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Sample records for effective magnetic fields

  1. Minireview: Biological effects of magnetic fields

    SciTech Connect

    Villa, M.; Mustarelli, P. ); Caprotti, M. )

    1991-01-01

    The literature about the biological effects of magnetic fields is reviewed. The authors begin by discussing the weak and/or time variable fields, responsible for subtle changes in the circadian rhythms of superior animals, which are believed to be induced by same sort of resonant mechanism. The safety issues related with the strong magnetic fields and gradients generated by clinical NMR magnets are then considered. The last portion summarizes the debate about the biological effects of strong and uniform magnetic fields.

  2. Magnetic field effects on microwave absorbing materials

    NASA Technical Reports Server (NTRS)

    Goldberg, Ira; Hollingsworth, Charles S.; Mckinney, Ted M.

    1991-01-01

    The objective of this program was to gather information to formulate a microwave absorber that can work in the presence of strong constant direct current (DC) magnetic fields. The program was conducted in four steps. The first step was to investigate the electrical and magnetic properties of magnetic and ferrite microwave absorbers in the presence of strong magnetic fields. This included both experimental measurements and a literature survey of properties that may be applicable to finding an appropriate absorbing material. The second step was to identify those material properties that will produce desirable absorptive properties in the presence of intense magnetic fields and determine the range of magnetic field in which the absorbers remain effective. The third step was to establish ferrite absorber designs that will produce low reflection and adequate absorption in the presence of intense inhomogeneous static magnetic fields. The fourth and final step was to prepare and test samples of such magnetic microwave absorbers if such designs seem practical.

  3. Abnormal Magnetic Field Effects on Electrogenerated Chemiluminescence

    NASA Astrophysics Data System (ADS)

    Pan, Haiping; Shen, Yan; Wang, Hongfeng; He, Lei; Hu, Bin

    2015-03-01

    We report abnormal magnetic field effects on electrogenerated chemiluminescence (MFEECL) based on triplet emission from the Ru(bpy)3Cl2-TPrA electrochemical system: the appearance of MFEECL after magnetic field ceases. In early studies the normal MFEECL have been observed from electrochemical systems during the application of magnetic field. Here, the abnormal MFEECL suggest that the activated charge-transfer [Ru(bpy)33+ … TPrA•] complexes may become magnetized in magnetic field and experience a long magnetic relaxation after removing magnetic field. Our analysis indicates that the magnetic relaxation can gradually increase the density of charge-transfer complexes within reaction region due to decayed magnetic interactions, leading to a positive component in the abnormal MFEECL. On the other hand, the magnetic relaxation facilitates an inverse conversion from triplets to singlets within charge-transfer complexes. The inverse triplet --> singlet conversion reduces the density of triplet light-emitting states through charge-transfer complexes and gives rise to a negative component in the abnormal MFEECL. The combination of positive and negative components can essentially lead to a non-monotonic profile in the abnormal MFEECL after ceasing magnetic field. Nevertheless, our experimental studies may reveal un-usual magnetic behaviors with long magnetic relaxation from the activated charge-transfer [Ru(bpy)33+ … TPrA•] complexes in solution at room temperature.

  4. Solar Magnetic Field: Zeeman and Hanle Effects

    NASA Astrophysics Data System (ADS)

    Stenflo, J.; Murdin, P.

    2001-10-01

    An external magnetic field causes the atomic energy levels to split into different sublevels, and the emitted radiation becomes polarized. This phenomenon is called the ZEEMAN EFFECT. When atoms in a magnetic field scatter radiation via bound-bound transitions, the phase relations or quantum interferences between the Zeeman-split sublevels give rise to POLARIZATION phenomena that go under the nam...

  5. Biological effects of high DC magnetic fields

    SciTech Connect

    Tenforde, T.S.

    1981-06-01

    The principal focus of the program is the analysis of magnetic field effects on physiological functions in experimental animals and selected organ and tissue systems. A major research effort has involved the use of electrical recording techniques to detect functional alterations in the cardiovascular, neural, and visual systems during the application of DC magnetic fields. These systems involve ionic conduction processes, and are therefore potentially sensitive to electrodynamic interactions with an applied magnetic field. In the specific case of the visual system, magnetic interactions could also arise through orientational effects on the magnetically anisotropic photopigment molecules within retinal photoreceptor cells. In addition to studies with potentially sensitive target tissues, an evaluation is being made of magnetic field effects on a broad range of other physiological functions in laboratory mammals, including the measurement of circadian rhythms using noninvasive recording techniques. Results of investigations of magnetic field effects on the conformation of DNA, and on the growth and development of plants and insects are also reported. Figures and tables provide a brief summary of some representative observations in each of the research areas described. No significant alterations were observed in any of the physiological parameters examined to date, with the exception of major changes that occur in the electrocardiogram during magnetic field exposure. Studies with several species of animals have provided evidence that this phenomenon is attributable to electrical potentials that are induced during pulsatile blood flow in the aorta and in other major vessels of the circulatory system.

  6. Effect of a magnetic field on sonoluminescence.

    PubMed

    Yasui, K

    1999-08-01

    The effect of a magnetic field on single-bubble sonoluminescence in water reported experimentally by Young, Schmiedel, and Kang [Phys. Rev. Lett. 77, 4816 (1996)] is studied theoretically. It is suggested that bubble dynamics is affected by the magnetic field because moving water molecules of the liquid suffer torque due to the Lorentz force acting on their electrical dipole moment, which results in the transformation of some of the kinetic energy into heat. It is shown that the magnetic field acts as if the ambient pressure of the liquid were increased. It is suggested that the effect increases as the amount of the liquid water increases. It is predicted that nonpolar liquid such as dodecane exhibits no effect of the magnetic field.

  7. Effects of static magnetic fields on plants.

    NASA Astrophysics Data System (ADS)

    Kuznetsov, O.

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

  8. Interplanetary stream magnetism: Kinematic effects. [solar magnetic fields and wind

    NASA Technical Reports Server (NTRS)

    Burlaga, L. F.; Barouch, E.

    1974-01-01

    The particle density, and the magnetic field intensity and direction are calculated in corotating streams of the solar wind, assuming that the solar wind velocity is constant and radial and that its azimuthal variations are not two rapid. The effects of the radial velocity profile in corotating streams on the magnetic fields were examined using kinematic approximation and a variety of field configurations on the inner boundary. Kinematic and dynamic effects are discussed.

  9. Magnetic field effect on spoke behaviour

    NASA Astrophysics Data System (ADS)

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

    2016-09-01

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

  10. Magnetic Catalysis in Graphene Effective Field Theory

    NASA Astrophysics Data System (ADS)

    DeTar, Carleton; Winterowd, Christopher; Zafeiropoulos, Savvas

    2016-12-01

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

  11. Magnetic Field Effects on Plasma Plumes

    NASA Technical Reports Server (NTRS)

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

    2012-01-01

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

  12. Effect of magnetic field inhomogeneity on ion cyclotron motion coherence at high magnetic field.

    PubMed

    Vladimirov, Gleb; Kostyukevich, Yury; Hendrickson, Christopher L; Blakney, Greg T; Nikolaev, Eugene

    2015-01-01

    A three-dimensional code based on the particle-in-cell algorithm modified to account for the inhomogeneity of the magnetic field was applied to determine the effect of Z(1), Z(2), Z(3), Z(4), X, Y, ZX, ZY, XZ(2) YZ(2), XY and X(2)-Y(2) components of an orthogonal magnetic field expansion on ion motion during detection in an FT-ICR cell. Simulations were performed for magnetic field strengths of 4.7, 7, 14.5 and 21 Tesla, including experimentally determined magnetic field spatial distributions for existing 4.7 T and 14.5 T magnets. The effect of magnetic field inhomogeneity on ion cloud stabilization ("ion condensation") at high numbers of ions was investigated by direct simulations of individual ion trajectories. Z(1), Z(2), Z(3) and Z(4) components have the largest effect (especially Z(1)) on ion cloud stability. Higher magnetic field strength and lower m/z demand higher relative magnetic field homogeneity to maintain cloud coherence for a fixed time period. The dependence of mass resolving power upper limit on Z(1) inhomogeneity is evaluated for different magnetic fields and m/z. The results serve to set the homogeneity requirements for various orthogonal magnetic field components (shims) for future FT-ICR magnet design.

  13. Anomaly induced effects in a magnetic field

    NASA Astrophysics Data System (ADS)

    Antoniadis, Ignatios; Boyarsky, Alexey; Ruchayskiy, Oleg

    2008-04-01

    We consider a modification of electrodynamics by an additional light massive vector field, interacting with the photon via Chern-Simons-like coupling. This theory predicts observable effects for the experiments studying the propagation of light in an external magnetic field, very similar to those, predicted by theories of axion and axion-like particles. We discuss a possible microscopic origin of this theory from a theory with non-trivial gauge anomaly cancellation between massive and light particles (including, for example, millicharged fermions). Due to the conservation of the gauge current, the production of the new vector field is suppressed at high energies. As a result, this theory can avoid both stellar bounds (which exist for axions) and the bounds from CMB considered recently, allowing for positive results in experiments like ALPS, LIPPS, OSQAR, PVLAS-2, BMV, Q&A, etc.

  14. Magnetic Field Effect on the Stability of Flow Induced by a Rotating Magnetic Field

    NASA Technical Reports Server (NTRS)

    Mazuruk, K.; Volz, M. P.; Gillies, D. C.

    1999-01-01

    A linear stability analysis has been performed for the flow induced by a rotating magnetic field in a cylindrical column filled with electrically conducting fluid. The first transition is time- independent and results in the generation of Taylor vortices. The critical value of the magnetic Taylor number has been examined as a function of the strength of the transverse rotating magnetic field, the strength of an axial static magnetic field, and thermal buoyancy. Increasing the transverse field increases the critical magnetic Taylor number and decreases the aspect ratio of the Taylor vortices at the onset of instability. An increase in the axial magnetic field also increases the critical magnetic Taylor number but increases the aspect ratio of the Taylor vortices. Thermal buoyancy is found to have only a negligible effect on the onset of instability.

  15. Magnetic Field Effect on the Stability of Flow Induced by a Rotating Magnetic Field

    NASA Technical Reports Server (NTRS)

    Mazuruk, K.; Gillies, D. C.; Volz, M. P.

    1999-01-01

    A linear stability analysis has been performed for the flow induced by a rotating magnetic field in a cylindrical column filled with electrically conducting fluid. The first transition is time-independent and results in the generation of Taylor vortices. The critical value of the magnetic Taylor number has been examined as a function of the strength of the transverse rotating magnetic field, the strength of an axial static magnetic field, and thermal buoyancy. Increasing the transverse field increases the critical magnetic Taylor number and decreases the aspect ratio of the Taylor vortices at the onset of instability. An increase in the axial magnetic field also increases the critical magnetic Taylor number but increases the aspect ratio of the Taylor vortices. Thermal buoyancy is found to have only a negligible effect on the onset of instability.

  16. Effect of zero magnetic field on cardiovascular system and microcirculation

    NASA Astrophysics Data System (ADS)

    Gurfinkel, Yu. I.; At'kov, O. Yu.; Vasin, A. L.; Breus, T. K.; Sasonko, M. L.; Pishchalnikov, R. Yu.

    2016-02-01

    The effects of zero magnetic field conditions on cardiovascular system of healthy adults have been studied. In order to generate zero magnetic field, the facility for magnetic fields modeling ;ARFA; has been used. Parameters of the capillary blood flow, blood pressure, and the electrocardiogram (ECG) monitoring were measured during the study. All subjects were tested twice: in zero magnetic field and, for comparison, in sham condition. The obtained results during 60 minutes of zero magnetic field exposure demonstrate a clear effect on cardiovascular system and microcirculation. The results of our experiments can be used in studies of long-term stay in hypo-magnetic conditions during interplanetary missions.

  17. Carbon nanotube field effect transistors under high magnetic fields

    NASA Astrophysics Data System (ADS)

    Fedorov, Georgy; Smirnov, Dmitry; Tselev, Alexander; Yang, Yanfei; Kalugin, Nikolay

    2006-03-01

    Magnetic field, when applied parallel to the CNT axis, alters the energy gap in the CNT electron spectrum with a period corresponding to one quantum of magnetic flux through the cross-section of the CNT. With available magnetic fields (10^1T by the order of magnitude), gap oscillations can be observed only in multi-wall CNTs with diameters larger than approx 5 nm, where effects of band structure variation are smeared out by defects and by quantum interference effects. As follows from [1], it is possible to separate effects of disorder from those of the band structure modification by studying magnetotransport in small diameter CNTs while controllably changing the position of the Fermi level of the CNT by electrostatic doping, i.e. by applying a gate voltage in the field effect transistor configuration. We have studied several samples of individual CTNs contacted by palladium electrodes placed on an oxidized heavily doped silicon substrate that served as a back-gate. We find that magnetoresistance of a CNT strongly depends on the Fermi level position with respect to the nanotube's charge neutrality point (CNP). Details and the analysis of our experimental data will be presented. [1] S. Roche, R. Saito, Phys. Rev. Lett. 87, 246803 (2001)

  18. Effects of static magnetic fields at the cellular level.

    PubMed

    Miyakoshi, Junji

    2005-01-01

    There have been few studies on the effects of static magnetic fields at the cellular level, compared to those of extremely low frequency magnetic fields. Past studies have shown that a static magnetic field alone does not have a lethal effect on the basic properties of cell growth and survival under normal culture conditions, regardless of the magnetic density. Most but not all studies have also suggested that a static magnetic field has no effect on changes in cell growth rate. It has also been shown that cell cycle distribution is not influenced by extremely strong static magnetic fields (up to a maximum of 10 T). A further area of interest is whether static magnetic fields cause DNA damage, which can be evaluated by determination of the frequency of micronucleus formation. The presence or absence of such micronuclei can confirm whether a particular treatment damages cellular DNA. This method has been used to confirm that a static magnetic field alone has no such effect. However, the frequency of micronucleus formation increases significantly when certain treatments (e.g., X-irradiation) are given prior to exposure to a 10 T static magnetic field. It has also been reported that treatment with trace amounts of ferrous ions in the cell culture medium and exposure to a static magnetic field increases DNA damage, which is detected using the comet assay. In addition, many studies have found a strong magnetic field that can induce orientation phenomena in cell culture.

  19. NONLINEAR EFFECTS IN PARTICLE TRANSPORT IN STOCHASTIC MAGNETIC FIELDS

    SciTech Connect

    Vlad, M.; Spineanu, F.; Croitoru, A.

    2015-12-10

    Collisional particle transport in stochastic magnetic fields is studied using a semi-analytical method. The aim is to determine the influence of the nonlinear effects that occur in the magnetic field line random walk on particle transport. We show that particle transport coefficients can be strongly influenced by the magnetic line trapping. The conditions that correspond to these nonlinear regimes are determined. We also analyze the effects produced by the space variation of the large-scale magnetic field. We show that an average drift is generated by the gradient of the magnetic field, which strongly increases and reverses its orientation in the nonlinear regime.

  20. Magnetic field effect on indole exciplexes: a comparative study

    NASA Astrophysics Data System (ADS)

    Sengupta, Tamal; Basu, Samita

    2004-04-01

    A comparative magnetic field effect (MFE) study was done on indole exciplexes with various acceptors, anthracene, pyrene, all-s- trans-1,4-diphenylbuta-1,3-diene and 9-cyanophenanthrene. A surprisingly low magnetic field effect was detected for the 9-cyanophenanthrene exciplexes and was correlated with exciplex geometry. The wavelength dependence of magnetic field effect confirms the presence of single charge-transfer complex for all the exciplexes with 1,2-dimethylindole.

  1. Magnetic field effects in chemistry and biology

    NASA Astrophysics Data System (ADS)

    Schulten, Klaus

    Chemical and biological photoprocesses which involve bimolecular reactions between non-zero spin intermediates, e.g. doublet molecules 2A+2B, often produce the intermediate molecular pair in a pure overall spin state, e.g. a singlet state 1(2A+2B). and select for the reaction channels again such spin states, e.g. a triplet state 3(2A+2B). The necessery transition 1(2A+2B)→3(2A+2B) is affected by magnetic interactions (hyperfine, Zeeman, zero field splitting) and can be influenced by magnetic fields. Examples are photoinduced electron transfer processes, e.g. the primary reaction of photosynthesis.

  2. Effect of magnetic field on the rotating filamentary molecular clouds

    NASA Astrophysics Data System (ADS)

    Aghili, P.; Kokabi, K.

    2017-04-01

    The Purpose of this work is to study the evolution of magnetized rotating filamentary molecular clouds. We consider cylindrical symmetric filamentary molecular clouds at an early stage of evolution. For the first time we consider the rotation of filamentary molecular in the presence of an axial and azimuthal magnetic field without any assumption of density and magnetic functions. We show that in addition to decreasing the radial collapse velocity, the rotational velocity is also affected by the magnetic field. The existence of rotation yields fragmentation of filaments. Moreover, we show that the magnetic field has a significant effect on the fragmentation of filamentary molecular clouds.

  3. Magnetic field control of the spin Seebeck effect

    NASA Astrophysics Data System (ADS)

    Ritzmann, Ulrike; Hinzke, Denise; Kehlberger, Andreas; Guo, Er-Jia; Kläui, Mathias; Nowak, Ulrich

    2015-11-01

    The origin of the suppression of the longitudinal spin Seebeck effect by applied magnetic fields is studied. We perform numerical simulations of the stochastic Landau-Lifshitz-Gilbert equation of motion for an atomistic spin model and calculate the magnon accumulation in linear temperature gradients for different strengths of applied magnetic fields and different length scales of the temperature gradient. We observe a decrease of the magnon accumulation with increasing magnetic field and we reveal that the origin of this effect is a field dependent change of the frequency distribution of the propagating magnons. With increasing field the magnonic spin currents are reduced due to a suppression of parts of the frequency spectrum. By comparison with measurements of the magnetic field dependent longitudinal spin Seebeck effect in YIG thin films with various thicknesses, we find qualitative agreement between our model and the experimental data, demonstrating the importance of this effect for experimental systems.

  4. Effects of static magnetic field on mutagenesis in in vitro

    NASA Astrophysics Data System (ADS)

    Ikehata, M.; Yoshie, S.; Hirota, N.; Hayakawa, T.

    2009-03-01

    Effects of static magnetic field up to 13 T were estimated in Escherichia coli and Saccharomyces cerevisiae. We observed that exposure to a 5 T static magnetic field resulted in a slight but significant increase in gene recombination frequency while frequency of reverse point mutation was not altered in S. cerevisiae. This mutagenic effect showed a dose response relationship as J-shape. To investigate an involvement of reactive oxygen species in possible mutagenic effect of static magnetic field, SOD deficient E. coli QC774 was used in thymine synthesis-based mutation assay. The result shows that static magnetic field up to 13 T did not indicate mutagenicity. Thus, it is suggested that frequency of point mutation does not changed under static magnetic field regardless of its susceptibility to superoxide. These results suggest that strong static magnetic field would have small but detectable mutagenic potential. Although mechanism of the mutagenic effect of static magnetic field has not been elucidated yet, the extent of this effect is estimated extremely small by comparison with other mutagens such as ultraviolet irradiation.

  5. Magnetic field effects in electron systems with imperfect nesting

    NASA Astrophysics Data System (ADS)

    Sboychakov, A. O.; Rakhmanov, A. L.; Kugel, K. I.; Rozhkov, A. V.; Nori, Franco

    2017-01-01

    We analyze the effects of an applied magnetic field on the phase diagram of a weakly correlated electron system with imperfect nesting. The Hamiltonian under study describes two bands: electron and hole ones. Both bands have spherical Fermi surfaces, whose radii are slightly mismatched due to doping. These types of models are often used in the analysis of magnetic states in chromium and its alloys, superconducting iron pnictides, AA-type bilayer graphene, borides, etc. At zero magnetic field, the uniform ground state of the system turns out to be unstable against electronic phase separation. The applied magnetic field affects the phase diagram in several ways. In particular, the Zeeman term stabilizes new antiferromagnetic phases. It also significantly shifts the boundaries of inhomogeneous (phase-separated) states. At sufficiently high fields, the Landau quantization gives rise to oscillations of the order parameters and of the Néel temperature as a function of the magnetic field.

  6. Effects of solar magnetic field on cosmic rays

    NASA Technical Reports Server (NTRS)

    Goncher, G. A.; Kolomeets, E. V.; Lyakhova, A. K.; Slyunyaeva, N. V.; Stekolnikov, N. V.

    1985-01-01

    Aspects of the problem of galactic cosmic ray propagation, including inversion of the solar total magnetic field and an analysis of data related to the heliomagnetic cycle are discussed. It is noted that the global structure of the solar magnetic field results in an additional flux of galactic cosmic rays generated by curvature and gradient drifts. An analysis of heliomagnetic cycle data shows that the latitudinal gradient results in a N-S asymmetry, with the amplitude of the effect growing with depth in the atmosphere. The inversion of the solar total magnetic field, drift effects, and other space distributions are found to contribute to a 22-year cycle of solar activity.

  7. Low-frequency magnetic field effect on cytoskeleton and chromatin.

    PubMed

    Kroupová, Jana; Bártová, Eva; Fojt, Lukás; Strasák, Ludek; Kozubek, Stanislav; Vetterl, Vladimír

    2007-01-01

    The effect of magnetic fields on the living systems is studied in vivo or in vitro in very broad spectrum of organisms, cells and tissues. The mechanism of their acting is not known until now. We studied low-frequency magnetic field effect on cytoskeleton and on the structure of chromatin in human cells. We used cell line of small lung carcinoma (A549) and the effects of magnetic field on cytoskeleton and higher-order chromatin structure were analyzed 96 h of magnetic field exposure. Magnetic field generated by the cylindrical soil was homogenous and the cells were cultivated at 37 degrees C in humidified atmosphere containing 5% CO(2). Magnetic field induction was B(m)=2 mT and the net frequency f=50 Hz. In such affected and control cells the F-actin was estimated using FITC-conjugated Phalloidin and mitochondria were studied using MitoTracker (Molecular Probes). Images of cytoskeleton and genetic loci were acquired using confocal microscopy and analysis was performed by FISH 2.0 software. Slight morphological changes of F-actin filaments and mitochondria were observed in affected cells and nuclear condensation was found. These effects could be related to the process of cell death apoptosis probably induced by magnetic field. The studies aimed at centromeric heterochromatin (9cen) did not show statistically significant changes. Therefore, we suggest that magnetic field has no influence on higher order chromatin structure but certain changes could be observed on the level of cytoskeleton. However, these statements need a thorough verification. Our preliminary experiments will be extended and the effect of magnetic field on another structures of cytoskeleton and cell nuclei will be further studied.

  8. Magnetic field effect on flow parameters of blood along with magnetic particles in a cylindrical tube

    NASA Astrophysics Data System (ADS)

    Sharma, Shashi; Singh, Uaday; Katiyar, V. K.

    2015-03-01

    In this paper, the effect of external uniform magnetic field on flow parameters of both blood and magnetic particles is reported through a mathematical model using magnetohydrodynamics (MHD) approach. The fluid is acted upon by a varying pressure gradient and an external uniform magnetic field is applied perpendicular to the cylindrical tube. The governing nonlinear partial differential equations were solved numerically and found that flow parameters are affected by the influence of magnetic field. Further, artificial blood (75% water+25% Glycerol) along with iron oxide magnetic particles were prepared and transported into a glass tube with help of a peristaltic pump. The velocity of artificial blood along with magnetic particles was experimentally measured at different magnetic fields ranging from 100 to 600 mT. The model results show that the velocity of blood and magnetic particles is appreciably reduced under the influence of magnetic field, which is supported by our experimental results.

  9. Interaction mechanisms and biological effects of static magnetic fields

    SciTech Connect

    Tenforde, T.S.

    1994-06-01

    Mechanisms through which static magnetic fields interact with living systems are described and illustrated by selected experimental observations. These mechanisms include electrodynamic interactions with moving, ionic charges (blood flow and nerve impulse conduction), magnetomechanical interactions (orientation and translation of molecules structures and magnetic particles), and interactions with electronic spin states in charge transfer reactions (photo-induced electron transfer in photosynthesis). A general summary is also presented of the biological effects of static magnetic fields. There is convincing experimental evidence for magnetoreception mechanisms in several classes of lower organisms, including bacteria and marine organisms. However, in more highly evolved species of animals, there is no evidence that the interactions of static magnetic fields with flux densities up to 2 Tesla (1 Tesla [T] = 10{sup 4} Gauss) produce either behavioral or physiolocical alterations. These results, based on controlled studies with laboratory animals, are consistent with the outcome of recent epidemiological surveys on human populations exposed occupationally to static magnetic fields.

  10. A magnetic field effect on learning in male golden hamsters.

    PubMed

    Łopuch, Sylwia

    2009-05-01

    The aim of this experiment was to investigate the influence of repeated exposure to 10, 20, 30 or 40 Hz magnetic fields at 0.1T on the learning of male golden hamsters in a Skinner box, in which the animals learned to press a lever to receive a food reward. The latency of the first response was not affected by exposure to the magnetic fields used in this experiment. No significant field-dependent effects on the performance of the task were observed in males exposed to 10 and 20 Hz magnetic fields at 0.1T. However, exposure significantly improved the learning of the task in animals exposed to 30 and 40 Hz magnetic fields at 0.1T.

  11. Magnetic properties of a nanoribbon: An effective-field theory

    NASA Astrophysics Data System (ADS)

    Wang, Jiu-Ming; Jiang, Wei; Zhou, Chen-Long; Shi, Zuo; Wu, Chuang

    2017-02-01

    An effective-field theory is proposed to study magnetic properties of a nanoribbon. The model consists of a core spin-3/2 and shell spin-2 with a ferrimagnetic exchange coupling, which is described by transverse Ising model with the anisotropy. Based on the differential operator technique, the magnetization and the susceptibility formulas of the nanoribbon are given. Numerical results of the magnetization, the susceptibility, the hysteresis loop of the system are discussed for specific values of the parameters. Magnetization plateaus exhibits on the magnetization curves at low temperature. The exchange coupling, the anisotropy and the transverse field have important roles in the magnetic properties for the nanoribbon. Results may provide some guidance to design in the nanoribbons.

  12. Chemical amplification of magnetic field effects relevant to avian magnetoreception

    NASA Astrophysics Data System (ADS)

    Kattnig, Daniel R.; Evans, Emrys W.; Déjean, Victoire; Dodson, Charlotte A.; Wallace, Mark I.; MacKenzie, Stuart R.; Timmel, Christiane R.; Hore, P. J.

    2016-04-01

    Magnetic fields as weak as the Earth's can change the yields of radical pair reactions even though the energies involved are orders of magnitude smaller than the thermal energy, kBT, at room temperature. Proposed as the source of the light-dependent magnetic compass in migratory birds, the radical pair mechanism is thought to operate in cryptochrome flavoproteins in the retina. Here we demonstrate that the primary magnetic field effect on flavin photoreactions can be amplified chemically by slow radical termination reactions under conditions of continuous photoexcitation. The nature and origin of the amplification are revealed by studies of the intermolecular flavin-tryptophan and flavin-ascorbic acid photocycles and the closely related intramolecular flavin-tryptophan radical pair in cryptochrome. Amplification factors of up to 5.6 were observed for magnetic fields weaker than 1 mT. Substantial chemical amplification could have a significant impact on the viability of a cryptochrome-based magnetic compass sensor.

  13. Effects of magnetic fields on dissolution of arthritis causing crystals

    NASA Astrophysics Data System (ADS)

    Takeuchi, Y.; Iwasaka, M.

    2015-05-01

    The number of gout patients has rapidly increased because of excess alcohol and salt intake. The agent responsible for gout is the monosodium urate (MSU) crystal. MSU crystals are found in blood and consist of uric acid and sodium. As a substitute for drug dosing or excessive water intake, physical stimulation by magnetic fields represents a new medical treatment for gout. In this study, we investigated the effects of a magnetic field on the dissolution of a MSU crystal suspension. The white MSU crystal suspension was dissolved in an alkaline solution. We measured the light transmission of the MSU crystal suspension by a transmitted light measuring system. The magnetic field was generated by a horizontal electromagnet (maximum field strength was 500 mT). The MSU crystal suspension that dissolved during the application of a magnetic field of 500 mT clearly had a higher dissolution rate when compared with the control sample. We postulate that the alkali solution promoted penetration upon diamagnetic rotation and this magnetic field orienting is because of the pronounced diamagnetic susceptibility anisotropy of the MSU crystal. The results indicate that magnetic fields represent an effective gout treatment approach.

  14. Biological effects due to weak magnetic field on plants

    NASA Astrophysics Data System (ADS)

    Belyavskaya, N. A.

    2004-01-01

    magnetic field may cause different biological effects at the cellular, tissue and organ levels. They may be functionally related to systems that regulate plant metabolism including the intracellular Ca 2+ homeostasis. However, our understanding of very complex fundamental mechanisms and sites of interactions between weak magnetic fields and biological systems is still incomplete and still deserve strong research efforts.

  15. Lattice Study of Magnetic Catalysis in Graphene Effective Field Theory

    NASA Astrophysics Data System (ADS)

    Winterowd, Christopher; Detar, Carleton; Zafeiropoulos, Savvas

    2016-03-01

    The discovery of graphene ranks as one of the most important developments in condensed matter physics in recent years. As a strongly interacting system whose low-energy excitations are described by the Dirac equation, graphene has many similarities with other strongly interacting field theories, particularly quantum chromodynamics (QCD). Graphene, along with other relativistic field theories, have been predicted to exhibit spontaneous symmetry breaking (SSB) when an external magnetic field is present. Using nonperturbative methods developed to study QCD, we study the low-energy effective field theory (EFT) of graphene subject to an external magnetic field. We find strong evidence supporting the existence of SSB at zero-temperature and characterize the dependence of the chiral condensate on the external magnetic field. We also present results for the mass of the Nambu-Goldstone boson and the dynamically generated quasiparticle mass that result from the SSB.

  16. Effect of a Magnetic Field on Drosophila under Supercooled Conditions

    PubMed Central

    Mihara, Makoto; Terayama, Hayato; Hatayama, Naoyuki; Hayashi, Shogo; Matsushita, Masayuki; Itoh, Masahiro

    2012-01-01

    Under subzero degree conditions, free water contained in biological cells tends to freeze and then most living things die due to low temperatures. We examined the effect of a variable magnetic field on Drosophila under supercooled conditions (a state in which freezing is not caused even below the freezing point). Under such supercooled conditions with the magnetic field at 0°C for 72 hours, −4°C for 24 hours and −8°C for 1 hour, the Drosophila all survived, while all conversely died under the supercooled conditions without the magnetic field. This result indicates a possibility that the magnetic field can reduce cell damage caused due to low temperatures in living things. PMID:23284809

  17. Influence of oblique magnetic field on electron cross-field transport in a Hall effect thruster

    SciTech Connect

    Miedzik, Jan; Daniłko, Dariusz; Barral, Serge

    2015-04-15

    The effects of the inclination of the magnetic field with respect to the channel walls in a Hall effect thruster are numerically studied with the use of a one-dimensional quasi-neutral Particle-In-Cell model with guiding center approximation of electron motion along magnetic lines. Parametric studies suggest that the incidence angle strongly influences electron transport across the magnetic field. In ion-focusing magnetic topologies, electrons collide predominantly on the side of the magnetic flux tube closer to the anode, thus increasing the electron cross-field drift. The opposite effect is observed in ion-defocussing topology.

  18. Effect of Static Magnetic Field on Cell Migration

    NASA Astrophysics Data System (ADS)

    Hashimoto, Yuichiro; Kawasumi, Masashi; Saito, Masao

    The effect of magnetic field on cell has long been investigated, but there are few quantitative investigations of the migration of cells. Cell-migration is important as one of the fundamental activities of the cell. This study proposes a method to evaluate quantitatively the cell-diffusion constant and the effect of static magnetic field on cell migration. The cell-lines are neuroblastoma (NG108-15), fibroblastoma (NIH/3T3) and osteoblastoma (MC3T3-E1). The static magnetic field of 30 mT or 120 mT is impressed by a permanent magnet in vertical or horizontal direction to the dish. It is shown that the cell-diffusion constant can represent the cell migration as the cell activity. It is found that the cell migration is enhanced by exposure to the magnetic field, depending on the kind of cell. It is conjectured that the effect of static magnetic field affects the cell migration, which is at the downstream of the information transmission.

  19. Effects of an oscillating magnetic field on homogeneous ferrofluid turbulence.

    PubMed

    Schumacher, Kristopher R; Riley, James J; Finlayson, Bruce A

    2010-01-01

    This paper presents the results from direct numerical simulations of homogeneous ferrofluid turbulence with a spatially uniform, applied oscillating magnetic field. Due to the strong coupling that exists between the magnetic field and the ferrofluid, we find that the oscillating field can affect the characteristics of the turbulent flow. The magnetic field does work on the turbulent flow and typically leads to an increased rate of energy loss via two dissipation modes specific to ferrofluids. However, under certain conditions this magnetic work results in injection, or a forcing, of turbulent kinetic energy into the flow. For the cases considered here, there is no mean shear and the mean components of velocity, vorticity, and particle spin rate are all zero. Thus, the effects shown are entirely due to the interactions between the turbulent fluctuations of the ferrofluid and the magnetic field. In addition to the effects of the oscillation frequency, we also investigate the effects of the choice of magnetization equation. The calculations focus on the approximate centerline conditions of the relatively low Reynolds number turbulent ferrofluid pipe flow experiments described previously [K. R. Schumacher, Phys. Rev. E 67, 026308 (2003)].

  20. Lifshitz effects on vector condensate induced by a magnetic field

    NASA Astrophysics Data System (ADS)

    Wu, Ya-Bo; Lu, Jun-Wang; Liu, Mo-Lin; Lu, Jian-Bo; Zhang, Cheng-Yuan; Yang, Zhuo-Qun

    2014-05-01

    By numerical and analytical methods, we study in detail the effects of the Lifshitz dynamical exponent z on the vector condensate induced by an applied magnetic field in the probe limit. Concretely, in the presence of the magnetic field, we obtain the Landau level independent of z, and we also find the critical value by coupling a Maxwell complex vector field and an SU(2) field into a (3+1)-dimensional Lifshitz black hole, respectively. The research results show that for the two models with the lowest Landau level, the increasing z improves the response of the critical temperature to the applied magnetic field even without the charge density, and the analytical results uphold the numerical results. In addition, we find that, even in the Lifshitz black hole, the Maxwell complex vector model is still a generalization of the SU(2) Yang-Mills model. Furthermore, we construct the square vortex lattice and discuss the implications of these results.

  1. Effects of Magnetic Field on Biological Cells and Applications

    NASA Astrophysics Data System (ADS)

    Chen, Ching-Jen

    2001-03-01

    While there has been extensive research performed in the physics of magnetic fields and the physics and chemistry in life sciences, independent of each other, there has been a paucity of scientific research and development investigating the possible applications of magnetic fields in life sciences. The focus of this presentation is to present the stimulation mechanism by which magnetic fields affect (a) yeast cells (b) plant cells and (c) mammalian normal and cancer cells. Recently we have found that the Saccharomyces Cerevsa yeast growth increases by about 30to a 1 tesla field and the production of CO2 increases by about 30of yeast metabolism may be due to an increase in intercellular interaction and protein channel alignment, the introduction of an alteration in the DNA from the magnetic field exposure or a combination of these mechanisms. We also have found that the application of high magnetic fields (1 tesla and above) can have marked effects on the germination and growth of plants, especially corn, beans and peas. This finding has opened up the possibility of technology developments in botanical growth systems to accelerate seed germination and crop harvesting. Most recently we have investigated the application of high magnetic fields on leukemia, CaCoII and HEP G2 cancer cell lines. We found that when leukemia are exposed to a 12 tesla field for 2 hours has an increase in cell death by about 30that were not exposed to the magnetic field. Viability of CaCoII cells sandwiched between permanent magnets of maximum strength of 1.2 tesla was measured. A decrease in viable cells by 33unexposed cells. HSP 70 was measured for HEPG2 cells that were exposed to permanent magnetic field of 1.2 tesla for 40 minutes and for unexposed cells. It was found that the exposed cells produce 19 times more HSP70 compared to unexposed cells. Our results together with other investigators report suggest a strong evidence of a reduction in the cell growth rate for cancer cells when

  2. Critical suppression of spin Seebeck effect by magnetic fields

    NASA Astrophysics Data System (ADS)

    Kikkawa, Takashi; Uchida, Ken-ichi; Daimon, Shunsuke; Qiu, Zhiyong; Shiomi, Yuki; Saitoh, Eiji

    2015-08-01

    The longitudinal spin Seebeck effect (LSSE) in Pt /Y3Fe5O12(YIG ) junction systems has been investigated at various magnetic fields and temperatures. We found that the LSSE voltage in a Pt/YIG-slab system is suppressed by applying high magnetic fields and this suppression is critically enhanced at low temperatures. The field-induced suppression of the LSSE in the Pt/YIG-slab system is too large at around room temperature to be explained simply by considering the effect of the Zeeman gap in magnon excitation. This result requires us to introduce a magnon-frequency-dependent mechanism into the scenario of LSSE; low-frequency magnons dominantly contribute to the LSSE. The magnetic field dependence of the LSSE voltage was observed to change by changing the thickness of YIG, suggesting that the thermospin conversion by the low-frequency magnons is suppressed in thin YIG films due to the long characteristic lengths of such magnons.

  3. Investigation of the effective field in magnetic fluids

    SciTech Connect

    Smirnov, V.I.

    1986-07-01

    The authors describe investigations of the effective field caused by the orientational interaction between ferroparticles for magnetic fluids with a conducting and a nonconducting base. The magnetic susceptibility of four magnetic fluid specimens was investigated. Specimens consisted of a colloid solution of magnetite in kerosene, stabilized with oleic acid; mercury-based magnetic fluids, a colloid solution of finely dispersed iron particles in mercury, a solution of iron particles with a lower degree of dispersion, and a solution of cobalt particles. Figures show the temperature dependences of the magnetic suceptibility of the fluid specimens. It was shown that under certain conditions, it is possible that instabilities can arise and heterophase impurities can form in accordance with the mechanism proposed previously in both electrically conducting and nonconducting magnetic fluids.

  4. Magnetic field effects on the NiO magnon spectra.

    SciTech Connect

    Milano, J.; Grimsditch, M.; Materials Science Division; Centro Atomico Bariloche; CIC Nanogune

    2010-03-15

    The effect of an external magnetic field on the eight antiferromagnetic resonance (AFMR) modes of NiO has been studied experimentally using Brillouin light scattering. The results are reproduced by a model that includes the effects of exchange, dipolar coupling, a small cubic anisotropy, and Zeeman terms. Magnetic fields up to 7 T were applied along several NiO crystalline directions. The agreement between theory and experiment provides additional proof that the model, recently introduced to explain the existence of the AFMR multiplet, is indeed valid. Deviations between simulations and experiments, together with a review of previously published results, indicate that large magnetostrictive effects are present in NiO.

  5. Magnetic field effects on reactive sintering of MnBi

    NASA Astrophysics Data System (ADS)

    Abematsu, Ken-ichi; Mitsui, Yoshifuru; Taira, Atsushi; Miyazaki, Daiki; Takaki, Akio; Umetsu, Rie Y.; Takahashi, Kohki; Koyama, Keiichi

    2016-08-01

    Annealing temperature of reactive sintering of MnBi was optimized. The highest fraction of MnBi phase was obtained to be 93wt.% at annealing temperature of 280°C. Magnetic field effects on solid- and liquid-state sintering of MnBi were described. The reacted fraction of MnBi was enhanced by the application of magnetic field of 15 T for solid- state sintering. In contract, reacted fraction was not influenced by magnetic field for liquid-state sintering. Both of in- field solid- and liquid-state sintered samples realized the highly crystal orientation of MnBi phase along the applied magnetic field direction. The Lotgering factor of the MnBi phase was obtained to be 1.0 for both in-field sintered samples, which was an "almost complete" uniaxial orientation. Due to the crystal orientation, anisotropic magnetic properties exhibited. The anisotropy field of the bulk sample was evaluated to be 4 T at room temperature, which also suggested the uniaxial orientation of the sample.

  6. Full particle orbit effects in regular and stochastic magnetic fields

    SciTech Connect

    Ogawa, Shun; Cambon, Benjamin P.; Leoncini, Xavier; Vittot, Michel; Del-Castillo-Negrete, Diego B; Dif-Pradalier, Guilhem; Garbet, Xavier

    2016-07-18

    Here we present a numerical study of charged particle motion in a time-independent magnetic field in cylindrical geometry. The magnetic field model consists of an unperturbed reversed-shear (non-monotonic q-profile) helical part and a perturbation consisting of a superposition of modes. Contrary to most of the previous studies, the particle trajectories are computed by directly solving the full Lorentz force equations of motion in a six-dimensional phase space using a sixth-order, implicit, symplectic Gauss-Legendre method. The level of stochasticity in the particle orbits is diagnosed using averaged, effective Poincare sections. It is shown that when only one mode is present, the particle orbits can be stochastic even though the magnetic field line orbits are not stochastic (i.e., fully integrable). The lack of integrability of the particle orbits in this case is related to separatrix crossing and the breakdown of the global conservation of the magnetic moment. Some perturbation consisting of two modes creates resonance overlapping, leading to Hamiltonian chaos in magnetic field lines. Then, the particle orbits exhibit a nontrivial dynamics depending on their energy and pitch angle. It is shown that the regions where the particle motion is stochastic decrease as the energy increases. The non-monotonicity of the q-profile implies the existence of magnetic ITBs (internal transport barriers) which correspond to shearless flux surfaces located in the vicinity of the q-profile minimum. It is shown that depending on the energy, these magnetic ITBs might or might not confine particles. That is, magnetic ITBs act as an energy-dependent particle confinement filter. Magnetic field lines in reversed-shear configurations exhibit topological bifurcations (from homoclinic to heteroclinic) due to separatrix reconnection. Finally, we show that a similar but more complex scenario appears in the case of particle orbits that depend in a non-trivial way on the energy and pitch angle

  7. Full particle orbit effects in regular and stochastic magnetic fields

    DOE PAGES

    Ogawa, Shun; Cambon, Benjamin P.; Leoncini, Xavier; ...

    2016-07-18

    Here we present a numerical study of charged particle motion in a time-independent magnetic field in cylindrical geometry. The magnetic field model consists of an unperturbed reversed-shear (non-monotonic q-profile) helical part and a perturbation consisting of a superposition of modes. Contrary to most of the previous studies, the particle trajectories are computed by directly solving the full Lorentz force equations of motion in a six-dimensional phase space using a sixth-order, implicit, symplectic Gauss-Legendre method. The level of stochasticity in the particle orbits is diagnosed using averaged, effective Poincare sections. It is shown that when only one mode is present, themore » particle orbits can be stochastic even though the magnetic field line orbits are not stochastic (i.e., fully integrable). The lack of integrability of the particle orbits in this case is related to separatrix crossing and the breakdown of the global conservation of the magnetic moment. Some perturbation consisting of two modes creates resonance overlapping, leading to Hamiltonian chaos in magnetic field lines. Then, the particle orbits exhibit a nontrivial dynamics depending on their energy and pitch angle. It is shown that the regions where the particle motion is stochastic decrease as the energy increases. The non-monotonicity of the q-profile implies the existence of magnetic ITBs (internal transport barriers) which correspond to shearless flux surfaces located in the vicinity of the q-profile minimum. It is shown that depending on the energy, these magnetic ITBs might or might not confine particles. That is, magnetic ITBs act as an energy-dependent particle confinement filter. Magnetic field lines in reversed-shear configurations exhibit topological bifurcations (from homoclinic to heteroclinic) due to separatrix reconnection. Finally, we show that a similar but more complex scenario appears in the case of particle orbits that depend in a non-trivial way on the energy and

  8. Induced magnetic-field effects in inductively coupled plasmas

    NASA Astrophysics Data System (ADS)

    Cohen, Ronald H.; Rognlien, Thomas D.

    1996-05-01

    In inductive plasma sources, the rapid spatial decay of the electric field arising from the skin effect produces a large radio frequency (RF) magnetic field via Faraday's law. It was previously shown that this magnetic field leads to a reduction of the electron density in the skin region, as well as a reduction in the collisionless heating rate. The electron deficit leads to the formation of an electrostatic potential which pulls electrons in to restore quasineutrality. Here the electron density calculation is extended to include both the induced and electrostatic fields. If the wave frequency is not too low, the ions respond only to the averaged fields, and hence the electrostatic field is oscillatory, predominantly at the second harmonic of the applied field. The potential required to establish a constant electron density is calculated and compared with numerical orbit-code calculations. For times short compared to ion transit times, the quasineutral density is just the initial ion density. For timescales long enough that the ions can relax, the density profile can be found from the solution of fluid equations with an effective (ponderomotive-like) potential added. Although the time-varying electrostatic potential is an extra source of heating, the net effect of the induced magnetic and electrostatic fields through trapping, early turning, and direct heating is a significant reduction in collisionless heating for parameters of interest.

  9. Induced magnetic-field effects in inductively coupled plasmas

    SciTech Connect

    Cohen, R.H.; Rognlien, T.D.

    1995-11-04

    In inductive plasma sources, the rapid spatial decay of the electric field arising from the skin effect produces a large radio frequency (RF) magnetic field via Faraday`s law. We previously determined that this magnetic field leads to a reduction of the electron density in the skin region, as well as a reduction in the collisionless heating rate. The electron deficit leads to the formation of an electrostatic potential which pulls electrons in to restore quasineutrality. Here we calculate the electron density including both the induced and electrostatic fields. If the wave frequency is not too low, the ions respond only to the averaged fields, and hence the electrostatic field is oscillatory, predominantly at the second harmonic of the applied field. We calculate the potential required to establish a constant electron density, and compare with numerical orbit-code calculations. For times short compared to ion transit times, the quasineutral density is just the initial ion density. For timescales long enough that the ions can relax, the density profile can be found from the solution of fluid equations with an effective (ponderomotive-like) potential added. Although the time-varying electrostatic potential is an extra source of heating, the net effect of the induced magnetic and electrostatic fields through trapping, early turning, and direct heating is a significant reduction in collisionless heating for parameters of interest.

  10. Planar Hall effect bridge magnetic field sensors

    SciTech Connect

    Henriksen, A. D.; Dalslet, B. T.; Skieller, D. H.; Lee, K. H.; Okkels, F.; Hansen, M. F.

    2010-07-05

    Until now, the planar Hall effect has been studied in samples with cross-shaped Hall geometry. We demonstrate theoretically and experimentally that the planar Hall effect can be observed for an exchange-biased ferromagnetic material in a Wheatstone bridge topology and that the sensor signal can be significantly enhanced by a geometric factor. For the samples in the present study, we demonstrate an enhancement of the sensor output by a factor of about 100 compared to cross-shaped sensors. The presented construction opens a new design and application area of the planar Hall effect, which we term planar Hall effect bridge sensors.

  11. Effects of static magnetic fields on growth of Paramecium caudatum.

    PubMed

    Elahee, Khouaildi B; Poinapen, Danny

    2006-01-01

    Little is known about the influence of magnetic fields on growth of primitive eukaryotes such as the ciliate Paramecium. The latter are known to exhibit interesting characteristics such as electrotaxis, gravitaxis, and membrane excitability not commonly encountered in higher organisms. This preliminary study reports the effects of static magnetic fields on growth of Paramecium caudatum. The microorganisms were either permanently or 24 h on-and-off exposed to North and South polarity magnetic fields of average field gradient 4.3 T/m, for a period of 96 h. The growth rate and lag phase of all exposed populations were not significantly different from control ones exposed to normal geomagnetic field (P > .05). However, a significant negative shift in t(max) (time taken for maximum growth) of 10.5%-12.2% and a significant decrease (P < .05) in population size of 10.2%-15.1% during the 96 h of experimental conditions were recorded for exposed populations compared to control. Our results suggest that magnetic fields, irrespective of polarity and exposure period reduce Paramecium growth by triggering early senescence of the population. The mechanisms underlying the small changes in population growth are unknown at this level, but various hypotheses have been suggested, including disorganization of swimming patterns resulting from (i) changes in cell membrane electric potential due to high speed movement through a gradient magnetic field and (ii) thermodynamic effect of anisotropic magnetic energies on cell membrane components affecting functioning of calcium channels. Altered swimming movements could in turn affect highly orchestrated processes such as conjugation, essential for survival of the organisms during development of adverse environmental conditions as thought to occur in the closed culture system used in this study.

  12. Wiggle Instability of Galactic Spiral Shocks: Effects of Magnetic Fields

    NASA Astrophysics Data System (ADS)

    Kim, Yonghwi; Kim, Woong-Tae; Elmegreen, Bruce G.

    2015-08-01

    It has been suggested that the wiggle instability (WI) of spiral shocks in a galactic disk is responsible for the formation of gaseous feathers observed in grand-design spiral galaxies. We perform both a linear stability analysis and numerical simulations to investigate the effect of magnetic fields on the WI. The disk is assumed to be infinitesimally thin, isothermal, and non-self-gravitating. We control the strengths of magnetic fields and spiral-arm forcing using the dimensionless parameters β and {F}, respectively. By solving the perturbation equations as a boundary-eigenvalue problem, we obtain dispersion relations of the WI for various values of β =1-∞ and {F}=5% and 10%. We find that the WI arising from the accumulation of potential vorticity at disturbed shocks is suppressed, albeit not completely, by magnetic fields. The stabilizing effect of magnetic fields is not from the perturbed fields but from the unperturbed fields that reduce the density compression factor in the background shocks. When {F}=5% and β ≲ 10 or {F}=10% and β ˜ 5-10, the most unstable mode has a wavelength of ˜0.1-0.2 times the arm-to-arm separation, which appears consistent with a mean spacing of observed feathers.

  13. Magnetic field effects in flavoproteins and related systems

    PubMed Central

    Evans, Emrys W.; Dodson, Charlotte A.; Maeda, Kiminori; Biskup, Till; Wedge, C. J.; Timmel, Christiane R.

    2013-01-01

    Within the framework of the radical pair mechanism, magnetic fields may alter the rate and yields of chemical reactions involving spin-correlated radical pairs as intermediates. Such effects have been studied in detail in a variety of chemical systems both experimentally and theoretically. In recent years, there has been growing interest in whether such magnetic field effects (MFEs) also occur in biological systems, a question driven most notably by the increasing body of evidence for the involvement of such effects in the magnetic compass sense of animals. The blue-light photoreceptor cryptochrome is placed at the centre of this debate and photoexcitation of its bound flavin cofactor has indeed been shown to result in the formation of radical pairs. Here, we review studies of MFEs on free flavins in model systems as well as in blue-light photoreceptor proteins and discuss the properties that are crucial in determining the magnetosensitivity of these systems. PMID:24511388

  14. The magnetic field effects on photochemical reactions in ionic liquids.

    PubMed

    Wakasa, Masanobu

    2007-08-16

    The magnetic field effects (MFEs) on photoinduced hydrogen abstraction reactions of benzophenone (BP) with thiophenol (PhSH) in the ionic liquids (ILs) N,N,N-trimethyl-N-propylammonium bis(trifluoromethanesulfonyl) imide (TMPA TFSI), N-methyl-N-propylpyrrolidinium bis(trifluoromethanesulfonyl) imide (P13 TFSI), and N-methyl-N-propylpiperidinium bis(trifluoromethanesulfonyl) imide (PP13 TFSI) were investigated at 296 K by using a nanosecond laser flash photolysis technique under magnetic fields of 0-1.7 T. Large MFEs were observed for the first time in the ILs. In TMPA TFSI, the yield of the benzophenone ketyl radical gradually decreased with increasing magnetic field strength from 0 to 1.7 T, producing a 20% decrease at 1.7 T.

  15. New approaches to thermoelectric cooling effects in magnetic fields

    SciTech Connect

    Migliori, A.; Darling, T.W.; Freibert, F.; Trugman, S.A.; Moshopoulou, E.; Sarrao, J.L.

    1997-08-01

    The authors review thermoelectric effects in a magnetic field at a phenomenological level. Discussions of the limiting performance and problems with its computation for both Peltier and Ettingshausen coolers are presented. New principles are discussed to guide the materials scientist in the search for better Ettingshausen materials, and a brief review of the subtle measurement problems is presented.

  16. Interstellar magnetic field effects on the heliosphere

    NASA Astrophysics Data System (ADS)

    Ratkiewicz, Romana; Ben-Jaffel, Lotfi; McKenzie, James F.; Webb, Gary M.

    2003-09-01

    This paper summarizes the numerical results obtained by three-dimensional MHD simulations of the interaction between the solar wind and interstellar medium in Ratkiewicz and Ben-Jaffel [2002], Ratkiewicz and McKenzie [2002], and Ratkiewicz and Webb [2002]. We analyze the configuration in which Maxwell stresses lead to squeezing and/or pushing the heliospheric boundary. In particular, we explain the mechanism giving rise to a suction effect of the heliopause. Numerical results for the case of aligned interstellar MHD flow are compared with previous studies.

  17. Effects of 3D Toroidally Asymmetric Magnetic Field on Tokamak Magnetic Surfaces

    NASA Astrophysics Data System (ADS)

    Lao, L. L.

    2005-10-01

    The effects of 3D error magnetic field on magnetic surfaces are investigated using the DIII-D internal coils (I-Coils). Slowly rotating n=1 traveling waves at 5 Hz and various amplitudes were applied to systematically perturb the edge surfaces by programming the I-Coil currents. The vertical separatrix location difference between EFIT magnetic reconstructions that assumes toroidal symmetry and Thomson scattering Te measurements responds in phase to the applied perturbed field. The oscillation amplitudes increase with the strength of the applied field but are much smaller than those expected from the applied field alone. The results indicate that plasma response is important. Various plasma response models based on results from the MHD codes MARS and GATO are being developed and compared to the experimental observations. To more accurately evaluate the effects of magnetic measurement errors, a new form of the magnetic uncertainty matrix is also being implemented into EFIT. Details will be presented.

  18. Quantification of static magnetic field effects on radiotherapy ionization chambers

    NASA Astrophysics Data System (ADS)

    Agnew, J.; O’Grady, F.; Young, R.; Duane, S.; Budgell, G. J.

    2017-03-01

    Integrated magnetic resonance (MR) imaging and radiotherapy (RT) delivery machines are currently being developed, with some already in clinical use. It is anticipated that the strong magnetic field used in some MR-RT designs will have a significant impact on routine measurements of dose in the MR-linac performed using ionization chambers, which provide traceability back to a primary standard definition of dose. In particular, the presence of small air gaps around ionization chambers may introduce unacceptably high uncertainty into these measurements. In this study, we investigate and quantify the variation attributable to air gaps for several routinely-used cylindrical ionization chambers in a magnetic field, as well as the effect of the magnetic field alone on the response of the chambers. The measurements were performed in a Co-60 beam, while the ionization chambers were positioned in custom-made Perspex phantoms between the poles of an electromagnet, which was capable of generating magnetic fields of up to 2 T field strength, although measurements were focused around 1.5 T. When an asymmetric air gap was rotated at cardinal angles around the ionization chambers investigated here, variation of up to 8.5  ±  0.2 percentage points (PTW 31006 chamber) was observed in an applied magnetic field of 1.5 T. The minimum peak-to-peak variation was 1.1  ±  0.1% (Exradin A1SL). When the same experiment was performed with a well-defined air gap of known position using the PTW 30013 chamber, a variation of 3.8  ±  0.2% was observed. When water was added to the phantom cavity to eliminate all air gaps, the variation for the PTW 30013 was reduced to 0.2  ±  0.01%.

  19. Quantification of static magnetic field effects on radiotherapy ionization chambers.

    PubMed

    Agnew, J; O'Grady, F; Young, R; Duane, S; Budgell, G J

    2017-03-07

    Integrated magnetic resonance (MR) imaging and radiotherapy (RT) delivery machines are currently being developed, with some already in clinical use. It is anticipated that the strong magnetic field used in some MR-RT designs will have a significant impact on routine measurements of dose in the MR-linac performed using ionization chambers, which provide traceability back to a primary standard definition of dose. In particular, the presence of small air gaps around ionization chambers may introduce unacceptably high uncertainty into these measurements. In this study, we investigate and quantify the variation attributable to air gaps for several routinely-used cylindrical ionization chambers in a magnetic field, as well as the effect of the magnetic field alone on the response of the chambers. The measurements were performed in a Co-60 beam, while the ionization chambers were positioned in custom-made Perspex phantoms between the poles of an electromagnet, which was capable of generating magnetic fields of up to 2 T field strength, although measurements were focused around 1.5 T. When an asymmetric air gap was rotated at cardinal angles around the ionization chambers investigated here, variation of up to 8.5  ±  0.2 percentage points (PTW 31006 chamber) was observed in an applied magnetic field of 1.5 T. The minimum peak-to-peak variation was 1.1  ±  0.1% (Exradin A1SL). When the same experiment was performed with a well-defined air gap of known position using the PTW 30013 chamber, a variation of 3.8  ±  0.2% was observed. When water was added to the phantom cavity to eliminate all air gaps, the variation for the PTW 30013 was reduced to 0.2  ±  0.01%.

  20. DC magnetic field sensing based on the nonlinear magnetoelectric effect in magnetic heterostructures

    NASA Astrophysics Data System (ADS)

    Burdin, Dmitrii; Chashin, Dmitrii; Ekonomov, Nikolai; Fetisov, Leonid; Fetisov, Yuri; Shamonin, Mikhail

    2016-09-01

    Recently, highly sensitive magnetic field sensors using the magnetoelectric effect in composite ferromagnetic-piezoelectric layered structures have been demonstrated. However, most of the proposed concepts are not useful for measuring dc magnetic fields, because the conductivity of piezoelectric layers results in a strong decline of the sensor’s sensitivity at low frequencies. In this paper, a novel functional principle of magnetoelectric sensors for dc magnetic field measurements is described. The sensor employs the nonlinear effect of voltage harmonic generation in a composite magnetoelectric structure under the simultaneous influence of a strong imposed ac magnetic field and a weak dc magnetic field to be measured. This physical effect arises due to the nonlinear dependence of the magnetostriction in the ferromagnetic layer on the magnetic field. A sensor prototype comprising of a piezoelectric fibre transducer sandwiched between two layers of the amorphous ferromagnetic Metglas® alloy was fabricated. The specifications regarding the magnetic field range, frequency characteristics, and noise level were studied experimentally. The prototype showed the responsivity of 2.5 V mT-1 and permitted the measurement of dc magnetic fields in the range of ~10 nT to about 0.4 mT. Although sensor operation is based on the nonlinear effect, the sensor response can be made linear with respect to the measured magnetic field in a broad dynamic range extending over 5 orders of magnitude. The underlying physics is explained through a simplified theory for the proposed sensor. The functionality, differences and advantages of the magnetoelectric sensor compare well with fluxgate magnetometers. The ways to enhance the sensor performance are considered.

  1. Biological effects of magnetic fields from superconducting magnetic energy storage systems

    SciTech Connect

    Tenforde, T.S.

    1989-12-01

    Physical interaction mechanisms and potential biological effects of static and slowly time-varying magnetic fields are summarized. The results of laboratory and human health studies on this topic are related to the fringe magnetic field levels anticipated to occur in the proximity of superconducting magnetic energy storage (SMES) systems. The observed biological effects of magnetic fields include: (1) magnetic induction of electrical potentials in the circulatory system and other tissues, (2) magneto-orientation of macromolecules and membranes in strong magnetic fields, and (3) Zeeman interactions with electronic spin states in certain classes of charge transfer reactions. In general, only the first of these interactions is relevant to the establishment of occupational exposure guidelines. Physical hazards posed by the interactions of magnetic fields with cardiac pacemakers and other implanted medical devices, e.g., aneurysm clips and prostheses, are important factors that must also be considered in establishing exposure guidelines. Proposed guidelines for limiting magnetic field exposure are discussed. 50 refs., 1 fig.

  2. Magnetic field effects on tactoids of plate-like colloids.

    PubMed

    Verhoeff, A A; Otten, R H J; van der Schoot, Paul; Lekkerkerker, H N W

    2011-01-28

    We investigate the effect of a magnetic field on the shape and director field of nematic droplets in dispersions of sterically stabilized and charge-stabilized colloidal gibbsite platelets with a negative diamagnetic anisotropy. Depending on the magnetic field strength and tactoid size, we observe with polarized light microscopy several interesting structures, with different shapes and director fields both with and without defects. In particular, our findings provide the first experimental evidence for the existence of the split-core defect structure predicted ten years ago by Mkaddem and Gartland [Phys. Rev. E 62, 6694 (2000)]. The split-core structure is a metastable director-field configuration that can be stabilized by a sufficiently strong externally applied magnetic field but only if the diamagnetic anisotropy of the particles is negative. To account for our observations, we present a calculation of the stability regions of different shapes and director-field structures as a function of tactoid size, anchoring conditions, surface tension, elastic constants, and magnetic field strength. By fitting the experimental data to the theoretically predicted structures, we are able to extract values for the splay elastic constant, interfacial tension, and anchoring strength. Remarkably, we find significant differences between the two systems studied: for sterically stabilized gibbsite in bromotoluene the anchoring strength is one order of magnitude larger than that of aqueous gibbsite, with the latter exhibiting weak and the former strong anchoring of the director field to the interface. The splay elastic constants that we obtain are in agreement with earlier experiments, simulations, and theory, while the interfacial tension and anchoring strength are considerably larger than what was found in earlier experiments.

  3. Generalized Magnetic Field Effects in Burgers' Nanofluid Model

    PubMed Central

    Rashidi, M. M.; Yang, Z.; Awais, Muhammad; Nawaz, Maria; Hayat, Tasawar

    2017-01-01

    Analysis has been conducted to present the generalized magnetic field effects on the flow of a Burgers' nanofluid over an inclined wall. Mathematical modelling for hydro-magnetics reveals that the term “σB02u/ρ” is for the Newtonian model whereas the generalized magnetic field term (as mentioned in Eq 4) is for the Burgers’ model which is incorporated in the current analysis to get the real insight of the problem for hydro-magnetics. Brownian motion and thermophoresis phenomenon are presented to analyze the nanofluidics for the non-Newtonian fluid. Mathematical analysis is completed in the presence of non-uniform heat generation/absorption. The constructed set of partial differential system is converted into coupled nonlinear ordinary differential system by employing the suitable transformations. Homotopy approach is employed to construct the analytical solutions which are shown graphically for sundr5y parameters including Deborah numbers, magnetic field, thermophoresis, Brownian motion and non-uniform heat generation/absorption. A comparative study is also presented showing the comparison of present results with an already published data. PMID:28045965

  4. Pulsed field UCu5 Hall effect and magnetization (I)

    SciTech Connect

    Mcdonald, Ross D; Ayala - Valenzuela, Oscar E; Ben, Ueland G; Corneliu, Miclea; Movshovich, R; Tompson, J. D.; Bauer, E; Batista, C. D.; Martin, I

    2011-01-14

    Prior studies of UCu{sub 5} identified the material as undergoing antiferromagnetic ordering at a temperature of 15 K with a subsequent reduction of the electronic density of states, evident as sharp upturn in resistance, at 1.4 K. High field magnetization measurements indicate a complex temperature-field phase diagram comprising of numerous phases below 15 K up and up to 60 T, with NMR and neutron measurements identifying both simple anitferromagnetic and 4Q-magnetic structures at low fields. The purpose of our investigations is to identify the possibly strong coupling between the itinerant electrons and the local spin structures, such as quantum amplification of the Hall effect due to (field induced) non-colinear spin textures. Comparison with prior literature indicates the sensitivity of the phase stability of the different spin textures to composition and sample preparation. However, the 'simplified' phase diagram of this composition offers the possibility of exploring, anomalous Hall properties arising from a field induced non-colinear spin texture over a wide range of temperatures and magnetic fields.

