveforms with only the light source, electrical drives/controls and detectors being off-chip. It modulates an individual pulse in a radio-frequency burst within 4?ns, achieving a reconfiguration speed three orders of magnitude faster than thermal tuning. The on-chip optical delay elements offer an integrated approach to accurately manipulating individual radio-frequency waveform features without constraints set by the speed and timing jitter of electronics, and should find applications ranging from high-speed wireless to defence electronics. PMID:25581847

  16. Reconfigurable radio-frequency arbitrary waveforms synthesized in a silicon photonic chip

    NASA Astrophysics Data System (ADS)

    Wang, Jian; Shen, Hao; Fan, Li; Wu, Rui; Niu, Ben; Varghese, Leo T.; Xuan, Yi; Leaird, Daniel E.; Wang, Xi; Gan, Fuwan; Weiner, Andrew M.; Qi, Minghao

    2015-01-01

    Photonic methods of radio-frequency waveform generation and processing can provide performance advantages and flexibility over electronic methods due to the ultrawide bandwidth offered by the optical carriers. However, bulk optics implementations suffer from the lack of integration and slow reconfiguration speed. Here we propose an architecture of integrated photonic radio-frequency generation and processing and implement it on a silicon chip fabricated in a semiconductor manufacturing foundry. Our device can generate programmable radio-frequency bursts or continuous waveforms with only the light source, electrical drives/controls and detectors being off-chip. It modulates an individual pulse in a radio-frequency burst within 4?ns, achieving a reconfiguration speed three orders of magnitude faster than thermal tuning. The on-chip optical delay elements offer an integrated approach to accurately manipulating individual radio-frequency waveform features without constraints set by the speed and timing jitter of electronics, and should find applications ranging from high-speed wireless to defence electronics.

  17. Non-invasive ultrasound-based temperature imaging for monitoring radiofrequency heating—phantom results

    NASA Astrophysics Data System (ADS)

    Daniels, M. J.; Varghese, T.; Madsen, E. L.; Zagzebski, J. A.

    2007-08-01

    Minimally invasive therapies (such as radiofrequency ablation) are becoming more commonly used in the United States for the treatment of hepatocellular carcinomas and liver metastases. Unfortunately, these procedures suffer from high recurrence rates of hepatocellular carcinoma (~34-55%) or metastases following ablation therapy. The ability to perform real-time temperature imaging while a patient is undergoing radiofrequency ablation could provide a significant reduction in these recurrence rates. In this paper, we demonstrate the feasibility of ultrasound-based temperature imaging on a tissue-mimicking phantom undergoing radiofrequency heating. Ultrasound echo signals undergo time shifts with increasing temperature, which are tracked using 2D correlation-based speckle tracking methods. Time shifts or displacements in the echo signal are accumulated, and the gradient of these time shifts are related to changes in the temperature of the tissue-mimicking phantom material using a calibration curve generated from experimental data. A tissue-mimicking phantom was developed that can undergo repeated radiofrequency heating procedures. Both sound speed and thermal expansion changes of the tissue-mimicking material were measured experimentally and utilized to generate the calibration curve relating temperature to the displacement gradient. Temperature maps were obtained, and specific regions-of-interest on the temperature maps were compared to invasive temperatures obtained using fiber-optic temperature probes at the same location. Temperature elevation during a radiofrequency ablation procedure on the phantom was successfully tracked to within ±0.5 °C.

  18. Paradox of Accessory Pathway Block After Radiofrequency Ablation in Patients with the Wolff-Parkinson-White Syndrome

    Microsoft Academic Search

    Kwo-Chang Ueng; Shih-Ann Chen; Chern-En Chiang; Chen-Chuan Cheng; Tsu-Juey Wu; Ching-Tai Tai; Shih-Huang Lee; Chuen-Wong Chiou; Chung-Yin Chen; Zu-Chi Wen; Mau-Song Chang

    1996-01-01

    Although pacing technique has demonstrated that the most common site of conduction block in a manifest accessory pathway (AP) was between the AP and the ventricle, most of the block sites have been found to be between the atrium and AP after successful radiofrequency ablation. Furthermore, the block site in a concealed AP after successful radiofrequency catheter ablation has not

  19. Nanoionics-Based Switches for Radio-Frequency Applications

    NASA Technical Reports Server (NTRS)

