WorldWideScience

Sample records for extremely small magnetic

  1. The Gravity and Extreme Magnetism Small Explorer (GEMS)

    Science.gov (United States)

    Kallman, T. R.

    2011-01-01

    The Gravity and Extreme Magnetism Small Explorer (GEMS) was selected by NASA for flight in 2014 to make a sensitive search for X-ray polarization from a wide set of source classes, including stellar black holes, Seyfert galaxies and quasars, blazars, rotation and accretion-powered pulsars, magnetars, shell supernova remnants and pulsar wind nebulae. Among the primary scientific objectives are determining the effects of the spin of black holes and the geometry of supermassive black hole accretion, determining the configurations of the magnetic fields and the X-ray emission of magnetars, and determining the magnetic structure of the supernova shocks in which cosmic rays are accelerated. GEMS will observe 23 targets during a 16 month prime mission, in observations that will be able to reach predicted levels of polarization. The mission can be extended to provide a guest observer phase. The GEMS instrument has time projection chamber polarimeters with high 2-10 keV efficiency at the focus of thin foil mirrors. The 4.5 m focal length mirrors will be deployed on an extended boom. The spacecraft with the instrument is rotated with a period of about 10 minutes to enable measurement and correction of systematic errors. A small Bragg reflection soft X-ray experiment takes advantage of this rotation to obtain a measurement at 0.5 keV. The design of the GEMS instrument and the mission, the expected performance and the planned science program will be discussed.

  2. The Gravity and Extreme Magnetism Small Expolorer Mission

    Science.gov (United States)

    Kallman, Timothy R.; Swank, J.; Jahoda, K.; GEMS Team

    2011-01-01

    Polarization is an inherently geometric quantity and provides information on source geometry inaccessible via spectroscopy or timing. To date, there have been reliable detections of X-ray polarization from only one object outside the solar system (the Crab nebula). Recent development of photoelectric polarimetry makes it possible to perform sensitive X-ray polarimetry with a modest mission. GEMS was recently selected by NASA to be the 13th Small Explorer mission with launch planned for 2014. GEMS will be 100× more sensitive than any previously flown X-ray polarimeter and should provide useful polarization measurements for dozens of sources, to lower than predicted levels. GEMS will lead to new insights into the nature of accreting black holes, highly magnetized neutron stars, and supernova remnants.

  3. Performance Verification of the Gravity and Extreme Magnetism Small Explorer GEMS X-Ray Polarimeter

    Science.gov (United States)

    Enoto, Teruaki; Black, J. Kevin; Kitaguchi, Takao; Hayato, Asami; Hill, Joanne E.; Jahoda, Keith; Tamagawa, Toru; Kanako, Kenta; Takeuchi, Yoko; Yoshikawa, Akifumi; Kenward, David

    2014-01-01

    olarimetry is a powerful tool for astrophysical observations that has yet to be exploited in the X-ray band. For satellite-borne and sounding rocket experiments, we have developed a photoelectric gas polarimeter to measure X-ray polarization in the 2-10 keV range utilizing a time projection chamber (TPC) and advanced micro-pattern gas electron multiplier (GEM) techniques. We carried out performance verification of a flight equivalent unit (1/4 model) which was planned to be launched on the NASA Gravity and Extreme Magnetism Small Explorer (GEMS) satellite. The test was performed at Brookhaven National Laboratory, National Synchrotron Light Source (NSLS) facility in April 2013. The polarimeter was irradiated with linearly-polarized monochromatic X-rays between 2.3 and 10.0 keV and scanned with a collimated beam at 5 different detector positions. After a systematic investigation of the detector response, a modulation factor greater than or equal to 35% above 4 keV was obtained with the expected polarization angle. At energies below 4 keV where the photoelectron track becomes short, diffusion in the region between the GEM and readout strips leaves an asymmetric photoelectron image. A correction method retrieves an expected modulation angle, and the expected modulation factor, approximately 20% at 2.7 keV. Folding the measured values of modulation through an instrument model gives sensitivity, parameterized by minimum detectable polarization (MDP), nearly identical to that assumed at the preliminary design review (PDR).

  4. Gravity and Extreme Magnetism SMEX

    Science.gov (United States)

    2012-01-01

    The Gravity and Extreme Magnetism SMEX mission will be the first mission to catalogue the X-ray polarisation of many astrophysical objects including black-holes and pulsars. This first of its kind mission is enabled by the novel use of a time projection chamber as an X-ray polarimeter. The detector has been developed over the last 5 years, with the current effort charged toward a demonstration of it's technical readiness to be at level 6 prior to the preliminary design review. This talk will describe the design GEMS polarimeter and the results to date from the engineering test unit.

  5. Magnetic slippery extreme icephobic surfaces

    Science.gov (United States)

    Irajizad, Peyman; Hasnain, Munib; Farokhnia, Nazanin; Sajadi, Seyed Mohammad; Ghasemi, Hadi

    2016-11-01

    Anti-icing surfaces have a critical footprint on daily lives of humans ranging from transportation systems and infrastructure to energy systems, but creation of these surfaces for low temperatures remains elusive. Non-wetting surfaces and liquid-infused surfaces have inspired routes for the development of icephobic surfaces. However, high freezing temperature, high ice adhesion strength, and high cost have restricted their practical applications. Here we report new magnetic slippery surfaces outperforming state-of-the-art icephobic surfaces with a ice formation temperature of -34 °C, 2-3 orders of magnitude higher delay time in ice formation, extremely low ice adhesion strength (~2 Pa) and stability in shear flows up to Reynolds number of 105. In these surfaces, we exploit the magnetic volumetric force to exclude the role of solid-liquid interface in ice formation. We show that these inexpensive surfaces are universal and can be applied to all types of solids (no required micro/nano structuring) with no compromise to their unprecedented properties.

  6. Evaluation of extremely small horizontal emittance

    Directory of Open Access Journals (Sweden)

    T. Okugi

    1999-02-01

    Full Text Available The KEK Accelerator Test Facility (KEK-ATF was constructed to develop technologies for producing a low-emittance beam which will be required by future linear colliders. The KEK-ATF consists of an injector linac, a damping ring, and a beam extraction line. The basic optical structure of the damping ring is a FOBO lattice, which reduces the horizontal dispersion at the center of the bending magnets and, as a consequence, can produce an extremely small emittance beam. To verify the performance of such a unique, low-emittance lattice, it is crucial to measure the horizontal emittance. The horizontal emittance was measured using wire scanners in the beam extraction line. Since the horizontal beam position was not stable, we established a method to correct the measured beam size for position fluctuation (“jitter” and we succeeded in the observation of the so far smallest horizontal emittance in any accelerator. The measured horizontal emittance was 1.37±0.03nm at a beam energy of 1.285 GeV and a bunch population of \\(3–5\\×10^{9}, in agreement with the design value of 1.27–1.34 nm at the beam energy and the bunch population.

  7. Magnetic Logic Circuits for Extreme Environments Project

    Data.gov (United States)

    National Aeronautics and Space Administration — The program aims to demonstrate a new genre of all-magnetic logic circuits which are radiation-tolerant and capable of reliable operation in extreme environmental...

  8. Gram-scale synthesis, thermal stability, magnetic properties, and microwave absorption application of extremely small Co-C core-shell nanoparticles

    Science.gov (United States)

    Kuang, Daitao; Hou, Lizhen; Yu, Bowen; Liang, Bingbing; Deng, Lianwen; Huang, Han; Ma, Songshan; He, Jun; Wang, Shiliang

    2017-07-01

    Co-C core-shell nanoparticles have been synthesized in large quantity (in grams) by metal-organic chemical vapor deposition with analytical cobalt (III) acetylacetonate as precursor. Extremely small nanoparticles with an average core diameter of 3 nm and a shell thickness of 1-2 nm, and relatively large nanoparticles with an average core diameter of 23 nm and a shell thickness of 5-20 nm were obtained, depending on the deposition regions. The 3 nm Co nanocores are thermally stable up to 200 °C in air atmosphere, and do not exhibit visible structural and morphological changes after exposure to air at room temperature for 180 d. The extremely small core-shell nanoparticles exhibit typical superparamagnetic behaviors with a small coercivity of 5 Oe, while the relative large nanoparticles are a typical ferromagnetic material with a high coercivity of 584 Oe. In the microwave absorption tests, a low reflection loss (RL) of  -80.3 dB and large effective bandwidth (frequency range for \\text{RL}≤slant -10~ dB) of 10.1 GHz are obtained in the nanoparticle-paraffin composites with appropriate layer thicknesses and particle contents. This suggests that the as-synthesized Co-C core-shell nanoparticles have a high potential as the microwave-absorbing materials.

  9. Dynamos at extreme magnetic Prandtl numbers

    CERN Document Server

    Verma, Mahendra K

    2015-01-01

    We present a MHD shell model suitable for the computation of various energy fluxes of magnetohydrodynamic turbulence for very small and very large magnetic Prandtl numbers $\\mathrm{Pm}$; such computations are inaccessible to direct numerical simulations. For small $\\mathrm{Pm}$, we observe that the both kinetic and magnetic energy spectra scale as $k^{-5/3}$ in the inertial range, but the dissipative magnetic energy scales as $k^{-17/3}$. Here, the kinetic energy at large length scale feeds the large-scale magnetic field that cascades to small-scale magnetic field, which gets dissipated by Joule heating. The large $\\mathrm{Pm}$ dynamo has a similar behaviour except that the dissipative kinetic energy scales as $k^{-13/3}$. For this case, the large-scale velocity field transfers energy to large-scale magnetic field, which gets transferred to small-scale velocity and magnetic fields. The energy of the small-scale magnetic field also gets transferred to the small-scale velocity field. The energy accumulated at s...

  10. On Destroying Extremal Magnetized Black Holes

    CERN Document Server

    Siahaan, Haryanto M

    2016-01-01

    The gedanken experiment by Wald to destroy a black hole using a test particle in the equatorial plane is adopted to the case of extremal magnetized black holes. We find that the presence of external magnetic fields resulting from the "magnetization" process using a Harrison-like transformation permits the test particle to have energies in the range which allows the destruction of black holes. However, from the corresponding effective potential we find that the test particle which may destroy the black hole can never reach the horizon.

  11. Magnetic Fields inside Extremely Fast Shock Waves

    NARCIS (Netherlands)

    Wiersma, J.

    2007-01-01

    The aim of my research on magnetic fields in extremely fast shock waves has been to predict the properties of shock waves that move almost with the speed of light. These shocks are created in the tenuous interstellar medium by catastrophic events such as the explosion of stars many times heavier

  12. Magnetic Fields inside Extremely Fast Shock Waves

    NARCIS (Netherlands)

    Wiersma, J.

    2007-01-01

    The aim of my research on magnetic fields in extremely fast shock waves has been to predict the properties of shock waves that move almost with the speed of light. These shocks are created in the tenuous interstellar medium by catastrophic events such as the explosion of stars many times heavier

  13. Magnetic Reconnection in Extreme Astrophysical Environments

    CERN Document Server

    Uzdensky, Dmitri A

    2011-01-01

    Magnetic reconnection is a basic plasma process of dramatic rearrangement of magnetic topology, often leading to a violent release of magnetic energy. It is important in magnetic fusion and in space and solar physics --- areas that have so far provided the context for most of reconnection research. Importantly, these environments consist just of electrons and ions and the dissipated energy always stays with the plasma. In contrast, in this paper I introduce a new direction of research, motivated by several important problems in high-energy astrophysics --- reconnection in high energy density (HED) radiative plasmas, where radiation pressure and radiative cooling become dominant factors in the pressure and energy balance. I identify the key processes distinguishing HED reconnection: special-relativistic effects; radiative effects (radiative cooling, radiation pressure, and Compton resistivity); and, at the most extreme end, QED effects, including pair creation. I then discuss the main astrophysical application...

  14. Occurrence rate of extreme magnetic storms

    CERN Document Server

    Yermolaev, Yu I; Nikolaeva, N S; Yermolaev, M Yu

    2013-01-01

    Statistical analysis of occurrence rate of magnetic storms induced by different types of interplanetary drivers is made on the basis of OMNI data for period 1976-2000. Using our catalog of large scale types of solar wind streams we study storms induced by interplanetary coronal mass ejections (ICME) (separately magnetic clouds (MC) and Ejecta) and both types of compressed regions: corotating interaction regions (CIR) and Sheaths. For these types of drivers we calculate integral probabilities of storms with minimum Dst < -50, -70, -100, -150, and -200 nT. The highest probability in this interval of Dst is observed for MC, probabilities for other drivers are 3-10 times lower than for MC. Extrapolation of obtained results to extreme storms shows that such a magnetic storm as Carrington storm in 1859 with Dst = -1760 nT is observed on the Earth with frequency 1 event during ~500 year.

  15. Small-scale dynamo at low magnetic Prandtl numbers.

    Science.gov (United States)

    Schober, Jennifer; Schleicher, Dominik; Bovino, Stefano; Klessen, Ralf S

    2012-12-01

    The present-day Universe is highly magnetized, even though the first magnetic seed fields were most probably extremely weak. To explain the growth of the magnetic field strength over many orders of magnitude, fast amplification processes need to operate. The most efficient mechanism known today is the small-scale dynamo, which converts turbulent kinetic energy into magnetic energy leading to an exponential growth of the magnetic field. The efficiency of the dynamo depends on the type of turbulence indicated by the slope of the turbulence spectrum v(ℓ)∝ℓ^{ϑ}, where v(ℓ) is the eddy velocity at a scale ℓ. We explore turbulent spectra ranging from incompressible Kolmogorov turbulence with ϑ=1/3 to highly compressible Burgers turbulence with ϑ=1/2. In this work, we analyze the properties of the small-scale dynamo for low magnetic Prandtl numbers Pm, which denotes the ratio of the magnetic Reynolds number, Rm, to the hydrodynamical one, Re. We solve the Kazantsev equation, which describes the evolution of the small-scale magnetic field, using the WKB approximation. In the limit of low magnetic Prandtl numbers, the growth rate is proportional to Rm^{(1-ϑ)/(1+ϑ)}. We furthermore discuss the critical magnetic Reynolds number Rm_{crit}, which is required for small-scale dynamo action. The value of Rm_{crit} is roughly 100 for Kolmogorov turbulence and 2700 for Burgers. Furthermore, we discuss that Rm_{crit} provides a stronger constraint in the limit of low Pm than it does for large Pm. We conclude that the small-scale dynamo can operate in the regime of low magnetic Prandtl numbers if the magnetic Reynolds number is large enough. Thus, the magnetic field amplification on small scales can take place in a broad range of physical environments and amplify week magnetic seed fields on short time scales.

  16. Small-scale dynamo at low magnetic Prandtl numbers

    Science.gov (United States)

    Schober, Jennifer; Schleicher, Dominik; Bovino, Stefano; Klessen, Ralf S.

    2012-12-01

    The present-day Universe is highly magnetized, even though the first magnetic seed fields were most probably extremely weak. To explain the growth of the magnetic field strength over many orders of magnitude, fast amplification processes need to operate. The most efficient mechanism known today is the small-scale dynamo, which converts turbulent kinetic energy into magnetic energy leading to an exponential growth of the magnetic field. The efficiency of the dynamo depends on the type of turbulence indicated by the slope of the turbulence spectrum v(ℓ)∝ℓϑ, where v(ℓ) is the eddy velocity at a scale ℓ. We explore turbulent spectra ranging from incompressible Kolmogorov turbulence with ϑ=1/3 to highly compressible Burgers turbulence with ϑ=1/2. In this work, we analyze the properties of the small-scale dynamo for low magnetic Prandtl numbers Pm, which denotes the ratio of the magnetic Reynolds number, Rm, to the hydrodynamical one, Re. We solve the Kazantsev equation, which describes the evolution of the small-scale magnetic field, using the WKB approximation. In the limit of low magnetic Prandtl numbers, the growth rate is proportional to Rm(1-ϑ)/(1+ϑ). We furthermore discuss the critical magnetic Reynolds number Rmcrit, which is required for small-scale dynamo action. The value of Rmcrit is roughly 100 for Kolmogorov turbulence and 2700 for Burgers. Furthermore, we discuss that Rmcrit provides a stronger constraint in the limit of low Pm than it does for large Pm. We conclude that the small-scale dynamo can operate in the regime of low magnetic Prandtl numbers if the magnetic Reynolds number is large enough. Thus, the magnetic field amplification on small scales can take place in a broad range of physical environments and amplify week magnetic seed fields on short time scales.

  17. Small and smart magnet design

    DEFF Research Database (Denmark)

    Frandsen, Cathrine; Beleggia, Marco; Brok, Erik

    2014-01-01

    Society faces an accumulated need to find ways to produce super strong magnets that can fulfill thegrowing demands for green technology products such as compact and efficient generators and motors. Next‐generation magnets could very likely be composite materials built bottom‐up from nanoparticles...

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

    DEFF Research Database (Denmark)

    Schüz, J; Grell, K; Kinsey, S

    2012-01-01

    A previous US study reported poorer survival in children with acute lymphoblastic leukemia (ALL) exposed to extremely low-frequency magnetic fields (ELF-MF) above 0.3 μT, but based on small numbers. Data from 3073 cases of childhood ALL were pooled from prospective studies conducted in Canada...

  19. Dynamos at extreme magnetic Prandtl numbers: insights from shell models

    Science.gov (United States)

    Verma, Mahendra K.; Kumar, Rohit

    2016-12-01

    We present an MHD shell model suitable for computation of various energy fluxes of magnetohydrodynamic turbulence for very small and very large magnetic Prandtl numbers $\\mathrm{Pm}$; such computations are inaccessible to direct numerical simulations. For small $\\mathrm{Pm}$, we observe that both kinetic and magnetic energy spectra scale as $k^{-5/3}$ in the inertial range, but the dissipative magnetic energy scales as $k^{-11/3}\\exp(-k/k_\\eta)$. Here, the kinetic energy at large length scale feeds the large-scale magnetic field that cascades to small-scale magnetic field, which gets dissipated by Joule heating. The large-$\\mathrm{Pm}$ dynamo has a similar behaviour except that the dissipative kinetic energy scales as $k^{-13/3}$. For this case, the large-scale velocity field transfers energy to the large-scale magnetic field, which gets transferred to small-scale velocity and magnetic fields; the energy of the small-scale magnetic field also gets transferred to the small-scale velocity field, and the energy thus accumulated is dissipated by the viscous force.

  20. The Estimation of Probability of Extreme Events for Small Samples

    Science.gov (United States)

    Pisarenko, V. F.; Rodkin, M. V.

    2017-02-01

    The most general approach to the study of rare extreme events is based on the extreme value theory. The fundamental General Extreme Value Distribution lies in the basis of this theory serving as the limit distribution for normalized maxima. It depends on three parameters. Usually the method of maximum likelihood (ML) is used for the estimation that possesses well-known optimal asymptotic properties. However, this method works efficiently only when sample size is large enough ( 200-500), whereas in many applications the sample size does not exceed 50-100. For such sizes, the advantage of the ML method in efficiency is not guaranteed. We have found that for this situation the method of statistical moments (SM) works more efficiently over other methods. The details of the estimation for small samples are studied. The SM is applied to the study of extreme earthquakes in three large virtual seismic zones, representing the regime of seismicity in subduction zones, intracontinental regime of seismicity, and the regime in mid-ocean ridge zones. The 68%-confidence domains for pairs of parameter (ξ, σ) and (σ, μ) are derived.

  1. Small Black Holes and Near-Extremal CFTs

    CERN Document Server

    Benjamin, Nathan; Fitzpatrick, A Liam; Maloney, Alexander; Perlmutter, Eric

    2016-01-01

    Pure theories of AdS$_3$ quantum gravity are conjectured to be dual to CFTs with sparse spectra of light primary operators. The sparsest possible spectrum consistent with modular invariance includes only black hole states above the vacuum. Witten conjectured the existence of a family of extremal CFTs, which realize this spectrum for all admissible values of the central charge. We consider the quantum corrections to the classical spectrum, and propose a specific modification of Witten's conjecture which takes into account the existence of "small" black hole states. These have zero classical horizon area, with a calculable entropy attributed solely to loop effects. Our conjecture passes various consistency checks, especially when generalized to include theories with supersymmetry. In theories with $\\mathcal{N}=2$ supersymmetry, this "near-extremal CFT" proposal precisely evades the no-go results of Gaberdiel et al.

  2. The Small-Scale Dynamo at Low Magnetic Prandtl Numbers

    CERN Document Server

    Schober, Jennifer; Bovino, Stefano; Klessen, Ralf S

    2012-01-01

    The present-day Universe is highly magnetized, even though the first magnetic seed fields were most probably extremely weak. To explain the growth of the magnetic field strength over many orders of magnitude fast amplification processes need to operate. The most efficient mechanism known today is the small-scale dynamo, which converts turbulent kinetic energy into magnetic energy leading to an exponential growth of the magnetic field. The efficiency of the dynamo depends on the type of turbulence indicated by the slope of the turbulence spectrum v(l) \\propto l^{theta}, where v(l) is the eddy velocity at a scale l. We explore turbulent spectra ranging from incompressible Kolmogorov turbulence with theta = 1/3 to highly compressible Burgers turbulence with theta = 1/2. In this work we analyze the properties of the small-scale dynamo for low magnetic Prandtl numbers Pm, which denotes the ratio of the magnetic Reynolds number, Rm, to the hydrodynamical one, Re. We solve the Kazantsev equation, which describes the...

  3. Abnormalities of the upper extremities on fetal magnetic resonance imaging.

    Science.gov (United States)

    Nemec, S F; Kasprian, G; Brugger, P C; Bettelheim, D; Amann, G; Nemec, U; Rotmensch, S; Graham, J M; Rimoin, D L; Lachman, R S; Prayer, D

    2011-11-01

    In view of the increasing use of fetal magnetic resonance imaging (MRI) as an adjunct to prenatal ultrasonography, we sought to demonstrate the visualization of upper extremity abnormalities and associated defects on MRI, with regard to fetal outcomes and compared with ultrasound imaging. This retrospective study included 29 fetuses with upper extremity abnormalities visualized with fetal MRI following suspicious ultrasound findings and confirmed by postnatal assessment or autopsy. On a 1.5-Tesla unit, dedicated sequences were applied to image the extremities. Central nervous system (CNS) and extra-CNS anomalies were assessed to define extremity abnormalities as isolated or as complex, with associated defects. Fetal outcome was identified from medical records. MRI and ultrasound findings, when available, were compared. Isolated upper extremity abnormalities were found in three (10.3%) fetuses. In 26 (89.7%) fetuses complex abnormalities, including postural extremity disorders (21/26) and structural extremity abnormalities (15/26), were demonstrated. Associated defects involved: face (15/26); musculoskeletal system (14/26); thorax and cardio/pulmonary system (12/26); lower extremities (12/26); brain and skull (10/26); and abdomen (8/26). Of the 29 cases, 18 (62.1%) pregnancies were delivered and 11 (37.9%) were terminated. MRI and US findings were compared in 27/29 cases: the diagnosis was concordant in 14 (51.9%) of these cases, and additional findings were made on MRI in 13/27 (48.1%) cases. Visualization of upper extremity abnormalities on fetal MRI enables differentiation between isolated defects and complex ones, which may be related to poor fetal prognosis. MRI generally confirms the ultrasound diagnosis, and may provide additional findings in certain cases. Copyright © 2011 ISUOG. Published by John Wiley & Sons, Ltd.

  4. Fake Superpotential for Large and Small Extremal Black Holes

    CERN Document Server

    Andrianopoli, L; Ferrara, S; Trigiante, M

    2010-01-01

    We consider the fist order, gradient-flow, description of the scalar fields coupled to spherically symmetric, asymptotically flat black holes in extended supergravities. Using the identification of the fake superpotential with Hamilton's characteristic function we clarify some of its general properties, showing in particular (besides reviewing the issue of its duality invariance) that W has the properties of a Liapunov's function, which implies that its extrema (associated with the horizon of extremal black holes) are asymptotically stable equilibrium points of the corresponding first order dynamical system (in the sense of Liapunov). Moreover, we show that the fake superpotential W has, along the entire radial flow, the same flat directions which exist at the attractor point. This allows to study properties of the ADM mass also for small black holes where in fact W has no critical points at finite distance in moduli space. In particular the W function for small non-BPS black holes can always be computed anal...

  5. Extremely low frequency magnetic fields and health risks

    Directory of Open Access Journals (Sweden)

    M.I. Buzdugan

    2009-10-01

    Full Text Available In a world abounding in artificially created electromagnetic fields, we consider that a new approach regarding their possible harmful effects on living beings becomes mandatory. The paper reviews briefly the results of some epidemiological studies, the ICNIRP (International Committee on Non-Ionizing Radiation Protection Guidelines and the latest document of the SCENIHR (an organism of the European Commission regarding extremely low frequency (ELF magnetic fields. We are convinced that the best conduct that might be adopted on this matter is the policy of the prudential avoidance. Several examples of possible harmful effects determined by extremely low frequency magnetic fields dedicated to building services engineering in residences are presented, along with several methods of mitigating them.

  6. Effect of anisotropy on small magnetic clusters

    CERN Document Server

    Hucht, Alfred; Sil, Shreekantha; Entel, Peter; 10.1103/PhysRevB.84.104438

    2012-01-01

    The effect of dipolar interaction and local uniaxial anisotropy on the magnetic response of small spin clusters where spins are located on the vertices of icosahedron, cuboctahedron, tetrahedron and square geometry have been investigated. We consider the ferromagnetic and antiferromagnetic spin-1/2 and spin-1 Heisenberg model with uniaxial anisotropy and dipolar interaction and apply numerical exact diagonalization technique in order to study the influence of frustration and anisotropy on the ground state properties of the spin-clusters. The ground state magnetization, spin-spin correlation and several thermodynamic quantities such as entropy and specific heat are calculated as a function of temperature and magnetic field.

  7. Fault Tolerant Magnetic Bearing Testing and Conical Magnetic Bearing Development for Extreme Temperature Environments

    Science.gov (United States)

    Keith, Theo G., Jr.; Clark, Daniel

    2004-01-01

    During the six month tenure of the grant, activities included continued research of hydrostatic bearings as a viable backup-bearing solution for a magnetically levitated shaft system in extreme temperature environments (1000 F), developmental upgrades of the fault-tolerant magnetic bearing rig at the NASA Glenn Research Center, and assisting in the development of a conical magnetic bearing for extreme temperature environments, particularly turbomachinery. It leveraged work from the ongoing Smart Efficient Components (SEC) and the Turbine-Based Combined Cycle (TBCC) program at NASA Glenn Research Center. The effort was useful in providing technology for more efficient and powerful gas turbine engines.

  8. EXTREMELY LOW FREQUENCY MAGNETIC FIELD SUSCEPTIBILITY OF VISUAL DISPLAY UNITS

    Institute of Scientific and Technical Information of China (English)

    2001-01-01

    Extremely low frequency (ELF) magnetic field susceptibility is an index of visual display unit (VDU) quality and performance. This paper provided field measured data on the susceptibility for a large variety of VDUs. A test rig was built to study the susceptibility of VDUs to magnetic fields at fundamental and third harmonic frequencies. It was found that the susceptibility level is largely dependent on refresh rate of the VDU and the orientation of the external ELF field. It was also found that the VDU susceptibility is significantly increased in the presence of harmonic frequency magnetic fields. About 30% of the tested samples have susceptibility levels higher than that stated in IEC 1000-4-8 standard.

  9. Peltier heat of a small polaron in a magnetic semiconductor

    Energy Technology Data Exchange (ETDEWEB)

    Liu, N.L.H.; Emin, D.

    1984-01-01

    The heat transported with a small polaron in both antiferromagnetic and ferromagnetic semiconductors is calculated. This heat, the Peltier heat, ..pi.., is obtained from the change of the entropy of the total system upon introduction of a charge carrier. We explicitly consider both the intrasite and intersite exchange interactions between a small polaron and the interacting spins of a spin-1/2 magnet. There are two competing magnetic contributions to the Peltier heat. First, adding the carrier increases the spin entropy of the system. This provides a positive contribution to ..pi... Second, the exchange between the carrier and the sites about it enhances the exchange binding between these sites. This reduces the energetically allowable spin configurations and provides a negative contribution to ..pi... At extremely high temperature when kT exceeds the intrasite exchange energy, the first effect dominates. Then ..pi.. is simply augmented by kTln2. However, well below the magnetic transition temperature the second effect dominates. In the experimentally accessible range between these limits both effects are comparable and sizable. The net magnetic contribution to the Peltier heat rises with temperature. Thus, a carrier's interactions with its magnetic environment produces a significant and distinctive contribution to its Peltier heat.

  10. Peltier heat of a small polaron in a magnetic semiconductor

    Energy Technology Data Exchange (ETDEWEB)

    Liu, N.H.; Emin, D.

    1985-04-15

    For the first time the heat transported with a small polaron in both antiferromagnetic and ferromagnetic semiconductors is calculated. This heat, the Peltier heat, ..pi.., is obtained from the change of the entropy of the total system upon introduction of a charge carrier. We explicitly consider both the intrasite and intersite exchange interactions between a small polaron and the interacting spins of a spin-1/2 magnet. There are two competing magnetic contributions to the Peltier heat. First, adding the carrier increases the spin entropy of the system. This provides a positive contribution to ..pi... Second, the exchange between the carrier and the sites about it enhances the exchange binding between these sites. This reduces the energetically allowable spin configurations and provides a negative contribution to ..pi... At extremely high temperatures when kT exceeds the intrasite exchange energy, the first effect dominates. Then ..pi.. is simply augmented by kT ln 2. However, well below the magnetic transition temperature the second effect dominates. In the experimentally accessible range between these limits both effects are comparable and sizable. The net magnetic contribution to the Peltier heat rises with temperature. Thus, a carrier's interactions with its magnetic environment produces a significant and distinctive contribution to its Peltier heat.

  11. Magnetic resonance imaging of the small bowel

    Energy Technology Data Exchange (ETDEWEB)

    Deeab, Dhafer A., E-mail: dhafer_ahmed@yahoo.co [Department of Radiology, St Mary' s Campus, Imperial College NHS Trust, London (United Kingdom); Dick, Elizabeth; Sergot, Antoni A.; Sundblon, Lauren; Gedroyc, Wady [Department of Radiology, St Mary' s Campus, Imperial College NHS Trust, London (United Kingdom)

    2011-02-15

    Magnetic Resonance Imaging of the Small Bowel (MR Enterography, or MRE) is becoming increasingly popular as the first imaging modality for the diagnosis and follow-up of small bowel diseases. The inherent advantages of MRI, including excellent soft tissue contrast, multiplanar capability and lack of ionising radiation are well known. In addition, the use of luminal contrast agents in MRE has the added advantage of demonstrating the lumen and the wall directly, something not possible to achieve with conventional small bowel barium follow-through imaging. This review will highlight recent technical advances to this low cost, simple technique which is easily achievable in all hospitals. It will also review normal and abnormal radiological findings and highlight the value of this technique to both the clinician and patient alike in the investigation of small bowel disease.

  12. Small Satellite Passive Magnetic Attitude Control

    Science.gov (United States)

    Gerhardt, David T.

    Passive Magnetic Attitude Control (PMAC) is capable of aligning a satellite within 5 degrees of the local magnetic field at low resource cost, making it ideal for a small satellite. However, simulation attempts to date have not been able to predict the attitude dynamics at a level sufficient for mission design. Also, some satellites have suffered from degraded performance due to an incomplete understanding of PMAC system design. This dissertation alleviates these issues by discussing the design, inputs, and validation of PMAC systems for small satellites. Design rules for a PMAC system are defined using the Colorado Student Space Weather Experiment (CSSWE) CubeSat as an example. A Multiplicative Extended Kalman Filter (MEKF) is defined for the attitude determination of a PMAC satellite without a rate gyro. After on-orbit calibration of the off-the-shelf magnetometer and photodiodes and an on-orbit fit to the satellite magnetic moment, the MEKF regularly achieves a three sigma attitude uncertainty of 4 degrees or less. CSSWE is found to settle to the magnetic field in seven days, verifying its attitude design requirement. A Helmholtz cage is constructed and used to characterize the CSSWE bar magnet and hysteresis rods both individually and in the flight configuration. Fitted parameters which govern the magnetic material behavior are used as input to a PMAC dynamics simulation. All components of this simulation are described and defined. Simulation-based dynamics analysis shows that certain initial conditions result in abnormally decreased settling times; these cases may be identified by their dynamic response. The simulation output is compared to the MEKF output; the true dynamics are well modeled and the predicted settling time is found to possess a 20 percent error, a significant improvement over prior simulation.

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

    Science.gov (United States)

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

    2014-04-01

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

  14. Extreme Particle Acceleration via Magnetic Reconnection in the Crab Nebula

    Science.gov (United States)

    Cerutti, Benoit; Uzdensky, D. A.; Begelman, M. C.

    2012-01-01

    The discovery by Agile and Fermi of intense day-long synchrotron gamma-ray flares above 100 MeV in the Crab Nebula challenges classical models of pulsar wind nebulae and particle acceleration. We argue that the flares are powered by magnetic reconnection in the nebula. Using relativistic test-particle simulations, we show that particles are naturally focused into a thin fan beam, deep inside the reconnection layer where the magnetic field is small. The particles then suffer less from synchrotron losses and pile up at the maximum energy given by the electric potential drop in the layer. Applying this model to the Crab Nebula, we find that the emerging synchrotron emission spectrum above 100 MeV is consistent with the September 2010 flare observations. No detectable emission is expected at other wavelengths. This scenario provides a viable explanation for the Crab Nebula gamma-ray flares.

  15. Laws of small numbers extremes and rare events

    CERN Document Server

    Falk, Michael; Hüsler, Jürg

    2004-01-01

    Since the publication of the first edition of this seminar book in 1994, the theory and applications of extremes and rare events have enjoyed an enormous and still increasing interest. The intention of the book is to give a mathematically oriented development of the theory of rare events underlying various applications. This characteristic of the book was strengthened in the second edition by incorporating various new results on about 130 additional pages. Part II, which has been added in the second edition, discusses recent developments in multivariate extreme value theory. Particularly notable is a new spectral decomposition of multivariate distributions in univariate ones which makes multivariate questions more accessible in theory and practice. One of the most innovative and fruitful topics during the last decades was the introduction of generalized Pareto distributions in the univariate extreme value theory. Such a statistical modelling of extremes is now systematically developed in the multivariate fram...

  16. Force-Free Magnetic Fields on AN Extreme Reissner-Nordström Spacetime and the Meissner Effect

    Science.gov (United States)

    Takamori, Yousuke; Ken-Ichi, Nakao; Hideki, Ishihara; Masashi, Kimura; Chul-Moon, Yoo

    It is known that the Meissner effect of black holes is seen in the vacuum solutions of blackhole magnetosphere: no non-monopole component of magnetic flux penetrates the event horizon if the black hole is extreme. In this article, in order to see the effects of charge currents, we study the force-free magnetic field on the extreme Reissner-Nordström background. In this case, we should solve one elliptic differential equation called the Grad-Shafranov equation which has singular points called light surfaces. In order to see the Meissner effect, we consider the region near the event horizon and try to solve the equation by Taylor expansion about the event horizon. Moreover, we assume that the small rotational velocity of the magnetic field, and then, we construct a perturbative method to solve the Grad-Shafranov equation considering the efftect of the inner light surface and study the behavior of the magnetic field near the event horizon.

  17. Small black holes and near-extremal CFTs

    Energy Technology Data Exchange (ETDEWEB)

    Benjamin, Nathan; Dyer, Ethan [Stanford Institute for Theoretical Physics,Via Pueblo, Stanford, CA 94305 (United States); Fitzpatrick, A. Liam [Boston University Physics Department,Commonwealth Avenue, Boston, MA 02215 (United States); Maloney, Alexander [McGill Physics Department,3600 rue University, Montréal, QC H3A 2T8 (Canada); Perlmutter, Eric [Department of Physics, Princeton University,Jadwin Hall, Princeton, NJ 08544 (United States)

    2016-08-02

    Pure theories of AdS{sub 3} quantum gravity are conjectured to be dual to CFTs with sparse spectra of light primary operators. The sparsest possible spectrum consistent with modular invariance includes only black hole states above the vacuum. Witten conjectured the existence of a family of extremal CFTs, which realize this spectrum for all admissible values of the central charge. We consider the quantum corrections to the classical spectrum, and propose a specific modification of Witten’s conjecture which takes into account the existence of “small” black hole states. These have zero classical horizon area, with a calculable entropy attributed solely to loop effects. Our conjecture passes various consistency checks, especially when generalized to include theories with supersymmetry. In theories with N=2 supersymmetry, this “near-extremal CFT” proposal precisely evades the no-go results of Gaberdiel et al.

  18. Small-scale characteristics of extremely high latitude aurora

    Directory of Open Access Journals (Sweden)

    J. A. Cumnock

    2009-09-01

    Full Text Available We examine 14 cases of an interesting type of extremely high latitude aurora as identified in the precipitating particles measured by the DMSP F13 satellite. In particular we investigate structures within large-scale arcs for which the particle signatures are made up of a group of multiple distinct thin arcs. These cases are chosen without regard to IMF orientation and are part of a group of 87 events where DMSP F13 SSJ/4 measures emissions which occur near the noon-midnight meridian and are spatially separated from both the dawnside and duskside auroral ovals by wide regions with precipitating particles typical of the polar cap. For 73 of these events the high-latitude aurora consists of a continuous region of precipitating particles. We focus on the remaining 14 of these events where the particle signatures show multiple distinct thin arcs. These events occur during northward or weakly southward IMF conditions and follow a change in IMF By. Correlations are seen between the field-aligned currents and plasma flows associated with the arcs, implying local closure of the FACs. Strong correlations are seen only in the sunlit hemisphere. The convection associated with the multiple thin arcs is localized and has little influence on the large-scale convection. This also implies that the sunward flow along the arcs is unrelated to the overall ionospheric convection.

  19. Structure of Small Magnetic Elements in the Solar Atmosphere

    CERN Document Server

    Domingo, V; Balmaceda, L A; Domínguez, S Vargas; Cabello, Iballa

    2012-01-01

    High resolution images at different wavelengths, spectrograms and magnetograms, representing different levels of the solar atmosphere obtained with Hinode have been combined to study the 3-dimensional structure of the small magnetic elements in relation to their radiance. A small magnetic element is described as example of the study.

  20. Small RNA transcriptomes of mangroves evolve adaptively in extreme environments.

    Science.gov (United States)

    Wen, Ming; Lin, Xingqin; Xie, Munan; Wang, Yushuai; Shen, Xu; Liufu, Zhongqi; Wu, Chung-I; Shi, Suhua; Tang, Tian

    2016-01-01

    MicroRNAs (miRNAs) and endogenous small interfering RNAs (siRNAs) are key players in plant stress responses. Here, we present the sRNA transcriptomes of mangroves Bruguiera gymnorrhiza and Kandelia candel. Comparative computational analyses and target predictions revealed that mangroves exhibit distinct sRNA regulatory networks that differ from those of glycophytes. A total of 32 known and three novel miRNA families were identified. Conserved and mangrove-specific miRNA targets were predicted; the latter were widely involved in stress responses. The known miRNAs showed differential expression between the mangroves and glycophytes, reminiscent of the adaptive stress-responsive changes in Arabidopsis. B. gymnorrhiza possessed highly abundant but less conserved TAS3 trans-acting siRNAs (tasiRNAs) in addition to tasiR-ARFs, with expanded potential targets. Our results indicate that the evolutionary alteration of sRNA expression levels and the rewiring of sRNA-regulatory networks are important mechanisms underlying stress adaptation. We also identified sRNAs that are involved in salt and/or drought tolerance and nutrient homeostasis as possible contributors to mangrove success in stressful environments.

  1. Analysis of the Extremely Low Frequency Magnetic Field Emission from Laptop Computers

    Directory of Open Access Journals (Sweden)

    Brodić Darko

    2016-03-01

    Full Text Available This study addresses the problem of magnetic field emission produced by the laptop computers. Although, the magnetic field is spread over the entire frequency spectrum, the most dangerous part of it to the laptop users is the frequency range from 50 to 500 Hz, commonly called the extremely low frequency magnetic field. In this frequency region the magnetic field is characterized by high peak values. To examine the influence of laptop’s magnetic field emission in the office, a specific experiment is proposed. It includes the measurement of the magnetic field at six laptop’s positions, which are in close contact to its user. The results obtained from ten different laptop computers show the extremely high emission at some positions, which are dependent on the power dissipation or bad ergonomics. Eventually, the experiment extracts these dangerous positions of magnetic field emission and suggests possible solutions.

  2. Two-dimensional resonant magnetic soft X-ray scattering set-up for extreme sample environment.

    Science.gov (United States)

    Stanescu, Stefan; Mocuta, Cristian; Merlet, Frederic; Barbier, Antoine

    2013-01-01

    The newly built MagSAXS (magnetic small-angle X-ray scattering) set-up dedicated to the direct two-dimensional measurement of magnetic scattering using polarized synchrotron radiation in extreme sample environments is presented. Pure optical transport of the image is used to record the magnetic scattering with a two-dimensional CCD visible-light camera. The set-up is able to probe magnetic correlation lengths from the micrometer down to the nanometer scale. A detailed layout is presented along with preliminary results obtained at several beamlines at Synchrotron SOLEIL. The presented examples underline the wide range of possible applications spanning from correlation lengths determination to Fourier transform holography.

  3. Electrically Small Magnetic Dipole Antennas with Magnetic Core

    DEFF Research Database (Denmark)

    Kim, Oleksiy S.; Breinbjerg, Olav

    2010-01-01

    This work extends the theory of a spherical magnetic dipole antenna with magnetic core by numerical results for practical antenna configurations that excite higher-order modes besides the main TE10 spherical mode. The multiarm spherical helix (MSH) and the spherical split ring (SSR) antennas...

  4. Extremal Black Holes in Strong Magnetic Fields: Near-Horizon Geometries and Meissner Effect

    CERN Document Server

    Hejda, Filip

    2016-01-01

    For extremal black holes, one can construct simpler, limiting spacetimes that describe the geometry near degenerate horizons. Since these spacetimes are known to have enhanced symmetry, the limiting objects coincide for different solutions. We show that this occurs for strongly magnetised Kerr-Newman solution, and how this is related to physical Meissner effect of expulsion of magnetic fields from extremal black holes.

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

    NARCIS (Netherlands)

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

    2014-01-01

    Although radio frequency (RF) electromagnetic fields emitted by mobile phones have received much attention, relatively little is known about the extremely low frequency (ELF) magnetic fields emitted by phones. This paper summarises ELF magnetic flux density measurements on global system for mobile c

  6. Generation of bright circularly-polarized extreme ultraviolet high harmonics for magnetic circular dichroism spectroscopy

    CERN Document Server

    Kfir, Ofer; Turgut, Emrah; Knut, Ronny; Zusin, Dmitriy; Popmintchev, Dimitar; Popmintchev, Tenio; Nembach, Hans; Shaw, Justin M; Fleicher, Avner; Kapteyn, Henry; Murnane, Margaret; Cohen, Oren

    2014-01-01

    Circularly-polarized extreme UV and X-ray radiation provides valuable access to the structural, electronic and magnetic properties of materials. To date, such experiments have been possible only using large-scale free-electron lasers or synchrotrons. Here we demonstrate the first bright extreme UV circularly-polarized high harmonics and use this new light source for magnetic circular dichroism measurements at the M-shell absorption edges of cobalt. This work paves the way towards element-specific imaging and spectroscopy of multiple elements simultaneously in magnetic and other chiral media with very high spatio-temporal resolution, all on a tabletop.

  7. [Small bowel perforation caused by magnetic toys].

    Science.gov (United States)

    Schroepfer, E; Siauw, C; Hoecht, B; Meyer, T

    2010-06-01

    Accidental ingestion of foreign bodies is a common problem in infants and childhood, but ingestion of magnetic construction toys is very rare. In the case of ingestion of multiple parts of these magnetic construction toys, they may attract each other through the intestinal walls, causing pressure necrosis, perforation, fistula formation or intestinal obstruction. A 20-month-old boy presented with a three-day history of abdominal pain and bilious vomiting. Physical examination revealed a slighted distended abdomen. The -white blood cell count was increased, but the C-reactive protein was normal. Ultrasound and X-ray of the abdomen showed a distended bowel loop in the right upper quadrant, a moderate amount of free intraperitoneal liquid and 4 foreign bodies. Emergency laparotomy was performed and 2 perforations in the ileum were detected. The perforations were caused by a magnetic construction toy and 2 iron globes. The fourth foreign body was a glass marble. The foreign bodies were removed, both perforations were primarily sutured. The child was discharged on postoperative day 10 after an uneventful recovery. Parents should be warned against the potential dangers of children's constructions toys that contain these kinds of magnets.

  8. Magnetic properties of ultra-small goethite nanoparticles

    DEFF Research Database (Denmark)

    Brok, Erik; Frandsen, Cathrine; Madsen, Daniel Esmarch

    2014-01-01

    Goethite (α-FeOOH) is a common nanocrystalline antiferromagnetic mineral. However, it is typically difficult to study the properties of isolated single-crystalline goethite nanoparticles, because goethite has a strong tendency to form particles of aggregated nanograins often with low-angle grain...... boundaries. This nanocrystallinity leads to complex magnetic properties that are dominated by magnetic fluctuations in interacting grains. Here we present a study of the magnetic properties of 5.7 nm particles of goethite by use of magnetization measurements, inelastic neutron scattering and Mo......¨ssbauer spectroscopy. The `ultra-small' size of these particles (i.e. that the particles consist of one or only a few grains) allows for more direct elucidation of the particles' intrinsic magnetic properties. We find from ac and dc magnetization measurements a significant upturn of the magnetization at very low...

  9. Torsional sensing of small-molecule binding using magnetic tweezers

    NARCIS (Netherlands)

    Lipfert, J.; Klijnhout, S.; Dekker, N.H.

    2010-01-01

    DNA-binding small molecules are widespread in the cell and heavily used in biological applications. Here, we use magnetic tweezers, which control the force and torque applied to single DNAs, to study three small molecules: ethidium bromide (EtBr), a well-known intercalator; netropsin, a minor-groove

  10. How to conserve threatened Chinese plant species with extremely small populations?

    Directory of Open Access Journals (Sweden)

    Sergei Volis

    2016-02-01

    Full Text Available The Chinese flora occupies a unique position in global plant diversity, but is severely threatened. Although biodiversity conservation in China has made significant progress over the past decades, many wild plant species have extremely small population sizes and therefore are in extreme danger of extinction. The concept of plant species with extremely small populations (PSESPs, recently adopted and widely accepted in China, lacks a detailed description of the methodology appropriate for conserving PSESPs. Strategies for seed sampling, reintroduction, protecting PSESP locations, managing interactions with the local human population, and other conservation aspects can substantially differ from those commonly applied to non-PSESPs. The present review is an attempt to provide a detailed conservation methodology with realistic and easy-to-follow guidelines for PSESPs in China.

  11. Rcscarch on Small-Scale Solar Magnetic Fields and Activities

    Institute of Scientific and Technical Information of China (English)

    ZHANG Jun; YANG Shuhong

    2011-01-01

    It has been known that there are different kinds of small-scale active phenomena on the Sun. They are classified into spicules, macrospicules, and H-alpha jets, X-ray jets, etc., according to their sizes, velocities, lifetimes, and so on. All these phenomena are related to small-scale magnetic fields. The problems of solar upper atmospheric heating and solar wind acceleration have never been solved. Small-scale magnetic fields and activities are considered to play key roles in heating upper atmosphere and in accelerating solar wind.

  12. Non-Collinearity in Small Magnetic Cobalt-Benzene Molecules

    CERN Document Server

    González, J W; Delgado, F; Aguilera-Granja, F; Ayuela, A

    2016-01-01

    Cobalt clusters covered with benzene in the form of rice-ball structures have recently been synthesized using laser ablation. Here, we investigate the types of magnetic order such clusters have, and whether they retain any magnetic order at all. We use different density functional theory (DFT) methods to study the experimentally relevant three cobalt atoms surrounded by benzene rings. We found that the benzene rings induce a ground state with non-collinear magnetization, with the magnetic moments localized on the cobalt centers and lying on the plane formed by the three cobalt atoms. This is surprising because nanostructures and small clusters based on pure cobalt typically have a predominantly ferromagnetic order, and additional organic ligands such as benzene tend to remove the magnetization. We analyze the magnetism of such a cluster using an anisotropic Heisenberg model where the involved parameters are obtained by a comparison with the DFT results. Moreover, we propose electron paramagnetic resonance as ...

  13. Multiple magnetic scattering in small-angle neutron scattering of Nd-Fe-B nanocrystalline magnet.

    Science.gov (United States)

    Ueno, Tetsuro; Saito, Kotaro; Yano, Masao; Ito, Masaaki; Shoji, Tetsuya; Sakuma, Noritsugu; Kato, Akira; Manabe, Akira; Hashimoto, Ai; Gilbert, Elliot P; Keiderling, Uwe; Ono, Kanta

    2016-06-20

    We have investigated the influence of multiple scattering on the magnetic small-angle neutron scattering (SANS) from a Nd-Fe-B nanocrystalline magnet. We performed sample-thickness- and neutron-wavelength-dependent SANS measurements, and observed the scattering vector dependence of the multiple magnetic scattering. It is revealed that significant multiple scattering exists in the magnetic scattering rather than the nuclear scattering of Nd-Fe-B nanocrystalline magnet. It is considered that the mean free path of the neutrons for magnetic scattering is rather short in Nd-Fe-B magnets. We analysed the SANS data by the phenomenological magnetic correlation model considering the magnetic microstructures and obtained the microstructural parameters.

  14. Extremely weak magnetic field exposure may inhibit hippocampal neurogenesis of Sprague Dawley rats

    Science.gov (United States)

    Zhang, B.; Tian, L.; Cai, Y.; Xu, H.; Pan, Y.

    2016-12-01

    Hippocampal neurogenesis occurs throughout life in mammals brains and can be influenced by animals' age as well as environmental factors. Lines of evidences have shown that the magnetic field is an important physics environmental factor influencing many animals' growth and development, and extremely weak magnetic field exposures have been proved having serious adverse effects on the metabolism and behaviors in some animals, but few studies have examined the response of hippocampal neurogenesis to it. In the present study, we experimentally examined the extremely weak magnetic field effects on neurogenesis of the dentate gyrus (DG) of hippocampus of adult Sprague Dawley (SD) rats. Two types of magnetic fields were used, an extremely weak magnetic field (≤ 0.5μT) and the geomagnetic fields (strength 31-58μT) as controls. Thirty-two SD rats (3-weeks old) were used in this study. New cell survival in hippocampus was assessed at 0, 14, 28, and 42 days after a 7-day intraperitoneal injections of 5-bromo-2'-deoxyuridine (BrdU). Meanwhile, the amounts of immature neurons and mature neurons which are both related to hippocampal neurogenesis, as documented by labeling with doublecortin (DCX) and neuron (NeuN), respectively, were also analyzed at 0, 14, 28, and 42 days. Compared with geomagnetic field exposure groups, numbers of BrdU-, DCX-positive cells of DG of hippocampus in tested rats reduces monotonously and more rapidly after 14 days, and NeuN-positive cells significantly decreases after 28days when exposed in the extremely weak magnetic field condition. Our data suggest that the exposure to an extremely weak magnetic field may suppress the neurogenesis in DG of SD rats.

  15. A Novel Technology for Measurements of Dielectric Properties of Extremely Small Volumes of Liquids

    Directory of Open Access Journals (Sweden)

    Wei-Na Liu

    2016-01-01

    Full Text Available A high sensitivity sensor for measurement radio frequency (RF dielectric permittivity of liquids is described. Interference is used and parasitic effects are cancellation, which makes the sensor can catch weak signals caused by liquids with extremely small volumes. In addition, we present the relationship between transmission coefficient and permittivity of liquids under test (LUT. Using this sensor, quantitative measurements of the dielectric properties at 5.8 GHz are demonstrated of LUTs. Experiments show that the proposed method only requires the volume of 160 nanoliters for liquids. Therefore, the technology can be used for RF spectroscopic analysis of biological samples and extremely precious liquids.

  16. Extreme ultraviolet imaging of three-dimensional magnetic reconnection in a solar eruption.

    Science.gov (United States)

    Sun, J Q; Cheng, X; Ding, M D; Guo, Y; Priest, E R; Parnell, C E; Edwards, S J; Zhang, J; Chen, P F; Fang, C

    2015-06-26

    Magnetic reconnection, a change of magnetic field connectivity, is a fundamental physical process in which magnetic energy is released explosively, and it is responsible for various eruptive phenomena in the universe. However, this process is difficult to observe directly. Here, the magnetic topology associated with a solar reconnection event is studied in three dimensions using the combined perspectives of two spacecraft. The sequence of extreme ultraviolet images clearly shows that two groups of oppositely directed and non-coplanar magnetic loops gradually approach each other, forming a separator or quasi-separator and then reconnecting. The plasma near the reconnection site is subsequently heated from ∼1 to ≥5 MK. Shortly afterwards, warm flare loops (∼3 MK) appear underneath the hot plasma. Other observational signatures of reconnection, including plasma inflows and downflows, are unambiguously revealed and quantitatively measured. These observations provide direct evidence of magnetic reconnection in a three-dimensional configuration and reveal its origin.

  17. Cosmic Ray Small Scale Anisotropies and Local Turbulent Magnetic Fields

    CERN Document Server

    López-Barquero, Vanessa; Xu, S; Desiati, P; Lazarian, A

    2015-01-01

    Cosmic ray anisotropy is observed in a wide energy range and at different angular scales by a variety of experiments. However, a comprehensive and satisfactory explanation has been elusive for over a decade now. The arrival distribution of cosmic rays on Earth is the convolution of the distribution of their sources and of the effects of geometry and properties of the magnetic field through which particles propagate. It is generally believed that the anisotropy topology at the largest angular scale is adiabatically shaped by diffusion in the structured interstellar magnetic field. On the contrary, the medium and small angular scale structure could be an effect of non diffusive propagation of cosmic rays in perturbed magnetic fields. In particular, a possible explanation of the observed small scale anisotropy observed at TeV energy scale, may come from the effect of particle scattering in turbulent magnetized plasmas. We perform numerical integration of test particle trajectories in low-$\\beta$ compressible mag...

  18. Magnetic properties of small Fe clusters: a nonorthogonal Hamiltonian study

    Institute of Scientific and Technical Information of China (English)

    2000-01-01

    We calculate the magnetic properties of small FeN clusters(N=2~7,9,13,15) by using a parameterized Hubbard tight-binding sp d-band model Hamiltonian, with the parameters obtained from nonorthogonal Ham il tonian parameters. the average magnetic moments, and the spin-polarized charge distribution within clusters are in agreement with those obtained by first-prin ciple and tight-binding calculations. The effect of the nonorthogonal basis is discussed.

  19. Magnetic nanoparticles studied by small angle X-ray scattering

    Energy Technology Data Exchange (ETDEWEB)

    Oliveira, Cristiano Luis Pinto [Universidade de Sao Paulo (IF/USP), SP (Brazil). Inst. de Fisica. Grupo de Fluidos Complexos; Antonel, Soledad; Negri, Martin [Universidad de Buenos Aires (UBA) (Argentina). Facultad de Ciencias Exactas y Naturales. Dept. de Quimica Inorganica, Analitica y Quimica Fisica

    2011-07-01

    nanoparticles are very interesting because they exhibit magnetic (ferromagnetic) and electrical properties in the same material. Then, the nickel nanoparticles could be used for the development of electroelastic materials. In this case, the electrical conductivity of the material can be strongly dependent on the applied magnetic field, for example the case of nickel metal nanoparticles dispersed in a polymer, resulting in an anisotropic material with combined piezomagnetic and piezoelectric properties. In order to investigate the structural characteristics of cobalt-iron oxides and nickel nanoparticles, powder samples of those magnetic materials were studied by Small-Angle X-Ray Scattering. As will be shown, from the analysis and modeling of the scattering data, structural information could be obtained, enabling a detailed description of the structural properties of the studied samples which could be directly correlated to the magnetic properties. (author)

  20. Single-Plane Magnetically Focused Elongated Small Field Proton Beams.

    Science.gov (United States)

    McAuley, Grant A; Slater, James M; Wroe, Andrew J

    2015-08-01

    We previously performed Monte Carlo simulations of magnetically focused proton beams shaped by a single quadrapole magnet and thereby created narrow elongated beams with superior dose delivery characteristics (compared to collimated beams) suitable for targets of similar geometry. The present study seeks to experimentally validate these simulations using a focusing magnet consisting of 24 segments of samarium cobalt permanent magnetic material adhered into a hollow cylinder. Proton beams with properties relevant to clinical radiosurgery applications were delivered through the magnet to a water tank containing a diode detector or radiochromic film. Dose profiles were analyzed and compared with analogous Monte Carlo simulations. The focused beams produced elongated beam spots with high elliptical symmetry, indicative of magnet quality. Experimental data showed good agreement with simulations, affirming the utility of Monte Carlo simulations as a tool to model the inherent complexity of a magnetic focusing system. Compared to target-matched unfocused simulations, focused beams showed larger peak to entrance ratios (26% to 38%) and focused simulations showed a two-fold increase in beam delivery efficiency. These advantages can be attributed to the magnetic acceleration of protons in the transverse plane that tends to counteract the particle outscatter that leads to degradation of peak to entrance performance in small field proton beams. Our results have important clinical implications and suggest rare earth focusing magnet assemblies are feasible and could reduce skin dose and beam number while delivering enhanced dose to narrow elongated targets (eg, in and around the spinal cord) in less time compared to collimated beams.

  1. Extremely long-lived magnetic excitations in supported Fe chains

    Science.gov (United States)

    Gauyacq, J. P.; Lorente, N.

    2016-07-01

    We report on a theoretical study of the lifetime of the first excited state of spin chains made of an odd number of Fe atoms on C u2N /Cu (100 ) . Yan, Choi, Burgess, Rolf-Pissarczyk, and Loth [Nat. Nanotech. 10, 40 (2015), 10.1038/nnano.2014.281] recently observed very long lifetimes in the case of F e3 chains. We consider the decay of the first excited state induced by electron-hole pair creation in the substrate. For a finite magnetic field, the two lowest-lying states in the chain have a quasi-Néel state structure. Decay from one state to the other strongly depends on the degree of entanglement of the local spins in the chain. The weak entanglement in the chain accounts for the long lifetimes that increase exponentially with chain length. Despite their apparently very different properties, the behavior of odd and even chains is governed by the same kind of phenomena, in particular entanglement effects. The present results account quite well for the lifetimes recently measured by Yan et al. on F e3 .

  2. Minimum Q Electrically Small Spherical Magnetic Dipole Antenna - Practice

    DEFF Research Database (Denmark)

    Kim, Oleksiy S.; Breinbjerg, Olav

    2009-01-01

    resonances of all other modes that are not sufficiently suppressed in the antenna. Numerical results for a 4-arm spherical helix antenna filled with magnetic material demonstrate the destroying effect of the parasitic TM11 mode on the antenna Q factor. Theoretical considerations as well as numerical results......Practical aspects of applying a magnetic core to approach the Chu lower bound for the radiation Q factor of an electrically small magnetic dipole antenna are considered. It is shown that although a magnetic core does reduce the Q factor, its effect is not as strong as predicted by Wheeler...... show that in a given range of magnetic permeabilities away from core resonances there is an optimum permeability for which the Q factor is lowest. In the given example, the antenna of the size ka~0.254 yields the Q ratio 1.28 times above the Chu lower bound....

  3. Electronic and Magnetic Properties of Small Iridium Clusters

    Institute of Scientific and Technical Information of China (English)

    KUANG Xiang-jun

    2004-01-01

    The electronic and magnetic properties of small IrN clusters (N=5, 6, 9, 13, and 19 ) are studied by using the discrete-variational local-spin-density-functional method. The equilibrium bond length in the chosen geometry for IrN clusters are determined and show bond contraction compared with the bulk interatomic spacing. The clusters with magnetic ground state have ferromagnetic interaction and their average magnetic moment per atom has a complex size dependence. At last, the reactivity of IrN clusters toward H2, N2 and CO molecules is predicted.

  4. Extremely low-frequency magnetic field exposure, electrical shocks and risk of Parkinson's disease

    NARCIS (Netherlands)

    van der Mark, Marianne; Vermeulen, Roel; Nijssen, Peter C. G.; Mulleners, Wim M.; Sas, Antonetta M. G.; van Laar, Teus; Kromhout, Hans; Huss, Anke

    2015-01-01

    Previous studies did not provide strong evidence for an increased Parkinson's disease (PD) risk after exposure to extremely low-frequency magnetic fields (ELF-MF), but were limited in their scope to address other exposures related to the use of electricity such as electrical shocks. We evaluated the

  5. Extremely low-frequency magnetic field exposure, electrical shocks and risk of Parkinson's disease

    NARCIS (Netherlands)

    van der Mark, Marianne; Vermeulen, Roel; Nijssen, Peter C. G.; Mulleners, Wim M.; Sas, Antonetta M. G.; van Laar, Teus; Kromhout, Hans; Huss, Anke

    Previous studies did not provide strong evidence for an increased Parkinson's disease (PD) risk after exposure to extremely low-frequency magnetic fields (ELF-MF), but were limited in their scope to address other exposures related to the use of electricity such as electrical shocks. We evaluated the

  6. Extremely low-frequency magnetic field exposure, electrical shocks and risk of Parkinson's disease

    NARCIS (Netherlands)

    van der Mark, Marianne; Vermeulen, Roel; Nijssen, Peter C G; Mulleners, Wim M; Sas, Antonetta M G; van Laar, Teus; Kromhout, Hans; Huss, Anke

    2015-01-01

    PURPOSE: Previous studies did not provide strong evidence for an increased Parkinson's disease (PD) risk after exposure to extremely low-frequency magnetic fields (ELF-MF), but were limited in their scope to address other exposures related to the use of electricity such as electrical shocks. We eval

  7. Range Detection of the Extremely Low-Frequency Magnetic Field Produced by Laptop's AC Adapter

    Science.gov (United States)

    Brodić, Darko; Amelio, Alessia

    2017-02-01

    Human exposure to extremely low frequency magnetic field represents a risk to their health. This paper takes into consideration the level of an extremely low-frequency magnetic field between 30 and 300 Hz emitted by an AC laptop adapter. The experiment consists of testing 17 different AC adapters for laptops. During the testing, laptops are operated in a normal operating conditions as well as under heavy load. The magnetic field measurement is conducted in the area around the AC adapter. Obtained data is evaluated according to the critical level of the magnetic field proposed by safety standards. Furthermore, data is classified by a K-medians method in order to determine the critical levels of the magnetic field exposure in the nearby area of the AC adapter. Obtained classifications are evaluated according to safety standards, giving a critical analysis of magnetic field areas at risk. Due to emission of a very strong magnetic field in certain areas, a recommendation for safety use of the AC adapter is proposed.

  8. Interaction between granulation and small-scale magnetic flux observed by Hinode

    Institute of Scientific and Technical Information of China (English)

    Jun Zhang; Shu-Hong Yang; Chun-Lan Jin

    2009-01-01

    With the polarimetric observations obtained by the Spectro-Polarimeter on board Hinode, we study the relationship between granular development and magnetic field evolution in the quiet Sun. Six typical cases are displayed to exhibit interaction be-tween granules and magnetic elements, and we have obtained the following results. (1) A granule develops centrosymmetrically when no magnetic flux emerges within the gran-ular cell. (2) A granule develops and splits noncentrosymmetrically while flux emerges at an outer part of the granular cell. (3) Magnetic flux emergence in a cluster of mixed polarities is detected at the position of a granule as soon as the granule breaks up. (4) A dipole emerges accompanied by the development of a granule, and the two elements of the dipole are rooted in the adjacent intergranular lanes and face each other across the gran-ule. Advected by the horizontal granular motion, the positive element of the dipole then cancels with the pre-existing negative flux. (5) Flux cancellation also takes place between a positive element, which is advected by granular flow, and its surrounding negative flux. (6) While magnetic flux cancellation takes place in a granular cell, the granule shrinks and then disappears. (7) Horizontal magnetic fields are enhanced at the places where dipoles emerge and where opposite polarities cancel each other, but only the horizontal fields between the dipolar elements point in an orderly way from the positive elements to the negative ones. Our results reveal that granules and small-scale magnetic fluxes influence each other. Granular flow advects magnetic flux, and magnetic flux evolution suppresses granular development. There exist extremely large Doppler blue-shifts at the site of one canceling magnetic element. This phenomenon may be caused by the upward flow pro-duced by magnetic reconnection below the photosphere.

  9. Extreme Ultraviolet Imaging of Three-dimensional Magnetic Reconnection in a Solar Eruption

    CERN Document Server

    Sun, J Q; Ding, M D; Guo, Y; Priest, E R; Parnell, C E; Edwards, S J; Zhang, J; Chen, P F; Fang, C

    2015-01-01

    Magnetic reconnection, a change of magnetic field connectivity, is a fundamental physical process in which magnetic energy is released explosively. It is responsible for various eruptive phenomena in the universe. However, this process is difficult to observe directly. Here, the magnetic topology associated with a solar reconnection event is studied in three dimensions (3D) using the combined perspectives of two spacecraft. The sequence of extreme ultraviolet (EUV) images clearly shows that two groups of oppositely directed and non-coplanar magnetic loops gradually approach each other, forming a separator or quasi-separator and then reconnecting. The plasma near the reconnection site is subsequently heated from $\\sim$1 to $\\ge$5 MK. Shortly afterwards, warm flare loops ($\\sim$3 MK) appear underneath the hot plasma. Other observational signatures of reconnection, including plasma inflows and downflows, are unambiguously revealed and quantitatively measured. These observations provide direct evidence of magneti...

  10. Pregnant woman with an extremely small uterus due to pelvic irradiation in childhood.

    Science.gov (United States)

    Watanabe, Takashi; Matsubara, Shigeki; Saito, Yutaka; Usui, Rie; Mugishima, Hideo; Suzuki, Mitsuaki

    2012-03-01

    A female cancer survivor, having suffered malignant lymphoma during childhood and received radio- and chemotherapy, became pregnant. Her uterus was extremely small and in the 22nd week of gestation, acute uterine contractions occurred, leading to preterm delivery and resulting in the death of the infant. Pelvic irradiation in childhood was considered to have caused a small uterus and thus brought on preterm delivery. The younger the patient, the more vulnerable the uterus is to irradiation. The exposure dose to the uterus in pediatric cancer patients should therefore be reduced, especially in younger patients. The cooperation of pediatric cancer specialists and obstetricians is necessary to preserve the future fertility of female cancer survivors.

  11. The design of the inelastic neutron scattering mode for the Extreme Environment Diffractometer with the 26 T High Field Magnet

    Energy Technology Data Exchange (ETDEWEB)

    Bartkowiak, Maciej, E-mail: maciej.bartkowiak@helmholtz-berlin.de; Stüßer, Norbert; Prokhnenko, Oleksandr

    2015-10-11

    The Extreme Environment Diffractometer is a neutron time-of-flight instrument, designed to work with a constant-field hybrid magnet capable of reaching fields over 26 T, unprecedented in neutron science; however, the presence of the magnet imposes both spatial and technical limitations on the surrounding instrument components. In addition to the existing diffraction and small-angle neutron scattering modes, the instrument will operate also in an inelastic scattering mode, as a direct time-of-flight spectrometer. In this paper we present the Monte Carlo ray-tracing simulations, the results of which illustrate the performance of the instrument in the inelastic-scattering mode. We describe the focussing neutron guide and the chopper system of the existing instrument and the planned design for the instrument upgrade. The neutron flux, neutron spatial distribution, divergence distribution and energy resolution are calculated for standard instrument configurations.

  12. Magnetic fields of our Galaxy on large and small scales

    CERN Document Server

    Han, Jinlin

    2007-01-01

    Magnetic fields have been observed on all scales in our Galaxy, from AU to kpc. With pulsar dispersion measures and rotation measures, we can directly measure the magnetic fields in a very large region of the Galactic disk. The results show that the large-scale magnetic fields are aligned with the spiral arms but reverse their directions many times from the inner-most arm (Norma) to the outer arm (Perseus). The Zeeman splitting measurements of masers in HII regions or star-formation regions not only show the structured fields inside clouds, but also have a clear pattern in the global Galactic distribution of all measured clouds which indicates the possible connection of the large-scale and small-scale magnetic fields.

