Sample records for non-ionizing radiofrequency fields

  1. Non-ionizing radiation safety: radiofrequency radiation, electric and magnetic fields

    Microsoft Academic Search

    J. H. Bernhardt

    1992-01-01

    The static, low-frequency and radiofrequency parts of the electromagnetic spectrum are used in various areas of human activity. Equipment utilizing this energy today is to be found in industry, medicine, commerce and private homes. The author provides a short survey of the biological effects and concentrates on the principal experimental and theoretical bases which allow the assessment of data on

  2. 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

  3. Radiofrequency fields and teratogenesis.

    PubMed

    Heynick, Louis N; Merritt, James H

    2003-01-01

    Experimental studies that sought teratologic effects or developmental abnormalities from exposure to radiofrequency electromagnetic fields (RFEMF) in the range 3 kHz-300 GHz are critically reviewed for their possible consequences on human health. Those studies were conducted on beetles, birds, rodents, and nonhuman primates. Collectively, those experimental studies indicate that teratologic effects can occur only from exposure levels that cause biologically detrimental increases in body temperature. No reliable experimental evidence was found for nonthermal teratologic effects; rodents, mouse fetuses, and perinatal mice are more susceptible to such effects than rats. The primary confirmed effect in rats at high RFEMF levels was initial weight deficits in fetuses and neonates that decreased with infant growth. More generally from findings with pregnant mammals, exposures at RFEMF levels far higher than those permitted under the IEEE human exposure guidelines are necessary to reach or exceed cited experimental thresholds for maternal temperature increases. Some results indicated that the levels necessary to cause such effects in pregnant mammals could exceed those lethal to the dams. In a behavioral study of squirrel monkeys, no effects were observed on usual dam-offspring interactions or EEGs, but unexpected deaths of a number of offspring had occurred. However, this finding was not confirmed in a study solely on infant death using a larger number of subjects for greater statistical validity. Also reviewed were epidemiologic studies of various human populations considered to have been chronically exposed to environmental levels of RFEMF. Early studies on the incidence of congenital anomalies yielded no credible evidence that chronic exposure of pregnant women or of fathers exposed to RFEMF from nearby sources at levels below those guidelines would cause any anomalies in their offspring. The findings of studies on pregnancy outcomes of female physiotherapists occupationally exposed while treating patients with RFEMF were mixed, but taken collectively, the findings were negative. PMID:14628313

  4. The non-ionizing electromagnetic field: Derivation of valid biological exposure metrics from Maxwell's equations of electromagnetism

    NASA Astrophysics Data System (ADS)

    Lundquist, Marjorie

    2003-03-01

    Standards for protecting health from exposure to non-ionizing electromagnetic radiation treat the power density (magnitude of Poynting vector) as the biological exposure metric. For a static electric or magnetic field, the presumed metric is field strength. Scientifically valid expressions for such exposure metrics have been derived theoretically [1]. Three regimes exist for which different expressions are obtained: high frequencies (where electric and magnetic fields are tightly coupled), low frequencies (where these fields are separable), and static fields (where time derivatives are zero). Unexpected results are obtained: * There are two exposure metrics: one for thermal, another for athermal effects. * In general, these two metrics are different. Only for a plane wave is the same metric (power density) valid for both effects. * Exposure metrics used today for static fields are invalid! These findings also apply in the ionizing portion of the electromagnetic spectrum. [1] Wireless Phones and Health II: State of the Science. G. Carlo, ed. NY: Kluwer Academic Publishers, 2000; Chapter 4.

  5. Superconducting surface impedance under radiofrequency field

    DOE PAGESBeta

    Xiao, Binping P [Thomas Jefferson National Accelerator Facility (TJNAF), Newport News, VA (United States); College of William and Mary, Williamsburg, VA (United States); Reece, Charles E [Thomas Jefferson National Accelerator Facility (TJNAF), Newport News, VA (United States); Kelley, Michael J [Thomas Jefferson National Accelerator Facility (TJNAF), Newport News, VA (United States); College of William and Mary, Williamsburg, VA (United States)

    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.

  6. 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

  7. 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

  8. Radiofrequency electromagnetic fields; male infertility and sex ratio of offspring.

    PubMed

    Baste, Valborg; Riise, Trond; Moen, Bente E

    2008-01-01

    Concern is growing about exposure to electromagnetic fields and male reproductive health. The authors performed a cross-sectional study among military men employed in the Royal Norwegian Navy, including information about work close to equipment emitting radiofrequency electromagnetic fields, one-year infertility, children and sex of the offspring. Among 10,497 respondents, 22% had worked close to high-frequency aerials to a "high" or "very high" degree. Infertility increased significantly along with increasing self-reported exposure to radiofrequency electromagnetic fields. In a logistic regression, odds ratio (OR) for infertility among those who had worked closer than 10 m from high-frequency aerials to a "very high" degree relative to those who reported no work near high-frequency aerials was 1.86 (95% confidence interval (CI): 1.46-2.37), adjusted for age, smoking habits, alcohol consumption and exposure to organic solvents, welding and lead. Similar adjusted OR for those exposed to a "high", "some" and "low" degree were 1.93 (95% CI: 1.55-2.40), 1.52 (95% CI: 1.25-1.84), and 1.39 (95% CI: 1.15-1.68), respectively. In all age groups there were significant linear trends with higher prevalence of involuntary childlessness with higher self-reported exposure to radiofrequency fields. However, the degree of exposure to radiofrequency radiation and the number of children were not associated. For self-reported exposure both to high-frequency aerials and communication equipment there were significant linear trends with lower ratio of boys to girls at birth when the father reported a higher degree of radiofrequency electromagnetic exposure. PMID:18415687

  9. Efficient scalar spin relaxation in the rotating frame for matched radio-frequency fields

    E-print Network

    Skrynnikov, Nikolai

    Efficient scalar spin relaxation in the rotating frame for matched radio-frequency fields N. R in the presence of two radio-frequency fields applied to each of the spins individually. It is demonstrated that the relaxation rate constant T1 1 of the spin I due to scalar relaxation sharply increases when the two radio-frequency

  10. Genetic, carcinogenic and teratogenic effects of radiofrequency fields.

    PubMed

    Verschaeve, L; Maes, A

    1998-04-01

    This paper reviews the literature data on the genetic toxicology of radiofrequency (RF) radiation. Whereas in the past most studies were devoted to microwave ovens and radar equipment, it is now mobile telecommunication that attracts most attention. Therefore we focus on mobile telephone frequencies where possible. According to a great majority of the papers, radiofrequency fields, and mobile telephone frequencies in particular, are not genotoxic: they do not induce genetic effects in vitro and in vivo, at least under non-thermal exposure conditions, and do not seem to be teratogenic or to induce cancer. Yet, some investigations gave rather alarming results that should be confirmed and completed by further experiments. Among them the investigation of synergistic effects and of possible mechanisms of action should be emphasised. PMID:9637234

  11. 78 FR 33654 - Reassessment of Exposure to Radiofrequency Electromagnetic Fields Limits and Policies

    Federal Register 2010, 2011, 2012, 2013, 2014

    2013-06-04

    ...Radiofrequency Electromagnetic Fields Limits and Policies AGENCY...515120 (updated for inflation in 2010). \\187\\ See...not be dominant in its field of operation. We are...515112 (updated for inflation in 2010...not be dominant in its field of...

  12. 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

  13. Anomalous Capacitive Sheath with Deep Radio-Frequency Electric-Field Penetration Igor D. Kaganovich

    E-print Network

    Kaganovich, Igor

    Anomalous Capacitive Sheath with Deep Radio-Frequency Electric-Field Penetration Igor D. Kaganovich; published 10 December 2002) A novel nonlinear effect of anomalously deep penetration of an external radio-frequency of the region is of order VT=!, where VT is the electron thermal velocity, and ! is the frequency

  14. 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

  15. The resonance shifts of aligned atoms in intense oscillating radiofrequency fields

    Microsoft Academic Search

    R. I. Jackson; S. Swain

    1982-01-01

    For a spin-1 atomic system subjected to an oscillating radiofrequency field applied at right angles to a DC magnetic field, the Block-Siegert shift has been calculated to sixth order in V, the amplitude of the oscillating field, and the three-quantum resonance has been calculated to eight order. The results are obtained for the three different polarisations- pi , sigma and

  16. Fundamentals of ion motion in electric radio-frequency multipole fields

    Microsoft Academic Search

    M. H. Friedman; A. L. Yergey; J. E. Campana

    1982-01-01

    The fundamentals of ion motion in electromagnetic fields are reviewed in detail with a special emphasis on electric radio-frequency (RF) fields which are used frequently in dynamic mass spectrometry. Forces and effects on ions in electromagnetic fields which are typically neglected, but which may be important in practical applications are reviewed and discussed for completeness. A method, based on complex

  17. Effect of external magnetic fields and resonance radiofrequency radiation on radical reactions

    NASA Astrophysics Data System (ADS)

    Molin, Yu. N.; Anisimov, O. A.; Koptyug, A. V.; Saik, V. O.; Antzutkin, O. N.

    1990-06-01

    It is well known that an external magnetic field can affect the rate of singlet-triplet transitions in a radical pair and hence its recombination probability in liquid. Resonance radiofrequency (RF) radiation induces quantum beats in the kinetics of radical pair recombination. At high RF field amplitudes the singlet-triplet transitions in radical pairs can be efficiently suppressed.

  18. Efficient scalar spin relaxation in the rotating frame for matched radio-frequency fields

    NASA Astrophysics Data System (ADS)

    Skrynnikov, N. R.; Lienin, S. F.; Brüschweiler, R.; Ernst, R. R.

    1998-05-01

    A theoretical analysis is presented for liquid-state T1? relaxation in a coupled two-spin system I=1/2, S=1 in the presence of two radio-frequency fields applied to each of the spins individually. It is demonstrated that the relaxation rate constant T1?-1 of the spin I due to scalar relaxation sharply increases when the two radio-frequency fields are matched according to the Hartmann-Hahn condition. Relaxation measurements on the amino-protons of 3-nitroaniline show good agreement with theory.

  19. 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.

  20. 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

  1. Size-dependent joule heating of gold nanoparticles using capacitively coupled radiofrequency fields

    Microsoft Academic Search

    Christine H. Moran; Sean M. Wainerdi; Tonya K. Cherukuri; Carter Kittrell; Benjamin J. Wiley; Nolan W. Nicholas; Steven A. Curley; John S. Kanzius; Paul Cherukuri

    2009-01-01

    Capacitively coupled shortwave radiofrequency fields (13.56 MHz) resistively heat low concentrations (?1 ppm) of gold nanoparticles\\u000a with a thermal power dissipation of ?380 kW\\/g of gold. Smaller diameter gold nanoparticles (< 50 nm) heat at nearly twice\\u000a the rate of larger diameter gold nanoparticles (?50 nm), which is attributed to the higher resistivity of smaller gold nanostructures.\\u000a A Joule heating

  2. 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

  3. 78 FR 33633 - Human Exposure to Radiofrequency Electromagnetic Fields

    Federal Register 2010, 2011, 2012, 2013, 2014

    2013-06-04

    ...not be dominant in its field of operation. We are...station is dominant in its field of operation. Accordingly...515112 (updated for inflation in 2010...not be dominant in its field of operation.\\197...LPRS''), and Multi-Use Radio...

  4. 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

  5. Anomalous Capacitive Sheath with Deep Radio-Frequency Electric-Field Penetration

    NASA Astrophysics Data System (ADS)

    Kaganovich, Igor D.

    2002-12-01

    A novel nonlinear effect of anomalously deep penetration of an external radio-frequency electric field into a plasma is described. A self-consistent kinetic treatment reveals a transition region between the sheath and the plasma. Because of the electron velocity modulation in the sheath, bunches in the energetic electron density are formed in the transition region adjacent to the sheath. The width of the region is of order VT/?, where VT is the electron thermal velocity, and ? is the frequency of the electric field. The presence of the electric field in the transition region results in a collisionless cooling of the energetic electrons and an additional heating of the cold electrons.

  6. Radiofrequency sheath fields above a metal-dielectric interface

    SciTech Connect

    Barnat, E.V.; Hebner, G.A. [Sandia National Laboratories, Albuquerque, New Mexico 87185-1423 (United States)

    2004-11-01

    Two-dimensional maps of the sheath electric fields formed around a metal-dielectric interface were measured in a radio frequency (rf) argon plasma using laser-induced fluorescence-dip spectroscopy. Experimentally determined Stark shifts of the argon Rydberg 13d[3/2]{sub 1} state were used to quantify the electric fields in the sheath as functions of the rf cycle, voltage, and pressure. Both the structure of the sheath fields and the discharge characteristics in the region above the electrode depend on the discharge conditions and the configuration of the surface. Dissimilar materials placed adjacent to each other result in electric fields with a component parallel to the electrode surface.

  7. Radiofrequency sheath fields at a metal-dielectric interface.

    SciTech Connect

    Hebner, Gregory Albert; Barnat, Edward V.

    2004-06-01

    Two-dimensional maps of the sheath electric fields formed around a metal-dielectric interface were measured in a radio frequency (rf) argon plasma using laser-induced fluorescence-dip spectroscopy. Experimentally determined Stark shifts of the argon Rydberg 13d[3/2]1 state were used to quantify the electric fields in the sheath as functions of the rf cycle, voltage, and pressure. Both the structure of the sheath fields and the discharge characteristics in the region above the electrode depend on the discharge conditions and the configuration of the surface. Dissimilar materials placed adjacent to each other result in electric fields with a component parallel to the electrode surface.

  8. 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.

  9. Near-field effects in radio-frequency emission from particle showers in a dense medium

    NASA Astrophysics Data System (ADS)

    Hyneman, Rachel; Wissel, Stephanie; Belov, Konstantin; Vahle, Patricia; Salzberg, David; Romero-Wolf, Andres; SLAC T-510 Collaboration

    2015-04-01

    Two mechanisms are expected to produce radio-frequency emission in ultra-high energy cosmic ray air showers. Askaryan emission, generated by an overall charge excess, has been studied in beam experiments previously. The emission due to Earth's magnetic field has been inferred from observations by cosmic-ray observatories, but not yet studied in a controlled laboratory environment. The SLAC T-510 experiment recently studied the effects of a magnetic field upon the radio-frequency emission from particle showers in high-density polyethylene as a way to model cosmic ray air showers. Ultra-High Frequency (UHF) and Very High Frequency (VHF) antennas were used to measure the signal from particle showers in the target at different positions. For an overview, see the talk by K. Mulrey in this conference. Several near-field runs were performed with the UHF antenna array closer to the target than in the majority of the data taking. Signal from the two mechanisms, Askaryan and Magnetic, were separated into orthogonal polarizations by the geometry of the system. We report on studies of the electric field for several positions in the near field. Initial results indicate that the electric field as a function of angle behaves consistently as the antennas are moved further from the target.

  10. 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

  11. COMAR technical information statement: expert reviews on potential health effects of radiofrequency electromagnetic fields and comments on the bioinitiative report.

    PubMed

    2009-10-01

    The Committee on Man and Radiation (COMAR) is a technical committee of the Engineering in Medicine and Biology Society (EMBS) of the Institute of Electrical and Electronics Engineers (IEEE). Its primary area of interest is biological effects of non-ionizing electromagnetic radiation, including radiofrequency (RF) energy. The public interest in possible health effects attributed to RF energy, such as emitted by mobile phones, wireless telephone base stations, TV and radio broadcasting facilities, Wi-Fi systems and many other sources, has been accompanied by commentary in the media that varies considerably in reliability and usefulness for their audience. The focus of this COMAR Technical Information Statement is to identify quality sources of scientific information on potential health risks from exposure to RF energy. This Statement provides readers with references to expert reports and other reliable sources of information about this topic, most of which are available on the Internet. This report summarizes the conclusions from several major reports and comments on the markedly different conclusions in the BioInitiative Report (abbreviated BIR below). Since appearing on the Internet in August 2007, the BIR has received much media attention but, more recently, has been criticized by several health organizations (see Section titled "Views of health agencies about BIR"). COMAR concludes that the weight of scientific evidence in the RF bioeffects literature does not support the safety limits recommended by the BioInitiative group. For this reason, COMAR recommends that public health officials continue to base their policies on RF safety limits recommended by established and sanctioned international organizations such as the Institute of Electrical and Electronics Engineers International Committee on Electromagnetic Safety and the International Commission on Non-Ionizing Radiation Protection, which is formally related to the World Health Organization. PMID:19741364

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

    PubMed

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

    2014-06-21

    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. PMID:24828836

  13. 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.

  14. 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.

  15. 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.

  16. Radio-frequency sheath-plasma interactions with magnetic field tangency points along the sheath surface

    SciTech Connect

    Kohno, H. [Department of Physics, Lehigh University, 16 Memorial Drive East, Bethlehem, Pennsylvania 18015 (United States)] [Department of Physics, Lehigh University, 16 Memorial Drive East, Bethlehem, Pennsylvania 18015 (United States); Myra, J. R.; D'Ippolito, D. A. [Lodestar Research Corporation, 2400 Central Avenue P-5, Boulder, Colorado 80301 (United States)] [Lodestar Research Corporation, 2400 Central Avenue P-5, Boulder, Colorado 80301 (United States)

    2013-08-15

    Computer simulations of radio-frequency (RF) waves propagating across a two-dimensional (2D) magnetic field into a conducting boundary are described. The boundary condition for the RF fields at the metal surface leads to the formation of an RF sheath, which has previously been studied in one-dimensional models. In this 2D study, it is found that rapid variation of conditions along the sheath surface promote coupling of the incident RF branch (either fast or slow wave) to a short-scale-length sheath-plasma wave (SPW). The SPW propagates along the sheath surface in a particular direction dictated by the orientation of the magnetic field with respect to the surface, and the wave energy in the SPW accumulates near places where the background magnetic field is tangent to the surface.

  17. High mobility flexible graphene field-effect transistors and ambipolar radio-frequency circuits

    NASA Astrophysics Data System (ADS)

    Liang, Yiran; Liang, Xuelei; Zhang, Zhiyong; Li, Wei; Huo, Xiaoye; Peng, Lianmao

    2015-06-01

    Field-effect transistors (GFETs) were fabricated on mechanically flexible substrates using chemical vapor deposition grown graphene. High current density (nearly 200 ?A ?m-1) with saturation, almost perfect ambipolar electron-hole behavior, high transconductance (120 ?S ?m-1) and good stability over 381 days were obtained. The average carrier mobility for holes (electrons) is 13 540 cm2 V-1 s-1 (12 300 cm2 V-1 s-1) with the highest value over 24 000 cm2 V-1 s-1 (20 000 cm2 V-1 s-1) obtained in flexible GFETs. Ambipolar radio-frequency circuits, frequency doubler, were constructed based on the high performed flexible GFET, which show record high output power spectra purity (~97%) and high conversion gain of -13.6 dB. Bending measurements show the flexible GFETs are able to work under modest strain. These results show that flexible GFETs are a very promising option for future flexible radio-frequency electronics.Field-effect transistors (GFETs) were fabricated on mechanically flexible substrates using chemical vapor deposition grown graphene. High current density (nearly 200 ?A ?m-1) with saturation, almost perfect ambipolar electron-hole behavior, high transconductance (120 ?S ?m-1) and good stability over 381 days were obtained. The average carrier mobility for holes (electrons) is 13 540 cm2 V-1 s-1 (12 300 cm2 V-1 s-1) with the highest value over 24 000 cm2 V-1 s-1 (20 000 cm2 V-1 s-1) obtained in flexible GFETs. Ambipolar radio-frequency circuits, frequency doubler, were constructed based on the high performed flexible GFET, which show record high output power spectra purity (~97%) and high conversion gain of -13.6 dB. Bending measurements show the flexible GFETs are able to work under modest strain. These results show that flexible GFETs are a very promising option for future flexible radio-frequency electronics. Electronic supplementary information (ESI) available. See DOI: 10.1039/c5nr02292d

  18. 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.

  19. High mobility flexible graphene field-effect transistors and ambipolar radio-frequency circuits.

    PubMed

    Liang, Yiran; Liang, Xuelei; Zhang, Zhiyong; Li, Wei; Huo, Xiaoye; Peng, Lianmao

    2015-07-01

    Field-effect transistors (GFETs) were fabricated on mechanically flexible substrates using chemical vapor deposition grown graphene. High current density (nearly 200 ?A ?m(-1)) with saturation, almost perfect ambipolar electron-hole behavior, high transconductance (120 ?S ?m(-1)) and good stability over 381 days were obtained. The average carrier mobility for holes (electrons) is 13?540 cm(2) V(-1) s(-1) (12?300 cm(2) V(-1) s(-1)) with the highest value over 24?000 cm(2) V(-1) s(-1) (20?000 cm(2) V(-1) s(-1)) obtained in flexible GFETs. Ambipolar radio-frequency circuits, frequency doubler, were constructed based on the high performed flexible GFET, which show record high output power spectra purity (?97%) and high conversion gain of -13.6 dB. Bending measurements show the flexible GFETs are able to work under modest strain. These results show that flexible GFETs are a very promising option for future flexible radio-frequency electronics. PMID:26061485

  20. Radio-frequency heating of sloshing ions in a straight field line mirror

    SciTech Connect

    Moiseenko, V.E.; Aagren, O. [Division of Electricity and Lightning Research, Angstroem Laboratory, Uppsala University, Box 534, SE-751 21 Uppsala (Sweden)

    2005-10-01

    A scenario to sustain a sloshing ion population with radio-frequency heating in a newly proposed mirror device, the straight field line mirror, is examined. The possibilities of ion cyclotron heating in two-ion species plasma have been analyzed and a scheme with longitudinal wave conversion and fundamental harmonic heating of deuterium ions in tritium plasma has been investigated. This scheme provides efficient ion heating for high deuterium 'minority' concentration without substantial conversion to slow waves and heating of the electrons. Numerical calculations carried out for a reactor-scale device show that conversion of the fast magnetosonic wave to the fast Alfven wave occurs. For reasons of strong cyclotron absorption of the fast Alfven wave, only a small portion of the wave energy transits through the cyclotron layer and penetrates to the central part of the trap. The power deposition is peaked at the plasma core. The amount of deposited power does not depend sensitively on the parameters of the discharge. The study uses numerical three-dimensional calculations for the time-harmonic boundary problem for Maxwell's equations. For radio-frequency heating in this scheme, a simple efficient strap antenna is proposed. It has low Q antenna and operates in the regime of global resonance overlapping.

  1. 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

  2. Cell bystander effect induced by radiofrequency electromagnetic fields and magnetic nanoparticles

    E-print Network

    G. F. Goya; L. Asin; M. P. Calatayud; A. Tres; M. R. Ibarra

    2015-06-03

    Induced effects by direct exposure to ionizing radiation (IR) are a central issue in many fields like radiation protection, clinic diagnosis and oncological therapies. Direct irradiation at certain doses induce cell death, but similar effects can also occur in cells no directly exposed to IR, a mechanism known as bystander effect. Non-IR (radiofrequency waves) can induce the death of cells loaded with MNPs in a focused oncological therapy known as magnetic hyperthermia. Indirect mechanisms are also able to induce the death of unloaded MNPs cells. Using in vitro cell models, we found that colocalization of the MNPs at the lysosomes and the non-increase of the temperature induces bystander effect under non-IR. Our results provide a landscape in which bystander effects are a more general mechanism, up to now only observed and clinically used in the field of radiotherapy.

  3. Cell bystander effect induced by radiofrequency electromagnetic fields and magnetic nanoparticles

    E-print Network

    Goya, G F; Calatayud, M P; Tres, A; Ibarra, M R

    2015-01-01

    Induced effects by direct exposure to ionizing radiation (IR) are a central issue in many fields like radiation protection, clinic diagnosis and oncological therapies. Direct irradiation at certain doses induce cell death, but similar effects can also occur in cells no directly exposed to IR, a mechanism known as bystander effect. Non-IR (radiofrequency waves) can induce the death of cells loaded with MNPs in a focused oncological therapy known as magnetic hyperthermia. Indirect mechanisms are also able to induce the death of unloaded MNPs cells. Using in vitro cell models, we found that colocalization of the MNPs at the lysosomes and the non-increase of the temperature induces bystander effect under non-IR. Our results provide a landscape in which bystander effects are a more general mechanism, up to now only observed and clinically used in the field of radiotherapy.

  4. 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.

  5. 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.

  6. Motion of free spins and NMR imaging without a radio-frequency magnetic field

    E-print Network

    Kees van Schenk Brill; Jassem Lahfadi; Tarek Khalil; Daniel Grucker

    2015-04-19

    NMR imaging without any radio-frequency magnetic field is explained by a quantum treatment of independent spin~$\\tfrac 12$. The total magnetization is determined by means of their individual wave function. The theoretical treatment, based on fundamental axioms of quantum mechanics and solving explicitly the Schr\\"{o}dinger equation with the kinetic energy part which gives the motion of free spins, is recalled. It explains the phase shift of the spin noise spectrum with its amplitude compared to the conventional NMR spectrum. Moreover it explains also the relatively good signal to noise ratio of NMR images obtained without a RF pulse. This derivation should be helpful for new magnetic resonance imaging sequences or for developing quantum computing by NMR.

  7. THE JOURNAL OF CHEMICAL PHYSICS VOLUME 58, NUMBER 10 15 MAY 1973 Zero-field level crossing and optical radio-frequency double resonance

    E-print Network

    Zare, Richard N.

    and optical radio-frequency double resonance studies of the A 2~ + states of OH and on K. R. German *, T. H hyper- fine measurements for the A state because of its short lifetime. Optical radio-frequency double. INTRODUCTION frequencies deviate from linearity as a function of magnetic field. This permits an initial

  8. Review of possible modulation-dependent biological effects of radiofrequency fields.

    PubMed

    Juutilainen, Jukka; Höytö, Anne; Kumlin, Timo; Naarala, Jonne

    2011-10-01

    The biological effects of modulated radiofrequency (RF) electromagnetic fields have been a subject of debate since early publications more than 30 years ago, suggesting that relatively weak amplitude-modulated RF electromagnetic fields have specific biological effects different from the well-known thermal effects of RF energy. This discussion has been recently activated by the increasing human exposure to RF fields from wireless communication systems. Modulation is used in all wireless communication systems to enable the signal to carry information. A previous review in 1998 indicated that experimental evidence for modulation-specific effects of RF energy is weak. This article reviews recent studies (published after 1998) on the biological effects of modulated RF fields. The focus is on studies that have compared the effects of modulated and unmodulated (continuous wave) RF fields, or compared the effects of different kinds of modulations; studies that used only one type of signal are not included. While the majority of recent studies have reported no modulation-specific effects, there are a few interesting exceptions indicating that there may be specific effects from amplitude-modulated RF fields on the human central nervous system. These findings warrant follow-up studies. PMID:21480304

  9. The effects of radio-frequency electromagnetic fields on T cell function during development.

    PubMed

    Ohtani, Shin; Ushiyama, Akira; Maeda, Machiko; Ogasawara, Yuki; Wang, Jianqing; Kunugita, Naoki; Ishii, Kazuyuki

    2015-05-01

    With the widespread use of radio-frequency devices, it is increasingly important to understand the biological effects of the associated electromagnetic fields. Thus, we investigated the effects of radio-frequency electromagnetic fields (RF-EMF) on T cell responses during development due to the lack of science-based evidence for RF-EMF effects on developmental immune systems. Sprague Dawley (SD) rats were exposed to 2.14-GHz wideband code division multiple-access (W-CDMA) RF signals at a whole-body specific absorption rate (SAR) of 0.2 W/kg. Exposures were performed for a total of 9 weeks spanning in utero development, lactation and the juvenile period. Rats were continuously exposed to RF-EMF for 20 h/day, 7 days/week. Comparisons of control and exposed rats using flow cytometry revealed no changes in the numbers of CD4/CD8 T cells, activated T cells or regulatory T cells among peripheral blood cells, splenocytes and thymocytes. Expression levels of 16 genes that regulate the immunological Th1/Th2 paradigm were analyzed using real-time PCR in the spleen and thymus tissues of control and RF-EMF-exposed rats. Although only the Il5 gene was significantly regulated in spleen tissues, Il4, Il5 and Il23a genes were significantly upregulated in thymus tissues following exposure to RF-EMF. However, ELISAs showed no changes in serum IL-4 protein concentrations. These data indicate no adverse effects of long-term RF-EMF exposure on immune-like T cell populations, T cell activation, or Th1/Th2 balance in developing rats, although significant transcriptional effects were observed. PMID:25835473

  10. Evidence of high-field radio-frequency hot spots due to trapped vortices in niobium cavities

    Microsoft Academic Search

    Gianluigi Ciovati; Alexander Gurevich

    2008-01-01

    Superconducting radio-frequency (rf) cavities made of high-purity niobium exhibit strong anomalous rf losses starting at peak surface magnetic fields of about 90-100 mT in the gigahertz range. This phenomenon is referred to as ``Q drop.'' Temperature maps of the cavity surface have revealed the presence of ``hot spots'' in the high magnetic field region of the cavities. Several models have

  11. Analysing radio-frequency coil arrays in high-field magnetic resonance imaging by the combined field integral equation method

    NASA Astrophysics Data System (ADS)

    Wang, Shumin; Duyn, Jeff H.

    2006-06-01

    We present the combined field integral equation (CFIE) method for analysing radio-frequency coil arrays in high-field magnetic resonance imaging (MRI). Three-dimensional models of coils and the human body were used to take into account the electromagnetic coupling. In the method of moments formulation, we applied triangular patches and the Rao-Wilton-Glisson basis functions to model arbitrarily shaped geometries. We first examined a rectangular loop coil to verify the CFIE method and also demonstrate its efficiency and accuracy. We then studied several eight-channel receive-only head coil arrays for 7.0 T SENSE functional MRI. Numerical results show that the signal dropout and the average SNR are two major concerns in SENSE coil array design. A good design should be a balance of these two factors.

  12. Residential characteristics and radiofrequency electromagnetic field exposures from bedroom measurements in Germany.

    PubMed

    Breckenkamp, J; Blettner, M; Schüz, J; Bornkessel, C; Schmiedel, S; Schlehofer, B; Berg-Beckhoff, G

    2012-03-01

    The objectives of this study were to assess total exposure to radiofrequency electromagnetic fields (RF-EMF) in bedrooms and the contribution of different radioservices (FM radio, analogue TV and DVB-T, TETRA, GSM900 downlink, GSM1800 downlink, UMTS downlink, DECT, and wireless LAN and blue tooth) to the total exposure. Additional aims were to describe the proportion of measuring values above the detection limit of the dosimeters and to characterize the differences in exposure patterns associated with self-reported residential characteristics. Exposure to RF sources in bedrooms was measured using Antennessa(®) EME Spy 120 dosimeters in 1,348 households in Germany; 280 measures were available for each frequency band per household. Mean electrical field strengths and power flux densities were calculated. Power flux densities allow the calculation of proportions of different radioservices on total exposure. Exposure was often below the detection limit (electrical field strength: 0.05 V/m) of the dosimeter. Total exposure varied, depending on residential characteristics (urban vs. rural areas and floor of a building the measurement took place). Major sources of exposure were cordless phones (DECT standard) and wireless LAN/blue tooth contributing about 82% of total exposure (20.5 ?W/m(2)). Exposure to RF-EMF is ubiquitous, but exposure levels are-if at all measurable-very low and far below the ICNIRP's exposure reference levels. PMID:21964673

  13. 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

  14. Resonant Mode Reduction in Radiofrequency Volume Coils for Ultrahigh Field Magnetic Resonance Imaging

    PubMed Central

    Pang, Yong; Xie, Zhentian; Li, Ye; Xu, Duan; Vigneron, Daniel; Zhang, Xiaoliang

    2011-01-01

    In a multimodal volume coil, only one mode can generate homogeneous Radiofrequency (RF) field for Magnetic Resonance Imaging. The existence of other modes may increase the volume coil design difficulties and potentially decreases coil performance. In this study, we introduce common-mode resonator technique to high and ultrahigh field volume coil designs to reduce the resonant mode while maintain the homogeneity of the RF field. To investigate the design method, the common-mode resonator was realized by using a microstrip line which was split along the central to become a pair of parallel transmission lines within which common-mode currents exist. Eight common-mode resonators were placed equidistantly along the circumference of a low loss dielectric cylinder to form a volume coil. Theoretical analysis and comparison between the 16-strut common-mode volume coil and a conventional 16-strut volume coil in terms of RF field homogeneity and efficiency was performed using Finite-Difference Time-Domain (FDTD) method at 298.2 MHz. MR imaging experiments were performed by using a prototype of the common-mode volume coil on a whole body 7 Tesla scanner. FDTD simulation results showed the reduced number of resonant modes of the common-mode volume coil over the conventional volume coil, while the RF field homogeneity of the two type volume coils was kept at the same level. MR imaging of a water phantom and a kiwi fruit showing the feasibility of the proposed method for simplifying the volume coil design is also presented. PMID:22081791

  15. Diffusion Measurements with the Aid of Nutation Spin Echoes Appearing after Two Inhomogeneous Radiofrequency Pulses in Inhomogeneous Magnetic Fields

    Microsoft Academic Search

    Attila Scharfenecker; Ioan Ardelean; Rainer Kimmich

    2001-01-01

    Nutation echoes are generated by radiofrequency (RF) pulses with an inhomogeneous amplitude, B1 = B1(r), in inhomogeneous magnetic fields, B0 = B0(r). The two gradients of strengths G1 and G0, respectively, must be aligned in parallel for a maximum echo signal. After two RF pulses, two echoes appear at times ?a = 2?1 + ?2 + (G1\\/G0)?1 and ?b =

  16. 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.

  17. Direct observation of microcirculatory parameters in rat brain after local exposure to radio-frequency electromagnetic field

    Microsoft Academic Search

    S. Hirota; M. Matsuura; H. Masuda; A. Ushiyama; K. Wake; S. Watanabe; M. Taki; C. Ohkubo

    2009-01-01

    A cranial window method modified for our experiment enabled to observe the cerebral microcirculation including the blood-brain\\u000a barrier permeability after a local expose to radio-frequency electromagnetic fields with a monopole antenna in rats. The present\\u000a report reviews our recent publications that reported no noticeable changes in the cerebral microcirculatory parameters due\\u000a to RF-EMF exposure.

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

    NASA Astrophysics Data System (ADS)

    Piot, P.; Brau, C. A.; Choi, B. K.; Blomberg, B.; Gabella, W. E.; Ivanov, B.; Jarvis, J.; Mendenhall, M. H.; Mihalcea, D.; Panuganti, H.; Prieto, P.; Reid, J.

    2014-06-01

    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 ˜106 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.

  19. DNA strand breaks are not induced in human cells exposed to 2.1425 GHz band CW and W-CDMA modulated radiofrequency fields allocated to mobile radio base stations.

    PubMed

    Sakuma, N; Komatsubara, Y; Takeda, H; Hirose, H; Sekijima, M; Nojima, T; Miyakoshi, J

    2006-01-01

    We conducted a large-scale in vitro study focused on the effects of low level radiofrequency (RF) fields from mobile radio base stations employing the International Mobile Telecommunication 2000 (IMT-2000) cellular system in order to test the hypothesis that modulated RF fields may act as a DNA damaging agent. First, we evaluated the responses of human cells to microwave exposure at a specific absorption rate (SAR) of 80 mW/kg, which corresponds to the limit of the average whole body SAR for general public exposure defined as a basic restriction in the International Commission on Non-Ionizing Radiation Protection (ICNIRP) guidelines. Second, we investigated whether continuous wave (CW) and Wideband Code Division Multiple Access (W-CDMA) modulated signal RF fields at 2.1425 GHz induced different levels of DNA damage. Human glioblastoma A172 cells and normal human IMR-90 fibroblasts from fetal lungs were exposed to mobile communication frequency radiation to investigate whether such exposure produced DNA strand breaks in cell culture. A172 cells were exposed to W-CDMA radiation at SARs of 80, 250, and 800 mW/kg and CW radiation at 80 mW/kg for 2 and 24 h, while IMR-90 cells were exposed to both W-CDMA and CW radiations at a SAR of 80 mW/kg for the same time periods. Under the same RF field exposure conditions, no significant differences in the DNA strand breaks were observed between the test groups exposed to W-CDMA or CW radiation and the sham exposed negative controls, as evaluated immediately after the exposure periods by alkaline comet assays. Our results confirm that low level exposures do not act as a genotoxicant up to a SAR of 800 mW/kg. PMID:16283663

  20. Occupational exposures to radiofrequency fields: results of an Israeli national survey.

    PubMed

    Hareuveny, R; Kavet, R; Shachar, A; Margaliot, M; Kheifets, L

    2015-06-01

    Relatively high exposures to radiofrequency (RF) fields can occur in the broadcast, medical, and communications industries, as well in occupations that use RF emitting equipment (e.g. law enforcement). Information on exposure to workers employed in these industries and occupations is limited. We present results of an Israeli National Survey of occupational RF field levels at frequencies between ~100?kHz and 40?GHz, representing Industrial Heating, Communications, Radar, Research, and Medicine. Almost 4300 measurements from 900 sources across 25 occupations were recorded and categorised as 'routine', 'incidental', or 'unintended'. The occupation-specific geometric means (GMs) of the percentage of the American Conference of Governmental Industrial Hygienists (ACGIH) threshold limit values (TLVs) for each of the three exposure scenarios are presented together with the geometric standard deviation (GSD). Additionally, we present estimates of occupation-specific annual personal exposures and collective exposures. The vast majority of the GM of routine exposures ranged from a fraction to less than 1% of ACGIH TLVs, except for Walkie-Talkie (GM 94% of ACGIH), Induction Heating (17%), Plastic Welding (11%), Industrial Heating (6%) and Diathermy (6%). The GM of incidental and unintended exposures exceeded the TLV for one and 14 occupations, respectively. In many cases, the within-occupation GSD was very large, and though the medians remained below TLV, variable fractions of these occupations were projected to exceed the TLV. In rank order, Walkie-Talkie, Plastic Welding, and Induction Heating workers had the highest annual cumulative personal exposure. For cumulative collective exposures within an occupation, Walkie-Talkie dominated with 96.3% of the total, reflecting both large population and high personal exposure. A brief exceedance of the TLV does not automatically translate to hazard as RF exposure limits (issued by various bodies, including ACGIH) include a 10-fold safety factor relative to thermal thresholds and are based on a 6?min averaging period. PMID:25978146

  1. 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

  2. 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

  3. Mobile phone use, exposure to radiofrequency electromagnetic field, and brain tumour: a case–control study

    Microsoft Academic Search

    T Takebayashi; N Varsier; Y Kikuchi; K Wake; M Taki; S Watanabe; S Akiba; N Yamaguchi

    2008-01-01

    In a case–control study in Japan of brain tumours in relation to mobile phone use, we used a novel approach for estimating the specific absorption rate (SAR) inside the tumour, taking account of spatial relationships between tumour localisation and intracranial radiofrequency distribution. Personal interviews were carried out with 88 patients with glioma, 132 with meningioma, and 102 with pituitary adenoma

  4. 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

  5. First Operation of an Ungated Diamond Field-Emission Array Cathode in a L-Band Radiofrequency Electron Source

    E-print Network

    Piot, P; Choi, B K; Blomberg, B; Gabella, W E; Ivanov, B; Jarvis, J; Mendenhall, M H; Mihalcea, D; Panuganti, S; Prieto, P; Reid, J

    2014-01-01

    We report on the first successful operation of a field-emitter-array cathode in a conventional L-band radio-frequency electron source. The cathode consisted of an array of $\\sim 10^6$ diamond diamond tips on pyramids. Maximum current on the order of 15~mA were 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. Numerical simulations of the beam dynamics are also presented.

  6. 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

  7. A radio-frequency source using direct digital synthesis and field programmable gate array for nuclear magnetic resonance

    NASA Astrophysics Data System (ADS)

    Liang, Xiao; Weimin, Wang

    2009-12-01

    A radio-frequency (rf) source for nuclear magnetic resonance (NMR) is described. With the application of direct digital synthesis (DDS), the rf source has the ability to yield rf pulses with short switching time and high resolution in frequency and phase. To facilitate the generation of a soft pulse, a field programmable gate array (FPGA) cooperating with a pulse programmer is used as the auxiliary controller of the DDS chip. Triggered by the pulse programmer, the FPGA automatically controls the DDS to generate soft pulse according to predefined parameters, and the operation mode of the pulse programmer is optimized. The rf source is suitable for being used as transmitter in low-field (<1 T) NMR applications, for example, magnetic resonance imaging and relaxation measurement. As a compact and low-cost module, the rf source is of general use for constructing low-field NMR spectrometer.