    Nessel, James; Lee, Richard

    2010-01-01

    Nanoionics-based devices have shown promise as alternatives to microelectromechanical systems (MEMS) and semiconductor diode devices for switching radio-frequency (RF) signals in diverse systems. Examples of systems that utilize RF switches include phase shifters for electronically steerable phased-array antennas, multiplexers, cellular telephones and other radio transceivers, and other portable electronic devices. Semiconductor diode switches can operate at low potentials (about 1 to 3 V) and high speeds (switching times of the order of nanoseconds) but are characterized by significant insertion loss, high DC power consumption, low isolation, and generation of third-order harmonics and intermodulation distortion (IMD). MEMS-based switches feature low insertion loss (of the order of 0.2 dB), low DC power consumption (picowatts), high isolation (>30 dB), and low IMD, but contain moving parts, are not highly reliable, and must be operated at high actuation potentials (20 to 60 V) generated and applied by use of complex circuitry. In addition, fabrication of MEMS is complex, involving many processing steps. Nanoionics-based switches offer the superior RF performance and low power consumption of MEMS switches, without need for the high potentials and complex circuitry necessary for operation of MEMS switches. At the same time, nanoionics-based switches offer the high switching speed of semiconductor devices. Also, like semiconductor devices, nanoionics-based switches can be fabricated relatively inexpensively by use of conventional integrated-circuit fabrication techniques. More over, nanoionics-based switches have simple planar structures that can easily be integrated into RF power-distribution circuits.

  20. Endovenous radiofrequency ablation for the treatment of varicose veins.

    PubMed

    Dietzek, Alan M

    2007-01-01

    Chronic venous insufficiency (CVI) is the most common vascular disease and represents a significant health care problem in the United States. Reflux of the great saphenous vein is the most common cause of this condition, whose symptoms include varicose veins, leg swelling, skin discoloration, and ulceration. The traditional treatment of this condition is saphenofemoral ligation with stripping of the saphenous vein followed by varicose vein removal, if necessary. Recent advances in minimally invasive endovenous therapy have led to the development of catheter-based radiofrequency ablation (RFA) of the saphenous vein, which has gained an increasing acceptance in clinical practice. Endovenous RFA was introduced into clinical practice in Europe in 1998 and in the United States in 1999. Since then, over 250,000 procedures have been performed worldwide. Procedure safety and efficacy are well understood, with over 60 publications on the subject in the peer review literature, including four randomized trials comparing this technology with traditional vein stripping surgery. With the advent of tumescent anesthesia, the majority of RFA procedures are now performed in an office setting. This article examines the current technology using RFA in saphenous vein ablation with the Closure catheter system. Procedural techniques and clinical outcome using RFA in saphenous vein ablation are discussed. Clinical data comparing RFA versus saphenous vein stripping are also examined. Lastly, the clinical utility of a new RFA catheter, ClosureFAST, is discussed. ClosureFAST is a new generation of RFA catheter and has exhibited significant improvement in the ease of use and the procedure speed over the previous generation catheters while maintaining the favorable patient recovery profile seen with the RFA technology. PMID:17976324

  1. Lung Tumor Radiofrequency Ablation: Where Do We Stand?

    SciTech Connect

    Baere, Thierry de, E-mail: debaere@igr.fr [Institut Gustave Roussy, Department of Interventional Radiology (France)

    2011-04-15

    Today, radiofrequency ablation (RFA) of primary and metastatic lung tumor is increasingly used. Because RFA is most often used with curative intent, preablation workup must be a preoperative workup. General anesthesia provides higher feasibility than conscious sedation. The electrode positioning must be performed under computed tomography for sake of accuracy. The delivery of RFA must be adapted to tumor location, with different impedances used when treating tumors with or without pleural contact. The estimated rate of incomplete local treatment at 18 months was 7% (95% confidence interval, 3-14) per tumor, with incomplete treatment depicted at 4 months (n = 1), 6 months (n = 2), 9 months (n = 2), and 12 months (n = 2). Overall survival and lung disease-free survival at 18 months were, respectively, 71 and 34%. Size is a key point for tumor selection because large size is predictive of incomplete local treatment and poor survival. The ratio of ablation volume relative to tumor volume is predictive of complete ablation. Follow-up computed tomography that relies on the size of the ablation zone demonstrates the presence of incomplete ablation. Positron emission tomography might be an interesting option. Chest tube placement for pneumothorax is reported in 8 to 12%. Alveolar hemorrhage and postprocedure hemoptysis occurred in approximately 10% of procedures and rarely required specific treatment. Death was mostly related to single-lung patients and hilar tumors. No modification of forced expiratory volume in the first second between pre- and post-RFA at 2 months was found. RFA in the lung provides a high local efficacy rate. The use of RFA as a palliative tool in combination with chemotherapy remains to be explored.

