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Sample records for magnetic potential barriers

  1. Electron optics with magnetic vector potential barriers in graphene

    International Nuclear Information System (INIS)

    Ghosh, Sankalpa; Sharma, Manish

    2009-01-01

    An analysis of electron transport in graphene in the presence of various arrangements of delta-function like magnetic barriers is presented. The motion through one such barrier gives an unusual non-specular refraction leading to asymmetric transmission. The symmetry is restored by putting two such barriers in opposite directions side by side. Periodic arrangements of such barriers can be used as Bragg reflectors whose reflectivity has been calculated using a transfer matrix formalism. Such Bragg reflectors can be used to make resonant cavities. We also analyze the associated band structure for the case of infinite periodic structures. (fast track communication)

  2. Magnetic properties and potential barrier between crystallites model of MgGa2-xFexO4 ceramics

    Directory of Open Access Journals (Sweden)

    V. A. dos S. Ribeiro

    Full Text Available Abstract The aim of this work was to investigate the magnetic properties and the electrical conductivity temperature dependence associated to the potential barrier between the crystallites model. Gallium and magnesium containing spinel ceramic has low magnetic coercivity and high electrical resistivity. MgGa2-xFexO4 samples (x= 0.01, 0.05, 0.15, 0.25, 0.35 were prepared by solid-state method and sintered at 800 °C for 8 h. X-ray diffraction analysis confirmed the formation of a single phase with compact cubic spinel structure. The magnetic measurements show that the saturation magnetization and remanence of all samples increased with increasing iron concentration. The coercive field decreased up to the concentration x= 0.15, and above x= 0.25 it was observed an increase in the coercive field. Through electrical characterization it was found that the samples presented highly insulating behavior for x= 0.01, and further increase in x above 0.15 gives a semiconductor behavior compatible with the potential barrier between the crystallites model, i.e. fulfills the condition L/2 > LD (crystallite size L in comparison with the Debye length LD, and the conduction is limited by potential barriers between the crystallites.

  3. Magnetic properties and potential barrier between crystallites model of MgGa{sub 2-x}Fe{sub x}O{sub 4} ceramics

    Energy Technology Data Exchange (ETDEWEB)

    Ribeiro, V.A. dos S.; Rubinger, R.M.; Oliveira, A.F.; Mendonca, C.S.P.; Silva, M.R. da, E-mail: vanderalkmin@gmail.com, E-mail: rero@unifei.edu.br, E-mail: adhimarflavio@unifei.edu.br, E-mail: sales.claudiney21@gmail.com, E-mail: mrsilva@unifei.edu.br [Universidade Federal de Itajuba (UNIFEI), MG (Brazil). Instituto de Fisica e Quimica

    2016-10-15

    The aim of this work was to investigate the magnetic properties and the electrical conductivity temperature dependence associated to the potential barrier between the crystallites model. Gallium and magnesium containing spinel ceramic has low magnetic coercivity and high electrical resistivity. MgGa{sub 2-x}Fe{sub x}O{sub 4} samples (x= 0.01, 0.05, 0.15, 0.25, 0.35) were prepared by solid-state method and sintered at 800 °C for 8 h. X-ray diffraction analysis confirmed the formation of a single phase with compact cubic spinel structure. The magnetic measurements show that the saturation magnetization and remanence of all samples increased with increasing iron concentration. The coercive field decreased up to the concentration x= 0.15, and above x= 0.25 it was observed an increase in the coercive field. Through electrical characterization it was found that the samples presented highly insulating behavior for x= 0.01, and further increase in x above 0.15 gives a semiconductor behavior compatible with the potential barrier between the crystallites model, i.e. fulfills the condition L/2 > L{sub D} (crystallite size L in comparison with the Debye length L{sub D}), and the conduction is limited by potential barriers between the crystallites. (author)

  4. Tunnel superpenetrability of potential barriers

    International Nuclear Information System (INIS)

    Zakhariev, B N.

    1982-01-01

    The transmission of two particles through the same barrier is considered. The limiting cases are compared when the particles are joined together in a single particle with double mass-energy and potential and when they pass the barrier independently. As an intermediate case a pair of particles bound in a quasideuteron of a finite size is considered. It is shown that long-range collective correlations of particles (of the superfluidity type and others) simplify very much for them passing through high potential barriers. This happens due to the transfer of the additional energy from the particles outside the barriers to those inside it

  5. Electron transmission through a periodically driven graphene magnetic barrier

    Energy Technology Data Exchange (ETDEWEB)

    Biswas, R., E-mail: rbiswas.pkc@gmail.com [Department of Physics, P. K. College, Contai, Purba Medinipur, West Bengal – 721401 (India); Maiti, S. [Ajodhya Hills G.S.A.T High School, Ajodhya, Purulia, West Bengal – 723152 (India); Mukhopadhyay, S. [Purulia Zilla School, Dulmi Nadiha, Purulia, West Bengal – 723102 (India); Sinha, C. [Department of Physics, P. K. College, Contai, Purba Medinipur, West Bengal – 721401 (India); Department of Theoretical Physics, Indian Association for the Cultivation of Science, Jadavpur – 700032 (India)

    2017-05-10

    Electronic transport through graphene magnetic barriers is studied theoretically in presence of an external time harmonic scalar potential in the framework of non-perturbative Landau–Floquet Formalism. The oscillating field mostly suppresses the transmission for rectangular magnetic barrier structure and exhibits the Fano resonance for multiphoton processes due to the presence of bound state inside the barrier. While, for a pair of delta function barriers of larger separation, the oscillating potential suppresses the usual Fabry–Perot oscillations in the transmission and a new type of asymmetric Fano resonance is noted for smaller separation, occurring due to extended states between the barriers. - Highlights: • Tunnelling of the Dirac Fermions through oscillating pure magnetic barriers is reported for the first time. • The high energy transmission through a graphene magnetic barrier is suppressed by the application of time periodic modulation. • Suppression of the Fabry Perot transmission is noted due to the application of an external time harmonic potential. • Two kinds of the Fano resonances are noted in transmission through a pair of modulated δ-function magnetic barriers.

  6. Double Barriers and Magnetic Field in Bilayer Graphene

    Science.gov (United States)

    Redouani, Ilham; Jellal, Ahmed; Bahlouli, Hocine

    2015-12-01

    We study the transmission probability in an AB-stacked bilayer graphene of Dirac fermions scattered by a double-barrier structure in the presence of a magnetic field. We take into account the full four bands structure of the energy spectrum and use the suitable boundary conditions to determine the transmission probability. Our numerical results show that for energies higher than the interlayer coupling, four ways for transmission are possible while for energies less than the height of the barrier, Dirac fermions exhibit transmission resonances and only one transmission channel is available. We show that, for AB-stacked bilayer graphene, there is no Klein tunneling at normal incidence. We find that the transmission displays sharp peaks inside the transmission gap around the Dirac point within the barrier regions while they are absent around the Dirac point in the well region. The effect of the magnetic field, interlayer electrostatic potential, and various barrier geometry parameters on the transmission probabilities is also discussed.

  7. Generalized magnetic Rosenbluth potentials

    International Nuclear Information System (INIS)

    Hassan, M.H.A.

    1977-12-01

    It is shown that the coefficients of friction and diffusion of the magnetized Balescu-Lenard equation describing the interaction of ion test particles with electron field particles can be derived from two scalar potentials, which reduce to the potentials derived previously when wave effects are neglected. The parts of the potentials describing ''wave effects'' are evaluated explicitly in the case of Maxwellian electrons and the results are compared with the unmagnetized Rosenbluth potentials. The correction is dominant when eta=Ωsub(e)/ωsub(e)(>)1

  8. Tunable delay time and Hartman effect in graphene magnetic barriers

    International Nuclear Information System (INIS)

    Ban, Yue; Wang, Lin-Jun; Chen, Xi

    2015-01-01

    Tunable group delay and Hartman effect have been investigated for massless Dirac electrons in graphene magnetic barriers. In the presence of magnetic field, dwell time is found to be equal to net group delay plus the group delay contributing from the lateral shifts. The group delay times are discussed in both cases of normal and oblique incidence, to clarify the nature of Hartman effect. In addition, the group delay in transmission can be modulated from subluminality to superluminality by adjusting the magnetic field, which may also lead to potential applications in graphene-based microelectronics

  9. Magnetized advective accretion flows: formation of magnetic barriers in magnetically arrested discs

    Science.gov (United States)

    Mondal, Tushar; Mukhopadhyay, Banibrata

    2018-05-01

    We discuss the importance of large-scale strong magnetic field in the removal of angular momentum outward, as well as the possible origin of different kinds of magnetic barrier in advective, geometrically thick, sub-Keplerian accretion flows around black holes. The origin of this large-scale strong magnetic field near the event horizon is due to the advection of the magnetic flux by the accreting gas from the environment, say, the interstellar medium or a companion star, because of flux freezing. In this simplest vertically averaged, 1.5-dimensional disc model, we choose the maximum upper limit of the magnetic field, which the disc around a black hole can sustain. In this so called magnetically arrested disc model, the accreting gas either decelerates or faces the magnetic barrier near the event horizon by the accumulated magnetic field depending on the geometry. The magnetic barrier may knock the matter to infinity. We suggest that these types of flow are the building block to produce jets and outflows in the accreting system. We also find that in some cases, when matter is trying to go back to infinity after knocking the barrier, matter is prevented being escaped by the cumulative action of strong gravity and the magnetic tension, hence by another barrier. In this way, magnetic field can lock the matter in between these two barriers and it might be a possible explanation for the formation of episodic jet.

  10. Electron tunneling across a tunable potential barrier

    International Nuclear Information System (INIS)

    Mangin, A; Anthore, A; Rocca, M L Della; Boulat, E; Lafarge, P

    2009-01-01

    We present an experiment where the elementary quantum electron tunneling process should be affected by an independent gate voltage parameter. We have realized nanotransistors where the source and drain electrodes are created by electromigration inducing a nanometer sized gap acting as a tunnel barrier. The barrier potential shape is in first approximation considered trapezoidal. The application of a voltage to the gate electrode close to the barrier region can in principle affect the barrier shape. Simulations of the source drain tunnel current as a function of the gate voltage predict modulations as large as one hundred percent. The difficulty of observing the predicted behaviour in our samples might be due to the peculiar geometry of the realized tunnel junction.

  11. Conductance of graphene based normal-superconductor junction with double magnetic barriers

    Science.gov (United States)

    Abdollahipour, B.; Mohebalipour, A.; Maleki, M. A.

    2018-05-01

    We study conductance of a graphene based normal metal-superconductor junction with two magnetic barriers. The magnetic barriers are induced via two applied magnetic fields with the same magnitudes and opposite directions accompanied by an applied electrostatic potential. We solve Dirac-Bogoliubov-De-Gennes (DBdG) equation to calculate conductance of the junction. We find that applying the magnetic field leads to suppression of the Andreev reflection and conductance for all energies. On the other hand, we observe a crossover from oscillatory to tunneling behavior of the conductance as a function of the applied potential by increasing the magnetic field.

  12. Renewable energy costs, potentials, barriers: Conceptual issues

    International Nuclear Information System (INIS)

    Verbruggen, Aviel; Fischedick, Manfred; Moomaw, William; Weir, Tony; Nadai, Alain; Nilsson, Lars J.; Nyboer, John; Sathaye, Jayant

    2010-01-01

    Renewable energy can become the major energy supply option in low-carbon energy economies. Disruptive transformations in all energy systems are necessary for tapping widely available renewable energy resources. Organizing the energy transition from non-sustainable to renewable energy is often described as the major challenge of the first half of the 21st century. Technological innovation, the economy (costs and prices) and policies have to be aligned to achieve full renewable energy potentials, and barriers impeding that growth need to be removed. These issues are also covered by IPCC's special report on renewable energy and climate change to be completed in 2010. This article focuses on the interrelations among the drivers. It clarifies definitions of costs and prices, and of barriers. After reviewing how the third and fourth assessment reports of IPCC cover mitigation potentials and commenting on definitions of renewable energy potentials in the literature, we propose a consistent set of potentials of renewable energy supplies.

  13. Magnetic Nanoparticles Cross the Blood-Brain Barrier: When Physics Rises to a Challenge

    Directory of Open Access Journals (Sweden)

    Maria Antònia Busquets

    2015-12-01

    Full Text Available The blood-brain barrier is a physical and physiological barrier that protects the brain from toxic substances within the bloodstream and helps maintain brain homeostasis. It also represents the main obstacle in the treatment of many diseases of the central nervous system. Among the different approaches employed to overcome this barrier, the use of nanoparticles as a tool to enhance delivery of therapeutic molecules to the brain is particularly promising. There is special interest in the use of magnetic nanoparticles, as their physical characteristics endow them with additional potentially useful properties. Following systemic administration, a magnetic field applied externally can mediate the capacity of magnetic nanoparticles to permeate the blood-brain barrier. Meanwhile, thermal energy released by magnetic nanoparticles under the influence of radiofrequency radiation can modulate blood-brain barrier integrity, increasing its permeability. In this review, we present the strategies that use magnetic nanoparticles, specifically iron oxide nanoparticles, to enhance drug delivery to the brain.

  14. One-way Ponderomotive Barrier in a Uniform Magnetic Field

    International Nuclear Information System (INIS)

    Dodin, I.Y.; Fisch, N.J.

    2005-01-01

    The possibility of an asymmetric ponderomotive barrier in a nonuniform dc magnetic field by high-frequency radiation near the cyclotron resonance for selected plasma species was contemplated in Physics of Plasmas 11 (November 2004) 5046-5064. Here we show that a similar one-way barrier, which reflects particles incident from one side while transmitting those incident from the opposite side, can be produced also in a uniform magnetic field, entirely due to inhomogeneity of high-frequency drive

  15. Quantum mechanical streamlines. I - Square potential barrier

    Science.gov (United States)

    Hirschfelder, J. O.; Christoph, A. C.; Palke, W. E.

    1974-01-01

    Exact numerical calculations are made for scattering of quantum mechanical particles hitting a square two-dimensional potential barrier (an exact analog of the Goos-Haenchen optical experiments). Quantum mechanical streamlines are plotted and found to be smooth and continuous, to have continuous first derivatives even through the classical forbidden region, and to form quantized vortices around each of the nodal points. A comparison is made between the present numerical calculations and the stationary wave approximation, and good agreement is found between both the Goos-Haenchen shifts and the reflection coefficients. The time-independent Schroedinger equation for real wavefunctions is reduced to solving a nonlinear first-order partial differential equation, leading to a generalization of the Prager-Hirschfelder perturbation scheme. Implications of the hydrodynamical formulation of quantum mechanics are discussed, and cases are cited where quantum and classical mechanical motions are identical.

  16. Enhanced voltage-controlled magnetic anisotropy in magnetic tunnel junctions with an MgO/PZT/MgO tunnel barrier

    Science.gov (United States)

    Chien, Diana; Li, Xiang; Wong, Kin; Zurbuchen, Mark A.; Robbennolt, Shauna; Yu, Guoqiang; Tolbert, Sarah; Kioussis, Nicholas; Khalili Amiri, Pedram; Wang, Kang L.; Chang, Jane P.

    2016-03-01

    Compared with current-controlled magnetization switching in a perpendicular magnetic tunnel junction (MTJ), electric field- or voltage-induced magnetization switching reduces the writing energy of the memory cell, which also results in increased memory density. In this work, an ultra-thin PZT film with high dielectric constant was integrated into the tunneling oxide layer to enhance the voltage-controlled magnetic anisotropy (VCMA) effect. The growth of MTJ stacks with an MgO/PZT/MgO tunnel barrier was performed using a combination of sputtering and atomic layer deposition techniques. The fabricated MTJs with the MgO/PZT/MgO barrier demonstrate a VCMA coefficient, which is ˜40% higher (19.8 ± 1.3 fJ/V m) than the control sample MTJs with an MgO barrier (14.3 ± 2.7 fJ/V m). The MTJs with the MgO/PZT/MgO barrier also possess a sizeable tunneling magnetoresistance (TMR) of more than 50% at room temperature, comparable to the control MTJs with an MgO barrier. The TMR and enhanced VCMA effect demonstrated simultaneously in this work make the MgO/PZT/MgO barrier-based MTJs potential candidates for future voltage-controlled, ultralow-power, and high-density magnetic random access memory devices.

  17. Potential barrier classification by short-time measurement

    International Nuclear Information System (INIS)

    Granot, Er'el; Marchewka, Avi

    2006-01-01

    We investigate the short-time dynamics of a delta-function potential barrier on an initially confined wave packet. There are mainly two conclusions: (A) At short times the probability density of the first particles that passed through the barrier is unaffected by it. (B) When the barrier is absorptive (i.e., its potential is imaginary) it affects the transmitted wave function at shorter times than a real potential barrier. Therefore, it is possible to distinguish between an imaginary and a real potential barrier by measuring its effect at short times only on the transmitting wave function

  18. Potential barrier classification by short-time measurement

    Science.gov (United States)

    Granot, Er'El; Marchewka, Avi

    2006-03-01

    We investigate the short-time dynamics of a delta-function potential barrier on an initially confined wave packet. There are mainly two conclusions: (A) At short times the probability density of the first particles that passed through the barrier is unaffected by it. (B) When the barrier is absorptive (i.e., its potential is imaginary) it affects the transmitted wave function at shorter times than a real potential barrier. Therefore, it is possible to distinguish between an imaginary and a real potential barrier by measuring its effect at short times only on the transmitting wave function.

  19. Conditions for plasmoid penetration across abrupt magnetic barriers

    International Nuclear Information System (INIS)

    Brenning, Nils; Hurtig, Tomas; Raadu, Michael A.

    2005-01-01

    The penetration of plasma clouds, or plasmoids, across abrupt magnetic barriers (of the scale less than a few ion gyro radii, using the plasmoid directed velocity) is studied. The insight gained earlier, from detailed experimental and computer simulation investigations of a case study, is generalized into other parameter regimes. It is concluded for what parameters a plasmoid should be expected to penetrate the magnetic barrier through self-polarization, penetrate through magnetic expulsion, or be rejected from the barrier. The scaling parameters are n e , v 0 , B perpendicular , m i , T i , and the width w of the plasmoid. The scaling is based on a model for strongly driven, nonlinear magnetic field diffusion into a plasma which is a generalization of the earlier laboratory findings. The results are applied to experiments earlier reported in the literature, and also to the proposed application of impulsive penetration of plasmoids from the solar wind into the Earth's magnetosphere

  20. Control of Internal Transport Barriers in Magnetically Confined Fusion Plasmas

    Science.gov (United States)

    Panta, Soma; Newman, David; Sanchez, Raul; Terry, Paul

    2016-10-01

    In magnetic confinement fusion devices the best performance often involves some sort of transport barriers to reduce the energy and particle flow from core to edge. Those barriers create gradients in the temperature and density profiles. If gradients in the profiles are too steep that can lead to instabilities and the system collapses. Control of these barriers is therefore an important challenge for fusion devices (burning plasmas). In this work we focus on the dynamics of internal transport barriers. Using a simple 7 field transport model, extensively used for barrier dynamics and control studies, we explore the use of RF heating to control the local gradients and therefore the growth rates and shearing rates for barrier initiation and control in self-heated fusion plasmas. Ion channel barriers can be formed in self-heated plasmas with some NBI heating but electron channel barriers are very sensitive. They can be formed in self-heated plasmas with additional auxiliary heating i.e. NBI and radio-frequency(RF). Using RF heating on both electrons and ions at proper locations, electron channel barriers along with ion channel barriers can be formed and removed demonstrating a control technique. Investigating the role of pellet injection in controlling the barriers is our next goal. Work supported by DOE Grant DE-FG02-04ER54741.

  1. Self-consistent potential variations in magnetic wells

    International Nuclear Information System (INIS)

    Kesner, J.; Knorr, G.; Nicholson, D.R.

    1981-01-01

    Self-consistent electrostatic potential variations are considered in a spatial region of weak magnetic field, as in the proposed tandem mirror thermal barriers (with no trapped ions). For some conditions, equivalent to ion distributions with a sufficiently high net drift speed along the magnetic field, the desired potential depressions are found. When the net drift speed is not high enough, potential depressions are found only in combination with strong electric fields on the boundaries of the system. These potential depressions are not directly related to the magnetic field depression. (author)

  2. Ballistic transport through graphene nanostructures of velocity and potential barriers

    International Nuclear Information System (INIS)

    Krstajic, P M; Vasilopoulos, P

    2011-01-01

    We investigate the electronic properties of graphene nanostructures when the Fermi velocity and the electrostatic potential vary in space. First, we consider the transmission T and conductance G through single and double barriers. We show that G for velocity barriers differs markedly from that for potential barriers for energies below the height of the latter and it exhibits periodic oscillations as a function of the energy for strong velocity modulation. Special attention is given to superlattices (SLs). It is shown that an applied bias can efficiently widen or shrink the allowed minibands of velocity-modulated SLs. The spectrum in the Kronig-Penney limit is periodic in the strength of the barriers. Collimation of an electron beam incident on an SL with velocity and potential barriers is present but it disappears when the potential barriers are absent. The number of additional Dirac points may change considerably if barriers and wells have sufficiently different Fermi velocities.

  3. Magnetization reversal processes of single nanomagnets and their energy barrier

    International Nuclear Information System (INIS)

    Krone, P.; Makarov, D.; Albrecht, M.; Schrefl, T.; Suess, D.

    2010-01-01

    Micromagnetic simulations were performed to investigate the influence of geometry and magnetic anisotropy constant on energy barrier and magnetization reversal mechanism of individual bits important for the bit patterned media concept in magnetic data storage. It is shown that dependency of the energy barrier on magnetic and geometric properties of bits can be described by an analytical approach in the case of quasi-coherent magnetization rotation process. However, when the bit size exceeds a critical size, for which an incoherent magnetization reversal is preferred, the analytical approach becomes invalid and no self-consistent theory is available. By systematically investigating the influence of bit size on the magnetization reversal mode, it was found that the transition from quasi-coherent to incoherent magnetization reversal mode can still be described analytically if an activation volume is considered instead of the bit volume. In this case, the nucleation volume is an important parameter determining thermal stability of the bit. If the volume of the bit is larger than twice the activation volume, the energy barrier stays nearly constant; with further increase in bit size, no gain in thermal stability can be achieved.

  4. Magnetic Transport Barriers in the DIII-D Tokamak

    Science.gov (United States)

    Kessler, J.; Volpe, F.; Evans, T. E.; Ali, H.; Punjabi, A.

    2009-11-01

    Large overlapping magnetic islands generate chaotic fields. However, a previous work [1] showed that second or third order perturbations of special topology and strength can also generate magnetic diffusion ``barriers" in the middle of stochastic regions. In the present study, we numerically assess their experimental feasibility at DIII-D. For this, realistic I- and C-coils perturbations are superimposed on the equilibrium field and puncture plots are generated with a field-line tracer. A criterion is defined for the automatic recognition of barriers and successfully tested on earlier symplectic maps in magnetic coordinates. The criterion is systematically applied to the new puncture plots in search for dependencies, e.g. upon the edge safety factor q95, which might be relevant to edge localized mode (ELM) stability, as well as to assess the robustness of barriers against fluctuations of the plasma parameters and coil currents. 8pt [1] H. Ali and A. Punjabi, Plasma Phys. Control. Fusion 49, 1565 (2007).

  5. Noble magnetic barriers in the ASDEX UG tokamak

    Science.gov (United States)

    Ali, Halima; Punjabi, Alkesh; Vazquez, Justin

    2010-02-01

    The second-order perturbation method of creating invariant tori inside chaos in Hamiltonian systems (Ali, H.; Punjabi, A. Plasma Phys. Contr. F. 2007, 49, 1565-1582) is applied to the axially symmetric divertor experiment upgrade (ASDEX UG) tokamak to build noble irrational magnetic barriers inside chaos created by resonant magnetic perturbations (m, n)=(3, 2)+(4, 3), with m and n the poloidal and toroidal mode numbers of the Fourier expansion of the magnetic perturbation. The radial dependence of the Fourier modes is ignored. The modes are considered to be locked and have the same amplitude δ. A symplectic mathematical mapping in magnetic coordinates is used to integrate magnetic field line trajectories in the ASDEX UG. Tori with noble irrational rotational transform are the last ones to be destroyed by perturbation in Hamiltonian systems. For this reason, noble irrational magnetic barriers are built inside chaos, and the strongest noble irrational barrier is identified. Three candidate locations for the strongest noble barrier in ASDEX UG are selected. All three candidate locations are chosen to be roughly midway between the resonant rational surfaces ψ32 and ψ43. ψ is the magnetic coordinate of the flux surface. The three candidate surfaces are the noble irrational surfaces close to the surface with q value that is a mediant of q=3/2 and 4/3, q value of the physical midpoint of the two resonant surfaces, and the q value of the surface where the islands of the two perturbing modes just overlap. These q values of the candidate surfaces are denoted by q MED, q MID, and q OVERLAP. The strongest noble barrier close to q MED has the continued fraction representation (CFR) [1;2,2,1∞] and exists for δ≤2.6599×10-4; the strongest noble barrier close to q MID has CFR [1;2,2,2,1∞] and exists for δ≤4.6311×10-4; and the strongest noble barrier close to q OVERLAP has CFR [1;2,2,6,2,1∞] and exists for δ≤1.367770×10-4. From these results, the strongest

  6. Magnet system for a thermal barrier Tandem Mirror Reactor

    International Nuclear Information System (INIS)

    Kim, N.S.; Conn, R.W.

    1981-01-01

    The magnet system for a thermal barrier D-D tandem mirror reactor has been studied as part of the UCLA tandem mirror reactor design study SATYR. Three main considerations in designing the SATYR magnet system are to obtain the desired field strength variation throughout the system, to have proper space for plasma and neutron shielding, and to satisfy the MHD stability to achieve maximum central cell /beta/. Due to the importance and the complexity, the 'internal' field reversal magnet is the main concern in the entire magnet system for SATYR. Two different magnet designs, a non-uniform current density solenoid and a higher-order solenoid, are discussed. Coil levitation for the internal field reversal magnet has been analyzed

  7. Estimates for diffusion barriers and atomic potentials in MGO

    International Nuclear Information System (INIS)

    Skala, L.; Kenkre, V.M.

    1991-01-01

    In this paper, as part of a program of investigation of microwave sintering, self-consistent CNDO/2 calculations are presented for diffusion barriers and potentials for the motion of interstitial atoms and vacancies in MgO. Clusters of 30 atoms are used in the calculations. Activation energies, diffusion barriers, shape of the potentials and electron densities are obtained

  8. Study of the dynamical potential barriers in heavy ion collisions

    International Nuclear Information System (INIS)

    Zhu, Long; Su, Jun; Xie, Wen-Jie; Zhang, Feng-Shou

    2013-01-01

    The nucleus–nucleus interaction potentials for the fusion reactions 16 O + 208 Pb, 64 Ni + 64 Ni, 58 Ni + 58 Ni and 16 O + 154 Sm are extracted from the improved isospin-dependent quantum molecular dynamics model. The shell correction effects are discussed. The negative shell correction energies lower potential barriers of a certain reaction. The incident energy dependence of the potential barrier is investigated for each system. A complex phenomenon of energy dependence is observed. It is also found that incident energy dependence of the barrier radius and barrier height shows opposite behaviors. The Coulomb potential shows weak energy dependence when distance of two colliding nuclei is lower than the touching distance. The isospin effects of the potential barrier are investigated. The orientation effects of the potential barrier is also discussed for the system 16 O + 154 Sm. The fusion cross sections that correspond to the equatorial orientation of 154 Sm are very low in sub-barrier region because of the high fusion barriers and the shallow potential pockets

  9. Universal potential-barrier penetration by initially confined wave packets

    International Nuclear Information System (INIS)

    Granot, Er'el; Marchewka, Avi

    2007-01-01

    The dynamics of an initially sharp-boundary wave packet in the presence of an arbitrary potential barrier is investigated. It is shown that the penetration through the barrier is universal in the sense that it depends only on the values of the wave function and its derivatives at the boundary. The dependence on the derivatives vanishes at long distances from the barrier, where the dynamics is governed solely by the initial value of the wave function at the boundary

  10. Universal potential-barrier penetration by initially confined wave packets

    Science.gov (United States)

    Granot, Er'El; Marchewka, Avi

    2007-07-01

    The dynamics of an initially sharp-boundary wave packet in the presence of an arbitrary potential barrier is investigated. It is shown that the penetration through the barrier is universal in the sense that it depends only on the values of the wave function and its derivatives at the boundary. The dependence on the derivatives vanishes at long distances from the barrier, where the dynamics is governed solely by the initial value of the wave function at the boundary.

  11. Reflectionlessness, kurtosis and top curvature of potential barriers

    International Nuclear Information System (INIS)

    Ahmed, Zafar

    2006-01-01

    Apart from the rectangular barrier, other barriers having a single maximum generally display reflectivity, R(E), as a smoothly decreasing function of energy. We conjecture that symmetric potential barriers with a single maximum entail zeros or sharp minima in R(E) provided they have either their coefficient of kurtosis lying in the range (1.8, 3.0), or their top curvature as zero, or both

  12. Review of potential subsurface permeable barrier emplacement and monitoring technologies

    International Nuclear Information System (INIS)

    Riggsbee, W.H.; Treat, R.L.; Stansfield, H.J.; Schwarz, R.M.; Cantrell, K.J.; Phillips, S.J.

    1994-02-01

    This report focuses on subsurface permeable barrier technologies potentially applicable to existing waste disposal sites. This report describes candidate subsurface permeable barriers, methods for emplacing these barriers, and methods used to monitor the barrier performance. Two types of subsurface barrier systems are described: those that apply to contamination.in the unsaturated zone, and those that apply to groundwater and to mobile contamination near the groundwater table. These barriers may be emplaced either horizontally or vertically depending on waste and site characteristics. Materials for creating permeable subsurface barriers are emplaced using one of three basic methods: injection, in situ mechanical mixing, or excavation-insertion. Injection is the emplacement of dissolved reagents or colloidal suspensions into the soil at elevated pressures. In situ mechanical mixing is the physical blending of the soil and the barrier material underground. Excavation-insertion is the removal of a soil volume and adding barrier materials to the space created. Major vertical barrier emplacement technologies include trenching-backfilling; slurry trenching; and vertical drilling and injection, including boring (earth augering), cable tool drilling, rotary drilling, sonic drilling, jetting methods, injection-mixing in drilled holes, and deep soil mixing. Major horizontal barrier emplacement technologies include horizontal drilling, microtunneling, compaction boring, horizontal emplacement, longwall mining, hydraulic fracturing, and jetting methods

  13. 7Li breakup polarization potential at near barrier energies

    International Nuclear Information System (INIS)

    Lubian, J. . E-mail lubian@if.uff.br; Correa, T.; Paes, B.; Figueira, J.M.; Abriola, D.; Fernandez Niello, J.O.; Arazi, A.; Capurro, O.A.; de Barbara, E.; Marti, G.V.; Martinez Heinmann, D.; Negri, A.E.; Pacheco, A.J.; Padron, I.; Gomes, P.R.S.

    2007-01-01

    Inelastic and one neutron transfer cross sections at energies around the Coulomb barrier were used to derive dynamic polarization potential (DPP) for the 7 Li + 27 Al system. The DPP due to breakup, obtained in a simple way, indicates that its real part is repulsive at near barrier energies

  14. Numerical evaluation of energy barriers and magnetic relaxation in interacting nanostructured magnetic systems

    International Nuclear Information System (INIS)

    Chubykalo-Fesenko, Oksana A.; Chantrell, Roy W.

    2004-01-01

    We discuss a model to quantify long-time thermally induced magnetization reversal in magnetic systems with distributed properties. Two algorithms, based on kinetic and Metropolis Monte Carlo are introduced. While the former requires the constant recalculation of all energy barriers and is useful when the interactions are weak, the latter uses the Metropolis Monte Carlo to estimate the magnetization trajectory and, consequently, only the most probable transition rates are evaluated. The ridge optimization method is used to evaluate the energy barriers in a multidimensional energy landscape. The algorithms are applied to a granular system modeled by means of Voronoi polyhedra and having random in-plane anisotropy

  15. A Hybrid Excited Machine with Flux Barriers and Magnetic Bridges

    Directory of Open Access Journals (Sweden)

    Marcin Wardach

    2018-03-01

    Full Text Available In this paper, an U-shape flux barrier rotor concept for a hybrid excited synchronous machine with flux magnetic bridges fixed on the rotor is presented. Using 3D finite element analysis, the influence of axial flux bridges on the field-weakening and -strengthening characteristics, electromagnetic torque, no-load magnetic flux linkage, rotor iron losses and back electromotive force is shown. Three different rotor designs are analyzed. Furthermore, the field control characteristics depending on additional DC control coil currents are shown.

  16. Flexible MgO Barrier Magnetic Tunnel Junctions.

    Science.gov (United States)

    Loong, Li Ming; Lee, Wonho; Qiu, Xuepeng; Yang, Ping; Kawai, Hiroyo; Saeys, Mark; Ahn, Jong-Hyun; Yang, Hyunsoo

    2016-07-01

    Flexible MgO barrier magnetic tunnel junction (MTJ) devices are fabricated using a transfer printing process. The flexible MTJ devices yield significantly enhanced tunneling magnetoresistance of ≈300% and improved abruptness of switching, as residual strain in the MTJ structure is released during the transfer process. This approach could be useful for flexible electronic systems that require high-performance memory components. © 2016 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

  17. Pulsed Magnetic Field Improves the Transport of Iron Oxide Nanoparticles through Cell Barriers

    Science.gov (United States)

    Min, Kyoung Ah; Shin, Meong Cheol; Yu, Faquan; Yang, Meizhu; David, Allan E.; Yang, Victor C.; Rosania, Gus R.

    2013-01-01

    Understanding how a magnetic field affects the interaction of magnetic nanoparticles (MNPs) with cells is fundamental to any potential downstream applications of MNPs as gene and drug delivery vehicles. Here, we present a quantitative analysis of how a pulsed magnetic field influences the manner in which MNPs interact with, and penetrate across a cell monolayer. Relative to a constant magnetic field, the rate of MNP uptake and transport across cell monolayers was enhanced by a pulsed magnetic field. MNP transport across cells was significantly inhibited at low temperature under both constant and pulsed magnetic field conditions, consistent with an active mechanism (i.e. endocytosis) mediating MNP transport. Microscopic observations and biochemical analysis indicated that, in a constant magnetic field, transport of MNPs across the cells was inhibited due to the formation of large (>2 μm) magnetically-induced MNP aggregates, which exceeded the size of endocytic vesicles. Thus, a pulsed magnetic field enhances the cellular uptake and transport of MNPs across cell barriers relative to a constant magnetic field by promoting accumulation while minimizing magnetically-induced MNP aggregates at the cell surface. PMID:23373613

  18. Tunnel magnetoresistance in asymmetric double-barrier magnetic tunnel junctions

    International Nuclear Information System (INIS)

    Useinov, N.Kh.; Petukhov, D.A.; Tagirov, L.R.

    2015-01-01

    The spin-polarized tunnel conductance and tunnel magnetoresistance (TMR) through a planar asymmetric double-barrier magnetic tunnel junction (DBMTJ) have been calculated using quasi-classical model. In DBMTJ nanostructure the magnetization of middle ferromagnetic metal layer can be aligned parallel or antiparallel with respect to the fixed magnetizations of the top and bottom ferromagnetic electrodes. The transmission coefficients of an electron to pass through the barriers have been calculated in terms of quantum mechanics. The dependencies of tunnel conductance and TMR on the applied voltage have been calculated in case of non-resonant transmission. Estimated in the framework of our model, the difference between the spin-channels conductances at low voltages was found relatively large. This gives rise to very high magnitude of TMR. - Highlights: • The spin-polarized conductance through the junction is calculated. • Dependencies of the tunnel conductance vs applied bias are shown. • Bias voltage dependence of tunnel magnetoresistance for the structure is shown

  19. Aptamer nanomedicine for cancer therapeutics: barriers and potential for translation.

    Science.gov (United States)

    Lao, Yeh-Hsing; Phua, Kyle K L; Leong, Kam W

    2015-03-24

    Aptamer nanomedicine, including therapeutic aptamers and aptamer nanocomplexes, is beginning to fulfill its potential in both clinical trials and preclinical studies. Especially in oncology, aptamer nanomedicine may perform better than conventional or antibody-based chemotherapeutics due to specificity compared to the former and stability compared to the latter. Many proof-of-concept studies on applying aptamers to drug delivery, gene therapy, and cancer imaging have shown promising efficacy and impressive safety in vivo toward translation. Yet, there remains ample room for improvement and critical barriers to be addressed. In this review, we will first introduce the recent progress in clinical trials of aptamer nanomedicine, followed by a discussion of the barriers at the design and in vivo application stages. We will then highlight recent advances and engineering strategies proposed to tackle these barriers. Aptamer cancer nanomedicine has the potential to address one of the most important healthcare issues of the society.

  20. Parametric enhancement of the tunneling transmission through a potential barrier

    International Nuclear Information System (INIS)

    Tanaka, Masatoshi; Iwata, Giiti.

    1992-01-01

    A possibility of indicated of enhancing the tunneling transmission of particle incident on a potential barrier with the aid of an auxiliary potential parametrically in resonance with incident particles. For a simple auxiliary potential, a train of two-step square wells, examples are presented in which the ratio of the transmission coefficients with and without the auxiliary potential can be very large, e.g. (2n + 1) 2L , where n is the positive integer and L the number of the period of the auxiliary potential. (author)

  1. Li breakup polarization potential at near barrier energies

    International Nuclear Information System (INIS)

    Lubian, F. J.; Correa, T.; Gomes, P.R.S.; Paes, B; Figueira, J. M.; Abriola, D.; Fernandez, J. O.; Capurro, O. A.; Marti, G.V.; Martinez, D.; Heimann; Negri, A.; Pacheco, A. J.; Padron, I.

    2007-01-01

    Inelastic and one neutron transfer cross sections at energies around the Coulomb barrier were used to derive dynamic polarization potential (DPP) for the 7 Li + 27 Al system. The DPP due to breakup, obtained in a simple way, indicates that its real part is repulsive at nearbarrier energies. (Author)

  2. The escape of brownian particle over potential barriers

    International Nuclear Information System (INIS)

    Zhong Yunxiao

    1985-01-01

    A convenient method is introduced to calculate the rate of escape of Brownian particle over potential barriers by exact solution of Smoluchowskian equation. This method is applied to calculate the nuclear fission probabilities. The results for four different cases are compared with the results of other theories

  3. A Stable Pentagonal Bipyramidal Dy(III) Single-Ion Magnet with a Record Magnetization Reversal Barrier over 1000 K.

    Science.gov (United States)

    Liu, Jiang; Chen, Yan-Cong; Liu, Jun-Liang; Vieru, Veacheslav; Ungur, Liviu; Jia, Jian-Hua; Chibotaru, Liviu F; Lan, Yanhua; Wernsdorfer, Wolfgang; Gao, Song; Chen, Xiao-Ming; Tong, Ming-Liang

    2016-04-27

    Single-molecule magnets (SMMs) with a large spin reversal barrier have been recognized to exhibit slow magnetic relaxation that can lead to a magnetic hysteresis loop. Synthesis of highly stable SMMs with both large energy barriers and significantly slow relaxation times is challenging. Here, we report two highly stable and neutral Dy(III) classical coordination compounds with pentagonal bipyramidal local geometry that exhibit SMM behavior. Weak intermolecular interactions in the undiluted single crystals are first observed for mononuclear lanthanide SMMs by micro-SQUID measurements. The investigation of magnetic relaxation reveals the thermally activated quantum tunneling of magnetization through the third excited Kramers doublet, owing to the increased axial magnetic anisotropy and weaker transverse magnetic anisotropy. As a result, pronounced magnetic hysteresis loops up to 14 K are observed, and the effective energy barrier (Ueff = 1025 K) for relaxation of magnetization reached a breakthrough among the SMMs.

  4. Generalization of Kramer's formula: Fission over a multidimensional potential barrier

    International Nuclear Information System (INIS)

    Jing-Shang, Z.; Weidenmueller, H.A.

    1983-01-01

    We generalize Kramers's rate expression for diffusion over a potential barrier to the case of a diffusion problem for n degrees of freedom. These can be thought of as the shape degrees of freedom of a fissioning nucleus. We present our formula for the fission width and discuss its dependence on the parameters: the mass tensor, the friction tensor, and the shape of the potential landscape

  5. Electronic transport for armchair graphene nanoribbons with a potential barrier

    International Nuclear Information System (INIS)

    Zhou Benliang; Zhou Benhu; Liao Wenhu; Zhou Guanghui

    2010-01-01

    We theoretically investigate the electronic transport properties through a rectangular potential barrier embedded in armchair-edge graphene nanoribbons (AGNRs) of various widths. Using the Landauer formula and Dirac equation with the continuity conditions for all segments of wave functions at the interfaces between regions inside and outside the barrier, we calculate analytically the conductance and Fano factor for the both metallic and semiconducting AGNRs, respectively. It is shown that, by some numerical examples, at Dirac point the both types of AGNRs own a minimum conductance associated with the maximum Fano factor. The results are discussed and compared with the previous relevant works.

  6. Monitoring long-term evolution of engineered barrier systems using magnets: Magnetic response.

    Science.gov (United States)

    Rigonat, N; Isnard, O; Harley, S L; Butler, I B

    2018-01-05

    Remote and non-destructive monitoring of the stability and performance of Engineered Barrier Systems for Geological Disposal Facility of is gaining considerable importance in establishing the safety cases for Higher Activity Wastes disposal. This study offers an innovative use of mineral magnetism for monitoring groundwater saturation of the barrier. Four mixtures of permanent magnets (Nd-Fe-B, coated and uncoated; SmCo and AlNiCo) and bentonite were reacted for 4, 8 and 12 months with mildly-saline, high-pH leachates, representing the fluids saturating a time-evolved engineered barrier. Coupled hysteresis and thermomagnetic analyses demonstrate how Nd-Fe-B feature a time-dependent transition from square-like ferromagnetic to superparamagnetic loop via pot-bellied and wasp-waist loops, whereas SmCo and AlNiCo do not show so extensive corrosion-related variations of the intrinsic and extrinsic magnetic properties. This study allowed to identify magnetic materials suitable for shorter- (Nd-Fe-B) and longer-term (SmCo and AlNiCo) monitoring purposes. Copyright © 2017 The Authors. Published by Elsevier B.V. All rights reserved.

  7. Electronic transport for armchair graphene nanoribbons with a potential barrier

    International Nuclear Information System (INIS)

    Ben-Hu, Zhou; Ben-Liang, Zhou; Guang-Hui, Zhou; Zi-Gang, Duan

    2010-01-01

    This paper studies the electronic transport property through a square potential barrier in armchair-edge graphene nanoribbon (AGNR). Using the Dirac equation with the continuity condition for wave functions at the interfaces between regions with and without a barrier, we calculate the mode-dependent transmission probability for both semiconducting and metallic AGNRs, respectively. It is shown that, by some numerical examples, the transmission probability is generally an oscillating function of the height and range of the barrier for both types of AGNRs. The main difference between the two types of systems is that the magnitude of oscillation for the semiconducting AGNR is larger than that for the metallic one. This fact implies that the electronic transport property for AGNRs depends sensitively on their widths and edge details due to the Dirac nature of fermions in the system

  8. Knowledge Exchange and Management Research: Barriers and Potentials

    DEFF Research Database (Denmark)

    Bager, Torben

    2018-01-01

    Purpose: The growing involvement of management researchers in knowledge exchange activities and collaborative research does not seem to be reflected in a growing academic output. The purpose of this paper is to explore barriers for academic output from these activities as well as the potential...... for ‘interesting’ papers. Design/methodology/approach: The paper uses secondary data and statistics as well as an illustrative case study to trace knowledge exchange activities and barriers for academic output based on these activities. Findings: The paper identifies a number of barriers for the turning of data...... derived from knowledge exchange activities and Mode 2 research into academic papers such as low priority of case study research in leading management journals, a growing practice orientation in the research funding systems, methodological challenges due to limited researcher control, and disincentives...

  9. Proton nuclear magnetic resonance study on the barrier function of pig corneal epithelium and endothelium

    International Nuclear Information System (INIS)

    Yokoi, Norihiko; Kinoshita, Shigeru; Morimoto, Taketoshi; Yoshizaki, Kazuo.

    1995-01-01

    Using gadolinium diethylenetriaminepentaacetic acid (Gd-DTPA) as a tracer, the barrier function of the corneal epithelium and endothelium was evaluated by proton nuclear magnetic resonance. Whole pig eyes and cornea excised with scleral rim, which had been incubated in dextran-added Gd-DTPA solution, were subjected to T 1 relaxation measurement and magnetic resonance imaging (MRI). After incubation, the T 1 relaxation rate (1/T 1 ) of the excised cornea increased to a steady value, whereas that of the cornea from the whole eye increased only slightly. These results indicated that the increase in the T 1 relaxation rate of the excised cornea was attributable to Gd-DTPA penetration from the corneal endothelium and that the corneal epithelium exhibited a strong barrier function against Gd-DTPA entry. The MRI study also confirmed the strong barrier, enhanced signals being detected within the aqueous fluid in the T 1 -weighted image only when the corneal epithelium was abraded. Since Gd-DTPA scarcely penetrates the intact corneal epithelium, Gd-DTPA-enhanced MRI shows potential as a quantitative tracer in evaluating epithelial barrier disruption. (author)

  10. Magnetic tunnel junctions with monolayer hexagonal boron nitride tunnel barriers

    Energy Technology Data Exchange (ETDEWEB)

    Piquemal-Banci, M.; Galceran, R.; Bouzehouane, K.; Anane, A.; Petroff, F.; Fert, A.; Dlubak, B.; Seneor, P. [Unité Mixte de Physique, CNRS, Thales, Univ. Paris-Sud, Université Paris-Saclay, Palaiseau 91767 (France); Caneva, S.; Martin, M.-B.; Weatherup, R. S.; Kidambi, P. R.; Robertson, J.; Hofmann, S. [Department of Engineering, University of Cambridge, Cambridge CB21PZ (United Kingdom); Xavier, S. [Thales Research and Technology, 1 avenue Augustin Fresnel, Palaiseau 91767 (France)

    2016-03-07

    We report on the integration of atomically thin 2D insulating hexagonal boron nitride (h-BN) tunnel barriers into Co/h-BN/Fe magnetic tunnel junctions (MTJs). The h-BN monolayer is directly grown by chemical vapor deposition on Fe. The Conductive Tip Atomic Force Microscopy (CT-AFM) measurements reveal the homogeneity of the tunnel behavior of our h-BN layers. As expected for tunneling, the resistance depends exponentially on the number of h-BN layers. The h-BN monolayer properties are also characterized through integration into complete MTJ devices. A Tunnel Magnetoresistance of up to 6% is observed for a MTJ based on a single atomically thin h-BN layer.

  11. Load management for refrigeration systems: Potentials and barriers

    Energy Technology Data Exchange (ETDEWEB)

    Grein, Arne, E-mail: a.grein@tu-berlin.de [University of Technology Berlin, Institute for Energy Technology, Department of Energy Systems, Einsteinufer 25 (TA8), 10587 Berlin (Germany); Pehnt, Martin [Institute for Energy and Environmental Research Heidelberg (ifeu), Wilckensstr. 3, 69120 Heidelberg (Germany)

    2011-09-15

    As a strategy to deal with the increasing intermittent input of renewable energy sources in Germany, the adaptation of power consumption is complementary to power-plant regulation, grid expansion and physical energy storage. One demand sector that promises strong returns for load management efforts is cooling and refrigeration. In these processes, thermal inertia provides a temporal buffer for shifting and adjusting the power consumption of cooling systems. We have conducted an empirical investigation to obtain a detailed and time-resolved bottom-up analysis of load management for refrigeration systems in the city of Mannheim, Germany. We have extrapolated our results to general conditions in Germany. Several barriers inhibit the rapid adoption of load management strategies for cooling systems, including informational barriers, strict compliance with legal cooling requirements, liability issues, lack of technical experience, an inadequate rate of return and organizational barriers. Small commercial applications of refrigeration in the food-retailing and cold storage in hotels and restaurants are particularly promising starting points for intelligent load management. When our results are applied to Germany, suitable sectors for load management have theoretical and achievable potential values of 4.2 and 2.8 GW, respectively, amounting to about 4-6% of the maximum power demand in Germany. - Highlights: > Potential and barriers for implementation of load shifting for refrigeration. > Empirical investigation for time-resolved bottom-up analysis in Mannheim, Germany. > Suitable sectors and further recommendations for introducing load management.> Extrapolation of results from local to national level.

  12. Crossing the Barriers: An Analysis of Land Access Barriers to Geothermal Development and Potential Improvement Scenarios

    Energy Technology Data Exchange (ETDEWEB)

    Levine, Aaron L [National Renewable Energy Laboratory (NREL), Golden, CO (United States); Young, Katherine R [National Renewable Energy Laboratory (NREL), Golden, CO (United States)

    2017-10-04

    Developers have identified many non-technical barriers to geothermal power development, including access to land. Activities required for accessing land, such as environmental review and private and public leasing can take a considerable amount of time and can delay or prevent project development. This paper discusses the impacts to available geothermal resources and deployment caused by land access challenges, including tribal and cultural resources, environmentally sensitive areas, biological resources, land ownership, federal and state lease queues, and proximity to military installations. In this analysis, we identified challenges that have the potential to prevent development of identified and undiscovered hydrothermal geothermal resources. We found that an estimated 400 MW of identified geothermal resource potential and 4,000 MW of undiscovered geothermal resource potential were either unallowed for development or contained one or more significant barriers that could prevent development at the site. Potential improvement scenarios that could be employed to overcome these barriers include (1) providing continuous funding to the U.S. Forest Service (USFS) for processing geothermal leases and permit applications and (2) the creation of advanced environmental mitigation measures. The model results forecast that continuous funding to the USFS could result in deployment of an additional 80 MW of geothermal capacity by 2030 and 124 MW of geothermal capacity by 2050 when compared to the business-as-usual scenario. The creation of advanced environmental mitigation measures coupled with continuous funding to the USFS could result in deployment of an additional 97 MW of geothermal capacity by 2030 and 152 MW of geothermal capacity by 2050 when compared to the business-as-usual scenario. The small impact on potential deployment in these improvement scenarios suggests that these 4,400 MW have other barriers to development in addition to land access. In other words, simply

  13. Resonant tunneling via spin-polarized barrier states in a magnetic tunnel junction

    NARCIS (Netherlands)

    Jansen, R.; Lodder, J.C.

    2000-01-01

    Resonant tunneling through states in the barrier of a magnetic tunnel junction has been analyzed theoretically for the case of a spin-polarized density of barrier states. It is shown that for highly spin-polarized barrier states, the magnetoresistance due to resonant tunneling is enhanced compared

  14. Electric-field effects on electronic tunneling transport in magnetic barrier structures

    International Nuclear Information System (INIS)

    Guo Yong; Wang Hao; Gu Binglin; Kawazoe, Yoshiyuki

    2000-01-01

    Electronic transport properties in magnetic barrier structures under the influence of an electric field have been investigated. The results indicate that the characteristics of transmission resonance are determined not only by the structure and the incident wave vector but also strongly by the electric field. It is shown that the transmission coefficient at resonance in the low-energy range is suppressed by applying the electric field for electron tunneling through the magnetic barrier structure, arranged with identical magnetic barriers and wells. It is also shown that the transmission resonance is first enhanced up to optimal resonance, and then suppressed with further increased electric field for electron tunneling through the magnetic barrier structure, arranged with unidentical building blocks. Strong suppression of the current density is also found in the magnetic barrier structure, arranged with two different building blocks

  15. Virtual-anode formation by an intense pulsed ion beam incident upon a magnetic barrier

    International Nuclear Information System (INIS)

    Robertson, S.; Wessel, F.

    1980-01-01

    An intense, pulsed, initially space-charge-neutral ion beam (100 kV, 1 kA, 600 nsec) has been propagated into a transversely oriented magnetic barrier. When the magnetic field is adjusted so that (rho/sub i/rho/sub e/)/sup 1/2/ very-much-less-than a < rho/sub i/, a virtual anode is formed whose potential oscillates at approx.ω/sub p/i about a value near the ion accelerating potential, where a is the transverse beam dimension, ω/sub tsp/i is the ion plasma frequency, and rho/sub e/ and rho/sub i/ are the electron and ion gyroradii. This behavior is similar to that predicted by Poukey and Rostoker for virtual cathodes

  16. l-dependent potential barriers and superdeformed states

    International Nuclear Information System (INIS)

    Gherghescu, R.A.; Royer, G.

    1999-01-01

    The macroscopic-microscopic energy of rotating nuclei moving in the fusion-like deformation valley has been determined within a generalized liquid drop model including the nuclear proximity energy, the two-center shell model and the Strutinsky method. The l-dependent potential barriers of the 84 Zr, 132 Ce, 152 Dy and 192 Hg nuclei have been determined. A first minimum having a pure microscopic origin and lodging the normally deformed states, progressively disappears with increasing angular momenta. The microscopic and macroscopic energies contribute to generate a second minimum where superdeformed states may survive. It becomes progressively the lowest one at intermediate spins. At still higher angular momenta, the minimum moves towards the foot of the external fission barrier leading to macroscopic hyper-deformed quasi-molecular states. (authors)

  17. Gate-tunable valley-spin filtering in silicene with magnetic barrier

    Energy Technology Data Exchange (ETDEWEB)

    Wu, X. Q., E-mail: xianqiangzhe@126.com [National Laboratory of Solid State Microstructures and Department of Physics, Nanjing University, Nanjing 210093 (China); Meng, H. [School of Physics and Telecommunication Engineering, Shanxi University of Technology, Hanzhong 723001 (China)

    2015-05-28

    We theoretically study the valley- and spin-resolved scattering through magnetic barrier in a one layer thick silicene, using the mode-matching method for the Dirac equation. We show that the spin-valley filtering effect can be achieved and can also be tuned completely through both a top and bottom gate. Moreover, when reversing the sign of the staggered potential, we find the direction of the valley polarization is switched while the direction of spin polarization is unchanged. These results can provide some meaningful information to design valley valve residing on silicene.

  18. Load management for refrigeration systems: Potentials and barriers

    International Nuclear Information System (INIS)

    Grein, Arne; Pehnt, Martin

    2011-01-01

    As a strategy to deal with the increasing intermittent input of renewable energy sources in Germany, the adaptation of power consumption is complementary to power-plant regulation, grid expansion and physical energy storage. One demand sector that promises strong returns for load management efforts is cooling and refrigeration. In these processes, thermal inertia provides a temporal buffer for shifting and adjusting the power consumption of cooling systems. We have conducted an empirical investigation to obtain a detailed and time-resolved bottom-up analysis of load management for refrigeration systems in the city of Mannheim, Germany. We have extrapolated our results to general conditions in Germany. Several barriers inhibit the rapid adoption of load management strategies for cooling systems, including informational barriers, strict compliance with legal cooling requirements, liability issues, lack of technical experience, an inadequate rate of return and organizational barriers. Small commercial applications of refrigeration in the food-retailing and cold storage in hotels and restaurants are particularly promising starting points for intelligent load management. When our results are applied to Germany, suitable sectors for load management have theoretical and achievable potential values of 4.2 and 2.8 GW, respectively, amounting to about 4-6% of the maximum power demand in Germany. - Highlights: → Potential and barriers for implementation of load shifting for refrigeration. → Empirical investigation for time-resolved bottom-up analysis in Mannheim, Germany. → Suitable sectors and further recommendations for introducing load management.→ Extrapolation of results from local to national level.

  19. Temperature dependence of interlayer coupling in perpendicular magnetic tunnel junctions with GdOX barriers

    Science.gov (United States)

    Newhouse-Illige, T.; Xu, Y. H.; Liu, Y. H.; Huang, S.; Kato, H.; Bi, C.; Xu, M.; LeRoy, B. J.; Wang, W. G.

    2018-02-01

    Perpendicular magnetic tunnel junctions with GdOX tunneling barriers have shown a unique voltage controllable interlayer magnetic coupling effect. Here, we investigate the quality of the GdOX barrier and the coupling mechanism in these junctions by examining the temperature dependence of the tunneling magnetoresistance and the interlayer coupling from room temperature down to 11 K. The barrier is shown to be of good quality with the spin independent conductance only contributing a small portion, 14%, to the total room temperature conductance, similar to AlOX and MgO barriers. The interlayer coupling, however, shows an anomalously strong temperature dependence including sign changes below 80 K. This non-trivial temperature dependence is not described by previous models of interlayer coupling and may be due to the large induced magnetic moment of the Gd ions in the barrier.

  20. Output voltage calculations in double barrier magnetic tunnel junctions with asymmetric voltage behavior

    KAUST Repository

    Useinov, Arthur; Mryasov, Oleg; Kosel, Jü rgen

    2011-01-01

    In this paper we study the asymmetric voltage behavior (AVB) of the tunnel magnetoresistance (TMR) for single and double barrier magnetic tunnel junctions (MTJs) in range of a quasi-classical free electron model. Numerical calculations of the TMR

  1. Magneto-transport in CdTe/CdMnTe dilute magnetic semiconductor single barrier structures

    International Nuclear Information System (INIS)

    Lyons, V.R.

    1999-03-01

    This thesis presents work done on electrical transport through dilute magnetic semiconductor (DMS) single barriers in both zero and non-zero magnetic fields. The fields are applied either perpendicular or parallel to the DMS layers. The main samples under investigation consist of 100 A and 200 A CdTe/Cd 0.8 Mn 0.2 Te/CdTe single barrier heterostructures. In addition electrical characterisation of the non magnetic layers is performed. Current through the barrier is measured as a function of voltage, magnetic field and temperature. A theoretical model is derived in order to calculate the current as a function of barrier height, barrier width, emitting layer carrier concentration, applied bias and temperature. These variables are then treated as fitting parameters and comparisons are made between the calculated and the experimental currents. The barriers are shown to produce non-Ohmic transport. The roles of quantum mechanical tunnelling and thermal activation across the barrier are investigated and shown to be highly mixed. An unexpectedly high degree of tunnelling is found to occur at high temperatures, within the region previously assumed to be dominated by thermal activation. Moreover the barrier height is found to be lower and the width greater than expected. These observations suggest that a high level of Mn diffusion occurs, possibly due to In dopant related effects. This suggestion is validated by the high emitting layer carrier concentration suggested by the fitting. At low temperatures and voltages the thicker barrier sample is shown to contain a parasitic leak path which short-circuits the barrier. This leak may exist in both samples but only becomes dominant where the barriers are sufficiently opaque to the incident carriers. Changes in a magnetic field are expected to be due to sp-d exchange induced giant Zeeman splitting in the barrier and either normal spin splitting or sp-d exchange effects in the emitter regions. The application of a magnetic field is

  2. Developing leadership as a trainee- opportunities, barriers and potential improvements.

    Science.gov (United States)

    Doherty, Rachel; Lawson, Sara; Mc Laughlin, Laura; Donaghy, Grainne; Courtney, Julia; Gardiner, Keith

    2018-05-01

    The General Medical Council explicitly state that doctors completing training should demonstrate capabilities in leadership and teamwork. 1 However, most trainees receive little formal training in leadership. In March 2017, at the Faculty of Medical Leadership and Management (FMLM) Northern Ireland Regional Conference, a workshop on developing leadership skills as a trainee was hosted and the views of doctors in training regarding current opportunities, potential barriers and improvements were sought. In Northern Ireland presently there are a number of opportunities available for trainees to gain experience in leadership - both by learning through observation and learning through experience. These range from informal activities which do not require significant time commitment to focused, immersive leadership experiences such as ADEPT (Achieve Develop Explore Programme for Trainees) 2 , and the Royal College of Physicians' Chief Registrar scheme. 3 Several barriers to developing leadership have been identified, including limited understanding of what constitutes leadership, a lack of senior support and little formal recognition for trainees leading teams. Time pressures, frequently rotating jobs, limited resources and difficulty upscaling can also undermine the sustainability of improvement and other leadership projects. Incorporating awareness of and training in leadership skills, as well as greater engagement with senior leaders and managers, at an early stage in training could promote understanding and encourage trainees. Formalising leadership roles within training posts may improve experience. Deaneries and Trusts can also enable leadership opportunities by facilitating study leave, raising awareness amongst supervisors, and providing career enhancing incentives for interested trainees.

  3. ICTs for rural development: potential applications and barriers involved

    Directory of Open Access Journals (Sweden)

    Anastasia Stratigea

    2013-03-01

    Full Text Available Rural policy nowadays is at the heart of the policy discussion in many countries all over the world, in the effort to address and effectively support the specific needs and opportunities of rural places and their population in the new era. Along these lines, the focus of the present paper is twofold: on the one hand it attempts to shed light on the role of ICTs and their applications as enabling tools empowering rural development; while on the other hand it explores the barriers appearing towards the adoption and use of ICTs in rural regions. In such a context, it firstly places emphasis on the evolving new rural development paradigm. Then, the range and potential of ICTs applications is explored, that can serve the implementation of the new policy paradigm in rural regions. It follows a discussion on the steps that are needed in order to develop value-added ICTs applications in rural regions and the barriers appearing in the adoption and use of ICTs in these regions. Finally, are presented some issues of policy concern in respect to the adoption and use of ICTs in a rural development perspective.

  4. Potential corridors and barriers for plague spread in central Asia

    Science.gov (United States)

    2013-01-01

    Background Plague (Yersinia pestis infection) is a vector-borne disease which caused millions of human deaths in the Middle Ages. The hosts of plague are mostly rodents, and the disease is spread by the fleas that feed on them. Currently, the disease still circulates amongst sylvatic rodent populations all over the world, including great gerbil (Rhombomys opimus) populations in Central Asia. Great gerbils are social desert rodents that live in family groups in burrows, which are visible on satellite images. In great gerbil populations an abundance threshold exists, above which plague can spread causing epizootics. The spatial distribution of the host species is thought to influence the plague dynamics, such as the direction of plague spread, however no detailed analysis exists on the possible functional or structural corridors and barriers that are present in this population and landscape. This study aims to fill that gap. Methods Three 20 by 20 km areas with known great gerbil burrow distributions were used to analyse the spatial distribution of the burrows. Object-based image analysis was used to map the landscape at several scales, and was linked to the burrow maps. A novel object-based method was developed – the mean neighbour absolute burrow density difference (MNABDD) – to identify the optimal scale and evaluate the efficacy of using landscape objects as opposed to square cells. Multiple regression using raster maps was used to identify the landscape-ecological variables that explain burrow density best. Functional corridors and barriers were mapped using burrow density thresholds. Cumulative resistance of the burrow distribution to potential disease spread was evaluated using cost distance analysis. A 46-year plague surveillance dataset was used to evaluate whether plague spread was radially symmetric. Results The burrow distribution was found to be non-random and negatively correlated with Greenness, especially in the floodplain areas. Corridors and

  5. Origin of methyl torsional potential barrier – An overview

    Indian Academy of Sciences (India)

    Unknown

    The effect of skeletal flexing on the picture of barrier .... views to explain the origin of the barrier to this rotation have been proposed, but none of .... molecule, a model is always advantageous to predict the barrier and its cause in a given.

  6. Scattering and pair production by a potential barrier

    International Nuclear Information System (INIS)

    Nikishov, A.I.

    2004-01-01

    Scattering and electron-positron pair production by a one-dimensional electric barrier is considered in the framework of the S-matrix formalism. The solution of the Dirac equation are classified according to frequency sign. The Bogolyubov transformations relating the in- and out-states are given. It is shown that the norm of a solution of the wave equation is determined by the largest amplitude of its asymptotic form when x 3 → ±∞. For the Sauter-type potential we give the explicit expressions for the complete in- and out-sets of orthonormalized wave functions. It is noted that in principle virtual vacuum processes in external field influence the phase of the wave function of the scattered particle [ru

  7. Effect of a gap opening on the conductance of graphene with magnetic barrier structures

    Science.gov (United States)

    Esmailpour, Mohammad

    2018-04-01

    In the present study Klein tunneling in a single-layer gapped graphene was investigated by transfer matrix method under normal magnetic field for one and two magnetic barriers. Calculations show that electron transmission through a magnetic barrier is deflected to positive angles and reduces as the magnitude of magnetic field and especially the energy gap increases. This reduction is even more significant in larger fields so that after reaching a specific value of energy gap, an effective confinement for fermions and suppression of Klein tunneling is reached particularly in normal incidence and the conductance becomes zero. Unlike one barrier, the process of tunneling through two magnetic barriers induces symmetric transmission probability versus the incident angle; even, for lower energy gaps, electron transmission probability increases which in turn reduces total conductance via proper changes in the value of the magnetic field and energy gap. In general, it is concluded that confining electrons in asymmetric transmission through one barrier is conducted better than two barriers.

  8. Directed Magnetic Particle Transport above Artificial Magnetic Domains Due to Dynamic Magnetic Potential Energy Landscape Transformation.

    Science.gov (United States)

    Holzinger, Dennis; Koch, Iris; Burgard, Stefan; Ehresmann, Arno

    2015-07-28

    An approach for a remotely controllable transport of magnetic micro- and/or nanoparticles above a topographically flat exchange-bias (EB) thin film system, magnetically patterned into parallel stripe domains, is presented where the particle manipulation is achieved by sub-mT external magnetic field pulses. Superparamagnetic core-shell particles are moved stepwise by the dynamic transformation of the particles' magnetic potential energy landscape due to the external magnetic field pulses without affecting the magnetic state of the thin film system. The magnetic particle velocity is adjustable in the range of 1-100 μm/s by the design of the substrate's magnetic field landscape (MFL), the particle-substrate distance, and the magnitude of the applied external magnetic field pulses. The agglomeration of magnetic particles is avoided by the intrinsic magnetostatic repulsion of particles due to the parallel alignment of the particles' magnetic moments perpendicular to the transport direction and parallel to the surface normal of the substrate during the particle motion. The transport mechanism is modeled by a quantitative theory based on the precise knowledge of the sample's MFL and the particle-substrate distance.

  9. The Insulation Vacuum Barrier for the Large Hadron Collider (LHC) Magnet Cryostats

    CERN Document Server

    Castoldi, M; Parma, Vittorio; Skoczen, Blazej; Trilhe, P

    2000-01-01

    The sectorisation of the insulation vacuum of the LHC magnet cryostats, housing the superconducting magnets, which operate in a 1.9 K superfluid helium bath, is achieved by means of vacuum barriers. Each vacuum barrier is a leak-tight austenitic stainless steel thin-wall structure, mainly composed of large diameter (between 0.6 m and 0.9 m) bellows and concentric corrugated cylinders. It is mounted in the Short Straight Section (SSS) [1], between the magnet helium enclosure and the vacuum vessel. This paper presents the design of the vacuum barrier, concentrating mostly on its expected thermal performance, to fulfil the tight LHC heat in-leak budgets. Pressure and leak test results, confirming the mechanical design of two prototypes manufactured in industry, and the preparation of one of these vacuum barriers for cryogenic testing in an SSS prototype, are also mentioned.

  10. Tunnel barrier and noncollinear magnetization effects on shot noise in ferromagnetic/semiconductor/ferromagnetic heterojunctions

    International Nuclear Information System (INIS)

    An Xingtao; Liu Jianjun

    2008-01-01

    Based on the scattering approach, we investigate transport properties of electrons in a one-dimensional waveguide that contains a ferromagnetic/semiconductor/ferromagnetic heterojunction and tunnel barriers in the presence of Rashba and Dresselhaus spin-orbit interactions. We simultaneously consider significant quantum size effects, quantum coherence, Rashba and Dresselhaus spin-orbit interactions and noncollinear magnetizations. It is found that the tunnel barrier plays a decisive role in the transmission coefficient and shot noise of the ballistic spin electron transport through the heterojunction. When the small tunnel barriers are considered, the transport properties of electrons are quite different from those without tunnel barriers

  11. Anti-collimation of ballistic electrons by a potential barrier

    Science.gov (United States)

    Coleridge, P. T.; Taylor, R. P.; Sachrajda, A. S.; Adams, J. A.

    1994-03-01

    A pair of Quantum Point Contacts separated by a continuous barrier have been fabricated using the surface gate technique. Transport measurements for each component of this system and for various combinations have shown both additive and non-additive behaviour. The results are explained by a combination of reflection by the barrier of electrons collimated by the Quantum Point Contacts and transport by diffusion across the barrier.

  12. Transport properties of electrons in fractal magnetic-barrier structures

    Science.gov (United States)

    Sun, Lifeng; Fang, Chao; Guo, Yong

    2010-09-01

    Quantum transport properties in fractal magnetically modulated structures are studied by the transfer-matrix method. It is found that the transmission spectra depend sensitively not only on the incident energy and the direction of the wave vector but also on the stage of the fractal structures. Resonance splitting, enhancement, and position shift of the resonance peaks under different magnetic modulation are observed at four different fractal stages, and the relationship between the conductance in the fractal structure and magnetic modulation is also revealed. The results indicate the spectra of the transmission can be considered as fingerprints for the fractal structures, which show the subtle correspondence between magnetic structures and transport behaviors.

  13. Magnetic tunnel junctions with AlN and AlNxOy barriers

    International Nuclear Information System (INIS)

    Schwickert, M. M.; Childress, J. R.; Fontana, R. E.; Kellock, A. J.; Rice, P. M.; Ho, M. K.; Thompson, T. J.; Gurney, B. A.

    2001-01-01

    Nonoxide tunnel barriers such as AlN are of interest for magnetic tunnel junctions to avoid the oxidation of the magnetic electrodes. We have investigated the fabrication and properties of thin AlN-based barriers for use in low resistance magnetic tunnel junctions. Electronic, magnetic and structural data of tunnel valves of the form Ta (100 Aa)/PtMn (300 Aa)/CoFe 20 (20 Aa - 25 Aa)/barrier/CoFe 20 (10 - 20 Aa)/NiFe 16 (35 - 40 Aa)/Ta (100 Aa) are presented, where the barrier consists of AlN, AlN x O y or AlN/AlO x with total thicknesses between 8 and 15 Aa. The tunnel junctions were sputter deposited and then lithographically patterned down to 2 x 2μm 2 devices. AlN was deposited by reactive sputtering from an Al target with 20% - 35% N 2 in the Ar sputter gas at room temperature, resulting in stoichiometric growth of AlN x (x=0.50±0.05), as determined by RBS. TEM analysis shows that the as-deposited AlN barrier is crystalline. For AlN barriers and AlN followed by natural O 2 oxidation, we obtain tunnel magnetoresistance >10% with specific junction resistance R j down to 60Ωμm 2 . [copyright] 2001 American Institute of Physics

  14. Magnetic Materials: Novel Monitors of Long-Term Evolution of Engineered Barrier Systems

    Directory of Open Access Journals (Sweden)

    Simon L. Harley

    2016-12-01

    Full Text Available Most safety cases for the deep geological disposal of radioactive waste are reliant on the swelling of bentonite in the engineered barrier system as it saturates with groundwater. Assurance of safety therefore requires effective monitoring of bentonite saturation. The time- and fluid-dependent corrosion of synthetic magnets embedded in bentonite is demonstrated here to provide a novel and passive means of monitoring saturation. Experiments have been conducted at 70 °C in which neo magnets, AlNiCo magnets, and ferrite magnets have been reacted with saline (NaCl, KCl, CaCl2 solutions and alkaline fluids (NaOH, KOH, Ca(OH2 solutions; pH = 12 in the presence of bentonite. Nd-Fe-B magnets undergo extensive corrosion that results in a dramatic change from ferromagnetic to superparamagnetic behaviour concomitant with bentonite saturation. AlNiCo magnets in saline solutions show corrosion but only limited decreases in their magnetic intensities, and ferrite magnets are essentially unreactive on the experimental timescales, retaining their initial magnetic properties. For all magnets the impact of their corrosion on bentonite swelling is negligible; alteration of bentonite is essentially governed by the applied fluid composition. In principle, synthetic magnet arrays can, with further development, be designed and embedded in bentonite to monitor its fluid saturation without compromising the integrity of the engineered barrier system itself.