  8. 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.

  9. Direct-current and radio-frequency characterizations of GaAs metal-insulator-semiconductor field-effect transistors enabled by

    E-print Network

    Ye, Peide "Peter"

    hysteresis-free Ids-Vgs characteristics and low flicker noise indicate that a high-quality SAND-GaAs MISFETs. We observe high-quality in- terface between SAND and GaAs by characterizing low fre- quency noiseDirect-current and radio-frequency characterizations of GaAs metal-insulator-semiconductor field

  10. Genetic, carcinogenic and teratogenic effects of radiofrequency fields 1 This is the second in a series of four papers, the first of which was published in Mutation Res. 387 (1997) pp. 165–171. 1

    Microsoft Academic Search

    L. Verschaeve; A. Maes

    1998-01-01

    This paper reviews the literature data on the genetic toxicology of radiofrequency (RF) radiation. Whereas in the past most studies were devoted to microwave ovens and radar equipment, it is now mobile telecommunication that attracts most attention. Therefore we focus on mobile telephone frequencies where possible. According to a great majority of the papers, radiofrequency fields, and mobile telephone frequencies

  11. Animal carcinogenicity studies on radiofrequency fields related to mobile phones and base stations

    SciTech Connect

    Dasenbrock, Clemens [Fraunhofer Institute of Toxicology and Experimental Medicine (ITEM), Nikolai-Fuchs-Str. 1, 30625 Hannover (Germany)]. E-mail: clemens-dasebrock@bc.boehringer-ingelheim.com

    2005-09-01

    Since a report in 1997 on an increased lymphoma incidence in mice chronically exposed to a mobile phone radiofrequency signal, none of the subsequent long-term studies in rodents have confirmed these results. On the other hand, several of the follow-up co- and carcinogenicity studies are still underway or are presently being initiated. Most of the published long-term studies used 1 exposure level only and suffer from a poor dosimetry which does not consider the animal's growth. Additional points of criticism are a limited, in some cases, questionable histopathology and inadequate group sizes. Overall, if dealing with new chemicals or drugs, these studies would not be acceptable for registration with the responsible authorities. The major critical points are taken into consideration within the European co- and carcinogenicity projects (CEMFEC and PERFORM-A), which are in their final stages and in the US long-term studies in mice and rats which are about to be initiated. Nevertheless, the WHO evaluation for health risk assessment of long-term telephone use and base station exposure will start in late 2005.

  12. Single-sided radio-frequency field gradient with two unsymmetrical loops: Applications to nuclear magnetic resonance.

    PubMed

    Guendouz, Laouès; Leclerc, Sébastien; Retournard, Alain; Hedjiedj, Ahcène; Canet, Daniel

    2008-12-01

    Magnetic field gradients are nowadays indispensable to most nuclear magnetic resonance experiments and are at the basis of magnetic resonance imaging (MRI). Most of the time, gradients of the static magnetic field are employed. Gradients of the radio-frequency (rf) field may constitute an interesting alternative. Until now, they were produced by a single loop. We demonstrate in this paper how two unsymmetrical series loops can be optimized to produce rf gradients of much better performances. This optimization is based on a thorough theoretical approach and the gradient uniformity is studied through accurate simulations. Two prototypes were devised: one for a 2.34 T horizontal magnet (used in MRI), and the other for a 4.7 T vertical magnet (used for pure spectroscopic applications). These two-loop systems were designed for proton resonance frequencies (100 and 200 MHz, respectively). Performances of both systems were verified (versus theoretical predictions) by means of experiments employing gradients in view of the determination of the self-diffusion coefficients of liquids. PMID:19123566

  13. Exposure to low level GSM 935 MHZ radiofrequency fields does not induce apoptosis in proliferating or differentiated murine neuroblastoma cells.

    PubMed

    Moquet, J; Ainsbury, E; Bouffler, S; Lloyd, D

    2008-01-01

    The aim of this study was to investigate whether radiofrequency (RF) fields characteristic of mobile phones at non-thermal levels can induce apoptosis in murine neuroblastoma (N2a) cells in both proliferating and differentiated states. Cells were exposed continuously for 24 h to one of the three 935-MHz RF signals: global system for mobile communication (GSM) basic, GSM talk and a continuous wave, unmodulated signal; all at a specific energy absorption rate of 2 W kg(-1). The measured increase in temperature of the cells due to the RF fields was around 0.06 degrees C. At a number of time points between 0 and 48 h post-exposure, the cells were assessed for apoptosis under a fluorescence microscope using three independent assays: Annexin V, caspase activation and in situ end-labelling. No statistically significant differences in apoptosis levels were observed between the exposed and sham-exposed cells using the three assays at any time point post-exposure. These data suggest that RF exposures, characteristic of GSM mobile phones, do not significantly affect the apoptosis levels in proliferating and differentiated murine neuroblastoma cell line N2a. PMID:18550513

  14. Evidence of high-field radio-frequency hot-spots due to trapped vortices in niobium cavities

    SciTech Connect

    Ciovati, Gianluigi; Gurevich, Alexander

    2008-12-01

    Superconducting radio-frequency (rf) cavities made of high-purity niobium exhibit strong anomalous rf losses starting at peak surface magnetic fields of about 90-100 mT in the gigahertz range. This phenomenon is referred to as "Q-drop". Temperature maps of the cavity surface have revealed the presence of "hot-spots" in the high magnetic field region of the cavities. Several models have been proposed over the years to explain this phenomenon but there is still no experimental evidence on the mechanisms behind such hot-spots. In this work we show that at least some of the hotspots are due to trapped vortices responsible for the anomalous losses. Here we report experiments in which a local thermal gradient was applied to the hot-spot regions of a cavity in order to displace the vortices. Temperature maps measured before and after applying the thermal gradient unambiguously show that the hotspot do move and change their intensities, allowing us to determine changes in

  15. Diffusion measurements with the aid of nutation spin echoes appearing after two inhomogeneous radiofrequency pulses in inhomogeneous magnetic fields.

    PubMed

    Scharfenecker, A; Ardelean, I; Kimmich, R

    2001-02-01

    Nutation echoes are generated by radiofrequency (RF) pulses with an inhomogeneous amplitude, B(1) = B(1)(r), in inhomogeneous magnetic fields, B(0) = B(0)(r). The two gradients of strengths G(1) and G(0), respectively, must be aligned in parallel for a maximum echo signal. After two RF pulses, two echoes appear at times tau(a) = 2 tau(1) + tau(2) + (G(1)/G(0))tau(1) and tau(b) = 2 tau(1) + tau(2) + 2(G(1)/G(0))tau(1), where tau(1) is the RF pulse duration and tau(2) the interpulse interval. It is shown that these echoes can favorably be employed for the determination of self-diffusion coefficients even in the poor experimental situation one often faces in low-resolution or low-field NMR. The signal intensity is comparable to that of ordinary Hahn echoes. Diffusion coefficients and spin-lattice relaxation times can be evaluated from the same experimental data set if both nutation echoes are recorded. Test experiments are in good agreement with literature data. Applications of the technique to "inside out" NMR, well logging NMR, surface coil NMR, toroid cavity NMR, etc., are suggested. PMID:11237643

  16. Nuclear and Non-Ionizing Energy-Loss for Coulomb Scattered Particles from Low Energy up to Relativistic Regime in Space Radiation Environment

    E-print Network

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

    2014-01-21

    In the space environment, instruments onboard of spacecrafts can be affected by displacement damage due to radiation. The differential scattering cross section for screened nucleus--nucleus interactions - i.e., including the effects due to screened Coulomb nuclear fields -, nuclear stopping powers and non-ionization energy losses are treated from about 50 keV/nucleon up to relativistic energies.

  17. Evaluation of Safety and Patient Subjective Efficacy of Using Radiofrequency and Pulsed Magnetic Fields for the Treatment of Striae (Stretch Marks)

    PubMed Central

    Dover, Jeffrey S.; Rothaus, Kenneth

    2014-01-01

    Stretch marks are common skin disorders that are dermal scars with associated epidermal atrophy. They are of significant concern or psychological concern to many. This manuscript describes the use of multipolar radiofrequency with pulsed magnetic fields that was successfully used to diminish these lesions in 16 subjects undergoing a series of treatments. The improvements noted were statistically significant and no serious adverse events were noted. PMID:25276274

  18. Effects of 1.8 GHz radiofrequency field on DNA damage and expression of heat shock protein 70 in human lens epithelial cells

    Microsoft Academic Search

    Sun Lixia; Ke Yao; Wang Kaijun; Lu Deqiang; Hu Huajun; Gao Xiangwei; Wang Baohong; Zheng Wei; Lou Jianling; Wu Wei

    2006-01-01

    To investigate the DNA damage, expression of heat shock protein 70 (Hsp70) and cell proliferation of human lens epithelial cells (hLEC) after exposure to the 1.8GHz radiofrequency field (RF) of a global system for mobile communications (GSM). An Xc-1800 RF exposure system was used to employ a GSM signal at 1.8GHz (217Hz amplitude-modulated) with the output power in the specific

  19. Studying the synergistic damage effects induced by 1.8 GHz radiofrequency field radiation (RFR) with four chemical mutagens on human lymphocyte DNA using comet assay in vitro

    Microsoft Academic Search

    Wang Baohong; He Jiliang; Jin Lifen; Lu Deqiang; Zheng Wei; Lou Jianlin; Deng Hongping

    2005-01-01

    The aim of this investigation was to study the synergistic DNA damage effects in human lymphocytes induced by 1.8GHz radiofrequency field radiation (RFR, SAR of 3W\\/kg) with four chemical mutagens, i.e. mitomycin C (MMC, DNA crosslinker), bleomycin (BLM, radiomimetic agent), methyl methanesulfonate (MMS, alkylating agent), and 4-nitroquinoline-1-oxide (4NQO, UV-mimetic agent). The DNA damage of lymphocytes exposed to RFR and\\/or with

  20. 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

  1. Magnetic Field Generation in an Inductively Coupled Radio-Frequency Power Transmission System

    Microsoft Academic Search

    Kathleen O'Brien; R. Teichmann; H. Gueldner

    2006-01-01

    This paper discusses various methods for the generation of an omni-directional magnetic field suitable for use in an inductively coupled power transmission system. The field characteristics are evaluated with a focus on minimizing undesired shielding effects while remaining within the boundaries set by international standards for occupational exposure to magnetic fields. The dynamic requirements of load resonant converters that allow

  2. Incidence of micronuclei in human peripheral blood lymphocytes exposed to modulated and unmodulated 2450?MHz radiofrequency fields.

    PubMed

    Vijayalaxmi; Reddy, Abhishek B; McKenzie, Raymond J; McIntosh, Robert L; Prihoda, Thomas J; Wood, Andrew W

    2013-10-01

    Peripheral blood samples from four healthy volunteers were collected and aliquots were exposed in vitro for 2?h to either (i) modulated (wideband code division multiple access, WCDMA) or unmodulated continuous wave (CW) 2450?MHz radiofrequency (RF) fields at an average specific absorption rate of 10.9?W/kg or (ii) sham-exposed. Aliquots of the same samples that were exposed in vitro to an acute dose of 1.5?Gy ionizing gamma-radiation (GR) were used as positive controls. Half of the aliquots were treated with melatonin (Mel) to investigate if such treatment offers protection to the cells from the genetic damage, if any, induced by RF and GR. The cells in all samples were cultured for 72?h and the lymphocytes were examined to determine the extent of genetic damage assessed from the incidence of micronuclei (MN). The results indicated the following: (i) the incidence of MN was similar in incubator controls, and those exposed to RF/sham and Mel alone; (ii) there were no significant differences between WCDMA and CW RF exposures; (iii) positive control cells exposed to GR alone exhibited significantly increased MN; and (iv) Mel treatment had no effect on cells exposed to RF and sham, while such treatment significantly reduced the frequency of MN in GR-exposed cells. PMID:23720062

  3. Study of Oxidative Stress in Human Lens Epithelial Cells Exposed to 1.8 GHz Radiofrequency Fields

    PubMed Central

    Ni, Shuang; Yu, Yibo; Zhang, Yidong; Wu, Wei; Lai, Kairan; Yao, Ke

    2013-01-01

    Objectives The aims of the present study were to determine oxidative stress and to explore possible reasons of reactive oxygen species (ROS) increase in human lens epithelial (HLE) B3 cells exposed to low intensity 1.8 GHz radiofrequency fields (RF). Methods The HLE B3 cells were divided into RF exposure and RF sham-exposure groups. The RF exposure intensity was at specific absorption rate (SAR) of 2, 3, or 4 W/kg. The ROS levels were measured by a fluorescent probe 2?7?-dichlorofluorescin diacetate (DCFH-DA) assay in the HLE B3 cells exposed to 1.8 GHz RF for 0.5, 1, and 1.5 h. Lipid peroxidation and cellular viability were detected by an MDA test and Cell Counting Kit-8 (CCK-8) assays, respectively, in the HLE B3 cells exposed to 1.8 GHz RF for 6, 12, and 24 h, respectively. The mRNA expression of SOD1, SOD2, CAT, and GPx1 genes and the expression of SOD1, SOD2, CAT, and GPx1 proteins was measured by qRT-PCR and Western blot assays in the HLE B3 cells exposed to 1.8 GHz RF for 1 h. Results The ROS and MDA levels significantly increased (P<0.05) in the RF exposure group and that the cellular viability, mRNA expression of four genes, and expression of four proteins significantly decreased (P<0.05) compared with the RF sham-exposure group. Conclusions Oxidative stress is present in HLE B3 cells exposed to 1.8 GHz low-intensity RF and that the increased production of ROS may be related to down-regulation of four antioxidant enzyme genes induced by RF exposure. PMID:23991100

  4. Detection of acoustic waves by NMR using a radiofrequency field gradient

    NASA Astrophysics Data System (ADS)

    Madelin, Guillaume; Baril, Nathalie; Lewa, Czeslaw J.; Franconi, Jean-Michel; Canioni, Paul; Thiaudiére, Eric; de Certaines, Jacques D.

    2003-03-01

    A B1 field gradient-based method previously described for the detection of mechanical vibrations has been applied to detect oscillatory motions in condensed matter originated from acoustic waves. A ladder-shaped coil generating a quasi-constant RF-field gradient was associated with a motion-encoding NMR sequence consisting in a repetitive binomial 1 3¯3 1¯ RF pulse train (stroboscopic acquisition). The NMR response of a gel phantom subject to acoustic wave excitation in the 20-200 Hz range was investigated. Results showed a linear relationship between the NMR signal and the wave amplitude and a spectroscopic selectivity of the NMR sequence with respect to the input acoustic frequency. Spin displacements as short as a few tens of nanometers were able to be detected with this method.

  5. Chemical Vapour Deposition Graphene Radio-Frequency Field-Effect Transistors

    Microsoft Academic Search

    Ma Peng; Jin Zhi; Guo Jian-Nan; Pan Hong-Liang; Liu Xin-Yu; Ye Tian-Chun; Wang Hong; Wang Guan-Zhong

    2012-01-01

    We report the dc and rf performance of graphene rf field-effect transistors, where the graphene films are grown on copper by using the chemical vapour deposition (CVD) method and transferred to SiO2\\/Si substrates. Composite materials, benzocyclobutene and atomic layer deposition Al2O3 are used as the gate dielectrics. The observation of n- and p-type transitions verifies the ambipolar characteristics in the

  6. Conduct of a personal radiofrequency electromagnetic field measurement study: proposed study protocol

    Microsoft Academic Search

    Martin Röösli; Patrizia Frei; John Bolte; Georg Neubauer; Elisabeth Cardis; Maria Feychting; Peter Gajsek; Sabine Heinrich; Wout Joseph; Simon Mann; Luc Martens; Evelyn Mohler; Roger C Parslow; Aslak Harbo Poulsen; Katja Radon; Joachim Schüz; György Thuroczy; Jean-François Viel; Martine Vrijheid

    2010-01-01

    BACKGROUND: The development of new wireless communication technologies that emit radio frequency electromagnetic fields (RF-EMF) is ongoing, but little is known about the RF-EMF exposure distribution in the general population. Previous attempts to measure personal exposure to RF-EMF have used different measurement protocols and analysis methods making comparisons between exposure situations across different study populations very difficult. As a result,

  7. Effects of an external magnetic field, and of oblique radio-frequency electric fields on multipactor discharge on a dielectric

    NASA Astrophysics Data System (ADS)

    Valfells, A.; Ang, L. K.; Lau, Y. Y.; Gilgenbach, R. M.

    2000-02-01

    This paper analyzes, separately, the effects of an external magnetic field, the rf magnetic field, and of an oblique rf electric field, on multipactor discharge on a dielectric. Using Monte Carlo simulation, we obtain the susceptibility diagram in terms of the magnetic field, the rf electric field, and the dc charging field for various dielectric materials. We find that a magnetic field parallel to either the rf electric field or the dc electric field does not qualitatively change the susceptibility diagram. However, an external magnetic field perpendicular to both the rf electric field and the dc electric field can significantly affect the susceptibility diagram. Thus oriented magnetic fields lower the upper susceptibility bound when the magnetic field strength is approximately equal to Bres[T]=0.036f(GHz), where f is the rf frequency. Both the lower and upper susceptibility boundary may be raised significantly by a large external magnetic field, B?Bres. Susceptibility to single surface multipactor is greatest when the rf electric field is nearly parallel to the dielectric, but is dramatically decreased for angles of obliqueness greater than approximately 5°-10°. The rf magnetic field does not affect the lower boundary, but may extend the upper boundary greatly.

  8. Searching for the perfect wave: the effect of radiofrequency electromagnetic fields on cells.

    PubMed

    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

  9. 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

  10. Chemical Vapour Deposition Graphene Radio-Frequency Field-Effect Transistors

    NASA Astrophysics Data System (ADS)

    Ma, Peng; Jin, Zhi; Guo, Jian-Nan; Pan, Hong-Liang; Liu, Xin-Yu; Ye, Tian-Chun; Wang, Hong; Wang, Guan-Zhong

    2012-05-01

    We report the dc and rf performance of graphene rf field-effect transistors, where the graphene films are grown on copper by using the chemical vapour deposition (CVD) method and transferred to SiO2/Si substrates. Composite materials, benzocyclobutene and atomic layer deposition Al2O3 are used as the gate dielectrics. The observation of n- and p-type transitions verifies the ambipolar characteristics in the graphene layers. While the intrinsic carrier mobility of CVD graphene is extracted to be 1200 cm2/V·s, the parasitic series resistances are demonstrated to have a serious impact on device performance. With a gate length of 1 ?m and an extrinsic transconductance of 72 mS/mm, a cutoff frequency of 6.6 GHz and a maximum oscillation frequency of 8.8 GHz are measured for the transistors, illustrating the potential of the CVD graphene for rf applications.

  11. Heteromaterial gate tunneling field-effect transistor for high-speed and radio-frequency applications.

    PubMed

    Yoon, Young Jun; Seo, Jae Hwa; Cho, Eou-Sik; Lee, Jung-Hee; Bae, Jin-Hyuk; Cho, Seongjae; Kang, In Man

    2014-11-01

    We propose a tunneling field-effect transistor (TFET) with a heteromaterial (HM)-gate not only for low standby power (LSTP) applications, which TFETs are genuinely suitable for, but also for high-speed performance by properly adjusting intrinsic gate capacitance (C(gg)). As a result of simulations in this work, the HM-gate TFET showed better subthreshold characteristics (smaller S) at an appropriate threshold voltage (V(th)) for LSTP applications, enhancing tunneling probability by modulating the difference in the metal workfunction (?(m)) between the source-side gate (S-gate) and the drain-side gate (D-gate). Further, the C(gg) of HM-gate TFET were extracted and compared against that of conventional TFETs having gates with various ?(m)'s. Since lower C(gg) can be formed by high ?(m) in the D-gate, the HM-gate TFET has an excellent cut-off frequency (f(T)) and intrinsic delay time (?) associated with the C(gg). We confirmed that the HM-gate TFET proposed in this work achieves superb performance for LSTP applications as well as high-frequency operations. PMID:25958487

  12. 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

  13. Conduct of a personal radiofrequency electromagnetic field measurement study: proposed study protocol

    PubMed Central

    2010-01-01

    Background The development of new wireless communication technologies that emit radio frequency electromagnetic fields (RF-EMF) is ongoing, but little is known about the RF-EMF exposure distribution in the general population. Previous attempts to measure personal exposure to RF-EMF have used different measurement protocols and analysis methods making comparisons between exposure situations across different study populations very difficult. As a result, observed differences in exposure levels between study populations may not reflect real exposure differences but may be in part, or wholly due to methodological differences. Methods The aim of this paper is to develop a study protocol for future personal RF-EMF exposure studies based on experience drawn from previous research. Using the current knowledge base, we propose procedures for the measurement of personal exposure to RF-EMF, data collection, data management and analysis, and methods for the selection and instruction of study participants. Results We have identified two basic types of personal RF-EMF measurement studies: population surveys and microenvironmental measurements. In the case of a population survey, the unit of observation is the individual and a randomly selected representative sample of the population is needed to obtain reliable results. For microenvironmental measurements, study participants are selected in order to represent typical behaviours in different microenvironments. These two study types require different methods and procedures. Conclusion Applying our proposed common core procedures in future personal measurement studies will allow direct comparisons of personal RF-EMF exposures in different populations and study areas. PMID:20487532

  14. 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

  15. 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

  16. Measurement and analysis of radiofrequency radiations from some mobile phone base stations in Ghana.

    PubMed

    Amoako, J K; Fletcher, J J; Darko, E O

    2009-08-01

    A survey of the radiofrequency electromagnetic radiation at public access points in the vicinity of 50 cellular phone base stations has been carried out. The primary objective was to measure and analyse the electromagnetic field strength levels emitted by antennae installed and operated by the Ghana Telecommunications Company. On all the sites measurements were made using a hand-held spectrum analyser to determine the electric field level with the 900 and 1800 MHz frequency bands. The results indicated that power densities at public access points varied from as low as 0.01 microW m(-2) to as high as 10 microW m(-2) for the frequency of 900 MHz. At a transmission frequency of 1800 MHz, the variation of power densities is from 0.01 to 100 microW m(-2). The results were found to be in compliant with the International Commission on Non-ionizing Radiological Protection guidance level but were 20 times higher than the results generally obtained for such a practice elsewhere. There is therefore a need to re-assess the situation to ensure reduction in the present level as an increase in mobile phone usage is envisaged within the next few years. PMID:19584141

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

    PubMed

    Mantiply, E D; Pohl, K R; Poppell, S W; Murphy, J A

    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 paper is organized into seven sections, each cataloging sources into appropriate RF frequency bands from very-low frequency (VLF) to super-high frequency (SHF), and covers frequencies from 10 kHz to 30 GHz. Sources included in this summary are the following: Coast Guard navigational transmitters, a Navy VLF transmitter, computer visual display terminals (VDTs), induction stoves or range tops, industrial induction and dielectric heaters, radio and television broadcast transmitters, amateur and citizens band (CB) transmitters, medical diathermy and electrosurgical units, mobile and handheld transmitters, cordless and cellular telephones, microwave ovens, microwave terrestrial relay and satellite uplinks, and police, air traffic, and aircraft onboard radars. For the sources included in this summary, the strongest fields are found near industrial induction and dielectric heaters, and close to the radiating elements or transmitter leads of high power antenna systems. Handheld transmitters can produce near fields of about 500 V/m at the antenna. Fields in the general urban environment are principally associated with radio and TV broadcast services and measure about 0.1 V/m root-mean-square (rms). Peak fields from air traffic radars sampled in one urban environment were about 10 V/m, 300 times greater than the rms value of 0.03 V/m when the duty factor associated with antenna rotation and pulsing are factored in. PMID:9383245

  18. Temperature changes associated with radiofrequency exposure near authentic metallic implants in the head phantom--a near field simulation study with 900, 1800 and 2450 MHz dipole.

    PubMed

    Matikka Virtanen, H; Keshvari, J; Lappalainen, R

    2010-10-01

    Along with increased use of wireless communication devices operating in the radiofrequency (RF) range, concern has been raised about the related possible health risks. Among other concerns, the interaction of medical implants and RF devices has been studied in order to assure the safety of implant carriers under various exposure conditions. In the RF range, the main established quantitative effect of electromagnetic (EM) fields on biological tissues is heating due to vibrational movements of water molecules. The temperature changes induced in tissues also constitute the basis for the setting of RF exposure limits and recommendations. In this study, temperature changes induced by electromagnetic field enhancements near passive metallic implants have been simulated in the head region. Furthermore, the effect of the implant material on the induced temperature change was evaluated using clinically used metals with the highest and the lowest thermal conductivities. In some cases, remarkable increases in maximum temperatures of tissues (as much as 8 °C) were seen in the near field with 1 W power level whereas at lower power levels significant temperature increases were not observed. PMID:20844329

  19. Temperature changes associated with radiofrequency exposure near authentic metallic implants in the head phantom—a near field simulation study with 900, 1800 and 2450 MHz dipole

    NASA Astrophysics Data System (ADS)

    Matikka (formerly Virtanen, H.; Keshvari, J.; Lappalainen, R.

    2010-10-01

    Along with increased use of wireless communication devices operating in the radiofrequency (RF) range, concern has been raised about the related possible health risks. Among other concerns, the interaction of medical implants and RF devices has been studied in order to assure the safety of implant carriers under various exposure conditions. In the RF range, the main established quantitative effect of electromagnetic (EM) fields on biological tissues is heating due to vibrational movements of water molecules. The temperature changes induced in tissues also constitute the basis for the setting of RF exposure limits and recommendations. In this study, temperature changes induced by electromagnetic field enhancements near passive metallic implants have been simulated in the head region. Furthermore, the effect of the implant material on the induced temperature change was evaluated using clinically used metals with the highest and the lowest thermal conductivities. In some cases, remarkable increases in maximum temperatures of tissues (as much as 8 °C) were seen in the near field with 1 W power level whereas at lower power levels significant temperature increases were not observed.

  20. Simple radio-frequency power source for ion guides and ion traps Ronald M. Jones

    E-print Network

    Anderson, Scott L.

    Simple radio-frequency power source for ion guides and ion traps Ronald M. Jones Department oscillator circuit, designed to power radio-frequency rf ion guides and traps, is described. The rf circuit by inhomoge- neous radio-frequency rf fields, in some cases with addi- tional inhomogeneous direct current dc

  1. Nanoscale memristive radiofrequency switches.

    PubMed

    Pi, Shuang; Ghadiri-Sadrabadi, Mohammad; Bardin, Joseph C; Xia, Qiangfei

    2015-01-01

    Radiofrequency switches are critical components in wireless communication systems and consumer electronics. Emerging devices include switches based on microelectromechanical systems and phase-change materials. However, these devices suffer from disadvantages such as large physical dimensions and high actuation voltages. Here we propose and demonstrate a nanoscale radiofrequency switch based on a memristive device. The device can be programmed with a voltage as low as 0.4?V and has an ON/OFF conductance ratio up to 10(12) with long state retention. We measure the radiofrequency performance of the switch up to 110?GHz and demonstrate low insertion loss (0.3?dB at 40?GHz), high isolation (30?dB at 40?GHz), an average cutoff frequency of 35?THz and competitive linearity and power-handling capability. Our results suggest that, in addition to their application in memory and computing, memristive devices are also a leading contender for radiofrequency switch applications. PMID:26108890

  2. Exposure to radio-frequency electromagnetic fields from broadcast transmitters and risk of childhood cancer: a census-based cohort study.

    PubMed

    Hauri, Dimitri D; Spycher, Ben; Huss, Anke; Zimmermann, Frank; Grotzer, Michael; von der Weid, Nicolas; Spoerri, Adrian; Kuehni, Claudia E; Röösli, Martin

    2014-04-01

    We investigated the association between exposure to radio-frequency electromagnetic fields (RF-EMFs) from broadcast transmitters and childhood cancer. First, we conducted a time-to-event analysis including children under age 16 years living in Switzerland on December 5, 2000. Follow-up lasted until December 31, 2008. Second, all children living in Switzerland for some time between 1985 and 2008 were included in an incidence density cohort. RF-EMF exposure from broadcast transmitters was modeled. Based on 997 cancer cases, adjusted hazard ratios in the time-to-event analysis for the highest exposure category (>0.2 V/m) as compared with the reference category (<0.05 V/m) were 1.03 (95% confidence interval (CI): 0.74, 1.43) for all cancers, 0.55 (95% CI: 0.26, 1.19) for childhood leukemia, and 1.68 (95% CI: 0.98, 2.91) for childhood central nervous system (CNS) tumors. Results of the incidence density analysis, based on 4,246 cancer cases, were similar for all types of cancer and leukemia but did not indicate a CNS tumor risk (incidence rate ratio = 1.03, 95% CI: 0.73, 1.46). This large census-based cohort study did not suggest an association between predicted RF-EMF exposure from broadcasting and childhood leukemia. Results for CNS tumors were less consistent, but the most comprehensive analysis did not suggest an association. PMID:24651167

  3. Evaluation of reproductive function of female rats exposed to radiofrequency fields (27. 12 MHz) near a shortwave diathermy device

    SciTech Connect

    Brown-Woodman, P.D.; Hadley, J.A.; Richardson, L.; Bright, D.; Porter, D.

    1989-04-01

    In recent years, there has been increased concern regarding effects of operator exposure to the electromagnetic (EM) field associated with shortwave diathermy devices. The present study was designed to investigate the effects, on rats, of repeated exposure to such an EM field. Following repeated exposure for 5 wk, a reduction in fertility occurred as indicated by a reduced number of matings in exposed rats compared to sham-irradiated rats and a reduction in the number of rats that conceived after mating. The data suggest that female operators could experience reduced fertility, if they remained close to the console for prolonged periods. This has particular significant for the physiotherapy profession.

  4. Pulsed radio-frequency electromagnetic fields: dose-dependent effects on sleep, the sleep EEG and cognitive performance

    Microsoft Academic Search

    SABINE J. REGEL; GILBERTE TINGUELY; JÜRGEN SCHUDERER; MARTIN ADAM; NIELS KUSTER; HANS-PETER LANDOLT; PETER ACHERMANN

    2007-01-01

    SUMMARY To establish a dose-response relationship between the strength of electromagnetic fields (EMF) and previously reported effects on the brain, we investigated the influence of EMF exposure by varying the signal intensity in three experimental sessions. The head of 15 healthy male subjects was unilaterally exposed for 30 min prior to sleep to a pulse- modulated EMF (GSM handset like

  5. Model for Initiation of Quality Factor Degradation at High Accelerating Fields in Superconducting Radio-Frequency Cavaties

    SciTech Connect

    Dzyuba, A.; /Fermilab /Novosibirsk State U.; Romanenko, A.; /Fermilab; Cooley, L.D.; /Fermilab

    2010-07-13

    A model for the onset of the reduction in SRF cavity quality factor, the so-called Q-drop, at high accelerating electric fields is presented. Since magnetic fields at the cavity equator are tied to accelerating electric fields by a simple geometric factor, the onset of magnetic flux penetration determines the onset of Q-drop. We consider breakdown of the surface barrier at triangular grooves to predict the magnetic field of first flux penetration H{sub pen}. Such defects were argued to be the worst case by Buzdin and Daumens, [1998 Physica C 294 257], whose approach, moreover, incorporates both the geometry of the groove and local contamination via the Ginzburg-Landau parameter {kappa}. Since previous Q-drop models focused on either topography or contamination alone, the proposed model allows new comparisons of one effect in relation to the other. The model predicts equivalent reduction of H{sub pen} when either roughness or contamination were varied alone, so smooth but dirty surfaces limit cavity performance about as much as rough but clean surfaces do. Still lower H{sub pen} was predicted when both effects were combined, i.e. contamination should exacerbate the negative effects of roughness and vice-versa. To test the model with actual data, coupons were prepared by buffered chemical polishing and electropolishing, and stylus profilometry was used to obtain distributions of angles. From these data, curves for surface resistance generated by simple flux flow as a function of magnetic field were generated by integrating over the distribution of angles for reasonable values of {kappa}. This showed that combined effects of roughness and contamination indeed reduce the Q-drop onset field by {approx}20%, and that that contamination contributes to Q-drop as much as roughness. The latter point may be overlooked by SRF cavity research, since access to the cavity interior by spectroscopy tools is very difficult, whereas optical images have become commonplace. The model was extended to fit cavity test data, which indicated that reduction of the superconducting gap by contaminants may also play a role in Q-drop.

  6. Optimization of cross-polarization at low radiofrequency fields for sensitivity enhancement in solid-state NMR of membrane proteins reconstituted in magnetically aligned bicelles.

    PubMed

    Koroloff, Sophie N; Nevzorov, Alexander A

    2015-07-01

    Solid-state NMR (ssNMR) of oriented membrane proteins (MPs) is capable of providing structural and dynamic information at nearly physiological conditions. However, NMR experiments performed on oriented membrane proteins generally suffer from low sensitivity. Moreover, utilization of high-power radiofrequency (RF) irradiations for magnetization transfer may give rise to sample heating, thereby decreasing the efficiency of conventional cross-polarization schemes. Here we have optimized the recently developed repetitive cross-polarization (REP-CP) sequence (Tang et al., 2011) to further increase the magnetization transfer efficiency for membrane proteins reconstituted in magnetically aligned bicelles and compared its performance to single-contact Hartmann-Hahn cross-polarization (CP), CP-MOIST and the adiabatic transfer. It has been found that employing the REP-CP sequence at RF amplitudes of 19kHz instead of the commonly used higher RF fields (>45kHz) enhances the efficiency of REP-CP. An additional 30% signal can be obtained as compared to the previously published REP-CP, and 20% when compared to the re-optimized REP-CP at 50kHz RF fields. Moreover, the (15)N signal gain of low-power REP-CP was found to be 40% over the adiabatic CP and up to 80% over CP-MOIST. Thus, the low-power REP-CP sequence surpasses all of the previous CP schemes in addition of having the tremendous advantage of reducing the RF powers by a factor of seven, thereby preserving the liquid-like bicelle sample. By contrast, in purely static (NAL crystal) and semi-rigid systems (Pf1 phage), the adiabatic CP was found to be more effective. Periodic oscillations of the intensity profile (distinct from the transient oscillations) as a function of the CP contact time and B1 RF field strengths were observed during the REP-CP optimization with the oscillations becoming more pronounced with lower RF fields. Many-spin simulations were performed to explain the oscillations and their periodicity. PMID:25965279

  7. 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

  8. A reverberation chamber for rodents' exposure to wideband radiofrequency electromagnetic fields with different small-scale fading distributions.

    PubMed

    Li, Congsheng; Yang, Lei; Lu, Bingsong; Xie, Yi; Wu, Tongning

    2014-09-26

    Abstract A reverberation chamber (RC) is realized for the rodents' in vivo exposure to electromagnetic fields (EMFs) with various small-scale fading characteristics. Its performance is evaluated to ensure the exposure experiments from 0.85 to 2.60?GHz. By different configurations, line-of-sight and non-line-of-sight exposures can be established. The measured electric field in the RC is analyzed to determine its statistical distribution. We accordingly reconstruct the EMF environment by numerical methods. Simulations are carried to compare the dosimetric variability due to different small-scale fading characteristics. It demonstrates that the surveyed fading distribution will not change the specific absorption rate in the rats. The possibility to reproduce the realistic multi-reflective EMF environment by adjusting the structures of the RC is discussed. It is the first reported in vivo exposure system aiming to provide the EMF exposure with different small-scale fading distributions. PMID:25259622

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

    PubMed

    Yatsuka, Eiichi; Kinjo, Kiyotake; Morikawa, Junji; Ogawa, Yuichi

    2009-02-01

    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. PMID:19256646

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

    NASA Astrophysics Data System (ADS)

    Yatsuka, Eiichi; Kinjo, Kiyotake; Morikawa, Junji; Ogawa, Yuichi

    2009-02-01

    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 2.45GHz, 2.5kW electron cyclotron heating (ECH), whereas diagnostics are carried out with a lower power (10W) separate frequency (1-2.1GHz) 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 35mm, 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 (1mm) antenna was used. As the preliminary results, we detected signals that have three characteristics of EBW, i.e., short wavelength, backward propagation, and electrostatic.

  11. Temperature changes associated with radiofrequency exposure near authentic metallic implants in the head phantom---a near field simulation study with 900, 1800 and 2450 MHz dipole

    Microsoft Academic Search

    J. Keshvari; R. Lappalainen

    2010-01-01

    Along with increased use of wireless communication devices operating in the radiofrequency (RF) range, concern has been raised about the related possible health risks. Among other concerns, the interaction of medical implants and RF devices has been studied in order to assure the safety of implant carriers under various exposure conditions. In the RF range, the main established quantitative effect

  12. Cylindrical waveguide applicator for in vitro exposure of cell culture samples to 1.9-GHz radiofrequency fields.

    PubMed

    Gajda, G B; McNamee, J P; Thansandote, A; Boonpanyarak, S; Lemay, E; Bellier, P V

    2002-12-01

    An applicator for in vitro cell culture exposure was developed based on a circularly polarized, cylindrical waveguide for the 1.9-GHz frequency band used by Personal Communications Services (PCS) in Canada. The applicator consists of two coaxial Petri dishes that sit on the open end of the cylindrical waveguide. The inner 60-mm Petri dish contains the cell culture while the outer 150-mm dish contains coolant water, which is circulated from a pump. A dosimetric evaluation was made using thermometric and E-field probe techniques. The latter allowed the entire inner dish to be scanned to determine the range of specific absorption rates (SARs) pertinent to the expected position of the cells. A representative SAR rate (SAR per unit of input power) of 8.6 +/- 2.1 W/kg/W (95th percentile) was determined 1 mm from the bottom, for a 10 ml sample volume of standard medium. Evaluation of the cooling system demonstrated that following an initial 0.3 degrees C temperature increase, a constant temperature was maintained for 24 h when the waveguide was energized to achieve an average sample SAR of 10 W/kg. These properties enable both acute and sub-acute in vitro bio-effect studies to be performed on a variety of cell culture samples. PMID:12395414

  13. Radiofrequency Ablation of Cancer

    SciTech Connect

    Friedman, Marc; Mikityansky, Igor; Kam, Anthony [National Institutes of Health, Diagnostic Radiology Department, Special Procedures Division (United States); Libutti, Steven K. [National Cancer Institute, National Institutes of Health, Surgery Branch (United States); Walther, McClellan M. [National Cancer Institute, National Institutes of Health, Urologic Oncology Branch (United States); Neeman, Ziv; Locklin, Julia K.; Wood, Bradford J. [National Institutes of Health, Diagnostic Radiology Department, Special Procedures Division (United States)], E-mail: bwood@nih.gov

    2004-09-15

    Radiofrequency ablation (RFA) has been used for over 18 years for treatment of nerve-related chronic pain and cardiac arrhythmias. In the last 10 years, technical developments have increased ablation volumes in a controllable, versatile, and relatively inexpensive manner. The host of clinical applications for RFA have similarly expanded. Current RFA equipment, techniques, applications, results, complications, and research avenues for local tumor ablation are summarized.

  14. Radiofrequency Ablation of Cancer

    PubMed Central

    Friedman, Marc; Mikityansky, Igor; Kam, Anthony; Libutti, Steven K.; Walther, McClellan M.; Neeman, Ziv; Locklin, Julia K.; Wood, Bradford J.