  2. Outcome after Radiofrequency Ablation of Sarcoma Lung Metastases

    SciTech Connect

    Koelblinger, Claus, E-mail: claus.koelblinger@bhs.at [KH Barmherzige Schwestern Ried, Department of Radiology (Austria); Strauss, Sandra, E-mail: s.strauss@ucl.ac.uk [UCL and UCLH, Department of Medical Oncology (United Kingdom); Gillams, Alice, E-mail: alliesorting@gmail.com [The London Clinic, Department of Radiology (United Kingdom)

    2013-05-14

    PurposeResection is the mainstay of management in patients with sarcoma lung metastases, but there is a limit to how many resections can be performed. Some patients with inoperable disease have small-volume lung metastases that are amenable to thermal ablation. We report our results after radiofrequency ablation (RFA).MethodsThis is a retrospective study of patients treated from 2007 to 2012 in whom the intention was to treat all sites of disease and who had a minimum CT follow-up of 4 months. Treatment was performed under general anesthesia/conscious sedation using cool-tip RFA. Follow-up CT scans were analyzed for local control. Primary tumor type, location, grade, disease-free interval, prior resection/chemotherapy, number and size of lung tumors, uni- or bilateral disease, complications, and overall and progression-free survival were recorded.ResultsTwenty-two patients [15 women; median age 48 (range 10–78) years] with 55 lung metastases were treated in 30 sessions. Mean and median tumor size and initial number were 0.9 cm and 0.7 (range 0.5–2) cm, and 2.5 and 1 (1–7) respectively. Median CT and clinical follow-up were 12 (4–54) and 20 (8–63) months, respectively. Primary local control rate was 52 of 55 (95 %). There were 2 of 30 (6.6 %) Common Terminology Criteria grade 3 complications with no long-term sequelae. Mean (median not reached) and 2- and 3-year overall survival were 51 months, and 94 and 85 %. Median and 1- and 2-year progression-free survival were 12 months, and 53 and 23 %. Prior disease-free interval was the only significant factor to affect overall survival.ConclusionRFA is a safe and effective treatment for patients with small-volume sarcoma metastases.

  3. Genotoxicity of radiofrequency radiation. DNA/Genetox Expert Panel.

    PubMed

    Brusick, D; Albertini, R; McRee, D; Peterson, D; Williams, G; Hanawalt, P; Preston, J

    1998-01-01

    During the past several years, concerns have been raised regarding the potential adverse effects of exposures to nonionizing radiation, particularly in the extremely low frequency (ELF) range (50 to 60 MHz) and radiofrequency radiation (RFR) with frequencies ranging from 30 KHz to 30,000 MHz. One focus of concern has been potential DNA interactions. Publications reviewing the genotoxicity of ELF radiation [McCann et al. (1993): Mutat Res 297(1):61-95; Murphy et al. (1993): Mutat Res 296:221-240; NAS (1997)], have been uniform in concluding that the weight of evidence does not indicate any genotoxic risk from exposure to this type of radiation. Concern that RFR may be associated with adverse biological effects [WHO, 1993], including recent allegations that they may be involved in the production of brain tumors in humans [Elmer-Dewit (1993): Time, February 8:42], has resulted in the production of a large number of publications describing the effects of RFR on the integrity of nucleic acids. Data from studies conducted in a frequency range from 800 to 3,000 MHz were reviewed and subjected to a weight-of-evidence evaluation. The evaluation focused on direct toxicological effects of RFR as well as on studies addressing basic biological responses to RFR at the cellular and molecular level. The data from over 100 studies suggest that RFR is not directly mutagenic and that adverse effects from exposure of organisms to high frequencies and high power intensities of RFR are predominantly the result of hyperthermia; however, there may be some subtle indirect effects on the replication and/or transcription of genes under relatively restricted exposure conditions. PMID:9707093

  4. Symptomatic improvement after radiofrequency catheter ablation for typical atrial flutter

    PubMed Central

    O'Callaghan, P; Meara, M; Kongsgaard, E; Poloniecki, J; Luddington, L; Foran, J; Camm, A; Rowland, E; Ward, D

