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Sample records for halbach magnet array

  1. Simplified Calculation Method for Magnetic Flux Density Distribution between Dual Halbach Arrays

    NASA Astrophysics Data System (ADS)

    Morishita, Mimpei; Yokoyama, Shuichi; Okuyama, Ryota

    Many software tools for magnetic field analysis give us distribution of magnetic flux density between Halbach arrays of permanent magnets. However, we need easier calculation tools in an early stage of development. This paper proposes an equivalent magnetic circuit method with high accuracy for field magnets provided with dual Halbach arrays.

  2. Design of nested Halbach cylinder arrays for magnetic refrigeration applications

    NASA Astrophysics Data System (ADS)

    Trevizoli, Paulo V.; Lozano, Jaime A.; Peixer, Guilherme F.; Barbosa, Jader R., Jr.

    2015-12-01

    We present an experimentally validated analytical procedure to design nested Halbach cylinder arrays for magnetic cooling applications. The procedure aims at maximizing the magnetic flux density variation in the core of the array for a given set of design parameters, namely the inner diameter of the internal magnet, the air gap between the magnet cylinders, the number of segments of each magnet and the remanent flux density of the Nd2Fe14B magnet grade. The design procedure was assisted and verified by 3-D numerical modeling using a commercial software package. An important aspect of the optimal design is to maintain an uniform axial distribution of the magnetic flux density in the region of the inner gap occupied by the active magnetocaloric regenerator. An optimal nested Halbach cylinder array was manufactured and experimentally evaluated for the magnetic flux density in the inner gap. The analytically calculated magnetic flux density variation agreed to within 5.6% with the experimental value for the center point of the magnet gap.

  3. Analysis and design of air-cored Halbach array permanent magnet BDCM

    NASA Astrophysics Data System (ADS)

    Zhao, Jianhui; Xu, Yanliang

    2006-11-01

    Aimed at the application of satellite attitude control/energy storage flywheel, outer-rotor air-cored permanent magnet brushless direct current machines (BDCM) with Halbach magnet array and the normal one are analyzed comparatively. A prototyped BDCM with Halbach array is designed and fabricated to verify the analysis and satisfy the performance demand of flywheel system.

  4. Analysis and comparison of two two-dimensional Halbach permanent magnet arrays for magnetically levitated planar motor

    NASA Astrophysics Data System (ADS)

    Zhang, Lu; Kou, Baoquan; Xing, Feng; Zhang, He

    2014-05-01

    A novel 2-D Halbach permanent magnet array which can be used in magnetically levitated planar motor is proposed in this paper. The air-gap flux density distribution of the novel 2-D Halbach permanent magnet array is solved by the scalar magnetic potential equation. In order to compare with the well-known Halbach magnet array that was used by Jansen et al. [IEEE Trans. Ind. Appl. 44(4), 1108 (2008)], harmonic analysis of the x- and z- component of the air-gap flux density are carried out by Fourier decomposition. Comparison of Bx and Bz between the two 2-D Halbach magnet arrays are made. And it is verified that the performance of the new Halbach magnet array is superior to the existing Halbach magnet arrays, its higher magnetic flux density and lower high-order harmonics will help to improve the performance of the magnetically levitated planar motor.

  5. Experiments on Inductive Magnetic Levitation with a Circular Halbach Array

    NASA Astrophysics Data System (ADS)

    Bean, Ian; Goncz, Doug; Raymer, Austin; Specht, Jason; Zalles, Ricardo; Majewski, Walerian

    2013-03-01

    Using a ring Halbach array, we are investigating a repulsive levitating force and a drag force acting on the magnet from a ring of inductors rotating below the magnet. After measuring induced currents, voltages and magnetic fields in the individual inductors (in the form of short solenoids), we investigated the dependence of lift/drag forces on the speed of relative rotation. The ratio of lift to drag increases with the angular velocity, as expected from a related theory of the induction effects in a linear motion. We are experimenting with the shape and density of inductors, and their material, in an attempt to maximize the lift at a minimal velocity of rotation. Eventually this design could have applications as frictionless bearings or as frictionless gear in a wide range of systems, especially in machinery that cannot be easily accessed.

  6. A low frequency vibration energy harvester using dual Halbach array suspended in magnetic springs

    NASA Astrophysics Data System (ADS)

    Salauddin, M.; Halim, M. A.; Park, J. Y.

    2015-12-01

    An electromagnetic (EM) low frequency vibration energy harvester is newly developed based on dual Halbach array which is suspended in two magnetic springs. Each Halbach array concentrates the magnetic flux lines on one side of the array while suppressing the flux lines on the other side. Dual Halbach array allows the concentrated magnetic flux lines to interact with the same coil in a way where maximum flux linkage occurs. With the goal of higher power generation in low amplitude and low frequency vibrations, the magnetic structures (both the dual Halbach array and the magnetic springs) were optimized in terms of operating frequency and power density. A prototype was fabricated and tested. It is capable of delivering maximum 1.09mW average power to 44? optimum load at 11Hz resonant frequency and 0.5g acceleration. The prototype device offers 33.4?Wcm-3 average power density which is much higher than recently reported electromagnetic energy harvesters.

  7. A new magnetic bearing using Halbach magnet arrays for a magnetic levitation stage

    NASA Astrophysics Data System (ADS)

    Choi, Young-Man; Lee, Moon G.; Gweon, Dae-Gab; Jeong, Jaehwa

    2009-04-01

    Next-generation lithography requires a high precision stage, which is compatible with a high vacuum condition. A magnetic levitation stage with six degrees-of-freedom is considered state-of-the-art technology for a high vacuum condition. The noncontact characteristic of magnetic levitation enables high precision positioning as well as no particle generation. To position the stage against gravity, z-directional electromagnetic levitation mechanisms are widely used. However, if electromagnetic actuators for levitation are used, heat is inevitably generated, which deforms the structures and degrades accuracy of the stage. Thus, a gravity compensator is required. In this paper, we propose a new magnetic bearing using Halbach magnet arrays for a magnetic levitation stage. The novel Halbach magnetic bearing exerts a force four times larger than a conventional magnetic bearing with the same volume. We also discuss the complementary characteristics of the two magnetic bearings. By modifying the height of the center magnet in a Halbach magnetic bearing, a performance compromise between levitating force density and force uniformity is obtained. The Halbach linear active magnetic bearing can be a good solution for magnetic levitation stages because of its large and uniform levitation force.

  8. Radial Halbach Magnetic Bearings

    NASA Technical Reports Server (NTRS)

    Eichenberg, Dennis J.; Gallo, Christopher A.; Thompson, William K.

    2009-01-01

    Radial Halbach magnetic bearings have been investigated as part of an effort to develop increasingly reliable noncontact bearings for future high-speed rotary machines that may be used in such applications as aircraft, industrial, and land-vehicle power systems and in some medical and scientific instrumentation systems. Radial Halbach magnetic bearings are based on the same principle as that of axial Halbach magnetic bearings, differing in geometry as the names of these two types of bearings suggest. Both radial and axial Halbach magnetic bearings are passive in the sense that unlike most other magnetic bearings that have been developed in recent years, they effect stable magnetic levitation without need for complex active control. Axial Halbach magnetic bearings were described in Axial Halbach Magnetic Bearings (LEW-18066-1), NASA Tech Briefs, Vol. 32, No. 7 (July 2008), page 85. In the remainder of this article, the description of the principle of operation from the cited prior article is recapitulated and updated to incorporate the present radial geometry. In simplest terms, the basic principle of levitation in an axial or radial Halbach magnetic bearing is that of the repulsive electromagnetic force between (1) a moving permanent magnet and (2) an electric current induced in a stationary electrical conductor by the motion of the magnetic field. An axial or radial Halbach bearing includes multiple permanent magnets arranged in a Halbach array ("Halbach array" is defined below) in a rotor and multiple conductors in the form of wire coils in a stator, all arranged so the rotary motion produces an axial or radial repulsion that is sufficient to levitate the rotor. A basic Halbach array (see Figure 1) consists of a row of permanent magnets, each oriented so that its magnetic field is at a right angle to that of the adjacent magnet, and the right-angle turns are sequenced so as to maximize the magnitude of the magnetic flux density on one side of the row while minimizing it on the opposite side. The advantage of this configuration is that it makes it possible to approach the theoretical maximum force per unit area that could be exerted by a given amount of permanent-magnet material. The configuration is named after physicist Klaus Halbach, who conceived it for use in particle accelerators. Halbach arrays have also been studied for use in magnetic-levitation ("maglev") railroad trains. In a radial Halbach magnetic bearing, the basic Halbach arrangement is modified into a symmetrical arrangement of sector-shaped permanent magnets mounted on the outer cylindrical surface of a drum rotor (see Figure 2). The magnets are oriented to concentrate the magnetic field on their radially outermost surface. The stator coils are mounted in a stator shell surrounding the rotor.

  9. Analysis and modeling of the EDS Maglev system based on the Halbach permanent magnet array

    NASA Astrophysics Data System (ADS)

    Han, Qinghua

    Electro-dynamic suspension (EDS) Magnetic levitation (Maglev) with its advantage in maintenance, safety, efficiency, speed, and noise is regarded as a leading candidate for the next generation transportation/space launch assist system. The Halbach array due to its unique magnetic field feature has been widely used in various applications. The EDS system using Halbach arrays leads to the potential EDS system without super-conductor (SC) technology. In this thesis, the Halbach array magnetic field and the dynamics of a novel Halbach array EDS Maglev system were considered. The practical Halbach array magnetic field was analyzed using both a Fourier series approach and the finite element method (FEM). In addition, the optimal Halbach array geometry was derived and analyzed. A novel active magnetic array was introduced and used in the Halbach array EDS Maglev configuration. Furthermore, since the system is self-regulated in lateral, roll, pitch, and yaw directions, the control was simplified and can be implemented electronically. The dynamic stability analysis and simulation results showed that the system is marginally stable and a control mechanism is needed for stability and ride comfort control. The six degree of freedom (DOF) dynamics, and the vehicle's mass center offset effects on those dynamics were investigated with multiple passive and active magnetic forces. The results indicated that the vehicle's mass center offset has a strong effect on the dynamics of the Maglev system due to the uniqueness of the magnetic force and also that the mass center offset can cause Maglev oscillations at the take off stage. In order to guarantee the dynamic stability and ride comfort of the Maglev system, an optimized active damping and a linear quadratic regulator (LQR) control were developed. Finally, the simulation confirmed the effectiveness of the proposed multi-input and multi-output (MIMO) control designs.

  10. Dynamics of magnetic particles in cylindrical Halbach array: implications for magnetic cell separation and drug targeting.

    TOXLINE Toxicology Bibliographic Information

    Babinec P; Krafcík A; Babincová M; Rosenecker J

    2010-08-01

    Magnetic nanoparticles for therapy and diagnosis are at the leading edge of the rapidly developing field of bionanotechnology. In this study, we have theoretically studied motion of magnetic nano- as well as micro-particles in the field of cylindrical Halbach array of permanent magnets. Magnetic flux density was modeled as magnetostatic problem by finite element method and particle motion was described using system of ordinary differential equations--Newton law. Computations were done for nanoparticles Nanomag-D with radius 65 nm, which are often used in magnetic drug targeting, as well as microparticles DynaBeads-M280 with radius 1.4 microm, which can be used for magnetic separation. Analyzing snapshots of trajectories of hundred magnetite particles of each size in the water as well as in the air, we have found that optimally designed magnetic circuits of permanent magnets in quadrupolar Halbach array have substantially shorter capture time than simple blocks of permanent magnets commonly used in experiments, therefore, such a Halbach array may be useful as a potential source of magnetic field for magnetic separation and targeting of magnetic nanoparticles as well as microparticles for delivery of drugs, genes, and cells in various biomedical applications.

  11. Halbach Magnetic Rotor Development

    NASA Technical Reports Server (NTRS)

    Gallo, Christopher A.

    2008-01-01

    The NASA John H. Glenn Research Center has a wealth of experience in Halbach array technology through the Fundamental Aeronautics Program. The goals of the program include improving aircraft efficiency, reliability, and safety. The concept of a Halbach magnetically levitated electric aircraft motor will help reduce harmful emissions, reduce the Nation s dependence on fossil fuels, increase efficiency and reliability, reduce maintenance and decrease operating noise levels. Experimental hardware systems were developed in the GRC Engineering Development Division to validate the basic principles described herein and the theoretical work that was performed. A number of Halbach Magnetic rotors have been developed and tested under this program. A separate test hardware setup was developed to characterize each of the rotors. A second hardware setup was developed to test the levitation characteristics of the rotors. Each system focused around a unique Halbach array rotor. Each rotor required original design and fabrication techniques. A 4 in. diameter rotor was developed to test the radial levitation effects for use as a magnetic bearing. To show scalability from the 4 in. rotor, a 1 in. rotor was developed to also test radial levitation effects. The next rotor to be developed was 20 in. in diameter again to show scalability from the 4 in. rotor. An axial rotor was developed to determine the force that could be generated to position the rotor axially while it is rotating. With both radial and axial magnetic bearings, the rotor would be completely suspended magnetically. The purpose of this report is to document the development of a series of Halbach magnetic rotors to be used in testing. The design, fabrication and assembly of the rotors will be discussed as well as the hardware developed to test the rotors.

  12. An adjustable linear Halbach array

    NASA Astrophysics Data System (ADS)

    Hilton, J. E.; McMurry, S. M.

    2012-07-01

    The linear Halbach array is a well-known planar magnetic structure capable, in the idealized case, of generating a one-sided magnetic field. We show that such a field can be created from an array of uniformly magnetized rods, and rotating these rods in an alternating fashion can smoothly transfer the resultant magnetic field through the plane of the device. We examine an idealized model composed of infinite line dipoles and carry out computational simulations on a realizable device using a magnetic boundary element method. Such an arrangement can be used for an efficient latching device, or to produce a highly tunable field in the space above the device.

  13. Vibration energy harvesting using the Halbach array

    NASA Astrophysics Data System (ADS)

    Zhu, Dibin; Beeby, Steve; Tudor, John; Harris, Nick

    2012-07-01

    This paper studies the feasibility of vibration energy harvesting using a Halbach array. A Halbach array is a specific arrangement of permanent magnets that concentrates the magnetic field on one side of the array while cancelling the field to almost zero on the other side. This arrangement can improve electromagnetic coupling in a limited space. The Halbach array offers an advantage over conventional layouts of magnets in terms of its concentrated magnetic field and low-profile structure, which helps improve the output power of electromagnetic energy harvesters while minimizing their size. Another benefit of the Halbach array is that due to the existence of an almost-zero magnetic field zone, electronic components can be placed close to the energy harvester without any chance of interference, which can potentially reduce the overall size of a self-powered device. The first reported example of a low-profile, planar electromagnetic vibration energy harvester utilizing a Halbach array was built and tested. Results were compared to ones for energy harvesters with conventional magnet layouts. By comparison, it is concluded that although energy harvesters with a Halbach array can have higher magnetic field density, a higher output power requires careful design in order to achieve the maximum magnetic flux gradient.

  14. Axial Halbach Magnetic Bearings

    NASA Technical Reports Server (NTRS)

    Eichenberg, Dennis J.; Gallo, Christopher A.; Thompson, William K.

    2008-01-01

    Axial Halbach magnetic bearings have been investigated as part of an effort to develop increasingly reliable noncontact bearings for future high-speed rotary machines that may be used in such applications as aircraft, industrial, and land-vehicle power systems and in some medical and scientific instrumentation systems. Axial Halbach magnetic bearings are passive in the sense that unlike most other magnetic bearings that have been developed in recent years, they effect stable magnetic levitation without need for complex active control.

  15. Halbach arrays consisting of cubic elements optimised for high field gradients in magnetic drug targeting applications

    NASA Astrophysics Data System (ADS)

    Barnsley, Lester C.; Carugo, Dario; Owen, Joshua; Stride, Eleanor

    2015-11-01

    A key challenge in the development of magnetic drug targeting (MDT) as a clinically relevant technique is designing systems that can apply sufficient magnetic force to actuate magnetic drug carriers at useful tissue depths. In this study an optimisation routine was developed to generate designs of Halbach arrays consisting of multiple layers of high grade, cubic, permanent magnet elements, configured to deliver the maximum pull or push force at a position of interest between 5 and 50 mm from the array, resulting in arrays capable of delivering useful magnetic forces to depths past 20 mm. The optimisation routine utilises a numerical model of the magnetic field and force generated by an arbitrary configuration of magnetic elements. Simulated field and force profiles of optimised arrays were evaluated, also taking into account the forces required for assembling the array in practice. The resultant selection for the array, consisting of two layers, was then constructed and characterised to verify the simulations. Finally the array was utilised in a set of in vitro experiments to demonstrate its capacity to separate and retain microbubbles loaded with magnetic nanoparticles against a constant flow. The optimised designs are presented as light-weight, inexpensive options for applying high-gradient, external magnetic fields in MDT applications.

  16. Halbach arrays consisting of cubic elements optimised for high field gradients in magnetic drug targeting applications.

    PubMed

    Barnsley, Lester C; Carugo, Dario; Owen, Joshua; Stride, Eleanor

    2015-11-01

    A key challenge in the development of magnetic drug targeting (MDT) as a clinically relevant technique is designing systems that can apply sufficient magnetic force to actuate magnetic drug carriers at useful tissue depths. In this study an optimisation routine was developed to generate designs of Halbach arrays consisting of multiple layers of high grade, cubic, permanent magnet elements, configured to deliver the maximum pull or push force at a position of interest between 5 and 50?mm from the array, resulting in arrays capable of delivering useful magnetic forces to depths past 20?mm. The optimisation routine utilises a numerical model of the magnetic field and force generated by an arbitrary configuration of magnetic elements. Simulated field and force profiles of optimised arrays were evaluated, also taking into account the forces required for assembling the array in practice. The resultant selection for the array, consisting of two layers, was then constructed and characterised to verify the simulations. Finally the array was utilised in a set of in vitro experiments to demonstrate its capacity to separate and retain microbubbles loaded with magnetic nanoparticles against a constant flow. The optimised designs are presented as light-weight, inexpensive options for applying high-gradient, external magnetic fields in MDT applications. PMID:26458056

  17. Analysis of eddy current losses in cylindrical linear oscillatory actuator with Halbach permanent magnet array mover

    NASA Astrophysics Data System (ADS)

    Ko, Kyoung-Jin; Choi, Ji-Hwan; Jang, Seok-Myeong; Choi, Jang-Young

    2012-04-01

    This paper describes calculations and comparisons of eddy current losses in a cylindrical linear oscillatory actuator with a Halbach array permanent magnet mover for different voltage source waveforms. Using the magnetic vector potential and a two-dimensional cylindrical coordinate system, the paper presents an analytical procedure and obtains solutions for the eddy current losses using the Poynting theorem. To verify the proposed method, the eddy current losses obtained from the analytical solutions are compared with the results of a non-linear finite element method. Moreover, this paper shows that the eddy current losses are more significant when the actuator is driven by a square voltage waveform than when it is driven by a sinusoidal voltage waveform.

  18. Circular Halbach array for fast magnetic separation of hyaluronan-expressing tissue progenitors.

    PubMed

    Joshi, Powrnima; Williams, P Stephen; Moore, Lee R; Caralla, Tonya; Boehm, Cynthia; Muschler, George; Zborowski, Maciej

    2015-10-01

    Connective tissue progenitors (CTPs) are a promising therapeutic agent for bone repair. Hyaluronan, a high molecular mass glycosaminoglycan, has been shown by us to be a suitable biomarker for magnetic separation of CTPs from bone marrow aspirates in a canine model. For the therapy to be applicable in humans, the magnetic separation process requires scale-up without compromising the viability of the cells. The scaled-up device presented here utilizes a circular Halbach array of diametrically magnetized, cylindrical permanent magnets. This allows precise control of the magnetic field gradient driving the separation, with theoretical analysis favoring a hexapole field. The separation vessel has the external diameter of a 50 mL conical centrifuge tube and has an internal rod that excludes cells from around the central axis. The magnet and separation vessel (collectively dubbed the hexapole magnet separator or HMS) was tested on four human and four canine bone marrow aspirates. Each CTP-enriched cell product was tested using cell culture bioassays as surrogates for in vivo engraftment quality. The magnetically enriched cell fractions showed statistically significant, superior performance compared to the unenriched and depleted cell fractions for all parameters tested, including CTP prevalence (CTPs per 10(6) nucleated cells), proliferation by colony forming unit (CFU) counts, and differentiation by staining for the presence of osteogenic and chondrogenic cells. The simplicity and speed of the HMS operation could allow both CTP isolation and engraftment during a single surgical procedure, minimizing trauma to patients and lowering cost to health care providers. PMID:26368657

  19. A Comparison of Two Magnetic Ultra-Cold Neutron Trapping Concepts Using a Halbach-Octupole Array

    NASA Astrophysics Data System (ADS)

    Leung, K.; Ivanov, S.; Martin, F.; Rosenau, F.; Simson, M.; Zimmer, O.

    2014-03-01

    This paper describes a new magnetic trap for ultra-cold neutrons (UCNs) made from a 1.2m long Halbach-octupole array of permanent magnets with an inner bore radius of 47mm combined with an assembly of superconducting end coils and bias field solenoid. The use of the trap in a vertical, magneto-gravitational and a horizontal setup are compared in terms of the effective volume and ability to control key systematic effects that need to be addressed in high precision neutron lifetime measurements.

  20. Halbach array motor/generators: A novel generalized electric machine

    SciTech Connect

    Merritt, B.T.; Post, R.F.; Dreifuerst, G.R.; Bender, D.A.

    1994-10-28

    In August 1979, Halbach submitted a paper entitled ``Design of Permanent Multipole Magnets with Oriented Rare Earth Cobalt Material.`` In this paper, he presented a novel method of generating multipole magnetic fields using non-intuitive geometrical arrangements of permanent magnets. In subsequent publications, he further defined these concepts. Of particular interest to one of the authors (RFP) was the special magnet array that generated a uniform dipole field. In 1990 Post proposed the construction of an electric machine (a motor/generator) using a dipole field based on Klaus Halbach`s array of permanent magnets. He further proposed that such a system should be employed as an integral part of ``an electromechanical battery`` (EMB), i.e., a modular flywheel system to be used as a device for storing electrical energy, as an alternative to the electrochemical storage battery. This paper reviews Halbach`s theory for the generation of a dipole field using an array of permanent magnet bars, presents a simple analysis of a family of novel ``ironless`` electric machines designed using the dipole Halbach array, and describes the results obtained when they were tested in the laboratory.

  1. Torque analysis and measurements of a permanent magnet type Eddy current brake with a Halbach magnet array based on analytical magnetic field calculations

    NASA Astrophysics Data System (ADS)

    Park, Min-Gyu; Choi, Jang-Young; Shin, Hyeon-Jae; Jang, Seok-Myeong

    2014-05-01

    This paper presents the torque analysis and measurements of a permanent magnet (PM) type eddy current brake (ECB) with a Halbach magnet array based on analytical magnetic field calculations. On the basis of a magnetic vector potential and using a two-dimensional (2D) polar coordinate system, the analytical solution for magnetic flux density, including the eddy current reaction is evaluated. Based on these solutions, the magnetic torque is also determined analytically. A 2D finite element analysis is employed to validate the method used. Practical issues in the analytical study of the PM type ECBs, such as the maximum braking torque, the required rotor speed, and the segment-dependent, are fully discussed. Finally, the braking torque as a function of the rotor speed is measured to verify the results of the analytical study.

  2. Numerical simulation of a simple low-speed model for an electrodynamic levitation system based on a Halbach magnet array

    NASA Astrophysics Data System (ADS)

    iguez, J.; Raposo, V.

    2010-05-01

    The design and analysis of a small prototype of a magnetic levitation system at low-speed using a Halbach-type magnet array is presented here. For that purpose, we have arranged a copper rim over a carbon fiber wheel, which is driven by an electric motor in presence of the magnet array, in such a manner that allows performing the experiment readily. The analysis of the system is undertaken under a two-dimensional (2D)-approach which permits computing and extending the study of our model to higher speeds. Our work is completed with a series of experimental measurements of lift and drag forces for different circumstances. Initially, the drag force is significant but after the compensation speed (when both forces balance) it slowly decreases. Conversely, the lift force becomes progressively bigger in such a manner that it attains quickly noteworthy values. We observe that the theoretical compensation speed is always minor than the experimental one and that the measured values for both forces are slightly smaller than the expected, although the main features of the experiment are well matched by our numerical simulation.

  3. Position sensor for linear synchronous motors employing halbach arrays

    DOEpatents

    Post, Richard Freeman

    2014-12-23

    A position sensor suitable for use in linear synchronous motor (LSM) drive systems employing Halbach arrays to create their magnetic fields is described. The system has several advantages over previously employed ones, especially in its simplicity and its freedom from being affected by weather conditions, accumulated dirt, or electrical interference from the LSM system itself.

  4. Halbach array DC motor/generator

    DOEpatents

    Merritt, Bernard T. (Livermore, CA); Dreifuerst, Gary R. (Livermore, CA); Post, Richard F. (Walnut Creek, CA)

    1998-01-01

    A new configuration of DC motor/generator is based on a Halbach array of permanent magnets. This motor does not use ferrous materials so that the only losses are winding losses and losses due to bearings and windage. An "inside-out" design is used as compared to a conventional motor/generator design. The rotating portion, i.e., the rotor, is on the outside of the machine. The stationary portion, i.e., the stator, is formed by the inside of the machine. The rotor contains an array of permanent magnets that provide a uniform field. The windings of the motor are placed in or on the stator. The stator windings are then "switched" or "commutated" to provide a DC motor/generator much the same as in a conventional DC motor. The commutation can be performed by mechanical means using brushes or by electronic means using switching circuits. The invention is useful in electric vehicles and adjustable speed DC drives.

  5. Halbach array DC motor/generator

    DOEpatents

    Merritt, B.T.; Dreifuerst, G.R.; Post, R.F.

    1998-01-06

    A new configuration of DC motor/generator is based on a Halbach array of permanent magnets. This motor does not use ferrous materials so that the only losses are winding losses and losses due to bearings and windage. An ``inside-out`` design is used as compared to a conventional motor/generator design. The rotating portion, i.e., the rotor, is on the outside of the machine. The stationary portion, i.e., the stator, is formed by the inside of the machine. The rotor contains an array of permanent magnets that provide a uniform field. The windings of the motor are placed in or on the stator. The stator windings are then ``switched`` or ``commutated`` to provide a DC motor/generator much the same as in a conventional DC motor. The commutation can be performed by mechanical means using brushes or by electronic means using switching circuits. The invention is useful in electric vehicles and adjustable speed DC drives. 17 figs.

  6. Energy harvesting from electric power lines employing the Halbach arrays

    NASA Astrophysics Data System (ADS)

    He, Wei; Li, Ping; Wen, Yumei; Zhang, Jitao; Lu, Caijiang; Yang, Aichao

    2013-10-01

    This paper proposes non-invasive energy harvesters to scavenge alternating magnetic field energy from electric power lines. The core body of a non-invasive energy harvester is a linear Halbach array, which is mounted on the free end of a piezoelectric cantilever beam. The Halbach array augments the magnetic flux density on the side of the array where the power line is placed and significantly lowers the magnetic field on the other side. Consequently, the magnetic coupling strength is enhanced and more alternating magnetic field energy from the current-carrying power line is converted into electrical energy. An analytical model is developed and the theoretical results verify the experimental results. A power of 566 ?W across a 196 k? resistor is generated from a single wire, and a power of 897 ?W across a 212 k? resistor is produced from a two-wire power cord carrying opposite currents at 10 A. The harvesters employing Halbach arrays for a single wire and a two-wire power cord, respectively, exhibit 3.9 and 3.2 times higher power densities than those of the harvesters employing conventional layouts of magnets. The proposed devices with strong response to the alternating currents are promising to be applied to electricity end-use environment in electric power systems.

  7. Energy harvesting from electric power lines employing the Halbach arrays.

    PubMed

    He, Wei; Li, Ping; Wen, Yumei; Zhang, Jitao; Lu, Caijiang; Yang, Aichao

    2013-10-01

    This paper proposes non-invasive energy harvesters to scavenge alternating magnetic field energy from electric power lines. The core body of a non-invasive energy harvester is a linear Halbach array, which is mounted on the free end of a piezoelectric cantilever beam. The Halbach array augments the magnetic flux density on the side of the array where the power line is placed and significantly lowers the magnetic field on the other side. Consequently, the magnetic coupling strength is enhanced and more alternating magnetic field energy from the current-carrying power line is converted into electrical energy. An analytical model is developed and the theoretical results verify the experimental results. A power of 566 ?W across a 196 k? resistor is generated from a single wire, and a power of 897 ?W across a 212 k? resistor is produced from a two-wire power cord carrying opposite currents at 10 A. The harvesters employing Halbach arrays for a single wire and a two-wire power cord, respectively, exhibit 3.9 and 3.2 times higher power densities than those of the harvesters employing conventional layouts of magnets. The proposed devices with strong response to the alternating currents are promising to be applied to electricity end-use environment in electric power systems. PMID:24182155

  8. Development and Testing of a Radial Halbach Magnetic Bearing

    NASA Technical Reports Server (NTRS)

    Eichenberg, Dennis J.; Gallo, Christopher A.; Thompson, William K.

    2006-01-01

    The NASA John H. Glenn Research Center has developed and tested a revolutionary Radial Halbach Magnetic Bearing. The objective of this work is to develop a viable non-contact magnetic bearing utilizing Halbach arrays for all-electric flight, and many other applications. This concept will help reduce harmful emissions, reduce the Nation s dependence on fossil fuels and mitigate many of the concerns and limitations encountered in conventional axial bearings such as bearing wear, leaks, seals and friction loss. The Radial Halbach Magnetic Bearing is inherently stable and requires no active feedback control system or superconductivity as required in many magnetic bearing designs. The Radial Halbach Magnetic Bearing is useful for very high speed applications including turbines, instrumentation, medical applications, manufacturing equipment, and space power systems such as flywheels. Magnetic fields suspend and support a rotor assembly within a stator. Advanced technologies developed for particle accelerators, and currently under development for maglev trains and rocket launchers, served as the basis for this application. Experimental hardware was successfully designed and developed to validate the basic principles and analyses. The report concludes that the implementation of Radial Halbach Magnetic Bearings can provide significant improvements in rotational system performance and reliability.

  9. Development and Testing of an Axial Halbach Magnetic Bearing

    NASA Technical Reports Server (NTRS)

    Eichenberg, Dennis J.; Gallo, Christopher A.; Thompson, William K.

    2006-01-01

    The NASA Glenn Research Center has developed and tested a revolutionary Axial Halbach Magnetic Bearing. The objective of this work is to develop a viable non-contact magnetic thrust bearing utilizing Halbach arrays for all-electric flight, and many other applications. This concept will help to reduce harmful emissions, reduce the Nation s dependence on fossil fuels and mitigate many of the concerns and limitations encountered in conventional axial bearings such as bearing wear, leaks, seals and friction loss. The Axial Halbach Magnetic Bearing is inherently stable and requires no active feedback control system or superconductivity as required in many magnetic bearing designs. The Axial Halbach Magnetic Bearing is useful for very high speed applications including turbines, instrumentation, medical systems, computer memory systems, and space power systems such as flywheels. Magnetic fields suspend and support a rotor assembly within a stator. Advanced technologies developed for particle accelerators, and currently under development for maglev trains and rocket launchers, served as the basis for this application. Experimental hardware was successfully designed and developed to validate the basic principles and analyses. The report concludes that the implementation of Axial Halbach Magnetic Bearings can provide significant improvements in rotational system performance and reliability.

  10. Automatic alignment of multiple magnets into Halbach cylinders

    NASA Astrophysics Data System (ADS)

    Chandrana, C. K.; Neal, J. A.; Platts, D.; Morgan, B.; Nath, P.

    2015-05-01

    Halbach cylinders have found various applications for their ability to produce strong and homogenous magnetostatic fields. Contrary to their conventional manual fabrication, we introduce a novel approach to automatically align multiple permanent magnets into a Halbach cylinder. The approach uses the magnetic field distribution from a diametrically magnetized cylindrical magnet to simultaneously align multiple magnets. The extent to which the automatic assembly can approximate a Halbach cylinder was analyzed using 3D Finite Element Modeling. Prototypes were built that demonstrated automatic alignment of eight magnets into Halbach cylinders. Automatic alignment eliminates the complexity of manually aligning Halbach cylinders.

  11. Optimal Halbach permanent magnet designs for maximally pulling and pushing nanoparticles

    NASA Astrophysics Data System (ADS)

    Sarwar, A.; Nemirovski, A.; Shapiro, B.

    2012-03-01

    Optimization methods are presented to design Halbach arrays to maximize the forces applied on magnetic nanoparticles at deep tissue locations. In magnetic drug targeting, where magnets are used to focus therapeutic nanoparticles to disease locations, the sharp fall off of magnetic fields and forces with distances from magnets has limited the depth of targeting. Creating stronger forces at a depth by optimally designed Halbach arrays would allow treatment of a wider class of patients, e.g. patients with deeper tumors. The presented optimization methods are based on semi-definite quadratic programming, yield provably globally optimal Halbach designs in 2 and 3-dimensions, for maximal pull or push magnetic forces (stronger pull forces can collect nanoparticles against blood forces in deeper vessels; push forces can be used to inject particles into precise locations, e.g. into the inner ear). These Halbach designs, here tested in simulations of Maxwell's equations, significantly outperform benchmark magnets of the same size and strength. For example, a 3-dimensional 36 element 2000 cm3 volume optimal Halbach design yields a 5 greater force at a 10 cm depth compared to a uniformly magnetized magnet of the same size and strength. The designed arrays should be feasible to construct, as they have a similar strength (?1 T), size (?2000 cm3), and number of elements (?36) as previously demonstrated arrays, and retain good performance for reasonable manufacturing errors (element magnetization direction errors ?5), thus yielding practical designs to improve magnetic drug targeting treatment depths.

  12. Halbach array generator/motor having mechanically regulated output voltage and mechanical power output

    DOEpatents

    Post, Richard F.

    2005-06-14

    A motor/generator has its stationary portion, i.e., the stator, positioned concentrically within its rotatable element, i.e., the rotor, along the axis of rotation of the rotor. The rotor includes a Halbach array of magnets. The voltage and power outputs are regulated by varying the radial gap in between the stator windings and the rotating Halbach array. The gap is varied by extensible and retractable supports attached to the stator windings that can move the windings in a radial direction.

  13. Magnet Guideways for Superconducting Maglevs: Comparison Between Halbach-Type and Conventional Arrangements of Permanent Magnets

    NASA Astrophysics Data System (ADS)

    Del-Valle, Nuria; Sanchez, Alvaro; Navau, Carles; Chen, Du-Xing

    2011-01-01

    The characteristics of the permanent magnets composing the guideway in superconducting magnetic levitation devices are very important for their performance in terms of levitation force and stability. From a model based on minimizing the magnetic energy in the superconductor and considering realistic parameters of actual maglev devices, we calculate the levitation and guidance forces and stability arising from both conventional arrangements and recently proposed Halbach-like arrangements. When a comparison is carefully made under similar conditions, we conclude that not always complicated arrangements based on Halbach arrays bring significant improvements with respect to some simpler arrangements that also provide large force. These results may help improving the design of actual maglev devices.

  14. Inductional Effects in a Halbach Magnet Motion Above Distributed Inductance

    NASA Astrophysics Data System (ADS)

    Tchatchoua, Yves; Conrow, Ary; Kim, Dong; Morgan, Daniel; Majewski, Walerian; Zafar, Zaeema

    2013-03-01

    We experimented with attempts to levitate a linear (bar) Halbach array of five 1'' Nd magnets above a linear inductive track. Next, in order to achieve a control over the relative velocity, we designed a different experiment. In it a large wheel with circumferentially positioned along its rim inducting coils rotates, while the magnet is suspended directly above the rim of the wheel on a force sensor. Faraday's Law with the Lenz's Rule is responsible for the lifting and drag forces on the magnet; the horizontal drag force is measured by another force sensor. Approximating the magnet's linear relative motion over inductors with a motion along a large circle, we may use formulas derived earlier in the literature for linear inductive levitation. We measured lift and drag forces as functions of relative velocity of the Halbach magnet and the inductive ``track,'' in an approximate agreement with the existing theory. We then vary the inductance and shape of the inductive elements to find the most beneficial choice for the lift/drag ratio at the lowest relative speed.

  15. Halbach array type focusing actuator for small and thin optical data storage device

    NASA Astrophysics Data System (ADS)

    Lee, Sung Q.; Park, Kang-Ho; Paek, Mun Chul

    2004-09-01

    The small form factor optical data storage devices are developing rapidly nowadays. Since it is designed for portable and compatibility with flesh memory, its components such as disk, head, focusing actuator, and spindle motor should be assembled within 5 mm. The thickness of focusing actuator is within 2 mm and the total working range is +/-100um, with the resolution of less than 1?m. Since the thickness is limited tightly, it is hard to place the yoke that closes the magnetic circuit and hard to make strong flux density without yoke. Therefore, Halbach array is adopted to increase the magnetic flux of one side without yoke. The proposed Halbach array type focusing actuator has the advantage of thin actuation structure with sacrificing less flex density than conventional magnetic array. The optical head unit is moved on the swing arm type tracking actuator. Focusing coil is attached to swing arm, and Halbach magnet array is positioned at the bottom of deck along the tracking line, and focusing actuator exerts force by the Fleming's left hand rule. The dynamics, working range, control resolution of focusing actuator are analyzed and performed.

  16. A comparative analysis of torque production in Halbach and conventional surface-mounted permanent-magnet synchronous motors

    SciTech Connect

    Ofori-Tenkorang, J.; Lang, J.H.

    1995-12-31

    The general question of when and why one should use a Halbach rotor in the design of surface-mounted permanent-magnet synchronous motors is addressed. The torque production capabilities of Halbach and conventional magnet arrays under the constraints of fixed magnet volume, and fixed power dissipation in slotless armature windings, are compared and the results presented in a graphical manner along with intuitive models that qualitatively explain these results. They conclude that, for permanent-magnet synchronous motors where the application precludes the use of a magnetic back-iron, the Halbach array always produces higher torque than the conventional array, for the same volume of magnets. The use of a magnetic back-iron in both designs increases the achievable torque. However, for magnetically-backed rotors, the conventional array, with an optimized pole-arc to pole-pitch ratio, produces higher torque than the Halbach array up to a certain thickness of magnets. Above this thickness, the Halbach array produces a higher torque.

  17. Intensity distribution of strong magnetic fields created by opposing linear Halbach assemblies of permanent magnets

    NASA Astrophysics Data System (ADS)

    eulka, Vclav; Pitora, Jaromr; Les?k, Michal; Straka, Pavel; Ciprian, Dalibor; Foukal, Jaroslav

    2013-11-01

    The work is devoted to the geometrical configuration of permanent magnets on the basis of opposing geometrically linear assemblies (e.g. Halbach arrays) for the generation of strong magnetic fields, which have been theoretically modeled and experimentally verified. The implementation of these opposing assemblies using NdFeB magnets of a total weight of 3.75 kg provided a value of magnetic induction in the middle of an air gap of a width of 20 mm that was higher by 56% in comparison with the simplest possible design. When the air gap width was 3 mm, the induction reached a value of 2.16 T, which represents an increase of more than 100%. Simultaneously, however, unlike in the simplest possible parallel configuration, opposing Halbach assemblies have shown, in the middle of an air gap, a significant decrease of the magnetic induction values when passing from the middle of the assemblies in the direction parallel to the x-axis.

  18. Laboratory Scale Prototype of a Low-Speed Electrodynamic Levitation System Based on a Halbach Magnet Array

    ERIC Educational Resources Information Center

    Iniguez, J.; Raposo, V.

    2009-01-01

    In this paper we analyse the behaviour of a small-scale model of a magnetic levitation system based on the Inductrack concept. Drag and lift forces acting on our prototype, moving above a continuous copper track, are studied analytically following a simple low-speed approach. The experimental results are in good agreement with the theoretical

  19. Laboratory Scale Prototype of a Low-Speed Electrodynamic Levitation System Based on a Halbach Magnet Array

    ERIC Educational Resources Information Center

    Iniguez, J.; Raposo, V.

    2009-01-01

    In this paper we analyse the behaviour of a small-scale model of a magnetic levitation system based on the Inductrack concept. Drag and lift forces acting on our prototype, moving above a continuous copper track, are studied analytically following a simple low-speed approach. The experimental results are in good agreement with the theoretical…

  20. Laboratory scale prototype of a low-speed electrodynamic levitation system based on a Halbach magnet array

    NASA Astrophysics Data System (ADS)

    iguez, J.; Raposo, V.

    2009-03-01

    In this paper we analyse the behaviour of a small-scale model of a magnetic levitation system based on the Inductrack concept. Drag and lift forces acting on our prototype, moving above a continuous copper track, are studied analytically following a simple low-speed approach. The experimental results are in good agreement with the theoretical calculations. 3D-numerical simulations are also used to highlight the significance of the edge effects and to extrapolate the results to higher speeds.

  1. Magnetic field homogeneity perturbations in finite Halbach dipole magnets.

    PubMed

    Turek, Krzysztof; Liszkowski, Piotr

    2014-01-01

    Halbach hollow cylinder dipole magnets of a low or relatively low aspect ratio attract considerable attention due to their applications, among others, in compact NMR and MRI systems for investigating small objects. However, a complete mathematical framework for the analysis of magnetic fields in these magnets has been developed only for their infinitely long precursors. In such a case the analysis is reduced to two-dimensions (2D). The paper details the analysis of the 3D magnetic field in the Halbach dipole cylinders of a finite length. The analysis is based on three equations in which the components of the magnetic flux density Bx, By and Bz are expanded to infinite power series of the radial coordinate r. The zeroth term in the series corresponds to a homogeneous magnetic field Bc, which is perturbed by the higher order terms due to a finite magnet length. This set of equations is supplemented with an equation for the field profile B(z) along the magnet axis, presented for the first time. It is demonstrated that the geometrical factors in the coefficients of particular powers of r, defined by intricate integrals are the coefficients of the Taylor expansion of the homogeneity profile (B(z)-Bc)/Bc. As a consequence, the components of B can be easily calculated with an arbitrary accuracy. In order to describe perturbations of the field due to segmentation, two additional equations are borrowed from the 2D theory. It is shown that the 2D approach to the perturbations generated by the segmentation can be applied to the 3D Halbach structures unless r is not too close to the inner radius of the cylinder ri. The mathematical framework presented in the paper was verified with great precision by computations of B by a highly accurate integration of the magnetostatic Coulomb law and utilized to analyze the inhomogeneity of the magnetic field in the magnet with the accuracy better than 1 ppm. PMID:24316186

  2. Magnetic field homogeneity perturbations in finite Halbach dipole magnets

    NASA Astrophysics Data System (ADS)

    Turek, Krzysztof; Liszkowski, Piotr

    2014-01-01

    Halbach hollow cylinder dipole magnets of a low or relatively low aspect ratio attract considerable attention due to their applications, among others, in compact NMR and MRI systems for investigating small objects. However, a complete mathematical framework for the analysis of magnetic fields in these magnets has been developed only for their infinitely long precursors. In such a case the analysis is reduced to two-dimensions (2D). The paper details the analysis of the 3D magnetic field in the Halbach dipole cylinders of a finite length. The analysis is based on three equations in which the components of the magnetic flux density Bx, By and Bz are expanded to infinite power series of the radial coordinate r. The zeroth term in the series corresponds to a homogeneous magnetic field Bc, which is perturbed by the higher order terms due to a finite magnet length. This set of equations is supplemented with an equation for the field profile B(z) along the magnet axis, presented for the first time. It is demonstrated that the geometrical factors in the coefficients of particular powers of r, defined by intricate integrals are the coefficients of the Taylor expansion of the homogeneity profile (B(z) - Bc)/Bc. As a consequence, the components of B can be easily calculated with an arbitrary accuracy. In order to describe perturbations of the field due to segmentation, two additional equations are borrowed from the 2D theory. It is shown that the 2D approach to the perturbations generated by the segmentation can be applied to the 3D Halbach structures unless r is not too close to the inner radius of the cylinder ri. The mathematical framework presented in the paper was verified with great precision by computations of B by a highly accurate integration of the magnetostatic Coulomb law and utilized to analyze the inhomogeneity of the magnetic field in the magnet with the accuracy better than 1 ppm.

  3. Magnetomechanics of internal-dipole, Halbach-array motor/generators.

    SciTech Connect

    Hull, J. R.; Turner, L. R.; Energy Technology

    2000-07-01

    The magnetomechanical behavior of internal-dipole, Halbach-type magnet arrays is analyzed for application as a motor/generator (M/G) with an energy-storage flywheel that is suspended by low-stiffness bearings. Scaling laws for the maximization of torque are derived as a function of geometry. The optimal geometry is relatively insensitive to gap and stator design and occurs approximately at a ratio of inner to outer diameter of the array of 0.8. Values are found for the angular extent of each phase of the stator coil that minimize the stiffness. The negative stiffness of the internal-dipole array is calculated for several manufacturable configurations and is shown to provide an upper limit on the available torque of the M/G according to the positive stiffness of the bearings. Experimental results are reported for an internal-dipole array used as a M/G for a flywheel suspended by a bearing consisting of a permanent-magnet assembly levitated over an array of high-temperature superconductors. Results show that the system is stable and that idling losses are low.

  4. Halbach array generator/motor having an automatically regulated output voltage and mechanical power output

    DOEpatents

    Post, Richard F.

    2005-02-22

    A motor/generator having its stationary portion, i.e., the stator, positioned concentrically within its rotatable element, i.e., the rotor, along its axis of rotation. The rotor includes a Halbach array. The stator windings are switched or commutated to provide a DC motor/generator much the same as in a conventional DC motor/generator. The voltage and power are automatically regulated by using centrifugal force to change the diameter of the rotor, and thereby vary the radial gap in between the stator and the rotating Halbach array, as a function of the angular velocity of the rotor.

  5. Single-sided mobile NMR with a Halbach magnet.

    PubMed

    Chang, Wei-Hao; Chen, Jyh-Horng; Hwang, Lian-Pin

    2006-10-01

    A single-sided mobile NMR apparatus with a small Halbach magnet was constructed for the first time. It is lightweight, compact and exhibits good sensitivity. The weight of the device is only 2 kg, and the NMR signal of the pencil eraser block can be detected in one shot using the device. This study describes the characteristics of this instrument, including the profile of static magnetic flux density, B0, the sensitivity in the depth direction and its effectiveness in one-dimensional profiling. Its usefulness in differentiating soft materials and evaluating the extent of damage of a material is demonstrated based on T2 relaxation data. The moisture absorbance also can be observed from the increase of the echo amplitude of the NMR spin echo signal. PMID:16997080

  6. Three-Dimensional Field Solutions for Multi-Pole Cylindrical Halbach Arrays in an Axial Orientation

    NASA Technical Reports Server (NTRS)

    Thompson, William K.

    2006-01-01

    This article presents three-dimensional B field solutions for the cylindrical Halbach array in an axial orientation. This arrangement has applications in the design of axial motors and passive axial magnetic bearings and couplers. The analytical model described here assumes ideal magnets with fixed and uniform magnetization. The field component functions are expressed as sums of 2-D definite integrals that are easily computed by a number of mathematical analysis software packages. The analysis is verified with sample calculations and the results are compared to equivalent results from traditional finite-element analysis (FEA). The field solutions are then approximated for use in flux linkage and induced EMF calculations in nearby stator windings by expressing the field variance with angular displacement as pure sinusoidal function whose amplitude depends on radial and axial position. The primary advantage of numerical implementation of the analytical approach presented in the article is that it lends itself more readily to parametric analysis and design tradeoffs than traditional FEA models.

  7. Design Methodology of a Dual-Halbach Array Linear Actuator with Thermal-Electromagnetic Coupling.

    PubMed

    Eckert, Paulo Roberto; Flores Filho, Aly Ferreira; Perondi, Eduardo; Ferri, Jeferson; Goltz, Evandro

    2016-01-01

    This paper proposes a design methodology for linear actuators, considering thermal and electromagnetic coupling with geometrical and temperature constraints, that maximizes force density and minimizes force ripple. The method allows defining an actuator for given specifications in a step-by-step way so that requirements are met and the temperature within the device is maintained under or equal to its maximum allowed for continuous operation. According to the proposed method, the electromagnetic and thermal models are built with quasi-static parametric finite element models. The methodology was successfully applied to the design of a linear cylindrical actuator with a dual quasi-Halbach array of permanent magnets and a moving-coil. The actuator can produce an axial force of 120 N and a stroke of 80 mm. The paper also presents a comparative analysis between results obtained considering only an electromagnetic model and the thermal-electromagnetic coupled model. This comparison shows that the final designs for both cases differ significantly, especially regarding its active volume and its electrical and magnetic loading. Although in this paper the methodology was employed to design a specific actuator, its structure can be used to design a wide range of linear devices if the parametric models are adjusted for each particular actuator. PMID:26978370

  8. Investigation of a 7-pole/6-slot Halbach-magnetized permanent-magnet linear alternator used for free-piston stirling engines

    NASA Astrophysics Data System (ADS)

    Zheng, Ping; Tong, Chengde; Zhao, Jing; Yu, Bin; Li, Lin; Bai, Jingang; Zhang, Lu

    2012-04-01

    This paper investigates a 7-pole/6-slot Halbach-magnetized permanent-magnet linear alternator used for free piston Stirling engines (FPSEs). Taking the advantages of Halbach array, a 1 kW prototype alternator is designed. Considering the rms value of electromotive force (EMF) and harmonic distortion, the optimal length ratio of the axial- and radial-magnetized permanent magnets and thicknesses of the permanent magnets are optimized by 2D finite element method. The alternator detent force, which is an important factor for smooth operation of FPSEs, is studied by optimizing slot tip and end tooth. The load and thermal performances of the final design are simulated. A prototype alternator was designed, built and tested. Experimental data indicated satisfactory design.

  9. A novel linear and rotary Halbach permanent magnet actuator with two degrees-of-freedom

    NASA Astrophysics Data System (ADS)

    Jin, Ping; Fang, Shuhua; Lin, Heyun; Wang, Xianbin; Zhou, Shigui

    2012-04-01

    This paper presents a novel linear and rotary Halbach permanent magnet actuator, which is capable of two degrees-of-freedom movements. The magnetic field distributions of the actuator are analytically analyzed using the magnetic scalar potential, where its tubular mover is transferred into a planar one by using a magnetic field curvature factor. The linear cogging force and rotary cogging torque and the stator flux-linkage of the actuator are subsequently predicted validated by the three-dimensional finite element method.

  10. The art and science of magnet design: Selected notes of Klaus Halbach. Volume 2

    SciTech Connect

    1995-02-01

    This volume contains a compilation of 57 notes written by Dr. Klaus Halbach selected from his collection of over 1650 such documents. It provides an historic snapshot of the evolution of magnet technology and related fields as the notes range from as early as 1965 to the present, and is intended to show the breadth of Dr. Halbach`s interest and ability that have long been an inspiration to his many friends and colleagues. As Halbach is an experimental physicist whose scientific interests span many areas, and who does his most innovative work with pencil and paper rather than at the workbench or with a computer, the vast majority of the notes in this volume were handwritten and their content varies greatly--some reflect original work or work for a specific project, while others are mere clarifications of mathematical calculations or design specifications. As the authors converted the notes to electronic form, some were superficially edited and corrected, while others were extensively re-written to reflect current knowledge and notation. The notes are organized under five categories which reflect their primary content: Beam Position Monitors, (bpm), Current Sheet Electron Magnets (csem), Magnet Theory, (thry), Undulators and Wigglers (u-w), and Miscellaneous (misc). Within the category, they are presented chronologically starting from the most recent note and working backwards in time.

  11. Comparison of Halbach magnetized brushless motors equipped with air-cored and iron-cored rotors

    NASA Astrophysics Data System (ADS)

    Xia, Z. P.; Zhu, Z. Q.; Jewell, G. W.; Howe, D.

    2003-05-01

    The performance of Halbach magnetized brushless motors equipped with air-cored and iron-cored rotors is investigated theoretically and experimentally. It is shown that an optimal combination of magnet thickness and pole number exists for maximum air-gap flux density. By employing a rotor back iron, the air-gap field and hence the output torque can be enhanced significantly if the ratio of the radial thickness of the magnet to the pole pitch is small.

  12. Torque Production in a Halbach Machine

    NASA Technical Reports Server (NTRS)

    Eichenberg, Dennis J.; Gallo, Christopher A.; Thompson, William K.; Vrnak, Daniel R.

    2006-01-01

    The NASA John H. Glenn Research Center initiated the investigation of torque production in a Halbach machine for the Levitated Ducted Fan (LDF) Project to obtain empirical data in determining the feasibility of using a Halbach motor for the project. LDF is a breakthrough technology for "Electric Flight" with the development of a clean, quiet, electric propulsor system. Benefits include zero emissions, decreased dependence on fossil fuels, increased efficiency, increased reliability, reduced maintenance, and decreased operating noise levels. A commercial permanent magnet brushless motor rotor was tested with a custom stator. An innovative rotor utilizing a Halbach array was designed and developed to fit directly into the same stator. The magnets are oriented at 90deg to the adjacent magnet, which cancels the magnetic field on the inside of the rotor and strengthens the field on the outside of the rotor. A direct comparison of the commercial rotor and the Halbach rotor was made. In addition, various test models were designed and developed to validate the basic principles described, and the theoretical work that was performed. The report concludes that a Halbach array based motor can provide significant improvements in electric motor performance and reliability.

  13. Design and Analysis of a Nested Halbach Permanent Magnet Magnetic Refrigerator

    NASA Astrophysics Data System (ADS)

    Tura, Armando

    A technology with the potential to create efficient and compact refrigeration devices is an active magnetic regenerative refrigerator (AMRR). AMRRs exploit the magnetocaloric effect displayed by magnetic materials whereby a reversible temperature change is induced when the material is exposed to a change in applied magnetic field. By using the magnetic materials in a regenerator as the heat storage medium and as the means of work input, one creates an active magnetic regenerator (AMR). Although several laboratory devices have been developed, no design has yet demonstrated the performance, reliability, and cost needed to compete with traditional vapor compression refrigerators. There are many reasons for this and questions remain as to the actual potential of the technology. The objective of the work described in this thesis is to quantify the actual and potential performance of a permanent magnet AMR system. A specific device configuration known as a dual-nested-Halbach system is studied in detail. A laboratory scale device is created and characterized over a wide range of operating parameters. A numerical model of the device is created and validated against experimental data. The resulting model is used to create a cost-minimization tool to analyze the conditions needed to achieve specified cost and efficiency targets. Experimental results include cooling power, temperature span, pumping power and work input. Although the magnetocaloric effect of gadolinium is small, temperature spans up to 30 K are obtained. Analysis of power input shows that the inherent magnetic work is a small fraction of the total work input confirming the assumption that potential cycle efficiencies can be large. Optimization of the device generates a number of areas for improvement and specific results depend upon targeted temperature spans and cooling powers. A competitive cost of cooling from a dual-nested-Halbach configuration is challenging and will depend on the ability to create regenerator matrices with near-ideal adiabatic temperature change scaling as a function of temperature.

  14. A portable Halbach magnet that can be opened and closed without force: The NMR-CUFF

    NASA Astrophysics Data System (ADS)

    Windt, Carel W.; Soltner, Helmut; Dusschoten, Dagmar van; Blümler, Peter

    2011-01-01

    Portable equipment for nuclear magnetic resonance (NMR) is becoming increasingly attractive for use in a variety of applications. One of the main scientific challenges in making NMR portable is the design of light-weight magnets that possess a strong and homogeneous field. Existing NMR magnets can provide such magnetic fields, but only for small samples or in small regions, or are rather heavy. Here we show a simple yet elegant concept for a Halbach-type permanent magnet ring, which can be opened and closed with minimal mechanical force. An analytical solution for an ideal Halbach magnet shows that the magnetic forces cancel if the structure is opened at an angle of 35.3° relative to its poles. A first prototype weighed only 3.1 kg, and provided a flux density of 0.57 T with a homogeneity better than 200 ppm over a spherical volume of 5 mm in diameter without shimming. The force needed to close it was found to be about 20 N. As a demonstration, intact plants were imaged and water (xylem) flow measured. Magnets of this type (NMR-CUFF = Cut-open, Uniform, Force Free) are ideal for portable use and are eminently suited to investigate small or slender objects that are part of a larger or immobile whole, such as branches on a tree, growing fruit on a plant, or non-metallic tubing in industrial installations. This new concept in permanent-magnet design enables the construction of openable, yet strong and homogeneous magnets, which aside from use in NMR or MRI could also be of interest for applications in accelerators, motors, or magnetic bearings.

  15. A portable Halbach magnet that can be opened and closed without force: the NMR-CUFF.

    PubMed

    Windt, Carel W; Soltner, Helmut; van Dusschoten, Dagmar; Blümler, Peter

    2011-01-01

    Portable equipment for nuclear magnetic resonance (NMR) is becoming increasingly attractive for use in a variety of applications. One of the main scientific challenges in making NMR portable is the design of light-weight magnets that possess a strong and homogeneous field. Existing NMR magnets can provide such magnetic fields, but only for small samples or in small regions, or are rather heavy. Here we show a simple yet elegant concept for a Halbach-type permanent magnet ring, which can be opened and closed with minimal mechanical force. An analytical solution for an ideal Halbach magnet shows that the magnetic forces cancel if the structure is opened at an angle of 35.3° relative to its poles. A first prototype weighed only 3.1 kg, and provided a flux density of 0.57 T with a homogeneity better than 200 ppm over a spherical volume of 5mm in diameter without shimming. The force needed to close it was found to be about 20 N. As a demonstration, intact plants were imaged and water (xylem) flow measured. Magnets of this type (NMR-CUFF = Cut-open, Uniform, Force Free) are ideal for portable use and are eminently suited to investigate small or slender objects that are part of a larger or immobile whole, such as branches on a tree, growing fruit on a plant, or non-metallic tubing in industrial installations. This new concept in permanent-magnet design enables the construction of openable, yet strong and homogeneous magnets, which aside from use in NMR or MRI could also be of interest for applications in accelerators, motors, or magnetic bearings. PMID:21036637

  16. Demonstration of Halbach-like magnets for improving microwave window power capacity

    NASA Astrophysics Data System (ADS)

    Chang, Chao; Liu, Yansheng; Ouyang, Xiaoping; Guo, Letian; Wu, Xiaolong; Sun, Xu; Wang, Limin

    2014-09-01

    The application of a resonant magnetic field to suppress the multipactor at the vacuum/dielectric interface of a high-power microwave window was theoretically proposed by Chang et al. [Appl. Phys. Lett. 96, 111502 (2010)] and the proof-of-principle was experimentally demonstrated by Chang et al. [Appl. Phys. Lett. 97, 141501 (2010)]. However, for transmitting gigawatt power, conventional large-scale magnets have the significant drawback of a nonuniform and heterogeneous B-field, which enhances the multipactor rather than suppresses it. The Halbach-like magnets for generating the transverse homogeneous B-field in a large scale are studied for suppressing the multipactor; the underlying physics in the particle-in-cell simulation was simulated, and the window breakdown threshold was significantly enhanced at multi-gigawatt.

  17. Dynamic response characteristics of high temperature superconducting maglev systems: Comparison between Halbach-type and normal permanent magnet guideways

    NASA Astrophysics Data System (ADS)

    Wang, B.; Zheng, J.; Che, T.; Zheng, B. T.; Si, S. S.; Deng, Z. G.

    2015-12-01

    The permanent magnet guideway (PMG) is very important for the performance of the high temperature superconducting (HTS) system in terms of electromagnetic force and operational stability. The dynamic response characteristics of a HTS maglev model levitating on two types of PMG, which are the normal PMG with iron flux concentration and Halbach-type PMG, were investigated by experiments. The dynamic signals for different field-cooling heights (FCHs) and loading/unloading processes were acquired and analyzed by a vibration analyzer and laser displacement sensors. The resonant frequency, stiffness and levitation height of the model were discussed. It was found that the maglev model on the Halbach-type PMG has higher resonant frequency and higher vertical stiffness compared with the normal PMG. However, the low lateral stiffness of the model on the Halbach-type PMG indicates poor lateral stability. Besides, the Halbach-type PMG has better loading capacity than the normal PMG. These results are helpful to design a suitable PMG for the HTS system in practical applications.

  18. Magnetic arrays

    DOEpatents

    Trumper, David L. (Plaistow, NH); Kim, Won-jong (Cambridge, MA); Williams, Mark E. (Pelham, NH)

    1997-05-20

    Electromagnet arrays which can provide selected field patterns in either two or three dimensions, and in particular, which can provide single-sided field patterns in two or three dimensions. These features are achieved by providing arrays which have current densities that vary in the windings both parallel to the array and in the direction of array thickness.

  19. Magnetic arrays

    DOEpatents

    Trumper, D.L.; Kim, W.; Williams, M.E.

    1997-05-20

    Electromagnet arrays are disclosed which can provide selected field patterns in either two or three dimensions, and in particular, which can provide single-sided field patterns in two or three dimensions. These features are achieved by providing arrays which have current densities that vary in the windings both parallel to the array and in the direction of array thickness. 12 figs.

  20. Two dimensional exchange NMR experiments of natural porous media with portable Halbach-Magnets

    NASA Astrophysics Data System (ADS)

    Haber, Agnes; Haber-Pohlmeier, Sabina; Casanova, Federico; Blmich, Bernhard

    2010-05-01

    The characterization of pore space and connectivity in soils of different textures is one topic within Cluster A, Partial Project A1. For this purpose low field mobile NMR became a powerful tool following the development of portable NMR sensors for well logging. By now there are numerous applications of mobile NMR in materials analysis and chemical engineering where, for example, unique information about the structure, morphology and dynamics of polymers is obtained, and new opportunities are provided for geophysical investigations [1]. In particular, dynamic information can be retrieved by two-dimensional Laplace exchange NMR, where the initial NMR relaxation environment is correlated with the final relaxation environment of molecules migrating from one environment to the other within a so-called NMR mixing time tm [2]. Relaxation-relaxation exchange experiments were performed with saturated and un-saturated soil samples at low and moderately inhomogeneous magnetic field with a simple, portable Halbach-Magnet. By conducting NMR transverse relaxation exchange experiments for several mixing times and inverting the results to 2D T2 distributions (similar to joint probability densities of transverse relaxation times T2) with the help of inverse 2D Laplace Transformation (ILT), we observed characteristic exchange processes: Soils consisting mainly of silt and clay components show predominantly exchange between the smaller pores at mixing times of some milliseconds. In addition, there exists also weaker exchange with the larger pores observable for longer mixing time. In contrast to that fine sand exhibits 2D T2 distributions with no exchange processes which can be interpreted that water molecules move within pores of the same size class. These results will be compared to the exchange behaviour under unsaturated conditions. References: 1. B. Blmich, J. Mauler, A. Haber, J. Perlo, E. Danieli, F. Casanova, Mobile NMR for geophysical analysis and material testing, Petroleum Science 6 (2009) 1-7. 2. K. E. Washburn, P.T. Callaghan, Tracking pore to pore exchange using relaxation exchange spectroscopy, Phys. Rev. Lett. 97 (2006) 175502.