  13. Extreme ultraviolet emission and confinement of tin plasmas in the presence of a magnetic field

    Energy Technology Data Exchange (ETDEWEB)

    Roy, Amitava, E-mail: roy@fzu.cz, E-mail: aroy@barc.gov.in [School of Nuclear Engineering and Center for Materials Under Extreme Environment(CMUXE), Purdue University, West Lafayette, Indiana 47907 (United States); HiLASE Project, Department of Diode-pumped Lasers, Institute of Physics of the ASCR, Na Slovance 2, 18221 Prague (Czech Republic); Murtaza Hassan, Syed; Harilal, Sivanandan S.; Hassanein, Ahmed [School of Nuclear Engineering and Center for Materials Under Extreme Environment(CMUXE), Purdue University, West Lafayette, Indiana 47907 (United States); Endo, Akira; Mocek, Tomas [HiLASE Project, Department of Diode-pumped Lasers, Institute of Physics of the ASCR, Na Slovance 2, 18221 Prague (Czech Republic)

    2014-05-15

    We investigated the role of a guiding magnetic field on extreme ultraviolet (EUV) and ion emission from a laser produced Sn plasma for various laser pulse duration and intensity. For producing plasmas, planar slabs of pure Sn were irradiated with 1064 nm, Nd:YAG laser pulses with varying pulse duration (5–15 ns) and intensity. A magnetic trap was fabricated with the use of two neodymium permanent magnets which provided a magnetic field strength ∼0.5 T along the plume expansion direction. Our results indicate that the EUV conversion efficiency do not depend significantly on applied axial magnetic field. Faraday Cup ion analysis of Sn plasma show that the ion flux reduces by a factor of ∼5 with the application of an axial magnetic field. It was found that the plasma plume expand in the lateral direction with peak velocity measured to be ∼1.2 cm/μs and reduced to ∼0.75 cm/μs with the application of an axial magnetic field. The plume expansion features recorded using fast photography in the presence and absence of 0.5 T axial magnetic field are simulated using particle-in-cell code. Our simulation results qualitatively predict the plasma behavior.

  14. Extremely low-frequency electromagnetic fields disrupt magnetic alignment of ruminants.

    Science.gov (United States)

    Burda, Hynek; Begall, Sabine; Cervený, Jaroslav; Neef, Julia; Nemec, Pavel

    2009-04-07

    Resting and grazing cattle and deer tend to align their body axes in the geomagnetic North-South direction. The mechanism(s) that underlie this behavior remain unknown. Here, we show that extremely low-frequency magnetic fields (ELFMFs) generated by high-voltage power lines disrupt alignment of the bodies of these animals with the geomagnetic field. Body orientation of cattle and roe deer was random on pastures under or near power lines. Moreover, cattle exposed to various magnetic fields directly beneath or in the vicinity of power lines trending in various magnetic directions exhibited distinct patterns of alignment. The disturbing effect of the ELFMFs on body alignment diminished with the distance from conductors. These findings constitute evidence for magnetic sensation in large mammals as well as evidence of an overt behavioral reaction to weak ELFMFs in vertebrates. The demonstrated reaction to weak ELFMFs implies effects at the cellular and molecular levels.

  15. Small oscillations of two interacting particles in a magnetic field

    Science.gov (United States)

    del Pino, L. A.; Curilef, S.

    2016-11-01

    The classical behavior of two interacting particles in the presence of a uniform magnetic field is studied in the small oscillations approximation. Using the Lagrangian formalism, the equations of motion are derived, as are their solutions and constants of motion. Normal modes of oscillations and their corresponding normal coordinates are obtained that strongly depend on the initial condition; therefore, we observe that the oscillation along the line that joins the particles is non-isochronous. In addition, particular attention has been paid to the planar motion, without the pseudomomentum component parallel to the magnetic field, where one longitudinal mode and two transversal modes are obtained.

  16. Small-sample likelihood inference in extreme-value regression models

    CERN Document Server

    Ferrari, Silvia L P

    2012-01-01

    We deal with a general class of extreme-value regression models introduced by Barreto- Souza and Vasconcellos (2011). Our goal is to derive an adjusted likelihood ratio statistic that is approximately distributed as \\c{hi}2 with a high degree of accuracy. Although the adjusted statistic requires more computational effort than its unadjusted counterpart, it is shown that the adjustment term has a simple compact form that can be easily implemented in standard statistical software. Further, we compare the finite sample performance of the three classical tests (likelihood ratio, Wald, and score), the gradient test that has been recently proposed by Terrell (2002), and the adjusted likelihood ratio test obtained in this paper. Our simulations favor the latter. Applications of our results are presented. Key words: Extreme-value regression; Gradient test; Gumbel distribution; Likelihood ratio test; Nonlinear models; Score test; Small-sample adjustments; Wald test.

  17. Extreme ultra-violet movie camera for imaging microsecond time scale magnetic reconnection.

    Science.gov (United States)

    Chai, Kil-Byoung; Bellan, Paul M

    2013-12-01

    An ultra-fast extreme ultra-violet (EUV) movie camera has been developed for imaging magnetic reconnection in the Caltech spheromak/astrophysical jet experiment. The camera consists of a broadband Mo:Si multilayer mirror, a fast decaying YAG:Ce scintillator, a visible light block, and a high-speed visible light CCD camera. The camera can capture EUV images as fast as 3.3 × 10(6) frames per second with 0.5 cm spatial resolution. The spectral range is from 20 eV to 60 eV. EUV images reveal strong, transient, highly localized bursts of EUV radiation when magnetic reconnection occurs.

  18. Destroying a near-extremal Kerr black hole with a charged particle: Can a test magnetic field serve as a cosmic censor?

    CERN Document Server

    Shaymatov, Sanjar; Ahmedov, Bobomurat; Joshi, Pankaj S

    2014-01-01

    We investigate effect of a test magnetic field on the process of destroying near-extremal Kerr black hole with a charged test particle. It has been shown that it would be possible to throw a charged test particle into the near extremal rotating black hole and make it go past the extremality i.e. turn Kerr black hole into the Kerr-Newmann naked singularity. Typically in an astrophysical scenario black holes are believed to be surrounded by a magnetic field. Magnetic field although small, affects motion of charged particles drastically due to the large Lorentz force, as the electromagnetic force is much stronger that the gravity. Thus a test magnetic field can affect the process of destroying black holes and restore the cosmic censorship in the astrophysical context. We show that a test magnetic field would act as a cosmic censor beyond a certain threshold value. We try to gauge the magnitude of the magnetic field by comparing its energy density with that of the change in the curvature induced by the test parti...

  19. Technical aspects of exposure to magnetic fields of extremely low frequencies (ELF in biomedical research

    Directory of Open Access Journals (Sweden)

    Paweł Bieńkowski

    2015-06-01

    Full Text Available Background: Experiments on the electromagnetic field influence on organisms are an important part of biophysical studies. It is an interdisciplinary research spanning biology and medicine with the engineering in generation and measurement of electromagnetic fields. The aim of the study consists in the analysis of parameters estimations and measurements of extremely low frequency magnetic field (ELF MF as well as exposure systems parameters in biomedical research. Material and Methods: Experiments were performed on 2 most popular low magnetic field exposure systems: the solenoid and Helmholtz coils. A theoretical analysis and a measurement verification of the magnetic field distribution inside the systems were carried out to evaluate the homogeneity of the magnetic field. Additional factors, vibrations and temperature changes, affecting the assessment of the biological effects of magnetic field exposure were also examined. Results: Based on the study results, a comparative analysis of solenoids and Helmholtz coils as the magnetic field exposure systems was presented. Proposals for the description of magnetic field exposure were also formulated. Conclusions: The authors emphasize the importance of a conscious choice of exposure conditions and their explicit description. These are fundamental requirements for both the reproduction of experimental conditions and the verification of results. Med. Pr. 2015;66(2:185–197

  20. Instrumentation development for magnetic and structural studies under extremes of pressure and temperature

    OpenAIRE

    Giriat, Gaetan

    2012-01-01

    The study of the magnetic and structural properties of matter under extreme conditions is a fast developing field. With the emergence of new techniques and innovative instruments for measuring physical properties, the need for compatible pressure generating devices is constantly growing. The work described in this thesis is focused on development, construction and testing of several high pressure (HP) cells of novel design. One of the cells is intended for single crystal X-r...

  1. Instrumentation development for magnetic and structural studies under extremes of pressure and temperature

    OpenAIRE

    Giriat, Gaetan

    2012-01-01

    The study of the magnetic and structural properties of matter under extreme conditions is a fast developing field. With the emergence of new techniques and innovative instruments for measuring physical properties, the need for compatible pressure generating devices is constantly growing. The work described in this thesis is focused on development, construction and testing of several high pressure (HP) cells of novel design. One of the cells is intended for single crystal X-r...

  2. Magnetic resonance imaging of acute 'wiiitis' of the upper extremity

    Energy Technology Data Exchange (ETDEWEB)

    Nett, Michael P.; Sperling, John W. [Mayo Clinic, Department of Orthopedic Surgery, Rochester, MN (United States); Collins, Mark S. [Mayo Clinic, Department of Radiology, Rochester, MN (United States)

    2008-05-15

    We present the first reported case of acute 'wiiitis', documented clinically and by imaging, of the upper extremity, caused by prolonged participation in a physically interactive virtual video-game. Unenhanced magnetic resonance imaging (MRI) demonstrated marked T2-weighted signal abnormality within several muscles of the shoulder and upper arm, without evidence of macroscopic partial- or full-thickness tearing of the muscle or of intramuscular hematoma. (orig.)

  3. Application of Advanced Magnetic Resonance Imaging Techniques in Evaluation of the Lower Extremity

    Science.gov (United States)

    Braun, Hillary J.; Dragoo, Jason L.; Hargreaves, Brian A.; Levenston, Marc E.; Gold, Garry E.

    2012-01-01

    Synopsis This article reviews current magnetic resonance imaging techniques for imaging the lower extremity, focusing on imaging of the knee, ankle, and hip joints. Recent advancements in MRI include imaging at 7 Tesla, using multiple receiver channels, T2* imaging, and metal suppression techniques, allowing more detailed visualization of complex anatomy, evaluation of morphological changes within articular cartilage, and imaging around orthopedic hardware. PMID:23622097

  4. Low-Q Electrically Small Spherical Magnetic Dipole Antennas

    DEFF Research Database (Denmark)

    Kim, Oleksiy S.

    2010-01-01

    Three novel electrically small antenna configurations radiating a TE10 spherical mode corresponding to a magnetic dipole are presented and investigated: multiarm spherical helix (MSH) antenna, spherical split ring resonator (S-SRR) antenna, and spherical split ring (SSR) antenna. All three antennas...... are self-resonant, with the input resistance tuned to 50 ohms by an excitation curved dipole/monopole. A prototype of the SSR antenna has been fabricated and measured, yielding results that are consistent with the numerical simulations. Radiation quality factors (Q) of these electrically small antennas (in...

  5. Conical Magnetic Bearing Development and Magnetic Bearing Testing for Extreme Temperature Environments

    Science.gov (United States)

    Keith, Theo G., Jr.; Jansen, Mark

    2004-01-01

    The main proposed research of this grant were: to design a high-temperature, conical magnetic bearing facility, to test the high-temperature, radial magnetic bearing facility to higher speeds, to investigate different backup bearing designs and materials, to retrofit the high-temperature test facility with a magnetic thrust bearing, to evaluate test bearings at various conditions, and test several lubricants using a spiral orbit tribometer. A high-temperature, conical magnetic bearing facility has been fully developed using Solidworks. The facility can reuse many of the parts of the current high-temperature, radial magnetic bearing, helping to reduce overall build costs. The facility has the ability to measure bearing force capacity in the X, Y, and Z directions through a novel bearing mounting design. The high temperature coils and laminations, a main component of the facility, are based upon the current radial design and can be fabricated at Texas A&M University. The coil design was highly successful in the radial magnetic bearing. Vendors were contacted about fabrication of the high temperature lamination stack. Stress analysis was done on the laminations. Some of the components were procured, but due to budget cuts, the facility build up was stopped.

  6. Spin dynamics of an ultra-small nanoscale molecular magnet

    Directory of Open Access Journals (Sweden)

    Ciftja Orion

    2007-01-01

    Full Text Available AbstractWe present mathematical transformations which allow us to calculate the spin dynamics of an ultra-small nanoscale molecular magnet consisting of a dimer system of classical (high Heisenberg spins. We derive exact analytic expressions (in integral form for the time-dependent spin autocorrelation function and several other quantities. The properties of the time-dependent spin autocorrelation function in terms of various coupling parameters and temperature are discussed in detail.

  7. A simple, small and low cost permanent magnet design to produce homogeneous magnetic fields.

    Science.gov (United States)

    Manz, B; Benecke, M; Volke, F

    2008-05-01

    A new portable, pocket-size NMR probe based on a novel permanent magnet arrangement is presented. It is based on a Halbach-type magnet design which mimics the field of a spherical dipole by using cylindrical bar and ring magnets. The magnet system is made up of only three individual magnets, and most field calculations and optimisations can be performed analytically. A prototype system has been built using a set of small, off the shelf commercially available permanent magnets. Proton linewidths of 50 ppm FWHM could be achieved at a field strength of 1T. Calculations show that with custom-sized permanent magnets, linewidths of less than 1 ppm can be achieved over sample volumes of up to 1 mm3, which would in theory enable chemical shift resolved proton spectroscopy on mass-limited samples. But even with the achieved linewidth of 50 ppm, this can be a useful portable sensor for small amounts of liquid samples with restricted molecular mobility, like gels, polymers or high viscosity liquids.

  8. Extreme particle acceleration in magnetic reconnection layers. Application to the gamma-ray flares in the Crab Nebula

    CERN Document Server

    Cerutti, Benoit; Begelman, Mitchell C

    2011-01-01

    The gamma-ray space telescopes AGILE and Fermi detected short and bright synchrotron gamma-ray flares at photon energies above 100 MeV in the Crab Nebula. This discovery suggests that electron-positron pairs in the nebula are accelerated to PeV energies in a mG magnetic field within a few days, which is difficult to explain with classical models of particle acceleration and pulsar wind nebulae. In this article, we investigate whether particle acceleration in a magnetic reconnection layer can account for the puzzling properties of the flares. We numerically integrate relativistic test-particle orbits in the vicinity of the layer, including the radiation reaction force, and using simple analytical expressions for the large-scale electromagnetic fields. As they get accelerated by the reconnection electric field, the particles are trapped and focused deep inside the current layer where the magnetic field is small. The electrons suffer less from synchrotron losses and are accelerated to extremely high energies. Po...

  9. Critical endpoint in the QCD phase diagram for extremely strong background magnetic fields

    CERN Document Server

    Endrodi, Gergely

    2015-01-01

    Lattice simulations have demonstrated that a background (electro)magnetic field reduces the chiral/deconfinement transition temperature of quantum chromodynamics for eB < 1 GeV^2. On the level of observables, this reduction manifests itself in an enhancement of the Polyakov loop and in a suppression of the light quark condensates (inverse magnetic catalysis) in the transition region. In this paper, we report on lattice simulations of 1+1+1-flavor QCD at an unprecedentedly high value of the magnetic field eB = 3.25 GeV^2. Based on the behavior of various observables, it is shown that even at this extremely strong field, inverse magnetic catalysis prevails and the transition, albeit becoming sharper, remains an analytic crossover. In addition, we develop an algorithm to directly simulate the asymptotically strong magnetic field limit of QCD. We find strong evidence for a first-order deconfinement phase transition in this limiting theory, implying the presence of a critical endpoint in the QCD phase diagram. ...

  10. [Mechanism of action of combined extremely weak magnetic field on aqueous solution of amino acid].

    Science.gov (United States)

    Zhadin, M N; Bakharev, B V; Bobkova, N V

    2014-01-01

    The fundamental physical mechanisms of resonance action of an extremely weak (40 nT) alternating magnetic field at the cyclotron frequency combined with a weak (40 μT) static magnetic field, on living systems are analyzed in the present work. The experimental effects of such sort of magnetic fields were described in different papers: the very narrow resonant peaks in electrical conductivity of the aqueous solutions in the in vitro experiments and the biomedical in vivo effects on living animals of magnetic fields with frequencies tuned to some amino acids. The existing experimental in vitro data had a good repeatability in different laboratories and countries. Unfortunately, for free ions such sort of effects are absolutely impossible because the dimensions of an ion rotation radius should be measured by meters at room temperature and at very low static magnetic fields used in all the above experiments. Even for bound ions these effects should be also absolutely impossible from the positions of classic physics because of rather high viscosity of biological liquid media (blood plasma, cerebrospinal liquid, cytoplasm). Only modern quantum electrodynamics of condensed media opens the new ways for solving these problems. The proposed article is devoted to analysis of quantum mechanisms of these effects.

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

    Science.gov (United States)

    Sirav, Bahriye; Sezgin, Gaye; Seyhan, Nesrin

    2014-12-01

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

  12. Development of Small-sized Fluid Control Valve with Self-holding Function Using Permanent Magnet

    Science.gov (United States)

    Akagi, Tetsuya; Dohta, Shujiro; Ueda, Hirofumi

    Recently, force feedback devices in virtual reality and power assisted nursing care systems have received much attention and active research. In such a control system, an actuator and a driving device such as a control valve are mounted on the human body. In this condition, the size and weight of the control valve become serious problems. At the same time, the valve should be operated with lower energy consumption because of using a limited electrical power. The typical electro magnetic solenoid valve drives its spool using a larger solenoid to open the valve. The complex construction of the valve for sealing makes its miniaturization and the fabrication of a low cost valve more difficult. In addition, the solenoid in the valve consumes more electrical power while the valve is kept opening. The purpose of our study is to develop a small-sized, lightweight, lower energy consumption and flexible control valve that can be safe enough to mount on the human body at a lower cost. In our pervious study, we proposed and tested the control valve that can open using a vibration motor. In this study, we propose and test a new type of fluid control valve with a self-holding function. The new valve uses a permanent magnet ball. It has a cylindrical magnet and two solenoids. The self-holding function of the valve is done as follows. When one side of the solenoid is stimulated by the current momentarily, the solenoid gives a repulsive force to the cylindrical magnet. The magnet moves toward the opposite side of the solenoid and is attracted to the iron core. Then, the magnet ball moves toward the cylindrical magnet and opens the orifice. The valve can keep open without electrical energy. As a result, the valve with the extremely lower energy consumption can be developed.

  13. Volume magnetization for system-level testing of magnetic materials within small satellites

    Science.gov (United States)

    Gerhardt, David T.; Palo, Scott E.

    2016-10-01

    Passive Magnetic Attitude Control (PMAC) is a popular among small satellites due to its low resource cost and simplicity of installation. However, predicting the performance of these systems can be a challenge, chiefly due to the difficulty of measurement and simulation of hysteresis materials. We present a low-cost method of magnetic measurement allowing for characterization of both hard and soft magnetic materials. A Helmholtz cage uniformly magnetizes a 30 cm×30 cm×30 cm test volume. The addition of a thin sense coil allows this system to characterize individual hysteresis rod performance when in close proximity to other hard and/or soft magnetic materials. This test setup is applied to hard and soft magnetic materials used aboard the Colorado Student Space Weather Experiment (CSSWE), a 3U CubeSat for space weather investigation which used a PMAC system. The measured hard magnet dipole of 0.80±0.017 A m2 is in good agreement with the dynamics-based satellite dipole moment fits. Five hysteresis rods from the same set as the CSSWE flight rods are tested; significant differences in dampening abilities are found. In addition, a limitation of the widely-used Flatley model is described. The interaction of two hysteresis rods in a variety of relative geometries are tested; perpendicular rods are found to have no significant interaction while parallel rods could have their dampening ability reduced by half, depending on the rod separation distance. Finally, the performance of the hysteresis rods are measured in their flight configuration, with hard and soft magnetic material dispersed as it is on CSSWE itself. For the CSSWE PMAC system design, interactions between rods have a greater affect than the magnetic flux density offset due to the onboard bar magnet.

  14. Magnetic storms and solar flares: can be analysed within similar mathematical framework with other extreme events?

    Science.gov (United States)

    Balasis, Georgios; Potirakis, Stelios M.; Papadimitriou, Constantinos; Zitis, Pavlos I.; Eftaxias, Konstantinos

    2015-04-01

    The field of study of complex systems considers that the dynamics of complex systems are founded on universal principles that may be used to describe a great variety of scientific and technological approaches of different types of natural, artificial, and social systems. We apply concepts of the nonextensive statistical physics, on time-series data of observable manifestations of the underlying complex processes ending up to different extreme events, in order to support the suggestion that a dynamical analogy characterizes the generation of a single magnetic storm, solar flare, earthquake (in terms of pre-seismic electromagnetic signals) , epileptic seizure, and economic crisis. The analysis reveals that all the above mentioned different extreme events can be analyzed within similar mathematical framework. More precisely, we show that the populations of magnitudes of fluctuations included in all the above mentioned pulse-like-type time series follow the traditional Gutenberg-Richter law as well as a nonextensive model for earthquake dynamics, with similar nonextensive q-parameter values. Moreover, based on a multidisciplinary statistical analysis we show that the extreme events are characterized by crucial common symptoms, namely: (i) high organization, high compressibility, low complexity, high information content; (ii) strong persistency; and (iii) existence of clear preferred direction of emerged activities. These symptoms clearly discriminate the appearance of the extreme events under study from the corresponding background noise.

  15. An Extremely Rare Case of Advanced Metastatic Small Cell Neuroendocrine Carcinoma of Sinonasal Tract

    Directory of Open Access Journals (Sweden)

    Yu Yu Thar

    2016-01-01

    Full Text Available Small cell neuroendocrine carcinoma (SNEC is a rare form of malignancy. It mainly presents as bronchogenic neoplasm, and the extrapulmonary form accounts for only 0.1% to 0.4% of all cancers. These extrapulmonary tumors have been described most frequently in the urinary bladder, prostate, esophagus, stomach, colon and rectum, gall bladder, head and neck, cervix, and skin. Primary SNEC of the sinonasal tract is extremely rare with only less than 100 cases reported in the literature. Because of extreme rarity and aggressiveness of the tumor, the management for this entity varies considerably mandating multimodality approach. In this paper, we report a patient presented with left-sided facial swelling, and the histopathologic examination confirmed primary SNEC of left sinonasal tract. The tumor involved multiple paranasal sinuses with invasion into the left orbit and left infratemporal fossa and metastasized to cervical lymph nodes and bone. The patient encountered devastating outcome in spite of optimal medical management and treatment with palliative chemotherapy highlighting the necessity for further research of primary SNEC of head and neck.

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

    Energy Technology Data Exchange (ETDEWEB)

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

    2015-03-15

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

  17. Magnetic resonance imaging of soft-tissue tumors of the extremities: A practical approach

    Institute of Scientific and Technical Information of China (English)

    Wing; P; Chan

    2013-01-01

    Diagnosis of extremity soft-tissue tumors can be challenging.Characteristics of tumor margins can help precisely identify locally aggressive or non-aggressive behavior for surgical planning,but cannot differentiate benign from malignant lesions.Most malignant tumors can have inhomogeneous signals on T2-weighted images.Although a uniform signal on T2-weighted images can be a reliable indication of a benign lesion,a well-defined mass with homogeneous internal signal intensity does not definitively identify a benign lesion.Some common and distinctive soft-tissue lesions can have specific clinical and imaging features allowing a diagnosis without biopsy.These are known as determinate lesions.This illustrative report presents a diagnostic guide for extremity soft-tissue tumors based on tissue signal and morphological characteristics on magnetic resonance images.It is important for clinicians to be familiar with the imaging characteristics of common determinate lesions.

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

    DEFF Research Database (Denmark)

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

    2017-01-01

    Purpose: Evidence of whether exposure to extremely low-frequency magnetic fields (ELF-MF) is related to central nervous system diseases is inconsistent. This study updates a previous study of the incidence of such diseases in a large cohort of Danish utility workers by almost doubling the period...... of exposure (≥1.0 µT), IRRs of 1.44, 1.78, 1.40 and 1.34 were observed for dementia, motor neurone disease, multiple sclerosis and epilepsy, respectively. Conclusions: We observed elevated risks of dementia, motor neurone disease, multiple sclerosis and epilepsy and lower risks of Parkinson disease...

  19. Probing the local, electronic and magnetic structure of matter under extreme conditions of temperature and pressure

    DEFF Research Database (Denmark)

    Torchio, R.; Boccato, S.; Cerantola, V.;

    2016-01-01

    In this paper we present recent achievements in the field of investigation of the local, electronic and magnetic structure of the matter under extreme conditions of pressure and temperature. These results were obtained thanks to the coupling of a compact laser heating system to the energy......-dispersive XAS technique available on the ID24 beamline at the ESRF synchrotron. The examples chosen concern the melting and the liquid structure of 3d metals and alloys under high pressures (HPs) and the observation of temperature-induced spin crossover in FeCO3 at HP....

  20. Relay transport of relativistic flows in extreme magnetic fields of stars

    Science.gov (United States)

    Yao, W. P.; Qiao, B.; Xu, Z.; Zhang, H.; Chang, H. X.; Zhou, C. T.; Zhu, S. P.; Wang, X. G.; He, X. T.

    2017-08-01

    We find that the transport of relativistic flows in extreme magnetic fields can be achieved in a relay manner by considering the quantum electromagnetic cascade process, where photons play a key role as a medium. During the transport, the flow emits particle energy into photons via quantum synchrotron radiation, and then gains particles back by magnetic pair creation, forming a "particle-photon-particle" relay. Particle-in-cell simulations demonstrate that forward transport of the flow density is realized by a self-replenishment process with photon-pair cascades, while that of the flow energy is accomplished due to a new coupling path through radiation of photons. This novel transport mechanism is closely associated with jet generation and disk accretion around the neutron star of X-Ray Binaries, offering a potential explanation for the powerful jets observed there.

  1. Effects of Extremely Low Frequency Magnetic Field on the Lens of the Rats

    Directory of Open Access Journals (Sweden)

    Uğur Keklikçi

    2008-12-01

    Full Text Available The present aim of the study is to evaluate the effects of extremely low frequency magnetic field (ELF MF on lens epithelial cells. Twenty adult female Spraque Dawley rats were divided into two groups, each containing 10 rats. The experimental group received magnetic field 2 hours/day for 7 days. The second group receiving standard laboratory care, was used as a control. The specimens were evaluated for cataractogenesis alteretion of lens and histological changes in lens epithelial cells.On biomicroscopic examination, no pathological damage to the lens was detected. In addition, on microscopic examination of materials in the controls, there were also no changes in lens fibrils and lens epithelial cells. In experimental group, however, only a slight pleomorphism was determined at the surface of epithelial cells.In the study, it is cocluded that ELF MF exposure do might not lead to histopathological alterations of the lens fibrils and lens epithelial cells.

  2. Magnetic resonance angiographic assessment of upper extremity vessels prior to vascular access surgery: feasibility and accuracy

    Energy Technology Data Exchange (ETDEWEB)

    Planken, Nils R. [Maastricht University Hospital, Department of Vascular Surgery, Maastricht (Netherlands); Maastricht University Hospital, Department of Radiology, Maastricht (Netherlands); Maastricht University Medical School, Cardiovascular Research Institute Maastricht, Maastricht (Netherlands); Tordoir, Jan H. [Maastricht University Hospital, Department of Vascular Surgery, Maastricht (Netherlands); Maastricht University Medical School, Cardiovascular Research Institute Maastricht, Maastricht (Netherlands); Duijm, Lucien E.; Bosch, Harrie C. van den [Catharina Hospital, Department of Radiology, Eindhoven (Netherlands); Sande, Frank M. van der; Kooman, Jeroen P. [Maastricht University Hospital, Department of Nephrology, Maastricht (Netherlands); Maastricht University Medical School, Cardiovascular Research Institute Maastricht, Maastricht (Netherlands); Haan, Michiel W. de; Leiner, Tim [Maastricht University Hospital, Department of Radiology, Maastricht (Netherlands); Maastricht University Medical School, Cardiovascular Research Institute Maastricht, Maastricht (Netherlands)

    2008-01-15

    A contrast-enhanced magnetic resonance angiography (CE-MRA) protocol for selective imaging of the entire upper extremity arterial and venous tree in a single exam has been developed. Twenty-five end-stage renal disease (ESRD) patients underwent CE-MRA and duplex ultrasonography (DUS) of the upper extremity prior to hemodialysis vascular access creation. Accuracy of CE-MRA arterial and venous diameter measurements were compared with DUS and intraoperative (IO) diameter measurements, the standard of reference. Upper extremity vasculature depiction was feasible with CE-MRA. CE-MRA forearm and upper arm arterial diameters were 2.94 {+-} 0.67 mm and 4.05 {+-} 0.84 mm, respectively. DUS arterial diameters were 2.80 {+-} 0.48 mm and 4.38 {+-} 1.24 mm; IO diameters were 3.00 {+-} 0.35 mm and 3.55 {+-} 0.51 mm. Forearm arterial diameters were accurately determined with both techniques. Both techniques overestimated upper arm arterial diameters significantly. Venous diameters were accurately determined with CE-MRA but not with DUS (forearm: CE-MRA: 2.64 {+-} 0.61 mm; DUS: 2.50 {+-} 0.44 mm, and IO: 3.40 {+-} 0.22 mm; upper arm: CE-MRA: 4.09 {+-} 0.71 mm; DUS: 3.02 {+-} 1.65 mm, and IO: 4.30 {+-} 0.78 mm). CE-MRA enables selective imaging of upper extremity vasculature in patients requiring hemodialysis access. Forearm arterial diameters can be assessed accurately by CE-MRA. Both CE-MRA and DUS slightly overestimate upper arm arterial diameters. In comparison to DUS, CE-MRA enables a more accurate determination of upper extremity venous diameters. (orig.)

  3. Experimental studies on extremely low frequency pulsed magnetic field inhibiting sarcoma and enhancing cellular immune functions

    Institute of Scientific and Technical Information of China (English)

    张沪生; 叶晖; 张传清; 曾繁清; 黄兴鼎; 张晴川; 李宗山; 杜碧

    1997-01-01

    The previous observation with an electron microscope showed that extremely low frequency (ELF) pulsed magnetic field (PMF) (with the maximum intensity of 0. 6-2. 0 T, gradient of 10-100 T. M-1, pulse width of 20-200 ms and frequency of 0. 16-1. 34 Hz) inhibited the growth of S-180 sarcoma in mice and enhanced the ability of immune cell’s dissolving sarcoma cells. In this study, the DNA contents of nuclei were assayed by using Faulgen Staining method. With an electron microscope and cell stereoscopy technology it was observed that magnetic field affected the sarcoma cell’s metabolism, lowered its malignancy, and restrained its rapid and heteromorphic growth. The magnetic field enhanced the cellular immune ability and the reaction of lymphocytes and plasma. Since ELF pulsed magnetic fields can inhibit the growth of sarcomas and enhance the cellular immune ability, it is possible to use it as a new method to treat cancer.

  4. Small body size and extreme cortical bone remodeling indicate phyletic dwarfism in Magyarosaurus dacus (Sauropoda: Titanosauria).

    Science.gov (United States)

    Stein, Koen; Csiki, Zoltan; Rogers, Kristina Curry; Weishampel, David B; Redelstorff, Ragna; Carballido, Jose L; Sander, P Martin

    2010-05-18

    Sauropods were the largest terrestrial tetrapods (>10(5) kg) in Earth's history and grew at rates that rival those of extant mammals. Magyarosaurus dacus, a titanosaurian sauropod from the Upper Cretaceous (Maastrichtian) of Romania, is known exclusively from small individuals (dwarfism (phyletic nanism) in dinosaurs, but a recent study suggested that the small Romanian titanosaurs actually represent juveniles of a larger-bodied taxon. Here we present strong histological evidence that M. dacus was indeed a dwarf (phyletic nanoid). Bone histological analysis of an ontogenetic series of Magyarosaurus limb bones indicates that even the smallest Magyarosaurus specimens exhibit a bone microstructure identical to fully mature or old individuals of other sauropod taxa. Comparison of histologies with large-bodied sauropods suggests that Magyarosaurus had an extremely reduced growth rate, but had retained high basal metabolic rates typical for sauropods. The uniquely decreased growth rate and diminutive body size in Magyarosaurus were adaptations to life on a Cretaceous island and show that sauropod dinosaurs were not exempt from general ecological principles limiting body size.

  5. Occupational Exposure Assessment of Tehran Metro Drivers to Extremely Low Frequency Magnetic Fields

    Directory of Open Access Journals (Sweden)

    mohammad reza Monazzam

    2016-03-01

    Full Text Available Introduction: Occupational exposure to Extremely Low Frequency Magnetic Fields (ELF-MFs in train drivers is an integral part of the driving task and creates concern about driving jobs. The present study was designed to investigate the occupational exposure of Tehran train drivers to extremely low frequency magnetic fields. Methods: In order to measure the driver’s exposure, from each line, a random sample in AC and DC type trains was selected and measurements were done according to the IEEE std 644-1994 using a triple axis TES-394 device. Train drivers were then compared with national occupational exposure limit guidelines. Results: The maximum and minimum mean exposure was found in AC external city trains (1.2±1.5 μT and DC internal city trains (0.31±0.2 μT, respectively. The maximum and minimum exposure was 9 μT and 0.08 μT in AC trains of line 5, respectively. In the internal train line, maximum and minimum values were 5.4 μT and 0.08 μT in AC trains. Conclusions: In none of the exposure scenarios in different trains, the exposure exceeded the national or international occupational exposure limit guidelines. However, this should not be the basis of safety in these fields

  6. Excessive portal flow causes graft failure in extremely small-for-size liver transplantation in pigs

    Institute of Scientific and Technical Information of China (English)

    Hong-Sheng Wang; Tomohiro Narita; Hideyuki Yamaya; Atsushi Nakamura; Satoshi Sekiguchi; Naoki Kawagishi; Akira Sato; Susumu Satomi; Nobuhiro Ohkohchi; Yoshitaka Enomoto; Masahiro Usuda; Shigehito Miyagi; Takeshi Asakura; Hiroo Masuoka; Takashi Aiso; Keisuke Fukushima

    2005-01-01

    AIM: To evaluate the effects of a portocaval shunt on the decrease of excessive portal flow for the prevention of sinusoidal microcirculatory injury in extremely smallfor-size liver transplantation in pigs.METHODS: The right lateral lobe of pigs, i.e. the 25%of the liver, was transplanted orthotopically. The pigs were divided into two groups: graft without portocaval shunt (n = 11) and graft with portocaval shunt (n=11).Survival rate, portal flow, hepatic arterial flow, and histological findings were investigated.RESULTS: In the group without portocaval shunt, all pigs except one died of liver dysfunction within 24 h after transplantation. In the group with portocaval shunt,eight pigs survived for more than 4 d. The portal flow volumes before and after transplantation in the group without portocaval shunt were 118.2±26.9 mL/min/100 g liver tissue and 270.5±72.9 mL/min/100 g liver tissue,respectively. On the other hand, in the group with portocaval shunt, those volumes were 124.2±27.8 mL/min/100 g liver tissue and 42.7±32.3 mL/min/100 g liver tissue, respectively (P<0.01). As for histological findings in the group without portocaval shunt, destruction of the sinusoidal lining and bleeding in the peri-portal areas were observed after reperfusion, but these findings were not recognized in the group with portocaval shunt.CONCLUSION: These results suggest that excessive portal flow is attributed to post transplant liver dysfunction after extreme small-for-size liver transplantation caused by sinusoidal microcirculatory injury.

  7. Extremely low frequency electric and magnetic fields as risk factors in chemical industry.

    Science.gov (United States)

    Troptcheva, T; Ivanova, M; Israel, M

    1998-09-01

    The risk assessment for staff in the chemical industry is usually related to accident hazards, production emergencies, blast and fire danger, or to the adverse effects of toxic substances. The combined effect of electric and magnetic fields with other factors combined with other hazards and working conditions, has not yet been studied. In all branches of industry, the members of staff who endure the most exposure to electric and magnetic fields, are electricians. This group is considered at high risk because of the increased probability of cancer. We studied electric and magnetic fields with low frequencies in the nitrogen chemical fertilizer plant "HIMCO", Vratza. Sources of extremely low frequency fields (50 Hz) are local thermal power plants, substations, open (110 kV) and closed (6 kV and 0.4 kV) distribution devices, transformers, compressors and turbocompressors, command halls, and video display units. The methods used for assessing exposure of low frequency electric and magnetic fields were based on the separate measurement of the electric and magnetic components of the field, using spot measurements and evaluation of the real time duration of exposure for different staff groups. The measured values for the different staff groups were within the limits of national and international standards. The measured magnetic flux densities in the "HIMCO" plant exceeded 3 mG, a value which is considered by many investigations in the literature, as a possible carcinogenic factor. The prolonged exposure to low frequency electric and magnetic fields determines the place of these physical factors in the complex of hazardous environmental factors for the staff. The simultaneous performance of combined investigations of all risk factors would result in the complete risk assessment for staff in the chemical industry. Electricians are considered to be a professional group who have an increased risk of contracting cancer. Extensive measurement and assessment of exposure of the

  8. Rotatable Small Permanent Magnet Array for Ultra-Low Field Nuclear Magnetic Resonance Instrumentation: A Concept Study.

    Directory of Open Access Journals (Sweden)

    Michael W Vogel

    Full Text Available We studied the feasibility of generating the variable magnetic fields required for ultra-low field nuclear magnetic resonance relaxometry with dynamically adjustable permanent magnets. Our motivation was to substitute traditional electromagnets by distributed permanent magnets, increasing system portability.The finite element method (COMSOL® was employed for the numerical study of a small permanent magnet array to calculate achievable magnetic field strength, homogeneity, switching time and magnetic forces. A manually operated prototype was simulated and constructed to validate the numerical approach and to verify the generated magnetic field.A concentric small permanent magnet array can be used to generate strong sample pre-polarisation and variable measurement fields for ultra-low field relaxometry via simple prescribed magnet rotations. Using the array, it is possible to achieve a pre-polarisation field strength above 100 mT and variable measurement fields ranging from 20-50 μT with 200 ppm absolute field homogeneity within a field-of-view of 5 x 5 x 5 cubic centimetres.A dynamic small permanent magnet array can generate multiple highly homogeneous magnetic fields required in ultra-low field nuclear magnetic resonance (NMR and magnetic resonance imaging (MRI instruments. This design can significantly reduce the volume and energy requirements of traditional systems based on electromagnets, improving portability considerably.

  9. NON-POTENTIAL FIELDS IN THE QUIET SUN NETWORK: EXTREME-ULTRAVIOLET AND MAGNETIC FOOTPOINT OBSERVATIONS

    Energy Technology Data Exchange (ETDEWEB)

    Chesny, D. L.; Oluseyi, H. M.; Orange, N. B. [Department of Physics and Space Sciences, Florida Institute of Technology, Melbourne, FL 32901 (United States)

    2013-11-20

    The quiet Sun (QS) magnetic network is known to contain dynamics which are indicative of non-potential fields. Non-potential magnetic fields forming ''S-shaped'' loop arcades can lead to the breakdown of static activity and have only been observed in high temperature X-ray coronal structures—some of which show eruptive behavior. Thus, analysis of this type of atmospheric structuring has been restricted to large-scale coronal fields. Here we provide the first identification of non-potential loop arcades exclusive to the QS supergranulation network. High-resolution Atmospheric Imaging Assembly data from the Solar Dynamics Observatory have allowed for the first observations of fine-scale ''S-shaped'' loop arcades spanning the network. We have investigated the magnetic footpoint flux evolution of these arcades from Heliospheric and Magnetic Imager data and find evidence of evolving footpoint flux imbalances accompanying the formation of these non-potential fields. The existence of such non-potentiality confirms that magnetic field dynamics leading to the build up of helicity exist at small scales. QS non-potentiality also suggests a self-similar formation process between the QS network and high temperature corona and the existence of self-organized criticality (SOC) in the form of loop-pair reconnection and helicity dissipation. We argue that this type of behavior could lead to eruptive forms of SOC as seen in active region (AR) and X-ray sigmoids if sufficient free magnetic energy is available. QS magnetic network dynamics may be considered as a coronal proxy at supergranular scales, and events confined to the network can even mimic those in coronal ARs.

  10. Exposure of children to extremely low frequency magnetic fields in France: Results of the EXPERS study.

    Science.gov (United States)

    Magne, Isabelle; Souques, Martine; Bureau, Isabelle; Duburcq, Anne; Remy, Emmanuel; Lambrozo, Jacques

    2017-09-01

    The assessment of magnetic field exposure in children is an important point in the context of epidemiological issues. EXPERS is the first study ever carried out measuring personal exposure to extremely low frequency magnetic fields at a national scale, involving 977 French children with 24 h personal measurements. Descriptive statistical analyses were performed for all the children, and only for children where no alarm clock was identified, as in some cases this requirement of the measurement protocol was not respected. The proportion of children with a 24 h arithmetic mean of ≥0.4 μT was 3.1% when considering all children and 0.8% when excluding alarm clocks. The alarm clocks were the main variable linked to the child exposure measurements. Magnetic field exposure increased when the home was located close to a high voltage power line. However, none of the 0.8% of children living at 0.4 μT. A multiple correspondence analysis showed the difficulty to build a statistical model predicting child exposure. The distribution of child personal exposure was significantly different from the distribution of exposure during sleep, questioning the exposure assessment in some epidemiological studies.

  11. ELF electric and magnetic fields: Pacific Northwest Laboratory studies. [Extremely Low Frequency (ELF)

    Energy Technology Data Exchange (ETDEWEB)

    Anderson, L.E.

    1992-06-01

    Studies have been conducted at Battelle, Pacific Northwest Laboratory, to examine extremely-low-frequency (ELF) electromagnetic fields for possible biological effects in animals. Three areas of investigation are reported here: (1) studies on the nervous system, including behavior and neuroendocrine function, (2) experiments on cancer development in animals, and (3) measurements of currents and electric fields induced in animal models by exposure to external magnetic fields. In behavioral experiments, rats have been shown to be responsive to ELF electric field exposure. Furthermore, experimental data indicate that short-term memory may be affected in albino rats exposed to combined ELF and static magnetic fields. Neuroendocrine studies have been conducted to demonstrate an apparent stress-related response in rats exposed to 60-Hz electric fields. Nighttime pineal melatonin levels have been shown to be significantly depressed in animals exposed to either electric or magnetic fields. A number of animal tumor models are currently under investigation to examine possible relationships between ELF exposure and carcinogenesis. Finally, theoretical and experimental measurements have been performed which form the basis for animals and human exposure comparisons.

  12. The Extreme Ultraviolet Deficit and Magnetically Arrested Accretion in Radio Loud Quasars

    CERN Document Server

    Punsly, Brian

    2014-01-01

    The Hubble Space Telescope composite quasar spectra presented in Telfer et al. show a significant deficit of emission in the extreme ultraviolet (EUV) for the radio loud component of the quasar population (RLQs), compared to the radio quiet component of the quasar population (RQQs). The composite quasar continuum emission between 1100 \\AA\\, and $\\sim$580 \\AA\\, is generally considered to be associated with the innermost regions of the accretion flow onto the central black hole. The deficit between 1100 \\AA\\, and 580 \\AA\\, in RLQs has a straightforward interpretation as a missing or a suppressed innermost region of local energy dissipation in the accretion flow. It is proposed that this can be the result of islands of large scale magnetic flux in RLQs that are located close to the central black hole that remove energy from the accretion flow as Poynting flux (sometimes called magnetically arrested accretion). These magnetic islands are natural sites for launching relativistic jets. Based on the Telfer et al. da...

  13. Counterstreaming electrons in small interplanetary magnetic flux ropes

    Science.gov (United States)

    Feng, H. Q.; Zhao, G. Q.; Wang, J. M.

    2015-12-01

    Small interplanetary magnetic flux ropes (SIMFRs) are commonly observed by spacecraft at 1 AU, and their origin still remains disputed. We investigated the counterstreaming suprathermal electron (CSE) signatures of 106 SIMFRs measured by Wind during 1995-2005. We found that 79 (75%) of the 106 flux ropes contain CSEs, and the percentages of counterstreaming vary from 8% to 98%, with a mean value of 51%. CSEs are often observed in magnetic clouds (MCs), and this indicates these MCs are still attached to the Sun at both ends. CSEs are also related to heliospheric current sheets (HCSs) and the Earth's bow shock. We divided the SIMFRs into two categories: The first category is far from HCSs, and the second category is in the vicinity of HCSs. The first category has 57 SIMFRs, and only 7 of 57 ropes have no CSEs. This ratio is similar to that of MCs. The second category has 49 SIMFRs; however, 20 of the 49 events have no CSEs. This ratio is larger than that of MCs. These two categories have different origins. One category originates from the solar corona, and most ropes are still connected to the Sun at both ends. The other category is formed near HCSs in the interplanetary space.

  14. The spatial distribution of threats to plant species with extremely small populations

    Science.gov (United States)

    Wang, Chunjing; Zhang, Jing; Wan, Jizhong; Qu, Hong; Mu, Xianyun; Zhang, Zhixiang

    2016-04-01

    Many biological conservationists take actions to conserve plant species with extremely small populations (PSESP) in China; however, there have been few studies on the spatial distribution of threats to PSESP. Hence, we selected distribution data of PSESP and made a map of the spatial distribution of threats to PSESP in China. First, we used the weight assignment method to evaluate the threat risk to PSESP at both country and county scales. Second, we used a geographic information system to map the spatial distribution of threats to PSESP, and explored the threat factors based on linear regression analysis. Finally, we suggested some effective conservation options. We found that the PSESP with high values of protection, such as the plants with high scientific research values and ornamental plants, were threatened by over-exploitation and utilization, habitat fragmentation, and a small sized wild population in broad-leaved forests and bush fallows. We also identified some risk hotspots for PSESP in China. Regions with low elevation should be given priority for ex- and in-situ conservation. Moreover, climate change should be considered for conservation of PSESP. To avoid intensive over-exploitation or utilization and habitat fragmentation, in-situ conservation should be practiced in regions with high temperatures and low temperature seasonality, particularly in the high risk hotspots for PSESP that we proposed. Ex-situ conservation should be applied in these same regions, and over-exploitation and utilization of natural resources should be prevented. It is our goal to apply the concept of PSESP to the global scale in the future.

  15. The spatial distribution of threats to plant species with extremely small populations

    Science.gov (United States)

    Wang, Chunjing; Zhang, Jing; Wan, Jizhong; Qu, Hong; Mu, Xianyun; Zhang, Zhixiang

    2017-03-01

    Many biological conservationists take actions to conserve plant species with extremely small populations (PSESP) in China; however, there have been few studies on the spatial distribution of threats to PSESP. Hence, we selected distribution data of PSESP and made a map of the spatial distribution of threats to PSESP in China. First, we used the weight assignment method to evaluate the threat risk to PSESP at both country and county scales. Second, we used a geographic information system to map the spatial distribution of threats to PSESP, and explored the threat factors based on linear regression analysis. Finally, we suggested some effective conservation options. We found that the PSESP with high values of protection, such as the plants with high scientific research values and ornamental plants, were threatened by over-exploitation and utilization, habitat fragmentation, and a small sized wild population in broad-leaved forests and bush fallows. We also identified some risk hotspots for PSESP in China. Regions with low elevation should be given priority for ex- and in-situ conservation. Moreover, climate change should be considered for conservation of PSESP. To avoid intensive over-exploitation or utilization and habitat fragmentation, in-situ conservation should be practiced in regions with high temperatures and low temperature seasonality, particularly in the high risk hotspots for PSESP that we proposed. Ex-situ conservation should be applied in these same regions, and over-exploitation and utilization of natural resources should be prevented. It is our goal to apply the concept of PSESP to the global scale in the future.

  16. Plant species with extremely small populations (PSESP in China: A seed and spore biology perspective

    Directory of Open Access Journals (Sweden)

    Ellie Merrett Wade

    2016-10-01

    Full Text Available Approximately one fifth of the world's plants are at risk of extinction. Of these, a significant number exist as populations of few individuals, with limited distribution ranges and under enormous pressure due to habitat destruction. In China, these most-at-risk species are described as ‘plant species with extremely small populations’ (PSESP. Implementing conservation action for such listed species is urgent. Storing seeds is one of the main means of ex situ conservation for flowering plants. Spore storage could provide a simple and economical method for fern ex situ conservation. Seed and spore germination in nature is a critical step in species regeneration and thus in situ conservation. But what is known about the seed and spore biology (storage and germination of at-risk species? We have used China's PSESP (the first group listing as a case study to understand the gaps in knowledge on propagule biology of threatened plant species. We found that whilst germination information is available for 28 species (23% of PSESP, storage characteristics are only known for 8% of PSESP (10 species. Moreover, we estimate that 60% of the listed species may require cryopreservation for long-term storage. We conclude that comparative biology studies are urgently needed on the world's most threatened taxa so that conservation action can progress beyond species listing.

  17. Complex Systems Theory to understand extremely low frequency magnetic fields interaction with immune cells

    Science.gov (United States)

    Vázquez-Coutiño, G. A.; Serrano-Luna, G.; Cañedo-Dorantes, L.; Godina-Nava, J. J.; Rodríguez-Segura, M. A.

    2003-09-01

    Well-documented studies about the interaction of extremely low frequency electromagnetic fields (ELF) with lymphocytes provide elements for the development of non-linear theoretical models. The Eichwald-Kaiser model of calcium oscillations was tested with a rectified cosine function at a frequency of 120 Hz. A change in dynamical behavior of calcium oscillations, from periodic in the normal case (without perturbation, what corresponds to a limit cycle) to the existence of very small micro-oscillations and a strange attractor in the perturbed case was found. It is concluded that the ELF configuration used in this model, alters the dynamical behavior of calcium oscillations in lymphocytes.

  18. Extreme Particle Acceleration in Magnetic Reconnection Layers: Application to the Gamma-Ray Flares in the Crab Nebula

    Science.gov (United States)

    Cerutti, Benoît; Uzdensky, Dmitri A.; Begelman, Mitchell C.

    2012-02-01

    The gamma-ray space telescopes AGILE and Fermi detected short and bright synchrotron gamma-ray flares at photon energies above 100 MeV in the Crab Nebula. This discovery suggests that electron-positron pairs in the nebula are accelerated to PeV energies in a milligauss magnetic field, which is difficult to explain with classical models of particle acceleration and pulsar wind nebulae. We investigate whether particle acceleration in a magnetic reconnection layer can account for the puzzling properties of the flares. We numerically integrate relativistic test-particle orbits in the vicinity of the layer, including the radiation reaction force, and using analytical expressions for the large-scale electromagnetic fields. As they get accelerated by the reconnection electric field, the particles are focused deep inside the current layer where the magnetic field is small. The electrons suffer less from synchrotron losses and are accelerated to extremely high energies. Population studies show that, at the end of the layer, the particle distribution piles up at the maximum energy given by the electric potential drop and is focused into a thin fan beam. Applying this model to the Crab Nebula, we find that the emerging synchrotron emission spectrum peaks above 100 MeV and is close to the spectral shape of a single electron. The flare inverse Compton emission is negligible and no detectable emission is expected at other wavelengths. This mechanism provides a plausible explanation for the gamma-ray flares in the Crab Nebula and could be at work in other astrophysical objects such as relativistic jets in active galactic nuclei.

  19. 3T3 cell motility and morphology before, during, and after exposure to extremely-low-frequency magnetic fields

    Energy Technology Data Exchange (ETDEWEB)

    Spadinger, I.; Palcic, B. [British Columbia Cancer Research Centre, Vancouver, British Columbia (Canada). Cancer Imaging; Agnew, D. [Ontario Hydro, Whitby, Ontario (Canada). Health and Safety Div.

    1995-08-01

    Automated image cytometry techniques were used to measure motility and morphology in 3T3 fibro-blasts exposed to extremely-low-frequency (ELF) magnetic fields. Cell motility and morphology were measured as a function of time before, during, and after 3--4 hour exposures to vertically oriented, 100 {mu}T{sub RMS} sinusoidal magnetic fields at various frequencies in the 10--63 Hz range. Sham exposures were also carried out. No static DC fields were applied, but the geomagnetic field was almost vertical and, therefore, had a large component (28.3 {mu}T) parallel to the applied AC field. The morphology and motile behavior of the cells were characterized by mathematically defined descriptors, which were calculated and averaged for the exposure period as well as for control periods that preceded and followed the exposure period. Each experiment involved the tracking of 100 cells that were subjected to one of the test frequencies (unless a sham exposure was being conducted). Statistical analysis of the results showed that even small changes of 10--20% could be significant at the P < .05 level. Changes on this order were measured in a significant proportion of the experiments. However, because such results were seen for both the sham-exposed and the ELF-exposed cells, and because the range of values that was obtained for the sham exposures was the same as that obtained for the ELF exposures, the authors concluded that there was no evidence to show that any of the measured changes were attributable to the applied ELF magnetic field.

  20. Design and Maxwell 3D simulation of small permanent magnetic actuator

    Institute of Scientific and Technical Information of China (English)

    Zhang Guangcai; Xu Yajie; Chang Yan; Chen Qiaoyan; Yang Xiaodong

    2014-01-01

    According to the magnetic circuit design theory and performance requirements of magnetic field, an H-type permanent magnetic actuator that generates uniform magnetic field larger than 0.4 T in the interested re- gion has been designed in this paper. The static magnetic field simulation analysis was done by Ansoft' s Max- well three-dimensional (3D) software. The simulation results showed that the magnetic field of this system can meet the requirements, and this permanent magnetic actuator designed in this paper can be used in small nuclear magnetic resonance (NMR) svstem.

  1. Stability and quench development study in small HTSC magnet

    NARCIS (Netherlands)

    Ilyin, Yu. A.; Vysotski, V.S.; Kiss, T.; Takeo, M.; Okamoto, H.; Irie, F.

    2001-01-01

    Stability and quench development in a HTSC magnet have been experimentally studied with the transport current in the magnet being below or above the “thermal quench current” level. The magnet was tested at both cryocooler cooling and liquid nitrogen cooling, with and without background magnetic fiel

  2. Stability and quench development study in small HTSC magnet

    NARCIS (Netherlands)

    Ilyin, Y.; Vysotski, V.S.; Kiss, T.; Takeo, M.; Okamoto, H.; Irie, F.

    2001-01-01

    Stability and quench development in a HTSC magnet have been experimentally studied with the transport current in the magnet being below or above the “thermal quench current” level. The magnet was tested at both cryocooler cooling and liquid nitrogen cooling, with and without background magnetic

  3. Low-cost, low-field dedicated extremity magnetic resonance imaging in early rheumatoid arthritis

    DEFF Research Database (Denmark)

    Lindegaard, Hanne Merete; Valloe, J.; Hørslev-Petersen, K.

    2006-01-01

    with rheumatoid arthritis with joint symptoms for hands and wrists, and E-MRI of the dominant wrist and MCP joints. RESULTS: At baseline, all......OBJECTIVE: To study the ability of low-cost low-field dedicated extremity magnetic resonance imaging (E-MRI) to assess and predict erosive joint damage in the wrist and metacarpophalangeal (MCP) joints of patients with early rheumatoid arthritis. METHODS: 24 previously untreated patients...... were excluded, the relative risk was 5.2. In patients with baseline MRI bone erosion or oedema, the relative risk of having x ray erosions at 1 year was 4.0, compared with patients without these signs at baseline (patient-centred analysis). CONCLUSION: In this group of patients with early rheumatoid...

  4. Exposure to extremely low-frequency magnetic field affects biofilm formation by cystic fibrosis pathogens.

    Science.gov (United States)

    Di Bonaventura, Giovanni; Pompilio, Arianna; Crocetta, Valentina; De Nicola, Serena; Barbaro, Filippo; Giuliani, Livio; D'Emilia, Enrico; Fiscarelli, Ersilia; Bellomo, Rosa Grazia; Saggini, Raoul

    2014-01-01

    To evaluate the in vitro effects of extremely low-frequency magnetic field (ELF-MF) on growth and biofilm formation by Staphylococcus aureus, Pseudomonas aeruginosa, Burkholderia cepacia and Stenotrophomonas maltophilia strains from cystic fibrosis patients. The motion of selected ions (Fe, Ca, Cu, Zn, Mg, K, Na) was stimulated by the ion resonance effect, then influence on growth and biofilm formation/viability was assessed by spectrophotometry or viability count. Generally, exposure to ELF-MF significantly increased bacterial growth and affected both biofilm formation and viability, although with differences with regard to ions and species considered. Exposure to ELF-MF represents a possible new approach for treatment of biofilm-associated cystic fibrosis lung infections.

  5. Dynamical instability of white dwarfs and breaking of spherical symmetry under the presence of extreme magnetic fields

    CERN Document Server

    Coelho, J G; Malheiro, M; Negreiros, R; Rueda, J A; Ruffini, R

    2013-01-01

    In this letter we discuss some basic properties of the equilibrium of magnetized white dwarfs, in particular the condition for dynamical instability of the star in the presence of an extremely large magnetic field. This will be done in the context of the virial theorem extended to include a magnetic term. We show, following the work of Chandrasekhar & Fermi of 1953, that when the star magnetic energy $W_B$ exceeds its gravitational potential energy $\\lvert W_G\\lvert$ ($W_B>\\lvert W_G\\lvert$), the system becomes dynamically unstable. In that seminal work it was shown that for extreme magnetic fields, a sphere is not the equilibrium configuration, and the star will become an oblate spheroid contracted along the symmetry axis. In light of this, the new mass limit for very magnetized and spherical white dwarf of 2.58$M_\\odot$, recently calculated, should be considered carefully, since these objects are unstable and unbound, and also because the extreme magnetic fields violate the spherical symmetry assumed to...

  6. The effect of extremely low frequency magnetic field on heart tissue iron density

    Directory of Open Access Journals (Sweden)

    Yusuf Nergiz

    2011-06-01

    Full Text Available The aim of this histological study was to investigate the effects of extremely low frequency, low intensity magnetic field on the heart muscle ıron density.Materials and methods: In this study, 45 male Spraque Dawley rats were introduced and were divided into three groups as sham, control and experiment group. The experimental group was exposed to a 0.25 mT to Extremely Low Frequency Magnetic Field (ELF-MF for 14 days, 3h a day in metacrylate boxes. The sham group was treated like the experimental group, except for ELF-MF exposure. For control, nothing applied to rats in this group and they completed their life cycle in the cage during the study period. After exposure period, the rats were sacrificed under ketalar anesthesia (50 mg / kg, intramuscularly. Heart tissues were immediately fixed in 10% neutral formaldehyde and embedded in paraffin blocks. Histological sections from cardiac tissue stained by hematoxylin-eosin, Perls’ Prussian blue for iron pigments. Histological slides were photographed under a Nikon DS-2MV photomicroscope.Results: The architecture and histology of the control, sham and experimental group were observed as normal. No differences were observed between the control, sham and experimental rat groups in the iron stain of heart tissues.Conclusion: As a result of our study, we did not observe differences between the control and ELF-MF (experimental group. In this investigation we demonstrated that the exposure of cardiac tissue of rats to the ELF-MF did not change in the iron stain study. J Clin Exp Invest 2011;2(2:144-8

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

    Directory of Open Access Journals (Sweden)

    Sang-Kon Lee

    2014-01-01

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

  8. Anomalous dynamics of the extremely compressed magnetosphere during 21 January 2005 magnetic storm

    CERN Document Server

    Dmitriev, A V; Chao, J -K; Wang, C B; Rastaetter, L; Panasyuk, M I; Lazutin, L L; Kovtyukh, A S; Veselovsky, I S; Myagkova, I N

    2014-01-01

    Dynamics of the dayside magnetosphere and proton radiation belt was analyzed during unusual magnetic storm on 21 January 2005. We have found that during the storm from 1712 to 2400 UT, the subsolar magnetopause was continuously located inside geosynchronous orbit due to strong compression. The compression was found to be extremely strong from 1846 to 2035 UT when the dense plasma of fast erupting filament produced the solar wind dynamic pressure Pd peaked up to >100 nPa and, in the first time, the upstream solar wind was observed at geosynchronous orbit during almost 2 hours. Under the extreme compression, the outer magnetosphere at L > 5 was pushed inward and the outer radiation belt particles with energies of several tens of keV moved earthward, became adiabatically accelerated and accumulated in the inner magnetosphere at L 20%, which is well appropriate for erupting filaments and which is in agreement with the upper 27% threshold for the He/H ratio obtained from Cluster measurements.

  9. Credible occurrence probabilities for extreme geophysical events: earthquakes, volcanic eruptions, magnetic storms

    Science.gov (United States)

    Love, Jeffrey J.

    2012-01-01

    Statistical analysis is made of rare, extreme geophysical events recorded in historical data -- counting the number of events $k$ with sizes that exceed chosen thresholds during specific durations of time $\\tau$. Under transformations that stabilize data and model-parameter variances, the most likely Poisson-event occurrence rate, $k/\\tau$, applies for frequentist inference and, also, for Bayesian inference with a Jeffreys prior that ensures posterior invariance under changes of variables. Frequentist confidence intervals and Bayesian (Jeffreys) credibility intervals are approximately the same and easy to calculate: $(1/\\tau)[(\\sqrt{k} - z/2)^{2},(\\sqrt{k} + z/2)^{2}]$, where $z$ is a parameter that specifies the width, $z=1$ ($z=2$) corresponding to $1\\sigma$, $68.3\\%$ ($2\\sigma$, $95.4\\%$). If only a few events have been observed, as is usually the case for extreme events, then these "error-bar" intervals might be considered to be relatively wide. From historical records, we estimate most likely long-term occurrence rates, 10-yr occurrence probabilities, and intervals of frequentist confidence and Bayesian credibility for large earthquakes, explosive volcanic eruptions, and magnetic storms.

  10. Effects of extremely low frequency magnetic field on anxiety level and spatial memory of adult rats

    Institute of Scientific and Technical Information of China (English)

    HE Li-hua; SHI Hong-mei; LIU Tong-tong; XUYing-chun; YE Kang-ping; WANG Sheng

    2011-01-01

    Background As the widespread use of electric devices in modern life,human are exposed to extremely low frequency magnetic fields (ELF MF) much more frequently than ever.Over the past decades,a substantial number of epidemiological and experimental studies have demonstrated that ELF MF (50 Hz) exposure is associated with increased risk of various health effects.The present study examined the effects of chronic exposure to ELF MF on anxiety level and spatial memory of adult rats.Methods The 50-Hz ELF MF was used during the whole experimental procedures and the value of magnetic field (MF)was set to 2 mT.Adult rats were divided randomly to control,MF 1 hour and MF 4 hours group.Anxiety-related behaviors were examined in the open field test and the elevated plus maze; changes in spatial learning and memory were determined in Morris water maze after 4 weeks of daily exposure.Results Rats in MF 4 hours group had increased anxiety-like behaviors with unaltered locomotor activity.In the Morris water maze test,rats had reduced latency to find the hidden platform and improved long-term memory of former location of platform without changes in short-term memory and locomotor activity.Conclusion Chronic ELF MF exposure has anxiogenic effect on rats,and the promoting effects on spatial learning and long-term retention of spatial memory.

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

    Energy Technology Data Exchange (ETDEWEB)

    Anderson, L.E.

    1994-03-01

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

  12. Effects of extremely low frequency magnetic field on production of mannatide by α-hemolytic Streptococcus.

    Science.gov (United States)

    Zhang, Jialan; Xu, Cui; Wan, Yunlei; Gao, Mengxiang

    2016-07-01

    The effect of the extremely low frequency magnetic field (ELF-MF) on biomass and mannatide production by α-hemolytic Streptococcus in liquid-state fermentation culture medium was studied during shake flask culture. Magnetic field (MF) inductions, exposure times, and exposure periods varied in a range of 0-1.5 mT, 0-16 h, and six periods of incubation time, respectively. Results showed both biomass and mannatide production increased significantly at MF induction 0.4, 0.6, and 0.9 mT and decreased at both 1.2 and 1.5 mT. Biomass increased by exposure for initial and middle stages of fermentation. Mannatide production increased significantly at 4-8, 8-12, and 17-21 h. Peak yield of biomass and mannatide production increased by 10.7% and 14.0% at 25 and 27 h of incubation at 0.6 mT MF induction and exposure to 8-12 h of incubation time, compared with the control experiment, respectively. ELF-MF could also enhance the growth rate and mannatide production rate of α-hemolytic Streptococcus. However, ELF-MF did not alter α-hemolytic Streptococcus cell growth and mannatide metabolizing regulation or fermentation pattern. Mannatide production was not associated with cellular growth but rather only partially associated. Bioelectromagnetics. 37:331-337, 2016. © 2016 Wiley Periodicals, Inc.

  13. Magnetic Field Gradiometer with Sub-Micron Spatial Resolution Based on Caesium Vapour in an Extremely Thin Cell

    Directory of Open Access Journals (Sweden)

    Auzinsh M.

    2015-06-01

    Full Text Available In this paper we present a device for measuring the magnetic field and its gradient with a spatial resolution of several hundred nanometres. This device is based on caesium metal vapour confined to an extremely thin cell (ETC. To measure magnetic signals, we use absorption and very low laser powers, which might be appealing for modern fabrication techniques. A portable, fully automated device was constructed.

  14. Applications concepts of small regenerative cryocoolers in superconducitng magnet systems

    NARCIS (Netherlands)

    Laan, van der M.T.G.; Tax, R.B.; Kate, ten H.H.J.

    1992-01-01

    Superconducting magnets are in growing use outside laboratories for example MRI scanners in hospitals. Other applications under development are magnet systems for separation, levitated trains and ship propulsion. The application of cryocoolers can make these systems more practical. Interfacing these

  15. Micromagnetic simulation of magnetic small-angle neutron scattering from two-phase nanocomposites

    Energy Technology Data Exchange (ETDEWEB)

    Michels, Andreas, E-mail: andreas.michels@uni.lu [Physics and Materials Science Research Unit, University of Luxembourg, 162A Avenue de la Faïencerie, L-1511 Luxembourg (Luxembourg); Erokhin, Sergey; Berkov, Dmitry; Gorn, Nataliya [INNOVENT Technology Development, Prüssingstraße 27B, D-07745 Jena (Germany)

    2014-01-15

    The recent development of a micromagnetic simulation methodology—suitable for multiphase magnetic nanocomposites—permits the computation of the magnetic microstructure and of the associated magnetic small-angle neutron scattering (SANS) cross section of these materials. In this review we summarize results on the micromagnetic simulation of magnetic SANS from two-phase nanocomposites. The decisive advantage of this approach resides in the possibility to scrutinize the individual magnetization Fourier contributions to the total magnetic SANS cross section, rather than their sum, which is generally obtained from the experiment. The procedure furnishes unique and fundamental information regarding magnetic neutron scattering from nanomagnets.

  16. Assessing future climatic changes of rainfall extremes at small spatio-temporal scales

    DEFF Research Database (Denmark)

    Gregersen, Ida Bülow; Sørup, Hjalte Jomo Danielsen; Madsen, Henrik;

    2013-01-01

    in relation to urban flooding. The present study focuses on high-resolution regional climate model (RCM) skill in simulating sub-daily rainfall extremes. Temporal and spatial characteristics of output from three different RCM simulations with 25 km resolution are compared to point rainfall extremes estimated......Climate change is expected to influence the occurrence and magnitude of rainfall extremes and hence the flood risks in cities. Major impacts of an increased pluvial flood risk are expected to occur at hourly and sub-hourly resolutions. This makes convective storms the dominant rainfall type...

  17. Magnetic resonance imaging of small bowel Crohn's disease.

    Science.gov (United States)

    Ramalho, Miguel; Herédia, Vasco; Cardoso, Cláudia; Matos, António P; Palas, João; De Freitas, João; Semelka, Richard C

    2012-01-01

    Crohn's disease (CD) is a chronic relapsing inflammatory disease of the gastrointestinal tract, which mostly affects young patients. Imaging techniques form a very important part for the evaluation of CD and for monitoring disease progression or response to therapy. Currently, imaging of CD is increasingly being performed by cross-sectional modalities, i.e. multidetector computed tomography (MDCT) and magnetic resonance imaging (MRI), since these techniques allow for simultaneous visualization of luminal, mural and extraintestinal disease extension. MR enterography has the potential to safely and noninvasively accomplish the imaging needs of patients with Crohn disease without exposing them to ionizing radiation. The new imaging paradigm should contemplate patient safety as a very important aspect when assessing the role of an imaging modality in comparison with others. For this reason, MRI may be the preferred modality for evaluation of small bowel disease, especially in young patients in the setting of CD, considering that the majority will undergo frequent repeat studies. Also, the information on disease activity is not matched by any other imaging method. In this review article, the authors discuss the essential aspects of MR evaluation of CD, including protocol and imaging findings, also referring the advantages over other radiological studies, concerning safety, accuracy and potential importance for therapeutic approach.