    2001-01-01

    OBJECTIVE—To assess the changes in quality of life, arrhythmia symptoms, and hospital resource utilisation following catheter ablation of typical atrial flutter.?DESIGN—Patient questionnaire to compare the time interval following ablation with a similar time interval before ablation.?SETTING—Tertiary referral centre.?PATIENTS—63 consecutive patients were studied. Four patients subsequently underwent an ablate and pace procedure, two died of co-morbid illnesses, and two were lost to follow up. The remaining 55 patients form the basis of the report.?RESULTS—Patients were followed for a mean (SD) of 12 (9.5) months. Atrial flutter ablation resulted in an improvement in quality of life (3.8 v 2.5, p < 0.001) and reductions in symptom frequency score (2.0 v 3.5, p < 0.001) and symptom severity score (2.0 v 3.8, p < 0.001) compared with preablation values. There was a reduction in the number of patients visiting accident and emergency departments (11% v 53%, p < 0.001), requiring cardioversion (7% v 51%, p < 0.001), or being admitted to hospital for a rhythm problem (11% v 56%, p < 0.001). Subgroup analysis confirmed that patients with atrial flutter and concomitant atrial fibrillation before ablation and those with atrial flutter alone both derived significant benefit from atrial flutter ablation. Patients with concomitant atrial fibrillation had an improvement in quality of life (3.5 v 2.5, p < 0.001) and reductions in symptom frequency score (2.3 v 3.5, p < 0.001) and symptom severity score (2.2 v 3.7, p < 0.001) compared with preablation values.?CONCLUSIONS—Ablation of atrial flutter is recommended both in patients with atrial flutter alone and in those with concomitant atrial fibrillation.???Keywords: atrial flutter; radiofrequency ablation; quality of life PMID:11454833

  5. Single-Session Radiofrequency Ablation of Bilateral Lung Metastases

    SciTech Connect

    Palussiere, Jean, E-mail: palussiere@bergonie.org; Gomez, Fernando; Cannella, Matthieu; Ferron, Stephane; Descat, Edouard [Institut Bergonie, Department of Radiology, Regional Cancer Centre (France); Fonck, Marianne [Institut Bergonie, Department of Digestive Oncology (France); Brouste, Veronique [Institut Bergonie, Clinical and Epidemiological Research Unit (France); Avril, Antoine [Institut Bergonie, Department of Surgery (France)

    2012-08-15

    Purpose: This retrospective study examined the feasibility and efficacy of bilateral lung radiofrequency ablation (RFA) performed in a single session. Methods: From 2002-2009, patients with bilateral lung metastases were treated by RFA, where possible in a single session under general anesthesia with CT guidance. The second lung was punctured only if no complications occurred after treatment of the first lung. Five lung metastases maximum per patient were treated by RFA and prospectively followed. The primary endpoint was the evaluation of acute and delayed complications. Secondary endpoints were calculation of hospitalization duration, local efficacy, median survival, and median time to tumor progression. Local efficacy was evaluated on CT or positron emission tomography (PET) CT. Results: Sixty-seven patients were treated for bilateral lung metastases with RFA (mean age, 62 years). Single-session treatment was not possible in 40 due to severe pneumothoraces (n = 24), bilateral pleural contact (n = 14), and operational exclusions (n = 2). Twenty-seven (41%) received single-session RFA of lesions in both lungs for 66 metastases overall. Fourteen unilateral and four bilateral pneumothoraces occurred (18 overall, 66.7%). Unilateral (n = 13) and bilateral (n = 2) chest tube drainage was required. Median hospitalization was 3 (range, 2-8) days. Median survival was 26 months (95% confidence interval (CI), 19-33). Four recurrences on RFA sites were observed (4 patients). Median time to tumor progression was 9.5 months (95% CI, 4.2-23.5). Conclusions: Although performing single-session bilateral lung RFA is not always possible due to pneumothoraces after RFA of first lung, when it is performed, this technique is safe and effective.

  6. Palliative Treatment of Rectal Carcinoma Recurrence Using Radiofrequency Ablation

    SciTech Connect

    Mylona, Sophia, E-mail: mylonasophia@yahoo.com; Karagiannis, Georgios, E-mail: gekaragiannis@yahoo.gr; Patsoura, Sofia, E-mail: sofia.patsoura@yahoo.gr [Hellenic Red Cross Hospital 'Korgialenio-Benakio' (Greece); Galani, Panagiota, E-mail: gioulagalani@yahoo.com [Amalia Fleming Hospital (Greece); Pomoni, Maria, E-mail: marypomoni@gmail.com [Evgenidion Hospital (Greece); Thanos, Loukas, E-mail: loutharad@yahoo.com [Sotiria Hospital (Greece)