    2008-01-01

    Radiofrequency ablation (RFA) has been used for over 18 years for treatment of nerve-related chronic pain and cardiac arrhythmias. In the last 10 years, technical developments have increased ablation volumes in a controllable, versatile, and relatively inexpensive manner. The host of clinical applications for RFA have similarly expanded. Current RFA equipment, techniques, applications, results, complications, and research avenues for local tumor ablation are summarized. PMID:15383844

  15. Nerve Regeneration After Radiofrequency Application

    Microsoft Academic Search

    Nobuyasu Ochiai; James P. Tasto; Seiji Ohtori; Norimasa Takahashi; Hideshige Moriya; David Amiel

    Background: Many patients with chronic tendinosis have experienced early pain relief after application of bipolar radiofrequency treatment. It is hypothesized that the mechanism of action may be the acute degeneration and\\/or ablation of sensory nerve fibers. Hypothesis: After ablation or degeneration by bipolar radiofrequency, nerve fibers will have the ability to regenerate with time. Study Design: Controlled laboratory study. Methods:

  16. 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

  17. Removal of organic pollutants by surfactant modified zeolite: comparison between ionizable phenolic compounds and non-ionizable organic compounds.

    PubMed

    Xie, Jie; Meng, Wenna; Wu, Deyi; Zhang, Zhenjia; Kong, Hainan

    2012-09-15

    The aim of this study was to examine the adsorption capability and mechanism of hexadecyltrimethylammonium modified zeolite, which was synthesized from coal fly ash, for the removal of ionizable phenolic compounds (phenol, p-chlorophenol and bisphenol A, with different pK(a)) and non-ionizable organic compounds (aniline, nitrobenzene, and naphthalene, with different hydrophobicity). The obtained zeolite was identified as type Na-P1 (Na(6)Al(6)Si(10)O(32)·12H(2)O, JCPDS code 39-0219), which is classified into the gismondine group with a pore size of 3.1 Å × 4.5 Å [100] and 2.8 Å × 4.8 Å [101]. The adsorption of the two kinds of organic compounds was due to loaded surfactant bilayer because modified zeolite showed great ability for the removal of organic chemicals while little adsorption by zeolite was observed. The isotherm data of ionizable compounds fitted well to the Langmuir model but those of non-ionizable chemicals followed a linear equation. Uptake of ionizable compounds depended greatly on pH, increasing at alkaline pH conditions. In contrary, adsorption of non-ionizable chemicals was essentially the same at all pH levels studied. The adsorption of both kinds of organic compounds correlated well to k(ow) value, suggesting that more hydrophobic organic contaminants are more easily retained by modified zeolite. Based on the different adsorption behavior, the uptake of non-ionizable pollutants was thought to be a single partitioning process into the surfactant bilayer. For ionizable compounds, however, interaction of the phenol group(s) with the positively charged "head" of surfactant additionally functions. PMID:22771348

  18. 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.

  19. 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.

  20. 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.

  1. 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.

  2. 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...

  3. Radiofrequency Ablation of Liver Tumors

    MedlinePLUS

    ... the procedure. top of page What does the equipment look like? View larger with caption Drawing illustrates ... and grounding pads may also be used. Radiofrequency equipment There are two types of needle electrodes: simple ...

  4. Nerve Regeneration After Radiofrequency Application

    Microsoft Academic Search

    Nobuyasu Ochiai; James P. Tasto; Seiji Ohtori; Norimasa Takahashi; Hideshige Moriya; David Amiel

    2007-01-01

    Background: Many patients with chronic tendinosis have experienced early pain relief after application of bipolar radiofrequency treatment. It is hypothesized that the mechanism of action may be the acute degeneration and\\/or ablation of sensory nerve fibers.Hypothesis: After ablation or degeneration by bipolar radiofrequency, nerve fibers will have the ability to regenerate with time.Study Design: Controlled laboratory study.Methods: Eighteen Sprague-Dawley rats

  5. 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.

  6. 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

  7. Geophysical subsurface probing with radio-frequency interferometry

    Microsoft Academic Search

    J. A. KONG; L. Tsang; GENE SIMMONS

    1974-01-01

    The radio-frequency interferometry method can be used to probe interiors of celestial bodies and terrestrial areas with low conductivity. Several glaciers have been studied with this technique. An experiment based on this method was designed for Apollo 17 to examine the lunar subsurface. In order to interpret the interference patterns, We have studied theoretically the electromagnetic fields due to a

  8. METHODS OF RADIO-FREQUENCY CURRENT DRIVE

    E-print Network

    METHODS OF RADIO-FREQUENCY CURRENT DRIVE N. J. FISCH* Princeton Plasma Physics Laboratory-670 Radio-frequency waves can penetrate thermonuclear plasmas, depositing momentum and energy with great. INTRODUCTION Using radio-frequency (rf) waves to drive the toroidal current in tokamak reactors is attractive

  9. Radiofrequency activation of epoxy resins

    SciTech Connect

    Palumbo, M.; Vallet, Y.; Alazard, P. [Ecole Nationale Superieure de Chimie de Toulouse (France)

    1995-12-01

    A DGEBA epoxy resin in presence of Diaminodiphenylmethane used as curing agent is crosslinked under radiofrequency (27.12 MHz) irradiation, at given electrical power or voltage. The mechanisms of the polymerization reaction are explained through the study of the time dependence of the electrical parameters and of the average temperature of the chemical medium. The determination of the glassy transition temperatures of the polymeric networks, initial and stabilized after intensive postcure, respectively correlated with the extent of conversion of the epoxy resin and the structural homogeneity shows that the radiofrequency irradiation is as efficient as the microwaves as for the activation of the cure of the epoxy resins.

  10. Radiofrequency thermal ablationof hepatic metastases

    Microsoft Academic Search

    Luigi Solbiati; Tiziana Ierace; Massimo Tonolini; Valeria Osti; Luca Cova

    2001-01-01

    Percutaneous radiofrequency (RF) ablation is a promising therapeutic option for liver metastases, which may result in prolonged survival and chance for cure. Recent technological advancements provide larger coagulation volumes, allowing treatment of medium- and large-size metastases. Candidates are patients with metachronous liver metastases from colorectal or other primary cancers, in whom surgery is contraindicated and with one to four nodules

  11. Dosimetry associated with exposure to non-ionizing radiation: very low frequency to microwaves

    Microsoft Academic Search

    Arthur W. Guy

    1987-01-01

    The interpretation of the effects in biological systems exposed to electromagnetic (EM) fields requires knowledge of the internal fields and absorbed energy. The quantification of the specific absorption rate (SAR) is called dosimetry. The SAR given in units of watts per kilogram is a complex function of the source configuration, shape and size of the exposed subjects, orientation of the

  12. Two dimensional profiles of electric fields in a radio-frequency argon plasma above non-uniformities present on a surface.

    SciTech Connect

    Hebner, Gregory Albert; Barnat, Edward V.

    2004-06-01

    Laser-induced fluorescence-dip spectroscopy was used to measure two-dimensional (2-D) maps of the electric field present in an argon discharge above a ratio frequency-powered, nonuniform surface. Electric fields were obtained from experimentally measured Stark shifts of the energy of argon Rydberg states. The 2-D maps of the electric fields demonstrated that nonuniformities present on an electrode have long-range effects on the structure of the sheath.

  13. Fine structure, hyperfine structure, and Stark effect in the NO A 2~+ state by optical radiofrequency double resonance

    E-print Network

    Zare, Richard N.

    Fine structure, hyperfine structure, and Stark effect in the NO A 2~+ state by optical radio·frequency, we observe the zero-field rho-doubling hyperfine transitions by optical radio-frequency double of Hz and Dz. 4 USing a variation of the optical-radio-frequency double resonance technique (ODR),5 we

  14. "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.

  15. 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.

  16. 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.

  17. Quench Localization in Superconducting Radio-frequency (SRF) Cavities

    E-print Network

    Baltisberger, Jay H.

    Quench Localization in Superconducting Radio-frequency (SRF) Cavities Ramesh Adhikari Lee Teng distance. Solution - Superconduting Radio-Frequency Cavities Ramesh Adhikari Quench Localization in SRF Cavities #12;Superconducting Radio-frequency Cavity (SRF) Accelerating structures for next generation

  18. Non-Ionizing Radiation: Evaluation of General Public's Exposures in Greece and Albania

    NASA Astrophysics Data System (ADS)

    Ylli, Fatos; Karabetsos, Efthymios; Dollani, Kostandin; Koutounidis, Dimitris

    2010-01-01

    With the growth of electric power generation and transmission, the development of new telecommunication systems and advances in medical and industrial applications, humans are increasingly exposed to electromagnetic fields (EMF). The need to understand the potentially harmful effects of EMF on human health has been met by several decades of research, but the development of exposure standards is more recent and a variety of national standards now exist. A number of organizations have formulated guidelines establishing limits for occupational and residential EMF exposure. The exposure limits for EMF developed by the ICNIRP were based in large reviews of scientific literature, including thermal and non-thermal effects.

  19. 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.

  20. Evaluation of electric and magnetic fields distribution and SAR induced in 3D models of water containers by radiofrequency radiation using FDTD and FEM simulation techniques

    E-print Network

    Abdelsamie, Maher A A; Mustafa, Shuhaimi; Hashim, Dzulkifly

    2014-01-01

    In this study, two software packages using different numerical techniques FEKO 6.3 with Finite-Element Method (FEM) and XFDTD 7 with Finite Difference Time Domain Method (FDTD) were used to assess exposure of 3D models of square, rectangular, and pyramidal shaped water containers to electromagnetic waves at 300, 900, and 2400 MHz frequencies. Using the FEM simulation technique, the peak electric field of 25, 4.5, and 2 V/m at 300 MHz and 15.75, 1.5, and 1.75 V/m at 900 MHz were observed in pyramidal, rectangular, and square shaped 3D container models, respectively. The FDTD simulation method confirmed a peak electric field of 12.782, 10.907, and 10.625 V/m at 2400 MHz in the pyramidal, square, and rectangular shaped 3D models, respectively. The study demonstrated an exceptionally high level of electric field in the water in the two identical pyramid shaped 3D models analyzed using the two different simulation techniques. Both FEM and FDTD simulation techniques indicated variations in the distribution of elect...

  1. Increased protein synthesis by cells exposed to a 1,800MHz radio-frequency mobile phone electromagnetic field, detected by proteome profiling

    Microsoft Academic Search

    Christopher Gerner; Verena Haudek; Ulla Schandl; Editha Bayer; Nina Gundacker; Hans Peter Hutter; Wilhelm Mosgoeller

    2010-01-01

    Purpose  To investigate whether or not low intensity radio frequency electromagnetic field exposure (RF-EME) associated with mobile\\u000a phone use can affect human cells, we used a sensitive proteome analysis method to study changes in protein synthesis in cultured\\u000a human cells.\\u000a \\u000a \\u000a \\u000a \\u000a Methods  Four different cell kinds were exposed to 2 W\\/kg specific absorption rate in medium containing 35S-methionine\\/cysteine, and autoradiography of 2D gel spots

  2. Radiofrequency coils for magnetic resonance applications: theory, design, and evaluation.

    PubMed

    Giovannetti, Giulio; Hartwig, Valentina; Positano, Vincenzo; Vanello, Nicola

    2014-01-01

    Magnetic resonance imaging and magnetic resonance spectroscopy are noninvasive diagnostic techniques based on the phenomenon of nuclear magnetic resonance. Radiofrequency coils are key components in both the transmission and receiving phases of magnetic resonance systems. Transmitter coils have to produce a highly homogeneous alternating field in a wide field of view, whereas receiver coils have to maximize signal detection while minimizing noise. Development of modern magnetic resonance coils often is based on numerical methods for simulating and predicting coil performance. Numerical methods allows the behavior of the coil in the presence of realistic loads to be simulated and the coil's efficiency at high magnetic fields to be investigated. After being built, coils have to be characterized in the laboratory to optimize their setting and performance by extracting several quality indices. Successively, coils performance has to be evaluated in a scanner using standardized image quality parameters with phantom and human experiments. This article reviews the principles of radiofrequency coils, coil performance parameters, and their estimation methods using simulations, workbench, and magnetic resonance experiments. Finally, an overview of future developments in radiofrequency coils technology is included. PMID:25403875

  3. Laser Navigation for Radiofrequency Ablation

    SciTech Connect

    Varro, Zoltan; Locklin, Julia K., E-mail: bwood@nih.gov; Wood, Bradford J. [National Institutes of Health, Warren G. Magnuson Clinical Center, Diagnostic Radiology Department (United States)

    2004-09-15

    A 45-year-old male with renal cell carcinoma secondary to von-Hippel Lindau (VHL) disease presented for radiofrequency ablation (RFA) of kidney tumors. Due to his prior history of several partial nephrectomies and limited renal reserve, RFA was chosen because of its relatively nephron-sparing nature. A laser guidance device was used to help guide probe placement in an attempt to reduce procedure time and improve targeting accuracy. The device was successful at guiding needle placement, as both tumors were located with a single pass. Follow-up CT scan confirmed accurate needle placement, showing an area of coagulation necrosis covering the previously seen tumor.

  4. Evaluation of radiofrequency dielectric heaters workers exposure.

    PubMed

    Benes, M; Del Frate, S; Villalta, R

    2008-01-01

    Radiofrequency dielectric heaters (RFDH) are widely used in the woodworking industry for gluing laminates by applying pressure and RF heating. The workers operating such equipment remain in the vicinity of the machinery all day and can therefore be exposed to considerable levels of electric and magnetic field at RFs. This work describes the method used to measure the strength of fields generated by this particular machinery. This procedure is based on current methods cited in the literature and introduces the necessary modifications to meet this specific case. In particular, as there is often a scarcity of technical data available relating to such heaters, it is suggested that a spectrum analyser be used for measurements in the frequencies domain. On the basis of the data obtained the norms of reference are established, the instrumentation to be used in successive stages determined as well as the identification of possible sources of interference from spurious signals. Furthermore, a mapping of the field strengths is presented and the means of determining the decay curve as a function of distance. This last type of measurement is done to estimate the effectiveness of grounding the machinery. The report ends with an estimate of the exposure of workers to electromagnetic fields and also some recommendations for reducing risk. PMID:17971347

  5. Computational modelling of temperature rises in the eye in the near field of radiofrequency sources at 380, 900 and 1800 MHz.

    PubMed

    Wainwright, P R

    2007-06-21

    This paper reports calculations of the temperature rises induced in the eye and lens by near-field exposure to radiation from communication handsets, using the finite difference time domain method and classical bioheat equation. Various models are compared, including the analytic solution for a sphere, a finite element model of an isolated eye and a modern model of the whole head. The role of the blood supply to the choroid in moderating temperature is discussed. Three different frequencies are considered, namely 380 MHz (used by TETRA), and 900 and 1800 MHz (used by GSM mobile phones). At 380 MHz, monopole and helical antennas are compared. An 'equivalent blood flow' is derived for the choroid in order to facilitate comparison of the whole head and isolated eye models. In the whole head model, the heating of the lens receives a significant contribution from energy absorbed outside the eye. The temperature rise in the lens is compared to the ICNIRP-recommended average specific energy absorption rate (SAR) and the SAR averaged over the eye alone. The temperature rise may reach 1.4 degrees C at the ICNIRP occupational exposure limit if an antenna is placed less than 24 mm from the eye and the exposure is sufficiently prolonged. PMID:17664547

  6. Thermal and nonthermal mechanisms of interaction of radio-frequency energy with biological systems

    Microsoft Academic Search

    Kenneth R. Foster

    2000-01-01

    This paper reviews thermal and nonthermal mechanisms of interaction between radiofrequency (RF) fields and biological systems, focusing on pulsed fields with high peak power but low duty cycle. Models with simplified geometry are used to illustrate the coupling between external electromagnetic fields and the body, and with cellular and subcellular structures. Mechanisms of interaction may be linear or nonlinear with

  7. Band-selective radiofrequency pulses

    NASA Astrophysics Data System (ADS)

    Geen, Helen; Freeman, Ray

    A theoretical treatment is given of the general problem of designing amplitude-modulated radiofrequency pulses that will excite a specified band of frequencies within a high-resolution NMR spectrum with uniform intensity and phase but with negligible excitation elsewhere. First a trial pulse envelope is defined in terms of a finite Fourier series and its frequency-domain profile calculated through the Bloch equations. The result is compared with the desired target profile to give a multidimensional error surface. The method of simulated annealing is then used to find the global minimum on this surface and the result refined by standard gradient-descent optimization. In this manner, a family of new shaped radio-frequency pulses, known as BURP ( band-selective, uniform response, pure-phase) pulses, has been created. These are of two classes—pulses that excite or invert z magnetization and those that act as general-rotation ?r/2 or ? pulses irrespective of the initial condition of the nuclear magnetization. It was found convenient to design the latter class as amplitude-modulated time-symmetric pulses. Tables of Fourier coefficients and pulse-shape ordinates are given for practical implementation of BURP pulses, together with the calculated frequency-domain responses and experimental verifications. Examples of the application of band-selective pulses in conventional and multidimensional spectroscopy are given. Pure-phase pulses of this type should also find applications in magnetic resonance imaging where refocusing schemes are undesirable.

  8. Radiofrequency and testicular cancer (review).

    PubMed

    Merimsky, O; Levita, M; Merimsky, E; Chaitchik, S

    1996-03-01

    Physical agents such as ultraviolet or ionizing radiation, heat, and repetitive trauma have been related to the causation of cancer in humans. Much less clear is the association between exposure to radiofrequency, i.e. radar and microwave radiation, emitted from television screens, antennas and detection equipment, to the development of cancer. Sporadic case reports and small series suggest that this type of radiation might lead to cancer or contribute to its evolution. The association between radiofrequency and testicular damage and cancer is unproved, but clinical and experimental data are suggestive of such possibility. We have recently encountered a case of secondary severe oligospermia, followed by seminoma, most probably induced by exposure to radar and microwave radiation, in an 18-year-old man. The population handling or repairing dangerous radar facilities is too small to be evaluated by epidemiological surveys. Even it were so, this material is handled in secrecy, either military or industrial. Arousing the alertness of the medical team in those facilities and bringing better protection to the employees is the aim of our report. PMID:21594374

  9. Radiofrequency Thermal Ablation of Hepatocellular Carcinomas

    PubMed Central

    2000-01-01

    Although surgical resection remains the best option as potentially curative therapy for hepatocellular carcinoma, radiofrequency thermal ablation has begun to receive much attention as an effective minimally invasive technique for the local control of unresectable malignant hepatic tumors. Most recent radiofrequency devices equipped with a powerful generator and larger needle electrode permit larger thermal lesions, up to 5 cm in diameter, with a single ablation. In this article, the author reviews the technical developments and early clinical results obtained with radiofrequency ablation techniques. PMID:11752952

  10. 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

  11. Esophageal papilloma: Flexible endoscopic ablation by radiofrequency.

    PubMed

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

    2015-03-16

    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 Barrx(TM) RFA in patients with esophageal papilloma. PMID:25789102

  12. 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

  13. Radiofrequency Thermal Ablation of a Splenic Metastasis

    PubMed Central

    Wood, Bradford J.; Bates, Susan

    2008-01-01

    Effective local ablation of large tumors with radiofrequency has been made possible by recent advancements. Tumor ablation with radiofrequency has been described mainly in the liver, but also recently in the kidney, adrenal gland, lung, and breast. A rapidly growing splenic metastasis from renal cell carcinoma was effectively treated percutaneously, with US guidance. Focal splenic disease may not be a common indication for ablation; however, further work is necessary to evaluate the safety and efficacy of this procedure in this setting. PMID:11265893

  14. 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

  15. Radiofrequency radiation leakage from microwave ovens.

    PubMed

    Lahham, Adnan; Sharabati, Afifeh

    2013-12-01

    This work presents data on the amount of radiation leakage from 117 microwave ovens in domestic and restaurant use in the West Bank, Palestine. The study of leakage is based on the measurements of radiation emissions from the oven in real-life conditions by using a frequency selective field strength measuring system. The power density from individual ovens was measured at a distance of 1 m and at the height of centre of door screen. The tested ovens were of different types, models with operating powers between 1000 and 1600 W and ages ranging from 1 month to >20 y, including 16 ovens with unknown ages. The amount of radiation leakage at a distance of 1 m was found to vary from 0.43 to 16.4 ?W cm(-2) with an average value equalling 3.64 ?W cm(-2). Leakages from all tested microwave ovens except for seven ovens (?6 % of the total) were below 10 ?W cm(-2). The highest radiation leakage from any tested oven was ?16.4 ?W cm(-2), and found in two cases only. In no case did the leakage exceed the limit of 1 mW cm(-2) recommended by the ICNIRP for 2.45-GHz radiofrequency. This study confirms a linear correlation between the amount of leakage and both oven age and operating power, with a stronger dependence of leakage on age. PMID:23861537

  16. 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

  17. Public Exposure from Indoor Radiofrequency Radiation in the City of Hebron, West Bank-Palestine.

    PubMed

    Lahham, Adnan; Sharabati, Afefeh; ALMasri, Hussien

    2015-08-01

    This work presents the results of measured indoor exposure levels to radiofrequency (RF) radiation emitting sources in one of the major cities in the West Bank-the city of Hebron. Investigated RF emitters include FM, TV broadcasting stations, mobile telephony base stations, cordless phones [Digital Enhanced Cordless Telecommunications (DECT)], and wireless local area networks (WLAN). Measurements of power density were conducted in 343 locations representing different site categories in the city. The maximum total power density found at any location was about 2.3 × 10 W m with a corresponding exposure quotient of about 0.01. This value is well below unity, indicating compliance with the guidelines of the International Commission on Non-ionizing Radiation Protection (ICNIRP). The average total exposure from all RF sources was 0.08 × 10 W m. The relative contributions from different sources to the total exposure in terms of exposure quotient were evaluated and found to be 46% from FM radio, 26% from GSM900, 15% from DECT phones, 9% from WLAN, 3% from unknown sources, and 1% from TV broadcasting. RF sources located outdoors contribute about 73% to the population exposure indoors. PMID:26107432

  18. Electromagnetic field interactions with the human body: observed effects and theories

    Microsoft Academic Search

    Raines

    1981-01-01

    The state of published knowledge about the effects of non-ionizing EM fields on humans is summarized. In addition to over 1000 written sources in-person meetings, telephone interviews and lecture tapes were used. It is indicated that there are good, bad and benign effects to be expected from non-ionizing EM fields and much more knowledge appears necessary to properly categorize and

  19. Percutaneous Tumor Ablation with Radiofrequency

    PubMed Central

    Wood, Bradford J.; Ramkaransingh, Jeffrey R.; Fojo, Tito; Walther, McClellan M.; Libutti, Stephen K.

    2008-01-01

    BACKGROUND Radiofrequency thermal ablation (RFA) is a new minimally invasive treatment for localized cancer. Minimally invasive surgical options require less resources, time, recovery, and cost, and often offer reduced morbidity and mortality, compared with more invasive methods. To be useful, image-guided, minimally invasive, local treatments will have to meet those expectations without sacrificing efficacy. METHODS Image-guided, local cancer treatment relies on the assumption that local disease control may improve survival. Recent developments in ablative techniques are being applied to patients with inoperable, small, or solitary liver tumors, recurrent metachronous hereditary renal cell carcinoma, and neoplasms in the bone, lung, breast, and adrenal gland. RESULTS Recent refinements in ablation technology enable large tumor volumes to be treated with image-guided needle placement, either percutaneously, laparoscopically, or with open surgery. Local disease control potentially could result in improved survival, or enhanced operability. CONCLUSIONS Consensus indications in oncology are ill-defined, despite widespread proliferation of the technology. A brief review is presented of the current status of image-guided tumor ablation therapy. More rigorous scientific review, long-term follow-up, and randomized prospective trials are needed to help define the role of RFA in oncology. PMID:11900230

  20. Radiofrequency radiation: activities and issues

    SciTech Connect

    Elder, J.A.

    1986-07-01

    The question of human safety relative to exposure to RF radiation obviously predates the first ANSI guideline established in 1966, but no enforceable Federal standards or guidelines exist for RF radiation exposure; the ANSI guideline revised in 1982 is voluntary or advisory. EPA has been pursuing the goal of promulgating guidance to control exposure of the public to RF radiation. In support of the regulatory activity, a report entitled Biological Effects of Radiofrequency Radiation was published in September 1984. The conclusion of the report was that biological effects occurred at a dose rate of about 1 W/kg, and that these effects may be significant under certain environmental conditions. Examples of adverse biological effects that occur in laboratory animals at dose rates of 2-6 W/kg are death and temporary male sterility. These effects as well as the behavioral changes that are the basis for the ANSI guideline can be attributed to heat stress in animals caused by absorption of RF energy. Some experimental results occur at very low exposure conditions that cause no significant thermal input; these responses are called nonthermal effects. The mechanisms of interaction of nonthermal effects and their physiological significance are a subject of scientific debate. RF radiation research budget reductions, which reflect changes in funding priorities, will leave unresolved many of the questions concerning the biological effects of RF radiation and their possible health implications.

  1. Characterization of superconducting radiofrequency breakdown by two-mode excitation

    SciTech Connect

    Eremeev, Grigory V. [JLAB, Newport News, VA (United States); Palczewski, Ari D. [JLAB, Newport News, VA (United States)

    2014-01-14

    We show that thermal and magnetic contributions to the breakdown of superconductivity in radiofrequency (RF) fields can be separated by applying two RF modes simultaneously to a superconducting surface. We develop a simple model that illustrates how mode-mixing RF data can be related to properties of the superconductor. Within our model the data can be described by a single parameter, which can be derived either from RF or thermometry data. Our RF and thermometry data are in good agreement with the model. We propose to use mode-mixing technique to decouple thermal and magnetic effects on RF breakdown of superconductors.

  2. 21 CFR 882.4400 - Radiofrequency lesion generator.

    Code of Federal Regulations, 2010 CFR

    2010-04-01

    ...generator. (a) Identification. A radiofrequency lesion generator is a device used to produce lesions in the nervous system or other tissue by the direct application of radiofrequency currents to selected sites. (b)...

  3. 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.

  4. Stochastic electron heating in bounded radio-frequency plasmas I. D. Kaganovich,a)

    E-print Network

    Kaganovich, Igor

    Stochastic electron heating in bounded radio-frequency plasmas I. D. Kaganovich,a) V. I. Kolobov is governed by three frequencies: the frequency of the rf field , the collision frequency , and the bounce frequency . Depending on the ratio between these frequencies, different electron dynamics and a variety

  5. Electromagnetic characterization of superconducting radio-frequency cavities for gw detection

    Microsoft Academic Search

    R. Ballantini; Ph Bernard; A. Chincarini; G. Gemme; R. Parodi; E. Picasso

    2004-01-01

    The electromagnetic properties of a prototype gravitational wave detector, based on two coupled superconducting microwave cavities, were tested. The radio-frequency (rf) detection system was carefully analysed. With the use of piezoelectric crystals small harmonic displacements of the cavity walls were induced and the parametric conversion of the electromagnetic field inside the cavities explored. Experimental results of bandwidth and sensitivity of

  6. Towards Optimization of Probe Placement for Radio-Frequency Ablation

    E-print Network

    Preusser, Tobias

    Towards Optimization of Probe Placement for Radio-Frequency Ablation Inga Altrogge1 , Tim Kr¨oger1 probes in radio-frequency (RF) ablation. The model is based on a numerical computation of the probe on Cartesian or tetrahedral grids. In this work we consider the radio-frequency (RF) ablation of liver tumors

  7. SOME UNSOLVED CHALLENGES IN RADIO-FREQUENCY HEATING AND

    E-print Network

    SOME UNSOLVED CHALLENGES IN RADIO-FREQUENCY HEATING AND CURRENT DRIVE N. J. FISCH* Princeton Plasma, 2013 doi:10.13182/FST13-682 Several unsolved challenges in radio-frequency heating and current drive in the electronic version. I. INTRODUCTION There are many methods by which radio-frequency (rf) waves drive

  8. Histopomorphic Evaluation of Radiofrequency Mediated Débridement Chondroplasty

    PubMed Central

    Ganguly, Kumkum; McRury, Ian D; Goodwin, Peter M; Morgan, Roy E; Augé II, Wayne K

    2010-01-01

    The use of radiofrequency devices has become widespread for surgical ablation procedures. When ablation devices have been deployed in treatment settings requiring tissue preservation like débridement chondroplasty, adoption has been limited due to the collateral damage caused by these devices in healthy tissue surrounding the treatment site. Ex vivo radiofrequency mediated débridement chondroplasty was performed on osteochondral specimens demonstrating surface fibrillation obtained from patients undergoing knee total joint replacement. Three radiofrequency systems designed to perform débridement chondroplasty were tested each demonstrating different energy delivery methods: monopolar ablation, bipolar ablation, and non-ablation energy. Treatment outcomes were compared with control specimens as to clinical endpoint and histopomorphic characteristics. Fibrillated cartilage was removed in all specimens; however, the residual tissue remaining at the treatment site displayed significantly different characteristics attributable to radiofrequency energy delivery method. Systems that delivered ablation-based energies caused tissue necrosis and collateral damage at the treatment site including corruption of cartilage Superficial and Transitional Zones; whereas, the non-ablation system created a smooth articular surface with Superficial Zone maintenance and without chondrocyte death or tissue necrosis. The mechanism of radiofrequency energy deposition upon tissues is particularly important in treatment settings requiring tissue preservation. Ablation-based device systems can cause a worsened state of articular cartilage from that of pre-treatment. Non-ablation energy can be successful in modifying/preconditioning tissue during débridement chondroplasty without causing collateral damage. Utilizing a non-ablation radiofrequency system provides the ability to perform successful débridement chondroplasty without causing additional articular cartilage tissue damage and may allow for other cartilage intervention success. PMID:20721322

  9. SU-E-J-160: Comparing the Setup Accuracy of Non-Ionizing Patient Localization Systems with CBCT to Reduce Imaging Dose in Prone Breast Treatments

    SciTech Connect

    Chung, E; Yamamoto, T; Mayadev, J; Dieterich, S [UC Davis Medical Center, Sacramento, CA (United States)

    2014-06-01

    Purpose: CBCT is the current gold standard to verify prone breast patient setup. We investigated in a phantom if non-ionizing localization systems can replace ionizing localization systems for prone breast treatments. Methods: An anthropomorphic phantom was positioned on a prone breast board. Electromagnetic transponders were attached on the left chest surface. The CT images of the phantom were imported to the treatment planning system. The isocenter was set to the center of the transponders. The positions of the isocenter and transponders transferred to the transponder tracking system. The posterior phantom surface was contoured and exported to the optical surface tracking system. A CBCT was taken for the initial setup alignment on the treatment machine. Using the electromagnetic and optical localization systems, the deviation of the phantom setup from the original CT images was measured. This was compared with the difference between the original CT and kV-CBCT images. Results: For the electromagnetic localization system, the phantom position deviated from the original CT in 1.5 mm, 0.0 mm and 0.5 mm in the anterior-posterior (AP), superior-inferior (SI) and left-right (LR) directions. For the optical localization system, the phantom position deviated from the original CT in 2.0 mm, ?2.0 mm and 0.1 mm in the AP, SI and LR directions. For the CBCT, the phantom position deviated from the original CT in 4.0 mm, 1.0 mm and ?1.0 mm in the AP, SI and LR directions. The measured values from the non-ionizing localization systems differed from those with the CBCT less than 3.0 mm in all directions. Conclusions: This phantom study showed the feasibility of using a combination of non-ionizing localization systems to achieve a similar setup accuracy as CBCT for prone breast patients. This could potentially eliminate imaging dose. As a next step, we are expanding this study to actual patients. This work has been in part supported by Departmental Research Award RODEPT1-JS001, Department of Radiation Oncology, UC Davis Medical Center.

  10. Radio-Frequency and Wideband Modulation Arraying

    NASA Technical Reports Server (NTRS)

    Brockman, M. H.

    1984-01-01

    Summing network receives coherent signals from all receivers in array. Method sums narrow-band radio-frequency (RF) carrier powers and wide-band spectrum powers of array of separate antenna/receiver systems designed for phase-locked-loop or suppressed-carrier operation.

  11. 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...

  12. Thermage: the nonablative radiofrequency for rejuvenation

    Microsoft Academic Search

    Sean A. Sukal; Roy G. Geronemus

    2008-01-01

    Thermage is a noninvasive nonablative device that uses monopolar radiofrequency energy to bulk heat underlying skin while protecting the epidermis to produce skin tightening. It is used for the treatment of rhytids on the face including the periorbital region and lower face, and more recently, for off-face applications. Studies have shown that it can impart mild tightening of periorbital mid,

  13. Complications of radiofrequency coagulation of liver tumours

    Microsoft Academic Search

    S. Mulier; P. Mulier; Y. Ni; Y. Miao; B. Dupas; G. Marchal; I. De Wever; L. Michel

    2002-01-01

    Background: Radiofrequency coagulation (RFC) is being promoted as a novel technique with a low morbidity rate in the treatment of liver tumours. The purpose of this study was to assess critically the complication rates of RFC in centres with both large and limited initial experience, and to establish causes and possible means of prevention and treatment. Methods: This is an

  14. 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...

  15. 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.

  16. Geophysical subsurface probing with radio-frequency interferometry

    NASA Technical Reports Server (NTRS)

    Kong, J. A.; Tsang, L.; Simmons, G.

    1974-01-01

    The radio-frequency interferometry method can be used to probe interiors of celestial bodies and terrestrial areas with low conductivity. In order to interpret the interference patterns, a theoretical study is made of the electromagnetic fields due to a dipole antenna on the surface of a horizontally stratified n-layered medium. Three approaches are used to calculate the interference patterns: direct numerical integration, asymptotic evaluation by the saddle point method, and a residue series approach. The asymptotic approach leads to the geometrical-optics interpretation. The residue approach leads to modal analysis. The validity of the formulation is checked by comparisons with analog model tank experiments and actual field data obtained from glaciers.

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

    E-print Network

    Barrella, Taylor; Saltzberg, David

    2010-01-01

    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.

  18. Fraxelated radiofrequency device for acne scars

    NASA Astrophysics Data System (ADS)

    Rao, Babar K.; Khokher, Sairah

    2012-09-01

    Acne scars can be improved with various treatments such as topical creams, chemical peels, dermal fillers, microdermabrasion, laser, and radiofrequency devices. Some of these treatments especially lasers and deep chemical peels can have significant side effects such as post inflammatory hyperpigmentation in darker skin types. Fraxelated RF Laser devices have been reported to have lower incidence of side effects in all skin phototypes. Nine patients between ages 18 and 35 of various skin phototypes were selected from a private practice and treated with a RF fraxelated device (E-matrix) for acne scars. Outcomes were measured by physician observation, subjective feedback received by patients, and comparison of before and after photographs. In this small group of patients with various skin phototypes, fraxelated radiofrequency device improved acne scars with minimal side effects and downtime.

  19. 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.

  20. 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.

  1. Hydroxyapatite thin films grown by pulsed laser deposition and radio-frequency magnetron sputtering: comparative study

    Microsoft Academic Search

    V. Nelea; C. Morosanu; M. Iliescu; I. N. Mihailescu

    2004-01-01

    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

  2. Ion energy distribution of an inductively coupled radiofrequency discharge in argon and oxygen

    Microsoft Academic Search

    Rainer Hippler; Jana Kredl; Vasile Vartolomei

    2008-01-01

    We report an experimental investigation of the ion energy distribution in an inductively coupled electron cyclotron wave resonance (ECWR) discharge with a superimposed static magnetic field. The inductively coupled discharge is sustained by applying a 13.56MHz radiofrequency (RF) power to an aluminium single-turn coil located inside the vacuum chamber. The source region was separated by a grid from the diffusion

  3. 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

    2015-01-01

    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

  4. 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.

  5. Radiofrequency ablation followed by resection of malignant liver tumors

    Microsoft Academic Search

    Charles H Scudamore; Shung I Lee; Emma J Patterson; Andrzej K Buczkowski; Laura V July; Stephen W Chung; Anne R Buckley; Stephen G. F Ho; David A Owen

    1999-01-01

    BACKGROUND: Radiofrequency ablation (RFA) has recently been used to treat liver tumors, but few clinical reports have described the pathological characteristics of radiofrequency ablation in human specimens. This study delineates the gross pathologic and histochemical changes induced by RFA in benign and malignant human liver tissue and confirms the tumor necrosis described in early clinical reports.METHODS:Ten patients with metastatic tumors

  6. 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

  7. Laparoscopic Radiofrequency Ablation of Neuroendocrine Liver Metastases

    Microsoft Academic Search

    Eren Berber; Nora Flesher; Allan E. Siperstein

    2002-01-01

      \\u000a We previously reported on the safety and\\u000a efficacy of laparoscopic radiofrequency thermal ablation (RFA) for\\u000a treating hepatic neuroendocrine metastases. The aim of\\u000a this study is to report our 5-year RFA experience in the treatment of\\u000a these challenging group of patients. Of the 222 patients with 803 liver\\u000a primary and secondary tumors undergoing laparoscopic RFA between\\u000a January 1996 and August

  8. Pushing the limits of radiofrequency (RF) neuronal telemetry.

    PubMed

    Yousefi, Tara; Diaz, Rodolfo E

    2015-01-01

    In a previous report it was shown that the channel capacity of an in vivo communication link using microscopic antennas at radiofrequency is severely limited by the requirement not to damage the tissue surrounding the antennas. For dipole-like antennas the strong electric field dissipates too much power into body tissues. Loop-type antennas have a strong magnetic near field and so dissipate much less power into the surrounding tissues but they require such a large current that the antenna temperature is raised to the thermal damage threshold of the tissue. The only solution was increasing the antenna size into hundreds of microns, which makes reporting on an individual neuron impossible. However, recently demonstrated true magnetic antennas offer an alternative not covered in the previous report. The near field of these antennas is dominated by the magnetic field yet they don't require large currents. Thus they combine the best characteristics of dipoles and loops. By calculating the coupling between identical magnetic antennas inside a model of the body medium we show an increase in the power transfer of up to 8 orders of magnitude higher than could be realized with the loops and dipoles, making the microscopic RF in-vivo transmitting antenna possible. PMID:26035824

  9. Plastic circuits and tags for 13.56 MHz radio-frequency communication

    NASA Astrophysics Data System (ADS)

    Myny, Kris; Steudel, Soeren; Vicca, Peter; Beenhakkers, Monique J.; van Aerle, Nick A. J. M.; Gelinck, Gerwin H.; Genoe, Jan; Dehaene, Wim; Heremans, Paul

    2009-12-01

    We discuss the design and implementation of 64-bit and 128-bit plastic transponder chips for radio-frequency identification tags. The 64-bit chips, comprising 414 organic thin-film transistors, are integrated into fully functional plastic radio-frequency identification tags with 13.56 MHz communication. The required supply voltage on the tag is generated from the AC input signal detected by the antenna, using a plastic double half-wave rectifier circuit. The tag is fully functional at a magnetic field strength of 1.26 A/m, which is below the minimum required radio-frequency magnetic field stated in the standards. We discuss the reading distance that can be achieved with our plastic rectifiers, and show that this reading distance is not limited by the performance of the plastic rectifier or transponder chip. The 128-bit transponder chip includes further features such as Manchester data encoding and a basic ALOHA anti-collision protocol. It employs 1286 organic thin-film transistors and generates the 128 bit sequence at 24 V supply voltage at a data rate of 1.5 kb/s. Data rates up to 2 kb/s could be achieved on chips with an 8-bit transponder chip.

  10. Children and adults exposed to low-frequency magnetic fields at the ICNIRP reference levels: theoretical assessment of the induced electric fields

    Microsoft Academic Search

    J F Bakker; M M Paulides; E Neufeld; A Christ; X L Chen; N Kuster; G C van Rhoon

    2012-01-01

    To avoid potentially adverse health effects, the International Commission on Non-Ionizing Radiation Protection (ICNIRP) has defined reference levels for time varying magnetic fields. Restrictions on the electric fields induced in the human body are provided based on biological response data for peripheral nerve stimulation and the induction of phosphenes. Numerical modeling is commonly used to assess the induced electric fields

  11. Evaporative cooling in a radio-frequency trap

    SciTech Connect

    Garrido Alzar, Carlos L.; Perrin, Helene; Lorent, Vincent [Laboratoire de Physique des Lasers, CNRS-Universite Paris 13, Villetaneuse (France); Garraway, Barry M. [Department of Physics and Astronomy, University of Sussex, Brighton BN1 9QH (United Kingdom)

    2006-11-15

    A theoretical investigation for implementing a scheme of forced evaporative cooling in radio-frequency (rf) adiabatic potentials is presented. Supposing the atoms to be trapped in a combination of a dc magnetic field and a rf field at frequency {omega}{sub 1}, the cooling procedure is facilitated using a second rf source at frequency {omega}{sub 2}. This second rf field produces a controlled coupling between the spin states dressed by {omega}{sub 1}. The evaporation is then possible in a pulsed or continuous mode. In the pulsed case, atoms with a given energy are transferred into untrapped dressed states by abruptly switching off the {omega}{sub 2} coupling. In the continuous case, it is possible for energetic atoms to adiabatically follow the doubly dressed states and escape out of the trap. Our results also show that when {omega}{sub 1} and {omega}{sub 2} are separated by at least the Rabi frequency associated with {omega}{sub 1}, additional evaporation zones appear which can make this process more efficient.