  5. Magnetic field effects on the motion of circumplanetary dust

    NASA Astrophysics Data System (ADS)

    Jontof-Hutter, Daniel Simon

    Hypervelocity impacts on satellites or ring particles replenish circumplanetary dusty rings with grains of all sizes. Due to interactions with the plasma environment and sunlight, these grains become electrically charged. We study the motion of charged dust grains launched at the Kepler orbital speed, under the combined effects of gravity and the electromagnetic force. We conduct numerical simulations of dust grain trajectories, covering a broad range of launch distances from the planetary surface to beyond synchronous orbit, and the full range of charge-to-mass ratios from ions to rocks, with both positive and negative electric potentials. Initially, we assume that dust grains have a constant electric potential, and, treating the spinning planetary magnetic field as an aligned and centered dipole, we map regions of radial instability (positive grains only), where dust grains are driven to escape or collide with the planet at high speed, and vertical instability (both positive and negative charges) whereby grains launched near the equatorial plane and are forced up magnetic field lines to high latitudes, where they may collide with the planet. We derive analytical criteria for local stability in the equatorial plane, and solve for the boundaries between all unstable and stable outcomes. Comparing our analytical solutions to our numerical simulations, we develop an extensive model for the radial, vertical and azimuthal motions of dust grains of arbitrary size and launch location. We test these solutions at Jupiter and Saturn, both of whose magnetic fields are reasonably well represented by aligned dipoles, as well as at the Earth, whose magnetic field is close to an anti-aligned dipole. We then evaluate the robustness of our stability boundaries to more general conditions. Firstly, we examine the effects of non-zero launch speeds, of up to 0.5 km s-1, in the frame of the parent body. Although these only weakly affect stability boundaries, we find that the influence

  6. Magnetic field effects on plant growth, development, and evolution

    PubMed Central

    Maffei, Massimo E.

    2014-01-01

    The geomagnetic field (GMF) is a natural component of our environment. Plants, which are known to sense different wavelengths of light, respond to gravity, react to touch and electrical signaling, cannot escape the effect of GMF. While phototropism, gravitropism, and tigmotropism have been thoroughly studied, the impact of GMF on plant growth and development is not well-understood. This review describes the effects of altering magnetic field (MF) conditions on plants by considering plant responses to MF values either lower or higher than those of the GMF. The possible role of GMF on plant evolution and the nature of the magnetoreceptor is also discussed. PMID:25237317

  7. The Effect of Varying Magnetic Field Gradient on Combustion Dynamic

    NASA Astrophysics Data System (ADS)

    Suzdalenko, Vera; Zake, Maija; Barmina, Inesa; Gedrovics, Martins

    2011-01-01

    The focus of the recent experimental research is to provide control of the combustion dynamics and complex measurements (flame temperature, heat production rate, and composition of polluting emissions) for pelletized wood biomass using a non-uniform magnetic field that produces magnetic force interacting with magnetic moment of paramagnetic oxygen. The experimental results have shown that a gradient magnetic field provides enhanced mixing of the flame compounds by increasing combustion efficiency and enhancing the burnout of volatiles.

  8. Effective field model of roughness in magnetic nano-structures

    SciTech Connect

    Lepadatu, Serban

    2015-12-28

    An effective field model is introduced here within the micromagnetics formulation, to study roughness in magnetic structures, by considering sub-exchange length roughness levels as a perturbation on a smooth structure. This allows the roughness contribution to be separated, which is found to give rise to an effective configurational anisotropy for both edge and surface roughness, and accurately model its effects with fine control over the roughness depth without the explicit need to refine the computational cell size to accommodate the roughness profile. The model is validated by comparisons with directly roughened structures for a series of magnetization switching and domain wall velocity simulations and found to be in excellent agreement for roughness levels up to the exchange length. The model is further applied to vortex domain wall velocity simulations with surface roughness, which is shown to significantly modify domain wall movement and result in dynamic pinning and stochastic creep effects.

  9. Metabolic effects of static magnetic fields on Streptococcus pyogenes.

    PubMed

    Morrow, A C; Dunstan, R H; King, B V; Roberts, T K

    2007-09-01

    This study aimed to develop a simple experimental system utilising bacterial cells to investigate the dose responses resulting from exposures to static magnetic flux densities ranging from 0.05 to 0.5 T on viability, bacterial metabolism and levels of DNA damage in Streptococcus pyogenes. Exposure of S. pyogenes to a field of 0.3 T at 24 degrees C under anaerobic conditions resulted in a significant (P < 0.05) decrease in growth rate, with an increased mean generation time of 199 +/- 6 min compared to the control cells at 165 +/- 6 min (P < 0.05). Conversely, exposure to magnetic fields of 0.5 T significantly accelerated the growth rate at 24 degrees C compared to control cells, with a decreased mean generation time of 147 +/- 4 min (P < 0.05). The patterns of metabolite release from cells incubated in phosphate buffered saline (PBS) at 24 degrees C and exposed to different magnetic flux densities (0.05-0.5 T) were significantly (P < 0.05) altered, compared to non-exposed controls. Concentrations of metabolites, with the exception of aspartic acid (r = 0.44), were not linearly correlated with magnetic flux density, with all other r < 0.20. Instead, "window" effects were observed, with 0.25-0.3 T eliciting the maximal release of the majority of metabolites, suggesting that magnetic fields of these strengths had significant impacts on metabolic homeostasis in S. pyogenes. The exposure of cells to 0.3 T was also found to significantly reduce the yield of 8-hydroxyguanine in extracted DNA compared to controls, suggesting some possible anti-oxidant protection to S. pyogenes at this field strength.

  10. Pair-breaking effects by parallel magnetic field in electric-field-induced surface superconductivity

    NASA Astrophysics Data System (ADS)

    Nabeta, Masahiro; Tanaka, Kenta K.; Onari, Seiichiro; Ichioka, Masanori

    2016-11-01

    We study paramagnetic pair-breaking in electric-field-induced surface superconductivity, when magnetic field is applied parallel to the surface. The calculation is performed by Bogoliubov-de Gennes theory with s-wave pairing, including the screening effect of electric fields by the induced carriers near the surface. Due to the Zeeman shift by applied fields, electronic states at higher-level sub-bands become normal-state-like. Therefore, the magnetic field dependence of Fermi-energy density of states reflects the multi-gap structure in the surface superconductivity.

  11. Magnetic field fiber sensor based on the magneto-birefringence effect of magnetic fluid

    NASA Astrophysics Data System (ADS)

    Lei, Xueqin; Chen, Jiajia; Shi, Fuquan; Chen, Daru; Ren, Zhijun; Peng, Baojin

    2016-09-01

    In this study, the magneto-birefringence effect of magnetic fluid (MF) is adopted to form an innovative fiber optic magnetic field sensor. The sensitive section is fabricated via a D-shaped microstructure inscribed in a high-birefringence fiber Sagnac loop with a femtosecond laser. The D-shaped microstructure facilitates good combination of the optical-fiber Sagnac interferometer with the magneto-birefringence effect of MF without suffering from absorption loss and manual alignment. Experimental results show the good performance of the magnetic field fiver sensor, particularly its high stable extinction ratio. Preliminary results are provided, and the magnetic field sensitivity of 0.0823 nm/mT can be further improved by increasing the depth and length of the D-shaped microstructure.

  12. Magnetic field evolution in white dwarfs: The hall effect and complexity of the field

    NASA Technical Reports Server (NTRS)

    Muslimov, A. G.; Van Horn, H. M.; Wood, M. A.

    1995-01-01

    We calculate the evolution of the magnetic fields in white dwarfs, taking into account the Hall effect. Because this effect depends nonlinearly upon the magnetic field strength B, the time dependences of the various multipole field components are coupled. The evolution of the field is thus significantly more complicated than has been indicated by previous investigations. Our calculations employ recent white dwarf evolutionary sequences computed for stars with masses 0.4, 0.6, 0.8, and 1.0 solar mass. We show that in the presence of a strong (up to approximately 10(exp 9) G) internal toroidal magnetic field; the evolution of even the lowest order poloidal modes can be substantially changed by the Hall effect. As an example, we compute the evolution of an initially weak quadrupole component, which we take arbitrarily to be approximately 0.1%-1% of the strength of a dominant dipole field. We find that coupling provided by the Hall effect can produce growth of the ratio of the quadrupole to the dipole component of the surface value of the magnetic field strength by more than a factor of 10 over the 10(exp 9) to 10(exp 10) year cooling lifetime of the white dwarf. Some consequences of these results for the process of magnetic-field evolution in white dwarfs are briefly discussed.

  13. The large-scale magnetic field in the solar wind. [interplanetary magnetic fields/solar activity effects

    NASA Technical Reports Server (NTRS)

    Burlaga, L. F.; Ness, N. F.

    1975-01-01

    A large-scale, three dimensional magnetic field in the interplanetary medium with an expected classical spiral pattern to zeroth order is discussed. Systematic and random deviations which are expected are treated. The sector structure which should be evident at high latitudes is examined. Interplanetary streams are discussed as determining the patterns of magnetic field intensity. It was proposed that the large-scale spiral field can induce a meridional flow which might alter the field geometry somewhat. The nonuniformities caused by streams will probably significantly influence the motion of solar and galactic particles. It was concluded that knowledge of the 3-dimensional field and its dynamical effects can be obtained by in situ measurements by a probe which goes over the sun's poles. Diagrams of the magnetic fields are given.

  14. Effects of guide field in driven magnetic reconnection

    NASA Astrophysics Data System (ADS)

    Cheng, C. Z.; Inoue, S.; Horiuchi, R.; Ono, Y.; Guo, X.

    2016-10-01

    Decoupling of electron and ion dynamics is the key physical process in the magnetic reconnection layer. It leads to the generation of parallel E-field and in-plane electrostatic E-field, and determines how particles gain energy. For antiparallel magnetic reconnection (zero guide field case), the electron and ion dynamics decoupling is due to meandering particle (unmagnetized) orbits in the field reversal region and particle acceleration by parallel electric field in the separatrix region. The parallel E-field is produced mainly from the driven inductive E-field due to the quadrupole out-of-plane magnetic field generation. The decoupling of electron and ion dynamics causes charge separation which produces the in-plane electrostatic E-field. If the guide field is stronger than the reconnecting magnetic field, both electrons and ions are magnetized in the entire magnetic reconnection domain, and the electron-ion dynamics decoupling process changes from the zero guide field case. Then, the structure of parallel and electrostatic E-fields, and thus how electrons/ions gain energy also changes. We will explain the physical mechanisms of electron-ion dynamics decoupling on the E-field generation, and how electron and ion are heated/accelerated based on the driven reconnection simulation results.

  15. Effects of non-linearities on magnetic field generation

    SciTech Connect

    Nalson, Ellie; Malik, Karim A.; Christopherson, Adam J. E-mail: achristopherson@gmail.com

    2014-09-01

    Magnetic fields are present on all scales in the Universe. While we understand the processes which amplify the fields fairly well, we do not have a ''natural'' mechanism to generate the small initial seed fields. By using fully relativistic cosmological perturbation theory and going beyond the usual confines of linear theory we show analytically how magnetic fields are generated. This is the first analytical calculation of the magnetic field at second order, using gauge-invariant cosmological perturbation theory, and including all the source terms. To this end, we have rederived the full set of governing equations independently. Our results suggest that magnetic fields of the order of 10{sup -30}- 10{sup -27} G can be generated (although this depends on the small scale cut-off of the integral), which is largely in agreement with previous results that relied upon numerical calculations. These fields are likely too small to act as the primordial seed fields for dynamo mechanisms.

  16. Internal Gravity Waves in the Magnetized Solar Atmosphere. I. Magnetic Field Effects

    NASA Astrophysics Data System (ADS)

    Vigeesh, G.; Jackiewicz, J.; Steiner, O.

    2017-02-01

    Observations of the solar atmosphere show that internal gravity waves are generated by overshooting convection, but are suppressed at locations of magnetic flux, which is thought to be the result of mode conversion into magnetoacoustic waves. Here, we present a study of the acoustic-gravity wave spectrum emerging from a realistic, self-consistent simulation of solar (magneto)convection. A magnetic field free, hydrodynamic simulation and a magnetohydrodynamic (MHD) simulation with an initial, vertical, homogeneous field of 50 G flux density were carried out and compared with each other to highlight the effect of magnetic fields on the internal gravity wave propagation in the Sun’s atmosphere. We find that the internal gravity waves are absent or partially reflected back into the lower layers in the presence of magnetic fields and argue that the suppression is due to the coupling of internal gravity waves to slow magnetoacoustic waves still within the high-β region of the upper photosphere. The conversion to Alfvén waves is highly unlikely in our model because there is no strongly inclined magnetic field present. We argue that the suppression of internal waves observed within magnetic flux concentrations may also be due to nonlinear breaking of internal waves due to vortex flows that are ubiquitously present in the upper photosphere and the chromosphere.

  17. Effect of the plasma-induced magnetic field on a magnetic nozzle

    NASA Astrophysics Data System (ADS)

    Merino, Mario; Ahedo, Eduardo

    2016-08-01

    A two-fluid, two-dimensional model of the plasma expansion in a divergent magnetic nozzle is used to investigate the effect of the plasma-induced magnetic field on the acceleration and divergence of the plasma jet self-consistently. The induced field is diamagnetic and opposes the applied one, increasing the divergence of the magnetic nozzle and weakening its strength. This has a direct impact on the propulsive performance of the device, the demagnetization and detachment of the plasma, and can lead to the appearance of zero-field points and separatrix surfaces downstream. In contrast, the azimuthal induced field, albeit non-zero, is small in all cases of practical interest.

  18. Precise quantization of anomalous Hall effect near zero magnetic field

    NASA Astrophysics Data System (ADS)

    Bestwick, Andrew; Fox, Eli; Kou, Xufeng; Pan, Lei; Wang, Kang; Goldhaber-Gordon, David

    2015-03-01

    The quantum anomalous Hall effect (QAHE) has recently been of great interest due to its recent experimental realization in thin films of Cr-doped (Bi, Sb)2Te3, a ferromagnetic 3D topological insulator. The presence of ferromagnetic exchange breaks time-reversal symmetry, opening a gap in the surface states, but gives rise to dissipationless chiral conduction at the edge of a magnetized film. Ideally, this leads to vanishing longitudinal resistance and Hall resistance quantized to h /e2 , where h is Planck's constant and e is the electron charge, but perfect quantization has so far proved elusive. Here, we study the QAHE in the limit of zero applied magnetic field, and measure Hall resistance quantized to within one part per 10,000. Deviation from quantization is due primarily to thermally activated carriers, which can be nearly eliminated through adiabatic demagnetization cooling. This result demonstrates an important step toward dissipationless electron transport in technologically relevant conditions.

  19. Effect of static magnetic field on endospore germination.

    PubMed

    Wu, Wen Jie; Liu, Si Li; Yung, Pun To

    2017-02-01

    This work investigated the effect of static magnetic field (SMF) on Bacillus atrophaeus endospore germination. Germination was triggered by L-alanine in 1.3-T SMF and characterized by ion release, Ca(2+) -dipicolinic acid release, and water influx. These events were monitored by electrical conductivity, Tb-DPA fluorescence, and optical density, respectively. Culturability of endospore germinated in SMF exposure was evaluated by CFU enumeration. Results indicated that 1.3-T SMF failed to significantly affect endospore germination and culturability, suggesting that the three aforementioned processes were not sensitive to SMF. Bioelectromagnetics. 38:121-127, 2017. © 2016 Wiley Periodicals, Inc.

  20. Magnetorheological effect in the magnetic field oriented along the vorticity

    SciTech Connect

    Kuzhir, P. Magnet, C.; Fezai, H.; Meunier, A.; Bossis, G.; Rodríguez-Arco, L.; López-López, M. T.; Zubarev, A.

    2014-11-01

    In this work, we have studied the magnetorheological (MR) fluid rheology in the magnetic field parallel to the fluid vorticity. Experimentally, the MR fluid flow was realized in the Couette coaxial cylinder geometry with the magnetic field parallel to the symmetry axis. The rheological measurements were compared to those obtained in the cone-plate geometry with the magnetic field perpendicular to the lower rheometer plate. Experiments revealed a quasi-Bingham behavior in both geometries with the stress level being just a few dozens of percent smaller in the Couette cylindrical geometry at the same internal magnetic field. The unexpectedly high MR response in the magnetic field parallel to the fluid vorticity is explained by stochastic fluctuations of positions and orientations of the particle aggregates. These fluctuations are induced by magnetic interactions between them. Once misaligned from the vorticity direction, the aggregates generate a high stress independent of the shear rate, and thus assimilated to the suspension apparent (dynamic) yield stress. Quantitatively, the fluctuations of the aggregate orientation are modeled as a rotary diffusion process with a diffusion constant proportional to the mean square interaction torque. The model gives a satisfactory agreement with the experimental field dependency of the apparent yield stress and confirms the nearly quadratic concentration dependency σ{sub Y}∝Φ{sup 2.2}, revealed in experiments. The practical interest of this study lies in the development of MR smart devices with the magnetic field nonperpendicular to the channel walls.

  1. Magnetic Field Effects on Relaxation Parameters of The Hexamethylenetetramine (HMT)

    NASA Astrophysics Data System (ADS)

    Dogan, Nurcan

    2013-03-01

    The use of low magnetic field is one of the method for improvement of the signal to noise ratio (SNR) of detection of the chemical compounds by nuclear quadrupole resonance (NQR). We investigated the FID phenomenon of nuclear quadrupole resonance (NQR) from hexamethylenetetramine (HMT), C6H12N4, under magnetic field. The influence of the low magnetic field (up to 30 mT) was investigated for the detection of the pulse NQR signal for HMT We detected the pure NQR FID signal of HMT with a short pulse interval. The intensity of the FID signal changed with applied magnetic field. The application of the low magnetic field produces the splitting and brodening of the NQR line. We observed T1, T2 and T2*. HMT has a long T2*(near 1.5ms). This one represents the suitable sample for investigation of the influence of low magnetic field for NQR detection. The application of the low magnetic field produces the splitting and brodening of the NQR line.

  2. Quantum transport in carbon nanotube field effect transistors in high magnetic fields

    NASA Astrophysics Data System (ADS)

    Stephens, Jeffrey Dale

    The dissertation is a study of data taken from carbon nanotube field effect transistors (CNTFET). The data presented was taken at two locations, University of Pennsylvania in Philadelphia, PA and at Lehigh University in Bethlehem, PA. The samples are exposed to very low temperature using dilution refrigerator techniques and placed in high magnetic fields using a superconducting magnet. One of the main focuses will be on the effect an external magnetic field can produce on the transport properties of a CNTFET. Particular attention will be paid to the Kondo effect and Coulomb blockade phenomena. Comparisons are drawn between the observed behavior of the samples studied and with published works on carbon nanotube electronics and traditional semiconductor quantum dots.

  3. The effect of Birkeland currents on magnetic field topology

    NASA Technical Reports Server (NTRS)

    Peroomian, Vahe; Lyons, Larry R.; Schulz, Michael

    1996-01-01

    A technique was developed for the inclusion of large scale magnetospheric current systems in magnetic field models. The region 1 and 2 Birkeland current systems are included in the source surface model of the terrestrial magnetosphere. The region 1 and 2 Birkeland currents are placed in the model using a series of field aligned, infinitely thin wire segments. The normal component of the magnetic field from these currents is calculated on the surface of the magnetopause and shielded using image current carrying wires placed outside of the magnetosphere. It is found that the inclusion of the Birkeland currents in the model results in a northward magnetic field in the near-midnight tail, leading to the closure of previously open flux in the tail, and a southward magnetic field in the flanks. A sunward shift in the separatrix is observed.

  4. Effect of a magnetic field generated by permanent magnets on the GPD polarization sensitivity

    NASA Astrophysics Data System (ADS)

    Soffitta, Paolo; Costa, Enrico; Morbidini, Alfredo; Muleri, Fabio; Rubini, Alda; Spiga, Daniele; Bellazzini, Ronaldo; Brez, Alessandro; de Ruvo, Luca; Minuti, Massimo; Pinchera, Michele; Spandre, Gloria

    2014-07-01

    The Gas Pixel Detector (GPD) is an imaging X-ray polarimeter with a moderate spectral resolution and a very good position resolution.1, 2 The GPD derives this information from the true 2-d charge image of the photoelectron track produced in gas and collected by an ASIC CMOS chip after its drift and its multiplication. In this paper we report on the experimental results of the study of the effect of a strong magnetic field in reducing the diffusion and increasing the sensitivity for a GPD filled with one bar of He-DME 20-80. We generated a magnetic field of about 1600 Gauss by means of commercial magnets made of an alloy of Neodymium-Iron-Boron configured as one ring and one cylinder. We compared the pixel size distributions and the modulation curves with and without magnets at two different drift fields, corresponding to different nominal diffusion properties, with both polarized and unpolarized sources. The results obtained show that a not sensitive improvement is present at this fields implying that a much larger magnetic field is necessary with this mixture, albeit a shift on the position angle of the modulation curve, derived from a polarized source, is observed.

  5. Interplanetary magnetic field effects on high latitude ionospheric convection

    NASA Technical Reports Server (NTRS)

    Heelis, R. A.

    1985-01-01

    Relations between the electric field and the electric current in the ionosphere can be established on the basis of a system of mathematical and physical equations provided by the equations of current continuity and Ohm's law. For this reason, much of the synthesis of electric field and plasma velocity data in the F-region is made with the aid of similar data sets derived from field-aligned current and horizontal current measurements. During the past decade, the development of a self-consistent picture of the distribution and behavior of these measurements has proceeded almost in parallel. The present paper is concerned with the picture as it applies to the electric field and plasma drift velocity and its dependence on the interplanetary magnetic field. Attention is given to the southward interplanetary magnetic field and the northward interplanetary magnetic field.

  6. Effect of external magnetic field on attenuation coefficient for magnetic substances.

    PubMed

    Kumar Gupta, Manoj; Dhaliwal, A S; Kahlon, K S

    2014-10-29

    The measurement of attenuation coefficient of some magnetic substances, to include diamagnetic: Cu, Zn, Ag, Te, Au, Pb, and Perspex; paramagnetic: Al, Ti, Mo, Dy, Ho, and Pt and ferromagnetic substances: Fe, Co, Ni, Gd, FeO, NiO, FeS, and Fe2O3, both in the presence and absence of an external magnetic field has been carried out using narrow beam transmission geometry by using gamma ray photons of incident energy 59.54keV from 100mCi, (241)Am point source. It was observed very keenly that the value of linear attenuation coefficient of various substances mentioned above decreased remarkably. It varied in the range of 1-2%, 2-6% and 6-9% for diamagnetic, paramagnetic and ferromagnetic substances respectively in the presence of an external magnetic field. Measured results elucidated it very clearly that linear attenuation coefficient at H=0T, 0.6T and 1.2T continued to decrease with a regular increase of magnetic field. It is also manifested that measurements of linear attenuation coefficient is not affected with the change in thickness of the given substance. Within error limits (1-3%) variations are observed with increases of thickness along with magnetic field. Further to it the obtained results of linear attenuation coefficient without magnetic field (H=0T) were compared with theoretical data tables of FFAST and WinXCOM. It was established that values obtained are well within the experimental errors. To the best of our knowledge no other study in relation to the effect of linear attenuation coefficient in the presence of magnetic field available as precedence.

  7. Performance of a Cylindrical Hall-Effect Thruster with Magnetic Field Generated by Permanent Magnets

    NASA Technical Reports Server (NTRS)

    Polzin, Kurt A.; Raitses, Yevgeny; Fisch, Nathaniel J.

    2008-01-01

    While Hall thrusters can operate at high efficiency at kW power levels, it is difficult to construct one that operates over a broad envelope down to 100W while maintaining an efficiency of 45- 55%. Scaling to low power while holding the main dimensionless parameters constant requires a decrease in the thruster channel size and an increase in the magnetic field strength. Increasing the magnetic field becomes technically challenging since the field can saturate the miniaturized inner components of the magnetic circuit and scaling down the magnetic circuit leaves very little room for magnetic pole pieces and heat shields. An alternative approach is to employ a cylindrical Hall thruster (CHT) geometry. Laboratory model CHTs have operated at power levels ranging from the order of 50 Watts up to 1 kW. These thrusters exhibit performance characteristics which are comparable to conventional, annular Hall thrusters of similar size. Compared to the annular Hall thruster, the CHT has a lower insulator surface area to discharge chamber volume ratio. Consequently, there is the potential for reduced wall losses in the channel of a CHT, and any reduction in wall losses should translate into lower channel heating rates and reduced erosion. This makes the CHT geometry promising for low-power applications. Recently, a CHT that uses permanent magnets to produce the magnetic field topology was tested. This thruster has the promise of reduced power consumption over previous CHT iterations that employed electromagnets. Data are presented for two purposes: to expose the effect different controllable parameters have on the discharge and to summarize performance measurements (thrust, Isp, efficiency) obtained using a thrust stand. These data are used to gain insight into the thruster's operation and to allow for quantitative comparisons between the permanent magnet CHT and the electromagnet CHT.

  8. Magnetic field effect in organic films and devices

    NASA Astrophysics Data System (ADS)

    Gautam, Bhoj Raj

    In this work, we focused on the magnetic field effect in organic films and devices, including organic light emitting diodes (OLEDs) and organic photovoltaic (OPV) cells. We measured magnetic field effect (MFE) such as magnetoconductance (MC) and magneto-electroluminescence (MEL) in OLEDs based on several pi- conjugated polymers and small molecules for fields |B|<100 mT. We found that both MC(B) and MEL(B) responses in bipolar devices and MC(B) response in unipolar devices are composed of two B-regions: (i) an 'ultra-small' region at |B| < 1-2 mT, and (ii) a monotonic response region at |B| >˜2mT. Magnetic field effect (MFE) measured on three isotopes of Poly (dioctyloxy) phenylenevinylene (DOO-PPV) showed that both regular and ultra-small effects are isotope dependent. This indicates that MFE response in OLED is mainly due to the hyperfine interaction (HFI). We also performed spectroscopy of the MFE including magneto-photoinduced absorption (MPA) and magneto-photoluminescence (MPL) at steady state conditions in several systems. This includes pristine Poly[2-methoxy-5-(2-ethylhexyl-oxy)-1,4-phenylene-vinylene] (MEH-PPV) films, MEH-PPV films subjected to prolonged illumination, and MEH-PPV/[6,6]-Phenyl C61 butyric acid methyl ester (PCBM) blend, as well as annealed and pristine C60 thin films. For comparison, we also measured MC and MEL in organic diodes based on the same materials. By directly comparing the MPA and MPL responses in films to MC and MEL in organic diodes based on the same active layers, we are able to relate the MFE in organic diodes to the spin densities of the excitations formed in the device, regardless of whether they are formed by photon absorption or carrier injection from the electrodes. We also studied magneto-photocurrent (MPC) and power conversion efficiency (PCE) of a 'standard' Poly (3-hexylthiophene)/PCBM device at various Galvinoxyl radical wt%. We found that the MPC reduction with Galvinoxyl wt% follows the same trend as that of the

  9. Thermoelectric effects in organic conductors in a strong magnetic field

    SciTech Connect

    Kirichenko, O. V.; Peschanskii, V. G. Hasan, R. A.

    2007-07-15

    The linear response of the electron system of a layered conductor to the temperature gradient in this system in a strong magnetic field is investigated theoretically. Thermoelectric emf is studied as a function of the magnitude and orientation of a strong external magnetic field; the experimental investigation of this function, combined with the study of the electric and thermal resistance, allows one to completely determine the structure of the energy spectrum of charge carriers.

  10. Electric current and magnetic field effects on bacterial biofilms

    NASA Astrophysics Data System (ADS)

    Sandvik, Elizabeth Louise

    The ability of bacteria to form and grow as biofilm presents a major challenge in clinical medicine. Through this work, two alternative electromagnetic treatment strategies were investigated to combat bacterial biofilms like those that cause chronic infections on indwelling medical devices. Direct electric current (DC) was applied at current densities of 0.7 to 1.8 mA/cm2 alone and in conjunction with antibiotic. Unlike most previous studies, chloride ions were included in the treatment solution at a physiologically-relevant concentration. Using this approach, low levels of DC alone were demonstrated to have a dose-responsive, biocidal effect against Staphylococcus epidermidis and Pseudomonas aeruginosa biofilms with no synergistic enhancement of antibiotic activity. Through a series of experiments using chemical measures, cell viability, and global gene expression, electrolytic generation of chlorine, a potent disinfectant, was identified as the predominant mechanism by which DC kills bacteria in biofilm. The second treatment strategy investigated weak, extremely low-frequency magnetic fields (ELF-MFs) as a noninvasive approach, involving an extension of concepts from well-studied ELF-MF effects observed in eukaryotic systems to bacterial biofilm. S. epidermidis biofilms grown in weak, extremely low-frequency magnetic fields (ELF-MFs) at Ca2+ and K+ ion resonance frequencies were assessed using global gene expression to determine if S. epidermidis in biofilm detect and respond to ELF-MFs. Frequency-dependent changes in gene expression were observed with upregulation of genes involved in transposase activity, signal transduction systems, and membrane transport processes indicating possible effects consistent with theories of ELF-MF induced changes in ion transport reported in eukaryotic cells. This is the first transcriptome study to indentify ELF-MF effects in bacteria. While no direct biocidal effect was observed with ELF-MF treatment, alteration of membrane

  11. Experimental Study of Magnetic Field Effect on dc Corona Discharge in Low Vacuum

    NASA Astrophysics Data System (ADS)

    Elabbas, K.

    2014-09-01

    In the present paper, an attempt was made to investigate the effect of applying a transverse magnetic field on the dc corona discharge behavior in low vacuum. In general, two experiments were carried out in this work: the first is the ionization-region magnetic field experiment, and the second was the drift region magnetic field experiment. In these experiments, permanent magnets were used to produce magnetic field. The degree of vacuum used in this test was 0.4×105 Pa. It is found that the effect of the magnetic field increases as the degree of vacuum increases. It is also seen from this study that the corona current values are higher with magnetic fields than without magnetic fields. The experimental results indicate that the enhancement of the magnetic field near the wire discharge electrode has a significant influence on the increment of the discharge current. The effect of the magnetic field on the discharge current is the most significant with the negative corona discharges rather than with positive corona discharge. In contrast to, the curves were demonstrated that the application of magnetic fields in drift region magnetic field does not significantly change the corona discharge current. Discharge characteristics of magnetically enhanced corona discharges, extracted from this study, can be applied to various industrial applications, such as, in an electrostatic enhancement filter for the purpose of capturing fine particles, and as effective method for production of high ozone concentrations in a generator as compared to the ultraviolet (UV) radiation method.

  12. Effects of Hall electric fields on the saturation of forced antiparallel magnetic field merging

    NASA Astrophysics Data System (ADS)

    Dorelli, John C.

    2003-08-01

    The role of Hall electric fields in flux pile-up antiparallel magnetic field merging is addressed. Analytical solutions of the resistive Hall magnetohydrodynamics (Hall-MHD) equations are obtained, describing stagnation point flows in a thin current sheet. The stagnation point flow solutions explain a number of interesting effects observed in two-dimensional resistive Hall-MHD simulations of forced magnetic reconnection. In particular, when Hall electric fields are important within the current sheet, less pile-up of magnetic energy is required upstream of the current sheet to support a given reconnection electric field. Fast electron flows transport magnetic flux into the diffusion layer without requiring a compensating drop in plasma pressure upstream of the current sheet. The maximum flux pile-up merging rate allowed by the external plasma pressure becomes independent of the Lundquist number, scaling like the square root of the ratio of the ion inertial length to the spatial scale of the stagnation point flow. Thus, Hall electric fields provide a possible solution to the problem of flux pile-up saturation in two-dimensional, resistive MHD models of forced magnetic reconnection.

  13. Magnetic noises generated by plants in microgravity: effect of external magnetic fields.

    NASA Astrophysics Data System (ADS)

    Bogatina, N.; Sheykina, N.; Kordyum, E.

    Magnetic Noises Generated by Plants in Microgravity, Effect of External Magnetic Field. N. Bogatina(1), N. Sheykina(1), E. Kordyum(2). (1) B.Verkin Institute for Low Temperature Physics&Engineering of National Academy of Sciences of Ukraine, Kharkov, Ukraine (2) N.Cholodny Institute of Botany of National Academy of Sciences of Ukraine, Kiev, Ukraine. e-mail:bogatina@ilt.kharkov.ua/Fax: 38-0572-322370. The object of the work is to determine the correlation between the magnetic noises generated by plants and accelaration value during their development in microgravity. The amplitude of magnetic noise spectral density will be mesured. Its dependence on the magnitude of gravity accelaration and magnitudes of static and alternating magnetic fields is supposed to reflect the mechanisms of gravi- and magnitopercrption. We shall try to answer the guestion whether the same mechanism or different mechanisms are responsible for gravi- and magnitopercrption. The gravitropic reaction of plants is needed to be studied simultaneously with observation of magnetic noises. The measurements in microgravity have to be fulfilled by a flux-gate magnetometer connected with Philips spectroanalyser There are two directions of experiments. The first one is experiments that will be carried out on Earth under the conditions of weakening of gravitational force. The preliminary parameters of the required magnetic fields have to be determined in these experiments. The second one is the same experiment in the space. These experiments are supposed to allow us to define the mechanisms of a gravitropic reaction of plants because any motion of ions ( indolil-acetic ions, for instance) is accompanied by an increase of magnetic noise. The experimental results obtained under onGround conditions by using the superconducting technique wwithout weakening the weight force are disscussed. .

  14. Effect of steady magnetic field on human lymphocytes

    SciTech Connect

    Mileva, M.; Ivanov, B.; Bulanova, M.; Pantev, T.

    1983-01-01

    Exposure to steady magnetic field (SMF) for different periods of time did not elicit statistically reliable increase in chromosome aberrations in human peripheral blood lymphocytes. Metaphase analysis of Crepis capilaris cells revealed that SMF (9 k0e, 200 0e/cm) for 2 days did not induce chromosome aberrations. Nor were any changes demonstrated in roots of beans, onions and L-fibroblasts of subcutaneous tissue of mice and Chinese hamsters. The obtained data are indicative of absence of cytogenetic effect of SMF. The level and spectrum of chromosome aberrations did not exceed the values for spontaneous chromatic fragments in cultures. Cytogenetic analysis of DEDE cells of the Chinese hamster revealed a mild mutagenic effect of SMF. Chromosomal aberrations were also demonstrated after exposure (5 min) of garlic roots.

  15. Precise quantization of anomalous Hall effect near zero magnetic field

    SciTech Connect

    Bestwick, A. J.; Fox, E. J.; Kou, Xufeng; Pan, Lei; Wang, Kang L.; Goldhaber-Gordon, D.

    2015-05-04

    In this study, we report a nearly ideal quantum anomalous Hall effect in a three-dimensional topological insulator thin film with ferromagnetic doping. Near zero applied magnetic field we measure exact quantization in the Hall resistance to within a part per 10,000 and a longitudinal resistivity under 1 Ω per square, with chiral edge transport explicitly confirmed by nonlocal measurements. Deviations from this behavior are found to be caused by thermally activated carriers, as indicated by an Arrhenius law temperature dependence. Using the deviations as a thermometer, we demonstrate an unexpected magnetocaloric effect and use it to reach near-perfect quantization by cooling the sample below the dilution refrigerator base temperature in a process approximating adiabatic demagnetization refrigeration.

  16. Magnetic field effects on superconductivity in alkali metal intercalates of MoS2

    NASA Technical Reports Server (NTRS)

    Woollam, J. A.; Flood, D. J.; Wagoner, D. E.; Somoano, R. B.; Rembaum, A.

    1972-01-01

    The effects of a magnetic field on the superconducting transition in MoS2 intercalated with potassium and sodium were studied. It was found that the potassium intercalated MoS2 has better properties in a magnetic field. In zero magnetic field the transition to superconductivity begins near 6.4 K. Diagrams of the basic circuitry for superconducting transition studies, and charts showing critical magnetic field versus critical temperature for the intercalated MoS2 are included.

  17. Magnetic field generator

    DOEpatents

    Krienin, Frank

    1990-01-01

    A magnetic field generating device provides a useful magnetic field within a specific retgion, while keeping nearby surrounding regions virtually field free. By placing an appropriate current density along a flux line of the source, the stray field effects of the generator may be contained. One current carrying structure may support a truncated cosine distribution, and it may be surrounded by a current structure which follows a flux line that would occur in a full coaxial double cosine distribution. Strong magnetic fields may be generated and contained using superconducting cables to approximate required current surfaces.

  18. Geomagnetic field modulates artificial static magnetic field effect on arterial baroreflex and on microcirculation

    NASA Astrophysics Data System (ADS)

    Gmitrov, Juraj

    2007-03-01

    Spreading evidence suggests that geomagnetic field (GMF) modulates artificial magnetic fields biological effect and associated with increased cardiovascular morbidity. To explore the underlying physiological mechanism we studied 350 mT static magnetic field (SMF) effect on arterial baroreflex-mediated skin microcirculatory response in conjunction with actual geomagnetic activity, reflected by K and K p indices. Fourteen experiments were performed in rabbits sedated by pentobarbital infusion (5 mg/kg/h). Mean femoral artery blood pressure, heart rate, and the ear lobe skin microcirculatory blood flow, measured by microphotoelectric plethysmogram (MPPG), were simultaneously recorded before and after 40 min of NdFeB magnets local exposure to sinocarotid baroreceptors. Arterial baroreflex sensitivity (BRS) was estimated from heart rate/blood pressure response to intravenous bolus injections of nitroprusside and phenylephrine. We found a significant positive correlation between SMF-induced increase in BRS and increment in microvascular blood flow (ΔBRS with ΔMPPG, r=0.7, p<0.009) indicated the participation of the arterial baroreflex in the regulation of the microcirculation and its enhancement after SMF exposure. Geomagnetic disturbance, as opposed to SMF, decreased both microcirculation and BRS, and counteracted SMF-induced increment in microcirculatory blood flow ( K-index with ΔMPPG; r s=-0.55, p<0.041). GMF probably affected central baroreflex pathways, diminishing SMF direct stimulatory effect on sinocarotid baroreceptors and on baroreflex-mediated vasodilatatory response. The results herein may thus point to arterial baroreflex as a possible physiological mechanism for magnetic-field cardiovascular effect. It seems that geomagnetic disturbance modifies artificial magnetic fields biological effect and should be taken into consideration in the assessment of the final effect.

  19. Biological effects due to weak magnetic fields on plants

    NASA Astrophysics Data System (ADS)

    Belyavskaya, N.

    In the evolution process, living organisms have experienced the action of the Earth's magnetic field (MF) that is a natural component of our environment. It is known that a galactic MF induction does not exceed 0.1 nT, since investigations of weak magnetic field (WMF) effects on biological systems have attracted attention of biologists due to planning long-term space flights to other planets where the magnetizing force is near 10-5 Oe. However, the role of WMF and its influence on organisms' functioning are still insufficiently investigated. A large number of experiments with seedlings of different plant species placed in WMF has found that the growth of their primary roots is inhibited during the early terms of germination in comparison with control. The proliferation activity and cell reproduction are reduced in meristem of plant roots under WMF application. The prolongation of total cell reproductive cycle is registered due to the expansion of G phase in1 different plant species as well as of G phase in flax and lentil roots along with2 relative stability of time parameters of other phases of cell cycle. In plant cells exposed to WMF, the decrease in functional activity of genome at early prereplicate period is shown. WMF causes the intensification in the processes of proteins' synthesis and break-up in plant roots. Qualitative and quantitative changes in protein spectrum in growing and differentiated cells of plant roots exposed to WMF are revealed. At ultrastructural level, there are observed such ultrastructural peculiarities as changes in distribution of condensed chromatin and nucleolus compactization in nuclei, noticeable accumulation of lipid bodies, development of a lytic compartment (vacuoles, cytosegresomes and paramural bodies), and reduction of phytoferritin in plastids in meristem cells of pea roots exposed to WMF. Mitochondria are the most sensitive organelle to WMF application: their size and relative volume in cells increase, matrix is electron

  20. Effects of chiral imbalance and magnetic field on pion superfluidity and color superconductivity

    NASA Astrophysics Data System (ADS)

    Cao, Gaoqing; Zhuang, Pengfei

    2015-11-01

    The effects of chiral imbalance and external magnetic field on pion superfluidity and color superconductivity are investigated in extended Nambu-Jona-Lasinio models. We take the Schwinger approach to treat the interaction between the charged pion condensate and magnetic field at finite isospin density and include simultaneously the chiral imbalance and magnetic field at finite baryon density. For the superfluidity, the chiral imbalance and magnetic field lead to catalysis and inverse catalysis effects, respectively. For the superconductivity, the chiral imbalance enhances the critical baryon density, and the magnetic field results in a de Haas-van Alphan oscillation on the phase transition line.

  1. Effects of Traveling Magnetic Field on Dynamics of Solidification

    NASA Technical Reports Server (NTRS)

    Mazuruk, Konstantin; Grugel, Richard; Motakef, Shariar

    2001-01-01

    TMF is based on imposing a controlled phase-shift in a train of electromagnets, forming a stack. Thus, the induced magnetic field can be considered to be travelling along the axis of the stack. The coupling of this traveling wave with an electrically conducting fluid results in a basic flow in a form of a single axisymmetric roll. The magnitude and direction of this flow can be remotely controlled. Furthermore, it is possible to localize the effect of this force field though activating only a number of the magnets. This force field generated in the fluid can, in principle, be used to control and modify convection in the molten material. For example, it can be used to enhance convective mixing in the melt, and thereby modify the interface shape, and macrosegregation. Alternatively, it can be used to counteract thermal and/or solutal buoyancy forces. High frequency TMF can be used in containerless processing techniques, such as float zoning, to affect the very edge of the fluid so that Marangoni flow can be counter balanced. The proposed program consists of basic fundamentals and applications. Our goal in conducting the following experiments and analyses is to establish the validity of TMF as a new tool for solidification processes. Due to its low power consumption and simplicity of design, this tool may find wide spread use in a variety of space experiments. The proposed ground based experiments are intended to establish the advantages and limitations of employing this technique. In the fundamentals component of the proposed program, we will use theoretical tools and experiments with mercury to establish the fundamental aspects of TMF-induced convection through a detailed comparison of theoretical predictions and experimental measurements of flow field. In this work, we will conduct a detailed parametric study involving the effects of magnetic field strength, frequency, wave vector, and the fluid geometry. The applications component of this work will be focused on

  2. Zero-magnetic field effect in pathogen bacteria

    NASA Astrophysics Data System (ADS)

    Creanga, D. E.; Poiata, A.; Morariu, V. V.; Tupu, P.

    2004-05-01

    Two lots of Gram-negative bacterial strains were tested for antibiotic drug resistance after exposure to zero-magnetic field. We found that the magneto-sensitive strains represent half of the analyzed samples (three Pseudomonas and five Enterobacter strains), some of them presenting two-three times modified resistance to antibiotic, while others revealed eight or 16 times changed resistance. Pseudomonas strain magnetic sensitivity is revealed better by ampicillin and tetracycline, while Enterobacter strain magnetic sensitivity is revealed better by ampicillin, kanamycin and ofloxacin.

  3. The effect of magnetic field on the intrinsic detection efficiency of superconducting single-photon detectors

    SciTech Connect

    Renema, J. J.; Rengelink, R. J.; Komen, I.; Wang, Q.; Kes, P.; Aarts, J.; Exter, M. P. van; Dood, M. J. A. de; Gaudio, R.; Hoog, K. P. M. op 't; Zhou, Z.; Fiore, A.; Sahin, D.; Driessen, E. F. C.

    2015-03-02

    We experimentally investigate the effect of a magnetic field on photon detection in superconducting single-photon detectors (SSPDs). At low fields, the effect of a magnetic field is through the direct modification of the quasiparticle density of states of the superconductor, and magnetic field and bias current are interchangeable, as is expected for homogeneous dirty-limit superconductors. At the field where a first vortex enters the detector, the effect of the magnetic field is reduced, up until the point where the critical current of the detector starts to be determined by flux flow. From this field on, increasing the magnetic field does not alter the detection of photons anymore, whereas it does still change the rate of dark counts. This result points at an intrinsic difference in dark and photon counts, and also shows that no enhancement of the intrinsic detection efficiency of a straight SSPD wire is achievable in a magnetic field.

  4. Effects of Magnetic Fields on Winds and Disks

    NASA Astrophysics Data System (ADS)

    Brown, J. C.; Cassinelli, J. P.

    2005-11-01

    The problems facing magnetically guided wind models for the generation of stellar disks are outlined, particularly in relation to Be stars. Various parametric, analytic and numerical treatments have been published; some with and some without rotation, but all considering dipole like magnetic fields that can steer the star's wind to create a compressed equatorial region, variously termed; Magnetically Torqued Disk ( MTD), Magnetically Rigidized Disk, or Magnetically Confined Wind Shocked Disk. The essential issues are A) What field and rotation are required to create a MTD that is dense enough to generate emission line Equivalent Widths, the observed level of intrinsic polarization, and IR excesses? B) Can semi-corotational velocity fields be reconciled with observed line profiles and with the long term V/R variations normally attributed to spiral density waves in a Keplerian disk? C) What limits the lifetime of such a disk? D) Can the Keplerian disks model be reconciled with the fact that recently observed B fields in some early B type stars are large enough for MTD production. E) Can any other model predict as well as MTD does, the range of Spectral types in which disks are observed. F) What are the critical observations that might test the MTD model?

  5. Effect of magnetic fields on melt-spun Nd2Fe14B-based ribbons

    NASA Astrophysics Data System (ADS)

    Van Nguyen, Vuong; Rong, Chuanbing; Ding, Yong; Liu, J. Ping

    2012-04-01

    The effect of a magnetic field on microstructure and magnetic properties of Nd2Fe14B-based melt-spun ribbons is investigated. The magnetic field was applied in perpendicular or parallel direction to the ribbon plane during quench with a field strength up to several kilo Oersteds. The XRD patterns and TEM graphs show a strong grain size reduction upon the magnetic field application. The magnetic field also enhances the (00l) texture of ribbons when the field is perpendicular to the ribbon plane. The refined microstructure with significantly reduced grain size leads to enhanced magnetic exchange interactions between the hard and soft phases in the Nd2Fe14B/Fe nanocomposite ribbons. This magnetic field-assisted melt-spinning technique is promising for producing nanocomposite magnets with enhanced energy density.

  6. Effect on FOG caused by non-uniform distribute magnetic field

    NASA Astrophysics Data System (ADS)

    Yin, Jianling; Lu, Jun; Mao, Shaojuan; Chen, Yudan

    2016-10-01

    Using matrix optics and optical propagation theory, a model for bias errors of an optical fiber gyroscope (FOG) caused by the nonuniform distribute magnetic field has been deduced. Based on the above model, the effect on the FOG caused by the nonuniform distribute magnetic field and common circuit board is also analyzed. Results indicate that, ⅰ) the nearer of distance between the center of magnetic field and the fiber loop, the bigger of the bias errors of FOG will be; ⅱ) relationship between bias and magnetic field direction is a inclined sine, which becomes more gradient when the distance between the center of magnetic field and the fiber loop is nearer; ⅲ) the bias error caused by the nonuniform magnetic field is bigger than that caused by uniform magnetic field of equal intensity, when R < 5r ( center of nonuniform magnetic field in fiber loop) or R < 0.5r ( center of nonuniform magnetic field out of fiber loop); ⅳ) the direction of magnetic axis is changed by the exit of nonuniform magnetic field; ⅴ) the common circuit board which radiate intensity is very weak can also cause unstable and direction related of the FOG's output. Above conclusions may be useful for understanding the effect of actual magnetic field.

  7. Effects of Traveling Magnetic Field on Dynamics of Solidification

    NASA Technical Reports Server (NTRS)

    2003-01-01

    The Lorentz body force induced in electrically conducting fluids can be utilized for a number of materials processing technologies. An application of strong static magnetic fields can be beneficial for damping convection present during solidification. On the other hand, alternating magnetic fields can be used to reduce as well as to enhance convection. However, only special types of time dependent magnetic fields can induce a non-zero time averaged Lorentz force needed for convection control. One example is the rotating magnetic field. This field configuration induces a swirling flow in circular containers. Another example of a magnetic field configuration is the traveling magnetic field (TMF). It utilizes axisymmetric magnetostatic waves. This type of field induces an axial recirculating flow that can be advantageous for controlling axial mass transport, such as during solidification in long cylindrical tubes. Incidentally, this is the common geometry for crystal growth research. The Lorentz force induced by TMF can potentially counter-balance the buoyancy force, diminishing natural convection, or even setting up the flow in reverse direction. Crystal growth process in presence of TMF can be then significantly modified. Such properties as the growth rate, interface shape and macro segregation can be affected and optimized. Melt homogenization is the other potential application of TMF. It is a necessary step prior to solidification. TMF can be attractive for this purpose, as it induces a basic flow along the axis of the ampoule. TMF can be a practical alloy mixing method especially suited for solidification research in space. In the theoretical part of this work, calculations of the induced Lorentz force in the whole frequency range have been completed. The basic flow characteristics for the finite cylinder geometry are completed and first results on stability analysis for higher Reynolds numbers are obtained. A theoretical model for TMF mixing is also developed

  8. Strong parallel magnetic field effects on the hydrogen molecular ion

    NASA Astrophysics Data System (ADS)

    Guan, Xiaoxu; Li, Baiwen; Taylor, K. T.

    2003-09-01

    Equilibrium distances, binding energies and dissociation energies for the ground and low-lying states of the hydrogen molecular ion in a strong magnetic field parallel to the internuclear axis are calculated and refined, by using the two-dimensional pseudospectral method. High-precision results are presented for the binding energies over a wider field regime than already given in the literature (Kravchenko and Liberman 1997 Phys. Rev. A 55 2701). The present work removes a long-standing discrepancy for the Req value in the 1sigmau state at a field strength of 1.0 × 106 T. The dissociation energies of the antibonding 1pig state induced by magnetic fields are determined accurately. We have also observed that the antibonding 1pig potential energy curve develops a minimum if the field is sufficiently strong. Some unreliable results in the literature are pointed out and discussed. A way to efficiently treat vibrational processes and coupling between the nuclear and the electronic motions in magnetic fields is also suggested within a three-dimensional pseudospectral scheme.

  9. Nuclear magnetic resonance dephasing effects in a spherical pore with a magnetic dipolar field

    NASA Astrophysics Data System (ADS)

    Valckenborg, R. M. E.; Huinink, H. P.; Kopinga, K.

    2003-02-01

    The NMR dephasing behavior of the nuclear spins of a fluid confined in a porous material can be investigated by Hahn spin echoes. Previous experimental results on water in a magnetically doped clay have shown a nonmonoexponentially decaying magnetization, which can be understood neither by the known dephasing rate of freely diffusing spins in a uniform gradient nor by spins diffusing in a restricted geometry. For a better understanding of NMR measurements on these systems, a systematic survey was performed of the various length scales that are involved. The standard length scales for the situation of a uniform gradient are diffusing length, structure length, and dephasing length. We show that for a nonuniform gradient, a new length scale has to be introduced: the magnetic-field curvature length. When a particle diffuses less than this length scale, it experiences a local uniform gradient. In that case the spin-echo decay can be described by the so-called local gradient approximation (LGA). When a particle diffuses over a longer distance than the structure length, the spin-echo decay can be described by the motional averaging regime. For both regimes, scaling laws are derived. In this paper, a random-walk model is used to simulate the dephasing effect of diffusing spins in a spherical pore in the presence of a magnetic dipole field. By varying the dipole magnitude, situations can be created in which the dephasing behavior scales according to the motional averaging regime or according to the LGA regime, for certain ranges of echo times. Two model systems are investigated: a spherical pore in the vicinity of a magnetic point dipole and a spherical pore adjacent to a magnetic dipolar grain of the same size as the pore. The simulated magnetization decay curves of both model systems confirm the scaling laws. The LGA, characterized by a nonmonoexponential magnetization decay, is also investigated by calculating the spatially resolved magnetization in the pore. For this

  10. Effect of axial magnetic field on a 2.45 GHz permanent magnet ECR ion source

    SciTech Connect

    Nakamura, T. Wada, H.; Furuse, M.; Asaji, T.

    2016-02-15

    Herein, we conduct a fundamental study to improve the generation efficiency of a multi-charged ion source using argon. A magnetic field of our electron cyclotron resonance ion source is composed of a permanent magnet and a solenoid coil. Thereby, the axial magnetic field in the chamber can be tuned. Using the solenoid coil, we varied the magnetic field strength in the plasma chamber and measured the ion beam current extracted at the electrode. We observed an approximately three times increase in the Ar{sup 4+} ion beam current when the magnetic field on the extractor-electrode side of the chamber was weakened. From our results, we can confirm that the multi-charged ion beam current changes depending on magnetic field intensity in the plasma chamber.

  11. Effect of solenoidal magnetic field on drifting laser plasma

    NASA Astrophysics Data System (ADS)

    Takahashi, Kazumasa; Okamura, Masahiro; Sekine, Megumi; Cushing, Eric; Jandovitz, Peter

    2013-04-01

    An ion source for accelerators requires to provide a stable waveform with a certain pulse length appropriate to the application. The pulse length of laser ion source is easy to control because it is expected to be proportional to plasma drifting distance. However, current density decay is proportional to the cube of the drifting distance, so large current loss will occur under unconfined drift. We investigated the stability and current decay of a Nd:YAG laser generated copper plasma confined by a solenoidal field using a Faraday cup to measure the current waveform. It was found that the plasma was unstable at certain magnetic field strengths, so a baffle was introduced to limit the plasma diameter at injection and improve the stability. Magnetic field, solenoid length, and plasma diameter were varied in order to find the conditions that minimize current decay and maximize stability.

  12. An effective magnetic field from optically driven phonons

    NASA Astrophysics Data System (ADS)

    Nova, T. F.; Cartella, A.; Cantaluppi, A.; Först, M.; Bossini, D.; Mikhaylovskiy, R. V.; Kimel, A. V.; Merlin, R.; Cavalleri, A.

    2016-10-01

    Light fields at terahertz and mid-infrared frequencies allow for the direct excitation of collective modes in condensed matter, which can be driven to large amplitudes. For example, excitation of the crystal lattice has been shown to stimulate insulator-metal transitions, melt magnetic order or enhance superconductivity. Here, we generalize these ideas and explore the simultaneous excitation of more than one lattice mode, which are driven with controlled relative phases. This nonlinear mode mixing drives rotations as well as displacements of the crystal-field atoms, mimicking the application of a magnetic field and resulting in the excitation of spin precession in the rare-earth orthoferrite ErFeO3. Coherent control of lattice rotations may become applicable to other interesting problems in materials research--for example, as a way to affect the topology of electronic phases.

  13. Predicting observational consequences of magnetic field effects in the Eagle Nebula

    NASA Astrophysics Data System (ADS)

    Ryutov1, D. D.; Kane1, J. O.; Mizuta2, A.; Pound3, M. W.; Remington1, B. A.

    2003-10-01

    Magnetic fields are thought to play a substantial role in photoevaporated molecular clouds, an example of which is the famous Eagle Nebula. On the other hand, any direct measurements of the magnetic fields in the Eagle Nebula are still absent. To help in developing the observational strategies, we consider two models of the magnetic field and discuss their general compatibility with the observed structures. We also consider other factors that can be used to derive the structure and the strength of the magnetic field. The two models are those of an initially quasi-homogeneous magnetic field permeating the cloud prior to the onset of hydrodynamic motion, and of a pre-existing "magnetostatic turbulence" [1]. We evaluate possible magnetic field strength in the ablated flow, magnetic field effects on the velocity distribution inside the cloud, and on the star formation. [1] D.D. Ryutov, B.A. Remington. PPCF, 44, B407, 2002.

  14. EFFECTS OF THE NON-RADIAL MAGNETIC FIELD ON MEASURING MAGNETIC HELICITY TRANSPORT ACROSS THE SOLAR PHOTOSPHERE

    SciTech Connect

    Song, Y. L.; Zhang, M.

    2015-05-10

    It is generally believed that the evolution of magnetic helicity has a close relationship with solar activity. Before the launch of the Solar Dynamics Observatory (SDO), earlier studies had mostly used Michelson Doppler Imager/SOHO line of sight (LOS) magnetograms and assumed that magnetic fields are radial when calculating the magnetic helicity injection rate from photospheric magnetograms. However, this assumption is not necessarily true. Here we use the vector magnetograms and LOS magnetograms, both taken by the Helioseismic and Magnetic Imager on SDO, to estimate the effects of the non-radial magnetic field on measuring the magnetic helicity injection rate. We find that: (1) the effect of the non-radial magnetic field on estimating tangential velocity is relatively small; (2) when estimating the magnetic helicity injection rate, the effect of the non-radial magnetic field is strong when active regions are observed near the limb and is relatively weak when active regions are close to disk center; and (3) the effect of the non-radial magnetic field becomes minor if the amount of accumulated magnetic helicity is the only concern.

  15. Effect of the magnetic material on AC losses in HTS conductors in AC magnetic field carrying AC transport current

    NASA Astrophysics Data System (ADS)

    Wan, Xing-Xing; Huang, Chen-Guang; Yong, Hua-Dong; Zhou, You-He

    2015-11-01

    This paper presents an investigation on the AC losses in several typical superconducting composite conductors using the H-formulation model. A single superconducting strip with ferromagnetic substrate or cores and a stack of coated conductors with ferromagnetic substrates are studied. We consider all the coated conductors carrying AC transport currents and simultaneously exposed to perpendicular AC magnetic fields. The influences of the amplitude, frequency, phase difference and ferromagnetic materials on the AC losses are investigated. The results show that the magnetization losses of single strip and stacked strips have similar characteristics. The ferromagnetic substrate can increase the magnetization loss at low magnetic field, and decrease the loss at high magnetic field. The ferromagnetic substrate can obviously increase the transport loss in stacked strips. The trends of total AC losses of single strip and stacked strips are similar when they are carrying current or exposed to a perpendicular magnetic field. The effect of the frequency on the total AC losses of single strip is related to the amplitude of magnetic field. The AC losses decrease with increasing frequency in low magnetic field region while increase in high magnetic field region. As the phase difference changes, there is a periodic variation for the AC losses. Moreover, when the strip is under only the transport current and magnetic field, the ferromagnetic cores will increase the AC losses for large transport current or field.

  16. Magnetodeformation effects and the swelling of ferrogels in a uniform magnetic field.

    PubMed

    Filipcsei, Genoveva; Zrínyi, Miklos

    2010-07-14

    Magnetic field sensitive gels (ferrogels or magnetoelastic gels) are three-dimensional cross-linked networks of flexible polymers swollen by ferrofluids or magnetic fluids. We have studied the response of magnetic field sensitive polymer gels to an external magnetic field. Two phenomena were investigated in detail: deformation and swelling under a uniform magnetic field. Gel spheres containing magnetic particles distributed randomly in the gel matrix as well as pearl chain aggregates chemically fixed in the network were exposed to a static homogeneous magnetic field. It was found that the spatial distribution of the magnetic particles plays an essential role in the magnetodeformation effect. A weak effect was observed for gels containing randomly distributed magnetic particles. In response to the magnetic field induction, these gel spheres elongated along the field lines and were compressed in the perpendicular direction. No magnetodeformation was observed for gels containing aligned particles in the polymer matrix. The influence of an external magnetic field on the equilibrium swelling degree was also the subject of this study. Using thermodynamic arguments it was shown that a uniform external field may result in deswelling of the ferrogels at high field intensities.

  17. Behavioral effects on rats of high strength magnetic fields generated by a resistive electromagnet.

    PubMed

    Houpt, Thomas A; Pittman, David W; Riccardi, Christina; Cassell, Jennifer A; Lockwood, Denesa R; Barranco, Jan M; Kwon, Bumsup; Smith, James C

    2005-10-15

    It has been reported previously that exposure to static high magnetic fields of 7 T or above in superconducting magnets has behavioral effects on rats. In particular, magnetic field exposure acutely but transiently suppressed rearing and induced walking in tight circles; the direction of circular locomotion was dependent on the rats' orientation within the magnet. Furthermore, when magnet exposure was paired with consumption of a palatable, novel solution, rats acquired a persistent taste aversion. In order to confirm these results under more controlled conditions, we exposed rats to static magnetic fields of 4 to 19.4 T in a 189 mm bore, 20 T resistive magnet. By using a resistive magnet, field strengths could be arbitrary varied from -19.4 to 19.4 T within the same bore. Rearing was suppressed after exposure to 4 T and above; circling was observed after 7 T and above. Conditioned taste aversion was acquired after 14 T and above. The effects of the magnetic fields were dependent on orientation. Exposure to +14 T induced counter-clockwise circling, while exposure to -14 T induced clockwise circling. Exposure with the rostral-caudal axis of the rat perpendicular to the magnetic field produced an attenuated behavioral response compared to exposure with the rostral-caudal axis parallel to the field. These results in a single resistive magnet confirm and extend our earlier findings using multiple superconducting magnets. They demonstrate that the behavioral effects of exposure within large magnets are dependent on the magnetic field, and not on non-magnetic properties of the machinery. Finally, the effects of exposure to 4 T are clinically relevant, as 4 T magnetic fields are commonly used in functional MRI assays.

  18. Magnetic field effects on liquid-phase reactive sintering of MnBi

    NASA Astrophysics Data System (ADS)

    Mitsui, Yoshifuru; Abematsu, Ken-ichi; Umetsu, Rie Y.; Takahashi, Kohki; Koyama, Keiichi

    2016-02-01

    Magnetic fields effects on liquid-phase reaction sintering on MnBi were investigated. The liquid-phase reaction was so fast even in a zero field that the fraction of in-field sintered ferromagnetic MnBi phase was independent of the external magnetic field. However, the ferromagnetic MnBi crystals in the in-field sintered sample were oriented along the external magnetic field direction. The Lotgering factor of the in-field sintered sample was 0.99. This result indicated that almost completely anisotropic MnBi phase could be obtained by in-field liquid phase reactive sintering.

  19. Effects of static magnetic field on human leukemic cell line HL-60.

    PubMed

    Sabo, J; Mirossay, L; Horovcak, L; Sarissky, M; Mirossay, A; Mojzis, J

    2002-05-15

    A number of structures with magnetic moments exists in living organisms that may be oriented by magnetic field. While most experimental efforts belong to the area of effects induced by weak and extremely low-frequency electromagnetic fields, we attempt to give an attention to the biological effects of strong static magnetic fields. The influence of static magnetic field (SMF) on metabolic activity of cells was examined. The metabolic activity retardation is observed in human leukemic cell line HL-60 exposed to 1-T SMF for 72 h. The retardation effect was observed as well as in the presence of the mixture of the antineoplastic drugs 5 fluorouracil, cisplatin, doxorubicin and vincristine.

  20. Effect of magnetic field on noncollinear magnetism in classical bilinear-biquadratic Heisenberg model

    NASA Astrophysics Data System (ADS)

    Pasrija, Kanika; Kumar, Sanjeev

    2016-05-01

    We present a Monte Carlo simulation study of a bilinear-biquadratic Heisenberg model on a two-dimensional square lattice in the presence of an external magnetic field. The study is motivated by the relevance of this simple model to the non-collinear magnetism and the consequent ferroelectric behavior in the recently discovered high-temperature multiferroic, cupric oxide (CuO). We show that an external magnetic field stabilizes a non-coplanar magnetic phase, which is characterized by a finite ferromagnetic moment along the direction of the applied magnetic field and a spiral spin texture if projected in the plane perpendicular to the magnetic field. Real-space analysis highlights a coexistence of non-collinear regions with ferromagnetic clusters. The results are also supported by simple variational calculations.

  1. Combined effects of ambient gas pressures and magnetic field on laser plasma expansion dynamics

    NASA Astrophysics Data System (ADS)

    Atif, Hussain; Xun, Gao; Qi, Li; Zuoqiang, Hao; Jingquan, Lin

    2017-01-01

    In this work, we investigated the influence of air gas pressures on the expansion features of nanosecond laser ablated aluminum plasma in the absence and presence of a nonuniform magnetic field using fast photography. A particular emphasis was given to the plume dynamics (shape, size) with the combined effects of ambient gas pressures and an external magnetic field. Free expansion, sharpening effect, and hemi-spherical structures of the aluminum plasma were observed without a magnetic field under different gas pressures. Analysis of the resulting plume images with the combined effects of air gas pressures and a magnetic field show significant changes, such as plume splitting, elliptical geometry changes, radial expansion, and plume confinement. Furthermore, the total size of the plasma plume with a magnetic field was measured to be smaller than the plasma plume without a magnetic field at several background pressures.

  2. Biological effects of electromagnetic fields and recently updated safety guidelines for strong static magnetic fields.