    2012-08-15

    Purpose: To evaluate the safety and efficacy of CT-guided radiofrequency (RF) ablation for the palliative treatment of recurrent unresectable rectal tumors. Materials and Methods: Twenty-seven patients with locally recurrent rectal cancer were treated with computed tomography (CT)-guided RF ablation. Therapy was performed with the patient under conscious sedation with a seven- or a nine-array expandable RF electrode for 8-10 min at 80-110 Degree-Sign C and a power of 90-110 W. All patients went home under instructions the next day of the procedure. Brief Pain Inventory score was calculated before and after (1 day, 1 week, 1 month, 3 months, and 6 months) treatment. Results: Complete tumor necrosis rate was 77.8% (21 of a total 27 procedures) despite lesion location. BPI score was dramatically decreased after the procedure. The mean preprocedure BPI score was 6.59, which decreased to 3.15, 1.15, and 0.11 at postprocedure day 1, week 1, and month 1, respectively, after the procedure. This decrease was significant (p < 0.01 for the first day and p < 0.001 for the rest of the follow-up intervals (paired Student t test; n - 1 = 26) for all periods during follow-up. Six patients had partial tumor necrosis, and we were attempted to them with a second procedure. Although the necrosis area showed a radiographic increase, no complete necrosis was achieved (secondary success rate 65.6%). No immediate or delayed complications were observed. Conclusion: CT-guided RF ablation is a minimally invasive, safe, and highly effective technique for treatment of malignant rectal recurrence. The method is well tolerated by patients, and pain relief is quickly achieved.

  7. Screen printed flexible radiofrequency identification tag for oxygen monitoring.

    PubMed

    Martínez-Olmos, A; Fernández-Salmerón, J; Lopez-Ruiz, N; Rivadeneyra Torres, A; Capitan-Vallvey, L F; Palma, A J

    2013-11-19

    In this work, a radiofrequency identification (RFID) tag with an optical indicator for the measurement of gaseous oxygen is described. It consists of an O2 sensing membrane of PtOEP together with a full electronic system for RFID communication, all printed on a flexible substrate. The membrane is excited by an LED at 385 nm wavelength and the intensity of the luminescence generated is registered by means of a digital color detector. The output data corresponding to the red coordinate of the RGB color space is directly related to the concentration of O2, and it is sent to a microcontroller. The RFID tag is designed and implemented by screen printing on a flexible substrate for the wireless transmission of the measurement to a remote reader. It can operate in both active and passive mode, obtaining the power supply from the electromagnetic waves of the RFID reader or from a small battery, respectively. This system has been fully characterized and calibrated including temperature drifts, showing a high-resolution performance that allows measurement of very low values of oxygen content. Therefore this system is perfectly suitable for its use in modified atmosphere packaging where the oxygen concentration is reduced below 2%. As the reading of the O2 concentration inside the envelope is carried out with an external RFID reader using wireless communication, there is no need for perforations for probes or wires, so the packaging remains completely closed. With the presented device, a limit of detection of 40 ppm and a resolution as low as 0.1 ppm of O2 can be reached with a low power consumption of 3.55 mA. PMID:24116378

  8. Interactions of radiofrequency radiation on 2-methoxyethanol teratogenicity in rats.

    PubMed

    Nelson, B K; Conover, D L; Shaw, P B; Snyder, D L; Edwards, R M

    1997-01-01

    Concurrent exposures to chemical and physical agents occur in the workplace; exposed workers include those involved with microelectronics industry, plastic sealers and electrosurgical units. Previous animal research indicates that hyperthermia induced by an elevation in ambient temperature can potentiate the toxicity and teratogenicity of some chemical agents. We previously demonstrated that combined exposure to radiofrequency (r.f.; 10 MHz) radiation, which also induces hyperthermia and is teratogenic to exposed animals, and the industrial solvent 2-methoxyethanol (2ME) produces enhanced teratogenicity in rats. A subsequent study replicated and extended that research by investigating the interactive dose-related teratogenicity of r.f. radiation (sham exposure or maintaining colonic temperatures at 42.0 degrees C for 0, 10, 20 or 30 min by r.f. radiation absorption) and 2ME (0, 75, 100, 125 or 150 mg/kg) on gestation days 9 or 13 of rats. The purpose of the present research is to determine the effects of r.f. radiation (sufficient to maintain colonic temperatures at 42.0 degrees C for 10 min) on a range of doses of 2ME (0, 20, 40, 60, 80, 100, 120 and 140 mg kg-1) administered on gestation day 13 of rats. Focusing on characterizing the dose-response pattern of interactions, this research seeks to determine the lowest interactive effect level. Day 20 fetuses were examined for external and skeletal malformations. The results are consistent with previous observations. Dose-related developmental toxicity was observed for 2ME both in the presence and absence of r.f. radiation. However, concurrent RF radiation exposure changed the shape of the dose-effect curve of 2ME. These data indicate that combined exposure effects should be considered when developing exposure guidelines and intervention strategies. PMID:9048225

  9. Energy Saving Glass Lamination via Selective Radio-Frequency Heating

    SciTech Connect

    Shulman, Holly S.; Allan, Shawn M.

