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Sample records for ac magnetic permeability

  1. AC photovoltaic module magnetic fields

    SciTech Connect

    Jennings, C.; Chang, G.J.; Reyes, A.B.; Whitaker, C.M.

    1997-12-31

    Implementation of alternating current (AC) photovoltaic (PV) modules, particularly for distributed applications such as PV rooftops and facades, may be slowed by public concern about electric and magnetic fields (EMF). This paper documents magnetic field measurements on an AC PV module, complementing EMF research on direct-current PV modules conducted by PG and E in 1993. Although not comprehensive, the PV EMF data indicate that 60 Hz magnetic fields (the EMF type of greatest public concern) from PV modules are comparable to, or significantly less than, those from household appliances. Given the present EMF research knowledge, AC PV module EMF may not merit considerable concern.

  2. Using magnetic permeability bits to store information

    NASA Astrophysics Data System (ADS)

    Timmerwilke, John; Petrie, J. R.; Wieland, K. A.; Mencia, Raymond; Liou, Sy-Hwang; Cress, C. D.; Newburgh, G. A.; Edelstein, A. S.

    2015-10-01

    Steps are described in the development of a new magnetic memory technology, based on states with different magnetic permeability, with the capability to reliably store large amounts of information in a high-density form for decades. The advantages of using the permeability to store information include an insensitivity to accidental exposure to magnetic fields or temperature changes, both of which are known to corrupt memory approaches that rely on remanent magnetization. The high permeability media investigated consists of either films of Metglas 2826 MB (Fe40Ni38Mo4B18) or bilayers of permalloy (Ni78Fe22)/Cu. Regions of films of the high permeability media were converted thermally to low permeability regions by laser or ohmic heating. The permeability of the bits was read by detecting changes of an external 32 Oe probe field using a magnetic tunnel junction 10 μm away from the media. Metglas bits were written with 100 μs laser pulses and arrays of 300 nm diameter bits were read. The high and low permeability bits written using bilayers of permalloy/Cu are not affected by 10 Mrad(Si) of gamma radiation from a 60Co source. An economical route for writing and reading bits as small at 20 nm using a variation of heat assisted magnetic recording is discussed.

  3. Magnetic permeability measurements and a lunar core

    NASA Technical Reports Server (NTRS)

    Goldstein, B. E.; Phillips, R. J.; Russell, C. T.

    1976-01-01

    Measurements of the magnetic field induced in the moon while it is in the geomagnetic tail lobes have been interpreted in terms of lunar magnetic permeability due to free iron content; such studies ignored the possibility that a highly conducting lunar core (Fe or FeS) would exclude magnetic fields with an apparent diamagnetic effect. Using lunar chemical and thermal models to determine plausible limits of magnetic permeability, we interpret measurements of the induced moment. The maximum likely radius of a lunar core is 580 km. Subsatellite and ALSEP measurements of the induced field are in disagreement. Resolving the differences is critical to determining whether a core could or does exist.

  4. Lunar electrical conductivity and magnetic permeability

    NASA Technical Reports Server (NTRS)

    Dyal, P.; Parkin, C. W.; Daily, W. D.

    1975-01-01

    Improved analytical techniques are applied to a large Apollo magnetometer data set to yield values of electroconductivity, temperature, magnetic permeability, and iron abundance. Average bulk electroconductivity of the moon is calculated to be .0007 mho/m; a rapid increase with depth to about .003 mho/m within 250 km is indicated. The temperature profile, obtained from the electroconductivity profile for olivine, indicates high lunar temperatures at relatively shallow depths. Magnetic permeability of the moon relative to its environment is calculated to be 1.008 plus or minus .005; a permeability relative to free space of 1.012 plus 0.011, minus 0.008 is obtained. Lunar iron abundances corresponding to this permeability value are 2.5 plus 2.3, minus 1.7 wt% free iron and 5.0-13.5 wt% total iron for a moon composed of a combination of free iron, olivine, and orthopyroxene.

  5. Lunar magnetic permeability studies and magnetometer sensitivity

    NASA Technical Reports Server (NTRS)

    King, J. H.; Ness, N. F.

    1977-01-01

    A regression of quiet magnetic field components simultaneously measured by the two Explorer 35 magnetometers reveals uncertainties in effective sensitivity factors of up to a few percent in one or both of these instruments. Given this, the validity of previous lunar permeability studies based on Explorer 35/ALSEP regressions, wherein inferences are drawn from regression line slopes differing from unity by the order of one percent, is called into question. We emphasize the need to critically address the question of small deviations in magnetometer sensitivity factors from nominal values as a part of any two-magnetometer lunar permeability study.

  6. Temperature Dependence of AC Magnetic Properties of FeCo-Based Soft Magnetic Alloys

    NASA Astrophysics Data System (ADS)

    Xiao, J. Q.; Yu, R. H.; Basu, S.

    1998-03-01

    AC magnetic properties of soft FeCo-based alloys have been studied at different temperatures and frequencies. Samples of Fe_49Co_49V2 (Hiperco50), Fe_49Co_49V_1.7Nb_0.3 (Hiperco 50HS), and Fe_72Co_27Cr_0.5Mn_0.5 (Hiperco 27) were selected and heat-treated to obtain different microstructures. TEM observation reveals that the ordering parameter of the BCC phase in Hiperco 50 series vary with the cooling rate, and a high temperature disordered phase with a high density of defects can be retained through rapid quenching, whereas Hiperco 27 exhibits a disordered structure which is insensitive to the heat treatment. Toroidal laminated samples were used to measure AC magnetic properties. At low frequencies, all the samples either with ordered or disordered phases show low coercivity H_c, high magnetization and initial permeability μ. As the frequency increases, Hc increases and μ decreases due to the damping effect of the magnetic domain walls. In a certain range of frequencies, magnetic permeability spectra show a dispersion zone where the permeability sharply decreases near to zero. This magnetic permeability dispersion zone shifts to lower frequencies with increasing temperature and decreasing ordering parameter. The effect of microstructure, frequency and temperature on core losses will be also presented.

  7. 21 CFR 886.4440 - AC-powered magnet.

    Code of Federal Regulations, 2012 CFR

    2012-04-01

    ... 21 Food and Drugs 8 2012-04-01 2012-04-01 false AC-powered magnet. 886.4440 Section 886.4440 Food... DEVICES OPHTHALMIC DEVICES Surgical Devices § 886.4440 AC-powered magnet. (a) Identification. An AC-powered magnet is an AC-powered device that generates a magnetic field intended to find and...

  8. 21 CFR 886.4440 - AC-powered magnet.

    Code of Federal Regulations, 2011 CFR

    2011-04-01

    ... 21 Food and Drugs 8 2011-04-01 2011-04-01 false AC-powered magnet. 886.4440 Section 886.4440 Food... DEVICES OPHTHALMIC DEVICES Surgical Devices § 886.4440 AC-powered magnet. (a) Identification. An AC-powered magnet is an AC-powered device that generates a magnetic field intended to find and...

  9. 21 CFR 886.4440 - AC-powered magnet.

    Code of Federal Regulations, 2014 CFR

    2014-04-01

    ... 21 Food and Drugs 8 2014-04-01 2014-04-01 false AC-powered magnet. 886.4440 Section 886.4440 Food... DEVICES OPHTHALMIC DEVICES Surgical Devices § 886.4440 AC-powered magnet. (a) Identification. An AC-powered magnet is an AC-powered device that generates a magnetic field intended to find and...

  10. 21 CFR 886.4440 - AC-powered magnet.

    Code of Federal Regulations, 2013 CFR

    2013-04-01

    ... 21 Food and Drugs 8 2013-04-01 2013-04-01 false AC-powered magnet. 886.4440 Section 886.4440 Food... DEVICES OPHTHALMIC DEVICES Surgical Devices § 886.4440 AC-powered magnet. (a) Identification. An AC-powered magnet is an AC-powered device that generates a magnetic field intended to find and...

  11. 21 CFR 886.4440 - AC-powered magnet.

    Code of Federal Regulations, 2010 CFR

    2010-04-01

    ... 21 Food and Drugs 8 2010-04-01 2010-04-01 false AC-powered magnet. 886.4440 Section 886.4440 Food... DEVICES OPHTHALMIC DEVICES Surgical Devices § 886.4440 AC-powered magnet. (a) Identification. An AC-powered magnet is an AC-powered device that generates a magnetic field intended to find and...

  12. Alternating current loss reduction for rectangular busbars by covering their edges with low permeable magnetic caps

    NASA Astrophysics Data System (ADS)

    Sasada, Ichiro

    2014-05-01

    A method to reduce ac conductive losses in a thin rectangular busbar made of copper is presented. The method is based on a technique, which makes the distribution of the ac current in the cross section of a busbar flatter. Edges of a thin busbar are covered with low permeability magnetic thin layers as caps. The magnetic cap makes the impedance experienced by the current flowing near the edge comparatively larger so that currents cannot get crowded near the edges of a busbar. This method is numerically verified.

  13. Alternating current loss reduction for rectangular busbars by covering their edges with low permeable magnetic caps

    SciTech Connect

    Sasada, Ichiro

    2014-05-07

    A method to reduce ac conductive losses in a thin rectangular busbar made of copper is presented. The method is based on a technique, which makes the distribution of the ac current in the cross section of a busbar flatter. Edges of a thin busbar are covered with low permeability magnetic thin layers as caps. The magnetic cap makes the impedance experienced by the current flowing near the edge comparatively larger so that currents cannot get crowded near the edges of a busbar. This method is numerically verified.

  14. Size- and Composition-Dependent Radio Frequency Magnetic Permeability of Iron Oxide Nanocrystals

    SciTech Connect

    Yun, H; Liu, XY; Paik, T; Palanisamy, D; Kim, J; Vogel, WD; Viescas, AJ; Chen, J; Papaefthymiou, GC; Kikkawa, JM; Allen, MG; Murray, CB

    2014-12-01

    We investigate the size- and composition-dependent ac magnetic permeability of superparamagnetic iron oxide nanocrystals for radio frequency (RF) applications. The nanocrystals are obtained through high-temperature decomposition synthesis, and their stoichiometry is determined by Mossbauer spectroscopy. Two sets of oxides are studied: (a) as-synthesized magnetite-rich and (b) aged maghemite nanocrystals. All nanocrystalline samples are confirmed to be in the superparamagnetic state at room temperature by SQUID magnetometry. Through the one-turn inductor method, the ac magnetic properties of the nanocrystalline oxides are characterized. In magnetite-rich iron oxide nanocrystals, size-dependent magnetic permeability is not observed, while maghemite iron oxide nanocrystals show clear size dependence. The inductance, resistance, and quality factor of hand-wound inductors with a superparamagnetic composite core are measured. The superparamagnetic nanocrystals are successfully embedded into hand-wound inductors to function as inductor cores.

  15. Size- and composition-dependent radio frequency magnetic permeability of iron oxide nanocrystals.

    PubMed

    Yun, Hongseok; Liu, Xiyu; Paik, Taejong; Palanisamy, Duraivelan; Kim, Jungkwun; Vogel, William D; Viescas, Arthur J; Chen, Jun; Papaefthymiou, Georgia C; Kikkawa, James M; Allen, Mark G; Murray, Christopher B

    2014-12-23

    We investigate the size- and composition-dependent ac magnetic permeability of superparamagnetic iron oxide nanocrystals for radio frequency (RF) applications. The nanocrystals are obtained through high-temperature decomposition synthesis, and their stoichiometry is determined by Mössbauer spectroscopy. Two sets of oxides are studied: (a) as-synthesized magnetite-rich and (b) aged maghemite nanocrystals. All nanocrystalline samples are confirmed to be in the superparamagnetic state at room temperature by SQUID magnetometry. Through the one-turn inductor method, the ac magnetic properties of the nanocrystalline oxides are characterized. In magnetite-rich iron oxide nanocrystals, size-dependent magnetic permeability is not observed, while maghemite iron oxide nanocrystals show clear size dependence. The inductance, resistance, and quality factor of hand-wound inductors with a superparamagnetic composite core are measured. The superparamagnetic nanocrystals are successfully embedded into hand-wound inductors to function as inductor cores. PMID:25390073

  16. Quantifying the complex permittivity and permeability of magnetic nanoparticles

    NASA Astrophysics Data System (ADS)

    Yao, B. M.; Gui, Y. S.; Worden, M.; Hegmann, T.; Xing, M.; Chen, X. S.; Lu, W.; Wroczynskyj, Y.; van Lierop, J.; Hu, C.-M.

    2015-04-01

    The complex permittivity and permeability of superparamagnetic iron-oxide nanoparticles has been quantified using a circular waveguide assembly with a static magnetic field to align the nanoparticle's magnetization. The high sensitivity of the measurement provides the precise resonant feature of nanoparticles. The complex permeability in the vicinity of ferromagnetic resonance is in agreement with the nanoparticle's measured magnetization via conventional magnetometry. A rigorous and self-consistent measure of complex permittivities and permeabilities of nanoparticles is crucial to ascertain accurately the dielectric behaviour as well as the frequency response of nanoparticle magnetization, necessary ingredients when designing and optimizing magnetic nanoparticles for biomedical applications.

  17. Composites with tuned effective magnetic permeability

    NASA Astrophysics Data System (ADS)

    Amirkhizi, Alireza V.; Nemat-Nasser, Sia

    2007-07-01

    Pendry et al. [J. B. Pendry, A. J. Holden, D. J. Robbins, and W. J. Stewart, IEEE Trans. Microwave Theory Tech. 47, 2075 (1999)] and Smith et al. [D. R. Smith, W. J. Padilla, D. C. Vier, S. C. Nemat-Nasser, and S. Schultz, Phys. Rev. Lett. 84, 4184 (2000)] have shown that the effective magnetic permeability, μ, of free space can be rendered negative over a certain frequency range by a periodic arrangement of very thin conductors with suitable magnetic resonance properties, the so-called split-ring resonators. Because of its rather bulky architecture, this structure does not lend itself to a proper integration into a reasonably thin real composite structural panel. To remedy this fundamental barrier, we invented a new magnetic resonator consisting of very thin folded plates that are suitably nested within one another to form folded-doubled resonators (FDRs) that can be integrated into an actual composite panel. Measurements, using a focused beam electromagnetic characterization system combined with time-domain numerical simulations of the reflection and transmission coefficients of such a composite slab have revealed that indeed the composite has a negative μ over a frequency range of about 9.1-9.35 GHz [S. Nemat-Nasser, S. C. Nemat-Nasser, T. A. Plaisted, A. Starr, and A. Vakil Amirkhizi, in Biomimetics: Biologically Inspired Technologies, edited by Y. Bar Cohen (CRC Press, Boca Raton, FL, 2006)]. Thus, it has become possible to construct a structural composite panel with negative index of refraction by simultaneously creating negative effective ɛ and μ [V. G. Veselago, Sov. Phys. Usp. 10, 509 (1968); R. A. Shelby, D. R. Smith, and S. Schultz, Science 292, 77 (2001); A. F. Starr, P. M. Rye, D. R. Smith, and S. Nemat-Nasser, Phys. Rev. B 70, 113102 (2004)].

  18. Lunar magnetic permeability, magnetic fields, and electrical conductivity temperature

    NASA Technical Reports Server (NTRS)

    Parkin, C. W.

    1978-01-01

    In the time period 1969-1972 a total of five magnetometers were deployed on the lunar surface during four Apollo missions. Data from these instruments, along with simultaneous measurements from other experiments on the moon and in lunar orbit, were used to study properties of the lunar interior and the lunar environment. The principal scientific results from analyses of the magnetic field data are discussed. The results are presented in the following main categories: (1) lunar electrical conductivity, temperature, and structure; (2) lunar magnetic permeability, iron abundance, and core size limits; (3) the local remnant magnetic fields, their interaction with the solar wind, and a thermoelectric generator model for their origin. Relevant publications and presented papers are listed.

  19. AC magnetic susceptibility of Bi2223-system

    NASA Astrophysics Data System (ADS)

    Kimishima, Y.; Inagaki, K.; Tanabe, K.; Nagata, N.; Ichiyanagi, Y.

    1998-01-01

    The AC magnetic susceptibilities χ AC of a Bi2223 sintered sample were measured by the Hartshorn bridge method. The linear AC χ' 0 showed the two-steps behavior at T C1 and T C2, where T C1 > T C2. The χ'0-data between T C1 and T C2 has no H AC-dependence and agreed well with those of powder specimen, and they can be regarded as the intragrain magnetic susceptibility. Below the inter-grain transition temperature T C2 the χ″ 0 showed a positive peak. The temperature dependence of χ' 0 and χ″ 0 were analyzed by the Bean's critical-state model. As a result, the temperature dependence of critical current density J C ∝ (1 - T/T C2) β was obtained with β = 2.3-2.6. The non-linear χ' 2 and χ″ 2 below T C2 resemble the behaviors derived from the Bean model, but the negative divergence of χ' 2 may show the evidence of d-wave paring in the present Bi2223-system.

  20. Numerical study on AC loss characteristics of superconducting power transmission cables comprising coated conductors with magnetic substrates

    NASA Astrophysics Data System (ADS)

    Amemiya, N.; Nakahata, M.

    2007-10-01

    Electromagnetic field analyses were made for mono-layer conductors comprising coated conductors for superconducting power transmission cables in order to evaluate their AC loss characteristics. We focused on the magnetic properties of the substrates of coated conductors. The current distribution in each coated conductor and the magnetic flux profile around each coated conductor were visualized. The influence of relative permeability and the space between coated conductors on the AC loss characteristics of mono-layer conductors were studied based on the visualized current and magnetic flux distributions. The influence of a saturated magnetic property on a calculated AC loss was also discussed.

  1. Demonstrations of Magnetic Phenomena: Measuring the Air Permeability Using Tablets

    ERIC Educational Resources Information Center

    Lara, V. O. M.; Amaral, D. F.; Faria, D.; Vieira, L. P.

    2014-01-01

    We use a tablet to experimentally determine the dependencies of the magnetic field (B) on the electrical current and the axial distance from a coil (z). Our data shows good precision on the inverse cubic dependence of the magnetic field on the axial distance, B?z[superscript -3]. We obtain the value of air permeability µ[subscript air] with good…

  2. Magnetic deflagration in the molecular magnet manganese-12-ac

    NASA Astrophysics Data System (ADS)

    McHugh, Sean

    In 1995, Paulsen and Park [1, 2] observed abrupt spontaneous reversals of the magnetization in crystals of the molecular magnet Mn12-ac, which they dubbed "magnetic avalanches". They suggested that the magnetic avalanches were a thermal runaway process where the reversing spins release heat stimulating further relaxation. Various exotic phenomena were proposed as an alternative explanations [3]. In 2005, Suzuki et al. [4] established that this spontaneous magnetic relaxation occurs as a "front" separating regions of opposing magnetization that propagates at a constant speed through the crystal. They suggested that this propagating front is analogous to a flame in chemical deflagration and introduced the thermal relaxation process, magnetic deflagration. The analysis presented there was limited by lack of data. A more thorough comparison with the theory would require the ability to trigger avalanches in a more controlled way rather than wait for their spontaneous occurrence. The work presented in this thesis is a continuation of the program initiated by Suzuki [4, 5]. Significant progress experimental progress has been made allowing us to trigger avalanches over a wide range of conditions. The magnetization dynamics and the ignition temperatures are studied in detail using an array of micro-sized Hall sensors and Germanium thermometers. In addition, we report the existence of a new species of avalanches consisting only of the fast-relaxing isomers of Mn12-ac, the so-called "minor species". We explore avalanches of both species, as well as the interaction between them. Finally, a detailed analysis is performed to compare the experiment with the theory of magnetic deflagration [6]. We find the theory of magnetic deflagration to be consistent with the data and extract values for the key physical quantities: the thermal diffusivity and avalanche front temperatures. Agreement between our predicted values and an independent measurement of these quantities would provide

  3. In situ detection method for obtaining permeability of Fe-based amorphous alloys: ac resistance measurement for Fe{sub 84}Nb{sub 7}B{sub 9}

    SciTech Connect

    Ichitsubo, Tetsu; Matsubara, Eiichiro; Tanaka, Satoshi; Nishiyama, Nobuyuki; Amiya, Kenji

    2005-01-17

    In this letter, we propose an in situ detection method for obtaining permeability of soft magnetic Fe-based amorphous alloys. The temperature dependence of ac resistance was measured at different frequencies during heat treatment of Fe{sub 84}Nb{sub 7}B{sub 9} amorphous alloys. A significant increase in the ac ({approx}1000 kHz) resistance appears at around 920 K during the heating process, which arises from the skin effect caused by a marked increase in sample permeability. This skin effect diminishes when the sample is heated to approximately 1100 K, which corresponds to the decrease in its permeability. Consequently, we note that the ac resistance measurement is useful for quick in situ assessment to achieve the soft magnetic property of an Fe-based amorphous alloy.

  4. Effects of discontinuous magnetic permeability on magnetodynamic problems

    NASA Astrophysics Data System (ADS)

    Guermond, J.-L.; Léorat, J.; Luddens, F.; Nore, C.; Ribeiro, A.

    2011-07-01

    A novel approximation technique using Lagrange finite elements is proposed to solve magneto-dynamics problems involving discontinuous magnetic permeability and non-smooth interfaces. The algorithm is validated on benchmark problems and is used for kinematic studies of the Cadarache von Kármán Sodium 2 (VKS2) experimental fluid dynamo.

  5. Optical investigation of effective permeability of dilute magnetic dielectrics with magnetic field

    NASA Astrophysics Data System (ADS)

    Banerjee, Ananya; Sarkar, A.

    2016-05-01

    The prime objective of this paper is to investigate the magnetic nature of dilute magnetic dielectrics (DMD) under variation of external magnetic field. The said variation is studied over developed nano-sized Gadolinium Oxide as a DMD system. The observed experimental field variation of the effective magnetic permeability is analyzed results of optical experiment. The experiment records the variation of Brewster angle of incident polarized LASER beam from the surface of developed DMD specimen with applied out of plane external magnetic field. The effective refractive index and hence relative magnetic permeability were estimated following electro-magnetic theory. The overall results obtained and agreement between theory and experiment are good.

  6. Stress state evaluation in low carbon and TRIP steels by magnetic permeability

    NASA Astrophysics Data System (ADS)

    Kouli, M.-E.; Giannakis, M.

    2016-03-01

    Magnetic permeability is an indicative factor for the steel health monitoring. The measurements of magnetic permeability lead to the evaluation of the stress state of any ferromagnetic steel. The magnetic permeability measurements were conducted on low carbon and TRIP steel samples, which were subjected to both tensile and compressive stresses. The results indicated a direct correlation of the magnetic permeability with the mechanical properties, the stress state and the microstructural features of the examined samples.

  7. Calculation of the energy loss in giant magnetic impedance elements using the complex magnetic permeability spectra

    NASA Astrophysics Data System (ADS)

    Rustemaj, Driton; Mukherjee, Debashis

    2013-01-01

    The giant magnetic impedance (GMI) effect in ferromagnetic materials has been investigated for sensing applications. The GMI properties were evaluated via numerical solution of the complex magnetic permeability of the material. MATLAB simulation was carried out to study the frequency dependence of magnetic permeability via obtaining solutions of the Landau-Lifshitz-Gilbert (LLG) and the Maxwell's equations. The results indicate that the complex magnetic permeability peaks at a frequency of 6 GHz, corresponding to the ferromagnetic resonant (FMR) frequency, where the energy loss is maximum. A variation of the Gilbert damping parameter (α) associated with the LLG equation inversely affects this peak value. The area under the curve of complex magnetic permeability, calculated through counting the number of pixels within the image, provides an estimate of the average energy loss density within the material and appears to be consistent with the variation of the peak intensity.

  8. Broadband non-unity magnetic permeability in planar hyperbolic metamaterials

    NASA Astrophysics Data System (ADS)

    Papadakis, Georgia Theano; Fleischman, Dagny; Davoyan, Artur R.; Thyagarajan, Krishnan; Atwater, Harry A.

    Metal/dielectric heterostructures with extreme anisotropy and topologically nontrivial dispersion are of fundamental and applied interest due to unique optical and opto-electronic properties. Here we demonstrate that, surprisingly, such systems exhibit a broadband non-unity magnetic response. Typically the electromagnetic properties of such metal-dielectric stacks are deduced from effective medium theories for unbounded, i.e., infinite in size periodic arrangements (c.f., Maxwell-Garnett approximation). In this talk, we show that this description is incomplete for metamaterials with finite number of layers. We demonstrate that a few-layer metal-dielectric metamaterial exhibits a non-unity magnetic permeability across the whole visible spectrum. The response can be diamagnetic or paramagnetic depending on the type of the terminating layers: metallic or dielectric, with non-resonant magnetic permeability that can be engineered to attain values as low as -2 or as high as 2. We have developed a theoretical model that explains the underlying mechanism. We further experimentally validate non-unity effective permeability in the optical range of frequencies. Ag/SiO2 and Ge-based metamaterials fabricated with electron beam evaporation are characterized by ellipsometric measurements and also phase and amplitude of transmittance/reflectance. These results open pathways for creating broadband subwavelength magnetic structures in the visible regime.

  9. Complex permeability and core loss of soft magnetic Fe-based nanocrystalline powder cores

    NASA Astrophysics Data System (ADS)

    Füzerová, Jana; Füzer, Ján; Kollár, Peter; Bureš, Radovan; Fáberová, Mária

    2013-11-01

    Rapidly quenched ribbons of Fe73Cu1Nb3Si16B7 were ball milled and cryomilled to get powder and warm consolidated to get bulk compacts. The data presented here are relative to different experimental procedures, one corresponding to milling at room temperature (sample R1) and the other corresponding to cryomilling at temperature of liquid nitrogen (sample L1). It was found that the properties of the initial powder influenced the density, the electrical resistivity and electromagnetic properties of the resulting bulk alloys. Permeability and core loss are structure sensitive and depend on factors such as powder size and shape, porosity, purity, and internal stress. Permeability spectra of sample R1 decreases with increasing the frequency and its values are larger than that for sample L1 at low frequencies. On the other hand the permeability of sample L1 remains steady up to 1 kHz and at certain frequency is larger than that for sample R1. Also there are different frequency dependences of the imaginary parts of permeability and loss factor, respectively. The cryomilling of the amorphous ribbon positively influences on the AC magnetic properties at higher frequencies (above 100 Hz) of resulting bulk sample.

  10. Reentrant ac Magnetic Susceptibility in Josephson-Junction Arrays

    SciTech Connect

    Araujo-Moreira, F.M.; Barbara, P.; Cawthorne, A.B.; Lobb, C.J.

    1997-06-01

    We have measured the complex ac magnetic susceptibility of unshunted Josephson-junction arrays as a function of temperature T , amplitude of the excitation field h{sub ac} , and external magnetic field H{sub dc} . For small h{sub ac} Meissner screening occurs. For larger h{sub ac} , however, the screening is reentrant in T . This reentrance is not thermodynamic but dynamic and arises from the paramagnetic contribution of multijunction loops. This result gives an alternative explanation of the paramagnetic Meissner effect observed in granular superconductors. Experimental results are in agreement with a simplified model based on a single loop containing four junctions. {copyright} {ital 1997} {ital The American Physical Society}

  11. Effects of domain, grain, and magnetic anisotropy distributions on magnetic permeability: Monte-Carlo approach

    SciTech Connect

    Chun, Jaehun; Jones, Anthony M.; McCloy, John S.

    2012-07-23

    Existing approaches for prediction of the tensor permeability of polycrystalline ferrites may not provide reasonable estimates of demagnetized permeability below the spin resonance (i.e., low-field loss region) or in cases of partial magnetization. We propose an approach which solves the coupled Landau-Lifshitz-Gilbert equation for the dynamic magnetic fields including the minimization of free energy to determine the equilibrium magnetization direction. Unlike previous models, we employ a Monte-Carlo approach to easily calculate the (ensemble) averages of permeability over various domain/grain structures and magnetic anisotropy conditions. Material differences, such as those resulting from different preparation methods, are expressed by using probability density functions (p.d.f.) for anisotropy angle (easy axis angle), grain demagnetization factor (ng), and domain demagnetization factor (nd). Effects on the permeability tensor of grain and domain demagnetization factors and anisotropy field relative to saturation magnetization are discussed for the partially magnetized states for polycrystalline ferrites. It is found that the grain structure (i.e., grain demagnetization distribution) has a smaller effect on the frequency dependent permeability than does the same distribution of domains (i.e., domain demagnetization distribution).

  12. Ac magnetic susceptibility study of in vivo nanoparticle biodistribution

    NASA Astrophysics Data System (ADS)

    Gutiérrez, L.; Mejías, R.; Barber, D. F.; Veintemillas-Verdaguer, S.; Serna, C. J.; Lázaro, F. J.; Morales, M. P.

    2011-06-01

    We analysed magnetic nanoparticle biodistribution, before and after cytokine conjugation, in a mouse model by ac susceptibility measurements of the corresponding resected tissues. Mice received repeated intravenous injections of nanoparticle suspension for two weeks and they were euthanized 1 h after the last injection. In general, only 10% of the total injected nanoparticles after multiple exposures were found in tissues. The rest of the particles may probably be metabolized or excreted by the organism. Our findings indicate that the adsorption of interferon to DMSA-coated magnetic nanoparticles changes their biodistribution, reducing the presence of nanoparticles in lungs and therefore their possible toxicity. The specific targeting of the particles to tumour tissues by the use of an external magnetic field has also been studied. Magnetic nanoparticles were observed by transmission electron microscopy in the targeted tissue and quantified by ac magnetic susceptibility.

  13. AC Loss Analysis on the Superconducting Coupling Magnet in MICE

    SciTech Connect

    Wu, Hong; Wang, Li; Green, Michael; Li, LanKai; Xu, FengYu; Liu, XiaoKun; Jia, LinXinag

    2008-07-08

    A pair of coupling solenoids is used in MICE experiment to generate magnetic field which keeps the muons within the iris of thin RF cavity windows. The coupling solenoids have a 1.5-meter inner diameter and will produce 7.4 T peak magnetic field. Three types of AC losses in coupling solenoid are discussed. The affect of AC losses on the temperature distribution within the cold mass during charging and rapid discharging process is analyzed also. The analysis result will be further confirmed by the experiment of the prototype solenoid for coupling solenoid, which will be designed, fabricated and tested at ICST.

  14. Magnetic flux penetration into twisted multifilamentary coated superconductors subjected to ac transverse magnetic fields

    NASA Astrophysics Data System (ADS)

    Amemiya, Naoyuki; Sato, Susumu; Ito, Takeshi

    2006-12-01

    ac losses in superconductors are generated by the magnetic flux and current penetration into them. To reveal the magnetic flux and current penetration processes in twisted multifilamentary coated superconductors in which the thin superconductor layer is subdivided into filaments and then twisted as a whole for ac loss reduction, a theoretical model for electromagnetic field analysis was developed based on the power law E-J (electric-field-current-density) characteristic for the superconductor and a thin strip approximation of the conductor. The developed theoretical model was implemented into a numerical code using the finite element method to calculate and visualize the current and magnetic flux distributions. The magnetization losses in twisted multifilamentary coated superconductors exposed to ac transverse magnetic fields were calculated from the temporal evolutions of the current distribution to demonstrate the effect of the twisted multifilamentary architecture on ac loss reduction.

  15. Nonlinear magnetization relaxation of superparamagnetic nanoparticles in superimposed ac and dc magnetic bias fields

    NASA Astrophysics Data System (ADS)

    Titov, Serguey V.; Déjardin, Pierre-Michel; El Mrabti, Halim; Kalmykov, Yuri P.

    2010-09-01

    The nonlinear ac response of the magnetization M(t) of a uniaxially anisotropic superparamagnetic nanoparticle subjected to both ac and dc bias magnetic fields of arbitrary strengths and orientations is determined by averaging Gilbert’s equation augmented by a random field with Gaussian white-noise properties in order to calculate exactly the relevant statistical averages. It is shown that the magnetization dynamics of the uniaxial particle driven by a strong ac field applied at an angle to the easy axis of the particle (so that the axial symmetry is broken) alters drastically leading to different nonlinear effects due to coupling of the thermally activated magnetization reversal mode with the precessional modes of M(t) via the driving ac field.

  16. Exchange anisotropy determined by magnetic field dependence of ac susceptibility

    NASA Astrophysics Data System (ADS)

    Rodríguez-Suárez, R. L.; Vilela Leão, L. H.; de Aguiar, F. M.; Rezende, S. M.; Azevedo, A.

    2003-10-01

    ac susceptibility measurements of ferromagnetic/antiferromagnetic (FM/AF) bilayers are usually performed as a function of the temperature. In this work we describe measurements of transverse biased ac susceptibility (χt) of FM/AF bilayers as a function of the applied magnetic field H0. The measurements were carried out at room temperature by means of an ac magneto-optical Kerr effect susceptometer. The χt-1(H0) dependence, at the saturation magnetization regime, exhibits a linear behavior with the applied field parallel and perpendicular to the exchange bias direction. The linear extrapolation of χt-1 versus H0 cuts the abscissa at asymmetrical values of field due to the exchange bias coupling. The inverse susceptibility is calculated in the saturation regime by a model, which takes into account the free energy of both layers plus a term corresponding to the interfacial coupling. The exchange coupling field (HE) and uniaxial anisotropy (HU) are extracted from the best fit to the experimental results. The results obtained are crosschecked by those obtained from ferromagnetic resonance (FMR) and dc magnetometry. The measurements of the exchange bias and the uniaxial field in all of the three analyzed bilayers gave values that are consistently lower when measured by FMR than those obtained by ac and dc magnetometry. It is argued that the apparently discrepant values of HE and HU, obtained by different techniques, might be explained by existence of unstable AF grains at the AF/FM interface.

  17. AC Losses in the MICE Channel Magnets -- Is This a Curse or aBlessing?

    SciTech Connect

    Green, M.A.; Wu, H.; Wang, L.; Kai, L.L.; Jia, L.X.; Yang, S.Q.

    2008-01-31

    This report discusses the AC losses in the MICE channelmagnets during magnet charging and discharging. This report talks aboutthe three types of AC losses in the MICE magnets; the hysteretic AC lossin the superconductor, the coupling AC loss in the superconductor and theeddy current AC loss in the magnet mandrel and support structure. AClosses increase the heat load at 4 K. The added heat load increases thetemperature of the second stage of the cooler. In addition, AC losscontributes to the temperature rise between the second stage cold headand the high field point of the magnet, which is usually close to themagnet hot spot. These are the curses of AC loss in the MICE magnet thatcan limit the rate at which the magnet can be charge or discharged. Ifone is willing to allow some of the helium that is around the magnet toboil away during a magnet charge or discharge, AC losses can become ablessing. The boil off helium from the AC losses can be used to cool theupper end of the HTS leads and the surrounding shield. The AC losses arepresented for all three types of MICE magnets. The AC loss temperaturedrops within the coupling magnet are presented as an example of how boththe curse and blessing of the AC losses can be combined.

  18. Testing of a First Order AC Magnetic Susceptometer

    NASA Astrophysics Data System (ADS)

    Fukuda, Ryan; Sunny, Smitha; Ho, Pei-Chun

    2011-11-01

    A first-order AC magnetic susceptometer has been constructed and tested to find the magnetic response of strongly correlated electron materials. The instrument works by using a primary coil to apply a small AC magnetic field of .104 Oe to a sample with a cylindrical coil space of length .635 cm and diameter .355 cm. A lock-in amplifier is used to monitor the induced voltage from a set of secondary coils. By coupling a temperature-controlled system with this instrument, the change in the magnetic signal with respect to temperature is measured. Monitoring the signal changes may indicate the temperature that causes the material to transition to either a ferromagnetic, anti-ferromagnetic, or superconducting state. A 122.47 mg Gd polycrystal was used to test our susceptometer. The data qualitatively agrees with the previous results of magnetization vs. temperature of Gd single crystals by Nigh et al. [1]: there is a steep increase in the pick-up signal at 300 K where Gd becomes ferromagnetic and a peak at 210 K [1]. This susceptometer will be used for our future investigation of magnetic properties of rare earth compounds and nanoparticles in the temperature range of 10 K to 300 K. [4pt] [1] H. E. Nigh, S. Legvold, and F. H. Spedding, Physical Review 132, 1092 (1963)

  19. AC Magnetic Field Frequency Dependence of Magnetoacoustic Emission

    NASA Technical Reports Server (NTRS)

    Namkung, M.; Wincheski, B.; Fulton, J. P.; DeNale, R.

    1992-01-01

    Our recent study has proved a strong correlation between the low-frequency AC applied magnetic field amplitude dependence of the asymmetry of the magnetoacoustic emission (MAE) burst and the strength of the domain wall-defect interaction in iron-base ferromagnets. For the present study the AC magnetic field frequency dependence of the asymmetry has been investigated in the range of 1 to 200 Hz. When represented by the third moment of the rectified acoustic emission pulses, the asymmetry becomes a bell-shaped function of frequency with its center located around 25 Hz. This experiment has been performed with low carbon, high yield stress steel specimens of three different levels of domain wall-defect interaction strength. The results show that the increase in the interaction strength causes a vertical down shift of the asymmetry in the entire frequency range investigated.

  20. Sensorless operation of surface mount permanent magnet AC (PMAC) motors

    SciTech Connect

    Toliyat, H.A.; Rahman, K.M.; Shet, D.S.

    1999-12-01

    A sensorless field oriented control scheme for surface mount permanent magnet ac (PMAC) motor with split phase stator windings is presented. This motor is obtained by splitting the phase windings of a conventional three phase motor. The six-phase motor, however is run as a three-phase motor by connecting the split phase stator windings in series, while the taps are made available for voltage measurements. By measuring the terminal voltages and the line currents, absolute position of the permanent magnet ac motor driven by a current regulated PWM inverter with a hysteresis controller is estimated. The estimated position information is independent of the stator resistance, thus this scheme is even applicable at low speeds. Results are presented to show the effectiveness of the new controller, and it is also shown that the position error is negligible.

  1. A flux-coupled ac/dc magnetizing device

    NASA Astrophysics Data System (ADS)

    Gopman, D. B.; Liu, H.; Kent, A. D.

    2013-06-01

    We report on an instrument for applying ac and dc magnetic fields by capturing the flux from a rotating permanent magnet and projecting it between two adjustable pole pieces. This can be an alternative to standard electromagnets for experiments with small samples or in probe stations in which an applied magnetic field is needed locally, with advantages that include a compact form-factor, very low power requirements and dissipation as well as fast field sweep rates. This flux capture instrument (FLUXCAP) can produce fields from -400 to +400 mT, with field resolution less than 1 mT. It generates static magnetic fields as well as ramped fields, with ramping rates as high as 10 T/s. We demonstrate the use of this apparatus for studying the magnetotransport properties of spin-valve nanopillars, a nanoscale device that exhibits giant magnetoresistance.

  2. Water Permeability of Chlorella Cell Membranes by Nuclear Magnetic Resonance

    PubMed Central

    Stout, Darryl G.; Steponkus, Peter L.; Bustard, Larry D.; Cotts, Robert M.

    1978-01-01

    Measurement by two nuclear magnetic resonance (NMR) techniques of the mean residence time τa of water molecules inside Chlorella vulgaris (Beijerinck) var. “viridis” (Chodot) is reported. The first is the Conlon and Outhred (1972 Biochim Biophys Acta 288: 354-361) technique in which extracellular water is doped with paramagnetic Mn2+ ions. Some complications in application of this technique are identified as being caused by the affinity of Chlorella cell walls for Mn2+ ions which shortens the NMR relaxation times of intra- and extracellular water. The second is based upon observations of effects of diffusion on the spin echo of intra- and extracellular water. Echo attenuation of intracellular water is distinguished from that of extracellular water by the extent to which diffusive motion is restricted. Intracellular water, being restricted to the cell volume, suffers less echo attenuation. From the dependence of echo amplitude upon gradient strength at several values of echo time, the mean residence time of intracellular water can be determined. From the mean residence time of intracellular water, the diffusional water permeability coefficient of the Chlorella membrane is calculated to be 2.1 ± 0.4 × 10−3 cm sec−1. PMID:16660456

  3. Hysteresis of sextupole and ac loss in Energy Doubler dipole magnets

    SciTech Connect

    Ishibashi, K.

    1982-06-18

    A simple model gave utilized for calculation of magnetization effects on ac loss and sextupole for Energy Doubler dipole magnets. The calculation in the simple model gave an underestimation of ac loss by about 30%. Results of computation on ac harmonics were also described.

  4. Measurements of magnetic permeability and H[sub c] of magnet steels using digital techniques

    SciTech Connect

    Thomas, R.; Morgan, G.

    1992-01-01

    The magnet-to-magnet variations in the dipole field of superconducting accelerator magnets must fall within specified tolerances to avoid excessive beam losses during injection. At injection field levels ([approximately] 0.4 T for RHIC), the variations in the field attributable to the iron arise from variations in the chemical impurities, cold working and heat treatment. These structure-sensitive effects can be characterized by measuring the permeability and coercive force, H[sub c], of iron samples. A digital permeameter was developed to perform precise measurements of the magnetic properties of ring samples. An arbitrary function generator and two high-precision digital multimeters were connected to a desktop computer using the IEEE-488 bus, and software was written to automatically acquire and analyze the data. Through the use of the arbitrary waveform generator, the effect of varying the period of the B-H loop and the effect of varying the shape of the H waveform were explored. The effects of annealing, bending and flattening, and temperature on H[sub c] and the relative permeability have been investigated for samples of magnet steel from several manufacturers.

  5. Measurements of magnetic permeability and H{sub c} of magnet steels using digital techniques

    SciTech Connect

    Thomas, R.; Morgan, G.

    1992-11-01

    The magnet-to-magnet variations in the dipole field of superconducting accelerator magnets must fall within specified tolerances to avoid excessive beam losses during injection. At injection field levels ({approximately} 0.4 T for RHIC), the variations in the field attributable to the iron arise from variations in the chemical impurities, cold working and heat treatment. These structure-sensitive effects can be characterized by measuring the permeability and coercive force, H{sub c}, of iron samples. A digital permeameter was developed to perform precise measurements of the magnetic properties of ring samples. An arbitrary function generator and two high-precision digital multimeters were connected to a desktop computer using the IEEE-488 bus, and software was written to automatically acquire and analyze the data. Through the use of the arbitrary waveform generator, the effect of varying the period of the B-H loop and the effect of varying the shape of the H waveform were explored. The effects of annealing, bending and flattening, and temperature on H{sub c} and the relative permeability have been investigated for samples of magnet steel from several manufacturers.

  6. Physical aspects of magnetic hyperthermia: Low-frequency ac field absorption in a magnetic colloid

    NASA Astrophysics Data System (ADS)

    L. Raikher, Yu.; Stepanov, V. I.

    2014-11-01

    A uniaxially anisotropic superparamagnetic particle suspended in a viscous fluid and subjected to an ac field is considered. Consistently taking into account both internal (Néel) and external (Brownian) magnetic relaxations, a simple expression for the dynamic susceptibility is obtained. This result, with regard to the ac field energy absorption, is compared to the common heuristic approach. This is done for a model polydisperse colloid containing maghemite nanoparticles, which are assumed to posses either bulk or surface magnetic anisotropy. It is shown that viscous losses caused by the particle motion in a fluid matrix make important contribution to the full magnetic response of a ferrocolloid and, thus, its ability to absorb the ac field energy. The obtained exact expression, which takes in both dissipation mechanisms, paves the way to correct optimization of the nanoparticle-mediated heating effect.

  7. Temperature dependence dynamical permeability characterization of magnetic thin film using near-field microwave microscopy.

    PubMed

    Hung, Le Thanh; Phuoc, Nguyen N; Wang, Xuan-Cong; Ong, C K

    2011-08-01

    A temperature dependence characterization system of microwave permeability of magnetic thin film up to 5 GHz in the temperature range from room temperature up to 423 K is designed and fabricated as a prototype measurement fixture. It is based on the near field microwave microscopy technique (NFMM). The scaling coefficient of the fixture can be determined by (i) calibrating the NFMM with a standard sample whose permeability is known; (ii) by calibrating the NFMM with an established dynamic permeability measurement technique such as shorted microstrip transmission line perturbation method; (iii) adjusting the real part of the complex permeability at low frequency to fit the value of initial permeability. The algorithms for calculating the complex permeability of magnetic thin films are analyzed. A 100 nm thick FeTaN thin film deposited on Si substrate by sputtering method is characterized using the fixture. The room temperature permeability results of the FeTaN film agree well with results obtained from the established short-circuited microstrip perturbation method. Temperature dependence permeability results fit well with the Landau-Lifshitz-Gilbert equation. The temperature dependence of the static magnetic anisotropy H(K)(sta), the dynamic magnetic anisotropy H(K)(dyn), the rotational anisotropy H(rot), together with the effective damping coefficient α(eff), ferromagnetic resonance f(FMR), and frequency linewidth Δf of the thin film are investigated. These temperature dependent magnetic properties of the magnetic thin film are important to the high frequency applications of magnetic devices at high temperatures. PMID:21895260

  8. Magnetic tweezers with high permeability electromagnets for fast actuation of magnetic beads

    SciTech Connect

    Chen, La; Offenhäusser, Andreas; Krause, Hans-Joachim

    2015-04-15

    As a powerful and versatile scientific instrument, magnetic tweezers have been widely used in biophysical research areas, such as mechanical cell properties and single molecule manipulation. If one wants to steer bead position, the nonlinearity of magnetic properties and the strong position dependence of the magnetic field in most magnetic tweezers lead to quite a challenge in their control. In this article, we report multi-pole electromagnetic tweezers with high permeability cores yielding high force output, good maneuverability, and flexible design. For modeling, we adopted a piece-wise linear dependence of magnetization on field to characterize the magnetic beads. We implemented a bi-linear interpolation of magnetic field in the work space, based on a lookup table obtained from finite element simulation. The electronics and software were custom-made to achieve high performance. In addition, the effects of dimension and defect on structure of magnetic tips also were inspected. In a workspace with size of 0.1 × 0.1 mm{sup 2}, a force of up to 400 pN can be applied on a 2.8 μm superparamagnetic bead in any direction within the plane. Because the magnetic particle is always pulled towards a tip, the pulling forces from the pole tips have to be well balanced in order to achieve control of the particle’s position. Active video tracking based feedback control is implemented, which is able to work at a speed of up to 1 kHz, yielding good maneuverability of the magnetic beads.

  9. Magnetic tweezers with high permeability electromagnets for fast actuation of magnetic beads.

    PubMed

    Chen, La; Offenhäusser, Andreas; Krause, Hans-Joachim

    2015-04-01

    As a powerful and versatile scientific instrument, magnetic tweezers have been widely used in biophysical research areas, such as mechanical cell properties and single molecule manipulation. If one wants to steer bead position, the nonlinearity of magnetic properties and the strong position dependence of the magnetic field in most magnetic tweezers lead to quite a challenge in their control. In this article, we report multi-pole electromagnetic tweezers with high permeability cores yielding high force output, good maneuverability, and flexible design. For modeling, we adopted a piece-wise linear dependence of magnetization on field to characterize the magnetic beads. We implemented a bi-linear interpolation of magnetic field in the work space, based on a lookup table obtained from finite element simulation. The electronics and software were custom-made to achieve high performance. In addition, the effects of dimension and defect on structure of magnetic tips also were inspected. In a workspace with size of 0.1 × 0.1 mm(2), a force of up to 400 pN can be applied on a 2.8 μm superparamagnetic bead in any direction within the plane. Because the magnetic particle is always pulled towards a tip, the pulling forces from the pole tips have to be well balanced in order to achieve control of the particle's position. Active video tracking based feedback control is implemented, which is able to work at a speed of up to 1 kHz, yielding good maneuverability of the magnetic beads. PMID:25933874

  10. New levitation scheme with AC superconducting magnet for EDS MAGLEV system

    SciTech Connect

    Kim, D.H.; Lee, J.K.; Hahn, S.Y.; Cha, G.

    1996-09-01

    This paper proposes a new magnetic levitation scheme which is able to generate levitation force for all speeds including a standstill. Auxiliary wheels which are needed in EDS MAGLEV vehicle can be eliminated. This scheme uses AC superconducting magnets to generate levitation force. In this paper, magnetic fields, forces and power dissipations generated by AC magnets moving above a conducting slab are calculated analytically. Results of calculation show characteristics of EDS system with AC magnet, such as levitation force and loss, are superior to those of EDS system with DC magnets for all speeds.

  11. ac susceptibility study of a magnetite magnetic fluid

    NASA Astrophysics Data System (ADS)

    Ayala-Valenzuela, O. E.; Matutes-Aquino, J. A.; Galindo, J. T. Elizalde; Botez, C. E.

    2009-04-01

    Magnetite nanometric powder was synthesized from metal salts using a coprecipitation technique. The powders were used to produce magnetic fluid via a peptization method, with hydrocarbon Isopar M as liquid carrier and oleic acid as surfactant. The complex magnetic susceptibility χ =χ'+iχ″ was measured as a function of temperature T in steps of 2.5 K from 3 to 298 K for frequencies ranging from f =10 to 10 000 Hz. The magnetic fluid real and imaginary components of the ac susceptibility show a prominent maximum at temperatures that increase with the measuring frequency, which is attributed to a spin-glass-like behavior. The peak temperature Tp1 of χ″ depends on f following the Vogel-Fulcher law f =f0 exp[E /kB(Tp1-T0)], where f0 and E are positive constants and T0 is a parameter related to particle interactions. There is another kind of peak temperature, Tp2, in the loss factor tan δ =χ″/χ' which is related to a magnetic aftereffect. The peak temperature Tp2 is far less than Tp1 and shows an Arrhenius-type dependence on f.

  12. Rapid magnetic microfluidic mixer utilizing AC electromagnetic field.

    PubMed

    Wen, Chih-Yung; Yeh, Cheng-Peng; Tsai, Chien-Hsiung; Fu, Lung-Ming

    2009-12-01

    This paper presents a novel simple micromixer based on stable water suspensions of magnetic nanoparticles (i.e. ferrofluids). The micromixer chip is built using standard microfabrication and simple soft lithography, and the design can be incorporated as a subsystem into any chemical microreactor or a miniaturized biological sensor. An electromagnet driven by an AC power source is used to induce transient interactive flows between a ferrofluid and Rhodamine B. The alternative magnetic field causes the ferrofluid to expand significantly and uniformly toward Rhodamine B, associated with a great number of extremely fine fingering structures on the interface in the upstream and downstream regions of the microchannel. These pronounced fingering patterns, which have not been observed by other active mixing methods utilizing only magnetic force, increase the mixing interfacial length dramatically. Along with the dominant diffusion effects occurring around the circumferential regions of the fine finger structures, the mixing efficiency increases significantly. The miscible fingering instabilities are observed and applied in the microfluidics for the first time. This work is carried with a view to developing functionalized ferrofluids that can be used as sensitive pathogen detectors and the present experimental results demonstrate that the proposed micromixer has excellent mixing capabilities. The mixing efficiency can be as high as 95% within 2.0 s and a distance of 3.0 mm from the inlet of the mixing channel, when the applied peak magnetic field is higher than 29.2 Oe and frequency ranges from 45 to 300 Hz. PMID:19921677

  13. Iron abundance and magnetic permeability of the moon

    NASA Technical Reports Server (NTRS)

    Parkin, C. W.; Daily, W. D.; Dyal, P.

    1974-01-01

    A set of simultaneous data from the Apollo 12 lunar surface magnetometer and the Explorer 35 Ames magnetometer are used to construct a whole-moon hysteresis curve, from which a new value of global lunar permeability is determined to be mu = 1.012 + or - 0.006. The corresponding global induced dipole moment is 2.1 x 10 to the 18th power gauss-cucm for typical inducing fields of .1000 gauss in the lunar environment. From the permeability measurement, lunar free iron abundance is determined to be 2.5 + or - 2.0 wt. %. Total iron abundance is calculated for two assumed compositional models of the lunar interior: a free iron/orthopyroxene lunar composition and a free iron/olivine composition. The overall lunar total iron abundance is determined to be 9.0 + or - 4.7 wt. %. Other lunar models with a small iron core and with a shallow iron-rich layer are discussed in light of the measured global permeability. Effects on permeability and iron content calculations due to a possible lunar ionosphere are also considered.

  14. Iron abundance and magnetic permeability of the moon

    NASA Technical Reports Server (NTRS)

    Parkin, C. W.; Daily, W. D.; Dyal, P.

    1974-01-01

    A larger set of simultaneous data from the Apollo 12 lunar surface magnetometer and the Explorer 35 Ames magnetometer are used to construct a whole-moon hysteresis curve, from which a new value of global lunar permeability is determined to be mu = 1.012 + or - 0.006. The corresponding global induced dipole moment is 2.1 times ten to the eighteenth power gauss-cu cm for typical inducing fields of one ten-thousandth gauss in the lunar environment. From the permeability measurement, lunar free iron abundance is determined to be 2.5 + or - 2.0 wt %. Total iron abundance (sum of iron in the ferromagnetic and paramagnetic states) is calculated for two assumed compositional models of the lunar interior: a free iron/orthopyroxene lunar composition and a free iron/olivine composition. The overall lunar total iron abundance is determined to be 9.0 + or - 4.7 wt %. Other lunar models with a small iron core and with a shallow iron-rich layer are discussed in light of the measured global permeability. Effects on permeability and iron content calculations due to a possible lunar ionosphere are also considered.

  15. A multi-state magnetic memory dependent on the permeability of Metglas

    SciTech Connect

    Petrie, J. R.; Wieland, K. A.; Timmerwilke, J. M.; Burke, R. A.; Newburgh, G. A.; Fischer, G. A.; Edelstein, A. S.; Barron, S. C.; Burnette, J. E.

    2015-04-06

    A three-state magnetic memory was developed based on differences in the magnetic permeability of a soft ferromagnetic media, Metglas 2826MB (Fe{sub 40}Ni{sub 38}Mo{sub 4}B{sub 18}). By heating bits of a 250 nm thick Metglas film with 70–100 mW of laser power, we were able to tune the local microstructure, and hence, the permeability. Ternary memory states were created by using lower laser power to enhance the initial permeability through localized atomic rearrangement and higher power to reduce the permeability through crystallization. The permeability of the bits was read by detecting variations in an external 32 Oe probe field within 10 μm of the media via a magnetic tunnel junction read head. Compared to data based on remanent magnetization, these multi-permeability bits have enhanced insensitivity to unexpected field and temperature changes. We found that data was not corrupted after exposure to fields of 1 T or temperatures of 423 K, indicating the effectiveness of this multi-state approach for safely storing large amounts of data.

  16. Permeability mapping in porous media by magnetization prepared centric-scan SPRITE

    NASA Astrophysics Data System (ADS)

    Romanenko, Konstantin V.; Balcom, Bruce J.

    2011-02-01

    The ability of porous media to transmit fluids is commonly referred to as permeability. The concept of permeability is central for hydrocarbon recovery from petroleum reservoirs and for studies of groundwater flow in aquifers. Spatially resolved measurements of permeability are of great significance for fluid dynamics studies. A convenient concept of local Darcy's law is suggested for parallel flow systems. The product of porosity and mean velocity images in the plane across the average flow direction is directly proportional to permeability. Single Point Ramped Imaging with T 1 Enhancement (SPRITE) permits reliable quantification of local fluid content and flow in porous media. It is particularly advantageous for reservoir rocks characterized by fast magnetic relaxation of a saturating fluid. Velocity encoding using the Cotts pulsed field gradient scheme improves the accuracy of measured flow parameters. The method is illustrated through measurements of 2D permeability maps in a capillary bundle, glass bead packs and composite sandstone samples.

  17. Ac magnetorestriction hysteresis and magnetization direction in grain oriented silicon steels

    SciTech Connect

    Mogi, Hisashi; Matsuo, Yukio; Kumano, Tomoji

    1999-09-01

    A hysteresis curve of ac magnetostriction was measured, magnetizing a grain oriented silicon steel in the direction deviated from rolling direction of a sample. The ac magnetostriction ({lambda} ac) curves were analyzed as harmonics in the interest of noise spectrum of such as a power transformer. The domain structure model in this magnetostriction process was proposed. The hysteresis was large in the magnetization direction inclined at 30 and 90{degree} from the rolling direction.

  18. Magnetic properties of Fe-based ribbons with controlled permeability prepared by continuous pulse annealing under tensile stress

    NASA Astrophysics Data System (ADS)

    Takagi, Kotaro; Yanai, Takeshi; Takahashi, Ken-ichiro; Nakano, Masaki; Fukunaga, Hirotoshi; Yoshizawa, Yoshihito

    2009-04-01

    An amorphous Fe73.5Cu1Nb3Si15.5B7 ribbon was pulse annealed continuously under tensile stress by being passed through in an infrared furnace switched on and off repeatedly for preparation of a nanocrystallized toroidal core with controlled permeability. Optimization of the duty ratio D(=Ton/T) of the furnace enabled us to obtain ribbons with low Hc(<10 A/m) and completely developed anisotropy under a high moving velocity of the ribbon, 50 cm/min. ac magnetic properties of a toroidal core, which is made from the pulse-annealed ribbon, at Bm=0.1 T were measured in the frequency range of 0.1-1 MHz. The loss of the prepared core at f =0.1 MHz is 0.50 J/m3, which is lower than those for a gapped ferrite, sendust powder, and amorphous powder core. The relative permeability of approximately 330 was constant up to 1 MHz. These results suggest that the continuous stress annealing by pulse annealing method is one of the hopeful methods for preparation of a long ribbon with excellent magnetic properties.

  19. AC magnetic field losses in BSCCO-2223 superconducting tapes

    SciTech Connect

    Lelovic, M.; Mench, S.; Deis, T.

    1997-09-01

    The AC magnetic losses at power frequencies (60 Hz) were investigated for mono- and multifilament Ag-sheathed (Bi, Pb){sub 2}Sr{sub 2}Ca{sub 2}Cu{sub 3}O{sub y} (BSCCO-2223) tapes with similar transport critical current (I{sub c}) values at 77 K. The multifilament sample exhibited higher losses than the monofilament under the same conditions. Loss peaks are discussed in terms of intergranular, intragranular and eddy current losses. Because of BSCCO`s anisotropy, field orientation has a large effect on the magnitude of these peaks, even at relatively small angles. Losses for fields applied parallel to the c-axis of the textured BSCCO grains are larger by more than one order of magnitude than those applied perpendicular.

  20. Spectroscopic AC susceptibility imaging (sASI) of magnetic nanoparticles

    NASA Astrophysics Data System (ADS)

    Ficko, Bradley W.; Nadar, Priyanka M.; Diamond, Solomon G.

    2015-02-01

    This study demonstrates a method for alternating current (AC) susceptibility imaging (ASI) of magnetic nanoparticles (mNPs) using low cost instrumentation. The ASI method uses AC magnetic susceptibility measurements to create tomographic images using an array of drive coils, compensation coils and fluxgate magnetometers. Using a spectroscopic approach in conjunction with ASI, a series of tomographic images can be created for each frequency measurement set and is termed sASI. The advantage of sASI is that mNPs can be simultaneously characterized and imaged in a biological medium. System calibration was performed by fitting the in-phase and out-of-phase susceptibility measurements of an mNP sample with a hydrodynamic diameter of 100 nm to a Brownian relaxation model (R2=0.96). Samples of mNPs with core diameters of 10 and 40 nm and a sample of 100 nm hydrodynamic diameter were prepared in 0.5 ml tubes. Three mNP samples were arranged in a randomized array and then scanned using sASI with six frequencies between 425 and 925 Hz. The sASI scans showed the location and quantity of the mNP samples (R2=0.97). Biological compatibility of the sASI method was demonstrated by scanning mNPs that were injected into a pork sausage. The mNP response in the biological medium was found to correlate with a calibration sample (R2=0.97, p<0.001). These results demonstrate the concept of ASI and advantages of sASI.

  1. Spectroscopic AC Susceptibility Imaging (sASI) of Magnetic Nanoparticles

    PubMed Central

    Ficko, Bradley W.; Nadar, Priyanka M.; Diamond, Solomon G.

    2014-01-01

    This study demonstrates a method for alternating current (AC) susceptibility imaging (ASI) of magnetic nanoparticles (mNPs) using low cost instrumentation. The ASI method uses AC magnetic susceptibility measurement to create tomographic images using an array of drive coils, compensation coils and fluxgate magnetometers. Using a spectroscopic approach in conjunction with ASI, a series of tomographic images can be created for each frequency measurement and is termed sASI. The advantage of sASI is that mNPs can be simultaneously characterized and imaged in a biological medium. System calibration was performed by fitting the in-phase and out-of-phase susceptibility measurements of an mNP sample with a hydrodynamic diameter of 100 nm to a Brownian relaxation model (R2 = 0.96). Samples of mNPs with core diameters of 10 and 40 nm and a sample of 100 nm hydrodynamic diameter were prepared in 0.5 ml tubes. Three mNP samples were arranged in a randomized array and then scanned using sASI with six frequencies between 425 and 925 Hz. The sASI scans showed the location and quantity of the mNP samples (R2 = 0.97). Biological compatibility of the sASI method was demonstrated by scanning mNPs that were injected into a pork sausage. The mNP response in the biological medium was found to correlate with a calibration sample (R2 = 0.97, p <0.001). These results demonstrate the concept of ASI and advantages of sASI. PMID:25477704

  2. Spectroscopic AC Susceptibility Imaging (sASI) of Magnetic Nanoparticles.

    PubMed

    Ficko, Bradley W; Nadar, Priyanka M; Diamond, Solomon G

    2015-02-01

    This study demonstrates a method for alternating current (AC) susceptibility imaging (ASI) of magnetic nanoparticles (mNPs) using low cost instrumentation. The ASI method uses AC magnetic susceptibility measurement to create tomographic images using an array of drive coils, compensation coils and fluxgate magnetometers. Using a spectroscopic approach in conjunction with ASI, a series of tomographic images can be created for each frequency measurement and is termed sASI. The advantage of sASI is that mNPs can be simultaneously characterized and imaged in a biological medium. System calibration was performed by fitting the in-phase and out-of-phase susceptibility measurements of an mNP sample with a hydrodynamic diameter of 100 nm to a Brownian relaxation model (R(2) = 0.96). Samples of mNPs with core diameters of 10 and 40 nm and a sample of 100 nm hydrodynamic diameter were prepared in 0.5 ml tubes. Three mNP samples were arranged in a randomized array and then scanned using sASI with six frequencies between 425 and 925 Hz. The sASI scans showed the location and quantity of the mNP samples (R(2) = 0.97). Biological compatibility of the sASI method was demonstrated by scanning mNPs that were injected into a pork sausage. The mNP response in the biological medium was found to correlate with a calibration sample (R(2) = 0.97, p <0.001). These results demonstrate the concept of ASI and advantages of sASI. PMID:25477704

  3. AC magnetic measurements of the ALS Booster Dipole Engineering Model Magnet

    SciTech Connect

    Green, M.I.; Keller, R.; Nelson, D.H.; Hoyer, E.

    1989-03-01

    10 Hz sine wave and 2 Hz sawtooth AC magnetic measurements of he curved ALS Booster Dipole Engineering Model Magnet have been accomplished. Long curved coils were utilized to measure the integral transfer function and uniformity. Point coils and a Hall Probe were used to measure magnetic induction and its uniformity. The data were logged and processed by a Tektronix 11401 digital oscilloscope. The dependence of the effective length on the field was determined from the ratio of the integral coil signals to the point coil signals. Quadrupole and sextupole harmonics were derived from the point and integral uniformity measurements. 5 refs., 4 figs., 2 tabs.

  4. Iron abundance and magnetic permeability of the moon

    NASA Technical Reports Server (NTRS)

    Parkin, C. W.; Daily, W. D.; Dyal, P.

    1974-01-01

    A larger set of simultaneous data from the Apollo 12 lunar surface magnetometer and the Explorer 35 Ames magnetometer are used to construct a whole-moon hysteresis curve, from which a new value of global lunar permeability is determined to be mu = 1.012 + or - 0.006. The corresponding global induced dipole moment is 2.1 x 10 to the 18th power gauss-cu cm for typical inducing fields of .0001 gauss in the lunar environment. From the permeability measurement, lunar free iron abundance is determined to be 2.5 + or - 2.0 wt. %. Total iron abundance (sum of iron in the ferromagnetic and paramagnetic states) is calculated for two assumed compositional models of the lunar interior: a free iron/orthopyroxene lunar composition and a free iron/olivine composition. The overall lunar total iron abundance is determined to be 9.0 + or - 4.7 wt. %. Other lunar models with a small iron core and with a shallow iron-rich layer are discussed in light of the measured global permeability.

  5. Magnetic permeability behaviors of FeCo micro hollow fiber composites

    NASA Astrophysics Data System (ADS)

    Choi, Moosung; Choi, Donchul; Kim, Jongryoul

    2015-09-01

    To achieve near-field electromagnetic wave absorption in the 1-10 GHz region, magnetic particles with high saturation magnetization ( M S ) and high anisotropy field ( H a ) have been widely used to fabricate composite sheets. Unlike for M S , H a can easily be controlled by managing the shape of the magnetic particles. Thus, hollow fibers with high H a appear to be a good candidate material for fabricating high frequency absorbing sheets. However, the details of frequency dependent permeability behaviors of these fibers and sheets have not been fully understood. In this study, we aimed to develop a simulation method by which to study the magnetic permeability of the fibers and sheets. To confirm the validity of the simulation method, FeCo hollow fibers were fabricated using electroless deposition on micro polymer fibers, after which they were incorporated into composite sheets. The magnetic behavior of the sheets was also analyzed. [Figure not available: see fulltext.

  6. Nonmonotonic field-dependent magnetic permeability of a paramagnetic ferrofluid emulsion

    NASA Astrophysics Data System (ADS)

    Ivanov, Alexey O.; Kuznetsova, Olga B.

    2012-04-01

    The ferrofluid emulsion, made of kerosene-based ferrofluid droplets suspended in nonmiscible aviation oil, demonstrates experimentally the nonmonotonic dependence of the effective magnetic permeability as a function of the uniform static magnetic field. In weak fields the emulsion permeability rapidly grows; it reaches its maximum at fields on the order of 1 kA/m; after that, it decays to zero. The theoretical explanation of the effect, as we show here, could be based on the following idea: In a weak magnetic field the growth of the induced droplet magnetic moment is faster than the linear one due to the droplet elongation accompanied by the reduction of the demagnetizing field. Further increase of the external magnetic field strength cannot lead to a significant decrease of the demagnetizing field, as the droplets are already highly elongated. On the other hand, the magnetic susceptibility of the ferrofluid reduces with the field strength. Thus, the effective magnetic permeability of the ferrofluid suspension starts decreasing. The developed theoretical model describes well the experimental observations.