  18. Magnetic resonance imaging for precise radiotherapy of small laboratory animals

    Energy Technology Data Exchange (ETDEWEB)

    Frenzel, Thorsten [Universitaetsklinikum Hamburg-Eppendorf, Hamburg (Germany). Bereich Strahlentherapie; Universitaetsklinikum Hamburg-Eppendorf, Hamburg (Germany). Inst. fuer Anatomie und Experimentelle Morphologie; Kaul, Michael Gerhard; Ernst, Thomas Michael; Salamon, Johannes [Universitaetsklinikum Hamburg-Eppendorf, Hamburg (Germany). Klinik und Poliklinik fuer Diagnostische und Interventionelle Radiologie; Jaeckel, Maria [Universitaetsklinikum Hamburg-Eppendorf, Hamburg (Germany). Klinik und Poliklinik fuer Strahlentherapie und Radioonkologie; Schumacher, Udo [Universitaetsklinikum Hamburg-Eppendorf, Hamburg (Germany). Inst. fuer Anatomie und Experimentelle Morphologie; Kruell, Andreas [Universitaetsklinikum Hamburg-Eppendorf, Hamburg (Germany). Bereich Strahlentherapie

    2017-05-01

    Radiotherapy of small laboratory animals (SLA) is often not as precisely applied as in humans. Here we describe the use of a dedicated SLA magnetic resonance imaging (MRI) scanner for precise tumor volumetry, radiotherapy treatment planning, and diagnostic imaging in order to make the experiments more accurate. Different human cancer cells were injected at the lower trunk of pfp/rag2 and SCID mice to allow for local tumor growth. Data from cross sectional MRI scans were transferred to a clinical treatment planning system (TPS) for humans. Manual palpation of the tumor size was compared with calculated tumor size of the TPS and with tumor weight at necropsy. As a feasibility study MRI based treatment plans were calculated for a clinical 6 MV linear accelerator using a micro multileaf collimator (μMLC). In addition, diagnostic MRI scans were used to investigate animals which did clinical poorly during the study. MRI is superior in precise tumor volume definition whereas manual palpation underestimates their size. Cross sectional MRI allow for treatment planning so that conformal irradiation of mice with a clinical linear accelerator using a μMLC is in principle feasible. Several internal pathologies were detected during the experiment using the dedicated scanner. MRI is a key technology for precise radiotherapy of SLA. The scanning protocols provided are suited for tumor volumetry, treatment planning, and diagnostic imaging.

  19. Small Explorer (SMEX) POsitron Electron Magnet Spectrometer (POEMS)

    Science.gov (United States)

    LHeureux, Jacques; Evenson, Paul A.; Aleman, R. (Technical Monitor)

    1995-01-01

    This report covers the activities of Louisiana State University (LSU) under subcontract 26053-EX between LSU and the Bartol Research Institute (Bartol), which began January 1, 1994. The purpose of this subcontract was for LSU to participate in and support Bartol in the work to define the SMEX (Small Explorer)/POEMS (Positron Electron Magnet Spectrometer) spaceflight mission under NASA Contract NAS5-38098 between NASA and Bartol. The conclusions of this study were that for a 1998 launch into a 600km altitude, 98 degrees, approximately sun synchronous orbit, (a) the total radiation dose would be typically a few k-rad per year, certainly less than 20 k-rad per year for the anticipated shielding and potential solar flare environment, (b) detector counting rates would be dominated by the South Atlantic Anomaly (SAA) and the horns of the Van Allen belts, (c) the galactic electron and positron 'signal' can be extracted from the albedo background and the trapped populations by detailed evaluation of the geomagnetic transmission function (cut-off) for each event, (d) POEMS could make significant contributions to magnetospheric science if sufficient downlink capacity were provided and, (e) a fully functioning, cost efficient, data processing and analysis facility design was developed for the mission. Overall, POEMS was found to be a relatively simple experiment to manifest, operate and analyze and had potential for fundamental new discoveries in cosmic, heliospheric, solar and magnetospheric science.

  20. Application concepts of small regenerative cryocoolers in superconducting magnet systems

    Science.gov (United States)

    van der Laan, M. T. G.; Tax, R. B.; ten Kate, H. H. J.

    Superconducting magnets are in growing use outside laboratories for example MRI scanners in hospitals. Other applications under development are magnet systems for separation, levitated trains and ship propulsion. The application of cryocoolers can make these systems more practical. Interfacing these cryocoolers to the magnets can be designed in several different ways. The four basic methods will be dealt with. Test results of a realized GM cryocooler-SC magnet system will be shown. It handles about a 1:3 scale MRI magnet of which one of the six coils has been successfully tested at temperatures between 10 and 14 K.

  1. Occupational extremely low-frequency magnetic field exposure and selected cancer outcomes in a prospective Dutch cohort

    NARCIS (Netherlands)

    Koeman, T.; Brandt, P.A. van den; Slottje, P.; Schouten, L.J.; Goldbohm, R.A.; Kromhout, H.; Vermeulen, R.

    2014-01-01

    Purpose: To investigate the association between exposure to occupational extremely low-frequency magnetic fields (ELF-MF) and the risk of a priori selected cancer outcomes within the prospective Netherlands Cohort Study. Methods: 120,852 men and women aged 55-69 years at time of enrollment in 1986

  2. Occupational exposure to extremely low-frequency magnetic fields and cardiovascular disease mortality in a prospective cohort study

    NARCIS (Netherlands)

    Slottje, Pauline; Kromhout, Hans; Schouten, Leo J.; Goldbohm, R. Alexandra; van den Brandt, Piet A.; Vermeulen, Roel; Koeman, T.

    2013-01-01

    Objectives Although a study among utility workers found an increased risk for acute myocardial infarction and arrhythmia-related deaths associated with occupational extremely low-frequency magnetic fields (ELF-MF) exposure, later studies largely failed to replicate these findings. This study investi

  3. A multicenter reliability study of extremity-magnetic resonance imaging in the longitudinal evaluation of rheumatoid arthritis

    DEFF Research Database (Denmark)

    Conaghan, Philip G; Ejbjerg, Bo; Lassere, Marissa;

    2007-01-01

    There are limited data on the reliability of extremity magnetic resonance imaging (E-MRI) in the longitudinal evaluation of rheumatoid arthritis (RA). Our aim was to assess the interreader reliability of the OMERACT RA MRI score in the assessment of change in disease activity and bone erosion sco...

  4. Temperature dependent small-angle neutron scattering of CTABr-magnetic fluid emulsion

    Indian Academy of Sciences (India)

    V K Aswal; J V Joshi; P S Goyal; Rajesh Patel; R V Upadhyay; R V Mehta

    2004-08-01

    Small-angle neutron scattering studies have been carried out to check the structural integrity of citryltrimethylammonium bromide (CTABr) micelles in a magnetic fluid for different magnetic fluid concentrations at two different temperatures 303 and 333 K. It is found that the CTABr micelles grow with increasing magnetic fluid concentration and there is a decrease in the micellar size with increase in temperature.

  5. Supine spinal magnetic resonance imaging with straightened lower extremities in spondylolisthesis: A comparison with the conventional technique

    Energy Technology Data Exchange (ETDEWEB)

    Daghighi, Mohammad Hossein; Poureisa, Masoud; Arablou, Farid [Department of Radiology, Imam Reza Teaching Center, Tabriz University of Medical Sciences, Tabriz (Iran, Islamic Republic of); Fouladi, Daniel F., E-mail: medicorelax@yahoo.com [Drug Applied Research Center, Tabriz University of Medical Sciences, Tabriz (Iran, Islamic Republic of)

    2015-05-15

    Highlights: • MR imaging with straightened lower extremities was tested in spondylolisthesis. • This technique is more accurate than conventional MR imaging in detecting slip. • Level of spondylolisthesis is the only independent predictor of severity of slip. - Abstract: Objectives: To compare the degree of slip in spondylolisthesis on supine magnetic resonance (MR) images obtained with flexed and straightened lower extremities. Methods: Supine spinal MR studies were performed in 100 cases of symptomatic spondylolisthesis with flexed and then straightened lower extremities. The angle of lumbar lordosis (by Cobb's method) and the degree of slip (by Taillard's method) were compared between the two sets of images. Results: The mean angle of lumbar lordosis increased from 51.65 ± 8.57° on MR images with flexed lower limbs to 57.39 ± 9.05° on MR images with straightened lower limbs (p < 0.001; mean percent increase: 11.51%). Similar change was also observed for the mean degree of slip (from 25.80 ± 7.74% to 28.68 ± 7.93%, p < 0.001; mean percent increase: 12.60%). After MR imaging with straightened lower extremities 22 out of 54 initially grade I cases had grade II disease (p < 0.001). Conclusions: Supine magnetic resonance imaging with straightened lower extremities detects higher degree of slippage in symptomatic patients with spondylolisthesis compared to conventional MRI with flexed lower extremities.

  6. Attitude dynamics of gyrostat-satellites under control by magnetic actuators at small perturbations

    Science.gov (United States)

    Doroshin, Anton V.

    2017-08-01

    The angular motion of gyrostat-satellites with one axial rotor is considered under control by magnetic actuators and at the action of small polyharmonic perturbations of the own dipole magnetic moment's components which are created proportionally to components of the angular velocity of the satellite. The attitude dynamics is investigated in conditions of the coincidence of the vector of magnetic induction of the external magnetic field and the initial angular momentum vector of the satellite. General and heteroclinic analytical solutions are obtained for dynamical parameters at the relative smallness of the magnetic torques. The chaotic regimes are examined on the base of the Melnikov method and Poincaré sections.

  7. Energy transfers in dynamos with small magnetic Prandtl numbers

    KAUST Repository

    Kumar, Rohit

    2015-06-25

    We perform numerical simulation of dynamo with magnetic Prandtl number Pm = 0.2 on 10243 grid, and compute the energy fluxes and the shell-to-shell energy transfers. These computations indicate that the magnetic energy growth takes place mainly due to the energy transfers from large-scale velocity field to large-scale magnetic field and that the magnetic energy flux is forward. The steady-state magnetic energy is much smaller than the kinetic energy, rather than equipartition; this is because the magnetic Reynolds number is near the dynamo transition regime. We also contrast our results with those for dynamo with Pm = 20 and decaying dynamo. © 2015 Taylor & Francis.

  8. Characterization of Extremely Low Frequency Magnetic Fields from Diesel, Gasoline and Hybrid Cars under Controlled Conditions

    Directory of Open Access Journals (Sweden)

    Ronen Hareuveny

    2015-01-01

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

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

    Directory of Open Access Journals (Sweden)

    Lucietta Betti

    2011-01-01

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

  10. Identifying neutrino mass hierarchy at extremely small theta13 through earth matter effects in a supernova signal.

    Science.gov (United States)

    Dasgupta, Basudeb; Dighe, Amol; Mirizzi, Alessandro

    2008-10-24

    Collective neutrino flavor transformations deep inside a supernova are sensitive to the neutrino mass hierarchy even at extremely small values of theta_(13). Exploiting this effect, we show that comparison of the antineutrino signals from a galactic supernova in two megaton class water Cherenkov detectors, one of which is shadowed by Earth, will enable us to distinguish between the hierarchies if sin(2)theta_(13) < or approximately 10(-5), where long baseline neutrino experiments would be ineffectual.

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

    Directory of Open Access Journals (Sweden)

    Ilaria Liorni

    2016-05-01

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

  12. Children's Personal Exposure Measurements to Extremely Low Frequency Magnetic Fields in Italy.

    Science.gov (United States)

    Liorni, Ilaria; Parazzini, Marta; Struchen, Benjamin; Fiocchi, Serena; Röösli, Martin; Ravazzani, Paolo

    2016-05-31

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

  13. Assessment of daily exposure of endodontic personnel to extremely low frequency magnetic fields.

    Science.gov (United States)

    Kim, D W; Choi, J L; Kwon, M K; Nam, T J; Lee, S J

    2012-08-01

    To measure daily exposure levels to extremely low frequency magnetic fields (ELF MFs) in endodontic clinics. In total, 10 subjects (five endodontic trainees, five hygienists) participated. Each volunteer wore a 60-Hz MF measurement device on the left upper arm during working hours. Measurements were taken continuously throughout the working day except at lunch time. Separate measurements were taken for specific items of equipment at several distances. The average MF exposure for the 10 personnel was 0.03±0.04micro-Tesla (μT) (range, 0.01-6.4μT). The average MF exposure of endodontic personnel was lower than that of other hospital personnel according to the literature. Furthermore, all monitored exposure levels were well below the maximum acute exposure level, 500μT, recommended by the International Committee on Non-ionizing Radiation Protection for the protection of workers against ELF MFs. However, relatively high levels of exposure occurred in an operating room and X-ray room, presumably as a result of the use of surgical equipment such as microscopes and monitors, various motors and power cables of X-ray machines with large current flows. The total average MF exposure level of 0.03μT was lower than the typical background level at home. Although high levels of exposure were measured in an operating room and X-ray room, the MF exposure level to dental personnel was minimal during routine endodontic clinical work. © 2012 International Endodontic Journal.

  14. Extremely low-frequency magnetic field exposure, electrical shocks and risk of Parkinson's disease.

    Science.gov (United States)

    van der Mark, Marianne; Vermeulen, Roel; Nijssen, Peter C G; Mulleners, Wim M; Sas, Antonetta M G; van Laar, Teus; Kromhout, Hans; Huss, Anke

    2015-02-01

    Previous studies did not provide strong evidence for an increased Parkinson's disease (PD) risk after exposure to extremely low-frequency magnetic fields (ELF-MF), but were limited in their scope to address other exposures related to the use of electricity such as electrical shocks. We evaluated the associations of PD with exposure to ELF-MF, electrical shocks and having worked in "electrical occupations." We conducted a hospital-based case-control study, including 444 PD patients and 876 age- and sex-matched controls. Occupational histories were collected in telephone interviews and were linked to job-exposure matrices on ELF-MF exposure and on electrical shocks. In addition, questions on use of household appliances involving ELF-MF exposure, experienced electrical shocks and potential confounders were asked. No association of PD risk with any of the evaluated exposures related to electricity was observed. We did, however, observe quite consistently reduced risk estimates across the majority of the exposure categories explored. Given the results of the previous studies and the absence of any postulated mechanism, this is unlikely to represent a true protective effect of ELF-MF or electrical shocks on the occurrence of PD. The results of this study suggest that no association exists between PD and exposure to ELF-MF, electrical shocks or having worked in "electrical occupations."

  15. Extremely low frequency magnetic fields induce oxidative stress in rat brain.

    Science.gov (United States)

    Manikonda, Pavan K; Rajendra, Pilankatta; Devendranath, D; Gunasekaran, B; Channakeshava; Aradhya, Shivakumara R S; Sashidhar, Rao B; Subramanyam, Chivukula

    2014-01-01

    The present investigation was conducted to understand the influence of long-term exposure of rats to extremely low frequency magnetic fields (ELF-MF), focusing on oxidative stress (OS) on different regions of rat's brain. Male Wistar rats (21-day-old) were exposed to ELF-MF (50 Hz; 50 and 100 µT) for 90 days continuously; hippocampal, cerebellar and cortical regions from rats were analyzed for (i) reactive oxygen species (ROS), (ii) metabolites indicative of OS and (iii) antioxidant enzymes. In comparison to control group rats, the rats that were continuously exposed to ELF-MF caused OS and altered glutathione (GSH/GSSG) levels in dose-dependent manner in all the regions of the brain. Accumulation of ROS, lipid peroxidation end products and activity of superoxide dismutase in different regions was in the descending order of cerebellum glutathione peroxidase activity were in the descending order of hippocampus 50 µT. Varied influences observed in different regions of the brain, as documented in this study, may contribute to altered metabolic patterns in its related regions of the central nervous system, leading to aberrant neuronal functions.

  16. Intergalactic Magnetic Fields and Gamma Ray Observations of Extreme TeV Blazars

    CERN Document Server

    Arlen, Timothy C; Weisgarber, Thomas; Wakely, Scott P; Shafi, S Yusef

    2012-01-01

    The intergalactic magnetic field (IGMF) can be indirectly probed through its effect on electromagnetic cascades initiated by a source of TeV gamma-rays, such as active galactic nuclei (AGN). AGN that are sufficiently luminous at TeV energies, extreme TeV blazars, can produce detectable levels of secondary radiation from Inverse Compton (IC) scattering of the electrons in the cascade, provided that the IGMF is not too large. We review recent work in the literature which utilizes this idea to derive constraints on the IGMF for three TeV-detected blazars-1ES 0229+200, 1ES 1218+304, and RGB J0710+591, and we also investigate four other hard-spectrum TeV blazars in the same context. Through a recently developed detailed Monte Carlo code, incorporating all major effects of QED and cosmological expansion, we research effects of major uncertainties such as the spectral properties of the source, uncertainty in the UV - far IR extragalactic background light (EBL), undersampled Very High Energy (VHE; energy > 100 GeV) c...

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

    Science.gov (United States)

    Liorni, Ilaria; Parazzini, Marta; Struchen, Benjamin; Fiocchi, Serena; Röösli, Martin; Ravazzani, Paolo

    2016-01-01

    Extremely low frequency magnetic fields (ELF-MFs) exposure is still a topic of concern due to their possible impact on children’s health. Although epidemiological studies claimed an evidence of a possible association between ELF-MF above 0.4 μT and childhood leukemia, biological mechanisms able to support a causal relationship between ELF-MF and this disease were not found yet. To provide further knowledge about children’s ELF-MF exposure correlated to children’s daily activities, a measurement study was conducted in Milan (Italy). Eighty-six children were recruited, 52 of whom were specifically chosen with respect to the distance to power lines and built-in transformers to oversample potentially highly exposed children. Personal and bedroom measurements were performed for each child in two different seasons. The major outcomes of this study are: (1) median values over 24-h personal and bedroom measurements were <3 μT established by the Italian law as the quality target; (2) geometric mean values over 24-h bedroom measurements were mostly <0.4 μT; (3) seasonal variations did not significantly influence personal and bedroom measurements; (4) the highest average MF levels were mostly found at home during the day and outdoors; (5) no significant differences were found in the median and geometric mean values between personal and bedroom measurements, but were found in the arithmetic mean. PMID:27258295

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

    Science.gov (United States)

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

    2011-08-15

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

  19. Minimum Q Electrically Small Spherical Magnetic Dipole Antenna - Theory

    DEFF Research Database (Denmark)

    Breinbjerg, Olav; Kim, Oleksiy S.

    2009-01-01

    The stored energies, radiated power, and quality factor of a magnetic-dipole antenna, consisting of a spherical electrical surface current density enclosing a magnetic core, is obtained through direct spatial integration of the internally and externally radiated field expressed in terms of spheri...

  20. Generation of Large-Scale Magnetic Fields by Small-Scale Dynamo in Shear Flows.

    Science.gov (United States)

    Squire, J; Bhattacharjee, A

    2015-10-23

    We propose a new mechanism for a turbulent mean-field dynamo in which the magnetic fluctuations resulting from a small-scale dynamo drive the generation of large-scale magnetic fields. This is in stark contrast to the common idea that small-scale magnetic fields should be harmful to large-scale dynamo action. These dynamos occur in the presence of a large-scale velocity shear and do not require net helicity, resulting from off-diagonal components of the turbulent resistivity tensor as the magnetic analogue of the "shear-current" effect. Given the inevitable existence of nonhelical small-scale magnetic fields in turbulent plasmas, as well as the generic nature of velocity shear, the suggested mechanism may help explain the generation of large-scale magnetic fields across a wide range of astrophysical objects.

  1. Energy transfers and magnetic energy growth in small-scale dynamo

    KAUST Repository

    Kumar, Rohit Raj

    2013-12-01

    In this letter we investigate the dynamics of magnetic energy growth in small-scale dynamo by studying energy transfers, mainly energy fluxes and shell-to-shell energy transfers. We perform dynamo simulations for the magnetic Prandtl number Pm = 20 on 10243 grid using the pseudospectral method. We demonstrate that the magnetic energy growth is caused by nonlocal energy transfers from the large-scale or forcing-scale velocity field to small-scale magnetic field. The peak of these energy transfers moves towards lower wave numbers as dynamo evolves, which is the reason why the integral scale of the magnetic field increases with time. The energy transfers U2U (velocity to velocity) and B2B (magnetic to magnetic) are forward and local. Copyright © EPLA, 2013.

  2. Energy transfers and magnetic energy growth in small-scale dynamo

    CERN Document Server

    Kumar, Rohit; Samtaney, Ravi

    2013-01-01

    In this letter we investigate the dynamics of magnetic energy growth in small-scale dynamo by studying energy transfers, mainly energy fluxes and shell-to-shell energy transfers. We perform dynamo simulation for magnetic Prandtl number $\\mathrm{Pm}=20$ on $1024^3$ grid using pseudospectral method. We demonstrate using flux and shell-to-shell energy transfer computations that the magnetic energy growth is caused by nonlocal energy transfers from the large scale velocity field to small scale magnetic field. The energy transfers $U2U$ (velocity to velocity) and $B2B$ (magnetic to magnetic) are forward and local. We also show that the magnetic energy grows exponentially with time, and it tends to have equipartition with kinetic energy.

  3. Magnetization Switching in a Small Disk with Shape Anisotropy

    Institute of Scientific and Technical Information of China (English)

    LU Dong-Li; XU Chen

    2010-01-01

    @@ We study the precessional switching of a single domain,uniaxial magnetic disk with shape anisotropy by the micromagnetic simulation.The results show that magnetic switching can be driven by a smaller magnetic field pulse in an elliptic disk with its long semiaxis perpendicular to the easy axis than in a circular disk.The shape anisotropy can change the height of the energy barrier,thus we may obtain an optimal fast magnetization switching by tuning the aspect ratio of the disk under the thermal stability condition.The switching behavior of the elliptic and circular disks is studied in detail.It is found that only properly choosing the pulse amplitude and duration can realize the fast precessional switching.

  4. Formation of small-scale magnetic elements: surface mechanism

    CERN Document Server

    Gadun, A S; Solanki, S K; 10.3103/50884591305030022

    2012-01-01

    We present the first results of a two-dimensional MHD simulation of the solar magnetogranulation. The medium was assumed to be compressible, gravitationally stratified, radiatively coupled, partially ionized, and turbulent. The simulated magnetogranulation evolved over the course of two hours of hydrodynamic (solar) time. A surface (magnetic plume-like) mechanism which forms thin magnetic elements was found to operate during the process of granule fragmentation. The activity of such a mechanism suggests that the magnetogranulation can concentrate and intensify the global magnetic flux at the boundaries of convective cells and can also form nearly vertical compact magnetic flux tubes by involving the weak horizontal photospheric field, which may be, in general, of local (turbulent) nature.

  5. Kinetic properties of small one-dimensional Ising magnetic

    Science.gov (United States)

    Udodov, Vladimir; Spirin, Dmitriy; Katanov Khakas State University Team

    2011-03-01

    Within the framework of a generalized Ising model, a one-dimensional magnetic of a finite length with free ends is considered. The correlation length critical exponent ν and kinetic critical exponent z of the magnet is calculated taking into account the next nearest neighbor interactions and the external field. Of special interest are non-equilibrium processes taking place within the critical temperature interval, which are characterized critical exponent y and dynamic critical index z . Due to significant difficulties encountered in the experimental investigations (e.g., measurement of z) , a natural solution to this complex problem would be modeling of those non-eqilibrium processes. This work addresses non-equilibrium processes in one-dimensional magnetics. Using the Monte Carlo method, an equilibrium critical exponent of the correlation length ν and the dynamic critical index z are calculated for a finite-size magnetic.

  6. Magnetic fields around AGNs at large and small scales

    Science.gov (United States)

    Tyul'bashev, S. A.

    2002-06-01

    The dipole structure of the magnetic field on distances ge 1 kpc from an active galactic nucleus is discussed. Two different models of the magnetic field around a supermassive black hole on the scale of the accretion disk are tested. The first model suggests a superstrong field of the order of 1010 Gauss (Kardashev \\cite{Kardashev95}), the other one proposed by Field & Rodgers (\\cite{Field93}) predicts much lower values ( ~ 104 Gauss).

  7. Electronic and magnetic properties of small rhodium clusters

    Energy Technology Data Exchange (ETDEWEB)

    Soon, Yee Yeen; Yoon, Tiem Leong [School of Physics, Universiti Sains Malaysia, 11800 USM, Penang (Malaysia); Lim, Thong Leng [Faculty of Engineering and Technology, Multimedia University, Melaka Campus, 75450 Melaka (Malaysia)

    2015-04-24

    We report a theoretical study of the electronic and magnetic properties of rhodium-atomic clusters. The lowest energy structures at the semi-empirical level of rhodium clusters are first obtained from a novel global-minimum search algorithm, known as PTMBHGA, where Gupta potential is used to describe the atomic interaction among the rhodium atoms. The structures are then re-optimized at the density functional theory (DFT) level with exchange-correlation energy approximated by Perdew-Burke-Ernzerhof generalized gradient approximation. For the purpose of calculating the magnetic moment of a given cluster, we calculate the optimized structure as a function of the spin multiplicity within the DFT framework. The resultant magnetic moments with the lowest energies so obtained allow us to work out the magnetic moment as a function of cluster size. Rhodium atomic clusters are found to display a unique variation in the magnetic moment as the cluster size varies. However, Rh{sub 4} and Rh{sub 6} are found to be nonmagnetic. Electronic structures of the magnetic ground-state structures are also investigated within the DFT framework. The results are compared against those based on different theoretical approaches available in the literature.

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

    Directory of Open Access Journals (Sweden)

    Simona Delle Monache

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

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

    Science.gov (United States)

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

    2013-01-01

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

  10. Foucault imaging and small-angle electron diffraction in controlled external magnetic fields.

    Science.gov (United States)

    Nakajima, Hiroshi; Kotani, Atsuhiro; Harada, Ken; Ishii, Yui; Mori, Shigeo

    2016-12-01

    We report a method for acquiring Foucault images and small-angle electron diffraction patterns in external magnetic fields using a conventional transmission electron microscope without any modification. In the electron optical system that we have constructed, external magnetic fields parallel to the optical axis can be controlled using the objective lens pole piece under weak excitation conditions in the Foucault mode and the diffraction mode. We observe two ferromagnetic perovskite-type manganese oxides, La0.7Sr0.3MnO3 (LSMO) and Nd0.5Sr0.5MnO3, in order to visualize magnetic domains and their magnetic responses to external magnetic fields. In rhombohedral-structured LSMO, pinning of magnetic domain walls at crystallographic twin boundaries was found to have a strong influence on the generation of new magnetic domains in external applied magnetic fields.

  11. Magnetic field diffusion modeling of a small enclosed firing system

    Energy Technology Data Exchange (ETDEWEB)

    Warne, L.K.; Merewether, K.O.

    1996-01-01

    Intense magnetic fields exist in the immediate vicinity of a lightning strike (and near power lines). Conducting barriers increase the rise time (and thus decrease the rise rate) interior to the barrier, but typically do not prevent penetration of the magnetic field, since the lightning current fall time may be larger than the barrier diffusion time. Thus, substantial energy is present in the interior field, although the degradation of rise rate makes it more difficult to couple into electrical circuits. This report assesses the threat posed by the diffusive magnetic field to interior components and wire loops (where voltages are induced). Analytical and numerical bounding analyses are carried out on a pill box shaped conducting barrier to develop estimates for the worst case magnetic field threats inside the system. Worst case induced voltages and energies are estimated and compared with threshold charge voltages and energies on the output capacitor of the system. Variability of these quantities with respect to design parameters are indicated. The interior magnetic field and induced voltage estimates given in this report can be used as excitations for more detailed interior and component models.

  12. Confirmation of Small Dynamical and Stellar Masses for Extreme Emission Line Galaxies at z~2

    CERN Document Server

    Maseda, Michael V; da Cunha, Elisabete; Rix, Hans-Walter; Pacifici, Camilla; Momcheva, Ivelina; Brammer, Gabriel B; Franx, Marijn; van Dokkum, Pieter; Bell, Eric F; Fumagalli, Mattia; Grogin, Norman A; Kocevski, Dale D; Koekemoer, Anton M; Lundgren, Britt F; Marchesini, Danilo; Nelson, Erica J; Patel, Shannon G; Skelton, Rosalind E; Straughn, Amber N; Trump, Jonathan R; Weiner, Benjamin J; Whitaker, Katherine E; Wuyts, Stijn

    2013-01-01

    Spectroscopic observations from the Large Binocular Telescope and the Very Large Telescope reveal kinematically narrow lines (~50 km/s) for a sample of 14 Extreme Emission Line Galaxies (EELGs) at redshifts 1.4 1. The stellar mass formed in this vigorous starburst phase represents a large fraction of the total (dynamical) mass, without a significantly massive underlying population of older stars. The occurrence of such intense events in shallow potentials strongly suggests that supernova-driven winds must be of critical importance in the subsequent evolution of these systems.

  13. Influence of Exposure to Extremely Low Frequency Magnetic Field on Neuroendocrine Cells and Hormones in Stomach of Rats

    OpenAIRE

    Hong, Min Eui; Yoon, Kyu Hyun; Jung, Yoon Yang; Lee, Tae Jin; Park, Eon Sub; Sohn, Uy Dong; Jeong, Ji Hoon

    2011-01-01

    Extremely low frequency magnetic fields (ELF-MF) have the ability to produce a variety of behavioral and physiological changes in animals. The stomach, as the most sensitive part of the neuroendocrine organ of the gastrointestinal tract, is crucial for the initiation of a full stress response against all harmful stress. Thus, the purpose of this study was to examine whether ELF-MF stimuli induce changes in the activity of neuroendocrine cells, considering their involvement in endocrine or par...

  14. Magnetostatic effects on switching in small magnetic tunnel junctions

    Energy Technology Data Exchange (ETDEWEB)

    Bapna, Mukund; Piotrowski, Stephan K.; Oberdick, Samuel D.; Majetich, Sara A., E-mail: sara@cmu.edu [Physics Department, Carnegie Mellon University, Pittsburgh, Pennsylvania 15213 (United States); Li, Mingen; Chien, C.-L. [Department of Physics and Astronomy, Johns Hopkins University, Baltimore, Maryland 21218 (United States)

    2016-01-11

    Perpendicular CoFeB/MgO/CoFeB magnetic tunnel junctions with diameters under 100 nm are investigated by conductive atomic force microscopy. Minor loops of the tunnel magnetoresistance as a function of applied magnetic field reveal the hysteresis of the soft layer and an offset due to the magnetostatic field of the hard layer. Within the hysteretic region, telegraph noise is observed in the tunnel current. Simulations show that in this range, the net magnetic field in the soft layer is spatially inhomogeneous, and that antiparallel to parallel switching tends to start near the edge, while parallel to antiparallel reversal favors nucleation in the interior of the soft layer. As the diameter of the tunnel junction is decreased, the average magnitude of the magnetostatic field increases, but the spatial inhomogeneity across the soft layer is reduced.

  15. Spin magnetic moments from single atoms to small Cr clusters

    Energy Technology Data Exchange (ETDEWEB)

    Boeglin, C.; Decker, R.; Bulou, H.; Scheurer, F.; Chado, I. [IPCMS-GSI - UMR 7504, 67037 Strasbourg Cedex (France); Ohresser, P. [LURE, 91405 Orsay (France); Dhesi, S.S. [ESRF, BP 220, 38043 Grenoble Cedex (France); Present permanent address: Diamond Light Source, Chilton, Didcot OX11 0QX (United Kingdom); Gaudry, E. [LMCP, 4, place Jussieu, 75252 Paris (France); Lazarovits, B. [CCMS, T.U. Vienna, Gumpendorfstr. 1a, 1060 Wien (Austria)

    2005-07-01

    Morphology studies at the first stages of the growth of Cr/Au(111) are reported and compared to the magnetic properties of the nanostructures. We analyze by Scanning Tunneling Microscopy and Low Energy Electron Diffraction the Cr clusters growth between 200 K and 300 K. In the early stages of the growth the morphology of the clusters shows monoatomic high islands located at the kinks of the herringbone reconstructed Au(111) surface. By X-ray Magnetic Circular Dichroism performed on the Cr L{sub 2,3} edges it is shown that the temperature dependent morphology strongly influences the magnetic properties of the Cr clusters. We show that in the sub-monolayer regime Cr clusters are antiferromagnetic and paramagnetic when the size reaches the atomic limit. (copyright 2005 WILEY-VCH Verlag GmbH and Co. KGaA, Weinheim) (orig.)

  16. Paramagnetic alignment of small grains: a novel method for measuring interstellar magnetic fields

    CERN Document Server

    Hoang, Thiem; Martin, P G

    2013-01-01

    We present a novel method to measure the strength of interstellar magnetic fields based on ultraviolet (UV) polarization of starlight, which is in part produced by weakly aligned, small interstellar grains. We begin with calculating degrees of alignment of small (size a~ 0.01 micron) and very small (a ~ 0.001 micron) grains in the interstellar magnetic field by the Davis-Greenstein paramagnetic relaxation and resonance paramagnetic relaxation. We compute the degrees of paramagnetic alignment with the ambient magnetic field B using Langevin equations. In this paper, we take into account various processes essential for the dynamics of small grains, including infrared (IR) emission, electric dipole emission, plasma drag and collisions with ionized species. We find that the alignment of small grains is necessary to reproduce the observed polarization in the UV, although the polarization arising from these small grains is negligible at the optical and IR wavelengths. Based on fitting theoretical models to observed...

  17. Relationship between EUV microflares and small-scale magnetic fields in the quiet Sun

    CERN Document Server

    Jiang, Fayu; Yang, Shuhong

    2015-01-01

    Microflares are small dynamic signatures observed in X-ray and extreme-ultraviolet channels. Because of their impulsive emission enhancements and wide distribution, they are thought to be closely related to coronal heating. By using the high resolution 171 {\\AA} images from the Atmospheric Imaging Assembly and the lines-of-sight magnetograms obtained by the Helioseismic and Magnetic Imager on board the Solar Dynamics Observatory, we trace 10794 microflares in a quiet region near the disk center with a field of view of 960 arcsec $\\times$ 1068 arcsec during 24 hr. The microflares have an occurrence rate of 4.4 $\\times$ 10$^{3}$ hr$^{-1}$ extrapolated over the whole Sun. Their average brightness, size, and lifetime are 1.7 I$_{0}$(of the quiet Sun), 9.6 Mm$^{2}$, and 3.6 min, respectively. There exists a mutual positive correlation between the microflares' brightness, area and lifetime. In general, the microflares distribute uniformly across the solar disk, but form network patterns locally, which are similar t...

  18. Angular Dependence of Lateral and Levitation Forces in Asymmetric Small Magnet/Superconducting Systems

    Institute of Scientific and Technical Information of China (English)

    H. M. Al-Khateeb; M. K. Alqadi; F. Y. Alzoubi; N. Y. Ayoub

    2007-01-01

    The dipole-dipole interaction model is used to calculate the angular dependence of lateral and levitation forces on a small permanent magnet and a cylindrical superconductor in the Meissner state lying laterally offthe symmetric axis of the cylinder. Under the assumption that the lateral displacement of the magnet is small compared with the physical dimensions of the system, we obtain analytical expressions for the lateral and levitation forces as functions of geometrical parameters of the superconductor as well as the height, the lateral displacement and the orientation of magnetic moment of the magnet. The effect of thickness and radius of the superconductor on the levitation force is similar to that for a symmetric magnet/superconducting cylinder system, but within the range of lateral displacement. The splitting in the levitation force increases with the increasing angle of orientation of the magnetic moment of the magnet. For a given lateral displacement of the magnet, the lateral force vanishes when the magnetic moment is perpendicular to the surface of the superconductor and has a maximum value when the moment is parallel to the surface. For a given orientation of the magnetic moment, the lateral force has a linear relationship with the lateral displacement. The stability of the magnet above the superconducting cylinder is discussed in detail.

  19. IS THE SMALL-SCALE MAGNETIC FIELD CORRELATED WITH THE DYNAMO CYCLE?

    Energy Technology Data Exchange (ETDEWEB)

    Karak, Bidya Binay; Brandenburg, Axel, E-mail: bbkarak@nordita.org [Nordita, KTH Royal Institute of Technology and Stockholm University, Roslagstullsbacken 23, SE-10691 Stockholm (Sweden)

    2016-01-01

    The small-scale magnetic field is ubiquitous at the solar surface—even at high latitudes. From observations we know that this field is uncorrelated (or perhaps even weakly anticorrelated) with the global sunspot cycle. Our aim is to explore the origin, and particularly the cycle dependence, of such a phenomenon using three-dimensional dynamo simulations. We adopt a simple model of a turbulent dynamo in a shearing box driven by helically forced turbulence. Depending on the dynamo parameters, large-scale (global) and small-scale (local) dynamos can be excited independently in this model. Based on simulations in different parameter regimes, we find that, when only the large-scale dynamo is operating in the system, the small-scale magnetic field generated through shredding and tangling of the large-scale magnetic field is positively correlated with the global magnetic cycle. However, when both dynamos are operating, the small-scale field is produced from both the small-scale dynamo and the tangling of the large-scale field. In this situation, when the large-scale field is weaker than the equipartition value of the turbulence, the small-scale field is almost uncorrelated with the large-scale magnetic cycle. On the other hand, when the large-scale field is stronger than the equipartition value, we observe an anticorrelation between the small-scale field and the large-scale magnetic cycle. This anticorrelation can be interpreted as a suppression of the small-scale dynamo. Based on our studies we conclude that the observed small-scale magnetic field in the Sun is generated by the combined mechanisms of a small-scale dynamo and tangling of the large-scale field.

  20. Electric and magnetic dipolar response of small dielectric particles: Scattering anisotropy and optical forces

    Directory of Open Access Journals (Sweden)

    R. Gomez-Medina

    2011-09-01

    Full Text Available We predict that real small dielectric particles made of non-magnetic materials present non-conventional scattering properties similar to those previously reported for somewhat hypothetical magnetodielectric particles.

  1. Design of a small centrifugal blood pump with magnetic bearings.

    Science.gov (United States)

    Jahanmir, Said; Hunsberger, Andrew Z; Ren, Zhaohui; Heshmat, Hooshang; Heshmat, Crystal; Tomaszewski, Michael J; Walton, James F

    2009-09-01

    Design of a blood pump with a magnetically levitated rotor requires rigorous evaluation of the magnetic bearing and motor requirements and analysis of rotor dynamics and hydraulic performance with attention to hemolysis and thrombosis potential. Given the desired geometric dimensions, the required operating speed, flow in both the main and wash flow regions, and magnetic bearing performance, one of several design approaches was selected for a new prototype. Based on the estimated operating speed and clearance between the rotor and stator, the motor characteristics and dimensions were estimated. The motor stiffness values were calculated and used along with the hydraulic loading due to the fluid motion to determine the best design for the axial and radial magnetic bearings. Radial and axial stability of the left ventricular assist device prototype was verified using finite element rotor dynamic analysis. The analysis indicated that the rotor could be completely levitated and spun to the desired operating speed with low power loss and no mechanical contact. In vitro experiments with a mock loop test setup were performed to evaluate the performance of the new blood pump prototype.

  2. Complex magnetic susceptibility setup for spectroscopy in the extremely low-frequency range

    NARCIS (Netherlands)

    Kuipers, B.W.M.; Bakelaar, I.A.; Klokkenburg, M.; Erne, B.H.

    2008-01-01

    A sensitive balanced differential transformer was built to measure complex initial parallel magnetic susceptibility spectra in the 0.01–1000 Hz range. The alternating magnetic field can be chosen sufficiently weak that the magnetic structure of the samples is only slightly perturbed and the low freq

  3. Static properties of small Josephson tunnel junctions in a transverse magnetic field

    DEFF Research Database (Denmark)

    Monaco, R.; Aarøe, Morten; Mygind, Jesper;

    2008-01-01

    The magnetic field distribution in the barrier of small planar Josephson tunnel junctions is numerically simulated in the case when an external magnetic field is applied perpendicular to the barrier plane. The simulations allow for heuristic analytical solutions for the Josephson static phase pro...

  4. Quality factor of an electrically small magnetic dipole antenna with magneto-dielectric core

    DEFF Research Database (Denmark)

    Kim, Oleksiy S.; Breinbjerg, Olav

    2010-01-01

    In this work, we investigate the radiation Q of electrically small magnetic dipole antennas with magneto-dielectric core versus the antenna electrical size, permittivity and permeability of the core. The investigation is based on the exact theory for a spherical magnetic dipole antenna...

  5. Small-scale primordial magnetic fields and anisotropies in the cosmic microwave background radiation

    Energy Technology Data Exchange (ETDEWEB)

    Jedamzik, Karsten [Laboratoire de Univers et Particules, UMR5299-CNRS, Université de Montpellier II, F-34095 Montpellier (France); Abel, Tom, E-mail: karsten.jedamzik@um2.fr, E-mail: tabel@slac.stanford.edu [Kavli Institute for Particle Astrophysics and Cosmology, SLAC/Stanford University, 2575 Sand Hill Road, Menlo Park, CA 94025 (United States)

    2013-10-01

    It is shown that small-scale magnetic fields present before recombination induce baryonic density inhomogeneities of appreciable magnitude. The presence of such inhomogeneities changes the ionization history of the Universe, which in turn decreases the angular scale of the Doppler peaks and increases Silk damping by photon diffusion. This unique signature could be used to (dis)prove the existence of primordial magnetic fields of strength as small as B ≅ 10{sup −11} Gauss by cosmic microwave background observations.

  6. The magnetic shear-current effect: generation of large-scale magnetic fields by the small-scale dynamo

    Science.gov (United States)

    Squire, J.; Bhattacharjee, A.

    2016-04-01

    > A novel large-scale dynamo mechanism, the magnetic shear-current effect, is discussed and explored. The effect relies on the interaction of magnetic fluctuations with a mean shear flow, meaning the saturated state of the small-scale dynamo can drive a large-scale dynamo - in some sense the inverse of dynamo quenching. The dynamo is non-helical, with the mean field coefficient zero, and is caused by the interaction between an off-diagonal component of the turbulent resistivity and the stretching of the large-scale field by shear flow. Following up on previous numerical and analytic work, this paper presents further details of the numerical evidence for the effect, as well as an heuristic description of how magnetic fluctuations can interact with shear flow to produce the required electromotive force. The pressure response of the fluid is fundamental to this mechanism, which helps explain why the magnetic effect is stronger than its kinematic cousin, and the basic idea is related to the well-known lack of turbulent resistivity quenching by magnetic fluctuations. As well as being interesting for its applications to general high Reynolds number astrophysical turbulence, where strong small-scale magnetic fluctuations are expected to be prevalent, the magnetic shear-current effect is a likely candidate for large-scale dynamo in the unstratified regions of ionized accretion disks. Evidence for this is discussed, as well as future research directions and the challenges involved with understanding details of the effect in astrophysically relevant regimes.

  7. Inclinations of small quiet-Sun magnetic features based on a new geometric approach

    CERN Document Server

    Jafarzadeh, S; Lagg, A; Rubio, L R Bellot; van Noort, M; Feller, A; Danilovic, S

    2014-01-01

    High levels of horizontal magnetic flux have been reported in the quiet-Sun internetwork, often based on Stokes profile inversions. Here we introduce a new method for deducing the inclination of magnetic elements and use it to test magnetic field inclinations from inversions. We determine accurate positions of a set of small, bright magnetic elements in high spatial resolution images sampling different photospheric heights obtained by the Sunrise balloon-borne solar observatory. Together with estimates of the formation heights of the employed spectral bands, these provide us with the inclinations of the magnetic features. We also compute the magnetic inclination angle of the same magnetic features from the inversion of simultaneously recorded Stokes parameters. Our new, geometric method returns nearly vertical fields (average inclination of around 14 deg with a relatively narrow distribution having a standard deviation of 6 deg). In strong contrast to this, the traditionally used inversions give almost horizo...

  8. The response of small SQUID pickup loops to magnetic fields

    Science.gov (United States)

    Kirtley, John R.; Paulius, Lisa; Rosenberg, Aaron J.; Palmstrom, Johanna C.; Schiessl, Daniel; Jermain, Colin L.; Gibbons, Jonathan; Holland, Connor M.; Fung, Y.-K.-K.; Huber, Martin E.; Ketchen, Mark B.; Ralph, Daniel C.; Gibson, Gerald W., Jr.; Moler, Kathryn A.

    2016-12-01

    In the past, magnetic images acquired using scanning superconducting quantum interference device (SQUID) microscopy have been interpreted using simple models for the sensor point spread function. However, more complicated modeling is needed when the characteristic dimensions of the field sensitive areas in these sensors become comparable to the London penetration depth. In this paper we calculate the response of SQUIDs with deep sub-micron pickup loops to different sources of magnetic fields by solving coupled London’s and Maxwell’s equations using the full sensor geometry. Tests of these calculations using various field sources are in reasonable agreement with experiments. These calculations allow us to more accurately interpret sub-micron spatial resolution data obtained using scanning SQUID microscopy.

  9. Ignition and burn of a small magnetized fuel target

    Energy Technology Data Exchange (ETDEWEB)

    Kirkpatrick, Ronald C. [Los Alamos National Lab. (LANL), Los Alamos, NM (United States)

    2012-06-01

    The crucial step for inertial confinement fusion (ICF) is ignition, which leads to sufficiently high gain to enable design of a power producing system. Thus far, this step has not been demonstrated. Magnetized targets may provide an alternative path to ignition. In addition, the 1-D calculations presented here suggest that this approach may provide the gain and other characteristics needed for a practical fusion reactor.

  10. Off like a shot: scaling of ballistic tongue projection reveals extremely high performance in small chameleons.

    Science.gov (United States)

    Anderson, Christopher V

    2016-01-04

    Stretching elastic tissues and using their recoil to power movement allows organisms to release energy more rapidly than by muscle contraction directly, thus amplifying power output. Chameleons employ such a mechanism to ballistically project their tongue up to two body lengths, achieving power outputs nearly three times greater than those possible via muscle contraction. Additionally, small organisms tend to be capable of greater performance than larger species performing similar movements. To test the hypothesis that small chameleon species outperform larger species during ballistic tongue projection, performance was examined during feeding among 20 chameleon species in nine genera. This revealed that small species project their tongues proportionately further than large species, achieving projection distances of 2.5 body lengths. Furthermore, feedings with peak accelerations of 2,590 m s(-2), or 264 g, and peak power output values of 14,040 W kg(-1) are reported. These values represent the highest accelerations and power outputs reported for any amniote movement, highlighting the previously underestimated performance capability of the family. These findings show that examining movements in smaller animals may expose movements harbouring cryptic power amplification mechanisms and illustrate how varying metabolic demands may help drive morphological evolution.

  11. A magnetic probe equipped with small-tip permanent magnet for sentinel lymph node biopsy

    Science.gov (United States)

    Kaneko, Miki; Ohashi, Kaichi; Chikaki, Shinichi; Kuwahata, Akihiro; Shiozawa, Mikio; Kusakabe, Moriaki; Sekino, Masaki

    2017-05-01

    We previously developed a magnetic probe equipped with a ring-shaped permanent magnet for detecting magnetic nanoparticle tracer accumulating in the sentinel lymph nodes (SLNs). The magnetic probe enables us to identify SLNs objectively, without the risk of radiation exposure, unlike the conventional technique using dye and radioisotope. A technical challenge of the probe is to reduce the tip diameter of magnet to identify smaller SLNs. In this study, we optimized the size of smaller-tip magnet based on numerical analyses using the finite element method and evaluated the expected sensitivity. According to the analysis results, the optimum tip diameter and length of convex-shaped magnet were 16 mm and 12 mm, respectively. The experimental results showed that the sensitivity of the probe with smaller-tip magnet was comparable to the previous one. We successfully developed a smaller tip magnet, maintaining the sensitivity to magnetic nanoparticles. The proposed probe will be capable of identifying the location of SLNs more easily.

  12. Occupational exposure to intermediate frequency and extremely low frequency magnetic fields among personnel working near electronic article surveillance systems.

    Science.gov (United States)

    Roivainen, Päivi; Eskelinen, Tuomo; Jokela, Kari; Juutilainen, Jukka

    2014-05-01

    Cashiers are potentially exposed to intermediate frequency (IF) magnetic fields at their workplaces because of the electronic article surveillance (EAS) systems used in stores to protect merchandise against theft. This study aimed at investigating occupational exposure of cashiers to IF magnetic fields in Finnish stores. Exposure to extremely low frequency (ELF) magnetic fields was also evaluated because cashiers work near various devices operating with 50 Hz electric power. The peak magnetic flux density was measured for IF magnetic fields, and was found to vary from 0.2 to 4 µT at the cashier's seat. ELF magnetic fields from 0.03 to 4.5 µT were found at the cashier's seat. These values are much lower than exposure limits. However, according to the International Commission on Non-Ionizing Radiation Protection (ICNIRP) occupational reference levels for IF magnetic fields (141 µT for the peak field) were exceeded in some cases (maximum 189 µT) for short periods of time when cashiers walked through the EAS gates. As the ICNIRP reference levels do not define any minimum time for exposure, additional investigations are recommended to determine compliance with basic restrictions. Even if the basic restrictions are not exceeded, persons working near EAS devices represent an exceptional group of workers with respect to exposure to electromagnetic fields. This group could serve as a basis for epidemiological studies addressing possible health effects of IF magnetic fields. Compliance with the reference levels for IF fields was evaluated using both broadband measurement of peak fields and the ICNIRP summation rule for multiple frequencies. The latter was generally more conservative, and the difference between the two methods was large (>10-fold) for EAS systems using a 58 kHz signal with complex waveform. This indicates that the ICNIRP multiple frequency rule can be unnecessarily conservative when measuring complex waveforms.

  13. Small amplitude nonlinear electron acoustic solitary waves in weakly magnetized plasma

    Energy Technology Data Exchange (ETDEWEB)

    Dutta, Manjistha; Khan, Manoranjan [Department of Instrumentation Science, Jadavpur University, Kolkata-700 032 (India); Ghosh, Samiran [Department of Applied Mathematics, University of Calcutta, 92, Acharya Prafulla Chandra Road, Kolkata-700 009 (India); Roychoudhury, Rajkumar [Indian Statistical Institute, Kolkata-700 108 (India); Chakrabarti, Nikhil [Saha Institute of Nuclear Physics, 1/AF Bidhannagar Kolkata-700 064 (India)

    2013-01-15

    Nonlinear propagation of electron acoustic waves in homogeneous, dispersive plasma medium with two temperature electron species is studied in presence of externally applied magnetic field. The linear dispersion relation is found to be modified by the externally applied magnetic field. Lagrangian transformation technique is applied to carry out nonlinear analysis. For small amplitude limit, a modified KdV equation is obtained, the modification arising due to presence of magnetic field. For weakly magnetized plasma, the modified KdV equation possesses stable solitary solutions with speed and amplitude increasing temporally. The solutions are valid upto some finite time period beyond which the nonlinear wave tends to wave breaking.

  14. The quasi-magnetic-hysteresis behavior of polydisperse ferrofluids with small coupling constant

    Energy Technology Data Exchange (ETDEWEB)

    Li Jian, E-mail: aizhong@swu.edu.cn [School of Physical Science and Technology, Southwest University, Chongqing 400715 (China); Lin Yueqiang; Liu Xiaodong; Lin Lihua; Zhang Qingmei; Fu Jun; Chen Longlong [School of Physical Science and Technology, Southwest University, Chongqing 400715 (China); Li Decai [School of Mechanical and Control Engineering, Beijing Jiaotong University, Beijing 100044 (China)

    2012-12-15

    The magnetization behaviors of ferrofluids based on {gamma}-Fe{sub 2}O{sub 3}/Ni{sub 2}O{sub 3} composite nanoparticles of size about 11 nm have been investigated. The dipole coupling constant {lambda} of these particles is so small (0.43) that they cannot form aggregates through magnetic interaction alone. Experimental results have shown that for a polydisperse ferrofluid with a particle volume fraction of {phi}{sub V}=2.4%, the magnetization curve exhibits quasi-magnetic-hysteresis behavior, i.e., the demagnetization curve lies above the magnetization curve in a high field. However, for a more dilute {gamma}-Fe{sub 2}O{sub 3}/Ni{sub 2}O{sub 3} ferrofluid with {phi}{sub V}=0.94%, the magnetization curve does not show such behavior. According to the bidisperse model for polydisperse ferrofluids, these magnetization behaviors may be attributed to field-induced effects of self-assembled pre-existing chain-like aggregates. For such pre-existing chain-like aggregates, the orientation of the moments inside the particles is not co-linear, so that during the magnetization and demagnetization processes, their apparent magnetizations at the high-field limit are different. As a consequence, the magnetization curve of the ferrofluid with {phi}{sub V}=2.4% displays quasi-magnetic-hysteresis.

  15. Simulation of turbulent magnetic reconnection in the small-scale solar wind

    Institute of Scientific and Technical Information of China (English)

    2000-01-01

    Some observational examples for the possible occurrence of the turbulent magnetic reconnection in the solar wind are found by analysing Helios spacecraft's high resolution data. The phenomena of turbulent magnetic reconnections in small scale solar wind are simulated by introducing a third order accuracy upwind compact difference scheme to the compressible two_dimensional MHD flow. Numerical results verify that the turbulent magnetic reconnection process could occur in small scale interplanetary solar wind, which is a basic feature characterizing the magnetic reconnection in high_magnetic Reynolds number (RM=2 000-10 000) solar wind. The configurations of the magnetic reconnection could evolve from a single X_line to a multiple X-line reconnection, exhibiting a complex picture of the formation, merging and evolution of magnetic islands, and finally the magnetic reconnection would evolve into a low_energy state. Its life_span of evolution is about one hour order of magnitude. Various magnetic and flow signatures are recorded in the numerical test for different evolution stages and along different crossing paths, which could in principle explain and confirm the observational samples from the Helios spacecraft. These results are helpful for revealing the basic physical processes in the solar wind turbulence.

  16. Modeling the Sun’s Small-scale Global Photospheric Magnetic Field

    Science.gov (United States)

    Meyer, K. A.; Mackay, D. H.

    2016-10-01

    We present a new model for the Sun’s global photospheric magnetic field during a deep minimum of activity, in which no active regions emerge. The emergence and subsequent evolution of small-scale magnetic features across the full solar surface is simulated, subject to the influence of a global supergranular flow pattern. Visually, the resulting simulated magnetograms reproduce the typical structure and scale observed in quiet Sun magnetograms. Quantitatively, the simulation quickly reaches a steady state, resulting in a mean field and flux distribution that are in good agreement with those determined from observations. A potential coronal magnetic field is extrapolated from the simulated full Sun magnetograms to consider the implications of such a quiet photospheric magnetic field on the corona and inner heliosphere. The bulk of the coronal magnetic field closes very low down, in short connections between small-scale features in the simulated magnetic network. Just 0.1% of the photospheric magnetic flux is found to be open at 2.5 R ⊙, around 10-100 times less than that determined for typical Helioseismic and Magnetic Imager synoptic map observations. If such conditions were to exist on the Sun, this would lead to a significantly weaker interplanetary magnetic field than is currently observed, and hence a much higher cosmic ray flux at Earth.

  17. Small ordered magnetic moment in a weak itinerant electron ferromagnet Sc{sub 3}In

    Energy Technology Data Exchange (ETDEWEB)

    Kamishima, K., E-mail: kamisima@fms.saitama-u.ac.jp [Graduate School of Science and Engineering, Saitama University, 255 Shimo-okubo, Saitama 338-8570 (Japan); Note, R. [Institute for Materials Research, Tohoku University, Sendai, Miyagi 980-8577 (Japan); Imakubo, T. [Department of Materials Science and Technology, Nagaoka University of Technology, Nagaoka, Niigata 940-2188 (Japan); Watanabe, K. [Global Research Cluster, Collaboration Promotion Unit, RIKEN, 2-1 Wako, Saitama 351-0198 (Japan); Katori, H.A. [Department of Applied Physics, Tokyo University of Agriculture and Technology, Koganei, Tokyo 184-8588 (Japan); Fujimori, A.; Sakai, M. [Graduate School of Science and Engineering, Saitama University, 255 Shimo-okubo, Saitama 338-8570 (Japan); Kamenev, K.V. [School of Engineering, University of Edinburgh, Erskine Williamson Building, The King’s Buildings, Mayfield Road, Edinburgh EH9 3JZ (United Kingdom)

    2014-03-15

    Highlights: • We performed the first neutron diffraction study of Sc–In alloy. • The ordered magnetic moment in this material is intrinsically tiny. • The resistivity depends on temperature as T{sup 3/2}. • The magnetization depends on magnetic fields as M{sup 5}/μ{sub 0}H in the vicinity of the Curie temperature. • This behavior can be explained by assuming that the total spin fluctuation amplitude is conserved. -- Abstract: We performed neutron diffraction study of Sc–In alloy which indicates that the ordered magnetic moment in this material is intrinsically tiny. This tiny magnetic moment (0.04–0.05 μ{sub B}/Sc) is not caused by the uncompensated antiferromagnetic ordering of large magnetic moments. The temperature dependence of the resistivity is in proportion to T{sup 3/2}, which suggests that this material is naturally close to the quantum critical point where ferromagnetism vanishes. This is consistent with the fact that this material shows ferromagnetism in an extremely narrow range of compositions which is typical of materials exhibiting quantum critical phenomenon. In the vicinity of the Curie temperature the magnetization depends on magnetic fields as M{sup 5}∝μ{sub 0}H. This behavior for itinerant ferromagnets can be explained by assuming that the total spin fluctuation amplitude is conserved.

  18. Seasonal occurrence of extreme events on example of long-term hydrometeorological observations from small catchment

    Science.gov (United States)

    Kaznowska, Ewa; Hejduk, Agnieszka; Hejduk, Leszek

    2014-05-01

    Periodical occurrence of floods and droughts is one of disadvantageous phenomenon of Polish climate. Forecasting of climate change for Poland in first half of the 21th century indicate a probability of more frequent occurrence of droughts, which will have the consequences in water deficits in significant areas of the country. Runoff characteristics are important indicators of water resources. Long-term observations carried out in small catchments are an important source of informations of water regime. The aim of the study was to analyze trends of occurrence floods and droughts in small, agricultural catchment of Zagożdżonka River, which is one of the few in Poland, with long-term records of rainfall and runoff. The catchment is located in central Poland, Mazovian Lowlands, about 100 km south form Warsaw. The area of the catchment till Płachty Stare station is 82 km2 and 23.4 km2 till Czarna station . The data used for statistical analysis of floods and droughts included 50 years (1963-2012) for Płachty Stare gauging station and the period of 22 years (1991-2012) for Czarna station. Based on daily hydrograph, floods and droughts were identified. In most cases the duration of floods and droughts is short (few days). Long-term floods occur in winter season and long-term drought occur in summer and autumn. In Płachty Stare decreased trend was indicated for number of days with flood discharge and increased trend was found for number of days with droughts. In Czarna gauging station opposite trends were found. Acknowledgment The paper has been prepared with financial support by grants NN 305 1445 40, NN 305 3168 40 both funded by National Science Center

  19. 3D magnetic field configuration of small-scale reconnection events in the solar plasma atmosphere

    CERN Document Server

    Shimizu, T

    2015-01-01

    The outer solar atmosphere, i.e., the corona and the chromosphere, is replete with small energy-release events, which are accompanied by transient brightening and jet-like ejections. These events are considered to be magnetic reconnection events in the solar plasma, and their dynamics have been studied using recent advanced observations from the Hinode spacecraft and other observatories in space and on the ground. These events occur at different locations in the solar atmosphere, and vary in their morphology and amount of the released energy. The magnetic field configurations of these reconnection events are inferred based on observations of magnetic fields at the photospheric level. Observations suggest that these magnetic configurations can be classified into two groups. In the first group, two anti-parallel magnetic fields reconnect to each other, yielding a 2D emerging flux configuration. In the second group, helical or twisted magnetic flux tubes are parallel or at a relative angle to each other. Reconne...

  20. Field-tuned quantum tunnelling of the magnetization in small magnetic particles

    NARCIS (Netherlands)

    García-Pablos, D.; García, N.; Raedt, H. De

    1998-01-01

    We present staircase magnetization curves for single-spin models of uniaxial magnets as obtained from the numerically exact solution of the time-dependent Schrödinger equation. Steps are shown to correspond to field-tuned tunnelling between different pairs of nearly degenerate energy levels. The rol

  1. Hazard zoning around electric substations of petrochemical industries by stimulation of extremely low-frequency magnetic fields.

    Science.gov (United States)

    Hosseini, Monireh; Monazzam, Mohammad Reza; Farhang Matin, Laleh; Khosroabadi, Hossein

    2015-05-01

    Electromagnetic fields in recent years have been discussed as one of the occupational hazards at workplaces. Hence, control and assessment of these physical factors is very important to protect and promote the health of employees. The present study was conducted to determine hazard zones based on assessment of extremely low-frequency magnetic fields at electric substations of a petrochemical complex in southern Iran, using the single-axis HI-3604 device. In measurement of electromagnetic fields by the single-axis HI-3604 device, the sensor screen should be oriented in a way to be perpendicular to the field lines. Therefore, in places where power lines are located in different directions, it is required to keep the device towards three axes of x, y, and z. For further precision, the measurements should be repeated along each of the three axes. In this research, magnetic field was measured, for the first time, in three axes of x, y, and z whose resultant value was considered as the value of magnetic field. Measurements were done based on IEEE std 644-1994. Further, the spatial changes of the magnetic field surrounding electric substations were stimulated using MATLAB software. The obtained results indicated that the maximum magnetic flux density was 49.90 μT recorded from boiler substation, while the minimum magnetic flux density of 0.02 μT was measured at the control room of the complex. As the stimulation results suggest, the spaces around incoming panels, transformers, and cables were recognized as hazardous zones of indoor electric substations. Considering the health effects of chronic exposure to magnetic fields, it would be possible to minimize exposure to these contaminants at workplaces by identification of risky zones and observation of protective considerations.

  2. Thin magnetic conductor substrate for placement-immune, electrically-small antennas.

    Energy Technology Data Exchange (ETDEWEB)

    Eubanks, Travis Wayne; McDonald, Jacob J.; Loui, Hung

    2011-09-01

    An antenna is considered to be placement-immune when the antenna operates effectively regardless of where it is placed. By building antennas on magnetic conductor materials, the radiated fields will be positively reinforced in the desired radiation direction instead of being negatively affected by the environment. Although this idea has been discussed thoroughly in theoretical research, the difficulty in building thin magnetic conductor materials necessary for in-phase field reflections prevents this technology from becoming more widespread. This project's purpose is to build and measure an electrically-small antenna on a new type of non-metallic, thin magnetic conductor. This problem has not been previously addressed because non-metallic, thin magnetic conductor materials have not yet been discovered. This work proposed the creation of an artificial magnetic conductor (AMC) with in-phase field reflections without using internal electric conductors, the placement of an electrically-small antenna on this magnetic conductor, and the development of a transmit-receive system that utilizes the substrate and electrically-small antenna. By not using internal electric conductors to create the AMC, the substrate thickness can be minimized. The electrically-small antenna will demonstrate the substrate's ability to make an antenna placement immune, and the transmit-receive system combines both the antenna and the substrate while adding a third layer of system complexity to demonstrate the complete idea.

  3. Primary cutaneous Ewing's sarcoma/primitive neuroectodermal tumor manifesting numerous small and huge ulcerated masses: its complete remission by chemotherapy and magnetic resonance imaging findings

    Energy Technology Data Exchange (ETDEWEB)

    Bahk, Won-Jong [The Catholic University of Korea, Department of Orthopedic Surgery, Uijeongbu St. Mary' s Hospital, Uijeongbu (Korea); Chang, Eun-Deok; Lee, An-Hee [The Catholic University of Korea, Department of Pathology, Uijeongbu St. Mary' s Hospital, Uijeongbu (Korea); Bae, Jung Min; Kim, Jin Woo [The Catholic University of Korea, Department of Dermatology, Uijeongbu St. Mary' s Hospital, Uijeongbu (Korea); Chun, Kyung-Ah [The Catholic University of Korea, Department of Radiology, Uijeongbu St. Mary' s Hospital, Uijeongbu (Korea); Rho, Sang-Young [The Catholic University of Korea, Department of Hemato-oncology, Uijeongbu St. Mary' s Hospital, Uijeongbu (Korea)

    2010-06-15

    Extraskeletal Ewing's sarcoma (ES) and primitive neuroectodermal tumor (PNET) are widely regarded as clinically and histologically identical tumors which consist of small blue round cells. Extraskeletal ESs/PNETs usually occur in the deep soft tissues of the paraspinal region, chest wall, or lower extremities. However, superficially located cases, so-called cutaneous ESs/PNETs, are exceedingly rare, and the vast majority of the reported cases present as a single small mass. We present magnetic resonance imaging (MRI) findings and clinical course of a unique case of primary cutaneous ES/PNET presenting as numerous huge masses with severe ulceration on them. (orig.)

  4. Magnetic field topology and chemical spot distributions in the extreme Ap star HD 75049

    CERN Document Server

    Kochukhov, O; Valenti, J A; Stempels, H C; Snik, F; Rodenhuis, M; Piskunov, N; Makaganiuk, V; Keller, C U; Johns-Krull, C M

    2014-01-01

    Intermediate-mass, magnetic chemically peculiar (Ap) stars provide a unique opportunity to study the topology of stellar magnetic fields in detail and to investigate magnetically driven processes of spot formation. Here we aim to derive the surface magnetic field geometry and chemical abundance distributions for the extraordinary Ap star HD 75049. This object hosts a surface field of ~30 kG, one of the strongest known for any non-degenerate star. We used time-series of high-resolution HARPS intensity and circular polarisation observations. These data were interpreted with the help of magnetic Doppler imaging and model atmospheres incorporating effects of a non-solar chemical composition and a strong magnetic field. We refined the rotational period of HD 75049 to Prot=4.048267+/-0.000036 d. We also derived basic stellar parameters, Teff=10250+/-250 K and logg=4.3+/-0.1. Magnetic Doppler imaging revealed that the field topology of HD 75049 is poloidal and dominated by a dipolar contribution with a peak surface ...

  5. A multicenter reliability study of extremity-magnetic resonance imaging in the longitudinal evaluation of rheumatoid arthritis

    DEFF Research Database (Denmark)

    Conaghan, Philip G; Ejbjerg, Bo; Lassere, Marissa

    2007-01-01

    There are limited data on the reliability of extremity magnetic resonance imaging (E-MRI) in the longitudinal evaluation of rheumatoid arthritis (RA). Our aim was to assess the interreader reliability of the OMERACT RA MRI score in the assessment of change in disease activity and bone erosion...... scores using 0.2 T E-MRI hand and wrist images from 2 timepoints, evaluated by 3 readers at different international centers. The intraclass correlation coefficients and smallest detectable difference results for the change scores were generally good for erosions and synovitis, but were not acceptable...

  6. The effects of exposure to extremely low-frequency magnetic field and amphetamine on the reduced glutathione in the brain.

    Science.gov (United States)

    Jelenković, Ankica; Janać, Branka; Pesić, Vesna; Jovanović, Marina D; Vasiljević, Ivana; Prolić, Zlatko

    2005-06-01

    Continuous exposure to extremely low-frequency magnetic field (ELF-MF, 50 Hz, 0.5 mT) alone and combined with D-amphetamine (1.5 mg/kg) affected the reduced glutathione content in brain regions of rats. Compared to sham-exposed rats, the glutathione content in the forebrain cortex of the ELF-MF-exposed rats decreased (P glutathione content was increased in the brain stem and cerebellum (P glutathione changes observed. The changes are not uniform in the brain regions examined.

  7. M-H loop tracer based on digital signal processing for low frequency characterization of extremely thin magnetic wires

    Energy Technology Data Exchange (ETDEWEB)

    Butta, M.; Ripka, P. [Department of Measurement, Faculty of Electrical Engineering, Czech Technical University in Prague, Prague 16627 (Czech Republic); Infante, G.; Badini-Confalonieri, G. A.; Vazquez, M. [Instituto de Ciencia de Materiales de Madrid (CSIC), Campus de Cantoblanco, Madrid 28049 (Spain)

    2009-08-15

    A high-sensitivity ac hysteresis loop tracer has been developed to measure the low frequency hysteresis loop of soft magnetic materials. It has been applied successfully to characterize straight pieces of amorphous glass-covered microwires with metallic nucleus down to 1.5 {mu}m thick. Based on the electromagnetic induction law, the proposed design is extremely simple and exploits the capabilities of commercially available data acquisition cards together with digital signal processing in order to achieve high-sensitivity without the need of expensive analog equipment.

  8. 3D magnetic field configuration of small-scale reconnection events in the solar plasma atmosphere

    Energy Technology Data Exchange (ETDEWEB)

    Shimizu, T., E-mail: shimizu@solar.isas.jaxa.jp [Institute of Space and Astronautical Science, Japan Aerospace Exploration Agency, 3-1-1 Yoshinodai, Chuo-ku, Sagamihara, Kanagawa 252-5210 (Japan); Department of Earth and Planetary Science, The University of Tokyo, 7-3-1 Hongo, Bunkyo-ku, Tokyo 113-0033 (Japan)

    2015-10-15

    The outer solar atmosphere, i.e., the corona and the chromosphere, is replete with small energy-release events, which are accompanied by transient brightening and jet-like ejections. These events are considered to be magnetic reconnection events in the solar plasma, and their dynamics have been studied using recent advanced observations from the Hinode spacecraft and other observatories in space and on the ground. These events occur at different locations in the solar atmosphere and vary in their morphology and amount of the released energy. The magnetic field configurations of these reconnection events are inferred based on observations of magnetic fields at the photospheric level. Observations suggest that these magnetic configurations can be classified into two groups. In the first group, two anti-parallel magnetic fields reconnect to each other, yielding a 2D emerging flux configuration. In the second group, helical or twisted magnetic flux tubes are parallel or at a relative angle to each other. Reconnection can occur only between anti-parallel components of the magnetic flux tubes and may be referred to as component reconnection. The latter configuration type may be more important for the larger class of small-scale reconnection events. The two types of magnetic configurations can be compared to counter-helicity and co-helicity configurations, respectively, in laboratory plasma collision experiments.