  1. Inductrack magnet configuration

    DOEpatents

    Post, Richard Freeman

    2003-12-16

    A magnet configuration comprising a pair of Halbach arrays magnetically and structurally connected together are positioned with respect to each other so that a first component of their fields substantially cancels at a first plane between them, and a second component of their fields substantially adds at this first plane. A track of windings is located between the pair of Halbach arrays and a propulsion mechanism is provided for moving the pair of Halbach arrays along the track. When the pair of Halbach arrays move along the track and the track is not located at the first plane, a current is induced in the windings and a restoring force is exerted on the pair of Halbach arrays.

  2. Inductrack magnet configuration

    DOEpatents

    Post, Richard Freeman

    2003-10-14

    A magnet configuration comprising a pair of Halbach arrays magnetically and structurally connected together are positioned with respect to each other so that a first component of their fields substantially cancels at a first plane between them, and a second component of their fields substantially adds at this first plane. A track of windings is located between the pair of Halbach arrays and a propulsion mechanism is provided for moving the pair of Halbach arrays along the track. When the pair of Halbach arrays move along the track and the track is not located at the first plane, a current is induced in the windings and a restoring force is exerted on the pair of Halbach arrays.

  3. Passive magnetic bearing for a horizontal shaft

    SciTech Connect

    Post, Richard F.

    2003-12-02

    A passive magnetic bearing is composed of a levitation element and a restorative element. The levitation element is composed of a pair of stationary arcuate ferromagnetic segments located within an annular radial-field magnet array. The magnet array is attached to the inner circumference of a hollow shaft end. An attractive force between the arcuate segments and the magnet array acts vertically to levitate the shaft, and also in a horizontal transverse direction to center the shaft. The restorative element is comprised of an annular Halbach array of magnets and a stationary annular circuit array located within the Halbach array. The Halbach array is attached to the inner circumference of the hollow shaft end. A repulsive force between the Halbach array and the circuit array increases inversely to the radial space between them, and thus acts to restore the shaft to its equilibrium axis of rotation when it is displaced therefrom.

  4. Metamaterial anisotropic flux concentrators and magnetic arrays

    NASA Astrophysics Data System (ADS)

    Bjrk, R.; Smith, A.; Bahl, C. R. H.

    2013-08-01

    A metamaterial magnetic flux concentrator is investigated in detail in combination with a Halbach cylinder of infinite length. A general analytical solution to the field is determined and the magnetic figure of merit is determined for a Halbach cylinder with a flux concentrator. It is shown that an ideal flux concentrator will not change the figure of merit of a given magnet design, while the non-ideal will always lower it. The geometric parameters producing maximum figure of merit, i.e., the most efficient devices, are determined. The force and torque between two concentric Halbach cylinders with flux concentrators is determined and the maximum torque is found. Finally, the effect of non-ideal flux concentrators and the practical use of flux concentrators, as well as demagnetization issues, is discussed.

  5. Comparison of adjustable permanent magnetic field sources

    NASA Astrophysics Data System (ADS)

    Bjørk, R.; Bahl, C. R. H.; Smith, A.; Pryds, N.

    2010-11-01

    A permanent magnet assembly in which the flux density can be altered by a mechanical operation is often significantly smaller than comparable electromagnets and also requires no electrical power to operate. In this paper five permanent magnet designs in which the magnetic flux density can be altered are analyzed using numerical simulations, and compared based on the generated magnetic flux density in a sample volume and the amount of magnet material used. The designs are the concentric Halbach cylinder, the two half Halbach cylinders, the two linear Halbach arrays and the four and six rod mangle. The concentric Halbach cylinder design is found to be the best performing design, i.e. the design that provides the most magnetic flux density using the least amount of magnet material. A concentric Halbach cylinder has been constructed and the magnetic flux density, the homogeneity and the direction of the magnetic field are measured and compared with numerical simulation and a good agrement is found.

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

    SciTech Connect

    Atallah, K.; Howe, D.

    1998-07-01

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

  7. A permanent magnet tubular linear generator for wave energy conversion

    NASA Astrophysics Data System (ADS)

    Yu, Haitao; Liu, Chunyuan; Yuan, Bang; Hu, Minqiang; Huang, Lei; Zhou, Shigui

    2012-04-01

    A novel three-phase permanent magnet tubular linear generator (PMTLG) with Halbach array is proposed for the sea wave energy conversion. Non-linear axi-symmetrical finite element method (FEM) is implemented to calculate the magnetic fields along air-gap for different Halbach arrays of PMTLGs. The PMTLG characteristics are analyzed and the simulation results are validated by the experiment. An assistant tooth is implemented to greatly minimize the end and cogging effects which cause the oscillatory detent force.

  8. Coherent magnetic semiconductor nanodot arrays

    PubMed Central

    2011-01-01

    In searching appropriate candidates of magnetic semiconductors compatible with mainstream Si technology for future spintronic devices, extensive attention has been focused on Mn-doped Ge magnetic semiconductors. Up to now, lack of reliable methods to obtain high-quality MnGe nanostructures with a desired shape and a good controllability has been a barrier to make these materials practically applicable for spintronic devices. Here, we report, for the first time, an innovative growth approach to produce self-assembled and coherent magnetic MnGe nanodot arrays with an excellent reproducibility. Magnetotransport experiments reveal that the nanodot arrays possess giant magneto-resistance associated with geometrical effects. The discovery of the MnGe nanodot arrays paves the way towards next-generation high-density magnetic memories and spintronic devices with low-power dissipation. PMID:21711627

  9. Biotemplated magnetic nanoparticle arrays.

    PubMed

    Galloway, Johanna M; Bramble, Jonathan P; Rawlings, Andrea E; Burnell, Gavin; Evans, Stephen D; Staniland, Sarah S

    2012-01-23

    Immobilized biomineralizing protein Mms6 templates the formation of uniform magnetite nanoparticles in situ when selectively patterned onto a surface. Magnetic force microscopy shows that the stable magnetite particles maintain their magnetic orientation at room temperature, and may be exchange coupled. This precision-mixed biomimetic/soft-lithography methodology offers great potential for the future of nanodevice fabrication. PMID:22052737

  10. DNA transport in magnetic arrays

    NASA Astrophysics Data System (ADS)

    Minc, Nicolas

    2005-03-01

    We present a experimental/theoretical study of the microfluidic electrophoresis of long DNA in an innovative matrix consisting of a hexagonal array of magnetic bead columns. Using videomicroscopy, we examined the motion of long T4 DNA (169 kbp) under a wide range of array densities and electric fields. By tracking the motion of many individual DNA molecules, we computed (i) the distribution of collision times; (ii) the collision probability; (iii) and the mean passage time through the viewing area. Based on our single molecule results, we will present a model focusing upon the non-Markovian characteristic of the transport in the array. DNA transport is represented by a Scher-Lax walk, where each molecule undergoes cycles of collisions. The model qualitatively and quantitatively captures the main features on separation in microarrays. As this work represents the first systematic theoretical study of dispersion in these devices, it is a significant step towards a detailed understanding of realistic miniaturized separation systems.

  11. Design and optimization of voice coil actuator for six degree of freedom active vibration isolation system using Halbach magnet array

    NASA Astrophysics Data System (ADS)

    Kim, MyeongHyeon; Kim, Hyunchang; Gweon, Dae-Gab

    2012-10-01

    This paper describes the design, modeling, optimization, and validation of an active vibration isolation system using a voice coil motor. The active vibration isolating method was constructed with a passive isolator and an active isolator. A spring was used for passive isolating; an actuator was used for active isolating. The proposed active vibration isolation system (AVIS) can isolate disturbances for many kinds of instruments. Until now, developed AVIS were able to isolate a six degree-of-freedom disturbance effectively. This paper proposes the realization of such a six degree-of-freedom active vibration isolation system that can work as a bench top device for precision measuring machines such as atomic force microscope, scanning probe microscope, etc.

  12. Design and optimization of voice coil actuator for six degree of freedom active vibration isolation system using Halbach magnet array.

    PubMed

    Kim, MyeongHyeon; Kim, Hyunchang; Gweon, Dae-Gab

    2012-10-01

    This paper describes the design, modeling, optimization, and validation of an active vibration isolation system using a voice coil motor. The active vibration isolating method was constructed with a passive isolator and an active isolator. A spring was used for passive isolating; an actuator was used for active isolating. The proposed active vibration isolation system (AVIS) can isolate disturbances for many kinds of instruments. Until now, developed AVIS were able to isolate a six degree-of-freedom disturbance effectively. This paper proposes the realization of such a six degree-of-freedom active vibration isolation system that can work as a bench top device for precision measuring machines such as atomic force microscope, scanning probe microscope, etc. PMID:23126814

  13. Surface modification of YIG by magnet array

    NASA Astrophysics Data System (ADS)

    Atalay, S.; Kolat, V. S.; Bak?r, H. G.; Izgi, T.; Kaya, A. O.; Kaya, O. A.; Gencer, H.

    2015-11-01

    In this work, magnetostatic surface spin waves (MSSW) were propagated along the single crystal YIG (Y3Fe5O12) film grown on GGG substrate. In order to obtain magnonic crystals, unlike the conventional methods, the surface of YIG films were magnetically modulated by magnet array in one and two-dimensions. The surface modulated YIG films formed sharp band gaps at approximately 6.55 GHz and 6.58 GHz at 1600 Oe magnetic field for one and two-dimensional magnonic crystals, respectively. It was found that a very small magnetic field change leads a large change in the peak value of band gap frequency.

  14. Magnetization dynamics in arrays of strongly interacting magnetic nanocrystals

    NASA Astrophysics Data System (ADS)

    Telem-Shafir, Tamar; Markovich, Gil

    2005-11-01

    Arrays of 6.6nm iron oxide nanocrystals coated with fatty acid molecules were produced using the Langmuir-Blodgett technique. The arrays had a varying number of layers stacked together, going from two dimensional to three dimensional and two different in-plane interparticle separations. While temperature-dependent ac susceptibility measurements of the isolated nanocrystals obeyed the Nel-Brown relaxation law, the array relaxation deviated significantly from this simple law. This deviation together with the observed dc field influence on the susceptibility-temperature curves, the large shifts in blocking temperatures and reduction in susceptibility-temperature curve widths on going from isolated particles to the arrays indicated collective magnetization dynamics during magnetization freezing. A scaling law analysis of this freezing dynamics yielded different powers for the two different interparticle separations with no dependence on dimensionality. In spite of the spin-glass-like behavior, it is possible that small, magnetically ordered domains of nanocrystals form at low temperature.

  15. Patterning metallic electrodeposits with magnet arrays

    NASA Astrophysics Data System (ADS)

    Dunne, Peter; Coey, J. M. D.

    2012-06-01

    The influence of a pattern of a magnetic field on the structure of metal deposits at the cathode of a small electrochemical cell is investigated for cobalt, nickel, copper, and zinc. The different magnetic properties of the ions in their oxidized and reduced states, together with the influence on the patterned electrodeposits of variables, including the structure of the array of small magnets used to generate the field pattern, applied magnetic field, ion concentration, cell orientation, and deposition time lead to an understanding of the physical processes involved. The results for direct deposits from paramagnetic cations such as Cu2+ when convection is minimized are largely explained in terms of magnetic pressure, which modifies the thickness of the diffusion layer that governs mass transport. Patterning is governed by the susceptibility of the electroactive species relative to the nonelectroactive background. No patterning is observed until the diffusion layer begins to form, as it requires orthogonal concentration and magnetic field gradients. An inverse effect, whereby deposits are structured in complementary patterns, such as antidot arrays, is observed when a strongly paramagnetic but nonelectroactive cation such as Dy3+ is present in the electrolyte, together with an electroactive cation such as Cu2+or Zn2. Inverse patterning is related to magnetically induced convection produced by the inhomogeneous magnetic field. Blocking of sites in the double layer by the rare-earth ions may also be involved. The inverse deposits are concentrated in regions where the magnitude of the field is lowest; they can also be produced directly by superposing a uniform magnetic field on that of the magnet array.

  16. Magnetic switching in submicron-scale periodic magnetic arrays.

    SciTech Connect

    Vavassori, P.; Donzelli, O.; Metlushko, V.; Grimsditch, M.; Ilic, B.; Neuzil, P.; Kumar, R.; Materials Science Division; Univ. di Ferrara; Cornell Univ.; Inst. of Microelectronics

    2000-07-15

    The influence of the element shape on the switching of the magnetization in dot arrays has been investigated using a joint in-field magnetic force microscopy analysis and magneto-optical Kerr measurements. The single- or multiple-domain nature of the magnetization at remanence is shown to depend strongly on the aspect ratio of the elements and on how rounded or pointed each element is.

  17. Note: Manipulation of supersonic atomic beams with static magnetic fields.

    PubMed

    Gardner, Jamie; Castillo-Garza, Rodrigo; Raizen, Mark G

    2013-09-01

    The inhomogeneous magnetic field of a permanent-magnet planar Halbach array is used to either deflect or to specularly reflect a supersonic beam of neutral atoms. Metastable neon and helium beams are tested to experimentally evaluate the performance of this array in a range of configurations. Results are compared with numerical simulations and the device is presented as a high precision tool for the manipulation of neutral atom beams. PMID:24028135

  18. Note: Manipulation of supersonic atomic beams with static magnetic fields

    NASA Astrophysics Data System (ADS)

    Gardner, Jamie; Castillo-Garza, Rodrigo; Raizen, Mark G.

    2013-09-01

    The inhomogeneous magnetic field of a permanent-magnet planar Halbach array is used to either deflect or to specularly reflect a supersonic beam of neutral atoms. Metastable neon and helium beams are tested to experimentally evaluate the performance of this array in a range of configurations. Results are compared with numerical simulations and the device is presented as a high precision tool for the manipulation of neutral atom beams.

  19. Magnetization Reversal in Dense Arrays of Nanoparticles

    NASA Astrophysics Data System (ADS)

    Skomski, R.; Kashyap, A.; Sellmyer, D. J.

    2003-03-01

    Recently, three-dimensional arrays of nanoparticles embedded in magnetic matrix have attracted renewed attention as potential permanent magnets with record energy products [1, 2]. A key problem is to ensure that the composites exhibit a sufficiently high coercivity. A lower bound to the coercivity is the nucleation field, at which the saturated magnetization state becomes unstable. The determination of the magnetic modes can be mapped onto the quantum-mechanical motion of a single electron [3], and in the case of arrays this reduces to a magnonic band-structure problem. The only difference is that magnetostatic interactions modify the wave-vector dependence of the energy levels. The nucleation field is determined by the s-band edge. For ideal periodic arrays, the edge is sharp and the nucleation field has a well-defined value, whereas real-structure disorder leads to an Urbach tail of low-lying localized states. This leads to a typically logarithmic dependence of the coercivity on the macroscopic size of the magnet. This research is supported by AFOSR, DOE, NSF MRSEC, and CMRA. [1] D. J. Sellmyer, Nature 420, 374 (2002). [2] H. Zeng, J. Li, J. P. Liu, Zh. L. Wang, and Sh.-H. Sun, Nature 420, 395 (2002). [3] R. Skomski and J. M. D. Coey, Phys. Rev. B 48, 15812 (1993).

  20. Three-Magnet Arrays for Unilateral Magnetic Resonance

    NASA Astrophysics Data System (ADS)

    Garcia Naranjo, Juan Carlos

    Unilateral Magnetic Resonance (UMR) has become, in different research areas, a powerful tool to interrogate samples of arbitrary size. The three-magnet array developed by the MRI Centre of the University of New Brunswick has features that make it a simple and robust approach for UMR. This thesis introduces a group of solutions to broaden the range of application of this design. Practical applications for non-destructive testing and reservoir core plug characterization are presented. We have shown that it is also possible to monitor the curing process of an epoxy/polyamidoamine system by employing a three-magnet array. A new version of the three-magnet array which features extended constant magnetic field gradients is also introduced. Constant gradients of more than 3 cm extent can be achieved in a very simple, compact and safe design. The application of the three-magnet array in combination with a solenoid as the RF probe for analysis of long core plugs has been presented. Core plugs of different diameter can be analyzed by simply changing the diameter of the RF probe employed for the measurement. Results of an initial survey of selective excitation in UMR are presented. The low SNR and inhomogeneities in the selective spot reduce the effectiveness of selective excitation for UMR.

  1. Passive magnetic bearing system

    DOEpatents

    Post, Richard F.

    2014-09-02

    An axial stabilizer for the rotor of a magnetic bearing provides external control of stiffness through switching in external inductances. External control also allows the stabilizer to become a part of a passive/active magnetic bearing system that requires no external source of power and no position sensor. Stabilizers for displacements transverse to the axis of rotation are provided that require only a single cylindrical Halbach array in its operation, and thus are especially suited for use in high rotation speed applications, such as flywheel energy storage systems. The elimination of the need of an inner cylindrical array solves the difficult mechanical problem of supplying support against centrifugal forces for the magnets of that array. Compensation is provided for the temperature variation of the strength of the magnetic fields of the permanent magnets in the levitating magnet arrays.

  2. Heat flow control in thermo-magnetic convective systems using engineered magnetic fields

    NASA Astrophysics Data System (ADS)

    Lee, Jaewook; Nomura, Tsuyoshi; Dede, Ercan M.

    2012-09-01

    We present the design of a magnetically controlled convective heat transfer system. The underlying thermo-magnetic instability phenomenon is described, and enhanced convective fluid flow patterns are determined using non-linear programming techniques plus a design sensitivity analysis. Specifically, the magnetic fluid body force is computed by finding the optimal distribution and magnetization direction of a magnetic field source, where the objective is to minimize the maximum temperature of a closed loop heat transfer system. Sizeable fluid recirculation zones are induced by arranging magnetic field generation elements in configurations similar to Halbach arrays. Applications include improved heat flow control for electromechanical systems.

  3. Arrays of elliptical Fe(001) nanoparticles: Magnetization reversal, dipolar interactions, and effects of finite array sizes

    NASA Astrophysics Data System (ADS)

    Hanson, Maj; Bru?as, Rimantas; Antosiewicz, Tomasz J.; Dumas, Randy K.; Hjrvarsson, Bjrgvin; Flovik, Vegard; Wahlstrm, Erik

    2015-09-01

    The magnetic properties of arrays of nanoparticles are determined by the interplay between the individual particle properties and the dipolar interactions between them. Here we present a study of arrays of elliptical Fe(001) particles of thickness 10-50 nm. The aspect ratios of the ellipses are 1:3, their short axes a =50 , 100, or 150 nm, and the periodicity of the rectangular arrays is either two or four times the corresponding axes of the ellipses. Magnetic measurements together with numerical and micromagnetic calculations yield a consistent picture of the arrays, comprising single-domain nanoparticles. We show that the magnetization reversal, occurring in the range 100-400 mT for fields applied along the long axis, is mainly determined by the properties of the corresponding single Fe ellipses. The interaction fields of the order of tens of mT can be tuned by the array configurations. For the actual arrays the interactions promote switching. For film thicknesses below the Bloch wall width parameter of Fe, lw=22 nm, magnetization reversal occurs without formation of domain walls or vortices. Within this range arrays may be tuned to obtain a well-defined switching field. Two general conclusions are drawn from the calculations: the character of the interaction, whether it promotes or delays magnetization reversal, is determined by the aspect ratio of the array grid, and the interaction strength saturates as the size of the array increases.

  4. The efficiency and the demagnetization field of a general Halbach cylinder

    NASA Astrophysics Data System (ADS)

    Bjrk, R.; Smith, A.; Bahl, C. R. H.

    2015-06-01

    The maximum magnetic efficiency of a general multipole Halbach cylinder of order p is found as function of p. The efficiency is shown to decrease for increasing absolute value of p. The optimal ratio between the inner and outer radius, i.e. the ratio resulting in the most efficient design, is also found as function of p and is shown to tend towards smaller and smaller magnet sizes. Finally, the demagnetizing field in a general p-Halbach cylinder is calculated, and it is shown that demagnetization is largest either at cos 2 p? = 1 or cos 2 p? = - 1. For the common case of a p=1 Halbach cylinder the maximum values of the demagnetizing field are either at ? = 0, ? at the outer radius, where the field is always equal to the remanence, or at ? = ? / 2 at the inner radius, where it is the magnitude of the field in the bore. Thus to avoid demagnetization the coercivity of the magnets must be larger than these values.

  5. Magnetic markers detection using PCB fluxgate array

    NASA Astrophysics Data System (ADS)

    Janosek, M.; Ripka, P.; Platil, A.

    2009-04-01

    We used an array of race-track fluxgate sensors, manufactured with printed circuit board (PCB) technology, forming a sensor head for detection of ferromagnetic and paramagnetic markers. The sensors were arranged perpendicularly to the measuring plane and we measured the difference of their output, giving us the horizontal gradient of normal component of the measured field. Due to the close match of the sensor's parameters, subtraction of the fluxgate output signals could be done directly at the input of a lock-in amplifier, increasing the signal-to-noise ratio for small gradients. When moving the sensor head, we were able to map field gradients smaller than 6 nT/mm, which was verified while measuring the magnetic markers on a dollar bill, while suppressing the background field by a factor of 5. In a line-scanning mode, we scanned a marker formed by a 0.2 mm diameter Permalloy wire in a distance of up to 10 mm. With the help of perpendicular ac excitation at 30 Hz, we were able to detect a 0.1 ml Endorem iron-oxide superparamagnetic marker at 2 mm; volume of 0.6 ml was detectable at 10 mm.

  6. The Inductrack Approach to Magnetic Levitation

    SciTech Connect

    Post, R.F.; Ryutov, D.D.

    2000-04-19

    Concepts developed during research on passive magnetic bearing systems at the Lawrence Livermore National Laboratory gave rise to a new approach to magnetic levitation, the Inductrack. A passive induced-current system employing permanent magnets on the moving vehicle, the Inductrack maximizes levitation forces by a combination of two elements. First, the permanent magnets on the vehicle are arranged in a ''Halbach array,'' a magnet configuration that optimally produces a periodic magnetic field below the array, while canceling the field above the array. Second, the track is made up of close-packed shorted electrical circuits. These circuits couple optimally to the magnetic field of the Halbach array. As a result, levitating forces of order 40 metric tonnes per square meter of Halbach array can be generated, using NdFeB magnets whose weight is a few percent of the levitated weight. Being an induced-current system, the levitation requires motion of the vehicle above a low transition speed. For maglev applications this speed is a few kilometers per hour, walking speed. At rest or in the station auxiliary wheels are needed. The Inductrack is thus fail-safe, that is, drive system failure would only result in the vehicle slowing down and finally settling on its auxiliary wheels. On the basis of theoretical analyses a small model vehicle and a 20-meter-long track was built and tested at speeds of order 12 meters per second. A second model, designed to achieve 10-g acceleration levels and much higher speeds, is under construction under NASA sponsorship, en route to the design of maglev-based launchers for rockets. Some of the presently perceived practical problems of implementing full-scale maglev systems based on the Inductrack concept will be discussed.

  7. Phase combination for self-cancellation of magnetic force in undulators

    NASA Astrophysics Data System (ADS)

    Kinjo, Ryota; Tanaka, Takashi

    2014-12-01

    A simple arrangement of undulator magnets having nearly zero magnetic force between the upper and lower magnet arrays is proposed, which significantly simplifies the mechanical structure of undulators. In this arrangement, each magnet array is divided into a number of sections, half of which are phase-shifted according to a particular rule without breaking the periodic condition required for the undulator field. Calculation results show that, when the gap over period is in practical range, more than or equal to 1 /18 , the magnetic force can be reduced down to less than 1 /50 of that in the Halbach undulator by applying the proposed scheme.

  8. Manipulation of Magnetic Particles for Use in Photonic Biosensor Arrays

    NASA Astrophysics Data System (ADS)

    Siebe, Craig

    Trapping magnetic nanoparticles in wells in a photonic crystal biosensor array using magnetophoresis is desirable because it would allow for covalent bonding of antibodies onto the particles which would lead to an increase in sensitivity of the sensor. It was hypothesized that this could be achieved by engineering a magnetic field at each well by placing a, "magnetic tip," under each well and exposing the array to a uniform magnetic field which would create a magnetic gradient at each well in order to trap magnetic particles. A computational COMSOL model was created to determine the ideal shapes for the magnetic tips, but fabrication factors and the COMSOL model led to the tips being the same shape as the wells. Dip coating, centrifuging, and electrophoresis of iron oxide particles were tried as methods to fabricate magnetic tips. Electroplating the particles was determined to be the best method. Microscale arrays were fabricated and tested with micron scale beads in 3 different well sizes. Then smaller grooves were created by drop casting PMMA groves using PDMS imprints of CDs. Electron beam lithography and stamping into spin coated PMMA were also tried briefly. Trapping of 350 nm magnetic beads was attempted but was unsuccessful. Probably this occurred because the gradient produced by the magnetic tips was not strong enough to overcome the hydrodynamic forces of water that was swept over the array with Couette flows to clean the surface.

  9. MRI RF array decoupling method with magnetic wall distributed filters.

    PubMed

    Connell, Ian R O; Gilbert, Kyle M; Abou-Khousa, Mohamed A; Menon, Ravi S

    2015-04-01

    Multi-channel radio-frequency (RF) transmit coil arrays have been developed to mitigate many of the RF challenges associated with ultra-high field ( ? 7T) magnetic resonance imaging (MRI). These arrays can be used for parallel RF transmission to produce spatially tailored RF excitation over the field of view. However, the realization of such arrays remains a challenge due to significant reactive interaction between the array coils, i.e., mutual coupling. In this paper, a novel bandstop filter ("magnetic wall") is used in an MRI RF transmit array to decouple individual coils. The proposed decoupling method is inspired by periodic resonator designs commonly used in frequency selective surfaces and is used as a distributed RF filter to suppress the transmission of RF energy between coils in an array. The decoupling of the magnetic wall (MW) is analyzed in terms of equivalent circuits that include terms for both magnetic and electric coupling for an arbitrary number of MW resonant conductors. Both frequency-and time-domain full-wave simulations were performed to analyze a specific MW structure. The performance of the proposed method is experimentally validated for both first-order coupling and higher-order coupling with a three-coil 7T array setup. Analysis and measurements confirm that the rejection band of the MW can be tuned to provide high isolation in the presence of cross coupling between RF array coils. PMID:25838388

  10. Fabrication, characterization and applications of magnetic nanowire arrays

    NASA Astrophysics Data System (ADS)

    Sharma, Gaurav

    Fe-Co-Ni ternary alloy nanowire arrays 32--106 nm in diameter are fabricated within nanoporous alumina membranes using 15 Vrms alternating current electrodeposition at frequencies of 50, 250, 500, 750, and 1000 Hz. The alumina membranes, 10--15 microns thick, are synthesized by anodization of aluminum foil using a two-step technique to increase pore uniformity. The alumina membrane structure is tailored with the end aim being uniform magnetic nanowire electrodeposition. Using an electrodeposition frequency of 1000 Hz, 15 Vrms, consistently and repeatably yield nanowire arrays over membranes several cm2 in extent. Electrochemical Impedance Spectroscopy (EIS) is used to explain the effects of AC electrodeposition frequency. The impedance of the residual alumina barrier layer, separating the underlying aluminum metal and the nanoporous membrane, decreases drastically with electrodeposition frequency facilitating uniform pore-filling of samples several cm2 in area. The magnetic coercivity and hysteresis loop squareness-ratio (Mr/Ms) were studied as functions of electrolyte composition, nanowire diameter, and nanowire aspect ratio. Anodic polarization studies on thin films having alloy compositions identical to the nanowires display excellent corrosion resistance properties. Two potential applications of the nanowire arrays are investigated. Iron nanowire arrays, oriented perpendicular to the substrate, are fabricated by electrodeposition of iron in nanoporous alumina membranes, followed by precise wet etching of the alumina membrane to partially expose the nanowire array. It is shown that oxidation of standing iron nanowire arrays, at 600C in an oxygen ambient leads to standing alpha-Fe2O3 (hematite) nanowire arrays. These hematite nanowire arrays show a distinct photocurrent response and can be used as photocatalysts. Second, protein adsorption studies on standing Fe-Co-Ni nanowire arrays and flat Fe-Co-Ni thin films show that nanowire array morphology leads to attenuation of protein adsorption. Since protein adsorption is the first step in the biofouling process magnetic nanowire arrays can potentially find applications as non-biofouling surfaces. Placing magnetic nanowire arrays in a sinusoidally varying magnetic field leads to their oscillation that further reduces protein adsorption in comparison to stationary nanowire arrays.

  11. Practical method using superposition of individual magnetic fields for initial arrangement of undulator magnets

    NASA Astrophysics Data System (ADS)

    Tsuchiya, K.; Shioya, T.

    2015-04-01

    We have developed a practical method for determining an excellent initial arrangement of magnetic arrays for a pure-magnet Halbach-type undulator. In this method, the longitudinal magnetic field distribution of each magnet is measured using a moving Hall probe system along the beam axis with a high positional resolution. The initial arrangement of magnetic arrays is optimized and selected by analyzing the superposition of all distribution data in order to achieve adequate spectral quality for the undulator. We applied this method to two elliptically polarizing undulators (EPUs), called U#16-2 and U#02-2, at the Photon Factory storage ring (PF ring) in the High Energy Accelerator Research Organization (KEK). The measured field distribution of the undulator was demonstrated to be excellent for the initial arrangement of the magnet array, and this method saved a great deal of effort in adjusting the magnetic fields of EPUs.

  12. Practical method using superposition of individual magnetic fields for initial arrangement of undulator magnets.

    PubMed

    Tsuchiya, K; Shioya, T

    2015-04-01

    We have developed a practical method for determining an excellent initial arrangement of magnetic arrays for a pure-magnet Halbach-type undulator. In this method, the longitudinal magnetic field distribution of each magnet is measured using a moving Hall probe system along the beam axis with a high positional resolution. The initial arrangement of magnetic arrays is optimized and selected by analyzing the superposition of all distribution data in order to achieve adequate spectral quality for the undulator. We applied this method to two elliptically polarizing undulators (EPUs), called U#16-2 and U#02-2, at the Photon Factory storage ring (PF ring) in the High Energy Accelerator Research Organization (KEK). The measured field distribution of the undulator was demonstrated to be excellent for the initial arrangement of the magnet array, and this method saved a great deal of effort in adjusting the magnetic fields of EPUs. PMID:25933853

  13. Practical method using superposition of individual magnetic fields for initial arrangement of undulator magnets

    SciTech Connect

    Tsuchiya, K.; Shioya, T.

    2015-04-15

    We have developed a practical method for determining an excellent initial arrangement of magnetic arrays for a pure-magnet Halbach-type undulator. In this method, the longitudinal magnetic field distribution of each magnet is measured using a moving Hall probe system along the beam axis with a high positional resolution. The initial arrangement of magnetic arrays is optimized and selected by analyzing the superposition of all distribution data in order to achieve adequate spectral quality for the undulator. We applied this method to two elliptically polarizing undulators (EPUs), called U#16-2 and U#02-2, at the Photon Factory storage ring (PF ring) in the High Energy Accelerator Research Organization (KEK). The measured field distribution of the undulator was demonstrated to be excellent for the initial arrangement of the magnet array, and this method saved a great deal of effort in adjusting the magnetic fields of EPUs.

  14. Collective Magnetic Behavior of Geometrically Frustrated Arrays with Perpendicular Anisotropy

    NASA Astrophysics Data System (ADS)

    Pan, Y.; Kohli, K. K.; Fraleigh, R.; Balk, A. L.; Finkel, D.; Zhang, S.; Li, J.; Gilbert, I.; Lammert, P. E.; Misra, R.; Crespi, V. H.; Schiffer, P.; Samarth, N.; Erickson, M.; Leighton, C.

    2012-02-01

    We use the magneto-optical Kerr effect (MOKE) to study the global and local magnetic behavior of geometrically frustrated arrays of single domain ferromagnetic islands with perpendicular anisotropy. MOKE measurements over macroscopic length scales probe the global properties of arrays with different lattice geometries and island spacings. The variation of switching field as a function of island spacing gives us insight into the influence of local frustration on the collective magnetic response of the arrays. The experimental results are compared with mean field calculations. Finally, we use spatially resolved Kerr microscopy to probe nucleation and domain propagation in the magnetization reversal process. Supported by U.S. Department of Energy Award DE-SC0005313. Lithography performed with the support of the National Nanotechnology Infrastructure Network

  15. Magnetic domain structure in small diameter magnetic nanowire arrays [rapid communication

    NASA Astrophysics Data System (ADS)

    Qin, Dong-Huan; Zhang, Hao-Li; Xu, Cai-Ling; Xu, Tao; Li, Hu-Lin

    2005-01-01

    Fe 0.3Co 0.7 alloy nanowire arrays were prepared by ac electrodepositing Fe 2+ and Co 2+ into a porous anodic aluminum oxide (PAO) template with diameter about 50 nm. The surface of the samples were polished by 100 nm diamond particle then chemical polishing to give a very smooth surface (below 10 nm/?m 2). The morphology properties were characterized by SEM and AFM. The bulk magnetic properties and domain structure of nanowire arrays were investigated by VSM and MFM respectively. We found that such alloy arrays showed strong perpendicular magnetic anisotropy with easy axis parallel to nanowire arrays. Each nanowire was in single domain structure with several opposite single domains surrounding it. Additionally, we investigated the domain structure with a variable external magnetic field applied parallel to the nanowire arrays. The MFM results showed a good agreement with our magnetic hysteresis loop.

  16. Periodic magnetic domains in single-crystalline cobalt filament arrays

    NASA Astrophysics Data System (ADS)

    Chen, Fei; Wang, Fan; Jia, Fei; Li, Jingning; Liu, Kai; Huang, Sunxiang; Luan, Zhongzhi; Wu, Di; Chen, Yanbin; Zhu, Jianmin; Peng, Ru-Wen; Wang, Mu

    2016-02-01

    Magnetic structures with controlled domain wall pattern may be applied as potential building blocks for three-dimensional magnetic memory and logic devices. Using a unique electrochemical self-assembly method, we achieve regular single-crystalline cobalt filament arrays with specific geometric profile and crystallographic orientation, and the magnetic domain configuration can be conveniently tailored. We report the transition of periodic antiparallel magnetic domains to compressed vortex magnetic domains depending on the ratio of height to width of the wires. A "phase diagram" is obtained to describe the dependence of the type of magnetic domain and the geometrical profiles of the wires. Magnetoresistance of the filaments demonstrates that the contribution of a series of 180∘ domain walls is over 0.15 % of the zero-field resistance ρ (H =0 ) . These self-assembled magnetic nanofilaments, with controlled periodic domain patterns, offer an interesting platform to explore domain-wall-based memory and logic devices.

  17. Large area magnetic micropallet arrays for cell colony sorting.

    PubMed

    Cox-Muranami, Wesley A; Nelson, Edward L; Li, G P; Bachman, Mark

    2015-12-15

    A new micropallet array platform for adherent cell colony sorting has been developed. The platform consisted of thousands of square plastic pallets, 270 μm by 270 μm on each side, large enough to hold a single colony of cells. Each pallet included a magnetic core, allowing them to be collected with a magnet after being released using a microscope mounted laser system. The micropallets were patterned from 1002F epoxy resist and were fabricated on translucent, gold coated microscope slides. The gold layer was used as seed for electroplating the ferromagnetic cores within every individual pallet. The gold layer also facilitated the release of each micropallet during laser release. This array allows for individual observation, sorting and collection of isolated cell colonies for biological cell colony research. In addition to consistent release and recovery of individual colonies, we demonstrated stable biocompatibility and minimal loss in imaging quality compared to previously developed micropallet arrays. PMID:26606460

  18. Electrodeposition of highly uniform magnetic nanoparticle arrays in ordered alumite

    NASA Astrophysics Data System (ADS)

    Sun, Ming; Zangari, Giovanni; Shamsuzzoha, Mohammad; Metzger, Robert M.

    2001-05-01

    We report the fabrication of nanometer scale ordered arrays of magnetic cylindrical nanoparticles with low aspect ratio (height/radius a=0.2-7) and ultrahigh uniformity. Anodization and electrochemical deposition are employed for template synthesis and metal particle growth, respectively. Particle uniformity is achieved by an electrodeposition scheme, utilizing pulse reverse voltage wave forms to control nucleation and growth of the particles. The resulting nanoparticles are polycrystalline and grains are randomly oriented. The magnetic properties of the array are dominated by particle shape and by interparticle magnetostatic interactions. A very clear transition of the anisotropy from perpendicular to in plane is observed at an aspect ratio a of about two. The arrays exhibit good thermal stability, demonstrating a great potential of these structures as future recording media in a patterned scheme. The pulse reverse electrodeposition technique shows great promise for the synthesis of nanostructures of various nature.

  19. Electrochemically synthesized magnetic nanowire heterostructures and arrays for acoustic sensing

    NASA Astrophysics Data System (ADS)

    McGary, Patrick David

    Biological cilia in humans and animals serve many functions, including sensing of acoustic and sensory signals and actuation for mobility in small species or for motion of bodily fluids in larger species. This work sought to fabricate nanowire arrays as artificial cilia. Arrays of tiny sensors at nanoscale dimensions have theoretical advantages to macroscale sensors including higher spatial resolution, miniscule size, and higher ultimate strength for each sensing element. Theoretical investigations showed that a magnetic/non-magnetic heterostructure would enable nanowires with improved sensitivity over single element nanowires. Here, nanowire structures included a soft magnetostrictive sensing segment (such as Ni or Fe1-xGax [also called galfenol]), a permanent magnetic segment to provide an integrated magnetic bias, and a long and hard non-magnetic end segment to increase the viscous drag force of the fluid on the nanowire. Galfenol is a new large magnetostrictive material that has moderate magnetostriction but excellent mechanical properties. This work included the first successful electroplating process for this unique alloy. This enabled the fabrication of these alloys into nanoscopic form. These nanowire structures were grown into nanoporous anodic aluminum oxide (AAO) templates using a robust two-step anodization process. When grown at the proper conditions (temperature, electrolyte, and voltage), the templates contained highly-ordered nanopores with small diameters (10-100 nm), short center-to-center distances (25-250 nm), and long lengths (0.1-100 mum). Metal contacts were deposited onto one side of the templates, and magnetostrictive, magnetic, and non-magnetic materials were sequentially electrodeposited into the nanopores. Controlling the non-magnetic segment lengths enabled control of the nanowire resonant frequency. By using graded nanowire lengths across the array, frequency filtering as a pre-filter for subsequent signal processing could be performed. The metallic electroplating of Fe-Ga alloys has been thoroughly described, and the process for producing the complete structure for magnetic heterostructures for biomimetic cilia has been achieved.

  20. Decoupled coil detector array in magnetic resonance imaging

    NASA Astrophysics Data System (ADS)

    Kwiat, Doron; Einav, Shmuel

    1991-07-01

    A method for Magnetic Resonance Imaging (MRI) was investigated, whereby an object is put under a homogeneous magnetic field, and the image is obtained by applying inverse source procedures to the data collected in an array of coil detectors surrounding the object. The induced current in each coil due to the precession of the magnetic dipole in each voxel depends on the characteristics of both the magnetic dipole frequency and strength, together with its distance from the coil, the coil direction in space and the electrical properties of the coils. By calculating the induced current signals over an array of coil detectors, a relationship is established between the set of signals and the structure of the body under investigation. Based on the proposed method, a computer simulation demonstrates the feasibility of this new modality. An improved method of multicoil recording is also suggested, whereby it is combined with the conventional zeugmatographic method with read and phase gradients, to result in a novel method of magnetic resonance imaging. In the combined method an equivalent number of coils is used instead of encoding gradients. The number of coils is thus reduced many times in comparison with the method where only a multicoil array is used. An experimental setup with a 9 coils detector array was built to give a coarse resolution of 3X3 pixels. By measuring the induced current signals over this array of coil detectors, a relationship is established between the set of signals and the structure of the body under investigation. The linear relation can then be represented in matrix notation, and inversion of this matrix will produce an image of the body.

  1. Power generation from human body motion through magnet and coil arrays with magnetic spring

    NASA Astrophysics Data System (ADS)

    Zhang, Qian; Wang, Yufeng; Kim, Eun Sok

    2014-02-01

    This article presents a hand-held electromagnetic energy harvester which can be used to harvest tens of mW power level from human body motion. A magnet array, aligned to a coil array for maximum magnetic flux change, is suspended by a magnetic spring for a resonant frequency of several Hz and is stabilized horizontally by graphite sheets for reducing the friction. An analytical model of vibration-driven energy harvester with magnetic spring through magnet and coil arrays is developed to explore the power generation from vibrations at low frequency and large amplitude. When the energy harvester (occupying 120 cc and weighing 180 g) is placed in a backpack of a human walking at various speeds, the power output increases as the walking speed increases from 0.45 m/s (slow walking) to 3.58 m/s (slow running), and reaches 32 mW at 3.58 m/s.

  2. Microfabricated atomic vapor cell arrays for magnetic field measurements

    SciTech Connect

    Woetzel, S.; Schultze, V.; IJsselsteijn, R.; Schulz, T.; Anders, S.; Stolz, R.; Meyer, H.-G.

    2011-03-15

    We describe a method for charging atomic vapor cells with cesium and buffer gas. By this, it is possible to adjust the buffer gas pressure in the cells with good accuracy. Furthermore, we present a new design of microfabricated vapor cell arrays, which combine silicon wafer based microfabrication and ultrasonic machining to achieve the arrays of thermally separated cells with 50 mm{sup 3} volume. With cells fabricated in the outlined way, intrinsic magnetic field sensitivities down to 300 fT/Hz{sup 1/2} are reached.

  3. Angular resonant absorption curves in magnetic nanowire arrays

    NASA Astrophysics Data System (ADS)

    Cimpoesu, Dorin; Ding, Junjia; Stoleriu, Laurentiu; Adeyeye, Adekunle; Stancu, Alexandru; Spinu, Leonard

    2013-06-01

    We systematically probed the dynamics of two-dimensional Ni80Fe20 nanowire arrays with different strengths of interwire interactions using angular dependent microwave absorption spectroscopy. The experimental results are analyzed in terms of a graphical representation of the resonant absorption data through a critical-curve-like approach. This representation has the advantage of offering a direct and complete visual representation of anisotropy, interactions, and magnetization dynamics effects in nanomagnet arrays. In the paper, the connection between the proposed image of polar resonant absorption curves and the static switching field critical curves is substantiated using both macrospin and fully micromagnetic simulation approaches.

  4. Micro-magnet arrays for specific single bacterial cell positioning

    NASA Astrophysics Data System (ADS)

    Pivetal, Jérémy; Royet, David; Ciuta, Georgeta; Frenea-Robin, Marie; Haddour, Naoufel; Dempsey, Nora M.; Dumas-Bouchiat, Frédéric; Simonet, Pascal

    2015-04-01

    In various contexts such as pathogen detection or analysis of microbial diversity where cellular heterogeneity must be taken into account, there is a growing need for tools and methods that enable microbiologists to analyze bacterial cells individually. One of the main challenges in the development of new platforms for single cell studies is to perform precise cell positioning, but the ability to specifically target cells is also important in many applications. In this work, we report the development of new strategies to selectively trap single bacterial cells upon large arrays, based on the use of micro-magnets. Escherichia coli bacteria were used to demonstrate magnetically driven bacterial cell organization. In order to provide a flexible approach adaptable to several applications in the field of microbiology, cells were magnetically and specifically labeled using two different strategies, namely immunomagnetic labeling and magnetic in situ hybridization. Results show that centimeter-sized arrays of targeted, isolated bacteria can be successfully created upon the surface of a flat magnetically patterned hard magnetic film. Efforts are now being directed towards the integration of a detection tool to provide a complete micro-system device for a variety of microbiological applications.

  5. Life on Magnets: Stem Cell Networking on Micro-Magnet Arrays

    PubMed Central

    Zablotskii, Vitalii; Dejneka, Alexandr; Kubinov, rka; Le-Roy, Damien; Dumas-Bouchiat, Frdric; Givord, Dominique; Dempsey, Nora M.; Sykov, Eva

    2013-01-01

    Interactions between a micro-magnet array and living cells may guide the establishment of cell networks due to the cellular response to a magnetic field. To manipulate mesenchymal stem cells free of magnetic nanoparticles by a high magnetic field gradient, we used high quality micro-patterned NdFeB films around which the stray fields value and direction drastically change across the cell body. Such micro-magnet arrays coated with parylene produce high magnetic field gradients that affect the cells in two main ways: i) causing cell migration and adherence to a covered magnetic surface and ii) elongating the cells in the directions parallel to the edges of the micro-magnet. To explain these effects, three putative mechanisms that incorporate both physical and biological factors influencing the cells are suggested. It is shown that the static high magnetic field gradient generated by the micro-magnet arrays are capable of assisting cell migration to those areas with the strongest magnetic field gradient, thereby allowing the build up of tunable interconnected stem cell networks, which is an elegant route for tissue engineering and regenerative medicine. PMID:23936425

  6. Design and optimization of arrays of neodymium iron boron-based magnets for magnetic tweezers applications

    SciTech Connect

    Zacchia, Nicholas A.; Valentine, Megan T.

    2015-05-15

    We present the design methodology for arrays of neodymium iron boron (NdFeB)-based magnets for use in magnetic tweezers devices. Using finite element analysis (FEA), we optimized the geometry of the NdFeB magnet as well as the geometry of iron yokes designed to focus the magnetic fields toward the sample plane. Together, the magnets and yokes form a magnetic array which is the basis of the magnetic tweezers device. By systematically varying 15 distinct shape parameters, we determined those features that maximize the magnitude of the magnetic field gradient as well as the length scale over which the magnetic force operates. Additionally, we demonstrated that magnetic saturation of the yoke material leads to intrinsic limitations in any geometric design. Using this approach, we generated a compact and light-weight magnetic tweezers device that produces a high field gradient at the image plane in order to apply large forces to magnetic beads. We then fabricated the optimized yoke and validated the FEA by experimentally mapping the magnetic field of the device. The optimization data and iterative FEA approach outlined here will enable the streamlined design and construction of specialized instrumentation for force-sensitive microscopy.

  7. Design and optimization of arrays of neodymium iron boron-based magnets for magnetic tweezers applications.

    PubMed

    Zacchia, Nicholas A; Valentine, Megan T

    2015-05-01

    We present the design methodology for arrays of neodymium iron boron (NdFeB)-based magnets for use in magnetic tweezers devices. Using finite element analysis (FEA), we optimized the geometry of the NdFeB magnet as well as the geometry of iron yokes designed to focus the magnetic fields toward the sample plane. Together, the magnets and yokes form a magnetic array which is the basis of the magnetic tweezers device. By systematically varying 15 distinct shape parameters, we determined those features that maximize the magnitude of the magnetic field gradient as well as the length scale over which the magnetic force operates. Additionally, we demonstrated that magnetic saturation of the yoke material leads to intrinsic limitations in any geometric design. Using this approach, we generated a compact and light-weight magnetic tweezers device that produces a high field gradient at the image plane in order to apply large forces to magnetic beads. We then fabricated the optimized yoke and validated the FEA by experimentally mapping the magnetic field of the device. The optimization data and iterative FEA approach outlined here will enable the streamlined design and construction of specialized instrumentation for force-sensitive microscopy. PMID:26026529

  8. Domain configuration and magnetization switching in arrays of permalloy nanostripes

    NASA Astrophysics Data System (ADS)

    Iglesias-Freire, .; Jaafar, M.; Prez, L.; de Abril, O.; Vzquez, M.; Asenjo, A.

    2014-04-01

    The proximity effect in the collective behavior of arrays of magnetic nanostripes is currently a subject of intensive research. The imperative of reducing the size and distances between elements in order to achieve higher storage capacity, faster access to the information as well as low energy consumption, brings consequences about the isolated behavior of the elements and devices. Parallel to each other permalloy nanostripes with high aspect ratio have been prepared by the nanolithography technique. The evolution of the closure domains and the magnetization direction in individual nanostructures has been imaged under applied magnetic fields using Variable Field Magnetic Force Microscopy. Moreover, the magnetostatic interactions between neighboring elements and the proximity effects in arrays of such nanostructures have been quantitatively analyzed by Magnetic Force Microscopy and micromagnetic simulations. The agreement between simulations and the experimental results allows us to conclude the relevance of those interactions depending on the geometry characteristics. In particular, results suggest that the magnetostatic coupling between adjacent nanostripes vanishes for separation distances higher than 500 nm.

  9. MEMS Batch Fabrication of the Bipolar Micro Magnet Array for Electromagnetic Vibration Harvester

    NASA Astrophysics Data System (ADS)

    Yamaguchi, K.; Fujita, T.; Tanaka, Y.; Takehira, N.; Sonoda, K.; Kanda, K.; Maenaka, K.

    2014-11-01

    This article introduces a MEMS batch fabrication process of micro magnet array with bipolar magnetic pole for an electromagnetic vibration energy harvester. In order to obtain the large electromotive force from large magnetic flux density change, we established the fine patterned alternating magnetized bipolar magnetic structure. The batch fabrication process of bipolar magnet array is composed of two wafers processing with S-pole and N-pole magnetization and bonding process. By the prototype fabrication of bipolar magnet with the 200 ?m SN-interval, we showed the usability of the batch fabrication process of the bipolar magnet array. In addition, we estimated the generated power of energy harvester with a bipolar magnet array. Compared to a harvester with monopolar magnet array, we showed the good result for bipolar one.

  10. Localization of dense intracranial electrode arrays using magnetic resonance imaging.

    PubMed

    Yang, Andrew I; Wang, Xiuyuan; Doyle, Werner K; Halgren, Eric; Carlson, Chad; Belcher, Thomas L; Cash, Sydney S; Devinsky, Orrin; Thesen, Thomas

    2012-10-15

    Intracranial electrode arrays are routinely used in the pre-surgical evaluation of patients with medically refractory epilepsy, and recordings from these electrodes have been increasingly employed in human cognitive neurophysiology due to their high spatial and temporal resolution. For both researchers and clinicians, it is critical to localize electrode positions relative to the subject-specific neuroanatomy. In many centers, a post-implantation MRI is utilized for electrode detection because of its higher sensitivity for surgical complications and the absence of radiation. However, magnetic susceptibility artifacts surrounding each electrode prohibit unambiguous detection of individual electrodes, especially those that are embedded within dense grid arrays. Here, we present an efficient method to accurately localize intracranial electrode arrays based on pre- and post-implantation MR images that incorporates array geometry and the individual's cortical surface. Electrodes are directly visualized relative to the underlying gyral anatomy of the reconstructed cortical surface of individual patients. Validation of this approach shows high spatial accuracy of the localized electrode positions (mean of 0.96 mm 0.81 mm for 271 electrodes across 8 patients). Minimal user input, short processing time, and utilization of radiation-free imaging are strong incentives to incorporate quantitatively accurate localization of intracranial electrode arrays with MRI for research and clinical purposes. Co-registration to a standard brain atlas further allows inter-subject comparisons and relation of intracranial EEG findings to the larger body of neuroimaging literature. PMID:22759995

  11. Dependence of magnetization process on thickness of Permalloy antidot arrays

    SciTech Connect

    Merazzo, K. J.; Real, R. P. del; Asenjo, A.; Vazquez, M.

    2011-04-01

    Nanohole films or antidot arrays of Permalloy have been prepared by the sputtering of Ni{sub 80}Fe{sub 20} onto anodic alumina membrane templates. The film thickness varies from 5 to 47 nm and the antidot diameters go from 42 to 61 nm, for a hexagonal lattice parameter of 105 nm. For the thinner antidot films (5 and 10 nm thick), magnetic moments locally distribute in a complex manner to reduce the magnetostatic energy, and their mostly reversible magnetization process is ascribed to spin rotations. In the case of the thicker (20 and 47 nm) antidot films, pseudodomain walls appear and the magnetization process is mostly irreversible where hysteresis denotes the effect of nanoholes pinning to wall motion.

  12. Size and shape dependence study of magnetization reversal in magnetic antidot lattice arrays

    NASA Astrophysics Data System (ADS)

    Mallick, Sougata; Bedanta, Subhankar

    2015-05-01

    Magnetic Antidot Lattice (MAL) arrays of Co have been prepared in micron range using ultraviolet (UV) lithography technique with different shapes and sizes. Magnetization reversal in such MAL systems has been studied by magneto-optic Kerr effect (MOKE) based microscopy by varying the angle between the easy axis and the external magnetic field. The domain images evidence that the magnetization reversal along easy axis is highly dominated by nucleation of domains which is subsequently accompanied by domain wall motion. We have observed that with increase in active magnetic area domain size increases but on the contrary coercivity decreases. The presence of periodic holes turns the MALs magnetically hard when compared to similar thickness of continuous thin film. The magnetization relaxation along easy axis for the Co MAL at constant dc field fits very well with the exponential law of Fatuzzo-Labrune indicating domain nucleated dominant process.

  13. Spinmotive force due to motion of magnetic bubble arrays driven by magnetic field gradient

    PubMed Central

    Yamane, Yuta; Hemmatiyan, Shayan; Ieda, Jun'ichi; Maekawa, Sadamichi; Sinova, Jairo

    2014-01-01

    Interaction between local magnetization and conduction electrons is responsible for a variety of phenomena in magnetic materials. It has been recently shown that spin current and associated electric voltage can be induced by magnetization that depends on both time and space. This effect, called spinmotive force, provides for a powerful tool for exploring the dynamics and the nature of magnetic textures, as well as a new source for electromotive force. Here we theoretically demonstrate the generation of electric voltages in magnetic bubble array systems subjected to a magnetic field gradient. It is shown by deriving expressions for the electric voltages that the present system offers a direct measure of phenomenological parameter ? that describes non-adiabaticity in the current induced magnetization dynamics. This spinmotive force opens a door for new types of spintronic devices that exploit the field-gradient. PMID:25365971

  14. Spinmotive force due to motion of magnetic bubble arrays driven by magnetic field gradient.

    PubMed

    Yamane, Yuta; Hemmatiyan, Shayan; Ieda, Jun'ichi; Maekawa, Sadamichi; Sinova, Jairo

    2014-01-01

    Interaction between local magnetization and conduction electrons is responsible for a variety of phenomena in magnetic materials. It has been recently shown that spin current and associated electric voltage can be induced by magnetization that depends on both time and space. This effect, called spinmotive force, provides for a powerful tool for exploring the dynamics and the nature of magnetic textures, as well as a new source for electromotive force. Here we theoretically demonstrate the generation of electric voltages in magnetic bubble array systems subjected to a magnetic field gradient. It is shown by deriving expressions for the electric voltages that the present system offers a direct measure of phenomenological parameter ? that describes non-adiabaticity in the current induced magnetization dynamics. This spinmotive force opens a door for new types of spintronic devices that exploit the field-gradient. PMID:25365971

  15. Spinmotive force due to motion of magnetic bubble arrays driven by magnetic field gradient

    NASA Astrophysics Data System (ADS)

    Yamane, Yuta; Hemmatiyan, Shayan; Ieda, Jun'ichi; Maekawa, Sadamichi; Sinova, Jairo

    2014-11-01

    Interaction between local magnetization and conduction electrons is responsible for a variety of phenomena in magnetic materials. It has been recently shown that spin current and associated electric voltage can be induced by magnetization that depends on both time and space. This effect, called spinmotive force, provides for a powerful tool for exploring the dynamics and the nature of magnetic textures, as well as a new source for electromotive force. Here we theoretically demonstrate the generation of electric voltages in magnetic bubble array systems subjected to a magnetic field gradient. It is shown by deriving expressions for the electric voltages that the present system offers a direct measure of phenomenological parameter ? that describes non-adiabaticity in the current induced magnetization dynamics. This spinmotive force opens a door for new types of spintronic devices that exploit the field-gradient.

  16. Parallel RNA extraction using magnetic beads and a droplet array

    PubMed Central

    Shi, Xu; Chen, Chun-Hong; Gao, Weimin; Meldrum, Deirdre R.

    2015-01-01

    Nucleic acid extraction is a necessary step for most genomic/transcriptomic analyses, but it often requires complicated mechanisms to be integrated into a lab-on-a-chip device. Here, we present a simple, effective configuration for rapidly obtaining purified RNA from low concentration cell medium. This Total RNA Extraction Droplet Array (TREDA) utilizes an array of surface-adhering droplets to facilitate the transportation of magnetic purification beads seamlessly through individual buffer solutions without solid structures. The fabrication of TREDA chips is rapid and does not require a microfabrication facility or expertise. The process takes less than 5 minutes. When purifying mRNA from bulk marine diatom samples, its repeatability and extraction efficiency are comparable to conventional tube-based operations. We demonstrate that TREDA can extract the total mRNA of about 10 marine diatom cells, indicating that the sensitivity of TREDA approaches single-digit cell numbers. PMID:25519439

  17. Development of a Magnetic Nanoparticle Susceptibility Magnitude Imaging Array

    PubMed Central

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

    2014-01-01

    There are several emerging diagnostic and therapeutic applications of magnetic nanoparticles (mNPs) in medicine. This study examines the potential for developing an mNP imager that meets these emerging clinical needs with a low cost imaging solution that uses arrays of digitally controlled drive coils in a multiple-frequency, continuous-wave operating mode and compensated fluxgate magnetometers. The design approach is described and a mathematical model is developed to support measurement and imaging. A prototype is used to demonstrate active compensation of up to 185 times the primary applied magnetic field, depth sensitivity up to 2.5 cm (p < 0.01), and linearity over 5 dilutions (R2 > 0.98, p <0.001). System frequency responses show distinguishable readouts for iron oxide mNPs with single magnetic domain core diameters of 10 nm and 40 nm, and multi-domain mNPs with a hydrodynamic diameter of 100 nm. Tomographic images show a contrast-to-noise ratio of 23 for 0.5 ml of 12.5 mg Fe/ml mNPs at 1 cm depth. A demonstration involving the injection of mNPs into pork sausage shows the potential for use in biological systems. These results indicate that the proposed mNP imaging approach can potentially be extended to a larger array system with higher-resolution. PMID:24504184

  18. Development of a magnetic nanoparticle susceptibility magnitude imaging array.

    PubMed

    Ficko, Bradley W; Nadar, Priyanka M; Hoopes, P Jack; Diamond, Solomon G

    2014-02-21

    There are several emerging diagnostic and therapeutic applications of magnetic nanoparticles (mNPs) in medicine. This study examines the potential for developing an mNP imager that meets these emerging clinical needs with a low cost imaging solution that uses arrays of digitally controlled drive coils in a multiple-frequency, continuous-wave operating mode and compensated fluxgate magnetometers. The design approach is described and a mathematical model is developed to support measurement and imaging. A prototype is used to demonstrate active compensation of up to 185 times the primary applied magnetic field, depth sensitivity up to 2.5 cm (p < 0.01), and linearity over five dilutions (R(2) > 0.98, p < 0.001). System frequency responses show distinguishable readouts for iron oxide mNPs with single magnetic domain core diameters of 10 and 40 nm, and multi-domain mNPs with a hydrodynamic diameter of 100 nm. Tomographic images show a contrast-to-noise ratio of 23 for 0.5 ml of 12.5 mg Fe ml(-1) mNPs at 1 cm depth. A demonstration involving the injection of mNPs into pork sausage shows the potential for use in biological systems. These results indicate that the proposed mNP imaging approach can potentially be extended to a larger array system with higher-resolution. PMID:24504184

  19. Development of a magnetic nanoparticle susceptibility magnitude imaging array

    NASA Astrophysics Data System (ADS)

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

    2014-02-01

    There are several emerging diagnostic and therapeutic applications of magnetic nanoparticles (mNPs) in medicine. This study examines the potential for developing an mNP imager that meets these emerging clinical needs with a low cost imaging solution that uses arrays of digitally controlled drive coils in a multiple-frequency, continuous-wave operating mode and compensated fluxgate magnetometers. The design approach is described and a mathematical model is developed to support measurement and imaging. A prototype is used to demonstrate active compensation of up to 185 times the primary applied magnetic field, depth sensitivity up to 2.5 cm (p < 0.01), and linearity over five dilutions (R2 > 0.98, p < 0.001). System frequency responses show distinguishable readouts for iron oxide mNPs with single magnetic domain core diameters of 10 and 40 nm, and multi-domain mNPs with a hydrodynamic diameter of 100 nm. Tomographic images show a contrast-to-noise ratio of 23 for 0.5 ml of 12.5 mg Fe ml-1 mNPs at 1 cm depth. A demonstration involving the injection of mNPs into pork sausage shows the potential for use in biological systems. These results indicate that the proposed mNP imaging approach can potentially be extended to a larger array system with higher-resolution.

  20. Probing arrays of circular magnetic microdots by ferromagnetic resonance.

    SciTech Connect

    Kakazei, G. N.; Mewes, T.; Wigen, P. E.; Hammel, P. C.; Slavin, A. N.; Pogorelov, Y. G.; Costa, M. D.; Golub, V. O.; Guslienko, K. Y.; Novosad, V.