  15. Magnetic barriers and their q95 dependence at DIII-D

    Science.gov (United States)

    Volpe, F. A.; Kessler, J.; Ali, H.; Evans, T. E.; Punjabi, A.

    2012-05-01

    It is well known that externally generated resonant magnetic perturbations (RMPs) can form islands in the plasma edge. In turn, large overlapping islands generate stochastic fields, which are believed to play a role in the avoidance and suppression of edge localized modes (ELMs) at DIII-D. However, large coalescing islands can also generate, in the middle of these stochastic regions, KAM surfaces effectively acting as ‘barriers’ against field-line dispersion and, indirectly, particle diffusion. It was predicted in Ali and Punjabi (2007 Plasma Phys. Control. Fusion 49 1565-82) that such magnetic barriers can form in piecewise analytic DIII-D plasma equilibria. In this work, the formation of magnetic barriers at DIII-D is corroborated by field-line tracing calculations using experimentally constrained EFIT (Lao et al 1985 Nucl. Fusion 25 1611) DIII-D equilibria perturbed to include the vacuum field from the internal coils utilized in the experiments. According to these calculations, the occurrence and location of magnetic barriers depend on the edge safety factor q95. It was thus suggested that magnetic barriers might contribute to narrowing the edge stochastic layer and play an indirect role in the RMPs failing to control ELMs for certain values of q95. The analysis of DIII-D discharges where q95 was varied, however, does not show anti-correlation between barrier formation and ELM suppression.

  16. Magnetic barriers and their q95 dependence at DIII-D

    International Nuclear Information System (INIS)

    Volpe, F.A.; Kessler, J.; Ali, H.; Punjabi, A.; Evans, T.E.

    2012-01-01

    It is well known that externally generated resonant magnetic perturbations (RMPs) can form islands in the plasma edge. In turn, large overlapping islands generate stochastic fields, which are believed to play a role in the avoidance and suppression of edge localized modes (ELMs) at DIII-D. However, large coalescing islands can also generate, in the middle of these stochastic regions, KAM surfaces effectively acting as ‘barriers’ against field-line dispersion and, indirectly, particle diffusion. It was predicted in Ali and Punjabi (2007 Plasma Phys. Control. Fusion 49 1565–82) that such magnetic barriers can form in piecewise analytic DIII-D plasma equilibria. In this work, the formation of magnetic barriers at DIII-D is corroborated by field-line tracing calculations using experimentally constrained EFIT (Lao et al 1985 Nucl. Fusion 25 1611) DIII-D equilibria perturbed to include the vacuum field from the internal coils utilized in the experiments. According to these calculations, the occurrence and location of magnetic barriers depend on the edge safety factor q 95 . It was thus suggested that magnetic barriers might contribute to narrowing the edge stochastic layer and play an indirect role in the RMPs failing to control ELMs for certain values of q 95 . The analysis of DIII-D discharges where q 95 was varied, however, does not show anti-correlation between barrier formation and ELM suppression. (paper)

  17. Tunnel magnetoresistance in alumina, magnesia and composite tunnel barrier magnetic tunnel junctions

    International Nuclear Information System (INIS)

    Schebaum, Oliver; Drewello, Volker; Auge, Alexander; Reiss, Guenter; Muenzenberg, Markus; Schuhmann, Henning; Seibt, Michael; Thomas, Andy

    2011-01-01

    Using magnetron sputtering, we have prepared Co-Fe-B/tunnel barrier/Co-Fe-B magnetic tunnel junctions with tunnel barriers consisting of alumina, magnesia, and magnesia-alumina bilayer systems. The highest tunnel magnetoresistance ratios we found were 73% for alumina and 323% for magnesia-based tunnel junctions. Additionally, tunnel junctions with a unified layer stack were prepared for the three different barriers. In these systems, the tunnel magnetoresistance ratios at optimum annealing temperatures were found to be 65% for alumina, 173% for magnesia, and 78% for the composite tunnel barriers. The similar tunnel magnetoresistance ratios of the tunnel junctions containing alumina provide evidence that coherent tunneling is suppressed by the alumina layer in the composite tunnel barrier. - Research highlights: → Transport properties of Co-Fe-B/tunnel barrier/Co-Fe-B magnetic tunnel junctions. → Tunnel barrier consists of MgO, Al-Ox, or MgO/Al-Ox bilayer systems. → Limitation of TMR-ratio in composite barrier tunnel junctions to Al-Ox values. → Limitation indicates that Al-Ox layer is causing incoherent tunneling.

  18. Magnetic edge states and magnetotransport in graphene antidot barriers

    DEFF Research Database (Denmark)

    Thomsen, M. R.; Power, Stephen; Jauho, Antti-Pekka

    2016-01-01

    Magnetic fields are often used for characterizing transport in nanoscale materials. Recent magnetotransport experiments have demonstrated that ballistic transport is possible in graphene antidot lattices (GALs). These experiments have inspired the present theoretical study of GALs in a perpendicu......Magnetic fields are often used for characterizing transport in nanoscale materials. Recent magnetotransport experiments have demonstrated that ballistic transport is possible in graphene antidot lattices (GALs). These experiments have inspired the present theoretical study of GALs...

  19. Origin of methyl torsional potential barrier – An overview

    Indian Academy of Sciences (India)

    Unknown

    This paper presents the evolution of views on methyl internal rotation ... recognized in the early years of quantum theory.1 Since then, detailed experimental and ..... C−C bond in the methyl conjugated molecules is an important factor for barrier.

  20. Comparative studies for different proximity potentials applied to sub-barrier fusion reactions

    Energy Technology Data Exchange (ETDEWEB)

    Zhang, G.L. [Beihang University, School of Physics and Nuclear Energy Engineering, Beijing (China); Beihang University, Key Laboratory of Micro-Nano Measurement-Manipulation and Physics (Ministry of Education), Beijing (China); Qu, W.W. [Medical College of Soochow University, School of Radiation Medicine and Protection, Soochow (China); Guo, M.F.; Qian, J.Q. [Beihang University, School of Physics and Nuclear Energy Engineering, Beijing (China); Zhang, H.Q. [China Institute of Atomic Energy, Beijing (China); Wolski, R. [Henryk Niewodniczanski Institute of Nuclear Physics PAS, Cracow (Poland)

    2016-02-15

    Coulomb barrier heights calculated by using 14 different versions of proximity potentials are studied and applied for experimental data of fusion in terms of a recently proposed energy scaling approach. The results show that the descriptions of proximity potentials 77 and 88 for the barrier heights seem to be closest to the values required by the systematics. On the basis of proximity potential 77, the parameterized formulas of the barrier height and radius are obtained. These formulas can calculate the barrier positions and barrier heights reasonably well within the error, respectively. Thus it provides a simple and direct way to calculate the barrier positions and barrier heights for heavy-ion fusion reactions. (orig.)

  1. Asymmetric voltage behavior of the tunnel magnetoresistance in double barrier magnetic tunnel junctions

    KAUST Repository

    Useinov, Arthur

    2012-06-01

    In this paper, we study the value of the tunnel magnetoresistance (TMR) as a function of the applied voltage in double barrier magnetic tunnel junctions (DMTJs) with the left and right ferromagnetic (FM) layers being pinned and numerically estimate the possible difference of the TMR curves for negative and positive voltages in the homojunctions (equal barriers and electrodes). DMTJs are modeled as two single barrier junctions connected in series with consecutive tunneling (CST). We investigated the asymmetric voltage behavior of the TMR for the CST in the range of a general theoretical model. Significant asymmetries of the experimental curves, which arise due to different annealing regimes, are mostly explained by different heights of the tunnel barriers and asymmetries of spin polarizations in magnetic layers. © (2012) Trans Tech Publications.

  2. Asymmetric voltage behavior of the tunnel magnetoresistance in double barrier magnetic tunnel junctions

    KAUST Repository

    Useinov, Arthur; Gooneratne, Chinthaka Pasan; Kosel, Jü rgen

    2012-01-01

    In this paper, we study the value of the tunnel magnetoresistance (TMR) as a function of the applied voltage in double barrier magnetic tunnel junctions (DMTJs) with the left and right ferromagnetic (FM) layers being pinned and numerically estimate the possible difference of the TMR curves for negative and positive voltages in the homojunctions (equal barriers and electrodes). DMTJs are modeled as two single barrier junctions connected in series with consecutive tunneling (CST). We investigated the asymmetric voltage behavior of the TMR for the CST in the range of a general theoretical model. Significant asymmetries of the experimental curves, which arise due to different annealing regimes, are mostly explained by different heights of the tunnel barriers and asymmetries of spin polarizations in magnetic layers. © (2012) Trans Tech Publications.

  3. Magnetic fields, special relativity and potential theory elementary electromagnetic theory

    CERN Document Server

    Chirgwin, B H; Kilmister, C W

    1972-01-01

    Magnetic Fields, Special Relativity and Potential Theory is an introduction to electromagnetism, special relativity, and potential theory, with emphasis on the magnetic field of steady currents (magnetostatics). Topics covered range from the origin of the magnetic field and the magnetostatic scalar potential to magnetization, electromagnetic induction and magnetic energy, and the displacement current and Maxwell's equations. This volume is comprised of five chapters and begins with an overview of magnetostatics, followed by a chapter on the methods of solving potential problems drawn from elec

  4. Electron internal transport barriers and magnetic topology in the stellarator TJ-II

    International Nuclear Information System (INIS)

    Estrada, T.; Alonso, A.; Castejon, F.; Hidalgo, C.; Pablos, J.L. de; Tereshin, V.; Krupnik, L.; Chmyga, A.A.; Dreval, N.; Khrebtov, S.M.; Komarov, A.D.; Kozachok, A.S.; Eliseev, L.; Melnikov, A.V.

    2005-01-01

    Electron Internal Transport Barriers (e-ITBs) are frequently observed in helical systems. e-ITBs are characterized by an increase in core electron temperature and plasma potential as well as an improvement in core electron heat confinement. A comparative study of transport barriers in different helical devices will be presented by Yokoyama et al at this conference. In most helical systems, and in particular in TJ-II stellarator, the formation of e-ITBs is observed in Electron Cyclotron Heated plasmas with high heating power density. In TJ-II, e-ITBs are also formed in magnetic configurations having a low order rational surface close to the plasma core where the ECH power is deposited. In such configurations the key element to improve heat confinement, i.e. the strong radial electric field, results from a synergistic effect between enhanced electron heat fluxes through the low order rational surface and pump-out mechanisms in the heat deposition zone. Recent experiments show a quasi-coherent mode associated with a rational surface that triggers the formation of the e-ITB. This quasi-coherent mode is observed by both ECE and HIBP diagnostics. The mode is found to be localized within the radial range ρ: 0.0 - 0.4, with a maximum amplitude around ρ: 0.25 - 0.35, close to the foot of the e- ITB. The quasi-coherent mode evolves during the formation/annihilation of the e-ITB and vanishes as the barrier is fully developed. These observations indicate that the quasi-coherent modes are modified by the radial electric fields that develop at the transitions, thereby showing the importance of ExB flows in the evolution of MHD instabilities linked to low-order rational surfaces. Further studies are in progress to investigate the influence of the order of the low rational surfaces (3/2, 5/3,...) in triggering core transitions. (author)

  5. Manufacture and test of prototype water pipe chase barrier in ITER Magnet Feeder system

    Energy Technology Data Exchange (ETDEWEB)

    Lu, Kun, E-mail: lukun@ipp.ac.cn [Institute of Plasma Physics, Shushan Hu Road 350, Hefei, Anhui (China); Wen, Xinjie; Liu, Chen; Song, Yuntao [Institute of Plasma Physics, Shushan Hu Road 350, Hefei, Anhui (China); Niu, Erwu [ITER China, 15B Fuxing Road, Beijing 100862 (China); Gung, Chenyu; Su, Man [ITER Organization, Route de Vinon-sur-Verdon – CS 90046, 13067 St Paul-lez-Durance Cedex (France)

    2016-11-01

    The Magnet Feeder system in the International Thermonuclear Experimental Reactor (ITER) deploys electrical currents and supercritical helium to the superconducting magnets and the magnet diagnostic signals to the operators. In the current design, the feeders located in the upper L3 level of the Tokamak gallery penetrate the Tokamak coolant water system vault, the biological shield and the cryostat. As a secondary confinement to contain the activated coolant water in the vault in the case of water pipe burst accident, a water barrier is welded between the penetration in the water pipe chase outer wall and the mid-plane of the vacuum jacket of the Feeder Coil Terminal Box (CTB). A thin-wall stainless steel diaphragm with an omega shape profile is welded around the CTB as the water barrier to endure 2 bar hydraulic pressure. In addition, the barrier is designed as a flexible compensator to withstand a maximum of 15 mm of axial displacement of the CTB in case of helium leak accident without failure. This paper presents the detail configuration, the manufacturing and assembly processes of the water barrier. Test results of the prototype water barrier under simulated accident conditions are also reported. Successful qualification of the design and manufacturing process of the water barrier lays a good foundation for the series production of this subsystem.

  6. The strongest magnetic barrier in the DIII-D tokamak and comparison with the ASDEX UG

    Science.gov (United States)

    Ali, Halima; Punjabi, Alkesh

    2013-05-01

    Magnetic perturbations in tokamaks lead to the formation of magnetic islands, chaotic field lines, and the destruction of flux surfaces. Controlling or reducing transport along chaotic field lines is a key challenge in magnetically confined fusion plasmas. A local control method was proposed by Chandre et al. [Nucl. Fusion 46, 33-45 (2006)] to build barriers to magnetic field line diffusion by addition of a small second-order control term localized in the phase space to the field line Hamiltonian. Formation and existence of such magnetic barriers in Ohmically heated tokamaks (OHT), ASDEX UG and piecewise analytic DIII-D [Luxon, J.L.; Davis, L.E., Fusion Technol. 8, 441 (1985)] plasma equilibria was predicted by the authors [Ali, H.; Punjabi, A., Plasma Phys. Control. Fusion 49, 1565-1582 (2007)]. Very recently, this prediction for the DIII-D has been corroborated [Volpe, F.A., et al., Nucl. Fusion 52, 054017 (2012)] by field-line tracing calculations, using experimentally constrained Equilibrium Fit (EFIT) [Lao, et al., Nucl. Fusion 25, 1611 (1985)] DIII-D equilibria perturbed to include the vacuum field from the internal coils utilized in the experiments. This second-order approach is applied to the DIII-D tokamak to build noble irrational magnetic barriers inside the chaos created by the locked resonant magnetic perturbations (RMPs) (m, n)=(3, 1)+(4, 1), with m and n the poloidal and toroidal mode numbers of the Fourier expansion of the magnetic perturbation with amplitude δ. A piecewise, analytic, accurate, axisymmetric generating function for the trajectories of magnetic field lines in the DIII-D is constructed in magnetic coordinates from the experimental EFIT Grad-Shafranov solver [Lao, L, et al., Fusion Sci. Technol. 48, 968 (2005)] for the shot 115,467 at 3000 ms in the DIII-D. A symplectic mathematical map is used to integrate field lines in the DIII-D. A numerical algorithm [Ali, H., et al., Radiat. Eff. Def. Solids Inc. Plasma Sc. Plasma Tech. 165, 83

  7. Determination of the thickness of Al2O3 barriers in magnetic tunnel junctions

    International Nuclear Information System (INIS)

    Buchanan, J.D.R.; Hase, T.P.A.; Tanner, B.K.; Hughes, N.D.; Hicken, R.J.

    2002-01-01

    The barrier thickness in magnetic spin-dependent tunnel junctions with Al 2 O 3 barriers has been measured using grazing incidence x-ray reflectivity and by fitting the tunneling current to the Simmons model. We have studied the effect of glow discharge oxidation time on the barrier structure, revealing a substantial increase in Al 2 O 3 thickness with oxidation. The greater thickness of barrier measured using grazing incidence x-ray reflectivity compared with that obtained by fitting current density-voltage to the Simmons electron tunneling model suggests that electron tunneling is localized to specific regions across the barrier, where the thickness is reduced by fluctuations due to nonconformal roughness

  8. Role of E x B Shear and Magnetic Shear in the Formation of Transport Barriers in DIII-D

    International Nuclear Information System (INIS)

    Burrell, K.H.

    2005-01-01

    Development of the E x B shear stabilization model to explain the formation of transport barriers in magnetic confinement devices is a major achievement of fusion research. This concept has the universality needed to explain the H-mode edge transport barriers seen in limiter and divertor tokamaks, stellarators, and mirror machines; the broader edge transport barrier seen in VH-mode plasmas; and the core transport barriers formed in tokamaks with low or negative magnetic shear. These examples of confinement improvement are of considerable physical interest; it is not often that a system self-organizes to reduce transport when an additional source of free energy is applied to it. The transport decrease associated with E x B velocity shear is also of great practical benefit to fusion research. The fundamental physics involved in transport reduction is the effect of E x B shear on the growth, radial extent, and phase correlation of turbulent eddies in the plasma. The same basic transport reduction process can be operational in various portions of the plasma because there are a number of ways to change the radial electric field E r . An important theme in this area is the synergistic effect of E x B velocity shear and magnetic shear. Although the E x B velocity shear appears to have an effect on broader classes of microturbulence, magnetic shear can mitigate some potentially harmful effects of E x B velocity shear and facilitate turbulence stabilization. The experimental results on DIII-D and other devices are generally consistent with the basic theoretical models

  9. Temperature dependence of shot noise in double barrier magnetic tunnel junctions

    Science.gov (United States)

    Niu, Jiasen; Liu, Liang; Feng, J. F.; Han, X. F.; Coey, J. M. D.; Zhang, X.-G.; Wei, Jian

    2018-03-01

    Shot noise reveals spin dependent transport properties in a magnetic tunnel junction. We report measurement of shot noise in CoFeB/MgO/CoFeB/MgO/CoFeB double barrier magnetic tunnel junctions, which shows a strong temperature dependence. The Fano factor used to characterize shot noise increases with decreasing temperature. A sequential tunneling model can be used to account for these results, in which a larger Fano factor results from larger spin relaxation length at lower temperatures.

  10. Modulation of spin transfer torque amplitude in double barrier magnetic tunnel junctions

    Science.gov (United States)

    Clément, P.-Y.; Baraduc, C.; Ducruet, C.; Vila, L.; Chshiev, M.; Diény, B.

    2015-09-01

    Magnetization switching induced by spin transfer torque is used to write magnetic memories (Magnetic Random Access Memory, MRAM) but can be detrimental to the reading process. It would be quite convenient therefore to modulate the efficiency of spin transfer torque. A solution is adding an extra degree of freedom by using double barrier magnetic tunnel junctions with two spin-polarizers, with controllable relative magnetic alignment. We demonstrate, for these structures, that the amplitude of in-plane spin transfer torque on the middle free layer can be efficiently tuned via the magnetic configuration of the electrodes. Using the proposed design could thus pave the way towards more reliable read/write schemes for MRAM. Moreover, our results suggest an intriguing effect associated with the out-of-plane (field-like) spin transfer torque, which has to be further investigated.

  11. Modulation of spin transfer torque amplitude in double barrier magnetic tunnel junctions

    International Nuclear Information System (INIS)

    Clément, P.-Y.; Baraduc, C.; Chshiev, M.; Diény, B.; Ducruet, C.; Vila, L.

    2015-01-01

    Magnetization switching induced by spin transfer torque is used to write magnetic memories (Magnetic Random Access Memory, MRAM) but can be detrimental to the reading process. It would be quite convenient therefore to modulate the efficiency of spin transfer torque. A solution is adding an extra degree of freedom by using double barrier magnetic tunnel junctions with two spin-polarizers, with controllable relative magnetic alignment. We demonstrate, for these structures, that the amplitude of in-plane spin transfer torque on the middle free layer can be efficiently tuned via the magnetic configuration of the electrodes. Using the proposed design could thus pave the way towards more reliable read/write schemes for MRAM. Moreover, our results suggest an intriguing effect associated with the out-of-plane (field-like) spin transfer torque, which has to be further investigated

  12. Experimental investigation on the repetitively nanosecond pulsed dielectric barrier discharge with the parallel magnetic field

    Science.gov (United States)

    Liu, Yidi; Yan, Huijie; Guo, Hongfei; Fan, Zhihui; Wang, Yuying; Ren, Chunsheng

    2018-02-01

    The effects of a parallel magnetic field on the unipolar positive nanosecond pulsed dielectric barrier discharge are experimentally investigated through electrical and spectral measurements. The discharge is produced between two parallel-plate electrodes in the ambient air with a parallel magnetic field of 1.4 T. Experimental results show that both the discharge intensity and uniformity are improved in the discharge with the parallel magnetic field. The intensity ratio of the spectrum at 371.1 nm and 380.5 nm, which describes the average electron density, is increased by the parallel magnetic field. Meanwhile, the intensity ratio of the spectrum at 391.4 nm and 337.1 nm, which describes the electron temperature, is also increased. It is speculated that both the average electron density and the electron temperature are increased by the parallel magnetic field. The aforementioned phenomena have been explained by the confinement effect of the parallel magnetic field on the electrons.

  13. Integrated control of the wastewater system – potentials and barriers

    DEFF Research Database (Denmark)

    Mollerup, Ane Loft; Grum, Morten; Muschalla, Dirk

    2013-01-01

    Applying integrated control to a sewer system and wastewater treatment plant often leads to additional benefits for both systems when compared to controlling them independently. However, barriers such as a lack of incentive for utilities to put this type of control in place mean that in practice...

  14. Potential solver for sloshing-ion thermal barriers

    International Nuclear Information System (INIS)

    Boghosian, B.M.; Campbell, R.B.; Gilmore, J.M.

    1981-01-01

    The quasineutrality equations at points (a) and (b) in a sloshing-ion thermal barrier are derived and an algorithm for their solution is given. The solution technique is sufficiently reliable and efficient to be used in a fluid code where it must be invoked at each time step. Circumstances under which the equations admit multiple solutions are noted and discussed

  15. Study on fusion potential barrier in heavy ion reactions based on the dynamical model

    International Nuclear Information System (INIS)

    Tian Junlong; Wu Xizhen; Li Zhuxia; Wang Ning; Liu Fuhu

    2004-01-01

    Based on an improved quantum molecular dynamics model the static and dynamic potential in the entrance channel of synthesis of superheavy nuclei are studied. The dependence of the static potential (and driving potential) on mass-asymmetry is obtained. From this study authors find out that the mass-symmetric system seems to be difficult to fuse and the fusing system with the largest driving potential could be the optimal choice of the projectile-target combination. By comparing the static potential barrier with the dynamic one authors find that the latter one is lower than former one obviously, and that the dynamical potential barrier is entrance energy dependent. The maximum and minimum of dynamic potential barriers approach to the diabatic (sudden approximation) and the adiabatic static potential barriers, respectively

  16. Electronic transport in armchair graphene nanoribbon under double magnetic barrier modulation

    Science.gov (United States)

    Wang, Haiyan; Wu, Chao; Xie, Fang; Zhang, Xiaojiao; Zhou, Guanghui

    2018-03-01

    We present a theoretical investigation of the transport properties and the magnetoresistance effect in armchair graphene nanoribbons (AGNRs) under modulation by two magnetic barriers. The energy levels are found to be degenerate for a metallic AGNR but are not degenerate for a semiconducting AGNR. However, the conductance characteristics show quantized plateaus in both the metallic and semiconducting cases. When the magnetization directions of the barriers change from parallel to antiparallel, the conductance plateau in the metallic AGNR shows a degenerate feature due to matching between the transport modes in different regions. As the barrier height increases, the conductance shows more oscillatory behavior with sharp peaks and troughs. Specifically, the initial position of nonzero conductance for the metallic AGNR system moves towards a higher energy regime, which indicates that an energy gap has been opened. In addition, the magnetoresistance ratio also shows plateau structures in certain specific energy regions. These results may be useful in the design of electron devices based on AGNR nanostructures.

  17. Ballistic charge carrier transmission through graphene multi-barrier structures in uniform magnetic field

    International Nuclear Information System (INIS)

    Zubarev, A; Dragoman, D

    2014-01-01

    We investigate charge carrier transport in graphene multi-barrier structures placed in a uniform magnetic field. The transmission coefficient is found analytically by generalizing the transfer matrix method for the case of graphene regions subjected to a uniform magnetic field. The transmission coefficient through the structure can be modulated by varying the gate voltages, the magnetic field and/or the width of the gated regions. Such a configuration could be used in multiple-valued logic circuits, since it has several output states with discrete and easily selectable transmission/current values. (paper)

  18. Transport properties of Dirac electrons in graphene based double velocity-barrier structures in electric and magnetic fields

    International Nuclear Information System (INIS)

    Liu, Lei; Li, Yu-Xian; Liu, Jian-Jun

    2012-01-01

    Using transfer matrix method, transport properties in graphene based double velocity-barrier structures under magnetic and electric fields are numerically studied. It is found that velocity barriers for the velocity ratio (the Fermi velocity inside the barrier to that outside the barrier) less than one (or for the velocity ratio greater than one) have properties similar to electrostatic wells (or barriers). The velocity barriers for the velocity ratio greater than one significantly enlarge the resonant tunneling region of electrostatic barriers. In the presence of magnetic field, the plateau width of the Fano factor with a Poissonian value shortens (or broadens) for the case of the velocity ratio less than one (or greater than one). When the Fermi energy is equal to the electrostatic barrier height, for different values of the velocity ratio, both the conductivities and the Fano factors remain fixed. -- Highlights: ► We model graphene based velocity-barrier structures in electric and magnetic fields. ► Velocity barrier for ξ 1) have property similar to electrostatic well (barrier). ► Velocity barrier for ξ>1 enlarge the resonant tunneling region of electrostatic barrier. ► The plateau width of Fano factor shortens (or broadens) for the case of ξ 1). ► The conductivity remains fixed at the point of E F =U 0 for different values of ξ.

  19. Quasibound states in graphene quantum-dot nanostructures generated by concentric potential barrier rings

    International Nuclear Information System (INIS)

    Jiang Zhao-Tan; Yu Cheng-Long; Dong Quan-Li

    2012-01-01

    We study the quasibound states in a graphene quantum-dot structure generated by the single-, double-, and triple-barrier electrostatic potentials. It is shown that the strongest quasibound states are mainly determined by the innermost barrier. Specifically, the positions of the quasibound states are determined by the barrier height, the number of the quasibound states is determined by the quantum-dot radius and the angular momentum, and the localization degree of the quasibound states is influenced by the width of the innermost barrier, as well as the outside barriers. Furthermore, according to the study on the double- and triple-barrier quantum dots, we find that an effective way to generate more quasibound states with even larger energy level spacings is to design a quantum dot defined by many concentric barriers with larger barrier-height differences. Last, we extend our results into the quantum dot of many barriers, which gives a complete picture about the formation of the quasibound states in the kind of graphene quantum dot created by many concentric potential barrier rings. (rapid communication)

  20. Consistent energy barrier distributions in magnetic particle chains

    International Nuclear Information System (INIS)

    Laslett, O.; Ruta, S.; Chantrell, R.W.; Barker, J.; Friedman, G.; Hovorka, O.

    2016-01-01

    We investigate long-time thermal activation behaviour in magnetic particle chains of variable length. Chains are modelled as Stoner–Wohlfarth particles coupled by dipolar interactions. Thermal activation is described as a hopping process over a multidimensional energy landscape using the discrete orientation model limit of the Landau–Lifshitz–Gilbert dynamics. The underlying master equation is solved by diagonalising the associated transition matrix, which allows the evaluation of distributions of time scales of intrinsic thermal activation modes and their energy representation. It is shown that as a result of the interaction dependence of these distributions, increasing the particle chain length can lead to acceleration or deceleration of the overall relaxation process depending on the initialisation procedure.

  1. Noble internal transport barriers and radial subdiffusion of toroidal magnetic lines

    Energy Technology Data Exchange (ETDEWEB)

    Misguich, J.H.; Reuss, J.D. [Association Euratom-CEA sur la Fusion, CEA/DSM/DRFC, 13 - Saint Paul lez Durance (France); Constantinescu, D.; Steinbrecher, G. [Association Euratom-N.A.S.T.I., Dept. of Physics, University of Craiova (Romania); Vlad, M.; Spineanu, F. [Association Euratom-N.A.S.T.I., National Institute of Laser, Plasma and Radiation Physics, Bucharest (Romania); Weyssow, B.; Balescu, R. [Association Euratom-Etat Belge sur la Fusion, Universite Libre de Bruxelles (Belgium)

    2002-02-01

    Internal transport barriers (ITB's) observed in tokamaks are described by a purely magnetic approach. Magnetic line motion in toroidal geometry with broken magnetic surfaces is studied from a previously derived Hamiltonian map in situation of incomplete chaos. This appears to reproduce in a realistic way the main features of a tokamak, for a given safety factor profile and in terms of a single parameter L representing the amplitude of the magnetic perturbation. New results are given concerning the Shafranov shift as function of L. For small values of L, closed magnetic surfaces exist (KAM tori) and island chains begin to appear on rational surfaces for higher values of L, with chaotic zones around hyperbolic points, as expected. Single trajectories of magnetic line motion indicate the persistence of a central protected plasma core, surrounded by a chaotic shell enclosed in a double-sided transport barrier. Magnetic lines which succeed to escape across this barrier begin to wander in a wide chaotic sea extending up to a very robust barrier (as long as L{<=}1). For values of L{>=}1, above the escape threshold, most magnetic lines succeed to escape out of the external barrier which has become a permeable Cantorus. Statistical analysis of a large number of trajectories, representing the evolution of a bunch of magnetic lines, indicate that the flux variable {psi} asymptotically grows in a diffuse manner as (L{sup 2}t) with a L{sup 2} scaling as expected, but that the average radial position r{sub m}(t) asymptotically grows as (L{sup 2}t){sup 1/4} while the mean square displacement around this average radius asymptotically grows in a sub-diffusive manner as (L{sup 2}t){sup 1/2}. This result shows the slower dispersion in the present incomplete chaotic regime, which is different from the usual quasilinear diffusion in completely chaotic situations. For physical times t{sub {phi}} of the order of the escape time defined by x{sub m}(t{sub {phi}}) {approx}1, the motion

  2. Noble internal transport barriers and radial subdiffusion of toroidal magnetic lines

    International Nuclear Information System (INIS)

    Misguich, J.H.; Reuss, J.D.; Constantinescu, D.; Steinbrecher, G.; Vlad, M.; Spineanu, F.; Weyssow, B.; Balescu, R.

    2002-02-01

    Internal transport barriers (ITB's) observed in tokamaks are described by a purely magnetic approach. Magnetic line motion in toroidal geometry with broken magnetic surfaces is studied from a previously derived Hamiltonian map in situation of incomplete chaos. This appears to reproduce in a realistic way the main features of a tokamak, for a given safety factor profile and in terms of a single parameter L representing the amplitude of the magnetic perturbation. New results are given concerning the Shafranov shift as function of L. For small values of L, closed magnetic surfaces exist (KAM tori) and island chains begin to appear on rational surfaces for higher values of L, with chaotic zones around hyperbolic points, as expected. Single trajectories of magnetic line motion indicate the persistence of a central protected plasma core, surrounded by a chaotic shell enclosed in a double-sided transport barrier. Magnetic lines which succeed to escape across this barrier begin to wander in a wide chaotic sea extending up to a very robust barrier (as long as L≤1). For values of L≥1, above the escape threshold, most magnetic lines succeed to escape out of the external barrier which has become a permeable Cantorus. Statistical analysis of a large number of trajectories, representing the evolution of a bunch of magnetic lines, indicate that the flux variable ψ asymptotically grows in a diffuse manner as (L 2 t) with a L 2 scaling as expected, but that the average radial position r m (t) asymptotically grows as (L 2 t) 1/4 while the mean square displacement around this average radius asymptotically grows in a sub-diffusive manner as (L 2 t) 1/2 . This result shows the slower dispersion in the present incomplete chaotic regime, which is different from the usual quasilinear diffusion in completely chaotic situations. For physical times t φ of the order of the escape time defined by x m (t φ ) ∼1, the motion appears to be super-diffusive, however, but less dangerous than

  3. Plane and hemispherical potential structures in magnetically expanding plasmas

    International Nuclear Information System (INIS)

    Takahashi, Kazunori; Igarashi, Yuichi; Fujiwara, Tamiya

    2010-01-01

    Two-dimensional potential structures are measured for different gas pressure in expanding argon plasma using permanent magnets, where the magnetic field is about 100 G in the source and several gauss in the diffusion chamber. The plane potential drop is observed near the source exit for 0.35 mTorr, while the potential structure becomes hemispherical when increasing up to 1 mTorr; the hemispherical structure results in the radial divergence of the ion beam. It is found that the trajectories of the accelerated ions and the electrons overcoming the potential drop are dominated by the potential structure and magnetic-field lines, respectively.

  4. Electron transport and noise spectroscopy in organic magnetic tunnel junctions with PTCDA and Alq3 barriers

    Science.gov (United States)

    Martinez, Isidoro; Cascales, Juan Pedro; Hong, Jhen-Yong; Lin, Minn-Tsong; Prezioso, Mirko; Riminucci, Alberto; Dediu, Valentin A.; Aliev, Farkhad G.

    2016-10-01

    The possible influence of internal barrier dynamics on spin, charge transport and their fluctuations in organic spintronics remains poorly understood. Here we present investigation of the electron transport and low frequency noise at temperatures down to 0.3K in magnetic tunnel junctions with an organic PTCDA barriers with thickness up to 5 nm in the tunneling regime and with 200 nm thick Alq3 barrier in the hopping regime. We observed high tunneling magneto-resistance at low temperatures (15-40%) and spin dependent super-poissonian shot noise in organic magnetic tunnel junctions (OMTJs) with PTCDA. The Fano factor exceeds 1.5-2 values which could be caused by interfacial states controlled by spin dependent bunching in the tunneling events through the molecules.1 The bias dependence of the low frequency noise in OMTJs with PTCDA barriers which includes both 1/f and random telegraph noise activated at specific biases will also be discussed. On the other hand, the organic junctions with ferromagnetic electrodes and thick Alq3 barriers present sub-poissonian shot noise which depends on the temperature, indicative of variable range hopping.

  5. Potential barriers to the use of health services among ethnic minorities : a review

    NARCIS (Netherlands)

    Scheppers, E.; van Dongen, E.; Dekker, J.; Geertzen, J.; Dekker, J.

    Background. Ethnic minority patients seem to be confronted with barriers when using health services. Yet, care providers are often oblivious to these barriers, although they may share to some extent the burden of responsibility for them. In order to enlighten care providers, as to the potential

  6. On the (DE-) stabilization of quantum mechanical binding by potential barriers

    International Nuclear Information System (INIS)

    Hogreve, H.

    1994-04-01

    Stabilization and destabilization effects caused by adding or rising a potential barrier are studied for a simple one-dimensional quantum system. Calculating the motion of the corresponding S-matrix poles for varying barrier width and height, this reveals the scenario for the transition between bound, virtual and resonance states. Our results show that the presence of a barrier leads to nonanalyticity of the ground state with respect to the involved coupling constants. Furthermore, for increasing barrier width the size of the virtual regime shrinks drastically, so that it might be hardly detectable in many practical situations. (author). 15 refs, 5 figs

  7. Electronic and transport properties of noncollinear magnetic monatomic Mn chains: Fano resonances in the superlattice of noncollinear magnetic barriers and magnetic anisotropic bands

    International Nuclear Information System (INIS)

    Dai, C.J.; Yan, X.H.; Xiao, Y.; Guo, Y.D.

    2015-01-01

    By means of the density functional theory combined with non-equilibrium Green's function method, ballistic transport properties of one-dimensional noncollinear magnetic monatomic chains were investigated using the single-atomic Mn chains as a model system. Fano resonances are found to exist in the monatomic Mn chains with spin-spiral structure. Furthermore, in the monatomic Mn chains with magnetic soliton lattice, Fano resonances are enhanced and cause the conductance splitting in the transmission spectra. The Fano resonances in the noncollinear magnetic single-atomic Mn chains are arising from the coupling of the localized d-states and the extended states of the quantum channels. By constructing a theoretical model and calculating its conductance, it is found that the phenomena of Fano resonances and the accompanying conductance splitting exist universally in the superlattice of one-dimensional noncollinear magnetic barriers, due to the interference of the incident waves and reflected waves by the interfaces between the neighboring barriers. Moreover, the band structures of the ferromagnetic and spin-spiral monatomic Mn chains exhibit a strong dependence on the spatial arrangement of the magnetic moments of Mn atoms when spin–orbit coupling is considered. - Highlights: • Transport properties of noncollinear magnetic monatomic Mn chains are studied. • Fano resonances are found in the noncollinear magnetic monatomic Mn chains. • Magnetic soliton lattice leads to conductance splitting in the transmission curve. • Fano resonances exist in the superlattice of noncollinear magnetic barriers. • Effect of SOC on the band structure of FM and spin-spiral Mn chains are studied

  8. Reactor potential for magnetized target fusion

    International Nuclear Information System (INIS)

    Dahlin, J.E.

    2001-06-01

    Magnetized Target Fusion (MTF) is a possible pathway to thermonuclear fusion different from both magnetic fusion and inertial confinement fusion. An imploding cylindrical metal liner compresses a preheated and magnetized plasma configuration until thermonuclear conditions are achieved. In this report the Magnetized Target Fusion concept is evaluated and a zero-dimensional computer model of the plasma, liner and circuit as a connected system is designed. The results of running this code are that thermonuclear conditions are achieved indeed, but only during a very short time. At peak compression the pressure from the compressed plasma and magnetic field is so large reversing the liner implosion into an explosion. The time period of liner motion reversal is termed the dwell time and is crucial to the performance of the fusion system. Parameters as liner thickness and plasma density are certainly of significant importance to the dwell time, but it seems like a reactor based on the MTF principle hardly can become economic if not innovative solutions are introduced. In the report two such solutions are presented as well

  9. Reactor potential for magnetized target fusion

    Energy Technology Data Exchange (ETDEWEB)

    Dahlin, J.E

    2001-06-01

    Magnetized Target Fusion (MTF) is a possible pathway to thermonuclear fusion different from both magnetic fusion and inertial confinement fusion. An imploding cylindrical metal liner compresses a preheated and magnetized plasma configuration until thermonuclear conditions are achieved. In this report the Magnetized Target Fusion concept is evaluated and a zero-dimensional computer model of the plasma, liner and circuit as a connected system is designed. The results of running this code are that thermonuclear conditions are achieved indeed, but only during a very short time. At peak compression the pressure from the compressed plasma and magnetic field is so large reversing the liner implosion into an explosion. The time period of liner motion reversal is termed the dwell time and is crucial to the performance of the fusion system. Parameters as liner thickness and plasma density are certainly of significant importance to the dwell time, but it seems like a reactor based on the MTF principle hardly can become economic if not innovative solutions are introduced. In the report two such solutions are presented as well.

  10. Anisotropy barrier reduction in fast-relaxing Mn12 single-molecule magnets

    Science.gov (United States)

    Hill, Stephen; Murugesu, Muralee; Christou, George

    2009-11-01

    An angle-swept high-frequency electron paramagnetic resonance (HFEPR) technique is described that facilitates efficient in situ alignment of single-crystal samples containing low-symmetry magnetic species such as single-molecule magnets (SMMs). This cavity-based technique involves recording HFEPR spectra at fixed frequency and field, while sweeping the applied field orientation. The method is applied to the study of a low-symmetry Jahn-Teller variant of the extensively studied spin S=10 Mn12 SMMs (e.g., Mn12 -acetate). The low-symmetry complex also exhibits SMM behavior, but with a significantly reduced effective barrier to magnetization reversal (Ueff≈43K) and, hence, faster relaxation at low temperature in comparison with the higher-symmetry species. Mn12 complexes that crystallize in lower symmetry structures exhibit a tendency for one or more of the Jahn-Teller axes associated with the MnIII atoms to be abnormally oriented, which is believed to be the cause of the faster relaxation. An extensive multi-high-frequency angle-swept and field-swept electron paramagnetic resonance study of [Mn12O12(O2CCH2But)16(H2O)4]ṡCH2Cl2ṡMeNO2 is presented in order to examine the influence of the abnormally oriented Jahn-Teller axis on the effective barrier to magnetization reversal. The reduction in the axial anisotropy, D , is found to be insufficient to account for the nearly 40% reduction in Ueff . However, the reduced symmetry of the Mn12 core gives rise to a very significant second-order transverse (rhombic) zero-field-splitting anisotropy, E≈D/6 . This, in turn, causes a significant mixing of spin projection states well below the top of the classical anisotropy barrier. Thus, magnetic quantum tunneling is the dominant factor contributing to the effective barrier reduction in fast relaxing Mn12 SMMs.

  11. Barrier breakdown mechanism in nano-scale perpendicular magnetic tunnel junctions with ultrathin MgO barrier

    Science.gov (United States)

    Lv, Hua; Leitao, Diana C.; Hou, Zhiwei; Freitas, Paulo P.; Cardoso, Susana; Kämpfe, Thomas; Müller, Johannes; Langer, Juergen; Wrona, Jerzy

    2018-05-01

    Recently, the perpendicular magnetic tunnel junctions (p-MTJs) arouse great interest because of its unique features in the application of spin-transfer-torque magnetoresistive random access memory (STT-MRAM), such as low switching current density, good thermal stability and high access speed. In this paper, we investigated current induced switching (CIS) in ultrathin MgO barrier p-MTJs with dimension down to 50 nm. We obtained a CIS perpendicular tunnel magnetoresistance (p-TMR) of 123.9% and 7.0 Ω.μm2 resistance area product (RA) with a critical switching density of 1.4×1010 A/m2 in a 300 nm diameter junction. We observe that the extrinsic breakdown mechanism dominates, since the resistance of our p-MTJs decreases gradually with the increasing current. From the statistical analysis of differently sized p-MTJs, we observe that the breakdown voltage (Vb) of 1.4 V is 2 times the switching voltage (Vs) of 0.7 V and the breakdown process exhibits two different breakdown states, unsteady and steady state. Using Simmons' model, we find that the steady state is related with the barrier height of the MgO layer. Furthermore, our study suggests a more efficient method to evaluate the MTJ stability under high bias rather than measuring Vb. In conclusion, we developed well performant p-MTJs for the use in STT-MRAM and demonstrate the mechanism and control of breakdown in nano-scale ultrathin MgO barrier p-MTJs.

  12. Tests of potential functional barriers for laminated multilayer food packages. Part I: Low molecular weight permeants.

    Science.gov (United States)

    Simal-Gándara, J; Sarria-Vidal, M; Koorevaar, A; Rijk, R

    2000-08-01

    The advent of the functional barrier concept in food packaging has brought with it a requirement for fast tests of permeation through potential barrier materials. In such tests it would be convenient for both foodstuffs and materials below the functional barrier (sub-barrier materials) to be represented by standard simulants. By means of inverse gas chromatography, liquid paraffin spiked with appropriate permeants was considered as a potential simulant of sub-barrier materials based on polypropylene (PP) or similar polyolefins. Experiments were performed to characterize the kinetics of the permeation of low molecular weight model permeants (octene, toluene and isopropanol) from liquid paraffin, through a surrogate potential functional barrier (25 microns-thick oriented PP) into the food stimulants olive oil and 3% (w/v) acetic acid. These permeation results were interpreted in terms of three permeation kinetic models regarding the solubility of a particular model permeant in the post-barrier medium (i.e. the food simulant). The results obtained justify the development and evaluation of liquid sub-barrier simulants that would allow flexible yet rigorous testing of new laminated multilayer packaging materials.

  13. Giant magnetoresistance effect in nanostructures consisting of magnetic-electric barriers

    International Nuclear Information System (INIS)

    Tang, Wei-Hua; Li, Chun-Shu; Kong, Yong-Hong; Zhang, Gui-Lian

    2007-01-01

    The GMR effect in magnetic-electric barrier nanostructure, which can be realized experimentally by depositing two parallel metallic ferromagnetic strips with an applied voltage on the top of heterostructure, is investigated theoretically. It is shown that a considerable GMR effect can be achieved in such nanosystems due to the significant transmission difference for electrons tunneling through parallel and antiparallel magnetization configurations. It is also shown that the magnetoresistance ratio is strongly dependent upon the applied voltage to metallic ferromagnetic strips in nanosystems, thus may leading to voltage-tunable GMR devices

  14. Probing the energy barriers and magnetization reversal processes of nanoperforated membrane based percolated media

    International Nuclear Information System (INIS)

    Neu, V; Schultz, L; Schulze, C; Makarov, D; Albrecht, M; Faustini, M; Grosso, D; Lee, J; Kim, S-K; Suess, D

    2013-01-01

    Magnetization reversal processes in Co/Pt multilayers prepared on nanoperforated templates are probed by magnetization relaxation measurements. The signature of pinning controlled domain wall movement as expected for percolated media is identified. This contrasts with the nucleation-type reversal mechanism of a Co/Pt reference film prepared on a smooth substrate. A zero field energy barrier of 93k B T is determined by fluctuation field measurements and is elucidated by micromagnetic calculations using the nudged elastic band method. This value is sufficiently large to qualify the material as a promising percolated medium. (paper)

  15. Discontinuity model for internal transport barrier formation in reversed magnetic shear plasmas

    International Nuclear Information System (INIS)

    Kishimoto, Y.; Kim, J-Y.; Horton, W.; Tajima, T.; LeBrun, M.J.

    2001-01-01

    To aid in understanding the internal transport barrier (ITB) being formed in reversed magnetic shear experiments, in addition to the well known shear flow effect, we point out an important nonlocal effect and/or finite size effect which comes from the complex behavior of the nonlocal mode over a finite radial region around the minimum q(safety factor)-surface. The nonlocal mode changes its structure depending on the sign of the magnetic shear and due to this fact, the nonlocal modes are weakly excited across the q min -surface. This leads to a discontinuity or gap which disconnects the phase relation in the global wave structure across the q min -surface. Once such a discontinuity (or gap) is formed, transport suppression occurs and therefore a transport barrier can be expected near the q min -surface. We confirm the existence of this discontinuity using a toroidal particle simulation. (author)

  16. Output voltage calculations in double barrier magnetic tunnel junctions with asymmetric voltage behavior

    KAUST Repository

    Useinov, Arthur

    2011-10-22

    In this paper we study the asymmetric voltage behavior (AVB) of the tunnel magnetoresistance (TMR) for single and double barrier magnetic tunnel junctions (MTJs) in range of a quasi-classical free electron model. Numerical calculations of the TMR-V curves, output voltages and I-V characteristics for negative and positive values of applied voltages were carried out using MTJs with CoFeB/MgO interfaces as an example. Asymmetry of the experimental TMR-V curves is explained by different values of the minority and majority Fermi wave vectors for the left and right sides of the tunnel barrier, which arises due to different annealing regimes. Electron tunneling in DMTJs was simulated in two ways: (i) Coherent tunneling, where the DMTJ is modeled as one tunnel system and (ii) consecutive tunneling, where the DMTJ is modeled by two single barrier junctions connected in series. © 2012 Elsevier B.V. All rights reserved.

  17. Building integrated photovoltaics (BIPV). Review, potentials, barriers and myths

    Energy Technology Data Exchange (ETDEWEB)

    Heinstein, Patrick; Ballif, Christophe [Ecole Polytechnique Federale de Lausanne (EPFL), Neuchatel (Switzerland). Photovoltaics and Thin Film Electronics Lab.; Perret-Aebi, Laure-Emmanuelle [CSEM, Neuchatel (Switzerland). PV-Center

    2013-07-01

    To date, none of the predictions that have been made about the emerging BIPV industry have really hit the target. The anticipated boom has so far stalled and despite developing and promoting a number of excellent systems and products, many producers around the world have been forced to quit on purely economic grounds. The authors believe that after this painful cleansing of the market, a massive counter trend will follow, enlivened and carried forward by more advanced PV technologies and ever-stricter climate policies designed to achieve energy neutrality in a cost-effective way. As a result, the need for BIPV products for use in construction will undergo first a gradual and then a massive increase. The planning of buildings with multifunctional, integrated roof and facade elements capable of fulfilling the technical and legal demands will become an essential, accepted part of the architectonic mainstream and will also contribute to an aesthetic valorisation. Until then, various barriers need to be overcome in order to facilitate and accelerate BIPV. Besides issues related to mere cost-efficiency ratio, psychological and social factors also play an evident role. The goal of energy change linked to greater use of renewables can be successfully achieved only when all aspects are taken into account and when visual appeal and energy efficiency thus no longer appear to be an oxymoron. (orig.)

  18. The potential around a test charge in magnetized dusty plasmas

    International Nuclear Information System (INIS)

    Shukla, P.K.; Salimullah, M.

    1996-01-01

    The potential of a test dust particle in a magnetized dusty plasma is calculated, taking into account the dielectric constant associated with electrostatic ion-cyclotron waves. Besides the well-known Debye-Hueckel screening potential, an oscillatory potential distribution around a test dust particle is found, which strongly depends on the strength of the external magnetic field. copyright 1996 American Institute of Physics

  19. Photospheric Driving of Non-Potential Coronal Magnetic Field Simulations

    Science.gov (United States)

    2016-09-19

    synthesize observable emission . In future, the computational speed of the MF model makes it a potential avenue for near- real time and/or ensemble...AFRL-AFOSR-UK-TR-2016-0030 PHOTOSPHERIC DRIVING OF NON-POTENTIAL CORONAL MAGNETIC FIELD SIMULATIONS Anthony Yeates UNIVERSITY OF DURHAM Final Report...Final 3. DATES COVERED (From - To)  15 Sep 2014 to 14 Sep 2017 4. TITLE AND SUBTITLE PHOTOSPHERIC DRIVING OF NON-POTENTIAL CORONAL MAGNETIC FIELD

  20. Optimization of a tunneling barrier in magnetic tunneling junction by tilted-plasma oxidation

    International Nuclear Information System (INIS)

    Nam, C.H.; Shim, Heejae; Kim, K.S.; Cho, B.K.

    2004-01-01

    Oxidation of an AlO x insulating barrier in a magnetic tunneling junction (MTJ) was carried out by a tilted-plasma oxidation method. It was found that the tilted-plasma oxidation induced a gradual change in the extent of oxidation of an insulating layer, which consequently led to a gradual change in the tunneling magnetoresistance (TMR) and specific junction resistance (RA) of the MTJ. We found a linear relation in the TMR versus RA curve with positive and negative slopes for less- and overoxidized junctions, respectively, and a parabolic relation for optimally oxidized junctions. The crossover in the TMR versus RA curves provides an effective and useful way to optimize (and monitor) the oxidation condition of a tunneling barrier in MTJs especially of a tunneling barrier less than 10 A thick. The tunneling junctions were also investigated after thermal annealing at various temperatures. The observations after thermal annealing were found to be consistent with transmission electrons microscopy images and a scenario of the partial formation of an additional ultrathin tunneling barrier at the top surface of the bottom magnetic layer

  1. Economic potential of magnetic fusion energy

    International Nuclear Information System (INIS)

    Henning, C.D.

    1981-01-01

    Scientific feasibility of magnetic fusion is no longer seriously in doubt. Rapid advances have been made in both tokamak and mirror research, leading to a demonstration in the TFTR tokamak at Princeton in 1982 and the tandem mirror MFTF-B at Livermore in 1985. Accordingly, the basis is established for an aggressive engineering thrust to develop a reactor within this century. However, care must be taken to guide the fusion program towards an economically and environmentally viable goal. While the fusion fuels are essentially free, capital costs of reactors appear to be at least as large as current power plants. Accordingly, the price of electricity will not decline, and capital availability for reactor constructions will be important. Details of reactor cost projections are discussed and mechanisms suggested for fusion power implementation. Also discussed are some environmental and safety aspects of magnetic fusion

  2. Potential and barrier study. Energy efficiency in Norwegian vocational buildings; Potensial- og barrierestudie. Energieffektivisering i norske yrkesbygg

    Energy Technology Data Exchange (ETDEWEB)

    Boehn, Trond Ivar; Palm, Linn Therese; Bakken, Line; Nossum, Aase; Jordell, Hanne

    2012-07-01

    On behalf of Enova SF, Multiconsult AS and Analyse og Strategi AS conducted an analysis to identify potential and barriers related to commercial buildings energy performance. The aim of this study was to determine what is the potential for energy efficiency for Norwegian vocational buildings that distinguishes between theoretical, technical, financial and real potential. Technical potential is the percentage of the theoretical potential that is technically feasible. Economic potential is the proportion of technical potential that is economically profitable to implement. Economic potential varies with the energy price. Build a small part of the total potential in 2020. In the calculation of the real potential is taken into account induced potential in terms of that, each year, a percentage actually implementing energy conservation measures (energy efficiency ratio 2%), a percentage rehabilitating / upgrading existing buildings (rehab rate 1.5%), and that a proportion of new buildings built better than regulatory requirements (rate 10%). In real potential for energy efficiency is the proportion of the economic potential that is not natural triggered but which is limited by various barriers. In real potential also varies with energy price. Respondents in our study is particularly concerned with the economic barriers, and least concerned the technical barriers. Attitudes and knowledge barriers are also very important. Lack of knowledge the effects and benefits of energy efficiency means that negative attitudes persist and that myths about the lack of profitability continues to exist. Many believe this is due to lack the knowledge and can be the cause of other types of barriers such as economic barriers. It has been analyzed which part of the real potential bounded by the barriers, and which type of institutions in society that can reduce these barriers with various categories of instrument. Main barriers for existing buildings practical barriers, economic barriers and

  3. Modified Debye screening potential in a magnetized quantum plasma

    International Nuclear Information System (INIS)

    Salimullah, M.; Hussain, A.; Sara, I.; Murtaza, G.; Shah, H.A.

    2009-01-01

    The effects of quantum mechanical influence and uniform static magnetic field on the Shukla-Nambu-Salimullah potential in an ultracold homogeneous electron-ion Fermi plasma have been examined in detail. It is noticed that the strong quantum effect arising through the Bohm potential and the ion polarization effect can give rise to a new oscillatory behavior of the screening potential beyond the shielding cloud which could explain a new type of possible robust ordered structure formation in the quantum magnetoplasma. However, the magnetic field enhances the Debye length perpendicular to the magnetic field in the weak quantum limit of the quantum plasma.

  4. Fabrication of magnetic tunnel junctions with a single-crystalline LiF tunnel barrier

    Science.gov (United States)

    Krishna Narayananellore, Sai; Doko, Naoki; Matsuo, Norihiro; Saito, Hidekazu; Yuasa, Shinji

    2018-04-01

    We fabricated Fe/LiF/Fe magnetic tunnel junctions (MTJs) by molecular beam epitaxy on a MgO(001) substrate, where LiF is an insulating tunnel barrier with the same crystal structure as MgO (rock-salt type). Crystallographical studies such as transmission electron microscopy and nanobeam electron diffraction observations revealed that the LiF tunnel barrier is single-crystalline and has a LiF(001)[100] ∥ bottom Fe(001)[110] crystal orientation, which is constructed in the same manner as MgO(001) on Fe(001). Also, the in-plane lattice mismatch between the LiF tunnel barrier and the Fe bottom electrode was estimated to be small (about 0.5%). Despite such advantages for the tunnel barrier of the MTJ, the observed tunnel magnetoresistance (MR) ratio was low (˜6% at 20 K) and showed a significant decrease with increasing temperature (˜1% at room temperature). The results imply that indirect tunneling and/or thermally excited carriers in the LiF tunnel barrier, in which the current basically is not spin-polarized, play a major role in electrical transport in the MTJ.

  5. Anisotropic sensor and memory device with a ferromagnetic tunnel barrier as the only magnetic element.

    Science.gov (United States)

    Lόpez-Mir, L; Frontera, C; Aramberri, H; Bouzehouane, K; Cisneros-Fernández, J; Bozzo, B; Balcells, L; Martínez, B

    2018-01-16

    Multiple spin functionalities are probed on Pt/La 2 Co 0.8 Mn 1.2 O 6 /Nb:SrTiO 3 , a device composed by a ferromagnetic insulating barrier sandwiched between non-magnetic electrodes. Uniquely, La 2 Co 0.8 Mn 1.2 O 6 thin films present strong perpendicular magnetic anisotropy of magnetocrystalline origin, property of major interest for spintronics. The junction has an estimated spin-filtering efficiency of 99.7% and tunneling anisotropic magnetoresistance (TAMR) values up to 30% at low temperatures. This remarkable angular dependence of the magnetoresistance is associated with the magnetic anisotropy whose origin lies in the large spin-orbit interaction of Co 2+ which is additionally tuned by the strain of the crystal lattice. Furthermore, we found that the junction can operate as an electrically readable magnetic memory device. The findings of this work demonstrate that a single ferromagnetic insulating barrier with strong magnetocrystalline anisotropy is sufficient for realizing sensor and memory functionalities in a tunneling device based on TAMR.

  6. Tunable magnetic vortex resonance in a potential well

    Science.gov (United States)

    Warnicke, P.; Wohlhüter, P.; Suszka, A. K.; Stevenson, S. E.; Heyderman, L. J.; Raabe, J.

    2017-11-01

    We use frequency-resolved x-ray microscopy to fully characterize the potential well of a magnetic vortex in a soft ferromagnetic permalloy square. The vortex core is excited with magnetic broadband pulses and simultaneously displaced with a static magnetic field. We observe a frequency increase (blueshift) in the gyrotropic mode of the vortex core with increasing bias field. Supported by micromagnetic simulations, we show that this frequency increase is accompanied by internal deformation of the vortex core. The ability to modify the inner structure of the vortex core provides a mechanism to control the dynamics of magnetic vortices.

  7. Resonant tunnel magnetoresistance in double-barrier planar magnetic tunnel junctions

    KAUST Repository

    Useinov, A. N.

    2011-08-24

    We present a theoretical approach to calculate the spin-dependent current and tunnel magnetoresistance (TMR) in a double-barrier magnetic tunnel junction (DMTJ), in which the magnetization of the middle ferromagnetic metal layer can be aligned parallel or antiparallel in relation to the fixed magnetizations of the left and right ferromagnetic electrodes. The electron transport through the DMTJ is considered as a three-dimensional problem, taking into account all transmitting electron trajectories as well as the spin-dependent momentum conservation law. The dependence of the transmission coefficient and spin-polarized currents on the applied voltage is derived as an exact solution to the quantum-mechanical problem for the spin-polarized transport. In the range of the developed physical model, the resonant tunneling, nonresonant tunneling, and enhanced spin filtering can be explained; the simulation results are in good agreement with experimental data.

  8. Resonant tunnel magnetoresistance in double-barrier planar magnetic tunnel junctions

    KAUST Repository

    Useinov, A. N.; Kosel, Jü rgen; Useinov, N. Kh.; Tagirov, L. R.

    2011-01-01

    We present a theoretical approach to calculate the spin-dependent current and tunnel magnetoresistance (TMR) in a double-barrier magnetic tunnel junction (DMTJ), in which the magnetization of the middle ferromagnetic metal layer can be aligned parallel or antiparallel in relation to the fixed magnetizations of the left and right ferromagnetic electrodes. The electron transport through the DMTJ is considered as a three-dimensional problem, taking into account all transmitting electron trajectories as well as the spin-dependent momentum conservation law. The dependence of the transmission coefficient and spin-polarized currents on the applied voltage is derived as an exact solution to the quantum-mechanical problem for the spin-polarized transport. In the range of the developed physical model, the resonant tunneling, nonresonant tunneling, and enhanced spin filtering can be explained; the simulation results are in good agreement with experimental data.

  9. Healthcare Access for Iraqi Refugee Children in Texas: Persistent Barriers, Potential Solutions, and Policy Implications.

    Science.gov (United States)

    Vermette, David; Shetgiri, Rashmi; Al Zuheiri, Haidar; Flores, Glenn

    2015-10-01

    To identify access barriers to healthcare and potential interventions to improve access for Iraqi refugee children. Four focus groups were conducted using consecutive sampling of Iraqi refugee parents residing in the US for 8 months to 5 years. Eight key-informant interviews also were conducted with employees of organizations serving Iraqi refugee families, recruited using snowball sampling. Focus groups and interviews were audiotaped, transcribed, and analyzed using margin coding and grounded theory. Iraqi refugees identified provider availability, Medicaid maintenance and renewal, language issues, and inadequate recognition of post-traumatic stress disorder as barriers to care for their children. Interviewees cited loss of case-management services and difficulties in understanding the Medicaid renewal process as barriers. Potential interventions to improve access include community-oriented efforts to educate parents on Medicaid renewal, obtaining services, and accessing specialists. Given the enduring nature of language and Medicaid renewal barriers, policies addressing eligibility alone are insufficient.

  10. Creation of second order magnetic barrier inside chaos created by NTMs in the ASDEX UG

    Science.gov (United States)

    Ali, Halima; Punjabi, Alkesh

    2012-10-01

    Understanding and stabilization of neoclassical tearing modes (NTM) in tokamaks is an important problem. For low temperature plasmas, tearing modes are believed to be mainly driven by current density gradient. For collisionless plasmas, even when plasma is stable to classical tearing modes, helical reduction in bootstrap current in O-point of an island can destabilize NTMs when an initial island is seeded by other global MHD instabilities or when microturbulence triggers the transition from a linear to nonlinear instability. The onset of NTMs leads to the most serious beta limit in ASDEX UG tokamak [O. Gubner et al 2005 NF 39 1321]. The important NTMs in the ASDDEX UG are (m,n)=(3,2)+(4,3)+(1,1). Realistic parameterization of these NTMs and the safety factor in ASDEX UG are given in [O. Dumbrajs et al 2005 POP 12 1107004]. We use a symplectic map in magnetic coordinates for the ASDEX UG to integrate field lines in presence of the NTMs. We add a second order control term [H. Ali and A. Punjabi 2007 PPCF 49 1565] to this ASDEX UG field line Hamiltonian to create an invariant magnetic surface inside the chaos generated by the NTMs. The relative strength, robustness, and resilience of this barrier are studied to ascertain the most desirable noble barrier in the ASDEX UG with NTMs. We present preliminary results of this work, and discuss its implications with regard to magnetic transport barriers for increasing strength of magnetic perturbations. This work is supported by the grants DE-FG02-01ER54624 and DE-FG02-04ER54793.

  11. Heavy-ion optical potential for sub-barrier fusion deduced from a dispersion relation

    International Nuclear Information System (INIS)

    Kim, B.T.; Kim, H.C.; Park, K.E.

    1988-01-01

    The heavy-ion energy-dependent optical potentials for the 16 O+ 208 Pb system are deduced from a dispersion relation. These potentials are used to analyze the elastic scattering, fusion, and spin distributions of compound nuclei for the system in a unified way based on the direct reaction theory. It turns out that the energy dependence of the optical potential is essential in explaining the data at near- and sub-barrier energies. The real part of the energy-dependent optical potential deduced was also used in calculating the elastic and fusion cross sections by the conventional barrier penetration model using an incoming wave boundary condition. The predictions of the elastic scattering, fusion cross sections, and the spin distributions of compound nuclei are not satisfactory compared with those from the direct reaction approach. It seems to originate from the fact that this model neglects absorption around the Coulomb barrier region

  12. Magnetic resonance imaging of blood brain/nerve barrier dysfunction and leukocyte infiltration: closely related or discordant?

    Directory of Open Access Journals (Sweden)

    Gesa eWeise

    2012-12-01

    Full Text Available Unlike other organs the nervous system is secluded from the rest of the organism by the blood brain (BBB or blood nerve barrier (BNB preventing passive influx of fluids from the circulation. Similarly, leukocyte entry to the nervous system is tightly controlled. Breakdown of these barriers and cellular inflammation are hallmarks of inflammatory as well as ischemic neurological diseases and thus represent potential therapeutic targets. The spatiotemporal relationship between BBB/BNB disruption and leukocyte infiltration has been a matter of debate. We here review contrast-enhanced magnetic resonance imaging (MRI as a non-invasive tool to depict barrier dysfunction and its relation to macrophage infiltration in the central and peripheral nervous system under pathological conditions. Novel experimental contrast agents like Gadofluorine M (Gf allow more sensitive assessment of BBB dysfunction than conventional Gadolinium (Gd-DTPA-enhanced MRI. In addition, Gf facilitates visualization of functional and transient alterations of the BBB remote from lesions. Cellular contrast agents such as superparamagnetic iron oxide particles (SPIO and perfluorocarbons (PFC enable assessment of leukocyte (mainly macrophage infiltration by MR technology. Combined use of these MR contrast agents disclosed that leukocytes can enter the nervous system independent from a disturbance of the BBB, and vice versa, a dysfunctional BBB/BNB by itself is not sufficient to attract inflammatory cells from the circulation. We will illustrate these basic imaging findings in animal models of multiple sclerosis (MS, cerebral ischemia and traumatic nerve injury and review corresponding findings in patients.

  13. Influence of the potential well and the potential barrier on the density distribution of confined-model fluids

    CERN Document Server

    Lee, B H; Lee, C H; Seong Baek Seok

    2000-01-01

    A density functional perturbative approximation, which is based on the density functional expansion of the one-particle direct correlation function of model fluids with respect to the bulk density, has been employed to investigate the influence of the potential well and the potential barrier on the density behavior of confined-model fluids. The mean spherical approximation has been used to calculate the two-particle direct correlation function of the model fluids. At lower densities, the density distributions are strongly affected by the barrier height and the well depth of the model potential, the contribution from the short-range repulsive part being especially important. However, the effects of the barrier height and the well depth of the model potential decrease with increasing bulk density. The calculated results also show that in the region where the effect of the wall-fluid interaction is relatively weak, the square-barrier part of the model potential leads to a nonuniformity in the density distributio...

  14. Transport barriers with and without shear flows in a magnetized plasma

    International Nuclear Information System (INIS)

    Martinell, Julio J.

    2014-01-01

    Different ways of producing a transport barrier in a toroidal magnetized plasma are discussed and the properties of the barriers are analyzed. The first mechanism is associated with the presence of a sheared plasma flow that is present in a limited region of the plasma, which creates a zonal flow. In contrast to the usual paradigm stating that the sheared flow reduces the turbulence correlation length and leads to suppression of the fluctuation driven transport in the region of highest shear, it is shown that from the perspective of chaotic transport of plasma particles in the fluctuation fields, the transport barrier is formed in the region of zero shear and it can be destroyed when the fluctuation level is high enough. It is also shown that finite gyroradius effects modify the dynamics and introduces new conditions for barrier formation. The second mechanism considers a method in which radio-frequency waves injected into the plasma can stabilize the drift waves and therefore the anomalous transport is reduced, creating a barrier. This process does not involve the presence of sheared flows and depends only on the effect of the RF wave field on the drift waves. The stabilizing effect in this case is due to the nonlinear ponderomotive force which acts in a way that offsets the pressure gradient destabilization. Finally, a mechanism based on the ponderomotive force of RF waves is described which produces poloidal plasma rotation around the resonant surface due to the asymmetry of induced transport; it creates a transport barrier by shear flow stabilization of turbulence

  15. ISO 14000: Origin, Structure, and Potential Barriers to Implementation.

    Science.gov (United States)

    Casto; Ellisen; Trnovec; Kross; Ginter

    1996-04-01

    The ISO 14000 is likely to become the international standard for environmental management. At present, it is an evolving series of individual voluntary standards and guideline reference documents that provide business management with the structure for managing environmental impacts. These encompass environmental management systems, environmental audits, eco-labeling, environmental performance evaluations, life-cycle assessment, and environmental aspects in product standards. The authors present the rationale for the ISO 14000 and the steps in its evolution so far, as well as its present provisions and their implications and its position with regard to regulatory agencies. Particular attention is paid to the consequences of voluntary disclosure and correction of violations. Hanley & Belfus, Inc. Int J Occup Environ Health 1077-3525 2 2 1996 April/June Perspectives on Rural Environmental Health in Central Europe 125 134 EN Tomas Trnovec Burton C. Kross CIREH-Room 352, International Center, University of Iowa, Iowa City, IA 52242, USA. Emil Ginter Life expectancy is about five to seven years less in Central European countries than in comparable countries in Western Europe. Environmental and occupational health risk factors, along with the socioeconomic and political conditions that have prevailed in this region for the past 40 years, are suspected contributing factors to this condition. The initial impression among observers was that environmental pollution by industry was the primary source of contamination leading to human health effects. Current thinking by the authors recognizes that combinations of personal habits, local environmental emissions (home heating), and occupational risk factors are more likely to be influencing the health of this region, particularly in rural areas. A predictive model for standard mortality rates determined that only three potential risk factors were statistically significant: consumption of alcoholic beverages, consumption of citrus

  16. Electronic tunneling through a potential barrier on the surface of a topological insulator

    Science.gov (United States)

    Zhou, Benliang; Zhou, Benhu; Zhou, Guanghui

    2016-12-01

    We investigate the tunneling transport for electrons on the surface of a topological insulator (TI) through an electrostatic potential barrier. By using the Dirac equation with the continuity conditions for all segments of wave functions at the interfaces between regions inside and outside the barrier, we calculate analytically the transmission probability and conductance for the system. It is demonstrated that, the Klein paradox can also been observed in the system same as in graphene system. Interestingly, the conductance reaches the minimum value when the incident electron energy is equal to the barrier strength. Moreover, with increasing barrier width, the conductance turns up some tunneling oscillation peaks, and larger barrier strength can cause lower conductance, shorter period but larger oscillation amplitude. The oscillation amplitude decreases as the barrier width increases, which is similar as that of the system consisting of the compressive uniaxial strain applied on a TI, but somewhat different from that of graphene system where the oscillation amplitude is a constant. The findings here imply that an electrostatic barrier can greatly influence the electron tunneling transport of the system, and may provide a new way to realize directional filtering of electrons.