    PubMed

    Yamaguchi-Sekino, Sachiko; Sekino, Masaki; Ueno, Shoogo

    2011-01-01

    Humans are exposed daily to artificial and naturally occurring magnetic fields that originate from many different sources. We review recent studies that examine the biological effects of and medical applications involving electromagnetic fields, review the properties of static and pulsed electromagnetic fields that affect biological systems, describe the use of a pulsed electromagnetic field in combination with an anticancer agent as an example of a medical application that incorporates an electromagnetic field, and discuss the recently updated safety guidelines for static electromagnetic fields. The most notable modifications to the 2009 International Commission on Non-Ionizing Radiation Protection guidelines are the increased exposure limits, especially for those who work with or near electromagnetic fields (occupational exposure limits). The recommended increases in exposure were determined using recent scientific evidence obtained from animal and human studies. Several studies since the 1994 publication of the guidelines have examined the effects on humans after exposure to high static electromagnetic fields (up to 9.4 tesla), but additional research is needed to ascertain further the safety of strong electromagnetic fields.

  3. Magneto-Dendrite Effect: Copper Electrodeposition under High Magnetic Field.

    PubMed

    Miura, Makoto; Oshikiri, Yoshinobu; Sugiyama, Atsushi; Morimoto, Ryoichi; Mogi, Iwao; Miura, Miki; Takagi, Satoshi; Yamauchi, Yusuke; Aogaki, Ryoichi

    2017-04-04

    Ionic vacancy is a by-product in electrochemical reaction, composed of polarized free space of the order of 0.1 nm with a 1 s lifetime, and playing key roles in nano-electrochemical processes. However, its chemical nature has not yet been clarified. In copper electrodeposition under a high magnetic field of 15 T, using a new electrode system called cyclotron magnetohydrodynamic (MHD) electrode (CMHDE) composed of a pair of concentric cylindrical electrodes, we have found an extraordinary dendritic growth with a drastic positive potential shift from hydrogen-gas evolution potential. Dendritic deposition is characterized by the co-deposition of hydrogen molecule, but such a positive potential shift makes hydrogen-gas evolution impossible. However, in the high magnetic field, instead of flat deposit, remarkable dendritic growth emerged. By examining the chemical nature of ionic vacancy, it was concluded that ionic vacancy works on the dendrite formation with the extraordinary potential shift.

  4. Two-jet astrosphere model: effect of azimuthal magnetic field

    NASA Astrophysics Data System (ADS)

    Golikov, E. A.; Izmodenov, V. V.; Alexashov, D. B.; Belov, N. A.

    2017-01-01

    Opher et al., Drake, Swisdak and Opher have shown that the heliospheric magnetic field results in formation of two-jet structure of the solar wind flow in the inner heliosheath, i.e. in the subsonic region between the heliospheric termination shock (TS) and the heliopause. In this scenario, the heliopause has a tube-like topology as compared with a sheet-like topology in the most models of the global heliosphere. In this paper, we explore the two-jet scenario for a simplified astrosphere in which (1) the star is at rest with respect to the circumstellar medium, (2) radial magnetic field is neglected as compared with azimuthal component and (3) the stellar wind outflow is assumed to be hypersonic (both the Mach number and the Alfvénic Mach number are much greater than unity at the inflow boundary). We have shown that the problem can be formulated in dimensionless form, in which the solution depends only on one dimensionless parameter ε that is reciprocal of the Alfvénic Mach number at the inflow boundary. This parameter is proportional to stellar magnetic field. We present the numerical solution of the problem for various values of ε. Three first integrals of the governing ideal magnetohydrodynamic equations are presented, and we make use of them in order to get the plasma distribution in the jets. Simple relations between distances to the TS, astropause and the size of the jet are established. These relations allow us to determine the stellar magnetic field from the geometrical pattern of the jet-like astrosphere.

  5. Molecules in Magnetic Fields

    NASA Astrophysics Data System (ADS)

    Berdyugina, Svetlana

    2015-08-01

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

  6. The effect of stress and incentive magnetic field on the average volume of magnetic Barkhausen jump in iron

    NASA Astrophysics Data System (ADS)

    Shu, Di; Guo, Lei; Yin, Liang; Chen, Zhaoyang; Chen, Juan; Qi, Xin

    2015-11-01

    The average volume of magnetic Barkhausen jump (AVMBJ) v bar generated by magnetic domain wall irreversible displacement under the effect of the incentive magnetic field H for ferromagnetic materials and the relationship between irreversible magnetic susceptibility χirr and stress σ are adopted in this paper to study the theoretical relationship among AVMBJ v bar(magneto-elasticity noise) and the incentive magnetic field H. Then the numerical relationship among AVMBJ v bar, stress σ and the incentive magnetic field H is deduced. Utilizing this numerical relationship, the displacement process of magnetic domain wall for single crystal is analyzed and the effect of the incentive magnetic field H and the stress σ on the AVMBJ v bar (magneto-elasticity noise) is explained from experimental and theoretical perspectives. The saturation velocity of Barkhausen jump characteristic value curve is different when tensile or compressive stress is applied on ferromagnetic materials, because the resistance of magnetic domain wall displacement is different. The idea of critical magnetic field in the process of magnetic domain wall displacement is introduced in this paper, which solves the supersaturated calibration problem of AVMBJ - σ calibration curve.

  7. Destabilizing effect of time-dependent oblique magnetic field on magnetic fluids streaming in porous media.

    PubMed

    El-Dib, Yusry O; Ghaly, Ahmed Y

    2004-01-01

    The present work studies Kelvin-Helmholtz waves propagating between two magnetic fluids. The system is composed of two semi-infinite magnetic fluids streaming throughout porous media. The system is influenced by an oblique magnetic field. The solution of the linearized equations of motion under the boundary conditions leads to deriving the Mathieu equation governing the interfacial displacement and having complex coefficients. The stability criteria are discussed theoretically and numerically, from which stability diagrams are obtained. Regions of stability and instability are identified for the magnetic fields versus the wavenumber. It is found that the increase of the fluid density ratio, the fluid velocity ratio, the upper viscosity, and the lower porous permeability play a stabilizing role in the stability behavior in the presence of an oscillating vertical magnetic field or in the presence of an oscillating tangential magnetic field. The increase of the fluid viscosity plays a stabilizing role and can be used to retard the destabilizing influence for the vertical magnetic field. Dual roles are observed for the fluid velocity in the stability criteria. It is found that the field frequency plays against the constant part for the magnetic field.

  8. Electric field effect on the magnetization process for a very thin Co60Fe40 film

    NASA Astrophysics Data System (ADS)

    Suzuki, K. Z.; Ranjbar, R.; Sugihara, A.; Kondo, Y.; Mizukami, S.

    2016-08-01

    The electric field effect on the magnetization process for a very thin Co60Fe40 film was studied. The magnetization process under the electric field was characterized using tunnel magnetoresistance curves measured in a fully-epitaxial (001)-oriented CoFe(1)/MgO/CoFe(3) (thickness in nanometers) magnetic tunnel junction, where both the CoFe electrodes are magnetized in- plane. The out-of-plane saturation field of the thinner CoFe electrode changed linearly by varying the applied voltage, and the field-induced change of saturation field was estimated to be -0.10 TV-1. This change in the saturation field is interpreted as the electric field induced change in a perpendicular magnetic anisotropy originating from the CoFe/MgO interface. The electric field effect efficiency was estimated to be about 200 fJV-1 m-1.

  9. The effect of the solar magnetic field on dust-particle orbits in the F corona

    NASA Astrophysics Data System (ADS)

    Rusk, Edwin T.

    1988-10-01

    In order to determine whether the solar magnetic field can align circumsolar dust into rings such as those described by Mizutani et al. (1984), the solar magnetic field is divided into its various multipole components and theoretical expressions are derived to determine the effect of each of these components on the orbital elements of circumsolar dust. Simulations are then carried out to determine the effect of a dynamic solar magnetic field on such particles using actual values of the solar magnetic field supplied by Hoeksema (1984). These results are compared to observations of the F corona.

  10. Safety Problems of Electric and Magnetic Fields and Experimental Magnetic Fusion Facilities 3.Biological Effects of Low-Frequency Electromagnetic Fields

    NASA Astrophysics Data System (ADS)

    Miyakoshi, Junji

    The possible health hazard of exposure to low-frequency magnetic fields has become an issue of considerable public concern. Although many epidemiological studies have done, the results are inconsistent to explain an association between exposure to the magnetic fields in the environment and apparent cancer. In in vitro studies, the existence of the effects of the magnetic fields at low flux density has also been contradictory in various reports. This paper reviews studies on cellular and molecular effects of low-frequency magnetic fields.

  11. Effects of fluctuating magnetic fields on a superconducting bulk rotor shielded with superconducting rings

    NASA Astrophysics Data System (ADS)

    Yamagishi, K.; Ogawa, J.; Tsukamoto, O.

    2014-05-01

    We study the effect of a fluctuating magnetic field, which is one of the technical problems for trapped magnetic fields in a bulk superconductor, to realize a practical bulk superconductor rotating machine. Previous research and other's research has shown that fluctuating magnetic fields reduce the strength of trapped magnetic fields in superconducting bulk modules [1, 2]. This deters development of applications of AC rotating machines because superconducting bulk modules are always exposed to a fluctuating magnetic field. Therefore, it is necessary to develop a method to control decrease of the trapped magnetic field. We propose a method to use the shielding ring of a superconducting wire to achieve this goal and the effects are confirmed experimentally [3]. We are now building test equipment for examining the performance of a shielding ring in a bulk rotating machine. This paper reports the test result for the shielding ring applied to the bulk superconducting rotor that is a part of the test equipment.

  12. Magnetic anisotropy of Co thin films: Playing with the shadowing effect, magnetic field and substrate spinning

    NASA Astrophysics Data System (ADS)

    Bertelli, T. P.; Bueno, T. E. P.; Krohling, A. C.; Silva, B. C.; Rodríguez-Suárez, R. L.; Nascimento, V. P.; Paniago, R.; Krambrock, K.; Larica, C.; Passamani, E. C.

    2017-03-01

    The shape and magneto-crystalline anisotropies of 10 nm thick Co sputtered films have shown to be dependent on the oblique deposition angle (αi), the angular velocity of the substrate-holder (ωS) and the applied magnetic field (H0) during the deposition. Oblique deposition geometry is natural in our sputtering setup, being α equal to 22° at the edge of 4 in. sample-holder and 32° at its central part. X-ray diffraction analysis has evidenced a (111) texturized fcc structure for all films. Ferromagnetic resonance has shown that samples prepared under H0 of 250 Oe present dominantly the uniaxial HU field contribution independent of the ωS-value, however its magnitude depends on αi. For a non-magnetic holder, Co films show a mixture of twofold (uniaxial) with fourfold (cubic) in-plane magnetic anisotropies. The fourfold contribution is small and it is not influenced by αi or ωS within the experimental error, while the dominant twofold contribution, which is governed by the shadowing effect, is reduced for higher ωS and for samples positioned at the center of the sample-holder. In addition, the intrinsic isotropic Gilbert damping dominates the relaxation process, which is followed by anisotropic twofold scattering mechanism due to stripes and defects, interestingly not influenced by the substrate rotation during depositions.

  13. The Disturbing Effect of the Stray Magnetic Fields on Magnetoimpedance Sensors.

    PubMed

    Wang, Tao; Zhou, Yong; Lei, Chong; Zhi, Shaotao; Guo, Lei; Li, Hengyu; Wu, Zhizheng; Xie, Shaorong; Luo, Jun; Pu, Huayan

    2016-10-17

    The disturbing effect of the stray magnetic fields of Fe-based amorphous ribbons on the giant magnetoimpedance (GMI) sensor has been investigated systematically in this paper. Two simple methods were used for examining the disturbing effect of the stray magnetic fields of ribbons on the GMI sensor. In order to study the influence of the stray magnetic fields on the GMI effect, the square-shaped amorphous ribbons were tested in front, at the back, on the left and on the top of a meander-line GMI sensor made up of soft ferromagnetic films, respectively. Experimental results show that the presence of ribbons in front or at the back of GMI sensor shifts the GMI curve to a lower external magnetic field. On the contrary, the presence of ribbons on the left or on the top of the GMI sensor shifts the GMI curve to a higher external magnetic field, which is related to the coupling effect of the external magnetic field and the stray magnetic fields. The influence of the area and angle of ribbons on GMI was also studied in this work. The GMI sensor exhibits high linearity for detection of the stray magnetic fields, which has made it feasible to construct a sensitive magnetometer for detecting the typical stray magnetic fields of general soft ferromagnetic materials.

  14. The Disturbing Effect of the Stray Magnetic Fields on Magnetoimpedance Sensors

    PubMed Central

    Wang, Tao; Zhou, Yong; Lei, Chong; Zhi, Shaotao; Guo, Lei; Li, Hengyu; Wu, Zhizheng; Xie, Shaorong; Luo, Jun; Pu, Huayan

    2016-01-01

    The disturbing effect of the stray magnetic fields of Fe-based amorphous ribbons on the giant magnetoimpedance (GMI) sensor has been investigated systematically in this paper. Two simple methods were used for examining the disturbing effect of the stray magnetic fields of ribbons on the GMI sensor. In order to study the influence of the stray magnetic fields on the GMI effect, the square-shaped amorphous ribbons were tested in front, at the back, on the left and on the top of a meander-line GMI sensor made up of soft ferromagnetic films, respectively. Experimental results show that the presence of ribbons in front or at the back of GMI sensor shifts the GMI curve to a lower external magnetic field. On the contrary, the presence of ribbons on the left or on the top of the GMI sensor shifts the GMI curve to a higher external magnetic field, which is related to the coupling effect of the external magnetic field and the stray magnetic fields. The influence of the area and angle of ribbons on GMI was also studied in this work. The GMI sensor exhibits high linearity for detection of the stray magnetic fields, which has made it feasible to construct a sensitive magnetometer for detecting the typical stray magnetic fields of general soft ferromagnetic materials. PMID:27763498

  15. Effect of alpha quenching on magnetic field size.

    PubMed

    Núñez, M

    2001-05-01

    It is commonly assumed that the alpha effect of mean-field magnetohydrodynamics essentially stops acting wherever the mean-field size reaches a certain value. We show that if the mean velocity is approximately constant, the regions where the field reaches such a threshold tend to shrink in size or the field tends to become constant there. The rate of this process is also estimated.

  16. Modelling of the magnetic field effects in hydrodynamic codes using a second order tensorial diffusion scheme

    NASA Astrophysics Data System (ADS)

    Breil, J.; Maire, P.-H.; Nicolaï, P.; Schurtz, G.

    2008-05-01

    In laser produced plasmas large self-generated magnetic fields have been measured. The classical formulas by Braginskii predict that magnetic fields induce a reduction of the magnitude of the heat flux and its rotation through the Righi-Leduc effect. In this paper a second order tensorial diffusion method used to correctly solve the Righi-Leduc effect in multidimensional code is presented.

  17. Magnetic Field Modulated Photoreflectance Study of the Electron Effective Mass in Dilute Nitride Semiconductors

    SciTech Connect

    Mori, N.; Hiejima, K.; Kubo, H.; Patane, A.; Eaves, L.

    2011-12-23

    Magnetic field modulated photoreflectance measurements are performed on the dilute nitride semiconductor Ga(AsN) in quantizing magnetic fields. From the measured cyclotron energies, the conduction band effective mass and its dependence on the nitrogen content are determined. The effective mass is found to become significantly heavier in samples with high nitrogen composition (>0.1%).

  18. Dynamic of the Dust Structures under Magnetic Field Effect in DC Glow Discharges

    SciTech Connect

    Vasiliev, M. M.; D'yachkov, L. G.; Antipov, S. N.; Petrov, O. F.; Fortov, V. E.

    2008-09-07

    In this work, we investigate dust structures in the striation of DC glow discharges under magnetic field actions. The dependence of rotation frequency of dusty plasma structures as a function of the magnetic field was investigated. For various magnetic fields kinetic temperatures of the dust particles, diffusion coefficients, and effective coupling coefficient {gamma}* have been determined. Obtained results are analyzed and compared with theoretical predictions.

  19. Effect of magnetic field on the ultrafiltration of bovine serum albumin.

    PubMed

    Vardanega, Renata; Tres, Marcus V; Mazutti, Marcio A; Treichel, Helen; de Oliveira, Débora; Di Luccio, Marco; Oliveira, J Vladimir

    2013-08-01

    This work evaluates the effects of a static magnetic field on the permeation of bovine serum albumin (BSA) in a tangential ultrafiltration membrane module. Experimental tests were carried out at different pHs using a poly(sulfone) membrane with molecular weight cut off of 60 kDa under the influence of a 0.4 T neodymium-iron-boron magnetic field. Results showed an increase in the permeate flux of water after the cleaning procedures of the new and reused membranes in the presence of the magnetic field. The elusive mechanism of magnetic memory is also shown to take place for the water fluxes fully recovered after the cleaning procedures when the magnetic field was applied to the system before the permeation. When the magnetic field was applied during permeation, the water fluxes presented lower percent of recuperation after the cleaning procedures, thus suggesting that the BSA solution may have somewhat been influenced by magnetic memory.

  20. Magnetic Pressure as a Scalar Representation of Field Effects in Magnetic Suspensions.

    PubMed

    Zborowski, Maciej; Moore, Lee R; Williams, P Stephen; Chalmers, Jeffrey J

    2010-01-01

    Magnetic microsphere suspensions undergo complex motion when exposed to finite sources of the magnetic field, such as small permanent magnets. The computational complexity is compounded by a difficulty in choosing a suitable choice of visualization tools because this often requires using the magnetic force vector field in three dimensions. Here we present a potentially simpler approach by using the magnetic pressure. It is a scalar quantity, pm = B(2)/2μ0, and its usefulness has been already demonstrated in applications to magnetohydrodynamics and ferrohydrodynamics (where B is the applied field and μ0 = 4π×10(-7) T.m/A). The equilibrium distribution of the magnetic bead plug in aqueous suspension is calculated as an isosurface of the magnitude of the magnetic pressure pm = const, in the field of two permanent magnet blocks calculated from closed formulas. The geometry was adapted from a publication on the magnetic bead suspensions in microsystems and the predicted bead plug distribution is shown to agree remarkably well with the experiment.

  1. Magnetic Pressure as a Scalar Representation of Field Effects in Magnetic Suspensions

    PubMed Central

    Zborowski, Maciej; Moore, Lee R.; Williams, P. Stephen; Chalmers, Jeffrey J.

    2014-01-01

    Magnetic microsphere suspensions undergo complex motion when exposed to finite sources of the magnetic field, such as small permanent magnets. The computational complexity is compounded by a difficulty in choosing a suitable choice of visualization tools because this often requires using the magnetic force vector field in three dimensions. Here we present a potentially simpler approach by using the magnetic pressure. It is a scalar quantity, pm = B2/2μ0, and its usefulness has been already demonstrated in applications to magnetohydrodynamics and ferrohydrodynamics (where B is the applied field and μ0 = 4π×10−7 T.m/A). The equilibrium distribution of the magnetic bead plug in aqueous suspension is calculated as an isosurface of the magnitude of the magnetic pressure pm = const, in the field of two permanent magnet blocks calculated from closed formulas. The geometry was adapted from a publication on the magnetic bead suspensions in microsystems and the predicted bead plug distribution is shown to agree remarkably well with the experiment. PMID:25382882

  2. Confinement effect of cylindrical-separatrix-type magnetic field on the plume of magnetic focusing type Hall thruster

    NASA Astrophysics Data System (ADS)

    Yu, Daren; Meng, Tianhang; Ning, Zhongxi; Liu, Hui

    2017-04-01

    A magnetic focusing type Hall thruster was designed with a cylindrical magnetic seperatrix. During the process of a hollow cathode crossing the separatrix, the variance of plume parameter distribution was monitored. Results show that the ion flux on the large spatial angle is significantly lower when the hollow cathode is located in the inner magnetic field. This convergence effect is preserved even in a distant area. A mechanism was proposed for plume divergence from the perspective of cathode-to-plume potential difference, through which the confinement effect of cylindrical-separatrix-type magnetic field on thruster plume was confirmed and proposed as a means of plume protection for plasma propulsion devices.

  3. The effects of magnetic field topology on secondary neutron spectra in Magnetized Liner Inertial Fusion

    NASA Astrophysics Data System (ADS)

    Appelbe, B.; Pecover, J.; Chittenden, J.

    2017-03-01

    The Magnetized Liner Inertial Fusion (MagLIF) concept involves the compression of a magnetized fuel such that the stagnated fuel contains a magnetic field that can suppress heat flow losses and confine α particles. Magnetic confinement of α particles reduces the fuel ρR required for ignition. Recent work [1,2] has demonstrated that the magnitude of the magnetic field in deuterium fuel can be inferred from the yields and spectra of secondary DT neutrons. In this work we investigate the potential for using the shape of the secondary neutron spectra to diagnose the magnetic field topology in the stagnated fuel. Three different field topologies that could possibly occur in MagLIF experiments are studied: (1) a cylindrical fuel column containing axial and azimuthal magnetic field components, (2) a fuel column which is pinched at the ends to form a magnetic mirror and (3) a fuel column that has a helical tube shape with magnetic field lines following the helical path of the tube's axis. Each topology is motivated by observations from experimental or simulated MagLIF data. For each topology we use a multi-physics model to investigate the shapes of the secondary neutron spectra emitted from a steady-state stagnated fuel column. It is found that the azimuthal and helical topologies are more suitable than the mirror topology for reproducing an asymmetry in the axial spectra that was observed in experiments. Gorgon MHD simulations of the MagLIF implosion in 1D are also carried out. These show that sufficient azimuthal magnetic field can penetrate from the liner into the fuel to qualitatively reproduce the observed spectral asymmetry.

  4. Static magnetic fields: A summary of biological interactions, potential health effects, and exposure guidelines

    SciTech Connect

    Tenforde, T.S.

    1992-05-01

    Interest in the mechanisms of interaction and the biological effects of static magnetic fields has increased significantly during the past two decades as a result of the growing number of applications of these fields in research, industry and medicine. A major stimulus for research on the bioeffects of static magnetic fields has been the effort to develop new technologies for energy production and storage that utilize intense magnetic fields (e.g., thermonuclear fusion reactors and superconducting magnet energy storage devices). Interest in the possible biological interactions and health effects of static magnetic fields has also been increased as a result of recent developments in magnetic levitation as a mode of public transportation. In addition, the rapid emergence of magnetic resonance imaging as a new clinical diagnostic procedure has, in recent years, provided a strong rationale for defining the possible biological effects of magnetic fields with high flux densities. In this review, the principal interaction mechanisms of static magnetic fields will be described, and a summary will be given of the present state of knowledge of the biological, environmental, and human health effects of these fields.

  5. Magnetic field effect in non-magnetic organic semiconductor thin film devices and its applications

    NASA Astrophysics Data System (ADS)

    Mermer, Omer

    Organic pi-conjugated materials have been used to manufacture devices such as organic light-emitting diodes (OLEDs), photovoltaic cells and field-effect transistors. Recently there has been growing interest in spin and magnetic field effects in these materials. In this thesis, I report on the discovery and experimental characterization of a large and intriguing magnetoresistance effect, which we dubbed organic magnetoresistance (OMAR), in various pi-conjugated polymer and small molecular OLEDs. OMAR may find application in magnetic field sensors in OLED interactive displays (patent pending). We discovered OMAR originally in devices made from the pi-conjugated polymer polyfluorene. We found ≈ 10% magnetoresistance at 10 mT fields at room temperature. The effect is independent of the field direction, and is only weakly temperature dependent. We show that OMAR is a bulk effect related to the majority carrier transport. Studying polymer films with different amount of disorder we found that low disorder/large mobility is not a necessary prerequisite for large OMAR response. We also studied a possible interrelation between spin-orbit coupling and the OMAR effect in platinum-containing polymers. We found that spin-orbit coupling has apparently little effect on OMAR. A large OMAR effect was also observed in devices made from the prototypical small molecule, Alq3 that is similar in size to that in the polyfluorene devices. Our study shows that the basic properties are equivalent to polymer devices. To the best of our knowledge, OMAR is not adequately described by any of the magnetoresistance mechanisms known to date. A future explanation for this effect may lead to a breakthrough in the scientific understanding of organic semiconductors. In a largely unrelated effort, we also modelled spin-dependent exciton formation in OLEDs. Our work leads to the following picture of exciton formation: Since the triplet exciton states lie lower in energy than singlets, more phonons must

  6. Observation of the Faraday effect via beam deflection in a longitudinal magnetic field

    SciTech Connect

    Ghosh, Ambarish; Hill, Winfield; Fischer, Peer

    2007-11-15

    We show that magnetic-field-induced circular differential deflection of light can be observed in reflection or refraction at a single interface. The difference in the reflection or refraction angles between the two circular polarization components is a function of the magnetic-field strength and the Verdet constant, and permits the observation of the Faraday effect not via polarization rotation in transmission, but via changes in the propagation direction. Deflection measurements do not suffer from n-{pi} ambiguities and are shown to be another means to map magnetic fields with high axial resolution, or to determine the sign and magnitude of magnetic-field pulses in a single measurement.

  7. Effect of the equilibrium magnetic field on plasma edge fluctuations

    SciTech Connect

    Carreras, B.A.; Leboeuf, J.N.; Lee, D.K.; Holmes, J.A.; Lynch, V.E.

    1990-01-01

    The magnetic field structure reflected in the safety factor (q) profile can play an important role in defining some of the basic structures of the magnetohydrodynamic (MHD) turbulence: it plays a role in the generation of spatial structures in the initial nonlinear phase, and it gives a radial dependence to the spectral average of the square of the poloidal mode number, {l angle}m{sup 2}{r angle}{sup 1/2}, that can modify the explicit dependences of an analytically derived expression for turbulence-induced anomalous losses. 12 refs., 4 figs.

  8. Edge effects on forces and magnetic fields produced by a conductor moving past a magnet

    NASA Astrophysics Data System (ADS)

    Mulcahy, T. M.; Hull, J. R.; Almer, J. D.; Rossing, T. D.

    Experiments were performed to further investigate the forces acting on magnets moving along and over the edge of a continuous conducting sheet and to produce a comprehensive data set for the validation of analysis methods. Mapping the magnetic field gives information about the eddy currents induced in the conductor, which agrees with numerical calculations.

  9. Effect of external and internal magnetic fields on the bias stability in a Zeeman laser gyroscope

    SciTech Connect

    Kolbas, Yu Yu; Saveliev, I I; Khokhlov, N I

    2015-06-30

    With the specific features of electronic systems of a Zeeman laser gyroscope taken into account, the basic physical mechanisms of the magnetic field effect on the bias stability and the factors giving rise to the internal magnetic fields are revealed. The hardware-based methods of reducing the effect of external and internal magnetic fields are considered, as well as the algorithmic methods for increasing the stability of the bias magnetic component by taking into account its reproducible temperature and time dependences. Typical experimental temperature and time dependences of the magnetic component of the Zeeman laser gyro bias are presented, and by their example the efficiency of the proposed methods for reducing the effect of magnetic fields is shown. (laser gyroscopes)

  10. Effect of magnetic helicity upon rectilinear propagation of charged particles in random magnetic fields

    NASA Technical Reports Server (NTRS)

    Earl, James A.

    1992-01-01

    When charged particles spiral along a large constant magnetic field, their trajectories are scattered by any random field components that are superposed on the guiding field. If the random field configuration embodies helicity, the scattering is asymmetrical with respect to a plane perpendicular to the guiding field, for particles moving into the forward hemisphere are scattered at different rates from those moving into the backward hemisphere. This asymmetry gives rise to new terms in the transport equations that describe propagation of charged particles. Helicity has virtually no impact on qualitative features of the diffusive mode of propagation. However, characteristic velocities of the coherent modes that appear after a highly anisotropic injection exhibit an asymmetry related to helicity. Explicit formulas, which embody the effects of helicity, are given for the anisotropies, the coefficient diffusion, and the coherent velocities. Predictions derived from these expressions are in good agreement with Monte Carlo simulations of particle transport, but the simulations reveal certain phenomena whose explanation calls for further analytical work.

  11. Magneto-Dendrite Effect: Copper Electrodeposition under High Magnetic Field

    PubMed Central

    Miura, Makoto; Oshikiri, Yoshinobu; Sugiyama, Atsushi; Morimoto, Ryoichi; Mogi, Iwao; Miura, Miki; Takagi, Satoshi; Yamauchi, Yusuke; Aogaki, Ryoichi

    2017-01-01

    Ionic vacancy is a by-product in electrochemical reaction, composed of polarized free space of the order of 0.1 nm with a 1 s lifetime, and playing key roles in nano-electrochemical processes. However, its chemical nature has not yet been clarified. In copper electrodeposition under a high magnetic field of 15 T, using a new electrode system called cyclotron magnetohydrodynamic (MHD) electrode (CMHDE) composed of a pair of concentric cylindrical electrodes, we have found an extraordinary dendritic growth with a drastic positive potential shift from hydrogen-gas evolution potential. Dendritic deposition is characterized by the co-deposition of hydrogen molecule, but such a positive potential shift makes hydrogen-gas evolution impossible. However, in the high magnetic field, instead of flat deposit, remarkable dendritic growth emerged. By examining the chemical nature of ionic vacancy, it was concluded that ionic vacancy works on the dendrite formation with the extraordinary potential shift. PMID:28374758

  12. [Effect of an alternating magnetic field on the development of spontaneous hypertension in rats].

    PubMed

    Markov, Kh M; Petrichuk, S V; Zavrieva, M K; Suslova, G F; Nartsissov, R P

    1984-12-01

    The effect of varying magnetic field on the development of spontaneous hypertension was studied in experiments on Okamoto rats. The influence of magnetic field during antenatal development caused persistent changes in lymphocyte and organ metabolism and accelerated the appearance of spontaneous hypertension in rats. Based on enzymatic activity of lymphocytes it is possible to predict the development of spontaneous arterial hypertension.

  13. Effects of continuous and intermittent magnetic fields on oxidative parameters in vivo.

    PubMed

    Coşkun, Sule; Balabanli, Barbaros; Canseven, Ayşe; Seyhan, Nesrin

    2009-02-01

    Continuous and intermittent 50 Hz, 1.5 mT magnetic field with the exposure period of 4 h/day for 4 days was used to investigate its possible effect on adult guinea pigs. Tissues and plasma specimens were assessed by biochemical parameters. Malondialdehyde (MDA), glutathione (GSH), nitric oxide (NO) levels and myeloperoxidase activity (MPO) were examined in plasma, liver and brain tissues. All parameters were determined by spectrophotometer. While intermittent magnetic field was effective on plasma lipid peroxidation, continuous magnetic field was found to be effective on plasma MPO activity and NO levels. Augmentation of lipid peroxidation was also observed in liver tissue both intermittent and continuous magnetic field exposures. These results indicate that both the intermittent and continuous magnetic field exposures affect various tissues in a distinct manner because of having different tissue antioxidant status and responses.

  14. Theory of light-induced effective magnetic field in Rashba ferromagnets

    NASA Astrophysics Data System (ADS)

    Qaiumzadeh, Alireza; Titov, Mikhail

    2016-07-01

    Motivated by recent experiments on all-optical magnetization reversal in conductive ferromagnetic thin films we use nonequilibrium formalism to calculate the effective magnetic field induced in a Rashba ferromagnet by a short laser pulse. The main contribution to the effect originates in the direct optical transitions between spin-split subbands. The resulting effective magnetic field is inversely proportional to the impurity scattering rate and can reach the amplitude of a few Tesla in the systems like Co/Pt bilayers. We show that the total light-induced effective magnetic field in ferromagnetic systems is the sum of two contributions: a helicity dependent term, which is an even function of magnetization, and a helicity independent term, which is an odd function of magnetization. The primary role of the spin-orbit interaction is to widen the frequency range for direct optical transitions.

  15. Nonlinear theory of a "shear-current" effect and mean-field magnetic dynamos.

    PubMed

    Rogachevskii, Igor; Kleeorin, Nathan

    2004-10-01

    The nonlinear theory of a "shear-current" effect in a nonrotating and nonhelical homogeneous turbulence with an imposed mean velocity shear is developed. The shear-current effect is associated with the W x J term in the mean electromotive force and causes the generation of the mean magnetic field even in a nonrotating and nonhelical homogeneous turbulence (where W is the mean vorticity and J is the mean electric current). It is found that there is no quenching of the nonlinear shear-current effect contrary to the quenching of the nonlinear alpha effect, the nonlinear turbulent magnetic diffusion, etc. During the nonlinear growth of the mean magnetic field, the shear-current effect only changes its sign at some value B (*) of the mean magnetic field. The magnitude B (*) determines the level of the saturated mean magnetic field which is less than the equipartition field. It is shown that the background magnetic fluctuations due to the small-scale dynamo enhance the shear-current effect and reduce the magnitude B (*) . When the level of the background magnetic fluctuations is larger than 1/3 of the kinetic energy of the turbulence, the mean magnetic field can be generated due to the shear-current effect for an arbitrary exponent of the energy spectrum of the velocity fluctuations.

  16. Chiral magnetic effect in protoneutron stars and magnetic field spectral evolution

    SciTech Connect

    Sigl, Günter; Leite, Natacha E-mail: natacha.leite@desy.de

    2016-01-01

    We investigate the evolution of the chiral magnetic instability in a protoneutron star and compute the resulting magnetic power and helicity spectra. The instability may act during the early cooling phase of the hot protoneutron star after supernova core collapse, where it can contribute to the buildup of magnetic fields of strength up to the order of 10{sup 14} G. The maximal field strengths generated by this instability, however, depend considerably on the temperature of the protoneutron star, on density fluctuations and turbulence spectrum of the medium. At the end of the hot cooling phase the magnetic field tends to be concentrated around the submillimeter to cm scale, where it is subject to slow resistive damping.

  17. The effects of pseudo magnetic fields in molecular spectra and scattering

    SciTech Connect

    Kendrick, B.

    1996-12-31

    Pseudo magnetic fields appear in the Born-Oppenheimer method for molecules when conical intersections or electronic angular momenta are taken into account. These fields are not real magnetic fields but they have the same mathematical properties and can lead to real observable effects in the dynamics of molecules. A general vector potential (gauge theory) approach for including these field effects in the Born-Oppenheimer method is introduced and applied to H + O{sub 2} scattering and the vibrational spectrum of Na{sub 3}(X) for zero total angular momentum (J = 0). The scattering results for HO{sub 2} show significant shifts in the resonance energies and lifetimes due to a magnetic solenoid type field originating from the C{sub 2v} conical intersection in HO{sub 2}. Significant changes in the state-to-state transition probabilities are also observed. The non-degenerate A{sub 1} and A{sub 2} vibrational spectra of Na{sub 3}(X) show significant shifts in the energy levels due to a magnetic solenoid type field originating from the D{sub 3h} conical intersection in Na{sub 3}. These two examples show that the effects of pseudo magnetic fields can be significant and in many cases they must be included in order to obtain agreement between theory and experiment. The newly developed gauge theory techniques for treating pseudo magnetic fields are also relevant for including the effects of real magnetic fields.

  18. The Effect of the Earth's and Stray Magnetic Fields on Mobile Mass Spectrometer Systems

    NASA Astrophysics Data System (ADS)

    Bell, Ryan J.; Davey, Nicholas G.; Martinsen, Morten; Short, R. Timothy; Gill, Chris G.; Krogh, Erik T.

    2015-02-01

    Development of small, field-portable mass spectrometers has enabled a rapid growth of in-field measurements on mobile platforms. In such in-field measurements, unexpected signal variability has been observed by the authors in portable ion traps with internal electron ionization. The orientation of magnetic fields (such as the Earth's) relative to the ionization electron beam trajectory can significantly alter the electron flux into a quadrupole ion trap, resulting in significant changes in the instrumental sensitivity. Instrument simulations and experiments were performed relative to the earth's magnetic field to assess the importance of (1) nonpoint-source electron sources, (2) vertical versus horizontal electron beam orientation, and (3) secondary magnetic fields created by the instrument itself. Electron lens focus effects were explored by additional simulations, and were paralleled by experiments performed with a mass spectrometer mounted on a rotating platform. Additionally, magnetically permeable metals were used to shield (1) the entire instrument from the Earth's magnetic field, and (2) the electron beam from both the Earth's and instrument's magnetic fields. Both simulation and experimental results suggest the predominant influence on directionally dependent signal variability is the result of the summation of two magnetic vectors. As such, the most effective method for reducing this effect is the shielding of the electron beam from both magnetic vectors, thus improving electron beam alignment and removing any directional dependency. The improved ionizing electron beam alignment also allows for significant improvements in overall instrument sensitivity.

  19. SU-E-T-368: Effect of a Strong Magnetic Field On Select Radiation Dosimeters

    SciTech Connect

    Mathis, M; Wen, Z; Tailor, R; Sawakuchi, G; Flint, D; Beddar, S; Ibbott, G

    2014-06-01

    Purpose: To determine the effect of a strong magnetic field on TLD-100, OSLD (Al{sub 2}O{sub 2}:C), and PRESAGE dosimetry devices. This study will help to determine which types of dosimeters can be used for quality assurance and in-vivo dosimetry measurements in a magnetic resonance imaginglinear accelerator (MRI-linac) system. Methods: The dosimeters were separated into two categories which were either exposed or not exposed to a strong magnetic field. In each category a set of dosimeters was irradiated with 0, 2, or 6 Gy. To expose the dosimeters to a magnetic field the samples in that category were place in a Bruker small animal magnetic resonance scanner at a field strength slightly greater than 2.5 T for at least 1 hour preirradiation and at least 1 hour post-irradiation. Irradiations were performed with a 6 MV x-ray beam from a Varian TrueBeam linac with 10×10 cm{sup 2} field at a 600 MU/min dose rate. The samples that received no radiation dose were used as control detectors. Results: The readouts of the dosimeters which were not exposed to a strong magnetic field were compared with the measurements of the dosimetry devices which were exposed to a magnetic field. No significant differences (less than 2% difference) in the performance of TLD, OSLD, or PRESAGE dosimeters due to exposure to a strong magnetic field were observed. Conclusion: Exposure to a strong magnetic field before and after irradiation does not appear to change the dosimetric properties of TLD, OSLD, or PRESAGE which indicates that these dosimeters have potential for use in quality assurance and in-vivo dosimetry in a MRI-linac. We plan to further test the effect of magnetic fields on these devices by irradiating them in the presence of a magnetic fields similar to those produced by a MRI-linac system. Elekta-MD Anderson Cancer Center Research Agreement.

  20. Effect of magnetic field on the accumulation of polyhydroxyalkanoates (PHAs) by microorganism in activated sludge.

    PubMed

    Zhu, Sai-Chang; Xu, Zhen-Lan; Meng, Hui-Juan; Zhou, Jun; Chen, Hong

    2012-08-01

    The effect of static magnetic field on polyhydroxyalkanoates (PHAs) syntheses by activated sludge under aerobic dynamic feeding (ADF) was evaluated in sequence batch reactors (SBR), with magnetic field intensities of 42, 21, 11 and 7 millitesla (mT) exposure in the feast, feast-famine and famine periods, respectively, and one control group without magnetic field exposure. Under each level of magnetic field intensity, the effect of magnetic field exposed in the famine period to PHAs syntheses was most significant in comparison with that in the feast or feast-famine period. Maximal hydroxybutyrate (HB) and (HV) yield occurred at 21 and 11 mT, respectively, and the minimal yield occurred at 42 mT during exposure in the famine period. The maximum biodegradable rate constant of PHA was noted at 11 mT during exposure in the famine period.

  1. Effect of Strong Orbital Magnetic Field on the Exciton Condensation in an Extended Falicov Kimball Model

    NASA Astrophysics Data System (ADS)

    Pradhan, S.; Taraphder, A.

    2016-10-01

    A spinless, extended Falicov-Kimball model in the presence of a perpendicular magnetic field is investigated employing a self-consistent mean-field theory in two dimensions. In the presence of the field the excitonic average Δ =< di † fi > is modified: the exciton responds in subtle different ways for different values of the magnetic flux. We examine the effects of Coulomb interaction and hybridization between the localized and itinerant electrons on the excitonic average, for rational values of the applied magnetic field. The excitonic average is found to get enhanced exponentially with the Coulomb interaction while it saturates at large hybridization. The orbital magnetic field suppresses the excitonic average in general, though a strong commensurability effect of the magnetic flux on the behaviour of the excitonic order parameter is observed.

  2. Effects of interstellar particles upon the interplanetary magnetic field

    NASA Technical Reports Server (NTRS)

    Coleman, P. J., Jr.; Winter, E. M.

    1972-01-01

    The flow of interstellar neutral particles into the interplanetary medium and their subsequent ionization in the presence of the electromagnetic field of the solar wind can cause a loss of field angular momentum by the solar wind. One effect of this loss of field angular momentum is a significant unwinding of the spiral field. This effect is evaluated using simple models for neutral density and ion production. For a free-stream interstellar medium with a neutral hydrogen density of 1 per cubic centimeter and a velocity relative to the sun of 10 to 20 km per second, the spiral angle at the orbit of Jupiter will be less than its nominal value of 45 deg at the orbit of the earth.

  3. Radial current density effects on rotating magnetic field current drive in field-reversed configurations

    SciTech Connect

    Clemente, R. A.; Gilli, M.; Farengo, R.

    2008-10-15

    Steady state solutions, suitable for field-reversed configurations (FRCs) sustained by rotating magnetic fields (RMFs) are obtained by properly including three-dimensional effects, in the limit of large FRC elongation, and the radial component of Ohm's law. The steady electrostatic potential, necessary to satisfy Ohm's law, is considered to be a surface function. The problem is analyzed at the midplane of the configuration and it is reduced to the solution of two coupled nonlinear differential equations for the real and imaginary parts of the phasor associated to the longitudinal component of the vector potential. Additional constraints are obtained by requesting that the steady radial current density and poloidal magnetic flux vanish at the plasma boundary which is set at the time-averaged separatrix. The results are presented in terms of the degree of synchronism of the electrons with the RMF and compared with those obtained when radial current effects are neglected. Three important differences are observed when compared with the case without radial current density. First, at low penetration of the RMF into the plasma there is a significant increase in the driven azimuthal current. Second, the RMF amplitude necessary to access the high synchronism regime, starting from low synchronism, is larger and the difference appears to increase as the separatrix to classical skin depth ratio increases. Third, the minimum RMF amplitude necessary to sustain almost full synchronism is reduced.

  4. Effect of electron reflection on magnetized plasma sheath in an oblique magnetic field

    SciTech Connect

    Wang, Ting-Ting; Ma, J. X. Wei, Zi-An

    2015-09-15

    Magnetized plasma sheaths in an oblique magnetic field were extensively investigated by conventionally assuming Boltzmann relation for electron density. This article presents the study of the magnetized sheath without using the Boltzmann relation but by considering the electron reflection along the magnetic field lines caused by the negative sheath potential. A generalized Bohm criterion is analytically derived, and sheath profiles are numerically obtained, which are compared with the results of the conventional model. The results show that the ion Mach number at the sheath edge normal to the wall has a strong dependence on the wall potential, which differs significantly from the conventional model in which the Mach number is independent of the wall potential. The floating wall potential is lower in the present model than that in the conventional model. Furthermore, the sheath profiles are appreciably narrower in the present model when the wall bias is low, but approach the result of the conventional model when the wall bias is high. The sheath thickness decreases with the increase of ion-to-electron temperature ratio and magnetic field strength but has a complex relationship with the angle of the magnetic field.

  5. Cosmological magnetic fields

    NASA Astrophysics Data System (ADS)

    Kunze, Kerstin E.

    2013-12-01

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

  6. Effect of a weak transverse magnetic field on the microstructure in directionally solidified peritectic alloys

    PubMed Central

    Li, Xi; Lu, Zhenyuan; Fautrelle, Yves; Gagnoud, Annie; Moreau, Rene; Ren, Zhongming

    2016-01-01

    Effect of a weak transverse magnetic field on the microstructures in directionally solidified Fe-Ni and Pb-Bi peritectic alloys has been investigated experimentally. The results indicate that the magnetic field can induce the formation of banded and island-like structures and refine the primary phase in peritectic alloys. The above results are enhanced with increasing magnetic field. Furthermore, electron probe micro analyzer (EPMA) analysis reveals that the magnetic field increases the Ni solute content on one side and enhances the solid solubility in the primary phase in the Fe-Ni alloy. The thermoelectric (TE) power difference at the liquid/solid interface of the Pb-Bi peritectic alloy is measured in situ, and the results show that a TE power difference exists at the liquid/solid interface. 3 D numerical simulations for the TE magnetic convection in the liquid are performed, and the results show that a unidirectional TE magnetic convection forms in the liquid near the liquid/solid interface during directional solidification under a transverse magnetic field and that the amplitude of the TE magnetic convection at different scales is different. The TE magnetic convections on the macroscopic interface and the cell/dendrite scales are responsible for the modification of microstructures during directional solidification under a magnetic field. PMID:27886265

  7. The effect of magnetic field on electrochemically deposited calcium phosphate/collagen coatings.

    PubMed

    Zhao, Xueni; He, Jianpeng; Zhang, Jing; Wang, Xudong; Wang, Wanying

    2014-01-01

    Nanostructured calcium phosphate/collagen (CaP/COL) coatings were deposited on the carbon/carbon (C/C) composites through electrochemical deposition (ECD) under magnetic field. The effect of magnetic fields with different orientations on the morphology and composition was investigated. Both the morphology and composition of the coatings could be altered by superimposed magnetic field. Under zero magnetic field and magnetic field, three-dimensional network structure consisting of collagen fibers and CaP were formed on the C/C substrate. The applied magnetic field in the electric field helped to form nanostructured and plate-like CaP on collagen fibers. For the ECD under magnetic field, the Ca/P molar ratio of the coatings was lower than the one under B=0. This may be contributed to the decreased electrical resistance or the increased electrical conductivity of electrolyte solutions under magnetic field. The nanosized CaP/COL coatings exhibited the similar morphology to the human bone and could present excellent cell bioactivity and osteoblast functions.

  8. Magnetic field effects on viscous fingering of a ferrofluid in a radial Hele Shaw cell

    NASA Astrophysics Data System (ADS)

    Herreman, Wietze; Molho, Pierre; Neveu, Sophie

    2005-03-01

    We have studied the effects of a magnetic field on viscous fingering when a ferrofluid is pushed in a more viscous liquid in a circular Hele-Shaw cell. The main effect of the magnetic field, as already known, is to stabilize interfaces parallel to the field and to destabilize interfaces normal to the field. Depending on the growth regime (quasi static, fingering, dendritic growth), which depends on parameters like the cell thickness and oil viscosity, the combination of field effect and anisotropy is analyzed through the various observed patterns.

  9. Effects of Preferential Solvation Revealed by Time-Resolved Magnetic Field Effects.

    PubMed

    Pham, Van Thi Bich; Hoang, Hao Minh; Grampp, Günter; Kattnig, Daniel Rudolf

    2017-03-06

    External magnetic fields can impact recombination yields of photo-induced electron transfer reactions by affecting the spin dynamics in transient, spin-correlated radical pair intermediates. For exciplex-forming donor-acceptor systems, this magnetic field effect (MFE) can be investigated sensitively by studying the delayed recombination fluorescence. Here, we investigate the effect of preferential solvation in micro-heterogeneous solvent mixtures on the radical pair dynamics of the system 9,10-dimethylanthracene (fluorophore) / N,N-dimethylaniline (quencher) by means of time-resolved magnetic field effect (TR-MFE) measurements, wherein the exciplex emission is recorded in the absence and the presence of an external magnetic field using Time-Correlated Single Photon Counting (TCSPC). In micro-heterogeneous environments, the MFE of the exciplex emission occurs on a faster timescale than in iso-dielectric homogeneous solvents. In addition, the local polarity reported by the exciplex is enhanced compared to homogeneous solvent mixtures of the same macroscopic permittivity. Detailed analyses of the TR-MFE reveal that the quenching reaction directly yielding the radical ion pair is favored in micro-heterogeneous environments. This is in stark contrast to homogeneous media, for which the MFE predominantly involves direct formation of the exciplex, its subsequent dissociation to the magneto-sensitive radical pair, and re-encounters. These observations provide evidence for polar micro-domains and enhanced caging, which are shown to have a significant impact on the reaction dynamics in micro-heterogeneous binary solvents.

  10. Effects of Preferential Solvation Revealed by Time-Resolved Magnetic Field Effects

    PubMed Central

    2017-01-01

    External magnetic fields can impact recombination yields of photoinduced electron transfer reactions by affecting the spin dynamics in transient, spin-correlated radical pair intermediates. For exciplex-forming donor–acceptor systems, this magnetic field effect (MFE) can be investigated sensitively by studying the delayed recombination fluorescence. Here, we investigate the effect of preferential solvation in microheterogeneous solvent mixtures on the radical pair dynamics of the system 9,10-dimethylanthracene (fluorophore)/N,N-dimethylaniline (quencher) by means of time-resolved magnetic field effect (TR-MFE) measurements, wherein the exciplex emission is recorded in the absence and the presence of an external magnetic field using time-correlated single photon counting (TCSPC). In microheterogeneous environments, the MFE of the exciplex emission occurs on a faster time scale than in iso-dielectric homogeneous solvents. In addition, the local polarity reported by the exciplex is enhanced compared to homogeneous solvent mixtures of the same macroscopic permittivity. Detailed analyses of the TR-MFE reveal that the quenching reaction directly yielding the radical ion pair is favored in microheterogeneous environments. This is in stark contrast to homogeneous media, for which the MFE predominantly involves direct formation of the exciplex, its subsequent dissociation to the magneto-sensitive radical pair, and re-encounters. These observations provide evidence for polar microdomains and enhanced caging, which are shown to have a significant impact on the reaction dynamics in microheterogeneous binary solvents. PMID:28263599

  11. The effects of inverter magnetic fields on early seed germination of mung beans.

    PubMed

    Huang, Hsin-Hsiung; Wang, Show-Ran

    2008-12-01

    The biological effects of extremely low frequency magnetic fields (ELF MFs) on living organisms have been explored in many studies. Most of them demonstrate the biological effects caused by 50/60 Hz magnetic fields or pulsed magnetic fields. However, as the development of power electronics flourishes, the magnetic fields induced are usually in other different waveforms. This study aims to assess the effects of magnetic fields generated by inverter systems on the early growth of plants using mung beans as an example. In the experiment, an inverter which can produce sinusoidal pulsed width modulation (SPWM) voltages was used to drive 3 specially made circular coils and an AC motor. Six SPWM voltages with different fundamental frequencies (10, 20, 30, 40, 50, and 60 Hz) set on the inverter drive the circuit to produce the specific kinds of MFs. The results indicate that the magnetic field induced by a 20 or 60 Hz SPWM voltage has an enhancing effect on the early growth of mung beans, but the magnetic fields induced by SPWM voltages of other frequencies (30, 40, and 50 Hz) have an inhibitory effect, especially at 50 Hz.

  12. In-medium covariant propagator of baryons under a strong magnetic field: Effect of the intrinsic magnetic moments

    NASA Astrophysics Data System (ADS)

    Aguirre, R. M.; De Paoli, A. L.

    2016-11-01

    We obtain the covariant propagator at finite temperature for interacting baryons immersed in a strong magnetic field. The effect of the intrinsic magnetic moments on the Green function are fully taken into account. We make an expansion in terms of eigenfunctions of a Dirac field, which leads us to a compact form of its propagator. We present some simple applications of these propagators, where the statistical averages of nuclear currents and energy density are evaluated.

  13. Gibberellins are involved in effect of near-null magnetic field on Arabidopsis flowering.

    PubMed

    Xu, Chunxiao; Yu, Yang; Zhang, Yuxia; Li, Yue; Wei, Shufeng

    2017-01-01

    We previously found that flowering of Arabidopsis was suppressed by near-null magnetic field, which was related to the modification of cryptochrome. To disclose the physiological mechanism of this effect, we detected gibberellin (GA) levels and expressions of GA biosynthetic and signaling genes in wild type Arabidopsis plants and cryptochrome double mutant, cry1/cry2, grown in near-null magnetic field. We found that levels of GA4 , GA9 , GA34 , and GA51 in wild type plants in near-null magnetic field were significantly decreased compared with local geomagnetic field controls. However, GA levels in cry1/cry2 mutants in near-null magnetic field were similar to controls. Expressions of three GA20-oxidase (GA20ox) genes (GA20ox1, GA20ox2, and GA20ox3) and four GA3-oxidase (GA3ox) genes (GA3ox1, GA3ox2, GA3ox3, and GA3ox4) in wild type plants in near-null magnetic field were significantly reduced compared with controls, while expressions of GA20ox4, GA20ox5, GA2-oxidase (GA2ox) genes, and GA signaling-related genes in wild type plants in near-null magnetic field were not significantly different from controls. In contrast, expressions of all the detected GA biosynthetic and signaling genes in cry1/cry2 mutants were not affected by near-null magnetic field. Moreover, transcriptions of flowering-related genes, LFY and SOC1, in wild type plants were downregulated by near-null magnetic field, while they were not affected by near-null magnetic field in cry1/cry2 mutants. Our results suggest that the effect of near-null magnetic field on Arabidopsis flowering is GA-related, which is caused by cryptochrome-involved suppression of GA biosynthesis. Bioelectromagnetics. 38:1-10, 2017. © 2016 Wiley Periodicals, Inc.

  14. Effects of static magnetic fields on cognition, vital signs, and sensory perception: a meta-analysis.

    PubMed

    Heinrich, Angela; Szostek, Anne; Nees, Frauke; Meyer, Patric; Semmler, Wolfhard; Flor, Herta

    2011-10-01

    To evaluate whether cognitive processes, sensory perception, and vital signs might be influenced by static magnetic fields in magnetic resonance imaging (MRI), which could pose a risk for health personnel and patients, we conducted a meta-analysis of studies that examined effects of static magnetic fields. Studies covering the time from 1992 to 2007 were selected. Cohen's d effects sizes were used and combined in different categories of neuropsychology (reaction time, visual processing, eye-hand coordination, and working memory). Additionally, effects of static magnetic fields on sensory perception and vital signs were analyzed. In the category "neuropsychology," only effects on the visual system were homogeneous, showing a statistically significant impairment as a result of exposure to static magnetic fields (d = -0.415). Vital signs were not affected and effects on sensory perceptions included an increase of dizziness and vertigo, primarily caused by movement during static magnetic field gradient exposures. The number of studies dealing with this topic is very small and the experimental set-up of some of the analyzed studies makes it difficult to accurately determine the effects of static magnetic fields by themselves, excluding nonspecific factors. The implications of these results for MRI lead to suggestions for improvement in research designs.

  15. Effect of high magnetic field on structure and magnetic properties of evaporated crystalline and amorphous Fe-Sm thin films

    NASA Astrophysics Data System (ADS)

    Li, Guojian; Li, Mengmeng; Wang, Jianhao; Du, Jiaojiao; Wang, Kai; Wang, Qiang

    2017-02-01

    Crystalline and amorphous Fe-Sm thin films have been fabricated by using molecular beam vapor deposition method. Then, the effects of both variation of Sm content and application of high magnetic field during film growth on the structure and magnetic properties of the Fe-Sm films have been explored. The results show that bcc structure of the Fe-Sm films with 5.8% Sm transforms to amorphization with 33.0% Sm. Meanwhile, nanocrystallite is formed in the amorphous Fe-Sm films. However, no Fe-Sm compound exists with the change of Sm content and with the application of high magnetic field. Nevertheless, high magnetic field decreases interplanar spacing. The structural evolution has a significant effect on magnetic properties. Saturation magnetization decreases 290% from 1456 emu/cm3 to 373 emu/cm3 with the increase of Sm content from 5.8% to 33.0%. The coercivity increases 1225% from 20 Oe to 265 Oe. Meanwhile, both the saturation magnetization and coercivity of the films decrease with the application of high magnetic field. The reason has been discussed.

  16. Effect of a magnetic field in simulating the plume field of an anode layer Hall thruster

    SciTech Connect

    Choi, Yongjun; Boyd, Iain D.; Keidar, Michael

    2009-01-01

    In this study, we present axisymmetric simulations of xenon plasma plume flow fields from a D55 anode layer Hall thruster. A hybrid particle-fluid method is used for the simulations. The magnetic field surrounding the Hall thruster exit is included in the calculation. The plasma properties obtained from a hydrodynamic model are used as boundary conditions for the simulations. The electron properties are calculated using the Boltzmann model and a detailed fluid model, collisions of heavy particle are modeled with the direct simulation Monte Carlo method, and ion transport in the electric field uses the particle-in-cell technique. The accuracy of the simulation is assessed through comparison with various measured data. It is found that a magnetic field significantly affects the profile of the plasma in the detailed model. The plasma has a potential of 80 V at 10 mm from the thruster exit in the case of zero magnetic field, which decreases to 60 V when the magnetic field is included. Results predicted by the detailed model with the magnetic field are found to be in better agreement with experimental data.

  17. Effects of conductor sag on spatial distribution of power line magnetic field

    SciTech Connect

    Mamishev, A.V.; Nevels, R.D.; Russell, B.D.

    1996-07-01

    Traditional extremely low frequency (ELF) magnetic field computation techniques assume that the current carrying power line conductors are straight horizontal wires. This assumption results in a model whose magnetic fields are distorted from those produced in reality. An exact solution and an approximation are proposed for modeling magnetic fields produced by the sagged conductors of power lines, by taking advantage of the fact that the equation of the catenary exactly describes the line sag. The proposed approaches differ in the required computational burden and in the precision of the results. A field mapping measurement example illustrates the applicability and the need for this analysis. The relative importance of the catenary effect is discussed.

  18. Effect of a magnetic field on the adsorptive removal of methylene blue onto wheat straw biochar.

    PubMed

    Li, Guoting; Zhu, Weiyong; Zhang, Chunyu; Zhang, Shen; Liu, Lili; Zhu, Lingfeng; Zhao, Weigao

    2016-04-01

    Biochar pyrolyzed from wheat straw was innovatively used for the adsorptive removal of cationic dye methylene blue through exposure to a magnetic field. The adsorption capability of the biochar pyrolyzed at 200 °C exceeded that of samples pyrolyzed at higher temperatures. The surface acidic functional groups of wheat straw biochar were deduced to be more sensitive to the effects of the external magnetic field. The enhancement of the magnetic field achieved by increases in the initial dye concentration, and a decrease in the biochar dosage and solution pH, were more significant compared with those caused by other conditions. Kinetic experiments indicated that chemisorption occurred during adsorption. The qmax values for dye adsorption without, and with, an external magnetic field were found to be 46.6 and 62.5mg/g, respectively. These demonstrated that wheat straw biochar could be used for the efficient adsorption of pollutants when assisted by an external magnetic field.

  19. Effect of the magnetic field direction on forced convection heat transfer enhancements in ferrofluids

    NASA Astrophysics Data System (ADS)

    Cherief, Wahid; Avenas, Yvan; Ferrouillat, Sébastien; Kedous-Lebouc, Afef; Jossic, Laurent; Berard, Jean; Petit, Mickael

    2015-07-01

    Applying a magnetic field on a ferrofluid flow induces a large increase of the convective heat transfer coefficient. In this paper, the thermal-hydraulic behaviors of two commercial ferrofluids are compared. The variations of both the pressure drop and the heat transfer coefficient due to the magnetic field are measured in the following conditions: square duct, laminar flow and uniform wall heat flux. The square section with two insulated walls allows for the characterization of the effect of the magnetic field direction. The experimental results show that the heat transfer is better enhanced when the magnetic field is perpendicular to the heat flux. In the best case, the local heat transfer coefficient increase is about 75%. On the contrary, another experimental setup shows no enhancement of thermal conductivity when the magnetic field is perpendicular to the heat flux. Contribution to the topical issue "Electrical Engineering Symposium (SGE 2014) - Elected submissions", edited by Adel Razek

  20. MO-G-BRF-09: Investigating Magnetic Field Dose Effects in Mice: A Monte Carlo Study

    SciTech Connect

    Rubinstein, A; Guindani, M; Followill, D; Melancon, A; Hazle, J; Court, L

    2014-06-15

    Purpose: In MRI-linac treatments, radiation dose distributions are affected by magnetic fields, especially at high-density/low-density interfaces. Radiobiological consequences of magnetic field dose effects are presently unknown; therefore, preclinical studies are needed to ensure the safe clinical use of MRI-linacs. This study investigates the optimal combination of beam energy and magnetic field strength needed for preclinical murine studies. Methods: The Monte Carlo code MCNP6 was used to simulate the effects of a magnetic field when irradiating a mouse-sized lung phantom with a 1.0cmx1.0cm photon beam. Magnetic field effects were examined using various beam energies (225kVp, 662keV[Cs-137], and 1.25MeV[Co-60]) and magnetic field strengths (0.75T, 1.5T, and 3T). The resulting dose distributions were compared to Monte Carlo results for humans with various field sizes and patient geometries using a 6MV/1.5T MRI-linac. Results: In human simulations, the addition of a 1.5T magnetic field caused an average dose increase of 49% (range:36%–60%) to lung at the soft tissue-to-lung interface and an average dose decrease of 30% (range:25%–36%) at the lung-to-soft tissue interface. In mouse simulations, the magnetic fields had no effect on the 225kVp dose distribution. The dose increases for the Cs-137 beam were 12%, 33%, and 49% for 0.75T, 1.5T, and 3.0T magnetic fields, respectively while the dose decreases were 7%, 23%, and 33%. For the Co-60 beam, the dose increases were 14%, 45%, and 41%, and the dose decreases were 18%, 35%, and 35%. Conclusion: The magnetic field dose effects observed in mouse phantoms using a Co-60 beam with 1.5T or 3T fields and a Cs-137 beam with a 3T field compare well with those seen in simulated human treatments with an MRI-linac. These irradiator/magnet combinations are suitable for preclinical studies investigating potential biological effects of delivering radiation therapy in the presence of a magnetic field. Partially funded by Elekta.

  1. Effects of high magnetic fields on thermal convection of conductive aqueous solution

    NASA Astrophysics Data System (ADS)

    Wang, Yan; Hirota, Noriyuki; Okada, Hidehiko; Sakka, Yoshio

    2015-07-01

    Effects of magnetic fields on the thermal convection in conductive aqueous solutions at ambient temperatures have been studied through heat transport measurements combined with shadowgraph technique-based visualization. The suppression of thermal convection by magnetic field was in fact observed in conductive diamagnetic aqueous solutions of ammonium sulfate. The magnitude of the suppression was found to depend on the applied magnetic field and the electrical conductivity of the sample fluid. These effects are qualitatively understood by assuming that Lorentz force acting on the fluid is a main player. Based on these results, a control method of heat transfer process using high magnetic fields has been demonstrated. It seems feasible to understand the behaviors of liquid metals by using electrolytes aqueous solution combined with a superconducting magnet, since flow conditions thereby are regarded as similar to those for liquid metals in industrial electromagnets.

  2. The effect of magnetic field intensity and treatment time on graphene / epoxy composites’ fracture toughness

    NASA Astrophysics Data System (ADS)

    Tian, Z. Q.; Zhang, L.; Fu, S.; Yuan, R. H.; Dong, Z. W.; Ren, X. M.

    2016-07-01

    The effect of the intensity of the magnetic field and the treatment time on the fracture toughness of graphene/epoxy composites is researched. Also, the mechanism of the effect of the magnetic field on the fracture toughness of graphene/epoxy composites and a method to improve the impact resistance is explored. Then, three-point bending tests are employed to characterize the fracture toughness of graphene/epoxy composite. The results show that the intervention of magnetic field could induce GNS to generated orientation arrangement, improving the fracture toughness of the graphene/epoxy composite. When the intensity of the magnetic field was increased, the growth rate of the fracture toughness slowed. However, when 2T magnetic was used to synthetically process the material, and when the processing time was less than 50 min, the fracture toughness of the composite material increased significantly.