  7. Nonmonotonic field-dependent magnetic permeability of a paramagnetic ferrofluid emulsion.

    PubMed

    Ivanov, Alexey O; Kuznetsova, Olga B

    2012-04-01

    The ferrofluid emulsion, made of kerosene-based ferrofluid droplets suspended in nonmiscible aviation oil, demonstrates experimentally the nonmonotonic dependence of the effective magnetic permeability as a function of the uniform static magnetic field. In weak fields the emulsion permeability rapidly grows; it reaches its maximum at fields on the order of 1 kA/m; after that, it decays to zero. The theoretical explanation of the effect, as we show here, could be based on the following idea: In a weak magnetic field the growth of the induced droplet magnetic moment is faster than the linear one due to the droplet elongation accompanied by the reduction of the demagnetizing field. Further increase of the external magnetic field strength cannot lead to a significant decrease of the demagnetizing field, as the droplets are already highly elongated. On the other hand, the magnetic susceptibility of the ferrofluid reduces with the field strength. Thus, the effective magnetic permeability of the ferrofluid suspension starts decreasing. The developed theoretical model describes well the experimental observations. PMID:22680473

  8. Evaluation of damage-induced permeability using a three-dimensional Adaptive Continuum/Discontinuum Code (AC/DC)

    NASA Astrophysics Data System (ADS)

    Fabian, Dedecker; Peter, Cundall; Daniel, Billaux; Torsten, Groeger

    Digging a shaft or drift inside a rock mass is a common practice in civil engineering when a transportation way, such as a motorway, railway tunnel or storage shaft is to be built. In most cases, the consequences of the disturbance on the medium must be known in order to estimate the behaviour of the disturbed rock mass. Indeed, excavating part of the rock causes a new distribution of the stress field around the excavation that can lead to micro-cracking and even to the failure of some rock volume in the vicinity of the shaft. Consequently, the formed micro-cracks modify the mechanical and hydraulic properties of the rock. In this paper, we present an original method for the evaluation of damage-induced permeability. ITASCA has developed and used discontinuum models to study rock damage by building particle assemblies and checking the breakage of bonds under stress. However, such models are limited in size by the very large number of particles needed to model even a comparatively small volume of rock. In fact, a large part of most models never experiences large strains and does not require the accurate description of large-strain/damage/post-peak behaviour afforded by a discontinuum model. Thus, a large model frequently can be separated into a strongly strained “core” area to be represented by a Discontinuum and a peripheral area for which continuum zones would be adequate. Based on this observation, Itasca has developed a coupled, three-dimensional, continuum/discontinuum modelling approach. The new approach, termed Adaptive Continuum/Discontinuum Code (AC/DC), is based on the use of a periodic discontinuum “base brick” for which more or less simplified continuum equivalents are derived. Depending on the level of deformation in each part of the model, the AC/DC code can dynamically select the appropriate brick type to be used. In this paper, we apply the new approach to an excavation performed in the Bure site, at which the French nuclear waste agency

  9. Dynamic permeability of electrically conducting fluids under magnetic fields in annular ducts.

    PubMed

    Cuevas, S; del Río, J A

    2001-07-01

    The dynamic response of an electrically conducting fluid (either Newtonian or Maxwellian) flowing between straight concentric circular cylinders under a constant radial magnetic field, is analyzed. The isothermal flow is studied using the time Fourier transform, so that the dynamic generalization of Darcy's law in the frequency domain is obtained and analytical expressions for the dynamic permeability are derived. For the Newtonian case, the range of frequencies where the dynamic permeability approaches the static value is enlarged the smaller the gap between the cylinders and the higher the magnetic-field strength. For the Maxwell fluid, the presence of the inner cylinder shifts the frequencies that lead to the enhancement of the real part of the dynamic permeability to larger values and increases its maximum values relative to the case where the inner cylinder is absent. In addition, the Ohmic dissipation causes the damping of the amplitude of the response. PMID:11461397

  10. Finite-element analysis of a magnetic sensor to detect permeability changes due to residual stresses in ferromagnetic materials

    NASA Astrophysics Data System (ADS)

    Govindaraju, Madhav R.; Katragadda, Gopichand; Wallace, John L.

    1998-03-01

    High strength steel alloys (such as 300 M) used in naval aircraft engine and landing gear components are subjected to cyclic loading in service and found to be highly susceptible to fatigue cracking. There is a critical need for nondestructive evaluation techniques which can detect both cracking and potential crack nucleation sites within these components. An innovative electromagnetic technology called the stress induced-magnetic-anisotropy (SMA) technique has been proposed to be used to detect and evaluate residual stresses. SMA measures residual stresses by sensing the changes in magnetic flux induced in directions parallel and perpendicular to the stress. A novel probe and instrumentation is being developed to simultaneously detect both subsurface residual stresses and stress-induced cracking in coated and uncoated ferromagnetic structures. Finite element analysis has been used to determine the distribution of magnetic flux density and inductance of the probe under varying AC fields. Using ANSYSTM EMAG, the effect of varying frequency of the excitation field, permeability and dimensions of the core have been analyzed. The paper describes how finite element analysis can be used in design and development of the probe and in understanding its behavior.

  11. Estimation of cell membrane permeability of the rat brain using diffusion magnetic resonance imaging

    NASA Astrophysics Data System (ADS)

    Imae, T.; Shinohara, H.; Sekino, M.; Ueno, S.; Ohsaki, H.; Mima, K.; Ootomo, K.

    2008-04-01

    We propose a method to noninvasively evaluate the permeability of the cell membrane in the rat brain using diffusion magnetic resonance imaging (MRI). Diffusion MRI reflects the intra- and extracellular diffusion coefficients of water and cell membrane permeability. The images were acquired using a 4.7T MRI system with applications to motion-probing gradients in six directions. Numerical simulations based on the finite-difference method were carried out for estimating diffusion MRI signals with various combinations of membrane permeability and intracellular diffusion coefficient values. We defined an evaluative function as the difference between the signals estimated by simulation and experimentally obtained signals. We found that the combination of membrane permeability and intracellular diffusion coefficient in the simulation corresponding to the minimum value of the evaluative function leads to an estimation of these properties of the rat brain. The estimated intracellular diffusion coefficient and membrane permeability were (1.3±0.1)×10-3mm2/s and 74±23μm/s, respectively. Our method is useful for noninvasively estimating the cell membrane permeability of biological tissues, and is easily applicable to human tissues.

  12. Magnetic images of the disintegration process of tablets in the human stomach by ac biosusceptometry

    NASA Astrophysics Data System (ADS)

    Corá, L. A.; Andreis, U.; Romeiro, F. G.; Américo, M. F.; Oliveira, R. B.; Baffa, O.; Miranda, J. R. A.

    2005-12-01

    Oral administration of solid dosage forms is usually preferred in drug therapy. Conventional imaging methods are essential tools to investigate the in vivo performance of these formulations. The non-invasive technique of ac biosusceptometry has been introduced as an alternative in studies focusing on gastrointestinal motility and, more recently, to evaluate the behaviour of magnetic tablets in vivo. The aim of this work was to employ a multisensor ac biosusceptometer system to obtain magnetic images of disintegration of tablets in vitro and in the human stomach. The results showed that the transition between the magnetic marker and the magnetic tracer characterized the onset of disintegration (t50) and occurred in a short time interval (1.1 ± 0.4 min). The multisensor ac biosusceptometer was reliable to monitor and analyse the in vivo performance of magnetic tablets showing accuracy to quantify disintegration through the magnetic images and to characterize the profile of this process.

  13. AC loss measurement of superconducting dipole magnets by the calorimetric method

    SciTech Connect

    Morita, Y.; Hara, K.; Higashi, N.; Kabe, A.

    1996-12-31

    AC losses of superconducting dipole magnets were measured by the calorimetric method. The magnets were model dipole magnets designed for the SSC. These were fabricated at KEK with 50-mm aperture and 1.3-m overall length. The magnet was set in a helium cryostat and cooled down to 1.8 K with 130 L of pressurized superfluid helium. Heat dissipated by the magnet during ramp cycles was measured by temperature rise of the superfluid helium. Heat leakage into the helium cryostat was 1.6 W and was subtracted from the measured heat to obtain AC loss of the magnet. An electrical measurement was carried out for calibration. Results of the two methods agreed within the experimental accuracy. The authors present the helium cryostat and measurement system in detail, and discuss the results of AC loss measurement.

  14. Magnetodielectric effect and electric-induced magnetic permeability in magnetoelectric laminate composite under low inspiring signal

    NASA Astrophysics Data System (ADS)

    Zhou, Jian-Ping; Zhang, Yu-Xiang; Zhang, Guang-Bin; Liu, Peng

    2013-01-01

    A theory based on equivalent circuit was proposed to demonstrate that magnetodielectric (MDE) effect and electric-induced magnetic permeability (EIMP) exist in the magnetoelectric composite. Both MDE and EIMP are sensitive to the amplitude of inspiring signal. They were researched in a simple Pb(Zr,Ti)O3/Terfenol-D laminate composite experimentally. A large MDE coefficient over 85% was found near the resonance frequency under a low magnetic field of 40 Oe. The EIMP was also observed in the composite. They are mainly originated from the magnetoelectric coupling between the piezoelectric and magnetostrictive components. These results are significant in the device applications of modulating dielectric constant and magnetic permeability at room temperature.

  15. Magnetic field extraction of trap-based electron beams using a high-permeability grid

    NASA Astrophysics Data System (ADS)

    Hurst, N. C.; Danielson, J. R.; Surko, C. M.

    2015-07-01

    A method to form high quality electrostatically guided lepton beams is explored. Test electron beams are extracted from tailored plasmas confined in a Penning-Malmberg trap. The particles are then extracted from the confining axial magnetic field by passing them through a high magnetic permeability grid with radial tines (a so-called "magnetic spider"). An Einzel lens is used to focus and analyze the beam properties. Numerical simulations are used to model non-adiabatic effects due to the spider, and the predictions are compared with the experimental results. Improvements in beam quality are discussed relative to the use of a hole in a high permeability shield (i.e., in lieu of the spider), and areas for further improvement are described.

  16. Magnetic field extraction of trap-based electron beams using a high-permeability grid

    SciTech Connect

    Hurst, N. C.; Danielson, J. R.; Surko, C. M.

    2015-07-15

    A method to form high quality electrostatically guided lepton beams is explored. Test electron beams are extracted from tailored plasmas confined in a Penning-Malmberg trap. The particles are then extracted from the confining axial magnetic field by passing them through a high magnetic permeability grid with radial tines (a so-called “magnetic spider”). An Einzel lens is used to focus and analyze the beam properties. Numerical simulations are used to model non-adiabatic effects due to the spider, and the predictions are compared with the experimental results. Improvements in beam quality are discussed relative to the use of a hole in a high permeability shield (i.e., in lieu of the spider), and areas for further improvement are described.

  17. Magnetic fluid hyperthermia (MFH): Cancer treatment with AC magnetic field induced excitation of biocompatible superparamagnetic nanoparticles

    NASA Astrophysics Data System (ADS)

    Jordan, Andreas; Scholz, Regina; Wust, Peter; Fähling, Horst; Felix, Roland

    1999-07-01

    The story of hyperthermia with small particles in AC magnetic fields started in the late 1950s, but most of the studies were unfortunately conducted with inadequate animal systems, inexact thermometry and poor AC magnetic field parameters, so that any clinical implication was far behind the horizon. More than three decades later, it was found, that colloidal dispersions of superparamagnetic (subdomain) iron oxide nanoparticles exhibit an extraordinary specific absorption rate (SAR [ W/ g]), which is much higher at clinically tolerable H 0 f combinations in comparison to hysteresis heating of larger multidomain particles. This was the renaissance of a cancer treatment method, which has gained more and more attention in the last few years. Due to the increasing number of randomized clinical trials preferentially in Europe with conventional E-field hyperthermia systems, the general medical and physical experience in hyperthermia application is also rapidly growing. Taking this increasing clinical experience carefully into account together with the huge amount of new biological data on heat response of cells and tissues, the approach of magnetic fluid hyperthermia (MFH) is nowadays more promising than ever before. The present contribution reviews the current state of the art and some of the future perspectives supported by advanced methods of the so-called nanotechnology.

  18. Direction detectable static magnetic field imaging by frequency-modulated magnetic force microscopy with an AC magnetic field driven soft magnetic tip

    NASA Astrophysics Data System (ADS)

    Saito, Hitoshi; Ito, Ryoichi; Egawa, Genta; Li, Zhenghua; Yoshimura, Satoru

    2011-04-01

    Direction detectable static magnetic field imaging, which directly distinguishes the up and down direction of static perpendicular magnetic field from a sample surface and the polarity of magnetic charges on the surface, was demonstrated for CoCrPt-SiO2 perpendicular magnetic recording media based on a frequency-modulated magnetic force microscopy (FM-MFM), which uses a frequency modulation of the cantilever oscillation induced by an alternating force from the tip-sample magnetic interaction. In this study, to generate the alternating force, we used a NiFe soft magnetic tip driven by the ac magnetic field of a soft ferrite core and imaged the direction and the amplitude of the static magnetic field from the recorded bits. This method enables measurement of the static magnetic field near a sample surface, which is masked by short range forces of the surface. The present method will be effective in analyzing the microscopic magnetic domain structure of hard magnetic samples.

  19. Stability improvement of AC superconducting magnet by forced-convection cooling

    SciTech Connect

    Ishigohka, T.; Kasuya, A.; Ninomiya, A.

    1996-07-01

    The authors propose a new improved cooling system of an AC(50/60Hz) superconducting magnet introducing a forced-convection flow of liquid helium. In this system, the flow through the cooling channel between the winding layers is generated by a screw rotating in a cylinder surrounding the magnet. A small experimental device composed of an AC superconducting magnet and a rotating screw was manufactured. The screw was rotated by an extended driving shaft. The experimental result shows that the stability of the magnet is improved by the rotation of the screw. That is, the thermal disturbance (heater input power) which generates the quench of the magnet increases as the rotational speed of the screw does. It is expected that this technique can be successfully applied to superconducting AC power apparatuses as transformers or reactors.

  20. Extending Nuclear Magnetic Resonance Data for Permeability Estimation in Fine-Grained Sediments

    NASA Astrophysics Data System (ADS)

    Daigle, H.; Dugan, B.

    2008-12-01

    We developed a method for using nuclear magnetic resonance (NMR) T2 data and gamma ray data to estimate lithology-dependent permeability in silt- and clay-rich sediments. This model, based on the Schlumberger-Doll Research (SDR) model, allows for high resolution (<1 m) permeability estimates throughout a logged interval. Our model was calibrated using direct measurements on core samples from Keathley Canyon Lease Block 151 in the northern Gulf of Mexico. From NMR and gamma ray data we are able to determine permeability from 10-18 to 10-14 m2 (0.001 to 10 millidarcies). Thus from discrete core samples and log data we were able to develop a permeability model for the entire sedimentary column (425 m). Lithologic variation was incorporated into the model by varying the A coefficient based on the gamma ray response. This provides a more accurate permeability model than assigning a constant value to A as is typically done. The relationship between A and intrinsic lithologic properties is unclear; simple pore system models suggest that A may be related to specific surface, tortuosity, and pore structure; we investigate simple models to quantify how these properties vary with sediment consolidation and what their relationship is to A. A comprehensive understanding that links NMR data and A to pore-scale properties will provide new constraints on deformation and flow in porous systems, and will contribute to our understanding of sediment properties for fluid flow modeling at local and regional scales.

  1. Depinning of flux lines and AC losses in magnet-superconductor levitation system

    SciTech Connect

    Terentiev, A. N.; Hull, J. R.; De Long, L. E.

    1999-11-29

    The AC loss characteristics of a magnet-superconductor system were studied with the magnet fixed to the free end of an oscillating cantilever located near a stationary melt-textured YBCO pellet. Below a threshold AC field amplitude {approx}2Oe, the dissipation of the oscillator is amplitude-independent, characteristic of a linear, non-hysteretic regime. Above threshold,dissipation increases with amplitude, reflecting the depinning and hysteretic motion of flux lines. The threshold AC field is an order of magnitude higher than that measured for the same YBCO material via AC susceptometry in a uniform DC magnetic field, A partial lock-in of flux lines between YBCO ab planes is proposed as the mechanism for the substantial increase of the depinning threshold.

  2. Study of effect of AC and DC magnetic fields on growth of Pisum sativum seeds

    NASA Astrophysics Data System (ADS)

    Bahar, Mahmood; Yasaie Mehrjardi, Yasaman; Sojoodi, Jaleh; Bayani, Hosien; Kazem Salem, Mohammad

    2013-08-01

    This paper concentrates on the effect of the AC and DC magnetic fields on plant growth. The effect of AC magnetic field with intensities of 2.25, 1.66 and 1.49 mT and DC magnetic field with intensities of 3.6, 2.41 and 2.05 mT in exposure durations of 2, 4, 6, 8, 10 and 12 min on two groups of dry and wet Pisum sativum seedlings was studied. In each experiment 10 seeds were used; the experiments were repeated three times for each group and there was a sham exposed group for comparison purposes. The light cycle was 12 h light/12 h darkness and the temperature was 25 ± 1° C. The index of growth is considered to be the root and stem elongation on the sixth day. It was observed that AC magnetic field has a positive effect on the growth in all durations and intensities. Moreover, it is highlighted that during the experiments, the mean growth of dry seedlings significantly increased by a factor of 11 in AC magnetic field with the lowest intensity of 1.49 mT (p < 0.05). It was also shown that AC magnetic fields had a more positive effect on the growth of plants in comparison to DC magnetic fields.

  3. Equilibrium State and Magnetic Permeability Tensor of the Epitaxial Ferrite Films

    NASA Astrophysics Data System (ADS)

    Bobkov, V. B.; Zavislyak, I. V.

    1997-12-01

    The analysis of the equilibrium state of an arbitrarily oriented epitaxial ferrite film with basic cubic symmetry has been carried out. The equilibrium orientation of the magnetization has been shown to coincide with the direction of the applied magnetic field for (n, n, m), (m, n, 0) and (112) films that are magnetized parallel to the surface along the axes 110, 100 and 111, respectively. Conditions of the stability of the equilibrium state have been found. For (100), (110) and (111) films a simple technique for determining the magnetic parameters of the films by the use of the spectra of magnetostatic waves has been proposed. For those films the magnetic permeability tensor has been obtained. Different algorithms have been proposed for processing the MSW spectra.

  4. Nonlinear hydro-magnetic convection at a permeable cylinder in a porous medium

    NASA Astrophysics Data System (ADS)

    van Gorder, Robert A.; Vajravelu, K.

    2011-10-01

    We consider the longitudinal steady nonlinear hydromagnetic convection flow over a permeable vertical cylinder in a porous medium. We assume that both the mainstream velocity at the outer edge of the boundary layer and the surface temperature of the cylinder vary linearly with axial distance from the leading edge, and extend the existing literature by including the nonlinear density temperature variation, magnetic field, and heat source/sink.

  5. Electric tuning of magnetization dynamics and electric field-induced negative magnetic permeability in nanoscale composite multiferroics

    NASA Astrophysics Data System (ADS)

    Jia, Chenglong; Wang, Fenglong; Jiang, Changjun; Berakdar, Jamal; Xue, Desheng

    2015-06-01

    Steering magnetism by electric fields upon interfacing ferromagnetic (FM) and ferroelectric (FE) materials to achieve an emergent multiferroic response bears a great potential for nano-scale devices with novel functionalities. FM/FE heterostructures allow, for instance, the electrical manipulation of magnetic anisotropy via interfacial magnetoelectric (ME) couplings. A charge-mediated ME effect is believed to be generally weak and active in only a few angstroms. Here we present an experimental evidence uncovering a new magnon-driven, strong ME effect acting on the nanometer range. For Co92Zr8 (20 nm) film deposited on ferroelectric PMN-PT we show via ferromagnetic resonance (FMR) that this type of linear ME allows for electrical control of simultaneously the magnetization precession and its damping, both of which are key elements for magnetic switching and spintronics. The experiments unravel further an electric-field-induced negative magnetic permeability effect.

  6. Electric tuning of magnetization dynamics and electric field-induced negative magnetic permeability in nanoscale composite multiferroics.

    PubMed

    Jia, Chenglong; Wang, Fenglong; Jiang, Changjun; Berakdar, Jamal; Xue, Desheng

    2015-01-01

    Steering magnetism by electric fields upon interfacing ferromagnetic (FM) and ferroelectric (FE) materials to achieve an emergent multiferroic response bears a great potential for nano-scale devices with novel functionalities. FM/FE heterostructures allow, for instance, the electrical manipulation of magnetic anisotropy via interfacial magnetoelectric (ME) couplings. A charge-mediated ME effect is believed to be generally weak and active in only a few angstroms. Here we present an experimental evidence uncovering a new magnon-driven, strong ME effect acting on the nanometer range. For Co92Zr8 (20 nm) film deposited on ferroelectric PMN-PT we show via ferromagnetic resonance (FMR) that this type of linear ME allows for electrical control of simultaneously the magnetization precession and its damping, both of which are key elements for magnetic switching and spintronics. The experiments unravel further an electric-field-induced negative magnetic permeability effect. PMID:26058060

  7. Electric tuning of magnetization dynamics and electric field-induced negative magnetic permeability in nanoscale composite multiferroics

    PubMed Central

    Jia, Chenglong; Wang, Fenglong; Jiang, Changjun; Berakdar, Jamal; Xue, Desheng

    2015-01-01

    Steering magnetism by electric fields upon interfacing ferromagnetic (FM) and ferroelectric (FE) materials to achieve an emergent multiferroic response bears a great potential for nano-scale devices with novel functionalities. FM/FE heterostructures allow, for instance, the electrical manipulation of magnetic anisotropy via interfacial magnetoelectric (ME) couplings. A charge-mediated ME effect is believed to be generally weak and active in only a few angstroms. Here we present an experimental evidence uncovering a new magnon-driven, strong ME effect acting on the nanometer range. For Co92Zr8 (20 nm) film deposited on ferroelectric PMN-PT we show via ferromagnetic resonance (FMR) that this type of linear ME allows for electrical control of simultaneously the magnetization precession and its damping, both of which are key elements for magnetic switching and spintronics. The experiments unravel further an electric-field-induced negative magnetic permeability effect. PMID:26058060

  8. Distribution of AC loss in a HTS magnet for SMES with different operating conditions

    NASA Astrophysics Data System (ADS)

    Xu, Y.; Tang, Y.; Ren, L.; Jiao, F.; Song, M.; Cao, K.; Wang, D.; Wang, L.; Dong, H.

    2013-11-01

    The AC loss induced in superconducting tape may affect the performance of a superconducting device applied to power system, such as transformer, cable, motor and even Superconducting Magnetic Energy Storage (SMES). The operating condition of SMES is changeable due to the need of compensation to the active or reactive power according to the demand of a power grid. In this paper, it is investigated that the distribution of AC loss for a storage magnet on different operating conditions, which is based on finite element method (FEM) and measured properties of BSCCO/Ag tapes. This analytical method can be used to optimize the SMES magnet.

  9. In vitro cytotoxicity of Selol-loaded magnetic nanocapsules against neoplastic cell lines under AC magnetic field activation

    NASA Astrophysics Data System (ADS)

    Falqueiro, A. M.; Siqueira-Moura, M. P.; Jardim, D. R.; Primo, F. L.; Morais, P. C.; Mosiniewicz-Szablewska, E.; Suchocki, P.; Tedesco, A. C.

    2012-04-01

    The goals of this study are to evaluate invitro compatibility of magnetic nanomaterials and their therapeutic potential against cancer cells. Highly stable ionic magnetic fluid sample (maghemite, γ-Fe2O3) and Selol were incorporated into polymeric nanocapsules by nanoprecipitation method. The cytotoxic effect of Selol-loaded magnetic nanocapsules was assessed on murine melanoma (B16-F10) and oral squamous cell carcinoma (OSCC) cell lines following AC magnetic field application. The influence of different nanocapsules on cell viability was investigated by colorimetric MTT 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyl tetrazolium bromide assay. In the absence of AC magnetic field Selol-loaded magnetic nanocapsules, containing 100 µg/mL Selol plus 5 × 1012 particle/mL, showed antitumoral activity of about 50% on B16-F10 melanoma cells while OSCC carcinoma cells demonstrated drug resistance at all concentrations of Selol and magnetic fluid (range of 100-500 µg/mL Selol and 5 × 1012-2.5 × 1013 particle/mL). On the other hand, under AC applied fields (1 MHz and 40 Oe amplitude) B16-F10 cell viability was reduced down to 40.5% (±3.33) at the highest concentration of nanoencapsulated Selol. The major effect, however, was observed on OSCC cells since the cell viability drops down to about 33.3% (±0.38) under application of AC magnetic field. These findings clearly indicate that the Selol-loaded magnetic nanocapsules present different toxic effects on neoplastic cell lines. Further, the cytotoxic effect was maximized under AC magnetic field application on OSCC, which emphasizes the effectiveness of the magnetohyperthermia approach.

  10. Development and application of setup for ac magnetic field in neutron scattering experiments.

    PubMed

    Klimko, Sergey; Zhernenkov, Kirill; Toperverg, Boris P; Zabel, Hartmut

    2010-10-01

    We report on a new setup developed for neutron scattering experiments in periodically alternating magnetic fields at the sample position. The assembly consisting of rf generator, amplifier, wide band transformer, and resonance circuit. It allows to generate homogeneous ac magnetic fields over a volume of a few cm(3) and variable within a wide range of amplitudes and frequencies. The applicability of the device is exemplified by ac polarized neutron reflectometry (PNR): a new method established to probe remagnetization kinetics in soft ferromagnetic films. Test experiments with iron films demonstrate that the ac field within the accessible range of frequencies and amplitudes produces a dramatic effect on the PNR signal. This shows that the relevant ac field parameters generated by the device match well with the scales involved in the remagnetization processes. Other possible applications of the rf unit are briefly discussed. PMID:21034083

  11. Development and application of setup for ac magnetic field in neutron scattering experiments

    SciTech Connect

    Klimko, Sergey; Zhernenkov, Kirill; Toperverg, Boris P.; Zabel, Hartmut

    2010-10-15

    We report on a new setup developed for neutron scattering experiments in periodically alternating magnetic fields at the sample position. The assembly consisting of rf generator, amplifier, wide band transformer, and resonance circuit. It allows to generate homogeneous ac magnetic fields over a volume of a few cm{sup 3} and variable within a wide range of amplitudes and frequencies. The applicability of the device is exemplified by ac polarized neutron reflectometry (PNR): a new method established to probe remagnetization kinetics in soft ferromagnetic films. Test experiments with iron films demonstrate that the ac field within the accessible range of frequencies and amplitudes produces a dramatic effect on the PNR signal. This shows that the relevant ac field parameters generated by the device match well with the scales involved in the remagnetization processes. Other possible applications of the rf unit are briefly discussed.

  12. AC driven magnetic domain quantification with 5 nm resolution.

    PubMed

    Li, Zhenghua; Li, Xiang; Dong, Dapeng; Liu, Dongping; Saito, H; Ishio, S

    2014-01-01

    As the magnetic storage density increases in commercial products, e.g. the hard disc drives, a full understanding of dynamic magnetism in nanometer resolution underpins the development of next-generation products. Magnetic force microscopy (MFM) is well suited to exploring ferromagnetic domain structures. However, atomic resolution cannot be achieved because data acquisition involves the sensing of long-range magnetostatic forces between tip and sample. Moreover, the dynamic magnetism cannot be characterized because MFM is only sensitive to the static magnetic fields. Here, we develop a side-band magnetic force microscopy (MFM) to locally observe the alternating magnetic fields in nanometer length scales at an operating distance of 1 nm. Variations in alternating magnetic fields and their relating time-variable magnetic domain reversals have been demonstrated by the side-band MFM. The magnetic domain wall motions, relating to the periodical rotation of sample magnetization, are quantified via micromagnetics. Based on the side-band MFM, the magnetic moment can be determined locally in a volume as small as 5 nanometers. The present technique can be applied to investigate the microscopic magnetic domain structures in a variety of magnetic materials, and allows a wide range of future applications, for example, in data storage and biomedicine. PMID:25011670

  13. a Study of Blood-Brain Barrier Permeability Variations in Vivo Using Magnetic Resonance Imaging.

    NASA Astrophysics Data System (ADS)

    Neuder, Michelle Sandy

    We have measured non-invasively the transcapillary transport of water and an extracellular marker, gadolinium diethylenetriamine pentaacetate (Gd-DTPA) in the living brain using conventional and rapid NMR imaging strategies. Detection of water exchange post-contrast and of Gd-DTPA leakage across an intact and hyperosmotically-disrupted blood-brain barrier (BBB) were investigated in animal models. The development of high speed magnetic resonance imaging methods provides a tool for measuring short-term variations in BBB permeability in vivo over relatively short experimental time periods, and for determining the influence of these permeability changes on other physiologic parameters. The overall aims of this thesis have been to exploit the high temporal resolution available with a fast scanning technique, echo-planar imaging, to (1) quantitate the permeability of the BBB to water before and after altering the exchange capacity of the capillary bed, (2) use these measurements to model small, reversible changes in permeability to Gd-DTPA in terms of the post -contrast relaxation characteristics of the blood and tissue spaces during the first- and multiple-pass phases of transport, and (3) explore the influence of an increased permeability on the first-pass kinetic behavior. We initially present the theory of two-site water exchange, a modification of the Bloch equations used to examine time-dependent changes in the nuclear spin magnetization with time. The solutions of these equations for our particular imaging experiment were initially validated in a well-characterized dialysis chamber in order to demonstrate the sensitivity of the experiment to detecting biexponential signal decay. Upon validating the theory, we measured water exchange times in vivo in rodent and canine brain. A biexponential model of NMR signal decay was used to determine both the intravascular blood volume and intravascular water lifetime. Mannitol, a hyperosmotic solution, which can increase BBB

  14. Encouragement of Enzyme Reaction Utilizing Heat Generation from Ferromagnetic Particles Subjected to an AC Magnetic Field

    PubMed Central

    Suzuki, Masashi; Aki, Atsushi; Mizuki, Toru; Maekawa, Toru; Usami, Ron; Morimoto, Hisao

    2015-01-01

    We propose a method of activating an enzyme utilizing heat generation from ferromagnetic particles under an ac magnetic field. We immobilize α-amylase on the surface of ferromagnetic particles and analyze its activity. We find that when α-amylase/ferromagnetic particle hybrids, that is, ferromagnetic particles, on which α-amylase molecules are immobilized, are subjected to an ac magnetic field, the particles generate heat and as a result, α-amylase on the particles is heated up and activated. We next prepare a solution, in which α-amylase/ferromagnetic particle hybrids and free, nonimmobilized chitinase are dispersed, and analyze their activities. We find that when the solution is subjected to an ac magnetic field, the activity of α-amylase immobilized on the particles increases, whereas that of free chitinase hardly changes; in other words, only α-amylase immobilized on the particles is selectively activated due to heat generation from the particles. PMID:25993268

  15. Fiber - Optic Devices as Temperature Sensors for Temperature Measurements in AC Magnetic Fields

    NASA Astrophysics Data System (ADS)

    Rablau, Corneliu; Lafrance, Joseph; Sala, Anca

    2007-10-01

    We report on the investigation of several fiber-optic devices as potential sensors for temperature measurements in AC magnetic fields. Common temperature sensors, such as thermocouples, thermistors or diodes, will create random and/or systematic errors when placed in a magnetic field. A DC magnetic field is susceptible to create a systematic offset to the measurement, while in an AC magnetic field of variable frequency random errors which cannot be corrected for can also be introduced. Fiber-Bragg-gratings and thin film filters have an inherent temperature dependence. Detrimental for their primary applications, the same dependence allows one to use such devices as temperature sensors. In an AC magnetic field, they present the advantage of being immune to electromagnetic interference. Moreover, for fiber-Bragg-gratings, the shape factor and small mass of the bare-fiber device make it convenient for temperature measurements on small samples. We studied several thin-film filters and fiber-Bragg-gratings and compared their temperature measurement capabilities in AC magnetic fields of 0 to 150 Gauss, 0 to 20 KHz to the results provided by off-the-shelf thermocouples and thermistor-based temperature measurement systems.

  16. Nonlinear ac stationary response and dynamic magnetic hysteresis of quantum uniaxial superparamagnets

    NASA Astrophysics Data System (ADS)

    Kalmykov, Yuri P.; Titov, Serguey V.; Coffey, William T.

    2015-11-01

    The nonlinear ac stationary response of uniaxial paramagnets and superparamagnets—nanoscale solids or clusters with spin number S ˜100-104 —in superimposed uniform ac and dc bias magnetic fields of arbitrary strength, each applied along the easy axis of magnetization, is determined by solving the evolution equation for the reduced density matrix represented as a finite set of three-term differential-recurrence relations for its diagonal matrix elements. The various harmonic components arising from the nonlinear response of the magnetization, dynamic magnetic hysteresis loops, etc., are then evaluated via matrix continued fractions indicating a pronounced dependence of the response on S arising from the quantum spin dynamics, which differ markedly from the magnetization dynamics of classical nanomagnets. In the linear response approximation, the results concur with existing solutions.

  17. Analysis incorporating electric conductivity and magnetic permeability on loop-loop EM data for detecting the magnetite ore body

    NASA Astrophysics Data System (ADS)

    Choi, Jihyang; Yi, Myeong-Jong; Son, Jeong-Sul; Kim, Jung-Ho; Park, Sam-Gyu

    2013-04-01

    As the price of mineral resources goes up, exploring small amount of mineral deposits, which have been considered non-economic in the past, is getting more economic. Loop-loop EM survey system can be the best choice for exploring small mineral mines because no ground contact is required and portable loops are freely positioned. EM responses are affected by electric conductivity, magnetic permeability and electric permittivity. In many cases, variation ranges of latter two components are so small and ignorable. However, changes of magnetic permeability affect the data in a serious way. Multidimensional EM inversion technique incorporating both electric conductivity and magnetic susceptibility is on the developing stage. EM responses are calculated in a model of layered earth embedding a magnetic anomaly. Considering the size of the reactions, changes of relative magnetic permeability are frequency-independent effects that can be seen as static. Loop-loop EM survey using PROMIS system was conducted on a small magnetite mine. Inversion with and without considering magnetic permeability was conducted for EM data with multi-frequency and multi-separation between a transmitter and a receiver. Ferromagnetic anomalous feature was distinguishable from the subsurface media, though, enhancement by incorporating magnetic permeability was not sufficiently noticeable.

  18. Millimeter wave complex dielectric permittivity and complex magnetic permeability measurements of absorbing materials

    NASA Astrophysics Data System (ADS)

    Tkachov, Igor Ivanovich

    2000-09-01

    for the materials are presented, discussed and compared with those obtained by using different techniques. The study of the magnetic properties of magnetic materials has been performed with the new spectrometer constructed with the electromagnet providing a constant magnetic field (of up to 10kOe) transverse to the direction of propagation of the millimeter wave radiation. This work presents the general principles and the first application of the transverse magneto-optical effect for the direct measurement of complex magnetic permeability in the millimeter wave range. This technique was applied to the measurement of the millimeter wave complex permeability of a standard soft microwave ferrite, hard oriented and non-oriented ferrites. Experiments demonstrate the high sensitivity of the millimeter wave magneto-optical method and its capability to provide accurate magnetic permeability data in the millimeter wave range. A new experimental procedure is described which leads to the determination of the millimeter wave permeability and permittivity of ferrites. The results of measurement of the real and the imaginary parts of millimeter-wave complex permeability are presented and discussed. The frequency dependence of the millimeter wave specific Faraday-rotation power have been measured in the magnetized Sr-hexaferrite and experimental results are discussed.

  19. Calorimetric method of ac loss measurement in a rotating magnetic field.

    PubMed

    Ghoshal, P K; Coombs, T A; Campbell, A M

    2010-07-01

    A method is described for calorimetric ac-loss measurements of high-T(c) superconductors (HTS) at 80 K. It is based on a technique used at 4.2 K for conventional superconducting wires that allows an easy loss measurement in parallel or perpendicular external field orientation. This paper focuses on ac loss measurement setup and calibration in a rotating magnetic field. This experimental setup is to demonstrate measuring loss using a temperature rise method under the influence of a rotating magnetic field. The slight temperature increase of the sample in an ac-field is used as a measure of losses. The aim is to simulate the loss in rotating machines using HTS. This is a unique technique to measure total ac loss in HTS at power frequencies. The sample is mounted on to a cold finger extended from a liquid nitrogen heat exchanger (HEX). The thermal insulation between the HEX and sample is provided by a material of low thermal conductivity, and low eddy current heating sample holder in vacuum vessel. A temperature sensor and noninductive heater have been incorporated in the sample holder allowing a rapid sample change. The main part of the data is obtained in the calorimetric measurement is used for calibration. The focus is on the accuracy and calibrations required to predict the actual ac losses in HTS. This setup has the advantage of being able to measure the total ac loss under the influence of a continuous moving field as experienced by any rotating machines. PMID:20687748

  20. Calorimetric method of ac loss measurement in a rotating magnetic field

    NASA Astrophysics Data System (ADS)

    Ghoshal, P. K.; Coombs, T. A.; Campbell, A. M.

    2010-07-01

    A method is described for calorimetric ac-loss measurements of high-Tc superconductors (HTS) at 80 K. It is based on a technique used at 4.2 K for conventional superconducting wires that allows an easy loss measurement in parallel or perpendicular external field orientation. This paper focuses on ac loss measurement setup and calibration in a rotating magnetic field. This experimental setup is to demonstrate measuring loss using a temperature rise method under the influence of a rotating magnetic field. The slight temperature increase of the sample in an ac-field is used as a measure of losses. The aim is to simulate the loss in rotating machines using HTS. This is a unique technique to measure total ac loss in HTS at power frequencies. The sample is mounted on to a cold finger extended from a liquid nitrogen heat exchanger (HEX). The thermal insulation between the HEX and sample is provided by a material of low thermal conductivity, and low eddy current heating sample holder in vacuum vessel. A temperature sensor and noninductive heater have been incorporated in the sample holder allowing a rapid sample change. The main part of the data is obtained in the calorimetric measurement is used for calibration. The focus is on the accuracy and calibrations required to predict the actual ac losses in HTS. This setup has the advantage of being able to measure the total ac loss under the influence of a continuous moving field as experienced by any rotating machines.

  1. Calorimetric method of ac loss measurement in a rotating magnetic field

    SciTech Connect

    Ghoshal, P. K.; Coombs, T. A.; Campbell, A. M.

    2010-07-15

    A method is described for calorimetric ac-loss measurements of high-T{sub c} superconductors (HTS) at 80 K. It is based on a technique used at 4.2 K for conventional superconducting wires that allows an easy loss measurement in parallel or perpendicular external field orientation. This paper focuses on ac loss measurement setup and calibration in a rotating magnetic field. This experimental setup is to demonstrate measuring loss using a temperature rise method under the influence of a rotating magnetic field. The slight temperature increase of the sample in an ac-field is used as a measure of losses. The aim is to simulate the loss in rotating machines using HTS. This is a unique technique to measure total ac loss in HTS at power frequencies. The sample is mounted on to a cold finger extended from a liquid nitrogen heat exchanger (HEX). The thermal insulation between the HEX and sample is provided by a material of low thermal conductivity, and low eddy current heating sample holder in vacuum vessel. A temperature sensor and noninductive heater have been incorporated in the sample holder allowing a rapid sample change. The main part of the data is obtained in the calorimetric measurement is used for calibration. The focus is on the accuracy and calibrations required to predict the actual ac losses in HTS. This setup has the advantage of being able to measure the total ac loss under the influence of a continuous moving field as experienced by any rotating machines.

  2. Characterization of tumor microvascular structure and permeability: comparison between magnetic resonance imaging and intravital confocal imaging

    NASA Astrophysics Data System (ADS)

    Reitan, Nina Kristine; Thuen, Marte; Goa, Pa˚L. Erik; de Lange Davies, Catharina

    2010-05-01

    Solid tumors are characterized by abnormal blood vessel organization, structure, and function. These abnormalities give rise to enhanced vascular permeability and may predict therapeutic responses. The permeability and architecture of the microvasculature in human osteosarcoma tumors growing in dorsal window chambers in athymic mice were measured by confocal laser scanning microscopy (CLSM) and dynamic contrast enhanced magnetic resonance imaging (DCE-MRI). Dextran (40 kDa) and Gadomer were used as molecular tracers for CLSM and DCE-MRI, respectively. A significant correlation was found between permeability indicators. The extravasation rate Ki as measured by CLSM correlated positively with DCE-MRI parameters, such as the volume transfer constant Ktrans and the initial slope of the contrast agent concentration-time curve. This demonstrates that these two techniques give complementary information. Extravasation was further related to microvascular structure and was found to correlate with the fractal dimension and vascular density. The structural parameter values that were obtained from CLSM images were higher for abnormal tumor vasculature than for normal vessels.

  3. Propagation of magnetic avalanches in Mn12Ac at high field sweep rates.

    PubMed

    Decelle, W; Vanacken, J; Moshchalkov, V V; Tejada, J; Hernández, J M; Macià, F

    2009-01-16

    Time-resolved measurements of the magnetization reversal in single crystals of Mn12Ac in pulsed magnetic fields, at magnetic field sweep rates from 1.5 kT/s up to 7 kT/s, suggest a new process that cannot be scaled onto a deflagrationlike propagation driven by heat diffusion. The sweep rate dependence of the propagation velocity, increasing from a few 100 m/s up to the speed of sound in Mn12Ac, indicates the existence of two new regimes at the highest sweep rates, with a transition around 4 kT/s that can be understood as a magnetic deflagration-to-detonation transition. PMID:19257315

  4. Self-consistent magnetic properties of magnetite tracers optimized for magnetic particle imaging measured by ac susceptometry, magnetorelaxometry and magnetic particle spectroscopy

    PubMed Central

    Ludwig, Frank; Remmer, Hilke; Kuhlmann, Christian; Wawrzik, Thilo; Arami, Hamed; Ferguson, R. Mathew; Krishnan, Kannan M.

    2015-01-01

    Sensitivity and spatial resolution in Magnetic Particle Imaging are affected by magnetic properties of the nanoparticle tracers used during imaging. Here, we have carried out a comprehensive magnetic characterization of single-core iron oxide nanoparticles that were designed for MPI. We used ac susceptometry, fluxgate magnetorelaxometry, and magnetic particle spectroscopy to evaluate the tracer’s magnetic core size, hydrodynamic size, and magnetic anisotropy. Our results present a self-consistent set of magnetic and structural parameters for the tracers that is consistent with direct measurements of size using transmission electron microscopy and dynamic light scattering and that can be used to better understand their MPI performance. PMID:25729125

  5. Self-consistent magnetic properties of magnetite tracers optimized for magnetic particle imaging measured by ac susceptometry, magnetorelaxometry and magnetic particle spectroscopy

    NASA Astrophysics Data System (ADS)

    Ludwig, Frank; Remmer, Hilke; Kuhlmann, Christian; Wawrzik, Thilo; Arami, Hamed; Ferguson, R. Mathew; Krishnan, Kannan M.

    2014-06-01

    Sensitivity and spatial resolution in magnetic particle imaging are affected by magnetic properties of the nanoparticle tracers used during imaging. Here, we have carried out a comprehensive magnetic characterization of single-core iron oxide nanoparticles that were designed for MPI. We used ac susceptometry, fluxgate magnetorelaxometry, and magnetic particle spectroscopy to evaluate the tracer's magnetic core size, hydrodynamic size, and magnetic anisotropy. Our results present a self-consistent set of magnetic and structural parameters for the tracers that is consistent with direct measurements of size using transmission electron microscopy and dynamic light scattering and that can be used to better understand their MPI performance.

  6. Quantitatively probing the magnetic behavior of individual nanoparticles by an AC field-modulated magnetic force microscopy.

    PubMed

    Li, Xiang; Lu, Wei; Song, Yiming; Wang, Yuxin; Chen, Aiying; Yan, Biao; Yoshimura, Satoru; Saito, Hitoshi

    2016-01-01

    Despite decades of advances in magnetic imaging, obtaining direct, quantitative information with nanometer scale spatial resolution remains an outstanding challenge. Current approaches, for example, Hall micromagnetometer and nitrogen-vacancy magnetometer, are limited by highly complex experimental apparatus and a dedicated sample preparation process. Here we present a new AC field-modulated magnetic force microscopy (MFM) and report the local and quantitative measurements of the magnetic information of individual magnetic nanoparticles (MNPs), which is one of the most iconic objects of nanomagnetism. This technique provides simultaneously a direct visualization of the magnetization process of the individual MNPs, with spatial resolution and magnetic sensitivity of about 4.8 nm and 1.85 × 10(-20) A m(2), respectively, enabling us to separately estimate the distributions of the dipolar fields and the local switching fields of individual MNPs. Moreover, we demonstrate that quantitative magnetization moment of individual MNPs can be routinely obtained using MFM signals. Therefore, it underscores the power of the AC field-modulated MFM for biological and biomedical applications of MNPs and opens up the possibility for directly and quantitatively probing the weak magnetic stray fields from nanoscale magnetic systems with superior spatial resolution. PMID:26932357

  7. Quantitatively probing the magnetic behavior of individual nanoparticles by an AC field-modulated magnetic force microscopy

    PubMed Central

    Li, Xiang; Lu, Wei; Song, Yiming; Wang, Yuxin; Chen, Aiying; Yan, Biao; Yoshimura, Satoru; Saito, Hitoshi

    2016-01-01

    Despite decades of advances in magnetic imaging, obtaining direct, quantitative information with nanometer scale spatial resolution remains an outstanding challenge. Current approaches, for example, Hall micromagnetometer and nitrogen-vacancy magnetometer, are limited by highly complex experimental apparatus and a dedicated sample preparation process. Here we present a new AC field-modulated magnetic force microscopy (MFM) and report the local and quantitative measurements of the magnetic information of individual magnetic nanoparticles (MNPs), which is one of the most iconic objects of nanomagnetism. This technique provides simultaneously a direct visualization of the magnetization process of the individual MNPs, with spatial resolution and magnetic sensitivity of about 4.8 nm and 1.85 × 10−20 A m2, respectively, enabling us to separately estimate the distributions of the dipolar fields and the local switching fields of individual MNPs. Moreover, we demonstrate that quantitative magnetization moment of individual MNPs can be routinely obtained using MFM signals. Therefore, it underscores the power of the AC field-modulated MFM for biological and biomedical applications of MNPs and opens up the possibility for directly and quantitatively probing the weak magnetic stray fields from nanoscale magnetic systems with superior spatial resolution. PMID:26932357

  8. Quantitatively probing the magnetic behavior of individual nanoparticles by an AC field-modulated magnetic force microscopy

    NASA Astrophysics Data System (ADS)

    Li, Xiang; Lu, Wei; Song, Yiming; Wang, Yuxin; Chen, Aiying; Yan, Biao; Yoshimura, Satoru; Saito, Hitoshi

    2016-03-01

    Despite decades of advances in magnetic imaging, obtaining direct, quantitative information with nanometer scale spatial resolution remains an outstanding challenge. Current approaches, for example, Hall micromagnetometer and nitrogen-vacancy magnetometer, are limited by highly complex experimental apparatus and a dedicated sample preparation process. Here we present a new AC field-modulated magnetic force microscopy (MFM) and report the local and quantitative measurements of the magnetic information of individual magnetic nanoparticles (MNPs), which is one of the most iconic objects of nanomagnetism. This technique provides simultaneously a direct visualization of the magnetization process of the individual MNPs, with spatial resolution and magnetic sensitivity of about 4.8 nm and 1.85 × 10-20 A m2, respectively, enabling us to separately estimate the distributions of the dipolar fields and the local switching fields of individual MNPs. Moreover, we demonstrate that quantitative magnetization moment of individual MNPs can be routinely obtained using MFM signals. Therefore, it underscores the power of the AC field-modulated MFM for biological and biomedical applications of MNPs and opens up the possibility for directly and quantitatively probing the weak magnetic stray fields from nanoscale magnetic systems with superior spatial resolution.

  9. Magnetic anisotropy and high frequency permeability of multilayered nanocomposite FeAlO thin films

    SciTech Connect

    Ma, Y. G.; Liu, Y.; Tan, C. Y.; Liu, Z. W.; Ong, C. K.

    2006-09-01

    A cool-down step deposition process (multistep deposition with cool-down interval) was used to grow nanocomposite FeAlO thin films of various thicknesses up to 440 nm by magnetron sputtering at a substrate temperature of 15 deg. C. The effect of the number of cool-down steps on the soft magnetic properties and high frequency characteristics of the nanocomposite FeAlO films were investigated. The deposition process was proved very effective in improving the soft magnetic properties and high frequency characteristics of the films. The eight-layered samples, fabricated by eight cool-down step deposition process, of thicknesses of 220 and 440 nm had obvious in-plane uniaxial anisotropies while the single-layered films were nearly isotropic. The resulting real permeability value of the eight-layered films was larger than 300 for the 220 nm film and between 200 and 300 for the 440 nm film.

  10. Numerical and theoretical evaluations of AC losses for single and infinite numbers of superconductor strips with direct and alternating transport currents in external AC magnetic field

    NASA Astrophysics Data System (ADS)

    Kajikawa, K.; Funaki, K.; Shikimachi, K.; Hirano, N.; Nagaya, S.

    2010-11-01

    AC losses in a superconductor strip are numerically evaluated by means of a finite element method formulated with a current vector potential. The expressions of AC losses in an infinite slab that corresponds to a simple model of infinitely stacked strips are also derived theoretically. It is assumed that the voltage-current characteristics of the superconductors are represented by Bean’s critical state model. The typical operation pattern of a Superconducting Magnetic Energy Storage (SMES) coil with direct and alternating transport currents in an external AC magnetic field is taken into account as the electromagnetic environment for both the single strip and the infinite slab. By using the obtained results of AC losses, the influences of the transport currents on the total losses are discussed quantitatively.

  11. AC current distribution and losses in multifilamentary superconductors exposed to longitudinal magnetic field

    SciTech Connect

    Le Naour, S.; Lacaze, A.; Laumond, Y.; Estop, P.; Verhaege, T.

    1996-07-01

    The current distribution and also AC losses, in a multifilamentary superconductor carrying a transport current, are influenced by the self and the external magnetic field. By using the Maxwell equations, a model has been developed in order to calculate the temporal evolution of current distribution in a single wire exposed or not to external magnetic field. This model is based on the actual relationship of electrical field E with current density J and takes into account the twist pitch of the wire. AC losses are calculated by adding all local losses through the cross section. This paper presents calculations of the influence of the cable twist coupled with the longitudinal magnetic field, and also gives some ideas how to decrease losses.

  12. Magnetic permeability based diagnostic test for the determination of the canine C-reactive protein concentration in undiluted whole blood

    NASA Astrophysics Data System (ADS)

    Ibraimi, Filiz; Kriz, Kirstin; Merin, Henrik; Kriz, Dario

    2009-05-01

    We describe an one-step 11-min magnetic permeability based two-site immunoassay for C-reactive protein (CRP) utilizing polyclonal anti-canine CRP antibody conjugated dextran iron oxide nanoparticles (79 nm) as superparamagnetic labels and polyclonal anti-canine CRP conjugated silica microparticles (15 to 40 μm) as carriers. An inductance based magnetic permeability reader was used to detect the target analyte, CRP, in 10 μL whole blood samples, by measuring the magnetic permeability increase of the silica microparticle sediment due to immuno complex superparamagnetic nanoparticles. Measurements on standards showed a linear response between 0 and 17.5 mg/L CRP. Measurements performed on 16 whole blood samples from mixed breeds showed good correlation with a commercially available ELISA assay.

  13. Monitoring colloidal stability of polymer-coated magnetic nanoparticles using AC susceptibility measurements.

    PubMed

    Herrera, Adriana P; Barrera, Carola; Zayas, Yashira; Rinaldi, Carlos

    2010-02-15

    The application of the response of magnetic nanoparticles to oscillating magnetic fields to probe transitions in colloidal state and structure of polymer-coated nanoparticles is demonstrated. Cobalt ferrite nanoparticles with narrow size distribution were prepared and shown to respond to oscillating magnetic fields through a Brownian relaxation mechanism, which is dependent on the mechanical coupling between the particle dipoles and the surrounding matrix. These nanoparticles were coated with covalently-attached poly(N-isopropylacrylamide) (pNIPAM) or poly(N-isopropylmethacrylamide) (pNIPMAM) through free radical polymerization. The temperature induced transitions of colloidal suspensions of these nanoparticles were studied through a combination of differential scanning calorimetry (DSC), dynamic light scattering (DLS), and AC susceptibility measurements. In the pNIPAM coated nanoparticles excellent agreement was found for a transition temperature of approximately 30 degrees C by all three methods, although the AC susceptibility measurements indicated aggregation which was not evident from the DLS results. Small-angle neutron scattering (SANS) results obtained for pNIPAM coated nanoparticles confirmed that aggregation indeed occurs above the lower critical transition temperature of pNIPAM. For the pNIPMAM coated nanoparticles DLS and AC susceptibility measurements indicated aggregation at a temperature of approximately 33-35 degrees C, much lower than the transition temperature peak at 40 degrees C observed by DSC. However, the transition observed by DSC is very broad, hence it is possible that aggregation begins to occur at temperatures lower than the peak, as indicated by the AC susceptibility and DLS results. These experiments and observations demonstrate the possibility of using AC susceptibility measurements to probe transitions in colloidal suspensions induced by external stimuli. Because magnetic measurements do not require optical transparency, these

  14. A self-powered AC magnetic sensor based on piezoelectric nanogenerator

    NASA Astrophysics Data System (ADS)

    Yu, Aifang; Song, Ming; Zhang, Yan; Kou, Jinzong; Zhai, Junyi; Wang, Zhong Lin

    2014-11-01

    An AC magnetic field, which is a carrier of information, is distributed everywhere and is continuous. How to use and detect this field has been an ongoing topic over the past few decades. Conventional magnetic sensors are usually based on the Hall Effect, the fluxgate, a superconductor quantum interface or magnetoelectric or magnetoresistive sensing. Here, a flexible, simple, low-cost and self-powered active piezoelectric nanogenerator (NG) is successfully demonstrated as an AC magnetic field sensor at room temperature. The amplitude and frequency of a magnetic field can both be accurately sensed by the NG. The output voltage of the NG has a good linearity with a measured magnetic field. The detected minute magnetic field is as low as 1.2 × 10-7 tesla, which is 400 times greater than a commercial magnetic sensor that uses the Hall Effect. In comparison to the existing technologies, an NG is a room-temperature self-powered active sensor that is very simple and very cheap for practical applications.

  15. A self-powered AC magnetic sensor based on piezoelectric nanogenerator.

    PubMed

    Yu, Aifang; Song, Ming; Zhang, Yan; Kou, Jinzong; Zhai, Junyi; Lin Wang, Zhong

    2014-11-14

    An AC magnetic field, which is a carrier of information, is distributed everywhere and is continuous. How to use and detect this field has been an ongoing topic over the past few decades. Conventional magnetic sensors are usually based on the Hall Effect, the fluxgate, a superconductor quantum interface or magnetoelectric or magnetoresistive sensing. Here, a flexible, simple, low-cost and self-powered active piezoelectric nanogenerator (NG) is successfully demonstrated as an AC magnetic field sensor at room temperature. The amplitude and frequency of a magnetic field can both be accurately sensed by the NG. The output voltage of the NG has a good linearity with a measured magnetic field. The detected minute magnetic field is as low as 1.2 × 10(-7) tesla, which is 400 times greater than a commercial magnetic sensor that uses the Hall Effect. In comparison to the existing technologies, an NG is a room-temperature self-powered active sensor that is very simple and very cheap for practical applications. PMID:25333328

  16. New Technique of AC drive in Tokamak using Permanent Magnets

    NASA Astrophysics Data System (ADS)

    Matteucci, Jackson; Zolfaghari, Ali

    2013-10-01

    This study investigates a new technique of capturing the rotational energy of alternating permanent magnets in order to inductively drive an alternating current in tokamak devices. The use of rotational motion bypasses many of the pitfalls seen in typical inductive and non-inductive current drives. Three specific designs are presented and assessed in the following criteria: the profile of the current generated, the RMS loop voltage generated as compared to the RMS power required to maintain it, the system's feasibility from an engineering perspective. All of the analysis has been done under ideal E&M conditions using the Maxwell 3D program. Preliminary results indicate that it is possible to produce an over 99% purely toroidal current with a RMS d Φ/dt of over 150 Tm2/s, driven by 20 MW or less of rotational power. The proposed mechanism demonstrates several key advantages including an efficient mechanical drive system, the generation of pure toroidal currents, and the potential for a quasi-steady state fusion reactor. The following quantities are presented for various driving frequencies and magnet strengths: plasma current generated, loop voltage, torque and power required. This project has been supported by DOE Funding under the SULI program.

  17. Comparative study of models for predicting permeability from nuclear magnetic resonance (NMR) logs in two Chinese tight sandstone reservoirs

    NASA Astrophysics Data System (ADS)

    Xiao, Liang; Liu, Xiao-Peng; Zou, Chang-Chun; Hu, Xiao-Xin; Mao, Zhi-Qiang; Shi, Yu-Jiang; Guo, Hao-Peng; Li, Gao-Ren

    2014-02-01

    Based on the analysis of mercury injection capillary pressure (MICP) and nuclear magnetic resonance (NMR) experimental data for core plugs, which were drilled from two Chinese tight sandstone reservoirs, permeability prediction models, such as the classical SDR, Timur-Coates, the Swanson parameter, the Capillary Parachor, the R10 and R35 models, are calibrated to estimating permeabilities from field NMR logs, and the applicabilities of these permeability prediction models are compared. The processing results of several field examples show that the SDR model is unavailable in tight sandstone reservoirs. The Timur-Coates model is effective once the optimal T 2cutoff can be acquired to accurately calculate FFI and BVI from field NMR logs. The Swanson parameter model and the Capillary Parachor model are not always available in tight sandstone reservoirs. The R35 based model cannot effectively work in tight sandstone reservoirs, while the R10 based model is optimal in permeability prediction.

  18. Late gadolinium enhanced cardiovascular magnetic resonance of lamin A/C gene mutation related dilated cardiomyopathy

    PubMed Central

    2011-01-01

    Background The purpose of this study was to identify early features of lamin A/C gene mutation related dilated cardiomyopathy (DCM) with cardiovascular magnetic resonance (CMR). We characterise myocardial and functional findings in carriers of lamin A/C mutation to facilitate the recognition of these patients using this method. We also investigated the connection between myocardial fibrosis and conduction abnormalities. Methods Seventeen lamin A/C mutation carriers underwent CMR. Late gadolinium enhancement (LGE) and cine images were performed to evaluate myocardial fibrosis, regional wall motion, longitudinal myocardial function, global function and volumetry of both ventricles. The location, pattern and extent of enhancement in the left ventricle (LV) myocardium were visually estimated. Results Patients had LV myocardial fibrosis in 88% of cases. Segmental wall motion abnormalities correlated strongly with the degree of enhancement. Myocardial enhancement was associated with conduction abnormalities. Sixty-nine percent of our asymptomatic or mildly symptomatic patients showed mild ventricular dilatation, systolic failure or both in global ventricular analysis. Decreased longitudinal systolic LV function was observed in 53% of patients. Conclusions Cardiac conduction abnormalities, mildly dilated LV and depressed systolic dysfunction are common in DCM caused by a lamin A/C gene mutation. However, other cardiac diseases may produce similar symptoms. CMR is an accurate tool to determine the typical cardiac involvement in lamin A/C cardiomyopathy and may help to initiate early treatment in this malignant familiar form of DCM. PMID:21689390

  19. Super-resolution high sensitivity AC Magnetic Field Imaging with NV Centers in Diamond

    NASA Astrophysics Data System (ADS)

    Bauch, Erik; Jaskula, Jean-Christophe; Trifonov, Alexei; Walsworth, Ronald

    2015-05-01

    The Nitrogen-Vacancy center in diamond (NV center), a defect consisting of a nitrogen atom next to a missing atom, has been successfully applied to sense magnetic field, electric field, temperature and can also be used as fluorescence marker and single photon emitter. We will present super-resolution imaging of NV centers and simultaneous sensing of AC magnetic fields with high sensitivity. To demonstrate the applicability of super-resolution magnetic field imaging, we resolve several NV centers with an optical resolution smaller than 20 nm and probe locally the gradient of a externally applied magnetic field. Additionally, we demonstrate the detection of magnetic field signals from 1H protons with subdiffraction image resolution. We will also show that our super-resolution magnetometer will benefit from a new readout method based on a spin-to-charge mapping that we have developed to increase the readout contrast.

  20. Time-resolved Measurements of Spontaneous Magnetic Deflagration of Mn12 tBuAc

    NASA Astrophysics Data System (ADS)

    Chen, Yizhang; Kent, A. D.; Zhang, Qing; Sarachik, M. P.; Baker, M. L.; Garanin, D. A.; Mhesn, Najah; Lampropoulos, Christos

    Magnetic deflagration in molecular magnets has been triggered by heat pulses and acoustic waves. In this work we report spontaneous magnetic deflagration (i.e. deflagration that occurs without an external trigger) in the axially symmetric single molecule magnet Mn12 tBuAc . Magnetic hysteresis measurements show steps due to resonant quantum tunneling (RQT) below 1K, confirming the spin-Hamiltonian parameters for this material and previous results. Deflagration speeds measured with a newly constructed higher bandwidth (2MHz) setup will be presented as a function of transverse and longitudinal fields Hx ⊗Hz both on and off resonance. A large increase in front velocity near RQT steps is observed in experiments with swept transverse fields and will be discussed in light of models of deflagration. Work supported by NSF-DMR-1309202 (NYU); ARO W911NF-13-1-0125 (CCNY); DMR-1161571(Lehman); Cottrell College Science Award (UNF).

  1. Magnetization AC losses in MgB2 wires made by IMD process

    NASA Astrophysics Data System (ADS)

    Kováč, J.; Šouc, J.; Kováč, P.; Hušek, I.

    2015-01-01

    Magnetization AC losses of MgB2 superconductors with one and four filaments made by an internal magnesium diffusion (IMD) into boron process were measured and analyzed. For AC loss measurement a system based on a calibration-free method was used. Short samples of MgB2 wires were exposed to an external magnetic field with amplitudes up to 0.07 T, frequencies up to 1200 Hz, and a temperature range between 15 K and 40 K. A strong effect of eddy current losses was found in single-core wire containing pure copper sheath, which was proved by the same wire measurement after Cu etching. The impact of coupling current losses in non-twisted four-filament wire and the decoupling effect after twisting were observed. Coupling current losses in a low-frequency region were effectively reduced in agreement with theoretical assumption. The degradation of transport currents due to torsion stress by twisting was taken into account and the normalized AC losses of MgB2 wires made by IMD and powder-in-tube processes were compared. It appears that the IMD process is more perspective for AC applications due to much higher current densities and smaller degradation of current-carrying capability by twisting.

  2. Advanced AC permanent magnet axial flux disc motor for electric passenger vehicle

    NASA Technical Reports Server (NTRS)

    Kliman, G. B.

    1982-01-01

    An ac permanent magnet axial flux disc motor was developed to operate with a thyristor load commutated inverter as part of an electric vehicle drive system. The motor was required to deliver 29.8 kW (40 hp) peak and 10.4 kW (14 hp) average with a maximum speed of 11,000 rpm. It was also required to run at leading power factor to commutate the inverter. Three motors were built.

  3. Analysis of anomalous electrical conductivity and magnetic permeability effects using a frequency domain controlled-source electromagnetic method

    NASA Astrophysics Data System (ADS)

    Noh, Kyubo; Oh, Seokmin; Seol, Soon Jee; Lee, Ki Ha; Byun, Joongmoo

    2016-03-01

    We present a series of processes for understanding and analysing controlled-source electromagnetic (CSEM) responses for a conductive and permeable earth. To realize the CSEM response, a new 3-D CSEM forward modelling algorithm based on an edge finite element method for both electrically conductive and magnetically permeable heterogeneities is developed. The algorithm shows highly accurate results in validation tests against a semi-analytic solution for stratified earth and an integral form of the scattered field. We describe the vector behaviour of an anomalous magnetic field originating from a conductive and permeable anomaly when the loop sources are deployed over a conductive half-space. The CSEM response of the conductive and permeable anomaly is classified into three effects originating from: conductivity perturbations, permeability perturbations and the coupling of these two effects. The separated individual results and the corresponding integral equation form of the anomalous field help to better understand the physical behaviour. We confirm the characteristic features of the CSEM response from the conductive and permeable anomaly, for example, (1) the general dominance of the induction effect in the out-of-phase response accompanied by a non-negligible magnetization effect from the magnetic anomaly in a conductive half-space and (2) the dominance of near frequency-independent magnetization effects in the in-phase response at relatively low frequencies and change in ruling part of the in-phase response into the induction effect as the frequency increases. We also demonstrate the effect of coupling mode and show that its maximum contribution is limited to a few per cent level of other two modes, induction and magnetization mode, even when the heterogeneity of our model is strong. In our synthetic survey, using examples of land-based profiling surveys of low induction number and intermediate regime, we find that the effect of magnetization can be used as an

  4. Gastrointestinal transit and disintegration of enteric coated magnetic tablets assessed by ac biosusceptometry.

    PubMed

    Corá, Luciana A; Romeiro, Fernando G; Américo, Madileine F; Oliveira, Ricardo Brandt; Baffa, Oswaldo; Stelzer, Murilo; Miranda, José Ricardo de Arruda

    2006-01-01

    The oral administration is a common route in the drug therapy and the solid pharmaceutical forms are widely used. Although much about the performance of these formulations can be learned from in vitro studies using conventional methods, evaluation in vivo is essential in product development. The knowledge of the gastrointestinal transit and how the physiological variables can interfere with the disintegration and drug absorption is a prerequisite for development of dosage forms. The aim of this work was to employing the ac biosusceptometry (ACB) to monitoring magnetic tablets in the human gastrointestinal tract and to obtain the magnetic images of the disintegration process in the colonic region. The ac biosusceptometry showed accuracy in the quantification of the gastric residence time, the intestinal transit time and the disintegration time (DT) of the magnetic formulations in the human gastrointestinal tract. Moreover, ac biosusceptometry is a non-invasive technique, radiation-free and harmless to the volunteers, as well as an important research tool in the pharmaceutical, pharmacological and physiological investigations. PMID:16188432

  5. A wide-frequency range AC magnetometer to measure the specific absorption rate in nanoparticles for magnetic hyperthermia

    NASA Astrophysics Data System (ADS)

    Garaio, E.; Collantes, J. M.; Garcia, J. A.; Plazaola, F.; Mornet, S.; Couillaud, F.; Sandre, O.

    2014-11-01

    Measurement of specific absorption rate (SAR) of magnetic nanoparticles is crucial to assert their potential for magnetic hyperthermia. To perform this task, calorimetric methods are widely used. However, those methods are not very accurate and are difficult to standardize. In this paper, we present AC magnetometry results performed with a lab-made magnetometer that is able to obtain dynamic hysteresis-loops in the AC magnetic field frequency range from 50 kHz to 1 MHz and intensities up to 24 kA m-1. In this work, SAR values of maghemite nanoparticles dispersed in water are measured by AC magnetometry. The so-obtained values are compared with the SAR measured by calorimetric methods. Both measurements, by calorimetry and magnetometry, are in good agreement. Therefore, the presented AC magnetometer is a suitable way to obtain SAR values of magnetic nanoparticles.

  6. Calculating transport AC losses in stacks of high temperature superconductor coated conductors with magnetic substrates using FEM

    NASA Astrophysics Data System (ADS)

    Ainslie, Mark D.; Flack, Tim J.; Campbell, Archie M.

    2012-01-01

    In this paper, the authors investigate the electromagnetic properties of stacks of high temperature superconductor (HTS) coated conductors with a particular focus on calculating the total transport AC loss. The cross-section of superconducting cables and coils is often modeled as a two-dimensional stack of coated conductors, and these stacks can be used to estimate the AC loss of a practical device. This paper uses a symmetric two dimensional (2D) finite element model based on the H formulation, and a detailed investigation into the effects of a magnetic substrate on the transport AC loss of a stack is presented. The number of coated conductors in each stack is varied from 1 to 150, and three types of substrate are compared: non-magnetic weakly magnetic and strongly magnetic. The non-magnetic substrate model is comparable with results from existing models for the limiting cases of a single tape (Norris) and an infinite stack (Clem). The presence of a magnetic substrate increases the total AC loss of the stack, due to an increased localized magnetic flux density, and the stronger the magnetic material, the further the flux penetrates into the stack overall. The AC loss is calculated for certain tapes within the stack, and the differences and similarities between the losses throughout the stack are explained using the magnetic flux penetration and current density distributions in those tapes. The ferromagnetic loss of the substrate itself is found to be negligible in most cases, except for small magnitudes of current. Applying these findings to practical applications, where AC transport current is involved, superconducting coils should be wound where possible using coated conductors with a non-magnetic substrate to reduce the total AC loss in the coil.

  7. Magnetic core test stand for energy loss and permeability measurements at a high constant magnetization rate and test results for nanocrystalline and ferrite materials.

    PubMed

    Burdt, Russell; Curry, Randy D

    2008-09-01

    A test stand was developed to measure the energy losses and unsaturated permeability of toroidal magnetic cores, relevant to applications of magnetic switching requiring a constant magnetization rate of the order of 1-10 T/micros. These applications in pulsed power include linear induction accelerators, pulse transformers, and discharge switches. The test stand consists of a coaxial transmission line pulse charged up to 100 kV that is discharged into a magnetic core load. Suitable diagnostics measure the voltage across and the current through a winding on the magnetic core load, from which the energy losses and unsaturated permeability are calculated. The development of the test stand is discussed, and test results for ferrite CN20 and the nanocrystalline material Finemet FT-1HS are compared to demonstrate the unique properties of a nanocrystalline material. The experimental data are compared with published data in a similar parameter space to demonstrate the efficacy of the experimental methods. PMID:19044442

  8. dc and ac magnetic properties of thin-walled Nb cylinders with and without a row of antidots.