  17. Superluminal tunneling of a relativistic half-integer spin particle through a potential barrier

    Directory of Open Access Journals (Sweden)

    Nanni Luca

    2017-11-01

    Full Text Available This paper investigates the problem of a relativistic Dirac half-integer spin free particle tunneling through a rectangular quantum-mechanical barrier. If the energy difference between the barrier and the particle is positive, and the barrier width is large enough, there is proof that the tunneling may be superluminal. For first spinor components of particle and antiparticle states, the tunneling is always superluminal regardless the barrier width. Conversely, the second spinor components of particle and antiparticle states may be either subluminal or superluminal depending on the barrier width. These results derive from studying the tunneling time in terms of phase time. For the first spinor components of particle and antiparticle states, it is always negative while for the second spinor components of particle and antiparticle states, it is always positive, whatever the height and width of the barrier. In total, the tunneling time always remains positive for particle states while it becomes negative for antiparticle ones. Furthermore, the phase time tends to zero, increasing the potential barrier both for particle and antiparticle states. This agrees with the interpretation of quantum tunneling that the Heisenberg uncertainty principle provides. This study’s results are innovative with respect to those available in the literature. Moreover, they show that the superluminal behaviour of particles occurs in those processes with high-energy confinement.

  18. Surface Treatment of Polypropylene Films Using Dielectric Barrier Discharge with Magnetic Field

    International Nuclear Information System (INIS)

    Wang Changquan; Zhang Guixin; Wang Xinxin; Chen Zhiyu

    2012-01-01

    Atmospheric pressure non-thermal plasma is of interest for industrial applications. In this study, polypropylene (PP) films are modified by a dielectric barrier discharge (DBD) with a non-uniform magnetic field in air at atmospheric pressure. The surface properties of the PP films before and after a DBD treatment are studied by using contact angle measurement, atomic force microscopy (AFM) and X-ray photoelectron spectroscopy (XPS). The effect of treatment time on the surface modification with and without a magnetic field is investigated. It is found that the hydrophilic improvement depends on the treatment time and magnetic field. It is also found that surface roughness and oxygen-containing groups are introduced onto the PP film surface after the DBD treatment. Surface roughness and oxygen-containing polar functional groups of the PP films increase with the magnetic induction density. The functional groups are identified as C-O, C=O and O-C=O by using XPS analysis. It is concluded that the hydrophilic improvement of PP films treated with a magnetic field is due to a greater surface roughness and more oxygen-containing groups. (plasma technology)

  19. Core density fluctuations in reverse magnetic shear plasmas with internal transport barrier on JT-60U

    International Nuclear Information System (INIS)

    Nazikian, R.; Shinohara, K.; Yoshino, R.; Fujita, T.; Shirai, H.; Kramer, G.T.

    1999-01-01

    First measurements of the radial correlation length of density fluctuations in JT-60U plasmas with internal transport barrier (ITB) is reported. The measurements are obtained using a newly installed correlation reflectometer operating in the upper X-mode. Before transport barrier formation in the low beam power current ramp-up phase of the discharge, reflectometer measurements indicate density fluctuation levels n-tilde/n∼0.1-0.2% and radial correlation lengths 2-3 cm (k r p i ≤0.5) in the central plasma region (r/a r p i ∼3. However, fluctuation levels are considerably higher than measured near the magnetic axis. Reflectometer measurements obtained at the foot of the ITB also indicate high fluctuation levels compared to measurements in the central region of the discharge. (author)

  20. Potential and barrier study. Energy efficiency of Norwegian homes; Potensial- og barrierestudie. Energieffektivisering av norske boliger

    Energy Technology Data Exchange (ETDEWEB)

    Mjoenes, Christian; Pettersen, Folke Vogn Haug; Kristoffersen, Bjoerge Sandberg; Birkeland, Bjoern Mangor; Essen, Jan von; Haarberg; Karl Johan

    2012-01-15

    On behalf of Enova SF, Prognosesenteret AS and Entelligens AS carried out a potential and barrier study of energy efficiency of the Norwegian housing stock. The study made use of newer and known studies of the Norwegian housing stock, known and documented barriers to energy efficiency, and new and extensive studies of several topics which have only been partially or never explored before. Through unique analysis and a case-based approach, it revealed a real energy efficiency potential in Norwegian homes with known technology and revealed representativeness, relevance, strength and extent of the barriers that prevent that one can realize most of the technical energy efficiency potential in the Norwegian housing stock. (eb)

  1. Magnetic resonance imaging-guided focused ultrasound to increase localized blood-spinal cord barrier permeability.

    Science.gov (United States)

    Payne, Allison H; Hawryluk, Gregory W; Anzai, Yoshimi; Odéen, Henrik; Ostlie, Megan A; Reichert, Ethan C; Stump, Amanda J; Minoshima, Satoshi; Cross, Donna J

    2017-12-01

    Spinal cord injury (SCI) affects thousands of people every year in the USA, and most patients are left with some permanent paralysis. Therapeutic options are limited and only modestly affect outcome. To address this issue, we used magnetic resonance imaging-guided focused ultrasound (MRgFUS) as a non-invasive approach to increase permeability in the blood-spinal cord barrier (BSCB). We hypothesize that localized, controlled sonoporation of the BSCB by MRgFUS will aid delivery of therapeutics to the injury. Here, we report our preliminary findings for the ability of MRgFUS to increase BSCB permeability in the thoracic spinal cord of a normal rat model. First, an excised portion of normal rat spinal column was used to characterize the acoustic field and to estimate the insertion losses that could be expected in an MRgFUS blood spinal cord barrier opening. Then, in normal rats, MRgFUS was applied in combination with intravenously administered microbubbles to the spinal cord region. Permeability of the BSCB was indicated as signal enhancement by contrast administered prior to T1-weighted magnetic resonance imaging and verified by Evans blue dye. Neurological testing using the Basso, Beattie, and Breshnahan scale and the ladder walk was normal in 8 of 10 rats tested. Two rats showed minor impairment indicating need for further refinement of parameters. No gross tissue damage was evident by histology. In this study, we have opened successfully the blood spinal cord barrier in the thoracic region of the normal rat spine using magnetic resonance-guided focused ultrasound combined with microbubbles.

  2. A regularization method for extrapolation of solar potential magnetic fields

    Science.gov (United States)

    Gary, G. A.; Musielak, Z. E.

    1992-01-01

    The mathematical basis of a Tikhonov regularization method for extrapolating the chromospheric-coronal magnetic field using photospheric vector magnetograms is discussed. The basic techniques show that the Cauchy initial value problem can be formulated for potential magnetic fields. The potential field analysis considers a set of linear, elliptic partial differential equations. It is found that, by introducing an appropriate smoothing of the initial data of the Cauchy potential problem, an approximate Fourier integral solution is found, and an upper bound to the error in the solution is derived. This specific regularization technique, which is a function of magnetograph measurement sensitivities, provides a method to extrapolate the potential magnetic field above an active region into the chromosphere and low corona.

  3. Magnetic moments of octet baryons in a chiral potential model

    Energy Technology Data Exchange (ETDEWEB)

    Barik, N; Das, M

    1986-12-01

    Incorporating the lowest-order pionic correction, the magnetic moments of the nucleon octet have been calculated in a chiral potential model. The potential, representing phenomenologically the nonperturbative gluon self-couplings, is chosen with equally mixed scalar and vector parts in a power-law form. The results are in reasonable agreement with experiment. 32 refs., 2 tables.

  4. Magnetic moments of octet baryons in a chiral potential model

    International Nuclear Information System (INIS)

    Barik, N.

    1986-01-01

    Incorporating the lowest-order pionic correction, the magnetic moments of the nucleon octet have been calculated in a chiral potential model. The potential, representing phenomenologically the nonperturbative gluon self-couplings, is chosen with equally mixed scalar and vector parts in a power-law form. The results are in reasonable agreement with experiment. (author)

  5. Reflection at a complex potential barrier in the semiclassical theory of scattering

    International Nuclear Information System (INIS)

    Avishai, Y.; Knoll, J.

    1976-01-01

    The reflection of spherical waves at a complex potential barrier is discussed in the semiclassical approximation. We study the complex WKB method and the Uniform Approximation in the special case of weakly absorptive barriers, typical of surface transparent optical potentials used in heavy-ion reactions. It is found that the complex WKB results lead to a very accurate cross-section despite their inaccuracy in the most important phase shifts. Thereby, the amazing stamina of the WKB has been confirmed once more. (orig.) [de

  6. Electric control of wave vector filtering in a hybrid magnetic-electric-barrier nanostructure

    Science.gov (United States)

    Kong, Yong-Hong; Lu, Ke-Yu; He, Ya-Ping; Liu, Xu-Hui; Fu, Xi; Li, Ai-Hua

    2018-06-01

    We theoretically investigate how to manipulate the wave vector filtering effect by a traverse electric field for electrons across a hybrid magnetic-electric-barrier nanostructure, which can be experimentally realized by depositing a ferromagnetic stripe and a Schottky-metal stripe on top and bottom of a GaAs/Al x Ga1- x As heterostructure, respectively. The wave vector filtering effect is found to be related closely to the applied electric field. Moreover, the wave vector filtering efficiency can be manipulated by changing direction or adjusting strength of the traverse electric field. Therefore, such a nanostructure can be employed as an electrically controllable electron-momentum filter for nanoelectronics applications.

  7. Toroidal equilibrium states with reversed magnetic shear and parallel flow in connection with the formation of Internal Transport Barriers

    Science.gov (United States)

    Kuiroukidis, Ap.; Throumoulopoulos, G. N.

    2015-08-01

    We construct nonlinear toroidal equilibria of fixed diverted boundary shaping with reversed magnetic shear and flows parallel to the magnetic field. The equilibria have hole-like current density and the reversed magnetic shear increases as the equilibrium nonlinearity becomes stronger. Also, application of a sufficient condition for linear stability implies that the stability is improved as the equilibrium nonlinearity correlated to the reversed magnetic shear gets stronger with a weaker stabilizing contribution from the flow. These results indicate synergetic stabilizing effects of reversed magnetic shear, equilibrium nonlinearity and flow in the establishment of Internal Transport Barriers (ITBs).

  8. Magnetic nanoparticles as potential candidates for biomedical and biological applications.

    Science.gov (United States)

    Zeinali Sehrig, Fatemeh; Majidi, Sima; Nikzamir, Nasrin; Nikzamir, Nasim; Nikzamir, Mohammad; Akbarzadeh, Abolfazl

    2016-05-01

    Magnetic iron oxide nanoparticles have become the main candidates for biomedical and biological applications, and the application of small iron oxide nanoparticles in in vitro diagnostics has been practiced for about half a century. Magnetic nanoparticles (MNPs), in combination with an external magnetic field and/or magnetizable grafts, allow the delivery of particles to the chosen target area, fix them at the local site while the medication is released, and act locally. In this review, we focus mostly on the potential use of MNPs for biomedical and biotechnological applications, and the improvements made in using these nanoparticles (NPs) in biological applications.

  9. Magnetic materials in Japan research, applications and potential

    CERN Document Server

    2013-01-01

    Please note this is a Short Discount publication. This, the third report in Elsevier's Materials Technology in Japan series, concentrates on magnetic materials as a topic gaining worldwide attention, and each chapter looks not only at current research, but also describes the technology as it is being applied and its future potential. Magnetic-related research is the second largest field of research in Japan after semiconductors, with the estimated number of researchers and engineers engaged in magnetics-related activities currently at 20,000. This research report serves as both a review of

  10. Internal transport barrier triggering by rational magnetic flux surfaces in tokamaks

    International Nuclear Information System (INIS)

    Joffrin, E.; Challis, C.D.; Conway, G.D.

    2003-01-01

    The formation of Internal Transport Barriers (ITBs) has been experimentally associated with the presence of rational q-surfaces in both JET and ASDEX Upgrade. The triggering mechanisms are related to the occurrence of magneto-hydrodynamic (MHD) instabilities such as mode coupling or fishbone activity. These events could locally modify the poloidal velocity and increase transiently the shearing rate to values comparable to the linear growth rate of ITG modes. For JET reversed magnetic shear scenarios, ITB emergence occurs preferentially when the minimum q reaches an integer value. In this case, transport effects localised in the vicinity of zero magnetic shear and close to rational q values may also contribute to the formation of ITBs.The role of rational q surfaces on ITB triggering stresses the importance of q profile control for advanced tokamak scenario and could contribute to lower substantially the access power to these scenarios in next step facilities. (author)

  11. Internal transport barrier triggering by rational magnetic flux surfaces in tokamaks

    International Nuclear Information System (INIS)

    Joffrin, E.; Challis, C.D.; Conway, G.D.

    2003-01-01

    The formation of internal transport barriers (ITBs) has been experimentally associated with the presence of rational q surfaces in both JET and ASDEX Upgrade. The triggering mechanisms are related to the occurrence of magneto-hydrodynamic (MHD) instabilities such as mode coupling and fishbone activity. These events could locally modify the poloidal velocity and increase transiently the shearing rate to values comparable with the linear growth rate of ion temperature gradient modes. For JET reversed magnetic shear scenarios, ITB emergence occurs preferentially when the minimum q reaches an integral value. In this case, transport effects localized in the vicinity of zero magnetic shear and close to rational q values may be at the origin of ITB formation. The role of rational q surfaces in ITB triggering stresses the importance of q profile control for an advanced tokamak scenario and could assist in substantially lowering the access power to these scenarios in next step facilities. (author)

  12. Internal Transport Barrier triggering by rational magnetic flux surfaces in tokamaks

    International Nuclear Information System (INIS)

    Joffrin, E.H.

    2002-01-01

    The formation of Internal Transport Barriers (ITBs) has been experimentally associated with the presence of rational q-surfaces in both JET and ASDEX Upgrade. The triggering mechanisms are related to the occurrence of magneto-hydrodynamic (MHD) instabilities such as mode coupling or fishbone activity. These events could locally modify the poloidal velocity and increase transiently the shearing rate to values comparable to the linear growth rate of ITG modes. For reversed magnetic shear scenario, ITB emergence occurs preferentially when the minimum q reaches an integer value. In this case, transport effects localised in the vicinity of zero magnetic shear and close to rational q values may also contribute to the formation of ITBs. The role of rational q surfaces on ITB triggering stresses the importance of q profile control for advanced tokamak scenario and could contribute to lower substantially the access power to these scenarios in next step facilities. (author)

  13. Electrically tunable tunneling rectification magnetoresistance in magnetic tunneling junctions with asymmetric barriers.

    Science.gov (United States)

    Wang, Jing; Huang, Qikun; Shi, Peng; Zhang, Kun; Tian, Yufeng; Yan, Shishen; Chen, Yanxue; Liu, Guolei; Kang, Shishou; Mei, Liangmo

    2017-10-26

    The development of multifunctional spintronic devices requires simultaneous control of multiple degrees of freedom of electrons, such as charge, spin and orbit, and especially a new physical functionality can be realized by combining two or more different physical mechanisms in one specific device. Here, we report the realization of novel tunneling rectification magnetoresistance (TRMR), where the charge-related rectification and spin-dependent tunneling magnetoresistance are integrated in Co/CoO-ZnO/Co magnetic tunneling junctions with asymmetric tunneling barriers. Moreover, by simultaneously applying direct current and alternating current to the devices, the TRMR has been remarkably tuned in the range from -300% to 2200% at low temperature. This proof-of-concept investigation provides an unexplored avenue towards electrical and magnetic control of charge and spin, which may apply to other heterojunctions to give rise to more fascinating emergent functionalities for future spintronics applications.

  14. Electron cooling and finite potential drop in a magnetized plasma expansion

    Energy Technology Data Exchange (ETDEWEB)

    Martinez-Sanchez, M. [Department of Aeronautics and Astronautics, Massachusetts Institute of Technology, 77 Massachusetts Avenue, Cambridge, Massachusetts 02139 (United States); Navarro-Cavallé, J. [Escuela Técnica Superior de Ingeniería Aeronáutica y del Espacio, Universidad Politécnica de Madrid, Plaza Cardenal Cisneros 3, Madrid 28040 (Spain); Ahedo, E. [Departamento de Bioingeniería e Ingeniería Aeroespacial, Universidad Carlos III de Madrid, Avda. Universidad 30, Leganés 28911, Madrid (Spain)

    2015-05-15

    The steady, collisionless, slender flow of a magnetized plasma into a surrounding vacuum is considered. The ion component is modeled as mono-energetic, while electrons are assumed Maxwellian upstream. The magnetic field has a convergent-divergent geometry, and attention is restricted to its paraxial region, so that 2D and drift effects are ignored. By using the conservation of energy and magnetic moment of particles and the quasi-neutrality condition, the ambipolar electric field and the distribution functions of both species are calculated self-consistently, paying attention to the existence of effective potential barriers associated to magnetic mirroring. The solution is used to find the total potential drop for a set of upstream conditions, plus the axial evolution of various moments of interest (density, temperatures, and heat fluxes). The results illuminate the behavior of magnetic nozzles, plasma jets, and other configurations of interest, showing, in particular, in the divergent plasma the collisionless cooling of electrons, and the generation of collisionless electron heat fluxes.

  15. Tunneling effect on double potential barriers GaAs and PbS

    Science.gov (United States)

    Prastowo, S. H. B.; Supriadi, B.; Ridlo, Z. R.; Prihandono, T.

    2018-04-01

    A simple model of transport phenomenon tunnelling effect through double barrier structure was developed. In this research we concentrate on the variation of electron energy which entering double potential barriers to transmission coefficient. The barriers using semiconductor materials GaAs (Galium Arsenide) with band-gap energy 1.424 eV, distance of lattice 0.565 nm, and PbS (Lead Sulphide) with band gap energy 0.41 eV distance of lattice is 18 nm. The Analysisof tunnelling effect on double potentials GaAs and PbS using Schrodinger’s equation, continuity, and matrix propagation to get transmission coefficient. The maximum energy of electron that we use is 1.0 eV, and observable from 0.0025 eV- 1.0 eV. The shows the highest transmission coefficient is0.9982 from electron energy 0.5123eV means electron can pass the barriers with probability 99.82%. Semiconductor from materials GaAs and PbS is one of selected material to design semiconductor device because of transmission coefficient directly proportional to bias the voltage of semiconductor device. Application of the theoretical analysis of resonant tunnelling effect on double barriers was used to design and develop new structure and combination of materials for semiconductor device (diode, transistor, and integrated circuit).

  16. Discontinuity model for internal transport barrier formation in reversed magnetic shear plasmas

    International Nuclear Information System (INIS)

    Kishimoto, Y.; Dettrick, S.A.; Li, J.Q.; Shirai, S.; Kim, J.Y.; Horton, W.; Tajima, T.; LeBrun, M.J.

    2000-01-01

    It is becoming clear that tokamak anomalous transport is dominated by radially extended non-local modes which originate from strong toroidal coupling of rational surfaces in non-uniform plasmas. To aid in understanding the internal transport barrier (ITB) formed in reversed magnetic shear experiments, in addition to the well known shear flow effect, the article points out an important non-local effect and/or finite size effect which comes from the complex behaviour of the mode over a finite radial region around the minimum q (safety factor) surface. The non-local mode, which is characterized by its radial extent and the degree of tilting in the poloidal direction (Δr, θ 0 ), changes its structure depending on the sign of the magnetic shear, and as a result such modes are weakly excited across the q min surface. This leads to a discontinuity or gap which disconnects the phase relation in the global wave structure across the q min surface. Once such a discontinuity (or gap) is formed, transport suppression occurs and therefore a transport barrier can be expected near the q min surface. The existence of this discontinuity is confirmed through use of a toroidal particle simulation. It is also shown that whether such a discontinuity is efficiently established depends on the presence of the radial electric field and the related plasma shear flow. (author)

  17. Potential and barrier study. Energy efficiency of Norwegian homes; Potensial- og barrierestudie. Energieffektivisering av norske boliger

    Energy Technology Data Exchange (ETDEWEB)

    NONE

    2012-07-01

    Enova has identified potentials and barriers for energy efficiency in Norwegian buildings. This report summarizes the results of this work. Efficient energy in buildings is important to ensure that future economic activity and growth can occur in a way that reduces the possibilities for an environmentally and economically sound development. (eb)

  18. Exact analytical modeling of magnetic vector potential in surface inset permanent magnet DC machines considering magnet segmentation

    Science.gov (United States)

    Jabbari, Ali

    2018-01-01

    Surface inset permanent magnet DC machine can be used as an alternative in automation systems due to their high efficiency and robustness. Magnet segmentation is a common technique in order to mitigate pulsating torque components in permanent magnet machines. An accurate computation of air-gap magnetic field distribution is necessary in order to calculate machine performance. An exact analytical method for magnetic vector potential calculation in surface inset permanent magnet machines considering magnet segmentation has been proposed in this paper. The analytical method is based on the resolution of Laplace and Poisson equations as well as Maxwell equation in polar coordinate by using sub-domain method. One of the main contributions of the paper is to derive an expression for the magnetic vector potential in the segmented PM region by using hyperbolic functions. The developed method is applied on the performance computation of two prototype surface inset magnet segmented motors with open circuit and on load conditions. The results of these models are validated through FEM method.

  19. Energy shift and conduction-to-valence band transition mediated by a time-dependent potential barrier in graphene

    Science.gov (United States)

    Chaves, Andrey; da Costa, D. R.; de Sousa, G. O.; Pereira, J. M.; Farias, G. A.

    2015-09-01

    We investigate the scattering of a wave packet describing low-energy electrons in graphene by a time-dependent finite-step potential barrier. Our results demonstrate that, after Klein tunneling through the barrier, the electron acquires an extra energy which depends on the rate of change of the barrier height with time. If this rate is negative, the electron loses energy and ends up as a valence band state after leaving the barrier, which effectively behaves as a positively charged quasiparticle.

  20. Effect of a two-dimensional potential on the rate of thermally induced escape over the potential barrier

    International Nuclear Information System (INIS)

    Han, S.; Lapointe, J.; Lukens, J.E.

    1992-01-01

    The thermally induced escape rate of a particle trapped in a two-dimensional (2D) potential well has been investigated through experiment and numerical simulations. The measurements were performed on a special type of superconducting quantum interference device (SQUID) which has 2 degrees of freedom. The energies associated with the motion perpendicular to (transverse) and along (longitudinal) the escape direction are quite different: the ratio between the transverse and longitudinal small oscillation frequencies is ω t /ω l ∼7. The SQUID's parameters, which were used to determine the potential shape and energy scales were all independently determined. All data were obtained under conditions for which the 2D thermal activation (TA) model is expected to be valid. The results were found in good agreement with the theoretical prediction. The measured thermal activation energy is found to be the same as the barrier height calculated from the independently determined potential parameters. No evidence of apparent potential barrier enhancement recently reported in a similar system was found. In addition, the results of our numerical simulations suggest that the region in which the 2D thermal activation model is applicable may be extended to barriers as low as ΔU∼k BT

  1. Quantum tunneling through a very narrow triangular potential barrier exact and WKB solution

    International Nuclear Information System (INIS)

    Ballo, P.; Harmatha, L.

    2011-01-01

    We have investigated the quantum-mechanical transmission of an electron in narrow potential barrier. It has been shown that application of WKB approximation could give enormous error if the slope of potential is rapid. Edification of this work is that unreasonable application of numerical approximations without the deep knowledge of theory should give wrong result. This we should remember every second, every day. (authors)

  2. Energy consumption and CO2 emissions of industrial process technologies. Saving potentials, barriers and instruments

    International Nuclear Information System (INIS)

    Fleiter, Tobias; Schlomann, Barbara; Eichhammer, Wolfgang

    2013-01-01

    Which contribution can the increase of energy efficiency achieve in the industry energy for the energy transition in Germany? To answer this question a model-based analysis of existing energy efficiency potentials of the energy-intensive industries is performed, which account for about 70% of the total energy demand of the industry. Based on this industry for each sector are instruments proposed for the implementation of the calculated potential and to overcome the existing barriers. [de

  3. Suppressing electron turbulence and triggering internal transport barriers with reversed magnetic shear in the National Spherical Torus Experiment

    Energy Technology Data Exchange (ETDEWEB)

    Peterson, J. L. [Lawrence Livermore National Laboratory, Livermore, California 94550 (United States); Bell, R.; Guttenfelder, W.; Hammett, G. W.; Kaye, S. M.; LeBlanc, B.; Mikkelsen, D. R. [Princeton Plasma Physics Laboratory, Princeton University, Princeton, New Jersey 08543 (United States); Candy, J. [General Atomics, San Diego, California 92186 (United States); Smith, D. R. [Department of Engineering Physics, University of Wisconsin-Madison, Madison, Wisconsin 53706 (United States); Yuh, H. Y. [Nova Photonics Inc., Princeton, New Jersey 08540 (United States)

    2012-05-15

    The National Spherical Torus Experiment (NSTX) [M. Ono et al., Nucl. Fusion 40, 557 (2000)] can achieve high electron plasma confinement regimes that are super-critically unstable to the electron temperature gradient driven (ETG) instability. These plasmas, dubbed electron internal transport barriers (e-ITBs), occur when the magnetic shear becomes strongly negative. Using the gyrokinetic code GYRO [J. Candy and R. E. Waltz, J. Comput. Phys. 186, 545 (2003)], the first nonlinear ETG simulations of NSTX e-ITB plasmas reinforce this observation. Local simulations identify a strongly upshifted nonlinear critical gradient for thermal transport that depends on magnetic shear. Global simulations show e-ITB formation can occur when the magnetic shear becomes strongly negative. While the ETG-driven thermal flux at the outer edge of the barrier is large enough to be experimentally relevant, the turbulence cannot propagate past the barrier into the plasma interior.

  4. Equivalent magnetic vector potential model for low-frequency magnetic exposure assessment

    Science.gov (United States)

    Diao, Y. L.; Sun, W. N.; He, Y. Q.; Leung, S. W.; Siu, Y. M.

    2017-10-01

    In this paper, a novel source model based on a magnetic vector potential for the assessment of induced electric field strength in a human body exposed to the low-frequency (LF) magnetic field of an electrical appliance is presented. The construction of the vector potential model requires only a single-component magnetic field to be measured close to the appliance under test, hence relieving considerable practical measurement effort—the radial basis functions (RBFs) are adopted for the interpolation of discrete measurements; the magnetic vector potential model can then be directly constructed by summing a set of simple algebraic functions of RBF parameters. The vector potentials are then incorporated into numerical calculations as the equivalent source for evaluations of the induced electric field in the human body model. The accuracy and effectiveness of the proposed model are demonstrated by comparing the induced electric field in a human model to that of the full-wave simulation. This study presents a simple and effective approach for modelling the LF magnetic source. The result of this study could simplify the compliance test procedure for assessing an electrical appliance regarding LF magnetic exposure.

  5. Potential of the test particle in the magnetic field. I

    International Nuclear Information System (INIS)

    Sestak, B.

    1980-01-01

    The problem of the test particle potential in an external homogeneous magnetic field is solved in an unmagnetized plasma. It is shown that for the case when the parallel velocity component of the test particle is greater than the thermal velocity of the background particles, the potential is of a Coulomb character while for the case where the parallel velocity component is less than the thermal velocity the potential is of a Debye character. The Larmor radius of the test particle appears as an additional parameter in these potentials. (author)

  6. Reliability enhancement due to in-situ post-oxidation of sputtered MgO barrier in double MgO barrier magnetic tunnel junction

    Directory of Open Access Journals (Sweden)

    Chikako Yoshida

    2017-06-01

    Full Text Available We have investigated the effects of in-situ post-oxidation (PO of a sputtered MgO barrier in a double-MgO-barrier magnetic tunnel junction (MTJ and found that the short error rate was significantly reduced, the magnetoresistance (MR ratio was increased approximately 18%, and the endurance lifetime was extend. In addition, we found that the distribution of breakdown number (a measure of endurance exhibits trimodal characteristics, which indicates competition between extrinsic and intrinsic failures. This improvement in reliability might be related to the suppression of Fe and Co diffusion to the MgO barrier, as revealed by electron energy-loss spectroscopy (EELS analysis.

  7. Investigation of the potential barrier lowering for quasi-ballistic transport in short channel MOSFETs

    International Nuclear Information System (INIS)

    Lee, Jaehong; Kwon, Yongmin; Ji, Junghwan; Shin, Hyungcheol

    2011-01-01

    In this paper, the quasi-ballistic carrier transport in short channel MOSFETs is investigated from the point of potential barrier lowering. To investigate the ballistic characteristic of transistors, we extracted the channel backscattering coefficient and the ballistic ratio from experimental data obtained by RF C-V and DC I-V measurements. Two factors that modulate the potential barrier height, besides the gate bias, are considered in this work: the drain bias (V DS ) and the channel doping concentration (N A ). We extract the critical length by calculating the potential drop in the channel region and conclude that the drain bias and the channel doping concentration affect the quasi-ballistic carrier transport.

  8. Spin-related tunneling through a nanostructured electric-magnetic barrier on the surface of a topological insulator.

    Science.gov (United States)

    Wu, Zhenhua; Li, Jun

    2012-01-27

    We investigate quantum tunneling through a single electric and/or magnetic barrier on the surface of a three-dimensional topological insulator. We found that (1) the propagating behavior of electrons in such system exhibits a strong dependence on the direction of the incident electron wavevector and incident energy, giving the possibility to construct a wave vector and/or energy filter; (2) the spin orientation can be tuned by changing the magnetic barrier structure as well as the incident angles and energies.PACS numbers: 72.25.Dc; 73.20.-r; 73.23.-b; 75.70.-i.

  9. Degradation of magnetic tunnel junctions with thin AlOx barrier

    Directory of Open Access Journals (Sweden)

    Tadashi Mihara, Yoshinari Kamakura, Masato Morifuji and Kenji Taniguchi

    2007-01-01

    Full Text Available The degradation of magnetic tunnel junctions (MTJs with AlOx barrier was experimentally investigated. Constant voltage stress (CVS measurement was carried out to monitor the time evolution of the conductance and tunneling magnetoresistance (TMR of MTJs. The gradual increase of the stress-induced leakage current (SILC was observed prior to the breakdown, following a power law function of stress time with an exponent of about 0.2–0.4, which is similar to the case of the ultrathin gate oxide films in MOSFETs. The measured TMR for SILC suggests that the spin-dependent current component would be involved in the early stage of degradation, while spin-independent conduction becomes dominant before the breakdown resulting in a decrease of TMR.

  10. Understanding electron magnetic circular dichroism in a transition potential approach

    Science.gov (United States)

    Barthel, J.; Mayer, J.; Rusz, J.; Ho, P.-L.; Zhong, X. Y.; Lentzen, M.; Dunin-Borkowski, R. E.; Urban, K. W.; Brown, H. G.; Findlay, S. D.; Allen, L. J.

    2018-04-01

    This paper introduces an approach based on transition potentials for inelastic scattering to understand the underlying physics of electron magnetic circular dichroism (EMCD). The transition potentials are sufficiently localized to permit atomic-scale EMCD. Two-beam and three-beam systematic row cases are discussed in detail in terms of transition potentials for conventional transmission electron microscopy, and the basic symmetries which arise in the three-beam case are confirmed experimentally. Atomic-scale EMCD in scanning transmission electron microscopy (STEM), using both a standard STEM probe and vortex beams, is discussed.

  11. Reversible rectification of vortex motion in magnetic and non-magnetic asymmetric pinning potentials

    International Nuclear Information System (INIS)

    Gonzalez, E.M.; Gonzalez, M.P.; Nunez, N.O.; Villegas, J.E.; Anguita, J.V.; Jaafa, M.; Asenjo, A.; Vicent, J.L.

    2006-01-01

    Nb films have been grown on arrays of asymmetric pinning centers. The lattice vortex dynamics could be modified, almost at will, by periodic pinning potentials. In the case of asymmetric pinning potentials a vortex ratchet effect occurs: the vortex lattice motion is rectified. That is, an injected ac current yields an output dc voltage, which polarity could be tuned. The output signal polarity could be switched with the applied magnetic field and the ac current strength. Ratchet effect occurs when asymmetric potentials induce outward particles flow under external fluctuations in the lack of driven direct outward forces. The output signal is similar using magnetic or non-magnetic submicrometric array of pinning centers. This device works as an adiabatic rocking ratchet. This superconducting ratchet could be a model to study biological motors

  12. Investigating the Potential Barrier Function of Nanostructured Materials Formed in Engineered Barrier Systems (EBS) Designed for Nuclear Waste Isolation.

    Science.gov (United States)

    Cuevas, Jaime; Ruiz, Ana Isabel; Fernández, Raúl

    2018-02-21

    Clay and cement are known nano-colloids originating from natural processes or traditional materials technology. Currently, they are used together as part of the engineered barrier system (EBS) to isolate high-level nuclear waste (HLW) metallic containers in deep geological repositories (DGR). The EBS should prevent radionuclide (RN) migration into the biosphere until the canisters fail, which is not expected for approximately 10 3  years. The interactions of cementitious materials with bentonite swelling clay have been the scope of our research team at the Autonomous University of Madrid (UAM) with participation in several European Union (EU) projects from 1998 up to now. Here, we describe the mineral and chemical nature and microstructure of the alteration rim generated by the contact between concrete and bentonite. Its ability to buffer the surrounding chemical environment may have potential for further protection against RN migration. © 2018 The Chemical Society of Japan & Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim.

  13. Exponential dependence of potential barrier height on biased voltages of inorganic/organic static induction transistor

    International Nuclear Information System (INIS)

    Zhang Yong; Yang Jianhong; Cai Xueyuan; Wang Zaixing

    2010-01-01

    The exponential dependence of the potential barrier height φ c on the biased voltages of the inorganic/organic static induction transistor (SIT/OSIT) through a normalized approach in the low-current regime is presented. It shows a more accurate description than the linear expression of the potential barrier height. Through the verification of the numerical calculated and experimental results, the exponential dependence of φ c on the applied biases can be used to derive the I-V characteristics. For both SIT and OSIT, the calculated results, using the presented relationship, are agreeable with the experimental results. Compared to the previous linear relationship, the exponential description of φ c can contribute effectively to reduce the error between the theoretical and experimental results of the I-V characteristics. (semiconductor devices)

  14. Quantum damped oscillator II: Bateman's Hamiltonian vs. 2D parabolic potential barrier

    International Nuclear Information System (INIS)

    Chruscinski, Dariusz

    2006-01-01

    We show that quantum Bateman's system which arises in the quantization of a damped harmonic oscillator is equivalent to a quantum problem with 2D parabolic potential barrier known also as 2D inverted isotropic oscillator. It turns out that this system displays the family of complex eigenvalues corresponding to the poles of analytical continuation of the resolvent operator to the complex energy plane. It is shown that this representation is more suitable than the hyperbolic one used recently by Blasone and Jizba

  15. Filament shape versus coronal potential magnetic field structure

    Science.gov (United States)

    Filippov, B.

    2016-01-01

    Solar filament shape in projection on disc depends on the structure of the coronal magnetic field. We calculate the position of polarity inversion lines (PILs) of coronal potential magnetic field at different heights above the photosphere, which compose the magnetic neutral surface, and compare with them the distribution of the filament material in Hα chromospheric images. We found that the most of the filament material is enclosed between two PILs, one at a lower height close to the chromosphere and one at a higher level, which can be considered as a height of the filament spine. Observations of the same filament on the limb by the Solar Terrestrial Relations Observatory spacecraft confirm that the height of the spine is really very close to the value obtained from the PIL and filament border matching. Such matching can be used for filament height estimations in on-disc observations. Filament barbs are housed within protruding sections of the low-level PIL. On the base of simple model, we show that the similarity of the neutral surfaces in potential and non-potential fields with the same sub-photospheric sources is the reason for the found tendency for the filament material to gather near the potential-field neutral surface.

  16. Barrier potential design criteria in multiple-quantum-well-based solar-cell structures

    Science.gov (United States)

    Mohaidat, Jihad M.; Shum, Kai; Wang, W. B.; Alfano, R. R.

    1994-01-01

    The barrier potential design criteria in multiple-quantum-well (MQW)-based solar-cell structures is reported for the purpose of achieving maximum efficiency. The time-dependent short-circuit current density at the collector side of various MQW solar-cell structures under resonant condition was numerically calculated using the time-dependent Schroedinger equation. The energy efficiency of solar cells based on the InAs/Ga(y)In(1-y)As and GaAs/Al(x)Ga(1-x)As MQW structues were compared when carriers are excited at a particular solar-energy band. Using InAs/Ga(y)In(1-y)As MQW structures it is found that a maximum energy efficiency can be achieved if the structure is designed with barrier potential of about 450 meV. The efficiency is found to decline linearly as the barrier potential increases for GaAs/Al(x)Ga(1-x)As MQW-structure-based solar cells.

  17. The Fuel Efficiency of Maritime Transport. Potential for improvement and analysis of barriers

    Energy Technology Data Exchange (ETDEWEB)

    Faber, J.; Nelissen, D.; Smit, M. [CE Delft, Delft (Netherlands); Behrends, B. [Marena Ltd., s.l. (United Kingdom); Lee, D.S. [Manchester Metropolitan University, Machester (United Kingdom)

    2012-02-15

    There is significant potential to improve the fuel efficiency of ships and thus contribute to reducing greenhouse gas emissions from maritime transport. It has long been recognised that this potential is not being fully exploited, owing to the existence of non-market barriers. This report analyses the barriers to implementing fuel efficiency improvements, and concludes that the most important of these are the split incentive between ship owners and operators, a lack of trusted data on new technologies, and transaction costs associated with evaluating measures. As a result, in practice about a quarter of the cost-effective abatement potential is unavailable. There are several ways to overcome these barriers. The split incentive can - to some extent - be overcome by providing more detailed information on the fuel efficiency of vessels, making due allowance for operational profiles. This would allow fuel consumption to be more accurately projected and a larger share of efficiency benefits to accrue to ship owners, thus increasing the return on investment in fuel-saving technologies. This would also require changes to standard charter parties. The credibility of information on new technologies can be improved through intensive collaboration between suppliers of new technologies and shipping companies. In order to overcome risk, government subsidies could provide an incentive. This could have the additional benefit that governments could require publication of results.

  18. Scattering matrix for magnetic potentials with Coulomb decay at infinity

    CERN Document Server

    Yafaev, D

    2003-01-01

    We consider the Schr\\"odinger operator $H$ in the space $L_2({\\R}^d)$ with a magnetic potential $A(x)$ decaying as $|x|^{-1}$ at infinity and satisfying the transversal gauge condition $ =0$. Such potentials correspond, for example, to magnetic fields $B(x)$ with compact support and hence are quite general. Our goal is to study properties of the scattering matrix $S(\\lambda)$ associated to the operator $H$. In particular, we find the essential spectrum $\\sigma_{ess}$ of $S(\\lambda)$ in terms of the behaviour of $A(x)$ at infinity. It turns out that $\\sigma_{ess}(S(\\lambda))$ is normally a rich subset of the unit circle ${\\Bbb T}$ or even coincides with ${\\Bbb T}$. We find also the diagonal singularity of the scattering amplitude (of the kernel of $S(\\lambda)$ regarded as an integral operator). In general, $S(\\lambda)$ is a sum of a multiplication operator and of a singular integral operator. However, if the magnetic field decreases faster than $ |x|^{-2}$ for $d\\geq 3$ (and the total magnetic flux is an integ...

  19. Physics of strong internal transport barriers in JT-60U reversed-magnetic-shear plasmas

    Energy Technology Data Exchange (ETDEWEB)

    Hayashi, N; Takizuka, T; Sakamoto, Y; Fujita, T; Kamada, Y; Ide, S; Koide, Y [Japan Atomic Energy Agency, 801-1 Mukouyama, Naka, Ibaraki 311-0193 (Japan)

    2006-05-15

    The physics of strong internal transport barriers (ITBs) in JT-60U reversed-magnetic-shear (RS) plasmas has been studied through the modelling on the 1.5 dimensional transport simulation. The key physics to produce two scalings on the basis of the JT-60U box-type ITB database are identified. As for the scaling for the narrow ITB width proportional to the ion poloidal gyroradius, the following three physics are important: (1) the sharp reduction of the anomalous transport below the neoclassical level in the RS region, (2) the autonomous formation of pressure and current profiles through the neoclassical transport and the bootstrap current and (3) the large difference between the neoclassical transport and the anomalous transport in the normal-shear region. As for the scaling for the energy confinement inside ITB ({epsilon}{sub f}{beta}{sub p,core} {approx} 0.25, where {epsilon}{sub f} is the inverse aspect ratio at the ITB foot and {beta}{sub p,core} is the core poloidal beta value), the value of 0.25 is found to be a saturation value due to the MHD equilibrium. The value of {epsilon}{sub f}{beta}{sub p,core} reaches the saturation value, when the box-type ITB is formed in the strong RS plasma with a large asymmetry of the poloidal magnetic field, regardless of the details of the transport and the non-inductively driven current.

  20. HfO2 and SiO2 as barriers in magnetic tunneling junctions

    Science.gov (United States)

    Shukla, Gokaran; Archer, Thomas; Sanvito, Stefano

    2017-05-01

    SiO2 and HfO2 are both high-k, wide-gap semiconductors, currently used in the microelectronic industry as gate barriers. Here we investigate whether the same materials can be employed to make magnetic tunnel junctions, which in principle can be amenable for integration in conventional Si technology. By using a combination of density functional theory and the nonequilibrium Green's functions method for quantum transport we have studied the transport properties of Co [0001 ] /SiO2[001 ] /Co [0001 ] and Fe [001 ] /HfO2[001 ] /Fe [001 ] junctions. In both cases we found a quite large magnetoresistance, which is explained through the analysis of the real band structure of the magnets and the complex one of the insulator. We find that there is no symmetry spin filtering for the Co-based junction since the high transmission Δ2' band crosses the Fermi level, EF, for both spin directions. However, the fact that Co is a strong ferromagnet makes the orbital contribution to the two Δ2' spin subbands different, yielding magnetoresistance. In contrast for the Fe-based junction symmetry filtering is active for an energy window spanning between the Fermi level and 1 eV below EF, with Δ1 symmetry contributing to the transmission.

  1. Spin asymmetry calculations of the TMR-V curves in single and double-barrier magnetic tunnel junctions

    KAUST Repository

    Useinov, Arthur; Kosel, Jü rgen

    2011-01-01

    in the single as well as double barrier magnetic tunnel junctions (SMTJ & DMTJ, which are constructed from CoFeB/MgO interfaces) and numerically estimate the possible difference of the TMR-V a curves for negative and positive voltages in the homojunctions

  2. Complex energy eigenvalues of a linear potential with a parabolical barrier

    International Nuclear Information System (INIS)

    Malherbe, J.B.

    1978-01-01

    The physical meaning and restrictions of complex energy eigenvalues are briefly discussed. It is indicated that a quasi-stationary phase describes an idealised disintegration system. Approximate resonance-eigenvalues of the one dimensional Schrodinger equation with a linear potential and parabolic barrier are calculated by means of Connor's semiclassical method. This method is based on the generalized WKB-method of Miller and Good. The results obtained confirm the correctness of a model representation which explains the unusual distribution of eigenvalues by certain other linear potentials in a complex energy level [af

  3. Potential facilitators and barriers to adopting standard treatment guidelines in clinical practice.

    Science.gov (United States)

    Sharma, Sangeeta; Pandit, Ajay; Tabassum, Fauzia

    2017-04-18

    Purpose The purpose of this paper is to assess medicines information sources accessed by clinicians, if sources differed in theory and practice and to find out the barriers and facilitators to effective guideline adoption. Design/methodology/approach In all, 183 doctors were surveyed. Barriers and facilitators were classified as: communication; potential adopters; innovation; organization characteristics and environmental/social/economic context. Findings Most of the clinicians accessed multiple information sources including standard treatment guidelines, but also consulted seniors/colleagues in practice. The top three factors influencing clinical practice guideline adoption were innovation characteristics, environmental context and individual characteristics. The respondents differed in the following areas: concerns about flexibility offered by the guideline; denying patients' individuality; professional autonomy; insights into gaps in current practice and evidence-based practice; changing practices with little or no benefit. Barriers included negative staff attitudes/beliefs, guideline integration into organizational structures/processes, time/resource constraints. Fearing third parties (government and insurance companies) restricting medicines reimbursement and poor liability protection offered by the guidelines emerged as the barriers. Facilitators include aligning organizational structures/processes with the innovation; providing leadership support to guide diffusion; increasing awareness and enabling early innovation during pre/in-service training, with regular feedback on outcomes and use. Practical implications Guideline adoption in clinical practice is partly within doctors' control. There are other key prevailing factors in the local context such as environmental, social context, professional and organizational culture affecting its adoption. Organizational policy and accreditation standards necessitating adherence can serve as a driver. Originality

  4. Spin-dependent scattering by a potential barrier on a nanotube

    International Nuclear Information System (INIS)

    Abranyos, Yonatan; Gumbs, Godfrey; Fekete, Paula

    2010-01-01

    The electron spin effects on the surface of a nanotube have been considered through the spin-orbit interaction (SOI), arising from the electron confinement on the surface of the nanotube. This is of the same nature as the Rashba-Bychkov SOI at a semiconductor heterojunction. We estimate the effect of disorder within a potential barrier on the transmission probability. Using a continuum model, we obtain analytic expressions for the spin-split energy bands for electrons on the surface of nanotubes in the presence of SOI. First we calculate analytically the amplitudes of scattering from a potential barrier located around the axis of the nanotube into spin-dependent states. The effect of disorder on the scattering process is included phenomenologically and induces a reduction in the transition probability. We analyze the relative role of SOI and disorder in the transmission probability which depends on the angular and linear momentum of the incoming particle, and its spin orientation. Finally we demonstrate that in the presence of disorder, perfect transmission may not be achieved for finite barrier heights.

  5. A Rising Female Empire? : Exploring the potential barriers women face in achieving leadership positions in the humanitarian sector

    OpenAIRE

    Eriksson, Lina Elisabeth

    2015-01-01

    This research aims to explore how women and men view and perceive potential barriers to women achieving leadership positions in the humanitarian sector. Female leadership is so far an under-researched area within the humanitarian sector, so it is unknown whether females encounter any barriers in accessing and attaining leadership positions. Three categories were identified; identity, perception and challenges through which the views and barriers are explored. Semi-structured interviews were c...

  6. Deactivation of SCR catalysts by potassium: A study of potential alkali barrier materials

    DEFF Research Database (Denmark)

    Olsen, Brian Kjærgaard; Kügler, Frauke; Castellino, Francesco

    2017-01-01

    The use of coatings in order to protect vanadia based SCR catalysts against potassium poisoning has been studied by lab- and pilot-scale experiments. Three-layer pellets, consisting of a layer ofa potential coating material situated between layers of fresh and potassium poisoned SCR catalyst, were...... the coating process. Potassium had to some extent penetrated the MgO coat, and SEM analysis revealed it to be rather thick and fragile. Despite these observations, the coating did protect the SCR catalyst against potassium poisoning to some degree, leaving promise of further optimization....... used to test the ability of the barrier layer to block the diffusion of potassium across the pellet. Of MgO, sepiolite and Hollandite manganese oxide, MgO was the most effective potassium barrier, and no potassium was detected in the MgO layer upon exposure to SCR conditions for 7 days. Two monoliths...

  7. Reactor potential of the magnetically insulated inertial fusion (MICF) system

    International Nuclear Information System (INIS)

    Kammash, T.; Galbraith, D.L.

    1987-01-01

    The Magnetically Insulated Inertial Confinement Fusion (MICF) scheme is examined with regard to its potential as a power-producing reactor. This approach combines the favorable aspects of both magnetic and inertial fusions in that physical containment of the plasma is provided by a metallic shell while thermal insulation of its energy is provided by a strong, self-generated magnetic field. The plasma is created at the core of the target as a result of irradiation of the fuel-coated inner surface by a laser beam that enters through a hole in the spherical shell. The instantaneous magnetic field is generated by the current loops formed by the laser-heated, laser-ablated electrons, and preliminary experimental results at Osaka University have confirmed the presence of such a field. These same experiments have also yielded a Lawson parameter of about 5x10 12 cm -3 sec, and because of these unique properties, the plasma lifetimes in MICF have been shown to be about two orders of magnitude longer than conventional, pusher type inertial fusion schemes. In this paper a quasi one dimensional, time dependent set of particle and energy balance equations for the thermal species, namely, electrons, ions and thermal alphas which also allows for an appropriate set of fast alpha groups is utilized to assess the reactor prospects of a DT-burning MICF system. (author) [pt

  8. Potential and barrier study. Passive house and near-zero energy buildings; Potensial- og barrierestudie. Passivhus og naer nullenergibygninger

    Energy Technology Data Exchange (ETDEWEB)

    NONE

    2012-07-01

    The main conclusion from the analysis is that the barriers to realize both passive and near zero-energy buildings are significant. In addition to being a mere economic assessment indicates that 30-70% of the technical potential is not profitable depending on energy price levels, the barriers is reducing the economic potential with approximately another half as a realistic market potential.(eb)

  9. The magnetic universe through vector potential SPMHD simulations

    Science.gov (United States)

    Stasyszyn, F. A.

    2017-10-01

    The use of Smoothed Particle Magneto Hydrodynamics (SPMHD) is getting nowadays more and more common in Astrophysics. From galaxy clusters to neutron starts, there are multiple applications already existing in the literature. I will review some of the common methods used and highlight the successful approach of using vector potentials to describe the evolution of the magnetic fields. The latter have some interesting advantages, and their results challenge previous findings, being the magnetic divergence problem naturally vanished. We select a few examples to discuss some areas of interest. First, we show some Galaxy Clusters from the MUSIC project. These cosmological simulations are done with the usual sub-grid recipes, as radiative cooling and star formation, being the first ones obtained with an SPH code in a self consistent way. This demonstrates the robustness of the new method in a variety of astrophysical scenarios.

  10. Exploring the efficiency potential for an active magnetic regenerator

    DEFF Research Database (Denmark)

    Eriksen, Dan; Engelbrecht, Kurt; Haffenden Bahl, Christian Robert

    2016-01-01

    A novel rotary state of the art active magnetic regenerator refrigeration prototype was used in an experimental investigation with special focus on efficiency. Based on an applied cooling load, measured shaft power, and pumping power applied to the active magnetic regenerator, a maximum second-la...... and replacing the packed spheres with a theoretical parallel plate regenerator. Furthermore, significant potential efficiency improvements through optimized regenerator geometries are estimated and discussed......., especially for the pressure drop, significant improvements can be made to the machine. However, a large part of the losses may be attributed to regenerator irreversibilities. Considering these unchanged, an estimated upper limit to the second-law efficiency of 30% is given by eliminating parasitic losses...

  11. Evaluating Zeta Potential and the Calcite/Aragonite Ratio as Potential Success Indicators for Magnetic Water Treatment

    National Research Council Canada - National Science Library

    Lambert, Kevin

    1999-01-01

    The potential benefits of anti-scale magnetic treatment (AMT) are not realized or reliably predicted because the factors measuring performance of magnetic treatment have either not been identified or are poorly defined...

  12. Effects of continuous feedback on households’ electricity consumption: Potentials and barriers

    International Nuclear Information System (INIS)

    Nilsson, Andreas; Bergstad, Cecilia Jakobsson; Thuvander, Liane; Andersson, David; Andersson, Kristin; Meiling, Pär

    2014-01-01

    Highlights: • Two studies on conservation behaviours using in home-displays are presented. • No significant effects on electricity consumption were found. • Display feedback does not necessarily contribute to lower electricity use. • Interviews conclude that different types of feedback techniques should be combined. • Two important barriers are difficulties to understand the display and a lack of interest. - Abstract: Two field experiments were carried out to study (a) the effects on energy savings of continuous visual feedback via in-home displays, and (b) the motives for responding or not. In study 1, 40 participants living in separate or semi-detached houses in two different towns participated. All participants received a questionnaire and a list of possible energy saving measures. Households were then randomly assigned to an experimental condition (display) or a control condition (no display). In study 2, 32 households in rented apartments participated. No significant differences between the conditions were found for either of the studies. In study 2, semi-structured interviews were conducted among nine of the households. Through an analysis of interview transcripts barriers were identified explaining why the feedback intervention was not sufficient to change behaviour and reduce consumption. The barriers experienced indicate that there is a risk of overconfidence in IHDs. For the development of energy policies and more wide-scale implementation, it is important to be aware of the potential obstacles to success

  13. Families' perceived benefits of home visits for managing paediatric obesity outweigh the potential costs and barriers.

    Science.gov (United States)

    Gehring, Nicole D; Ball, Geoff D C; Perez, Arnaldo; Holt, Nicholas L; Neuman, Daniel; Spence, Nicholas; Mercier, Laura; Jetha, Mary

    2018-02-01

    Home visits have successfully been used to deliver various health services, but what role could they play in paediatric weight management? Low treatment initiation and high attrition prompted our multidisciplinary paediatric weight management clinic to investigate how families perceived the benefits and barriers of home visits. We focused on children with obesity aged 2-17 who were enrolled in our tertiary-level clinic in Alberta, Canada. None had received a home visit. The families were interviewed face-to-face from October 2015 to October 2016, and we used a qualitative description methodological framework and manifest content analysis. The parents were the main interviewees. Of the 56 families, 89% were interested in a home visit, 82% wanted support from a dietician and 54% from an exercise specialist. The perceived benefits of home visits included comprehensive assessment (95%), convenience (86%), tailored care (29%) and family involvement (13%), while the costs and barriers included clinicians' potential judgmental attitudes (30%), loss of privacy (19%) and distractions (10%). Some thought clinicians would find home visits inconvenient (25%), with bureaucratic challenges (14%) and sustainability issues (5%). Families felt home visits were a convenient option for managing paediatric obesity and identified important benefits and barriers that could guide such interventions. ©2017 Foundation Acta Paediatrica. Published by John Wiley & Sons Ltd.

  14. Transmission through a potential barrier in Luttinger liquids with a topological spin gap

    Science.gov (United States)

    Kainaris, Nikolaos; Carr, Sam T.; Mirlin, Alexander D.

    2018-03-01

    We study theoretically the transport of the one-dimensional single-channel interacting electron gas through a strong potential barrier in the parameter regime where the spin sector of the low-energy theory is gapped by interaction (Luther-Emery liquid). There are two distinct phases of this nature, of which one is of particular interest as it exhibits nontrivial interaction-induced topological properties. Focusing on this phase and using bosonization and an expansion in the tunneling strength we calculate the conductance through the barrier as a function of the temperature as well as the local density of states (LDOS) at the barrier. Our main result concerns the mechanism of bound-state-mediated tunneling. The characteristic feature of the topological phase is the emergence of protected zero-energy bound states with fractional spin located at the impurity position. By flipping this fractional spin, single electrons can tunnel across the impurity even though the bulk spectrum for spin excitations is gapped. This results in a finite LDOS below the bulk gap and in a nonmonotonic behavior of the conductance. The system represents an important physical example of an interacting symmetry-protected topological phase, which combines features of a topological spin insulator and a topological charge metal, in which the topology can be probed by measuring transport properties.

  15. Caspase-14 Expression Impairs Retinal Pigment Epithelium Barrier Function: Potential Role in Diabetic Macular Edema

    Directory of Open Access Journals (Sweden)

    Selina Beasley

    2014-01-01

    Full Text Available We recently showed that caspase-14 is a novel molecule in retina with potential role in accelerated vascular cell death during diabetic retinopathy (DR. Here, we evaluated whether caspase-14 is implicated in retinal pigment epithelial cells (RPE dysfunction under hyperglycemia. The impact of high glucose (HG, 30 mM D-glucose on caspase-14 expression in human RPE (ARPE-19 cells was tested, which showed significant increase in caspase-14 expression compared with normal glucose (5 mM D-glucose + 25 mM L-glucose. We also evaluated the impact of modulating caspase-14 expression on RPE cells barrier function, phagocytosis, and activation of other caspases using ARPE-19 cells transfected with caspase-14 plasmid or caspase-14 siRNA. We used FITC-dextran flux assay and electric cell substrate impedance sensing (ECIS to test the changes in RPE cell barrier function. Similar to HG, caspase-14 expression in ARPE-19 cells increased FITC-dextran leakage through the confluent monolayer and decreased the transcellular electrical resistance (TER. These effects of HG were prevented by caspase-14 knockdown. Furthermore, caspase-14 knockdown prevented the HG-induced activation of caspase-1 and caspase-9, the only activated caspases by HG. Phagocytic activity was unaffected by caspase-14 expression. Our results suggest that caspase-14 contributes to RPE cell barrier disruption under hyperglycemic conditions and thus plays a role in the development of diabetic macular edema.

  16. Potential barrier heights at metal on oxygen-terminated diamond interfaces

    Energy Technology Data Exchange (ETDEWEB)

    Muret, P., E-mail: pierre.muret@neel.cnrs.fr; Traoré, A.; Maréchal, A.; Eon, D. [Inst. NEEL, Univ. Grenoble Alpes, F-38042 Grenoble, France and CNRS, Inst. NEEL, F-38042 Grenoble (France); Pernot, J. [Univ. Grenoble Alpes, Inst. NEEL, F-38042 Grenoble, (France); CNRS, Inst. NEEL, F-38042 Grenoble, (France); Institut Universitaire de France, 103 Boulevard Saint-Michel, F-75005 Paris (France); Pinero, J. C.; Villar, M. P.; Araujo, D., E-mail: daniel.araujo@uca.es [Dpto. Ciencias de los Materiales, Universidad de Cádiz, 11510 Puerto Real (Cádiz) (Spain)

    2015-11-28

    Electrical properties of metal-semiconductor (M/SC) and metal/oxide/SC structures built with Zr or ZrO{sub 2} deposited on oxygen-terminated surfaces of (001)-oriented diamond films, comprised of a stack of lightly p-doped diamond on a heavily doped layer itself homoepitaxially grown on an Ib substrate, are investigated experimentally and compared to different models. In Schottky barrier diodes, the interfacial oxide layer evidenced by high resolution transmission electron microscopy and electron energy losses spectroscopy before and after annealing, and barrier height inhomogeneities accounts for the measured electrical characteristics until flat bands are reached, in accordance with a model which generalizes that by Tung [Phys. Rev. B 45, 13509 (1992)] and permits to extract physically meaningful parameters of the three kinds of interface: (a) unannealed ones, (b) annealed at 350 °C, (c) annealed at 450 °C with the characteristic barrier heights of 2.2–2.5 V in case (a) while as low as 0.96 V in case (c). Possible models of potential barriers for several metals deposited on well defined oxygen-terminated diamond surfaces are discussed and compared to experimental data. It is concluded that interface dipoles of several kinds present at these compound interfaces and their chemical evolution due to annealing are the suitable ingredients that are able to account for the Mott-Schottky behavior when the effect of the metal work function is ignored, and to justify the reverted slope observed regarding metal work function, in contrast to the trend always reported for all other metal-semiconductor interfaces.

  17. Quantum damped oscillator II: Bateman’s Hamiltonian vs. 2D parabolic potential barrier

    Science.gov (United States)

    Chruściński, Dariusz

    2006-04-01

    We show that quantum Bateman’s system which arises in the quantization of a damped harmonic oscillator is equivalent to a quantum problem with 2D parabolic potential barrier known also as 2D inverted isotropic oscillator. It turns out that this system displays the family of complex eigenvalues corresponding to the poles of analytical continuation of the resolvent operator to the complex energy plane. It is shown that this representation is more suitable than the hyperbolic one used recently by Blasone and Jizba.

  18. Josephson-like currents in graphene for arbitrary time-dependent potential barriers

    OpenAIRE

    Savel'ev, Sergey E.; Hausler, Wolfgang; Hanggi, Peter

    2011-01-01

    From the exact solution of the Dirac-Weyl equation we find unusual currents j_y running in y-direction parallel to a time-dependent scalar potential barrier W(x,t) placed upon a monolayer of graphene, even for vanishing momentum component p_y. In their sine-like dependence on the phase difference of wave functions, describing left and right moving Dirac fermions, these currents resemble Josephson currents in superconductors, including the occurance of Shapiro steps at certain frequencies of p...

  19. Speeding up the first-passage for subdiffusion by introducing a finite potential barrier

    International Nuclear Information System (INIS)

    Palyulin, Vladimir V; Metzler, Ralf

    2014-01-01

    We show that for a subdiffusive continuous time random walk with scale-free waiting time distribution the first-passage dynamics on a finite interval can be optimized by introduction of a piecewise linear potential barrier. Analytical results for the survival probability and first-passage density based on the fractional Fokker–Planck equation are shown to agree well with Monte Carlo simulations results. As an application we discuss an improved design for efficient translocation of gradient copolymers compared to homopolymer translocation in a quasi-equilibrium approximation. (fast track communications)

  20. Observation of potential barriers on barium strontium titanate PTCR ceramics by electrostatic force microscopy

    International Nuclear Information System (INIS)

    Manfredini, J.P.; Paulin Filho, P.I.; Gheno, S.M.

    2011-01-01

    A composition of PTCR ceramic based in barium titanate with isovalent replacement of part of barium by strontium using lanthanum and manganese as additives was investigated. The transition temperature, typical of these materials, was shifted below the room temperature by the presence of strontium, whose behavior was detected by tests of DC resistivity and impedance spectroscopy. The observation of potential barriers at grain boundaries was possible through the technique of electrostatic force microscopy (EFM). The results also showed the presence of space charges in regions inside grains, possibly at subgrain boundaries. (author)

  1. Engineered barrier system and waste package design concepts for a potential geologic repository at Yucca Mountain

    International Nuclear Information System (INIS)

    Short, D.W.; Ruffner, D.J.; Jardine, L.J.

    1991-10-01

    We are using an iterative process to develop preliminary concept descriptions for the Engineered Barrier System and waste-package components for the potential geologic repository at Yucca Mountain. The process allows multiple design concepts to be developed subject to major constraints, requirements, and assumptions. Involved in the highly interactive and interdependent steps of the process are technical specialists in engineering, metallic and nonmetallic materials, chemistry, geomechanics, hydrology, and geochemistry. We have developed preliminary design concepts that satisfy both technical and nontechnical (e.g., programmatic or policy) requirements

  2. Animal Study Registries: Results from a Stakeholder Analysis on Potential Strengths, Weaknesses, Facilitators, and Barriers.

    Science.gov (United States)

    Wieschowski, Susanne; Silva, Diego S; Strech, Daniel

    2016-11-01

    Publication bias in animal research, its extent, its predictors, and its potential countermeasures are increasingly discussed. Recent reports and conferences highlight the potential strengths of animal study registries (ASRs) in this regard. Others have warned that prospective registration of animal studies could diminish creativity, add administrative burdens, and complicate intellectual property issues in translational research. A literature review and 21 international key-informant interviews were conducted and thematically analyzed to develop a comprehensive matrix of main- and subcategories for potential ASR-related strengths, weaknesses, facilitators, and barriers (SWFBs). We identified 130 potential SWFBs. All stakeholder groups agreed that ASRs could in various ways improve the quality and refinement of animal studies while allowing their number to be reduced, as well as supporting meta-research on animal studies. However, all stakeholder groups also highlighted the potential for theft of ideas, higher administrative burdens, and reduced creativity and serendipity in animal studies. Much more detailed reasoning was captured in the interviews than is currently found in the literature, providing a comprehensive account of the issues and arguments around ASRs. All stakeholder groups highlighted compelling potential strengths of ASRs. Although substantial weaknesses and implementation barriers were highlighted as well, different governance measures might help to minimize or even eliminate their impact. Such measures might include confidentiality time frames for accessing prospectively registered protocols, harmonized reporting requirements across ASRs, ethics reviews, lab notebooks, and journal submissions. The comprehensive information gathered in this study could help to guide a more evidence-based debate and to design pilot tests for ASRs.

  3. Animal Study Registries: Results from a Stakeholder Analysis on Potential Strengths, Weaknesses, Facilitators, and Barriers.

    Directory of Open Access Journals (Sweden)

    Susanne Wieschowski

    2016-11-01

    Full Text Available Publication bias in animal research, its extent, its predictors, and its potential countermeasures are increasingly discussed. Recent reports and conferences highlight the potential strengths of animal study registries (ASRs in this regard. Others have warned that prospective registration of animal studies could diminish creativity, add administrative burdens, and complicate intellectual property issues in translational research. A literature review and 21 international key-informant interviews were conducted and thematically analyzed to develop a comprehensive matrix of main- and subcategories for potential ASR-related strengths, weaknesses, facilitators, and barriers (SWFBs. We identified 130 potential SWFBs. All stakeholder groups agreed that ASRs could in various ways improve the quality and refinement of animal studies while allowing their number to be reduced, as well as supporting meta-research on animal studies. However, all stakeholder groups also highlighted the potential for theft of ideas, higher administrative burdens, and reduced creativity and serendipity in animal studies. Much more detailed reasoning was captured in the interviews than is currently found in the literature, providing a comprehensive account of the issues and arguments around ASRs. All stakeholder groups highlighted compelling potential strengths of ASRs. Although substantial weaknesses and implementation barriers were highlighted as well, different governance measures might help to minimize or even eliminate their impact. Such measures might include confidentiality time frames for accessing prospectively registered protocols, harmonized reporting requirements across ASRs, ethics reviews, lab notebooks, and journal submissions. The comprehensive information gathered in this study could help to guide a more evidence-based debate and to design pilot tests for ASRs.

  4. A Novel Magnetic Actuation Scheme to Disaggregate Nanoparticles and Enhance Passage across the Blood–Brain Barrier

    Directory of Open Access Journals (Sweden)

    Ali Kafash Hoshiar

    2017-12-01

    Full Text Available The blood–brain barrier (BBB hinders drug delivery to the brain. Despite various efforts to develop preprogramed actuation schemes for magnetic drug delivery, the unmodeled aggregation phenomenon limits drug delivery performance. This paper proposes a novel scheme with an aggregation model for a feed-forward magnetic actuation design. A simulation platform for aggregated particle delivery is developed and an actuation scheme is proposed to deliver aggregated magnetic nanoparticles (MNPs using a discontinuous asymmetrical magnetic actuation. The experimental results with a Y-shaped channel indicated the success of the proposed scheme in steering and disaggregation. The delivery performance of the developed scheme was examined using a realistic, three-dimensional (3D vessel simulation. Furthermore, the proposed scheme enhanced the transport and uptake of MNPs across the BBB in mice. The scheme presented here facilitates the passage of particles across the BBB to the brain using an electromagnetic actuation scheme.

  5. Potential of kaolin-based particle film barriers for Formosan subterranean termite (Isoptera: Rhinotermitidae) control

    Science.gov (United States)

    Wiltz, B.A.; Woodson, W.D.; Puterka, G.J.

    2010-01-01

    Effects of three particle film products on Formosan subterranean termites, Coptotermes formosanus Shiraki, were evaluated in feeding, tunneling, and contact assays. The particle films, hydrophobic M96-018 and hydrophilic Surround and Surround WP are based on the inert clay mineral kaolin. In 2-week long no-choice feeding tests, significant mortality occurred only with M96-018-coated wood. When a choice was provided, M96-018 and Surround were consumed at higher rates than untreated wood. Surround WP did not differ from controls in either test. In the tunneling assay termites were given the option of crossing a kaolin-sand mixture to reach an alternate food source. After 3-weeks, rates of 1% and 5% M96-018 provided an effective barrier to Formosan termite tunneling, while termites were not stopped by rates as high as 20% Surround and Surround WP. Dust treatments of all three formulations caused significant increases in mortality within 24 h, with mortality rates ranging from 72.0 - 97.3% within 72 h of treatment. The particle films were most effective when moisture levels were low, suggesting that desiccation was the mechanism for mortality. All particle films showed potential for use in above ground applications while hydrophobic M06-018 has the most potential as a soil barrier to subterranean termites.

  6. Spin asymmetry calculations of the TMR-V curves in single and double-barrier magnetic tunnel junctions

    KAUST Repository

    Useinov, Arthur

    2011-10-01

    Spin-polarization asymmetry is the key parameter in asymmetric voltage behavior (AVB) of the tunnel magnetoresistance (TMR) in magnetic tunnel junctions. In this paper, we study the value of the TMR as a function of the applied voltage Va in the single as well as double barrier magnetic tunnel junctions (SMTJ & DMTJ, which are constructed from CoFeB/MgO interfaces) and numerically estimate the possible difference of the TMR-V a curves for negative and positive voltages in the homojunctions. As a result, we found that AVB may help to determine the exact values of Fermi wave vectors for minority and majority conducting spin sub-bands. Moreover, significant asymmetry of the experimental TMR-Va curves, which arises due to different annealing regimes, is explained by different heights of the tunnel barriers and values of the spin asymmetry. The numerical TMR-V a data are in good agreement with experimental ones. © 2011 IEEE.

  7. Evidence-based dentistry for planning restorative treatments: barriers and potential solutions.

    Science.gov (United States)

    Afrashtehfar, K I; Eimar, H; Yassine, R; Abi-Nader, S; Tamimi, F

    2017-11-01

    Evidence-based dentistry (EBD) can help provide the best treatment option for every patient, however, its implementation in restorative dentistry is very limited. This study aimed at assessing the barriers preventing the implementation of EBD among dental undergraduate and graduate students in Montreal, and explore possible solutions to overcome these barriers. A cross-sectional survey was conducted by means of a paper format self-administrated questionnaire distributed among dental students. The survey assessed the barriers and potential solutions for implementation of an evidence-based practice. Sixty-one students completed the questionnaire. Forty-one percent of respondents found evidence-based literature to be the most reliable source of information for restorative treatment planning, however, only 16% used it. They considered that finding reliable information was difficult and they sometimes encountered conflicting information when consulting different sources. Dental students had positive attitudes towards the need for better access to evidence-based literature to assist learning and decision making in restorative treatment planning and to improve treatment outcomes. Even for dentists trained in EBD, online searching takes too much time, and even though it can provide information of better quality than personal intuition, it might not be enough to identify the best available evidence. Even though dental students are aware of the importance of EBD in restorative dentistry they rarely apply the concept, mainly due to time constraints. For this reason, implementation of EBD would probably require faster access to evidence-based knowledge. © 2016 John Wiley & Sons A/S. Published by John Wiley & Sons Ltd.

  8. Effect of the δ-potential on spin-dependent electron tunneling in double barrier semiconductor heterostructure

    Science.gov (United States)

    Chandrasekar, L. Bruno; Gnanasekar, K.; Karunakaran, M.

    2018-06-01

    The effect of δ-potential was studied in GaAs/Ga0.6Al0·4As double barrier heterostructure with Dresselhaus spin-orbit interaction. The role of barrier height and position of the δ- potential in the well region was analysed on spin-dependent electron tunneling using transfer matrix method. The spin-separation between spin-resonances on energy scale depends on both height and position of the δ- potential, whereas the tunneling life time of electrons highly influenced by the position of the δ- potential and not on the height. These results might be helpful for the fabrication of spin-filters.