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

    PubMed

    Nguyen, Sonca V T; Foster, John E; Gallimore, Alec D

    2009-08-01

    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(i) approximately = n(e), where n(i) is the positive ion density. But in the electronegative water plasma, quasineutrality requires n(i+) = n(i-) + n(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. PMID:19725651

  13. 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

  14. 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?

  15. Simulation studies promote technological development of radiofrequency phased array hyperthermia.

    PubMed

    Wust, P; Seebass, M; Nadobny, J; Deuflhard, P; Mönich, G; Felix, R

    1996-01-01

    A treatment planning program package for radiofrequency hyperthermia has been developed. It consists of software modules for processing three-dimensional computerized tomography (CT) data sets, manual segmentation, generation of tetrahedral grids, numerical calculation and optimisation of three-dimensional E field distributions using a volume surface integral equation algorithm as well as temperature distributions using an adaptive multilevel finite-elements code, and graphical tools for simultaneous representation of CT data and simulation results. Heat treatments are limited by hot spots in healthy tissues caused by E field maxima at electrical interfaces (bone/muscle). In order to reduce or avoid hot spots suitable objective functions are derived from power deposition patterns and temperature distributions, and are utilised to optimise antenna parameters (phases, amplitudes). The simulation and optimisation tools have been applied to estimate the improvements that could be reached by upgrades of the clinically used SIGMA-60 applicator (consisting of a single ring of four antenna pairs). The investigated upgrades are increased number of antennas and channels (triple-ring of 3 x 8 antennas and variation of antenna inclination. Significant improvement of index temperatures (1-2 degrees C) is achieved by upgrading the single ring to a triple ring with free phase selection for every antenna or antenna pair. Antenna amplitudes and inclinations proved as less important parameters. PMID:8877472

  16. Numerical investigation on electrical characterization of a capacitive coupled radio-frequency plasma

    NASA Astrophysics Data System (ADS)

    Yao, H.; He, X.; Chen, J. P.; Zhang, Y. C.

    2015-05-01

    This paper presents the main electrical features of capacitive coupled radio-frequency (CCRF) discharges in gas. A two-dimensional, time-dependent fluid model was established. Capacitive coupled plasmas (CCP) were produced by applying radio-frequency voltage to a pair of parallel plate electrodes which are separated from the plasma by dielectric layers. The electron equation and the electron transport equations were solved and yielded the electron number density and electron temperature. The electrostatic field was obtained by the solution of the Poisson equation. The distribution of electron temperature and electron number density was studied under different conditions: radio-frequency applied voltages (VRF=100-2000V), frequencies (f=3.0-40.68MHz), pressures (p=0.001-1torr), and gas species (O2, Ar, He, N2). The results show that electron number density presents a minimum near the electrodes, and presents a maximum between the positive and the negative electrodes. The distinguishing feature of CCP is the presence of oscillating sheaths near electrodes where displacement current dominates conduction current. These informations will help us to analyze the characters of CCP for application.

  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. Radio-frequency low-coherence interferometry.

    PubMed

    Fernández-Pousa, Carlos R; Mora, José; Maestre, Haroldo; Corral, Pablo

    2014-06-15

    A method for retrieving low-coherence interferograms, based on the use of a microwave photonics filter, is proposed and demonstrated. The method is equivalent to the double-interferometer technique, with the scanning interferometer replaced by an analog fiber-optics link and the visibility recorded as the amplitude of its radio-frequency (RF) response. As a low-coherence interferometry system, it shows a decrease of resolution induced by the fiber's third-order dispersion (?3). As a displacement sensor, it provides highly linear and slope-scalable readouts of the interferometer's optical path difference in terms of RF, even in the presence of third-order dispersion. In a proof-of-concept experiment, we demonstrate 20-?m displacement readouts using C-band EDFA sources and standard single-mode fiber. PMID:24978555

  19. 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.

  20. Optical generation of radio-frequency power

    NASA Astrophysics Data System (ADS)

    Hietala, V. M.; Vawter, G. A.; Brennan, T. M.; Hammons, B. E.; Meyer, W. J.

    1994-11-01

    An optical technique for high-power radio-frequency (RF) signal generation is described. The technique uses a unique photodetector based on a traveling-wave design driven by an appropriately modulated light source. The traveling-wave photodetector (TWPD) exhibits simultaneously a theoretical quantum efficiency approaching 100% and a very large electrical bandwidth. Additionally, it is capable of dissipating the high-power levels required for the RF generation technique. The modulated light source is formed by either the beating together of two lasers or by the direct modulation of a light source. A system example is given which predicts RF power levels of 100's of mW's at millimeter wave frequencies with a theoretical 'wall-plug' efficiency approaching 34%.

  1. Optical generation of radio-frequency power

    SciTech Connect

    Hietala, V.M.; Vawter, G.A.; Brennan, T.M.; Hammons, B.E.; Meyer, W.J.

    1994-11-01

    An optical technique for high-power radio-frequency (RF) signal generation is described. The technique uses a unique photodetector based on a traveling-wave design driven by an appropriately modulated light source. The traveling-wave photodetector (TWPD) exhibits simultaneously a theoretical quantum efficiency approaching 100 % and a very large electrical bandwidth. Additionally, it is capable of dissipating the high-power levels required for the RF generation technique. The modulated light source is formed by either the beating together of two lasers or by the direct modulation of a light source. A system example is given which predicts RF power levels of 100`s of mW`s at millimeter wave frequencies with a theoretical ``wall-plug`` efficiency approaching 34%.

  2. Palliative Radiofrequency Ablation for Recurrent Prostate Cancer

    SciTech Connect

    Jindal, Gaurav; Friedman, Marc; Locklin, Julia, E-mail: JHvizda@cc.nih.gov; Wood, Bradford J. [National Institutes of Health, Diagnostic Radiology Department (United States)

    2006-06-15

    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 patients. Tumors which are surgically unresectable and incompatible for complete ablation present the opportunity for RFA to be used in a new paradigm. Cancer pain runs the gamut from minor discomfort relieved with mild pain medication to unrelenting suffering for the patient, poorly controlled by conventional means. RFA is a tool which can potentially palliate intractable cancer pain. We present here a case in which RFA provided pain relief in a patient with metastatic prostate cancer with pain uncontrolled by conventional methods.

  3. [Potentials of interventional radiology: percutaneous radiofrequency ablation].

    PubMed

    Péter, Mózes; Tóth, Judit

    2004-02-15

    The efficacy of the treatment of hepatic malignancies has improved, mostly due to the physical procedures which affect the tumors locally. The authors performed 210 radio-frequency ablations in 1.38 patients. They recommend this procedure based on their experiences. RF treatment is performed together with other therapeutical procedures done by cooperation of oncology clinic. The main indication for the treatment of tumors is, lesions less than 4 cm in diameter and the number of masses is less than 4. The treatment can be performed by CT guidance and is documented well. The applied RF generator is made by Radionics, electrodes are cooled. In 68% of the tumors they achieved complete necrosis using this procedure. After the intervention patients experienced no serious complications. The only side effects were abdominal pain and discomfort. RF tumor ablation is an important and effective procedure in the treatment of hepatic tumors. PMID:15049060

  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. 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...

  6. 21 CFR 882.4725 - Radiofrequency lesion probe.

    Code of Federal Regulations, 2010 CFR

    2010-04-01

    ...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...

  7. Radiofrequency detector coil performance maps for parallel MRI applications

    E-print Network

    Lattanzi, Riccardo

    2006-01-01

    Parallel MRI techniques allow acceleration of MR imaging beyond traditional speed limits. In parallel MRI, arrays of radiofrequency (RF) detector coil arrays are used to perform some degree of spatial encoding which ...

  8. Radio-frequency spectroscopy of ultracold atomic Fermi gases

    E-print Network

    Schirotzek, Andre

    2010-01-01

    This thesis presents experiments investigating the phase diagram of ultracold atomic Fermi gases using radio-frequency spectroscopy. The tunability of many experimental parameters including the temperature, the interparticle ...

  9. 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.

  10. Atrio-oesophageal fistula: an emergent complication of radiofrequency ablation.

    PubMed

    Hazell, Wayne; Heaven, David; Kazemi, Alex; Fourie, Dean

    2009-08-01

    A 72-year-old presented with features of sepsis, neurological sequelae and chest pain after a radiofrequency ablation for AF. Chest CT scan revealed a life-threatening condition not previously reported in emergency medicine journals. PMID:19682020

  11. Cytogenetic and Carcinogenic Effects of Exposure to Radiofrequency Radiation

    Microsoft Academic Search

    JAMES P. MCNAMEE; PASCALE V. BELLIER

    Radiofrequency radiation (RFR) is a portion of the electromagnetic spectrum with frequencies of 3 kHz–300 GHz. RFR is produced\\u000a by many man-made sources, including mobile phones and base stations, television and radio broadcasting facilities, radar,\\u000a medical equipment, microwave ovens, radiofrequency heaters as well as a diverse variety of other electronic devices within\\u000a our living and working environments. Owing to ongoing

  12. Pain Relief Through an Antinociceptive Effect After Radiofrequency Application

    Microsoft Academic Search

    Norimasa Takahashi; James P. Tasto; Mark Ritter; Nobuyasu Ochiai; Seiji Ohtori; Hideshige Moriya; David Amiel

    2007-01-01

    Background: Many patients with chronic tendinosis have experienced early pain relief after application of bipolar radiofrequency treatment. Pathologic nerve ingrowth or nerve irritation in the tendon has been considered as a possible cause of the pain experienced with tendinosis.Hypothesis: Bipolar radiofrequency treatment will ablate nerve fibers, resulting in pain relief.Study Design: Controlled laboratory study.Methods: Eighteen Sprague-Dawley rats were used in

  13. 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.

  14. Successful treatment of refractory pudendal neuralgia with pulsed radiofrequency.

    PubMed

    Rhame, Ellen E; Levey, Kenneth A; Gharibo, Christopher G

    2009-01-01

    Pudendal neuralgia (PN) involves severe, sharp pain along the course of the pudendal nerve, often aggravated with sitting. Current therapies include medication management, nerve blocks, decompression surgery, and neuromodulation. The ideal management for PN has not been determined. We present a case of a female with 1.5 years of sharp, burning pain of the left gluteal and perineal regions. She could not sit for longer than 10 to 15 minutes. Sacroiliac joint, epidural, and piriformis injections did not improve her pain. She had tried physical therapy, occupational therapy, massage, and acupuncture but the pain persisted. Medication treatment with oxycodone-acetaminophen, extended release morphine sulfate, amitriptyline, and gabapentin provided only minor relief and she had failed other multianalgesic therapy. She had been unable to work at her desk job for over a year. She had a positive response to 2 diagnostic pudendal nerve blocks with lidocaine that provided pain relief for several hours. This patient elected to undergo pulsed radiofrequency (PRF) of the left pudendal nerve in hopes of achieving a longer duration and improved pain relief. PRF was carried out at a frequency of 2 Hz and a pulse width of 20 milliseconds for a duration of 120 seconds at 42 degrees Celsius. After the procedure she reported tolerating sitting for 4 to 5 hours. Her multianalgesic therapy was successfully weaned. At 5 months follow-up she felt motivated to return to work. One and a half years after the procedure the patient is only taking oxycodone-acetaminophen for pain relief and still has good sitting tolerance. There were no procedure-related complications. To our knowledge PRF for the treatment of PN has not been reported elsewhere in the literature. PRF is a relatively new procedure and is felt to be safer than continuous radiofrequency. Current literature suggests that PRF delivers an electromagnetic field, which modifies neuro-cellular function with minimal cellular destruction. We conclude that PRF of the pudendal nerve offers promise as a potential treatment of PN that is refractory to conservative therapy. PMID:19461829

  15. Answer to comments by A. Lerchl on "Radiofrequency electromagnetic fields (UMTS, 1,950 MHz) induce genotoxic effects in vitro in human fibroblasts but not in lymphocytes" published by C. Schwarz et al. 2008.

    PubMed

    Rüdiger, Hugo W

    2009-01-01

    Genotoxic effects induced in vitro by the third generation mobile communication standard UMTS have recently been described by Schwarz et al. (Int Arch Occup Environ Health 81:755-767, 2008). These findings which may have considerable significance for environmental health have been commented upon by Lerchl (Int Arch Occup Environ Health in press, 2008) (this issue). These comments which are invalid in part have to be set right. Although some of his minor points are correct the objected inconsistencies are largely based on the author's incomplete and superficial consideration of published data in the field. Moreover, the statistical points being made cannot cast doubts on the validity of the experimental data reported by Schwarz et al. and may not change the principal conclusion of in vitro genotoxic action of UMTS signals. PMID:18481076

  16. 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).

  17. Radiofrequency signal affects alpha band in resting electroencephalogram.

    PubMed

    Ghosn, Rania; Yahia-Cherif, Lydia; Hugueville, Laurent; Ducorps, Antoine; Lemaréchal, Jean-Didier; Thuróczy, György; de Seze, René; Selmaoui, Brahim

    2015-04-01

    The aim of the present work was to investigate the effects of the radiofrequency (RF) electromagnetic fields (EMFs) on human resting EEG with a control of some parameters that are known to affect alpha band, such as electrode impedance, salivary cortisol, and caffeine. Eyes-open and eyes-closed resting EEG data were recorded in 26 healthy young subjects under two conditions: sham exposure and real exposure in double-blind, counterbalanced, crossover design. Spectral power of EEG rhythms was calculated for the alpha band (8-12 Hz). Saliva samples were collected before and after the study. Salivary cortisol and caffeine were assessed by ELISA and HPLC, respectively. The electrode impedance was recorded at the beginning of each run. Compared with the sham session, the exposure session showed a statistically significant (P < 0.0001) decrease of the alpha band spectral power during closed-eyes condition. This effect persisted in the postexposure session (P < 0.0001). No significant changes were detected in electrode impedance, salivary cortisol, and caffeine in the sham session compared with the exposure one. These results suggest that GSM-EMFs of a mobile phone affect the alpha band within spectral power of resting human EEG. PMID:25695646

  18. 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

  19. 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.

  20. Radiofrequency treatment alters cancer cell phenotype

    PubMed Central

    Ware, Matthew J.; Tinger, Sophia; Colbert, Kevin L.; Corr, Stuart J.; Rees, Paul; Koshkina, Nadezhda; Curley, Steven; Summers, H. D.; Godin, Biana

    2015-01-01

    The importance of evaluating physical cues in cancer research is gradually being realized. Assessment of cancer cell physical appearance, or phenotype, may provide information on changes in cellular behavior, including migratory or communicative changes. These characteristics are intrinsically different between malignant and non-malignant cells and change in response to therapy or in the progression of the disease. Here, we report that pancreatic cancer cell phenotype was altered in response to a physical method for cancer therapy, a non-invasive radiofrequency (RF) treatment, which is currently being developed for human trials. We provide a battery of tests to explore these phenotype characteristics. Our data show that cell topography, morphology, motility, adhesion and division change as a result of the treatment. These may have consequences for tissue architecture, for diffusion of anti-cancer therapeutics and cancer cell susceptibility within the tumor. Clear phenotypical differences were observed between cancerous and normal cells in both their untreated states and in their response to RF therapy. We also report, for the first time, a transfer of microsized particles through tunneling nanotubes, which were produced by cancer cells in response to RF therapy. Additionally, we provide evidence that various sub-populations of cancer cells heterogeneously respond to RF treatment. PMID:26165830

  1. Thoracoscopic radiofrequency ablation of the myocardium.

    PubMed

    Watanabe, G; Misaki, T; Nakajima, K; Ueda, T; Yamashita, A

    1998-03-01

    Radiofrequency (RF) catheter ablation has been used for the treatment of ventricular tachycardia (VT), however, in some patients VT might result from subepicardial macroreentry that could be successfully terminated by epicardial approach. This study examined the feasibility of thoracoscopic RF ablation of myocardium from epicardium using a custom made electrode. In five mongrel dogs, the thoracoscope was introduced through the 7th intercostal space. A 500-KHz continuous wave RF energy was connected to a custom made multiple electrode probe. Under thoracoscopic guidance, the heart was exposed and the RF probe was introduced. RF ablation was performed on the nonvascular ventricular wall of the beating heart. The left ventricular free wall and right ventricular outflow tract were satisfactorily visualized and ablated. The total dose of RF energy ranged from 50 to 500 J, and the estimated volume of ablated lesions ranged from 41.0-799 mm3. There were significant correlations between the RF discharge output and the irradiated lesion volume (P < 0.01), and the depth of the lesions (P < 0.01). Grossly, after RF ablation the ventricular myocardium demonstrated a circular, well-demarcated area of thermal injury. Volume and depth of the lesion depended upon the total dose of delivered RF energy. Thoracoscopic RF ablation appears to be a minimally invasive and useful method for creating irradiated myocardial lesions from epicardial surface. This method could be technically feasible for the treatment of Vts for which endocardial RF ablation is ineffective. PMID:9558687

  2. Radiofrequency radiation effects on the common bean

    SciTech Connect

    Thomkins, K.; Griggs, L.; Myles, E.L. [Tennessee State Univ., Nashville, TN (United States)] [and others

    1995-07-01

    Our environment is bombarded daily with thousands of objects we can visually detect. However, invisible to humans are the electromagnetic waves that penetrate our environment. Electromagnetic waves consist of a large spectrum of waves including the harmful gamma rays, x-rays, and ultraviolet rays. The question that has increased tremendously is: can low energy electromagnetic waves become harmful to living organisms? The purpose of this study is to determine the effect of radiofrequency radiation on protein synthesis of the common bean. Phaseolus vulgaris (kidney bean) was surface-sterilized and allowed to germinate on Mushurage and Skoog`s medium for 1 week. Hypocotyls were wounded and placed on media to initiate callus production. Six petri dishes containing 1 g of callus were used in the experiment. Three dishes were exposed to 100kH in a Crawford cell for 24h. The remaining three petri dishes with callus were used as a control. After the exposure period, the protein from callus was extracted and analyzed by one-dimensional gel electrophoresis. The results show that hypocotyl growth was not different between control and experimental groups after 24 h. The result of one-dimensional gel electrophoresis did not show observable differences in protein synthesized by the control and experimental groups. Analysis of protein synthesis is still ongoing.

  3. 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.

  4. Errors in radio-frequency quadrupole structures

    SciTech Connect

    Lysenko, W.P.

    1983-01-01

    Performance degradation caused by certain radio-frequency quadrupole (RFQ) machine errors was studied using an efficient 3-D particle-tracing simulation code for a high-brightness example. Matched beams, for which no emittance growth occurs, exist for periodic structures and were used as input beams for particle tracing in the presence of errors. We considered both slowly varying and fast (random) errors that destroy periodicity. Random dipole errors cause emittance growth because of the mismatches they introduce and also result in a motion of the beam centroid that causes a reduction in acceptance. Because of the way RFQs are manufactured, the random error amplitudes can be kept below harmful levels. More important are the slow errors, which are harmful because they reduce acceptance even though they maintain a match (up to the point of particle loss). Slow dipole errors steer the beam toward the wall, and voltage deficiencies cause instabilities in the longitudinal direction resulting in particles not being accelerated to full energy.

  5. 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.

  6. 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.

  7. Magnetic field properties in a birdcage coil P. Boissoles and G. Caloz

    E-print Network

    Boyer, Edmond

    Magnetic field properties in a birdcage coil P. Boissoles and G. Caloz March 15, 2006 Abstract Radiofrequency magnetic fields used in MRI experiments have to sat- isfy specific properties. First, they need they generate an adequate homogeneous radiofrequency magnetic field. Since then several studies have used

  8. Characterization of Boron Carbonitride (BCN) Thin Films Deposited by Radiofrequency and Microwave Plasma Enhanced Chemical Vapor Deposition

    Microsoft Academic Search

    M. A. Mannan; M. Nagano; K. Shigezumi; T. Kida; N. Hirao; Y. Baba

    Boron carbonitride (BCN) thin films with a thickness of ~4 ?m were synthesized on Si (100) substrate by radiofrequency and microwave plasma enhanced chemical vapor deposition using trimethylamine borane ((CH3)3N.BH3)) as a molecular precursor. The microstructures of the films were evaluated using field emission scanning electron microscopy (FE-SEM) and X-ray diffractometry (XRD). Fourier transform infrared spectroscopy (FT-IR) and X-ray photoelectron

  9. 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

  10. A Rare Complication of Radiofrequency Tonsil Ablation: Horner Syndrome

    PubMed Central

    Ozbay, Isa; Yildirim, Nadir; Zeybek Sivas, Zuhal; Canbaz Kabay, Sibel

    2015-01-01

    Chronic tonsillitis is a common disease, and several different surgical techniques are used to treat this condition. In recent years, techniques such as radiofrequency ablation and coblation have been commonly used for tonsil surgery. In this report, we present the cases of two pediatric patients who developed ptosis, miosis, and enophthalmos (Horner syndrome) after radiofrequency ablation for tonsil reduction and discuss the technique of radiofrequency ablation of the tonsils. In the early postoperative period, miosis and ptosis were observed on the right side in one patient and on the left side in the other patient. Both patients were treated with 1?mg/kg/day methylprednisolone, which were tapered by halving the dose every 3 days. Miosis and ptosis improved after treatment in both patients. Along with the case presentation, we discuss the effectiveness and complications of radiofrequency ablation of the tonsils. These unusual complications of tonsil ablation may help ENT physicians who do not yet have a preferred surgical technique for tonsillectomy to make an informed decision. Limited data are available about the possible complications of radiofrequency ablation of the tonsils. The present report contributes to the literature on this topic.

  11. 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...

  12. 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...

  13. 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.

  14. PHYSICAL REVIEW B VOLUME 48, NUMBER 13 1 OCTOBER 1993-1 Determination of the absolute sign of nuclear quadrupole interactions by laser radio-frequency

    E-print Network

    Suter, Dieter

    PHYSICAL REVIEW B VOLUME 48, NUMBER 13 1 OCTOBER 1993-1 Determination of the absolute sign of nuclear quadrupole interactions by laser radio-frequency double-resonance experiments Tilo Blasberg the quadrupole moment of nuclear spins I > + with the electric-field-gradient (EFG) tensor leads to a splitting

  15. 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

  16. Simplified radio-frequency generator for driving ion guides, traps, and other capacitive loads

    E-print Network

    Anderson, Scott L.

    NOTES Simplified radio-frequency generator for driving ion guides, traps, and other capacitive 2000 We report the design and construction details for a very simple radio-frequency rf generator-5 A few years ago, we published the design for a high voltage radio-frequency rf oscillator circuit

  17. SIMULATION OF RADIO-FREQUENCY ABLATION USING COMPOSITE FINITE ELEMENT METHODS

    E-print Network

    Preusser, Tobias

    SIMULATION OF RADIO-FREQUENCY ABLATION USING COMPOSITE FINITE ELEMENT METHODS T. PREUSSER AND H¨urich, Winterthurerstrasse 190, 8057 Z¨urich, Switzerland This paper deals with a model for the simulation of the radio-frequency step size. A multigrid solver further enhances the performance of the method. 1. Introduction The radio-frequency

  18. Multi-Scale Optimization of the Probe Placement for Radio-Frequency Ablation ,

    E-print Network

    Preusser, Tobias

    Multi-Scale Optimization of the Probe Placement for Radio-Frequency Ablation , Inga Altrogge in radio-frequency (RF) ablation. The model is based on a system of partial differential equations which to artificial test scenarios as well as a comparison to a real RF ablation are presented. Key words: Radio-Frequency

  19. 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.

  20. Thermal Protection with 5% Dextrose Solution Blanket During Radiofrequency Ablation

    SciTech Connect

    Chen, Enn Alexandria, E-mail: echen@cc.nih.gov; Neeman, Ziv; Lee, Fred T.; Kam, Anthony; Wood, Brad [National Institutes of Health, Radiology Department, Warren G. Magmison Clinical Center (United States)

    2006-12-15

    A serious complication for any thermal radiofrequency ablation is thermal injury to adjacent structures, particularly the bowel, which can result in additional major surgery or death. Several methods using air, gas, fluid, or thermometry to protect adjacent structures from thermal injury have been reported. In the cases presented in this report, 5% dextrose water (D5W) was instilled to prevent injury to the bowel and diaphragm during radiofrequency ablation. Creating an Insulating envelope or moving organs with D5W might reduce risk for complications such as bowel perforation.

  1. Pulsed radiofrequency neuromodulation for the treatment of saphenous neuralgia.

    PubMed

    Han, Bo Ram; Choi, Hyuk Jai; Kim, Min Ki; Cho, Yong-Jun

    2013-08-01

    A 65-year-old male presented with pain in his right medial calf. An imaging study revealed no acute lesions, and a diagnosis of saphenous neuralgia was made by a nerve conduction study. He received temporary pain relief with saphenous nerve blocks twice in a one-week interval. Pulsed radiofrequency neuromodulation reduced pain to 10% of the maximal pain intensity. At 6 months after the procedure, the pain intensity was not aggravated even without medication. Pulsed radiofrequency neuromodulation of the saphenous nerve may offer an effective and minimally invasive treatment for patients with saphenous neuralgia who are refractory to conservative management. PMID:24175030

  2. 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

  3. Biological indicators in response to radiofrequency/microwave exposure.

    PubMed

    Marjanovi?, Ana Marija; Pavi?i?, Ivan; Troši?, Ivan?ica

    2012-09-01

    Over the years, due to rapid technological progress, radiation from man-made sources exceeded that of natural origin. There is a general concern regarding a growing number of appliances that use radiofrequency/ microwave (RF/MW) radiation with particular emphasis on mobile communication systems. Since nonthermal biological effects and mechanisms of RF/MW radiation are still uncertain, laboratory studies on animal models, tissues, cells, and cell free system are of extraordinary importance in bioelectromagnetic research. We believe that such investigations play a supporting role in public risk assessment. Cellular systems with the potential for a clear response to RF/MW exposures should be used in those studies. It is known that organism is a complex electrochemical system where processes of oxidation and reduction regularly occur. One of the plausible mechanisms is connected with generation of reactive oxygen species (ROS). Depending on concentration, ROS can have both beneficial and deleterious effects. Positive effects are connected with cell signalling, defence against infectious agents, and proliferative cell ability. On the other hand, excessive production, which overloads antioxidant defence mechanism, leads to cellular damage with serious potential for disease development. ROS concentration increase within the cell caused by RF/MW radiation seems to be a biologically relevant hypothesis to give clear insight into the RF/MW action at non-thermal level of radiation. In order to better understand the exact mechanism of action and its consequences, further research is needed in the field. We would like to present current knowledge on possible biological mechanisms of RF/MW actions. PMID:23152390

  4. A radio-frequency coil for the microwave characterization of vortex dynamics in thin film superconductors

    NASA Astrophysics Data System (ADS)

    Cuadra-Solís, Pedro-de-Jesús; Fernández-Martínez, Antoni; Hernàndez, Joan Manel; García-Santiago, Antoni; Vanacken, Johan; Moshchalkov, Victor V.

    2015-06-01

    A radio-frequency coil for the experimental investigation of the magnetic properties of thin superconducting films under microwave fields at different values of temperature and dc magnetic field has been developed. The system has been used for low-temperature microwave frequency-dependent magnetization measurements in a Pb thin film with an engineered periodical antidot array. The characteristic frequencies and the electric and magnetic fields of the resonant system formed by a multi-turn coil with a sample loaded in its core are estimated using the helical approach. A good agreement of the calculated values with those recorded in swept-frequency spectra is obtained. The relation between the characteristics of the resonant structure and the frequency-driven magnetic response of the sample at different nominal microwave powers documents the capability and sensitivity of the layout.

  5. A radio-frequency coil for the microwave characterization of vortex dynamics in thin film superconductors.

    PubMed

    Cuadra-Solís, Pedro-de-Jesús; Fernández-Martínez, Antoni; Hernàndez, Joan Manel; García-Santiago, Antoni; Vanacken, Johan; Moshchalkov, Victor V

    2015-06-01

    A radio-frequency coil for the experimental investigation of the magnetic properties of thin superconducting films under microwave fields at different values of temperature and dc magnetic field has been developed. The system has been used for low-temperature microwave frequency-dependent magnetization measurements in a Pb thin film with an engineered periodical antidot array. The characteristic frequencies and the electric and magnetic fields of the resonant system formed by a multi-turn coil with a sample loaded in its core are estimated using the helical approach. A good agreement of the calculated values with those recorded in swept-frequency spectra is obtained. The relation between the characteristics of the resonant structure and the frequency-driven magnetic response of the sample at different nominal microwave powers documents the capability and sensitivity of the layout. PMID:26133852

  6. 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

  7. Clinical Results of Radiofrequency Endovenous Obliteration for Varicose Veins

    Microsoft Academic Search

    Tomohiro Ogawa; Shunichi Hoshino; Hirofumi Midorikawa; Kouichi Sato

    2005-01-01

    Purpose Radiofrequency (RF) endovenous obliteration is performed in the United States and several European countries for the minimally invasive treatment of saphenous-type varicose veins. We evaluated the clinical results of RF endovenous obliteration to treat varicose veins at Fukushima Daiichi Hospital. Methods We performed endovenous obliteration of 25 great saphenous varicose veins in 20 patients, under duplex ultrasound guidance. None

  8. 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

  9. 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

  10. [Thrombus visualisation during radiofrequency catheter ablation. A case report].

    PubMed

    Maciag, Aleksander; Szwed, Hanna; Pytkowski, Mariusz; Kraska, Alicja; Sterli?ski, Maciej

    2005-10-01

    We report two patients in whom thrombus formation during radiofrequency catheter ablation was detected by echocardiography. Resolution of thrombus after intravenous use of heparin was observed in both patients. Transesophageal and intracardiac echocardiography may be useful in management of this complication. PMID:16273488

  11. Radio-Frequency Electron Accelerators for Industrial Applications

    NASA Astrophysics Data System (ADS)

    Cleland, Marshall R.

    2011-02-01

    Two types of radio-frequency electron accelerators are described in this article. They operate in the frequency range of 100-200MHz and are energized with triode or tetrode tubes instead of klystrons. They can provide more powerful electron beams than typical microwave linear accelerators.

  12. Radiofrequency Ablation for Hepatocellular Carcinoma: Updated Review in 2010

    Microsoft Academic Search

    Masatoshi Kudo

    2010-01-01

    Percutaneous radiofrequency ablation (RFA) for hepatocellular carcinoma (HCC) was introduced in Japan in 1999. It has been established as a main local treatment method worldwide including Japan. On comparing outcomes between resection and RFA, they were comparable when cases were limited to those with 3 or fewer tumors 3 cm or smaller in many reports, based on which RFA has

  13. 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.

  14. Unipolar radiofrequency treatment to improve the appearance of cellulite

    Microsoft Academic Search

    Jeffrey S. Dover; Kenneth A. Arndt

    2008-01-01

    Background: Previous studies suggest that radiofrequency (RF) energy may be effective as a treatment for cellulite. Objective: This bilateral paired blinded comparative study assesses the efficacy and safety of a unipolar RF device for improving the appearance of cellulite using a new quantitative cellulite grading system. Methods: In this randomized, blinded, split-design study, 10 individuals (aged 32-57 years) with a

  15. Radio-frequency scanning tunnelling microscopy U. Kemiktarak1

    E-print Network

    the dimin- ished high-frequency response of the tunnel current readout circuitry. Here we overcomeLETTERS Radio-frequency scanning tunnelling microscopy U. Kemiktarak1 , T. Ndukum3 , K. C. Schwab3 between a sharp probe tip and a conducting sample to attain atomic-scale spatial resolution. In the 25

  16. Radio-Frequency Interference from Digital Television Patrick C. Crane

    E-print Network

    Ellingson, Steven W.

    Radio-Frequency Interference from Digital Television Patrick C. Crane 29 April 2008 Digital television (DTV) signals have intermittently been observed during measurements of radio and includes the VHF television channels 2-6 (54-60, 60-66, 66-72, 76-82, and 82-88 MHz); for example

  17. Radiofrequency Ablation in 447 Complex Unresectable Liver Tumors: Lessons Learned

    Microsoft Academic Search

    Richard J. Bleicher; David P. Allegra; Dean T. Nora; Thomas F. Wood; Leland J. Foshag; Anton J. Bilchik

    2003-01-01

    Background: Radiofrequency ablation (RFA) is a promising technique for unresectable hepatic malignancies. We reviewed our RFA experience to identify variables affecting local recurrence. Methods: Patients undergoing RFA between 1997 and 2001 were reviewed for demographics, tumor size, pathology, diagnosis, recurrence, procedures, survival, and complications. Results: The 447 unresectable liver tumors were ablated in 198 procedures. The 153 patients averaged 61.9

  18. Review of radiofrequency exposure systems for in vitro biological experiments

    Microsoft Academic Search

    A. Paffi; F. Apollonio; M. Liberti; R. Pinto; G. A. Lovisolo

    2010-01-01

    In this work, the radiofrequency exposure systems for in vitro experiments, published in the last ten years, have been reviewed and classified. Classification is based on the experimental protocol, whether off-line or real-time systems. Moreover, according to their reference electromagnetic structure, systems have been divided in radiating, propagating and resonant. For each of these families, the main general features have

  19. Current uses of radiofrequency in arthroscopic knee surgery.

    PubMed

    Tasto, J P; Ash, S A

    1999-01-01

    Radiofrequency energy is a promising new technology in arthroscopy. Further basic science work is needed to define the mechanical characteristics of tissues in vivo at different times postoperatively. Long-term clinical follow-up studies are needed to determine the useful applications of this technology in the future. PMID:10496471

  20. 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...

  1. Modular System Concept For Soil Heating Using Radio-Frequency Energy

    NASA Astrophysics Data System (ADS)

    Holzer, Frank; Lippik, Dirk; Heimbold, Tilo; Roland, Ulf; Kopinke, Frank-Dieter; Schenk, Joachim

    2010-06-01

    Soil is one of the most important natural resources and its exploitation, preservation and regeneration are huge challenges for modern industrial society. For this reason it is essential to have innovative, efficient, cost-effective and reliable technologies for the decontamination and soil remediation. These technologies should be flexibly applicable for a wide spectrum of contaminants. Beside other biological, physical and chemical methods, research on thermally-supported soil remediation methods has increased over the last years. Due to a controlled heating of soil, the mobility of pollutants, their water solubility and their vapor pressures can be enhanced. To support biodegradation of pollutants, the maximum activity of most microorganisms can be realized by moderate heating independent of ambient temperature and seasonal conditions. A new technological approach for direct heating of large volumes of contaminated soil using radio-frequency (RF) energy is described. This method can be used to thermally enhance a variety of remediation techniques such as biodegradation and soil vapor extraction. The technical basis, a container-based modular and mobile radio-frequency platform is presented and the benefits of this platform working under harsh field conditions are demonstrated. Additionally, aspects of electromagnetic compatibility, system reliability and safety are discussed.

  2. 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

  3. A precautionary public health protection strategy for the possible risk of childhood leukaemia from exposure to power frequency magnetic fields

    Microsoft Academic Search

    Myron Maslanyj; Tracy Lightfoot; Joachim Schüz; Zenon Sienkiewicz; Alastair McKinlay

    2010-01-01

    BACKGROUND: Epidemiological evidence showing a consistent association between the risk of childhood leukaemia and exposure to power frequency magnetic fields has been accumulating. This debate considers the additional precautionary intervention needed to manage this risk, when it exceeds the protection afforded by the exposure guidelines as recommended by the International Commission on Non-Ionizing Radiation Protection. METHODS: The Bradford-Hill Criteria are

  4. Radiofrequency thermoneurolysis for the treatment of Morton's neuroma.

    PubMed

    Moore, Joshua L; Rosen, Ritchard; Cohen, Jeffrey; Rosen, Brad

    2012-01-01

    Pedal neuroma is a common disorder. The authors undertook a review of 32 feet in 29 patients with a symptomatic neuroma treated between January 2007 and January 2010 to evaluate the effectiveness of radiofrequency thermoneurolysis therapy in alleviating symptoms. Overall relief of symptoms was rated as complete by 24 (83%) patients, with 5 patients experiencing minimal to no relief. Two patients were lost to follow-up after 1 month, 2 patients opted for no further intervention, and 1 patient went to open resection of the neuroma. Average follow-up was 13 months and total recovery time was 2 days. Complications included 1 foot with cellulitis treated by a course of oral antibiotics. The results of this retrospective study indicate radiofrequency thermoneurolysis therapy is a safe, effective, and minimally invasive alternative treatment for symptomatic neuromas of the foot. PMID:22055491

  5. 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

  6. Radiofrequency ablation for treatment of hypersplenism: A feasible therapeutic option.

    PubMed

    Martins, Guilherme Lopes P; Bernardes, Joao Paulo G; Rovella, Marcello S; Andrade, Raphael G; Viana, Publio Cesar C; Herman, Paulo; Cerri, Giovanni Guido; Menezes, Marcos Roberto

    2015-05-28

    We present a case of a patient with hypersplenism secondary to portal hypertension due to hepato-splenic schistosomiasis, which was accompanied by severe and refractory thrombocytopenia. We performed spleen ablation and measured the total spleen and ablated volumes with contrast-enhanced computed tomography and volumetry. No major complications occurred, thrombocytopenia was resolved, and platelet levels remained stable, which allowed for early treatment of the patient's underlying disease. Previous work has shown that splenic radiofrequency ablation is an attractive alternative treatment for hypersplenism induced by liver cirrhosis. We aimed to contribute to the currently sparse literature evaluating the role of radiofrequency ablation (RFA) in the management of hypersplenism. We conclude that splenic RFA appears to be a viable and promising option for the treatment of hypersplenism. PMID:26034376

  7. Radiofrequency ablation for treatment of hypersplenism: A feasible therapeutic option

    PubMed Central

    Martins, Guilherme Lopes P; Bernardes, Joao Paulo G; Rovella, Marcello S; Andrade, Raphael G; Viana, Publio Cesar C; Herman, Paulo; Cerri, Giovanni Guido; Menezes, Marcos Roberto

    2015-01-01

    We present a case of a patient with hypersplenism secondary to portal hypertension due to hepato-splenic schistosomiasis, which was accompanied by severe and refractory thrombocytopenia. We performed spleen ablation and measured the total spleen and ablated volumes with contrast-enhanced computed tomography and volumetry. No major complications occurred, thrombocytopenia was resolved, and platelet levels remained stable, which allowed for early treatment of the patient’s underlying disease. Previous work has shown that splenic radiofrequency ablation is an attractive alternative treatment for hypersplenism induced by liver cirrhosis. We aimed to contribute to the currently sparse literature evaluating the role of radiofrequency ablation (RFA) in the management of hypersplenism. We conclude that splenic RFA appears to be a viable and promising option for the treatment of hypersplenism. PMID:26034376

  8. Irrigated tip catheters for radiofrequency ablation in ventricular tachycardia.

    PubMed

    Müssigbrodt, Andreas; Grothoff, Matthias; Dinov, Borislav; Kosiuk, Jedrzej; Richter, Sergio; Sommer, Philipp; Breithardt, Ole A; Rolf, Sascha; 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

  9. 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.

  10. 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.

  11. 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.