    2008-06-01

    X-band ferromagnetic resonance (FMR) was used to characterize in-plane magnetic anisotropies in rectangular and square arrays of circular nickel and Permalloy microdots. In the case of a rectangular lattice, as interdot distances in one direction decrease, the in-plane uniaxial anisotropy field increases, in good agreement with a simple theory of magnetostatically interacting uniformly magnetized dots. In the case of a square lattice a four-fold anisotropy of the in-plane FMR field H(r) was found when the interdot distance a gets comparable to the dot diameter D. This anisotropy, not expected in the case of uniformly magnetized dots, was explained by a non-uniform magnetization m(r) in a dot in response to dipolar forces in the patterned magnetic structure. It is well described by an iterative solution of a continuous variation procedure. In the case of perpendicular magnetization multiple sharp resonance peaks were observed below the main FMR peak in all the samples, and the relative positions of these peaks were independent of the interdot separations. Quantitative description of the observed multiresonance FMR spectra was given using the dipole-exchange spin wave dispersion equation for a perpendicularly magnetized film where in-plane wave vector is quantized due to the finite dot radius, and the inhomogenetiy of the intradot static demagnetization field in the nonellipsoidal dot is taken into account. It was demonstrated that ferromagnetic resonance force microscopy (FMRFM) can be used to determine both local and global properties of patterned submicron ferromagnetic samples. Local spectroscopy together with the possibility to vary the tip-sample spacing enables the separation of those two contributions to a FMRFM spectrum. The global FMR properties of circular submicron dots determined using magnetic resonance force microscopy are in a good agreement with results obtained using conventional FMR and with theoretical descriptions.

  1. Probing arrays of circular magnetic microdots by ferromagnetic resonance.

    PubMed

    Kakazei, G N; Mewes, T; Wigen, P E; Hammel, P C; Slavin, A N; Pogorelov, Yu G; Costa, M D; Golub, V O; Guslienko, K Yu; Novosad, V

    2008-06-01

    X-band ferromagnetic resonance (FMR) was used to characterize in-plane magnetic anisotropies in rectangular and square arrays of circular nickel and Permalloy microdots. In the case of a rectangular lattice, as interdot distances in one direction decrease, the in-plane uniaxial anisotropy field increases, in good agreement with a simple theory of magnetostatically interacting uniformly magnetized dots. In the case of a square lattice a four-fold anisotropy of the in-plane FMR field H(r) was found when the interdot distance a gets comparable to the dot diameter D. This anisotropy, not expected in the case of uniformly magnetized dots, was explained by a non-uniform magnetization m(r) in a dot in response to dipolar forces in the patterned magnetic structure. It is well described by an iterative solution of a continuous variation procedure. In the case of perpendicular magnetization multiple sharp resonance peaks were observed below the main FMR peak in all the samples, and the relative positions of these peaks were independent of the interdot separations. Quantitative description of the observed multiresonance FMR spectra was given using the dipole-exchange spin wave dispersion equation for a perpendicularly magnetized film where in-plane wave vector is quantized due to the finite dot radius, and the inhomogenetiy of the intradot static demagnetization field in the nonellipsoidal dot is taken into account. It was demonstrated that ferromagnetic resonance force microscopy (FMRFM) can be used to determine both local and global properties of patterned submicron ferromagnetic samples. Local spectroscopy together with the possibility to vary the tip-sample spacing enables the separation of those two contributions to a FMRFM spectrum. The global FMR properties of circular submicron dots determined using magnetic resonance force microscopy are in a good agreement with results obtained using conventional FMR and with theoretical descriptions. PMID:18681017

  2. Analysis and design optimization of ironless linear permanent magnet synchronous motors with non-overlapping concentrated windings for ultra-precision positioning system

    NASA Astrophysics Data System (ADS)

    Li, Liyi; Tang, Yongbin; Liu, Jiaxi; Chen, Qiming

    2013-01-01

    This paper presents the electromagnetic design of Ironless permanent magnet linear synchronous motor with non-overlapping concentrated windings based on the Equivalent Magnetizing Current(EMC) method. For one such motor structure we give analytical formulae for its magnetic field and thrust density and analyze to improve air-gap flux density and thrust density by varying motor design parameters. In order to minimize thrust ripple and improve thrust density, we analyze the superiority of ILPMLSM with Halbach magnet array and fractional-slot concentrated winding. The validity of the proposed technique is confirmed with 2-D Finite Element (FE) analysis.

  3. Ordered magnetic multilayer nanobowl array by nanosphere template method

    NASA Astrophysics Data System (ADS)

    Zhang, Y. J.; Wang, Y. X.; Billups, W. E.; Liu, H. B.; Yang, J. H.

    2010-12-01

    Ordered magnetic multilayer [Co/Pt] n nanobowls have been fabricated over a silicon substrate based on a polystyrene (PS) monolayer film. The ordered PS monolayer was first prepared by the self-assembly technique, which was used as the template for the multilayer film [Co/Pt] n deposition. The ordered magnetic multilayer [Co/Pt] n nanobowl array was obtained after the transferring and the selective etching process. The nanobowls show a uniform size and smooth surfaces. The nanobowls stuck to the neighbors and notches were observed in the bowl brims because of the contact points between the closed-packed PS beads. The nanobowls could be separated from their neighbors by thinning the PS beads before the film deposition and no notches were observed anymore. Compared to the chemical method, this method showed more flexible choices of the material to fabricate the nanobowls, which extended the application scope of the nanobowls greatly.

  4. A superconducting quadrupole magnet array for a heavy ion fusion driver

    SciTech Connect

    Caspi, S.; Bangerter, r.; Chow, K.; Faltens, A.; Gourley, S.; Hinkins, R.; Gupta, R.; Lee, E.; McInturff, A.; Scanlan, R.; Taylor, C.; Wolgast, D.

    2000-06-27

    A multi-channel quadrupole array has been proposed to increase beam intensity and reduce space charge effects in a Heavy Ion Fusion Driver. A single array unit composed of several quadrupole magnets, each with its own beam line, will be placed within a ferromagnetic accelerating core whose cost is directly affected by the array size. A large number of focusing arrays will be needed along the accelerating path. The use of a superconducting quadrupole magnet array will increase the field and reduce overall cost. We report here on the design of a compact 3 x 3 superconducting quadrupole magnet array. The overall array diameter and length including the cryostat is 900 x 700 mm. Each of the 9 quadrupole magnets has a 78 mm warm bore and an operating gradient of 50 T/m over an effective magnetic length of 320 mm.

  5. A Microsystem for Magnetic Immunoassay Based on Planar Microcoil Array.

    PubMed

    Zheng, Yushan; Shang, Nan; Haddad, Pierre S; Sawan, Mohamad

    2016-04-01

    This work focuses on the circuit and system implementation of a microsystem platform for magnetic immunoassay, which is a novel type of diagnostic method using magnetic beads as labels. Three main challenges facing this work-design of a high performance sensor, packaging technique and design of integrated circuits are discussed. Planar microcoil array are exploited as sensor of magnetic beads, whereas ultra thin bottom microplate in traditional ELISA is used for the assay. Main circuits blocks include bidirectional current supply circuit, magnetic field sensing circuit and on-chip temperature sensor. Experiments using mouse IgG with different densities were performed on the proposed platform, results show that a minimum density of 100 pg/mL can be detected, which is a comparable sensitivity to conventional optical ELISA, and a quantitative relationship can be acquired in the range from 1 ng/ml to 1 ug/ml, thus this platform is suitable for quantitative analysis in practical health and environment application and has potential for medical diagnostics, food pathogen detection or water analysis. PMID:26173219

  6. Two-dimensional Magnetism in Arrays of Superconducting Rings

    NASA Astrophysics Data System (ADS)

    Reich, Daniel H.

    1996-03-01

    An array of superconducting rings in an applied field corresponding to a flux of ?0 /2 per ring behaves like a 2D Ising antiferromagnet. Each ring has two energetically equivalent states with equal and opposite magnetic moments due to fluxoid quantization, and the dipolar coupling between rings favors antiparallel alignment of the moments. Using SQUID magnetometry and scanning Hall probe microscopy, we have studied the dynamics and magnetic configurations of micron-size aluminum rings on square, triangular, honeycomb, and kagom lattices. We have found that there are significant antiferromagnetic correlations between rings, and that effects of geometrical frustration can be observed on the triangular and kagom lattices. Long range correlations on the other lattices are suppressed by the analog of spin freezing that locks the rings in metastable states at low temperatures, and by quenched disorder due to imperfections in the fabrication. This disorder produces a roughly 1% variation in the rings' areas, which translates into an effective random field on the spins. The ring arrays are thus an extremely good realization of the 2D random-field Ising model. (Performed in collaboration with D. Davidovi?, S. Kumar, J. Siegel, S. B. Field, R. C. Tiberio, R. Hey, and K. Ploog.) (Supported by NSF grants DMR-9222541, and DMR-9357518, and by the David and Lucile Packard Foundation.)

  7. Magnetic antenna excitation of whistler modes. II. Antenna arrays

    SciTech Connect

    Stenzel, R. L.; Urrutia, J. M.

    2014-12-15

    The excitation of whistler modes from magnetic loop antennas has been investigated experimentally. The field topology of the excited wave driven by a single loop antenna has been measured for different loop orientations with respect to the uniform background field. The fields from two or more antennas at different locations are then created by superposition of the single-loop data. It is shown that an antenna array can produce nearly plane waves which cannot be achieved with single antennas. By applying a phase shift along the array, oblique wave propagation is obtained. This allows a meaningful comparison with plane wave theory. The Gendrin mode and oblique cyclotron resonance are demonstrated. Wave helicity and polarization in space and time are demonstrated and distinguished from the magnetic helicity of the wave field. The superposition of two oblique plane whistler modes produces in a “whistler waveguide” mode whose polarization and helicity properties are explained. The results show that single point measurements cannot properly establish the wave character of wave packets. The laboratory observations are relevant for excitation and detection of whistler modes in space plasmas.

  8. Magnetic antenna excitation of whistler modes. II. Antenna arrays

    NASA Astrophysics Data System (ADS)

    Stenzel, R. L.; Urrutia, J. M.

    2014-12-01

    The excitation of whistler modes from magnetic loop antennas has been investigated experimentally. The field topology of the excited wave driven by a single loop antenna has been measured for different loop orientations with respect to the uniform background field. The fields from two or more antennas at different locations are then created by superposition of the single-loop data. It is shown that an antenna array can produce nearly plane waves which cannot be achieved with single antennas. By applying a phase shift along the array, oblique wave propagation is obtained. This allows a meaningful comparison with plane wave theory. The Gendrin mode and oblique cyclotron resonance are demonstrated. Wave helicity and polarization in space and time are demonstrated and distinguished from the magnetic helicity of the wave field. The superposition of two oblique plane whistler modes produces in a "whistler waveguide" mode whose polarization and helicity properties are explained. The results show that single point measurements cannot properly establish the wave character of wave packets. The laboratory observations are relevant for excitation and detection of whistler modes in space plasmas.

  9. Optimum receiver array design for magnetic induction tomography.

    PubMed

    Grsoy, Doga; Scharfetter, Hermann

    2009-05-01

    Magnetic induction tomography (MIT) is an imaging modality that aims at mapping the distribution of the electrical conductivity inside the body. Eddy currents are induced in the body by magnetic induction and the resulting fields are measured by an array of receiver coils. In MIT, the location of the receivers affects the quality of the image reconstruction. In this paper, a fast deterministic algorithm was applied to obtain optimum receiver array designs for a given specific excitation. The design strategy is based on the iterative exclusion of receiver locations, which yield poor conductivity information, from the space spanning all possible locations until a feasible design is reached. The applicability of "regionally focused" MIT designs that increase the image resolution at a particular region was demonstrated. Currently used design geometries and the corresponding reconstructed images were compared to the images obtained by optimized designs. The eigenvalue analysis of the Hessian matrix showed that the algorithm tends to maintain identical conductivity information content sensed by the receivers. Although the method does not guarantee finding the optimum design globally, the results demonstrate the practical usability of this algorithm in MIT experimental designs. PMID:19203883

  10. Comparing artificial frustrated magnets: geometric effects in nanomagnet arrays

    NASA Astrophysics Data System (ADS)

    Li, Jie; Ke, Xianglin; Nisoli, Cristiano; Lammert, Paul; Crespi, Vincent; Schiffer, Peter

    2009-03-01

    We have studied arrays of single-domain ferromagnetic islands arranged on lattices such that the magnetostatic interactions between the islands are frustrated by the geometry of the arrays. We compare results for three different lattice geometries: the previously studied square ``artificial spin ice'' lattice[1,2], a hexagonal lattice, and a ladder lattice which is topologically-equivalent to the former one. After the ac demagnetization the magnetic moment configurations are imaged via Magnetic Force Microscopy (MFM). We find that the ladder lattice shows local correlations which are similar to those of the square lattice, suggesting it as a basis for comparison of the energetics of the other two lattices. The normalized magnetostatic energy of all three geometries decreases with decreasing demagnetization step size, but the lattices approach their ground states at different rates. 1. R. F. Wang, C. Nisoli, R. S. Freitas, J. Li, W. McConville, B. J. Cooley, M. S. Lund, N. Samarth, C. Leighton, V. H. Crespi, and P. Schiffer, Nature 439, 303 (2006). 2. X. Ke, J. Li, C. Nisoli, P. E. Lammert, W. McConville, R. F. Wang, V. H. Crespi, and P. Schiffer, Phys. Rev. Lett. 101, 037205 (2008).

  11. Magnetic field effects in artificial dielectrics with arrays of magnetic wires at microwaves

    NASA Astrophysics Data System (ADS)

    Panina, L. V.; Ipatov, M.; Zhukova, V.; Zhukov, A.; Gonzalez, J.

    2011-03-01

    A magnetic field tunable electromagnetic response in periodic lattices of conducting magnetic wires is demonstrated. The wire medium having a negative permittivity in the lower frequency band is customarily investigated as an important component of so-called double negative metamaterials. Here we are interested in a strong dispersion of the permittivity in these structures and a possibility to alter it by changing the losses in magnetic wires with an external magnetic field. The theoretical approach is based on calculating the relaxation parameter depending on the wire surface impedance, and hence, on the wire magnetic properties. Thus, in arrays of Co-based amorphous wires the application of a moderate magnetic field (of about 1-2 kA/m) which causes the magnetization reorientation is capable of few fold permittivity change in the frequency range of 1-2 GHz. Such efficient tuning for certain structural and magnetic parameters was confirmed experimentally by measuring the transmission and reflection spectra from lattices of Co66Fe3.5B16Si11Cr3.5 glass-coated amorphous wires with a different wire cross-section and a different lattice period. The chosen wires are also confirmed to show a large magnetoimpedance effect at GHz frequencies, which constitutes the underlying mechanism of magnetic field dependent permittivity in wire media.

  12. Vibrational Properties of High- Superconductors Levitated Above a Bipolar Permanent Magnetic Guideway

    NASA Astrophysics Data System (ADS)

    Liu, Lu; Wang, Jiasu

    2014-05-01

    A bipolar permanent magnetic guideway (PMG) has a unique magnetic field distribution profile which may introduce a better levitation performance and stability to the high- superconducting (HTS) maglev system. The dynamic vibration properties of multiple YBCO bulks arranged into different arrays positioned above a bipolar PMG and free to levitate were investigated. The acceleration and resonance frequencies were experimentally measured, and the stiffness and damping coefficients were evaluated for dynamic stability. Results indicate that the levitation stiffness is closely related to the field-cooling-height and sample positioning. The damping ratio was found to be low and nonlinear for the Halbach bipolar HTS-PMG system.

  13. Computational analysis of magnetic field induced deposition of magnetic particles in lung alveolus in comparison to deposition produced with viscous drag and gravitational force

    NASA Astrophysics Data System (ADS)

    Krafcik, Andrej; Babinec, Peter; Frollo, Ivan

    2015-04-01

    Magnetic targeting of drugs attached to magnetic nanoparticles with diameter ? 100 nm after their intravenous administration is an interesting method of drug delivery widely investigated both theoretically as well as experimentally. Our aim in this study is theoretical analysis of a magnetic aerosol targeting to the lung. Due to lung anatomy magnetic particles up to 5 ?m can be safely used, therefore the magnetic force would be stronger, moreover drag force exerted on the particle is according to Stokes law linearly dependent on the viscosity, would be weaker, because the viscosity of the air in the lung is approximately 200 fold smaller than viscosity of the blood. Lung therefore represents unique opportunity for magnetic drug targeting, as we have shown in this study by the analysis of magnetic particle dynamics in a rhythmically expanding and contracting distal and proximal alveolus subjected to high-gradient magnetic field generated by quadrupolar permanent Halbach magnet array.

  14. Two-dimensional field-sensing map and magnetic anisotropy dispersion in magnetic tunnel junction arrays

    NASA Astrophysics Data System (ADS)

    Zhang, Wenzhe; Xiao, Gang; Carter, Matthew J.

    2011-04-01

    Due to the inherent disorder in local structures, anisotropy dispersion exists in almost all systems that consist of multiple magnetic tunnel junctions (MTJs). Aided by micromagnetic simulations based on the Stoner-Wohlfarth (S-W) model, we used a two-dimensional field-sensing map to study the effect of anisotropy dispersion in MTJ arrays. First, we recorded the field sensitivity value of an MTJ array as a function of the easy- and hard-axis bias fields, and then extracted the anisotropy dispersion in the array by comparing the experimental sensitivity map to the simulated map. Through a mean-square-error-based image processing technique, we found the best match for our experimental data, and assigned a pair of dispersion numbers (anisotropy angle and anisotropy constant) to the array. By varying each of the parameters one at a time, we were able to discover the dependence of field sensitivity on magnetoresistance ratio, coercivity, and magnetic anisotropy dispersion. The effects from possible edge domains are also discussed to account for a correction term in our analysis of anisotropy angle distribution using the S-W model. We believe this model is a useful tool for monitoring the formation and evolution of anisotropy dispersion in MTJ systems, and can facilitate better design of MTJ-based devices.

  15. Levitation Force Investigation of Bulk HTSC Above Halbach PMG with Different Cross-Section Physical Dimensions by 3D-Modeling Numerical Method

    NASA Astrophysics Data System (ADS)

    Lu, Yiyun; Liu, Guoliang; Qin, Yujie

    2014-10-01

    The levitation force of a bulk high temperature superconductor (HTSC) over Halbach permanent magnet guideways (PMG) with different cross-section configuration is studied by numerical method. The Halbach PMG is composed of three host permanent magnets (HPMs) and two slave permanent magnets (SPMs). One cylindrical bulk HTSC with a diameter of 30 mm and height of 15 mm is used. The 3D-modeling is formulated by the H-method. The numerical resolving codes are practiced using finite element method (FEM). The E-J power law is used to describe the electric current nonlinear characteristics of bulk HTSC. By the method, the influence of the cross-section physical dimensions of Halbach PMG on the levitation forces of bulk HTSC levitated above the PMG is studied. The simulation results show that increasing the width of SPM ( can enhance the bulk HTSC levitation performance immediately under the condition of keeping the ratio of ( : the width of HPM) to between 1.6 and 1.8, the ratio of td (the height of the PMG) to between 1.2 and 1.4. By the method, the bulk HTSC better levitation performance can be expected.

  16. Self-organized magnetic nanowire arrays based on alumina and titania templates.

    PubMed

    Prida, V M; Pirota, K R; Navas, D; Asenjo, A; Hernndez-Vlez, M; Vzquez, M

    2007-01-01

    Densely packed arrays of magnetic nanowires have been synthesized by electrodeposition filling of nanopores in alumina and titania membranes formed by self-assembling during anodization process. Emphasis is made on the control of the production parameters leading to ordering degree and lattice parameter of the array as well as nanowires diameter and length. Structural, morphological and magnetic properties exhibited by nanowire arrays have been studied for several nanowire compositions, different ordering degree and for different nanowire aspect ratios. The magnetic behaviour of nanowires array is governed by the balance between different energy contributions: shape anisotropy of individual nanowires, the magnetostatic interaction of dipolar origin among nanowires, and magnetocrystalline and magnetoelastic anisotropies induced by the pattern templates. These novel nanocomposites, based on ferromagnetic nanowires embedded in anodic nanoporous templates, are becoming promising candidates for technological applications such as functionalised arrays for magnetic sensing, ultrahigh density magnetic storage media or spin-based electronic devices. PMID:17455492

  17. Imaging collective magnonic modes in 2D arrays of magnetic nanoelements.

    PubMed

    Kruglyak, V V; Keatley, P S; Neudert, A; Hicken, R J; Childress, J R; Katine, J A

    2010-01-15

    We have used time resolved scanning Kerr microscopy to image collective spin wave modes within a 2D array of magnetic nanoelements. Long wavelength spin waves are confined within the array as if it was a continuous element of the same size but with effective material properties determined by the structure of the array and its constituent nanoelements. The array is an example of a magnonic metamaterial, the demonstration of which provides new opportunities within the emerging field of magnonics. PMID:20366622

  18. Enhanced magnetism in highly ordered magnetite nanoparticle-filled nanohole arrays.

    PubMed

    Duong, Binh; Khurshid, Hafsa; Gangopadhyay, Palash; Devkota, Jagannath; Stojak, Kristen; Srikanth, Hariharan; Tetard, Laurene; Norwood, Robert A; Peyghambarian, N; Phan, Manh-Huong; Thomas, Jayan

    2014-07-23

    A new approach to develop highly ordered magnetite (Fe3O4) nanoparticle-patterned nanohole arrays with desirable magnetic properties for a variety of technological applications is presented. In this work, the sub-100 nm nanohole arrays are successfully fabricated from a pre-ceramic polymer mold using spin-on nanoprinting (SNAP). These nanoholes a then filled with monodispersed, spherical Fe3O4 nanoparticles of about 10 nm diameter using a novel magnetic drag and drop procedure. The nanohole arrays filled with magnetic nanoparticles a imaged using magnetic force microscopy (MFM). Magnetometry and MFM measurements reveal room temperature ferromagnetism in the Fe3O4-filled nanohole arrays, while the as-synthesized Fe3O4 nanoparticles exhibit superparamagnetic behavior. As revealed by MFM measurements, the enhanced magnetism in the Fe3O4-filled nanohole arrays originates mainly from the enhanced magnetic dipole interactions of Fe3 O4 nanoparticles within the nanoholes and between adjacent nanoholes. Nanoparticle filled nanohole arrays can be highly beneficial in magnetic data storage and other applications such as microwave devices and biosensor arrays that require tunable and anisotropic magnetic properties. PMID:24706405

  19. Magnetic circular dichroism of non-local surface lattice resonances in magnetic nanoparticle arrays.

    PubMed

    Kataja, Mikko; Pourjamal, Sara; van Dijken, Sebastiaan

    2016-02-22

    Subwavelength metallic particles support plasmon resonances that allow extreme confinement of light down to the nanoscale. Irradiation with left- and right hand circularly polarized light results in the excitation of circular plasmon modes with opposite helicity. The Lorenz force lifts the degeneracy of the two modes in magnetic nanoparticles. Consequently, the confinement and frequency of localized surface plasmon resonances can be tuned by an external magnetic field. In this paper, we experimentally demonstrate this effect for nickel nanoparticles using magnetic circular dichroism (MCD). Besides, we show that non-local surface lattice resonances in periodic arrays of the same nanoparticles significantly enhance the MCD signal. A numerical model based on the modified long wavelength approximation is used to reproduce the main features in the experimental spectra and provide design rules for large MCD effects in sensing applications. PMID:26907013

  20. Effect of substrate rotation on domain structure and magnetic relaxation in magnetic antidot lattice arrays

    NASA Astrophysics Data System (ADS)

    Mallick, Sougata; Mallik, Srijani; Bedanta, Subhankar

    2015-08-01

    Microdimensional triangular magnetic antidot lattice arrays were prepared by varying the speed of substrate rotation. The pre-deposition patterning has been performed using photolithography technique followed by a post-deposition lift-off. Surface morphology taken by atomic force microscopy depicted that the growth mechanism of the grains changes from chain like formation to island structures due to the substrate rotation. Study of magnetization reversal via magneto optic Kerr effect based microscopy revealed reduction of uniaxial anisotropy and increase in domain size with substrate rotation. The relaxation measured under constant magnetic field becomes faster with rotation of the substrate during deposition. The nature of relaxation for the non-rotating sample can be described by a double exponential decay. However, the relaxation for the sample with substrate rotation is well described either by a double exponential or a Fatuzzo-Labrune like single exponential decay, which increases in applied field.

  1. Local magnetization unit for GMR array based magnetic flux leakage inspection

    NASA Astrophysics Data System (ADS)

    Pelkner, M.; Neubauer, A.; Reimund, V.; Kreutzbruck, M.

    2012-05-01

    GMR sensors are increasingly used for magnetic surface inspection due to their high sensitivity and high spatial resolution. In case of simple planar or cylindrical shaped components, the GMR-based inspection procedure can be automated easily. We present GMR measurements of real fatigue cracks. In addition, we present a probe design using a local magnetization unit and commercially available GMR sensors. The design was carried out by means of finite-element method (FEM) simulations. Using the local probe we measured bearings containing artificial reference cracks of different depths and orientations. Cracks with a depth of 40 ?m could be resolved with a signal-to-noise ratio better than 6. A further reduction of the measuring time can be obtained using a sensor array. For this purpose we present a study of the optimized size of the sensing GMR-layers for a NDE-adapted sensor array. The geometric sensor parameters were investigated through simulations of the magnetic flux leakage of surface cracks using an analytic model.

  2. Effect of the Array Distance on the Magnetization Configuration of Submicorn-Sized Ferromagnetic Rings

    NASA Astrophysics Data System (ADS)

    Miyawaki, T.; Toyoda, K.; Kohda, M.; Fujita, A.; Nitta, J.

    2008-10-01

    Magnetization characteristics of one dimensionally arrayed submicron-sized ferromagnetic rings were investigated by MOKE varying inter-ring distance lx. Changing of onion-to-vortex and vortex-to-onion transition fields, HOV and HVO, respectively, due to magnetostatic interaction were found to be proportional to the power of lx. The interaction was found to cause significant change of magnetic configuration and enhance the lx-dependence of HOV and HVO than considering only the decay of magnetostatic energy of uniform-magnetized ring array. Energies of the ring array were also calculated and lx-dependence of HOV and HVO was discussed qualitatively.

  3. Magnetic field mapping of the UCNTau magneto-gravitational trap: design study

    SciTech Connect

    Libersky, Matthew Murray

    2014-09-04

    The beta decay lifetime of the free neutron is an important input to the Standard Model of particle physics, but values measured using different methods have exhibited substantial disagreement. The UCN r experiment in development at Los Alamos National Laboratory (LANL) plans to explore better methods of measuring the neutron lifetime using ultracold neutrons (UCNs). In this experiment, UCNs are confined in a magneto-gravitational trap formed by a curved, asymmetric Halbach array placed inside a vacuum vessel and surrounded by holding field coils. If any defects present in the Halbach array are sufficient to reduce the local field near the surface below that needed to repel the desired energy level UCNs, loss by material interaction can occur at a rate similar to the loss by beta decay. A map of the magnetic field near the surface of the array is necessary to identify any such defects, but the array's curved geometry and placement in a vacuum vessel make conventional field mapping methods difficult. A system consisting of computer vision-based tracking and a rover holding a Hall probe has been designed to map the field near the surface of the array, and construction of an initial prototype has begun at LANL. The design of the system and initial results will be described here.

  4. Design of a magnetic field mapping rover system for a neutron lifetime experiment

    NASA Astrophysics Data System (ADS)

    Libersky, Matthew; UCNTau Collaboration

    2014-09-01

    The beta decay lifetime of the free neutron is an important input to the Standard Model of particle physics, but values measured using different methods have exhibited substantial disagreement. The UCN ? experiment in development at Los Alamos National Laboratory (LANL) plans to explore better methods of measuring the neutron lifetime using ultracold neutrons (UCNs). In this experiment, UCNs are confined in a magneto-gravitational trap formed by a curved, asymmetric Halbach array placed inside a vacuum vessel and surrounded by holding field coils. If any defects present in the Halbach array are sufficient to reduce the local field near the surface below that needed to repel the desired energy level UCNs, loss by material interaction can occur at a rate similar to the loss by beta decay. A map of the magnetic field near the surface of the array is necessary to identify any such defects, but the array's curved geometry and placement in a vacuum vessel make conventional field mapping methods difficult. A system consisting of computer vision-based tracking and a rover holding a Hall probe has been designed to map the field near the surface of the array, and construction of an initial prototype has begun at LANL. A description of the design and prototype will be presented.

  5. Fabrication and magnetic characterization of cobalt antidot arrays: effect of the surrounding continuous film.

    PubMed

    Castn-Guerrero, C; Ses, J; Bartolom, J; Bartolom, F; Herrero-Albillos, J; Kronast, F; Strichovanec, P; Merazzo, K J; Vzquez, M; Vavassori, P; Garca, L M

    2012-09-01

    We have performed an experimental study on the influence of a ferromagnetic continuous film in the magnetization reversal processes in discrete submicrometric antidot arrays fabricated on it. In order to compare the magnetic properties, two sets of antidot arrays have been fabricated over a cobalt thin film: embedded in the continuous film, and isolated by a trench surrounding the array. X-ray photoemission electron microscopy images of the virgin state show the same magnetic domain distribution in both sets of samples, finding no evidence of any effect of the surrounding film. This result is supported by the hysteresis loops measured with magneto-optical Kerr effect, as isolated and non-isolated arrays present almost coincident loops. A huge increase of the coercivity of the film is achieved, and the expected dependence on the geometrical parameters of the array is found, connecting the previous studies on the micro- and nanometric scales. PMID:23035490

  6. Ordered arrays of magnetic metal nanotubes and nanowires encapsulated with carbon tubes.

    PubMed

    Gao, Culling; Tao, Feifei; Lin, Weiwei; Xu, Zheng; Xue, Ziling

    2008-09-01

    The ordered arrays of magnetic metal (including Fe, Co and Ni) nanotubes and nanowires encapsulated with carbon tubes are controllably synthesized by employing the array of C tubes as second-order template and combining with electrodeposition technique. The wall thickness and diameter of carbon nanotubes are uniform along the whole tubes; also the wall thickness of inner metal nanotubes is adjustable from 25 nm to solid nanowires. These composite structures are characterized by X-ray diffractometer (XRD), energy-dispersive spectrometry (EDS), Raman scattering spectrum, transmission electron microscopy (TEM) and scanning electron microscopy (SEM). The magnetic properties show that coaxial nanotubes and nanocables composite arrays all exhibit magnetic anisotropy with the easy direction perpendicular to axis of the metal nanotubes or nanowires except the Ni at C coaxial nanotubes array that has no preferable magnetization axis. PMID:19049046

  7. Development of a Two-Dimensional Micro-SQUID Array for Investigation of Magnetization Spatial Distribution

    NASA Astrophysics Data System (ADS)

    Sakuma, Daisuke; Shinozaki, Tomoya; Nago, Yusuke; Ishiguro, Ryosuke; Kashiwaya, Satoshi; Nomura, Shintaro; Kono, Kimitoshi; Takayanagi, Hideaki

    2016-03-01

    We developed a two-dimensional array of superconducting quantum interference devices (SQUIDs) for investigation of fine spatial distribution of magnetization in superconducting Sr2 RuO4 . Micrometer-sized SQUIDs based on homogeneously formed Al/AlOx /Al tunnel-type Josephson junctions were fabricated using shadow evaporation technique. Unnecessary electrodes formed by the shadow evaporation were removed by inductively coupled plasma reactive ion etching, in order to realize a dense array of SQUIDs. We measured the magnetic modulation of the maximum Josephson current of each SQUID in the array and evaluated the interaction among the SQUIDs.

  8. Magnetic characteristics of CoPd and FePd antidot arrays on nanoperforated Al2O3 templates

    NASA Astrophysics Data System (ADS)

    Maximenko, A.; Fedotova, J.; Marszałek, M.; Zarzycki, A.; Zabila, Y.

    2016-02-01

    Hard magnetic antidot arrays show promising results in context of designing of percolated perpendicular media. In this work the technology of magnetic FePd and CoPd antidot arrays fabrication is presented and correlation between surface morphology, structure and magnetic properties is discussed. CoPd and FePd antidot arrays were fabricated by deposition of Co/Pd and Fe/Pd multilayers (MLs) on porous anodic aluminum oxide templates with bowl-shape cell structure with inclined intercellular regions. FePd ordered L10 structure was obtained by successive vacuum annealing at elevated temperatures (530 °C) and confirmed by XRD analysis. Systematic analysis of magnetization curves evidenced perpendicular magnetic anisotropy of CoPd antidot arrays, while FePd antidot arrays revealed isotropic magnetic anisotropy with increased out-of-plane magnetic contribution. MFM images of antidots showed more complicated contrast, with alternating magnetic dots oriented parallel and antiparallel to tip magnetization moment.

  9. 2D and 3D ordered arrays of Co magnetic nanowires

    NASA Astrophysics Data System (ADS)

    Garcia, J.; Prida, V. M.; Vega, V.; Rosa, W. O.; Caballero-Flores, R.; Iglesias, L.; Hernando, B.

    2015-06-01

    Cobalt nanowire arrays spatially distributed in 2D and 3D arrangements have been performed by pulsed electrodeposition into the pores of planar and cylindrical nanoporous anodic alumina membranes, respectively. Morphological characterization points out the good filling factor reached by electroplated Co nanowires in both kinds of alumina membranes exhibiting hexagonally self-ordered porous structures. Co nanowires grown in both kinds of alumina templates exhibit the same crystalline phases. DC magnetometry and First Order Reversal Curve (FORC) analysis were carried out in order to determine the overall magnetic behavior for both nanowire array geometries. It is found that when the Co nanowires of two kinds of arrays are perpendicularly magnetized, both hysteresis loops are identical, suggesting that neither the intrinsic magnetic behavior of the nanowires nor the collective one depend on the arrays geometry. FORC analysis performed along the radial direction of the Co nanowire arrays embedded in the cylindrical alumina template reveals that the contribution of each nanowire to the magnetization reversal process involves its specific orientation with respect to the applied field direction. Furthermore, the comparison between the magnetic properties for both kinds of Co nanowire arrays allows discussing about the effect of the cylindrical geometry of the template on the magnetostatic interaction among nanowires.

  10. Effects of magnetically induced optical incoherence in arrayed Faraday rotator crystals

    NASA Astrophysics Data System (ADS)

    Garzarella, A.; Shinn, M. A.; Wu, Dong Ho

    2015-06-01

    Bismuth doped iron garnet films were studied in arrayed structures to improve sensitivity in polarimetric magnetic field sensors. The sensitivity gained from the arrayed configuration was found to depend on the ferromagnetic domain geometry of the films. Under small, externally applied fields, films with planar anisotropy yielded an optical modulation depth which increased linearly with the number of crystals in the array. In films with perpendicular anisotropy, linearity and sensitivity were obstructed by a mechanism of optical polarization incoherence which was found to be generated within the magnetic domains. Our results indicate that optimal sensitivity in arrayed configurations requires planar anisotropies, or a direction of laser propagation that is perpendicular to the local domain magnetization.

  11. Structural and Magnetic model of self-assembled FePt nanoparticle arrays

    SciTech Connect

    Thomson, T

    2004-05-13

    Chemically ordered, self-assembled FePt nanoparticle arrays with high magnetic anisotropy are considered a candidate medium for data storage beyond 1 Tbit/in{sup 2}. We report comprehensive structural and magnetic studies on thin (3 layer) assemblies of polyethylenimine (PEI) and 4 nm Fe{sub 58}Pt{sub 42} nanoparticles using X-ray diffraction, small angle neutron scattering and magnetometry. We show that prior to annealing FePt nanoparticles in the PEI-FePt assembly consist of a metallic, magnetic core surrounded by a weakly magnetic or non-magnetic shell. High temperature annealing creates the desired L1{sub 0} chemical ordering and results in high coercivity FePt nanoparticles. However, we find that the high temperatures necessary to establish full chemical ordering leads to particle sintering and agglomeration. Understanding the magnetic and physical properties of these assemblies allows future research directions to be clarified for nanoparticle arrays as data storage media.

  12. Terabit Density Magnetic Nanowire Arrays Using Self-Assembled Diblock Copolymer Templates

    NASA Astrophysics Data System (ADS)

    Ursache, Andrei; Schotter, Jrg; Bal, Mustafa; Thurn-Albrecht, Thomas; Russell, Thomas; Tuominen, Mark; Shibauchi, Takasada; Krusin-Elbaum, Lia; Guarini, Kathryn; Black, C. T.

    2001-03-01

    We use nanoporous diblock copolymer thick films as templates for fabricating ultra-high density vertical arrays of magnetic nanowires over a wide range of aspect ratios. The self-assembled morphology of the asymmetric diblock copolymers provides us an ordered hexagonal array of cylindrical nanopores with controllable dimensions (11 nm typical diameter), spacing (22 nm typical spacing) and areal pore density in excess of 1.2 x 10^12 pores/in^2. We have grown ferromagnetic cobalt nanowires with well-controlled length into the pores of the template by means of DC electrodeposition. We have found enhanced coercivities with the magnetic nanowire arrays that make them suitable candidates for ultra-high density perpendicular magnetic recording media. The effects of applying a magnetic field during the electrodeposition process and manipulating electrodeposition parameters will also be discussed. This work is supported by NSF grant CTS-9871792.

  13. A decoupled control approach for magnetic suspension systems using electromagnets mounted in a planar array

    NASA Technical Reports Server (NTRS)

    Groom, Nelson J.

    1993-01-01

    A decoupled control approach for a Large Gap Magnetic Suspension System (LGMSS) is presented. The control approach is developed for an LGMSS which provides five degree-of-freedom control of a cylindrical suspended element that contains a core composed of permanent magnet material. The suspended element is levitated above five electromagnets mounted in a planar array. Numerical results are obtained by using the parameters of the Large Angle Magnetic Suspension Test Fixture (LAMSTF) which is a small scale laboratory model LGMSS.

  14. Optimal magnet configurations for Lorentz force velocimetry in low conductivity fluids

    NASA Astrophysics Data System (ADS)

    Alferenok, A.; Pothrat, A.; Luedtke, U.

    2013-06-01

    We show that the performances of flowmeters based on the measurement of Lorentz force in duct flows can be sufficiently optimized to be applied to fluids of low electrical conductivity. The main technological challenge is to design a system with permanent magnets generating a strong enough field for the Lorentz force generated when a fluid of low conductivity passes through it to be reliably measured. To achieve this, we optimize the design of a magnet system based on Halbach arrays placed on either side of the duct. In the process, we show that the fluid flow can be approximated as a moving solid bar with practically no impact on the optimization result and devise a rather general iterative optimization procedure, which incurs drastically less computational cost than a direct procedure of equivalent precision. We show that both the Lorentz force and the efficiency of the system (defined as the ratio of the Lorentz force to the weight of the system) can be increased several fold by using Halbach arrays made of three, five, seven or nine magnets on either side of the duct but that this improvement comes at a cost in terms of the precision required to position the system.

  15. Kilohertz magnetic field focusing and force enhancement using a metallic loop array

    NASA Astrophysics Data System (ADS)

    Dede, Ercan M.; Lee, Jaewook; Guo, Yuanbo; Qin Zhou, Li; Zhang, Minjuan; Banerjee, Debasish

    2012-07-01

    We present a device capable of focusing a kilohertz magnetic field and enhancing the associated magnetic force. The device comprises a two-by-two array of electrically conductive metallic loops embedded in a base substrate. Analytical calculations and numerical simulations verify that the induced electrical current in the loop structure influences the magnetic field distribution thus leading to magnetic force enhancement. Experimental measurements of the magnetic force generated by the device operating at one kilohertz are compared with measurements of a control sample without loops. Such devices have logical applications in electromechanical actuators and transducers.

  16. Tilted Microstrip Phased Arrays With Improved Electromagnetic Decoupling for Ultrahigh-Field Magnetic Resonance Imaging

    PubMed Central

    Pang, Yong; Wu, Bing; Jiang, Xiaohua; Vigneron, Daniel B.; Zhang, Xiaoliang

    2014-01-01

    Abstract One of the technical challenges in designing a dedicated transceiver radio frequency (RF) array for MR imaging in humans at ultrahigh magnetic fields is how to effectively decouple the resonant elements of the array. In this work, we propose a new approach using tilted microstrip array elements for improving the decoupling performance and potentially parallel imaging capability. To investigate and validate the proposed design technique, an 8-channel volume array with tilted straight-type microstrip elements was designed, capable for human imaging at the ultrahigh field of 7 Tesla. In this volume transceiver array, its electromagnetic decoupling behavior among resonant elements, RF field penetration to biological samples, and parallel imaging performance were studied through bench tests and in vivo MR imaging experiments. In this specific tilted element array design, decoupling among array elements changes with the tilted angle of the elements and the best decoupling can be achieved at certain tilted angle. In vivo human knee MR images were acquired using the tilted volume array at 7 Tesla for method validation. Results of this study demonstrated that the electromagnetic decoupling between array elements and the B1 field strength can be improved by using the tilted element method in microstrip RF coil array designs at the ultrahigh field of 7T. PMID:25526481

  17. Magnetic Property in Large Array Niobium Antidot Thin Films

    NASA Astrophysics Data System (ADS)

    Tinghui, Chen; Hsiang-Hsi, Kung; Wei-Li, Lee; Institute of Physics, Academia Sinica, Taipei, Taiwan Team

    2014-03-01

    In a superconducting ring, the total flux inside the ring is required to be an integer number of the flux quanta. Therefore, a supercurrent current can appear within the ring in order to satisfy this quantization rule, which gives rise to certain magnetic response. By using a special monolayer polymer/nanosphere hybrid we developed previously, we fabricated a series of superconducting niobium antidot thin films with different antidot diameters. The antidots form well-ordered triangular lattice with a lattice spacing about 200 nm and extend over an area larger than 1 cm2, which enables magnetic detections simply by a SQUID magnetometer. We observed magnetization oscillation with external magnetic field due to the supercurrent screening effect, where different features for large and small antidot thin films were found. Detailed size and temperature dependencies of the magnetization in niobium antidot nanostructures will be presented.

  18. Modeling the collective magnetic behavior of highly-packed arrays of multi-segmented nanowires

    NASA Astrophysics Data System (ADS)

    Agramunt-Puig, S.; Del-Valle, N.; Pellicer, E.; Zhang, J.; Nogués, J.; Navau, C.; Sanchez, A.; Sort, J.

    2016-01-01

    A powerful model to evaluate the collective magnetic response of large arrays of segmented nanowires comprising two magnetic segments of dissimilar coercivity separated by a non-magnetic spacer is introduced. The model captures the essential aspects of the underlying physics in these systems while being at the same time computationally tractable for relatively large arrays. The minimum lateral and vertical distances rendering densely packed weakly-interacting nanowires and segments are calculated for optimizing their performance in applications like magnetic sensors or recording media. The obtained results are appealing for the design of multifunctional miniaturized devices actuated by external magnetic fields, whose successful implementation relies on achieving a delicate balance between two opposing technological demands: the need for an ultra-high density of nanowires per unit area and the minimization of inter-wire and inter-segment dipolar interactions.

  19. A large-area mesoporous array of magnetic nanostructure with perpendicular anisotropy integrated on Si wafers.

    PubMed

    Rahman, M Tofizur; Shams, Nazmun N; Lai, Chih-Huang

    2008-08-13

    Large-area, over several square centimeters, mesoporous array of magnetic nanostructure with perpendicular anisotropy is prepared by depositing Co/Pt multilayers (MLs) on a mesopore array of anodized alumina (AAO) fabricated on Si wafers. The MLs are mainly deposited on the top of AAO walls and perimeters of the pores; very small amounts of magnetic material reach the bottom due to the high aspect ratio of AAO. Consequently, ordered pores are present in the magnetic MLs. The mean pore diameter of the fabricated mesoporous array is 8.83nm with a standard deviation of 3.16nm and density of about 2.1 10(11)cm(-2). The Co/Pt MLs deposited on AAO and Si both exhibit strong perpendicular magnetic anisotropy, but the perpendicular coercivity (H(c)) increases by 15 times on AAO compared to that on Si. On the other hand, the magnetic cluster size decreases from 1000nm (on Si) to 100nm due to the presence of high-density pores. The dramatic increase in H(c) and the decrease in magnetic cluster size suggest that the pores behave as effective pinning sites. The magnetization-switching characteristics of the fabricated porous structure are different from those of the continuous films or Stoner-Wohlfarth-type (S-W) particles. One of the potential applications of this mesoporous structure may be in the field of high-density magnetic data storage. PMID:21828809

  20. Magnetic wall decoupling method for monopole coil array in ultrahigh field MRI: a feasibility test

    PubMed Central

    Yan, Xinqiang; Zhang, Xiaoliang; Wei, Long

    2014-01-01

    Ultrahigh field (UHF) MR imaging of deeply located target in high dielectric biological samples faces challenges due to the reduced penetration depth at the corresponding high frequencies. Radiative coils, e.g., dipole and monopole coils, have recently been applied for UHF MRI applications to obtain better signal-noise-ratio (SNR) in the area deep inside the human head and body. However, due to the unique structure of radiative coil elements, electromagnetic (EM) coupling between elements in radiative coil arrays cannot be readily addressed by using traditional decoupling methods such as element overlapping and L/C decoupling network. A new decoupling method based on induced current elimination (ICE) or magnetic wall technique has recently been proposed and has demonstrated feasibility in designing microstrip transmission line (MTL) arrays and L/C loop arrays. In this study, an array of two monopole elements decoupled using magnetic wall decoupling technique was designed, constructed and analyzed numerically and experimentally to investigate the feasibility of the decoupling technique in radiative coil array designs for MR imaging at 7 T. An L-shaped capacitive network was employed as the matching circuit and the reflection coefficients (S11) of the monopole element achieved 30 dB or better. Isolation between the two monopole elements was improved from about 10 dB (without decoupling treatment) to better than 30 dB with the ICE/magnetic wall decoupling method. B1 maps and MR images of the phantom were acquired and SNR maps were measured and calculated to evaluate the performance of the ICE/magnetic wall decoupling method. Compared with the monopole elements without decoupling methods, the ICE-decoupled array demonstrated more independent image profiles from each element and had a higher SNR in the peripheral area of the imaging subject. The experimental and simulation results indicate that the ICE/magnetic wall decoupling technique might be a promising solution to reducing the EM coupling of monopole arrays for UHF MRI. PMID:24834419

  1. Exact asymptotic behavior of magnetic stripe domain arrays

    NASA Astrophysics Data System (ADS)

    Johansen, Tom H.; Pan, Alexey V.; Galperin, Yuri M.

    2013-02-01

    The classical problem of magnetic stripe domain behavior in films and plates with uniaxial magnetic anisotropy is addressed. Exact analytical results are derived for the stripe domain widths as a function of applied perpendicular field H, in the regime where the domain period becomes large. The stripe period diverges as (Hc-H)-1/2, where Hc is the critical (infinite period) field, an exact result confirming a previous conjecture. The magnetization approaches saturation as (Hc-H)1/2, a behavior that compares excellently with experimental data obtained for a 4-?m thick ferrite garnet film. The exact analytical solution provides a new basis for precise characterization of uniaxial magnetic films and plates, illustrated by a simple way to measure the domain wall energy. The mathematical approach is applicable for similar analysis of a wide class of systems with competing interactions where a stripe domain phase is formed.

  2. Design and fabrication of magnetically functionalized flexible micropillar arrays for rapid and controllable microfluidic mixing.

    PubMed

    Zhou, Bingpu; Xu, Wei; Syed, Ahad A; Chau, Yeungyeung; Chen, Longqing; Chew, Basil; Yassine, Omar; Wu, Xiaoxiao; Gao, Yibo; Zhang, Jingxian; Xiao, Xiao; Kosel, Jürgen; Zhang, Xi-Xiang; Yao, Zhaohui; Wen, Weijia

    2015-05-01

    Magnetically functionalized PDMS-based micropillar arrays have been successfully designed, fabricated and implanted for controllable microfluidic mixing. The arrangement of PDMS micropillar arrays inside the microchannel can be flexibly controlled by an external magnetic field. As a consequence, the flow fields inside the microchannel can be regulated at will via magnetic activation conveniently. When a microchannel is implanted with such micropillar arrays, two microstreams can be mixed easily and controllably upon the simple application of an on/off magnetic signal. Mixing efficiencies based on micropillar arrays with different densities were investigated and compared. It was found that micropillar arrays with higher density (i.e. smaller pillar pitch) would render better mixing performance. Our microfluidic system is capable of generating highly reproducible results within many cycles of mixing/non-mixing conversion. We believe that the simple mixing-triggering method together with rapid and controllable mixing control will be extraordinarily valuable for various biological or chemical applications in the future. PMID:25849640

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

    NASA Astrophysics Data System (ADS)

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

    2008-08-01

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

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

    SciTech Connect

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

    2008-08-11

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

  5. Discrete breathers in an one-dimensional array of magnetic dots

    NASA Astrophysics Data System (ADS)

    Pylypchuk, Roman L.; Zolotaryuk, Yaroslav

    2015-09-01

    The dynamics of the one-dimensional array of magnetic particles (dots) with the easy-plane anisotropy is investigated. The particles interact with each other via the magnetic dipole interaction and the whole system is governed by the set of Landau-Lifshitz equations. The spatially localized and time-periodic solutions known as discrete breathers (or intrinsic localized modes) are identified. These solutions have no analogue in the continuum limit and consist of the core where the magnetization vectors precess around the hard axis and the tails where the magnetization vectors oscillate around the equilibrium position.

  6. Multi-modal vibration energy harvesting approach based on nonlinear oscillator arrays under magnetic levitation

    NASA Astrophysics Data System (ADS)

    Abed, I.; Kacem, N.; Bouhaddi, N.; Bouazizi, M. L.

    2016-02-01

    We propose a multi-modal vibration energy harvesting approach based on arrays of coupled levitated magnets. The equations of motion which include the magnetic nonlinearity and the electromagnetic damping are solved using the harmonic balance method coupled with the asymptotic numerical method. A multi-objective optimization procedure is introduced and performed using a non-dominated sorting genetic algorithm for the cases of small magnet arrays in order to select the optimal solutions in term of performances by bringing the eigenmodes close to each other in terms of frequencies and amplitudes. Thanks to the nonlinear coupling and the modal interactions even for only three coupled magnets, the proposed method enable harvesting the vibration energy in the operating frequency range of 4.6–14.5 Hz, with a bandwidth of 190% and a normalized power of 20.2 {mW} {{cm}}-3 {{{g}}}-2.

  7. Magnetic microscopy/metrology potential of metamaterials using nanosized spherical particle arrays

    NASA Astrophysics Data System (ADS)

    Eason, Kwaku; Luk'yanchuk, Boris; Zhou, Yi; Miroshnichenko, Andrey E.; Kivshar, Yuri S.

    2011-12-01

    Techniques for imaging and characterizing magnetic samples have been widely used in many areas of research involving magnetic materials. Nowadays, magnetic microscopy techniques play a critical role in characterizing magnetic thin film structures. In considering the various techniques, optical techniques offer some unique advantages over alternative techniques (e.g. MFM), as they are least affected by magnetic noise and, for the same underlying reasons, have also proven to be more suitable for "high speed" magnetization measurements of magnetization dynamics, which are increasingly important in many of today's research scopes. At the same time, development of metamaterials are opening the doors for newly behaving materials, such as those demonstrating negative refractive index, potentially useful in a variety of applications, such as imaging. Metamaterials deploying arrays of silicon particles, and even alternating silicon particles and split ring resonators have recently been shown to demonstrate interesting behavior, such as negative magnetic susceptibility and large resonant peaks in the Terahertz regime. Such high frequencies offer the potential bandwidth of extraordinarily fast dynamics, which are increasingly being generated in magnetic materials, for example, in optically-induced demagnetization and all-optical magnetic recording. Here, initial investigations toward ultra high-speed imaging and/or information extraction from magnetic samples is discussed considering metamaterials deploying mainly spherical particle arrays. In addition to the frequency spectrums of the system, the response of the system to external magnetic fields and background permeability changes due to external fields are investigated. Our results suggest a significant potential of metamaterials for use in probing information from magnetic materials.

  8. Single crystalline cylindrical nanowires - toward dense 3D arrays of magnetic vortices.

    PubMed

    Ivanov, Yurii P; Chuvilin, Andrey; Vivas, Laura G; Kosel, Jurgen; Chubykalo-Fesenko, Oksana; Vázquez, Manuel

    2016-01-01

    Magnetic vortex-based media have recently been proposed for several applications of nanotechnology; however, because lithography is typically used for their preparation, their low-cost, large-scale fabrication is a challenge. One solution may be to use arrays of densely packed cobalt nanowires that have been efficiently fabricated by electrodeposition. In this work, we present this type of nanoscale magnetic structures that can hold multiple stable magnetic vortex domains at remanence with different chiralities. The stable vortex state is observed in arrays of monocrystalline cobalt nanowires with diameters as small as 45 nm and lengths longer than 200 nm with vanishing magnetic cross talk between closely packed neighboring wires in the array. Lorentz microscopy, electron holography and magnetic force microscopy, supported by micromagnetic simulations, show that the structure of the vortex state can be adjusted by varying the aspect ratio of the nanowires. The data we present here introduce a route toward the concept of 3-dimensional vortex-based magnetic memories. PMID:27030143

  9. Ordering, thermal excitations and phase transitions in dipolar coupled mono-domain magnet arrays

    NASA Astrophysics Data System (ADS)

    Kapaklis, Vassilios

    2015-03-01

    Magnetism has provided a fertile test bed for physical models, such as the Heisenberg and Ising models. Most of these investigations have focused on solid materials and relate to their atomic properties such as the atomic magnetic moments and their interactions. Recently, advances in nanotechnology have enabled the controlled patterning of nano-sized magnetic particles, which can be arranged in extended lattices. Tailoring the geometry and the magnetic material of these lattices, the magnetic interactions and magnetization reversal energy barriers can be tuned. This enables interesting interaction schemes to be examined on adjustable length and energy scales. As a result such nano-magnetic systems represent an ideal playground for the study of physical model systems, being facilitated by direct magnetic imaging techniques. One particularly interesting case is that of systems exhibiting frustration, where competing interactions cannot be simultaneously satisfied. This results in a degeneracy of the ground state and intricate thermodynamic properties. An archetypical frustrated physical system is water ice. Similar physics can be mirrored in nano-magnetic arrays, by tuning the arrangement of neighboring magnetic islands, referred to as artificial spin ice. Thermal excitations in such systems resemble magnetic monopoles. In this presentation key concepts related to nano-magnetism and artificial spin ice will be introduced and discussed, along with recent experimental and theoretical developments.

  10. Highly stable and finely tuned magnetic fields generated by permanent magnet assemblies.

    PubMed

    Danieli, E; Perlo, J; Blmich, B; Casanova, F

    2013-05-01

    Permanent magnetic materials are the only magnetic source that can be used to generate magnetic fields without power consumption or maintenance. Such stand-alone magnets are very attractive for many scientific and engineering areas, but they suffer from poor temporal field stability, which arises from the strong sensitivity of the magnetic materials and mechanical support to temperature variation. In this work, we describe a highly efficient method useful to cancel the temperature coefficient of permanent magnet assemblies in a passive and accurate way. It is based on the combination of at least two units made of magnetic materials with different temperature coefficients arranged in such a way that the ratio of the fields generated by each unit matches the ratio of their effective temperature coefficients defined by both the magnetic and mechanical contributions. Although typically available magnetic materials have negative temperature coefficients, the cancellation is achieved by aligning the fields generated by each unit in the opposite direction. We demonstrate the performance of this approach by stabilizing the field generated by a dipolar Halbach magnet, recently proposed to achieve high field homogeneity. Both the field drift and the homogeneity are monitored via nuclear magnetic resonance spectroscopy experiments. The results demonstrate the compatibility of the thermal compensation approach with existing strategies useful to fine-tune the spatial dependence of the field generated by permanent magnet arrays. PMID:23683185

  11. Highly Stable and Finely Tuned Magnetic Fields Generated by Permanent Magnet Assemblies

    NASA Astrophysics Data System (ADS)

    Danieli, E.; Perlo, J.; Blmich, B.; Casanova, F.

    2013-05-01

    Permanent magnetic materials are the only magnetic source that can be used to generate magnetic fields without power consumption or maintenance. Such stand-alone magnets are very attractive for many scientific and engineering areas, but they suffer from poor temporal field stability, which arises from the strong sensitivity of the magnetic materials and mechanical support to temperature variation. In this work, we describe a highly efficient method useful to cancel the temperature coefficient of permanent magnet assemblies in a passive and accurate way. It is based on the combination of at least two units made of magnetic materials with different temperature coefficients arranged in such a way that the ratio of the fields generated by each unit matches the ratio of their effective temperature coefficients defined by both the magnetic and mechanical contributions. Although typically available magnetic materials have negative temperature coefficients, the cancellation is achieved by aligning the fields generated by each unit in the opposite direction. We demonstrate the performance of this approach by stabilizing the field generated by a dipolar Halbach magnet, recently proposed to achieve high field homogeneity. Both the field drift and the homogeneity are monitored via nuclear magnetic resonance spectroscopy experiments. The results demonstrate the compatibility of the thermal compensation approach with existing strategies useful to fine-tune the spatial dependence of the field generated by permanent magnet arrays.

  12. Magnetic properties of Sr-ferrite dot arrays by electron beam lithography

    NASA Astrophysics Data System (ADS)

    Liu, Xiaoxi; Itoh, Fumitake

    2003-05-01

    We have successfully prepared Sr-ferrite dot arrays with perpendicular magnetic anisotropy by electron beam lithography. Virgin magnetic configurations detected by magnetic force microscopy (MFM) show single domain configuration for a 0.5 ?m dot, while multidomain configurations are found for larger dots. The magnetization reversal mechanism in dots larger than 0.5 ?m is found to be domain wall motion. While the magnetization reversal mechanism in 0.5 ?m dots is found to be magnetization rotation. A normalized dc demagnetization remanence curve (DCD) measured by a superconducting quantum interference device (SQUID) indicates that with a decrease of dot size, the DCD curve is approaching the curve predicted by the coherent rotation model. Both MFM and SQUID results indicate that the single-domain dots reversed individually free from interdot magnetostatic coupling.

  13. Magnetic Field Measurements in Wire-Array Z-Pinches using Magneto-Optically Active Waveguides

    SciTech Connect

    Syed, Wasif; Blesener, Isaac; Hammer, David A.; Lipson, Michal

    2009-01-21

    Understanding the magnetic field topology in wire-array Z-pinches as a function of time is of great significance to understanding these high-energy density plasmas especially for their ultimate application to stockpile stewardship and inertial confinement fusion. We are developing techniques to measure magnetic fields as a function of space and time using Faraday rotation of a single longitudinal mode (SLM) laser through a magneto-optically active bulk waveguide (multicomponent terbium borate glass) placed adjacent to, or within, the wire array in 1 MA experiments. We have measured fields >10 T with 100 ns rise times outside of a wire-array for the entire duration of the current pulse and as much as {approx}2 T inside a wire-array for {approx}40 ns from the start of current. This is the first time that such rapidly varying and large fields have been measured using these materials. In a dense Z-pinch, these sensing devices may not survive for long but may provide the magnetic field at the position of the sensor that can be used to corroborate magnetic probes, with which we compare our results.

  14. ``Optical'' soft x-ray arrays for fluctuation diagnostics in magnetic fusion energy experiments

    NASA Astrophysics Data System (ADS)

    Delgado-Aparicio, L. F.; Stutman, D.; Tritz, K.; Finkenthal, M.; Kaita, R.; Roquemore, L.; Johnson, D.; Majeski, R.

    2004-10-01

    We are developing large pixel count, fast (?100 kHz) and continuously sampling soft x-ray (SXR) array for the diagnosis of magnetohydrodynamics (MHD) and turbulent fluctuations in magnetic fusion energy plasmas. The arrays are based on efficient scintillators, high thoughput multiclad fiber optics, and multichannel light amplification and integration. Compared to conventional x-ray diode arrays, such systems can provide vastly increased spatial coverage, and access to difficult locations with small neutron noise and damage. An eight-channel array has been built using columnar CsI:Tl as an SXR converter and a multianode photomultiplier tube as photoamplifier. The overall system efficiency is measured using laboratory SXR sources, while the time response and signal-to-noise performance have been evaluated by recording MHD activity from the spherical tori (ST) Current Drive Experiment-Upgrade and National Spherical Torus Experiment, both at Princeton Plasma Physics Laboratory.

  15. Study on magnetic mirror array image intensifier to work at room temperature.

    PubMed

    Tang, Yuanhe; Yu, Yang; Gao, HaiYang; Liu, Shulin; Wang, Xiaolin

    2015-09-10

    In order to improve the detection capability of the current low-light-level (LLL) imaging systems at room temperature, a new device, a magnetic mirror array image intensifier (MMAII), is proposed in this paper. A magnetic mirror array device (MMAD) is coupled into an image intensifier which sits between the photocathode and the microchannel plate (MCP). The trace photoelectrons, one after another, are first sufficiently accumulated by the MMAD over a long time at room temperature, and then they are released and enter the MCP for further gain. These two steps are used to improve the detection capability at the LLL imaging system at room temperature. After the two-dimensional magnetic field distribution of the magnetic mirror array (MMA) is calculated, the MMA is designed and optimized with a rubidium Nd-Fe-B permanent magnet. Three groups of ideal parameters for the Nd-Fe-B permanent magnet MMAD, with a magnetic mirror ratio of 1.69, for all of them have been obtained. According to the research results on the noise of the escape cone of the MMAII, the angle between the incident direction and the axis is greater than 57°, so the trace electrons must be constrained by the magnetic mirror. We made 54 MMAs from Nd-Fe-B permanent magnets and packaged them in a container. Then the system was evacuated to 10-3  Pa at room temperature. It was found by experiment that the trace electrons could be actually constrained by the MMAD. The MMAII can be applied to images for static LLL objects. PMID:26368978

  16. Open-loop characteristics of magnetic suspension systems using electromagnets mounted in a planar array

    NASA Technical Reports Server (NTRS)

    Groom, Nelson J.; Britcher, Colin P.

    1992-01-01

    The open-loop characteristics of a Large-Gap Magnetic Suspension System (LGMSS) were studied and numerical results are presented. The LGMSS considered provides five-degree-of-freedom control. The suspended element is a cylinder that contains a core composed of permanent magnet material. The magnetic actuators are air core electromagnets mounted in a planar array. Configurations utilizing five, six, seven, and eight electromagnets were investigated and all configurations were found to be controllable from coil currents and observable from suspended element positions. Results indicate that increasing the number of coils has an insignificant effect on mode shapes and frequencies.