    PubMed

    Tsindlekht, M I; Genkin, V M; Felner, I; Zeides, F; Katz, N; Gazi, Š; Chromik, Š; Dobrovolskiy, O V; Sachser, R; Huth, M

    2016-06-01

    dc and ac magnetic properties of two thin-walled superconducting Nb cylinders with a rectangular cross-section are reported. Magnetization curves and the ac response were studied on as-prepared and patterned samples in magnetic fields parallel to the cylinder axis. A row of micron-sized antidots (holes) was made in the film along the cylinder axis. Avalanche-like jumps of the magnetization are observed for both samples at low temperatures for magnetic fields not only above H c1, but in fields lower than H c1 in the vortex-free region. The positions of the jumps are not reproducible and they change from one experiment to another, resembling vortex lattice instabilities usually observed for magnetic fields larger than H c1. At temperatures above [Formula: see text] and [Formula: see text] the magnetization curves become smooth for the patterned and the as-prepared samples, respectively. The magnetization curve of a reference planar Nb film in the parallel field geometry does not exhibit jumps in the entire range of accessible temperatures. The ac response was measured in constant and swept dc magnetic field modes. Experiment shows that ac losses at low magnetic fields in a swept field mode are smaller for the patterned sample. For both samples the shapes of the field dependences of losses and the amplitude of the third harmonic are the same in constant and swept field near H c3. This similarity does not exist at low fields in a swept mode. PMID:27143621

  9. Magnetic nanoparticle thermometer: an investigation of minimum error transmission path and AC bias error.

    PubMed

    Du, Zhongzhou; Su, Rijian; Liu, Wenzhong; Huang, Zhixing

    2015-01-01

    The signal transmission module of a magnetic nanoparticle thermometer (MNPT) was established in this study to analyze the error sources introduced during the signal flow in the hardware system. The underlying error sources that significantly affected the precision of the MNPT were determined through mathematical modeling and simulation. A transfer module path with the minimum error in the hardware system was then proposed through the analysis of the variations of the system error caused by the significant error sources when the signal flew through the signal transmission module. In addition, a system parameter, named the signal-to-AC bias ratio (i.e., the ratio between the signal and AC bias), was identified as a direct determinant of the precision of the measured temperature. The temperature error was below 0.1 K when the signal-to-AC bias ratio was higher than 80 dB, and other system errors were not considered. The temperature error was below 0.1 K in the experiments with a commercial magnetic fluid (Sample SOR-10, Ocean Nanotechnology, Springdale, AR, USA) when the hardware system of the MNPT was designed with the aforementioned method. PMID:25875188

  10. Magnetic Nanoparticle Thermometer: An Investigation of Minimum Error Transmission Path and AC Bias Error

    PubMed Central

    Du, Zhongzhou; Su, Rijian; Liu, Wenzhong; Huang, Zhixing

    2015-01-01

    The signal transmission module of a magnetic nanoparticle thermometer (MNPT) was established in this study to analyze the error sources introduced during the signal flow in the hardware system. The underlying error sources that significantly affected the precision of the MNPT were determined through mathematical modeling and simulation. A transfer module path with the minimum error in the hardware system was then proposed through the analysis of the variations of the system error caused by the significant error sources when the signal flew through the signal transmission module. In addition, a system parameter, named the signal-to-AC bias ratio (i.e., the ratio between the signal and AC bias), was identified as a direct determinant of the precision of the measured temperature. The temperature error was below 0.1 K when the signal-to-AC bias ratio was higher than 80 dB, and other system errors were not considered. The temperature error was below 0.1 K in the experiments with a commercial magnetic fluid (Sample SOR-10, Ocean Nanotechnology, Springdale, AR, USA) when the hardware system of the MNPT was designed with the aforementioned method. PMID:25875188

  11. The effect of surface grain reversal on the AC losses of sintered Nd-Fe-B permanent magnets

    NASA Astrophysics Data System (ADS)

    Moore, Martina; Roth, Stefan; Gebert, Annett; Schultz, Ludwig; Gutfleisch, Oliver

    2015-02-01

    Sintered Nd-Fe-B magnets are exposed to AC magnetic fields in many applications, e.g. in permanent magnet electric motors. We have measured the AC losses of sintered Nd-Fe-B magnets in a closed circuit arrangement using AC fields with root mean square-values up to 80 mT (peak amplitude 113 mT) over the frequency range 50 to 1000 Hz. Two magnet grades with different dysprosium content were investigated. Around the remanence point the low grade material (1.7 wt% Dy) showed significant hysteresis losses; whereas the losses in the high grade material (8.9 wt% Dy) were dominated by classical eddy currents. Kerr microscopy images revealed that the hysteresis losses measured for the low grade magnet can be mainly ascribed to grains at the sample surface with multiple domains. This was further confirmed when the high grade material was subsequently exposed to DC and AC magnetic fields. Here a larger number of surface grains with multiple domains are also present once the step in the demagnetization curve attributed to the surface grain reversal is reached and a rise in the measured hysteresis losses is evident. If in the low grade material the operating point is slightly offset from the remanence point, such that zero field is not bypassed, its AC losses can also be fairly well described with classical eddy current theory.

  12. Can commercial ferrofluids be exploited in AC magnetic hyperthermia treatment to address diverse biomedical aspects?

    NASA Astrophysics Data System (ADS)

    Angelakeris, M.; Li, Zi-An; Sakellari, D.; Simeonidis, K.; Spasova, M.; Farle, M.

    2014-07-01

    Multifunctional magnetic nanoparticles are considered as promising candidates for various applications combining diagnosis, imaging and therapy. In the present work, we elaborate on the commercial colloidal solution "FluidMAG" (from Chemicell GmbH) as a possible candidate for magnetic hyperthermia application. The current product is a dispersion of magnetite nanoparticles employed for purification or separation of biotinylated biomolecules from different sources (e.g. blood). Transmission Electron Microscopy showed that the NPs have a spherical shape with mean diameter of 12.3 nm (± 20%), and SQUID magnetometry revealed their superparamagnetic character. Our promising results of the AC hyperthermia efficiency of "FluidMAG" suggest that with the appropriate manipulation it can also be exploited as magnetic hyperthermia agent.

  13. Ac magnetotransport in La 0.7Sr 0.3Mn 0.95Fe 0.05O 3 at low dc magnetic fields

    NASA Astrophysics Data System (ADS)

    Barik, S. K.; Mahendiran, R.

    2011-12-01

    We report the ac electrical response of La 0.7Sr 0.3Mn 1- xFe xO 3(x=0.05) as a function of temperature, magnetic field (H) and frequency of radio frequency ( rf) current ( f=0.1-20 MHz). The ac impedance (Z) was measured while rf current directly passes through the sample as well as in a coil surrounding the sample. It is found that with increasing frequency of the rf current, Z(T) shows an abrupt increase accompanied by a peak at the ferromagnetic Curie temperature. The peak decreases in magnitude and shifts down with increasing value of H. We find a magnetoimpedance of ΔZ/Z=-21% for ΔH=500 Oe at f=1 MHz around room temperature when the rf current flows directly through the sample and ΔZ/Z=-65.9% when the rf current flows through a coil surrounding the sample. It is suggested that the magnetoimpedance observed is a consequence of suppression of transverse permeability which enhances skin depth for current flow. Our results indicate that the magnetic field control of high frequency impedance of manganites is more useful than direct current magnetoresistance for low-field applications.

  14. Magnetic anisotropy and permeability in sputtered iron aluminum nitride thin-film materials

    NASA Astrophysics Data System (ADS)

    Liu, Yi-Kuang

    Significant improvement in magnetic properties of FeXN (X = Al, Zr, Ta...) thin films deposited on the sloping surfaces, especially at 60°, was achieved by using various interlayer materials or proper sputtering conditions. The oblique incidence problems in permalloy and CoZrRe thin films were also greatly improved. Test heads fabricated using these materials showed improved permeability. Significant improvement of the thermal stability in FeXN thin films was also achieved. Sputtered at the reduced target-substrate spacing of 38 mm, 200 nm thick thermally stable FeXN thin films were obtained. They had hard axis coercivity ≈0.1--2.0 Oe, easy axis coercivity ≈1.5--3.0 Oe, Hk = 8--16 Oe and Bs = 19--20 kG. Results from transverse field annealing experiments in a uniform field of 700 Oe show no significant change of magnetic properties at 150°C for 3 hours. At 150°C for 24 hours, Hk decreased by 2--4 Oe. Their easy/hard axes did not rotate and the coercivity remained almost unchanged. This superior thermal stability of FeXN films is promising for high moment write heads. The effects of N doping on the magnetic and structural properties of a series of 100 nm FeAlN films sputtered in the presence of N partial pressures were investigated. Increasing N doping increased film resistivity but decreased MS. Extended x-ray absorption fine structure spectra of the short-range atomic order in the Fe(Al) lattices directly indicated that the N went into octahedral sites of bcc Fe and fcc Fe in alpha-Fe and gamma'-Fe 4N phases, respectively, and triggered the order-disorder phase transition observed in x-ray 0--20 diffraction spectra. Mild N doping decreased the grain size and reduced Hc. It also increased the local atomic disorder, which coincided with the maximal value of Ku and the in-plane anisotropic behaviors in the as-deposited films. The roles of N doping in FeXN film optimization processes and its effects on magnetic and structural properties, especially the uniaxial

  15. Effects of humidity on the magnetic and woody characteristics of powder-type magnetic wood

    NASA Astrophysics Data System (ADS)

    Oka, H.; Tokuta, H.; Namizaki, Y.; Sekino, N.

    2004-05-01

    Among three types of proposed magnetic wood, powder-type magnetic wood can be made of recycled magnetic materials from IT devices, consumer electronics and waste wood. Because of its wood powder content, powder-type magnetic wood shows special characteristics different from those of typical magnetic materials. We focused on the relationship between humidity and magnetic characteristics of powder-type magnetic wood. The magnetic powder ratio, wood powder density and magnetic binder density were all examined as parameters for AC permeability.

  16. AC transport in p-Ge/GeSi quantum well in high magnetic fields

    SciTech Connect

    Drichko, I. L.; Malysh, V. A.; Smirnov, I. Yu.; Golub, L. E.; Tarasenko, S. A.; Suslov, A. V.; Mironov, O. A.; Kummer, M.; Känel, H. von

    2014-08-20

    The contactless surface acoustic wave technique is implemented to probe the high-frequency conductivity of a high-mobility p-Ge/GeSi quantum well structure in the regime of integer quantum Hall effect (IQHE) at temperatures 0.3–5.8 K and magnetic fields up to 18 T. It is shown that, in the IQHE regime at the minima of conductivity, holes are localized and ac conductivity is of hopping nature and can be described within the “two-site” model. The analysis of the temperature and magnetic-field-orientation dependence of the ac conductivity at odd filing factors enables us to determine the effective hole g-factor, |g{sub zz}|≈4.5. It is shown that the in-plane component of the magnetic field leads to a decrease in the g-factor as well as increase in the cyclotron mass, which is explained by orbital effects in the complex valence band of germanium.

  17. Effects of eddy current and dispersion of magnetic anisotropy on the high-frequency permeability of Fe-based nanocomposites

    NASA Astrophysics Data System (ADS)

    Han, M.; Rozanov, K. N.; Zezyulina, P. A.; Wu, Yan-Hui

    2015-06-01

    Fe-Cu-Nb-Si-B microflakes have been prepared by ball milling. The structural, magnetostatic and microwave permeability of the flakes and flake-filled composites have been studied. Two ferromagnetic phases, nanograins and amorphous matrix, are found in the flakes. The Mössbauer study shows that the nanograins are α-Fe3(Si) with D03 superlattice structure. High resolution transmission electron microscopy shows that the nanograins are well dispersed in the matrix. The microwave permeability of composites containing the flakes has been measured. The comparison of the intrinsic permeability of the flakes obtained from the permeability measurements and from the anisotropy field distribution reveals a disagreement in the magnetic loss peak location. It is concluded that the low-frequency loss in the composites is not due to the effect of eddy currents. The low-frequency loss may be attributed to other sources, such as domain wall motion or peculiarities of the magnetic structure of the flakes in the composite.

  18. Design of a novel phase-decoupling permanent magnet brushless ac motor

    NASA Astrophysics Data System (ADS)

    Cui, Wei; Chau, K. T.; Jiang, J. Z.; Fan, Ying

    2005-05-01

    This paper presents a phase-decoupling permanent magnet brushless ac motor which can offer better controllability, faster response, and smoother torque than its counterparts. The key is due to its different motor configuration and simple scalar control. The motor configuration is so unique that it inherently offers the features of phase decoupling, flux focusing, and flux shaping, hence achieving independent phase control, fast response, and smooth torque. The scalar control is fundamentally different from the complicated vector control. It can achieve direct torque control through independent control of the phase currents. The proposed motor is prototyped and experimentally verified.

  19. An adaptive fuzzy controller for permanent-magnet AC servo drives

    SciTech Connect

    Le-Huy, H.

    1995-12-31

    This paper presents a theoretical study on a model-reference adaptive fuzzy logic controller for vector-controlled permanent-magnet ac servo drives. In the proposed system, fuzzy logic is used to implement the direct controller as well as the adaptation mechanism. The operation of the direct fuzzy controller and the fuzzy logic based adaptation mechanism is studied. The control performance of the adaptive fuzzy controller is evaluated by simulation for various operating conditions. The results are compared with that provided by a non-adaptive fuzzy controller. The implementation of proposed adaptive fuzzy controller is discussed.

  20. 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.

  1. Dynamic melting and impurity particle tracking in continuously adjustable AC magnetic field

    NASA Astrophysics Data System (ADS)

    Bojarevics, V.; Pericleous, K.

    2016-07-01

    The analysis of semi-levitation melting is extended to account for the presence of particles (impurities, broken metal dendrite agglomerates, bubbles) during the full melting cycle simulated numerically using the pseudo-spectral schemes. The AC coil is dynamically moving with the melt front progress, while the generated Joule heat serves to enhance the melting rate. The electromagnetic force is decomposed into the time average and the oscillating parts. The time average effects on the particle transport are investigated previously using approximations derived for a locally uniform magnetic field. This paper presents expressions for the skin-layer type of the AC force containing also the pulsating part which contributes to the particle drag by the ‘history’ and ‘added mass’ contributions. The intense turbulence in the bulk of molten metal additionally contributes to the particle dispersion. The paper attempts to demonstrate the importance of each of the mentioned effects onto the particle transport during the melting until the final pouring stage. The method could be extended to similar AC field controlled melting/solidification processes.

  2. Swept frequency permeameters for measuring the complex, off-diagonal permeability tensor components of anisotropic, thin magnetic films

    NASA Astrophysics Data System (ADS)

    Grimes, Craig A.; Prodan, John V.

    1993-05-01

    To better understand wave propagation through magnetic media we have measured the high-frequency off-diagonal permeability tensor components of magnetic thin films using a thin-film permeameter. Although the off-diagonal components are commonly considered to be of negligible value, for some materials they are substantial, of a magnitude comparable to that of the diagonal terms. Since the out-of-plane off-diagonal coupling terms are primarily imaginary below resonance, and real above, they may introduce unexpected phase errors into the read/write process of magnetic recording and bulk material measurements and are therefore worthy of attention. The permeameters used to measured the off-diagonal terms are based upon the design of C. A. Grimes, P. L. Trouilloid, and R. M. Walser [IEEE Trans. Magn. MAG-24, 603 (1988)], which measure diagonal terms, but with different pickup coil and sample seat geometries. For z normal to the film, and with x and y defining, respectively, the hard and easy magnetization axes of the basal plane we measure μxy and μxz. A microwave scattering parameter test set is used to measure the scattering parameters of the jig from which the complex permeability is determined. The permeameters reported on here operate over the frequency range of approximately 10-600 MHz, and have a low level permeance detection limit of about 1 μm. Measurements of cosputtered amorphous Co55Zr45 thin films show that the out-of-plane permeability coupling term μxz is a significant fraction of the basal plane hard axis permeability.

  3. Coherence-population-trapping transients induced by an ac magnetic field

    NASA Astrophysics Data System (ADS)

    Margalit, L.; Rosenbluh, M.; Wilson-Gordon, A. D.

    2012-06-01

    Coherent-population-trapping transients induced by an ac magnetic field are investigated theoretically for a realistic three-level Λ system in the D1 line of 87Rb. The contributions to the transient probe absorption from the various subsystems that compose the realistic atomic system are examined and the absorption of each Λ subsystem is compared to that of a simple Λ system. The population redistribution due to optical pumping is shown to be the dominant cause of the difference between the contributions of the various subsystems to the oscillatory character of the probe absorption. We also discuss the series of transients that reappear every half-cycle time of a modulated magnetic field when the system is in two-photon resonance, and we study the transient behavior as a function of the probe detuning. The effect of a buffer gas on the amplitude and shape of the transients is considered.

  4. Test Results of the AC Field Measurements of Fermilab Booster Corrector Magnets

    SciTech Connect

    DiMarco, E.Joseph; Harding, D.J.; Kashikhin, V.S.; Kotelnikov, S.K.; Lamm, M.J.; Makulski, A.; Nehring, R.; Orris, D.F.; Schlabach, P.; Sylvester, C.; Tartaglia, Michael Albert; /Fermilab

    2008-06-25

    Multi-element corrector magnets are being produced at Fermilab that enable correction of orbits and tunes through the entire cycle of the Booster, not just at injection. The corrector package includes six different corrector elements--normal and skew orientations of dipole, quadrupole, and sextupole--each independently powered. The magnets have been tested during typical AC ramping cycles at 15Hz using a fixed coil system to measure the dynamic field strength and field quality. The fixed coil is comprised of an array of inductive pick-up coils around the perimeter of a cylinder which are sampled simultaneously at 100 kHz with 24-bit ADC's. The performance of the measurement system and a summary of the field results are presented and discussed.

  5. Influence of the ac magnetic field frequency on the magnetoimpedance of amorphous wire

    NASA Astrophysics Data System (ADS)

    Chen, A. P.; García, C.; Zhukov, A.; Domínguez, L.; Blanco, J. M.; González, J.

    2006-05-01

    Experimental and theoretical studies on the influence of ac magnetic field frequency on the axial diagonal (ζzz) and off-diagonal (ζphiz) components of the magnetoimpedance (MI) tensor in (Co0.94Fe0.06)72.5Si12.5B15 amorphous wires have been performed. The frequency (f) of an ac current flowing along the wire was varied from 1 to 20 MHz with the current amplitude less than 15 mA. In order to enhance the ζphiz component, the amorphous wire was submitted to torsion annealing for developing and preserving a helical magnetic anisotropy in the surface of the wire. The experimental measurements show that the value of the impedance is proportional to the square-root of the ac current frequency, \\sqrt f , in the vicinity of Hex < HK and this increase is due to the contribution of the resistance (real part of the impedance). The measurements also indicate that the peaks of the MI curve shift slightly towards higher field values with increasing f. In a theoretical study the magnetoimpedance expressions ζzz and ζphiz have been deduced using the Faraday law in combination with the solutions of the Maxwell and Landau-Lifshitz-Gilbert (LLG) equations. By analysing quantitatively the spectra of ζzz and ζphiz, the phenomenon of the shift in the peaks of the MI curve with f has been considered as a characteristic of the helical anisotropy in the domain structure of the wire surface.

  6. Creep Void Detection for Low Alloy Steel Using AC Magnetic Method

    SciTech Connect

    Shiwa, M.; Cheng, W.; Kume, R.

    2004-02-26

    Nondestructive detection of creep void was developed for low alloy steel by using AC magnetic method. Two types of 2.25Cr-1Mo steel specimens, base metal (BM) and simulated heat affected zone (HAZ) under aging and creep damage, were prepared for the tests. A differential type probe was used to detect AC magnetic signals. The exciting and detecting coils were coaxially arranged with a ferrite core. Signals were recorded using a 2-channel waveform recorder. The equivalent hysteresis loss (HL) was analyzed. It was observed that the HL of BM and HAZ changed in opposite direction, that is, HL of BM increased and HL of HAZ decreased with aging time. On the other hand, the HLs of both BM and HAZ decreased with creep time. The HL of creep samples was affected by both aging and stress-induced damage. In order to evaluate creep damage, stress-induced damage (SID) parameter was proposed to remove aging factor of materials from HL. Creep void were observed by scanning electron microscope (SEM) for all creep damage samples of SID value under 0.8.

  7. Dynamic model tracking design for low inertia, high speed permanent magnet ac motors.

    PubMed

    Stewart, P; Kadirkamanathan, V

    2004-01-01

    Permanent magnet ac (PMAC) motors have existed in various configurations for many years. The advent of rare-earth magnets and their associated highly elevated levels of magnetic flux makes the permanent magnet motor attractive for many high performance applications from computer disk drives to all electric racing cars. The use of batteries as a prime storage element carries a cost penalty in terms of the unladen weight of the vehicle. Minimizing this cost function requires the minimum electric motor size and weight to be specified, while still retaining acceptable levels of output torque. This tradeoff can be achieved by applying a technique known as flux weakening which will be investigated in this paper. The technique allows the speed range of a PMAC motor to be greatly increased, giving a constant power range of more than 4:1. A dynamic model reference controller is presented which has advantages in ease of implementation, and is particularly suited to dynamic low inertia applications such as clutchless gear changing in high performance electric vehicles. The benefits of this approach are to maximize the torque speed envelope of the motor, particularly advantageous when considering low inertia operation. The controller is examined experimentally, confirming the predicted performance. PMID:15000141

  8. Thermodynamics of the Mn12-ac molecule in a skew magnetic field at T \\gtrsim 21 K

    NASA Astrophysics Data System (ADS)

    Rojas, Onofre; Thomaz, M. T.; Corrêa Silva, E. V.; de Souza, S. M.

    2009-01-01

    We derive the high-temperature expansion of the Helmholtz free energy of the quantum and classical models for the Mn12-ac molecule in the presence of a skew magnetic field, including the transverse term in the Hamiltonians, for T \\gtrsim 21 K. In this region of temperature, we show that the transverse term can give a measurable contribution to the x component of the magnetization. We obtain the specific heat per site of a powder sample of Mn12-ac under a constant magnetic field. For strong skew magnetic fields (h/D>1), the specific heat differs up to 20% from its value of a crystal sample under purely longitudinal magnetic fields. Finally, we obtain that in the limit T \\rightarrow \\infty , the values of the classical and quantum specific heat differ; in particular, for \\vec {h}= \\vec 0 this difference is 0.96%.

  9. Magnetic and microwave absorbing properties of Co2+ substituted nickel-zinc ferrites with the emphasis on initial permeability studies

    NASA Astrophysics Data System (ADS)

    Ghodake, J. S.; Kambale, Rahul C.; Shinde, T. J.; Maskar, P. K.; Suryavanshi, S. S.

    2016-03-01

    Nanocrystalline Co2+ substituted Zn0.35Ni0.60-xCoxFe2.05O4 (Where x=0.0, 0.1, 0.2, 0.3 and 0.4) system have been synthesized by citrate-nitrate combustion route. X-ray diffraction study shows the formation of single phase cubic spinel structure without any impurity phases. Morphological observation shows agglomerated grains with different shapes and sizes which is the typical characteristics of magnetic nanoparticles prepared by combustion route. The saturation magnetization of cobalt substituted Ni-Zn ferrites is found to be higher than that of pure Ni-Zn ferrite. The coercivity and retentivity of cobalt substituted Ni-Zn ferrite increases with the increasing cobalt content. Initial permeability and loss factor have been studied as the function of composition and frequency. The real (μ‧) and imaginary (μ‧‧) part of initial permeability of cobalt substituted Ni-Zn ferrites decreases while its loss factor increases with the increasing cobalt content. In the lower frequency region the imaginary part of initial permeability (μ‧‧) of all samples is found to be decreasing rapidly with increasing frequency. The microwave absorption properties of cobalt substituted Ni-Zn ferrites were also investigated; all samples exhibit the absorption in the frequency range 2.3-2.5 GHz. Thus, the prepared materials can be used as a rubber composite microwave absorber and may be useful in RADAR application.

  10. dc and ac magnetic properties of thin-walled Nb cylinders with and without a row of antidots

    NASA Astrophysics Data System (ADS)

    Tsindlekht, M. I.; Genkin, V. M.; Felner, I.; Zeides, F.; Katz, N.; Gazi, Š.; Chromik, Š.; Dobrovolskiy, O. V.; Sachser, R.; Huth, M.

    2016-06-01

    dc and ac magnetic properties of two thin-walled superconducting Nb cylinders with a rectangular cross-section are reported. Magnetization curves and the ac response were studied on as-prepared and patterned samples in magnetic fields parallel to the cylinder axis. A row of micron-sized antidots (holes) was made in the film along the cylinder axis. Avalanche-like jumps of the magnetization are observed for both samples at low temperatures for magnetic fields not only above H c1, but in fields lower than H c1 in the vortex-free region. The positions of the jumps are not reproducible and they change from one experiment to another, resembling vortex lattice instabilities usually observed for magnetic fields larger than H c1. At temperatures above 0.66{{T}\\text{c}} and 0.78{{T}\\text{c}} the magnetization curves become smooth for the patterned and the as-prepared samples, respectively. The magnetization curve of a reference planar Nb film in the parallel field geometry does not exhibit jumps in the entire range of accessible temperatures. The ac response was measured in constant and swept dc magnetic field modes. Experiment shows that ac losses at low magnetic fields in a swept field mode are smaller for the patterned sample. For both samples the shapes of the field dependences of losses and the amplitude of the third harmonic are the same in constant and swept field near H c3. This similarity does not exist at low fields in a swept mode.

  11. Measurements on magnetized GdBCO pellets subjected to small transverse ac magnetic fields at very low frequency: Evidence for a slowdown of the magnetization decay

    NASA Astrophysics Data System (ADS)

    Fagnard, Jean-Francois; Kirsch, Sébastien; Morita, Mitsuru; Teshima, Hidekazu; Vanderheyden, Benoit; Vanderbemden, Philippe

    2015-05-01

    Due to their ability to trap large magnetic inductions, superconducting bulk materials can be used as powerful permanent magnets. The permanent magnetization of such materials, however, can be significantly affected by the application of several cycles of a transverse variable magnetic field. In this work, we study, at T = 77 K, the long term influence of transverse ac magnetic fields of small amplitudes (i.e. much smaller than the full penetration field) on the axial magnetization of a bulk single grain superconducting GdBCO pellet over a wide range of low frequencies (1 mHz-20 Hz). Thermocouples are placed against the pellet surface to probe possible self-heating of the material during the experiments. A high sensitivity cryogenic Hall probe is placed close to the surface to record the local magnetic induction normal to the surface. The results show first that, for a given number of applied triangular transverse cycles, higher values of dBapp/dt induce smaller magnetization decays. An important feature of practical interest is that, after a very large number of cycles which cause the loss of a substantial amount of magnetization (depending on the amplitude and the frequency of the field), the rate of the magnetization decay goes back to its initial value, corresponding to the relaxation of the superconducting currents due to flux creep only. In the amplitude and frequency range investigated, the thermocouples measurements and a 2D magneto-thermal modelling show no evidence of sufficient self-heating to affect the magnetization so that the effect of the transverse magnetic field cycles on the trapped magnetic moment is only attributed to a redistribution of superconducting currents in the volume of the sample and not to a thermal effect.

  12. A laboratory study to estimate pore geometric parameters of sandstones using complex conductivity and nuclear magnetic resonance for permeability prediction

    NASA Astrophysics Data System (ADS)

    Osterman, Gordon; Keating, Kristina; Binley, Andrew; Slater, Lee

    2016-06-01

    We estimate parameters from the Katz and Thompson permeability model using laboratory complex electrical conductivity (CC) and nuclear magnetic resonance (NMR) data to build permeability models parameterized with geophysical measurements. We use the Katz and Thompson model based on the characteristic hydraulic length scale, determined from mercury injection capillary pressure estimates of pore throat size, and the intrinsic formation factor, determined from multisalinity conductivity measurements, for this purpose. Two new permeability models are tested, one based on CC data and another that incorporates CC and NMR data. From measurements made on forty-five sandstone cores collected from fifteen different formations, we evaluate how well the CC relaxation time and the NMR transverse relaxation times compare to the characteristic hydraulic length scale and how well the formation factor estimated from CC parameters compares to the intrinsic formation factor. We find: (1) the NMR transverse relaxation time models the characteristic hydraulic length scale more accurately than the CC relaxation time (R2 of 0.69 and 0.33 and normalized root mean square errors (NRMSE) of 0.16 and 0.21, respectively); (2) the CC estimated formation factor is well correlated with the intrinsic formation factor (NRMSE=0.23). We demonstrate that that permeability estimates from the joint-NMR-CC model (NRMSE=0.13) compare favorably to estimates from the Katz and Thompson model (NRMSE=0.074). This model advances the capability of the Katz and Thompson model by employing parameters measureable in the field giving it the potential to more accurately estimate permeability using geophysical measurements than are currently possible.

  13. Stability Of Superposed Fluids Through Magnetic Field With Suspended Particles Of Different Permeability Saturated Through Porous Layer

    NASA Astrophysics Data System (ADS)

    Singh, M.

    2015-12-01

    The instability of plane interface between two superposed Rivlin-Ericksen elastico-viscous fluids saturated through a porous medium has been studied to include the suspended (dust) particles effect. Following the linearized stability theory and normal mode analysis the dispersion relation is obtained. For stationary convection, the Rivlin-Ericksen elastico-viscous fluid behaves like Newtonian fluids. It found that for a potentially stable arrangement the Rivlin-Ericksen elastico-viscous fluid of different permeabilities in the presence of suspended particles in a porous medium is stable, whereas in a potentially unstable case instability of the system occurs. In the presence of a magnetic field for a potentially stable arrangement the system is always stable and for the potentially unstable arrangement, the magnetic field succeeds in stabilizing certain wave-number band which was unstable in the absence of the magnetic field.

  14. Nonlinear Dynamics of Magnons observed by AC Spin Pumping in Magnetic Hybrid Structures

    NASA Astrophysics Data System (ADS)

    Vilela-Leao, L. H.; Cunha, R. O.; Azevedo, A.; Rodriguez-Suarez, R. L.; Rezende, S. M.

    2015-03-01

    The electron spin degree of freedom constitutes the basic means to carry and store information in the field of spintronics. In the spin pumping process, the microwave driven magnetization dynamics in a ferromagnetic film generates a spin current in an attached metallic layer that can be converted into a charge current by means of the inverse spin Hall effect and detected by a voltage signal. While the time independent component (DC) of the spin current has been widely investigated in a variety of material structures, recently it has been recognized that the alternating current (AC) component is much larger, though more difficult to detect, and has many attractive features. We report experiments with microwave driven DC and AC spin pumping in bilayers made of the insulating ferrimagnet yttrium iron garnet (YIG) and platinum that reveal the nonlinear dynamics involving the driven mode and a pair of magnon modes with half frequency. This process occurs when the frequency is lowered below a critical value so that a three-magnon splitting process with energy conservation is made possible. The results are explained by a model with coupled nonlinear equations describing the time evolution of the magnon modes.

  15. ac magnetic trackers for biomedical application: now and in the near future

    NASA Astrophysics Data System (ADS)

    Murry, Herschell F.

    1996-04-01

    A number of ac magnetic trackers have been, and are now being, used in the medical community for varied applications from describing electronically the exact shape of a subject to tracking movement of objects. A good reason for using this technology is that the magnetic fields pass through the body without occlusions and without ionizing radiation. This paper commences with descriptions of several such tools readily available, including our 3D input stylus and 3DRAW tablet defining object dimensions to 0.01' accuracy and our close-in Short Ranger transmitter operating precisely between 2' - 12' over the subject. For the future, R&D and military electronics sponsored topics such as a metal distortion insensitive magnetic source, a high performance 240 Hz (or up to eight sensors each operating at 30 Hz) tracker with the processing power to virtually eliminate metal distortion effects and an approach for building a biologically insertible tracker are discussed to indicate the potential for new tracking tools. Discussion of needs from the medical community is encouraged in order to better guide efforts in applying our specialty technology to biomedical applications where ewe are neophytes.

  16. Generation of liquid metal structures of high aspect ratio by application of an ac magnetic field

    NASA Astrophysics Data System (ADS)

    Andreev, Oleg; Pothérat, Alban; Thess, André

    2010-06-01

    We study how the shape of parts obtained through the LASER cladding process can be controlled by application of an ac magnetic field by means of two simple physical models: a numerical and an experimental one. More specifically, we show that straight metallic joints of high aspect ratio can be obtained by using inductors of triangular cross-section that concentrate electromagnetic forces at the bottom of the joint. The effect is first demonstrated on a numerical model for an infinitely long joint such as: we illustrate how the joint shape can be controlled by varying the inclination of the inductor and for a magnetic Bond number Bom=60 (which measures the ratio of electromagnetic to capillary forces), we obtain a joint of aspect ratio up to 7.2. We further find that inductor angles in the range 15°-25° lead to joint side faces that are close to vertical. These findings are then verified experimentally by placing a liquid metal drop in a purpose built inductor of triangular cross-section. We find a good agreement between the theoretical prediction of our two-dimensional model and the real three-dimensional drop. For the highest magnetic Bond number our generator could deliver, Bom=20.19, we achieved a drop aspect ratio of 2.73.

  17. Modified MgFe2O4 Ferrimagnetic Nanoparticles to Improve Magnetic and AC Magnetically-Induced Heating Characteristics for Hyperthermia.

    PubMed

    Lee, Sanghoon; Jeun, Minhong

    2015-12-01

    A ferrimagnetic nanoparticle with a smaller size, a narrower size distribution, and a higher ac heat generation ability has been still studied for intra-arterial or intra-tumoral hyperthermia. In this study, we manipulate the calcining temperature in the range of 400-600 degrees C to modify MgFe2O4 ferrimagnetic nanoparticles (FMNPs) during modified sol-gel process. The modified MgFe2O4 FMNPs have well controlled with small size and narrow size distribution, so that their magnetic and ac magnetically-induced heating characteristics are significantly improved. In particular, MgFe2O4 nanoparticles synthesized at the calcining temperature of 600 degrees C and sintering temperature of 700 degrees C show the most suitable size (58 nm ± 13 nm) and its distribution (22%) resulting in the highest ac magnetically-induced heating temperature (T(AC,mag), ΔT = 93 degrees C) and SLP (Specific Loss Power, 600 W/g) at the biologically tolerable range of magnetic field (H(appl) = 140 Oe) and frequency (f(appl) = 110 kHz). It is found to be due to the improvement of magnetic softness and saturation magnetization resulting in the largest hysteresis loss power. All the results in this work clearly demonstrate that calcining process is one of the key parameters to control the proper size and size distribution for improving magnetic and ac magnetically-induced heating characteristics of MgFe2O4 FMNPs, which can be applicable to hyperthermia agents in nanomedicine. PMID:26682384

  18. Use of an advanced composite material in construction of a high pressure cell for magnetic ac susceptibility measurements

    NASA Astrophysics Data System (ADS)

    Wang, X.; Misek, M.; Jacobsen, M. K.; Kamenev, K. V.

    2014-10-01

    The applicability of fibre-reinforced polymers for fabrication of high pressure cells was assessed using finite element analysis and experimental testing. Performance and failure modes for the key components of the cell working in tension and in compression were evaluated and the ways for optimising the designs were established. These models were used in construction of a miniature fully non-metallic diamond anvil cell for magnetic ac susceptibility measurements in a magnetic property measurement system. The cell is approximately 14 mm long, 8.5 mm in diameter and was demonstrated to reach a pressure of 5.6 GPa. AC susceptibility data collected on Dy2O3 demonstrate the performance of the cell in magnetic property measurements and confirm that there is no screening of the sample by the environment which typically accompanies the use of conventional metallic high pressure cells in oscillating magnetic fields.

  19. Edge pinch instability of liquid metal sheet in a transverse high-frequency ac magnetic field.

    PubMed

    Priede, Jānis; Etay, Jacqueline; Fautrelle, Yves

    2006-06-01

    We analyze the linear stability of the edge of a thin liquid metal layer subject to a transverse high-frequency ac magnetic field. The layer is treated as a perfectly conducting liquid sheet that allows us to solve the problem analytically for both a semi-infinite geometry with a straight edge and a thin disk of finite radius. It is shown that the long-wave perturbations of a straight edge are monotonically unstable when the wave number exceeds the critical value k(c) = F0/(gamma l0), which is determined by the linear density of the electromagnetic force F0 acting on the edge, the surface tension gamma, and the effective arclength of edge thickness l0. Perturbations with wavelength shorter than critical are stabilized by the surface tension, whereas the growth rate of long-wave perturbations reduces as similar to k for k --> 0. Thus, there is the fastest growing perturbation with the wave number k max = 2/3 k(c). When the layer is arranged vertically, long-wave perturbations are stabilized by the gravity, and the critical perturbation is characterized by the capillary wave number k(c) = square root of (g rho/gamma), where g is the acceleration due to gravity and rho is the density of metal. In this case, the critical linear density of electromagnetic force is F(0,c) = 2k(c)l0 gamma, which corresponds to the critical current amplitude I(0,c) = 4 square root of (pi k(c) l0L gamma/mu 0) when the magnetic field is generated by a straight wire at the distance L directly above the edge. By applying the general approach developed for the semi-infinite sheet, we find that a circular disk of radius R0 placed in a transverse uniform high-frequency ac magnetic field with the induction amplitude B0 becomes linearly unstable with respect to exponentially growing perturbation with the azimuthal wave number m = 2 when the magnetic Bond number exceeds Bm(c) = B(0)2 R(0)2 / (2 mu 0 l0 gamma) = 3 pi. For Bm > Bm(c), the wave number of the fastest growing perturbation is m(max) = [2

  20. Production Of Multi-magnetron Plasma By Using Polyphase Ac Glow Discharge In An Improved Multi-pole Magnetic Field

    NASA Astrophysics Data System (ADS)

    Matsumoto, Kazunori; Motoki, Kentaro; Miyamoto, Masahiro; Uetani, Yasuhiro

    1998-10-01

    Effects of an improved multi-pole magnetic field on a plasma production generated by a polyphase ac glow discharge with multiple electrodes have been investigated. Conventional configuration of the multi-pole magnetic filed has been modified to suppress plasma losses at both ends of the chamber due to ExB drift motion. The modified multi-pole magnetic field has enabled us to produce a multiple magnetron-plasma at a considerably low pressure less than mTorr. The low temperature plasma has been widely used as the fine processing technology of a dry etching and as the thin film formation technology of a sputtering coating. Large-scale plasmas which can be generated at a low gas-pressure have been desired for more wider dry etching and greater sputter coating. The purpose of this study is to develop a large-scale and low-cost plasma generator by using a polyphase ac power source with the low frequency. In this session, we will present the experimental result as to a multiple magnetron-plasma generated in the modified twenty-four poles magnetic field by using the twenty-four-phase ac power source with the commercial electric power frequency of 60Hz. The ac power is supplied to twenty-four electrodes which are fixed to the water-cooled chamber-wall through sheet insulators so that the electrodes can be cooled indirectly.

  1. Effects of AC/DC magnetic fields, frequency, and nanoparticle aspect ratio on cellular transfection of gene vectors

    NASA Astrophysics Data System (ADS)

    Ford, Kris; Mair, Lamar; Fisher, Mike; Rowshon Alam, Md.; Juliano, Rudolph; Superfine, Richard

    2008-10-01

    In order to make non-viral gene delivery a useful tool in the study and treatment of genetic disorders, it is imperative that these methodologies be further refined to yield optimal results. Transfection of magnetic nanoparticles and nanorods are used as non-viral gene vectors to transfect HeLa EGFP-654 cells that stably express a mutated enhanced green fluorescent protein (EGFP) gene. We deliver antisense oligonucleotides to these cells designed to correct the aberrant splicing caused by the mutation in the EGFP gene. We also transfect human bronchial endothelial cells and immortalized WI-38 lung cells with pEGFP-N1 vectors. To achieve this we bind the genes to magnetic nanoparticles and nanorods and introduce magnetic fields to effect transfection. We wish to examine the effects of magnetic fields on the transfection of these particles and the benefits of using alternating (AC) magnetic fields in improving transfection rates over direct (DC) magnetic fields. We specifically look at the frequency dependence of the AC field and particle aspect ratio as it pertains to influencing transfection rate. We posit that the increase in angular momentum brought about by the AC field and the high aspect ratio of the nanorod particles, is vital to generating the force needed to move the particle through the cell membrane.

  2. Quantitative permeability magnetic resonance imaging in acute ischemic stroke: how long do we need to scan?

    PubMed

    Vidarsson, Logi; Thornhill, Rebecca E; Liu, Fang; Mikulis, David J; Kassner, Andrea

    2009-11-01

    Blood-brain barrier (BBB) permeability estimation with dynamic contrast-enhanced MRI (DCE-MRI) has shown significant potential for predicting hemorrhagic transformation (HT) in patients presenting with acute ischemic stroke (AIS). In this work, the effects of scan duration on quantitative BBB permeability estimates (KPS) were investigated. Data from eight patients (three with HT) aged 37-93 years old were retrospectively studied by directly calculating the standard deviation of KPS as a function of scan time. The uncertainty in KPS was reduced only slightly for a scan time of 3 min and 30 s (4% reduction in P value from .047 to .045). When more than 3 min and 30 s of data were used, quantitative permeability MRI was able to separate those patients who proceeded to HT from those who did not (P value <.05). Our findings indicate that reducing permeability acquisition times is feasible in keeping with the need to maintain time-efficient MR protocols in the setting of AIS. PMID:19695816

  3. Second VAMAS a.c. loss measurement intercomparison: a.c. magnetization measurement of hysteresis and coupling losses in NbTi multifilamentary strands

    NASA Astrophysics Data System (ADS)

    Schmidt, C.; Itoh, K.; Wada, H.

    The article summarizes results of part of the second VAMAS a.c. loss measurement intercomparison. This program was carried out at 17 participating laboratories on two sets of multifilamentary NbTi strands (Set No. 1: copper matrix, fil. diam. between 0.5 and 12 μm; Set No. 2: cupronickel matrix, fil. diam. between 0.4 and 1.2 μm). The results reported here were measured by means of a.c. magnetization methods and separated into hysteresis and coupling losses. One laboratory used a calorimetric method. The data scatter in measured hysteresis losses among the participating laboratories was reasonably small for different measuring methods adopted and experimental arrangements used. On the other hand, the data scatter in coupling losses was large, mainly because in most laboratories a.c. losses were measured only at low frequencies (below 1 Hz), where the separation of coupling losses from total losses tends to be inaccurate. The comparison of measured hysteresis losses with the critical state model showed a large disagreement, which is assumed to be due to proximity effect coupling between filaments. 1997 Elsevier Science Limited

  4. The magnetisation profiles and ac magnetisation losses in a single layer YBCO thin film caused by travelling magnetic field waves

    NASA Astrophysics Data System (ADS)

    Wang, Wei; Coombs, Timothy

    2015-05-01

    This paper studies the magnetisation and ac magnetisation losses caused by a travelling magnetic wave on a single-layer YBCO thin film. This work provides thorough investigations on how the critical magnetic field gradient has been changed by the application of a travelling wave. Several conditions were studied such as zero-field cooling (ZFC), field cooling (FC) and a delta-shaped trapped field. It was found that the travelling wave tends to attenuate the existing critical magnetic field gradients in all these conditions. This interesting magnetic behaviour can be well predicted by the finite element (FEM) software with the E-J power law and Maxwell’s equations. The numerical simulations show that the existing critical current density has been compromised after applying the travelling wave. The magnetisation profile caused by the travelling wave is very different from the standing wave, while the magnetisation based on the standing wave can be interpreted by the Bean model and constant current density assumption. Based on the numerical method, which has reliability that has been solidly proven in the study, we have extended the study to the ac magnetisation losses. Comparisons were made between the travelling wave and the standing wave for this specific YBCO sample. It was found that by applying the magnetic wave of the same amplitude, the ac magnetisation loss caused by the travelling wave is about 1/3 of that caused by the standing wave. These results are helpful in understanding the general magnetism problems and ac magnetisation loss in the travelling magnetic wave conditions such as inside a high temperature superconducting (HTS) rotating machine, etc.

  5. Model selection in magnetic resonance imaging measurements of vascular permeability: Gadomer in a 9L model of rat cerebral tumor.

    PubMed

    Ewing, James R; Brown, Stephen L; Lu, Mei; Panda, Swayamprava; Ding, Guangliang; Knight, Robert A; Cao, Yue; Jiang, Quan; Nagaraja, Tavarekere N; Churchman, Jamie L; Fenstermacher, Joseph D

    2006-03-01

    Vasculature in and around the cerebral tumor exhibits a wide range of permeabilities, from normal capillaries with essentially no blood-brain barrier (BBB) leakage to a tumor vasculature that freely passes even such large molecules as albumin. In measuring BBB permeability by magnetic resonance imaging (MRI), various contrast agents, sampling intervals, and contrast distribution models can be selected, each with its effect on the measurement's outcome. Using Gadomer, a large paramagnetic contrast agent, and MRI measures of T(1) over a 25-min period, BBB permeability was estimated in 15 Fischer rats with day-16 9L cerebral gliomas. Three vascular models were developed: (1) impermeable (normal BBB); (2) moderate influx (leakage without efflux); and (3) fast leakage with bidirectional exchange. For data analysis, these form nested models. Model 1 estimates only vascular plasma volume, v(D), Model 2 (the Patlak graphical approach) v(D) and the influx transfer constant K(i). Model 3 estimates v(D), K(i), and the reverse transfer constant, k(b), through which the extravascular distribution space, v(e), is calculated. For this contrast agent and experimental duration, Model 3 proved the best model, yielding the following central tumor means (+/-s.d.; n = 15): v(D) = 0.07 +/- 0.03 for K(i) = 0.0105 +/- 0.005 min(-1) and v(e) = 0.10 +/- 0.04. Model 2 K(i) estimates were approximately 30% of Model 3, but highly correlated (r = 0.80, P < 0.0003). Sizable inhomogeneity in v(D), K(i), and k(b) appeared within each tumor. We conclude that employing nested models enables accurate assessment of transfer constants among areas where BBB permeability, contrast agent distribution volumes, and signal-to-noise vary. PMID:16079791

  6. Sensor-less pseudo-sinusoidal drive for a permanent-magnet brushless ac motor

    NASA Astrophysics Data System (ADS)

    Liu, Li-Hsiang; Chern, Tzuen-Lih; Pan, Ping-Lung; Huang, Tsung-Mou; Tsay, Der-Min; Kuang, Jao-Hwa

    2012-04-01

    The precise rotor-position information is required for a permanent-magnet brushless ac motor (BLACM) drive. In the conventional sinusoidal drive method, either an encoder or a resolver is usually employed. For position sensor-less vector control schemes, the rotor flux estimation and torque components are obtained by complicated coordinate transformations. These computational intensive methods are susceptible to current distortions and parameter variations. To simplify the method complexity, this work presents a sensor-less pseudo-sinusoidal drive scheme with speed control for a three-phase BLACM. Based on the sinusoidal drive scheme, a floating period of each phase current is inserted for back electromotive force detection. The zero-crossing point is determined directly by the proposed scheme, and the rotor magnetic position and rotor speed can be estimated simultaneously. Several experiments for various active angle periods are undertaken. Furthermore, a current feedback control is included to minimize and compensate the torque fluctuation. The experimental results show that the proposed method has a competitive performance compared with the conventional drive manners for BLACM. The proposed scheme is straightforward, bringing the benefits of sensor-less drive and negating the need for coordinate transformations in the operating process.

  7. The attenuation of the levitation force of HTS bulk exposed to AC magnetic field on the above NdFeB guideway

    NASA Astrophysics Data System (ADS)

    Liu, Minxian; Wang, Yan

    2012-01-01

    In the present High Temperature Superconducting (HTS) maglev vehicle system, the air gaps between the adjacent permanent magnets make the magnetic fields above the NdFeB guideway non-uniform. So it is required to study the characteristics of levitation force of the HTS bulk affected by the non-uniform applied magnetic fields along the moving direction. In this paper, we have studied the characteristics of the levitation force relaxation by an experiment in which AC magnetic field generated by an electromagnet is used to simulate the time-varying magnetic field caused by the inhomogeneity of the NdFeB guideway. From the experiment results, it is found that the levitation force is attenuated with the application of the AC field, and the attenuation is increased with the amplitude of the AC field, but the attenuation is almost independent of the frequency the AC magnetic field.

  8. Analysis and comparison for rotor eddy current losses of permanent magnet synchronous generator according to dc and ac load conditions

    NASA Astrophysics Data System (ADS)

    Jang, Seok-Myeong; Kim, Hyun-Kyu; Choi, Jang-Young; Ko, Kyoung-Jin

    2009-04-01

    This paper presents an analytical procedure for the calculation of the eddy current losses of permanent magnet synchronous generator (PMSG). The dc and ac loading effects on the eddy current is examined through the suggested analytical procedure that considers the radial and tangential flux density waveform through a phase current harmonic analysis. The corresponding test results are also presented to quantify and compare those loading effects on the eddy current. The results verified the suggested analytical procedures and show that the rotor eddy current losses for PMSG with the dc loads turned out to be more significant than those with the ac loads.

  9. Analyze and experiment on AC magnetic field's effect to fiber optic gyroscopes in compact stabilization control systems

    NASA Astrophysics Data System (ADS)

    Zhang, Chao; Mao, Yao; Tian, Jing; Li, Zhijun

    2015-10-01

    Fiber optic gyroscopes (FOG) are getting more and more attention in areas such as stabilization control systems as they are all solid state and have a wide bandwidth. In stabilization systems that require wide bandwidth control, motors are usually used as actuating mechanism for active disturbance restrain. Voice coil motors (VCMs) are usually used in compact stabilization systems that require large torque and fast response. However, AC magnetic field, which can affect the output of FOG due to Faraday effect, will be generated during operation of VCMs. The frequency range affected by the AC magnetic field to the FOG's output is the same as VCMs drive signal frequency range, which is also exactly the stabilization system's working range. Therefore the effect of the AC magnetic field to FOGs must be evaluated to verify the feasibility of a stable system design that uses both FOGs and VCMs. In this article, the basic structure and operating principle of stabilization system is introduced. The influence of AC magnetic field to FOG is theoretically analyzed. The magnetic field generated by VCMs is numerically simulated based on the theory deduction of the magnetic field near energized wires. To verify the influence of the VCM generated magnetic field to the FOGs in practical designs, a simplified random fiber coil model is built for it's hard to accurately test the exact polarize axis's twisting rate in a fiber coil. The influence to the FOG's output of different random coil model is simulated and the result shows a same trend that the influence of the VCM's magnetic field to the FOG is reduced as the distance between the VCM and the FOG increasing. The influence of a VCM to a FOG with the same parameters is experimentally tested. In the Fourier transformed FOG data the same frequency point as the VCM drive signal frequency can be read. The result fit simulated result that as the distance increases, the influence decreases. The amplitude of the frequency point is just

  10. Vortex activation energy in the AC magnetic response of superconducting YBa2Cu3O7 thin films with complex pinning structures

    NASA Astrophysics Data System (ADS)

    Ivan, I.; Ionescu, A. M.; Miu, D.; Mele, P.; Miu, L.

    2016-09-01

    The vortex activation energy U AC in the AC magnetic response of superconductors exhibits a logarithmic variation with the screening current density J (regardless of the pinning structure details), and takes surprisingly high values in the vicinity of the DC irreversibility line, especially at low external DC magnetic fields, as often reported. This is essentially different from the behaviour of the vortex-creep activation energy at long relaxation time scales in DC magnetic measurements, and is not completely understood. We investigated the DC relaxation and the AC response for YBa2Cu3O7 films containing nanorods and nanoparticles, with the DC and AC fields oriented perpendicular to the film surface. It is shown that the large U AC values in the vicinity of the DC irreversibility line, where the critical-state-related AC signal occurs, are generated by a non-diffusive vortex motion during the AC cycle, with the mean vortex hopping length longer than the average distance between the pinning centres. In these conditions, the smearing of the vortex pinning potential by thermally induced vortex fluctuations is weak, and U AC mainly results from the strong influence of the pinning-enhanced viscous drag on the vortex hopping process. The logarithmic U AC(J) dependence is consistent with a high U AC.

  11. Decay Characteristics of Levitation Force of YBCO Bulk Exposed to AC Magnetic Field above NdFeB Guideway

    NASA Astrophysics Data System (ADS)

    Liu, Minxian; Lu, Yiyun; Wang, Suyu; Ma, Guangtong

    2011-04-01

    The superconducting maglev vehicle is one of the most promising applications of HTS bulks. In such a system, the nonuniformity of the magnetic field along the movement direction above the NdFeB guideway is inevitable due to the assembly error and inhomogeneity of the material property of the NdFeB magnet. So it is required to study the characteristics of levitation force of the bulks affected by the non-uniform applied magnetic fields along the moving direction. In this paper, we will study the characteristics of the levitation force relaxation between the HTS bulk and the NdFeB guideway by an experiment in which AC external magnetic field generated by an electromagnet is used to simulate the time-varying external magnetic field caused by the inhomogeneity of the guideway. From the experimental results, it has found that the levitation force is decreasing with the application of the AC external magnetic field, and the decay increasing with the amplitude of the applied magnetic field and is almost independent of the frequency.

  12. Study of the Dependence on Magnetic Field and Bias Voltage of an AC-Biased TES Microcalorimeter

    NASA Technical Reports Server (NTRS)

    Bandler, Simon

    2011-01-01

    At SRON we are studying the performance of a Goddard Space Flight Center single pixel TES microcalorimeter operated in the AC bias configuration. For x-ray photons at 6keV the AC biased pixel shows a best energy resolution of 3.7eV, which is about a factor of 2 worse than the energy resolution observed in identical DC-biased pixels. To better understand the reasons of this discrepancy, we investigated the detector performance as a function of temperature, bias working point and applied magnetic field. A strong periodic dependence of the detector noise on the TES AC bias voltage is measured. We discuss the results in the framework of the recent weak-link behaviour observed inTES microcalorimeters.

  13. AC magnetic response of superconducting YBa2Cu3O7/PrBa2Cu3O7 superlattices

    NASA Astrophysics Data System (ADS)

    Miu, L.; Ivan, I.; Ionescu, A. M.; Miu, D.

    2016-06-01

    Vortex activation energy UAC in the critical-state related AC magnetic response of superconductors (appearing in the vicinity of the DC irreversibility line) takes large values, as often reported, which is not yet understood. This behavior is essentially different from that of the vortex-creep activation energy at long relaxation time scales, and may become important for AC applications of superconductors. To elucidate this aspect, we investigated the AC signal of almost decoupled [Y Ba2Cu3O7]n/[PrBa2Cu3O7]4 superlattices (with n = 11 or 4 units cells) in perpendicular DC and AC magnetic fields. In these model samples, the length of the hopping vortex segment is fixed by the thickness of superconducting layers and vortices are disentangled, at least at low DC fields. It is shown that the high UAC values result from the large contribution of the pinning enhanced viscous drag in the conditions of thermally activated, non-diffusive vortex motion at short time scales, where the influence of thermally induced vortex fluctuations on pinning is weak.

  14. Comparative nuclear magnetic resonance studies of diffusional water permeability of red blood cells from sheep and cow.

    PubMed

    Benga, G; Borza, T; Popescu, O; Poruţiu, D; Matei, H

    1993-03-01

    1. The diffusional water permeability (p) of sheep and cow red blood cell (RBC) membrane has been monitored by a doping nuclear magnetic resonance (NMR) technique on control cells and following inhibition with p-chloromercuribenzene sulfonate (PCMBS). 2. There were no significant differences in the water permeability of sheep and cow RBCs, the values of p being around 3 x 10(-3) cm/sec at 20 degrees C and 5 x 10(-3) cm/sec at 37 degrees C. 3. Systematic studies of the effects of PCMBS on water diffusion indicated that in both species the maximal inhibition is reached in 60-90 min at 37 degrees C with 1 mM PCMBS. 4. The degree of inhibition increased as the temperature of measurement decreased, regardless of PCMBS concentration and incubation time. 5. The values of maximal inhibition ranged from 60-70% at 20 degrees C to 50-60% at 37 degrees C in the case of sheep RBCs, and from 45-55% at 20 degrees C to 40-50% at 37 degrees C in the case of cow RBCs. 6. The basal permeability to water of sheep RBCs was estimated as 1.0 x 10(-3) cm/sec at 20 degrees C and 2.2 x 10(-3) cm/sec at 37 degrees C, and that of cow RBCs as 1.6 x 10(-3) cm/sec at 20 degrees C and 2.7 x 10(-3) cm/sec at 37 degrees C. 7. In both species the activation energy of water diffusion was around 23 kJ/mol in control cells and reached values of around 30 kJ/mol after incubation with PCMBS in conditions of maximal inhibition of water diffusion.(ABSTRACT TRUNCATED AT 250 WORDS) PMID:8482080

  15. Comparative nuclear magnetic resonance studies on water diffusional permeability of red blood cells from mice and rats.

    PubMed

    Benga, G; Matei, H; Borza, T; Poruţiu, D; Lupşe, C

    1993-03-01

    1. The diffusional water permeability (P) of mouse and rat red blood cell (RBC) membrane has been monitored by a doping nuclear magnetic resonance (NMR) technique on control cells and following exposure to various concentrations of p-chloromercuribenzene sulfonate (PCMBS). 2. There were no significant differences in the water permeability of mouse and rat RBCs, the values of P being around 6 x 10(-3)/sec at 20 degrees C and 11 x 10(-3) cm/sec at 37 degrees C. 3. Systematic studies of the effects of PCMBS on water diffusion indicated that the maximal inhibition is reached in 60 min at 20 degrees C with 1 mM PCMBS for the mouse RBCs and with 2 mM PCMBS for the rat RBCs. 4. The values of maximal inhibition ranged from 55-57% at 37 degrees C and reached values around 70% at 10 degrees C. 5. The degree of inhibition increased as the temperature of measurement decreased, regardless of PCMBS concentration and incubation time. 6. The basal permeability to water of mouse RBCs was estimated as 1.8 x 10(-3) cm/sec at 20 degrees C and 4.6 x 10(-3) cm/sec at 37 degrees C, and that of rat RBCs as 2.2 x 10(-3) cm/sec at 20 degrees C and 4.2 x 10(-3) cm/sec at 37 degrees C. 7. In both species the activation energy was around 27 kJ/mol and reached values over 40 kJ/mol after incubation with PCMBS in the conditions of maximal inhibition of water diffusion. PMID:8097150

  16. Development of integrated AC-DC magnetometer using high-Tc SQUID for magnetic properties evaluation of magnetic nanoparticles in solution

    NASA Astrophysics Data System (ADS)

    Mawardi Saari, Mohd; Takagi, Ryuki; Kusaka, Toki; Ishihara, Yuichi; Tsukamoto, Yuya; Sakai, Kenji; Kiwa, Toshihiko; Tsukada, Keiji

    2014-05-01

    We developed an integrated AC-DC magnetometer using a high critical temperature superconducting quantum interference device (high-Tc SQUID) to evaluate the static and dynamic magnetic properties of magnetic nanoparticles (MNPs) in solution. The flux-transformer method consisted of first-order planar and axial differential coils that were constructed for static and dynamic magnetization measurements, respectively. Vibrating-sample and harmonic detection techniques were used to reduce interference from excitation magnetic fields in the static and dynamic magnetization measurements, respectively. Static and dynamic magnetization measurements were performed on commercially available iron oxide nanoparticles in diluted solutions. The magnetic responses increased with the increase in concentration of the solutions in both measurement results. The magnetization curves showed that the diamagnetic signal due to the carrier liquid of the iron oxide nanoparticles existed in a dilute solution. Biasing with a proper DC magnetic field in the dynamic magnetization measurement resulted in improved signals of the second and third harmonics. Therefore, highly sensitive magnetic characterizations of MNPs utilizing the static and dynamic magnetization measurement are possible via the developed system.

  17. High-permeability functionalized silicone magnetic microspheres with low autofluorescence for biomedical applications.

    PubMed

    Evans, Benjamin A; Ronecker, Julia C; Han, David T; Glass, Daniel R; Train, Tonya L; Deatsch, Alison E

    2016-05-01

    Functionalized magnetic microspheres are widely used for cell separations, isolation of proteins and other biomolecules, in vitro diagnostics, tissue engineering, and microscale force spectroscopy. We present here the synthesis and characterization of a silicone magnetic microsphere which can be produced in diameters ranging from 0.5 to 50μm via emulsion polymerization of a silicone ferrofluid precursor. This bottom-up approach to synthesis ensures a uniform magnetic concentration across all sizes, leading to significant advances in magnetic force generation. We demonstrate that in a size range of 5-20μm, these spheres supply a full order of magnitude greater magnetic force than leading commercial products. In addition, the unique silicone matrix exhibits autofluorescence two orders of magnitude lower than polystyrene microspheres. Finally, we demonstrate the ability to chemically functionalize our silicone microspheres using a standard EDC reaction, and show that our folate-functionalized silicone microspheres specifically bind to targeted HeLa and Jurkat cells. These spheres show tremendous potential for replacing magnetic polystyrene spheres in applications which require either large magnetic forces or minimal autofluorescence, since they represent order-of-magnitude improvements in each. In addition, the unique silicone matrix and proven biocompatibility suggest that they may be useful for encapsulation and targeted delivery of lipophilic pharmaceuticals. PMID:26952493

  18. Microwave and millimeter wave dielectric permittivity and magnetic permeability of epsilon-gallium-iron-oxide nano-powders

    NASA Astrophysics Data System (ADS)

    Chao, Liu; Afsar, Mohammed N.; Ohkoshi, Shin-ichi

    2015-05-01

    In millimeter wave frequency range, hexagonal ferrites with high uniaxial anisotropic magnetic fields are used as absorbers. These ferrites include M-type barium ferrite (BaFe12O19) and strontium ferrite (SrFe12O19), which have natural ferromagnetic resonant frequency range from 40 GHz to 60 GHz. However, the higher frequency range lacks suitable materials that support the higher frequency ferromagnetic resonance. A series of gallium-substituted ɛ-iron oxides (ɛ-GaxFe2-xO3) are synthesized, which have ferromagnetic resonant frequencies appearing over the frequency range of 30 GHz to 150 GHz. The ɛ-GaxFe2-xO3 is synthesized by the sol-gel method. The particle sizes are observed to be smaller than 100 nm. In this paper, in-waveguide transmission and reflection method and the free space magneto-optical approach have been employed to study these newly developed ɛ-GaxFe2-xO3 particles in millimeter waves. These techniques enable to obtain precise transmission spectra to determine the dielectric and magnetic properties of both isotropic and anisotropic ferrites in the microwave and millimeter wave frequency range from single set of direct measurements. The complex dielectric permittivity and magnetic permeability spectra of ɛ-GaxFe2-xO3 are shown in this paper. Strong ferromagnetic resonances at different frequencies determined by the x parameter are found.

  19. Calorimetric AC loss measurement of MgB2 superconducting tape in an alternating transport current and direct magnetic field

    NASA Astrophysics Data System (ADS)

    See, K. W.; Xu, X.; Horvat, J.; Cook, C. D.; Dou, S. X.

    2012-11-01

    Applications of MgB2 superconductors in electrical engineering have been widely reported, and various studies have been made to define their alternating current (AC) losses. However, studies on the transport losses with an applied transverse DC magnetic field have not been conducted, even though this is one of the favored conditions in applications of practical MgB2 tapes. Methods and techniques used to characterize and measure these losses have so far been grouped into ‘electrical’ and ‘calorimetric’ approaches with external conditions set to resemble the application conditions. In this paper, we present a new approach to mounting the sample and employ the calorimetric method to accurately determine the losses in the concurrent application of AC transport current and DC magnetic fields that are likely to be experienced in practical devices such as generators and motors. This technique provides great simplification compared to the pickup coil and lock-in amplifier methods and is applied to a long length (˜10 cm) superconducting tape. The AC loss data at 20 and 30 K will be presented in an applied transport current of 50 Hz under external DC magnetic fields. The results are found to be higher than the theoretical predictions because of the metallic fraction of the tape that contributes quite significantly to the total losses. The data, however, will allow minimization of losses in practical MgB2 coils and will be used in the verification of numerical coil models.

  20. Can Lucifer Yellow Indicate Correct Permeability of Biological Cell Membrane under An Electric and Magnetic Field?

    PubMed

    Pourmirjafari Firoozabadi, Tahereh; Shankayi, Zeinab; Izadi, Azam; Pourmirjafari Firoozabadi, Seyed Mohammad

    2015-01-01

    The effect of external magnetic and electric fields, in the range of electroporation and magnetoporation, on Lucifer Yellow (LY) fluorescence in the absence of cells is studied. Electric-field-induced quenching and magnetic field-induced increase are observed for fluorescence intensity of LY. Regard to the fact that the variation of field-induced fluorescence, even in the absence of cells, can be observed, the application of LY, as a marker, is debatable in electroporation and magnetoporation techniques. PMID:25685747

  1. Inductive heat property of Fe3O4/polymer composite nanoparticles in an ac magnetic field for localized hyperthermia.

    PubMed

    Zhao, Dong-Lin; Zhang, Hai-Long; Zeng, Xian-Wei; Xia, Qi-Sheng; Tang, Jin-Tian

    2006-12-01

    The magnetite (Fe(3)O(4)) nanoparticles were prepared by coprecipitation of Fe(3+) and Fe(2+) with an aqueous NaOH solution. The Fe(3)O(4)/polyaniline (PANI) magnetic composite nanoparticles with a core-shell structure with a diameter of 30-50 nm were prepared via an in situ polymerization of aniline in an aqueous solution containing the Fe(3)O(4) magnetic fluid. The inductive heat property of Fe(3)O(4)/PANI composite nanoparticles in an alternating current (ac) magnetic field was investigated. The potential of Fe(3)O(4)/PANI nanoparticles was evaluated for localized hyperthermia treatment of cancers. The saturation magnetization, M(s), and coercivity, H(c), are 50.05 emu g(-1) and 137 Oe for Fe(3)O(4) nanoparticles and 26.34 emu g(-1) and 0 Oe for Fe(3)O(4)/PANI composite nanoparticles, respectively. Exposed in the ac magnetic field for 29 min, the temperatures of physiological saline suspensions containing Fe(3)O(4) nanoparticles or Fe(3)O(4)/PANI composite nanoparticles are 63.6 degrees C and 52.4 degrees C, respectively. The Fe(3)O(4)/PANI composite nanoparticles would be useful as good thermoseeds for localized hyperthermia treatment of cancers. PMID:18458406

  2. Magnetic nanobeads present during enzymatic amplification and labeling for a simplified DNA detection protocol based on AC susceptometry

    NASA Astrophysics Data System (ADS)

    Bejhed, Rebecca S.; Strømme, Maria; Svedlindh, Peter; Ahlford, Annika; Strömberg, Mattias

    2015-12-01

    Magnetic biosensors are promising candidates for low-cost point-of-care biodiagnostic devices. For optimal efficiency it is crucial to minimize the time and complexity of the assay protocol including target recognition, amplification, labeling and read-out. In this work, possibilities for protocol simplifications for a DNA biodetection principle relying on hybridization of magnetic nanobeads to rolling circle amplification (RCA) products are investigated. The target DNA is recognized through a padlock ligation assay resulting in DNA circles serving as templates for the RCA process. It is found that beads can be present during amplification without noticeably interfering with the enzyme used for RCA (phi29 polymerase). As a result, the bead-coil hybridization can be performed immediately after amplification in a one-step manner at elevated temperature within a few minutes prior to read-out in an AC susceptometer setup, i.e. a combined protocol approach. Moreover, by recording the phase angle ξ = arctan(χ″/χ'), where χ and χ″ are the in-phase and out-of-phase components of the AC susceptibility, respectively, at one single frequency the total assay time for the optimized combined protocol would be no more than 1.5 hours, often a relevant time frame for diagnosis of cancer and infectious disease. Also, applying the phase angle method normalization of AC susceptibility data is not needed. These findings are useful for the development of point-of-care biodiagnostic devices relying on bead-coil binding and magnetic AC susceptometry.