  12. Radiofrequency Catheter Ablation of Supraventricular Tachycardia in Children and Adolescents

    Microsoft Academic Search

    Vladimiro L. Vida; Gonzalo S. Calvimontes; Maximo O. Macs; Patricia Aparicio; Joaquin Barnoya; Aldo R. Castañeda

    2006-01-01

    The objective of this study is to provide results and costs of catheter ablation in children and adolescents in a low-income\\u000a country. Reports from first-world countries have demonstrated the cost-effectiveness of radiofrequency catheter ablation (RFCA)\\u000a compared to medical treatment of supraventricular tachycardia (SVT). The study included 28 patients younger than 18 years\\u000a of age with SVT in a pediatric cardiology

  13. Radiofrequency ablation of atrial fibrillation during mitral valve surgery

    Microsoft Academic Search

    David C. Kress; Jasbir Sra; David Krum; Anil Goel; Jennifer Campbell; Jeff Fox

    2002-01-01

    Twenty-three patients underwent endocardial radiofrequency ablation of atrial fibrillation (AF) during mitral valve procedures with a previously described left atrial lesion pattern. A temperature-controlled 7-coil surgical probe delivered 60-second lesions at 80°C. The left atrial appendage was oversewn after ablation. Ages ranged from 28 to 88 years. Nineteen patients had chronic AF that was present for over 1 year in

  14. Thermal Ablation for Benign Thyroid Nodules: Radiofrequency and Laser

    PubMed Central

    Lee, Jeong Hyun; Valcavi, Roberto; Pacella, Claudio M.; Rhim, Hyunchul; Na, Dong Gyu

    2011-01-01

    Although ethanol ablation has been successfully used to treat cystic thyroid nodules, this procedure is less effective when the thyroid nodules are solid. Radiofrequency (RF) ablation, a newer procedure used to treat malignant liver tumors, has been valuable in the treatment of benign thyroid nodules regardless of the extent of the solid component. This article reviews the basic physics, techniques, applications, results, and complications of thyroid RF ablation, in comparison to laser ablation. PMID:21927553

  15. Radiofrequency treatment weakens the fatigue characteristics of rabbit anterior cruciate ligament

    Microsoft Academic Search

    A Merter Ozenci; Manohar M Panjabi

    2003-01-01

    Objective. To evaluate the radiofrequency treatment applied to an intact anterior cruciate ligament, and to quantify the mechanical effects of controlled cyclic loading (simulating activities of daily living) post-treatment.Design. An in vitro radiofrequency energy application to the rabbit anterior cruciate ligament and cyclic loading of the treated ligament.Background. Effect of cyclic loading on the radiofrequency treated ligament in a controlled

  16. Surface Impedance Measurements of Single Crystal MgB2 Films for Radiofrequency Superconductivity Applications

    SciTech Connect

    Binping Xiao, Xin Zhao, Joshua Spradlin, Charles Reece, Michael Kelley, Teng Tan, Xi Xiaoxing

    2012-07-01

    We report microstructure analyses and superconducting radiofrequency (SRF) measurements of large scale epitaxial MgB{sub 2} films. MgB{sub 2} films on 5 cm dia. sapphire disks were fabricated by a Hybrid Physical Chemical Vapor Deposition (HPCVD) technique. The electron-beam backscattering diffraction (EBSD) results suggest that the film is a single crystal complying with a MgB{sub 2}(0001) {parallel} Al{sub 2}O{sub 3}(0001) epitaxial relationship. The SRF properties of different film thicknesses (200 nm and 350 nm) were evaluated under different temperatures and applied fields at 7.4 GHz. A surface resistance of 9 {+-} 2 {mu}{Omega} has been observed at 2.2 K.

  17. Elimination of Radio-Frequency Noise by Identifying and Diverting Large RF Ground Currents

    NASA Astrophysics Data System (ADS)

    Perkins, R. J.; Bellan, P. M.

    2011-12-01

    The problem of electromagnetic interference in scientific instruments is compounded for high-power plasma experiments by the large currents and voltages as well as by the broad bandwidths of the instruments. Ground loops are known to allow stray magnetic fields to drive large ground currents that can induce spurious signals and damage electronics. Furthermore, even when a ground loop is broken, capacitive coupling can still permit the flow of radio-frequency current, resulting in high-frequency spurious signals that can overwhelm the desired signal. We present the effects of RF ground loops on the output of vacuum photodiodes used in the Caltech Solar Loop Experiment and demonstrate the elimination of the spurious signals by diverting the ground currents away from the most vulnerable point of the signal line. Techniques for identifying the RF ground loops are also discussed. These techniques should be valuable in many high-power systems where interference from spurious coupling is an issue.

  18. Elimination of Radio-Frequency Noise by Identifying and Diverting Large RF Ground Currents

    SciTech Connect

    Perkins, R. J.; Bellan, P. M. [Applied Physics, California Institute of Technology (United States)

    2011-12-23

    The problem of electromagnetic interference in scientific instruments is compounded for high-power plasma experiments by the large currents and voltages as well as by the broad bandwidths of the instruments. Ground loops are known to allow stray magnetic fields to drive large ground currents that can induce spurious signals and damage electronics. Furthermore, even when a ground loop is broken, capacitive coupling can still permit the flow of radio-frequency current, resulting in high-frequency spurious signals that can overwhelm the desired signal. We present the effects of RF ground loops on the output of vacuum photodiodes used in the Caltech Solar Loop Experiment and demonstrate the elimination of the spurious signals by diverting the ground currents away from the most vulnerable point of the signal line. Techniques for identifying the RF ground loops are also discussed. These techniques should be valuable in many high-power systems where interference from spurious coupling is an issue.

  19. 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.

  20. The Project 8 Radiofrequency Tritium Neutrino Experiment

    NASA Astrophysics Data System (ADS)

    Monreal, Benjamin

    The Project 8 experiment aims to determine the electron neutrino mass by measuring the spectrum of tritium beta decay electrons near the 18.6 keV endpoint. Unlike past tritium experiments, which used electrostatic and magnetostatic spectrometers, Project 8 will detect decay electrons nondestructively via their cyclotron radiation emission in a magnetic field. An individual electron is expected to emit a detectable pulse of microwaves at a frequency which depends on the electron energy. Precise measurement of these pulse frequencies is a novel spectroscopy technique particularly well-suited for the high rate, high precision, low background needs of a tritium experiment. The collaboration is currently operating a prototype designed to detect single 83mKr conversion electron decays in an 0.9T magnetic field. We report on recent activities on the prototype, and on progress towards the design of a large tritium experiment with new neutrino-mass sensitivity.

  1. Measurement of the Radiofrequency-microwave Pulse Produced in Experiments of Laser-plasma Interaction in the ABC Laser Facility

    NASA Astrophysics Data System (ADS)

    Consoli, Fabrizio; De Angelis, Riccardo; Andreoli, Pierluigi; Cristofari, Giuseppe; Di Giorgioa, Giorgio

    The emission of electromagnetic waves in the radiofrequency-microwave range has been observed in many experiments of laser- plasma interaction. These fields can have very high intensity and estimated frequency band up to several gigahertz. The radiation normally affects the behaviour of most of the detectors, often up to hundreds of nanoseconds from the laser pulse, and can represent a serious limitation for the time-of-flight detection of fast particles, and in general for the safe operation of the electronic equipment. In this work we describe the measurements of this electromagnetic pulse, under different conditions of laser-plasma interaction.

  2. Racetrack microtron radio-frequency system

    SciTech Connect

    Tallerico, P.J.; Mitra, A.K.

    1981-01-01

    The design and construction progress of a prototype rf system to drive the Los Alamos-NBS racetrack microtron (RTM) electron accelerator is described. The rf system requires 450-kW cw at 2380 MHz from a single klystron. The output from the klystron is split three ways to drive a capture section, a preaccelerator section, and the main accelerator section. The fields in each section are phase- and amplitude-controlled to tight tolerances. Temperature control of the accelerator sections also is linked to the amplitude-control system, because the system's average power is so high.

  3. 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.

  4. Radiofrequency magnetoelastic resonators for magnetoelectric applications

    NASA Astrophysics Data System (ADS)

    Lasheras, A.; Gutiérrez, J.; Balza, A.; Barandiarán, J. M.; Rodríguez Pierna, A.

    2014-08-01

    Magnetoelastic resonance measurements are carried out in short ribbons (down to 1 cm length) of Fe59Co16Si15B10 metallic glasses, both as-quenched and after annealing at 400 °C for 10 min. The resonant frequency exceeds 200 kHz with good Q factors for the shortest elements in the as-quenched state. Sandwich-type laminated magnetoelectric (ME) composites are prepared by gluing these ribbons to a PVDF piezoelectric polymer layer, showing good ME response. This effect is discussed as a function of the as-quenched or annealed state, and the length of the magnetoelastic ribbon, and is of interest for near field communication applications.

  5. Auxiliary radiofrequency heating of tokamaks, Task 3

    SciTech Connect

    Scharer, J.E.

    1991-07-01

    The research performed under this grant during the past three years has been concentrated on the following several key tokamak ICRF (Ion Cyclotron Range of Frequencies) coupling and heating issues: efficient coupling during the L- to H-mode transition by analysis and computer simulation of ICRF antennas edge plasma profiles; analysis of both dielectric-filled waveguide and coil ICRF antenna coupling to plasma edge profiles; benchmarking the codes to compare with current JET, D-IIID and ASDEX experimental results; ICRF full-wave field solutions, power conservation and heating analyses; and the effects of fusion alpha particle or ion tail populations on the ICRF absorption. Research progress, publications, and conference and workshop presentations are summarized in this report. 15 refs.

  6. Understanding Pound-Drever-Hall locking using voltage controlled radio-frequency oscillators: An undergraduate experiment

    E-print Network

    Le Roy, Robert J.

    Understanding Pound-Drever-Hall locking using voltage controlled radio-frequency oscillators techniques using radio-frequency electronics. The primary objective is to frequency stabilize a volt- age is commonly applied to stabilize lasers at optical frequencies. By using only radio- frequency equipment

  7. Numerical studies of current generation by radio-frequency traveling waves

    E-print Network

    Karney, Charles

    Numerical studies of current generation by radio-frequency traveling waves Charles F. F. Karney January 1979; final manuscript received 7 May 1979) By injecting radio-frequency traveling waves of the fusion power output. Recently,' the damping of high-phase-velocity radio- frequency traveling waves has

  8. High-temperature superconducting multi-band radio-frequency metamaterial atoms

    E-print Network

    Anlage, Steven

    High-temperature superconducting multi-band radio-frequency metamaterial atoms Behnood G. Ghamsari spectrum from radio-frequency (RF) up to visible and ultra- violet wavelengths. Nevertheless, at the low-frequency-fabricated compact high-temperature superconducting (HTS) metamaterial atom operating at a frequency as low as $53

  9. A high-performance cryogenic amplifier based on a radio-frequency single electron transistor

    E-print Network

    Segall, Ken

    amplifier based on a radio-frequency single-electron- transistor rf-SET . The high charge sensitivity impedance sources. In this letter we present a demonstration of a high- performance amplifier based on a rfA high-performance cryogenic amplifier based on a radio-frequency single electron transistor K

  10. 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

  11. Radiofrequency Catheter Ablation of Atrioventricular Nodal Reentrant Tachycardia after Orthotopic Heart Transplantation

    Microsoft Academic Search

    Farooq A. Padder; Sabrina L. Wilbur; Bharat K. Kantharia; Alexander Lee; Fania Samuels; Steven P. Kutalek

    1999-01-01

    Patients with orthotopic heart transplantation may develop a variety of arrhythmias. Successful radiofrequency catheter ablation for tachyarrhythmias from manifest and concealed accessory bypass tracts in transplant patients has been previously reported. We present a patient with orthotopic heart transplantation who developed typical atrioventricular nodal tachycardia, which was successfully treated by radiofrequency catheter ablation.

  12. THE ROLE OF RADIOFREQUENCY CATHETER ABLATION IN THE TREATMENT OF NONISCHEMIC VENTRICULAR TACHYCARDIA

    Microsoft Academic Search

    Dubravko Petra

    SUMMARY ñ Radiofrequency catheter ablation can be used for the treatment of different patient groups with nonischemic ventricular tachycardia (VT). Concerning the small area of induced ventricular injury, a high degree success is expected in patients with idiopathic VT and in patients with bundle branch reen- trant VT. The long-term success rate of radiofrequency ablation in the cure of idiopathic

  13. Nonlinear Exothermic Contributions to RadioFrequency Bonding of Adhesives 1

    E-print Network

    Nonlinear Exothermic Contributions to Radio­Frequency Bonding of Adhesives 1 H.T. Banks 2 S This work describes an effort to model the radio­frequency curing of epoxy adhesives in bonding and adhesively bonded in sandwich fashion around their perimeters to form rigid structures. The adhesive

  14. Electromagnetic Radiofrequency Radiation Emitted from GSM Mobile Phones Decreases the Accuracy of Home Blood Glucose Monitors

    PubMed Central

    Mortazavi, SMJ; Gholampour, M; Haghani, M; Mortazavi, G; Mortazavi, AR

    2014-01-01

    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

  15. Radiofrequency catheter ablation of septal accessory atrioventricular pathways.

    PubMed Central

    Xie, B; Heald, S C; Bashir, Y; Camm, A J; Ward, D E

    1994-01-01

    OBJECTIVE--Septal accessory atrioventricular pathways are recognised as being more difficult to ablate than pathways in other locations. This paper describes an experience of 48 consecutive patients with septal accessory pathways who had catheter ablation with radiofrequency current. PATIENTS AND METHODS--There were 28 male and 20 female patients, mean (SD) age 35 (17). 43 patients had a single accessory pathway and 5 patients had multiple accessory pathways. Pre-excitation was present in 37 patients, and 11 patients had concealed accessory pathways. 21 patients had had a previous electrophysiological study. Catheter ablation was undertaken with radiofrequency current delivered by a standard unipolar technique or by delivery of current across the septum (the bipolar technique). RESULTS--The median total procedure time was 167 (83) minutes including a 30-40 minute observation period after the abolition of conduction by the accessory pathway. The median total fluoroscopic time was 56 (30) minutes. 42 (88%) out of 48 patients had successful ablation of the pathway during the first session. In the six patients in whom the procedure failed, five had a midseptal pathway and one had a right anteroseptal pathway. A second attempt at ablation was made in two patients and succeeded in both. In total, 49 accessory pathways were successfully ablated in 44 (92%) out of 48 patients. The bipolar technique was used in 11 patients and succeeded in 10 patients. Standard unipolar current delivery had previously failed in seven of the 11 patients. Complications developed in two patients with a mid septal pathway (one with complete atrioventricular block and the other with a small pericardial effusion). CONCLUSION--Radiofrequency catheter ablation of septal accessory pathways is efficacious and safe. The procedure time can be shortened and success rate can be increased after improvement of the technique--that is, consideration of a bipolar approach for energy delivery in difficult cases. PMID:7946782

  16. Single-electron transistor as a radio-frequency mixer R. Knobel, C. S. Yung, and A. N. Clelanda)

    E-print Network

    Knobel, Robert

    Single-electron transistor as a radio-frequency mixer R. Knobel, C. S. Yung, and A. N. Clelanda-electron transistor as a radio-frequency mixer, based on the nonlinear dependence of current on gate charge of the SET is matched to a 50 cable. This technique, termed a radio-frequency SET rf-SET , allows operation

  17. Fast modeling of the low-pressure capacitively coupled radio-frequency discharge based on the nonlocal approach

    E-print Network

    Kaganovich, Igor

    Fast modeling of the low-pressure capacitively coupled radio-frequency discharge based August 1996 The results of modeling a low-pressure capacitively coupled radio-frequency rf discharge of electron and ion processes in low-pressure radio-frequency rf glow dis- charges has stimulated experimental

  18. 3742 IEEE TRANSACTIONS ON GEOSCIENCE AND REMOTE SENSING, VOL. 47, NO. 11, NOVEMBER 2009 Microwave Radiometer Radio-Frequency

    E-print Network

    Ruf, Christopher

    Radiometer Radio-Frequency Interference Detection Algorithms: A Comparative Study Sidharth Misra, Priscilla N, and Joel T. Johnson, Fellow, IEEE Abstract--Two algorithms used in microwave radiometry for radio-frequency of radio-frequency interference (RFI) have begun to be observed by a number of spaceborne microwave

  19. 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.

  20. A Novel Technique of Partial Splenectomy Using Radiofrequency Ablation

    Microsoft Academic Search

    Jan Jin Bong; Rajesh Kumar; Duncan Spalding

    2011-01-01

    Introduction  Partial splenectomy has frequently been advocated to avoid the risk of overwhelming postsplenectomy sepsis. Concerns over\\u000a adequate haemostasis during partial splenectomy, however, have limited its widespread use. We have previously reported our\\u000a experience of using radiofrequency (RF) ablation to minimise blood loss during hepatic and splenic resections.\\u000a \\u000a \\u000a \\u000a \\u000a Methods  In this video, we illustrate the technique of partial splenectomy assisted by RF

  1. Time-domain simulation of nonlinear radiofrequency phenomena

    NASA Astrophysics Data System (ADS)

    Jenkins, Thomas G.; Austin, Travis M.; Smithe, David N.; Loverich, John; Hakim, Ammar H.

    2013-01-01

    Nonlinear effects associated with the physics of radiofrequency wave propagation through a plasma are investigated numerically in the time domain, using both fluid and particle-in-cell (PIC) methods. We find favorable comparisons between parametric decay instability scenarios observed on the Alcator C-MOD experiment [J. C. Rost, M. Porkolab, and R. L. Boivin, Phys. Plasmas 9, 1262 (2002)] and PIC models. The capability of fluid models to capture important nonlinear effects characteristic of wave-plasma interaction (frequency doubling, cyclotron resonant absorption) is also demonstrated.

  2. Radio-frequency quadrupole: general properties and specific applications

    SciTech Connect

    Stokes, R.H.; Crandall, K.R.; Hamm, R.W.

    1980-01-01

    The radio-frequency quadrupole (RFQ) linac structure is being developed for the acceleration of low-velocity ions. Recent experimental tests have confirmed its expected performance and have led to an increased interest in a wide range of possible applications. The general properties of RFQ accelerators are reviewed and beam dynamics simulation results are presented for their use in a variety of accelerating systems. These include the low-beta sections of the Fusion Materials Irradiation Test Accelerator, a 200-MHz proton linear accelerator, and a xenon accelerator for heavy ion fusion.

  3. 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.

  4. Intraductal radiofrequency ablation for management of malignant biliary obstruction.

    PubMed

    Rustagi, Tarun; Jamidar, Priya A

    2014-11-01

    Self-expandable metal stents (SEMS) are the current standard of care for the palliative management of malignant biliary strictures. Recently, endoscopic ablative techniques with direct affect to local tumor have been developed to improve SEMS patency. Several reports have demonstrated the technical feasibility and safety of intraductal radiofrequency ablation (RFA), by both endoscopic and percutaneous approaches, in palliation of malignant strictures of the bile duct. Intraductal RFA has also been used in the treatment of occlusion of both covered and uncovered SEMS occlusion from tumor ingrowth or overgrowth. This article provides a comprehensive review of intraductal RFA in the management of malignant biliary obstruction. PMID:24906696

  5. Pulmonary Artery Pseudoaneurysm Related to Radiofrequency Ablation of Lung Tumor

    SciTech Connect

    Sakurai, Jun, E-mail: sakurai@cc.okayama-u.ac.jp; Mimura, Hidefumi; Gobara, Hideo; Hiraki, Takao; Kanazawa, Susumu [Okayama University Medical School, Department of Radiology (Japan)

    2010-04-15

    We describe a case of pulmonary artery (PA) pseudoaneurysm related to radiofrequency ablation (RFA) of lung tumor. We performed RFA for a pulmonary epithelioid hemangioendothelioma directly adjacent to a branch of the PA. Seventeen days later, the patient complained of hemoptysis. A chest CT image revealed PA pseudoaneurysm. Transcatheter coil embolization was performed 59 days after RFA. Although PA pseudoaneurysm is rare, with an incidence of 0.2% (1/538 sessions) at our institution, it should be recognized as a risk when treating lung tumors adjacent to a branch of the PA.

  6. Esophageal perforation after radiofrequency ablation for atrial fibrillation.

    PubMed

    Manouchehri, Namdar; Turner, Simon R; Lockwood, Evan; Sterns, Laurence D; Bédard, Eric Lr

    2014-11-01

    A 69-year-old man underwent left atrial radiofrequency ablation for atrial fibrillation. After 10 minutes, the procedure was terminated due to pericardial tamponade secondary to perforation during mapping. Pericardiocentesis resolved the tamponade. Ablation was completed one week later, and the patient was discharged. Two days later, he presented with odynophagia. Computed tomography demonstrated small bilateral pleural effusions. He was judged to be stable and was discharged again, but returned 2 days later with chest pain. He was found to have esophageal perforation with empyema, which was repaired using a muscle patch and esophageal stenting, successfully treating the lesion with minimal morbidity. PMID:24887888

  7. Probing properties of cold radiofrequency plasma with polymer probe

    NASA Astrophysics Data System (ADS)

    Bormashenko, E.; Chaniel, G.; Multanen, V.

    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.

  8. Silicon nanowire based radio-frequency spectrum analyzer.

    PubMed

    Corcoran, Bill; Vo, Trung D; Pelusi, Mark D; Monat, Christelle; Xu, Dan-Xia; Densmore, Adam; Ma, Rubin; Janz, Siegfried; Moss, David J; Eggleton, Benjamin J

    2010-09-13

    We demonstrate a terahertz bandwidth silicon nanowire based radio-frequency spectrum analyzer using cross-phase modulation. We show that the device provides accurate characterization of 640Gbaud on-off-keyed data stream and demonstrate its potential for optical time-division multiplexing optimization and optical performance monitoring of ultrahigh speed signals on a silicon chip. We analyze the impact of free carrier effects on our device, and find that the efficiency of the device is not reduced by two-photon or free-carrier absorption, nor its accuracy compromised by free-carrier cross-chirp. PMID:20940910

  9. Radiofrequency Ablation of Thyroid Nodules: Basic Principles and Clinical Application

    PubMed Central

    Shin, Ji Hoon; Baek, Jung Hwan; Ha, Eun Ju; Lee, Jeong Hyun

    2012-01-01

    Radiofrequency (RF) ablation has been gaining popularity as a minimally invasive treatment for benign thyroid nodules regardless of the extent of the solid component. RF ablation of benign nodules demonstrated volume reductions of 33–58% after one month and 51–85% after six months, while solving nodule-related clinical problems. RF ablation has recently shown positive short-term results for locoregional control as well as symptom improvement in patients with recurrent thyroid cancers. This paper reviews the basic physics, indications, patient preparation, devices, procedures, clinical results, and complications of RF ablation. PMID:23133449

  10. Further developments in oxidation of methane traces with radiofrequency discharge

    NASA Technical Reports Server (NTRS)

    Flamm, D. L.; Wydeven, T. J.

    1977-01-01

    The radiofrequency discharge, previously shown to oxidize trace levels of methane in oxygen, was studied with contaminated air at 50, 600, and 760 torr. As with oxygen, the concentration of methane traces could be reduced by several orders of magnitude, and no organic reaction products were detected in the effluent; however, substantial concentrations of NOx (0.1-6%) were formed during treatment. The concentration of NOx was decreased by using a large diameter electrode. There is evidence that the process will oxidize N2 and NO as well as organic impurities in oxygen or oxygen/inert gas atmospheres.

  11. 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.

  12. 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.

  13. Bipolar radiofrequency treatment for snoring with mild to moderate sleep apnea: a comparative study between the radiofrequency assisted uvulopalatoplasty technique and the channeling technique

    Microsoft Academic Search

    Ahmed Bassiouny; Ahmed El Salamawy; Mohamed Abd El-Tawab; Ahmed Atef

    2007-01-01

    We compared radiofrequency techniques used in the treatment of snoring and obstructive sleep apnea [radiofrequency assisted\\u000a uvulopalatoplasty (RAUP) and channeling] as regard the efficacy and morbidity. A pilot, prospective randomized single blinded\\u000a study was conducted on 40 patients in the ENT Department, Kasr Al-Aini Hospital, Cairo University during the period from April\\u000a to December 2003. Patients were randomized into two groups

  14. Application of Modulation Techniques to Atomic Emission Spectrometry with Inductively-Coupled Radio-Frequency Plasma and Radio-Frequency Glow Discharge Plasma

    Microsoft Academic Search

    Kazuaki Wagatsuma

    2002-01-01

    Three novel measuring systems for modulation technique to be applied to atomic emission spectrometry are reviewed. A plasma gas modulation technique is employed for an improvement in the detection sensitivity in inductively-coupled radio-frequency plasma atomic emission spectrometry (ICP-AES). Both an amplitude modulation technique and a bias current modulation technique are effective for obtaining better analytical performance in radio-frequency glow discharge

  15. 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

  16. Osteoid Osteoma: Experience with Laser- and Radiofrequency-Induced Ablation

    SciTech Connect

    Gebauer, Bernhard [Charite, Medical University Berlin, Department of Radiology (Germany)], E-mail: bernhard.gebauer@charite.de; Tunn, Per-Ulf [Charite, Medical University Berlin, Department of Surgery and Surgical Oncology (Germany); Gaffke, Gunnar [Charite, Medical University Berlin, Department of Radiology (Germany); Melcher, Ingo [Charite, Medical University Berlin, Campus Virchow-Clinic, Department of Trauma and Reconstructive Surgery (Germany); Felix, Roland; Stroszczynski, Christian [Charite, Medical University Berlin, Department of Radiology (Germany)

    2006-04-15

    The purpose of this study was to analyze the clinical outcome of osteoid osteoma treated by thermal ablation after drill opening. A total of 17 patients and 20 procedures were included. All patients had typical clinical features (age, pain) and a typical radiograph showing a nidus. In 5 cases, additional histological specimens were acquired. After drill opening of the osteoid osteoma nidus, 12 thermal ablations were induced by laser interstitial thermal therapy (LITT) (9F Power-Laser-Set; Somatex, Germany) and 8 ablations by radiofrequency ablation (RFA) (RITA; StarBurst, USA). Initial clinical success with pain relief has been achieved in all patients after the first ablation. Three patients had an osteoid osteoma recurrence after 3, 9, and 10 months and were successfully re-treated by thermal ablation. No major complication and one minor complication (sensible defect) were recorded. Thermal ablation is a safe and minimally invasive therapy option for osteoid osteoma. Although the groups are too small for a comparative analysis, we determined no difference between laser- and radiofrequency-induced ablation in clinical outcome after ablation.

  17. Radiofrequency ablation of liver tumors (I): biological background.

    PubMed

    Vanagas, Tomas; Gulbinas, Antanas; Pundzius, Juozas; Barauskas, Giedrius

    2010-01-01

    Majority of patients suffering from liver tumors are not candidates for surgery. Currently, minimal invasive techniques have become available for local destruction of hepatic tumors. Radiofrequency ablation is based on biological response to tissue hyperthermia. The aim of this article is to review available biological data on tissue destruction mechanisms. Experimental evidence shows that tissue injury following thermal ablation occurs in two distinct phases. The initial phase is direct injury, which is determined by energy applied, tumor biology, and tumor microenvironment. The temperature varies along the ablation zone and this is reflected by different morphological changes in affected tissues. The local hyperthermia alters metabolism, exacerbates tissue hypoxia, and increases thermosensitivity. The second phase - indirect injury - is observed after the cessation of heat stimulus. This phase represents a balance of several promoting and inhibiting mechanisms, such as induction of apoptosis, heat shock proteins, Kupffer cell activation, stimulation of the immune response, release of cytokines, and ischemia-reperfusion injury. A deeper understanding of the underlying mechanisms may possibly lead to refinements in radiofrequency ablation technology, resulting in advanced local tumor control and prolonged overall survival. PMID:20234157

  18. NIOSH comments to EPA on radiofrequency radiation by J. D. Millar, December 5, 1986

    SciTech Connect

    Not Available

    1986-12-05

    The testimony concerned the opinions of NIOSH in regards to occupational exposures to radiofrequency (RF) radiation. Based on available literature the arguments for using a safety factor in recommending RF exposure limits were excellent. NIOSH argued against setting the thresholds for adverse effects at or near SAR levels where death and other extremely severe biological effects occur in animals. It was noted that there was an uncertainty factor and two major points had to be considered in establishing it. The first point concerned research reports in which the SAR was not reported and the orientation of the animal relative to the incident field was not specified. The second point concerned the disagreement between measured SAR values in human volunteers and the predicted SAR values in humans. Setting exposure limits as low as even 2 milliwatts/square centimeter (mW/sq m) did not prevent RF shocks and/or burns. Human contact with long or large, electrically conductive objects measured in RF fields resulted in involuntary startle reactions and/or burns at exposure levels even below 2mW/sq m. NIOSH suggests that the Environmental Protection Agency should consider requiring open circuit voltage measurements between capacitively charged objects in an RF field and surrounding points at ground potential with which people could come in contact. An open circuit, RF voltage of 140 volts is an approximate threshold for RF shocks and burns.

  19. 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

  20. 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

  1. A theoretical comparison of two optimization methods for radiofrequency drive schemes in high frequency MRI resonators.

    PubMed

    Liu, Feng; Beck, Barbara L; Fitzsimmons, Jeffrey R; Blackband, Stephen J; Crozier, Stuart

    2005-11-21

    In this paper, numerical simulations are used in an attempt to find optimal source profiles for high frequency radiofrequency (RF) volume coils. Biologically loaded, shielded/unshielded circular and elliptical birdcage coils operating at 170 MHz, 300 MHz and 470 MHz are modelled using the FDTD method for both 2D and 3D cases. Taking advantage of the fact that some aspects of the electromagnetic system are linear, two approaches have been proposed for the determination of the drives for individual elements in the RF resonator. The first method is an iterative optimization technique with a kernel for the evaluation of RF fields inside an imaging plane of a human head model using pre-characterized sensitivity profiles of the individual rungs of a resonator; the second method is a regularization-based technique. In the second approach, a sensitivity matrix is explicitly constructed and a regularization procedure is employed to solve the ill-posed problem. Test simulations show that both methods can improve the B(1)-field homogeneity in both focused and non-focused scenarios. While the regularization-based method is more efficient, the first optimization method is more flexible as it can take into account other issues such as controlling SAR or reshaping the resonator structures. It is hoped that these schemes and their extensions will be useful for the determination of multi-element RF drives in a variety of applications. PMID:16264253

  2. 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.

  3. 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.

  4. 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.

  5. Radio-frequency sheaths physics: Experimental characterization on Tore Supra and related self-consistent modeling

    NASA Astrophysics Data System (ADS)

    Jacquot, Jonathan; Milanesio, Daniele; Colas, Laurent; Corre, Yann; Goniche, Marc; Gunn, Jamie; Heuraux, Stéphane; Kubi?, Martin

    2014-06-01

    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.

  6. 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.

  7. Effect of the levitating microparticle cloud on radiofrequency argon plasma

    SciTech Connect

    Mitic, S.; Pustylnik, M. Y.; Klumov, B. A.; Morfill, G. E. [Max-Planck-Institut fuer Extraterrestrische Physik, Giessenbachstrasse 1, 85741, Garching (Germany)

    2010-06-16

    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.

  8. 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.

  9. Treatment of trigeminal neuralgia: role of radiofrequency ablation.

    PubMed

    Emril, Dessy R; Ho, Kok-Yuen

    2010-01-01

    Trigeminal neuralgia (TN) is a neuropathic pain condition affecting the face. It has a significant impact on the quality of life and physical function of patients. Evidence suggests that the likely etiology is vascular compression of the trigeminal nerve leading to focal demyelination and aberrant neural discharge. Secondary causes such as multiple sclerosis or brain tumors can also produce symptomatic TN. Treatment must be individualized to each patient. Carbamazepine remains the drug of choice in the first-line treatment of TN. Minimally invasive interventional pain therapies and surgery are possible options when drug therapy fails. Younger patients may benefit from microvascular decompression. Elderly patients with poor surgical risk may be more suitable for percutaneous trigeminal nerve rhizolysis. The technique of radiofrequency rhizolysis of the trigeminal nerve is described in detail in this review. PMID:21311718

  10. SUPERCONDUCTING RADIO-FREQUENCY MODULES TEST FACILITY OPERATING EXPERIENCE

    SciTech Connect

    Soyars, W.; Bossert, R.; Darve, C.; Degraff, B.; Klebaner, A.; Martinez, A.; Pei, L.; Theilacker, J. [Fermi National Accelerator Laboratory Batavia, IL, 60510 (United States)

    2008-03-16

    Fermilab is heavily engaged and making strong technical contributions to the superconducting radio-frequency research and development program (SRF R and 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 the SRF R and D needs. The project's first stage 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 Meson Detector Building (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.

  11. Treatment of trigeminal neuralgia: role of radiofrequency ablation

    PubMed Central

    Emril, Dessy R; Ho, Kok-Yuen

    2010-01-01

    Trigeminal neuralgia (TN) is a neuropathic pain condition affecting the face. It has a significant impact on the quality of life and physical function of patients. Evidence suggests that the likely etiology is vascular compression of the trigeminal nerve leading to focal demyelination and aberrant neural discharge. Secondary causes such as multiple sclerosis or brain tumors can also produce symptomatic TN. Treatment must be individualized to each patient. Carbamazepine remains the drug of choice in the first-line treatment of TN. Minimally invasive interventional pain therapies and surgery are possible options when drug therapy fails. Younger patients may benefit from microvascular decompression. Elderly patients with poor surgical risk may be more suitable for percutaneous trigeminal nerve rhizolysis. The technique of radiofrequency rhizolysis of the trigeminal nerve is described in detail in this review. PMID:21311718

  12. 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

  13. Image-guided percutaneous radiofrequency ablation for osteoid osteomas.

    PubMed

    Venbrux, Anthony C; Montague, Brian J; Murphy, Kieran P J; Bobonis, Lauren A; Washington, Stanley B; Soltes, Amy P; Frassica, Frank J

    2003-03-01

    The authors present a retrospective analysis of the technical and clinical successes, complications, and clinical follow-up of image-guided percutaneous radiofrequency (RF) ablation of osteoid osteomas. Nine patients with osteoid osteomas underwent image-guided localization of osteoid osteomas. Outpatient percutaneous therapy (13 procedures) was performed under general anesthesia after image-guided localization of the nidus. Initial technical success was achieved in seven of nine patients. Two initial technical and clinical failures occurred early in this experience because of failure to adequately enter the nidus with use of fluoroscopic imaging alone. Clinical success was achieved in eight of nine patients. No major immediate or delayed complications were observed. PMID:12631644

  14. Radiofrequency superconductivity applied to free-electron lasers

    SciTech Connect

    Bohn, C.L.; Benson, S.V. [Thomas Jefferson National Accelerator Facility, Newport News, VA (United States)

    1998-01-01

    Low wall losses and low wakefields inherent in superconducting radiofrequency (srf) cavities make them attractive candidates for accelerators that operate efficiently at high continuous-wave (cw) gradients. Such accelerators are desirable for free-electron lasers (FELs) that extract high-power cw light from a high-average-current electron beam, or that produce ultrashort-wavelength light from a high-energy electron beam. Efficiency is a prime consideration in the former case, while high electron-beam quality is a prime consideration in the latter case. This paper summarizes the status of FEL projects involving srf accelerators. It also introduces Jefferson Lab`s srf FEL and surveys its design because it is a new machine, with commissioning having commenced in October 1997. Once commissioning is complete, this FEL should produce tunable, cw, kW-level light at 3-6 {mu}m wavelength.

  15. 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.

  16. Reactivable passive radio-frequency identification temperature indicator

    NASA Astrophysics Data System (ADS)

    Windl, Roman; Bruckner, Florian; Abert, Claas; Suess, Dieter; Huber, Thomas; Vogler, Christoph; Satz, Armin

    2015-05-01

    A low cost, passive radio-frequency identification (RFID) temperature indicator with (re-) activation at any point of time is presented. The capability to detect a temperature excursion is realized by magnets and a solution with a melting point at the critical temperature. As the critical temperature is exceeded, a magnetic indicator switches to non-reversible and this can be monitored via a giant magnetoresistance sensor connected to a RFID tag. Depending on the solutions or metal alloys, detection of critical temperatures in a wide range from below 0 °C and up to more than 100 °C is possible. The information if a threshold temperature was exceeded (indicator state) as well as the identification number, current temperature, and user defined data can be obtained via RFID.

  17. 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.

  18. Single-crystalline graphene radio-frequency nanoswitches

    NASA Astrophysics Data System (ADS)

    Li, Peng; Cui, Tianhong

    2015-07-01

    Growth of monolayer single-crystalline graphene (SCG) using the low-pressure chemical vapor deposition method is reported. Graphene’s superb quality and single-crystalline nature were characterized and verified by Raman microscopy, atomic force microscopy, and carrier mobility measurement. Radio-frequency (RF) nanoelectromechanical switches based on coplanar waveguide double-clamped SCG membrane were achieved, and the superb properties of SCG enable the switches to operate at a pull-in voltage as low as 1?V, with switch time in the nanosecond regime. Owing to their single-crystalline nature, the switches’ lifetime (>5000 times) is much longer than that of polycrystalline graphene ones reported. The RF devices exhibit good isolation (?30?dB at 40?GHz (Ka band)), which can be further improved by SCG’s conductivity variation due to actuation voltage.

  19. Osteoid Osteoma: Can Impedance Levels in Radiofrequency Thermocoagulation Predict Recurrence?

    PubMed Central

    Ockendon, Matthew; Gregory, Jonathan J.; Cribb, Gillian L.; Cool, W. Paul; Mangham, D. Charles; Lalam, Radhesh

    2011-01-01

    Objective. To evaluate rise in impedance during percutaneous radiofrequency thermocoagulation (PRFTC) of osteoid osteomas as a predictor of local recurrence. Design and Patients. A prospective study of 23 patients (24 PRFTC procedures) with minimum of 2.25-year followup (average 3.3 years). Average age 19.6 years (range 4–44), sex ratio 15?:?8 (male?:?female), 16 nondiaphyseal, 7 diaphyseal. Results. In 19 procedures, an increase in impedance was measured—no recurrences have occurred in this group to date. In 5 procedures, no increase in impedance was seen (3 non-diaphyseal, 2 diaphyseal), and 1 recurrence has been seen in this group to date. This difference is statistically significant with a P value of .05. PMID:22091385

  20. Laparoscopic Ultrasound-Guided Radiofrequency Ablation of Uterine Fibroids

    SciTech Connect

    Milic, Andrea [University of Toronto, Department of Medical Imaging (Canada); Asch, Murray R. [Lakeridge Health Corporation, Department of Diagnostic Radiology (Canada)], E-mail: masch@lakeridgehealth.on.ca; Hawrylyshyn, Peter A.; Allen, Lisa M. [Mount Sinai Hospital, Department of Obstetrics and Gynecology (Canada); Colgan, Terence J. [Mount Sinai Hospital, Department of Pathology (Canada); Kachura, John R. [Toronto General Hospital, Department of Diagnostic Imaging (Canada); Hayeems, Eran B. [Mount Sinai Hospital, Department of Diagnostic Imaging (Canada)

    2006-08-15

    Four patients with symptomatic uterine fibroids measuring less than 6 cm underwent laparoscopic ultrasound-guided radiofrequency ablation (RFA) using multiprobe-array electrodes. Follow-up of the treated fibroids was performed with gadolinium-enhanced magnetic resonance imaging (MRI) and patients' symptoms were assessed by telephone interviews. The procedure was initially technically successful in 3 of the 4 patients and MRI studies at 1 month demonstrated complete fibroid ablation. Symptom improvement, including a decrease in menstrual bleeding and pain, was achieved in 2 patients at 3 months. At 7 months, 1 of these 2 patients experienced symptom worsening which correlated with recurrent fibroid on MRI. The third, initially technically successfully treated patient did not experience any symptom relief after the procedure and was ultimately diagnosed with adenomyosis. Our preliminary results suggest that RFA is a technically feasible treatment for symptomatic uterine fibroids in appropriately selected patients.

  1. Ultrafast electron diffraction with radio-frequency compressed electron pulses

    SciTech Connect

    Chatelain, Robert P.; Morrison, Vance R.; Godbout, Chris; Siwick, Bradley J. [Departments of Physics and Chemistry, Center for the Physics of Materials, McGill University, Montreal (Canada)

    2012-08-20

    We report on the complete characterization of time resolution in an ultrafast electron diffraction (UED) instrument based on radio-frequency electron pulse compression. The temporal impulse response function of the instrument was determined directly in pump-probe geometry by performing electron-laser pulse cross-correlation measurements using the ponderomotive interaction. With optimal settings, a stable impulse response of 334{+-}10 fs was measured at a bunch charge of 0.1 pC (6.24 Multiplication-Sign 10{sup 5} electrons/pulse); a dramatic improvement compared to performance without pulse compression. Phase stability currently limits the impulse response of the UED diffractometer to the range of 334-500 fs, for bunch charges ranging between 0.1 and 0.6 pC.