    2009-11-11

    This Inventions and Innovations program supported the technical and commercial research and development needed to elevate Ceralink's energy saving process for flat glass lamination from bench scale to a self-supporting technology with significant potential for growth. Radio-frequency heating was any un-explored option for laminating glass prior to this program. With significant commercial success through time and energy savings in the wood, paper, and plastics industries, RF heating was found to have significant promise for the energy intensive glass lamination industry. A major technical goal of the program was to demonstrate RF lamination across a wide range of laminate sizes and materials. This was successfully accomplished, dispelling many skeptics' concerns about the abilities of the technology. Ceralink laminated panels up to 2 ft x 3 ft, with four sets processed simultaneously, in a 3 minute cycle. All major categories of interlayer materials were found to work with RF lamination. In addition to laminating glass, other materials including photovoltaic silicon solar cells, light emitting diodes, metallized glass, plastics (acrylic and polycarbonate), and ceramics (alumina) were found compatible with the RF process. This opens up a wide range of commercial opportunities beyond the initially targeted automotive industry. The dramatic energy savings reported for RF lamination at the bench scale were found to be maintained through the scale up of the process. Even at 2 ft x 3 ft panel sizes, energy savings are estimated to be at least 90% compared to autoclaving or vacuum lamination. With targeted promotion through conference presentations, press releases and internet presence, RF lamination has gained significant attention, drawing large audiences at American Ceramic Society meetings. The commercialization success of the project includes the establishment of a revenue-generating business model for providing process development and demonstrations for potential RF lamination users. A path to industrial energy benefits and revenue through industrial equipment sales was established in a partnership with Thermex Thermatron, a manufacturer of RF equipment.

  10. Background radio-frequency radiation and its impact on radio astronomy Michelle C. Storey, Bruce MacA Thomas and John M. Sarkissian

    E-print Network

    Sarkissian, John M.

    1 Background radio-frequency radiation and its impact on radio astronomy Michelle C. Storey, Bruce 1710 Email:mstorey@atnf.csiro.au Abstract: The use of radio-frequency telecommunications equipment is dramatically increasing, and one consequence is that background levels of radio-frequency radiation

  11. Radiofrequency pulses for simultaneous short T2 excitation and long T2 suppression.

    PubMed

    Carl, Michael; Bydder, Mark; Du, Jiang; Han, Eric

    2011-02-01

    Magnetic resonance imaging of short T(2) musculoskeletal tissues such as ligaments, tendon, and cortical bone often requires specialized pulse sequences to detect sufficiently high levels of signal, as well as additional techniques to suppress unwanted long T(2) signals. We describe a specialized radiofrequency technique for imaging short T(2) tissues based on applying hard 180° radiofrequency excitation pulses to achieve simultaneous short T(2) tissue excitation and long T(2) tissue signal suppression for three-dimensional ultrashort echo time applications. A criterion for the pulse duration of the 180° radiofrequency pulses is derived that allows simultaneous water and fat suppression. This opens up possibilities for direct imaging of short T(2) tissues, without the need for additional suppression techniques. Bloch simulations and experimental studies on short T(2) phantoms and specimen were used to test the sequence performance. PMID:20872861

  12. Experimental investigation of an adaptive feedback algorithm for hot spot reduction in radio-frequency phased-array hyperthermia.

    PubMed

    Fenn, A J; King, G A

    1996-03-01

    A computer-controlled adaptive phased array radiofrequency hyperthermia system for improved therapeutic tumor heating is experimentally investigated. Adaptive array feedback techniques are used to modify the electric-field in hyperthermia experiments with a homogeneous saline phantom target. A hyperthermia phased-array antenna system has been modified to implement adaptive nulling and adaptive focusing algorithms. The hyperthermia system is a ring phased-array antenna applicator with four independently controlled RF transmitter channels operating at a CW frequency of 100 MHz. The hyperthermia phased array is made adaptive by software modifications which invoke a gradient-search feedback algorithm that controls the amplitude and phase of each transmitter channel. The gradient-search algorithm implements the method of steepest descent for adaptive nulling (power minimization) and the method of steepest ascent for adaptive focusing (power maximization). The feedback signals are measured by electric-field short-dipole probe antennas. The measured data indicate that with an adaptive hyperthermia array it may be possible to maximize the applied electric field at a tumor position in a complex scattering target body and simultaneously minimize or reduce the electric field at target positions where undesired high-temperature regions (hot spots) occur. PMID:8682539

  13. Submucosal resection of a microcystic oropharyngeal lymphatic malformation using radiofrequency ablation.

    PubMed

    Thottam, Prasad John; Al-Barazi, Randa; Madgy, David N; Rozzelle, Arlene

    2013-09-01

    Lymphatic malformations (LMs) are uncommon congenital anomalies noted to have a prevalence of 1 per 5000 births and comprise roughly 6% of all pediatric soft tissue lesions. Recently radiofrequency ablation has been described as a surgical option for the treatment microcystic LMs in the oral cavity, more specifically the tongue. The following case describes the use of radiofrequency ablation for the submucosal removal of a large obstructing pharyngeal LM in a 4-year-old female. The mucosal sparing approach and surgical method of extirpation are discussed in detail. To the authors' knowledge this is the first description of a submucosal coblation technique being used as treatment for pharyngeal LMs. PMID:23830038