  9. Influence of extremely low frequency magnetic fields on Ca2+ signaling and NMDA receptor functions in rat hippocampus.

    Science.gov (United States)

    Manikonda, Pavan K; Rajendra, P; Devendranath, D; Gunasekaran, B; Channakeshava; Aradhya, R S S; Sashidhar, R B; Subramanyam, C

    2007-02-14

    Extremely low frequency (ELFelectromagnetic fields affect several neuronal activities including memory. Because ELF magnetic fields cause altered Ca(2+) homeostasis in neural tissues, we examined their influence on Ca(2+) signaling enzymes in hippocampus and related them with NMDA receptor functions. Hippocampal regions were obtained from brains of 21-day-old rats that were exposed for 90 days to 50Hz magnetic fields at 50 and 100 microT intensities. In comparison to controls, ELF exposure caused increased intracellular Ca(2+) levels concomitant with increased activities of Ca(2+)-dependent protein kinase C (PKC), cAMP-dependent protein kinase and calcineurin as well as decreased activity of Ca(2+)-calmodulin-dependent protein kinase in hippocampal regions. Simultaneous ligand-binding studies revealed decreased binding to N-methyl-D-aspartic acid (NMDA) receptors. The combined results suggest that perturbed neuronal functions caused by ELF exposure may involve altered Ca(2+) signaling events contributing to aberrant NMDA receptor activities.

  10. Three-dimensional extremely-short optical pulses in carbon nanotube arrays in the presence of an external magnetic field

    Science.gov (United States)

    Zhukov, Alexander V.; Bouffanais, Roland; Belonenko, Mikhail B.; Galkina, Elena N.

    2016-12-01

    In this paper, we study the behavior of three-dimensional extremely-short optical pulses propagating in a system made of carbon nanotubes in the presence of an external magnetic field applied perpendicular both to the nanotube axis and to the direction of propagation of the pulse. The evolution of the electromagnetic field is classically derived on the basis of the Maxwell’s equations. The electronic system of carbon nanotubes is considered in the low-temperature approximation. Our analysis reveals the novel and unique ability of controlling the shape of propagating short optical pulses by tuning the intensity of the applied magnetic field. This effect paves the way for the possible development of innovative applications in optoelectronics.

  11. Fast synthesis and bioconjugation of (68) Ga core-doped extremely small iron oxide nanoparticles for PET/MR imaging.

    Science.gov (United States)

    Pellico, Juan; Ruiz-Cabello, Jesús; Saiz-Alía, Marina; Del Rosario, Gilberto; Caja, Sergio; Montoya, María; Fernández de Manuel, Laura; Morales, M Puerto; Gutiérrez, Lucia; Galiana, Beatriz; Enríquez, Jose A; Herranz, Fernando

    2016-05-01

    Combination of complementary imaging techniques, like hybrid PET/MRI, allows protocols to be developed that exploit the best features of both. In order to get the best of these combinations the use of dual probes is highly desirable. On this sense the combination of biocompatible iron oxide nanoparticles and 68Ga isotope is a powerful development for the new generation of hybrid systems and multimodality approaches. Our objective was the synthesis and application of a chelator-free 68Ga-iron oxide nanotracer with improved stability, radiolabeling yield and in vivo performance in dual PET/MRI. We carried out the core doping of iron oxide nanoparticles, without the use of any chelator, by a microwave-driven protocol. The synthesis allowed the production of extremely small (2.5 nm) 68Ga core-doped iron oxide nanoparticles. The microwave approach allowed an extremely fast synthesis with a 90% radiolabeling yield and T1 contrast in MRI. With the same microwave approach the nano-radiotracer was functionalized in a fast and efficient way. We finally evaluated these dual targeting nanoparticles in an angiogenesis murine model by PET/MR imaging. Copyright © 2016 John Wiley & Sons, Ltd. Copyright © 2016 John Wiley & Sons, Ltd.

  12. State-of-art methodology of marine natural products chemistry: structure determination with extremely small sample amounts.

    Science.gov (United States)

    Murata, M; Oishi, T; Yoshida, M

    2006-01-01

    Structure elucidation studies on natural products are reviewed emphasizing extremely small sample amounts. Previous studies on insect pheromones, periplanones, and bean-originating kairomones, glycinoeclepins, are described briefly. Recent examples are selected from marine natural products such as ciguatoxin, dolastatin-3, and aurisides. A more detailed description is given of a sperm-activating and attracting factor (SAAF), which may be the smallest sample amount used in the structure elucidation of novel non-peptidic natural products. SAAF was isolated from the eggs of the ascidian, Ciona intestinalis, and its structure was deduced with only approximately 4 microg (6 nmol) of sample. Based upon the proposed structure, two epimers were synthesized from chenodeoxycholic acid in 17 steps, leading to the identification of SAAF as a novel sterol sulfate.

  13. Temporal changes in allele frequencies in a small marble trout Salmo marmoratus population threatened by extreme flood events.

    Science.gov (United States)

    Pujolar, J M; Vincenzi, S; Zane, L; Crivelli, A J

    2016-03-01

    The effect of extreme floods on the genetic composition of marble trout Salmo marmoratus living in Lipovscek, a tributary of the Soca River in Slovenia, which has been affected by multiple destructive flood events for centuries was investigated. By monitoring genetic variability during the period 2004-2011, apparent signatures of genetic erosion including a decline in observed and expected heterozygosities and allelic richness were observed. Contemporary effective population size was estimated between 11 and 55 individuals, which is congruent with census data. The data suggest asymmetric gene flow between the two sections of the river. The existence of substantial downstream migration (15-19%) was confirmed by paternity analysis. A small (1-3%) upstream migration was also suggested, which was confirmed by tagging data. Overall, low genetic diversity has not prevented the survival of the Lipovscek population, which might be a common feature of salmonid freshwater populations.

  14. Multiwavelength Observations of Small-Scale Reconnection Events triggered by Magnetic Flux Emergence in the Solar Atmosphere

    CERN Document Server

    Guglielmino, S L; Zuccarello, F; Aulanier, G; Domínguez, S Vargas; Kamio, S

    2010-01-01

    The interaction between emerging magnetic flux and the pre-existing ambient field has become a "hot" topic for both numerical simulations and high-resolution observations of the solar atmosphere. The appearance of brightenings and surges during episodes of flux emergence is believed to be a signature of magnetic reconnection processes. We present an analysis of a small-scale flux emergence event in NOAA 10971, observed simultaneously with the Swedish 1-m Solar Telescope on La Palma and the \\emph{Hinode} satellite during a joint campaign in September 2007. Extremely high-resolution G-band, H$\\alpha$, and \\ion{Ca}{2} H filtergrams, \\ion{Fe}{1} and \\ion{Na}{1} magnetograms, EUV raster scans, and X-ray images show that the emerging region was associated with chromospheric, transition region and coronal brightenings, as well as with chromospheric surges. We suggest that these features were caused by magnetic reconnection at low altitude in the atmosphere. To support this idea, we perform potential and linear force...

  15. Measurement of interaction force between small distances sandwiched with magnetic fluid under magnetic field

    Energy Technology Data Exchange (ETDEWEB)

    Miyazaki, T.; Shibayama, A.; Sato, T.; Fujita, T. E-mail: fujita@ipc.akita-u.ac.jp

    2002-11-01

    In this contribution, the interactive force measurement between 10 nm distance under magnetic field is carried out. Previous measurement of the interactive force is reported by Israelachivili et al. However, its measurement under magnetic field has not been performed. The methodology described in this paper is easier as the distance between two surfaces is not measured optically but dynamically. Therefore, it is different from the previous reported studies. Based on the results of the measurement of the interactive force, the diameter of the particle suspended in a solution under magnetic field is also estimated. Moreover, it may be predictable how the clusters have been formed. The method described will be very useful for new productions based on magnetic fluid.

  16. Updating magnetic resonance imaging of small bowel: Imaging protocols and clinical indications

    Institute of Scientific and Technical Information of China (English)

    Jiong Zhu; Jian-Rong Xu; Hong-Xia Gong; Yan Zhou

    2008-01-01

    High soft tissue contrast resolution,acquisition of multi-planar images and the possibility to obtain functional information make magnetic resonance an interesting imaging technique to evaluate the small bowel disease.The absence of ionizing radiation is an important feature of magnetic resonance imaging (MRI) examinations because inflammatory diseases such as Crohn's disease (CD) are studied most frequently,which are prevalent among children and young adults.MRI,using modern equipment and a rigorous technical approach,can offer detailed morphologic information and functional data on the small bowel.This article discusses the MRI protocols for small bowel and the MR imaging findings of small bowel diseases,such as CD and small bowel neoplasms.

  17. Statistical evolution of quiet-Sun small scale magnetic features using Sunrise observations

    CERN Document Server

    Anusha, L S; Hirzberger, Johann; Feller, Alex

    2016-01-01

    The evolution of small magnetic features in quiet regions of the Sun provides a unique window to probing solar magneto-convection. Here we analyze small scale magnetic features in the quiet Sun, using the high resolution, seeing-free observations from the Sunrise balloon borne solar observatory. Our aim is to understand the contribution of different physical processes, such as splitting, merging, emergence and cancellation of magnetic fields to the rearrangement, addition and removal of magnetic flux in the photosphere. We employ a statistical approach for the analysis and the evolution studies are carried out using a feature tracking technique. In this paper we provide a detailed description of the feature tracking algorithm that we have newly developed and we present the results of a statistical study of several physical quantities. The results on the fractions of the flux in the emergence, appearance, splitting, merging, disappearance and cancellation qualitatively agrees with other recent studies. To summ...

  18. Clusters of small eruptive flares produced by magnetic reconnection in the sun

    CERN Document Server

    Archontis, V

    2015-01-01

    We report on the formation of small solar flares produced by patchy magnetic reconnection between interacting magnetic loops. A three-dimensional (3D) magnetohydrodynamic (MHD) numerical experiment was performed, where a uniform magnetic flux sheet was injected into a fully developed convective layer. The gradual emergence of the field into the solar atmosphere results in a network of magnetic loops, which interact dynamically forming current layers at their interfaces. The formation and ejection of plasmoids out of the current layers leads to patchy reconnection and the spontaneous formation of several small (size ? 1-2Mm) flares. We find that these flares are short-lived (30 s - 3 min) bursts of energy in the range O(10^25 - 10^27) ergs, which is basically the nanoflare-microflare range. Their persistent formation and co-operative action and evolution leads to recurrent emission of fast EUV/X-ray jets and considerable plasma heating in the active corona.

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

    Directory of Open Access Journals (Sweden)

    Elżbieta Ciejka

    2014-10-01

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

  20. Effect of extremely weak pulsed magnetic field type Bemer 3000 on ratings of perceived exertion

    Directory of Open Access Journals (Sweden)

    D Gazurek

    2008-06-01

    Full Text Available The aim of this study was to examine whether is an influence of the exposition on different inductions of magnetic fields on rating of perceived exertion during 10 min long standardised physical cycloergometer exercise. The investigation was performed in 40 healthy, non-smoking, fit men, mean age 202. The participants were randomly attributed to 4 groups, each including 10 subjects. The first one (group E18 consisted of subjects exposed to the magnetic field with the intensity of 18 μT, the second one (group E64 exposed to the magnetic field with the intensity of 64 μT. Two control groups were formed to accompany these exposed to the magnetic field. In these placebo groups (S-T subjects were not exposed to the magnetic field (so called false therapy, „sham treatment”. The study consisted of 4 steps: pilot study, the first endurance test, exposure to the magnetic field, the second endurance test. The aim of the pilot study was to define subjective feelings of the participant during the effort, his reaction to the effort and also practical familiarization with the character and rules of the endurance test and Borg scale interpretation during 10 min of endurance cycloergometer test. The first endurance test was performed two days after the pilot study with the same rules and its goal was to measure the level of tiredness according to the Borg scale during 10 min long standardised physical effort. The second endurance test was performed according to the same rules as the first one and its goal was to analyse the effect of 20 exposures to the magnetic field with the intensity of 18 and 64 μT repeated daily on the perception of tiredness increase as expressed in the Borg scale when performing 10 min long standardised physical effort. In subjects exposed to 18 μT magnetic field neither changes in the perception of fatigue nor changes in the heart rate at particular levels of the Borg scale have been observed. When compared with both control

  1. Magnetic resonance imaging of peripheral nerve tumours in the upper extremity

    DEFF Research Database (Denmark)

    Nilsson, Jessica; Sandberg, Kristina; Søe Nielsen, Niels;

    2009-01-01

    extremity. Medical records of 19 patients (20 MRI examinations) with 29 histopathologically verified benign nerve tumours were examined retrospectively. In 12/20 cases MRI suggested a correct diagnosis of the type of nerve tumour. An additional 3/20 cases had an uncertain diagnosis, but nerve relations...

  2. Monte Carlo simulation of magnetization switching in a Heisenberg model for small ferromagnetic particles

    OpenAIRE

    Hinzke, Denise; Nowak, Ulrich

    1999-01-01

    Using Monte Carlo methods we investigate the thermally activated magnetization switching of small ferromagnetic particles driven by an external magnetic field. For low uniaxial anisotropy one expects that the spins rotate coherently while for sufficiently large anisotropy the reversal should be due to nucleation. The latter case has been investigated extensively by Monte Carlo simulation of corresponding Ising models. In order to study the crossover from coherent rotation to nucleation we use...

  3. Prenatal ultrasound and magnetic resonance imaging depiction of a small sublingual ranula.

    Science.gov (United States)

    Tamaru, Shunsuke; Kikuchi, Akihiko; Ono, Kyoko; Kita, Mariko; Horikoshi, Tsuguhiro; Takagi, Kimiyo

    2010-01-01

    Prenatal diagnosis of a congenital ranula has rarely been reported. We describe the case of a small ranula depicted on prenatal sonogram and magnetic resonance imaging, in which we could confirm the intact airway. Although the size of the ranula noted in our fetus was the smallest among the cases reported in the English literature, both of these imaging modalities clearly presented typical diagnostic features present on both ultrasound and magnetic resonance imaging.

  4. A ten-year review of lower extremity burns in diabetics: small burns that lead to major problems.

    Science.gov (United States)

    Barsun, Alura; Sen, Soman; Palmieri, Tina L; Greenhalgh, David G

    2013-01-01

    Diabetes mellitus with its resulting neurovascular changes may lead to an increased risk of burns and impaired wound healing. The purpose of this article is to review 10 years of experience with foot and lower leg burns in patients with diabetes at a single adult burn center. Patients with lower extremity burns and diabetes mellitus, between May 1999 and December 2009, were identified in the Trauma Registry of the American College of Surgeons database, and their charts were reviewed for data related to their outcomes. Sixty-eight diabetic patients, 87% male, with a mean age of 54 years, sustained foot or lower extremity burns with 37 having burns resulting from insensate feet. The pathogenesis included walking on a hot or very cold surface (8), soaking feet in hot water (22), warming feet on or near something hot such as a heater (13), or spilling hot water (7). The majority of patients were taking insulin (59.6%) or oral hyperglycemic medications (34.6%). Blood sugar levels were not well controlled (mean glucose, 215.8 mg/dl; mean hemoglobin A1c, 9.08%). Renal disease was common with admission serum blood urea nitrogen (27.5 mg/dl) and creatinine (2.21 mg/dl), and 13 were on dialysis preinjury. Cardiovascular problems were common with 39 (57%) having hypertension or cardiac disease, 3 having peripheral vascular disease, and 9, previous amputations. The mean burn size was 4.2% TBSA (range, 0.5-15%) with 57% being full thickness. Despite the small burn, the mean length of stay was 15.2 days (range, 1-95), with 5.65 days per 1% TBSA. Inability to heal these wounds was evident in 19 patients requiring readmission (one required 10 operative procedures). At least one patient sustained more than one burn. There were 62 complications with 30 episodes of infection (cellulitis, 28; osteomyelitis, 4; deep plantar infections, 2; ruptured Achilles tendon, 1) and 3 deaths. Eleven patients needed amputations (7 below-knee amputations, 4 transmetatarsal amputations, and 20 toe

  5. Recent progresses in the simulation of small-scale magnetic fields

    CERN Document Server

    Steiner, Oskar

    2007-01-01

    New high-resolution observations reveal that small-scale magnetic flux concentrations have a delicate substructure on a spatial scale of 0.1''. Its basic structure can be interpreted in terms of a magnetic flux sheet or tube that vertically extends through the ambient weak-field or field-free atmosphere with which it is in mechanical equilibrium. A more refined interpretation comes from new three-dimensional magnetohydrodynamic simulations that are capable of reproducing the corrugated shape of magnetic flux concentrations and their signature in the visible continuum. Furthermore it is shown that the characteristic asymmetric shape of the contrast profile of facular granules is an effect of radiative transfer across the rarefied atmosphere of the magnetic flux concentration. I also discuss three-dimensional radiation magnetohydrodynamic simulations of the integral layers from the top of the convection zone to the mid-chromosphere. They show a highly dynamic chromospheric magnetic field, marked by rapidly movi...

  6. Retrospective comparison of Computed Tomography Enterography and Magnetic Resonance Enterography in diagnosing small intestine disease.

    Science.gov (United States)

    Pei-You, Gong; Jun-Xia, Li; Feng-Li, Liu; Liang-Ming, Zhang; Hai-Zhu, Xie; Yan-Bin, Sui

    2015-07-01

    To compare the efficacy of computed tomography enterography and magnetic resonance enterography in diagnosing small intestinal diseases. The retrospective study comparing computed tomography enterography and magnetic resonance enterography for diagnosing diseases related to small intestine was conducted at Department of Radiology, Yantai Yuhuangding Hospital, Shandong, China, from July 2012 to February 2014. The efficacy of computed tomography enterography and magnetic resonance enterography results were evaluated for randomly-selected cases to compare the location and characteristics of small intestinal diseases together with small bowel endoscopy and clinical pathology observations. Of the 30 patients in the study, 19(63.3%) were males and 11 (36.7%) were females with an overall mean age of 33.6±19.2 years (range: 24-67 years). the clinical diagnostic accuracy of computed tomography enterography and magnetic resonance enterography was 24(80%) and 21(70%) cases respectively (p>0.05). Computed tomography enterography and magnetic resonance enterography are two techniques that complement each other for diagnostic purposes.

  7. Assessing the Impact of Small-Scale Magnetic Morphology on Solar Variability

    Science.gov (United States)

    Peck, Courtney; Rast, Mark; Criscuoli, Serena

    2017-08-01

    Spectral solar irradiance (SSI), the radiant energy flux per wavelength of the Sun received at Earth, is an important driver of chemical reactions in the Earth’s atmosphere. Accurate measurements of SSI are therefore necessary as an input for global climate models. While models and observations of the spectrally-integrated total solar irradiance (TSI) variations agree within ˜ 95%, they can disagree on the sign and magnitude of the SSI variations. In this work, we examine the contribution of currently-unresolved small-scale magnetic structures to SSI variations in the photosphere. We examine the emergent spectra of two atmospheres with differing imposed-field conditions — one with a small-scale dynamo and the other with a predominantly vertical magnetic field — with similar mean field strengths at wavelengths spanning from visible to infrared. Comparing the radiative output at various viewing angles of pixels of equal vertical magnetic field strength between the two simulations, we find that the small-scale dynamo simulations produce higher radiative output than those in the predominantly vertical field simulation. This implies that the radiative output of a small magnetic structure depends on the magnetic morphology of the environment in which it is embedded, which is currently not included in SSI models. We deduce the effect on inferred irradiance by comparing the disk-integrated irradiance of these two atmospheres with standard 1D model atmospheres used in SSI modeling.

  8. Magnetic properties of iron adatoms and small iron clusters on Ag(1 0 0)

    Science.gov (United States)

    Lazarovits, B.; Szunyogh, L.; Weinberger, P.

    2002-02-01

    A Green's function embedding technique based on the fully relativistic spin-polarized Screened Korringa-Kohn-Rostoker method is used to calculate the electronic and magnetic properties of magnetic nanostructures. Strongly enhanced spin and orbital moments are obtained for an Fe adatom and for small clusters of Fe on a Ag(1 0 0) surface. As a consequence, for an Fe adatom a magnetic anisotropy energy is found that is about 10 times larger than for an Fe monolayer. Furthermore, the exchange coupling energy between two Fe adatoms is calculated in terms of the force theorem, showing a very rapid decay with increasing distance.

  9. Nonlinear dynamics of magnetic islands imbedded in small-scale turbulence.

    Science.gov (United States)

    Muraglia, M; Agullo, O; Benkadda, S; Garbet, X; Beyer, P; Sen, A

    2009-10-02

    The nonlinear dynamics of magnetic tearing islands imbedded in a pressure gradient driven turbulence is investigated numerically in a reduced magnetohydrodynamic model. The study reveals regimes where the linear and nonlinear phases of the tearing instability are controlled by the properties of the pressure gradient. In these regimes, the interplay between the pressure and the magnetic flux determines the dynamics of the saturated state. A secondary instability can occur and strongly modify the magnetic island dynamics by triggering a poloidal rotation. It is shown that the complex nonlinear interaction between the islands and turbulence is nonlocal and involves small scales.

  10. Stable oscillation in spin torque oscillator excited by a small in-plane magnetic field

    Energy Technology Data Exchange (ETDEWEB)

    Taniguchi, Tomohiro; Tsunegi, Sumito; Kubota, Hitoshi [National Institute of Advanced Industrial Science and Technology (AIST), Spintronics Research Center, Tsukuba 305-8568 (Japan); Ito, Takahiro; Utsumi, Yasuhiro [Faculty of Engineering, Mie University, Tsu, Mie 514-8507 (Japan)

    2015-08-07

    Theoretical conditions to excite self-oscillation in a spin torque oscillator consisting of a perpendicularly magnetized free layer and an in-plane magnetized pinned layer are investigated by analytically solving the Landau-Lifshitz-Gilbert equation. The analytical relation between the current and oscillation frequency is derived. It is found that a large amplitude oscillation can be excited by applying a small field pointing to the direction anti-parallel to the magnetization of the pinned layer. The validity of the analytical results is confirmed by comparing with numerical simulation, showing good agreement especially in a low current region.

  11. Nonlinear Dynamics of Magnetic Islands Imbedded in Small-Scale Turbulence

    CERN Document Server

    Muraglia, Magali; Benkadda, Sadruddin; Garbet, Xavier; Beyer, P; Sen, Abhijit; 10.1103/PhysRevLett.103.145001

    2011-01-01

    The nonlinear dynamics of magnetic tearing islands imbedded in a pressure gradient driven turbulence is investigated numerically in a reduced magnetohydrodynamic model. The study reveals regimes where the linear and nonlinear phases of the tearing instability are controlled by the properties of the pressure gradient. In these regimes, the interplay between the pressure and the magnetic flux determines the dynamics of the saturated state. A secondary instability can occur and strongly modify the magnetic island dynamics by triggering a poloidal rotation. It is shown that the complex nonlinear interaction between the islands and turbulence is nonlocal and involves small scales.

  12. Diffusion and radiation in magnetized collisionless plasmas with small-scale Whistler turbulence

    Science.gov (United States)

    Keenan, Brett D.; Medvedev, Mikhail V.

    2016-04-01

    > Magnetized high-energy-density plasmas can often have strong electromagnetic fluctuations whose correlation scale is smaller than the electron Larmor radius. Radiation from the electrons in such plasmas - which markedly differs from both synchrotron and cyclotron radiation - is tightly related to their energy and pitch-angle diffusion. In this paper, we present a comprehensive theoretical and numerical study of particle transport in cold, `small-scale' Whistler-mode turbulence and its relation to the spectra of radiation simultaneously produced by these particles. We emphasize that this relation is a superb diagnostic tool of laboratory, astrophysical, interplanetary and solar plasmas with a mean magnetic field and strong small-scale turbulence.

  13. A small scale magnetically levitated train for project-based laboratory education

    Directory of Open Access Journals (Sweden)

    Glehn Gregor

    2015-12-01

    Full Text Available The drive train of a small scale magnetically levitated train reveals the principles of a mechatronic system and offers challenges related to design, construction and control. Therefore, it is used at the Institute of electrical Machines (IEM of the RWTH Aachen University as a demonstrator for engineering solutions. Instead of being a part of a static predefined student laboratory, the small scale magnetically levitated train is part of dynamic individual student projects. This approach provides the advantage that the students are directly involved in the engineering process and gain motivation out of their personal ideas becoming reality.

  14. [Magnetic resonance imaging (MRI) in the diagnosis of recurrences of ovarian cancer in the small pelvis].

    Science.gov (United States)

    Bulanova, I M; Bulanova, T V; Burenchev, D V

    2005-01-01

    The paper provides the results of small pelvic magnetic resonance tomography (MRI) in 62 patients with ovarian cancer after primary special treatment. Out of them 50 patients were found to have recurrences and metastases of the underlying disease, 12 patients had clinical remission. The study yielded MR signs and MR semiotics of recurrences of ovarian cancer in the small pelvis. The capacities of MRI with low and high intensities of a magnetic field were comparatively studied in the diagnosis of recurrences and metastases of ovarian cancer.

  15. Electromagnet configurations for extreme attitude testing in magnetic suspension and balance systems

    Science.gov (United States)

    Britcher, C. P.

    1980-01-01

    The inclusion of adequate versatility into the electromagnet array configuration requires sizing the electromagnets to satisfy particular absolute force and moment requirements. Magnetic performance of a permanent magnet model core, air cored electromagnet may easily and reliably be computed by using the FORCE program which calculates model forces and moments via representations of the model as an assembly of dipoles and the electromagnets as an assembly of line currents. Some aspects of the performance of an ellipsoidal iron cored model may be inferred from the above under certain circumstances.

  16. Synthesis and characterization of extremely small gold nanoshells, and comparison of their photothermal conversion capacity with gold nanorods

    Science.gov (United States)

    Durán-Meza, A. L.; Moreno-Gutiérrez, D. S.; Ruiz-Robles, J. F.; Bañuelos-Frías, A.; Segovia-González, X. F.; Longoria-Hernández, A. M.; Gomez, E.; Ruiz-García, J.

    2016-05-01

    The current methods for preparing gold nanoshells (AuNSs) produce shells with a diameter of approximately 40 nm or larger, with a relatively large polydispersity. However, AuNSs with smaller diameters and more monodispersity are better suited for biomedical applications. In this work, we present a modified method for the preparation of AuNSs, based on the use of sacrificial silver nanoparticles (AgNPs). We customized the Lee-Meisel method to prepare small and monodisperse AgNPs that were used as sacrificial nanoparticles to prepare extremely small monodispersed AuNSs with an average diameter from 17 to 25 +/- 4 nm. We found that these AuNSs are faceted, and that the oxidized silver likely dissolves out of the nanoparticles through some of the facets on the AuNSs. This leads to a silver oxide plug on the surface of the AuNSs, which has not been reported before. The smaller AuNSs, prepared under the best conditions, absorb in the near infrared region (NIR) that is appropriate for applications, such as photothermal therapy or medical imaging. The AuNSs showed absorption peaks in the NIR similar to those of gold nanorods (AuNRs) but with better photothermal capacity. In addition, because of their negative charge, these AuNSs are more biocompatible than the positively charged AuNRs. The synthesis of small, monodisperse, stable and biocompatible nanoparticles, like the ones presented in this work, is of prime importance in biomedical applications.The current methods for preparing gold nanoshells (AuNSs) produce shells with a diameter of approximately 40 nm or larger, with a relatively large polydispersity. However, AuNSs with smaller diameters and more monodispersity are better suited for biomedical applications. In this work, we present a modified method for the preparation of AuNSs, based on the use of sacrificial silver nanoparticles (AgNPs). We customized the Lee-Meisel method to prepare small and monodisperse AgNPs that were used as sacrificial nanoparticles to

  17. Extremely large bandwidth and ultralow-dispersion slow light in photonic crystal waveguides with magnetically controllability

    DEFF Research Database (Denmark)

    Pu, Shengli; Wang, Haotian; Wang, Ning;

    2013-01-01

    A line-defect waveguide within a two-dimensional magnetic-fluid-based photonic crystal with 45o-rotated square lattice is presented to have excellent slow light properties. The bandwidth centered at $$ \\lambda_{0} $$ = 1,550 nm of our designed W1 waveguide is around 66 nm, which is very large tha...

  18. Cosmic-Ray Small-scale Anisotropies and Local Turbulent Magnetic Fields

    Science.gov (United States)

    López-Barquero, V.; Farber, R.; Xu, S.; Desiati, P.; Lazarian, A.

    2016-10-01

    Cosmic-ray anisotropy has been observed in a wide energy range and at different angular scales by a variety of experiments over the past decade. However, no comprehensive or satisfactory explanation has been put forth to date. The arrival distribution of cosmic rays at Earth is the convolution of the distribution of their sources and of the effects of geometry and properties of the magnetic field through which particles propagate. It is generally believed that the anisotropy topology at the largest angular scale is adiabatically shaped by diffusion in the structured interstellar magnetic field. On the contrary, the medium- and small-scale angular structure could be an effect of nondiffusive propagation of cosmic rays in perturbed magnetic fields. In particular, a possible explanation for the observed small-scale anisotropy observed at the TeV energy scale may be the effect of particle propagation in turbulent magnetized plasmas. We perform numerical integration of test particle trajectories in low-β compressible magnetohydrodynamic turbulence to study how the cosmic rays’ arrival direction distribution is perturbed when they stream along the local turbulent magnetic field. We utilize Liouville’s theorem for obtaining the anisotropy at Earth and provide the theoretical framework for the application of the theorem in the specific case of cosmic-ray arrival distribution. In this work, we discuss the effects on the anisotropy arising from propagation in this inhomogeneous and turbulent interstellar magnetic field.

  19. Lower Bound for the Radiation $Q$ of Electrically Small Magnetic Dipole Antennas With Solid Magnetodielectric Core

    DEFF Research Database (Denmark)

    Kim, Oleksiy S.; Breinbjerg, Olav

    2011-01-01

    A new lower bound for the radiation $Q$ of electrically small spherical magnetic dipole antennas with solid magnetodielectric core is derived in closed form using the exact theory. The new bound approaches the Chu lower bound from above as the antenna electrical size decreases. For $ka, the new...

  20. Small-angle neutron-scattering studies of the magnetic phase diagram of MnSi

    DEFF Research Database (Denmark)

    Harris, P.; Lebech, B.; Hae Seop Shim;

    1995-01-01

    The antiferromagnetic order of MnSi has been studied as function of temperature and applied magnetic field using small-angle neutron scattering. The results were analyzed using the three-dimensional resolution function and the scattering cross-section to model the diffraction data. Physical param...

  1. Two Rare Magnetic Cataclysmic Variables with Extreme Cyclotron Features Identified in the Sloan Digital Sky Survey

    CERN Document Server

    Szkody, P; Schmidt, G; Hall, P B; Margon, B; Miceli, A; Subba-Rao, M; Frith, W J; Harris, H; Szkody, Paula; Anderson, Scott F.; Schmidt, Gary; Hall, Patrick B.; Margon, Bruce; Miceli, Antonino; Rao, Mark Subba; Frith, James; Harris, Hugh

    2003-01-01

    Two newly identified magnetic cataclysmic variables discovered in the Sloan Digital Sky Survey (SDSS), SDSSJ155331.12+551614.5 and SDSSJ132411.57+032050.5, have spectra showing highly prominent, narrow, strongly polarized cyclotron humps with amplitudes that vary on orbital periods of 4.39 and 2.6 hrs, respectively. In the former, the spacing of the humps indicates the 3rd and 4th harmonics in a magnetic field of ~60 MG. The narrowness of the cyclotron features and the lack of strong emission lines imply very low temperature plasmas and very low accretion rates, so that the accreting area is heated by particle collisions rather than accretion shocks. The detection of rare systems like these exemplifies the ability of the SDSS to find the lowest accretion rate close binaries.

  2. Effects of extremely low frequency magnetic fields on gap junctional intercellular communication and its mechanism

    Institute of Scientific and Technical Information of China (English)

    2002-01-01

    The study on biological effect of electromagnetic fields has been paid close attention in recent years. Gap junctional intercellular communication (GJIC) plays an important role in the maintenance of cell proliferation and differentiation, and in the multistage process of carcinogenesis. A series of researches showed that xtremely low frequency (ELF) magnetic fields not only enhance the inhibition of GJIC induced by 12-O-tetradecanoylphorbol-13-acetate, but also inhibit GJIC directly when the intensity is equal to or more than 0.4  mT, and that the mechanisms of GJIC inhibition by ELF magnetic fields are due to hyperphosphorylation of connexin 43, which is mediated by protein kinase C-activated signal transduction, and the internalization of connexin 43 from plasma membrane to cytoplasm.

  3. Levitation force of small clearance superconductor-magnet system under non-coaxial condition

    Science.gov (United States)

    Xu, Jimin; Jin, Yingze; Yuan, Xiaoyang; Miao, Xusheng

    2017-03-01

    A novel superconducting tilting-pad bearing was proposed for the advanced research of reusable liquid hydrogen turbopump in liquid rocket. The bearing is a combination of superconducting magnetic bearing and hydrodynamic fluid-film bearing. Since the viscosity of cryogenic fuel to activate superconducting state and form hydrodynamic fluid-film is very low, bearing clearance will be very small. This study focuses on the investigation of superconducting levitation force in this kind of small clearance superconductor-magnet system. Based on Bean critical state model and three-dimensional finite element method, an analysis method is presented to obtain the levitation force under such situation. Since the complicated operational conditions and structural arrangement for application in liquid rocket, center lines of bulk superconductor and magnet rotor will usually be in non-coaxial state. Superconducting levitation forces in axial direction and radial direction under non-coaxial situation are also analyzed by the presented method.

  4. High-frequency oscillations in small magnetic elements observed with Sunrise/SuFI

    CERN Document Server

    Jafarzadeh, Shahin; Stangalini, M; Steiner, O; Cameron, R H; Danilovic, S

    2016-01-01

    We characterize waves in small magnetic elements and investigate their propagation in the lower solar atmosphere from observations at high spatial and temporal resolution. We use the wavelet transform to analyze oscillations of both horizontal displacement and intensity in magnetic bright points found in the 300 nm and the Ca II H 396.8 nm passbands of the filter imager on board the Sunrise balloon-borne solar observatory. Phase differences between the oscillations at the two atmospheric layers corresponding to the two passbands reveal upward propagating waves at high-frequencies (up to 30 mHz). Weak signatures of standing as well as downward propagating waves are also obtained. Both compressible and incompressible (kink) waves are found in the small-scale magnetic features. The two types of waves have different, although overlapping, period distributions. Two independent estimates give a height difference of approximately 450+-100 km between the two atmospheric layers sampled by the employed spectral bands. ...

  5. Gracing incidence small angle neutron scattering of incommensurate magnetic structures in MnSi thin films

    Energy Technology Data Exchange (ETDEWEB)

    Wiedemann, Birgit; Pfleiderer, Christian; Boeni, Peter [Physik Department, Technische Universitaet Muenchen (Germany); Zhang, Shilei; Hesjedal, Thorsten [Clarendon Laboratory, Department of Physics, University of Oxford (United Kingdom); Khaydukov, Yury; Soltwedel, Olaf; Keller, Thomas [Max-Planck-Institut fuer Festkoerperforschung (Germany); Max Planck Society, Outstation at FRM-II (Germany); Muehlbauer, Sebastian [Forschungsneutronenquelle Heinz Maier Leibnitz, Technische Universitaet Muenchen (Germany); Chacon, Alfonso [Physik Department, Technische Universitaet Muenchen (Germany); Forschungsneutronenquelle Heinz Maier Leibnitz, Technische Universitaet Muenchen (Germany)

    2015-07-01

    The topological stability of skyrmions in bulk samples of MnSi and the observation of spin transfer torque effects at ultra-low current densities have generated great interest in skyrmions in chiral magnets as a new route towards next generation spintronics devices. Yet, the formation of skyrmions in MBE grown thin films of MnSi reported in the literature is highly controversial. We report gracing incidence small angle neutron scattering (GISANS) of the magnetic order in selected thin films of MnSi grown by state of the art MBE techniques. In combination with polarised neutron reflectometry (PNR) and magnetisation measurements of the same samples our data provide direct reciprocal space information of the incommensurate magnetic order, clarifying the nature of magnetic phase diagram.

  6. Small-scale anisotropic intermittency in magnetohydrodynamic turbulence at low magnetic Reynolds numbers.

    Science.gov (United States)

    Okamoto, Naoya; Yoshimatsu, Katsunori; Schneider, Kai; Farge, Marie

    2014-03-01

    Small-scale anisotropic intermittency is examined in three-dimensional incompressible magnetohydrodynamic turbulence subjected to a uniformly imposed magnetic field. Orthonormal wavelet analyses are applied to direct numerical simulation data at moderate Reynolds number and for different interaction parameters. The magnetic Reynolds number is sufficiently low such that the quasistatic approximation can be applied. Scale-dependent statistical measures are introduced to quantify anisotropy in terms of the flow components, either parallel or perpendicular to the imposed magnetic field, and in terms of the different directions. Moreover, the flow intermittency is shown to increase with increasing values of the interaction parameter, which is reflected in strongly growing flatness values when the scale decreases. The scale-dependent anisotropy of energy is found to be independent of scale for all considered values of the interaction parameter. The strength of the imposed magnetic field does amplify the anisotropy of the flow.

  7. Influence of external resonant magnetic perturbation field on edge plasma of small tokamak HYBTOK-II

    Energy Technology Data Exchange (ETDEWEB)

    Hayashi, Y., E-mail: hayashi-yuki13@ees.nagoya-u.ac.jp [Nagoya University, Furo-cho, Chikusa-ku, Nagoya, Aichi 464-8603 (Japan); Suzuki, Y.; Ohno, N. [Nagoya University, Furo-cho, Chikusa-ku, Nagoya, Aichi 464-8603 (Japan); Okamoto, M. [Ishikawa National College of Technology, Kitachujo, Tsubata-cho, Kahoku-gun, Ishikawa 929-0392 (Japan); Kikuchi, Y. [University of Hyogo, 2167 Shosha, Himeji, Hyogo 671-2280 (Japan); Sakakibara, S.; Watanabe, K.; Takemura, Y. [National Institute for Fusion Science, 322-6 Oroshi-cho, Toki, Gifu 509-5292 (Japan)

    2015-08-15

    Radial profile of externally applied resonant magnetic perturbation (RMP) field with mode numbers of m = 6 and n = 2 in a small tokamak device HYBTOK-II have been investigated using a magnetic probe array, which is able to measure the radial profile of magnetic field perturbation induced by applying RMP. Results of RMP penetration into the plasma show that the RMP decreased toward the plasma center, while they were amplified around the resonant surface with a safety factor q = 3 due to the formation of magnetic islands. This suggests that RMP fields for controlling edge plasmas may trigger some kind of MHD instabilities. In addition, simulation results, based on a linearized four-field model, which agrees with the experimental ones, indicates that the penetration and amplification process of RMP strongly depend on a Doppler-shifted frequency between the RMP and plasma rotation.

  8. Magnetic Fluctuations with a Zero Mean Field in a Random Fluid Flow with a Finite Correlation Time and a Small Magnetic Diffusion

    CERN Document Server

    Kleeorin, N; Sokoloff, D D

    2002-01-01

    Magnetic fluctuations with a zero mean field in a random flow with a finite correlation time and a small yet finite magnetic diffusion are studied. Equation for the second-order correlation function of a magnetic field is derived. This equation comprises spatial derivatives of high orders due to a non-local nature of magnetic field transport in a random velocity field with a finite correlation time. For a random Gaussian velocity field with a small correlation time the equation for the second-order correlation function of the magnetic field is a third-order partial differential equation. For this velocity field and a small magnetic diffusion with large magnetic Prandtl numbers the growth rate of the second moment of magnetic field is estimated. The finite correlation time of a turbulent velocity field causes an increase of the growth rate of magnetic fluctuations. It is demonstrated that the results obtained for the cases of a small yet finite magnetic diffusion and a zero magnetic diffusion are different. As...

  9. Asymbiotic seed germination and in vitro seedling development of Paphiopedilum spicerianum: An orchid with an extremely small population in China

    Directory of Open Access Journals (Sweden)

    Ying Chen

    2015-01-01

    Full Text Available Paphiopedilum spicerianum  is listed as one of the country’s Wild Plants with Extremely Small Populations (PSESP. Procedures were developed for asymbiotic seed germination and seedling development aimed at producing seedlings for reintroduction. The highest germination was achieved in RECW with a 24 h dark cycle after pretreatment with 1% NaOCl for 40 min after 30 days from germination. However, these protocorms remained white and did not develop further. Although germination was lower under the same conditions in MSCW, it resulted in healthier and greener protocorms. Of four suitable media tested to promote seedling formation, Hyponex No 1 medium with 1.0mgl−1α-naphthalene acetic acid, 0.5gl−1 activated charcoal and 10% banana homogenate was the most effective. Advanced seedling development was seen in all six tested media during a 4 month growing period, with the highest leaf growth rate seen in the same media used for seedling formation, supplemented with 1.0mgl−16-benzyladenine added to promote leaf growth. Fluorescein diacetate (FDA tests on seeds showed that higher salt concentrations in the medium and longer duration of exposure to NaOCl reduce germination because of damaging effects on the testa and the embryo cells.

  10. A connection between extremely strong Damped Lyman-alpha Systems and Lyman-alpha Emitting Galaxies at small impact parameters

    CERN Document Server

    Noterdaeme, P; Paris, I; Cai, Z; Finley, H; Ge, J; Pieri, M M; York, D G

    2014-01-01

    We present a study of ~100 high redshift (z~2-4) extremely strong damped Lyman-alpha systems (ESDLA, with N(HI)>0.5x10^22 cm^-2) detected in quasar spectra from the Baryon Oscillation Spectroscopic Survey SDSS-III DR11. We study the neutral hydrogen, metal, and dust content of this elusive population of absorbers and confirm our previous finding that the high column density end of the N(HI) frequency distribution has a relatively shallow slope with power-law index -3.6, similar to what is seen from 21-cm maps in nearby galaxies. The stacked absorption spectrum indicates a typical metallicity ~1/20th solar, similar to the mean metallicity of the overall DLA population. The relatively small velocity extent of the low-ionisation lines suggests that ESDLAs do not arise from large-scale flows of neutral gas. The high column densities involved are in turn more similar to what is seen in DLAs associated with gamma-ray burst afterglows (GRB-DLAs), which are known to occur close to star forming regions. This indicates...

  11. Magnetic Moment and Spin of the Extremely Proton-Rich Nucleus {sup 23}Al

    Energy Technology Data Exchange (ETDEWEB)

    Matsuta, K., E-mail: matsuta@vg.phys.sci.osaka-u.ac.jp; Nakashima, Y.; Nagatomo, T.; Mihara, M.; Kumashiro, S.; Fujiwara, H.; Ogura, M.; Fukuda, M.; Minamisono, T. [Osaka University, Department of Physics (Japan); Sumikama, T. [RIKEN (Japan); Ozawa, A. [University of Tsukuba, Institute of Physics (Japan); Yamada, K. [Rikkyo University, College of Science (Japan); Momota, S.; Nojiri, Y. [Tosayamada, Kochi University of Technology (Japan); Ota, M.; Ohtsubo, T.; Izumikawa, T. [Niigata University, Department of Physics (Japan); Yoshida, K. [RIKEN (Japan); Minamisono, K. [TRIUMF (Canada); Suzuki, T. [Saitama University, Department of Physics (Japan)

    2004-12-15

    The g-factor of the exteremely proton-rich nucleus {sup 23}Al(T{sub 1/2} 0.47 s) has been measured for the first time, applying {beta}-NMR technique on this nucleus implanted in Si. The obtained vertical bar g vertical bar (1.58 {+-} 0.2) suggests that the spin of the ground state of {sup 23}Al is 5 / 2. The magnetic moment is determined as vertical bar {mu} vertical bar (3.95 {+-} 0.55) {mu}{sub N}.

  12. Navigated Transcranial Magnetic Stimulation: A Biologically Based Assay of Lower Extremity Impairment and Gait Velocity

    Science.gov (United States)

    Dunning, Kari; Ying, Jun; Laine, Jarmo; Page, Stephen J.

    2017-01-01

    Objectives. (a) To determine associations among motor evoked potential (MEP) amplitude, MEP latency, lower extremity (LE) impairment, and gait velocity and (b) determine the association between the presence of a detectable MEP signal with LE impairment and with gait velocity. Method. 35 subjects with chronic, stable LE hemiparesis were undergone TMS, the LE section of the Fugl-Meyer Impairment Scale (LE FM), and 10-meter walk test. We recorded presence, amplitude, and latency of MEPs in the affected tibialis anterior (TA) and soleus (SO). Results. MEP presence was associated with higher LEFM scores in both the TA and SO. MEP latency was larger in subjects with lower LEFM and difficulty walking. Conclusion. MEP latency appears to be an indicator of LE impairment and gait. Significance. Our results support the precept of using TMS, particularly MEP latency, as an adjunctive LE outcome measurement and prognostic technique. PMID:28243474

  13. The magnetic shear-current effect: generation of large-scale magnetic fields by the small-scale dynamo

    CERN Document Server

    Squire, Jonathan

    2015-01-01

    A novel large-scale dynamo mechanism, the magnetic shear-current effect, is discussed and explored. The effect relies on the interaction of magnetic fluctuations with a mean shear flow, meaning the saturated state of the small-scale dynamo can drive a large-scale dynamo -- in some sense the inverse of dynamo quenching. The dynamo is nonhelical, with the mean-field $\\alpha$ coefficient zero, and is caused by the interaction between an off-diagonal component of the turbulent resistivity and the stretching of the large-scale field by shear flow. Following up on previous numerical and analytic work, this paper presents further details of the numerical evidence for the effect, as well as an heuristic description of how magnetic fluctuations can interact with shear flow to produce the required electromotive force. The pressure response of the fluid is fundamental to this mechanism, which helps explain why the magnetic effect is stronger than its kinematic cousin, and the basic idea is related to the well-known lack...

  14. Pocket atlas of sectional anatomy: computed tomography and magnetic resonance imaging. Vol. 3. Spine, extremities, joints

    Energy Technology Data Exchange (ETDEWEB)

    Moeller, T.B.; Reif, E. [Caritas Hospital, Dillingen (Germany). Dept. of Radiology

    2007-07-01

    Magnetic resonance imaging (MRI) of the musculoskeletal system is an established and important component in the diagnosis of diseases of the joints, soft tissues, bones, and bone marrow. We are therefore pleased to collect together images of the joints and the spinal column in a separate volume on the musculoskeletal system. Demonstrating the growing importance of new developments in MRI in recent years, with ever-increasing resolution, many images were acquired with 3-tesla units. We are deeply grateful to the manufacturers, Siemens and Philips, for making this possible. We believe that colored atlases are the ideal medium to represent the highly detailed images achieved nowadays with improved resolution techniques. Volume 3 of the Pocket Atlas of Sectional Anatomay provides a color illustration facing each magnetic resonance image, as in the preceding volumes on the skull, thorax, and abdomen. To ensure the greatest possible precision in details, we still produce these illustrations ourselves. Each is accompanied by a sectional image and an orientation aid. Uniform color schemes ensure optimal clarity, as similar structures, such as arteries, veins, nerves, tendons, etc., are consistently represented in the same color. Individual muscle groups are represented uniformly, but differentiated from other muscle groups, so that classification is possible even when numerous groups of muscles are shown in the same image. Maximal lucidity prevails even in highly detailed representations. This is made possible by the high quality of the production and printing process that are characteristic of Thieme International. (orig.)

  15. The Use of Magnets for Introducing Primary School Students to Some Properties of Forces through Small-Group Pedagogy

    Science.gov (United States)

    Carruthers, Rebecca; de Berg, Kevin

    2010-01-01

    Seventeen Grade Six students were divided into small groups to study the concept of forces in the context of magnets and their properties. The researcher, a pre-service primary school teacher, encouraged the students into conversation about magnets and it was found that, without hesitation, they talked about their prior experience of magnets. The…

  16. Kerr/CFT correspondence in a 4D extremal rotating regular black hole with a non-linear magnetic monopole

    Directory of Open Access Journals (Sweden)

    Shingo Takeuchi

    2017-08-01

    Full Text Available We carry out the Kerr/CFT correspondence in a four-dimensional extremal rotating regular black hole with a non-linear magnetic monopole (NLMM. One problem in this study would be whether our geometry can be a solution or not. We search for the way making our rotating geometry into a solution based on the fact that the Schwarzschild regular geometry can be a solution. However, in the attempt to extend the Schwarzschild case that we can naturally consider, it turns out that it is impossible to construct a model in which our geometry can be a exact solution. We manage this problem by making use of the fact that our geometry can be a solution approximately in the whole space-time except for the black hole's core region. As a next problem, it turns out that the equation to obtain the horizon radii is given by a fifth-order equation due to the regularization effect. We overcome this problem by treating the regularization effect perturbatively. As a result, we can obtain the near-horizon extremal Kerr (NHEK geometry with the correction of the regularization effect. Once obtaining the NHEK geometry, we can obtain the central charge and the Frolov–Thorne temperature in the dual CFT. Using these, we compute its entropy through the Cardy formula, which agrees with the one computed from the Bekenstein–Hawking entropy.

  17. Solar Coronal Loops Associated with Small-scale Mixed Polarity Surface Magnetic Fields

    Science.gov (United States)

    Chitta, L. P.; Peter, H.; Solanki, S. K.; Barthol, P.; Gandorfer, A.; Gizon, L.; Hirzberger, J.; Riethmüller, T. L.; van Noort, M.; Blanco Rodríguez, J.; Del Toro Iniesta, J. C.; Orozco Suárez, D.; Schmidt, W.; Martínez Pillet, V.; Knölker, M.

    2017-03-01

    How and where are coronal loops rooted in the solar lower atmosphere? The details of the magnetic environment and its evolution at the footpoints of coronal loops are crucial to understanding the processes of mass and energy supply to the solar corona. To address the above question, we use high-resolution line-of-sight magnetic field data from the Imaging Magnetograph eXperiment instrument on the Sunrise balloon-borne observatory and coronal observations from the Atmospheric Imaging Assembly onboard the Solar Dynamics Observatory of an emerging active region. We find that the coronal loops are often rooted at the locations with minor small-scale but persistent opposite-polarity magnetic elements very close to the larger dominant polarity. These opposite-polarity small-scale elements continually interact with the dominant polarity underlying the coronal loop through flux cancellation. At these locations we detect small inverse Y-shaped jets in chromospheric Ca ii H images obtained from the Sunrise Filter Imager during the flux cancellation. Our results indicate that magnetic flux cancellation and reconnection at the base of coronal loops due to mixed polarity fields might be a crucial feature for the supply of mass and energy into the corona.

  18. Extreme changes in the dayside ionosphere during a Carrington-type magnetic storm

    Directory of Open Access Journals (Sweden)

    Mannucci Anthony J.

    2012-06-01

    Full Text Available It is shown that during the 30 October 2003 superstorm, dayside O+ ions were uplifted to DMSP altitudes (~850 km. Peak densities were ~9 × 105 cm−3 during the magnetic storm main phase (peak Dst = −390 nT. By comparison the 1–2 September 1859 Carrington magnetic storm (peak Dst estimated at −1760 nT was considerably stronger. We investigate the impact of this storm on the low- to mid-latitude ionosphere using a modified version of the NRL SAMI2 ionospheric code. It is found that the equatorial region (LAT = 0° ± 15° is swept free of plasma within 15 min (or less of storm onset. The plasma is swept to higher altitudes and higher latitudes due to E × B convection associated with the prompt penetration electric field. Equatorial Ionization Anomaly (EIA O+ density enhancements are found to be located within the broad range of latitudes ~ ± (25°–40° at ~500–900 km altitudes. Densities within these peaks are ~6 × 106 oxygen ions-cm−3 at ~700 km altitude, approximately +600% quiet time values. The oxygen ions at the top portions (850–1000 km of uplifted EIAs will cause strong low-altitude satellite drag. Calculations are currently being performed on possible uplift of oxygen neutrals by ion-neutral coupling to understand if there might be further significant satellite drag forces present.

  19. Investigation of EEG changes during exposure to extremely low-frequency magnetic field to conduct brain signals.

    Science.gov (United States)

    Shafiei, S A; Firoozabadi, S M; Tabatabaie, K Rasoulzadeh; Ghabaee, M

    2014-11-01

    There are evidences that confirm the effect of magnetic fields (MFs) on brain signals and some psychological disorders such as headache, migraine and depression. The aim of the present study was to investigate changes in EEG power spectrum due to localized exposure in different parts of the brain by extremely low-frequency magnetic fields (ELF-MFs) to extract some protocols for treatment of some psychological disorders. In addition, regular effects were investigated by increasing intensity of ELF-MF. Therefore, EEG relative power spectrum was evaluated at T4, T3, F3, F4, and Cz points, when all the points were exposed to MFs with 45, 17, 10, 5, and 3 Hz frequencies, separately. Intensity of MF was 0, 100, 240, or 360 μT in four sessions. Significant changes were observed in different EEG bands caused by locally exposing to ELF-MF in different points of brain (P conduct the brain signals that is necessary to evaluate clinically.

  20. A small survey of the magnetic fields of planet-host stars

    CERN Document Server

    Fares, Rim; Donati, Jean-François; Catala, Claude; Shkolnik, Evgenya; Jardine, Moira; Cameron, Andrew; Deleuil, Magali

    2013-01-01

    Using spectropolarimetry, we investigate the large-scale magnetic topologies of stars hosting close-in exoplanets. A small survey of ten stars has been done with the twin instruments TBL/NARVAL and CFHT/ESPaDOnS between 2006 and 2011. Each target consists of circular-polarization observations covering 7 to 22 days. For each of the 7 targets in which a magnetic field was detected, we reconstructed the magnetic field topology using Zeeman-Doppler imaging. Otherwise, a detection limit has been estimated. Three new epochs of observations of Tau Boo are presented, which confirm magnetic polarity reversal. We estimate that the cycle period is 2 years, but recall that a shorter period of 240 days can not still be ruled out. The result of our survey is compared to the global picture of stellar magnetic field properties in the mass-rotation diagram. The comparison shows that these giant planet-host stars tend to have similar magnetic field topologies to stars without detected hot-Jupiters. This needs to be confirmed w...

  1. Magnetism, structure and chemical order in small CoPd clusters: A first-principles study

    Energy Technology Data Exchange (ETDEWEB)

    Mokkath, Junais Habeeb, E-mail: Junais.Mokkath@kaust.edu.sa

    2014-01-15

    The structural, electronic and magnetic properties of small Co{sub m}Pd{sub n}(N=m+n=8,m=0−N) nanoalloy clusters are studied in the framework of a generalized-gradient approximation to density-functional theory. The optimized cluster structures have a clear tendency to maximize the number of nearest-neighbor CoCo pairs. The magnetic order is found to be ferromagnetic-like (FM) for all the ground-state structures. Antiferromagnetic-like spin arrangements were found in some low-lying isomers. The average magnetic moment per atom μ{sup ¯}{sub N} increases approximately linearly with Co content. A remarkable enhancement of the local Co moments is observed as a result of Pd doping. This is a consequence of the increase in the number of Co d holes, due to CoPd charge transfer, combined with the reduced local coordination. The influence of spin–orbit interactions on the cluster properties is also discussed. - Highlights: • This work analyses the structural and magnetic properties of CoPd nanoclusters. • The magnetic order is found to be ferromagnetic-like for all the ground-state structures. • The average magnetic moment per atom increases approximately linearly with Co content. • The influence of spin–orbit interactions on the cluster properties is discussed.

  2. Emergence and cancellation of small-scale magnetic flux in a quiet region

    Institute of Scientific and Technical Information of China (English)

    2009-01-01

    This paper studies the relationship between the development of granules and emergence (cancellation) of magnetic flux at small spatial scales (~1 ) in a quiet region taken with the spectro-polarimeter (SP) of the Solar Optical Telescope (SOT) aboard the Hinode satellite. By examining 6 granular cell events, we have uncovered that a granular structure develops in a regular shape with a size as large as 2-3 , while the granule is pure, i.e. no magnetic flux emerges in the granule during its development. However, a granular structure develops in an irregular shape while emerging flux accompanies the granular development. Magnetic flux cancellation takes place between new emerging flux and pre-existing one. The transverse magnetic field significantly appears at the place where a tiny bipole emerges and where two opposite polarities cancel each other, but only the transverse field of emerging bipole points from the positive element to the negative element. In some cases, violent Doppler blueshifts at the early emerging stage of the magnetic elements appear. We suggest that the excess of the blue-shifts in the inter-granular lanes are produced by the magnetic reconnection below the photosphere

  3. Emergence and cancellation of small-scale magnetic flux in a quiet region

    Institute of Scientific and Technical Information of China (English)

    ZHANG Jun; JIN ChunLan

    2009-01-01

    This paper studies the relationship between the development of granules and emergence (cancellation) of magnetic flux at small spatial scales (~1″) in a quiet region taken with the spectro-polarimeter (SP) of the Solar Optical Telescope (SOT) aboard the Hinode satellite. By examining 6 granular cell events, we have uncovered that a granular structure develops in a regular shape with a size as large as 2-3″, while the granule is pure, i.e. no magnetic flux emerges in the granule during its development. How-ever, a granular structure develops in an irregular shape while emerging flux accompanies the granular development. Magnetic flux cancellation takes place between new emerging flux and pre-existing one. The transverse magnetic field significantly appears at the place where a tiny bipole emerges and where two opposite polarities cancel each other, but only the transverse field of emerging bipole points from the positive element to the negative element. In some cases, violent Doppler blueshifts at the early emerging stage of the magnetic elements appear. We suggest that the excess of the blue-shifts in the inter-granular lanes are produced by the magnetic reconnection below the photosphere

  4. Extreme secular excitation of eccentricity inside mean motion resonance. Small bodies driven into star-grazing orbits by planetary perturbations

    Science.gov (United States)

    Pichierri, Gabriele; Morbidelli, Alessandro; Lai, Dong

    2017-09-01

    Context. It is well known that asteroids and comets fall into the Sun. Metal pollution of white dwarfs and transient spectroscopic signatures of young stars like β-Pic provide growing evidence that extra solar planetesimals can attain extreme orbital eccentricities and fall into their parent stars. Aims: We aim to develop a general, implementable, semi-analytical theory of secular eccentricity excitation of small bodies (planetesimals) in mean motion resonances with an eccentric planet valid for arbitrary values of the eccentricities and including the short-range force due to General Relativity. Methods: Our semi-analytic model for the restricted planar three-body problem does not make use of series expansion and therefore is valid for any eccentricity value and semi-major axis ratio. The model is based on the application of the adiabatic principle, which is valid when the precession period of the longitude of pericentre of the planetesimal is much longer than the libration period in the mean motion resonance. In resonances of order larger than 1 this is true except for vanishingly small eccentricities. We provide prospective users with a Mathematica notebook with implementation of the model allowing direct use. Results: We confirm that the 4:1 mean motion resonance with a moderately eccentric (e' ≲ 0.1) planet is the most powerful one to lift the eccentricity of planetesimals from nearly circular orbits to star-grazing ones. However, if the planet is too eccentric, we find that this resonance is unable to pump the planetesimal's eccentricity to a very high value. The inclusion of the General Relativity effect imposes a condition on the mass of the planet to drive the planetesimals into star-grazing orbits. For a planetesimal at 1 AU around a solar mass star (or white dwarf), we find a threshold planetary mass of about 17 Earth masses. We finally derive an analytical formula for this critical mass. Conclusions: Planetesimals can easily fall into the central star

  5. Spatial resolution on a small animal RPC-PET prototype operating under magnetic field

    Energy Technology Data Exchange (ETDEWEB)

    Blanco, A. [LIP, Laboratorio de Instrumentacao e Fisica Experimental de Particulas, 3004-516 Coimbra (Portugal)]. E-mail: alberto@coimbra.lip.pt; Carolino, N. [LIP, Laboratorio de Instrumentacao e Fisica Experimental de Particulas, 3004-516 Coimbra (Portugal); Correia, C.M.B.A. [CEI, Centro de Electronica e Instrumentacao, Universidade de Coimbra, 3004-516 Coimbra (Portugal); Fazendeiro, L. [LIP, Laboratorio de Instrumentacao e Fisica Experimental de Particulas, 3004-516 Coimbra (Portugal); Ferreira, Nuno C. [IBILI, Instituto Biomedico de Investigacao de Luz e Imagem, Faculty of Medicine, 3000-548, Coimbra (Portugal); Ferreira Marques, M.F. [ICEMS, Departamento de Fisica, Universidade de Coimbra, 3004-516 Coimbra (Portugal); Ferreira Marques, R. [LIP, Laboratorio de Instrumentacao e Fisica Experimental de Particulas, 3004-516 Coimbra (Portugal); Departamento de Fisica, Faculdade de Ciencias e Tecnologia da Universidade de Coimbra, 3004-516, Coimbra (Portugal); Fonte, P. [LIP, Laboratorio de Instrumentacao e Fisica Experimental de Particulas, 3004-516 Coimbra (Portugal); ISEC, Instituto Superior de Engenharia de Coimbra, Quinta da Nora, 3030-199 Coimbra (Portugal); Gil, C. [ICEMS, Departamento de Fisica, Universidade de Coimbra, 3004-516 Coimbra (Portugal); Macedo, M.P. [CEI, Centro de Electronica e Instrumentacao, Universidade de Coimbra, 3004-516 Coimbra (Portugal); ISEC, Instituto Superior de Engenharia de Coimbra, Quinta da Nora, 3030-199 Coimbra (Portugal)

    2006-08-15

    It has been demonstrated in previous work that the RPC-PET technology is able to deliver radioisotope image resolutions approaching the physical limits of the PET principle. Here we study, by simulation, the effect of the magnetic field on the positron range to evaluate whether the spatial resolution of the RPC-PET could be improved by using an intense magnetic field. Six positron emitters of interest to small animal PET imaging ({sup 18}F, {sup 11}C, {sup 15}O, {sup 68}G, {sup 62}Cu and {sup 86}Y) are considered. Results suggest that a three-fold improvement on the spatial resolution may be obtained under a magnetic field of 10 T for the higher energy radioisotopes like {sup 86}Y or {sup 62}Cu, and by about 20% for the lower energy ones, like {sup 18}F or {sup 11}C.

  6. Small-scale Magnetic Field Diagnostics outside Sunspots: Comparison of Different Methods

    Indian Academy of Sciences (India)

    D. N. Rachkovsky; T. T. Tsap; V. G. Lozitsky

    2005-12-01

    We analyse different observational data related to the problem of intrinsic magnetic field strength in small-scale fluxtubes outside sunspots. We conclude that the kG range of fluxtube fields follows from not only classical line ratio method, but also from other old and new techniques. For the quiet regions on the Sun, the most probable mode of such fields has a magnetic field strength of 1.2–1.5 kG assuming the rectangular field profile. To best interpret the observations, a weak background field between fluxtubes should be assumed, and its magnetic field strength is expected to increase with the filling factor of fluxtubes. The alternative point of view about subkilogauss fluxtube fields is critically examined, and possible sources of different conclusions are presented.

  7. A SMALL UNBALANCED MAGNETRON SPUTTERING SOURCE WITH MULTIPOLE MAGNETIC FIELD ANODE

    Institute of Scientific and Technical Information of China (English)

    郑思孝; 孙官清; 等

    1994-01-01

    A small unbalanced magnetron atom source with multipole cusp magnetic field anode is described.The co-axial magnetron rpinciple is extended to the circular planar magnetron atom source,which raises the efficiency of sputtering target area up to 60%.The multipole magnetic field is put in the anode.which makes the unbalanced magnetron atom source run in a higher discharge current at a lower arc voltage condition.Meanwhile.the sputtering atoms through out the anode can be ionized partially,because the electron reaching the anode have to suffer multiple collisons in order to advance across the multipole magnetic field lines in the anode,which enhances the chemical reactivity of the ejecting atoms in film growth and improve the property of film depositing.

  8. Ultrastructure and calcium balance in meristem cells of pea roots exposed to extremely low magnetic fields

    Science.gov (United States)

    Belyavskaya, N. A.

    2001-01-01

    Investigations of low magnetic field (LMF) effects on biological systems have attracted attention of biologists due to planned space flights to other planets where the field intensity does not exceed 10 -5 Oe. Pea ( Pisum sativum L.) seeds were grown in an environment of LMF 3 days. In meristem cells of roots exposed to LMF, one could observe such ultrastructural peculiarities as a noticeable accumulation of lipid bodies, development of a lytic compartment (vacuoles, cytosegresomes and paramural bodies), and reduction of phytoferritin in plastids. Mitochondria were the most sensitive organelle to LMF application. Their size and relative volume in cells increased, matrix was electron-transparent, and cristae reduced. Because of the significant role of calcium signalling in plant responses to different environmental factors, calcium participation in LMF effects was investigated using a pyroantimonate method to identify the localization of free calcium ions. The intensity of cytochemical reaction in root cells after LMF application was strong. The Ca 2+ pyroantimonate deposits were observed both in all organelles and in a hyaloplasm of the cells. Data obtained suggest that the observed LMF effects on ultrastructure of root cells were due to disruptions in different metabolic systems including effects on Ca 2+ homeostasis.

  9. Diffusion and Radiation in Magnetized Collisionless Plasmas with High-Frequency Small-Scale Turbulence

    CERN Document Server

    Keenan, Brett D

    2015-01-01

    Magnetized high-energy-density plasmas can often have strong electromagnetic fluctuations whose correlation scale is smaller than the electron Larmor radius. Radiation from the electrons in such plasmas, which markedly differs from both synchrotron and cyclotron radiation, and their energy and pitch-angle diffusion are tightly related. In this paper, we present a comprehensive theoretical and numerical study of the particles' transport in both cold, "small-scale" Langmuir and Whistler-mode turbulence and its relation to the spectra of radiation simultaneously produced by these particles. We emphasize that this relation is a superb diagnostic tool of laboratory, astrophysical, interplanetary, and solar plasmas with a mean magnetic field and strong small-scale turbulence.

  10. Small Amplitude Dynamics of Nonhomogeneous Magnetization Distributions: The Excitation Spectrum of Stripe Domains

    Science.gov (United States)

    Ebels, Ursula; Buda, Liliana D.; Ounadjela, Kamel; Wigen, Phillip E.

    The general purpose of this review is to introduce to the dynamics of small amplitude excitations of nonhomogeneous magnetization distributions. This is in contrast to the dynamics of the magnetization reversal process, which corresponds to large amplitude perturbations, discussed in other contributions of this book. Small amplitude oscillations can be studied by ferromagnetic resonance or Brillouin light scattering. The latter technique isused to investigate the excitation spectrum in laterally constrained structures.This review introduces ferromagnetic resonance and focuses on the role of the pumping field orientation. Upon varying the pumping field orientation, fundamental modes can be selectively excited, giving, in particular, access to regions of varying magnetic orientation. This is demonstrated for the excitation spectrum of magnetic domains and domain walls of the stripe domain structure in metallic thin films. These stripe domains can be considered laterally constrained magnetic units 40-100 nm wide, separated by domain walls.Such experiments provide information on the domain and domain wall structure and in principle yield the internal fields and the coupling fields of the domains, as well as the wall mass and the stabilizing forces of the domain walls. The wall mass itself is a dynamic parameter which intervenes upon wall acceleration but is of less importance when considering steady-state wall propagation in the magnetization reversal process. However, the wall mass depends sensitively on the spin configuration inside the wall, and therefore resonance experiments can provide insight into the structure of the domain wall. The wall structure, on the other hand, plays an important role in spin-polarized transport experiments, investigating the contribution of a domain wall to the resistance [1] or the transfer of momentum from the conduction electrons to the wall [2,3].

  11. Dynamical process of skyrmion-helical magnetic transformation of the chiral-lattice magnet FeGe probed by small-angle resonant soft x-ray scattering

    Science.gov (United States)

    Yamasaki, Y.; Morikawa, D.; Honda, T.; Nakao, H.; Murakami, Y.; Kanazawa, N.; Kawasaki, M.; Arima, T.; Tokura, Y.