  2. Electromagnetic and mechanical design of gridded radio-frequency cavity windows

    SciTech Connect

    Alsharo'a, Mohammad M.

    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.

  3. Virtual Radiofrequency Ablation of Liver Caroline Villard, Luc Soler, Nicolas Papier, Vincent Agnus, Sylvain Thery,

    E-print Network

    Essert-Villard, Caroline

    , high intensity focused ultrasound, cryotherapy, and radiofrequency (RF) that appears to be the easiest margin [2], which is mandatory to prevent local recurrence of a tumor after treatment, and to reduce

  4. Measurement of radio-frequency magnetic fluctuations in the VTF magnetic reconnection experiment

    E-print Network

    Whitney, John Peter, 1982-

    2004-01-01

    In this thesis work, I designed, fabricated, and calibrated, a radio-frequency magnetic probe, subsequently used to measure magnetic turbulance in the reconnecting plasmas of the Versatile Toroidal Facility (VTF). Reconnecting ...

  5. 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 ...

  6. Combined radiofrequency ablation and doxorubicin-eluting polymer implants for liver cancer treatment

    E-print Network

    Gao, Jinming

    .a.30926 Abstract: Previously, biodegradable polymer implants (polymer millirods) to release Mater Res 81A: 205­213, 2007 Key words: biodegradable polymer; polymer implants; intratumoral drugCombined radiofrequency ablation and doxorubicin- eluting polymer implants for liver cancer

  7. 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...

  8. Radio-Frequency Driven Dielectric Heaters for Non-Nuclear Testing in Nuclear Core Development

    NASA Technical Reports Server (NTRS)

    Sims, William Herbert, III (Inventor); Godfroy, Thomas J. (Inventor); Bitteker, Leo (Inventor)

    2006-01-01

    Apparatus and methods are provided through which a radiofrequency dielectric heater has a cylindrical form factor, a variable thermal energy deposition through variations in geometry and composition of a dielectric, and/or has a thermally isolated power input.

  9. Excessive Hyperthermic Necrosis of a Pulmonary Lobe after Hypertonic Saline-Enhanced Monopolar Radiofrequency Ablation

    SciTech Connect

    Kim, Tae Sung, E-mail: tskim@smc.samsung.co.kr; Lim, Hyo K. [Sungkyunkwan University School of Medicine, Department of Radiology and Center for Imaging Science, Samsung Medical Center (Korea, Republic of); Kim, Hojoong [Sungkyunkwan University School of Medicine, Division of Pulmonary and Critical Care Medicine, The Department of Medicine, Samsung Medical Center (Korea, Republic of)

    2006-02-15

    Although there has been a feasibility study of saline-enhanced radiofrequency ablation of the lung in rabbits, there has been no report on hypertonic saline-enhanced radiofrequency ablation of human pulmonary tumors or its complication. We report a case in which a large necrotic cavity was produced in the lung after hypertonic saline-enhanced radiofrequency ablation of recurrent metastatic tumor from hepatocellular carcinoma. Although hypertonic saline-enhanced radiofrequency ablation is powerful and efficient in local ablation, it is difficult to predict the exact extent of ablation, especially in the lungs. This can be dangerous, as there is a high chance of producing an ablation area much larger than expected and, hence, major complications. Special attention is required not to overablate while using this technique.

  10. Radiofrequency catheter ablation of atrioventricular nodal reciprocating tachycardia using intracardiac echocardiography in pregnancy.

    PubMed

    Bongiorni, Maria Grazia; Di Cori, Andrea; Soldati, Ezio; Zucchelli, Giulio; Segreti, Luca; Solarino, Gianluca; De Lucia, Raffaele; Marzilli, Mario

    2008-08-01

    We describe a case report of a 32-year-old woman during the 10th week of pregnancy with symptomatic and recurrent atrioventricular nodal reciprocating tachycardia successfully treated by conventional radiofrequency ablation, under intracardiac echocardiography surveillance. PMID:18460548

  11. A linear-in-dB radio-frequency power detector

    Microsoft Academic Search

    Janne-Wha Wu; Kai-Cheng Hsu; Wei-Ju Lai; Chih-Ho To; Sheng-Wen Chen; Ching-Wen Tang; Ying-Zong Juang

    2011-01-01

    An integrated circuit of radio-frequency power detection by a 0.18?m CMOS process with the output voltage linearly proportional to the input power in decibel is presented. The target dynamic range of this radio-frequency power detector design is 40 dB with the log-error being within ±1dB. Whatever the point of view is on dynamic range or logarithmic error, the working range

  12. Understanding Pound-Drever-Hall locking using voltage controlled radio-frequency oscillators: An undergraduate experiment

    Microsoft Academic Search

    C. E. Liekhus-Schmaltz; J. D. D. Martin

    2011-01-01

    We have developed a senior undergraduate experiment that illustrates frequency stabilization techniques using radio-frequency electronics. The primary objective is to frequency stabilize a voltage controlled oscillator to a cavity resonance at 800 MHz using the Pound-Drever-Hall method. This technique is commonly applied to stabilize lasers at optical frequencies. By using only radio-frequency equipment it is possible to systematically study aspects

  13. Electrochromic properties of niobium oxide thin films prepared by radio-frequency magnetron sputtering method

    Microsoft Academic Search

    Toshiro Maruyama; Susumu Arai

    1993-01-01

    Electrochromic niobium oxide thin films were prepared by a radio-frequency magnetron sputtering method. Amorphous Nb2O5 thin films deposited at radio-frequency power 100 W showed the electrochromic behavior: Reduction and oxidation of the films in 0.1 M Na2CO3+0.1 M NaHCO3 buffer solution resulted in coloration and bleaching, respectively. Coulometry indicated that the coloration efficiency was 10 cm2\\/C.

  14. Radiofrequency Ablation of Benign Thyroid Nodules and Recurrent Thyroid Cancers: Consensus Statement and Recommendations

    PubMed Central

    Na, Dong Gyu; Lee, Jeong Hyun; Jung, So Lyung; Kim, Ji-hoon; Sung, Jin Yong; Shin, Jung Hee; Kim, Eun-Kyung; Lee, Joon Hyung; Kim, Dong Wook; Park, Jeong Seon; Kim, Kyu Sun; Baek, Seon Mi; Lee, Younghen; Chong, Semin; Sim, Jung Suk; Huh, Jung Yin; Bae, Jae-Ik; Kim, Kyung Tae; Han, Song Yee; Bae, Min Young; Kim, Yoon Suk

    2012-01-01

    Thermal ablation using radiofrequency is a new, minimally invasive modality employed as an alternative to surgery in patients with benign thyroid nodules and recurrent thyroid cancers. The Task Force Committee of the Korean Society of Thyroid Radiology has developed recommendations for the optimal use of radiofrequency ablation for thyroid nodules. These recommendations are based on a comprehensive analysis of the current literature, the results of multicenter studies, and expert consensus. PMID:22438678

  15. Effects of Cell Phone Radiofrequency Signal Exposure on Brain Glucos Metabolism

    SciTech Connect

    Volkow, N.D.; Wang, G.; Volkow, N.D.; Tomasi, D.; Wang, G.-J.; Vaska, P.; Fowler, J.S.; Telang, F.; Alexoff, D.; Logan, J.; Wong, C.

    2011-03-01

    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. To evaluate if acute cell phone exposure affects brain glucose metabolism, a marker of brain activity. 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 ({sup 18}F)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 cm{sup 3}) and P < .05 (corrected for multiple comparisons) were considered significant. Brain glucose metabolism computed as absolute metabolism ({micro}mol/100 g per minute) and as normalized metabolism (region/whole brain). 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 {micro}mol/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). 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.

  16. 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

  17. 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

  18. Workgroup Report: Base Stations and Wireless Networks—Radiofrequency (RF) Exposures and Health Consequences

    PubMed Central

    Valberg, Peter A.; van Deventer, T. Emilie; Repacholi, Michael H.

    2007-01-01

    Radiofrequency (RF) waves have long been used for different types of information exchange via the airwaves—wireless Morse code, radio, television, and wireless telephony (i.e., construction and operation of telephones or telephonic 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 telephony and base stations are not likely to adversely affect human health. PMID:17431492

  19. 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

  20. Male reproductive health under threat: Short term exposure to radiofrequency radiations emitted by common mobile jammers

    PubMed Central

    Mortazavi, SMJ; Parsanezhad, ME; Kazempour, M; Ghahramani, P; Mortazavi, AR; Davari, M

    2013-01-01

    BACKGROUND: Modern life prompted man to increasingly generate, transmit and use electricity that leads to exposure to different levels of electromagnetic fields (EMFs). Substantial evidence indicates that exposure to common sources of EMF such as mobile phones, laptops or wireless internet-connected laptops decreases human semen quality. In some countries, mobile jammers are occasionally used in offices, shrines, conference rooms and cinemas to block the signal. AIMS: To the best of our knowledge, this is the first study to investigate the effect of short term exposure of human sperm samples to radiofrequency (RF) radiations emitted by common mobile jammers. SUBJECTS AND METHODS: Fresh semen samples were collected by masturbation from 30 healthy donors who had referred to Infertility Treatment Center at the Mother and Child Hospital with their wives. Female problem was diagnosed as the reason for infertility in these couples. STATISTICAL ANALYSIS: T-test and analysis of variance were used to show statistical significance. RESULTS: The motility of sperm samples exposed to jammer RF radiation for 2 or 4 h were significantly lower than those of sham-exposed samples. These findings lead us to the conclusion that mobile jammers may significantly decrease sperm motility and the couples’ chances of conception. CONCLUSION: Based on these results, it can be suggested that in countries that have not banned mobile jammer use, legislations should be urgently passed to restrict the use of these signal blocking devices in public or private places. PMID:24082653

  1. Percutaneous microwave ablation vs radiofrequency ablation in the treatment of hepatocellular carcinoma

    PubMed Central

    Poulou, Loukia S; Botsa, Evanthia; Thanou, Ioanna; Ziakas, Panayiotis D; Thanos, Loukas

    2015-01-01

    Hepatocellular cancer ranks fifth among cancers and is related to chronic viral hepatitis, alcohol abuse, steatohepatitis and liver autoimmunity. Surgical resection and orthotopic liver transplantation have curative potential, but fewer than 20% of patients are suitable candidates. Interventional treatments are offered to the vast majority of patients. Radiofrequency (RFA) and microwave ablation (MWA) are among the therapeutic modalities, with similar indications which include the presence of up to three lesions, smaller than 3 cm in size, and the absence of extrahepatic disease. The therapeutic effect of both methods relies on thermal injury, but MWA uses an electromagnetic field as opposed to electrical current used in RFA. Unlike MWA, the effect of RFA is partially limited by the heat-sink effect and increased impedance of the ablated tissue. Compared with RFA, MWA attains a more predictable ablation zone, permits simultaneous treatment of multiple lesions, and achieves larger coagulation volumes in a shorter procedural time. Major complications of both methods are comparable and infrequent (approximately 2%-3%), and they include haemorrhage, infection/abscess, visceral organ injury, liver failure, and pneumothorax. RFA may incur the additional complication of skin burns. Nevertheless, there is no compelling evidence for differences in clinical outcomes, including local recurrence rates and survival. PMID:26052394

  2. Development of a novel radio-frequency negative hydrogen ion source in conically converging configuration.

    PubMed

    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. PMID:24593552

  3. Investigation of niobium surface structure and composition for improvement of superconducting radio-frequency cavities

    NASA Astrophysics Data System (ADS)

    Trenikhina, Yulia

    Nano-scale investigation of intrinsic properties of niobium near-surface is a key to control performance of niobium superconducting radio-frequency cavities. Mechanisms responsible for the performance limitations and their empirical remedies needs to be justified in order to reproducibly control fabrication of SRF cavities with desired characteristics. The high field Q-slope and mechanism behind its cure (120°C mild bake) were investigated by comparison of the samples cut out of the cavities with high and low dissipation regions. Material evolution during mild field Q-slope nitrogen treatment was characterized using the coupon samples as well as samples cut out of nitrogen treated cavity. Evaluation of niobium near-surface state after some typical and novel cavity treatments was accomplished. Various TEM techniques, SEM, XPS, AES, XRD were used for the structural and chemical characterization of niobium near-surface. Combination of thermometry and structural temperature-dependent comparison of the cavity cutouts with different dissipation characteristics revealed precipitation of niobium hydrides to be the reason for medium and high field Q-slopes. Step-by-step effect of the nitrogen treatment processing on niobium surface was studied by analytical and structural characterization of the cavity cutout and niobium samples, which were subject to the treatment. Low concentration nitrogen doping is proposed to explain the benefit of nitrogen treatment. Chemical characterization of niobium samples before and after various surface processing (Electropolishing (EP), 800°C bake, hydrofluoric acid (HF) rinsing) showed the differences that can help to reveal the microscopic effects behind these treatments as well as possible sources of surface contamination.

  4. 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

  5. OFDR based distributed temperature sensor using the three-channel simultaneous radio-frequency lock-in technique

    NASA Astrophysics Data System (ADS)

    Chen, Ke; Zhou, Xinlei; Peng, Wei; Yu, Qingxu

    2015-05-01

    Weak signal detection for single-mode fiber-optic distributed temperature sensor (DTS) is a key technology to achieve better performance. A hybrid technique combining the incoherent optical frequency domain reflectometry (IOFDR) and the three-channel simultaneous radio-frequency (RF) lock-in amplifier (LIA) is presented to improve the signal-to-noise ratio (SNR) of the measured spontaneous Raman backscattered light. The field programmable gate array (FPGA) based RF-LIA is designed with a novel and simple structure. The measurement frequency range is achieved from 1 kHz to 100 MHz. Experimental results show that the backscattered light signal of picowatt level can be detected with high SNR. With a 2.5 km single-mode fiber, a 1064 nm laser source, and the measurement time of 500 s, this sensing system can reach a spatial resolution of 0.93 m and a temperature resolution of about 0.2°C.

  6. Formation of spatially periodic fronts of high-energy electrons in a radio-frequency driven surface microdischarge

    SciTech Connect

    Dedrick, J.; Boswell, R. W.; Charles, C. [Space Plasma, Power and Propulsion Laboratory, Research School of Physics and Engineering, Australian National University, ACT 0200 (Australia)] [Space Plasma, Power and Propulsion Laboratory, Research School of Physics and Engineering, Australian National University, ACT 0200 (Australia); O'Connell, D.; Gans, T. [York Plasma Institute, Department of Physics, University of York, Heslington, York YO10 5DD (United Kingdom)] [York Plasma Institute, Department of Physics, University of York, Heslington, York YO10 5DD (United Kingdom)

    2013-01-21

    The generation of spatially periodic fronts of high-energy electrons (>13.48 eV) has been investigated in a radio-frequency surface microdischarge in atmospheric-pressure argon. Optical emission spectroscopy is used to study the Ar I 2p{sub 1}-1s{sub 2} transition surrounding a filamentary microdischarge, both spatially and with respect to the phase of the applied voltage. The formation of excitation fronts, which remain at a constant propagation distance throughout the RF cycle and for the duration of the pulse, may be explained by a localized increase in the electric field at the tip of surface-charge layers that are deposited during the extension phase.

  7. Radiofrequency catheter ablation of atypical atrial flutter in dogs.

    PubMed

    Santilli, Roberto A; Ramera, Lucia; Perego, Manuela; Moretti, Paolo; Spadacini, Giammario

    2014-03-01

    Five dogs were presented to our institution for fatigue caused by an incessant supraventricular tachycardia. In all dogs, an ECG on admission showed a narrow QRS complex tachycardia with a median ventricular cycle length of 220 ms (range 180-360 ms), and a positive atrial depolarization identifiable in the ST segment following the previous QRS complex. There was a 1:1 atrioventricular conduction ratio in all but one dog, which presented with 2:1 atrioventricular block. Electrophysiologic studies identified the underlying arrhythmogenic mechanism as a right atrial macro-reentrant tachycardia with two distinct isthmic areas: right septal (RS) in three dogs and right atrial free wall (RAFW) in two dogs. Linear radiofrequency catheter ablation was performed during tachycardia in all dogs at the identified isthmic area, which acutely blocked the macroreentrant circuit. At 18-month follow-up, 3 dogs (1 with RAFW isthmus and 2 with RS isthmus) showed no recurrence of the arrhythmia on Holter monitoring. One dog with RS isthmus showed recurrence of the supraventricular tachycardia 15 days post-ablation, and 1 dog with RAFW isthmus presented with persistent atrial fibrillation 2 months post-ablation. PMID:24461642

  8. Percutaneous radiofrequency ablation of spinal osteoid osteoma under CT guidance

    PubMed Central

    Morassi, L G; Kokkinis, K; Karargyris, O; Vlachou, I; Kalokairinou, K; Pneumaticos, S G

    2014-01-01

    Objective: Osteoid osteoma (OO) accounts for approximately 10–12% of all benign bone tumours and 3% of all bone tumours. Spinal involvement appears in 10–25% of all cases. The purpose of this study was to evaluate the safety and efficacy of CT-guided radiofrequency (RF) ablation in the treatment of spinal OOs and report our experience. Methods: 13 patients suffering from spinal OO and treated at the authors' institution using CT-guided RF ablation were retrospectively evaluated. The RF probe was introduced through a 11-G Jamshidi® needle, and the lesion was heated at 90?°C for 6?min. Results: All procedures were considered technically successful as the correct positioning of the probe was proven by CT. 11 of the 13 patients reported pain relief after RF ablation. In two cases, RF ablation was repeated 1 month after the first procedure. Pain relief was achieved in both cases after the second procedure. No recurrence was reported throughout the follow-up. No complications like skin burn, soft-tissue haematoma, infection, vessel damage or neurological deficit were reported. Conclusion: This study demonstrates that CT-guided percutaneous RF ablation is a safe and effective method for the treatment of spinal OOs. Advances in knowledge: The data of this study support the efficacy and safety of the recently applied CT-guided percutaneous RF ablation technique for the treatment of spinal OOs. PMID:24712322

  9. A prospective clinical trial of radiofrequency ablation for pulmonary metastases

    PubMed Central

    WANG, YIZONG; LU, XUEGUAN; WANG, YING; LI, WENTAO; LI, GUODONG; ZHOU, JUN

    2015-01-01

    Pulmonary oligometastases can be treated by local treatment options, such as resection, radiofrequency ablation (RFA), and radiotherapy, in selected patients. In the present study, 67 patients with 115 pulmonary metastases were treated, and all the lesions were treated by RFA and followed with a computed tomography scan. The local control, overall survival (OS), progression-free survival (PFS) and treatment-related toxicity were observed. Median follow-up duration after the initial RFA was 24 months (range, 3–39 months). The median PFS from RFA was 14 months [95% confidence interval (CI), 11.6–16.4]. The 6-, 12- and 18-month PFS rates were 82.1, 55.7 and 27.5%, respectively. The median OS rate from RFA was 24 months (95% CI, 18.2–29.8). The 1-, 2- and 3-year OS rates were 83.6, 46.3 and 14.3%, respectively. Primary tumor was significantly correlated to PFS and OS on multivariate analysis, and other variates showed no significance. Therefore, RFA is safe for patient treatment and can be considered as a promising treatment option for patients with pulmonary metastases. PMID:26137267

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

    SciTech Connect

    Lencioni, Riccardo, E-mail: Lencioni@do.med.unipi.it; Crocetti, Laura; Cioni, Roberto [University of Pisa, Division of Diagnostic and Interventional Radiology, Department of Oncology, Transplants, and Advanced Technologies in Medicine (Italy); Mussi, Alfredo [University of Pisa, Division of Thoracic Surgery, Cardiac and Thoracic Department (Italy); Fontanini, Gabriella [University of Pisa, Division of Pathology, Department of Oncology, Transplants, and Advanced Technologies in Medicine (Italy); Ambrogi, Marcello [University of Pisa, Division of Thoracic Surgery, Cardiac and Thoracic Department (Italy); Franchini, Chiara; Cioni, Dania [University of Pisa, Division of Diagnostic and Interventional Radiology, Department of Oncology, Transplants, and Advanced Technologies in Medicine (Italy); Fanucchi, Olivia [University of Pisa, Division of Thoracic Surgery, Cardiac and Thoracic Department (Italy); Gemignani, Raffaello; Baldassarri, Rubia [Cisanello University Hospital, Division of Anesthesiology (Italy); Angeletti, Carlo Alberto [University of Pisa, Division of Thoracic Surgery, Cardiac and Thoracic Department (Italy); Bartolozzi, Carlo [University of Pisa, Division of Diagnostic and Interventional Radiology, Department of Oncology, Transplants, and Advanced Technologies in Medicine (Italy)

    2004-11-15

    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 malignancies. In theory, lung tumors are well suited to RF ablation because the surrounding air in adjacent normal parenchyma provides an insulating effect, thus facilitating energy concentration within the tumor tissue. Experimental studies in rabbits have confirmed that lung RF ablation can be safely and effectively performed via a percutaneous, transthoracic approach, and have prompted the start of clinical investigation. Pilot clinical studies have shown that RF ablation enables successful treatment of relatively small lung malignancies with a high rate of complete response and acceptable morbidity, and have suggested that the technique could represent a viable alternate or complementary treatment method for patients with non-small cell lung cancer or lung metastases of favorable histotypes who are not candidates for surgical resection. This article gives an overview of lung RF ablation, discussing experimental animal findings, rationale for clinical application, technique and methodology, clinical results, and complications.

  11. 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.

  12. Dynamic impedance measurements during radio-frequency heating of cornea.

    PubMed

    Choi, Bernard; Kim, Jihoon; Welch, Ashley J; Pearce, John A

    2002-12-01

    Hyperopia affects approximately 25% of the population. The aim of different heating modalities for the treatment of hyperopia is to steepen the central curvature of the cornea. Conductive keratoplasty (CK) involves the placement of radio-frequency (RF) lesions around a 7-mm-diameter ring concentric with the pupil of the eye. Dynamics of lesion formation during CK depend on corneal electrical impedance, which is expected to change during each 600-ms-long macropulse. The purpose of this study was to measure impedance dynamics during CK. RF lesions were made in in vitro porcine eyes at different power settings. Voltage and current measurements were acquired using a high-speed computer-based data acquisition system. Root-mean-square voltages (VRMS) and curre (IRMS) were calculated for each micropulse, and impedance was determined by calculating the quotient VRMS/IRMS. Initial corneal impedance in vitro was approximately 2000 ohms. During the macropulse, impedance decreased initially due to increased mobility of conductive ions. At higher power settings (e.g., > 70%, or maximum peak-to-peak voltage of 233 V), impedance increased after the initial decrease, indicative of local water vaporization and/or tissue coagulation. Preliminary impedance data obtained for in vivo porcine eyes were similar in magnitude to the in vitro values. PMID:12549743

  13. 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).

  14. Radio-frequency capacitance spectroscopy of metallic nanoparticles.

    PubMed

    Frake, James C; Kano, Shinya; Ciccarelli, Chiara; Griffiths, Jonathan; Sakamoto, Masanori; Teranishi, Toshiharu; Majima, Yutaka; Smith, Charles G; Buitelaar, Mark R

    2015-01-01

    Recent years have seen great progress in our understanding of the electronic properties of nanomaterials in which at least one dimension measures less than 100?nm. However, contacting true nanometer scale materials such as individual molecules or nanoparticles remains a challenge as even state-of-the-art nanofabrication techniques such as electron-beam lithography have a resolution of a few nm at best. Here we present a fabrication and measurement technique that allows high sensitivity and high bandwidth readout of discrete quantum states of metallic nanoparticles which does not require nm resolution or precision. This is achieved by coupling the nanoparticles to resonant electrical circuits and measurement of the phase of a reflected radio-frequency signal. This requires only a single tunnel contact to the nanoparticles thus simplifying device fabrication and improving yield and reliability. The technique is demonstrated by measurements on 2.7?nm thiol coated gold nanoparticles which are shown to be in excellent quantitative agreement with theory. PMID:26042729

  15. A biomechanical assessment of tendon repair after radiofrequency treatment.

    PubMed

    Tibor, Lisa M; Leek, Bryan T; Chase, Derek C; Healey, Robert M; Linn, Michael S; Tasto, James P; Amiel, David

    2012-09-01

    After acute tendon injury, rapid mobilization prevents adhesions and improves the ultimate strength of the repair. Radiofrequency (RF) ablation is proposed to enhance angiogenesis in the early stages of healing. The mechanism and effect of RF have not yet been described in an animal model of tendon injury. To investigate the biomechanical effect of bipolar RF on acute injury in a rabbit model of partial Achilles tendon transection and suture repair, RF-treated tendon repairs were compared to untreated tendons. Cross-sectional area, Young's modulus, and ultimate tensile strength were determined. At 6 and 12 weeks after repair, RF-treated tendons had significant increases in cross-sectional area (P<.001; P< .0001) and ultimate tensile strength (P<.0001; P<.01). Young modulus of RF-treated tendons was increased at 6 weeks but not at 12 weeks (P<.01) Compared with untreated tendons, RF-treated tendons showed faster return to mechanical integrity. This may allow earlier rehabilitation. PMID:23365813

  16. 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.

  17. 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.

  18. 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.

  19. Suppression of hydride precipitates in niobium superconducting radio-frequency cavities

    NASA Astrophysics Data System (ADS)

    Ford, Denise C.; Cooley, Lance D.; Seidman, David N.

    2013-10-01

    Niobium hydride is a suspected contributor to degraded niobium superconducting radio-frequency (SRF) cavity performance by Q slope and Q disease. The concentration and distribution of hydrogen atoms in niobium can be strongly affected by the cavity processing treatments. This study provides guidance for cavity processing based on density functional theory calculations of the properties of common processing impurity species—hydrogen, oxygen, nitrogen, and carbon—in the body-centered cubic (bcc) niobium lattice. We demonstrate that some fundamental properties are shared between the impurity atoms, such as anionic character in niobium. The strain field produced, however, by hydrogen atoms is both geometrically different and substantially weaker than the strain field produced by the other impurities. We focus on the interaction between oxygen and hydrogen atoms in the lattice, and demonstrate that the elastic interactions between these species and the bcc niobium lattice cause trapping of hydrogen and oxygen atoms by bcc niobium lattice vacancies. We also show that the attraction of oxygen to a lattice vacancy is substantially stronger than the attraction of hydrogen to the vacancy. Additionally, hydrogen dissolved in niobium tetrahedral interstitial sites can be trapped by oxygen, nitrogen and possibly carbon atoms dissolved in octahedral interstitial sites. These results indicate that the concentration of oxygen in the bcc lattice can have a strong impact on the ability of hydrogen to form detrimental phases. Based on our results and a literature survey, we propose a mechanism for the success of the low-temperature annealing step applied to niobium SRF cavities. We also recommend further examination of nitrogen and carbon in bcc niobium, and particularly the role that nitrogen can play in preventing detrimental hydride phase formation.

  20. Optoacoustic monitoring of real-time lesion formation during radiofrequency catheter ablation

    NASA Astrophysics Data System (ADS)

    Pang, Genny A.; Bay, Erwin; Deán-Ben, Xosé L.; Razansky, Daniel

    2015-03-01

    Current radiofrequency cardiac ablation procedures lack real-time lesion monitoring guidance, limiting the reliability and efficacy of the treatment. The objective of this work is to demonstrate that optoacoustic imaging can be applied to develop a diagnostic technique applicable to radiofrequency ablation for cardiac arrhythmia treatment with the capabilities of real-time monitoring of ablated lesion size and geometry. We demonstrate an optoacoustic imaging method using a 256-detector optoacoustic imaging probe and pulsed-laser illumination in the infrared wavelength range that is applied during radiofrequency ablation in excised porcine myocardial tissue samples. This technique results in images with high contrast between the lesion volume and unablated tissue, and is also capable of capturing time-resolved image sequences that provide information on the lesion development process. The size and geometry of the imaged lesion were shown to be in excellent agreement with the histological examinations. This study demonstrates the first deep-lesion real-time monitoring for radiofrequency ablation generated lesions, and the technique presented here has the potential for providing critical feedback that can significantly impact the outcome of clinical radiofrequency ablation procedures.

  1. 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

  2. Radiofrequency balloon angioplasty. Rationale and proof of principle

    SciTech Connect

    Becker, G.J.; Lee, B.I.; Waller, B.F.; Barry, K.J.; Kaplan, J.; Connolly, R.; Dreesen, R.G.; Nardella, P.

    1988-11-01

    Post-angioplasty restenosis (PARS) in atherosclerotic lesions of medium and small arteries occurs in about one-third of cases in the first year following percutaneous transluminal angioplasty (PTA) (early PARS). PARS includes acute spasm, dissection with reclosure, elastic recoil, fibrocellular proliferative response, and progressive atheromatous disease. Fibrocellular proliferation (possibly initiated by platelet derived growth factor) is felt to be culpable in many cases of early PARS (months). Pharmacologic regimens, stents, and thermal welding of the intimal-medial cracks of PTA are among the interventions being developed to deal with PARS. Radiofrequency (RF) current as a source of thermal energy may be useful in combination with balloon angioplasty to reduce PARS. Ideally, this combination would (1) weld intimal-medial cracks of PTA; (2) mold plaque and normal vessel to increase lumen diameters without creating intimal-medial cracks; and (3) destroy medial smooth muscle cells and multipotential cells (cellular substrate of PARS). Canine in vivo studies have established the feasibility of RF-mediated vascular tissue welding. Human aortic specimens (N = 28) were manually dissected into intima-media and media-adventitia layers. Bipolar RF energy (650 KHz, total 300 J) and mechanical pressure (1 atm) (experimental group, N = 24) or mechanical pressure alone (control group, N = 4) were applied to the reapposed specimen layers in a special chamber. The chamber was modified with a bipolar electrode designed to reproduce that planned for an RF balloon angioplasty catheter. Welding was demonstrated in normal and atherosclerotic treated specimens (23/24 or 96%) but not controls (0/4).

  3. Radiofrequency ablation during continuous saline infusion can extend ablation margins

    PubMed Central

    Ishikawa, Toru; Kubota, Tomoyuki; Horigome, Ryoko; Kimura, Naruhiro; Honda, Hiroki; Iwanaga, Akito; Seki, Keiichi; Honma, Terasu; Yoshida, Toshiaki

    2013-01-01

    AIM: To determine whether fluid injection during radiofrequency ablation (RFA) can increase the coagulation area. METHODS: Bovine liver (1-2 kg) was placed on an aluminum tray with a return electrode affixed to the base, and the liver was punctured by an expandable electrode. During RFA, 5% glucose; 50% glucose; or saline fluid was infused continuously at a rate of 1.0 mL/min through the infusion line connected to the infusion port. The area and volume of the thermocoagulated region of bovine liver were determined after RFA. The Joule heat generated was determined from the temporal change in output during the RFA experiment. RESULTS: No liquid infusion was 17.3 ± 1.6 mL, similar to the volume of a 3-cm diameter sphere (14.1 mL). Mean thermocoagulated volume was significantly larger with continuous infusion of saline (29.3 ± 3.3 mL) than with 5% glucose (21.4 ± 2.2 mL), 50% glucose (16.5 ± 0.9 mL) or no liquid infusion (17.3 ± 1.6 mL). The ablated volume for RFA with saline was approximately 1.7-times greater than for RFA with no liquid infusion, representing a significant difference between these two conditions. Total Joule heat generated during RFA was highest with saline, and lowest with 50% glucose. CONCLUSION: RFA with continuous saline infusion achieves a large ablation zone, and may help inhibit local recurrence by obtaining sufficient ablation margins. RFA during continuous saline infusion can extend ablation margins, and may be prevent local recurrence. PMID:23483097

  4. 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.

  5. Radiofrequency neurotomy for the treatment of third occipital headache

    PubMed Central

    Govind, J; King, W; Bailey, B; Bogduk, N

    2003-01-01

    Objective: To evaluate the efficacy of a revised technique of percutaneous radiofrequency neurotomy for third occipital headache. Methods: The revisions included using a large gauge electrode, ensuring minimum separation between the three electrode placements, and holding the electrode in place by hand. The revised technique was used to treat 51 nerves in 49 patients diagnosed as suffering from third occipital headache on the basis of controlled diagnostic blocks of the third occipital nerve. The criteria for successful outcome were complete relief of pain for at least 90 days associated with restoration of normal activities of daily living, and no use of drug treatment for the headache. Results: Of the 49 patients, 43 (88%) achieved a successful outcome. The median duration of relief in these patients was 297 days, with eight patients continuing to have ongoing relief. Fourteen patients underwent a repeat neurotomy to reinstate relief, with 12 (86%) achieving a successful outcome. The median duration of relief in these patients was 217 days, with six patients having ongoing relief. Side effects of the procedure were consistent with coagulation of the third occipital nerve and consisted of slight ataxia, numbness, and temporary dysaesthesia. No side effects required intervention, and they were tolerated by the patients in exchange for the relief of headache. Conclusions: Use of the revised procedure greatly improved the rather low success rate previously encountered with third occipital neurotomy. Although the relief of headache is limited in duration, it is profound and can be reinstated by repeat neurotomy. No other form of treatment has been validated for this common form of headache. PMID:12486273

  6. IEEE TRANSACTIONS ON GEOSCIENCE AND REMOTE SENSING, VOL. 46, NO. 10, OCTOBER 2008 3123 Detection of Radio-Frequency Interference

    E-print Network

    Ruf, Christopher

    of Radio-Frequency Interference for the Aquarius Radiometer Sidharth Misra and Christopher S. Ruf, Fellow, IEEE Abstract--A radio-frequency interference (RFI) detection algo- rithm has been developed to measure SSS [2]. The contamination of radiometer data is possible if man-made sources of radio- frequency

  7. Radio-frequency single-electron transistor: Toward the shot-noise limit A. Aassime,a)

    E-print Network

    Radio-frequency single-electron transistor: Toward the shot-noise limit A. Aassime,a) D. Gunnarsson for publication 28 September 2001 We have fabricated an aluminum single-electron transistor and characterized is embedded. We measured the charge sensitivity of this radio-frequency single-electron transistor to be 3

  8. Biophysical characteristics of radiofrequency lesion formation in vivo: Dynamics of catheter tip–tissue contact evaluated by intracardiac echocardiography

    Microsoft Academic Search

    Jonathan M. Kalman; Adam P. Fitzpatrick; Jeffrey E. Olgin; Michael C. Chin; Randall J. Lee; Melvin M. Scheinman; Michael D. Lesh

    1997-01-01

    During clinical radiofrequency catheter ablation a wide range of delivered power may be necessary to achieve success despite an apparently stable catheter position on fluoroscopy. The purpose of this study was to use intracardiac echocardiography to characterize the relation between catheter tip–tissue contact and the efficiency of heating during applications of radiofrequency energy in vivo and to determine whether intracardiac

  9. Characterization of buried glands before and after radiofrequency ablation by using 3-dimensional optical coherence tomography (with videos)

    PubMed Central

    Zhou, Chao; Tsai, Tsung-Han; Lee, Hsiang-Chieh; Kirtane, Tejas; Figueiredo, Marisa; Tao, Yuankai K.; Ahsen, Osman O.; Adler, Desmond C.; Schmitt, Joseph M.; Huang, Qin; Fujimoto, James G.; Mashimo, Hiroshi

    2012-01-01

    Background Radiofrequency ablation (RFA) is an endoscopic technique used to eradicate Barrett’s esophagus (BE). However, such ablation can commonly lead to neosquamous epithelium overlying residual BE glands not visible by conventional endoscopy and may evade detection on random biopsy samples. Objective To demonstrate the capability of endoscopic 3-dimensional optical coherence tomography (3D-OCT) for the identification and characterization of buried glands before and after RFA therapy. Design Cross-sectional study. Setting Single teaching hospital. Patients Twenty-six male and 1 female white patients with BE undergoing RFA treatment. Interventions 3D-OCT was performed at the gastroesophageal junction in 18 patients before attaining complete eradication of intestinal metaplasia (pre–CE-IM group) and in 16 patients after CE-IM (post–CE-IM group). Main Outcome Measurements Prevalence, size, and location of buried glands relative to the squamocolumnar junction. Results 3D-OCT provided an approximately 30 to 60 times larger field of view compared with jumbo and standard biopsy and sufficient imaging depth for detecting buried glands. Based on 3D-OCT results, buried glands were found in 72% of patients (13/18) in the pre–CE-IM group and 63% of patients (10/16) in the post–CE-IM group. The number (mean [standard deviation]) of buried glands per patient in the post–CE-IM group (7.1 [9.3]) was significantly lower compared with the pre–CE-IM group (34.4 [44.6]; P = .02). The buried gland size (P = .69) and distribution (P = .54) were not significantly different before and after CE-IM. Limitations A single-center, cross-sectional study comparing patients at different time points in treatment. Lack of 1-to-1 coregistered histology for all OCT data sets obtained in vivo. Conclusion Buried glands were frequently detected with 3D-OCT near the gastroesophageal junction before and after radiofrequency ablation. PMID:22482920

  10. Evidence for thermal boundary resistance effects on superconducting radiofrequency cavity performances

    NASA Astrophysics Data System (ADS)

    Palmieri, Vincenzo; Rossi, Antonio Alessandro; Stark, Sergey Yu; Vaglio, Ruggero

    2014-08-01

    The majority of the literature on superconducting cavities for particle accelerators concentrates on the interaction of a radiofrequency (RF) electromagnetic field with a superconductor cooled in liquid helium, generally either at a fixed temperature of 4.2 K or 1.8 K, basing the analysis of experimental results on the assumption that the superconductor is at the same temperature as the infinite reservoir of liquid helium. Only a limited number of papers have extended their analysis to the more complex overall system composed of an RF field, a superconductor and liquid helium. Only a few papers have analyzed, for example, the problem of the Kapitza resistance, i.e. the thermal boundary resistance between the superconductor and the superfluid helium. Among them, the general conclusion is that the Kapitza resistance, one of the most controversial and less understood topics in physics, is generally negligible, or not relevant for the performance enhancement of cavities. In our work presented here, studying the performance of 6 GHz niobium (Nb) test cavities, we have discovered and studied a new effect consisting of an abrupt change in the surface resistance versus temperature at the superfluid helium lambda transition T?. This abrupt change (or ‘jump’) clearly appears when the RF measurement of a cavity is performed at constant power rather than at a constant field. We have correlated this jump to a change in the thermal exchange regime across the lambda transition, and, through a simple thermal model and further reasonable assumptions, we have calculated the thermal boundary resistance between niobium and liquid helium in the temperature range between 4.2 K and 1.8 K. We find that the absolute values of the thermal resistance both above and below the lambda point are fully compatible with the data reported in the literature for heat transfer to pool boiling helium I (HeI) above T? and for the Kapitza interface resistance (below T?) between a polished metal surface and superfluid HeII. Finally, based on the well-documented evidence that the surface status of metal to liquid helium influences the heat exchange towards the fluid, and specifically the Kapitza resistance below T?, we have tested an anodization process external to the cavity, comparing the performances of the cavity before and after external anodization. The tests were done without breaking the vacuum inside the cavity or modifying the inner superconducting layer in any way, and were repeated on different samples. The results show that when the cavity is externally anodized, both the Q-factor and the maximum accelerating field increase. Again, when the oxide layer is removed, the Q-factor shifts towards a lower level and the maximum accelerating field is also reduced.