  9. Renewable energy in South Africa. Potentials, barriers and options for support

    Energy Technology Data Exchange (ETDEWEB)

    Pegels, Anna [German Development Institute/Deutsches Institut fuer Entwicklungspolitik, Tulpenfeld 6, 53113 Bonn (Germany)

    2010-09-15

    The challenge of transforming entire economies is enormous; even more so if a country is as fossil fuel based and emission intensive as South Africa. However, in an increasingly carbon constrained world and already now facing climate change impacts South Africa has to reduce greenhouse gas emissions intensity soon and decidedly. The South African electricity sector is a vital part of the economy and at the same time contributes most to the emissions problem. First steps have been taken by the South African government to enhance energy efficiency and promote renewable energy, however, they fail to show large-scale effects. This paper seeks to identify the relevant barriers to renewable energy investments and, based on experience from other countries, provide policy recommendations. The major barrier identified in the paper is based on the economics of renewable energy technologies, i.e. their cost and risk structures, two main factors in investment planning. As a solution, the South African government introduced several renewable energy support measures, such as a feed-in tariff. The paper discusses the potential and possible shortcomings of this and other existing support schemes and identifies complementing measures on a national scale. (author)

  10. Renewable energy in South Africa: Potentials, barriers and options for support

    Energy Technology Data Exchange (ETDEWEB)

    Pegels, Anna, E-mail: anna.pegels@die-gdi.d [German Development Institute/Deutsches Institut fuer Entwicklungspolitik, Tulpenfeld 6, 53113 Bonn (Germany)

    2010-09-15

    The challenge of transforming entire economies is enormous; even more so if a country is as fossil fuel based and emission intensive as South Africa. However, in an increasingly carbon constrained world and already now facing climate change impacts South Africa has to reduce greenhouse gas emissions intensity soon and decidedly. The South African electricity sector is a vital part of the economy and at the same time contributes most to the emissions problem. First steps have been taken by the South African government to enhance energy efficiency and promote renewable energy, however, they fail to show large-scale effects. This paper seeks to identify the relevant barriers to renewable energy investments and, based on experience from other countries, provide policy recommendations. The major barrier identified in the paper is based on the economics of renewable energy technologies, i.e. their cost and risk structures, two main factors in investment planning. As a solution, the South African government introduced several renewable energy support measures, such as a feed-in tariff. The paper discusses the potential and possible shortcomings of this and other existing support schemes and identifies complementing measures on a national scale.

  11. Renewable energy in South Africa: Potentials, barriers and options for support

    International Nuclear Information System (INIS)

    Pegels, Anna

    2010-01-01

    The challenge of transforming entire economies is enormous; even more so if a country is as fossil fuel based and emission intensive as South Africa. However, in an increasingly carbon constrained world and already now facing climate change impacts South Africa has to reduce greenhouse gas emissions intensity soon and decidedly. The South African electricity sector is a vital part of the economy and at the same time contributes most to the emissions problem. First steps have been taken by the South African government to enhance energy efficiency and promote renewable energy, however, they fail to show large-scale effects. This paper seeks to identify the relevant barriers to renewable energy investments and, based on experience from other countries, provide policy recommendations. The major barrier identified in the paper is based on the economics of renewable energy technologies, i.e. their cost and risk structures, two main factors in investment planning. As a solution, the South African government introduced several renewable energy support measures, such as a feed-in tariff. The paper discusses the potential and possible shortcomings of this and other existing support schemes and identifies complementing measures on a national scale.

  12. Co2FeAl based magnetic tunnel junctions with BaO and MgO/BaO barriers

    Directory of Open Access Journals (Sweden)

    J. Rogge

    2015-07-01

    Full Text Available We succeed to integrate BaO as a tunneling barrier into Co2FeAl based magnetic tunnel junctions (MTJs. By means of Auger electron spectroscopy it could be proven that the applied annealing temperatures during BaO deposition and afterwards do not cause any diffusion of Ba neither into the lower Heusler compound lead nor into the upper Fe counter electrode. Nevertheless, a negative tunnel magnetoresistance (TMR ratio of -10% is found for Co2FeAl (24 nm / BaO (5 nm / Fe (7 nm MTJs, which can be attributed to the preparation procedure and can be explained by the formation of Co- and Fe-oxides at the interfaces between the Heusler and the crystalline BaO barrier by comparing with theory. Although an amorphous structure of the BaO barrier seems to be confirmed by high-resolution transmission electron microscopy (TEM, it cannot entirely be ruled out that this is an artifact of TEM sample preparation due to the sensitivity of BaO to moisture. By replacing the BaO tunneling barrier with an MgO/BaO double layer barrier, the electric stability could effectively be increased by a factor of five. The resulting TMR effect is found to be about +20% at room temperature, although a fully antiparallel state has not been realized.

  13. A Conditionally Integrable Bi-confluent Heun Potential Involving Inverse Square Root and Centrifugal Barrier Terms

    Science.gov (United States)

    Ishkhanyan, Tigran A.; Krainov, Vladimir P.; Ishkhanyan, Artur M.

    2018-05-01

    We present a conditionally integrable potential, belonging to the bi-confluent Heun class, for which the Schrödinger equation is solved in terms of the confluent hypergeometric functions. The potential involves an attractive inverse square root term x-1/2 with arbitrary strength and a repulsive centrifugal barrier core x-2 with the strength fixed to a constant. This is a potential well defined on the half-axis. Each of the fundamental solutions composing the general solution of the Schrödinger equation is written as an irreducible linear combination, with non-constant coefficients, of two confluent hypergeometric functions. We present the explicit solution in terms of the non-integer order Hermite functions of scaled and shifted argument and discuss the bound states supported by the potential. We derive the exact equation for the energy spectrum and approximate that by a highly accurate transcendental equation involving trigonometric functions. Finally, we construct an accurate approximation for the bound-state energy levels.

  14. Design of Magnetic Charged Particle Lens Using Analytical Potential Formula

    Science.gov (United States)

    Al-Batat, A. H.; Yaseen, M. J.; Abbas, S. R.; Al-Amshani, M. S.; Hasan, H. S.

    2018-05-01

    In the current research was to benefit from the potential of the two cylindrical electric lenses to be used in the product a mathematical model from which, one can determine the magnetic field distribution of the charged particle objective lens. With aid of simulink in matlab environment, some simulink models have been building to determine the distribution of the target function and their related axial functions along the optical axis of the charged particle lens. The present study showed that the physical parameters (i.e., the maximum value, Bmax, and the half width W of the field distribution) and the objective properties of the charged particle lens have been affected by varying the main geometrical parameter of the lens named the bore radius R.

  15. Potential implementation of reservoir computing models based on magnetic skyrmions

    Science.gov (United States)

    Bourianoff, George; Pinna, Daniele; Sitte, Matthias; Everschor-Sitte, Karin

    2018-05-01

    Reservoir Computing is a type of recursive neural network commonly used for recognizing and predicting spatio-temporal events relying on a complex hierarchy of nested feedback loops to generate a memory functionality. The Reservoir Computing paradigm does not require any knowledge of the reservoir topology or node weights for training purposes and can therefore utilize naturally existing networks formed by a wide variety of physical processes. Most efforts to implement reservoir computing prior to this have focused on utilizing memristor techniques to implement recursive neural networks. This paper examines the potential of magnetic skyrmion fabrics and the complex current patterns which form in them as an attractive physical instantiation for Reservoir Computing. We argue that their nonlinear dynamical interplay resulting from anisotropic magnetoresistance and spin-torque effects allows for an effective and energy efficient nonlinear processing of spatial temporal events with the aim of event recognition and prediction.

  16. Some Danish experience with product-service systems and their potentials and barriers to sustainable development

    DEFF Research Database (Denmark)

    Jørgensen, Michael Søgaard

    2003-01-01

    This paper is one of the first attempts to scan the Danish experience with product-service systems and analyse the experiences with respect to potentials and barriers to sustainable development, i.e. reduced resource consumption and reduced environmental impact. The scan shows a variety of product-service-systems......: some have been around for many years and have not be set up for sustainability purposes, while others are rather new and are attempts to contribute to a more sustainable development. Some of the systems identified are so to say born as product-service-systems (like food catering), while others have...... been developed from being a product system into being a product-service-systems in order to support the marketing of more environmental friendly products....

  17. Tests of potential functional barriers for laminated multilayer food packages. Part II: Medium molecular weight permeants.

    Science.gov (United States)

    Simal-Gándara, J; Sarria-Vidal, M; Rijk, R

    2000-09-01

    Experiments were performed to characterize the kinetics of the permeation of different medium molecular weight model permeants: bisphenol A, warfarin and anthracene, from liquid paraffin, through a surrogate potential functional barrier (25 microns-thick orientated polypropylene--OPP) into the food simulants olive oil and 3% (w/v) acetic acid. The characterization of permeation kinetics generally observed the permeation models previously reported to explain the experimental permeation results obtained for a low molecular weight group of model permeants. In general, the model permeants exhibited behaviour consistent with their relative molecular weights with respect to (a) the time taken to attain steady-state permeation into the food simulant in which they were more soluble, (b) their subsequent steady-state permeation rates, and (c) their partition between liquid paraffin and the OPP membrane.

  18. Effects of magnetic barriers on transport and magnetoresistance in a two-dimensional electronic device

    Energy Technology Data Exchange (ETDEWEB)

    He, H. L.; Zhang, X. W., E-mail: hedge80@sina.com.cn; Dai, B.; Ren, Y. [State Key Laboratory Cultivation Base for Nonmetal Composites and Functional Materials, Southwest University of Science and Technology, Mianyang 621010 (China); Wang, Z. P. [Institute of Chemical Materials, China Academy of Engineering Physics, Mianyang 621900 (China)

    2016-05-15

    We study theoretically the giant magnetoresistance (GMR) effect of 2-dimensional electron system (2DES) by the transfer matrix method. To produce the inhomogeneous magnetic field, two magnetic strips are pre-deposited on the surface of 2DES. In our work, we fix the magnetization M in one magnetic strip and adjust the tilting angle θ of magnetization in the other. The result shows that the electronic transmission and conductance vary significantly for different θ. The minimum conductance can be obtained at θ = π which corresponds to the magnetization anti-parallel alignment. The magnetoresistance ratio (MRR) calculation also indicates we would get the maximum in that case. Furthermore, we consider the magnetization M dependence of MRR in this work. When M increases, MRR peaks get higher and broader and more numbers of peaks can be observed. These results offer an alternative to get a tunable GMR device which can be controlled by adjusting the magnetization M and the magnetized angle θ.

  19. Identification of potential biomarkers for gut barrier failure in broiler chickens

    Directory of Open Access Journals (Sweden)

    Juxing eChen

    2015-05-01

    Full Text Available The objective of the present study was to identify potential biomarkers for gut barrier failure in chickens. A total of 144 day-of-hatch Ross 308 male broiler chickens were housed in 24 battery cages with 6 chicks per cage. Cages were randomly assigned to either a control group (CON or gut barrier failure (GBF group. During the first 13 d, birds in CON or GBF groups were fed a common corn-soy starter diet. On d 14, CON chickens were switched to a corn grower diet and GBF chickens were switched to rye-wheat-barley grower diet. In addition, on d 21, GBF chickens were orally challenged with a coccidiosis vaccine. At d 21 and d 28, birds were weighed by cage and feed intake was recorded to calculate feed conversion ratio. At d 28, one chicken from each cage was euthanized to collect intestinal samples for morphometric analysis, blood for serum, and intestinal mucosa scrapings for gene expression. Overall performance and feed efficiency was severely affected (P < 0.05 by a GBF model when compared with CON group at d 21 and d 28. Duodenum of GBF birds had wider villi, longer crypt depth, and higher crypt depth/villi height ratio than CON birds. Similarly, GBF birds had longer crypt depth in jejunum and ileum when compared with CON birds. An increase (P <0.05 in serum endotoxin, α1-acid glycoprotein (AGP, as well as interleukin (IL-8, IL-1β, transforming growth factor (TGF-β4 and fatty-acid-binding protein (FABP 6 mRNA levels were increased in GBF birds compared to CON; however, FABP2 mRNA levels were decreased (P <0.05 in GBF birds compared to CON. Occludin was numerically reduced by 24% (P = 0.107 and mucin 2 (MUC2 was reduced by 29 % (P = 0.088 in GBF birds compared to CON birds. The results from the present study suggest that serum endotoxin and AGP, as well as, gene expression of FABP2, FABP6, IL-8, IL-1β and TGF-β4 in mucosa may work as potential biomarkers for gut barrier health in chickens.

  20. Coupling parameter series expansion for fluid with square-well plus repulsive-square-barrier potential

    Directory of Open Access Journals (Sweden)

    Shiqi Zhou

    2013-10-01

    Full Text Available Monte Carlo simulations in the canonical ensemble are performed for fluid with potential consisting of a square-well plus a square-barrier to obtain thermodynamic properties such as pressure, excess energy, constant volume excess heat capacity, and excess chemical potential, and structural property such as radial distribution function. The simulations cover a wide density range for the fluid phase, several temperatures, and different combinations of the parameters defining the potential. These simulation data have been used to test performances of a coupling parameter series expansion (CPSE recently proposed by one of the authors [S. Zhou, Phys. Rev. E 74, 031119 (2006], and a traditional 2nd-order high temperature series expansion (HTSE based on a macroscopic compressibility approximation (MAC used with confidence since its introduction in 1967. It is found that (i the MCA-based 2nd-order HTSE unexpectedly and depressingly fails for most situations investigated, and the present simulation results can serve well as strict criteria for testing liquid state theories. (ii The CPSE perturbation scheme is shown to be capable of predicting very accurately most of the thermodynamic properties simulated, but the most appropriate level of truncating the CPSE differs and depends on the range of the potential to be calculated; in particular, the shorter the potential range is, the higher the most appropriate truncating level can be, and along with rising of the potential range the performance of the CPSE perturbation scheme will decrease at higher truncating level. (iii The CPSE perturbation scheme can calculate satisfactorily bulk fluid rdf, and such calculations can be done for all fluid states of the whole phase diagram. (iv The CPSE is a convergent series at higher temperatures, but show attribute of asymptotic series at lower temperatures, and as a result, the surest asymptotic value occurs at lower-order truncation.

  1. Effect of parallel magnetic field on repetitively unipolar nanosecond pulsed dielectric barrier discharge under different pulse repetition frequencies

    Science.gov (United States)

    Liu, Yidi; Yan, Huijie; Guo, Hongfei; Fan, Zhihui; Wang, Yuying; Wu, Yun; Ren, Chunsheng

    2018-03-01

    A magnetic field, with the direction parallel to the electric field, is applied to the repetitively unipolar positive nanosecond pulsed dielectric barrier discharge. The effect of the parallel magnetic field on the plasma generated between two parallel-plate electrodes in quiescent air is experimentally studied under different pulse repetition frequencies (PRFs). It is indicated that only the current pulse in the rising front of the voltage pulse occurs, and the value of the current is increased by the parallel magnetic field under different PRFs. The discharge uniformity is improved with the decrease in PRF, and this phenomenon is also observed in the discharge with the parallel magnetic field. By using the line-ratio technique of optical emission spectra, it is found that the average electron density and electron temperature under the considered PRFs are both increased when the parallel magnetic field is applied. The incremental degree of average electron density is basically the same under the considered PRFs, while the incremental degree of electron temperature under the higher-PRFs is larger than that under the lower-PRFs. All the above phenomena are explained by the effect of parallel magnetic field on diffusion and dissipation of electrons.

  2. A consistent derivation of the real and imaginary parts of the heavy ion potential below and above the Coulomb barrier

    International Nuclear Information System (INIS)

    Vinh Mau, N.

    1987-03-01

    In a model including approximately a large set of non elastic channels, the real and imaginary potentials are consistently derived. The anomaly of the real potential which sharply increases in the vicinity of the Coulomb barrier where the imaginary potential is strongly reduced is studied in 16 0+ 40 Ca and 16 O+ 208 Pb systems. The results on the imaginary potential are discussed and compared to our previous calculation

  3. Blood-brain barrier leakage after status epilepticus in rapamycin-treated rats I: Magnetic resonance imaging.

    Science.gov (United States)

    van Vliet, Erwin A; Otte, Willem M; Wadman, Wytse J; Aronica, Eleonora; Kooij, Gijs; de Vries, Helga E; Dijkhuizen, Rick M; Gorter, Jan A

    2016-01-01

    The mammalian target of rapamycin (mTOR) pathway has received increasing attention as a potential antiepileptogenic target. Treatment with the mTOR inhibitor rapamycin after status epilepticus reduces the development of epilepsy in a rat model. To study whether rapamycin mediates this effect via restoration of blood-brain barrier (BBB) dysfunction, contrast-enhanced magnetic resonance imaging (CE-MRI) was used to determine BBB permeability throughout epileptogenesis. Imaging was repeatedly performed until 6 weeks after kainic acid-induced status epilepticus in rapamycin (6 mg/kg for 6 weeks starting 4 h after SE) and vehicle-treated rats, using gadobutrol as contrast agent. Seizures were detected using video monitoring in the week following the last imaging session. Gadobutrol leakage was widespread and extensive in both rapamycin and vehicle-treated epileptic rats during the acute phase, with the piriform cortex and amygdala as the most affected regions. Gadobutrol leakage was higher in rapamycin-treated rats 4 and 8 days after status epilepticus compared to vehicle-treated rats. However, during the chronic epileptic phase, gadobutrol leakage was lower in rapamycin-treated epileptic rats along with a decreased seizure frequency. This was confirmed by local fluorescein staining in the brains of the same rats. Total brain volume was reduced by this rapamycin treatment regimen. The initial slow recovery of BBB function in rapamycin-treated epileptic rats indicates that rapamycin does not reduce seizure activity by a gradual recovery of BBB integrity. The reduced BBB leakage during the chronic phase, however, could contribute to the decreased seizure frequency in post-status epilepticus rats treated with rapamycin. Furthermore, the data show that CE-MRI (using step-down infusion with gadobutrol) can be used as biomarker for monitoring the effect of drug therapy in rats. Wiley Periodicals, Inc. © 2015 International League Against Epilepsy.

  4. Magnetic field induced suppression of the forward bias current in Bi2Se3/Si Schottky barrier diodes

    Science.gov (United States)

    Jin, Haoming; Hebard, Arthur

    Schottky diodes formed by van der Waals bonding between freshly cleaved flakes of the topological insulator Bi2Se3 and doped silicon substrates show electrical characteristics in good agreement with thermionic emission theory. The motivation is to use magnetic fields to modulate the conductance of the topologically protected conducting surface state. This surface state in close proximity to the semiconductor surface may play an important role in determining the nature of the Schottky barrier. Current-voltage (I-V) and capacitance-voltage (C-V) characteristics were obtained for temperatures in the range 50-300 K and magnetic fields, both perpendicular and parallel to the interface, as high as 7 T. The I-V curve shows more than 6 decades linearity on semi-logarithmic plots, allowing extraction of parameters such as ideality (η), zero-voltage Schottky barrier height (SBH), and series resistance (Rs). In forward bias we observe a field-induced decrease in current which becomes increasingly more pronounced at higher voltages and lower temperature, and is found to be correlated with changes in Rs rather than other barrier parameters. A comparison of changes in Rs in both field direction will be made with magnetoresistance in Bi2Se3 transport measurement. The work is supported by NSF through DMR 1305783.

  5. Radio-frequency shot-noise measurement in a magnetic tunnel junction with a MgO barrier

    International Nuclear Information System (INIS)

    Rehman, Mushtaq; Park, Junghwan; Song, Woon; Chong, Yonuk; Lee, Yeonsub; Min, Byoungchul; Shin, Kyungho; Ryu, Sangwan; Khim, Zheong

    2010-01-01

    We measured the noise power of a magnetic tunnel junction in the frequency range of 710 ∼ 1200 MHz. A low-noise cryogenic HEMT amplifier was used to measure the small noise signal at a high frequency with wide bandwidth. The MgO-barrier tunnel junction showed large tunnel magnetoresistance ratio of 215% at low temperature, which indicates electronic transport through the tunnel barrier without any significant spin-flip scattering. In the bias-dependent noise measurement, however, the zero-bias shot noise was enhanced compared to the value expected from a perfect tunnel barrier or the value observed from a good Al-AlO x -Al tunnel junction. We assume that this enhanced noise comes from inelastic tunneling processes through the barrier, which may be related to the observed zero-bias anomaly in the differential resistance of the tunnel junctions. We present a simple phenomenological model for how the inelastic scattering process can enhance the zero-bias noise in a tunnel junction.

  6. Low frequency noise in asymmetric double barrier magnetic tunnel junctions with a top thin MgO layer

    International Nuclear Information System (INIS)

    Guo Hui-Qiang; Tang Wei-Yue; Liu Liang; Wei Jian; Li Da-Lai; Feng Jia-Feng; Han Xiu-Feng

    2015-01-01

    Low frequency noise has been investigated at room temperature for asymmetric double barrier magnetic tunnel junctions (DBMTJs), where the coupling between the top and middle CoFeB layers is antiferromagnetic with a 0.8-nm thin top MgO barrier of the CoFeB/MgO/CoFe/CoFeB/MgO/CoFeB DBMTJ. At enough large bias, 1/f noise dominates the voltage noise power spectra in the low frequency region, and is conventionally characterized by the Hooge parameter α mag . With increasing external field, the top and bottom ferromagnetic layers are aligned by the field, and then the middle free layer rotates from antiparallel state (antiferromagnetic coupling between top and middle ferromagnetic layers) to parallel state. In this rotation process α mag and magnetoresistance-sensitivity-product show a linear dependence, consistent with the fluctuation dissipation relation. With the magnetic field applied at different angles (θ) to the easy axis of the free layer, the linear dependence persists while the intercept of the linear fit satisfies a cos(θ) dependence, similar to that for the magnetoresistance, suggesting intrinsic relation between magnetic losses and magnetoresistance. (rapid communication)

  7. Demand-side mitigation options of the agricultural sector: potential, barriers and ways forward

    Directory of Open Access Journals (Sweden)

    Brunelle Thierry

    2017-01-01

    Full Text Available This paper reviews the potential and barriers of demand-side mitigation options in the agricultural sector based on the recent academic literature and on a survey conducted on a sample of 788 respondents living in France. The mitigation potential of such measures as reducing losses in the food supply chain and shifting diets toward less animal products is estimated to be particularly high, higher, in particular, than supply-side mitigation options. However, to ensure that these measures do not entail a reduction in protein intake, these estimations should consider both caloric and protein units, and take into account the digestibility differentials between protein sources. Our survey shows that people are relatively reluctant to eat more sustainably, preferring to reduce their emissions in other areas such as housing or equipment. This relative reluctance is mainly due to individual perceptions linked to health concerns, taste or habits. Some obstacles could easily be overcome through well-designed policies aiming to, for example, advertise a lower consumption of red meat for health benefits. National governments are, however, rather inactive on this topic, leaving the initiative to the civil society.

  8. Dielectric and magnetic characterizations of capacitor structures with an ionic liquid/MgO barrier and a ferromagnetic Pt electrode

    Directory of Open Access Journals (Sweden)

    D. Hayakawa

    2016-11-01

    Full Text Available The dielectric and magnetic properties of electric double layer (EDL capacitor structures with a perpendicularly magnetized Pt/Co/Pt electrode and an insulating cap layer (MgO are investigated. An electric field is applied through a mixed ionic liquid/MgO barrier to the surface of the top Pt layer, at which the magnetic moment is induced by the ferromagnetic proximity effect. The basic dielectric properties of the EDL capacitor are studied by varying the thickness of the MgO cap layer. The results indicate that the capacitance, i.e., the accumulated charge density at the Pt surface, is reduced with increasing the MgO thickness. From the MgO thickness dependence of the capacitance value, the effective dielectric constant of the ionic liquid is evaluated. Almost no electric field effect on the magnetic moment, the coercivity, or the Curie temperature is confirmed in the top Pt layer with the thickness of 1.3 nm, regardless of the presence or absence of the MgO cap layer, whereas the a clear change in the magnetic moment is observed when the top Pt layer is replaced by a Pd layer of 1.7 nm.

  9. Potential Pathways for CNS Drug Delivery Across the Blood-Cerebrospinal Fluid Barrier

    OpenAIRE

    Strazielle, Nathalie; Ghersi-Egea, Jean-Fran?ois

    2016-01-01

    The blood-brain interfaces restrict the cerebral bioavailability of pharmacological compounds. Various drug delivery strategies have been developed to improve drug penetration into the brain. Most strategies target the microvascular endothelium forming the blood-brain barrier proper. Targeting the blood-cerebrospinal fluid (CSF) barrier formed by the epithelium of the choroid plexuses in addition to the blood-brain barrier may offer added-value for the treatment of central nervous system dise...

  10. Electron internal transport barriers and magnetic topology in the stellarator TJ-II

    Energy Technology Data Exchange (ETDEWEB)

    Estrada, T.; Lopez-Bruna, D.; Alosno, A.; Ascasibar, E.; Baciero, A.; Cappa, A.; Castejon, F.; Fernandez, A.; Herranz, J.; Hidalgo, C.; Pablos, J. L. de; Pastor, I.; Sanchez, E.; Sanchez, J.

    2005-07-01

    In most helical systems electron Internal Transport Barriers (e-ITB) are observed in Electron Cyclotron Heated (ECH) plasmas with high heating power density. In the stellarator TJ-II, e- ITBs are easily achievable by positioning a low order rational surface close to the plasma core, because this increases the density range in which the e-ITB can form. Experiments with different low order rationals show a dependence of the threshold density and barrier quality on the order of the rational (3/2, 4/2, 5/3, ...). In addition, during the formation of e-ITB quasicoherent modes are frequently observed in the plasma core region. The mode can exist before or after the e-ITB phenomenon at the radial location of the transport barrier foot but vanishes as the barrier is fully developed. (Author)

  11. Chaotic motion of a harmonically bound charged particle in a magnetic field, in the presence of a half-plane barrier

    NARCIS (Netherlands)

    Geurts, Bernardus J.; Wiegel, F.W.; Creswick, Richard J.

    1991-01-01

    The motion in the plane of an harmonically bound charged particle interacting with a magnetic field and a half-plane barrier along the positive x-axis is studied. The magnetic field is perpendicular to the plane in which the particle moves. This motion is integrable in between collisions of the

  12. On the generalized Hartman effect for symmetric double-barrier point potentials

    International Nuclear Information System (INIS)

    Lee, Molly A; Manzoni, Luiz A; Nyquist, Erik A; Lunardi, José T

    2015-01-01

    We consider the scattering of a non-relativistic particle by a symmetrical arrangement of two identical barriers in one-dimension, with the barriers given by the well-known four-parameter family of point interactions. We calculate the phase time and the stationary Salecker-Wigner-Peres clock time for the particular cases of a double δ and a double δ' barrier and investigate the off-resonance behavior of these time scales in the limit of opaque barriers, addressing the question of emergence of the generalized Hartman effect

  13. [Repetitive transcranial magnetic stimulation: A potential therapy for cognitive disorders?

    Science.gov (United States)

    Nouhaud, C; Sherrard, R M; Belmin, J

    2017-03-01

    Considering the limited effectiveness of drugs treatments in cognitive disorders, the emergence of noninvasive techniques to modify brain function is very interesting. Among these techniques, repetitive transcranial magnetic stimulation (rTMS) can modulate cortical excitability and have potential therapeutic effects on cognition and behaviour. These effects are due to physiological modifications in the stimulated cortical tissue and their associated circuits, which depend on the parameters of stimulation. The objective of this article is to specify current knowledge and efficacy of rTMS in cognitive disorders. Previous studies found very encouraging results with significant improvement of higher brain functions. Nevertheless, these few studies have limits: a few patients were enrolled, the lack of control of the mechanisms of action by brain imaging, insufficiently formalized technique and variability of cognitive tests. It is therefore necessary to perform more studies, which identify statistical significant improvement and to specify underlying mechanisms of action and the parameters of use of the rTMS to offer rTMS as a routine therapy for cognitive dysfunction. Copyright © 2016 Société Nationale Française de Médecine Interne (SNFMI). Published by Elsevier SAS. All rights reserved.

  14. Effect of nanodimensional polyethylenimine layer on surface potential barriers of hybrid structures based on silicon single crystal

    Science.gov (United States)

    Malyar, Ivan V.; Gorin, Dmitry A.; Stetsyura, Svetlana V.

    2013-01-01

    In this report we present the analysis of I-V curves for MIS-structures like silicon substrate / nanodimensional polyelectrolyte layer / metal probe (contact) which is promising for biosensors, microfluidic chips, different devices of molecular electronics, such as OLEDs, solar cells, where polyelectrolyte layers can be used to modify semiconductor surface. The research is directed to investigate the contact phenomena which influence the resulting signal of devices mentioned above. The comparison of I-V characteristics of such structures measured by scanning tunnel microscopy (contactless technique) and using contact areas deposited by thermal evaporation onto the organic layer (the contact one) was carried out. The photoassisted I-V measurements and complex analysis based on Simmons and Schottky models allow one to extract the potential barriers and to observe the changes of charge transport in MIS-structures under illumination and after polyelectrolyte adsorption. The direct correlation between the thickness of the deposited polyelectrolyte layer and both equilibrium tunnel barrier and Schottky barrier height was observed for hybrid structures with polyethylenimine. The possibility of control over the I-V curves of hybrid structure and the height of the potential barriers (for different charge transports) by illumination was confirmed. Based on experimental data and complex analysis the band diagrams were plotted which illustrate the changes of potential barriers for MIS-structures due to the polyelectrolyte adsorption and under the illumination.

  15. Effects of magnetic barriers on transport and magnetoresistance in a two-dimensional electronic device

    Directory of Open Access Journals (Sweden)

    H. L. He

    2016-05-01

    Full Text Available We study theoretically the giant magnetoresistance (GMR effect of 2-dimensional electron system (2DES by the transfer matrix method. To produce the inhomogeneous magnetic field, two magnetic strips are pre-deposited on the surface of 2DES. In our work, we fix the magnetization M in one magnetic strip and adjust the tilting angle θ of magnetization in the other. The result shows that the electronic transmission and conductance vary significantly for different θ. The minimum conductance can be obtained at θ = π which corresponds to the magnetization anti-parallel alignment. The magnetoresistance ratio (MRR calculation also indicates we would get the maximum in that case. Furthermore, we consider the magnetization M dependence of MRR in this work. When M increases, MRR peaks get higher and broader and more numbers of peaks can be observed. These results offer an alternative to get a tunable GMR device which can be controlled by adjusting the magnetization M and the magnetized angle θ.

  16. Retrofitting the Low Impact Development Practices into Developed Urban areas Including Barriers and Potential Solution

    Science.gov (United States)

    Shafique, Muhammad; Kim, Reeho

    2017-06-01

    Low impact development (LID)/green infrastructure (GI) practices have been identified as the sustainable practices of managing the stormwater in urban areas. Due to the increasing population, most of the cities are more developing which results in the change of natural area into impervious areas (roads, buildings etc.). Moreover, urbanization and climate change are causing many water-related problems and making over cities unsafe and insecure. Under these circumstances, there is a need to introduce new stormwater management practices into developed cities to reduce the adverse impacts of urbanization. For this purpose, retrofitting low impact development practices demands more attention to reduce these water-related problems and trying to make our cities sustainable. In developed areas, there is a little space is available for the retrofitting of LID practices for the stormwater management. Therefore, the selection of an appropriate place to retrofitting LID practices needs more concern. This paper describes the successfully applied retrofitting LID practices around the globe. It also includes the process of applying retrofitting LID practices at the suitable place with the suitable combination. Optimal places for the retrofitting of different LID practices are also mentioned. This paper also highlights the barriers and potential solutions of retrofitting LID practices in urban areas.

  17. Retrofitting the Low Impact Development Practices into Developed Urban areas Including Barriers and Potential Solution

    Directory of Open Access Journals (Sweden)

    Shafique Muhammad

    2017-06-01

    Full Text Available Low impact development (LID/green infrastructure (GI practices have been identified as the sustainable practices of managing the stormwater in urban areas. Due to the increasing population, most of the cities are more developing which results in the change of natural area into impervious areas (roads, buildings etc.. Moreover, urbanization and climate change are causing many water-related problems and making over cities unsafe and insecure. Under these circumstances, there is a need to introduce new stormwater management practices into developed cities to reduce the adverse impacts of urbanization. For this purpose, retrofitting low impact development practices demands more attention to reduce these water-related problems and trying to make our cities sustainable. In developed areas, there is a little space is available for the retrofitting of LID practices for the stormwater management. Therefore, the selection of an appropriate place to retrofitting LID practices needs more concern. This paper describes the successfully applied retrofitting LID practices around the globe. It also includes the process of applying retrofitting LID practices at the suitable place with the suitable combination. Optimal places for the retrofitting of different LID practices are also mentioned. This paper also highlights the barriers and potential solutions of retrofitting LID practices in urban areas.

  18. Practical Aspects of Suspension Plasma Spray for Thermal Barrier Coatings on Potential Gas Turbine Components

    Science.gov (United States)

    Ma, X.; Ruggiero, P.

    2018-04-01

    Suspension plasma spray (SPS) process has attracted extensive efforts and interests to produce fine-structured and functional coatings. In particular, thermal barrier coatings (TBCs) applied by SPS process gain increasing interest due to its potential for superior thermal protection of gas turbine hot sections as compared to conventional TBCs. Unique columnar architectures and nano- and submicrometric grains in the SPS-TBC demonstrated some advantages of thermal shock durability, low thermal conductivity, erosion resistance and strain-tolerant microstructure. This work aimed to look into some practical aspects of SPS processing for TBC applications before it becomes a reliable industry method. The spray capability and applicability of SPS process to achieve uniformity thickness and microstructure on curved substrates were emphasized in designed spray trials to simulate the coating fabrication onto industrial turbine parts with complex configurations. The performances of the SPS-TBCs were tested in erosion, falling ballistic impact and indentational loading tests as to evaluate SPS-TBC performances in simulated turbine service conditions. Finally, a turbine blade was coated and sectioned to verify SPS sprayability in multiple critical sections. The SPS trials and test results demonstrated that SPS process is promising for innovative TBCs, but some challenges need to be addressed and resolved before it becomes an economic and capable industrial process, especially for complex turbine components.

  19. Binding of higher alcohols onto Mn(12) single-molecule magnets (SMMs): access to the highest barrier Mn(12) SMM.

    Science.gov (United States)

    Lampropoulos, Christos; Redler, Gage; Data, Saiti; Abboud, Khalil A; Hill, Stephen; Christou, George

    2010-02-15

    Two new members of the Mn(12) family of single-molecule magnets (SMMs), [Mn(12)O(12)(O(2)CCH(2)Bu(t))(16)(Bu(t)OH)(H(2)O)(3)].2Bu(t)OH (3.2Bu(t)OH) and [Mn(12)O(12)(O(2)CCH(2)Bu(t))(16)(C(5)H(11)OH)(4)] (4) (C(5)H(11)OH is 1-pentanol), are reported. They were synthesized from [Mn(12)O(12)(O(2)CMe)(16)(H(2)O)(4)].2MeCO(2)H.4H(2)O (1) by carboxylate substitution and crystallization from the appropriate alcohol-containing solvent. Complexes 3 and 4 are new members of the recently established [Mn(12)O(12)(O(2)CCH(2)Bu(t))(16)(solv)(4)] (solv = H(2)O, alcohols) family of SMMs. Only one bulky Bu(t)OH can be accommodated into 3, and even this causes significant distortion of the [Mn(12)O(12)] core. Variable-temperature, solid-state alternating current (AC) magnetization studies were carried out on complexes 3 and 4, and they established that both possess an S = 10 ground state spin and are SMMs. However, the magnetic behavior of the two compounds was found to be significantly different, with 4 showing out-of-phase AC peaks at higher temperatures than 3. High-frequency electron paramagnetic resonance (HFEPR) studies were carried out on single crystals of 3.2Bu(t)OH and 4, and these revealed that the axial zero-field splitting constant, D, is very different for the two compounds. Furthermore, it was established that 4 is the Mn(12) SMM with the highest kinetic barrier (U(eff)) to date. The results reveal alcohol substitution as an additional and convenient means to affect the magnetization relaxation barrier of the Mn(12) SMMs without major change to the ligation or oxidation state.

  20. Magnetophoretic potential at the movement of cluster products of electrochemical reactions in an inhomogeneous magnetic field

    International Nuclear Information System (INIS)

    Gorobets, O. Yu.; Gorobets, Yu. I.; Rospotniuk, V. P.

    2015-01-01

    An electric field arises from the influence of a nonuniform static magnetic field on charged colloid particles with magnetic susceptibility different from that of the surrounding liquid. It arises, for example, under the influence of a nonuniform static magnetic field in clusters of electrochemical reaction products created during metal etching, deposition, and corrosion processes without an external electric current passing through an electrolyte near a magnetized electrode surface. The corresponding potential consists of a Nernst potential of inhomogeneous distribution of concentration of colloid particles and a magnetophoretic potential (MPP). This potential has been calculated using a thermodynamic approach based on the equations of thermodynamics of nonequilibrium systems and the Onsager relations for a mass flow of correlated magnetic clusters under a gradient magnetic force in the electrolyte. The conditions under which the MPP contribution to the total electric potential may be significant are discussed with a reference to the example of a corroding spherical ferromagnetic steel electrode

  1. Magnetophoretic potential at the movement of cluster products of electrochemical reactions in an inhomogeneous magnetic field

    Energy Technology Data Exchange (ETDEWEB)

    Gorobets, O. Yu., E-mail: pitbm@ukr.net; Gorobets, Yu. I., E-mail: Gorobets@imag.kiev.ua [National Technical University of Ukraine “KPI”, Peremogy Avenue 37, Kyiv 03056 (Ukraine); Institute of Magnetism NAS of Ukraine and National Academy of Sciences of Ukraine, Vernadsky Avenue, 36-b, Kyiv 03142 (Ukraine); Rospotniuk, V. P. [National Technical University of Ukraine “KPI”, Peremogy Avenue 37, Kyiv 03056 (Ukraine)

    2015-08-21

    An electric field arises from the influence of a nonuniform static magnetic field on charged colloid particles with magnetic susceptibility different from that of the surrounding liquid. It arises, for example, under the influence of a nonuniform static magnetic field in clusters of electrochemical reaction products created during metal etching, deposition, and corrosion processes without an external electric current passing through an electrolyte near a magnetized electrode surface. The corresponding potential consists of a Nernst potential of inhomogeneous distribution of concentration of colloid particles and a magnetophoretic potential (MPP). This potential has been calculated using a thermodynamic approach based on the equations of thermodynamics of nonequilibrium systems and the Onsager relations for a mass flow of correlated magnetic clusters under a gradient magnetic force in the electrolyte. The conditions under which the MPP contribution to the total electric potential may be significant are discussed with a reference to the example of a corroding spherical ferromagnetic steel electrode.

  2. 2D Analytical Modeling of Magnetic Vector Potential in Surface Mounted and Surface Inset Permanent Magnet Machines

    Directory of Open Access Journals (Sweden)

    A. Jabbari

    2017-12-01

    Full Text Available A 2D analytical method for magnetic vector potential calculation in inner rotor surface mounted and surface inset permanent magnet machines considering slotting effects, magnetization orientation and winding layout has been proposed in this paper. The analytical method is based on the resolution of Laplace and Poisson equations as well as Maxwell equation in quasi- Cartesian coordinate by using sub-domain method and hyperbolic functions. The developed method is applied on the performance computation of two prototypes surface mounted permanent magnet motors and two prototypes surface inset permanent magnet motors. A radial and a parallel magnetization orientation is considered for each type of motor. The results of these models are validated through FEM method.

  3. Diuron tolerance and potential degradation by pelagic microbiomes in the Great Barrier Reef lagoon

    Directory of Open Access Journals (Sweden)

    Florent E. Angly

    2016-03-01

    Full Text Available Diuron is a herbicide commonly used in agricultural areas where excess application causes it to leach into rivers, reach sensitive marine environments like the Great Barrier Reef (GBR lagoon and pose risks to marine life. To investigate the impact of diuron on whole prokaryotic communities that underpin the marine food web and are integral to coral reef health, GBR lagoon water was incubated with diuron at environmentally-relevant concentration (8 µg/L, and sequenced at specific time points over the following year. 16S rRNA gene amplicon profiling revealed no significant short- or long-term effect of diuron on microbiome structure. The relative abundance of prokaryotic phototrophs was not significantly altered by diuron, which suggests that they were largely tolerant at this concentration. Assembly of a metagenome derived from waters sampled at a similar location in the GBR lagoon did not reveal the presence of mutations in the cyanobacterial photosystem that could explain diuron tolerance. However, resident phages displayed several variants of this gene and could potentially play a role in tolerance acquisition. Slow biodegradation of diuron was reported in the incubation flasks, but no correlation with the relative abundance of heterotrophs was evident. Analysis of metagenomic reads supports the hypothesis that previously uncharacterized hydrolases carried by low-abundance species may mediate herbicide degradation in the GBR lagoon. Overall, this study offers evidence that pelagic phototrophs of the GBR lagoon may be more tolerant of diuron than other tropical organisms, and that heterotrophs in the microbial seed bank may have the potential to degrade diuron and alleviate local anthropogenic stresses to inshore GBR ecosystems.

  4. Diuron tolerance and potential degradation by pelagic microbiomes in the Great Barrier Reef lagoon

    Science.gov (United States)

    Pantos, Olga; Morgan, Thomas C.; Rich, Virginia; Tonin, Hemerson; Bourne, David G.; Mercurio, Philip; Negri, Andrew P.; Tyson, Gene W.

    2016-01-01

    Diuron is a herbicide commonly used in agricultural areas where excess application causes it to leach into rivers, reach sensitive marine environments like the Great Barrier Reef (GBR) lagoon and pose risks to marine life. To investigate the impact of diuron on whole prokaryotic communities that underpin the marine food web and are integral to coral reef health, GBR lagoon water was incubated with diuron at environmentally-relevant concentration (8 µg/L), and sequenced at specific time points over the following year. 16S rRNA gene amplicon profiling revealed no significant short- or long-term effect of diuron on microbiome structure. The relative abundance of prokaryotic phototrophs was not significantly altered by diuron, which suggests that they were largely tolerant at this concentration. Assembly of a metagenome derived from waters sampled at a similar location in the GBR lagoon did not reveal the presence of mutations in the cyanobacterial photosystem that could explain diuron tolerance. However, resident phages displayed several variants of this gene and could potentially play a role in tolerance acquisition. Slow biodegradation of diuron was reported in the incubation flasks, but no correlation with the relative abundance of heterotrophs was evident. Analysis of metagenomic reads supports the hypothesis that previously uncharacterized hydrolases carried by low-abundance species may mediate herbicide degradation in the GBR lagoon. Overall, this study offers evidence that pelagic phototrophs of the GBR lagoon may be more tolerant of diuron than other tropical organisms, and that heterotrophs in the microbial seed bank may have the potential to degrade diuron and alleviate local anthropogenic stresses to inshore GBR ecosystems. PMID:26989611

  5. Diuron tolerance and potential degradation by pelagic microbiomes in the Great Barrier Reef lagoon.

    Science.gov (United States)

    Angly, Florent E; Pantos, Olga; Morgan, Thomas C; Rich, Virginia; Tonin, Hemerson; Bourne, David G; Mercurio, Philip; Negri, Andrew P; Tyson, Gene W

    2016-01-01

    Diuron is a herbicide commonly used in agricultural areas where excess application causes it to leach into rivers, reach sensitive marine environments like the Great Barrier Reef (GBR) lagoon and pose risks to marine life. To investigate the impact of diuron on whole prokaryotic communities that underpin the marine food web and are integral to coral reef health, GBR lagoon water was incubated with diuron at environmentally-relevant concentration (8 µg/L), and sequenced at specific time points over the following year. 16S rRNA gene amplicon profiling revealed no significant short- or long-term effect of diuron on microbiome structure. The relative abundance of prokaryotic phototrophs was not significantly altered by diuron, which suggests that they were largely tolerant at this concentration. Assembly of a metagenome derived from waters sampled at a similar location in the GBR lagoon did not reveal the presence of mutations in the cyanobacterial photosystem that could explain diuron tolerance. However, resident phages displayed several variants of this gene and could potentially play a role in tolerance acquisition. Slow biodegradation of diuron was reported in the incubation flasks, but no correlation with the relative abundance of heterotrophs was evident. Analysis of metagenomic reads supports the hypothesis that previously uncharacterized hydrolases carried by low-abundance species may mediate herbicide degradation in the GBR lagoon. Overall, this study offers evidence that pelagic phototrophs of the GBR lagoon may be more tolerant of diuron than other tropical organisms, and that heterotrophs in the microbial seed bank may have the potential to degrade diuron and alleviate local anthropogenic stresses to inshore GBR ecosystems.

  6. What do patients choose to tell their doctors? Qualitative analysis of potential barriers to reattributing medically unexplained symptoms.

    Science.gov (United States)

    Peters, Sarah; Rogers, Anne; Salmon, Peter; Gask, Linda; Dowrick, Chris; Towey, Maria; Clifford, Rebecca; Morriss, Richard

    2009-04-01

    Despite both parties often expressing dissatisfaction with consultations, patients with medically unexplained symptoms (MUS) prefer to consult their general practitioners (GPs) rather than any other health professional. Training GPs to explain how symptoms can relate to psychosocial problems (reattribution) improves the quality of doctor-patient communication, though not necessarily patient health. To examine patient experiences of GPs' attempts to reattribute MUS in order to identify potential barriers to primary care management of MUS and improvement in outcome. Qualitative study. Patients consulting with MUS whose GPs had been trained in reattribution. A secondary sample of patients of control GPs was also interviewed to ascertain if barriers identified were specific to reattribution or common to consultations about MUS in general. Thematic analysis of in-depth interviews. Potential barriers include the complexity of patients' problems and patients' judgements about how to manage their presentation of this complexity. Many did not trust doctors with discussion of emotional aspects of their problems and chose not to present them. The same barriers were seen amongst patients whose GPs were not trained, suggesting the barriers are not particular to reattribution. Improving GP explanation of unexplained symptoms is insufficient to reduce patients' concerns. GPs need to (1) help patients to make sense of the complex nature of their presenting problems, (2) communicate that attention to psychosocial factors will not preclude vigilance to physical disease and (3) ensure a quality of doctor-patient relationship in which patients can perceive psychosocial enquiry as appropriate.

  7. Scattering of a two skyrmion configuration on potential holes or barriers in a model Landau-Lifshitz equation

    International Nuclear Information System (INIS)

    Collins, J C; Zakrzewski, W J

    2009-01-01

    The dynamics of a baby-skyrmion configuration, in a model Landau-Lifshitz equation, was studied in the presence of various potential obstructions. The baby-skyrmion configuration was constructed from two Q = 1 hedgehog solutions to the baby-skyrme model in (2+1) dimensions. The potential obstructions were created by introducing a new term into the Lagrangian which resulted in a localized inhomogeneity in the potential terms' coefficient. In the barrier system, the normal circular path was deformed as the skyrmions traversed the barrier. During the same period, it was seen that the skyrmions sped up as they went over the barrier. For critical values of the barrier height and width, the skyrmions were no longer bound and were free to separate. In the case of a potential hole, the baby skyrmions no longer formed a bound state and moved asymptotically along the axis of the hole. It is shown how to modify the definition of the angular momentum to include the effects of the obstructions, so that it is conserved

  8. Quantum tunneling time of a Bose-Einstein condensate traversing through a laser-induced potential barrier

    International Nuclear Information System (INIS)

    Duan Zhenglu; Fan Bixuan; Yuan Chunhua; Zhang Weiping; Cheng Jing; Zhu Shiyao

    2010-01-01

    We theoretically study the effect of atomic nonlinearity on the tunneling time in the case of an atomic Bose-Einstein condensate (BEC) traversing the laser-induced potential barrier. The atomic nonlinearity is controlled to appear only in the region of the barrier by employing the Feshbach resonance technique to tune interatomic interaction in the tunneling process. Numerical simulation shows that the atomic nonlinear effect dramatically changes the tunneling behavior of the BEC matter wave packet and results in the violation of the Hartman effect and the occurrence of negative tunneling time.

  9. Uses and evaluation methods of potential hydrogen permeation barriers for nuclear reactor materials

    International Nuclear Information System (INIS)

    Noga, J.O.; Piercy, G.R.; Bowker, J.T.

    1985-07-01

    This report summarizes results on the use of coatings as hydrogen permeation barriers on nuclear reactor component materials. Two classes of base materials were considered, exothermic hydrogen absorbers and endothermic hydrogen absorbers. The results of the tests indicate that substantial reductions in the amount of hydrogen absorbed by a metal can be achieved through the use of hydrogen permeation barrier coatings. Gold was determined to provide an effective hydrogen permeation barrier on Zr-2-1/2 Nb pressure tube material. Tin was determined to be a suitable hydrogen permeation barrier when applied on AISI 410 stainless steel and iron. Both gas phase and electrochemical permeation techniques were used to determine hydrogen permeabilities through coatings and base materials

  10. MAGNETIC BACTERIA AND THEIR POTENTIAL APPLICATIONS: A REVIEW ARTICLE

    Directory of Open Access Journals (Sweden)

    Sara Rajab Eljmeli

    2017-03-01

    Full Text Available Introduction: This outline explores the scientific discovery concerning the magnetotactic bacteria (MTB. The results of the discovery are used in microbiology, mineralogy, limnology, physics, biophysics, chemistry, biochemistry, geology, crystallography, and astrobiology. Magnetosomes of the MTB are organized in linear chains and orient the cell body along geomagnetic field lines while flagella actively propel the cells, resulting in so-called magnetotaxis. Materials and Methods: The review article about the magnetotactic bacteria is a collection of many research papers from different institutes. The emerging important points about this review lie in: (1 any biological system is capable of producing magnetic biomaterials such as magnetite (Fe3O4 and gregite (Fe3S4; (2 the navigation of these nano-crystals in the biological system is interconnected with the Earth’s magnetic field. Results: The researchers involved in the study have shown that the magnetotactic bacteria do respond to a magnetic field. This makes them attractive for biomedical and industrial applications because of the availability of superior electromagnets, superconducting magnets and permanent magnet. Magnetic bacteria can also be used as a diagnostic tool in the detection of imperfections even at the nanoscale. Discussion and Conclusions: Although the importance of this issue is still limitedly used in medical area, more performance is necessary to explore the world of these bacteria that are candidate for new industry and new therapy strategies in biotechnology and medical fields.

  11. Transcranial magnetic stimulation potentiates glutamatergic neurotransmission in depressed adolescents.

    Science.gov (United States)

    Croarkin, Paul E; Nakonezny, Paul A; Wall, Christopher A; Murphy, Lauren L; Sampson, Shirlene M; Frye, Mark A; Port, John D

    2016-01-30

    Abnormalities in glutamate neurotransmission may have a role in the pathophysiology of adolescent depression. The present pilot study examined changes in cortical glutamine/glutamate ratios in depressed adolescents receiving high-frequency repetitive transcranial magnetic stimulation. Ten adolescents with treatment-refractory major depressive disorder received up to 30 sessions of 10-Hz repetitive transcranial magnetic stimulation at 120% motor threshold with 3000 pulses per session applied to the left dorsolateral prefrontal cortex. Baseline, posttreatment, and 6-month follow-up proton magnetic resonance spectroscopy scans of the anterior cingulate cortex and left dorsolateral prefrontal cortex were collected at 3T with 8-cm(3) voxels. Glutamate metabolites were quantified with 2 distinct proton magnetic resonance spectroscopy sequences in each brain region. After repetitive transcranial magnetic stimulation and at 6 months of follow-up, glutamine/glutamate ratios increased in the anterior cingulate cortex and left dorsolateral prefrontal cortex with both measurements. The increase in the glutamine/glutamate ratio reached statistical significance with the TE-optimized PRESS sequence in the anterior cingulate cortex. Glutamine/glutamate ratios increased in conjunction with depressive symptom improvement. This reached statistical significance with the TE-optimized PRESS sequence in the left dorsolateral prefrontal cortex. High-frequency repetitive transcranial magnetic stimulation applied to the left dorsolateral prefrontal cortex may modulate glutamate neurochemistry in depressed adolescents. Copyright © 2015 Elsevier Ireland Ltd. All rights reserved.

  12. Mode suppression of a two-dimensional potential relaxation instability in a weakly magnetized discharge plasma

    Science.gov (United States)

    Gyergyek, T.; Čerček, M.; Jelić, N.; Stanojević, M.

    1993-05-01

    A potential relaxation instability (PRI) is modulated by an external signal using an additional grid to modulate the radial plasma potential profile in a magnetized plasma column in a linear magnetized discharge plasma device. It is observed that the electrode current oscillations follow the van der Pol equation with an external forcing term, and the linear growth rate of the instability is measured.

  13. Potential and barriers for biogas production in Denmark at widely expanded organic farming with focus on the soil carbon content; Potentiale og barrierer for biogasproduktion i Danmark ved omfattende oekologisk jordbrug med fokus paa dyrkningsjordens kulstofforhold

    Energy Technology Data Exchange (ETDEWEB)

    Buch Salomonsen, K.

    2000-06-01

    The Ph.D. thesis describes the influence from continued expansion of organic farming systems to the potential for energy production from biogas in Denmark. The project analyses the consequence from three categories of barriers: 1) Practical barriers, 2) The attitude of organic farmers, and 3) Agricultural biological problems. Economic and political barriers are not examined. When the barriers can be quantified, they are included in the calculation of the maximum biogas potential. When not, the implications of barriers are expressed qualitatively. It has been a particular goal to provide new information on whether agricultural biological problems are a barrier to biogas production in organic farming systems. One important question in this connection is whether biogas production has a negative influence on the soil carbon content compared to composting. This question is investigated by an experiment. The project is based on technical and natural science disciplines, with an interdisciplinary basis ranging over energy planning, agricultural science, microbiology, and crop, and animal operation. (au)

  14. Multi-layered Chalcogenides with potential for magnetism and superconductivity

    Energy Technology Data Exchange (ETDEWEB)

    Li, Li, E-mail: lil2@ornl.gov [Materials Science & Technology Division, Oak Ridge National Laboratory, Oak Ridge, TN 37831 (United States); Parker, David S. [Materials Science & Technology Division, Oak Ridge National Laboratory, Oak Ridge, TN 37831 (United States); Cruz, Clarina R. dela [Quantum Condensed Matter Division, Oak Ridge National Laboratory, Oak Ridge, TN 37831 (United States); Sefat, Athena S., E-mail: sefata@ornl.gov [Materials Science & Technology Division, Oak Ridge National Laboratory, Oak Ridge, TN 37831 (United States)

    2016-12-15

    Highlights: • A comprehensive study on multi-layered thallium copper chalcogenides TlCu{sub 2n}Ch{sub n+1}. • All the TlCu{sub 2n}Ch{sub n+1} exhibit metallic behaviors with no long-range magnetism. • Calculations suggest a lack of Fermi-level spectral weight for magnetic instability. • Our results suggest a likelihood of magnetism for multiple structural layers with Fe. - Abstract: Layered thallium copper chalcogenides can form single, double, or triple layers of Cu–Ch separated by Tl sheets. Here we report on the preparation and properties of Tl-based materials of TlCu{sub 2}Se{sub 2}, TlCu{sub 4}S{sub 3}, TlCu{sub 4}Se{sub 3} and TlCu{sub 6}S{sub 4}. Having no long-range magnetism for these materials is quite surprising considering the possibilities of inter- and intra-layer exchange interactions through Cu 3d, and we measure by magnetic susceptibility and confirm by neutron diffraction. First principles density-functional theory calculations for both the single-layer TlCu{sub 2}Se{sub 2} (isostructural to the ‘122’ iron-based superconductors) and the double-layer TlCu{sub 4}Se{sub 3} suggest a lack of Fermi-level spectral weight that is needed to drive a magnetic or superconducting instability. However, for multiple structural layers with Fe, there is much greater likelihood for magnetism and superconductivity.

  15. Edible moisture barriers: how to assess of their potential and limits in food products shelf-life extension?

    Science.gov (United States)

    Bourlieu, C; Guillard, V; Vallès-Pamiès, B; Guilbert, S; Gontard, N

    2009-05-01

    Control of moisture transfer inside composite food products or between food and its environment remains today a major challenge in food preservation. A wide rage of film-forming compounds is now available and facilitates tailoring moisture barriers with optimized functional properties. Despite these huge potentials, a realistic assessment of the film or coating efficacy is still critical. Due to nonlinear water sorption isotherms, water-dependent diffusivities, and variations of physical state, modelling transport phenomena through edible barriers is complex. Water vapor permeability can hardly be considered as an inherent property of films and only gives a relative indication of the barrier efficacy. The formal or mechanistic models reported in literature that describe the influence of testing conditions on the barrier properties of edible films are reviewed and discussed. Most of these models have been validated on a narrow range of conditions. Conversely, few original predictive models based on Fick's Second Law have been developed to assess shelf-life extension of food products including barriers. These models, assuming complex and realistic hypothesis, have been validated in various model foods. The development of nondestructive methods of moisture content measurement should speed up model validation and allow a better comprehension of moisture transfer through edible films.

  16. Dirac and non-Dirac conditions in the two-potential theory of magnetic charge

    Science.gov (United States)

    Scott, John; Evans, Timothy J.; Singleton, Douglas; Dzhunushaliev, Vladimir; Folomeev, Vladimir

    2018-05-01

    We investigate the Cabbibo-Ferrari, two-potential approach to magnetic charge coupled to two different complex scalar fields, Φ _1 and Φ _2, each having different electric and magnetic charges. The scalar field, Φ _1, is assumed to have a spontaneous symmetry breaking self-interaction potential which gives a mass to the "magnetic" gauge potential and "magnetic" photon, while the other "electric" gauge potential and "electric" photon remain massless. The magnetic photon is hidden until one reaches energies of the order of the magnetic photon rest mass. The second scalar field, Φ _2, is required in order to make the theory non-trivial. With only one field one can always use a duality rotation to rotate away either the electric or magnetic charge, and thus decouple either the associated electric or magnetic photon. In analyzing this system of two scalar fields in the Cabbibo-Ferrari approach we perform several duality and gauge transformations, which require introducing non-Dirac conditions on the initial electric and magnetic charges. We also find that due to the symmetry breaking the usual Dirac condition is altered to include the mass of the magnetic photon. We discuss the implications of these various conditions on the charges.

  17. Potential interference of small neodymium magnets with cardiac pacemakers and implantable cardioverter-defibrillators.

    Science.gov (United States)

    Wolber, Thomas; Ryf, Salome; Binggeli, Christian; Holzmeister, Johannes; Brunckhorst, Corinna; Luechinger, Roger; Duru, Firat

    2007-01-01

    Magnetic fields may interfere with the function of cardiac pacemakers and implantable cardioverter-defibrillators (ICDs). Neodymium-iron-boron (NdFeB) magnets, which are small in size but produce strong magnetic fields, have become widely available in recent years. Therefore, NdFeB magnets may be associated with an emerging risk of device interference. We conducted a clinical study to evaluate the potential of small NdFeB magnets to interfere with cardiac pacemakers and ICDs. The effect of four NdFeB magnets (two spherical magnets 8 and 10 mm in diameter, a necklace made of 45 spherical magnets, and a magnetic name tag) was tested in forty-one ambulatory patients with a pacemaker and 29 patients with an ICD. The maximum distance at which the magnetic switch of a device was influenced was observed. Magnetic interference was observed in all patients. The maximum distance resulting in device interference was 3 cm. No significant differences were found with respect to device manufacturer and device types. Small NdFeB magnets may cause interference with cardiac pacemakers and ICDs. Patients should be cautioned about the interference risk associated with NdFeB magnets during daily life.

  18. Tuning anisotropy barriers in a family of tetrairon(III) single-molecule magnets with an S = 5 ground state.

    Science.gov (United States)

    Accorsi, Stefania; Barra, Anne-Laure; Caneschi, Andrea; Chastanet, Guillaume; Cornia, Andrea; Fabretti, Antonio C; Gatteschi, Dante; Mortalo, Cecilia; Olivieri, Emiliano; Parenti, Francesca; Rosa, Patrick; Sessoli, Roberta; Sorace, Lorenzo; Wernsdorfer, Wolfgang; Zobbi, Laura

    2006-04-12

    Tetrairon(III) Single-Molecule Magnets (SMMs) with a propeller-like structure exhibit tuneable magnetic anisotropy barriers in both height and shape. The clusters [Fe4(L1)2(dpm)6] (1), [Fe4(L2)2(dpm)6] (2), [Fe4(L3)2(dpm)6].Et2O (3.Et2O), and [Fe4(OEt)3(L4)(dpm)6] (4) have been prepared by reaction of [Fe4(OMe)6(dpm)6] (5) with tripodal ligands R-C(CH2OH)3 (H3L1, R = Me; H3L2, R = CH2Br; H3L3, R = Ph; H3L4, R = tBu; Hdpm = dipivaloylmethane). The iron(III) ions exhibit a centered-triangular topology and are linked by six alkoxo bridges, which propagate antiferromagnetic interactions resulting in an S = 5 ground spin state. Single crystals of 4 reproducibly contain at least two geometric isomers. From high-frequency EPR studies, the axial zero-field splitting parameter (D) is invariably negative, as found in 5 (D = -0.21 cm(-1)) and amounts to -0.445 cm(-1) in 1, -0.432 cm(-1) in 2, -0.42 cm(-1) in 3.Et2O, and -0.27 cm(-1) in 4 (dominant isomer). The anisotropy barrier Ueff determined by AC magnetic susceptibility measurements is Ueff/kB = 17.0 K in 1, 16.6 K in 2, 15.6 K in 3.Et2O, 5.95 K in 4, and 3.5 K in 5. Both |D| and U(eff) are found to increase with increasing helical pitch of the Fe(O2Fe)3 core. The fourth-order longitudinal anisotropy parameter B4(0), which affects the shape of the anisotropy barrier, concomitantly changes from positive in 1 ("compressed parabola") to negative in 5 ("stretched parabola"). With the aid of spin Hamiltonian calculations the observed trends have been attributed to fine modulation of single-ion anisotropies induced by a change of helical pitch.

  19. Potential Success and Barrier Factors for Implementation of the Transition to Independence (TIP Model

    Directory of Open Access Journals (Sweden)

    Christopher M. Kalinyak

    2017-01-01

    Full Text Available In this qualitative study, 28 key stakeholders who work with transition-aged youth participated in focus group discussions addressing success and barrier factors regarding implementation of a transition to independence process (TIP program for youth, ages 14–29, in three Midwestern cities. All participants had prior knowledge of TIP. The paradigm shift to client-oriented goals and services was acknowledged by respondents as the prime benefit of TIP; youth are more motivated to follow through on self-determined goals. Barrier factors for providers involved collaboration with agencies adhering to provider-oriented interventions, provision of TIP methods training, and reallocation of time and money. Barrier factors for youth involved mistrust of service providers, overcoming maturational deficits, and acquiring and maintaining relationships, reputations, and social supports.

  20. Potential Pathways for CNS Drug Delivery Across the Blood-Cerebrospinal Fluid Barrier

    Science.gov (United States)

    Strazielle, Nathalie; Ghersi-Egea, Jean-François

    2016-01-01

    The blood-brain interfaces restrict the cerebral bioavailability of pharmacological compounds. Various drug delivery strategies have been developed to improve drug penetration into the brain. Most strategies target the microvascular endothelium forming the blood-brain barrier proper. Targeting the blood-cerebrospinal fluid (CSF) barrier formed by the epithelium of the choroid plexuses in addition to the blood-brain barrier may offer added-value for the treatment of central nervous system diseases. For instance, targeting the CSF spaces, adjacent tissue, or the choroid plexuses themselves is of interest for the treatment of neuroinflammatory and infectious diseases, cerebral amyloid angiopathy, selected brain tumors, hydrocephalus or neurohumoral dysregulation. Selected CSF-borne materials seem to reach deep cerebral structures by mechanisms that need to be understood in the context of chronic CSF delivery. Drug delivery through both barriers can reduce CSF sink action towards parenchymal drugs. Finally, targeting the choroid plexus-CSF system can be especially relevant in the context of neonatal and pediatric diseases of the central nervous system. Transcytosis appears the most promising mechanism to target in order to improve drug delivery through brain barriers. The choroid plexus epithelium displays strong vesicular trafficking and secretory activities that deserve to be explored in the context of cerebral drug delivery. Folate transport and exosome release into the CSF, plasma protein transport, and various receptor-mediated endocytosis pathways may prove useful mechanisms to exploit for efficient drug delivery into the CSF. This calls for a clear evaluation of transcytosis mechanisms at the blood-CSF barrier, and a thorough evaluation of CSF drug delivery rates. PMID:27464721

  1. Evaluation of the potential of PV noise barrier technology for electricity production and market share. Final report

    International Nuclear Information System (INIS)

    Goetzberger, A.; Kleiss, G.; Castello, S.; Hille, G.; Reise, C.; Wiemken, E.; Betcke, J.W.H.; Van Dijk, V.A.P.; Pearsall, N.; Hynes, K.; Gaidddon, B.; Nordmann, T.; Froelich, A.

    1999-06-01

    The analysis of existing and planned noise barriers along rails and roads has been carried out by the national partners together with national authorities, which are experts and responsible for the required data. The methodical approach of this study includes the set-up of a grid along longitude and latitudes with 1 by 1 degrees for Germany, Italy, France, United Kingdom and 0.5 by 0.5 degrees for the Netherlands and Switzerland. For each degree the length and orientation of rails and roads, the existing and planned noise barriers are registered and grouped according to their orientations. The solar radiation is based on data of a METEONORM data set. This includes the solar radiation on horizontal orientation as well as various inclination angles for all possible orientations. Moreover, possible shading has been considered. The technical specifications of noise barriers (PVNB) are based on the comprehensive knowledge of TNC GmbH and TNC AG with various plants realised. Technologies have been considered for both state-of-the-art and innovative concepts such as bifacial PVNB. In bifacial PVNB the PV-module is mounted vertically on both sides and is used at the same time as noise reflecting material. Installed PV power and produced electricity have been calculated for: 1. theoretical potential 2. technical potential 3. short-term resp. European extrapolated potential 4. anticipated potential 5. EU-member assessment The result of this study confirms the current activities to implement PV on noise barriers as an important share in the PV market.The report is subdivided into two volumes: Volume 1 contains the main topics and results, and Volume 2 contains additional information on the solar radiation, typical concepts as an excerpt of the various potentials and all country maps with the required explanations. 95 refs

  2. Thermally assisted interlayer magnetic coupling through Ba_0_._0_5Sr_0_._9_5TiO_3 barriers

    International Nuclear Information System (INIS)

    Carreira, Santiago J.; Steren, Laura B.; Avilés Félix, Luis; Alejandro, Gabriela; Sirena, Martín

    2016-01-01

    We report on the interlayer exchange coupling across insulating barriers observed on Ni_8_0Fe_2_0/Ba_0_._0_5Sr_0_._9_5TiO_3/La_0_._6_6Sr_0_._3_3MnO_3 (Py/BST_0_._0_5/LSMO) trilayers. The coupling mechanism has been analyzed in terms of the barrier thickness, samples' substrate, and temperature. We examined the effect of MgO (MGO) and SrTiO_3 (STO) (001) single-crystalline substrates on the magnetic coupling and also on the magnetic anisotropies of the samples in order to get a deeper understanding of the magnetism of the structures. We measured a weak coupling mediated by spin-dependent tunneling phenomena whose sign and strength depend on barrier thickness and substrate. An antiferromagnetic (AF) exchange prevails for most of the samples and smoothly increases with the barrier thicknesses as a consequence of the screening effects of the BST_0_._0_5. The coupling monotonically increases with temperature in all the samples and this behavior is attributed to thermally assisted mechanisms. The magnetic anisotropy of both magnetic components has a cubic symmetry that in the case of permalloy is added to a small uniaxial component.

  3. Thermally assisted interlayer magnetic coupling through Ba{sub 0.05}Sr{sub 0.95}TiO{sub 3} barriers

    Energy Technology Data Exchange (ETDEWEB)

    Carreira, Santiago J.; Steren, Laura B. [Centro Atómico Constituyentes, San Martín, Buenos Aires 1650 (Argentina); Consejo Nacional de Investigaciones Científicas y Técnicas, Ciudad Autonoma de Buenos Aires C1425FQB (Argentina); Avilés Félix, Luis; Alejandro, Gabriela [Consejo Nacional de Investigaciones Científicas y Técnicas, Ciudad Autonoma de Buenos Aires C1425FQB (Argentina); Centro Atómico Bariloche, Bariloche, Rio Negro 8400 (Argentina); Sirena, Martín [Consejo Nacional de Investigaciones Científicas y Técnicas, Ciudad Autonoma de Buenos Aires C1425FQB (Argentina); Centro Atómico Bariloche, Bariloche, Rio Negro 8400 (Argentina); Instituto Balseiro-CNEA & Univ. Nac. de Cuyo, Bariloche, Rio Negro 8400 (Argentina)

    2016-08-08

    We report on the interlayer exchange coupling across insulating barriers observed on Ni{sub 80}Fe{sub 20}/Ba{sub 0.05}Sr{sub 0.95}TiO{sub 3}/La{sub 0.66}Sr{sub 0.33}MnO{sub 3} (Py/BST{sub 0.05}/LSMO) trilayers. The coupling mechanism has been analyzed in terms of the barrier thickness, samples' substrate, and temperature. We examined the effect of MgO (MGO) and SrTiO{sub 3} (STO) (001) single-crystalline substrates on the magnetic coupling and also on the magnetic anisotropies of the samples in order to get a deeper understanding of the magnetism of the structures. We measured a weak coupling mediated by spin-dependent tunneling phenomena whose sign and strength depend on barrier thickness and substrate. An antiferromagnetic (AF) exchange prevails for most of the samples and smoothly increases with the barrier thicknesses as a consequence of the screening effects of the BST{sub 0.05}. The coupling monotonically increases with temperature in all the samples and this behavior is attributed to thermally assisted mechanisms. The magnetic anisotropy of both magnetic components has a cubic symmetry that in the case of permalloy is added to a small uniaxial component.