  3. Angular Dependence of Transport AC Losses in Superconducting Wire with Position-Dependent Critical Current Density in a DC Magnetic Field

    NASA Astrophysics Data System (ADS)

    Su, Xing-liang; Xiong, Li-ting; Gao, Yuan-wen; Zhou, You-he

    2013-07-01

    Transport AC losses play a very important role in high temperature superconductors (HTSs), which usually carry AC transport current under applied magnetic field in typical application-like conditions. In this paper, we propose the analytical formula for transport AC losses in HTS wire by considering critical current density of both inhomogeneous and anisotropic field dependent. The angular dependence of critical current density is described by effective mass theory, and the HTS wire has inhomogeneous distribution cross-section of critical current density. We calculate the angular dependence of normalized AC losses under different DC applied magnetic fields. The numerical results of this formula agree well with the experiment data and are better than the results of Norris formula. This analytical formula can explain the deviation of experimental transport current losses from the Norris formula and apply to calculate transport AC losses in realistic practical condition.

  4. Tilted Magnetic Levitation Enables Measurement of the Complete Range of Densities of Materials with Low Magnetic Permeability.

    PubMed

    Nemiroski, Alex; Soh, Siowling; Kwok, Sen Wai; Yu, Hai-Dong; Whitesides, George M

    2016-02-01

    Magnetic levitation (MagLev) of diamagnetic or weakly paramagnetic materials suspended in a paramagnetic solution in a magnetic field gradient provides a simple method to measure the density of small samples of solids or liquids. One major limitation of this method, thus far, has been an inability to measure or manipulate materials outside of a narrow range of densities (0.8 g/cm(3) < ρ < 2.3 g/cm(3)) that are close in density to the suspending, aqueous medium. This paper explores a simple method-"tilted MagLev"-to increase the range of densities that can be levitated magnetically. Tilting the MagLev device relative to the gravitational vector enables the magnetic force to be decreased (relative to the magnetic force) along the axis of measurement. This approach enables many practical measurements over the entire range of densities observed in matter at ambient conditions-from air bubbles (ρ ≈ 0) to osmium and iridium (ρ ≈ 23 g/cm(3)). The ability to levitate, simultaneously, objects with a broad range of different densities provides an operationally simple method that may find application to forensic science (e.g., for identifying the composition of miscellaneous objects or powders), industrial manufacturing (e.g., for quality control of parts), or resource-limited settings (e.g., for identifying and separating small particles of metals and alloys). PMID:26722977

  5. Magnetically induced structural anisotropy in binary colloidal gels and its effect on diffusion and pressure driven permeability.

    PubMed

    Abrahamsson, Christoffer; Nordstierna, Lars; Bergenholtz, Johan; Altskär, Annika; Nydén, Magnus

    2014-06-28

    We report on the synthesis, microstructure and mass transport properties of a colloidal hydrogel self-assembled from a mixture of colloidal silica and nontronite clay plates at different particle concentrations. The gel-structure had uniaxial long-range anisotropy caused by alignment of the clay particles in a strong external magnetic field. After gelation the colloidal silica covered the clay particle network, fixing the orientation of the clay plates. Comparing gels with a clay concentration between 0 and 0.7 vol%, the magnetically oriented gels had a maximum water permeability and self-diffusion coefficient at 0.3 and 0.7 vol% clay, respectively. Hence the specific clay concentration resulting in the highest liquid flux was pressure dependent. This study gives new insight into the effect of anisotropy, particle concentration and bound water on mass transport properties in nano/microporous materials. Such findings merit consideration when designing porous composite materials for use in for example fuel cell, chromatography and membrane technology. PMID:24803339

  6. Pore fabric geometry inferred from magnetic and acoustic anisotropies in rocks with various mineralogy, permeability and porosity

    NASA Astrophysics Data System (ADS)

    Robion, Philippe; David, Christian; Dautriat, Jérémie; Colombier, Jean-Christian; Zinsmeister, Louis; Collin, Pierre-Yves

    2014-08-01

    The ferrofluid impregnation technique combined with anisotropy of magnetic susceptibility measurements (AMSff) is one of the ways to analyze the 3-D geometry of the pore space in a rock and indirectly to infer the anisotropy of permeability. We applied this method on different types of rocks (sandstones and carbonates) with a range of different porosity values (10-30%) and permeability (1 mD to 1 D). To get additional information on both the pore aspect ratio and the directional anisotropy we used another technique, measuring the anisotropy of P-waves velocity (APV) in dry and water saturated conditions. Comparing between both methods shows that despite the good agreement in directional data, inferring the true shape of the porosity is not straightforward. Modeling the presence of an elastic anisotropy in the solid matrix for sandstones allows one to get more consistent values for the pore aspect ratio obtained from both APV and AMSff. However for the carbonate rocks, due to an intricate distribution of microstructures, the aspect ratios obtained show significant discrepancies between the two methods. The ferrofluid method is very sensitive to the quality of the impregnation and suffers from a major drawback which is the threshold size of investigation, limited by the size of the magnetite nanoparticles (10 nm) and probably this method doesn't see all the porosity. On the other hand with acoustic methods, the range of porosity investigated is probably larger but several microstructural attributes can contribute to the elastic anisotropy which makes the pore shape effect more difficult to decipher. Therefore, we promote the combined use of both methods in order to get more reliable information on the pore shape in porous media.

  7. Study of the Dependency on Magnetic Field and Bias Voltage of an AC-Biased TES Microcalorimeter

    NASA Technical Reports Server (NTRS)

    Gottardi, L.; Bruijn, M.; denHartog, R.; Hoevers, H.; deKorte, P.; vanderKuur, J.; Linderman, M.; Adams, J.; Bailey, C.; Bandler, S.; Chervenak, J.; Eckart, M.; Finkbeiner, F.; Kelley, R.; Kilbourne, C.; Porter, F.; Sadlier, J.; Smith, S.

    2012-01-01

    At SRON we are studying the performance of a Goddard Space Flight Center single pixel TES microcalorimeter operated in an AC bias configuration. For x-ray photons at 6 keV the pixel shows an x-ray energy resolution Delta E(sub FWHM) = 3.7 eV, which is about a factor 2 worse than the energy resolution observed in an identical DC-biased pixel. In order to better understand the reasons for this discrepancy we characterized the detector as a function of temperature, bias working point and applied perpendicular magnetic field. A strong periodic dependency of the detector noise on the TES AC bias voltage is measured. We discuss the results in the framework of the recently observed weak-link behaviour of a TES microcalorimeter.

  8. Superconducting-magnetic heterostructures: a method of decreasing AC losses and improving critical current density in multifilamentary conductors.

    PubMed

    Glowacki, B A; Majoros, M

    2009-06-24

    Magnetic materials can help to improve the performance of practical superconductors on the macroscale/microscale as magnetic diverters and also on the nanoscale as effective pinning centres. It has been established by numerical modelling that magnetic shielding of the filaments reduces AC losses in self-field conditions due to decoupling of the filaments and, at the same time, it increases the critical current of the composite. This effect is especially beneficial for coated conductors, in which the anisotropic properties of the superconductor are amplified by the conductor architecture. However, ferromagnetic coatings are often chemically incompatible with YBa(2)Cu(3)O(7) and (Pb,Bi)(2)Sr(2)Ca(2)Cu(3)O(9) conductors, and buffer layers have to be used. In contrast, in MgB(2) conductors an iron matrix may remain in direct contact with the superconducting core. The application of superconducting-magnetic heterostructures requires consideration of the thermal and electromagnetic stability of the superconducting materials used. On one hand, magnetic materials reduce the critical current gradient across the individual filaments but, on the other hand, they often reduce the thermal conductivity between the superconducting core and the cryogen, which may cause destruction of the conductor in the event of thermal instability. A possible nanoscale method of improving the critical current density of superconducting conductors is the introduction of sub-micron magnetic pinning centres. However, the volumetric density and chemical compatibility of magnetic inclusions has to be controlled to avoid suppression of the superconducting properties. PMID:21828430

  9. Microwave and millimeter wave dielectric permittivity and magnetic permeability of epsilon-gallium-iron-oxide nano-powders

    SciTech Connect

    Chao, Liu Afsar, Mohammed N.; Ohkoshi, Shin-ichi

    2015-05-07

    In millimeter wave frequency range, hexagonal ferrites with high uniaxial anisotropic magnetic fields are used as absorbers. These ferrites include M-type barium ferrite (BaFe{sub 12}O{sub 19}) and strontium ferrite (SrFe{sub 12}O{sub 19}), which have natural ferromagnetic resonant frequency range from 40 GHz to 60 GHz. However, the higher frequency range lacks suitable materials that support the higher frequency ferromagnetic resonance. A series of gallium-substituted ε-iron oxides (ε-Ga{sub x}Fe{sub 2−x}O{sub 3}) are synthesized, which have ferromagnetic resonant frequencies appearing over the frequency range of 30 GHz to 150 GHz. The ε-Ga{sub x}Fe{sub 2−x}O{sub 3} is synthesized by the sol-gel method. The particle sizes are observed to be smaller than 100 nm. In this paper, in-waveguide transmission and reflection method and the free space magneto-optical approach have been employed to study these newly developed ε-Ga{sub x}Fe{sub 2−x}O{sub 3} particles in millimeter waves. These techniques enable to obtain precise transmission spectra to determine the dielectric and magnetic properties of both isotropic and anisotropic ferrites in the microwave and millimeter wave frequency range from single set of direct measurements. The complex dielectric permittivity and magnetic permeability spectra of ε-Ga{sub x}Fe{sub 2−x}O{sub 3} are shown in this paper. Strong ferromagnetic resonances at different frequencies determined by the x parameter are found.

  10. EFFECT OF ANNEALING TEMPERATURE ON THE STRUCTURE AND AC MAGNETIC PROPERTIES OF Fe73Cu1Nb3.5-xVxSi13.5B9 (x = 1.0, 1.5, 2.0) NANOCRYSTALLINE SOFT MAGNETIC ALLOYS

    NASA Astrophysics Data System (ADS)

    Lu, Wei; Huang, Ping; Wang, Yuxin; Yan, Biao

    2013-07-01

    In this paper, Nb element was partially replaced by V element in Finemet-type Fe73Cu1Nb3.5-xVxSi13.5B9 (x = 1, 1.5, 2) alloys and the effect of annealing temperatures on the microstructure and AC magnetic properties of the samples are studied. The annealing temperatures affect the grain sizes of the bcc α-Fe phase greatly. When the annealing temperature is between 540-560°C, the samples have better AC magnetic properties than the samples annealed at other temperatures. The optimized annealing temperature of the studied samples is around 560°C. The coercivity and iron loss of the V2 sample is a little bit higher than that of V1 and V1.5 alloys while the amplitude permeability of V2 alloy is larger than that of V1 and V1.5, which indicate that the content of V element has strong influence on the magnetic properties of nanocrystalline soft magnetic alloys.

  11. Time-resolved magnetic flux and AC-current distributions in superconducting yttrium barium copper oxide thin films and multifilaments

    NASA Astrophysics Data System (ADS)

    Yang, Ran

    Time-resolved magneto-optical imaging (TRMOI) technique allows dynamic ac transport measurements on superconductors. The high time and spatial resolutions of the measurements also offer good quantitative data analysis of the MO images. YBa2Cu 3O7-delta (YBCO) was discovered as a high-temperature superconductor (HTSC) which has wide applications due to its high critical temperature of Tc = 91 K, and high critical current density Jc in the order of 106-7 Acm-2. Many of the applications require high ac current load and a high magnetic field. We study the interaction behavior of YBCO thin films in an ac transport current and a dc magnetic field by the TRMOI technique. In this dissertation, I first introduce the applications of high-temperature superconductors with focus on YBCO and describe the advantages of the TRMOI technique we developed over other methods to map the magnetic flux distribution of superconductors. The theories to understand the magnetic properties of HTSC are presented, followed by theoretical models. I also introduce a newly developed finite elemental method (FEM) simulation which is proved to be a better theoretical guideline to our data analysis. The TRMOI experimental setup and the procedures are discussed in detail. I show step-by-step the calibration of light intensity profiles averaged from MO images to determine magnetic field distribution, and a numerical inversion of the Biot-Savart law to calculate the current density distributions. The current density evolution in YBCO thin films is studied by TRMOI as a function of the phase of an ac current applied simultaneously with a perpendicular dc magnetic field. The measurements show that an ac current enables the vortex matter in YBCO thin films to reorganize into two coexisting steady states of driven vortex motion with different characteristics. To study the transport current effects in YBCO thin films, we present a new empirical method to separate the total current distribution into a

  12. Superconductor-Mediated Modification of Gravity? AC Motor Experiments with Bulk YBCO Disks in Rotating Magnetic Fields

    NASA Technical Reports Server (NTRS)

    Noever, David A.; Koczor, Ronald J.; Roberson, Rick

    1998-01-01

    We have previously reported results using a high precision gravimeter to probe local gravity changes in the neighborhood of large bulk-processed high-temperature superconductors. Podkietnov, et al (Podkietnov, E. and Nieminen, R. (1992) A Possibility of Gravitational Force Shielding by Bulk YBa2 Cu3 O7-x Superconductor, Physica C, C203:441-444.) have indicated that rotating AC fields play an essential role in their observed distortion of combined gravity and barometric pressure readings. We report experiments on large (15 cm diameter) bulk YBCO ceramic superconductors placed in the core of a three-phase, AC motor stator. The applied rotating field produces up to a 12,000 revolutions per minute magnetic field. The field intensity decays rapidly from the maximum at the outer diameter of the superconducting disk (less than 60 Gauss) to the center (less than 10 Gauss). This configuration was applied with and without a permanent DC magnetic field levitating the superconducting disk, with corresponding gravity readings indicating an apparent increase in observed gravity of less than 1 x 10(exp -6)/sq cm, measured above the superconductor. No effect of the rotating magnetic field or thermal environment on the gravimeter readings or on rotating the superconducting disk was noted within the high precision of the observation. Implications for propulsion initiatives and power storage flywheel technologies for high temperature superconductors will be discussed for various spacecraft and satellite applications.

  13. Simultaneous ac and dc magnetic field measurements in residential areas: Implications for resonance theories of biological effects

    SciTech Connect

    Wong, P.S.; Sastre, A.

    1995-10-01

    The goal of this study was to obtain data that could be used to evaluate the applicability of ``resonance`` theories of biological effects in residential settings. The authors first describe a measurement system which allows the study of ac and dc magnetic fields simultaneously in space and in time. Sample measurements were taken near two power lines, two objects and in two residential homes. The results show that the earth`s (dc) magnetic field was unaffected near power lines. The compass orientation of the power line influenced the relative values of the ac components parallel and perpendicular to the dc field. The electric heating system greatly affected the ac field levels in the home, causing the levels to increase from less than 1 mG to a maximum of 7.5 mG during heating. The magnitudes of the dc field in the two homes varied from about 380 to 650 mG, with the larger variations near metallic or magnetic objects such as the refrigerator or a metallic air duct. The earth`s field was elevated above its natural level within a distance of 8 feet from a subcompact passenger car, e.g., the level changed from about 540 to 1,100 mG beside the headlight. A steel chair changed the earth`s field by up to 60 mG within a distance of one foot. These results suggest that some of the narrow ``resonances`` described in laboratory studies may be difficult to observe against the variations in do field amplitude and direction resulting from the presence of everyday metallic objects.

  14. Early detection of colonic dysplasia by magnetic resonance molecular imaging with a contrast agent raised against the colon cancer marker MUC5AC.

    PubMed

    Rossez, Yannick; Burtea, Carmen; Laurent, Sophie; Gosset, Pierre; Léonard, Renaud; Gonzalez, Walter; Ballet, Sébastien; Raynal, Isabelle; Rousseaux, Olivier; Dugué, Timothée; Vander Elst, Luce; Michalski, Jean-Claude; Muller, Robert N; Robbe-Masselot, Catherine

    2016-05-01

    Human gastric mucin MUC5AC is secreted in the colonic mucus of cancer patients and is a specific marker of precancerous lesions called aberrant crypt foci. Using MUC5AC as a specific marker can improve sensitivity in the detection of early colorectal cancer. Here we demonstrated that the accumulation of MUC5AC in xenograft and mouse stomach can be detected by magnetic resonance imaging (MRI). We used ultrasmall particles of iron oxide (USPIOs) conjugated with disulfide constrained heptapeptide that were identified using a screening phage display. To accomplish this, we employed positive selection of the phage display library on MUC5AC purified from fresh human colonic adenomas in combination with negative selection of the phage library on purified human MUC2, which is predominantly found in normal colorectal tissues. This conjugate was tested on human colorectal cancer cell lines that were either able or unable to secrete MUC5AC, both in vitro and in vivo. MUC5AC-USPIO contrast agent and USPIOs alone were not detected in cell lines unable to secrete MUC5AC. A combination of MRI and microscopy studies was performed to detect a specific accumulation of the contrast agent in vivo. Thus, the MUC5AC contrast agent enabled non-invasive detection of precancerous lesions and colorectal cancer, highlighting its potential use in diagnostics, in the early detection of colorectal cancer recurrences after treatment and in mechanistic studies implicating MUC5AC. Copyright © 2016 John Wiley & Sons, Ltd. PMID:26762591

  15. Increasing the high-frequency magnetic permeability of MnZn ferrite in polyaniline composites by incorporating silver

    NASA Astrophysics Data System (ADS)

    Babayan, V.; Kazantseva, N. E.; Sapurina, I.; Moučka, R.; Stejskal, J.; Sáha, P.

    2013-05-01

    A hybrid composite containing 73 vol% of MnZn ferrite, 21 vol% of polyaniline, and 6 vol% of silver is obtained by oxidative polymerization of aniline with silver nitrate in the presence of ferrite powder. The hybrid composite contains ferrite particles with a size of 40-80 μm coated by an inhomogeneous layer of polyaniline in the conducting emeraldine form. Silver in the form of nano- and submicrometre -size particles is localized both on the surface of ferrite particles and in the bulk of polyaniline coating. The electrical and magnetic properties of the hybrid composite are investigated and compared with the properties of a composite with 71 vol% of MnZn ferrite coated by a conducting polyaniline layer (29 vol%). The hybrid composite containing silver exhibits an increase in the real and imaginary parts of the complex permeability in the radio-frequency band by more than one and a half times compared with those of the MnZn ferrite-polyaniline composite. The high-frequency permittivity of both composites is determined by the properties of core-shell structure: electric properties of shell as well as its composition and uniformity.

  16. Membrane-Permeable Mn(III) Complexes for Molecular Magnetic Resonance Imaging of Intracellular Targets.

    PubMed

    Barandov, Ali; Bartelle, Benjamin B; Gonzalez, Beatriz A; White, William L; Lippard, Stephen J; Jasanoff, Alan

    2016-05-01

    Intracellular compartments make up roughly two-thirds of the body, but delivery of molecular imaging probes to these spaces can be challenging. This situation is particularly true for probes designed for detection by magnetic resonance imaging (MRI), a high-resolution but relatively insensitive modality. Most MRI contrast agents are polar and membrane impermeant, making it difficult to deliver them in sufficient quantities for measurement of intracellular analytes. Here we address this problem by introducing a new class of planar tetradentate Mn(III) chelates assembled from a 1,2-phenylenediamido (PDA) backbone. Mn(III)-PDA complexes display T1 relaxivity comparable to that of Gd(III)-based contrast agents and undergo spontaneous cytosolic localization via defined mechanisms. Probe variants incorporating enzyme-cleavable acetomethoxy ester groups are processed by intracellular esterases and accumulate in cells. Probes modified with ethyl esters preferentially label genetically modified cells that express a substrate-selective esterase. In each case, the contrast agents gives rise to robust T1-weighted MRI enhancements, providing precedents for the detection of intracellular targets by Mn(III)-PDA complexes. These compounds therefore constitute a platform from which to develop reagents for molecular MRI of diverse processes inside cells. PMID:27088782

  17. Quantitative imaging of cell-permeable magnetic resonance contrast agents using x-ray fluorescence.

    PubMed

    Endres, Paul J; Macrenaris, Keith W; Vogt, Stefan; Allen, Matthew J; Meade, Thomas J

    2006-01-01

    The inability to transduce cellular membranes is a limitation of current magnetic resonance imaging probes used in biologic and clinical settings. This constraint confines contrast agents to extracellular and vascular regions of the body, drastically reducing their viability for investigating processes and cycles in developmental biology. Conversely, a contrast agent with the ability to permeate cell membranes could be used in visualizing cell patterning, cell fate mapping, gene therapy, and, eventually, noninvasive cancer diagnosis. Therefore, we describe the synthesis and quantitative imaging of four contrast agents with the capability to cross cell membranes in sufficient quantity for detection. Each agent is based on the conjugation of a Gd(III) chelator with a cellular transduction moiety. Specifically, we coupled Gd(III)-diethylenetriaminepentaacetic acid DTPA and Gd(III)-1,4,7,10-tetraazacyclododecane-1,4,7,10-tetraacetic acid with an 8-amino acid polyarginine oligomer and an amphipathic stilbene molecule, 4-amino-4'-(N,N-dimethylamino)stilbene. The imaging modality that provided the best sensitivity and spatial resolution for direct detection of the contrast agents is synchrotron radiation x-ray fluorescence (SR-XRF). Unlike optical microscopy, SR-XRF provides two-dimensional images with resolution 10(3) better than (153)Gd gamma counting, without altering the agent by organic fluorophore conjugation. The transduction efficiency of the intracellular agents was evaluated by T(1) analysis and inductively coupled plasma mass spectrometry to determine the efficacy of each chelate-transporter combination. PMID:17150161

  18. AC driven magnetic domain quantification with 5 nm resolution

    PubMed Central

    Li, Zhenghua; Li, Xiang; Dong, Dapeng; Liu, Dongping; Saito, H.; Ishio, S.

    2014-01-01

    As the magnetic storage density increases in commercial products, e.g. the hard disc drives, a full understanding of dynamic magnetism in nanometer resolution underpins the development of next-generation products. Magnetic force microscopy (MFM) is well suited to exploring ferromagnetic domain structures. However, atomic resolution cannot be achieved because data acquisition involves the sensing of long-range magnetostatic forces between tip and sample. Moreover, the dynamic magnetism cannot be characterized because MFM is only sensitive to the static magnetic fields. Here, we develop a side-band magnetic force microscopy (MFM) to locally observe the alternating magnetic fields in nanometer length scales at an operating distance of 1 nm. Variations in alternating magnetic fields and their relating time-variable magnetic domain reversals have been demonstrated by the side-band MFM. The magnetic domain wall motions, relating to the periodical rotation of sample magnetization, are quantified via micromagnetics. Based on the side-band MFM, the magnetic moment can be determined locally in a volume as small as 5 nanometers. The present technique can be applied to investigate the microscopic magnetic domain structures in a variety of magnetic materials, and allows a wide range of future applications, for example, in data storage and biomedicine. PMID:25011670

  19. Dielectric and magnetic permeability behavior of BaCo 2- xNi xFe 16O 27 W-type hexaferrites

    NASA Astrophysics Data System (ADS)

    Abo El Ata, A. M.; El Nimr, M. K.; El Kony, D.; AL-Hammadi, A. H.

    1999-09-01

    A series of polycrystalline W-type hexagonal ferrite samples with the composition BaCo 2- xNi xFe 16 O 27 were prepared by the well-known double-sintering ceramic process. The dielectric constant ɛ', dielectric loss tangent tan δ and initial magnetic permeability μ0 was investigated as a function of frequency, temperature and composition. It was found that both dielectric constant ɛ' and dielectric loss tangent tan δ increase with increasing nickel ions substitution. The behavior of the dielectric constant with frequency and temperature was explained on the basis of the hopping conduction mechanism and Rezlescu model. The anomaly of the initial magnetic permeability with temperature was attributed to the behavior of the magnetocrystalline anisotropy constant with temperature and composition.

  20. Tools and Setups for Experiments with AC and Rotating Magnetic Fields

    ERIC Educational Resources Information Center

    Ponikvar, D.

    2010-01-01

    A rotating magnetic field is the basis for the transformation of electrical energy to mechanical energy. School experiments on the rotating magnetic field are rare since they require the use of specially prepared mechanical setups and/or relatively large, three-phase power supplies to achieve strong magnetic fields. This paper proposes several…

  1. Ground penetrating radar inversion in 1-D: an approach for the estimation of electrical conductivity, dielectric permittivity and magnetic permeability1

    NASA Astrophysics Data System (ADS)

    Lázaro-Mancilla, O.; Gómez-Treviño, E.

    2000-03-01

    This paper presents a method for inverting ground penetrating radargrams in terms of one-dimensional profiles. We resort to a special type of linearization of the damped E-field wave equation to solve the inverse problem. The numerical algorithm for the inversion is iterative and requires the solution of several forward problems, which we evaluate using the matrix propagation approach. Analytical expressions for the derivatives with respect to physical properties are obtained using the self-adjoint Green's function method. We consider three physical properties of materials; namely dielectrical permittivity, magnetic permeability and electrical conductivity. The inverse problem is solved minimizing the quadratic norm of the residuals using quadratic programming optimization. In the iterative process to speed up convergence we use the Levenberg-Mardquardt method. The special type of linearization is based on an integral equation that involves derivatives of the electric field with respect to magnetic permeability, electrical conductivity and dielectric permittivity; this equation is the result of analyzing the implication of the scaling properties of the electromagnetic field. The ground is modeled using thin horizontal layers to approximate general variations of the physical properties. We show that standard synthetic radargrams due to dielectric permittivity contrasts can be matched using electrical conductivity or magnetic permeability variations. The results indicate that it is impossible to differentiate one property from the other using GPR data.

  2. Effective method to measure back emfs and their harmonics of permanent magnet ac motors

    NASA Astrophysics Data System (ADS)

    Jiang, Q.; Bi, C.; Lin, S.

    2006-04-01

    As the HDD spindle motors become smaller and smaller, the back electromotive forces (emfs) measurement faces the new challenges due to their low inertias and small sizes. This article proposes a novel method to measure the back emfs and their harmonic components of PM ac motors only through a freewheeling procedure. To eliminate the influence of the freewheeling deceleration, the phase flux linkages are employed to obtain the back emf amplitudes and phases of the fundamental and harmonic components by using finite Fourier series analysis. The proposed method makes the freewheeling measurement of the back emfs and their harmonics accurate and fast. It is especially useful for the low inertia PM ac motors, such as spindle motors for small form factor HDDs.

  3. Rotational Brownian dynamics simulations of non-interacting magnetized ellipsoidal particles in d.c. and a.c. magnetic fields

    NASA Astrophysics Data System (ADS)

    Sánchez, Jorge H.; Rinaldi, Carlos

    2009-10-01

    The rotational Brownian motion of magnetized tri-axial ellipsoidal particles (orthotropic particles) suspended in a Newtonian fluid, in the dilute suspension limit, under applied d.c. and a.c. magnetic fields was studied using rotational Brownian dynamics simulations. The algorithm describing the change in the suspension magnetization was obtained from the stochastic angular momentum equation using the fluctuation-dissipation theorem and a quaternion formulation of orientation space. Simulation results are in agreement with the Langevin function for equilibrium magnetization and with single-exponential relaxation from equilibrium at small fields using Perrin's effective relaxation time. Dynamic susceptibilities for ellipsoidal particles of different aspect ratios were obtained from the response to oscillating magnetic fields of different frequencies and described by Debye's model for the complex susceptibility using Perrin's effective relaxation time. Simulations at high equilibrium and probe fields indicate that Perrin's effective relaxation time continues to describe relaxation from equilibrium and response to oscillating fields even beyond the small field limit.

  4. Mathematical Analysis of Hall Effect on Transient Hartman Flow about a Rotating Horizontal Permeable Surface in a Porous Medium under Inclined Magnetic Field

    PubMed Central

    Suresh, M.; Manglik, A.

    2014-01-01

    This paper proposes the exact solution for unsteady flow of a viscous incompressible electrically conducting fluid past a impulsively started infinite horizontal surface which is rotating with an angular velocity embedded in a saturated porous medium under the influence of strong magnetic field with hall effect. Our study focuses on the change of direction of the external magnetic field on the flow system which leads to change in the flow behavior and skin frictional forces at the boundary. Systems of flow equations are solved using Laplace transform technique. The impacts of control parameters Hartman number, rotation of the system, hall effect, inclination of the magnetic field, and Darcy number on primary and secondary velocities are shown graphically, skin friction at horizontal boundary in tabular form. For validating our results, in the absence of permeability of the porous medium and inclination of the magnetic field the results are in good agreement with the published results.

  5. Characterization of magnetic property depth profiles of surface-modified materials using a model-assisted swept frequency modulation field technique

    NASA Astrophysics Data System (ADS)

    Lo, C. C. H.

    2009-04-01

    This paper reports on a model-assisted approach to characterizing surface-modified materials whose magnetic properties vary continuously with depth. The technique involves measuring ac permeability profiles under a quasistatic biasing field superimposed with an ac modulation field of adjustable frequency and amplitude to control field penetration depth. A frequency dependent magnetic hysteresis model was used to model ac permeability profiles at different modulation field frequencies for direct comparison with measurement results. The approach was applied to characterize a series of surface hardened Fe-C samples. The depth dependence of the magnetic properties was determined by obtaining the best fits of the modeled ac permeability profiles to experimental data at multiple modulation frequencies. The midpoints of the inverted magnetic property profiles and the measured hardness profiles were found to be in agreement.

  6. Development of a nano-tesla magnetic field shielded chamber and highly precise AC-susceptibility measurement coil at μK temperatures

    NASA Astrophysics Data System (ADS)

    Kumar, Anil; Prakash, Om; Ramakrishanan, S.

    2014-04-01

    A special sample measurement chamber has been developed to perform experiments at ultralow temperatures and ultralow magnetic field. A high permeability material known as cryoperm 10 and Pb is used to shield the measurement space consisting of the signal detecting set-up and the sample. The detecting setup consists of a very sensitive susceptibility coil wound on OFHC Cu bobbin.

  7. Layer-by-layer self-assembly of micro-capsules for the magnetic activation of semi-permeable nano-shells

    NASA Astrophysics Data System (ADS)

    Prouty, Malcolm D.

    2007-12-01

    Layer-by-layer (LbL) self-assembly has demonstrated broad perspectives for encapsulating, and the controllable delivery, of drugs. The nano-scale polymer layers have the capability of material protection. Magnetic nanoparticles have great potential to be applied with LbL technology to achieve both "focusing" of the encapsulated drugs to a specific location followed by "switching" them on to release the encapsulated drugs. In this work, Phor21-betaCG(ala), dextran, and dexamethasone were used as model drugs. Encapsulation of these drugs with layer-by-layer self-assembly formed biolnano robotic capsules for controlled delivery and drug release. Silica nanoparticles coated with polyelectrolyte layers of sodium carboxymethyl cellulose (CMC) or gelatin B, along with an oppositely charged peptide drug (Phor2l-betaCG(ala)), were prepared using LbL self-assembly and confirmed using QCM and zeta potential measurements. The peptide drug was assembled as a component of the multilayer walls. The release kinetics of the embedded peptide were determined. Up to 18% of the embedded Phor21-betaCG(ala) was released from the CMC multilayers over a period of 28 hours. The release was based on physiological conditions, and an external control mechanism using magnetic nanoparticles needed to be developed. Magnetic permeability control experiments were setup by applying LbL self-assembly on MnCO3 micro-cores to fabricate polyelectrolyte microcapsules embedded with superparamagnetic gold coated cobalt (Co Au) nanoparticles. An alternating magnetic field was applied to the microcapsules to check for changes in permeability. Permeability experiments were achieved by adding fluorescein isothiocyanate (FITC) labeled dextran to the microcapsule solution. Before an alternating magnetic field was applied, the capsules remained impermeable to the FITC-dextran; however, after an alternating magnetic field was applied for 30 minutes, approximately 99% of the capsules were filled with FITC

  8. Collective modes, ac response, and magnetic properties of the three-dimensional Dirac semimetal in the triplet superconducting state

    NASA Astrophysics Data System (ADS)

    Rosenstein, B.; Shapiro, B. Ya.; Shapiro, I.

    2015-08-01

    It was recently shown that conventional phonon-electron interactions may induce a triplet pairing state in time-reversal invariant three-dimensional Dirac semimetals. Starting from the microscopic model of the isotropic Dirac semimetal, the Ginzburg-Landau equations for the vector order parameter is derived using the Gor'kov technique. The collective modes including gapless Goldstone modes and gapped Higgs modes of various polarizations are identified. They are somewhat analogous to the modes in the B phase of He3, although in the present case quantitatively there is a pronounced difference between longitudinal and transverse components. The difference is caused by the vector nature of the order parameter leading to two different coherence lengths or penetration depths. The system is predicted to be highly dissipative due to the Goldstone modes. The time-dependent Ginzburg-Landau model in the presence of external fields is used to investigate some optical and magnetic properties of such superconductors. The ac conductivity of a clean sample depends on the orientation of the order parameter. It is demonstrated that the difference between the penetration depths results in rotation of the polarization vector of microwave passing a slab made of this material. The upper critical magnetic field Hc 2 was found. It turns out that at fields close to Hc 2 the order parameter orients itself perpendicular to the field direction. In certain range of parameters the triplet superconducting phase persists at arbitrarily high magnetic field like in some p -wave superconductors.

  9. Nonlinear and ac Susceptibility of the Dilute Ising Magnet LiHoxY1-xF4

    NASA Astrophysics Data System (ADS)

    Quilliam, Jeffrey; Meng, Shuchao; Mugford, Chas; Kycia, Jan

    2008-03-01

    Recent work has called into question the existence of a spin glass transition in the dilute dipolar Ising magnet LiHoxY1-xF4 [1]. Other work has suggested that there is an exotic spin liquid phase found at a Ho concentration of x = 0.045 [2]. In order to carefully study the dynamics of this system, we have put together a SQUID magnetometer which allows for measurements of ac susceptibility and nonlinear susceptibility over a large frequency range. We present results from measurements on single crystals of LiHoxY1-xF4, particularly on an x = 0.045 sample, in an attempt to either reproduce the exotic ``anti-glass'' physics that was previously observed or to detect a spin glass transition. [1] P. E. Jonnson et al. PRL 98, 256403 (2007) [2] S. Ghosh et al. Science 296, 2195 (2002)

  10. Linearity of the Faraday-rotation-type ac magnetic-field sensor with a ferrimagnetic or ferromagnetic rotator film

    NASA Astrophysics Data System (ADS)

    Mori, Hiroshi; Asahara, Yousuke

    1996-03-01

    We analyze the linearity and modulation depth of ac magnetic-field sensors or current sensors, using a ferrimagnetic or ferromagnetic film as the Faraday rotator and employing the detection of only the zeroth-order optical diffraction component from the rotator. It is theoretically shown that for this class of sensor the condition of a constant modulation depth and that of a constant ratio error give an identical series of curves for the relationship between Faraday rotation angle greater than or equals V and polarizer/analyzer relative angle Phi . We give some numerical examples to demonstrate the usefulness of the result with reference to a rare-earth iron garnet film as the rotator.

  11. Monitoring of changes in cluster structures in water under AC magnetic field

    NASA Astrophysics Data System (ADS)

    Usanov, A. D.; Ulyanov, S. S.; Ilyukhina, N. S.; Usanov, D. A.

    2016-01-01

    A fundamental possibility of visualizing cluster structures formed in distilled water by an optical method based on the analysis of dynamic speckle structures is demonstrated. It is shown for the first time that, in contrast to the existing concepts, water clusters can be rather large (up to 200 -m in size), and their lifetime is several tens of seconds. These clusters are found to have an internal spatially inhomogeneous structure, constantly changing in time. The properties of magnetized and non-magnetized water are found to differ significantly. In particular, the number of clusters formed in magnetized water is several times larger than that formed in the same volume of non-magnetized water.

  12. Influence of Critical Current Density on Guidance Force Decay of HTS Bulk Exposed to AC Magnetic Field Perturbation in a Maglev Vehicle System

    NASA Astrophysics Data System (ADS)

    Longcai, Zhang; Jianguo, Kong

    2012-07-01

    Superconducting maglev vehicle is one of the most promising applications of HTS bulks. In such a system, the HTS bulks are always exposed to AC external magnetic field, which is generated by the inhomogeneous surface magnetic field of the NdFeB guideway. In our previous work, we studied the guidance force decay of the YBCO bulk over the NdFdB guideway used in the High-temperature superconducting maglev vehicle system with the application of the AC external magnetic field, and calculated the guidance force decay as a function of time based on an analytic model. In this paper, we investigated the influence of the critical current density on the guidance force decay of HTS bulk exposed to AC field perturbation in the maglev vehicle system and try to adopt a method to suppress the decay. From the results, it was found that the guidance force decay rate was higher for the bulk with lower critical current density. Therefore, we could suppress the guidance force decay of HTS bulk exposed to AC external magnetic field perturbation in the maglev vehicle system by improving critical current density of the bulk.

  13. Water permeability of capillaries in the subfornical organ of rats determined by Gd-DTPA2- enhanced 1H magnetic resonance imaging

    PubMed Central

    Seo, Yoshiteru; Takamata, Akira; Ogino, Takashi; Morita, Hironobu; Nakamura, Shun; Murakami, Masataka

    2002-01-01

    The water permeability of capillaries in the subfornical organ (SFO) of rat was measured by a 1H nuclear magnetic resonance method in combination with a venous injection of a relaxation reagent, gadolinium-diethylene triamine-N,N,N′,N″,N″-pentaacetic acid (Gd-DTPA2-), which could not pass through the blood-brain barrier (BBB). Judging from results of Gd-DTPA2- dose dependency in the intact brain and the BBB-permeabilized brain, Gd-DTPA2- could not have leaked out from the capillaries in the cortex, thalamus or SFO, but it could have been extravasated in the posterior lobe of the pituitary gland. The longitudinal (T1) relaxation time of water in the SFO region was measured by inversion-recovery magnetic resonance imaging at 4.7 T. The T1 relaxation rates (1/T1) before and after Gd-DTPA2- infusion were 0.70 ± 0.02 s−1 (mean ± s.e.m., n = 9) and 1.53 ± 0.11 s−1 (n = 9), respectively. The rate constant for water influx to the capillaries was estimated to be 0.84 ± 0.11 s−1 (n = 9) which corresponds with a diffusive membrane permeability (Pd) of 3.7 × 10−3 cm s−1. Compared with values found in the literature available on this subject, this Pd value for the capillaries in the SFO was the same order of magnitude as that for transmembrane permeability of water for the vasa recta, and it may be 10–100 times larger than that of the blood-brain barrier in the cortex. Areas of the cortex and thalamus showed minimal changes in the T1 relaxation rate (ca 0.09 s−1), but these values were not statistically significant and they corresponded to Pd values much smaller than those found in the SFO. From these results, we conclude that the capillaries in the SFO have one of the highest water permeability values among all of the capillaries in the brain. It is also suggested that this magnetic resonance imaging, based on T1 relaxation rate, is a useful method to detect local water permeability in situ. PMID:12433962

  14. Review of russian literature on biological action of DC and low-frequency AC magnetic fields.

    PubMed

    Zhadin, M N

    2001-01-01

    This review considers the Russian scientific literature on the influence of weak static and of low-frequency alternating magnetic fields on biological systems. The review covers the most interesting works and the main lines of investigation during the period 1900 to the present. Shown here are the historical roots, beginning with the ideas of V. Vernadsky and A. Chizhevsky, which led in the field of Russian biology to an increasing interest in magnetic fields, based on an intimate connection between solar activity and life on the Earth, and which determined the peculiar development of Russian magnetobiology. The variety of studies on the effects of magnetic storms and extremely low-frequency, periodic variations of the geomagnetic field on human beings and animals as well as on social phenomena are described. The diverse experiments involving artificial laboratory magnetic fields acting on different biological entities under different conditions are also considered. A series of theoretical advances are reviewed that have paved the way for a step-by-step understanding of the mechanisms of magnetic field effects on biological systems. The predominantly unfavorable influence of magnetic fields on living beings is shown, but the cases of favorable influence of magnetic fields on human beings and lower animals are demonstrated as well. The majority of Russian investigations in this area of science has been unknown among the non-Russian speaking audience for many reasons, primarily because of a language barrier. Therefore, it is hoped that this review may be of interest to the international scientific community. PMID:11122491

  15. Study of AC Magnetic Properties and Core Losses of Fe/Fe3O4-epoxy Resin Soft Magnetic Composite

    NASA Astrophysics Data System (ADS)

    Laxminarayana, T. A.; Manna, Subhendu Kumar; Fernandes, B. G.; Venkataramani, N.

    Soft Magnetic Composites (SMC) were prepared by coating of nanocrystalline Fe3O4 particles, synthesized by co-precipitation method, on atomized iron powder of particle size less than 53 μm in size using epoxy resin as a binder between iron and Fe3O4. Fe3O4 was chosen, for its high electric resistivity and suitable magnetic properties, to keep the coating layer magnetic and seek improvement to the magnetic properties of SMC. SEM images and XRD patterns were recorded in order to investigate the coatings on the surface of iron powder. A toroid was prepared by cold compaction of coated iron powder at 1050 MPa and subsequently cured at 150˚C for 1 hr in argon atmosphere. For comparison of properties, a toroid of uncoated iron powder was also compacted at 1050 MPa and annealed at 600˚C for 2 hr in argon atmosphere. The coated iron powder composite has a resistivity of greater than 200 μΩm, measured by four probe method. A comparison of Magnetic Hysteresis loops and core losses using B-H Loop tracer in the frequency range 0 to 1500 Hz on the coated and uncoated iron powder is reported.

  16. A cluster-glass magnetic state in R5Pd2 (R = Ho, Tb) compounds evidenced by AC-susceptibility and neutron scattering measurements.

    PubMed

    Gubkin, A F; Sherstobitova, E A; Terentyev, P B; Hoser, A; Baranov, N V

    2013-06-12

    AC- and DC-susceptibility, high-field magnetization and neutron diffraction measurements have been performed in order to study the magnetic state of R5Pd2 (R = Ho, Tb) compounds. The results show that both compounds undergo cluster-glass freezing upon cooling below Tf. According to the neutron diffraction a long-range magnetic order is absent down to 2 K and magnetic clusters with short-range incommensurate antiferromagnetic correlations exist not only below Tf but also in a wide temperature range above the freezing temperature (at least up to 2Tf). A complex cluster-glass magnetic state existing in Ho5Pd2 and Tb5Pd2 down to low temperatures results in rather complicated magnetization behavior in DC and AC magnetic fields. Such an unusual magnetic state in compounds with a high rare-earth concentration may be associated with the layered type of their crystal structure and with substantial atomic disorder, which results in frustrations in the magnetic subsystem. PMID:23676314

  17. On the temperature dependence of the ac susceptibility of Fe 3O 4 magnetic fluids

    NASA Astrophysics Data System (ADS)

    Abu-Aljarayesh, I.; Al-Rawi, A.; Abu-Safia, H.

    1993-02-01

    The temperature dependence of the frequency-dependent magnetic susceptibility has been measured for Fe 3O 4 magnetic fluids with Isopar-M as a liquid carrier. The temperature range was 80 K ≤ T ≤ 300 K, and the volume fractions ɛ ranged from 0.004 to 0.062. With increasing temperature the in-phase magnetic susceptibility χ' increased from its initial value to a maximum at a temperature TB, then decreased monotonically until around the melting point of the liquid carrier, Tm ≈ 200 K. For T ≤ Tm, χ' increased rapidly to a second maximum at T = TB1. This behaviour was qualitatively similar for all studied samples. For the sample with ɛ = 0.047, χ' decreased with increasing frequency at all temperatures. When a static magnetic field was applied, a reduction in χ' was also observed. The effects of interparticle interactions on the static initial susceptibility χ i, are discussed. Analysis of the data yields information about the effective anisotropy energy, the median magnetic diameter, and relaxation times. The distribution of blocking temperature was calculated from the superparamagnetic blocking model of Wohlfarth. The results are further analysed and discussed within the framework of Lundgren model of spin glasses.

  18. Attenuation of Mouse Melanoma by A/C Magnetic Field after Delivery of Bi-Magnetic Nanoparticles by Neural Progenitor Cells

    PubMed Central

    Rachakatla, Raja Shekar; Balivada, Sivasai; Seo, Gwi-Moon; Myers, Carl B; Wang, Hongwang; Samarakoon, Thilani N.; Dani, Raj; Pyle, Marla; Kroh, Franklin O.; Walker, Brandon; Leaym, Xiaoxuan; Koper, Olga B.; Chikan, Viktor; Bossmann, Stefan H.; Tamura, Masaaki; Troyer, Deryl L.

    2010-01-01

    Localized magnetic hyperthermia as a treatment modality for cancer has generated renewed interest, particularly if it can be targeted to the tumor site. We examined whether tumor-tropic neural progenitor cells (NPCs) could be utilized as cell delivery vehicles for achieving preferential accumulation of core/shell iron/iron oxide magnetic nanoparticles (MNPs) within a mouse model of melanoma. We developed aminosiloxane-porphyrin functionalized MNPs, evaluated cell viability and loading efficiency, and transplanted neural progenitor cells loaded with this cargo into mice with melanoma. NPCs were efficiently loaded with core/shell Fe/Fe3O4 MNPs with minimal cytotoxicity; the MNPs accumulated as aggregates in the cytosol. The NPCs loaded with MNPs could travel to subcutaneous melanomas, and after A/C (alternating current) magnetic field (AMF) exposure, the targeted delivery of MNPs by the cells resulted in a measurable regression of the tumors. The tumor attenuation was significant (p<0.05) a short time (24 hours) after the last of three AMF exposures. PMID:21058696

  19. Applied AC and DC magnetic fields cause alterations in the mitotic cycle of early sea urchin embryos

    SciTech Connect

    Levin, M.; Ernst, S.G.

    1995-09-01

    This study demonstrates that exposure to 60 Hz magnetic fields (3.4--8.8 mt) and magnetic fields over the range DC-600 kHz (2.5--6.5 mT) can alter the early embryonic development of sea urchin embryos by inducing alterations in the timing of the cell cycle. Batches of fertilized eggs were exposed to the fields produced by a coil system. Samples of the continuous cultures were taken and scored for cell division. The times of both the first and second cell divisions were advanced by ELF AC fields and by static fields. The magnitude of the 60 Hz effect appears proportional to the field strength over the range tested. the relationship to field frequency was nonlinear and complex. For certain frequencies above the ELF range, the exposure resulted in a delay of the onset of mitosis. The advance of mitosis was also dependent on the duration of exposure and on the timing of exposure relative to fertilization.

  20. Dual AC Dipole Excitation for the Measurement of Magnetic Multipole Strength from Beam Position Monitor Data

    SciTech Connect

    M. Spata, G.A. Krafft

    2011-09-01

    An experiment was conducted at Jefferson Lab's Continuous Electron Beam Accelerator Facility to develop a technique for characterizing the nonlinear fields of the beam transport system. Two air-core dipole magnets were simultaneously driven at two different frequencies to provide a time-dependent transverse modulation of the electron beam. Fourier decomposition of beam position monitor data was then used to measure the amplitude of these frequencies at different positions along the beamline. For a purely linear transport system one expects to find solely the frequencies that were applied to the dipoles with amplitudes that depend on the phase advance of the lattice. In the presence of nonlinear fields one expects to also find harmonics of the driving frequencies that depend on the order of the nonlinearity. The technique was calibrated using one of the sextupole magnets in a CEBAF beamline and then applied to a dipole to measure the sextupole and octupole strength of the magnet. A comparison is made between the beam-based measurements, results from TOSCA and data from our Magnet Measurement Facility.

  1. Crustal Permeability

    NASA Astrophysics Data System (ADS)

    Ingebritsen, S.; Gleeson, T.

    2014-12-01

    Existing data and models support a distinction between the hydrodynamics of the brittle upper crust, where topography, permeability contrasts, and magmatic heat sources dominate patterns of flow and externally derived (meteoric) fluids are common, and the ductile lower crust, dominated by devolatilization reactions and internally derived fluids. The permeability structure of the uppermost (~<1 km) crust is highly heterogeneous, and controls include primary lithology, porosity, rheology, geochemistry, and tectonic and time-temperature histories of the rocks. Systematic permeability differences among original lithologies persist to contact-metamorphic depths of 3-10 km, but are not evident at regional-metamorphic depths of 10-30+ km - presumably because, at such depths, metamorphic textures become largely independent of the original lithology. Permeability can vary in time as well as space, and its temporal evolution may be gradual or abrupt: streamflow responses to moderate to large earthquakes demonstrate that dynamic stresses can instantaneously change permeability by factors of up to 20 on a regional scale, whereas a 10-fold decrease in the permeability of a package of shale in a compacting basin may require 107years. Temporal variation is enhanced by strong chemical and thermal disequilibrium; thus lab experiments involving hydrothermal flow in crystalline rocks under pressure, temperature, and chemistry gradients often result in 10-fold permeability decreases over daily to sub-annual time scales. Recent research on enhanced geothermal reservoirs, ore-forming systems, and the hydrologic effects of earthquakes consistently shows that shear dislocation caused by tectonic forcing or fluid injection can increase near-to intermediate-field permeability by factors of 100 to 1000. Nonetheless, considering permeability as static parameter is often a reasonable assumption for low-temperature hydrogeologic investigations with time scales of days to decades.

  2. Simulation of fluid flow induced by opposing ac magnetic fields in a continuous casting mold

    SciTech Connect

    Chang, F.C.; Hull, J.R.; Beitelman, L.

    1995-07-01

    A numerical simulation was performed for a novel electromagnetic stirring system employing two rotating magnetic fields. The system controls stirring flow in the meniscus region of a continuous casting mold independently from the stirring induced within the remaining volume of the mold by a main electromagnetic stirrer (M-EMS). This control is achieved by applying to the meniscus region an auxiliary electromagnetic field whose direction of rotation is opposite to that of the main magnetic field produced by the M-EMS. The model computes values and spatial distributions of electromagnetic parameters and fluid flow in the stirred pools of mercury in cylindrical and square geometries. Also predicted are the relationships between electromagnetics and fluid flows pertinent to a dynamic equilibrium of the opposing stirring swirls in the meniscus region. Results of the numerical simulation compared well with measurements obtained from experiments with mercury pools.

  3. A Fast-sampling, Planar Array for Measuring the AC Field of Fermilab Pulsed Extraction Magnets

    SciTech Connect

    DiMarco, E.Joseph; Johnstone, C.; Kiemschies, O.; Kotelnikov, S.K.; Lamm, M.J.; Makulski, A.; Nehring, R.; Orris, D.F.; Russell, A.D.; Tartaglia, Michael Albert; Velev, G.; /Fermilab

    2008-06-25

    A system employing a planar array of inductive pick-up coils has been developed for measurements of the rapidly changing dipole field in pulsed extraction magnets for the Fermilab MuCool project. The magnets are of C-type and deigned to support a peak field of 0.65 T during 8.33 millisecond half-sine pulse at a 15 Hz repetition rate. The coils of the measurement system are fabricated on a single, 97.5 mm wide, 2-layer circuit board. The array of coils is simultaneously sampled at data rates of up to 100 kHz with 10 kHz bandwidth using 24-bit ADC's. A detailed overview of the system and data analysis is presented, along with a characterization of results and system performance.

  4. Magnetoresistive DNA chips based on ac field focusing of magnetic labels

    NASA Astrophysics Data System (ADS)

    Ferreira, H. A.; Cardoso, F. A.; Ferreira, R.; Cardoso, S.; Freitas, P. P.

    2006-04-01

    A study was made on the sensitivity of a magnetoresistive DNA-chip platform being developed for cystic fibrosis diagnostics. The chip, comprised of an array of 2.5×80 μm2 U-shaped spin-valve sensors integrated within current line structures for magnetic label manipulation, enabled the detection at 30 Hz of 250 nm magnetic nanoparticles from 100 pM down to the pM range (or a target DNA concentration of 500 pM). It was observed that the sensor response increased linearly with label concentration. Noise spectra obtained for these sensors showed a thermal noise of 10-17 V2/Hz with a 1/f knee at 50 kHz at a 1 mA sense current, showing that lower detection limits are possible.

  5. Ac-susceptibility investigations of superspin blocking and freezing in interacting magnetic nanoparticle ensembles

    NASA Astrophysics Data System (ADS)

    Botez, Cristian E.; Morris, Joshua L.

    2016-03-01

    We have investigated the effect of dipolar interactions on the superspin blocking and freezing of 9 nm average size Fe3O4 magnetic nanoparticle ensembles. Our dynamic susceptibility data reveals a two-regime behavior of the blocking temperature, T B, upon diluting a Fe3O4/hexane magnetic fluid. As the nanoparticle volume ratio, Φ, is reduced from an as-prepared reference Φ = 1 to Φ = 1/96, the blocking temperature decreases from 46.1 K to 34.2 K, but higher values reenter upon further diluting the magnetic fluid to Φ = 1/384 (where T B = 42.5 K). We found evidence that cooling below T B within the higher concentration range (Φ > 1/48) leads to the collective freezing of the superspins, whereas individual superspin blocking occurs in the presence of weaker interactions (Φ < 1/96). The unexpected increase of the blocking temperature with the decrease of the inter-particle interactions observed at low nanoparticle concentrations is well described by the Mørup-Tronc model.

  6. AC-susceptibility investigations of superspin blocking and freezing in interacting magnetic nanoparticle ensembles

    NASA Astrophysics Data System (ADS)

    Morris, Joshua Logan

    We have investigated the effect of dipolar interactions on the superspin blocking and freezing of 10 nm average size Fe3O4 magnetic nanoparticle ensembles. Our dynamic susceptibility data reveals a two-regime behavior of the blocking temperature, TB, upon diluting a Fe 3O4/hexane magnetic nanoparticle fluid. As the nanoparticle volume ratio, Phi, is reduced from an as-prepared reference Phi = 1 to Phi = 1/96, the blocking temperature decreases from 46.1 K to 34.2 K, but higher values reenter upon further diluting the magnetic fluid to Phi = 1/384 (where TB = 42.5 K). We show that cooling below TB within the higher concentration range (Phi > 1/48) leads to the collective freezing of the superspins in a spin-glass-like fashion, whereas individual superspin blocking occurs in the presence of weaker dipolar interactions (Phi < 1/96). The unexpected increase of the blocking temperature with the decrease of the interparticle interactions observed at low nanoparticle concentrations is well described by the Morup-Tronc (MT) model.

  7. Ac-susceptibility investigations of superspin blocking and freezing in interacting magnetic nanoparticle ensembles.

    PubMed

    Botez, Cristian E; Morris, Joshua L

    2016-03-18

    We have investigated the effect of dipolar interactions on the superspin blocking and freezing of 9 nm average size Fe3O4 magnetic nanoparticle ensembles. Our dynamic susceptibility data reveals a two-regime behavior of the blocking temperature, T(B), upon diluting a Fe3O4/hexane magnetic fluid. As the nanoparticle volume ratio, Φ, is reduced from an as-prepared reference Φ = 1 to Φ = 1/96, the blocking temperature decreases from 46.1 K to 34.2 K, but higher values reenter upon further diluting the magnetic fluid to Φ = 1/384 (where T(B) = 42.5 K). We found evidence that cooling below T B within the higher concentration range (Φ > 1/48) leads to the collective freezing of the superspins, whereas individual superspin blocking occurs in the presence of weaker interactions (Φ < 1/96). The unexpected increase of the blocking temperature with the decrease of the inter-particle interactions observed at low nanoparticle concentrations is well described by the Mørup-Tronc model. PMID:26876797

  8. Effect of Si addition on AC and DC magnetic properties of (Fe-P)-Si alloy

    NASA Astrophysics Data System (ADS)

    Gautam, Ravi; Prabhu, D.; Chandrasekaran, V.; Gopalan, R.; Sundararajan, G.

    2016-05-01

    We report a new (Fe-P)-Si based alloy with relatively high induction (1.8-1.9 T), low coercivity (< 80 A/m), high resistivity (˜38 μΩ cm) and low core loss (217 W/kg @ 1 T/1 kHz) comparable to the commercially available M530-50 A5 Si-steel. The attractive magnetic and electrical properties are attributed to i) the two phase microstructure of fine nano precipitates of Fe3P dispersed in α-Fe matrix achieved by a two-step heat-treatment process and ii) Si addition enhancing the resistivity of the α-Fe matrix phase. As the alloy processing is by conventional wrought metallurgy method, it has the potential for large scale production.

  9. The effect of nickel content on the ac magnetic properties of 49Fe-49Co-2V alloys

    NASA Astrophysics Data System (ADS)

    Novotny, P. M.

    1988-04-01

    Experimental alloys containing between 0.03 and 0.67 wt. % nickel were produced to determine the effect of low nickel content on the ac magnetic properties of Carpenter's 49Fe-49Co-2V Hiperco (a registered trademark of Carpenter Technology Corp.) 50A alloy. The alloys were processed into 1.02×10-4 m (0.004 in.) thick strip, wound into tape toroids, annealed then tested for core loss at 60 and 400 Hz for induction levels of 1.0, 1.5, and 2.0 T. Toroids annealed at 885 °C in hydrogen, followed by slow cooling, exhibited a linear increase in core loss as nickel content increased due to the presence of a second phase in the microstructure. When the annealing temperature was decreased to 845 °C the second phase was eliminated and the core loss did not vary with nickel content. STEM examination of the samples determined that the second phase was a heavily dislocated bcc α'1 phase which had martensitically transformed from the fcc γ1 phase despite the slow cooling rate. Thermal expansion testing determined that increasing the Ni content in the range of 0-1 wt. % decreased the α1 +γ1 /α1 transformation temperature of the 49Fe-49Co-2V alloy.

  10. Advanced single permanent magnet axipolar ironless stator ac motor for electric passenger vehicles

    NASA Technical Reports Server (NTRS)

    Beauchamp, E. D.; Hadfield, J. R.; Wuertz, K. L.

    1983-01-01

    A program was conducted to design and develop an advanced-concept motor specifically created for propulsion of electric vehicles with increased range, reduced energy consumption, and reduced life-cycle costs in comparison with conventional systems. The motor developed is a brushless, dc, rare-earth cobalt, permanent magnet, axial air gap inductor machine that uses an ironless stator. Air cooling is inherent provided by the centrifugal-fan action of the rotor poles. An extensive design phase was conducted, which included analysis of the system performance versus the SAE J227a(D) driving cycle. A proof-of-principle model was developed and tested, and a functional model was developed and tested. Full generator-level testing was conducted on the functional model, recording electromagnetic, thermal, aerodynamic, and acoustic noise data. The machine demonstrated 20.3 kW output at 1466 rad/s and 160 dc. The novel ironless stator demonstated the capability to continuously operate at peak current. The projected system performance based on the use of a transistor inverter is 23.6 kW output power at 1466 rad/s and 83.3 percent efficiency. Design areas of concern regarding electric vehicle applications include the inherently high windage loss and rotor inertia.

  11. Second VAMAS a.c. loss measurement intercomparison: magnetization measurement of low-frequency (hysteretic) a.c. loss in NbTi multifilamentary strands

    NASA Astrophysics Data System (ADS)

    Collings, E. W.; Sumption, M. D.; Itoh, K.; Wada, H.; Tachikawa, K.

    The results of the 2 nd VAMAS measurement intercomparison program on low-frequency (hysteretic) a.c. loss are presented and discussed. Two sets of multifilamentary NbTi strands (Set No. 1: copper matrix, fil. diams 0.5, 1, 3, and 12 μm; Set No. 2: cupronickel matrix, fil. diams 0.4, 0.5, and 1 μm) were subjected to interlaboratory testing. In an initial series of tests, samples in various forms (e.g. wire bundles, coils) were measured mostly by vibrating-sample- and SQUID magnetometry. Considerable scatter was noted especially in the small-filament-diameter a.c.-loss data. In a study of measurement accuracy, a supplementary series of tests compared the results of VSM measurement of a given pair of copper-matrix samples. In the light of all the results, factors contributing to a.c. loss error are discussed and recommendations are made concerning the specification of future a.c.-loss measurement intercomparisons.

  12. Automated ac galvanomagnetic measurement system

    NASA Technical Reports Server (NTRS)

    Szofran, F. R.; Espy, P. N.

    1985-01-01

    An automated, ac galvanomagnetic measurement system is described. Hall or van der Pauw measurements in the temperature range 10-300 K can be made at a preselected magnetic field without operator attendance. Procedures to validate sample installation and correct operation of other system functions, such as magnetic field and thermometry, are included. Advantages of ac measurements are discussed.

  13. Mixed convection flow along a vertical permeable plate embedded in a porous medium in the presence of a transverse magnetic field

    SciTech Connect

    Chamkha, A.J.

    1998-07-01

    Continuum boundary layer equations are derived for governing steady, laminar, hydromagnetic, mixed convection flow along a vertical semi-infinite permeable plate maintained at constant heat flux and embedded in a uniform porous medium with heat generation and magnetic dissipation. A mixed-convection parameter covering the entire range from pure forced convection to pure free convection is introduced. The governing equations are transformed using a non-similarity transformation and solved numerically by an implicit finite difference method. Typical results for the skin friction coefficient and the wall heat transfer are presented and discussed for various parametric conditions. The investigation of forced, mixed, and free convection heat transfer from surfaces embedded in porous media has received considerable attention in view of its importance in the petroleum industries, filtration, heat exchanger design, thermal insulation, chemical catalytic reactors, burying of drums containing heat-generating chemicals in the earth, and underground spread of pollutants.

  14. Wide band negative magnetic permeability materials (NMPM) with composite metalsemiconductor structures based on the Drude model, and applications to negative-refractive index (NIM).

    PubMed

    Benedetti, A; Sibilia, C; Bertolotti, M

    2007-05-28

    Composite structures based on metal open rings and thin wires are well established, for obtaining efficient negative index materials (NIM), acting as metamaterials in the long wavelength regime. The main losses are due both to metal absorption and to the inner electric resistance of metals; to overcome this latter loss we propose a new metal-semiconductor structure dimensioned by direct synthesis method, which offers an almost perfect Drude-like effective magnetic permeability. The choice of particular semiconductor components allows to get a negative resistance for the current induced by the electromagnetic field, which cancels that of the metal but puts a limit to the spectral response of the metamaterial. We consider some parasite effects, such as bianisotropy and incorrect values of structural parameters, to see limitations and features of this new NIM technology. PMID:19546961

  15. New petrophysical magnetic methods MACC and MAFM in permeability characterisation of petroleum reservoir rock cleaning, flooding modelling and determination of fines migration in formation damage

    NASA Astrophysics Data System (ADS)

    Ivakhnenko, O. P.

    2012-04-01

    Potential applications of magnetic techniques and methods in petroleum engineering and petrophysics (Ivakhnenko, 1999, 2006; Ivakhnenko & Potter, 2004) reveal their vast advantages for the petroleum reservoir characterisation and formation evaluation. In this work author proposes for the first time developed systematic methods of the Magnetic Analysis of Core Cleaning (MACC) and Magnetic Analysis of Fines Migration (MAFM) for characterisation of reservoir core cleaning and modelling estimations of fines migration for the petroleum reservoir formations. Using example of the one oil field we demonstrate results in application of these methods on the reservoir samples. Petroleum reservoir cores samples have been collected within reservoir using routine technique of reservoir sampling and preservation for PVT analysis. Immediately before the MACC and MAFM studies samples have been exposed to atmospheric air for a few days. The selected samples have been in detailed way characterised after fluid cleaning and core flooding by their mineralogical compositions and petrophysical parameters. Mineralogical composition has been estimated utilizing XRD techniques. The petrophysical parameters, such as permeability and porosity have been measured on the basis of total core analysis. The results demonstrate effectiveness and importance of the MACC and MAFM methods for the routine core analysis (RCAL) and the special core analysis (SCAL) in the reservoir characterisation, core flooding and formation damage analysis.

  16. Effect of ordered array of magnetic dots on the dynamics of Josephson vortices in stacked SNS Josephson junctions under DC and AC current

    NASA Astrophysics Data System (ADS)

    Berdiyorov, Golibjon R.; Savel'ev, Sergey; Kusmartsev, Feodor V.; Peeters, François M.

    2015-11-01

    We use the anisotropic time-dependent Ginzburg-Landau theory to investigate the effect of a square array of out-of-plane magnetic dots on the dynamics of Josephson vortices (fluxons) in artificial stacks of superconducting-normal-superconducting (SNS) Josephson junctions in the presence of external DC and AC currents. Periodic pinning due to the magnetic dots distorts the triangular lattice of fluxons and results in the appearance of commensurability features in the current-voltage characteristics of the system. For the larger values of the magnetization, additional peaks appear in the voltage-time characteristics of the system due to the creation and annihilation of vortex-antivortex pairs. Peculiar changes in the response of the system to the applied current is found resulting in a "superradiant" vortex-flow state at large current values, where a rectangular lattice of moving vortices is formed. Synchronizing the motion of fluxons by adding a small ac component to the biasing dc current is realized. However, we found that synchronization becomes difficult for large magnetization of the dots due to the formation of vortex-antivortex pairs.

  17. Superparamagnetic state by linear and non-linear AC magnetic susceptibility in Mn0.5Zn0.5Fe2O4 ferrites nanoparticles.

    PubMed

    Suneetha, T; Kundu, S; Kashyap, Subhash C; Gupta, H C; Nath, T K

    2013-01-01

    The Mn0.5Zn0.5Fe2O4 nanoparticles has been synthesized using citrate-gel-precursor method. The direct mixing of nitrates and acetates yields homogeneous nanoparticles. Phase formation and crystal structure of the synthesized powder were examined through the X-ray diffraction (XRD). Fourier transform infrared (FTIR) spectra of the sample confirm the spinel structure. The average particle size was determined by transmission electron microscopy (TEM) and field emission scanning electron microscopy (FESEM). The average particle size is found to be about 13 nm. Superparamagnetic-like nature of the nanoparticles of Mn0.5Zn0.5Fe2O4 has been revealed through various dc and linear and non-linear ac magnetization measurements. However, the nanoparticles do not behave like ideal non-interacting superparamagnets. The magnetic particle size is found to be about 8 nm with saturation magnetization about 18.1 emu/g. The blocking temperature (T(B)) of the nanoparticle assembly is found to be about 150 K as observed from dc and ac magnetization measurements. The frequency dependence of the blocking temperature (T(B)) is found to follow Vogel-Fulcher law. The associated characteristic time tau0 is found to be 10(-5) s. This value is different from that generally found for non-interacting superparamagnetic (SPM) systems (tau0 = 10(-9)-10(-10) s). PMID:23646726

  18. AC Magnetic Susceptibility of the Assembled-Metal Complex {NBu4[FeIIFeIII(ox)3]}∞ (Bu=n-C4H9, ox=oxalato)

    NASA Astrophysics Data System (ADS)

    Bhattacharjee, Ashis; Nakazawa, Yasuhiro; Kobayashi, Hayao; Sorai, Michio

    2002-09-01

    AC magnetic susceptibility (χAC=χ\\prime-iχ\\prime\\prime) of {NBu4[FeIIFeIII(ox)3]}∞ was measured in the 4-50 K range for different frequencies (0.1-1000 Hz). Both of the χ\\prime(T) and χ\\prime\\prime(T) plots showed two peaks in two temperature regions: 4-33 K and 33-50 K. The χ\\prime(T) and χ\\prime\\prime(T) peaks in the 33-50 K range can be associated with the magnetic phase transition at the Néel temperature (43.3 K). However, the χ\\prime(T) peak in the 4-33 K range was found to be shifted towards lower temperature from 15.5 K to 13.5 K with increasing frequency, accompanied by a decrease in peak height. The fractional relative change in the peak temperature per decade change in frequency was calculated. The χ\\prime\\prime(T) in the 4-33 K range exhibited a broad peak around 25 K. The frequency dependence of χ\\prime(T) and χ\\prime\\prime(T) in the 4-33 K range occurred in the region where the irreversibilities in the ZFC (zero-field-cooled)-FC (field cooled) susceptibilities appeared. In this temperature range, a small heat capacity anomaly was detected and the negative magnetization effect took place in earlier reports. The wait-time dependence study of ZFC magnetization revealed an aging phenomenon. The frequency dependent peaks observed in the AC susceptibility and the aging phenomenon occurred below the Néel temperature might be indicative of the existence of a spin glass-like state in the present material at low temperatures.