  11. Photonic radio-frequency dissemination via optical fiber with high-phase stability.

    PubMed

    Wang, Xiaocheng; Liu, Zhangweiyi; Wang, Siwei; Sun, Dongning; Dong, Yi; Hu, Weisheng

    2015-06-01

    We demonstrate a photonic radio-frequency transmission system via optical fiber. Optical radio-frequency signal is generated utilizing a Mach-Zehnder modulator based on double-side-band with carrier suppression modulation scheme. The phase error induced by optical fiber transmission is transferred to an intermediate frequency signal by the dual-heterodyne phase error transfer scheme, and then canceled by a phase locked loop. With precise phase compensation, a radio frequency with high-phase stability can be obtained at the remote end. We performed 20.07-GHz radio-frequency transfer over 100-km optical fiber, and achieved residual phase noise of -65??dBc/Hz at 1-Hz offset frequency, and the RMS timing jitter in the frequency range from 0.01 Hz to 1 MHz reaches 110 fs. The long-term frequency stability also achieves 8×10-17 at 10,000 s averaging time. PMID:26030572

  12. Surgical hepatic resection vs. ultrasonographic guided radiofrequency ablation in colorectal liver metastases: what should we choose?

    PubMed

    Ungureanu, Bogdan S; Sandulescu, Larisa; ?urlin, Valeriu; Spârchez, Zeno; S?ftoiu, Adrian

    2014-06-01

    Clinical evolution of the colorectal carcinoma occurs in up to 60% with colorectal liver metastases (CRLM). Although hepatic resection is considered to be the golden standard in CRLM, novel less invasive techniques have emerged, of which radiofrequency ablation has received a high credibility. When tumors are not eligible for surgery, guided radiofrequency ablation is considered an alternative. This method is appropriate when there are no more than 5 lesions with a diameter of less than 3 cm. While open surgery guarantees a more precise tumor excision, the effectiveness of ablation must be evaluated either by contrast-enhanced computer tomography, magnetic resonance, or ultrasound. This paper aim to review the current standings in radiofrequency ablation for CRLM and to compare the technique with surgical resection in order to find which one is the best treatment option. PMID:24791846

  13. Understanding Pound-Drever-Hall locking using voltage controlled radio-frequency oscillators: An undergraduate experiment

    E-print Network

    Liekhus-Schmaltz, C E

    2011-01-01

    A senior undergraduate experiment has been developed for learning about frequency stabilization techniques using radio-frequency electronics. The primary objective is to frequency stabilize a voltage controlled oscillator to a cavity resonance at 800 MHz using the Pound-Drever-Hall scheme. This technique is commonly applied to stabilize lasers at optical frequencies, but by using radio-frequency equipment exclusively it is possible to systematically study various aspects of the technique more thoroughly, inexpensively, and free from eye hazards. Students also learn about modular radio-frequency electronics and basic feedback control loops. By varying the temperature of the resonator, the students may determine the thermal expansion coefficients of copper, aluminum, and super invar.

  14. Pulsed Radiofrequency Neuromodulation Treatment on the Lateral Femoral Cutaneous Nerve for the Treatment of Meralgia Paresthetica

    PubMed Central

    Choi, Hyuk Jai; Choi, Seok Keun; Lim, Young Jin

    2011-01-01

    We describe a rare case of pulsed radiofrequency treatment for pain relief associated with meralgia paresthetica. A 58-year-old female presented with pain in the left anterior lateral thigh. An imaging study revealed no acute lesions compared with a previous imaging study, and diagnosis of meralgia paresthetica was made. She received temporary pain relief with lateral femoral cutaneous nerve blocks twice. We performed pulsed radiofrequency treatment, and the pain declined to 25% of the maximal pain intensity. At 4 months after the procedure, the pain intensity did not aggravate without medication. Pulsed radiofrequency neuromodulation treatment on the lateral femoral cutaneous nerve may offer an effective, low risk treatment in patients with meralgia paresthetica who are refractory to conservative medical treatment. PMID:22053239

  15. A High-Conversion-Factor, Double-Resonance Structure for High-Field Dynamic Nuclear Polarization

    Microsoft Academic Search

    G. Annino; J. A. Villanueva-Garibay; P. J. M. van Bentum; A. A. K. Klaassen; A. P. M. Kentgens

    2010-01-01

    This contribution presents a novel design of a double-resonance structure for high-field dynamic nuclear polarization operating\\u000a at 95 GHz and 144 MHz, in which a miniaturized radiofrequency coil is integrated within a single-mode nonradiative dielectric\\u000a resonator. After a detailed discussion of the design principles, the conversion factors of this system are determined by means\\u000a of microwave and radiofrequency measurements. The obtained results,

  16. 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

  17. 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.

  18. 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.

  19. Transcatheter Arterial Embolization for Tumor Seeding in the Chest Wall After Radiofrequency Ablation for Hepatocellular Carcinoma

    SciTech Connect

    Shibata, Toshiya, E-mail: ksj@kuhp.kyoto-u.ac.jp; Shibata, Toyomichi; Maetani, Yoji; Kubo, Takeshi [Kyoto University Graduate School of Medicine, Department of Diagnostic Imaging and Nuclear Medicine (Japan); Nishida, Naoshi [Kyoto University Graduate School of Medicine, Endocrinology (Japan); Itoh, Kyo [Kyoto University Graduate School of Medicine, Department of Diagnostic Imaging and Nuclear Medicine (Japan)

    2006-06-15

    Tumor seeding in the chest wall was depicted at follow-up CT obtained 9 months after radiofrequency ablation for hepatocellular carcinoma. Transcatheter arterial embolization was successfully performed, injecting emulsion of 10 mg of epirubicin and 1 ml of iodized oil followed by gelatin sponge particles via the microcatheter placed in the right eleventh intercostal artery. The patient died of tumor growth in the liver one year after the embolization, but no progression of the tumor seeding was noted during the follow-up period. We conclude that transcatheter arterial embolization was effective for the control of tumor seeding after radiofrequency ablation for hepatocellular carcinoma.

  20. Successful control of life-threatening polymorphic ventricular tachycardia by radiofrequency catheter ablation in an infant.

    PubMed

    Abe, Yuriko; Sumitomo, Naokata; Okuma, Hiromi; Nakamura, Takahiro; Fukuhara, Junji; Ichikawa, Rie; Matsumura, Masaharu; Miyashita, Michio; Kamiyama, Hiroshi; Ayusawa, Mamoru; Watanabe, Mamie; Joo, Kunitaka; Makita, Naomasa; Horie, Minoru

    2014-05-01

    We present a case of a 9-month-old girl in whom malignant polymorphic ventricular tachycardia (VT) was successfully controlled by radiofrequency catheter ablation under guidance with a three-dimensional mapping system. The VTs originated from the left ventricular lateral wall, left ventricular anterior wall, and left ventricular apex. At least six types of VTs were documented during the electrophysiology study. All VTs were successfully controlled after two sessions of radiofrequency catheter ablation, and she was discharged from our hospital on propranolol, mexiletine, flecainide, and aprindine. PMID:23836069

  1. 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.

  2. Influence of Surgical Staples on Radiofrequency Ablation Using Multitined Expandable Electrodes

    SciTech Connect

    Sakuhara, Yusuke, E-mail: YRB03514@nifty.com; Shimizu, Tadashi; Abo, Daisuke; Hasegawa, Yu; Kato, Fumi; Kodama, Yoshihisa; Shirato, Hiroki [Hokkaido University School of Medicine, Department of Radiology (Japan)

    2007-11-15

    Purpose. During radiofrequency ablation (RFA), there is a risk that the multitined expandable electrode will come into contact with one of the surgical staples used to treat local recurrence after surgical operations. Our objective was to evaluate whether a surgical staple would influence the RFA of egg white using a multitined expandable electrode. Methods. Multitined expandable electrodes, LeVeen needles (expandable diameter 3.0 cm), were sunk into an egg white bath with (a) no surgical staple, (b) a surgical staple touching one of the tines, or (c) a surgical staple touching two of the tines simultaneously. By connecting the LeVeen needle and copper plate at the bottom of the bath, RFA was then performed on the egg whites as a substitute for human tissue. Ten egg white baths were ablated under each of conditions (a), (b), and (c), for a total of 30 sets of coagulated egg white. Results. There was no significant difference in the time from the power-on to the roll-off (i.e., the completion and shutting off of the electric circuit) or in the maximum diameter of the thermal lesion between conditions (a) and (b) or (a) and (c). However, the minimum diameter of the thermal lesion was significantly smaller in (c) compared with (a) (p < 0.01). Conclusions. Surgical staples have the capacity to interfere with the electromagnetic field and decrease the minimum diameter of the thermal lesion in the event that a staple touches two of the tines of a multitined expandable electrode during RFA. Although the difference might be small enough to be neglected under many clinical circumstances, we recommend that, if possible, the tines not be expanded near metallic material.

  3. 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

  4. Laser nitriding for niobium superconducting radio-frequency accelerator cavities

    SciTech Connect

    Senthilraja Singaravelu, John Klopf, Gwyn Williams, Michael Kelley

    2010-10-01

    Particle accelerators are a key tool for scientific research ranging from fundamental studies of matter to analytical studies at light sources. Cost-forperformance is critical, both in terms of initial capital outlay and ongoing operating expense, especially for electricity. It depends on the niobium superconducting radiofrequency (SRF) accelerator cavities at the heart of most of these machines. Presently Nb SRF cavities operate near 1.9 K, well (and expensively) below the 4.2 K atmospheric boiling point of liquid He. Transforming the 40 nm thick active interior surface layer from Nb to delta NbN (Tc = 17 K instead of 9.2 K) appears to be a promising approach. Traditional furnace nitriding appears to have not been successful for this. Further, exposing a complete SRF cavity to the time-temperature history required for nitriding risks mechanical distortion. Gas laser nitriding instead has been applied successfully to other metals [P.Schaaf, Prog. Mat. Sci. 47 (2002) 1]. The beam dimensions and thermal diffusion length permit modeling in one dimension to predict the time course of the surface temperature for a range of per-pulse energy densities. As with the earlier work, we chose conditions just sufficient for boiling as a reference point. We used a Spectra Physics HIPPO nanosecond laser (l = 1064 nm, Emax= 0.392 mJ, beam spot@ 34 microns, PRF =15 – 30 kHz) to obtain an incident fluence of 1.73 - 2.15 J/cm2 for each laser pulse at the target. The target was a 50 mm diameter SRF-grade Nb disk maintained in a nitrogen atmosphere at a pressure of 550 – 625 torr and rotated at a constant speed of 9 rpm. The materials were examined by scanning electron microscopy (SEM), electron probe microanalysis (EPMA) and x-ray diffraction (XRD). The SEM images show a sharp transition with fluence from a smooth, undulating topography to significant roughening, interpreted here as the onset of ablation. EPMA measurements of N/Nb atom ratio as a function of depth found a constant value to depths greater than the SRF active layer thickness. Certain irradiation conditions resulted in values consistent with formation of delta NbN. Under certain irradiation conditions, XRD data were consistent only with delta NbN on top of Nb metal. Funding: authored by Jefferson Science Associates LLC under US DOE Contract De-AC05-06OR23177. We are indebted to Prof. P. Schaaf (Goettingen) for the simulation code and helpful discussions.

  5. Radiofrequency Ablation of Adrenal Tumors and Adrenocortical Carcinoma Metastases

    PubMed Central

    Wood, Bradford J.; Abraham, Jame; Hvizda, Julia L.; Alexander, H. Richard; Fojo, Tito

    2008-01-01

    BACKGROUND The current study was performed to analyze the feasibility, safety, imaging appearance, and short-term efficacy of image-guided percutaneous radiofrequency ablation (RFA) of primary and metastatic adrenal neoplasms including adrenocortical carcinoma. METHODS The procedure was performed using 36 treatment spheres on 15 adrenocortical carcinoma primary or metastatic tumors in eight patients over 27 months. Tumors ranged from 15 to 90 mm in greatest dimension with a mean of 43 mm. All patients had unresectable tumors or were poor candidates for surgery. Mean follow-up was 10.3 months. RESULTS All patients were discharged or were free of procedure-related medical care 6?48 hours after the procedures without major complications. All treatments resulted in presumptive coagulation necrosis by imaging criteria, which manifested as loss of previous contrast enhancement in ablated tissue. Eight of 15 (53%) posttreatment thermal lesions lost enhancement and stopped growing on latest follow-up computed tomographic scan. Three of 15 (20%) demonstrated interval growth and four did not change in size. Of these four lesions, two showed contrast enhancement. For smaller tumors with a mean greatest dimension less than or equal to 5 cm, 8 of 12 (67%) tumors were completely ablated, as defined by decreasing size and complete loss of contrast enhancement. Three of 15 (20 %) tumors and related thermal lesions were found to have disappeared nearly completely on imaging. CONCLUSIONS Percutaneous, image-guided RFA is a safe and well tolerated procedure for the treatment of unresectable primary or metastatic adrenocortical carcinoma. The procedure is effective for the short-term local control of small adrenal tumors, and is most effective for tumors less than 5 cm. The survival rate for patients with adrenocortical carcinoma improves when radical excision is performed in selected patients. Aggressive local disease control may potentially influence survival as well. However, further study is required to evaluate survival impact, document long-term efficacy, and to determine if RFA can obviate repeated surgical intervention in specific clinical scenarios. PMID:12548596

  6. A study on high current rectifier systems with mitigated time-varying magnetic field generation at ac input and dc output busbars

    Microsoft Academic Search

    Yongsug Suh; Changwoo Kim

    2011-01-01

    This paper investigates occupational exposure to time-varying magnetic field generation in high power rectifier systems. Two different kinds of high power rectifier systems rated for 25kA are modeled and analyzed. The performance is compared and evaluated on the basis of exposure guidelines from ICNIRP(International Commission on Non-Ionizing Radiation Protection). In order to focus on the qualitative effect of rectifier operation,

  7. Radiated radiofrequency immunity testing of automated external defibrillators - modifications of applicable standards are needed

    PubMed Central

    2011-01-01

    Background We studied the worst-case radiated radiofrequency (RF) susceptibility of automated external defibrillators (AEDs) based on the electromagnetic compatibility (EMC) requirements of a current standard for cardiac defibrillators, IEC 60601-2-4. Square wave modulation was used to mimic cardiac physiological frequencies of 1 - 3 Hz. Deviations from the IEC standard were a lower frequency limit of 30 MHz to explore frequencies where the patient-connected leads could resonate. Also testing up to 20 V/m was performed. We tested AEDs with ventricular fibrillation (V-Fib) and normal sinus rhythm signals on the patient leads to enable testing for false negatives (inappropriate "no shock advised" by the AED). Methods We performed radiated exposures in a 10 meter anechoic chamber using two broadband antennas to generate E fields in the 30 - 2500 MHz frequency range at 1% frequency steps. An AED patient simulator was housed in a shielded box and delivered normal and fibrillation waveforms to the AED's patient leads. We developed a technique to screen ECG waveforms stored in each AED for electromagnetic interference at all frequencies without waiting for the long cycle times between analyses (normally 20 to over 200 s). Results Five of the seven AEDs tested were susceptible to RF interference, primarily at frequencies below 80 MHz. Some induced errors could cause AEDs to malfunction and effectively inhibit operator prompts to deliver a shock to a patient experiencing lethal fibrillation. Failures occurred in some AEDs exposed to E fields between 3 V/m and 20 V/m, in the 38 - 50 MHz range. These occurred when the patient simulator was delivering a V-Fib waveform to the AED. Also, we found it is not possible to test modern battery-only-operated AEDs for EMI using a patient simulator if the IEC 60601-2-4 defibrillator standard's simulated patient load is used. Conclusions AEDs experienced potentially life-threatening false-negative failures from radiated RF, primarily below the lower frequency limit of present AED standards. Field strengths causing failures were at levels as low as 3 V/m at frequencies below 80 MHz where resonance of the patient leads and the AED input circuitry occurred. This plus problems with the standard's' prescribed patient load make changes to the standard necessary. PMID:21801368

  8. Intracellular gold nanoparticles enhance non-invasive radiofrequency thermal destruction of human gastrointestinal cancer cells

    PubMed Central

    Gannon, Christopher J; Patra, Chitta Ranjan; Bhattacharya, Resham; Mukherjee, Priyabrata; Curley, Steven A

    2008-01-01

    Background Novel approaches to treat human cancer that are effective with minimal toxicity profiles are needed. We evaluated gold nanoparticles (GNPs) in human hepatocellular and pancreatic cancer cells to determine: 1) absence of intrinsic cytotoxicity of the GNPs and 2) external radiofrequency (RF) field-induced heating of intracellular GNPs to produce thermal destruction of malignant cells. GNPs (5 nm diameter) were added to 2 human cancer cell lines (Panc-1, Hep3B). 3-(4,5-Dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide (MTT) assay and propidium iodide-fluorescence associated cell sorting (PI-FACS) assessed cell proliferation and GNP-related cytotoxicity. Other GNP-treated cells were exposed to a 13.56 MHz RF field for 1, 2, or 5 minutes, and then incubated for 24 hours. PI-FACS measured RF-induced cytotoxicity. Results GNPs had no impact on cellular proliferation by MTT assay. PI-FACS confirmed that GNPs alone produced no cytotoxicity. A GNP dose-dependent RF-induced cytotoxicity was observed. For Hep3B cells treated with a 67 ?M/L dose of GNPs, cytotoxicity at 1, 2 and 5 minutes of RF was 99.0%, 98.5%, and 99.8%. For Panc-1 cells treated at the 67 ?M/L dose, cytotoxicity at 1, 2, and 5 minutes of RF was 98.5%, 98.7%, and 96.5%. Lower doses of GNPs were associated with significantly lower rates of RF-induced thermal cytotoxicity for each cell line (P < 0.01). Cells not treated with GNPs but treated with RF for identical time-points had less cytotoxicity (Hep3B: 17.6%, 21%, and 75%; Panc-1: 15.3%, 26.4%, and 39.8%, all P < 0.01). Conclusion We demonstrate that GNPs 1) have no intrinsic cytotoxicity or anti-proliferative effects in two human cancer cell lines in vitro and 2) GNPs release heat in a focused external RF field. This RF-induced heat release is lethal to cancer cells bearing intracellular GNPs in vitro. PMID:18234109

  9. Prospective randomized comparison of left atrial and biatrial radiofrequency ablation in the treatment of atrial fibrillation

    Microsoft Academic Search

    Jiangang Wang; Xu Meng; Hui Li; Yongqiang Cui; Jie Han; Chunlei Xu

    2009-01-01

    Objective: The aim of this study was to compare, in patients with permanent atrial fibrillation (AF), the efficacy and safety of left atrial ablation with that of a biatrial procedure and to assess the risk factors for late failure of sinus rhythm restoration. Methods: Between January 2004 and January 2007, 299 consecutive patients underwent the radiofrequency ablation procedure for AF

  10. Mutual inductance of air-cored coils: Effect on design of radio-frequency coupled implants

    Microsoft Academic Search

    F. C. Flack; E. D. James; D. M. Schlapp

    1971-01-01

    Values of mutual inductance between two circular conductors lying in parallel planes have been computed. The results are presented\\u000a in graphical form and their relevance to the design of radio-frequency coupled implant systems is mentioned.

  11. REDUCTION IN METABOLIC HEAT PRODUCTION DURING EXPOSURE TO RADIO-FREQUENCY RADIATION IN THE RAT

    EPA Science Inventory

    Male Sprague-Dawley rats were maintained at an ambient temperature (Ta) of 10 C and exposed to 600 MHz radiofrequency (RF) radiation while metabolic rate (MR) was measured by indirect calorimetry. RF radiation exposures were made in a waveguide-type system which permitted the con...

  12. Hash-based Enhancement of Location Privacy for Radio-Frequency Identification Devices using Varying Identifiers

    Microsoft Academic Search

    Dirk Henrici; Paul Müller

    2004-01-01

    Radio-Frequency Identification Devices (RFID) may emerge as one of the most pervasive computing technologies in history. On the one hand, with tags affixed to consumer items as well as letters, packets or vehicles costs in the supply chain can be greatly reduced and new applications introduced. On the other hand, unique means of identificatio n in each tag like serial

  13. Pulse-Density Modulation for RF Applications: The Radio-Frequency Power Amplifier (RF PA)

    E-print Network

    Sanders, Seth

    3563 Pulse-Density Modulation for RF Applications: The Radio-Frequency Power Amplifier (RF PA-D power amplifier for RF applications in low-GHz frequency bands. We describe the motivation for using be relevant for RF applications. Here we present an RF power amplifier (RF PA) implemented as a power digital

  14. Effective piezoelectric activity of zinc oxide films grown by radio-frequency planar magnetron sputtering

    Microsoft Academic Search

    B. Wacogne; M. P. Roe; T. J. Pattinson; C. N. Pannell

    1995-01-01

    We present a study of the effective piezoelectric activity of thin ZnO films produced by radio-frequency (rf) planar magnetron sputtering. The energetic plasma particles which bombard the substrate in the above deposition system increase the substrate temperature, thus causing a gradual variation in film structure during the beginning of the film growth. As a result, a precursor layer is formed

  15. Radio-frequency nanoelectronics: A new paradigm in electronic systems design

    Microsoft Academic Search

    Luca Pierantoni; Fabio Coccetti

    2010-01-01

    Owing to the new qualitative and quantitative improvements that nanotechnology allows, nanoelectronics has the potential to introduce a paradigm shift in electronic systems design similar to that of the transition from vacuum tubes to semiconductor technology. Since many nano-scale devices and materials exhibit their most interesting properties at radiofrequencies (RF), nanoelectronics represent an enormous and yet largely undiscovered opportunity for

  16. Some Notes on Linear and Grid-Modulated Radio-Frequency Amplifiers

    Microsoft Academic Search

    F. E. Terman; R. R. Buss

    1941-01-01

    It is shown that the regulation of the radio-frequency exciter of a grid-modulated amplifier can be greatly improved by connecting across the exciter a diode biased so that at the peak of the modulation cycle the diode is just beginning to draw current. The exciter can then be designed on the basis of the peak exciting power required, and without

  17. RADIO-CONTROLLED CYBORG BEETLES: A RADIO-FREQUENCY SYSTEM FOR

    E-print Network

    Maharbiz, Michel

    RADIO-CONTROLLED CYBORG BEETLES: A RADIO-FREQUENCY SYSTEM FOR INSECT NEURAL FLIGHT CONTROL H. Sato1, University of Michigan, Ann Arbor, MI, USA ABSTRACT We present the first report of radio control of a cyborg-controlled cyborg Mecynorhina beetle; (a) live beetle platform (Mecynorhina, 4 - 10 g, 4 - 8 cm), (b) RF transmitter

  18. STUDY OF RADIOACTIVE IMPURITIES IN SOLIDS. II. EFFECTS OF RELAXATION AND RADIOFREQUENCY

    E-print Network

    Boyer, Edmond

    565 STUDY OF RADIOACTIVE IMPURITIES IN SOLIDS. II. EFFECTS OF RELAXATION AND RADIOFREQUENCY D impureté radioactive dans un solide, dépendent des propriétés des niveaux mis en jeu par les processus magnétique et l'orientation nucléaire). Abstract. 2014 The nuclear radiation characteristics of a radioactive

  19. Esophageal perforation during left atrial radiofrequency ablation: Is the risk too high?

    Microsoft Academic Search

    Nicolas Doll; Michael A. Borger; Alexander Fabricius; Susann Stephan; Jan Gummert; Friedrich W. Mohr; Johann Hauss; Hans Kottkamp; Gerd Hindricks

    2003-01-01

    Objective: Intraoperative radiofrequency ablation of atrial fibrillation (IRAAF) is a recently developed procedure being performed in an increasing number of patients. We have performed left atrial IRAAF in 387 patients since August 1998. The purpose of this article is to describe a serious complication of this procedure, namely IRAAF-induced esophageal perforation, in detail to identify possible risk factors.Methods: Left atrial

  20. NORMALIZING THE THERMAL EFFECTS OF RADIOFREQUENCY RADIATION: BODY MASS VERSUS TOTAL BODY SURFACE AREA

    EPA Science Inventory

    The current guideline for exposure to radiofrequency radiation (RFR) of 0.4 W/kg may have inadvertently been set to high. The guideline is based on the rate of RFR absorption normalized with respect to body mass. Based primarily on data for work stoppage in the rat, the 0.4 W/kg ...

  1. PHOTONIC SYNTHESIS AND HARDWARE CORRELATIONS OF ULTRABROADBAND RADIO-FREQUENCY WAVEFORMS AND POWER

    E-print Network

    Purdue University

    PHOTONIC SYNTHESIS AND HARDWARE CORRELATIONS OF ULTRABROADBAND RADIO-FREQUENCY WAVEFORMS AND POWER Purdue University West Lafayette, Indiana #12;ii This thesis is dedicated to my Father Tsing-Fa Lin who.....................................10 2.4.1 Introduction to Ultra-Wide Bandwidth Impulse Radio

  2. Floating low-temperature radio-frequency plasma oxidation of polycrystalline silicon-germanium

    E-print Network

    Floating low-temperature radio-frequency plasma oxidation of polycrystalline silicon silicon­germanium poly-SiGe is more preferable than polycrystalline silicon poly-Si in AMLCD because displays. However, low temperature oxide is prone to have defects at the SiO2 /polycrystalline

  3. Determining Electromagnetic Energy Loss Through a Radio-Frequency Transmission Line by Infrared Thermal Imaging

    Microsoft Academic Search

    Atef Alnukari; Philippe Guillemet; Yves Scudeller; Serge Toutain

    2011-01-01

    This paper presents a technique for measuring local electromagnetic energy loss through a transmission line by infra- red thermal imaging. The technique offers an attractive route to investigate solid-state radio-frequency (RF) structures with differ- ent sizes and an arbitrary layout of lines by achieving an electro- magnetic energy mapping over a wide frequency range between 300 MHz and 6 GHz.

  4. Recent Developments of the Class B Audio and Radio-Frequency Amplifiers

    Microsoft Academic Search

    L. E. Barton

    1936-01-01

    Class B audio-frequency and radio-frequency amplifiers have many applications and the distortion can be kept to a very low value if the necessary precautions are taken to prevent nonlinearity of such amplifiers. Undoubtedly, the most important factor in the design of a class B amplifier for low distortion is the characteristic of the driver system. Tube characteristics and the use

  5. Towards realistic radiofrequency ablation of hepatic tumors 3D simulation and planning

    E-print Network

    Essert-Villard, Caroline

    . The simulator takes into account the cooling effect of local vessels greater than 3mm in diameter, making, such as microwave, laser, ultrasound, cryotherapy, and radiofrequency (RF) that appears to be the easiest, safest with a 0.5 to 1 cm security margin,2 which is mandatory to prevent local recurrence of a tumor after

  6. Radiofrequency ablation of hepatic tumors: simulation, planning, and contribution of virtual reality and haptics

    E-print Network

    Essert-Villard, Caroline

    into account the cooling effect of local vessels greater than 3mm in diameter, making necrosis shapes more in different forms, such as microwave, laser, ultrasound, cryotherapy, and radiofrequency (RF) that appears is mandatory to prevent local recurrence of a tumor after treatment, and to reduce the effects of a possible

  7. Radiofrequency Ablation Therapy Combined with Cementoplasty for Painful Bone Metastases: Initial Experience

    Microsoft Academic Search

    Naoyuki Toyota; Akira Naito; Hideaki Kakizawa; Masashi Hieda; Nobuhiko Hirai; Toshihiro Tachikake; Tomoki Kimura; Hideki Fukuda; Katsuhide Ito

    2005-01-01

    The purpose of this study was to assess the efficacy and safety of percutaneous radiofrequency (RF) ablation therapy combined with cementoplasty under computed tomography and fluoroscopic guidance for painful bone metastases. Seventeen adult patients with 23 painful bone metastases underwent RF ablation therapy combined with cementoplasty during a 2-year period. The mean tumor size was 52 × 40 × 59

  8. Radiofrequency modified maze in patients with atrial fibrillation undergoing concomitant cardiac surgery

    Microsoft Academic Search

    Hauw T. Sie; Willem P. Beukema; Anand R. Ramdat Misier; Arif Elvan; Jacob J. Ennema; Max M. P. Haalebos; Hein J. J. Wellens

    2001-01-01

    Objective: In the majority of patients with chronic atrial fibrillation the arrhythmia will persist after correction of the underlying structural abnormality. The maze procedure is an effective surgical method to eliminate atrial fibrillation and to restore atrial contractility. Methods: In this study we used radiofrequency energy to create lines of conduction block in both atria during cardiac surgery as a

  9. DOSE DEPENDENCE OF ACETYLCHOLINESTERASE ACTIVITY IN NEUROBLASTOMA CELLS EXPOSED TO MODULATED RADIOFREQUENCY RADIATION

    EPA Science Inventory

    Radiofrequency radiation (RFR) at 915 and at 147 MHz, when sinusoidally amplitude modulated (AM) at 16 Hz, has been shown to enhance release of calcium ions from neuroblastoma cells in culture. he dose response is unusual, consisting of two power density 'windows' in which enhanc...

  10. CHRONIC EXPOSURE OF RATS TO 100-MHZ (CW) RADIOFREQUENCY RADIATION: ASSESSMENT OF BIOLOGICAL EFFECTS

    EPA Science Inventory

    A multidisciplinary approach was employed to assess the possible biological effects of chronic exposure of rats to 100-MHz continuous wave (CW) radiofrequency (RF) radiation. A group of 20 time-bred rats were exposed in a transverse electronmagnetic mode (TEM) transmission line t...

  11. CONTROL OF ENERGY ABSORPTION RATE IN TRANSMISSION LINE RADIOFREQUENCY EXPOSURE SYSTEMS (JOURNAL VERSION)

    EPA Science Inventory

    A frequent problem in the radiofrequency (RF) irradiation of experimental animals in health effects studies is the temporal variation of the specific absorption rate (SAR) with animal movement. An RF power controller which regulates the energy absorption rate has been designed fo...

  12. Treatment of cellulite with a bipolar radiofrequency, infrared heat, and pulsatile suction device: a pilot study

    Microsoft Academic Search

    Rungsima Wanitphakdeedecha

    2006-01-01

    Summary Background Ve ry few therapeutic options have proven effective in the treatment of cellulite. Aims To evaluate the effectiveness and adverse effects of a bipolar radiofrequency (RF), infrared (IR) heat and pulsatile suction device for the treatment of cellulite. Methods Twelve subjects were treated with the RF-light-based device. All subjects were treated twice weekly for a total number of

  13. Effects of Cell Phone Radiofrequency Signal Exposure on Brain Glucos Metabolism

    Microsoft Academic Search

    N. D. Volkow; G. Wang; D. Tomasi; P. Vaska; J. S. Fowler; F. Telang; D. Alexoff; J. Logan; C. Wong

    2011-01-01

    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. To evaluate if acute cell phone exposure affects brain glucose metabolism, a marker of brain activity. Randomized crossover study conducted between January 1 and December 31,

  14. a Theoretical and Experimental Analysis of AN Eighteen Stage Radio-Frequency Mass Spectrometer

    Microsoft Academic Search

    Gurdev Singh Bajwa

    1962-01-01

    The design and development of an l8 stage radiofrequency mass ; spectrometer for use in conjunction with a 2 meter grazing incidence vacuum ; monochromator is discussed. The ions to be mass analyzed are accelerated by a d-; c potential V\\/sub i\\/ into the analyzer, which consists of two sets of grids. ; Alternating potentials are applied to them, and

  15. GPU-based Real-Time Approximation of the Ablation Zone for Radiofrequency Ablation

    Microsoft Academic Search

    Christian Rieder; Tim Kroeger; Christian Schumann; Horst K. Hahn

    2011-01-01

    Fig. 1. The RF applicator is placed into the tumor, and the corresponding approximative ablation zone incorporating the heat-sink effect is displayed as red isolines. The blue isolines represent the thermal cooling of the blood vessels around the lesion. Abstract—Percutaneous radiofrequency ablation (RFA) is becoming a standard minimally invasive clinical procedure for the treatment of liver tumors. However, planning the

  16. Percutaneous Sonographically Guided Saline-Enhanced Radiofrequency Ablation of Hepatocellular Carcinoma

    Microsoft Academic Search

    Antonio Giorgio; Luciano Tarantino; Giorgio de Stefano; Vincenzo Scala; Giulia Liorre; Ferdinando Scarano; Anna Perrotta; Nunzia Farella; Vincenza Aloisio; Nicola Mariniello; Carmine Coppola; Giampiero Francica; Giovanna Ferraioli

    OBJECTIVE. The purpose of our study was to analyze the efficacy, side effects, and short- term complications of saline-enhanced percutaneous radiofrequency ablation performed under sonographic guidance in a series of cirrhotic patients with hepatocellular carcinoma. SUBJECTS AND METHODS. Between September 2000 and June 2002, 84 patients (55 men and 29 women) with cirrhosis who ranged in age from 48 to

  17. Percutaneous Stereotactic Radiofrequency Thermal Rhizotomy for the Treatment of Trigeminal Neuralgia

    Microsoft Academic Search

    ERNES TS

    Background: Trigeminal neuralgia (TN) is the most common cephalic neuralgia in people over the age of fifty, with a mean incidence of 4 per 100,000. Percutaneous stereotactic differential radiofrequency thermal rhizotomy (RTR) is a well-recognized surgical treatment for TN. The purpose of this study was to evaluate a management algorithm for TN and to evaluate the effectiveness of RTR for

  18. Hypertensive Crisis in a Patient Undergoing Percutaneous Radiofrequency Ablation of an Adrenal Mass Under General Anesthesia

    Microsoft Academic Search

    Eduardo N. Chini; Michael J. Brown; Michael A. Farrell; J. William Charboneau

    2004-01-01

    Radiofrequency ablation (RFA) is an effective thera- peutic intervention for a variety of neoplastic lesions. Many of these procedures are conducted with patients under general anesthesia. Although RFA is associated withinfrequentcomplications,itisnotwithoutrisk.In- jury to adjacent normal structures is a major concern during RFA of cancerous lesions. Unintended injury to normal adrenal tissue during RFA of adrenal tumors can lead to hypertensive

  19. Comb-based radio-frequency photonic filtering with 20 ns bandwidth reconfiguration

    E-print Network

    Purdue University

    Comb-based radio-frequency photonic filtering with 20 ns bandwidth reconfiguration Rui Wu,* Minhyup We present a scheme to generate a 10 GHz optical frequency comb that is bandwidth reconfigurable to demonstrate, for the first time to our knowledge, bandwidth-reconfigurable RF filtering with transition times

  20. Radiofrequency cordotomy for the relief of spasticity in decerebrate cats1

    Microsoft Academic Search

    Daniel Soriano; Richard Herman

    1971-01-01

    The effectiveness of radiofrequency (RF) cordotomy of segmental motoneurone pools of the lumbosacral cord in reducing spasticity of decerebrate cats is evaluated. The need for a new form of therapy for clinical spasticity is based upon the limitations of contemporary methods, including surgical and pharmacological techniques. In man, spasticity of spinal origin may be treated effectively by intrathecal administration of

  1. Two-Dimensional Numerical Modeling of Radio-Frequency Ion Engine Discharge

    E-print Network

    Two-Dimensional Numerical Modeling of Radio-Frequency Ion Engine Discharge Michael Meng-Tsuan Tsay-Frequency Ion Engine Discharge Michael Meng-Tsuan Tsay, Manuel Martinez-Sanchez August 2010 SSL # 14 to the Department of Aeronautics and Astronautics in partial fulfillment of the requirements for the degree

  2. Modeling thermal responses in human subjects following extended exposure to radiofrequency energy

    Microsoft Academic Search

    Kenneth R Foster; Eleanor R Adair

    2004-01-01

    BACKGROUND: This study examines the use of a simple thermoregulatory model for the human body exposed to extended (45 minute) exposures to radiofrequency\\/microwave (RF\\/MW) energy at different frequencies (100, 450, 2450 MHz) and under different environmental conditions. The exposure levels were comparable to or above present limits for human exposure to RF energy. METHODS: We adapted a compartmental model for

  3. Treatment of pathologic spinal fractures with combined radiofrequency ablation and balloon kyphoplasty

    Microsoft Academic Search

    Pavlos Katonis; Dritan Pasku; Kalliopi Alpantaki; Artan Bano; George Tzanakakis; Apostolos Karantanas

    2009-01-01

    BACKGROUND: In oncologic patients with metastatic spinal disease, the ideal treatment should be well tolerated, relieve the pain, and preserve or restore the neurological function. The combination of fluoroscopic guided radiofrequency ablation (RFA) and kyphoplasty may fulfill these criteria. METHODS: We describe three pathological vertebral fractures treated with a combination of fluoroscopic guided RFA and kyphoplasty in one session: a

  4. Radio-Frequency Driven Dielectric Heaters for Non-Nuclear Testing in Nuclear Core Development

    NASA Technical Reports Server (NTRS)

    Sims, William Herbert, III (Inventor); Godfroy, Thomas J. (Inventor); Bitteker, Leo (Inventor)

    2004-01-01

    Apparatus and methods are provided through which a radio-frequency dielectric heater has a cylindrical form factor, a variable thermal energy deposition through variations in geometry and composition of a dielectric, and/or has a thermally isolated power input.

  5. Global survey and statistics of radio-frequency interference in AMSR-E land observations

    Microsoft Academic Search

    Eni G. Njoku; Peter Ashcroft; Tsz K. Chan; Li Li

    2005-01-01

    Radio-frequency interference (RFI) is an increasingly serious problem for passive and active microwave sensing of the Earth. To satisfy their measurement objectives, many spaceborne passive sensors must operate in unprotected bands, and future sensors may also need to operate in unprotected bands. Data from these sensors are likely to be increasingly contaminated by RFI as the spectrum becomes more crowded.

  6. BIOLOGICAL EFFECTS OF RADIOFREQUENCY RADIATION: REVIEW DRAFT. PARTS 1, 2, AND 3

    EPA Science Inventory

    The document presents a critical and comprehensive review of the available literature on the biological effects of radiofrequency (RF) radiation through 1980. The objective is to determine whether the existing data base can contribute to the formulation of RF-radiation exposure g...

  7. Nonablative Wrinkle Treatment of the Face and Neck Using a Combined Diode Laser and Radiofrequency Technology

    Microsoft Academic Search

    NEIL S. SADICK; MARIO A. TRELLES; Fundación Antoni de Gimbernat

    2005-01-01

    BACKGROUND. Nonablative laser systems that integrate optical and conducted radiofrequency (RF) energies are a novel technol- ogy for the treatment of wrinkles. OBJECTIVE. This two-center study investigated the safety and effectiveness of combination diode laser (900 nm) and RF for the treatment of wrinkles and skin texture. METHODS. Patients with grade II to IV wrinkling on the face, according to

  8. BODY TEMPERATURE IN THE MOUSE, HAMSTER, AND RAT EXPOSED TO RADIOFREQUENCY RADIATION: AN INTERSPECIES COMPARISON

    EPA Science Inventory

    Colonic temperatures of BALB/c and CBA/J mice, golden hamsters, and Sprague-Dawley rats were taken immediately after exposure for 90 min to radiofrequency (RF) radiation. Exposures were made in 2450 MHz (mouse and hamster) or 600 MHz (rat) waveguide exposure systems while the dos...

  9. Hepatic radiofrequency ablation with internally cooled probes: effect of coolant temperature on lesion size

    Microsoft Academic Search

    Dieter Haemmerich; Louay Chachati; Andrew S. Wright; David M. Mahvi; J. G. Webster

    2003-01-01

    Radiofrequency (RF) ablation is a minimally invasive method for treatment of primary and metastatic liver tumors. One of the currently commercially available devices employs an internally cooled 17-gauge needle probe. Within the probe, cool water is circulated during ablation, which cools tissue close to the probe resulting in larger lesions. We evaluated the effect of different cooling water temperatures on

  10. WHO's health risk assessment of ELF fields.

    PubMed

    Repacholi, M H

    2003-01-01

    The World Health Organization (WHO), the International Commission on Non-Ionizing Radiation Protection (ICNIRP), WHO's scientific collaborating centres (including the UK's National Radiological Protection Board (NRPB)) and over 50 participating Member States are participants of WHO's International EMF Project. As part of WHO's health risk assessment process for extremely low frequency fields (ELF), this workshop was convened by NRPB to assist WHO in evaluating the potential health impacts of electrical currents and fields induced by ELF in molecules, cells, tissues and organs of the body. This paper describes the process by which WHO will conduct its health risk assessment. WHO is also trying to provide information on why exposure to ELF magnetic fields seems to be associated with an increased incidence of childhood leukaemia. Are there mechanisms that could lead to this health outcome or does the epidemiological evidence incorporate biases or other factors that need to be further explored? PMID:14690270

  11. Painless, safe, and efficacious noninvasive skin tightening, body contouring, and cellulite reduction using multisource 3DEEP radiofrequency.