  14. Combined MRI and Fluoroscopic Guided Radiofrequency Ablation of a Renal Tumor

    SciTech Connect

    Fotiadis, Nikolas I., E-mail: fotiadis.nicholas@gmail.co [Royal London Hospital, Department of Interventional Radiology (United Kingdom); Sabharwal, Tarun [Guy's and St Thomas' Hospital, Interventional Radiology Department (United Kingdom); Gangi, Afshin [University Hospital of Strasbourg, Radiology Department (France); Adam, Andreas [Guy's and St Thomas' Hospital, Interventional Radiology Department (United Kingdom)

    2009-01-15

    Percutaneous CT- and ultrasound-guided radiofrequency ablation of renal cell carcinoma (RCC) has been shown to have very promising medium-term results. We present a unique case of recurrent RCC after partial nephrectomy in a patient with a single kidney and impaired renal function. This tumor could not be visualized either with CT or with ultrasound. A combination of magnetic resonance imaging and fluoroscopic guidance was used, to the best of our knowledge for the first time, to ablate the tumor with radiofrequency. The patient was cancer-free and off dialysis at 30-month follow up.

  15. Intralesional radiofrequency ablation for nodular angiolymphoid hyperplasia on forehead: a minimally invasive approach.

    PubMed

    Singh, Saurabh; Dayal, Madhukar; Walia, Ritika; Arava, Sudheer; Sharma, Raju; Gupta, Somesh

    2014-01-01

    Angiolymphoid hyperplasia with eosinophilia (ALHE) is an idiopathic acquired condition characterized by erythematous papulo-nodular lesions with a predilection for the head and neck. The lesions are cosmetically disfiguring, resistant to most medical and surgical therapies and tend to recur. We report the novel use of radiofrequency equipment in the management of nodular ALHE on forehead of a 53-year-old man. Intra-lesional radiofrequency ablation was done using a modified 18 gauge intravenous cannula and three sittings over a period of four years yielded cosmetically acceptable results with no recurrence and minimal side effects. PMID:25201842

  16. Experimental and clinical studies with radiofrequency-induced thermal endometrial ablation for functional menorrhagia

    SciTech Connect

    Phipps, J.H.; Lewis, B.V.; Prior, M.V.; Roberts, T. (Watford General Hospital, Herts (England))

    1990-11-01

    A method of ablating the endometrium has been introduced into clinical practice that uses radiofrequency electromagnetic energy to heat the endometrium, using a probe inserted through the cervix. Preliminary studies suggest that over 80% of patients treated will develop either amenorrhea or a significant reduction in flow. The advantages of radiofrequency endometrial ablation over laser ablation or resection are the avoidance of intravascular fluid absorption, simplicity (no special operative hysteroscopic skills are required), speed of operation, and reduced cost compared with the Nd:YAG laser. In this paper, we describe the experimental studies performed during development of this new technique.

  17. Radio-frequency radiation energy transfer in an ionospheric layer with random small-scale inhomogeneities

    SciTech Connect

    Zabotin, N.A.

    1994-06-01

    The equation of radiation energy balance in a randomly inhomogeneous plane-stratified plasma layer was derived based on the phenomenological approach. The use of the small-angle scattering approximation in the invariate ray coordinates allows it to be transformed into a drift-type equation. The latter describes the deformation of the spatial distribution of the radio-frequency radiation energy due to multiple scattering by anisotropic inhomogeneities. Two effects are investigated numerically: shift of the radio wave arrival angles under a slightly oblique propagation, and variation of the intensity of the radio-frequency radiation reflected from a plasma layer.

  18. Hydroxyapatite thin films grown by pulsed laser deposition and radio-frequency magnetron sputtering: comparative study

    NASA Astrophysics Data System (ADS)

    Nelea, V.; Morosanu, C.; Iliescu, M.; Mihailescu, I. N.