  4. Biofuel and other biomass based products from contaminated sites - Potentials and barriers from Swedish perspectives

    Energy Technology Data Exchange (ETDEWEB)

    Andersson-Skoeld, Yvonne; Enell, Anja; Rihm, Thomas; Haglund, Kristina; Wik, Ola [Swedish Geotechnical Institute, Linkoeping (Sweden); Blom, Sonja; Angelbratt, Alexandra [FB Engineering AB, Goeteborg (Sweden); Bardos, Paul [r3 Environmental Technology Ltd, Reading (United Kingdom); Track, Thomas [DECHEMA e. V., Frankfurt am Main (Germany); Keuning, Sytze [Bioclear b.v., Groningen (Netherlands)

    2009-07-01

    In this report, results are presented based on interviews and literature surveys on the triggers and stoppers for non food crop on contaminated land in Sweden. The report also includes a first estimate of potential marginal land for biofuel production in Sweden. The report is a first step to explore the feasibility of a range of possible approaches to combine risk based land management (RBLM) with non-food crop land-uses and organic matter re-use as appropriate in a Swedish context. The focus of the report is on the treatment of contaminated land by phyto-remediation and on biofuel cultivation. In Sweden, like all other countries in Europe, areas of land have been degraded by past use. Such previously developed land includes areas affected by mining, fallout from industrial processes such as smelting, areas elevated with contaminated dredged sediments, former landfill sites and many other areas where the decline of industrial activity has left a legacy of degraded land and communities. The extent of contamination may not be sufficient to trigger remediation under current regulatory conditions, and there may be little economic incentive to regenerate the affected areas. An ideal solution would be a land management approach that is able to pay for itself. Biomass from coppice or other plantations has long been seen as a possible means of achieving this goal. Phyto remediation offers a low cost method for remediation of areas that are not candidates for conventional regeneration. The optimal conditions for phyto remediation are large land areas of low or mediate contamination. Phyto remediation is also suitable to prevent spreading of contaminants, for example in green areas such as in cities, as waste water buffer and small size remediation areas with diffuse spreading. Phyto remediation implies that plants, fungi or algae are used to remediate, control or increase the natural attenuation of contaminants. Depending on the contaminating species and the site conditions

  5. Biofuel and other biomass based products from contaminated sites - Potentials and barriers from Swedish perspectives

    Energy Technology Data Exchange (ETDEWEB)

    Andersson-Skoeld, Yvonne; Enell, Anja; Rihm, Thomas; Haglund, Kristina; Wik, Ola (Swedish Geotechnical Institute, Linkoeping (Sweden)); Blom, Sonja; Angelbratt, Alexandra (FB Engineering AB, Goeteborg (Sweden)); Bardos, Paul (r3 Environmental Technology Ltd, Reading (United Kingdom)); Track, Thomas (DECHEMA e. V., Frankfurt am Main (Germany)); Keuning, Sytze (Bioclear b.v., Groningen (Netherlands))

    2009-07-01

    In this report, results are presented based on interviews and literature surveys on the triggers and stoppers for non food crop on contaminated land in Sweden. The report also includes a first estimate of potential marginal land for biofuel production in Sweden. The report is a first step to explore the feasibility of a range of possible approaches to combine risk based land management (RBLM) with non-food crop land-uses and organic matter re-use as appropriate in a Swedish context. The focus of the report is on the treatment of contaminated land by phyto-remediation and on biofuel cultivation. In Sweden, like all other countries in Europe, areas of land have been degraded by past use. Such previously developed land includes areas affected by mining, fallout from industrial processes such as smelting, areas elevated with contaminated dredged sediments, former landfill sites and many other areas where the decline of industrial activity has left a legacy of degraded land and communities. The extent of contamination may not be sufficient to trigger remediation under current regulatory conditions, and there may be little economic incentive to regenerate the affected areas. An ideal solution would be a land management approach that is able to pay for itself. Biomass from coppice or other plantations has long been seen as a possible means of achieving this goal. Phyto remediation offers a low cost method for remediation of areas that are not candidates for conventional regeneration. The optimal conditions for phyto remediation are large land areas of low or mediate contamination. Phyto remediation is also suitable to prevent spreading of contaminants, for example in green areas such as in cities, as waste water buffer and small size remediation areas with diffuse spreading. Phyto remediation implies that plants, fungi or algae are used to remediate, control or increase the natural attenuation of contaminants. Depending on the contaminating species and the site conditions

  6. Energy barriers in nanometer sized magnetic islands prepared from alloyed and multilayered Co/Pt films

    NARCIS (Netherlands)

    Abelmann, Leon; de Vries, Jeroen; Bolhuis, Thijs; Kikuchi, Nobuaki

    2014-01-01

    By means of Anomalous Hall Effect measurements, we investigated the thermal switching field distribution of individual magnetic thin film circular elements with out-of-plane easy axis in a temperature range from 10K to 300K. We compared this behavior for elements prepared from either Co80Pt20

  7. A new barrier potential and alpha-decay half-lives of even–even nuclei in the 82⩽Z⩽92 regime

    Energy Technology Data Exchange (ETDEWEB)

    Hassanabadi, Hasan [Physics Department, Shahrood University of Technology, Shahrood (Iran, Islamic Republic of); Javadimanesh, ELham, E-mail: elham_javadimanesh89@yahoo.com [Department of Basic Sciences, Shahrood Branch, Islamic Azad University, Shahrood (Iran, Islamic Republic of); Zarrinkamar, Saber [Department of Basic Sciences, Garmsar Branch, Islamic Azad University, Garmsar (Iran, Islamic Republic of)

    2013-05-15

    The alpha-decay half-life in a nuclear reaction is mainly affected by the penetration probability, which itself depends on the choice of the barrier potential. Here, we propose a new barrier potential to investigate the alpha-decay half-lives in the even–even nuclei from {sup 178}Po to {sup 238}U. The obtained results are motivating.

  8. Description of the Magnetic Field and Divergence of Multisolenoid Aharonov-Bohm Potential

    Directory of Open Access Journals (Sweden)

    Araz R. Aliev

    2016-01-01

    Full Text Available Explicit formulas for the magnetic field and divergence of multisolenoid Aharonov-Bohm potential are obtained; the mathematical essence of this potential is explained. It is shown that the magnetic field and divergence of this potential are very singular generalized functions concentrated at a finite number of thin solenoids. Deficiency index is found for the minimal operator generated by the Aharonov-Bohm differential expression.

  9. Imaging and modification of the tumor vascular barrier for improvement in magnetic nanoparticle uptake and hyperthermia treatment efficacy

    Science.gov (United States)

    Hoopes, P. Jack; Petryk, Alicia A.; Tate, Jennifer A.; Savellano, Mark S.; Strawbridge, Rendall R.; Giustini, Andrew J.; Stan, Radu V.; Gimi, Barjor; Garwood, Michael

    2013-02-01

    The predicted success of nanoparticle based cancer therapy is due in part to the presence of the inherent leakiness of the tumor vascular barrier, the so called enhanced permeability and retention (EPR) effect. Although the EPR effect is present in varying degrees in many tumors, it has not resulted in the consistent level of nanoparticle-tumor uptake enhancement that was initially predicted. Magnetic/iron oxide nanoparticles (mNPs) have many positive qualities, including their inert/nontoxic nature, the ability to be produced in various sizes, the ability to be activated by a deeply penetrating and nontoxic magnetic field resulting in cell-specific cytotoxic heating, and the ability to be successfully coated with a wide variety of functional coatings. However, at this time, the delivery of adequate numbers of nanoparticles to the tumor site via systemic administration remains challenging. Ionizing radiation, cisplatinum chemotherapy, external static magnetic fields and vascular disrupting agents are being used to modify the tumor environment/vasculature barrier to improve mNP uptake in tumors and subsequently tumor treatment. Preliminary studies suggest use of these modalities, individually, can result in mNP uptake improvements in the 3-10 fold range. Ongoing studies show promise of even greater tumor uptake enhancement when these methods are combined. The level and location of mNP/Fe in blood and normal/tumor tissue is assessed via histopathological methods (confocal, light and electron microscopy, histochemical iron staining, fluorescent labeling, TEM) and ICP-MS. In order to accurately plan and assess mNP-based therapies in clinical patients, a noninvasive and quantitative imaging technique for the assessment of mNP uptake and biodistribution will be necessary. To address this issue, we examined the use of computed tomography (CT), magnetic resonance imaging (MRI), and Sweep Imaging With Fourier Transformation (SWIFT), an MRI technique which provides a

  10. Barriers, facilitators, and potential strategies for increasing HPV vaccination: A statewide assessment to inform action

    Directory of Open Access Journals (Sweden)

    Kathleen B. Cartmell

    2018-06-01

    Full Text Available Objective: The objective was to investigate how state level strategies in South Carolina could maximize HPV vaccine uptake. Design: An environmental scan identified barriers, facilitators, and strategies for improving HPV vaccination in South Carolina. Interviews were conducted with state leaders from relevant organizations such as public health agencies, medical associations, K-12 schools, universities, insurers, and cancer advocacy organizations. A thematic content analysis design was used. Digital interview files were transcribed, a data dictionary was created and data were coded using the data dictionary. Results: Thirty four interviews were conducted with state leaders. Barriers to HPV vaccination included lack of HPV awareness, lack of provider recommendation, HPV vaccine concerns, lack of access and practice-level barriers. Facilitators included momentum for improving HPV vaccination, school-entry Tdap requirement, pharmacy-based HPV vaccination, state immunization registry, HEDIS measures and HPV vaccine funding. Strategies for improving HPV vaccination fell into three categories: 1 addressing lack of awareness about the importance of HPV vaccination among the public and providers; 2 advocating for policy changes around HPV vaccine coverage, vaccine education, and pharmacy-based vaccination; and 3 coordination of efforts. Discussion: A statewide environmental scan generated a blueprint for action to be used to improve HPV vaccination in the state. Keywords: HPV, HPV vaccines, Cervical cancer, Prevention, Health systems, Barriers, Facilitators, Strategies, South Carolina

  11. Potential use of superconducting magnets for neutron therapy

    Energy Technology Data Exchange (ETDEWEB)

    Duthil, R; Kircher, F; Lottin, J C; Palanque, S [CEA/Saclay, 91 - Gif-sur-Yvette (France); Aucouturier, J; Fache, P [DT, CGR MeV, 78 Buc (France)

    1984-01-01

    The results of a feasibility study on the use of superconducting magnets for neutron therapy devices will be reported. Two possibilities can be foreseen: - SC magnets used in the isocentric primary beam transport line. The advantage is to increase the energy of the particles which can be transported (up to 70 MeV for protons), compared to existing systems, with a lower weight. This solution could be used very quickly. - A SC isocentric cyclotron, working at on average field of 4.7 T for accelerating deuterons up to 30 MeV. The feasibility of such a machine is fairly established but technical developments are needed, mainly in view of the rotation and of the miniaturisation of the cyclotron.

  12. Electric and Magnetic Coulomb Potentials in the Deuteron

    Directory of Open Access Journals (Sweden)

    Bernard Schaeffer

    2013-09-01

    Full Text Available After one century of nuclear physics, the underlying fun- damental laws of nuclear physics are still missing. Bohr had found a formula for the H atom and another for the H2 molecule but no equivalent formula exists for the deuteron 2H. The only known Coulomb interaction in a nucleus by the mainstream nuclear physics is the long range repulsion between protons, forgetting that the neutron contains elec- tric charges with no net charge. The neutron is attracted by the proton in a way discovered two millenaries ago by the Greeks. This attraction is equilibrated by the repulsion between the opposite magnetic moments of the proton and of the neutron in the deuteron. The bare application of ge- ometry together with electric and magnetic Coulomb’s in- teractions accounts for the binding energy of the deuteron, without fitting, with only 4 per cent discrepancy, proving the electromagnetic nature of the nuclear energy.

  13. Barriers and Incentives to Potential Adoption of Biofuels Crops by Smallholder Farmers in the Eastern Cape Province, South Africa

    OpenAIRE

    Cheteni, Priviledge; Mushunje, Abbyssinia; Taruvinga, Amon

    2014-01-01

    The main objective of this study was to identify barriers and incentives that influence the potential adoption of biofuel crops by smallholder farmers. The study utilized a semi-structured questionnaire to record responses from 129 smallholder farmers that were identified through a snowballing sampling technique. The respondents were from the Oliver Tambo and Chris Hani District Municipalities in the Eastern Cape Province, South Africa. A Heckman two-step model was applied to analyze the dat...

  14. Bias voltage dependence of magnetic tunnel junctions comprising amorphous ferromagnetic CoFeSiB layer with double barriers

    International Nuclear Information System (INIS)

    Yim, H.I.; Lee, S.Y.; Hwang, J.Y.; Rhee, J.R.; Chun, B.S.; Wang, K.L.; Kim, Y.K.; Kim, T.W.; Lee, S.S.; Hwang, D.G.

    2008-01-01

    Double-barrier magnetic tunnel junctions (DMTJs) with and without an amorphous ferromagnetic material such as CoFeSiB 10, CoFe 5/CoFeSiB 5, and CoFe 10 (nm) were prepared and compared to investigate the bias voltage dependence of the tunneling magnetoresistance (TMR) ratio. Typical DMTJ structures were Ta 45/Ru 9.5/IrMn 10/CoFe 7/AlO x /free layer 10/AlO x /CoFe 7/IrMn 10/Ru 60 (in nanometers). The interlayer coupling field and the normalized TMR ratios at the applied voltages of +0.4 and -0.4 V of the amorphous CoFeSiB free-layer DMTJ offer lower and higher values than that of the polycrystalline CoFe free-layer DMTJ, respectively. An amorphous ferromagnetic CoFeSiB layer improves the interface roughness of the free layer/tunnel barrier and, as a result, the interlayer coupling field and bias voltage dependence of the TMR ratio are suppressed at a given voltage. (copyright 2008 WILEY-VCH Verlag GmbH and Co. KGaA, Weinheim) (orig.)

  15. Low-resistance magnetic tunnel junctions prepared by partial remote plasma oxidation of 0.9 nm Al barriers

    International Nuclear Information System (INIS)

    Ferreira, Ricardo; Freitas, Paulo P.; MacKenzie, Maureen; Chapman, John N.

    2005-01-01

    Current perpendicular to the plane read-head elements suitable for high-density magnetic storage require low resistance while maintaining a reasonable magnetoresistive (MR) signal (RxA 2 and MR>20% for areal densities >200 Gb/in 2 ). This letter shows that competitive low RxA junctions can be produced using underoxidized barriers starting from 0.9 nm thick Al layers. For as-deposited junctions, tunneling magnetoresistance (TMR) ∼20% for RxA∼2-15 Ω μm 2 is obtained, while in the RxA∼60-150 Ω μm 2 range, TMR values between 40% to 45% are achieved. A limited number of junctions exhibits considerably lower RxA values with respect to the average, while keeping a similar MR (down to 0.44 Ω μm 2 with TMR of 20% and down to 2.2 Ω μm 2 with TMR of 52%). Experimental data suggest that current confinement to small regions (barrier defects/hot spots) may explain these results

  16. The gastro-esophageal reflux barrier: biophysical analysis on 3D models of anatomy from magnetic resonance imaging.

    Science.gov (United States)

    Roy, S; Fox, M R; Curcic, J; Schwizer, W; Pal, A

    2012-07-01

    The function and structure of the gastro-esophageal junction (GEJ) determine its efficacy as a reflux barrier. This study presents a novel methodology for the quantitative assessment of GEJ and proximal gastric morphology from magnetic resonance (MR) imaging. Based on this data we propose a new conceptualization of the hypothesis that a flap valve mechanism contributes to reflux protection. 3D models of the GEJ and proximal stomach were reconstructed from MR images in 12 healthy volunteers during respiration and on eating a test meal to maximum satiation. A rotating plane analysis measured the gastro-esophageal insertion angle and span of contact. An ellipsoid fit provided quantitative assessment of gastric shape and orientation relative to a fixed anatomical reference point. Position of the esophageal insertion on the 'gastric ellipse' was noted. An ellipsoid-cylinder model was designed to analyze the relationships among parameters describing the GEJ morphology. The insertion angle became more acute on expiration, but did not change with meal ingestion. In contrast the span of contact did not vary with respiration, but increased with gastric filling. Changes in gastric morphology with distension further augmented the span of gastro-esophageal contact in almost 70% of the studies. Novel MR imaging and biophysical analysis of the GEJ and proximal stomach provide a quantitative description of structures contributing to the reflux barrier. Changes in these parameters during respiration and on eating support the hypothesis that structural components of a functional 'flap valve' like mechanism contribute to reflux protection. © 2012 Blackwell Publishing Ltd.

  17. Spherical Magnetic Vortex in an External Potential Field: A Dissipative Contraction

    Science.gov (United States)

    Solov'ev, A. A.

    2013-09-01

    We consider the dissipative evolution of a spherical magnetic vortex with a force-free internal structure, located in a resistive medium and held in equilibrium by the potential external field. The magnetic field inside the sphere is force-free (the model of Chandrasekhar in Proc. Natl. Acad. Sci. 42, 1, 1956). Topologically, it is a set of magnetic toroids enclosed in spherical layers. A new exact MHD solution has been derived, describing a slow, uniform, radial compression of a magnetic spheroid under the pressure of an ambient field, when the plasma density and pressure are growing inside it. There is no dissipation in the potential field outside the sphere, but inside the sphere, where the current density can be high enough, the magnetic energy is continuously converted into heat. Joule dissipation lowers the magnetic pressure inside the sphere, which balances the pressure of the ambient field. This results in radial contraction of the magnetic sphere with a speed defined by the conductivity of the plasma and the characteristic spatial scale of the magnetic field inside the sphere. Formally, the sphere shrinks to zero within a finite time interval (magnetic collapse). The time of compression can be relatively small, within a day, even for a sphere with a radius of about 1 Mm, if the magnetic helicity trapped initially in the sphere (which is proportional to the number of magnetic toroids in the sphere) is quite large. The magnetic system is open along its axis of symmetry. On this axis, the magnetic and electric fields are strictly radial and sign-variable along the radius, so the plasma will be ejected along the axis of magnetic sphere outwards in both directions (as jets) at a rate much higher than the diffusive one, and the charged particles will be accelerated unevenly, in spurts, creating quasi-regular X-ray spikes. The applications of the solution to solar flares are discussed.

  18. Ultrafast spin injection from Cd1-x Mn x Te magnetic barriers into a CdTe quantum well studied by pump-probe spectroscopy

    International Nuclear Information System (INIS)

    Aoshima, I.; Nishibayashi, K.; Souma, I.; Murayama, A.; Oka, Y.

    2006-01-01

    Spin injection from diluted magnetic semiconductor (DMS) barriers of Cd 1- x Mn x Te into a quantum well (QW) of CdTe is studied, by means of pump-probe absorption spectroscopy in magnetic fields. Fast decay characteristics of circularly polarized differential absorbances of spin-polarized excitons in the DMS barrier show the exciton injection time of 6 ps from the barriers into the QW. In accordance with the fast relaxation of the spin-polarized excitons from the barrier, we observe the rise of circular polarization degree for the differential absorption of the CdTe QW in magnetic fields, evidently indicating the spin injection. In addition, the circular polarization degree up to 0.3 is developed in the well immediately after pumping, originating from the fast relaxation of a heavy hole (hh) spin less than 0.2 ps, due to the giant Zeeman effect caused by the penetration of the hh wave function into the DMS barriers

  19. Interfacial mixing in double-barrier magnetic tunnel junctions with amorphous NiFeSiB layers

    International Nuclear Information System (INIS)

    Chun, B.S.; Ko, S.P.; Hwang, J.Y.; Rhee, J.R.; Kim, T.W.; Kim, Y.K.

    2007-01-01

    Double-barrier magnetic tunnel junctions (DMTJs) comprising Ta 45/Ru 9.5/IrMn 10/CoFe 7/AlO x /free layer (CoFe 4/NiFeSiB 2/CoFe 4, CoFe 10, or NiFeSiB 10)/AlO x /CoFe 7/IrMn 10/Ru 60 (nm) have been examined with an emphasis given on understanding the interfacial mixing effects. The DMTJ, consisted of NiFeSiB, shows low switching field and low bias voltage dependence because the amorphous NiFeSiB has lower M S (=800 emu/cm 3 ) and offers smoother interfaces than polycrystalline CoFe. An interesting feature observed in the CoFe/NiFeSiB/CoFe sandwich free layered DMTJ is the presence of a wavy MR transfer curve at high-resistance region. Because the polycrystalline CoFe usually grows into a columnar structure, diamagnetic CoSi, paramagnetic FeSi, and/or diamagnetic CoB might have been formed during the sputter-deposition process. By employing electron energy loss spectrometry (EELS) and Auger electron spectroscopy (AES), we were able to confirm that Si and B atoms were arranged evenly in the top and bottom portions of AlO x /CoFe interfaces. This means that the interfacial mixing resulted in a distorted magnetization reversal process

  20. RELATIVE CONTRIBUTION OF THE MAGNETIC FIELD BARRIER AND SOLAR WIND SPEED IN ICME-ASSOCIATED FORBUSH DECREASES

    International Nuclear Information System (INIS)

    Bhaskar, Ankush; Vichare, Geeta; Subramanian, Prasad

    2016-01-01

    We study 50 cosmic-ray Forbush decreases (FDs) from the Oulu neutron monitor data during 1997–2005 that were associated with Earth-directed interplanetary coronal mass ejections (ICMEs). Such events are generally thought to arise due to the shielding of cosmic rays by a propagating diffusive barrier. The main processes at work are the diffusion of cosmic rays across the large-scale magnetic fields carried by the ICME and their advection by the solar wind. In an attempt to better understand the relative importance of these effects, we analyze the relationship between the FD profiles and those of the interplanetary magnetic field (B) and the solar wind speed (V sw ). Over the entire duration of a given FD, we find that the FD profile is generally (anti)correlated with the B and V sw profiles. This trend holds separately for the FD main and recovery phases too. For the recovery phases, however, the FD profile is highly anti-correlated with the V sw profile, but not with the B profile. While the total duration of the FD profile is similar to that of the V sw profile, it is significantly longer than that of the B profile. Using the convection–diffusion model, a significant contribution of advection by solar wind is found during the recovery phases of the FD.

  1. Suppressing Electron Turbulence and Triggering Internal Transport Barriers with Reversed Magnetic Shear in the National Spherical Torus Experiment

    Science.gov (United States)

    Peterson, Jayson Luc

    2011-10-01

    Observations in the National Spherical Torus Experiment (NSTX) have found electron temperature gradients that greatly exceed the linear threshold for the onset for electron temperature gradient-driven (ETG) turbulence. These discharges, deemed electron internal transport barriers (e-ITBs), coincide with a reversal in the shear of the magnetic field and with a reduction in electron-scale density fluctuations, qualitatively consistent with earlier gyrokinetic predictions. To investigate this phenomenon further, we numerically model electron turbulence in NSTX reversed-shear plasmas using the gyrokinetic turbulence code GYRO. These first-of-a-kind nonlinear gyrokinetic simulations of NSTX e-ITBs confirm that reversing the magnetic shear can allow the plasma to reach electron temperature gradients well beyond the critical gradient for the linear onset of instability. This effect is very strong, with the nonlinear threshold for significant transport approaching three times the linear critical gradient in some cases, in contrast with moderate shear cases, which can drive significant ETG turbulence at much lower gradients. In addition to the experimental implications of this upshifted nonlinear critical gradient, we explore the behavior of ETG turbulence during reversed shear discharges. This work is supported by the SciDAC Center for the Study of Plasma Microturbulence, DOE Contract DE-AC02-09CH11466, and used the resources of NCCS at ORNL and NERSC at LBNL. M. Ono et al., Nucl. Fusion 40, 557 (2000).

  2. RELATIVE CONTRIBUTION OF THE MAGNETIC FIELD BARRIER AND SOLAR WIND SPEED IN ICME-ASSOCIATED FORBUSH DECREASES

    Energy Technology Data Exchange (ETDEWEB)

    Bhaskar, Ankush; Vichare, Geeta [Indian Institute of Geomagnetism, Kalamboli Highway, New Panvel, Navi Mumbai 410218 (India); Subramanian, Prasad, E-mail: ankushbhaskar@gmail.com [Indian Institute of Science Education and Research, Dr. Homi Bhabha Road, Pashan, Pune 411008 (India)

    2016-09-10

    We study 50 cosmic-ray Forbush decreases (FDs) from the Oulu neutron monitor data during 1997–2005 that were associated with Earth-directed interplanetary coronal mass ejections (ICMEs). Such events are generally thought to arise due to the shielding of cosmic rays by a propagating diffusive barrier. The main processes at work are the diffusion of cosmic rays across the large-scale magnetic fields carried by the ICME and their advection by the solar wind. In an attempt to better understand the relative importance of these effects, we analyze the relationship between the FD profiles and those of the interplanetary magnetic field (B) and the solar wind speed (V {sub sw}). Over the entire duration of a given FD, we find that the FD profile is generally (anti)correlated with the B and V {sub sw} profiles. This trend holds separately for the FD main and recovery phases too. For the recovery phases, however, the FD profile is highly anti-correlated with the V {sub sw} profile, but not with the B profile. While the total duration of the FD profile is similar to that of the V {sub sw} profile, it is significantly longer than that of the B profile. Using the convection–diffusion model, a significant contribution of advection by solar wind is found during the recovery phases of the FD.

  3. Magnetic nanoparticles: reactive oxygen species generation and potential therapeutic applications

    Science.gov (United States)

    Mai, Trang; Hilt, J. Zach

    2017-07-01

    Magnetic nanoparticles have been demonstrated to produce reactive oxygen species (ROS), which play a major role in various cellular pathways, via Fenton and Haber-Weiss reaction. ROS act as a double-edged sword inside the body. At normal conditions, the generation of ROS is in balance with their elimination by scavenger systems, and they can promote cell proliferation as well as differentiation. However, at an increased level, they can cause damages to protein, lead to cellular apoptosis, and contribute to many diseases including cancer. Many recent studies proposed a variety of strategies to either suppress toxicity of ROS generation or exploit the elevated ROS levels for cancer therapy.

  4. Self-regulated magnetic fluid hyperthermia: A potential cancer therapy

    Science.gov (United States)

    Bagaria, Hitesh Ghanshyam

    An emerging cancer therapy, self-regulated magnetic fluid hyperthermia (MFH), is the motivation for this work. In this therapy, cancer is annihilated by heating the tumor to desired therapeutic temperatures (˜45°C) by using magnetic nanoparticles of controlled Curie temperatures (Tc). This work was aimed at preparing and characterizing FePt, NiPd and NiPt nanoparticles for self-regulated MFH because their Tc could be tuned by changing their composition. Based on the excellent colloidal stability, size tunability and toxicity considerations, FePt was an obvious choice for self-regulated MFH. The 3.2 nm Fe61Pt39 particles displayed a Tc of 151°C, which is well below the Tc of bulk Fe61Pt39 (˜327°C). To reach the desired Tc of 45°C the composition of iron needs to be increased. However, a major obstacle was the formation of iron oxide shells with increase in iron composition of the particles. A recent finding that the composition of individual FePt particles deviated significantly from the average value encouraged us to study the mechanism of formation of FePt particles. Our analysis showed that early in the reaction the particles were Pt-rich and as the reaction proceeded the Fe content increased. It was found that the wide distribution in the composition of individual particles started early in the synthesis, suggesting that the compositional variability may be attributed to the Pt nuclei. The synthesized FePt particles are unsuitable for biological applications because of their hydrophobic surface. Hence, their surface was modified by ligand exchange with mercapto alkanoic acids. After ligand exchange, stable FePt dispersions could be formed in alkaline water. The study revealed that both the carboxylate and thiol groups were required to form stable FePt dispersions. In addition, 15 nm gold particles were successfully conjugated to genetically modified adenoviruses that selectively bind to cancer tumors. We also modeled the thermal transport in tissues during

  5. Potential Magnetic Field around a Helical Flux-rope Current Structure in the Solar Corona

    OpenAIRE

    Petrie, G. J. D.

    2007-01-01

    We consider the potential magnetic field associated with a helical electric line current flow, idealizing the near-potential coronal field within which a highly localized twisted current structure is embedded. It is found that this field has a significant axial component off the helical magnetic axis where there is no current flow, such that the flux winds around the axis. The helical line current field, in including the effects of flux rope writhe, is therefore more topologically complex tha...

  6. [Effect of pulse magnetic field on distribution of neuronal action potential].

    Science.gov (United States)

    Zheng, Yu; Cai, Di; Wang, Jin-Hai; Li, Gang; Lin, Ling

    2014-08-25

    The biological effect on the organism generated by magnetic field is widely studied. The present study was aimed to observe the change of sodium channel under magnetic field in neurons. Cortical neurons of Kunming mice were isolated, subjected to 15 Hz, 1 mT pulse magnetic stimulation, and then the currents of neurons were recorded by whole-cell patch clamp. The results showed that, under magnetic stimulation, the activation process of Na(+) channel was delayed, and the inactivation process was accelerated. Given the classic three-layer model, the polarization diagram of cell membrane potential distribution under pulse magnetic field was simulated, and it was found that the membrane potential induced was associated with the frequency and intensity of magnetic field. Also the effect of magnetic field-induced current on action potential was simulated by Hodgkin-Huxley (H-H) model. The result showed that the generation of action potential was delayed, and frequency and the amplitudes were decreased when working current was between -1.32 μA and 0 μA. When the working current was higher than 0 μA, the generation frequency of action potential was increased, and the change of amplitudes was not obvious, and when the working current was lower than -1.32 μA, the time of rising edge and amplitudes of action potential were decreased drastically, and the action potential was unable to generate. These results suggest that the magnetic field simulation can affect the distribution frequency and amplitude of action potential of neuron via sodium channel mediation.

  7. Potential Strategies to Address the Major Clinical Barriers Facing Stem Cell Regenerative Therapy for Cardiovascular Disease: A Review.

    Science.gov (United States)

    Nguyen, Patricia K; Neofytou, Evgenios; Rhee, June-Wha; Wu, Joseph C

    2016-11-01

    Although progress continues to be made in the field of stem cell regenerative medicine for the treatment of cardiovascular disease, significant barriers to clinical implementation still exist. To summarize the current barriers to the clinical implementation of stem cell therapy in patients with cardiovascular disease and to discuss potential strategies to overcome them. Information for this review was obtained through a search of PubMed and the Cochrane database for English-language studies published between January 1, 2000, and July 25, 2016. Ten randomized clinical trials and 8 systematic reviews were included. One of the major clinical barriers facing the routine implementation of stem cell therapy in patients with cardiovascular disease is the limited and inconsistent benefit observed thus far. Reasons for this finding are unclear but may be owing to poor cell retention and survival, as suggested by numerous preclinical studies and a small number of human studies incorporating imaging to determine cell fate. Additional studies in humans using imaging to determine cell fate are needed to understand how these factors contribute to the limited efficacy of stem cell therapy. Treatment strategies to address poor cell retention and survival are under investigation and include the following: coadministration of immunosuppressive and prosurvival agents, delivery of cardioprotective factors packaged in exosomes rather than the cells themselves, and use of tissue-engineering strategies to provide structural support for cells. If larger grafts are achieved using these strategies, it will be imperative to carefully monitor for the potential risks of tumorigenicity, immunogenicity, and arrhythmogenicity. Despite important achievements to date, stem cell therapy is not yet ready for routine clinical implementation. Significant research is still needed to address the clinical barriers outlined herein before the next wave of large clinical trials is under way.

  8. Diffusion of Ag ions under random potential barriers in silver-containing chalcogenide glasses

    Czech Academy of Sciences Publication Activity Database

    Stehlík, Štěpán; Shimakawa, K.; Wágner, T.; Frumar, M.

    2012-01-01

    Roč. 45, č. 20 (2012), s. 1-5 ISSN 0022-3727 Institutional research plan: CEZ:AV0Z10100521 Keywords : Ag ion diffusion * chalcogenide glass * Nyquist plots Subject RIV: BM - Solid Matter Physics ; Magnetism Impact factor: 2.528, year: 2012 http://iopscience.iop.org/0022-3727/45/20/205304/

  9. Barriers and Potential Solutions for Energy Renovation of Buildings in Denmark

    DEFF Research Database (Denmark)

    Meyer, Niels I; Mathiesen, Brian vad; Hvelplund, Frede

    2014-01-01

    the supply and demand side for heat, electricity and transport. Implementing such Smart Energy Systems requires integrated strategic energy planning on the national and local level. With the fundamental changes in the energy supply technologies expected during the coming years, it is important to synchronize...... investments in energy conservation measures with investments in the supply side, in order to avoid overinvestment in supply systems and thus to minimize the total costs of the transformation to Smart Energy Systems. This paper highlights some of the most important barriers for renovation of existing buildings...

  10. Expanding Midscale Solar: Examining the Economic Potential, Barriers, and Opportunities at Offices, Hotels, Warehouses, and Universities

    Energy Technology Data Exchange (ETDEWEB)

    Bird, Lori [National Renewable Energy Lab. (NREL), Golden, CO (United States); Gagnon, Pieter [National Renewable Energy Lab. (NREL), Golden, CO (United States); Heeter, Jenny [National Renewable Energy Lab. (NREL), Golden, CO (United States)

    2016-09-01

    The midscale market for solar photovoltaics (PV), defined as behind-the-meter systems between 100 kW and 2 MW, has grown more slowly than other PV market segments in recent years. A number of key barriers have impeded growth, including tenant and landlord split incentives, contracting challenges, the mismatch in building lease and PV financing terms, and high transaction costs relative to project sizes. This report explores prospects for expansion of the midscale solar market, with a focus on four building segments: offices, hotels, warehouses, and universities.

  11. Heavy quark potential in a static and strong homogeneous magnetic field

    Energy Technology Data Exchange (ETDEWEB)

    Hasan, Mujeeb; Chatterjee, Bhaswar; Patra, Binoy Krishna [Indian Institute of Technology Roorkee, Department of Physics, Roorkee (India)

    2017-11-15

    We have investigated the properties of quarkonia in a thermal QCD medium in the background of strong magnetic field. For that purpose, we employ the Schwinger proper-time quark propagator in the lowest Landau level to calculate the one-loop gluon self-energy, which in the sequel gives the effective gluon propagator. As an artifact of strong magnetic field approximation (eB >> T{sup 2} and eB >> m{sup 2}), the Debye mass for massless flavors is found to depend only on the magnetic field which is the dominant scale in comparison to the scales prevalent in the thermal medium. However, for physical quark masses, it depends on both magnetic field and temperature in a low temperature and high magnetic field but the temperature dependence is very meager and becomes independent of the temperature beyond a certain temperature and magnetic field. With the above mentioned ingredients, the potential between heavy quark (Q) and anti-quark (anti Q) is obtained in a hot QCD medium in the presence of a strong magnetic field by correcting both short- and long-range components of the potential in the real-time formalism. It is found that the long-range part of the quarkonium potential is affected much more by magnetic field as compared to the short-range part. This observation facilitates us to estimate the magnetic field beyond which the potential will be too weak to bind Q anti Q together. For example, the J/ψ is dissociated at eB ∝ 10 m{sub π}{sup 2} and Υ is dissociated at eB ∝ 100 m{sub π}{sup 2} whereas its excited states, ψ{sup '} and Υ{sup '} are dissociated at smaller magnetic field eB = m{sub π}{sup 2}, 13 m{sub π}{sup 2}, respectively. (orig.)

  12. Structural support of a yin-yang magnet for a tandem mirror reactor with thermal barriers

    International Nuclear Information System (INIS)

    Erickson, J.L.; Ojalvo, I.U.; Myall, J.O.

    1980-01-01

    This report contains a comprehensive summary covering work performed by Grumman Aerospace Corporation, in conjunction with the Lawrence Livermore National Laboratory, on the TMP yin-yang coils. The yin-yang coil pair used for our analysis has a major arc radius of 2.7 m and a minor arc radius of 1.18 m, compared with 2.5 m and 0.75 m for the MFTF. The maximum field on the present conductor is 9.05 Tesla. This magnetic field is created by, and interacts with, a conductor current which produces a 360 million Newton total force, tending to separate the parallel lobes of the major arcs

  13. Breaking down barriers: exploring the potential for social care practice with trans survivors of domestic abuse.

    Science.gov (United States)

    Rogers, Michaela

    2016-01-01

    There is increasing recognition that domestic abuse takes place outside the heteronormative paradigm of social life. This paper presents a discussion of the findings of doctoral research which explores trans people's experiences of domestic abuse, their social care needs and whether these are met by domestic abuse agencies. This paper foregrounds debate on the intersections of domestic abuse, trans communities and social care provision as this research, and previous studies, suggests that trans survivors do not seek out or benefit from social care intervention. Qualitative data, collected via narrative interviews, were collected during 2012 from participants mainly located in the United Kingdom (two participants were based in the United States). A total of 24 interviews were undertaken with trans people (n = 15) and social care practitioners (n = 9). Data were examined using a voice-centred relational technique. The findings reveal that barriers are multiple and complex but work could be undertaken to encourage help-seeking behaviours. Barriers include expectations of a transphobic response and 'Othering' practices; lack of entitlement felt by trans people; lack of knowledge/misunderstandings about trans social care needs; heteronormative bias of existing services; and practitioner attitudes fixed to notions about gender as binary. The paper ends by proposing a framework for practice with trans survivors which incorporates a person-centred, narrative approach. © 2015 John Wiley & Sons Ltd.

  14. Barriers Inhibiting Inquiry-Based Science Teaching and Potential Solutions: Perceptions of Positively Inclined Early Adopters

    Science.gov (United States)

    Fitzgerald, Michael; Danaia, Lena; McKinnon, David H.

    2017-07-01

    In recent years, calls for the adoption of inquiry-based pedagogies in the science classroom have formed a part of the recommendations for large-scale high school science reforms. However, these pedagogies have been problematic to implement at scale. This research explores the perceptions of 34 positively inclined early-adopter teachers in relation to their implementation of inquiry-based pedagogies. The teachers were part of a large-scale Australian high school intervention project based around astronomy. In a series of semi-structured interviews, the teachers identified a number of common barriers that prevented them from implementing inquiry-based approaches. The most important barriers identified include the extreme time restrictions on all scales, the poverty of their common professional development experiences, their lack of good models and definitions for what inquiry-based teaching actually is, and the lack of good resources enabling the capacity for change. Implications for expectations of teachers and their professional learning during educational reform and curriculum change are discussed.

  15. An educational path for the magnetic vector potential and its physical implications

    International Nuclear Information System (INIS)

    Barbieri, S; Cavinato, M; Giliberti, M

    2013-01-01

    We present an educational path for the magnetic vector potential A aimed at undergraduate students and pre-service physics teachers. Starting from the generalized Ampère–Laplace law, in the framework of a slowly varying time-dependent field approximation, the magnetic vector potential is written in terms of its empirical references, i.e. the conduction currents. Therefore, once the currents are known, our approach allows for a clear and univocal physical determination of A, overcoming the mathematical indeterminacy due to the gauge transformations. We have no need to fix a gauge, since for slowly varying time-dependent electric and magnetic fields, the ‘natural’ gauge for A is the Coulomb one. We stress the difference between our approach and those usually presented in the literature. Finally, a physical interpretation of the magnetic vector potential is discussed and some examples of the calculation of A are analysed. (paper)

  16. A magnetic vector potential corresponding to a centrally conservative current element force

    International Nuclear Information System (INIS)

    Minteer, Timothy M

    2015-01-01

    The magnetic vector potential (Coulomb gauge) is commonly introduced in magnetostatic chapters of electromagnetism textbooks. However, what is not typically presented are the infinite subsets of the Coulomb gauge associated with differential current elements. This work provides a comparison of various differential magnetic vector potentials, differential magnetostatic potential energies, as well as differential current element forces as a collective work not available elsewhere. The differential magnetic vector potential highlighted in this work is the Coulomb–Ampère gauge corresponding to the centrally conservative Ampère current element force. The centrally conservative force is modeled as a mean valued continual exchange of energy carrier mediators accounting for both the differential magnetostatic potential energy and Ampère current element force of two differential current elements. (paper)

  17. [Implementing daily physical education in primary school - potentials and barriers from the involved actor's point of view].

    Science.gov (United States)

    Sterdt, E; Liersch, S; Henze, V; Röbl, M; Suermann, T; Krauth, C; Walter, U

    2015-04-01

    The objective was to determine to what extent daily physical education can be implemented in primary schools, what barriers exist and how to overcome the mentioned barriers. Moreover, it was analysed to what extent daily physical education is accepted by teachers, external trainers, parents and students. Semi-structured interviews with parents (n=7), teachers (n=5) and external trainers (n=6) of the intervention schools. The intervention students (n=44) were surveyed within focus groups. All surveyed groups appraised the implementation of daily school sports as successful. The cooperation between the schools and the sports club should be maintained during a comprehensive implementation of daily physical education. Besides an improved lessons quality teachers and external trainers reported an improved social behaviour of the children. Parents perceived positive effects on the child development. All groups believe that daily physical education increases the enjoyment of children in sports. As a certain barrier a lack of resources (e. g., facilities, equipment, financial resources) in the schools were mentioned. The cooperation between the schools and the sports club proved to be an applicable model to implement daily physical education. The combination of teachers and external trainers can contribute to a higher lesson quality. Considering the perceived potentials of daily physical education by all surveyed groups, a comprehensive implementation of systematic daily physical activity promotion in the primary school setting should be tapped more strongly in future. © Georg Thieme Verlag KG Stuttgart · New York.

  18. Quantum Effects for a Proton in a Low-Barrier, Double-Well Potential: Core Level Photoemission Spectroscopy of Acetylacetone.

    Science.gov (United States)

    Feyer, Vitaliy; Prince, Kevin C; Coreno, Marcello; Melandri, Sonia; Maris, Assimo; Evangelisti, Luca; Caminati, Walther; Giuliano, Barbara M; Kjaergaard, Henrik G; Carravetta, Vincenzo

    2018-02-01

    We have performed core level photoemission spectroscopy of gaseous acetylacetone, its fully deuterated form, and two derivatives, benzoylacetone and dibenzoylmethane. These molecules show intramolecular hydrogen bonds, with a proton located in a double-well potential, whose barrier height is different for the three compounds. This has allowed us to examine the effect of the double-well potential on photoemission spectra. Two distinct O 1s core hole peaks are observed, previously assigned to two chemical states of oxygen. We provide an alternative assignment of the double-peak structure of O 1s spectra by taking full account of the extended nature of the wave function associated with the nuclear motion of the proton, the shape of the ground and final state potentials in which the proton is located, and the nonzero temperature of the samples. The peaks are explained in terms of an unusual Franck-Condon factor distribution.

  19. Technological barriers to the growth of the export potential of Russian grain industry

    Directory of Open Access Journals (Sweden)

    O. A. Eremchenko

    2017-01-01

    Full Text Available Russia is the world's largest wheat exporter. The sales volume on foreign markets in 2015 amounted to $3.9 billion, or 10.1% of global exports. By the end of 2015, the volume of exports of agricultural products exceeded revenues from sales of arms in foreign markets. However, in dollar terms, wheat exports correspond to only a fifth place in the world. The article analyzes the reasons for a significant gap in the volume of exports and revenue, barriers to the development of export of agricultural deep processed products. The assumption is made that the development of technologies for deep processing of grain crops will increase the share of exports of Russian products with high added value.

  20. Observation of ion confining potential enhancement due to thermal barrier potential formation and its scaling law in the tandem mirror GAMMA 10

    International Nuclear Information System (INIS)

    Cho, Teruji; Nakashima, Yousuke; Foote, J.H.

    1987-01-01

    In the tandem mirror GAMMA 10, (i) the enhancement of the ion confining potential, φ c , only during the period of the thermal barrier potential φ b -formation, has been observed first by using not only end-loss-analysers (ELA's) of GAMMA 10 but an end-loss-ion-spectrometer (ELIS) installed from TMX-U. This results in strong end-loss-ion plugging with increased central cell density. (ii) The first experimental observation of the φ c vs φ b -scaling law is obtained, where φ c increases with φ b . This scaling law is consistently interpreted by Cohen's theories of the weak-ECH and the strong-ECH in the plug region. (iii) Good agreement of the plug potential measured with the ELA's and the ELIS is achieved. (author)

  1. Barriers and Potential Solutions for Energy Renovation of Buildings in Denmark

    Directory of Open Access Journals (Sweden)

    Niels I. Meyer

    2014-02-01

    Full Text Available Buildings account for a substantial part of the total energy consumption. In Denmark this number is about 40 % and this is approximately the same in most industrial countries. On this background there is an urgent need to develop strategies for reducing the energy demand in the building sector. Renovation of existing buildings must have high priority as houses often last for 50 to 100 years, while the time perspective for the desired transformation to low-energy houses is less than 30 years in order to mitigate global warming and avoid irreversible tipping-points. The only sustainable energy supply in the perspective of centuries is renewable energy provided by the sun and exploited in the form of solar heat, solar electricity (PVs, wind power, hydropower, wave power, and some types of biomass etc. A future dominating role of intermittent renewable sources requires new integrated systems thinking on both the supply and demand side for heat, electricity and transport. Implementing such Smart Energy Systems requires integrated strategic energy planning on the national and local level. With the fundamental changes in the energy supply technologies expected during the coming years, it is important to synchronize investments in energy conservation measures with investments in the supply side, in order to avoid overinvestment in supply systems and thus to minimize the total costs of the transformation to Smart Energy Systems. This paper highlights some of the most important barriers for renovation of existing buildings in Denmark and points to policies for overcoming these barriers. Some of the policies have been presented in the reports of a recent Danish research project (CEESA

  2. Photopatternable Magnetic Hollowbots by Nd-Fe-B Nanocomposite for Potential Targeted Drug Delivery Applications

    Directory of Open Access Journals (Sweden)

    Hui Li

    2018-04-01

    Full Text Available In contrast to traditional drug administration, targeted drug delivery can prolong, localize, target and have a protected drug interaction with the diseased tissue. Drug delivery carriers, such as polymeric micelles, liposomes, dendrimers, nanotubes, and so on, are hard to scale-up, costly, and have short shelf life. Here we show the novel fabrication and characterization of photopatternable magnetic hollow microrobots that can potentially be utilized in microfluidics and drug delivery applications. These magnetic hollowbots can be fabricated using standard ultraviolet (UV lithography with low cost and easily accessible equipment, which results in them being easy to scale up, and inexpensive to fabricate. Contact-free actuation of freestanding magnetic hollowbots were demonstrated by using an applied 900 G external magnetic field to achieve the movement control in an aqueous environment. According to the movement clip, the average speed of the magnetic hollowbots was estimated to be 1.9 mm/s.

  3. Infinite dwell time and group delay in resonant electron tunneling through double complex potential barrier

    Science.gov (United States)

    Opacak, Nikola; Milanović, Vitomir; Radovanović, Jelena

    2017-12-01

    Tunneling times in complex potentials are investigated. Analytical expressions for dwell time, self-interference time and group delay are obtained for the case of complex double delta potentials. It is shown that we can always find a set of parameters of the potential so that the tunneling times achieve very large values and even approach infinity for the case of resonance. The phenomenon of infinite tunneling times occurs for only one particular positive value of the imaginary part of the potential, if all other parameters are given.

  4. Controlled fabrication of nano-scale double barrier magnetic tunnel junctions using focused ion beam milling method

    International Nuclear Information System (INIS)

    Wei, H.X.; Wang, T.X.; Zeng, Z.M.; Zhang, X.Q.; Zhao, J.; Han, X.F.

    2006-01-01

    The controlled fabrication method for nano-scale double barrier magnetic tunnel junctions (DBMTJs) with the layer structure of Ta(5)/Cu(10)/Ni 79 Fe 21 (5)/Ir 22 Mn 78 (12)/Co 6 Fe 2 B 2 (4)/Al(1) -oxide/Co 6 Fe 2 B 2 (6)/Al (1)-oxide/Co 6 Fe 2 B 2 (4)/Ir 22 Mn 78 (12)/Ni 79 Fe 21 (5)/Ta(5) (thickness unit: nm) was used. This method involved depositing thin multi-layer stacks by sputtering system, and depositing a Pt nano-pillar using a focused ion beam which acted both as a top contact and as an etching mask. The advantages of this process over the traditional process using e-beam and optical lithography in that it involve only few processing steps, e.g. it does not involve any lift-off steps. In order to evaluate the nanofabrication techniques, the DBMTJs with the dimensions of 200 nmx400 nm, 200 nmx200 nm nano-scale were prepared and their R-H, I-V characteristics were measured.

  5. Transferrin-conjugated magnetic dextran-spermine nanoparticles for targeted drug transport across blood-brain barrier.

    Science.gov (United States)

    Ghadiri, Maryam; Vasheghani-Farahani, Ebrahim; Atyabi, Fatemeh; Kobarfard, Farzad; Mohamadyar-Toupkanlou, Farzaneh; Hosseinkhani, Hossein

    2017-10-01

    Application of many vital hydrophilic medicines have been restricted by blood-brain barrier (BBB) for treatment of brain diseases. In this study, a targeted drug delivery system based on dextran-spermine biopolymer was developed for drug transport across BBB. Drug loaded magnetic dextran-spermine nanoparticles (DS-NPs) were prepared via ionic gelation followed by transferrin (Tf) conjugation as targeting moiety. The characteristics of Tf conjugated nanoparticles (TDS-NPs) were analyzed by different methods and their cytotoxicity effects on U87MG cells were tested. The superparamagnetic characteristic of TDS-NPs was verified by vibration simple magnetometer. Capecitabine loaded TDS-NPs exhibited pH-sensitive release behavior with enhanced cytotoxicity against U87MG cells, compared to DS-NPs and free capecitabine. Prussian-blue staining and TEM-imaging showed the significant cellular uptake of TDS-NPs. Furthermore, a remarkable increase of Fe concentrations in brain was observed following their biodistribution and histological studies in vivo, after 1 and 7 days of post-injection. Enhanced drug transport across BBB and pH-triggered cellular uptake of TDS-NPs indicated that these theranostic nanocarriers are promising candidate for the brain malignance treatment. © 2017 Wiley Periodicals, Inc. J Biomed Mater Res Part A: 105A: 2851-2864, 2017. © 2017 Wiley Periodicals, Inc.

  6. Prescriber barriers and enablers to minimising potentially inappropriate medications in adults: a systematic review and thematic synthesis.

    Science.gov (United States)

    Anderson, Kristen; Stowasser, Danielle; Freeman, Christopher; Scott, Ian

    2014-12-08

    To synthesise qualitative studies that explore prescribers' perceived barriers and enablers to minimising potentially inappropriate medications (PIMs) chronically prescribed in adults. A qualitative systematic review was undertaken by searching PubMed, EMBASE, Scopus, PsycINFO, CINAHL and INFORMIT from inception to March 2014, combined with an extensive manual search of reference lists and related citations. A quality checklist was used to assess the transparency of the reporting of included studies and the potential for bias. Thematic synthesis identified common subthemes and descriptive themes across studies from which an analytical construct was developed. Study characteristics were examined to explain differences in findings. All healthcare settings. Medical and non-medical prescribers of medicines to adults. Prescribers' perspectives on factors which shape their behaviour towards continuing or discontinuing PIMs in adults. 21 studies were included; most explored primary care physicians' perspectives on managing older, community-based adults. Barriers and enablers to minimising PIMs emerged within four analytical themes: problem awareness; inertia secondary to lower perceived value proposition for ceasing versus continuing PIMs; self-efficacy in regard to personal ability to alter prescribing; and feasibility of altering prescribing in routine care environments given external constraints. The first three themes are intrinsic to the prescriber (eg, beliefs, attitudes, knowledge, skills, behaviour) and the fourth is extrinsic (eg, patient, work setting, health system and cultural factors). The PIMs examined and practice setting influenced the themes reported. A multitude of highly interdependent factors shape prescribers' behaviour towards continuing or discontinuing PIMs. A full understanding of prescriber barriers and enablers to changing prescribing behaviour is critical to the development of targeted interventions aimed at deprescribing PIMs and reducing the

  7. Investigating transfer gate potential barrier by feed-forward effect measurement

    NARCIS (Netherlands)

    Xu, Y.; Ge, X.; Theuwissen, A.J.P.

    2015-01-01

    In a 4T pixel, the transfer gate (TG) “OFF” surface potential is one of the important parameters, which determines the pinned photodiode (PPD) full well capacity. The feed-forward effect measurement is a powerful tool to characterize the relationship of the PPD injection potential and the

  8. Current-current correlation function in presence of chemical potential and external magnetic field

    International Nuclear Information System (INIS)

    Apresyan, E.A.

    2017-01-01

    The (2+1)-dimensional electron system was observed, where relation between the Green functions and conductivity was used. The current-current correlation function Π_μ_ν(B) for the fermion system was calculated in presence of non-quantizing magnetic field B, chemical potential η and gap m. From this function it is possible to obtain the equation for polarization operator calculated without the magnetic field. The result is also applicable for graphene

  9. Effect of potential barrier growth of auto-localized excitons decay on radiation defects in AHC at low lattice symmetry

    International Nuclear Information System (INIS)

    Shunkeev, K.; Sagimbaeva, Sh.; Shunkeev, S.

    2007-01-01

    Effect of auto-localized excitons (ALE) luminescence strengthening is conditioned by two mechanisms: either decrease of potential barrier divided of quasi-free states and auto-localized states or decrease of emission-less channel effectiveness of exciton decay on primary radiation defects. In considered range (80 K) all excitons are only in auto-localized state. Therefore a realization of the first mechanism is improbable, For instant, in KI crystal at 80-100 K luminescence of free exciton is completely putting out, and ALE luminescence has maximal intensity. It is known that in the temperature range when ALE luminescence putting out is beginning an effectiveness of radiation defects is beginning to grow. This effect is related with predominating at that time emission-less exciton decay on radiation defects (F-H pairs). Experimentally by luminescence spectroscopy method activation energy of temperature putting out of ALE in AHC under uniaxial deformation. It is revealed, that increase of activation energy value has observed in a number of crystals: KBr→NaCl→KI→Na Br→CsBr→RbI. It is concluded, that effect of ALE intensity building-up and decrease of effectiveness of radiation defect formation are interpreted by growth of potential barrier of ALE decay into radiation defects under low symmetry of AHC lattice of low-temperature uniaxial deformation

  10. Nature of potential barrier in (Ca 1/4,Cu 3/4)TiO 3 polycrystalline perovskite

    Science.gov (United States)

    Marques, V. P. B.; Bueno, P. R.; Simões, A. Z.; Cilense, M.; Varela, J. A.; Longo, E.; Leite, E. R.

    2006-04-01

    The nonohmic electrical features of (Ca 1/4,Cu 3/4)TiO 3 perovskite ceramics, which have very strong gigantic dielectric is believed originate from potential barriers at the grain boundaries. In the present study, we used the admittance and impedance spectroscopy technique to investigate (Ca 1/4,Cu 3/4)TiO 3 perovskite ceramics with low nonohmic electrical properties. The study was conducted under two different conditions: on as-sintered ceramics and on ceramics thermally treated in an oxygen-rich atmosphere. The results confirm that thermal treatment in oxygen-rich atmospheres influence the nonohmic properties. Annealing at oxygen-rich atmospheres improve the nonohmic behavior and annealing at oxygen-poor atmospheres decrease the nonohmic properties, a behavior already reported for common metal oxide nonohmic devices and here firstly evidenced for the (Ca 1/4,Cu 3/4)TiO 3 perovskite related materials. The results show that oxygen also influences the capacitance values at low frequencies, a behavior that is indicative of the Schottky-type nature of the potential barrier.

  11. Quantum corrections to potential energy surfaces and their influence on barriers

    International Nuclear Information System (INIS)

    Reinhard, P.G.; Goeke, K.W.; Bonn Univ.

    1980-01-01

    A microscopic theory suitable for the description of fission processes and other large-amplitude collective phenomena is presented. The approach makes use of an optimal collective path, which is constructed by means of adiabatic time-dependent Hartree-Fock (TDHF) techniques as to show maximal de-coupling of collective and non-collective degrees of freedom. Although this involves a classical concept, the theory fully incorporates quantum effects associated with extracting a collective Schroedinger equation from adiabatic time-dependent Hartree-Fock theories (ATDHF). The quantum corrections are discussed extensively, and calculations in the two-centre shell model show, e.g. that they reduce the second barrier by 2 MeV and the life-time by a factor of 10 -7 . The relationships of the presented quantized ATDHF approach to the random-phase approximation (RPA) and a generalized dynamic generator co-ordinate method are investigated. For the construction of the optimal fission path, simple step-by-step methods are suggested. (author)

  12. Passing through the renal clearance barrier: toward ultrasmall sizes with stable ligands for potential clinical applications

    Directory of Open Access Journals (Sweden)

    Zhang XD

    2014-04-01

    Full Text Available Xiao-Dong Zhang,1 Jiang Yang,2 Sha-Sha Song,1 Wei Long,1 Jie Chen,1 Xiu Shen,1 Hao Wang,1 Yuan-Ming Sun,1 Pei-Xun Liu,1 Saijun Fan11Tianjin Key Laboratory of Molecular Nuclear Medicine, Institute of Radiation Medicine, Chinese Academy of Medical Sciences and Peking Union Medical College, Tianjin, People's Republic of China; 2Department of Biological Systems Engineering, University of Wisconsin-Madison, Madison, WI, USAAbstract: The use of nanoparticles holds promise for medical applications, such as X-ray imaging, photothermal therapy and radiotherapy. However, the in vivo toxicity of inorganic nanoparticles raises some concern regarding undesirable side effects which prevent their further medical application. Ultrasmall sub-5.5 nm particles can pass through the barrier for renal clearance, minimizing their toxicity. In this letter we address some recent interesting work regarding in vivo toxicity and renal clearance, and discuss the possible strategy of utilizing ultrasmall nanomaterials. We propose that small hydrodynamic sized nanoclusters can achieve both nontoxic and therapeutic clinical features.Keywords: in vivo clearance, gold nanoparticles, small size

  13. Opportunities and Barriers to Bioenergy Conversion Techniques and Their Potential Implementation on Swine Manure

    Directory of Open Access Journals (Sweden)

    Mahmoud A. Sharara

    2018-04-01

    Full Text Available The objectives of this article are to offer a comprehensive evaluation of the opportunities and barriers for swine manure conversion technologies and to shed light on the gaps that might require further investigation to improve the applicability of these technologies. The challenges of manure management have been propagated alongside the global growth of swine production. Various technologies that target the production of energy, fuels, and bioproducts from swine manure have been reported. These technologies include pretreatments, i.e., drying, and solid separation; biological techniques, i.e., composting, anaerobic digestion, and biodrying; and thermochemical techniques, i.e., combustion, gasification, pyrolysis, liquefaction, and carbonization. The review highlights the yields and qualities of products, i.e., energy, gaseous fuel, liquid fuel, and solid fuel, of each technology. It exhibits that the choice of a conversion technology predominantly depends on the feedstock properties, the specifics of the conversion technique, the market values of the end products as well as the local regulations. The challenges associated with the presented techniques are discussed to ameliorate research and development in these areas. The notable finding of this paper is that there is a need for full-scale research in the area of thermochemical conversion of solid-separated swine manure.

  14. The stability of internal transport barriers to MHD ballooning modes and drift waves: A formalism for low magnetic shear and for velocity shear

    International Nuclear Information System (INIS)

    Connor, J.W.; Hastie, R.J.; Webster, A.J.; Wilson, H.R.

    2005-01-01

    Tokamak discharges with internal transport barriers (ITBs) provide improved confinement, so it is important to understand their stability properties. The stability to an important class of modes with high wave-numbers perpendicular to the magnetic field, is usually studied with the standard ballooning transformation and eikonal approach. However, ITBs are often characterised by radial q profiles that have regions of negative or low magnetic shear and by radially sheared electric fields. Both these features affect the validity of the standard method. A new approach to calculating stability in these circumstances is developed and applied to ideal MHD ballooning modes and to micro-instabilities responsible for anomalous transport. (author)

  15. Effects of inhomogeneity on the Shukla-Nambu-Salimullah potential in a magnetized plasma

    International Nuclear Information System (INIS)

    Salimullah, M.; Shah, H.A.; Murtaza, G.; Nitta, H.; Tessarotto, M.

    2007-01-01

    Detailed properties of the electrostatic Shukla-Nambu-Salimullah potential in an inhomogeneous magnetoplasma in the presence of ion streaming due to diamagnetic drift as in a laboratory discharge plasma have been examined analytically. The potential becomes a sensitive function of the external static magnetic field, the scalelength of inhomogeneity, and the diamagnetic ion streaming velocity. For a decreasing ion density gradient, there is a limit of existence of this static modified shielding potential

  16. Fabrication of Mg-X-O (X = Fe, Co, Ni, Cr, Mn, Ti, V, and Zn) barriers for magnetic tunnel junctions

    Science.gov (United States)

    Yakushiji, K.; Kitagawa, E.; Ochiai, T.; Kubota, H.; Shimomura, N.; Ito, J.; Yoda, H.; Yuasa, S.

    2018-05-01

    We fabricated magnetic tunnel junctions with a 3d-transition material(X)-doped MgO (Mg-X-O) barrier, and evaluated the effect of the doping on magnetoresistance (MR) and microstructure. Among the variations of X (X = Fe, Co, Ni, Cr, Mn, Ti, V, and Zn), X = Fe and Mn showed a high MR ratio of more than 100%, even at a low resistance-area product of 3 Ωμm2. The microstructure analysis revealed that (001) textured orientation formed for X = Fe and Mn despite substantial doping (about 10 at%). The elemental mappings indicated that Fe atoms in the Mg-Fe-O barrier were segregated at the interfaces, while Mn atoms were evenly involved in the Mg-Mn-O barrier. This suggests that MgO has high adaptability for Fe and Mn dopants in terms of high MR ratio.

  17. Calculation of the magnetic vector potential in the TJ-II

    International Nuclear Information System (INIS)

    Lopez Fraguas, A.; Lopez Bruna, D.; Romero, J. A.

    2005-01-01

    The properties of the vector magnetic potential and its usefulness to calculate magnetic fluxes in both stationary and time-dependent conditions are p revised in this report. We have adapted to the TJ-II Flexible Heliac efficient numerical expressions to calculate the vector potential, calculating in addition the magnetic flux with this formalism in circumstances whose complexity makes very convenient the use of the vector potential. The result on induced voltages offer theoretical support to the measurements of induced voltage due to the OH coils in the plasma, like the measurements provided by the loop voltage diagnostic installed in the TJ-II, as well as to the cylindrical approximation of the plasma often used to interpret experimental data. (Author) 11 refs

  18. Beyond Bias and Barriers: Fulfilling the Potential of Women in Academic Science and Engineering

    Science.gov (United States)

    Agogino, Alice

    2007-04-01

    Review of the report by the National Academies, with a focus on action strategies in the physical sciences. Women face barriers to hiring and promotion in research universities in many fields of science and engineering; a situation that deprives the United States of an important source of talent as the country faces increasingly stiff global competition in higher education, science and technology, and the marketplace. Eliminating gender bias in universities requires immediate, overarching reform and decisive action by university administrators, professional societies, government agencies, and Congress. Forty years ago, women made up only 3 percent of America's scientific and technical workers, but by 2003 they accounted for nearly one-fifth. In addition, women have earned more than half of the bachelor's degrees awarded in science and engineering since 2000. However, their representation on university and college faculties fails to reflect these gains. Among science and engineering Ph.D.s, four times more men than women hold full-time faculty positions. And minority women with doctorates are less likely than white women or men of any racial or ethnic group to be in tenure positions. The report urges higher education organizations and professional societies to form collaborative, self-monitoring body that would recommend standards for faculty recruitment, retention, and promotion; collect data; and track compliance across institutions. A ``report card'' template is provided in the report. To read the report online, add a comment, or purchase hard copy, go to: http://www.engineeringpathway.com/ep/learningresource/summary/index.jhtml?id=94A4929D-F1B2-432E-8167-63335569CB4E.

  19. THE POSSIBLE IMPACT OF L5 MAGNETOGRAMS ON NON-POTENTIAL SOLAR CORONAL MAGNETIC FIELD SIMULATIONS

    Energy Technology Data Exchange (ETDEWEB)

    Weinzierl, Marion; Yeates, Anthony R. [Department of Mathematical Sciences, Durham University South Road, Durham DH1 3LE (United Kingdom); Mackay, Duncan H. [School of Mathematics and Statistics, University of St. Andrews North Haugh, St. Andrews, Fife KY16 9SS (United Kingdom); Pevtsov, Alexei A., E-mail: marion.weinzierl@durham.ac.uk [National Solar Observatory 3010 Coronal Loop, sunspot NM 88349 (United States)

    2016-09-10

    The proposed Carrington-L5 mission would bring instruments to the L5 Lagrange point to provide us with crucial data for space weather prediction. To assess the importance of including a magnetograph, we consider the possible differences in non-potential solar coronal magnetic field simulations when magnetograph observations are available from the L5 point, compared with an L1-based field of view (FOV). A timeseries of synoptic radial magnetic field maps is constructed to capture the emergence of two active regions from the L5 FOV. These regions are initially absent in the L1 magnetic field maps, but are included once they rotate into the L1 FOV. Non-potential simulations for these two sets of input data are compared in detail. Within the bipolar active regions themselves, differences in the magnetic field structure can exist between the two simulations once the active regions are included in both. These differences tend to reduce within 5 days of the active region being included in L1. The delayed emergence in L1 can, however, lead to significant persistent differences in long-range connectivity between the active regions and the surrounding fields, and also in the global magnetic energy. In particular, the open magnetic flux and the location of open magnetic footpoints, are sensitive to capturing the real-time of emergence. These results suggest that a magnetograph at L5 could significantly improve predictions of the non-potential corona, the interplanetary magnetic field, and of solar wind source regions on the Sun.

  20. Large magnetocurrents in double-barrier tunneling transistors

    International Nuclear Information System (INIS)

    Lee, J.H.; Jun, K.-I.; Shin, K.-H.; Park, S.Y.; Hong, J.K.; Rhie, K.; Lee, B.C.

    2005-01-01

    Magnetic tunneling transistors (MTT) with double tunneling barriers are fabricated. The structure of the transistor is AFM/FM/I/FM/I/FM/AFM, and ferromagnetic layers serve as the emitter, base and collector. This double-barrier tunneling transistor (DBTT) has an advantage of controlling the potential between the base and collector, compared to the Schottky-barrier-based base and collector of MTT. We found that the collector current density of DBTT is at least 10 3 times larger than that of conventional MTT, since tunneling through AlO x barrier provides much larger current density than that through Schottky barrier

  1. Adjunctive role of preoperative liver magnetic resonance imaging for potentially resectable pancreatic cancer.

    Science.gov (United States)

    Kim, Hyoung Woo; Lee, Jong-Chan; Paik, Kyu-Hyun; Kang, Jingu; Kim, Young Hoon; Yoon, Yoo-Seok; Han, Ho-Seong; Kim, Jaihwan; Hwang, Jin-Hyeok

    2017-06-01

    The adjunctive role of magnetic resonance imaging of the liver before pancreatic ductal adenocarcinoma has been unclear. We evaluated whether the combination of hepatic magnetic resonance imaging with multidetector computed tomography using a pancreatic protocol (pCT) could help surgeons select appropriate candidates and decrease the risk of early recurrence. We retrospectively enrolled 167 patients in whom complete resection was achieved without grossly visible residual tumor; 102 patients underwent pCT alone (CT group) and 65 underwent both hepatic magnetic resonance imaging and pCT (magnetic resonance imaging group). By adding hepatic magnetic resonance imaging during preoperative evaluation, hepatic metastases were newly discovered in 3 of 58 patients (5%) without hepatic lesions on pCT and 17 of 53 patients (32%) with indeterminate hepatic lesions on pCT. Patients with borderline resectability, a tumor size >3 cm, or preoperative carbohydrate antigen 19-9 level >1,000 U/mL had a greater rate of hepatic metastasis on subsequent hepatic magnetic resonance imaging. Among 167 patients in whom R0/R1 resection was achieved, the median overall survival was 18.2 vs 24.7 months (P = .020) and the disease-free survival was 8.5 vs 10.0 months (P = .016) in the CT and magnetic resonance imaging groups, respectively (median follow-up, 18.3 months). Recurrence developed in 82 (80%) and 43 (66%) patients in the CT and magnetic resonance imaging groups, respectively. The cumulative hepatic recurrence rate was greater in the CT group than in the magnetic resonance imaging group (P magnetic resonance imaging should be considered in patients with potentially resectable pancreatic ductal adenocarcinoma, especially those with high tumor burden. Copyright © 2017 Elsevier Inc. All rights reserved.

  2. Thickness-, Composition-, and Magnetic-Field-Dependent Complex Impedance Spectroscopy of Granular-Type-Barrier Co/Co-Al2O3/Co MTJs

    Science.gov (United States)

    Tuan, Nguyen Anh; Anh, Nguyen Tuan; Nga, Nguyen Tuyet; Tue, Nguyen Anh; Van Cuong, Giap

    2016-06-01

    The alternating-current (ac) electrical properties of granular-type-barrier magnetic tunnel junctions (GBMTJs) based on Co/Co x (Al2O3)1- x ( t)/Co trilayer structures have been studied using complex impedance spectroscopy (CIS). Their CIS characteristics were investigated in external magnetic fields varying from 0 kOe to 3 kOe as a function of Co composition x at 10 at.%, 25 at.%, and 35 at.%, with barrier layer thickness t of 20 nm to 90 nm. The influence of these factors on the behaviors of the ac impedance response of the GBMTJs was deeply investigated and attributed to the dielectric or conducting nature of the Co-Al2O3 barrier layer. The most remarkable typical phenomena observed in these behaviors, even appearing paradoxical, include lower impedance for thicker t for each given x, a declining trend of Z with increasing x, a clear decrease of Z with H, and especially a partition of Z into zones according to the H value. All these effects are analyzed and discussed to demonstrate that diffusion-type and mass-transfer-type phenomena can be inferred from processes such as spin tunneling and Coulomb or spin blockade in the Co-Al2O3 barrier layer.

  3. Formation of an internal transport barrier and magnetohydrodynamic activity in experiments with the controlled density of rational magnetic surfaces in the T-10 Tokamak

    International Nuclear Information System (INIS)

    Razumova, K. A.; Andreev, V. F.; Bel’bas, I. S.; Gorshkov, A. V.; Dnestrovskij, A. Yu.; Dyabilin, K. S.; Kislov, A. Ya.; Lysenko, S. E.; Notkin, G. E.; Timchenko, N. N.; Chudnovskiy, A. N.; Shelukhin, D. A.