    2015-12-01

    Small-angle soft x-ray scattering in resonance with Fe L absorption edge has been investigated for helical magnetic order and magnetic skyrmion crystal (SkX) in B20-type cubic FeGe. Transformation of magnetic structures among helical, conical, SkX, and field-polarized spin-collinear forms is observed with the application of a magnetic field parallel to the incident soft x-ray. The resonant soft x-ray scattering with high q -resolution revealed a transient dynamics of SkX, such as rotation of SkX and variation of the SkX lattice constant, upon the change of magnetic field.

  12. Functionally interpretable local coordinate systems for the upper extremity using inertial & magnetic measurement systems.

    Science.gov (United States)

    de Vries, W H K; Veeger, H E J; Cutti, A G; Baten, C; van der Helm, F C T

    2010-07-20

    Inertial Magnetic Measurement Systems (IMMS) are becoming increasingly popular by allowing for measurements outside the motion laboratory. The latest models enable long term, accurate measurement of segment motion in terms of joint angles, if initial segment orientations can accurately be determined. The standard procedure for definition of segmental orientation is based on the measurement of positions of bony landmarks (BLM). However, IMMS do not deliver position information, so an alternative method to establish IMMS based, anatomically understandable segment orientations is proposed. For five subjects, IMMS recordings were collected in a standard anatomical position for definition of static axes, and during a series of standardized motions for the estimation of kinematic axes of rotation. For all axes, the intra- and inter-individual dispersion was estimated. Subsequently, local coordinate systems (LCS) were constructed on the basis of the combination of IMMS axes with the lowest dispersion and compared with BLM based LCS. The repeatability of the method appeared to be high; for every segment at least two axes could be determined with a dispersion of at most 3.8 degrees. Comparison of IMMS based with BLM based LCS yielded compatible results for the thorax, but less compatible results for the humerus, forearm and hand, where differences in orientation rose to 17.2 degrees. Although different from the 'gold standard' BLM based LCS, IMMS based LCS can be constructed repeatable, enabling the estimation of segment orientations outside the laboratory. A procedure for the definition of local reference frames using IMMS is proposed. 2010 Elsevier Ltd. All rights reserved.

  13. Solar coronal loops associated with small-scale mixed polarity surface magnetic fields

    CERN Document Server

    Chitta, L P; Solanki, S K; Barthol, P; Gandorfer, A; Gizon, L; Hirzberger, J; Riethmueller, T L; van Noort, M; Rodriguez, J Blanco; Iniesta, J C Del Toro; Suarez, D Orozco; Schmidt, W; Pillet, V Martinez; Knoelker, M

    2016-01-01

    How and where are coronal loops rooted in the solar lower atmosphere? The details of the magnetic environment and its evolution at the footpoints of coronal loops are crucial to understanding the processes of mass and energy supply to the solar corona. To address the above question, we use high resolution line-of-sight magnetic field data from the Imaging Magnetograph eXperiment (IMaX) instrument on the Sunrise balloon-borne observatory and coronal observations from the Atmospheric Imaging Assembly (AIA) onboard the Solar Dynamics Observatory (SDO) of an emerging active region. We find that the coronal loops are often rooted at the locations with minor small-scale but persistent opposite polarity magnetic elements very close to the larger dominant polarity. These opposite polarity small-scale elements continually interact with the dominant polarity underlying the coronal loop through flux cancellation. At these locations we detect small inverse Y-shaped jets in chromospheric Ca II H images obtained from the S...

  14. A multireader reliability study comparing conventional high-field magnetic resonance imaging with extremity low-field MRI in rheumatoid arthritis

    DEFF Research Database (Denmark)

    Bird, Paul; Ejbjerg, Bo; Lassere, Marissa;

    2007-01-01

    The use of extremity low-field magnetic resonance imaging (E-MRI) is increasing, but relatively few data exist on its reproducibility and accuracy in comparison with high-field MRI, especially for multiple readers. The aim of this multireader exercise of rheumatoid arthritis wrist...

  15. A multireader reliability study comparing conventional high-field magnetic resonance imaging with extremity low-field MRI in rheumatoid arthritis

    DEFF Research Database (Denmark)

    Bird, Paul; Ejbjerg, Bo; Lassere, Marissa;

    2007-01-01

    The use of extremity low-field magnetic resonance imaging (E-MRI) is increasing, but relatively few data exist on its reproducibility and accuracy in comparison with high-field MRI, especially for multiple readers. The aim of this multireader exercise of rheumatoid arthritis wrist and metacarpoph...

  16. Effects of low-frequency repetitive transcranial magnetic stimulation and neuromuscular electrical stimulation on upper extremity motor recovery in the early period after stroke: a preliminary study.

    Science.gov (United States)

    Tosun, Aliye; Türe, Sabiha; Askin, Ayhan; Yardimci, Engin Ugur; Demirdal, Secil Umit; Kurt Incesu, Tülay; Tosun, Ozgur; Kocyigit, Hikmet; Akhan, Galip; Gelal, Fazıl Mustafa

    2017-07-01

    To assess the efficacy of inhibitory repetitive transcranial magnetic stimulation (rTMS) and neuromuscular electrical stimulation (NMES) on upper extremity motor function in patients with acute/subacute ischemic stroke. Twenty-five ischemic acute/subacute stroke subjects were enrolled in this randomized controlled trial. Experimental group 1 received low frequency (LF) rTMS to the primary motor cortex of the unaffected side + physical therapy (PT) including activities to improve strength, flexibility, transfers, posture, balance, coordination, and activities of daily living, mainly focusing on upper limb movements; experimental group 2 received the same protocol combined with NMES to hand extensor muscles; and the control group received only PT. Functional magnetic resonance imaging (fMRI) scan was used to evaluate the activation or inhibition of the affected and unaffected primary motor cortex. No adverse effect was reported. Most of the clinical outcome scores improved significantly in all groups, however no statistically significant difference was found between groups due to the small sample sizes. The highest percent improvement scores were observed in TMS + NMES group (varying between 48 and 99.3%) and the lowest scores in control group (varying between 13.1 and 28.1%). Hand motor recovery was significant in both experimental groups while it did not change in control group. Some motor cortex excitability changes were also observed in fMRI. LF-rTMS with or without NMES seems to facilitate the motor recovery in the paretic hand of patients with acute/subacute ischemic stroke. TMS or the combination of TMS + NMES may be a promising additional therapy in upper limb motor training. Further studies with larger numbers of patients are needed to establish their effectiveness in upper limb motor rehabilitation of stroke.

  17. SU-D-304-02: Magnetically Focused Proton Irradiation of Small Field Targets

    Energy Technology Data Exchange (ETDEWEB)

    McAuley, GA; Slater, JM [Loma Linda University, Loma Linda, CA (United States); Slater, JD; Wroe, AJ [Loma Linda University Medical Center, Loma Linda, CA (United States)

    2015-06-15

    Purpose: To investigate the use of magnetic focusing for small field proton irradiations. It is hypothesized that magnetic focusing will provide significant dose distribution benefits over standard collimated beams for fields less than 10 mm diameter. Methods: Magnets consisting of 24 segments of radiation hard samarium-cobalt adhered into hollow cylinders were designed and manufactured. Two focusing magnets were placed on a positioning track on our Gantry 1 treatment table. Proton beams with energies of 127 and 157 MeV, 15 and 30 mm modulation, and 8 mm initial diameters were delivered to a water tank using single-stage scattering. Depth dose distributions were measured using a PTW PR60020 diode detector and transverse profiles were measured with Gafchromic EBT3 film. Monte Carlo simulations were also performed - both for comparison with experimental data and to further explore the potential of magnetic focusing in silica. For example, beam spot areas (based on the 90% dose contour) were matched at Bragg depth between simulated 100 MeV collimated beams and simulated beams focused by two 400 T/m gradient magnets. Results: Preliminary experimental results show 23% higher peak to entrance dose ratios and flatter spread out Bragg peak plateaus for 8 mm focused beams compared with uncollimated beams. Monte Carlo simulations showed 21% larger peak to entrance ratios and a ∼9 fold more efficient dose to target delivery compared to spot-sized matched collimated beams. Our latest results will be presented. Conclusion: Our results suggest that rare earth focusing magnet assemblies could reduce skin dose and beam number while delivering dose to nominally spherical radiosurgery targets over a much shorter time compared to unfocused beams. Immediate clinical applications include those associated with proton radiosurgery and functional radiosurgery of the brain and spine, however expanded treatment sites can be also envisaged.

  18. A method for aircraft magnetic interference compensation based on small signal model and LMS algorithm

    Institute of Scientific and Technical Information of China (English)

    Zhou Jianjun; Lin Chunsheng; Chen Hao

    2014-01-01

    Aeromagnetic interference could not be compensated effectively if the precision of parameters which are solved by the aircraft magnetic field model is low. In order to improve the compensation effect under this condition, a method based on small signal model and least mean square (LMS) algorithm is proposed. According to the method, the initial values of adaptive filter’s weight vector are calculated with the solved model parameters through small signal model at first, then the small amount of direction cosine and its derivative are set as the input of the filter, and the small amount of the interference is set as the filter’s expected vector. After that, the aircraft mag-netic interference is compensated by LMS algorithm. Finally, the method is verified by simulation and experiment. The result shows that the compensation effect can be improved obviously by the LMS algorithm when original solved parameters have low precision. The method can further improve the compensation effect even if the solved parameters have high precision.

  19. Extremely low-frequency magnetic fields and risk of childhood leukemia: A risk assessment by the ARIMMORA consortium.

    Science.gov (United States)

    Schüz, Joachim; Dasenbrock, Clemens; Ravazzani, Paolo; Röösli, Martin; Schär, Primo; Bounds, Patricia L; Erdmann, Friederike; Borkhardt, Arndt; Cobaleda, César; Fedrowitz, Maren; Hamnerius, Yngve; Sanchez-Garcia, Isidro; Seger, Rony; Schmiegelow, Kjeld; Ziegelberger, Gunde; Capstick, Myles; Manser, Melissa; Müller, Meike; Schmid, Christoph D; Schürmann, David; Struchen, Benjamin; Kuster, Niels

    2016-03-15

    Exposure to extremely low-frequency magnetic fields (ELF-MF) was evaluated in an International Agency for Research on Cancer (IARC) Monographs as "possibly carcinogenic to humans" in 2001, based on increased childhood leukemia risk observed in epidemiological studies. We conducted a hazard assessment using available scientific evidence published before March 2015, with inclusion of new research findings from the Advanced Research on Interaction Mechanisms of electroMagnetic exposures with Organisms for Risk Assessment (ARIMMORA) project. The IARC Monograph evaluation scheme was applied to hazard identification. In ARIMMORA for the first time, a transgenic mouse model was used to mimic the most common childhood leukemia: new pathogenic mechanisms were indicated, but more data are needed to draw definitive conclusions. Although experiments in different animal strains showed exposure-related decreases of CD8+ T-cells, a role in carcinogenesis must be further established. No direct damage of DNA by exposure was observed. Overall in the literature, there is limited evidence of carcinogenicity in humans and inadequate evidence of carcinogenicity in experimental animals, with only weak supporting evidence from mechanistic studies. New exposure data from ARIMMORA confirmed that if the association is nevertheless causal, up to 2% of childhood leukemias in Europe, as previously estimated, may be attributable to ELF-MF. In summary, ARIMMORA concludes that the relationship between ELF-MF and childhood leukemia remains consistent with possible carcinogenicity in humans. While this scientific uncertainty is dissatisfactory for science and public health, new mechanistic insight from ARIMMORA experiments points to future research that could provide a step-change in future assessments. Bioelectromagnetics. © 2016 Wiley Periodicals, Inc. © 2016 Wiley Periodicals, Inc.

  20. Multifractal Analysis of the Small Time-Scale Boundary-Layer Characteristics of the Wind: the Anisotropy and Extremes

    Science.gov (United States)

    Fitton, G. F.; Tchiguirinskaia, I.; Schertzer, D. J.; Lovejoy, S.

    2012-12-01

    anisotropic over high frequencies, where u1 most scales as Bolgiano-Obukhov and u2 scales as Kolmogorov. The scaling law of the vertical shears of the horizontal wind in the array varied from Kolmogorov to Bolgiano-Obukhov with height depending on the condition of stability. We interpret the results with the UM anisotropic model that greatly enhances our understanding of the ABL structure. Comparing the two case studies we found in both cases the multifractality parameter of about 1.6, which remains close to the estimates obtained for the free atmosphere. From the UM parameters, the exponent of the power law of the distribution of the extremes can be predicted. Over small scales, this exponent is of about 7.5 for the wind velocity, which is a crucial result for applications within the field of wind energy.

  1. Structural and magnetic properties of ultra-small scale eutectic CoFeZr alloys

    Energy Technology Data Exchange (ETDEWEB)

    Manjura Hoque, S. [Dept. of Materials Engineering, Indian Institute of Science, Bangalore (India); Materials Science Division, Atomic Energy Centre, Bangladesh Atomic Energy Commission, Dhaka (Bangladesh); Makineni, S.K. [Dept. of Materials Engineering, Indian Institute of Science, Bangalore (India); Pal, A.; Ayyub, P. [Dept. of Condensed Matter Physics and Materials Science, Tata Institute of Fundamental Research, Mumbai (India); Chattopadhyay, K. [Dept. of Materials Engineering, Indian Institute of Science, Bangalore (India)

    2015-01-25

    Highlights: • Development of ultra-small scale eutectic CoFeZr alloys. • Hardness of 713 VHN was obtained for Co{sub 49.2}Fe{sub 49.2}Zr by lamellar spacing of 113 nm. • Highest moment of 1.92 μ{sub B} at 5 K was obtained for Co{sub 49.2}Fe{sub 49.2}Zr. • Decay of magnetization at low temperature can be described by spin wave excitation. - Abstract: Aiming to develop high mechanical strength and toughness by tuning ultrafine lamellar spacing of magnetic eutectic alloys, we report the mechanical and magnetic properties of the binary eutectic alloys Co{sub 90.5}Zr{sub 9.5} and Fe{sub 90.2}Zr{sub 9.8}, as well as the pseudo-binary eutectic alloys Co{sub 82.4}Fe{sub 8}Zr{sub 9.6}, Co{sub 78}Fe{sub 12.4}Zr{sub 9.6} and Co{sub 49.2}Fe{sub 49.2}Zr{sub 9.6} developed by suction-casting. The lower lamellar spacing around 100 nm of the eutectics Co{sub 49.2}Fe{sub 49.2}Zr{sub 9.6} yields a high hardness of 713(±20) VHN. Magnetic measurements reveal high magnetic moment of 1.92 μ{sub B} (at 5 K) and 1.82 μ{sub B} (at 300 K) per formula unit for this composition. The magnetization vs. applied field data at 5 K show a directional preference to some extent and therefore smaller non-collinear magnetization behavior compared to Co{sub 11}Zr{sub 2} reported in the literature due to exchange frustration and transverse spin freezing owing to the presence of smaller Zr content. The decay of magnetization as a function of temperature along the easy axis of magnetization of all the eutectic compositions can be described fairly well by the spin wave excitation equation ΔM/M(0) = BT{sup 3/2} + CT{sup 5/2}.

  2. Fifty hertz extremely low-frequency magnetic field exposure elicits redox and trophic response in rat-cortical neurons.

    Science.gov (United States)

    Di Loreto, Silvia; Falone, Stefano; Caracciolo, Valentina; Sebastiani, Pierluigi; D'Alessandro, Antonella; Mirabilio, Alessandro; Zimmitti, Vincenzo; Amicarelli, Fernanda

    2009-05-01

    Large research activity has raised around the mechanisms of interaction between extremely low-frequency magnetic fields (ELF-MFs) and biological systems. ELF-MFs may interfere with chemical reactions involving reactive oxygen species (ROS), thus facilitating oxidative damages in living cells. Cortical neurons are particularly susceptible to oxidative stressors and are also highly dependent on the specific factors and proteins governing neuronal development, activity and survival. The aim of the present work was to investigate the effects of exposures to two different 50 Hz sinusoidal ELF-MFs intensities (0.1 and 1 mT) in maturing rat cortical neurons' major anti-oxidative enzymatic and non-enzymatic cellular protection systems, membrane peroxidative damage, as well as growth factor, and cytokine expression pattern. Briefly, our results showed that ELF-MFs affected positively the cell viability and concomitantly reduced the levels of apoptotic death in rat neuronal primary cultures, with no significant effects on the main anti-oxidative defences. Interestingly, linear regression analysis suggested a positive correlation between reduced glutathione (GSH) and ROS levels in 1 mT MF-exposed cells. On this basis, our hypothesis is that GSH could play an important role in the antioxidant defence towards the ELF-MF-induced redox challenge. Moreover, the GSH-based cellular response was achieved together with a brain-derived neurotrophic factor over-expression as well as with the interleukin 1beta-dependent regulation of pro-survival signaling pathways after ELF-MF exposure.

  3. Oxidative effects of extremely low frequency magnetic field and radio frequency radiation on testes tissues of diabetic and healthy rats.

    Science.gov (United States)

    Kuzay, D; Ozer, C; Sirav, B; Canseven, A G; Seyhan, N

    2017-01-01

    With the development of technology, people are increasingly under the exposure of electromagnetic fields. Individuals with chronic diseases such as diabetes are now long-term exposed to Radio Frequency-RF radiation and extremely low frequency (ELF) magnetic fields (MFs). The purpose of this present study is to investigate oxidative effects and antioxidant parameters of ELF MFs and RF radiation on testis tissue in diabetic and healthy rats. Wistar male rats were divided into 10 groups. Intraperitoneal single dose STZ (65 mg/kg) dissolved in citrate buffer (0.1M (pH 4.5)) was injected to diabetes groups. ELF MFs and RF radiation were used as an electromagnetic exposure for 20 min/day, 5 days/week for one month. Testis tissue oxidant malondialdehyde (MDA), and antioxidants glutathione (GSH), and total nitric oxide (NOx) levels were determined. The results of ANOVA and Mann-Whitney tests were compared; p radiation resulted in an increase in testicular tissue MDA and NOX levels (p radiation practices increased the oxidative stress in testis tissue while causing a decrease in antioxidant level which was more distinctive in diabetic rats (Tab. 1, Fig. 3, Ref. 30).

  4. Magnetic resonance venography in consecutive patients with suspected deep vein thrombosis of the upper extremity: initial experience

    Energy Technology Data Exchange (ETDEWEB)

    Baarslag, H.J.; Reekers, J.A. [Academic Medical Centre, Amsterdam (Netherlands). Dept. of Radiology; Beek, E.J. van [Royal Hallamshire Hospital, Sheffield (United Kingdom). Unit of Academic Radiology

    2004-02-01

    To assess the feasibility and accuracy of two magnetic resonance (MR) venography methods in a consecutive series of patients with suspected deep vein thrombosis of the upper extremity (DVTUE). Consecutive in- and outpatients who were referred for imaging of suspected DVTUE in a large teaching hospital during the period April 2001 to October 2002 were eligible for inclusion. All patients were scheduled to undergo contrast venography with the intention to perform additional MR venography. Both time-of-flight and gadolinium-enhanced 3D MR venography were scheduled. All MR imaging were interpreted independently by consensus of two experienced radiologists, who were blinded for contrast venography outcome. Patients were managed based on contrast venography only. A total of 44 patients were eligible for inclusion. Thirteen patients were excluded (5 refused consent, 2 inability to gain venous access, 2 renal failure, 4 logistic reasons). Contrast venography was performed in 31 patients, and demonstrated DVTUE in 11 patients. MR imaging was not feasible in 10 patients (4 unable to lie flat, 3 claustrophobia, 1 too large for MR scanner, 1 osteosynthesis of shoulder, 1 pacemaker). The sensitivity and specificity of TOF MRV versus Gadolinium 3D MRV was 71% and 89% versus 50% and 80%, respectively. A high number of patients were unable to undergo MR venography in this setting. Contrast-enhanced MRV did not improve diagnostic accuracy. The clinical utility of MR venography in the setting of suspected DVTUE seems disappointing.

  5. Noise in small magnetic systems-applications to very sensitive magnetoresistive sensors

    Energy Technology Data Exchange (ETDEWEB)

    Pannetier, M. [CAPMAG/DRECAM, CEA Saclay 91191 Gif-sur-Yvette Cedex (France)]. E-mail: mpannetier@cea.fr; Fermon, C. [CAPMAG/DRECAM, CEA Saclay 91191 Gif-sur-Yvette Cedex (France); Le Goff, G. [CAPMAG/DRECAM, CEA Saclay 91191 Gif-sur-Yvette Cedex (France); Simola, J. [Elekta Neuromag Oy, P.O. Box 68, FIN-00511 Helsinki (Finland); Kerr, E. [SFI-Nanosciences Laboratory, Physics Department, Trinity College, Dublin 2 (Ireland); Coey, J.M.D. [SFI-Nanosciences Laboratory, Physics Department, Trinity College, Dublin 2 (Ireland)

    2005-04-15

    Reduction for 1/f noise (or random telegraph noise) is a crucial issue for small magnetic sensors which is strongly related to structural properties and magnetic configuration. We show how it is possible to eliminate magnetic noise at low frequency in GMR/TMR sensors by a combination of cross anisotropies, window frame shapes and suitably designed magnetoresisitive stack. These sensors are superior to almost all existing field and flux sensors. Results are presented on a mixed sensor, where a superconducting loop acts as a flux-to-field transformer to the GMR sensor. This device is suitable for detection of biomagnetic signals, such as in magnetocardiography or in magnetoencephalography. Measurements on niobium-based and YBCO-based sensors are presented, leading to sensitivity of 30 fT/{radical}Hz at 77 K for small samples. Sensitivity lower than 1 fT/{radical}(Hz) is expected with appropriate design and use of TMR or CMR layers, which makes these a powerful alternative to SQUIDs.

  6. High-frequency Oscillations in Small Magnetic Elements Observed with Sunrise/SuFI

    Science.gov (United States)

    Jafarzadeh, S.; Solanki, S. K.; Stangalini, M.; Steiner, O.; Cameron, R. H.; Danilovic, S.

    2017-04-01

    We characterize waves in small magnetic elements and investigate their propagation in the lower solar atmosphere from observations at high spatial and temporal resolution. We use the wavelet transform to analyze oscillations of both horizontal displacement and intensity in magnetic bright points found in the 300 nm and the Ca ii H 396.8 nm passbands of the filter imager on board the Sunrise balloon-borne solar observatory. Phase differences between the oscillations at the two atmospheric layers corresponding to the two passbands reveal upward propagating waves at high frequencies (up to 30 mHz). Weak signatures of standing as well as downward propagating waves are also obtained. Both compressible and incompressible (kink) waves are found in the small-scale magnetic features. The two types of waves have different, though overlapping, period distributions. Two independent estimates give a height difference of approximately 450 ± 100 km between the two atmospheric layers sampled by the employed spectral bands. This value, together with the determined short travel times of the transverse and longitudinal waves provide us with phase speeds of 29 ± 2 km s‑1 and 31 ± 2 km s‑1, respectively. We speculate that these phase speeds may not reflect the true propagation speeds of the waves. Thus, effects such as the refraction of fast longitudinal waves may contribute to an overestimate of the phase speed.

  7. Persistent detwinning of EuFe{sub 2}As{sub 2} by small magnetic fields

    Energy Technology Data Exchange (ETDEWEB)

    Maiwald, Jannis; Stingl, Christian; Bach, Nora; Jeevan, H.S.; Gegenwart, Philipp [Experimentalphysik VI, Universitaet Augsburg (Germany); Zapf, Sina; Jiang, Shuai; Neubauer, David; Loehle, Anja; Clauss, Conrad; Dressel, Martin [1. Physikalisches Institut, Universitaet Stuttgart (Germany); Post, Kirk; Basov, Dimitri [Department of Physics, UC San Diego (United States)

    2015-07-01

    The formation of twin domains in the orthorhombic phase of high-temperature superconductors is impeding the investigation of the in-plane anisotropy of these materials. Recently, we have shown how the brief application of a small magnetic field of ∝ 1 Tesla in the EuFe{sub 2}As{sub 2} iron pnictide leads to a substantial detwinning of the system, which is persistent up to the structural transition at ∝ 190 K even after the magnetic field has been switched off. This offers researchers the opportunity to investigate the detwinned iron arsenide without the application of any external symmetry breaking force, like the pressure of a mechanical clamp, or a magnetic field present during measurement. We will present angular dependent magnetoresistance, magnetostriction, thermal expansion and thermoelectric power measurements on the EuFe{sub 2}As{sub 2} parent compound as well as on various doped variants in order to shed further light on the mechanism behind the field induced detwinning, i.e. the interplay of the involved magnetic moments stemming form the Eu and Fe atoms in these compounds.

  8. Correlation functions of small-scale fluctuations of the interplanetary magnetic field

    CERN Document Server

    Németh, Z; Lucek, E A

    2010-01-01

    The Interplanetary Magnetic Field shows complex spatial and temporal variations. Single spacecraft measurements reveal only a one dimensional section of this rich four dimensional phenomenon. Multi-point measurements of the four Cluster spacecraft provide a unique tool to study the spatiotemporal structure of the field. Using Cluster data we determined three dimensional correlation functions of the fluctuations. By means of the correlation function one can describe and measure field variations. Our results can be used to verify theoretical predictions, to understand the formation and nature of solar wind turbulence. We found that the correlation length varies over almost six orders of magnitude. The IMF turbulence shows significant anisotropy with two distinct populations. In certain time intervals the ratio of the three axes of the correlation ellipse is 1/2.2/6 while in the remaining time we found extremely high correlation along one axis. We found favoured directions in the orientation of the correlation e...

  9. The small scale dynamo and the amplification of magnetic fields in massive primordial haloes

    CERN Document Server

    Latif, M A; Schmidt, W; Niemeyer, J

    2012-01-01

    While our present standard model of cosmology yields no clear prediction for the initial magnetic field strength, efficient dynamo action may compensate for initially weak seed fields via rapid amplification. In particular, the small-scale dynamo is expected to exponentially amplify any weak magnetic field in the presence of turbulence. We explore whether this scenario is viable using cosmological magneto-hydrodynamics simulations modeling the formation of the first galaxies, which are expected to form in so-called atomic cooling halos with virial temperatures $\\rm T_{vir} \\geq 10^{4}$ K. As previous calculations have shown that a high Jeans resolution is needed to resolve turbulent structures and dynamo effects, our calculations employ resolutions of up to 128 cells per Jeans length. The presence of the dynamo can be clearly confirmed for resolutions of at least 64 cells per Jeans length, while saturation occurs at approximate equipartition with turbulent energy. As a result of the large Reynolds numbers in ...

  10. Spectro-Polarimetric Properties of Small-Scale Plasma Eruptions Driven by Magnetic Vortex Tubes

    CERN Document Server

    Kitiashvili, Irina N

    2014-01-01

    Highly turbulent nature of convection on the Sun causes strong multi-scale interaction of subsurface layers with the photosphere and chromosphere. According to realistic 3D radiative MHD numerical simulations ubiquitous small-scale vortex tubes are generated by turbulent flows below the visible surface and concentrated in the intergranular lanes. The vortex tubes can capture and amplify magnetic field, penetrate into chromospheric layers and initiate quasi-periodic flow eruptions that generates Alfv\\'enic waves, transport mass and energy into the solar atmosphere. The simulations revealed high-speed flow patterns, and complicated thermodynamic and magnetic structures in the erupting vortex tubes. The spontaneous eruptions are initiated and driven by strong pressure gradients in the near-surface layers, and accelerated by the Lorentz force in the low chromosphere. In this paper, the simulation data are used to further investigate the dynamics of the eruptions, their spectro-polarimetric characteristics for the...

  11. Magnetic microstructure of nanocrystalline gadolinium: a small-angle neutron scattering study

    Energy Technology Data Exchange (ETDEWEB)

    Doebrich, Frank [University of Luxembourg, 162A Avenue de la Faiencerie, L-1511 Luxembourg (Luxembourg); Universitaet des Saarlandes, D-66041 Saarbruecken (Germany); Eckerlebe, Helmut; Sharp, Melissa [GKSS Forschungszentrum, D-21502 Geesthacht (Germany); Kohlbrecher, Joachim [Paul Scherrer Institute, CH-5232 Villigen PSI (Switzerland); Birringer, Rainer [Universitaet des Saarlandes, D-66041 Saarbruecken (Germany); Michels, Andreas [University of Luxembourg, 162A Avenue de la Faiencerie, L-1511 Luxembourg (Luxembourg)

    2011-07-01

    We report on grain-size dependent magnetic small-angle neutron scattering (SANS) experiments on nanocrystalline Gd, which was synthesized using the low-capturing isotope {sup 160}Gd. The angular variation of the two-dimensional SANS cross-section at different applied magnetic fields is discussed with a special focus on the rather unusual scattering contribution of the clover-leaf-type found for nanocrystalline Gd at intermediate field values. Additionally we have calculated from experimental data the autocorrelation function of the spin misalignment. This approach allows in particular for the extraction of the field-dependent correlation length of static spin misalignment fluctuations induced by microstructural defects. The data analysis suggests that the grain boundaries constitute a major source of spin disorder in this material, which may be attributed to local atomic site disorder and modified coupling at internal interfaces.

  12. Electrically Small Magnetic Dipole Antennas With Quality Factors Approaching the Chu Lower Bound

    DEFF Research Database (Denmark)

    Kim, Oleksiy S.; Breinbjerg, Olav; Yaghjian, Arthur D.

    2010-01-01

    permeability yields the quality factor Q that constitutes the lower bound for a magnetic dipole antenna with a magneto-dielectric core. Furthermore, the smaller the antenna the closer its quality factor Q can approach the Chu lower bound. Simulated results for the TE10-mode multiarm spherical helix antenna......We investigate the quality factor Q for electrically small current distributions and practical antenna designs radiating the TE10 magnetic dipole field. The current distributions and the antenna designs employ electric currents on a spherical surface enclosing a magneto-dielectric material...... numerically. It is found that for a given antenna size and permittivity there is an optimum permeability that ensures the lowest possible Q, and this optimum permeability is inversely proportional to the square of the antenna electrical radius. When the relative permittivity is equal to 1, the optimum...

  13. Small for gestational age and poor fluid intelligence in childhood predict externalizing behaviors among young adults born at extremely low birth weight.

    Science.gov (United States)

    Lahat, Ayelet; Van Lieshout, Ryan J; Saigal, Saroj; Boyle, Michael H; Schmidt, Louis A

    2015-02-01

    Although infants born at extremely low birth weight (ELBW; birth weight intelligence. As young adults, a subset of ELBW survivors free of major neurosensory impairments provided self-reports of personality characteristics related to psychopathology. Data from 66 participants indicated that, as predicted, the association between ELBW and externalizing behaviors was moderated by fluid intelligence. Specifically, ELBW individuals with poor fluid intelligence who were born small for gestational age (birth weight intelligence might be a cognitive mechanism contributing to the development of psychopathology among nonimpaired individuals who were born at ELBW and small for gestational age.

  14. Dipolar structures in magnetite ferrofluids studied with small-angle neutron scattering with and without applied magnetic field

    NARCIS (Netherlands)

    Klokkenburg, M.; Erne, B.H.; Wiedenmann, A.; Petukhov, A.V.; Philipse, A.P.

    2007-01-01

    Field-induced structure formation in a ferrofluid with well-defined magnetite nanoparticles with a permanent magnetic dipole moment was studied with small-angle neutron scattering (SANS) as a function of the magnetic interactions. The interactions were tuned by adjusting the size of the well-defined

  15. Dipolar structures in magnetite ferrofluids studied with small-angle neutron scattering with and without applied magnetic field

    NARCIS (Netherlands)

    Klokkenburg, M.; Erne, B.H.; Wiedenmann, A.; Petukhov, A.V.; Philipse, A.P.

    2007-01-01

    Field-induced structure formation in a ferrofluid with well-defined magnetite nanoparticles with a permanent magnetic dipole moment was studied with small-angle neutron scattering (SANS) as a function of the magnetic interactions. The interactions were tuned by adjusting the size of the well-defined

  16. Low-temperature dynamics of magnetic colloids studied by time-resolved small-angle neutron scattering

    NARCIS (Netherlands)

    Wiedenmann, A.; Keiderling, U.; Meissner, M.; Wallacher, D.; Gähler, R.; May, R.P.; Prévost, S.; Klokkenburg, M.; Erne, B.H.; Kohlbrecher, J.

    2008-01-01

    The dynamics of ordering and relaxation processes in magnetic colloids has been studied by means of stroboscopic small angle neutron scattering techniques in an oscillating magnetic field. Surfactant stabilized ferrofluids (FFs) of Fe3O4 and Co nanoparticles have been investigated as a function of t

  17. Small Bowel Obstruction Following Computed Tomography and Magnetic Resonance Enterography Using Psyllium Seed Husk As an Oral Contrast Agent

    Directory of Open Access Journals (Sweden)

    Yingming Amy Chen

    2014-01-01

    Full Text Available The authors report a case series describing four patients who developed small bowel obstruction following the use of psyllium seed husk as an oral contrast agent for computed tomography or magnetic resonance enterography. Radiologists who oversee computed tomography and magnetic resonance enterography should be aware of this potential complication when using psyllium seed husk and other bulking agents, particularly when imaging patients with known or suspected small bowel strictures or active inflammation.

  18. Small bowel obstruction following computed tomography and magnetic resonance enterography using psyllium seed husk as an oral contrast agent.

    Science.gov (United States)

    Chen, Yingming Amy; Cervini, Patrick; Kirpalani, Anish; Vlachou, Paraskevi A; Grover, Samir C; Colak, Errol

    2014-01-01

    The authors report a case series describing four patients who developed small bowel obstruction following the use of psyllium seed husk as an oral contrast agent for computed tomography or magnetic resonance enterography. Radiologists who oversee computed tomography and magnetic resonance enterography should be aware of this potential complication when using psyllium seed husk and other bulking agents, particularly when imaging patients with known or suspected small bowel strictures or active inflammation.

  19. Small-scale dynamo magnetism as the driver for heating the solar atmosphere.

    Science.gov (United States)

    Amari, Tahar; Luciani, Jean-François; Aly, Jean-Jacques

    2015-06-11

    The long-standing problem of how the solar atmosphere is heated has been addressed by many theoretical studies, which have stressed the relevance of two specific mechanisms, involving magnetic reconnection and waves, as well as the necessity of treating the chromosphere and corona together. But a fully consistent model has not yet been constructed and debate continues, in particular about the possibility of coronal plasma being heated by energetic phenomena observed in the chromosphere. Here we report modelling of the heating of the quiet Sun, in which magnetic fields are generated by a subphotospheric fluid dynamo intrinsically connected to granulation. We find that the fields expand into the chromosphere, where plasma is heated at the rate required to match observations (4,500 watts per square metre) by small-scale eruptions that release magnetic energy and drive sonic motions. Some energetic eruptions can even reach heights of 10 million metres above the surface of the Sun, thereby affecting the very low corona. Extending the model by also taking into account the vertical weak network magnetic field allows for the existence of a mechanism able to heat the corona above, while leaving unchanged the physics of chromospheric eruptions. Such a mechanism rests on the eventual dissipation of Alfvén waves generated inside the chromosphere and that carry upwards the required energy flux of 300 watts per square metre. The model shows a topologically complex magnetic field of 160 gauss on the Sun's surface, agreeing with inferences obtained from spectropolarimetric observations, chromospheric features (contributing only weakly to the coronal heating) that can be identified with observed spicules and blinkers, and vortices that may be possibly associated with observed solar tornadoes.

  20. A small scale remote cooling system for a superconducting cyclotron magnet

    Science.gov (United States)

    Haug, F.; Berkowitz Zamorra, D.; Michels, M.; Gomez Bosch, R.; Schmid, J.; Striebel, A.; Krueger, A.; Diez, M.; Jakob, M.; Keh, M.; Herberger, W.; Oesterle, D.

    2017-02-01

    Through a technology transfer program CERN is involved in the R&D of a compact superconducting cyclotron for future clinical radioisotope production, a project led by the Spanish research institute CIEMAT. For the remote cooling of the LTc superconducting magnet operating at 4.5 K, CERN has designed a small scale refrigeration system, the Cryogenic Supply System (CSS). This refrigeration system consists of a commercial two-stage 1.5 W @ 4.2 K GM cryocooler and a separate forced flow circuit. The forced flow circuit extracts the cooling power of the first and the second stage cold tips, respectively. Both units are installed in a common vacuum vessel and, at the final configuration, a low loss transfer line will provide the link to the magnet cryostat for the cooling of the thermal shield with helium at 40 K and the two superconducting coils with two-phase helium at 4.5 K. Currently the CSS is in the testing phase at CERN in stand-alone mode without the magnet and the transfer line. We have added a “validation unit” housed in the vacuum vessel of the CSS representing the thermo-hydraulic part of the cyclotron magnet. It is equipped with electrical heaters which allow the simulation of the thermal loads of the magnet cryostat. A cooling power of 1.4 W at 4.5 K and 25 W at the thermal shield temperature level has been measured. The data produced confirm the design principle of the CSS which could be validated.

  1. Static and quasi-elastic small angle neutron scattering on biocompatible ionic ferrofluids: magnetic and hydrodynamic interactions

    CERN Document Server

    Gazeau, F; Dubois, E; Perzynski, R

    2003-01-01

    We investigate the structure and dynamics of ionic magnetic fluids (MFs), based on ferrite nanoparticles, dispersed at pH approx 7 either in H sub 2 O or in D sub 2 O. Polarized and non-polarized static small angle neutron scattering (SANS) experiments in zero magnetic field allow us to study both the magnetic and the nuclear contributions to the neutron scattering. The magnetic interparticle attraction is probed separately from the global thermodynamic repulsion and compares well to direct magnetic susceptibility measurements. The magnetic interparticle correlation is in these fluid samples independent of the probed spatial scale. In contrast, a spatial dependence of the interparticle correlation is evidenced at large PHI by the nuclear structure factor. A model of magnetic interaction quantitatively explains the under-field anisotropy of the SANS nuclear contribution. In a quasi-elastic neutron spin-echo experiment, we probe the Brownian dynamics of translation of the nanoparticles in the range 1.3 sup<=...

  2. Magnetism, structure and chemical order in small CoPd clusters: A first-principles study

    KAUST Repository

    Mokkath, Junais Habeeb

    2014-01-01

    The structural, electronic and magnetic properties of small ComPdn (N=m+n=8,m=0-N) nanoalloy clusters are studied in the framework of a generalized-gradient approximation to density-functional theory. The optimized cluster structures have a clear tendency to maximize the number of nearest-neighbor CoCo pairs. The magnetic order is found to be ferromagnetic-like (FM) for all the ground-state structures. Antiferromagnetic-like spin arrangements were found in some low-lying isomers. The average magnetic moment per atom μ̄N increases approximately linearly with Co content. A remarkable enhancement of the local Co moments is observed as a result of Pd doping. This is a consequence of the increase in the number of Co d holes, due to CoPd charge transfer, combined with the reduced local coordination. The influence of spin-orbit interactions on the cluster properties is also discussed. © 2013 Elsevier B.V.

  3. ``Pheudo-cyclotron'' radiation of non-relativistic particles in small-scale magnetic turbulence

    Science.gov (United States)

    Keenan, Brett; Ford, Alex; Medvedev, Mikhail V.

    2014-03-01

    Plasma turbulence in some astrophysical objects (e.g., weakly magnetized collisionless shocks in GRBs and SN) has small-scale magnetic field fluctuations. We study spectral characteristics of radiation produced by particles moving in such turbulence. It was shown earlier that relativistic particles produce jitter radiation, which spectral characteristics are markedly different from synchrotron radiation. Here we study radiation produced by non-relativistic particles. In the case of a homogeneous fields, such radiation is cyclotron and its spectrum consists of just a single harmonic at the cyclotron frequency. However, in the sub-Larmor-scale turbulence, the radiation spectrum is much reacher and reflects statistical properties of the underlying magnetic field. We present both analytical estimates and results of ab initio numerical simulations. We also show that particle propagation in such turbulence is diffusive and evaluate the diffusion coefficient. We demonstrate that the diffusion coefficient correlates with some spectral parameters. These results can be very valuable for remote diagnostics of laboratory and astrophysical plasmas. Supported by grant DOE grant DE-FG02-07ER54940 and NSF grant AST-1209665.

  4. Cine Magnetic Resonance Imaging of the Small Bowel: Comparison of Different Oral Contrast Media

    Energy Technology Data Exchange (ETDEWEB)

    Asbach, P.; Breitwieser, C.; Diederichs, G.; Eisele, S.; Kivelitz, D.; Taupitz, M.; Zeitz, M.; Hamm, B.; Klessen, C. [Charite - Universitatsmedizin Berlin, Charite Campus Mitte, Berlin (Germany). Dept. of Radiology

    2006-11-15

    Purpose: To evaluate several substances regarding small bowel distension and contrast on balanced steady-state free precession (bSSFP) cine magnetic resonance (MR) images. Material and Methods: Luminal contrast was evaluated in 24 volunteers after oral application of two different contrast agent groups leading to either bright lumen (pineapple, blueberry juice) or dark lumen (tap water, orange juice) on T1-weighted images. Bowel distension was evaluated in 30 patients ingesting either methylcellulose or mannitol solution for limiting intestinal absorption. Fifteen patients with duodeno-jejunal intubation served as the control. Quantitative evaluation included measurement of luminal signal intensities and diameters of four bowel segments, qualitative evaluation assessed luminal contrast and distension on a five-point scale. Results: Quantitative and qualitative evaluation of the four contrast agents revealed no significant differences regarding luminal contrast on bSSFP images. Quantitative evaluation revealed significantly lower (P<0.05) small bowel distension for three out of four segments (qualitative evaluation: two out of four segments) for methylcellulose in comparison to the control. Mannitol was found to be equal to the control. Conclusion: Oral ingestion of tap water or orange juice in combination with mannitol is recommended for cine MR imaging of the small bowel regarding luminal contrast and small bowel distension on bSSFP sequences.

  5. Mid-Range Coil Array for Magnetic Resonance Imaging of Small Animals

    Science.gov (United States)

    Solis, S. E.; Tomasi, D.; Rodríguez, A. O.

    2008-08-01

    The vast majority of articles on MRI RF coils over the past two decades have focused on large coils, where sample losses dominate, or on micro-coils, where sample and capacitor losses are negligible. Few have addressed the mid-range coils, seen in the majority of small-animal applications, where all the sources of loss are important, for example, mouse brain and body coils from 125 to 750 MHz. We developed a four-saddle coil array for magnetic resonance imaging of small animals. The saddle coil elements in the array were evenly distributed to cover the rat's head. The coil array was tuned to the resonant frequency of 170 MHz. Due to the close proximity of the coil elements, it was necessary to decouple the coil array using nonmagnetic trimmers and, it was operated in the transceiver mode and quadrature-driven. To test the coil array performance at high field, phantom images were acquired with our saddle coil array and standard pulse sequences on a research-dedicated 4 Tesla scanner. Ex vivo brain images of a rat were also acquired, and proved the feasibility of the scaled version of a saddle coil array and, its compatibility with standard pulse sequences when used in a high field magnetic resonance imager.

  6. Three-dimensional magnetic nanoparticle imaging using small field gradient and multiple pickup coils

    Science.gov (United States)

    Sasayama, Teruyoshi; Tsujita, Yuya; Morishita, Manabu; Muta, Masahiro; Yoshida, Takashi; Enpuku, Keiji

    2017-04-01

    We propose a magnetic particle imaging (MPI) method based on third harmonic signal detection using a small field gradient and multiple pickup coils. First, we developed a system using two pickup coils and performed three-dimensional detection of two magnetic nanoparticle (MNP) samples, which were spaced 15 mm apart. In the experiments, an excitation field strength of 1.6 mT was used at an operating frequency of 3 kHz. A DC gradient field with a typical value of 0.2 T/m was also used to produce the so-called field-free line. A third harmonic signal generated by the MNP samples was detected using the two pickup coils, and the samples were then mechanically scanned to obtain field maps. The field maps were subsequently analyzed using the nonnegative least squares method to obtain three-dimensional position information for the MNP samples. The results show that the positions of the two MNP samples were estimated with good accuracy, despite the small field gradient used. Further improvement in MPI performance will be achieved by increasing the number of pickup coils used.

  7. Magnetic material in mean-field dynamos driven by small scale helical flows

    CERN Document Server

    Giesecke, Andre; Gerbeth, Gunter

    2014-01-01

    We perform kinematic simulations of dynamo action driven by a helical small scale flow of a conducting fluid in order to deduce mean-field properties of the combined induction action of small scale eddies. We examine two different flow patterns in the style of the G.O. Roberts flow but with a mean vertical component and with internal fixtures that are modelled by regions with vanishing flow. These fixtures represent either rods that lie in the center of individual eddies, or internal dividing walls that provide a separation of the eddies from each other. The fixtures can be made of magnetic material with a relative permeability larger than one which can alter the dynamo behavior. The investigations are motivated by the widely unknown induction effects of the forced helical flow that is used in the core of liquid sodium cooled fast reactors, and from the key role of soft iron impellers in the von-K\\'arm\\'an-Sodium (VKS) dynamo. For both examined flow configurations the consideration of magnetic material within...

  8. Light-dependent and -independent behavioral effects of extremely low frequency magnetic fields in a land snail are consistent with a parametric resonance mechanism

    Energy Technology Data Exchange (ETDEWEB)

    Prato, F.S.; Thomas, A.W. [Univ. of Western Ontario, London, Ontario (Canada)]|[St. Joseph`s Health Centre, London, Ontario (Canada); Kavaliers, M. [Univ. of Western Ontario, London, Ontario (Canada); Cullen, A.P. [Univ. of Waterloo, Ontario (Canada). School of Optometry

    1997-05-01

    Exposure to extremely low frequency (ELF) magnetic fields has been shown to attenuate endogenous opioid peptide mediated antinociception or analgesia in the terrestrial pulmonate snail, Cepaea nemoralis. Here the authors examine the roles of light in determining this effect and address the mechanisms associated with mediating the effects of the ELF magnetic fields in both the presence and absence of light. Specifically, they consider whether the magnetic field effects involve an indirect induced electric current mechanism or a direct effect such as a parametric resonance mechanism (PRM). They exposed snails in both the presence and absence of light at three different frequencies (30, 60, and 120 Hz) with static field values (B{sub DC}) and ELF magnetic field amplitude (peak) and direction (B{sub AC}) set according to the predictions of the PRM for Ca{sup 2+}. Analgesia was induced in snails by injecting them with an enkephalinase inhibitor, which augments endogenous opioid (enkephalin) activity. They found that the magnetic field exposure reduced this opioid-induced analgesia significantly more if the exposure occurred in the presence rather than the absence of light. However, the percentage reduction in analgesia in both the presence and absence of light was not dependent on the ELF frequency. This finding suggests that in both the presence and the absence of light the effect of the ELF magnetic field was mediated by a direct magnetic field detection mechanism such as the PRM rather than an induced current mechanism.

  9. Levitation force between a small magnet and a superconducting sample of finite size in the Meissner state

    Science.gov (United States)

    Lugo, Jorge; Sosa, Victor

    1999-10-01

    The repulsion force between a cylindrical superconductor in the Meissner state and a small permanent magnet was calculated under the assumption that the superconductor was formed by a continuous array of dipoles distributed in the finite volume of the sample. After summing up the dipole-dipole interactions with the magnet, we obtained analytical expressions for the levitation force as a function of the superconductor-magnet distance, radius and thickness of the sample. We analyzed two configurations, with the magnet in a horizontal or vertical orientation.

  10. Magnetic field amplification by small-scale dynamo action: dependence on turbulence models and Reynolds and Prandtl numbers.

    Science.gov (United States)

    Schober, Jennifer; Schleicher, Dominik; Federrath, Christoph; Klessen, Ralf; Banerjee, Robi

    2012-02-01

    The small-scale dynamo is a process by which turbulent kinetic energy is converted into magnetic energy, and thus it is expected to depend crucially on the nature of the turbulence. In this paper, we present a model for the small-scale dynamo that takes into account the slope of the turbulent velocity spectrum v(ℓ)proportional ℓ([symbol see text])V}, where ℓ and v(ℓ) are the size of a turbulent fluctuation and the typical velocity on that scale. The time evolution of the fluctuation component of the magnetic field, i.e., the small-scale field, is described by the Kazantsev equation. We solve this linear differential equation for its eigenvalues with the quantum-mechanical WKB approximation. The validity of this method is estimated as a function of the magnetic Prandtl number Pm. We calculate the minimal magnetic Reynolds number for dynamo action, Rm_{crit}, using our model of the turbulent velocity correlation function. For Kolmogorov turbulence ([symbol see text] = 1/3), we find that the critical magnetic Reynolds number is Rm(crit) (K) ≈ 110 and for Burgers turbulence ([symbol see text] = 1/2) Rm(crit)(B) ≈ 2700. Furthermore, we derive that the growth rate of the small-scale magnetic field for a general type of turbulence is Γ proportional Re((1-[symbol see text])/(1+[symbol see text])) in the limit of infinite magnetic Prandtl number. For decreasing magnetic Prandtl number (down to Pm >/~ 10), the growth rate of the small-scale dynamo decreases. The details of this drop depend on the WKB approximation, which becomes invalid for a magnetic Prandtl number of about unity.

  11. Magnetic properties of the ammonolysis product of α-Fe powder containing a small amount of aluminum

    Energy Technology Data Exchange (ETDEWEB)

    Tsugawa, Yuta; Maubuchi, Yuji; Motohashi, Teruki; Kikkawa, Shinichi, E-mail: kikkawa@eng.hokudai.ac.jp

    2015-02-15

    Magnetite was prepared containing a small amount of aluminum and its nitride was generated through low temperature ammonolysis following reduction under hydrogen. The nitrided product was determined by XRD to be a mixture of “α″-Fe{sub 16}N{sub 2}” having a slightly deformed crystal structure from α″-Fe{sub 16}N{sub 2} and the residual α-Fe. Magnetic coercivity of the mixture was decreased from the value of 150 mT obtained for the nitride product made without aluminum, due to the precipitation of nonmagnetic amorphous alumina in the low temperature nitrided bcc (Fe{sub 1−x}Al{sub x}) with x≤0.03. The aluminum-doped nitride product in which the “α″-Fe{sub 16}N{sub 2}” fraction was 30 at% exhibited magnetization at 1.5 T of approximately 200 Am{sup 2}kg{sup −1} at room temperature and its magnetic coercivity was 20 mT. - Graphical abstract: Magnetic iron nitride particles were separated by nonmagnetic amorphous γ-alumina. Magnetic coercivity was decreased by reducing the magnetic interaction between the particles. - Highlights: • Magnetic coercivity decreased in α”-Fe{sub 16}N{sub 2} like compound as a soft magnet. • Small amount of Al addition was effective in its preparation. • Magnetic interaction decreased between the “α”-Fe{sub 16}N{sub 2}” particles.

  12. The Superiority of Intraoperative O-arm Navigation-assisted Surgery in Instrumenting Extremely Small Thoracic Pedicles of Adolescent Idiopathic Scoliosis

    Science.gov (United States)

    Liu, Zhen; Jin, Mengran; Qiu, Yong; Yan, Huang; Han, Xiao; Zhu, Zezhang

    2016-01-01

    Abstract To investigate the accuracy of O-arm navigation-assisted screw insertion in extremely small thoracic pedicles and to compare it with free-hand pedicle screw insertion in adolescent idiopathic scoliosis (AIS). A total of 344 pedicle screws were inserted in apical region (defined as 2 vertebrae above and below the apex each) of 46 AIS patients (age range 13–18 years) with O-arm navigation and 712 screws were inserted in 92 AIS patients (age range 11–17 years) with free-hand technique. According to the narrowest diameter orthogonal to the long axis of the pedicle on a trajectory entering the vertebral body on preoperative computed tomography, the pedicles were classified into large (>3 mm) and small (≤3 mm) subgroups. Furthermore, a subset of extremely small pedicles (≤2 mm in the narrowest diameter) was specifically discussed. Screw accuracy was categorized as grade 0: no perforation, grade 1: perforation by less than 2 mm, grade 2: perforation by 2 to 4 mm, grade 3: perforation over 4 mm. In the O-arm group, the mean thoracic pedicle diameters were 2.23 mm (range 0.7–2.9 mm) and 3.48 mm (3.1–7.1 mm) for small and large pedicles, respectively. In the free-hand group, the small and large thoracic pedicle diameters were 2.42 mm (range 0.6–2.9 mm) and 3.75 mm (3.1–6.9 mm), respectively. The overall accuracies of screw insertion in large and small thoracic pedicles (grade 0, 1) were significantly higher in O-arm group (large: 93.8%, 210/224, small: 91.7%, 110/120) than those of free-hand group (large: 84.9%, 353/416, small: 78.4%, 232/296) (P < 0.05). Importantly, the overall accuracy of screw placement in extremely small pedicles was significantly higher in the O-arm group (84.3%, 48/57) compared with 62.7% (79/126) in free-hand group (P < 0.05), and the incidence of medial perforation was significantly lower in O-arm group (11.1%, 1/9) compared with 17.0% (8/47) in free-hand group (P < 0.05). The O

  13. Magnetic material in mean-field dynamos driven by small scale helical flows

    Science.gov (United States)

    Giesecke, A.; Stefani, F.; Gerbeth, G.

    2014-07-01

    We perform kinematic simulations of dynamo action driven by a helical small scale flow of a conducting fluid in order to deduce mean-field properties of the combined induction action of small scale eddies. We examine two different flow patterns in the style of the G O Roberts flow but with a mean vertical component and with internal fixtures that are modelled by regions with vanishing flow. These fixtures represent either rods that lie in the center of individual eddies, or internal dividing walls that provide a separation of the eddies from each other. The fixtures can be made of magnetic material with a relative permeability larger than one which can alter the dynamo behavior. The investigations are motivated by the widely unknown induction effects of the forced helical flow that is used in the core of liquid sodium cooled fast reactors, and from the key role of soft iron impellers in the von-Kármán-sodium dynamo. For both examined flow configurations the consideration of magnetic material within the fluid flow causes a reduction of the critical magnetic Reynolds number of up to 25%. The development of the growth-rate in the limit of the largest achievable permeabilities suggests no further significant reduction for even larger values of the permeability. In order to study the dynamo behavior of systems that consist of tens of thousands of helical cells we resort to the mean-field dynamo theory (Krause and Rädler 1980 Mean-field Magnetohydrodynamics and Dynamo Theory (Oxford: Pergamon)) in which the action of the small scale flow is parameterized in terms of an α- and β-effect. We compute the relevant elements of the α- and the β-tensor using the so called testfield method. We find a reasonable agreement between the fully resolved models and the corresponding mean-field models for wall or rod materials in the considered range 1\\leqslant {{\\mu }_{r}}\\leqslant 20. Our results may be used for the development of global large scale models with recirculation

  14. Exposure assessment of arc welders to extremely low frequency magnetic field: its relationship with the secretion of paratormone hormone and mood states

    Directory of Open Access Journals (Sweden)

    Roohalah Hajizadeh

    2016-09-01

    Full Text Available Introduction: Nowadays, exposure to extremely low frequency (ELF magnetic field has been interested in many studies due to possible effects on human physical-mental health. Therefore, this study aimed to assess arc welders’ exposure to extremely low frequency magnetic field and to determine its relationship with the secretion of paratormone (PTH hormone and mood states. Material and Method: The present study has been conducted among 35 healthy production workers (as exposed group and 35 healthy administrative personnel (as unexposed group. After checking the work activities of participants according to the guide recommended by the National Institute for Occupational Safety and Health (NIOSH, ELF magnetic fields were measured using an ELF measurement device in the regions including trunk, head, and neck. The plasma levels of PTH hormone of both groups were evaluated by the Electrochemiluminescence method. Stress-Arousal Checklist (SACL was used to assess the mode states of subjects in both groups. The collected data were analyzed by SPSS software version 16. Result: There was a significant difference between the exposed and unexposed groups with respect to the exposure level to ELF magnetic fields (P-value<0.0001. Mean PTH hormone level in exposed group (34.54 pg/ml was lower than unexposed ones (37 pg/ml, however these mean values weren’t significantly different (P-value=0.67. Score of “stress” subscale related to the “pleasure” and score of “arousal” subscale  related to the “activities and alertness” in the unexposed group were significantly higher than those in exposed group (p<0.0001. Regarding the relationship between exposure level to ELF electromagnetic field and scores of  stress, arousal, and PTH hormone level in the two groups, it should be stated that only a significant and positive association was found between the average exposure to ELF magnetic fields and PTH levels in the exposed group (P-value<0.009, r=0

  15. Relationships between Fluid Vorticity, Kinetic Helicity, and Magnetic Field on Small-scales (Quiet-Network) on the Sun

    Science.gov (United States)

    Sangeetha, C. R.; Rajaguru, S. P.

    2016-06-01

    We derive horizontal fluid motions on the solar surface over large areas covering the quiet-Sun magnetic network from local correlation tracking of convective granules imaged in continuum intensity and Doppler velocity by the Helioseismic and Magnetic Imager (HMI) on board the Solar Dynamics Observatory. From these we calculate the horizontal divergence, the vertical component of vorticity, and the kinetic helicity of fluid motions. We study the correlations between fluid divergence and vorticity, and between vorticity (kinetic helicity) and the magnetic field. We find that the vorticity (kinetic helicity) around small-scale fields exhibits a hemispherical pattern (in sign) similar to that followed by the magnetic helicity of large-scale active regions (containing sunspots). We identify this pattern to be a result of the Coriolis force acting on supergranular-scale flows (both the outflows and inflows), consistent with earlier studies using local helioseismology. Furthermore, we show that the magnetic fields cause transfer of vorticity from supergranular inflow regions to outflow regions, and that they tend to suppress the vortical motions around them when magnetic flux densities exceed about 300 G (from HMI). We also show that such an action of the magnetic fields leads to marked changes in the correlations between fluid divergence and vorticity. These results are speculated to be of importance to local dynamo action (if present) and to the dynamical evolution of magnetic helicity at the small-scale.

  16. 极低频磁场与癌症%Extremely low-frequency magnetic fields and cancers

    Institute of Scientific and Technical Information of China (English)

    王学斌; 刘凤莲

    2007-01-01

    OBJECTIVE: All the people in modern world are exposed to the industrial frequency magnetism (extremeiy low-frequency magnetic fields, ELFMF). There are important academic and practical significance to understand the influence of ELFMF on human diseases.DATA SOURCES: A computer-based online search was conducted in HighWire database for English literatures about the relation between ELFMF and human cancers from January 1991 to March 2006 by using the key words of "extremely low frequency magnetic fields, cancer".STUDY SELECTION: All the collected literatures were screened. Inclusion criteria: ① To browse the abstracts of the literatures to examine primitively, and select the articles experimented with the cytological, molecular biological and epidemiological methods. ② Choosing the separate articles by studying with different animals but having got the same results.③ Comparing and analyzing the original and reviewed articles about the relations between ELFMF and cancers.DATA EXTRACTION: A total 90 original and 4 reviewed literatures about ELFMF and cancers were collected and 29 and 4 papers were accordance with the criteria, respectively. In the 47 eliminated articles, 32 of them were unrelated or repetitive to our topic, 5 of them were published earlier or the conclusions were ambiguous, and other 10 of them used only the epidemiological methods.DATA SYNTHESIS : ① For a long time, the question whether 50/60 Hz ELFMF has the carcinogenic effects has been disputed in epidemiology and cytology. ② Majority statistical results in epidemiology showed that the crowds exposed to ELFMF for long or frequent time had an higher ratios suffering cancers than the normal, thereinto, the dangerousness such as leucocythemia, brain cancer and breast cancer is especially high. ③ However, the observation in cytology indicated that the normal cultural cells exposed to ELFMF had not increased the cell divisions or appeared cancer signals, and even in some reports, ELFMF may

  17. X-Ray and Extreme Ultraviolet Emission from Small-Sized Kr Clusters Irradiated by 150-fs Laser Pulses

    Institute of Scientific and Technical Information of China (English)

    王骐; 程元丽; 赵永蓬; 夏元钦; 陈建新; 肖亦凡

    2003-01-01

    x-ray and extreme ultraviolet (EUV) emission from Kr clusters irradiated by 150-fs laser pulses at the peak laser intensity of 5×1015W/cm2 was experimentally investigated. Strong transitions (10nm-13nm) from Kr X and Kr 1X were observed and some spectral lines from Kr ⅩⅢ and Kr ⅩⅣ, which have been predicted to be not produced by optical-field-ionization at the laser intensity used, also appeared. The laser energy absorption and the intensity of x-ray emission started to grow remarkably above the backing pressure of 0.5 MPa and to decrease at the backing pressure of 3 MPa. It is suggested that an optimum backing pressure may exist for Kr clusters heated by 150 fs laser pulses at a certain laser intensity to produce x-ray emission.

  18. Small plastic piston-cylinder cell for pulsed magnetic field studies at cryogenic temperatures

    Science.gov (United States)

    Coniglio, William A.; Graf, David E.; Tozer, Stanley W.

    2013-06-01

    A plastic piston-cylinder cell based on a thick wall test-tube has been designed for pulsed magnetic field studies. The small 12.7 mm diameter and overall height of 19.3 mm allow the cell to freely rotate in a cryostat with a diameter of 21.5 mm. Electrical leads, coax cable or microstrip transmission lines can be introduced into the pressure chamber for a variety of measurements such as electrical transport, de Haas-van Alphen, Shubnikov-de Haas and Hall effect. A fiber optic has been introduced for the purpose of calibrating the pressure via a ruby manometer. The fiber optic opens up additional experimental techniques such as photoluminescence, photoconductivity and, with use of a special fiber with a Bragg grating, magnetostriction and thermal expansion. Maximum pressures of 0.35 GPa at room temperature have been obtained.

  19. Fast magnetic reconnection supported by sporadic small-scale Petschek-type shocks

    Energy Technology Data Exchange (ETDEWEB)

    Shibayama, Takuya, E-mail: shibayama@stelab.nagoya-u.ac.jp; Nakabou, Takashi [Institute for Space-Earth Environmental Research, Nagoya University, Furo-cho, Chikusa-ku, Nagoya, Aichi 464-8601 (Japan); Kusano, Kanya [Institute for Space-Earth Environmental Research, Nagoya University, Furo-cho, Chikusa-ku, Nagoya, Aichi 464-8601 (Japan); Japan Agency for Marine-Earth Science and Technology (JAMSTEC), Kanazawa-ku, Yokohama, Kanagawa 236-0001 (Japan); Miyoshi, Takahiro [Department of Physical Science, Graduate School of Science, Hiroshima University, Higashi-Hiroshima 739-8526 (Japan); Vekstein, Grigory [Jodrell Bank Centre for Astrophysics, University of Manchester, Manchester M13 9PL (United Kingdom)

    2015-10-15

    Standard magnetohydrodynamic (MHD) theory predicts reconnection rate that is far too slow to account for a wide variety of reconnection events observed in space and laboratory plasmas. Therefore, it was commonly accepted that some non-MHD (kinetic) effects play a crucial role in fast reconnection. A recently renewed interest in simple MHD models is associated with the so-called plasmoid instability of reconnecting current sheets. Although it is now evident that this effect can significantly enhance the rate of reconnection, many details of the underlying multiple-plasmoid process still remain controversial. Here, we report results of a high-resolution computer simulation which demonstrate that fast albeit intermittent magnetic reconnection is sustained by numerous small-scale Petschek-type shocks spontaneously formed in the current sheet due to its plasmoid instability.

  20. Design of permanent magnet eddy current brake for a small scaled electromagnetic launch model

    Science.gov (United States)

    Zhou, Shigui; Yu, Haitao; Hu, Minqiang; Huang, Lei

    2012-04-01

    A variable pole-pitch double-sided permanent magnet (PM) linear eddy current brake (LECB) is proposed for a small scaled electromagnetic launch model. A two-dimensional (2D) analytical steady state model is presented for the double-sided PM-LECB, and the expression for the braking force is derived. Based on the analytical model, the material and eddy current skin effect of the conducting plate are analyzed. Moreover, a variable pole-pitch double-sided PM-LECB is proposed for the effective braking of the moving plate. In addition, the braking force is predicted by finite element (FE) analysis, and the simulated results are in good agreement with the analytical model. Finally, a prototype is presented to test the braking profile for validation of the proposed design.

  1. Experiments on the magnetic coupling in a small scale counter rotating marine current turbine

    Science.gov (United States)

    Kim, I. C.; Lee, N. J.; Wata, J.; Hyun, B. S.; Lee, Y. H.

    2016-05-01

    Modern economies are dependent on energy consumption to ensure growth or sustainable development. Renewable energy sources provide a source of energy that can provide energy security and is renewable. Tidal energy is more predictable than other sources or renewable energy like the sun or wind. Horizontal axis marine current turbines are currently the most advanced and commercially feasible option for tidal current convertors. A dual rotor turbine is theoretically able to produce more power than a single rotor turbine at the same fluid velocity. Previous experiments for a counter rotating dual rotor horizontal axis marine current turbine used a mechanical oil seal coupling that caused mechanical losses when water entered through small gaps at the shaft. A new magnetic coupling assembly eliminates the need for a shaft to connect physically with the internal mechanisms and is water tight. This reduces mechanical losses in the system and the effect on the dual rotor performance is presented in this paper.

  2. Measurement of the magnetic field of small magnets with a smartphone: a very economical laboratory practice for introductory physics courses

    Science.gov (United States)

    Arribas, Enrique; Escobar, Isabel; Suarez, Carmen P.; Najera, Alberto; Beléndez, Augusto

    2015-11-01

    In this work, we propose an inexpensive laboratory practice for an introductory physics course laboratory for any grade of science and engineering study. This practice was very well received by our students, where a smartphone (iOS, Android, or Windows) is used together with mini magnets (similar to those used on refrigerator doors), a 20 cm long school rule, a paper, and a free application (app) that needs to be downloaded and installed that measures magnetic fields using the smartphone’s magnetic field sensor or magnetometer. The apps we have used are: Magnetometer (iOS), Magnetometer Metal Detector, and Physics Toolbox Magnetometer (Android). Nothing else is needed. Cost of this practice: free. The main purpose of the practice is that students determine the dependence of the component x of the magnetic field produced by different magnets (including ring magnets and sphere magnets). We obtained that the dependency of the magnetic field with the distance is of the form x-3, in total agreement with the theoretical analysis. The secondary objective is to apply the technique of least squares fit to obtain this exponent and the magnetic moment of the magnets, with the corresponding absolute error.

  3. Direct Observations of Magnetic Reconnection Outflow and CME Triggering in a Small Erupting Solar Prominence

    CERN Document Server

    Reeves, Katharine K; Tian, Hui

    2015-01-01

    We examine a small prominence eruption that occurred on 2014 May 1 at 01:35 UT and was observed by the Interface Region Imaging Spectrometer (IRIS) and the Atmospheric Imaging Assembly (AIA) on the Solar Dynamics Observatory (SDO). Pre- and post-eruption images were taken by the X-Ray Telescope (XRT) on Hinode. Pre-eruption, a dome-like structure exists above the prominence, as demarcated by coronal rain. As the eruption progresses, we find evidence for reconnection between the prominence magnetic field and the overlying field. Fast flows are seen in AIA and IRIS, indicating reconnection outflows. Plane-of-sky flows of ~300 km s$^{-1}$ are observed in the AIA 171 A channel along a potentially reconnected field line. IRIS detects intermittent fast line-of-sight flows of ~200 km s$^{-1}$ coincident with the AIA flows. Differential emission measure calculations show heating at the origin of the fast flows. Post-eruption XRT images show hot loops probably due to reconfiguration of magnetic fields during the erupt...

  4. Demonstration of variable speed permanent magnet generator at small, low-head hydro site

    Energy Technology Data Exchange (ETDEWEB)

    Brown Kinloch, David [Shaker Landing Hydro Associates, Inc., Louisville, KY (United States)

    2015-12-18

    Small hydro developers face a limited set of bad choices when choosing a generator for a small low-head hydro site. Direct drive synchronous generators are expensive and technically complex to install. Simpler induction generators are higher speed, requiring a speed increaser, which results in inefficiencies and maintenance problems. In addition, both induction and synchronous generators turn at a fixed speed, causing the turbine to run off its peak efficiency curve whenever the available head is different than the designed optimum head.The solution to these problems is the variable speed Permanent Magnet Generators (PMG). At the Weisenberger Mill in Midway, KY, a variable speed Permanent Magnet Generator has been installed and demonstrated. This new PMG system replaced an existing induction generator that had a HTD belt drive speed increaser system. Data was taken from the old generator before it was removed and compared to data collected after the PMG system was installed. The new variable speed PMG system is calculated to produce over 96% more energy than the old induction generator system during an average year. This significant increase was primarily due to the PMG generator operating at the correct speed at the maximum head, and the ability for the PMG generator to reduce its speed to lower optimum speeds as the stream flow increased and the net head decreased.This demonstration showed the importance of being able to adjust the speed of fixed blade turbines. All fixed blade turbines with varying net heads could achieve higher efficiencies if the speed can be matched to the optimum speed as the head changes. In addition, this demonstration showed that there are many potential efficiencies that could be realized with variable speed technology at hydro sites where mismatched turbine and generator speeds result in lower power output, even at maximum head. Funding for this project came from the US Dept. of Energy, through Award Number DE-EE0005429.