    2004-04-01

    Hydroxyapatite (HA) thin films for applications in the biomedical field were grown by pulsed laser deposition (PLD) and radio-frequency magnetron sputtering (RF-MS) techniques. The depositions were performed from pure hydroxyapatite targets on Ti-5Al-2.5Fe (TiAlFe) alloys substrates. In order to prevent the HA film penetration by Ti atoms or ions diffused from the Ti-based alloy during and after deposition, the substrates were pre-coated with a thin buffer layer of TiN. In both cases, TiN was introduced by reactive PLD from TiN targets in low-pressure N 2. The PLD films were grown in vacuum onto room temperature substrates. The RF-MS films were deposited in low-pressure argon on substrates heated at 550 °C. The initially amorphous PLD thin films were annealed at 550 °C for 1 h in ambient air in order to restore the initial crystalline structure of HA target. The thickness of the PLD and RF-MS films were ˜1 ?m and ˜350 nm, respectively. All films were structurally studied by scanning electron microscopy (SEM), grazing incidence X-ray diffraction (GIXRD), energy dispersive X-ray spectrometry (EDS) and white light confocal microscopy (WLCM). The mechanical properties of the films were tested by Berkovich nano-indentation. Both PLD and RF-MS films mostly contain HA phase and exhibit good mechanical characteristics. Peaks of CaO were noticed as secondary phase in the GIXRD patterns only for RF-MS films. By its turn, the sputtered films were smoother as compared to the ones deposited by PLD (50 nm versus 250 nm average roughness). The RF-MS films were harder, more mechanically resistant and have a higher Young modulus.

  19. Radio-frequency current application in bipolar technique for interstitial thermotherapy (rf-ITT)

    NASA Astrophysics Data System (ADS)

    Desinger, Kai; Stein, Thomas; Mueller, Gerhard J.

    1996-12-01

    For the interstitial treatment of pathologic tissue, e.g. tumors, the benign prostate hyperplasia or the concha hyperplasia in otorhinolaryngology, the method of interstitial laser photocoagulation and the monopolar RF- needle coagulation can be used as well as other methods, e.g. the microwave exposure, alcohol injection, ultrasound or hot water irrigation. This article will present latest results of interstitial thermotherapy with radio-frequency alternating current in bipolar technique. Therefore basic investigations of the thermal field distribution in in vitro samples were performed. THe efficiency of the developed applicators were examined using egg white and in in vitro experiments with porcine liver tissue. Bipolar needles with different diameters were built and tested. Carbonization and dehydration can be avoided by irrigation of the tissue during treatment through an integrated central flushing port. A bipolar needle has been developed for the treatment of concha hyperplasia which can be used as the monopolar pendant with similar results in partial tissue coagulation but without current flow in the sensitive head region. First pathologic investigations pointed out that with the use of the bipolar technique the surface of the concha with the ciliary epithelium is less affected due tot he limited spatial current distribution. Furthermore the design of a multi-electrode needle is presented which could probably offer an additional increase of safety and a simplification of performing a concha coagulation procedure. The new design of a bipolar needle electrode enables the surgeon the use of a partial application of radio frequency current for ITT. Less power is needed due to the limited current distribution at the immediate operation site, which means that a neutral electrode is not needed. Thus a highly safe procedure can be performed by the surgeon.

  20. Radiofrequency heating and magnetically induced displacement of dental magnetic attachments during 3.0 T MRI

    PubMed Central

    Miyata, K; Hasegawa, M; Abe, Y; Tabuchi, T; Namiki, T; Ishigami, T

    2012-01-01

    Objective The aim of this study was to estimate the risk of injury from dental magnetic attachments due to their radiofrequency (RF) heating and magnetically induced displacement during 3.0 T MRI. Methods To examine the magnetic attachments, we adopted the American Society for Testing and Materials F2182-02a and F2052-06 standards in two MRI systems (Achieva 3.0 T Nova Dual; Philips, Tokyo, Japan, and Signa HDxt 3.0 T; GE Healthcare, Milwaukee, WI). The temperature change was measured in a cylindrical keeper (GIGAUSS D600; GC, Tokyo, Japan) with coping of the casting alloy and a keeper with a dental implant at the maximum specific absorption rate (SAR) for 20 min. To measure the magnetically induced displacement force, three sizes of keepers (GIGAUSS D400, D600 and D1000) were used in deflection angle tests conducted at the point of the maximum magnetic field strength. Results Temperature elevations of both coping and implant were higher in the Signa system than in the Achieva system. The highest temperature changes in the keeper with implant and keeper with coping were 0.6 °C and 0.8 °C in the Signa system, respectively. The temperature increase did not exceed 1.0 °C at any location. The deflection angle (?) was not measurable because it exceeded 90°. GIGAUSS D400 required an extra 3.0 g load to constrain the deflection angle to less than 45°; GIGAUSS D600 and D1000 required 5.0 and 9.0 g loads, respectively. Conclusions Dental magnetic attachments pose no risk due to RF heating and magnetically induced displacement at 3.0 T MRI. However, it is necessary to confirm that these keepers are securely attached to the prosthesis before imaging. PMID:22499128