  17. A microfabricated magnetic actuation device for mechanical conditioning of arrays of 3D microtissues.

    PubMed

    Xu, Fan; Zhao, Ruogang; Liu, Alan S; Metz, Tristin; Shi, Yu; Bose, Prasenjit; Reich, Daniel H

    2015-06-01

    This paper describes an approach to actuate magnetically arrays of microtissue constructs for long-term mechanical conditioning and subsequent biomechanical measurements. Each construct consists of cell/matrix material self-assembled around a pair of flexible poly(dimethylsiloxane) (PDMS) pillars. The deflection of the pillars reports the tissues' contractility. Magnetic stretching of individual microtissues via magnetic microspheres mounted on the cantilevers has been used to elucidate the tissues' elastic modulus and response to varying mechanical boundary conditions. This paper describes the fabrication of arrays of micromagnetic structures that can transduce an externally applied uniform magnetic field to actuate simultaneously multiple microtissues. These structures are fabricated on silicon-nitride coated Si wafers and contain electrodeposited Ni bars. Through-etched holes provide optical and culture media access when the devices are mounted on the PDMS microtissue scaffold devices. Both static and AC forces (up to 20 μN on each microtissue) at physiological frequencies are readily generated in external fields of 40 mT. Operation of the magnetic arrays was demonstrated via measurements of elastic modulus and dynamic stiffening in response to AC actuation of fibroblast populated collagen microtissues. PMID:25959132

  18. Pulse electrodeposition and electrochemical quartz crystal microbalance techniques for high perpendicular magnetic anisotropy cobalt nanowire arrays

    SciTech Connect

    Ursache, Andrei; Goldbach, James T.; Russell, Thomas P.; Tuominen, Mark T.

    2005-05-15

    This research is focused on the development of pulse electrodeposition techniques to fabricate a high-density array of vertically oriented, high-magnetic anisotropy cobalt nanowires using a porous polymer film template. This type of array is a competitive candidate for future perpendicular magnetic media capable of storage densities exceeding 1 Terabit/in.{sup 2} The polymer template, derived from a self-assembling P(S-b-MMA) diblock copolymer film, provides precise control over the nanowire diameter (15 nm) and interwire spacing (24 nm), whereas nanowire length (typically 50 to 1000 nm) is controlled accurately with the aid of real-time electrochemical quartz crystal monitoring. Pulse and pulse-reversed electrodeposition techniques, as compared to dc, are shown to significantly enhance the perpendicular magnetic anisotropy of the magnetic nanowire array and ultimately result in coercivity as large as 2.7 kOe at 300 K. Magnetic and structural characterizations suggest that these properties arise from an improved degree of magnetocrystalline anisotropy (due to c-axis oriented crystal growth and improvements in crystal quality) that strongly supplements the basic shape anisotropy of the nanowires. Low temperature magnetometry is used to investigate exchange bias effects due to the incorporation of CoO antiferromagnetic impurities during the electrodeposition process and subsequent Co oxidation in air.

  19. Arrays of nanoscale magnetic dots: Fabrication by x-ray interference lithography and characterization

    SciTech Connect

    Heyderman, L.J.; Solak, H.H.; David, C.; Atkinson, D.; Cowburn, R.P.; Nolting, F.

    2004-11-22

    X-ray interference lithography (XIL) was employed in combination with electrodeposition to fabricate arrays of nanoscale nickel dots which are uniform over 40 {mu}m and have periods down to 71 nm. Using extreme-ultraviolet light, XIL has the potential to produce magnetic dot arrays over large areas with periods well below 50 nm, and down to a theoretical limit of 6.5 nm for a 13 nm x-ray wavelength. In the nickel dot arrays, we observed the effect of interdot magnetic stray field interactions. Measuring the hysteresis loops using the magneto-optical Kerr effect, a double switching via the vortex state was observed in the nickel dots with diameters down to 44 nm and large dot separations. As the dot separations are reduced to below around 50 nm a single switching, occurring by collective rotation of the magnetic spins, is favored due to interdot magnetic stray field interactions. This results in magnetic flux closure through several dots which could be visualized with micromagnetic simulations. Further evidence of the stray field interactions was seen in photoemission electron microscopy images, where bands of contrast corresponding to chains of coupled dots were observed.

  20. A microfabricated magnetic actuation device for mechanical conditioning of arrays of 3D microtissues

    PubMed Central

    Xu, Fan; Zhao, Ruogang; Liu, Alan S.; Metz, Tristin; Shi, Yu; Bose, Prasenjit; Reich, Daniel H.

    2015-01-01

    This paper describes an approach to actuate magnetically arrays of microtissue constructs for long-term mechanical conditioning and subsequent biomechanical measurements. Each construct consists of cell/matrix material self-assembled around a pair of flexible poly(dimethylsiloxane) (PDMS) pillars. The deflection of the pillars reports the tissues contractility. Magnetic stretching of individual microtissues via magnetic microspheres mounted on the cantilevers has been used to elucidate the tissues elastic modulus and response to varying mechanical boundary conditions. This paper describes the fabrication of arrays of micromagnetic structures that can transduce an externally applied uniform magnetic field to actuate simultaneously multiple microtissues. These structures are fabricated on silicon-nitride coated Si wafers and contain electrodeposited Ni bars. Through-etched holes provide optical and culture media access when the devices are mounted on the PDMS microtissue scaffold devices. Both static and AC forces (up to 20 ?N on each microtissue) at physiological frequencies are readily generated in external fields of 40 mT. Operation of the magnetic arrays was demonstrated via measurements of elastic modulus and dynamic stiffening in response to AC actuation of fibroblast populated collagen microtissues. PMID:25959132

  1. Least Squares Magnetic-Field Optimization for Portable Nuclear Magnetic Resonance Magnet Design

    SciTech Connect

    Paulsen, Jeffrey L; Franck, John; Demas, Vasiliki; Bouchard, Louis-S.

    2008-03-27

    Single-sided and mobile nuclear magnetic resonance (NMR) sensors have the advantages of portability, low cost, and low power consumption compared to conventional high-field NMR and magnetic resonance imaging (MRI) systems. We present fast, flexible, and easy-to-implement target field algorithms for mobile NMR and MRI magnet design. The optimization finds a global optimum ina cost function that minimizes the error in the target magnetic field in the sense of least squares. When the technique is tested on a ring array of permanent-magnet elements, the solution matches the classical dipole Halbach solution. For a single-sided handheld NMR sensor, the algorithm yields a 640 G field homogeneous to 16 100 ppm across a 1.9 cc volume located 1.5 cm above the top of the magnets and homogeneous to 32 200 ppm over a 7.6 cc volume. This regime is adequate for MRI applications. We demonstrate that the homogeneous region can be continuously moved away from the sensor by rotating magnet rod elements, opening the way for NMR sensors with adjustable"sensitive volumes."

  2. Stable Divergence Angles of a Magnetic Dipole Spiral Array

    NASA Astrophysics Data System (ADS)

    Fan, X. D.; Bursill, L. A.

    An analytical model is introduced for the experiment of Douady and Couder [Phys. Rev. Lett. 68, 2098 (1992), where phyllotactic patterns appear as a dynamical result of the interaction between magnetic dipoles. The difference equation for the divergence angle (i.e. the angle between successive radial vectors) is obtained by solving the equations of motion with a second nearest neighbor (SNN) approximation. A one-dimensional map analysis as well as a comprehensive analytical proof shows that the divergence angle always converges to a single attractor regardless of the initial conditions. This attractor is approximately the Fibonacci angle(~ 138) within variations due to a growth factor ? of the pattern. The system is proved to be stable with the SNN approximation. Further analysis with a third nearest neighbor approximation (TNN) shows extra linearly stable attractors may appear around the Lucas angle (~ 99.5).

  3. Preparing magnetic yttrium iron garnet nanodot arrays by ultrathin anodic alumina template on silicon substrate

    NASA Astrophysics Data System (ADS)

    Zheng, Hui; Han, Mangui; Zheng, Liang; Zheng, Peng; Wu, Qiong; Deng, Longjiang; Qin, Huibin

    2015-08-01

    Ultrahigh density periodically ordered magnetic yttrium iron garnet (Y3Fe5O12, YIG) nanodot arrays have been prepared by pulsed laser deposition through an ultrathin alumina mask (UTAM). UTAM having periodically ordered circularly shaped holes with 350 nm in diameter, 450 nm in inter-pore distance, and 700 nm in height has been prepared on silicon substrate. Furthermore, the microstructure and magnetic properties of YIG nanodot arrays have been characterized. Nanodot arrays with a sharp distribution in diameter centered at 340 nm with standard deviation of 10 nm have been fabricated. Moreover, typical hysteresis loops and ferromagnetic resonance spectra in in-plane and out-of-plane revealed that this unique structure greatly influences the magnetics properties of YIG. First, coercivity of YIG nanodot arrays in in-plane was increased about from 15 Oe of YIG films to 500 Oe. Then, the degree of uniformity about nanodot height decided that two or more resonance peaks in out-of-plane were detected in the spectra. The peak-to-peak linewidth values were about 94 Oe and 40 Oe in the parallel and perpendicular directions, respectively, which indicated that the values were larger by the two-magnon scattering. Consequently, this pattering method creates opportunities for studying physics in oxide nanomagnets and may be applied in spin-wave devices.

  4. An Orientation Measurement Method Based on Hall-effect Sensors for Permanent Magnet Spherical Actuators with 3D Magnet Array

    NASA Astrophysics Data System (ADS)

    Yan, Liang; Zhu, Bo; Jiao, Zongxia; Chen, Chin-Yin; Chen, I.-Ming

    2014-10-01

    An orientation measurement method based on Hall-effect sensors is proposed for permanent magnet (PM) spherical actuators with three-dimensional (3D) magnet array. As there is no contact between the measurement system and the rotor, this method could effectively avoid friction torque and additional inertial moment existing in conventional approaches. Curved surface fitting method based on exponential approximation is proposed to formulate the magnetic field distribution in 3D space. The comparison with conventional modeling method shows that it helps to improve the model accuracy. The Hall-effect sensors are distributed around the rotor with PM poles to detect the flux density at different points, and thus the rotor orientation can be computed from the measured results and analytical models. Experiments have been conducted on the developed research prototype of the spherical actuator to validate the accuracy of the analytical equations relating the rotor orientation and the value of magnetic flux density. The experimental results show that the proposed method can measure the rotor orientation precisely, and the measurement accuracy could be improved by the novel 3D magnet array. The study result could be used for real-time motion control of PM spherical actuators.

  5. An Orientation Measurement Method Based on Hall-effect Sensors for Permanent Magnet Spherical Actuators with 3D Magnet Array

    PubMed Central

    Yan, Liang; Zhu, Bo; Jiao, Zongxia; Chen, Chin-Yin; Chen, I-Ming

    2014-01-01

    An orientation measurement method based on Hall-effect sensors is proposed for permanent magnet (PM) spherical actuators with three-dimensional (3D) magnet array. As there is no contact between the measurement system and the rotor, this method could effectively avoid friction torque and additional inertial moment existing in conventional approaches. Curved surface fitting method based on exponential approximation is proposed to formulate the magnetic field distribution in 3D space. The comparison with conventional modeling method shows that it helps to improve the model accuracy. The Hall-effect sensors are distributed around the rotor with PM poles to detect the flux density at different points, and thus the rotor orientation can be computed from the measured results and analytical models. Experiments have been conducted on the developed research prototype of the spherical actuator to validate the accuracy of the analytical equations relating the rotor orientation and the value of magnetic flux density. The experimental results show that the proposed method can measure the rotor orientation precisely, and the measurement accuracy could be improved by the novel 3D magnet array. The study result could be used for real-time motion control of PM spherical actuators. PMID:25342000

  6. An orientation measurement method based on Hall-effect sensors for permanent magnet spherical actuators with 3D magnet array.

    PubMed

    Yan, Liang; Zhu, Bo; Jiao, Zongxia; Chen, Chin-Yin; Chen, I-Ming

    2014-01-01

    An orientation measurement method based on Hall-effect sensors is proposed for permanent magnet (PM) spherical actuators with three-dimensional (3D) magnet array. As there is no contact between the measurement system and the rotor, this method could effectively avoid friction torque and additional inertial moment existing in conventional approaches. Curved surface fitting method based on exponential approximation is proposed to formulate the magnetic field distribution in 3D space. The comparison with conventional modeling method shows that it helps to improve the model accuracy. The Hall-effect sensors are distributed around the rotor with PM poles to detect the flux density at different points, and thus the rotor orientation can be computed from the measured results and analytical models. Experiments have been conducted on the developed research prototype of the spherical actuator to validate the accuracy of the analytical equations relating the rotor orientation and the value of magnetic flux density. The experimental results show that the proposed method can measure the rotor orientation precisely, and the measurement accuracy could be improved by the novel 3D magnet array. The study result could be used for real-time motion control of PM spherical actuators. PMID:25342000

  7. Numerical Study of a Crossed Loop Coil Array for Parallel Magnetic Resonance Imaging

    NASA Astrophysics Data System (ADS)

    Hernndez, J.; Solis, S. E.; Rodriguez, A. O.

    2008-08-01

    A coil design has been recently proposed by Temnikov (Instrum Exp Tech. 2005;48;636-637), with higher experimental signal-to-noise ratio than that of the birdcage coil. It is also claimed that it is possible to individually tune it with a single chip capacitor. This coil design shows a great resemble to the gradiometer coil. These results motivated us to numerically simulate a three-coil array for parallel magnetic resonance imaging and in vivo magnetic resonance spectroscopy with multi nuclear capability. The magnetic field was numerical simulated by solving Maxwell's equations with the finite element method. Uniformity profiles were calculated at the midsection for one single coil and showed a good agreement with the experimental data. Then, two more coils were added to form two different coil arrays: coil elements were equally distributed by an angle of a 30 angle. Then, uniformity profiles were calculated again for all cases at the midsection. Despite the strong interaction among all coil elements, very good field uniformity can be achieved. These numerical results indicate that this coil array may be a good choice for magnetic resonance imaging parallel imaging.

  8. Magnetic properties of Ni-Fe nanowire arrays: effect of template material and deposition conditions

    SciTech Connect

    Singleton, John; Aravamudhan, Shyan; Goddard, Paul A; Bhansali, Shekhar

    2008-01-01

    The objective of this work is to study the magnetic properties of arrays of Ni-Fe nanowires electrodeposited in different template materials such as porous silicon, polycarbonate and alumina. Magnetic properties were studied as a function of template material, applied magnetic field (parallel and perpendicular) during deposition, wire length, as well as magnetic field orientation during measurement. The results show that application of magnetic field during deposition strongly influences the c-axis preferred orientation growth of Ni-Fe nanowires. The samples with magnetic field perpendicular to template plane during deposition exhibits strong perpendicular anisotropy with greatly enhanced coercivity and squareness ratio, particularly in Ni-Fe nanowires deposited in polycarbonate templates. In case of polycarbonate template, as magnetic field during deposition increases, both coercivity and squareness ratio also increase. The wire length dependence was also measured for polycarbonate templates. As wire length increases, coercivity and squarness ratio decrease, but saturation field increases. Such magnetic behavior (dependence on template material, magnetic field, wire length) can be qualitatively explained by preferential growth phenomena, dipolar interactions among nanowires, and perpendicular shape anisotropy in individual nanowires.

  9. Discovery of hard-magnetic domains in two-dimensional arrays of soft-magnetic Fe3O4 nanocubes

    NASA Astrophysics Data System (ADS)

    Ma, Ji; Sun, Shuangshuang; Wang, Tiantian; Chen, Kezheng

    2015-08-01

    In this study, abnormal hard-magnetic domains were discovered in Fe3O4@C composite material, in which well-ordered 16-nm-sized Fe3O4 cubes were tightly embedded into carbon sheets of tens of nanometers thick. It was found that ca. 40 columns of Fe3O4 nanocubes magnetically self-assembled into a single strip-type domain with perpendicular magnetic anisotropy. More strikingly, remarkable domain misalignments, which were very similar to common edge dislocations among atomic planes in crystal lattices, were clearly observed and termed as "domain dislocation" in this work. The hard-magnetic properties of Fe3O4@C material, including large coercivity of 2150 Oe, high MR/MS value of 0.9, and strong anisotropy energy of 3.772 105 erg/cm3, were further ascertained by carefully designed electromagnetic absorption contrast experiments. It is anticipated that the discovery of hard-magnetic domains and domain dislocations within 2-D arrays of soft-magnetic nanomaterials will shed new light on the development of high-density perpendicular magnetic recording industry.

  10. A fully automated in vitro diagnostic system based on magnetic tunnel junction arrays and superparamagnetic particles

    NASA Astrophysics Data System (ADS)

    Lian, Jie; Chen, Si; Qiu, Yuqin; Zhang, Suohui; Shi, Stone; Gao, Yunhua

    2012-04-01

    A fully automated in vitro diagnostic (IVD) system for diagnosing acute myocardial infarction was developed using high sensitivity MTJ array as sensors and nano-magnetic particles as tags. On the chip is an array of 12 × 106 MTJ devices integrated onto a 3 metal layer CMOS circuit. The array is divided into 48 detection areas, therefore 48 different types of bio targets can be analyzed simultaneously if needed. The chip is assembled with a micro-fluidic cartridge which contains all the reagents necessary for completing the assaying process. Integrated with electrical, mechanical and micro-fluidic pumping devices and with the reaction protocol programed in a microprocessor, the system only requires a simple one-step analyte application procedure to operate and yields results of the three major AMI bio-markers (cTnI, MYO, CK-MB) in 15 mins.

  11. Magnetic response at visible and near-infrared frequencies from black phosphorus sheet arrays.

    PubMed

    Wang, Tiecheng; Zhang, Xiangdong

    2015-11-30

    We study theoretically optical properties of black phosphorus (BP) sheet arrays being embedded in the dielectric multilayer structure using transfer-matrix method. It is found that the dielectric multilayer structures containing BP sheet arrays can exhibit rich optical properties. In some frequency regions, strong anisotropy appears for the scattering and absorption of polarized waves. Thus, they can be used as the selective absorption materials for two kinds of polarized wave. In contrast, in some visible and near-infrared frequency regions, low absorption and strong magnetic response have been observed. This means that they can be also used as good magnetic response materials at visible and near-infrared frequencies. Our results could find applications in various control of polarized waves. PMID:26698699

  12. Magnetization reversal in lithographically patterned sub-200-nm Co particle arrays

    NASA Astrophysics Data System (ADS)

    Hao, Y.; Castao, F. J.; Ross, C. A.; Vgeli, B.; Walsh, M. E.; Smith, Henry I.

    2002-05-01

    A series of Co particle arrays with rectangular elements having a thickness of 10 nm, a width of 90 nm and aspect ratios of 1.3, 2.2, and 3.3, has been fabricated using interference lithography. The switching behavior of these arrays has been studied by measuring isothermal remanence measurement (IRM), dc demagnetization measurement (DCD), and hysteresis loops using magnetometry and magnetic force microscopy (MFM). The single domain structure is the only stable structure at remanence. Nonuniformity and redeposition debris from ion beam etching (IBE) cause a large reversible magnetization component. The comparison between IRM and DVD curves shows that the interactions between the dots are negligible. Both vibrating sample magnetometer (VSM) measurements and MFM images show that the dots switch over a large range of fields, which is believed due mainly to the crystallographic orientation distribution of the grams within each element.

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

    SciTech Connect

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

    2008-06-25

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

  14. Magnetic alignment of high-aspect ratio microwires into vertical arrays

    NASA Astrophysics Data System (ADS)

    Beardslee, Joseph

    Fundamental studies of magnetic alignment of highly anisotropic mesostructures can enable the clean-room-free fabrication of flexible, array-based solar and electronic devices, in which preferential orientation of nano- or microwire-type objects is desired. In this study, ensembles of 100 micron long Si microwires with ferromagnetic Ni and Co coatings are oriented vertically in the presence of magnetic fields. The degree of vertical alignment and threshold field strength depend on geometric factors, such as microwire length and ferromagnetic coating thickness, as well as interfacial interactions, which are modulated by varying solvent and substrate surface chemistry. Microwire ensembles with vertical alignment over 97% within 10 degrees of normal, as measured by X-ray diffraction, are achieved over square cm scale areas and set into flexible polymer films. A force balance model has been developed as a predictive tool for magnetic alignment, incorporating magnetic torque and empirically derived surface adhesion parameters. As supported by these calculations, microwires are shown to detach from the surface and align vertically in the presence of magnetic fields on the order of 100 gauss. Microwires aligned in this manner are set into a polydimethylsiloxane film where they retain their vertical alignment after the field has been removed and can subsequently be used as a flexible solar absorber layer. Finally, these microwires arrays can be protected for use in electrochemical cells by the conformal deposition of a graphene layer.

  15. Ordering and thermal excitations in dipolar coupled single domain magnet arrays (Presentation Recording)

    NASA Astrophysics Data System (ADS)

    stman, Erik; Arnalds, Unnar; Kapaklis, Vassilios; Hjrvarsson, Bjrgvin

    2015-09-01

    For a small island of a magnetic material the magnetic state of the island is mainly determined by the exchange interaction and the shape anisotropy. Two or more islands placed in close proximity will interact through dipolar interactions. The state of a large system will thus be dictated by interactions at both these length scales. Enabling internal thermal fluctuations, e.g. by the choice of material, of the individual islands allows for the study of thermal ordering in extended nano-patterned magnetic arrays [1,2]. As a result nano-magnetic arrays represent an ideal playground for the study of physical model systems. Here we present three different studies all having used magneto-optical imaging techniques to observe, in real space, the order of the systems. The first study is done on a square lattice of circular islands. The remanent magnetic state of each island is a magnetic vortex structure and we can study the temperature dependence of the vortex nucleation and annihilation fields [3]. The second are long chains of dipolar coupled elongated islands where the magnetization direction in each island only can point in one of two possible directions. This creates a system which in many ways mimics the Ising model [4] and we can relate the correlation length to the temperature. The third one is a spin ice system where elongated islands are placed in a square lattice. Thermal excitations in such systems resemble magnetic monopoles [2] and we can investigate their properties as a function of temperature and lattice parameters. [1] V. Kapaklis et al., New J. Phys. 14, 035009 (2012) [2] V. Kapaklis et al., Nature Nanotech 9, 514(2014) [3] E. stman et al.,New J. Phys. 16, 053002 (2014) [4] E. stman et al.,Thermal ordering in mesoscopic Ising chains, In manuscript.

  16. Magnetic properties of self-organized lateral arrays of (Fe,Ag)/Mo(110) nanostripes

    NASA Astrophysics Data System (ADS)

    Borca, B.; Fruchart, O.; Meyer, C.

    2006-04-01

    We report the fabrication of self-organized arrays of Fe nanostripes with a lateral period of 3.5 nm by sequential deposition of Fe and Ag on Mo(110). The wires display a strong in-plane uniaxial magnetic anisotropy along their length and are superparamagnetic above TB=185+/-15 K. The large value of nucleation volumes, which is inferred from the analysis of the thermal dependence of coercivity below TB, suggests the existence of interactions between the wires.

  17. Numerical Studies on Quantum Transport in Antidot Arrays in Magnetic Fields

    NASA Astrophysics Data System (ADS)

    Ishizaka, Satoshi; Nihey, Fumiyuki; Nakamura, Kazuo; Sone, Jun'ichi; Ando, Tsuneya

    1995-08-01

    The density of states and the conductivity tensor in antidot arrays in magnetic fields are calculated numerically by the self-consistent Born approximation (SCBA). The peak positions of the density of states agree well with the quantization condition for several short-periodic orbits. The behavior of calculated magnetoresistivity agrees with that of experimental data. However, the behavior of the conductivity tensor is very complicated, and it is not explained simply by the periodic orbit expression for the conductivity tensor.

  18. High spatial resolution Hall sensor array for edge plasma magnetic field measurements

    SciTech Connect

    Liu Yuhong; Maurer, David A.; Navratil, Gerald A.; Rivera, Nicholas

    2005-09-15

    A one-dimensional, high-spatial resolution, 20-element Hall sensor array has been developed to directly measure the edge plasma perpendicular magnetic field and its fluctuations as a function of radius with 4-mm resolution. The array employs new small-area, high-sensitivity indium antimonide (InSb) Hall probes in combination with a high-density seven-layer printed circuit board to provide for connections to supply Hall current, record the measured Hall voltage output signals, and mitigate inductive pickup. A combination of bench and in situ measurements is described that provides absolute calibration of the diagnostic array in the presence of a strong transverse magnetic field component that is approximately 1000 times greater than the perpendicular fluctuating field needed to be resolved by the diagnostic. The Hall probes calibrated using this method are capable of magnetic field measurements with a sensitivity of 7 V/T over the frequency band from 0 to 20 kHz.

  19. Lithographically Patterned Nanoscale Electrodeposition of Plasmonic, Bimetallic, Semiconductor, Magnetic, and Polymer Nanoring Arrays

    PubMed Central

    2015-01-01

    Large area arrays of magnetic, semiconducting, and insulating nanorings were created by coupling colloidal lithography with nanoscale electrodeposition. This versatile nanoscale fabrication process allows for the independent tuning of the spacing, diameter, and width of the nanorings with typical values of 1.0 ?m, 750 nm, and 100 nm, respectively, and was used to form nanorings from a host of materials: Ni, Co, bimetallic Ni/Au, CdSe, and polydopamine. These nanoring arrays have potential applications in memory storage, optical materials, and biosensing. A modified version of this nanoscale electrodeposition process was also used to create arrays of split gold nanorings. The size of the split nanoring opening was controlled by the angle of photoresist exposure during the fabrication process and could be varied from 50% down to 10% of the ring circumference. The large area (cm2 scale) gold split nanoring array surfaces exhibited strong polarization-dependent plasmonic absorption bands for wavelengths from 1 to 5 ?m. Plasmonic nanoscale split ring arrays are potentially useful as tunable dichroic materials throughout the infrared and near-infrared spectral regions. PMID:25553204

  20. Shielding of Sensitive Electronic Devices in Magnetic Nanoparticle Hyperthermia Using Arrays of Coils

    NASA Astrophysics Data System (ADS)

    Spirou, S. V.; Tsialios, P.; Loudos, G.

    2015-09-01

    In Magnetic Nanoparticle Hyperthermia (MNH) an externally applied electromagnetic field transfers energy to the magnetic nanoparticles in the body, which in turn convert this energy into heat, thus locally heating the tissue they are located in. This external electromagnetic field is sufficiently strong so as to cause interference and affect sensitive electronic equipment. Standard shielding of magnetic fields involves Faraday cages or coating with high-permeability shielding alloys; however, these techniques cannot be used with optically sensitive devices, such as those employed in Optical Coherence Tomography or radionuclide imaging. In this work we present a method to achieve magnetic shielding using an array of coils. The magnetic field generated by a single coil was calculated using the COMSOL physics simulation toolkit. Software was written in C/C++ to import the single-coil data, and then calculate the positions, number of turns and currents in the shielding coils in order to minimize the magnetic field strength at the desired location. Simulations and calculations have shown that just two shielding coils can reduce the magnetic field by 2-3 orders of magnitude.

  1. Temperature dependent magnetization in Co-base nanowire arrays: Role of crystalline anisotropy

    NASA Astrophysics Data System (ADS)

    Vivas, L. G.; Vzquez, M.; Vega, V.; Garca, J.; Rosa, W. O.; del Real, R. P.; Prida, V. M.

    2012-04-01

    Co, Co(1-x)Pdx, and Co(1-y)Niy nanowire arrays have been prepared by electrochemical template-assisted growth. Hcp, fcc or both phases are detected in Co nanowires depending on their length (300 nm to 40 ?m) and on the content of Pd (0 ? x ? 0.4) and Ni (0 ? y ? 0.8). Their magnetic behavior has been studied under longitudinal and perpendicular applied fields. The effective magnetic anisotropy is mostly determined by the balance between the shape and the crystalline terms, the latter depending on the fractional volume of hcp phase with strong perpendicular anisotropy and fcc phase with weaker longitudinal anisotropy. The temperature dependence of remanence and coercivity and the eventual observation of compensation temperature is interpreted as due to the different temperature dependence of shape and hcp crystalline anisotropy. Optimum longitudinal magnetic anisotropy is achieved in low Pd-content CoPd nanowires and in short Co nanowires.

  2. The origin of magnetic fields in galaxies: Observational tests with the Square Kilometre Array

    NASA Astrophysics Data System (ADS)

    Beck, R.

    2006-06-01

    The all-sky survey of Faraday rotation, a Key Science Project of the planned Square Kilometre Array, will accumulate tens of millions of rotation measure measurements toward background radio sources and will provide a unique database for characterizing the overall magnetic geometry of magnetic fields in galaxies and in the intergalactic medium. Deep imaging of the polarized synchrotron emission from a large number of nearby galaxies, combined with Faraday rotation data, will allow us to test primordial, gas flow, and dynamo models for field origin and amplification. The SKA will find the first magnetic fields in young galaxies and determine the timescale for building up small-scale turbulent and large-scale coherent fields. The spectrum of dynamo modes, if existing, will be resolved. The present-day coherent field may keep memory of the direction of the seed field which can be used for mapping the structure of the seed field before galaxy formation.

  3. Magnetic shielding of large high-power-satellite solar arrays using internal currents

    NASA Technical Reports Server (NTRS)

    Parker, L. W.; Oran, W. A.

    1979-01-01

    Present concepts for solar power satellites involve dimensions up to tens of kilometers and operating internal currents up to hundreds of kiloamperes. A question addressed is whether the local magnetic fields generated by these strong currents during normal operation can shield the array against impacts by plasma ions and electrons (and from thruster plasmas) which can cause possible losses such as power leakage and surface erosion. One of several prototype concepts was modeled by a long narrow rectangular panel 2 km wide and 20 km long. The currents flow in a parallel across the narrow dimension (sheet current) and along the edge (wire currents). The wire currents accumulate from zero to 100 kiloamp and are the dominant sources. The magnetic field is approximated analytically. The equations of motion for charged particles in this magnetic field are analyzed. The ion and electron fluxes at points on the surface are represented analytically for monoenergetic distributions and are evaluated.

  4. Magnetization reversal and coercivity of Fe3Se4 nanowire arrays

    NASA Astrophysics Data System (ADS)

    Li, D.; Li, S. J.; Zhou, Y. T.; Bai, Y.; Zhu, Y. L.; Ren, W. J.; Long, G.; Zeng, H.; Zhang, Z. D.

    2015-05-01

    The microstructure and magnetic properties of Fe3Se4 nanowire (NW) arrays in anodic aluminum oxide (AAO) porous membrane are studied. Cross-sectional SEM and plane-view TEM images show that the mean wire diameter (dw) and the center-to-center spacing (D) of Fe3Se4 nanowires are about 220 nm and 330 nm, respectively. The field-cooled magnetization dependent on the temperature indicates a Curie temperature around 334 K for the Fe3Se4 nanowires. The coercivities of Fe3Se4 nanowires at 10 K, obtained from the in-plane and out-of-plane hysteresis loops, are as high as 22.4 kOe and 23.3 kOe, which can be understood from the magnetocrystalline anisotropy and the magnetization reversal process.

  5. Magnetic Nanoparticle Arrays Self-Assembled on Perpendicular Magnetic Recording Media

    PubMed Central

    Mohtasebzadeh, Abdul Rahman; Ye, Longfei; Crawford, Thomas M.

    2015-01-01

    We study magnetic-field directed self-assembly of magnetic nanoparticles onto templates recorded on perpendicular magnetic recording media, and quantify feature width and height as a function of assembly time. Feature widths are determined from Scanning Electron Microscope (SEM) images, while heights are obtained with Atomic Force Microscopy (AFM). For short assembly times, widths were ~150 nm, while heights were ~14 nm, a single nanoparticle on average with a 10:1 aspect ratio. For long assembly times, widths approach 550 nm, while the average height grows to 3 nanoparticles, ~35 nm; a 16:1 aspect ratio. We perform magnetometry on these self-assembled structures and observe the slope of the magnetic moment vs. field curve increases with time. This increase suggests magnetic nanoparticle interactions evolve from nanoparticlenanoparticle interactions to clustercluster interactions as opposed to featurefeature interactions. We suggest the aspect ratio increase occurs because the magnetic field gradients are strongest near the transitions between recorded regions in perpendicular media. If these gradients can be optimized for assembly, strong potential exists for using perpendicular recording templates to assemble complex heterogeneous materials. PMID:26307967

  6. Magnetization mechanisms in ordered arrays of polycrystalline Fe100-xCox nanowires

    NASA Astrophysics Data System (ADS)

    Viqueira, M. S.; Bajales, N.; Urreta, S. E.; Bercoff, P. G.

    2015-05-01

    Magnetization reversal processes and coercivity mechanisms in polycrystalline Fe100-xCox nanowire arrays, resulting from an AC electrodeposition process, are investigated. The array coercivity is described on the basis of polarization reversal mechanisms operating in individual wires, under the effect of inter-wire dipolar interactions described by a mean field approximation. For individual wires, a reversal mechanism involving the nucleation and further expansion of domain-wall like spin configuration is considered. The wires have a mean grain size larger than both the nanowire diameter and the exchange length, so localized and non-cooperative nucleation modes are considered. As the Co content increases, the alloy saturation polarization gradually decreases, but the coercive field and the relative remanence of the arrays increase, indicating that they are not controlled by the shape anisotropy in all the composition range. The coercive field dependence on the angle between the applied field and the wire long axis is not well described by reversal mechanisms involving nucleation and further displacement of neither vortex nor transverse ideal domain walls. On the contrary, the angular dependence of the coercive field observed at room temperature is well predicted by a model considering nucleation of inverse domains by localized curling, in regions smaller than the grain size, exhibiting quite small aspect ratios as compared to those of the entire nanowire. In arrays with higher Co contents, a transition from an initial (small angle) localized curling nucleation mechanism to another one, involving localized coherent rotation is observed at about ?/4.

  7. A nested phosphorus and proton coil array for brain magnetic resonance imaging and spectroscopy.

    PubMed

    Brown, Ryan; Lakshmanan, Karthik; Madelin, Guillaume; Parasoglou, Prodromos

    2016-01-01

    A dual-nuclei radiofrequency coil array was constructed for phosphorus and proton magnetic resonance imaging and spectroscopy of the human brain at 7T. An eight-channel transceive degenerate birdcage phosphorus module was implemented to provide whole-brain coverage and significant sensitivity improvement over a standard dual-tuned loop coil. A nested eight-channel proton module provided adequate sensitivity for anatomical localization without substantially sacrificing performance on the phosphorus module. The developed array enabled phosphorus spectroscopy, a saturation transfer technique to calculate the global creatine kinase forward reaction rate, and single-metabolite whole-brain imaging with 1.4cm nominal isotropic resolution in 15min (2.3cm actual resolution), while additionally enabling 1mm isotropic proton imaging. This study demonstrates that a multi-channel array can be utilized for phosphorus and proton applications with improved coverage and/or sensitivity over traditional single-channel coils. The efficient multi-channel coil array, time-efficient pulse sequences, and the enhanced signal strength available at ultra-high fields can be combined to allow volumetric assessment of the brain and could provide new insights into the underlying energy metabolism impairment in several neurodegenerative conditions, such as Alzheimer's and Parkinson's diseases, as well as mental disorders such as schizophrenia. PMID:26375209

  8. Magnetic-optical bifunctional CoPt3/Co multilayered nanowire arrays

    NASA Astrophysics Data System (ADS)

    Su, Yi-Kun; Yan, Zhi-Long; Wu, Xi-Ming; Liu, Huan; Ren, Xiao; Yang, Hai-Tao

    2015-10-01

    CoPt3/Co multilayered nanowire (NW) arrays are synthesized by pulsed electrodeposition into nanoporous anodic aluminum oxide (AAO) templates. The electrochemistry deposition parameters are determined by cyclic voltammetry to realize the well control of the ratio of Co to Pt and the length of every segment. The x-ray diffraction (XRD) patterns show that both Co and CoPt3 NWs exhibit face-centered cubic (fcc) structures. In the UV-visible absorption spectra, CoPt3/Co NW arrays show a red-shift with respect to pure CoPt3NWs. Compared with the pure Co nanowire arrays, the CoPt3/Co multilayered nanowire arrays show a weak shape anisotropy and well-modulated magnetic properties. CoPt3/Co multilayered nanowires are highly encouraging that new families of bimetallic nanosystems may be developed to meet the needs of nanomaterials in emerging multifunctional nanotechnologies. Project supported by the National Natural Science Foundation of China (Grant Nos. 51472165, 51471185, and 11274370).

  9. Influence of the properties of soft collective spin wave modes on the magnetization reversal in finite arrays of dipolarly coupled magnetic dots

    NASA Astrophysics Data System (ADS)

    Stebliy, Maxim; Ognev, Alexey; Samardak, Alexander; Chebotkevich, Ludmila; Verba, Roman; Melkov, Gennadiy; Tiberkevich, Vasil; Slavin, Andrei

    2015-06-01

    Magnetization reversal in finite chains and square arrays of closely packed cylindrical magnetic dots, having vortex ground state in the absence of the external bias field, has been studied experimentally by measuring static hysteresis loops, and also analyzed theoretically. It has been shown that the field Bn of a vortex nucleation in a dot as a function of the finite number N of dots in the array's side may exhibit a monotonic or an oscillatory behavior depending on the array geometry and the direction of the external bias magnetic field. The oscillations in the dependence Bn(N) are shown to be caused by the quantization of the collective soft spin wave mode, which corresponds to the vortex nucleation in a finite array of dots. These oscillations are directly related to the form and symmetry of the dispersion law of the soft SW mode: the oscillation could appear only if the minimum of the soft mode spectrum is not located at any of the symmetric points inside the first Brillouin zone of the array's lattice. Thus, the purely static measurements of the hysteresis loops in finite arrays of coupled magnetic dots can yield important information about the properties of the collective spin wave excitations in these arrays.

  10. Velocity-selected magnetic guiding of Zeeman-decelerated hydrogen atoms

    NASA Astrophysics Data System (ADS)

    Dulitz, Katrin; Softley, Timothy P.

    2016-01-01

    An original design of magnetic guide is presented, suitable for use with Zeeman-decelerated supersonic beams of ground-state hydrogen atoms and other light paramagnetic species. Three-dimensional particle trajectory simulations show that, by combining a series of permanent-magnet Halbach arrays with pulsed high-current wire electromagnets, this guide can be used to efficiently transmit the slow, decelerated atoms and discard the faster, undecelerated atoms and other species in the gas beam. The curved guide would be suitable for guiding hydrogen atoms into an ion trap to investigate low temperature ion-molecule collisions. It is also shown that the device could be used for the guiding or velocity selection from an undecelerated supersonic or effusive beam.

  11. Application of an array processor to the analysis of magnetic data for the Doublet III tokamak

    SciTech Connect

    Wang, T.S.; Saito, M.T.

    1980-08-01

    Discussed herein is a fast computational technique employing the Floating Point Systems AP-190L array processor to analyze magnetic data for the Doublet III tokamak, a fusion research device. Interpretation of the experimental data requires the repeated solution of a free-boundary nonlinear partial differential equation, which describes the magnetohydrodynamic (MHD) equilibrium of the plasma. For this particular application, we have found that the array processor is only 1.4 and 3.5 times slower than the CDC-7600 and CRAY computers, respectively. The overhead on the host DEC-10 computer was kept to a minimum by chaining the complete Poisson solver and free-boundary algorithm into one single-load module using the vector function chainer (VFC). A simple time-sharing scheme for using the MHD code is also discussed.

  12. Ion Beam Stabilization of FePt Nanoparticle Arrays for Magnetic Storage Media

    SciTech Connect

    Toney, Michael F

    2003-07-31

    The authors describe the use of ion beam induced crosslinking to harden the organic matrix material of self-assembled arrays of monodisperse (4 nm) FePt nanoparticles, providing diamondlike carbon barriers to inhibit agglomeration of the nanoparticles under heat treatment. Such stabilization is necessary for the particles to survive the > 500 C annealing required for growth of the fct L 1{sub 0} phase of FePt, whose magnetic anisotropy is necessary for application of such arrays for high density perpendicular recording. Selective area irradiation of continuous nanoparticle coatings, using ion beams patterned over a full disk by stencil mask or with ion projection optics, followed by dissolution of the unexposed coating, is proposed as a means of fabricating extended bit patterns consisting of isolated islands of FePt nanoparticles, with characteristic dimensions of tens of nanometers.

  13. Diffraction-induced subradiant transverse-magnetic lattice plasmon modes in metal nanoparticle arrays

    SciTech Connect

    Nikitin, Andrey G.

    2014-02-10

    This Letter reports theoretical and experimental study of transverse-magnetic-like lattice plasmon modes originating from diffraction in periodic two dimensional arrays of metal nanoparticles. These modes lead to the transmission and reflection spectra exhibiting narrow linewidth Fano-like resonances which can appear as maxima, minima, or can have asymmetric peak-and-dip profile. The dependencies of the position and lineshape of the resonance on the lattice periodicity and angle of incidence are investigated. Numerical simulations of electric field distributions for different excitation conditions of lattice plasmon modes are also performed.

  14. Standing-wave excited soft x-ray photoemission microscopy: application to Co microdot magnetic arrays

    SciTech Connect

    Gray, Alexander; Kronast, Florian; Papp, Christian; Yang, See-Hun; Cramm, Stefan; Krug, Ingo P.; Salmassi, Farhad; Gullikson, Eric M.; Hilken, Dawn L.; Anderson, Erik H.; Fischer, Peter; Durr, Hermann A.; Schneider, Claus M.; Fadley, Charles S.

    2010-10-29

    We demonstrate the addition of depth resolution to the usual two-dimensional images in photoelectron emission microscopy (PEEM), with application to a square array of circular magnetic Co microdots. The method is based on excitation with soft x-ray standing-waves generated by Bragg reflection from a multilayer mirror substrate. Standing wave is moved vertically through sample simply by varying the photon energy around the Bragg condition. Depth-resolved PEEM images were obtained for all of the observed elements. Photoemission intensities as functions of photon energy were compared to x-ray optical calculations in order to quantitatively derive the depth-resolved film structure of the sample.

  15. A six-degree-of-freedom magnetic levitation fine stage for a high-precision and high-acceleration dual-servo stage

    NASA Astrophysics Data System (ADS)

    Kim, MyeongHyeon; Jeong, Jae-heon; Kim, HyoYoung; Gweon, DaeGab

    2015-10-01

    This paper presents a novel six-degree-of-freedom magnetic levitation fine stage for a dual-servo stage. The proposed fine stage is levitated and actuated, using a voice coil motor actuator with a Halbach magnet array. For a dual-servo stage, fine stage performance is deeply intertwined with coarse stage performance. Because the fine stage is installed over the coarse stage, the overall size of the fine stage can be limited by the moving plate of the coarse stage. Therefore, magnetic flux modeling and optimization are performed to manufacture optimal fine stages. To control the fine stage, actuator kinetics and sensor kinematics are proposed. Homing control is implemented by using linear variable differential transformers, whereas fine control is implemented by capacitance sensors and laser interferometers. Finally, experimental results of in-position stability, moving range, and repeatability are presented.

  16. Implementation of a decoupled controller for a magnetic suspension system using electromagnets mounted in a planar array

    NASA Technical Reports Server (NTRS)

    Cox, D. E.; Groom, N. J.

    1994-01-01

    An implementation of a decoupled, single-input/single-output control approach for a large angle magnetic suspension test fixture is described. Numerical and experimental results are presented. The experimental system is a laboratory model large gap magnetic suspension system which provides five degree-of-freedom control of a cylindrical suspended element. The suspended element contains a core composed of permanent magnet material and is levitated above five electromagnets mounted in a planar array.

  17. Dense arrays of cobalt nanorods as rare-earth free permanent magnets

    NASA Astrophysics Data System (ADS)

    Anagnostopoulou, E.; Grindi, B.; Lacroix, L.-M.; Ott, F.; Panagiotopoulos, I.; Viau, G.

    2016-02-01

    We demonstrate in this paper the feasibility to elaborate rare-earth free permanent magnets based on cobalt nanorods assemblies with energy product (BH)max exceeding 150 kJ m-3. The cobalt rods were prepared by the polyol process and assembled from wet suspensions under a magnetic field. Magnetization loops of dense assemblies with remanence to a saturation of 0.99 and squareness of 0.96 were measured. The almost perfect M(H) loop squareness together with electron microscopy and small angle neutron scattering demonstrate the excellent alignment of the rods within the assemblies. The magnetic volume fraction was carefully measured by coupling magnetic and thermogravimetric analysis and found in the range from 45 to 55%, depending on the rod diameter and the alignment procedure. This allowed a quantitative assessment of the (BH)max values. The highest (BH)max of 165 kJ m-3 was obtained for a sample combining a high magnetic volume fraction and a very large M(H) loop squareness. This study shows that this bottom-up approach is very promising to get new hard magnetic materials that can compete in the permanent magnet panorama and fill the gap between the ferrites and the NdFeB magnets.We demonstrate in this paper the feasibility to elaborate rare-earth free permanent magnets based on cobalt nanorods assemblies with energy product (BH)max exceeding 150 kJ m-3. The cobalt rods were prepared by the polyol process and assembled from wet suspensions under a magnetic field. Magnetization loops of dense assemblies with remanence to a saturation of 0.99 and squareness of 0.96 were measured. The almost perfect M(H) loop squareness together with electron microscopy and small angle neutron scattering demonstrate the excellent alignment of the rods within the assemblies. The magnetic volume fraction was carefully measured by coupling magnetic and thermogravimetric analysis and found in the range from 45 to 55%, depending on the rod diameter and the alignment procedure. This allowed a quantitative assessment of the (BH)max values. The highest (BH)max of 165 kJ m-3 was obtained for a sample combining a high magnetic volume fraction and a very large M(H) loop squareness. This study shows that this bottom-up approach is very promising to get new hard magnetic materials that can compete in the permanent magnet panorama and fill the gap between the ferrites and the NdFeB magnets. Electronic supplementary information (ESI) available: Transmission electron microscopy images of the cobalt nanorods; thermogravimetric analysis of a dense array of cobalt nanorods; Table S1 details on the rod washing and alignment procedure. See DOI: 10.1039/c5nr07143g

  18. Structure -- Magnetic Property Correlations in TiO 2 Nanotube Arrays

    NASA Astrophysics Data System (ADS)

    Mohammad Hosseinpour, Pegah

    TiO2 nanotube arrays are promising candidates for applications such as photocatalysis and for potential employment in spin-electronic (spintronic) devices. The functionality of TiO2-based nanotubes is highly dependent on their structure (microstructure and crystallographic symmetry) and magnetic properties. Unified understanding of the influence of these factors on the electronic structure of TiO2 is of paramount importance towards engineering these materials. This Dissertation aims at investigating the correlations of the morphology, crystallinity, crystal structure, electronic structure and magnetic properties of TiO2 nanotubes, with potential relevance to their functionality. Self-ordered arrays of amorphous TiO2 nanotubes (pure and Fe-doped with cationic concentration of ~2.1 at%) were synthesized by the electrochemical anodization technique, followed by subjecting them to thermal treatments up to 450 C to crystallize these nanostructures. A variety of probes---morphological, structural, magnetic and spectroscopic---were used to characterize the properties of these nanostructures as functions of their processing conditions and the dopant content. Structure-functionality relationships in these nanostructures were verified by examining the photodegradation rate of methyl orange (a model water pollutant) in presence of TiO2 nanotubes under UV-Visible light irradiation. Results from this Dissertation research demonstrated that post-synthesis processing conditions---specifically, the nature of the annealing environment, as well as the presence of an external dopant, can alter the crystal structure and local electronic environment in TiO2 nanotubes, with subsequent effects on the magnetic properties of these nanostructures. The fundamental knowledge obtained in this research, on the interrelations of structural-magnetic properties and their potential influence on the functionality of TiO 2-based nanotubes, can be extended to the metal oxide semiconducting systems in general and is anticipated to provide avenues toward novel materials with enhanced functionality that originates from such tailored structural and magnetic characteristics. Despite the success achieved in this Dissertation, there are still open questions to be addressed in order to further enhance the fundamental knowledge of structure---magnetic property correlations in TiO2 nanotubes. In this regard, the concluding section of this Dissertation provides recommendations for additional experiments. Accomplishment of these recommendations is anticipated to provide enhanced insight into the various aspects of property-functionality relationships in TiO2-based nanomaterials, and provides paths to engineer novel multifunctional oxide-based materials for energy-related applications.

  19. A comparison of sensors for minimizing the primary signal in planar-array magnetic induction tomography.

    PubMed

    Watson, S; Igney, C H; Dssel, O; Williams, R J; Griffiths, H

    2005-04-01

    In magnetic induction tomography reducing the influence of the primary excitation field on the sensors can provide a significant improvement in SNR and/or allow the operating frequency to be reduced. For the purposes of imaging, it would be valuable if all, or a useful subset, of the detection coils could be rendered insensitive to the primary field for any excitation coil activated. Suitable schemes which have been previously suggested include the use of axial gradiometers and coil-orientation methods (Bx sensors). This paper examines the relative performance of each method through computer simulation of the sensitivity profiles produced by a single sensor, and comparison of reconstructed images produced by sensor arrays. A finite-difference model was used to determine the sensitivity profiles obtained with each type of sensor arrangement. The modelled volume was a cuboid of dimensions 50 cmx50 cmx12 cm with a uniform conductivity of 1 S m-1. The excitation coils were of 5 cm diameter and the detection coils of 5 mm diameter. The Bx sensors provided greater sensitivity than the axial gradiometers at all depths, other than on the surface layer of the volume. Images produced using a single-planar array were found to contain distortion which was reduced by the addition of a second array. PMID:15798244

  20. Cryogenic Characterization and Testing of Magnetically-Actuated Microshutter Arrays for the James Webb Space Telescope

    NASA Technical Reports Server (NTRS)

    King, T. T.; Kletetschka, G.; Jah, M. A.; Li, M. J.; Jhabvala, M. D.; Wang, L. L.; Beamesderfer, M. A.; Kutyrev, A. S.; Silverberg, R. F.; Rapchun, D.; Schwinger, D. S.

    2004-01-01

    Two-dimensional MEMS microshutter arrays (MSA) have been fabricated at the NASA Goddard Space Flight Center (GSFC) for the James Webb Space Telescope (JWST) to enable cryogenic (approximately 35 K) spectrographic astronomy measurements in the near-infrared region. Functioning as a focal plane object selection device, the MSA is a 2-D programmable aperture mask with fine resolution, high efficiency and high contrast. The MSA are close- packed silicon nitride shutters (cell size of 100 x 200 microns) patterned with a torsion flexure to allow opening to 90 degrees. A layer of magnetic material is deposited onto each shutter to permit magnetic actuation. Two electrodes are deposited, one onto each shutter and another onto the support structure side-wall, permitting electrostatic latching and 2-D addressing. New techniques were developed to test MSA under mission-similar conditions (8 K less than or equal to T less than 300K). The magnetic rotisserie has proven to be an excellent tool for rapid characterization of MSA. Tests conducted with the magnetic rotisserie method include accelerated cryogenic lifetesting of unpackaged 128 x 64 MSA and parallel measurement of the magneto-mechanical stiffness of shutters in pathfinder test samples containing multiple MSA designs. Lifetest results indicate a logarithmic failure rate out to approximately 10(exp 6) shutter actuations. These results have increased our understanding of failure mechanisms and provide a means to predict the overall reliability of MSA devices.

  1. Surface lattice resonances and magneto-optical response in magnetic nanoparticle arrays

    PubMed Central

    Kataja, M.; Hakala, T. K.; Julku, A.; Huttunen, M. J.; van Dijken, S.; Trm, P.

    2015-01-01

    Structuring metallic and magnetic materials on subwavelength scales allows for extreme confinement and a versatile design of electromagnetic field modes. This may be used, for example, to enhance magneto-optical responses, to control plasmonic systems using a magnetic field, or to tailor magneto-optical properties of individual nanostructures. Here we show that periodic rectangular arrays of magnetic nanoparticles display surface plasmon modes in which the two directions of the lattice are coupled by the magnetic field-controllable spinorbit coupling in the nanoparticles. When breaking the symmetry of the lattice, we find that the optical response shows Fano-type surface lattice resonances whose frequency is determined by the periodicity orthogonal to the polarization of the incident field. In striking contrast, the magneto-optical Kerr response is controlled by the period in the parallel direction. The spectral separation of the response for longitudinal and orthogonal excitations provides versatile tuning of narrow and intense magneto-optical resonances. PMID:25947368

  2. Dynamic Magnetic Responsive Wall Array with Droplet Shedding-off Properties.

    PubMed

    Wang, Lei; Zhang, Miaoxin; Shi, Weiwei; Hou, Yongping; Liu, Chengcheng; Feng, Shile; Guo, Zhenyu; Zheng, Yongmei

    2015-01-01

    Directional control of droplets on a surface is an important issue for tasks of long-range liquid-transport, self-cleaning and water repellency. However, it is still challenging to control the structure motions in orientations so as to control the shedding-off of droplets. Herein, we report a novel dynamic magnetic responsive wall (DMRW) array on PDMS (polydimethylsiloxane)-based surface. The walls can easily tilt through the effect of the external magnet because of the magnetic material in the DMRW. The droplets can be shed off directionally on the surface. Particularly, with the shape recovery and flexible properties, it achieves simultaneous control of the tilt angles (0-60°) of DMRW for shedding-off of droplets with different volumes (1-15 μL) under magnetic action on DMRW. The mechanism of droplet shedding-off on DMRW is elucidated by theory of interfaces. It offers an insight into design of dynamic interface for water repellency. This strategy realizes the preparation of multifunctional, tunable and directional drive functions. PMID:26061176

  3. Size-tuned Highly-ordered Magnetic Nanodot Arrays via ALD-Assisted Block Copolymer Nanolithography

    NASA Astrophysics Data System (ADS)

    Polisetty, Srinivas; Lin, Chun-Hao; Gladfelter, Wayne L.; Hillmyer, Marc H.; Leighton, Chris

    2014-03-01

    Block copolymer nanolithography of large-area well-ordered magnetic nanostructures is now possible via a variety of approaches and holds considerable appeal for fundamental science and for bit patterned recording media. Here, we demonstrate a non-lift-off damascene-type approach combined with low temperature atomic layer deposition (ALD) of a conformal ZnO layer to provide size-controlled magnetic nanodots. Perpendicularly-aligned nonporous templates were achieved by solvent annealing polystyrene- b-polylactide (PS-PLA) films. Low temperature ALD was then used to conformally coat the template with a ZnO layer of variable thickness to systematically reduce the pore diameter. Our damascene-type non-lift-off process was then used to synthesize Ni80Fe20 dot arrays from such templates, achieving tunable dot diameters (6-30 nm) and controlled dot height (by Ar milling time). Magnetic measurements were used as a probe of island volume, good agreement being obtained between simple calculations, imaging, and blocking temperature measurements. The results demonstrate a simple route to size control from a fixed polymer template, enabling detailed studies of separation-dependent inter-dot magnetic interactions for example. This work was supported primarily by the NSF through the University of Minnesota MRSEC under Award Number DMR-0819885.

  4. Dynamic Magnetic Responsive Wall Array with Droplet Shedding-off Properties

    PubMed Central

    Wang, Lei; Zhang, Miaoxin; Shi, Weiwei; Hou, Yongping; Liu, Chengcheng; Feng, Shile; Guo, Zhenyu; Zheng, Yongmei

    2015-01-01

    Directional control of droplets on a surface is an important issue for tasks of long-range liquid-transport, self-cleaning and water repellency. However, it is still challenging to control the structure motions in orientations so as to control the shedding-off of droplets. Herein, we report a novel dynamic magnetic responsive wall (DMRW) array on PDMS (polydimethylsiloxane) -based surface. The walls can easily tilt through the effect of the external magnet because of the magnetic material in the DMRW. The droplets can be shed off directionally on the surface. Particularly, with the shape recovery and flexible properties, it achieves simultaneous control of the tilt angles (0-60°) of DMRW for shedding-off of droplets with different volumes (1-15 μL) under magnetic action on DMRW. The mechanism of droplet shedding-off on DMRW is elucidated by theory of interfaces. It offers an insight into design of dynamic interface for water repellency. This strategy realizes the preparation of multifunctional, tunable and directional drive functions. PMID:26061176

  5. Dynamic Magnetic Responsive Wall Array with Droplet Shedding-off Properties

    NASA Astrophysics Data System (ADS)

    Wang, Lei; Zhang, Miaoxin; Shi, Weiwei; Hou, Yongping; Liu, Chengcheng; Feng, Shile; Guo, Zhenyu; Zheng, Yongmei

    2015-06-01

    Directional control of droplets on a surface is an important issue for tasks of long-range liquid-transport, self-cleaning and water repellency. However, it is still challenging to control the structure motions in orientations so as to control the shedding-off of droplets. Herein, we report a novel dynamic magnetic responsive wall (DMRW) array on PDMS (polydimethylsiloxane) -based surface. The walls can easily tilt through the effect of the external magnet because of the magnetic material in the DMRW. The droplets can be shed off directionally on the surface. Particularly, with the shape recovery and flexible properties, it achieves simultaneous control of the tilt angles (0-60) of DMRW for shedding-off of droplets with different volumes (1-15??L) under magnetic action on DMRW. The mechanism of droplet shedding-off on DMRW is elucidated by theory of interfaces. It offers an insight into design of dynamic interface for water repellency. This strategy realizes the preparation of multifunctional, tunable and directional drive functions.

  6. Probing Quantum Magnetism in 2D with an Array of Hundreds of Trapped Ions

    NASA Astrophysics Data System (ADS)

    Bollinger, John

    2015-03-01

    Quantum simulations using AMO systems promise a new way to experimentally study emergent quantum phenomena, but few systems have demonstrated the capability to control ensembles in which quantum effects cannot be directly computed. The 2D array of 100's of 9Be+ ions in a Penning trap, crystallized in a triangular lattice when laser cooled, is a promising platform for intractable quantum simulations using the 9Be+ valence electron spin as a qubit. Spin-dependent forces are employed to modify the strong Coulomb interaction of the ions, mimicking a quantum magnetic interaction. The range of the magnetic interaction can be tuned from infinite to a dipole-dipole like coupling. Combining the application of the spin-dependent force with a transverse magnetic field should lead to the development of quantum correlations between the spins, which can be measured through optical readout of the spin state, both globally and with site-resolved imaging. In this way, trapped atomic ions can be used to probe novel and intractable aspects of quantum magnetism, including the effects of long-range interactions and simulations of quantum non-equilibrium phenomena. In addition to a general overview, I will discuss recent work from a new Penning trap set-up at NIST. In collaboration with Joseph Britton, Brian Sawyer, and Justin Bohnet.

  7. Probing the Dynamics of Cellular Traction Forces with Magnetic Micropost Arrays

    NASA Astrophysics Data System (ADS)

    Kramer, Corinne; Chen, Christopher; Reich, Daniel

    2009-03-01

    Mechanical forces on living cells are associated with changes in cellular function. For example, vascular smooth muscle cells are known to undergo a mechanical feedback response to increased stress, which can result in atherosclerosis. We have recently developed a magnetic micropost array, a novel device for measuring cellular traction forces that simultaneously enables the application of localized external forces to cells. The device consists of an array of micrometer scale elastomeric posts that act as force sensors for cells cultured on their tips. An external force is applied to the adherent surface of a cell via a magnetic torque on a cobalt nanowire embedded in a single post. Initial results showed an active and non-local cellular response to applied forces in mouse fibroblast cells.ootnotetextN. Sniadecki, et. al, Proc Natl Acad Sci, 104, 14553 (2007). We will present results on the spatially resolved dynamics of traction forces exerted by smooth muscle cells over time in response to constant and time-varying stimulation. The observation of biochemical and mechanical regulation of the subcellular redistribution of force may allow insights into cellular mechanotransduction and control of cell function.

  8. Ambient-temperature passive magnetic bearings: Theory and design equations

    SciTech Connect

    Post, R.F.; Ryutov, D.D.

    1997-12-30

    Research has been underway at the Lawrence Livermore National Laboratory to build a theoretical and experimental base for the design of ambient-temperature passive magnetic bearings for a variety of possible applications. in the approach taken the limitations imposed by Earnshaw`s theorem with respect to the stability of passive magnetic bearing systems employing axially symmetric permanent-magnet elements are overcome by employing special combinations of elements, as follows: Levitating and restoring forces are provided by combinations of permanent-magnet-excited elements chosen to provide positive stiffnesses (negative force derivatives) for selected displacements (i.e., those involving translations or angular displacement of the axis of rotation). As dictated by Eamshaw`s theorem, any bearing system thus constructed will be statically unstable for at least one of the remaining possible displacements. Stabilization against this displacement is accomplished by using periodic arrays (`Halbach arrays`) of permanent magnets to induce currents in close-packed inductively loaded circuits, thereby producing negative force derivatives stabilizing the system while in rotation. Disengaging mechanical elements stabilize the system when at rest and when below a low critical speed. The paper discusses theory and equations needed for the design of such systems.