  5. A Miniaturized Magnetic Induction Sensor Using Geomagnetism for Turn Count of Small-Caliber Ammunition

    Directory of Open Access Journals (Sweden)

    Jong-Soo Oh

    2006-07-01

    Full Text Available This paper presents a miniaturized magnetic induction sensor (MMIS, wheregeomagnetism and high rpm rotation of ammunition are used to detect the turn number ofthe ammunition for applications to small-caliber turn-counting fuzes. The MMIS, composedof cores and a coil, has a robust structure without moving parts to increase the shocksurvivability in a gunfire environment of ~30,000 g’s. The MMIS is designed and fabricatedon the basis of the simulation results of an electromagnetic analysis tool, Maxwell® 3D. Inthe experimental study, static MMIS test using a solenoid-coil apparatus and dynamicMMIS test (firing test have been made. The present MMIS has shown that an inductionvoltage of 6.5 mVp-p is generated at a magnetic flux density of 0.05 mT and a rotationalvelocity of 30,000 rpm. From the measured signal, MMIS has shown a signal-to-noise ratioof 44.0 dB, a nonlinearity of 0.59%, a frequency-normalized sensitivity of 0.256±0.010V/T·Hz and a drift of 0.27% in the temperature range of -30~ 43°C. Firing test has shownthat the MMIS can be used as a turn-counting sensor for small-caliber ammunition,verifying the shock survivability of the MMIS in a high-g environment.

  6. Small population size and extremely low levels of genetic diversity in island populations of the platypus, Ornithorhynchus anatinus.

    Science.gov (United States)

    Furlan, Elise; Stoklosa, J; Griffiths, J; Gust, N; Ellis, R; Huggins, R M; Weeks, A R

    2012-04-01

    Genetic diversity generally underpins population resilience and persistence. Reductions in population size and absence of gene flow can lead to reductions in genetic diversity, reproductive fitness, and a limited ability to adapt to environmental change increasing the risk of extinction. Island populations are typically small and isolated, and as a result, inbreeding and reduced genetic diversity elevate their extinction risk. Two island populations of the platypus, Ornithorhynchus anatinus, exist; a naturally occurring population on King Island in Bass Strait and a recently introduced population on Kangaroo Island off the coast of South Australia. Here we assessed the genetic diversity within these two island populations and contrasted these patterns with genetic diversity estimates in areas from which the populations are likely to have been founded. On Kangaroo Island, we also modeled live capture data to determine estimates of population size. Levels of genetic diversity in King Island platypuses are perilously low, with eight of 13 microsatellite loci fixed, likely reflecting their small population size and prolonged isolation. Estimates of heterozygosity detected by microsatellites (H(E)= 0.032) are among the lowest level of genetic diversity recorded by this method in a naturally outbreeding vertebrate population. In contrast, estimates of genetic diversity on Kangaroo Island are somewhat higher. However, estimates of small population size and the limited founders combined with genetic isolation are likely to lead to further losses of genetic diversity through time for the Kangaroo Island platypus population. Implications for the future of these and similarly isolated or genetically depauperate populations are discussed.

  7. Development of Technique to Detect and Classify Small-Scale Magnetic Flux Cancellation and Rapid Blueshifted Excursions

    CERN Document Server

    Chen, Xin; Lamb, Derek A; Jing, Ju; Liu, Chang; Liu, Rui; Park, Sung-Hong; Wang, Haimin

    2015-01-01

    We present a set of tools for detecting small-scale solar magnetic cancellations and the disk counterpart of type II spicules (the so-called Rapid Blueshifted Excursions (RBEs)), using line-of-sight photospheric magnetograms and chromospheric spectroscopic observations, respectively. For tracking magnetic cancellation, we improve the Southwest Automatic Magnetic Identification Suite (SWAMIS) so that it is able to detect certain obscure cancellations that can be easily missed. For detecting RBEs, we use a normalized reference profile to reduce false-positive detections caused by the non-uniform background and seeing condition. Similar to the magnetic feature tracking in SWAMIS, we apply a dual-threshold method to enhance the accuracy of RBE detection. These tools are employed to analyze our coordinated observations using the Interferometric BIdimensional Spectrometer at Dunn Solar Telescope (DST) of the National Solar Observatory (NSO) and Hinode. We present the statistical properties of magnetic cancellations...

  8. Relationships between fluid vorticity, kinetic helicity and magnetic field at the small-scale (quiet-network) on the Sun

    CERN Document Server

    Sangeetha, C R

    2016-01-01

    We derive horizontal fluid motions on the solar surface over large areas covering the quiet-Sun magnetic network from local correlation tracking of convective granules imaged in continuum intensity and Doppler velocity by the Helioseismic and Magnetic Imager (HMI) onboard the Solar Dynamics Observatory (SDO). From these we calculate horizontal divergence, vertical component of vorticity, and kinetic helicity of fluid motions. We study the correlations between fluid divergence and vorticity, and that between vorticity (kinetic helicity) and magnetic field. We find that the vorticity (kinetic helicity) around small-scale fields exhibits a hemispherical pattern (in sign) similar to that followed by the magnetic helicity of large-scale active regions (containing sunspots). We identify this pattern to be a result of the Coriolis force acting on supergranular-scale flows (both the outflows and inflows), and is consistent with earlier studies using local helioseismology. Further, we show that the magnetic fields cau...

  9. Advancing Cardiovascular, Neurovascular, and Renal Magnetic Resonance Imaging in Small Rodents Using Cryogenic Radiofrequency Coil Technology.

    Science.gov (United States)

    Niendorf, Thoralf; Pohlmann, Andreas; Reimann, Henning M; Waiczies, Helmar; Peper, Eva; Huelnhagen, Till; Seeliger, Erdmann; Schreiber, Adrian; Kettritz, Ralph; Strobel, Klaus; Ku, Min-Chi; Waiczies, Sonia

    2015-01-01

    Research in pathologies of the brain, heart and kidney have gained immensely from the plethora of studies that have helped shape new methods in magnetic resonance (MR) for characterizing preclinical disease models. Methodical probing into preclinical animal models by MR is invaluable since it allows a careful interpretation and extrapolation of data derived from these models to human disease. In this review we will focus on the applications of cryogenic radiofrequency (RF) coils in small animal MR as a means of boosting image quality (e.g., by supporting MR microscopy) and making data acquisition more efficient (e.g., by reducing measuring time); both being important constituents for thorough investigational studies on animal models of disease. This review attempts to make the (bio)medical imaging, molecular medicine, and pharmaceutical communities aware of this productive ferment and its outstanding significance for anatomical and functional MR in small rodents. The goal is to inspire a more intense interdisciplinary collaboration across the fields to further advance and progress non-invasive MR methods that ultimately support thorough (patho)physiological characterization of animal disease models. In this review, current and potential future applications for the RF coil technology in cardiovascular, neurovascular, and renal disease will be discussed.

  10. Magnetic resonance enterography for the evaluation of the deep small intestine in Crohn's disease.

    Science.gov (United States)

    Ohtsuka, Kazuo; Takenaka, Kento; Kitazume, Yoshio; Fujii, Toshimitsu; Matsuoka, Katsuyoshi; Kimura, Maiko; Nagaishi, Takashi; Watanabe, Mamoru

    2016-04-01

    For the control of Crohn's disease (CD) a thorough assessment of the small intestine is essential; several modalities may be utilized, with cross-sectional imaging being important. Magnetic resonance (MR) enterography, i.e., MRE is recommended as a modality with the highest accuracy for CD lesions. MRE and MR enteroclysis are the two methods performed following distension of the small intestine. MRE has sensitivity and specificity comparable to computed tomography enterography (CTE); although images obtained using MRE are less clear compared with CTE, MRE does not expose the patient to radiation and is superior for soft-tissue contrast. Furthermore, it can assess not only static but also dynamic and functional imaging and reveals signs of CD, such as abscess, comb sign, fat edema, fistula, lymph node enhancement, less motility, mucosal lesions, stricture, and wall enhancement. Several indices of inflammatory changes and intestinal damage have been proposed for objective evaluation. Recently, diffusion-weighted imaging has been proposed, which does not need bowel preparation and contrast enhancement. Comprehension of the characteristics of MRE and other modalities is important for better management of CD.

  11. Advancing Cardiovascular, Neurovascular and Renal Magnetic Resonance Imaging in Small Rodents Using Cryogenic Radiofrequency Coil Technology

    Directory of Open Access Journals (Sweden)

    Thoralf eNiendorf

    2015-11-01

    Full Text Available Research in pathologies of the brain, heart and kidney have gained immensely from the plethora of studies that have helped shape new methods in magnetic resonance (MR for characterizing preclinical disease models. Methodical probing into preclinical animal models by MR is invaluable since it allows a careful interpretation and extrapolation of data derived from these models to human disease. In this review we will focus on the applications of cryogenic radiofrequency (RF coils in small animal MR as a means of boosting image quality (e.g. by supporting MR microscopy and making data acquisition more efficient (e.g. by reducing measuring time; both being important constituents for thorough investigational studies on animal models of disease. This review attempts to make the (biomedical imaging, molecular medicine and pharmaceutical communities aware of this productive ferment and its outstanding significance for anatomical and functional MR in small rodents. The goal is to inspire a more intense interdisciplinary collaboration across the fields to further advance and progress non-invasive MR methods that ultimately support thorough (pathophysiological characterization of animal disease models. In this review, current and potential future applications for the RF coil technology in cardiovascular, neurovascular and renal disease will be discussed.

  12. Advancing Cardiovascular, Neurovascular, and Renal Magnetic Resonance Imaging in Small Rodents Using Cryogenic Radiofrequency Coil Technology

    Science.gov (United States)

    Niendorf, Thoralf; Pohlmann, Andreas; Reimann, Henning M.; Waiczies, Helmar; Peper, Eva; Huelnhagen, Till; Seeliger, Erdmann; Schreiber, Adrian; Kettritz, Ralph; Strobel, Klaus; Ku, Min-Chi; Waiczies, Sonia

    2015-01-01

    Research in pathologies of the brain, heart and kidney have gained immensely from the plethora of studies that have helped shape new methods in magnetic resonance (MR) for characterizing preclinical disease models. Methodical probing into preclinical animal models by MR is invaluable since it allows a careful interpretation and extrapolation of data derived from these models to human disease. In this review we will focus on the applications of cryogenic radiofrequency (RF) coils in small animal MR as a means of boosting image quality (e.g., by supporting MR microscopy) and making data acquisition more efficient (e.g., by reducing measuring time); both being important constituents for thorough investigational studies on animal models of disease. This review attempts to make the (bio)medical imaging, molecular medicine, and pharmaceutical communities aware of this productive ferment and its outstanding significance for anatomical and functional MR in small rodents. The goal is to inspire a more intense interdisciplinary collaboration across the fields to further advance and progress non-invasive MR methods that ultimately support thorough (patho)physiological characterization of animal disease models. In this review, current and potential future applications for the RF coil technology in cardiovascular, neurovascular, and renal disease will be discussed. PMID:26617515

  13. Low-cost, low-field dedicated extremity magnetic resonance imaging in early rheumatoid arthritis: a 1-year follow-up study

    DEFF Research Database (Denmark)

    Lindegaard, H.M.; Vallø, J.; Hørslev-Petersen, K.;

    2006-01-01

    OBJECTIVE: To study the ability of low-cost low-field dedicated extremity magnetic resonance imaging (E-MRI) to assess and predict erosive joint damage in the wrist and metacarpophalangeal (MCP) joints of patients with early rheumatoid arthritis. METHODS: 24 previously untreated patients with rhe......OBJECTIVE: To study the ability of low-cost low-field dedicated extremity magnetic resonance imaging (E-MRI) to assess and predict erosive joint damage in the wrist and metacarpophalangeal (MCP) joints of patients with early rheumatoid arthritis. METHODS: 24 previously untreated patients...... with rheumatoid arthritis with joint symptoms for treatment with conventional clinical or biochemical examinations, x rays of both hands and wrists, and E-MRI of the dominant wrist and MCP joints. RESULTS: At baseline, all...... patients showed magnetic resonance imaging (MRI) synovitis, and MRI erosions were detected in 21 bones (10 patients). 6 (29%) of these, distributed among two patients, were seen on x ray. One x ray erosion was not detected by MRI. At 1 year, MRI and x ray detected 15 and 8 new erosions, respectively...

  14. Open-source, small-animal magnetic resonance-guided focused ultrasound system.

    Science.gov (United States)

    Poorman, Megan E; Chaplin, Vandiver L; Wilkens, Ken; Dockery, Mary D; Giorgio, Todd D; Grissom, William A; Caskey, Charles F

    2016-01-01

    MR-guided focused ultrasound or high-intensity focused ultrasound (MRgFUS/MRgHIFU) is a non-invasive therapeutic modality with many potential applications in areas such as cancer therapy, drug delivery, and blood-brain barrier opening. However, the large financial costs involved in developing preclinical MRgFUS systems represent a barrier to research groups interested in developing new techniques and applications. We aim to mitigate these challenges by detailing a validated, open-source preclinical MRgFUS system capable of delivering thermal and mechanical FUS in a quantifiable and repeatable manner under real-time MRI guidance. A hardware and software package was developed that includes closed-loop feedback controlled thermometry code and CAD drawings for a therapy table designed for a preclinical MRI scanner. For thermal treatments, the modular software uses a proportional integral derivative controller to maintain a precise focal temperature rise in the target given input from MR phase images obtained concurrently. The software computes the required voltage output and transmits it to a FUS transducer that is embedded in the delivery table within the magnet bore. The delivery table holds the FUS transducer, a small animal and its monitoring equipment, and a transmit/receive RF coil. The transducer is coupled to the animal via a water bath and is translatable in two dimensions from outside the magnet. The transducer is driven by a waveform generator and amplifier controlled by real-time software in Matlab. MR acoustic radiation force imaging is also implemented to confirm the position of the focus for mechanical and thermal treatments. The system was validated in tissue-mimicking phantoms and in vivo during murine tumor hyperthermia treatments. Sonications were successfully controlled over a range of temperatures and thermal doses for up to 20 min with minimal temperature overshoot. MR thermometry was validated with an optical temperature probe, and focus

  15. The application of the boundary element method in BEM++ to small extreme Chebyshev ice particles and the remote detection of the ice crystal number concentration of small atmospheric ice particles

    Science.gov (United States)

    Baran, Anthony J.; Groth, Samuel P.

    2017-09-01

    The measurement of the shape and size distributions of small atmospheric ice particles (i.e. less than about 100 μm in size) is still an unresolved problem in atmospheric physics. This paper is composed of two parts, each addressing one of these measurements. In the first part, we report on an application of a new open-source electromagnetic boundary element method (BEM) called ;BEM++; to characterise the shape of small ice particles through the simulation of the two-dimensional (2D) light scattering patterns of extreme Chebyshev ice particles. Previous electromagnetic studies of Chebyshev particles have concentrated upon high Chebyshev orders, but with low Chebyshev deformation parameters. Here, we extend such studies by concentrating on the 2D light scattering properties of Chebyshev particles with extreme deformation parameters, up to 0.5, and with Chebyshev orders up to 16, at a size parameter of 15, in a fixed orientation. The results demonstrate the applicability of BEM++ to the study of the electromagnetic scattering properties of extreme particles and the usefulness of measuring the light scattering patterns of particles in 2D to mimic the scattering behaviours of highly irregular particles, such as dendritic atmospheric ice or hazardous biological and/or aerosol particles. In the second part, we demonstrate the potential application of remotely sensed very-high-resolution brightness temperature measurements of optically thin cirrus between wavelengths of about 8.0 and 12.0 μm to resolve the current atmospheric physics issue of determining the number concentration of small ice particles with size less than about 100 μm.

  16. A modelling approach to assess the hydrological response of small Mediterranean catchments to the variability of soil characteristics in a context of extreme events

    Directory of Open Access Journals (Sweden)

    C. Manus

    2008-09-01

    Full Text Available This paper presents a modeling study aiming at quantifying the possible impact of soil characteristics on the hydrological response of small ungauged catchments in a context of extreme events. The study focuses on the September 2002 event in the Gard region (South-Eastern France, which led to catastrophic flash-floods. The proposed modeling approach is able to take into account rainfall variability and soil profiles variability. Its spatial discretization is determined using Digital Elevation Model (DEM and a soil map. The model computes infiltration, ponding and vertical soil water distribution, as well as river discharge. The model is set up without any calibration and the soil parameter specification is based on an existing soil database. To perform the simulations, radar rainfall estimations are used at a 1 km2 and 5 min resolution. To specify the soil hydraulic properties, two types of pedotransfer function (PTF are compared. It is shown that the PTF including information about soil structure reflects better the spatial variability that can be encountered in the field. The study is focused on four small ungauged catchments of less than 10 km2, which experienced casualties. Simulated specific peak discharges are found to be in agreement with estimations from a post-event in situ investigation. Examining the dynamics of simulated infiltration and saturation degrees, two different behaviors are shown which correspond to different runoff production mechanisms that could be encountered within catchments of less than 10 km2. They produce simulated runoff coefficients that evolve in time and highlight the variability of the infiltration capacity of the various soil types. Therefore, we propose a cartography distinguishing between areas prone to saturation excess and areas prone only to infiltration excess mechanisms. The questions raised by this modeling study will be useful to improve field observations, aiming at

  17. How extreme are extremes?

    Science.gov (United States)

    Cucchi, Marco; Petitta, Marcello; Calmanti, Sandro

    2016-04-01

    High temperatures have an impact on the energy balance of any living organism and on the operational capabilities of critical infrastructures. Heat-wave indicators have been mainly developed with the aim of capturing the potential impacts on specific sectors (agriculture, health, wildfires, transport, power generation and distribution). However, the ability to capture the occurrence of extreme temperature events is an essential property of a multi-hazard extreme climate indicator. Aim of this study is to develop a standardized heat-wave indicator, that can be combined with other indices in order to describe multiple hazards in a single indicator. The proposed approach can be used in order to have a quantified indicator of the strenght of a certain extreme. As a matter of fact, extremes are usually distributed in exponential or exponential-exponential functions and it is difficult to quickly asses how strong was an extreme events considering only its magnitude. The proposed approach simplify the quantitative and qualitative communication of extreme magnitude

  18. Stochastic spatial disaggregation of extreme precipitation to validate a Regional Climate Model and to evaluate climate change impacts over a small watershed

    Directory of Open Access Journals (Sweden)

    P. Gagnon

    2013-06-01

    Full Text Available Regional Climate Models (RCMs are valuable tools to evaluate impacts of climate change (CC at regional scale. However, as the size of the area of interest decreases, the ability of a RCM to simulate extreme precipitation events decreases due to the spatial resolution. Thus, it is difficult to evaluate whether a RCM bias on localized extreme precipitation is caused by the spatial resolution or by a misrepresentation of the physical processes in the model. Thereby, it is difficult to trust the CC impact projections for localized extreme precipitation. Stochastic spatial disaggregation models can bring the RCM precipitation data at a finer scale and reduce the bias caused by spatial resolution. In addition, disaggregation models can generate an ensemble of outputs, producing an interval of possible values instead of a unique discrete value. The objective of this work is to evaluate whether a stochastic spatial disaggregation model applied on annual maximum daily precipitation: (i enables the validation of a RCM for a period of reference, and (ii modifies the evaluation of CC impacts over a small area. Three simulations of the Canadian RCM (CRCM covering the period 1961–2099 are used over a small watershed (130 km2 located in southern Québec, Canada. The disaggregation model applied is based on Gibbs sampling and accounts for physical properties of the event (wind speed, wind direction, and convective available potential energy (CAPE, leading to realistic spatial distributions of precipitation. The results indicate that disaggregation has a significant impact on the validation. However it does not provide a precise estimate of the simulation bias because of the difference in resolution between disaggregated values (4 km and observations, and because of the underestimation of the spatial variability by the disaggregation model for the most convective events. Nevertheless, disaggregation permits to determine that the simulations used mostly

  19. Redox magnetohydrodynamic enhancement of stripping voltammetry: toward portable analysis using disposable electrodes, permanent magnets, and small volumes.

    Science.gov (United States)

    Weston, Melissa C; Anderson, Emily C; Arumugam, Prabhu U; Narasimhan, Padhmodhbhava Yoga; Fritsch, Ingrid

    2006-12-01

    The use of redox magnetohydrodynamics (MHD) to enhance the anodic stripping voltammetry (ASV) response of heavy metals has been investigated, with respect to achieving portability: disposable electrodes consisting of screen-printed carbon (SPC) on a low temperature co-fired ceramic (LTCC) substrate, small volumes, and permanent magnets. The analytes tested (Cd(2+), Cu(2+), and Pb(2+)) were codeposited on SPC with Hg(2+) to form a Hg thin film electrode. High concentrations of Fe(3+) were used to produce a high cathodic current which generates a significant Lorentz force in the presence of a magnetic field. This Lorentz force induces solution convection during the deposition step, enhancing the mass transport of analytes to the electrode and increasing their preconcentrated quantity in the mercury thin film. Therefore, larger ASV peaks and improved sensitivities are obtained, compared to analyses performed without a magnet. The effects on ASV signal of varying Hg(2+) concentration (0.10 and 1.0 mM), deposition time (10-600 s), and electrode surface roughness were investigated. In addition, analyses were performed using a real lake water matrix. By using the disposable LTCC-SPC working electrodes in small volumes (150 microL) and with small permanent magnets (0.78 T), peak areas were increased by 75% when compared to the signal obtained in the absence of a magnetic field. A limit of detection of 25 nM for Cd(2+) was observed with only a 1 min preconcentration time.

  20. Magnetic Field Amplification by Small-Scale Dynamo Action: Dependence on Turbulence Models, Reynolds and Prandtl Numbers

    CERN Document Server

    Schober, Jennifer; Federrath, Christoph; Klessen, Ralf; Banerjee, Robi

    2011-01-01

    The small-scale dynamo is a process by which turbulent kinetic energy is converted into magnetic energy, and thus is expected to depend crucially on the nature of turbulence. In this work, we present a model for the small-scale dynamo that takes into account the slope of the turbulent velocity spectrum v(l) ~ l^theta, where l and v(l) are the size of a turbulent fluctuation and the typical velocity on that scale. The time evolution of the fluctuation component of the magnetic field, i.e., the small-scale field, is described by the Kazantsev equation. We solve this linear differential equation for its eigenvalues with the quantum-mechanical WKB-approximation. The validity of this method is estimated as a function of the magnetic Prandtl number Pm. We calculate the minimal magnetic Reynolds number for dynamo action, Rm_crit, using our model of the turbulent velocity correlation function. For Kolmogorov turbulence (theta=1/3), we find that the critical magnetic Reynolds number is approximately 110 and for Burger...

  1. Deciphering Solar Magnetic Activity I: On The Relationship Between The Sunspot Cycle And The Evolution Of Small Magnetic Features

    CERN Document Server

    McIntosh, Scott W; Leamon, Robert J; Davey, Alisdair R; Howe, Rachel; Krista, Larisza D; Malanushenko, Anna V; Cirtain, Jonathan W; Gurman, Joseph B; Thompson, Michael J

    2014-01-01

    Sunspots are a canonical marker of the Sun's internal magnetic field which flips polarity every ~22-years. The principal variation of sunspots, an ~11-year variation in number, modulates the amount of magnetic field that pierces the solar surface and drives significant variations in our Star's radiative, particulate and eruptive output over that period. This paper presents observations from the Solar and Heliospheric Observatory and Solar Dynamics Observatory indicating that the 11-year sunspot variation is intrinsically tied it to the spatio-temporal overlap of the activity bands belonging to the 22-year magnetic activity cycle. Using a systematic analysis of ubiquitous coronal brightpoints, and the magnetic scale on which they appear to form, we show that the landmarks of sunspot cycle 23 can be explained by considering the evolution and interaction of the overlapping activity bands of the longer scale variability.

  2. Deciphering solar magnetic activity. I. On the relationship between the sunspot cycle and the evolution of small magnetic features

    Energy Technology Data Exchange (ETDEWEB)

    McIntosh, Scott W.; Wang, Xin; Markel, Robert S.; Thompson, Michael J. [High Altitude Observatory, National Center for Atmospheric Research, P.O. Box 3000, Boulder, CO 80307 (United States); Leamon, Robert J.; Malanushenko, Anna V. [Department of Physics, Montana State University, Bozeman, MT 59717 (United States); Davey, Alisdair R. [Harvard-Smithsonian Center for Astrophysics, 60 Garden Street, Cambridge, MA 02138 (United States); Howe, Rachel [School of Physics and Astronomy, University of Birmingham, Edgbaston, Birmingham, B15 2TT (United Kingdom); Krista, Larisza D. [Cooperative Institute for Research in Environmental Sciences, University of Colorado, Boulder, CO 80205 (United States); Cirtain, Jonathan W. [Marshall Space Flight Center, Code ZP13, Huntsville, AL 35812 (United States); Gurman, Joseph B.; Pesnell, William D., E-mail: mscott@ucar.edu [Solar Physics Laboratory, NASA Goddard Space Flight Center, Greenbelt, MD 20771 (United States)

    2014-09-01

    Sunspots are a canonical marker of the Sun's internal magnetic field which flips polarity every ∼22 yr. The principal variation of sunspots, an ∼11 yr variation, modulates the amount of the magnetic field that pierces the solar surface and drives significant variations in our star's radiative, particulate, and eruptive output over that period. This paper presents observations from the Solar and Heliospheric Observatory and Solar Dynamics Observatory indicating that the 11 yr sunspot variation is intrinsically tied to the spatio-temporal overlap of the activity bands belonging to the 22 yr magnetic activity cycle. Using a systematic analysis of ubiquitous coronal brightpoints and the magnetic scale on which they appear to form, we show that the landmarks of sunspot cycle 23 can be explained by considering the evolution and interaction of the overlapping activity bands of the longer-scale variability.

  3. Deciphering Solar Magnetic Activity I: On The Relationship Between The Sunspot Cycle And The Evolution Of Small Magnetic Features

    OpenAIRE

    McIntosh, Scott W.; Wang, Xin; Leamon, Robert J.; Howe, Rachel; Krista, Larisza D.; Malanushenko, Anna V.; Cirtain, Jonathan W.; Gurman, Joseph B.; Thompson, Michael J

    2014-01-01

    Sunspots are a canonical marker of the Sun's internal magnetic field which flips polarity every ~22-years. The principal variation of sunspots, an ~11-year variation in number, modulates the amount of magnetic field that pierces the solar surface and drives significant variations in our Star's radiative, particulate and eruptive output over that period. This paper presents observations from the Solar and Heliospheric Observatory and Solar Dynamics Observatory indicating that the 11-year sunsp...

  4. Metastability of the Two-Dimensional Blume-Capel Model with Zero Chemical Potential and Small Magnetic Field

    Science.gov (United States)

    Landim, C.; Lemire, P.

    2016-07-01

    We consider the two-dimensional Blume-Capel model with zero chemical potential and small magnetic field evolving on a large but finite torus. We obtain sharp estimates for the transition time, we characterize the set of critical configurations, and we prove the metastable behavior of the dynamics as the temperature vanishes.

  5. Evidence of nuclear fusion neutrons in an extremely small plasma focus device operating at 0.1 Joules

    Science.gov (United States)

    Soto, Leopoldo; Pavéz, Cristián; Moreno, José; Altamirano, Luis; Huerta, Luis; Barbaglia, Mario; Clausse, Alejandro; Mayer, Roberto E.

    2017-08-01

    We report on D-D fusion neutron emission in a plasma device with an energy input of only 0.1 J, within a range where fusion events have been considered very improbable. The results presented here are the consequence of scaling rules we have derived, thus being the key point to assure the same energy density plasma in smaller devices than in large machines. The Nanofocus (NF)—our device—was designed and constructed at the P4 Lab of the Chilean Nuclear Energy Commission. Two sets of independent measurements, with different instrumentation, were made at two laboratories, in Chile and Argentina. The neutron events observed are 20σ greater than the background. The NF plasma is produced from a pulsed electrical discharge using a submillimetric anode, in a deuterium atmosphere, showing empirically that it is, in fact, possible to heat and compress the plasma. The strong evidence presented here stretches the limits beyond what was expected. A thorough understanding of this could possibly tell us where the theoretical limits actually lie, beyond conjectures. Notwithstanding, a window is thus open for low cost endeavours for basic fusion research. In addition, the development of small, portable, safe nonradioactive neutron sources becomes a feasible issue.

  6. Extreme patterns of variance in small populations: placing limits on human Y-chromosome diversity through time in the Vanuatu Archipelago.

    Science.gov (United States)

    Cox, M

    2007-05-01

    Small populations are dominated by unique patterns of variance, largely characterized by rapid drift of allele frequencies. Although the variance components of genetic datasets have long been recognized, most population genetic studies still treat all sampling locations equally despite differences in sampling and effective population sizes. Because excluding the effects of variance can lead to significant biases in historical reconstruction, variance components should be incorporated explicitly into population genetic analyses. The possible magnitude of variance effects in small populations is illustrated here via a case study of Y-chromosome haplogroup diversity in the Vanuatu Archipelago. Deme-based modelling is used to simulate allele frequencies through time, and conservative confidence bounds are placed on the accumulation of stochastic variance effects, including diachronic genetic drift and contemporary sampling error. When the information content of the dataset has been ascertained, demographic models with parameters falling outside the confidence bounds of the variance components can then be accepted with some statistical confidence. Here I emphasize how aspects of the demographic history of a population can be disentangled from stochastic variance effects, and I illustrate the extreme roles of genetic drift and sampling error for many small human population datasets.

  7. X-ray magnetic circular dichroism and small angle neutron scattering study of thiol capped gold nanoparticles.

    Energy Technology Data Exchange (ETDEWEB)

    de la Venta, J.; Bouzas, V.; Pucci, A.; Laguna-Marco, M. A.; Haskel, D.; Pinel, E. F.; te Velthuis, S. G. E.; Hoffmann, A.; Lal, J.; Bleuel, M.; Ruggeri, G.; de Julian, C.; Garcia, M. A.; Univ. Complutense de Madrid; Inst. de Magnetismo Aplicado UCM; Univ. Pisa; Univ. di Padova

    2009-11-01

    X-ray magnetic circular dichroism (XMCD) and Small Angle Neutron Scattering (SANS) measurements were performed on thiol capped Au nanoparticles (NPs) embedded into polyethylene. An XMCD signal of 0.8 {center_dot} 10{sup -4} was found at the Au L{sub 3} edge of thiol capped Au NPs embedded in a polyethylene matrix for which Superconducting Quantum Interference Device (SQUID) magnetometry yielded a saturation magnetization, M{sub s}, of 0.06 emu/g{sub Au}. SANS measurements showed that the 3.2 nm average-diameter nanoparticles are 28% polydispersed, but no detectable SANS magnetic signal was found with the resolution and sensitivity accessible with the neutron experiment. A comparison with previous experiments carried out on Au NPs and multilayers, yield to different values between XMCD signals and magnetization measured by SQUID magnetometer. We discuss the origin of those differences.

  8. X-ray magnetic circular dichroism and small angle neutron scattering studies of thiol capped gold nanoparticles.

    Energy Technology Data Exchange (ETDEWEB)

    de la Venta, J.; Bouzas, V.; Pucci, A.; Laguna-Marco, M. A.; Haskel, D.; te Velthuis, S. G. E; Hoffmann, A.; Lal, J.; Bleuel, M.; Ruggeri, G.; de Julian Fernandez, C.; Garcia, M. A.; Univ.Complutense de Madrid; Inst. de Magnetismo Aplicado; Univ. of Pisa; Lab. di Magnetismo Molecolare

    2009-01-01

    X-ray magnetic circular dichroism (XMCD) and Small Angle Neutron Scattering (SANS) measurements were performed on thiol capped Au nanoparticles (NPs) embedded into polyethylene. An XMCD signal of 0.8 {center_dot} 10{sup -4} was found at the Au L{sub 3} edge of thiol capped Au NPs embedded in a polyethylene matrix for which Superconducting Quantum Interference Device (SQUID) magnetometry yielded a saturation magnetization, M{sub s}, of 0.06 emu/g{sub Au}. SANS measurements showed that the 3.2 nm average-diameter nanoparticles are 28% polydispersed, but no detectable SANS magnetic signal was found with the resolution and sensitivity accessible with the neutron experiment. A comparison with previous experiments carried out on Au NPs and multilayers, yield to different values between XMCD signals and magnetization measured by SQUID magnetometer. We discuss the origin of those differences.

  9. Magnetic field-dependent shape anisotropy in small patterned films studied using rotating magnetoresistance

    OpenAIRE

    Xiaolong Fan; Hengan Zhou; Jinwei Rao; Xiaobing Zhao; Jing Zhao; Fengzhen Zhang; Desheng Xue

    2015-01-01

    Based on the electric rotating magnetoresistance method, the shape anisotropy of a Co microstrip has been systematically investigated. We find that the shape anisotropy is dependent not only on the shape itself, but also on the magnetization distribution controlled by an applied magnetic field. Together with micro-magnetic simulations, we present a visualized picture of how non-uniform magnetization affects the values and polarities of the anisotropy constants and . From the perspective of po...

  10. Plasma Physics of Extreme Astrophysical Environments

    CERN Document Server

    Uzdensky, Dmitri A

    2014-01-01

    Certain classes of astrophysical objects, namely magnetars and central engines of supernovae and gamma-ray bursts (GRBs), are characterized by extreme physical conditions not encountered elsewhere in the Universe. In particular, they possess magnetic fields that exceed the critical quantum field of 44 teragauss. Figuring out how these complex ultra-magnetized systems work requires understanding various plasma processes, both small-scale kinetic and large-scale magnetohydrodynamic (MHD). However, an ultra-strong magnetic field modifies the underlying physics to such an extent that many relevant plasma-physical problems call for building QED-based relativistic quantum plasma physics. In this review, after describing the extreme astrophysical systems of interest and identifying the key relevant plasma-physical problems, we survey the recent progress in the development of such a theory. We discuss how a super-critical field modifies the properties of vacuum and matter and outline the basic theoretical framework f...

  11. Prospective evaluation of magnetic resonance enterography for the detection of mesenteric small bowel tumours

    Energy Technology Data Exchange (ETDEWEB)

    Amzallag-Bellenger, Elisa; Hoeffel, Christine [Hopital Robert Debre, Department of Radiology, Reims Cedex (France); Soyer, Philippe [Hopital Lariboisiere, Assistance Publique-Hopitaux de Paris, Department of Radiology, Paris (France); Universite Paris-Diderot, Sorbonne Paris Cite, Paris (France); Barbe, Coralie [Hopital Robert Debre, Department of Statistics, Reims Cedex (France); Diebold, Marie-Daniele [Hopital Robert Debre, Department of Pathology, Reims Cedex (France); Cadiot, Guillaume [Hopital Robert Debre, Department of Gastroenterology, Reims Cedex (France)

    2013-07-15

    To prospectively evaluate magnetic resonance (MR) enterography for detecting mesenteric small-bowel tumours (MSBTs) and assess the added value of gadolinium-chelate injection. Over a 2-year period MR enterography examinations of 75 patients (33 men, 42 women; mean age, 53.8 years; range, 19-85) with suspected MSBT were blindly analysed by two readers for the presence of MSBT. Sensitivities, specificities, predictive positive values (PPVs), negative predictive values (NPVs) and accuracies of MR enterography for the detection of MSBT were calculated on per-patient and per-lesion bases. The McNemar test was used to compare sensitivities and specificities of the unenhanced and gadolinium-enhanced sets of MR enterographies. Thirty-seven MSBTs were pathologically confirmed in 26 patients. The mean tolerance score of the examinations was 0.7. On a per-patient basis, sensitivity, specificity, PPV, NPV and accuracy for detection of MSBT were 96 % [95 % CI, 89-100 %], 96 % [90-100 %], 93 % [83-100 %], 98 % [94-100 %] and 96 % [92-100 %], respectively. On a per-lesion basis, sensitivity and PPV were 70 % [56-85 %] and 93 % [83-100 %], respectively. Gadolinium injection yielded higher sensitivities on both bases (P = 0.008). MR enterography is an accurate and well-tolerated imaging modality for detecting MSBT. Intravenous administration of gadolinium-chelate improves sensitivity for MSBT detection. (orig.)

  12. Increasing 14N NQR signal by 1H-14N level crossing with small magnetic fields.

    Science.gov (United States)

    Thurber, Kent R; Sauer, Karen L; Buess, Michael L; Klug, Christopher A; Miller, Joel B

    2005-11-01

    NQR detection of materials, such as TNT, is hindered by the low signal-to-noise ratio at low NQR frequencies. Sweeping small (0-26 mT) magnetic fields to shift the (1)H NMR frequency relative to the (14)N NQR frequencies can provide a significant increase of the (14)N NQR signal-to-noise ratio. Three effects of (1)H-(14)N level crossing are demonstrated in diglycine hydrochloride and TNT. These effects are (1) transferring (1)H polarization to one or more of the (14)N transitions, including the use of an adiabatic flip of the (1)H polarization during the field sweep, (2) shortening the effective (14)N T(1) by the interaction of (1)H with the (14)N transitions, (3) "level transfer" effect where the third (14)N (spin 1) energy level or other (14)N sites with different NQR frequency are used as a reservoir of polarization which is transferred to the measured (14)N transition by the (1)H. The (14)N NQR signal-to-noise ratio can be increased by a factor of 2.5 for one (14)N site in diglycine hydrochloride (and 2.2 in TNT), even though the maximum (1)H frequency used in this work, 111 6 kHz, is only 30% larger than the measured (14)N frequencies (834 kHz for diglycine hydrochloride and 843 kHz for TNT).

  13. Magnetic hysteresis in small-grained CoxPd1-x nanowire arrays

    Science.gov (United States)

    Viqueira, M. S.; Pozo-López, G.; Urreta, S. E.; Condó, A. M.; Cornejo, D. R.; Fabietti, L. M.

    2015-11-01

    Co-Pd nanowires with small grain size are fabricated by AC electrodeposition into hexagonally ordered alumina pores, 20-35 nm in diameter and about 1 μm long. The effects of the alloy composition, the nanowire diameter and the grain size on the hysteresis properties are considered. X-ray diffraction indicates that the nanowires are single phase, a fcc Co-Pd solid solution; electron microscopy results show that they are polycrystalline, with randomly oriented grains (7-12 nm), smaller than the wire diameter. Nanowire arrays are ferromagnetic, with an easy magnetization axis parallel to the nanowire long axis. Both, the coercive field and the loop squareness monotonously increase with the Co content and with the grain size, but no clear correlation with the wire diameter is found. The Co and Co-rich nanowire arrays exhibit coercive fields and reduced remanence values quite insensitive to temperature in the range 4 K-300 K; on the contrary, in Pd-rich nanowires both magnitudes are smaller and they largely increase during cooling below 100 K. These behaviors are systematized by considering the strong dependences displayed by the magneto-crystalline anisotropy and the saturation magnetostriction on composition and temperature. At low temperatures the effective anisotropy value and the domain-wall width to grain size ratio drastically change, promoting less cooperative and harder nucleation modes.

  14. Small-scale heating events in the solar atmosphere. II. Lifetime, total energy, and magnetic properties

    Science.gov (United States)

    Guerreiro, N.; Haberreiter, M.; Hansteen, V.; Schmutz, W.

    2017-07-01

    Context. Small-scale heating events (SSHEs) are believed to play a fundamental role in understanding the process responsible for heating of the solar corona, the pervading redshifts in the transition region, and the acceleration of spicules. Aims: We determine the properties of the SSHEs and the atmospheric response to them in 3D magnetohydrodynamics (3D-MHD) simulations of the solar atmosphere. Methods: We developed a method for identifying and following SSHEs over their lifetime, and applied it to two simulation models. We identified the locations where the energy dissipation is greatest inside the SSHEs volume, and we traced the SSHEs by following the spatial and temporal evolution of the maximum energy dissipation inside the SSHEs volume. Results: The method is effective in following the SSHEs. We can determine their lifetime, total energy, and properties of the plasma, as well as the magnetic field orientation in the vicinity of the SSHEs. Conclusions: We determine that the SSHEs that have the potential to heat the corona live less than 4 min, and typically the energy they release ranges from 1020 to 1024 erg. In addition, the directional change of the field lines on the two sides of the current sheet constituting the SSHEs ranges from 5° to 15° at the moment of the absolute maximum energy dissipation.

  15. Simulation of f-Mode Propagation Through a Cluster of Small Identical Magnetic Flux Tubes

    CERN Document Server

    Daiffallah, Khalil

    2013-01-01

    Motivated by the question of how to distinguish seismically between monolithic and cluster models of sunspots, we have simulated the propagation of an $f$-mode wave packet through two identical small magnetic flux tubes (R=200 km), embedded in a stratified atmosphere. We want to study the effect of separation $d$ and incidence angle $\\chi$ on the scattered wave. We have demonstrated that the horizontal compact pair of tubes ($d/R=2$, $\\chi=0$) oscillate as a single tube when the incident wave is propagating, which gives a scattered wave amplitude of about twice that from a single tube. The scattered amplitude decreases with increasing $d$ when $d$ is about $\\lambda/2\\pi$ where $\\lambda$ is the wavelength of the incident wave packet. In this case the individual tubes start to oscillate separately in the manner of near-field scattering. When $d$ is about twice of $\\lambda/2\\pi$, scattering from individual tubes reaches the far-field regime, giving rise to coherent scattering with an amplitude similar to the cas...

  16. Small amplitude electron acoustic solitary waves in a magnetized superthermal plasma

    Science.gov (United States)

    Devanandhan, S.; Singh, S. V.; Lakhina, G. S.; Bharuthram, R.

    2015-05-01

    The propagation of electron acoustic solitary waves in a magnetized plasma consisting of fluid cold electrons, electron beam and superthermal hot electrons (obeying kappa velocity distribution function) and ion is investigated in a small amplitude limit using reductive perturbation theory. The Korteweg-de-Vries-Zakharov-Kuznetsov (KdV-ZK) equation governing the dynamics of electron acoustic solitary waves is derived. The solution of the KdV-ZK equation predicts the existence of negative potential solitary structures. The new results are: (1) increase of either the beam speed or temperature of beam electrons tends to reduce both the amplitude and width of the electron acoustic solitons, (2) the inclusion of beam speed and temperature pushes the allowed Mach number regime upwards and (3) the soliton width maximizes at certain angle of propagation (αm) and then decreases for α >αm . In addition, increasing the superthermality of the hot electrons also results in reduction of soliton amplitude and width. For auroral plasma parameters observed by Viking, the obliquely propagating electron-acoustic solitary waves have electric field amplitudes in the range (7.8-45) mV/m and pulse widths (0.29-0.44) ms. The Fourier transform of these electron acoustic solitons would result in a broadband frequency spectra with peaks near 2.3-3.5 kHz, thus providing a possible explanation of the broadband electrostatic noise observed during the Burst a.

  17. Small-scale magnetic flux emergence in a sunspot light bridge

    Science.gov (United States)

    Louis, Rohan E.; Bellot Rubio, Luis R.; de la Cruz Rodríguez, Jaime; Socas-Navarro, Héctor; Ortiz, Ada

    2015-12-01

    granular light bridge seem to be caused by the emergence of a small-scale, flat Ω-loop with highly inclined footpoints of opposite polarity that brings new magnetic field to the surface. The gas motions detected in the two footpoints are reminiscent of a siphon flow. The rising loop is probably confined to the lower atmosphere by the overlying sunspot magnetic field and the interaction between the two flux systems may be responsible for temperature enhancements in the upper photosphere/lower chromosphere. This is the first time that magnetic flux is observed to emerge in the strongly magnetised environment of sunspots, pushed upwards by the convective flows of a granular light bridge. The movie associated to Fig. 2 is available in electronic form at http://www.aanda.org

  18. Reply to “Comment on ‘Ultrafast Demagnetization Measurements Using Extreme Ultraviolet Light: Comparison of Electronic and Magnetic Contributions’ ”

    Directory of Open Access Journals (Sweden)

    Emrah Turgut

    2013-09-01

    Full Text Available In the following, we show that the conclusions of our article titled “Ultrafast Demagnetization Measurements Using Extreme Ultraviolet Light: Comparison of Electronic and Magnetic Contributions” are correct. The Comment of Vodungbo et al. argues that a unique determination of the refractive index variation over time is not possible using the data set presented in our paper. Furthermore, it was suggested that the lack of uniqueness allows for the possibility of a very specific time-dependent trajectory of the refractive index in the complex plane that could give rise to a large nonmagnetic modulation of the measured asymmetry, in spite of a negligible change in the s-polarized reflectivity. In this Reply, we conclusively show that any nonmagnetic contribution to the measured asymmetry is indeed negligible (<2%, below the noise level of the magnetic-asymmetry measurements. First, we use a few additional measurements to unambiguously rule out the presence of any nonmagnetic contributions to the signal. Second, we show that the scenario proposed by Vodungbo et al. would require both exotic time and energy dependences of the refractive index near the M edge that are extremely unlikely (virtually impossible in real materials. Thus, the conclusions of our original article are preserved.

  19. Emergence of noncollinear magnetic ordering in small magnetic clusters: Mn$_n$ and As@Mn$_n$

    CERN Document Server

    Kabir, Mukul; Mookerjee, Abhijit

    2007-01-01

    Using first-principles density functional calculations, we have studied the magnetic ordering in pure Mn$_n$ ($n=2-$10, 13, 15, 19) and As@Mn$_n$ ($n=1-$10) clusters. Although, for both pure and doped manganese clusters, there exists many collinear and noncollinear isomers close in energy, the smaller clusters with $n\\leqslant$5 have collinear magnetic ground state and the emergence of noncollinear ground states is seen for $n\\geqslant$6 clusters. Due to strong $p-d$ hybridization in As@Mn$_n$ clusters, the binding energy is substantially enhanced and the magnetic moment is reduced compared to the corresponding pure Mn$_n$ clusters.

  20. Extreme magnetic anisotropy and multiple superconducting transition signatures in a [Nb(23 nm)/Ni(5 nm)] 5 multilayer

    Science.gov (United States)

    De Long, L. E.; Kryukov, S. A.; Joshi, Amish G.; Xu, Wentao; Bosomtwi, A.; Kirby, B. J.; Fitzsimmons, M. R.

    2008-04-01

    We have applied polarized neutron reflectometry, and novel SQUID and vibrating reed magnetometry to probe a [Nb(23 nm)/Ni(5 nm)]5 multilayer (ML) whose superconducting state magnetic anisotropy is dominated by confined (in-plane) supercurrents in DC magnetic fields, H, applied nearly parallel to the ML plane. The upper critical field exhibits abrupt shifts (0.1-0.6 K) in near-parallel fields, but is field-independent for μ0H < 0.8 T when the ML is exactly aligned with the DC field, indicating suppression of orbital pairbreaking and the possible presence of unconventional superconducting pairing states.

  1. Discovery of an extremely weak magnetic field in the white dwarf LTT 16093 = WD2047+372

    CERN Document Server

    Landstreet, J D; Martin, A; Valyavin, G

    2016-01-01

    Magnetic fields have been detected in several hundred white dwarfs, with strengths ranging from a few kG to several hundred MG. Only a few of the known fields have a mean magnetic field modulus below about 1 MG. We are searching for new examples of magnetic white dwarfs with very weak fields, and trying to model the few known examples. Our search is intended to be sensitive enough to detect fields at the few kG level. We have been surveying bright white dwarfs for very weak fields using spectropolarimeters at the Canada-France-Hawaii telescope, the William Herschel telescope, the European Southern Observatory, and the Russian Special Astrophysical Observatory. We discuss in some detail tests of the WHT spectropolarimeter ISIS using the known magnetic strong-field Ap star HD 215441 (Babcock's star) and the long-period Ap star HD 201601 (gamma Equ). We report the discovery of a field with a mean field modulus of about 57 kG in the white dwarf LTT 16093 = WD2047+372. The field is clearly detected through the Zee...

  2. Magnetic Particle Spectroscopy Reveals Dynamic Changes in the Magnetic Behavior of Very Small Superparamagnetic Iron Oxide Nanoparticles During Cellular Uptake and Enables Determination of Cell-Labeling Efficacy.

    Science.gov (United States)

    Poller, Wolfram C; Löwa, Norbert; Wiekhorst, Frank; Taupitz, Matthias; Wagner, Susanne; Möller, Konstantin; Baumann, Gert; Stangl, Verena; Trahms, Lutz; Ludwig, Antje

    2016-02-01

    In vivo tracking of nanoparticle-labeled cells by magnetic resonance imaging (MRI) crucially depends on accurate determination of cell-labeling efficacy prior to transplantation. Here, we analyzed the feasibility and accuracy of magnetic particle spectroscopy (MPS) for estimation of cell-labeling efficacy in living THP-1 cells incubated with very small superparamagnetic iron oxide nanoparticles (VSOP). Cell viability and proliferation capacity were not affected by the MPS measurement procedure. In VSOP samples without cell contact, MPS enabled highly accurate quantification. In contrast, MPS constantly overestimated the amount of cell associated and internalized VSOP. Analyses of the MPS spectrum shape expressed as harmonic ratio A₅/A₃ revealed distinct changes in the magnetic behavior of VSOP in response to cellular uptake. These changes were proportional to the deviation between MPS and actual iron amount, therefore allowing for adjusted iron quantification. Transmission electron microscopy provided visual evidence that changes in the magnetic properties correlated with cell surface interaction of VSOP as well as with alterations of particle structure and arrangement during the phagocytic process. Altogether, A₅/A₃-adjusted MPS enables highly accurate, cell-preserving VSOP quantification and furthermore provides information on the magnetic characteristics of internalized VSOP.

  3. Hybrid magnet devices for molecule manipulation and small scale high gradient-field applications

    Science.gov (United States)

    Humphries, David E.; Hong, Seok-Cheol; Cozzarelli, legal representative, Linda A.; Pollard, Martin J.; Cozzarelli, Nicholas R.

    2009-01-06

    The present disclosure provides a high performance hybrid magnetic structure made from a combination of permanent magnets and ferromagnetic pole materials which are assembled in a predetermined array. The hybrid magnetic structure provides means for separation and other biotechnology applications involving holding, manipulation, or separation of magnetizable molecular structures and targets. Also disclosed are hybrid magnetic tweezers able to exert approximately 1 nN of force to 4.5 .mu.m magnetic bead. The maximum force was experimentally measured to be .about.900 pN which is in good agreement with theoretical estimations and other measurements. In addition, a new analysis scheme that permits fast real-time position measurement in typical geometry of magnetic tweezers has been developed and described in detail.

  4. A modeling approach to assess the hydrological response of small mediterranean catchments to the variability of soil characteristics in a context of extreme events

    Directory of Open Access Journals (Sweden)

    C. Manus

    2009-02-01

    Full Text Available This paper presents a modeling study aiming at quantifying the possible impact of soil characteristics on the hydrological response of small ungauged catchments in a context of extreme events. The study focuses on the September 2002 event in the Gard region (South-Eastern France, which led to catastrophic flash-floods. The proposed modeling approach is able to take into account rainfall variability and soil profiles variability. Its spatial discretization is determined using Digital Elevation Model (DEM and a soil map. The model computes infiltration, ponding and vertical soil water distribution, as well as river discharge. In order to be applicable to ungauged catchments, the model is set up without any calibration and the soil parameter specification is based on an existing soil database. The model verification is based on a regional evaluation using 17 estimated discharges obtained from an extensive post-flood investigation. Thus, this approach provides a spatial view of the hydrological response across a large range of scales. To perform the simulations, radar rainfall estimations are used at a 1 km2 and 5 min resolution. To specify the soil hydraulic properties, two types of pedotransfer function (PTF are compared. It is shown that the PTF including information about soil structure reflects better the spatial variability that can be encountered in the field. The study is focused on four small ungauged catchments of less than 10 km2, which experienced casualties. Simulated specific peak discharges are found to be in agreement with estimations from a post-event in situ investigation. Examining the dynamics of simulated infiltration and saturation degrees, two different behaviors are shown which correspond to different runoff production mechanisms that could be encountered within catchments of less than 10 km2. They produce simulated runoff coefficients that evolve in time and highlight the variability of the

  5. Wireless magnetic sensors applied in the signal control of small and medium-sized cities

    Institute of Scientific and Technical Information of China (English)

    Liang Zijun; Zhang Bo; Huang Zhen; Song Zhihong

    2015-01-01

    This topic is mainly about the typical applications of Wireless magnetic sensors in the signal control of smal and medium-sized cities. Based on the traffic characteristics of Fenghua city, through the networked control of Wireless magnetic sensors and signal controler, from "point, line, face" three aspects to optimize the traffic flow of Fenghua. The application results show that Wireless magnetic sensors can effectively improve the efficiency of traffic signal control in Fenghua.

  6. Magnetic-resonance-imaging-coupled broadband near-infrared tomography system for small animal brain studies

    Science.gov (United States)

    Xu, Heng; Springett, Roger; Dehghani, Hamid; Pogue, Brian W.; Paulsen, Keith D.; Dunn, Jeff F.

    2005-04-01

    A novel magnetic-resonance-coupled broadband near-infrared (NIR) tomography system for small animal brain studies is described. Several features of the image formation approach are new in NIR tomography and represent major advances in the path to recovering high-resolution hemoglobin and oxygen saturation images of tissue. The NIR data were broadband and continuous wave and were used along with a second-derivative-based estimation of the path length from water absorption. The path length estimation from water was then used along with the attenuation spectrum to recover absorption and reduced scattering coefficient images at multiple wavelengths and then to recover images of total hemoglobin and oxygen saturation. Going beyond these basics of NIR tomography, software has been developed to allow inclusion of structures derived from MR imaging (MRI) for the external and internal tissue boundaries, thereby improving the accuracy and spatial resolution of the properties in each tissue type. The system has been validated in both tissue-simulating phantoms, with 10% accuracy observed, and in a rat cranium imaging experiment. The latter experiment used variation in inspired oxygen (FiO2) to vary the observed hemoglobin and oxygen saturation images. Quantitative agreement was observed between the changes in deoxyhemoglobin values derived from NIR and the changes predicted with blood-oxygen-level-dependent (BOLD) MRI. This system represents the initial stage in what will likely be a larger role for NIR tomography, coupled to MRI, and illustrates that the technological challenges of using continuous-wave broadband data and inclusion of a priori structural information can be met with careful phantom studies.

  7. MAGNET

    CERN Multimedia

    Benoit Curé.

    The magnet operation restarted end of June this year. Quick routine checks of the magnet sub-systems were performed at low current before starting the ramps up to higher field. It appeared clearly that the end of the field ramp down to zero was too long to be compatible with the detector commissioning and operations plans. It was decided to perform an upgrade to keep the ramp down from 3.8T to zero within 4 hours. On July 10th, when a field of 1.5T was reached, small movements were observed in the forward region support table and it was decided to fix this problem before going to higher field. At the end of July the ramps could be resumed. On July 28th, the field was at 3.8T and the summer CRAFT exercise could start. This run in August went smoothly until a general CERN wide power cut took place on August 3rd, due to an insulation fault on the high voltage network outside point 5. It affected the magnet powering electrical circuit, as it caused the opening of the main circuit breakers, resulting in a fast du...

  8. Magnetic field-dependent shape anisotropy in small patterned films studied using rotating magnetoresistance.

    Science.gov (United States)

    Fan, Xiaolong; Zhou, Hengan; Rao, Jinwei; Zhao, Xiaobing; Zhao, Jing; Zhang, Fengzhen; Xue, Desheng

    2015-11-13

    Based on the electric rotating magnetoresistance method, the shape anisotropy of a Co microstrip has been systematically investigated. We find that the shape anisotropy is dependent not only on the shape itself, but also on the magnetization distribution controlled by an applied magnetic field. Together with micro-magnetic simulations, we present a visualized picture of how non-uniform magnetization affects the values and polarities of the anisotropy constants K1 and K2. From the perspective of potential appliantions, our results are useful in designing and understanding the performance of micro- and nano-scale patterned ferromagnetic units and the related device properties.

  9. A magnetically actuated ball valve applicable for small-scale fluid flows

    DEFF Research Database (Denmark)

    Smistrup, Kristian; Stone, Howard A.

    2007-01-01

    We present three possible designs for magnetically actuated ball valves that can be scaled down to nanometer length scales. Analytical expressions are presented for the hydraulic resistance of the ball valve as a function of geometric parameters and the state of the valve, and we also present...... analytical expressions for the hydrodynamic force on the magnetic bead that functions as the ball in the valve. We verify these expressions numerically and calculate the magnetic forces that can be exerted on the magnetic bead using the proposed structures. Finally, for typical parameters we show...

  10. Numerical analysis of thermally actuated magnets for magnetization of superconductors

    Energy Technology Data Exchange (ETDEWEB)

    Li Quan; Yan Yu; Rawlings, Colin; Coombs, Tim, E-mail: ql229@cam.ac.u [EPEC Superconductivity Group, Engineering Department, University of Cambridge, Trumpington Street. Cambridge, CB2 1PZ (United Kingdom)

    2010-06-01

    Superconductors, such as YBCO bulks, have extremely high potential magnetic flux densities, comparing to rare earth magnets. Therefore, the magnetization of superconductors has attracted broad attention and contribution from both academic research and industry. In this paper, a novel technique is proposed to magnetize superconductors. Unusually, instead of using high magnetic fields and pulses, repeatedly magnetic waves with strength of as low as rare earth magnets are applied. These magnetic waves, generated by thermally controlling a Gadolinium (Gd) bulk with a rare earth magnet underneath, travel over the flat surface of a YBCO bulk and get trapped little by little. Thus, a very small magnetic field can be used to build up a very large magnetic field. In this paper, the modelling results of thermally actuated magnetic waves are presented showing how to transfer sequentially applied thermal pulses into magnetic waves. The experiment results of the magnetization of YBCO bulk are also presented to demonstrate how superconductors are progressively magnetized by small magnetic field

  11. On the log-normality of historical magnetic-storm intensity statistics: implications for extreme-event probabilities

    Science.gov (United States)

    Love, Jeffrey J.; Rigler, E. Joshua; Pulkkinen, Antti; Riley, Pete

    2015-01-01

    An examination is made of the hypothesis that the statistics of magnetic-storm-maximum intensities are the realization of a log-normal stochastic process. Weighted least-squares and maximum-likelihood methods are used to fit log-normal functions to −Dst storm-time maxima for years 1957-2012; bootstrap analysis is used to established confidence limits on forecasts. Both methods provide fits that are reasonably consistent with the data; both methods also provide fits that are superior to those that can be made with a power-law function. In general, the maximum-likelihood method provides forecasts having tighter confidence intervals than those provided by weighted least-squares. From extrapolation of maximum-likelihood fits: a magnetic storm with intensity exceeding that of the 1859 Carrington event, −Dst≥850 nT, occurs about 1.13 times per century and a wide 95% confidence interval of [0.42,2.41] times per century; a 100-yr magnetic storm is identified as having a −Dst≥880 nT (greater than Carrington) but a wide 95% confidence interval of [490,1187] nT.

  12. On the Log-Normality of Historical Magnetic-Storm Intensity Statistics: Implications for Extreme-Event Probabilities

    Science.gov (United States)

    Love, J. J.; Rigler, E. J.; Pulkkinen, A. A.; Riley, P.

    2015-12-01

    An examination is made of the hypothesis that the statistics of magnetic-storm-maximum intensities are the realization of a log-normal stochastic process. Weighted least-squares and maximum-likelihood methods are used to fit log-normal functions to -Dst storm-time maxima for years 1957-2012; bootstrap analysis is used to established confidence limits on forecasts. Both methods provide fits that are reasonably consistent with the data; both methods also provide fits that are superior to those that can be made with a power-law function. In general, the maximum-likelihood method provides forecasts having tighter confidence intervals than those provided by weighted least-squares. From extrapolation of maximum-likelihood fits: a magnetic storm with intensity exceeding that of the 1859 Carrington event, -Dst > 850 nT, occurs about 1.13 times per century and a wide 95% confidence interval of [0.42, 2.41] times per century; a 100-yr magnetic storm is identified as having a -Dst > 880 nT (greater than Carrington) but a wide 95% confidence interval of [490, 1187] nT. This work is partially motivated by United States National Science and Technology Council and Committee on Space Research and International Living with a Star priorities and strategic plans for the assessment and mitigation of space-weather hazards.

  13. Study the effect of prolonged exposure to extremely low-frequency electromagnetic fields on the α 1 adrenergic system in the small intestine of male rat

    Directory of Open Access Journals (Sweden)

    M jaafari

    2015-12-01

    Full Text Available Back ground & aim: In the recent years, the increasing use of electronic devices which generate electromagnetic fields, focused researchers’ attention to investigate the electromagnetic fields effects on human health. Therefore, the purpose of the present study was to investigate the effect of prolonged exposure to extremely low frequency electromagnetic fields (ELF on the adrenergic system in the small intestine of male rats. Methods: In the present experimental study, 21 Adult male rats (wistar were divided into three groups: experimental group, which were exposed to ELF (50Hz, 1mT for 75 days, the sham-operated group, which were kept in similar conditions exception Off solenoid and the control group, which were kept in normal conditions. After 75 days, the rats were anesthetized by intra peritoneal injection of pentobarbital sodium (50 mg/k. Then, the ileum tissue was dissected and divided into 1 cm strips. The strips were placed in organ baths containing oxygenated, pH=7.4 Krebs solution. Furthermore, the mechanical activity of the tissue was recorded with force transducer of bridge amplifier which was linked to A-D Instrument power lab in response to Phenylephrine(4 ×10-6 M. Data was analyzed using one way ANOVA test. Results: Relaxation changes of isolated ileum tissue was displayed in two ileum strips with same length and in the same animal, According to the obtained results, the ileum relaxation in exposure to ELF (experimental compared to the control and sham groups significantly increased (p&le0.05. Accordingly, the relaxation changes of ileum in response to the phenylephrine at different times and after deducting the basic tension represented a significant increase (p&le0.05 of Ileum relaxation in the experimental group compared to the sham and control groups. Conclusion: It can be concluded that prolonged exposure to extremely low-frequency electromagnetic fields may lead to increase of  the &alpha1-adrenergic receptors

  14. The Effect of Prolonged Exposure to Extremely Low Frequency Electromagnetic Fields on the β2 Adrenergic System Activity in the Small Intestine of Male Rats

    Directory of Open Access Journals (Sweden)

    Esmaeil Khoshnam

    2016-12-01

    Full Text Available Background & Objective: Electromagnetic waves with the frequencies of 0–300 Hz and the intensity of 0.1–100 millitesla can affect several cellular activities. Therefore, the purpose of this study is to investigate the effect of prolonged exposure to extremely low frequency electromagnetic fields (ELF on the adrenergic system in the small intestine. Materials & Methods: 21 adult male rats were divided into three groups. The first group was experimental group which exposed to ELF (50Hz, 1mT for 75 days in powered on solenoid. The second group was sham group which was kept in similar conditions as the first group but in powered off solenoid. The third group or the control group was kept in animal house condition. The isolated strips of the colon were inserted into organ bath and were linked to power lab A to D system force transducer and their mechanical activity were recorded in response to different doses of Isoproterenol (10-4 M and10-5 M. The data were analyzed using one-way ANOVA test. Result: The results showed a significant increase (p≤0.05 of ileum basal contractions in experimental group compared to control and sham groups. While the relaxation changes of ileum in response to the different doses of isoproterenol (β2 adrenergic receptors agonist in the experimental group compared to the sham and control groups was not statistically significant. Conclusion: It can be concluded that prolonged exposure to extremely low frequency electromagnetic fields may not affect β2 -adrenergic receptors activity.

  15. Analytical model for the levitation force between a small magnet and a superconducting cylinder in the critical state

    Science.gov (United States)

    de la Cruz, Artorix; Badía, Antonio

    2002-08-01

    In this work a simple analytical model is presented, which allows to obtain closed-form expressions for the maximum magnetic field trapped by a cylindrical superconductor as well as the levitation force between the sample and a small magnet. Previous models of this kind could not properly account for the behaviour of the repulsion force with the variation of the sample dimensions. In particular, the so-called Js+ Jv model (J. Appl. Phys. 72 (1992) 1013) incorporates size effects by means of a surface current density ( Js) which tends to zero for disc-shaped samples. However, we show that the features encountered both in experimental works and numerical models reported in the literature can be reproduced by a suitable modification of the Js+ Jv model. Analytical expressions of the levitation force are obtained as a function of length and radius of the sample and as well the superconductor-magnet distance.

  16. Generation of strong magnetic fields via the small-scale dynamo during the formation of the first stars

    CERN Document Server

    Banerjee, Robi; Federrath, Christoph; Schleicher, Dominik R G; Klessen, Ralf S

    2012-01-01

    Here we summarize our recent results of high-resolution computer simulations on the turbulent amplification of weak magnetic seed fields showing that such fields will be exponentially amplified also during the gravitational collapse reminiscent to the situation during primordial star formation. The exponential magnetic field amplification is driven by the turbulent small-scale dynamo that can be only observed in computer simulations if the turbulent motions in the central core are sufficiently resolved. We find that the Jeans length, which determines the central core region, has to be resolved by at least 30 grid cells to capture the dynamo activity. We conclude from our studies that strong magnetic fields will be unavoidably created already during the formation of the first stars in the Universe, potentially influencing their evolution and mass distribution.

  17. Small Signal Modeling and Comprehensive Analysis of Magnetically Coupled Impedance Source Converters

    DEFF Research Database (Denmark)

    Forouzesh, Mojtaba; Siwakoti, Yam Prasad; Blaabjerg, Frede

    2016-01-01

    Magnetically coupled impedance-source (MCIS) networks are recently introduced impedance networks intended for various high-boost applications. It employs coupled magnetic in the circuit to achieve higher voltage gain. Various MCIS networks have been proposed in the literature for myriad applicati...

  18. Magnetic Behaviour of Tb/Si Nanoscale Multilayers with Small Thickness of Rare Earth Layers

    Institute of Scientific and Technical Information of China (English)

    A.V.Svalov; V.O.Vas'kovskiy; G.V.Kurlyandskaya; J.M.Barandiaran; N.N.Schegoleva; A.N.Sorokin

    2007-01-01

    We report the magnetic properties of Tb/Si multilayers obtained by rf-sputtering at the Tb layer thickness LTb = 3 nm. Analysis of the magnetization processes indicates more complex behaviour than canonical spin-glass transition. It is more probable that these multilayers contain both Tb superparamagnetic particles and Tb-Si spin-glass alloys.

  19. Investigation of magnetic nanoparticle targeting in a simplified model of small vessel aneurysm

    Science.gov (United States)

    Mirzababaei, S. N.; Gorji, Tahereh B.; Baou, M.; Gorji-Bandpy, M.; Fatouraee, Nasser

    2017-03-01

    An in simulacra study was conducted to investigate the capture efficiency (CE) of magnetic nanoparticles (MNPs) in aneurysm model, under the effect of a bipolar permanent magnetic system positioned at the vicinity of the model vessel. The bipolar magnetic system with an active space of 9 cm was designed by FEMM software. The MNPs were magnetite nanoparticles synthesized by the hydrothermal method which were characterized by X-ray diffraction, Fourier transform infrared spectroscopy, scanning electron microscope and magnetometer measurements. Ferrofluid velocity, magnetic field strength, and aneurysm volume all proved to be important parameters which affect the capturing of MNPs. Overall, the results of this in simulacra study confirmed the effectiveness of magnetic targeting for possible aneurysm embolization.

  20. Iris si iv line profiles: An indication for the plasmoid instability during small-scale magnetic reconnection on the sun

    CERN Document Server

    Innes, Davina; Huang, YiMin; Bhattacharjee, Amitava

    2015-01-01

    Our understanding of the process of fast reconnection has undergone a dramatic change in the last 10 years driven, in part, by the availability of high-resolution numerical simulations that have consistently demonstrated the break-up of current sheets into magnetic islands, with reconnection rates that become independent of Lundquist number, challenging the belief that fast magnetic reconnection in flares proceeds via the Petschek mechanism that invokes pairs of slow-mode shocks connected to a compact diffusion region. The reconnection sites are too small to be resolved with images but these reconnection mechanisms, Petschek and the plasmoid instability, have reconnection sites with very different density and velocity structures and so can be distinguished by high-resolution line-profiles observations. Using IRIS spectroscopic observations we obtain a survey of typical line profiles produced by small-scale events thought to be reconnection sites on the Sun. Slit-jaw images are used to investigate the plasma h...