    2013-01-01

    Results are presented from experiments on the formation of an internal electron transport barrier near the q = 1.5 rational surface in the T-10 tokamak. The experiments were carried out in the regime with off-axis electron cyclotron resonance (ECR) heating followed by a fast plasma current ramp-up. After suppressing sawtooth oscillations by off-axis ECR heating, an internal transport barrier began to form near the q = 1.5 rational surface. In the phase of the current ramp-up, the quality of the transport barrier improved; as a result, the plasma energy confinement time increased 2–2.5 times. The intentionally produced flattening of the profile of the safety factor q(r) insignificantly affected magnetohydrodynamic activity in the plasma column in spite of the theoretical possibility of formation of substantial m/n = 3/2 and 2/1 magnetic islands. Conditions are discussed under which the flattening of the profile of the safety factor q near low-order rational surfaces leads to the formation of either an internal transport barrier or the development of an island magnetic structure induced by tearing modes

  4. Perpendicular magnetic tunnel junction with tunneling magnetoresistance ratio of 64% using MgO (100) barrier layer prepared at room temperature

    International Nuclear Information System (INIS)

    Ohmori, Hideto; Hatori, Tomoya; Nakagawa, Shigeki

    2008-01-01

    MgO (100) textured films can be prepared by reactive facing targets sputtering at room temperature without postdeposition annealing process when they were deposited on (100) oriented Fe buffer layers. This method allows fabrication of perpendicular magnetic tunnel junction (p-MTJ) with MgO (100) tunneling barrier layer and rare-earth transition metal (RE-TM) alloy thin films as perpendicularly magnetized free and pinned layers. The 3-nm-thick MgO tunneling barrier layer in p-MTJ multilayer prepared on glass substrate revealed (100) crystalline orientation. Extraordinary Hall effect measurement clarified that the perpendicular magnetic components of 3-nm-thick Fe buffer layers on the two ends of MgO tunneling barrier layer were increased by exchange coupling with RE-TM alloy layers. The RA of 35 kΩ μm 2 and tunneling magnetoresistance ratio of 64% was observed in the multilayered p-MTJ element by current-in-plane-tunneling

  5. Views of potential research participants on financial conflicts of interest: barriers and opportunities for effective disclosure.

    Science.gov (United States)

    Weinfurt, Kevin P; Friedman, Joëlle Y; Allsbrook, Jennifer S; Dinan, Michaela A; Hall, Mark A; Sugarman, Jeremy

    2006-09-01

    There is little guidance regarding how to disclose researchers' financial interests to potential research participants. To determine what potential research participants want to know about financial interests, their capacity to understand disclosed information and its implications, and the reactions of potential research participants to a proposed disclosure statement. Sixteen focus groups in 3 cities, including 6 groups of healthy adults, 6 groups of adults with mild chronic illness, 1 group of parents of healthy children, 1 group of parents of children with leukemia or brain tumor, 1 group of adults with heart failure, and 1 group of adults with cancer. Focus group discussions covered a range of topics including financial relationships in clinical research, whether people should be told about them, and how they should be told. Audio-recordings of focus groups were transcribed, verified, and coded for analysis. Participants wanted to know about financial interests, whether or not those interests would affect their participation. However, they varied in their desire and ability to understand the nature and implications of financial interests. Whether disclosure was deemed important depended upon the risk of the research. Trust in clinicians was also related to views regarding disclosure. If given the opportunity to ask questions during the consent process, some participants would not have known what to ask; however, after the focus group sessions, participants could identify information they would want to know. Financial interests are important to potential research participants, but obstacles to effective disclosure exist.

  6. Magnetic field effects on the open circuit potential of ferromagnetic electrodes in corroding solutions.

    Science.gov (United States)

    Dass, Amala; Counsil, Joseph A; Gao, Xuerong; Leventis, Nicholas

    2005-06-02

    Magnetic fields shift the open circuit potential (OCP) of ferromagnetic electrodes (Fe, Co, and Ni) in corroding solutions. The OCP changes we observe (a) follow the series Fe>Co>Ni; (b) increase with the magnetic flux density; (c) reach a maximum with disk electrodes approximately 1 mm in diameter; and (d) depend on the orientation of the electrode. We report that when the surface of the electrode is oriented parallel (theta = 90 degrees) or perpendicular (theta = 0 degrees) to the magnetic field, the open circuit potential moves in opposite directions (positive and negative, respectively) with the largest changes occurring when the electrode surface is parallel to the magnetic field. Nonconvective sleeve electrodes produce the same behavior. The overall experimental evidence suggests that the magnetic field changes the OCP by modifying the surface concentrations of the paramagnetic participants in the corrosion process of the ferromagnetic electrode by species in solution; this in turn is accomplished by imposing a field-gradient driven mode of mass transfer upon paramagnetic species in solution (magnetophoresis). Simulations of the magnetic field around the ferromagnetic electrode at the two extreme orientations considered here show that in one case (theta = 90 degrees) field gradients actually repel, while in the other case (theta = 0 degrees) they attract paramagnetic species in the vicinity of the electrode.

  7. Monitoring the environment and human sentiment on the Great Barrier Reef: Assessing the potential of collective sensing.

    Science.gov (United States)

    Becken, Susanne; Stantic, Bela; Chen, Jinyan; Alaei, Ali Reza; Connolly, Rod M

    2017-12-01

    With the growth of smartphone usage the number of social media posts has significantly increased and represents potentially valuable information for management, including of natural resources and the environment. Already, evidence of using 'human sensor' in crises management suggests that collective knowledge could be used to complement traditional monitoring. This research uses Twitter data posted from the Great Barrier Reef region, Australia, to assess whether the extent and type of data could be used to Great Barrier Reef organisations as part of their monitoring program. The analysis reveals that large amounts of tweets, covering the geographic area of interest, are available and that the pool of information providers is greatly enhanced by the large number of tourists to this region. A keyword and sentiment analysis demonstrates the usefulness of the Twitter data, but also highlights that the actual number of Reef-related tweets is comparatively small and lacks specificity. Suggestions for further steps towards the development of an integrative data platform that incorporates social media are provided. Copyright © 2017 Elsevier Ltd. All rights reserved.

  8. Potential of Lactobacillus plantarum CCFM639 in Protecting against Aluminum Toxicity Mediated by Intestinal Barrier Function and Oxidative Stress.

    Science.gov (United States)

    Yu, Leilei; Zhai, Qixiao; Tian, Fengwei; Liu, Xiaoming; Wang, Gang; Zhao, Jianxin; Zhang, Hao; Narbad, Arjan; Chen, Wei

    2016-12-02

    Aluminum (Al) is a ubiquitous metal that can seriously harm the health of animals and humans. In our previous study, we demonstrated that Lactobacillus plantarum CCFM639 can decrease Al burden in the tissues of mice by inhibiting intestinal Al absorption. The main aim of the present research was to investigate whether the protection by the strain is also associated with enhancement of the intestinal barrier, alleviation of oxidative stress and modulation of the inflammatory response. In an in vitro cell model, two protection modes (intervention and therapy) were examined and the results indicated that L. plantarum CCFM639 alleviated Al-induced cytotoxicity. In a mouse model, L. plantarum CCFM639 treatment was found to significantly alleviate oxidative stress in the intestinal tract, regulate the function of the intestinal mucosal immune system, restore the integrity of tight junction proteins and maintain intestinal permeability. These results suggest that in addition to Al sequestration, L. plantarum CCFM639 can also inhibit Al absorption by protecting the intestinal barrier, alleviating Al-induced oxidative stress and inflammatory response. Therefore, L. plantarum CCFM639 has the potential to be a dietary supplement ingredient that provides protection against Al-induced gut injury.

  9. Potential of Lactobacillus plantarum CCFM639 in Protecting against Aluminum Toxicity Mediated by Intestinal Barrier Function and Oxidative Stress

    Directory of Open Access Journals (Sweden)

    Leilei Yu

    2016-12-01

    Full Text Available Aluminum (Al is a ubiquitous metal that can seriously harm the health of animals and humans. In our previous study, we demonstrated that Lactobacillus plantarum CCFM639 can decrease Al burden in the tissues of mice by inhibiting intestinal Al absorption. The main aim of the present research was to investigate whether the protection by the strain is also associated with enhancement of the intestinal barrier, alleviation of oxidative stress and modulation of the inflammatory response. In an in vitro cell model, two protection modes (intervention and therapy were examined and the results indicated that L. plantarum CCFM639 alleviated Al-induced cytotoxicity. In a mouse model, L. plantarum CCFM639 treatment was found to significantly alleviate oxidative stress in the intestinal tract, regulate the function of the intestinal mucosal immune system, restore the integrity of tight junction proteins and maintain intestinal permeability. These results suggest that in addition to Al sequestration, L. plantarum CCFM639 can also inhibit Al absorption by protecting the intestinal barrier, alleviating Al-induced oxidative stress and inflammatory response. Therefore, L. plantarum CCFM639 has the potential to be a dietary supplement ingredient that provides protection against Al-induced gut injury.

  10. Studies on polyaspartamide gadolinium complexes as potential magnetic resonance imaging contrast agents

    International Nuclear Information System (INIS)

    Yan Guoping; Liu Maili; Li Liyun

    2005-01-01

    Purpose: A series of polyaspartamide gadolinium complexes containing pyridoxamine groups were studied as the potential magnetic resonance imaging (MRI) contrast agents for liver enhancement. Methods: These polyaspartamide gadolinium complexes were prepared and evaluated by relaxivity, acute toxicity studies and magnetic resonance imaging of the liver in rats. Results: These polyaspartamide gadolinium complexes have higher relaxation effectiveness than that of the clinically used gadolinium diethylenetriaminepentaacetic acid and possess the low intravenous acute toxicities to Institute for Cancer Research (ICR) mice. Magnetic resonance imaging of the liver in rats indicated that they greatly enhance the contrast of magnetic resonance images and provide prolonged intravascular duration in the liver. Conclusion: These results indicated that the polyaspartamide gadolinium complexes containing pyridoxamine groups could be considered as the appropriate MRI contrast agents for liver enhancement

  11. Potential use of calcareous mudstones in low hydraulic conductivity earthen barriers for environmental applications.

    Science.gov (United States)

    Musso, T B; Francisca, F M; Musso, T B; Musso, T B

    2013-01-01

    Earthen layers play a significant role in isolating contaminants in the subsurface, controlling the migration of contaminant plumes, and as landfill liners and covers. The physical, chemical and mineralogical properties of three calcareous mudstones from the Jagüel and Roca formations in North Patagonia, Argentina, are evaluated to determine their potential for the construction of liners. These mudstones were deposited in a marine environment in the Upper Cretaceous-Paleocene. The tested specimens mainly comprise silt and clay-sized particles, and their mineralogy is dominated by a smectite/illite mixed layer (70-90% Sm) and calcite in smaller proportion. Powdered mudstone samples have little viscosity and swelling potential when suspended in water. The hydraulic conductivity of compacted mudstones and sand-mudstone mixtures is very low (around 1-3 x 10(-10) m/s) and in good agreement with the expected hydraulic behaviour of compacted earthen layers. This behaviour can be attributed to the large amount of fine particles, high specific surface and the close packing of particles as confirmed by scanning electron microscope analysis. The tested materials also show a high cation exchange capacity (50-70 cmol/kg), indicating a high contaminant retardation capability. The calcareous mudstones show satisfactory mineralogical and chemical properties as well as an adequate hydraulic behaviour, demonstrating the potential use of these materials for the construction of compacted liners for the containment of leachate or as covers in landfills. These findings confirm the potential usage of marine calcareous mudstones as a low-cost geomaterial in environmental engineering projects.

  12. Corrosion of similar and dissimilar metal crevices in the engineered barrier system of a potential nuclear waste repository

    International Nuclear Information System (INIS)

    He, X.; Dunn, D.S.; Csontos, A.A.

    2007-01-01

    Crevice corrosion is considered possible if the corrosion potential (E corr ) exceeds the repassivation potential for crevice corrosion (E rcrev ). In this study, potentiodynamic polarization and potentiostatic hold were used to determine the E rcrev of similar and dissimilar metal crevices in the engineered barrier system of the potential Yucca Mountain repository in 0.5 M NaCl, 4 M NaCl, and 4 M MgCl 2 solutions at 95 deg. C. The results were compared with data previously obtained using crevices formed between Alloy 22 and polytetrafluoroethylene. It was observed that, except for Type 316L stainless steel, all other metal-to-metal crevices were less susceptible to crevice corrosion than the corresponding metal-to-polytetrafluoroethylene crevices. Measurements of galvanic coupling were used to evaluate the crevice corrosion propagation behavior in 5 M NaCl solution at 95 deg. C. The crevice specimens were coupled to either an Alloy 22 or a Titanium Grade 7 plate using metal or polytetrafluoroethylene crevice washers. Crevice corrosion of Type 316L stainless steel propagated without repassivation. For all the tests using a polytetrafluoroethylene crevice washer, crevice corrosion of Alloy 22 was initiated at open circuit potential by the addition of CuCl 2 as an oxidant, whereas no crevice corrosion of Alloy 22 was initiated for all the tests using Alloy 22 or Titanium Grade 7 metals as crevice washer. However, crevice corrosion propagation was found to be very limited under such test conditions

  13. Experimental study of neutron-optical potential with absorption using Fabry-Perot magnetic resonator

    International Nuclear Information System (INIS)

    Hino, M.; Tasaki, S.; Ebisawa, T.; Kawai, T.; Achiwa, N.; Yamazaki, D.

    1999-01-01

    Complete text of publication follows. Recently spin precession angles of neutrons tunneling and non-tunneling through [Permalloy45(PA)-germanium(Ge)]-PA Fabry-Perot magnetic resonator have been observed [1]. The spin precession angle is well reproduced by the theoretical phase difference of up and down spin neutron wave function based on one-dimensional Schroedinger equation using optical potential model [2]. Spin precession angle and transmission probability of neutron through PA-(Ge/Gd)-PA Fabry-Perot magnetic resonator are presented, where the gap(Ge/Gd) layer consists of germanium and gadolinium atoms, and the optical potential model for magnetic multilayer system with absorption is discussed. (author) [1] M. Hino, et al., Physica B 241-243, 1083 (1998).; [2] S. Yamada, et al., Annu. Rep. Res. Reactor Inst. Kyoto Univ. 11, 8 (1978)

  14. Recognizing potential barriers to setting and achieving effective rehabilitation goals for patients with persistent pain.

    Science.gov (United States)

    Schmidt, Stephen G

    2016-07-01

    Although the process of goal setting in rehabilitation of individuals with persistent pain is considered a fundamental and requisite skill, it is frequently reported as a challenging element of clinical practice. Factors which may contribute to the complexity of goal setting include the potential for unrecognized shifts in cognitive function, psychological comorbidities, and the social context of both providers and patients. This review aims to describe factors which may confound the process of setting and achieving collaborative rehabilitation goals using a biopsychosocial framework and to provide recommendations to enhance goal setting effectiveness.

  15. Involvement of patients with cancer in patient safety: a qualitative study of current practices, potentials and barriers.

    Science.gov (United States)

    Martin, Helle Max; Navne, Laura Emdal; Lipczak, Henriette

    2013-10-01

    Patient involvement in patient safety is widely advocated but knowledge regarding implementation of the concept in clinical practice is sparse. To investigate existing practices for patient involvement in patient safety, and opportunities and barriers for further involvement. A qualitative study of patient safety involvement practices in patient trajectories for prostate, uterine and colorectal cancer in Denmark. Observations from four hospital wards and interviews with 25 patients with cancer, 11 hospital doctors, 10 nurses, four general practitioners and two private practicing gynaecologists were conducted using ethnographic methodology. Patient safety was not a topic of attention for patients or dominant in communication between patients and healthcare professionals. The understanding of patient safety in clinical practice is almost exclusively linked to disease management. Involvement of patients is not systematic, but healthcare professionals and patients express willingness to engage. Invitation and encouragement of patients to become involved could be further systematised and developed. Barriers include limited knowledge of patient safety, of specific patient safety involvement techniques and concern regarding potential negative impact on doctor-patient relationship. Involvement of patients in patient safety must take into account that despite stated openness to the idea of involvement, patients and health professionals may not in practice show immediate concern. Lack of systematic involvement can also be attributed to limited knowledge about how to implement involvement beyond the focus of self-monitoring and compliance and a concern about the consequences of patient involvement for treatment outcomes. To realise the potential of patients' and health professionals' shared openness towards involvement, there is a need for more active facilitation and concrete guidance on how involvement can be practiced by both parties.

  16. Comment on ‘An educational path for the magnetic vector potential and its physical implications’

    International Nuclear Information System (INIS)

    Heras, José A

    2014-01-01

    In their recent paper, Barbieri et al (2013 Eur. J. Phys. 34 1209) proposed an educational path for the magnetic vector potential. In this comment I point out that this educational path involves several inconsistencies and is therefore unattractive from a pedagogical point of view. (letters and comments)

  17. Observability of the effects of curl-free magnetic vector potential on ...

    Indian Academy of Sciences (India)

    We discuss here the prediction, based on a formalism by the author, on the observable effects of a curl-free magnetic vector potential on the macroscale as against the microscale of the Aharonov–Bohm effect. A new quantum concept – the 'transition amplitude wave' – postulated in the formalism has already been shown to ...

  18. Magnon spin transport driven by the magnon chemical potential in a magnetic insulator

    NARCIS (Netherlands)

    Cornelissen, L J; Peters, K J H; Bauer, G. E. W.; Duine, R A; van Wees, B J

    2016-01-01

    We develop a linear-response transport theory of diffusive spin and heat transport by magnons in magnetic insulators with metallic contacts. The magnons are described by a position-dependent temperature and chemical potential that are governed by diffusion equations with characteristic relaxation

  19. Magnon spin transport driven by the magnon chemical potential in a magnetic insulator

    NARCIS (Netherlands)

    Cornelissen, L.J.; Peters, K. J H; Bauer, G.E.; Duine, R. A.; Van Wees, B. J.

    2016-01-01

    We develop a linear-response transport theory of diffusive spin and heat transport by magnons in magnetic insulators with metallic contacts. The magnons are described by a position-dependent temperature and chemical potential that are governed by diffusion equations with characteristic relaxation

  20. Magnon spin transport driven by the magnon chemical potential in a magnetic insulator

    NARCIS (Netherlands)

    Cornelissen, Ludo J.; Peters, Kevin J. H.; Duine, Rembert A.|info:eu-repo/dai/nl/304830127; Bauer, Gerrit E. W.; Wees, Bart J. van

    2016-01-01

    We develop a linear-response transport theory of diffusive spin and heat transport by magnons in magnetic insulators with metallic contacts. The magnons are described by a position dependent temperature and chemical potential that are governed by diffusion equations with characteristic relaxation

  1. Role of potential scattering in the Shiba-Rusinov theory of the magnetic impurities in superconductors

    International Nuclear Information System (INIS)

    Okabe, Y.; Nagi, A.D.S.

    1983-01-01

    The Shiba-Rusinov theory of magnetic impurities in a superconductor is investigated, with special attention paid to the role of the potential scattering term in the electron-impurity interaction. The meaning of Anderson's theorem in the Shiba-Rusinov theory is discussed

  2. Muscle potentials evoked by magnetic stimulation of the sciatic nerve in unilateral sciatic nerve dysfunction

    NARCIS (Netherlands)

    Van Soens, I.; Struys, M. M. R. F.; Van Ham, L. M. L.

    Magnetic stimulation of the sciatic nerve and subsequent recording of the muscle-evoked potential (MEP) was performed in eight dogs and three cats with unilateral sciatic nerve dysfunction. Localisation of the lesion in the sciatic nerve was based on the history, clinical neurological examination

  3. Students' attitudes towards the introduction of a Personal and Professional Development portfolio: potential barriers and facilitators.

    Science.gov (United States)

    Ross, Sarah; Maclachlan, Alison; Cleland, Jennifer

    2009-12-01

    Portfolios, widely used in undergraduate and postgraduate medicine, have variable purposes, formats and success. A recent systematic review summarised factors necessary for successful portfolio introduction but there are no studies investigating the views of students inexperienced in portfolio use towards portfolio learning. This study's aim was to survey student views about a prospective Professional and Personal Development (PPD) portfolio. This was a qualitative, focus group study. All focus groups were taped and transcribed verbatim, and anonymised. The transcripts were analysed inductively, using framework analysis. Four focus groups were carried out with 32 undergraduate medical students naïve in portfolio use. Three themes relevant to portfolio introduction emerged. The first theme was the need for clear information and support for portfolio introduction, and anxieties about how this could be supported effectively. The second was that students had negative views about reflective learning and whether this could be taught and assessed, believing formal assessment could foster socially acceptable content. The third was that participants revealed little understanding of reflective learning and its potential benefits. Rather portfolios were seen as useful for concrete purposes (e.g., job applications) not intrinsic benefits. Undergraduate medical students without experience of portfolios are anxious about portfolio introduction. They require support in developing reflective learning skills. Care must be taken to ensure students do not see portfolios as merely yet another assessment hurdle.

  4. Material properties of plasticized hardwood xylans for potential application as oxygen barrier films.

    Science.gov (United States)

    Gröndahl, Maria; Eriksson, Lisa; Gatenholm, Paul

    2004-01-01

    Free films based on glucuronoxylan isolated from aspen wood were prepared by casting from aqueous solutions and drying in a controlled environment. Addition of xylitol or sorbitol facilitated film formation and thus examination of the material properties of these films. The mechanical properties of the films were evaluated using tensile testing and dynamic mechanical analysis in a controlled ambient relative humidity. The strain at break increased, and the stress at break and Young's modulus of the films decreased with increasing amounts of xylitol and sorbitol due to plasticization. At high amount of plasticizer, it was found that films with xylitol gave lower extensibility. Wide-angle X-ray scattering analysis showed that xylitol crystallized in a distinct phase, which we believe contributes to the more brittle behavior of these films. The effect of the plasticizers on the glass transition temperature was determined using dynamic mechanical analysis and differential scanning calorimetry. An increased amount of plasticizer shifted the glass transition to lower temperatures. The effect of moisture on the properties of plasticized films was investigated using water vapor sorption isotherms and by humidity scans in dynamic mechanical analysis. Sorption isotherms showed a transition from type II to type III when adding plasticizer. The films showed low oxygen permeability and thus have a potential application in food packaging.

  5. HIV testing sites' communication about adolescent confidentiality: potential barriers and facilitators to testing.

    Science.gov (United States)

    Hyden, Christel; Allegrante, John P; Cohall, Alwyn T

    2014-03-01

    This study sought to evaluate HIV testing locations in New York City in terms of staff communication of confidentiality policies for adolescent clients. Using the New York State Directory of HIV Counseling and Testing Resources as a sampling frame, this study made telephone contact with 164 public HIV testing locations in New York City and used a semistructured interview to ask questions about confidentiality, parental permission, and parent access to test results. At 48% of locations, either HIV testing was not offered or we were unable to reach a staff member to ask questions about testing options and confidentiality. At the remaining sites, information provided regarding confidentiality, parental consent, and privacy of test results was correct only 69% to 85% of the time. Additionally, 23% of sites successfully contacted offered testing exclusively between 9:00 a.m. and 3:00 p.m. weekdays, when most adolescents are in school. Our findings point to a need for increased training and quality control at the clinical level to ensure that consumers in need of HIV testing are provided with accurate information and accessible services. Furthermore, these results highlight the need for more "patient-centric" sites with enhanced accessibility for potential clients, particularly youth.

  6. [The potential of general magnetic therapy for the treatment and rehabilitation (a review)].

    Science.gov (United States)

    Kulikov, A G; Voronina, D D

    2016-01-01

    This paper was designed to describe the main characteristics of general magnetic therapy and the mechanisms underlying its biological and therapeutic action. Special attention is given to the extensive application of this method in the routine clinical practice. The publications in the current scientific literature are reviewed in order to evaluate the potential of general magnetic therapy as a component of the combined treatment of various somatic pathologies, rehabilitation of the patients after surgical intervention with special reference to the management of the patients presenting with the oncological problems. The data suggesting good tolerability and high therapeutic effectiveness of the physiotherapeutic method under consideration.

  7. Numerical simulations of a sounding rocket in ionospheric plasma: Effects of magnetic field on the wake formation and rocket potential

    Science.gov (United States)

    Darian, D.; Marholm, S.; Paulsson, J. J. P.; Miyake, Y.; Usui, H.; Mortensen, M.; Miloch, W. J.

    2017-09-01

    The charging of a sounding rocket in subsonic and supersonic plasma flows with external magnetic field is studied with numerical particle-in-cell (PIC) simulations. A weakly magnetized plasma regime is considered that corresponds to the ionospheric F2 layer, with electrons being strongly magnetized, while the magnetization of ions is weak. It is demonstrated that the magnetic field orientation influences the floating potential of the rocket and that with increasing angle between the rocket axis and the magnetic field direction the rocket potential becomes less negative. External magnetic field gives rise to asymmetric wake downstream of the rocket. The simulated wake in the potential and density may extend as far as 30 electron Debye lengths; thus, it is important to account for these plasma perturbations when analyzing in situ measurements. A qualitative agreement between simulation results and the actual measurements with a sounding rocket is also shown.

  8. Geometric approach to inverse scattering for the Schroedinger equation with magnetic and electric potentials

    International Nuclear Information System (INIS)

    Arians, S.

    1997-01-01

    We consider the Hamiltonian H=(p-A(x)) 2 /(2m)+V(x) of a quantum particle in a magnetic field B=rotA and a potential V in space dimensions ν≥2. If V is of short range, then the high-velocity limit of the scattering operator uniquely determines the magnetic field B and the potential V. If, in addition, long-range potentials V l are present, some knowledge of (the far out tail of) V l is needed to define a modified Dollard wave operator and a scattering operator S D . Again its high- velocity limit uniquely determines B and V=V s +V l . Moreover, we give explicit error bounds which are inverse proportional to the velocity. copyright 1997 American Institute of Physics

  9. Hyperpolarized Porous Silicon Nanoparticles: Potential Theragnostic Material for ²⁹Si Magnetic Resonance Imaging.

    Science.gov (United States)

    Seo, Hyeonglim; Choi, Ikjang; Whiting, Nicholas; Hu, Jingzhe; Luu, Quy Son; Pudakalakatti, Shivanand; McCowan, Caitlin; Kim, Yaewon; Zacharias, Niki; Lee, Seunghyun; Bhattacharya, Pratip; Lee, Youngbok

    2018-05-20

    Porous silicon nanoparticles have recently garnered attention as potentially-promising biomedical platforms for drug delivery and medical diagnostics. Here, we demonstrate porous silicon nanoparticles as contrast agents for ²⁹Si magnetic resonance imaging. Size-controlled porous silicon nanoparticles were synthesized by magnesiothermic reduction of silica nanoparticles and were surface activated for further functionalization. Particles were hyperpolarized via dynamic nuclear polarization to enhance their ²⁹Si MR signals; the particles demonstrated long ²⁹Si spin-lattice relaxation (T₁) times (~ 25 mins), which suggests potential applicability for medical imaging. Furthermore, ²⁹Si hyperpolarization levels were sufficient to allow ²⁹Si MRI in phantoms. These results underscore the potential of porous silicon nanoparticles that, when combined with hyperpolarized magnetic resonance imaging, can be a powerful theragnostic deep tissue imaging platform to interrogate various biomolecular processes in vivo. © 2018 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

  10. Overcoming barriers to seedling regeneration during forest restoration on tropical pasture land and the potential value of woody weeds

    Directory of Open Access Journals (Sweden)

    Amelia eElgar

    2014-05-01

    Full Text Available Combating the legacy of deforestation on tropical biodiversity requires the conversion to forest of large areas of established pasture, where barriers to native plant regeneration include competition with pasture grasses and poor propagule supply (seed availability. In addition, initial woody plants that colonise pasture are often invasive non-native species whose ecological roles and management in the context of forest regeneration are contested. In a restoration experiment at two 0.64 ha sites we quantified the response of native woody vegetation recruitment to (1 release from competition with introduced pasture grasses, and (2 local facilitation of frugivore-assisted seed dispersal provided by scattered woody plants and artificial bird perches. Herbicide pasture grass suppression during 20 months caused a significant but modest increase in density of native woody seedlings, together with abundant co-recruitment of the prominent non-native pioneer wild tobacco (Solanum mauritianum. Recruitment of native species was further enhanced by local structure in herbicide-treated areas, being consistently greater under live trees and dead non-native shrubs (herbicide-treated than in open areas, and intermediate under bird perches. Native seedling recruitment comprised 28 species across 0.25 ha sampled but was dominated by two rainforest pioneers (Homalanthus novoguineensis, Polyscias murrayi. These early results are consistent with the expected increase in woody vegetation recruitment in response to release from competitive and dispersive barriers to rainforest regeneration. The findings highlight the need for a pragmatic consideration of the ecological roles of woody weeds and the potential roles of ‘new forests’ more broadly in accelerating succession of humid tropical forest across large areas of retired agricultural land.

  11. A combined vector potential-scalar potential method for FE computation of 3D magnetic fields in electrical devices with iron cores

    Science.gov (United States)

    Wang, R.; Demerdash, N. A.

    1991-01-01

    A method of combined use of magnetic vector potential based finite-element (FE) formulations and magnetic scalar potential (MSP) based formulations for computation of three-dimensional magnetostatic fields is introduced. In this method, the curl-component of the magnetic field intensity is computed by a reduced magnetic vector potential. This field intensity forms the basic of a forcing function for a global magnetic scalar potential solution over the entire volume of the region. This method allows one to include iron portions sandwiched in between conductors within partitioned current-carrying subregions. The method is most suited for large-scale global-type 3-D magnetostatic field computations in electrical devices, and in particular rotating electric machinery.

  12. Non-potential Field Formation in the X-shaped Quadrupole Magnetic Field Configuration

    Energy Technology Data Exchange (ETDEWEB)

    Kawabata, Y.; Shimizu, T. [Department of Earth and Planetary Science, The University of Tokyo, 7-3-1 Hongo, Bunkyo-ku, Tokyo 113-0033 (Japan); Inoue, S., E-mail: kawabata.yusuke@ac.jaxa.jp [Max-Planck-Institute for Solar System Research, Justus-von-Liebig-Weg 3 D-37077 Göttingen (Germany)

    2017-06-20

    Some types of solar flares are observed in X-shaped quadrupolar field configuration. To understand the magnetic energy storage in such a region, we studied non-potential field formation in an X-shaped quadrupolar field region formed in the active region NOAA 11967, which produced three X-shaped M-class flares on 2014 February 2. Nonlinear force-free field modeling was applied to a time series of vector magnetic field maps from the Solar Optical Telescope on board Hinode and the Helioseismic and Magnetic Imager on board the Solar Dynamics Observatory . Our analysis of the temporal three-dimensional magnetic field evolution shows that the sufficient free energy had already been stored more than 10 hr before the occurrence of the first M-class flare and that the storage was observed in a localized region. In this localized region, quasi-separatrix layers (QSLs) started to develop gradually from 9 hr before the first M-class flare. One of the flare ribbons that appeared in the first M-class flare was co-spatial with the location of the QSLs, suggesting that the formation of the QSLs is important in the process of energy release. These QSLs do not appear in the potential field calculation, indicating that they were created by the non-potential field. The formation of the QSLs was associated with the transverse photospheric motion of the pre-emerged flux and the emergence of a new flux. This observation indicates that the occurrence of the flares requires the formation of QSLs in the non-potential field in which free magnetic energy is stored in advance.

  13. PVA gel as a potential adhesion barrier: a safety study in a large animal model of intestinal surgery.

    Science.gov (United States)

    Renz, Bernhard W; Leitner, Kurt; Odermatt, Erich; Worthley, Daniel L; Angele, Martin K; Jauch, Karl-Walter; Lang, Reinhold A

    2014-03-01

    Intra-abdominal adhesions following surgery are a major source of morbidity and mortality including abdominal pain and small bowel obstruction. This study evaluated the safety of PVA gel (polyvinyl alcohol and carboxymethylated cellulose gel) on intestinal anastomoses and its potential effectiveness in preventing adhesions in a clinically relevant large animal model. Experiments were performed in a pig model with median laparotomy and intestinal anastomosis following small bowel resection. The primary endpoint was the safety of PVA on small intestinal anastomoses. We also measured the incidence of postoperative adhesions in PVA vs. control groups: group A (eight pigs): stapled anastomosis with PVA gel compared to group B (eight pigs), which had no PVA gel; group C (eight pigs): hand-sewn anastomosis with PVA gel compared to group B (eight pigs), which had no anti-adhesive barrier. Animals were sacrificed 14 days after surgery and analyzed. All anastomoses had a patent lumen without any stenosis. No anastomoses leaked at an intraluminal pressure of 40 cmH2O. Thus, anastomoses healed very well in both groups, regardless of whether PVA was administered. PVA-treated animals, however, had significantly fewer adhesions in the area of stapled anastomoses. The hand-sewn PVA group also had weaker adhesions and trended towards fewer adhesions to adjacent organs. These results suggest that PVA gel does not jeopardize the integrity of intestinal anastomoses. However, larger trials are needed to investigate the potential of PVA gel to prevent adhesions in gastrointestinal surgery.

  14. Collisional effects on interaction potential in complex plasma in presence of magnetic field

    Energy Technology Data Exchange (ETDEWEB)

    Bezbaruah, Pratikshya, E-mail: pratphd@tezu.ernet.in; Das, Nilakshi [Department of Physics, Tezpur University, Tezpur, Assam 784028 (India)

    2016-04-15

    Interaction potential in complex plasma with streaming ions is derived analytically in presence of ion-neutral collision and magnetic field. The linear dielectric response function obtained describes the behavior of charged micron sized dust particles in strong collisional limit. A new type of repulsive potential is found to be operative among the dust grains apart from the normal Debye–Hückel potential. The amplitude and shielding length involved in the potential are substantially affected by the parameters describing ion cyclotron frequency, collision frequency among ions and neutrals, and ion streaming. It is also observed that the usual mechanism of ion focusing surrounding the grain is inhibited due to collision. As a result, the attractive wake potential structure is destroyed in the ion flow direction. The horizontal interaction involves only Debye–Hückel potential.

  15. Collisional effects on interaction potential in complex plasma in presence of magnetic field

    International Nuclear Information System (INIS)

    Bezbaruah, Pratikshya; Das, Nilakshi

    2016-01-01

    Interaction potential in complex plasma with streaming ions is derived analytically in presence of ion-neutral collision and magnetic field. The linear dielectric response function obtained describes the behavior of charged micron sized dust particles in strong collisional limit. A new type of repulsive potential is found to be operative among the dust grains apart from the normal Debye–Hückel potential. The amplitude and shielding length involved in the potential are substantially affected by the parameters describing ion cyclotron frequency, collision frequency among ions and neutrals, and ion streaming. It is also observed that the usual mechanism of ion focusing surrounding the grain is inhibited due to collision. As a result, the attractive wake potential structure is destroyed in the ion flow direction. The horizontal interaction involves only Debye–Hückel potential.

  16. Creation of a magnetic barrier at a noble q close to physical midpoint between two resonant surfaces in the ASDEX UG tokamak

    Science.gov (United States)

    Vazquez, Justin; Ali, Halima; Punjabi, Alkesh

    2009-11-01

    Ciraolo, Vittot and Chandre method of building invariant manifolds inside chaos in Hamiltonian systems [Ali H. and Punjabi A, Plasma Phys. Control. Fusion, 49, 1565--1582 (2007)] is used in the ASDEX UG tokamak. In this method, a second order perturbation is added to the perturbed Hamiltonian [op cit]. It creates an invariant torus inside the chaos, and reduces the plasma transport. The perturbation that is added to the equilibrium Hamiltonian is at least an order of magnitude smaller than the perturbation that causes chaos. This additional term has a finite, limited number of Fourier modes. Resonant magnetic perturbations (m,n) = (3,2)+(4,3) are added to the field line Hamiltonian for the ASDEX UG. An area-preserving map for the field line trajectories in the ASDEX UG is used. The common amplitude δ of these modes that gives complete chaos between the resonant surfaces ψ43 and ψ32 is determined. A magnetic barrier is built at a surface with noble q that is very nearly equals to the q at the physical midpoint between the two resonant surfaces. The maximum amplitude of magnetic perturbation for which this barrier can be sustained is determined. This work is supported by US Department of Energy grants DE-FG02-07ER54937, DE-FG02-01ER54624 and DE-FG02-04ER54793.

  17. Quantum size effects on spin-transfer torque in a double barrier magnetic tunnel junction with a nonmagnetic-metal (semiconductor) spacer

    International Nuclear Information System (INIS)

    Daqiq, Reza; Ghobadi, Nader

    2016-01-01

    We study the quantum size effects of an MgO-based double barrier magnetic tunnel junction with a nonmagnetic-metal (DBMTJ-NM) (semiconductor (DBMTJ-SC)) spacer on the charge current and the spin-transfer torque (STT) components using non-equilibrium Green's function (NEGF) formalism. The results show oscillatory behavior due to the resonant tunneling effect depending on the structure parameters. We find that the charge current and the STT components in the DBMTJ-SC demonstrate the magnitude enhancement in comparison with the DBMTJ-NM. The bias dependence of the STT components in a DBMTJ-NM shows different behavior in comparison with spin valves and conventional MTJs. Therefore, by choosing a specific SC spacer with suitable thickness in a DBMTJ the charge current and the STT components significantly increase so that one can design a device with high STT and faster magnetization switching. - Highlights: • The quantum size effects are studied in double barrier magnetic tunnel junctions. • Spin torque (ST) components oscillate for increasing of middle spacer thicknesses. • Due to the resonant tunneling in the quantum well, oscillations have appeared. • By replacement a metal spacer with a semiconductor (ZnO) ST has increased. • The ST components vs. bias show gradually decreasing unlike spin valves or MTJs.

  18. Quantum size effects on spin-transfer torque in a double barrier magnetic tunnel junction with a nonmagnetic-metal (semiconductor) spacer

    Energy Technology Data Exchange (ETDEWEB)

    Daqiq, Reza; Ghobadi, Nader

    2016-07-15

    We study the quantum size effects of an MgO-based double barrier magnetic tunnel junction with a nonmagnetic-metal (DBMTJ-NM) (semiconductor (DBMTJ-SC)) spacer on the charge current and the spin-transfer torque (STT) components using non-equilibrium Green's function (NEGF) formalism. The results show oscillatory behavior due to the resonant tunneling effect depending on the structure parameters. We find that the charge current and the STT components in the DBMTJ-SC demonstrate the magnitude enhancement in comparison with the DBMTJ-NM. The bias dependence of the STT components in a DBMTJ-NM shows different behavior in comparison with spin valves and conventional MTJs. Therefore, by choosing a specific SC spacer with suitable thickness in a DBMTJ the charge current and the STT components significantly increase so that one can design a device with high STT and faster magnetization switching. - Highlights: • The quantum size effects are studied in double barrier magnetic tunnel junctions. • Spin torque (ST) components oscillate for increasing of middle spacer thicknesses. • Due to the resonant tunneling in the quantum well, oscillations have appeared. • By replacement a metal spacer with a semiconductor (ZnO) ST has increased. • The ST components vs. bias show gradually decreasing unlike spin valves or MTJs.

  19. CORONAL MAGNETIC FIELDS DERIVED FROM SIMULTANEOUS MICROWAVE AND EUV OBSERVATIONS AND COMPARISON WITH THE POTENTIAL FIELD MODEL

    Energy Technology Data Exchange (ETDEWEB)

    Miyawaki, Shun; Nozawa, Satoshi [Department of Science, Ibaraki University, Mito, Ibaraki 310-8512 (Japan); Iwai, Kazumasa; Shibasaki, Kiyoto [Nobeyama Solar Radio Observatory, National Astronomical Observatory of Japan, Minamimaki, Nagano 384-1305 (Japan); Shiota, Daikou, E-mail: shunmi089@gmail.com [Solar-Terrestrial Environment Laboratory, Nagoya University, Nagoya, Aichi 464-8601 (Japan)

    2016-02-10

    We estimated the accuracy of coronal magnetic fields derived from radio observations by comparing them to potential field calculations and the differential emission measure measurements using EUV observations. We derived line-of-sight components of the coronal magnetic field from polarization observations of the thermal bremsstrahlung in the NOAA active region 11150, observed around 3:00 UT on 2011 February 3 using the Nobeyama Radioheliograph at 17 GHz. Because the thermal bremsstrahlung intensity at 17 GHz includes both chromospheric and coronal components, we extracted only the coronal component by measuring the coronal emission measure in EUV observations. In addition, we derived only the radio polarization component of the corona by selecting the region of coronal loops and weak magnetic field strength in the chromosphere along the line of sight. The upper limits of the coronal longitudinal magnetic fields were determined as 100–210 G. We also calculated the coronal longitudinal magnetic fields from the potential field extrapolation using the photospheric magnetic field obtained from the Helioseismic and Magnetic Imager. However, the calculated potential fields were certainly smaller than the observed coronal longitudinal magnetic field. This discrepancy between the potential and the observed magnetic field strengths can be explained consistently by two reasons: (1) the underestimation of the coronal emission measure resulting from the limitation of the temperature range of the EUV observations, and (2) the underestimation of the coronal magnetic field resulting from the potential field assumption.

  20. Role of the current density profile on drift wave stability in internal transport barrier reversed magnetic shear experiments at JET and Tore Supra

    Energy Technology Data Exchange (ETDEWEB)

    Fourment, C; Hoang, G T; Eriksson, L-G; Garbet, X; Litaudon, X; Tresset, G [EURATOM-CEA Association, CEA/DSM/DRFC, CEA Cadarache, 13108 St Paul-lez-Durance (France)

    2003-03-01

    The role of the current density profile on drift wave stability is investigated using a linear electrostatic gyro-kinetic code. The growth rates are shown to have a linear dependence on the normalized temperature gradients above a certain threshold. A parametric study of the threshold shows a dramatic stabilizing effect of negative magnetic shear, especially for large scale instabilities. A set of handy formulae fitting the threshold as a function of the magnetic shear and the safety factor is proposed. Analysis of reversed magnetic shear discharges with internal transport barrier (ITB) in JET shows that ion ITBs can be triggered by the negative magnetic shear in the core of the plasma. Subsequently, the increase of the ExB shearing rate allows for the expansion of the ITB, despite the increase of the linear growth rates due to the temperature gradient peaking. In the case of the electron ITB obtained in the Tore Supra LHEP mode, the central increase of the confinement is associated with the stabilization of large scale trapped electron modes by the negative magnetic shear effect, whereas the steep electron temperature gradient destabilizes the small scale electron temperature gradient modes, which prevent the electron heat transport to reach neoclassical levels.

  1. Fabrication of fully epitaxial magnetic tunnel junctions with a Co2MnSi thin film and a MgO tunnel barrier

    International Nuclear Information System (INIS)

    Kijima, H.; Ishikawa, T.; Marukame, T.; Matsuda, K.-I.; Uemura, T.; Yamamoto, M.

    2007-01-01

    Fully epitaxial magnetic tunnel junctions (MTJs) were fabricated with a Co-based full-Heusler alloy Co 2 MnSi (CMS) thin film having the ordered L2 1 structure as a lower electrode, a MgO tunnel barrier, and a Co 50 Fe 50 upper electrode. Reflection high-energy electron diffraction patterns observed in situ for each layer in the MTJ layer structure during fabrication clearly indicated that all layers of the CMS lower electrode, MgO tunnel barrier, and Co 50 Fe 50 upper electrode grew epitaxially. The microfabricated fully epitaxial CMS/MgO/Co 50 Fe 50 MTJs demonstrated relatively high tunnel magnetoresistance ratios of 90% at room temperature and 192% at 4.2 K

  2. Comparison of sensitivity of magnetic resonance imaging and evoked potentials in the detection of brainstem involvement in multiple sclerosis

    International Nuclear Information System (INIS)

    Comi, G.; Martinelli, V.; Medaglini, S.; Locatelli, T.; Magnani, G.; Poggi, A.; Triulzi, F.

    1988-01-01

    A comparison was made of the sensitivity of magnetic resonance imaging and the combined use of Brainstem Auditory Evoked Potential and Median Somatosensory Evoked Potential in the detection of brainstem dysfunction in 54 multiple sclerosis patients. 10 refs.; 2 tabs

  3. Transport barriers in plasmas

    International Nuclear Information System (INIS)

    Caldas, I L; Szezech, J D Jr; Kroetz, T; Marcus, F A; Roberto, M; Viana, R L; Lopes, S R

    2012-01-01

    We discuss the creation of transport barriers in magnetically confined plasmas with non monotonic equilibrium radial profiles. These barriers reduce the transport in the shearless region (i.e., where the twist condition does not hold). For the chaotic motion of particles in an equilibrium electric field with a nonmonotonic radial profile, perturbed by electrostatic waves, we show that a nontwist transport barrier can be created in the plasma by modifying the electric field radial profile. We also show non twist barriers in chaotic magnetic field line transport in the plasma near to the tokamak wall with resonant modes due to electric currents in external coils.

  4. Phase-dependent dynamic potential of magnetically coupled two-degree-of-freedom bistable energy harvester.

    Science.gov (United States)

    Kim, Pilkee; Nguyen, Minh Sang; Kwon, Ojin; Kim, Young-Jin; Yoon, Yong-Jin

    2016-09-28

    A system of magnetically coupled oscillators has been recently considered as a promising compact structure to integrate multiple bistable energy harvesters (BEHs), but its design is not straightforward owing to its varying potential energy pattern, which has not been understood completely yet. This study introduces the concept of phase-dependent dynamic potential in a magnetically coupled BEH system with two degrees of freedom (DOFs) to explain the underlying principle of the complicated dynamics of the system. Through theoretical simulations and analyses, two distinct dynamic regimes, called the out-of-phase and in-phase mode regimes in this report, are found to exist in the frequency regions of the 1 st and 2 nd primary intrawell resonances. For the out-of-phase mode regime, the frequency displacement (and output power) responses of the 2-DOF BEH system exhibit typical double-well dynamics, whereas for the in-phase mode regime, only single-well dynamics is observed though the system is statically bistable. These dynamic regimes are also revealed to be caused by the difference in the dynamic potential energy trajectories propagating on a high-dimensional potential energy surface. The present approach to the dynamics of the 2-DOF BEH system can be extended and applied to higher-DOF systems, which sheds light on compact and efficient designs of magnetically coupled BEH chain structures.

  5. Barrier bucket experiment at the AGS

    Directory of Open Access Journals (Sweden)

    M. Fujieda

    1999-12-01

    Full Text Available A barrier bucket experiment with two dedicated barrier cavities was performed at the Brookhaven AGS. One of the barrier cavities was a magnetic alloy (MA–loaded cavity and the other was a ferrite-loaded cavity. They generated a single sine wave with a peak voltage of 40 kV at a repetition rate of 351 kHz. A barrier rf system was established with these cavities and five bunches from the AGS booster were accumulated. A total of 3×10^{13} protons were stored without beam loss, and were successfully rebunched and accelerated. The longitudinal emittance growth was observed during accumulation by the barrier bucket, the blowup factor of which was about 3. The longitudinal mismatch between the rf bucket and the beam bunch was the main reason for the emittance growth. The potential distortions by beam loading of the ferrite cavity and the overshooting voltage of the MA cavity disturbed the smooth debunching.

  6. Potential barrier behavior in BiCuVOX materials Comportamento da barreira de potencial em materiais BiCuVOX

    Directory of Open Access Journals (Sweden)

    S. M. Gheno

    2011-12-01

    Full Text Available The BiMeVOX materials appear being high attractive for applications at low temperatures when the ionic conductivity is the determining parameter. The occurrence of many types substitution was confirmed for numerous Me ions, but the greatest interest have been focused on the BiCuVOX materials. The objective of this study was to image the potential barriers in BiCuVOX. The sample was sintered for 4 h at 750 °C and the results show that the high density compound can be obtained. Simultaneously, topography and electric force microscopy (EFM images are viewed side-by-side. EFM experiments were performed and the results show the maps of the electric field distribution on the surface of BiCuVOX. The formation of potential barrier was observed and the width and intensity were measured.Materiais do tipo BiMeVOX são muito atrativos para aplicações em baixas temperaturas quando a condutividade iônica for o parâmetro determinante. A ocorrência de muitos tipos de substituições foi confirmada para numerosos íons Me, dentre os quais, existe um grande interesse no estudo de materiais BiCuVOX. O objetivo deste estudo foi realizar o imageamento das barreiras de potencial em uma amostra de material BiCuVOX. A amostra foi sinterizada 4 h a 750 °C e apresentou alta densidade. Imagens da superfície topográfica e de microscopia de força elétrica (EFM foram obtidas simultaneamente em um microscópio de varredura por sonda. Os experimentos EFM mostraram um mapa da distribuição do campo elétrico na superfície do material BiCuVOx. A formação da barreira de potencial foi observada e tanto a largura quanto a altura foram medidas.

  7. Calculation of multidimensional potential energy surfaces for even-even transuranium nuclei: systematic investigation of the triaxiality effect on the fission barrier

    Science.gov (United States)

    Chai, Qing-Zhen; Zhao, Wei-Juan; Liu, Min-Liang; Wang, Hua-Lei

    2018-05-01

    Static fission barriers for 95 even-even transuranium nuclei with charge number Z = 94–118 have been systematically investigated by means of pairing self-consistent Woods-Saxon-Strutinsky calculations using the potential energy surface approach in multidimensional (β 2, γ, β 4) deformation space. Taking the heavier 252Cf nucleus (with the available fission barrier from experiment) as an example, the formation of the fission barrier and the influence of macroscopic, shell and pairing correction energies on it are analyzed. The results of the present calculated β 2 values and barrier heights are compared with previous calculations and available experiments. The role of triaxiality in the region of the first saddle is discussed. It is found that the second fission barrier is also considerably affected by the triaxial deformation degree of freedom in some nuclei (e.g., the Z=112–118 isotopes). Based on the potential energy curves, general trends of the evolution of the fission barrier heights and widths as a function of the nucleon numbers are investigated. In addition, the effects of Woods-Saxon potential parameter modifications (e.g., the strength of the spin-orbit coupling and the nuclear surface diffuseness) on the fission barrier are briefly discussed. Supported by National Natural Science Foundation of China (11675148, 11505157), the Project of Youth Backbone Teachers of Colleges and Universities of Henan Province (2017GGJS008), the Foundation and Advanced Technology Research Program of Henan Province (162300410222), the Outstanding Young Talent Research Fund of Zhengzhou University (1521317002) and the Physics Research and Development Program of Zhengzhou University (32410017)

  8. Modulation of amplitude and latency of motor evoked potential by direction of transcranial magnetic stimulation

    Science.gov (United States)

    Sato, Aya; Torii, Tetsuya; Iwahashi, Masakuni; Itoh, Yuji; Iramina, Keiji

    2014-05-01

    The present study analyzed the effects of monophasic magnetic stimulation to the motor cortex. The effects of magnetic stimulation were evaluated by analyzing the motor evoked potentials (MEPs). The amplitude and latency of MEPs on the abductor pollicis brevis muscle were used to evaluate the effects of repetitive magnetic stimulation. A figure eight-shaped flat coil was used to stimulate the region over the primary motor cortex. The intensity of magnetic stimulation was 120% of the resting motor threshold, and the frequency of magnetic stimulation was 0.1 Hz. In addition, the direction of the current in the brain was posterior-anterior (PA) or anterior-posterior (AP). The latency of MEP was compared with PA and AP on initial magnetic stimulation. The results demonstrated that a stimulus in the AP direction increased the latency of the MEP by approximately 2.5 ms. MEP amplitude was also compared with PA and AP during 60 magnetic stimulations. The results showed that a stimulus in the PA direction gradually increased the amplitude of the MEP. However, a stimulus in the AP direction did not modulate the MEP amplitude. The average MEP amplitude induced from every 10 magnetic pulses was normalized by the average amplitude of the first 10 stimuli. These results demonstrated that the normalized MEP amplitude increased up to approximately 150%. In terms of pyramidal neuron indirect waves (I waves), magnetic stimulation inducing current flowing backward to the anterior preferentially elicited an I1 wave, and current flowing forward to the posterior elicited an I3 wave. It has been reported that the latency of the I3 wave is approximately 2.5 ms longer than the I1 wave elicitation, so the resulting difference in latency may be caused by this phenomenon. It has also been reported that there is no alteration of MEP amplitude at a frequency of 0.1 Hz. However, this study suggested that the modulation of MEP amplitude depends on stimulation strength and stimulation direction.

  9. Evaluation of the potential toxicity of unmodified and modified cyclodextrins on murine blood-brain barrier endothelial cells.

    Science.gov (United States)

    Shityakov, Sergey; Salmas, Ramin Ekhteiari; Salvador, Ellaine; Roewer, Norbert; Broscheit, Jens; Förster, Carola

    2016-04-01

    In this study, we investigated the cytotoxic effects of unmodified α-cyclodextrin (α-CD) and modified cyclodextrins, including trimethyl-β-cyclodextrin (TRIMEB) and hydroxypropyl-β-cyclodextrin (HPβCD), on immortalized murine microvascular endothelial (cEND) cells of the blood-brain barrier (BBB). A CellTiter-Glo viability test, performed on the cEND cells showed significant differences among the different cyclodextrins. After 24 hr of incubation, TRIMEB was the most cytotoxic, and HPβCD was non-toxic. α-CD and TRIMEB exhibited greater cytotoxicity in the Dulbecco's modified Eagle's medium than in heat-inactivated human serum indicating protective properties of the human serum. The predicted dynamic toxicity profiles (Td) for α-CD and TRIMEB indicated higher cytotoxicity for these cyclodextrins compared to the reference compound (dimethylsulfoxide). Molecular dynamics simulation of cholesterol binding to the CDs suggested that not just cholesterol but phospholipids extraction might be involved in the cytotoxicity. Overall, the results demonstrate that HPβCD has the potential to be used as a candidate for drug delivery vector development and signify a correlation between the in vitro cytotoxic effect and cholesterol binding of cyclodextrins.

  10. Low-field EPR studies of levels near the top of the barrier in Mn 12-acetate reveal a new magnetization relaxation pathway

    Science.gov (United States)

    Rakvin, Boris; Žilić, Dijana; Dalal, Naresh S.; Harter, Andrew; Sanakis, Yiannis

    2006-07-01

    We show that X-band electron paramagnetic resonance (EPR) measurements using a dual-mode resonance cavity can directly probe the levels near the top of the magnetization reversal barrier in the single-molecule magnet (SMM) Mn 12-acetate. The observed transitions are much sharper than those reported in high-field EPR studies. The observed temperature dependence of the line positions points to the presence of a spin-diffusional mode. The correlation time for such fluctuations is of the order of 6×10 -8 s at 10 K, and follows an Arrhenius activation energy of 35-40 K. These results open a new avenue for understanding the mechanism of tunneling and spin-lattice relaxations in these SMMs.

  11. Apparatus and method for transfer of information by means of a curl-free magnetic vector potential field

    International Nuclear Information System (INIS)

    Gelinas, R.C.

    1984-01-01

    A system for transmission of information using a curl-free magnetic vector potential radiation field. The system includes current-carrying apparatus for generating a magnetic vector potential field with a curl-free component coupled to apparatus for modulating the current applied to the field generating apparatus. Receiving apparatus includes a detector with observable properties that vary with the application of an applied curl-free magnetic vector potential field. Analyzing apparatus for determining the information content of modulation imposed on the curl-free vector potential field can be established in materials that are not capable of transmitting more common electromagnetic radiation

  12. MAGNETIC CIRCUIT EQUIVALENT OF THE SYNCHRONOUS MOTOR WITH INCORPORATED MAGNETS

    Directory of Open Access Journals (Sweden)

    Fyong Le Ngo

    2015-01-01

    Full Text Available Magnetic circuitry computation is one of the central stages of designing a synchronous motor with incorporated magnets, which can be performed by means of a simplified method of the magnetic-circuits equivalent modeling. The article studies the magnetic circuit of the motor with the rotor-incorporated magnets, which includes four sectors: constant magnets with the field pole extension made of magnetically soft steel, magniflux dispersion sections containing air barriers and steel bridges; the air gap; the stator grooves, cogs and the frame yoke. The authors introduce an equivalent model of the magnetic circuit. High-energy magnets with a linear demagnetization curve are employed in the capacity of constant magnets. Two magnets create the magnetic flux for one pole. The decline of magnetic potential in the steel of the pole is negligible consequent on the admission that the poles magnetic inductivity µ = ∞. The rotor design provides for the air barriers and the steel bridges that close leakage flux. The induction-permeability curve linearization serves for the bridges magnetic saturation accountability and presents a polygonal line consisting of two linear sections. The estimation of the magnet circuit section including the cogs and the frame yoke is executed with account of the steel saturation, their magnetic conductivities thereat being dependent on the saturation rate. Relying on the equivalent model of the magnetic circuit, the authors deduce a system of two equations written from the first and the second Kirchhoff laws of the magnetic circuits. These equations allow solving two problems: specifying dimensions of the magnets by the preset value of the magnetic flow in the clearance and determining the clearance magnetic flow at the preset motor rotor-and-stator design.

  13. Maori Potential: Barriers to Creating Culturally-Responsive Learning Environments in Aotearoa/new Zealand: Te Timatanga O Te Ara--Kei Whea Te Ara?

    Science.gov (United States)

    Henderson, Lesleigh

    2013-01-01

    New Zealand Education reforms aligned with raising Maori student success are yet to result in Maori students reaching their educational potential (Howard, 2010; ERO, 2008; 2010). Why do many New Zealand teachers struggle to create and deliver programmes which allow Maori learners to succeed as Maori? What barriers and enablers exist today in New…

  14. Potential in vitro model for testing the effect of exposure to nanoparticles on the lung alveolar epithelial barrier

    Directory of Open Access Journals (Sweden)

    Raymond Derk

    2015-03-01

    Full Text Available Pulmonary barrier function plays a pivotal role in protection from inhaled particles. However, some nano-scaled particles, such as carbon nanotubes (CNT, have demonstrated the ability to penetrate this barrier in animal models, resulting in an unusual, rapid interstitial fibrosis. To delineate the underlying mechanism and specific bio-effect of inhaled nanoparticles in respiratory toxicity, models of lung epithelial barriers are required that allow accurate representation of in vivo systems; however, there is currently a lack of consistent methods to do so. Thus, this work demonstrates a well-characterized in vitro model of pulmonary barrier function using Calu-3 cells, and provides the experimental conditions required for achieving tight junction complexes in cell culture, with trans-epithelial electrical resistance measurement used as a biosensor for proper barrier formation and integrity. The effects of cell number and serum constituents have been examined and we found that changes in each of these parameters can greatly affect barrier formation. Our data demonstrate that use of 5.0 × 104 Calu-3 cells/well in the Transwell cell culture system, with 10% serum concentrations in culture media is optimal for assessing epithelial barrier function. In addition, we have utilized CNT exposure to analyze the dose-, time-, and nanoparticle property-dependent alterations of epithelial barrier permeability as a means to validate this model. Such high throughput in vitro cell models of the epithelium could be used to predict the interaction of other nanoparticles with lung epithelial barriers to mimic respiratory behavior in vivo, thus providing essential tools and bio-sensing techniques that can be uniformly employed.

  15. Hearing loss and potential hazards of metallic middle-ear implants in NMR-magnetic fields

    International Nuclear Information System (INIS)

    Huettenbrink, K.B.

    1987-01-01

    Concurrent with the expanding clinical applications of nuclear magnetic resonance (NMR) imaging, patients with metallic middle-ear implants will certainly be exposed to this strong magnetic field in the future. To determine potential hazards, associated with movements of steel- or Platinium stapes-prostheses, several tests were performed in a 0.5 tesla NMR unit and the induced forces were calculated. Although the commonly used paramagnetic steel-wire or platinium-alloys will not dislodge in vivo, ferromagnetic prostheses may present a hazardous risk. Prior to exposure to the magnetic field, information about the implanted material should therefore be obtained. A side-effect of the induced current flow is the attenuation of the sound-vibrations of the stapes prosthesis. This, 5-10 dB impairment of transmission develops only at a certain position of the patient's head, when the prosthesis vibrates perpendicularly to the magnetic field's Z-axis. Patients with a metallic prosthesis should be informed about this purely physical, harmless phenomenon prior to entering the NMR-cylinder. (orig.) [de

  16. Numerical methods for finding periodic points in discrete maps. High order islands chains and noble barriers in a toroidal magnetic configuration

    Energy Technology Data Exchange (ETDEWEB)

    Steinbrecher, G. [Association Euratom-Nasti Romania, Dept. of Theoretical Physics, Physics Faculty, University of Craiova (Romania); Reuss, J.D.; Misguich, J.H. [Association Euratom-CEA Cadarache, 13 - Saint-Paul-lez-Durance (France). Dept. de Recherches sur la Fusion Controlee

    2001-11-01

    We first remind usual physical and mathematical concepts involved in the dynamics of Hamiltonian systems, and namely in chaotic systems described by discrete 2D maps (representing the intersection points of toroidal magnetic lines in a poloidal plane in situations of incomplete magnetic chaos in Tokamaks). Finding the periodic points characterizing chains of magnetic islands is an essential step not only to determine the skeleton of the phase space picture, but also to determine the flux of magnetic lines across semi-permeable barriers like Cantori. We discuss here several computational methods used to determine periodic points in N dimensions, which amounts to solve a set of N nonlinear coupled equations: Newton method, minimization techniques, Laplace or steepest descend method, conjugated direction method and Fletcher-Reeves method. We have succeeded to improve this last method in an important way, without modifying its useful double-exponential convergence. This improved method has been tested and applied to finding periodic points of high order m in the 2D 'Tokamap' mapping, for values of m along rational chains of winding number n/m converging towards a noble value where a Cantorus exists. Such precise positions of periodic points have been used in the calculation of the flux across this Cantorus. (authors)

  17. [On Atomic Nuclear Fusion Processes at Low-Temperatures. An Enhancement of the Probability of Transition through a Potential Barrier Due to the So-Called Barrier Anti-Zeno Effect].

    Science.gov (United States)

    Namiot, V A

    2016-01-01

    It is known that in quantum mechanics the act of observing the experiment can affect the experimental findings in some cases. In particular, it happens under the so-called Zeno effect. In this work it is shown that in contrast to the "standard" Zeno-effect where the act of observing a process reduces the probability of its reality, an inverse situation when a particle transmits through a potential barrier (a so-called barrier anti-Zeno effect) can be observed, the observation of the particle essentially increases the probability of its transmission through the barrier. The possibility of using the barrier anti-Zeno effect is discussed to explain paradoxical results of experiments on "cold nuclear fusion" observed in various systems including biological ones. (According to the observers who performed the observations, the energy generation, which could not be explained by any chemical processes, as well as the change in the isotope and even element composition of the studied object may occur in these systems.

  18. Direct nuclear magnetic resonance identification and quantification of geometric isomers of conjugated linoleic acid in milk lipid fraction without derivatization steps: Overcoming sensitivity and resolution barriers

    International Nuclear Information System (INIS)

    Tsiafoulis, Constantinos G.; Skarlas, Theodore; Tzamaloukas, Ouranios; Miltiadou, Despoina; Gerothanassis, Ioannis P.

    2014-01-01

    Highlights: • The first NMR quantification of four geometric 18:2 CLA isomers has been achieved. • Sensitivity and resolution NMR barriers have been overcome. • Selective suppression and reduced 13 C spectral width have been utilized. • The method is applied in the milk lipid fraction without derivatization steps. • The method is selective, sensitive with very good analytical characteristics. - Abstract: We report the first successful direct and unequivocal identification and quantification of four minor geometric (9-cis, 11-trans) 18:2, (9-trans, 11-cis) 18:2, (9-cis, 11-cis) 18:2 and (9-trans, 11-trans) 18:2 conjugated linoleic acid (CLA) isomers in lipid fractions of lyophilized milk samples with the combined use of 1D 1 H-NMR, 2D 1 H- 1 H TOCSY and 2D 1 H- 13 C HSQC NMR. The significant sensitivity barrier has been successfully overcome under selective suppression of the major resonances, with over 10 4 greater equilibrium magnetization of the -(CH 2 ) n - 1 H spins compared to that of the 1 H spins of the conjugated bonds of the CLA isomers. The resolution barrier has been significantly increased using reduced 13 C spectral width in the 2D 1 H- 13 C HSQC experiment. The assignment was confirmed with spiking experiments with CLA standard compounds and the method does not require any derivatization steps for the lipid fraction. The proposed method is selective, sensitive and compares favorably with the GS-MS method of analysis

  19. Change of the work function and potential barrier transparency of W(100) and GaAs(110) single crystals during removing the inherent surface oxide layer

    International Nuclear Information System (INIS)

    Asalkhanov, Yu.I.; Saneev, Eh.L.

    2002-01-01

    Changes of current voltage characteristics of slow monoenergetic electron beam through the surfaces of W(100) and GaAs(100) single crystals have been measured in the process of surface oxide layers elimination. It is shown that work function is decreased and transparency coefficient of surface potential barrier is increased under increasing the temperature of vacuum annealing. Peculiarities of surface potential change under oxide layer elimination in metals and semiconductors are discussed [ru

  20. Theory of the time orbiting potential (TOP) quadrupole magnetic trap for cold atoms

    Energy Technology Data Exchange (ETDEWEB)

    Minogin, V.G.; Richmond, J.A.; Opat, G.I.

    1997-12-31

    An analytical theory of the time orbiting potential (TOP) quadrupole magnetic trap for cold atoms is developed. It is shown that the rotating magnetic filed used to create the time-average harmonic potential is responsible for the formation of quasi-energy states of an atom in the trap. It is found that the motion of an atom near the origin of the trap can be represented as consisting of slow motion in the effective potential and fast oscillations with small amplitude. Dipole, quadrupole and higher order atomic transitions between quasi-energy states are shown to be responsible for an additional effective potential for slow atomic motion which is proportional to the fourth power of the atomic co-ordinate. Eigenstates and eigenfunctions are used to calculate the co-ordinate distribution for a single atom. It is concluded that at low temperature the quantum statistical co-ordinate distribution for a single atom exhibits a narrow central peak due to the ground state population, together with relatively broad wings due to the excited state population. (authors). 20 refs., 1 tab., 6 figs.

  1. Effects of low-frequency repetitive transcranial magnetic stimulation on event-related potential P300

    Science.gov (United States)

    Torii, Tetsuya; Sato, Aya; Iwahashi, Masakuni; Iramina, Keiji

    2012-04-01

    The present study analyzed the effects of repetitive transcranial magnetic stimulation (rTMS) on brain activity. P300 latency of event-related potential (ERP) was used to evaluate the effects of low-frequency and short-term rTMS by stimulating the supramarginal gyrus (SMG), which is considered to be the related area of P300 origin. In addition, the prolonged stimulation effects on P300 latency were analyzed after applying rTMS. A figure-eight coil was used to stimulate left-right SMG, and intensity of magnetic stimulation was 80% of motor threshold. A total of 100 magnetic pulses were applied for rTMS. The effects of stimulus frequency at 0.5 or 1 Hz were determined. Following rTMS, an odd-ball task was performed and P300 latency of ERP was measured. The odd-ball task was performed at 5, 10, and 15 min post-rTMS. ERP was measured prior to magnetic stimulation as a control. Electroencephalograph (EEG) was measured at Fz, Cz, and Pz that were indicated by the international 10-20 electrode system. Results demonstrated that different effects on P300 latency occurred between 0.5-1 Hz rTMS. With 1 Hz low-frequency magnetic stimulation to the left SMG, P300 latency decreased. Compared to the control, the latency time difference was approximately 15 ms at Cz. This decrease continued for approximately 10 min post-rTMS. In contrast, 0.5 Hz rTMS resulted in delayed P300 latency. Compared to the control, the latency time difference was approximately 20 ms at Fz, and this delayed effect continued for approximately 15 min post-rTMS. Results demonstrated that P300 latency varied according to rTMS frequency. Furthermore, the duration of the effect was not similar for stimulus frequency of low-frequency rTMS.

  2. Materials Characterization of Feraheme/Ferumoxytol and Preliminary Evaluation of Its Potential for Magnetic Fluid Hyperthermia

    Directory of Open Access Journals (Sweden)

    Jon Dobson

    2013-08-01

    Full Text Available Feraheme, is a recently FDA-cleared superparamagnetic iron oxide nanoparticle (SPION-based MRI contrast agent that is also employed in the treatment of iron deficiency anemia. Feraheme nanoparticles have a hydrodynamic diameter of 30 nm and consist of iron oxide crystallites complexed with a low molecular weight, semi-synthetic carbohydrate. These features are attractive for other potential biomedical applications such as magnetic fluid hyperthermia (MFH, since the carboxylated polymer coating affords functionalization of the particle surface and the size allows for accumulation in highly vascularized tumors via the enhanced permeability and retention effect. This work presents morphological and magnetic characterization of Feraheme by transmission electron microscopy (TEM, Energy dispersive X-ray spectroscopy (EDX, and superconducting quantum interference device (SQUID magnetometry. Additionally, the results of an initial evaluation of the suitability of Feraheme for MFH applications are described, and the data indicate the particles possess promising properties for this application.

  3. Plasma potential in a magnetic mirror with electron-cyclotron-resonance heating

    International Nuclear Information System (INIS)

    Smith, P.K.

    1983-01-01

    Experimental and theoretical studies of the ECRH plasma in the University of Wisconsin DE Machine magnetic mirror have been undertaken. Typical plasma parameters in these experiments were T/sub e/ - 10 to 30 eV, T/sub i/ - 4 eV, V/sub po/ (plasma potential at midplane) - 20 to 50 V, midplane plasma density n 0 - 10 16 m - 3 , B 0 (magnetic field strength on axis at midplane) - .005 to .01 T, mirror ratio R - 5 to 20. The principal experimental findings were the appearance of strong density peaks (approx. 2 x background) and notable V/sub f/ dips (approx. kT/sub e//e) in a narrow (approx. 1 cm) region near the axial positions of cyclotron resonance. The properties of these dips do not change greatly over the range of operating parameters, but are narrower at higher pressures

  4. Balloon dilation of the eustachian tube in a cadaver model: technical considerations, learning curve, and potential barriers.

    Science.gov (United States)

    McCoul, Edward D; Singh, Ameet; Anand, Vijay K; Tabaee, Abtin

    2012-04-01

    The surgical management options for eustachian tube dysfunction have historically been limited. The goal of the current study was to evaluate the technical considerations, learning curve, and potential barriers for balloon dilation of the eustachian tube (BDET) as an alternative treatment modality. Prospective preclinical trial of BDET in a cadaver model. A novel balloon catheter device was used for eustachian tube dilation. Twenty-four BDET procedures were performed by three independent rhinologists with no prior experience with the procedure (eight procedures per surgeon). The duration and number of attempts of the individual steps and overall procedure were recorded. Endoscopic examination of the eustachian tube was performed after each procedure, and the surgeon was asked to rate the subjective difficulty on a five-point scale. Successful completion of the procedure occurred in each case. The overall mean duration of the procedure was 284 seconds, and a mean number of 1.15 attempts were necessary to perform the individual steps. The mean subjective procedure difficulty was noted as somewhat easy. Statistically shorter duration and subjectively easier procedure were noted in the second compared to the first half of the series, indicating a favorable learning curve. Linear fissuring within the eustachian tube lumen without submucosal disruption (nine procedures, 37%) and with submucosal disruption (five procedures, 21%) were noted. The significance of these physical findings is unclear. Preclinical testing of BDET is associated with favorable duration, learning curve, and overall ease of completion. Clinical trials are necessary to evaluate safety and efficacy. Copyright © 2012 The American Laryngological, Rhinological, and Otological Society, Inc.