  9. Morphology and magnetic properties of Fe3O 4 nanodot arrays using template-assisted epitaxial growth.

    PubMed

    Guan, Xiao-Fen; Chen, Dan; Quan, Zhi-Yong; Jiang, Feng-Xian; Deng, Chen-Hua; Gehring, Gillian Anne; Xu, Xiao-Hong

    2015-12-01

    Arrays of epitaxial Fe3O4 nanodots were prepared using laser molecular beam epitaxy (LMBE), with the aid of ultrathin porous anodized aluminum templates. An Fe3O4 film was also prepared using LMBE. Atomic force microscopy and scanning electron microscopy images showed that the Fe3O4 nanodots existed over large areas of well-ordered hexagonal arrays with dot diameters (D) of 40, 70, and 140 nm; height of approximately 20 nm; and inter-dot distances (D int) of 67, 110, and 160 nm. The calculated nanodot density was as high as 0.18 Tb in.(-2) when D?=?40 nm. X-ray diffraction patterns indicated that the as-grown Fe3O4 nanodots and the film had good textures of (004) orientation. Both the film and the nanodot arrays exhibited magnetic anisotropy; the anisotropy of the nanoarray weakened with decreasing dot size. The Verwey transition temperature of the film and nanodot arrays with D???70 nm was observed at around 120 K, similar to that of the Fe3O4 bulk; however, no clear transition was observed from the small nanodot array with D?=?40 nm. Results showed that magnetic properties could be tailored through the morphology of nanodots. Therefore, Fe3O4 nanodot arrays may be applied in high-density magnetic storage and spintronic devices. PMID:26055471

  10. Improved plasma equilibrium reconstruction for the HSX stellarator using an optimized array of magnetic coils

    NASA Astrophysics Data System (ADS)

    Chlechowitz, Enrico

    Controlling magnetically confined plasmas in a steady state regime requires knowledge about the plasma equilibrium, which is characterized by the plasma current profile and plasma pressure profile. The aim of this work has been to accurately reconstruct the plasma equilibrium for the HSX stellarator using the V3FIT code and a newly installed and optimized set of radial and poloidal magnetic diagnostics. The results of eddy current modeling are also included in the equilibrium reconstruction. As a result of the diagnostic optimization, which is based on three different concepts, specific magnetic coils have an increased sensitivity to either the bootstrap current or the Pfirsch-Schluter current. This drastically reduces the uncertainty in the reconstruction compared to results from an array of external diagnostics and a set of virtual diagnostics inside the vessel whose position was not optimized. Eddy currents in the vacuum vessel are caused by changes in the plasma current and the main field coil current; the magnitude and impact of these currents on the magnetic diagnostic response is calculated using the SPARK code. Including this eddy current impact in the reconstruction for the existing external and the new internal magnetic diagnostics leads to a better agreement between the reconstruction results in both cases. This is especially true during the plasma decay, when the largest eddy currents are driven from the plasma current ramp-down. The existence of net-toroidal eddy currents also explains the difference between the internal and external Rogowski coil measurement. The suppression of plasma currents in the edge of HSX through the radial insertion of a limiter is successfully reconstructed. Finally, low-order rational surfaces are generated inside the plasma through the use of auxiliary field coils and the evolution of the plasma current. The spontaneous appearance of these surfaces is reconstructed, which validates the results from plasma equilibrium reconstructions.

  11. Resolving sub-cellular force dynamics using arrays of magnetic microposts

    NASA Astrophysics Data System (ADS)

    Reich, Daniel

    2010-03-01

    The biological response of cells to mechanical forces is integral to both normal cell function and the progression of many diseases, such as hypertensive vascular wall thickening. This likely results from the fact that mechanical stresses can directly affect many cellular processes, including signal transduction, gene expression, growth, differentiation, and survival. The need to understand the relationship between applied forces and the mechanical response of cells as a critical step towards understanding mechanotransduction calls for tools that can apply forces to cells while measuring their contractile response. This talk will describe an approach that simultaneously allows local mechanical stimulation of the adherent surface of a cell and spatially resolved measurement of the local force fields generated throughout the cell in response to this stimulation. Cells are cultured on the top surfaces of arrays of micrometer-scale posts made from a flexible elastomer (PDMS), and the contractile forces generated by an adherent cell bend the posts. Measurements of the displacement of each post allow the contractile force field of the cell to be mapped out with sub-cellular precision. To apply forces to cells, rod- shaped magnetic nanoparticles are embedded in some of the posts so that externally applied magnetic fields selectively deform these ``magnetic posts,'' thereby exerting tunable local, mechanical stresses to the adherent surface of attached cells. Alternatively, magnetic particles bound to or internalized by the cell may be employed to apply forces and torques to the cell. With either approach, measuring the deflection of the surrounding non-magnetic posts probes the full mechanical response of the cell to these stresses. Results that illustrate the temporal dynamics and spatial distribution of the non-local response of fibroblasts and smooth muscle cells to local stresses will be discussed.

  12. Probing cellular traction forces with magnetic nanowires and microfabricated force sensor arrays

    NASA Astrophysics Data System (ADS)

    Lin, Yi-Chia; Kramer, Corinne M.; Chen, Christopher S.; Reich, Daniel H.

    2012-02-01

    In this paper, the use of magnetic nanowires for the study of cellular response to force is demonstrated. High-aspect ratio Ni rods with diameter 300 nm and lengths up to 20 ?m were bound to or internalized by pulmonary artery smooth muscle cells (SMCs) cultured on arrays of flexible micropost force sensors. Forces and torques were applied to the cells by driving the nanowires with AC magnetic fields in the frequency range 0.1-10 Hz, and the changes in cellular contractile forces were recorded with the microposts. These local stimulations yield global force reinforcement of the cells traction forces, but this contractile reinforcement can be effectively suppressed upon addition of a calcium channel blocker, ruthenium red, suggesting the role of calcium channels in the mechanical response. The responsiveness of the SMCs to actuation depends on the frequency of the applied stimulation. These results show that the combination of magnetic nanoparticles and micropatterned, flexible substrates can provide new approaches to the study of cellular mechanotransduction.

  13. Controlled Phase and Tunable Magnetism in Ordered Iron Oxide Nanotube Arrays Prepared by Atomic Layer Deposition

    PubMed Central

    Zhang, Yijun; Liu, Ming; Peng, Bin; Zhou, Ziyao; Chen, Xing; Yang, Shu-Ming; Jiang, Zhuang-De; Zhang, Jie; Ren, Wei; Ye, Zuo-Guang

    2016-01-01

    Highly-ordered and conformal iron oxide nanotube arrays on an atomic scale are successfully prepared by atomic layer deposition (ALD) with controlled oxidization states and tunable magnetic properties between superparamagnetism and ferrimagnetism. Non-magnetic α-Fe2O3 and superparamagnetic Fe3O4 with a blocking temperature of 120 K are in-situ obtained by finely controlling the oxidation reaction. Both of them exhibit a very small grain size of only several nanometers due to the nature of atom-by-atom growth of the ALD technique. Post-annealing α-Fe2O3 in a reducing atmosphere leads to the formation of the spinel Fe3O4 phase which displays a distinct ferrimagnetic anisotropy and the Verwey metal-insulator transition that usually takes place only in single crystal magnetite or thick epitaxial films at low temperatures. The ALD deposition of iron oxide with well-controlled phase and tunable magnetism demonstrated in this work provides a promising opportunity for the fabrication of 3D nano-devices to be used in catalysis, spintronics, microelectronics, data storages and bio-applications. PMID:26813143

  14. Exotic magnetism of s-electron cluster arrays: Ferromagnetism, ferrimagnetism and antiferromagnetism

    NASA Astrophysics Data System (ADS)

    Nakano, Takehito; Hanh, Duong Thi; Nozue, Yasuo; Nam, Nguyen Hoang; Duan, Truong Cong; Araki, Shingo

    2013-08-01

    Alkali metal nanoclusters can be stabilized in the regular cages of zeolite crystals by the loading of guest alkali metals. Cages are connected by the sharing of windows of the framework, and arrayed in simple cubic, diamond and body centered cubic structures in zeolites A, X and sodalite, respectively. The s-electrons have the localized nature of nanoclusters with magnetic moments, and have mutual interactions through the windows of cages. They show exotic magnetism depending on the structure type of zeolites, the kind of alkali metals and the average loading density of alkali atoms per cage. In zeolite A, potassium clusters are formed in ?-cages that have an inside diameter of 11 . They exhibit ferromagnetic properties explained by the canted antiferromagnetism of the Mott insulator, where the 1 p-like degenerate orbitals of clusters play an essential role in the magnetic properties. Na-K alloy clusters generated at supercages and ?-cages of low-silica X (LSX) zeolite exhibit Nel's N-type ferrimagnetism at specific loading densities of alkali metals. Alkali metal clusters in sodalite show the ideal Heisenberg antiferromagnetism of the Mott insulator.

  15. Correlations among magnetic, electrical and magneto-transport properties of NiFe nanohole arrays.

    PubMed

    Leitao, D C; Ventura, J; Teixeira, J M; Sousa, C T; Pinto, S; Sousa, J B; Michalik, J M; De Teresa, J M; Vazquez, M; Araujo, J P

    2013-02-13

    In this work, we use anodic aluminum oxide (AAO) templates to build NiFe magnetic nanohole arrays. We perform a thorough study of their magnetic, electrical and magneto-transport properties (including the resistance R(T), and magnetoresistance MR(T)), enabling us to infer the nanohole film morphology, and the evolution from granular to continuous film with increasing thickness. In fact, different physical behaviors were observed to occur in the thickness range of the study (2 nm < t < 100 nm). For t < 10 nm, an insulator-to-metallic crossover was visible in R(T), pointing to a granular film morphology, and thus being consistent with the presence of electron tunneling mechanisms in the magnetoresistance. Then, for 10 nm < t < 50 nm a metallic R(T) allied with a larger anisotropic magnetoresistance suggests the onset of morphological percolation of the granular film. Finally, for t > 50 nm, a metallic R(T) and only anisotropic magnetoresistance behavior were obtained, characteristic of a continuous thin film. Therefore, by combining simple low-cost bottom-up (templates) and top-down (sputtering deposition) techniques, we are able to obtain customized magnetic nanostructures with well-controlled physical properties, showing nanohole diameters smaller than 35 nm. PMID:23315433

  16. Tailoring magnetic properties in arrays of pulse-electrodeposited Co nanowires: The role of Cu additive

    NASA Astrophysics Data System (ADS)

    Esmaeili, A.; Almasi Kashi, M.; Ramazani, A.; Montazer, A. H.

    2016-01-01

    In this study, we aim to report the role of Cu additive in arrays of pulse-electrodeposited Co nanowires (NWs) with diameters from 30 to 75 nm, embedded in porous aluminum oxide templates. This features the role of Cu additive in composition and crystalline characteristics as well as in the magnetic properties of Co NWs. Increasing the duration of off-time between pulses during the electrodeposition of Co NWs made it possible to increase the amount of Cu content, so that Co-rich CoCu NWs were obtained. The parallel coercivity and squareness values increased up to 1500 Oe and 0.8 for 30 nm diameter Co94Cu6 NWs, starting from 500 Oe and 0.3 for pure Co NWs. On the other hand, although there was a substantial difference between the crystalline characteristics of 75 nm diameter pure Co and CoCu NWs, no considerable change in their magnetic properties was observed using hysteresis loop measurements. In this respect, the first-order reversal curve (FORC) analysis revealed strong inter-wire magnetostatic interactions for the CoCu NWs. Moreover, we studied the effect of thermal annealing, which resulted in an increase in the coercivity of CoCu NWs with different diameters up to 15%. As a result, the addition of small amount of Cu provides an alternative approach to tailoring the magnetic properties of Co NWs.

  17. Controlled Phase and Tunable Magnetism in Ordered Iron Oxide Nanotube Arrays Prepared by Atomic Layer Deposition

    NASA Astrophysics Data System (ADS)

    Zhang, Yijun; Liu, Ming; Peng, Bin; Zhou, Ziyao; Chen, Xing; Yang, Shu-Ming; Jiang, Zhuang-De; Zhang, Jie; Ren, Wei; Ye, Zuo-Guang

    2016-01-01

    Highly-ordered and conformal iron oxide nanotube arrays on an atomic scale are successfully prepared by atomic layer deposition (ALD) with controlled oxidization states and tunable magnetic properties between superparamagnetism and ferrimagnetism. Non-magnetic α-Fe2O3 and superparamagnetic Fe3O4 with a blocking temperature of 120 K are in-situ obtained by finely controlling the oxidation reaction. Both of them exhibit a very small grain size of only several nanometers due to the nature of atom-by-atom growth of the ALD technique. Post-annealing α-Fe2O3 in a reducing atmosphere leads to the formation of the spinel Fe3O4 phase which displays a distinct ferrimagnetic anisotropy and the Verwey metal-insulator transition that usually takes place only in single crystal magnetite or thick epitaxial films at low temperatures. The ALD deposition of iron oxide with well-controlled phase and tunable magnetism demonstrated in this work provides a promising opportunity for the fabrication of 3D nano-devices to be used in catalysis, spintronics, microelectronics, data storages and bio-applications.

  18. Controlled Phase and Tunable Magnetism in Ordered Iron Oxide Nanotube Arrays Prepared by Atomic Layer Deposition.

    PubMed

    Zhang, Yijun; Liu, Ming; Peng, Bin; Zhou, Ziyao; Chen, Xing; Yang, Shu-Ming; Jiang, Zhuang-De; Zhang, Jie; Ren, Wei; Ye, Zuo-Guang

    2016-01-01

    Highly-ordered and conformal iron oxide nanotube arrays on an atomic scale are successfully prepared by atomic layer deposition (ALD) with controlled oxidization states and tunable magnetic properties between superparamagnetism and ferrimagnetism. Non-magnetic α-Fe2O3 and superparamagnetic Fe3O4 with a blocking temperature of 120 K are in-situ obtained by finely controlling the oxidation reaction. Both of them exhibit a very small grain size of only several nanometers due to the nature of atom-by-atom growth of the ALD technique. Post-annealing α-Fe2O3 in a reducing atmosphere leads to the formation of the spinel Fe3O4 phase which displays a distinct ferrimagnetic anisotropy and the Verwey metal-insulator transition that usually takes place only in single crystal magnetite or thick epitaxial films at low temperatures. The ALD deposition of iron oxide with well-controlled phase and tunable magnetism demonstrated in this work provides a promising opportunity for the fabrication of 3D nano-devices to be used in catalysis, spintronics, microelectronics, data storages and bio-applications. PMID:26813143

  19. Degradation of Phosphate Ester Hydraulic Fluid in Power Station Turbines Investigated by a Three-Magnet Unilateral Magnet Array

    PubMed Central

    Guo, Pan; He, Wei; García-Naranjo, Juan C.

    2014-01-01

    A three-magnet array unilateral NMR sensor with a homogeneous sensitive spot was employed for assessing aging of the turbine oils used in two different power stations. The Carr-Purcell-Meiboom-Gill (CPMG) sequence and Inversion Recovery-prepared CPMG were employed for measuring the 1H-NMR transverse and longitudinal relaxation times of turbine oils with different service status. Two signal components with different lifetimes were obtained by processing the transverse relaxation curves with a numeric program based on the Inverse Laplace Transformation. The long lifetime components of the transverse relaxation time T2eff and longitudinal relaxation time T1 were chosen to monitor the hydraulic fluid aging. The results demonstrate that an increase of the service time of the turbine oils clearly results in a decrease of T2eff,long and T1,long. This indicates that the T2eff,long and T1,long relaxation times, obtained from the unilateral magnetic resonance measurements, can be applied as indices for degradation of the hydraulic fluid in power station turbines. PMID:24736132

  20. Magnetostatic nearest neighbor interactions in a Co48Fe52 nanowire array probed by in-field magnetic force microscopy

    NASA Astrophysics Data System (ADS)

    Vock, S.; Tschulik, K.; Uhlemann, M.; Hengst, C.; Fhler, S.; Schultz, L.; Neu, V.

    2015-12-01

    The magnetization behavior of nanowires embedded in an array is influenced by the sum of the dipolar fields produced by all surrounding nanowires. These magnetostatic interactions largely modify the array properties and thus complicate the reconstruction of the ensemble averaged behavior of the individual nanowires, such as the intrinsic switching field distribution. Simply correcting the shearing of the hysteresis in a mean-field approach does not account for the locally fluctuating demagnetizing field, which originates from the individual magnetization configuration in the close surrounding of each nanowire. We present an in-field Magnetic Force Microscopy study of electrochemically produced Co48Fe52 nanowires, in which the influence of the magnetic nearest neighbor configuration on the switching behavior of the individual embedded nanowires is clearly detected. Based on this finding, a statistical evaluation method of nearest neighbor histograms is proposed, which potentially allows to judge the strength of the local magnetostatic interactions against the magnitude of the intrinsic switching field distribution.

  1. Permanent-magnet helicon sources and arrays: a new type of RF plasma

    NASA Astrophysics Data System (ADS)

    Chen, Francis F.

    2008-11-01

    Among radiofrequency (rf) plasma sources used for materials processing in industry, helicon sources are well known for their high density but seldom used because they require a large dc magnetic field, making the source larger, heavier, more complex, and costlier than other available sources. Placing the plasma inside an annular permanent magnet (PM) does not work because the field lines carry the plasma into the wall before it can be ejected towards a substrate. However, a ring magnet has a stagnation point below which the field is weaker but almost straight. Use of a ``low-field peak'' partly compensates for the weak field by spacing a back plate so that the reflected wave constructively interferes. Strong PM helicon discharges were produced in a proof-of principle experiment. The discharge tube was optimized using the HELIC code, resulting in 2'' diam by 2'' high, with a three-turn m = 0 antenna at the bottom end. The NeFeB magnet is 3'' ID x 5'' OD by 1'' high. To cover large substrates, an 8-tube array was constructed with 7'' between tubes. Array sources have three problems: 1) the power must be distributed equally, 2) all tubes cannot be the same distance from the matching circuit, and 3) the transmission lines have to handle the voltage at startup and the current in CW operation. These have been solved in the Medusa 2 experiment which is in a ``sweet spot'' in which the small antennas have the right inductance for the rf system. With 3kW total @ 13.56 MHz, at 7'' below the sources, the density is 5 x 10^11 cm-3 at 1.3 eV in 15 mTorr of argon, uniform to 3% over the area covered by the tubes. Possible applications are to optical coating, roll-to-roll web processing, flexible and OLED displays, solar cells, and ``smart windows'' with organic solar cells. F.F. Chen and H. Torreblanca, Plasma Phys. Control. Fusion 49, A81 (2007). D. Arnush, Phys. Plasmas 7, 3042 (2000).

  2. Transport current carrying superconducting film with periodic pinning array under strong magnetic fields

    NASA Astrophysics Data System (ADS)

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

    2011-02-01

    The transport current carrying dissipative (flux flow) and dissipationless (pinned) vortex configurations and their dynamics are investigated numerically in the framework of the time-dependent Ginzburg-Landau approach. Assuming that magnetic induction is nearly uniform, the model is generalized to include strong inhomogeneous electric fields. Hexagonal array nanoholes of the size of coherence length and density npin was considered for various filling factors [defined as f=B/(?0npin)]. The vortex depinning is closely associated with the appearance of a strongly varying electric field. For the matching field, f=1, the critical current is maximal and the transition to the resistive state occurs as a coherent depinning of the entire vortex lattice. For a system with interstitial vortices, f>1, the mechanism of depinning depends on the current direction with respect to the pinning array. There are two qualitatively distinct geometries: the obstacle and channel geometries. In the obstacle geometry lines of interstitial vortices are blocked by strongly pinned vortices, while in the channel geometry the lines move unimpeded confined in channels. It was found that slightly above the critical current the trajectories of the moving vortices are not straight, but rather acquire a snakelike shape enveloping the system of pins. In contrast to f=1, the transition to a resistive state is not coherent and is going through formation of snakelike vortex trajectories. The critical current in the obstacle geometry is significantly larger than in the channel one.

  3. Magnetic hysteresis in small-grained CoxPd1-x nanowire arrays

    NASA Astrophysics Data System (ADS)

    Viqueira, M. S.; Pozo-Lpez, G.; Urreta, S. E.; Cond, A. M.; Cornejo, D. R.; Fabietti, L. M.

    2015-11-01

    Co-Pd nanowires with small grain size are fabricated by AC electrodeposition into hexagonally ordered alumina pores, 20-35 nm in diameter and about 1 ?m long. The effects of the alloy composition, the nanowire diameter and the grain size on the hysteresis properties are considered. X-ray diffraction indicates that the nanowires are single phase, a fcc Co-Pd solid solution; electron microscopy results show that they are polycrystalline, with randomly oriented grains (7-12 nm), smaller than the wire diameter. Nanowire arrays are ferromagnetic, with an easy magnetization axis parallel to the nanowire long axis. Both, the coercive field and the loop squareness monotonously increase with the Co content and with the grain size, but no clear correlation with the wire diameter is found. The Co and Co-rich nanowire arrays exhibit coercive fields and reduced remanence values quite insensitive to temperature in the range 4 K-300 K; on the contrary, in Pd-rich nanowires both magnitudes are smaller and they largely increase during cooling below 100 K. These behaviors are systematized by considering the strong dependences displayed by the magneto-crystalline anisotropy and the saturation magnetostriction on composition and temperature. At low temperatures the effective anisotropy value and the domain-wall width to grain size ratio drastically change, promoting less cooperative and harder nucleation modes.

  4. Size and space controlled hexagonal arrays of superparamagnetic iron oxide nanodots: magnetic studies and application

    PubMed Central

    Ghoshal, Tandra; Maity, Tuhin; Senthamaraikannan, Ramsankar; Shaw, Matthew T.; Carolan, Patrick; Holmes, Justin D.; Roy, Saibal; Morris, Michael A.

    2013-01-01

    Highly dense hexagonally arranged iron oxide nanodots array were fabricated using PS-b-PEO self-assembled patterns. The copolymer molecular weight, composition and choice of annealing solvent/s allows dimensional and structural control of the nanopatterns at large scale. A mechanism is proposed to create scaffolds through degradation and/or modification of cylindrical domains. A methodology based on selective metal ion inclusion and subsequent processing was used to create iron oxide nanodots array. The nanodots have uniform size and shape and their placement mimics the original self-assembled nanopatterns. For the first time these precisely defined and size selective systems of ordered nanodots allow careful investigation of magnetic properties in dimensions from 50 nm to 10 nm, which delineate the nanodots are superparamagnetic, well-isolated and size monodispersed. This diameter/spacing controlled iron oxide nanodots systems were demonstrated as a resistant mask over silicon to fabricate densely packed, identical ordered, high aspect ratio silicon nanopillars and nanowire features. PMID:24072037

  5. Static and dynamic magnetic properties of Co2FeAl-based stripe arrays

    NASA Astrophysics Data System (ADS)

    Belmeguenai, M.; Gabor, M. S.; Zighem, F.; Berling, D.; Roussigné, Y.; Petrisor, T.; Chérif, S. M.; Tiusan, C.; Brinza, O.; Moch, P.

    2016-02-01

    25 nm to 50 nm Co2FeAl (CFA) thick wire arrays with varying widths and spacing have been patterned from continuous CFA films deposited on MgO(001) using e-beam lithography and Ar ion milling. Magneto-optical Kerr effect, transverse bias initial inverse susceptibility and torque measurements reveal that the in-plane magnetic anisotropy of the wires is dominantly monitored by a uniaxial term, in contrast with the continuous films where it is governed by the superposition of a fourfold term and of a smaller uniaxial term. The microstrip ferromagnetic resonance spectra performed using a magnetic field H, applied in the plane of the studied sample along various directions, or perpendicularly to this plane, gave us access to various quantized modes originating from the patterning. In addition, Brillouin light scattering also exhibits quantized modes. A large part of the experimental observations can be quantitatively interpreted as resulting from the demagnetizing terms induced by the geometrical patterning. However, the presented model, simply built on the effect of the demagnetizing field, is not able to give account of all the quantized modes present in the resonance spectra. When H is parallel to the wires, a more complete description is used: it considers the wave-vector quantization induced by the patterning. For the magnetic modes concerned by both approaches, the correspondence between the 2 models is easily established. When H is not parallel to the wires quantitative descriptions of the behavior of the field dependence of the observed modes still can often be performed. Finally, in all the studied patterned samples, the uniform magnetic mode, termed "film mode", relative to the parent continuous film is observed by ferromagnetic resonance: such a behavior, which has been reported previously, remains to be completely interpreted.

  6. Electromagnetic vibration energy harvesting with high power density using a magnet array

    NASA Astrophysics Data System (ADS)

    Tang, Xiudong; Lin, Teng; Zuo, Lei

    2012-04-01

    Electromagnetic vibration energy harvesters have been widely used to convert the vibration energy into electricity. However, one of the main challenges of using electromagnetic vibration energy harvesters is that they are usually in very large size with low power density. In this paper, a new type of electromagnetic vibration energy harvester with remarkably high power density is developed. By putting the strong rare-earth magnets in alternating directions and using high-magnetic-conductive casing, magnetic flux density up to 0.9T are obtained. This configuration also has a small current loop with less electrical reluctance, which further increases the high power density when the coil is designed to follow the current loop. The prototype, the size of which is 142x140x86 mm3, can provided up to 727Ns/m damping coefficient, which means 428 kNs/m4 damping density when it is shunt with 70? external resistive load which is set to the same as the internal resistor of the harvester to achieve maximum power. The corresponding power density is 725 ?W/cm3 at 15HZ harmonic force excitation of 2.54mm peak-to-peak amplitude. When shot-circuited, 1091Ns/m damping coefficient and 638 kNs/m4 damping density is achieved. The effectiveness of this novel vibration energy harvester is shown both by FEA and experiments. The eddy current damper is also discussed in this paper for comparison. The proposed configuration of the magnet array can also be extended for both micro-scale and large-scale energy harvesting applications, such as vibration energy harvesting from tall buildings, long bridges and railways.

  7. Geometrical Design of a Scalable Overlapping Planar Spiral Coil Array to Generate a Homogeneous Magnetic Field

    PubMed Central

    Jow, Uei-Ming; Ghovanloo, Maysam

    2014-01-01

    We present a design methodology for an overlapping hexagonal planar spiral coil (hex-PSC) array, optimized for creation of a homogenous magnetic field for wireless power transmission to randomly moving objects. The modular hex-PSC array has been implemented in the form of three parallel conductive layers, for which an iterative optimization procedure defines the PSC geometries. Since the overlapping hex-PSCs in different layers have different characteristics, the worst case coil-coupling condition should be designed to provide the maximum power transfer efficiency (PTE) in order to minimize the spatial received power fluctuations. In the worst case, the transmitter (Tx) hex-PSC is overlapped by six PSCs and surrounded by six other adjacent PSCs. Using a receiver (Rx) coil, 20 mm in radius, at the coupling distance of 78 mm and maximum lateral misalignment of 49.1 mm (1/√3 of the PSC radius) we can receive power at a PTE of 19.6% from the worst case PSC. Furthermore, we have studied the effects of Rx coil tilting and concluded that the PTE degrades significantly when θ > 60°. Solutions are: 1) activating two adjacent overlapping hex-PSCs simultaneously with out-of-phase excitations to create horizontal magnetic flux and 2) inclusion of a small energy storage element in the Rx module to maintain power in the worst case scenarios. In order to verify the proposed design methodology, we have developed the EnerCage system, which aims to power up biological instruments attached to or implanted in freely behaving small animal subjects’ bodies in long-term electrophysiology experiments within large experimental arenas. PMID:24782576

  8. A digital magnetic resonance imaging spectrometer using digital signal processor and field programmable gate array

    NASA Astrophysics Data System (ADS)

    Liang, Xiao; Binghe, Sun; Yueping, Ma; Ruyan, Zhao

    2013-05-01

    A digital spectrometer for low-field magnetic resonance imaging is described. A digital signal processor (DSP) is utilized as the pulse programmer on which a pulse sequence is executed as a subroutine. Field programmable gate array (FPGA) devices that are logically mapped into the external addressing space of the DSP work as auxiliary controllers of gradient control, radio frequency (rf) generation, and rf receiving separately. The pulse programmer triggers an event by setting the 32-bit control register of the corresponding FPGA, and then the FPGA automatically carries out the event function according to preset configurations in cooperation with other devices; accordingly, event control of the spectrometer is flexible and efficient. Digital techniques are in widespread use: gradient control is implemented in real-time by a FPGA; rf source is constructed using direct digital synthesis technique, and rf receiver is constructed using digital quadrature detection technique. Well-designed performance is achieved, including 1 ?s time resolution of the gradient waveform, 1 ?s time resolution of the soft pulse, and 2 MHz signal receiving bandwidth. Both rf synthesis and rf digitalization operate at the same 60 MHz clock, therefore, the frequency range of transmitting and receiving is from DC to 27 MHz. A majority of pulse sequences have been developed, and the imaging performance of the spectrometer has been validated through a large number of experiments. Furthermore, the spectrometer is also suitable for relaxation measurement in nuclear magnetic resonance field.

  9. A digital magnetic resonance imaging spectrometer using digital signal processor and field programmable gate array.

    PubMed

    Liang, Xiao; Binghe, Sun; Yueping, Ma; Ruyan, Zhao

    2013-05-01

    A digital spectrometer for low-field magnetic resonance imaging is described. A digital signal processor (DSP) is utilized as the pulse programmer on which a pulse sequence is executed as a subroutine. Field programmable gate array (FPGA) devices that are logically mapped into the external addressing space of the DSP work as auxiliary controllers of gradient control, radio frequency (rf) generation, and rf receiving separately. The pulse programmer triggers an event by setting the 32-bit control register of the corresponding FPGA, and then the FPGA automatically carries out the event function according to preset configurations in cooperation with other devices; accordingly, event control of the spectrometer is flexible and efficient. Digital techniques are in widespread use: gradient control is implemented in real-time by a FPGA; rf source is constructed using direct digital synthesis technique, and rf receiver is constructed using digital quadrature detection technique. Well-designed performance is achieved, including 1 ?s time resolution of the gradient waveform, 1 ?s time resolution of the soft pulse, and 2 MHz signal receiving bandwidth. Both rf synthesis and rf digitalization operate at the same 60 MHz clock, therefore, the frequency range of transmitting and receiving is from DC to ~27 MHz. A majority of pulse sequences have been developed, and the imaging performance of the spectrometer has been validated through a large number of experiments. Furthermore, the spectrometer is also suitable for relaxation measurement in nuclear magnetic resonance field. PMID:23742570

  10. Nonlinear effects in magnetic garnet films and nonreciprocal optical Bloch oscillations in waveguide arrays

    NASA Astrophysics Data System (ADS)

    Kumar, Pradeep

    This dissertation presents detailed experimental and theoretical investigations of nonlinear and nonreciprocal effects in magnetic garnet films. The dissertation thus comprises two major sections. The first section concentrates on the study of a new class of nonlinear magneto-optic thin film materials possessing strong higher order magnetic susceptibility for nonlinear optical applications. The focus was on enlarging the nonlinear performance of ferrite garnet films by strain generation and compositional gradients in the sputter-deposition growth of these films. Under this project several bismuth-substituted yttrium iron garnet (Bi,Y)3(Fe,Ga)5O12 (acronym as Bi:YIG) films have been sputter-deposited over gadolinium gallium garnet (Gd 3Ga5O12) substrates and characterized for their nonlinear optical response. One of the important findings of this work is that lattice mismatch strain drives the second harmonic (SH) signal in the Bi:YIG films, in agreement with theoretical predictions; whereas micro-strain was found not to correlate significantly with SH signal at the micro-strain levels present in these films. This study also elaborates on the role of the film's constitutive elements and their concentration gradients in nonlinear response of the films. Ultrahigh sensitivity delivered by second harmonic generation provides a new exciting tool for studying magnetized surfaces and buried interfaces, making this work important from both a fundamental and application point of view. The second part of the dissertation addresses an important technological need; namely the development of an on-chip optical isolator for use in photonic integrated circuits. It is based on two related novel effects, nonreciprocal and unidirectional optical Bloch oscillations (BOs), recently proposed and developed by Professor Miguel Levy and myself. This dissertation work has established a comprehensive theoretical background for the implementation of these effects in magneto-optic waveguide arrays. The model systems we developed consist of photonic lattices in the form of one-dimensional waveguide arrays where an optical force is introduced into the array through geometrical design turning the beam sideways. Laterally displaced photons are periodically returned to a central guide by photonic crystal action. The effect leads to a novel oscillatory optical phenomenon that can be magnetically controlled and rendered unidirectional. An on-chip optical isolator was designed based on the unidirectionality of the magneto-opticBloch oscillatory motion. The proposed device delivers an isolation ratio as high as 36 dB that remains above 30 dB in a 0.7 nm wavelength bandwidth, at the telecommunication wavelength 1.55 mum. Slight modifications in isolator design allow one to achieve an even more impressive isolation ratio ~ 55 dB, but at the expense of smaller bandwidth. Moreover, the device allows multifunctionality, such as optical switching with a simultaneous isolation function, well suited for photonic integrated circuits.

  11. Giant magnetoresistance sensors. 1. Internally calibrated readout of scanned magnetic arrays.

    PubMed

    Nordling, John; Millen, Rachel L; Bullen, Heather A; Porter, Marc D; Tondra, Mark; Granger, Michael C

    2008-11-01

    This paper describes efforts aimed at setting the stage for the application of giant magnetoresistance sensor (GMRs) networks as readers for quantification of biolytes selectively captured and then labeled with superparamagnetic particles on a scanned chip-scale array. The novelty and long-range goal of this research draws from the potential development of a card-swipe instrument through which an array of micrometer-sized, magnetically tagged addresses (i.e., a sample stick) can be interrogated in a manner analogous to a credit card reader. This work describes the construction and testing of a first-generation instrument that uses a GMR sensor network to read the response of a "simulated" sample stick. The glass sample stick is composed of 20-nm-thick films of permalloy that have square or rectangular lateral footprints of up to a few hundred micrometers. Experiments were carried out to gain a fundamental understanding of the dependence of the GMR response on the separation between, and planarity of, the scanned sample stick and sensor. Results showed that the complex interplay between these experimentally controllable variables strongly affect the shape and magnitude of the observed signal and, ultimately, the limit of detection. This study also assessed the merits of using on-sample standards as internal references as a facile means to account for small variations in the gap between the sample stick and sensor. These findings were then analyzed to determine various analytical figures of merit (e.g., limit of detection in terms of the amount of magnetizable material on each address) for this readout strategy. An in-depth description of the first-generation test equipment is presented, along with a brief discussion of the potential widespread applicability of the concept. PMID:18826239

  12. Tunable configurational anisotropy in collective magnetization dynamics of Ni80Fe20 nanodot arrays with varying dot shapes

    NASA Astrophysics Data System (ADS)

    Mahato, B. K.; Choudhury, S.; Mandal, R.; Barman, S.; Otani, Y.; Barman, A.

    2015-06-01

    We present broadband ferromagnetic resonance measurements of tunable spin wave anisotropy in arrays of nanodots with different dot shapes. Magnetization dynamics of the circular dot array shows two modes, while square, diamond, and triangular dot arrays show three, three, and four modes, respectively. Various distinct rotational symmetries in the configurational anisotropy of the nanodot arrays are observed with the variation of dot shape. The observed spin wave modes are reproduced by micromagnetic simulations and the calculated mode profiles show different collective modes determined by internal and stray magnetic fields. Effects of dot shapes are observed in combination with the effects of lattice symmetry and the shape of the boundary of the array. The collective behaviour is observed to be weakest in the diamond shaped dots and strongest in circular shaped dots. This is further confirmed by the stray field calculation. The large variation of spin wave mode frequencies and their configurational anisotropies with dot shapes are important for selection of suitable basis structures for future magnonic crystals.

  13. Precision formed micro magnets: LDRD project summary report

    SciTech Connect

    CHRISTENSON,TODD R.; GARINO,TERRY J.; VENTURINI,EUGENE L.

    2000-02-01

    A microfabrication process is described that provides for the batch realization of miniature rare earth based permanent magnets. Prismatic geometry with features as small as 5 microns, thicknesses up through several hundred microns and with submicron tolerances may be accommodated. The processing is based on a molding technique using deep x-ray lithography as a means to generate high aspect-ratio precision molds from PMMA (poly methyl methacrylate) used as an x-ray photoresist. Subsequent molding of rare-earth permanent magnet (REPM) powder combined with a thermosetting plastic binder may take place directly in the PMMA mold. Further approaches generate an alumina form replicated from the PMMA mold that becomes an intermediate mold for pressing higher density REPM material and allows for higher process temperatures. Maximum energy products of 3--8 MGOe (Mega Gauss Oersted, 1 MGOe = 100/4{pi} kJ/m{sup 3}) are obtained for bonded isotropic forms of REPM with dimensions on the scale of 100 microns and up to 23 MGOe for more dense anisotropic REPM material using higher temperature processing. The utility of miniature precision REPMs is revealed by the demonstration of a miniature multipole brushless DC motor that possesses a pole-anisotropic rotor with dimensions that would otherwise prohibit multipole magnetization using a multipole magnetizing fixture at this scale. Subsequent multipole assembly also leads to miniaturized Halbach arrays, efficient magnetic microactuators, and mechanical spring-like elements which can offset miniaturized mechanical scaling behavior.

  14. Low-temperature cross-talk magnetic-field sensor based on tapered all-solid waveguide-array fiber and magnetic fluids.

    PubMed

    Miao, Yinping; Ma, Xixi; Wu, Jixuan; Song, Binbin; Zhang, Hao; Zhang, Kailiang; Liu, Bo; Yao, Jianquan

    2015-08-15

    A compact fiber-optic magnetic-field sensor based on tapered all-solid waveguide-array fiber (WAF) and magnetic fluid (MF) has been proposed and experimentally demonstrated. The tapered all-solid WAF is fabricated by using a fusion splicer, and the sensor is formed by immersing the tapered all-solid WAF into the MF. The transmission spectra have been measured and analyzed under different magnetic-field intensities. Experimental results show that the acquired magnetic-field sensitivity is 44.57 pm/Oe for a linear magnetic-field intensity range from 50 to 200 Oe. All-solid WAF has very similar thermal expansion coefficient for high- and low-refractive-index glasses, so mode profile is not affected by thermal drifts. Also, magnetically induced refractive-index changes into the ferrofluid are of the order of ∼5×10(-2), while the corresponding thermally induced refractive-index changes into the ferrofluid are expected to be lower. The temperature response has also been detected, and the temperature-induced wavelength shift perturbation is less than 0.3 nm from temperature of 26.9°C-44°C. The proposed magnetic-field sensor has such advantages as low temperature sensitivity, simple structure, and ease of fabrication. It also indicates that the magnetic-field sensor based on tapered all-solid WAF and MF is helpful to reduce temperature cross-sensitivity for the measurement of magnetic field. PMID:26274690

  15. A primary field compensation scheme for planar array magnetic induction tomography.

    PubMed

    Watson, S; Morris, A; Williams, R J; Griffiths, H; Gough, W

    2004-02-01

    In biomedical magnetic induction tomography (MIT), measurement precision may be improved by incorporating some form of primary field compensation/cancellation scheme. Schemes which have been described previously include gradiometric approaches and the use of 'back-off' coils. In each of these methods, however, the primary field cancellation was achieved only for a single transmitter/receiver combination. For the purpose of imaging, it would be desirable for a fully electronically scanned MIT system to provide a complete set of measurements, all with the primary field cancelled. A single channel suitable for incorporation into an MIT system with planar-array geometry is described. The transmitter is a 6-turn coil of wire 5 cm in diameter. The receiver is a surface mount inductor, of inductance 10 microH, mounted such that, in principle, no net primary field flux threads it. The results of measurements carried out with the single channel system suggest that the signal due to the primary excitation field can be reduced on average by a factor of 298 by the sensor geometry over the operating frequency range 1-10 MHz. The standard deviation and drift of the signal with the system adjusted for maximum primary field cancellation, expressed as a percentage of the signal when the receiver coil was rotated until its axis of sensitivity lay along the primary field, were 0.0009% and 0.009%, respectively. The filter time constant used was 30 ms. PMID:15005321

  16. Enrichment and identification of glycoproteins in human saliva using lectin magnetic bead arrays.

    PubMed

    Caragata, Michael; Shah, Alok K; Schulz, Benjamin L; Hill, Michelle M; Punyadeera, Chamindie

    2016-03-15

    Aberrant glycosylation of proteins is a hallmark of tumorigenesis and could provide diagnostic value in cancer detection. Human saliva is an ideal source of glycoproteins due to the relatively high proportion of glycosylated proteins in the salivary proteome. Moreover, saliva collection is noninvasive and technically straightforward, and the sample collection and storage is relatively easy. Although differential glycosylation of proteins can be indicative of disease states, identification of differential glycosylation from clinical samples is not trivial. To facilitate salivary glycoprotein biomarker discovery, we optimized a method for differential glycoprotein enrichment from human saliva based on lectin magnetic bead arrays (saLeMBA). Selected lectins from distinct reactivity groups were used in the saLeMBA platform to enrich salivary glycoproteins from healthy volunteer saliva. The technical reproducibility of saLeMBA was analyzed with liquid chromatography-tandem mass spectrometry (LC-MS/MS) to identify the glycosylated proteins enriched by each lectin. Our saLeMBA platform enabled robust glycoprotein enrichment in a glycoprotein- and lectin-specific manner consistent with known protein-specific glycan profiles. We demonstrated that saLeMBA is a reliable method to enrich and detect glycoproteins present in human saliva. PMID:26743719

  17. Robotic apparatuses, systems and methods

    NASA Technical Reports Server (NTRS)

    Ross, William P. (Inventor); Hoburg, James F. (Inventor); Fromme, Christopher (Inventor); Bares, John (Inventor); DeLouis, Mark (Inventor)

    2006-01-01

    A mobile device for traversing a ferromagnetic surface. The device includes a frame and at least one surface contacting device attached to the frame. The device also includes a Halbach magnet array attached to the frame, wherein the Halbach magnet array provides a magnetic force to maintain the surface contacting device substantially into contact with the ferromagnetic surface.

  18. Robotic apparatuses, systems and methods

    NASA Technical Reports Server (NTRS)

    Ross, William P. (Inventor); Hoburg, James F. (Inventor); Fromme, Christopher (Inventor); Bares, John (Inventor); DeLouis, Mark (Inventor)

    2004-01-01

    A mobile device for traversing a ferromagnetic surface. The device includes a frame and at least one surface contacting device attached to the frame. The device also includes a Halbach magnet array attached to the frame, wherein the Halbach magnet array provides a magnetic force to maintain the surface contacting device substantially into contact with the ferromagnetic surface.

  19. The 3D Vector Potential, Magnetic Field and Stored Energy in a Thin cos2 theta Coil Array

    SciTech Connect

    Caspi, S.

    1997-07-09

    The vector potential and the magnetic field have been derived for an arrays of quadrupole magnets with thin Cos(2{theta}) current sheet placed at r = R.{sup bc}. The field strength of each coil within the array, varies purely as a Fourier sinusoidal series of the longidutinal coordinate z in proportion to {omega}{sub m}z, where {omega}{sub m} = (2m-1){pi}/L, L denotes the half-period, and m = 1,2,3 etc. The analysis is based on the expansion of the vector potential in the region external to the windings of a linear 3D quad, and a revision of that expansion by the application of the 'Addition Theorem' from that around the coil center to that around any arbitrary point in space.

  20. Study of the magnetization behavior of ferromagnetic nanowire array: Existence of growth defects revealed by micromagnetic simulations

    NASA Astrophysics Data System (ADS)

    Nguyen Vien, G.; Rioual, S.; Gloaguen, F.; Rouvellou, B.; Lescop, B.

    2016-03-01

    High aspect ratio nanowires were electrodeposited in nanoporous anodic alumina template by a potentiostatic method. The angular dependence of the coercive field and remanence magnetization extracted from magnetometry measurements are compared with micromagnetic simulations. Inclusion of magnetostatic interactions between Ni nanowires in simulations is required to explain some of the properties of the magnetization reversal. However, it is not sufficient to reproduce fully the angular dependence of the coercive field. Due to the polycrystalline nature of nanowires and thus to the presence of grain boundaries, defects are included in simulations. A good agreement between theory and experiment is then clearly highlighted, in particular in the nanowire easy axis direction. The achieved results allow a description of several experimental data published in the literature and consequently to get a better understanding of reversal mechanisms that operate in such nanowire arrays. A complementary study of composite nanowire array is successfully performed to prove the adequacy of the simulations method to describe the magnetic properties of nanowire array.

  1. Large voltage modulation in magnetic field sensors from two-dimensional arrays of Y-Ba-Cu-O nano Josephson junctions

    NASA Astrophysics Data System (ADS)

    Cybart, Shane A.; Cho, E. Y.; Wong, T. J.; Glyantsev, V. N.; Huh, J. U.; Yung, C. S.; Moeckly, B. H.; Beeman, J. W.; Ulin-Avila, E.; Wu, S. M.; Dynes, R. C.

    2014-02-01

    We have fabricated and tested two-dimensional arrays of YBa2Cu3O7-δ superconducting quantum interference devices. The arrays contain over 36 000 nano Josephson junctions fabricated from ion irradiation of YBa2Cu3O7-δ through narrow slits in a resist-mask that was patterned with electron beam lithography and reactive ion etching. Measurements of current-biased arrays in magnetic field exhibit large voltage modulations as high as 30 mV.

  2. Magnetic interaction and conical self-reorganization of aligned tin oxide nanowire array under field emission conditions

    NASA Astrophysics Data System (ADS)

    Bazargan, Samad; Thomas, Joseph P.; Leung, K. T.

    2013-06-01

    Magnetic interactions are induced between non-magnetic, vertically aligned tin dioxide nanowires under field-emission conditions. Vertically aligned nanowires of tin dioxide are synthesized along the [100] direction by pulsed laser deposition of an epitaxial (200) seed layer on c-cut sapphire substrates followed by vapor-liquid-solid growth using catalyst-assisted pulsed laser deposition method. Due to the dense arrangement of the vertically aligned ultra-long nanowires deposited in this study, magnetic interactions between the nanowires carrying parallel currents become significant within 1 ?m radius and lead to their self-reorganization into conical tipi structures under field emission conditions. Optimization of the aerial density of the emission tips and reduction in the field screening effects upon self-reorganization of the nanowire array can account for the large field enhancement factor of 2.6 104 at low turn-on field of 3 V/?m.

  3. Magnetic field dependent small-angle neutron scattering on a Co nanorod array: evidence for intraparticle spin misalignment.

    PubMed

    Gnther, A; Bick, J-P; Szary, P; Honecker, D; Dewhurst, C D; Keiderling, U; Feoktystov, A V; Tschpe, A; Birringer, R; Michels, A

    2014-06-01

    The structural and magnetic properties of a cobalt nanorod array have been studied by means of magnetic field dependent small-angle neutron scattering (SANS). Measurement of the unpolarized SANS cross section d?/d? of the saturated sample in the two scattering geometries where the applied magnetic field H is either perpendicular or parallel to the wavevector k i of the incoming neutron beam allows one to separate nuclear from magnetic SANS, without employing the usual sector-averaging procedure. The analysis of the SANS data in the saturated state provides structural parameters (rod radius and centre-to-centre distance) that are in good agreement with results from electron microscopy. Between saturation and the coercive field, a strong field dependence of d?/d? is observed (in both geometries), which cannot be explained using the conventional expression of the magnetic SANS cross section of magnetic nanoparticles in a homogeneous nonmagnetic matrix. The origin of the strong field dependence of d?/d? is believed to be related to intradomain spin misalignment, due to magnetocrystalline and magnetoelastic anisotropies and magnetostatic stray fields. PMID:24904245

  4. Magnetic field dependent small-angle neutron scattering on a Co nanorod array: evidence for intraparticle spin misalignment

    PubMed Central

    Gnther, A.; Bick, J.-P.; Szary, P.; Honecker, D.; Dewhurst, C. D.; Keiderling, U.; Feoktystov, A. V.; Tschpe, A.; Birringer, R.; Michels, A.

    2014-01-01

    The structural and magnetic properties of a cobalt nanorod array have been studied by means of magnetic field dependent small-angle neutron scattering (SANS). Measurement of the unpolarized SANS cross section d?/d? of the saturated sample in the two scattering geometries where the applied magnetic field H is either perpendicular or parallel to the wavevector k i of the incoming neutron beam allows one to separate nuclear from magnetic SANS, without employing the usual sector-averaging procedure. The analysis of the SANS data in the saturated state provides structural parameters (rod radius and centre-to-centre distance) that are in good agreement with results from electron microscopy. Between saturation and the coercive field, a strong field dependence of d?/d? is observed (in both geometries), which cannot be explained using the conventional expression of the magnetic SANS cross section of magnetic nanoparticles in a homogeneous nonmagnetic matrix. The origin of the strong field dependence of d?/d? is believed to be related to intradomain spin misalignment, due to magnetocrystalline and magnetoelastic anisotropies and magnetostatic stray fields. PMID:24904245

  5. Arrays of nanostructured antidot in Ni80Fe20 magnetic thin films by photolithography of polystyrene nanospheres

    NASA Astrophysics Data System (ADS)

    Tiberto, Paola; Boarino, Luca; Celegato, Federica; Barrera, Gabriele; De Leo, Natascia; Coisson, Marco; Vinai, Franco; Allia, Paolo

    2012-10-01

    Ordered nanostructures consisting in arrays of nanopores and nanoholes in magnetic thin films have been the subject of intensive research. In this work, a novel multi-step lithography process based on self-assembling of polystyrene nanospheres is proposed to pattern arrays of nanoholes on a Ni80Fe20 thin film. Such a method allows antidot patterns to be fabricated on a wider area with respect to the standard sequential lithography. A polymeric mask is created by depositing a layer of polystyrene nanospheres on a photoresist subsequently exposed to a mercury lamp. The novelty in the procedure lies in exploiting low-cost and fast, non-sequential optical lithography with enhanced spatial resolution. Arrays of holes having mean size ranging in the interval of 250-280 nm depending on the experimental conditions have been prepared in Ni80Fe20 films of different thickness (between 20 and 60 nm). Sample morphology has been checked by scanning electron microscopy. Magnetic and magnetotransport properties have been measured as a function of temperature on films of different thickness. An anisotropic magnetoresistance effect has been observed in all patterned films independent on the film thickness. This result, similar to the ones reported for patterned nanostructure obtained with conventional lithography techniques, confirms the potential of the proposed technique.

  6. Pseudo-one-dimensional Zn-Fe-O Nanostructure Arrays: Controlled Fabrication, Magnetic Properties and Photocatalytic Applications

    NASA Astrophysics Data System (ADS)

    Guo, Xuan

    In the present thesis, several kinds of pseudo-one-dimensional Zn-Fe-O nanostructure arrays with tunable chemical compositions, crystal structures and morphologies are successfully synthesized via a simple wet-chemical ZnO-nanowire-array templating method. Vertically-aligned ZnO nanowire arrays are firstly fabricated on several different substrates and then serve as templates for other nanostructured arrays growth. The ZnO nanowires not only act as morphology-defining skeleton but also contribute chemically to the final composition of the nanostructures. By controlling the reaction time between ZnO and FeCl3 solution, ZnO/ZnFe2O4 nanocable arrays, stoichiometric ZnFe 2O4 nanotube arrays, nonstoichiometric ZnFe2O 4 nanotube arrays, ZnFe2O4/alpha-Fe2O 3 nanotube arrays and alpha-Fe2O3 nanotube arrays can be synthesized in a controlled manner after calcination. Both ZnFe 2O4 and alpha-Fe2O3 nanotube arrays exhibit visible light absorption and their bandgap are estimated to be 2.3 eV and 1.7 eV, respectively. The detailed structural information of the ZnFe2O4 nanotube arrays are obtained by electron energy loss spectroscopy (EELS). In particular, EELS are carried out for two different series (i.e., temperature and stoichiometric series). The magnetic properties of these samples are found to closely correlate to their structural characteristics. Firstly, with the decrease of the calcination temperature from 600 C to 400 C, more Fe3+ ions occupy A sites (tetrahedral sites in spinel structure) rather than their equilibrium B sites (octahedral sites in spinel structure). The deviation from the normal spinel structure leads to the enhancement of superexchange interactions between Fe3+ ions in A and B sites, and thus results in an increase in blocking temperature (T B), magnetic anisotropic constant (K), saturation magnetization (MS, at 3 K and 300 K), coercivity (H C, at 3 K) and a decrease in MS (3K)/MS(300 K) ratios. Secondly, by comparing stoichiometric and nonstoichiometric ZnFe2O4 nanotubes calcinated at the same temperature, we found that the nonstoichiometric nanotubes (Fe:Zn > 2) shows similar ratios of Fe3+ in A and B sites to that of the stoichiometric one. The extra Fe3+ in the crystal also enhances the superexchange interactions of Fe3+, which results in larger T B, K, MS (at 3 K and 300 K) and HC (at 3 K), and smaller MS(3 K)/MS(300 K) ratio. Lastly, alpha-Fe2O 3 nanotubes, as an extreme case of the nonstoichiometric sample, show typical Morin-transition characterization under small external field, and field-induced spin-flop transition at large external field. On the other hand, we found that the visible-light-driven photodegradation activities of ZnO/ZnFe2O4 nanocable arrays are superior to those of the ZnO nanowire arrays and ZnFe2O4 nanotube arrays using RhB as the probe molecules. All the three nanostructures show degradation of RhB molecules under visible light irradiation, but they take different degradation pathways. The degradation of RhB in the presence of ZnO nanowire arrays is attributed to the dye-sensitized mechanism, and the photodegradation activity is the worst. ZnO/ZnFe2O4 nanocable arrays and ZnFe2O4 nanotube arrays have the same degradation mechanism, that is, reactive radicals produced by photogenerated electron-hole pairs in the visible-light-active ZnFe2O4 are responsible for the photodegradation of RhB. However, the nanocable arrays show much higher degradation capability. This is owing to the type II band alignment between ZnO and ZnFe2O4, which greatly promotes the separation of photogenerated electrons and holes in ZnFe2O 4.

  7. Standing spin-wave mode structure and linewidth in partially disordered hexagonal arrays of perpendicularly magnetized sub-micron Permalloy discs

    SciTech Connect

    Ross, N. Kostylev, M.; Stamps, R. L.

    2014-09-21

    Standing spin wave mode frequencies and linewidths in partially disordered perpendicular magnetized arrays of sub-micron Permalloy discs are measured using broadband ferromagnetic resonance and compared to analytical results from a single, isolated disc. The measured mode structure qualitatively reproduces the structure expected from the theory. Fitted demagnetizing parameters decrease with increasing array disorder. The frequency difference between the first and second radial modes is found to be higher in the measured array systems than predicted by theory for an isolated disc. The relative frequencies between successive spin wave modes are unaffected by reduction of the long-range ordering of discs in the array. An increase in standing spin wave resonance linewidth at low applied magnetic fields is observed and grows more severe with increased array disorder.

  8. Electronic properties of a quasi-periodic array of tight binding rings immersed in a magnetic field

    NASA Astrophysics Data System (ADS)

    Sengupta, Sheelan; Chakrabarti, Arunava

    2004-08-01

    Electronic properties of model mesoscopic rings of two different sizes placed in contact with each other in a quasi-periodic Fibonacci sequence have been examined within the tight binding framework. The array of the rings is immersed in a constant magnetic field. The resonant one electron transport is analysed for selected sizes of the rings. It is found that the resonance is a result of a subtle positional correlation, sometimes revealed only when the field assumes special values. The energy eigenvalues at resonance all correspond to a six-cycle of the full matrix map of the Fibonacci array of rings. Interestingly, we find that for a certain combination of the rings, the charge density at the band centre displays a cross-over, going from a perfectly extended (even periodic) character to a fractal behavior as a function of the external field.

  9. Microfluidic multiplexed partitioning enables flexible and effective utilization of magnetic sensor arrays.

    PubMed

    Bechstein, Daniel J B; Ng, Elaine; Lee, Jung-Rok; Cone, Stephanie G; Gaster, Richard S; Osterfeld, Sebastian J; Hall, Drew A; Weaver, James A; Wilson, Robert J; Wang, Shan X

    2015-10-27

    We demonstrate microfluidic partitioning of a giant magnetoresistive sensor array into individually addressable compartments that enhances its effective use. Using different samples and reagents in each compartment enables measuring of cross-reactive species and wide dynamic ranges on a single chip. This compartmentalization technique motivates the employment of high density sensor arrays for highly parallelized measurements in lab-on-a-chip devices. PMID:26395039

  10. Performance of a multi-axis ionization chamber array in a 1.5 T magnetic field

    NASA Astrophysics Data System (ADS)

    Smit, K.; Kok, J. G. M.; Lagendijk, J. J. W.; Raaymakers, B. W.

    2014-04-01

    At the UMC Utrecht a prototype MR-linac has been installed. The system consists of an 8 MV Elekta linear accelerator and a 1.5 T Philips MRI system. This paper investigates the performance of the IC PROFILER, a multi-axis ionization chamber array, in a 1.5 T magnetic field. The influence of the magnetic field on the IC PROFILER reproducibility, dose response linearity, pulse rate frequency dependence, power to electronics, panel orientation and ionization chamber shape were investigated. The linearity, reproducibility, pulse rate frequency dependence, panel orientation and ionization chamber shape are unaffected by the magnetic field. When the measurements results are normalized to the centre reference chamber, the measurements can commence unaltered. Orientation of the ionization chambers in the magnetic field is of importance, therefore caution must be taken when comparing or normalizing results from several different axes. IC PROFILER dose profiles were compared with film dose profiles obtained simultaneously in the MR-linac. Deviation between the film and the IC PROFILER data was caused by the noise in the film, indicating correct performance of the IC PROFILER in the transverse 1.5 T magnetic field.

  11. Performance of a multi-axis ionization chamber array in a 1.5 T magnetic field.

    PubMed

    Smit, K; Kok, J G M; Lagendijk, J J W; Raaymakers, B W

    2014-04-01

    At the UMC Utrecht a prototype MR-linac has been installed. The system consists of an 8 MV Elekta linear accelerator and a 1.5 T Philips MRI system. This paper investigates the performance of the IC PROFILER, a multi-axis ionization chamber array, in a 1.5 T magnetic field. The influence of the magnetic field on the IC PROFILER reproducibility, dose response linearity, pulse rate frequency dependence, power to electronics, panel orientation and ionization chamber shape were investigated. The linearity, reproducibility, pulse rate frequency dependence, panel orientation and ionization chamber shape are unaffected by the magnetic field. When the measurements results are normalized to the centre reference chamber, the measurements can commence unaltered. Orientation of the ionization chambers in the magnetic field is of importance, therefore caution must be taken when comparing or normalizing results from several different axes. IC PROFILER dose profiles were compared with film dose profiles obtained simultaneously in the MR-linac. Deviation between the film and the IC PROFILER data was caused by the noise in the film, indicating correct performance of the IC PROFILER in the transverse 1.5 T magnetic field. PMID:24625540

  12. Magnetization Reversal and Magnetic Anisotropy in Ordered CoNiP Nanowire Arrays: Effects of Wire Diameter

    PubMed Central

    Van Thiem, Luu; Tu, Le Tuan; Phan, Manh-Huong

    2015-01-01

    Ordered CoNiP nanowires with the same length of 4 µm and varying diameters (d = 100 nm–600 nm) were fabricated by electrodeposition of CoNiP onto polycarbonate templates. X-ray diffraction, scanning electron microscopy, and high-resolution transmission electron microscopy confirmed the quality of the fabricated nanowires. Magnetic measurements and theoretical analysis revealed that the magnetization reversal and magnetic anisotropy were significantly influenced by varying of the diameters of the nanowires. There existed a critical wire diameter (dc ≈ 276 nm), below which the magnetization reversal occurred via a coherent rotation mode, and above which the magnetization reversal occurred via a curling rotation mode. The easy axis of the magnetization tended to change in direction from parallel to perpendicular with respect to the wire axis as the wire diameter exceeded dc ≈ 276 nm. With increasing wire diameter, the coercive field (Hc) and the remanent to saturation magnetization ratio (Mr/Ms) were also found to rapidly decrease in the range d = 100–400 nm and gradually decrease for d > 400 nm. PMID:25760054

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

    NASA Astrophysics Data System (ADS)

    Liang, Xiao; Weimin, Wang

    2009-12-01

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

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

    PubMed

    Liang, Xiao; Weimin, Wang

    2009-12-01

    A radio-frequency (rf) source for nuclear magnetic resonance (NMR) is described. With the application of direct digital synthesis (DDS), the rf source has the ability to yield rf pulses with short switching time and high resolution in frequency and phase. To facilitate the generation of a soft pulse, a field programmable gate array (FPGA) cooperating with a pulse programmer is used as the auxiliary controller of the DDS chip. Triggered by the pulse programmer, the FPGA automatically controls the DDS to generate soft pulse according to predefined parameters, and the operation mode of the pulse programmer is optimized. The rf source is suitable for being used as transmitter in low-field (<1 T) NMR applications, for example, magnetic resonance imaging and relaxation measurement. As a compact and low-cost module, the rf source is of general use for constructing low-field NMR spectrometer. PMID:20059160

  15. Dense arrays of cobalt nanorods as rare-earth free permanent magnets.

    PubMed

    Anagnostopoulou, E; Grindi, B; Lacroix, L-M; Ott, F; Panagiotopoulos, I; Viau, G

    2016-02-11

    We demonstrate in this paper the feasibility to elaborate rare-earth free permanent magnets based on cobalt nanorods assemblies with energy product (BH)max exceeding 150 kJ m(-3). The cobalt rods were prepared by the polyol process and assembled from wet suspensions under a magnetic field. Magnetization loops of dense assemblies with remanence to a saturation of 0.99 and squareness of 0.96 were measured. The almost perfect M(H) loop squareness together with electron microscopy and small angle neutron scattering demonstrate the excellent alignment of the rods within the assemblies. The magnetic volume fraction was carefully measured by coupling magnetic and thermogravimetric analysis and found in the range from 45 to 55%, depending on the rod diameter and the alignment procedure. This allowed a quantitative assessment of the (BH)max values. The highest (BH)max of 165 kJ m(-3) was obtained for a sample combining a high magnetic volume fraction and a very large M(H) loop squareness. This study shows that this bottom-up approach is very promising to get new hard magnetic materials that can compete in the permanent magnet panorama and fill the gap between the ferrites and the NdFeB magnets. PMID:26817959

  16. Comparing artificial frustrated magnets by tuning the symmetry of nanoscale permalloy arrays

    NASA Astrophysics Data System (ADS)

    Li, J.; Ke, X.; Zhang, S.; Garand, D.; Nisoli, C.; Lammert, P.; Crespi, V. H.; Schiffer, P.

    2010-03-01

    We study the impact of geometry on magnetostatically frustrated single-domain nanomagnet arrays. We examine square and hexagonal lattice arrays, as well as a brickwork geometry that combines the anisotropy of the square lattice and the topology of the hexagonal lattice. We find that the more highly frustrated hexagonal lattice allows for the most thorough minimization of the magnetostatic energy, and that the pairwise correlations between moments differ qualitatively between hexagonal and brickwork lattices, although they share the same lattice topology. The results indicate that the symmetry of local interaction is more important than overall lattice topology in the accommodation of frustrated interactions.