  1. EXPLAINING THE COEXISTENCE OF LARGE-SCALE AND SMALL-SCALE MAGNETIC FIELDS IN FULLY CONVECTIVE STARS

    Energy Technology Data Exchange (ETDEWEB)

    Yadav, Rakesh K.; Poppenhaeger, Katja; Wolk, Scott J. [Harvard-Smithsonian Center for Astrophysics, 60 Garden Street, Cambridge, MA 02138 (United States); Christensen, Ulrich R.; Gastine, Thomas [Max-Planck-Institut für Sonnensystemforschung, Justus-von-Liebig-Weg 3, D-37077 Göttingen (Germany); Morin, Julien [LUPM, Université de Montpellier, CNRS, Place Eugène Bataillon, F-34095 (France); Reiners, Ansgar, E-mail: rakesh.yadav@cfa.harvard.edu [Institut für Astrophysik, Universität Göttingen, Friedrich Hund Platz 1, D-37077 Göttingen (Germany)

    2015-11-10

    Despite the lack of a shear-rich tachocline region, low-mass fully convective (FC) stars are capable of generating strong magnetic fields, indicating that a dynamo mechanism fundamentally different from the solar dynamo is at work in these objects. We present a self-consistent three-dimensional model of magnetic field generation in low-mass FC stars. The model utilizes the anelastic magnetohydrodynamic equations to simulate compressible convection in a rotating sphere. A distributed dynamo working in the model spontaneously produces a dipole-dominated surface magnetic field of the observed strength. The interaction of this field with the turbulent convection in outer layers shreds it, producing small-scale fields that carry most of the magnetic flux. The Zeeman–Doppler-Imaging technique applied to synthetic spectropolarimetric data based on our model recovers most of the large-scale field. Our model simultaneously reproduces the morphology and magnitude of the large-scale field as well as the magnitude of the small-scale field observed on low-mass FC stars.

  2. SMALL VOLUME LONG PULSE X RAY PREIONISED XeCl LASER WITH DOUBLE DISCHARGE AND FAST FERRITE MAGNETIC SWITCH

    OpenAIRE

    J. Hueber; Kobhio, M.; Fontaine, B.; Delaporte, Ph.; Sentis, M.; Forestier, B.

    1991-01-01

    Experimental results obtained with a high efficiency small volume long pulse X-Ray preionised XeCl laser with double discharge and very fast ferrite magnetic switch are presented and compared with the results given by a new XeCl laser numerical self consistant model. The model takes into account most recent kinetic data and time variation of discharge impedence and switch inductance. There is a good agreement between experiment and model on electrical and laser parameters for typical conditions.

  3. Discovery of an extremely weak magnetic field in the white dwarf LTT 16093 = WD 2047+372

    Science.gov (United States)

    Landstreet, J. D.; Bagnulo, S.; Martin, A.; Valyavin, G.

    2016-06-01

    Context. Magnetic fields have been detected in several hundred white dwarfs, with strengths ranging from a few kG to several hundred MG. Only a few of the known fields have a mean magnetic field modulus below about 1 MG. Aims: We are searching for new examples of magnetic white dwarfs with very weak fields, and trying to model the few known examples. Our search is intended to be sensitive enough to detect fields at the few kG level. Methods: We have been surveying bright white dwarfs for very weak fields using spectropolarimeters at the Canada-France-Hawaii telescope, the William Herschel Telescope (WHT), the European Southern Observatory, and the Russian Special Astrophysical Observatory. We discuss in some detail tests of the WHT spectropolarimeter ISIS using the known magnetic strong-field Ap star HD 215441 (Babcock's star) and the long-period Ap star HD 201601 (γ Equ). Results: We report the discovery of a field with a mean field modulus of about 57 kG in the white dwarf LTT 16093 = WD 2047+372. The field is clearly detected through the Zeeman splitting of Hα seen in two separate circularly polarised spectra from two different spectropolarimeters. Zeeman circular polarisation is also detected, but only barely above the 3σ level. Conclusions: The discovery of this field is significant because it is the third weakest field ever unambiguously discovered in a white dwarf, while still being large enough that we should be able to model the field structure in some detail with future observations. Based on observations made with the William Herschel Telescope operated on the island of La Palma by the Isaac Newton Group in the Spanish Observatorio del Roque de los Muchachos of the Instituto de Astrofisica de Canarias, and on observations obtained at the Canada-France-Hawaii Telescope (CFHT) which is operated by the National Research Council of Canada, the Institut National des Sciences de l'Univers of the Centre National de la Recherche Scientifique of France, and

  4. Low-cost, low-field dedicated extremity magnetic resonance imaging in early rheumatoid arthritis: a 1-year follow-up study

    DEFF Research Database (Denmark)

    Lindegaard, H.M.; Vallø, J.; Hørslev-Petersen, K.

    2006-01-01

    with rheumatoid arthritis with joint symptoms for hands and wrists, and E-MRI of the dominant wrist and MCP joints. RESULTS: At baseline, all......OBJECTIVE: To study the ability of low-cost low-field dedicated extremity magnetic resonance imaging (E-MRI) to assess and predict erosive joint damage in the wrist and metacarpophalangeal (MCP) joints of patients with early rheumatoid arthritis. METHODS: 24 previously untreated patients...... were excluded, the relative risk was 5.2. In patients with baseline MRI bone erosion or oedema, the relative risk of having x ray erosions at 1 year was 4.0, compared with patients without these signs at baseline (patient-centred analysis). CONCLUSION: In this group of patients with early rheumatoid...

  5. Magnetic resonance imaging in a juvenile type of distal and segmental muscular atrophy of the upper extremities

    Energy Technology Data Exchange (ETDEWEB)

    Hasuo, K. [Dept. of Radiology, Faculty of Medicine, Kyushu Univ., Fukuoka (Japan); Uchino, A. [Dept. of Radiology, Faculty of Medicine, Kyushu Univ., Fukuoka (Japan); Matsumoto, S. [Dept. of Radiology, Faculty of Medicine, Kyushu Univ., Fukuoka (Japan); Yoshida, K. [Dept. of Radiology, Faculty of Medicine, Kyushu Univ., Fukuoka (Japan); Kira, J. [Dept. of Neurology, Faculty of Medicine, Kyushu Univ., Fukuoka (Japan); Masuda, K. [Dept. of Radiology, Faculty of Medicine, Kyushu Univ., Fukuoka (Japan)

    1994-04-01

    Eight patients with a juvenile type of distal and segmental muscular atrophy of the upper extremities (DSMA), a type of cervical flexion myelopathy, were evaluated using MR imaging. In the neutral position there was no spinal cord compression, but in flexion the spinal cord was displaced anteriorly and was compressed by the posterior surfaces or margins of the vertebrae and/or any herniated disks in all cases. In flexion, compression of the cord was exaggerated in seven patients by the anterior displacement of the posterior margin of the thecal sac, which was accompanied by dilated posterior internal vertebral veins. In patients suspected of having DSMA, MR images made in flexion are regarded essential for verifying the diagnosis. (orig.)

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

    Science.gov (United States)

    Maes, Annemarie; Verschaeve, Luc

    2012-02-01

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

  7. Magnetic dynamics of small alpha-Fe2O3 and NiO particles

    DEFF Research Database (Denmark)

    Lefmann, K.; Bødker, Franz; Hansen, Mikkel Fougt;

    1999-01-01

    We have studied the magnetic dynamics in nanocrystalline samples of alpha-Fe2O3 (hematite) and NiO by inelastic neutron scattering. By measuring around the structural and the antiferromagnetic reflections, we have probed uniform and staggered magnetic oscillations, respectively. In the hematite...... as a sign of superparamagnetic relaxation. Studies of the antiferromagnetic signal from NiO also show evidence of collective magnetic excitations, but with a higher energy of the precession state than for hematite. The inelastic signal at the structural reflection of NiO presents evidence for uniform...

  8. A Limit on Primordial Small-Scale Magnetic Fields from CMB Distortions

    CERN Document Server

    Jedamzik, K; Olinto, A V

    2000-01-01

    Spatially varying primordial magnetic fields may be efficiently dissipated prior to the epoch of recombination due to the large viscosity of the baryon-photon fluid. We show that this dissipation may result in observable chemical potential mu and Compton y distortions in the cosmic microwave background radiation (CMB) spectrum. Current upper limits on mu and y from FIRAS constrain magnetic fields to have strength B_0 < 3\\times 10^{-8}Gauss (scaled to the present) between comoving coherence length \\approx 400 pc and primordial magnetic fields to date.

  9. Heterogenized Bimetallic Pd-Pt-Fe3O4 Nanoflakes as Extremely Robust, Magnetically Recyclable Catalysts for Chemoselective Nitroarene Reduction.

    Science.gov (United States)

    Byun, Sangmoon; Song, Yeami; Kim, B Moon

    2016-06-15

    A very simple synthesis of bimetallic Pd-Pt-Fe3O4 nanoflake-shaped alloy nanoparticles (NPs) for cascade catalytic reactions such as dehydrogenation of ammonia-borane (AB) followed by the reduction of nitro compounds (R-NO2) to anilines or alkylamines (R-NH2) in methanol at ambient temperature is described. The Pd-Pt-Fe3O4 NPs were easily prepared via a solution phase hydrothermal method involving the simple one-pot coreduction of potassium tetrachloroplatinate (II) and palladium chloride (II) in polyvinylpyrrolidone with subsequent deposition on commercially available Fe3O4 NPs. The bimetallic Pd-Pt alloy NPs decorated on Fe3O4 NPs provide a unique synergistic effect for the catalysis of cascade dehydrogenation/reduction. Various nitroarene derivatives were reduced to anilines with very specific chemoselectivity in the presence of other reducible functional groups. The bimetallic Pd-Pt-Fe3O4 NPs provide a unique synergistic effect for the catalysis of cascade dehydrogenation/reduction. The nitro reduction proceeded in 5 min with nearly quantitative conversions and yields. Furthermore, the magnetically recyclable nanocatalysts were readily separated using an external magnet and reused up to 250 times without any loss of catalytic activity. A larger scale (10 mmol) reaction was also successfully performed with >99% yield. This efficient, recyclable Pd-Pt-Fe3O4 NPs system can therefore be repetitively utilized for the reduction of various nitro-containing compounds.

  10. Possible Kondo-Lattice-Enhanced Magnetic Ordering at Anomalously High Temperature in Nd Metal under Extreme Compression

    Science.gov (United States)

    Schilling, James S.; Song, Jing; Soni, Vikas; Lim, Jinhyuk

    Most elemental lanthanides order magnetically at temperatures To well below ambient, the highest being 292 K for Gd. Sufficiently high pressure is expected to destabilize the well localized magnetic 4 f state of the heavy lanthanides, leading to increasing influence of Kondo physics on the RKKY interaction. For pressures above 80 GPa, To for Dy and Tb begins to increase dramatically, extrapolating for Dy to a record-high value near 400 K at 160 GPa. This anomalous increase may be an heretofore unrecognized feature of the Kondo lattice state; if so, one would expect To to pass through a maximum and fall rapidly at even higher pressures. A parallel is suggested to the ferromagnet CeRh3B2 where To = 115 K at ambient pressure, a temperature more than 100-times higher than anticipated from simple de Gennes scaling. Here we discuss recent experiments on Nd where anomalous behavior in To (P) is found to occur at lower pressures, perhaps reflecting the fact that Nd's 4 f wave function is less localized. Work at Washington University is supported by NSF Grant DMR-1104742 and CDAC through NNSA/DOE Grant DE-FC52-08NA28554.

  11. Magnetic Bearings for Small Satellite CMG's and Other Miniature Spacecraft Mechanisms Project

    Data.gov (United States)

    National Aeronautics and Space Administration — NASA sees an increasing role in the near future for small satellites in the 5-100 kg size range. A potentially disruptive technology, small satellites, which are low...

  12. Role of magnetic resonance imaging in entrapment and compressive neuropathy - what, where, and how to see the peripheral nerves on the musculoskeletal magnetic resonance image: part 1. Overview and lower extremity

    Energy Technology Data Exchange (ETDEWEB)

    Kim, Sungjun [Yonsei University, Department of Diagnostic Radiology, College of Medicine, Seoul (Korea); Hanyang University, Kuri Hospital, Department of Diagnostic Radiology, College of Medicine, Kuri City, Kyunggi-do (Korea); Choi, Jin-Young; Huh, Yong-Min; Song, Ho-Taek; Lee, Sung-Ah [Yonsei University, Department of Diagnostic Radiology, College of Medicine, Seoul (Korea); Kim, Seung Min [Yonsei University, Department of Neurology, College of Medicine, Seoul (Korea); Suh, Jin-Suck [Yonsei University, Department of Diagnostic Radiology, College of Medicine, Seoul (Korea); Yonsei University, Research Institute of Radiological Science, College of Medicine, Seoul (Korea)

    2007-01-15

    The diagnosis of nerve entrapment and compressive neuropathy has been traditionally based on the clinical and electrodiagnostic examinations. As a result of improvements in the magnetic resonance (MR) imaging modality, it plays not only a fundamental role in the detection of space-occupying lesions but also a compensatory role in clinically and electrodiagnostically inconclusive cases. Although ultrasound has undergone further development in the past decades and shows high resolution capabilities, it has inherent limitations due to its operator dependency. We review the general concepts that should be known to evaluate the entrapment and compressive neuropathy in MR imaging. We also review the course of normal peripheral nerves, as well as various clinical demonstrations and pathological features of compressed and entrapped nerves in the lower extremities on MR imaging, according to the nerves involved. The common sites of nerve entrapment of the lower extremity are as follows: sciatic nerve around the piriformis muscle; tibial nerve at the popliteal fossa and tarsal tunnel, common peroneal nerve around the fibular neck, and digital nerve near the metatarsal head. Although MR imaging can depict the peripheral nerves in the extremities effectively, radiologists should be familiar with nerve pathways, common sites of nerve compression, and common space-occupying lesions resulting in nerve compression in MR imaging. (orig.)

  13. Role of magnetic resonance imaging in entrapment and compressive neuropathy - what, where, and how to see the peripheral nerves on the musculoskeletal magnetic resonance image: Part 2. Upper extremity

    Energy Technology Data Exchange (ETDEWEB)

    Kim, Sungjun [Yonsei University, Department of Diagnostic Radiology, College of Medicine, Seoul (Korea); Hanyang University, Kuri Hospital, Department of Diagnostic Radiology, College of Medicine, Kuri City, Kyunggi-do (Korea); Choi, Jin-Young; Huh, Yong-Min; Song, Ho-Taek; Lee, Sung-Ah [Yonsei University, Department of Diagnostic Radiology, College of Medicine, Seoul (Korea); Kim, Seung Min [Yonsei University, Department of Neurology, College of Medicine, Seoul (Korea); Suh, Jin-Suck [Yonsei University, Department of Diagnostic Radiology, College of Medicine, Seoul (Korea); Yonsei University, Research Institute of Radiological Science, College of Medicine, Seoul (Korea)

    2007-02-15

    The diagnosis of nerve entrapment and compressive neuropathy has been traditionally based on the clinical and electrodiagnostic examinations. As a result of improvements in the magnetic resonance (MR) imaging modality, it plays not only a fundamental role in the detection of space-occupying lesions, but also a compensatory role in clinically and electrodiagnostically inconclusive cases. Although ultrasound has undergone further development in the past decades and shows high resolution capabilities, it has inherent limitations due to its operator dependency. We review the course of normal peripheral nerves, as well as various clinical demonstrations and pathological features of compressed and entrapped nerves in the upper extremities on MR imaging, according to the nerves involved. The common sites of nerve entrapment of the upper extremity are as follows: the brachial plexus of the thoracic outlet; axillary nerve of the quadrilateral space; radial nerve of the radial tunnel; ulnar nerve of the cubital tunnel and Guyon's canal; median nerve of the pronator syndrome, anterior interosseous nerve syndrome, and carpal tunnel syndrome. Although MR imaging can depict the peripheral nerves in the extremities effectively, radiologists should be familiar with nerve pathways, common sites of nerve compression, and common space-occupying lesions resulting in nerve compression in MR imaging. (orig.)

  14. Using magnetization measurements to detect small amounts of plutonium hydride formation in plutonium metal

    Energy Technology Data Exchange (ETDEWEB)

    Kim, Jae Wook [Rutgers Univ., New Brunswick, NJ (United States); Mielke, Charles H. [Los Alamos National Lab. (LANL), Los Alamos, NM (United States); Zapf, Vivien [Los Alamos National Lab. (LANL), Los Alamos, NM (United States); Baiardo, Joseph P. [Los Alamos National Lab. (LANL), Los Alamos, NM (United States); Mitchell, Jeremy N. [Los Alamos National Lab. (LANL), Los Alamos, NM (United States); Richmond, Scott [Los Alamos National Lab. (LANL), Los Alamos, NM (United States); Schwartz, Daniel S. [Los Alamos National Lab. (LANL), Los Alamos, NM (United States); Mun, Eun D. [Los Alamos National Lab. (LANL), Los Alamos, NM (United States); Smith, Alice Iulia [Los Alamos National Lab. (LANL), Los Alamos, NM (United States)

    2014-10-20

    We report the formation of plutonium hydride in 2 at % Ga-stabilized δ-Pu, with 1 atomic % H charging. We show that magnetization measurements are a sensitive, quantitative measure of ferromagnetic plutonium hydride against the nonmagnetic background of plutonium. It was previously shown that at low hydrogen concentrations, hydrogen forms super-abundant vacancy complexes with plutonium, resulting in a bulk lattice contraction. Here we use magnetization, X-ray and neutron diffraction measurements to show that in addition to forming vacancy complexes, at least 30% of the H atoms bond with Pu to precipitate PuHx, largely on the surface of the sample with x ~ 1.9. We observe magnetic hysteresis loops below 40 K with magnetic remanence, consistent with precipitates of ferromagnetic PuH1.9.

  15. Small-scale ion flux and magnetic field fluctuations in solar wind, foreshock and magnetosheath

    Institute of Scientific and Technical Information of China (English)

    N. N. Shevyrev; Du Jian; G. N. Zastenker; Wang Chi; P. E. Eigesa

    2007-01-01

    We have continued investigation of waves in the regions of undisturbed solar wind, foreshock and magnetosheath. The analysis of ion flux and magnetic field variations with the time interval l-240s was performed in the regions above. Very large variation in such a time interval can be considered the common feature of the foreshock and magnetosheath. The results of case and statistical studies showed that the level of relative variations of ion flux and magnetic field magnitude in foreshock is about 3 times larger than in undisturbed solar wind. Variations of these parameters in the magnetosheath topologically connected with the quasi-parallel bow shock are about two times larger than those behind the quasi-perpendicular. We also compared the results from Interball-1 data analysis with those from statistical analysis of cluster magnetic field measurements. The magnetic field variations obtained from the different satellite data coincide with each other very well not only in quality but also in quantity.

  16. Magnetism and exchange interaction of small rare-earth clusters; Tb as a representative

    CERN Document Server

    Peters, Lars; Sanyal, Biplab; van Dijk, Chris; Bowlan, John; de Heer, Walt; Delin, Anna; Di Marco, Igor; Eriksson, Olle; Katsnelson, Mikhail I; Johansson, Börje; Kirilyuk, Andrei

    2016-01-01

    Here we follow, both experimentally and theoretically, the development of magnetism in Tb clusters from the atomic limit, adding one atom at a time. The exchange interaction is, surprisingly, observed to drastically increase compared to that of bulk, and to exhibit irregular oscillations as a function of the interatomic distance. From electronic structure theory we find that the theoretical magnetic moments oscillate with cluster size in exact agreement with experimental data. Unlike the bulk, the oscillation is not caused by the RKKY mechanism. Instead, the inter-atomic exchange is shown to be driven by a competition between wave-function overlap of the 5d shell and the on-site exchange interaction, which leads to a competition between ferromagnetic double-exchange and antiferromagnetic super-exchange. This understanding opens up new ways to tune the magnetic properties of rare-earth based magnets with nano-sized building blocks.

  17. On the properties of slow mhd sausage waves within small-scale photospheric magnetic structures

    CERN Document Server

    Freij, N; Morton, R J; Ruderman, M S; Karlovsky, V; Erdekyi, R

    2015-01-01

    The presence of magneto-acoustic waves in magnetic structures in the solar atmosphere is well-documented. Applying the technique of solar magneto-seismology (SMS) allows us to infer the background properties of these structures. Here, we aim to identify properties of the observed magneto-acoustic waves and study the background properties of magnetic structures within the lower solar atmosphere. Using the Dutch Open Telescope (DOT) and Rapid Oscillations in the Solar Atmosphere (ROSA) instruments, we captured two series of high-resolution intensity images with short cadence of two isolated magnetic pores. Combining wavelet analysis and empirical mode decomposition (EMD), we determined characteristic periods within the cross-sectional (i.e., area) and intensity time series. Then, by applying the theory of linear magnetohydrodynamics (MHD), we identified the mode of these oscillations within the MHD framework. Several oscillations have been detected within these two magnetic pores. Their periods range from 3 to ...

  18. Are rheumatoid arthritis patients discernible from other early arthritis patients using 1.5T extremity magnetic resonance imaging? a large cross-sectional study.

    Science.gov (United States)

    Stomp, Wouter; Krabben, Annemarie; van der Heijde, Désirée; Huizinga, Tom W J; Bloem, Johan L; van der Helm-van Mil, Annette H M; Reijnierse, Monique

    2014-08-01

    Magnetic resonance imaging (MRI) is increasingly used in rheumatoid arthritis (RA) research. A European League Against Rheumatism (EULAR) task force recently suggested that MRI can improve the certainty of RA diagnosis. Because this recommendation may reflect a tendency to use MRI in daily practice, thorough studies on the value of MRI are required. Thus far no large studies have evaluated the accuracy of MRI to differentiate early RA from other patients with early arthritis. We performed a large cross-sectional study to determine whether patients who are clinically classified with RA differ in MRI features compared to patients with other diagnoses. In our study, 179 patients presenting with early arthritis (median symptom duration 15.4 weeks) underwent 1.5T extremity MRI of unilateral wrist, metacarpophalangeal, and metatarsophalangeal joints according to our arthritis protocol, the foot without contrast. Images were scored according to OMERACT Rheumatoid Arthritis Magnetic Resonance Imaging Scoring (RAMRIS) by 2 independent readers. Tenosynovitis was also assessed. The main outcome was fulfilling the 1987 American College of Rheumatology (ACR) criteria for RA. Test characteristics and areas under the receiver-operator-characteristic curves (AUC) were evaluated. In subanalyses, the 2010 ACR/EULAR criteria were used as outcome, and analyses were stratified for anticitrullinated protein antibodies (ACPA). The ACR 1987 criteria were fulfilled in 43 patients (24.0%). Patients with RA had higher scores for synovitis, tenosynovitis, and bone marrow edema (BME) than patients without RA (p arthritis patients.

  19. Assessment of genotoxic and cytotoxic hazards in brain and bone marrow cells of newborn rats exposed to extremely low-frequency magnetic field.

    Science.gov (United States)

    Rageh, Monira M; El-Gebaly, Reem H; El-Bialy, Nihal S

    2012-01-01

    The present study aimed to evaluate the association between whole body exposure to extremely low frequency magnetic field (ELF-MF) and genotoxic , cytotoxic hazards in brain and bone marrow cells of newborn rats. Newborn rats (10 days after delivery) were exposed continuously to 50 Hz, 0.5 mT for 30 days. The control group was treated as the exposed one with the sole difference that the rats were not exposed to magnetic field. Comet assay was used to quantify the level of DNA damage in isolated brain cells. Also bone marrow cells were flushed out to assess micronucleus induction and mitotic index. Spectrophotometric methods were used to measure the level of malondialdehyde (MDA) and the activity of glutathione (GSH) and superoxide dismutase (SOD). The results showed a significant increase in the mean tail moment indicating DNA damage in exposed group (P < 0.01, 0.001, 0.0001). Moreover ELF-MF exposure induced a significant (P < 0.01, 0.001) four folds increase in the induction of micronucleus and about three folds increase in mitotic index (P < 0.0001). Additionally newborn rats exposed to ELF-MF showed significant higher levels of MDA and SOD (P < 0.05). Meanwhile ELF-MF failed to alter the activity of GSH. In conclusion, the present study suggests an association between DNA damage and ELF-MF exposure in newborn rats.

  20. Assessment of Genotoxic and Cytotoxic Hazards in Brain and Bone Marrow Cells of Newborn Rats Exposed to Extremely Low-Frequency Magnetic Field

    Directory of Open Access Journals (Sweden)

    Monira M. Rageh

    2012-01-01

    Full Text Available The present study aimed to evaluate the association between whole body exposure to extremely low frequency magnetic field (ELF-MF and genotoxic , cytotoxic hazards in brain and bone marrow cells of newborn rats. Newborn rats (10 days after delivery were exposed continuously to 50 Hz, 0.5 mT for 30 days. The control group was treated as the exposed one with the sole difference that the rats were not exposed to magnetic field. Comet assay was used to quantify the level of DNA damage in isolated brain cells. Also bone marrow cells were flushed out to assess micronucleus induction and mitotic index. Spectrophotometric methods were used to measure the level of malondialdehyde (MDA and the activity of glutathione (GSH and superoxide dismutase (SOD. The results showed a significant increase in the mean tail moment indicating DNA damage in exposed group (P<0.01,0.001,0.0001. Moreover ELF-MF exposure induced a significant (P<0.01,0.001 four folds increase in the induction of micronucleus and about three folds increase in mitotic index (P<0.0001. Additionally newborn rats exposed to ELF-MF showed significant higher levels of MDA and SOD (P<0.05. Meanwhile ELF-MF failed to alter the activity of GSH. In conclusion, the present study suggests an association between DNA damage and ELF-MF exposure in newborn rats.

  1. THE FORMATION AND ERUPTION OF A SMALL CIRCULAR FILAMENT DRIVEN BY ROTATING MAGNETIC STRUCTURES IN THE QUIET SUN

    Energy Technology Data Exchange (ETDEWEB)

    Yang, Bo; Jiang, Yunchun; Yang, Jiayan; Hong, Junchao; Xu, Zhe, E-mail: boyang@ynao.ac.cn, E-mail: yjy@ynao.ac.cn [Yunnan Observatories, Chinese Academy of Sciences, P.O. Box 110, Kunming 650011 (China)

    2015-04-20

    We present the first observation of the formation and eruption of a small circular filament driven by a rotating network magnetic field (RNF) in the quiet Sun. In the negative footpoint region of an inverse J-shaped dextral filament, the RNF was formed by the convergence to supergranular junctions of several magnetic flux patches of the same polarity, and it then rotated counterclockwise (CCW) for approximately 11 hr and showed up as a CCW rotating EUV cyclone, during which time the filament gradually evolved into a circular filament that surrounded the cyclone. When the calculated convergence and vortex flows appeared around the RNF during its formation and rotation phases, the injected magnetic helicity calculation also showed negative helicity accumulation during the RNF rotation that was consistent with the dextral chirality of the filament. Finally, the RNF rotation stopped and the cyclone disappeared, and, probably due to an emerging bipole and its forced cancellation with the RNF, the closure filament underwent an eruption along its axis in the (clockwise) direction opposite to the rotation directions of the RNF and cyclone. These observations suggest that the RNFs might play an important role in the formation of nearby small-scale circular filaments as they transport and inject magnetic energy and helicity, and the formation of the EUV cyclones may be a further manifestation of the helicity injected into the corona by the rotation of the RNFs in the photosphere. In addition, the new emerging bipole observed before the filament eruption might be responsible for destabilizing the system and triggering the magnetic reconnection which proves useful for the filament eruption.

  2. The Formation and Eruption of a Small Circular Filament Driven by Rotating Magnetic Structures in the Quiet Sun

    Science.gov (United States)

    Yang, Bo; Jiang, Yunchun; Yang, Jiayan; Hong, Junchao; Xu, Zhe

    2015-04-01

    We present the first observation of the formation and eruption of a small circular filament driven by a rotating network magnetic field (RNF) in the quiet Sun. In the negative footpoint region of an inverse J-shaped dextral filament, the RNF was formed by the convergence to supergranular junctions of several magnetic flux patches of the same polarity, and it then rotated counterclockwise (CCW) for approximately 11 hr and showed up as a CCW rotating EUV cyclone, during which time the filament gradually evolved into a circular filament that surrounded the cyclone. When the calculated convergence and vortex flows appeared around the RNF during its formation and rotation phases, the injected magnetic helicity calculation also showed negative helicity accumulation during the RNF rotation that was consistent with the dextral chirality of the filament. Finally, the RNF rotation stopped and the cyclone disappeared, and, probably due to an emerging bipole and its forced cancellation with the RNF, the closure filament underwent an eruption along its axis in the (clockwise) direction opposite to the rotation directions of the RNF and cyclone. These observations suggest that the RNFs might play an important role in the formation of nearby small-scale circular filaments as they transport and inject magnetic energy and helicity, and the formation of the EUV cyclones may be a further manifestation of the helicity injected into the corona by the rotation of the RNFs in the photosphere. In addition, the new emerging bipole observed before the filament eruption might be responsible for destabilizing the system and triggering the magnetic reconnection which proves useful for the filament eruption.

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

    Directory of Open Access Journals (Sweden)

    Piotr Skomro

    2012-12-01

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

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

    Science.gov (United States)

    Skomro, Piotr; Lietz-Kijak, Danuta; Kijak, Edward; Bogdziewicz-Wałęsa, Olga; Opalko, Krystyna

    2012-12-11

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

  5. Radio spectrum evolution and magnetic field in extreme GPS radio sources. The case of RXJ1459+3337

    CERN Document Server

    Orienti, M

    2007-01-01

    Aims: The knowledge of the properties of the youngest radio sources is very important in order to trace the earliest phase of the evolution of the radio emission. RXJ1459+3337, with its high turnover frequency (~25 GHz) provides a unique opportunity to study this class of extreme objects. Methods: High-sensitivity multi-frequency VLA observations have been carried out to measure the flux-density with high accuracy, while multi-frequency VLBA observations were performed, aimed at determining the pc-scale structure. Archival ROSAT data have been used to infer the X-ray luminosity. Results: The comparison between our new VLA data and those available in the literature shows a steady increment of the flux-density in the optically-thick part of the spectrum and a decrement of the turnover frequency. In the optically-thin regime, the source flux density has already started to decrease. Such a variability can be explained in terms of an adiabatically-expanding homogeneous radio component. The frequency range spanned ...

  6. Reduction in Current Consumption of Small DC Motor with Rare-Earth Flexible Bonded Magnets Prepared by Powder Compacting Press and Hot Rolling

    Science.gov (United States)

    Yamashita, Fumitoshi; Watanabe, Akihiko; Fukunaga, Hirotoshi

    The usage of high-performance rare-earth magnets is one of the key technologies in the development of efficient small motors. Ring-shaped melt-spun Nd-Fe-B bonded magnets, prepared using a powder compacting press and/or injection molding, are generally used in typical applications to small efficient motors. For exploiting the maximum characteristics according to the variety of magnetic powder, however, the preparation method of the magnet, the magnet form, and the motor design needs to be changed for high-productivity as well as for improving total performance, including the magnetic properties of bonded magnets. This paper reports recent achievements in new preparation processes for rare-earth bonded magnets and small motors using new materials other than Nd-Fe-B melt-spun powder. This paper especially focuses on the method for maximally exploiting certain rare-earth magnetic powders . Furthermore, reduction in the current consumption of the small DC motor using the developed technique is reported.

  7. Electro/Magnetically Induced Controllable Rotation In Small-scale Liquid Flow

    CERN Document Server

    Amjadi, A; Sobhani, S O; Shirsavar, R

    2013-01-01

    We study all the possibilities of producing rotating flow in an incompressible fluid by electric and magnetic fields. We start with a general theoretical basis and look for different configurations and set-ups which electric/magnetic field and an electric current affect the vorticity of fluid resulting in rotation on liquid flow. We assume steady-state conditions and time-independent electric and magnetic fields as the external body torque. Regarding the theoretical basis, we propose three experimental set-ups in which by applying fields on a fluid, rotational vortices are produced: (a) a uniform electric field and a uniform electric current, (b) a uniform electric current and a non-uniform magnetic field, and (c) a non-uniform electric current and a uniform magnetic field. The first case has been reported in detail named "Liquid Film Motor". The two other cases are experimentally investigated here for a cubic an cylindrical cells. The rotational velocity patterns are obtained by PIV technique, and the result...

  8. Magnetic-Driven Winds from Post-AGB Stars: Solutions for High Speed Winds and Extreme Collimation

    CERN Document Server

    García-Segura, G; Franco, J; Garcia-Segura, Guillermo; Lopez, Jose Alberto; Franco, Jose

    2004-01-01

    This paper explores the effects of post-AGB winds driven solely by magnetic pressure from the stellar surface. It is found that winds can reach high speeds under this assumption, and lead to the formation of highly collimated proto-planetary nebulae. Bipolar knotty jets with periodic features and constant velocity are well reproduced by the models. Several wind models with terminal velocities from a few tens of $\\kms$ up to $10^3$ $\\kms$ are calculated, yielding outflows with linear momenta in the range $10^{36}-10^{40} \\gcms$, and kinetic energies in the range $10^{42}-10^{47} $ erg. These results are in accord with recent observations of proto-planetary nebulae that have pointed out serious energy and momentum deficits if radiation pressure is considered as the only driver for these outflows. Our models strengthen the notion that the large mass-loss rates of post-AGB stars, together with the short transition times from the late AGB to the planetary nebula stage, could be directly linked with the generation ...

  9. Method for locating a small magnetic object in the human body

    Energy Technology Data Exchange (ETDEWEB)

    Kaufman, L.; Williamson, S.J.; Ilmoniemi, R.J.; Weinberg, H.; Boyd, A.D.

    1988-02-29

    A piece of a thin acupuncture needle lodged under the right scapula of a patient could not be found in surgical procedures accompanied by studies of 30 standard x-ray images. To locate it, the authors mapped the magnetic-field component normal to a plane lying above the object, using a superconducting quantum interference device (SQUID). Assuming that the needle could be modeled as a magnetic dipole, the authors were able to infer its lateral position, depth, orientation, and magnetic moment. With this information, directed CT scans, high-resolution x-ray films, and the subsequent surgical removal of the needle proved that it could be located in the body with an accuracy of about three millimeters.

  10. ON THE PROPERTIES OF SLOW MHD SAUSAGE WAVES WITHIN SMALL-SCALE PHOTOSPHERIC MAGNETIC STRUCTURES

    Energy Technology Data Exchange (ETDEWEB)

    Freij, N.; Ruderman, M. S.; Erdélyi, R. [Solar Physics and Space Plasma Research Centre (SP2RC), School of Mathematics and Statistics, University of Sheffield, Hicks Building, Hounsfield Road, Sheffield, S3 7RH (United Kingdom); Dorotovič, I. [Slovak Central Observatory, P.O. Box 42, SK-94701 Hurbanovo (Slovakia); Morton, R. J. [Mathematical Modelling Lab, Northumbria University, Pandon Building, Camden Street, Newcastle upon Tyne, NE1 8ST (United Kingdom); Karlovský, V., E-mail: n.freij@sheffield.ac.uk, E-mail: ivan.dorotovic@suh.sk, E-mail: richard.morton@northumbria.ac.uk, E-mail: m.s.ruderman@sheffield.ac.uk, E-mail: astrokar@hl.cora.sk, E-mail: robertus@sheffield.ac.uk [Hlohovec Observatory and Planetarium, Sládkovičova 41, SK-92001 Hlohovec (Slovakia)

    2016-01-20

    The presence of magnetoacoustic waves in magnetic structures in the solar atmosphere is well-documented. Applying the technique of solar magneto-seismology (SMS) allows us to infer the background properties of these structures. Here, we aim to identify properties of the observed magnetoacoustic waves and study the background properties of magnetic structures within the lower solar atmosphere. Using the Dutch Open Telescope and Rapid Oscillations in the Solar Atmosphere instruments, we captured two series of high-resolution intensity images with short cadences of two isolated magnetic pores. Combining wavelet analysis and empirical mode decomposition (EMD), we determined characteristic periods within the cross-sectional (i.e., area) and intensity time series. Then, by applying the theory of linear magnetohydrodynamics (MHD), we identified the mode of these oscillations within the MHD framework. Several oscillations have been detected within these two magnetic pores. Their periods range from 3 to 20 minutes. Combining wavelet analysis and EMD enables us to confidently find the phase difference between the area and intensity oscillations. From these observed features, we concluded that the detected oscillations can be classified as slow sausage MHD waves. Furthermore, we determined several key properties of these oscillations such as the radial velocity perturbation, the magnetic field perturbation, and the vertical wavenumber using SMS. The estimated range of the related wavenumbers reveals that these oscillations are trapped within these magnetic structures. Our results suggest that the detected oscillations are standing harmonics, and this allows us to estimate the expansion factor of the waveguides by employing SMS. The calculated expansion factor ranges from 4 to 12.

  11. Active shimming method for a 21.3 MHz small-animal MRI magnet

    Science.gov (United States)

    Chen, Shanshan; Xia, Tian; Miao, Zhiying; Xu, Luoyuan; Wang, Hongzhi; Dai, Shuguang

    2017-04-01

    In a 21.3 MHz animal nuclear magnetic resonance (NMR) analyzer and imaging system, high uniformity of the static field B 0 is a crucial prerequisite for obtaining high-quality images and detecting weak signals with short relaxation time. Using only passive shimming and gradient shimming, it is impossible to achieve perfect B 0 uniformity. This paper presents an approach involving high-order active shimming for an NMR analyzer and an imaging magnet. The diameter spherical volume (DSV) of the magnet is only 60 mm. The spherical harmonic function is introduced to analyze the magnetic field and provide a foundation for active shimming. Eleven pairs of bi-planar active shim coils (X, Y, Z, XZ, YZ, Z 2, X 2  +  Y 2, X 2  -  Y 2, Z 3, Z 4, Z 5) were designed using the target field-and stream-function methods, and coils were manufactured with printed circuit board technology in this research. The magnetic field created by these electrified shim coils compensates effectively and accurately for the static magnetic field B 0. The full width at half maximum of the resonance spectrum was used to measure the shimming effect. The results of practical shimming experiments in a 21.3 MHz animal NMR analyzer and imaging device showed that this new approach helps to reduce inhomogeneity from 24 ppm (24  ×  10-6) to 0.39 ppm (0.39  ×  10-6) over a 60 mm DSV, which meets the requirements of imaging and analytical practice.

  12. On the Properties of Slow MHD Sausage Waves within Small-scale Photospheric Magnetic Structures

    Science.gov (United States)

    Freij, N.; Dorotovič, I.; Morton, R. J.; Ruderman, M. S.; Karlovský, V.; Erdélyi, R.

    2016-01-01

    The presence of magnetoacoustic waves in magnetic structures in the solar atmosphere is well-documented. Applying the technique of solar magneto-seismology (SMS) allows us to infer the background properties of these structures. Here, we aim to identify properties of the observed magnetoacoustic waves and study the background properties of magnetic structures within the lower solar atmosphere. Using the Dutch Open Telescope and Rapid Oscillations in the Solar Atmosphere instruments, we captured two series of high-resolution intensity images with short cadences of two isolated magnetic pores. Combining wavelet analysis and empirical mode decomposition (EMD), we determined characteristic periods within the cross-sectional (i.e., area) and intensity time series. Then, by applying the theory of linear magnetohydrodynamics (MHD), we identified the mode of these oscillations within the MHD framework. Several oscillations have been detected within these two magnetic pores. Their periods range from 3 to 20 minutes. Combining wavelet analysis and EMD enables us to confidently find the phase difference between the area and intensity oscillations. From these observed features, we concluded that the detected oscillations can be classified as slow sausage MHD waves. Furthermore, we determined several key properties of these oscillations such as the radial velocity perturbation, the magnetic field perturbation, and the vertical wavenumber using SMS. The estimated range of the related wavenumbers reveals that these oscillations are trapped within these magnetic structures. Our results suggest that the detected oscillations are standing harmonics, and this allows us to estimate the expansion factor of the waveguides by employing SMS. The calculated expansion factor ranges from 4 to 12.

  13. Modeling the effect of small-scale magnetic turbulence on the X-ray properties of Pulsar Wind Nebulae

    Science.gov (United States)

    Bucciantini, N.; Bandiera, R.; Olmi, B.; Del Zanna, L.

    2017-10-01

    Pulsar Wind Nebulae (PWNe) constitute an ideal astrophysical environment to test our current understanding of relativistic plasma processes. It is well known that magnetic fields play a crucial role in their dynamics and emission properties. At present, one of the main issues concerns the level of magnetic turbulence present in these systems, which in the absence of space resolved X-ray polarization measures cannot be directly constrained. In this work, we investigate, for the first time using simulated synchrotron maps, the effect of a small-scale fluctuating component of the magnetic field on the emission properties in X-ray. We illustrate how to include the effects of a turbulent component in standard emission models for PWNe and which consequences are expected in terms of net emissivity and depolarization, showing that the X-ray surface brightness maps can provide already some rough constraints. We then apply our analysis to the Crab and Vela nebulae and by comparing our model with Chandra and Vela data, we found that the typical energies in the turbulent component of the magnetic field are about 1.5-3 times the one in the ordered field.

  14. Small-amplitude magnetic Rayleigh-Taylor instability growth in cylindrical liners and Z-pinches imploded in an axial magnetic field

    Science.gov (United States)

    Velikovich, A. L.; Giuliani, J. L.; Clark, R. W.; Mikitchuk, D.; Kroupp, E.; Maron, Y.; Fisher, A.; Schmit, P. F.

    2014-10-01

    Recent progress in developing the MagLIF approach to pulsed-power driven inertial confinement fusion has stimulated the interest in observation and mitigation of the magnetic Rayleigh-Taylor instability (MRTI) of liners and Z-pinches imploded in an axial magnetic field. Theoretical analysis of these issues is particularly important because direct numerical simulation of the MRTI development is challenging due to intrinsically 3D helical structure of the fastest-growing modes. We review the analytical small-amplitude theory of the MRTI perturbation development and the weakly nonlinear theory of MRTI mode interaction, emphasizing basic physics, opportunity for 3D code verification against exact analytical solutions, and stabilization criteria. The theory is compared to the experimental results obtained at Weizmann Institute with gas-puff Z pinches and on the Z facility at Sandia with solid liners imploded in an axial magnetic field. Work supported by the US DOE/NNSA, and by the US-Israel Binational Science Foundation. Sandia National Laboratories is a multi-program laboratory managed and operated by Sandia Corporation, a wholly owned subsidiary of Lockheed Martin Corporation, for the U.S. Department of Energy's National Nuclear Security Administration under Contract DE-AC04-94AL85000.

  15. High-resolution small field-of-view magnetic resonance image acquisition system using a small planar coil and a pneumatic manipulator in an open MRI scanner.

    Science.gov (United States)

    Miki, Kohei; Masamune, Ken

    2015-10-01

    Low-field open magnetic resonance imaging (MRI) is frequently used for performing image-guided neurosurgical procedures. Intraoperative magnetic resonance (MR) images are useful for tracking brain shifts and verifying residual tumors. However, it is difficult to precisely determine the boundary of the brain tumors and normal brain tissues because the MR image resolution is low, especially when using a low-field open MRI scanner. To overcome this problem, a high-resolution MR image acquisition system was developed and tested. An MR-compatible manipulator with pneumatic actuators containing an MR signal receiver with a small radiofrequency (RF) coil was developed. The manipulator had five degrees of freedom for position and orientation control of the RF coil. An 8-mm planar RF coil with resistance and inductance of 2.04 [Formula: see text] and 1.00 [Formula: see text] was attached to the MR signal receiver at the distal end of the probe. MR images of phantom test devices were acquired using the MR signal receiver and normal head coil for signal-to-noise ratio (SNR) testing. The SNR of MR images acquired using the MR signal receiver was 8.0 times greater than that of MR images acquired using the normal head coil. The RF coil was moved by the manipulator, and local MR images of a phantom with a 2-mm grid were acquired using the MR signal receiver. A wide field-of-view MR image was generated from a montage of local MR images. A small field-of-view RF system with a pneumatic manipulator was integrated in a low-field MRI scanner to allow acquisition of both wide field-of-view and high-resolution MR images. This system is promising for image-guided neurosurgery as it may allow brain tumors to be observed more clearly and removed precisely.

  16. Evolution of small-scale magnetic elements in the vicinity of granular-size swirl convective motions

    CERN Document Server

    Dominguez, S Vargas; Balmaceda, L; Cabello, I; Domingo, V

    2014-01-01

    Advances in solar instrumentation have led to a widespread usage of time series to study the dynamics of solar features, specially at small spatial scales and at very fast cadences. Physical processes at such scales are determinant as building blocks for many others occurring from the lower to the upper layers of the solar atmosphere and beyond, ultimately for understanding the bigger picture of solar activity. Ground-based (SST) and space-borne (Hinode) high-resolution solar data are analyzed in a quiet Sun region displaying negative polarity small-scale magnetic concentrations and a cluster of bright points observed in G-band and Ca II H images. The studied region is characterized by the presence of two small-scale convective vortex-type plasma motions, one of which appears to be affecting the dynamics of both, magnetic features and bright points in its vicinity and therefore the main target of our investigations. We followed the evolution of bright points, intensity variations at different atmospheric heig...

  17. A system for simultaneous exposure of small animals to 60-Hz electric and magnetic fields

    Energy Technology Data Exchange (ETDEWEB)

    Baum, J.W.; Kuehner, A.V.; Benz, R.D.; Carsten, A.L. (Department of Nuclear Energy, Brookhaven National Laboratory, Upton, NY (USA))

    1991-01-01

    Equipment designed for simultaneous exposure of rodents to 60-Hz electric and magnetic fields is described. Three identical systems were constructed, each capable of continuous exposure of 256 rats or 640 mice to a nominal electric field at less than 50 kV/m, and to horizontal and vertical magnetic fields at less than 1 mT. Design features, construction details, and results of various tests of the systems are described. Tests were made: of phase relations between electric and magnetic fields; of uniformity of electric and magnetic fields; of changes across time in electric-field intensity as a result of animals' soiling of cages and various washing routines; of resistance of bedding material during humid and dry conditions; and of acoustic noise due to background, to field-generation equipment, and to air conditioning equipment. The results demonstrated that fields were effectively generated but that significant and troublesome changes in electric-field intensity occurred because of cage-soiling. However, when cages were frequently cleaned, field intensities were consistent from one exposure to another.

  18. Static properties of small Josephson tunnel junctions in an oblique magnetic field

    DEFF Research Database (Denmark)

    Monaco, Roberto; Aarøe, Morten; Mygind, Jesper;

    2009-01-01

    We have carried out a detailed experimental investigation of the static properties of planar Josephson tunnel junctions in presence of a uniform external magnetic field applied in an arbitrary orientation with respect to the barrier plane. We considered annular junctions, as well as rectangular j...

  19. Extreme winter warming events more negatively impact small rather than large soil fauna: shift in community composition explained by traits not taxa

    NARCIS (Netherlands)

    Bokhorst, S.; Phoenix, G.K.; Berke, J.W.; Callaghan, T.V.; Huyer-Brugman, F.; Berg, M.P.

    2012-01-01

    Extreme weather events can have negative impacts on species survival and community structure when surpassinglethal thresholds. Extreme winter warming events in the Arctic rapidly melt snow and expose ecosystems to unseasonablywarm air (2–10 °C for 2–14 days), but returning to cold winter climate exp

  20. Prospects for x-ray polarimetry measurements of magnetic fields in magnetized liner inertial fusion plasmas

    Energy Technology Data Exchange (ETDEWEB)

    Lynn, Alan G., E-mail: lynn@ece.unm.edu; Gilmore, Mark [Department of Electrical and Computer Engineering, University of New Mexico, Albuquerque, New Mexico 87131 (United States)

    2014-11-15

    Magnetized Liner Inertial Fusion (MagLIF) experiments, where a metal liner is imploded to compress a magnetized seed plasma may generate peak magnetic fields ∼10{sup 4} T (100 Megagauss) over small volumes (∼10{sup −10}m{sup 3}) at high plasma densities (∼10{sup 28}m{sup −3}) on 100 ns time scales. Such conditions are extremely challenging to diagnose. We discuss the possibility of, and issues involved in, using polarimetry techniques at x-ray wavelengths to measure magnetic fields under these extreme conditions.

  1. Prospects for x-ray polarimetry measurements of magnetic fields in magnetized liner inertial fusion plasmas

    Science.gov (United States)

    Lynn, Alan G.; Gilmore, Mark

    2014-11-01

    Magnetized Liner Inertial Fusion (MagLIF) experiments, where a metal liner is imploded to compress a magnetized seed plasma may generate peak magnetic fields ˜104 T (100 Megagauss) over small volumes (˜10-10m3) at high plasma densities (˜1028m-3) on 100 ns time scales. Such conditions are extremely challenging to diagnose. We discuss the possibility of, and issues involved in, using polarimetry techniques at x-ray wavelengths to measure magnetic fields under these extreme conditions.

  2. Prospects for x-ray polarimetry measurements of magnetic fields in magnetized liner inertial fusion plasmas.

    Science.gov (United States)

    Lynn, Alan G; Gilmore, Mark

    2014-11-01

    Magnetized Liner Inertial Fusion (MagLIF) experiments, where a metal liner is imploded to compress a magnetized seed plasma may generate peak magnetic fields ∼10(4) T (100 Megagauss) over small volumes (∼10(-10)m(3)) at high plasma densities (∼10(28)m(-3)) on 100 ns time scales. Such conditions are extremely challenging to diagnose. We discuss the possibility of, and issues involved in, using polarimetry techniques at x-ray wavelengths to measure magnetic fields under these extreme conditions.

  3. Magnetic-field-dependent assembly of silica-coated magnetite nanoclusters probed by Ultra-Small-Angle X-ray Scattering (USAXS)

    Energy Technology Data Exchange (ETDEWEB)

    Malik, Vikash [Physics Department, University of Wisconsin Milwaukee, 1900 E. Kenwood Blvd., Milwaukee, WI 53211 (United States); Suthar, Kamleshkumar J. [Advanced Photon Source, Argonne National Laboratory, 9700 S. Cass Ave., Argonne, IL 60439 (United States); Mancini, Derrick C. [Physical Sciences and Engineering, Argonne National Laboratory, 9700 S. Cass Ave., Argonne, IL 60439 (United States); Ilavsky, Jan, E-mail: ilavsky@aps.anl.gov [Advanced Photon Source, Argonne National Laboratory, 9700 S. Cass Ave., Argonne, IL 60439 (United States)

    2014-03-15

    Colloidal suspension of the silica coated magnetic nanoclusters (MNCs) was used to study the magnetic field mediated assembly of magnetic nanoparticles. The spatial arrangement of these MNCs in colloidal suspension was studied using the ultra-small-angle X-ray scattering (USAXS) technique with magnetic field applied in directions orthogonal and parallel to the scattering vector. In situ magnetic field analysis of the USAXS scattering measurement showed anisotropic behavior that can be attributed to the formation of colloidal crystals. During magnetization, the clustered magnetic core induces a large dipole moment, and the thickness of the silica shell helps keep distance between the neighboring particles. The assembly of these hybrid nanostructured particles was found to be dependent on the strength and orientation of this external magnetic field. The dipolar chains formed of MNCs arranged themselves into colloidal crystals formed by two-dimensional magnetic sheets. The structure factor calculations suggested that the lattice parameters of these colloidal crystals can be tuned by changing the strength of the external magnetic field. These experiments shed light on the stimuli-responsive assembly of magnetic colloidal nanoparticles that leads to the creation of tunable photonic crystals. - Highlights: • In situ analysis of Magnetically tunable colloidal nanocluster using Ultra Small Angle X-ray Scattering (USAXS) under uniform magnetic field. • The colloidal super-lattice structure was analyzed in magnetic field along the direction parallel and perpendicular to scattering vector. • Structure factors were extracted by subtracting form factor from the USAXS data using Irena software tool. • The observed super-lattice structural spacing can be tuned by extent of the strength of external magnetic field. • The structure factor calculations showed that the colloidal crystal has the hexagonal packing.

  4. Detection of small hepatocellular carcinoma: Comparison of dynamic enhancement magnetic resonance imaging and multiphase multirow-detector helical CT scanning

    Institute of Scientific and Technical Information of China (English)

    Hong Zhao; Jin-Lin Yao; Ying Wang; Kang-Rong Zhou

    2007-01-01

    AIM: To compare the gadolinium-enhanced multiphase dynamic magnetic resonance imaging (MRI) and multiphase multirow-detector helical CT (MDCT)scanning for detection of small hepatocellular carcinoma (HCC).METHODS: MDCT scanning and baseline MRI with SE T1-WI and T2-WI sequence combined with FMPSPGR sequence were performed in 37 patients with 43 small HCCs. Receiver operating characteristic (ROC) curves were plotted to analyze the results for modality.RESULTS: The areas below ROC curve (Az) were calculated. There was no statistical difference in dynamic enhancement MDCT and MRI. The detection rate of small HCC was 97.5%-97.6% on multiphase MDCT scanning and 90.7%-94.7% on MRI, respectively. The sensitivity of detection for small HCC on MDCT scanning was higher than that on dynamic enhancement MRI. The sensitivity of detection for minute HCC (tumor diameter ≤ 1 cm)was 90.0%-95.0% on MDCT scanning and 70.0%-85.0% on MRI, respectively.CONCLUSION: MDCT scanning should be performed for early detection and effective treatment of small HCC in patients with chronic hepatitis and cirrhosis during follow-up.

  5. Flywheel induction motor-generator for magnet power supply in small fusion device

    Science.gov (United States)

    Hatakeyma, S.; Yoshino, F.; Tsutsui, H.; Tsuji-Iio, S.

    2016-04-01

    A flywheel motor-generator (MG) for the toroidal field (TF) coils of a small fusion device was developed which utilizes a commercially available squirrel-cage induction motor. Advantages of the MG are comparably-long duration, quick power response, and easy implementation of power control compared with conventional capacitor-type power supply. A 55-kW MG was fabricated, and TF coils of a small fusion device were energized. The duration of the current flat-top was extended to 1 s which is much longer than those of conventional small devices (around 10-100 ms).

  6. Channeling 5-min photospheric oscillations into the solar outer atmosphere through small-scale vertical magnetic flux tubes

    CERN Document Server

    Khomenko, E; Collados, M; Bueno, J Trujillo

    2008-01-01

    We report two-dimensional MHD simulations which demonstrate that photospheric 5-min oscillations can leak into the chromosphere inside small-scale vertical magnetic flux tubes. The results of our numerical experiments are compatible with those inferred from simultaneous spectropolarimetric observations of the photosphere and chromosphere obtained with the Tenerife Infrared Polarimeter (TIP) at 10830 A. We conclude that the efficiency of energy exchange by radiation in the solar photosphere can lead to a significant reduction of the cut-off frequency and may allow for the propagation of the 5 minutes waves vertically into the chromosphere.

  7. Extreme Heat

    Science.gov (United States)

    ... Landslides & Debris Flow Nuclear Blast Nuclear Power Plants Power Outages Pandemic Radiological Dispersion Device Severe Weather Snowstorms & Extreme ... Landslides & Debris Flow Nuclear Blast Nuclear Power Plants Power Outages Pandemic Radiological Dispersion Device Severe Weather Snowstorms & Extreme ...

  8. Two-Color Magneto-Optical Trap with Small Magnetic Field for Ytterbium

    CERN Document Server

    Kawasaki, Akio; Yu, QinQin; Vuletić, Vladan

    2015-01-01

    We report a two-color magneto-optical trap (MOT) for ytterbium atoms operating at a low magnetic field gradient down to 2 G/cm where a conventional MOT using the singlet transition (6s^2 1S0 -> 6s6p 1P1) is unable to trap atoms. By simultaneously applying laser light on both the broad-linewidth singlet transition and the narrow-linewidth triplet transition (6s^2 1S0 -> 6s6p 3P1), we load and trap 4.0 x 10^5 atoms directly from an atomic beam at 700 K. In the two-color MOT, the slowing and trapping functions are separately performed by the singlet transition light and the triplet transition light, respectively. The two-color MOT is highly robust against laser power imbalance even at very low magnetic field gradients.

  9. Double pancake superconducting coil design for maximum magnetic energy storage in small scale SMES systems

    Science.gov (United States)

    Hekmati, Arsalan; Hekmati, Rasoul

    2016-12-01

    Electrical power quality and stability is an important issue nowadays and technology of Superconducting Magnetic Energy Storage systems, SMES, has brought real power storage capability to power systems. Therefore, optimum SMES design to achieve maximum energy with the least length of tape has been quite a matter of concern. This paper provides an approach to design optimization of solenoid and toroid types of SMES, ensuring maximum possible energy storage. The optimization process, based on Genetic Algorithm, calculates the operating current of superconducting tapes through intersection of a load line with the surface indicating the critical current variation versus the parallel and perpendicular components of magnetic flux density. FLUX3D simulations of SMES have been utilized for energy calculations. Through numerical analysis of obtained data, formulations have been obtained for the optimum dimensions of superconductor coil and maximum stored energy for a given length and cross sectional area of superconductor tape.

  10. Designing Of Permanent Magnet Synchronous Machine For Applications In Small Hydro Power Plants

    Directory of Open Access Journals (Sweden)

    Jayashree Sharma

    2015-07-01

    Full Text Available The need of the hour, as we all genuinely know from the global scenario is the production of electricity from the renewable resources of energy. Most widely used among them are the solar and the wind potential. Besides these, the hydroelectric resources also play a remarkable role as hydroelectricity accounts for a major share in the energy sector throughout the world. The trend at present is of the stand alone hydro power plants wherein the turbine used is the Hydrokinetic turbine , which works with the speed of flow of the water stream. Permanent magnet synchronous machines, known for their robust nature, variable speed, and high power to weight ratio are the most suitable ones for the construction of the turbine for low speed operation. This paper presents the design of permanent magnet synchronous machine and the machine has been modeled and simulated in RMXprt and Ansys Maxwell.

  11. Improvement of neurofeedback therapy for improved attention through facilitation of brain activity using local sinusoidal extremely low frequency magnetic field exposure.

    Science.gov (United States)

    Zandi Mehran, Yasaman; Firoozabadi, Mohammad; Rostami, Reza

    2015-04-01

    Traditional neurofeedback (NF) is a training approach aimed at altering brain activity using electroencephalography (EEG) rhythms as feedback. In NF training, external factors such as the subjects' intelligence can have an effect. In contrast, a low-energy NF system (LENS) does not require conscious effort from the subject, which results in fewer attendance sessions. However, eliminating the subject role seems to eliminate an important part of the NF system. This study investigated the facilitating effect on the theta-to-beta ratio from NF training, using a local sinusoidal extremely low frequency magnetic field (LSELF-MF) versus traditional NF. Twenty-four healthy, intelligent subjects underwent 10 training sessions to enhance beta (15-18 Hz), and simultaneously inhibit theta (4-7 Hz) and high beta (22-30 Hz) activity, at the Cz point in a 3-boat-race video game. Each session consisted of 3 statuses, PRE, DURING, and POST. In the DURING status, the NF training procedure lasted 10 minutes. Subjects were led to believe that they would be exposed to a magnetic field during NF training; however, 16 of the subjects who were assigned to the experimental group were really exposed to 45 Hz-360 µT LSELF-MF at Cz. For the 8 other subjects, only the coil was located at the Cz point with no exposure. The duty cycle of exposure was 40% (2-second exposure and 3-second pause). The results show that the theta-to-beta ratio in the DURING status of each group differs significantly from the PRE and POST statuses. Between-group analysis shows that the theta-to-beta ratio in the DURING status of the experimental group is significantly (P < .001) lower than in the sham group. The result shows the effect of LSELF-MF on NF training.

  12. A detailed ethological analysis of the mouse open field test: effects of diazepam, chlordiazepoxide and an extremely low frequency pulsed magnetic field.

    Science.gov (United States)

    Choleris, E; Thomas, A W; Kavaliers, M; Prato, F S

    2001-05-01

    The open field test (OFT) is a widely used procedure for examining the behavioral effects of drugs and anxiety. Detailed ethological assessments of animal behavior are lacking. Here we present a detailed ethological assessment of the effects of acute treatment with the benzodiazepines, diazepam (DZ, 1.5mg/kg) and chlordiazepoxide (CDP, 5.0 and 10.0mg/kg), as well as exposure to a non-pharmacological agent, a specific pulsed extremely low frequency magnetic field (MAG) on open field behavior. We examined the duration, frequency and time course of various behaviors (i.e. exploration, walk, rear, stretch attend, return, groom, sit, spin turn, jump and sleep) exhibited by male mice in different regions of a novel open field. Both DZ and CDP consistently reduced the typical anxiety-like behaviors of stretch attend and wall-following (thigmotaxis), along with that of an additional new measure: 'returns', without producing any overall effects on total locomotion. The drugs also differed in their effects. CDP elicited a shift in the locomotor pattern from a 'high explore' to a 'high walk', while DZ mainly elicited alterations in sit and groom. The MAG treatment was repeated twice with both exposures reducing horizontal and vertical (rearing) activity and increasing grooming and spin turns. However, the anxiety-like behaviors of stretch attend and return were marginally reduced by only the first exposure. We conclude that a detailed ethological analysis of the OFT allows not only the detection of specific effects of drugs and non-pharmacological agents (i.e. pulsed magnetic field) on anxiety-like behaviors, but also permits the examination of non-specific effects, in particular those on general activity.

  13. Mandelbrot's Extremism

    NARCIS (Netherlands)

    Beirlant, J.; Schoutens, W.; Segers, J.J.J.

    2004-01-01

    In the sixties Mandelbrot already showed that extreme price swings are more likely than some of us think or incorporate in our models.A modern toolbox for analyzing such rare events can be found in the field of extreme value theory.At the core of extreme value theory lies the modelling of maxima

  14. Radiation from particles moving in small-scale magnetic fields created in solid-density laser-plasma laboratory experiments

    Energy Technology Data Exchange (ETDEWEB)

    Keenan, Brett D., E-mail: bdkeenan@ku.edu; Medvedev, Mikhail V. [Department of Physics and Astronomy, University of Kansas, Lawrence, Kansas 66045 (United States)

    2015-11-15

    Plasmas created by high-intensity lasers are often subject to the formation of kinetic-streaming instabilities, such as the Weibel instability, which lead to the spontaneous generation of high-amplitude, tangled magnetic fields. These fields typically exist on small spatial scales, i.e., “sub-Larmor scales.” Radiation from charged particles moving through small-scale electromagnetic (EM) turbulence has spectral characteristics distinct from both synchrotron and cyclotron radiation, and it carries valuable information on the statistical properties of the EM field structure and evolution. Consequently, this radiation from laser-produced plasmas may offer insight into the underlying electromagnetic turbulence. Here, we investigate the prospects for, and demonstrate the feasibility of, such direct radiative diagnostics for mildly relativistic, solid-density laser plasmas produced in lab experiments.

  15. Phase Formation and Magnetic Properties of Nanocomposite Nd-Fe-B Adjusted by Small Amount of Dy and Co

    Institute of Scientific and Technical Information of China (English)

    T S Jang; T W Lim; H S Aum; D H Lee; M B Kim

    2004-01-01

    In order to improve and stabilize the magnetic properties of nanocomposite Nd2Fe14B/α-Fe magnetic alloys by a compositional adjustment, small amount of Dy and/or Co was added to Nd9Fe84B7 alloys. DTA analysis on the amorphous of the alloys took place as the soft magnetic phases were crystallized, and then the hard magnetic Nd2Fe14B was precipitated from them. While α-Fe and a metastable 1:7 (TbCu7-type) phase were formed simultaneously in Dy and Co-free alloys, they were crystallized separately at different temperatures after Dy or Co was added. This phase separation occurred more clearly in the Dy-treated alloys and the other soft magnetic phase Fe3B was also stabilized by Dy and/or Co. The 1: 7 phase that was stabilized by Dy and/or Co was not eliminated at 700 ℃, decreasing magnetic properties of the alloys. It was eventually disappeared above 725 ℃, but Fe3B was not eliminated even at 750 ℃ when Dy was added more than 0.5 at% or Co was added more than 2.0 at%. Amount of Nd2Fe14B in the alloys tended to increase as Dy addition increased,whereas Co addition did not lead to any appreciable change in the ratio of α-Fe and Nd2Fe14B. Moreover, Dy addition apparently increased coercivity of an alloy while Co addition had a beneficial effect on remanence. The grains in the Dytreated alloys were usually finer than those in the Co-treated alloys. The grain size of both α-Fe and Nd2Fe14B in the alloys exhibiting mr ≥ 0.72 was in the range of 20 ~ 40 nm or even larger 50 nm, which is larger than the theoretical optimum size ( ~ 10 nm). Typical magnetic properties obtained from a Nd7.5Dy1.5Fe82.5Co1.5B7 alloy annealed for 12 min at 725 ℃were iHc=4.85 kOe, Br= 11.32 kG, (BH)max = 15.73 MGOe, and mr=0.73.

  16. A theoretical study on small iridium clusters: structural evolution, electronic and magnetic properties, and reactivity predictors.

    Science.gov (United States)

    Du, Jiguang; Sun, Xiyuan; Chen, Jun; Jiang, Gang

    2010-12-16

    The structural, electronic, and magnetic properties of iridium clusters with sizes of n = 2-15 are investigated by employing the generalized gradient approximation of density functional theory. Simple cube evolution pattern is revealed for Ir(2-15) clusters, as predicted by previous reports. It is remarkable that for Ir(10), Ir(11) clusters, new generated isomers with higher stabilities relative to those reported in previous studies are obtained. The even-sized clusters are more stable than the odd-sized species. The Ir-Ir bonds in the cubic Ir(8) and Ir(12) clusters, which are considered as the basic units in the structural evolution present covalent character. Starting from n = 8, the magnetic moments of Ir(n) clusters decrease sharply. The moments of magnetic clusters show 5d characters. The reactive site selectivity of studied clusters with n = 5-15 is analyzed with condensed Fukui function. The capped atoms in certain clusters (Ir(9), Ir(10), Ir(11), and Ir(13)) generally show extraordinary activity for both nucleophilic and electrophilic attack.

  17. First-principles study of magnetism, structure and chemical order in small FeRh alloy clusters

    CERN Document Server

    Mokkath, Junais Habeeb

    2011-01-01

    The structural, electronic and magnetic properties of small ${\\rm Fe}_m {\\rm Rh}_n$ clusters having $N = m+n \\leq 8$ atoms are studied in the framework of a generalized-gradient approximation to density-functional theory. The correlation between structure, chemical order, and magnetic behavior is analyzed as a function of size and composition. For $N = m+n \\leq 6$ a thorough sampling of all cluster topologies has been performed, while for N = 7 and 8 only a few representative topologies are considered. In all cases the entire concentration range is systematically investigated. All the clusters show ferromagnetic-like order in the optimized structures. As a result, the average magnetic moment per atom $\\bar\\mu_N$ increases monotonously, which is almost linear over a wide range of concentration with Fe content. A remarkable enhancement of the local Fe moments beyond 3 $\\mu_B$ is observed as result of Rh doping. This is a consequence of the increase in the number of Fe $d$ holes, due to charge transfer from Fe t...

  18. Effects of Exposure to Extremely Low Frequency Electro-magnetic Fields on Circadian Rhythms and Distribution of Some Leukocyte Differentiation Antigens in Dairy Cows

    Institute of Scientific and Technical Information of China (English)

    CALOGERO STELLETTA; PAOLA DE NARDO; FRANCESCO SANTIN; GIUSEPPE BASSO; BARBARA MICHIELOTTO; GIUSEPPE PICCIONE; MASSIMO MORGANTE

    2007-01-01

    Objective To investigate the effects of extremely low frequency magnetic and electric fields (ELFEMFs) emitted from 380 kV transmission lines on some leukocyte differentiation antigens in dairy cows. Methods The study was carried out in 5 cows exposed to 1.98-3.28 μT of ELFEMFs and in 5 control cows exposed to 0.2-0.7 μT of ELFEMFs. Following haematological and immunologic parameters were measured in both groups: WBC, CD45R, CD6, CI4, CD8, CD21, and CD1 1B leukocyte antigen expression. Results Some of the haematological and immunologic parameters under investigation were similar in both groups. However, CD8 (T lymphocyte surface antigen) was higher in the exposed group (1.35 ± 0.120 vs 0.50 ± 0.14 × 103/mL). Furthermore, the CD4/CD8 ratio (0.84 ± 0.05 and 2.19 ± 0.16 for exposed and not exposed cows respectively) and circadian rhythm were different between the two groups. Conclusion Exposure to ELFEMFs is responsible of the abnormal temporal variations and distribution of some haematological and immunological parameters in dairy cows.

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

    Science.gov (United States)

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

    2008-11-01

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

  20. Extremely low frequency magnetic field and the hatching rate of Fasciola hepatica eggs, the fecundity and survival of liver fluke-infected snail, Lymnaea truncatula.