  5. Heavy-ion fusion: Channel-coupling effects, the barrier penetration model, and the threshold anomaly for heavy-ion potentials

    International Nuclear Information System (INIS)

    Satchler, G.R.; Nagarajan, M.A.; Lilley, J.S.; Thompson, I.J.

    1987-01-01

    We study the formal structure of the influence of channel coupling on near- and sub-barrier fusion. The reduction to a one-channel description is studied, with emphasis on the channel-coupling effects being manifest primarily as an energy dependence (the ''threshold anomaly'') of the real nuclear potential. The relation to the barrier penetration model is examined critically. The results of large-scale coupled-channel calculations are used as ''data'' to illustrate the discussion. Particular emphasis is placed on the importance of reproducing correctly the partial-wave (or ''spin'') distributions. The simple barrier penetration model is found to be adequate to exhibit the strong enhancements due to channel couplings when the threshold anomaly is taken into account, although there may be important corrections due to the long-ranged peripheral absorption, especially from Coulomb excitation. copyright 1987 Academic Press, Inc

  6. Experimental research on electric field jump in low magnetic fields: Detection of damage in new ex-situ MgB{sub 2} barriers in MgB{sub 2} wires

    Energy Technology Data Exchange (ETDEWEB)

    Gajda, D., E-mail: dangajda@op.pl [International Laboratory of High Magnetic Fields and Low Temperatures, Gajowicka 95, 53-421 Wroclaw (Poland); Morawski, A. [Institute of High Pressure Physics, Polish Academy of Sciences, Sokolowska 29/37, 01-142 Warszawa (Poland); Zaleski, A. [Institute of Low Temperature and Structure Research, Polish Academy of Sciences, Okólna 2, 50-422 Wroclaw (Poland); Hossain, M.S.A. [Institute for Superconducting and Electronic Materials, AIIM, University of Wollongong, North Wollongong, NSW 2519 (Australia); Rindfleisch, M. [Hyper Tech Research, Inc, 1275 Kinnear Road, Columbus, OH 43212 (United States); Cetner, T. [Institute of High Pressure Physics, Polish Academy of Sciences, Sokolowska 29/37, 01-142 Warszawa (Poland)

    2015-10-25

    We explored the incorporation of field sweep (constant current and rapidly increasing magnetic field) into the four-probe method as a new technique to detect defects in barrier layers in superconducting MgB{sub 2} wires. This method allows us to observe jumps in the electric field in low magnetic fields. The scanning electron microscopy results indicate that such a jump originates from cracks in Nb barriers and ex-situ MgB{sub 2} barriers. Our research indicates that the field sweep allows us to detect damage to barriers that are made of superconducting materials. This method can be the basis for an industrial method for detecting damages in MgB{sub 2} wires. These defects reduce the critical current of MgB{sub 2} wire. Detection and removal of these defects will allow us to produce MgB{sub 2} wires with ex-situ MgB{sub 2} and Nb barriers that will have improved critical current density. Manufacturing of MgB{sub 2} wires with new ex-situ MgB{sub 2} barriers is a new technological concept. This type of barrier is cheaper and easier to manufacture, leading to cheaper MgB{sub 2} wires. Moreover, we show that critical current can be measured by two methods: current sweep (constant magnetic field and quickly increasing current) and field sweep. - Graphical abstract: Our results indicate that the jump electric field low magnetic fields. This jump indicates damage in Nb and ex situ MgB{sub 2} barrier. Detection and removal of defects will increase J{sub c} in MgB{sub 2} wires and will increase the applicability of MgB{sub 2} wire. - Highlights: • Jump electric field in the 1 T indicates damage to the Nb barrier. • Jump resistance at 9 K indicates damage to the Nb barrier. • Jump electric field in low magnetic field indicates damage to ex situ MgB{sub 2} barrier. • Damage Nb and ex situ MgB{sub 2} barrier significantly reduces the critical current density in the MgB{sub 2} wire.

  7. Bilateral somatosensory evoked potentials following intermittent theta-burst repetitive transcranial magnetic stimulation.

    Science.gov (United States)

    Premji, Azra; Ziluk, Angela; Nelson, Aimee J

    2010-08-05

    Intermittent theta-burst stimulation (iTBS) is a form of repetitive transcranial magnetic stimulation that may alter cortical excitability in the primary somatosensory cortex (SI). The present study investigated the effects of iTBS on subcortical and early cortical somatosensory evoked potentials (SEPs) recorded over left, iTBS stimulated SI and the right-hemisphere non-stimulated SI. SEPs were recorded before and at 5, 15, and 25 minutes following iTBS. Compared to pre-iTBS, the amplitude of cortical potential N20/P25 was significantly increased for 5 minutes from non-stimulated SI and for 15 to 25 minutes from stimulated SI. Subcortical potentials recorded bilaterally remained unaltered following iTBS. We conclude that iTBS increases the cortical excitability of SI bilaterally and does not alter thalamocortical afferent input to SI. ITBS may provide one avenue to induce cortical plasticity in the somatosensory cortex.

  8. Nonlinear absorption coefficient and relative refraction index change for an asymmetrical double δ-doped quantum well in GaAs with a Schottky barrier potential

    International Nuclear Information System (INIS)

    Rojas-Briseño, J.G.; Martínez-Orozco, J.C.; Rodríguez-Vargas, I.; Mora-Ramos, M.E.; Duque, C.A.

    2013-01-01

    In this work we are reporting the energy level spectrum for a quantum system consisting of an n-type double δ-doped quantum well with a Schottky barrier potential in a Gallium Arsenide matrix. The calculated states are taken as the basis for the evaluation of the linear and third-order nonlinear contributions to the optical absorption coefficient and to the relative refractive index change, making particular use of the asymmetry of the potential profile. These optical properties are then reported as a function of the Schottky barrier height (SBH) and the separation distance between the δ-doped quantum wells. Also, the effects of the application of hydrostatic pressure are studied. The results show that the amplitudes of the resonant peaks are of the same order of magnitude of those obtained in the case of single δ-doped field effect transistors; but tailoring the asymmetry of the confining potential profile allows the control the resonant peak positions

  9. Nonlinear absorption coefficient and relative refraction index change for an asymmetrical double δ-doped quantum well in GaAs with a Schottky barrier potential

    Energy Technology Data Exchange (ETDEWEB)

    Rojas-Briseño, J.G.; Martínez-Orozco, J.C.; Rodríguez-Vargas, I. [Unidad Académica de Física, Universidad Autónoma de Zacatecas, Calzada Solidaridad esquina con Paseo la Bufa S/N, C.P. 98060, Zacatecas, Zac. (Mexico); Mora-Ramos, M.E. [Facultad de Ciencias, Universidad Autónoma del Estado de Morelos, Av. Universidad 1001, CP 62209, Cuernavaca, Morelos (Mexico); Instituto de Física, Universidad de Antioquia, AA 1226, Medellín (Colombia); Duque, C.A., E-mail: cduque@fisica.udea.edu.co [Instituto de Física, Universidad de Antioquia, AA 1226, Medellín (Colombia)

    2013-09-01

    In this work we are reporting the energy level spectrum for a quantum system consisting of an n-type double δ-doped quantum well with a Schottky barrier potential in a Gallium Arsenide matrix. The calculated states are taken as the basis for the evaluation of the linear and third-order nonlinear contributions to the optical absorption coefficient and to the relative refractive index change, making particular use of the asymmetry of the potential profile. These optical properties are then reported as a function of the Schottky barrier height (SBH) and the separation distance between the δ-doped quantum wells. Also, the effects of the application of hydrostatic pressure are studied. The results show that the amplitudes of the resonant peaks are of the same order of magnitude of those obtained in the case of single δ-doped field effect transistors; but tailoring the asymmetry of the confining potential profile allows the control the resonant peak positions.

  10. Magnets

    International Nuclear Information System (INIS)

    Young, I.R.

    1984-01-01

    A magnet pole piece for an NMR imaging magnet is made of a plurality of magnetic wires with one end of each wire held in a non-magnetic spacer, the other ends of the wires being brought to a pinch, and connected to a magnetic core. The wires may be embedded in a synthetic resin and the magnetisation and uniformity thereof can be varied by adjusting the density of the wires at the spacer which forms the pole piece. (author)

  11. Uniaxial Magnetization Performance of Textured Fe Nanowire Arrays Electrodeposited by a Pulsed Potential Deposition Technique

    Science.gov (United States)

    Neetzel, C.; Ohgai, T.; Yanai, T.; Nakano, M.; Fukunaga, H.

    2017-11-01

    Textured ferromagnetic Fe nanowire arrays were electrodeposited using a rectangular-pulsed potential deposition technique into anodized aluminum oxide nanochannels. During the electrodeposition of Fe nanowire arrays at a cathodic potential of - 1.2 V, the growth rate of the nanowires was ca. 200 nm s-1. The aspect ratio of Fe nanowires with a diameter of 30 ± 5 nm reached ca. 2000. The long axis of Fe nanowires corresponded with the direction when a large overpotential during the on-time pulse was applied, whereas it orientated to the direction under the potentiostatic condition with a small overpotential. By shifting the on-time cathode potential up to - 1.8 V, the texture coefficient for the (200) plane, TC200, reached up to 1.94. Perpendicular magnetization performance was observed in Fe nanowire arrays. With increasing TC200, the squareness of Fe nanowire arrays increased up to 0.95 with the coercivity maintained at 1.4 kOe at room temperature. This research result has opened a novel possibility of Fe nanowire arrays that can be applied for a new permanent magnetic material without rare-earth metals.

  12. Ferumoxytol-enhanced magnetic resonance angiography for the assessment of potential kidney transplant recipients

    Energy Technology Data Exchange (ETDEWEB)

    Stoumpos, Sokratis; Mark, Patrick B. [Queen Elizabeth University Hospital, Renal and Transplant Unit, Glasgow (United Kingdom); University of Glasgow, Institute of Cardiovascular and Medical Sciences, BHF Glasgow Cardiovascular Research Centre, Glasgow (United Kingdom); Hennessy, Martin; Kasthuri, Ram; Roditi, Giles [Queen Elizabeth University Hospital, Department of Radiology, Glasgow (United Kingdom); Vesey, Alex T.; Kingsmore, David B. [Queen Elizabeth University Hospital, Renal and Transplant Unit, Glasgow (United Kingdom); Radjenovic, Aleksandra [University of Glasgow, Institute of Cardiovascular and Medical Sciences, BHF Glasgow Cardiovascular Research Centre, Glasgow (United Kingdom)

    2018-01-15

    Traditional contrast-enhanced methods for scanning blood vessels using magnetic resonance imaging (MRI) or CT carry potential risks for patients with advanced kidney disease. Ferumoxytol is a superparamagnetic iron oxide nanoparticle preparation that has potential as an MRI contrast agent in assessing the vasculature. Twenty patients with advanced kidney disease requiring aorto-iliac vascular imaging as part of pre-operative kidney transplant candidacy assessment underwent ferumoxytol-enhanced magnetic resonance angiography (FeMRA) between December 2015 and August 2016. All scans were performed for clinical indications where standard imaging techniques were deemed potentially harmful or inconclusive. Image quality was evaluated for both arterial and venous compartments. First-pass and steady-state FeMRA using incremental doses of up to 4 mg/kg body weight of ferumoxytol as intravenous contrast agent for vascular enhancement was performed. Good arterial and venous enhancements were achieved, and FeMRA was not limited by calcification in assessing the arterial lumen. The scans were diagnostic and all patients completed their studies without adverse events. Our preliminary experience supports the feasibility and utility of FeMRA for vascular imaging in patients with advanced kidney disease due for transplant listing, which has the advantages of obtaining both arteriography and venography using a single test without nephrotoxicity. (orig.)

  13. Stochastic simulation of pitting degradation of multi-barrier waste container in the potential repository at Yucca Mountain

    International Nuclear Information System (INIS)

    Lee, J.H.; Atkins, J.E.; Andrews, R.W.

    1995-01-01

    A detailed stochastic waste package degradation simulation model was developed incorporating the humid-air and aqueous general and pitting corrosion models for the carbon steel corrosion-allowance outer barrier and aqueous pitting corrosion model for the Alloy 825 corrosion-resistant inner barrier. The uncertainties in the individual corrosion models were also incorporated to capture the variability in the corrosion degradation among waste packages and among pits in the same waste package. Within the scope of assumptions employed in the simulations, the corrosion modes considered, and the near-field conditions from the drift-scale thermohydrologic model, the results of the waste package performance analyses show that the current waste package design appears to meet the 'controlled design assumption' requirement of waste package performance, which is currently defined as having less than 1% of waste packages breached at 1,000 years. It was shown that, except for the waste packages that fail early, pitting corrosion of the corrosion-resistant inner barrier has a greater control on the failure of waste packages and their subsequent degradation than the outer barrier. Further improvement and substantiation of the inner barrier pitting model (currently based on an elicitation) is necessary in future waste package performance simulation model

  14. Brain Tumor Targeting of Magnetic Nanoparticles for Potential Drug Delivery: Effect of Administration Route and Magnetic Field Topography

    Science.gov (United States)

    Chertok, Beata; David, Allan E.; Yang, Victor C.

    2011-01-01

    Our previous studies demonstrated feasibility of magnetically-mediated retention of iron-oxide nanoparticles in brain tumors after intravascular administration. The purpose of this study was to elucidate strategies for further improvement of this promising approach. In particular, we explored administration of the nanoparticles via a non-occluded carotid artery as a way to increase the passive exposure of tumor vasculature to nanoparticles for subsequent magnetic entrapment. However, aggregation of nanoparticles in the afferent vasculature interfered with tumor targeting. The magnetic setup employed in our experiments was found to generate a relatively uniform magnetic flux density over a broad range, exposing the region of the afferent vasculature to high magnetic force. To overcome this problem, the magnetic setup was modified with a 9-mm diameter cylindrical NdFeB magnet to exhibit steeper magnetic field topography. Six-fold reduction of the magnetic force at the injection site, achieved with this modification, alleviated the aggregation problem under the conditions of intact carotid blood flow. Using this setup, carotid administration was found to present 1.8-fold increase in nanoparticle accumulation in glioma compared to the intravenous route at 350 mT. This increase was found to be in reasonable agreement with the theoretically estimated 1.9-fold advantage of carotid administration, Rd. The developed approach is expected to present an even greater advantage when applied to drug-loaded nanoparticles exhibiting higher values of Rd. PMID:21763736

  15. Cold atoms near surfaces: designing potentials by sculpturing wires

    International Nuclear Information System (INIS)

    Della Pietra, Leonardo; Aigner, Simon; Hagen, Christoph vom; Lezec, Henri J; Schmiedmayer, Joerg

    2005-01-01

    The magnetic trapping potentials for atoms on atom chips are determined by the current flow pattern in the chip wires. By modifying the wire shape using focused ion beam nano-machining we can design specialized current flow patterns and therefore micro-design the magnetic trapping potentials. We give designs for a barrier, a quantum dot, and a double well or double barrier and show preliminary experiments with ultra cold atoms in these designed potentials

  16. MHD Equilibrium with Reversed Current Density and Magnetic Islands Revisited: the Vacuum Vector Potential Calculus

    Science.gov (United States)

    L. Braga, F.

    2013-10-01

    The solution of Grad-Shafranov equation determines the stationary behavior of fusion plasma inside a tokamak. To solve the equation it is necessary to know the toroidal current density profile. Recent works show that it is possible to determine a magnetohydrodynamic (MHD) equilibrium with reversed current density (RCD) profiles that presents magnetic islands. In this work we show analytical MHD equilibrium with a RCD profile and analyze the structure of the vacuum vector potential associated with these equilibria using the virtual casing principle.

  17. Statistical analysis of internal transport barriers in JET

    Energy Technology Data Exchange (ETDEWEB)

    Maget, P [Association Euratom-CEA, Cadarache, F-13108 St Paul-lez-Durance (France); Esposito, B [Associazione Euratom-ENEA sulla Fusione, C.R. Frascati, Frascati (Italy); Joffrin, E [Association Euratom-CEA, Cadarache, F-13108 St Paul-lez-Durance (France); Hawkes, N [Euratom-UKAEA Fusion Association, Culham Science Centre, Abingdon, Oxon OX14 3DB (United Kingdom); Mazon, D [Association Euratom-CEA, Cadarache, F-13108 St Paul-lez-Durance (France); Baranov, Y [Euratom-UKAEA Fusion Association, Culham Science Centre, Abingdon, Oxon OX14 3DB (United Kingdom); Fourment, C [Association Euratom-CEA, Cadarache, F-13108 St Paul-lez-Durance (France); Hoang, G T [Association Euratom-CEA, Cadarache, F-13108 St Paul-lez-Durance (France)

    2003-08-01

    The potential role of magnetic shear, rational safety factor surfaces and shearing rate on the confinement is investigated on the basis of a database analysis of JET internal transport barriers (ITBs). The ITB is quantified using the JET ITB criterion (Tresset G et al 2002 Nucl. Fusion 42 520). The relation between the shearing rate and the magnetic shear, already established for positive magnetic shear barrier (Tala T J J et al 2001 Plasma Phys. Control. Fusion 43 507), is investigated at low and negative magnetic shear, where the threshold in shearing rate is found to be lower than for positive magnetic shear barriers. Defining the ITB from the departure from profile stiffness is found to be consistent with the database results, and the critical gradient length is found to be minimum at low magnetic shear. Finally, ITBs are found to be localized in the vicinity of integer safety factor surfaces in positive magnetic shear plasmas, whereas no correlation is found with integer values when the barrier is localized in negative magnetic shear regions.

  18. Novel Magnetic Cross-Linked Cellulase Aggregates with a Potential Application in Lignocellulosic Biomass Bioconversion

    Directory of Open Access Journals (Sweden)

    Junqi Jia

    2017-02-01

    Full Text Available The utilization of renewable biomass resources to produce high-value chemicals by enzymatic processes is beneficial for alternative energy production, due to the accelerating depletion of fossil fuels. As immobilization techniques can improve enzyme stability and reusability, a novel magnetic cross-linked cellulase aggregate has been developed and applied for biomass bioconversion. The crosslinked aggregates could purify and immobilize enzymes in a single operation, and could then be combined with magnetic nanoparticles (MNPs, which provides easy separation of the materials. The immobilized cellulase showed a better activity at a wider temperature range and pH values than that of the free cellulase. After six cycles of consecutive reuse, the immobilized cellulase performed successful magnetic separation and retained 74% of its initial activity when carboxylmethyl cellulose (CMC was used as the model substrate. Furthermore, the structure and morphology of the immobilized cellulase were studied by Fourier transform infrared spectroscopy (FTIR and scanning electron microscopy (SEM. Moreover, the immobilized cellulase was shown to hydrolyze bamboo biomass with a yield of 21%, and was re-used in biomass conversion up to four cycles with 38% activity retention, which indicated that the immobilized enzyme has good potential for biomass applications.

  19. Novel Magnetic Cross-Linked Cellulase Aggregates with a Potential Application in Lignocellulosic Biomass Bioconversion.

    Science.gov (United States)

    Jia, Junqi; Zhang, Weiwei; Yang, Zengjie; Yang, Xianling; Wang, Na; Yu, Xiaoqi

    2017-02-10

    The utilization of renewable biomass resources to produce high-value chemicals by enzymatic processes is beneficial for alternative energy production, due to the accelerating depletion of fossil fuels. As immobilization techniques can improve enzyme stability and reusability, a novel magnetic cross-linked cellulase aggregate has been developed and applied for biomass bioconversion. The crosslinked aggregates could purify and immobilize enzymes in a single operation, and could then be combined with magnetic nanoparticles (MNPs), which provides easy separation of the materials. The immobilized cellulase showed a better activity at a wider temperature range and pH values than that of the free cellulase. After six cycles of consecutive reuse, the immobilized cellulase performed successful magnetic separation and retained 74% of its initial activity when carboxylmethyl cellulose (CMC) was used as the model substrate. Furthermore, the structure and morphology of the immobilized cellulase were studied by Fourier transform infrared spectroscopy (FTIR) and scanning electron microscopy (SEM). Moreover, the immobilized cellulase was shown to hydrolyze bamboo biomass with a yield of 21%, and was re-used in biomass conversion up to four cycles with 38% activity retention, which indicated that the immobilized enzyme has good potential for biomass applications.

  20. Projecting the range of potential future climate change as an aid in the assessment of the effectiveness of the Hanford Site Permanent Isolation Barrier

    Energy Technology Data Exchange (ETDEWEB)

    Petersen, K.L.

    1993-10-01

    The Hanford Site Permanent Isolation Barrier Development Program was organized to develop an in-place disposal capability for low-level nuclear waste for the US Department of Energy at the Hanford Site in south-eastern Washington. Layered earthen and engineered barriers are being developed by Westinghouse Hanford Company and the Pacific Northwest Laboratory that will function in what is presently a semiarid environment (annual precipitation 150 mm) for at least 1,000 yr by limiting the infiltration of water through the waste. The Long-Term Climate Change Task is one of several key barrier tasks. Based on the recommendation of a panel of internationally recognized climate and modeling experts, climatic data for this task is being acquired in a step-wise and multi-disciplinary manner. The specific research strategy includes literature review and specialized studies to obtain pollen-derived climatic reconstruction, documented historic weather patterns, and Global Circulation Model output of potential future climate changes related to both the greenhouse effect and the cycling into the next ice age. The specific goals of the task are to: (1) obtain defensible probabilistic projections of the long-term climate variability in the Hanford Site region at many different time scales into the future, (2) develop several test case climate scenarios that bracket the range of potential future climate, and (3) use the climate scenarios both to test and to model protective barrier performance.

  1. Survey nonresponse among ethnic minorities in a national health survey - a mixed-method study of participation, barriers, and potentials

    DEFF Research Database (Denmark)

    Ahlmark, Nanna; Algren, Maria Holst; Holmberg, Teresa

    2015-01-01

    , to alienation generated by the questions' focus on disease and cultural assumptions, or mistrust regarding anonymity. Ethnic minorities seem particularly affected by such barriers. To increase survey participation, questions could be sensitized to reflect multicultural traditions, and the impact of sender......Objectives. The participation rate in the Danish National Health Survey (DNHS) 2010 was significantly lower among ethnic minorities than ethnic Danes. The purpose was to characterize nonresponse among ethnic minorities in DNHS, analyze variations in item nonresponse, and investigate barriers...... and incentives to participation. Design. This was a mixed-method study. Logistic regression was used to analyze nonresponse using data from DNHS (N = 177,639 and chi-square tests in item nonresponse analyses. We explored barriers and incentives regarding participation through focus groups and cognitive...

  2. Everyday physical activity in ambulatory heart transplant candidates: the role of expected health benefits, social support, and potential barriers.

    Science.gov (United States)

    Gerhardt, Andreas; Weidner, Gerdi; Grassmann, Mariel; Spaderna, Heike

    2014-04-01

    Physical activity (PA) is recommended for stable patients with advanced heart failure (HF). We evaluated expected health benefits of PA and social support as facilitators of PA, and physical symptom distress and psychological distress (depression, anxiety) as barriers to PA. Additionally, we investigated if facilitators of PA are of particular importance for patients who report barriers. We analyzed data assessed at time of waitlisting in 231 ambulatory patients (53.4 ± 10.3 years, 18 % women) who were enrolled in the multisite Waiting for a New Heart Study in 1 Austrian and 16 German hospitals. Self-reported everyday PA scores (number of activities, duration of activities) was regressed on demographic characteristics and indicators of disease severity (ejection fraction, peak oxygen consumption), facilitators (expected health benefits of PA, perceived emotional support, perceived support for PA), and barriers to PA (physical symptom distress, psychological distress). Interaction terms of facilitators with barriers were also examined. PA was positively associated with higher peak oxygen consumption, validating self-reported PA. Regarding facilitators, expected health benefits of PA were independently associated with higher PA (p values barriers, depression tended to be associated with fewer activities (p = 0.068). However, in the presence of barriers (depression, physical symptoms), feeling supported for being physically active was positively associated with PA (p values < 0.05). Interventions to improve PA may benefit from strengthening positive expectations of health outcomes associated with everyday PA and fostering PA-specific social support for those distressed by HF symptoms or depression.

  3. Barrier cell sheath formation

    International Nuclear Information System (INIS)

    Kesner, J.

    1980-04-01

    The solution for electrostatic potential within a simply modeled tandem mirror thermal barrier is seen to exhibit a sheath at each edge of the cell. The formation of the sheath requires ion collisionality and the analysis assmes that the collisional trapping rate into the barrier is considerably slower than the barrier pump rate

  4. Magnetism of hexagonal close-packed nickel calculated by full-potential linearized augmented plane wave method

    International Nuclear Information System (INIS)

    Tian, F.; Tian, H.; Whitmore, L.; Ye, L.Y.

    2015-01-01

    The energy dependent on volume of hexagonal close-packed (hcp) nickel with different magnetism is calculated by full-potential linearized augmented plane wave method. Based on the calculation ferromagnetic state is found to be the most stable state. The magnetic moment of hcp Ni is calculated and compared to those calculated by different pseudo-potential methods. Furthermore, it is also compared to that of face-centered cubic (fcc) one with the reason discussed

  5. Metal-oxo containing polymer nanobeads as potential contrast agents for magnetic resonance imaging

    Science.gov (United States)

    Pablico, Michele Huelar

    Magnetic resonance imaging (MRI) has greatly revolutionized the way diseases are detected and treated, as it is a non-invasive imaging modality solely based on the interaction of radiowaves and hydrogen nuclei in the presence of an external magnetic field. It is widely used today for the diagnosis of diseases as it offers an efficient method of mapping structure and function of soft tissues in the body. Most MRI examinations utilize paramagnetic materials known as contrast agents, which enhance the MR signal by decreasing the longitudinal (T1) and transverse (T2) relaxation times of the surrounding water protons in biological systems. This results into increased signal intensity differences thereby allowing better interpretation and analysis of pathological tissues. Contrast agents function by lowering the T1 or lowering the T2, resulting into bright and dark contrasts, respectively. The most common MRI contrast agents that are in clinical use today are gadolinium chelates and superparamagnetic iron oxide nanoparticles, both of which have their own advantages in terms of contrast enhancement properties. In the past few years, however, there has been interest in utilizing metal-containing clusters for MRI contrast enhancement as these materials bridge the gap between the constrained structure and magnetic properties of the gadolinium chelates with the superparamagnetic behavior of the iron oxide nanoparticles. Recently, metallic clusters containing Mn and Fe metal centers have received increased attention mainly because of their potential for high spin states and benign nature. In the quest to further develop novel imaging agents, this research has focused on investigating the use of metal-oxo clusters as potential contrast agents for MRI. The primary goal of this project is to identify clusters that meet the following criteria: high paramagnetic susceptibility, water-soluble, stable, cheap, contain environmentally benign metals, and easily derivatized. This work is

  6. Multifunctional carbon-coated magnetic sensing graphene oxide-cyclodextrin nanohybrid for potential cancer theranosis

    Science.gov (United States)

    Hsu, Yu-Hsuan; Hsieh, Hui-Ling; Viswanathan, Geetha; Voon, Siew Hui; Kue, Chin Siang; Saw, Wen Shang; Yeong, Chai Hong; Azlan, Che Ahmad; Imae, Toyoko; Kiew, Lik Voon; Lee, Hong Boon; Chung, Lip Yong

    2017-11-01

    We functionalized graphene oxide (GO) with cyclodextrin (CD) to increase the drug loading and cellular uptake of GO, and bound the GO-CD to carbon-coated iron nanoparticles (Fe@C) with superparamagnetic properties for potential magnetic-directed drug delivery and as a diagnostic agent. The GO-CD/Fe@C was loaded with an anticancer drug, doxorubicin (DOX), to form a multifunctional GO-CD/Fe@C/DOX nanohybrid. A cumulative increase in DOX loading was observed probably due to DOX adsorption to the graphitic domains in Fe@C and also to the GO-CD. In acidic pH that resembles the pH of the tumor environment, a higher amount of DOX was released from the GO-CD/Fe@C/DOX nanohybrid when compared to the amount released at physiological pH. The signal intensity and the contrast enhancement in magnetic resonance imaging of Fe@C decreased with its concentration. Besides, the cellular uptake of GO-CD/Fe@C/DOX nanohybrid was significantly higher by 2.5-fold than that of Fe@C/DOX in MDA-MB-231 human breast cancer model. The nanohybrids were internalized into the tumor cells via an energy-dependent process and localized mainly in the nuclei, where it exerts its cytotoxic effect, and some in the lysosomes and mitochondria. This has resulted in significant cytotoxicity in tumor cells treated with GO-CD/Fe@C/DOX. These findings highlight the potential use of multifunctional GO-CD/Fe@C nanohybrid for magnetic sensing anticancer drug delivery to tumor cells. [Figure not available: see fulltext.

  7. Grain size dependent potential for self generation of magnetic anomalies on Mars via thermoremanent magnetic acquisition and magnetic interaction of hematite and magnetite

    Czech Academy of Sciences Publication Activity Database

    Kletetschka, Günther; Ness, F. N.; Connerney, J. E. P.; Acuna, M. H.; Wasilewski, P. J.

    2005-01-01

    Roč. 148, 2-4 (2005), s. 149-156 ISSN 0031-9201 Institutional research plan: CEZ:AV0Z30130516 Keywords : magnetic mineralogy * self-magnetization * blocking temperature * Martian crust Subject RIV: BM - Solid Matter Physics ; Magnetism Impact factor: 2.420, year: 2005

  8. Finite-size, chemical-potential and magnetic effects on the phase transition in a four-fermion interacting model

    Energy Technology Data Exchange (ETDEWEB)

    Correa, E.B.S. [Universidade Federal do Sul e Sudeste do Para, Instituto de Ciencias Exatas, Maraba (Brazil); Centro Brasileiro de Pesquisas Fisicas-CBPF/MCTI, Rio de Janeiro (Brazil); Linhares, C.A. [Universidade do Estado do Rio de Janeiro, Instituto de Fisica, Rio de Janeiro (Brazil); Malbouisson, A.P.C. [Centro Brasileiro de Pesquisas Fisicas-CBPF/MCTI, Rio de Janeiro (Brazil); Malbouisson, J.M.C. [Universidade Federal da Bahia, Instituto de Fisica, Salvador (Brazil); Santana, A.E. [Universidade de Brasilia, Instituto de Fisica, Brasilia, DF (Brazil)

    2017-04-15

    We study effects coming from finite size, chemical potential and from a magnetic background on a massive version of a four-fermion interacting model. This is performed in four dimensions as an application of recent developments for dealing with field theories defined on toroidal spaces. We study effects of the magnetic field and chemical potential on the size-dependent phase structure of the model, in particular, how the applied magnetic field affects the size-dependent critical temperature. A connection with some aspects of the hadronic phase transition is established. (orig.)

  9. A NEW TECHNIQUE FOR THE PHOTOSPHERIC DRIVING OF NON-POTENTIAL SOLAR CORONAL MAGNETIC FIELD SIMULATIONS

    Energy Technology Data Exchange (ETDEWEB)

    Weinzierl, Marion; Yeates, Anthony R. [Department of Mathematical Sciences, Durham University, South Road, Durham DH1 3LE (United Kingdom); Mackay, Duncan H. [School of Mathematics and Statistics, University of St. Andrews, North Haugh, St. Andrews, Fife KY16 9SS (United Kingdom); Henney, Carl J.; Arge, C. Nick, E-mail: marion.weinzierl@durham.ac.uk [Air Force Research Lab/Space Vehicles Directorate, 3550 Aberdeen Avenue SE, Kirtland AFB, NM (United States)

    2016-05-20

    In this paper, we develop a new technique for driving global non-potential simulations of the Sun’s coronal magnetic field solely from sequences of radial magnetic maps of the solar photosphere. A primary challenge to driving such global simulations is that the required horizontal electric field cannot be uniquely determined from such maps. We show that an “inductive” electric field solution similar to that used by previous authors successfully reproduces specific features of the coronal field evolution in both single and multiple bipole simulations. For these cases, the true solution is known because the electric field was generated from a surface flux-transport model. The match for these cases is further improved by including the non-inductive electric field contribution from surface differential rotation. Then, using this reconstruction method for the electric field, we show that a coronal non-potential simulation can be successfully driven from a sequence of ADAPT maps of the photospheric radial field, without including additional physical observations which are not routinely available.

  10. Observation of scaling laws of ion confining potential versus thermal barrier depth and of axial particle confinement time in the tandem mirror GAMMA 10

    International Nuclear Information System (INIS)

    Cho, T.; Inutake, M.; Ishii, K.

    1988-01-01

    In the thermal barrier tandem mirror GAMMA 10, the scaling law governing the enhancement of the ion confining potential, φ c , resulting from thermal barrier formation, is obtained experimentally, and is consistently interpreted in terms of the weak and strong ECH theories set up by Cohen and co-workers. The scaling law on the axial particle confinement time, τ pparallel , related to this φ c formation, is also demonstrated in detail; it is in good agreement with the Pastukhov theory as modified by Cohen and co-workers. This scaling is verified at any radial position in the core plasma region and at any time through the various stages of a discharge; this indicates a scaling with drastic improvement of τ pparallel , due to the potential formation in the tandem mirror plasma. (author). 41 refs, 12 figs

  11. Examining the potential for modal change : motivators and barriers for bicycle commuting in Dar-es-Salaam

    NARCIS (Netherlands)

    Nkurunziza, A.; Zuidgeest, M.H.P.; Brussel, M.J.G.; van Maarseveen, M.F.A.M.

    2012-01-01

    The paper examines the effect of various motivators, barriers and policy related interventions (i.e., personal, social and physical–environmental factors) on bicycle commuting in Dares-Salaam, Tanzania. The research shows that these factors have different effects on people depending on the stage of

  12. Interaction of organic contaminant with natural clay type geo sorbents: potential use as geologic barrier in urban landfill

    International Nuclear Information System (INIS)

    Sanchez Jimenez, N.; Procopio, J. R.; Sevilla, T.; Cuevas, J.; Rodirguez, M.

    2009-01-01

    The great amount of municipal solid wastes generated by the cities can be processed in different ways such as incineration, derivation to composting plants or, simply, deposition in controlled landfills. One of the landfill characteristics is possess and adequate geological barrier for contaminant contention. The most important chemical processes an adequate geological battier for contaminant contention. (Author)

  13. Effect of Rashba and Dresselhaus Spin-Orbit Couplings on Electron Spin Polarization in a Hybrid Magnetic-Electric Barrier Nanostructure

    Science.gov (United States)

    Yang, Shi-Peng; Lu, Mao-Wang; Huang, Xin-Hong; Tang, Qiang; Zhou, Yong-Long

    2017-04-01

    A theoretical study has been carried out on the spin-dependent electron transport in a hybrid magnetic-electric barrier nanostructure with both Rashba and Dresselhaus spin-orbit couplings, which can be experimentally realized by depositing a ferromagnetic strip and a Schottky metal strip on top of a semiconductor heterostructure. The spin-orbit coupling-dependent transmission coefficient, conductance, and spin polarization are calculated by solving the Schrödinger equation exactly with the help of the transfer-matrix method. We find that both the magnitude and sign of the electron spin polarization vary strongly with the spin-orbit coupling strength. Thus, the degree of electron spin polarization can be manipulated by properly adjusting the spin-orbit coupling strength, and such a nanosystem can be employed as a controllable spin filter for spintronics applications.

  14. Natural vs. Anthropogenic Contribution to Atmospheric Dust at Rural Site: Potential of Environmental Magnetism

    Science.gov (United States)

    Petrovsky, E.; Kapicka, A.; Grison, H.; Kotlik, B.; Zboril, R.; Korbelova, Z.

    2013-05-01

    Magnetic properties of environmental samples are very sensitive in detecting strongly magnetic compounds such as magnetite and maghemite and can help in assessing concentration and grain-size distribution of these minerals. This information can be helpful in estimating, e.g., the source of pollutants, monitoring pollution load, or investigating seasonal and climatic effects. We studied magnetic properties of particulate matter ( PM1, PM2.5, PM10 and TSP - total suspended particles), collected over 32-48 hours in a small settlement in south Bohemia during heating and non-heating season. The site is rather remote, with negligible traffic and industrial contributions to air pollution. Thus, the suggested seasonal effect should be dominantly due to local (domestic) heating, burning wood or coal. Our results show typical differences in PMx concentration, which is much higher in the winter (heating) sample, accompanied by SEM analyses and magnetic data oriented on concentration and grain-size distribution of magnetite/maghemite particles. While PM concentrations are significantly higher in winter, differeces between concentration of Fe-oxides in summer and winter are not that significant. In both summer and winter, more FeO was in coarser PM10 than in the finer fractions. This is in good agreement with SEM observations. Grain-size sensitive parameters are different for summer and winter PMx samples, suggesting different source of PMx. It seems that domestic heating does not produce significant amount of FeO oxides in this site, its contribution during heating season compensates for the decay from natural sources (and/or agriculture) during summer. Our results prove the high sensitivity of magnetic methods in terms of concentration of ferrimagnetic Fe-oxides. However, their potential to discriminate unambiguously their origin is still questioned. This study is supported by the Czech Science Foundation through grant #P210/10/0554.; Fig. 1. Relative enhancement (determined

  15. Potential Applications of Microtesla Magnetic Resonance Imaging Detected Using a Superconducting Quantum Interference Device

    International Nuclear Information System (INIS)

    Myers, Whittier R.

    2006-01-01

    This dissertation describes magnetic resonance imaging (MRI) of protons performed in a precession field of 132 (micro)T. In order to increase the signal-to-noise ratio (SNR), a pulsed 40-300 mT magnetic field prepolarizes the sample spins and an untuned second-order superconducting gradiometer coupled to a low transition temperature superconducting quantum interference device (SQUID) detects the subsequent 5.6-kHz spin precession. Imaging sequences including multiple echoes and partial Fourier reconstruction are developed. Calculating the SNR of prepolarized SQUID-detected MRI shows that three-dimensional Fourier imaging yields higher SNR than slice-selection imaging. An experimentally demonstrated field-cycling pulse sequence and post-processing algorithm mitigate image artifacts caused by concomitant gradients in low-field MRI. The magnetic field noise of SQUID untuned detection is compared to the noise of SQUID tuned detection, conventional Faraday detection, and the Nyquist noise generated by conducting biological samples. A second-generation microtesla MRI system employing a low-noise SQUID is constructed to increase SNR. A 2.4-m cubic, eddy-current shield with 6-mm thick aluminum walls encloses the experiment to attenuate external noise. The measured noise is 0.75 fT Hz -1/2 referred to the bottom gradiometer loop. Solenoids wound from 30-strand braided wire to decrease Nyquist noise and cooled by either liquid nitrogen or water polarize the spins. Copper wire coils wound on wooden supports produce the imaging magnetic fields and field gradients. Water phantom images with 0.8 x 0.8 x 10 mm 3 resolution have a SNR of 6. Three-dimensional 1.6 x 1.9 x 14 mm 3 images of bell peppers and 3 x 3 x 26 mm 3 in vivo images of the human arm are presented. Since contrast based on the transverse spin relaxation rate (T 1 ) is enhanced at low magnetic fields, microtesla MRI could potentially be used for tumor imaging. The measured T 1 of ex vivo normal and cancerous

  16. Bond-order potential for magnetic body-centered-cubic iron and its transferability

    Science.gov (United States)

    Lin, Yi-Shen; Mrovec, M.; Vitek, V.

    2016-06-01

    We derived and thoroughly tested a bond-order potential (BOP) for body-centered-cubic (bcc) magnetic iron that can be employed in atomistic calculations of a broad variety of crystal defects that control structural, mechanical, and thermodynamic properties of this technologically important metal. The constructed BOP reflects correctly the mixed nearly free electron and covalent bonding arising from the partially filled d band as well as the ferromagnetism that is actually responsible for the stability of the bcc structure of iron at low temperatures. The covalent part of the cohesive energy is determined within the tight-binding bond model with the Green's function of the Schrödinger equation determined using the method of continued fractions terminated at a sufficient level of the moments of the density of states. This makes the BOP an O (N ) method usable for very large numbers of particles. Only d d bonds are included explicitly, but the effect of s electrons on the covalent energy is included via their screening of the corresponding d d bonds. The magnetic part of the cohesive energy is included using the Stoner model of itinerant magnetism. The repulsive part of the cohesive energy is represented, as in any tight-binding scheme, by an empirical formula. Its functional form is physically justified by studies of the repulsion in face-centered-cubic (fcc) solid argon under very high pressure where the repulsion originates from overlapping s and p closed-shell electrons just as it does from closed-shell s electrons in transition metals squeezed into the ion core under the influence of the large covalent d bonding. Testing of the transferability of the developed BOP to environments significantly different from those of the ideal bcc lattice was carried out by studying crystal structures and magnetic states alternative to the ferromagnetic bcc lattice, vacancies, divacancies, self-interstitial atoms (SIAs), paths continuously transforming the bcc structure to

  17. Potential Applications of Microtesla Magnetic Resonance ImagingDetected Using a Superconducting Quantum Interference Device

    Energy Technology Data Exchange (ETDEWEB)

    Myers, Whittier Ryan [Univ. of California, Berkeley, CA (United States)

    2006-01-01

    This dissertation describes magnetic resonance imaging (MRI) of protons performed in a precession field of 132 μT. In order to increase the signal-to-noise ratio (SNR), a pulsed 40-300 mT magnetic field prepolarizes the sample spins and an untuned second-order superconducting gradiometer coupled to a low transition temperature superconducting quantum interference device (SQUID) detects the subsequent 5.6-kHz spin precession. Imaging sequences including multiple echoes and partial Fourier reconstruction are developed. Calculating the SNR of prepolarized SQUID-detected MRI shows that three-dimensional Fourier imaging yields higher SNR than slice-selection imaging. An experimentally demonstrated field-cycling pulse sequence and post-processing algorithm mitigate image artifacts caused by concomitant gradients in low-field MRI. The magnetic field noise of SQUID untuned detection is compared to the noise of SQUID tuned detection, conventional Faraday detection, and the Nyquist noise generated by conducting biological samples. A second-generation microtesla MRI system employing a low-noise SQUID is constructed to increase SNR. A 2.4-m cubic, eddy-current shield with 6-mm thick aluminum walls encloses the experiment to attenuate external noise. The measured noise is 0.75 fT Hz-1/2 referred to the bottom gradiometer loop. Solenoids wound from 30-strand braided wire to decrease Nyquist noise and cooled by either liquid nitrogen or water polarize the spins. Copper wire coils wound on wooden supports produce the imaging magnetic fields and field gradients. Water phantom images with 0.8 x 0.8 x 10 mm3 resolution have a SNR of 6. Three-dimensional 1.6 x 1.9 x 14 mm3 images of bell peppers and 3 x 3 x 26 mm3 in vivo images of the human arm are presented. Since contrast based on the transverse spin relaxation rate (T1) is enhanced at low magnetic fields, microtesla MRI could potentially be used for tumor imaging. The

  18. Effects of dust grain charge fluctuation on obliquely propagating dust-acoustic potential in magnetized dusty plasmas

    International Nuclear Information System (INIS)

    Mamun, A.A.; Hassan, M.H.A.

    1999-05-01

    Effects of dust grain charge fluctuation, obliqueness and external magnetic field on finite amplitude dust-acoustic solitary potential in a magnetized dusty plasma, consisting of electrons, ions and charge fluctuating dust grains, have been investigated by the reductive perturbation method. It has been shown that such a magnetized dusty plasma system may support dust-acoustic solitary potential on a very slow time scale involving the motion of dust grains, whose charge is self-consistently determined by local electron and ion currents. The effects of dust grain charge fluctuation, external magnetic field and obliqueness are found to modify the properties of this dust-acoustic solitary potential significantly. The implications of these results to some space and astrophysical dusty plasma systems, especially to planetary ring-systems and cometary tails, are briefly mentioned. (author)

  19. Vibrational deactivation on chemically reactive potential surfaces: An exact quantum study of a low barrier collinear model of H + FH, D + FD, H + FD and D + FH

    International Nuclear Information System (INIS)

    Schatz, G.C.; Kuppermann, A.

    1980-01-01

    We study vibrational deactivation processes on chemically reactive potential energy surfaces by examining accurate quantum mechanical transition probabilities and rate constants for the collinear H + FH(v), D + FD(v), H + FD(v), and D + FH(v) reactions. A low barrier (1.7 kcal/mole) potential surface is used in these calculations, and we find that for all four reactions, the reactive inelastic rate constants are larger than the nonreactive ones for the same initial and final vibrational states. However, the ratios of these reactive and nonreactive rate constants depend strongly on the vibrational quantum number v and the isotopic composition of the reagents. Nonreactive and reactive transition probabilities for multiquantum jump transitions are generally comparable to those for single quantum transitions. This vibrationally nonadiabatic behavior is a direct consequence of the severe distortion of the diatomic that occurs in a collision on a low barrier reactive surface, and can make chemically reactive atoms like H or D more efficient deactivators of HF or DF than nonreactive collision partners. Many conclusions are in at least qualitative agreement with those of Wilkin's three dimensional quasiclassical trajectory study on the same systems using a similar surface. We also present results for H + HF(v) collisions which show that for a higher barrier potential surface (33 rather than 1.7 kcal/mole), the deactivation process becomes similar in character to that for nonreactive partners, with v→v-1 processes dominating

  20. Potential formation in a collisionless plasma produced in an open magnetic field in presence of volume negative ion source

    International Nuclear Information System (INIS)

    Phukan, Ananya; Goswami, K. S.; Bhuyan, P. J.

    2014-01-01

    The electric potential near a wall for a multi-species plasma with volume produced negative ions in presence of axially varying magnetic field is studied following an analytical-numerical approach. A constant negative ion source is assumed throughout the plasma volume, along with finite temperature positive ions and Boltzmann electrons. The particles are assumed to be guided by an open magnetic field that has its maximum at the centre, and field strength decreasing towards the walls. The one dimensional (1D) Poisson equation is derived using an analytical approach, and then solved numerically to study the potential profiles. Effect of (a) negative ion production rate, (b) magnetic field profile, and (c) negative ion temperature on the potential profile has been investigated. A potential peak appears near the wall when the negative ion temperature and density are sufficiently high. Also, the presence of negative ions further decreases the potential in the plasma region for a finite Debye Length (λ D )

  1. Three dimensional magnetic fields in extra high speed modified Lundell alternators computed by a combined vector-scalar magnetic potential finite element method

    Science.gov (United States)

    Demerdash, N. A.; Wang, R.; Secunde, R.

    1992-01-01

    A 3D finite element (FE) approach was developed and implemented for computation of global magnetic fields in a 14.3 kVA modified Lundell alternator. The essence of the new method is the combined use of magnetic vector and scalar potential formulations in 3D FEs. This approach makes it practical, using state of the art supercomputer resources, to globally analyze magnetic fields and operating performances of rotating machines which have truly 3D magnetic flux patterns. The 3D FE-computed fields and machine inductances as well as various machine performance simulations of the 14.3 kVA machine are presented in this paper and its two companion papers.

  2. Linear and nonlinear intersubband optical absorption in a disk-shaped quantum dot with a parabolic potential plus an inverse squared potential in a static magnetic field

    Energy Technology Data Exchange (ETDEWEB)

    Liu Guanghui [Department of Physics, College of Physics and Electronic Engineering, Guangzhou University, Guangzhou 510006 (China); Guo Kangxian, E-mail: axguo@sohu.com [Department of Physics, College of Physics and Electronic Engineering, Guangzhou University, Guangzhou 510006 (China); Wang Chao [Institute of Public Administration, Guangzhou University, Guangzhou 510006 (China)

    2012-06-15

    The linear and nonlinear optical absorption in a disk-shaped quantum dot (DSQD) with parabolic potential plus an inverse squared potential in the presence of a static magnetic field are theoretically investigated within the framework of the compact-density-matrix approach and iterative method. The energy levels and the wave functions of an electron in the DSQD are obtained by using the effective mass approximation. Numerical calculations are presented for typical GaAs/AlAs DSQD. It is found that the optical absorption coefficients are strongly affected not only by a static magnetic field, but also by the strength of external field, the confinement frequency and the incident optical intensity.

  3. Linear and nonlinear intersubband optical absorption in a disk-shaped quantum dot with a parabolic potential plus an inverse squared potential in a static magnetic field

    International Nuclear Information System (INIS)

    Liu Guanghui; Guo Kangxian; Wang Chao

    2012-01-01

    The linear and nonlinear optical absorption in a disk-shaped quantum dot (DSQD) with parabolic potential plus an inverse squared potential in the presence of a static magnetic field are theoretically investigated within the framework of the compact-density-matrix approach and iterative method. The energy levels and the wave functions of an electron in the DSQD are obtained by using the effective mass approximation. Numerical calculations are presented for typical GaAs/AlAs DSQD. It is found that the optical absorption coefficients are strongly affected not only by a static magnetic field, but also by the strength of external field, the confinement frequency and the incident optical intensity.

  4. Claudin-3 expression in radiation-exposed rat models: A potential marker for radiation-induced intestinal barrier failure

    Energy Technology Data Exchange (ETDEWEB)

    Shim, Sehwan; Lee, Jong-geol; Bae, Chang-hwan; Lee, Seung Bum [National Radiation Emergency Medical Center, Korea Institute of Radiological and Medical Sciences, Seoul (Korea, Republic of); Jang, Won-Suk; Lee, Sun-Joo [Laboratory of Experimental Pathology, Korea Cancer Center Hospital, Seoul (Korea, Republic of); Lee, Seung-Sook [National Radiation Emergency Medical Center, Korea Institute of Radiological and Medical Sciences, Seoul (Korea, Republic of); Department of Pathology, Korea Cancer Center Hospital, Seoul (Korea, Republic of); Park, Sunhoo, E-mail: sunhoo@kcch.re.kr [National Radiation Emergency Medical Center, Korea Institute of Radiological and Medical Sciences, Seoul (Korea, Republic of); Department of Pathology, Korea Cancer Center Hospital, Seoul (Korea, Republic of)

    2015-01-02

    Highlights: • Irradiation increased intestinal bacterial translocation, accompanied by claudin protein expression in rats. • Neurotensin decreased the bacterial translocation and restored claudin-3 expression. • Claudin-3 can be used as a marker in evaluating radiation induced intestinal injury. - Abstract: The molecular events leading to radiation-induced intestinal barrier failure are not well known. The influence of the expression of claudin proteins in the presence and absence of neurotensin was investigated in radiation-exposed rat intestinal epithelium. Wistar rats were randomly divided into control, irradiation, and irradiation + neurotensin groups, and bacterial translocation to the mesenteric lymph node and expression of claudins were determined. Irradiation led to intestinal barrier failure as demonstrated by significant bacterial translocation. In irradiated terminal ilea, expression of claudin-3 and claudin-4 was significantly decreased, and claudin-2 expression was increased. Administration of neurotensin significantly reduced bacterial translocation and restored the structure of the villi as seen by histologic examination. Among the three subtype of claudins, only claudin-3 expression was restored. These results suggest that the therapeutic effect of neurotensin on the disruption of the intestinal barrier is associated with claudin-3 alteration and that claudin-3 could be used as a marker in evaluating radiation-induced intestinal injury.

  5. Improved ring potential of QED at finite temperature and in the presence of weak and strong magnetic fields

    International Nuclear Information System (INIS)

    Sadooghi, N.; Anaraki, K. Sohrabi

    2008-01-01

    Using the general structure of the vacuum polarization tensor Π μν (k 0 ,k) in the infrared (IR) limit, k 0 →0, the ring contribution to the QED effective potential at finite temperature and the nonzero magnetic field is determined beyond the static limit, (k 0 →0, k→0). The resulting ring potential is then studied in weak and strong magnetic field limits. In the weak magnetic field limit, at high temperature and for α→0, the improved ring potential consists of a term proportional to T 4 α 5/2 , in addition to the expected T 4 α 3/2 term arising from the static limit. Here, α is the fine structure constant. In the limit of the strong magnetic field, where QED dynamics is dominated by the lowest Landau level, the ring potential includes a novel term consisting of dilogarithmic function (eB)Li 2 (-(2α/π)(eB/m 2 )). Using the ring improved (one-loop) effective potential including the one-loop effective potential and ring potential in the IR limit, the dynamical chiral symmetry breaking of QED is studied at finite temperature and in the presence of the strong magnetic field. The gap equation, the dynamical mass and the critical temperature of QED in the regime of the lowest Landau level dominance are determined in the improved IR as well as in the static limit. For a given value of the magnetic field, the improved ring potential is shown to be more efficient in decreasing the critical temperature arising from the one-loop effective potential.

  6. Enhanced detection of gametocytes by magnetic deposition microscopy predicts higher potential for Plasmodium falciparum transmission

    Directory of Open Access Journals (Sweden)

    Zborowski Maciej

    2008-04-01

    Full Text Available Abstract Background Aggregated haemozoin crystals within malaria-infected erythrocytes confer susceptibility of parasitized cells to a magnetic field. Here the utility of this method for diagnosis of human malaria is evaluated in a malaria-endemic region of Papua New Guinea (PNG. Methods and findings Individuals with Plasmodium falciparum malaria symptoms (n = 55 provided samples for conventional blood smear (CBS and magnetic deposition microscopy (MDM diagnosis. Standard Giemsa staining and light microscopy was performed to evaluate all preparations. Plasmodium falciparum parasitaemia observed on MDM slides was consistently higher than parasitaemia observed by (CBS for ring (CBS = 2.6 vs. MDM = 3.4%; t-test P-value = 0.13, trophozoite (CBS = 0.5 vs. MDM = 1.6%; t-test P-value = 0.01, schizont (CBS = 0.003 vs. MDM = 0.1%; t-test P-value = 0.08 and gametocyte (CBS = 0.001 vs. MDM = 0.4%; t-test P-value = 0.0002 parasitaemias. Gametocyte prevalence determined by CBS compared to MDM increased from 7.3% to 45%, respectively. Conclusion MDM increased detection sensitivity of P. falciparum-infected, haemozoin-containing erythrocytes from infected humans while maintaining detection of ring-stage parasites. Gametocyte prevalence five-fold higher than observed by CBS suggests higher malaria transmission potential in PNG endemic sites compared to previous estimates.

  7. Electric detection of the spin-Seebeck effect in magnetic insulator in the presence of interface barrier

    International Nuclear Information System (INIS)

    Uchida, K; Ota, T; Kajiwara, Y; Saitoh, E; Umezawa, H; Kawai, H

    2011-01-01

    The spin-Seebeck effect (SSE), the spin-voltage generation as a result of a temperature gradient, has recently been observed in ferrimagnetic insulator LaY 2 Fe 5 O 12 films by means of the inverse spin-Hall effect in Pt films. Here we investigate the SSE using LaY 2 Fe 5 O 12 /SiO 2 (Cu)/Pt systems, where the LaY 2 Fe 5 O 12 and Pt layers are separated by SiO 2 (Cu) thin-film barriers. The experimental results show that the SSE signal disappears in the LaY 2 Fe 5 O 12 /SiO 2 /Pt system, but the finite signal appears in the LaY 2 Fe 5 O 12 /Cu/Pt system, indicating that the direct contacts between the LaY 2 Fe 5 O 12 and normal metals is necessary for generating the SSE signal.

  8. Transport in a magnetic field modulated graphene superlattice.

    Science.gov (United States)

    Li, Yu-Xian

    2010-01-13

    Using the transfer matrix method, we study the transport properties through a magnetic field modulated graphene superlattice. It is found that the electrostatic barrier, the magnetic vector potential, and the number of wells in a superlattice modify the transmission remarkably. The angular dependent transmission is blocked by the magnetic vector potential because of the appearance of the evanescent states at certain incident angles, and the region of Klein tunneling shifts to the left. The angularly averaged conductivities exhibit oscillatory behavior. The magnitude and period of oscillation depend sensitively on the height of the electrostatic barrier, the number of wells, and the strength of the modulated magnetic field.

  9. Atoms confined in a penetrable potential: effect of the atom position on the electric and magnetic responses

    Energy Technology Data Exchange (ETDEWEB)

    Acosta Coden, Diego S; Gomez, Sergio S; Romero, Rodolfo H, E-mail: rhromero@exa.unne.edu.ar [Instituto de Modelado e Innovacion Tecnologica, CONICET and Facultad de Ciencias Exactas y Naturales y Agrimensura, Universidad Nacional del Nordeste, Avenida Libertad 5500 (3400) Corrientes (Argentina)

    2011-02-14

    We report results of the calculation of polarizability and the nuclear magnetic shielding tensors of two-electron atoms confined within an attractive Gaussian potential well. The electric and magnetic responses are obtained within the random phase approximation (RPA) of the polarization propagator. The influence of the depth and range of the potential on the electronic structure is also studied. The dependence of the parallel (along the displacement) and perpendicular components of the polarizability and shielding tensors on the distance of the atom to the centre of the well is calculated and rationalized as a dissociation-type process of the artificial diatomic molecule formed between the Coulomb and the well potentials.

  10. Atoms confined in a penetrable potential: effect of the atom position on the electric and magnetic responses

    International Nuclear Information System (INIS)

    Acosta Coden, Diego S; Gomez, Sergio S; Romero, Rodolfo H

    2011-01-01

    We report results of the calculation of polarizability and the nuclear magnetic shielding tensors of two-electron atoms confined within an attractive Gaussian potential well. The electric and magnetic responses are obtained within the random phase approximation (RPA) of the polarization propagator. The influence of the depth and range of the potential on the electronic structure is also studied. The dependence of the parallel (along the displacement) and perpendicular components of the polarizability and shielding tensors on the distance of the atom to the centre of the well is calculated and rationalized as a dissociation-type process of the artificial diatomic molecule formed between the Coulomb and the well potentials.

  11. Barriers and Potential Improvements for Needle and Syringe Exchange Programs (NSPs in China: A Qualitative Study from Perspectives of Both Health and Public Security Sectors.

    Directory of Open Access Journals (Sweden)

    Fung Kuen Koo

    Full Text Available This study explores the acceptability, the barriers to the implementation of needle and syringe exchange programs (NSPs and the potential improvement strategies in China from the perspectives of governmental health and public security officials. Purposive sampling was used for recruitment of participants who had been involved in NSPs implementation. Semi-Structured individual interviews were conducted in Mandarin to address three aspects of NSPs: (1 participants' attitudes towards NSPs, (2 participants' opinions on the effectiveness and barriers of NSPs, and (3 suggestions for improving the program. Content analysis was used to analyse the translated interview data. A total of 68 participants from 12 Hunan counties were interviewed (34 from each of the Bureau of Health and the Narcotic Division. Both groups recognised the importance and effectiveness of NSPs in HIV prevention, but public security officials regarded NSPs as a temporary intervention in place of punitive measures. Most health officials (32/34 regarded the main barriers to its implementation as administrative and structural, whereas participants from Narcotics Division (n=24 questioned the legitimacy of NSPs and concerned about the poor management of drug users' risk behaviours. Close cooperation between the health and public security sectors, engagement of the drug user community and an enabling policy environment were reportedly to be critical for potential improvements of NSPs in China. Misconceptions about NSPs encourage drug users' addictive behaviour, and an unclear leadership and insufficient support de-motivate the participants from the Bureau of Health and the Narcotics Division to actively support the program implementation.

  12. Global, finite energy, weak solutions for the NLS with rough, time-dependent magnetic potentials

    Science.gov (United States)

    Antonelli, Paolo; Michelangeli, Alessandro; Scandone, Raffaele

    2018-04-01

    We prove the existence of weak solutions in the space of energy for a class of nonlinear Schrödinger equations in the presence of a external, rough, time-dependent magnetic potential. Under our assumptions, it is not possible to study the problem by means of usual arguments like resolvent techniques or Fourier integral operators, for example. We use a parabolic regularisation, and we solve the approximating Cauchy problem. This is achieved by obtaining suitable smoothing estimates for the dissipative evolution. The total mass and energy bounds allow to extend the solution globally in time. We then infer sufficient compactness properties in order to produce a global-in-time finite energy weak solution to our original problem.

  13. Magnetic resonance imaging compared with trimodal evoked potentials in possible multiple sclerosis

    International Nuclear Information System (INIS)

    Roullet, E.; Leger-Ravet, M.B.; Amarenco, P.; Marteau, R.; Lavallard-Rousseau, M.-C.; Dupuch, K.; Iba-Zizen, M.T.; Tamraz, J.; Cabanis, E.A.

    1988-01-01

    Magnetic Resonance Imaging (MRI) of the brain and Evoked Potentials (EP) can both demonstrate the presence of clinically unsuspected demyelinating lesions and have proven to be sensitive (but not specific) in the diagnosis of multiple sclerosis (MS). MRI and EP are positive in 90 to 100% of patients with a definite diagnosis of MS. However, few studies have been conducted in patients with a lesser diagnostic certainty. In possible or suspected MS they gave conflicting results, possibly because of technical discrepancies and different clinical inclusion criteria. Since a number of putative new treatments can be evaluated in patients who have a definite diagnosis of MS, but nevertheless a short duration of disease and a low disability, it was decided to compare the sensitivity of MRI and EP as diagnostic tools in possible MS patients. MRI is shown to be more sensitive, shows more multiple lesions and gives a clearer appreciation of their size and exact location than EP. 10 refs.; 3 tabs

  14. Repetitive transcranial magnetic stimulation as a neuropsychiatric tool: present status and future potential.

    Science.gov (United States)

    Post, R M; Kimbrell, T A; McCann, U D; Dunn, R T; Osuch, E A; Speer, A M; Weiss, S R

    1999-03-01

    Repetitive transcranial magnetic stimulation (rTMS) has emerged as a promising therapeutic intervention in the treatment of affective disorders. The differences in the type of electrical stimulation required for therapeutic efficacy by rTMS and electroconvulsive therapy (ECT) are discussed. In contrast to ECT, rTMS would not appear to require the generation of a major motor seizure to achieve therapeutic efficacy. Accordingly, it carries the potentially important clinical advantages of not requiring anesthesia and of avoiding side effects such as transient memory loss. Preclinical studies on long-term potentiation (LTP) and long-term depression (LTD) in hippocampal and amygdala slices, as well as clinical data from neuroimaging studies, have provided encouraging clues for potential frequency-dependent effects of rTMS. Preliminary evidence from position emission tomography (PET) scans suggests that higher frequency (20 Hz) stimulation may increase brain glucose metabolism in a transsynaptic fashion, whereas lower frequency (1 Hz) stimulation may decrease it. Therefore, the ability of rTMS to control the frequency as well as the location of stimulation, in addition to its other advantages, has opened up new possibilities for clinical explorations and treatments of neuropsychiatric conditions.

  15. Bilateral somatosensory evoked potentials following intermittent theta-burst repetitive transcranial magnetic stimulation

    Directory of Open Access Journals (Sweden)

    Ziluk Angela

    2010-08-01

    Full Text Available Abstract Background Intermittent theta-burst stimulation (iTBS is a form of repetitive transcranial magnetic stimulation that may alter cortical excitability in the primary somatosensory cortex (SI. The present study investigated the effects of iTBS on subcortical and early cortical somatosensory evoked potentials (SEPs recorded over left, iTBS stimulated SI and the right-hemisphere non-stimulated SI. SEPs were recorded before and at 5, 15, and 25 minutes following iTBS. Results Compared to pre-iTBS, the amplitude of cortical potential N20/P25 was significantly increased for 5 minutes from non-stimulated SI and for 15 to 25 minutes from stimulated SI. Subcortical potentials recorded bilaterally remained unaltered following iTBS. Conclusion We conclude that iTBS increases the cortical excitability of SI bilaterally and does not alter thalamocortical afferent input to SI. ITBS may provide one avenue to induce cortical plasticity in the somatosensory cortex.

  16. PAMAM Dendrimers as Potential Carriers of Gadolinium Complexes of Iminodiacetic Acid Derivatives for Magnetic Resonance Imaging

    Directory of Open Access Journals (Sweden)

    Magdalena Markowicz-Piasecka

    2015-01-01

    Full Text Available This is the first study describing the utilization of PAMAM dendrimers as delivery vehicles of novel magnetic resonance imaging (MRI contrast agents. The purpose of this paper was to establish the potential of G4 PAMAM dendrimers as carriers of gadolinium complexes of iminodiacetic acid derivatives and determine imaging properties of synthesized compounds in in vivo studies. Furthermore, we examined the influence of four synthesized complexes on the process of clot formation, stabilization, and lysis and on amidolytic activity of thrombin. Biodistribution studies have shown that the compounds composed of PAMAM G4 dendrimers and gadolinium complexes of iminodiacetic acid derivatives increase signal intensity preferably in liver in range of 59–116% in MRI studies which corresponds with the greatest accumulation of gadolinium after administration of the compounds. Synthesized compounds affect kinetic parameters of the proces of clot formation, its stabilization, and lysis. However, only one synthesized compound at concentration 10-fold higher than potential plasma concentrations contributed to the increase of general parameters such as the overall potential of clot formation and lysis (↑CLAUC and total time of the process (↑T. Results of described studies provide additional insight into delivery properties of PAMAM dendrimers but simultaneously underscore the necessity for further research.

  17. Combined magnetic vector-scalar potential finite element computation of 3D magnetic field and performance of modified Lundell alternators in Space Station applications. Ph.D. Thesis

    Science.gov (United States)

    Wang, Ren H.

    1991-01-01

    A method of combined use of magnetic vector potential (MVP) based finite element (FE) formulations and magnetic scalar potential (MSP) based FE formulations for computation of three-dimensional (3D) magnetostatic fields is developed. This combined MVP-MSP 3D-FE method leads to considerable reduction by nearly a factor of 3 in the number of unknowns in comparison to the number of unknowns which must be computed in global MVP based FE solutions. This method allows one to incorporate portions of iron cores sandwiched in between coils (conductors) in current-carrying regions. Thus, it greatly simplifies the geometries of current carrying regions (in comparison with the exclusive MSP based methods) in electric machinery applications. A unique feature of this approach is that the global MSP solution is single valued in nature, that is, no branch cut is needed. This is again a superiority over the exclusive MSP based methods. A Newton-Raphson procedure with a concept of an adaptive relaxation factor was developed and successfully used in solving the 3D-FE problem with magnetic material anisotropy and nonlinearity. Accordingly, this combined MVP-MSP 3D-FE method is most suited for solution of large scale global type magnetic field computations in rotating electric machinery with very complex magnetic circuit geometries, as well as nonlinear and anisotropic material properties.

  18. Resonant tunneling through double-barrier structures on graphene

    International Nuclear Information System (INIS)

    Deng Wei-Yin; Zhu Rui; Deng Wen-Ji; Xiao Yun-Chang

    2014-01-01

    Quantum resonant tunneling behaviors of double-barrier structures on graphene are investigated under the tight-binding approximation. The Klein tunneling and resonant tunneling are demonstrated for the quasiparticles with energy close to the Dirac points. The Klein tunneling vanishes by increasing the height of the potential barriers to more than 300 meV. The Dirac transport properties continuously change to the Schrödinger ones. It is found that the peaks of resonant tunneling approximate to the eigen-levels of graphene nanoribbons under appropriate boundary conditions. A comparison between the zigzag- and armchair-edge barriers is given. (condensed matter: electronic structure, electrical, magnetic, and optical properties)

  19. MAGNET

    CERN Multimedia

    by B. Curé

    2011-01-01

    The magnet operation was very satisfactory till the technical stop at the end of the year 2010. The field was ramped down on 5th December 2010, following the successful regeneration test of the turbine filters at full field on 3rd December 2010. This will limit in the future the quantity of magnet cycles, as it is no longer necessary to ramp down the magnet for this type of intervention. This is made possible by the use of the spare liquid Helium volume to cool the magnet while turbines 1 and 2 are stopped, leaving only the third turbine in operation. This obviously requires full availability of the operators to supervise the operation, as it is not automated. The cryogenics was stopped on 6th December 2010 and the magnet was left without cooling until 18th January 2011, when the cryoplant operation resumed. The magnet temperature reached 93 K. The maintenance of the vacuum pumping was done immediately after the magnet stop, when the magnet was still at very low temperature. Only the vacuum pumping of the ma...

  20. Martian Bow Shock and Magnetic Pile-Up Barrier Formation Due to the Exosphere Ion Mass-Loading

    Directory of Open Access Journals (Sweden)

    Eojin Kim

    2011-03-01

    Full Text Available Bow shock, formed by the interaction between the solar wind and a planet, is generated in different patterns depending on the conditions of the planet. In the case of the earth, its own strong magnetic field plays a critical role in determining the position of the bow shock. However, in the case of Mars of which has very a small intrinsic magnetic field, the bow shock is formed by the direct interaction between the solar wind and the Martian ionosphere. It is known that the position of the Martian bow shock is affected by the mass loading-effect by which the supersonic solar wind velocity becomes subsonic as the heavy ions originating from the planet are loaded on the solar wind. We simulated the Martian magnetosphere depending on the changes of the density and velocity of the solar wind by using the three-dimensional magnetohydrodynamic model built by modifying the comet code that includes the mass loading effect. The Martian exosphere model of was employed as the Martian atmosphere model, and only the photoionization by the solar radiation was considered in the ionization process of the neutral atmosphere. In the simulation result under the normal solar wind conditions, the Martian bow shock position in the subsolar point direction was consistent with the result of the previous studies. The three-dimensional simulation results produced by varying the solar wind density and velocity were all included in the range of the Martian bow shock position observed by Mariner 4, Mars 2, 3, 5, and Phobos 2. Additionally, the simulation result also showed that the change of the solar wind density had a greater effect on the Martian bow shock position than the change of the solar wind velocity. Our result may be useful in analyzing the future observation data by Martian probes.