  17. Fabrication of CoFe2O4 ferrite nanowire arrays in porous silicon template and their local magnetic properties

    NASA Astrophysics Data System (ADS)

    Hui, Zheng; Man-Gui, Han; Long-Jiang, Deng

    2016-02-01

    CoFe2O4 ferrite nanowire arrays are fabricated in porous silicon templates. The porous silicon templates are prepared via metal-assisted chemical etching with gold (Au) nanoparticles as the catalyst. Subsequently, CoFe2O4 ferrite nanowires are successfully synthesized into porous silicon templates by the sol–gel method. The magnetic hysteresis loop of nanowire array shows an isotropic feature of magnetic properties. The coercivity and squareness ratio (Mr/Ms) of ensemble nanowires are found to be 630 Oe (1 Oe, = 79.5775 A·m‑1 and 0.4 respectively. However, the first-order reversal curve (FORC) is adopted to reveal the probability density function of local magnetostatic properties (i.e., interwire interaction field and coercivity). The FORC diagram shows an obvious distribution feature for interaction field and coercivity. The local coercivity with a value of about 1000 Oe is found to have the highest probability. Project supported by the National Natural Science Foundation of China (Grant No. 61271039), the Scientific Projects of Sichuan Province, China (Grant No. 2015HH0016), and the Natural Science Foundations of Zhejiang Province, China (Grant Nos. LQ12E02001 and Y107255).

  18. Simultaneous isolation and detection of circulating tumor cells with a microfluidic silicon-nanowire-array integrated with magnetic upconversion nanoprobes.

    PubMed

    Wang, Chao; Ye, Min; Cheng, Liang; Li, Rui; Zhu, Wenwen; Shi, Zhen; Fan, Chunhai; He, Jinkang; Liu, Jian; Liu, Zhuang

    2015-06-01

    The development of sensitive and convenient methods for detection, enrichment, and analysis of circulating tumor cells (CTCs), which serve as an importance diagnostic indicator for metastatic progression of cancer, has received tremendous attention in recent years. In this work, a new approach characteristic of simultaneous CTC capture and detection is developed by integrating a microfluidic silicon nanowire (SiNW) array with multifunctional magnetic upconversion nanoparticles (MUNPs). The MUNPs were conjugated with anti-EpCAM antibody, thus capable to specifically recognize tumor cells in the blood samples and pull them down under an external magnetic field. The capture efficiency of CTCs was further improved by the integration with a microfluidic SiNW array. Due to the autofluorescence free nature in upconversion luminescence (UCL) imaging, our approach allows for highly sensitive detection of small numbers of tumor cells, which afterward could be collected for further analysis and re-culturing. We have further demonstrated that this approach can be applied to detect CTCs in clinical blood samples from lung cancer patients, and obtained consistent results by analyzing the UCL signals and the clinical outcomes of lung cancer metastasis. Therefore our approach represents a promising platform in CTC capture and detection with potential clinical utilization in cancer diagnosis and prognosis. PMID:25907039

  19. Tuning of structural, optical, and magnetic properties of ultrathin and thin ZnO nanowire arrays for nano device applications

    PubMed Central

    2014-01-01

    One-dimensional (1-D) ultrathin (15 nm) and thin (100 nm) aligned 1-D (0001) and (0001¯) oriented zinc oxide (ZnO) nanowire (NW) arrays were fabricated on copper substrates by one-step electrochemical deposition inside the pores of polycarbonate membranes. The aspect ratio dependence of the compressive stress because of the lattice mismatch between NW array/substrate interface and crystallite size variations is investigated. X-ray diffraction results show that the polycrystalline ZnO NWs have a wurtzite structure with a = 3.24 Å, c = 5.20 Å, and [002] elongation. HRTEM and SAED pattern confirmed the polycrystalline nature of ultrathin ZnO NWs and lattice spacing of 0.58 nm. The crystallite size and compressive stress in as-grown 15- and 100-nm wires are 12.8 nm and 0.2248 GPa and 22.8 nm and 0.1359 GPa, which changed to 16.1 nm and 1.0307 GPa and 47.5 nm and 1.1677 GPa after annealing at 873 K in ultrahigh vacuum (UHV), respectively. Micro-Raman spectroscopy showed that the increase in E2 (high) phonon frequency corresponds to much higher compressive stresses in ultrathin NW arrays. The minimum-maximum magnetization magnitude for the as-grown ultrathin and thin NW arrays are approximately 8.45 × 10−3 to 8.10 × 10−3 emu/g and approximately 2.22 × 10−7 to 2.190 × 10−7 emu/g, respectively. The magnetization in 15-nm NW arrays is about 4 orders of magnitude higher than that in the 100 nm arrays but can be reduced greatly by the UHV annealing. The origin of ultrathin and thin NW array ferromagnetism may be the exchange interactions between localized electron spin moments resulting from oxygen vacancies at the surfaces of ZnO NWs. The n-type conductivity of 15-nm NW array is higher by about a factor of 2 compared to that of the 100-nm ZnO NWs, and both can be greatly enhanced by UHV annealing. The ability to tune the stresses and the structural and relative occupancies of ZnO NWs in a wide range by annealing has important implications for the design of advanced photonic, electronic, and magneto-optic nano devices. PMID:24636275

  20. Tuning of structural, optical, and magnetic properties of ultrathin and thin ZnO nanowire arrays for nano device applications.

    PubMed

    Shrama, Satinder K; Saurakhiya, Neelam; Barthwal, Sumit; Kumar, Rudra; Sharma, Ashutosh

    2014-01-01

    One-dimensional (1-D) ultrathin (15 nm) and thin (100 nm) aligned 1-D (0001) and (0001¯) oriented zinc oxide (ZnO) nanowire (NW) arrays were fabricated on copper substrates by one-step electrochemical deposition inside the pores of polycarbonate membranes. The aspect ratio dependence of the compressive stress because of the lattice mismatch between NW array/substrate interface and crystallite size variations is investigated. X-ray diffraction results show that the polycrystalline ZnO NWs have a wurtzite structure with a = 3.24 Å, c = 5.20 Å, and [002] elongation. HRTEM and SAED pattern confirmed the polycrystalline nature of ultrathin ZnO NWs and lattice spacing of 0.58 nm. The crystallite size and compressive stress in as-grown 15- and 100-nm wires are 12.8 nm and 0.2248 GPa and 22.8 nm and 0.1359 GPa, which changed to 16.1 nm and 1.0307 GPa and 47.5 nm and 1.1677 GPa after annealing at 873 K in ultrahigh vacuum (UHV), respectively. Micro-Raman spectroscopy showed that the increase in E2 (high) phonon frequency corresponds to much higher compressive stresses in ultrathin NW arrays. The minimum-maximum magnetization magnitude for the as-grown ultrathin and thin NW arrays are approximately 8.45 × 10-3 to 8.10 × 10-3 emu/g and approximately 2.22 × 10-7 to 2.190 × 10-7 emu/g, respectively. The magnetization in 15-nm NW arrays is about 4 orders of magnitude higher than that in the 100 nm arrays but can be reduced greatly by the UHV annealing. The origin of ultrathin and thin NW array ferromagnetism may be the exchange interactions between localized electron spin moments resulting from oxygen vacancies at the surfaces of ZnO NWs. The n-type conductivity of 15-nm NW array is higher by about a factor of 2 compared to that of the 100-nm ZnO NWs, and both can be greatly enhanced by UHV annealing. The ability to tune the stresses and the structural and relative occupancies of ZnO NWs in a wide range by annealing has important implications for the design of advanced photonic, electronic, and magneto-optic nano devices. PMID:24636275

  1. Towards a programmable microfluidic valve: Formation dynamics of two-dimensional magnetic bead arrays in transient magnetic fields

    NASA Astrophysics Data System (ADS)

    Wittbracht, F.; Eickenberg, B.; Weddemann, A.; Hütten, A.

    2011-06-01

    The induction of dipolar coupling has proven to allow for the initiation of self-assembled, reconfigurable particle clusters of superparamagnetic microbeads suspended in a carrier liquid. The adjustment of the interplay between magnetic and hydrodynamic forces opens various possibilities for guiding strategies of these superstructures within microfluidic devices. In this work, the formation dynamics of such particle clusters under the influence of a rotating magnetic field are studied. Different agglomeration regimes are characterized by the dimensionality of the confined objects. The growth dynamics of the obtained agglomerates are analyzed quantitatively in order to deduce the microscopic growth mechanisms. The growth of two-dimensional clusters is governed by the addition of bead chains to previously formed agglomerates. Time scales for the cluster growth are characterized by the chain dissociation rate. Based on the experimental findings, we may conclude to a linear dependence of the chain dissociation rate on the rotation frequency of the applied magnetic field.

  2. Magnetization mechanisms in ordered arrays of polycrystalline Fe{sub 100?x}Co{sub x} nanowires

    SciTech Connect

    Viqueira, M. S.; Bajales, N.; Urreta, S. E.; Bercoff, P. G.

    2015-05-28

    Magnetization reversal processes and coercivity mechanisms in polycrystalline Fe{sub 100?x}Co{sub x} nanowire arrays, resulting from an AC electrodeposition process, are investigated. The array coercivity is described on the basis of polarization reversal mechanisms operating in individual wires, under the effect of inter-wire dipolar interactions described by a mean field approximation. For individual wires, a reversal mechanism involving the nucleation and further expansion of domain-wall like spin configuration is considered. The wires have a mean grain size larger than both the nanowire diameter and the exchange length, so localized and non-cooperative nucleation modes are considered. As the Co content increases, the alloy saturation polarization gradually decreases, but the coercive field and the relative remanence of the arrays increase, indicating that they are not controlled by the shape anisotropy in all the composition range. The coercive field dependence on the angle between the applied field and the wire long axis is not well described by reversal mechanisms involving nucleation and further displacement of neither vortex nor transverse ideal domain walls. On the contrary, the angular dependence of the coercive field observed at room temperature is well predicted by a model considering nucleation of inverse domains by localized curling, in regions smaller than the grain size, exhibiting quite small aspect ratios as compared to those of the entire nanowire. In arrays with higher Co contents, a transition from an initial (small angle) localized curling nucleation mechanism to another one, involving localized coherent rotation is observed at about ?/4.

  3. Research on ambient temperature passive magnetic bearings at the Lawrence Livermore National Laboratory

    SciTech Connect

    Post, R.F.; Ryitov, D.D.` Smith, J.R.; Tung, L.S.

    1997-04-01

    Research performed at the Lawrence Livermore National Laboratory on the equilibrium and stability of a new class of ambient-temperature passive bearing systems is described. The basic concepts involved are: (1) Stability of the rotating system is only achieved in the rotating state. That is, disengaging mechanical systems are used to insure stable levitation at rest (when Earnshaw`s theorem applies). (2) Stable levitation by passive magnetic elements can be achieved if the vector sum of the force derivatives of the several elements of the system is net negative (i.e. restoring) for axial, transverse, and tilt-type perturbations from equilibrium. To satisfy the requirements of (2) using only permanent magnet elements we have employed periodic ``Halbach arrays.`` These interact with passive inductive loaded circuits and act as stabilizers, with the primary forces arising from axially symmetric permanent-magnet elements. Stabilizers and other elements needed to create compact passive magnetic bearing systems have been constructed. Novel passive means for stabilizing classes of rotor-dynamic instabilities in such systems have also been investigated.

  4. Large voltage modulation in magnetic field sensors from two-dimensional arrays of Y-Ba-Cu-O nano Josephson junctions

    SciTech Connect

    Cybart, Shane A. Dynes, R. C.; Cho, E. Y.; Wong, T. J.; Glyantsev, V. N.; Huh, J. U.; Yung, C. S.; Moeckly, B. H.; Beeman, J. W.; Ulin-Avila, E.; Wu, S. M.

    2014-02-10

    We have fabricated and tested two-dimensional arrays of YBa{sub 2}Cu{sub 3}O{sub 7−δ} superconducting quantum interference devices. The arrays contain over 36 000 nano Josephson junctions fabricated from ion irradiation of YBa{sub 2}Cu{sub 3}O{sub 7−δ} through narrow slits in a resist-mask that was patterned with electron beam lithography and reactive ion etching. Measurements of current-biased arrays in magnetic field exhibit large voltage modulations as high as 30 mV.

  5. Reliability of Signal Propagation in Magnetostatically Coupled Arrays of Magnetic Nanoelements

    NASA Astrophysics Data System (ADS)

    van Mourik, Reinier; Gao, Li; Hughes, Brian; Rettner, Charles; Koopmans, Bert; Parkin, Stuart

    2013-03-01

    Nanomagnetic logic (NML) has promise as a low-power, non-volatile, and radiation resistant alternative to CMOS-based computational devices. Lines of magnetostatically coupled magnetic nano-elements (NEs) propagate information, and the intersections between lines form logic gates. We present simulations and experiments exploring the reliability of signal propagation in NML devices composed of lines of nominally rectangular permalloy NEs, typically 90 60 nm2 in size. An external magnetic field sets the magnetic state of an input bit and also resets each of the NEs' magnetizations along their hard axis direction. As the field is reduced to zero the input state propagates along the line of NEs as they successively relax into one of two equilibrium states. The state of the NEs is probed by (i) a magnetic tunnel junction sensing device integrated with the output NE and (ii) magnetic force microscopy imaging. We conclude that signal propagation is inherently unreliable both through variations in fabrication of the NEs and due to the innate lack of directionality of the flow of information. We demonstrate an alternative clocking method where a domain wall passing underneath an NML device clocks each NE sequentially, thereby increasing the success of signal propagation. IBM: San Jose, CA; Eindhoven University: Eindhoven, the Netherlands; Mainz Graduate school: Mainz, Germany

  6. Commensurate states on incommensurate lattices. [for superconducting arrays in magnetic fields

    NASA Technical Reports Server (NTRS)

    Grest, Gary S.; Chaikin, Paul M.; Levine, Dov

    1988-01-01

    A simple one-dimensional model related to flux quantization on superconducting networks or charged particles on a substrate is proposed to investigate whether commensurate states can exist on incommensurate lattices. For both periodic and quasi-crystalline patterns, a set of low-energy states is found which is related to decimation symmetry and periodicity. It is suggested that the present quasi-periodic arrays which possess a decimation operation can be generalized to more-dimensional quasi-crystalline systems.

  7. Cryogenic phased-array for high resolution magnetic resonance imaging (MRI); assessment of clinical and research applications

    NASA Astrophysics Data System (ADS)

    Ip, Flora S.

    Magnetic Resonance (MR) imaging is one of the most powerful tools in diagnostic medicine for soft tissue imaging. Image acquisition techniques and hardware receivers are very important in achieving high contrast and high resolution MR images. An aim of this dissertation is to design single and multi-element room and cryogenic temperature arrays and make assessments of their signal-to-noise ratio (SNR) and SNR gain. In this dissertation, four sets of MR receiver coils are built. They are the receiver-only cryo-coils that are not commercially available. A tuning and matching circuit is attached to each coil. The tuning and matching circuits are simple; however, each device component has to operate at a high magnetic field and cryogenic temperature environment. Remote DC bias of the varactor controls the tuning and matching outside the scanner room. Active detuning of the resonator is done by two p-i-n junction (PIN) diodes. Cooling of the receiver is done by a customized liquid nitrogen cryostat. The first application is to build a 3-Tesla 2x1 horseshoe counter-rotating current (CRC) cryogenic array to image the tibia in a human body. With significant increase in SNR, the surface coil should deliver high contrast and resolution images that can show the trabecular bone and bone marrow structure. This structural image will be used to model the mechanical strength of the bone as well as bone density and chance of fracture. The planar CRC is a unique design of this surface array. The second application is to modify the coil design to 7-Tesla to study the growth of infant rhesus monkey eyes. Fast scan MR images of the infant monkey heads are taken for monitoring shapes of their eyeballs. The monkeys are induced with shortsightedness by eye lenses, and they are scanned periodically to get images of their eyeballs. The field-of-view (FOV) of these images is about five centimeters and the area of interest is two centimeters deep from the surface. Because of these reasons, the MR counter-rotating current coil is sufficient and demonstrated its simplicity over a phased array in this application.

  8. Gas-assisted growth of boron-doped nickel nanotube arrays: rapid synthesis, growth mechanisms, tunable magnetic properties, and super-efficient reduction of 4-nitrophenol

    NASA Astrophysics Data System (ADS)

    Li, Xiang-Zi; Wu, Kong-Lin; Ye, Yin; Wei, Xian-Wen

    2013-04-01

    Highly ordered noncrystalline boron-doped nickel nanotube arrays are rapidly synthesized within 150 s by template-based electroless deposition. The as-prepared nanotubes have tunable magnetic properties and exhibit super efficient catalytic activity (~70 s) for the reduction of 4-nitrophenol.Highly ordered noncrystalline boron-doped nickel nanotube arrays are rapidly synthesized within 150 s by template-based electroless deposition. The as-prepared nanotubes have tunable magnetic properties and exhibit super efficient catalytic activity (~70 s) for the reduction of 4-nitrophenol. Electronic supplementary information (ESI) available. See DOI: 10.1039/c3nr00411b

  9. Amplification of electromagnetic waves excited by a chain of propagating magnetic vortices in YBa2Cu3O7-? Josephson-junction arrays at 77 K and above

    NASA Astrophysics Data System (ADS)

    Chesca, Boris; John, Daniel; Mellor, Christopher J.

    2014-08-01

    When a soliton propagates in a discrete lattice it excites small-amplitude linear waves in its wake. In a dc current-biased Josephson-junction (JJ) array these manifest as electromagnetic (EM) waves excited by a (magnetic field induced) chain of propagating magnetic vortices. When the vortex velocity and the phase velocity of one of the excited EM waves match, phase-locking occurs. This produces resonant steps in the current-voltage characteristics where amplification of EM radiation occurs. We report the first observation of phase-locking-induced amplification of EM radiation at 77 K and above in JJ arrays made of high temperature superconductors.

  10. Increased Efficiency of a Permanent Magnet Synchronous Generator through Optimization of NdFeB Magnet Arrays

    NASA Astrophysics Data System (ADS)

    Khazdozian, Helena; Hadimani, Ravi; Jiles, David

    2014-03-01

    The United States is currently dependent on fossil fuels for the majority of its energy needs, which has many negative consequences such as climate change. Wind turbines present a viable alternative, with the highest energy return on investment among even fossil fuel generation. Traditional commercial wind turbines use an induction generator for energy conversion. However, induction generators require a gearbox to increase the rotational speed of the drive shaft. These gearboxes increase the overall cost of the wind turbine and account for about 35 percent of reported wind turbine failures. Direct drive permanent magnet synchronous generators (PMSGs) offer an alternative to induction generators which eliminate the need for a gearbox. Yet, PMSGs can be more expensive than induction generators at large power output due to their size and weight. To increase the efficiency of PMSGs, the geometry and configuration of NdFeB permanent magnets were investigated using finite element techniques. The optimized design of the PMSG increases flux density and minimizes cogging torque with NdFeB permanent magnets of a reduced volume. These factors serve to increase the efficiency and reduce the overall cost of the PMSG. This work is supported by a National Science Foundation IGERT fellowship and the Barbara and James Palmer Endowment at the Department of Electrical and Computer Engineering of Iowa State University.

  11. Force measurements of a magnetic micro actuator proposed for a microvalve array

    NASA Astrophysics Data System (ADS)

    Chang, Pauline J.; Chang, Frank W.; Yuen, Michelle C.; Otillar, Robert; Horsley, David A.

    2014-03-01

    Low-cost, easily-fabricated and power-efficient microvalves are necessary for many microfluidic lab-on-a-chip applications. In this study, we present a simple, low-power, scalable, CMOS-compatible magnetic actuator for microvalve applications composed of a paramagnetic bead as the ball valve over a picoliter reaction well etched into a silicon substrate. The paramagnetic bead, composed of either pure FeSi or magnetite in a SiO2 matrix, is actuated by the local magnetic field gradient generated by a microcoil in an aqueous environment, and the reaction well is situated at the microcoil center. A permanent magnet beneath the microvalve device provides an external magnetic biasing field that magnetizes the bead, enabling bidirectional actuation and reducing the current required to actuate the bead to a level below 10 mA. The vertical and radial magnetic forces exerted on the bead by the microcoil were measured for both pure FeSi and composite beads and agree well with the predictions of 2D axisymmetric finite element method models. Vertical forces were within a range of 13-80 nN, and radial forces were 11-60 nN depending on the bead type. The threshold current required to initiate bead actuation was measured as a function of bead diameter and is found to scale inversely with volume for small beads, as expected based on the magnetic force model. To provide an estimate of the stiction force acting between the bead and the passivation layer on the substrate, repeated actuation trials were used to study the bead throw distance for substrates coated with silicon dioxide, Parylene-C, and photoresist. The stiction observed was lowest for a photoresist-coated substrate, while silicon dioxide and Parylene-C coated substrates exhibited similar levels of stiction.

  12. Preparation and magnetic properties of cylindrical NiFe films and antidot arrays.

    PubMed

    Sanz, R; Navas, D; Vazquez, M; Hernndez-Vlez, M; Ross, C A

    2010-10-01

    Continuous NiFe (Permalloy) cylindrical films and arrays of cylindrical NiFe antidots 7 nm thick have been prepared by sputtering onto cylindrical aluminum wires and onto wires anodized to form a porous anodic alumina layer. The antidots are arranged in a close-packed pattern determined by the hexagonal pore arrangement in the porous alumina, with period 103 nm and diameter 42 nm. Hysteresis loops were measured at different angles with respect to the cylinder axis and indicate an easy plane normal to the radius of the wire. The antidots enhance the coercivity compared to the continuous cylindrical film. PMID:21137795

  13. Domain configurations in Co/Pd and L10-FePt nanowire arrays with perpendicular magnetic anisotropy

    NASA Astrophysics Data System (ADS)

    Ho, Pin; Tu, Kun-Hua; Zhang, Jinshuo; Sun, Congli; Chen, Jingsheng; Liontos, George; Ntetsikas, Konstantinos; Avgeropoulos, Apostolos; Voyles, Paul M.; Ross, Caroline A.

    2016-02-01

    Perpendicular magnetic anisotropy [Co/Pd]15 and L10-FePt nanowire arrays of period 63 nm with linewidths 38 nm and 27 nm and film thickness 27 nm and 20 nm respectively were fabricated using a self-assembled PS-b-PDMS diblock copolymer film as a lithographic mask. The wires are predicted to support Néel walls in the Co/Pd and Bloch walls in the FePt. Magnetostatic interactions from nearest neighbor nanowires promote a ground state configuration consisting of alternating up and down magnetization in adjacent wires. This was observed over ~75% of the Co/Pd wires after ac-demagnetization but was less prevalent in the FePt because the ratio of interaction field to switching field was much smaller. Interactions also led to correlations in the domain wall positions in adjacent Co/Pd nanowires. The reversal process was characterized by nucleation of reverse domains, followed at higher fields by propagation of the domains along the nanowires. These narrow wires provide model system for exploring domain wall structure and dynamics in perpendicular anisotropy systems.Perpendicular magnetic anisotropy [Co/Pd]15 and L10-FePt nanowire arrays of period 63 nm with linewidths 38 nm and 27 nm and film thickness 27 nm and 20 nm respectively were fabricated using a self-assembled PS-b-PDMS diblock copolymer film as a lithographic mask. The wires are predicted to support Néel walls in the Co/Pd and Bloch walls in the FePt. Magnetostatic interactions from nearest neighbor nanowires promote a ground state configuration consisting of alternating up and down magnetization in adjacent wires. This was observed over ~75% of the Co/Pd wires after ac-demagnetization but was less prevalent in the FePt because the ratio of interaction field to switching field was much smaller. Interactions also led to correlations in the domain wall positions in adjacent Co/Pd nanowires. The reversal process was characterized by nucleation of reverse domains, followed at higher fields by propagation of the domains along the nanowires. These narrow wires provide model system for exploring domain wall structure and dynamics in perpendicular anisotropy systems. Electronic supplementary information (ESI) available. See DOI: 10.1039/c5nr08865h

  14. Stability considerations for magnetic suspension systems using electromagnets mounted in a planar array

    NASA Technical Reports Server (NTRS)

    Groom, Nelson J.; Britcher, Colin P.

    1991-01-01

    Mathematical models of a 5, 6, 7, and 8 coil large gap magnetic suspension system (MSDS) are presented. Some of the topics covered include: force and torque equations, reduction of state-space form, natural modes, origins of modes, effect of rotation in azimuth (yaw), future work, and n-coil ring conclusions.

  15. Taking a hard line with biotemplating: cobalt-doped magnetite magnetic nanoparticle arrays.

    PubMed

    Bird, Scott M; Galloway, Johanna M; Rawlings, Andrea E; Bramble, Jonathan P; Staniland, Sarah S

    2015-04-28

    Rapid advancements made in technology, and the drive towards miniaturisation, means that we require reliable, sustainable and cost effective methods of manufacturing a wide range of nanomaterials. In this bioinspired study, we take advantage of millions of years of evolution, and adapt a biomineralisation protein for surface patterning of biotemplated magnetic nanoparticles (MNPs). We employ soft-lithographic micro-contact printing to pattern a recombinant version of the biomineralisation protein Mms6 (derived from the magnetotactic bacterium Magnetospirillum magneticum AMB-1). The Mms6 attaches to gold surfaces via a cysteine residue introduced into the N-terminal region. The surface bound protein biotemplates highly uniform MNPs of magnetite onto patterned surfaces during an aqueous mineralisation reaction (with a mean diameter of 90 ± 15 nm). The simple addition of 6% cobalt to the mineralisation reaction maintains the uniformity in grain size (with a mean diameter of 84 ± 14 nm), and results in the production of MNPs with a much higher coercivity (increased from ≈ 156 Oe to ≈ 377 Oe). Biotemplating magnetic nanoparticles on patterned surfaces could form a novel, environmentally friendly route for the production of bit-patterned media, potentially the next generation of ultra-high density magnetic data storage devices. This is a simple method to fine-tune the magnetic hardness of the surface biotemplated MNPs, and could easily be adapted to biotemplate a wide range of different nanomaterials on surfaces to create a range of biologically templated devices. PMID:25825205

  16. Preliminary design of a superconducting coil array for NASA prototype magnetic balance. M.S. Thesis

    NASA Technical Reports Server (NTRS)

    Alishahi, M. M.

    1980-01-01

    Using a computer program a partly optimized configuration for a supeconducting version of side and lift coil system of NASA-MIT prototype is presented. Cable size for the mentioned coils and also for superconducting drag and magnetizing coils regarding the overall computed field was determined.

  17. Controllable step motors and rectifiers of magnetic flux quanta using periodic arrays of asymmetric pinning defects

    NASA Astrophysics Data System (ADS)

    Zhu, B. Y.; Marchesoni, F.; Moshchalkov, V. V.; Nori, Franco

    2003-07-01

    We study the transport of vortices in superconductors with regular arrays of asymmetric pinning wells when applying an alternating electrical current. The asymmetric traps are modelled by the superposition of two interpenetrating square lattices of weak and strong pinning centers with separation smaller than the lattice constant. We show that this system can induce a net rectifying or diode effect for the vortex motion, including collective step-motor-type dynamics, where many vortices move forward a controlled and exact number of pin-lattice spacings at each cycle of the ac driving force. This system exhibits a remarkable net dc response with striking sawtooth-type oscillations. The net dc voltage response Vdc of the ac-driven vortices versus both the half period P and the amplitude FL of the square wave ac drive has been detailed in the present work. The influence of the equilibrium thermal noise, the shift between the two pinning sublattices, the degree of translational and orientational disorder, and the size of the simulation system on the Vdc response of the vortex motion at ac drive has also been addressed. Devil staircase and Arnolds tongue structures are revealed. We also analytically derive all the key features of our numerical results. This system provides a very controllable stepmotor for the control of collective motion. Our results apply mutatis mutandis to arrays of Josephson junctions, colloidal systems with optical traps, Wigner crystals, and any system with repelling movable objects that can be pinned by a lattice of traps.

  18. Gas-assisted growth of boron-doped nickel nanotube arrays: rapid synthesis, growth mechanisms, tunable magnetic properties, and super-efficient reduction of 4-nitrophenol.

    PubMed

    Li, Xiang-Zi; Wu, Kong-Lin; Ye, Yin; Wei, Xian-Wen

    2013-05-01

    Highly ordered noncrystalline boron-doped nickel nanotube arrays are rapidly synthesized within 150 s by template-based electroless deposition. The as-prepared nanotubes have tunable magnetic properties and exhibit super efficient catalytic activity (?70 s) for the reduction of 4-nitrophenol. PMID:23546439

  19. Structure and magnetic properties of three-dimensional (La,Sr)MnO{sub 3} nanofilms on ZnO nanorod arrays

    SciTech Connect

    Gao Haiyong; Gao Puxian; Shimpi, Paresh; Guo Yanbing; Cai Wenjie; Lin Huijan; Staruch, M.; Jain, Menka

    2011-03-21

    Three-dimensional (3D) cubic perovskite (La,Sr)MnO{sub 3} (LSMO) nanofilms have been deposited on ZnO nanorod arrays with controlled dimensionality and crystallinity by radio frequency (rf) magnetron sputtering and post thermal annealing. Compared to the two-dimensional (2D) LSMO nanofilm on flat Si, the structure and magnetic properties of 3D LSMO nanofilms on ZnO nanorod arrays have a strong anisotropic morphology and thickness dependence. Ferromagnetic property has been observed in both 2D and 3D LSMO nanofilms while a ferromagnetic-superparamagnetic transition was revaled in 3D LSMO nanofilms on ZnO nanorod array with decreasing nanofilm thickness, due to a large surface dispersion effect. The LSMO/ZnO nanofilm/nanorod structures could open up new avenues for intriguing magnetic properties studies and applications of nanoscale perovskites.

  20. Laminated track design for inductrack maglev systems

    SciTech Connect

    Post, Richard F.

    2004-07-06

    A magnet configuration comprising a pair of Halbach arrays magnetically and structurally connected together are positioned with respect to each other so that a first component of their fields substantially cancels at a first plane between them, and a second component of their fields substantially adds at this first plane. A track is located between the pair of Halbach arrays and a propulsion mechanism is provided for moving the pair of Halbach arrays along the track. When the pair of Halbach arrays move along the track and the track is not located at the first plane, a current is induced in the windings and a restoring force is exerted on the pair of Halbach arrays.

  1. Taking a hard line with biotemplating: cobalt-doped magnetite magnetic nanoparticle arrays

    NASA Astrophysics Data System (ADS)

    Bird, Scott M.; Galloway, Johanna M.; Rawlings, Andrea E.; Bramble, Jonathan P.; Staniland, Sarah S.

    2015-04-01

    Rapid advancements made in technology, and the drive towards miniaturisation, means that we require reliable, sustainable and cost effective methods of manufacturing a wide range of nanomaterials. In this bioinspired study, we take advantage of millions of years of evolution, and adapt a biomineralisation protein for surface patterning of biotemplated magnetic nanoparticles (MNPs). We employ soft-lithographic micro-contact printing to pattern a recombinant version of the biomineralisation protein Mms6 (derived from the magnetotactic bacterium Magnetospirillum magneticum AMB-1). The Mms6 attaches to gold surfaces via a cysteine residue introduced into the N-terminal region. The surface bound protein biotemplates highly uniform MNPs of magnetite onto patterned surfaces during an aqueous mineralisation reaction (with a mean diameter of 90 +/- 15 nm). The simple addition of 6% cobalt to the mineralisation reaction maintains the uniformity in grain size (with a mean diameter of 84 +/- 14 nm), and results in the production of MNPs with a much higher coercivity (increased from ~156 Oe to ~377 Oe). Biotemplating magnetic nanoparticles on patterned surfaces could form a novel, environmentally friendly route for the production of bit-patterned media, potentially the next generation of ultra-high density magnetic data storage devices. This is a simple method to fine-tune the magnetic hardness of the surface biotemplated MNPs, and could easily be adapted to biotemplate a wide range of different nanomaterials on surfaces to create a range of biologically templated devices.Rapid advancements made in technology, and the drive towards miniaturisation, means that we require reliable, sustainable and cost effective methods of manufacturing a wide range of nanomaterials. In this bioinspired study, we take advantage of millions of years of evolution, and adapt a biomineralisation protein for surface patterning of biotemplated magnetic nanoparticles (MNPs). We employ soft-lithographic micro-contact printing to pattern a recombinant version of the biomineralisation protein Mms6 (derived from the magnetotactic bacterium Magnetospirillum magneticum AMB-1). The Mms6 attaches to gold surfaces via a cysteine residue introduced into the N-terminal region. The surface bound protein biotemplates highly uniform MNPs of magnetite onto patterned surfaces during an aqueous mineralisation reaction (with a mean diameter of 90 +/- 15 nm). The simple addition of 6% cobalt to the mineralisation reaction maintains the uniformity in grain size (with a mean diameter of 84 +/- 14 nm), and results in the production of MNPs with a much higher coercivity (increased from ~156 Oe to ~377 Oe). Biotemplating magnetic nanoparticles on patterned surfaces could form a novel, environmentally friendly route for the production of bit-patterned media, potentially the next generation of ultra-high density magnetic data storage devices. This is a simple method to fine-tune the magnetic hardness of the surface biotemplated MNPs, and could easily be adapted to biotemplate a wide range of different nanomaterials on surfaces to create a range of biologically templated devices. Electronic supplementary information (ESI) available. See DOI: 10.1039/c5nr00651a

  2. The MAIN Shirt: a textile-integrated magnetic induction sensor array.

    PubMed

    Teichmann, Daniel; Kuhn, Andreas; Leonhardt, Steffen; Walter, Marian

    2014-01-01

    A system is presented for long-term monitoring of respiration and pulse. It comprises four non-contact sensors based on magnetic eddy current induction that are textile-integrated into a shirt. The sensors are technically characterized by laboratory experiments that investigate the sensitivity and measuring depth, as well as the mutual interaction between adjacent pairs of sensors. The ability of the device to monitor respiration and pulse is demonstrated by measurements in healthy volunteers. The proposed system (called the MAIN (magnetic induction) Shirt) does not need electrodes or any other skin contact. It is wearable, unobtrusive and can easily be integrated into an individual's daily routine. Therefore, the system appears to be a suitable option for long-term monitoring in a domestic environment or any other unsupervised telemonitoring scenario. PMID:24412900

  3. The MAIN Shirt: A Textile-Integrated Magnetic Induction Sensor Array

    PubMed Central

    Teichmann, Daniel; Kuhn, Andreas; Leonhardt, Steffen; Walter, Marian

    2014-01-01

    A system is presented for long-term monitoring of respiration and pulse. It comprises four non-contact sensors based on magnetic eddy current induction that are textile-integrated into a shirt. The sensors are technically characterized by laboratory experiments that investigate the sensitivity and measuring depth, as well as the mutual interaction between adjacent pairs of sensors. The ability of the device to monitor respiration and pulse is demonstrated by measurements in healthy volunteers. The proposed system (called the MAIN (magnetic induction) Shirt) does not need electrodes or any other skin contact. It is wearable, unobtrusive and can easily be integrated into an individual's daily routine. Therefore, the system appears to be a suitable option for long-term monitoring in a domestic environment or any other unsupervised telemonitoring scenario. PMID:24412900

  4. Development of multielement SQUID arrays for magnetic source imaging. Final report

    SciTech Connect

    Hassenzahl, W.V.; Casper, T.A.; Miller, D.E.

    1995-06-01

    Superconducting quantum interference devices (SQUIDs) were initially developed in the late 1960s as biomagnetic detectors to monitor electrical activity in the body. Research in this area has increased in recent years as electronics and computer diagnositcs have improved. The basis of this proposal was to asses: (1) the advantages of using this technique over other technologies and (2) the requirements for development of a complete system that would advance the state of the art. In our assessment of this technology, we collaborated with the Medical School at the University of California, San Francisco (UCSF), General Electric (GE), Biomagnetic Technologies (BTi), and Conductus, each of which has unqiue expertise in biomedical applications. UCSF is one of the foremost clinical institutions in the US developing imaging techniques. GE is the primary US supplier of medical imaging systems. Conductus is the major US supplier of SQUIDs and BTi is a developer of SQUID array systems.

  5. A family of rare earth molybdenum bronzes: Oxides consisting of periodic arrays of interacting magnetic units

    NASA Astrophysics Data System (ADS)

    Schneemeyer, L. F.; Siegrist, T.; Besara, T.; Lundberg, M.; Sun, J.; Singh, D. J.

    2015-07-01

    The family of rare earth molybdenum bronzes, reduced ternary molybdates of composition LnMo16O44, was synthesized and a detailed structural study carried out. Bond valence sum (BVS) calculations clearly show that the molybdenum ions in tetrahedral coordination are hexavalent while the electron count in the primitive unit cell is odd. Yet, measurements show that the phases are semiconductors. The temperature dependence of the magnetic susceptibility of samples containing several different rare earth elements was measured. These measurements verified the presence of a 6.5 K magnetic phase transition not arising from the rare earth constituent, but likely associated with the unique isolated ReO3-type Mo8O36 structural subunits in this phase. To better understand the behavior of these materials, electronic structure calculations were performed within density functional theory. Results suggest a magnetic state in which these structural moieties have an internal ferromagnetic arrangement, with small ~1/8 ?B moments on each Mo. We suggest that the Mo8O36 units behave like pseudoatoms with spin 1/2 derived from a single hole distributed over the eight Mo atoms that are strongly hybridized with the O atoms of the subunit. Interestingly, while the compound is antiferromagnetic, our calculations suggest that a field-stabilized ferromagnetic state, if achievable, will be a narrow band half-metal.

  6. Domain configurations in Co/Pd and L10-FePt nanowire arrays with perpendicular magnetic anisotropy.

    PubMed

    Ho, Pin; Tu, Kun-Hua; Zhang, Jinshuo; Sun, Congli; Chen, Jingsheng; Liontos, George; Ntetsikas, Konstantinos; Avgeropoulos, Apostolos; Voyles, Paul M; Ross, Caroline A

    2016-02-25

    Perpendicular magnetic anisotropy [Co/Pd]15 and L10-FePt nanowire arrays of period 63 nm with linewidths 38 nm and 27 nm and film thickness 27 nm and 20 nm respectively were fabricated using a self-assembled PS-b-PDMS diblock copolymer film as a lithographic mask. The wires are predicted to support Nel walls in the Co/Pd and Bloch walls in the FePt. Magnetostatic interactions from nearest neighbor nanowires promote a ground state configuration consisting of alternating up and down magnetization in adjacent wires. This was observed over ?75% of the Co/Pd wires after ac-demagnetization but was less prevalent in the FePt because the ratio of interaction field to switching field was much smaller. Interactions also led to correlations in the domain wall positions in adjacent Co/Pd nanowires. The reversal process was characterized by nucleation of reverse domains, followed at higher fields by propagation of the domains along the nanowires. These narrow wires provide model system for exploring domain wall structure and dynamics in perpendicular anisotropy systems. PMID:26883011

  7. Observation of Non-local Mechanical Responses to Locally Applied Forces in Cells using Magnetic Micropost Arrays

    NASA Astrophysics Data System (ADS)

    Lamb, Corinne; Liu, Yaohua; Reich, Daniel; Sniadecki, Nathan; Chen, Christopher

    2008-03-01

    The process of force transduction by living cells is linked to changes in cellular function. To study the cellular response to applied forces, we have developed a novel force detection device, which can also be used to apply external forces to a cell. Cells are cultured atop an array of micrometer scale elastomeric posts, which act as independent sensors to cellular traction forces. An external force is applied to the adherent surface of the cell via a magnetic torque on a cobalt nanowire embedded in a single post. Results measuring the spatially resolved forces exerted by the cell over time indicate two responses: a sudden or a gradual global relaxation of the cell in response to a single force actuation. ootnotetextN. Sniadecki, et. al, ``Magnetic microposts as an approach to apply forces to living cells,'' Proc Natl Acad Sci, 104, no. 37 (2007): 14553 In both cases, the subcellular distribution of loss in traction forces was not concentrated near the point of stimulation but occurred instead at discrete locations around the cell's periphery. Observation of these adaptive non-local responses is potentially important in understanding how external forces are transduced into biochemical regulators of cell function.

  8. Design and Application of Combined 8-Channel Transmit and 10-Channel Receive Arrays and Radiofrequency Shimming for 7-T Shoulder Magnetic Resonance Imaging

    PubMed Central

    Brown, Ryan; Deniz, Cem Murat; Zhang, Bei; Chang, Gregory; Sodickson, Daniel K.; Wiggins, Graham C.

    2014-01-01

    Objective The objective of the study was to investigate the feasibility of 7-T shoulder magnetic resonance imaging by developing transmit and receive radiofrequency (RF) coil arrays and exploring RF shim methods. Materials and Methods A mechanically flexible 8-channel transmit array and an anatomically conformable 10-channel receive array were designed and implemented. The transmit performance of various RF shim methods was assessed through local flip angle measurements in the right and left shoulders of 6 subjects. The receive performance was assessed through signal-to-noise ratio measurements using the developed 7-T coil and a baseline commercial 3-T coil. Results The 7-T transmit array driven with phase-coherent RF shim weights provided adequate B1+ efficiency and uniformity for turbo spin echo shoulder imaging. B1+ twisting that is characteristic of high-field loop coils necessitates distinct RF shim weights in the right and left shoulders. The 7-T receive array provided a 2-fold signal-to-noise ratio improvement over the 3-T array in the deep articular shoulder cartilage. Conclusions Shoulder imaging at 7-T is feasible with a custom transmit/receive array either in a single-channel transmit mode with a fixed RF shim or in a parallel transmit mode with a subject-specific RF shim. PMID:24056112

  9. Seismo-magnetic multi-point ULF studies before the 2009 L'Aquila earthquake using the South European GeoMagnetic Array

    NASA Astrophysics Data System (ADS)

    Prattes, G.; Schwingenschuh, K.; Eichelberger, H.; Besser, B.; Magnes, W.; Stachel, M.; Vellante, M.; Villante, U.; Nenovski, P.

    2010-05-01

    A strong earthquake (Ml=5.8, Mw=6.3) hit L'Aquila (Central Italy, Abruzzo region, LT=UT+1) on April 6, 2009, 01:32 UT, causing more than 300 deaths. We present a seismo-magnetic analysis of local ULF measurements for the time period one year before the main stroke. As part of the South European GeoMagnetic Array (SEGMA) the evaluated station L'Aquila in closest distance to the epicentre of the main seismic event is ~ 6 km. We consider three further SEGMA stations: Castello Tesino, Ranchio (both Italy) and Nagycenk (Hungary) for comparison and the Kp geomagnetic index to distinguish local- , global- and geomagnetic effects. Further local seismic activities are respected. The instrumentation consists of fluxgate magnetometers with a sampling frequency of 1 Hz. Concerning signal processing the standardized polarization method was applied based on the ratio between the vertical and horizontal power spectral density. A frequency band from 10-100 mHz focused on 10-15 mHz was used during the nighttime period from 22.00 - 02.00 UT. The polarization analysis was introduced and applied for previous seismic events by Hayakawa et al., GRL, 23, 241, 1996.; Molchanov et al., GRL, 19, 1495, 1992.; Prattes et al., NHESS, 2008. A sophisticated method was performed by Ida, et al, NHESS, 2008. With these calculations we expect clearer precursor signatures and they could contribute to EQ forecast. The results are explained using a simple source magnetic dipole model near the EQ focus. The results obtained are explained by the attenuation in the electrical conductive lithosphere.

  10. Vortex pinning vs superconducting wire network: origin of periodic oscillations induced by applied magnetic fields in superconducting films with arrays of nanomagnets

    NASA Astrophysics Data System (ADS)

    Gomez, A.; del Valle, J.; Gonzalez, E. M.; Chiliotte, C. E.; Carreira, S. J.; Bekeris, V.; Prieto, J. L.; Schuller, Ivan K.; Vicent, J. L.

    2014-06-01

    Hybrid magnetic arrays embedded in superconducting films are ideal systems to study the competition between different physical (such as the coherence length) and structural length scales such as are available in artificially produced structures. This interplay leads to oscillation in many magnetically dependent superconducting properties such as the critical currents, resistivity and magnetization. These effects are generally analyzed using two distinct models based on vortex pinning or wire network. In this work, we show that for magnetic dot arrays, as opposed to antidot (i.e. holes) arrays, vortex pinning is the main mechanism for field induced oscillations in resistance R(H), critical current Ic(H), magnetization M(H) and ac-susceptibility ? ac(H) in a broad temperature range. Due to the coherence length divergence at Tc, a crossover to wire network behaviour is experimentally found. While pinning occurs in a wide temperature range up to Tc, wire network behaviour is only present in a very narrow temperature window close to Tc. In this temperature interval, contributions from both mechanisms are operational but can be experimentally distinguished.

  11. Magnetic measurements using array of integrated Hall sensors on the CASTOR tokamak

    NASA Astrophysics Data System (ADS)

    Ďuran, Ivan; Hronová, Olena; Stöckel, Jan; Sentkerestiová, Jana; Havlicek, Josef

    2008-10-01

    We have performed the first tests of ``integrated'' Hall sensors (IHSs) in a tokamak in-vessel environment. IHS combines the sensing element together with the complex electronic circuitry on a single small chip. The on-chip integrated circuits provide stabilization of the supply voltage, output amplification, noise suppression, and elimination of temperature dependencies. Eight IHSs of A1322LUA type produced by Allegro MicroSystems, Inc. were mounted on a stainless steel ring symmetrically encircling the CASTOR plasmas in poloidal direction 10 mm outside the limiter radius. IHSs were oriented such that they measure the horizontal and vertical magnetic fields. We found out that these sensors qualify for in-vessel use of small to middle sized fusion devices where the radiation is not an issue and the temperature below 150 °C can be guaranteed. The main advantages over the traditional pickup coils are the smaller size and more straightforward interpretation of output without the need of rather cumbersome integration and drift removal procedure associated with the use of inductive loops. We successfully exploited the sensors for determination of vertical plasma displacement on CASTOR. This new diagnostic helped us to shed more light into long term observed discrepancy on CASTOR between vertical plasma displacement as deduced by standard magnetic and by nonmagnetic diagnostics (Langmuir probes, bolometers).

  12. Magnetic measurements using array of integrated Hall sensors on the CASTOR tokamak

    SciTech Connect

    Duran, Ivan; Hronova, Olena; Stoeckel, Jan; Havlicek, Josef

    2008-10-15

    We have performed the first tests of 'integrated' Hall sensors (IHSs) in a tokamak in-vessel environment. IHS combines the sensing element together with the complex electronic circuitry on a single small chip. The on-chip integrated circuits provide stabilization of the supply voltage, output amplification, noise suppression, and elimination of temperature dependencies. Eight IHSs of A1322LUA type produced by Allegro MicroSystems, Inc. were mounted on a stainless steel ring symmetrically encircling the CASTOR plasmas in poloidal direction 10 mm outside the limiter radius. IHSs were oriented such that they measure the horizontal and vertical magnetic fields. We found out that these sensors qualify for in-vessel use of small to middle sized fusion devices where the radiation is not an issue and the temperature below 150 deg. C can be guaranteed. The main advantages over the traditional pickup coils are the smaller size and more straightforward interpretation of output without the need of rather cumbersome integration and drift removal procedure associated with the use of inductive loops. We successfully exploited the sensors for determination of vertical plasma displacement on CASTOR. This new diagnostic helped us to shed more light into long term observed discrepancy on CASTOR between vertical plasma displacement as deduced by standard magnetic and by nonmagnetic diagnostics (Langmuir probes, bolometers)

  13. Magnetic measurements using array of integrated Hall sensors on the CASTOR tokamaka)

    NASA Astrophysics Data System (ADS)

    Duran, Ivan; Hronová, Olena; Stöckel, Jan; Sentkerestiová, Jana; Havlicek, Josef

    2008-10-01

    We have performed the first tests of "integrated" Hall sensors (IHSs) in a tokamak in-vessel environment. IHS combines the sensing element together with the complex electronic circuitry on a single small chip. The on-chip integrated circuits provide stabilization of the supply voltage, output amplification, noise suppression, and elimination of temperature dependencies. Eight IHSs of A1322LUA type produced by Allegro MicroSystems, Inc. were mounted on a stainless steel ring symmetrically encircling the CASTOR plasmas in poloidal direction 10 mm outside the limiter radius. IHSs were oriented such that they measure the horizontal and vertical magnetic fields. We found out that these sensors qualify for in-vessel use of small to middle sized fusion devices where the radiation is not an issue and the temperature below 150 °C can be guaranteed. The main advantages over the traditional pickup coils are the smaller size and more straightforward interpretation of output without the need of rather cumbersome integration and drift removal procedure associated with the use of inductive loops. We successfully exploited the sensors for determination of vertical plasma displacement on CASTOR. This new diagnostic helped us to shed more light into long term observed discrepancy on CASTOR between vertical plasma displacement as deduced by standard magnetic and by nonmagnetic diagnostics (Langmuir probes, bolometers).

  14. Magnetic measurements using array of integrated Hall sensors on the CASTOR tokamak.

    PubMed

    Duran, Ivan; Hronová, Olena; Stöckel, Jan; Sentkerestiová, Jana; Havlicek, Josef

    2008-10-01

    We have performed the first tests of "integrated" Hall sensors (IHSs) in a tokamak in-vessel environment. IHS combines the sensing element together with the complex electronic circuitry on a single small chip. The on-chip integrated circuits provide stabilization of the supply voltage, output amplification, noise suppression, and elimination of temperature dependencies. Eight IHSs of A1322LUA type produced by Allegro MicroSystems, Inc. were mounted on a stainless steel ring symmetrically encircling the CASTOR plasmas in poloidal direction 10 mm outside the limiter radius. IHSs were oriented such that they measure the horizontal and vertical magnetic fields. We found out that these sensors qualify for in-vessel use of small to middle sized fusion devices where the radiation is not an issue and the temperature below 150 degrees C can be guaranteed. The main advantages over the traditional pickup coils are the smaller size and more straightforward interpretation of output without the need of rather cumbersome integration and drift removal procedure associated with the use of inductive loops. We successfully exploited the sensors for determination of vertical plasma displacement on CASTOR. This new diagnostic helped us to shed more light into long term observed discrepancy on CASTOR between vertical plasma displacement as deduced by standard magnetic and by nonmagnetic diagnostics (Langmuir probes, bolometers). PMID:19044607

  15. Ambient-Temperature Passive Magnetic Bearings for Flywheel Energy Storage Systems

    SciTech Connect

    Bender, D.; Post, R.

    2000-05-26

    Based on prior work at the Lawrence Livermore National Laboratory ambient-temperature passive magnetic bearings are being adapted for use in high-power flywheel energy storage systems developed at the Trinity Flywheel Power company. En route to this goal specialized test stands have been built and computer codes have been written to aid in the development of the component parts of these bearing systems. The Livermore passive magnetic bearing system involves three types of elements, as follows: (1) Axially symmetric levitation elements, energized by permanent magnets., (2) electrodynamic ''stabilizers'' employing axially symmetric arrays of permanent magnet bars (''Halbach arrays'') on the rotating system, interacting with specially wound electrically shorted stator circuits, and, (3) eddy-current-type vibration dampers, employing axially symmetric rotating pole assemblies interacting with stationary metallic discs. The theory of the Livermore passive magnetic bearing concept describes specific quantitative stability criteria. The satisfaction of these criteria will insure that, when rotating above a low critical speed, a bearing system made up of the three elements described above will be dynamically stable. That is, it will not only be stable for small displacements from equilibrium (''Earnshaw-stable''), but will also be stable against whirl-type instabilities of the types that can arise from displacement-dependent drag forces, or from mechanical-hysteritic losses that may occur in the rotor. Our design problem thus becomes one of calculating and/or measuring the relevant stiffnesses and drag coefficients of the various elements and comparing our results with the theory so as to assure that the cited stability criteria are satisfied.

  16. Tunable configurational anisotropy in collective magnetization dynamics of Ni{sub 80}Fe{sub 20} nanodot arrays with varying dot shapes

    SciTech Connect

    Mahato, B. K.; Choudhury, S.; Mandal, R.; Barman, S.; Barman, A.; Otani, Y.

    2015-06-07

    We present broadband ferromagnetic resonance measurements of tunable spin wave anisotropy in arrays of nanodots with different dot shapes. Magnetization dynamics of the circular dot array shows two modes, while square, diamond, and triangular dot arrays show three, three, and four modes, respectively. Various distinct rotational symmetries in the configurational anisotropy of the nanodot arrays are observed with the variation of dot shape. The observed spin wave modes are reproduced by micromagnetic simulations and the calculated mode profiles show different collective modes determined by internal and stray magnetic fields. Effects of dot shapes are observed in combination with the effects of lattice symmetry and the shape of the boundary of the array. The collective behaviour is observed to be weakest in the diamond shaped dots and strongest in circular shaped dots. This is further confirmed by the stray field calculation. The large variation of spin wave mode frequencies and their configurational anisotropies with dot shapes are important for selection of suitable basis structures for future magnonic crystals.

  17. Monolayer CoPt magnetic nanoparticle array using multiple thin film depositions

    NASA Astrophysics Data System (ADS)

    Kim, Jung H.; Kim, Jeon; Oh, Nuri; Kim, Young-Ho; Kim, Chang Kyung; Yoon, Chong Seung; Jin, Sungho

    2007-01-01

    A monolayer of L10 CoPt nanoparticles was prepared on a polyimide film by depositing Co-Pt and annealing the resulting film stack at 650-800C. To obtain well-separated magnetic nanoparticles avoiding substantial coarsening often seen on annealing of thicker films, a multiple deposition of thinner Co-Pt alloy films with intentionally increased Co composition was employed. The multiple depositions relying on heterogeneous nucleation on the preexisting CoPt nanoparticles allowed the average particle size to increase from 4to7nm. The monolayer of 7nm sized CoPt nanoparticles exhibited a coercivity of 9.8kOe with a remanence ratio of 0.72.

  18. Development of a magnetic electrochemical bar code array for point mutation detection in the H5N1 neuraminidase gene.

    PubMed

    Krejcova, Ludmila; Hynek, David; Kopel, Pavel; Rodrigo, Miguel Angel Merlos; Adam, Vojtech; Hubalek, Jaromir; Babula, Petr; Trnkova, Libuse; Kizek, Rene

    2013-07-01

    Since its first official detection in the Guangdong province of China in 1996, the highly pathogenic avian influenza virus of H5N1 subtype (HPAI H5N1) has reportedly been the cause of outbreaks in birds in more than 60 countries, 24 of which were European. The main issue is still to develop effective antiviral drugs. In this case, single point mutation in the neuraminidase gene, which causes resistance to antiviral drug and is, therefore, subjected to many studies including ours, was observed. In this study, we developed magnetic electrochemical bar code array for detection of single point mutations (mismatches in up to four nucleotides) in H5N1 neuraminidase gene. Paramagnetic particles Dynabeads® with covalently bound oligo (dT)₂₅ were used as a tool for isolation of complementary H5N1 chains (H5N1 Zhejin, China and Aichi). For detection of H5N1 chains, oligonucleotide chains of lengths of 12 (+5 adenine) or 28 (+5 adenine) bp labeled with quantum dots (CdS, ZnS and/or PbS) were used. Individual probes hybridized to target molecules specifically with efficiency higher than 60%. The obtained signals identified mutations present in the sequence. Suggested experimental procedure allows obtaining further information from the redox signals of nucleic acids. Moreover, the used biosensor exhibits sequence specificity and low limits of detection of subnanogram quantities of target nucleic acids. PMID:23860384

  19. Development of a Magnetic Electrochemical Bar Code Array for Point Mutation Detection in the H5N1 Neuraminidase Gene

    PubMed Central

    Krejcova, Ludmila; Hynek, David; Kopel, Pavel; Merlos Rodrigo, Miguel Angel; Adam, Vojtech; Hubalek, Jaromir; Babula, Petr; Trnkova, Libuse; Kizek, Rene

    2013-01-01

    Since its first official detection in the Guangdong province of China in 1996, the highly pathogenic avian influenza virus of H5N1 subtype (HPAI H5N1) has reportedly been the cause of outbreaks in birds in more than 60 countries, 24 of which were European. The main issue is still to develop effective antiviral drugs. In this case, single point mutation in the neuraminidase gene, which causes resistance to antiviral drug and is, therefore, subjected to many studies including ours, was observed. In this study, we developed magnetic electrochemical bar code array for detection of single point mutations (mismatches in up to four nucleotides) in H5N1 neuraminidase gene. Paramagnetic particles Dynabeads® with covalently bound oligo (dT)25 were used as a tool for isolation of complementary H5N1 chains (H5N1 Zhejin, China and Aichi). For detection of H5N1 chains, oligonucleotide chains of lengths of 12 (+5 adenine) or 28 (+5 adenine) bp labeled with quantum dots (CdS, ZnS and/or PbS) were used. Individual probes hybridized to target molecules specifically with efficiency higher than 60%. The obtained signals identified mutations present in the sequence. Suggested experimental procedure allows obtaining further information from the redox signals of nucleic acids. Moreover, the used biosensor exhibits sequence specificity and low limits of detection of subnanogram quantities of target nucleic acids. PMID:23860384

  20. Leaves and stems, rotons and solitons, magnets and arrays, one ground state lost, many found, and two fields

    NASA Astrophysics Data System (ADS)

    Nisoli, Cristiano

    A complete physical system typically requires three elements: particle, interaction, and manifold. Condensed matter physics provides a rich framework for generating new effective particles and new interactions such as quasiparticles, Cooper pairs or composite fermions. Rather than generate new effective particles or interactions within familiar flat space, one can also ask how novel geometrical constraints on the underlying manifold can generate new physics, even for old familiar interactions [1, 2]. Perhaps the simplest effective interaction is a featureless long-ranged repulsion, which leads to simple structures in flat space: in two dimensions, a triangular lattice. In contrast, interacting repulsive particles on a cylinder generate a rich degenerate family of helical structures that follow Fibonacci rules first seen in phyllotaxis, the study of plant morphology [3, 4, 5, 6, 7, 8]. After demonstrating phyllotactic patterns in an experimental "magnetic cactus" we show that linear dynamics of phyllotaxis generates rotons and the nonlinear regime supports a large family of dynamically stable topological solitons that can fragment, merge, or interconvert upon collision, with propagation speeds governed by energy conservation and phase matching. These new phenomena should be observable in a wide range of systems, from quantum to classical and from nanometer-scale to macroscopic. In an attempt to mimic the zero point entropy of water and spin ice [9, 10, 11], we have engineered arrays of nanoislands, called "artificial spin ice" such that their simple magnetic interaction can be frustrated by their mutual disposition. While the magnetic cactus was degenerate---although not extensively so---yet could be annealed into its ground state, the artificial spin ice is theoretically non degenerate, yet attempts to anneal it yield a disordered state, described by an athermal manifold of extensive degeneracy. We show how to predict its non trivial thermodynamics with good agreement with experimental data and no fitted parameters, using a principle of maximum likelihood reminiscent of entropy. When a flat graphene sheet is rolled in the cylindrical geometry of a carbon nanotube, a mesoscopic system is born, with macroscopic length, yet atomic scale radius [12, 13, 14]. We will show here how to adapt to it the standard elastic formalism for macroscopic objects so that its atomic complexities can be taken into account, and yet still solved analytically. Disparate experimental and numerical results find explanation in this unifying framework.

  1. Magnetic and electrical properties of PbTiO3/Mn-Zn ferrite multiphase nanotube arrays by electro-deposition

    NASA Astrophysics Data System (ADS)

    Guo, Limin; Wang, Xiaohui; Nan, Cewen; Li, Longtu

    2012-11-01

    Composite nanotube (NT) array layers incorporating PbTiO3 and Mn-Zn ferrite were prepared by electrophoretic deposition and hydrothermal method using TiO2 NT arrays as templates. Crystal structure and micrograph of the hybrid NTs were characterized by x-ray diffraction and field-emission scanning electron microscopy. The samples showed multiphase of tetragonal PbTiO3 and spinel Mn-Zn ferrite structure. Temperature depended magnetic properties of the layers were studied when the applied field paralleled the NT's channel axis. Temperature increasing caused an increase in magnetization by the enhanced shape anisotropy at higher temperatures. Good ferroelectricity and piezoelectricity were well remained in the hybrid NT layers. A maximum displacement of 0.3 nm and d33* of 55 pm V-1 was observed in the layers.

  2. Submillimeter Array Observations of Magnetic Fields in G240.31+0.07: An Hourglass in a Massive Cluster-forming Core

    NASA Astrophysics Data System (ADS)

    Qiu, Keping; Zhang, Qizhou; Menten, Karl M.; Liu, Hauyu B.; Tang, Ya-Wen; Girart, Josep M.

    2014-10-01

    We report the first detection of an hourglass magnetic field aligned with a well-defined outflow rotation system in a high-mass, star-forming region. The observations were performed with the Submillimeter Array toward G240.31+0.07, which harbors a massive, flattened, and fragmenting molecular cloud core and a wide-angle bipolar outflow. The polarized dust emission at 0.88 mm reveals a clear hourglass-shaped magnetic field aligned within 20° of the outflow axis. Maps of high-density tracing spectral lines, e.g., H13CO+ (4-3), show that the core is rotating about its minor axis, which is also aligned with the magnetic field axis. Therefore, both the magnetic field and kinematic properties observed in this region are surprisingly consistent with the theoretical predictions of the classic paradigm of isolated low-mass star formation. The strength of the magnetic field in the plane of sky is estimated to be ~1.1 mG, resulting in a mass-to-magnetic flux ratio of 1.4 times the critical value and a turbulent-to-ordered magnetic energy ratio of 0.4. We also find that the specific angular momentum almost linearly decreases from r ~ 0.6 pc to 0.03 pc scales, which is most likely attributed to magnetic braking.

  3. SUBMILLIMETER ARRAY OBSERVATIONS OF MAGNETIC FIELDS IN G240.31+0.07: AN HOURGLASS IN A MASSIVE CLUSTER-FORMING CORE

    SciTech Connect

    Qiu, Keping; Zhang, Qizhou; Menten, Karl M.; Liu, Hauyu B.; Tang, Ya-Wen; Girart, Josep M.

    2014-10-10

    We report the first detection of an hourglass magnetic field aligned with a well-defined outflow rotation system in a high-mass, star-forming region. The observations were performed with the Submillimeter Array toward G240.31+0.07, which harbors a massive, flattened, and fragmenting molecular cloud core and a wide-angle bipolar outflow. The polarized dust emission at 0.88mm reveals a clear hourglass-shaped magnetic field aligned within 20 of the outflow axis. Maps of high-density tracing spectral lines, e.g., H{sup 13}CO{sup +} (4-3), show that the core is rotating about its minor axis, which is also aligned with the magnetic field axis. Therefore, both the magnetic field and kinematic properties observed in this region are surprisingly consistent with the theoretical predictions of the classic paradigm of isolated low-mass star formation. The strength of the magnetic field in the plane of sky is estimated to be ?1.1 mG, resulting in a mass-to-magnetic flux ratio of 1.4times the critical value and a turbulent-to-ordered magnetic energy ratio of 0.4. We also find that the specific angular momentum almost linearly decreases from r ? 0.6 pc to 0.03pc scales, which is most likely attributed to magnetic braking.