  3. Effect of different magnetic field distributions on laminar ferroconvection heat transfer in horizontal tube

    NASA Astrophysics Data System (ADS)

    Sheikhnejad, Yahya; Hosseini, Reza; Saffar-avval, Majid

    2015-09-01

    The forced convection heat transfer of ferrofluid steady state laminar flow through a circular axisymmetric horizontal pipe under different magnetic field is the focus of this study. The pipe is under constant heat flux while different linear axial magnetic fields were applied on the ferrofluid with equal magnetic energy. In this scenario, viscosity of ferrofluid is temperature dependent, to capture ferrofluid real behavior a nonlinear Langevin equation was considered for equilibrium magnetization. For this purpose, the set of nonlinear governing PDEs was solved using proper CFD techniques: the finite volume method and SIMPLE algorithm were used to discretize and numerically solve the governing equation in order to obtain thermohydrodynamic flow characteristics. The numerical results show a promising enhancement of up to 135.7% in heat transfer as a consequence of the application of magnetic field. The magnetic field also increases pressure loss of up to 77% along the pipe; but effectiveness (favorable to unfavorable effect ratio) of the magnetic field as a performance index economically justifies its application such that higher magnetic field intensity causes higher effectiveness of up to 1.364.

  4. Magnetic fields from inflation?

    SciTech Connect

    Demozzi, Vittoria; Mukhanov, Viatcheslav; Rubinstein, Hector E-mail: viatcheslav.mukhanov@physik.uni-muenchen.de

    2009-08-01

    We consider the possibility of generation of the primordial magnetic field on inflation and show that the effect of the back reaction of this field can be very important. Assuming that the back reaction does not spoil inflation we find a rather strong restriction on the amplitude of the primordial field which could be generated on inflation. Namely, this amplitude recalculated to the present epoch cannot exceed 10{sup −32}G in Mpc scales. This field seems to be too small to be amplified to the observable values by a possible dynamo mechanism.

  5. Numerical simulation of dielectric bubbles coalescence under the effects of uniform magnetic field

    NASA Astrophysics Data System (ADS)

    Hadidi, Amin; Jalali-Vahid, Davood

    2016-06-01

    In this research, the co-axial coalescence of a pair of gas bubbles rising in a viscous liquid column under the effects of an external uniform magnetic field is simulated numerically. Considered fluids are dielectric, and applied magnetic field is uniform. Effects of different strengths of magnetic field on the interaction of in-line rising bubbles and coalescence between them were investigated. For numerical modeling of the problem, a computer code was developed to solve the governing equations which are continuity, Navier-Stokes equation, magnetic field equation and level set and reinitialization of level set equations. The finite volume method is used for the discretization of the continuity and momentum equations using SIMPLE scheme where the finite difference method is used to discretization of the magnetic field equations. Also a level set method is used to capture the interface of two phases. The results are compared with available numerical and experimental results in the case of no-magnetic field effect which show a good agreement. It is found that uniform magnetic field accelerates the coalescence of the bubbles in dielectric fluids and enhances the rise velocity of the coalesced bubble.

  6. Behavioral effects on rats of motion within a high static magnetic field.

    PubMed

    Houpt, Thomas A; Carella, Lee; Gonzalez, Dani; Janowitz, Ilana; Mueller, Anthony; Mueller, Kathleen; Neth, Bryan; Smith, James C

    2011-03-01

    Some human subjects report vestibular disturbances such as vertigo, apparent motion, and nausea around or within high strength MRI systems operating at 4 T to 9.4 T. These vestibular effects have been ascribed to the consequences of movement through the high magnetic field. We have previously found that exposure to magnetic fields above 7 T suppresses rearing, causes locomotor circling, and induces conditioned taste aversion (CTA) in rodents. The present experiments were designed to test the effects on rats of motion through the magnetic field of the 14.1 T superconducting magnet. In Experiment 1, we compared the effects of multiple rapid insertions and removals from the center of the magnet to the effects of continuous exposure. Repeated traversal of the magnetic field gradient with only momentary exposure to 14.1 T was sufficient to suppress rearing and induce a significant CTA. Repeated insertion and removal from the magnet, however, did not have a greater effect than a single 30-min exposure on either acute locomotor behavior or CTA acquisition. Prolonged exposure was required to induce locomotor circling. In the second series of experiments, we controlled the rate of insertion and removal by means of an electric motor. Locomotor circling appeared to be dependent on the speed of insertion and removal, but the suppression of rearing and the acquisition of CTA were independent of speed of insertion and removal. In Experiment 3, we inserted rats into the center of the magnet and then rotated them about their rostral-caudal axis during a 30-min 14.1 T exposure. Rotation within the magnet did not modulate the behavioral effects of exposure. We conclude that, in rats, movement through the steep gradient of a high magnetic field has some behavioral effects, but sustained exposure to the homogenous center of the field is required for the full behavioral consequences.

  7. Magnetic field effects on dental amalgam in divers welding and cutting electrically underwater

    SciTech Connect

    Ortendahl, T.W.; Hoegstedt, P.

    1988-11-01

    Divers have for some years been complaining about a metallic taste in the mouth while electrically welding and cutting underwater. This paper reports on results from an assessment of this problem. It was hypothesized that the magnetic fields arising from the welding or cutting current could correlate with the reported symptoms. The intraoral magnetic flux density was calculated to 1.15 mT, at 650 ADC, in a normal cutting situation. This was verified in vivo. This magnetic field was shown to contain an AC component that is a candidate for inducing secondary currents in the oral tissues and restorative materials. Five submerged divers exposed to a magnetic field of 0.35 mT did not report any metallic taste. Magnetophosphenes were reported by 1 diver. (Magnetophosphenes are luminous impressions due to excitement of the retina by a magnetic field in addition to or in place of impingement of light rays.) Only a slight shielding effect to magnetic fields was observed due to a copper-brass helmet. An in vitro model for exposure of dental amalgams to magnetic fields was designed. Recommendations for decreasing the magnetic field surrounding the diver in practical work is given.

  8. Magnetic field effects on dental amalgam in divers welding and cutting electrically underwater.

    PubMed

    Ortendahl, T W; Högstedt, P

    1988-11-01

    Divers have for some years been complaining about a metallic taste in the mouth while electrically welding and cutting underwater. This paper reports on results from an assessment of this problem. It was hypothesized that the magnetic fields arising from the welding or cutting current could correlate with the reported symptoms. The intraoral magnetic flux density was calculated to 1.15 mT, at 650 ADC, in a normal cutting situation. This was verified in vivo. This magnetic field was shown to contain an AC component that is a candidate for inducing secondary currents in the oral tissues and restorative materials. Five submerged divers exposed to a magnetic field of 0.35 mT did not report any metallic taste. Magnetophosphenes were reported by 1 diver. (Magnetophosphenes are luminous impressions due to excitement of the retina by a magnetic field in addition to or in place of impingement of light rays.) Only a slight shielding effect to magnetic fields was observed due to a copper-brass helmet. An in vitro model for exposure of dental amalgams to magnetic fields was designed. Recommendations for decreasing the magnetic field surrounding the diver in practical work is given.

  9. Genotoxic Effects of Superconducting Static Magnetic Fields (SMFs) on Wheat (Triticum aestivum) Pollen Mother Cells (PMCs)

    NASA Astrophysics Data System (ADS)

    Zhang, Pingping; Yin, Ruochun; Chen, Zhiyou; Wu, Lifang; Yu, Zengliang

    2007-04-01

    The effects of superconducting static magnetic fields (SMFs) on the pollen mother cells (PMCs) of wheat were investigated in order to evaluate the possible genotoxic effect of such non-ionizing radiation. The seeds of wheat were exposed to static magnetic fields with either different magnetic flux densities (0, 1, 3, 5 and 7 Tesla) for 5 h or different durations (1, 3 and 5 h) at a magnetic flux density of 7 Tesla. The seeds were germinated at 23oC after exposure and the seedlings were transplanted into the field. The PMCs from young wheat ears were taken and slides were made following the conventional method. The genotoxic effect was evaluated in terms of micronucleus (MN), chromosomal bridge, lagging chromosome and fragments in PMCs. Although the exposed groups of a low field intensity (below 5 Tesla) showed no statistically significant difference in the aberration frequency compared with the unexposed control groups and sham exposed groups, a significant increase in the chromosomal bridge, lagging chromosome, triple-polar segregation or micronucleus was observed at a field strength of 5 Tesla or 7 Tesla, respectively. The analysis of dose-effect relationships indicated that the increased frequency of meiotic abnormal cells correlated with the flux density of the magnetic field and duration, but no linear relationship was observed. Such statistically significant differences indicated a potential genotoxic effect of high static magnetic fields above 5 T.

  10. Finite temperature Casimir effect for massless Majorana fermions in a magnetic field

    SciTech Connect

    Erdas, Andrea

    2011-01-15

    The zeta function regularization technique is used to study the finite temperature Casimir effect for a massless Majorana fermion field confined between parallel plates and satisfying bag boundary conditions. A magnetic field perpendicular to the plates is included. An expression for the zeta function is obtained, which is exact to all orders in the magnetic field strength, temperature and plate distance. The zeta function is used to calculate the Helmholtz free energy of the Majorana field and the pressure on the plates, in the case of weak magnetic field and strong magnetic field. In both cases, simple analytic expressions are obtained for the free energy and pressure which are very accurate and valid for all values of the temperature and plate distance.

  11. Effect of a Transverse Magnetic Field on Stray Grain Formation of Ni-Based Single Crystal Superalloy During Directional Solidification

    NASA Astrophysics Data System (ADS)

    Xuan, Weidong; Liu, Huan; Lan, Jian; Li, Chuanjun; Zhong, Yunbo; Li, Xi; Cao, Guanghui; Ren, Zhongming

    2016-12-01

    The effect of a transverse magnetic field on stray grain formation during directional solidification of superalloy was investigated. Experimental results indicated that the transverse magnetic field effectively suppressed the stray grain formation on the side the primary dendrite diverges from the mold wall. Moreover, the quenched experimental results indicated that the solid/liquid interface shape was obviously changed in a transverse magnetic field. The effect of a transverse magnetic field on stray grain formation was discussed.

  12. Effect of interplanetary magnetic field on ionosphere over the magnetic equator

    NASA Technical Reports Server (NTRS)

    Rastogi, R. G.; Patel, V. L.

    1975-01-01

    Large and quick changes of the latitude of the interplanetary magnetic field from its southward to northward direction are shown to be associated with the disappearance of the Es-q layer (Knecht, 1959) at the equatorial ionosphere during the daytime or with the reversal of E region horizontal and F region vertical electron drifts during both night and day. This phenomenon is suggested as the imposition of an electric field in the ionosphere in a direction opposite to that of the Sq electric field. The resultant electrostatic field on the equatorial ionosphere would be decreased or even reversed from its normal direction, resulting in the reduction of electron drift velocity. When the normal Sq field is over-compensated by the magnetospheric electric field, the electron drifts are reversed and the irregularities in the E region due to the cross-field instabilities are inhibited, resulting in the sudden disappearance of the Es-q layers.

  13. Preliminary Results of Performance Measurements on a Cylindrical Hall-Effect Thruster with Magnetic Field Generated by Permanent Magnets

    NASA Technical Reports Server (NTRS)

    Polzin, K. A.; Raitses, Y.; Merino, E.; Fisch, N. J.

    2008-01-01

    The performance of a low-power cylindrical Hall thruster, which more readily lends itself to miniaturization and low-power operation than a conventional (annular) Hall thruster, was measured using a planar plasma probe and a thrust stand. The field in the cylindrical thruster was produced using permanent magnets, promising a power reduction over previous cylindrical thruster iterations that employed electromagnets to generate the required magnetic field topology. Two sets of ring-shaped permanent magnets are used, and two different field configurations can be produced by reorienting the poles of one magnet relative to the other. A plasma probe measuring ion flux in the plume is used to estimate the current utilization for the two magnetic configurations. The measurements indicate that electron transport is impeded much more effectively in one configuration, implying a higher thrust efficiency. Preliminary thruster performance measurements on this configuration were obtained over a power range of 100-250 W. The thrust levels over this power range were 3.5-6.5 mN, with anode efficiencies and specific impulses spanning 14-19% and 875- 1425 s, respectively. The magnetic field in the thruster was lower for the thrust measurements than the plasma probe measurements due to heating and weakening of the permanent magnets, reducing the maximum field strength from 2 kG to roughly 750-800 G. The discharge current levels observed during thrust stand testing were anomalously high compared to those levels measured in previous experiments with this thruster.

  14. Magnetic field instability in a neutron star driven by the electroweak electron-nucleon interaction versus the chiral magnetic effect

    NASA Astrophysics Data System (ADS)

    Dvornikov, Maxim; Semikoz, Victor B.

    2015-03-01

    We show that the Standard Model electroweak interaction of ultrarelativistic electrons with nucleons (the e N interaction) in a neutron star (NS) permeated by a seed large-scale helical magnetic field provides its growth up to ≳1 015 G during a time comparable with the ages of young magnetars ˜1 04 yr . The magnetic field instability originates from the parity violation in the e N interaction entering the generalized Dirac equation for right and left massless electrons in an external uniform magnetic field. We calculate the average electric current given by the solution of the modified Dirac equation containing an extra current for right and left electrons (positrons), which turns out to be directed along the magnetic field. Such a current includes both a changing chiral imbalance of electrons and the e N potential given by a constant neutron density in a NS. Then we derive the system of the kinetic equations for the chiral imbalance and the magnetic helicity which accounts for the e N interaction. By solving this system, we show that a sizable chiral imbalance arising in a neutron protostar due to the Urca process eL-+p →N +νeL diminishes very rapidly because of a huge chirality-flip rate. Thus the e N term prevails over the chiral effect, providing a huge growth of the magnetic helicity and the helical magnetic field.

  15. Delineation of electric and magnetic field effects of extremely low frequency electromagnetic radiation on transcription

    SciTech Connect

    Greene, J.J.; Skowronski, W.J.; Mullins, J.M.; Nardone, R.M.; Penafiel, M.; Meister, R. )

    1991-01-31

    The relative effects of the electric and magnetic field components of extremely low frequency electromagnetic radiation (ELF) on transcription were examined in human leukemia HL-60 cells. Delineation of the individual field contributions was achieved by irradiating cells in separate concentric compartments of a culture dish within a solenoid chamber. This exposure system produced a homogeneous magnetic field with a coincident electric field whose strength varied directly with distance from the center of the culture dish. Irradiation of HL-60 cells with sine wave ELF at 60 Hz and a field strength of 10 Gauss produced a transient increase in the transcriptional rates which reached a maximum of 50-60% enhancement at 30-120 minutes of irradiation and declined to near basal levels by 18 hours. Comparison of transcription responses to ELF of cells in different concentric compartments revealed that the transcriptional effects were primarily the result of the electric field component with little or no contribution from the magnetic field.

  16. Bio-effects of high magnetic fields: a study using a simple animal model.

    PubMed

    Weiss, J; Herrick, R C; Taber, K H; Contant, C; Plishker, G A

    1992-01-01

    The desire to do clinical imaging and spectroscopy at magnetic field strengths greater than 2 Tesla (T) necessitates investigation of possible bioeffects at these high fields. A simple T-maze was utilized to evaluate the aversive effects of exposure to three levels of static magnetic field (0, 1.5, and 4 T). The right arm of the maze extended into the center of a 30-cm horizontal bore magnet, while the left arm extended into a mock magnet bore with the same dimensions. The self-shielded design of the magnet reduces the fringe field to zero within 1 m of the bore, placing the start box of the maze outside the 5-G line of the magnet. Each rat performed a total of ten trials at each level of magnetic field strength. A follow-up subset was run at 4 T with the maze reversed. At 0 T, the rats entered the magnet freely. No significant differences from the control were observed at 1.5 T. At 4 T, however, in 97% of the trials the rats would not enter the magnet. In the maze-reversed subset a majority of the rats turned toward the magnet, indicating that they had learned an aversive response from the previous trials at 4 T. However, in only 4 decisions out of 58 did the rats actually enter the magnet. Eighteen decisions to turn around were made at the edge of the magnet in a region of strong field gradients (up to 13 T/m) and a field strength up to 1.75 T.(ABSTRACT TRUNCATED AT 250 WORDS)

  17. VECTOR TOMOGRAPHY FOR THE CORONAL MAGNETIC FIELD. II. HANLE EFFECT MEASUREMENTS

    SciTech Connect

    Kramar, M.; Inhester, B.; Lin, H.; Davila, J. E-mail: Joseph.M.Davila@nasa.gov E-mail: lin@ifa.hawaii.edu

    2013-09-20

    In this paper, we investigate the feasibility of saturated coronal Hanle effect vector tomography or the application of vector tomographic inversion techniques to reconstruct the three-dimensional magnetic field configuration of the solar corona using linear polarization measurements of coronal emission lines. We applied Hanle effect vector tomographic inversion to artificial data produced from analytical coronal magnetic field models with equatorial and meridional currents and global coronal magnetic field models constructed by extrapolation of real photospheric magnetic field measurements. We tested tomographic inversion with only Stokes Q, U, electron density, and temperature inputs to simulate observations over large limb distances where the Stokes I parameters are difficult to obtain with ground-based coronagraphs. We synthesized the coronal linear polarization maps by inputting realistic noise appropriate for ground-based observations over a period of two weeks into the inversion algorithm. We found that our Hanle effect vector tomographic inversion can partially recover the coronal field with a poloidal field configuration, but that it is insensitive to a corona with a toroidal field. This result demonstrates that Hanle effect vector tomography is an effective tool for studying the solar corona and that it is complementary to Zeeman effect vector tomography for the reconstruction of the coronal magnetic field.

  18. Magnetic fields as triggers of microalga growth: evaluation of its effect on Spirulina sp.

    PubMed

    Deamici, Kricelle Mosquera; Costa, Jorge Alberto Vieira; Santos, Lucielen Oliveira

    2016-11-01

    This study aimed at evaluating the influence of magnetic field on the growth and biomass composition of Spirulina sp., cultivated in vertical tubular photobioreactors. Magnetic fields of 5, 30 and 60mT generated by electric current and ferrite magnets were applied at different lengths of time. The magnetic field of 30 and 60mT for 1hd(-1) stimulated the growth, thus leading to higher biomass concentration by comparison with the control culture. Increase in productivity, protein and carbohydrate contents were 105.1% (60mT for 1hd(-1)), 16.6% (60mT for 24hd(-1)) and 133.2% (30mT for 24hd(-1)), respectively. These values were higher than the ones of the control. Results showed that magnetic field may influence the growth of Spirulina sp., since it triggers a stimulating effect and can leads to twofold biomass concentration in equal cultivation time periods.

  19. Kinetic effects of magnetic field on the γ /α interface controlled reaction in iron

    NASA Astrophysics Data System (ADS)

    Garcin, Thomas; Rivoirard, Sophie; Gaucherand, Franck; Beaugnon, Eric

    2010-05-01

    The effect of magnetic field on the austenite (γ) to ferrite (α) transformation kinetics is studied in iron by means of dilatation measurements under magnetic field. In the frame of the Johnson-Mehl-Avrami-Kolmogorov analysis and considering a spherical growth mode for the ferrite grains, the Avrami exponent and the activation energy for the interface mobility are calculated. These parameters are found to be weakly influenced by the application of a 16 T magnetic field. This indicates that they are related mainly to the total amount of energy available for the transformation whatever its origin (whether magnetic or chemical). Whereas the magnetic field strongly affects the α /γ thermodynamic equilibrium through the Gibbs free energy of phases, it has a non noticeable influence on the transformation kinetics itself.

  20. Experimental Investigation of Effectiveness of Magnetic Field on Food Freezing Process

    NASA Astrophysics Data System (ADS)

    Suzuki, Toru; Takeuchi, Yuri; Masuda, Kazunori; Watanabe, Manabu; Shirakashi, Ryo; Fukuda, Yutaka; Tsuruta, Takaharu; Yamamoto, Kazutaka; Koga, Nobumitsu; Hiruma, Naoya; Ichioka, Jun; Takai, Kiyoshi

    Recently, several food refrigeration equipments that utilize magnetic field have attracted much attention from food production companies, consumers and mass media. However, the effectiveness of the freezers is not scientifically examined. Therefore, the effectiveness should be clarified by experiments or theoretical considerations. In this study, the effect of weak magnetic field (about 0.0005 T) on freezing process of several kinds of foods was investigated by using a specially designed freezer facilitated with magnetic field generator. The investigation included the comparison of freezing curves, drip amount, physicochemical evaluations on color and texture, observation of microstructure, and sensory evaluation. From the results of the control experiments, it can be concluded that weak magnetic field around 0.0005 T provided no significant difference on temperature history during freezing and on the qualities of frozen foods, within our experimental conditions.

  1. Differential magnetic field effects on heart rate and nociception in anosmic pigeons.

    PubMed

    Del Seppia, Cristina; Mencacci, Resi; Luschi, Paolo; Varanini, Maurizio; Ghione, Sergio

    2012-05-01

    Several studies have shown that exposure to altered magnetic fields affects nociception by suppressing stress-induced hypoalgesia, and that this effect is reduced or abolished if the treatment is performed in the absence of light. This raises the question as to whether other sources of sensory stimuli may also modulate these magnetic effects. We investigated the possible role of olfaction in the magnetically induced effects on sensitivity to nociceptive stimuli and heart rate (HR) in restraint-stressed homing pigeons exposed to an Earth-strength, irregularly varying (<1 Hz) magnetic field. The magnetic treatment decreased the nociceptive threshold in normally smelling birds and an opposite effect was observed in birds made anosmic by nostril plugging. Conversely, no differential effect of olfactory deprivation was observed on HR, which was reduced by the magnetic treatment both in smelling and anosmic pigeons. The findings highlight an important role of olfactory environmental information in the mediation of magnetic effects on nociception, although the data cannot be interpreted unambiguously because of the lack of an additional control group of olfactory-deprived, non-magnetically exposed pigeons. The differential effects on a pigeon's sensitivity to nociceptive stimulus and HR additionally indicate that the magnetic stimuli affect nociception and the cardiovascular system in different ways.

  2. Effects of exomoon’s magnetic field on generation of radio emissions

    NASA Astrophysics Data System (ADS)

    Griffith, John; Noyola, Joaquin; Satyal, Suman; Musielak, Zdzislaw E.

    2017-01-01

    In the recent work by Noyola et al. (2014, 2016), a novel technique of detection of exomoons through the radio emissions produced by the magnetic field interactions between exoplanet-exomoon pair is emulated based upon the processes occurring in the Jupiter-Io system. Their calculations have shown that the radio signal from the distant extra-solar planetary systems is detectable by current technology provided that the systems emanating the radio waves are relatively closer, have some form of atmosphere, and have larger exomoons. In this work, we explore the effect of exomoon’s magnetic field on the radio emission processes by considering a hypothetical magnetic exomoon and re-calculating the resulting radio flux. Then, a limit to the exomoon’s magnetic field is proposed based on the signal amplification versus the dampening effect the magnetic field induces on the secondary conditions such as the containment of ions within the exomoon’s magnetic field and the effect of the plasma torus density that co-orbits with the moon. The energy from the exomoon’s magnetic field is expected to amplify the radio signal, hence increasing the probability of detection of the first exomoons.

  3. Effect of drifts on the diffusion of runaway electrons in tokamak stochastic magnetic fields

    SciTech Connect

    Myra, J.R.; Catto, P.J. )

    1992-01-01

    The quasilinear diffusion of runaway electrons in tokamak stochastic magnetic fields is examined. Previous models are generalized with respect to the spatial location and coherency of the perturbing magnetic fields, treatment of the radial as well as poloidal drift motion of the electrons, and the role of sidebands that arise from the beating of the electron drift motion with the applied perturbing fields. It is found that drift effects act to reduce the level of quasilinear diffusion by an amount that depends on the poloidal distribution of the magnetic turbulence. The results are employed to estimate the internal magnetic fluctuation levels at the edge during recent experiments on the TEXT tokamak (Phys. Fluids B {bold 3}, 2038 (1991)), where the drift modification effects are shown to be small. It is inferred that intrinsic magnetic turbulence controls runaway diffusion, but not the thermal diffusivity of the background electrons.

  4. Rashba spin orbit interaction effect on nonlinear optical properties of quantum dot with magnetic field

    NASA Astrophysics Data System (ADS)

    Jha, Pradip Kumar; Kumar, Manoj; Lahon, Siddhartha; Gumber, Sukirti; Mohan, Man

    2014-01-01

    Here we have investigated the influence of external magnetic field on the optical absorption and refractive index changes of a parabolically confined quantum dot in the presence of Rashba spin orbit interaction. We have used density matrix formulation for obtaining optical properties within the effective mass approximation. The results are presented as a function of quantum confinement potential, magnetic field, Rashba spin orbit interaction strength and photon energy. Our results indicate the important influence of magnetic field on the peak positions of absorption coefficient and refractive index changes. The role of confinement strength and spin orbit interaction strength as control parameters on the linear and nonlinear properties have been demonstrated.

  5. Magnetic field effect on the liquidus boundary of Bi-Mn binary system

    NASA Astrophysics Data System (ADS)

    Mitsui, Yoshifuru; Koyama, Keiichi; Oikawa, Katsunari; Watanabe, Kazuo

    2014-10-01

    The magnetic field effect (MFE) on liquidus boundary of Bi-Mn binary system was investigated by differential thermal analysis (DTA) and the computer coupling of phase diagram method (CALPHAD). The liquidus boundary for Bi-18at.%Mn and Bi-24at.%Mn rose clearly by the application of the magnetic fields. The MFE for liquidus boundary temperature Tliq changed from ΔTliq∝B2 to ΔTliq∝B because of the large increase of the peritectic temperature from BiMn and BiMn1.08 by the application of magnetic field.

  6. On the effects of an imposed magnetic field on the elliptical instability in rotating spheroids

    NASA Astrophysics Data System (ADS)

    Herreman, W.; Le Bars, M.; Le Gal, P.

    2009-04-01

    The effects of an imposed magnetic field on the development of the elliptical instability in a rotating spheroid filled with a conducting fluid are considered. Theoretical and experimental studies of the spin-over mode, as well as a more general short-wavelength Lagrangian approach, demonstrate that the linear growth rate of the instability and the square amplitude of the induced magnetic field fall down linearly with the square of the imposed magnetic field. Application of the results to the Galilean moon Io confirms the fundamental role played by the elliptical instability at the planetary scale.

  7. Effect of Magnetic Field Gradient on Plasma Detachment Induced by Breaking of Adiabatic Plasma Expansion

    NASA Astrophysics Data System (ADS)

    Chung, K. S.; Kim, June Young; Chung, Kyoung-Jae; Hwang, Y. S.

    2016-10-01

    A magnetic field gradient that is a variation in the magnetic field around the ion flow has been investigated as a primary parameter for ion detachment in the magnetic nozzle geometries. Some scale lengths of magnetic field are controlled by two solenoid coils outside the diffusion chamber of a ECR-driven linear plasma device. The axial and radial profiles of the plasma potential and electron temperature are measured by a Langmuir probe array for the various magnetic field configurations in the downstream. The local adiabaticity, strong constant magnetic moment, is satisfied with a linear relationship between the change in effective electron temperature and the change in plasma potential in the low magnetic field gradient. Whereas, with an increasing non-homogeneity of the magnetic field in the direction of the flow, the breaking of adiabatic plasma expansion is identified to measure the nonlinear process which is the variation for an adiabatic exponent. Such the loss of adiabaticity is also explained in terms of non-adiabaticity parameter i.e. degree of demagnetization. This research was supported by National R&D Program through the National Research Foundation of Korea (NRF) funded by the Ministry of Science, ICT & Future Planning (Nos. 2014M1A7A1A02030165 and 2014M1A7A1A03045367).

  8. The effect of magnetic field on nanofluids heat transfer through a uniformly heated horizontal tube

    NASA Astrophysics Data System (ADS)

    Hatami, N.; Kazemnejad Banari, A.; Malekzadeh, A.; Pouranfard, A. R.

    2017-02-01

    In this study, the effects of magnetic field on forced convection heat transfer of Fe3O4-water nanofluid with laminar flow regime in a horizontal pipe under constant heat flux conditions were studied, experimentally. The convective heat transfer of magnetic fluid flow inside the heated pipe with uniform magnetic field was measured. Fe3O4 nanoparticles with diameters less than 100 nm dispersed in water with various volume concentrations are used as the test fluid. The effect of the external magnetic field (Ha = 33.4 ×10-4 to 136.6 ×10-4) and nanoparticle concentrations (φ = 0, 0.1, 0.5, 1%) on heat transfer characteristics were investigated. Results showed that by the presence of a magnetic field, increase in nanoparticle concentration caused reduction of convection heat transfer coefficient. In this condition, heat transfer decreased up to 25%. Where, in the absence of an external magnetic field, adding magnetic nanoparticles increased convection heat transfer more than 60%. It was observed that the Nusselt number decreased by increasing the Hartmann number at a specified concentration of magnetic nanofluids, that reduction about 25% in heat transfer rate could be found.

  9. Magnetic-field-dosimetry system

    DOEpatents

    Lemon, D.K.; Skorpik, J.R.; Eick, J.L.

    1981-01-21

    A device is provided for measuring the magnetic field dose and peak field exposure. The device includes three Hall-effect sensors all perpendicular to each other, sensing the three dimensional magnetic field and associated electronics for data storage, calculating, retrieving and display.

  10. Photonic Magnetic Field Sensor

    DTIC Science & Technology

    2007-11-02

    reduce feedback in fiber optic links can be the basis for excellent magnetic field sensors. Based on the giant magneto-optical ( GMO ) or Faraday...Squids are those based upon the giant magneto-optical ( GMO ) effect in ferrimagnetic materials or YIG garnets and the giant magneto-resistance (GMR...effect in manganese based compounds. The development of the GMO material was mostly motivated by the need for compact, in-line fiber optical

  11. Effect of transverse magnetic field on the steady state properties of Plasma Diodes

    NASA Astrophysics Data System (ADS)

    Pramanik, Sourav; Kuznetsov, Victor; Chakrabarti, Nikhil

    2016-10-01

    A study of the steady-states of the Plasma Diodes (e.g., Bursian diode, Pierce diode etc.) driven by a cold electron beam is presented in presence of an external transverse magnetic field is presented. Both the regimes of no electron-reflection and electron-reflection are taken into account. Steady state solutions are evaluated using emitter electric field as a characteristic parameters, for fixed values of the diode length, applied voltage, and magnetic field strength. For our purpose, both the Eulerian and Lagrangian descriptions are employed. It is shown that transverse magnetic field has profound influences on the space charge limit, maximum diode current, aperiodic instability and other characteristic parameters. An external magnetic field can be used to design fast electronic switches based on its effects on the Plasma diode.

  12. Magnetic field and atomic order effect on the martensitic transformation of a metamagnetic alloy.

    PubMed

    Barandiaran, J M; Chernenko, V A; Cesari, E; Salas, D; Gutierrez, J; Lazpita, P

    2013-12-04

    The martensitic transformation (MT) of metamagnetic shape memory alloys is very sensitive to the applied magnetic field and atomic order. We analyze the alloy Ni50Mn34.5In15.5 in magnetic fields up to 13 T. The alloy has been prepared both in an ordered state by slow cooling, and in a disordered state by rapid quenching. In both cases the dependence of the martensitic transition temperature on the field is highly nonlinear. Such departure from linearity is due to a decrease of the entropy change at the transition, ΔS, with the applied field. This can be explained by the ordering effect of the magnetic field on the frustrated magnetic structure of the alloy in the martensitic phase. Compliance with a recent model, relying on the strong magnetoelastic interactions in these compounds, is very satisfactory.

  13. Effects of self-generated magnetic fields on hohlraum simulation at NIF

    NASA Astrophysics Data System (ADS)

    Farmer, W. A.; Strozzi, D. J.; Hinkel, D. E.; Rosen, M. D.; Jones, O. S.; Koning, J. M.; Marinak, M. M.

    2016-10-01

    Non-parallel density and pressure gradients that develop during matter ablation on a laser irradiated target lead to self-generated magnetic fields through the well-known Biermann-battery effect. For laser intensities present during ICF relevant scenarios on NIF, megagauss fields can develop. The presence of large magnetic fields leads to a non-negligible Hall parameter, defined as the product of the electron cyclotron frequency and the electrion-ion collision time. When the Hall parameter is of order unity or greater, a significant reduction in the cross-field heat flux occurs. Large magnetic fields are limited by the inclusion of the Nernst term, which advects the magnetic fields in the direction of the heat flux (or from the ablation front into the denser wall). This advection combined with resistive diffusion of the magnetic field limits the strength of the self-generated field within the hohlraum. We report changes in simulation results obtained when using the MHD package in the radiation-hydrodynamics code, HYDRA, which models the evolutions of the magnetic fields. This work was supported by the U.S. Department of Energy by Lawrence Livermore National Laboratory under Contract DE-AC52-07NA27344.

  14. The mitigating effect of magnetic fields on Rayleigh-Taylor unstable inertial confinement fusion plasmas

    SciTech Connect

    Srinivasan, Bhuvana; Tang, Xian-Zhu

    2013-05-15

    Rayleigh-Taylor (RT) instabilities at interfaces of disparate mass densities have long been known to generate magnetic fields during inertial confinement fusion implosions. An externally applied magnetic field can also be efficiently amplified by RT instabilities. The focus here is on magnetic field generation and amplification at the gas-ice interface which is RT unstable during the deceleration phase of the implosion. RT instabilities lead to undesirable mix of hot and cold plasmas which enhances thermal energy loss and tends to produce a more massive warm-spot instead of a hot-spot. Two mechanisms are shown here to mitigate the thermal energy loss from the hot-spot. The first mechanism is the reduction of electron thermal conductivity with interface-aligned magnetic fields. This can occur through self-generated magnetic fields via the Biermann battery effect as well as through externally applied magnetic fields that undergo an exponential growth via the stretch-and-fold magnetohydrodynamic dynamo. Self-generated magnetic fields during RT evolution can result in a factor of 2−10 decrease in the electron thermal conductivity at the gas-ice interface, while externally applied magnetic fields that are compressed to 6–1000 T at the onset of deceleration (corresponding to pre-implosion external fields of 0.06–10 T) could result in a factor of 2–500 reduction in electron thermal conductivity at the gas-ice interface. The second mechanism to mitigate thermal energy loss from the hot-spot is to decrease the interface mixing area between the hot and cold plasmas. This is achieved through large external magnetic fields of 1000 T at the onset of deceleration which damp short-wavelength RT modes and long-wavelength Kelvin-Helmholtz modes thus significantly slowing the RT growth and reducing mix.

  15. Magnetization switching by combining electric field and spin-transfer torque effects in a perpendicular magnetic tunnel junction

    PubMed Central

    Zhang, Xiangli; Wang, Chengjie; Liu, Yaowen; Zhang, Zongzhi; Jin, Q. Y.; Duan, Chun-Gang

    2016-01-01

    Effective manipulation of magnetization orientation driven by electric field in a perpendicularly magnetized tunnel junction introduces technologically relevant possibility for developing low power magnetic memories. However, the bipolar orientation characteristic of toggle-like magnetization switching possesses intrinsic difficulties for practical applications. By including both the in-plane (T//) and field-like (T⊥) spin-transfer torque terms in the Landau-Lifshitz-Gilbert simulation, reliable and deterministic magnetization reversal can be achieved at a significantly reduced current density of 5×109 A/m2 under the co-action of electric field and spin-polarized current, provided that the electric-field pulse duration exceeds a certain critical value τc. The required critical τc decreases with the increase of T⊥ strength because stronger T⊥ can make the finally stabilized out-of-plane component of magnetization stay in a larger negative value. The power consumption for such kind of deterministic magnetization switching is found to be two orders of magnitude lower than that of the switching driven by current only. PMID:26732287

  16. Magnetic field effect on blood flow of Casson fluid in axisymmetric cylindrical tube: A fractional model

    NASA Astrophysics Data System (ADS)

    Ali, Farhad; Sheikh, Nadeem Ahmad; Khan, Ilyas; Saqib, Muhammad

    2017-02-01

    The effects of magnetohydrodynamics on the blood flow when blood is represented as a Casson fluid, along with magnetic particles in a horizontal cylinder is studied. The flow is due to an oscillating pressure gradient. The Laplace and finite Hankel transforms are used to obtain the closed form solutions of the fractional partial differential equations. Effects of various parameters on the flow of both blood and magnetic particles are shown graphically. The analysis shows that, the model with fractional order derivatives bring a remarkable changes as compared to the ordinary model. The study highlights that applied magnetic field reduces the velocities of both the blood and magnetic particles.

  17. Effect of temperature and magnetic field on two-flavor superconducting quark matter

    NASA Astrophysics Data System (ADS)

    Mandal, Tanumoy; Jaikumar, Prashanth

    2016-10-01

    We investigate the effect of turning on temperature for the charge neutral phase of two-flavor color superconducting (2SC) dense quark matter in the presence of constant external magnetic field. Within the Nambu-Jona-Lasinio model, by tuning the diquark coupling strength, we study the interdependent evolution of the quark Bardeen-Cooper-Schrieffer gap and dynamical mass as functions of temperature and magnetic field. We find that magnetic field B ≳0.02 GeV2 (1 018 G ) leads to anomalous temperature behavior of the gap in the gapless 2SC phase (moderately strong coupling), reminiscent of previous results in the literature found in the limit of weak coupling without magnetic field. The 2SC gap in the strong coupling regime is abruptly quenched at ultrahigh magnetic field due to the mismatched Fermi surfaces of up and down quarks imposed by charge neutrality and oscillation of the gap due to Landau level quantization. The dynamical quark mass also displays strong oscillation and magnetic catalysis at high magnetic field, although the latter effect is tempered by nonzero temperature. We discuss the implications for newly born compact stars with superconducting quark cores.

  18. Crossing and anti-crossing effects of polaritons in a magnetic-semiconductor superlattice influenced by an external magnetic field

    NASA Astrophysics Data System (ADS)

    Tuz, Vladimir R.; Fesenko, Volodymyr I.; Fedorin, Illia V.; Sun, Hong-Bo; Shulga, Valeriy M.

    2017-03-01

    Crossing and anti-crossing effects in dispersion characteristics of both bulk and surface polaritons in a magnetic-semiconductor superlattice influenced by an external static magnetic field being in the Faraday geometry are discussed. The bulk polaritons are classified as eigenwaves with right-handed and left-handed elliptically polarized states, whereas the surface polaritons are considered as hybrid modes having a predominant effect of either magnetic or semiconductor subsystem, and distinctions in dispersion characteristics of such polaritons are revealed involving the concept of critical points.

  19. Effects of a 60 Hz magnetic field on central cholinergic systems of the rat

    SciTech Connect

    Lai, H.; Carino, M.A.; Horita, A.; Guy, A.W. )

    1993-03-15

    The authors studied the effects of an acute exposure to a 60 Hz magnetic field on sodium-dependent, high-affinity choline uptake in the brain of the rat. Decreases in uptake were observed in the frontal cortex and hippocampus after the animals were exposed to a magnetic field at flux densities [>=] 0.75 mT. These effects of the magnetic field were blocked by pretreating the animals with the narcotic antagonist naltrexone, but not by the peripheral opioid antagonist, naloxone methiodide. These data indicate that the magnetic-field-induced decreases in high-affinity choline uptake in the rat brain were mediated by endogenous opioids in the central nervous systems.

  20. The Effect of Magnetic Fields on the Quorum Sensing-Regulated Luminescence of Vibrio fischeri

    NASA Astrophysics Data System (ADS)

    Barron, Addie; Hagen, Steve; Son, Minjun

    2015-03-01

    Quorum sensing (QS) is a mechanism by which bacteria communicate through the secretion and detection of extracellular signaling molecules known as autoinducers. This research focuses on the quorum sensing regulated bioluminescence of Vibrio fischeri, a marine bacterium that lives in symbiosis with certain fish and squid species. Previous studies of V. harveyi, a close relative of V. fisheri, indicate that a strong magnetic field has a positive effect on V.harveyi bioluminescence. However the effect of magnetic fields on quorum sensing-regulated luminescence is in general poorly understood. We grew V. fischeri in solid and liquid growth media, subject to strong static magnetic fields, and imaged the bioluminescence over a period of forty-eight hours. Luminescence patterns were analyzed in both the spatial and time dimensions. We find no indication that a magnetic field influences Vibrio fischeri luminescence either positively or negatively. This research was funded by the Grant Number NSF DMR-1156737.

  1. Fast superconducting magnetic field switch

    DOEpatents

    Goren, Yehuda; Mahale, Narayan K.

    1996-01-01

    The superconducting magnetic switch or fast kicker magnet is employed with electron stream or a bunch of electrons to rapidly change the direction of flow of the electron stream or bunch of electrons. The apparatus employs a beam tube which is coated with a film of superconducting material. The tube is cooled to a temperature below the superconducting transition temperature and is subjected to a constant magnetic field which is produced by an external dc magnet. The magnetic field produced by the dc magnet is less than the critical field for the superconducting material, thus, creating a Meissner Effect condition. A controllable fast electromagnet is used to provide a magnetic field which supplements that of the dc magnet so that when the fast magnet is energized the combined magnetic field is now greater that the critical field and the superconducting material returns to its normal state allowing the magnetic field to penetrate the tube. This produces an internal field which effects the direction of motion and of the electron stream or electron bunch. The switch can also operate as a switching mechanism for charged particles.

  2. Fast superconducting magnetic field switch

    DOEpatents

    Goren, Y.; Mahale, N.K.

    1996-08-06

    The superconducting magnetic switch or fast kicker magnet is employed with electron stream or a bunch of electrons to rapidly change the direction of flow of the electron stream or bunch of electrons. The apparatus employs a beam tube which is coated with a film of superconducting material. The tube is cooled to a temperature below the superconducting transition temperature and is subjected to a constant magnetic field which is produced by an external dc magnet. The magnetic field produced by the dc magnet is less than the critical field for the superconducting material, thus, creating a Meissner Effect condition. A controllable fast electromagnet is used to provide a magnetic field which supplements that of the dc magnet so that when the fast magnet is energized the combined magnetic field is now greater that the critical field and the superconducting material returns to its normal state allowing the magnetic field to penetrate the tube. This produces an internal field which effects the direction of motion and of the electron stream or electron bunch. The switch can also operate as a switching mechanism for charged particles. 6 figs.

  3. Time variations of fields in superconducting magnets and their effects on accelerators

    SciTech Connect

    Herrup, D.A.; Syphers, M.J.; Johnson, D.E.; Johnson, R.P.; Tollestrup, A.V.; Hanft, R.W.; Brown, B.C.; Lamm, M.J.; Kuchnir, M.; McInturff, A.D.

    1988-08-22

    A report on the time dependence of magnetic fields in the superconducting magnets of the Fermilab Tevatron has been published. A field variation of order 1 gauss at the aperture radius is observed. Studies on both full sized Tevatron, dipoles and prototype magnets have been used to elucidate these effects. Explanations based on eddy currents in the coil matrix or on flux creep in the superconducting filaments are explored with these tests. Measurement results and techniques for controlling the effect based on new laboratory tests and the latest accelerator operation are presented. 9 refs., 4 figs.

  4. Effects of magnetic fields on improving mass transfer in flue gas desulfurization using a fluidized bed

    NASA Astrophysics Data System (ADS)

    Zhang, Qi; Gui, Keting; Wang, Xiaobo

    2016-02-01

    The effects of magnetic fields on improving the mass transfer in flue gas desulfurization using a fluidized bed are investigated in the paper. In this research, the magnetically fluidized bed (MFB) is used as the reactor in which ferromagnetic particles are fluidized with simulated flue gas under the influence of an external magnetic field. Lime slurry is continuously sprayed into the reactor. As a consequence, the desulfurization reaction and the slurry drying process take place simultaneously in the MFB. In this paper, the effects of ferromagnetic particles and external magnetic fields on the desulphurization efficiency are studied and compared with that of quartz particles as the fluidized particles. Experimental results show that the ferromagnetic particles not only act as a platform for lime slurry to precipitate on like quartz particles, but also take part in the desulfurization reaction. The results also show that the specific surface area of ferromagnetic particles after reaction is enlarged as the magnetic intensity increases, and the external magnetic field promotes the oxidation of S(IV), improving the mass transfer between sulphur and its sorbent. Hence, the efficiency of desulphurization under the effects of external magnetic fields is higher than that in general fluidized beds.

  5. Nuclear magnetic resonance relaxation and diffusion in the presence of internal gradients: the effect of magnetic field strength.

    PubMed

    Mitchell, J; Chandrasekera, T C; Johns, M L; Gladden, L F; Fordham, E J

    2010-02-01

    It is known that internal magnetic field gradients in porous materials, caused by susceptibility differences at the solid-fluid interfaces, alter the observed effective Nuclear Magnetic Resonance transverse relaxation times T2,eff. The internal gradients scale with the strength of the static background magnetic field B0. Here, we acquire data at various magnitudes of B0 to observe the influence of internal gradients on T2-T2 exchange measurements; the theory discussed and observations made are applicable to any T2-T2 analysis of heterogeneous materials. At high magnetic field strengths, it is possible to observe diffusive exchange between regions of local internal gradient extrema within individual pores. Therefore, the observed exchange pathways are not associated with pore-to-pore exchange. Understanding the significance of internal gradients in transverse relaxation measurements is critical to interpreting these results. We present the example of water in porous sandstone rock and offer a guideline to determine whether an observed T2,eff relaxation time distribution reflects the pore size distribution for a given susceptibility contrast (magnetic field strength) and spin echo separation. More generally, we confirm that for porous materials T1 provides a better indication of the pore size distribution than T2,eff at high magnetic field strengths (B0>1 T), and demonstrate the data analysis necessary to validate pore size interpretations of T2,eff measurements.

  6. Effects of Extremely Low Frequency Electric and Magnetic Fields on Roots of ’Vicia faba’.

    DTIC Science & Technology

    Roots of Vicia faba were exposed to electric and magnetic fields comparable to but at levels higher than those associated with Project Sanguine...examined to detect any effects of exposure of growing primary roots of Vicia faba (Horse Bean, Mung Bean) to ELF electric and magnetic fields simulating...those near the Sanguine transmitter: growth rate, mitotic index, chromosomal abnormalities in dividing meristematic cells. The choice of Vicia faba

  7. Quantifying the motion of magnetic particles in excised tissue: Effect of particle properties and applied magnetic field

    NASA Astrophysics Data System (ADS)

    Kulkarni, Sandip; Ramaswamy, Bharath; Horton, Emily; Gangapuram, Sruthi; Nacev, Alek; Depireux, Didier; Shimoji, Mika; Shapiro, Benjamin

    2015-11-01

    This article presents a method to investigate how magnetic particle characteristics affect their motion inside tissues under the influence of an applied magnetic field. Particles are placed on top of freshly excised tissue samples, a calibrated magnetic field is applied by a magnet underneath each tissue sample, and we image and quantify particle penetration depth by quantitative metrics to assess how particle sizes, their surface coatings, and tissue resistance affect particle motion. Using this method, we tested available fluorescent particles from Chemicell of four sizes (100 nm, 300 nm, 500 nm, and 1 μm diameter) with four different coatings (starch, chitosan, lipid, and PEG/P) and quantified their motion through freshly excised rat liver, kidney, and brain tissues. In broad terms, we found that the applied magnetic field moved chitosan particles most effectively through all three tissue types (as compared to starch, lipid, and PEG/P coated particles). However, the relationship between particle properties and their resulting motion was found to be complex. Hence, it will likely require substantial further study to elucidate the nuances of transport mechanisms and to select and engineer optimal particle properties to enable the most effective transport through various tissue types under applied magnetic fields.

  8. QUANTIFYING THE MOTION OF MAGNETIC PARTICLES IN EXCISED TISSUE: EFFECT OF PARTICLE PROPERTIES AND APPLIED MAGNETIC FIELD

    PubMed Central

    Kulkarni, Sandip; Ramaswamy, Bharath; Horton, Emily; Gangapuram, Sruthi; Nacev, Alek; Depireux, Didier; Shimoji, Mika; Shapiro, Benjamin

    2015-01-01

    This article presents a method to investigate how magnetic particle characteristics affect their motion inside tissues under the influence of an applied magnetic field. Particles are placed on top of freshly excised tissue samples, a calibrated magnetic field is applied by a magnet underneath each tissue sample, and we image and quantify particle penetration depth by quantitative metrics to assess how particle sizes, their surface coatings, and tissue resistance affect particle motion. Using this method, we tested available fluorescent particles from Chemicell of four sizes (100 nm, 300 nm, 500 nm, and 1 µm diameter) with four different coatings (starch, chitosan, lipid, PEG/P) and quantified their motion through freshly excised rat liver, kidney, and brain tissues. In broad terms, we found that the applied magnetic field moved chitosan particles most effectively through all three tissue types (as compared to starch, lipid, and PEG/P coated particles). However, the relationship between particle properties and their resulting motion was found to be complex. Hence, it will likely require substantial further study to elucidate the nuances of transport mechanisms and to select and engineer optimal particle properties to enable the most effective transport through various tissue types under applied magnetic fields. PMID:26120240

  9. QUANTIFYING THE MOTION OF MAGNETIC PARTICLES IN EXCISED TISSUE: EFFECT OF PARTICLE PROPERTIES AND APPLIED MAGNETIC FIELD.

    PubMed

    Kulkarni, Sandip; Ramaswamy, Bharath; Horton, Emily; Gangapuram, Sruthi; Nacev, Alek; Depireux, Didier; Shimoji, Mika; Shapiro, Benjamin

    2015-11-01

    This article presents a method to investigate how magnetic particle characteristics affect their motion inside tissues under the influence of an applied magnetic field. Particles are placed on top of freshly excised tissue samples, a calibrated magnetic field is applied by a magnet underneath each tissue sample, and we image and quantify particle penetration depth by quantitative metrics to assess how particle sizes, their surface coatings, and tissue resistance affect particle motion. Using this method, we tested available fluorescent particles from Chemicell of four sizes (100 nm, 300 nm, 500 nm, and 1 µm diameter) with four different coatings (starch, chitosan, lipid, PEG/P) and quantified their motion through freshly excised rat liver, kidney, and brain tissues. In broad terms, we found that the applied magnetic field moved chitosan particles most effectively through all three tissue types (as compared to starch, lipid, and PEG/P coated particles). However, the relationship between particle properties and their resulting motion was found to be complex. Hence, it will likely require substantial further study to elucidate the nuances of transport mechanisms and to select and engineer optimal particle properties to enable the most effective transport through various tissue types under applied magnetic fields.

  10. Analysis of high gradient magnetic field effects on distribution of nanoparticles injected into pulsatile blood stream

    NASA Astrophysics Data System (ADS)

    Reza Habibi, Mohammad; Ghassemi, Majid; Hossien Hamedi, Mohammad

    2012-04-01

    Magnetic nanoparticles are widely used in a wide range of applications including data storage materials, pharmaceutical industries as magnetic separation tools, anti-cancer drug carriers and micro valve applications. The purpose of the current study is to investigate the effect of a non-uniform magnetic field on bio-fluid (blood) with magnetic nanoparticles. The effect of particles as well as mass fraction on flow field and volume concentration is investigated. The governing non-linear differential equations, concentration and Navier-stokes are coupled with the magnetic field. To solve these equations, a finite volume based code is developed and utilized. A real pulsatile velocity is utilized as inlet boundary condition. This velocity is extracted from an actual experimental data. Three percent nanoparticles volume concentration, as drug carrier, is steadily injected in an unsteady, pulsatile and non-Newtonian flow. A power law model is considered for the blood viscosity. The results show that during the systole section of the heartbeat when the blood velocity increases, the magnetic nanoparticles near the magnetic source are washed away. This is due to the sudden increase of the hydrodynamic force, which overcomes the magnetic force. The probability of vein blockage increases when the blood velocity reduces during the diastole time. As nanoparticles velocity injection decreases (longer injection time) the wall shear stress (especially near the injection area) decreases and the retention time of the magnetic nanoparticles in the blood flow increases.

  11. Photospheric magnetic fields

    NASA Technical Reports Server (NTRS)

    Howard, R.

    1972-01-01

    Knowledge on the nature of magnetic fields on the solar surface is reviewed. At least a large part of the magnetic flux in the solar surface is confined to small bundles of lines of force within which the field strength is of the order of 500 gauss. Magnetic fields are closely associated with all types of solar activity. Magnetic flux appears at the surface at the clearly defined birth or regeneration of activity of an active region. As the region ages, the magnetic flux migrates to form large-scale patterns and the polar fields. Some manifestations of the large-scale distribution are discussed.

  12. Modelling effect of magnetic field on material removal in dry electrical discharge machining

    NASA Astrophysics Data System (ADS)

    Abhishek, Gupta; Suhas, S. Joshi

    2017-02-01

    One of the reasons for increased material removal rate in magnetic field assisted dry electrical discharge machining (EDM) is confinement of plasma due to Lorentz forces. This paper presents a mathematical model to evaluate the effect of external magnetic field on crater depth and diameter in single- and multiple-discharge EDM process. The model incorporates three main effects of the magnetic field, which include plasma confinement, mean free path reduction and pulsating magnetic field effects. Upon the application of an external magnetic field, Lorentz forces that are developed across the plasma column confine the plasma column. Also, the magnetic field reduces the mean free path of electrons due to an increase in the plasma pressure and cycloidal path taken by the electrons between the electrodes. As the mean free path of electrons reduces, more ionization occurs in plasma column and eventually an increase in the current density at the inter-electrode gap occurs. The model results for crater depth and its diameter in single discharge dry EDM process show an error of 9%-10% over the respective experimental values.

  13. The effect of saturation magnetization of nanocatalyst and oscillating magnetic field for green urea synthesis

    NASA Astrophysics Data System (ADS)

    Yahya, Noorhana; Alqasem, Bilal; Irfan, Muhammad; Qureshi, Saima; Rehman, Zia Ur; Shafie, Afza; Soleimani, Hassan

    2017-02-01

    Hematite and cupric oxide nanowires have been synthesized using the oxidation method for green urea production. Hematite nanowires were obtained by the oxidation of an iron wire at a temperature of 650 °C and ambient pressure in the presence of N2 and O2 gases. Cupric oxide nanowires were obtained by the same method at 700 °C, using a copper wire. The X-ray diffraction results show the formation of rhombohedral structure of α-Fe2O3 and monoclinic phase of CuO. FE-SEM results reveal the formation of nanowires with dimensions ranging between 5-15 μm and 4-12 μm in length and a diametere ranging between 50-150 nm and 50-250 nm for α-Fe2O3 and CuO respectively. The VSM results show that the saturation magnetization values for hematite and cupric oxide were 132.8700 and 0.0124 emu/g, respectively. The nanowires were used as catalyst for green urea synthesis in the presence of an oscillating and a static magnetic fields. The use of nanocatalyst with high saturation magnetization gives a higher yield of urea due to the increase in the singlet to triplet conversion. The highest yield of urea 11243 ppm was achieved by applying an oscillating magnetic field of frequency 0.5 MHz and using α-Fe2O3 nanowires as nanocatalyst.

  14. North-South Asymmetries in Earth's Magnetic Field. Effects on High-Latitude Geospace

    NASA Astrophysics Data System (ADS)

    Laundal, K. M.; Cnossen, I.; Milan, S. E.; Haaland, S. E.; Coxon, J.; Pedatella, N. M.; Förster, M.; Reistad, J. P.

    2017-03-01

    The solar-wind magnetosphere interaction primarily occurs at altitudes where the dipole component of Earth's magnetic field is dominating. The disturbances that are created in this interaction propagate along magnetic field lines and interact with the ionosphere-thermosphere system. At ionospheric altitudes, the Earth's field deviates significantly from a dipole. North-South asymmetries in the magnetic field imply that the magnetosphere-ionosphere-thermosphere (M-I-T) coupling is different in the two hemispheres. In this paper we review the primary differences in the magnetic field at polar latitudes, and the consequences that these have for the M-I-T coupling. We focus on two interhemispheric differences which are thought to have the strongest effects: 1) A difference in the offset between magnetic and geographic poles in the Northern and Southern Hemispheres, and 2) differences in the magnetic field strength at magnetically conjugate regions. These asymmetries lead to differences in plasma convection, neutral winds, total electron content, ion outflow, ionospheric currents and auroral precipitation.

  15. The effect of strong static magnetic field on lymphocytes.

    PubMed

    Aldinucci, Carlo; Garcia, Julian Blanco; Palmi, Mitri; Sgaragli, Gianpietro; Benocci, Alberto; Meini, Antonella; Pessina, Federica; Rossi, Claudio; Bonechi, Claudia; Pessina, Gian Paolo

    2003-02-01

    We investigated whether static electromagnetic fields (EMFs) at a flux density of 4.75 T, generated by an NMR apparatus (NMRF), could promote movements of Ca2+, cell proliferation, and the eventual production of proinflammatory cytokines in human peripheral blood mononuclear cells (PBMC) as well as in Jurkat cells, after exposure to the field for 1 h. The same study was also performed after activation of cells with 5 mg/ml phytohaemagglutinin (PHA). Our results clearly demonstrate that static NMRF exposure has neither proliferative, nor activating, nor proinflammatory effects on both normal and PHA activated PBMC. Moreover, the concentration of interleukin-1beta, interleukin-2, interleukin-6, interferon, and tumour necrosis factor alpha (TNFalpha) remained unvaried in exposed cells. Exposure of Jurkat cells statistically decreased the proliferation and the proliferation indexes, which 24 and 48 h after exposure were 0.7 +/- 0.29 and 0.87 +/- 0.12, respectively. Moreover, in Jurkat cells the [Ca2+]i was higher than in PBMC and was reduced significantly to about one half after exposure. This is consistent with the decrease of proliferation and with the low levels of IL-2 measured. On the whole, our data suggest that NMRF exposure failed to affect the physiologic behaviour of normal lymphomonocytes. Instead in Jurkat cells, by changing the properties of cell membranes, NMRF can influence Ca2+ transport processes, and hence Ca2+ homeostasis with improvement of proliferation.

  16. Effect of carbon substitution on low magnetic field AC losses in MgB 2 single crystals

    NASA Astrophysics Data System (ADS)

    Ciszek, M.; Rogacki, K.; Karpiński, J.

    2011-11-01

    The DC magnetization and AC magnetic susceptibilities were measured for MgB2 single crystals, unsubstituted and carbon substituted with the composition of Mg(B0.94C0.06)2. AC magnetic losses were derived from the AC susceptibility data as a function of the AC amplitude and the DC bias magnetic field. From the DC magnetization loops critical current densities were derived as a function of temperature and DC field. Results show that the substitution with carbon decreases critical current densities at low external magnetic fields, in contrast to the well known effect of an increase of the critical current densities at higher magnetic fields.

  17. Estimation of the effects of strong static magnetic fields on plants.

    NASA Astrophysics Data System (ADS)

    Kuznetsov, O.

    In our recent studies we extensively used ponderomotive magnetic forces in high gradient magnetic fields (HGMF) for displacing organelles inside plant gravity receptor cells. Such displacement is a convenient tool both for investigating plant gravity perception mechanism and for physical characterization of the cell interior, and can have future practical applications in providing a directional stimulus for plants in microgravity. This method takes advantage of the magnetic heterogeneity of the receptor cells, namely stronger diamagnetism of starch-filled amyloplasts compared to cytoplasm (? æ < 0). Such particles are repelled from the zones of stronger field in a non-uniform field. To exert a force on amyloplasts, which is comparable to the gravity force, the dynamic factor of the field grad(H2 /2) needs to be 109 - 1 01 0 Oe 2 /cm, and the field intensity in the experimental magnetic systems typically varies from 0 to 2.5-104 Oe, while the size of the area of non-uniformity is 10-2 to 1 cm. Possible effects of such static magnetic fields on plants other than magnetophoresis of amyloplasts were estimated theoretically and tested experimentally. No statistically significant differences in growth rates or rates of gravicurvature were observed in experiments with Linum, Arabidopsis, Hordeum, Avena, Ceratodon and Chara between the plants grown in uniform magnetic fields of various intensities (102 to 2.5-104 Oe) and those grown in the Earth's magnetic field. Microscopic studies also did not detect any structural differences between test and control plants. The magnitudes of possible effects of static magnetic fields on plant cells and organs (including effects on ion currents, magneto-hydrodynamic effects in moving cytoplasm, ponderomotive forces on other cellular structures, effects on some biochemical reactions and biomolecules) were estimated theoretically. The estimations have shown, that these effects are small compared to the thermodynamic noise and thus are

  18. Magnetic field effects on copper metal deposition from copper sulfate aqueous solution.

    PubMed

    Udagawa, Chikako; Maeda, Aya; Katsuki, Akio; Maki, Syou; Morimoto, Shotaro; Tanimoto, Yoshifumi

    2014-05-08

    Effects of a magnetic field (≤0.5 T) on electroless copper metal deposition from the reaction of a copper sulfate aqueous solution and a zinc thin plate were examined in this study. In a zero field, a smooth copper thin film grew steadily on the plate. In a 0.38 T field, a smooth copper thin film deposited on a zinc plate within about 1 min. Then, it peeled off repeatedly from the plate. The yield of consumed copper ions increased about 2.1 times compared with that in a zero field. Mechanism of this magnetic field effect was discussed in terms of Lorentz force- and magnetic force-induced convection and local volta cell formation.

  19. The effects of superhigh magnetic fields on the equations of state of neutron stars

    NASA Astrophysics Data System (ADS)

    Gao, Z. F.; Wang, N.; Xu, Y.; Shan, H.; Li, X.-D.

    2015-11-01

    By introducing Dirac's δ-function in superhigh magnetic fields, we deduce a general formula for the pressure of degenerate and relativistic electrons, Pe, which is suitable for superhigh magnetic fields, discuss the quantization of Landau levels of electrons, and consider the quantum electrodynamic(QED) effects on the equations of states (EOSs) for different matter systems. The main conclusions are as follows: the stronger the magnetic field strength, the higher the electron pressure becomes; compared with a common radio pulsar, a magnetar could be a more compact oblate spheroid-like deformed neutron star due to the anisotropic total pressure; and an increase in the maximum mass of a magnetar is expected because of the positive contribution of the magnetic field energy to the EoS of the star. Since this is an original work in which some uncertainties could exist, modifications and improvements of our theory should be considered in our future studies.

  20. Experimental Realization of Strong Effective Magnetic Fields in an Optical Lattice

    SciTech Connect

    Aidelsburger, M.; Atala, M.; Trotzky, S.; Chen, Y.-A.; Bloch, I.; Nascimbene, S.

    2011-12-16

    We use Raman-assisted tunneling in an optical superlattice to generate large tunable effective magnetic fields for ultracold atoms. When hopping in the lattice, the accumulated phase shift by an atom is equivalent to the Aharonov-Bohm phase of a charged particle exposed to a staggered magnetic field of large magnitude, on the order of 1 flux quantum per plaquette. We study the ground state of this system and observe that the frustration induced by the magnetic field can lead to a degenerate ground state for noninteracting particles. We provide a measurement of the local phase acquired from Raman-induced tunneling, demonstrating time-reversal symmetry breaking of the underlying Hamiltonian. Furthermore, the quantum cyclotron orbit of single atoms in the lattice exposed to the magnetic field is directly revealed.

  1. Investigation of the effects of magnetic field exposure on human melatonin. Interim report

    SciTech Connect

    Graham, C.; Cook, M.R.; Cohen, H.D.

    1994-08-01

    Several rodent studies have suggested that magnetic field exposure may alter the daily pattern of melatonin secretion. This study investigated melatonin levels in mean exposed overnight to magnetic fields of 10 mG and 200 mG. The study also assessed the potential effects of exposure on a number of performance and self-reported endpoints in the subjects. Investigation of this area is important, as altered diurnal melatonin cycles have been linked to a variety of endpoints, including reproductive outcome, neurobehavioral function, and carcinogenesis. The results of this investigation did not support the a priori hypothesis that exposure to 60-Hz magnetic fields of 10 mG and 200 mG alters nighttime melatonin levels in a population of adult males. However, the data suggested the possibility of differential sensitivity to magnetic fields based on an individual`s baseline melatonin level.

  2. Effects of magnetic fields during high voltage live-line maintenance

    NASA Astrophysics Data System (ADS)

    Göcsei, Gábor; Kiss, István, Dr; Németh, Bálint

    2015-10-01

    In case of transmission and distribution networks, extra low frequency (typically 50 or 60 Hz) electric and magnetic fields have to be taken into consideration separately from each other. Health effects have been documented from exposures to both types of fields. Magnetic fields are qualified as possibly carcinogenic to humans (category “2B”) by WHO's cancer research institute, International Agency for Research on Cancer (IARC), so it is essential to protect the workers against their harmful effects. During live-line maintenance (LLM) electric fields can be shielded effectively by different kinds of conductive clothing, which are enclosed metal surfaces acting as a Faraday-cage. In practice laboratory measurements also prove their efficiency, the required shielding ratio is above 99% by the related standard.. A set of measurements have proved that regular conductive clothing used against the electric fields cannot shield the magnetic fields effectively at all. This paper introduces the possible risks of LLM from the aspect of the health effects of magnetic fields. Although in this case the principle of shielding the electric fields cannot be applied, new considerations in equipment design and technology can be used as a possible solution. Calculations and simulations based on the data of the Hungarian transmission network - which represents the European grid as a part of ENTSO-E - and high-current laboratory measurement results also prove the importance of the topic.