  19. Calibrating NMR measured porosity/permeability relationships using µXRCT measurements

    NASA Astrophysics Data System (ADS)

    Mason, H. E.; Smith, M. M.; Hao, Y.; Carroll, S.

    2015-12-01

    Carbonate reservoirs have garnered interest for potential use in carbon capture and storage (CCS) activities. To be suitable for long term carbon dioxide (CO2) storage, they must possess sufficient permeability either through existing connected pore space, or due to reactivity with CO2-acidified fluids. Adequate assessment of the target formation permeability will rely on accurate downhole well-logging tools. Primary among these tools is nuclear magnetic resonance (NMR) well-logging. Application of this tool relies on our ability to relate the porosity and pore distributions measured by NMR to permeability. These methods are challenging to apply in carbonate reservoirs with complex mineralogies where pores sizes often span orders of magnitudes. We have assessed the ability of NMR methods to measure permeability using rocks from the Weyburn-Midale CO2 Monitoring and Storage Project Saskatchewan, Canada and the Arbuckle injection zone at the Wellington CO2 storage demonstration site, Kansas. Results of laboratory measured permeability values of these rocks indicate that the standard NMR methods for predicting permeability values can produce values off by orders of magnitude within the same flow units. In this presentation, we present the results of a combined NMR and micro X-ray computed tomography (μXRCT) study of these rock cores to better estimate downhole permeability values of carbonate rocks. The results of the study suggest that the dramatic differences in predicted permeability values derive from large differences in the matrix porosity, pore network tortuosities, and mineralogy of the various rock units. We will present new laboratory measurements, and methodologies aimed at producing a universal NMR calibration procedure for determining permeability in carbonate reservoirs. This work was performed under the auspices of the U.S. Department of Energy by Lawrence Livermore National Laboratory under Contract DE-AC52-07NA27344.

  20. Tevatron AC dipole system

    SciTech Connect

    Miyamoto, R.; Kopp, S.E.; Jansson, A.; Syphers, M.J.; /Fermilab

    2007-06-01

    The AC dipole is an oscillating dipole magnet which can induce large amplitude oscillations without the emittance growth and decoherence. These properties make it a good tool to measure optics of a hadron synchrotron. The vertical AC dipole for the Tevatron is powered by an inexpensive high power audio amplifier since its operating frequency is approximately 20 kHz. The magnet is incorporated into a parallel resonant system to maximize the current. The use of a vertical pinger magnet which has been installed in the Tevatron made the cost relatively inexpensive. Recently, the initial system was upgraded with a more powerful amplifier and oscillation amplitudes up to 2-3{sigma} were achieved with the 980 GeV proton beam. This paper discusses details of the Tevatron AC dipole system and also shows its test results.

  1. Comparative nuclear magnetic resonance studies of diffusional water permeability of red blood cells from different species. V--Rabbit (Oryctolagus cuniculus).

    PubMed

    Benga, G; Matei, H; Borza, T; Poruţiu, D; Lupşe, C

    1993-10-01

    1. The diffusional water permeability (Pd) of rabbit red blood cell (RBC) membrane has been monitored by a doping nuclear magnetic resonance (NMR) technique on control cells and following inhibition with p-chloromercuribenzene sulfonate (PCMBS). 2. The values of Pd were around 6.3 x 10(-3) cm/sec at 15 degrees C, 7.0 x 10(-3) cm/sec at 20 degrees C, 8.0 x 10(-3) cm/sec at 25 degrees C, 9.1 x 10(-3) cm/sec at 30 degrees C and 10.7 x 10(-3) cm/sec at 37 degrees C. 3. Systematic studies on the effects of PCMBS on water diffusion indicated that the maximal inhibition was reached in 15 min at 37 degrees C with 0.5 mM PCMBS. 4. The values of maximal inhibition were around 71-74% at all temperatures. 5. The basal permeability to water was estimated as 1.6 x 10(-3) cm/sec at 15 degrees C, 2.0 x 10(-3) cm/sec at 20 degrees C, 2.4 x 10(-3) cm/sec at 25 degrees C, 2.6 x 10(-3) cm/sec at 30 degrees C, and 3.1 x 10(-3) cm/sec at 37 degrees C. 6. The activation energy of water diffusion was around 18 kJ/mol and increased to 27 kcal/mol after incubation with PCMBS in conditions of maximal inhibition of water diffusion. 7. The membrane polypeptide electrophoretic pattern of rabbit RBCs has been compared with its human counterpart. 8. The rabbit membrane contained a higher amount of spectrin (bands 1 and 2), while the band 6 (glyceraldehyde-3-phosphate dehydrogenase) was markedly less intense.(ABSTRACT TRUNCATED AT 250 WORDS) PMID:8243057

  2. The use of field dependence of AC susceptibility for the interpretation of magnetic mineralogy and magnetic fabrics in the HSDP-2 basalts, Hawaii [rapid communication

    NASA Astrophysics Data System (ADS)

    Vahle, Carsten; Kontny, Agnes

    2005-09-01

    We applied the field dependence parameter χHd (%) = [( k300A/m - k30A/m) / k300A/m] × 100 given by de Wall for the subaerial and submarine basalts drilled by the 3109 m deep HSDP-2 borehole on Hawaii in order to verify the hypothesis that mainly composition controls the field dependence of AC susceptibility in titanomagnetite of natural occurrences. When we used this parameter, our data showed a significant scattering compared to data presented in earlier studies. In addition to composition, the effect of measurement temperature, grain size and anisotropy on the field dependent susceptibility were examined and found to be critical. The impact of grain size is weaker than the other effects. It cannot be totally excluded that the observed effects arise indirectly through an overlap of the other effects for the investigated basalts. The most important factor for the variation of field dependence is the degree of oxidation, causing a modification of the titanomagnetite composition or formation of titanomaghemite, and the mixing of Ti-rich with Ti-poor titanomagnetites, which strongly reduces the χHd parameter. Field dependence is not only related to titanomagnetite composition, especially for intermediate titanomagnetites with TCs between 100 and 300 °C. Temperature dependent susceptibility measurements at different field amplitudes for these intermediate types showed at constant geometry of the k( T) curve great differences in susceptibility, resulting in significant changes of the field dependence parameter over the temperature interval from - 100 to 260 °C. Therefore variations of the ambient measurement temperatures are able to influence the field dependence. The second important effect is the degree of particle shape and alignment, which controls the field dependence in different orientations especially for the intermediate titanomagnetite, which is intensively intergrown with elongated hemoilmenite grains. As a consequence, samples with higher degrees of

  3. Hysteretic Dependence of Magnetic Flux Density on Primary AC Current in Flat-Type Inductive Fault Current Limiter with YBCO Thin Film Discs

    NASA Astrophysics Data System (ADS)

    Harada, Masayuki; Yokomizu, Yasunobu; Matsumura, Toshiro

    2014-05-01

    This paper focuses on a flat-type inductive superconducting FCL (FIS-FCL) consisting of a pancake coil and a YBCO thin layer disc. AC current injection experiments and magnetic field analysis were carried out for two kinds of FIS-FCL, single-disc model and double-discs model. In the former, the pancake coil was putted on the YBCO disc. In the latter, the pancake coil was sandwiched with two YBCO discs. The double-discs model cancels out the magnetic flux density more effectively than the single-disc model. In the double-discs model, the superconducting state period is longer than in the single-disc model. Thus, it may be concluded that the double-discs model is considered to be suitable for FIS-FCL.

  4. Comparison of AC losses, magnetic field/current distributions and critical currents of superconducting circular pancake coils and infinitely long stacks using coated conductors

    NASA Astrophysics Data System (ADS)

    Yuan, Weijia; Campbell, A. M.; Hong, Z.; Ainslie, M. D.; Coombs, T. A.

    2010-08-01

    A model is presented for calculating the AC losses, magnetic field/current density distribution and critical currents of a circular superconducting pancake coil. The assumption is that the magnetic flux lines will lie parallel to the wide faces of tapes in the unpenetrated area of the coil. Instead of using an infinitely long stack to approximate the circular coil, this paper gives an exact circular coil model using elliptic integrals. A new efficient numerical method is introduced to yield more accurate and fast computation. The computation results are in good agreement with the assumptions. For a small value of the coil radius, there is an asymmetry along the coil radius direction. As the coil radius increases, this asymmetry will gradually decrease, and the AC losses and penetration depth will increase, but the critical current will decrease. We find that if the internal radius is equal to the winding thickness, the infinitely long stack approximation overestimates the loss by 10% and even if the internal radius is reduced to zero, the error is still only 60%. The infinitely long stack approximation is therefore adequate for most practical purposes. In addition, the comparison result shows that the infinitely long stack approximation saves computation time significantly.

  5. Nitrogen Transformations in Three Types of Permeable Pavement

    EPA Science Inventory

    In 2009, USEPA constructed a 0.4-ha (1-ac) parking lot at the Edison Environmental Center in Edison, NJ, that incorporated three different permeable pavement types - permeable interlocking concrete pavers (PICP), pervious concrete (PC), and porous asphalt (PA). The driving lanes...

  6. Design for a 1 MHz soft magnetic material hysteresisgraph (abstract)

    NASA Astrophysics Data System (ADS)

    Dennison, Eric

    1993-05-01

    Until recently, high frequency (1 MHz) testing of magnetically soft materials has been typically limited to measurement of core loss and peak or inductive ac permeability. A high frequency hysteresisgraph allows direct examination of the hysteresis loop and calculation of values for magnetic parameters such as coercivity (Hc), peak permeability (μp), remanence (Br), core loss (Pc,Pcv,Pcm), bias drive field strength (Hbias), maximum H drive (Hmax) and maximum or saturation induction (Bmax). This paper describes the methods used to construct and calibrate a commercial high frequency magnetic hysteresisgraph which is capable of recording the primary current and secondary voltage waveforms of magnetic cores driven at up to 1 MHz. A system accuracy of 2% (for B and H parameter values) and 5% (for core loss) was achieved through careful control and calibration of signal phase shifts within the circuitry. System calibration, magnetic field calculations, and use of FFT post-processing of the acquired waveforms are discussed. The ability to accurately record the hysteresis loop of a material at 1 MHz allows high frequency core materials to be characterized not only by core loss and permeability, but by their hysteresis loop shape, coercivity, and remanence, both under pure ac and dc biased ac drive conditions. Changes in material characteristics due to dc biasing, temperature variations, defects, or mechanical stresses can be readily observed and described in terms of changes to the hysteresis curve shape.

  7. Detail study on ac-dc magnetic and dye absorption properties of Fe3O4 hollow spheres for biological and industrial application.

    PubMed

    Sarkar, Debasish; Mandal, Kalyan; Mandal, Madhuri

    2014-03-01

    Here solvo-thermal technique has been used to synthesize hollow-nanospheres of magnetite. We have shown that PVP plays an important role to control the particle size and also helps the particles to take the shape of hollow spheres. Structural analysis was done by XRD measurement and morphological measurements like SEM and TEM were performed to confirm the hollow type spherical particles formation and their shape and sizes were also investigated. The detail ac-dc magnetic measurements give an idea about the application of these nano spheres for hyperthermia therapy and spontaneous dye adsorption properties (Gibbs free energy deltaG0 = -0.526 kJ/mol for Eosin and -1.832 kJ/mol for MB) of these particles indicate its use in dye manufacturing company. Being hollow in structure and magnetic in nature such materials will also be useful in other application fields like in drug delivery, arsenic and heavy metal removal by adsorption technique, magnetic separation etc. PMID:24745226

  8. Experimental observation of further frequency upshift from dc to ac radiation converter with perpendicular dc magnetic field

    PubMed

    Higashiguchi; Yugami; Gao; Niiyama; Sasaki; Takahashi; Ito; Nishida

    2000-11-20

    A frequency upshift of a short microwave pulse is generated by the interaction between a relativistic underdense ionization front and a periodic electrostatic field with a perpendicular dc magnetic field. When the dc magnetic field is applied, further frequency upshift of 3 GHz is observed with respect to an unmagnetized case which has typically a GHz range. The radiation frequency depends on both the plasma density and the strength of the dc magnetic field, i.e., the plasma frequency and the cyclotron frequency. The frequency of the emitted radiation is in reasonable agreement with the theoretical values. PMID:11082591

  9. Magnetic Properties of the WC-Co Cermet Powders

    NASA Astrophysics Data System (ADS)

    Serban, V. A.; Malaescu, I.; Ercuta, A.; Marin, C. N.; Stefu, N.; Opris, C.; Codrean, C.; Utu, D.

    2010-08-01

    The magnetic behavior, both quasistatic (50 Hz) and dynamic (10 kHz-1 MHz) of a set of three powder samples from the WC-Co cermet system were investigated in the as-cast state. The results have shown magnetic hysteresis in the low frequency AC fields. In high frequency fields, the complex magnetic permeability was examined; a weak maximum of the imaginary component that was detected in the frequency range close to 100 kHz was attributed to structure-dependent magnetic relaxation.

  10. Hiding objects in AC magnetic fields of power grid frequency by two-shell ferromagnetic/superconducting cloak

    NASA Astrophysics Data System (ADS)

    Šouc, J.; Solovyov, M.; Gömöry, F.

    2016-07-01

    Performance of magnetic cloak made from commercially available materials has been tested by verifying its ability to suppress the magnetic signatures of metallic and ferromagnetic objects. The range of magnetic field amplitudes from 0.1 to 10 mT and frequencies around 50-60 Hz were used. The cloak combines the inner tube from high-temperature superconductor that should be cooled by liquid nitrogen, with the outer tube made from MnZn ferrite powder mixed in plastic matter. Superconductor is in the form of tapes wound in helical manner on a round former. Such design is promising when the objects with dimensions reaching several centimeters should be cloaked. Performance of the small model manufactured following this design was demonstrated by observing ˜20 times reduction of the magnetic signature of metallic or ferromagnetic objects.

  11. Specific absorption rate dependence on temperature in magnetic field hyperthermia measured by dynamic hysteresis losses (ac magnetometry)

    NASA Astrophysics Data System (ADS)

    Garaio, Eneko; Sandre, Olivier; Collantes, Juan-Mari; Garcia, Jose Angel; Mornet, Stéphane; Plazaola, Fernando

    2015-01-01

    Magnetic nanoparticles (NPs) are intensively studied for their potential use for magnetic hyperthermia, a treatment that has passed a phase II clinical trial against severe brain cancer (glioblastoma) at the end of 2011. Their heating power, characterized by the ‘specific absorption rate (SAR)’, is often considered temperature independent in the literature, mainly because of the difficulties that arise from the measurement methodology. Using a dynamic magnetometer presented in a recent paper, we measure here the thermal dependence of SAR for superparamagnetic iron oxide (maghemite) NPs of four different size-ranges corresponding to mean diameters around 12 nm, 14 nm, 15 nm and 16 nm. The article reports a parametrical study extending from 10 to 60 {}^\\circ C in temperature, from 75 to 1031 kHz in frequency, and from 2 to 24 kA m-1 in magnetic field strength. It was observed that SAR values of smaller NPs decrease with temperature whereas for the larger sample (16 nm) SAR values increase with temperature. The measured variation of SAR with temperature is frequency dependent. This behaviour is fully explained within the scope of linear response theory based on Néel and Brown relaxation processes, using independent magnetic measurements of the specific magnetization and the magnetic anisotropy constant. A good quantitative agreement between experimental values and theoretical values is confirmed in a tri-dimensional space that uses as coordinates the field strength, the frequency and the temperature.

  12. A Pilot Study Measuring the Distribution and Permeability of a Vaginal HIV Microbicide Gel Vehicle Using Magnetic Resonance Imaging, Single Photon Emission Computed Tomography/Computed Tomography, and a Radiolabeled Small Molecule.

    PubMed

    Fuchs, Edward J; Schwartz, Jill L; Friend, David R; Coleman, Jenell S; Hendrix, Craig W

    2015-11-01

    Vaginal microbicide gels containing tenofovir have proven effective in HIV prevention, offering the advantage of reduced systemic toxicity. We studied the vaginal distribution and effect on mucosal permeability of a gel vehicle. Six premenopausal women were enrolled. In Phase 1, a spreading gel containing (99m)technetium-DTPA ((99m)Tc) radiolabel and gadolinium contrast for magnetic resonance imaging (MRI) was dosed intravaginally. MRI was obtained at 0.5, 4, and 24 h, and single photon emission computed tomography with conventional computed tomography (SPECT/CT) at 1.5, 5, and 25 h postdosing. Pads and tissues were measured for activity to determine gel loss. In Phase 2, nonoxynol-9 (N-9), containing (99m)Tc-DTPA, was dosed as a permeability control; permeability was measured in blood and urine for both phases. SPECT/CT showed the distribution of spreading gel throughout the vagina with the highest concentration of radiosignal in the fornices and ectocervix; signal intensity diminished over 25 h. MRI showed the greatest signal accumulation in the fornices, most notably 1-4 h postdosing. The median (interquartile range) isotope signal loss from the vagina through 6 h was 29.1% (15.8-39.9%). Mucosal permeability to (99m)Tc-DTPA following spreading gel was negligible, in contrast to N-9, with detectable radiosignal in plasma, peaking at 8 h (5-12). Following spreading gel dosing, 0.004% (0.001-2.04%) of the radiosignal accumulated in urine over 12 h compared to 8.31% (7.07-11.01%) with N-9, (p=0.043). Spreading gel distributed variably throughout the vagina, persisting for 24 h, with signal concentrating in the fornices and ectocervix. The spreading gel had no significant effect on vaginal mucosal permeability. PMID:26077739

  13. Finite-element simulations of hysteretic alternating current losses in a magnetically coated superconducting tubular wire subject to an oscillating transverse magnetic field

    NASA Astrophysics Data System (ADS)

    Genenko, Y. A.; Rauh, H.; Kurdi, S.

    2015-06-01

    Numerical simulations of hysteretic ac losses in a tubular superconductor/paramagnet heterostructure subject to an oscillating transverse magnetic field are performed within the quasistatic approach, calling upon the COMSOL finite-element software package and exploiting magnetostatic-electrostatic analogues. It is shown that one-sided magnetic shielding of a thin, type-II superconducting tube by a coaxial paramagnetic support results in a slight increase of hysteretic ac losses as compared to those for a vacuum environment, when the support is placed inside; a spectacular shielding effect with a possible reduction of hysteretic ac losses by orders of magnitude, however, ensues, depending on the magnetic permeability and the amplitude of the applied magnetic field, when the support is placed outside.

  14. Engineered Trehalose Permeable to Mammalian Cells

    PubMed Central

    Abazari, Alireza; Meimetis, Labros G.; Budin, Ghyslain; Bale, Shyam Sundhar; Weissleder, Ralph; Toner, Mehmet

    2015-01-01

    Trehalose is a naturally occurring disaccharide which is associated with extraordinary stress-tolerance capacity in certain species of unicellular and multicellular organisms. In mammalian cells, presence of intra- and extracellular trehalose has been shown to confer improved tolerance against freezing and desiccation. Since mammalian cells do not synthesize nor import trehalose, the development of novel methods for efficient intracellular delivery of trehalose has been an ongoing investigation. Herein, we studied the membrane permeability of engineered lipophilic derivatives of trehalose. Trehalose conjugated with 6 acetyl groups (trehalose hexaacetate or 6-O-Ac-Tre) demonstrated superior permeability in rat hepatocytes compared with regular trehalose, trehalose diacetate (2-O-Ac-Tre) and trehalose tetraacetate (4-O-Ac-Tre). Once in the cell, intracellular esterases hydrolyzed the 6-O-Ac-Tre molecules, releasing free trehalose into the cytoplasm. The total concentration of intracellular trehalose (plus acetylated variants) reached as high as 10 fold the extracellular concentration of 6-O-Ac-Tre, attaining concentrations suitable for applications in biopreservation. To describe this accumulation phenomenon, a diffusion-reaction model was proposed and the permeability and reaction kinetics of 6-O-Ac-Tre were determined by fitting to experimental data. Further studies suggested that the impact of the loading and the presence of intracellular trehalose on cellular viability and function were negligible. Engineering of trehalose chemical structure rather than manipulating the cell, is an innocuous, cell-friendly method for trehalose delivery, with demonstrated potential for trehalose loading in different types of cells and cell lines, and can facilitate the wide-spread application of trehalose as an intracellular protective agent in biopreservation studies. PMID:26115179

  15. High-frequency permeability spectra of FeCoSiN/Al{sub 2}O{sub 3} laminated films: Tuning of damping by magnetic couplings dependent on the thickness of each ferromagnetic layer

    SciTech Connect

    Xu Feng; Zhang Xiaoyu; Nguyen Nguyen Phuoc; Ma Yungui; Ong, C. K.

    2009-02-15

    In this work, we investigate the high-frequency permeability spectra of as-sputtered FeCoSiN/Al{sub 2}O{sub 3} laminated films, and discuss their dependence on the thickness of each FeCoSiN layer, based on the phenomenological Landau-Lifshitz-Gilbert equation. The damping factor and coercivity show their minima with lamination, deviating from the expectation based on the grain size confinement effect. Such dependences on the layer thickness indicate the influence of magnetic coupling. The decreases in the damping factor and the coercivities with lamination can be partially attributed to the decrease in the magnetostatic coupling induced by ripple structures. The enhanced damping and enlarged coercivity values obtained with further lamination are ascribed to the enhanced Neel couplings. The dependences show that the lamination can be effective in tuning the magnetization dynamics by changing the magnetic couplings.

  16. Slow Relaxation of Magnetization in an Isostructural Series of Zinc-Lanthanide Complexes: An Integrated EPR and AC Susceptibility Study.

    PubMed

    Amjad, Asma; Madalan, Augustin M; Andruh, Marius; Caneschi, Andrea; Sorace, Lorenzo

    2016-08-26

    We report the synthesis, structure, and spectroscopic and dynamic magnetic properties of a series of heterodinuclear complexes, [ZnLn(LH4 )2 ](NO3 )3 ⋅6 H2 O (Ln=Nd, Tb, Dy, Ho, Er, and Yb), with the singly deprotonated form of a new compartmentalized Schiff-base ligand, LH5 . The Ln(III) ions in these systems show a distorted square-antiprism geometry with an LnO8 coordination sphere. EPR spectroscopy and DC magnetic studies have shown that the anisotropic nature of the complexes is far more complicated than predicted on the basis of a simple electrostatic model. Among the investigated systems, only the Dy(III) derivative showed single-ion magnet behavior, in zero and an applied magnetic field, both in pure polycrystalline samples and in a series of polycrystalline samples with different degrees of dilution at the single-crystal level in the isostructural Y(III) derivative. The rich dynamics observed as functions of frequency, field, and temperature reveals that multiple relaxation mechanisms are at play, resulting in a barrier of 189 cm(-1) , which is among the highest reported for a dinuclear Zn-Dy system. Analysis of the dynamic behavior as a function of dilution degree further evidenced the persistence of non-negligible intermolecular interactions, even at the lowest concentration of 1 %. PMID:27465998

  17. ELECTRICAL AND ELECTRONIC INDUSTRIAL CONTROL. A-C CONVENTIONAL MAGNETIC MOTOR CONTROL, PART I, UNIT 5, ASSIGNMENTS.

    ERIC Educational Resources Information Center

    SUTTON, MACK C.

    THIS GUIDE IS FOR INDIVIDUAL STUDENT USE IN STUDYING ALTERNATING CURRENT CONVENTIONAL MAGNETIC MOTOR CONTROL IN ELECTRICAL-ELECTRONIC PROGRAMS. IT WAS DEVELOPED BY AN INSTRUCTIONAL MATERIALS SPECIALIST AND ADVISERS. EACH OF THE 10 ASSIGNMENT SHEETS PROVIDES THE LESSON SUBJECT, PURPOSE, INTRODUCTORY INFORMATION, STUDY REFERENCES, SUPPLEMENTARY…

  18. ELECTRICAL AND ELECTRONIC INDUSTRIAL CONTROL. A-C CONVENTIONAL MAGNETIC MOTOR CONTROL, PART I, UNIT 5, INSTRUCTOR'S GUIDE.

    ERIC Educational Resources Information Center

    SUTTON, MACK C.

    THIS GUIDE IS FOR TEACHER USE IN DIRECTING INDIVIDUAL STUDY OF ALTERNATING CURRENT CONVENTIONAL MAGNETIC MOTOR CONTROL IN ELECTRICAL-ELECTRONIC PROGRAMS. IT WAS DEVELOPED BY AN INSTRUCTIONAL MATERIALS SPECIALIST AND ADVISERS. EACH OF THE 10 INSTRUCTOR'S SHEETS GIVES THE LESSON SUBJECT, PURPOSE, INTRODUCTORY INFORMATION, REFERENCES, AND…

  19. ELECTRICAL AND ELECTRONIC INDUSTRIAL CONTROL. A-C CONVENTIONAL MAGNETIC MOTOR CONTROL, PART II, UNIT 6, INSTRUCTOR'S GUIDE.

    ERIC Educational Resources Information Center

    SUTTON, MACK C.

    THIS GUIDE IS FOR TEACHER USE IN DIRECTING INDIVIDUAL STUDY OF ALTERNATING CURRENT CONVENTIONAL MAGNETIC MOTOR CONTROL IN ELECTRICAL-ELECTRONIC PROGRAMS. IT WAS DEVELOPED BY AN INSTRUCTIONAL MATERIALS SPECIALIST AND ADVISERS. EACH OF THE 10 INSTRUCTOR'S SHEETS GIVES THE LESSON SUBJECT, PURPOSE, INTRODUCTORY INFORMATION, REFERENCES, SUPPLEMENTARY…

  20. ELECTRICAL AND ELECTRONIC INDUSTRIAL CONTROL. A-C CONVENTIONAL MAGNETIC MOTOR CONTROL, PART II, UNIT 6, ASSIGNMENTS.

    ERIC Educational Resources Information Center

    SUTTON, MACK C.

    THIS STUDY GUIDE IS FOR INDIVIDUAL STUDENT USE IN STUDYING ALTERNATING CURRENT CONVENTIONAL MAGNETIC MOTOR CONTROL IN ELECTRICAL-ELECTRONIC PROGRAMS. IT WAS DEVELOPED BY AN INSTRUCTIONAL MATERIALS SPECIALIST AND ADVISERS. EACH OF THE 10 ASSIGNMENT SHEETS PROVIDES THE LESSON SUBJECT, PURPOSE, INTRODUCTORY INFORMATION, STUDY REFERENCES,…

  1. Improvement of microstructure, initial permeability, magnetization and dielectric properties of nanocrystalline LixCu0.1Co0.1Zn0.8-2xFe2+xO4

    NASA Astrophysics Data System (ADS)

    Parvin, Roksana; Momin, A. A.; Hossain, A. K. M. Akther

    2016-03-01

    Structural, magnetic and dielectric properties of Li substituted LixCu0.1Co0.1Zn0.8-2xFe2+xO4 (where x=0.00-0.40) prepared by auto combustion method have been investigated. The X-ray diffraction patterns of these compositions confirmed the formation of the single phase spinel structure. Disc- and toroid-shaped samples are prepared from each composition and sintered at various temperatures (1100-1300 °C) in air for 1 h. The lattice parameter decreases with the increase in Li1+ content obeying Vegard's law. The particle size of the starting powder compositions varied from 24 to 46 nm. The bulk density and permeability increases up to a certain level of Li1+ substitution, beyond that all these properties decrease with increase in Li1+ content. The bulk density increases with increase in sintering temperatures up to 1150 °C both for the parent and substituted compositions. Due to substitution of Li1+, the real part of the initial permeability increases from 18 to 61 for x=0.10 for the samples sintered at 1150 °C. The ferrites with higher initial permeability have relatively lower resonance frequency which obey Snoek's law. The initial permeability strongly depends on average grain size and intragranular porosity but at higher sintering temperatures some voids are present in the samples which reduce the density and hence permeability of the samples. The ferri to paramagnetic transition temperature, TC, for the parent sample is below room temperature. The TC increases almost linearly with increasing Li content.The saturation magnetization, Ms, and the number of Bohr magneton, n (μB), increases up to x=0.30 due to the enhancement of the A-B interaction in the AB2O4 spinel type ferrites. Beyond that value of x, the Ms and the n (μB) values are decreased. The substitution of Li1+ influences the magnetic parameters due to modification of the cation distribution. Dielectric constant (ε ‧) decreases with increase in frequency which is rapid at lower frequencies and

  2. Permeability of Clay Concretes

    NASA Astrophysics Data System (ADS)

    Solomon, F.; Ekolu, S. O.

    2015-11-01

    This paper presents an investigation on the effect of clay addition on water permeability and air permeability of concretes. Clay concrete mixes consisted of 0 to 40% clay content incorporated as cement replacement. Flow methods using triaxial cells and air permeameters were used for measuring the injected water and air flows under pressure. It was found that the higher the clay content in the mixture, the greater the permeability. At higher water-cement ratios (w/c), the paste matrix is less dense and easily allows water to ingress into concrete. But at high clay contents of 30 to 40% clay, the variation in permeability was significantly diminished among different concrete mixtures. It was confirmed that air permeability results were higher than the corresponding water permeability values when all permeability coefficients were converted to intrinsic permeability values.

  3. EPA Permeable Surface Research

    EPA Science Inventory

    EPA recognizes permeable surfaces as an effective post-construction infiltration-based Best Management Practice to mitigate the adverse effects of stormwater runoff. The professional user community conceptually embraces permeable surfaces as a tool for making runoff more closely...

  4. Modified Solenoid Coil That Efficiently Produces High Amplitude AC Magnetic Fields With Enhanced Uniformity for Biomedical Applications

    PubMed Central

    Bordelon, David E.; Goldstein, Robert C.; Nemkov, Valentin S.; Kumar, Ananda; Jackowski, John K.; DeWeese, Theodore L.; Ivkov, Robert

    2014-01-01

    In this paper, we describe a modified solenoid coil that efficiently generates high amplitude alternating magnetic fields (AMF) having field uniformity (≤10%) within a 125-cm3 volume of interest. Two-dimensional finite element analysis (2D-FEA) was used to design a coil generating a targeted peak AMF amplitude along the coil axis of ~100 kA/m (peak-to-peak) at a frequency of 150 kHz while maintaining field uniformity to >90% of peak for a specified volume. This field uniformity was realized by forming the turns from cylindrical sections of copper plate and by adding flux concentrating rings to both ends of the coil. Following construction, the field profile along the axes of the coil was measured. An axial peak field value of 95.8 ± 0.4 kA/m was measured with 650 V applied to the coil and was consistent with the calculated results. The region of axial field uniformity, defined as the distance over which field ≥90% of peak, was also consistent with the simulated results. We describe the utility of such a device for calorimetric measurement of nanoparticle heating for cancer therapy and for magnetic fluid hyperthermia in small animal models of human cancer. PMID:25392562

  5. Monitoring Vascular Permeability and Remodeling After Endothelial Injury in a Murine Model Using a Magnetic Resonance Albumin-Binding Contrast Agent

    PubMed Central

    Phinikaridou, Alkystis; Lorrio, Silvia; Zaragoza, Carlos; Botnar, René M.

    2015-01-01

    Background— Despite the beneficial effects of vascular interventions, these procedures may damage the endothelium leading to increased vascular permeability and remodeling. Re-endothelialization of the vessel wall, with functionally and structurally intact cells, is controlled by endothelial nitric oxide synthase (NOS3) and is crucial for attenuating adverse effects after injury. We investigated the applicability of the albumin-binding MR contrast agent, gadofosveset, to noninvasively monitor focal changes in vascular permeability and remodeling, after injury, in NOS3-knockout (NOS3−/−) and wild-type (WT) mice in vivo. Methods and Results— WT and NOS3−/− mice were imaged at 7, 15, and 30 days after aortic denudation or sham-surgery. T1 mapping (R1=1/T1, s−1) and delayed-enhanced MRI were used as measurements of vascular permeability (R1) and remodeling (vessel wall enhancement, mm2) after gadofosveset injection, respectively. Denudation resulted in higher vascular permeability and vessel wall enhancement 7 days after injury in both strains compared with sham-operated animals. However, impaired re-endothelialization and increased neovascularization in NOS3−/− mice resulted in significantly higher R1 at 15 and 30 days post injury compared with WT mice that showed re-endothelialization and lack of neovascularization (R1 [s−1]=15 days: NOS3−/−4.02 [interquartile range, IQR, 3.77–4.41] versus WT2.39 [IQR, 2.35–2.92]; 30 days: NOS3−/−4.23 [IQR, 3.94–4.68] versus WT2.64 [IQR, 2.33–2.80]). Similarly, vessel wall enhancement was higher in NOS3−/− but recovered in WT mice (area [mm2]=15 days: NOS3−/−5.20 [IQR, 4.68–6.80] versus WT2.13 [IQR, 0.97–3.31]; 30 days: NOS3−/−7.35 [IQR, 5.66–8.61] versus WT1.60 [IQR, 1.40–3.18]). Ex vivo histological studies corroborated the MRI findings. Conclusions— We demonstrate that increased vascular permeability and remodeling, after injury, can be assessed noninvasively using an

  6. Influence of clamping plate permeability and metal screen structures on three-dimensional magnetic field and eddy current loss in end region of a turbo-generator by numerical analysis

    NASA Astrophysics Data System (ADS)

    Likun, Wang; Weili, Li; Yi, Xue; Chunwei, Guan

    2013-11-01

    A significant problem of turbogenerators on complex end structures is overheating of local parts caused by end losses in the end region. Therefore, it is important to investigate the 3-D magnetic field and eddy current loss in the end. In end region of operating large turbogenerator at thermal power plants, magnetic leakage field distribution is complex. In this paper, a 3-D mathematical model used for the calculation of the electromagnetic field in the end region of large turbo-generators is given. The influence of spatial locations of end structures, the actual shape and material of end windings, clamping plate, and copper screen are considered. Adopting the time-step finite element (FE) method and taking the nonlinear characteristics of the core into consideration, a 3-D transient magnetic field is calculated. The objective of this paper is to investigate the influence of clamping plate permeability and metal screen structures on 3-D electromagnetic field distribution and eddy current loss in end region of a turbo-generator. To reduce the temperature of copper screen, a hollow metal screen is proposed. The eddy current loss, which is gained from the 3D transient magnetic field, is used as heat source for the thermal field of end region. The calculated temperatures are compared with test data.

  7. A superconducting magnetic gear

    NASA Astrophysics Data System (ADS)

    Campbell, A. M.

    2016-05-01

    A comparison is made between a magnetic gear using permanent magnets and superconductors. The objective is to see if there are any fundamental reasons why superconducting magnets should not provide higher power densities than permanent magnets. The gear is based on the variable permeability design of Attilah and Howe (2001 IEEE Trans. Magn. 37 2844-46) in which a ring of permanent magnets surrounding a ring of permeable pole pieces with a different spacing gives an internal field component at the beat frequency. Superconductors can provide much larger fields and forces but will saturate the pole pieces. However the gear mechanism still operates, but in a different way. The magnetisation of the pole pieces is now constant but rotates with angle at the beat frequency. The result is a cylindrical Halbach array which produces an internal field with the same symmetry as in the linear regime, but has an analytic solution. In this paper a typical gear system is analysed with finite elements using FlexPDE. It is shown that the gear can work well into the saturation regime and that the Halbach array gives a good approximation to the results. Replacing the permanent magnets with superconducting tapes can give large increases in torque density, and for something like a wind turbine a combined gear and generator is possible. However there are major practical problems. Perhaps the most fundamental is the large high frequency field which is inevitably present and which will cause AC losses. Also large magnetic fields are required, with all the practical problems of high field superconducting magnets in rotating machines. Nevertheless there are ways of mitigating these difficulties and it seems worthwhile to explore the possibilities of this technology further.

  8. RHIC spin flipper AC dipole controller

    SciTech Connect

    Oddo, P.; Bai, M.; Dawson, C.; Gassner, D.; Harvey, M.; Hayes, T.; Mernick, K.; Minty, M.; Roser, T.; Severino, F.; Smith, K.

    2011-03-28

    The RHIC Spin Flipper's five high-Q AC dipoles which are driven by a swept frequency waveform require precise control of phase and amplitude during the sweep. This control is achieved using FPGA based feedback controllers. Multiple feedback loops are used to and dynamically tune the magnets. The current implementation and results will be presented. Work on a new spin flipper for RHIC (Relativistic Heavy Ion Collider) incorporating multiple dynamically tuned high-Q AC-dipoles has been developed for RHIC spin-physics experiments. A spin flipper is needed to cancel systematic errors by reversing the spin direction of the two colliding beams multiple times during a store. The spin flipper system consists of four DC-dipole magnets (spin rotators) and five AC-dipole magnets. Multiple AC-dipoles are needed to localize the driven coherent betatron oscillation inside the spin flipper. Operationally the AC-dipoles form two swept frequency bumps that minimize the effect of the AC-dipole dipoles outside of the spin flipper. Both AC bumps operate at the same frequency, but are phase shifted from each other. The AC-dipoles therefore require precise control over amplitude and phase making the implementation of the AC-dipole controller the central challenge.

  9. Permeability and relative permeability in rocks

    SciTech Connect

    Blair, S.C.; Berryman, J.G.

    1990-10-01

    Important features of the topology of the pore space of rocks can be usefully quantified by analyzing digitized images of rock cross sections. One approach computes statistical correlation functions using modern image processing techniques. These correlation functions contain information about porosity, specific surface area, tortuosity, formation factor, and elastic constants, as well as the fluid permeability and relative permeability. The physical basis of this approach is discussed and examples of the results for various sandstones are presented. The analysis shows that Kozeny-Carman relations and Archie's empirical laws must be modified to account for finite percolation thresholds in order to avoid unphysical behavior in the calculated relative permeabilities. 33 refs., 4 figs., 1 tab.

  10. Permeability of Dentine

    PubMed Central

    Ghazali, Farid Bin Che

    2003-01-01

    This is an update on the present integrated knowledge regarding dentine permeability that assumed a role in dentine sensitivity and contribute clinically to the effective bonding properties of restorative dental materials. This paper will attempt to refer to in vivo and in vitro studies of dentine permeability and the various interrelated factors governing it. PMID:23365497

  11. Magnetic properties and domain structures in primary recrystallized thin-gauge Si-Fe with orientation near (110)[001

    SciTech Connect

    Abe, N.; Iwasaki, M. . Technical Development Bureau); Ushigami, Y.; Nozawa, T. . Technical Development Bureau)

    1994-07-01

    The magnetic properties and features of magnetic domain structures of newly developed grain-oriented 15--50 [mu]m thickness 3% Si-Fe with very high permeability were investigated. The induction of these materials was 1.70--1.95 T at 800 A/m. These high inductions developed low core losses. The losses of toroidal cores made of 50 [mu]m thick material were W15/400 = 8 W/kg. Despite very small primary recrystallized grain size, they consist of simple magnetic domains with 180[degree] domain walls and ac magnetization is achieved by simple main domain wall displacement.

  12. Investigation of magnetic spin glass property in La{sub 0.5}Bi{sub 0.5}MnO{sub 3} sample using non-linear AC susceptibility measurements

    SciTech Connect

    Kumar, Punith V. Manju, M. R. Dayal, Vijaylakshmi

    2014-04-24

    We present a comprehensive study on origin of Spin Glass (SG) property in polycrystalline La{sub 0.5}Bi{sub 0.5}MnO{sub 3} perovskite oxide using linear and higher order ac susceptibility (χ) measurements. The third order harmonic susceptibility (χ{sub 3}) vs. temperature (K) with varying magnetic fields from 0.95 to 9.45 Oe and the divergence in their χ{sub 3} (max) allows us to infer the SG behavior occurring in the sample possibly due to co-operative freezing of the spins.

  13. Magnetic measurements at Lawrence Berkeley Laboratory. Revision

    SciTech Connect

    Green, M.I.; Barale, P.; Callapp, L.; Case-Fortier, M.; Lerner, D.; Nelson, D.; Schermer, R.; Skipper, G.; Van Dyke, D.; Cork, C.; Halbach, K.; Hassenzahl, W.; Hoyer, E.; Marks, S.; Harten, T.; Luchini, K.; Milburn, J.; Tanabe, J.; Zucca, F.; Keller, R.; Selph, F.; Gilbert, W.; Green, M.A.; O`Neil, J.; Schafer, R.; Taylor, C.; Greiman, W.; Hall, D.; MacFarlane, J.

    1991-08-01

    Recent magnetic measurement activities at LBL have been concentrated in two separate areas, electro-magnets and permanent magnets for the Advanced Light Source (ALS), and superconducting magnets for the Superconducting Super Collider Laboratory (SSCL). A survey of the many different measurement systems is presented. These include: AC magnetic measurements of an ALS booster dipole engineering model magnet, dipole moment measurements of permanent magnet blocks for ALS wigglers and undulators, permeability measurements of samples destined for wiggler and undulator poles, harmonic error analysis of SSC one meter model dipoles and quadrupoles and five meter long SSC prototype quadrupoles, harmonic error analysis of ALS dipoles, quadrupoles, and sextupoles, precision Hall probe mapping of ALS storage ring combined function magnets, and the design of the ALS insertion device magnets mapping system. We also describe a new UNIX based data acquisition system that is being developed for the SSC. Probes used for magnetic measurements include Helmholtz coils, integral coils, point coils, and bucking harmonic analysis coils, several different types of Hall probes, and nuclear magnetic resonance magnetometers. Both analog and digital integrators are used with the coils. Some problems that occurred and their rectification is described. The mechanisms used include rotating systems with optical encoders, X-Y mapping systems with optical encoders and a laser position measuring device. 10 refs., 3 figs., 1 tab.

  14. Magnetic measurements at Lawrence Berkeley Laboratory

    SciTech Connect

    Green, M.I.; Barale, P.; Callapp, L.; Case-Fortier, M.; Lerner, D.; Nelson, D.; Schermer, R.; Skipper, G.; Van Dyke, D.; Cork, C.; Halbach, K.; Hassenzahl, W.; Hoyer, E.; Marks, S.; Harten, T.; Luchini, K.; Milburn, J.; Tanabe, J.; Zucca, F.; Keller, R.; Selph, F.; Gilbert, W.; Green, M.A.; O'Neil, J.; Schafer, R.; Taylor, C.; Greiman, W.; Hall, D.; MacFarlane, J.

    1991-08-01

    Recent magnetic measurement activities at LBL have been concentrated in two separate areas, electro-magnets and permanent magnets for the Advanced Light Source (ALS), and superconducting magnets for the Superconducting Super Collider Laboratory (SSCL). A survey of the many different measurement systems is presented. These include: AC magnetic measurements of an ALS booster dipole engineering model magnet, dipole moment measurements of permanent magnet blocks for ALS wigglers and undulators, permeability measurements of samples destined for wiggler and undulator poles, harmonic error analysis of SSC one meter model dipoles and quadrupoles and five meter long SSC prototype quadrupoles, harmonic error analysis of ALS dipoles, quadrupoles, and sextupoles, precision Hall probe mapping of ALS storage ring combined function magnets, and the design of the ALS insertion device magnets mapping system. We also describe a new UNIX based data acquisition system that is being developed for the SSC. Probes used for magnetic measurements include Helmholtz coils, integral coils, point coils, and bucking harmonic analysis coils, several different types of Hall probes, and nuclear magnetic resonance magnetometers. Both analog and digital integrators are used with the coils. Some problems that occurred and their rectification is described. The mechanisms used include rotating systems with optical encoders, X-Y mapping systems with optical encoders and a laser position measuring device. 10 refs., 3 figs., 1 tab.

  15. Seismic waves increase permeability.

    PubMed

    Elkhoury, Jean E; Brodsky, Emily E; Agnew, Duncan C

    2006-06-29

    Earthquakes have been observed to affect hydrological systems in a variety of ways--water well levels can change dramatically, streams can become fuller and spring discharges can increase at the time of earthquakes. Distant earthquakes may even increase the permeability in faults. Most of these hydrological observations can be explained by some form of permeability increase. Here we use the response of water well levels to solid Earth tides to measure permeability over a 20-year period. At the time of each of seven earthquakes in Southern California, we observe transient changes of up to 24 degrees in the phase of the water level response to the dilatational volumetric strain of the semidiurnal tidal components of wells at the Piñon Flat Observatory in Southern California. After the earthquakes, the phase gradually returns to the background value at a rate of less than 0.1 degrees per day. We use a model of axisymmetric flow driven by an imposed head oscillation through a single, laterally extensive, confined, homogeneous and isotropic aquifer to relate the phase response to aquifer properties. We interpret the changes in phase response as due to changes in permeability. At the time of the earthquakes, the permeability at the site increases by a factor as high as three. The permeability increase depends roughly linearly on the amplitude of seismic-wave peak ground velocity in the range of 0.21-2.1 cm s(-1). Such permeability increases are of interest to hydrologists and oil reservoir engineers as they affect fluid flow and might determine long-term evolution of hydrological and oil-bearing systems. They may also be interesting to seismologists, as the resulting pore pressure changes can affect earthquakes by changing normal stresses on faults. PMID:16810253

  16. Temperature evolution of superparamagnetic clusters in single-crystal La0.85Sr0.15CoO3 characterized by nonlinear magnetic ac response and neutron depolarization

    NASA Astrophysics Data System (ADS)

    Lazuta, A. V.; Ryzhov, V. A.; Runov, V. V.; Khavronin, V. P.; Deriglazov, V. V.

    2015-07-01

    The representative measurements of the second harmonic in ac magnetization complemented by neutron depolarization have been performed for single-crystal La0.85Sr0.15CoO3 in the temperature range 97 KMagnetic, geometrical, and dynamical parameters of the FMC system have been evaluated in the temperature range T <140 K, where superparamagnetic regime installs, by means of the formalism involving the Fokker-Planck equation. With lowering the temperature, the amount of clusters fraction, the cluster size, and magnetic moment along with its diffusion relaxation time strongly increase, each in its own temperature interval. Below 130 K, FMC contribute essentially to the total linear magnetic susceptibility. The damping factor of the order 10-1 proves the importance of precession in thermal relaxation of the cluster magnetic moment. The FMC are a precursor of long-range ferromagnetic correlations seen below 100 K with neutron-scattering techniques.

  17. RHIC AC DIPOLE DESIGN AND CONSTRUCTION.

    SciTech Connect

    BAI,M.; METH,M.; PAI,C.; PARKER,B.; PEGGS,S.; ROSER,T.; SANDERS,R.; TRBOJEVIC,D.; ZALTSMAN,A.

    2001-06-18

    Two ac dipoles with vertical and horizontal magnetic field have been proposed at RHIC for applications in linear and non-linear beam dynamics and spin manipulations. A magnetic field amplitude of 380 Gm is required to produce a coherent oscillation of 5 times the rms beam size at the top energy. We take the ac dipole frequency to be 1.0% of the revolution frequency away from the betatron frequency. To achieve the strong magnetic field with minimum power loss, an air-core magnet with two seven turn winding of low loss Litz wire resonating at 64 kHz is designed. The system is also designed to allow one to connect the two magnet winding in series to resonate at 37 kHz for the spin manipulation. Measurements of a half length prototype magnet are also presented.

  18. AC losses and heat removal in three-dimensional winding pack of Samsung superconducting test facility under pulsed magnetic field operation

    NASA Astrophysics Data System (ADS)

    Wang, Qiuliang; Seong Yoon, Cheon; Baang, Sungkeun; Kim, Myungkyu; Park, Hyunki; Kim, Yongjin; Lee, Sangil; Kim, Keeman

    2001-04-01

    The Samsung superconducting test facility (SSTF) will be operated under the highly pulsed field to simulate the operating conditions of KSTAR. An analysis has been performed to study the transient heat removal characteristics and temperature margin for the main, blip and compensating coils in the SSTF. This method is based on a quasi-three-dimensional model, which the thermal coupling of turn-to-turn, pancake-to-pancake and channel-to-channel is taken into account, to simulate the conductor temperature rise and the thermal expansion of supercritical helium due to the high AC losses under the pulsed field. The local AC losses, which include coupling loss, eddy current loss and hysteresis loss in the cable-in-conduit conductor, are estimated. The temperature margin, mass flow rate, distribution of AC losses are studied under the given operating scenario. The mass flow reduction and peak temperature rise depending on the inlet pressure and inlet position of CICC are studied. It is shown that the initial mass flow rate remarkably influences on the peak temperature of superconducting strands. The large mass flow rate can reduce the temperature rise when the inlet of helium is located at the high field region. By contrast, because of heat induced flow to improve the cooling condition of the superconducting strands, the small initial mass flow rate results in the low peak temperature in strands when the inlet of helium is located at the low field region.

  19. The Permeable Classroom.

    ERIC Educational Resources Information Center

    Sandy, Leo R.

    1998-01-01

    Discusses the concept of permeability as knowledge flow into and out of the classroom and applies it to three college courses taught by the author at Plymouth State College (New Hampshire). Experiential knowledge comes into the classroom through interviews, guest speakers, and panel presentations, and flows out through service-learning students…

  20. Scales of rock permeability

    NASA Astrophysics Data System (ADS)

    Guéguen, Y.; Gavrilenko, P.; Le Ravalec, M.

    1996-05-01

    Permeability is a transport property which is currently measured in Darcy units. Although this unit is very convenient for most purposes, its use prevents from recognizing that permeability has units of length squared. Physically, the square root of permeability can thus be seen as a characteristic length or a characteristic pore size. At the laboratory scale, the identification of this characteristic length is a good example of how experimental measurements and theoretical modelling can be integrated. Three distinct identifications are of current use, relying on three different techniques: image analysis of thin sections, mercury porosimetry and nitrogen adsorption. In each case, one or several theoretical models allow us to derive permeability from the experimental data (equivalent channel models, statistical models, effective media models, percolation and network models). Permeability varies with pressure and temperature and this is a decisive point for any extrapolation to crustal conditions. As far as pressure is concerned, most of the effect is due to cracks and a model which does not incorporate this fact will miss its goal. Temperature induced modifications can be the result of several processes: thermal cracking (due to thermal expansion mismatch and anisotropy, or to fluid pressure build up), and pressure solution are the two main ones. Experimental data on pressure and temperature effects are difficult to obtain but they are urgently needed. Finally, an important issue is: up to which point are these small scale data and models relevant when considering formations at the oil reservoir scale, or at the crust scale? At larger scales the identification of the characteristic scale is also a major goal which is examined.

  1. ACS Quicklook PDF products

    NASA Astrophysics Data System (ADS)

    Suchkov, Anatoly

    1999-12-01

    This report details the features of the ACS quicklook PDF products produced by the HST data pipeline. The requirements closely follow the design of paper products recommended by the Data Quality Committee, with appropriate changes required to fully support ACS.

  2. Thermal hysteresis of permeability and transport properties of Mn substituted Mg Cu Zn ferrites

    NASA Astrophysics Data System (ADS)

    Manjurul Haque, M.; Huq, M.; Hakim, M. A.

    2008-03-01

    Mn substituted Mg-Cu-Zn ferrites of composition Mg0.35Cu0.20Zn0.45O(Fe2-xMnx O3)0.97 have been prepared by the standard double sintering ceramic technique. X-ray diffraction patterns of the samples showed single phase cubic spinel structure without any detectable impurity phases. The lattice constant is found to increase linearly with increase in Mn3+ ion concentration obeying Vegard's law. The initial permeability (μi) of the Mg-Cu-Zn ferrites exhibits thermal hysteresis when the temperature is cycled from above the Curie temperature TC to below. The sharp decrease of μi at T = TC indicates that the samples have high homogeneity according to Globus et al. The Curie temperature TC of the studied ferrite system was determined from the μi-T curves where the Hopkinson type of effect at the TC has been observed with the manifestation of a sharp fall in permeability. The Curie temperature TC is found to increase with increasing Mn content. Dc electrical resistivity increases significantly with the increase in Mn content. The ac resistivity (ρac) and dielectric constant (ɛ') of the samples are found to decrease with increase in frequency, exhibiting normal ferrimagnetic behaviour. Dielectric relaxation peaks were observed for the frequency dependence of dielectric loss tangent curves. ɛ' increases as the temperature increases, which is the normal dielectric behaviour of the magnetic semiconductor ferrite. The observed variation of electrical and dielectric properties are explained on the basis of Fe2+/Fe3+ ionic concentration as well as the electronic hopping frequency between Fe2+ and Fe3+ ions in the present samples.

  3. EPA Permeable Surface Research - Poster

    EPA Science Inventory

    EPA recognizes permeable surfaces as an effective post-construction infiltration-based Best Management Practice to mitigate the adverse effects of stormwater runoff. The professional user community conceptually embraces permeable surfaces as a tool for making runoff more closely...

  4. Glutathione permeability of CFTR.

    PubMed

    Linsdell, P; Hanrahan, J W

    1998-07-01

    The cystic fibrosis transmembrane conductance regulator (CFTR) forms an ion channel that is permeable both to Cl- and to larger organic anions. Here we show, using macroscopic current recording from excised membrane patches, that the anionic antioxidant tripeptide glutathione is permeant in the CFTR channel. This permeability may account for the high concentrations of glutathione that have been measured in the surface fluid that coats airway epithelial cells. Furthermore, loss of this pathway for glutathione transport may contribute to the reduced levels of glutathione observed in airway surface fluid of cystic fibrosis patients, which has been suggested to contribute to the oxidative stress observed in the lung in cystic fibrosis. We suggest that release of glutathione into airway surface fluid may be a novel function of CFTR. PMID:9688865

  5. Liquid-permeable electrode

    DOEpatents

    Folser, George R.

    1980-01-01

    Electrodes for use in an electrolytic cell, which are liquid-permeable and have low electrical resistance and high internal surface area are provided of a rigid, porous, carbonaceous matrix having activated carbon uniformly embedded throughout. The activated carbon may be catalyzed with platinum for improved electron transfer between electrode and electrolyte. Activated carbon is mixed with a powdered thermosetting phenolic resin and compacted to the desired shape in a heated mold to melt the resin and form the green electrode. The compact is then heated to a pyrolyzing temperature to carbonize and volatilize the resin, forming a rigid, porous structure. The permeable structure and high internal surface area are useful in electrolytic cells where it is necessary to continuously remove the products of the electrochemical reaction.

  6. Stainless Steel Permeability

    SciTech Connect

    Buchenauer, Dean A.; Karnesky, Richard A.

    2015-09-01

    An understanding of the behavior of hydrogen isotopes in materials is critical to predicting tritium transport in structural metals (at high pressure), estimating tritium losses during production (fission environment), and predicting in-vessel inventory for future fusion devices (plasma driven permeation). Current models often assume equilibrium diffusivity and solubility for a class of materials (e.g. stainless steels or aluminum alloys), neglecting trapping effects or, at best, considering a single population of trapping sites. Permeation and trapping studies of the particular castings and forgings enable greater confidence and reduced margins in the models. For FY15, we have continued our investigation of the role of ferrite in permeation for steels of interest to GTS, through measurements of the duplex steel 2507. We also initiated an investigation of the permeability in work hardened materials, to follow up on earlier observations of unusual permeability in a particular region of 304L forgings. Samples were prepared and characterized for ferrite content and coated with palladium to prevent oxidation. Issues with the poor reproducibility of measurements at low permeability were overcome, although the techniques in use are tedious. Funding through TPBAR and GTS were secured for a research grade quadrupole mass spectrometer (QMS) and replacement turbo pumps, which should improve the fidelity and throughput of measurements in FY16.

  7. Preasymptotic hydrodynamic dispersion as a quantitative probe of permeability.

    PubMed

    Brosten, Tyler R; Vogt, Sarah J; Seymour, Joseph D; Codd, Sarah L; Maier, Robert S

    2012-04-01

    We interpret a generalized short-time expansion of stochastic hydrodynamic dispersion dynamics in the case of small Reynolds number flow through macroscopically homogenous permeable porous media to directly determine hydrodynamic permeability. The approach allows determination of hydrodynamic permeability from pulsed field gradient spin-echo nuclear magnetic resonance measurement of the short-time effective hydrodynamic dispersion coefficient. The analytical expansion of asymptotic dynamics agrees with experimental NMR data and lattice Boltzmann simulation of hydrodynamic dispersion in consolidated random sphere pack media. PMID:22680531

  8. A Multi-Level Grid Interactive Bi-directional AC/DC-DC/AC Converter and a Hybrid Battery/Ultra-capacitor Energy Storage System with Integrated Magnetics for Plug-in Hybrid Electric Vehicles

    SciTech Connect

    Onar, Omer C

    2011-01-01

    This study presents a bi-directional multi-level power electronic interface for the grid interactions of plug-in hybrid electric vehicles (PHEVs) as well as a novel bi-directional power electronic converter for the combined operation of battery/ultracapacitor hybrid energy storage systems (ESS). The grid interface converter enables beneficial vehicle-to-grid (V2G) interactions in a high power quality and grid friendly manner; i.e, the grid interface converter ensures that all power delivered to/from grid has unity power factor and almost zero current harmonics. The power electronic converter that provides the combined operation of battery/ultra-capacitor system reduces the size and cost of the conventional ESS hybridization topologies while reducing the stress on the battery, prolonging the battery lifetime, and increasing the overall vehicle performance and efficiency. The combination of hybrid ESS is provided through an integrated magnetic structure that reduces the size and cost of the inductors of the ESS converters. Simulation and experimental results are included as prove of the concept presenting the different operation modes of the proposed converters.

  9. Magnetically attached sputter targets

    DOEpatents

    Makowiecki, D.M.; McKernan, M.A.

    1994-02-15

    An improved method and assembly for attaching sputtering targets to cathode assemblies of sputtering systems which includes a magnetically permeable material is described. The magnetically permeable material is imbedded in a target base that is brazed, welded, or soldered to the sputter target, or is mechanically retained in the target material. Target attachment to the cathode is achieved by virtue of the permanent magnets and/or the pole pieces in the cathode assembly that create magnetic flux lines adjacent to the backing plate, which strongly attract the magnetically permeable material in the target assembly. 11 figures.

  10. Magnetically attached sputter targets

    DOEpatents

    Makowiecki, Daniel M.; McKernan, Mark A.

    1994-01-01

    An improved method and assembly for attaching sputtering targets to cathode assemblies of sputtering systems which includes a magnetically permeable material. The magnetically permeable material is imbedded in a target base that is brazed, welded, or soldered to the sputter target, or is mechanically retained in the target material. Target attachment to the cathode is achieved by virtue of the permanent magnets and/or the pole pieces in the cathode assembly that create magnetic flux lines adjacent to the backing plate, which strongly attract the magnetically permeable material in the target assembly.

  11. The application of Halbach cylinders to brushless ac servo motors

    SciTech Connect

    Atallah, K.; Howe, D.

    1998-07-01

    Halbach cylinders are applied to brushless ac servo motors. It is shown that a sinusoidal back-emf waveform and a low cogging torque can be achieved without recourse to conventional design features such as distributed windings and/or stator/rotor skew. A technique for imparting a multipole Halbach magnetization distribution on an isotropic permanent magnet cylinder is described, and it is shown that the torque capability of a Halbach ac servo motor can be up to 33% higher than conventional brushless permanent magnet ac motors.

  12. Critical field measurements in superconductors using ac inductive techniques

    NASA Astrophysics Data System (ADS)

    Campbell, S. A.; Ketterson, J. B.; Crabtree, G. W.

    1983-09-01

    The ac in-phase and out-of-phase response of type II superconductors is discussed in terms of dc magnetization curves. Hysteresis in the dc magnetization is shown to lead to a dependence of the ac response on the rate at which an external field is swept. This effect allows both Hc1 and Hc2 to be measured by ac techniques. A relatively simple mutual inductance bridge for making such measurements is described in the text, and factors affecting bridge sensitivity are discussed in the Appendix. Data for the magnetic superconductor ErRh4B4 obtained using this bridge are reported.

  13. Optimized anisotropic magnetoelectric response of Fe61.6Co16.4Si10.8B11.2/PVDF/Fe61.6Co16.4Si10.8B11.2 laminates for AC/DC magnetic field sensing

    NASA Astrophysics Data System (ADS)

    Reis, S.; Silva, M. P.; Castro, N.; Correia, V.; Gutierrez, J.; Lasheras, A.; Lanceros-Mendez, S.; Martins, P.

    2016-05-01

    The anisotropic magnetoelectric (ME) effect on a Fe61.6Co16.4Si10.8B11.2/PVDF Fe61.6Co16.4Si10.8B11.2 laminate composite has been used for the development of a magnetic field sensor able to detect both the magnitude and direction of AC and DC magnetic fields. The accuracy (99% for both AC and DC sensors), linearity (92% for the DC sensor and 99% for the AC sensor) and reproducibility (99% for both sensors) indicate the suitability of the sensor for applications. Furthermore, the sensitivity of the Fe61.6Co16.4Si10.8B11.2/PVDF/Fe61.6Co16.4Si10.8B11.2 anisotropic magnetic sensor—15 and 1400 mV Oe‑1 for the DC and AC fields, respectively—are the highest reported in the literature for polymer-based ME materials. Such features, combined with its flexibility, versatility, light weight, low cost and low-temperature fabrication, lead to the suitability of the developed sensor for use in magnetic sensor applications.

  14. AC loss in superconducting tapes and cables

    NASA Astrophysics Data System (ADS)

    Oomen, Marijn Pieter

    High-temperature superconductors are developed for use in power-transmission cables, transformers and motors. The alternating magnetic field in these devices causes AC loss, which is a critical factor in the design. The study focuses on multi-filament Bi-2223/Ag tapes exposed to a 50-Hz magnetic field at 77 K. The AC loss is measured with magnetic, electric and calorimetric methods. The results are compared to theoretical predictions based mainly on the Critical-State Model. The loss in high- temperature superconductors is affected by their characteristic properties: increased flux creep, high aspect ratio and inhomogeneties. Filament intergrowths and a low matrix resistivity cause a high coupling-current loss especially when the filaments are fully coupled. When the wide side of the tape is parallel to the external magnetic field, the filaments are decoupled by twisting. In a perpendicular field the filaments can be decoupled only by combining a short twist pitch with a transverse resistivity much higher than that of silver. The arrangement of the inner filaments determines the transverse resistivity. Ceramic barriers around the filaments cause partial decoupling in perpendicular magnetic fields at power frequencies. The resultant decrease in AC loss is greater than the accompanying decrease in critical current. With direct transport current in alternating magnetic field, the transport-current loss is well described with a new model for the dynamic resistance. The Critical- State Model describes well the magnetisation and total AC loss in parallel magnetic fields, at transport currents up to 0.7 times the critical current. When tapes are stacked face-to-face in a winding, the AC-loss density in perpendicular fields is greatly decreased due to the mutual shielding of the tapes. Coupling currents between the tapes in a cable cause an extra AC loss, which is reduced by a careful cable design. The total AC loss in complex devices with many tapes is generally well

  15. Barometric pressure transient testing applications at the Nevada Test Site: formation permeability analysis. Final report

    SciTech Connect

    Hanson, J.M.

    1984-12-01

    The report evaluates previous investigations of the gas permeability of the rock surrounding emplacement holes at the Nevada Test Site. The discussion sets the framework from which the present uncertainty in gas permeability can be overcome. The usefulness of the barometric pressure testing method has been established. Flow models were used to evaluate barometric pressure transients taken at NTS holes U2fe, U19ac and U20ai. 31 refs., 103 figs., 18 tabs. (ACR)

  16. Relative permeability through fractures

    SciTech Connect

    Diomampo, Gracel, P.

    2001-08-01

    The mechanism of two-phase flow through fractures is of importance in understanding many geologic processes. Currently, two-phase flow through fractures is still poorly understood. In this study, nitrogen-water experiments were done on both smooth and rough parallel plates to determine the governing flow mechanism for fractures and the appropriate methodology for data analysis. The experiments were done using a glass plate to allow visualization of flow. Digital video recording allowed instantaneous measurement of pressure, flow rate and saturation. Saturation was computed using image analysis techniques. The experiments showed that gas and liquid phases flow through fractures in nonuniform separate channels. The localized channels change with time as each phase path undergoes continues breaking and reforming due to invasion of the other phase. The stability of the phase paths is dependent on liquid and gas flow rate ratio. This mechanism holds true for over a range of saturation for both smooth and rough fractures. In imbibition for rough-walled fractures, another mechanism similar to wave-like flow in pipes was also observed. The data from the experiments were analyzed using Darcy's law and using the concept of friction factor and equivalent Reynold's number for two-phase flow. For both smooth- and rough-walled fractures a clear relationship between relative permeability and saturation was seen. The calculated relative permeability curves follow Corey-type behavior and can be modeled using Honarpour expressions. The sum of the relative permeabilities is not equal one, indicating phase interference. The equivalent homogeneous single-phase approach did not give satisfactory representation of flow through fractures. The graphs of experimentally derived friction factor with the modified Reynolds number do not reveal a distinctive linear relationship.

  17. Magnetostrictive materials and method for improving AC characteristics in same

    DOEpatents

    Pulvirenti, Patricia P.; Jiles, David C.

    2001-08-14

    The present invention provides Terfenol-D alloys ("doped" Terfenol) having optimized performances under the condition of time-dependent magnetic fields. In one embodiment, performance is optimized by lowering the conductivity of Terfenol, thereby improving the frequency response. This can be achieved through addition of Group III or IV elements, such as Si and Al. Addition of these types of elements provides scattering sites for conduction electrons, thereby increasing resistivity by 125% which leads to an average increase in penetration depth of 80% at 1 kHz and an increase in energy conversion efficiency of 55%. The permeability of doped Terfenol remains constant over a wider frequency range as compared with undoped Terfenol. These results demonstrate that adding impurities, such as Si and Al, are effective in improving the ac characteristics of Terfenol. A magnetoelastic Gruneisen parameter, .gamma..sub.me, has also been derived from the thermodynamic equations of state, and provides another means by which to characterize the coupling efficiency in magnetostrictive materials on a more fundamental basis.

  18. Change in the microhardness of nonmagnetic crystals after their exposure to the Earth's magnetic field and AC pump field in the EPR scheme

    NASA Astrophysics Data System (ADS)

    Alshits, V. I.; Darinskaya, E. V.; Koldaeva, M. V.; Petrzhik, E. A.

    2012-02-01

    Changes in the microhardness of ZnO, triglycine sulfate (TGS), and potassium acid phthalate (KAP) crystals after their exposure to crossed ultralow magnetic fields, i.e., the Earth's field B Earth ≈ 50 μT and the alternating-current field tilde B ≈ 3 μ T orthogonal to it, have been revealed. In ZnO crystals, the microhardness increases, whereas in TGS and KAP, it decreases. A maximum change (10-15%) is reached within 1-3 h after magnetic treatment; then, the microhardness gradually recovers to its initial value for the first day. After a sufficient pause, the effect is completely reproduced under the same conditions. The resonant frequency of the pump field tilde B corresponds to the EPR condition with a g-factor close to two. The magnetic memory exhibits a strong anisotropy: for each of the crystals, a direction is found, which, being coincident with the Earth's magnetic field vector B Earth, causes complete or partial suppression of the effect. In ZnO and TGS crystals, these are symmetry axes 6 and 2, respectively. In the KAP crystal, it is the direction in the cleavage plane orthogonal the 2 axis. Possible physical mechanisms of the observed phenomena have been discussed.

  19. Effect of Temperature and Grain Size on Magnetic Properties of Soft Magnetic Iron-Cobalt Alloys

    NASA Astrophysics Data System (ADS)

    Kozlowski, G.; Fingers, R. T.; Coate, J. E.; Rogacki, K.; Dabrowski, B.

    1997-03-01

    Two specific iron-cobalt alloys have been tested as part of the magnetic materials characterization program at Wright Laboratory. The first material is Hiperco Alloy 50HS from Carpenter Technology and the second is HS50 from Telcon Ltd. The planned use of such materials in cyclic high temperature high stress environments (generators and magnetic bearings) gives impetus to determining material properties. These soft magnetic alloys exhibit high magnetic saturation, high yield strength, and moderate core loss. In order to better understand the overall behavior of these alloys, both mechanical and magnetic phenomena have been investigated. Specimens of these materials have been heat treated by various recipes ranging in temperature from 1300 degF to 1350 degF and magnetic saturation along hysteresis loop measurements were made using a vibrating sample magnetometer and an a.c. susceptometer. Measurements of remanence, coercivity, permeabilities and saturation were made as a function of temperature. Mechanical testing was also conducted and these results were used in conjunction with the magnetic behavior to characterize the two specific alloys. Etching and sample preparation processes were developed and microstructural analyses were performed. The effect of composition and heat treatment of these two soft magnetic materials and how they may influence potential applications is discussed.