  1. Low signal-to-noise FDEM in-phase data: Practical potential for magnetic susceptibility modelling

    Science.gov (United States)

    Delefortrie, Samuël; Hanssens, Daan; De Smedt, Philippe

    2018-05-01

    In this paper, we consider the use of land-based frequency-domain electromagnetics (FDEM) for magnetic susceptibility modelling. FDEM data comprises both out-of-phase and in-phase components, which can be related to the electrical conductivity and magnetic susceptibility of the subsurface. Though applying the FDEM method to obtain information on the subsurface conductivity is well established in various domains (e.g. through the low induction number approximation of subsurface apparent conductivity), the potential for susceptibility mapping is often overlooked. Especially given a subsurface with a low magnetite and maghemite content (e.g. most sedimentary environments), it is generally assumed that susceptibility is negligible. Nonetheless, the heterogeneity of the near surface and the impact of anthropogenic disturbances on the soil can cause sufficient variation in susceptibility for it to be detectable in a repeatable way. Unfortunately, it can be challenging to study the potential for susceptibility mapping due to systematic errors, an often poor low signal-to-noise ratio, and the intricacy of correlating in-phase responses with subsurface susceptibility and conductivity. Alongside use of an accurate forward model - accounting for out-of-phase/in-phase coupling - any attempt at relating the in-phase response with subsurface susceptibility requires overcoming instrument-specific limitations that burden the real-world application of FDEM susceptibility mapping. Firstly, the often erratic and drift-sensitive nature of in-phase responses calls for relative data levelling. In addition, a correction for absolute levelling offsets may be equally necessary: ancillary (subsurface) susceptibility data can be used to assess the importance of absolute in-phase calibration though hereby accurate in-situ data is required. To allow assessing the (importance of) in-phase calibration alongside the potential of FDEM data for susceptibility modelling, we consider an experimental

  2. Is there potential for repetitive Transcranial Magnetic Stimulation (rTMS) as a treatment of OCD?

    Science.gov (United States)

    Zaman, Rashid; Robbins, Trevor W

    2017-09-01

    Obsessive-Compulsive Disorder (OCD) is a common and highly debilitating psychiatric disorder. Amongst OCD sufferers are a significant number (40-60%) of so-called non-responders who do not fully respond to commonly available treatments, which include medications (Selective Serotonin Reuptake Inhibitors-SSRIs) and cognitive behavior therapy (CBT). Modern 'neuromodulatory' techniques such as Deep Brain Stimulation (DBS), repetitive Transcranial Magnetic Stimulation (rTMS) and transcranial Direct Current Stimulation (tDCS) potentially offer alternative forms of treatment for OCD patients who either do not respond to, or are unable or unwilling to take SSRIs and undergo CBT. Although shown to be effective in treatment resistant OCD, DBS requires invasive neurosurgical procedures with associated risks. On the other hand, rTMS and tDCS are non-invasive forms of treatment, which are largely risk free, but the evidence of their efficacy so far is somewhat limited, with only small number of published studies. In this brief survey we will address the potential of rTMS as a therapeutic tool for OCD and review the published literature on the cortical targets for rTMS used so far. We will also discuss some of the newer variants of rTMS techniques only a few of which have been employed so far, and speculate whether there might be a place for rTMS as a standard treatment in OCD, along side CBT, SSRIs and DBS.

  3. Preliminary biocompatibility investigation of magnetic albumin nanosphere designed as a potential versatile drug delivery system

    Directory of Open Access Journals (Sweden)

    Estevanato L

    2011-08-01

    Full Text Available Luciana Estevanato1, Débora Cintra1, Nayara Baldini1, Flávia Portilho1, Luzirlane Barbosa1, Olímpia Martins2, Bruno Lacava3, Ana Luisa Miranda-Vilela1, Antônio Cláudio Tedesco2, Sônia Báo1, Paulo C Morais4, Zulmira GM Lacava11Instituto de Ciências Biológicas, Universidade de Brasília, 2Departamento de Química, Laboratório de Fotobiologia e Fotomedicina, Faculdade de Filosofia, Ciências e Letras de Ribeirão Preto, Universidade de São Paulo, Ribeirão Preto, 3Instituto de Química, Universidade de Brasília, Brasília, 4Instituto de Física, Universidade de Brasília, Brasília, BrazilBackground: The magnetic albumin nanosphere (MAN, encapsulating maghemite nanoparticles, was designed as a magnetic drug delivery system (MDDS able to perform a variety of biomedical applications. It is noteworthy that MAN was efficient in treating Ehrlich's tumors by the magnetohyperthermia procedure.Methods and materials: In this study, several nanotoxicity tests were systematically carried out in mice from 30 minutes until 30 days after MAN injection to investigate their biocompatibility status. Cytometry analysis, viability tests, micronucleus assay, and histological analysis were performed.Results: Cytometry analysis and viability tests revealed MAN promotes only slight and temporary alterations in the frequency of both leukocyte populations and viable peritoneal cells, respectively. Micronucleus assay showed absolutely no genotoxicity or cytotoxicity effects and histological analysis showed no alterations or even nanoparticle clusters in several investigated organs but, interestingly, revealed the presence of MAN clusters in the central nervous system (CNS.Conclusion: The results showed that MAN has desirable in vivo biocompatibility, presenting potential for use as a MDDS, especially in CNS disease therapy.Keywords: nanotoxicity, nanoparticle, genotoxicity, cytotoxicity, brain

  4. Extracting Visual Evoked Potentials from EEG Data Recorded During fMRI-guided Transcranial Magnetic Stimulation

    Science.gov (United States)

    Sadeh, Boaz; Yovel, Galit

    2014-01-01

    Transcranial Magnetic Stimulation (TMS) is an effective method for establishing a causal link between a cortical area and cognitive/neurophysiological effects. Specifically, by creating a transient interference with the normal activity of a target region and measuring changes in an electrophysiological signal, we can establish a causal link between the stimulated brain area or network and the electrophysiological signal that we record. If target brain areas are functionally defined with prior fMRI scan, TMS could be used to link the fMRI activations with evoked potentials recorded. However, conducting such experiments presents significant technical challenges given the high amplitude artifacts introduced into the EEG signal by the magnetic pulse, and the difficulty to successfully target areas that were functionally defined by fMRI. Here we describe a methodology for combining these three common tools: TMS, EEG, and fMRI. We explain how to guide the stimulator's coil to the desired target area using anatomical or functional MRI data, how to record EEG during concurrent TMS, how to design an ERP study suitable for EEG-TMS combination and how to extract reliable ERP from the recorded data. We will provide representative results from a previously published study, in which fMRI-guided TMS was used concurrently with EEG to show that the face-selective N1 and the body-selective N1 component of the ERP are associated with distinct neural networks in extrastriate cortex. This method allows us to combine the high spatial resolution of fMRI with the high temporal resolution of TMS and EEG and therefore obtain a comprehensive understanding of the neural basis of various cognitive processes. PMID:24893706

  5. Extracting visual evoked potentials from EEG data recorded during fMRI-guided transcranial magnetic stimulation.

    Science.gov (United States)

    Sadeh, Boaz; Yovel, Galit

    2014-05-12

    Transcranial Magnetic Stimulation (TMS) is an effective method for establishing a causal link between a cortical area and cognitive/neurophysiological effects. Specifically, by creating a transient interference with the normal activity of a target region and measuring changes in an electrophysiological signal, we can establish a causal link between the stimulated brain area or network and the electrophysiological signal that we record. If target brain areas are functionally defined with prior fMRI scan, TMS could be used to link the fMRI activations with evoked potentials recorded. However, conducting such experiments presents significant technical challenges given the high amplitude artifacts introduced into the EEG signal by the magnetic pulse, and the difficulty to successfully target areas that were functionally defined by fMRI. Here we describe a methodology for combining these three common tools: TMS, EEG, and fMRI. We explain how to guide the stimulator's coil to the desired target area using anatomical or functional MRI data, how to record EEG during concurrent TMS, how to design an ERP study suitable for EEG-TMS combination and how to extract reliable ERP from the recorded data. We will provide representative results from a previously published study, in which fMRI-guided TMS was used concurrently with EEG to show that the face-selective N1 and the body-selective N1 component of the ERP are associated with distinct neural networks in extrastriate cortex. This method allows us to combine the high spatial resolution of fMRI with the high temporal resolution of TMS and EEG and therefore obtain a comprehensive understanding of the neural basis of various cognitive processes.

  6. Health professional's perceptions of and potential barriers to smoking cessation care: a survey study at a dental school hospital in Japan

    Directory of Open Access Journals (Sweden)

    Makiishi Takemi

    2010-12-01

    to hospital patients. In order to overcome the potential barriers, it is necessary to provide staff with appropriate training and create an atmosphere supportive of smoking cessation activities.

  7. The dependence of potential well formation on the magnetic field strength and electron injection current in a polywell device

    International Nuclear Information System (INIS)

    Cornish, S.; Gummersall, D.; Carr, M.; Khachan, J.

    2014-01-01

    A capacitive probe has been used to measure the plasma potential in a polywell device in order to observe the dependence of potential well formation on magnetic field strength, electron injection current, and polywell voltage bias. The effectiveness of the capacitive probe in a high energy electron plasma was determined by measuring the plasma potential of a planar diode with an axial magnetic field. The capacitive probe was translated along the axis of one of the field coils of the polywell, and the spatial profile of the potential well was measured. The confinement time of electrons in the polywell was estimated with a simple analytical model which used the experimentally observed potential well depths, as well as a simulation of the electron trajectories using particle orbit theory

  8. Assessment of Tumor Radioresponsiveness and Metastatic Potential by Dynamic Contrast-Enhanced Magnetic Resonance Imaging

    International Nuclear Information System (INIS)

    Ovrebo, Kirsti Marie; Gulliksrud, Kristine; Mathiesen, Berit; Rofstad, Einar K.

    2011-01-01

    Purpose: It has been suggested that gadolinium diethylene-triamine penta-acetic acid (Gd-DTPA)-based dynamic contrast-enhanced magnetic resonance imaging (DCE-MRI) may provide clinically useful biomarkers for personalized cancer treatment. In this preclinical study, we investigated the potential of DCE-MRI as a noninvasive method for assessing the radioresponsiveness and metastatic potential of tumors. Methods and Materials: R-18 melanoma xenografts growing in BALB/c nu/nu mice were used as experimental tumor models. Fifty tumors were subjected to DCE-MRI, and parametric images of K trans (the volume transfer constant of Gd-DTPA) and v e (the fractional distribution volume of Gd-DTPA) were produced by pharmacokinetic analysis of the DCE-MRI series. The tumors were irradiated after the DCE-MRI, either with a single dose of 10 Gy for detection of radiobiological hypoxia (30 tumors) or with five fractions of 4 Gy in 48 h for assessment of radioresponsiveness (20 tumors). The host mice were then euthanized and examined for lymph node metastases, and the primary tumors were resected for measurement of cell survival in vitro. Results: Tumors with hypoxic cells showed significantly lower K trans values than tumors without significant hypoxia (p trans decreased with increasing cell surviving fraction for tumors given fractionated radiation treatment (p trans values than tumors in metastasis-negative mice (p e and tumor hypoxia, radioresponsiveness, or metastatic potential could not be detected. Conclusions: R-18 tumors with low K trans values are likely to be resistant to radiation treatment and have a high probability of developing lymph node metastases. The general validity of these observations should be investigated further by studying preclinical tumor models with biological properties different from those of the R-18 tumors.

  9. Bilateral theta-burst magnetic stimulation influence on event-related brain potentials.

    Science.gov (United States)

    Pinto, Nuno; Duarte, Marta; Gonçalves, Helena; Silva, Ricardo; Gama, Jorge; Pato, Maria Vaz

    2018-01-01

    Theta-burst stimulation (TBS) can be a non-invasive technique to modulate cognitive functions, with promising therapeutic potential, but with some contradictory results. Event related potentials are used as a marker of brain deterioration and can be used to evaluate TBS-related cognitive performance, but its use remains scant. This study aimed to study bilateral inhibitory and excitatory TBS effects upon neurocognitive performance of young healthy volunteers, using the auditory P300' results. Using a double-blind sham-controlled study, 51 healthy volunteers were randomly assigned to five different groups, two submitted to either excitatory (iTBS) or inhibitory (cTBS) stimulation over the left dorsolateral pre-frontal cortex (DLPFC), two other actively stimulated the right DLPFC and finally a sham stimulation group. An oddball based auditory P300 was performed just before a single session of iTBS, cTBS or sham stimulation and repeated immediately after. P300 mean latency comparison between the pre- and post-TBS stimulation stages revealed significantly faster post stimulation latencies only when iTBS was performed on the left hemisphere (p = 0.003). Right and left hemisphere cTBS significantly delayed P300 latency (right p = 0.026; left p = 0.000). Multiple comparisons for N200 showed slower latencies after iTBS over the right hemisphere. No significant difference was found in amplitude variation. TBS appears to effectively influence neural networking involved in P300 formation, but effects seem distinct for iTBS vs cTBS and for the right or the left hemisphere. P300 evoked potentials can be an effective and practical tool to evaluate transcranial magnetic stimulation related outcomes.

  10. Testing of the permanent magnet material Mn-Al-C for potential use in propulsion motors for electric vehicles

    Science.gov (United States)

    Abdelnour, Z.; Mildrun, H.; Strant, K.

    1981-01-01

    The development of Mn-Al-C permanent magnets is reviewed. The general properties of the material are discussed and put into perspective relative to alnicos and ferrites. The traction motor designer's demands of a permanent magnet for potential use in electric vehicle drives are reviewed. Tests determined magnetic design data and mechanical strength properties. Easy axis hysteresis and demagnetization curves, recoil loops and other minor loop fields were measured over a temperature range from -50 to 150 C. Hysteresis loops were also measured for three orthogonal directions (the one easy and two hard axes of magnetization). Extruded rods of three different diameters were tested. The nonuniformity of properties over the cross section of the 31 mm diameter rod was studied. Mechanical compressive and bending strength at room temperature was determined on individual samples from the 31 mm rod.

  11. MAGNET

    CERN Multimedia

    Benoit Curé

    2010-01-01

    Operation of the magnet has gone quite smoothly during the first half of this year. The magnet has been at 4.5K for the full period since January. There was an unplanned short stop due to the CERN-wide power outage on May 28th, which caused a slow dump of the magnet. Since this occurred just before a planned technical stop of the LHC, during which access in the experimental cavern was authorized, it was decided to leave the magnet OFF until 2nd June, when magnet was ramped up again to 3.8T. The magnet system experienced a fault also resulting in a slow dump on April 14th. This was triggered by a thermostat on a filter choke in the 20kA DC power converter. The threshold of this thermostat is 65°C. However, no variation in the water-cooling flow rate or temperature was observed. Vibration may have been the root cause of the fault. All the thermostats have been checked, together with the cables, connectors and the read out card. The tightening of the inductance fixations has also been checked. More tem...

  12. MAGNET

    CERN Multimedia

    B. Curé

    2012-01-01

      The magnet was energised at the beginning of March 2012 at a low current to check all the MSS safety chains. Then the magnet was ramped up to 3.8 T on 6 March 2012. Unfortunately two days later an unintentional switch OFF of the power converter caused a slow dump. This was due to a misunderstanding of the CCC (CERN Control Centre) concerning the procedure to apply for the CMS converter control according to the beam-mode status at that time. Following this event, the third one since 2009, a discussion was initiated to define possible improvement, not only on software and procedures in the CCC, but also to evaluate the possibility to upgrade the CMS hardware to prevent such discharge from occurring because of incorrect procedure implementations. The magnet operation itself was smooth, and no power cuts took place. As a result, the number of magnetic cycles was reduced to the minimum, with only two full magnetic cycles from 0 T to 3.8 T. Nevertheless the magnet suffered four stops of the cryogeni...

  13. MAGNET

    CERN Multimedia

    B. Curé

    2012-01-01

      Following the unexpected magnet stops last August due to sequences of unfortunate events on the services and cryogenics [see CMS internal report], a few more events and initiatives again disrupted the magnet operation. All the magnet parameters stayed at their nominal values during this period without any fault or alarm on the magnet control and safety systems. The magnet was stopped for the September technical stop to allow interventions in the experimental cavern on the detector services. On 1 October, to prepare the transfer of the liquid nitrogen tank on its new location, several control cables had to be removed. One cable was cut mistakenly, causing a digital input card to switch off, resulting in a cold-box (CB) stop. This tank is used for the pre-cooling of the magnet from room temperature down to 80 K, and for this reason it is controlled through the cryogenics control system. Since the connection of the CB was only allowed for a field below 2 T to avoid the risk of triggering a fast d...

  14. Magnetic properties study of iron-oxide nanoparticles/PVA ferrogels with potential biomedical applications

    International Nuclear Information System (INIS)

    Mendoza Zélis, P.; Muraca, D.; Gonzalez, J. S.; Pasquevich, G. A.; Alvarez, V. A.; Pirota, K. R.; Sánchez, F. H.

    2013-01-01

    A study of the magnetic behavior of maghemite nanoparticles (NPs) in polyvinyl alcohol (PVA) polymer matrices prepared by physical cross-linking is reported. The magnetic nanocomposites (ferrogels) were obtained by the in situ co-precipitation of iron salts in the presence of PVA polymer, and subsequently subjected to freezing–thawing cycles. The magnetic behavior of these ferrogels was compared with that of similar systems synthesized using the glutaraldehyde. This type of chemical cross-linking agents presents several disadvantages due to the presence of residual toxic molecules in the gel, which are undesirable for biological applications. Characteristic particle size determined by several techniques are in the range 7.9–9.3 nm. The iron oxidation state in the NPs was studied by X-ray absorption spectroscopy. Mössbauer measurements showed that the NP magnetic moments present collective magnetic excitations and superparamagnetic relaxations. The blocking and irreversibility temperatures of the NPs in the ferrogels, and the magnetic anisotropy constant, were obtained from magnetic measurements. An empirical model including two magnetic contributions (large NPs slightly departed from thermodynamic equilibrium below 200 K, and small NPs at thermodynamic equilibrium) was used to fit the experimental magnetization curves. A deviation from the superparamagnetic regime was observed. This deviation was explained on the basis of an interacting superparamagnetic model. From this model, relevant magnetic and structural properties were obtained, such as the magnitude order of the dipolar interaction energy, the NPs magnetic moment, and the number of NPs per ferrogel mass unit. This study contributes to the understanding of the basic physics of a new class of materials that could emerge from the PVA-based magnetic ferrogels.

  15. Potential uses of high gradient magnetic filtration for high-temperature water purification in boiling water reactors

    International Nuclear Information System (INIS)

    Elliott, H.H.; Holloway, J.H.; Abbott, D.G.

    1979-01-01

    Studies of various high-temperature filter devices indicate a potentially positive impact for high gradient magnetic filtration on boiling water reactor radiation level reduction. Test results on in-plant water composition and impurity crystallography are presented for several typical boiling water reactors (BWRs) on plant streams where high-temperature filtration may be particularly beneficial. An experimental model on the removal of red iron oxide (hematite) from simulated reactor water with a high gradient magnetic filter is presented, as well as the scale-up parameters used to predict the filtration efficiency on various high temperature, in-plant streams. Numerical examples are given to illustrate the crud removal potential of high gradient magnetic filters installed at alternative stream locations under typical, steady-state, plant operating conditions

  16. Exact diagonalization of cubic lattice models in commensurate Abelian magnetic fluxes and translational invariant non-Abelian potentials

    DEFF Research Database (Denmark)

    Burrello, M.; Fulga, Ion Cosma; Lepori, L.

    2017-01-01

    of a translational invariant non-Abelian coupling for multi-component spinors does not affect the dimension of the minimal Hamiltonian blocks, nor the dimension of the magnetic Brillouin zone. General formulas are presented for the U(2) case and explicit examples are investigated involving π and 2π/3 magnetic fluxes......We present a general analytical formalism to determine the energy spectrum of a quantum particle in a cubic lattice subject to translationally invariant commensurate magnetic fluxes and in the presence of a general spaceindependent non-Abelian gauge potential. We first review and analyze the case...... of purely Abelian potentials, showing also that the so-called Hasegawa gauge yields a decomposition of the Hamiltonian into sub-matrices having minimal dimension. Explicit expressions for such matrices are derived, also for general anisotropic fluxes. Later on, we show that the introduction...

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

    Energy Technology Data Exchange (ETDEWEB)

    Tenforde, T.S.

    1992-05-01

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

  18. Molecular Imaging With Optical, Magnetic Resonance, and Radioisotope Techniques: Potentials and Relative Limitations

    National Research Council Canada - National Science Library

    Budinger, Thomas

    2001-01-01

    The technology advances include photodiode arrays for optical methods high field magnets proposed to 12 Tesla for functional imaging and multinuclear spectroscopy 3D ultrasound and positron tomography...

  19. Magnetic resonance imaging of the cardiovascular system: present state of the art and future potential

    International Nuclear Information System (INIS)

    Jacobson, H.G.

    1988-01-01

    State-of-the-art magnetic resonance imaging (MRI) generates high-resolution images of the cardiovascular system. Conventional MRI techniques provide images in six to ten minutes per tomographic slice. New strategies have substantially improved the speed of imaging. The technology is relatively expensive, and its cost-effectiveness remains to be defined in relation to other effective, less expensive, and noninvasive technologies, such as echocardiography and nuclear medicine. The ultimate role of MRI will depend on several factors, including the development of specific applications such as (1) noninvasive angiography, especially of the coronary arteries;(2) noninvasive, high-resolution assessment of regional myocardial blood flow distribution (e.g., using paramagnetic contrast agents); (3) characterization of myocardial diseases using proton-relaxation property changes; and (4) evaluation of in vivo myocardial biochemistry. The three-dimensional imaging capability and the ability to image cardiovascular structures without contrast material give MRI a potential advantage over existing noninvasive diagnostic imaging techniques. This report analyzes current applications of MRI to the cardiovascular system and speculates on their future

  20. Reactor potential of the Magnetically Insulated Inertial Confinement Fusion (MICF) system

    International Nuclear Information System (INIS)

    Kammash, T.; Galbraith, D.L.

    1987-01-01

    In this paper a quasi one dimensional, time dependent set of particle and energy balance equations for the thermal species, namely, electrons, ions and thermal alphas which also allows for an appropriate set of fast alpha groups is utilized to assess the reactor prospects of a DT-burning Magnetically Insulated Inertial Confinement Fusion (MICF) system. A reference reactor consisting of an initial plasma with density of 10 21 cm -3 , temperature of keV, a radius of 0.25 cm is shown to ignite and yield an energy multiplication factor ''Q'' of about 60 when the plasma is allowed to burn for 2 microseconds. When the burntime is extended to 9 microseconds for the same initial conditions our calculations show that Q almost doubles just before the final radius becomes equal to the inner radius of the shell. These preliminary results seem to indicate that MICF does indeed have the potential for a reactor although some relevant physics issues need to be addressed first. 42 refs., 6 figs

  1. Characterization of colloidal manganese hydroxylapatite: A potential magnetic resonance contrast agent

    Science.gov (United States)

    Dorshow, Richard B.; Kofi Adzamli, I.; Nosco, Dennis L.; Joslin, Frederick L.

    1996-03-01

    Particulate contrast agents for blood pool imaging need to be constructed with the appropriate particle size distribution (PSD), and need to be resistant to opsonization. Hence, the PSD of an aqueous colloidal suspension of polyethylene glycol (PEG)-stabilized manganese hydroxylapatite (potentially useful as a magnetic resonance contrast agent for blood pool imaging) has been investigated as a function of PEG concentration and molecular weight. At low PEG concentrations, dynamic light scattering (DLS) and sedimentation field flow fractionation measurements yield a broad PSD, with the largest particle diameters near 100nm. Flow field flow fractionation (FlFFF) measurements, however, yield a distinct population near 10nm, which is not readily detectable by the other two techniques. As the PEG concentration is increased, the PSD shifts toward the lower size population. At the highest PEG concentration employed, only particles of diameter 10nm remain, verified by both FlFFF and DLS. Thus, the search for an optimum PSD for blood pool imaging is facilitated by choice of PEG molecular weight and concentration, and by employing complementary use of light scattering and field flow fractionation techniques.

  2. Focused Ultrasound-Induced Blood-Brain Barrier Opening: Association with Mechanical Index and Cavitation Index Analyzed by Dynamic Contrast-Enhanced Magnetic-Resonance Imaging.

    Science.gov (United States)

    Chu, Po-Chun; Chai, Wen-Yen; Tsai, Chih-Hung; Kang, Shih-Tsung; Yeh, Chih-Kuang; Liu, Hao-Li

    2016-09-15

    Focused ultrasound (FUS) with microbubbles can temporally open the blood-brain barrier (BBB), and the cavitation activities of microbubbles play a key role in the BBB-opening process. Previous attempts used contrast-enhanced magnetic resonance imaging (CE-MRI) to correlate the mechanical index (MI) with the scale of BBB-opening, but MI only partially gauged acoustic activities, and CE-MRI did not fully explore correlations of pharmacodynamic/pharmacokinetic behaviors. Recently, the cavitation index (CI) has been derived to serve as an indicator of microbubble-ultrasound stable cavitation, and may also serve as a valid indicator to gauge the level of FUS-induced BBB opening. This study investigates the feasibility of gauging FUS-induced BBB opened level via the two indexes, MI and CI, through dynamic contrast-enhanced (DCE)-MRI analysis as well as passive cavitation detection (PCD) analysis. Pharmacodynamic/pharmacokinetic parameters derived from DCE-MRI were characterized to identify the scale of FUS-induced BBB opening. Our results demonstrated that DCE-MRI can successfully access pharmacodynamic/pharmacokinetic BBB-opened behavior, and was highly correlated both with MI and CI, implying the feasibility in using these two indices to gauge the scale of FUS-induced BBB opening. The proposed finding may facilitate the design toward using focused ultrasound as a safe and reliable noninvasive CNS drug delivery.

  3. Hyperpolarized 3He magnetic resonance imaging: Preliminary evaluation of phenotyping potential in chronic obstructive pulmonary disease

    International Nuclear Information System (INIS)

    Mathew, Lindsay; Kirby, Miranda; Etemad-Rezai, Roya; Wheatley, Andrew; McCormack, David G.; Parraga, Grace

    2011-01-01

    Rationale and objectives: Emphysema and small airway obstruction are the pathological hallmarks of chronic obstructive pulmonary disease (COPD). The aim of this pilot study in a small group of chronic obstructive pulmonary disease (COPD) patients was to quantify hyperpolarized helium-3 ( 3 He) magnetic resonance imaging (MRI) functional and structural measurements and to explore the potential role for 3 He MRI in detecting the lung structural and functional COPD phenotypes. Materials and methods: We evaluated 20 ex-smokers with stage I (n = 1), stage II (n = 9) and stage III COPD (n = 10). All subjects underwent same-day plethysmography, spirometry, 1 H MRI and hyperpolarized 3 He MRI at 3.0 T. 3 He ventilation defect percent (VDP) was generated from 3 He static ventilation images and 1 H thoracic images and the 3 He apparent diffusion coefficient (ADC) was derived from diffusion-weighted MRI. Results: Based on the relative contribution of normalized ADC and VDP, there was evidence of a predominant 3 He MRI measurement in seven patients (n = 3 mainly ventilation defects or VDP dominant (VD), n = 4 mainly increased ADC or ADC dominant (AD)). Analysis of variance (ANOVA) showed significantly lower ADC for subjects with predominantly elevated VDP (p = 0.02 compared to subjects with predominantly elevated ADC; p = 0.008 compared to mixed group) and significantly decreased VDP for subjects with predominantly elevated ADC (p = 0.003, compared to mixed group). Conclusion: In this small pilot study, a preliminary analysis shows the potential for 3 He MRI to categorize or phenotype COPD ex-smokers, providing good evidence of feasibility for larger prospective studies.

  4. Recording visual evoked potentials and auditory evoked P300 at 9.4T static magnetic field.

    Science.gov (United States)

    Arrubla, Jorge; Neuner, Irene; Hahn, David; Boers, Frank; Shah, N Jon

    2013-01-01

    Simultaneous recording of electroencephalography (EEG) and functional magnetic resonance imaging (fMRI) has shown a number of advantages that make this multimodal technique superior to fMRI alone. The feasibility of recording EEG at ultra-high static magnetic field up to 9.4 T was recently demonstrated and promises to be implemented soon in fMRI studies at ultra high magnetic fields. Recording visual evoked potentials are expected to be amongst the most simple for simultaneous EEG/fMRI at ultra-high magnetic field due to the easy assessment of the visual cortex. Auditory evoked P300 measurements are of interest since it is believed that they represent the earliest stage of cognitive processing. In this study, we investigate the feasibility of recording visual evoked potentials and auditory evoked P300 in a 9.4 T static magnetic field. For this purpose, EEG data were recorded from 26 healthy volunteers inside a 9.4 T MR scanner using a 32-channel MR compatible EEG system. Visual stimulation and auditory oddball paradigm were presented in order to elicit evoked related potentials (ERP). Recordings made outside the scanner were performed using the same stimuli and EEG system for comparison purposes. We were able to retrieve visual P100 and auditory P300 evoked potentials at 9.4 T static magnetic field after correction of the ballistocardiogram artefact using independent component analysis. The latencies of the ERPs recorded at 9.4 T were not different from those recorded at 0 T. The amplitudes of ERPs were higher at 9.4 T when compared to recordings at 0 T. Nevertheless, it seems that the increased amplitudes of the ERPs are due to the effect of the ultra-high field on the EEG recording system rather than alteration in the intrinsic processes that generate the electrophysiological responses.

  5. Evaluation of swimming capability and potential velocity barrier problems for fish. Part B: New telemetric approaches to the assessment of fish swimming performance

    International Nuclear Information System (INIS)

    Scruton, D. A.; Goosney, R. G.; McKinley, R. S.; Booth, R. K.; Colavecchia, M.

    1998-08-01

    This report represents the second part of a study undertaken to develop information related to swimming capability of several important fish species. The study will provide biological design criteria to mitigate potential velocity barrier problems associated with hydroelectric power plants. This part of the report focuses on the development and evaluation of approaches to assessing locomotory activity, swimming performance and energy load costs to fish under naturally occurring conditions and in relation to potential barriers. The study involved implantation of a bio-sensitive radio transmitter (electromyogram (EMG)) tag in the swimming muscle of fish, calibration of locomotory ability and energetic scope, and subsequent use of EMG signals to assess swimming performance and metabolic costs in situ. Digital signal processing (DSP) with antennae switching was also used to study high speed swimming performance, behaviour, and migratory strategy in relation to ascent of an experimental flume. The techniques and technologies developed indicate the complexity of factors that regulate fish swimming energy expenditure that need to be considered in the design and operation of fish passage facilities. 84 refs., 6 tabs., figs., 2 appendices

  6. Reply to Comment on ‘An educational path for the magnetic vector potential and its physical implications’

    International Nuclear Information System (INIS)

    Barbieri, S; Cavinato, M; Giliberti, M

    2014-01-01

    In this reply we respond to the comment made by Heras on our paper (Barbieri et al 2013 Eur. J. Phys. 34 1209), in which we presented an educational path on the magnetic vector potential A, aimed at undergraduate students and pre-service physics teachers. (letters and comments)

  7. Interaction of organic contaminants with natural clay type geosorbents: potential use as geologic barrier in urban landfill.

    Science.gov (United States)

    Sánchez-Jiménez, N; Sevilla, M T; Cuevas, J; Rodríguez, M; Procopio, J R

    2012-03-01

    The aim of this work is to characterize the capability of several clay materials as preservative of organic pollution for use as landfill barrier. Interaction of representative organic pollutants with different polarity and water solubility (atrazine, benzamide, methomyl, paraquat and toluene) with several clay materials coming from several locations of Spain were studied. Batch suspension method was used to study the pesticide adsorption onto the clay sorbents in solution conditions that simulate the composition of a young leachate in its aerobic acetogenic stage (pH=5 and I=0.15) The obtained data of the analytes sorption were modelized by several sorption isotherm models, and the best fitted data were got with a generalized Langmuir adsorption isotherm. The higher maxima adsorptions were observed for paraquat (50-62 mmol kg(-1)) and toluene (19-34 mmol kg(-1)) whereas more hydrophobic compounds present lower adsorption (0.7-2.5 mmol kg(-1)). Paraquat is the compound that presents the higher bonding coefficients. Therefore these clays could be used as components of the multibarriers in controlled urban landfill. Copyright © 2011 Elsevier Ltd. All rights reserved.

  8. Propranolol transport across the inner blood-retinal barrier: potential involvement of a novel organic cation transporter.

    Science.gov (United States)

    Kubo, Yoshiyuki; Shimizu, Yoshimi; Kusagawa, Yusuke; Akanuma, Shin-Ichi; Hosoya, Ken-Ichi

    2013-09-01

    The influx transport of propranolol across the inner blood-retinal barrier (BRB) was investigated. In the in vivo analysis of carotid artery single-injection method, [(3) H]propranolol uptake by the retina was greater than that of an internal reference compound, and was reduced by several organic cations. In the in vitro uptake study, TR-iBRB2 cells, an in vitro model of the inner BRB, showed a time-, concentration-, pH- and temperature-dependent [(3) H]propranolol uptake, suggesting the involvement of a carrier-mediated transport process in the influx of propranolol across the inner BRB. In the inhibition study, various organic cations, including drugs and candidates for the treatment of the retinal diseases, inhibited the [(3) H]propranolol uptake by TR-iBRB2 cells with no significant effects by the substrates and inhibitors of well-characterized organic cation transporters, suggesting that the influx transport of propranolol is performed by a novel transporter at the inner BRB. An analysis of the relationship between the inhibitory effect and the lipophilicity of inhibitors suggests a lipophilicity-dependent inhibitory effect of amines on the [(3) H]propranolol uptake by TR-iBRB2 cells. These results showed that influx transport of propranolol across the inner BRB is performed by a carrier-mediated transport process, suggesting the involvement of a novel organic cation transporter. Copyright © 2013 Wiley Periodicals, Inc.

  9. MAGNET

    CERN Multimedia

    B. Curé

    2012-01-01

      The magnet and its sub-systems were stopped at the beginning of the winter shutdown on 8th December 2011. The magnet was left without cooling during the cryogenics maintenance until 17th January 2012, when the cryoplant operation resumed. The magnet temperature reached 93 K. The vacuum pumping was maintained during this period. During this shutdown, the yearly maintenance was performed on the cryogenics, the vacuum pumps, the magnet control and safety systems, and the power converter and discharge lines. Several preventive actions led to the replacement of the electrovalve command coils, and the 20A DC power supplies of the magnet control system. The filters were cleaned on the demineralised water circuits. The oil of the diffusion pumps was changed. On the cryogenics, warm nitrogen at 343 K was circulated in the cold box to regenerate the filters and the heat exchangers. The coalescing filters have been replaced at the inlet of both the turbines and the lubricant trapping unit. The active cha...

  10. MAGNET

    CERN Multimedia

    B. Curé

    2013-01-01

      The magnet was operated without any problem until the end of the LHC run in February 2013, apart from a CERN-wide power glitch on 10 January 2013 that affected the CMS refrigerator, causing a ramp down to 2 T in order to reconnect the coldbox. Another CERN-wide power glitch on 15 January 2013 didn’t affect the magnet subsystems, the cryoplant or the power converter. At the end of the magnet run, the reconnection of the coldbox at 2.5 T was tested. The process will be updated, in particular the parameters of some PID valve controllers. The helium flow of the current leads was reduced but only for a few seconds. The exercise will be repeated with the revised parameters to validate the automatic reconnection process of the coldbox. During LS1, the water-cooling services will be reduced and many interventions are planned on the electrical services. Therefore, the magnet cryogenics and subsystems will be stopped for several months, and the magnet cannot be kept cold. In order to avoid unc...

  11. MAGNET

    CERN Multimedia

    Benoit Curé

    2010-01-01

    The magnet was successfully operated at the end of the year 2009 despite some technical problems on the cryogenics. The magnet was ramped up to 3.8 T at the end of November until December 16th when the shutdown started. The magnet operation met a few unexpected stops. The field was reduced to 3.5 T for about 5 hours on December 3rd due to a faulty pressure sensor on the helium compressor. The following day the CERN CCC stopped unintentionally the power converters of the LHC and the experiments, triggering a ramp down that was stopped at 2.7 T. The magnet was back at 3.8 T about 6 hours after CCC sent the CERN-wide command. Three days later, a slow dump was triggered due to a stop of the pump feeding the power converter water-cooling circuit, during an intervention on the water-cooling plant done after several disturbances on the electrical distribution network. The magnet was back at 3.8 T in the evening the same day. On December 10th a break occurred in one turbine of the cold box producing the liquid ...

  12. MAGNET

    CERN Multimedia

    B. Curé

    2011-01-01

    The CMS magnet has been running steadily and smoothly since the summer, with no detected flaw. The magnet instrumentation is entirely operational and all the parameters are at their nominal values. Three power cuts on the electrical network affected the magnet run in the past five months, with no impact on the data-taking as the accelerator was also affected at the same time. On 22nd June, a thunderstorm caused a power glitch on the service electrical network. The primary water cooling at Point 5 was stopped. Despite a quick restart of the water cooling, the inlet temperature of the demineralised water on the busbar cooling circuit increased by 5 °C, up to 23.3 °C. It was kept below the threshold of 27 °C by switching off other cooling circuits to avoid the trigger of a slow dump of the magnet. The cold box of the cryogenics also stopped. Part of the spare liquid helium volume was used to maintain the cooling of the magnet at 4.5 K. The operators of the cryogenics quickly restarted ...

  13. Magnetic control of potential microrobotic drug delivery systems: nanoparticles, magnetotactic bacteria and self-propelled microjets

    NARCIS (Netherlands)

    Khalil, I.S.M.; Magdanz, V.; Sanchez, Stefan; Sanchez, S.; Schmidt, O.G.; Abelmann, Leon; Misra, Sarthak

    2013-01-01

    Development of targeted drug delivery systems using magnetic microrobots increases the therapeutic indices of drugs. These systems have to be incorporated with precise motion controllers. We demonstrate closed-loop motion control of microrobots under the influence of controlled magnetic fields.

  14. Beam-induced magnetic property modifications: Basics, nanostructure fabrication and potential applications

    International Nuclear Information System (INIS)

    Devolder, T.; Bernas, H.; Ravelosona, D.; Chappert, C.; Pizzini, S.; Vogel, J.; Ferre, J.; Jamet, J.-P.; Chen, Y.; Mathet, V.

    2001-01-01

    We have developed an irradiation technique that allows us to tune the magnetic properties of thin films without affecting their roughness. We discuss the mechanisms involved and the applications. He + ion irradiation of Co/Pt multilayers lowers their magnetic anisotropy in a controlled way, reducing the coercive force and then leading to in-plane magnetization. By X-ray reflectometry, we study how irradiation-induced structural modifications correlate with magnetic properties. We also report the L1 0 chemical ordering of FePt by irradiation at 280 deg. C, and the consequent increase of magnetic anisotropy. Planar magnetic patterning at the sub 50 nm scale can be achieved when the irradiation is performed through a mask. New magnetic behaviors result from the fabrication process. They appear to arise from collateral damage. We model these effects in the case of SiO 2 and W masks. The planarity of irradiation-induced patterning and its ability to independently control nanostructure size and coercivity make it very appealing for magnetic recording on nanostructured media. Finally, possible applications to the granular media used in current hard disk drive storage technology are discussed

  15. Revival of cloaking effect in a driven bilayer graphene vector barrier

    Science.gov (United States)

    Maiti, S.; Panigrahi, A.; Biswas, R.; Sinha, C.

    2018-05-01

    Transmission profiles in bilayer graphene are studied theoretically through a rectangular vector potential (magnetic) barrier with and without the presence of an oscillatory potential. Unlike the electrostatic barrier, the Fano resonances (FR) are noted in the transmission spectra both for normal and glancing incidences due to non-conservation of chirality for a static vector barrier. The results for normal incidence indicate that the cloaking effect is a manifestation of the chirality conservation in charge transport through bilayer graphene scalar barriers. It is also noted that the aforesaid FR for a static vector barrier might disappear (photon induced electronic cloaking effect) due to the predominant photon exchange processes in presence of an external oscillating potential. The study of Fano resonances in transmission spectrum is in high demand in respect of localization of charge carriers in graphene nano structures for its potential applications in digital device fabrications.

  16. Decreased plasma thiol antioxidant barrier and selenoproteins as potential biomarkers for ongoing methylmercury intoxication and an individual protective capacity.

    Science.gov (United States)

    Usuki, Fusako; Fujimura, Masatake

    2016-04-01

    Manifestation of methylmercury (MeHg) toxicity depends on individual susceptibility to MeHg, as well as MeHg burden level. Therefore, biomarkers that reflect the protective capacity against MeHg are needed. The critical role of oxidative stress in the pathogenesis of MeHg cytotoxicity has been demonstrated. Because MeHg has high affinity for selenohydryl groups, sulfhydryl groups, and selenides, and causes posttranscriptional defects in selenoenzymes, proteins with selenohydryl and sulfhydryl groups should play a critical role in mediating MeHg-induced oxidative stress. Here, plasma oxidative stress markers and selenoproteins were investigated in MeHg-intoxicated rats showing neuropathological changes after 4 weeks of MeHg exposure. The thiol antioxidant barrier (-SHp) level significantly decreased 2 weeks after MeHg exposure, which is an early stage at which no systemic oxidative stress, histopathological changes, or clinical signs were detected. Diacron reactive oxidant metabolite (d-ROM) levels significantly increased 3 weeks after MeHg exposure, indicating the occurrence of systemic oxidative stress. Rats treated with lead acetate or cadmium chloride showed no changes in levels of -SHp and d-ROM. Selenoprotein P1 abundance significantly decreased in MeHg-treated rats, whereas it significantly increased in rats treated with Pb or Cd. Plasma selenium-dependent glutathione peroxidase (GPx3) activity also significantly decreased after MeHg exposure, whereas plasma non-selenoenzyme glutathione reductase activity significantly increased in MeHg-treated rats. The results suggest that decreased capacity of -SHp and selenoproteins (GPx3 and selenoprotein P) can be useful biomarkers of ongoing MeHg cytotoxicity and the individual protective capacity against the MeHg body burden.

  17. Remaining Physiological Barriers in Porcine Kidney Xenotransplantation: Potential Pathways behind Proteinuria as well as Factors Related to Growth Discrepancies following Pig-to-Kidney Xenotransplantation.

    Science.gov (United States)

    Shah, Jigesh A; Lanaspa, Miguel A; Tanabe, Tatsu; Watanabe, Hironosuke; Johnson, Richard J; Yamada, Kazuhiko

    2018-01-01

    Considerable shortages in the supply of available organs continue to plague the field of solid organ transplantation. Despite changes in allocation, as well as the utilization of extended criteria and living donors, the number of patients waiting for organs continues to grow at an alarming pace. Xenotransplantation, cross-species solid organ transplantation, offers one potential solution to this dilemma. Previous extensive research dedicated to this field has allowed for resolution of xenograft failure due to acute rejection, leaving new areas of unresolved challenges as barriers to success in large animal models. Specific to kidney xenotransplantation, recent data seems to indicate that graft compromise can occur due to discrepancies in growth between breeds of donors and significant proteinuria leading to nephrotic syndrome in the recipient. Given these potential limitations, herein, we review potential pathways behind proteinuria, as well as potential causative factors related to growth discrepancies. Control of both of these has the potential to allow xenotransplantation to become clinically applicable in an effort to resolve this organ shortage crisis.

  18. Potential scattering in the presence of a static magnetic field and a radiation field of arbitrary polarization

    Science.gov (United States)

    Ferrante, G.; Zarcone, M.; Nuzzo, S.; McDowell, M. R. C.

    1982-05-01

    Expressions are obtained for the total cross sections for scattering of a charged particle by a potential in the presence of a static uniform magnetic field and a radiation field of arbitrary polarization. For a Coulomb field this is closely related to the time reverse of photoionization of a neutral atom in a magnetic field, including multiphoton effects off-resonance. The model is not applicable when the radiation energy approaches one of the quasi-Landau state separations. The effects of radiation field polarization are examined in detail.

  19. ABCXYZ: vector potential (A) and magnetic field (B) code (C) for Cartesian (XYZ) geometry using general current elements

    International Nuclear Information System (INIS)

    Anderson, D.V.; Breazeal, J.; Finan, C.H.; Johnston, B.M.

    1976-01-01

    ABCXYZ is a computer code for obtaining the Cartesian components of the vector potential and the magnetic field on an observed grid from an arrangement of current-carrying wires. Arbitrary combinations of straight line segments, arcs, and loops are allowed in the specification of the currents. Arbitrary positions and orientations of the current-carrying elements are also allowed. Specification of the wire diameter permits the computation of well-defined fields, even in the interiors of the conductors. An optical feature generates magnetic field lines. Extensive graphical and printed output is available to the user including contour, grid-line, and field-line plots. 12 figures, 1 table

  20. MAGNET

    CERN Multimedia

    B. Curé

    2011-01-01

    The magnet ran smoothly in the last few months until a fast dump occurred on 9th May 2011. Fortunately, this occurred in the afternoon of the first day of the technical stop. The fast dump was due to a valve position controller that caused the sudden closure of a valve. This valve is used to regulate the helium flow on one of the two current leads, which electrically connects the coil at 4.5 K to the busbars at room temperature. With no helium flow on the lead, the voltage drop and the temperatures across the leads increase up to the defined thresholds, triggering a fast dump through the Magnet Safety System (MSS). The automatic reaction triggered by the MSS worked properly. The helium release was limited as the pressure rise was just at the limit of the safety valve opening pressure. The average temperature of the magnet reached 72 K. It took four days to recover the temperature and refill the helium volumes. The faulty valve controller was replaced by a spare one before the magnet ramp-up resumed....

  1. Comparative measurements of plasma potential with ball-pen and Langmuir probe in low-temperature magnetized plasma

    International Nuclear Information System (INIS)

    Zanáška, M.; Kudrna, P.; Tichý, M.; Adámek, J.; Peterka, M.

    2015-01-01

    The ball-pen probe (BPP) is used for direct plasma potential measurements in magnetized plasma. The probe can adjust the ratio of the electron and ion saturation currents I sat − /I sat + to be close to one and therefore its I-V characteristic becomes nearly symmetric. If this is achieved, the floating potential of the BPP is close to the plasma potential. Because of its rather simple construction, it offers an attractive probe for measurements in magnetized plasma. Comparative measurements of plasma potential by BPPs of different dimensions as well as one Langmuir probe (LP) in an argon discharge plasma of a cylindrical magnetron were performed at various experimental conditions. An additional comparison by an emissive probe was also performed. All these types of probes provide similar values of plasma potential in a wide range of plasma parameters. Our results for three different BPP dimensions indicate that the BPP can be operated in a cylindrical magnetron DC argon discharge if the value of the ratio of the magnetic field and neutral gas pressure, B/p, is greater than approximately 10 mT/Pa

  2. Comparative measurements of plasma potential with ball-pen and Langmuir probe in low-temperature magnetized plasma

    Science.gov (United States)

    Zanáška, M.; Adámek, J.; Peterka, M.; Kudrna, P.; Tichý, M.

    2015-03-01

    The ball-pen probe (BPP) is used for direct plasma potential measurements in magnetized plasma. The probe can adjust the ratio of the electron and ion saturation currents Isat-/Isat+ to be close to one and therefore its I-V characteristic becomes nearly symmetric. If this is achieved, the floating potential of the BPP is close to the plasma potential. Because of its rather simple construction, it offers an attractive probe for measurements in magnetized plasma. Comparative measurements of plasma potential by BPPs of different dimensions as well as one Langmuir probe (LP) in an argon discharge plasma of a cylindrical magnetron were performed at various experimental conditions. An additional comparison by an emissive probe was also performed. All these types of probes provide similar values of plasma potential in a wide range of plasma parameters. Our results for three different BPP dimensions indicate that the BPP can be operated in a cylindrical magnetron DC argon discharge if the value of the ratio of the magnetic field and neutral gas pressure, B/p, is greater than approximately 10 mT/Pa.

  3. Comparative measurements of plasma potential with ball-pen and Langmuir probe in low-temperature magnetized plasma

    Energy Technology Data Exchange (ETDEWEB)

    Zanáška, M.; Kudrna, P.; Tichý, M. [Faculty of Mathematics and Physics, Charles University in Prague, Ke Karlovu 3, 12116 Prague 2 (Czech Republic); Adámek, J. [Institute of Plasma Physics AS CR, v.v.i., Za Slovankou 3, 18200 Prague 8 (Czech Republic); Peterka, M. [Faculty of Mathematics and Physics, Charles University in Prague, Ke Karlovu 3, 12116 Prague 2 (Czech Republic); Institute of Plasma Physics AS CR, v.v.i., Za Slovankou 3, 18200 Prague 8 (Czech Republic)

    2015-03-15

    The ball-pen probe (BPP) is used for direct plasma potential measurements in magnetized plasma. The probe can adjust the ratio of the electron and ion saturation currents I{sub sat}{sup −}/I{sub sat}{sup +} to be close to one and therefore its I-V characteristic becomes nearly symmetric. If this is achieved, the floating potential of the BPP is close to the plasma potential. Because of its rather simple construction, it offers an attractive probe for measurements in magnetized plasma. Comparative measurements of plasma potential by BPPs of different dimensions as well as one Langmuir probe (LP) in an argon discharge plasma of a cylindrical magnetron were performed at various experimental conditions. An additional comparison by an emissive probe was also performed. All these types of probes provide similar values of plasma potential in a wide range of plasma parameters. Our results for three different BPP dimensions indicate that the BPP can be operated in a cylindrical magnetron DC argon discharge if the value of the ratio of the magnetic field and neutral gas pressure, B/p, is greater than approximately 10 mT/Pa.

  4. Potential damage to dc superconducting magnets due to high frequency electromagnetic waves

    Science.gov (United States)

    Gabriel, G. J.; Burkhart, J. A.

    1977-01-01

    Studies of a d.c. superconducting magnet coil indicate that the large coil behaves as a straight waveguide structure. Voltages between layers within the coil sometimes exceeded those recorded at terminals where protective resistors are located. Protection of magnet coils against these excessive voltages could be accomplished by impedance matching throughout the coil system. The wave phenomenon associated with superconducting magnetic coils may create an instability capable of converting the energy of a quiescent d.c. superconducting coil into dissipative a.c. energy, even in cases when dielectric breakdown does not take place.

  5. Potential for thermal damage to the blood–brain barrier during craniotomy: implications for intracortical recording microelectrodes

    Science.gov (United States)

    Shoffstall, Andrew J.; Paiz, Jen E.; Miller, David M.; Rial, Griffin M.; Willis, Mitchell T.; Menendez, Dhariyat M.; Hostler, Stephen R.; Capadona, Jeffrey R.

    2018-06-01

    Objective. Our objective was to determine how readily disruption of the blood–brain barrier (BBB) occurred as a result of bone drilling during a craniotomy to implant microelectrodes in rat cortex. While the phenomenon of heat production during bone drilling is well known, practices to evade damage to the underlying brain tissue are inconsistently practiced and reported in the literature. Approach. We conducted a review of the intracortical microelectrode literature to summarize typical approaches to mitigate drill heating during rodent craniotomies. Post mortem skull-surface and transient brain-surface temperatures were experimentally recorded using an infrared camera and thermocouple, respectively. A number of drilling conditions were tested, including varying drill speed and continuous versus intermittent contact. In vivo BBB permeability was assayed 1 h after the craniotomy procedure using Evans blue dye. Main results. Of the reviewed papers that mentioned methods to mitigate thermal damage during craniotomy, saline irrigation was the most frequently cited (in six of seven papers). In post mortem tissues, we observed increases in skull-surface temperature ranging from  +3 °C to  +21 °C, dependent on drill speed. In vivo, pulsed-drilling (2 s-on/2 s-off) and slow-drilling speeds (1000 r.p.m.) were the most effective methods we studied to mitigate heating effects from drilling, while inconclusive results were obtained with saline irrigation. Significance. Neuroinflammation, initiated by damage to the BBB and perpetuated by the foreign body response, is thought to play a key role in premature failure of intracortical recording microelectrodes. This study demonstrates the extreme sensitivity of the BBB to overheating caused by bone drilling. To avoid damage to the BBB, the authors recommend that craniotomies be drilled with slow speeds and/or with intermittent drilling with complete removal of the drill from the skull during ‘off’ periods. While

  6. Comparison of S3-3 polar cap potential drops with the interplanetary magnetic field and models of magnetopause reconnection

    International Nuclear Information System (INIS)

    Wygant, J.R.; Torbert, R.B.; Mozer, F.S.

    1983-01-01

    Measurements of the cross polar cap electric potential, by the double probe electric field experiment aboard S3-3, from 55 orbits in the dawn-dusk plane are compared with the reconnection electric fields predicted by a variety of models, both theoretical and experimental. The purpose of these comparisons is to understand the extent to which nonreconnection contributes to the polar cap potential must be included, to determine the time response of the polar cap potential to time varying reconnection rates, and to determine the efficiency and saturation levels of the reconnection process. It is found that (1) After several hours of northward interplanetary magnetic field, the cross polar cap potential declines to progressively lower values than those after 1 hour of northward interplanetary magnetic field. This suggests that it requires several hours for the ionospheric polar cap potential to respond to the ''turning off'' of ''turning down'' of the reconnection process. (2) The decay of the polar cap potential is used to demonstrate that contirubtions to the polar cap potential not associated with the reconnection process can be limited to less than 20 kV. It is shown that contributions to the polar cap potential that scale with the dynamic pressure of the solar wind are limited to less than 1 kV. (3) The cross polar cap electric potential is best predicted by a weighted sum of contributions from interplanetary magnetic field parameter over the 4 hours previous to the measurement. The weighting functions have the form of an exponential decay 2--3 hours with the strongest weight on interplanetary parameters over the 1 hour previous to the measurement

  7. [Changes of somatosensory and transcranial magnetic stimulation motor evoked potentials in experimental spinal cord injury].

    Science.gov (United States)

    Hou, Yong; Nie, Lin; Liu, Li-hong; Shao, Jun; Yuan, Yong-jian

    2008-03-18

    To study the changes of somatosensory evoked potential (SEP) and transcranial magnetic simulation motor evoked potential (TMS-MEP) in experimental spinal cord injury (SCI). Thirty-two rabbits were randomly divided into 4 equal groups. All rabbits were anesthetized for 90 min. A group (Group A) underwent only laminectomy of T12 without SCI, stimulation with different intensities was used to induce SEP and TMS-MEP to determine the most appropriate stimulation intensity. The EPs were recorded before and after the operation. The other 3 groups underwent laminectomy of T12 to expose the dura, and a spinal cord compressing apparatus weighing 40 g was put on the intact dura and dorsal surface of spinal cord underneath for 5, 15, and 30 min respectively (Groups B, C, and D). SEP and TMS-MEP were detected after anesthesia, after exposure of spinal cord, and 5 and 30 min, 1 and 6 h, and 1, 3, and 7 d. The latency and amplitude of each wave were measured. The data were analyzed by analysis of variance, t-test and linear correlation. Tarlov behavior score was used to assess the motor function before the operation and 1, 3, and 7 days after SCI. It was found that 100% intensity stimulus obtained stable and reliable MEP waves. Anesthetic did not influence the EPs. The amplitude of SEP began to decrease 5 min after SCI and the latency began to increase 30 min after SCI. And both the amplitude and latency, especially the former, of MEP began to significantly change 5 min after SCI. The latency levels of SEP and MEP increased and the amplitude decreased after compression time-dependently during a certain range of time (all P TMS-MEP are very sensitive to SCI, in particular, the change of amplitude is more sensitive then the latency change and can more accurately reflect the degree of SCI. Combination of SEP and TMS-MEP objectively reflects the SCI degree. EP measurement, as a noninvasive technique, has great value in monitoring spinal cord function.

  8. Near fifty percent sodium substituted lanthanum manganites—A potential magnetic refrigerant for room temperature applications

    Energy Technology Data Exchange (ETDEWEB)

    Sethulakshmi, N.; Anantharaman, M. R., E-mail: mraiyer@yahoo.com [Department of Physics, Cochin University of Science and Technology, Cochin 682022, Kerala (India); Al-Omari, I. A. [Department of Physics, Sultan Qaboos University, PC 123 Muscat, Sultanate of Oman (Oman); Suresh, K. G. [Department of Physics, Indian Institute of Technology Bombay, Powai, Mumbai 400076 (India)

    2014-03-03

    Nearly half of lanthanum sites in lanthanum manganites were substituted with monovalent ion-sodium and the compound possessed distorted orthorhombic structure. Ferromagnetic ordering at 300 K and the magnetic isotherms at different temperature ranges were analyzed for estimating magnetic entropy variation. Magnetic entropy change of 1.5 J·kg{sup −1}·K{sup −1} was observed near 300 K. An appreciable magnetocaloric effect was also observed for a wide range of temperatures near 300 K for small magnetic field variation. Heat capacity was measured for temperatures lower than 300 K and the adiabatic temperature change increases with increase in temperature with a maximum of 0.62 K at 280 K.

  9. Protein-functionalized magnetic iron oxide nanoparticles: time efficient potential-water treatment

    International Nuclear Information System (INIS)

    Okoli, Chuka; Boutonnet, Magali; Järås, Sven; Rajarao-Kuttuva, Gunaratna

    2012-01-01

    Recent advances in nanoscience suggest that the existing issues involving water quality could be resolved or greatly improved using nanomaterials, especially magnetic iron oxide nanoparticles. Magnetic nanoparticles have been synthesized for the development and use, in association with natural coagulant protein for water treatment. The nanoparticles size, morphology, structure, and magnetic properties were characterized by transmission electron microscope, X-ray diffraction, and superconducting quantum interference device magnetometry. Purified Moringa oleifera protein was attached onto microemulsions-prepared magnetic iron oxide nanoparticles (ME-MION) to form stable protein-functionalized magnetic nanoparticles (PMO+ME-MION). The turbidity removal efficiency in both synthetic and surface water samples were investigated and compared with the commonly used synthetic coagulant (alum) as well as PMO. More than 90 % turbidity could be removed from the surface waters within 12 min by magnetic separation of PMO+ME-MION; whereas gravimetrically, 70 % removal in high and low turbid waters can be achieved within 60 min. In contrast, alum requires 180 min to reduce the turbidity of low turbid water sample. These data support the advantage of separation with external magnetic field (magnetophoresis) over gravitational force. Time kinetics studies show a significant enhancement in ME-MION efficiency after binding with PMO implying the availability of large surface of the ME-MION. The coagulated particles (impurities) can be removed from PMO+ME-MION by washing with mild detergent or cleaning solution. To our knowledge, this is the first report on surface water turbidity removal using protein-functionalized magnetic nanoparticle.

  10. Protein-functionalized magnetic iron oxide nanoparticles: time efficient potential-water treatment

    Energy Technology Data Exchange (ETDEWEB)

    Okoli, Chuka [Royal Institute of Technology (KTH), Environmental Microbiology (Sweden); Boutonnet, Magali; Jaeras, Sven [Royal Institute of Technology (KTH), Chemical Technology (Sweden); Rajarao-Kuttuva, Gunaratna, E-mail: gkr@kth.se [Royal Institute of Technology (KTH), Environmental Microbiology (Sweden)

    2012-10-15

    Recent advances in nanoscience suggest that the existing issues involving water quality could be resolved or greatly improved using nanomaterials, especially magnetic iron oxide nanoparticles. Magnetic nanoparticles have been synthesized for the development and use, in association with natural coagulant protein for water treatment. The nanoparticles size, morphology, structure, and magnetic properties were characterized by transmission electron microscope, X-ray diffraction, and superconducting quantum interference device magnetometry. Purified Moringa oleifera protein was attached onto microemulsions-prepared magnetic iron oxide nanoparticles (ME-MION) to form stable protein-functionalized magnetic nanoparticles (PMO+ME-MION). The turbidity removal efficiency in both synthetic and surface water samples were investigated and compared with the commonly used synthetic coagulant (alum) as well as PMO. More than 90 % turbidity could be removed from the surface waters within 12 min by magnetic separation of PMO+ME-MION; whereas gravimetrically, 70 % removal in high and low turbid waters can be achieved within 60 min. In contrast, alum requires 180 min to reduce the turbidity of low turbid water sample. These data support the advantage of separation with external magnetic field (magnetophoresis) over gravitational force. Time kinetics studies show a significant enhancement in ME-MION efficiency after binding with PMO implying the availability of large surface of the ME-MION. The coagulated particles (impurities) can be removed from PMO+ME-MION by washing with mild detergent or cleaning solution. To our knowledge, this is the first report on surface water turbidity removal using protein-functionalized magnetic nanoparticle.

  11. Protein-functionalized magnetic iron oxide nanoparticles: time efficient potential-water treatment

    Science.gov (United States)

    Okoli, Chuka; Boutonnet, Magali; Järås, Sven; Rajarao-Kuttuva, Gunaratna

    2012-10-01

    Recent advances in nanoscience suggest that the existing issues involving water quality could be resolved or greatly improved using nanomaterials, especially magnetic iron oxide nanoparticles. Magnetic nanoparticles have been synthesized for the development and use, in association with natural coagulant protein for water treatment. The nanoparticles size, morphology, structure, and magnetic properties were characterized by transmission electron microscope, X-ray diffraction, and superconducting quantum interference device magnetometry. Purified Moringa oleifera protein was attached onto microemulsions-prepared magnetic iron oxide nanoparticles (ME-MION) to form stable protein-functionalized magnetic nanoparticles (PMO+ME-MION). The turbidity removal efficiency in both synthetic and surface water samples were investigated and compared with the commonly used synthetic coagulant (alum) as well as PMO. More than 90 % turbidity could be removed from the surface waters within 12 min by magnetic separation of PMO+ME-MION; whereas gravimetrically, 70 % removal in high and low turbid waters can be achieved within 60 min. In contrast, alum requires 180 min to reduce the turbidity of low turbid water sample. These data support the advantage of separation with external magnetic field (magnetophoresis) over gravitational force. Time kinetics studies show a significant enhancement in ME-MION efficiency after binding with PMO implying the availability of large surface of the ME-MION. The coagulated particles (impurities) can be removed from PMO+ME-MION by washing with mild detergent or cleaning solution. To our knowledge, this is the first report on surface water turbidity removal using protein-functionalized magnetic nanoparticle.

  12. Asymmetry of magnetic motor evoked potentials recorded in calf muscles of the dominant and non-dominant lower extremity.

    Science.gov (United States)

    Olex-Zarychta, Dorota; Koprowski, Robert; Sobota, Grzegorz; Wróbel, Zygmunt

    2009-08-07

    The aim of the study was to determine the applicability of magnetic stimulation and magnetic motor evoked potentials (MEPs) in motor asymmetry studies by obtaining quantitative and qualitative measures of efferent activity during low intensity magnetic stimulation of the dominant and non-dominant lower extremities. Magnetic stimulation of the tibial nerve in the popliteal fossa was performed in 10 healthy male right-handed and right-footed young adults. Responses were recorded from the lateral head of the gastrocnemius muscles of the right and left lower extremities. Response characteristics (duration, onset latency, amplitude) were analyzed in relation to the functional dominance of the limbs and in relation to the direction of the current in the magnetic coil by use of the Wilcoxon pair sequence test. The CCW direction of coil current was related to reduced amplitudes of recorded MEPs. Greater amplitudes of evoked potentials were recorded in the non-dominant extremity, both in the CW and CCW coil current directions, with the statistical significance of this effect (p=0.005). No differences in duration of response were found in the CW current direction, while in CCW the time of the left-side response was prolonged (p=0.01). In the non-dominant extremity longer onset latencies were recorded in both current directions, but only for the CW direction the side asymmetries showed a statistical significance of p=0.005. In the dominant extremity the stimulation correlated with stronger paresthesias, especially using the CCW direction of coil current. The results indicate that low intensity magnetic stimulation may be useful in quantitative and qualitative research into the motor asymmetry.

  13. Probing the dynamic response of antivortex, interstitial and trapped vortex lattices on magnetic periodic pinning potentials

    International Nuclear Information System (INIS)

    Gomez, A; Gonzalez, E M; Vicent, J L; Gilbert, D A; Liu Kai; Milošević, M V

    2013-01-01

    The dynamics of the pinned vortex, antivortex and interstitial vortex have been studied in superconducting/magnetic hybrids consisting of arrays of Co/Pd multilayer nanodots embedded in Nb films. The magnetic nanodots show out-of-plane magnetization at the remanent state. This magnetic state allows for superconducting vortex lattices of different types in an applied homogeneous magnetic field. We experimentally and theoretically show three such lattices: (i) a lattice containing only antivortices; (ii) a vortex lattice entirely pinned on the dots; and (iii) a vortex lattice with pinned and interstitial vortices. Between the flux creep (low vortex velocity) and the free flux flow (high vortex velocity) regimes the interaction between the magnetic array and the vortex lattice governs the vortex dynamics, which in turn enables distinguishing experimentally the type of vortex lattice which governs the dissipation. We show that the vortex lattice with interstitial vortices has the highest onset velocity where the lattice becomes ordered, whereas the pinned vortex lattice has the smallest onset velocity. Further, for this system, we directly estimate that the external force needed to depin vortices is 60% larger than the one needed to depin antivortices; therefore we are able to decouple the antivortex–vortex motion. (paper)

  14. MAGNET

    CERN Multimedia

    Benoit Curé

    2010-01-01

    The magnet worked very well at 3.8 T as expected, despite a technical issue that manifested twice in the cryogenics since June. All the other magnet sub-systems worked without flaw. The issue in the cryogenics was with the cold box: it could be observed that the cold box was getting progressively blocked, due to some residual humidity and air accumulating in the first thermal exchanger and in the adsorber at 65 K. This was later confirmed by the analysis during the regeneration phases. An increase in the temperature difference between the helium inlet and outlet across the heat exchanger and a pressure drop increase on the filter of the adsorber were observed. The consequence was a reduction of the helium flow, first compensated by the automatic opening of the regulation valves. But once they were fully opened, the flow and refrigeration power reduced as a consequence. In such a situation, the liquid helium level in the helium Dewar decreased, eventually causing a ramp down of the magnet current and a field...

  15. MAGNET

    CERN Multimedia

    B. Curé

    MAGNET During the winter shutdown, the magnet subsystems went through a full maintenance. The magnet was successfully warmed up to room temperature beginning of December 2008. The vacuum was broken later on by injecting nitrogen at a pressure just above one atmosphere inside the vacuum tank. This was necessary both to prevent any accidental humidity ingress, and to allow for a modification of the vacuum gauges on the vacuum tank and maintenance of the diffusion pumps. The vacuum gauges had to be changed, because of erratic variations on the measurements, causing spurious alarms. The new type of vacuum gauges has been used in similar conditions on the other LHC experiments and without problems. They are shielded against the stray field. The lubricants of the primary and diffusion pumps have been changed. Several minor modifications were also carried out on the equipment in the service cavern, with the aim to ease the maintenance and to allow possible intervention during operation. Spare sensors have been bough...

  16. MAGNET

    CERN Multimedia

    Benoit Curé.

    The magnet operation restarted end of June this year. Quick routine checks of the magnet sub-systems were performed at low current before starting the ramps up to higher field. It appeared clearly that the end of the field ramp down to zero was too long to be compatible with the detector commissioning and operations plans. It was decided to perform an upgrade to keep the ramp down from 3.8T to zero within 4 hours. On July 10th, when a field of 1.5T was reached, small movements were observed in the forward region support table and it was decided to fix this problem before going to higher field. At the end of July the ramps could be resumed. On July 28th, the field was at 3.8T and the summer CRAFT exercise could start. This run in August went smoothly until a general CERN wide power cut took place on August 3rd, due to an insulation fault on the high voltage network outside point 5. It affected the magnet powering electrical circuit, as it caused the opening of the main circuit breakers, resulting in a fast du...

  17. MAGNET

    CERN Multimedia

    B. Curé

    2013-01-01

    The magnet is fully stopped and at room temperature. The maintenance works and consolidation activities on the magnet sub-systems are progressing. To consolidate the cryogenic installation, two redundant helium compressors will be installed as ‘hot spares’, to avoid the risk of a magnet downtime in case of a major failure of a compressor unit during operation. The screw compressors, their motors, the mechanical couplings and the concrete blocks are already available and stored at P5. The metallic structure used to access the existing compressors in SH5 will be modified to allow the installation of the two redundant ones. The plan is to finish the installation and commissioning of the hot spare compressors before the summer 2014. In the meantime, a bypass on the high-pressure helium piping will be installed for the connection of a helium drier unit later during the Long Shutdown 1, keeping this installation out of the schedule critical path. A proposal is now being prepared for the con...

  18. Novel Fabrication of Biodegradable Superabsorbent Microspheres with Diffusion Barrier through Thermo-Chemical Modification and Their Potential Agriculture Applications for Water Holding and Sustained Release of Fertilizer.

    Science.gov (United States)

    Feng, Diejing; Bai, Bo; Wang, Honglun; Suo, Yourui

    2017-07-26

    Synergistic utilization of water and fertilizer has vital contribution to the modern production of agriculture. This work reports on a simple and facile strategy to prepare biodegradable yeast/sodium alginate/poly(vinyl alcohol) superabsorbent microspheres with a diffusion barrier merit by thermo-chemical modification route. The integrated performances, including water absorbency, water retention, water evaporation ratio, leaching loss control, sustained-release behaviors, and degradation in soil, were systematically investigated. The results revealed that the modified microspheres were a triumphant water and fertilizer manager to effectively hold water and control the unexpected leakage of fertilizer for sustained release. Therefore, this work provides a promising approach to ameliorate the utilization efficiency of water and fertilizer in potential agriculture applications.

  19. Built-in potential shift and Schottky-barrier narrowing in organic solar cells with UV-sensitive electron transport layers.

    Science.gov (United States)

    Li, Cheng; Credgington, Dan; Ko, Doo-Hyun; Rong, Zhuxia; Wang, Jianpu; Greenham, Neil C

    2014-06-28

    The performance of organic solar cells incorporating solution-processed titanium suboxide (TiOx) as electron-collecting layers can be improved by UV illumination. We study the mechanism of this improvement using electrical measurements and electroabsorption spectroscopy. We propose a model in which UV illumination modifies the effective work function of the oxide layer through a significant increase in its free electron density. This leads to a dramatic improvement in device power conversion efficiency through several mechanisms - increasing the built-in potential by 0.3 V, increasing the conductivity of the TiOx layer and narrowing the interfacial Schottky barrier between the suboxide and the underlying transparent electrode. This work highlights the importance of considering Fermi-level equilibration when designing multi-layer transparent electrodes.

  20. The Isolation of DNA by Polycharged Magnetic Particles: An Analysis of the Interaction by Zeta Potential and Particle Size.

    Science.gov (United States)

    Haddad, Yazan; Xhaxhiu, Kledi; Kopel, Pavel; Hynek, David; Zitka, Ondrej; Adam, Vojtech

    2016-04-20

    Magnetic isolation of biological targets is in major demand in the biotechnology industry today. This study considers the interaction of four surface-modified magnetic micro- and nanoparticles with selected DNA fragments. Different surface modifications of nanomaghemite precursors were investigated: MAN37 (silica-coated), MAN127 (polyvinylpyrrolidone-coated), MAN158 (phosphate-coated), and MAN164 (tripolyphosphate-coated). All particles were positive polycharged agglomerated monodispersed systems. Mean particle sizes were 0.48, 2.97, 2.93, and 3.67 μm for MAN37, MAN127, MAN164, and MAN158, respectively. DNA fragments exhibited negative zeta potential of -0.22 mV under binding conditions (high ionic strength, low pH, and dehydration). A decrease in zeta potential of particles upon exposure to DNA was observed with exception of MAN158 particles. The measured particle size of MAN164 particles increased by nearly twofold upon exposure to DNA. Quantitative PCR isolation of DNA with a high retrieval rate was observed by magnetic particles MAN127 and MAN164. Interaction between polycharged magnetic particles and DNA is mediated by various binding mechanisms such as hydrophobic and electrostatic interactions. Future development of DNA isolation technology requires an understanding of the physical and biochemical conditions of this process.