    PubMed

    Harth, Yoram

    2015-03-01

    In the last decade, Radiofrequency (RF) energy has proven to be safe and highly efficacious for face and neck skin tightening, body contouring, and cellulite reduction. In contrast to first-generation Monopolar/Bipolar and "X -Polar" RF systems which use one RF generator connected to one or more skin electrodes, multisource radiofrequency devices use six independent RF generators allowing efficient dermal heating to 52-55°C, with no pain or risk of other side effects. In this review, the basic science and clinical results of body contouring and cellulite treatment using multisource radiofrequency system (Endymed PRO, Endymed, Cesarea, Israel) will be discussed and analyzed. PMID:25598274

  12. Radio-Frequency Wave Excitation and Damping on a High Beta Plasma Column.

    NASA Astrophysics Data System (ADS)

    Meuth, Hermann

    Azimuthally symmetric (m = 0) radio-frequency (RF) waves for zero and for finite axial wave number k(,z) are investigated on the High-Beta Q Machine, a two-meter, 20 cm-diameter, low-compression linear theta pinch (T (GREATERTHEQ) 200 eV, n (DBLTURN) 10('15)cm('-3)) fast rising (0.4 (mu)s) compression field. The (k(,z) = 0) modes occur spontaneously following the implosion phase of the discharge. A novel 100-MWatt, 1 to 1.3-MHz, short wavelength current drive excites the plasma column in the vicinity of the lowest fast magnetoacoustic mode at various filling pressures. This current drive is designed as an integral part of the compression coil, which is segmented with a 20-cm axial wavelength (k(,z) = 0.314 cm('-1)). The electron density oscillations along major and minor chords at various positions are measured by interferometry perpendicular to the pinch axis. The oscillatory radial magnetic field component between pinch wall and hot plasma edge is measured by probes. Phases, amplitudes and radial mode structure are studied for the free (k = 0) modes and the externally driven (k (NOT=) 0) modes for various filling pressures of deuterium. In the first case, the damping is determined from the e-folding time of the decaying oscillations. In the latter case, the phases and amplitudes indicate a broad resonance structure, from which we extract the damping constant. The energy deposition from the externally driven RF wave leads to a radial expansion of the plasma column, as observed by axial interferometry and by excluded flux measurements. We compare these experimental results with damping phenomena as predicted by MHD-like collisional (viscous) and collisionless (ion-Landau and cyclotron) damping models. It is found that the viscous model overestimates the observed (k = 0) damping by at least an order of magnitude, while both the viscous and kinetic models underestimate the (k (NOT=) 0) damping by at least an order of magnitude. The characteristic and resonant frequencies, as well as the oscillatory radial mode structure, can be understood within the ideal MHD description. The experimentally observed damping and wave-energy deposition are consistent with the magnitude of the density oscillations. The efficiency of the RF energy deposition is at least 27%, somewhat exceeding that observed in other high-beta magnetoacoustic experiments.

  13. Design and multiphysics analysis of a 176Â MHz continuous-wave radio-frequency quadrupole

    NASA Astrophysics Data System (ADS)

    Kutsaev, S. V.; Mustapha, B.; Ostroumov, P. N.; Barcikowski, A.; Schrage, D.; Rodnizki, J.; Berkovits, D.

    2014-07-01

    We have developed a new design for a 176 MHz cw radio-frequency quadrupole (RFQ) for the SARAF upgrade project. At this frequency, the proposed design is a conventional four-vane structure. The main design goals are to provide the highest possible shunt impedance while limiting the required rf power to about 120 kW for reliable cw operation, and the length to about 4 meters. If built as designed, the proposed RFQ will be the first four-vane cw RFQ built as a single cavity (no resonant coupling required) that does not require ?-mode stabilizing loops or dipole rods. For this, we rely on very detailed 3D simulations of all aspects of the structure and the level of machining precision achieved on the recently developed ATLAS upgrade RFQ. A full 3D model of the structure including vane modulation was developed. The design was optimized using electromagnetic and multiphysics simulations. Following the choice of the vane type and geometry, the vane undercuts were optimized to produce a flat field along the structure. The final design has good mode separation and should not need dipole rods if built as designed, but their effect was studied in the case of manufacturing errors. The tuners were also designed and optimized to tune the main mode without affecting the field flatness. Following the electromagnetic (EM) design optimization, a multiphysics engineering analysis of the structure was performed. The multiphysics analysis is a coupled electromagnetic, thermal and mechanical analysis. The cooling channels, including their paths and sizes, were optimized based on the limiting temperature and deformation requirements. The frequency sensitivity to the RFQ body and vane cooling water temperatures was carefully studied in order to use it for frequency fine-tuning. Finally, an inductive rf power coupler design based on the ATLAS RFQ coupler was developed and simulated. The EM design optimization was performed using cst Microwave Studio and the results were verified using both hfss and ansys. The engineering analysis was performed using hfss and ansys and most of the results were verified using the newly developed cst Multiphysics package.

  14. A radiofrequency coil to facilitate B?? shimming and parallel imaging acceleration in three dimensions at 7 T.

    PubMed

    Gilbert, Kyle M; Curtis, Andrew T; Gati, Joseph S; Klassen, L Martyn; Menon, Ravi S

    2011-08-01

    A 15-channel transmit-receive (transceive) radiofrequency (RF) coil was developed to image the human brain at 7 T. A hybrid decoupling scheme was implemented that used both capacitive decoupling and the partial geometric overlapping of adjacent coil elements. The decoupling scheme allowed coil elements to be arrayed along all three Cartesian axes; this facilitated shimming of the transmit field, B??, and parallel imaging acceleration along the longitudinal direction in addition to the standard transverse directions. Each channel was independently controlled during imaging using a 16-channel console and a 16 × 1-kW RF amplifier-matrix. The mean isolation between all combinations of coil elements was 18 ± 7 dB. After B?? shimming, the standard deviation of the transmit field uniformity was 11% in an axial plane and 32% over the entire brain superior to the mid-cerebellum. Transmit uniformity was sufficient to acquire fast spin echo images of this region of the brain with a single B?? shim solution. Signal-to-noise ratio (SNR) maps showed higher SNR in the periphery vs center of the brain, and higher SNR in the occipital and temporal lobes vs the frontal lobe. Parallel imaging acceleration in a rostral-caudal oblique plane was demonstrated. The implication of the number of channels in a transmit-receive coil was discussed: it was determined that improvements in SNR and B?? shimming can be expected when using more than 15 independently controlled transmit-receive channels. PMID:21834005

  15. Radio-Frequency Illuminated Superconductive Disks: Reverse Josephson Effects and Implications for Precise Measuring of Proposed Gravity Effects

    NASA Technical Reports Server (NTRS)

    Noever, David A.; Koczor, Ronald J.

    1998-01-01

    We have previously reported results using a high precision gravimeter to probe local gravity changes in the neighborhood of large bulk-processed high-temperature superconductors. It have been indicated three essential components to achieve anomalous gravity effects, namely large, two-layer high-temperature YBCO superconductors, magnetic levitation and AC input in the form of radio-frequency (RF) electromagnetic fields. We report experiments on RF-illuminated (1-15 MHz) superconducting disks with corresponding gravity readings indicating an apparent increase in observed gravity of approximately 3-5 x l0(exp -5)cm/sq s, above and to the side of the superconductor. In this preliminary study, RF- illumination is achieved using a series of large radius (15 cm) spiral antenna with RF power inputs equal to or greater than 90 W. The observed gravitational modification range is significantly lower than the 2.1% gravity modification. The error analyses of thermal and electromagnetic interference in a magnetically shielded gravimeter with vacuum enclosures, Faraday cages and shielded instrument leads, are outlined both experimentally and theoretically. The nearly exact correspondence between the peak gravity effects reported and the well-known peak in AC resistance in superconductors (2-7 MHz, owing to reverse Josephson quantum effects) suggests that electrical resistance will arise in this frequency range and subsequently any trapped magnetic fields in the superconductor may disperse partially into the measuring instrument's local environment. Implications for propulsion initiatives and RF-heating in superconductors will be discussed.

  16. Synthesis of Bio-Compatible SPION-based Aqueous Ferrofluids and Evaluation of RadioFrequency Power Loss for Magnetic Hyperthermia.

    PubMed

    Reena Mary, A P; Narayanan, T N; Sunny, Vijutha; Sakthikumar, D; Yoshida, Yasuhiko; Joy, P A; Anantharaman, M R

    2010-01-01

    Bio-compatible magnetic fluids having high saturation magnetization find immense applications in various biomedical fields. Aqueous ferrofluids of superparamagnetic iron oxide nanoparticles with narrow size distribution, high shelf life and good stability is realized by controlled chemical co-precipitation process. The crystal structure is verified by X-ray diffraction technique. Particle sizes are evaluated by employing Transmission electron microscopy. Room temperature and low-temperature magnetic measurements were carried out with Superconducting Quantum Interference Device. The fluid exhibits good magnetic response even at very high dilution (6.28 mg/cc). This is an advantage for biomedical applications, since only a small amount of iron is to be metabolised by body organs. Magnetic field induced transmission measurements carried out at photon energy of diode laser (670 nm) exhibited excellent linear dichroism. Based on the structural and magnetic measurements, the power loss for the magnetic nanoparticles under study is evaluated over a range of radiofrequencies. PMID:21076702

  17. Synthesis of Bio-Compatible SPION–based Aqueous Ferrofluids and Evaluation of RadioFrequency Power Loss for Magnetic Hyperthermia

    PubMed Central

    2010-01-01

    Bio-compatible magnetic fluids having high saturation magnetization find immense applications in various biomedical fields. Aqueous ferrofluids of superparamagnetic iron oxide nanoparticles with narrow size distribution, high shelf life and good stability is realized by controlled chemical co-precipitation process. The crystal structure is verified by X-ray diffraction technique. Particle sizes are evaluated by employing Transmission electron microscopy. Room temperature and low-temperature magnetic measurements were carried out with Superconducting Quantum Interference Device. The fluid exhibits good magnetic response even at very high dilution (6.28 mg/cc). This is an advantage for biomedical applications, since only a small amount of iron is to be metabolised by body organs. Magnetic field induced transmission measurements carried out at photon energy of diode laser (670 nm) exhibited excellent linear dichroism. Based on the structural and magnetic measurements, the power loss for the magnetic nanoparticles under study is evaluated over a range of radiofrequencies. PMID:21076702

  18. Adverse Health Effects of ELF and RF Electromagnetic Fields that Serve as Basis for Setting Safety Limits

    Microsoft Academic Search

    G. FILIPPOPOULOS E. KARABETSOS

    As technology advances the general public is every day exposed to Extremely Low Frequency (ELF) electric and magnetic fields and radiofrequency (RF) electromagnetic fields emitted by existing as well as novel applications. Common sources of ELF electric and magnetic fields are high voltage power lines and electrical appliances, whereas RF electromagnetic fields are emitted by communication systems like mobile phones

  19. Radiofrequency tissue ablation: Importance of local temperature along the electrode tip exposure in determining lesion shape and size

    Microsoft Academic Search

    S. Nahum Goldberg; G. Scott Gazelle; Elkan F. Halpern; William J. Rittman; Peter R. Mueller; Daniel I. Rosenthal

    1996-01-01

    Rationale and ObjectivesWe determined whether heat distribution along a radiofrequency (RF) electrode would be uniform when longer tip exposures are used and whether local temperature effects would influence the shape of induced tissue coagulation.

  20. Nonlinear nonresonant forces by radio-frequency waves in plasmas

    SciTech Connect

    Gao Zhe; Fisch, Nathaniel J.; Qin, Hong; Myra, J. R. [Department of Engineering Physics, Tsinghua University, Beijing 100084 (China); Princeton Plasma Physics Laboratory, Princeton University, Princeton, New Jersey 08543 (United States); Lodestar Research Corporation, Boulder, Colorado 80301 (United States)

    2007-08-15

    Nonresonant forces by applied rf waves in plasmas are analyzed. Along the background dc magnetic field, the force arises from the gradient of the ponderomotive potential. Only when the dc magnetic field is straight, however, is this parallel force completely consistent with that from the single particle picture, where the ponderomotive force depends on the gradients of rf fields only. Across the dc magnetic field, besides the ponderomotive force from the particle picture, additional Reynolds stress and polarization stress contribute to the total force. For waves with frequency much lower than the cyclotron frequency, the perpendicular forces from the particle and fluid pictures can have opposite signs. In plasmas with a symmetry angle (e.g., toroidal systems), nonresonant forces cannot drive net flow or current in the flux surface, but the radial force may influence macroscopic behavior of plasma. Moreover, nonresonant forces may drive flow or current in linear plasmas or in a localized region of toroidal plasmas.

  1. Radiofrequency sheath formation and excitation around a stepped electrode.

    SciTech Connect

    Hebner, Gregory Albert; Barnat, Edward V.

    2004-07-01

    Plasma and sheath structure around a rf excited stepped electrode is investigated. Laser-induced fluorescence dip spectroscopy is used to spatially resolve sheath fields in an argon discharge while optical emission and laser-induced fluorescence are used to measure the spatial structure of the surrounding discharge for various discharge conditions and step-junction configurations. The presence of the step perturbs the spatial structure of the fields around the step as well as the excitation in the region above the step.

  2. Epicardial unipolar radiofrequency ablation for left ventricular aneurysm related ventricular arrhythmia

    PubMed Central

    2013-01-01

    We report a case of a 62-year-old Chinese man with typical triple-vessel lesions and apical left ventricular aneurysm accompanied with ventricular tachycardia. Off-pump coronary artery bypass (OPCAB) grafting was performed in combination with epicardial unipolar radiofrequency ablation and linear closure of left ventricular aneurysm. The patient recovered well without postoperative complications. Holter monitoring showed no recurrence of the ventricular arrhythmia and the attack frequency of arrhythmia decreased significantly. The patient has been angina-free for 25 months since the operation and shows increasing exercise tolerance. Thus, left ventricular aneurysm plication combined with epicardial unipolar radiofrequency ablation during OPCAB may be beneficial for patients with ventricular aneurysm and preoperative malignant ventricular arrhythmia. PMID:23651741

  3. Percutaneous radiofrequency rhizotomy of lumbar spinal facets: the results of 46 cases.

    PubMed

    Göçer, A I; Cetinalp, E; Tuna, M; Ildan, F; Ba?dato?lu, H; Haciyakupo?lu, S

    1997-01-01

    The results of percutaneous radiofrequency rhizotomy of lumbar spinal facets in 46 patients followed at least three months (mean 15 months) are reported and compared with those reported previously. Satisfactory pain relief three months after the procedure was achieved in 36.4 percent of patients without operations and in 41.7 percent of patients, with operations other than fusion. No patient had previously undergone fusion. Treatment of low-back pain by using radio-frequency thermocoagulation of spinal facets is a simple, safe, and well-tolerated procedure. It can be used to relief of pain in spite of decreasing rates of success within the follow-up period. PMID:9226670

  4. Use of Radiofrequency Ablation in Benign Thyroid Nodules: A Literature Review and Updates

    PubMed Central

    Wong, Kai-Pun; Lang, Brian Hung-Hin

    2013-01-01

    Successful thermal ablation using radiofrequency has been reported in various tumors including liver or kidney tumors. Nonsurgical minimally invasive ablative therapy such as radiofrequency ablation (RFA) has been reported to be a safe and efficient treatment option in managing symptomatic cold thyroid nodules or hyperfunctioning thyroid nodules. Pressure and cosmetic symptoms have been shown to be significantly improved both in the short and long terms after RFA. For hyperfunctioning thyroid nodules, RFA is indicated for whom surgery or radioiodine are not indicated or ineffective or for those who refuse surgery or radio-iodine. Improvement of thyroid function with decreased need for antithyroid medications has been reported. Complication rate is relatively low. By reviewing the current literature, we reported its efficacy and complications and compared the efficacy of RFA relative to other ablative options such as ethanol ablation and laser ablation. PMID:24298282

  5. Radiofrequency-Treated Recurrence of Urothelial Carcinoma of the Upper Urinary Tract After Nephroureterectomy

    PubMed Central

    Álvarez, Manuel; Capilla, Jesús; Páez, Álvaro

    2014-01-01

    Local recurrence after radical nephroureterectomy (RNU) owing to urothelial carcinoma of the upper urinary tract is rare. The usual treatment is systemic chemotherapy followed by optional resection of the mass. We introduce the case of a 73-year-old male patient with multiple comorbidities in whom retroperitoneal carcinoma recurrence of 31 mm was diagnosed via positron emission tomography-computed tomography scan with 18-fluorodeoxyglucose about 5 years after he had undergone RNU owing to urothelial carcinoma of the upper urinary tract. The patient was treated with computed tomography-guided percutaneous radiofrequency ablation. Later scans with contrast controls showed lack of contrast uptake and a decrease of the lesion's size. Twenty-four months after the procedure, the patient is free of the disease. To date, this is the first case of recurrence of urothelial carcinoma that was treated with percutaneous radiofrequency ablation, thus establishing an alternative to chemotherapy in patients with substantial comorbidities. PMID:25512821

  6. Effects of radiofrequency radiation on rabbit kidney: a morphological and immunological study

    SciTech Connect

    Accinni, L.; De Martino, C.; Mariutti, G.

    1988-08-01

    The histopathology of the acute and chronic kidney reaction to low-frequency nonionizing electromagnetic radiation was evaluated in New Zealand white rabbits treated with multiple exposure to 27.12-MHz radiofrequencies. At the end of treatment, the animals exhibited focal tubular necrosis and focal and segmental glomerular sclerosis which in a few months evolved into a membranous nephropathy. The latter was characterized by a diffuse, granular localization of rabbit gamma-globulin and complement in most glomeruli and by electron-dense deposits in the subepithelial zone of the glomerular capillary walls, suggesting that these glomerular changes are induced by the localization of antigen-antibody complexes. The data obtained provide strong evidence for the potential nephrotoxicity of radiofrequency radiation and indicate that these nonionizing types of radiation may be capable of eliciting autoimmune phenomena that are likely responsible for the evolution of renal disease in rabbits.

  7. Statistical properties of radio-frequency and envelope-detected signals with applications to medical ultrasound

    Microsoft Academic Search

    Robert F. Wagner; Michael F. Insana; David G. Brown

    1987-01-01

    Both radio-frequency (rf) and envelope-detected signal anlayses have lead to successful tissue discrimination in medical ultrasound. The extrapolation from tissue discrimination to a description of the tissue structure requires an analysis of the statistics of complex signals. To that end, first- and second-order statistics of complex random signals are reviewed, and an example is taken from rf signal analysis of

  8. Three-Dimensional Finite-Element Analyses for Radio-Frequency Hepatic Tumor Ablation

    Microsoft Academic Search

    Supan Tungjitkusolmun; S. Tyler Staelin; Dieter Haemmerich; Jang-Zern Tsai; Hong Cao; John G. Webster; Fred T. Lee; David M. Mahvi; Vicken R. Vorperian

    2002-01-01

    Radio-frequency (RF) hepatic ablation, offers an alternative method for the treatment of hepatic malignancies. We employed finite-element method (FEM) analysis to determine tissue temperature distribution during RF hepatic ablation. We constructed three-dimensional (3-D) thermal-electrical FEM models consisting of a four-tine RF probe, hepatic tissue, and a large blood vessel (10-mm diameter) located at different locations. We simulated our FEM analyses

  9. Radio-Controlled Cyborg Beetles: A Radio-Frequency System for Insect Neural Flight Control

    Microsoft Academic Search

    H. SatoI; Y. Peeri; E. Baghoomian; C. W. Berry; M. M. Maharbiz

    2009-01-01

    We present the first report of radio control of a cyborg beetle in free-flight. The microsystem (Figs. 1,2) consisted of a radio-frequency receiver assembly, a micro battery and a live giant flower beetle platform (Mecynorhina polyphemus or Mecynorhina torquata). The assembly had six electrode stimulators implanted into the left and right optic lobes, brain, posterior pronotum (counter electrode), right and

  10. Diffuse intrahepatic recurrence after percutaneous radiofrequency ablation for solitary and small hepatocellular carcinoma

    Microsoft Academic Search

    Yoshiyuki Mori; Hideyuki Tamai; Naoki Shingaki; Kosaku Moribata; Tatsuya Shiraki; Hisanobu Deguchi; Kazuki Ueda; Shotaro Enomoto; Hiroto Magari; Izumi Inoue; Takao Maekita; Mikitaka Iguchi; Kimihiko Yanaoka; Masashi Oka; Masao Ichinose

    2009-01-01

    Two patients developed segmental, diffuse intrahepatic recurrence after percutaneous radiofrequency ablation (RFA) to treat\\u000a a primary, solitary, and small (2.5 cm) hepatocellular carcinoma (HCC). Despite the size of the HCC, levels of the tumor markers\\u000a (?-fetoprotein, ?-fetoprotein-L3%, and des-?-carboxyprothrombin) were all elevated before RFA, and tumors in both patients\\u000a were contiguous with a major branch of the portal vein. Tumor biopsies

  11. Radiofrequency Guide Wire Recanalization of Venous Occlusions in Patients with Malignant Superior Vena Cava Syndrome

    SciTech Connect

    Davis, Robert M.; David, Elizabeth; Pugash, Robyn A.; Annamalai, Ganesan, E-mail: ganesan.annamalai@sunnybrook.ca [Sunnybrook Health Sciences Centre, Department of Interventional Radiology (Canada)

    2012-06-15

    Fibrotic central venous occlusions in patients with thoracic malignancy and prior radiotherapy can be impassable with standard catheters and wires, including the trailing or stiff end of a hydrophilic wire. We report two patients with superior vena cava syndrome in whom we successfully utilized a radiofrequency guide wire (PowerWire, Baylis Medical, Montreal, Quebec, Canada) to perforate through the occlusion and recanalize the occluded segment to alleviate symptoms.

  12. Successful Irrigated-Tip Catheter Ablation of Atrial Flutter Resistant to Conventional Radiofrequency Ablation

    Microsoft Academic Search

    Pierre Jais; Michel Haissaguerre; Dipen C. Shah; Atsushi Takahashi; Meleze Hocini; Thomas Lavergne; Stephane Lafitte; Alain Le Mouroux; Bruno Fischer; Jacques Clementy

    2010-01-01

    Background—Catheter ablation of typical right atrial flutter is now widely performed. The best end point has been demonstrated to be bidirectional isthmus block. We investigated the use of irrigated-tip catheters in a small subset of patients who failed isthmus ablation with conventional radiofrequency (RF) ablation. Methods and Results—Of 170 patients referred for ablation of common atrial flutter, conventional ablation of

  13. Enhanced corrosion resistance properties of radiofrequency cold plasma nitrided carbon steel: Gravimetric and electrochemical results

    Microsoft Academic Search

    F. Z. Bouanis; F. Bentiss; M. Traisnel; C. Jama

    2009-01-01

    Cold plasma nitriding treatment was performed to improve the corrosion resistance of C38 carbon steel. Nitriding process was conducted using a radiofrequency nitrogen plasma discharge for different times of treatment on non-heated substrates. The modification of the corrosion resistance characteristic of the C38 steel due to the treatment in acid medium (1M HCl) were investigated by gravimetric and electrochemical tests

  14. Characteristics of radio-frequency atmospheric pressure dielectric-barrier discharge with dielectric electrodes

    NASA Astrophysics Data System (ADS)

    Hussain, S.; Qazi, H. I. A.; Badar, M. A.

    2014-03-01

    An experimental investigation to characterize the properties and highlight the benefits of atmospheric pressure radio-frequency dielectric-barrier discharge (rf DBD) with dielectric electrodes fabricated by anodizing aluminium substrate is presented. The current-voltage characteristics and millisecond images are used to distinguish the ? and ? modes. This atmospheric rf DBD is observed to retain the discharge volume without constriction in ? mode. Optical emission spectroscopy demonstrates that the large discharge current leads to more abundant reactive species in this plasma source.

  15. Assessment of Liver Tissue After Radiofrequency Ablation: Findings with Different Imaging Procedures

    Microsoft Academic Search

    Gerald Antoch; Florian M. Vogt; Patrick Veit; Lutz S. Freudenberg; Nina Blechschmid; Olaf Dirsch; Andreas Bockisch; Michael Forsting; F. Debatin; Hilmar Kuehl

    Our goal was to assess the typical appearance of normal liver tissue immediately after radiofrequency ablation (RF-ablation) when imaged with contrast-enhanced ultrasound, CT, MRI, 18F- FDG PET, and PET\\/CT. Methods: Nineteen RF-ablation ses- sions were performed on nontumorous liver tissue of 10 Got - tingen Mini Pigs. CT, ultrasound, MRI, 18F-FDG PET, and PET\\/CT were performed immediately after the intervention.

  16. Optical and electrical characteristics of amorphous boron carbonitride thin films deposited by radiofrequency sputtering

    Microsoft Academic Search

    A. Essafti; E. Ech-Chamikh

    2011-01-01

    Amorphous boron carbonitride (a-BCN) thin films were deposited by reactive radiofrequency (RF) sputtering onto silicon and\\u000a glass substrates, from a boron carbide target in an atmosphere composed of a mixture of argon and nitrogen. The a-BCN films\\u000a were highly transparent (almost 85%) in the visible and near-infrared regions. The optical band gap and the refractive index\\u000a in the near-infrared region

  17. Biological effects on human health due to radiofrequency\\/microwave exposure: a synopsis of cohort studies

    Microsoft Academic Search

    Jürgen Breckenkamp; Gabriele Berg; Maria Blettner

    2003-01-01

    We evaluated the methods and results of nine cohort studies dealing with the biological effects on human health from exposure to radiofrequencies\\/microwaves, published between 1980 and 2002. The size of the cohorts varied between 304 (3,362 person years) and nearly 200,000 persons (2.7 million person years). As exposures were defined: dielectric heaters in a plastic manufacturing plant, working with radio

  18. Coronary microcatheter mapping of coronary arteries during radiofrequency ablation in children

    Microsoft Academic Search

    Hasim Olgun; Tevfik Karagoz; Alpay Celiker

    2010-01-01

    Introduction  Radiofrequency catheter ablation (RFCA) is a safe and effective treatment option for children with refractory supraventricular\\u000a tachycardias. RFCA of right-sided accessory pathways (APs) continues to be challenging, resulting in lower success rates and\\u000a higher recurrence rates. One of the reasons for a prolonged or failed procedure is mapping error and changes in cardiac anatomy.\\u000a The right coronary artery (RCA) runs

  19. Electrophysiologic Studies and Radiofrequency Catheter Ablation of Ectopic Atrial Tachycardia in Children

    Microsoft Academic Search

    Keiko Toyohara; Hitoo Fukuhara; Jun Yoshimoto; Noriyasu Ozaki; Yoshihide Nakamura

    2011-01-01

    Ectopic atrial tachycardia (EAT) often resists medical therapy, making radiofrequency catheter ablation (RFCA) the preferred\\u000a treatment. This study reviewed the records of 35 patients who underwent electrophysiologic studies (EPS) and 39 RFCA procedures\\u000a for EAT during a 10-year period. Of the 35 patients, 10 (28%) presented with decreased ventricular function and tachycardia-induced\\u000a cardiomyopathy (TIC). The EAT originated on the right

  20. Radiofrequency Ablation for Supraventricular Tachycardia in Children ?15 kg Is Safe and Effective

    Microsoft Academic Search

    R. Aiyagari; E. V. Saarel; S. P. Etheridge; D. J. Bradley; M. Dick II; P. S. Fischbach

    2005-01-01

    Risks associated with radiofrequency ablation (RFA) have been reported to be increased in children ?15 kg. We sought to compare\\u000a the safety and efficacy of RFA in children <15 kg with those between 15.1 and 20 kg. Clinical, electrophysiologic, and RFA\\u000a data for all patients ?20 kg who underwent RFA for supraventricular tachycardia between January 1994 and January 2003 were

  1. METHANE AND n-BUTANE OXIDATION WITH CO2 UNDER RADIOFREQUENCY PLASMAS OF MODERATE PRESSURES (*)

    E-print Network

    Boyer, Edmond

    1205 METHANE AND n-BUTANE OXIDATION WITH CO2 UNDER RADIOFREQUENCY PLASMAS OF MODERATE PRESSURES) Résumé. 2014 L'oxydation du méthane et du n-butane avec CO2 a été étudiée dans des décharges électriques intermédiaires en C2 (C2H2, C2H4, C2H6) qui est la voie principale pour convertir mé- thane et n-butane en CO

  2. Radio-Frequency Single-Electron Transistor as Readout Device for Qubits: Charge Sensitivity and Backaction

    Microsoft Academic Search

    A. Aassime; G. Johansson; G. Wendin; R. J. Schoelkopf; P. Delsing

    2001-01-01

    We study the radio-frequency single-electron transistor (rf-SET) as a readout device for charge qubits. We measure the charge sensitivity of an rf-SET to be 6.3mue\\/Hz and evaluate the backaction of the rf-SET on a single Cooper-pair box. This allows us to compare the needed measurement time with the mixing time of the qubit imposed by the measurement. We find that

  3. Sensitivity of a micromechanical displacement detector based on the radio-frequency single-electron transistor

    Microsoft Academic Search

    Miles P. Blencowe; Martin N. Wybourne

    2000-01-01

    We investigate the tunneling shot noise limits on the sensitivity of a micromechanical displacement detector based on a metal junction, radio-frequency single-electron transistor (rf SET). In contrast with the charge sensitivity of the rf-SET electrometer, the displacement sensitivity improves with increasing gate voltage bias and, with a suitably optimized rf SET, displacement sensitivities of 10?6 Å\\/Hz may be possible.

  4. Diagnostics of a Radio-Frequency Plasma Expanding Through a Nozzle (PETN) at Low Pressure

    Microsoft Academic Search

    R. Avni; S. F. Miralaï; F. Prevot; D. Morvan; J. Amoroux; H. Nickel

    1997-01-01

    The diagnostics of the radio-frequency (induction mode) plasma expanded through a nozzle (PETN) at low pressures (100–1000 Pa) was performed by on-line optical emission spectroscopy (OES) and on line quadrupole mass spectrometry (QMS). The OES was used for evaluating the electronic, vibrational, and rotational temperatures (Te, Tv, and Tr) along the plasma reactor before and after the nozzle. The PETN

  5. Hepatocellular cancer response to radiofrequency tumor ablation: contrast-enhanced ultrasound

    Microsoft Academic Search

    Tommaso Vincenzo Bartolotta; Adele Taibbi; Massimo Midiri; Marcello De Maria

    2008-01-01

    \\u000a Abstract\\u000a   Radiofrequency ablation (RFA) is increasingly being used as percutaneous treatment of choice for patients with early stage\\u000a hepatocellular carcinoma (HCC). An accurate assessment of the RFA therapeutic response is of crucial importance, considering\\u000a that a complete tumor ablation significantly increases patient survival, whereas residual unablated tumor calls for additional\\u000a treatment. Imaging modalities play a pivotal role in accomplishing this

  6. Injection of subphrenic saline during radiofrequency ablation to minimize diaphragmatic injury.

    PubMed

    Kapoor, Baljendra S; Hunter, David W

    2003-01-01

    An 82-year-old man with a history of colorectal cancer presented with metastatic disease to the liver (Couinaud segment 8). We describe the techniques that we employed to successfully perform radiofrequency ablation of a liver metastasis near the dome of the diaphragm utilizing subphrenic infusion of normal saline. The aim of this technique was to prevent thermal injury of the diaphragm. PMID:14562984

  7. Cellulite treatment using a novel combination radiofrequency, infrared light, and mechanical tissue manipulation device

    Microsoft Academic Search

    Tina S. Alster; Elizabeth L. Tanzi

    2005-01-01

    Background. Most post-pubertal women exhibit cellulite, particularly in the thigh and buttock regions. The prevalence of cellulite has led to many attempts at treatment, including a variety of topical solutions, massage-based therapies, and surgical techniques—most with suboptimal clinical effects. The purpose of this controlled study was to evaluate a novel combination device involving radiofrequency, infrared light, and mechanical tissue manipulation

  8. Circumference reduction and cellulite treatment with a TriPollar radiofrequency device: a pilot study

    Microsoft Academic Search

    W Manuskiatti; C Wachirakaphan; N Lektrakul; S Varothai

    2009-01-01

    Background A wide variety of treatments for circumference reduction and cellulite are available, but most procedures offer suboptimal clinical effect and\\/or delayed therapeutic outcome. Objective To determine the safety and efficacy of the TriPollar radiofrequency device for cellulite treatment and circumference reduction. Methods Thirty-nine females with cellulite received eight weekly TriPollar treatments. Treatment areas included the abdomen, thighs, buttocks and

  9. Three-Tone Characterization of Nonlinear Memory Effects in Radio-Frequency Power Amplifiers

    Microsoft Academic Search

    Damian Rönnow; David Wisell; Magnus Isaksson

    2007-01-01

    A stepped three-tone measurement technique based on digitally modulated baseband signals is used in characterizing radio-frequency power amplifiers (PAs). The bandwidths of the stepped measurement were 8.8 MHz for the input signal and 26.4 MHz for the output signal. A PA designed for third-generation mobile telecommunication system was analyzed. The amplitude and phase of the third-order Volterra kernel were determined

  10. EUS-guided radiofrequency ablation in the pancreas: results in a porcine model

    Microsoft Academic Search

    S. Nahum Goldberg; Shawn Mallery; G. Scott Gazelle; William R. Brugge

    1999-01-01

    Background:  Our aim in this study was to investigate the feasibility and safety of performing radiofrequency (RF) ablation in the pancreas with endoscopic ultrasound (EUS). Methods:  RF was applied to normal pancreatic tissue in 13 anesthetized Yorkshire pigs with specially modified 19-gauge needle electrodes (1.0 to 1.5 cm tip). The pancreas was localized with EUS and punctured through a transgastric

  11. Radio-frequency glow discharge ion source for high resolution mass spectrometry

    Microsoft Academic Search

    A. I. Saprykin; F.-G. Melchers; J. S. Becker; H.-J. Dietze

    1995-01-01

    A radio-frequency powered glow discharge ion source has been developed for a double-focusing mass spectrometer. The sputtering and ionization of conducting, semiconducting and insulating materials have been realized using a 13.56 MHz generator to supply the discharge operating potential. The glow discharge ion source operates stably at argon pressures of 0.1–1 hPa and radio frequency powers of 10–50 W. The

  12. Histological findings in adipocytes when cellulite is treated with a variable-emission radiofrequency system

    Microsoft Academic Search

    Mario A. Trelles; Claudia van der Lugt; Serge Mordon; Adriana Ribé; Marwan Al-Zarouni

    2010-01-01

    Cellulite is a disorder of the subcutaneous fat layer and the overlying superficial skin. Recently, radiofrequency (RF) has\\u000a been proposed as an effective treatment of cellulite; however, the mechanism through which the absorbed electrical energy\\u000a acts on the tissue is still not fully clear. This study reports on the histological findings from biopsies taken immediately\\u000a after a single RF treatment

  13. Characteristics of radio-frequency atmospheric pressure dielectric-barrier discharge with dielectric electrodes

    SciTech Connect

    Hussain, S., E-mail: shussain@uos.edu.pk, E-mail: shussainuos@yahoo.com; Qazi, H. I. A.; Badar, M. A. [Department of Physics, University of Sargodha, 40100 Sargodha (Pakistan)] [Department of Physics, University of Sargodha, 40100 Sargodha (Pakistan)

    2014-03-15

    An experimental investigation to characterize the properties and highlight the benefits of atmospheric pressure radio-frequency dielectric-barrier discharge (rf DBD) with dielectric electrodes fabricated by anodizing aluminium substrate is presented. The current-voltage characteristics and millisecond images are used to distinguish the ? and ? modes. This atmospheric rf DBD is observed to retain the discharge volume without constriction in ? mode. Optical emission spectroscopy demonstrates that the large discharge current leads to more abundant reactive species in this plasma source.

  14. Passive 5.8GHz radio-frequency identification tag for monitoring oil drill pipe

    Microsoft Academic Search

    Berndie Strassner; Kai Chang

    2003-01-01

    This paper reports a new passive 5.8-GHz radio-frequency identification tag proposed for monitoring oil drill pipe (patent pending). The tag is to be inserted into the tool joint of the drill pipe in order to predict the pipe's lifetime and to provide inventory control. The tag requires a minimal incident power density of 13.5 mW\\/cm2 to establish a link and

  15. Radio-Frequency Spectroscopy of a Strongly Interacting Two-Dimensional Fermi Gas

    Microsoft Academic Search

    Bernd Fröhlich; Michael Feld; Enrico Vogt; Marco Koschorreck; Wilhelm Zwerger; Michael Köhl

    2011-01-01

    We realize and study a strongly interacting two-component atomic Fermi gas confined to two dimensions in an optical lattice. Using radio-frequency spectroscopy we measure the interaction energy of the strongly interacting gas. We observe the confinement-induced Feshbach resonance on the attractive side of the 3D Feshbach resonance and find the existence of confinement-induced molecules in very good agreement with theoretical

  16. Radiofrequency energy delivery to the gastroesophageal junction for the treatment of GERD

    Microsoft Academic Search

    George Triadafilopoulos; John K. DiBaise; Timothy T. Nostrant; Neil H. Stollman; Paul K. Anderson; Steven A. Edmundowicz; Donald O. Castell; Michael S. Kim; John C. Rabine; David S. Utley

    2001-01-01

    Background: In this multi-center study, the feasibility, safety, and efficacy of radiofrequency (RF) energy delivery to the gastroesophageal junction (GEJ) for the treatment of gastroesophageal reflux disease (GERD) were investigated. Methods: Forty-seven patients with classic symptoms of GERD (heartburn and\\/or regurgitation), a daily anti-secretory medication requirement, and at least partial symptom response to drugs were enrolled. All patients had pathologic

  17. Effective epilation of white and blond hair using combined radiofrequency and optical energy

    Microsoft Academic Search

    Neil S Sadick; Sharyn A Laughlin

    2004-01-01

    OBJECTIVE: The present study exam- ined the long-term photoepilatory effect on blond and white hair of a combined intense pulsed light (680-980 nm) device with a bipolar radiofrequency component produ- cing electrical current at a depth of 4 mm. MATERIALS AND METHODS: Thirty-six adult women with white and blond hair (skin phenotypes I-V) were included in the study. The chin

  18. Radiofrequency (27.12 MHz) Processing of Thermosetting DGEBA Epoxy Resins

    Microsoft Academic Search

    Albert J. Gourdenne

    2005-01-01

    Radiofrequencies (27.12 MHz) or RF are used to activate the curing reaction of a DGEBA epoxy resin in presence of 4,41 -diaminodiphenylmethane as cross-linking agent. The article is divided into four parts. The introduction is devoted to the presentation of the principle of the RF activation of the processing of the epoxy prepolymers. Afterwards, in the experimental part, the applied

  19. In Vivo Guidance and Assessment of Liver Radio-Frequency Ablation with Acoustic Radiation Force Elastography

    Microsoft Academic Search

    Brian J. Fahey; Rendon C. Nelson; Stephen J. Hsu; David P. Bradway; Douglas M. Dumont; Gregg E. Trahey

    2008-01-01

    The initial results from clinical trials investigating the utility of acoustic radiation force impulse (ARFI) imaging for use with radio-frequency ablation (RFA) procedures in the liver are presented. To date, data have been collected from 6 RFA procedures in 5 unique patients. Large displacement contrast was observed in ARFI images of both pre-ablation malignancies (mean 7.5 dB, range 5.7–11.9 dB)

  20. WindSat radio-frequency interference signature and its identification over land and ocean

    Microsoft Academic Search

    L. Li; Peter W. Gaiser; Michael H. Bettenhausen; William Johnston

    2006-01-01

    Radio-frequency interference (RFI) in the spaceborne multichannel radiometer data of WindSat and the Advanced Microwave Scanning Radiometer-EOS is currently being detected using a spectral difference technique. Such a technique does not explicitly utilize multichannel correlations of radiometer data, which are key information in separating RFI from natural radiations. Furthermore, it is not optimal for radiometer data observed over ocean regions