  20. The evaluation of rock permeability with streaming current measurements

    NASA Astrophysics Data System (ADS)

    Wang, Jun; Hu, Hengshan; Guan, Wei

    2016-06-01

    Rock permeability is an important parameter for the formation evaluation. In this paper, a new method with streaming current is proposed to determine the sample permeability based on the electrokinetic effects, and is proved by the experimental measurements. Corresponding to this method, we have designed an experimental setup and a test system, then performed the streaming current (potential) and electroosmosis pressure experiments with 23 sandstone samples at 0.05 mol/l NaCl solution. The streaming current (potential) coefficient and electroosmosis pressure coefficient are obtained respectively with the experimental data at low frequencies with AC lock-in technique. The electrokinetic permeabilities are further calculated with these coefficients. The results are consistent well with the gas permeability measured with Darcy's law, which verifies the current method for estimating rock permeability. Our measurements are also analyzed and compared with previous measurements. The results indicate that our method can reflect the essence of electrokinetic effects better and simplify the electrokinetic measurements as well. In addition, we discuss the influences of experimental artefacts (core-holder and confining pressure installation) on the electrokinetic data. The results show that the trough phenomenon, appeared in frequency curves of streaming current (potential) coefficients, is induced by the resonance of the core-holder/vibrator system. This is important for the design of electrokinetic setup and the analysis of low frequency response of the electrokinetic coupling coefficients.

  1. Sensitivity of the magnetization curves of different austenitic stainless tube and pipe steels to mechanical fatigue

    NASA Astrophysics Data System (ADS)

    Niffenegger, M.; Leber, H. J.

    2008-07-01

    In meta-stable austenitic stainless steels, fatigue is accompanied by a partial strain-induced transformation of paramagnetic austenite to ferromagnetic martensite [G.B. Olsen, M. Cohen, Kinetics of strain induced martensite nucleation, Metall. Trans. 6 (1975) 791-795]. The associated changes of magnetic properties as the eddy current impedance, magnetic permeability or the remanence field may serve as an indication for the degree of fatigue and therefore the remaining lifetime of a component, even though the exact causal relationship between martensite formation and fatigue is not fully understood. However, measuring these properties by magnetic methods may be limited by the low affinity for strain-induced martensite formation. Thus other methods have to be found which are able to detect very small changes of ferromagnetic contents. With this aim the influence of cyclic strain loading on the magnetization curves of the austenitic stainless tube and pipe steels TP 321, 347, 304L and 316L is analysed in the present paper. The measured characteristic magnetic properties, which are the saturation magnetization, residual magnetization, coercive field and the field dependent permeability (AC-magnetization), are sensitive to fatigue and the corresponding material changes (martensitic transformation). In particular, the AC-magnetization was found to be very sensitive to small changes of the amount of strain induced martensite and therefore also to the degree of fatigue. Hence we conclude that applying magnetic minor loops are promising for the non-destructive evaluation of fatigue in austenitic stainless steel, even if a very small amount of strain induced martensite is formed.

  2. Permeability across lipid membranes.

    PubMed

    Shinoda, Wataru

    2016-10-01

    Molecular permeation through lipid membranes is a fundamental biological process that is important for small neutral molecules and drug molecules. Precise characterization of free energy surface and diffusion coefficients along the permeation pathway is required in order to predict molecular permeability and elucidate the molecular mechanisms of permeation. Several recent technical developments, including improved molecular models and efficient sampling schemes, are illustrated in this review. For larger penetrants, explicit consideration of multiple collective variables, including orientational, conformational degrees of freedom, are required to be considered in addition to the distance from the membrane center along the membrane normal. Although computationally demanding, this method can provide significant insights into the molecular mechanisms of permeation for molecules of medical and pharmaceutical importance. This article is part of a Special Issue entitled: Biosimulations edited by Ilpo Vattulainen and Tomasz Róg. PMID:27085977

  3. Electromagnetic imaging of lithosphere permeable zones

    NASA Astrophysics Data System (ADS)

    Litvinova, Tamara; Petrova Petrova, Alevtina; Petrishchev Petrishchev, Maxim

    2014-05-01

    By way of strong minima of magnetic anomalies studies we are investigated the features of the lithosphere structure by magnetic and gravity data. Exploration methods included the application of existing and open source near-surface aeromagnetic (WDMAM) with satellite data both at 100 km and 400 km in altitude (CHAMP) and gravity satellite data (GRACE). Aeromagnetic data have been used for the 2D geomagnetic model for a depth range from 3 to 50 km plotting. Gravity data has allowed to study the 2D density model for a depth range from 5 to 200 km plotting. At the heart of the geomagnetic and density model plotting lies the technique of the spectral-spatial representation of a geomagnetic field converted in a deep geomagnetic model. The technique of the spectral-spatial analysis (SPAN) is used to differentiate the weakly magnetic heterogeneities within the basement. In this paper we have studied the structure of the lithosphere in the area of deep magnetic minima in the vicinity of the eastern part of the Fennoscandian Shield, Central Europe and the northern part of South America. We have found powerful (more than 10 km) permeable feeble magnetic zones in the middle crust (20-30 km in depth) that are detected as feebly magnetic layer using the geomagnetic data. The magnetic minimum at 100 and 400 km in altitude corresponds to this feeble magnetic layer. It stands out as the low density layer at depth 20-35 km and, after the break, at depth 60-100 km. Ground-based magnetotelluric survey has allowed to allocate the high-conductivity layer at depth 15-30 and 60-110 km. It suggests that the detected layers can be rheological weak. The same is for the regions of Central Europe and South America. The powerful feebly magnetic layers have been detected in the middle and bottom crust (30-50 km for the Central Europe and 30-40 km for South America). The low density layers have been found for 20-35 km and 50-80 km in depth. The ground based measurement has confirmed the presence

  4. Non-dipole interaction of helix inclusions in metamaterials with artificial permeability

    NASA Astrophysics Data System (ADS)

    Starostenko, Sergey N.; Rozanov, Konstantin N.

    2015-06-01

    An analytic approach to calculate induced permeability of metamaterial filled with helix inclusions is developed. For an electrically small coil, the dynamic magnetization is determined by lumped inductance, capacitance, and resistance that are calculated from the coil design. The susceptibility of a coil is shown to be close to that of diamagnetic ellipsoid of the same elongation. Contrary to permeable particles in a composite, the coils screen each other thus decreasing the magnetic response of metamaterial compared to total response of comprised coils. The filling effect on magnetic spectrum of metamaterial is analyzed and verified by measurements for the case of identical coaxially placed coreless coils. The critical filling where magnetic response of metamaterial is maximal depends on coil shape and resistance. The coil-filled metamaterials may find applications as permeable EMI suppressors or microwave absorbers free of Snoek or Acher limitations on the high-frequency permeability, as well as of Curie limitation on the high-temperature magnetic performance.

  5. Electrokinetic effects and fluid permeability

    NASA Astrophysics Data System (ADS)

    G. Berryman, James

    2003-10-01

    Fluid permeability of porous media depends mainly on connectivity of the pore space and two physical parameters: porosity and a pertinent length-scale parameter. Electrical imaging methods typically establish connectivity and directly measure electrical conductivity, which can then often be related to porosity by Archie's law. When electrical phase measurements are made in addition to the amplitude measurements, information about the pertinent length scale can then be obtained. Since fluid permeability controls the ability to flush unwanted fluid contaminants from the subsurface, inexpensive maps of permeability could improve planning strategies for remediation efforts. Detailed knowledge of fluid permeability is also important for oil field exploitation, where knowledge of permeability distribution in three dimensions is a common requirement for petroleum reservoir simulation and analysis, as well as for estimates on the economics of recovery.

  6. High-frequency permeability of Fe-Co and Co granular composite materials

    NASA Astrophysics Data System (ADS)

    Kasagi, Teruhiro; Tsutaoka, Takanori; Tsurunaga, Aiko; Hatakeyama, Kenichi

    2013-06-01

    The relative complex permeability and permittivity spectra of Fe50Co50 (Permendur) and Co granular composite materials containing heat-treated particles have been studied in the microwave frequency range up to 20 GHz. Fe50Co50 granular composite materials have a larger relative permeability value than Co composites at the same particle content owing to the differences in the magnetizations and the magnetic anisotropies between Fe50Co50 and Co particles. Negative permeability dispersions were observed in both composites at frequencies above 6 GHz. The effect of a dc magnetic field on the permeability spectra revealed that the permeability dispersion of Co composites could mainly be attributed to the gyromagnetic spin resonance in the microwave range. From the relative permittivity spectrum, these two metal granular composites have a dielectric property even at high particle contents.

  7. Study on electro-magnetic properties of La substituted Ni-Cu-Zn ferrite synthesized by auto-combustion method

    NASA Astrophysics Data System (ADS)

    Roy, P. K.; Nayak, Bibhuti B.; Bera, J.

    (Ni 0.25Cu 0.20Zn 0.55)La xFe 2-xO 4 ferrite with x=0.00, 0.025, 0.050 and 0.075 compositions were synthesized through nitrate-citrate auto-combustion method. Crystalline spinel ferrite phase with about 16-19 nm crystallite size was present in the as-burnt ferrite powder. These powders were calcined, compacted and sintered at 950 °C for 4 h. Initial permeability, magnetic loss and AC resistivity of different compositions were measured in the frequency range from 10 Hz to 10 MHz. Saturation magnetization and hysteresis parameters were measured at room temperature with a maximum magnetic field of 10 kOe. Permeability and AC resistivity were found to increase and magnetic loss decreased with La substitution for Fe, up to x=0.025. Saturation magnetization and coercive field also increases up to that limit. The electromagnetic properties were found best in the ferrite composition of x=0.025, which would be better for more miniaturized multi layer chip inductor.

  8. Permeability-porosity relationships in sedimentary rocks

    USGS Publications Warehouse

    Nelson, Philip H.

    1994-01-01

    In many consolidated sandstone and carbonate formations, plots of core data show that the logarithm of permeability (k) is often linearly proportional to porosity (??). The slope, intercept, and degree of scatter of these log(k)-?? trends vary from formation to formation, and these variations are attributed to differences in initial grain size and sorting, diagenetic history, and compaction history. In unconsolidated sands, better sorting systematically increases both permeability and porosity. In sands and sandstones, an increase in gravel and coarse grain size content causes k to increase even while decreasing ??. Diagenetic minerals in the pore space of sandstones, such as cement and some clay types, tend to decrease log(k) proportionately as ?? decreases. Models to predict permeability from porosity and other measurable rock parameters fall into three classes based on either grain, surface area, or pore dimension considerations. (Models that directly incorporate well log measurements but have no particular theoretical underpinnings from a fourth class.) Grain-based models show permeability proportional to the square of grain size times porosity raised to (roughly) the fifth power, with grain sorting as an additional parameter. Surface-area models show permeability proportional to the inverse square of pore surface area times porosity raised to (roughly) the fourth power; measures of surface area include irreducible water saturation and nuclear magnetic resonance. Pore-dimension models show permeability proportional to the square of a pore dimension times porosity raised to a power of (roughly) two and produce curves of constant pore size that transgress the linear data trends on a log(k)-?? plot. The pore dimension is obtained from mercury injection measurements and is interpreted as the pore opening size of some interconnected fraction of the pore system. The linear log(k)-?? data trends cut the curves of constant pore size from the pore-dimension models

  9. Optimization of spin-torque switching using AC and DC pulses

    SciTech Connect

    Dunn, Tom; Kamenev, Alex

    2014-06-21

    We explore spin-torque induced magnetic reversal in magnetic tunnel junctions using combined AC and DC spin-current pulses. We calculate the optimal pulse times and current strengths for both AC and DC pulses as well as the optimal AC signal frequency, needed to minimize the Joule heat lost during the switching process. The results of this optimization are compared against numeric simulations. Finally, we show how this optimization leads to different dynamic regimes, where switching is optimized by either a purely AC or DC spin-current, or a combination AC/DC spin-current, depending on the anisotropy energies and the spin-current polarization.

  10. Can the imaginary part of permeability be negative?

    PubMed

    Markel, Vadim A

    2008-08-01

    When new composite optical materials are developed experimentally or studied in numerical simulations, it is essential to have a set of fundamental constraints that the optical constants of such materials must satisfy. In this paper I argue that positivity of the imaginary part of the magnetic permeability may not be one of such constraints, particularly in naturally occurring diamagnetics and in artificial materials that exhibit diamagnetic response to low-frequency or static magnetic fields. PMID:18850963

  11. Water permeability of elastomers.

    PubMed

    Held, H R; Landi, S

    1977-01-01

    In a previous study it has been shown that the free moisture content in freeze-dried BCG vaccine dispensed in vials sealed with rubber stoppers increased during storage. The search for the source of this increase led us to explore the possibility that this additional moisture could originate from the rubber stoppers themselves. Therefore, the water permeability of various rubber stoppers has been studied, and the water content of grey butyl stoppers during some operations (autoclaving, oven-drying, freeze-drying, storage) used in the manufacturing of BCG vaccine has been determined. Our experiments showed: rapid water uptake during steam-autoclaving and rapid water release during subsequent oven-drying of the stoppers; a slow water uptake of the stoppers during freeze-drying and a slow water permeation through the stoppers when vials containing Indicating Drierite were stored in a water-saturated atmosphere. Among 12 types of rubber stoppers tested, the grey butyl stoppers and the silicone stoppers showed the lowest water uptake. Moisture-resistant wrappings decreased significantly the moisture uptake of Drierite. To delay moisture from reaching the vaccine it is recommended that the stoppers employed be as dry as possible. PMID:881425

  12. Permeable membrane experiment

    NASA Technical Reports Server (NTRS)

    Slavin, Thomas J.; Cao, Tuan Q.; Kliss, Mark H.

    1993-01-01

    The purpose of the Permeable Membrane Experiment is to gather flight data on three areas of membrane performance that are influenced by the presence of gravity. These areas are: (1) Liquid/gas phase separation, (2) gas bubble interference with diffusion through porous membranes and (3) wetting characteristics of hydrophilic membrane surfaces. These data are important in understaning the behavior of membrane/liquid/gas interfaces where surface tension forces predominate. The data will be compared with 1-g data already obtained and with predicted micrograviity behavior. The data will be used to develop designs for phase separation and plant nutrient delivery systems and will be available to the life support community for use in developing technologies which employ membranes. A conceptual design has been developed to conduct three membrane experiments, in sequence, aboard a single Complex Autonomous Payload (CAP) carrier to be carried in the Shuttle Orbiter payload bay. One experiment is conducted for each of the three membrane performance areas under study. These experiments are discussed in this paper.

  13. Microfabricated AC impedance sensor

    DOEpatents

    Krulevitch, Peter; Ackler, Harold D.; Becker, Frederick; Boser, Bernhard E.; Eldredge, Adam B.; Fuller, Christopher K.; Gascoyne, Peter R. C.; Hamilton, Julie K.; Swierkowski, Stefan P.; Wang, Xiao-Bo

    2002-01-01

    A microfabricated instrument for detecting and identifying cells and other particles based on alternating current (AC) impedance measurements. The microfabricated AC impedance sensor includes two critical elements: 1) a microfluidic chip, preferably of glass substrates, having at least one microchannel therein and with electrodes patterned on both substrates, and 2) electrical circuits that connect to the electrodes on the microfluidic chip and detect signals associated with particles traveling down the microchannels. These circuits enable multiple AC impedance measurements of individual particles at high throughput rates with sufficient resolution to identify different particle and cell types as appropriate for environmental detection and clinical diagnostic applications.

  14. Relative Permeability of Fractured Rock

    SciTech Connect

    Mark D. Habana

    2002-06-30

    Contemporary understanding of multiphase flow through fractures is limited. Different studies using synthetic fractures and various fluids have yielded different relative permeability-saturation relations. This study aimed to extend the understanding of multiphase flow by conducting nitrogen-water relative permeability experiments on a naturally-fractured rock from The Geysers geothermal field. The steady-state approach was used. However, steady state was achieved only at the endpoint saturations. Several difficulties were encountered that are attributed to phase interference and changes in fracture aperture and surface roughness, along with fracture propagation/initiation. Absolute permeabilities were determined using nitrogen and water. The permeability values obtained change with the number of load cycles. Determining the absolute permeability of a core is especially important in a fractured rock. The rock may change as asperities are destroyed and fractures propagate or st rain harden as the net stresses vary. Pressure spikes occurred in water a solute permeability experiments. Conceptual models of an elastic fracture network can explain the pressure spike behavior. At the endpoint saturations the water relative permeabilities obtained are much less than the nitrogen gas relative permeabilities. Saturations were determined by weighing and by resistivity calculations. The resistivity-saturation relationship developed for the core gave saturation values that differ by 5% from the value determined by weighing. Further work is required to complete the relative permeability curve. The steady-state experimental approach encountered difficulties due to phase interference and fracture change. Steady state may not be reached until an impractical length of time. Thus, unsteady-state methods should be pursued. In unsteady-state experiments the challenge will be in quantifying rock fracture change in addition to fluid flow changes.

  15. A Magnetic Paradox

    ERIC Educational Resources Information Center

    Arndt, Ebe

    2006-01-01

    Two recent articles in this journal described how an air core solenoid connected to an ac power source may restore the magnetization of a bar magnet with an alternating magnetic field (see Figs. 1 and 2). Although we are quite accustomed to using a constant magnetic field in an air core solenoid to remagnetize a ferromagnet, it is puzzling that we…

  16. AC magnetohydrodynamic microfluidic switch

    SciTech Connect

    Lemoff, A V; Lee, A P

    2000-03-02

    A microfluidic switch has been demonstrated using an AC Magnetohydrodynamic (MHD) pumping mechanism in which the Lorentz force is used to pump an electrolytic solution. By integrating two AC MHD pumps into different arms of a Y-shaped fluidic circuit, flow can be switched between the two arms. This type of switch can be used to produce complex fluidic routing, which may have multiple applications in {micro}TAS.

  17. ACS Symposium Support

    SciTech Connect

    Kenneth D. Jordan

    2010-02-20

    The funds from this DOE grant were used to help cover the travel costs of five students and postdoctoral fellows who attended a symposium on 'Hydration: From Clusters to Aqueous Solutions' held at the Fall 2007 American Chemical Society Meeting in Boston, MA, August 19-23. The Symposium was sponsored by the Physical Chemistry Division, ACS. The technical program for the meeting is available at http://phys-acs.org/fall2007.html.

  18. Thermal treatment of low permeability soils using electrical resistance heating

    SciTech Connect

    Udell, K.S.

    1996-08-01

    The acceleration of recovery rates of second phase liquid contaminants from the subsurface during gas or water pumping operations is realized by increasing the soil and ground water temperature. Electrical heating with AC current is one method of increasing the soil and groundwater temperature and has particular applicability to low permeability soils. Several mechanisms have been identified that account for the enhanced removal of the contaminants during electrical heating. These are vaporization of liquid contaminants with low boiling points, temperature-enhanced evaporation rates of semi-volatile components, and removal of residual contaminants by the boiling of residual water. Field scale studies of electrical heating and fluid extraction show the effectiveness of this technique and its applicability to contaminants found both above and below the water table and within low permeability soils. 10 refs., 8 figs.

  19. Geothermal Permeability Enhancement - Final Report

    SciTech Connect

    Joe Beall; Mark Walters

    2009-06-30

    The overall objective is to apply known permeability enhancement techniques to reduce the number of wells needed and demonstrate the applicability of the techniques to other undeveloped or under-developed fields. The Enhanced Geothermal System (EGS) concept presented in this project enhances energy extraction from reduced permeability zones in the super-heated, vapor-dominated Aidlin Field of the The Geysers geothermal reservoir. Numerous geothermal reservoirs worldwide, over a wide temperature range, contain zones of low permeability which limit the development potential and the efficient recovery of heat from these reservoirs. Low permeability results from poorly connected fractures or the lack of fractures. The Enhanced Geothermal System concept presented here expands these technologies by applying and evaluating them in a systematic, integrated program.

  20. Respiratory mucosal permeability in asthma

    SciTech Connect

    Elwood, R.K.; Kennedy, S.; Belzberg, A.; Hogg, J.C.; Pare, P.D.

    1983-09-01

    The permeability of respiratory mucosa to technetium-labeled diethylenetriamine pentacetic acid (/sup 99m/Tc-DTPA) was measured in 10 clinically stable chronic asthmatics and the results were compared with those in 9 nonasthmatic control subjects. Nonspecific bronchial reactivity was measured using methacholine, and the PC20 was calculated. The intrapulmonary distribution and dose of the inhaled /sup 99m/Tc-DTPA was determined by a gamma camera and the half-life of the aerosolized label in the lung was calculated. The accumulation of radioactivity in the blood was monitored and a permeability index was calculated at 10, 25, and 60 min after aerosolization. Despite marked differences in airway reactivity, no differences in either parameter of permeability could be detected between the asthmatics and the control group. It is concluded that clinically stable asthmatics do not demonstrate increase mucosal permeability to small solutes when compared with normal subjects.

  1. Permeability within basaltic oceanic crust

    NASA Astrophysics Data System (ADS)

    Fisher, Andrew T.

    1998-05-01

    Water-rock interactions within the seafloor are responsible for significant energy and solute fluxes between basaltic oceanic crust and the overlying ocean. Permeability is the primary hydrologic property controlling the form, intensity, and duration of seafloor fluid circulation, but after several decades of characterizing shallow oceanic basement, we are still learning how permeability is created and distributed and how it changes as the crust ages. Core-scale measurements of basaltic oceanic crust yield permeabilities that are quite low (generally 10-22 to 10-17 m²), while in situ measurements in boreholes suggest an overlapping range of values extending several orders of magnitude higher (10-18 to 10-13 m²). Additional indirect estimates include calculations made from borehole temperature and flow meter logs (10-16 to 10-11 m²), numerical models of coupled heat and fluid flow at the ridge crest and within ridge flanks (10-16 to 10-9 m²), and several other methods. Qualitative indications of permeability within the basaltic oceanic crust come from an improved understanding of crustal stratigraphy and patterns of alteration and tectonic modification seen in ophiolites, seafloor samples and boreholes. Difficulties in reconciling the wide range of estimated permeabilities arise from differences in experimental scale and critical assumptions regarding the nature and distribution of fluid flow. Many observations and experimental and modeling results are consistent with permeability varying with depth into basement and with primary basement lithology. Permeability also seems to be highly heterogeneous and anisotropic throughout much of the basaltic crust, as within crystalline rocks in general. A series of focused experiments is required to resolve permeability in shallow oceanic basement and to directly couple upper crustal hydrogeology to magmatic, tectonic, and geochemical crustal evolution.

  2. Permeability of soils in Mississippi

    USGS Publications Warehouse

    O'Hara, Charles G.

    1994-01-01

    The permeability of soils in Mississippi was determined and mapped using a geographic information system (GIS). Soil permeabilities in Mississippi were determined to range in value from nearly 0.0 to values exceeding 5.0 inches per hour. The U.S. Soil Conservation Service's State Soil Geographic Data Base (STATSGO) was used as the primary source of data for the determination of area-weighted soil permeability. STATSGO provides soil layer properties that are spatially referenced to mapped areas. These mapped areas are referred to as polygons in the GIS. The polygons arc boundaries of soils mapped as a group and are given unique Map Unit Identifiers (MUIDs). The data describing the physical characteristics of the soils within each polygon are stored in a tabular data base format and are referred to as attributes. The U.S. Soil Conservation Service developed STATSGO to be primarily used as a guide for regional resource planning, management, and monitoring. STATSGO was designed so that soil information could be extracted from properties tables at the layer level, combined by component, and statistically expanded to cover the entire map unit. The results of this study provide a mapped value for permeability which is representative of the vertical permeability of soils in that area. The resultant permeability map provides a representative vertical soil permeability for a given area sufficient for county, multi- county, and area planning, and will be used as the soil permeability data component in the evaluation of the susceptibility of major aquifers to contami- nation in Mississippi.

  3. Permeability extraction: A sonic log inversion

    SciTech Connect

    Akbar, N.; Kim, J.J.

    1994-12-31

    In this paper the authors provide the missing important link between permeability and acoustic velocities by generating a permeability-dependent synthetic sonic log in a carbonate reservoir. The computations are based on Akbar`s theory that relates wave velocity to frequency, rock properties (e.g., lithology, permeability, and porosity), and fluid saturation and properties (viscosity, density, and compressibility). An inverted analytical expression of the theory is used to extract permeability from sonic velocity. The synthetic sonic and the computed permeability are compared with the observed sonic log and with plug permeability, respectively. The results demonstrate, as predicted by theory, that permeability can be related directly to acoustic velocities.

  4. Initial tests of an AC dipole for the Tevatron

    SciTech Connect

    Miyamoto, R.; Jansson, A.; Kopp, S.; Syphers, M.; /Fermilab

    2006-06-01

    The AC dipole is a device to diagnose transverse motions of a beam. It can achieve large-amplitude oscillations without two inevitable problems of conventional kicker/pinger magnets: decoherence and emittance growth. While not the first synchrotron to operate with an AC dipole, the Tevatron can now make use of its recently upgraded BPM system, providing unprecedented resolution for use with an AC dipole, to measure both linear and nonlinear properties of the accelerator. Plans are to provide AC dipole systems for both transverse degrees of freedom. Preliminary tests have been done using an audio power amplifier with an existing vertical pinger magnet, producing oscillation amplitudes up to 2{sigma} at 150 GeV. In this paper, we will present the configuration of this system. We also show the analysis of a first few data sets, including the direct measurement of beta functions at BPM locations.

  5. MAGNETS

    DOEpatents

    Hofacker, H.B.

    1958-09-23

    This patent relates to nmgnets used in a calutron and more particularly to means fur clamping an assembly of magnet coils and coil spacers into tightly assembled relation in a fluid-tight vessel. The magnet comprises windings made up of an assembly of alternate pan-cake type coils and spacers disposed in a fluid-tight vessel. At one end of the tank a plurality of clamping strips are held firmly against the assembly by adjustable bolts extending through the adjacent wall. The foregoing arrangement permits taking up any looseness which may develop in the assembly of coils and spacers.

  6. Diffusive suppression of AC-Stark shifts in atomic magnetometers

    PubMed Central

    Sulai, I. A.; Wyllie, R.; Kauer, M.; Smetana, G. S.; Wakai, R. T.; Walker, T. G.

    2016-01-01

    In atomic magnetometers, the vector AC-Stark shift associated with circularly polarized light generates spatially varying effective magnetic fields, which limit the magnetometer response and serve as sources of noise. We describe a scheme whereby optically pumping a small subvolume of the magnetometer cell and relying on diffusion to transport polarized atoms allows a magnetometer to be operated with minimal sensitivity to the AC-Stark field. © 2013 Optical Society of America PMID:23503278

  7. ac bidirectional motor controller

    NASA Technical Reports Server (NTRS)

    Schreiner, K.

    1988-01-01

    Test data are presented and the design of a high-efficiency motor/generator controller at NASA-Lewis for use with the Space Station power system testbed is described. The bidirectional motor driver is a 20 kHz to variable frequency three-phase ac converter that operates from the high-frequency ac bus being designed for the Space Station. A zero-voltage-switching pulse-density-modulation technique is used in the converter to shape the low-frequency output waveform.

  8. Dielectric and permeability

    NASA Technical Reports Server (NTRS)

    Cole, K. D.

    1982-01-01

    Using the unabridged Maxwell equations (including vectors D, E and H) new effects in collisionless plasmas are uncovered. In a steady state, it is found that spatially varying energy density of the electric field (E perpendicular) orthogonal to B produces electric current leading, under certain conditions, to the relationship P perpendicular+B(2)/8 pi-epsilon E perpendicular(2)/8 pi = constant, where epsilon is the dielectric constant of the plasma for fields orthogonal to B. In steady state quasi-two-dimensional flows in plasmas, a general relationship between the components of electric field parallel and perpendicular to B is found. These effects are significant in goephysical and astrophysical plasmas. The general conditions for a steady state in collisionless plasma are deduced. With time variations in a plasma, slow compared to ion-gyroperiod, there is a general current, (j*), which includes the well-known polarisation current, given by J*=d/dt (ExM)+(PxB)xB B(-2) where M and P are the magnetization and polarization vectors respectively.

  9. Dynamic magnetic characteristics of Fe78Si13B9 amorphous alloy subjected to operating temperature

    NASA Astrophysics Data System (ADS)

    He, Aina; Wang, Anding; Yue, Shiqiang; Zhao, Chengliang; Chang, Chuntao; Men, He; Wang, Xinmin; Li, Run-Wei

    2016-06-01

    The operating temperature dependence of dynamic magnetic characteristics of the annealed Fe78Si13B9 amorphous alloy core was systematically investigated. The core loss, magnetic induction intensity and complex permeability of the amorphous core were analyzed by means of AC B-H loop tracer and impedance analyzer. It is found that the operating temperature below 403 K has little impact on core loss when the induction (B) is less than 1.25 T. As B becomes higher, core loss measured at high temperature becomes higher. For the cores measured at power frequency, the B at 80 A/m and the coercivity (Hc) at 1 T decline slightly as the temperature goes up. Furthermore, the real part of permeability (μ‧) increases with the rise of temperature. The imaginary part of permeability (μ″) maxima shifts to lower frequency side with increasing temperature, indicating the magnetic relaxation behavior in the sample. In addition, with the rise in the operating temperature of the annealed amorphous core, the relaxation time tends to increase.

  10. Measuring Vascular Permeability In Vivo.

    PubMed

    Meijer, Eelco F J; Baish, James W; Padera, Timothy P; Fukumura, Dai

    2016-01-01

    Over the past decades, in vivo vascular permeability measurements have provided significant insight into vascular functions in physiological and pathophysiological conditions such as the response to pro- and anti-angiogenic signaling, abnormality of tumor vasculature and its normalization, and delivery and efficacy of therapeutic agents. Different approaches for vascular permeability measurements have been established. Here, we describe and discuss a conventional 2D imaging method to measure vascular permeability, which was originally documented by Gerlowski and Jain in 1986 (Microvasc Res 31:288-305, 1986) and further developed by Yuan et al. in the early 1990s (Microvasc Res 45:269-289, 1993; Cancer Res 54:352-3356, 1994), and our recently developed 3D imaging method, which advances the approach originally described by Brown et al. in 2001 (Nat Med 7:864-868, 2001). PMID:27581015

  11. Fibrinogen induces endothelial cell permeability

    PubMed Central

    Tyagi, Neetu; Roberts, Andrew M.; Dean, William L.; Tyagi, Suresh C.

    2010-01-01

    Many cardiovascular and cerebrovascular disorders are accompanied by an increased blood content of fibrinogen (Fg), a high molecular weight plasma adhesion protein. Fg is a biomarker of inflammation and its degradation products have been associated with microvascular leakage. We tested the hypothesis that at pathologically high levels, Fg increases endothelial cell (EC) permeability through extracellular signal regulated kinase (ERK) signaling and by inducing F-actin formation. In cultured ECs, Fg binding to intercellular adhesion molecule-1 and to α5β1 integrin, caused phosphorylation of ERK. Subsequently, F-actin formation increased and coincided with formation of gaps between ECs, which corresponded with increased permeability of ECs to albumin. Our data suggest that formation of F-actin and gaps may be the mechanism for increased albumin leakage through the EC monolayer. The present study indicates that elevated un-degraded Fg may be a factor causing microvascular permeability that typically accompanies cardiovascular and cerebrovascular disorders. PMID:17849175

  12. Diagnostics of the Fermilab Tevatron using an AC dipole

    SciTech Connect

    Miyamoto, Ryoichi

    2008-08-01

    The Fermilab Tevatron is currently the world's highest energy colliding beam facility. Its counter-rotating proton and antiproton beams collide at 2 TeV center-of-mass. Delivery of such intense beam fluxes to experiments has required improved knowledge of the Tevatron's beam optical lattice. An oscillating dipole magnet, referred to as an AC dipole, is one of such a tool to non-destructively assess the optical properties of the synchrotron. We discusses development of an AC dipole system for the Tevatron, a fast-oscillating (f ~ 20 kHz) dipole magnet which can be adiabatically turned on and off to establish sustained coherent oscillations of the beam particles without affecting the transverse emittance. By utilizing an existing magnet and a higher power audio amplifier, the cost of the Tevatron AC dipole system became relatively inexpensive. We discuss corrections which must be applied to the driven oscillation measurements to obtain the proper interpretation of beam optical parameters from AC dipole studies. After successful operations of the Tevatron AC dipole system, AC dipole systems, similar to that in the Tevatron, will be build for the CERN LHC. We present several measurements of linear optical parameters (beta function and phase advance) for the Tevatron, as well as studies of non-linear perturbations from sextupole and octupole elements.

  13. Diagnostics of the Fermilab Tevatron using an AC dipole

    NASA Astrophysics Data System (ADS)

    Miyamoto, Ryoichi

    The Fermilab Tevatron is currently the world's highest energy colliding beam facility. Its counter-rotating proton and antiproton beams collide at 2 TeV center-of-mass. Delivery of such intense beam fluxes to experiments has required improved knowledge of the Tevatron's beam optical lattice. An oscillating dipole magnet, referred to as an AC dipole, is one of such a tool to non-destructively assess the optical properties of the synchrotron. We discusses development of an AC dipole system for the Tevatron, a fast-oscillating (f˜20 kHz) dipole magnet which can be adiabatically turned on and off to establish sustained coherent oscillations of the beam particles without affecting the transverse emittance. By utilizing an existing magnet and a higher power audio amplifier, the cost of the Tevatron AC dipole system became relatively inexpensive. We discuss corrections which must be applied to the driven oscillation measurements to obtain the proper interpretation of beam optical parameters from AC dipole studies. After successful operations of the Tevatron AC dipole system, AC dipole systems, similar to that in the Tevatron, will be build for the CERN LHC. We present several measurements of linear optical parameters (beta function and phase advance) for the Tevatron, as well as studies of non-linear perturbations from sextupole and octupole elements.

  14. Controlling ferrofluid permeability across the blood-brain barrier model

    NASA Astrophysics Data System (ADS)

    Shi, Di; Sun, Linlin; Mi, Gujie; Sheikh, Lubna; Bhattacharya, Soumya; Nayar, Suprabha; Webster, Thomas J.

    2014-02-01

    In the present study, an in vitro blood-brain barrier model was developed using murine brain endothelioma cells (b.End3 cells). Confirmation of the blood-brain barrier model was completed by examining the permeability of FITC-Dextran at increasing exposure times up to 96 h in serum-free medium and comparing such values with values from the literature. After such confirmation, the permeability of five novel ferrofluid (FF) nanoparticle samples, GGB (ferrofluids synthesized using glycine, glutamic acid and BSA), GGC (glycine, glutamic acid and collagen), GGP (glycine, glutamic acid and PVA), BPC (BSA, PEG and collagen) and CPB (collagen, PVA and BSA), was determined using this blood-brain barrier model. All of the five FF samples were characterized by zeta potential to determine their charge as well as TEM and dynamic light scattering for determining their hydrodynamic diameter. Results showed that FF coated with collagen passed more easily through the blood-brain barrier than FF coated with glycine and glutamic acid based on an increase of 4.5% in permeability. Through such experiments, diverse magnetic nanomaterials (such as FF) were identified for: (1) MRI use since they were less permeable to penetrate the blood-brain barrier to avoid neural tissue toxicity (e.g. GGB) or (2) brain drug delivery since they were more permeable to the blood-brain barrier (e.g. CPB).

  15. Controlling ferrofluid permeability across the blood–brain barrier model.

    PubMed

    Shi, Di; Sun, Linlin; Mi, Gujie; Sheikh, Lubna; Bhattacharya, Soumya; Nayar, Suprabha; Webster, Thomas J

    2014-02-21

    In the present study, an in vitro blood–brain barrier model was developed using murine brain endothelioma cells (b.End3 cells). Confirmation of the blood–brain barrier model was completed by examining the permeability of FITCDextran at increasing exposure times up to 96 h in serum-free medium and comparing such values with values from the literature. After such confirmation, the permeability of five novel ferrofluid (FF) nanoparticle samples, GGB (ferrofluids synthesized using glycine, glutamic acid and BSA), GGC (glycine, glutamic acid and collagen), GGP (glycine, glutamic acid and PVA), BPC (BSA, PEG and collagen) and CPB (collagen, PVA and BSA), was determined using this blood–brain barrier model. All of the five FF samples were characterized by zeta potential to determine their charge as well as TEM and dynamic light scattering for determining their hydrodynamic diameter. Results showed that FF coated with collagen passed more easily through the blood–brain barrier than FF coated with glycine and glutamic acid based on an increase of 4.5% in permeability. Through such experiments, diverse magnetic nanomaterials (such as FF) were identified for: (1) MRI use since they were less permeable to penetrate the blood–brain barrier to avoid neural tissue toxicity (e.g. GGB) or (2) brain drug delivery since they were more permeable to the blood–brain barrier (e.g. CPB). PMID:24457539

  16. Permeability enhancement by shock cooling

    NASA Astrophysics Data System (ADS)

    Griffiths, Luke; Heap, Michael; Reuschlé, Thierry; Baud, Patrick; Schmittbuhl, Jean

    2015-04-01

    The permeability of an efficient reservoir, e.g. a geothermal reservoir, should be sufficient to permit the circulation of fluids. Generally speaking, permeability decreases over the life cycle of the geothermal system. As a result, is usually necessary to artificially maintain and enhance the natural permeability of these systems. One of the methods of enhancement -- studied here -- is thermal stimulation (injecting cold water at low pressure). This goal of this method is to encourage new thermal cracks within the reservoir host rocks, thereby increasing reservoir permeability. To investigate the development of thermal microcracking in the laboratory we selected two granites: a fine-grained (Garibaldi Grey granite, grain size = 0.5 mm) and a course-grained granite (Lanhelin granite, grain size = 2 mm). Both granites have an initial porosity of about 1%. Our samples were heated to a range of temperatures (100-1000 °C) and were either cooled slowly (1 °C/min) or shock cooled (100 °C/s). A systematic microstructural (2D crack area density, using standard stereological techniques, and 3D BET specific surface area measurements) and rock physical property (porosity, P-wave velocity, uniaxial compressive strength, and permeability) analysis was undertaken to understand the influence of slow and shock cooling on our reservoir granites. Microstructurally, we observe that the 2D crack surface area per unit volume and the specific surface area increase as a result of thermal stressing, and, for the same maximum temperature, crack surface area is higher in the shock cooled samples. This observation is echoed by our rock physical property measurements: we see greater changes for the shock cooled samples. We can conclude that shock cooling is an extremely efficient method of generating thermal microcracks and modifying rock physical properties. Our study highlights that thermal treatments are likely to be an efficient method for the "matrix" permeability enhancement of

  17. PERMEABILITY OF BACTERIAL SPORES I.

    PubMed Central

    Black, S. H.; Gerhardt, Philipp

    1961-01-01

    Black, S. H. (The University of Michigan, Ann Arbor) and Philipp Gerhardt. Permeability of bacterial spores. I. Characterization of glucose uptake. J. Bacteriol. 82:743–749. 1961.—The total uptake of glucose by masses of clean, dormant spores was measured to assess their permeability. After correction for intercellular space, packed spores of Bacillus cereus strain terminalis were found in 87 determinations to be permeated by glucose to 40% of their weight. The glucose uptake was relatively independent of environmental variables, and thus was concluded to occur principally through a process of passive diffusion. PMID:13869665

  18. Improved magnetoelectric effect in magnetostrictive/piezoelectric composite with flux concentration effect for sensitive magnetic sensor

    NASA Astrophysics Data System (ADS)

    Zhang, Hao; Lu, Caijiang; Xu, Changbao; Xiao, Yingjie; Gui, Junguo; Lin, Chenhui; Xiao, Yong

    2015-04-01

    The magnetoelectric (ME) composite with the flux concentration effect is designed, fabricated, and characterized for detecting weak ac magnetic-field. The high-permeability Fe73.5Cu1Nb3Si13.5B9 (FeCuNbSiB) foils act as flux concentrators and are bonded at the free ends of traditional ME laminates. With the improved ME responses in the proposed ME composite based on the flux concentration effect, the output sensitivities under zero-biased magnetic field can reach 7 V/Oe and 15.8 mV/Oe under the resonance frequency of 177.36 kHz and the off-resonance frequency of 1 kHz, respectively. The results indicate that the proposed ME composites show promising applications for high-sensitivity self-biased magnetic field sensors and ME transducers.

  19. AC/RF Superconductivity

    SciTech Connect

    Ciovati, Gianluigi

    2015-02-01

    This contribution provides a brief introduction to AC/RF superconductivity, with an emphasis on application to accelerators. The topics covered include the surface impedance of normal conductors and superconductors, the residual resistance, the field dependence of the surface resistance, and the superheating field.

  20. AC solar cell

    SciTech Connect

    Schutten, H.P.; Benjamin, J.A.; Lade, R.W.

    1986-03-18

    An AC solar cell is described comprising: a pair of PN junction type solar cells connected in antiparallel between a pair of main terminals; and means for electrically directing light alternatingly without mechanical movement on the PN junctions to generate an alternating potential across the main terminals.

  1. AC 67 Launch Video

    NASA Technical Reports Server (NTRS)

    1987-01-01

    Live footage of the Unmanned Atlas Centaur (AC) 67 launch is presented on March 26, 1987 at the WESH television station in Florida. Lightning is shown after 49 seconds into the flight. The vehicle is totally destroyed due to a cloud-to-ground lightning flash.

  2. Ac-dc converter firing error detection

    SciTech Connect

    Gould, O.L.

    1996-07-15

    Each of the twelve Booster Main Magnet Power Supply modules consist of two three-phase, full-wave rectifier bridges in series to provide a 560 VDC maximum output. The harmonic contents of the twelve-pulse ac-dc converter output are multiples of the 60 Hz ac power input, with a predominant 720 Hz signal greater than 14 dB in magnitude above the closest harmonic components at maximum output. The 720 Hz harmonic is typically greater than 20 dB below the 500 VDC output signal under normal operation. Extracting specific harmonics from the rectifier output signal of a 6, 12, or 24 pulse ac-dc converter allows the detection of SCR firing angle errors or complete misfires. A bandpass filter provides the input signal to a frequency-to-voltage converter. Comparing the output of the frequency-to-voltage converter to a reference voltage level provides an indication of the magnitude of the harmonics in the ac-dc converter output signal.

  3. Total AC loss study of 2G HTS coils for fully HTS machine applications

    NASA Astrophysics Data System (ADS)

    Zhang, Min; Yuan, Weijia; Kvitkovic, Jozef; Pamidi, Sastry

    2015-11-01

    The application of HTS coils for fully HTS machines has become a new research focus. In the stator of an electrical machine, HTS coils are subjected to a combination of an AC applied current and AC external magnetic field. There is a phase shift between the AC current and AC magnetic field. In order to understand and estimate the total AC loss of HTS coils for electrical machines, we designed and performed a calorimetric measurement for a 2G HTS racetrack coil. Our measurement indicates that the total AC loss is greatly influenced by the phase shift between the applied current and the external magnetic field when the magnetic field is perpendicular to the tape surface. When the applied current and the external magnetic field are in phase, the total AC loss is the highest. When there is a 90 degree phase difference, the total AC loss is the lowest. In order to explain this phenomenon, we employ H formulation and finite element method to model the 2G HTS racetrack coil. Our calculation agrees well with experimental measurements. Two parameters are defined to describe the modulation of the total AC loss in terms of phase difference. The calculation further reveals that the influence of phase difference varies with magnetic field direction. The greatest influence of phase difference is in the perpendicular direction. The study provides key information for large-scale 2G HTS applications, e.g. fully HTS machines and superconducting magnetic energy storage, where the total AC loss subjected to both applied currents and external magnetic fields is a critical parameter for the design.

  4. High membrane permeability for melatonin.

    PubMed

    Yu, Haijie; Dickson, Eamonn J; Jung, Seung-Ryoung; Koh, Duk-Su; Hille, Bertil

    2016-01-01

    The pineal gland, an endocrine organ in the brain, synthesizes and secretes the circulating night hormone melatonin throughout the night. The literature states that this hormone is secreted by simple diffusion across the pinealocyte plasma membrane, but a direct quantitative measurement of membrane permeability has not been made. Experiments were designed to compare the cell membrane permeability to three indoleamines: melatonin and its precursors N-acetylserotonin (NAS) and serotonin (5-HT). The three experimental approaches were (1) to measure the concentration of effluxing indoleamines amperometrically in the bath while cells were being dialyzed internally by a patch pipette, (2) to measure the rise of intracellular indoleamine fluorescence as the compound was perfused in the bath, and (3) to measure the rate of quenching of intracellular fura-2 dye fluorescence as indoleamines were perfused in the bath. These measures showed that permeabilities of melatonin and NAS are high (both are uncharged molecules), whereas that for 5-HT (mostly charged) is much lower. Comparisons were made with predictions of solubility-diffusion theory and compounds of known permeability, and a diffusion model was made to simulate all of the measurements. In short, extracellular melatonin equilibrates with the cytoplasm in 3.5 s, has a membrane permeability of ∼1.7 µm/s, and could not be retained in secretory vesicles. Thus, it and NAS will be "secreted" from pineal cells by membrane diffusion. Circumstances are suggested when 5-HT and possibly catecholamines may also appear in the extracellular space passively by membrane diffusion. PMID:26712850

  5. Permeability of compacting porous lavas

    NASA Astrophysics Data System (ADS)

    Ashwell, P. A.; Kendrick, J. E.; Lavallée, Y.; Kennedy, B. M.; Hess, K.-U.; Aulock, F. W.; Wadsworth, F. B.; Vasseur, J.; Dingwell, D. B.

    2015-03-01

    The highly transient nature of outgassing commonly observed at volcanoes is in part controlled by the permeability of lava domes and shallow conduits. Lava domes generally consist of a porous outer carapace surrounding a denser lava core with internal shear zones of variable porosity. Here we examine densification using uniaxial compression experiments on variably crystalline and porous rhyolitic dome lavas from the Taupo Volcanic Zone. Experiments were conducted at 900°C and an applied stress of 3 MPa to 60% strain, while monitoring acoustic emissions to track cracking. The evolution of the porous network was assessed via X-ray computed tomography, He-pycnometry, and relative gas permeability. High starting connected porosities led to low apparent viscosities and high strain rates, initially accompanied by abundant acoustic emissions. As compaction ensued, the lavas evolved; apparent viscosity increased and strain rate decreased due to strain hardening of the suspensions. Permeability fluctuations resulted from the interplay between viscous flow and brittle failure. Where phenocrysts were abundant, cracks had limited spatial extent, and pore closure decreased axial and radial permeability proportionally, maintaining the initial anisotropy. In crystal-poor lavas, axial cracks had a more profound effect, and permeability anisotropy switched to favor axial flow. Irrespective of porosity, both crystalline samples compacted to a threshold minimum porosity of 17-19%, whereas the crystal-poor sample did not achieve its compaction limit. This indicates that unconfined loading of porous dome lavas does not necessarily form an impermeable plug and may be hindered, in part by the presence of crystals.

  6. High membrane permeability for melatonin

    PubMed Central

    Yu, Haijie; Dickson, Eamonn J.; Jung, Seung-Ryoung; Koh, Duk-Su

    2016-01-01

    The pineal gland, an endocrine organ in the brain, synthesizes and secretes the circulating night hormone melatonin throughout the night. The literature states that this hormone is secreted by simple diffusion across the pinealocyte plasma membrane, but a direct quantitative measurement of membrane permeability has not been made. Experiments were designed to compare the cell membrane permeability to three indoleamines: melatonin and its precursors N-acetylserotonin (NAS) and serotonin (5-HT). The three experimental approaches were (1) to measure the concentration of effluxing indoleamines amperometrically in the bath while cells were being dialyzed internally by a patch pipette, (2) to measure the rise of intracellular indoleamine fluorescence as the compound was perfused in the bath, and (3) to measure the rate of quenching of intracellular fura-2 dye fluorescence as indoleamines were perfused in the bath. These measures showed that permeabilities of melatonin and NAS are high (both are uncharged molecules), whereas that for 5-HT (mostly charged) is much lower. Comparisons were made with predictions of solubility-diffusion theory and compounds of known permeability, and a diffusion model was made to simulate all of the measurements. In short, extracellular melatonin equilibrates with the cytoplasm in 3.5 s, has a membrane permeability of ∼1.7 µm/s, and could not be retained in secretory vesicles. Thus, it and NAS will be “secreted” from pineal cells by membrane diffusion. Circumstances are suggested when 5-HT and possibly catecholamines may also appear in the extracellular space passively by membrane diffusion. PMID:26712850

  7. Dynamically tuned high-Q AC-dipole implementation

    SciTech Connect

    Oddo, P.; Bai, M.; Dawson, W.C.; Meng, W.; Mernick, K.; Pai, C.; Roser, T.; Russo, T.

    2010-05-02

    AC-dipole magnets are typically implemented as a parallel LC resonant circuit. To maximize efficiency, it's beneficial to operate at a high Q. This, however, limits the magnet to a narrow frequency range. Current designs therefore operate at a low Q to provide a wider bandwidth at the cost of efficiency. Dynamically tuning a high Q resonant circuit tries to maintain a high efficiency while providing a wide frequency range. The results of ongoing efforts at BNL to implement dynamically tuned high-Q AC dipoles will be presented.

  8. AC power systems handbook

    SciTech Connect

    Whitaker, J.

    1991-01-01

    Transient disturbances are what headaches are made of. Whatever you call them-spikes, surges, are power bumps-they can take your equipment down and leave you with a complicated and expensive repair job. Protection against transient disturbances is a science that demands attention to detail. This book explains how the power distribution system works, what can go wrong with it, and how to protect a facility against abnormalities. system grounding and shielding are covered in detail. Each major method of transient protection is analyzed and its relative merits discussed. The book provides a complete look at the critical elements of the ac power system. Provides a complete look at the ac power system from generation to consumption. Discusses the mechanisms that produce transient disturbances and how to protect against them. Presents diagrams to facilitate system design. Covers new areas, such as the extent of the transient disturbance problem, transient protection options, and stand-by power systems.

  9. Quantifying Evaporation in a Permeable Pavement System

    EPA Science Inventory

    Studies quantifying evaporation from permeable pavement systems are limited to a few laboratory studies and one field application. This research quantifies evaporation for a larger-scale field application by measuring the water balance from lined permeable pavement sections. Th...

  10. Permeable Pavement Research - Edison, New Jersey

    EPA Science Inventory

    This presentation provides the background and summary of results collected at the permeable pavement parking lot monitored at the EPA facility in Edison, NJ. This parking lot is surfaced with permeable interlocking concrete pavers (PICP), pervious concrete, and porous asphalt. ...

  11. DESIGN OF AN AC-DIPOLE FOR USE IN RHIC.

    SciTech Connect

    PARKER,B.; BAI,M.; JAIN,A.; MCINTYRE,G.; METH,M.; PEGGS,S.; ROSER,T.; SANDERS,R.; TRBOJEVIC,D.

    1999-03-29

    We present two options for implementing a pair of AC-dipoles in RHIC for spin flipping, measuring linear optical functions and nonlinear diagnostics. AC-dipoles are magnets that can be adiabatically excited and de-excited with a continuous sine-wave in order to coherently move circulating beam out to large betatron amplitudes without incurring emittance blow up [1]. The AGS already uses a similar device for getting polarized proton beams through depolarizing resonances [2]. By placing the magnets in the IP4 common beam region, two AC-dipoles are sufficient to excite both horizontal and vertical motion in both RHIC rings. While we initially investigated an iron-dominated magnet design using available steel tape cores; we now favor a new air coil plus ferrite design featuring mechanical frequency tuning, in order to best match available resources to demanding frequency sweeping requirements. Both magnet designs are presented here along with model magnet test results. The challenge is to make AC-dipoles available for year 2000 RHIC running.

  12. Novel additives to retard permeable flow

    SciTech Connect

    Golombok, Michael; Crane, Carel; Ineke, Erik; Welling, Marco; Harris, Jon

    2008-09-15

    Low concentrations of surfactant and cosolute in water, can selectively retard permeable flow in high permeability rocks compared to low permeability ones. This represents a way forward for more efficient areal sweep efficiency when water flooding a reservoir during improved oil recovery. (author)

  13. Review of hydrogen isotope permeability through materials

    SciTech Connect

    Steward, S.A.

    1983-08-15

    This report is the first part of a comprehensive summary of the literature on hydrogen isotope permeability through materials that do not readily form hydrides. While we mainly focus on pure metals with low permeabilities because of their importance to tritium containment, we also give data on higher-permeability materials such as iron, nickel, steels, and glasses.

  14. Vapor-liquid phase separator permeability results

    NASA Technical Reports Server (NTRS)

    Yuan, S. W. K.; Frederking, T. H. K.

    1981-01-01

    Continued studies are described in the area of vapor-liquid phase separator work with emphasis on permeabilities of porous sintered plugs (stainless steel, nominal pore size 2 micrometer). The temperature dependence of the permeability has been evaluated in classical fluid using He-4 gas at atmospheric pressure and in He-2 on the basis of a modified, thermosmotic permeability of the normal fluid.

  15. Structure/Permeability Relationships Of Polyimide Membranes

    NASA Technical Reports Server (NTRS)

    St. Clair, A. K.; Yamamoto, H.; Mi, Y.; Stern, S. A.

    1995-01-01

    Report describes experimental study of permeabilities, by each of five gases, of membranes made of four different polyimides. Conducted to gain understanding of effects of molecular structures of membranes on permeabilities and to assess potential for exploitation of selective permeability in gas-separation processes. Gases used: H2, O2, N2, CO2, and CH4.

  16. Superconducting magnet and fabrication method

    NASA Technical Reports Server (NTRS)

    Israelsson, Ulf E. (Inventor); Strayer, Donald M. (Inventor)

    1994-01-01

    A method of trapping a field in a block of superconductor material, includes providing (i) a block of material defining a bore, (ii) a high permeability core within the bore that defines a low reluctance path through the bore, (iii) a high permeability external structure on the exterior of the block of material that defines a low reluctance path between opposite ends of the core, and (iv) an electromagnet configured to apply a magnetic field around the high permeability core. The method proceeds by energizing the electromagnet to produce an applied magnetic field around the high permeability core, cooling the block of material sufficiently to render the block of material superconducting, de-energizing the electromagnet to result in a trapped magnetic field, and at least partially removing the low reluctance path defined by the core and the external structure in order to increase the magnetic flux density of the trapped magnetic field.

  17. Permeability enhancement using explosive techniques

    SciTech Connect

    Adams, T.F.; Schmidt, S.C.; Carter, W.J.

    1980-01-01

    In situ recovery methods for many of our hydrocarbon and mineral resources depend on the ability to create or enhance permeability in the resource bed to allow uniform and predictable flow. To meet this need, a new branch of geomechanics devoted to computer prediction of explosive rock breakage and permeability enhancement has developed. The computer is used to solve the nonlinear equations of compressible flow, with the explosive behavior and constitutive properties of the medium providing the initial/boundary conditions and material response. Once the resulting computational tool has been verified and calibrated with appropriate large-scale field tests, it can be used to develop and optimize commercially useful explosive techniques for in situ resource recovery.

  18. Scale-dependent permeability of fractured andesite

    NASA Astrophysics Data System (ADS)

    Heap, Michael; Kennedy, Ben

    2016-04-01

    Extension fractures in volcanic systems exist on all scales, from microscopic fractures to large fissures. They play a fundamental role in the movement of fluids and distribution of pore pressure, and therefore exert considerable influence over volcanic eruption recurrence. We present here laboratory permeability measurements for porous (porosity = 0.03-0.6) andesites before (i.e. intact) and after failure in tension (i.e., the samples host a throughgoing tensile fracture). The permeability of the intact andesites increases with increasing porosity, from 2 × 10-17 to 5 × 10-11 m2. Following fracture formation, the permeability of the samples (the effective permeability) falls within a narrow range regardless of their initial porosity: 2-6 × 10-11 m2. However, laboratory measurements of fractured samples likely overestimate the effective permeability due to the inherent scale-dependence of permeability. To better understand this scale-dependence, we first determined the permeability of the tensile fractures using a two-dimensional model that considers flow in parallel layers. Our calculations highlight that tensile fractures in low-porosity samples are more permeable (as high as 2.3 × 10-9 m2) than those in high-porosity samples (as low as 3.0 × 10-10 m2), a difference that can be explained by an increase in fracture tortuosity with porosity. We then use our fracture permeability data to model the effective permeability of rock with different host rock permeabilities (10-17 to 10-11 m2) populated by tensile fractures over a wide range of lengthscale. We find that the effective permeability of fractured andesite depends heavily on the initial host rock permeability and the scale of interest. At a given lengthscale, the effective permeability of high-permeability rock (10-12 to 10-11 m2) is essentially unaffected by the presence of numerous tensile fractures. By contrast, a single tensile fracture increases the effective permeability of low-permeability rock

  19. AC Zeeman potentials for atom chip-based ultracold atoms

    NASA Astrophysics Data System (ADS)

    Fancher, Charles; Pyle, Andrew; Ziltz, Austin; Aubin, Seth

    2015-05-01

    We present experimental and theoretical progress on using the AC Zeeman force produced by microwave magnetic near-fields from an atom chip to manipulate and eventually trap ultracold atoms. These AC Zeeman potentials are inherently spin-dependent and can be used to apply qualitatively different potentials to different spin states simultaneously. Furthermore, AC Zeeman traps are compatible with the large DC magnetic fields necessary for accessing Feshbach resonances. Applications include spin-dependent trapped atom interferometry and experiments in 1D many-body physics. Initial experiments and results are geared towards observing the bipolar detuning-dependent nature of the AC Zeeman force at 6.8 GHz with ultracold 87Rb atoms trapped in the vicinity of an atom chip. Experimental work is also underway towards working with potassium isotopes at frequencies of 1 GHz and below. Theoretical work is focused on atom chip designs for AC Zeeman traps produced by magnetic near-fields, while also incorporating the effect of the related electric near-fields. Electromagnetic simulations of atom chip circuits are used for mapping microwave propagation in on-chip transmission line structures, accounting for the skin effect, and guiding impedance matching.

  20. Constant permeability properties of Fe-based amorphous ribbon with inorganic coating

    NASA Astrophysics Data System (ADS)

    Okazaki, Y.; Kitagawa, H.; Yanase, S.; Handa, S.

    2000-06-01

    Magnetic properties of Fe-based amorphous ribbon with an inorganic coating of lithium silicate have been investigated in a single sheet at 50 Hz. The high-permeability characteristics of Fe-based amorphous ribbons deteriorated by the coating and constant permeability of μ≅900 at H=900 A/m and μ≅330 at H=2500 A/m was obtained after annealing at 425 °C and 450 °C, respectively.

  1. Combining SIP and NMR Measurements to Develop Improved Estimates of Permeability in Sandstone Cores

    NASA Astrophysics Data System (ADS)

    Keating, K.; Binley, A. M.

    2013-12-01

    Permeability is traditionally measured in-situ by inducing groundwater flow using pumping, slug, or packer tests; however, these methods require the existence of wells, can be labor intensive and can be constrained by measurement support volumes. Indirect estimates of permeability based on geophysical techniques benefit from relatively short measurement times, do not require fluid extraction, and are non-invasive when made from the surface (or minimally invasive when made in a borehole). However, estimates of permeability based on a single geophysical method often require calibration for rock type, and cannot be used to uniquely determine all of the physical properties required to accurately determine permeability. In this laboratory study we present the first critical step towards developing a method for estimating permeability based on the synergistic coupling of two complementary geophysical methods: spectral induced polarization (SIP) and nuclear magnetic resonance (NMR). To develop an improved model for estimating permeability, laboratory SIP and NMR measurements were collected on a series of sandstone cores, covering a wide range of permeabilities. Current models for estimating permeability from each individual geophysical measurement were compared to independently obtained estimates of permeability. The comparison confirmed previous research showing that estimates from SIP or NMR alone only yield the permeability within order of magnitude accuracy and must be calibrated for rock type. Next, the geophysical parameters determined from SIP and NMR were compared to independent measurements the physical properties of the sandstone cores including gravimetric porosity and pores-size distributions (obtained from mercury injection porosimetry); this comparison was used to evaluate which geophysical parameter more consistently and accurately predicted each physical property. Finally, we present an improved method for estimating permeability in sandstone cores based

  2. Magnetic

    NASA Astrophysics Data System (ADS)

    Aboud, Essam; El-Masry, Nabil; Qaddah, Atef; Alqahtani, Faisal; Moufti, Mohammed R. H.

    2015-06-01

    The Rahat volcanic field represents one of the widely distributed Cenozoic volcanic fields across the western regions of the Arabian Peninsula. Its human significance stems from the fact that its northern fringes, where the historical eruption of 1256 A.D. took place, are very close to the holy city of Al-Madinah Al-Monawarah. In the present work, we analyzed aeromagnetic data from the northern part of Rahat volcanic field as well as carried out a ground gravity survey. A joint interpretation and inversion of gravity and magnetic data were used to estimate the thickness of the lava flows, delineate the subsurface structures of the study area, and estimate the depth to basement using various geophysical methods, such as Tilt Derivative, Euler Deconvolution and 2D modeling inversion. Results indicated that the thickness of the lava flows in the study area ranges between 100 m (above Sea Level) at the eastern and western boundaries of Rahat Volcanic field and getting deeper at the middle as 300-500 m. It also showed that, major structural trend is in the NW direction (Red Sea trend) with some minor trends in EW direction.

  3. Synthesis and complex permeability of Ni/SiO2 nanocomposite

    NASA Astrophysics Data System (ADS)

    Tang, N. J.; Zhong, W.; Liu, W.; Y Jiang, H.; Wu, X. L.; Du, Y. W.

    2004-12-01

    The magnetic properties of Ni/SiO2 nanocomposite prepared by a simple sol-gel combined hydrogen reduction method are reported. The real part \\mu ' of the permeability for Ni/SiO2 nanoparticles is almost independent of frequency up to at least 1 GHz, and the loss of \\mu '' is very small. Our method provides a promising route to fabricate fine soft-magnetic materials with good magnetic properties, especially in the high-frequency range.

  4. Coalbed methane reservoir characterization using magnetic susceptibility

    NASA Astrophysics Data System (ADS)

    Ivakhnenko, Aleksandr; Makhatova, Meruyert; Kalbekov, Arkhat; Baibussinova, Zhanar; Moldagereyeva, Anel

    2016-04-01

    This research describes a study of the dependence of the magnetic susceptibility (MS) and permeability as a new approach for coalbed methane (CBM) reservoir characterization. Experimental measurements were undertaken in coal cores from Kazakhstan (Karaganda Basin). The well sections containing coal are the area of high interest where regular deposition of sandstone, shale and coal is observed. The MS measurements were made by the core logging sensor with the sensitive area of the probe providing volume magnetic susceptibility values. Permeability has been determined by air permeameter. Both magnetic susceptibility and permeability have been measured at the same points. The obtained values of permeability and magnetic susceptibility exhibit the predicted pattern of deposition of reservoir rocks. Coal reservoirs generally is spaced between shale layers with extremely high MS values and highly low permeability. Sandstone with shale interlayers tends to be a transition area between shale and coal. Such tendency appears within several sections. The experimental results showed a strong correspondence between measured magnetic susceptibility and permeability of coal core samples. Therefore, inverse proportionality between magnetic susceptibility and permeability is observed. Generally, the high values of magnetic susceptibility correspond to low permeability, likewise the low diamagnetic MS values comply with high permeability of production zones. In a point of fact, linear proportionality appears as well due to fractures. In this case, permeability must be recalculated in relation to degree of fracturing. Magnetic susceptibility results could sometimes be affected by small content of ferrimagnetic minerals that resulted in high MS values. However, MS data demonstrated good correlations with permeability. The application of magnetic susceptibility values for coalbed methane reservoir characterization could be a non-destructive and rapid method potentially used in both

  5. Design of the ac dipole and compensation of saturation effects for the LANL synchrotron

    SciTech Connect

    Liu, J.; Greene, S.

    1987-08-01

    An ac dipole magnet, which can work in two accelerator energy modes of 45 GeV and 60 GeV, is reported for the LANL synchrotron. In order to reach high uniformity of magnetic field distribution in good field region, some effective measures are presented to compensate field errors due to the saturation at both edges of magnet poles.

  6. Identification of /sup 233/Ac

    SciTech Connect

    Chu, Y.Y.; Zhou, M.L.

    1983-09-01

    We report in this paper identification of the new isotope /sup 233/Ac. Uranium targets were irradiated with 28 GeV protons; after rapid retrieval of the target and separation of actinium from thorium, /sup 233/Ac was allowed to decay into the known /sup 233/Th daughter. Exhaustive chemical purification was employed to permit the identification of /sup 233/Th via its characteristic ..gamma.. radiations. The half-life derived for /sup 233/Ac from several experiments is 2.3 +- 0.3 min. The production cross section for /sup 233/Ac is 100 ..mu..b.

  7. AC resistance measuring instrument

    DOEpatents

    Hof, P.J.

    1983-10-04

    An auto-ranging AC resistance measuring instrument for remote measurement of the resistance of an electrical device or circuit connected to the instrument includes a signal generator which generates an AC excitation signal for application to a load, including the device and the transmission line, a monitoring circuit which provides a digitally encoded signal representing the voltage across the load, and a microprocessor which operates under program control to provide an auto-ranging function by which range resistance is connected in circuit with the load to limit the load voltage to an acceptable range for the instrument, and an auto-compensating function by which compensating capacitance is connected in shunt with the range resistance to compensate for the effects of line capacitance. After the auto-ranging and auto-compensation functions are complete, the microprocessor calculates the resistance of the load from the selected range resistance, the excitation signal, and the load voltage signal, and displays of the measured resistance on a digital display of the instrument. 8 figs.

  8. AC Resistance measuring instrument

    DOEpatents

    Hof, Peter J.

    1983-01-01

    An auto-ranging AC resistance measuring instrument for remote measurement of the resistance of an electrical device or circuit connected to the instrument includes a signal generator which generates an AC excitation signal for application to a load, including the device and the transmission line, a monitoring circuit which provides a digitally encoded signal representing the voltage across the load, and a microprocessor which operates under program control to provide an auto-ranging function by which range resistance is connected in circuit with the load to limit the load voltage to an acceptable range for the instrument, and an auto-compensating function by which compensating capacitance is connected in shunt with the range resistance to compensate for the effects of line capacitance. After the auto-ranging and auto-compensation functions are complete, the microprocessor calculates the resistance of the load from the selected range resistance, the excitation signal, and the load voltage signal, and displays of the measured resistance on a digital display of the instrument.

  9. Biopolymer system for permeability modification in porous media

    SciTech Connect

    Stepp, A.K.; Bryant, R.S.; Llave, F.M.

    1995-12-31

    New technologies are needed to reduce the current high rate of well abandonment. Improved sweep efficiency, reservoir conformance, and permeability modification can have a significant impact on oil recovery processes. Microorganisms can be used to selectively plug high-permeability zones to improve sweep efficiency and impart conformance control. Studies of a promising microbial system for polymer production were conducted to evaluate reservoir conditions in which this system would be effective. Factors which can affect microbial growth and polymer production include salinity, pH, temperature, divalent ions, presence of residual oil, and rock matrix. Flask tests and coreflooding experiments were conducted to optimize and evaluate the effectiveness of this system. Nuclear magnetic resonance imaging (NMRI) was used to visualize microbial polymer production in porous media. Changes in fluid distribution within the pore system of the core were detected.

  10. Magnetic transit-time flowmeter

    DOEpatents

    Forster, George A.

    1976-07-06

    The flow rate of a conducting fluid in a stream is determined by disposing two permanent-magnet flowmeters in the stream, one downstream of the other. Flow of the conducting fluid causes the generation of both d-c and a-c electrical signals, the a-c comprising flow noise. Measurement of the time delay between similarities in the a-c signals by cross-correlation methods provides a measure of the rate of flow of the fluid.

  11. Steam-water relative permeability

    SciTech Connect

    Ambusso, W.; Satik, C.; Home, R.N.