  3. An investigation of magnetic field effects on plume density and temperature profiles of an applied-field MPD thruster

    NASA Technical Reports Server (NTRS)

    Bullock, S. Ray; Myers, R. M.

    1994-01-01

    Applied-field magnetoplasmadynamic (MPD) thruster performance is below levels required for primary propulsion missions. While MPD thruster performance has been found to increase with the magnitude of the applied-field strength, there is currently little understanding of the impact of applied-field shape on thruster performance. The results of a study in which a single applied-field thruster was operated using three solenoidal magnets with diameters of 12.7, 15.2, and 30.4-cm are presented. Thruster voltage and anode power deposition were measured for each applied field shape over a range of field strengths. Plume electron number density and temperature distributions were measured using a Langmuir probe in an effort to determine the effect of field shape on plume confinement by the diverging magnetic-field for each of the three magnetic field shapes. Results show that the dependence of the measured thruster characteristics on field shape were non-monotonic and that the field shape had a significant effect on the plume density and temperature profiles.

  4. Effects silver nanoparticles and magnetic field on growth of fodder maize (Zea mays L.).

    PubMed

    Berahmand, Ali Asghar; Ghafariyan Panahi, Ali; Sahabi, Hossein; Feizi, Hassan; Rezvani Moghaddam, Parviz; Shahtahmassebi, Nasser; Fotovat, Amir; Karimpour, Hossein; Gallehgir, Omran

    2012-12-01

    Two experiments were done in 2008 and 2009 to study the effects of magnetic field and silver nanoparticles on fodder maize (Zea mays L.). These experiments were done with seven treatments based on a randomized complete block design in four replications. The treatments were as follows: magnetic field and silver nanoparticles + Kemira fertilizer (T1), magnetic field and silver nanoparticles + Humax fertilizer (T2), magnetic field and silver nanoparticles (T3), Kemira fertilizer (T4), Librel fertilizer (T5), Humax fertilizer (T6), and a control (T7). Results showed that fresh yield was higher in treatments T3 and T4. Treatments T3 and T4 had increased maize fresh yields of 35 and 17.5 % in comparison to the control, respectively. The dry matter yield of those plants exposed to magnetic field and silver nanoparticles was significantly higher than that from any of the other treatments. Magnetic field and silver nanoparticle treatments (T3 and T1) showed higher percentages for ears, and the lowest percentages were found in treatments T7 and T5. In general, the soil conditions for crop growth were more favorable in 2009 than in 2008, which caused the maize to respond better to treatments tested in the study; therefore, treatments had more significant effects on studied traits in 2008 than in 2009.

  5. The effect of magnetic field on copper in various corrosive medium

    SciTech Connect

    Ang, L. Y.; Othman, N. K.; Jalar, A.; Ismail, I.

    2014-09-03

    The effect of applied magnetic field on the corrosion behaviour of copper within various corrosive medium is investigated. The copper coupon is immersed in 0.5 M HCl, 0.5 M NaCl and 0.5 M NaOH with or without applying up to 40 mT magnetic fields for 24 hours. The weight loss of copper coupon in HCl increased up to 96.56% with applied magnetic fields. However, in NaOH medium, only 33.33% more weight loss was observed and no difference were observed for coupons in NaCl when magnetic field is applied. This observation indicates that corrosion behaviour in HCl and NaOH is controlled by mass transport that can be influenced by the induced magneto hydrodynamics effect when magnetic field is applied. There was no change in weight loss of copper in NaCl when magnetic field is applied because the corrosion mechanism of copper in NaCl is governed by electron charge transfer.

  6. Synthetic gauge potential and effective magnetic field in a Raman medium undergoing molecular modulation

    NASA Astrophysics Data System (ADS)

    Yuan, Luqi; Wang, Da-wei; Fan, Shanhui

    2017-03-01

    We theoretically demonstrate nontrivial topological effects for a probe field in a Raman medium undergoing molecular modulation processes. The medium is driven by two noncollinear pump beams. We show that the angle between the pumps is related to an effective gauge potential and an effective magnetic field for the probe field in the synthetic space consisting of a synthetic frequency dimension and a spatial dimension. As a result of such an effective magnetic field, the probe field can exhibit a topologically protected one-way edge state in the synthetic space, as well as Landau levels which manifest as suppression of both diffraction and sideband generation. Our work identifies a previously unexplored route towards creating topological photonics effects and highlights an important connection between topological photonics and nonlinear optics.

  7. EFFECTS OF MAGNETIC FIELD STRENGTH AND ORIENTATION ON MOLECULAR CLOUD FORMATION

    SciTech Connect

    Heitsch, Fabian; Hartmann, Lee W.; Stone, James M.

    2009-04-10

    We present a set of numerical simulations addressing the effects of magnetic field strength and orientation on the flow-driven formation of molecular clouds. Fields perpendicular to the flows sweeping up the cloud can efficiently prevent the formation of massive clouds but permit the buildup of cold, diffuse filaments. Fields aligned with the flows lead to substantial clouds, whose degree of fragmentation and turbulence strongly depends on the background field strength. Adding a random field component leads to a 'selection effect' for molecular cloud formation: high column densities are only reached at locations where the field component perpendicular to the flows is vanishing. Searching for signatures of colliding flows should focus on the diffuse, warm gas, since the cold gas phase making up the cloud will have lost the information about the original flow direction because the magnetic fields redistribute the kinetic energy of the inflows.

  8. The Effects of Ion heating in Martian Magnetic Crustal Fields: Particle Tracing and Ion Distributions

    NASA Astrophysics Data System (ADS)

    Fowler, C. M.; Andersson, L.

    2014-12-01

    Ion heating is a process that may allow low energy ions within the Martian ionosphere to be accelerated and escape. Ion heating can be especially efficient if the ions stay in the heating region for long time durations. With this in mind, the magnetic crustal field regions on Mars are particularly interesting. We focus on ions present within these regions, where changes in magnetic field strength and direction can heat these ions. Since crustal magnetic fields can maintain a trapped particle population it is unclear how efficiently plasma can be built up that can later escape to space. We investigate here two drivers: rotation of the planet and the solar wind pressure. As crustal fields rotate from the wake of the planet to the sub solar point and back, they experience compression and expansion over time scales of ~24 hours. The solar wind pressure on the other hand can cause variations over much shorter time scales (minutes). The effect of these two drivers using a particle tracing simulation that solves the Lorentz force is presented. O+ ions are seeded within the simulation box. The magnetic environment is a linear sum of a dipole field and a solar wind magnetic field. The dipole field represents the magnetic crustal field and the dipole strength is chosen to be consistent with MGS magnetometer observations of Martian crustal field regions. By increasing the solar wind strength the magnetic dipole is compressed. Decreasing solar wind strength allows the dipole to expand. Small magnitude, short time scale variations can be imposed over the top of this larger variation to represent short time scale solar wind variations. Since the purpose of this analysis is to understand the changes of the ion distribution inside the crustal field, simplistic assumptions of the field outside the crustal field can be made. Initial results are presented, with the focus on two main questions: (a) can low energy ions be heated and escape the closed dipole field lines as a result of

  9. Organic magnetic field sensor

    DOEpatents

    McCamey, Dane; Boehme, Christoph

    2017-01-24

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

  10. Effect of PEGylated superparamagnetic iron oxide nanoparticles (SPIONs) under magnetic field on amyloid beta fibrillation process.

    PubMed

    Mirsadeghi, Somayeh; Shanehsazzadeh, Saeed; Atyabi, Fatemeh; Dinarvand, Rassoul

    2016-02-01

    Superparamagnetic iron oxide nanoparticles (SPIONs) with specific surface coatings have been shown appropriate potential in the diagnosis and treatment of various brain diseases such as Alzheimer's. Comprehensive understanding of SPIONs interactions with amyloid beta (Aβ) and other amyloidogenic proteins is essential for their clinical application. SPIONs could be delivered to the target tissue under the magnetic field, while they might be influenced by the applied field. In this work, we exhibit the effect of different SPIONs (magnetized or non-magnetized with different surface charges) on the kinetics of Aβ fibrillation in aqueous solution by the aid of ThT assay. The results showed that applying of magnetic field to the SPIONs influences on the Aβ fibrillation because of its effect on the size due to surface charge. It was found that under magnetic field and high concentrations of nanoparticles (SPIONs-PEG-NH2), the Aβ fibrillation process accelerates, while at lower concentrations the fibrillation is inhibited. Furthermore, the coating charge has a considerable role in fibrillation process and the positively charged SPIONs/magnetized, at lower particle concentrations, accelerate the fibrillation compared with the negatively charged or uncharged SPIONs. This hints that SPIONs with a positive charge have dual effects on the Aβ fibrillation process. They influence on the concentration of monomeric protein in solution and thereby the nucleation time. Also, SPIONs have an effect on binding during the protein conformation.

  11. Photopyroelectric Calorimetry of Magnetic Nanofluids: Effect of Type of Surfactant and Magnetic Field

    NASA Astrophysics Data System (ADS)

    Dadarlat, D.; Longuemart, S.; Turcu, R.; Streza, M.; Vekas, L.; Hadj Sahraoui, A.

    2014-11-01

    Five types of magnetic nanofluids, based on nanoparticles with water as the carrier liquid, were investigated by using the two photopyroelectric (PPE) detection configurations (back (BPPE) and front (FPPE)), together with the thermal-wave resonator cavity (TWRC) technique as the scanning procedure. The difference between the nanofluids was the type of surfactant: double layers of lauric (LA-LA), oleic (OA-OA), and miristic (MA-MA) acids and also double layers of lauric-miristic (LA-MA) and palmitic-oleic (PA-OA) fatty acids were used. In both detection configurations, the information was contained in the phase of the PPE signal. The thermal diffusivity of nanofluids was obtained in the BPPE configuration, from the scan of the phase of the signal as a function of the liquid's thickness. Using the same scanning procedure in the FPPE configuration, the thermal effusivity was directly measured. The influence of a 0.12 kG magnetic field on the thermal effusivity and thermal diffusivity was also investigated. Because of different surfactants, the thermal effusivity of the investigated nanofluids ranges from to , and the thermal diffusivity, from to . The magnetic field has practically no influence on the thermal effusivity, and produces a maximum increase of the thermal diffusivity (LA-LA surfactant) of about 4 %.

  12. Near-Earth Magnetic Field Effects of Large-Scale Magnetospheric Currents

    NASA Technical Reports Server (NTRS)

    Luehr, Hermann; Xiong, Chao; Olsen, Nils; Le, Guan

    2016-01-01

    Magnetospheric currents play an important role in the electrodynamics of near- Earth space. This has been the topic of many space science studies. Here we focus on the magnetic fields they cause close to Earth. Their contribution to the geomagnetic field is the second largest after the core field. Significant progress in interpreting the magnetic fields from the different sources has been achieved thanks to magnetic satellite missions like Ørsted, CHAMP and now Swarm. Of particular interest for this article is a proper representation of the magnetospheric ring current effect. Uncertainties in modelling its effect still produce the largest residuals between observations and present-day geomagnetic field models. A lot of progress has been achieved so far, but there are still open issues like the characteristics of the partial ring current. Other currents discussed are those flowing in the magnetospheric tail. Also their magnetic contribution at LEO orbits is non-negligible. Treating them as an independent source is a more recent development, which has cured some of the problems in geomagnetic field modelling. Unfortunately there is no index available for characterizing the tail current intensity. Here we propose an approach that may help to properly quantify the magnetic contribution from the tail current for geomagnetic field modelling. Some open questions that require further investigation are mentioned at the end.

  13. Near-Earth Magnetic Field Effects of Large-Scale Magnetospheric Currents

    NASA Astrophysics Data System (ADS)

    Lühr, Hermann; Xiong, Chao; Olsen, Nils; Le, Guan

    2017-03-01

    Magnetospheric currents play an important role in the electrodynamics of near-Earth space. This has been the topic of many space science studies. Here we focus on the magnetic fields they cause close to Earth. Their contribution to the geomagnetic field is the second largest after the core field. Significant progress in interpreting the magnetic fields from the different sources has been achieved thanks to magnetic satellite missions like Ørsted, CHAMP and now Swarm. Of particular interest for this article is a proper representation of the magnetospheric ring current effect. Uncertainties in modelling its effect still produce the largest residuals between observations and present-day geomagnetic field models. A lot of progress has been achieved so far, but there are still open issues like the characteristics of the partial ring current. Other currents discussed are those flowing in the magnetospheric tail. Also their magnetic contribution at LEO orbits is non-negligible. Treating them as an independent source is a more recent development, which has cured some of the problems in geomagnetic field modelling. Unfortunately there is no index available for characterising the tail current intensity. Here we propose an approach that may help to properly quantify the magnetic contribution from the tail current for geomagnetic field modelling. Some open questions that require further investigation are mentioned at the end.

  14. Sub-millitesla magnetic field effects on the recombination reaction of flavin and ascorbic acid radicals

    NASA Astrophysics Data System (ADS)

    Evans, Emrys W.; Kattnig, Daniel R.; Henbest, Kevin B.; Hore, P. J.; Mackenzie, Stuart R.; Timmel, Christiane R.

    2016-08-01

    Even though the interaction of a <1 mT magnetic field with an electron spin is less than a millionth of the thermal energy at room temperature (kBT), it still can have a profound effect on the quantum yields of radical pair reactions. We present a study of the effects of sub-millitesla magnetic fields on the photoreaction of flavin mononucleotide with ascorbic acid. Direct control of the reaction pathway is achieved by varying the rate of electron transfer from ascorbic acid to the photo-excited flavin. At pH 7.0, we verify the theoretical prediction that, apart from a sign change, the form of the magnetic field effect is independent of the initial spin configuration of the radical pair. The data agree well with model calculations based on a Green's function approach that allows multinuclear spin systems to be treated including the diffusive motion of the radicals, their spin-selective recombination reactions, and the effects of the inter-radical exchange interaction. The protonation states of the radicals are uniquely determined from the form of the magnetic field-dependence. At pH 3.0, the effects of two chemically distinct radical pair complexes combine to produce a pronounced response to ˜500 μT magnetic fields. These findings are relevant to the magnetic responses of cryptochromes (flavin-containing proteins proposed as magnetoreceptors in birds) and may aid the evaluation of effects of weak magnetic fields on other biologically relevant electron transfer processes.

  15. A study on the effect of magnetic field on the corrosion behavior of materials

    NASA Astrophysics Data System (ADS)

    Pondichery, Soundarya

    Corrosion causes deterioration of a material due to its environment. Corrosion control has been one of the biggest challenges in most industries since many years. There are various notable and unknown factors that influence the rate of corrosion of a certain material/environment system. Magnetic fields and their driven effects on an electrochemical system has been recently gained interest. Various magnetic field driven forces occurring in an electrolyte have been reported during an electrochemical reaction. Lorentz force driven convection in the electrolyte, known as MHD effect and paramagnetic gradient forces are reported to be the most effective. This research studies the effects of an external magnetic field on the electrochemical nature of materials in 3.5% NaCl solution. To understand and analyze magnetic field effects on a wide range of materials, both ferromagnetic and non-magnetic materials which are active, active-passive type are studied in near sea water solution i.e. 3.5% NaCl solution. Potentiodynamic polarization and corrosion potential vs time tests were carried out to study and analyze corrosion behavior in 3.5% NaCl solution. Corrosion tests results were obtained both with and without the influence of an external magnetic field of 0.75T. On comparing the electrochemical analysis results of both conditions in 3.5% NaCl solution, it clearly depicts the effect of an external magnetic field on the corrosion potential and corrosion rate. In the case of ferromagnetic materials like 416 SS and 1018 carbon steel, a cathodic shift of the corrosion potential and increase in the corrosion rate was observed. While for ferrous but non-magnetic and passivating material like 304 SS, no effect of the magnetic field was observed which can be attributed to its non-magnetic austenitic phase and highly stable oxide formation tendency. Also, no effect was observed on the non-ferrous alloys like Ti alloy (Ti6Al4V) and Zn due to not only because of diamagnetic nature of

  16. Spinodal instabilities and the distillation effect in nuclear matter under strong magnetic fields

    SciTech Connect

    Rabhi, A.; Providencia, C.; Providencia, J. Da

    2009-01-15

    We study the effect of strong magnetic fields, of the order of 10{sup 18}-10{sup 19} G, on the instability region of nuclear matter at subsaturation densities. Relativistic nuclear models both with constant couplings and with density-dependent parameters are considered. It is shown that a strong magnetic field can have large effects on the instability regions giving rise to bands of instability and wider unstable regions. As a consequence, we predict larger transition densities at the inner edge of the crust of compact stars with strong magnetic fields. The direction of instability gives rise to a very strong distillation effect if the last Landau level is only partially filled. However, for almost completed Landau levels, an antidistillation effect may occur.

  17. Magnetic field effects in a polymer/fullerene blend photovoltaic cell

    NASA Astrophysics Data System (ADS)

    Jang, Hyuk-Jae; Basham, James I.; Gundlach, David J.; Richter, Curt A.

    Organic photovoltaic (OPV) systems based on blends of conjugated polymers and fullerene derivatives have shown great promise for low-cost and efficient photovoltaic applications. Recent findings suggest that a weak external magnetic field can disturb the spin configuration of excited states and subsequently change properties of OPV cells such as photocurrent. These changes are referred to as magnetic field effects (MFEs). In order to have a better understanding of the underlying mechanisms responsible for the MFEs in polymer/fullerene blend photovoltaic systems, we fabricated poly-3-hexylthiophene (P3HT):phenyl-C61-butyric acid methyl ester (PC61BM) cells and carried out photovoltaic device performance and impedance spectroscopy measurements with and without an externally applied magnetic field. A significant reduction in short circuit current (JSC) as well as open circuit voltage (VOC) was observed with an applied magnetic field of a 0.1 tesla compared to those measured without a magnetic field under the same intensity of illumination. Impedance spectroscopy data gives insights into the influence of an external magnetic field on charge generation and recombination near normal photovoltaic operating conditions.

  18. Effects of high-gradient magnetic fields on living cell machinery

    NASA Astrophysics Data System (ADS)

    Zablotskii, V.; Lunov, O.; Kubinova, S.; Polyakova, T.; Sykova, E.; Dejneka, A.

    2016-12-01

    A general interest in biomagnetic effects is related to fundamental studies of the influence of magnetic fields on living objects on the cellular and whole organism levels. Emerging technologies offer new directions for the use of high-gradient magnetic fields to control cell machinery and to understand the intracellular biological processes of the emerging field of nanomedicine. In this review we aim at highlighting recent advances made in identifying fundamental mechanisms by which magnetic gradient forces act on cell fate specification and cell differentiation. The review also provides an analysis of the currently available magnetic systems capable of generating magnetic fields with spatial gradients of up to 10 MT m-1, with the focus on their suitability for use in cell therapy. Relationships between experimental factors and underlying biophysical mechanisms and assumptions that would ultimately lead to a deeper understanding of cell machinery and the development of more predictive models for the evaluation of the effects of magnetic fields on cells, tissue and organisms are comprehensively discussed.

  19. Vestibular stimulation by magnetic fields

    PubMed Central

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

    2015-01-01

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

  20. Confinement effects of magnetic field on two-dimensional hydrogen atom in plasmas

    SciTech Connect

    Bahar, M. K.; Soylu, A.

    2015-05-15

    In this study, for the first time, the Schrödinger equation with more general exponential cosine screened Coulomb (MGECSC) potential is solved numerically in the presence and in the absence of an external magnetic field within two-dimensional formalism using the asymptotic iteration method. The MGECSC potential includes four different potential forms when considering different sets of the parameters in the potential. The plasma screening effects in the weak and strong magnetic field regimes as well as the confinement effects of magnetic field on the two-dimensional hydrogen atom in Debye and quantum plasmas are investigated by solving the corresponding equations. It is found that applying a uniform magnetic field on the hydrogen atom embedded in a plasma leads to change in the profile of the total interaction potential. Thus, confinement effects of magnetic field on hydrogen atom embedded in Debye and quantum plasmas modeled by a MGECSC potential lead to shift bound state energies. This effect would be important to isolate the plasma from the external environment in the experimental applications of plasma physics.

  1. Confinement effects of magnetic field on two-dimensional hydrogen atom in plasmas

    NASA Astrophysics Data System (ADS)

    Bahar, M. K.; Soylu, A.

    2015-05-01

    In this study, for the first time, the Schrödinger equation with more general exponential cosine screened Coulomb (MGECSC) potential is solved numerically in the presence and in the absence of an external magnetic field within two-dimensional formalism using the asymptotic iteration method. The MGECSC potential includes four different potential forms when considering different sets of the parameters in the potential. The plasma screening effects in the weak and strong magnetic field regimes as well as the confinement effects of magnetic field on the two-dimensional hydrogen atom in Debye and quantum plasmas are investigated by solving the corresponding equations. It is found that applying a uniform magnetic field on the hydrogen atom embedded in a plasma leads to change in the profile of the total interaction potential. Thus, confinement effects of magnetic field on hydrogen atom embedded in Debye and quantum plasmas modeled by a MGECSC potential lead to shift bound state energies. This effect would be important to isolate the plasma from the external environment in the experimental applications of plasma physics.

  2. Magnetic Field Induced Circular Photogalvanic Effect in InAs Quantum Wells

    DTIC Science & Technology

    2001-06-01

    St Petersburg, Russia We report on the first observation of a magnetic field induced circular photogalvanic effect ( CPGE ) in quantum wells (QWs). The...the magnetic field. For the sake of brevity we refer to the effect under consideration as to the magneto- CPGE . For bulk materials this effect was...theoretically treated in [2, 3] and observed in p-GaAs [4]. Phenomenologically, the magneto- CPGE is described by a third-rank tensor as J, = itaiýyBj•i (E x

  3. The effects of magnetic fields on the growth of thermal instabilities in cooling flows

    NASA Technical Reports Server (NTRS)

    David, Laurence P.; Bregman, Joel N.

    1989-01-01

    The effects of heat conduction and magnetic fields on the growth of thermal instabilities in cooling flows are examined using a time-dependent hydrodynamics code. It is found that, for magnetic field strengths of roughly 1 micro-Gauss, magnetic pressure forces can completely suppress shocks from forming in thermally unstable entropy perturbations with initial length scales as large as 20 kpc, even for initial amplitudes as great as 60 percent. Perturbations with initial amplitudes of 50 percent and initial magnetic field strengths of 1 micro-Gauss cool to 10,000 K on a time scale which is only 22 percent of the initial instantaneous cooling time. Nonlinear perturbations can thus condense out of cooling flows on a time scale substantially less than the time required for linear perturbations and produce significant mass deposition of cold gas while the accreting intracluster gas is still at large radii.

  4. Biologic effects of prolonged exposure to ELF electromagnetic fields in rats. 2: 50 Hz magnetic fields

    SciTech Connect

    Margonato, V.; Cerretelli, P.; Nicolini, P.; Conti, R.; Zecca, L.; Veicsteinas, Z.

    1995-12-31

    To provide possible laboratory support to health risk evaluation associated with long-term, low-intensity magnetic field exposure, 256 male albino rats and an equal number of control animals (initial age 12 weeks) were exposed 22 h/day to a 50 Hz magnetic flux density of 5 {micro}T for 32 weeks (a total of about 5,000 h). Hematology was studied from blood samples before exposure to the field and at 12 week intervals. Morphology and histology of liver, heart, mesenteric lymph nodes, and testes as well as brain neurotransmitters were assessed at the end of the exposure period. In two identical sets of experiments, no significant differences in the investigated variables were found between exposed and sham-exposed animals. It is concluded that continuous exposure to a 50 Hz magnetic field of 5 {micro}T from week 12 to week 44, which makes up {approximately}70% of the life span of the rat before sacrifice, does not cause changes in growth rate, in the morphology and histology of liver, heart, mesenteric lymph nodes, testes, and bone marrow, in hematology and hematochemistry, or in the neurotransmitters dopamine and serotonin.

  5. The effect of the magnetic field stretching on the development of the ring current

    NASA Astrophysics Data System (ADS)

    Ilie, R.; Toth, G.; Liemohn, M. W.; Skoug, R. M.

    2010-12-01

    While the dipolar solution for the geomagnetic field during quiet times represents a reasonable assumption, during storm activity this assumption becomes invalid. Theoretical and numerical modifications to an inner magnetosphere - Hot Electron Ion Drift Integrator (HEIDI)- model are implemented, in order to accommodate for a non-dipolar arbitrary magnetic field. HEIDI solves the time dependent, gyration and bounced averaged kinetic equation for the phase space density of one or more ring current species. In this study the effect of the magnetic field stretching on the build-up of the ring current is examined for both real and idealized input conditions.

  6. No effect of exposure to static and sinusoidal magnetic fields on nitric oxide production by macrophages

    SciTech Connect

    Mnaimneh, S. |; Bizri, M. |; Veyret, B.

    1996-12-31

    The effects of exposure to static (1--100 mT) or sinusoidal (1 Hz, 1.6 mT) magnetic fields on the production of nitric oxide (NO) by murine BCG-activated macrophages were investigated. In these cells, the inducible isoform of NO synthase is present. No significant differences were observed in nitrite levels among exposed, sham-exposed, or control macrophages after exposure for 14 h to static fields of 1, 10, 50, and 100 mT and to sinusoidal 1.6 mT, 1 Hz magnetic fields.

  7. Elementary excitations of a Bose-Einstein condensate in an effective magnetic field

    SciTech Connect

    Murray, D. R.; Barnett, Stephen M.; Oehberg, P.; Gomila, Damia

    2007-11-15

    We calculate the low-energy elementary excitations of a Bose-Einstein condensate in an effective magnetic field. The field is created by the interplay between light beams carrying orbital angular momentum and the trapped atoms [G. Juzeliunas et al., Phys. Rev. A 71, 053614 (2005)]. We examine the role of the homogeneous magnetic field, familiar from studies of rotating condensates, and also investigate spectra for vector potentials with a more general radial dependence. We discuss the instabilities which arise and how these may be manifested.

  8. Decoherence of trapped-ion internal and vibrational modes: The effect of fluctuating magnetic fields

    NASA Astrophysics Data System (ADS)

    Brouard, S.; Plata, J.

    2004-07-01

    The effect of ambient magnetic fields on the dynamics of a single trapped ion is studied analytically. We consider two electronic states with energy separation stochastically varied by magnetic-field perturbations and coupled to the vibrational modes by a laser. For Gaussian white noise, a master equation is derived and solved. The results obtained reveal how the effective Rabi frequencies and the decay rates depend on the noise strength and on the number state index. The detection of features specific to magnetic-field noise in the evolution of states that can be prepared under standard experimental conditions is discussed. A comparison with the effects of laser intensity and phase fluctuations is presented. Implications for the realization of logic gates are analyzed.

  9. Effect of electric field and strain on the magnetic properties of phase separated manganites

    NASA Astrophysics Data System (ADS)

    Grant, Daniel M.

    Perovskite manganese oxide (manganites) have attracted research attention due to a wide variety of complex behaviors observed, including colossal responses to external perturbations. More recent work has focused on the competing ground states and the coexistence of magnetic and non-magnetic phases in manganites. Anisotropic resistance changes have been observed in high quality thin film manganites, possibly due to dielectrophoresis, upon application of an electric field. Dielectrophoresis is usually observed in fluid-like systems in an electric field but is surprisingly useful in explaining the transport properties of manganites due to the fluid-like behavior of competing phases. A main goal of this dissertation is to explore the role of magnetic interactions on the dielectrophoresis effects on ferromagnetic metallic regions in phase separated manganite thin films. The combined effect of electric and magnetic fields in these manganites could reveal a novel form of magnetoelectric effect. In one set of experiments, a magnetic field decreased the amount of time needed for the dielectrophoresis to lead to a large drop in the resistance along one direction, showing the importance of magnetic interactions in dielectrophoresis. In another set of experiments, breaking down the large resistance of a manganite sample produced a small change in coercive field, further confirming the relationship between electric and magnetic effects in manganites. However, the largest effect on the magnetic properties of the thin films was from confinement of the competing phases in micrometer scale structures fabricated on the thin films. Coercive field increases of about 100- 400% were observed in a certain range of film thicknesses. To analyze such behavior in manganites, high quality thin films of the phase-separated manganite (La1-xPrx)1-yCa yMnO3 (LPCMO) were grown on NdGaO3 (NGO) substrates using pulsed laser deposition. Mangetotransport, magnetization, and scanning probe microscopy

  10. The Effect of Extremely Low Frequency Alternating Magnetic Field on the Behavior of Animals in the Presence of the Geomagnetic Field

    PubMed Central

    Belova, Natalia A.; Acosta-Avalos, Daniel

    2015-01-01

    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. PMID:26823664

  11. The effect of supernova rate on the magnetic field evolution in barred galaxies

    NASA Astrophysics Data System (ADS)

    Kulpa-Dybeł, K.; Nowak, N.; Otmianowska-Mazur, K.; Hanasz, M.; Siejkowski, H.; Kulesza-Żydzik, B.

    2015-03-01

    Context. For the first time, our magnetohydrodynamical numerical calculations provide results for a three-dimensional model of barred galaxies involving a cosmic-ray driven dynamo process that depends on star formation rates. Furthermore, we argue that the cosmic-ray driven dynamo can account for a number of magnetic features in barred galaxies, such as magnetic arms observed along the gaseous arms, magnetic arms in the inter-arm regions, polarized emission that is at the strongest in the central part of the galaxy, where the bar is situated, polarized emission that forms ridges coinciding with the dust lanes along the leading edges of the bar, as well as their very strong total radio intensity. Aims: Our numerical model probes what kind of physical processes could be responsible for the magnetic field topology observed in barred galaxies (modes, etc.). We compare our modelled results directly with observations, constructing models of high-frequency (Faraday rotation-free) polarized radio emission maps out of the simulated magnetic field and cosmic ray pattern in our modeled galaxy. We also take the effects of projection into account as well as the limited resolution. Methods: We applied global 3D numerical calculations of a cosmic-ray driven dynamo in barred galaxies with different physical input parameters such as the supernova (SN) rate. Results: Our simulation results lead to the modelled magnetic field structure similar to the one observed on the radio maps of barred galaxies. Moreover, they cast new light on a number of properties in barred and spiral galaxies, such as fast exponential growth of the total magnetic energy to the present values. The quadrupole modes of magnetic field are often identified in barred galaxies, but the dipole modes (e.g., in NGC 4631) are found very seldom. In our simulations the quadrupole configuration dominates and the dipole configuration only appears once in the case of model S100, apparently as a consequence of the choice of

  12. Technical Note: A Monte Carlo study of magnetic-field-induced radiation dose effects in mice

    PubMed Central

    Liao, Zhongxing; Melancon, Adam D.; Guindani, Michele; Followill, David S.; Tailor, Ramesh C.; Hazle, John D.; Court, Laurence E.

    2015-01-01

    Purpose: Magnetic fields are known to alter radiation dose deposition. Before patients receive treatment using an MRI-linear accelerator (MRI-Linac), preclinical studies are needed to understand the biological consequences of magnetic-field-induced dose effects. In the present study, the authors sought to identify a beam energy and magnetic field strength combination suitable for preclinical murine experiments. Methods: Magnetic field dose effects were simulated in a mouse lung phantom using various beam energies (225 kVp, 350 kVp, 662 keV [Cs-137], 2 MV, and 1.25 MeV [Co-60]) and magnetic field strengths (0.75, 1.5, and 3 T). The resulting dose distributions were compared with those in a simulated human lung phantom irradiated with a 6 or 8 MV beam and orthogonal 1.5 T magnetic field. Results: In the human lung phantom, the authors observed a dose increase of 45% and 54% at the soft-tissue-to-lung interface and a dose decrease of 41% and 48% at the lung-to-soft-tissue interface for the 6 and 8 MV beams, respectively. In the mouse simulations, the magnetic fields had no measurable effect on the 225 or 350 kVp dose distribution. The dose increases with the Cs-137 beam for the 0.75, 1.5, and 3 T magnetic fields were 9%, 29%, and 42%, respectively. The dose decreases were 9%, 21%, and 37%. For the 2 MV beam, the dose increases were 16%, 33%, and 31% and the dose decreases were 9%, 19%, and 30%. For the Co-60 beam, the dose increases were 19%, 54%, and 44%, and the dose decreases were 19%, 42%, and 40%. Conclusions: The magnetic field dose effects in the mouse phantom using a Cs-137, 3 T combination or a Co-60, 1.5 or 3 T combination most closely resemble those in simulated human treatments with a 6 MV, 1.5 T MRI-Linac. The effects with a Co-60, 1.5 T combination most closely resemble those in simulated human treatments with an 8 MV, 1.5 T MRI-Linac. PMID:26328998

  13. Technical Note: A Monte Carlo study of magnetic-field-induced radiation dose effects in mice

    SciTech Connect

    Rubinstein, Ashley E.; Liao, Zhongxing; Melancon, Adam D.; Followill, David S.; Tailor, Ramesh C.; Guindani, Michele; Hazle, John D.; Court, Laurence E.

    2015-09-15

    Purpose: Magnetic fields are known to alter radiation dose deposition. Before patients receive treatment using an MRI-linear accelerator (MRI-Linac), preclinical studies are needed to understand the biological consequences of magnetic-field-induced dose effects. In the present study, the authors sought to identify a beam energy and magnetic field strength combination suitable for preclinical murine experiments. Methods: Magnetic field dose effects were simulated in a mouse lung phantom using various beam energies (225 kVp, 350 kVp, 662 keV [Cs-137], 2 MV, and 1.25 MeV [Co-60]) and magnetic field strengths (0.75, 1.5, and 3 T). The resulting dose distributions were compared with those in a simulated human lung phantom irradiated with a 6 or 8 MV beam and orthogonal 1.5 T magnetic field. Results: In the human lung phantom, the authors observed a dose increase of 45% and 54% at the soft-tissue-to-lung interface and a dose decrease of 41% and 48% at the lung-to-soft-tissue interface for the 6 and 8 MV beams, respectively. In the mouse simulations, the magnetic fields had no measurable effect on the 225 or 350 kVp dose distribution. The dose increases with the Cs-137 beam for the 0.75, 1.5, and 3 T magnetic fields were 9%, 29%, and 42%, respectively. The dose decreases were 9%, 21%, and 37%. For the 2 MV beam, the dose increases were 16%, 33%, and 31% and the dose decreases were 9%, 19%, and 30%. For the Co-60 beam, the dose increases were 19%, 54%, and 44%, and the dose decreases were 19%, 42%, and 40%. Conclusions: The magnetic field dose effects in the mouse phantom using a Cs-137, 3 T combination or a Co-60, 1.5 or 3 T combination most closely resemble those in simulated human treatments with a 6 MV, 1.5 T MRI-Linac. The effects with a Co-60, 1.5 T combination most closely resemble those in simulated human treatments with an 8 MV, 1.5 T MRI-Linac.

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

    PubMed

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

    2015-03-01

    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 F1 hybrid males were exposed to 10, 100 or 300μT of 50Hz magnetic fields for 2 or 15h. 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 1Gy 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.

  15. Effect of steady and time-harmonic magnetic fields on macrosegragation in alloy solidification

    SciTech Connect

    Incropera, F.P.; Prescott, P.J.

    1995-12-31

    Buoyancy-induced convection during the solidification of alloys can contribute significantly to the redistribution of alloy constituents, thereby creating large composition gradients in the final ingot. Termed macrosegregation, the condition diminishes the quality of the casting and, in the extreme, may require that the casting be remelted. The deleterious effects of buoyancy-driven flows may be suppressed through application of an external magnetic field, and in this study the effects of both steady and time-harmonic fields have been considered. For a steady magnetic field, extremely large field strengths would be required to effectively dampen convection patterns that contribute to macrosegregation. However, by reducing spatial variations in temperature and composition, turbulent mixing induced by a time-harmonic field reduces the number and severity of segregates in the final casting.

  16. Experimental concept for examination of biological effects of magnetic field concealed by gravity.

    PubMed

    Yamashita, M; Tomita-Yokotani, K; Hashimoto, H; Takai, M; Tsushima, M; Nakamura, T

    2004-01-01

    Space is not only a place to study biological effects of gravity, but also provides unique opportunities to examine other environmental factors, where the biological actions are masked by gravity on the ground. Even the earth's magnetic field is steadily acting on living systems, and is known to influence many biological processes. A systematic survey and assessment of its action are difficult to conduct in the presence of dominant factors, such as gravity. Investigation of responses of biological systems against the combined environment of zero-gravity and zero-magnetic field might establish the baseline for the analysis of biological effects of magnetic factors. We propose, in this paper, an experimental concept in this context, together with a practical approach of the experiments, both in orbit and on the ground, with a thin magnetic shielding film. Plant epicotyl growth was taken as an exemplar index to evaluate technical and scientific feasibility of the proposed system concept.

  17. Commensurability effects in a Josephson tunnel junction in the field of an array of magnetic particles

    SciTech Connect

    Samokhvalov, A. V.

    2007-03-15

    Commensurability effects have been theoretically studied in a hybrid system consisting of a Josephson junction located in a nonuniform field induced by an array of magnetic particles. A periodic phase-difference distribution in the junction that is caused by the formation of a regular lattice of Abrikosov vortices generated by the magnetic field of the particles in superconducting electrodes is calculated. The dependence of the critical current through the junction I{sub c} on the applied magnetic field H is shown to differ strongly from the conventional Fraunhofer diffraction pattern because of the periodic modulation of the Josephson phase difference created by the vortices. More specifically, the I{sub c}(H) pattern contains additional resonance peaks, whose positions and heights depend on the parameters and magnetic state of the particles in the array. These specific features of the I{sub c}(H) dependence are observed when the period of the Josephson current modulation by the field of the magnetic particles and the characteristic scale of the change in the phase difference by the applied magnetic field are commensurable. The conditions that determine the positions of the commensurability peaks are obtained, and they are found to agree well with experimental results.

  18. The heating effect of iron-cobalt magnetic nanofluids in an alternating magnetic field: application in magnetic hyperthermia treatment

    NASA Astrophysics Data System (ADS)

    Shokuhfar, Ali; Seyyed Afghahi, Seyyed Salman

    2013-12-01

    In this research, FeCo alloy magnetic nanofluids were prepared by reducing iron(III) chloride hexahydrate and cobalt(II) sulfate heptahydrate with sodium borohydride in a water/CTAB/hexanol reverse micelle system for application in magnetic hyperthermia treatment. X-ray diffraction, electron microscopy, selected area electron diffraction, and energy-dispersive analysis indicate the formation of bcc-structured iron-cobalt alloy. Magnetic property assessment of nanoparticles reveals that some samples are single-domain superparamagnetic, while others are single- or multi-domain ferromagnetic. The stability of the magnetic fluids was achieved by using a CTAB/1-butanol surfactant bilayer. Results of Gouy magnetic susceptibility balance experiments indicate good stability of FeCo nanoparticles even after dilution. The inductive properties of corresponding magnetic fluids including temperature rise and specific absorption rate were determined. Results show that with increasing of the nanoparticle size in the single-domain size regime, the generated heat increases, indicating the significant effect of the hysteresis loss. Finally, the central parameter controlling the specific absorption rate of nanoparticles was introduced, the experimental results were compared with those of the Stoner-Wohlfarth model and linear response theory, and the best sample for magnetic hyperthermia treatment was specified.

  19. The heating effect of iron-cobalt magnetic nanofluids in an alternating magnetic field: application in magnetic hyperthermia treatment.

    PubMed

    Shokuhfar, Ali; Seyyed Afghahi, Seyyed Salman

    2013-12-20

    In this research, FeCo alloy magnetic nanofluids were prepared by reducing iron(III) chloride hexahydrate and cobalt(II) sulfate heptahydrate with sodium borohydride in a water/CTAB/hexanol reverse micelle system for application in magnetic hyperthermia treatment. X-ray diffraction, electron microscopy, selected area electron diffraction, and energy-dispersive analysis indicate the formation of bcc-structured iron-cobalt alloy. Magnetic property assessment of nanoparticles reveals that some samples are single-domain superparamagnetic, while others are single- or multi-domain ferromagnetic. The stability of the magnetic fluids was achieved by using a CTAB/1-butanol surfactant bilayer. Results of Gouy magnetic susceptibility balance experiments indicate good stability of FeCo nanoparticles even after dilution. The inductive properties of corresponding magnetic fluids including temperature rise and specific absorption rate were determined. Results show that with increasing of the nanoparticle size in the single-domain size regime, the generated heat increases, indicating the significant effect of the hysteresis loss. Finally, the central parameter controlling the specific absorption rate of nanoparticles was introduced, the experimental results were compared with those of the Stoner-Wohlfarth model and linear response theory, and the best sample for magnetic hyperthermia treatment was specified.

  20. Interacting electrons in a two-dimensional disordered environment: effect of a zeeman magnetic field.

    PubMed

    Denteneer, P J H; Scalettar, R T

    2003-06-20

    The effect of a Zeeman magnetic field coupled to the spin of the electrons on the conducting properties of the disordered Hubbard model is studied. Using the determinant quantum Monte Carlo method, the temperature- and magnetic-field-dependent conductivity is calculated, as well as the degree of spin polarization. We find that the Zeeman magnetic field suppresses the metallic behavior present for certain values of interaction and disorder strength and is able to induce a metal-insulator transition at a critical field strength. It is argued that the qualitative features of magnetoconductance in this microscopic model containing both repulsive interactions and disorder are in agreement with experimental findings in two-dimensional electron and hole gases in semiconductor structures.

  1. Competition between Abelian and Zeeman magnetic field effects in a two dimensional ultracold gas of fermions

    SciTech Connect

    Cichy, Agnieszka; Polak, Tomasz P.

    2015-03-15

    The ground state of ultracold fermions in the presence of effects of orbital and Zeeman magnetic fields is analyzed. Five different states are found: unpolarized superconducting state, partially and fully polarized normal states and phase separated regions, partially or fully polarized. The system, in the presence of orbital synthetic magnetic field effects, shows non-monotonous changes of the phase boundaries when electron concentration is varied. We observe not only reentrant phenomena, but also density dependent oscillations of different areas of the phase diagram. Moreover the chemical potential shows oscillatory behavior and discontinuities with respect to changes in the number of fermions.

  2. Effect of external magnetic field on the coexistence of superconductivity and JT distortion in iron pnictides

    NASA Astrophysics Data System (ADS)

    Pradhan, B.; Goi, S. K.; Mishra, R. N.

    2016-12-01

    We have presented a theoretical study for the coexistence of superconductivity (SC) and Jahn-Teller (JT) effect with applied magnetic field on iron based high-Tc superconductors in s-wave symmetry. The analytic expressions for the temperature dependence of the SC and JT order parameters are derived by Zubarev's technique of double time single particle Green's function method and solved self-consistently. It is observed that in the interplay region, both the gap parameters exhibit very strong dependence of their gap values. The effect of external magnetic field on the gap parameters and the electronic density of states (DOS) is studied.

  3. Considerations of variations in ionospheric field effects in mapping equatorial lithospheric Magsat magnetic anomalies

    NASA Technical Reports Server (NTRS)

    Ravat, D.; Hinze, W. J.

    1993-01-01

    The longitudinal, seasonal, and altitude-dependent variability of the magnetic field in equatorial latitudes is investigated to determine the effect of these variabilities on the isolation of lithospheric Magsat magnetic anomalies. It was found that the amplitudes of the dawn dip-latitude averages were small compared to the dusk averages, and that they were of the opposite sign. The longitudinal variation in the equatorial amplitudes of the dawn dip-latitude averages was not entirely consistent with the present knowledge of the electrojet field. Based on the results, a procedure is implemented for reducing the equatorial ionospheric effects from the Magsat data on the lithospheric component.

  4. Effect of static magnetic fields and phloretin on antioxidant defense system of human fibroblasts.

    PubMed

    Pawłowska-Góral, Katarzyna; Kimsa-Dudek, Magdalena; Synowiec-Wojtarowicz, Agnieszka; Orchel, Joanna; Glinka, Marek; Gawron, Stanisław

    2016-08-01

    The available evidence from in vitro and in vivo studies is deemed not sufficient to draw conclusions about the potential health effects of static magnetic field (SMF) exposure. Therefore, the aim of the present study was to determine the influence of static magnetic fields and phloretin on the redox homeostasis of human dermal fibroblasts. Control fibroblasts and fibroblasts treated with phloretin were subjected to the influence of static magnetic fields. Three chambers with static magnetic fields of different intensities (0.4, 0.55, and 0.7 T) were used in the study. Quantification of superoxide dismutase 1 (SOD1), superoxide dismutase 2 (SOD2), glutathione peroxidase 1 (GPX1), microsomal glutathione S-transferase 1 (MGST1), glutathione reductase (GSR), and catalase (CAT) messenger RNAs (mRNAs) was performed by means of real-time reverse transcription PCR (QRT-PCR) technique. Superoxide dismutase (SOD), glutathione peroxidase (GPx), and catalase (CAT) activities were measured using a commercially available kit. No significant differences were found in SOD1, SOD2, GPX1, MGST1, GSR, and CAT mRNA levels among the studied groups in comparison to the control culture without phloretin and without the magnet. There were also no changes in SOD, GPx, and CAT activities. In conclusion, our study indicated that static magnetic fields generated by permanent magnets do not exert a negative influence on the oxidative status of human dermal fibroblasts. Based on these studies, it may also be concluded that phloretin does not increase its antioxidant properties under the influence of static magnetic fields. However, SMF-induced modifications at the cellular and molecular level require further clarification.

  5. Cosmic Magnetic Fields - An Overview

    NASA Astrophysics Data System (ADS)

    Wielebinski, Richard; Beck, Rainer

    Magnetic fields have been known in antiquity. Aristotle attributes the first of what could be called a scientific discussion on magnetism to Thales, who lived from about 625 BC. In China “magnetic carts” were in use to help the Emperor in his journeys of inspection. Plinius comments that in the Asia Minor province of Magnesia shepherds' staffs get at times “glued” to a stone, a alodestone. In Europe the magnetic compass came through the Arab sailors who met the Portuguese explorers. The first scientific treatise on magnetism, “De Magnete”, was published by William Gilbert who in 1600 described his experiments and suggested that the Earth was a huge magnet. Johannes Kepler was a correspondent of Gilbert and at times suggested that planetary motion was due to magnetic forces. Alas, this concept was demolished by Isaac Newton,who seeing the falling apple decided that gravity was enough. This concept of dealing with gravitational forces only remains en vogue even today. The explanations why magnetic effects must be neglected go from “magnetic energy is only 1% of gravitation” to “magnetic fields only complicate the beautiful computer solutions”. What is disregarded is the fact that magnetic effects are very directional(not omni-directional as gravity) and also the fact that magnetic fields are seen every where in our cosmic universe.

  6. Effect of transverse magnetic fields on a simulated in-line 6 MV linac

    NASA Astrophysics Data System (ADS)

    St. Aubin, J.; Steciw, S.; Fallone, B. G.

    2010-08-01

    The effects of a transverse magnetic field on an in-line side-coupled 6 MV linear accelerator are given. The results are directly applicable to a linac-MR system used for real-time image guided adaptive radiotherapy. Our previously designed end-to-end linac simulation incorporated the results from the axisymmetric 2D electron gun program EGN2w. However, since the magnetic fields being investigated are non-axisymmetric in nature for the work presented here, the electron gun simulation was performed using OPERA-3d/SCALA. The simulation results from OPERA-3d/SCALA showed excellent agreement with previous results. Upon the addition of external magnetic fields to our fully 3D linac simulation, it was found that a transverse magnetic field of 6 G resulted in a 45 ± 1% beam loss, and by 14 G, no electrons were incident on the target. Transverse magnetic fields on the linac simulation produced a highly asymmetric focal spot at the target, which translated into a 13% profile asymmetry at 6 G. Upon translating the focal spot with respect to the target coordinates, profile symmetry was regained at the expense of a lateral shift in the dose profiles. It was found that all points in the penumbra failed a 1%/1 mm acceptance criterion for fields between 4 and 6 G. However, it was also found that the lateral profile shifts were corrected by adjusting the jaw positions asymmetrically.

  7. Magnetic field effects on the static quark potential at zero and finite temperature

    NASA Astrophysics Data System (ADS)

    Bonati, Claudio; D'Elia, Massimo; Mariti, Marco; Mesiti, Michele; Negro, Francesco; Rucci, Andrea; Sanfilippo, Francesco

    2016-11-01

    We investigate the static Q Q ¯ potential at zero and finite temperature in the presence of a constant and uniform external magnetic field B →, for several values of the lattice spacing and for different orientations with respect to B →. As a byproduct, we provide continuum limit extrapolated results for the string tension, the Coulomb coupling and the Sommer parameter at T =0 and B =0 . We confirm the presence in the continuum of a B -induced anisotropy, regarding essentially the string tension, for which it is of the order of 15% at |e |B ˜1 GeV2 and would suggest, if extrapolated to larger fields, a vanishing string tension along the magnetic field for |e |B ≳4 GeV2. The angular dependence for |e |B ≲1 GeV2 can be nicely parametrized by the first allowed term in an angular Fourier expansion, corresponding to a quadrupole deformation. Finally, for T ≠0 , the main effect of the magnetic field is a general suppression of the string tension, leading to a early loss of the confining properties: this happens even before the appearance of inverse magnetic catalysis in the chiral condensate, supporting the idea that the influence of the magnetic field on the confining properties is the leading effect originating the decrease of Tc as a function of B .

  8. Unraveling the temperature and voltage dependence of magnetic field effects in organic semiconductors

    NASA Astrophysics Data System (ADS)

    Janssen, Paul; Wouters, Steinar H. W.; Cox, Matthijs; Koopmans, Bert

    2013-11-01

    In recent years, it was discovered that the current through an organic semiconductor, sandwiched between two non-magnetic electrodes, can be changed significantly by applying a small magnetic field. This surprisingly large magnetoresistance effect, often dubbed as organic magnetoresistance (OMAR), has puzzled the young field of organic spintronics during the last decade. Here, we present a detailed study on the voltage and temperature dependence of OMAR, aiming to unravel the lineshapes of the magnetic field effects and thereby gain a deeper fundamental understanding of the underlying microscopic mechanism. Using a full quantitative analysis of the lineshapes, we are able to extract all linewidth parameters and the voltage and temperature dependencies are explained with a recently proposed trion mechanism. Moreover, explicit microscopic simulations show a qualitative agreement to the experimental results.

  9. Effective realization of random magnetic fields in compounds with large single-ion anisotropy

    NASA Astrophysics Data System (ADS)

    Herbrych, J.; Kokalj, J.

    2017-03-01

    We show that spin S =1 system with large and random single-ion anisotropy can be at low energies mapped to a S =1 /2 system with random magnetic fields. This is, for example, realized in Ni (Cl1 -xBrx)2-4 SC (NH2)2 compound (DTNX) and therefore it represents a long-sought realization of random local (on-site) magnetic fields in antiferromagnetic systems. We support the mapping by numerical study of S =1 and effective S =1 /2 anisotropic Heisenberg chains and find excellent agreement for static quantities and also for the spin conductivity. Such systems can therefore be used to study the effects of local random magnetic fields on transport properties.

  10. Findings point to complexity of health effects of electric, magnetic fields

    SciTech Connect

    Hileman, B.

    1994-07-18

    Significant findings on the physiological consequences of exposure to electric and magnetic fields (EMF) have been coming from current research in various areas: cell function, epidemiology, bone healing, health effects of video display terminals, and whole-animal studies. But as results presented to more than 500 attendees at the 16th annual meeting of the Bioelectromagnetics Society in Copenhagen in mid-June clearly showed, research on EMF is complicated. The most comprehensive results presented at the meeting were in the area of breast cancer. Taken together, data from epidemiological, cellular, hormonal, and animal studies give a multifaceted picture of how EMF might promote the disease. One theory linking EMF and breast cancer is that magnetic fields lower the amount of the hormone melatonin produced in humans. As a consequence, the natural suppressive effect of melatonin on breast cancer cell growth is reduced. Another theory is that magnetic fields may directly interfere with melatonin's suppressive action on breast cancer cell proliferation.

  11. Adiabatic measurements of magneto-caloric effects in pulsed high magnetic fields up to 55 T

    NASA Astrophysics Data System (ADS)

    Kihara, T.; Kohama, Y.; Hashimoto, Y.; Katsumoto, S.; Tokunaga, M.

    2013-07-01

    Magneto-caloric effects (MCEs) measurement system in adiabatic condition is proposed to investigate the thermodynamic properties in pulsed magnetic fields up to 55 T. With taking the advantage of the fast field-sweep rate in pulsed field, adiabatic measurements of MCEs were carried out at various temperatures. To obtain the prompt response of the thermometer in the pulsed field, a thin film thermometer is grown directly on the sample surfaces. The validity of the present setup was demonstrated in the wide temperature range through the measurements on Gd at about room temperature and on Gd3Ga5O12 at low temperatures. The both results show reasonable agreement with the data reported earlier. By comparing the MCE data with the specific heat data, we could estimate the entropy as functions of magnetic field and temperature. The results demonstrate the possibility that our approach can trace the change in transition temperature caused by the external field.

  12. The effects of magnetic field in plume region on the performance of multi-cusped field thruster

    SciTech Connect

    Hu, Peng Liu, Hui Yu, Daren; Gao, Yuanyuan; Mao, Wei

    2015-10-15

    The performance characteristics of a Multi-cusped Field Thruster depending on the magnetic field in the plume region were investigated. Five magnetic field shielding rings were separately mounted near the exit of discharge channel to decrease the strength of magnetic field in the plume region in different levels, while the magnetic field in the upstream was well maintained. The test results show that the electron current increases with the decrease of magnetic field strength in the plume region, which gives rise to higher propellant utilization and lower current utilization. On the other hand, the stronger magnetic field in the plume region improves the performance at low voltages (high current mode) while lower magnetic field improves the performance at high voltages (low current mode). This work can provide some optimal design ideas of the magnetic strength in the plume region to improve the performance of thruster.

  13. Field-free magnetization reversal by spin-Hall effect and exchange bias.

    PubMed

    van den Brink, A; Vermijs, G; Solignac, A; Koo, J; Kohlhepp, J T; Swagten, H J M; Koopmans, B

    2016-03-04

    As the first magnetic random access memories are finding their way onto the market, an important issue remains to be solved: the current density required to write magnetic bits becomes prohibitively high as bit dimensions are reduced. Recently, spin-orbit torques and the spin-Hall effect in particular have attracted significant interest, as they enable magnetization reversal without high current densities running through the tunnel barrier. For perpendicularly magnetized layers, however, the technological implementation of the spin-Hall effect is hampered by the necessity of an in-plane magnetic field for deterministic switching. Here we interface a thin ferromagnetic layer with an anti-ferromagnetic material. An in-plane exchange bias is created and shown to enable field-free S HE-driven magnetization reversal of a perpendicularly magnetized Pt/Co/IrMn structure. Aside from the potential technological implications, our experiment provides additional insight into the local spin structure at the ferromagnetic/anti-ferromagnetic interface.

  14. Field-free magnetization reversal by spin-Hall effect and exchange bias

    NASA Astrophysics Data System (ADS)

    van den Brink, A.; Vermijs, G.; Solignac, A.; Koo, J.; Kohlhepp, J. T.; Swagten, H. J. M.; Koopmans, B.

    2016-03-01

    As the first magnetic random access memories are finding their way onto the market, an important issue remains to be solved: the current density required to write magnetic bits becomes prohibitively high as bit dimensions are reduced. Recently, spin-orbit torques and the spin-Hall effect in particular have attracted significant interest, as they enable magnetization reversal without high current densities running through the tunnel barrier. For perpendicularly magnetized layers, however, the technological implementation of the spin-Hall effect is hampered by the necessity of an in-plane magnetic field for deterministic switching. Here we interface a thin ferromagnetic layer with an anti-ferromagnetic material. An in-plane exchange bias is created and shown to enable field-free S HE-driven magnetization reversal of a perpendicularly magnetized Pt/Co/IrMn structure. Aside from the potential technological implications, our experiment provides additional insight into the local spin structure at the ferromagnetic/anti-ferromagnetic interface.

  15. The Effect of Magnetic Field on Mean Flow Generation by Rotating Two-dimensional Convection

    NASA Astrophysics Data System (ADS)

    Currie, Laura K.

    2016-11-01

    Motivated by the significant interaction of convection, rotation, and magnetic field in many astrophysical objects, we investigate the interplay between large-scale flows driven by rotating convection and an imposed magnetic field. We utilize a simple model in two dimensions comprised of a plane layer that is rotating about an axis inclined to gravity. It is known that this setup can result in strong mean flows; we numerically examine the effect of an imposed horizontal magnetic field on such flows. We show that increasing the field strength in general suppresses the time-dependent mean flows, but in some cases it organizes them, leading to stronger time-averaged flows. Furthermore, we discuss the effect of the field on the correlations responsible for driving the flows and the competition between Reynolds and Maxwell stresses. A change in behavior is observed when the (fluid and magnetic) Prandtl numbers are decreased. In the smaller Prandtl number regime, it is shown that significant mean flows can persist even when the quenching of the overall flow velocity by the field is relatively strong.

  16. THE EFFECT OF LOWER MANTLE METALLIZATION ON MAGNETIC FIELD GENERATION IN ROCKY EXOPLANETS

    SciTech Connect

    Vilim, R.; Stanley, S.; Elkins-Tanton, L.

    2013-05-10

    Recent theoretical and experimental evidence indicates that many of the materials that are thought to exist in the mantles of terrestrial exoplanets will metallize and become good conductors of electricity at mantle pressures. This allows for strong electromagnetic coupling of the core and the mantle in these planets. We use a numerical dynamo model to study the effect of a metallized lower mantle on the dynamos of terrestrial exoplanets using several inner core sizes and mantle conductivities. We find that the addition of an electrically conducting mantle results in stronger core-mantle boundary fields because of the increase in magnetic field stretching. We also find that a metallized mantle destabilizes the dynamo resulting in less dipolar, less axisymmetric poloidal magnetic fields at the core-mantle boundary. The conducting mantle efficiently screens these fields to produce weaker surface fields. We conclude that a conducting mantle will make the detection of extrasolar terrestrial magnetic fields more difficult while making the magnetic fields in the dynamo region stronger.

  17. Electron Inertia Effects in Hall-Driven Magnetic Field Penetration in Electron-Magnetohydrodynamics

    NASA Astrophysics Data System (ADS)

    Richardson, Andrew; Angus, Justin; Swanekamp, Stephen; Schumer, Joseph; Ottinger, Paul

    2015-11-01

    Magnetic field penetration in electron-magnetohydrodynamics (EMHD) can be driven by density gradients through the Hall term. Here we describe the effect of electron inertia on simplified one- and two- dimensional models of a magnetic front. Nonlinear effects due to inertia cause the 1D model to develop peaked solitary waves, while in 2D a shear-driven Kelvin-Helholtz like instability causes the front to break into a series of vortices which propagate into the plasma. The combination of these two effects means that in 2D, Hall driven magnetic field penetration will typically happen in the form of complex vortex-dominated penetration, rather than as a transversely-smooth shock front. This work was supported by the Naval Research Laboratory Base Program.

  18. THE EFFECT OF MAGNETIC FIELD ERRORS ON DYNAMICAL FRICTION IN ELECTRON COOLERS.

    SciTech Connect

    FEDOTOV, A.V.; LITVINENKO, V.N.

    2005-05-16

    A proposed luminosity upgrade to the Relativistic Heavy Ion Collider (RHIC) includes a novel electron cooling section [1], which would use -55 MeV electrons to cool fully-ionized 100 GeV/nucleon gold ions. A strong (1-5 T) solenoidal field will be used to magnetize the electrons and thus enhance the dynamical friction force on the ions. The physics of magnetized friction is being simulated for RHIC parameters [2,3,4], using the VORPAL code [5]. Most theoretical treatments for magnetized dynamical friction do not consider the effect of magnetic field errors, except in a parametric fashion. However, field errors can in some cases dramatically reduce the velocity drag and corresponding cooling rate. We present two simple analytical models for the magnetic field errors. The simulated dynamical friction for the case of a perfect solenoidal field is compared with results from these new models. We simulate parameters for the existing cooler of the CELSIUS ring, because recent experiments [6] provide data that will later be used for code validation.

  19. Geomagnetic and strong static magnetic field effects on growth and chlorophyll a fluorescence in Lemna minor.

    PubMed

    Jan, Luka; Fefer, Dušan; Košmelj, Katarina; Gaberščik, Alenka; Jerman, Igor

    2015-04-01

    The geomagnetic field (GMF) varies over Earth's surface and changes over time, but it is generally not considered as a factor that could influence plant growth. The effects of reduced and enhanced GMFs and a strong static magnetic field on growth and chlorophyll a (Chl a) fluorescence of Lemna minor plants were investigated under controlled conditions. A standard 7 day test was conducted in extreme geomagnetic environments of 4 µT and 100 µT as well as in a strong static magnetic field environment of 150 mT. Specific growth rates as well as slow and fast Chl a fluorescence kinetics were measured after 7 days incubation. The results, compared to those of controls, showed that the reduced GMF significantly stimulated growth rate of the total frond area in the magnetically treated plants. However, the enhanced GMF pointed towards inhibition of growth rate in exposed plants in comparison to control, but the difference was not statistically significant. This trend was not observed in the case of treatments with strong static magnetic fields. Our measurements suggest that the efficiency of photosystem II is not affected by variations in GMF. In contrast, the strong static magnetic field seems to have the potential to increase initial Chl a fluorescence and energy dissipation in Lemna minor plants.

  20. External and internal magnetic-field effects on ferroelectricity in orthorhombic rare-earth manganites

    NASA Astrophysics Data System (ADS)

    Kuwahara, H.; Noda, K.; Akaki, M.

    2006-03-01

    We report the dielectric and magnetic properties of the perovskite (Eu,Y)MnO3 crystal without the presence of the 4f magnetic moments of the rare earth ions. The subject compound, (Eu,Y)MnO3, was controlled the average ionic radius of the A site so that it was the same as that of TbMnO3 in which the intriguing magnetoelectric effect has been recently discovered. The (Eu,Y)MnO3 crystal was found to have two distinct ferroelectric phases with polarization along the a (Pa, T<=23K) and c (Pc, 23K<=T<=25K) axes in the orthorhombic Pbnm setting in a zero magnetic field. In addition, we have demonstrated a magnetic-field-induced switching between these ferroelectric phases: Pa changed to Pc by the application of magnetic fields parallel to the a axis (Ha). In analogy to the case of Pc in TbMnO3, this result is possibly interpreted as follows. In the case of (Eu,Y)MnO3, Mn 3d spins rotate in the ab plane and Pa would emerge in a zero field. In the Ha, the field will force the spins to rotate in the bc plane, in which Pc would be stabilized. Magnetization measurements supported this interpretation: We confirmed the change of the spin rotation axis of the helix from the c axis to the a axis induced by application of the Ha because there is no 4f moments acting as an internal magnetic field and interacting with the 3d spins. Results obtained with other rare-earth manganites such as (Gd,Tb)MnO3 and (Eu,Ho)MnO3 will be presented.

  1. The unique effect of in-plane anisotropic strain in the magnetization control by electric field

    NASA Astrophysics Data System (ADS)

    Zhao, Y. Y.; Wang, J.; Hu, F. X.; Liu, Y.; Kuang, H.; Wu, R. R.; Sun, J. R.; Shen, B. G.