    Science.gov (United States)

    Kołodziejczyk, Lidia; Kuźna-Grygiel, Wanda; Gonet, Bolesław; Podraza, Wojciech

    2010-01-01

    Eggs of Fasciola hepatica were exposed for 10 days to extremely low frequency magnetic field (ELFMF) at the frequency of 50 Hz and density of 2 mT (rms). The results show an accelerated hatching of F. hepatica eggs in relation to control (non-exposed) group. The host snails, Lymnaea truncatula, were divided into three groups; those of groups I and II were infected with the miracidia of F. hepatica hatched from control egg culture, whereas those of group III were infected with miracidia hatched from eggs affected by ELFMF. Thereafter, snails of groups II and III were exposed to ELFMF for 53 days, whereas those of group I were not exposed. At day 14 post infection, a significant decrease was observed in the number of cocoons laid by snails of group III, compared with control. Also, significant mortality in group III snails was observed 42 days post infection. The increased mortality and a lower number of cocoons laid by group III snails have probably resulted from enhanced stimulation of metacercarial parthenogenetic reproduction in consequence of infecting the molluscs with miracidia reared under ELFMF.

  1. Magnetic Resonance Imaging of Phosphocreatine and Determination of BOLD Kinetics in Lower Extremity Muscles using a Dual-Frequency Coil Array.

    Science.gov (United States)

    Brown, Ryan; Khegai, Oleksandr; Parasoglou, Prodromos

    2016-07-28

    Magnetic resonance imaging (MRI) provides the unique ability to study metabolic and microvasculature functions in skeletal muscle using phosphorus and proton measurements. However, the low sensitivity of these techniques can make it difficult to capture dynamic muscle activity due to the temporal resolution required for kinetic measurements during and after exercise tasks. Here, we report the design of a dual-nuclei coil array that enables proton and phosphorus MRI of the human lower extremities with high spatial and temporal resolution. We developed an array with whole-volume coverage of the calf and a phosphorus signal-to-noise ratio of more than double that of a birdcage coil in the gastrocnemius muscles. This enabled the local assessment of phosphocreatine recovery kinetics following a plantar flexion exercise using an efficient sampling scheme with a 6 s temporal resolution. The integrated proton array demonstrated image quality approximately equal to that of a clinical state-of-the-art knee coil, which enabled fat quantification and dynamic blood oxygen level-dependent measurements that reflect microvasculature function. The developed array and time-efficient pulse sequences were combined to create a localized assessment of calf metabolism using phosphorus measurements and vasculature function using proton measurements, which could provide new insights into muscle function.

  2. Magnetic Resonance Imaging of Phosphocreatine and Determination of BOLD Kinetics in Lower Extremity Muscles using a Dual-Frequency Coil Array

    Science.gov (United States)

    Brown, Ryan; Khegai, Oleksandr; Parasoglou, Prodromos

    2016-07-01

    Magnetic resonance imaging (MRI) provides the unique ability to study metabolic and microvasculature functions in skeletal muscle using phosphorus and proton measurements. However, the low sensitivity of these techniques can make it difficult to capture dynamic muscle activity due to the temporal resolution required for kinetic measurements during and after exercise tasks. Here, we report the design of a dual-nuclei coil array that enables proton and phosphorus MRI of the human lower extremities with high spatial and temporal resolution. We developed an array with whole-volume coverage of the calf and a phosphorus signal-to-noise ratio of more than double that of a birdcage coil in the gastrocnemius muscles. This enabled the local assessment of phosphocreatine recovery kinetics following a plantar flexion exercise using an efficient sampling scheme with a 6 s temporal resolution. The integrated proton array demonstrated image quality approximately equal to that of a clinical state-of-the-art knee coil, which enabled fat quantification and dynamic blood oxygen level-dependent measurements that reflect microvasculature function. The developed array and time-efficient pulse sequences were combined to create a localized assessment of calf metabolism using phosphorus measurements and vasculature function using proton measurements, which could provide new insights into muscle function.

  3. Exposure to an Extremely-Low-Frequency Magnetic Field Stimulates Adrenal Steroidogenesis via Inhibition of Phosphodiesterase Activity in a Mouse Adrenal Cell Line.

    Science.gov (United States)

    Kitaoka, Kazuyoshi; Kawata, Shiyori; Yoshida, Tomohiro; Kadoriku, Fumiya; Kitamura, Mitsuo

    2016-01-01

    Extremely low-frequency magnetic fields (ELF-MFs) are generated by power lines and household electrical devices. In the last several decades, some evidence has shown an association between ELF-MF exposure and depression and/or anxiety in epidemiological and animal studies. The mechanism underlying ELF-MF-induced depression is considered to involve adrenal steroidogenesis, which is triggered by ELF-MF exposure. However, how ELF-MFs stimulate adrenal steroidogenesis is controversial. In the current study, we investigated the effect of ELF-MF exposure on the mouse adrenal cortex-derived Y-1 cell line and the human adrenal cortex-derived H295R cell line to clarify whether the ELF-MF stimulates adrenal steroidogenesis directly. ELF-MF exposure was found to significantly stimulate adrenal steroidogenesis (p steroidogenesis via an increase in intracellular cAMP caused by the inhibition of phosphodiesterase activity in Y-1 cells. The same mechanism may trigger the increase in adrenal steroid secretion in mice observed in our previous study.

  4. Mathematical model of a novel small magnetorheological damper by using outer magnetic field

    Directory of Open Access Journals (Sweden)

    Liutian Huang

    2017-03-01

    Full Text Available In order to realize small loading and small damping, a mini Magneto-rheological fluid (MRF damper is suggested by using new method of outer coils, and its physical model is established firstly. It was found that the landing force is only 1.74∼8N, the landing force is the third-order function with the current by polynomial fitting of the experimental data, which shows a force-current model. The results of force-displacement and force-velocity indicate that it has nonlinear hysteretic damping characteristics. Based on the new mini-mode principle and the damping characteristics, an improved nonlinear dynamics model is proposed, and its parameter expressions are obtained by parameter identification and regression fitting. Model curves fit well with experimental curves, and the improved model has fully demonstrated the dynamic characteristics of the mini-MRF damper. It will provide scientific method and physical model for the small MRF damper development.

  5. Characteristics of Jeffrey fluid model for peristaltic flow of chyme in small intestine with magnetic field

    Science.gov (United States)

    Akbar, Noreen Sher; Nadeem, S.; Lee, Changhoon

    In the present article we have analyzed the Jeffrey fluid model for the peristaltic flow of chyme in the small intestine. We have formulated the problem using two non-periodic sinusoidal waves of different wavelengths propagating with same speed c along the outer wall of the tube. Governing equations for the problem under consideration have been simplified under the assumptions of long wavelength and low Reynolds number approximation (such assumptions are consistent since Re (Reynolds number) is very small and long wavelength approximation also exists in the small intestine). Exact solutions have been calculated for velocity and pressure rise. Physical behavior of different parameters of Jeffrey fluid has been presented graphically for velocity, pressure rise, pressure gradient and frictional forces. The trapping phenomenon is also discussed at the end of the article.

  6. Analysis of the electrical and magnetic properties of elastomeric composites and their applicability in small flexible wearable antennas

    Science.gov (United States)

    Al-Sehemi, Abdullah G.; Al-Ghamdi, Ahmed A.; Dishovsky, Nikolay T.; Malinova, Petrunka A.; Atanasov, Nikolay T.; Atanasova, Gabriela L.

    2017-07-01

    The aim of the research is to obtain conductive elastomer based composites with different degree of filling and specific properties that are applicable for manufacturing of small flexible wearable antennas. The mechanical, electrical and magnetic properties of the composites based on butadiene-acrylonitrile rubber and conductive carbon black have been determined and the possibilities for their use have been analyzed. It has been found that regarding the requirements for elastomer composites application as substrates in such kind of antennas for the 2.4-2.5 GHz frequency range (in respect to the tensile strength, elasticity, volume resistivity, real part of permittivity and permeability, tangent of dielectric and magnetic losses), the most suitable composites are those containing conductive carbon black at 5-10 phr. The prepared composites have been used as monolayered or multilayered substrates for manufacturing prototypes of small flexible wearable antennas for medical, sport and military applications for the 2.4-2.5 GHz frequency range, which demonstrate reliable performance and meet the requirements of the Federal Communication Commission.

  7. Image tuning techniques for enhancing the performance of pure permanent magnet undulators with small gap/period ratios

    Energy Technology Data Exchange (ETDEWEB)

    Tatchyn, R. [Stanford Univ., CA (United States)

    1995-12-31

    The on-axis field of a small-gap undulator constricted out of pure permanent magnet (PM) blocks arranged in an alternating-dipole (i.e., 2 dipoles/period) array can be substantially varied by positioning monolithic permeable plates above and below the undulator jaws. This simple technique, which can be used to control the 1st harmonic energy in conventional synchrotron radiation (SR) or Free Electron Laser (FEL) applications requiring sub-octave tuning, can also be shown to suppress magnetic inhomogeneities that can contribute to the undulator`s on-axis field errors. If a standard 4 block/period Halbach undulator, composed of PM blocks with square cross sections, is rearranged into an alternating-dipole array with the same period, the peak field that can be generated with superimposed image plates can substantially exceed that of the pure-PM Halbach array. This design technique, which can be viewed as intermediate between the {open_quotes}pure-PM{close_quotes} and standard {open_quotes}hybrid/PM{close_quotes} configurations, provides a potentially cost-effective method of enhancing the performance of small-gap, pure-PM insertion devices. In this paper we report on the analysis and recent characterization of pure-PM undulator structures with superimposed image plates, and discuss possible applications to FEL research.

  8. The Production Management Improvement Model of Small and Medium-sized Permanent Magnetic Materials Manufacturing Companies

    Institute of Scientific and Technical Information of China (English)

    TIAN Zhong-qu; ZHANG Shu-juan; JIN Ya-juan; REN Miao; AN Pei

    2016-01-01

    An integrated production planning and control model based on MRPⅡand JIT is put forward through analyzing the characteristics of magnetic materials manufacturing companies. Master Production Schedule with limited capacity and operational plan in workshop level based on the basic data of flow chart are formulated by this model which applied JIT idea and based on customer order demand. Push production is adapted during execution phase combined with process flow cards. The model is helpful to reduce inventory, keep certain flexbility of production and improve continuity and equilibrium of manufacturing process.

  9. Small satellite attitude control for sun-oriented operations utilizing a momentum bias with magnetic actuators

    Science.gov (United States)

    Wolfe, Scott M.

    1995-03-01

    The feasibility of using a three axis control, momentum bias system with magnetic actuators for sun-oriented operations is explored. Relevant equations of motion are developed for a sun-oriented coordinate system and control laws are developed for initial spacecraft capture after launch vehicle separation; reorientation from Earth oriented to a sun oriented operations mode; sun-oriented attitude control; and momentum wheel control. Simulations demonstrating the stability and time responsiveness of the system are performed. Sensor noise input tests are performed to investigate the systems susceptibility to imperfect conditions. Cross product of inertia effects are also input to test for system instability.

  10. Small-scale features in the Earth's magnetic field observed by Magsat.

    Science.gov (United States)

    Cain, J.C.; Schmitz, D.R.; Muth, L.

    1984-01-01

    A spherical harmonic expansion to degree and order 29 is derived using a selected magnetically quiet sample of Magsat data. Global maps representing the contribution due to terms of the expansion above n = 13 at 400 km altitude are compared with previously published residual anomaly maps and shown to be similar, even in polar regions. An expansion with such a high degree and order displays all but the sharpest features seen by the satellite and gives a more consistent picture of the high-order field structure at a constant altitude than do component maps derived independently. -Authors

  11. Electron Spectral Changes Observed Near L=4.2 by 9 CXD Instruments During a Recent Small Magnetic Storm

    Science.gov (United States)

    Cayton, T. E.; Friedel, R. H.; Varotsou, A.

    2008-12-01

    The current phase of the solar cycle is characterized by long intervals between significant magnetic storms during which the trapped electron population decays and electron spectra harden significantly. Indeed, during the long recovery phase between storms a characteristic lower-energy (0.1 to 1.5 MeV) feature develops systematically as the magnetic equator is approached and is most significant at the lowest L-shell visited along the orbit of GPS satellites; such features have been reported previously for this region of the magnetosphere.1-4 Following the main phase of a magnetic storm a smooth featureless increase below about 1.5 MeV replaces the low-energy structure mentioned above -- a spectral characteristic of the electron population near the geostationary orbit. Electron spectral results at the magnetic equator from 9 Combined X-ray senor and Dosimeter instruments will be presented here for the small (55 nT) storm of 4 September 2008. 1. A. L. Vampola, J. B. Blake, and G. A. Paulikas, "A New Study of the Magentospheric Electron Environment," Journal of Spacecraft and Rockets 14, 690 (1977). 2. J. B. Reagan, R. W. Nightingale, E. E. Gaines, W. L. Imhof, and E. G. Stassinopoulos, "Outer Zone Energetic Electron Spectral Measurements," Journal of Spacecraft and Rockets 18, 83 (1981). 3. A. L. Vampola, "Solar Cycle Effects on Trapped Energetic Particles," Journal of Spacecraft and Rockets 26, 416 (1989). 4. W. D. Pesnell, "Fluxes of Relativistic Electrons in Low-Earth Orbit during the Decline of Solar Cycle 22," IEEE Transactions on Nuclear Science 48, 2016 (2001).

  12. Magnetic-field-dependent assembly of silica-coated magnetite nanoclusters probed by Ultra-Small-Angle X-ray Scattering (USAXS)

    Science.gov (United States)

    Malik, Vikash; Suthar, Kamleshkumar J.; Mancini, Derrick C.; Ilavsky, Jan

    2014-03-01

    Colloidal suspension of the silica coated magnetic nanoclusters (MNCs) was used to study the magnetic field mediated assembly of magnetic nanoparticles. The spatial arrangement of these MNCs in colloidal suspension was studied using the ultra-small-angle X-ray scattering (USAXS) technique with magnetic field applied in directions orthogonal and parallel to the scattering vector. In situ magnetic field analysis of the USAXS scattering measurement showed anisotropic behavior that can be attributed to the formation of colloidal crystals. During magnetization, the clustered magnetic core induces a large dipole moment, and the thickness of the silica shell helps keep distance between the neighboring particles. The assembly of these hybrid nanostructured particles was found to be dependent on the strength and orientation of this external magnetic field. The dipolar chains formed of MNCs arranged themselves into colloidal crystals formed by two-dimensional magnetic sheets. The structure factor calculations suggested that the lattice parameters of these colloidal crystals can be tuned by changing the strength of the external magnetic field. These experiments shed light on the stimuli-responsive assembly of magnetic colloidal nanoparticles that leads to the creation of tunable photonic crystals.

  13. Clinical and magnetic resonance observations in cerebral small-vessel disease

    NARCIS (Netherlands)

    Kwa, V.I.H.

    1999-01-01

    The study reported in this thesis tried to address the following questions: 1. Is it possible to detect genetic factors and vascular risk factors that are specifically associated with the development of small- or large-vessel disease? 2. Are the different clinical and MRI manifestations, that are at

  14. Diffusion nuclear magnetic resonance spectroscopy detects substoichiometric concentrations of small molecules in protein samples

    NARCIS (Netherlands)

    Ribeiro, João P.; Palczewska, Małgorzata; André, Sabine; Cañada, F. Javier; Gabius, Hans-Joachim; Jiménez-Barbero, Jesús; Mellström, Britt; Naranjo, José R.; Scheffers, Dirk-Jan; Groves, Patrick

    2010-01-01

    Small molecules are difficult to detect in protein solutions, whether they originate from elution during affinity chromatography (e.g., imidazole, lactose), buffer exchange (Tris), stabilizers (e.g., β-mercaptoethanol, glycerol), or excess labeling reagents (fluorescent reagents). Mass spectrometry

  15. Clinical and magnetic resonance observations in cerebral small-vessel disease

    NARCIS (Netherlands)

    Kwa, V.I.H.

    1999-01-01

    The study reported in this thesis tried to address the following questions: 1. Is it possible to detect genetic factors and vascular risk factors that are specifically associated with the development of small- or large-vessel disease? 2. Are the different clinical and MRI manifestations, that are

  16. Prenatal magnetic resonance and ultrasonographic findings in small-bowel obstruction: imaging clues and postnatal outcomes

    Energy Technology Data Exchange (ETDEWEB)

    Rubio, Eva I.; Blask, Anna R.; Bulas, Dorothy I. [Children' s National Medical System, Division of Diagnostic Imaging and Radiology, Washington, DC (United States); Badillo, Andrea T. [Children' s National Medical System, Division of General and Thoracic Surgery, Washington, DC (United States)

    2017-04-15

    Prenatal small-bowel obstruction can result from single or multiple atresias, and it can be an isolated abnormality or part of a syndrome. It is sometimes the first manifestation of cystic fibrosis. Accurate prediction of the level of obstruction and length of bowel affected can be difficult, presenting a challenge for counseling families and planning perinatal management. To review the prenatal US and MRI findings of small-bowel obstruction and to assess whether fetal MRI adds information that could improve prenatal counseling and perinatal management. We retrospectively reviewed 12 prenatally diagnosed cases of small-bowel obstruction evaluated by both US and MRI from 2005 to 2015. We analyzed gestational age at evaluation, US and MRI findings, gestational age at delivery and postnatal outcomes. The final diagnoses were jejunal atresia (7), ileal atresia (1), cystic fibrosis (3) and combined jejunal and anal atresia (1). Four of the eight with jejunal atresia were found to have multiple small-bowel atresias. Prenatal perforation was noted in three. We identified a trend of increasing complexity of bowel contents corresponding to progressively distal level of obstruction, as indicated by increasing US echogenicity and high T1 signal on MRI. Seven cases of jejunal atresia and one case of ileal atresia demonstrated small ascending, transverse and descending colon (microcolon) with filling of a normal-diameter rectum. In contrast, all three fetuses with cystic fibrosis and the fetus with jejunal-anal atresia demonstrated microcolon as well as abnormal paucity or absence of rectal meconium. Polyhydramnios was present in nine. Eight were delivered prematurely, of whom seven had polyhydramnios. The fetus with jejunal and anal atresia died in utero. Postnatally, three had short gut syndrome, all resulting from multiple jejunal atresias; these three were among a subset of four fetuses whose bowel diameter measured more than 3 cm. Eight infants had no further

  17. A Preliminary Survey of Extremely Small Populations of Wild Plants in Bawangling,Hainan Island%海南岛霸王岭极小种群野生植物调查初报

    Institute of Scientific and Technical Information of China (English)

    许洋瑜; 罗文; 韩文涛; 彭慧

    2014-01-01

    According to the existing literature's analysis, there are 17 kinds of extremely small populations of wild plants in Bawangling , through the survey of 17 kinds of extremely small populations of wild plants, has got a preliminary understanding about the distribution of small populations in Bawangling ,and analyzed the correlation between the distribution of extremely small populations and the altitude, slope direction, slope, veg-etation habitat factors , the main threats factors. Found that the extremely small populations in Bawangling was at risk, which need protected timely, and at the same time put forward some suggestions for protection.%根据已有文献资料分析统计,霸王岭地区有分布记录的极小种群野生植物17种,通过对17种极小种群野生植物的调查,初步了解霸王岭地区极小种群的分布资源状况,并分析极小种群的分布与海拔、坡向、坡度、植被等生境因子的相关性以及所面临的主要威胁,据此可知霸王岭保护区的极小种群植物资源已处于亟待保护的危险状态,并提出了一些保护建议。

  18. Correlation between structural, electronic and magnetic properties on nm-small Co Islands

    Energy Technology Data Exchange (ETDEWEB)

    Oka, Hirofumi; Rodary, Guillemin; Wedekind, Sebastian; Sander, Dirk; Kirschner, Juergen [Max-Planck-Institut fuer Mikrostrukturphysik, Halle (Germany)

    2009-07-01

    We used spin-polarized low-temperature scanning tunneling microscopy and spectroscopy in field to study the correlation between local magnetic and electronic properties within single Co nano-islands. Differential conductance (dI/dV) hysteresis loops, which we produce by plotting the dI/dV signal while changing the external magnetic field, are analyzed. We measured spatially-resolved hysteresis loops as a function of position on single Co islands. Co islands grown on Cu(111) clearly show spin-polarized d{sub z}{sup 2} resonant states around the center of the island. Strain-induced structural relaxations in the islands affect the energy position of the states close to the edge of the island. Clear ferromagnetic dI/dV hysteresis loops were observed within the area where the Co island show the resonant states. Just around the edge, the resonant states are strongly diminished in intensity and rim states develop. We present dI/dV hysteresis loops measured close to the island edge and discuss the results, also in view of recent work.

  19. Particle-in-Cell Modeling of Magnetized Argon Plasma Flow Through Small Mechanical Apertures

    Energy Technology Data Exchange (ETDEWEB)

    Adam B. Sefkow and Samuel A. Cohen

    2009-04-09

    Motivated by observations of supersonic argon-ion flow generated by linear helicon-heated plasma devices, a three-dimensional particle-in-cell (PIC) code is used to study whether stationary electrostatic layers form near mechanical apertures intersecting the flow of magnetized plasma. By self-consistently evaluating the temporal evolution of the plasma in the vicinity of the aperture, the PIC simulations characterize the roles of the imposed aperture and applied magnetic field on ion acceleration. The PIC model includes ionization of a background neutral-argon population by thermal and superthermal electrons, the latter found upstream of the aperture. Near the aperture, a transition from a collisional to a collisionless regime occurs. Perturbations of density and potential, with mm wavelengths and consistent with ion acoustic waves, propagate axially. An ion acceleration region of length ~ 200-300 λD,e forms at the location of the aperture and is found to be an electrostatic double layer, with axially-separated regions of net positive and negative charge. Reducing the aperture diameter or increasing its length increases the double layer strength.

  20. Application of ultradisperse magnetic adsorbents for removal of small concentrations of pollutants from large volumes of water

    Science.gov (United States)

    Nechitailo, Galina S.; Kuznetsov, Anatoli; Kuznetsov, Oleg

    2016-07-01

    Pollution of natural bodies of water (rivers, lakes, ground water, etc) is unfortunately very common, both from natural sources like volcanic activity; and, even more importantly, from human activity, including disposal of industrial and municipal waste, mining, etc. Many toxic substances are harmful for humans and other organisms even in very low concentrations (e.g., less than 1 µg/L of cadmium is harmful, for Hg it is 0.5 µg/L, for phenol - 1 µg/L), and can remain in water for decades or longer. Cleaning large volumes of water even from low concentrations of pollutants is a challenging technological task and is very expensive. We propose to use suspension of ultradisperse magnetic adsorbents, for example, nanostructured ferro-carbon particles, produced by plasmachemical technique, for removing small concentrations of pollutants from large volumes of water. The suspension is introduced into the water. Due to their small sizes and densities similar to water (we measured the density of FC-4 ferro-carbon to be about 1 g/cm3; presumably due to porosity) the particles do not sediment for a long time (hours, days or longer), move due to Brownian motion and adsorb a variety of substances from the water. The particle surface can be modified to provide selectivity of the adsorption. Sorption capacities of ferro-carbon adsorbents is in dozens of percent. Therefore, to collect 1 kg of a pollutant, 2 to 20 kg of the adsorbents is required. Then the particles with the adsorbed contaminant can be collected (e.g., downstream of the river) using a variety of magnetic traps. The traps can consist of ferromagnetic wires and permanent magnets, a variety of simple and inexpensive designs are available. As a model system, the kinetics of adsorption of a highly diluted (0.002 mg/ml) aqueous solution of a low molecular weight compound (toluidine blue) by a small concentration of a ferro-carbon powder (FC-4) was studied by spectrophotometry. Before each measurement, the particles

  1. Attitude control of a small satellite using magnetic bearing momentum wheel

    OpenAIRE

    Terui, Fuyuto; Nakajima, Atsushi; 照井 冬人; 中島 厚

    1996-01-01

    An attitude controller for a 50 kg-class micro satellite which could be launched by H-2 rocket as a piggyback payload of a main satellite is considered. The survey of the proposals of the mission using a micro satellite from national institutes, universities and private companies shows that the development of a small, light and inexpensive three axis attitude controller is widely expected. One of the candidate configurations for such an attitude controller is bias momentum control using a mag...

  2. On the probability distribution function of small-scale interplanetary magnetic field fluctuations

    Directory of Open Access Journals (Sweden)

    R. Bruno

    2004-11-01

    Full Text Available In spite of a large number of papers dedicated to the study of MHD turbulence in the solar wind there are still some simple questions which have never been sufficiently addressed, such as:

    a Do we really know how the magnetic field vector orientation fluctuates in space? b What are the statistics followed by the orientation of the vector itself? c Do the statistics change as the wind expands into the interplanetary space?

    A better understanding of these points can help us to better characterize the nature of interplanetary fluctuations and can provide useful hints to investigators who try to numerically simulate MHD turbulence.

    This work follows a recent paper presented by some of the authors which shows that these fluctuations might resemble a sort of random walk governed by Truncated Lévy Flight statistics. However, the limited statistics used in that paper did not allow for final conclusions but only speculative hypotheses. In this work we aim to address the same problem using more robust statistics which, on the one hand, forces us not to consider velocity fluctuations but, on the other hand, allows us to establish the nature of the governing statistics of magnetic fluctuations with more confidence.

    In addition, we show how features similar to those found in the present statistical analysis for the fast speed streams of solar wind are qualitatively recovered in numerical simulations of the parametric instability. This might offer an alternative viewpoint for interpreting the questions raised above.

  3. Why do people buy dogs with potential welfare problems related to extreme conformation and inherited disease? A representative study of Danish owners of four small dog breeds

    DEFF Research Database (Denmark)

    Sandøe, Peter; Kondrup, Sara Vincentzen; Bennett, P.C.

    2017-01-01

    number of dog breeds suffer from welfare problems due to extreme phenotypes and high levels of inherited diseases but the popularity of such breeds is not declining. Using a survey of owners of two popular breeds with extreme physical features (French Bulldog and Chihuahua), one with a high load...... of inherited diseases not directly related to conformation (Cavalier King Charles Spaniel), and one representing the same size range but without extreme conformation and with the same level of disease as the overall dog population (Cairn Terrier), we investigated this seeming paradox. We examined planning...... and motivational factors behind acquisition of the dogs, and whether levels of experienced health and behavior problems were associated with the quality of the owner-dog relationship and the intention to re-procure a dog of the same breed. Owners of each of the four breeds (750/breed) were randomly drawn from...

  4. On the probability distribution function of small scale interplanetary magnetic field fluctuations

    CERN Document Server

    Bruno, R; Carbone, V; Primavera, L; Malara, F; Sorriso-Valvo, L; Veltri, P

    2004-01-01

    In spite of a large number of papers dedicated to study MHD turbulence in the solar wind there are still some simple questions which have never been sufficiently addressed like: a)do we really know how the magnetic field vector orientation fluctuates in space? b) what is the statistics followed by the orientation of the vector itself? c) does the statistics change as the wind expands into the interplanetary space? A better understanding of these points can help us to better characterize the nature of interplanetary fluctuations and can provide useful hints to investigators who try to numerically simulate MHD turbulence. This work follows a recent paper presented by the same authors. This work follows a recent paper presented by some of the authors which shows that these fluctuations might resemble a sort of random walk governed by a Truncated Leevy Flight statistics. However, the limited statistics used in that paper did not allow final conclusions but only speculative hypotheses. In this work we aim to addre...

  5. Small-scale magnetic flux emergence in a sunspot light bridge

    CERN Document Server

    Louis, Rohan E; Rodriguez, Jaime de la Cruz; Socas-Navarro, Hector; Ortiz, Ada

    2015-01-01

    We analyse a sequence of high-resolution spectropolarimetric observations of a sunspot taken at the 1-m SST, to determine the nature of flux emergence in a light bridge and the processes related to its evolution in the photosphere and chromosphere. Blueshifts of about 2 km/s are seen near the entrance of a granular light bridge on the limbward side of the spot. They lie next to a strongly redshifted patch that appeared 6 mins earlier. Both patches are seen for 25 mins until the end of the sequence. The blueshifts coincide with an elongated emerging granule, while the redshifts appear at the end of it. In the photosphere, the development of the blueshifts is accompanied by a simultaneous increase in field strength and inclination, with the field becoming nearly horizontal. In the redshifted patch, the magnetic field is equally horizontal but of opposite polarity. An intense brightening is seen in the Ca filtergrams over these features, 17 mins after they emerge in the photosphere. The brightening is due to emi...

  6. Magnetic resonance enterography versus capsule endoscopy activity indices for quantification of small bowel inflammation in Crohn’s disease

    Science.gov (United States)

    Kopylov, Uri; Klang, Eyal; Yablecovitch, Doron; Lahat, Adi; Avidan, Benjamin; Neuman, Sandra; Levhar, Nina; Greener, Tomer; Rozendorn, Noa; Beytelman, Arkadi; Yanai, Henit; Dotan, Iris; Chowers, Yehuda; Weiss, Batya; Ben-Horin, Shomron; Amitai, Marianne M.; Eliakim, Rami

    2016-01-01

    Background: Video capsule endoscopy (VCE) and magnetic resonance enterography (MRE) are the prime modalities for the evaluation of small bowel (SB) Crohn’s disease (CD). Mucosal inflammation on VCE is quantified using the Lewis score (LS). Diffusion-weighted (DW) magnetic resonance imaging (MRI) allows for accurate assessment of SB inflammation without administration of intravenous contrast material. The Magnetic Resonance Index of Activity (MaRiA) and the Clermont index are quantitative activity indices validated for contrast-enhanced MRE and DW-MRE, respectively. The aim of this study was to compare the quantification of distal SB inflammation by VCE and MR-related activity indices. Methods: Patients with known quiescent SB CD were prospectively recruited and underwent MRE and VCE. LS, MaRIA and Clermont scores were calculated for the distal SB. Results: Both MRI-based indices significantly correlated with the LS and the Clermont index (r = 0.50, p = 0.001 and r = 0.53, p = 0.001, respectively). Both MaRIA and Clermont scores were significantly lower in patients with mucosal healing (LS < 135). The area under the curve (AUC) with both MR scores was moderate for prediction of any mucosal inflammation (LS ⩾ 135) and excellent for prediction of moderate-to-severe inflammation (LS ⩾ 790) (0.71 and 0.74 versus 0.93 and 0.91 for MaRIA and Clermont score, respectively). Conclusions: Modest correlation between VCE- and MRE-based quantitative indices of inflammation in patients with quiescent SB CD was observed. Between-modality correlation was higher in patients with endoscopically severe disease. DW-MRE gauged by Clermont score was at least as accurate as contrast-enhanced MRE for quantification of SB inflammation. PMID:27582877

  7. Detector tests in a high magnetic field and muon spectrometer triggering studies on a small prototype for an LHC experiment

    CERN Document Server

    Ambrosi, G; Basile, M; Battiston, R; Bergsma, F; Castro, H; Cifarelli, Luisa; Cindolo, F; Contin, A; De Pasquale, S; Gálvez, J; Gentile, S; Giusti, P; Laurent, G; Levi, G; Lin, Q; Maccarrone, G D; Mattern, D; Nania, R; Rivera, F; Schioppa, M; Sharma, A; CERN. Geneva. Detector Research and Development Committee

    1990-01-01

    The "Large Area Devices" group of the LAA project is working on R&D for muon detection at a future super-collider. New detectors are under development and the design of a muon spectrometer for an LHC experiment is under study. Our present choice is for a compact, high field, air-core toroidal muon spectrometer. Good momentum resolution is achievable in this compact solution, with at least one plane of detection elements inside the high field region. A new detector, the Blade Chamber, making use of blades instead of wires, has been developed for the forward and backward regions of the spectrometer, where polar coordinate readings are desirable.The assembling of a CERN high energy beam line, equipped with high resolution drift chambers and a strong field magnet could give us the opportunity to test our chambers in a high magnetic field and to study the muon trigger capabilities of a spectrometer, like the one proposed, on a small prototype.

  8. MAGNET

    CERN Multimedia

    by B. Curé

    2011-01-01

    The magnet operation was very satisfactory till the technical stop at the end of the year 2010. The field was ramped down on 5th December 2010, following the successful regeneration test of the turbine filters at full field on 3rd December 2010. This will limit in the future the quantity of magnet cycles, as it is no longer necessary to ramp down the magnet for this type of intervention. This is made possible by the use of the spare liquid Helium volume to cool the magnet while turbines 1 and 2 are stopped, leaving only the third turbine in operation. This obviously requires full availability of the operators to supervise the operation, as it is not automated. The cryogenics was stopped on 6th December 2010 and the magnet was left without cooling until 18th January 2011, when the cryoplant operation resumed. The magnet temperature reached 93 K. The maintenance of the vacuum pumping was done immediately after the magnet stop, when the magnet was still at very low temperature. Only the vacuum pumping of the ma...

  9. Optically detunable, inductively coupled coil for self-gating in small animal magnetic resonance imaging.

    Science.gov (United States)

    Korn, Matthias; Umathum, Reiner; Schulz, Jessica; Semmler, Wolfhard; Bock, Michael

    2011-03-01

    An inductively coupled coil concept is presented, which improves the compensation of physiological motion by the self-gating (SG) technique. The animal is positioned in a conventional volume coil encompassing the whole animal. A small, resonant surface coil (SG-coil) is placed on the thorax so that its sensitive region includes the heart. Via inductive coupling the SG-coil amplifies selectively the MR signal of the beating heart. With an optical detuning mechanism, this coupling can be switched off during acquisition of the MR image information, whereas it is active during SG data sampling to provide the physiological information. In vivo experiments on a mouse show an amplification of the SG signal by at least 40%. Copyright © 2010 Wiley-Liss, Inc.

  10. The Effect of Extremely Low Frequency Alternating Magnetic Field on the Behavior of Animals in the Presence of the Geomagnetic Field

    Directory of Open Access Journals (Sweden)

    Natalia A. Belova

    2015-01-01

    Full Text Available It is known that the geomagnetic field can influence animal migration and homing. The magnetic field detection by animals is known as magnetoreception and it is possible due to two different transduction mechanisms: the first one through magnetic nanoparticles able to respond to the geomagnetic field and the second one through chemical reactions influenced by magnetic fields. Another behavior is the magnetic alignment where animals align their bodies to the geomagnetic field. It has been observed that magnetic alignment of cattle can be disrupted near electric power lines around the world. Experimentally, it is known that alternating magnetic fields can influence living beings, but the exact mechanism is unknown. The parametric resonance model proposes a mechanism to explain that effect on living beings and establishes that, in the presence of a constant magnetic field, molecules associated with biochemical reactions inside cells can absorb resonantly alternating magnetic fields with specific frequencies. In the present paper, a review is made about animal magnetoreception and the effects of alternating magnetic fields in living beings. It is suggested how alternating magnetic fields can interfere in the magnetic alignment of animals and a general conclusion is obtained: alternating magnetic field pollution can affect the magnetic sensibility of animals.

  11. Enhancing the strain sensitivity of CoFe₂O₄ at low magnetic fields without affecting the magnetostriction coefficient by substitution of small amounts of Mg for Fe.

    Science.gov (United States)

    Anantharamaiah, P N; Joy, P A

    2016-04-21

    Attaining high magnetostrictive strain sensitivity (dλ/dH) with high magnetostriction strain (λ) is desirable for sintered polycrystalline cobalt ferrite for various applications. It is shown that substitution of a small amount of Fe(3+) by Mg(2+) in CoMgxFe2-xO4 (x magnetostriction coefficient to that of the unsubstituted counterpart, with large improvement in the strain sensitivity at relatively low magnetic fields. A large increase in the magnetostriction coefficient is obtained at low magnetic fields for the substituted compositions. The magnetostriction parameters are further enhanced by magnetic field annealing of the sintered products. The results are analyzed based on powder XRD, Raman spectroscopy, XPS and magnetic measurements and based on the results from these studies, the changes in the magnetostriction parameters are correlated with the changes in the cation distribution, magnetic anisotropy and microstructure.

  12. A small-scale dynamo in feedback-dominated galaxies as the origin of cosmic magnetic fields. I-the kinematic phase

    CERN Document Server

    Rieder, Michael

    2015-01-01

    Astrophysical dynamo theories provide various mechanisms for magnetic field amplification inside galaxies, where weak initial fields grow exponentially on various timescales. We investigate the particular role played by stellar feedback mechanisms in creating strong fluid turbulence, allowing for a magnetic dynamo to emerge. Performing magnetohydrodynamic simulations of isolated cooling halos, for both dwarf and Milky Way sized objects, we compare the magnetic field evolution for various initial field topologies and various stellar feedback mechanisms. We find that feedback can indeed drive strong gas turbulence which gives rise to a fast exponential magnetic field growth. Our simulations feature typical properties of Kolmogorov turbulence with a $k ^{-5/3}$ kinetic energy spectrum, as well as the characteristic properties of a small-scale dynamo, with a $k^{3/2}$ magnetic energy spectrum as predicted by Kazantsev dynamo theory. In these feedback-dominated galaxies, stellar feedback provides forcing on large ...

  13. Radiofrequency ablation of small liver malignancies under magnetic resonance guidance: progress in targeting and preliminary observations with temperature monitoring

    Energy Technology Data Exchange (ETDEWEB)

    Terraz, Sylvain; Cernicanu, Alexandru; Lepetit-Coiffe, Matthieu; Viallon, Magalie; Salomir, Rares; Becker, Christoph D. [University Hospitals of Geneva, Department of Radiology, Geneva 14 (Switzerland); Mentha, Gilles [University Hospitals of Geneva, Department of Visceral Surgery and Transplantation, Geneva (Switzerland)

    2010-04-15

    To evaluate the feasibility and effectiveness of magnetic resonance (MR)-guided radiofrequency (RF) ablation for small liver tumours with poor conspicuity on both contrast-enhanced ultrasonography (US) and computed tomography (CT), using fast navigation and temperature monitoring. Sixteen malignant liver nodules (long-axis diameter, 0.6-2.4 cm) were treated with multipolar RF ablation on a 1.5-T wide-bore MR system in ten patients. Targeting was performed interactively, using a fast steady-state free precession sequence. Real-time MR-based temperature mapping was performed, using gradient echo-echo planar imaging (GRE-EPI) and hardware filtering. MR-specific treatment data were recorded. The mean follow-up time was 19 {+-} 7 months. Correct placement of RF electrodes was obtained in all procedures (image update, <500 ms; mean targeting time, 21 {+-} 11 min). MR thermometry was available for 14 of 16 nodules (88%) with an accuracy of 1.6 C in a non-heated region. No correlation was found between the size of the lethal thermal dose and the ablation zone at follow-up imaging. The primary and secondary effectiveness rates were 100% and 91%, respectively. RF ablation of small liver tumours can be planned, targeted, monitored and controlled with MR imaging within acceptable procedure times. Temperature mapping is technically feasible, but the clinical benefit remains to be proven. (orig.)

  14. Magnetic, optical, and electron transport properties of n -type CeO2: Small polarons versus Anderson localization

    Science.gov (United States)

    Kolodiazhnyi, Taras; Charoonsuk, Thitirat; Seo, Yu-Seong; Chang, Suyong; Vittayakorn, Naratip; Hwang, Jungseek

    2017-01-01

    We report magnetic susceptibility, electrical conductivity and optical absorption of Ce1 -xMxO2 where M = Nb,Ta and 0 ≤x ≤0.03 . The dc conductivity follows a simple thermally activated Arrhenius-type behavior in the T =70 -700 K range with a change in slope at T*≈155 K. The high-temperature activation energy shows gradual increase from ≈170 to 220 meV as the dopant concentration increases. The activation energy of the low-temperature conductivity shows a broad minimum of ≈77 meV at x ≈0.01 . Electron transport and localization mechanisms are analyzed in the framework of the Holstein small polaron, Anderson localization, and Jahn-Teller distortion models. The fit to the small polaron mobility is dramatically improved when, instead of the longitudinal phonons, the transverse optical phonons are considered in the phonon-assisted electron transport. This serves as an indirect evidence of a strong 4 f1 orbital interaction with the oxygen ligands, similar to the case of PrO2. Based on comparison of the experimental data to the models, it is proposed that the defect-induced random electric fields make the dominant contribution to the electron localization in donor-doped ceria.

  15. Validation of Body Condition Indices and Quantitative Magnetic Resonance in Estimating Body Composition in a Small Lizard

    Science.gov (United States)

    WARNER, DANIEL A.; JOHNSON, MARIA S.; NAGY, TIM R.

    2017-01-01

    Measurements of body condition are typically used to assess an individual’s quality, health, or energetic state. Most indices of body condition are based on linear relationships between body length and mass. Although these indices are simple to obtain, nonlethal, and useful indications of energetic state, their accuracy at predicting constituents of body condition (e.g., fat and lean mass) are often unknown. The objectives of this research were to (1) validate the accuracy of another simple and noninvasive method, quantitative magnetic resonance (QMR), at estimating body composition in a small-bodied lizard, Anolis sagrei, and (2) evaluate the accuracy of two indices of body condition (based on length–mass relationships) at predicting body fat, lean, and water mass. Comparisons of results from QMR scans to those from chemical carcass analysis reveal that QMR measures body fat, lean, and water mass with excellent accuracy in male and female lizards. With minor calibration from regression equations, QMR will be a reliable method of estimating body composition of A. sagrei. Body condition indices were positively related to absolute estimates of each constituent of body composition, but these relationships showed considerable variation around regression lines. In addition, condition indices did not predict fat, lean, or water mass when adjusted for body mass. Thus, our results emphasize the need for caution when interpreting body condition based upon linear measurements of animals. Overall, QMR provides an alternative noninvasive method for accurately measuring fat, lean, and water mass in these small-bodied animals. PMID:28035770

  16. Extreme cosmos

    CERN Document Server

    Gaensler, Bryan

    2011-01-01

    The universe is all about extremes. Space has a temperature 270°C below freezing. Stars die in catastrophic supernova explosions a billion times brighter than the Sun. A black hole can generate 10 million trillion volts of electricity. And hypergiants are stars 2 billion kilometres across, larger than the orbit of Jupiter. Extreme Cosmos provides a stunning new view of the way the Universe works, seen through the lens of extremes: the fastest, hottest, heaviest, brightest, oldest, densest and even the loudest. This is an astronomy book that not only offers amazing facts and figures but also re

  17. Statistical analysis and ANN modeling for predicting hydrological extremes under climate change scenarios: the example of a small Mediterranean agro-watershed.

    Science.gov (United States)

    Kourgialas, Nektarios N; Dokou, Zoi; Karatzas, George P

    2015-05-01

    The purpose of this study was to create a modeling management tool for the simulation of extreme flow events under current and future climatic conditions. This tool is a combination of different components and can be applied in complex hydrogeological river basins, where frequent flood and drought phenomena occur. The first component is the statistical analysis of the available hydro-meteorological data. Specifically, principal components analysis was performed in order to quantify the importance of the hydro-meteorological parameters that affect the generation of extreme events. The second component is a prediction-forecasting artificial neural network (ANN) model that simulates, accurately and efficiently, river flow on an hourly basis. This model is based on a methodology that attempts to resolve a very difficult problem related to the accurate estimation of extreme flows. For this purpose, the available measurements (5 years of hourly data) were divided in two subsets: one for the dry and one for the wet periods of the hydrological year. This way, two ANNs were created, trained, tested and validated for a complex Mediterranean river basin in Crete, Greece. As part of the second management component a statistical downscaling tool was used for the creation of meteorological data according to the higher and lower emission climate change scenarios A2 and B1. These data are used as input in the ANN for the forecasting of river flow for the next two decades. The final component is the application of a meteorological index on the measured and forecasted precipitation and flow data, in order to assess the severity and duration of extreme events.

  18. MODELING AND STUDY OF HYDROELECTRIC GENERATING SETS OF SMALL HYDRO POWER PLANTS WITH FREQUENCY-CONTROLLED PERMANENT MAGNET SYNCHRONOUS GENERATORS

    Directory of Open Access Journals (Sweden)

    R. I. Mustafayev

    2016-01-01

    Full Text Available Currently, the hydroelectric generating sets of small HPPs with Pelton turbines employ as their generating units conventional synchronous generators with electromagnetic excitation. To deal with the torque pulsatile behaviour, they generally install a supplementary flywheel on the system shaft that levels the pulsations. The Pelton turbine power output is adjusted by the needle changing water flow in the nozzle, whose advancement modifies the nozzle area and eventually – the flow. They limit the needle full stroke time to 20–40 sec. since quick shutting the nozzle for swift water flow reduction may result in pressure surges. For quick power adjustment so-called deflectors are employed, whose task is retraction of water jets from the Pelton turbine buckets. Thus, the mechanical method of power output regulation requires agreement between the needle stroke inside the turbine nozzles and the deflector. The paper offers employing frequency-controlled synchronous machines with permanent magnets qua generating units for the hydroelectric generating sets of small HPPs with Pelton turbines. The developed computer model reveals that this provides a higher level of adjustability towards rapid-changing loads in the grid. Furthermore, this will replace the power output mechanical control involving the valuable deflector drive and the turbine nozzle needles with electrical revolution rate and power output regulation by a frequency converter located in the generator stator circuit. Via frequency start, the controllable synchronous machine ensures stable operation of the hydroelectric generating set with negligibly small amount of water (energy carrier. Finally, in complete absence of water, the frequency-relay start facilitates shifting the generator operation to the synchronous capacitor mode, which the system operating parameter fluctograms obtained through computer modeling prove. 

  19. MAGNET

    CERN Multimedia

    B. Curé

    2012-01-01

      The magnet was energised at the beginning of March 2012 at a low current to check all the MSS safety chains. Then the magnet was ramped up to 3.8 T on 6 March 2012. Unfortunately two days later an unintentional switch OFF of the power converter caused a slow dump. This was due to a misunderstanding of the CCC (CERN Control Centre) concerning the procedure to apply for the CMS converter control according to the beam-mode status at that time. Following this event, the third one since 2009, a discussion was initiated to define possible improvement, not only on software and procedures in the CCC, but also to evaluate the possibility to upgrade the CMS hardware to prevent such discharge from occurring because of incorrect procedure implementations. The magnet operation itself was smooth, and no power cuts took place. As a result, the number of magnetic cycles was reduced to the minimum, with only two full magnetic cycles from 0 T to 3.8 T. Nevertheless the magnet suffered four stops of the cryogeni...

  20. MAGNET

    CERN Multimedia

    Benoit Curé

    2010-01-01

    Operation of the magnet has gone quite smoothly during the first half of this year. The magnet has been at 4.5K for the full period since January. There was an unplanned short stop due to the CERN-wide power outage on May 28th, which caused a slow dump of the magnet. Since this occurred just before a planned technical stop of the LHC, during which access in the experimental cavern was authorized, it was decided to leave the magnet OFF until 2nd June, when magnet was ramped up again to 3.8T. The magnet system experienced a fault also resulting in a slow dump on April 14th. This was triggered by a thermostat on a filter choke in the 20kA DC power converter. The threshold of this thermostat is 65°C. However, no variation in the water-cooling flow rate or temperature was observed. Vibration may have been the root cause of the fault. All the thermostats have been checked, together with the cables, connectors and the read out card. The tightening of the inductance fixations has also been checked. More tem...

  1. MAGNET

    CERN Multimedia

    B. Curé

    2012-01-01

      Following the unexpected magnet stops last August due to sequences of unfortunate events on the services and cryogenics [see CMS internal report], a few more events and initiatives again disrupted the magnet operation. All the magnet parameters stayed at their nominal values during this period without any fault or alarm on the magnet control and safety systems. The magnet was stopped for the September technical stop to allow interventions in the experimental cavern on the detector services. On 1 October, to prepare the transfer of the liquid nitrogen tank on its new location, several control cables had to be removed. One cable was cut mistakenly, causing a digital input card to switch off, resulting in a cold-box (CB) stop. This tank is used for the pre-cooling of the magnet from room temperature down to 80 K, and for this reason it is controlled through the cryogenics control system. Since the connection of the CB was only allowed for a field below 2 T to avoid the risk of triggering a fast d...

  2. Effects of various extremely low frequency magnetic fields on the free radical processes, natural antioxidant system and respiratory burst system activities in the heart and liver tissues.

    Science.gov (United States)

    Canseven, Ayse Gulnihal; Coskun, Sule; Seyhan, Nesrin

    2008-10-01

    Magnetic fields (MFs) can affect biological systems by increasing the release of free radicals that are able to alter cell defense systems and breakdown tissue homeostasis. In the present study, the effects of extremely low frequency (ELF) electromagnetic fields (EMF) were investigated on free radical levels, natural antioxidant systems and respiratory burst system activities in heart and liver tissues of guinea pigs exposed to 50 Hz MFs of 1, 2 and 3 mT for 4 h/day and 8 h/day for 5 days by measuring malondialdehyde (MDA), nitric oxide (NO), glutathione (GSH) levels and myeloperoxidase (MPO) activity. A total of sixty-two male guinea pigs, 10-12 weeks old were studied in seven groups as control and exposure groups: Group I (control), II (1 mT, 4 h/day), III (1 mT, 8 h/day), IV (2 mT, 4 h/day), V (2 mT, 8 h/day), VI (3 mT, 4 h/day), and VII (3 mT, 8 h/day). Controls were kept under the same conditions without any exposure to MF. MDA levels increased in liver in groups II and IV, but decreased in group VII for both liver and heart tissues. NOx levels declined in heart in groups II and III and in liver in groups III, V, and VI, but increased in liver in group VII. GSH levels increased in heart in groups II, IV, V, and in liver in groups V and VI and VI, but decreased in groups II and IV in liver. MPO activity decreased in liver in groups III, IV, VI and VII with respect to controls and in heart tissues in groups II, III and IV; however, there was a significant increase MPO activity in heart in group VII. From the results, it can be concluded that the intensity and exposure duration of MFs are among the effective conditions on the formation of free radicals and behaviour of antioxidant enzymes.

  3. Why do people buy dogs with potential welfare problems related to extreme conformation and inherited disease? A representative study of Danish owners of four small dog breeds

    Science.gov (United States)

    Kondrup, S. V.; Bennett, P. C.; Forkman, B.; Meyer, I; Proschowsky, H. F.; Serpell, J. A.; Lund, T. B.

    2017-01-01

    A number of dog breeds suffer from welfare problems due to extreme phenotypes and high levels of inherited diseases but the popularity of such breeds is not declining. Using a survey of owners of two popular breeds with extreme physical features (French Bulldog and Chihuahua), one with a high load of inherited diseases not directly related to conformation (Cavalier King Charles Spaniel), and one representing the same size range but without extreme conformation and with the same level of disease as the overall dog population (Cairn Terrier), we investigated this seeming paradox. We examined planning and motivational factors behind acquisition of the dogs, and whether levels of experienced health and behavior problems were associated with the quality of the owner-dog relationship and the intention to re-procure a dog of the same breed. Owners of each of the four breeds (750/breed) were randomly drawn from a nationwide Danish dog registry and invited to participate. Of these, 911 responded, giving a final sample of 846. There were clear differences between owners of the four breeds with respect to degree of planning prior to purchase, with owners of Chihuahuas exhibiting less. Motivations behind choice of dog were also different. Health and other breed attributes were more important to owners of Cairn Terriers, whereas the dog’s personality was reported to be more important for owners of French Bulldogs and Cavalier King Charles Spaniels but less important for Chihuahua owners. Higher levels of health and behavior problems were positively associated with a closer owner-dog relationship for owners of Cavalier King Charles Spaniels and Chihuahuas but, for owners of French Bulldogs, high levels of problems were negatively associated with an intention to procure the same breed again. In light of these findings, it appears less paradoxical that people continue to buy dogs with welfare problems. PMID:28234931

  4. Why do people buy dogs with potential welfare problems related to extreme conformation and inherited disease? A representative study of Danish owners of four small dog breeds.

    Science.gov (United States)

    Sandøe, P; Kondrup, S V; Bennett, P C; Forkman, B; Meyer, I; Proschowsky, H F; Serpell, J A; Lund, T B

    2017-01-01

    A number of dog breeds suffer from welfare problems due to extreme phenotypes and high levels of inherited diseases but the popularity of such breeds is not declining. Using a survey of owners of two popular breeds with extreme physical features (French Bulldog and Chihuahua), one with a high load of inherited diseases not directly related to conformation (Cavalier King Charles Spaniel), and one representing the same size range but without extreme conformation and with the same level of disease as the overall dog population (Cairn Terrier), we investigated this seeming paradox. We examined planning and motivational factors behind acquisition of the dogs, and whether levels of experienced health and behavior problems were associated with the quality of the owner-dog relationship and the intention to re-procure a dog of the same breed. Owners of each of the four breeds (750/breed) were randomly drawn from a nationwide Danish dog registry and invited to participate. Of these, 911 responded, giving a final sample of 846. There were clear differences between owners of the four breeds with respect to degree of planning prior to purchase, with owners of Chihuahuas exhibiting less. Motivations behind choice of dog were also different. Health and other breed attributes were more important to owners of Cairn Terriers, whereas the dog's personality was reported to be more important for owners of French Bulldogs and Cavalier King Charles Spaniels but less important for Chihuahua owners. Higher levels of health and behavior problems were positively associated with a closer owner-dog relationship for owners of Cavalier King Charles Spaniels and Chihuahuas but, for owners of French Bulldogs, high levels of problems were negatively associated with an intention to procure the same breed again. In light of these findings, it appears less paradoxical that people continue to buy dogs with welfare problems.

  5. MAGNET

    CERN Multimedia

    B. Curé

    2012-01-01

      The magnet and its sub-systems were stopped at the beginning of the winter shutdown on 8th December 2011. The magnet was left without cooling during the cryogenics maintenance until 17th January 2012, when the cryoplant operation resumed. The magnet temperature reached 93 K. The vacuum pumping was maintained during this period. During this shutdown, the yearly maintenance was performed on the cryogenics, the vacuum pumps, the magnet control and safety systems, and the power converter and discharge lines. Several preventive actions led to the replacement of the electrovalve command coils, and the 20A DC power supplies of the magnet control system. The filters were cleaned on the demineralised water circuits. The oil of the diffusion pumps was changed. On the cryogenics, warm nitrogen at 343 K was circulated in the cold box to regenerate the filters and the heat exchangers. The coalescing filters have been replaced at the inlet of both the turbines and the lubricant trapping unit. The active cha...

  6. MAGNET

    CERN Multimedia

    Benoit Curé

    2010-01-01

    The magnet was successfully operated at the end of the year 2009 despite some technical problems on the cryogenics. The magnet was ramped up to 3.8 T at the end of November until December 16th when the shutdown started. The magnet operation met a few unexpected stops. The field was reduced to 3.5 T for about 5 hours on December 3rd due to a faulty pressure sensor on the helium compressor. The following day the CERN CCC stopped unintentionally the power converters of the LHC and the experiments, triggering a ramp down that was stopped at 2.7 T. The magnet was back at 3.8 T about 6 hours after CCC sent the CERN-wide command. Three days later, a slow dump was triggered due to a stop of the pump feeding the power converter water-cooling circuit, during an intervention on the water-cooling plant done after several disturbances on the electrical distribution network. The magnet was back at 3.8 T in the evening the same day. On December 10th a break occurred in one turbine of the cold box producing the liquid ...

  7. MAGNET

    CERN Multimedia

    B. Curé

    2013-01-01

      The magnet was operated without any problem until the end of the LHC run in February 2013, apart from a CERN-wide power glitch on 10 January 2013 that affected the CMS refrigerator, causing a ramp down to 2 T in order to reconnect the coldbox. Another CERN-wide power glitch on 15 January 2013 didn’t affect the magnet subsystems, the cryoplant or the power converter. At the end of the magnet run, the reconnection of the coldbox at 2.5 T was tested. The process will be updated, in particular the parameters of some PID valve controllers. The helium flow of the current leads was reduced but only for a few seconds. The exercise will be repeated with the revised parameters to validate the automatic reconnection process of the coldbox. During LS1, the water-cooling services will be reduced and many interventions are planned on the electrical services. Therefore, the magnet cryogenics and subsystems will be stopped for several months, and the magnet cannot be kept cold. In order to avoid unc...

  8. MAGNET

    CERN Multimedia

    B. Curé

    2011-01-01

    The CMS magnet has been running steadily and smoothly since the summer, with no detected flaw. The magnet instrumentation is entirely operational and all the parameters are at their nominal values. Three power cuts on the electrical network affected the magnet run in the past five months, with no impact on the data-taking as the accelerator was also affected at the same time. On 22nd June, a thunderstorm caused a power glitch on the service electrical network. The primary water cooling at Point 5 was stopped. Despite a quick restart of the water cooling, the inlet temperature of the demineralised water on the busbar cooling circuit increased by 5 °C, up to 23.3 °C. It was kept below the threshold of 27 °C by switching off other cooling circuits to avoid the trigger of a slow dump of the magnet. The cold box of the cryogenics also stopped. Part of the spare liquid helium volume was used to maintain the cooling of the magnet at 4.5 K. The operators of the cryogenics quickly restarted ...

  9. Evaluation of Landing Characteristics Achieved by Simulations and Flight Tests on a Small-scaled Model Related to Magnetically Levitated Advanced Take-off and Landing Operations

    NARCIS (Netherlands)

    Rohacs, D.; Voskuijl, M.; Siepenkotter, N.

    2014-01-01

    The goal of this paper is to simulate and measure on a small-scaled model the landing characteristics related to take-off and landing (TOL) operations supported by a magnetic levitation (MAGLEV) system as ground-based power supply. The technical feasibility and the potential benefits of using ground

  10. Structural and magnetic properties of inverse opal photonic crystals studied by x-ray diffraction, scanning electron microscopy, and small-angle neutron scattering

    NARCIS (Netherlands)

    Grigoriev, S.V.; Napolskii, K.S.; Grigoryeva, N.A.; Vasilieva, A.V.; Mistonov, A.A.; Chernyshov, D.Y.; Petukhov, A.V.; Belov, D.V.; Eliseev, A.A.; Lukashin, A.V.; Tretyakov, Y.D.; Sinitskii, A.S.; Eckerlebe, H.

    2009-01-01

    The structural and magnetic properties of nickel inverse opal photonic crystal have been studied by complementary experimental techniques, including scanning electron microscopy, wide-angle and small-angle diffraction of synchrotron radiation, and polarized neutrons. The sample was fabricated by ele

  11. Evaluation of Landing Characteristics Achieved by Simulations and Flight Tests on a Small-scaled Model Related to Magnetically Levitated Advanced Take-off and Landing Operations

    NARCIS (Netherlands)

    Rohacs, D.; Voskuijl, M.; Siepenkotter, N.

    2014-01-01

    The goal of this paper is to simulate and measure on a small-scaled model the landing characteristics related to take-off and landing (TOL) operations supported by a magnetic levitation (MAGLEV) system as ground-based power supply. The technical feasibility and the potential benefits of using ground

  12. Spin-up flow in non-small magnetic fields: Numerical evaluation of the predictions of the common magnetization relaxation equations

    Science.gov (United States)

    Chaves-Guerrero, Arlex; Peña-Cruz, Víctor A.; Rinaldi, Carlos; Fuentes-Díaz, David

    2017-07-01

    The flow of a ferrofluid between two parallel infinitely long plates generated by a rotating magnetic field has been studied analytically and numerically using spin diffusion theory for a broad range of frequencies and intensities of the magnetic field. This work was motivated by interest in obtaining better agreement between the theoretical predictions and the experimental observations of the dependence of the flow magnitude on the amplitude and frequency of the magnetic field. These discrepancies have been attributed to the use of asymptotic solutions to assess velocity profiles obtained to moderate magnetic field strength and to the need to use a more accurate magnetization equation to high amplitudes and frequencies of the magnetic field. For such reasons, the objective of this work was to evaluate the effect of the magnetization equations derived by Shliomis [Sov. Phys. JETP 34, 1291 (1972)] (Sh-72) and by Martsenyuk, Raikher, and Shliomis [Sov. Phys. JETP 38, 413 (1974)] (MRSh-74) on the flow predictions of the spin diffusion theory using a simple geometry. It was found that the flow predictions for the two cases studied match with an asymptotic solution in the limit of low field strength when the Langevin parameter (α ) is less than 0.1, for any value of the dimensionless frequency (Ω ˜ ) . Marked differences were found in the predictions of flow magnitude dependence on the amplitude and frequency of the magnetic field when Sh-72 or MRSh-74 was used for α >1 . Results also show that there is a critical value of frequency above which the velocity of the ferrofluid decreases with increasing magnetic field amplitude. Whereas the value of the critical frequency predicted by the Sh-72 magnetization equation is approximately unity for any value of the magnetic field amplitude, the MRSh-74 equation predicts that the critical frequency increases with increasing magnetic field amplitude. Predictions of the MRSh-74 equation are in qualitative agreement with

  13. MAGNETS

    Science.gov (United States)

    Hofacker, H.B.

    1958-09-23

    This patent relates to nmgnets used in a calutron and more particularly to means fur clamping an assembly of magnet coils and coil spacers into tightly assembled relation in a fluid-tight vessel. The magnet comprises windings made up of an assembly of alternate pan-cake type coils and spacers disposed in a fluid-tight vessel. At one end of the tank a plurality of clamping strips are held firmly against the assembly by adjustable bolts extending through the adjacent wall. The foregoing arrangement permits taking up any looseness which may develop in the assembly of coils and spacers.

  14. Study on the Protection Countermeasures to Extremely Small Population of Wild Plant of Guangxi%广西极小种群野生植物保护对策探讨

    Institute of Scientific and Technical Information of China (English)

    黎德丘; 彭定人

    2009-01-01

    This paper gave a full description of the current situation of 20 extremely small population of wild plant of population quantities and distribution in Guangxi. Based on the threat analysis of population decline and habitat loss were faced, some countermeasures to strengthen protection was discussed.%全面阐述了广西分布的20种极小种群野生植物的种群数量、分布等现状,在分析其面临的种群衰退、生境丧失等主要威胁的基础上,探讨了加强保护的对策.

  15. Failure-tolerant control for small agile satellites using single-gimbal control moment gyros and magnetic torquers

    Institute of Scientific and Technical Information of China (English)

    Tao Meng; Saburo Matunaga

    2012-01-01

    This paper focuses on the attitude control problem of small agile satellites using single-gimbal control moment gyros (CMG) and magnetic torquers (MTQ).CMGs are regarded as effective torque generators for agile satellites because of their torque amplification capability.However,they are vulnerable to failure due to their complex inner mechanism.In this paper,different failure cases of CMGs are analyzed.A flexible failure-tolerant control strategy is developed by automatically redistributing the required control torque among the operating CMGs and MTQs,with a variable limiter to accommodate the actuator dynamics changes introduced by CMG failures.The performances of maneuvers about different directions under different failure cases are also discussed and examined.Numerical simulations demonstrate that the proposed strategy maintains certain agility in the cases of one or two CMGs failing.Moreover,a survival strategy with only one CMG left is also verified.Both sun-pointing stabilization and earth-pointing stabilization can be achieved in this case,which fulfill some basic mission requirements.

  16. A small-scale dynamo in feedback-dominated galaxies as the origin of cosmic magnetic fields - I. The kinematic phase

    Science.gov (United States)

    Rieder, Michael; Teyssier, Romain

    2016-04-01

    The origin and evolution of magnetic fields in the Universe is still an open question. Their observations in galaxies suggest strong magnetic fields already at high redshift as well as at present time. However, neither primordial magnetic fields nor battery processes can account for such high field strengths, which implies the presence of a dynamo process with rapid growth rates in high-redshift galaxies and subsequent maintenance against decay. We investigate the particular role played by feedback mechanisms in creating strong fluid turbulence, allowing for a magnetic dynamo to emerge. Performing magnetohydrodynamic simulations of isolated cooling gas haloes, we compare the magnetic field evolution for various initial field topologies and various stellar feedback mechanisms. We find that feedback can indeed drive strong gas turbulence and dynamo action. We see typical properties of Kolmogorov turbulence with a k-5/3 kinetic energy spectrum, as well as a small-scale dynamo, with a k3/2 magnetic energy spectrum predicted by Kazantsev dynamo theory. We also investigate simulations with a final quiescent phase. As turbulence decreases, the galactic fountain settles into a thin, rotationally supported disc. The magnetic field develops a large-scale well-ordered structure with even symmetry, which is in good agreement with magnetic field observations of nearby spirals. Our findings suggest that weak initial seed fields were first amplified by a small-scale dynamo during a violent feedback-dominated early phase in the galaxy formation history, followed by a more quiescent evolution, where the fields have slowly decayed or were maintained via large-scale dynamo action.

  17. MAGNET

    CERN Multimedia

    B. Curé

    2011-01-01

    The magnet ran smoothly in the last few months until a fast dump occurred on 9th May 2011. Fortunately, this occurred in the afternoon of the first day of the technical stop. The fast dump was due to a valve position controller that caused the sudden closure of a valve. This valve is used to regulate the helium flow on one of the two current leads, which electrically connects the coil at 4.5 K to the busbars at room temperature. With no helium flow on the lead, the voltage drop and the temperatures across the leads increase up to the defined thresholds, triggering a fast dump through the Magnet Safety System (MSS). The automatic reaction triggered by the MSS worked properly. The helium release was limited as the pressure rise was just at the limit of the safety valve opening pressure. The average temperature of the magnet reached 72 K. It took four days to recover the temperature and refill the helium volumes. The faulty valve controller was replaced by a spare one before the magnet ramp-up resumed....

  18. Extracting magnetic cluster size and its distributions in advanced perpendicular recording media with shrinking grain size using small angle x-ray scattering

    Energy Technology Data Exchange (ETDEWEB)

    Mehta, Virat; Ikeda, Yoshihiro; Takano, Ken; Terris, Bruce D.; Hellwig, Olav [San Jose Research Center, HGST a Western Digital company, 3403 Yerba Buena Rd., San Jose, California 95135 (United States); Wang, Tianhan [Department of Materials Science and Engineering, Stanford University, Stanford, California 94035 (United States); Stanford Institute for Materials and Energy Science (SIMES), SLAC National Accelerator Laboratory, 2575 Sand Hill Road, Menlo Park, California 94025 (United States); Wu, Benny; Graves, Catherine [Stanford Institute for Materials and Energy Science (SIMES), SLAC National Accelerator Laboratory, 2575 Sand Hill Road, Menlo Park, California 94025 (United States); Department of Applied Physics, Stanford University, Stanford, California 94035 (United States); Dürr, Hermann A.; Scherz, Andreas; Stöhr, Jo [Stanford Institute for Materials and Energy Science (SIMES), SLAC National Accelerator Laboratory, 2575 Sand Hill Road, Menlo Park, California 94025 (United States)

    2015-05-18

    We analyze the magnetic cluster size (MCS) and magnetic cluster size distribution (MCSD) in a variety of perpendicular magnetic recording (PMR) media designs using resonant small angle x-ray scattering at the Co L{sub 3} absorption edge. The different PMR media flavors considered here vary in grain size between 7.5 and 9.5 nm as well as in lateral inter-granular exchange strength, which is controlled via the segregant amount. While for high inter-granular exchange, the MCS increases rapidly for grain sizes below 8.5 nm, we show that for increased amount of segregant with less exchange the MCS remains relatively small, even for grain sizes of 7.5 and 8 nm. However, the MCSD still increases sharply when shrinking grains from 8 to 7.5 nm. We show evidence that recording performance such as signal-to-noise-ratio on the spin stand correlates well with the product of magnetic cluster size and magnetic cluster size distribution.

  19. Comparison of parameters influencing the behavior of concentration of nitrates and phosphates during different extreme rainfall-runoff events in small watersheds

    Directory of Open Access Journals (Sweden)

    J. Moravcová

    2013-10-01

    Full Text Available The behavior of solute concentrations during storm events is completely different from their behaviour under normal conditions, and very often results in hysteresis. This study aim is to explore the relationship between the biogeochemical and hydrological parameters describing natural conditions and the reciprocal interactions between changes in concentration of selected indicators of water quality in water and the discharge dynamics during different types of extreme rainfall-runoff events in the Jenínský stream and the Kopaninský stream catchment (Czech Republic. The relationship between concentrations and runoffs is explained by concentration-discharge hysteretic loops. As the statistical method used for cross analyzing the impact of the parameters there was chosen the RDA analysis. The relationships between the particular parameters were examined separately by conditions of spring snow melt and summer storm events. The results than confirmed the very strong relationship between parameters describing water quality and percentage of stable parts of the catchment and also of infiltration vulnerable sites.

  20. MAGNET

    CERN Multimedia

    B. Curé

    2013-01-01

    The magnet is fully stopped and at room temperature. The maintenance works and consolidation activities on the magnet sub-systems are progressing. To consolidate the cryogenic installation, two redundant helium compressors will be installed as ‘hot spares’, to avoid the risk of a magnet downtime in case of a major failure of a compressor unit during operation. The screw compressors, their motors, the mechanical couplings and the concrete blocks are already available and stored at P5. The metallic structure used to access the existing compressors in SH5 will be modified to allow the installation of the two redundant ones. The plan is to finish the installation and commissioning of the hot spare compressors before the summer 2014. In the meantime, a bypass on the high-pressure helium piping will be installed for the connection of a helium drier unit later during the Long Shutdown 1, keeping this installation out of the schedule critical path. A proposal is now being prepared for the con...