    1997-12-31

    A set of relative permeability relations for simultaneous flow of steam and water in porous media have been measured in steady state experiments conducted under the conditions that eliminate most errors associated with saturation and pressure measurements. These relations show that the relative permeabilities for steam-water flow in porous media vary approximately linearly with saturation. This departure from the nitrogen/water behavior indicates that there are fundamental differences between steam/water and nitrogen/water flows. The saturations in these experiments were measured by using a high resolution X-ray computer tomography (CT) scanner. In addition the pressure gradients were obtained from the measurements of liquid phase pressure over the portions with flat saturation profiles. These two aspects constitute a major improvement in the experimental method compared to those used in the past. Comparison of the saturation profiles measured by the X-ray CT scanner during the experiments shows a good agreement with those predicted by numerical simulations. To obtain results that are applicable to general flow of steam and water in porous media similar experiments will be conducted at higher temperature and with porous rocks of different wetting characteristics and porosity distribution.

  12. Determination of permeability index using Stoneley slowness analysis, NMR models, and formation evaluations: a case study from a gas reservoir, south of Iran

    NASA Astrophysics Data System (ADS)

    Hosseini, Mirhasan; Javaherian, Abdolrahim; Movahed, Bahram

    2014-10-01

    In hydrocarbon reservoirs, permeability is one of the most critical parameters with a significant role in the production of hydrocarbon resources. Direct determination of permeability using Stoneley waves has always had some difficulties. In addition, some un-calibrated empirical models such as Nuclear Magnetic Resonance (NMR) models and petrophysical evaluation model (intrinsic permeability) do not provide reliable estimates of permeability in carbonate formations. Therefore, utilizing an appropriate numerical method for direct determination of permeability using Stoneley waves as well as an appropriate calibration method for the empirical models is necessary to have reliable results. This paper shows the application of a numerical method, called bisection method, in the direct determination of permeability from Stoneley wave slowness. In addition, a linear regression (least squares) method was used to calibrate the NMR models including Schlumberger Doll Research (SDR) and Timur-Coates models as well as the intrinsic permeability equation (permeability from petrophysical evaluations). The Express Pressure Tester (XPT) permeability was considered as an option for the reference permeability. Therefore, all permeability models were validated for the Stoneley permeability and calibrated for the empirical models with the XPT permeability. In order to have a quantitative assessment on the results and compare the results before and after the calibration, the Root Mean Squares Error (RMSE) was calculated for each of the used models. The results for the Stoneley permeability showed that, in many points there was not much difference between the Stoneley permeability calculated by the bisection method and the XPT permeability. Comparing the results showed that the calibration of the empirical models reduced their RMSE values. As a result of the calibration, the RMSE was decreased by about 39% for the SDR model, 18% for the Timur-Coates model, and 91% for the petrophysical

  13. Experimental demonstration of isotropic negative permeability in a three-dimensional dielectric composite.

    PubMed

    Zhao, Qian; Kang, Lei; Du, B; Zhao, H; Xie, Q; Huang, X; Li, B; Zhou, J; Li, L

    2008-07-11

    Isotropic negative permeability resulting from Mie resonance is demonstrated in a three-dimensional (3D) dielectric composite consisting of an array of dielectric cubes. A strong subwavelength magnetic resonance, corresponding to the first Mie resonance, was excited in dielectric cubes by electromagnetic wave. Negative permeability is verified in the magnetic resonance area via microwave measurement and the dispersion properties. The resonance relies on the size and permittivity of the cubes. It is promising for construction of novel isotropic 3D left-handed materials with a simple structure. PMID:18764227

  14. An Approach to Measurment of Permeability/Permittivity Tensor of Ferrofluids

    NASA Astrophysics Data System (ADS)

    Mayer, Daniel

    2015-09-01

    The magnetic field acting on the ferrofluids causes microstructural conversions that result in a change of their permeability. For this physical phenomenon is referred to as field induced magnetism (FIMA). An experimental method is described for ferrofluids in this state to examine their permeability tensor. Also an analogous phenomenon is described also when there is a change of the ferrofluids permittivity. We call it field induced dielectric anisotropy (FIDA). The contribution describes the method of measuring of the permittivity tensor. It can be expected that the FIMA and FIDA of ferrofluids will find interesting applications in designing of various sensors, in measurement technology, in mechatronic and in other areas of practice.

  15. Quenching characteristics of a.c. superconducting coils

    NASA Astrophysics Data System (ADS)

    Akita, S.; Kasahara, H.; Torii, S.

    Quenching characteristics of two superconducting coils for a.c. use are investigated at different frequencies. One is impregnated with epoxy resin and the other is not. Both coils have experienced over 40 quenches in a.c. and d.c. The impregnated coil shows steady quenching currents for a.c. and the values are nearly the same as for d.c. On the other hand, quenching currents for a.c. in the non-impregnated coil are almost 80% of the trained-up d.c. quenching current and are scattered. Furthermore, the relationship between quenching currents and the estimated a.c. losses of the superconducting cable at the highest magnetic field point is investigated. According to the results of this investigation, the cause of quench in the impregnated coil is assumed to be the temperature rise of the winding due to a.c. losses, while the cause in the non-impregnated coil might be wire motion.

  16. Cooling Floor AC Systems

    NASA Astrophysics Data System (ADS)

    Jun, Lu; Hao, Ding; Hong, Zhang; Ce, Gao Dian

    The present HVAC equipments for the residential buildings in the Hot-summer-and-Cold-winter climate region are still at a high energy consuming level. So that the high efficiency HVAC system is an urgently need for achieving the preset government energy saving goal. With its advantage of highly sanitary, highly comfortable and uniform of temperature field, the hot-water resource floor radiation heating system has been widely accepted. This paper has put forward a new way in air-conditioning, which combines the fresh-air supply unit and such floor radiation system for the dehumidification and cooling in summer or heating in winter. By analyze its advantages and limitations, we found that this so called Cooling/ Heating Floor AC System can improve the IAQ of residential building while keep high efficiency quality. We also recommend a methodology for the HVAC system designing, which will ensure the reduction of energy cost of users.

  17. Digital ac monitor

    DOEpatents

    Hart, George W.; Kern, Jr., Edward C.

    1987-06-09

    An apparatus and method is provided for monitoring a plurality of analog ac circuits by sampling the voltage and current waveform in each circuit at predetermined intervals, converting the analog current and voltage samples to digital format, storing the digitized current and voltage samples and using the stored digitized current and voltage samples to calculate a variety of electrical parameters; some of which are derived from the stored samples. The non-derived quantities are repeatedly calculated and stored over many separate cycles then averaged. The derived quantities are then calculated at the end of an averaging period. This produces a more accurate reading, especially when averaging over a period in which the power varies over a wide dynamic range. Frequency is measured by timing three cycles of the voltage waveform using the upward zero crossover point as a starting point for a digital timer.

  18. Thermionic triode generates ac power

    NASA Technical Reports Server (NTRS)

    Kniazzeh, A. G. F.; Scharz, F. C.

    1970-01-01

    Electrostatic grid controls conduction cycle of thermionic diode to convert low dc output voltages to high ac power without undesirable power loss. An ac voltage applied to the grid of this new thermionic triode enables it to convert heat directly into high voltage electrical power.

  19. Vortex rings impinging on permeable boundaries

    NASA Astrophysics Data System (ADS)

    Mujal-Colilles, Anna; Dalziel, Stuart B.; Bateman, Allen

    2015-01-01

    Experiments with vortex rings impinging permeable and solid boundaries are presented in order to investigate the influence of permeability. Utilizing Particle Image Velocimetry, we compared the behaviour of a vortex ring impinging four different reticulated foams (with permeability k ˜ 26 - 85 × 10-8 m2) and a solid boundary. Results show how permeability affects the stretching phenomena of the vortex ring and the formation and evolution of the secondary vortex ring with opposite sign. Moreover, permeability also affects the macroscopic no-slip boundary condition found on the solid boundary, turning it into an apparent slip boundary condition for the most permeable boundary. The apparent slip-boundary condition and the flux exchange between the ambient fluid and the foam are jointly responsible for both the modified formation of the secondary vortex and changes on the vortex ring diameter increase.

  20. Modeling Mechanically-Induced Permeability Changes in Subsurface Reservoirs

    NASA Astrophysics Data System (ADS)

    White, J. A.

    2012-12-01

    Several energy technologies---including carbon sequestration, geothermal energy, and shale gas production---involve injecting large volumes of fluid into the subsurface. These injections inevitably change in-situ effective stress condition, which in turn can lead to important changes in permeability. New fluid migration pathways may be created, and existing ones may be enhanced. From a computational perspective, modeling these processes introduces a variety of challenges---including strong hydromechanical coupling, large length-scale disparities, and highly nonlinear constitutive behavior. As a motivating example, here we consider a mixed finite element formulation of multiphase fluid flow through deformable porous media. A coupled damage/permeability model is introduced to model the rock constitutive behavior. At each timestep, the resulting discrete, nonlinear system is solved using a Newton-Krylov algorithm. A key challenge that has prevented wide-scale adoption of fully-coupled models is the lack of good preconditioning strategies for this class of problems. In light of this need, we discuss a block-structured approach that leads to scalable behavior. This work was performed under the auspices of the U.S. Department of Energy by Lawrence Livermore National Laboratory under Contract DE-AC52-07NA27344.

  1. Permeability and corrosion behavior of phenoxy coatings

    SciTech Connect

    Tiburcio, A.C.; Manson, J.A.

    1993-12-31

    The corrosion behavior of a glass-bead-filled phenoxy coating system was studied by correlating permeability and electrochemical measurements with actual corrosion performance. The study emphasized the effects of filler and filler/polymer matrix interactions on corrosion behavior. Water vapor permeability, dissolved oxygen permeability and conductivity measurements were made to determine the rate of transport of the three key ingredients in cathodic delamination and corrosion process (H{sub 2}O, O{sub 2}, and cation). The glass bead filler had a greater effect on both cathodic delamination and corrosion behavior than filler/polymer matrix interaction. Overall, the permeability behavior controlled the delamination and corrosion performance.

  2. Shape effect on the negative equivalent permeabilities of chevronic thin films of silver

    NASA Astrophysics Data System (ADS)

    Jen, Yi-Jun; Yu, Ching-Wei; Wang, Yu-Hsiung

    2010-08-01

    In this work, the chevronic films composed of silver nanorods are fabricated using glancing angle deposition (GLAD). The chevronic structure is grown by bidepositing opposite nanorods sequentially: the substrate is oriented at the polar angle Φ=0 deg (about the substrate's normal) for the bottom rods and Φ180 deg for the top rods. When the applied electric field is parallel to the plane Φ= deg, the induced magnetic dipole moment between nanorods leads to a negative real part of the equivalent permeability. The equivalent refractive indices, the equivalent permittivities and the equivalent permeabilities of chevronic films with thickness 230 +/- 5 nm for p-polarized light are measured by walk-off interferometer. The equivalent permeabilities of chevronic films with lengths of top rods 291 nm, 409 and 509 nm and bottom rods 512 nm, 378 nm and 301 nm are measured to be -2.406+0.443 i, -3.870+2.109 i and -2.126+0.904 i at the wavelength of 639 nm, respectively. The shape affects the real part of the equivalent permeability significantly. When the length of the top rods is longer than that of the bottom rods, the magnetic dipole moment between nanorods is suppressed and the quantity of the equivalent permeability becomes small. The real part of equivalent permeability of the chevronic film is related to the lengths of top and bottom nanorods.

  3. Introducing AC inductive reactance with a power tool

    NASA Astrophysics Data System (ADS)

    Bryant, Wesley; Baker, Blane

    2016-09-01

    The concept of reactance in AC electrical circuits is often non-intuitive and difficult for students to grasp. In order to address this lack of conceptual understanding, classroom exercises compare the predicted resistance of a power tool, based on electrical specifications, to measured resistance. Once students discover that measured resistance is smaller than expected, they are asked to explain these observations using previously studied principles of magnetic induction. Exercises also introduce the notion of inductive reactance and impedance in AC circuits and, ultimately, determine self-inductance of the motor windings within the power tool.

  4. Study of AC/RF properties of SRF ingot niobium

    SciTech Connect

    Dhakal, Pashupati; Tsindlekht, Menachem I; Genkin, Valery M; Ciovati, Gianluigi; Myneni, Ganapati Rao

    2013-09-01

    In an attempt to correlate the performance of superconducting radiofrequency cavities made of niobium with the superconducting properties, we present the results of the magnetization and ac susceptibility of the niobium used in the superconducting radiofrequency cavity fabrication. The samples were subjected to buffer chemical polishing (BCP) surface and high temperature heat treatments, typically applied to the cavities fabrications. The analysis of the results show the different surface and bulk ac conductivity for the samples subjected to BCP and heat treatment. Furthermore, the RF surface impedance is measured on the sample using a TE011 microwave cavity for a comparison to the low frequency measurements.

  5. EXT-II: a second generation advanced ac propulsion system

    SciTech Connect

    Bates, B.; Patil, P.B.; Ciccarelli, M.F.

    1986-01-01

    This paper discusses the characteristics of the concept and includes discussion of the system constraints, including traction battery constraints, and brief descriptions of the major subsystems being developed. The components discussed include: the system controller, dc to ac inverter, an internal permanent magnet ac motor and a two-speed automatic transmission with an integral final drive and differential. The motor and transmission are on a common axis and are integrated into one compact unit that is integral with the rear axle of the vehicle.

  6. Modulation of Blood–Brain Barrier Permeability in Mice Using Synthetic E-Cadherin Peptide

    PubMed Central

    2015-01-01

    The present work characterizes the effects of synthetic E-cadherin peptide (HAV) on blood–brain barrier (BBB) integrity using various techniques including magnetic resonance imaging (MRI) and near-infrared fluorescent imaging (NIRF). The permeability of small molecular weight permeability marker gadolinium diethylenetriaminepentaacetate (Gd-DTPA) contrast agent, the large molecular weight permeability marker, IRDye 800CW PEG, and the P-glycoprotein (P-gp) efflux transporter contrast agent, rhodamine 800 (R800), were examined in the presence and absence of HAV peptide. The results consistently demonstrated that systemic iv administration of HAV peptide resulted in a reversible disruption of BBB integrity and enhanced the accumulation of all the dyes examined. The magnitude of increase ranged from 2-fold to 5-fold depending on the size and the properties of the permeability markers. The time frame for BBB disruption with HAV peptide was rapid, occurring within 3–6 min following injection of the peptide. Furthermore, modulation of BBB permeability was reversible with the barrier integrity being restored within 60 min of the injection. The increased BBB permeability observed following HAV peptide administration was not attributable to changes in cerebral blood flow. These studies support the potential use of cadherin peptides to rapidly and reversibly modulate BBB permeability of a variety of therapeutic agents. PMID:24495091

  7. Permeability of the blood–brain barrier predicts conversion from optic neuritis to multiple sclerosis

    PubMed Central

    Modvig, Signe; Simonsen, Helle J.; Frederiksen, Jette L.; Larsson, Henrik B. W.

    2015-01-01

    Optic neuritis is an acute inflammatory condition that is highly associated with multiple sclerosis. Currently, the best predictor of future development of multiple sclerosis is the number of T2 lesions visualized by magnetic resonance imaging. Previous research has found abnormalities in the permeability of the blood–brain barrier in normal-appearing white matter of patients with multiple sclerosis and here, for the first time, we present a study on the capability of blood–brain barrier permeability in predicting conversion from optic neuritis to multiple sclerosis and a direct comparison with cerebrospinal fluid markers of inflammation, cellular trafficking and blood–brain barrier breakdown. To this end, we applied dynamic contrast-enhanced magnetic resonance imaging at 3 T to measure blood–brain barrier permeability in 39 patients with monosymptomatic optic neuritis, all referred for imaging as part of the diagnostic work-up at time of diagnosis. Eighteen healthy controls were included for comparison. Patients had magnetic resonance imaging and lumbar puncture performed within 4 weeks of onset of optic neuritis. Information on multiple sclerosis conversion was acquired from hospital records 2 years after optic neuritis onset. Logistic regression analysis showed that baseline permeability in normal-appearing white matter significantly improved prediction of multiple sclerosis conversion (according to the 2010 revised McDonald diagnostic criteria) within 2 years compared to T2 lesion count alone. There was no correlation between permeability and T2 lesion count. An increase in permeability in normal-appearing white matter of 0.1 ml/100 g/min increased the risk of multiple sclerosis 8.5 times whereas having more than nine T2 lesions increased the risk 52.6 times. Receiver operating characteristic curve analysis of permeability in normal-appearing white matter gave a cut-off of 0.13 ml/100 g/min, which predicted conversion to multiple sclerosis with a

  8. Factors affecting initial permeability of Co-substituted Ni-Zn-Cu ferrites

    SciTech Connect

    Byun, T.Y.; Byeon, S.C.; Hong, K.S.; Kim, C.K.

    1999-09-01

    Iron deficient compositions of (Ni{sub 0.2}Cu{sub 0.2}Zn{sub 0.6}){sub 1.02{minus}x}Co{sub x}Fe{sub 1.98}O{sub 4} (0 {le} x {le} 0.05) were prepared to investigate their initial permeability dependence on cobalt contents. Extrinsic factors such as grain size and sintered density change little in samples sintered at 900 C, so their effects on permeability can be neglected. Intrinsic factors such as saturation magnetization, magnetocrystalline anisotropy (K{sub 1}) and magnetoelastic anisotropy (K{sub {sigma}}) can not account for the variation of initial permeability with Co content. Measurement of thermoelectric power shows that the concentration of cation vacancies increases with Co content. Therefore, the local induced anisotropy increases by the ordering of Co ions cia increased cation vacancy concentration. This increase in induced anisotropy results in the decrease of initial permeability.

  9. Magnetic elastomers for stretchable inductors.

    PubMed

    Lazarus, Nathan; Meyer, Chris D; Bedair, Sarah S; Slipher, Geoffrey A; Kierzewski, Iain M

    2015-05-20

    In this work, silicone loaded with magnetic particles is investigated for creating a composite with higher permeability while still maintaining stretchability. Magnetic and mechanical properties are first characterized for composites based on both spherical and platelet particle geometries. The first magnetic-core stretchable inductors are then demonstrated using the resulting ferroelastomer. Solenoid inductors based on liquid metal galinstan are then demonstrated around a ferroelastomeric core and shown to survive uniaxial strains up to 100%. Soft elastomers loaded with magnetic particles were found to increase the core permeability and inductance density of stretchable inductors by nearly 200%. PMID:25945395

  10. Operation Method for AC Motor Control during Power Interruption in Direct AC/AC Converter System

    NASA Astrophysics Data System (ADS)

    Shizu, Keiichiro; Azuma, Satoshi

    Direct AC/AC converters have been studied due to their potential use in power converters with no DC-link capacitor, which can contribute to the miniaturization of power converters. However, the absence of a DC-link capacitor makes it difficult to control the AC motor during power interruption. First, this paper proposes a system that realizes AC motor control during power interruption by utilizing a clamp capacitor. In general, direct AC/AC converters have a clamp circuit consisting of a rectifier diode(s) and a clamp capacitor in order to avoid over-voltages. In the proposed system, there is an additional semiconductor switch reverse-parallel to the rectifier diode(s), and the clamp capacitor voltage can be utilized for AC motor control by turning on the additional switch. Second, this paper discusses an operation method for AC motor control and clamp capacitor voltage control during power interruption. In the proposed method “DC-link voltage control”, the kinetic energy in the AC motor is transformed into electrical energy and stored in the clamp capacitor; the clamp capacitor is therefore charged and the capacitor voltage is controlled to remain constant at an instruction value. Third, this paper discusses a switching operation during power interruption. A dead-time is introduced between the operation of turning off all switches on the rectifier side and the operation of turning on the additional switch, which prevents the occurrence of a short circuit between the interrupted power source and the clamp capacitor. Finally, experimental results are presented. During power interruptions, an output current was continuously obtained and the clamp capacitor voltage was maintained to be equal to the instruction value of the capacitor voltage. These results indicate that both AC motor control and capacitor voltage control were successfully achieved by using the proposed system.

  11. Permeability determination through NMR detection of acoustically induced fluid oscillation.

    PubMed

    Looyestijn, Wim J; Smits, Robert M M; Abu-Shiekah, Issa; Kuvshinov, Boris; Hofman, Jan P; Schwing, Alex

    2006-11-01

    We present a novel approach for directly measuring the permeability of reservoir rocks by an instrument lowered in a well bore. The measurement is made by creating an oscillatory motion of fluids in the pores by acoustic stimulation and by detecting the amplitude response as a phase shift on a nuclear magnetic resonance relaxation signal. A full theoretical description is given. The feasibility of the method has been verified in the laboratory on a set of sandstone and carbonate samples spanning the entire range of practical interest. PMID:17071341

  12. Effective permeability tensor and double resonance of interacting bistable ferromagnetic nanowires

    NASA Astrophysics Data System (ADS)

    Boucher, Vincent; Carignan, Louis-Philippe; Kodera, Toshiro; Caloz, Christophe; Yelon, Arthur; Ménard, David

    2009-12-01

    We present a model for the effective permeability tensor of nonsaturated arrays of axially magnetized bistable ferromagnetic wires based on a Maxwell-Garnett formalism generalized to include the case of two oppositely magnetized wire populations. Explicit expressions for the complex diagonal and off-diagonal components of the effective permeability tensor are derived to describe the magnetic response of the array and its dependence upon microwave frequency and external magnetic field. The model accounts for the geometrical parameters and the static magnetic configuration of the array, as well as the shape and intrinsic properties of the wires. We incorporate the effect of the static and dynamic interwire dipolar interactions and obtain explicit expressions for the position and relative amplitude of the two ferromagnetic resonance peaks associated with the effective permeability of nonsaturated arrays. The two absorption peaks arise due to the presence of the up and down wire populations, which are predominantly excited by the right-handed and left-handed circularly polarized magnetic field components of the electromagnetic wave propagating inside the array. Excellent agreement is found between the model and experimental results obtained from S -parameter broadband microstrip line measurements. Small discrepancies when the array is magnetically unsaturated or when the peaks are close to each other are discussed and attributed to spatial variations of the local interaction field not accounted for by the present model.

  13. Permeability-porosity data sets for sandstones

    USGS Publications Warehouse

    Nelson, P.H.

    2004-01-01

    Due to the variable nature of permeability-porosity relations, core should be obtained and permeability (k) and porosity (??) should be determined on core plugs in the laboratory for the formation of interest. A catalog of k versus (??) data sets is now available on the Web. Examples from the catalog are considered to illustrate some aspects of k versus ?? dependencies in siliciclastic reservoirs.

  14. Pressure sensitivity of low permeability sandstones

    USGS Publications Warehouse

    Kilmer, N.H.; Morrow, N.R.; Pitman, J.K.

    1987-01-01

    Detailed core analysis has been carried out on 32 tight sandstones with permeabilities ranging over four orders of magnitude (0.0002 to 4.8 mD at 5000 psi confining pressure). Relationships between gas permeability and net confining pressure were measured for cycles of loading and unloading. For some samples, permeabilities were measured both along and across bedding planes. Large variations in stress sensitivity of permeability were observed from one sample to another. The ratio of permeability at a nominal confining pressure of 500 psi to that at 5000 psi was used to define a stress sensitivity ratio. For a given sample, confining pressure vs permeability followed a linear log-log relationship, the slope of which provided an index of pressure sensitivity. This index, as obtained for first unloading data, was used in testing relationships between stress sensitivity and other measured rock properties. Pressure sensitivity tended to increase with increase in carbonate content and depth, and with decrease in porosity, permeability and sodium feldspar. However, scatter in these relationships increased as permeability decreased. Tests for correlations between pressure sensitivity and various linear combinations of variables are reported. Details of pore structure related to diagenetic changes appears to be of much greater significance to pressure sensitivity than mineral composition. ?? 1987.

  15. Effect of Dead Algae on Soil Permeability

    SciTech Connect

    Harvey, R.S.

    2003-02-21

    Since existing basins support heavy growths of unicellular green algae which may be killed by temperature variation or by inadvertent pH changes in waste and then deposited on the basin floor, information on the effects of dead algae on soil permeability was needed. This study was designed to show the effects of successive algal kills on the permeability of laboratory soil columns.

  16. Intestinal permeability and contractility in murine colitis.

    PubMed Central

    van Meeteren, M E; van Bergeijk, J D; van Dijk, A P; Tak, C J; Meijssen, M A; Zijlstra, F J

    1998-01-01

    We developed an in vitro organ bath method to measure permeability and contractility simultaneously in murine intestinal segments. To investigate whether permeability and contractility are correlated and influenced by mucosal damage owing to inflammation, BALB/c mice were exposed to a 10% dextran sulphate sodium (DSS) solution for 8 days to induce colitis. The effect of pharmacologically induced smooth muscle relaxation and contraction on permeability was tested in vitro. Regional permeability differences were observed in both control and 10% DSS-treated mice. Distal colon segments were less permeable to 3H-mannitol and 14C-PEG 400 molecules compared with proximal colon and ileum. Intestinal permeability in control vs. 10% DSS mice was not altered, although histologic inflammation score and IFN-gamma pro-inflammatory cytokine levels were significantly increased in proximal and distal colon. IL-1beta levels were enhanced in these proximal and distal segments, but not significantly different from controls. Any effect of pharmacologically induced contractility on intestinal permeability could not be observed. In conclusion, intestinal permeability and contractility are not correlated in this model of experimentally induced colitis in mice. Although simultaneous measurement in a physiological set-up is possible, this method has to be further validated. PMID:9705603

  17. Accurate determination of characteristic relative permeability curves

    NASA Astrophysics Data System (ADS)

    Krause, Michael H.; Benson, Sally M.

    2015-09-01

    A recently developed technique to accurately characterize sub-core scale heterogeneity is applied to investigate the factors responsible for flowrate-dependent effective relative permeability curves measured on core samples in the laboratory. The dependency of laboratory measured relative permeability on flowrate has long been both supported and challenged by a number of investigators. Studies have shown that this apparent flowrate dependency is a result of both sub-core scale heterogeneity and outlet boundary effects. However this has only been demonstrated numerically for highly simplified models of porous media. In this paper, flowrate dependency of effective relative permeability is demonstrated using two rock cores, a Berea Sandstone and a heterogeneous sandstone from the Otway Basin Pilot Project in Australia. Numerical simulations of steady-state coreflooding experiments are conducted at a number of injection rates using a single set of input characteristic relative permeability curves. Effective relative permeability is then calculated from the simulation data using standard interpretation methods for calculating relative permeability from steady-state tests. Results show that simplified approaches may be used to determine flowrate-independent characteristic relative permeability provided flow rate is sufficiently high, and the core heterogeneity is relatively low. It is also shown that characteristic relative permeability can be determined at any typical flowrate, and even for geologically complex models, when using accurate three-dimensional models.

  18. Influence of fiber packing structure on permeability

    NASA Technical Reports Server (NTRS)

    Cai, Zhong; Berdichevsky, Alexander L.

    1993-01-01

    The study on the permeability of an aligned fiber bundle is the key building block in modeling the permeability of advanced woven and braided preforms. Available results on the permeability of fiber bundles in the literature show that a substantial difference exists between numerical and analytical calculations on idealized fiber packing structures, such as square and hexagonal packing, and experimental measurements on practical fiber bundles. The present study focuses on the variation of the permeability of a fiber bundle under practical process conditions. Fiber bundles are considered as containing openings and fiber clusters within the bundle. Numerical simulations on the influence of various openings on the permeability were conducted. Idealized packing structures are used, but with introduced openings distributed in different patterns. Both longitudinal and transverse flow are considered. The results show that openings within the fiber bundle have substantial effect on the permeability. In the longitudinal flow case, the openings become the dominant flow path. In the transverse flow case, the fiber clusters reduce the gap sizes among fibers. Therefore the permeability is greatly influenced by these openings and clusters, respectively. In addition to the porosity or fiber volume fraction, which is commonly used in the permeability expression, another fiber bundle status parameter, the ultimate fiber volume fraction, is introduced to capture the disturbance within a fiber bundle.

  19. Relating P-wave attenuation to permeability

    SciTech Connect

    Akbar, N.; Dvorkin, J.; Nur, A. . Dept. of Geophysics)

    1993-01-01

    To relate P-wave attenuation to permeability, the authors examine a three-dimensional (3-D) theoretical model of a cylindrical pore filled with viscous fluid and embedded in an infinite isotropic elastic medium. They calculate both attenuation and permeability as functions of the direction of wave propagation. Attenuation estimates are based on the squirt flow mechanism; permeability is calculated using the Kozeny-Carmen relation. They find that in the case when a plane P-wave propagates parallel to this orientation (Q[sup [minus]1][delta] = 90[degree]), attenuation is always higher than when a wave propagates parallel to this orientation (Q[sup [minus]1][delta] = 0[degree]). The ratio of these two attenuation values Q[sup [minus]1][delta] = 90[degree]/Q[sup [minus]1] = 0[degree] increases with an increasing pore radius and decreasing frequency and saturation. By changing permeability, varying the radius of the pore, they find that the permeability-attenuation relation is characterized by a peak that shifts toward lower permeabilities as frequency decreases. Therefore, the attenuation of a low-frequency wave decreases with increasing permeability. They observe a similar trend on relations between attenuation and permeability experimentally obtained on sandstone samples.

  20. A method of determination of permeability

    SciTech Connect

    Kuznetsov, S.V.; Trofimov, V.A.

    2007-11-15

    A method is proposed for determining permeability of coals under conditions of steady-state deformation and stationary filtration mode by employing a reference core made of gas-non-sorbing material with a known permeability. The approach has been developed to assess the time of transition to the stable filtration.

  1. MRI evaluation of BBB disruption after adjuvant AcSDKP treatment of stroke with tPA in rat.

    PubMed

    Ding, G; Zhang, Z; Chopp, M; Li, L; Zhang, L; Li, Q; Wei, M; Jiang, Q

    2014-06-20

    The primary limitation of thrombolytic treatment of ischemic stroke with tissue plasminogen activator (tPA) is the hemorrhagic risk. We tested AcSDKP (N-acetyl-seryl-aspartyl-lysyl-proline), as an auxiliary therapeutic agent, to reduce blood-brain barrier (BBB) disruption in a combination tPA thrombolytic treatment of stroke. Wistar rats subjected to embolic stroke were randomly assigned to either the tPA monotherapy group (n=9) or combination of tPA and AcSDKP treatment group (n=9) initiated at 4 h after ischemia. Magnetic resonance imaging (MRI) measurements were performed before and after the treatments. Immunohistochemical staining and measurements were performed to confirm MRI findings. Longitudinal MRI permeability measurements with gadolinium-diethylenetriamine penta-acetic acid (Gd-DTPA) demonstrated that combination treatment of acute embolic stroke with AcSDKP and tPA significantly reduced BBB leakage, compared to tPA monotherapy, at 3 and 6 days (18.3±9.8 mm3 vs. 65.0±21.0 mm3, p<0.001) after the onset of stroke, although BBB leakage was comparable between the two groups prior to the treatments (6.8±4.4 mm3 vs. 4.3±3.3 mm3, p>0.18). The substantial reduction of BBB leakage observed in the combination treatment group was closely associated with reduced ischemic lesions measured by T2 maps (113.6±24.9 mm3 vs. 188.1±60.8 mm3, p<0.04 at 6 days). Histopathological analysis of the same population of rats showed that the combination treatment significantly reduced parenchymal fibrin deposition (0.063±0.059 mm2 vs. 0.172±0.103 mm2, p<0.03) and infarct volume (146.7±35.9 mm3 vs. 199.3±60.4 mm3, p<0.05) compared to the tPA monotherapy at 6days after stroke. MRI provides biological insight into the therapeutic benefit of combination treatment of stroke with tPA and AcSDKP 4h after onset, and demonstrates significantly improved cerebrovascular integrity with neuroprotective effects compared with tPA monotherapy. PMID:24769225

  2. Thermal and magnetic dual-responsive liposomes with a cell-penetrating peptide-siRNA conjugate for enhanced and targeted cancer therapy.

    PubMed

    Yang, Yanfang; Xie, Xiangyang; Xu, Xueqing; Xia, Xuejun; Wang, Hongliang; Li, Lin; Dong, Wujun; Ma, Panpan; Yang, Yang; Liu, Yuling; Mei, Xingguo

    2016-10-01

    Due to the absence of effective in vivo delivery systems, the employment of small interfering RNA (siRNA) in the clinic has been hindered. Here, we describe a novel siRNA targeting system that combines features of biological (cell-permeable peptides, CPPs) and physical (magnetic) siRNA targeting for use in magnetic hyperthermia-triggered release. A siRNA-CPPs conjugate (siRNA-CPPs) was loaded into thermal and magnetic dual-responsive liposomes (TML) (siRNA-CPPs/TML), and in vitro siRNA-CPPs thermosensitive release activity, targeted cellular uptake, gene silencing efficiency, in vivo targeted delivery and in vivo antitumor activity were determined. The results demonstrated that siRNA-CPPs/TML exhibited good physicochemical properties, effective cellular uptake, endosomal escape and a significant gene silencing efficiency in MCF-7 cells in vitro. Additionally, in the in vivo study, siRNA-CPPs/TML under an alternating current (AC) magnetic field displayed a superior in vivo targeted delivery efficacy, antitumor efficacy and gene silencing efficiency in a MCF-7 xenograft murine model. In conclusion, the application of siRNA-CPPs/TML under an AC magnetic field represents a new strategy for the selective and efficient delivery of siRNA. PMID:27429294

  3. A complex permittivity and permeability measurement system for elevated temperatures

    NASA Technical Reports Server (NTRS)

    Friederich, Paul

    1990-01-01

    The three goals of this research include: (1) to fully develop a method to measure the permittivity and permeability of special materials as a function of frequency in the range of 2.6 to 18 GHz, and of temperatures in the range of 25 to 1100 C; (2) to assist LeRC in setting up an in-house system for the measurement of high-temperature permittivity and permeability; and (3) to measure the complex permittivity and permeability of special materials as a function of frequency and temperature to demonstrate the capability of the method. The method chosen for characterizing the materials relies on perturbation of a resonant cavity with a small volume of sample material. Different field configurations in the cavity can be used to separate electric and magnetic effects. The cavity consists of a section of rectangular waveguide terminated at each end of a vertical slot iris. The center of one wall is a small hole through which the sample is introduced.

  4. A complex permittivity and permeability measurement system for elevated temperatures

    NASA Technical Reports Server (NTRS)

    Friederich, Paul

    1990-01-01

    The three goals of this research include: (1) to fully develop a method to measure the permittivity and permeability of special materials as a function of frequency in the range of 2.6 to 18 GHz, and of temperature in the range of 25 to 1100 C; (2) to assist LeRC in setting up an in-house system for the measurement of high-temperature permittivity and permeability; and (3) to measure the complex permittivity and permeability of special materials as a function of frequency and temperature to demonstrate the capability of the method. The method chosen for characterizing the materials relies on perturbation of a resonant cavity with a small volume of sample material. Different field configurations in the cavity can be used to separate electric and magnetic effects. The cavity consists of a section of rectangular waveguide terminated at each end of a vertical slot iris. In the center of one wall is a small hole through which the sample is introduced.

  5. Ac loss characteristics of YBCO superconducting tapes fabricated by TFA-MOD technique

    NASA Astrophysics Data System (ADS)

    Iwakuma, Masataka; Nigo, Masahiro; Inoue, Daisuke; Miyamoto, Naoya; Kiss, Takanobu; Funaki, Kazuo; Iijima, Yasuhiro; Saitoh, Takashi; Izumi, Teruo; Yamada, Yutaka; Shiohara, Yuu

    2005-10-01

    We investigated the ac loss properties of a YBCO superconducting tape fabricated by TFA-MOD technique. The thickness of the YBCO layer is 1.2 μm. A 6-tape stack of 50 mm in length and 10 mm in width was inserted into a saddle-shaped pickup coil. The ac loss was measured at 35-77 K by applying an external ac magnetic field. The magnetic field angle was changed by rotating the sample stack around its longitudinal axis. The effective penetration field, which corresponds to the breaking point of an ac loss curve, decreased with increasing field angle though it was much smaller than that which was estimated for a superconducting slab with the same thickness as the width of a tape. As a result, the ac loss increased monotonically with an increasing field angle against the wide surface for any amplitude. The observed field angular dependence of the ac loss agreed with the theoretically predicted one by using the observed ac losses in perpendicular magnetic field. Anyway the ac loss for a larger amplitude than the effective penetration field was proportional to the critical current density and the projective width of a tape in the direction of the applied magnetic field for any field angle and any temperature as well known. In addition we estimated the magnetic field, B, dependence of the critical current, Ic, from the observed magnetization curves. It was shown that zero-field Ic appeared to be a linear function of temperature and Ic-B characteristics was scaled with zero-field Ic. We also discussed a difference in Ic-B characteristics and its temperature dependence between TFA-MOD tapes and IBAD-PLD ones.

  6. Quantitative Perfusion and Permeability Biomarkers in Brain Cancer from Tomographic CT and MR Images

    PubMed Central

    Eilaghi, Armin; Yeung, Timothy; d’Esterre, Christopher; Bauman, Glenn; Yartsev, Slav; Easaw, Jay; Fainardi, Enrico; Lee, Ting-Yim; Frayne, Richard

    2016-01-01

    Dynamic contrast-enhanced perfusion and permeability imaging, using computed tomography and magnetic resonance systems, are important techniques for assessing the vascular supply and hemodynamics of healthy brain parenchyma and tumors. These techniques can measure blood flow, blood volume, and blood–brain barrier permeability surface area product and, thus, may provide information complementary to clinical and pathological assessments. These have been used as biomarkers to enhance the treatment planning process, to optimize treatment decision-making, and to enable monitoring of the treatment noninvasively. In this review, the principles of magnetic resonance and computed tomography dynamic contrast-enhanced perfusion and permeability imaging are described (with an emphasis on their commonalities), and the potential values of these techniques for differentiating high-grade gliomas from other brain lesions, distinguishing true progression from posttreatment effects, and predicting survival after radiotherapy, chemotherapy, and antiangiogenic treatments are presented. PMID:27398030

  7. Superconducting shielded core reactor with reduced AC losses

    DOEpatents

    Cha, Yung S.; Hull, John R.

    2006-04-04

    A superconducting shielded core reactor (SSCR) operates as a passive device for limiting excessive AC current in a circuit operating at a high power level under a fault condition such as shorting. The SSCR includes a ferromagnetic core which may be either closed or open (with an air gap) and extends into and through a superconducting tube or superconducting rings arranged in a stacked array. First and second series connected copper coils each disposed about a portion of the iron core are connected to the circuit to be protected and are respectively wound inside and outside of the superconducting tube or rings. A large impedance is inserted into the circuit by the core when the shielding capability of the superconducting arrangement is exceeded by the applied magnetic field generated by the two coils under a fault condition to limit the AC current in the circuit. The proposed SSCR also affords reduced AC loss compared to conventional SSCRs under continuous normal operation.

  8. ac susceptibility of chosen chromium compounds with noncollinear spin structure

    NASA Astrophysics Data System (ADS)

    Juszczyk, S.; Gogołowicz, M.

    1993-11-01

    Results from the preliminary ac susceptibility χ ac( T) measurements at H( rms)=80 A/ m and ƒ=1 kHz on the chosen chromate Zn 1- xA xCr 2Se 4 with noncollinear spin structure for A=Cu and Ga {2}/{3} are presented. From the temperature position peak of the in-phase (real, χ') part of the complex susceptibility the transition temperatures from a magnetically ordered phase to a paramagnetic one have been determined. The out-of-phase (imaginary of absorptive, χ″) peak is discussed in terms of different spin-lattice relaxation processes causing a dissipation of energy. A proposal that in both the real and imaginary part of the ac susceptibility a significant role can be played by a skin size effect is also presented.

  9. Compact rock material gas permeability properties

    NASA Astrophysics Data System (ADS)

    Wang, Huanling; Xu, Weiya; Zuo, Jing

    2014-09-01

    Natural compact rocks, such as sandstone, granite, and rock salt, are the main materials and geological environment for storing underground oil, gas, CO2, shale gas, and radioactive waste because they have extremely low permeabilities and high mechanical strengths. Using the inert gas argon as the fluid medium, the stress-dependent permeability and porosity of monzonitic granite and granite gneiss from an underground oil storage depot were measured using a permeability and porosity measurement system. Based on the test results, models for describing the relationships among the permeability, porosity, and confining pressure of rock specimens were analyzed and are discussed. A power law is suggested to describe the relationship between the stress-dependent porosity and permeability; for the monzonitic granite and granite gneiss (for monzonitic granite (A-2), the initial porosity is approximately 4.05%, and the permeability is approximately 10-19 m2; for the granite gneiss (B-2), the initial porosity is approximately 7.09%, the permeability is approximately 10-17 m2; and the porosity-sensitivity exponents that link porosity and permeability are 0.98 and 3.11, respectively). Compared with moderate-porosity and high-porosity rocks, for which φ > 15%, low-porosity rock permeability has a relatively lower sensitivity to stress, but the porosity is more sensitive to stress, and different types of rocks show similar trends. From the test results, it can be inferred that the test rock specimens' permeability evolution is related to the relative particle movements and microcrack closure.

  10. Ac traction gets on track

    SciTech Connect

    O`Connor, L.

    1995-09-01

    This article describes inverter-based ac traction systems which give freight locomotives greater adhesion, pulling power, and braking capacity. In the 1940s, dc traction replaced the steam engine as a source of train propulsion, and it has ruled the freight transportation industry ever since. But now, high-performance ac-traction systems, with their unprecedented levels of pulling power and adhesion, are becoming increasingly common on America`s freight railroads. In thousands of miles of demonstration tests, today`s ac-traction systems have outperformed traditional dc-motor driven systems. Major railroad companies are convinced enough of the benefits of ac traction to have integrated it into their freight locomotives.

  11. Analysis of Instrumentation Selection and Placement to Monitor the Hydrologic Performance of Permeable Pavement Systems and Bioinfiltration Areas at the Edison Environmental Center in New Jersey

    EPA Science Inventory

    In 2009, the U.S. Environmental Protection Agency constructed a 0.4-ha (1-ac) parking lot surfaced with three different permeable pavement types (interlocking concrete pavers, porous concrete, and porous asphalt) and six bioinfiltration areas with three different drainage area to...

  12. Permeability of naturally fractured reservoirs

    SciTech Connect

    Teufel, L.W. )

    1991-03-01

    Hydraulic fracture stress data collected from carbonate and clastic reservoirs show that the minimum horizontal in situ stress decreases with reservoir depletion and pore pressure drawdown. The reduction in minimum horizontal stress is, in part, a poro-elastic effect that is linear with pore pressure drawdown and can be approximated by an unlaxial compaction model. The observed change in horizontal stress is equal to 40% to 80% of the net change in pore pressure. This type of stress behavior has important implications for reservoir management of naturally fractured reservoirs, because conductivity of fractures is highly stress sensitive. Laboratory studies clearly demonstrate that with increasing effective normal stress fracture apertures close and conductivity decreases. Accordingly, in sharp contrast to the standard procedure, predictions of changes in fracture permeability during reservoir depletion should not be made simply as a function of pore pressure drawdown, but more importantly should be based on how the effective in situ stresses change during drawdown and the orientation of natural fractures relative to the in situ stress field. The increase in the effective overburden stress will be the largest and equal to the magnitude of the pore pressure decline because the overburden stress is constant and does not change with drawdown. However, the increase in the effective minimum horizontal stress will be much smaller. Accordingly, for a reservoir with several sets of fractures with similar morphology, the reduction in fracture conductivity during drawdown will be greatest for horizontal fractures and least for vertical fractures aligned with the maximum horizontal stress direction.

  13. A Poroelastic Description of Permeability Evolution

    NASA Astrophysics Data System (ADS)

    Hassanzadegan, Alireza; Zimmermann, Günter

    2014-07-01

    Pore pressure changes in a geothermal reservoir, as a result of injection and/or production of water, result in changes of stress acting on the reservoir rock and, consequently, changes in the mechanical and transport properties of the rock. Bulk modulus and permeability were measured at different pressures and temperatures. An outcropping equivalent of Rotliegend reservoir rock in the North German Basin (Flechtinger sandstone) was used to perform hydrostatic tests and steady state fluid flow tests. Permeability measurements were conducted while cycling confining pressure; the dependence of permeability on stress was determined at a constant downstream pressure of 1 MPa. Also, temperature was increased stepwise from 30 to 140 °C and crack porosity was calculated at different temperatures. Although changes in the volumes of cracks are not significant, the cracks control fluid flow pathways and, consequently, the permeability of the rock. A new model was derived which relates microstructure of porosity, the stress-strain curve, and permeability. Porosity change was described by the first derivative of the stress-strain curve. Permeability evolution was ascribed to crack closure and was related to the second derivative of the stress-strain curve. The porosity and permeability of Flechtinger sandstone were reduced by increasing the effective pressure and decreased after each pressure cycle.

  14. Fluid permeability of deformable fracture networks

    SciTech Connect

    Brown, S.R.; Bruhn, R.L.

    1997-04-01

    The authors consider the problem of defining the fracture permeability tensor for each grid lock in a rock mass from maps of natural fractures. For this purpose they implement a statistical model of cracked rock due to M. Oda [1985], where the permeability tensor is related to the crack geometry via a volume average of the contribution from each crack in the population. In this model tectonic stress is implicitly coupled to fluid flow through an assumed relationship between crack aperture and normal stress across the crack. The authors have included the following enhancements to the basic model: (1) a realistic model of crack closure under stress has been added along with the provision to apply tectonic stresses to the fracture system in any orientation, the application of stress results in fracture closure and consequently a reduction in permeability; (2) the fracture permeability can be superimposed onto an arbitrary anisotropic matrix permeability; (3) the fracture surfaces are allowed to slide under the application of shear stress, causing fractures to dilate and result in a permeability increase. Through an example, the authors demonstrate that significant changes in permeability magnitudes and orientations are possible when tectonic stress is applied to a fracture system.

  15. Permeable Gas Flow Influences Magma Fragmentation Speed.

    NASA Astrophysics Data System (ADS)

    Richard, D.; Scheu, B.; Spieler, O.; Dingwell, D.

    2008-12-01

    Highly viscous magmas undergo fragmentation in order to produce the pyroclastic deposits that we observe, but the mechanisms involved remain unclear. The overpressure required to initiate fragmentation depends on a number of physical parameters, such as the magma's vesicularity, permeability, tensile strength and textural properties. It is clear that these same parameters control also the speed at which a fragmentation front travels through magma when fragmentation occurs. Recent mathematical models of fragmentation processes consider most of these factors, but permeable gas flow has not yet been included in these models. However, it has been shown that permeable gas flow through a porous rock during a sudden decompression event increases the fragmentation threshold. Fragmentation experiments on natural samples from Bezymianny (Russia), Colima (Mexico), Krakatau (Indonesia) and Augustine (USA) volcanoes confirm these results and suggest in addition that high permeable flow rates may increase the speed of fragmentation. Permeability from the investigated samples ranges from as low as 5 x 10-14 to higher than 9 x 10- 12 m2 and open porosity ranges from 16 % to 48 %. Experiments were performed for each sample series at applied pressures up to 35 MPa. Our results indicate that the rate of increase of fragmentation speed is higher when the permeability is above 10-12 m2. We confirm that it is necessary to include the influence of permeable flow on fragmentation dynamics.

  16. Direct Experimental Observation of a Practical AC Zeeman Force

    NASA Astrophysics Data System (ADS)

    Fancher, Charles; Pyle, Andrew; Rotunno, Andrew; Du, Shuangli; Aubin, Seth

    2016-05-01

    We present measurements of the spin-dependent AC Zeeman force produced by microwave magnetic near-field gradients on an atom chip. We measure the AC Zeeman force on ultracold 87 Rb atoms by observing its effect on the motion of atoms in free-fall and on those confined in a trap. We have studied the force as a function of microwave frequency detuning from a hyperfine transition at 6.8 GHz at several magnetic field strengths and have observed its characteristic bipolar and resonant features predicted by two-level dressed atom theory. We find that the force is several times the strength of gravity in our setup, and that it can be targeted to a specific hyperfine transition while leaving other hyperfine states and transitions relatively unaffected. We find that our measurements are reasonably consistent with theory and are working towards a parameter-free comparison. AC Zeeman potentials offer the possibility of targeting qualitatively different trapping potentials to different spin states, a capability currently absent from the toolbox of atomic quantum control techniques. In particular, an AC Zeeman potential could be used as the beamsplitter for a spin-dependent atom interferometer or for engineering a quantum gate. Work supported by AFOSR and W&M, and in part by AFRL.

  17. Permeability Barrier Generation in the Martian Lithosphere

    NASA Astrophysics Data System (ADS)

    Schools, Joe; Montési, Laurent

    2015-11-01

    Permeability barriers develop when a magma produced in the interior of a planet rises into the cooler lithosphere and crystallizes more rapidly than the lithosphere can deform (Sparks and Parmentier, 1991). Crystallization products may then clog the porous network in which melt is propagating, reducing the permeability to almost zero, i.e., forming a permeability barrier. Subsequent melts cannot cross the barrier. Permeability barriers have been useful to explain variations in crustal thickness at mid-ocean ridges on Earth (Magde et al., 1997; Hebert and Montési, 2011; Montési et al., 2011). We explore here under what conditions permeability barriers may form on Mars.We use the MELTS thermodynamic calculator (Ghiorso and Sack, 1995; Ghiorso et al., 2002; Asimow et al., 2004) in conjunction with estimated Martian mantle compositions (Morgan and Anders, 1979; Wänke and Dreibus, 1994; Lodders and Fegley, 1997; Sanloup et al., 1999; Taylor 2013) to model the formation of permeability barriers in the lithosphere of Mars. In order to represent potential past and present conditions of Mars, we vary the lithospheric thickness, mantle potential temperature (heat flux), oxygen fugacity, and water content.Our results show that permeability layers can develop in the thermal boundary layer of the simulated Martian lithosphere if the mantle potential temperature is higher than ~1500°C. The various Martian mantle compositions yield barriers in the same locations, under matching variable conditions. There is no significant difference in barrier location over the range of accepted Martian oxygen fugacity values. Water content is the most significant influence on barrier development as it reduces the temperature of crystallization, allowing melt to rise further into the lithosphere. Our lower temperature and thicker lithosphere model runs, which are likely the most similar to modern Mars, show no permeability barrier generation. Losing the possibility of having a permeability

  18. Permeability estimation from NMR diffusion measurements in reservoir rocks.

    PubMed

    Balzarini, M; Brancolini, A; Gossenberg, P

    1998-01-01

    It is well known that in restricted geometries, such as in porous media, the apparent diffusion coefficient (D) of the fluid depends on the observation time. From the time dependence of D, interesting information can be derived to characterise geometrical features of the porous media that are relevant in oil industry applications. In particular, the permeability can be related to the surface-to-volume ratio (S/V), estimated from the short time behaviour of D(t), and to the connectivity of the pore space, which is probed by the long time behaviour of D(t). The stimulated spin-echo pulse sequence, with pulsed magnetic field gradients, has been used to measure the diffusion coefficients on various homogeneous and heterogeneous sandstone samples. It is shown that the petrophysical parameters obtained by our measurements are in good agreement with those yielded by conventional laboratory techniques (gas permeability and electrical conductivity). Although the diffusing time is limited by T1, eventually preventing an observation of the real asymptotic behaviour, and the surface-to-volume ratio measured by nuclear magnetic resonance is different from the value obtained by BET because of the different length scales probed, the measurement remains reliable and low-time consuming. PMID:9803918

  19. WITHDRAWN: Complex Study of Transport AC Loss in Various 2G HTS Racetrack Coils

    NASA Astrophysics Data System (ADS)

    Chen, Yiran; Zhang, Min; Chudy, Michal; Matsuda, Koichi; Coombs, Tim

    2013-06-01

    HTS racetrack coils are becoming important elements of an emerging number of superconducting devices such as generators or motors. In these devices the issue of AC loss is crucial, as performance and cooling power are derived from this quantity. This paper presents a comparative study of transport AC loss in two different types of 2G HTS racetrack coils. In this study, both experimental measurements and computer simulation approaches were employed. All the experiments were performed using classical AC electrical method. The finite-element computer model was used to estimate electromagnetic properties and calculate transport AC loss. The main difference between the characterized coils is covered inside tape architectures. While one coil uses tape based on RABITS magnetic substrate, the second coil uses a non-magnetic tape. Ferromagnetic loss caused by a magnetic substrate is an important issue involved in the total AC loss. As a result, the coil with the magnetic substrate surprised with high AC loss and rather low performance.

  20. Complex study of transport AC loss in various 2G HTS racetrack coils

    NASA Astrophysics Data System (ADS)

    Chen, Yiran; Zhang, Min; Chudy, Michal; Matsuda, Koichi; Coombs, Tim

    2013-04-01

    HTS racetrack coils are becoming important elements of an emerging number of superconducting devices such as generators or motors. In these devices the issue of AC loss is crucial, as performance and cooling power are derived from this quantity. This paper presents a comparative study of transport AC loss in two different types of 2G HTS racetrack coils. In this study, both experimental measurements and computer simulation approaches were employed. All the experiments were performed using classical AC electrical method. The finite-element computer model was used to estimate electromagnetic properties and calculate transport AC loss. The main difference between the characterized coils is covered inside tape architectures. While one coil uses tape based on RABITS magnetic substrate, the second coil uses a non-magnetic tape. Ferromagnetic loss caused by a magnetic substrate is an important issue involved in the total AC loss. As a result, the coil with the magnetic substrate surprised with high AC loss and rather low performance.

  1. Effective permeabilities for model heterogeneous porous media

    SciTech Connect

    Otevo, C.; Rusinek, I. ); Saez, A.E. )

    1990-01-01

    This paper presents a technique to evaluate effective absolute permeabilities for heterogeneous porous media. The technique is based on a perturbation analysis of the equations of motion of a slightly compressible fluid in a homogeneous porous medium at low Reynolds numbers. The effective permeabilities can be calculated once the local geometry of the heterogeneous medium is specified. The technique is used to evaluate two- and three-dimensional effective vertical permeabilities in porous media with shale intercalations, including the case in which the porous matrix is anisotropic.

  2. Gas Permeable Chemochromic Compositions for Hydrogen Sensing

    NASA Technical Reports Server (NTRS)

    Bokerman, Gary (Inventor); Mohajeri, Nahid (Inventor); Muradov, Nazim (Inventor); Tabatabaie-Raissi, Ali (Inventor)

    2013-01-01

    A (H2) sensor composition includes a gas permeable matrix material intermixed and encapsulating at least one chemochromic pigment. The chemochromic pigment produces a detectable change in color of the overall sensor composition in the presence of H2 gas. The matrix material provides high H2 permeability, which permits fast permeation of H2 gas. In one embodiment, the chemochromic pigment comprises PdO/TiO2. The sensor can be embodied as a two layer structure with the gas permeable matrix material intermixed with the chemochromic pigment in one layer and a second layer which provides a support or overcoat layer.

  3. Superconducting magnetic energy storage for asynchronous electrical systems

    DOEpatents

    Boenig, Heinrich J.

    1986-01-01

    A superconducting magnetic energy storage coil connected in parallel between converters of two or more ac power systems provides load leveling and stability improvement to any or all of the ac systems. Control is provided to direct the charging and independently the discharging of the superconducting coil to at least a selected one of the ac power systems.

  4. Mapping the Fluid Pathways and Permeability Barriers of a Large Gas Hydrate Reservoir

    NASA Astrophysics Data System (ADS)

    Campbell, A.; Zhang, Y. L.; Sun, L. F.; Saleh, R.; Pun, W.; Bellefleur, G.; Milkereit, B.

    2012-12-01

    An understanding of the relationship between the physical properties of gas hydrate saturated sedimentary basins aids in the detection, exploration and monitoring one of the world's upcoming energy resources. A large gas hydrate reservoir is located in the MacKenzie Delta of the Canadian Arctic and geophysical logs from the Mallik test site are available for the gas hydrate stability zone (GHSZ) between depths of approximately 850 m to 1100 m. The geophysical data sets from two neighboring boreholes at the Mallik test site are analyzed. Commonly used porosity logs, as well as nuclear magnetic resonance, compressional and Stoneley wave velocity dispersion logs are used to map zones of elevated and severely reduced porosity and permeability respectively. The lateral continuity of horizontal permeability barriers can be further understood with the aid of surface seismic modeling studies. In this integrated study, the behavior of compressional and Stoneley wave velocity dispersion and surface seismic modeling studies are used to identify the fluid pathways and permeability barriers of the gas hydrate reservoir. The results are compared with known nuclear magnetic resonance-derived permeability values. The aim of investigating this heterogeneous medium is to map the fluid pathways and the associated permeability barriers throughout the gas hydrate stability zone. This provides a framework for an understanding of the long-term dissociation of gas hydrates along vertical and horizontal pathways, and will improve the knowledge pertaining to the production of such a promising energy source.

  5. Towards an AC-MOT of CaF

    NASA Astrophysics Data System (ADS)

    Anderegg, Loic; Chae, Eunmi; Ravi, Aakash; Augenbraun, Benjamin; Hemmerling, Boerge; Drayna, Garrett; Hutzler, Nicholas; Collopy, Alejandra; Wu, Yewei; Ding, Shiqian; Ye, Jun; Ketterle, Wolfgang; Doyle, John

    2016-05-01

    Ultra-cold diatomic molecules have rich prospects as candidates to study controlled ultra-cold chemistry, strongly correlated systems and precision measurements. They are also considered as possible qubits in quantum computing and simulation schemes. We report on progress towards loading CaF into a molecular magneto-optical trap (MOT). An AC-MOT will be used to actively remix magnetic dark states via both polarization and magnetic field switching. In order to load a molecular MOT, we have successfully laser slowed a CaF beam to near the expected capture velocity. We describe our AC-MOT apparatus, which is designed to co-trap CaF and Li. We outline our planned study of CaF-Li collisions to explore the feasibility of sympathetically cooling molecules to ultra-cold temperatures.

  6. Apparatus and method for handling magnetic particles in a fluid

    DOEpatents

    Holman, David A.; Grate, Jay W.; Bruckner-Lea, Cynthia J.

    2000-01-01

    The present invention is an apparatus and method for handling magnetic particles suspended in a fluid, relying upon the known features of a magnetic flux conductor that is permeable thereby permitting the magnetic particles and fluid to flow therethrough; and a controllable magnetic field for the handling. The present invention is an improvement wherein the magnetic flux conductor is a monolithic porous foam.

  7. Comparison study of ferrofluid and powder iron oxide nanoparticle permeability across the blood-brain barrier.

    PubMed

    Hoff, Dan; Sheikh, Lubna; Bhattacharya, Soumya; Nayar, Suprabha; Webster, Thomas J

    2013-01-01

    In the present study, the permeability of 11 different iron oxide nanoparticle (IONP) samples (eight fluids and three powders) was determined using an in vitro blood-brain barrier model. Importantly, the results showed that the ferrofluid formulations were statistically more permeable than the IONP powder formulations at the blood-brain barrier, suggesting a role for the presently studied in situ synthesized ferrofluid formulations using poly(vinyl) alcohol, bovine serum albumin, collagen, glutamic acid, graphene, and their combinations as materials which can cross the blood-brain barrier to deliver drugs or have other neurological therapeutic efficacy. Conversely, the results showed the least permeability across the blood-brain barrier for the IONP with collagen formulation, suggesting a role as a magnetic resonance imaging contrast agent but limiting IONP passage across the blood-brain barrier. Further analysis of the data yielded several trends of note, with little correlation between permeability and fluid zeta potential, but a larger correlation between permeability and fluid particle size (with the smaller particle sizes having larger permeability). Such results lay the foundation for simple modification of iron oxide nanoparticle formulations to either promote or inhibit passage across the blood-brain barrier, and deserve further investigation for a wide range of applications. PMID:23426527

  8. Dynamic nanomagnetism characterization of individual magnetic nanoparticles by frequency-modulated magnetic force microscopy

    NASA Astrophysics Data System (ADS)

    Li, Xiang; Li, Zhenghua; Pan, Deng; Yoshimura, Satoru; Saito, Hitoshi

    2014-05-01

    In this study, stroboscopic imaging of an alternating magnetic field (AC magnetic field) from individual superparamagnetic Fe3O4 nanoparticles was achieved using the developed frequency modulated-magnetic force microscopy (FM-MFM) technique, which enables the imaging of the vector signals of AC magnetic fields, such as a combination of in-phase and quadrature signals or that of amplitude and phase signals. FM-MFM uses the frequency modulation of cantilever oscillation, caused by the application of an off-resonant AC magnetic field to a mechanically oscillated cantilever, and visualises the vector signals of the AC magnetic field by adding a frequency demodulator and a lock-in amplifier to a conventional magnetic force microscope. Stroboscopic imaging of an AC magnetic field was carried out by varying the phase of the measured in-phase and quadrature signals via a signal processing technique. For the superparamagnetic Fe3O4 nanoparticles, stroboscopic imaging of the time-variable AC magnetic field, caused by the rotation of the magnetic moments within the particles, was demonstrated. This article describes the present status of FM-MFM technology, with particular attention to the feasibility of detecting magnetic moments of individual nanoparticles, and the possible application of FM-MFM in biological imaging.

  9. Flexible Sandwich Diaphragms Are Less Permeable

    NASA Technical Reports Server (NTRS)

    Michalovic, John G.; Vassallo, Franklin A.

    1993-01-01

    Diaphragms for use in refrigerator compressors made as laminates of commercially available elastomers and metals. Diaphragms flexible, but less permeable by chlorofluorocarbon refrigerant fluids than diaphragms made of homogeneous mixtures of materials.

  10. Variability of permeability with diameter of conduit

    NASA Astrophysics Data System (ADS)

    Adegoke, J. A.; Olowofela, J. A.

    2008-05-01

    An entry length is always observed before laminar flow is achieved in fluid flowing in a conduit. This depends on the Reynolds number of the flow and the degree of smoothness of the conduit. This work examined this region and the point where laminar flow commences in the context of flow through conduit packed with porous material like beads, of known porosity. Using some theoretical assumptions, it is demonstrated that permeability varies from zero at wall-fluid boundary to maximum at mid-stream, creating a permeability profile similar to the velocity profile. An equation was obtained to establish this. We also found that peak values of permeability increase with increasing porosity, and therefore entry length increases with increasing porosity with all other parameters kept constant. A plot of peak permeability versus porosity revealed that they are linearly related.

  11. Method for determining permeability in hydrocarbon wells

    SciTech Connect

    Boone, D.E.

    1990-10-09

    This patent describes a method of determining at the earth's surface the permeability of a subsurface earth formation having a known nominal hydrocarbon pore saturation value. The formation is tranversed by a borehole resulting from drilling with a drill bit.

  12. Specific surface area model for foam permeability.

    PubMed

    Pitois, O; Lorenceau, E; Louvet, N; Rouyer, F

    2009-01-01

    Liquid foams were recognized early to be porous materials, as liquid flowed between the gas bubbles. Drainage theories have been established, and foam permeability has been modeled from the microscopic description of the equivalent pores geometry, emphasizing similarities with their solid counterparts. But to what extent can the theoretical work devoted to the permeability of solid porous materials be useful to liquid foams? In this article, the applicability of the Carman-Kozeny model on foam is investigated. We performed measurements of the permeability of foams with nonmobile surfactants, and we show that, in introducing an equivalent specific surface area for the foam, the model accurately describes the experimental data over two orders of magnitude for the foam liquid fraction, without any additional parameters. Finally, it is shown that this model includes the previous permeability models derived for foams in the dry foams limit. PMID:19032030

  13. NASA In-step: Permeable Membrane Experiment

    NASA Technical Reports Server (NTRS)

    1992-01-01

    Viewgraphs on the Permeable Membrane Experiment are presented. An experiment overview is given. The Membrane Phase Separation Experiment, Membrane Diffusion Interference Experiment, and Membrane Wetting Experiment are described. Finally, summary and conclusions are discussed.

  14. Permeability After Impact Testing of Composite Laminates

    NASA Technical Reports Server (NTRS)

    Nettles, Alan T.

    2003-01-01

    Since composite laminates are beginning to be identified for use in reusable launch vehicle propulsion systems, an understanding of their permeance is needed. A foreign object impact event can cause a localized area of permeability (leakage) in a polymer matrix composite and it is the aim of this study to assess a method of quantifying permeability-after-impact results. A simple test apparatus is presented and variables that could affect the measured values of permeability-after-impact were assessed. Once it was determined that valid numbers were being measured, a fiber/resin system was impacted at various impact levels and the resulting permeability measured, first with a leak check solution (qualitative) then using the new apparatus (quantitative). The results showed that as the impact level increased, so did the measured leakage. As the pressure to the specimen was increased, the leak rate was seen to increase in a non-linear fashion for almost all of the specimens tested.

  15. Permeability After Impact Testing of Composite Laminates

    NASA Technical Reports Server (NTRS)

    Nettles, A.T.; Munafo, Paul (Technical Monitor)

    2002-01-01

    Since composite laminates are beginning to be identified for use in reusable launch vehicle propulsion systems, an understanding of their permeance is needed. A foreign object impact event can cause a localized area of permeability (leakage) in a polymer matrix composite and it is the aim of this study to assess a method of quantifying permeability-after-impact results. A simple test apparatus is presented and variables that could affect the measured values of permeability-after-impact were assessed. Once it was determined that valid numbers were being measured, a fiber/resin system was impacted at various impact levels and the resulting permeability measured, first with a leak check solution (qualitative) then using the new apparatus (quantitative). The results showed that as the impact level increased, so did the measured leakage. As the pressure to the specimen was increased, the leak rate was seen to increase in a non-linear fashion for almost all of the specimens tested.

  16. Measuring Permeability of Composite Cryotank Laminants

    NASA Technical Reports Server (NTRS)

    Oliver, Stanley T.; Selvidge, Shawn; Watwood, Michael C.

    2004-01-01

    This paper describes a test method developed to identify whether certain materials and material systems are suitable candidates for large pressurized reusable cryogenic tanks intended for use in current and future manned launch systems. It provides a quick way to screen numerous candidate materials for permeability under anticipated loading environments consistent with flight conditions, as well as addressing reusability issues. cryogenic tank, where the major design issue was hydrogen permeability. It was successfully used to evaluate samples subjected to biaxial loading while maintaining test temperatures near liquid hydrogen. After each sample was thermally preconditioned, a cyclic pressure load was applied to simulate the in-plane strain. First permeability was measured while a sample was under load. Then the sample was unloaded and allowed to return to ambient temperature. The test was repeated to simulate reusability, in order to evaluate its effects on material permeability.

  17. Permeability of rayon based polymer composites

    NASA Technical Reports Server (NTRS)

    Stokes, E. H.

    1992-01-01

    Several types of anomalous rayon based phenolic behavior have been observed in post-fired nozzles and exit cones. Many of these events have been shown to be related to the development of internal gas pressure within the material. The development of internal gas pressure is a function of the amount of gas produced within the material and the rate at which that gas is allowed to escape. The latter property of the material is referred to as the material's permeability. The permeability of two dimensional carbonized rayon based phenolic composites is a function of material direction, temperature, and stress/strain state. Recently significant differences in the permeability of these materials has been uncovered which may explain their inconsistent performance. This paper summarizes what is known about the permeability of these materials to date and gives possible implications of these finding to the performance of these materials in an ablative environment.

  18. PERMEABILITY OF POLYMERIC MEMBRANE LINING MATERIALS

    EPA Science Inventory

    Permeabilities to three gases (carbon dioxide, methane, and nitrogen), water vapor, and five solvents (methanol, acetone, cyclohexane, xylene, and chloroform) are reported for a broad range of commercial polymeric membranes. Gas and water vapor transmission (WVT) data were determ...

  19. Vascular permeability, vascular hyperpermeability and angiogenesis

    PubMed Central

    Nagy, Janice A.; Benjamin, Laura; Zeng, Huiyan; Dvorak, Ann M.