    2016-05-01

    The electric field control of magnetization in both (100)- and (011)-Pr0.7Sr0.3MnO3/Pb(Mg1/3Nb2/3)0.7Ti0.3O3(PSMO/PMN-PT) heterostructures were investigated. It was found that the in-plane isotropic strain induced by electric field only slightly reduces the magnetization at low temperature in (100)-PSMO/PMN-PT film. On the other hand, for (011)-PSMO/PMN-PT film, the in-plane anisotropic strain results in in-plane anisotropic, nonvolatile change of magnetization at low-temperature. The magnetization, remanence and coercivity along in-plane [100] direction are suppressed by the electric field while the ones along [01-1] direction are enhanced, which is ascribed to the extra effective magnetic anisotropy induced by the electric field via anisotropic piezostrains. More interestingly, such anisotropic modulation behaviors are nonvolatile, demonstrating a memory effect.

  2. Magnetic field effect on the Coulomb interaction of acceptors in semimagnetic quantum dot

    SciTech Connect

    Kalpana, P.; Merwyn, A.; Nithiananthi, P.; Jayakumar, K.; Reuben, Jasper D.

    2015-06-24

    The Coulomb interaction of holes in a Semimagnetic Cd{sub 1-x}Mn{sub x}Te / CdTe Spherical and Cubical Quantum Dot (SMQD) in a magnetic field is studied using variational approach in the effective mass approximation. Since these holes in QD show a pronounced collective behavior, while distinct single particle phenomena is suppressed, their interaction in confined potential becomes very significant. It has been observed that acceptor-acceptor interaction is more in cubical QD than in spherical QD which can be controlled by the magnetic field. The results are presented and discussed.

  3. The Effect of Rotating a Faraday Disc Perpendicular to an Applied Magnetic Field Theory and Experiment

    NASA Technical Reports Server (NTRS)

    Mazuruk, Konstantin; Grugel, Richard N.

    2003-01-01

    A magnetohydrodynamic model that examines the effect of rotating an electrically conducting cylinder with a uniform external magnetic field applied orthogonal to its axis is presented. Noting a simple geometry, it can be classified as a fundamental dynamo problem. For the case of an infinitely long cylinder, an analytical solution is obtained and analyzed in detail. A semi-analytical model was developed that considers a finite cylinder. Experimental data from a spinning brass wheel in the presence of Earth's magnetic field were compared to the proposed theory and found to fit well.

  4. Effects of shear flow and transverse magnetic field on Richtmyer-Meshkov instability

    SciTech Connect

    Cao Jintao; Ren Haijun; Li Ding; Wu Zhengwei

    2008-04-15

    The effects of shear flow and transverse magnetic field on Richtmyer-Meshkov instability are examined and the expression of the interface perturbation is obtained by analytically solving the linear ideal magnetohydrodynamics equations. It shows that the perturbation evolves exponentially rather than linearly in the presence of shear flow and magnetic field when v{sub a}<{radical}(1-A{sub T}{sup 2}){delta}{sub u}/2, where v{sub a} is the modified Alfven velocity, A{sub T} is the Atwood number, and {delta}{sub u} is the relative shear velocity, respectively. The shear flow acts as a destabilizing source, while the magnetic field is a stabilizing mechanism of the shocked corrugated interface problem. The whole analysis is based on the assumption that the fluid is incompressible.

  5. Effects Of Pressure Anisotropy On The Magnetic Field In The Inner Magnetosphere

    NASA Astrophysics Data System (ADS)

    Wu, L.; Toffoletto, F. R.; Wolf, R. A.

    2007-12-01

    We present results from a version of an equilibrium solver that has been modified to include the effects of anisotropic pressure. The equilibrium solver uses a frictional technique to iterate a set of modified MHD equations to equilibrium. The initial pressure distribution is determined from an empirical model of Lui et al [1994] that specifies the pressure anisotropy as a function of position in the tail. In this model, the region beyond approximately 15 Re is assumed to have isotropic pressure, consistent with observations. The initial magnetic field is a Tsyganenko [1989] magnetic field model. For various magnetospheric conditions, we will display the differences between the resulting anisotropic-equilibrium magnetic field and an equilibrium computed from the isotropic version of the code for the same total thermal energy.

  6. Magnetic field effects on the solute luminescence of alkane solutions irradiated with heavy ions

    SciTech Connect

    LaVerne, J.A.; Brocklehurst, B.

    1996-02-01

    The effects of track structure on the luminescence decays in cyclohexane and in 2,2,4-trimethylpentane (isoocatane) solutions of 2,5-diphenyloxazole (PPO) have been determined in the presence and in the absence of an external magnetic field. Irradiations were performed with protons of 1-15 MeV and with helium ions of 2-20 MeV energy. Companion studies were performed with {sup 90}Sr-{sup 90}Y {Beta}-radiolysis. The magnetic field effect is due to the hyperfine interaction of nuclear spins in the geminate pair of solvent radical ions produced. In both solvents, the effect of the magnetic field on luminescence decreases with increasing linear energy transfer (LET) from about 40% for {Beta}-particles to only a few percent with helium ions. Magnetic field effects with protons decrease in time whereas they are constant with {Beta}-particles. This result is attributed to the overlap of initially isolated spurs during the evolution of the proton track; the probability of nongeminate recombination increases with the number of neighboring ion pairs. The total luminescence intensity per incident particle remains constant with proton energy but increases slightly with increasing helium ion energy. At a given particle energy, the intensity is greater in cyclohexane than in isoocatane. The pulse shapes of the luminescence decays reflect the distributions in ion recombination times, and very little variation in luminescence decay rates is observed with increasing LET. 37 refs., 7 figs., 1 tab.

  7. Pedestal magnetic field measurements using a motional Stark effect polarimeter.

    PubMed

    Lanctot, M J; Holcomb, C T; Allen, S L; Fenstermacher, M E; Luce, T C

    2012-10-01

    Temperature-controlled, 0.15 nm interference filters were installed on an edge-viewing system of the motional Stark effect (MSE) polarimeter on the DIII-D tokamak. The upgraded system provides a factor of two reduction in the bandpass compared to the previous design, and linear control of the bandpass, which is unaltered by wavelength tuning. With the new system, there is a reduced dependence of the inferred polarization angle on the filter wavelength calibration. Recent measurements from the calibrated edge-viewing system show increased agreement with other MSE arrays.

  8. Magnetoelectric effect and phase transitions in CuO in external magnetic fields

    PubMed Central

    Wang, Zhaosheng; Qureshi, Navid; Yasin, Shadi; Mukhin, Alexander; Ressouche, Eric; Zherlitsyn, Sergei; Skourski, Yurii; Geshev, Julian; Ivanov, Vsevolod; Gospodinov, Marin; Skumryev, Vassil

    2016-01-01

    Apart from being so far the only known binary multiferroic compound, CuO has a much higher transition temperature into the multiferroic state, 230 K, than any other known material in which the electric polarization is induced by spontaneous magnetic order, typically lower than 100 K. Although the magnetically induced ferroelectricity of CuO is firmly established, no magnetoelectric effect has been observed so far as direct crosstalk between bulk magnetization and electric polarization counterparts. Here we demonstrate that high magnetic fields of ≈50 T are able to suppress the helical modulation of the spins in the multiferroic phase and dramatically affect the electric polarization. Furthermore, just below the spontaneous transition from commensurate (paraelectric) to incommensurate (ferroelectric) structures at 213 K, even modest magnetic fields induce a transition into the incommensurate structure and then suppress it at higher field. Thus, remarkable hidden magnetoelectric features are uncovered, establishing CuO as prototype multiferroic with abundance of competitive magnetic interactions. PMID:26776921

  9. Magnetization switching in a CoFeB/MgO magnetic tunnel junction by combining spin-transfer torque and electric field-effect

    SciTech Connect

    Kanai, S.; Nakatani, Y.; Yamanouchi, M.; Ikeda, S.; Sato, H.; Matsukura, F.; Ohno, H.

    2014-05-26

    We propose and demonstrate a scheme for magnetization switching in magnetic tunnel junctions, in which two successive voltage pulses are applied to utilize both spin-transfer torque and electric field effect. Under this switching scheme, a CoFeB/MgO magnetic tunnel junction with perpendicular magnetic easy axis is shown to switch faster than by spin-transfer torque alone and more reliably than that by electric fields alone.

  10. Effects of anisotropies in turbulent magnetic diffusion in mean-field solar dynamo models

    SciTech Connect

    Pipin, V. V.; Kosovichev, A. G.

    2014-04-10

    We study how anisotropies of turbulent diffusion affect the evolution of large-scale magnetic fields and the dynamo process on the Sun. The effect of anisotropy is calculated in a mean-field magnetohydrodynamics framework assuming that triple correlations provide relaxation to the turbulent electromotive force (so-called the 'minimal τ-approximation'). We examine two types of mean-field dynamo models: the well-known benchmark flux-transport model and a distributed-dynamo model with a subsurface rotational shear layer. For both models, we investigate effects of the double- and triple-cell meridional circulation, recently suggested by helioseismology and numerical simulations. To characterize the anisotropy effects, we introduce a parameter of anisotropy as a ratio of the radial and horizontal intensities of turbulent mixing. It is found that the anisotropy affects the distribution of magnetic fields inside the convection zone. The concentration of the magnetic flux near the bottom and top boundaries of the convection zone is greater when the anisotropy is stronger. It is shown that the critical dynamo number and the dynamo period approach to constant values for large values of the anisotropy parameter. The anisotropy reduces the overlap of toroidal magnetic fields generated in subsequent dynamo cycles, in the time-latitude 'butterfly' diagram. If we assume that sunspots are formed in the vicinity of the subsurface shear layer, then the distributed dynamo model with the anisotropic diffusivity satisfies the observational constraints from helioseismology and is consistent with the value of effective turbulent diffusion estimated from the dynamics of surface magnetic fields.

  11. Experimental comparison of ring and diamond shaped planar Hall effect bridge magnetic field sensors

    NASA Astrophysics Data System (ADS)

    Henriksen, Anders Dahl; Rizzi, Giovanni; Hansen, Mikkel Fougt

    2015-09-01

    Planar Hall effect magnetic field sensors with ring and diamond shaped geometries are experimentally compared with respect to their magnetic field sensitivity and total signal variation. Theoretically, diamond shaped sensors are predicted to be 41% more sensitive than corresponding ring shaped sensors for negligible shape anisotropy. To experimentally validate this, we have fabricated both sensor geometries in the exchange-biased stack Ni80Fe20(tFM)/Cu(tCu)/Mn80Ir20(10 nm) with tFM=10 , 20, and 30 nm and tCu=0 , 0.3, and 0.6 nm. Sensors from each stack were characterized by external magnetic field sweeps, which were analyzed in terms of a single domain model. The total signal variation of the diamond sensors was generally found to be about 40% higher than that for the ring sensors in agreement with theoretical predictions. However, for the low-field sensitivity, the corresponding improvement varied from 0% to 35% where the largest improvement was observed for sensor stacks with comparatively strong exchange bias. This is explained by the ring sensors being less affected by shape anisotropy than the diamond sensors. To study the effect of shape anisotropy, we also characterized sensors that were surrounded by the magnetic stack with a small gap of 3 μm. These sensors were found to be less affected by shape anisotropy and thus showed higher low-field sensitivities.

  12. The magnetic field dependence of cross-effect dynamic nuclear polarization under magic angle spinning

    SciTech Connect

    Mance, Deni; Baldus, Marc; Gast, Peter; Huber, Martina; Ivanov, Konstantin L.

    2015-06-21

    We develop a theoretical description of Dynamic Nuclear Polarization (DNP) in solids under Magic Angle Spinning (MAS) to describe the magnetic field dependence of the DNP effect. The treatment is based on an efficient scheme for numerical solution of the Liouville-von Neumann equation, which explicitly takes into account the variation of magnetic interactions during the sample spinning. The dependence of the cross-effect MAS-DNP on various parameters, such as the hyperfine interaction, electron-electron dipolar interaction, microwave field strength, and electron spin relaxation rates, is analyzed. Electron spin relaxation rates are determined by electron paramagnetic resonance measurements, and calculations are compared to experimental data. Our results suggest that the observed nuclear magnetic resonance signal enhancements provided by MAS-DNP can be explained by discriminating between “bulk” and “core” nuclei and by taking into account the slow DNP build-up rate for the bulk nuclei.

  13. Reexamination of magnetic isotope and field effects on adenosine triphosphate production by creatine kinase.

    PubMed

    Crotty, Darragh; Silkstone, Gary; Poddar, Soumya; Ranson, Richard; Prina-Mello, Adriele; Wilson, Michael T; Coey, J M D

    2012-01-31

    The influence of isotopically enriched magnesium on the creatine kinase catalyzed phosphorylation of adenosine diphosphate is examined in two independent series of experiments where adenosine triphosphate (ATP) concentrations were determined by a luciferase-linked luminescence end-point assay or a real-time spectrophotometric assay. No increase was observed between the rates of ATP production with natural Mg, (24)Mg, and (25)Mg, nor was any significant magnetic field effect observed in magnetic fields from 3 to 1,000 mT. Our results are in conflict with those reported by Buchachenko et al. [J Am Chem Soc 130:12868-12869 (2008)], and they challenge these authors' general claims that a large (two- to threefold) magnetic isotope effect is "universally observable" for ATP-producing enzymes [Her Russ Acad Sci 80:22-28 (2010)] and that "enzymatic phosphorylation is an ion-radical, electron-spin-selective process" [Proc Natl Acad Sci USA 101:10793-10796 (2005)].

  14. Torsion effects on condensed matter: like a magnetic field but not so much

    NASA Astrophysics Data System (ADS)

    Lima, Anderson A.; Filgueiras, Cleverson; Moraes, Fernando

    2017-02-01

    In this work, we study the effects of torsion due to a uniform distribution of topological defects (screw dislocations) on free spin/carrier dynamics in elastic solids. When a particle moves in such a medium, the effect of the torsion associated to the defect distribution is analogous to that of an applied magnetic field but with subtle differences. Analogue Landau levels are present in this system but they cannot be confined to two dimensions. In the case of spinless carriers, zero modes, which do not appear in the magnetic Landau levels, show up for quantized values of the linear momentum projected on the defects axis. Particles with spin are subjected to a Zeeman-like coupling between spin and torsion, which is insensitive to charge. This suggests the possibility of spin resonance experiments without a magnetic field for charged carriers or quasiparticles without electrical charge, like triplet excitons, for instance.

  15. Magnetic healing, quackery, and the debate about the health effects of electromagnetic fields.

    PubMed

    Macklis, R M

    1993-03-01

    Although the biological effects of low-frequency electromagnetic radiation have been studied since the time of Paracelsus, there is still no consensus on whether these effects are physiologically significant. The recent discovery of deposits of magnetite within the human brain as well as recent, highly publicized tort litigation charging adverse effects after exposure to magnetic fields has rekindled the debate. New data suggest that electromagnetic radiation generated from power lines may lead to physiologic effects with potentially dangerous results. Whether these effects are important enough to produce major epidemiologic consequences remains to be established. The assumption of quackery that has attended this subject since the time of Mesmer's original "animal magnetism" investigations continues to hamper efforts to compile a reliable data base on the health effects of electromagnetic fields.

  16. Shell thickness and dynamic magnetic field effects on the critical phenomena of magnetic core-shell nanoparticles with spherical geometry

    NASA Astrophysics Data System (ADS)

    Yüksel, Yusuf

    2017-03-01

    By using Monte Carlo simulations for classical Heisenberg spins, we study the critical phenomena and ferrimagnetic properties of spherical nanoparticles with core-shell geometry. The particle core is composed of ferromagnetic spins, and it is coated by a ferromagnetic shell. Total size of the particle is fixed but the thickness of the shell is varied in such a way that the shell layer is grown at the expense of the core. Effects of the shell thickness, as well as dynamic magnetic field parameters such as oscillation period and field amplitude on the magnetization profiles, dynamic hysteresis loops and phase diagrams have been investigated for the present system. It has been found that as the shell thickness varies then the easy axis magnetization of the overall system may exhibit Q-, P-, L- and N- type behaviors based on the Neél terminology. We also found that three distinct anomalies originate in the thermal variation of specific heat with increasing field period. Dynamic hysteresis loops corresponding to off-axial magnetization components exhibit unconventional behavior such as double rings with symmetric shapes around the vertical axis over the h (t) = 0 line which may originate due to the stochastic resonance behavior of these components.

  17. Note: Spectral motional Stark effect diagnostic for measurement of magnetic fields below 0.3 T

    SciTech Connect

    Lizunov, A.; Donin, A.; Savkin, V.

    2013-08-15

    The paper reports on development of the spectral motional Stark effect (MSE) diagnostic in the midplane of the gas dynamic trap (GDT) linear system for magnetic confinement of anisotropic hot-ion plasma. The axially symmetric GDT vacuum magnetic field has a minimum value in the midplane, which varies from 0.2 to 0.35 T in different regimes of operation. Buildup of 15 keV ion population generates a diamagnetic reduction of magnetic field in the plasma core of up to 30% in the maximum density region, as measured by the existing eight-line MSE diagnostic. Commissioning of the midplane MSE provided first direct measurements of diamagnetic modifications in the minimum magnetic field GDT section, a necessary complement to the understanding of equilibrium and self-organization of high-β plasmas in GDT. Making use of the stable short-pulse diagnostic beam and calibration of the apparent spectral width of beam emission lines allow for the measurement of the plasma magnetic field of 0.29 ± 0.007 T with the integration time of 200 μs.

  18. Effective tight-binding model for MX2 under electric and magnetic fields

    DOE PAGES

    Shanavas, Kavungal Veedu; Satpathy, S.

    2015-06-15

    We present a systematic method for developing a five band Hamiltonian for the metal d orbitals that can be used to study the effect of electric and magnetic fields on multilayer MX2 (M=Mo,W and X=S,Se) systems. On a hexagonal lattice of d orbitals, the broken inversion symmetry of the monolayers is incorporated via fictitious s orbitals at the chalcogenide sites. A tight-binding Hamiltonian is constructed and then downfolded to get effective d orbital overlap parameters using quasidegenerate perturbation theory. The steps to incorporate the effects of multiple layers, external electric and magnetic fields are also detailed. We find that anmore » electric field produces a linear-k Rashba splitting around the Γ point, while a magnetic field removes the valley pseudospin degeneracy at the ±K points. Lastly, our model provides a simple tool to understand the recent experiments on electric and magnetic control of valley pseudospin in monolayer dichalcogendies.« less

  19. The effects of Peltier marking on semiconductor growth in a magnetic field

    NASA Astrophysics Data System (ADS)

    Sellers, Cheryl Casper

    This research represents a model for three dimensional semiconductor growth in a vertical Bridgman process within an externally applied magnetic field with the additional effects of Peltier marking. The magnetic field is strong enough that inertial effects can be neglected and that viscous effects are confined to boundary layers. The objective of this research is a first step in the development of a method to accurately predict the distribution of dopants and species in the melt after a current pulse with a given duration and strength, with a given magnetic field and with a given crystal-melt interface shape. The first model involves an asymptotic solution to provide physical clarification of the flow. In both models the crystal/melt interface is modeled as fr=3r2 where 3≪1 . The first model incorporates a variable, a which ranges from 0.25 to 1.0. The second model involves an analytical solution with an arbitrary Ha and a≪1 . These models show the how the azimuthal velocity varies with increasing Ha and how the stream function varies in the meridional problem. This gives insight into how the dopant is mixed during the crystal growth process. The results demonstrate that current pulses with relatively weak magnetic fields and modest interface curvature can lead to very strong mixing in the melt.

  20. Effects of variation in solar conditions and crustal sources' orientation on the Martian magnetic field topology

    NASA Astrophysics Data System (ADS)

    Ulusen, D.; Luhmann, J. G.; Ma, Y.; Brain, D. A.

    2013-12-01

    Strong crustal magnetic sources on the surface of Mars directly interact with the solar magnetic field and plasma, resulting a very dynamic environment near the planet. Effects of the orientation of these remnant magnetic sources with respect to the sun and variation of the solar conditions on the Martian plasma interaction have been investigated in a previous paper. In this previous study, magnetic topology maps obtained from ~7 years of Mars Global Surveyor (MGS) directional electron observations (obtained by Dave Brain) were compared with the topology maps obtained from a set of BATS-R-US MHD simulations for Mars. One conclusion from this study was that although the MHD model is consistent with the data and provides insight about the global magnetic field topology variation with changing crustal field orientation and solar parameters, detailed investigation of local effects is difficult due to MGS orbital bias. Moreover, proper comparison of the observations with the model requires more careful data selection rather than using 7 years time averages. In this paper, we readdress the study to tackle the problems of our previous work by performing more detailed data analysis and present the results of the updated model-data comparison.

  1. A first-order magnetic phase transition near 15 K with novel magnetic-field-induced effects in Er5Si3.

    PubMed

    Mohapatra, Niharika; Mukherjee, K; Iyer, Kartik K; Sampathkumaran, E V

    2011-12-14

    We present magnetic characterization of a binary rare-earth intermetallic compound Er(5)Si(3), crystallizing in Mn(5)Si(3)-type hexagonal structure, through magnetization, heat capacity, electrical resistivity and magnetoresistance measurements. Our investigations confirm that the compound exhibits two magnetic transitions with decreasing temperature, the first one at 35 K and the second one at 15 K. The present results reveal that the second magnetic transition is a disorder-broadened first-order transition, as shown by thermal hysteresis in the measured data. Another important finding is that, below 15 K, there is a magnetic-field-induced transition with a hysteretic effect with the electrical resistance getting unusually enhanced at this transition and the magnetoresistance is found to exhibit intriguing magnetic-field dependence, indicating novel magnetic phase coexistence phenomenon. It thus appears that this compound is characterized by interesting magnetic anomalies in the temperature-magnetic-field phase diagram.

  2. Magnetic field effects in organic semiconductors and their applications in displays

    NASA Astrophysics Data System (ADS)

    Veeraraghavan, Govindarajan

    Organic semiconductors have been widely expected to replace inorganic semiconductors in the field of display electronics since the advent of organic light emitting diodes (OLEDs). Organic pi-conjugated materials have also been used to manufacture photovoltaic cells and field-effect transistors. Recent years have seen a surge in interest in the magnetotransport properties of these materials because they show great potential for such applications as magnetic field sensors and spintronics devices. In this thesis, I experimentally characterize a large magnetoresistance effect, which was recently discovered at the University of Iowa and was dubbed organic magnetoresistance (OMAR). We focus on two materials that show particularly great promise; one a macromolecular polymer called polyfluorene, the other a prototypical small molecule called Alq3. Building on the work of a prior student; in this thesis I report on the magnetic field dependence of current, photocurrent and electroluminescence in OLEDs made from Alq3 and polyfluorene. We provide a comprehensive overview of all these three types of magnetic field effects. In particular, we show that they are all caused by the same mechanism, in contrast to some claims by others. To the best of our knowledge, the mechanism causing OMAR and the other magnetic field effects is currently not known with certainty. Moreover, we show that experiments in bipolar, electroluminescent devices do not allow determination whether the mechanism acts on the carrier density or carrier mobility. This is a crucial gap in knowledge since it makes any attempt of explaining it ambiguous. As a remedy, we performed magnetoresistance measurements in hole-only polyfluorene devices and show that the mechanism acts on the carrier mobility rather than carrier recombination. We present an outline of a possible explanation which will be studied in more detail in another thesis. In my thesis I focus on possible applications of OMAR. I present the design

  3. Magnetosheath magnetic field variability

    NASA Technical Reports Server (NTRS)

    Sibeck, D. G.

    1994-01-01

    A case study using simulations IRM and CCE observations demonstrates that transient magnetospheric events correspond to pressure pulses in the magnetosheath, inward bow shock motion, and magnetopause compression. Statistical surveys indicate that the magnetosheath magnetic field orientation rarely remains constant during periods of magnetopause and bow shock motion (both characterized by periods of 1 to 10 min). There is no tendency for bow shock motion to occur for southward interplanetary magnetic field (IMF) orientations.

  4. Magnetic field dosimeter development

    SciTech Connect

    Lemon, D.K.; Skorpik, J.R.; Eick, J.L.

    1980-09-01

    In recent years there has been increased concern over potential health hazards related to exposure of personnel to magnetic fields. If exposure standards are to be established, then a means for measuring magnetic field dose must be available. To meet this need, the Department of Energy has funded development of prototype dosimeters at the Battelle Pacific Northwest Laboratory. This manual reviews the principle of operation of the dosimeter and also contains step-by-step instructions for its operation.

  5. The effect of an intramedullary implant with a static magnetic field on the healing of the osteotomised rabbit femur.

    PubMed

    Aydin, Nuri; Bezer, Murat

    2011-01-01

    Static magnetic fields are a type of electromagnetic fields used in clinical practice. To ascertain what effect a static magnetic intramedullary device implanted in the rabbit femur had on fracture healing, 20 male New Zealand white rabbits with magnetic/nonmagnetic intramedullary implants were examined histologically, radiologically and for bone mineral density. Three groups were constituted according to the poles of the magnets. During surgery the intramedullary device was driven into the medulla. A femoral osteotomy was created with a mini Gigli wire at the centre point of the rod. Radiographs were obtained at the second and fourth weeks. Histological examination and bone mineral density were evaluated at the fourth week. The results of this study verified that an intramedullary implant with a static magnetic field improves bone healing in the first two weeks radiologically and that the configuration difference in magnetic poles has an effect on bone quality. Static magnetic fields have minor effects on bone mineral density values.

  6. Cold equation of state in a strong magnetic field - Effects of inverse beta-decay

    NASA Technical Reports Server (NTRS)

    Lai, Dong; Shapiro, Stuart L.

    1991-01-01

    The influence of a high magnetic field (B is greater than 10 exp 12 G) on the degenerate matter equation of state appropriate to a neutron star is studied. The regime dominated by relativistic electrons up to the neutron drip density is highlighted. The equilibrium matter composition and equation of state, allowing for inverse beta-decay. Two different equilibrium models are determined: an ideal neutron-proton-electron (npe) gas and the more realistic model of Baym, Pethick, and Sutherland (1971) consisting of a Coulomb lattice of heavy nuclei embedded in an electron gas. For a sufficiently high field strength, the magnetic field has an appreciable effect, changing the adiabatic index of the matter and the nuclear transition densities. The influence of a strong field on some simple nonequilibrium processes, including beta-decay and inverse beta-decay (electron capture) is also considered. The effects produced by the magnetic field are mainly due to the changes in the transverse electron quantum orbits and the allowed electron phase space induced by the field.

  7. Passive shielding effect on space profile of magnetic field emissions for wireless power transfer to vehicles

    SciTech Connect

    Batra, T. Schaltz, E.

    2015-05-07

    Magnetic fields emitted by wireless power transfer systems are of high importance with respect to human safety and health. Aluminum and ferrite are used in the system to reduce the fields and are termed as passive shielding. In this paper, the influence of these materials on the space profile has been investigated with the help of simulations on Comsol for the four possible geometries—no shielding, ferrite, aluminum, and full shielding. As the reflected impedance varies for the four geometries, the primary current is varied accordingly to maintain constant power transfer to the secondary side. Surrounding magnetic field plots in the vertical direction show that maxima's of the two coils for the no shielding geometry are centered at the respective coils and for the remaining three are displaced closer to each other. This closeness would lead to more effective addition of the two coil fields and an increase in the resultant field from space point of view. This closeness varies with distance in the horizontal direction and vertical gap between the coils and is explained in the paper. This paper provides a better understanding of effect of the passive shielding materials on the space nature of magnetic fields for wireless power transfer for vehicle applications.

  8. Time-resolved luminescence measurements of the magnetic field effect on paramagnetic photosensitizers in photodynamic reactions

    NASA Astrophysics Data System (ADS)

    Mermut, O.; Bouchard, J.-P.; Cormier, J.-F.; Desroches, P.; Diamond, K. R.; Fortin, M.; Gallant, P.; Leclair, S.; Marois, J.-S.; Noiseux, I.; Morin, J.-F.; Patterson, M. S.; Vernon, M.

    2008-02-01

    The development of multimodal molecular probes and photosensitizing agents for use in photodynamic therapy (PDT) is vital for optimizing and monitoring cytotoxic responses. We propose a combinatorial approach utilizing photosensitizing molecules that are both paramagnetic and luminescent with multimodal functionality to perturb, control, and monitor molecular-scale reaction pathways in PDT. To this end, a time-domain single photon counting lifetime apparatus with a 400 nm excitation source has been developed and integrated with a variable low field magnet (0- 350mT). The luminescence lifetime decay function was measured in the presence of a sweeping magnetic field for a custom designed photosensitizing molecule in which photoinduced electron transfer was studied The photosensitizer studied was a donor-acceptor complex synthesized using a porphyrin linked to a fullerene molecule. The magneto-optic properties were investigated for the free-base photosensitizer complex as well as those containing either diamagnetic (paired electron) or paramagnetic (unpaired electron) metal centers, Zn(II) and Cu(II). The magnetic field was employed to affect and modify the spin states of radical pairs of the photosensitizing agents via magnetically induced hyperfine and Zeeman effects. Since the Type 1 reaction pathway of an excited triplet state photosensitizer involves the production of radical species, lifetime measurements were conducted at low dissolved oxygen concentration (0.01ppm) to elucidate the dependence of the magnetic perturbation on the photosensitization mechanistic pathway. To optimize the magnetic response, a solvent study was performed examining the dependence of the emission properties on the magnetic field in solutions of varying dielectric constants. Lastly, the cytotoxicity in murine tumor cell suspensions was investigated for the novel porphyrin-fullerene complex by inducing photodynamic treatments and determining the associated cell survival.

  9. Magnetic field induced mixed level Kondo effect in two-level quantum dots

    NASA Astrophysics Data System (ADS)

    Wong, Arturo; Ngo, Anh; Ulloa, Sergio

    2012-02-01

    Semiconductor quantum dots provide an easily tunable environment in which to investigate the Kondo effect. As it is known, Kondo correlations are suppressed by magnetic fields, showing e.g. a drop in the conductance of a quantum dot device. However, certain systems may exhibit an increasing conductance as a function of an applied magnetic field [1]. In this work we use the numerical renormalization group method to study a two-level quantum dot system with on-level and interlevel Coulomb repulsion, coupled to a single channel. When there is a finite detuning between levels, and a local singlet develops in one of them, the linear conductance of the device shows a maximum structure as a function of an in-plane magnetic field, which depends on the temperature of the system. This maximum occurs at a magnetic field strength such that the spin up state of one of the levels and spin down of the other are degenerate, allowing a ``mixed level'' Kondo effect. The respective spectral functions feature a resonance at the Fermi energy, commensurate with the Kondo physics. We discuss the properties of this mixed level Kondo state in terms of the detuning and the other parameters of the system. [4pt] [1] R. Sakano and N. Kawakami, PRB 73, 155332 (2006)

  10. Quadratic Zeeman effect and spin-lattice relaxation of Tm3 +:YAG at high magnetic fields

    NASA Astrophysics Data System (ADS)

    Veissier, Lucile; Thiel, Charles W.; Lutz, Thomas; Barclay, Paul E.; Tittel, Wolfgang; Cone, Rufus L.

    2016-11-01

    Anisotropy of the quadratic Zeeman effect for the H36→H34 transition at 793 nm wavelength in 3+169Tm-doped Y3Al5O12 is studied, revealing shifts ranging from near zero up to +4.69 GHz/T 2 for ions in magnetically inequivalent sites. This large range of shifts is used to spectrally resolve different subsets of ions and study nuclear spin relaxation as a function of temperature, magnetic field strength, and orientation in a site-selective manner. A rapid decrease in spin lifetime is found at large magnetic fields, revealing the weak contribution of direct phonon absorption and emission to the nuclear spin-lattice relaxation rate. We furthermore confirm theoretical predictions for the phonon coupling strength, finding much smaller values than those estimated in the limited number of past studies of thulium in similar crystals. Finally, we observe a significant—and unexpected—magnetic field dependence of the two-phonon Orbach spin relaxation process at higher field strengths, which we explain through changes in the electronic energy-level splitting arising from the quadratic Zeeman effect.

  11. Magnetic fields during galaxy mergers

    NASA Astrophysics Data System (ADS)

    Rodenbeck, Kai; Schleicher, Dominik R. G.

    2016-09-01

    Galaxy mergers are expected to play a central role for the evolution of galaxies and may have a strong effect on their magnetic fields. We present the first grid-based 3D magnetohydrodynamical simulations investigating the evolution of magnetic fields during merger events. For this purpose, we employed a simplified model considering the merger event of magnetized gaseous disks in the absence of stellar feedback and without a stellar or dark matter component. We show that our model naturally leads to the production of two peaks in the evolution of the average magnetic field strength within 5 kpc, within 25 kpc, and on scales in between 5 and 25 kpc. The latter is consistent with the peak in the magnetic field strength previously reported in a merger sequence of observed galaxies. We show that the peak on the galactic scale and in the outer regions is most likely due to geometrical effects, as the core of one galaxy enters the outskirts of the other one. In addition, the magnetic field within the central ~5 kpc is physically enhanced, which reflects the enhancement in density that is due to efficient angular momentum transport. We conclude that high-resolution observations of the central regions will be particularly relevant for probing the evolution of magnetic field structures during merger events.

  12. Saturn's magnetic field periodicities at high latitudes and the effects of spacecraft motion and position

    NASA Astrophysics Data System (ADS)

    Carbary, J. F.; Provan, G.

    2017-02-01

    Lomb periodogram analyses have been applied to magnetic field observations made by the Cassini spacecraft during its high-latitude orbits from 2006 to 2009. Only data from open-field regions (OFRs), identified by absence of thermal electrons, were used to separate pure north and south periodic signals. In agreement with previous investigations, the periodograms reveal signals at 10.6 h in the northern OFR and at 10.8 h in the southern OFR but only for the Bθ and Bϕ components. The Br component exhibited essentially no periodicity in either the north or south, or at least its periodicity amplitude was too small for detection. In addition, the Bθ and Bϕ components displayed signals at 10.0 h and 11.2 h in the north and 10.2 h and 11.5 h and possibly 9.6 h in the south. These periods can be reproduced by a simulation by using a rotating "searchlight" model with different north and south periods and an r-3 dependence. This investigation employs a Lomb-Scargle method to analyze magnetic field periodicities and confirms that the magnetic fields have "pure" north and south periods in the respective hemispheres. The results also imply that a radial dependence in these fields exists, which is expected if the fields are produced by field-aligned currents. Using this model, the effects of spacecraft motion and position can be readily detected in the Lomb analyses.

  13. The effect of magnetic field on chiral transmission in p-n-p graphene junctions

    PubMed Central

    Li, Yuan; Wan, Qi; Peng, Yingzi; Wang, Guanqing; Qian, Zhenghong; Zhou, Guanghui; Jalil, Mansoor B. A.

    2015-01-01

    We investigate Klein tunneling in graphene heterojunctions under the influence of a perpendicular magnetic field via the non-equilibrium Green’s function method. We find that the angular dependence of electron transmission is deflected sideways, resulting in the suppression of normally incident electrons and overall decrease in conductance. The off-normal symmetry axis of the transmission profile was analytically derived. Overall tunneling conductance decreases to almost zero regardless of the potential barrier height when the magnetic field (B-field) exceeds a critical value, thus achieving effective confinement of Dirac fermions. The critical field occurs when the width of the magnetic field region matches the diameter of the cyclotron orbit. The potential barrier also induces distinct Fabry-Pérot fringe patterns, with a “constriction region” of low transmission when is close to the Fermi energy. Application of B-field deflects the Fabry-Pérot interference pattern to an off-normal angle. Thus, the conductance of the graphene heterojunctions can be sharply modulated by adjusting the B-field strength and the potential barrier height relative to the Fermi energy. PMID:26679991

  14. Magnetic fields from phase transitions

    NASA Astrophysics Data System (ADS)

    Hindmarsh, Mark; Everett, Allen

    1998-11-01

    The generation of primordial magnetic fields from cosmological phase transitions is discussed, paying particular attention to the electroweak transition and to the various definitions of the ``average'' field that have been put forward. It is emphasized that only the volume average has dynamical significance as a seed for galactic dynamos. On rather general grounds of causality and energy conservation, it is shown that, in the absence of MHD effects that transfer power in the magnetic field from small to large scales, processes occurring at the electroweak transition cannot generate fields stronger than 10-20 G on a scale of 0.5 Mpc. However, it is implausible that this upper bound could ever be reached, as it would require all the energy in the Universe to be turned into a magnetic field coherent at the horizon scale. Non-linear MHD effects seem therefore to be necessary if the electroweak transition is to create a primordial seed field.

  15. Faraday-Effect Polarimeter Diagnostic for Internal Magnetic Field Fluctuation Measurements in DIII-D

    NASA Astrophysics Data System (ADS)

    Chen, Jie; Ding, W. X.; Brower, D. L.

    2015-11-01

    A high-resolution Faraday-effect polarimeter-interferometer diagnostic currently under construction at the DIII-D tokamak has three overall measurement goals: (1) determine the current density dynamics at the magnetic axis, J(0,t), for torque-free plasmas (no NBI) and bootstrap current in the pedestal region; (2) resolve both coherent and broadband magnetic fluctuations [at the level δb <= 1 Gauss with up to 2 MHz bandwidth] associated with MHD perturbations, energetic particle driven modes and broadband turbulence (e.g. microtearing modes), and (3) identify non-axisymmetric structures and plasma response to externally applied RMP (resonant magnetic perturbation) fields being developed for ELM control as well as MHD events. These goals will be achieved using a 650-700 GHz source and heterodyne receiver system to measure the line-integrated Faraday-effect and density along three horizontal chords positioned at the magnetic axis and +/-15 cm off-axis. The system will be double-pass and cornercube retroreflectors have already been installed. Simultaneous measurement of density and Faraday effect allows isolation of the fluctuating magnetic field component in the radial direction. Supported by US DOE under DE-FG03-01ER54615 and DE-FC02-04ER54698.

  16. Resonance of a Metal Drop under the Effect of Amplitude-Modulated High Frequency Magnetic Field

    NASA Astrophysics Data System (ADS)

    Guo, Jiahong; Lei, Zuosheng; Zhu, Hongda; Zhang, Lijie; Magnetic Hydrodynamics(Siamm) Team; Magnetic Mechanics; Engineering(Smse) Team

    2016-11-01

    The resonance of a sessile and a levitated drop under the effect of high frequency amplitude-modulated magnetic field (AMMF) is investigated experimentally and numerically. It is a new method to excite resonance of a metal drop, which is different from the case in the presence of a low-frequency magnetic field. The transient contour of the drop is obtained in the experiment and the simulation. The numerical results agree with the experimental results fairly well. At a given frequency and magnetic flux density of the high frequency AMMF, the edge deformations of the drop with an azimuthal wave numbers were excited. A stability diagram of the shape oscillation of the drop and its resonance frequency spectrum are obtained by analysis of the experimental and the numerical data. The results show that the resonance of the drop has a typical character of parametric resonance. The National Natural Science Foundation of China (No. 51274237 and 11372174).

  17. Planarian activity differences when maintained in water pre-treated with magnetic fields: a nonlinear effect.

    PubMed

    Gang, Noa; Persinger, Michael A

    2011-12-01

    There have been multiple claims that exposing water to a static magnetic field affects its properties which influence living systems. To test this hypothesis, planarian subsequent to dissection were maintained in spring water that had been previously exposed for only one day to one of three (16, 160, or 1,600 G) intensity static magnetic fields or to a reference condition. Although there was no significant difference in regeneration rates over the subsequent seven-day period, there was a statistically significant nonlinear effect for planarian mobility and diffusion rates. Both mobility rates and diffusion velocity of a liquid within the water that had been exposed to the 16 G field was about twice that for water exposed to the other intensities. These results imply that nonlinear biophysical effects may emerge under specific conditions of intensity ranges for particular volumes of water.

  18. Effects of magnetic field intensity on carbon diffusion coefficient in pure iron in γ-Fe temperature region

    NASA Astrophysics Data System (ADS)

    Wu, Yan; Duan, Guosheng; Zhao, Xiang

    2015-03-01

    Effects of magnetic field intensity on carbon diffusion coefficient in pure iron in the γ-Fe temperature region were investigated using carburizing technology. The carbon penetration profiles from the iron surface to interior were measured by field emission electron probe microanalyzer. The carbon diffusion coefficient in pure iron carburized with different magnetic field intensities was calculated according to the Fick's second law. It was found that the magnetic field intensity could obviously affect the carbon diffusion coefficient in pure iron in the γ-Fe temperature region, and the carbon diffusion coefficient decreased obviously with the enhancement of magnetic field intensity, when the magnetic field intensity was higher than 1 T, the carbon diffusion coefficient in field annealed specimen was less than half of that of the nonfield annealed specimen, further enhancing the magnetic field intensity, the carbon diffusion coefficient basically remains unchanged. The stiffening of lattice due to field-induced magnetic ordering was responsible for an increase in activation barrier for jumping carbon atoms. The greater the magnetic field intensity, the stronger the inhibiting effect of magnetic field on carbon diffusion.

  19. Photonic Magnetic Field Sensor

    NASA Astrophysics Data System (ADS)

    Wyntjes, Geert

    2002-02-01

    Small, in-line polarization rotators or isolators to reduce feedback in fiber optic links can be the basis for excellent magnetic field sensors. Based on the giant magneto-optical (GMO) or Faraday effect in iron garnets, they with a magnetic field of a few hundred Gauss, (20 mT) for an interaction length for an optical beam of a few millimeters achieve a polarization rotation or phase shift of 45 deg (1/8 cycle). When powered by a small laser diode, with the induced linear phase shift recovered at the shot noise limit, we have demonstrated sensitivities at the 3.3 nT/Hz1/2 level for frequencies from less than 1 Hz to frequencies into the high kHz range. Through further improvements; an increase in interaction length, better materials and by far the greatest factor, the addition of a flux concentrator, sensitivities at the pT/Hz1/2 level appear to be within reach. We will detail such a design and discuss the issues that may limit achieving these goals.

  20. Solar Wind Magnetic Fields

    NASA Technical Reports Server (NTRS)

    Smith, E. J.

    1995-01-01

    The magnetic fields originate as coronal fields that are converted into space by the supersonic, infinitely conducting, solar wind. On average, the sun's rotation causes the field to wind up and form an Archimedes Spiral. However, the field direction changes almost continuously on a variety of scales and the irregular nature of these changes is often interpreted as evidence that the solar wind flow is turbulent.

  1. In vitro effects of 50 Hz magnetic fields on oxidatively damaged rabbit red blood cells

    SciTech Connect

    Fiorani, M.; Biagiarelli, B.; Vetrano, F.; Guidi, G.; Dacha, M.; Stocchi, V.

    1997-05-01

    The aim of this study was to investigate the effects of 50 Hz magnetic fields on rabbit red blood cells (RBCs) that were exposed simultaneously to the action of an oxygen radical-generating system, Fe(II)/ascorbate. Previous data obtained in the authors` laboratory showed that the exposure of rabbit erythrocytes or reticulocytes to Fe(II)/ascorbate induces hexokinase inactivation, whereas the other glycolytic enzymes do not show any decay. The authors also observed depletion of reduced glutathione (GSH) content with a concomitant intracellular and extracellular increase in oxidized glutathione (GSSG) and a decrease in energy charge. In this work, they investigated whether 50 Hz magnetic fields could influence the intracellular impairments that occur when erythrocytes or reticulocytes are exposed to this oxidant system, namely, inactivation of hexokinase activity, GSH depletion, a change in energy charge, and hemoglobin oxidation. The results obtained indicate that a 0.5 mT magnetic field had no effect on intact RBCs, whereas it increased the damage in an oxidatively stressed erythrocyte system. In fact, exposure of intact erythrocytes incubated with Fe(II)/ascorbate to a 0.5 mT magnetic field induced a significant further decay in hexokinase activity as well as a twofold increase in methemoglobin production compared with RBCs that were exposed to the oxidant system alone. Although further studies will be needed to determine the physiological implications of these data, the results reported in this study demonstrate that the effects of the magnetic fields investigated are able to potentiate the cellular damage induced in vitro by oxidizing agents.

  2. In vitro effects of 50 Hz magnetic fields on oxidatively damaged rabbit red blood cells.

    PubMed

    Fiorani, M; Biagiarelli, B; Vetrano, F; Guidi, G; Dachà, M; Stocchi, V

    1997-01-01

    The aim of this study was to investigate the effects of 50 Hz magnetic fields (0.2-0.5 mT) on rabbit red blood cells (RBCs) that were exposed simultaneously to the action of an oxygen radical-generating system, Fe(II)/ascorbate. Previous data obtained in our laboratory showed at the exposure of rabbit erythrocytes or reticulocytes to Fe(II)/ascorbate hexokinase inactivation, whereas the other glycolytic enzymes do not show any decay. We also observed depletion of reduced glutathione (GSH) content with a concomitant intracellular and extracellular increase in oxidized glutathione (GSSG) and a decrease in energy charge. In this work we investigated whether 50 Hz magnetic fields could influence the intracellular impairments that occur when erythrocytes or reticulocytes are exposed to this oxidant system, namely, inactivation of hexokinase activity, GSH depletion, a change in energy charge, and hemoglobin oxidation. The results obtained indicate the a 0.5 mT magnetic field had no effect on intact RBCs, whereas it increased the damage with Fe(II)/ascorbate to a 0.5 mT magnetic field induced a significant further decay in hexokinase activity (about 20%) as well as a twofold increase in methemoglobin production compared with RBCs that were exposed to the oxidant system alone. Although further studies will be needed to determine the physiological implications of these data, the results reported in this study demonstrate that the effects of the magnetic fields investigated are able to potentiate the cellular damage induced in vitro by oxidizing agents.

  3. The effects of intense magnetic fields on Landau levels in a neutron star

    NASA Astrophysics Data System (ADS)

    Gao, Z. F.; Wang, N.; Song, D. L.; Yuan, J. P.; Chou, C.-K.

    2011-08-01

    In this paper, an approximate method of calculating the Fermi energy of electrons ( E F ( e)) in a high-intensity magnetic field, based on the analysis of the distribution of a neutron star magnetic field, has been proposed. In the interior of a neutron star, different forms of intense magnetic field could exist simultaneously and a high electron Fermi energy could be generated by the release of magnetic field energy. The calculation results show that: E F ( e) is related to density ρ, the mean electron number per baryon Y e and magnetic field strength B.

  4. The suppression effect of external magnetic field on the high-power microwave window multipactor phenomenon

    SciTech Connect

    Zhang, Xue Wang, Yong; Fan, Junjie

    2015-02-15

    To suppress the surface multipactor phenomenon and improve the transmitting power of the high-power microwave window, the application of external magnetic fields is theoretically analyzed and simulated. A Monte Carlo algorithm is used to track the secondary electron trajectories and study the multipactor scenario on the surface of a cylinder window. It is confirmed that over-resonant magnetic fields (an external magnetic field whose magnitude is slightly greater than that of a resonant magnetic field) will generate a compensating trajectory and collision, which can suppress the secondary electron avalanche. The optimal value of this external magnetic field that will avoid the multipactor phenomenon on cylinder windows is discussed.

  5. Magnetic-Field Hazards Bibliography.

    DTIC Science & Technology

    1985-09-01

    Puchalska, I. B., Influence of magnetic fields on frog sciatic nerve , Biochem. Biophys. Res. Comm. 91:118 (1979). 35. Fardon, 3. C., "Effect of magnetic...fields, Bioelectromagnetic 2:357 (1981). 41. Gaffey, C. T. and Tenforde, T. S., Bioelectric properties of frog sciatic nerves during exposure to...available from: U.S. Dept. of Energy, Bonneville Power Administration, Portland, Oregon 97208 (1982). 29. Levy , R. H., and Jones, G. S., "Plasma

  6. Evaluation of potential health effects of 10 kHz magnetic fields: a rodent reproductive study.

    PubMed

    Dawson, B V; Robertson, I G; Wilson, W R; Zwi, L J; Boys, J T; Green, A W

    1998-01-01

    New technology involving the use of high-frequency inductive power distribution (HID) has recently been developed for use in materials handling and personnel transfer. Sinusoidal magnetic fields at a frequency of 10 kHz with field intensities of approximately 0.2 mT are generated directly between the current-carrying coils of this equipment. Effects of 10 kHz magnetic fields on cell division, migration, and differentiation have never been previously investigated. To evaluate potential effects on these parameters, a rodent reproductive study was undertaken using Wistar rats. Exposures were at 0.095, 0.24, and 0.95 mT with a background exposure of 5-10 microT. Three sets of parental rats were exposed continuously for 20-23.5 h/day to the fields: maternal rats during gestation, paternal rats for at least 45 days prior to mating and maternal rats 1 month prior to mating. Exposure phases thus covered spermatogenesis, maturation of the ovum and ovulation, fertilization, implantation, embryogenesis, organogenesis, and maturation of the fetus immediately prior to parturition. In all experiments pregnancy outcome was assessed. These studies failed to demonstrate any reproductive toxicity resulting from maternal or fetal exposure during gestation or following paternal or maternal exposure for several weeks prior to mating. No quantitative or qualitative effects on spermatogenesis occurred after exposure, and no effects on the estrous cycle or ovulation could be demonstrably linked to the 10 kHz magnetic field exposure at 0.095, 0.25, or 0.95 mT. Where possible, parental clinical chemistry and hematology were also examined. As in mouse toxicology studies previously reported, minor differences were observed between control and treated groups. These were regarded as statistically, but not biologically, significant and could not categorically be attributed to magnetic field exposure.

  7. Spin superconductivity and ac-Josephson effect in Graphene system under strong magnetic field

    NASA Astrophysics Data System (ADS)

    Liu, Haiwen; Jiang, Hua; Sun, Qing-Feng; Xie, X. C.; Collaborative Innovation Center of Quantum Matter, Beijing, China Collaboration

    We study the spin superconductivity in Graphene system under strong magnetic field. From the microscopically Gor'kov method combined with the Aharonov-Casher effect, we derive the effective Landau-Ginzburg free energy and analyze the time evolution of order parameter, which is confirmed to be the off-diagonal long range order. Meanwhile, we compare the ground state of spin superconductivity to the canted-antiferromagnetic state, and demonstrate the equivalence between these two states. Moreover, we give out the pseudo-field flux quantization condition of spin supercurrent, and propose an experimental measurable ac-Josephson effect of spin superconductivity in this system.

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

    PubMed

    Bastami, Tahereh Rohani; Entezari, Mohammad H

    2012-07-01

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

  9. Investigating the Effect of Line Dipole Magnetic Field on Hydrothermal Characteristics of a Temperature-Sensitive Magnetic Nanofluid Using Two-Phase Simulation.

    PubMed

    Bahiraei, Mehdi; Hangi, Morteza

    2016-12-01

    Hydrothermal characteristics of a temperature-sensitive magnetic nanofluid between two parallel plates are investigated in the presence of magnetic field produced by one or multiple line dipole(s) using the two-phase mixture model. As the nanofluid reaches the region where the magnetic field is applied, a rotation is developed due to the dependency of magnetization on temperature. This can lead to mixing in the flow and more uniform distribution of temperature due to the disturbance caused in the boundary layer, and consequently, enhancement in convective heat transfer. The results indicate that the disturbance in boundary layer adjacent to the lower wall is more significant than the upper wall. By application of the magnetic field, the convective heat transfer increases locally for both walls. Due to the intensified mixing, a sudden pressure drop occurs when the fluid reaches the region where the magnetic field is applied. For greater magnetic field strengths and lower Reynolds numbers, the improvement in convective heat transfer is more significant. For small magnetic field strengths, the effect of applying magnetic field on the upper wall is much smaller than that on the lower wall; however, this effect becomes almost the same for both walls at great magnetic field strengths.

  10. Effect of magnetic field on beta processes in a relativistic moderately degenerate plasma

    NASA Astrophysics Data System (ADS)

    Ognev, I. S.

    2016-10-01

    The effect of a magnetic field of arbitrary strength on the beta decay and crossing symmetric processes is analyzed. A covariant calculation technique is used to derive the expression for the squares of S-matrix elements of these reactions, which is also valid in reference frames in which the medium moves as a single whole along magnetic field lines. Simple analytic expressions obtained for the neutrino and antineutrino emissivities for a moderately degenerate plasma fully characterize the emissivity and absorbability of the studied medium. It is shown that the approximation used here is valid for core collapse supernovae and accretion disks around black holes; beta processes in these objects are predominantly neutrino reactions. The analytic expressions obtained for the emissivities can serve as a good approximation for describing the interaction of electron neutrinos and antineutrinos with the medium of the objects in question and hold for an arbitrary magnetic field strength. Due to their simplicity, these expressions can be included in the magnetohydrodynamic simulation of supernovae and accretion disks to calculate neutrino and antineutrino transport in them. The rates of beta processes and the energy and momentum emitted in them are calculated for an optically transparent matter. It is shown that the macroscopic momentum transferred in the medium increases linearly with the magnetic field strength and can substantially affect the dynamics of supernovae and accretion disks in the regions of a degenerate matter. It is also shown that the rates of beta processes and the energy emission for a magnetic field strength of B ≲ 1015 G typical of supernovae and accretion disks are lower than in the absence of field. This suppression is stronger for reactions with neutrinos.

  11. Magnetic field can alleviate toxicological effect induced by cadmium in mungbean seedlings.

    PubMed

    Chen, Yi-ping; Li, Ran; He, Jun-Min

    2011-06-01

    To alleviate toxicological effect induced by cadmium in mungbean seedlings, seeds were divided into four groups: The controls groups (CK, without treatment), magnetic field treated groups (MF), cadmium treated groups (CS), and magnetic field treated followed by cadmium treated groups (MF + CS).The results showed: (i) Compared with the controls, cadmium stress resulted in enhancing in the concentration of malondialdehyde, H(2)O(2) and O(2-), and the conductivity of electrolyte leakage while decreasing in the nitrice oxide synthase (NOS) activity, the concentration of nitrice oxide (NO), chlorophyll and total carbon and nitrogen, the net photosynthetic rate, the stomatal conductance, the transpiration rate, the water use efficiency, the lateral number and seedlings growth except for intercellular CO(2) concentration increase. However, the seedlings treated with 600 mT magnetic field followed by cadmium stress the concentration of malondialdehyde, H(2)O(2) and O(2-), and the conductivity of electrolyte leakage decreased, while the above mentioned NO concentration, NOS activity, photosynthesis and growth parameters increased compared to cadmium stress alone. (ii) Compared with the cadmium stress (CS), the seedling growth were inhibited when the seeds were treated with NO scavenger (hemoglobin, HB) and inhibition of NO generating enzyme (sodium tungstate, ST), conversely, the seedling growth were improved by the NO donor sodium nitroprusside (SNP) and CaCl(2). In the case of the HB and ST treatment followed by magnetic field and then the seedling subjected to CS, the seedlings growth was better than that of hemoglobin (HB) followed by CS and ST followed by CS. The seeds were treated with SNP and CaCl(2) followed by MF, and then subjected to CS, the seedlings growth were better than that of SNP followed by CS, and CaCl(2) followed by CS. These results suggested that magnetic field compensates for the toxicological effects of cadmium exposure are related to NO signal.

  12. Magnetic field effects in few-level quantum dots: Theory and application to experiment

    NASA Astrophysics Data System (ADS)

    Wright, Christopher J.; Galpin, Martin R.; Logan, David E.

    2011-09-01

    We examine several effects of an applied magnetic field on Anderson-type models for both single- and two-level quantum dots, and we make direct comparison between numerical renormalization group (NRG) calculations and recent conductance measurements. On the theoretical side, the focus is on magnetization, single-particle dynamics, and zero-bias conductance, with emphasis on the universality arising in strongly correlated regimes, including a method to obtain the scaling behavior of field-induced Kondo resonance shifts over a very wide field range. NRG is also used to interpret recent experiments on spin-(1)/(2) and spin-1 quantum dots in a magnetic field, which we argue do not wholly probe universal regimes of behavior, and the calculations are shown to yield good qualitative agreement with essentially all features seen in experiment. The results capture in particular the observed field dependence of the Kondo conductance peak in a spin-(1)/(2) dot, with quantitative deviations from experiment occurring at fields in excess of ˜5T, indicating the eventual inadequacy of using the equilibrium single-particle spectrum to calculate the conductance at finite bias.

  13. Magnetic field effects on the accuracy of ionospheric mirror models for geolocation

    NASA Astrophysics Data System (ADS)

    Dao, Eugene V.; McNamara, Leo F.; Colman, Jonah J.

    2016-04-01

    The geolocation of an uncooperative HF emitter is based on observations of the azimuth and elevation (angle of arrival; AoA) of its signals as they arrive at a surveillance site, along with a model of the propagation medium. The simplest propagation model that provides an estimate of the location of the emitter is based on the use of a horizontal mirror placed at the appropriate altitude. If there are large-scale horizontal ionospheric gradients or traveling ionospheric disturbances present, tilts derived from a suitable ionosonde or from the AoA of convenient known emitters (check targets) may be applied to the mirror before geolocation is performed. However, the methodology of this approach to geolocation completely ignores the Earth's magnetic field, producing errors that can reach 25% of range for a short range (less than 100 km) low-latitude target. The errors are generally smaller at midlatitudes. This paper investigates and characterizes these errors in terms of wave polarization, magnetic dip, circuit length, and azimuth relative to the direction of the magnetic field. The magnetic field also affects the procedure of using tilts derived from check-target AoA because the field effects can masquerade as tilts of unknown magnitude.

  14. Effects of a perpendicular magnetic field in the dipolar Heisenberg model with dominant exchange interaction.

    PubMed

    Abu-Labdeh, A M; MacIsaac, A B; De'Bell, K

    2011-07-27

    The effects of a uniform magnetic field on the phase diagram of the dipolar Heisenberg model with a dominant antiferromagnetic exchange interaction have been investigated. The model consists of a square lattice of classical spin vectors, where the spins interact through an antiferromagnetic exchange interaction of strength J and a dipole-dipole interaction of strength g. The spins couple to a magnetic surface anisotropy of strength κ and to an applied external magnetic field of strength H. The external field is applied perpendicular to the plane of the lattice. From extensive Monte Carlo simulations, representative magnetic phase diagrams have been determined as a function of the ratios κ/g and T/g, where T is temperature, and at three different ratios of H/g (H/g = 10, 20, 27). These results are compared to the previously investigated case of H/g = 0 and to analytic calculations for the ground state energies. The nature of the equilibrium phases and order of the phase boundaries separating them are considered and changes due to the strength of the applied field are highlighted.

  15. Effect of temperature and magnetic field on magnetomechanical damping of Fe-based bulk metallic glasses

    NASA Astrophysics Data System (ADS)

    Torrens-Serra, J.; Solivelles, F.; Corró, M. L.; Stoica, M.; Kustov, S.

    2016-12-01

    Temperature and magnetic field dependence of magnetomechanical damping (MMD) of two ferromagnetic Fe-based bulk metallic glasses with different Curie temperatures, T C, have been studied over a broad temperature interval from the para-ferromagnetic transition down to 15 K. The damping has been scanned under periodic magnetic field at certain preselected temperatures in the ferromagnetic and paramagnetic phases. The selection of bulk metallic glasses for investigations allowed us to eliminate all dislocation-related anelastic effects and facilitated separation of the MMD components. Under zero field, the non-linear MMD emerges at T C and first increases linearly with (T C  -  T), then levels off until a maximum is formed at around 36 K. At lower temperatures, the magnetic domain wall related non-linear MMD component is partially or completely supressed, depending on the alloy composition. Qualitatively similar anomaly is found in the temperature dependence of the linear macroeddy current damping. These anomalies in the temperature spectra are concomitant with the emergence of a notable hysteresis in MMD versus periodic field dependences and of a maximum of non-linear MMD close to the position of the macroeddy damping peak. The uncovered phenomena are attributed to abrupt change of magnetic properties of ferromagnetic bulk metallic glasses at low temperatures, presumably due to the re-entrant spin glass transition.

  16. An Experimental Study of the Effects of A Rotating Magnetic Field on Electrically Conducting Aqueous Solutions

    NASA Technical Reports Server (NTRS)

    Ramachandran Narayanan; Mazuruk, Konstantin

    1998-01-01

    The use of a rotating magnetic field for stirring metallic melts has been a commonly adopted practice for a fairly long period. The elegance of the technique stems from its non-intrusive nature and the intense stirring it can produce in an electrically conducting medium. A further application of the method in recent times has been in the area of crystal growth from melts (e.g. germanium). The latter experiments have been mainly research oriented in order to understand the basic physics of the process and to establish norms for optimizing such a technique for the commercial production of crystals. When adapted for crystal growth applications, the rotating magnetic field is used to induce a slow flow or rotation in the melt which in effect significantly curtails temperature field oscillations in the melt. These oscillations are known to cause dopant striations and thereby inhomogeneities in the grown crystal that essentially degrades the crystal quality. The applied field strength is typically of the order of milli-Teslas with a frequency range between 50-400 Hz. In this investigation, we report findings from experiments that explore the feasibility of applying a rotating magnetic field to aqueous salt solutions, that are characterized by conductivities that are several orders of magnitude smaller than semi-conductor melts. The aim is to study the induced magnetic field and consequently the induced flow in such in application. Detailed flow field description obtained through non-intrusive particle displacement tracking will be reported along with an analytical assessment of the results. It is anticipated that the obtained results will facilitate in establishing a parameter range over which the technique can be applied to obtain a desired flow field distribution. This method can find applicability in the growth of crystals from aqueous solutions and give an experimenter another controllable parameter towards improving the quality of the grown crystal.

  17. Magnetoconvection in sheared magnetic fields

    SciTech Connect

    Bian, N. H.; Garcia, O. E.

    2008-10-15

    The development of magnetoconvection in a sheared magnetic field is investigated. The equilibrium magnetic field B{sub 0} is horizontal and its orientation varies linearly along the vertical axis. Preliminary consideration of the transition from the inertial to the viscous regime of the gravitational resistive interchange instability, reveals that the latter is characterized by the existence of viscoresistive boundary layers of vertical width which scales as Q{sup -1/6}, where Q is the Chandrasekhar number. The situation is analogous to the one encountered in magnetically confined laboratory plasmas, where convective flows are constrained by the magnetic shear to develop in boundary layers located around resonant magnetic surfaces in order to fulfill the 'interchange condition'k{center_dot}B{sub 0}=0, where k is the wave vector of the magnetic perturbation. It follows that when the effect of thermal diffusion is taken into account in the process, convection can only occur above a certain critical value of the Rayleigh number which scales as Q{sup 2/3} for large Q. At the onset, the convection pattern is a superposition of identically thin convective rolls everywhere aligned with the local magnetic field lines and which therefore adopt the magnetic field geometry, a situation also reminiscent of the penumbra of sunspots. Using this degeneracy, equations describing the weakly nonlinear state are obtained and discussed. A reduced magnetohydrodynamic description of magnetoconvection is introduced. Since it is valid for arbitrary magnetic field configurations, it allows a simple extension to the case where there exists an inclination between the direction of gravity and the plane spanned by the equilibrium magnetic field. These reduced magnetohydrodynamic equations are proposed as a powerful tool for further investigations of magnetoconvection in more complex field line geometries.

  18. Effect of the {delta} meson on the instabilities of nuclear matter under strong magnetic fields

    SciTech Connect

    Rabhi, A.; Providencia, C.; Da Providencia, J.

    2009-08-15

    We study the influence of the isovector-scalar meson on the spinodal instabilities and the distillation effect in asymmetric nonhomogenous nuclear matter under strong magnetic fields of the order of 10{sup 18}-10{sup 19} G. Relativistic nuclear models both with constant couplings (NLW) and with density-dependent parameters (DDRH) are considered. A strong magnetic field can have large effects on the instability regions giving rise to bands of instability and wider unstable regions. It is shown that for neutron-rich matter the inclusion of the {delta} meson increases the size of the instability region for NLW models and decreases it for the DDRH models. The effect of the {delta} meson on the transition density to homogeneous {beta}-equilibrium matter is discussed. The DDRH{delta} model predicts the smallest transition pressures, about half the values obtained for NL{delta}.

  19. Magnetic Field Solver

    NASA Technical Reports Server (NTRS)

    Ilin, Andrew V.

    2006-01-01

    The Magnetic Field Solver computer program calculates the magnetic field generated by a group of collinear, cylindrical axisymmetric electromagnet coils. Given the current flowing in, and the number of turns, axial position, and axial and radial dimensions of each coil, the program calculates matrix coefficients for a finite-difference system of equations that approximates a two-dimensional partial differential equation for the magnetic potential contributed by the coil. The program iteratively solves these finite-difference equations by use of the modified incomplete Cholesky preconditioned-conjugate-gradient method. The total magnetic potential as a function of axial (z) and radial (r) position is then calculated as a sum of the magnetic potentials of the individual coils, using a high-accuracy interpolation scheme. Then the r and z components of the magnetic field as functions of r and z are calculated from the total magnetic potential by use of a high-accuracy finite-difference scheme. Notably, for the finite-difference calculations, the program generates nonuniform two-dimensional computational meshes from nonuniform one-dimensional meshes. Each mesh is generated in such a way as to minimize the numerical error for a benchmark one-dimensional magnetostatic problem.