  4. Array of Hall Effect Sensors for Linear Positioning of a Magnet Independently of Its Strength Variation. A Case Study: Monitoring Milk Yield during Milking in Goats

    PubMed Central

    García-Diego, Fernando-Juan; Sánchez-Quinche, Angel; Merello, Paloma; Beltrán, Pedro; Peris, Cristófol

    2013-01-01

    In this study we propose an electronic system for linear positioning of a magnet independent of its modulus, which could vary because of aging, different fabrication process, etc. The system comprises a linear array of 24 Hall Effect sensors of proportional response. The data from all sensors are subject to a pretreatment (normalization) by row (position) making them independent on the temporary variation of its magnetic field strength. We analyze the particular case of the individual flow in milking of goats. The multiple regression analysis allowed us to calibrate the electronic system with a percentage of explanation R2 = 99.96%. In our case, the uncertainty in the linear position of the magnet is 0.51 mm that represents 0.019 L of goat milk. The test in farm compared the results obtained by direct reading of the volume with those obtained by the proposed electronic calibrated system, achieving a percentage of explanation of 99.05%. PMID:23793020

  5. Magnetic resonance tomography using elongated transmitter and in-loop receiver arrays for time-efficient 2-D imaging of subsurface aquifer structures

    NASA Astrophysics Data System (ADS)

    Jiang, C.; Mller-Petke, M.; Lin, J.; Yaramanci, U.

    2015-02-01

    Surface nuclear magnetic resonance (surface-NMR) is a promising technique for exploring shallow subsurface aquifer structures. Surface-NMR can be applied in environments that are characterized as a 1-D layered Earth. The technique utilizes a single loop and is referred to as magnetic resonance sounding. The technique referred to as magnetic resonance tomography (MRT) allows complex 2-D aquifer structures to be explored. Currently, MRT requires multiple loops and a roll along measurement scheme, which causes long survey time. We propose a loop layout using an elongated transmitter and an in-loop receiver arrays (ETRA) to conduct a 2-D survey with just one measurement. We present a comprehensive comparison between the new layout and the common approaches based on sensitivity and resolution analyses and show synthetic and field data. The results show that ETRA generates subsurface images at sufficient resolution with significantly lower survey times than other loop layouts.

  6. Spin-wave bound modes in a circular array of magnetic inclusions embedded into a metallized ferromagnetic thin-film matrix

    NASA Astrophysics Data System (ADS)

    Barabanenkov, Yuri; Osokin, Sergey; Kalyabin, Dmitry; Nikitov, Sergey

    2015-06-01

    A general theory of forward volume magnetostatic spin-wave multiple scattering by a finite two-dimensional ensemble of cylindrical magnetic inclusions in a ferromagnetic film (matrix) metallized from both sides is developed. It is predicted that bound spin-wave modes are excited around these inclusions. The set of self-consistent equations for spin-wave multiple scattering inside the matrix with inclusions is obtained by using an invariant addition theorem for the cylindrical wave functions. This set of equations is solved by an iterative process. We derive simple expressions for eigenmodes (bound modes) in a form of Bloch-like spin waves propagating along the inclusion circular array. The theory is illustrated on practically significant examples: (i) bound-mode excitation by propagating spin waves; (ii) helix components of the spin-wave-scattered field around magnetic inclusions; and (iii) a high-quality spin-wave resonator based on a small number of magnetic inclusions.

  7. ZnO@Co hybrid nanotube arrays growth from electrochemical deposition: structural, optical, photocatalytic and magnetic properties.

    PubMed

    Fan, Li-Yuan; Yu, Shu-Hong

    2009-05-21

    Well-aligned ZnO@Co hybrid nanotube arrays on conductive glass substrates have been obtained by an electrochemical deposition approach. Vertical-aligned ZnO nanotubes with sizes between 300 and 600 nm in diameter and wall thickness of approximately 100 nm have been prepared by selective dissolution from the nanorods. The ZnO@Co heterostructures can be prepared by optimizing the deposition time and controlling the stability of Co2+ ions. Compared to the nanorod arrays, both nanotube arrays and the ZnO@Co heterostructures show enhanced photoluminescent properties. In addition, ZnO and ZnO@Co nanotubes show improved photocatalytic properties compared with the bare ZnO nanorod array, and the hybrid nanotubes exhibit better adsorptive properties than the bare ZnO nanotubes. Furthermore, the ZnO@Co hybrid nanotube arrays show ferromagnetism at room temperature. PMID:19421482

  8. The reliability of the seismo-magnetic method derived from ULF/ELF observations by the South European Geomagnetic Array (SEGMA)

    NASA Astrophysics Data System (ADS)

    Schwingenschuh, Konrad; Prattes, Gustav; Eichelberger, Hans Ulrich; Magnes, Werner; Berghofer, Gerhard; Aydogar, zer; Besser, Bruno P.; Boudjada, Mohammed; Stangl, Gnter; Zhang, Tie Long; Wolbang, Daniel; Vellante, Massimo; Villante, Umberto; Rozhnoi, Alexander; Solovieva, Maria; Nenovski, Petko; Veztergom, Victor; Szendr?i, Judith

    2013-04-01

    In the frame of the South European GeoMagnetic Array (SEGMA) project magnetic field variations are studied in the frequency range from several milli-Hz to several Hz. The fluxgate and induction coil magnetometers are located in Italy, Bulgaria and Hungary. The scientific objectives comprises field-line resonances, space weather phenomena and seismo-magnetic (SM) studies. In our present study on the reliability of the seismo-magnetic method we emphasize on the influence of external non-seismic sources on the quality of seismo-magnetic studies. External magnetic sources include lightning, power lines, railway and traffic as well as geomagnetic variations of magnetospheric origin. We observe anomalies of the ratio of the vertical to horizontal magnetic field component in the ultra/extreme-low-frequency (ULF/ELF) frequency range up to several Hz [2]. These signals can be produced in the lithosphere near a seismic active region and are interpreted as earthquake precursors. In order to differentiate geomagnetic from seismo-magnetic fluctuations, we use mainly observations around midnight because the night time geomagnetic fluctuations are much smaller than during day time. The SEGMA network provides the unique opportunity to use multipoint observations, which are also useful to distinguish local from global phenomena. In order to get undisturbed magnetic field observations, the stations are located outside populated areas [2]. The electrical conductivity of the soil in the vicinity of magnetometers on the terrestrial surface is a further source for interferences. This type of disturbances caused by induced electrical currents can be minimized either by a careful selection of the magnetometer site ans/or by the measurement of the conductivity profile in the vicinity of the instrument site. In the frame of the investigation of the April 6, 2009 L'Aquila earthquake magneto-telluric methods have been used to measure the conductivity profile near the epicenter of the earthquake and thus correct the observed magnetic field fluctuations [1]. A further interference source which can reduce the sensitivity of the seismo-magnetic methods (SM) is the mechanical vibration of the magnetometer sensors. We present a SM reliability number taking into account all above mentioned interference sources. The SM number can be used to improve the sensitivity of the seismo-magnetic method. References [1] G. Prattes, et al.: Ultra Low Frequency (ULF) European multi station magnetic field analysis before and during the 2009 earthquake at L'Aquila regarding regional geotechnical information, Nat. Hazards Earth Syst. Sci., 11, 1959-1968, 2011 [2] K. Schwingenschuh, et al.: 'Clean' observations of magnetic field fluctuations on planetary surfaces, Aerospace EMC, 2012 Proceedings ESA Workshop on 21-23 May 2012, 4 p., 2012.

  9. Wireless charing pillow for a fully implantable hearing aid: Design of a circular array coil based on finite element analysis for reducing magnetic weak zones.

    PubMed

    Lim, Hyung-Gyu; Kim, Jong Hoon; Shin, Dong Ho; Woo, Seong Tak; Seong, Ki Woong; Lee, Jyung Hyun; Kim, Myoung Nam; Wei, Qun; Cho, Jin-Ho

    2015-01-01

    Many types of fully implantable hearing aids have been developed. Most of these devices are implanted behind the ear. To maintain the implanted device for a long period of time, a rechargeable battery and wireless power transmission are used. Because inductive coupling is the most renowned method for wireless power transmission, many types of fully implantable hearing aids are transcutaneously powered using inductively coupled coils. Some patients with an implantable hearing aid require a method for conveniently charging their hearing aid while they are resting or sleeping. To address this need, a wireless charging pillow has been developed that employs a circular array coil as one of its primary parts. In this device, all primary coils are simultaneously driven to maintain an effective charging area regardless of head motion. In this case, however, there may be a magnetic weak zone that cannot be charged at the specific secondary coil's location on the array coil. In this study, assuming that a maximum charging distance is 4 cm, a circular array coil-serving as a primary part of the charging pillow-was designed using finite element analysis. Based on experimental results, the proposed device can charge an implantable hearing aid without a magnetic weak zone within 4 cm of the perpendicular distance between the primary and secondary coils. PMID:26405942

  10. Development of a miniature permanent magnetic circuit for nuclear magnetic resonance chip

    NASA Astrophysics Data System (ADS)

    Lu, Rongsheng; Yi, Hong; Wu, Weiping; Ni, Zhonghua

    2013-07-01

    The existing researches of miniature magnetic circuits focus on the single-sided permanent magnetic circuits and the Halbach permanent magnetic circuits. In the single-sided permanent magnetic circuits, the magnetic flux density is always very low in the work region. In the Halbach permanent magnetic circuits, there are always great difficulties in the manufacturing and assembly process. The static magnetic flux density required for nuclear magnetic resonance(NMR) chip is analyzed based on the signal noise ratio(SNR) calculation model, and then a miniature C-shaped permanent magnetic circuit is designed as the required magnetic flux density. Based on Kirchhoff's law and magnetic flux refraction principle, the concept of a single shimming ring is proposed to improve the performance of the designed magnetic circuit. Using the finite element method, a comparative calculation is conducted. The calculation results demonstrate that the magnetic circuit improved with a single shimming has higher magnetic flux density and better magnetic field homogeneity than the one improved with no shimming ring or double shimming rings. The proposed magnetic circuit is manufactured and its experimental test platform is also built. The magnetic flux density measured in the work region is 0.7 T, which is well coincided with the theoretical design. The spatial variation of the magnetic field is within the range of the instrument error. At last, the temperature dependence of the magnetic flux density produced by the proposed magnetic circuit is investigated through both theoretical analysis and experimental study, and a linear functional model is obtained. The proposed research is crucial for solving the problem in the application of NMR-chip under different environmental temperatures.

  11. Tuning the magnetic anisotropy of Co-Ni nanowires: comparison between single nanowires and nanowire arrays in hard-anodic aluminum oxide membranes.

    PubMed

    Vega, V; Bhnert, T; Martens, S; Waleczek, M; Montero-Moreno, J M; Grlitz, D; Prida, V M; Nielsch, K

    2012-11-23

    Co(x)Ni(1-x) alloy nanowires with varying Co content (0 ? x ? 0.95), having a diameter of 130 nm and length of around 20 ?m, are synthesized by template-assisted electrodeposition into the nanopores of SiO(2) conformal coated hard-anodic aluminum oxide membranes. The magneto-structural properties of both single isolated nanowires and hexagonally ordered nanowire arrays of Co-Ni alloys are systematically studied by means of magneto-optical Kerr effect magnetometry and vibrating sample magnetometry, respectively, allowing us to compare different alloy compositions and to distinguish between the magnetostatic and magnetocrystalline contributions to the effective magnetic anisotropy for each system. The excellent tunable soft magnetic properties and magnetic bistability exhibited by low Co content Co-Ni nanowires indicate that they might become the material of choice for the development of nanostructured magnetic systems and devices as an alternative to Fe-Ni alloy based systems, being chemically more robust. Furthermore, Co contents higher than 51 at.% allow us to modify the magnetic behavior of Co-rich nanowires by developing well controlled magnetocrystalline anisotropy, which is desirable for data storage applications. PMID:23095457

  12. Determination of radial location of rotating magnetic islands by use of poloidal soft x-ray detector arrays in the STOR-M tokamak

    SciTech Connect

    Dreval, M.; Xiao, C.; Elgriw, S.; Trembach, D.; Hirose, A.; Wolfe, S.

    2011-05-15

    A technique is presented for determining the radial location of the rotating magnetic islands in the STOR-M tokamak by use of soft x-ray (SXR) detector arrays. The location is determined by examining the difference in the integrated SXR emission intensities through two adjacent lines of sight. A model for calculating dependence of the line integrated SXR emission intensity on the radius, the mode numbers and the magnetic island geometry, has been developed. The SXR difference signal shows phase inversion when the impact parameter of the line of sight sweeps across the magnetic islands. Experimentally, the difference SXR signals significantly reduce noise and suppress the influence of background plasma fluctuations through common mode rejection when a dominant mode exists in the STOR-M tokamak. The radial locations of the m= 2 magnetic islands have been determined under several experimental conditions in the STOR-M discharges. With the decrease in the tokamak discharge current and thus the increase of the safety factor at the edge, the radial location of the m= 2 magnetic islands has been found to move radially inward.

  13. Nonuniform radiation damage in permanent magnet quadrupoles

    NASA Astrophysics Data System (ADS)

    Danly, C. R.; Merrill, F. E.; Barlow, D.; Mariam, F. G.

    2014-08-01

    We present data that indicate nonuniform magnetization loss due to radiation damage in neodymium-iron-boron Halbach-style permanent magnet quadrupoles. The proton radiography (pRad) facility at Los Alamos uses permanent-magnet quadrupoles for magnifying lenses, and a system recently commissioned at GSI-Darmsdadt uses permanent magnets for its primary lenses. Large fluences of spallation neutrons can be produced in close proximity to these magnets when the proton beam is, intentionally or unintentionally, directed into the tungsten beam collimators; imaging experiments at LANL's pRad have shown image degradation with these magnetic lenses at proton beam doses lower than those expected to cause damage through radiation-induced reduction of the quadrupole strength alone. We have observed preferential degradation in portions of the permanent magnet quadrupole where the field intensity is highest, resulting in increased high-order multipole components.

  14. Nonuniform radiation damage in permanent magnet quadrupoles.

    PubMed

    Danly, C R; Merrill, F E; Barlow, D; Mariam, F G

    2014-08-01

    We present data that indicate nonuniform magnetization loss due to radiation damage in neodymium-iron-boron Halbach-style permanent magnet quadrupoles. The proton radiography (pRad) facility at Los Alamos uses permanent-magnet quadrupoles for magnifying lenses, and a system recently commissioned at GSI-Darmsdadt uses permanent magnets for its primary lenses. Large fluences of spallation neutrons can be produced in close proximity to these magnets when the proton beam is, intentionally or unintentionally, directed into the tungsten beam collimators; imaging experiments at LANL's pRad have shown image degradation with these magnetic lenses at proton beam doses lower than those expected to cause damage through radiation-induced reduction of the quadrupole strength alone. We have observed preferential degradation in portions of the permanent magnet quadrupole where the field intensity is highest, resulting in increased high-order multipole components. PMID:25173260

  15. Nonuniform radiation damage in permanent magnet quadrupoles

    SciTech Connect

    Danly, C. R.; Merrill, F. E.; Barlow, D.; Mariam, F. G.

    2014-08-15

    We present data that indicate nonuniform magnetization loss due to radiation damage in neodymium-iron-boron Halbach-style permanent magnet quadrupoles. The proton radiography (pRad) facility at Los Alamos uses permanent-magnet quadrupoles for magnifying lenses, and a system recently commissioned at GSI-Darmsdadt uses permanent magnets for its primary lenses. Large fluences of spallation neutrons can be produced in close proximity to these magnets when the proton beam is, intentionally or unintentionally, directed into the tungsten beam collimators; imaging experiments at LANL’s pRad have shown image degradation with these magnetic lenses at proton beam doses lower than those expected to cause damage through radiation-induced reduction of the quadrupole strength alone. We have observed preferential degradation in portions of the permanent magnet quadrupole where the field intensity is highest, resulting in increased high-order multipole components.

  16. Magnetic field induced controllable self-assembly of maghemite nanocrystals: From 3D arrays to 1D nanochains

    NASA Astrophysics Data System (ADS)

    Tang, Yan; Chen, Qianwang; Chen, Rongsheng

    2015-08-01

    A hydrothermal process has been used to synthesize walnut-like maghemite superstructures which can be further self-assembled in a controllable manner into ordered three-dimensional (3D) architectures and one-dimensional (1D) nanochains in the presence of different external magnetic field. The assembly behavior of the maghemite nanoparticles isclosely related to the van der Waals interactions and external-field-induced magnetic dipole interactions. The magnetic properties of these nanostructures are also investigated.

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

    NASA Astrophysics Data System (ADS)

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

    2015-11-01

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

  18. Electrodeposited Co{sub 93.2}P{sub 6.8} nanowire arrays with core-shell microstructure and perpendicular magnetic anisotropy

    SciTech Connect

    Nasirpouri, F.; Peighambari, S. M.; Samardak, A. S. Ognev, A. V.; Sukovatitsina, E. V.; Modin, E. B.; Chebotkevich, L. A.; Komogortsev, S. V.; Bending, S. J.

    2015-05-07

    We demonstrate the formation of an unusual core-shell microstructure in Co{sub 93.2}P{sub 6.8} nanowires electrodeposited by alternating current (ac) in an alumina template. By means of transmission electron microscopy, it is shown that the coaxial-like nanowires contain amorphous and crystalline phases. Analysis of the magnetization data for Co-P alloy nanowires indicates that a ferromagnetic core is surrounded by a weakly ferromagnetic or non-magnetic phase, depending on the phosphor content. The nanowire arrays exhibit an easy axis of magnetization parallel to the wire axis. For this peculiar composition and structure, the coercivity values are 2380 ± 50 and 1260 ± 35 Oe, parallel and perpendicular to the plane directions of magnetization, respectively. This effect is attributed to the core-shell structure making the properties and applications of these nanowires similar to pure cobalt nanowires with an improved perpendicular anisotropy.

  19. Quantitative Study of Liver Magnetic Resonance Spectroscopy Quality at 3T Using Body and Phased Array Coils with Physical Analysis and Clinical Evaluation

    PubMed Central

    Xu, Li; Gu, Shiyong; Feng, Qianjin; Liang, Changhong; Xin, Sherman Xuegang

    2015-01-01

    This study aims to investigate the quality difference of short echo time (TE) breathhold 1H magnetic resonance spectroscopy (MRS) of the liver at 3.0T using the body and phased array coils, respectively. In total, 20 pairs of single-voxel proton spectra of the liver were acquired at 3.0T using the phased array and body coils as receivers. Consecutive stacks of breathhold spectra were acquired using the point resolved spectroscopy (PRESS) technique at a short TE of 30 ms and a repetition time (TR) of 1500 ms. The first spectroscopy sequence was copied for the second acquisition to ensure identical voxel positioning. The MRS prescan adjustments of shimming and water suppression, signal-to noise ratio (SNR), and major liver quantitative information were compared between paired spectra. Theoretical calculation of the SNR and homogeneity of the region of interest (ROI, 2 cm2 cm2 cm) using different coils loaded with 3D liver electromagnetic model of real human body was implemented in the theoretical analysis. The theoretical analysis showed that, inside the ROI, the SNR of the phase array coil was 2.8387 times larger than that of body coil and the homogeneity of the phase array coil and body coil was 80.10% and 93.86%, respectively. The experimental results showed excellent correlations between the paired data (all r > 0.86). Compared with the body coil group, the phased array group had slightly worse shimming effect and better SNR (all P values < .01). The discrepancy of the line width because of the different coils was approximately 0.8 Hz (0.00625 ppm). No significant differences of the major liver quantitative information of Cho/Lip2 height, Cho/Lip2 area, and lipid content were observed (all P values >0.05). The theoretical analysis and clinical experiment showed that the phased array coil was superior to the body coil with respect to 3.0T breathhold hepatic proton MRS. PMID:25881016

  20. OH MASER SOURCES IN W49N: PROBING MAGNETIC FIELD AND DIFFERENTIAL ANISOTROPIC SCATTERING WITH ZEEMAN PAIRS USING THE VERY LONG BASELINE ARRAY

    SciTech Connect

    Deshpande, Avinash A.; Goss, W. M.; Mendoza-Torres, J. E. E-mail: mgoss@aoc.nrao.edu

    2013-09-20

    Our analysis of a Very Long Baseline Array 12 hr synthesis observation of the OH masers in the well-known star-forming region W49N has yielded valuable data that enable us to probe distributions of magnetic fields in both the maser columns and the intervening interstellar medium (ISM). The data, consisting of detailed high angular resolution images (with beam width ?20 mas) of several dozen OH maser sources, or spots, at 1612, 1665, and 1667 MHz, reveal anisotropic scatter broadening with typical sizes of a few tens of milliarcseconds and axial ratios between 1.5 and 3. Such anisotropies have been reported previously by Desai et al. and have been interpreted as being induced by the local magnetic field parallel to the Galactic plane. However, we find (1) apparent angular sizes of, on average, a factor of about 2.5 less than those reported by Desai et al., indicating significantly less scattering than inferred previously, and (2) a significant deviation in the average orientation of the scatter-broadened images (by ?10) from that implied by the magnetic field in the Galactic plane. More intriguingly, for a few Zeeman pairs in our set, significant differences (up to 6?) are apparent in the scatter-broadened images for the two hands of circular polarization, even when the apparent velocity separation is less than 0.1 km s{sup 1}. This may possibly be the first example of a Faraday rotation contribution to the diffractive effects in the ISM. Using the Zeeman pairs, we also study the distribution of the magnetic field in the W49N complex, finding no significant trend in the spatial structure function. In this paper, we present the details of our observations and analysis leading to these findings, discuss implications of our results for the intervening anisotropic magneto-ionic medium, and suggest possible implications for the structure of magnetic fields within this star-forming region.

  1. Use of a SQUID array to detect T-cells with magnetic nanoparticles in determining transplant rejection

    NASA Astrophysics Data System (ADS)

    Flynn, Edward R.; Bryant, H. C.; Bergemann, Christian; Larson, Richard S.; Lovato, Debbie; Sergatskov, Dmitri A.

    2007-04-01

    Acute rejection in organ transplant is signaled by the proliferation of T-cells that target and kill the donor cells requiring painful biopsies to detect rejection onset. An alternative non-invasive technique is proposed using a multi-channel superconducting quantum interference device (SQUID) magnetometer to detect T-cell lymphocytes in the transplanted organ labeled with magnetic nanoparticles conjugated to antibodies specifically attached to lymphocytic ligand receptors. After a magnetic field pulse, the T-cells produce a decaying magnetic signal with a characteristic time of the order of a second. The extreme sensitivity of this technique, 10 5 cells, can provide early warning of impending transplant rejection and monitor immune-suppressive chemotherapy.

  2. Structural and magnetic characterization of as-prepared and annealed FeCoCu nanowire arrays in ordered anodic aluminum oxide templates

    SciTech Connect

    Rodrguez-Gonzlez, B.; Bran, C.; Warnatz, T.; Vazquez, M.; Rivas, J.

    2014-04-07

    Herein, we report on the preparation, structure, and magnetic characterization of FeCoCu nanowire arrays grown by DC electrodeposition inside self-assembled ordered nanopores of anodic aluminum oxide templates. A systematic study of their structure has been performed both in as-prepared samples and after annealing in the temperature range up to 800?C, although particular attention has been paid to annealing at 700?C after which maximum magnetic hardening is achieved. The obtained nanowires have a diameter of 40?nm and their Fe{sub 0.28}Co{sub 0.67}Cu{sub 0.05} composition was confirmed by energy dispersive X-ray spectroscopy (EDS). Focused ion-beam lamellas of two samples (as-prepared and annealed at 700?C) were prepared for their imaging in the high-resolution transmission electron microscopy (HRTEM) perpendicularly to the electron beam, where the obtained EDS compositional mappings show a homogeneous distribution of the elements. X-ray diffraction analysis, and selected area electron diffraction (SAED) patterns confirm that nanowires exhibit a bcc cubic structure (space group Im-3m). In addition, bright-dark field images show that the nanowires have a polycrystalline structure that remains essentially the same after annealing, but some modifications were observed: (i) an overall increase and sharpening of recrystallized grains, and (ii) an apparent shrinkage of the nanowires diameter. Obtained SAED patterns also show strong textured components with determined <111> and <112> crystalline directions parallel to the wires growth direction. The presence of both directions was also confirmed in the HRTEM images doing Fourier transform analyses. Magnetic measurements show strong magnetic anisotropy with magnetization easy axis parallel to the nanowires in as-prepared and annealed samples. The magnetic properties are tuned by suitable thermal treatments so that, maximum enhanced coercivity (?2.7 kOe) and normalized remanence (?0.91 Ms) values are achieved after annealing at temperature of 700?C. The contribution of the changes in the crystalline structure, induced by the heat treatment, to the magnetic hardening of the FeCoCu nanowires is discussed.

  3. Structural and magnetic characterization of as-prepared and annealed FeCoCu nanowire arrays in ordered anodic aluminum oxide templates

    NASA Astrophysics Data System (ADS)

    Rodrguez-Gonzlez, B.; Bran, C.; Warnatz, T.; Rivas, J.; Vazquez, M.

    2014-04-01

    Herein, we report on the preparation, structure, and magnetic characterization of FeCoCu nanowire arrays grown by DC electrodeposition inside self-assembled ordered nanopores of anodic aluminum oxide templates. A systematic study of their structure has been performed both in as-prepared samples and after annealing in the temperature range up to 800 C, although particular attention has been paid to annealing at 700 C after which maximum magnetic hardening is achieved. The obtained nanowires have a diameter of 40 nm and their Fe0.28Co0.67Cu0.05 composition was confirmed by energy dispersive X-ray spectroscopy (EDS). Focused ion-beam lamellas of two samples (as-prepared and annealed at 700 C) were prepared for their imaging in the high-resolution transmission electron microscopy (HRTEM) perpendicularly to the electron beam, where the obtained EDS compositional mappings show a homogeneous distribution of the elements. X-ray diffraction analysis, and selected area electron diffraction (SAED) patterns confirm that nanowires exhibit a bcc cubic structure (space group Im-3m). In addition, bright-dark field images show that the nanowires have a polycrystalline structure that remains essentially the same after annealing, but some modifications were observed: (i) an overall increase and sharpening of recrystallized grains, and (ii) an apparent shrinkage of the nanowires diameter. Obtained SAED patterns also show strong textured components with determined ?111? and ?112? crystalline directions parallel to the wires growth direction. The presence of both directions was also confirmed in the HRTEM images doing Fourier transform analyses. Magnetic measurements show strong magnetic anisotropy with magnetization easy axis parallel to the nanowires in as-prepared and annealed samples. The magnetic properties are tuned by suitable thermal treatments so that, maximum enhanced coercivity (2.7 kOe) and normalized remanence (0.91 Ms) values are achieved after annealing at temperature of 700 C. The contribution of the changes in the crystalline structure, induced by the heat treatment, to the magnetic hardening of the FeCoCu nanowires is discussed.

  4. Syntheses and structure characterizations of multi- dimensional cyanide-bridged lanthanide-transition metal arrays: Studies on their magnetic properties

    NASA Astrophysics Data System (ADS)

    Du, Bin

    2000-11-01

    Novel cyanide bridged lanthanide-transition metal arrays were prepared. Two-dimensional [K(DMF)7Ln[M(CN)4]2] ∞ (Ln = Eu, Yb; M = Ni, Pt) are made of puckered sheets and interstitial K2[M(CN)4]. Three-dimensional [(NH4)(DMF) 4Yb[Pt(CN)4]2]∞ consists of parallel columns bundled through hydrogen bonds and is the first example in which Ln(III) is coordinated to four [M(CN)4]2- groups. Monohydrate complexes form either a zigzag chain or ``stairway-like'' structure. The latter resembles previously reported ``diamond-like'' structure, but with its trans-bridging [Pt(CN)4] 2- perpendicular to the ``diamonds''. Oligomeric (H 2O)n(DMF)(12-n)Ln2[M(CN) 4]3 is formed if there is multiple ligating water. [(H2O)2(DMF)8Ln2[M(CN)4] 3]∞ (Ln = Dy, Yb) were obtained from solid state H 2O-DMF ligand exchange reactions, with the retention of basic structures of parent compounds. Structural isomers were obtained for one-dimensional arrays containing [Ni(CN)4]2-. An improved synthetic route for these complexes reduces reaction time from 2 weeks to 30 minutes. Type B isomers are the thermodynamically stable ones whereas Type A isomers are the kinetically favored ones. Ln(III) does not affect the formation of structural isomers. Assembly mechanisms were proposed for all array complexes based on two complex ion-pairs [(DMF)6Ln[M(CN)4] 2]- and [(DMF)7Ln[M(CN)4

  5. Fabrication and magnetic properties of La-X (X = Co, Ni, and Fe) nanotube arrays prepared by electrodeposition methods

    NASA Astrophysics Data System (ADS)

    Chen, J. Y.; Shi, D. W.; Ahmad, N.; Liu, D. P.; Zhou, W. P.; Han, X. F.

    2013-08-01

    Well-ordered La-X (X = Co, Ni and Fe) nanotubes, with the average diameter of 200 nm, wall thicknesses of 40 nm, have been fabricated into anodized aluminum oxide template by potentiostatic electrodeposition method. Various composition of La-X nanotubes were obtained by tuning the applied deposition potential. Magnetization measurements reveal that doped La could enhance the coercivity (Hc) of La-X nanotubes and their easy axis is perpendicular to the nanotube axis. There is a transition from the curling to transverse mode with increase of angle. Temperature dependent magnetization indicates the existence of superparamagnetic nanoparticles and that the surface effect results in the increase of saturation magnetization (Ms) at low temperature. Abnormal behavior of temperature dependent Hc may result from thermal excitation, magnetoelastic anisotropy, as well as oxide layer of nanotube inner surface induced coupling. These one-dimensional rare-earth transition metal nanostructures could have potential applications in novel spintronics device, ultra-small magnetic media, drug delivery, or other nanodevice.

  6. Magnetic nanohole superlattices

    DOEpatents

    Liu, Feng

    2013-05-14

    A magnetic material is disclosed including a two-dimensional array of carbon atoms and a two-dimensional array of nanoholes patterned in the two-dimensional array of carbon atoms. The magnetic material has long-range magnetic ordering at a temperature below a critical temperature Tc.

  7. Influence of Y-doped induced defects on the optical and magnetic properties of ZnO nanorod arrays prepared by low-temperature hydrothermal process

    PubMed Central

    2012-01-01

    One-dimensional pure zinc oxide (ZnO) and Y-doped ZnO nanorod arrays have been successfully fabricated on the silicon substrate for comparison by a simple hydrothermal process at the low temperature of 90C. The Y-doped nanorods exhibit the same c-axis-oriented wurtzite hexagonal structure as pure ZnO nanorods. Based on the results of photoluminescence, an enhancement of defect-induced green-yellow visible emission is observed for the Y-doped ZnO nanorods. The decrease of E2(H) mode intensity and increase of E1(LO) mode intensity examined by the Raman spectrum also indicate the increase of defects for the Y-doped ZnO nanorods. As compared to pure ZnO nanorods, Y-doped ZnO nanorods show a remarked increase of saturation magnetization. The combination of visible photoluminescence and ferromagnetism measurement results indicates the increase of oxygen defects due to the Y doping which plays a crucial role in the optical and magnetic performances of the ZnO nanorods. PMID:22768847

  8. Magnetic Forces Simulation of Bulk HTS over Permanent Magnetic Railway with Numerical Method

    NASA Astrophysics Data System (ADS)

    Lu, Yiyun; Zhuang, Shujun

    2012-10-01

    Magnetic levitation forces of bulk high temperature superconductor (HTS) above two types permanent magnet railway (PMR) is simulated using finite element method (FEM). The models are formulated by H-formulation and resolving codes is developed using Finite Element Program Generator (FEPG). The E- J power law is used to describe the electrical field vs. current density nonlinear characteristic of HTS. The applied magnetic fields induced by the PMR are calculated by the standard analysis method with the equivalent surface current model. By the method, the calculation formulation of magnetic fields generated by Halbach PMR and symmetrical PMR is derived respectively. The simulation results show that the finite element dynamic mesh rebuilding problem of HTS magnetic levitation transportation system comprised of bulk HTS and PMR can be easily avoided by the methods.

  9. Flow-orthogonal bead oscillation in a microfluidic chip with a magnetic anisotropic flux-guide array.

    PubMed

    van Pelt, Stijn; Derks, Roy; Matteucci, Marco; Hansen, Mikkel Fougt; Dietzel, Andreas

    2011-04-01

    A new concept for the manipulation of superparamagnetic beads inside a microfluidic chip is presented in this paper. The concept allows for bead actuation orthogonal to the flow direction inside a microchannel. Basic manipulation functionalities were studied by means of finite element simulations and results were oval-shaped steady state oscillations with bead velocities up to 500?m/s. The width of the trajectory could be controlled by prescribing external field rotation. Successful verification experiments were performed on a prototype chip fabricated with excimer laser ablation in polycarbonate and electroforming of nickel flux-guides. Bead velocities up to 450?m/s were measured in a 75?m wide channel. By prescribing the currents in the external quadrupole magnet, the shape of the bead trajectory could be controlled. PMID:21165700

  10. An improved permanent magnet quadrupole design with larger good field region for high intensity proton linacs

    NASA Astrophysics Data System (ADS)

    Mathew, Jose V.; Rao, S. V. L. S.; Krishnagopal, S.; Singh, P.

    2013-11-01

    The Low Energy High Intensity Proton Accelerator (LEHIPA), being developed at the Bhabha Atomic Research Centre (BARC) will produce a 20 MeV, 30 mA, continuous wave (CW) proton beam. At these low velocities, space-charge forces dominate, and could lead to larger beam sizes and beam halos. Hence in the design of the focusing lattice of the LEHIPA drift tube linac (DTL) using permanent magnet quadrupoles (PMQs), a larger good field region is preferred. Here we study, using the two dimensional (2D) and three dimensional (3D) simulation codes PANDIRA and RADIA, four different types of cylindrical PMQ designs: 16-segment trapezoidal Halbach configuration, bullet-nosed geometry and 8- and 16-segment rectangular geometries. The trapezoidal Halbach geometry is used in a variety of accelerators since it provides very high field gradients in small bores, while the bullet-nosed geometry, which is a combination of the trapezoidal and rectangular designs, is used in some DTLs. This study shows that a larger good field region is possible in the 16-segment rectangular design as compared to the Halbach and bullet-nosed designs, making it more attractive for high-intensity proton linacs. An improvement in good-field region by 16% over the Halbach design is obtained in the optimized 16-segment rectangular design, although the field gradient is lower by 20%. Tolerance studies show that the rectangular segment PMQ design is substantially less sensitive to the easy axis orientation errors and hence will be a better choice for DTLs.

  11. Nanocylinder arrays

    DOEpatents

    Tuominen, Mark (Shutesbury, MA); Schotter, Joerg (Bielefeld, DE); Thurn-Albrecht, Thomas (Freiburg, DE); Russell, Thomas P. (Amherst, MA)

    2009-08-11

    Pathways to rapid and reliable fabrication of nanocylinder arrays are provided. Simple methods are described for the production of well-ordered arrays of nanopores, nanowires, and other materials. This is accomplished by orienting copolymer films and removing a component from the film to produce nanopores, that in turn, can be filled with materials to produce the arrays. The resulting arrays can be used to produce nanoscale media, devices, and systems.

  12. Nanocylinder arrays

    DOEpatents

    Tuominen, Mark; Schotter, Joerg; Thurn-Albrecht, Thomas; Russell, Thomas P.

    2007-03-13

    Pathways to rapid and reliable fabrication of nanocylinder arrays are provided. Simple methods are described for the production of well-ordered arrays of nanopores, nanowires, and other materials. This is accomplished by orienting copolymer films and removing a component from the film to produce nanopores, that in turn, can be filled with materials to produce the arrays. The resulting arrays can be used to produce nanoscale media, devices, and systems.

  13. Method and apparatus for control of a magnetic structure

    DOEpatents

    Challenger, Michael P. (Bothell, WA); Valla, Arthur S. (Bothell, WA)

    1996-06-18

    A method and apparatus for independently adjusting the spacing between opposing magnet arrays in charged particle based light sources. Adjustment mechanisms between each of the magnet arrays and the supporting structure allow the gap between the two magnet arrays to be independently adjusted. In addition, spherical bearings in the linkages to the magnet arrays permit the transverse angular orientation of the magnet arrays to also be adjusted. The opposing magnet arrays can be supported above the ground by the structural support.

  14. Interference mode-locking of 2D magnetized colloids driven by dc and ac forces in periodic pinning arrays

    NASA Astrophysics Data System (ADS)

    Song, K. N.; Wang, H. L.; Ren, J.; Cao, Y. G.

    2015-01-01

    Using the Langevin simulation, we investigate the interference mode-locking of two-dimensional (2D) magnetized colloids on a substrate with periodic pinning centers. The colloidal particles are prepared initially in a 2D crystalline state and then driven simultaneously by direct-current (dc) and alternating-current (ac) forces. In the presence of a superimposed ac force, we find pronounced mode-locking steps in the characteristics of the averaged velocity versus dc force within a certain range of amplitude and frequency of the ac force. The mode-locking steps are attributed to an interference effect between the ac force and the modulation generated by the coherent motion of colloidal particles in a weak pinning potential. The step width ?fdc is found to oscillate in a Bessel function-like form with the amplitude of the ac force, in good agreement with previous results of vortex lattices. But, we find that ?fdc changes in an inverted parabola form with the frequency of the ac force and the substrate pinning strength as well as the interaction strength between colloidal particles. The averaged velocity at the step vstep is shown to increase linearly with the frequency of the ac force and the interaction strength between colloidal particles. The obtained results are helpful for fractionation of mesoscopic particles.

  15. Hybrid photomultiplier tube and photodiode parallel detection array for wideband optical spectroscopy of the breast guided by magnetic resonance imaging

    PubMed Central

    Mastanduno, Michael A.; Jiang, Shudong; Pogue, Brian W.; Paulsen, Keith D.

    2013-01-01

    Abstract. A new optical parallel detection system of hybrid frequency and continuous-wave domains was developed to improve the data quality and accuracy in recovery of all breast optical properties. This new system was deployed in a previously existing system for magnetic resonance imaging (MRI)-guided spectroscopy, and allows incorporation of additional near-infrared wavelengths beyond 850 nm, with interlaced channels of photomultiplier tubes (PMTs) and silicon photodiodes (PDs). The acquisition time for obtaining frequency-domain data at six wavelengths (660, 735, 785, 808, 826, and 849 nm) and continuous-wave data at three wavelengths (903, 912, and 948 nm) is 12 min. The dynamic ranges of the detected signal are 105 and 106 for PMT and PD detectors, respectively. Compared to the previous detection system, the SNR ratio of frequency-domain detection was improved by nearly 103 through the addition of an RF amplifier and the utilization of programmable gain. The current system is being utilized in a clinical trial imaging suspected breast cancer tumors as detected by contrast MRI scans. PMID:23979460

  16. Hybrid photomultiplier tube and photodiode parallel detection array for wideband optical spectroscopy of the breast guided by magnetic resonance imaging.

    PubMed

    El-Ghussein, Fadi; Mastanduno, Michael A; Jiang, Shudong; Pogue, Brian W; Paulsen, Keith D

    2014-01-01

    A new optical parallel detection system of hybrid frequency and continuous-wave domains was developed to improve the data quality and accuracy in recovery of all breast optical properties. This new system was deployed in a previously existing system for magnetic resonance imaging (MRI)-guided spectroscopy, and allows incorporation of additional near-infrared wavelengths beyond 850 nm, with interlaced channels of photomultiplier tubes (PMTs) and silicon photodiodes (PDs). The acquisition time for obtaining frequency-domain data at six wavelengths (660, 735, 785, 808, 826, and 849 nm) and continuous-wave data at three wavelengths (903, 912, and 948 nm) is 12 min. The dynamic ranges of the detected signal are 105 and 106 for PMT and PD detectors, respectively. Compared to the previous detection system, the SNR ratio of frequency-domain detection was improved by nearly 103 through the addition of an RF amplifier and the utilization of programmable gain. The current system is being utilized in a clinical trial imaging suspected breast cancer tumors as detected by contrast MRI scans. PMID:23979460

  17. Hybrid photomultiplier tube and photodiode parallel detection array for wideband optical spectroscopy of the breast guided by magnetic resonance imaging

    NASA Astrophysics Data System (ADS)

    El-Ghussein, Fadi; Mastanduno, Michael A.; Jiang, Shudong; Pogue, Brian W.; Paulsen, Keith D.

    2014-01-01

    A new optical parallel detection system of hybrid frequency and continuous-wave domains was developed to improve the data quality and accuracy in recovery of all breast optical properties. This new system was deployed in a previously existing system for magnetic resonance imaging (MRI)-guided spectroscopy, and allows incorporation of additional near-infrared wavelengths beyond 850 nm, with interlaced channels of photomultiplier tubes (PMTs) and silicon photodiodes (PDs). The acquisition time for obtaining frequency-domain data at six wavelengths (660, 735, 785, 808, 826, and 849 nm) and continuous-wave data at three wavelengths (903, 912, and 948 nm) is 12 min. The dynamic ranges of the detected signal are 105 and 106 for PMT and PD detectors, respectively. Compared to the previous detection system, the SNR ratio of frequency-domain detection was improved by nearly 103 through the addition of an RF amplifier and the utilization of programmable gain. The current system is being utilized in a clinical trial imaging suspected breast cancer tumors as detected by contrast MRI scans.

  18. Magnetic and dielectric properties of one-dimensional array of S = 1/2 linear trimer system Na2Cu3Ge4O12

    NASA Astrophysics Data System (ADS)

    Yasui, Yukio; Kawamura, Yuji; Kobayashi, Yoshiaki; Sato, Masatoshi

    2014-05-01

    Magnetic susceptibility χ, specific heat C, capacitance Cp, and 23Na-NMR measurements have been carried out on polycrystalline samples of quantum spin linear trimer system Na2Cu3Ge4O12, which has the one-dimensional array of Cu3O8 trimers formed of edge-sharing three CuO4 square planes. The exchange interactions between the Cu2+ (S = 1/2) spins have been determined by analyzing χ-T and C-T curves. By employing the isolated S = 1/2 Heisenberg trimer model above 70 K, the nearest-neighbor exchange couplings J1 and the second-neighbor one J2 in trimer have been evaluated to J1/kB = 30 ± 20 K (antiferromagnetic) and J2/kB = 340 ± 20 K. At low temperature region, two spins of the edge in the Cu3O8 trimers form a nonmagnetic singlet by strong antiferromagnetic interaction J2, and the spin left in the center of the Cu3O8 trimer forms one-dimensional chains by the exchange interaction J3 between the trimers. By employing the S = 1/2 uniform Heisenberg chain model below 70 K, we have evaluated to J3/kB = 18 ± 1 K. The mechanism of multiferroic behavior at Tc = 2 K is discussed.

  19. Striped tape arrays

    NASA Technical Reports Server (NTRS)

    Drapeau, Ann L.; Katz, Randy H.

    1992-01-01

    A growing number of applications require high capacity, high throughput tertiary storage systems. How data striping ideas apply to arrays of magnetic tape drives is investigated. Data striping increases throughput and reduces response time for large accesses to a storage system. Striped magnetic tape systems are particularly appealing because many inexpensive magnetic tape drives have low bandwidth; striping may offer dramatic performance improvements for these systems. There are several important issues in designing striped tape systems: the choice of tape drives and robots, whether to stripe within or between robots, and the choice of the best scheme for distributing data on cartridges. One of the most troublesome problems in striped tape arrays is the synchronization of transfers across tape drives. Another issue is how improved devices will affect the desirability of striping in the future. The results of simulations comparing the performance of striped tape systems to non-striped systems are presented.

  20. Striped tertiary storage arrays

    NASA Technical Reports Server (NTRS)

    Drapeau, Ann L.

    1993-01-01

    Data stripping is a technique for increasing the throughput and reducing the response time of large access to a storage system. In striped magnetic or optical disk arrays, a single file is striped or interleaved across several disks; in a striped tape system, files are interleaved across tape cartridges. Because a striped file can be accessed by several disk drives or tape recorders in parallel, the sustained bandwidth to the file is greater than in non-striped systems, where access to the file are restricted to a single device. It is argued that applying striping to tertiary storage systems will provide needed performance and reliability benefits. The performance benefits of striping for applications using large tertiary storage systems is discussed. It will introduce commonly available tape drives and libraries, and discuss their performance limitations, especially focusing on the long latency of tape accesses. This section will also describe an event-driven tertiary storage array simulator that is being used to understand the best ways of configuring these storage arrays. The reliability problems of magnetic tape devices are discussed, and plans for modeling the overall reliability of striped tertiary storage arrays to identify the amount of error correction required are described. Finally, work being done by other members of the Sequoia group to address latency of accesses, optimizing tertiary storage arrays that perform mostly writes, and compression is discussed.

  1. Wiggler improvement based on single axis magnetic measurement, synthesized 3-D field simulation of trajectories and sorting of lateral focusing magnets

    NASA Astrophysics Data System (ADS)

    Marks, H. S.; Volshonok, M.; Dyunin, E.; Gover, A.; Lasser, Y.; Shershevski, R.; Yahalom, A.

    2011-12-01

    A method is presented for correcting magnetic field imperfections in an assembled wiggler of the Halbach configuration. The method is employed in a configuration in which lateral focusing is needed along the wiggler (at low beam energies and large length) and is provided by external magnet bars alongside the wiggler. Field deviations in both vertical and lateral dimensions due to wiggler imperfections are repaired by sorting and reassembly of the focusing magnets. A single Hall probe measurement along the wiggler axis and individual measurements of the focusing magnet bars provide sufficient data for sorting and optimal choice of the positions of the focusing magnets. Moreover, this data enables 3D simulation of the e-beam transport trajectories in the virtually synthesized field of the wiggler with the contemplated repair configuration of the focusing magnet bars before actually assembling them. It thus provides in advance a realistic prediction of the quality of the repair.

  2. CONDENSED MATTER: ELECTRONICSTRUCTURE, ELECTRICAL, MAGNETIC, AND OPTICALPROPERTIES: Phase Locking and Chaos in a Josephson Junction Array Shunted by a Common Resistance

    NASA Astrophysics Data System (ADS)

    Zhou, Tie-Ge; Mao, Jing; Liu, Ting-Shu; Lai, Yue; Yan, Shao-Lin

    2009-07-01

    The dynamics of a Josephson junction array shunted by a common resistance are investigated by using numerical methods. Coexistence of phase locking and chaos is observed in the system when the resistively and capacitively shunted junction model is adopted. The corresponding parameter ranges for phase locking and chaos are presented. When there are three resistively shunted junctions in the array, chaos is found for the first time and the parameter range for chaos is also presented. According to the theory of Chernikov and Schmidt, when there are four or more junctions in the array, the system exhibits chaotic behavior. Our results indicate that the theory of Chernikov and Schmidt is not exactly appropriate.

  3. Enthalpy arrays

    NASA Astrophysics Data System (ADS)

    Torres, Francisco E.; Kuhn, Peter; de Bruyker, Dirk; Bell, Alan G.; Wolkin, Michal V.; Peeters, Eric; Williamson, James R.; Anderson, Gregory B.; Schmitz, Gregory P.; Recht, Michael I.; Schweizer, Sandra; Scott, Lincoln G.; Ho, Jackson H.; Elrod, Scott A.; Schultz, Peter G.; Lerner, Richard A.; Bruce, Richard H.

    2004-06-01

    We report the fabrication of enthalpy arrays and their use to detect molecular interactions, including protein-ligand binding, enzymatic turnover, and mitochondrial respiration. Enthalpy arrays provide a universal assay methodology with no need for specific assay development such as fluorescent labeling or immobilization of reagents, which can adversely affect the interaction. Microscale technology enables the fabrication of 96-detector enthalpy arrays on large substrates. The reduction in scale results in large decreases in both the sample quantity and the measurement time compared with conventional microcalorimetry. We demonstrate the utility of the enthalpy arrays by showing measurements for two protein-ligand binding interactions (RNase A + cytidine 2'-monophosphate and streptavidin + biotin), phosphorylation of glucose by hexokinase, and respiration of mitochondria in the presence of 2,4-dinitrophenol uncoupler.

  4. Microlens arrays

    NASA Astrophysics Data System (ADS)

    Hutley, Michael C.; Stevens, Richard F.; Daly, Daniel J.

    1992-04-01

    Microlenses have been with us for a long time as indeed the very word lens reminds us. Many early lenses,including those made by Hooke and Leeuwenhoek in the 17th century were small and resembled lentils. Many languages use the same word for both (French tilentillelt and German "Linse") and the connection is only obscure in English because we use the French word for the vegetable and the German for the optic. Many of the applications for arrays of inicrolenses are also well established. Lippmann's work on integral photography at the turn of the century required lens arrays and stimulated an interest that is very much alive today. At one stage, lens arrays played an important part in high speed photography and various schemes have been put forward to take advantage of the compact imaging properties of combinations of lens arrays. The fact that many of these ingenious schemes have not been developed to their full potential has to a large degree been due to the absence of lens arrays of a suitable quality and cost.

  5. Very large array and green bank telescope observations of Orion B (NGC 2024, W12): photodissociation region properties and magnetic field

    SciTech Connect

    Roshi, D. Anish; Goss, W. M.; Jeyakumar, S. E-mail: mgoss@nrao.edu

    2014-10-01

    We present images of C110α and H110α radio recombination line (RRL) emission at 4.8 GHz and images of H166α, C166α, and X166α RRL emission at 1.4 GHz, observed toward the star-forming region NGC 2024. The 1.4 GHz image with angular resolution ∼70'' is obtained using Very Large Array (VLA) data. The 4.8 GHz image with angular resolution ∼17'' is obtained by combining VLA and Green Bank Telescope data in order to add the short and zero spacing data in the uv plane. These images reveal that the spatial distributions of C110α line emission is confined to the southern rim of the H II region close to the ionization front whereas the C166α line emission is extended in the north-south direction across the H II region. The LSR velocity of the C110α line is 10.3 km s{sup –1} similar to that of lines observed from molecular material located at the far side of the H II region. This similarity suggests that the photodissociation region (PDR) responsible for C110α line emission is at the far side of the H II region. The LSR velocity of C166α is 8.8 km s{sup –1}. This velocity is comparable with the velocity of molecular absorption lines observed from the foreground gas, suggesting that the PDR is at the near side of the H II region. Non-LTE models for carbon line-forming regions are presented. Typical properties of the foreground PDR are T {sub PDR} ∼ 100 K, n{sub e}{sup PDR}∼5 cm{sup –3}, n {sub H} ∼ 1.7 × 10{sup 4} cm{sup –3}, and path length l ∼ 0.06 pc, and those of the far side PDR are T {sub PDR} ∼ 200 K, n{sub e}{sup PDR}∼ 50 cm{sup –3}, n {sub H} ∼ 1.7 × 10{sup 5} cm{sup –3}, and l ∼ 0.03 pc. Our modeling indicates that the far side PDR is located within the H II region. We estimate the magnetic field strength in the foreground PDR to be 60 μG and that in the far side PDR to be 220 μG. Our field estimates compare well with the values obtained from OH Zeeman observations toward NGC 2024. The H166α spectrum shows narrow (1.7 km s{sup –1}) and broad (33 km s{sup –1}) line features. The narrow line has spatial distribution and central velocity (∼9 km s{sup –1}) similar to that of the foreground carbon line emission, suggesting that they are associated. Modeling the narrow H166α emission provides physical properties T {sub PDR} ∼ 50 K, n{sub e}{sup PDR}∼4 cm{sup –3}, and l ∼ 0.01 pc and implies an ionization fraction of ∼10{sup –4}. The broad H166α line originates from the H II region. The X166α line has a different spatial distribution compared to other RRLs observed toward NGC 2024 and is probably associated with cold dust clouds. Based on the expected low depletion of sulfur in such clouds and the –8.1 km s{sup –1} velocity separation between the X166α and C166α lines, we interpret that the X166α transition arises from sulfur.

  6. Very Large Array and Green Bank Telescope Observations of Orion B (NGC 2024, W12): Photodissociation Region Properties and Magnetic Field

    NASA Astrophysics Data System (ADS)

    Roshi, D. Anish; Goss, W. M.; Jeyakumar, S.

    2014-10-01

    We present images of C110? and H110? radio recombination line (RRL) emission at 4.8 GHz and images of H166?, C166?, and X166? RRL emission at 1.4 GHz, observed toward the star-forming region NGC 2024. The 1.4 GHz image with angular resolution ~70'' is obtained using Very Large Array (VLA) data. The 4.8 GHz image with angular resolution ~17'' is obtained by combining VLA and Green Bank Telescope data in order to add the short and zero spacing data in the uv plane. These images reveal that the spatial distributions of C110? line emission is confined to the southern rim of the H II region close to the ionization front whereas the C166? line emission is extended in the north-south direction across the H II region. The LSR velocity of the C110? line is 10.3 km s-1 similar to that of lines observed from molecular material located at the far side of the H II region. This similarity suggests that the photodissociation region (PDR) responsible for C110? line emission is at the far side of the H II region. The LSR velocity of C166? is 8.8 km s-1. This velocity is comparable with the velocity of molecular absorption lines observed from the foreground gas, suggesting that the PDR is at the near side of the H II region. Non-LTE models for carbon line-forming regions are presented. Typical properties of the foreground PDR are T PDR ~ 100 K, n_e^{PDR} \\sim 5 cm-3, n H ~ 1.7 104 cm-3, and path length l ~ 0.06 pc, and those of the far side PDR are T PDR ~ 200 K, n_e^{PDR} \\sim 50 cm-3, n H ~ 1.7 105 cm-3, and l ~ 0.03 pc. Our modeling indicates that the far side PDR is located within the H II region. We estimate the magnetic field strength in the foreground PDR to be 60 ?G and that in the far side PDR to be 220 ?G. Our field estimates compare well with the values obtained from OH Zeeman observations toward NGC 2024. The H166? spectrum shows narrow (1.7 km s-1) and broad (33 km s-1) line features. The narrow line has spatial distribution and central velocity (~9 km s-1) similar to that of the foreground carbon line emission, suggesting that they are associated. Modeling the narrow H166? emission provides physical properties T PDR ~ 50 K, n_e^{PDR} \\sim 4 cm-3, and l ~ 0.01 pc and implies an ionization fraction of ~10-4. The broad H166? line originates from the H II region. The X166? line has a different spatial distribution compared to other RRLs observed toward NGC 2024 and is probably associated with cold dust clouds. Based on the expected low depletion of sulfur in such clouds and the -8.1 km s-1 velocity separation between the X166? and C166? lines, we interpret that the X166? transition arises from sulfur.

  7. Direct measurements of the magnetic entropy change.

    PubMed

    Nielsen, K K; Bez, H N; von Moos, L; Bjrk, R; Eriksen, D; Bahl, C R H

    2015-10-01

    An experimental device that can accurately measure the magnetic entropy change, ?s, as a function of temperature, T, and magnetic field, H, is presented. The magnetic field source is in this case a set of counter-rotating concentric Halbach-type magnets, which produce a highly homogeneous applied field with constant orientation. The field may be varied from 0 to 1.5 T in a continuous way. The temperature stability of the system is controlled to within 10 mK and the standard range for the current setup is from 230 K to 330 K. The device is under high vacuum and we show that thermal losses to the ambient are negligible in terms of the calorimetric determination of the magnetic entropy change, while the losses cannot be ignored when correcting for the actual sample temperature. We apply the device to two different types of samples; one is commercial grade Gd, i.e., a pure second-order phase transition material, while the other is Gd5Si2Ge2, a first order magnetic phase transition material. We demonstrate the device's ability to fully capture the thermal hysteresis of the latter sample by following appropriate thermal resetting scheme and magnetic resetting scheme. PMID:26520967

  8. Direct measurements of the magnetic entropy change

    NASA Astrophysics Data System (ADS)

    Nielsen, K. K.; Bez, H. N.; von Moos, L.; Bjrk, R.; Eriksen, D.; Bahl, C. R. H.

    2015-10-01

    An experimental device that can accurately measure the magnetic entropy change, ?s, as a function of temperature, T, and magnetic field, H, is presented. The magnetic field source is in this case a set of counter-rotating concentric Halbach-type magnets, which produce a highly homogeneous applied field with constant orientation. The field may be varied from 0 to 1.5 T in a continuous way. The temperature stability of the system is controlled to within 10 mK and the standard range for the current setup is from 230 K to 330 K. The device is under high vacuum and we show that thermal losses to the ambient are negligible in terms of the calorimetric determination of the magnetic entropy change, while the losses cannot be ignored when correcting for the actual sample temperature. We apply the device to two different types of samples; one is commercial grade Gd, i.e., a pure second-order phase transition material, while the other is Gd5Si2Ge2, a first order magnetic phase transition material. We demonstrate the device's ability to fully capture the thermal hysteresis of the latter sample by following appropriate thermal resetting scheme and magnetic resetting scheme.

  9. Global Arrays

    SciTech Connect

    2006-02-23

    The Global Arrays (GA) toolkit provides an efficient and portable ?shared-memory? programming interface for distributed-memory computers. Each process in a MIMD parallel program can asynchronously access logical blocks of physically distributed dense multi-dimensional arrays, without need for explicit cooperation by other processes. Unlike other shared-memory environments, the GA model exposes to the programmer the non-uniform memory access (NUMA) characteristics of the high performance computers and acknowledges that access to a remote portion of the shared data is slower than to the local portion. The locality information for the shared data is available, and a direct access to the local portions of shared data is provided. Global Arrays have been designed to complement rather than substitute for the message-passing programming model. The programmer is free to use both the shared-memory and message-passing paradigms in the same program, and to take advantage of existing message-passing software libraries. Global Arrays are compatible with the Message Passing Interface (MPI).

  10. Pacific Array

    NASA Astrophysics Data System (ADS)

    Kawakatsu, H.; Takeo, A.; Isse, T.; Nishida, K.; Shiobara, H.; Suetsugu, D.

    2014-12-01

    Based on our recent results on broadband ocean bottom seismometry, we propose a next generation large-scale array experiment in the ocean. Recent advances in ocean bottom broadband seismometry (e.g., Suetsugu & Shiobara, 2014, Annual Review EPS), together with advances in the seismic analysis methodology, have now enabled us to resolve the regional 1-D structure of the entire lithosphere/asthenosphere system, including seismic anisotropy (both radial and azimuthal), with deployments of ~10-15 broadband ocean bottom seismometers (BBOBSs) (namely "ocean-bottom broadband dispersion survey"; Takeo et al., 2013, JGR; Kawakatsu et al., 2013, AGU; Takeo, 2014, Ph.D. Thesis; Takeo et al., 2014, JpGU). Having ~15 BBOBSs as an array unit for 2-year deployment, and repeating such deployments in a leap-frog way (an array of arrays) for a decade or so would enable us to cover a large portion of the Pacific basin. Such efforts, not only by giving regional constraints on the 1-D structure, but also by sharing waveform data for global scale waveform tomography, would drastically increase our knowledge of how plate tectonics works on this planet, as well as how it worked for the past 150 million years. International collaborations might be sought.

  11. Global Arrays

    Energy Science and Technology Software Center (ESTSC)

    2006-02-23

    The Global Arrays (GA) toolkit provides an efficient and portable “shared-memory” programming interface for distributed-memory computers. Each process in a MIMD parallel program can asynchronously access logical blocks of physically distributed dense multi-dimensional arrays, without need for explicit cooperation by other processes. Unlike other shared-memory environments, the GA model exposes to the programmer the non-uniform memory access (NUMA) characteristics of the high performance computers and acknowledges that access to a remote portion of the sharedmore » data is slower than to the local portion. The locality information for the shared data is available, and a direct access to the local portions of shared data is provided. Global Arrays have been designed to complement rather than substitute for the message-passing programming model. The programmer is free to use both the shared-memory and message-passing paradigms in the same program, and to take advantage of existing message-passing software libraries. Global Arrays are compatible with the Message Passing Interface (MPI).« less

  12. Allen Telescope Array

    NASA Astrophysics Data System (ADS)

    Bower, Geoffrey

    2007-05-01

    The Allen Telescope Array (ATA) is a pioneering centimeter-wavelength radio telescope that will produce science that cannot be done with any other instrument. The ATA is the first radio telescope designed for commensal observing; it will undertake the most comprehensive and sensitive SETI surveys ever done as well as the deepest and largest area continuum and spectroscopic surveys. Science operations will commence this year with a 42-element array. The ATA will ultimately comprise 350 6-meter dishes at Hat Creek in California, and will make possible large, deep radio surveys that were not previously feasible. The telescope incorporates many new design features including hydroformed antenna surfaces, a log-periodic feed covering the entire range of frequencies from 500 MHz to 11.2 GHz, low noise, wide-band amplifiers with a flat response over the entire band. The full array has the sensitivity of the Very Large Array but with a survey capability that is greater by an order of magnitude due to the wide field of view of the 6-meter dishes. Even with 42 elements, the ATA will be one of the most powerful radio survey telescopes. Science goals include the Five GHz sky survey (FiGSS) to match the 1.4-GHz NRAO VLA Sky Survey (NVSS) and the Sloan Digital Sky Survey within the first year of operation with the 42 element array, and a deep all-sky survey of extragalactic hydrogen to investigate galaxy evolution and intergalactic gas accretion. Transient and variable source surveys, pulsar science, spectroscopy of new molecular species in the galaxy, large-scale mapping of galactic magnetic filaments, and wide-field imaging of comets and other solar system objects are among the other key science objectives of the ATA. SETI surveys will reach sufficient sensitivity to detect an Arecibo planetary radar from 1,000,000 stars to distances of 300 pc.

  13. Electromagnetically Clean Solar Arrays

    NASA Technical Reports Server (NTRS)

    Stem, Theodore G.; Kenniston, Anthony E.