    2008-01-01

    The vascular system has the critical function of supplying tissues with nutrients and clearing waste products. To accomplish these goals, the vasculature must be sufficiently permeable to allow the free, bidirectional passage of small molecules and gases and, to a lesser extent, of plasma proteins. Physiologists and many vascular biologists differ as to the definition of vascular permeability and the proper methodology for its measurement. We review these conflicting views, finding that both provide useful but complementary information. Vascular permeability by any measure is dramatically increased in acute and chronic inflammation, cancer, and wound healing. This hyperpermeability is mediated by acute or chronic exposure to vascular permeabilizing agents, particularly vascular permeability factor/vascular endothelial growth factor (VPF/VEGF, VEGF-A). We demonstrate that three distinctly different types of vascular permeability can be distinguished, based on the different types of microvessels involved, the composition of the extravasate, and the anatomic pathways by which molecules of different size cross-vascular endothelium. These are the basal vascular permeability (BVP) of normal tissues, the acute vascular hyperpermeability (AVH) that occurs in response to a single, brief exposure to VEGF-A or other vascular permeabilizing agents, and the chronic vascular hyperpermeability (CVH) that characterizes pathological angiogenesis. Finally, we list the numerous (at least 25) gene products that different authors have found to affect vascular permeability in variously engineered mice and classify them with respect to their participation, as far as possible, in BVP, AVH and CVH. Further work will be required to elucidate the signaling pathways by which each of these molecules, and others likely to be discovered, mediate the different types of vascular permeability. PMID:18293091

  20. Pneumatic fracturing of low permeability media

    SciTech Connect

    Schuring, J.R.

    1996-08-01

    Pneumatic fracturing of soils to enhance the removal and treatment of dense nonaqueous phase liquids is described. The process involves gas injection at a pressure exceeding the natural stresses and at a flow rate exceeding the permeability of the formation. The paper outlines geologic considerations, advantages and disadvantages, general technology considerations, low permeability media considerations, commercial availability, efficiency, and costs. Five case histories of remediation using pneumatic fracturing are briefly summarized. 11 refs., 2 figs., 1 tab.

  1. Fracture-permeability behavior of shale

    SciTech Connect

    Carey, J. William; Lei, Zhou; Rougier, Esteban; Mori, Hiroko; Viswanathan, Hari

    2015-05-08

    The fracture-permeability behavior of Utica shale, an important play for shale gas and oil, was investigated using a triaxial coreflood device and X-ray tomography in combination with finite-discrete element modeling (FDEM). Fractures generated in both compression and in a direct-shear configuration allowed permeability to be measured across the faces of cylindrical core. Shale with bedding planes perpendicular to direct-shear loading developed complex fracture networks and peak permeability of 30 mD that fell to 5 mD under hydrostatic conditions. Shale with bedding planes parallel to shear loading developed simple fractures with peak permeability as high as 900 mD. In addition to the large anisotropy in fracture permeability, the amount of deformation required to initiate fractures was greater for perpendicular layering (about 1% versus 0.4%), and in both cases activation of existing fractures are more likely sources of permeability in shale gas plays or damaged caprock in CO₂ sequestration because of the significant deformation required to form new fracture networks. FDEM numerical simulations were able to replicate the main features of the fracturing processes while showing the importance of fluid penetration into fractures as well as layering in determining fracture patterns.

  2. Simulating perforation permeability damage and cleanup

    SciTech Connect

    Morris, J P; Lomov, I N; Glenn, L A

    2000-12-15

    Completion of cased and cemented wells by shaped charge perforation causes its own damage to the formation, potentially reducing well productivity. In practice it is found that underbalance conditions clean up the damaged zone to some extent, however, the mechanisms of these processes are poorly understood. Most hydrocodes typically used to simulate rock response to shaped charge penetration do not provide permeability estimates. Furthermore, the time scales for formation clean up are potentially much longer than the period of jet penetration. We have developed a simple, yet accurate model for the evolution of porosity and permeability which can easily be incorporated into existing hydrocodes using information from the history of each cell. In addition, we have developed a code that efficiently simulates fines migration during the post-shot surge period using initial conditions taken directly from hydrocode simulations of jet penetration. Results from a one-dimensional model simulation are in excellent agreement with measured permeability distributions. We also present two-dimensional numerical results which qualitatively reproduce experimentally obtained permeability maps for different values of underbalance. Although initial results have been promising, further comparison with experiment is essential to tune the coupling between the hydrocode and fines migration simulator. Currently the permeability model is most appropriate for high permeability sandstones (such as Berea), but with little effort, the model can be extended to other rock types, given sufficient experimental data.

  3. Simulating Perforation Permeability Damage and Cleanup

    SciTech Connect

    Morris, J.P.; Lomov, I.N.; Glenn, L.A.

    2000-09-01

    Completion of cased and cemented wells by shaped charge perforation causes its own damage to the formation, potentially reducing well productivity. In practice it is found that underbalance conditions clean up the damaged zone to some extent, however, the mechanisms of these processes are poorly understood. Most hydrocodes typically used to simulate rock response to shaped charge penetration do not provide permeability estimates. Furthermore, the time scales for formation clean up are potentially much longer than the period of jet penetration. We have developed a simple, yet accurate model for the evolution of porosity and permeability which can easily be incorporated into existing hydrocodes using information from the history of each cell. In addition, we have developed a code that efficiently simulates fines migration during the post-shot surge period using initial conditions taken directly from hydrocode simulations of jet penetration. Results from a one-dimensional model simulation are in excellent agreement with measured fines and permeability distributions. We also present two-dimensional numerical results which qualitatively reproduce experimentally obtained permeability maps for different values of underbalance. Although initial results have been promising, further comparison with experiment is essential to tune the coupling between the hydrocode and fines migration simulator. Currently the permeability model is most appropriate for high permeability sandstones (such as Berea), but with little effort, the model can be extended to other rock types, given sufficient experimental data.

  4. Fracture-permeability behavior of shale

    DOE PAGESBeta

    Carey, J. William; Lei, Zhou; Rougier, Esteban; Mori, Hiroko; Viswanathan, Hari

    2015-05-08

    The fracture-permeability behavior of Utica shale, an important play for shale gas and oil, was investigated using a triaxial coreflood device and X-ray tomography in combination with finite-discrete element modeling (FDEM). Fractures generated in both compression and in a direct-shear configuration allowed permeability to be measured across the faces of cylindrical core. Shale with bedding planes perpendicular to direct-shear loading developed complex fracture networks and peak permeability of 30 mD that fell to 5 mD under hydrostatic conditions. Shale with bedding planes parallel to shear loading developed simple fractures with peak permeability as high as 900 mD. In addition tomore » the large anisotropy in fracture permeability, the amount of deformation required to initiate fractures was greater for perpendicular layering (about 1% versus 0.4%), and in both cases activation of existing fractures are more likely sources of permeability in shale gas plays or damaged caprock in CO₂ sequestration because of the significant deformation required to form new fracture networks. FDEM numerical simulations were able to replicate the main features of the fracturing processes while showing the importance of fluid penetration into fractures as well as layering in determining fracture patterns.« less

  5. Hormonal Regulation of Nuclear Permeability*◆

    PubMed Central

    O'Brien, Elizabeth M.; Gomes, Dawidson A.; Sehgal, Sona; Nathanson, Michael H.

    2010-01-01

    Transport into the nucleus is critical for regulation of gene transcription and other intranuclear events. Passage of molecules into the nucleus depends in part upon their size and the presence of appropriate targeting sequences. However, little is known about the effects of hormones or their second messengers on transport across the nuclear envelope. We used localized, two-photon activation of a photoactivatable green fluorescent protein to investigate whether hormones, via their second messengers, could alter nuclear permeability. Vasopressin other hormones that increase cytosolic Ca2+ and activate protein kinase C increased permeability across the nuclear membrane of SKHep1 liver cells in a rapid unidirectional manner. An increase in cytosolic Ca2+ was both necessary and sufficient for this process. Furthermore, localized photorelease of caged Ca2+ near the nuclear envelope resulted in a local increase in nuclear permeability. Neither activation nor inhibition of protein kinase C affected nuclear permeability. These findings provide evidence that hormones linking to certain G protein-coupled receptors increase nuclear permeability via cytosolic Ca2+. Short term regulation of nuclear permeability may provide a novel mechanism by which such hormones permit transcription factors and other regulatory molecules to enter the nucleus, thereby regulating gene transcription in target cells. PMID:17158097

  6. Cell permeability beyond the rule of 5.

    PubMed

    Matsson, Pär; Doak, Bradley C; Over, Björn; Kihlberg, Jan

    2016-06-01

    Drug discovery for difficult targets that have large and flat binding sites is often better suited to compounds beyond the "rule of 5" (bRo5). However, such compounds carry higher pharmacokinetic risks, such as low solubility and permeability, and increased efflux and metabolism. Interestingly, recent drug approvals and studies suggest that cell permeable and orally bioavailable drugs can be discovered far into bRo5 space. Tactics such as reduction or shielding of polarity by N-methylation, bulky side chains and intramolecular hydrogen bonds may be used to increase cell permeability in this space, but often results in decreased solubility. Conformationally flexible compounds can, however, combine high permeability and solubility, properties that are keys for cell permeability and intestinal absorption. Recent developments in computational conformational analysis will aid design of such compounds and hence prediction of cell permeability. Transporter mediated efflux occurs for most investigated drugs in bRo5 space, however it is commonly overcome by high local intestinal concentrations on oral administration. In contrast, there is little data to support significant impact of transporter-mediated intestinal absorption in bRo5 space. Current knowledge of compound properties that govern transporter effects of bRo5 drugs is limited and requires further fundamental and comprehensive studies. PMID:27067608

  7. Development of a boundary magnetic charge method for computing magnetic fields in a system containing saturated magnetic materials

    NASA Astrophysics Data System (ADS)

    Murata, H.; Ishigami, M.; Shimoyama, H.

    2016-01-01

    In previous research, we developed a three-dimensional (3D) boundary magnetic charge method (BMCM) for high-accuracy field calculations in a static magnetic field, even when there exist great differences between the magnitudes of permeability between neighboring magnetic materials. This method, however, cannot be applied to a system that contains saturated magnetic materials. In the present study, therefore, we have developed a novel method that addresses this issue. According to this new method, we divide the region containing the magnetic material into small-volume elements and divide the boundaries between neighboring small-volume elements into small-surface elements, assigning each element an appropriate initial value of permeability. The magnetic field inside and outside of the magnetic material is calculated using this permeability. The value of the permeability of each element is iteratively updated using μ-H data. The updated value of the permeability after the i-th iteration, μi, is compared with that of the previous value, μi-1. If the difference between the two values is within a preset range, the iteration process is judged to have converged and the value of μi is regarded as the final converged value of the permeability. The magnetic field at an arbitrary point in space and/or inside the body of the magnetic material is calculated from the converged permeability of each element. As a result, we have succeeded in developing a novel BMCM for the calculation of a static magnetic field with high accuracy in a system containing saturated magnetic materials.

  8. Permeability properties of erythrocyte ghosts.

    PubMed

    TEORELL, T

    1952-05-01

    1. Erythrocyte ghosts from human blood were produced by gentle water hemolysis. The ghost-containing hemolysate (about 20 mN) was added to media of different composition (KCl, NaCl, glucose, sucrose, etc.) and varying concentration ranging from 8 to 840 mN. The volume changes of the ghost cells were followed by a light absorption method. The potassium and sodium concentrations were also analyzed in some representative cases. 2. The ghosts shrank, or swelled, in two stages. An initial phase with a momentary expulsion, or uptake, of water leading to an osmotic equilibrium, was followed by a second phase in which a slow swelling or shrinking proceeded toward a final constant volume. 3. The ghosts were semipermeable in the sense that water always passed rapidly in either direction so as to maintain isotonicity with the external medium. The relation between ghost cell volumes (V) and the total concentration (C(e)) of the suspension medium can be expressed by a modified van't Hoff-Mariotte law: (C(e) + a)(V - b) = constant. Here a is a term correcting for an internal pressure and b is the non-solvent volume of the ghost cells. This means that the ghosts behave as perfect osmometers. 4. On the other hand appreciable concentration differences of the K and Na ions could be maintained across the intact ghost cell membranes for long periods. Whether this phenomenon is due simply to very low cation permeability or to active transport processes cannot be decided, although the first assumption appears more probable. 5. When the ghosts were treated with small concentrations of a lytic substance like Na oleate, the alkali ion transfer was greatly increased. This seems to be a simple exchange diffusion process with simultaneous, continued maintenance of osmotic equilibrium (= the second phase). A simplified theory is also given for the kinetics of the volume variations and ion exchange during the second phase (cf. the Appendix). 6. Miscellaneous observations on the effects of p

  9. Comparative field permeability measurement of permeable pavements using ASTM C1701 and NCAT permeameter methods.

    PubMed

    Li, Hui; Kayhanian, Masoud; Harvey, John T

    2013-03-30

    Fully permeable pavement is gradually gaining support as an alternative best management practice (BMP) for stormwater runoff management. As the use of these pavements increases, a definitive test method is needed to measure hydraulic performance and to evaluate clogging, both for performance studies and for assessment of permeability for construction quality assurance and maintenance needs assessment. Two of the most commonly used permeability measurement tests for porous asphalt and pervious concrete are the National Center for Asphalt Technology (NCAT) permeameter and ASTM C1701, respectively. This study was undertaken to compare measured values for both methods in the field on a variety of permeable pavements used in current practice. The field measurements were performed using six experimental section designs with different permeable pavement surface types including pervious concrete, porous asphalt and permeable interlocking concrete pavers. Multiple measurements were performed at five locations on each pavement test section. The results showed that: (i) silicone gel is a superior sealing material to prevent water leakage compared with conventional plumbing putty; (ii) both methods (NCAT and ASTM) can effectively be used to measure the permeability of all pavement types and the surface material type will not impact the measurement precision; (iii) the permeability values measured with the ASTM method were 50-90% (75% on average) lower than those measured with the NCAT method; (iv) the larger permeameter cylinder diameter used in the ASTM method improved the reliability and reduced the variability of the measured permeability. PMID:23434738

  10. An assessment of alternative soft magnetic materials in rotary variable differential transformers

    SciTech Connect

    Midgley, G.W.; Howe, D.; Mellor, P.H.

    1997-04-01

    Position sensors are a key technology for controlled actuation systems, which are required to meet increasingly exacting dynamic performance specifications. Of the various sensing technologies, variable differential transformers are capable of satisfying stringent performance criteria, in terms of resolution, repeatability, and stability of output, while operating in the harshest of environments. They utilize the variation of mutual inductance which occurs between a primary and two secondary coils as a ferromagnetic core is moved by the object whose position is to be measured. The article is concerned with rotary variable differential transformers, which currently use high permeability magnetic alloys, such as nickel{endash}iron, either solid or laminated. However, since they are being required to operate at increased excitation frequencies, up to 5 kHz, there is interest in the use of powder composite magnetic materials, which, although having a lower permeability, have a higher electrical resistivity, and hence reduced eddy current effects. The potential for such materials is investigated by steady-state ac finite element analysis, and shown to be promising. {copyright} {ital 1997 American Institute of Physics.}

  11. Rhubarb Antagonizes Matrix Metalloproteinase-9-induced Vascular Endothelial Permeability

    PubMed Central

    Cui, Yun-Liang; Zhang, Sheng; Tian, Zhao-Tao; Lin, Zhao-Fen; Chen, De-Chang

    2016-01-01

    Background: Intact endothelial structure and function are critical for maintaining microcirculatory homeostasis. Dysfunction of the latter is an underlying cause of various organ pathologies. In a previous study, we showed that rhubarb, a traditional Chinese medicine, protected intestinal mucosal microvascular endothelial cells in rats with metastasizing septicemia. In this study, we investigated the effects and mechanisms of rhubarb on matrix metalloproteinase-9 (MMP9)-induced vascular endothelial (VE) permeability. Methods: Rhubarb monomers were extracted and purified by a series of chromatography approaches. The identity of these monomers was analyzed by hydrogen-1 nuclear magnetic resonance (NMR), carbon-13 NMR, and distortionless enhancement by polarization transfer magnetic resonance spectroscopy. We established a human umbilical vein endothelial cell (HUVEC) monolayer on a Transwell insert. We measured the HUVEC permeability, proliferation, and the secretion of VE-cadherin into culture medium using fluorescein isothiocyanate-dextran assay, 3-(4,5-dimethyl-2-thiazolyl)-2,5-diphenyl-2-H-tetrazolium bromide assay, and enzyme-linked immunosorbent assay, respectively, in response to treatment with MMP9 and/or rhubarb monomers. Results: A total of 21 rhubarb monomers were extracted and identified. MMP9 significantly increased the permeability of the HUVEC monolayer, which was significantly reduced by five individual rhubarb monomer (emodin, 3,8-dihydroxy-1-methyl-anthraquinone-2-carboxylic acid, 1-O-caffeoyl-2-(4-hydroxyl-O-cinnamoyl)-β-D-glucose, daucosterol linoleate, and rhein) or a combination of all five monomers (1 μmol/L for each monomer). Mechanistically, the five-monomer mixture at 1 μmol/L promoted HUVEC proliferation. In addition, MMP9 stimulated the secretion of VE-cadherin into the culture medium, which was significantly inhibited by the five-monomer mixture. Conclusions: The rhubarb mixture of emodin, 3,8-dihydroxy-1-methyl-anthraquinone-2

  12. Lunar electrical conductivity, permeability,and temperature from Apollo magnetometer experiments

    NASA Technical Reports Server (NTRS)

    Dyal, P.; Parkin, C. W.; Daily, W. D.

    1974-01-01

    Magnetometers were deployed at four Apollo sites on the moon to measure remanent and induced lunar magnetic fields. Measurements from this network of instruments were used to calculate the electrical conductivity, temperature, magnetic permeability, and iron abundance of the lunar interior. Global lunar fields due to eddy currents, induced in the lunar interior by magnetic transients, were analyzed to calculate and electrical conductivity profile for the moon, and those profiles were used to calculate the lunar temperature for an assumed lunar material of olivine. Simultaneous measurements by magnetometers on the lunar surface and in orbit around the moon were use to construct a whole-moon hysteresis curve, from which the global lunar magnetic permeability is determined. Total iron abundance (sum of iron in the ferromagnetic and paramagnetic states) was calculated for two assumed compositional models of the lunar interior. Other lunar models with an iron core and with a shallow iron-rich layer also discussed in light of the measured global lunar permeability. Simultaneous magnetic field and solar plasma pressure measurements show that the remanent fields at the Apollo 12 and 16 sites interact with, and are compressed by, the solar wind. Velocities and thicknesses of the earth's magnetopause and bow shock were also estimated from simultaneous magnetometer measurements.

  13. An effective way to increase the high-frequency permeability of Fe3O4 nanorods.

    PubMed

    Ren, Xiao; Yang, Haitao; Tang, Jin; Li, Zi-An; Su, Yi Kun; Geng, Sai; Zhou, Jun; Zhang, Xiangqun; Cheng, Zhaohua

    2016-07-14

    Uniform Fe3O4 magnetic nanorods (NRs) were successfully synthesized and oriented in epoxy resin under a rotating magnetic field. Magnetic induction fields within and around a single Fe3O4 nanorod in the remanence state were obtained by off-axis electron holography. The induction fields indicated a single domain state of the highly anisotropic Fe3O4 nanorod due to its strong magnetic shape anisotropy. Quantitative magnetic moment analysis of the obtained phase image yielded an average magnetization of 0.53 T of a single Fe3O4 nanorod. Moreover, the real part of the permeability (μ') of magnetic-oriented Fe3O4 NRs is obviously higher than that of random Fe3O4 NRs in the GHz range. The oriented Fe3O4 NRs exhibit a higher resonance peak at 4.75 GHz compared to the bulk counterpart (1.2 GHz) in the frequency dependence of μ in the range of 1-10 GHz. Moreover, the calculated μ value of the oriented Fe3O4 NRs could be improved to 4.22 with the increased dipolar interaction strength using the OOMMF software. These results could play a guiding significance in the development of an effective method to improve the permeability of magnetic nanomaterials at GHz working frequency. PMID:27305587

  14. Lunar electrical conductivity, permeability and temperature from Apollo magnetometer experiments

    NASA Technical Reports Server (NTRS)

    Dyal, P.; Parkin, C. W.; Daily, W. D.

    1977-01-01

    Magnetometers were deployed at four Apollo sites on the moon to measure remanent and induced lunar magnetic fields. Measurements from this network of instruments were used to calculate the electrical conductivity, temperature, magnetic permeability, and iron abundance of the lunar interior. The measured lunar remanent fields range from 3 gammas minimum at the Apollo 15 site to 327 gammas maximum at the Apollo 16 site. Simultaneous magnetic field and solar plasma pressure measurements show that the remanent fields at the Apollo 12 and 16 sites interact with, and are compressed by, the solar wind. Remanent fields at Apollo 12 and Apollo 16 are increased 16 gammas and 32 gammas, respectively, by a solar plasma bulk pressure increase of 1.5 X 10 to the -7th power dynes/sq cm. Global lunar fields due to eddy currents, induced in the lunar interior by magnetic transients, were analyzed to calculate an electrical conductivity profile for the moon. From nightside magnetometer data in the solar wind it was found that deeper than 170 km into the moon the conductivity rises from .0003 mhos/m to .10 mhos/m at 100 km depth. Recent analysis of data obtained in the geomagnetic tail, in regions free of complicating plasma effects, yields results consistent with nightside values.

  15. ISTTOK upgrade towards AC and remote operation

    NASA Astrophysics Data System (ADS)

    Fernandes, H.; Silva, C.; Carvalho, B.; Sousa, J.; Valcárcel, D.; Neto, A.; Fortunato, J.; Carvalho, I.; Varandas, C. A. F.

    2006-12-01

    ISTTOK has performed one of the earliest experiments of AC tokamak operation showing that long discharges could be produced merely with inductive current drive. However, due to the design of the machine, the data acquisition system and the power supplies, a limit of 250 ms (six times the nominal forward shot duration) is currently imposed. In this paper the relevant constrains to attain current operation up to the limit of the stable toroidal magnetic field (3s) are discussed and the work being carried out to achieve this goal is presented. The conditions that shall be accomplished are: (i) removing the power deposited on the limiters; (ii) density control through gas puffing and monitoring the recycling from the walls; (iii) assessment of the free magnetic flux available on the iron core (Wmax=0.2 Vs); (iv) reformulation of the data acquisition system towards an event driven philosophy maintaining the actual distributed architecture but allowing a real-time control; (v) active control of the equilibrium magnetic fields implementing a digital plasma position estimator and actuator through new power supplies for the poloidal magnetic fields. As a new high level software was needed to implement all this features, the ISTTOK data acquisition system and control has been totally redesigned in JAVA/SQL database technology and time stamps events were adopted to catalogue the data. This software has been design keeping in mind the needs for remote participation and operation of the machine. Therefore, a cooperative environment has been implemented where several persons can be connected together to the platform, programming their own devices and exchanging knowledge or opinions through an embedded chat.

  16. ISTTOK upgrade towards AC and remote operation

    SciTech Connect

    Fernandes, H.; Silva, C.; Carvalho, B.; Sousa, J.; Valcarcel, D.; Neto, A.; Fortunato, J.; Carvalho, I.; Varandas, C. A. F.

    2006-12-04

    ISTTOK has performed one of the earliest experiments of AC tokamak operation showing that long discharges could be produced merely with inductive current drive. However, due to the design of the machine, the data acquisition system and the power supplies, a limit of 250 ms (six times the nominal forward shot duration) is currently imposed.In this paper the relevant constrains to attain current operation up to the limit of the stable toroidal magnetic field (3s) are discussed and the work being carried out to achieve this goal is presented.The conditions that shall be accomplished are: (i) removing the power deposited on the limiters; (ii) density control through gas puffing and monitoring the recycling from the walls; (iii) assessment of the free magnetic flux available on the iron core (Wmax=0.2 Vs); (iv) reformulation of the data acquisition system towards an event driven philosophy maintaining the actual distributed architecture but allowing a real-time control; (v) active control of the equilibrium magnetic fields implementing a digital plasma position estimator and actuator through new power supplies for the poloidal magnetic fields. As a new high level software was needed to implement all this features, the ISTTOK data acquisition system and control has been totally redesigned in JAVA/SQL database technology and time stamps events were adopted to catalogue the data. This software has been design keeping in mind the needs for remote participation and operation of the machine. Therefore, a cooperative environment has been implemented where several persons can be connected together to the platform, programming their own devices and exchanging knowledge or opinions through an embedded chat.

  17. Low magnetic fields for flow propagators in permeable rocks.

    PubMed

    Singer, Philip M; Leu, Gabriela; Fordham, Edmund J; Sen, Pabitra N

    2006-12-01

    Pulsed field gradient NMR flow propagators for water flow in Bentheimer sandstone are measured at low fields (1H resonance 2 MHz), using both unipolar and bipolar variants of the pulsed gradient method. We compare with propagators measured at high fields (1H resonance 85 MHz). We show that (i) measured flow propagators appear to be equivalent, in this rock, and (ii) the lower signal to noise ratio at low fields is not a serious limitation. By comparing different pulse sequences, we study the effects of the internal gradients on the propagator measurement at 2 MHz, which for certain rocks may persist even at low fields. PMID:16962343

  18. Proppant effects on maintaining fracture permeability in shale.

    NASA Astrophysics Data System (ADS)

    Ingraham, M. D.; Bauer, S. J.; Bolintineanu, D.; Rao, R. R.; Lechman, J. B.; Romero, J. A.

    2014-12-01

    A series of tests have been performed on manually fractured and propped shale. The shale used in this study contained 5-10% porosity, and 10-40% clay. Samples were fractured subparallel to bedding. Quartz sand (0.60-0.85 mm) was used as a proppant; proppant was manually placed on a fracture surface, resulting in a monolayer with random distribution. The specimens were repeatedly subjected to reservoir conditions, 20.7 MPa confining, 6.9 MPa differential stress, and temperature of 75 C. System permeability was measured during testing by flowing DI water through the specimen, flow rates were set to 0.002 ml/min, with the downstream vented to atmosphere. Upstream pressure varied to maintain the flow rate, and was approximately 1.4 MPa in the most recent (lowest permeability) test. Between test periods, specimens were removed from the test system and scanned with x-ray μCT. There is significant decrease in flow with subsequent testing due fracture closure. This is attributed to observations of clay swelling, proppant embedment, proppant fracture and shale wall sloughing. These lead to a decrease in effective fracture aperture. Flow induced particle transport clogs flow paths and impedes flow. Isolated grains tend to crush whereas continuous grains in proppant patches tend fracture with little displacement and tend towards embedment. Corresponding numerical simulations are underway to capture the change in crack flow due to these mechanisms. Images from the CT scans of the proppant filled crack are segmented and meshed. Then flow simulations are performed via the finite element method. Preliminary results are discussed. This work is a precursor to laboratory-scale shale fracture and proppant testing; cores will be hydraulically fractured and propped with appropriate proppant and fluid rheology. Proppant life and permeability reduction will be monitored and specimens will be scanned with μCT. Tests will be used to inform proppant flow models which seek to model

  19. Permeability reduction in granite under hydrothermal conditions

    USGS Publications Warehouse

    Morrow, C.A.; Moore, Diane E.; Lockner, D.A.

    2001-01-01

    The formation of impermeable fault seals between earthquake events is a feature of many models of earthquake generation, suggesting that earthquake recurrence may depend in part on the rate of permeability reduction of fault zone materials under hydrothermal conditions. In this study, permeability measurements were conducted on intact, fractured, and gouge-bearing Westerly granite at an effective pressure of 50 MPa and at temperatures from 150?? to 500??C, simulating conditions in the earthquake-generating portions of fault zones. Pore fluids were cycled back and forth under a 2 MPa pressure differential for periods of up to 40 days. Permeability of the granite decreased with time t, following the exponential relation k = c(10-rt). For intact samples run between 250?? and 500??C the time constant for permeability decrease r was proportional to temperature and ranged between 0.001 and 0.1 days-1 (i.e., between 0.4 and 40 decades year-1 loss of permeability). Values of r for the lower-temperature experiments differed little from the 250??C runs. In contrast, prefractured samples showed higher rates of permeability decrease at a given temperature. The surfaces of the fractured samples showed evidence of dissolution and mineral growth that increased in abundance with both temperature and time. The experimentally grown mineral assemblages varied with temperature and were consistent with a rock-dominated hydrothermal system. As such mineral deposits progressively seal the fractured samples, their rates of permeability decrease approach the rates for intact rocks at the same temperature. These results place constraints on models of precipitation sealing and suggest that fault rocks may seal at a rate consistent with earthquake recurrence intervals of typical fault zones.

  20. Magnetic Nernst effect

    NASA Astrophysics Data System (ADS)

    Brechet, Sylvain D.; Ansermet, Jean-Philippe

    2015-09-01

    The thermodynamics of irreversible processes in continuous media predicts the existence of a magnetic Nernst effect that results from a magnetic analog to the Seebeck effect in a ferromagnet and magnetophoresis occurring in a paramagnetic electrode in contact with the ferromagnet. Thus, a voltage that has DC and AC components is expected across a Pt electrode as a response to the inhomogeneous magnetic induction field generated by magnetostatic waves of an adjacent YIG slab subject to a temperature gradient. The voltage frequency and dependence on the orientation of the applied magnetic induction field are quite distinct from that of spin pumping.

  1. Magnetic bearing and motor

    NASA Technical Reports Server (NTRS)

    Studer, Philip A. (Inventor)

    1983-01-01

    A magnetic bearing assembly (10) has an intermediate rotatable section (33) having an outer cylindrical member (30) coaxially suspended by a torsion wire (72) around an axially polarized cylindrical magnet (32). Axial alignment between the pole faces (40-43) of the intermediate section (33) and end surfaces (50-53) of opposed end bells (20, 22) provides a path of least reluctance across intervening air gaps (60-63) for the magnetic flux emanating from magnet (32). Radial dislocation increases the reluctance and creates a radial restoring force. Substitution of radially polarized magnets 107 fixed to a magnetically permeable cylinder (32') and insertion of pairs of armature coil windings (109-112) between the cylinder pair (33') provides an integral magnetic bearing and torsion motor (100) able to provide arcuately limited rotational drive.

  2. The ac53, ac78, ac101, and ac103 Genes Are Newly Discovered Core Genes in the Family Baculoviridae

    PubMed Central

    Garavaglia, Matías Javier; Miele, Solange Ana Belén; Iserte, Javier Alonso; Belaich, Mariano Nicolás

    2012-01-01

    The family Baculoviridae is a large group of insect viruses containing circular double-stranded DNA genomes of 80 to 180 kbp, which have broad biotechnological applications. A key feature to understand and manipulate them is the recognition of orthology. However, the differences in gene contents and evolutionary distances among the known members of this family make it difficult to assign sequence orthology. In this study, the genome sequences of 58 baculoviruses were analyzed, with the aim to detect previously undescribed core genes because of their remote homology. A routine based on Multi PSI-Blast/tBlastN and Multi HaMStR allowed us to detect 31 of 33 accepted core genes and 4 orthologous sequences in the Baculoviridae which were not described previously. Our results show that the ac53, ac78, ac101 (p40), and ac103 (p48) genes have orthologs in all genomes and should be considered core genes. Accordingly, there are 37 orthologous genes in the family Baculoviridae. PMID:22933288

  3. Simple Equipment for Imaging AC.

    ERIC Educational Resources Information Center

    Kamata, Masahiro; Anayama, Takayuki

    2003-01-01

    Presents an effective way to demonstrate the difference between direct current and alternating current using red and green LEDs. Describes how to make a tool that shows how an AC voltage changes with time using the afterimage effect of the LEDs. (Author/NB)

  4. Semiconductor ac static power switch

    NASA Technical Reports Server (NTRS)

    Vrancik, J.

    1968-01-01

    Semiconductor ac static power switch has long life and high reliability, contains no moving parts, and operates satisfactorily in severe environments, including high vibration and shock conditions. Due to their resistance to shock and vibration, static switches are used where accidental switching caused by mechanical vibration or shock cannot be tolerated.

  5. Energy saving in ac generators

    NASA Technical Reports Server (NTRS)

    Nola, F. J.

    1980-01-01

    Circuit cuts no-load losses, without sacrificing full-load power. Phase-contro circuit includes gate-controlled semiconductor switch that cuts off applied voltage for most of ac cycle if generator idling. Switch "on" time increases when generator is in operation.

  6. Analysis of nonlocal effective permittivity and permeability in symmetric metal–dielectric multilayer metamaterials

    NASA Astrophysics Data System (ADS)

    Sun, Lei; Yang, Xiaodong; Gao, Jie

    2016-06-01

    A generalized nonlocal effective medium theory is derived based on the transfer-matrix method to determine the nonlocal effective permittivity and permeability for the symmetric and periodic metal–dielectric multilayer metamaterials, with respect to both transverse-electric and transverse-magnetic polarized light at arbitrary angle of incidence. The nonlocal effective permittivity and permeability tensors are analyzed in detail as functions of the wavelength, the angle of incidence, and the multilayer period. Our generalized nonlocal effective medium theory in consideration of both permittivity and permeability can accurately predict the dispersion relation, the transmission and reflection spectra, and the optical field distributions of symmetric metal–dielectric multilayer stacks with either subwavelength or wavelength-scale period of the unit cell.

  7. Strain-dependent permeability of volcanic rocks.

    NASA Astrophysics Data System (ADS)

    Farquharson, Jamie; Heap, Michael; Baud, Patrick

    2016-04-01

    We explore permeability evolution during deformation of volcanic materials using a suite of rocks with varying compositions and physical properties (such as porosity ϕ). 40 mm × 20 mm cylindrical samples were made from a range of extrusive rocks, including andesites from Colima, Mexico (ϕ˜0.08; 0.18; 0.21), Kumamoto, Japan (ϕ˜0.13), and Ruapehu, New Zealand (ϕ˜0.15), and basalt from Mt Etna, Italy (ϕ˜0.04). Gas permeability of each sample was measured before and after triaxial deformation using a steady-state benchtop permeameter. To study the strain-dependence of permeability in volcanic rocks, we deformed samples to 2, 3, 4, 6, and 12 % axial strain at a constant strain rate of 10‑5 s‑1. Further, the influence of failure mode - dilatant or compactant - on permeability was assessed by repeating experiments at different confining pressures. During triaxial deformation, porosity change of the samples was monitored by a servo-controlled pore fluid pump. Below an initial porosity of ˜0.18, and at low confining pressures (≤ 20 MPa), we observe a dilatant failure mode (shear fracture formation). With increasing axial strain, stress is accommodated by fault sliding and the generation of ash-sized gouge between the fracture planes. In higher-porosity samples, or at relatively higher confining pressures (≥ 60 MPa), we observe compactant deformation characterised by a monotonous decrease in porosity with increasing axial strain. The relative permeability k' is given by the change in permeability divided by the initial reference state. When behaviour is dilatant, k' tends to be positive: permeability increases with progressive deformation. However, results suggest that after a threshold amount of strain, k' can decrease. k' always is negative (permeability decreases during deformation) when compaction is the dominant behaviour. Our results show that - in the absence of a sealing or healing process - the efficiency of a fault to transmit fluids is

  8. Gastrointestinal permeability in patients with irritable bowel syndrome assessed using a four probe permeability solution

    PubMed Central

    Del Valle-Pinero, Arseima Y.; Van Deventer, Hendrick E.; Fourie, Nicolaas H.; Martino, Angela C.; Patel, Nayan S.; Remaley, Alan T.; Henderson, Wendy A.

    2013-01-01

    Background Abnormal gastrointestinal permeability has been linked to irritable bowel syndrome (IBS). The lactulose-to-mannitol ratio is traditionally used to assess small intestine permeability while sucralose and sucrose are used to assess colonic and gastric permeability respectively. We used a single 4-probe test solution to assess permeability throughout the gastrointestinal tract in IBS patients and healthy controls by measuring the recovery of the probes in urine after ingestion using a modified liquid chromatography mass spectrometry protocol. Methods Fasting participants (N = 59) drank a permeability test solution (100 ml: sucralose, sucrose, mannitol, and lactulose). Urine was collected over a 5-h period and kept frozen until analysis. Urinary sugar concentrations were measured using an liquid chromatography/triple quadruple mass spectrometer. Results Colonic permeability was significantly lower in IBS patients when compared to healthy controls (p = 0.011). Gastric and small intestinal permeability did not significantly differ between the groups. Conclusions The study demonstrates the clinical potential of this non-invasive method for assessing alterations in gastrointestinal permeability in patients with IBS. PMID:23328210

  9. Quantitative Permeability Prediction for Anisotropic Porous Media

    NASA Astrophysics Data System (ADS)

    Sheng, Q.; Thompson, K. E.

    2012-12-01

    Pore-scale modeling as a predictive tool has become an integral to both research and commercial simulation in recent years. Permeability is one of the most important of the many properties that can be simulated. Traditionally, permeability is determined using Darcy's law, based on the assumption that the pressure gradient is aligned with the principal flow direction. However, a wide variety of porous media exhibit anisotropic permeability due to particle orientation or laminated structure. In these types of materials, the direction of fluid flow is not aligned with the pressure gradient (except along the principal directions). Thus, it is desirable to predict the full permeability tensor for anisotropic materials using a first-principles pore-scale approach. In this work, we present a fast method to determine the full permeability tensor and the principal directions using a novel network modeling algorithm. We also test the ability of network modeling (which is an approximate method) to detect anisotropy in various structures. Both computational fluid dynamics (CFD) methods and network modeling have emerged as effective techniques to predict rock properties. CFD models are more rigorous but computationally expensive. Network modeling involves significant approximations but can be orders-of-magnitude more efficient computationally, which is important for both speed and the ability to model larger scales. This work uses network modeling, with simulations performed on two types of anisotropic materials: laminated packings (with layers of different sized particles) and oriented packings (containing particles with preferential orientation). Pore network models are created from the porous media data, and a novel method is used to determine the permeability tensor and principal flow direction using pore network modeling. The method is verified by comparing the calculated principal directions with the known anisotropy and also by comparing permeability with values from CFD

  10. Quenching of the initial ac Susceptibility in Single Domain Ni Nanobars

    SciTech Connect

    Gai, Zheng; Zhang, Xiaoguang; Kravchenko, Ivan I; Retterer, Scott T; Wendelken, J F

    2012-01-01

    The ac susceptibility measurement probes the dynamic properties of a magnetic material, which is believed to consist of magnetization rotation and domain wall motion contributions. Here we report the observation of a complete quenching of the initial ac susceptibility for a single domain Ni nanobar array, when the ac field is aligned with the long axis of the bars. The vanishing of the susceptibility in one direction is a unique nanoscale phenomena, allowing an unambiguous determination of the magnetic state of the nanostructure and a clean separation of different contributions to its dynamic properties. For example, an unambiguous determination of the surface anisotropy energy is obtained when the field is applied perpendicular to the long axis.

  11. Peculiarities in electromagnetic behavior of MF NbTi composites for AC use

    SciTech Connect

    Hlasnik, I.; Fukui, S.; Amemiya, N.

    1994-07-01

    The paper presents results obtained in the study of the current-voltage characteristics, critical and quenching currents as well as of the AC transport current and magnetization losses in four series of fine filament NbTi composites prepared by Showa Electric Wire and Cable Co., Japan. Complementary measurements have been made also on a commercially available type T AC superconducting wire produced by GEC Alsthom Company, France. The samples differ in filament diameter, matrix thickness between filaments and in the number and structure of filament bundles in the composite. In two series of samples barrier type artificial pinning centers have been introduced to increase J{sub c} and decrease the normalized magnetization losses. The conclusions concerning the optimization of multifilamentary composites and cables for AC use at low working magnetic field are briefly reviewed.

  12. Gas Permeability in Rubbery Polyphosphazene Membranes

    SciTech Connect

    Frederick F. Stewart; Christopher J. Orme; John R. Klaehn; Mason K. Harrup; Thomas A. Luther; Eric S. Peterson

    2006-09-01

    The synthesis, characterization, and gas permeability of ten new polyphosphazenes has been studied. Additionally, the first gas permeation data has been collected on hydrolytically unstable poly[bis-(chloro)phosphazene]. Gases used in this study include CO2, CH4, O2, N2, H2, and Ar. CO2 was the most permeable gas through any of the phosphazenes and a direct correlation between the Tg of the polymer and CO2 transport was noted with permeability increasing with decreasing polymer Tg. To a lesser degree, permeability of all the other gases studied also yielded increases with decreasing polymer Tg. The trend observed for these new polymers was further supported by published data for other phosphazenes. Furthermore, permeability data for all gases were found to correlate to the gas condensability and the gas critical pressures, except for hydrogen, suggesting that the nature of the gas is also a significant factor for permeation through rubbery phosphazene membranes. Ideal separation factors (á) for the CO2/H2 and CO2/CH4 gas pairs were calculated. For CO2/CH4, no increase in á was observed with decreasing Tg, however increases in á were noted for the CO2/H2 pair.

  13. Honeycomb Core Permeability Under Mechanical Loads

    NASA Technical Reports Server (NTRS)

    Glass, David E.; Raman, V. V.; Venkat, Venki S.; Sankaran, Sankara N.

    1997-01-01

    A method for characterizing the air permeability of sandwich core materials as a function of applied shear stress was developed. The core material for the test specimens was either Hexcel HRP-3/16-8.0 and or DuPont Korex-1/8-4.5 and was nominally one-half inch thick and six inches square. The facesheets where made of Hercules' AS4/8552 graphite/epoxy (Gr/Ep) composites and were nominally 0.059-in. thick. Cytec's Metalbond 1515-3M epoxy film adhesive was used for co-curing the facesheets to the core. The permeability of the specimens during both static (tension) and dynamic (reversed and non-reversed) shear loads were measured. The permeability was measured as the rate of air flow through the core from a circular 1-in2 area of the core exposed to an air pressure of 10.0 psig. In both the static and dynamic testing, the Korex core experienced sudden increases in core permeability corresponding to a core catastrophic failure, while the URP core experienced a gradual increase in the permeability prior to core failure. The Korex core failed at lower loads than the HRP core both in the transverse and ribbon directions.

  14. Changes in permeability caused by earthquakes

    NASA Astrophysics Data System (ADS)

    Manga, Michael; Wang, Chi-Yuen; Shi, Zheming

    2016-04-01

    Earthquakes induce a range of hydrological responses, including changes in streamflow and changes in the water level in wells. Here we show that many of these responses are caused the changes in permeability produced by the passage of seismic waves. First we analyze streams that were dry or nearly dry before the 2014 M6 Napa, California, earthquake butstarted to flow after the earthquake. We show that the new flows were meteoric in origin and originate in the nearby mountains. Responses are not correlated with the sign of static strains implying seismic waves liberated this water, presumably by changing permeability. We also analyze a large network of wells in China that responded to 4 large earthquakes. We monitor permeability changes through their effect on the water level response to solid Earth tides. We find that when earthquakes produce sustained changes in water level, permeability also changes. Wells with water level changes that last for only days show no evidence for changes in aquifer permeability.

  15. Permeability of Rigid Fibrous Refractory Insulations

    NASA Technical Reports Server (NTRS)

    Marschall, J.; Milos, F. S.; Rasky, Daniel J. (Technical Monitor)

    1996-01-01

    Rigid fibrous refractory insulations (TPS tiles) are integral components of many spacecraft thermal protection systems. These materials are composed of refractory fibers With diameters on the order of 1 to 15 micrometers. They are lightweight and have an open, highly porous microstructure. Typical densities are less than 500 kilograms per cubic meters, and porosities generally exceed 0.8. Because of their open porosity, these materials are permeable to gas glow. There are numerous instances in which internal gas transport in a thermal protection system could be important; examples include the penetration of hot boundary-layer gases into the insulation, the flow of decomposition (pyrolysis) products from the interior, the use of convective flows to mitigate ice formation caused by cryopumping, and the design of refractory vents for pressure equilibration during atmospheric entry. Computational analysis of gas flow through porous media requires values of permeability which have not previously been available for the rigid fibrous insulations used in thermal protection systems. This paper will document measurements of permeability for a variety of insulations from NASA's LI, FRCI, and AETB families of lightweight ceramic ablators. The directional anisotropy of permeability and its dependence on gas pressure and material density will be presented. It will be shown that rarified-flow effects are significant in the flow through such materials. Connections will be drawn between the insulation microstructure and permeability. The paper will also include representative computations of flow through rigid fibrous insulations.

  16. Comparison of Steady State Method and Transient Methods for Water Permeability Measurement in Low Permeability Rocks

    NASA Astrophysics Data System (ADS)

    Boulin, P. F.; Bretonnier, P.; Gland, N.

    2010-12-01

    Very low permeability geomaterials (order of nanoDarcy (10-21 m2)), such as clays rocks, are studied for many industrial applications such as production from unconventional reserves of oil and gas, CO2 geological storage and deep geological disposal of high-level long-lived nuclear wastes. For these last two applications, clay efficiency as barrier relies mainly on their very low permeability. Laboratory measurement of low permeability to water (below 10-19 m2) remains a technical challenge. Some authors argue that steady state methods are irrelevant due to the time required to stabilize water fluxes in such low permeability media. Most of the authors measuring low permeabilities use a transient technique called pulse decay. This study aims to compare objectively these different types of permeability tests performed on a single clay sample. For the steady state method, a high precision pump was used to impose a pressure gradient and to measure the small resulting water flow rate at steady state. We show that with a suitable set-up, the steady state method enables to measure a very low permeability of 8 10-22 m2 in a period of three days. For a comparable duration, the pulse decay test, most commonly used for such low permeability measurements, provides only an average estimate of the permeability. Permeability measurements by pulse decay require to perform simulations to interpret the pressure relaxation signals. Many uncertainties remain such as the determination of the reservoirs storage factor, micro leakage effect, or the determination of the initial pulse pressure. All these uncertainties have a very significant impact on the determination of sample permeability and specific storage. Opposite to the wide-spread idea that transient techniques are required to measure very low permeability, we show that direct steady state measurement of water permeability with suitable equipments can be much faster and more accurate than measurement by pulse decay, especially in

  17. Reactive Transport Modeling of CO2-induced Porosity and Permeability Changes in Heterogeneous Carbonate Rocks

    NASA Astrophysics Data System (ADS)

    Hao, Y.; Smith, M. M.; Mason, H. E.; Carroll, S.

    2015-12-01

    It has long been appreciated that chemical interactions have a major effect on rock porosity and permeability evolution and may alter the behavior or performance of both natural and engineered reservoir systems. Such reaction-induced permeability evolution is of particular importance for geological CO2 sequestration and storage associated with enhanced oil recovery. In this study we used a three-dimensional Darcy scale reactive transport model to simulate CO2 core flood experiments in which the CO2-equilibrated brine was injected into dolostone cores collected from the Arbuckle carbonate reservoir, Wellington, Kansas. Heterogeneous distributions of macro pores, fractures, and mineral phases inside the cores were obtained from X-ray computed microtomography (XCMT) characterization data, and then used to construct initial model macroscopic properties including porosity, permeability, and mineral compositions. The reactive transport simulations were performed by using the Nonisothermal Unsaturated Flow and Transport (NUFT) code, and their results were compared with experimental data. It was observed both experimentally and numerically that the dissolution fronts became unstable in highly heterogeneous and less permeable formations, leading to the development of highly porous flow paths or wormholes. Our model results indicate that the continuum-scale reactive transport models are able to adequately capture the evolution of distinct dissolution fronts as observed in carbonate rocks at a core scale. The impacts of rock heterogeneity, chemical kinetics and porosity-permeability relationships were also examined in this study. The numerical model developed in this study will not only help improve understanding of coupled physical and chemical processes controlling carbonate dissolution, but also provide a useful basis for upscaling transport and reaction properties from core scale to field scale. This work was performed under the auspices of the U.S. Department of Energy

  18. Voltage controller/current limiter for ac

    NASA Technical Reports Server (NTRS)

    Wu, T. T.

    1980-01-01

    Circuit protects ac power systems for overload failures, limits power surge and short-circuit currents to 150 percent of steady state level, regulates ac output voltage, and soft starts loads. Limiter generates dc error signal in response to line fluctuations and dumps power when overload is reached. Device is inserted between ac source and load.

  19. GROUNDWATER FLOW IN LOW-PERMEABILITY ENVIRONMENTS.

    USGS Publications Warehouse

    Neuzil, C.E.

    1986-01-01

    Certain geologic media are known to have small permeability; subsurface environments composed of these media and lacking well developed secondary permeability have groundwater flow systems with many distinctive characteristics. Moreover, groundwater flow in these environments appears to influence the evolution of certain hydrologic, geologic, and geochemical systems, may affect the accumulation of petroleum and ores, and probably has a role in the structural evolution of parts of the crust. Such environments are also important in the context of waste disposal. This review attempts to synthesize the diverse contributions of various disciplines to the problem of flow in low-permeability environments. Problems hindering analysis are enumerated together with suggested approaches to overcoming them. A common thread running through the discussion is the significance of size- and time-scale limitations of the ability to directly observe flow behavior and make significance of size- and time-scale limitations of the ability to directly observe flow behavior and make measurements of parameters.

  20. Permeability of Hollow Microspherical Membranes to Helium

    NASA Astrophysics Data System (ADS)

    Zinoviev, V. N.; Kazanin, I. V.; Pak, A. Yu.; Vereshchagin, A. S.; Lebiga, V. A.; Fomin, V. M.

    2016-01-01

    This work is devoted to the study of the sorption characteristics of various hollow microspherical membranes to reveal particles most suitable for application in the membrane-sorption technologies of helium extraction from a natural gas. The permeability of the investigated sorbents to helium and their impermeability to air and methane are shown experimentally. The sorption-desorption dependences of the studied sorbents have been obtained, from which the parameters of their specific permeability to helium are calculated. It has been established that the physicochemical modification of the original particles exerts a great influence on the coefficient of the permeability of a sorbent to helium. Specially treated cenospheres have displayed high efficiency as membranes for selective extraction of helium.

  1. The effect of heat on skin permeability

    PubMed Central

    Park, Jung-Hwan; Lee, Jeong-Woo; Kim, Yeu-Chun; Prausnitz, Mark R.

    2008-01-01

    Although the effects of long exposure (≫ 1 s) to moderate temperatures (≤ 100 °C) have been well characterized, recent studies suggest that shorter exposure (< 1 s) to higher temperatures (> 100 °C) can dramatically increase skin permeability. Previous studies suggest that by keeping exposures short, thermal damage can be localized to the stratum corneum without damaging deeper tissue. Initial clinical trials have progressed to Phase II (see http://clinicaltrials.gov), which indicates the procedure can be safe. Because the effect of heating under these conditions has received little systematic or mechanistic study, we heated full-thickness skin, epidermis and stratum corneum samples from human and porcine cadavers to temperatures ranging from 100°C to 315°C for times ranging from 100 ms to 5 s. Tissue samples were analyzed using skin permeability measurements, differential scanning calorimetry, thermomechanical analysis, thermal gravimetric analysis, brightfield and confocal microscopy, and histology. Skin permeability was shown to be a very strong function of temperature and a less strong function of the duration of heating. At optimal conditions used in this study, transdermal delivery of calcein was increased up to 760-fold by rapidly heating the skin at high temperature. More specifically, skin permeability was increased (I) by a few fold after heating to approximately 100°C – 150°C, (II) by one to two orders of magnitude after heating to approximately 150°C – 250°C and (III) by three orders of magnitude after heating above 300°C. These permeability changes were attributed to (I) disordering of stratum corneum lipid structure, (II) disruption of stratum corneum keratin network structure and (III) decomposition and vaporization of keratin to create micron-scale holes in the stratum corneum, respectively. We conclude that heating the skin with short, high temperature pulses can increase skin permeability by orders of magnitude due to structural

  2. Measurements of AC Losses and Current Distribution in Superconducting Cables

    SciTech Connect

    Nguyen, Doan A; Ashworth, Stephen P; Duckworth, Robert C; Carter, Bill; Fleshler, Steven

    2011-01-01

    This paper presents our new experimental facility and techniques to measure ac loss and current distribution between the layers for High Temperature Superconducting (HTS) cables. The facility is powered with a 45 kVA three-phase power supply which can provide three-phase currents up to 5 kA per phase via high current transformers. The system is suitable for measurements at any frequency between 20 and 500 Hz to better understand the ac loss mechanisms in HTS cables. In this paper, we will report techniques and results for ac loss measurements carried out on several HTS cables with and without an HTS shielding layer. For cables without a shielding layer, care must be taken to control the effect of the magnetic fields from return currents on loss measurements. The waveform of the axial magnetic field was also measured by a small pick-up coil placed inside a two-layer cable. The temporal current distribution between the layers can be calculated from the waveform of the axial field.

  3. In-situ permeability determining method

    SciTech Connect

    Dowling, D.J.; Arnold, D.M.; Richter, A.P. Jr.; Warren, W.F.

    1985-01-29

    A method of determining the permeability of a particular stratum in an earth formation traversed by a borehole includes injecting a liquid into the borehole at a first pressure thereby causing liquid flow into the stratum. A first flow rate of the liquid is determined at the first pressure. The pressure of the liquid being injected into the borehole is then changed to a second pressure level and a second flow rate of the liquid flowing into the stratum is determined at the second pressure. An indication of the permeability of the stratum is then derived in accordance with the two pressures, the two flow rates and known characteristics of the stratum.

  4. Development of an Improved Permeability Modification Simulator

    SciTech Connect

    Gao, H.W.; Elphnick, J.

    1999-03-09

    This report describes the development of an improved permeability modification simulator performed jointly by BDM Petroleum Technologies and Schlumberger Dowell under a cooperative research and development agreement (CRADA) with the US Department of Energy. The improved simulator was developed by modifying NIPER's PC-GEL permeability modification simulator to include a radial model, a thermal energy equation, a wellbore simulator, and a fully implicit time-stepping option. The temperature-dependent gelation kinetics of a delayed gel system (DGS) is also included in the simulator.

  5. Water Permeability of Asymmetric Planar Lipid Bilayers

    PubMed Central

    Krylov, Andrey V.; Pohl, Peter; Zeidel, Mark L.; Hill, Warren G.

    2001-01-01

    To understand how plasma membranes may limit water flux, we have modeled the apical membrane of MDCK type 1 cells. Previous experiments demonstrated that liposomes designed to mimic the inner and outer leaflet of this membrane exhibited 18-fold lower water permeation for outer leaflet lipids than inner leaflet lipids (Hill, W.G., and M.L. Zeidel. 2000. J. Biol. Chem. 275:30176–30185), confirming that the outer leaflet is the primary barrier to permeation. If leaflets in a bilayer resist permeation independently, the following equation estimates single leaflet permeabilities: 1/PAB = 1/PA + 1/PB (Eq. l), where PAB is the permeability of a bilayer composed of leaflets A and B, PA is the permeability of leaflet A, and PB is the permeability of leaflet B. Using for the MDCK leaflet–specific liposomes gives an estimated value for the osmotic water permeability (Pf) of 4.6 × 10−4 cm/s (at 25°C) that correlated well with experimentally measured values in intact cells. We have now constructed both symmetric and asymmetric planar lipid bilayers that model the MDCK apical membrane. Water permeability across these bilayers was monitored in the immediate membrane vicinity using a Na+-sensitive scanning microelectrode and an osmotic gradient induced by addition of urea. The near-membrane concentration distribution of solute was used to calculate the velocity of water flow (Pohl, P., S.M. Saparov, and Y.N. Antonenko. 1997. Biophys. J. 72:1711–1718). At 36°C, Pf was 3.44 ± 0.35 × 10−3 cm/s for symmetrical inner leaflet membranes and 3.40 ± 0.34 × 10−4 cm/s for symmetrical exofacial membranes. From , the estimated permeability of an asymmetric membrane is 6.2 × 10−4 cm/s. Water permeability measured for the asymmetric planar bilayer was 6.7 ± 0.7 × 10−4 cm/s, which is within 10% of the calculated value. Direct experimental measurement of Pf for an asymmetric planar membrane confirms that leaflets in a bilayer offer independent and additive resistances to

  6. Noise modeling from high-permeability shields using Kirchhoff equations

    SciTech Connect

    Sandin, Henrik J; Volegov, Petr L; Espy, Michelle A; Matlashov, Andrei N; Savukov, Igor M; Schultz, Larry J

    2010-01-01

    Progress in the development of high-sensitivity magnetic-field measurements has stimulated interest in understanding magnetic noise of conductive materials, especially of magnetic shields (DC or rf) based on high-permeability materials and/or high-conductivity materials. For example, SQUIDs and atomic magnetometers have been used in many experiments with mu-metal shields, and additionally SQUID systems frequently have rf shielding based on thin conductive materials. Typical existing approaches to modeling noise only work with simple shield and sensor geometries while common experimental setups today consist of multiple sensor systems arbitrary shapes and complex shield geometries. With complex sensor arrays used in, for example, MEG and Ultra Low Field MRI studies the knowledge of the noise correlation between sensors is as important as the knowledge of the noise itself. This is crucial for incorporating efficient noise cancelation schemes for the system. We developed an approach that allows us to calculate the Johnson noise for any geometrically shaped shield and multiple sensor systems. The approach uses a fraction of the processing power of other approaches and with a multiple sensor system our approach not only calculates the noise for each sensor but it also calculates the noise correlation matrix between sensors. Here we will show the algorithm and examples where it can be implemented.

  7. Giant uniaxial stress-permeability effect on electrical parameters of heterotypic MnZn ferrite devices and electromagnetic effect

    NASA Astrophysics Data System (ADS)

    Fang, X.; Wang, Z. L.; Zhang, N.; Mao, J. M.

    2009-09-01

    The effects of uniaxial stress on permeability and electrical parameters of heterotypic manganite zinc (MnZn) ferrite devices have been investigated. Giant stress-permeability, stress-capacitance and stress-impedance that are independent of skin effects have been simultaneously observed to exist in a wide range of frequency at room temperature. All the uniaxial stress effects enhance with increasing the permeability of the ferrite. The stress-inductance is same as the stress-impedance and reverse to the stress-capacitance in phase. The stress effects under uniaxial pulling force are analogical with those under uniaxial pressing force. A composite of electrostrain/stress-permeability has been fabricated. Its electromagnetic effects have been observed to be homologous with the stress effects and can also exist in wide range of frequency but display some maximums. Analysis shows that both stress and electromagnetic effects originate from the variation of the magnetic domain structure in the ferrites caused by applied mechanical stress.

  8. Predicting the permeability of sediments entering subduction zones

    NASA Astrophysics Data System (ADS)

    Daigle, Hugh; Screaton, Elizabeth J.

    2015-07-01

    Using end-member permeabilities defined by a worldwide compilation of sediment permeabilities at convergent margins, we compare permeability predictions using a geometric mean and a two-component effective medium theory (EMT). Our implementation of EMT includes a threshold fraction of the high-permeability component that determines whether flow occurs dominantly in the high- or low-permeability component. We find that this threshold fraction in most cases is equal to the silt + sand-sized fraction of the sediment. This suggests that sediments undergoing primary consolidation tend to exhibit flow equally distributed between the high- and low-permeability components. We show that the EMT method predicts permeability better than the weighted geometric mean of the end-member values for clay fractions <0.6. This work provides insight into the microstructural controls on permeability in subducting sediments and valuable guidance for locations which lack site-specific permeability results but have available grain-size information.

  9. Simultaneous distribution of AC and DC power

    DOEpatents

    Polese, Luigi Gentile

    2015-09-15

    A system and method for the transport and distribution of both AC (alternating current) power and DC (direct current) power over wiring infrastructure normally used for distributing AC power only, for example, residential and/or commercial buildings' electrical wires is disclosed and taught. The system and method permits the combining of AC and DC power sources and the simultaneous distribution of the resulting power over the same wiring. At the utilization site a complementary device permits the separation of the DC power from the AC power and their reconstruction, for use in conventional AC-only and DC-only devices.

  10. ac-resistance-measuring instrument

    SciTech Connect

    Hof, P.J.

    1981-04-22

    An auto-ranging ac resistance measuring instrument for remote measurement of the resistance of an electrical device or circuit connected to the instrument includes a signal generator which generates an ac excitation signal for application to a load, including the device and the transmission line, a monitoring circuit which provides a digitally encoded signal representing the voltage across the load, and a microprocessor which operates under program control to provide an auto-ranging function by which range resistance is connected in circuit with the load to limit the load voltage to an acceptable range for the instrument, and an auto-compensating function by which compensating capacitance is connected in shunt with the range resistance to compensate for the effects of line capacitance.

  11. Quantitative Measurement of Blood-Brain Barrier Permeability in Human Using Dynamic Contrast-Enhanced MRI with Fast T1 Mapping

    PubMed Central

    Taheri, Saeid; Gasparovic, Charles; Shah, Nadim Jon; Rosenberg, Gary A.

    2016-01-01

    Breakdown of the blood-brain barrier (BBB), occurring in many neurological diseases, has been difficult to measure noninvasively in humans. Dynamic contrast-enhanced magnetic resonance imaging measures BBB permeability. However, important technical challenges remain and normative data from healthy humans is lacking. We report the implementation of a method for measuring BBB permeability, originally developed in animals, to estimate BBB permeability in both healthy subjects and patients with white matter pathology. Fast T1 mapping was used to measure the leakage of contrast agent Gadolinium diethylene triamine pentaacetic acid (Gd-DTPA) from plasma into brain. A quarter of the standard Gd-DTPA dose for dynamic contrast-enhanced magnetic resonance imaging was found to give both sufficient contrast-to-noise and high T1 sensitivity. The Patlak graphical approach was used to calculate the permeability from changes in 1/T1. Permeability constants were compared with cerebrospinal fluid albumin index. The upper limit of the 95% confidence interval for white matter BBB permeability for normal subjects was 3 × 10−4 L/g min. MRI measurements correlated strongly with levels of cerebrospinal fluid albumin in those subjects undergoing lumbar puncture. Dynamic contrast-enhanced magnetic resonance imaging with low dose Gd-DTPA and fast T1 imaging is a sensitive method to measure subtle differences in BBB permeability in humans and may have advantages over techniques based purely on the measurement of pixel contrast changes. PMID:21413067

  12. Vascular Permeability and Drug Delivery in Cancers

    PubMed Central

    Azzi, Sandy; Hebda, Jagoda K.; Gavard, Julie

    2013-01-01

    The endothelial barrier strictly maintains vascular and tissue homeostasis, and therefore modulates many physiological processes such as angiogenesis, immune responses, and dynamic exchanges throughout organs. Consequently, alteration of this finely tuned function may have devastating consequences for the organism. This is particularly obvious in cancers, where a disorganized and leaky blood vessel network irrigates solid tumors. In this context, vascular permeability drives tumor-induced angiogenesis, blood flow disturbances, inflammatory cell infiltration, and tumor cell extravasation. This can directly restrain the efficacy of conventional therapies by limiting intravenous drug delivery. Indeed, for more effective anti-angiogenic therapies, it is now accepted that not only should excessive angiogenesis be alleviated, but also that the tumor vasculature needs to be normalized. Recovery of normal state vasculature requires diminishing hyperpermeability, increasing pericyte coverage, and restoring the basement membrane, to subsequently reduce hypoxia, and interstitial fluid pressure. In this review, we will introduce how vascular permeability accompanies tumor progression and, as a collateral damage, impacts on efficient drug delivery. The molecular mechanisms involved in tumor-driven vascular permeability will next be detailed, with a particular focus on the main factors produced by tumor cells, especially the emblematic vascular endothelial growth factor. Finally, new perspectives in cancer therapy will be presented, centered on the use of anti-permeability factors and normalization agents. PMID:23967403

  13. A microdevice for parallelized pulmonary permeability studies.

    PubMed

    Bol, Ludivine; Galas, Jean-Christophe; Hillaireau, Hervé; Le Potier, Isabelle; Nicolas, Valérie; Haghiri-Gosnet, Anne-Marie; Fattal, Elias; Taverna, Myriam

    2014-04-01

    We describe a compartmentalized microdevice specifically designed to perform permeability studies across a model of lung barrier. Epithelial cell barriers were reproduced by culturing Calu-3 cells at the air-liquid interface (AIC) in 1 mm² microwells made from a perforated glass slide with an embedded porous membrane. We created a single basolateral reservoir for all microwells which eliminated the need to renew the growth medium during the culture growth phase. To perform drug permeability studies on confluent cell layers, the cell culture slide was aligned and joined to a collection platform consisting in 35 μL collection reservoirs connected at the top and bottom with microchannels. The integrity and functionality of the cell barriers were demonstrated by measurement of trans-epithelial electrical resistance (TEER), confocal imaging and permeability assays of ¹⁴C-sucrose. Micro-cell barriers were able to form confluent layers in 1 week, demonstrating a similar bioelectrical evolution as the Transwell systems used as controls. Tight junctions were observed throughout the cell-cell interfaces, and the low permeability coefficients of ¹⁴C-sucrose confirmed their functional presence, creating a primary barrier to the diffusion of solutes. This microdevice could facilitate the monitoring of biomolecule transport and the screening of formulations promoting their passage across the pulmonary barrier, in order to select candidates for pulmonary administration to patients. PMID:24337430

  14. EVALUATION OF PERMEABLE REACTIVE BARRIER PERFORMANCE

    EPA Science Inventory

    The permeable reactive barrier (PRB) technology represents a passive option for long-term treatment of ground-water contamination. PRBs are a potentially more cost-effective treatment option for a variety of dissolved contaminants, such as certain types of chlorinated solvents, ...

  15. A permeable rotating-wheel solvent extractor

    NASA Technical Reports Server (NTRS)

    Kahn, D. R.; Nady, L. A.

    1972-01-01

    Column-type device reported employs circular permeable structures of wire mesh screen for extracting solvents from systems with low density differences and low interfacial tensions. Rotating screen wheels of structure fasten to shaft; stationary screen structures are supported by circular bands connected by radial metal arms.

  16. Permeable pavement research – Edison, New Jersey

    EPA Science Inventory

    These are the slides for the New York City Concrete Promotional Council Pervious Concrete Seminar presentation. The basis for the project, the monitoring design and some preliminary monitoring data from the permeable pavement parking lot at the Edison Environmental Center are pre...

  17. Tailoring wall permeabilities for enhanced filtration

    NASA Astrophysics Data System (ADS)

    Herterich, J. G.; Vella, D.; Field, R. W.; Hankins, N. P.; Griffiths, I. M.

    2015-05-01

    The build-up of contaminants at the wall of cross-flow membrane filtration systems can be detrimental to the operation of such systems because of, amongst other things, the osmotic backflow it may induce. In this paper, we propose a strategy to avoid the negative effects of backflow due to osmosis by using 2D channels bounded by walls with a combination of permeable and impermeable segments. We show that preventing flow through the final portion of the channel can increase the efficiency of filtration and we determine the optimal fraction occupied by the permeable wall that maximizes efficiency. Our analysis uses a combination of numerical techniques and asymptotic analysis in the limit of low wall permeabilities. Finally, we consider how the energy cost of filtration depends on the Péclet number and show that the energy cost per unit of filtered water may be minimized by appropriately choosing both the Péclet number and the permeable-region fraction.

  18. Estimating Plastic Film Permeability Under Field Conditions

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Fumigant emission is an important air quality and human health concern. Plastic films are used to reduce emissions. Laboratory tests have shown large differences in permeability between various films, including the typical polyethylene films (PEs), virtually impermeable films (VIFs), and semi-impe...

  19. Pump and treat in low permeability media

    SciTech Connect

    Mackay, D.M.

    1996-08-01

    Pump and Treat (P&T) is a commonly applied technology whose primary promise for the low permeability environments of interest to these technology reviews is almost certainly containment of the problem. Conventional P&T would be expected to offer little promise of complete restoration in such environments, unless very long time frames (decades or centuries) are considered. A variety of approaches have been proposed to enhance the efficiency of P&T; some appear to offer little promise in low or mixed permeability environments, while others may offer more promise (e.g. hydro- or pneumatic-fracturing, which are described elsewhere in this document, and application of vacuum to the extraction well(s), which is a proprietary technology whose promise is currently difficult to assess objectively). Understanding the potential advantages and means of optimizing these enhancement approaches requires more understanding of the basic processes limiting P&T performance in low or mixed permeability media. These efforts are probably also necessary to understand the advantages and means of optimizing many of the very different remedial technologies that may be applicable to low or mixed permeability environments. Finally, since a reasonably certain capability of P&T is containment (i.e. prevention of further migration of contaminants), P&T may generally be required as a sort of safety net around sites at which the alternative technologies are being tested or applied. 23 refs.

  20. SINGLE-INTERVAL GAS PERMEABILITY ESTIMATION

    EPA Science Inventory

    Single-interval, steady-steady-state gas permeability testing requires estimation of pressure at a screened interval which in turn requires measurement of friction factors as a function of mass flow rate. Friction factors can be obtained by injecting air through a length of pipe...