  20. Eddy current effects in plain and hollow cylinders spinning inside homogeneous magnetic fields: Application to magnetic resonance

    NASA Astrophysics Data System (ADS)

    Aubert, G.; Jacquinot, J.-F.; Sakellariou, D.

    2012-10-01

    We present a thorough analysis of eddy currents that develop in a rectangular cross section toroid rotating in a uniform magnetic field. The slow rotation regime is assumed. Compact expressions for the current density, the total dissipated power, and the braking torque are given. Examination of the topology of current lines reveals that depending upon the relative dimensions of the side and length of the toroid two different regimes exist. The conditions of existence of the two regimes are analytically established. In view of nuclear magnetic resonance (NMR) applications, we derive the angular variation of the magnetic field created by eddy currents and lay down the formalism necessary for calculating the effect of this field on the NMR spectra of the conductor itself or of a sample co-rotating with the conductor, a situation encountered when dealing with rotating detectors. Examples of calculations for cases of practical interest are presented. The theory is confronted with available data, and we give guidelines for the design of optimized rotating micro-coils.

  1. CMOS Compatible 3-Axis Magnetic Field Sensor using Hall Effect Sensing

    NASA Astrophysics Data System (ADS)

    Locke, Joshua R.

    The purpose of this study is to design, fabricate and test a CMOS compatible 3-axis Hall effect sensor capable of detecting the earth's magnetic field, with strength's of ˜50 muT. Preliminary testing of N-well Van Der Pauw structures using strong neodymium magnets showed proof of concept for hall voltage sensing, however, poor geometry of the structures led to a high offset voltage. A 1-axis Hall effect sensor was designed, fabricated and tested with a sensitivity of 1.12x10-3 mV/Gauss using the RIT metal gate PMOS process. Poor geometry and insufficient design produced an offset voltage of 0.1238 volts in the 1-axis design; prevented sensing of the earth's magnetic field. The new design features improved geometry for sensing application, improved sensitivity and use the RIT sub-CMOS process. The completed 2-axis device showed an average sensitivity to large magnetic fields of 0.0258 muV/Gauss at 10 mA supply current.

  2. Numerical analysis of the effects of a high gradient magnetic field on flowing erythrocytes in a membrane oxygenator

    NASA Astrophysics Data System (ADS)

    Mitamura, Yoshinori; Okamoto, Eiji

    2015-04-01

    This study was carried out to clarify the effect of a high gradient magnetic field on pressure characteristics of blood in a hollow fiber membrane oxygenator in a solenoid coil by means of numerical analysis. Deoxygenated erythrocytes are paramagnetic, and oxygenated erythrocytes are diamagnetic. Blood changes its magnetic susceptibility depending on whether it is carrying oxygen or not. Motion of blood was analyzed by solving the continuous equation and the Navier-Stokes equation. It was confirmed that oxygenation of deoxygenated blood in the downstream side of the applied magnetic field was effective for pressure rise in a non-uniform magnetic field. The pressure rise was enhanced greatly by an increase in magnetic field intensity. The results suggest that a membrane oxygenator works as an actuator and there is a possibility of self-circulation of blood through an oxygenator in a non-uniform magnetic field.

  3. Effects of 50 Hz magnetic fields on mouse spermatogenesis monitored by flow cytometric analysis

    SciTech Connect

    Vita, R. de; Cavallo, D.; Raganella, L.; Eleuteri, P.; Grollino, M.G.; Calugi, A.

    1995-12-01

    Flow cytometry (FCM) was performed to monitor the cellular effects of extremely-low-frequency magnetic field on mouse spermatogenesis. Groups of five male hybrid F1 mice aged 8--10 weeks were exposed to 50 Hz magnetic field. The strength of the magnetic field was 1.7 mT. Exposure times of 2 and 4 h were chosen. FCM measurements were performed 7, 14, 21, 28, 35, and 42 days after treatment. For each experimental point, a sham-treated group was used as a control. The possible effects were studied by analyzing the DNA content distribution of the different cell types involved in spermatogenesis and using the elongated spermatids as the reference population. The relative frequencies of the various testicular cell types were calculated using specific software. In groups exposed for 2 h, no effects were observed. In groups exposed for 4 h, a statistically significant (P < 0.001) decrease in elongated spermatids was observed at 28 days after treatment. This change suggests a possible cytotoxic and/or cytostatic effect on differentiating spermatogonia. However, further studies are being carried out to investigate the effects of longer exposure times.

  4. Some effects of high- gradient magnetic field on tropism of roots of higher plants

    NASA Astrophysics Data System (ADS)

    Kondrachuk, A.; Belyavskaya, N.

    The perception of gravity in living organisms is mostly based on the response of the gravisensing system to displacement of some specific mass caused by gravitational force. According to the starch-statolith hypothesis the amyloplasts play the role of specific mass in gravisensing cells of higher plants. Kuznetsov & Hasenstein (1996) have demonstrated that the high-gradient magnetic field (HGMF) exerts a directional ponderomotive force on diamagnetic substances, in particular, statoliths. This effect of the HGMF causes root response similar to that produced by the change in gravity vector. Their studies supported the starch-statolith hypothesis and showed that ponderomotive force can be used to modify force acting on statoliths by manipulating statolith locations within gravisensing cells. We have designed the HGMF facility that allows for generating the HGMF and analyzing its effects on higher plants' roots. It records by videosystem and measures with the help of image analysis software the parameters of kinetics of root bending under both the HGMF action and gravistimulation. Two species of plants (pea and cress) have been examined. The main results of the work are the following: 1) The magnetotropic effect of HGMF on root growth was found for both species. 2) The critical value of ponderomotive force that caused the magnetotropic effect was estimated by modeling the magnetic field spatial distribution in the region of root apex. 3) The electron-microscopic analysis of statocytes after the HGMF treatment was carried out. The displacement of amyloplasts in root statocytes of two species of plants in HGMF was firstly demonstrated at the ultrastructural level. 4) Spatial distribution of exogenous proton fluxes (pH) along the roots was studied. The changes in pH distribution along curvature zone and apices of roots were revealed in the HGMF. It is known that application of HGMFs or strong uniform magnetic fields may influence ion transport due to Ampere force. It

  5. MODELING OF COUPLED EDGE STOCHASTIC AND CORE RESONANT MAGNETIC FIELD EFFECTS IN DIVERTED TOKAMAKS

    SciTech Connect

    EVANS, T.E.; MOYER, R.A.

    2002-06-01

    Attaining the highest performance in poloidally diverted tokamaks requires resonant magnetic perturbation coils to avoid core instabilities (locked, resistive wall and neoclassical tearing modes). These coils also perturb the pedestal and edge region, causing varying degrees of stochasticity with remnant islands. The effects of the DIII-D locked mode control coil on the edge and core of Ohmic plasmas are modeled with the field line integration code TRIP3D and compared with experimental measurements. Without detailed profile analysis and field line integration, it is difficult to establish whether a given response is due to a ''core mode'' or an ''edge stochastic boundary.'' In diverted Ohmic plasmas, the boundary stochastic layer displays many characteristics associated with such layers in non-diverted tokamaks. Comparison with stochastic boundary results from non-diverted tokamaks indicates that a significant difference in diverted tokamaks is a ''focusing'' of the magnetic field line loss into the vicinity of the divertor.

  6. Effects of magnetic field and the built-in internal fields on the absorption coefficients in a strained wurtzite GaN/AlGaN quantum dot

    NASA Astrophysics Data System (ADS)

    Minimala, N. S.; Peter, A. John

    2013-02-01

    Effects of magnetic field strength and the built-in electric fields on the exciton binding energy and the non-linear optical property such as absorption coefficients in a GaN/AlGaN wide band gap heterostructure are investigated. The internal fields due to spontaneous and piezo-electric polarizations are included in the Hamiltonian. Our results show that the optical absorption coefficients strongly depend on the internal fields and the applied magnetic field.

  7. Perturbative calculations of quantum spin tunneling in effective spin systems with a transversal magnetic field and transversal anisotropy

    NASA Astrophysics Data System (ADS)

    Krizanac, M.; Vedmedenko, E. Y.; Wiesendanger, R.

    2017-01-01

    We present a perturbative approach for the resonant tunnel splittings of an arbitrary effective single spin system. The Hamiltonian of such a system contains a uniaxial anisotropy, a transversal magnetic field and a second-order transversal anisotropy. Further, we investigate the influence of the transversal magnetic field on the energy splittings for higher integer quantum spins and we introduce an exact formula, which defines values of the transversal magnetic field, the transversal anisotropy and the uniaxial anisotropy where the contribution of the transversal magnetic field to the energy splitting is at least equal to the contribution of the transversal anisotropy.

  8. The effect of magnetic field and disorders on the electronic transport in graphene nanoribbons.

    PubMed

    Kumar, S Bala; Jalil, M B A; Tan, S G; Liang, Gengchiau

    2010-09-22

    We developed a unified mesoscopic transport model for graphene nanoribbons, which combines the nonequilibrium Green's function (NEGF) formalism with the real-space π-orbital model. Based on this model, we probe the spatial distribution of electrons under a magnetic field, in order to obtain insights into the various signature Hall effects in disordered armchair graphene nanoribbons (AGNR). In the presence of a uniform perpendicular magnetic field (B[Symbol: see text]-field), a perfect AGNR shows three distinct spatial current profiles at equilibrium, depending on its width. Under nonequilibrium conditions (i.e. in the presence of an applied bias), the net electron flow is restricted to the edges and occurs in opposite directions depending on whether the Fermi level lies within the valence or conduction band. For electrons at an energy level below the conduction window, the B[Symbol: see text]-field gives rise to local electron flux circulation, although the global flux is zero. Our study also reveals the suppression of electron backscattering as a result of the edge transport which is induced by the B[Symbol: see text]-field. This phenomenon can potentially mitigate the undesired effects of disorder, such as bulk and edge vacancies, on the transport properties of AGNR. Lastly, we show that the effect of [Formula: see text]-field on electronic transport is less significant in the multimode compared to the single-mode electron transport.

  9. Joule Heating Effect on Field-Free Magnetization Switching by Spin-Orbit Torque in Exchange-Biased Systems

    NASA Astrophysics Data System (ADS)

    Razavi, Seyed Armin; Wu, Di; Yu, Guoqiang; Lau, Yong-Chang; Wong, Kin L.; Zhu, Weihua; He, Congli; Zhang, Zongzhi; Coey, J. M. D.; Stamenov, Plamen; Khalili Amiri, Pedram; Wang, Kang L.

    2017-02-01

    Switching of magnetization via spin-orbit torque provides an efficient alternative for nonvolatile memory and logic devices. However, to achieve deterministic switching of perpendicular magnetization, an external magnetic field collinear with the current is usually required, which makes these devices inappropriate for practical applications. In this work, we examine the current-induced magnetization switching in a perpendicularly magnetized exchange-biased Pt /CoFe /IrMn system. A magnetic field annealing technique is used to introduce in-plane exchange biases, which are quantitatively characterized. Under proper conditions, field-free current-driven switching is achieved. We study the Joule heating effect, and we show how it can decrease the in-plane exchange bias and degrade the field-free switching. Furthermore, we discuss that the exchange-bias training effect can have similar effects.

  10. Effect of magnetic field on laser-induced breakdown spectroscopy of graphite plasma

    NASA Astrophysics Data System (ADS)

    Arshad, Atiqa; Bashir, Shazia; Hayat, Asma; Akram, Mahreen; Khalid, Ayesha; Yaseen, Nazish; Ahmad, Qazi Salman

    2016-03-01

    The effect of transverse magnetic field on laser-induced breakdown spectroscopy of graphite plasma as a function of fluence has been investigated. Graphite targets were exposed to Nd:YAG (1064 nm, 10 ns) laser pulses at various laser fluences ranging from 0.4 to 2.9 J cm-2 under two different environment of air and Ar at a pressure of 150 and 760 torr. A transverse magnetic field of strength 0.5 tesla was employed by using permanent magnets. It is revealed that due to the presence of the magnetic field the emission intensity, electron temperature and number density of graphite plasma have been increased at all fluences and for all environmental conditions. The enhancement in plasma parameters is attributed to magnetic confinement effect and Joule heating effect. Initially by increasing the fluence from 0.4 to 1.5 J cm-2 (in air) and 0.4 to 1.8 J cm-2 (in Ar), the emission intensity, electron temperature and number density have been increased and have attained their maximum values. Further increase in fluence was responsible for the decreasing trend in all plasma parameters. More increase in fluence (beyond 1.8 J cm-2 in case of air and 2.2 J cm-2 in case of Ar) up to a maximum value of 2.9 J cm-2, the saturation or self-sustained regime was achieved, which is responsible for insignificant changes in plasma parameters. The value of plasma parameter " β" was also evaluated analytically, and it was less than one for all conditions (fluences as well as environments), which confirmed the existence of confinement effect.

  11. Magnetic fields at uranus.

    PubMed

    Ness, N F; Acuña, M H; Behannon, K W; Burlaga, L F; Connerney, J E; Lepping, R P; Neubauer, F M

    1986-07-04

    The magnetic field experiment on the Voyager 2 spacecraft revealed a strong planetary magnetic field of Uranus and an associated magnetosphere and fully developed bipolar masnetic tail. The detached bow shock wave in the solar wind supersonic flow was observed upstream at 23.7 Uranus radii (1 R(U) = 25,600 km) and the magnetopause boundary at 18.0 R(U), near the planet-sun line. A miaximum magnetic field of 413 nanotesla was observed at 4.19 R(U ), just before closest approach. Initial analyses reveal that the planetary magnetic field is well represented by that of a dipole offset from the center of the planet by 0.3 R(U). The angle between Uranus' angular momentum vector and the dipole moment vector has the surprisingly large value of 60 degrees. Thus, in an astrophysical context, the field of Uranus may be described as that of an oblique rotator. The dipole moment of 0.23 gauss R(3)(U), combined with the large spatial offset, leads to minimum and maximum magnetic fields on the surface of the planet of approximately 0.1 and 1.1 gauss, respectively. The rotation period of the magnetic field and hence that of the interior of the planet is estimated to be 17.29+/- 0.10 hours; the magnetotail rotates about the planet-sun line with the same period. Thelarge offset and tilt lead to auroral zones far from the planetary rotation axis poles. The rings and the moons are embedded deep within the magnetosphere, and, because of the large dipole tilt, they will have a profound and diurnally varying influence as absorbers of the trapped radiation belt particles.

  12. Effect of a seed magnetic field on two-fluid plasma Richtmyer-Meshkov instability

    NASA Astrophysics Data System (ADS)

    Bond, Daryl; Wheatley, Vincent; Samtaney, Ravi; Pullin, Dale

    2016-11-01

    We investigate the effect of a uniform seed magnetic field on the plasma Richtmyer-Meshkov instability (RMI) using two-fluid simulations. These couple sets of conservation equations for the ions and electrons to the full Maxwell's equations. We consider cases where the seed magnetic field is normal to the interface and where the reference Debye length and Larmor radius range from a tenth to a thousandth of the interface perturbation wavelength. In ideal magnetohydrodynamics (MHD), it has been shown that in the presence of such a seed magnetic field, the growth of the RMI is suppressed by the transport of vorticity from the interface by MHD shocks. Our two-fluid plasma simulations reveal that while the RMI is suppressed in the presence of the seed field, the suppression mechanism varies depending on the plasma length-scales. Two-fluid plasma RMI simulations also reveal a secondary, high-wavenumber, electron-driven interface instability. This is not suppressed by the presence of the seed field. This work was partially supported by the KAUST Office of Sponsored Research under Award URF/1/2162-01.

  13. Interaction of magnetic field in flow of Maxwell nanofluid with convective effect

    NASA Astrophysics Data System (ADS)

    Hayat, T.; Muhammad, Taseer; Shehzad, S. A.; Chen, G. Q.; Abbas, Ibrahim A.

    2015-09-01

    Magnetohydrodynamic (MHD) three-dimensional flow of Maxwell nanofluid subject to the convective boundary condition is investigated. The flow is generated by a bidirectional stretching surface. Thermophoresis and Brownian motion effects are present. Fluid is electrically conducted in the presence of a constant applied magnetic field. Unlike the previous cases even in the absence of nanoparticles, the correct formulation for the flow of Maxwell fluid in the presence of a magnetic field is established. Newly proposed boundary condition with the zero nanoparticles mass flux at the boundary is employed. The governing nonlinear boundary layer equations through appropriate transformations are reduced in the nonlinear ordinary differential system. The resulting nonlinear system has been solved for the velocities, temperature and nanoparticles concentration distributions. Convergence of the constructed solutions is verified. Effects of emerging parameters on the temperature and nanoparticles concentration are plotted and discussed. Numerical values of local Nusselt number are computed and analyzed. It is observed that the effects of magnetic parameter and the Biot number on the temperature and nanoparticles concentration are quite similar. Both the temperature and nanoparticles concentration are enhanced for the increasing value of magnetic parameter and Biot number.

  14. Effect of a magnetic field on intersubband polaritons in a quantum well: strong to weak coupling conversion.

    PubMed

    Pervishko, A A; Kibis, O V; Shelykh, I A

    2016-08-01

    We investigate theoretically the effect of a magnetic field on intersubband polaritons in an asymmetric quantum well placed inside an optical resonator. It is demonstrated that the field-induced diamagnetic shift of electron subbands in the well increases the broadening of optical lines corresponding to intersubband electron transitions. As a consequence, the magnetic field can switch the polariton system from the regime of strong light-matter coupling to the regime of a weak one. This effect paves a way for the effective control of polaritonic devices with a magnetic field.

  15. Large-scale magnetic field in the accretion discs of young stars: the influence of magnetic diffusion, buoyancy and Hall effect

    NASA Astrophysics Data System (ADS)

    Khaibrakhmanov, S. A.; Dudorov, A. E.; Parfenov, S. Yu.; Sobolev, A. M.

    2017-01-01

    We investigate the fossil magnetic field in the accretion and protoplanetary discs using the Shakura and Sunyaev approach. The distinguishing feature of this study is the accurate solution of the ionization balance equations and the induction equation with Ohmic diffusion, magnetic ambipolar diffusion, buoyancy and the Hall effect. We consider the ionization by cosmic rays, X-rays and radionuclides, radiative recombinations, recombinations on dust grains and also thermal ionization. The buoyancy appears as the additional mechanism of magnetic flux escape in the steady-state solution of the induction equation. Calculations show that Ohmic diffusion and magnetic ambipolar diffusion constraint the generation of the magnetic field inside the `dead' zones. The magnetic field in these regions is quasi-vertical. The buoyancy constraints the toroidal magnetic field strength close to the disc inner edge. As a result, the toroidal and vertical magnetic fields become comparable. The Hall effect is important in the regions close to the borders of the `dead' zones because electrons are magnetized there. The magnetic field in these regions is quasi-radial. We calculate the magnetic field strength and geometry for the discs with accretion rates (10^{-8}-10^{-6}) {M}_{⊙} {yr}^{-1}. The fossil magnetic field geometry does not change significantly during the disc evolution while the accretion rate decreases. We construct the synthetic maps of dust emission polarized due to the dust grain alignment by the magnetic field. In the polarization maps, the `dead' zones appear as the regions with the reduced values of polarization degree in comparison to those in the adjacent regions.

  16. The effect of external magnetic field on the Raman peaks in manganites

    SciTech Connect

    Sahu, A. K.; Rout, G. C.

    2014-04-24

    We report here a microscopic theoretical model study exhibiting the effect of external magnetic field on the Raman excitation peaks in the CMR manganite system. The Hamiltonian consists of Jahn-Teller (J-T) distortion in e{sub g} band, the double exchange interaction and the Heisenberg spin-spin interaction. Further the phonons are coupled to e{sub g} band electrons, J-T distorted e{sub g} band and the double exchange interaction. The Raman spectral intensity is calculated from the imaginary part of the phonon Green function. The spectra exhibits three peaks besides a very weak high energy peak. The magnetic field effect on these peaks are reported.

  17. Effects of magnetic field and Hall current to the blood velocity and LDL transfer

    NASA Astrophysics Data System (ADS)

    Abdullah, I.; Naser, N.; Talib, A. H.; Mahali, S.

    2015-09-01

    The magnetic field and Hall current effects have been considered on blood velocity and concentration of low-density lipoprotein (LDL). It is important to observe those effects to the flowing blood in a stenosed artery. The analysis from the obtained results may be useful to some clinical procedures, such as MRI, where the radiologists may have more information in the investigations before cardiac operations could be done. In this study, the uniform magnetic field and Hall current are applied to the Newtonian blood flow through an artery having a cosine-shaped stenosis. The governing equations are coupled with mass transfer and solved employing a finite difference Marker and Cell (MAC) method with an appropriate initial and boundary conditions. The graphical results of velocity profiles and LDL concentration are presented in this paper and the results show that the velocity increases and concentration decreases as Hall parameter increased.

  18. Magnetic Field Effect on Convective Fluid Flow in a Vertical Bridgman System

    NASA Technical Reports Server (NTRS)

    Wang, J. C.; Lehoczky, S. L.; Watring, D. A.

    1998-01-01

    We studied the magnetic field effects on convective fluid flow in a differentially heated HgCdTe Bridgman growth system with linearly stratified vertical HgTe concentration. We followed J. E. Hart's system set-up, boundary conditions, and formulation. We obtained analytical steady parallel flow solutions for fluid flow's velocity and solutal concentration. These solutions depend only on solutal Rayleigh number. Our analytical solutions had different expressions from that of Hart's, but had similar numerical simulation results for the mean fluid velocity and solutal concentration gradient as a function of solutal Rayleigh number. We studied the effects of a transverse magnetic field on the fluid flow of the Bridgman growth systems both on the ground and in the space. The simulation results and comparison with experimental results will be presented.

  19. Effects of magnetic fields produced by simulated and real geomagnetic storms on rats

    NASA Astrophysics Data System (ADS)

    Martínez-Bretón, J. L.; Mendoza, B.

    2016-03-01

    In this paper we report experiments of arterial pressure (AP) measurements of ten Wistar rats subjected to geomagnetic field changes and to artificially stimulated magnetic field variations. Environmental electromagnetic effects were screened using a semianechoic chamber, which allowed us to discern the effects associated with geomagnetic storms. We stimulated the subjects with a linear magnetic profile constructed from the average changes of sudden storm commencement (SSC) and principal phases of geomagnetic storms measured between 1996 and 2008 with Dst ⩽ -100 nT. Although we found no statistically significant AP variations, statistically significant AP changes were found when a geomagnetic storm occurred during the experimental period. Using the observed geomagnetic storm variations to construct a geomagnetic profile to stimulate the rats, we found that the geomagnetic field variations associated to the SSC day were capable of increasing the subjects AP between 7% and 9% from the reference value. Under this magnetic variation, the subjects presented a notably restless behavior not seen under other conditions. We conclude that even very small changes in the geomagnetic field associated with a geomagnetic storm can produce a measurable and reproducible physiological response.

  20. Monte Carlo characterization of skin doses in 6 MV transverse field MRI-linac systems: Effect of field size, surface orientation, magnetic field strength, and exit bolus

    SciTech Connect

    Oborn, B. M.; Metcalfe, P. E.; Butson, M. J.; Rosenfeld, A. B.

    2010-10-15

    Purpose: The main focus of this work is to continue investigations into the Monte Carlo predicted skin doses seen in MRI-guided radiotherapy. In particular, the authors aim to characterize the 70 {mu}m skin doses over a larger range of magnetic field strength and x-ray field size than in the current literature. The effect of surface orientation on both the entry and exit sides is also studied. Finally, the use of exit bolus is also investigated for minimizing the negative effects of the electron return effect (ERE) on the exit skin dose. Methods: High resolution GEANT4 Monte Carlo simulations of a water phantom exposed to a 6 MV x-ray beam (Varian 2100C) have been performed. Transverse magnetic fields of strengths between 0 and 3 T have been applied to a 30x30x20 cm{sup 3} phantom. This phantom is also altered to have variable entry and exit surfaces with respect to the beam central axis and they range from -75 deg. to +75 deg. The exit bolus simulated is a 1 cm thick (water equivalent) slab located on the beam exit side. Results: On the entry side, significant skin doses at the beam central axis are reported for large positive surface angles and strong magnetic fields. However, over the entry surface angle range of -30 deg. to -60 deg., the entry skin dose is comparable to or less than the zero magnetic field skin dose, regardless of magnetic field strength and field size. On the exit side, moderate to high central axis skin dose increases are expected except at large positive surface angles. For exit bolus of 1 cm thickness, the central axis exit skin dose becomes an almost consistent value regardless of magnetic field strength or exit surface angle. This is due to the almost complete absorption of the ERE electrons by the bolus. Conclusions: There is an ideal entry angle range of -30 deg. to -60 deg. where entry skin dose is comparable to or less than the zero magnetic field skin dose. Other than this, the entry skin dose increases are significant, especially at

  1. Mercury's Magnetic Field

    NASA Astrophysics Data System (ADS)

    Johnson, C. L.

    2014-12-01

    Mercury is the only inner solar system body other than Earth to possess an active core dynamo-driven magnetic field and the only planet with a small, highly dynamic magnetosphere. Measurements made by the MErcury Surface, Space ENvironment, GEochemistry, and Ranging (MESSENGER) spacecraft have provided a wealth of data on Mercury's magnetic field environment. Mercury's weak magnetic field was discovered 40 years ago by the Mariner 10 spacecraft, but its large-scale geometry, strength and origin could not be definitively established. MESSENGER data have shown that the field is dynamo-generated and can be described as an offset axisymmetric dipole field (hereafter OAD): the magnetic equator lies ~0.2 RM (RM = 2440 km) north of the geographic equator and the dipole moment is 2.8 x1019 Am2 (~0.03% that of Earth's). The weak internal field and the high, but variable, solar wind ram pressure drive vigorous magnetospheric dynamics and result in an average distance from the planet center to the sub-solar magnetopause of only 1.42 RM. Magnetospheric models developed with MESSENGER data have allowed re-analysis of the Mariner 10 observations, establishing that there has been no measureable secular variation in the internal field over 40 years. Together with spatial power spectra for the OAD, this provides critical constraints for viable dynamo models. Time-varying magnetopause fields induce secondary core fields, the magnitudes of which confirm the core radius estimated from MESSENGER gravity and Earth-based radar data. After accounting for large-scale magnetospheric fields, residual signatures are dominated by additional external fields that are organized in the local time frame and that vary with magnetospheric activity. Birkeland currents have been identified, which likely close in the planetary interior at depths below the base of the crust. Near-periapsis magnetic field measurements at altitudes greater than 200 km have tantalizing hints of crustal fields, but crustal

  2. THE EFFECTS OF MAGNETIC FIELDS AND INHOMOGENEITIES ON ACCRETION DISK SPECTRA AND POLARIZATION

    SciTech Connect

    Davis, Shane W.; Blaes, Omer M.; Hirose, Shigenobu; Krolik, Julian H.

    2009-09-20

    We present the results of one- and three-dimensional radiative transfer calculations of polarized spectra emerging from snapshots of radiation magnetohydrodynamical simulations of the local vertical structure of black hole accretion disks. The simulations cover a wide range of physical regimes relevant for the high/soft state of black hole X-ray binaries. We constrain the uncertainties in theoretical spectral color correction factors due to the presence of magnetic support of the disk surface layers and strong density inhomogeneities. For the radiation-dominated simulation, magnetic support increases the color correction factor by about 10%, but this is largely compensated by a 10% softening due to inhomogeneities. We also compute the effects of inhomogeneities and Faraday rotation on the resulting polarization. Magnetic fields in the simulations are just strong enough to produce significant Faraday depolarization near the spectral peak of the radiation field. X-ray polarimetry may therefore be a valuable diagnostic of accretion disk magnetic fields, being able to directly test simulations of magnetorotational turbulence.

  3. Magnetic field and particle concentration competitive effects on ferrofluid based silicone elastomer microstructure

    SciTech Connect

    Balasoiu, M.; Lebedev, V. T.; Orlova, D. N.; Bica, I.

    2011-12-15

    Structural peculiarities of ferroelastomers composed of polydimetylsiloxane with embedded magnetite particles during polymerization have been studied by small-angle neutron scattering. The effects of ferroparticles' concentration in the range of C = 0-6 wt %, and external magnetic fields of induction B = 0-1 kG applied during the polymerization on the structure of polymeric matrix and particles distribution in polymer were analyzed.

  4. [Effects of weak magnetic fields on different phases of planarian regeneration].

    PubMed

    Tiras, Kh P; Petrova, O N; Miakisheva, S N; Popova, S S; Aslanidi, K B

    2015-01-01

    We analyzed the effects of weak combined magnetic fields, tuned to the cyclotron resonance condition for calcium ions, obtained in different phases of planarian regeneration. We showed that the result of regeneration in 72 hours after decapitation depends on the length of exposure, and the time between decapitation and initiation of a half-hour exposure. The experimental dependence can be explained by a multiplicity of enzymatic targets activated in different phases of the regeneration process.

  5. The effects of direct-current magnetic fields on turtle retinas vitro

    SciTech Connect

    Raybourn, M.S.

    1983-05-13

    Direct-current magnetic fields of 10 to 100 gauss cause a significant short-term reduction of the in vitro electroretinographic b-wave response in turtle retina. This response compression is not accompanied by the usual reduction in retinal sensitivity that occurs with background illumination. Furthermore, this effect is obtained only briefly after the offset of ambient lighting in the diurnal light-dark cycle of nonhibernating animals.

  6. Magnetic Field Effects on Convection and Solidification in Normal and Microgravity

    NASA Technical Reports Server (NTRS)

    Li, Ben Q.; deGroh, H. C., III

    2003-01-01

    It has been well understood that convective flows induced by g-jitter forces associated with spacecraft are responsible for defects formation and irregularity in product quality during melt growth of single crystals in microgravity. This research is concerned about numerical simulations and experimental measurements for the purpose of developing a fundamental understanding of the g-jitter induced fluid flows and their effects on solidification in microgravity with and without the presence of additional damping forces that are derived from the applied DC magnetic fields. The numerical models include both 2-D and 3-D transient fluid flow, heat transfer, mass transfer and solidification under the combined action of g-jitter and magnetic fields. Numerical simulations using both the 2-D and 3-D models are conducted for both idealized, synthesized and real g-jitter forces, and 2-D simulations are tested against the experimental measurements taken on the thermal oscillator. 2-D solidification models have also been developed and simulations are conducted. Results show that the numerical model predictions compare well with the measurements. Analysis of these results illustrates that an applied magnetic field can have a drastic influence on the convective flows induced by g-jitter and can be particularly useful to suppress the effects resulting from the spiking of g-jitter signatures, which are considered the most detrimental effects on quality of crystals grown in space. Work in progress includes developing 3-D numerical models for solidification phenomena with the presence of both g-jitter and magnetic fields and measurements of flow fluid and its effect on solidification in both transparent fluid and low melting point melts to verify numerical predictions.

  7. The mitigating effect of self-generated magnetic field on Rayleigh-Taylor unstable inertial confinement fusion plasmas

    NASA Astrophysics Data System (ADS)

    Srinivasan, Bhuvana

    2012-10-01

    It has long been expected that Rayleigh-Taylor instabilities (RTI) in ICF can generate magnetic fields at the gas-ice interface and at the ice-ablator interface during the deceleration phase of target implosion. The focus here is on the gas-ice interface where the temperature gradient is the largest. Nonlinear evolution of RTI leads to undesirable mixing of hot and cold plasmas and enhances target energy loss. RTI is also expected to generate magnetic fields via the Biermann battery effect, which is related to fluid vorticity generation by RTI. The magnetic field wraps around the bubbles and spikes and concentrates in flux bundles at the perturbed gas-ice interface where fluid vorticity is large. The generated magnetic field can then be further amplified via the MHD dynamo effect. While the planar 2-D simulations only generate out-of-plane magnetic fields, 3-D simulations will result in further amplification of the complex magnetic field structures via the MHD dynamo. This is studied by including a seed in-plane magnetic field in 2-D and examining the resulting magnetic field structure and magnitude. The self-generated out-of-plane magnetic fields depend on ICF parameters via the scaling law, mi√A g/λ where mi is the ion mass, A is the Atwood number, g is the acceleration, and λ is the wavelength. These magnetic fields grow to magnitudes of 10^2-10^3 T for ICF relevant parameter regimes. While this is dynamically insignificant due to the plasma pressure far exceeding the magnetic pressure, it can significantly reduce perpendicular electron thermal conductivity by a factor of 2-10. Such a reduction in thermal conductivity perpendicular to the magnetic field contributes to lowering of radial energy transport in the implosion target.

  8. Compressibility Effect on the Rayleigh-Taylor Instability with Sheared Magnetic Fields

    NASA Astrophysics Data System (ADS)

    Ruderman, M. S.

    2017-04-01

    We study the effect of plasma compressibility on the Rayleigh-Taylor instability of a magnetic interface with a sheared magnetic field. We assume that the plasma is ideal and the equilibrium quantities are constant above and below the interface. We derive the dispersion equation. Written in dimensionless variables, it contains seven dimensionless parameters: the ratio of plasma densities above and below the interface ζ, the ratio of magnetic field magnitude squared χ, the shear angle α, the plasma beta above and below the interface, β2 and β1, the angle between the perturbation wave number and the magnetic field direction above the interface φ, and the dimensionless wave number κ. Only six of these parameters are independent because χ, β1, and β2 are related by the condition of total pressure continuity at the interface. Only perturbations with the wave number smaller than the critical wave number are unstable. The critical wave number depends on φ, but it is independent of β1 and β2, and is the same as that in the incompressible plasma approximation. The dispersion equation is solved numerically with ζ= 100, χ= 1, and β1 = β2 = β. We obtain the following results. When β decreases, so does the maximum instability increment. However, the effect is very moderate. It is more pronounced for high values of α. We also calculate the dependence on φ of the maximum instability increment with respect to κ. The instability increment takes its maximum at φ= φm. Again, the decrease of β results in the reduction of the instability increment. This reduction is more pronounced for high values of |φ- φm|. When both α and |φ- φm| are small, the reduction effect is practically negligible. The theoretical results are applied to the magnetic Rayleigh-Taylor instability of prominence threads in the solar atmosphere.

  9. Solar wind interaction effects on the magnetic fields around Mars: Consequences for interplanetary and crustal field measurements

    NASA Astrophysics Data System (ADS)

    Luhmann, J. G.; Ma, Y.-J.; Brain, D. A.; Ulusen, D.; Lillis, R. J.; Halekas, J. S.; Espley, J. R.

    2015-11-01

    The first unambiguous detections of the crustal remanent magnetic fields of Mars were obtained by Mars Global Surveyor (MGS) during its initial orbits around Mars, which probed altitudes to within ∼110 km of the surface. However, the majority of its measurements were carried out around 400 km altitude, fixed 2 a.m. to 2 p.m. local time, mapping orbit. While the general character and planetary origins of the localized crustal fields were clearly revealed by the mapping survey data, their effects on the solar wind interaction could not be investigated in much detail because of the limited mapping orbit sampling. Previous analyses (Brain et al., 2006) of the field measurements on the dayside nevertheless provided an idea of the extent to which the interaction of the solar wind and planetary fields leads to non-ideal field draping at the mapping altitude. In this study we use numerical simulations of the global solar wind interaction with Mars as an aid to interpreting that observed non-ideal behavior. In addition, motivated by models for different interplanetary field orientations, we investigate the effects of induced and reconnected (planetary and external) fields on the Martian field's properties derived at the MGS mapping orbit altitude. The results suggest that inference of the planetary low order moments is compromised by their influence. In particular, the intrinsic dipole contribution may differ from that in the current models because the induced component is so dominant.

  10. Effect of magnetic field on Fe - Si - Al alloy properties with zero magnetostriction

    NASA Astrophysics Data System (ADS)

    Naimi, E. K.; Kaputkin, D. E.

    2012-09-01

    A method and results for a study of the effect of permanent and variable (up to about 1.5 kHz) magnetic fields with intensity H = 0-1050 A/m on internal friction Q -1 and Young's modulus defect ∆ E/ E in magnetically-soft alloy of the system Fe - Si - Al (sendast type) with mechanical vibration frequency about 105 Hz are provided. The range of strain rate amplitudes ɛ0 within which Q -1 and ∆ E/ E are independent of H, and the range where they increase linearly with an increase in S0 over the whole range of change in H are determined. Results obtained are analyzed within the framework of existing relaxation theory and hysteresis mechanism of elastic vibration damping within magnetically soft materials.

  11. Generalized magnetotail equilibria: Effects of the dipole field, thin current sheets, and magnetic flux accumulation

    NASA Astrophysics Data System (ADS)

    Sitnov, M. I.; Merkin, V. G.

    2016-08-01

    Generalizations of the class of quasi-1-D solutions of the 2-D Grad-Shafranov equation, first considered by Schindler in 1972, are investigated. It is shown that the effect of the dipole field, treated as a perturbation, can be included into the original 1972 class solution by modification of the boundary conditions. Some of the solutions imply the formation of singularly thin current sheets. Equilibrium solutions for such sheets resolving their singular current structure on the scales comparable to the thermal ion gyroradius can be obtained assuming anisotropic and nongyrotropic plasma distributions. It is shown that one class of such equilibria with the dipole-like boundary perturbation describes bifurcation of the near-Earth current sheet. Another class of weakly anisotropic equilibria with thin current sheets embedded into a thicker plasma sheet helps explain the formation of thin current sheets in a relatively distant tail, where such sheets can provide ion Landau dissipation for spontaneous magnetic reconnection. The free energy for spontaneous reconnection can be provided due to accumulation of the magnetic flux at the tailward end of the closed field line region. The corresponding hump in the normal magnetic field profile Bz(x,z = 0) creates a nonzero gradient along the tail. The resulting gradient of the equatorial magnetic field pressure is shown to be balanced by the pressure gradient and the magnetic tension force due to the higher-order correction of the latter in the asymptotic expansion of the tail equilibrium in the ratio of the characteristic tail current sheet variations across and along the tail.

  12. Epilepsy and electromagnetic fields: effects of simulated atmospherics and 100-Hz magnetic fields on audiogenic seizure in rats

    NASA Astrophysics Data System (ADS)

    Juutilainen, J.; Björk, E.; Saali, K.

    1988-03-01

    In order to study the possible association between epileptic seizures and natural electromagnetic fields, 32 female audiogenic seizure (AGS)-susceptible rats were exposed to simulated 10 kHz and 28 kHz atmospherics and to a sinusoidally oscillating magnetic field with a frequency of 100 Hz and field strength of 1 A/m. After the electromagnetic exposure, seizures were induced in the rats with a sound stimulus. The severity of the seizure was determined on an ordinal scale, the audiogenic response score (ARS). The time from the beginning of the sound stimulus to the onset of the seizure (seizure latency) and the duration of the convulsion was measured. No differences from the control experiments were found in the experiments with simulated atmospherics, but the 100 Hz magnetic field increased the seizure latency by about 13% ( P<0.02). The results do not support the hypothesis that natural atmospheric electromagnetic signals could affect the onset of epileptic seizures, but they suggest that AGS-susceptible rats may be a useful model for studying the biological effects of electromagnetic fields.

  13. Intrinsic surface magnetic anisotropy in Y3Fe5O12 as the origin of low-magnetic-field behavior of the spin Seebeck effect

    NASA Astrophysics Data System (ADS)

    Uchida, Ken-ichi; Ohe, Jun-ichiro; Kikkawa, Takashi; Daimon, Shunsuke; Hou, Dazhi; Qiu, Zhiyong; Saitoh, Eiji

    2015-07-01

    The magnetic-field dependence of the longitudinal spin Seebeck effect (LSSE) in a Pt /Y3Fe5O12 (YIG)-slab junction system was found to deviate from a bulk magnetization curve of the YIG slab in a low field range. In this paper, we show that the deviation originates from the difference between surface and bulk magnetization processes in the YIG slab and that it appears even when removing possible extrinsic magnetic anisotropy due to surface roughness and replacing the Pt layer with different materials. This result indicates that the anomalous field dependence of the LSSE is due to an intrinsic magnetic property of the YIG surface. Our numerical calculation based on the Landau-Lifshitz-Gilbert equation shows that the deviation between the LSSE and bulk magnetization curves is qualitatively explained by introducing easy-axis perpendicular magnetic anisotropy near the surface of YIG.

  14. [Immunocorrective effect of alternating magnetic field in the postoperative period in malignant bladder cancer].

    PubMed

    Zlatnik, E Iu; Kapkina, N N; Zaderin, V P; Zakora, G I

    2001-01-01

    The study deals with immune status of patients operated for bladder cancer and exposed postoperatively to alternating magnetic field (MF) (hypothalamus and operative field). MF application was followed by higher T- and B-lymphocyte and CD4+, CD16+ cell levels as well as enhanced T-cell activity; no postoperative complications were registered and tumor relapse rates were relatively low. The effect was likely to be due to antistressor influence of MF. The procedure may substitute drug therapy for immunocorrection and to avoid recurrence of bladder cancer.

  15. Transient particle acceleration in strongly magnetized neutron stars. II - Effects due to a dipole field geometry

    NASA Technical Reports Server (NTRS)

    Fatuzzo, Marco; Melia, Fulvio

    1991-01-01

    Sheared Alfven waves generated by nonradial crustal disturbances above the polar cap of a strongly magnetized neutron star induce an electric field component parallel to B. An attempt is made to determine the manner in which the strong radial dependence of B affects the propagation of these sheared Alfven waves, and whether this MHD process is still an effective particle accelerator. It is found that although the general field equation is quite complicated, a simple wavelike solution can still be obtained under the conditions of interest for which the Alfven phase velocity decouples from the wave equation. The results may be applicable to gamma-ray burst sources.

  16. The effects of random field at surface on the magnetic properties in the Ising nanotube and nanowire

    NASA Astrophysics Data System (ADS)

    Kaneyoshi, T.

    2016-12-01

    The phase diagrams and temperature dependences of total magnetization mT in two nanosystems (nanotube and nanowire) with a random magnetic field at the surface shell are studied by the uses of the effective-field theory with correlations. Some characteristic phenomena (reentrant phenomena and unconventional thermal variation of total magnetization) are found in the two systems. They are rather different between the two systems, which mainly come from the structural differences of the cores

  17. Magnetic field effects in dye-sensitized solar cells controlled by different cell architecture

    NASA Astrophysics Data System (ADS)

    Klein, M.; Pankiewicz, R.; Zalas, M.; Stampor, W.

    2016-07-01

    The charge recombination and exciton dissociation are generally recognized as the basic electronic processes limiting the efficiency of photovoltaic devices. In this work, we propose a detailed mechanism of photocurrent generation in dye-sensitized solar cells (DSSCs) examined by magnetic field effect (MFE) technique. Here we demonstrate that the magnitude of the MFE on photocurrent in DSSCs can be controlled by the radius and spin coherence time of electron-hole (e-h) pairs which are experimentally modified by the photoanode morphology (TiO2 nanoparticles or nanotubes) and the electronic orbital structure of various dye molecules (ruthenium N719, dinuclear ruthenium B1 and fully organic squaraine SQ2 dyes). The observed MFE is attributed to magnetic-field-induced spin-mixing of (e-h) pairs according to the Δg mechanism.

  18. Dissociation of ultracold molecules via Feshbach resonances: The effect of magnetic-field fluctuations

    NASA Astrophysics Data System (ADS)

    Brouard, S.; Plata, J.

    2005-08-01

    The effect of random magnetic fields on the dissociation of ultracold molecules with Feshbach resonances is studied analytically. The dissociation spectrum and the evolution of the molecule fraction are obtained for a general form of the magnetic-field ramp and different noise properties relevant to standard experimental conditions. The results uncover the robustness against noise of some characteristics of the dissociation process, in particular, of the dependence of the mean atomic kinetic energy on the system parameters. Implications for the applicability of a method proposed to determine the width of the Feshbach resonances from the measurement of the dissociation spectrum are analyzed. Moreover, we discuss how the presence of fluctuations can affect the use of particular ramp shapes to tailor the properties of the generated atomic distribution.

  19. Effects of external magnetic field on oblique propagation of ion acoustic cnoidal wave in nonextensive plasma

    NASA Astrophysics Data System (ADS)

    Farhad Kiyaei, Forough; Dorranian, Davoud

    2017-01-01

    Effects of the obliqueness and the strength of external magnetic field on the ion acoustic (IA) cnoidal wave in a nonextensive plasma are investigated. The reductive perturbation method is employed to derive the corresponding KdV equation for the IA wave. Sagdeev potential is extracted, and the condition of generation of IA waves in the form of cnoidal waves or solitons is discussed in detail. In this work, the domain of allowable values of nonextensivity parameter q for generation of the IA cnoidal wave in the plasma medium is considered. The results show that only the compressive IA wave may generate and propagate in the plasma medium. Increasing the strength of external magnetic field will increase the frequency of the wave and decrease its amplitude, while increasing the angle of propagation will decrease the frequency of the wave and increase its amplitude.

  20. Hydrogenation-induced edge magnetization in armchair MoS2 nanoribbon and electric field effects

    NASA Astrophysics Data System (ADS)

    Ouyang, Fangping; Yang, Zhixiong; Ni, Xiang; Wu, Nannan; Chen, Yu; Xiong, Xiang

    2014-02-01

    We performed density functional theory study on the electronic and magnetic properties of armchair MoS2 nanoribbons (AMoS2NR) with different edge hydrogenation. Although bare and fully passivated AMoS2NRs are nonmagnetic semiconductors, it was found that hydrogenation in certain patterns can induce localized ferromagnetic edge state in AMoS2NRs and make AMoS2NRs become antiferromagnetic semiconductors or ferromagnetic semiconductors. Electric field effects on the bandgap and magnetic moment of AMoS2NRs were investigated. Partial edge hydrogenation can change a small-sized AMoS2NR from semiconductor to metal or semimetal under a moderate transverse electric field. Since the rate of edge hydrogenation can be controlled experimentally via the temperature, pressure and concentration of H2, our results suggest edge hydrogenation is a useful method to engineer the band structure of AMoS2NRs.

  1. [Biological and health effects on electric and magnetic fields at extremely low frequencies].

    PubMed

    Torregrossa, M V

    2005-01-01

    While the enormous benefits of using electricity in everyday life and health care are unquestioned, during the past 20 years the general public has become increasingly concerned about potential adverse health effects of exposure to electric and magnetic fields at extremely low frequencies (ELF). Such exposures arise mainly from the transmission and use of electrical energy at the power frequencies of 50/60 Hz. The international scientific community is addressing the associated health issues through in vitro, in vivo and epidemiological studies, although present research results are often contradictory. The purpose of this paper is to provide information about the possible impacts of exposure to electric and magnetic field at ELF frequencies on health within the community and the workplace. Information comes from recent research studies on this subject and from epidemiological pooled studies recently reviewed by eminent authorities.

  2. Magnetic field effects in dye-sensitized solar cells controlled by different cell architecture

    PubMed Central

    Klein, M.; Pankiewicz, R.; Zalas, M.; Stampor, W.

    2016-01-01

    The charge recombination and exciton dissociation are generally recognized as the basic electronic processes limiting the efficiency of photovoltaic devices. In this work, we propose a detailed mechanism of photocurrent generation in dye-sensitized solar cells (DSSCs) examined by magnetic field effect (MFE) technique. Here we demonstrate that the magnitude of the MFE on photocurrent in DSSCs can be controlled by the radius and spin coherence time of electron-hole (e-h) pairs which are experimentally modified by the photoanode morphology (TiO2 nanoparticles or nanotubes) and the electronic orbital structure of various dye molecules (ruthenium N719, dinuclear ruthenium B1 and fully organic squaraine SQ2 dyes). The observed MFE is attributed to magnetic-field-induced spin-mixing of (e-h) pairs according to the Δg mechanism. PMID:27440452

  3. Effective exchange fields in spin-torque resonance of magnetic insulators

    NASA Astrophysics Data System (ADS)

    Chiba, Takahiro; Bauer, Gerrit E. W.; Takahashi, Saburo

    2016-02-01

    We report additional results on the spin-torque ferromagnetic resonance (ST-FMR) of a bilayer system made from a magnetic insulator such as Y3 Fe5 O12 (YIG) and a heavy normal metal such as Pt in terms of the interface spin-mixing conductance and including spin pumping. We analyze experimental ST-FMR spectra for out-of-plane and in-plane magnetization configurations in terms of an anisotropic imaginary part Gi of the mixing conductance (or interface effective field). The estimated ratio between imaginary and real parts Gi /Gr ≲ 0.3 is sensitive to an (unknown) phase shift between microwave current bias and associated Oersted field.

  4. Effect of the tilted magnetic field on the magnetosubbands and conductance in the bilayer quantum wire

    NASA Astrophysics Data System (ADS)

    Chwiej, T.

    2016-10-01

    We theoretically study the single electron magnetotransport in GaAs and InGaAs vertically stacked bilayer nanowires. In considered geometry, the tilted magnetic field is always perpendicular to the main (transport) axis of the quantum wire and, therefore its transverse and vertical components allow separately for changing the magnitude of intralayer and interlayer subbands mixing. We study the changes introduced to energy dispersion relation E(k) by tilted magnetic field of strength up to several tesla and analyze their origins for symmetric as well as asymmetric confining potentials in the growth direction. Calculated energy dispersion relations are thereafter used to show that the value of a conductance of the bilayer nanowire may abruptly rise as well as fall by few conductance quanta when the Fermi energy in nanosystem is changed. It is also shown that such conductance oscillations, in conjunction with spin Zeeman effect, may give a moderately spin polarized current in the bilayer nanowire.

  5. Effect of applied magnetic field on sound transmission loss of MR-based sandwich panels

    NASA Astrophysics Data System (ADS)

    Hemmatian, Masoud; Sedaghati, Ramin

    2017-02-01

    This study aims to investigate the sound transmission loss (STL) capability of sandwich panels treated with Magnetorheological (MR) fluids at low frequencies. An experimental setup has been designed to investigate the effect of the intensity of applied magnetic field on the natural frequencies and STL of a clamped circular panel. It is shown that the fundamental natural frequency of the MR sandwich panel increases in proportion to the applied magnetic field. In addition, the STL of the panel at the resonance frequency increases as the magnetic field is amplified. Furthermore, the classical plate theory and Ritz method have been utilized to develop the governing equations of motion of the finite multilayered circular panels comprising two elastic face sheets and MR fluid core layer. The radiated sound power from the panel is derived using Rayleigh integral as a function of the transverse velocity of the panel which is subsequently used to evaluate the STL. The theoretical study is validated comparing the simulation results with the experimental measurements. Experimental and analytical parametric study have also been conducted to study the effect of the core layers’ thickness on the natural frequency and the STL of sandwich panel.

  6. Catalogue of averaged stellar effective magnetic fields. I. Chemically peculiar A and B type stars

    NASA Astrophysics Data System (ADS)

    Bychkov, V. D.; Bychkova, L. V.; Madej, J.

    2003-08-01

    This paper presents the catalogue and the method of determination of averaged quadratic effective magnetic fields < B_e > for 596 main sequence and giant stars. The catalogue is based on measurements of the stellar effective (or mean longitudinal) magnetic field strengths B_e, which were compiled from the existing literature. We analysed the properties of 352 chemically peculiar A and B stars in the catalogue, including Am, ApSi, He-weak, He-rich, HgMn, ApSrCrEu, and all ApSr type stars. We have found that the number distribution of all chemically peculiar (CP) stars vs. averaged magnetic field strength is described by a decreasing exponential function. Relations of this type hold also for stars of all the analysed subclasses of chemical peculiarity. The exponential form of the above distribution function can break down below about 100 G, the latter value representing approximately the resolution of our analysis for A type stars. Table A.1 and its references are only available in electronic form at the CDS via anonymous ftp to cdsarc.u-strasbg.fr (130.79.128.5) or via http://cdsweb.u-strasbg.fr/cgi-bin/qcat?J/A+A/407/631 and Tables 3 to 9 are only available in electronic form at http://www.edpsciences.org

  7. The Effect of the Random Magnetic Field Component on the Parker Instability

    NASA Astrophysics Data System (ADS)

    Kim, Jongsoo; Ryu, Dongsu

    2001-11-01

    The Parker instability is considered to play important roles in the evolution of the interstellar medium. Most studies on the development of the instability so far have been based on an initial equilibrium system with a uniform magnetic field. However, the Galactic magnetic field possesses a random component in addition to the mean uniform component, with comparable strength of the two components. Parker and Jokipii have recently suggested that the random component can suppress the growth of small wavelength perturbations. Here we extend their analysis by including gas pressure, which was ignored in their work, and study the stabilizing effect of the random component in the interstellar gas with finite pressure. Following Parker and Jokipii, we model the magnetic field as a mean azimuthal component, B(z), plus a random radial component, ɛ(z)B(z), where ɛ(z) is a random function of height from the equatorial plane. We show that for the observationally suggested values of <ɛ2>1/2, the tension due to the random component becomes important, so that the growth of the instability is either significantly reduced or completely suppressed. When the instability still works, the radial wavenumber of the most unstable mode is found to be zero. That is, the instability is reduced to be effectively two-dimensional. We discuss briefly the implications of our finding.

  8. High field superconducting magnets

    NASA Technical Reports Server (NTRS)

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

    2011-01-01

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

  9. The protective effect of a constant magnetic field. [reduction of molecular cell pathology

    NASA Technical Reports Server (NTRS)

    Sosunov, A. V.; Tripuzov, A. N.

    1974-01-01

    The protective effect of a constant magnetic field sharply reduced spontaneous lysis of E. coli cells when subjected to ultraviolet radiation. A protective effect of a CMF was found in a study of tissue cultures of normally growing cells (kidney epithelium) and cancer cells (cells from a cancer of the larynx). The protective effect of a CMF is also seen in a combined exposure of tissue cultures to X-rays and CMF energy (strength of the CMF was 2000 oersteds with a gradient of 500 oersteds/cm). The data obtained are of interest to experimental oncology (development of new methods of treating malignant tumors).

  10. The effects of weak extremely low frequency magnetic fields on calcium/calmodulin interactions.

    PubMed Central

    Hendee, S P; Faour, F A; Christensen, D A; Patrick, B; Durney, C H; Blumenthal, D K

    1996-01-01

    Mechanisms by which weak electromagnetic fields may affect biological systems are of current interest because of their potential health effects. Lednev has proposed an ion parametric resonance hypothesis (Lednev, 1991, Bioelectromagnetics, 12:71-75), which predicts that when the ac, frequency of a combined dc-ac magnetic field equals the cyclotron frequency of calcium, the affinity of calcium for calcium-binding proteins such as calmodulin will be markedly affected. The present study evaluated Lednev's theory using two independent systems, each sensitive to changes in the affinity of calcium for calmodulin. One of the systems used was the calcium/calmodulin-dependent activation of myosin light chain kinase, a system similar to that previously used by Lednev. The other system monitored optical changes in the binding of a fluorescent peptide to the calcium/calmodulin complex. Each system was exposed to a 20.9 microT static field superimposed on a 20.9 microT sinusoidal field over a narrow frequency range centered at 16 Hz, the cyclotron frequency of the unhydrated calcium ion. In contrast to Lednev's predictions, no significant effect of combined dc-ac magnetic fields on calcium/calmodulin interactions was indicated in either experimental system. PMID:8744329

  11. The interplanetary magnetic field

    NASA Technical Reports Server (NTRS)

    Davis, L., Jr.

    1972-01-01

    Large-scale properties of the interplanetary magnetic field as determined by the solar wind velocity structure are examined. The various ways in which magnetic fields affect phenomena in the solar wind are summarized. The dominant role of high and low velocity solar wind streams that persist, with fluctuations and evolution, for weeks or months is emphasized. It is suggested that for most purposes the sector structure is better identified with the stream structure than with the magnetic polarity and that the polarity does not necessarily change from one velocity sector to the next. Several mechanisms that might produce the stream structure are considered. The interaction of the high and low velocity streams is analyzed in a model that is steady state when viewed in a frame that corotates with the sun.

  12. Approaching magnetic field effects in biology using the radical pair mechanism

    NASA Astrophysics Data System (ADS)

    Canfield, Jeffrey Michael

    1997-11-01

    The overall goal of this thesis has been to explain any of the reported magnetic field effects in biology (magnetic orientation of many species and/or health effects, such as cancer, due to man-made electromagnetic fields) using the radical pair mechanism, a quantum mechanical mechanism known for over 20 years that lets singlet-to-triplet yields (which can be related to reaction rates) of radical pair reactions depend on applied magnetic fields. This goal seems reasonable considering the known roles of many biological free radicals in cancer, disease, aging, development, and cellular signaling, the constant reminders in the media to take anti-oxidant vitamins to protect against certain deleterious free radicals, and the success of the radical pair mechanism in explaining magnetic field effects in photosynthetic reaction centers. To approach the above goal, this thesis develops several methods (using perturbation theory and other techniques in the Schrodinger and Liouville formalisms) for calculating singlet-to-triplet yields in combinations of steady and oscillating fields (some of these algorithms are more versatile or efficient while others give more insight, and all serve as cross-checks on each other) and uses these tools to explore and explain a number of interesting phenomena such as yields sensitive to the magnitude and orientation of earth-strength (0.5 G) steady fields as well as the magnitude, orientation, and frequency of very weak (7 mG or less) oscillating fields. In particular, this thesis examines such effects in several coenzyme B12 systems, systems long studied by EPR (Electron Paramagnetic Resonance, the chief method for determining the spin Hamiltonians, spin relaxation rates, and other parameters needed for calculations) in which organometallic cobalt-carbon bonds are often cleaved homolytically to form radical pairs. Among the B12-dependent enzymes are ribonucleotide reductase (which converts RNA to DNA nucleotides), methyl malonyl CoA mutase

  13. High pressure effects on isotropic Nd2Fe14B magnet accompanying change in coercive field

    NASA Astrophysics Data System (ADS)

    Mito, M.; Goto, H.; Nagai, K.; Tsuruta, K.; Deguchi, H.; Tajiri, T.; Konishi, K.

    2015-10-01

    We investigated the effects of hydrostatic pressure on an isotropic Nd2Fe14B magnet (the exact chemical formula is Nd2.0Fe14.1B) consisting of nanocrystals, with the size of approximately 30 nm, by magnetization measurements at pressures (P's) up to 9.3 GPa and structural analyses up to 4.3 GPa. Magnetization curves were measured by using a miniature diamond anvil cell made of Ti alloy with spatially uniform magnetization. The initial value of coercive field Hc at 300 K is 840 kA/m (=10.6 kOe), and Hc initially increases to approximately 1180 kA/m (=15.0 kOe) almost linearly against the pressure. The increase in Hc, however, saturates at around P = 3 GPa. The change in Hc is understood by the decrease in the saturation magnetization Ms within the framework of the constant anisotropy of the single domain phase. The crystalline strain increases for P < 1 GPa. Afterward, the crystalline size (D) starts to decrease with increasing pressure, and the reduction tends to saturate at above approximately 3 GPa. Furthermore, the change in Ms is actually related with both the change in strain and that in D. The data on the temperature dependence of Hc at P = 0, 6.6, and 9.3 GPa exhibit pressure-induced suppression of the Curie temperature. The maximum energy product decreases with increasing pressure over the whole temperature range.

  14. Bidirectional effect of magnetic field on electronic thermal transport of metals from all-electron first-principles calculations

    NASA Astrophysics Data System (ADS)

    Yang, Jia-Yue; Yue, Sheng-Ying; Hu, Ming

    2016-12-01

    Considerable discussions have occurred about the critical role played by free electrons in the transport of heat in pure metals. In principle, any environment that can influence the dynamical behaviors of electrons would have impact on electronic thermal conductivity (κel) of metals. Over the past decades, significant progress and comprehensive understanding have been gained from theoretical, as well as experimental, investigations by taking into account the effects of various conditions, typically temperature, impurities, strain, dimensionality, interface, etc. However, the effect of external magnetic field has received less attention. In this paper, the magnetic-field dependence of electron-phonon scattering, the electron's lifetime, and κel of representative metals (Al, Ni, and Nb) are investigated within the framework of all-electron spin-density functional theory. For Al and Ni, the induced magnetization vector field and difference in electron density under external magnetic-field aggregate toward the center of unit cell, leading to the enhanced electron-phonon scattering, the damped electron's lifetime, and thus the reduced κel. On the contrary, for Nb with strong intrinsic electron-phonon interaction, the electron's lifetime and κel slightly increase as external magnetic field is enhanced. This is mainly attributed to the separately distributed magnetization vector field and difference in electron density along the corner of unit cell. This paper sheds light on the origin of influence of external magnetic field on κel for pure metals and offers a new route for robust manipulation of electronic thermal transport via applying external magnetic field.

  15. Biological effects of ELF (extremely-low-frequency) electric and magnetic fields

    SciTech Connect

    Anderson, L.E.

    1989-10-01

    Studies have been conducted at the Pacific Northwest Laboratory to examine extremely-low-frequency (ELF) electromagnetic fields for possible biological effects in animals. Two areas of investigation are reported here: (1) studies on the nervous system, including behavior and neuroendocrine function, and (2) experiments on cancer development in animals. In behavioral experiments, preliminary data suggest that short term memory may be affected in albino rats exposed to combined ELF and static magnetic fields. Neuroendocrine studies were conducted to demonstrate an apparent stress-related response in rats exposed to 60-Hz electric fields. Finally, using a chemically-induced mammary tumor model, experiments were conducted in which rats, chronically exposed to 60-Hz electric fields, showed an enhancement in the number of tumors per tumor bearing animal.

  16. The transverse magnetic field effect on steady-state solutions of the Bursian diode

    SciTech Connect

    Pramanik, Sourav; Chakrabarti, Nikhil

    2015-04-15

    A study of steady-states of a planar vacuum diode driven by a cold electron beam (the Bursian diode) under an external transverse magnetic field is presented. The regime of no electrons turned around by a magnetic field only is under the consideration. The emitter electric field is evaluated as a characteristic function for the existence of solutions depending on the diode length, the applied voltage, and the magnetic field strength. At certain conditions, it is shown that a region of non-unique solutions exists in the Bursian diode when the magnetic field is absent. An expression for the maximum current transmitted through the diode is derived. The external magnetic field is put forth to control fast electronic switches based on the Bursian diode.

  17. Effect of Static Magnetic Fields on the Peripheral Blood Mononuclear-like Cells

    NASA Astrophysics Data System (ADS)

    Godina-Nava, J. J.; García-Cantú, R.; Cañedo, L.; Rodríguez-Segura, M. A.; Serrano, G.; Alvarado-Alvarez, R.; Toledo-Ramos, F.

    2002-08-01

    In this article the role of static magnetic fields (SMF) in the generation of Ca2+ currents in peripheral blood mononuclear-like cells (PBMLC) is described. Using the sensitivity of Ca2+ channels and pumps to membrane potential and ion concentration we propose a method which uses the conductivity as a dynamical coefficient in the Onsager's reciprocity relations, and the dynamics of the calcium ions described by the electrodiffusion equation deduced by Pelce. The enhanced influx of calcium ion in PBMLC was studied parametrizing the static magnetic fields effects on the conductivity by the coefficients γ, ρ and κ. The parametrization was made according to the symmetry properties of Onsager's reciprocity relations using the most simple expressions. As an example we used available experimental data over chromaffin cell and employing physical considerations concerning to PBMLC, an order of magnitude for the value of ρ ≈ O(-10-5 mol/(Vm2s)), κ = 0, γ ≈ O(-10-3 mol/(VT2m2s) was obtained. The γ parameter was found graphically. With this parametrization, the time to induce calcium current in the cell was always less than the situation without magnetic field application.

  18. Biological effects of electrical or magnetic field application. (Latest citations from the Life Sciences Collection database). Published Search

    SciTech Connect

    1995-03-01

    The bibliography contains citations concerning the electrical and magnetic field effects on biological materials. Citations discuss effects on cell structures, electromagnetic penetration into biological tissues, induced currents in humans, implantable stimulators, artificial muscles, genetic engineering, and neural activity. Studies of biological effects of electrical and magnetic field applications in biomedical engineering and health care are included. (Contains a minimum of 97 citations and includes a subject term index and title list.)

  19. Magnetic field effects for copper suspended nanofluid venture through a composite stenosed arteries with permeable wall

    NASA Astrophysics Data System (ADS)

    Akbar, Noreen Sher; Butt, Adil Wahid

    2015-05-01

    In the present paper magnetic field effects for copper nanoparticles for blood flow through composite stenosis in arteries with permeable wall are discussed. The copper nanoparticles for the blood flow with water as base fluid is not explored yet. The equations for the Cu-water nanofluid are developed first time in the literature and simplified using long wavelength and low Reynolds number assumptions. Exact solutions have been evaluated for velocity, pressure gradient, the solid volume fraction of the nanoparticles and temperature profile. The effect of various flow parameters on the flow and heat transfer characteristics is utilized.

  20. Effect of Interface Shape and Magnetic Field on the Microstructure of Bulk Ge:Ga

    NASA Technical Reports Server (NTRS)

    Cobb, S. D.; Szofran, F. R.; Volz, M. P.

    1999-01-01

    Thermal and compositional gradients induced during the growth process contribute significantly to the development of defects in the solidified boule. Thermal gradients and the solid-liquid interface shape can be greatly effected by ampoule material. Compositional gradients are strongly influenced by interface curvature and convective flow in the liquid. Results of this investigation illustrate the combined influences of interface shape and convective fluid flow. An applied magnetic field was used to reduce the effects of convective fluid flow in the electrically conductive melt during directional solidification. Several 8 mm diameter boules of Ga-doped Ge were grown at different field strengths, up to 5 Tesla, in four different ampoule materials. Compositional profiles indicate mass transfer conditions ranged from completely mixed to diffusion controlled. The influence of convection in the melt on the developing crystal microstructure and defect density was investigated as a function of field strength and ampoule material. Chemical etching and electron backscattered electron diffraction were used to map the crystal structure of each boule along the center plane. Dislocation etch pit densities were measured for each boule. Results show the influence of magnetic field strength and ampoule material on overall crystal quality.

  1. The Effects of a Magnetic Field on the Crystallization of a Fluorozirconate Glass

    NASA Technical Reports Server (NTRS)

    Tucker, Dennis S.; Lapointe, Michael R.; Jia, Zhiyong

    2006-01-01

    An axial magnetic field of 0.1T was applied to ZrF4-BaF2-LaF3-AlF3-NaF (ZBLAN) fibers during heating to the glass crystallization temperature. Scanning electron microscopy and x-ray diffraction were used to identify crystal phases. It was shown that fibers exposed to the magnetic field did not crystallize while fibers not exposed to the field did crystallize. A hypothesis based on magnetic work was proposed to explain the results and tested by measuring the magnetic susceptibilities of the glass and crystal.

  2. Structural and magnetic field effects on spin fluctuations in Sr3Ru2O7

    NASA Astrophysics Data System (ADS)

    Mukherjee, Shantanu; Lee, Wei-Cheng

    2016-08-01

    We investigate the evolution of magnetic excitations in Sr3Ru2O7 in the paramagnetic metallic phase using a three-band tight-binding model. The effect of Mn or Ti dopant ions on the Sr3Ru2O7 band structure has been included by taking into account the dopant-induced suppression of the oxygen octahedral rotation in the tight-binding band structure. We find that the low-energy spin fluctuations are dominated by three wave vectors around q ⃗=( (0 ,0 ) ,(π /2 ,π /2 ) ) and (π ,0 ) , which compete with each other. As the octahedral rotation is suppressed with increasing doping, the three wave vectors evolve differently. In particular, the undoped compound has dominant wave vectors at q ⃗=( (0 ,0 ) ,(π /2 ,π /2 ) ) , but doping Sr3Ru2O7 leads to a significant enhancement in the spin susceptibility at the q ⃗=(π ,0 ) wave vector, bringing the system closer to a magnetic instability. All the features calculated from our model are in agreement with neutron scattering experiments. We have also studied the effect of a c -axis Zeeman field on the low-energy spin fluctuations. We find that an increasing magnetic field suppresses the antiferromagnetic (AFM) fluctuations and leads to stronger competition between the AFM and ferromagnetic spin fluctuations. The magnetic field dependence observed in our calculations therefore supports the scenario that the observed nematic phase in the metamagnetic region in Sr3Ru2O7 is intimately related to the presence of a competing ferromagnetic instability.

  3. Magnetic effects on thermocouples

    NASA Astrophysics Data System (ADS)

    Beguš, Samo; Bojkovski, Jovan; Drnovšek, Janko; Geršak, Gregor

    2014-03-01

    Thermometers in laboratory environment and industrial applications are often subject to extraneous, usually unwanted and uncontrolled magnetic fields. Magnetic field influence can be minimized, but cannot be fully cancelled out. Even more, in most cases, there is no awareness of the existence of magnetic fields, let alone their effect on measurement instrumentation. In the past, sensitivity to high dc magnetic fields has been investigated in cryogenics and at high temperatures. More recently, the magnetic effect on weak dc magnetic fields was presented. The goal of this paper was to analyse and empirically and experimentally prove the magnetic sensitivity of thermocouples exposed to low magnetic fields: both dc and ac. Precision and uniform alternating and direct magnetic flux densities were generated by means of permanent magnets and power amplifiers with air-cored coils. The magnetic effect on ferromagnetic and non-ferromagnetic thermocouples at liquid-nitrogen-boiling point (-196 °C), ice point (0 °C), in water (17 °C) and at melting point of gallium fixed point cell (29.7646 °C) was investigated. Magnetic-field-dependent temperature errors of up to 700 mK (at 5.3 mT: dc) and up to 1 °C (at 10 mT: ac 50 Hz magnetic fields) were detected. From the results, it can be concluded that, ideally for temperature measurements of the highest accuracy in the above-cryogenic temperature range, magnetic sensitivity should be estimated and taken into account either as the correction of an error and/or as an additional source of measurement uncertainty. Special consideration should be given to thermocouple orientation relative to the magnetic field direction, influence of metal enclosures and magnetization effects on ferromagnetic components of thermocouples.

  4. Pulsed high-magnetic-field experiments: New insights into the magnetocaloric effect in Ni-Mn-In Heusler alloys

    SciTech Connect

    Salazar Mejía, C. Nayak, A. K.; Felser, C.; Nicklas, M.; Ghorbani Zavareh, M.; Wosnitza, J.; Skourski, Y.

    2015-05-07

    The present pulsed high-magnetic-field study on Ni{sub 50}Mn{sub 35}In{sub 15} gives an extra insight into the thermodynamics of the martensitic transformation in Heusler shape-memory alloys. The transformation-entropy change, ΔS, was estimated from field-dependent magnetization experiments in pulsed high magnetic fields and by heat-capacity measurements in static fields. We found a decrease of ΔS with decreasing temperature. This behavior can be understood by considering the different signs of the lattice and magnetic contributions to the total entropy. Our results further imply that the magnetocaloric effect will decrease with decreasing temperature and, furthermore, the martensitic transition is not induced anymore by changing the temperature in high magnetic fields.

  5. Effects of Magnetic Field on the Turbulent Wake of a Cylinder in MHD Channel Flow

    SciTech Connect

    John Rhoads; Edlundd, Eric; Ji, Hantao

    2013-04-01

    Results from a free-surface MHD flow experiment are presented detailing the modi cation of vortices in the wake of a circular cylinder with its axis parallel to the applied magnetic fi eld. Experiments were performed with a Reynolds number near Re ~ 104 as the interaction parameter, N = |j x B| / |ρ (υ • ∇), was increased through unity. By concurrently sampling the downstream fluid velocity at sixteen cross-stream locations in the wake, it was possible to extract an ensemble of azimuthal velocity profi les as a function of radius for vortices shed by the cylinder at varying strengths of magnetic field. Results indicate a signi cant change in vortex radius and rotation as N is increased. The lack of deviations from the vortex velocity pro file at high magnetic fi elds suggests the absence of small-scale turbulent features. By sampling the wake at three locations downstream in subsequent experiments, the decay of the vortices was examined and the effective viscosity was found to decrease as N-049±0.4. This reduction in effective viscosity is due to the modi cation of the small-scale eddies by the magnetic fi eld. The slope of the energy spectrum was observed to change from a k-1.8 power-law at low N to a k-3.5 power-law for N > 1. Together, these results suggest the flow smoothly transitioned to a quasi-two-dimensional state in the range 0 < N < 1.

  6. Effects of strong magnetic fields on cell growth and radiation response of human T-lymphocytes in culture.

    PubMed

    Norimura, T; Imada, H; Kunugita, N; Yoshida, N; Nikaido, M

    1993-06-01

    Experiments were undertaken in order to verify whether or not a strong magnetic field would have any biological effects on the cell growth, viability and radiation response of mammalian cells. Magnetic field exposures were conducted using a superconducting magnet with freshly-isolated human peripheral blood T-lymphocytes maintained at their normal growing temperature of 37 degrees C. The static magnetic fields with intensities up to 6.3-tesla (T) exerted little influence on the cell growth and viability of actively-growing T-lymphocytes under normal cell-culture conditions. On the other hand, the T cells exposed to the magnetic fields (4 T-6.3 T) during PHA stimulation were inhibited in their cell growth when compared to controls. The effects of the magnetic fields with intensities up to 2 T on cell growth properties, however, were minimal in this system. Also, the radiosensitivity of T-lymphocytes previously exposed to the strong magnetic fields was more sensitive than that of control cells. These results suggest that exposure to a static magnetic field of 4 T or stronger might lead to physiological and growth abnormalities at the cellular level.

  7. The effect of fringe fields from patterned magnetic domains on the electroluminescence of organic light-emitting diodes

    NASA Astrophysics Data System (ADS)

    Harmon, Nicholas J.; Wohlgennant, Markus; Flatté, Michael E.

    2016-10-01

    Large magnetic field effects, either in conduction or luminescence, have been observed in organic light-emitting diodes (OLEDs) for over a decade now. The physical processes are largely understood when exciton formation and recombination lead to the magnetic field effects. Recently, magnetic field effects in some co-evaporated blends have shown that exciplexes deliver even larger responses. In either case, the magnetic field effects arise from some spin-mixing mechanism and spin-selective processes in either the exciton formation or the exciplex recombination. Precise control of light output is not possible when the spin mixing is either due to hyper-fine fields or differences in the Lande g-factor. We theoretically examine the optical output when a patterned magnetic film is deposited near the OLED. The fringe fields from the magnetic layers supply an additionally source of spin mixing that can be easily controlled. In the absence of other spin mixing mechanisms, the luminescence from exciplexes can be modified by 300%. When other spin-mixing mechanisms are present, fringe fields from remanent magnetic states act as a means to either boost or reduce light emission from those mechanisms. Lastly, we examine the influence of spin decoherence on the optical output.

  8. General relativistic simulations of black-hole-neutron-star mergers: Effects of magnetic fields

    NASA Astrophysics Data System (ADS)

    Etienne, Zachariah B.; Liu, Yuk Tung; Paschalidis, Vasileios; Shapiro, Stuart L.

    2012-03-01

    As a neutron star (NS) is tidally disrupted by a black hole (BH) companion at the end of a black-hole-neutron-star (BHNS) binary inspiral, its magnetic fields will be stretched and amplified. If sufficiently strong, these magnetic fields may impact the gravitational waveforms, merger evolution and mass of the remnant disk. Formation of highly-collimated magnetic field lines in the disk+spinning BH remnant may launch relativistic jets, providing the engine for a short-hard GRB. We analyze this scenario through fully general relativistic, magnetohydrodynamic BHNS simulations from inspiral through merger and disk formation. Different initial magnetic field configurations and strengths are chosen for the NS interior for both nonspinning and moderately spinning (aBH/MBH=0.75) BHs aligned with the orbital angular momentum. Only strong interior (Bmax⁡˜1017G) initial magnetic fields in the NS significantly influence merger dynamics, enhancing the remnant disk mass by 100% and 40% in the nonspinning and spinning BH cases, respectively. However, detecting the imprint of even a strong magnetic field may be challenging for Advanced LIGO. Though there is no evidence of mass outflows or magnetic field collimation during the preliminary simulations we have performed, higher resolution, coupled with longer disk evolutions and different initial magnetic field configurations, may be required to definitively assess the possibility of BHNS binaries as short-hard gamma-ray burst progenitors.

  9. Biological Effects of Static Magnetic Fields: Ideal Experiments for Introductory Courses

    ERIC Educational Resources Information Center

    Kendler, Barry S.; Grove, Patricia A.

    2005-01-01

    A serendipitous finding involving static magnetic fields can be used to design experiments suitable for both science and nonscience majors. It has been reported that organisms respond differently to high-gauss magnetic fields generated by north poles than they do to those generated by south poles. Experimental tests of this hypothesis are ideal…

  10. Effect of a magnetic field on the diffusion of an electron-hole plasma in germanium.

    NASA Technical Reports Server (NTRS)

    Gurnee, M. N.; Hooke, W. M.; Goldsmith, G. J.; Brennan, M. H.

    1972-01-01

    Study in germanium of an optically injected electron-hole plasma, parallel and perpendicular to an applied magnetic field. The density gradient within the crystal was measured directly by an infrared-beam-absorption technique. Diffusion measurements made parallel to the magnetic field are adequately explained by the theory.

  11. Effect of static magnetic field on electricity production and wastewater treatment in microbial fuel cells.

    PubMed

    Tao, Qinqin; Zhou, Shaoqi

    2014-12-01

    The effect of a magnetic field (MF) on electricity production and wastewater treatment in two-chamber microbial fuel cells (MFCs) has been investigated. Electricity production capacity could be improved by the application of a low-intensity static MF. When a MF of 50 mT was applied to MFCs, the maximum voltage, total phosphorus (TP) removal efficiency, and chemical oxygen demand (COD) removal efficiency increased from 523 ± 2 to 553 ± 2 mV, ∼93 to ∼96 %, and ∼80 to >90 %, respectively, while the start-up time and coulombic efficiency decreased from 16 to 10 days and ∼50 to ∼43 %, respectively. The MF effects were immediate, reversible, and not long lasting, and negative effects on electricity generation and COD removal seemed to occur after the MF was removed. The start-up and voltage output were less affected by the MF direction. Nitrogen compounds in magnetic MFCs were nitrified more thoroughly; furthermore, a higher proportion of electrochemically inactive microorganisms were found in magnetic systems. TP was effectively removed by the co-effects of microbe absorption and chemical precipitation. Chemical precipitates were analyzed by a scanning electron microscope capable of energy-dispersive spectroscopy (SEM-EDS) to be a mixture of phosphate, carbonate, and hydroxyl compounds.

  12. Reexamination of magnetic isotope and field effects on adenosine triphosphate production by creatine kinase

    PubMed Central

    Crotty, Darragh; Silkstone, Gary; Poddar, Soumya; Ranson, Richard; Prina-Mello, Adriele; Wilson, Michael T.; Coey, J. M. D.

    2012-01-01

    The influence of isotopically enriched magnesium on the creatine kinase catalyzed phosphorylation of adenosine diphosphate is examined in two independent series of experiments where adenosine triphosphate (ATP) concentrations were determined by a luciferase-linked luminescence end-point assay or a real-time spectrophotometric assay. No increase was observed between the rates of ATP production with natural Mg, 24Mg, and 25Mg, nor was any significant magnetic field effect observed in magnetic fields from 3 to 1,000 mT. Our results are in conflict with those reported by Buchachenko et al. [J Am Chem Soc 130:12868–12869 (2008)], and they challenge these authors’ general claims that a large (two- to threefold) magnetic isotope effect is “universally observable” for ATP-producing enzymes [Her Russ Acad Sci 80:22–28 (2010)] and that “enzymatic phosphorylation is an ion-radical, electron-spin-selective process” [Proc Natl Acad Sci USA 101:10793–10796 (2005)]. PMID:22198842

  13. Effects of reconstructed magnetic field from sparse noisy boundary measurements on localization of active neural source.

    PubMed

    Shen, Hui-min; Lee, Kok-Meng; Hu, Liang; Foong, Shaohui; Fu, Xin

    2016-01-01

    Localization of active neural source (ANS) from measurements on head surface is vital in magnetoencephalography. As neuron-generated magnetic fields are extremely weak, significant uncertainties caused by stochastic measurement interference complicate its localization. This paper presents a novel computational method based on reconstructed magnetic field from sparse noisy measurements for enhanced ANS localization by suppressing effects of unrelated noise. In this approach, the magnetic flux density (MFD) in the nearby current-free space outside the head is reconstructed from measurements through formulating the infinite series solution of the Laplace's equation, where boundary condition (BC) integrals over the entire measurements provide "smooth" reconstructed MFD with the decrease in unrelated noise. Using a gradient-based method, reconstructed MFDs with good fidelity are selected for enhanced ANS localization. The reconstruction model, spatial interpolation of BC, parametric equivalent current dipole-based inverse estimation algorithm using reconstruction, and gradient-based selection are detailed and validated. The influences of various source depths and measurement signal-to-noise ratio levels on the estimated ANS location are analyzed numerically and compared with a traditional method (where measurements are directly used), and it was demonstrated that gradient-selected high-fidelity reconstructed data can effectively improve the accuracy of ANS localization.

  14. Effects of static magnetic fields in biology: role of free radicals.

    PubMed

    Okano, Hideyuki

    2008-05-01

    Biological systems can respond to a wide range of static magnetic fields (SMF). Some of these responses seem to be mediated partly through free radical reactions. For example, in magnetic sense and navigation using the geomagnetic field, one of the most promising mechanisms for explaining magnetic compass is "a radical pair mechanism". Biological free radicals are most commonly oxygen or nitrogen based with an unpaired electron, leading to the terms "reactive oxygen species (ROS)" or "reactive nitrogen species (RNS)". When applying SMF to medical treatment, coupling SMF exposure with possible chemotherapy of cancers is a novel fascinating area that SMF could enhance agent-induced ROS production against tumors. In addition, one of the potent mechanisms of SMF effects on hemodynamics and blood pressure has sometimes been linked to nitric oxide pathway. However, health and environmental concerns have been raised because the SMF effects on oxidative stress leading to genetic mutation and apoptosis/necrosis have been found. It seems to take place from free radical generation.

  15. Effects of static magnetic field on magnetosome formation and expression of mamA, mms13, mms6 and magA in Magnetospirillum magneticum AMB-1.

    PubMed

    Wang, Xiaoke; Liang, Likun

    2009-05-01

    Magnetotactic bacteria produce nanometer-size intracellular magnetic crystals. The superior crystalline and magnetic properties of magnetosomes have been attracting much interest in medical applications. To investigate effects of intense static magnetic field on magnetosome formation in Magnetospirillum magneticum AMB-1, cultures inoculated with either magnetic or non-magnetic pre-cultures were incubated under 0.2 T static magnetic field or geomagnetic field. The results showed that static magnetic field could impair the cellular growth and raise C(mag) values of the cultures, which means that the percentage of magnetosome-containing bacteria was increased. Static magnetic field exposure also caused an increased number of magnetic particles per cell, which could contribute to the increased cellular magnetism. The iron depletion in medium was slightly increased after static magnetic field exposure. The linearity of magnetosome chain was also affected by static magnetic field. Moreover, the applied intense magnetic field up-regulated mamA, mms13, magA expression when cultures were inoculated with magnetic cells, and mms13 expression in cultures inoculated with non-magnetic cells. The results implied that the interaction of the magnetic field created by magnetosomes in AMB-1 was affected by the imposed magnetic field. The applied static magnetic field could affect the formation of magnetic crystals and the arrangement of the neighboring magnetosome.

  16. Biological effects of electrical- or magnetic-field application. (Latest citations from the Life Sciences Collection data base). Published Search

    SciTech Connect

    Not Available

    1992-09-01

    The bibliography contains citations concerning the application of electrical or magnetic fields to organisms. Changes in cell structure, cell shape, metabolism, mitosis, cell orientation, neuron response, germination response, and growth rates are discussed. The citations also examine the effects of electrical or magnetic field exposure from transmission lines. Biological applications of electric field cited include genetic transfer, plant cell fusion, and seed disinfection. (Contains 250 citations and includes a subject term index and title list.)

  17. Effect of the magnetic field on coexisting stimulated Raman and Brillouin backscattering of an extraordinary mode

    SciTech Connect

    Vyas, Ashish Singh, Ram Kishor Sharma, R. P.

    2016-01-15

    This paper presents a model to study the interplay between the stimulated Raman scattering (SRS) and stimulated Brillouin scattering (SBS) in the presence of background magnetic field. This formalism is applicable to laser produced plasma as well as to heating mechanism in toroidal system by an extraordinary electromagnetic wave. In the former case, the magnetic field is self-generated, while in the latter case (toroidal plasmas) magnetic field is applied externally. The behavior of one scattering process is explicitly dependent on the coexisting scattering process as well as on the magnetic field. Explicit expressions for the back-reflectivity of scattered beams (SRS and SBS) are presented. It has been demonstrated that due to the magnetic field and coexistence of the scattering processes (SRS and SBS) the back-reflectivity gets modified significantly. Results are also compared with the three wave interaction case (isolated SRS or SBS case)

  18. Experimental and theoretical study on effects of magnetic field topology on near wall conductivity in a Hall thruster

    NASA Astrophysics Data System (ADS)

    Yu, Daren; Li, Hong; Wu, Zhiwen; Ning, Zhongxi; Yan, Guojun

    2009-10-01

    An experiment has been made to investigate the effect of curved magnetic field topology on near wall conductivity in the ion acceleration region of Hall thrusters. The experimental results show that the electron current due to near wall conductivity is of the minimum in the case of focused topology and increases in the cases of both less-focus and over-focus topologies. This finding cannot be explained properly by the magnetic mirror effect, which is the one and only reported effect related to the magnetic field curvature so far. Based on the analysis of interaction between the plasma and the wall, a new physical effect is proposed. The difference of magnetic field topology causes different electric potential distribution, leads to different ion flux to the wall, results in the change of sheath property and secondary electron emission, and finally affects the electron current due to near wall conductivity. This effect is further justified by the agreement between the experiment and simulation which is performed with a particle-in-cell model. Therefore, we conclude that the ion flow injection is a significant effect to near wall conductivity in the scope of curved magnetic field topology besides the magnetic mirror effect. Moreover, we find that the focus topology of magnetic field is favorable to obtain a high thruster performance from both the ion acceleration aspect and the electron conduction aspect and so is useful practically for thruster optimization.

  19. On the effects of magnetic field line topology on the energy propagation in the solar corona

    NASA Astrophysics Data System (ADS)

    Candelaresi, Simon

    2016-05-01

    Using the MHD approximation, we study the propagation of energy from photospheric footpoint motions into the corona. Our model consists of a magnetic carpet with closed and open magnetic field lines. Magnetic null points are present close at the surface. The applied photospheric driver twists the field into a topologically non-trivial configuration which leads to reconnection and a change in field line topology. Prior to this event, the energy propagation into the corona is largely inhibited due to closed field lines. After such events the energy is free to propagate into the corona.

  20. Effect of steel metallurgy on it magneto-mechanical behavior in weak magnetic fields

    SciTech Connect

    Robertson, I.M. )

    1994-03-01

    The magneto-mechanical behavior of five steels, mild steel, HSLA 80, HY100 and a quenched alloy steel, has been investigated. Magnetic fields of the order of the Earth's field and compressive stresses up to 200 MPa were applied to the steels. The increase in magnetization due to stress cycling in a constant applied field and to field cycling at constant stress was measured. The results show that the differential permeability of the steel largely determines the magnetization increase and that steels with similar microstructures have similar microstructures have similar magneto-mechanical response. The strength or hardness of the steel is a less reliable indicator of magneto-mechanical response.

  1. Random crystal field effect on the magnetic and hysteresis behaviors of a spin-1 cylindrical nanowire

    NASA Astrophysics Data System (ADS)

    Zaim, N.; Zaim, A.; Kerouad, M.

    2017-02-01

    In this work, the magnetic behavior of the cylindrical nanowire, consisting of a ferromagnetic core of spin-1 atoms surrounded by a ferromagnetic shell of spin-1 atoms is studied in the presence of a random crystal field interaction. Based on Metropolis algorithm, the Monte Carlo simulation has been used to investigate the effects of the concentration of the random crystal field p, the crystal field D and the shell exchange interaction Js on the phase diagrams and the hysteresis behavior of the system. Some characteristic behaviors have been found, such as the first and second-order phase transitions joined by tricritical point for appropriate values of the system parameters, triple and isolated critical points can be also found. Depending on the Hamiltonian parameters, single, double and para hysteresis regions are explicitly determined.

  2. Effects of intrinsic magnetostriction on tube-topology magnetoelectric sensors with high magnetic field sensitivity

    SciTech Connect

    Gillette, Scott M.; Fitchorov, Trifon; Obi, Ogheneyunume; Chen, Yajie Harris, Vincent G.; Jiang, Liping; Hao, Hongbo; Wu, Shuangxia

    2014-05-07

    Three quasi-one-dimensional magnetoelectric (ME) magnetic field sensors, each with a different magnetostrictive wire material, were investigated in terms of sensitivity and noise floor. Magnetostrictive Galfenol, iron-cobalt-vanadium, and iron-nickel wires were examined. Sensitivity profiles, hysteresis effects, and noise floor measurements for both optimally biased and zero-biased conditions are presented. The FeNi wire (FN) exhibits high sensitivity (5.36 mV/Oe) at bias fields below 22 Oe and an optimal bias of 10 Oe, whereas FeGa wire (FG) exhibits higher sensitivity (6.89 mW/Oe) at bias fields >22 Oe. The sensor of FeCoV wire (FC) presents relatively low sensitivity (2.12 mV/Oe), due to low magnetostrictive coefficient. Each ME tube-topology sensor demonstrates relatively high sensitivity at zero bias field, which results from a magnetic shape anisotropy and internal strain of the thin magnetostrictive wire.

  3. Dynamic effects of restoring footpoint symmetry on closed magnetic field lines

    NASA Astrophysics Data System (ADS)

    Reistad, J. P.; Østgaard, N.; Tenfjord, P.; Laundal, K. M.; Snekvik, K.; Haaland, S.; Milan, S. E.; Oksavik, K.; Frey, H. U.; Grocott, A.

    2016-05-01

    Here we present an event where simultaneous global imaging of the aurora from both hemispheres reveals a large longitudinal shift of the nightside aurora of about 3 h, being the largest relative shift reported on from conjugate auroral imaging. This is interpreted as evidence of closed field lines having very asymmetric footpoints associated with the persistent positive y component of the interplanetary magnetic field before and during the event. At the same time, the Super Dual Auroral Radar Network observes the ionospheric nightside convection throat region in both hemispheres. The radar data indicate faster convection toward the dayside in the dusk cell in the Southern Hemisphere compared to its conjugate region. We interpret this as a signature of a process acting to restore symmetry of the displaced closed magnetic field lines resulting in flux tubes moving faster along the banana cell than the conjugate orange cell. The event is analyzed with emphasis on Birkeland currents (BC) associated with this restoring process, as recently described by Tenfjord et al. (2015). Using data from the Active Magnetosphere and Planetary Electrodynamics Response Experiment (AMPERE) during the same conditions as the presented event, the large-scale BC pattern associated with the event is presented. It shows the expected influence of the process of restoring symmetry on BCs. We therefore suggest that these observations should be recognized as being a result of the dynamic effects of restoring footpoint symmetry on closed field lines in the nightside.

  4. High-temperature annealing effects on multiwalled carbon nanotubes: electronic structure, field emission and magnetic behaviors.

    PubMed

    Ray, Sekhar Chandra; Pao, Chih-Wen; Tsai, Huang-Ming; Chen, Huang-Chin; Chen, Yu-Shin; Wu, Shang-Lun; Ling, Dah-Chin; Lin, I-Nan; Pong, Way-Faung; Gupta, Sanju; Giorcelli, Mauro; Bianco, Stefano; Musso, Simone; Tagliaferro, Alberto

    2009-12-01

    This work elucidates the effects of high-temperature annealing on the microscopic and electronic structure of multiwalled carbon nanotubes (MWCNTs) using high-resolution transmission electron microscopy, micro-Raman spectroscopy, X-ray diffraction, X-ray absorption near-edge structure (XANES) and valence-band photoemission spectroscopy (VBPES), respectively. The field emission and magnetization behaviors are also presented. The results of annealing are as follows: (1) MWCNTs tend to align in the form of small fringes along their length, promote graphitization and be stable in air, (2) XANES indicates an enhancement in oxygen content on the sample, implying that it can be adopted for sensing and storing oxygen gas, (3) the electron field emission current density (J) is enhanced and the turn-on electric field (E(TOE)) reduced, suggesting potential use in field emission displays and as electron sources in microwave tube amplifiers and (4) as-grown MWCNTs with embedded iron nanoparticles exhibits significantly higher coercivity approximately 750 Oe than its bulk counterpart (Fe(bulk) approximately 0.9 Oe), suggesting its potential use as low-dimensional high-density magnetic recording media.

  5. Magnetic fields and cancer

    SciTech Connect

    Jones, T.L.

    1993-10-01

    This letter is a response to an article by Savitz and Kaune, EHP 101:76-80. W-L wire code was applied to data from a 1988 Denver study, and an association was reported between high W-L wire code and childhood cancer. This author discusses several studies and provides explanations which weakens the argument that classification error resulted in an appreciable reduction in the association between W-L high wire code and childhood cancer. In conclusion, the fact that new wire code is only weakly correlated with magnetic field measurements (in the same manner as the original W-L wire code) suggests that the newly reported stronger association with childhood cancer is likely due to factors other than magnetic fields. Differential residential mobility and differential residential age are two possible explanations and are suggestive that the reported association may be false.

  6. Deformation of Water by a Magnetic Field

    ERIC Educational Resources Information Center

    Chen, Zijun; Dahlberg, E. Dan

    2011-01-01

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

  7. Magnetic field reconnection

    NASA Astrophysics Data System (ADS)

    Axford, W. I.

    The fundamental principles of particle acceleration by magnetic reconnection in cosmic plasmas are reviewed. The history of reconnection models is traced, and consideration is given to the Kelvin-Helmholtz theorem, the frozen-field theorem, the application of the Kelvin-Helmholtz theorem to a collisionless plasma, solutions to specific reconnection problems, and configurational instability. Diagrams and graphs are provided, and the objections raised by critics of the reconnection theory and/or its astrophysical applications are discussed.

  8. Bioeffects of Static Magnetic Fields: Oxidative Stress, Genotoxic Effects, and Cancer Studies

    PubMed Central

    Ghodbane, Soumaya; Lahbib, Aida; Sakly, Mohsen; Abdelmelek, Hafedh

    2013-01-01

    The interaction of static magnetic fields (SMFs) with living organisms is a rapidly growing field of investigation. The magnetic fields (MFs) effect observed with radical pair recombination is one of the well-known mechanisms by which MFs interact with biological systems. Exposure to SMF can increase the activity, concentration, and life time of paramagnetic free radicals, which might cause oxidative stress, genetic mutation, and/or apoptosis. Current evidence suggests that cell proliferation can be influenced by a treatment with both SMFs and anticancer drugs. It has been recently found that SMFs can enhance the anticancer effect of chemotherapeutic drugs; this may provide a new strategy for cancer therapy. This review focuses on our own data and other data from the literature of SMFs bioeffects. Three main areas of investigation have been covered: free radical generation and oxidative stress, apoptosis and genotoxicity, and cancer. After an introduction on SMF classification and medical applications, the basic phenomena to understand the bioeffects are described. The scientific literature is summarized, integrated, and critically analyzed with the help of authoritative reviews by recognized experts; international safety guidelines are also cited. PMID:24027759

  9. Effects of static magnetic field exposure on plasma element levels in rat.

    PubMed

    Aida, Lahbib; Soumaya, Ghodbane; Myriam, Elferchichi; Mohsen, Sakly; Hafedh, Abdelmelek

    2014-07-01

    The interaction of static magnetic fields (SMFs) with living organisms is a rapidly growing field of investigation. The magnetic fields (MFs) effect observed with radical pair recombination is one of the well-known mechanisms by which MFs interact with biological systems. SMF influenced cellular antioxidant defense mechanisms by affecting antioxidant enzymes such as superoxide dismutase (SOD), glutathione peroxidase (GPx), and catalase (CAT). However, there were insufficient reports about the effects of SMF on macro and trace elements in serum, and the results were contradictory until now. In the current study, 12 rats were divided into two groups, namely as control and exposure group (128 mT and 1 h/day during five consecutive days). The macro and trace element concentrations in serum were examined. No significant difference was observed in the sodium (Na), potassium (K), calcium (Ca), phosphorus (P), and selenium (Se) levels in rat compared to control. By contrast, exposure to SMF showed an increase in the zinc (Zn) level and a decrease in iron (Fe) concentration. Under our experimental conditions, SMF exposure cannot affect the plasma levels of macroelements, while it can disrupt Zn and Fe concentrations in rat.

  10. Effect of the plasma-generated magnetic field on relativistic electron transport.

    PubMed

    Nicolaï, Ph; Feugeas, J-L; Regan, C; Olazabal-Loumé, M; Breil, J; Dubroca, B; Morreeuw, J-P; Tikhonchuk, V

    2011-07-01

    In the fast-ignition scheme, relativistic electrons transport energy from the laser deposition zone to the dense part of the target where the fusion reactions can be ignited. The magnetic fields and electron collisions play an important role in the collimation or defocusing of this electron beam. Detailed description of these effects requires large-scale kinetic calculations and is limited to short time intervals. In this paper, a reduced kinetic model of fast electron transport coupled to the radiation hydrodynamic code is presented. It opens the possibility to carry on hybrid simulations in a time scale of tens of picoseconds or more. It is shown with this code that plasma-generated magnetic fields induced by noncollinear temperature and density gradients may strongly modify electron transport in a time scale of a few picoseconds. These fields tend to defocus the electron beam, reducing the coupling efficiency to the target. This effect, that was not seen before in shorter time simulations, has to be accounted for in any ignition design using electrons as a driver.

  11. Primordial Magnetic Field Effects on the CMB and Large-Scale Structure

    DOE PAGES

    Yamazaki, Dai G.; Ichiki, Kiyotomo; Kajino, Toshitaka; ...

    2010-01-01

    Mmore » agnetic fields are everywhere in nature, and they play an important role in every astronomical environment which involves the formation of plasma and currents. It is natural therefore to suppose that magnetic fields could be present in the turbulent high-temperature environment of the big bang. Such a primordial magnetic field (PMF) would be expected to manifest itself in the cosmic microwave background (CMB) temperature and polarization anisotropies, and also in the formation of large-scale structure. In this paper, we summarize the theoretical framework which we have developed to calculate the PMF power spectrum to high precision. Using this formulation, we summarize calculations of the effects of a PMF which take accurate quantitative account of the time evolution of the cutoff scale. We review the constructed numerical program, which is without approximation, and an improvement over the approach used in a number of previous works for studying the effect of the PMF on the cosmological perturbations. We demonstrate how the PMF is an important cosmological physical process on small scales. We also summarize the current constraints on the PMF amplitude B λ and the power spectral index n B which have been deduced from the available CMB observational data by using our computational framework.« less

  12. Age-dependent effect of static magnetic field on brain tissue hydration.

    PubMed

    Deghoyan, Anush; Nikoghosyan, Anna; Heqimyan, Armenuhi; Ayrapetyan, Sinerik

    2014-01-01

    Age-dependent effect of Static Magnetic Field (SMF) on rats in a condition of active and inactive Na(+)/K(+) pump was studied for comparison of brain tissues hydration state changes and magnetic sensitivity. Influence of 15 min 0, 2 Tesla (T) SMF on brain tissue hydration of three aged groups of male albino rats was studied. Tyrode's physiological solution and 10(-4) M ouabain was used for intraperitoneal injections. For animal immobilization, the liquid nitrogen was used and the definition of tissue water content was performed by tissue drying method. Initial water content in brain tissues of young animals is significantly higher than in those of adult and aged ones. SMF exposure leads to decrease of water content in brain tissues of young animals and increase in brain tissues of adult and aged ones. In case of ouabain-poisoned animals, SMF gives reversal effects on brain tissue's hydration both in young and aged animals, while no significant effect on adults is observed. It is suggested that initial state of tissue hydration could play a crucial role in animal age-dependent magnetic sensitivity and the main reason for this could be age-dependent dysfunction of Na(+)/K(+) pump.

  13. Effects of Strong Static Magnetic Fields on Amphibian Development and Gene Expression

    NASA Astrophysics Data System (ADS)

    Kawakami, Satomi; Kashiwagi, Keiko; Furuno, Nobuaki; Yamashita, Masamichi; Kashiwagi, Akihiko; Tanimoto, Yoshifumi

    2006-07-01

    This investigation attempts to clarify the effects of strong vertical and static magnetic fields (SMFs) of 11-15 T on Xenopus laevis development and on Xotx2 (an important regulator of fore- and midbrain morphogenesis) and Xag1 (essential for cement gland formation) gene expression. Results showed that (1) a strong SMF significantly retarded normal development and induced microcephaly, two heads, abnormal cement glands and multiple malformations, indicating that SMF inhibits normal embryonic development, (2) a strong SMF suppressed Xotx2 and Xag1 expression.

  14. Effects of a high magnetic field on the primary zinc-rich crystals in hypoeutectic Zn-Sn alloy

    NASA Astrophysics Data System (ADS)

    Li, Lei; Ban, Chunyan; Shi, Xuchen; Zhang, Haitao; Zuo, Yubo; Zhu, Qingfeng; Wang, Xiangjie; Zhang, Hui; Cui, Jianzhong; Nagaumi, Hiromi

    2017-04-01

    The effects of a high magnetic field on the primary zinc-rich crystals during the solidification process of hypoeutectic Zn-Sn were investigated, along with the analysis of crystallographic orientations of them. The results show that the primary zinc-rich crystals in two dimensions show column-like or dendritic forms whether without and with the HMF. However, they are highly aligned and textured by the application of a high magnetic field: with the longer axis parallel to but the crystallographic c axis perpendicular to the magnetic field. The two-dimensional forms of the primary zinc-rich crystals are related to their orientations relative to the observation planes. The orientation and alignment modification by the magnetic field arises from the induced magnetic torques due to the magnetocrystalline anisotropy of the zinc-rich crystals, which makes them in energetically optimal orientations.

  15. New measurements of sextupole field decay and snapback effect on Tevatron dipole magnets

    SciTech Connect

    Velev, G.V.; Bauer, P.; Carcagno, R.; DiMarco, J.; Lamm, M.; Orris, D.; Schlabach, P.; Sylvester, C.; Tartaglia, M.; Tompkins, J.; /Fermilab

    2006-07-01

    To perform detailed studies of the dynamic effects in superconducting accelerator magnets, a fast continuous harmonics measurement system based on the application of a digital signal processor (DSP) has been built at Fermilab. Using this new system, the dynamic effects in the sextupole field, such as the field decay during the dwell at injection and the rapid subsequent ''snapback'' during the first few seconds of the energy ramp, are evaluated for more than ten Tevatron dipoles from the spare pool. The results confirm the previously observed fast drift in the first several seconds of the sextupole decay and provide additional information on a scaling law for predicting snapback duration. The information presented here can be used for an optimization of the Tevatron and for future LHC operations.

  16. The effect of stress and magnetic field orientation on surface Barkhausen noise in pipeline steel

    SciTech Connect

    Jagadish, C.; Clapham, L.; Atherton, D.L. . Dept. of Physics)

    1990-01-01

    Surface Barkhausen noise (SBN) measurements were mae on a 2-percent Mn pipeline steel sample subjected to different levels of applied tensile and compressive isostress. The magnetic field direction was varied through a full 360{degrees}. SBN voltage was found to depend on both stress level and magnetic field direction. The results were analyzed in terms of the reorientation of magnetic moments from axial to circumferential directions with increasing tension. Compression was found to re-align the magnetic moments in the axial direction.

  17. Magnetic ordering and crystal field effects in quasi-caged structure compound PrFe2Al8

    NASA Astrophysics Data System (ADS)

    Nair, Harikrishnan S.; Ghosh, Sarit K.; Ramesh Kumar, K.; Strydom, André M.

    2016-04-01

    The compound PrFe2Al8 possesses a three-dimensional network structure resulting from the packing of Al polyhedra centered at the transition metal element Fe and the rare earth Pr. Along the c-axis, Fe and Pr form chains which are separated from each other by the Al-network. In this paper, the magnetism and crystalline electric field effects in PrFe2Al8 are investigated through the analysis of magnetization and specific heat data. A magnetic phase transition in the Pr lattice is identified at TNPr ≈ 4 K in dc magnetization and ac susceptibility data. At 2 K, the magnetization isotherm presents a ferromagnetic saturation, however, failing to reach full spin-only ferromagnetic moment of Pr3+. Metamagnetic step-like low-field features are present in the magnetization curve at 2 K which is shown to shift upon field-cooling the material. Arrott plots centered around TPrN display "S"-like features suggestive of an inhomogeneous magnetic state. The magnetic entropy, Sm, estimated from specific heat outputs a value of R ln(2) at TN2 suggesting a doublet state for Pr3+. The magnetic specific heat is modeled by using a 9-level Schottky equation pertinent to the Pr3+ ion with J=4. Given the crystalline electric field situation of Pr3+, the inference of a doublet state from specific heat and consequent long-range magnetic order is an unexpected result.

  18. Magnetic field effects on the energy deposition spectra of MV photon radiation.

    PubMed

    Kirkby, C; Stanescu, T; Fallone, B G

    2009-01-21

    Several groups worldwide have proposed various concepts for improving megavoltage (MV) radiotherapy that involve irradiating patients in the presence of a magnetic field-either for image guidance in the case of hybrid radiotherapy-MRI machines or for purposes of introducing tighter control over dose distributions. The presence of a magnetic field alters the trajectory of charged particles between interactions with the medium and thus has the potential to alter energy deposition patterns within a sub-cellular target volume. In this work, we use the MC radiation transport code PENELOPE with appropriate algorithms invoked to incorporate magnetic field deflections to investigate electron energy fluence in the presence of a uniform magnetic field and the energy deposition spectra within a 10 microm water sphere as a function of magnetic field strength. The simulations suggest only very minor changes to the electron fluence even for extremely strong magnetic fields. Further, calculations of the dose-averaged lineal energy indicate that a magnetic field strength of at least 70 T is required before beam quality will change by more than 2%.

  19. Probing the effective nuclear-spin magnetic field in a single quantum dot via full counting statistics

    SciTech Connect

    Xue, Hai-Bin; Nie, Yi-Hang; Chen, Jingzhe; Ren, Wei

    2015-03-15

    We study theoretically the full counting statistics of electron transport through a quantum dot weakly coupled to two ferromagnetic leads, in which an effective nuclear-spin magnetic field originating from the configuration of nuclear spins is considered. We demonstrate that the quantum coherence between the two singly-occupied eigenstates and the spin polarization of two ferromagnetic leads play an important role in the formation of super-Poissonian noise. In particular, the orientation and magnitude of the effective field have a significant influence on the variations of the values of high-order cumulants, and the variations of the skewness and kurtosis values are more sensitive to the orientation and magnitude of the effective field than the shot noise. Thus, the high-order cumulants of transport current can be used to qualitatively extract information on the orientation and magnitude of the effective nuclear-spin magnetic field in a single quantum dot. - Highlights: • The effective nuclear-spin magnetic field gives rise to the off-diagonal elements of the reduced density matrix of single QD. • The off-diagonal elements of reduced density matrix of the QD have a significant impact on the high-order current cumulants. • The high-order current cumulants are sensitive to the orientation and magnitude of the effective nuclear-spin magnetic field. • The FCS can be used to detect the orientation and magnitude of the effective nuclear-spin magnetic field in a single QD.

  20. The effect of giant impactors on the magnetic field energy of an early Martian dynamo.

    NASA Astrophysics Data System (ADS)

    Drummond, McGregor; Thieulot, Cedric; Monteux, Julien

    2016-04-01

    Through the cratering record embedded on its surface, Mars is one of the key planets required for investigating the formation and impact frequency in the early history of our Solar System. This record also holds clues to the events that may have caused the observed hemispheric dichotomy and cessation of the magnetic field that was present within the first 500 Myr of the planets' formation. We investigate the influence of giant impacts on the early Martian dynamo using the numerical dynamo modelling code PARODY-JA [1]. We hypothesize that the input heat from a giant impact will decrease the total heat flux at the CMB through mantle heating which leads to a decrease in the Rayleigh number of the core. As boundary conditions for the heat flux anomaly size, we use numerical results of a 750 km diameter impactor from the Monteux and Arkani-Hamed, 2014 [2] study which investigated impact heating and core merging of giant impacts in early Mars. We also determine the decrease in Rayleigh number from the change in total heat flux at the CMB using these results, where the decrease after impact is due to shock heating at the CMB. We calculate the time-averaged total magnetic field energy for an initial homogeneous heat flux model using a range of Rayleigh numbers (5 x 103 - 1 x 10^5). The Rayleigh number is then decreased for three new models - homogeneous, north pole impact and equatorial impact - and the time-averaged energy again determined. We find that the energy decreases more in our impact models, compared with the homogeneous, along with a variation in energy between the north pole and equatorial impact models. We conclude that giant impacts in Mars' early history would have decreased the total magnetic energy of the field and the decrease in energy is also dependent on the location of the impact. The magnetic field could have been disrupted beyond recovery from a planetesimal-sized collision; such as the suggested Borealis basin forming impact, or through the

  1. Health effects of magnetic fields generated from power lines: new clues for an old puzzle.

    PubMed

    Comba, Pietro; Fazzo, Lucia

    2009-01-01

    Thirty years ago, Nancy Wertheimer and Ed Leeper published the first report on the association between childhood cancer and "electrical current configuration" of houses in Denver, Colorado. In 2001 the International Agency for Research on Cancer defined 50-60 Hz magnetic fields as "possibly carcinogenic to humans" because of the "limited evidence" of carcinogenicity of residential exposure relatively to childhood leukemia. With respect to health effects other than cancer, namely neurodegenerative disorders, miscarriage, subtle differences in the timing of melatonin release, altered autonomic control of the heart, and changes in the number of natural killer cells, some open questions still remain. Several authors recommended further investigation of the possible long-term effects of magnetic fields, focussing on populations experiencing high exposure levels. In this frame a research team of ISS searched for a suitable location to implement an epidemiological study aimed at a wide range of outcomes for which a priori hypotheses could be formulated. The recently published findings of this project showed an increase of primary and secondary malignant neoplasms, ischaemic disease and haematological diseases. Future studies should thus address the most exposed sectors of the population, take into account different outcomes (all neoplasms, neurodegenerative diseases, immunological disorders, specific cardiovascular effects) and follow research protocols that enable subsequent pooled analyses. A precautionary approach may provide the frame for decision making where the available resources for environmental remediation be prioritatively allocated to worst-off situations.

  2. Non-Fermi-liquid magic angle effects in high magnetic fields

    NASA Astrophysics Data System (ADS)

    Lebed, A. G.

    2016-07-01

    We investigate a theoretical problem of electron-electron interactions in an inclined magnetic field in a quasi-one-dimensional (Q1D) conductor. We show that they result in strong non-Fermi-liquid corrections to a specific heat, provided that the direction of the magnetic field is far from the so-called Lebed's magic angles (LMAs). If magnetic field is directed close to one of the LMAs, the specific heat corrections become small and the Fermi-liquid picture restores. As a result, we predict Fermi-liquid-non-Fermi-liquid angular crossovers in the vicinities of the LMA directions of the field. We suggest to perform the corresponding experiment in the Q1D conductor (Per) 2Au (mnt) 2 under pressure in magnetic fields of the order of H ≃25 T .

  3. Effect of the Earth's magnetic field spatial distribution on the electromagnetic coupling at the fluid core boundaries for nutations

    NASA Astrophysics Data System (ADS)

    Koot, L.; Dumberry, M.

    2011-12-01

    Nutations are periodic variations in the orientation of the Earth's rotation axis in space. This motion is generated by the gravitational torque applied on the Earth's equatorial bulge by the Moon, the Sun, and the other planets. Because the mantle, the fluid outer core and the solid inner core react differently to the applied torque, the nutation motion is characterized by differential rotations between these three regions. Since the boundaries of the fluid outer core are permeated by a background magnetic field (the geodynamo field), the differential rotation at the fluid core boundaries induces a secondary magnetic field by shear and advection of the background field. The associated electric currents produce Lorentz forces and torques between the outer core, inner core, and mantle, that tend to oppose the differential rotation. A previous study has shown that the magnitude of the electromagnetic (EM) torque is mainly determined by the electrical conductivities on both sides of the outer core boundaries and by the mean RMS strength of the background magnetic field, with the spatial distribution of this magnetic field being unimportant to first order. The goal of the present work is to reassess the role of the magnetic field spatial distribution on the strength of the EM torque using a new model of the EM coupling for nutations that we have recently developed. Our model differs from previous ones in that we use a global approach to describe the induced magnetic field. Moreover, we also include in the torque the contribution from the poloidal component of the induced field, an effect neglected in previous models. In addition, we do not assume a priori that the non-dipolar components of the background magnetic field can be represented by a uniform field with the same power but instead we calculate the torque on the basis of the full geometry of the field. This is particularly important for the poloidal torque as it depends directly on the surface gradient of the

  4. Rapporteur report: cellular, animal and epidemiological studies of the effects of static magnetic fields relevant to human health.

    PubMed

    Leszczynski, Dariusz

    2005-01-01

    Three talks were presented in the session on "Cellular, Animal and Epidemiological Studies of the Effects of Static Magnetic Fields Relevant to Human Health". The first talk presented the in vitro effects of static magnetic fields on cell cultures. The second talk presented the in vivo evidence obtained from animal studies. The final, third talk, presented the evidence obtained from epidemiological studies. The overall conclusion of the three presentations and the following general discussion was that the scientific evidence available to date is weak and contains large gaps in knowledge either due to the poor quality of published studies or because of the lack of published research on certain health-related topics. It was emphasized that the rapid development of new technological applications of static magnetic fields (e.g. magnetic levitation trains or magnetic resonance imaging-MRI) results in the human population at large, in certain occupations, and in a selected population of clinical patients being exposed to ever increasing static magnetic field strengths. It is of concern that the knowledge presently available concerning the health effects of these strong static magnetic fields is lagging a long way behind technological development. In conclusion, it was suggested that there is an urgent need to perform new studies in all research areas (in vitro, in vivo and epidemiology) in order to fill the present gaps in knowledge and provide assurance that this technology will not cause any unwanted and unexpected health side effects.

  5. Magnetic Field Topology in Jets

    NASA Technical Reports Server (NTRS)

    Gardiner, T. A.; Frank, A.

    2000-01-01

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

  6. Low field magnetic resonance imaging

    SciTech Connect

    Pines, Alexander; Sakellariou, Dimitrios; Meriles, Carlos A.; Trabesinger, Andreas H.

    2010-07-13

    A method and system of magnetic resonance imaging does not need a large homogenous field to truncate a gradient field. Spatial information is encoded into the spin magnetization by allowing the magnetization to evolve in a non-truncated gradient field and inducing a set of 180 degree rotations prior to signal acquisition.

  7. Effects of magnetic fields from underwater electrical cutting on in vitro corrosion of dental amalgam

    SciTech Connect

    Ortendahl, T.W.; Hoegstedt, P.O.; Odelius, H.; Noren, J.G.

    1988-11-01

    Metallic taste has been reported from divers working with underwater electric welding and cutting. An in vitro model was designed to simulate the intraoral situation of the divers with respect to the magnetic field. Potentiostatic analyses were performed on amalgam samples exposed to AC and DC magnetic fields. Morphologic changes were analyzed using differential interference light microscopy and scanning electron microscopy. Chemical changes on the surface of the amalgam samples were analyzed with secondary ion mass spectrometry. Results demonstrated that dental amalgams exposed to a specific AC magnetic field underwent morphologic and chemical changes in the superficial amalgam layers.

  8. Effects of magnetic fields from underwater electrical cutting on in vitro corrosion of dental amalgam.

    PubMed

    Ortendahl, T W; Högstedt, P; Odelius, H; Norén, J G

    1988-11-01

    Metallic taste has been reported from divers working with underwater electric welding and cutting. An in vitro model was designed to simulate the intraoral situation of the divers with respect to the magnetic field. Potentiostatic analyses were performed on amalgam samples exposed to AC and DC magnetic fields. Morphologic changes were analyzed using differential interference light microscopy and scanning electron microscopy. Chemical changes on the surface of the amalgam samples were analyzed with secondary ion mass spectrometry. Results demonstrated that dental amalgams exposed to a specific AC magnetic field underwent morphologic and chemical changes in the superficial amalgam layers.

  9. Magnetic field switchable dry adhesives.

    PubMed

    Krahn, Jeffrey; Bovero, Enrico; Menon, Carlo

    2015-02-04

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

  10. A Comparison Between Magnetic Field Effects in Excitonic and Exciplex Organic Light-Emitting Diodes

    NASA Astrophysics Data System (ADS)

    Sahin Tiras, Kevser; Wang, Yifei; Harmon, Nicholas J.; Wohlgenannt, Markus; Flatte, Michael E.

    In flat-panel displays and lighting applications, organic light emitting diodes (OLEDs) have been widely used because of their efficient light emission, low-cost manufacturing and flexibility. The electrons and holes injected from the anode and cathode, respectively, form a tightly bound exciton as they meet at a molecule in organic layer. Excitons occur as spin singlets or triplets and the ratio between singlet and triplet excitons formed is 1:3 based on spin degeneracy. The internal quantum efficiency (IQE) of fluorescent-based OLEDs is limited 25% because only singlet excitons contribute the light emission. To overcome this limitation, thermally activated delayed fluorescent (TADF) materials have been introduced in the field of OLEDs. The exchange splitting between the singlet and triplet states of two-component exciplex systems is comparable to the thermal energy in TADF materials, whereas it is usually much larger in excitons. Reverse intersystem crossing occurs from triplet to singlet exciplex state, and this improves the IQE. An applied small magnetic field can change the spin dynamics of recombination in TADF blends. In this study, magnetic field effects on both excitonic and exciplex OLEDs will be presented and comparison similarities and differences will be made.

  11. Combined effect of demagnetizing field and induced magnetic anisotropy on the magnetic properties of manganese-zinc ferrite composites

    NASA Astrophysics Data System (ADS)

    Babayan, V.; Kazantseva, N. E.; Moučka, R.; Sapurina, I.; Spivak, Yu. M.; Moshnikov, V. A.

    2012-01-01

    This work is devoted to the analysis of factors responsible for the high-frequency shift of the complex permeability (μ*) dispersion region in polymer composites of manganese-zinc (MnZn) ferrite, as well as to the increase in their thermomagnetic stability. The magnetic spectra of the ferrite and its composites with polyurethane (MnZn-PU) and polyaniline (MnZn-PANI) are measured in the frequency range from 1 MHz to 3 GHz in a longitudinal magnetization field of up to 700 Ое and in the temperature interval from -20 °С to +150 °С. The approximation of the magnetic spectra by a model, which takes into account the role of domain wall motion and magnetization rotation, allows one to determine the specific contribution of resonance processes associated with domain wall motion and the natural ferromagnetic resonance to the μ*. It is established that, at high frequencies, the μ* of the MnZn ferrite is determined solely by magnetization rotation, which occurs in the region of natural ferromagnetic resonance when the ferrite is in the “single domain” state. In the polymer composites of the MnZn ferrite, the high-frequency permeability is also determined mainly by the magnetization rotation; however, up to high values of magnetizing fields, there is a contribution of domain wall motion, thus the “single domain” state in ferrite is not reached. The frequency and temperature dependence of μ* in polymer composites are governed by demagnetizing field and the induced magnetic anisotropy. The contribution of the induced magnetic anisotropy is crucial for MnZn-PANI. It is attributed to the elastic stresses that arise due to the domain wall pinning by a polyaniline film adsorbed on the surface of the ferrite during in-situ polymerization.

  12. Superhorizon magnetic fields

    NASA Astrophysics Data System (ADS)

    Campanelli, Leonardo

    2016-03-01

    We analyze the evolution of superhorizon-scale magnetic fields from the end of inflation till today. Whatever is the mechanism responsible for their generation during inflation, we find that a given magnetic mode with wave number k evolves, after inflation, according to the values of k ηe , nk , and Ωk , where ηe is the conformal time at the end of inflation, nk is the number density spectrum of inflation-produced photons, and Ωk is the phase difference between the two Bogoliubov coefficients which characterize the state of that mode at the end of inflation. For any realistic inflationary magnetogenesis scenario, we find that nk-1≪|k ηe|≪1 , and three evolutionary scenarios are possible: (i) |Ωk∓π |=O (1 ) , in which case the evolution of the magnetic spectrum Bk(η ) is adiabatic, a2Bk(η )=const , with a being the expansion parameter; (ii) |Ωk∓π |≪|k ηe| , in which case the evolution is superadiabatic, a2Bk(η )∝η ; (iii) |k ηe|≪|Ωk∓π |≪1 or |k ηe|˜|Ωk∓π |≪1 , in which case an early phase of adiabatic evolution is followed, after a time η⋆˜|Ωk∓π |/k , by a superadiabatic evolution. Once a given mode reenters the horizon, it remains frozen into the plasma and then evolves adiabatically till today. As a corollary of our results, we find that inflation-generated magnetic fields evolve adiabatically on all scales and for all times in conformal-invariant free Maxwell theory, while they evolve superadiabatically after inflation on superhorizon scales in the nonconformal-invariant Ratra model, where the inflaton is kinematically coupled to the electromagnetic field. The latter result supports and, somehow, clarifies our recent claim that the Ratra model can account for the presence of cosmic magnetic fields without suffering from both backreaction and strong-coupling problems.

  13. Baryon onset in a magnetic field

    SciTech Connect

    Haber, Alexander; Preis, Florian; Schmitt, Andreas

    2016-01-22

    The critical baryon chemical potential for the onset of nuclear matter is a function of the vacuum mass and the binding energy. Both quantities are affected by an external magnetic field. We show within two relativistic mean-field models – including magnetic catalysis, but omitting the anomalous magnetic moment – that a magnetic field increases both the vacuum mass and the binding energy. For sufficiently large magnetic fields, the effect on the vacuum mass dominates and as a result the critical baryon chemical potential is increased.

  14. Effect of magnetic field on the photovoltaic properties of YBa2Cu3O6.96/Ag heterojunction

    NASA Astrophysics Data System (ADS)

    Yang, Feng; Han, Mengyuan; Chu, Zhuang; Ma, Zhipan; Chang, Fanggao

    2017-02-01

    The obvious photovoltaic effect (Voc ˜ 30 μV) induced by purple-laser illumination at high Tc superconductor YBa2Cu3O6.96/Ag (YBCO/Ag) heterojunction has been observed, revealing that there exists an electrical field across the YBCO/Ag interface. It has been found that magnetic field can dramatically change the photo-induced voltage in the vicinity of superconducting transition. With increasing magnetic fields up to 3 T, the photovoltage at 74 K and 30 mW/mm2 is reduced from 15 μV to zero and then reaches -15 μV. The polarity of the voltage can be switched by applying an external magnetic field, as well as by varying the laser intensity. Our results can be understood in terms of the magnetic vortex penetrating in high Tc superconductors and provide strong evidence for the existence of an interface electrical field in the superconductor/metal heterojunction.

  15. Development and evaluation of intermediate frequency magnetic field exposure system for studies of in vitro biological effects.

    PubMed

    Fujita, Atsushi; Hirota, Izuo; Kawahara, Yoshinobu; Omori, Hideki

    2007-10-01

    We have developed an intermediate frequency (IF) magnetic field exposure system for in vitro studies. Since there are no previous studies on exposure to heating-frequency magnetic fields generated from an induction heating (IH) cook top, there is a strong need for such an exposure system and for biological studies of IF magnetic fields. This system mainly consists of a magnetic-field-generating coil housed inside an incubator, inside which cultured cells can be exposed to magnetic field. Two systems were prepared to allow the experiment to be conducted in a double-blind manner. The level of the generated magnetic field was set to 532 microT rms in the exposure space, 23 kHz, 80 times the value in the International Commission on Non-ionizing Radiation Protection (ICNIRP) guidelines, with a spatial field uniformity better than 3.8%. The waveforms were nearly sinusoidal. It was also confirmed that the parasitic electric field was 157 V/m rms and the induced electric field was 1.9 V/m rms. The temperature was maintained at 36.5 +/- 0.5 degrees C for 2 h. Furthermore, leaked magnetic flux density was 0.7 microT rms or lower at extremely low frequency (ELF) and IF in the stopped system when the other system was being operated, and the environmental magnetic flux density was 0.1 microT rms or lower at the center of the coils. As a result, it was confirmed that this system could be successfully used to evaluate the biological effects of exposure to IF magnetic fields.

  16. Pairing of Fermions with Unequal Effective Charges in an Artificial Magnetic Field

    NASA Astrophysics Data System (ADS)

    Ünal, F. Nur; Oktel, M. Ö.

    2016-01-01

    Artificial magnetic fields (AMFs) created for ultracold systems depend sensitively on the internal structure of the atoms. In a mixture, each component experiences a different AMF depending on its internal state. This enables the study of Bardeen-Cooper-Schrieffer pairing of fermions with unequal effective charges. In this Letter, we investigate the superconducting (SC) transition of a system formed by such pairs as a function of field strength. We consider a homogeneous two-component Fermi gas of unequal effective charges but equal densities with attractive interactions. We find that the phase diagram is altered drastically compared to the usual balanced charge case. First, for some AMFs there is no SC transition and isolated SC phases are formed, reflecting the discrete Landau level (LL) structure. SC phases become reentrant both in AMF and temperature. For extremely high fields where both components are confined to their lowest LLs, the effect of the charge imbalance is suppressed. Charge asymmetry reduces the critical temperature even in the low-field semiclassical regime. We discuss a pair breaking mechanism due to the unequal Lorentz forces acting on the components of the Cooper pairs to identify the underlying physics.

  17. Electric and magnetic fields

    NASA Technical Reports Server (NTRS)

    Kaufman, H. R.; Robinson, R. S.; Etters, R. D.

    1982-01-01

    A number of energy momentum anomalies are described that result from the use of Abraham-Lorentz electromagnetic theory. These anomalies have in common the motion of charged bodies or current carrying conductors relative to the observer. The anomalies can be avoided by using the nonflow approach, based on internal energy of the electromagnetic field. The anomalies can also be avoided by using the flow approach, if all contributions to flow work are included. The general objective of this research is a fundamental physical understanding of electric and magnetic fields which, in turn, might promote the development of new concepts in electric space propulsion. The approach taken is to investigate quantum representations of these fields.

  18. Effect of uniform magnetic and electric fields on microstructure and substructure characteristics of combustion products of aluminum nanopowder in air

    NASA Astrophysics Data System (ADS)

    Il'in, A. P.; Mostovshchikov, A. V.; Pak, A. Ya.

    2016-12-01

    We have analyzed the effect of constant electric and magnetic fields on the micro- and substructure characteristics of the combustion products of aluminum nanopowder in air. It has been found that the combustion of aluminum nanopowder in a magnetic field leads to the formation of single crystals of the hexagonal habitus, while the combustion in an electric field results in the formation of faceted crystallites with layered morphology. The fields noticeably affect the crystal lattice parameters of aluminum oxide and nitride (reduce the coherent scattering regions in aluminum nitride and increase such regions in aluminum γ-oxide). At the same time, the displacement of atoms relative to the equilibrium position becomes noticeably smaller for all crystal phases under the action of the fields (except for aluminum nitride in a magnetic field). These results have been explained by the orienting and stabilizing actions of the fields on the combustion products of aluminum nanopowder in air.

  19. Subchronic in vivo effects of a high static magnetic field (9.4 T) in rats.

    PubMed

    High, W B; Sikora, J; Ugurbil, K; Garwood, M

    2000-07-01

    The potential adverse biologic effects of sub chronic (cumulatively 10 weeks) exposure to a high magnetic field (9.4 T) were evaluated in young adult male and female Fischer rats as well as in their progeny. Biologic end points in adult rats included changes in daily clinical observations; spatial memory tests; weekl