    2008-01-01

    The term 'electromagnetically clean solar array' ('EMCSA') refers to a panel that contains a planar array of solar photovoltaic cells and that, in comparison with a functionally equivalent solar-array panel of a type heretofore used on spacecraft, (1) exhibits less electromagnetic interferences to and from other nearby electrical and electronic equipment and (2) can be manufactured at lower cost. The reduction of electromagnetic interferences is effected through a combination of (1) electrically conductive, electrically grounded shielding and (2) reduction of areas of current loops (in order to reduce magnetic moments). The reduction of cost is effected by designing the array to be fabricated as a more nearly unitary structure, using fewer components and fewer process steps. Although EMCSAs were conceived primarily for use on spacecraft they are also potentially advantageous for terrestrial applications in which there are requirements to limit electromagnetic interference. In a conventional solar panel of the type meant to be supplanted by an EMCSA panel, the wiring is normally located on the back side, separated from the cells, thereby giving rise to current loops having significant areas and, consequently, significant magnetic moments. Current-loop geometries are chosen in an effort to balance opposing magnetic moments to limit far-0field magnetic interactions, but the relatively large distances separating current loops makes full cancellation of magnetic fields problematic. The panel is assembled from bare photovoltaic cells by means of multiple sensitive process steps that contribute significantly to cost, especially if electomagnetic cleanliness is desired. The steps include applying a cover glass and electrical-interconnect-cell (CIC) sub-assemble, connecting the CIC subassemblies into strings of series-connected cells, laying down and adhesively bonding the strings onto a panel structure that has been made in a separate multi-step process, and mounting the wiring on the back of the panel. Each step increases the potential for occurrence of latent defects, loss of process control, and attrition of components. An EMCSA panel includes an integral cover made from a transparent material. The silicone cover supplants the individual cover glasses on the cells and serves as an additional unitary structural support that offers the advantage, relative to glass, of the robust, forgiving nature of the silcone material. The cover contains pockets that hold the solar cells in place during the lamination process. The cover is coated with indium tin oxide to make its surface electrically conductive, so that it serves as a contiguous, electrically grounded shield over the entire panel surface. The cells are mounted in proximity to metallic printed wiring. The painted-wiring layer comprises metal-film traces on a sheet of Kapton (or equivalent) polyimide. The traces include contact pads on one side of the sheet for interconnecting the cells. Return leads are on the opposite side of the sheet, positioned to form the return currents substantially as mirror images of, and in proximity to, the cell sheet currents, thereby minimizing magnetic moments. The printed-wiring arrangement mimics the back-wiring arrangement of conventional solar arrays, but the current-loop areas and the resulting magnetic moments are much smaller because the return-current paths are much closer to the solar-cell sheet currents. The contact pads are prepared with solder fo electrical and mechanical bonding to the cells. The pocketed cover/shield, the solar cells, the printed-wiring layer, an electrical bonding agent, a mechanical-bonding agent, a composite structural front-side face sheet, an aluminum honeycomb core, and a composite back-side face sheet are all assembled, then contact pads are soldered to the cells and the agents are cured in a single lamination process.

  14. Genotyping Arrays

    NASA Astrophysics Data System (ADS)

    Lodes, Michael J.; Suciu, Dominic; Danley, David; McShea, Andrew

    Although the most common use of DNA microarrays is gene expression profiling, microarrays are also used for many other applications, including genotyping, resequencing, SNP analysis, and DNA methylation assays. Here we describe genotyping arrays for Influenza A subtype identification and for upper respiratory pathogen diagnostics using standard hybridization techniques and we also describe resequencing, SNP, and methylation assays using an enzyme-based strategy [25, 26].

  15. Magnetic

    NASA Astrophysics Data System (ADS)

    Aboud, Essam; El-Masry, Nabil; Qaddah, Atef; Alqahtani, Faisal; Moufti, Mohammed R. H.

    2015-06-01

    The Rahat volcanic field represents one of the widely distributed Cenozoic volcanic fields across the western regions of the Arabian Peninsula. Its human significance stems from the fact that its northern fringes, where the historical eruption of 1256 A.D. took place, are very close to the holy city of Al-Madinah Al-Monawarah. In the present work, we analyzed aeromagnetic data from the northern part of Rahat volcanic field as well as carried out a ground gravity survey. A joint interpretation and inversion of gravity and magnetic data were used to estimate the thickness of the lava flows, delineate the subsurface structures of the study area, and estimate the depth to basement using various geophysical methods, such as Tilt Derivative, Euler Deconvolution and 2D modeling inversion. Results indicated that the thickness of the lava flows in the study area ranges between 100 m (above Sea Level) at the eastern and western boundaries of Rahat Volcanic field and getting deeper at the middle as 300-500 m. It also showed that, major structural trend is in the NW direction (Red Sea trend) with some minor trends in EW direction.

  16. Magnetic Cusp Configuration of the SPL Plasma Generator

    NASA Astrophysics Data System (ADS)

    Kronberger, Matthias; Chaudet, Elodie; Favre, Gilles; Lettry, Jacques; Kchler, Detlef; Moyret, Pierre; Paoluzzi, Mauro; Prever-Loiri, Laurent; Schmitzer, Claus; Scrivens, Richard; Steyaert, Didier

    2011-09-01

    The Superconducting Proton Linac (SPL) is a novel linear accelerator concept currently studied at CERN. As part of this study, a new Cs-free, RF-driven external antenna H- plasma generator has been developed to withstand an average thermal load of 6 kW. The magnetic configuration of the new plasma generator includes a dodecapole cusp field and a filter field separating the plasma heating and H- production regions. Ferrites surrounding the RF antenna serve in enhancing the coupling of the RF to the plasma. Due to the space requirements of the plasma chamber cooling circuit, the cusp magnets are pushed outwards compared to Linac4 and the cusp field strength in the plasma region is reduced by 40% when N-S magnetized magnets are used. The cusp field strength and plasma confinement can be improved by replacing the N-S magnets with offset Halbach elements of which each consists of three magnetic sub-elements with different magnetization direction. A design challenge is the dissipation of RF power induced by eddy currents in the cusp and filter magnets which may lead to overheating and demagnetization. In view of this, a copper magnet cage has been developed that shields the cusp magnets from the radiation of the RF antenna.

  17. Magnetic Cusp Configuration of the SPL Plasma Generator

    SciTech Connect

    Kronberger, Matthias; Chaudet, Elodie; Favre, Gilles; Lettry, Jacques; Kuechler, Detlef; Moyret, Pierre; Paoluzzi, Mauro; Prever-Loiri, Laurent; Schmitzer, Claus; Scrivens, Richard; Steyaert, Didier

    2011-09-26

    The Superconducting Proton Linac (SPL) is a novel linear accelerator concept currently studied at CERN. As part of this study, a new Cs-free, RF-driven external antenna H{sup -} plasma generator has been developed to withstand an average thermal load of 6 kW. The magnetic configuration of the new plasma generator includes a dodecapole cusp field and a filter field separating the plasma heating and H{sup -} production regions. Ferrites surrounding the RF antenna serve in enhancing the coupling of the RF to the plasma. Due to the space requirements of the plasma chamber cooling circuit, the cusp magnets are pushed outwards compared to Linac4 and the cusp field strength in the plasma region is reduced by 40% when N-S magnetized magnets are used. The cusp field strength and plasma confinement can be improved by replacing the N-S magnets with offset Halbach elements of which each consists of three magnetic sub-elements with different magnetization direction. A design challenge is the dissipation of RF power induced by eddy currents in the cusp and filter magnets which may lead to overheating and demagnetization. In view of this, a copper magnet cage has been developed that shields the cusp magnets from the radiation of the RF antenna.

  18. Silane modified magnetic nanoparticles as a novel adsorbent for determination of morphine at trace levels in human hair samples by high-performance liquid chromatography with diode array detection.

    PubMed

    Boojaria, Ali; Masrournia, Mahboubeh; Ghorbani, Hamideh; Ebrahimitalab, Abdolhossein; Miandarhoie, Mina

    2015-12-01

    In this paper we report a novel, sensitive, and rapid method of magnetic solid phase extraction based on surface modified magnetic nanoparticles as a novel nano sorbent for HPLC determination of morphine with diode array detection in human hair samples. Factors affecting the extraction efficiency of the proposed method, including the sample pH, quantity of magnetic nanoparticles, sample volume, desorption solvent type and its volume, and extraction time were investigated and optimized. Under the optimized experimental conditions, a good linearity was observed in the range of 1-800 µgL(-1) for the morphine, with a correlation coefficient (R (2)) of 0.990. The pre-concentration factor of 208.69 was achieved in this method. The detection limit of the method was 0.1 μgL(-1) based on S/N = 3 and good reproducibility with a relative standard deviations lower than (n = 5) 2.59 %. The proposed method has been successfully applied to the analysis of trace amounts of morphine in human hair samples with satisfactory results. This method can be applied in medical toxicology research and forensic medical centers. PMID:26318597

  19. Emerging Protein Array Technologies for Proteomics

    PubMed Central

    Lee, Jung-Rok; Magee, Dewey Mitchell; Gaster, Richard Samuel; LaBaer, Joshua; Wang, Shan X.

    2014-01-01

    Numerous efforts have been made to understand fundamental biology of diseases based on gene expressions. However, the relationship between gene expressions and onset of diseases often remains obscure. The great advances in protein microarrays allow us to investigate this unclear question through protein profiles, which are regarded as more reliable than gene expressions to serve as the harbinger of disease onset or as the biomarker of disease treatment monitoring. We review two relatively new platforms of protein arrays, along with an introduction to the common basis of protein array technologies. Immobilization of proteins on the surface of arrays and neutralizing reactive areas after the immobilization are key practical issues in the field of protein array. One of the emerging protein array technologies is the magneto-nanosensor array where giant magnetoresistive (GMR) sensors are used to quantitatively measure analyte of interest which are labeled with magnetic nanoparticles (MNP). Similar to GMR, several different ways of utilizing magnetic properties for biomolecular detection have been developed and are reviewed here. Another emerging protein array technology is Nucleic Acid Programmable Protein Arrays (NAPPA), which have thousands of protein features directly expressed by nucleic acids on array surface. We anticipate these two emerging protein array platforms can be combined to produce synergistic benefits and open new applications in proteomics and clinical diagnostics. PMID:23414360

  20. Nonvolatile Power-Gating Field-Programmable Gate Array Using Nonvolatile Static Random Access Memory and Nonvolatile Flip-Flops Based on Pseudo-Spin-Transistor Architecture with Spin-Transfer-Torque Magnetic Tunnel Junctions

    NASA Astrophysics Data System (ADS)

    Yamamoto, Shuu'ichirou; Shuto, Yusuke; Sugahara, Satoshi

    2012-11-01

    We proposed and computationally analyzed a nonvolatile power-gating field-programmable gate array (NVPG-FPGA) based on pseudo-spin-transistor architecture with spin-transfer-torque magnetic tunnel junctions (STT-MTJs). The circuit employs nonvolatile static random memory (NV-SRAM) cells and nonvolatile flip-flops (NV-FFs) as the storage circuits of the NVPG-FPGA. The circuit configuration and microarchitecture are compatible with SRAM-based FPGAs, and the additional nonvolatile memory functionality makes it possible to execute efficient power gating (PG). The break-even time (BET) for the nonvolatile configuration logic block (NV-CLB) of the NVPG-FPGA was also analyzed, and reduction techniques of the BET, which allows highly efficient PG operations with fine granularity, were proposed.

  1. Variable permanent magnet sextupole lens for focusing of pulsed cold neutrons

    NASA Astrophysics Data System (ADS)

    Iwashita, Y.; Tajima, Y.; Ichikawa, M.; Nakamura, S.; Ino, T.; Muto, S.; Shimizu, H. M.

    2008-02-01

    A Variable Permanent Magnet Sextupole (VPMS) lens that can focus pulsed slow neutrons is under development. It is based on the extended Halbach configuration to generate stronger magnetic field. In order to adjust the strength, the magnet is divided into two nested rings, where the inner ring is fixed and the outer ring can be rotated. This device will focus cold neutrons with wavelength of a few to several Angstroms at about 10 m focal length. We fabricated a half-scale model to measure the strength and the torque as functions of the rotor angle. Because the torque is measured as high as more than 30 N m, a mechanism to rotate the rotor is carefully designed. After installation of such a mechanism, a motor will drive the rotor and the temperature rise caused from eddy current loss will be measured. Detailed development of the system will be presented.

  2. Selective separation and determination of the synthetic colorants in beverages by magnetic solid-phase dispersion extraction based on a Fe3 O4 /reduced graphene oxide nanocomposite followed by high-performance liquid chromatography with diode array detection.

    PubMed

    Wang, Xi; Chen, Ning; Han, Qing; Yang, Zaiyue; Wu, Jinhua; Xue, Cheng; Hong, Junli; Zhou, Xuemin; Jiang, Huijun

    2015-06-01

    A facile adsorbent, a nanocomposite of Fe3 O4 and reduced graphene oxide, was fabricated for the selective separation and enrichment of synthetic aromatic azo colorants by magnetic solid-phase dispersion extraction. The nanocomposite was synthesized in a one-step reduction reaction and characterized by atomic force microscopy, scanning electron microscopy, Fourier transform infrared spectroscopy, Raman spectroscopy, X-ray diffraction and Brunauer-Emmett-Teller analysis. The colorants in beverages were quickly adsorbed onto the surface of the nanocomposite with strong ?-? interactions between colorants and reduced graphene oxide, and separated with the assistance of an external magnetic field. Moreover, the four colorants in beverages were detected at different wavelengths by high performance liquid chromatography with diode array detection. A linear dependence of peak area was obtained over 0.05-10 ?g/mL with the limits of detection of 10.02, 11.90, 10.41, 15.91 ng/mL for tartrazine, allure red, amaranth, and new coccine, respectively (signal to noise = 3). The recoveries for the spiked colorants were in the range of 88.95-95.89% with the relative standard deviation less than 2.66%. The results indicated that the nanocomposite of Fe3 O4 and reduced graphene oxide could be used as an excellent selective adsorbent for aromatic compounds and has potential applications in sample pretreatment. PMID:25864558

  3. nanotube arrays

    NASA Astrophysics Data System (ADS)

    Tan, Yu; Zhang, Shenghan; Liang, Kexin

    2014-02-01

    We reported Ce and its oxide-modified TiO2 nanotube arrays (TNTs) and their semiconductor properties. The TNTs were prepared by anodic oxidation on pure Ti and investigated by electrochemical photocurrent response analysis. Then, the TNT electrodes were deposited of Ce by cathodic reduction of Ce(NO3)3 6H2O. After deposition, the TNT electrodes were fabricated by anodic oxidation at E = 1.0 V(SCE) for various electricity as Ce-Ce2O3-CeO2 modification. The Ce-deposited TNTs (band gap energy E g = 2.92 eV) exhibited enhanced photocurrent responses under visible light region and indicated more negative flat band potential ( E fb) compared with the TNTs without deposition. After anodic oxidation, the mixed Ce and its oxide (Ce2O3-CeO2)-modified TNT photoelectrodes exhibited higher photocurrent responses under both visible and UV light regions than the TNTs without deposition. The photocurrent responses and E fb were found to be strongly dependent on the contents of Ce2O3 and CeO2 deposited on TNTs. A new characteristic of E g = 2.1 0.1 eV was investigated in the Ce2O3- and CeO2-modified photoelectrodes. X-ray diffraction (XRD), scanning electron microscopy (SEM), and X-ray photoelectron spectroscopy (XPS) were also employed to characterize various modified TNTs photoelectrodes.

  4. 7-T magnetic resonance imaging of the inner ear's anatomy by using dual four-element radiofrequency coil arrays and the VIBE sequence

    NASA Astrophysics Data System (ADS)

    Kim, Kyoung-Nam; Heo, Phil; Kim, Young-Bo; Han, Gyu-Cheol

    2015-02-01

    An ultra-high-field magnetic resonance (MR) scanner and a specially-optimized radiofrequency (RF) coil and sequence protocol are required to obtain high-resolution images of the inner ear that can noninvasively confirm pathologic diagnoses. In phantom studies, the MR signal distribution of the gradient echo MR images generated by using a customized RF coil was compared with that of a commercial volume coil. The MR signal intensity of the customized RF coil decreases rapidly from near the RF coil plane toward the exterior of the phantom. However, the signal sensitivity of this coil is superior on both sides of the phantom, corresponding to the petrous pyramid. In in-vivo 7-T MR imaging, a customized RF coil and a volumetric-interpolated breath-hold examination imaging sequence are employed for visualization of the inner ear's structure. The entire membranous portion of the cochlear and the three semicircular canals, including the ductus reunions, oval window, and round window with associated nervous tissue, were clearly depicted with sufficient spatial coverage for adequate inspection of the surrounding anatomy. Developments from a new perspective to inner ear imaging using the 7-T modality could lead to further improved image sensitivity and, thus, enable ultra-structural MR imaging.

  5. Magnetic bead based immuno-detection of Listeria monocytogenes and Listeria ivanovii from infant formula and leafy green vegetables using the Bio-Plex suspension array system.

    PubMed

    Day, J B; Basavanna, U

    2015-04-01

    Listeriosis, a disease contracted via the consumption of foods contaminated with pathogenic Listeria species, can produce severe symptoms and high mortality in susceptible people and animals. The development of molecular methods and immuno-based techniques for detection of pathogenic Listeria in foods has been challenging due to the presence of assay inhibiting food components. In this study, we utilize a macrophage cell culture system for the isolation and enrichment of Listeria monocytogenes and Listeria ivanovii from infant formula and leafy green vegetables for subsequent identification using the Luminex xMAP technique. Macrophage monolayers were exposed to infant formula, lettuce and celery contaminated with L. monocytogenes or L. ivanovii. Magnetic microspheres conjugated to Listeria specific antibody were used to capture Listeria from infected macrophages and then analyzed using the Bio-Plex 200 analyzer. As few as 10 CFU/mL or g of L. monocytogenes was detected in all foods tested. The detection limit for L. ivanovii was 10 CFU/mL in infant formula and 100 CFU/g in leafy greens. Microsphere bound Listeria obtained from infected macrophage lysates could also be isolated on selective media for subsequent confirmatory identification. This method presumptively identifies L. monocytogenes and L. ivanovii from infant formula, lettuce and celery in less than 28 h with confirmatory identifications completed in less than 48 h. PMID:25475329

  6. Development of a monolithic ferrite memory array

    NASA Technical Reports Server (NTRS)

    Heckler, C. H., Jr.; Bhiwandker, N. C.

    1972-01-01

    The results of the development and testing of ferrite monolithic memory arrays are presented. This development required the synthesis of ferrite materials having special magnetic and physical characteristics and the development of special processes; (1) for making flexible sheets (laminae) of the ferrite composition, (2) for embedding conductors in ferrite, and (3) bonding ferrite laminae together to form a monolithic structure. Major problems encountered in each of these areas and their solutions are discussed. Twenty-two full-size arrays were fabricated and fired during the development of these processes. The majority of these arrays were tested for their memory characteristics as well as for their physical characteristics and the results are presented. The arrays produced during this program meet the essential goals and demonstrate the feasibility of fabricating monolithic ferrite memory arrays by the processes developed.

  7. Design and characteristics analysis of linear oscillatory actuator with ferrite permanent magnet for refrigerator compressor

    NASA Astrophysics Data System (ADS)

    Kim, Kwan-Ho; Jang, Seok-Myeong; Ahn, Ji-Hun; Choi, Jang-Young; Jeong, Sang-Sub

    2015-05-01

    Actuators using NdFeB permanent magnets (PMs) are widely used, but they are costly and are affected by unstable material supply. In this study, a linear oscillatory actuator (LOA) using a ferrite PM is designed for use in the compressor for refrigerators, instead of the NdFeB PM. In spite of benefits of ferrite PM, it has not been widely used because the residual magnetic flux density of the ferrite PM is normally 35% less than that of a NdFeB PM. To overcome this shortcoming, we analyze the mover features of the LOA using two types of the ferrite PMs: interior PM type and Halbach PM type. The LOA designed has the same outer stator outer radius and number of coil turns as a conventional LOA with the NdFeB PM. The validity of the designed model is verified by comparing the analysis results using the nonlinear finite element method.

  8. Resonance spectra of diabolo optical antenna arrays

    NASA Astrophysics Data System (ADS)

    Guo, Hong; Simpkins, Blake; Caldwell, Joshua D.; Guo, Junpeng

    2015-10-01

    A complete set of diabolo optical antenna arrays with different waist widths and periods was fabricated on a sapphire substrate by using a standard e-beam lithography and lift-off process. Fabricated diabolo optical antenna arrays were characterized by measuring the transmittance and reflectance with a microscope-coupled FTIR spectrometer. It was found experimentally that reducing the waist width significantly shifts the resonance to longer wavelength and narrowing the waist of the antennas is more effective than increasing the period of the array for tuning the resonance wavelength. Also it is found that the magnetic field enhancement near the antenna waist is correlated to the shift of the resonance wavelength.

  9. Head-to-Head Comparison of Ultra-High-Performance Liquid Chromatography with Diode Array Detection versus Quantitative Nuclear Magnetic Resonance for the Quantitative Analysis of the Silymarin Complex in Silybum marianum Fruit Extracts.

    PubMed

    Cheilari, Antigoni; Sturm, Sonja; Intelmann, Daniel; Seger, Christoph; Stuppner, Hermann

    2016-02-24

    Quantitative nuclear magnetic resonance (qNMR) spectroscopy is known as an excellent alternative to chromatography-based mixture analysis. NMR spectroscopy is a non-destructive method, needs only limited sample preparation, and can be readily automated. A head-to-head comparison of qNMR to an ultra-high-performance liquid chromatography with diode array detection (uHPLC-DAD)-based quantitative analysis of six flavonolignan congeners (silychristin, silydianin, silybin A, silybin B, isosilybin A, and isosilybin B) of the Silybum marianum silymarin complex is presented. Both assays showed similar performance characteristics (linear range, accuracy, precision, and limits of quantitation) with analysis times below 30 min/sample. The assays were applied to industrial S. marianum extracts (AC samples) and to extracts locally prepared from S. marianum fruits (PL samples). An assay comparison by Bland-Altman plots (relative method bias AC samples, -0.1%; 2SD range, 5.1%; relative method bias PL samples, -0.3%; 2SD range, 7.8%) and Passing-Bablok regression analysis (slope and intercept for AC and PL samples not significantly different from 1.00 and 0.00, respectively; Spearman's coefficient of rank correlation, >0.99) did show that qNMR and uHPLC-DAD can be used interchangeably to quantitate flavonolignans in the silymarin complex. PMID:26806429

  10. Analysis on operational power and eddy current losses for applying coreless double-sided permanent magnet synchronous motor/generator to high-power flywheel energy storage system

    NASA Astrophysics Data System (ADS)

    Jang, Seok-Myeong; Park, Ji-Hoon; You, Dae-Joon; Choi, Sang-Ho

    2009-04-01

    This paper deals with analytical approach of operational power defined as load power and rotor loss represented as eddy current loss for applying a permanent magnet (PM) synchronous motor/generator to the high-power flywheel energy storage system. The used model is composed of a double-sided Halbach magnetized PM rotor and coreless three-phase winding stator. For one such motor/generator structure, we provide the magnetic field and eddy current with space and time harmonics via magnetic vector potential in two-dimensional (2D) polar coordinate system. From these, the operational power is estimated by backelectromotive force according to the PM rotor speed, and the rotor loss is also calculated from Poynting theorem.

  11. Interferometric Array Design

    NASA Astrophysics Data System (ADS)

    Holdaway, M. A.; Helfer, Tamara T.

    We investigate some of the principles which lead to the design of radio interferometric arrays and array configurations, including both abstract issues such as sensitivity and Fourier plane coverage, and practical issues such as moving antennas and site topographical constraints. We draw on the design and history of existing arrays and also give a glimpse of what ideas and algorithms are helping design new instruments such as the Submillimeter Array (SMA) and the Millimeter Array (MMA).

  12. Magnetic multipole redirector of moving plasmas

    DOEpatents

    Crow, James T. (Albuquerque, NM); Mowrer, Gary R. (Cedar Crest, NM)

    1999-01-01

    A method and apparatus for redirecting moving plasma streams using a multiple array of magnetic field generators (e.g., permanent magnets or current bearing wires). Alternate rows of the array have opposite magnetic field directions. A fine wire mesh may be employed to focus as well as redirect the plasma.

  13. In-plane anisotropy of coercive field in permalloy square ring arrays.

    SciTech Connect

    Goncharov, A. V.; Zhukov, A. A.; Metlushko, V. V.; Bordignon, G.; Fangohr, H.; Karapetrov, G.; de Groot, P. A. J.; Ilic, B.; Materials Science Division; Univ. Southampton; Univ. Illinois at Chicago; Cornell Univ.

    2006-04-15

    Magnetic ring arrays are promising candidates for application in magnetic random access memory devices. The magnetic reversal processes and anisotropy of the coercivity in arrays of square-shaped nanorings with different spacings were investigated by vector magneto-optical Kerr effect magnetometry, magnetic force microscopy, and micromagnetic simulations. Two-step magnetization reversal demonstrates fourfold symmetry in the film plane resulting from the shape anisotropy in rings. Our numerical simulations show good agreement with the experiment.

  14. SUPERCONDUCTING QUADRUPOLE ARRAYS FOR MULTIPLE BEAM TRANSPORT

    SciTech Connect

    Rainer Meinke Carl Goodzeit Penny Ball Roger Bangerter

    2003-10-01

    The goal of this research was to develop concepts for affordable, fully functional arrays of superconducting quadrupoles for multi-beam transport and focusing in heavy ion fusion (HIF)accelerators. Previous studies by the Virtual National Laboratory (VNL) collaboration have shown that the multi-beam transport system (consisting of alternating gradient quadrupole magnets, a beam vacuum system, and the beam monitor and control system) will likely be one of the most expensive and critical parts of such an accelerator. This statement is true for near-term fusion research accelerators as well as accelerators for the ultimate goal of power production via inertial fusion. For this reason, research on superconducting quadrupole arrays is both timely and important for the inertial fusion energy (IFE) research program. This research will also benefit near-term heavy ion fusion facilities such as the Integrated Research Experiment (IRE)and/or the Integrated Beam Experiment (IBX). We considered a 2-prong approach that addresses the needs of both the nearer and longer term requirements of the inertial fusion program. First, we studied the flat coil quadrupole design that was developed by LLNL; this magnet is 150 mm long with a 50 mm aperture and thus is suitable for near term experiments that require magnets of a small length to aperture ratio. Secondly, we studied the novel double-helix quadrupole (DHQ) design in a small (3 x 3) array configuration; this design can provide an important step to the longer term solution of low-cost, easy to manufacture array constructions. Our Phase I studies were performed using the AMPERES magnetostatic analysis software. Consideration of these results led to plans for future magnet R&D construction projects. The first objective of Phase I was to develop the concept of a superconducting focusing array that meets the specific requirements of a heavy ion fusion accelerator. Detailed parameter studies for such quadrupole arrays were performed. Based on these studies, the primary magnet parameters and the general features required for a complete array system (including vacuum and cryostat) were identified. Basic system concepts were formulated to serve as guides for future development work. A related issue was to compare the applicability and benefits of two different magnet technologies for use in such a quadrupole array. Analytical studies were performed for each of the two coil designs, a flat coil based on an HCX quadrupole designed by LLNL and a doublehelix quadrupole designed by AML. These studies have confirmed the feasibility of using either of the two coil designs in a small array.

  15. Coil Array Design Inspired on the Kepler's Lenten Pretzel

    NASA Astrophysics Data System (ADS)

    Vazquez, F.; Solis, S. E.; Rodrguez, A. O.

    2008-08-01

    The RF coil arrays are an important part in Magnetic Resonance Imaging, since they are the main device for transmission and reception of the magnetic resonance signal. An RF coil array with a new configuration based on the Kepler's Lenten pretzel for the geocentric path of Mars is proposed in this work. The evenly distributed trajectories may serve as the basic configuration to form a coil array to adequately cover a region of interest for magnetic resonance experiments. The main goal is to investigate the electromagnetic properties of this coil array geometry to obtain an optimal design for its further construction. Hence, the electromagnetic properties of the coil array were numerical simulated using the finite element method and the quasi-static approach. Resulting simulations showed that there is an important concentration of magnetic field lines at the centre of the coil array. This is an advantage over other coil arrays where the magnetic field usually decreased at their geometrical centre. Both the electric and magnetic fields had also a very good uniformity. These characteristics made this coil design a good candidate for applications where the use of multi-coil technology is mandatory.

  16. Geometrical optimization of microstripe arrays for microbead magnetophoresis.

    PubMed

    Henriksen, Anders Dahl; Rozlosnik, Noemi; Hansen, Mikkel Fougt

    2015-09-01

    Manipulation of magnetic beads plays an increasingly important role in molecular diagnostics. Magnetophoresis is a promising technique for selective transportation of magnetic beads in lab-on-a-chip systems. We investigate periodic arrays of exchange-biased permalloy microstripes fabricated using a single lithography step. Magnetic beads can be continuously moved across such arrays by combining the spatially periodic magnetic field from microstripes with a rotating external magnetic field. By measuring and modeling the magnetophoresis properties of thirteen different stripe designs, we study the effect of the stripe geometry on the magnetophoretic transport properties of the magnetic microbeads between the stripes. We show that a symmetric geometry with equal width of and spacing between the microstripes facilitates faster transportation and that the optimal period of the periodic stripe array is approximately three times the height of the bead center over the microstripes. PMID:26543515

  17. Parallel arrays of Josephson junctions for submillimeter local oscillators

    NASA Technical Reports Server (NTRS)

    Pance, Aleksandar; Wengler, Michael J.

    1992-01-01

    In this paper we discuss the influence of the DC biasing circuit on operation of parallel biased quasioptical Josephson junction oscillator arrays. Because of nonuniform distribution of the DC biasing current along the length of the bias lines, there is a nonuniform distribution of magnetic flux in superconducting loops connecting every two junctions of the array. These DC self-field effects determine the state of the array. We present analysis and time-domain numerical simulations of these states for four biasing configurations. We find conditions for the in-phase states with maximum power output. We compare arrays with small and large inductances and determine the low inductance limit for nearly-in-phase array operation. We show how arrays can be steered in H-plane using the externally applied DC magnetic field.

  18. Magnetic and dielectric properties of one-dimensional array of S?=?1/2 linear trimer system Na{sub 2}Cu{sub 3}Ge{sub 4}O{sub 12}

    SciTech Connect

    Yasui, Yukio; Kawamura, Yuji; Kobayashi, Yoshiaki; Sato, Masatoshi

    2014-05-07

    Magnetic susceptibility ?, specific heat C, capacitance C{sub p}, and {sup 23}Na-NMR measurements have been carried out on polycrystalline samples of quantum spin linear trimer system Na{sub 2}Cu{sub 3}Ge{sub 4}O{sub 12}, which has the one-dimensional array of Cu{sub 3}O{sub 8} trimers formed of edge-sharing three CuO{sub 4} square planes. The exchange interactions between the Cu{sup 2+} (S?=?1/2) spins have been determined by analyzing ?-T and C-T curves. By employing the isolated S?=?1/2 Heisenberg trimer model above 70?K, the nearest-neighbor exchange couplings J{sub 1} and the second-neighbor one J{sub 2} in trimer have been evaluated to J{sub 1}/k{sub B}?=?30??20?K (antiferromagnetic) and J{sub 2}/k{sub B}?=?340??20?K. At low temperature region, two spins of the edge in the Cu{sub 3}O{sub 8} trimers form a nonmagnetic singlet by strong antiferromagnetic interaction J{sub 2}, and the spin left in the center of the Cu{sub 3}O{sub 8} trimer forms one-dimensional chains by the exchange interaction J{sub 3} between the trimers. By employing the S?=?1/2 uniform Heisenberg chain model below 70?K, we have evaluated to J{sub 3}/k{sub B}?=?18??1?K. The mechanism of multiferroic behavior at T{sub c}?=?2?K is discussed.

  19. Vortex chirality in an array of ferromagnetic dots.

    SciTech Connect

    Grimsditch, M.; Vavassori, P.; Novosad, V.; Metlushko, V.; Shima, H.; Otani, Y.; Fukamichi, K.; Materials Science Division; Univ. di Ferrara; Univ. of Illinois at Chicago; Tohoku Univ.; Japan Science and Technology Corp.

    2002-05-01

    Magnetization of an array of submicron permalloy dots was investigated using the diffracted magneto-optical Kerr effect. The shapes of the higher-order hysteresis loops are explained by the magnetic form factors associated with a vortex spin structure in each disk. The imaginary part of the form factor also explains the unexpected measured differences between hysteresis loops obtained on positive and negative diffraction orders. Shape effects account for the coherent chirality of the vortices over the array.

  20. Thermophotovoltaic Array Optimization

    SciTech Connect

    SBurger; E Brown; K Rahner; L Danielson; J Openlander; J Vell; D Siganporia

    2004-07-29

    A systematic approach to thermophotovoltaic (TPV) array design and fabrication was used to optimize the performance of a 192-cell TPV array. The systematic approach began with cell selection criteria that ranked cells and then matched cell characteristics to maximize power output. Following cell selection, optimization continued with an array packaging design and fabrication techniques that introduced negligible electrical interconnect resistance and minimal parasitic losses while maintaining original cell electrical performance. This paper describes the cell selection and packaging aspects of array optimization as applied to fabrication of a 192-cell array.

  1. Demonstration of successful construction of linear arrays of Hall probes used to digitally image

    NASA Technical Reports Server (NTRS)

    1996-01-01

    Researchers at Marshall's Space Science Laboratory successfully demonstrate that linear arrays of Hall probes can be constructed in high Hall coefficient films and used to digitally image magnetic fields. This research is beneficial to visually imaging any magnetic field.

  2. Solar array switching unit

    NASA Technical Reports Server (NTRS)

    Craig, Jr., Calvin L. (Inventor)

    2000-01-01

    A solar array switching (SASU) unit (22) according to the present invention includes a control system (24), a solar cell array (26) and switch circuits (28). The SASU unit (22) is associated with a power card (30) for receiving an output from the array (26). The array (26) has a number (0.5Y) of rows (38) each of which includes a pair of cell strings (42) separated by one of the switch circuits (28). Each of the strings (42) includes a number (X) of cells in electrical series. The SASU (22) switches the array (26) between a short string configuration where the array (26) effectively includes Y strings of X length, and a long string configuration where the array (26) effectively includes 0.5Y strings of 2X length. The SASU (22) thereby facilitates the use of solar power for space missions where solar intensity, operating temperature or other factors vary significantly.

  3. The NASA Inductrack Model Rocket Launcher at the Lawrence Livermore National Laboratory

    NASA Technical Reports Server (NTRS)

    Tung, L. S.; Post, R. F.; Cook, E.; Martinez-Frias, J.

    2000-01-01

    The Inductrack magnetic levitation system, developed at the Lawrence Livermore National Laboratory, is being studied for its possible use for launching rockets. Under NASA sponsorship, a small model system is being constructed at the Laboratory to pursue key technical aspects of this proposed application. The Inductrack is a passive magnetic levitation system employing special arrays of high-field permanent magnets (Halbach arrays) on the levitating carrier, moving above a "track" consisting of a close-packed array of shorted coils with which are interleaved with special drive coils. Halbach arrays produce a strong spatially periodic magnetic field on the front surface of the arrays, while canceling the field on their back surface. Relative motion between the Halbach arrays and the track coils induces currents in those coils. These currents levitate the carrier cart by interacting with the horizontal component of the magnetic field. Pulsed currents in the drive coils, synchronized with the motion of the carrier, interact with the vertical component of the magnetic field to provide acceleration forces. Motional stability, including resistance to both vertical and lateral aerodynamic forces, is provided by having Halbach arrays that interact with both the upper and the lower sides of the track coils. In its completed form the model system that is under construction will have a track approximately 100 meters in length along which the carrier cart will be propelled up to peak speeds of Mach 0.4 to 0.5 before being decelerated. Preliminary studies of the parameters of a full-scale system have also been made. These studies address the problems of scale-up, including means to simplify the track construction and to reduce the cost of the pulsed-power systems needed for propulsion.

  4. Exploration of Artificial Frustrated Magnets

    SciTech Connect

    Samarth, Nitin; Schiffer, Peter

    2015-02-17

    This program encompasses experimental and theoretical studies of arrays of nanometer-scale magnets known as “artificial frustrated magnets”. These magnets are small and closely spaced, so that their behavior as a collective group is complex and reveals insights into how such collections of interacting objects behave as a group. In particular, the placement of the magnets is such that the interactions between them are “frustrated”, in that they compete with each other. These systems are analogs to a class of magnetic materials in which the lattice geometry frustrates interactions between individual atomic moments, and in which a wide range of novel physical phenomena have been recently observed. The advantage to studying the arrays is that they are both designable and resolvable: i.e., the experiments can control all aspects of the array geometry, and can also observe how individual elements of the arrays behave. This research program demonstrated a number of phenomena including the role of multiple collective interactions, the feasibility of using systems with their magnetism aligned perpendicular to the plane of the array, the importance of disorder in the arrays, and the possibility of using high temperatures to adjust the magnet orientations. All of these phenomena, and others explored in this program, add to the body of knowledge around collective magnetic behavior and magnetism in general. Aside from building scientific knowledge in an important technological area, with relevance to computing and memory, the program also gave critical support to the education of students working on the experiments.

  5. Reconfigurable multivariable MEMS sensor array

    NASA Astrophysics Data System (ADS)

    van der Velden, Stephen; Powlesland, Ian; Singh, Jugdutt

    2010-04-01

    Research into operational aspects of mini (<5kg) unmanned aerial vehicles (UAV) and structural health monitoring systems (SHM) is being conducted at the Defence Science and Technology Organisation and La Trobe University. A fundamental area of interest is investigating the problems associated with robustness of the control and health monitoring sensors for such systems. While many technologies for UAV and SHM systems can be, and have been, adapted from those currently available in large manned aircraft; cost, weight, and size constraints have prevented mini UAVs from including many of the robust mechanisms common to larger aircraft. Moreover, the ubiquitous nature of the sensing requirements for SHM systems has limited their uptake, due mainly to the same issues of cost, weight and size. This paper details the design of a reconfigurable multivariable MEMS (Micro Electro Mechanical System) array to address these issues. This array is composed of multiple instances of identical sensors, which can be dynamically reconfigured to achieve the desired measurand(s) with tradeoffs against accuracy. The available measurands include such items as; accelerations, rotational rates, magnetic fields (X, Y and Z directions), temperature and pressure. The paper presents the design of a reconfigurable multivariable MEMS sensor array together with simulation results.

  6. The HELIOS silicon detector array

    NASA Astrophysics Data System (ADS)

    Marley, S. T.

    2008-10-01

    A prototype detector array has been constructed for use in the Helical Orbit Spectrometer (HELIOS) at the ATLAS facility at Argonne National Laboratory. HELIOS is a high-resolution spectrometer for use in studying reactions in inverse kinematics on hydrogen or helium targets. HELIOS consists of a large bore, 3T superconducting solenoid oriented with the magnetic and beam axes aligned. The detector array is comprised of four modules each with six 1.2 x 5.6cm position sensitive silicon detectors. On each module, the detectors were affixed with conductive epoxy and wire bonded to custom made multi-layer printed circuit boards. To keep the radial extent of the detectors to a minimum, the modules were assembled on a hollow 1.6 x 1.6 x 68.8 cm aluminum rail centered on the beam axis located upstream from the target. To characterize the timing, position, and energy resolutions, the detectors were evaluated at the Western Michigan University Accelerator Laboratory using elastic proton-proton scattering. The construction, assembly and preliminary testing of the array will be discussed.

  7. Energy Minimization and ac Demagnetization in a Nanomagnet Array

    NASA Astrophysics Data System (ADS)

    Ke, X.; Li, J.; Nisoli, C.; Lammert, Paul E.; McConville, W.; Wang, R. F.; Crespi, V. H.; Schiffer, P.

    2008-07-01

    We study ac demagnetization in frustrated arrays of single-domain ferromagnetic islands, exhaustively resolving every (Ising-like) magnetic degree of freedom in the systems. Although the net moment of the arrays is brought near zero by a protocol with sufficiently small step size, the final magnetostatic energy of the demagnetized array continues to decrease for finer-stepped protocols and does not extrapolate to the ground-state energy. The resulting complex disordered magnetic state can be described by a maximum-entropy ensemble constrained to satisfy just nearest-neighbor correlations.

  8. Superconducting Bolometer Array Architectures

    NASA Technical Reports Server (NTRS)

    Benford, Dominic; Chervenak, Jay; Irwin, Kent; Moseley, S. Harvey; Shafer, Rick; Staguhn, Johannes; Wollack, Ed; Oegerle, William (Technical Monitor)

    2002-01-01

    The next generation of far-infrared and submillimeter instruments require large arrays of detectors containing thousands of elements. These arrays will necessarily be multiplexed, and superconducting bolometer arrays are the most promising present prospect for these detectors. We discuss our current research into superconducting bolometer array technologies, which has recently resulted in the first multiplexed detections of submillimeter light and the first multiplexed astronomical observations. Prototype arrays containing 512 pixels are in production using the Pop-Up Detector (PUD) architecture, which can be extended easily to 1000 pixel arrays. Planar arrays of close-packed bolometers are being developed for the GBT (Green Bank Telescope) and for future space missions. For certain applications, such as a slewed far-infrared sky survey, feedhorncoupling of a large sparsely-filled array of bolometers is desirable, and is being developed using photolithographic feedhorn arrays. Individual detectors have achieved a Noise Equivalent Power (NEP) of -10(exp 17) W/square root of Hz at 300mK, but several orders of magnitude improvement are required and can be reached with existing technology. The testing of such ultralow-background detectors will prove difficult, as this requires optical loading of below IfW. Antenna-coupled bolometer designs have advantages for large format array designs at low powers due to their mode selectivity.

  9. Programmable Aperture with MEMS Microshutter Arrays

    NASA Technical Reports Server (NTRS)

    Moseley, Samuel; Li, Mary; Kutyrev, Alexander; Kletetschka, Gunther; Fettig, Rainer

    2011-01-01

    A microshutter array (MSA) has been developed for use as an aperture array for multi-object selections in James Webb Space Telescope (JWST) technology. Light shields, molybdenum nitride (MoN) coating on shutters, and aluminum/aluminum oxide coatings on interior walls are put on each shutter for light leak prevention, and to enhance optical contrast. Individual shutters are patterned with a torsion flexure that permits shutters to open 90 deg. with a minimized mechanical stress concentration. The shutters are actuated magnetically, latched, and addressed electrostatically. Also, micromechanical features are tailored onto individual shutters to prevent stiction. An individual shutter consists of a torsion hinge, a shutter blade, a front electrode that is coated on the shutter blade, a backside electrode that is coated on the interior walls, and a magnetic cobalt-iron coating. The magnetic coating is patterned into stripes on microshutters so that shutters can respond to an external magnetic field for the magnetic actuation. A set of column electrodes is placed on top of shutters, and a set of row electrodes on sidewalls is underneath the shutters so that they can be electrostatically latched open. A linear permanent magnet is aligned with the shutter rows and is positioned above a flipped upside-down array, and sweeps across the array in a direction parallel to shutter columns. As the magnet sweeps across the array, sequential rows of shutters are rotated from their natural horizontal orientation to a vertical open position, where they approach vertical electrodes on the sidewalls. When the electrodes are biased with a sufficient electrostatic force to overcome the mechanical restoring force of torsion bars, shutters remain latched to vertical electrodes in their open state. When the bias is removed, or is insufficient, the shutters return to their horizontal, closed positions. To release a shutter, both the electrode on the shutter and the one on the back wall where the shutter sits are grounded. The shutters with one or both ungrounded electrodes are held open. Sub-micron bumps underneath light shields and silicon ribs on back walls are the two features to prevent stiction. These features ensure that the microshutter array functions properly in mechanical motions. The MSA technology can be used primarily in multi-object imaging and spectroscopy, photomask generation, light switches, and in the stepper equipment used to make integrated circuits and MEMS (microelectromechanical systems) devices.

  10. Microshutter Arrays for James Webb Space Telescope

    NASA Technical Reports Server (NTRS)

    Li, Mary J.; Acuna, Nadine; Beamesderfer, Michael; Ewin, Audrey; Fettig, Rainer; Franz, Dave; Hess, Larry; Hu, Ron; Kelly, Dan; King, Todd

    2004-01-01

    Two-dimensional MEMS microshutter arrays are being developed at NASA Goddard Space Flight Center for use in the near-infrared region on the James Webb Space Telescope (JWST). The microshutter arrays are designed for the selective transmission of light with high efficiency and high contrast. The JWST environment requires cryogenic operation at 35K. Microshutter arrays are fabricated out of silicon-oxide-insulated (SOI) silicon wafers. Arrays are close-packed silicon nitride membranes with a pixel size of 100x200 p. Individual shutters are patterned with a torsion flexure permitting shutters to open 90 degrees with a minimized mechanical stress concentration. The mechanical shutter arrays are fabricated using MEMS technologies. The processing includes a multi- layer metal deposition and patterning of shutter electrodes and magnetic pads, reactive ion etching (NE) of the front side to form shutters out of the nitride membrane, an anisotropic back-etch for wafer thinning, followed by a deep RIE (DRIE) back-etch down to the nitride shutter membrane to form W e s and relieve shutters from the silicon substrate. An additional metal deposition and patterning is used to form back electrodes. Shutters are actuated using a magnetic force and latched using an electrostatic force. . . . KEYWORDS: microshutter, MEMS, RIE, DRIE, micro-optics, near inbred, space telescope

  11. Electronic Switch Arrays for Managing Microbattery Arrays

    NASA Technical Reports Server (NTRS)

    Mojarradi, Mohammad; Alahmad, Mahmoud; Sukumar, Vinesh; Zghoul, Fadi; Buck, Kevin; Hess, Herbert; Li, Harry; Cox, David

    2008-01-01

    Integrated circuits have been invented for managing the charging and discharging of such advanced miniature energy-storage devices as planar arrays of microscopic energy-storage elements [typically, microscopic electrochemical cells (microbatteries) or microcapacitors]. The architecture of these circuits enables implementation of the following energy-management options: dynamic configuration of the elements of an array into a series or parallel combination of banks (subarrarys), each array comprising a series of parallel combination of elements; direct addressing of individual banks for charging/or discharging; and, disconnection of defective elements and corresponding reconfiguration of the rest of the array to utilize the remaining functional elements to obtain the desited voltage and current performance. An integrated circuit according to the invention consists partly of a planar array of field-effect transistors that function as switches for routing electric power among the energy-storage elements, the power source, and the load. To connect the energy-storage elements to the power source for charging, a specific subset of switches is closed; to connect the energy-storage elements to the load for discharging, a different specific set of switches is closed. Also included in the integrated circuit is circuitry for monitoring and controlling charging and discharging. The control and monitoring circuitry, the switching transistors, and interconnecting metal lines are laid out on the integrated-circuit chip in a pattern that registers with the array of energy-storage elements. There is a design option to either (1) fabricate the energy-storage elements in the corresponding locations on, and as an integral part of, this integrated circuit; or (2) following a flip-chip approach, fabricate the array of energy-storage elements on a separate integrated-circuit chip and then align and bond the two chips together.

  12. Optimized Superconducting Quadrupole Arrays for Multiple Beam Transport

    SciTech Connect

    Meinke, Rainer, B.; Goodzeit, Carl, L.; Ball, Millicent, J.

    2005-09-20

    This research project advanced the development of reliable, cost-effective arrays of superconducting quadrupole magnets for use in multi-beam inertial fusion accelerators. The field in each array cell must be identical and meet stringent requirements for field quality and strength. An optimized compact array design using flat double-layer pancake coils was developed. Analytical studies of edge termination methods showed that it is feasible to meet the requirements for field uniformity in all cells and elimination of stray external field in several ways: active methods that involve placement of field compensating coils on the periphery of the array or a passive method that involves use of iron shielding.

  13. Carbon nanotube nanoelectrode arrays

    DOEpatents

    Ren, Zhifeng; Lin, Yuehe; Yantasee, Wassana; Liu, Guodong; Lu, Fang; Tu, Yi

    2008-11-18

    The present invention relates to microelectode arrays (MEAs), and more particularly to carbon nanotube nanoelectrode arrays (CNT-NEAs) for chemical and biological sensing, and methods of use. A nanoelectrode array includes a carbon nanotube material comprising an array of substantially linear carbon nanotubes each having a proximal end and a distal end, the proximal end of the carbon nanotubes are attached to a catalyst substrate material so as to form the array with a pre-determined site density, wherein the carbon nanotubes are aligned with respect to one another within the array; an electrically insulating layer on the surface of the carbon nanotube material, whereby the distal end of the carbon nanotubes extend beyond the electrically insulating layer; a second adhesive electrically insulating layer on the surface of the electrically insulating layer, whereby the distal end of the carbon nanotubes extend beyond the second adhesive electrically insulating layer; and a metal wire attached to the catalyst substrate material.

  14. Reconfigurable mosaic annular arrays.

    PubMed

    Thomenius, Kai E; Wodnicki, Robert; Cogan, Scott D; Fisher, Rayette A; Burdick, Bill; Smith, L Scott; Khuri-Yakub, Pierre; Lin, Der-Song; Zhuang, Xuefeng; Bonitz, Barry; Davies, Todd; Thomas, Glen; Woychik, Charles

    2014-07-01

    Mosaic annular arrays (MAA) based on reconfigurable array (RA) transducer electronics assemblies are presented as a potential solution for future highly integrated ultrasonic transducer subsystems. Advantages of MAAs include excellent beam quality and depth of field resulting from superior elevational focus compared with 1-D electronically scanned arrays, as well as potentially reduced cost, size, and power consumption resulting from the use of a limited number of beamforming channels for processing a large number of subelements. Specific design tradeoffs for these highly integrated arrays are discussed in terms of array specifications for center frequency, element pitch, and electronic switch-on resistance. Large-area RAs essentially function as RC delay lines. Efficient architectures which take into account RC delay effects are presented. Architectures for integration of the transducer and electronics layers of large-area array implementations are reviewed. PMID:24960699

  15. Solar array automation limitations

    NASA Technical Reports Server (NTRS)

    Trumble, Terry M.

    1990-01-01

    Significant progress in the automation of the spacecraft electrical power systems has been made within the past few years. This is especially important with the development of the space station and the increasing demand on the electrical power systems for future satellites. The key element of the spacecraft power system, the solar arrays which supply the power, will have to grow to supply many tens of kilowatts of power within the next twenty years. This growth will be accompanied by the problems associated with large distributed power systems. The growth of the arrays, the on-array management problems and potential solutions to array degradation or failure are discussed. Multilowatt arrays for unmanned spacecraft with comments on the implications of array degradation for manned spacecraft are discussed.

  16. Experiments with Electrodynamic Wheels

    NASA Astrophysics Data System (ADS)

    Gaul, Nathan; Corey, Daniel; Cordrey, Vincent; Majewski, Walerian

    2015-04-01

    Our experiments were involving inductive magnetic levitation. A Halbach array is a system in which a series of magnets is arranged in a manner such that the magnetic field is cancelled on one side of the array while strengthening the field on the other. We constructed two circular Halbach wheels, making the strong magnetic field on the outer rim of the ring. Such system is usually dubbed as an Electrodynamic Wheel (EDW). Rotating this wheel around a horizontal axis above a flat conducting surface should induce eddy currents in said surface through the variable magnetic flux. The eddy currents produce, in turn, their own magnetic fields which interact with the magnets of the EDW. We demonstrated that these interactions produce both drag and lift forces on the EDW which can theoretically be used for lift and propulsion of the EDW. The focus of our experiments is determining how to maximize the lift-to-drag ratio by the proper choice of the induction element. We will also describe our experiments with a rotating circular Halbach array having the strong magnetic field of about 1 T on the flat side of the ring, and acting as a hovercraft.

  17. Rectenna array measurement results

    NASA Astrophysics Data System (ADS)

    Dickinson, R. M.

    1980-12-01

    The measured performance characteristics of a rectenna array are reviewed and compared to the performance of a single element. It is shown that the performance may be extrapolated from the individual element to that of the collection of elements. Techniques for current and voltage combining are demonstrated. The array performance as a function of various operating parameters is characterized and techniques for overvoltage protection and automatic fault clearing in the array are demonstrated. A method for detecting failed elements also exists. Instrumentation for deriving performance effectiveness is described. Measured harmonic radiation patterns and fundamental frequency scattered patterns for a low level illumination rectenna array are presented.

  18. Solar array cost reductions.

    NASA Technical Reports Server (NTRS)

    Bernatowicz, D. T.

    1972-01-01

    There is great interest in reducing the cost of solar arrays, which will continue to be the prime power source for unmanned spacecraft for some time. The cost of solar power systems over the last decade, and means by which cost reductions may be achieved in the future are discussed. It is shown that the total system cost index is a function of solar array area, and that cost decreases as production of solar arrays goes up. This effect can be exploited more than has been done in the past by making common building blocks from which a variety of arrays can be assembled.

  19. Integrated avalanche photodiode arrays

    DOEpatents

    Harmon, Eric S.

    2015-07-07

    The present disclosure includes devices for detecting photons, including avalanche photon detectors, arrays of such detectors, and circuits including such arrays. In some aspects, the detectors and arrays include a virtual beveled edge mesa structure surrounded by resistive material damaged by ion implantation and having side wall profiles that taper inwardly towards the top of the mesa structures, or towards the direction from which the ion implantation occurred. Other aspects are directed to masking and multiple implantation and/or annealing steps. Furthermore, methods for fabricating and using such devices, circuits and arrays are disclosed.

  20. Sorting white blood cells in microfabricated arrays

    NASA Astrophysics Data System (ADS)

    Castelino, Judith Andrea Rose

    Fractionating white cells in microfabricated arrays presents the potential for detecting cells with abnormal adhesive or deformation properties. A possible application is separating nucleated fetal red blood cells from maternal blood. Since fetal cells are nucleated, it is possible to extract genetic information about the fetus from them. Separating fetal cells from maternal blood would provide a low cost noninvasive prenatal diagnosis for genetic defects, which is not currently available. We present results showing that fetal cells penetrate further into our microfabricated arrays than adult cells, and that it is possible to enrich the fetal cell fraction using the arrays. We discuss modifications to the array which would result in further enrichment. Fetal cells are less adhesive and more deformable than adult white cells. To determine which properties limit penetration, we compared the penetration of granulocytes and lymphocytes in arrays with different etch depths, constriction size, constriction frequency, and with different amounts of metabolic activity. The penetration of lymphocytes and granulocytes into constrained and unconstrained arrays differed qualitatively. In constrained arrays, the cells were activated by repeated shearing, and the number of cells stuck as a function of distance fell superexponentially. In unconstrained arrays the number of cells stuck fell slower than an exponential. We attribute this result to different subpopulations of cells with different sticking parameters. We determined that penetration in unconstrained arrays was limited by metabolic processes, and that when metabolic activity was reduced penetration was limited by deformability. Fetal cells also contain a different form of hemoglobin with a higher oxygen affinity than adult hemoglobin. Deoxygenated cells are paramagnetic and are attracted to high magnetic field gradients. We describe a device which can separate cells using 10 ?m magnetic wires to deflect the paramagnetic cells. We present preliminary results from a test system that separates paramagnetic beads from latex beads. The separation is limited by our ability to produce the high field gradients which are necessary to separate cells according to their hemoglobin content, and we present estimates of the magnetic gradients we achieved.

  1. Spherical Wire-Array Implosion Experiments

    NASA Astrophysics Data System (ADS)

    Hall, G. N.; Ciardi, A.; Palmer, J. B. A.

    2005-10-01

    The results of the first spherical wire array z-pinch implosion experiments are presented. Arrays were driven by the MAGPIE generator (1MA, 240ns) and consisted of 8x25?m aluminium wires forming the lines of longitude of a sphere with an equatorial diameter of 21mm. Plasma dynamics around each pole of the spherical array are comparable to those observed in radial wire array z-pinch experiments. The smaller radius at the poles produces a higher magnetic field than at the equator, leading to a higher rate of ablation of the wires into plasma. The ablated plasma from each pole forms a jet; and the jets from the poles collide near the centre of the sphere to produce a high-density precursor plasma. Later in time the array implodes, with a pair of plasma bubbles being launched from the poles towards the centre of the array, driving a pair of shock waves onto the precursor plasma. This research was sponsored by Sandia National Laboratories Albuquerque, the SSAA program of NNSA under DOE Cooperative Agreement DE-FC03-02NA00057.

  2. Testing Microshutter Arrays Using Commercial FPGA Hardware

    NASA Technical Reports Server (NTRS)

    Rapchun, David

    2008-01-01

    NASA is developing micro-shutter arrays for the Near Infrared Spectrometer (NIRSpec) instrument on the James Webb Space Telescope (JWST). These micro-shutter arrays allow NIRspec to do Multi Object Spectroscopy, a key part of the mission. Each array consists of 62414 individual 100 x 200 micron shutters. These shutters are magnetically opened and held electrostatically. Individual shutters are then programmatically closed using a simple row/column addressing technique. A common approach to provide these data/clock patterns is to use a Field Programmable Gate Array (FPGA). Such devices require complex VHSIC Hardware Description Language (VHDL) programming and custom electronic hardware. Due to JWST's rapid schedule on the development of the micro-shutters, rapid changes were required to the FPGA code to facilitate new approaches being discovered to optimize the array performance. Such rapid changes simply could not be made using conventional VHDL programming. Subsequently, National Instruments introduced an FPGA product that could be programmed through a Labview interface. Because Labview programming is considerably easier than VHDL programming, this method was adopted and brought success. The software/hardware allowed the rapid change the FPGA code and timely results of new micro-shutter array performance data. As a result, numerous labor hours and money to the project were conserved.

  3. Focal plane array with modular pixel array components for scalability

    SciTech Connect

    Kay, Randolph R; Campbell, David V; Shinde, Subhash L; Rienstra, Jeffrey L; Serkland, Darwin K; Holmes, Michael L

    2014-12-09

    A modular, scalable focal plane array is provided as an array of integrated circuit dice, wherein each die includes a given amount of modular pixel array circuitry. The array of dice effectively multiplies the amount of modular pixel array circuitry to produce a larger pixel array without increasing die size. Desired pixel pitch across the enlarged pixel array is preserved by forming die stacks with each pixel array circuitry die stacked on a separate die that contains the corresponding signal processing circuitry. Techniques for die stack interconnections and die stack placement are implemented to ensure that the desired pixel pitch is preserved across the enlarged pixel array.

  4. Solar array stepping to minimize array excitation

    NASA Technical Reports Server (NTRS)

    Bhat, Mahabaleshwar K. P. (Inventor); Liu, Tung Y. (Inventor); Plescia, Carl T. (Inventor)

    1989-01-01

    Mechanical oscillations of a mechanism containing a stepper motor, such as a solar-array powered spacecraft, are reduced and minimized by the execution of step movements in pairs of steps, the period between steps being equal to one-half of the period of torsional oscillation of the mechanism. Each pair of steps is repeated at needed intervals to maintain desired continuous movement of the portion of elements to be moved, such as the solar array of a spacecraft. In order to account for uncertainty as well as slow change in the period of torsional oscillation, a command unit may be provided for varying the interval between steps in a pair.

  5. Investigation of magnetic field manipulated electrons produced from laser-driven ultrafast x-ray sources using x-ray emission spectroscopy

    NASA Astrophysics Data System (ADS)

    Lee, Changju; Davidson, R. Andrew; Guo, Ting

    2015-03-01

    We used x-ray emission spectroscopy to study energetic electrons (10-100?keV) generated at the laser focus of an intense ultrafast laser interacting with a primary thin film tape target. The electrons penetrated the tape and reached a secondary target of thin metal foils as the probe. The trajectories of these electrons were manipulated with an external magnetic field generated from a home-made Halbach magnet. The interaction of these energetic electrons with the probe produced characteristic x-rays, which were used to infer the flux and temperature of the electrons emitted from the laser focus at the primary tape target. A potential application using these energetic electrons is discussed.

  6. Solar array deployment mechanism

    NASA Astrophysics Data System (ADS)

    Calassa, Mark C.; Kackley, Russell

    1995-05-01

    This paper describes a Solar Array Deployment Mechanism (SADM) used to deploy a rigid solar array panel on a commercial spacecraft. The application required a deployment mechanism design that was not only lightweight, but also could be produced and installed at the lowest possible cost. This paper covers design, test, and analysis of a mechanism that meets these requirements.

  7. ISS Solar Array Management

    NASA Technical Reports Server (NTRS)

    Williams, James P.; Martin, Keith D.; Thomas, Justin R.; Caro, Samuel

    2010-01-01

    The International Space Station (ISS) Solar Array Management (SAM) software toolset provides the capabilities necessary to operate a spacecraft with complex solar array constraints. It monitors spacecraft telemetry and provides interpretations of solar array constraint data in an intuitive manner. The toolset provides extensive situational awareness to ensure mission success by analyzing power generation needs, array motion constraints, and structural loading situations. The software suite consists of several components including samCS (constraint set selector), samShadyTimers (array shadowing timers), samWin (visualization GUI), samLock (array motion constraint computation), and samJet (attitude control system configuration selector). It provides high availability and uptime for extended and continuous mission support. It is able to support two-degrees-of-freedom (DOF) array positioning and supports up to ten simultaneous constraints with intuitive 1D and 2D decision support visualizations of constraint data. Display synchronization is enabled across a networked control center and multiple methods for constraint data interpolation are supported. Use of this software toolset increases flight safety, reduces mission support effort, optimizes solar array operation for achieving mission goals, and has run for weeks at a time without issues. The SAM toolset is currently used in ISS real-time mission operations.

  8. Solar array cost reduction

    NASA Technical Reports Server (NTRS)

    Bernatowicz, D. T.

    1972-01-01

    A brief description is given of the cost of solar power systems over the last decade and means by which cost reductions may be achieved in the future. Costs were broken down into nonrecurring and recurring costs for solar array, battery, and power conditioning. Correlation of costs with power were poor; however, costs correlated reasonably well with the array area.

  9. Solar array deployment mechanism

    NASA Technical Reports Server (NTRS)

    Calassa, Mark C.; Kackley, Russell

    1995-01-01

    This paper describes a Solar Array Deployment Mechanism (SADM) used to deploy a rigid solar array panel on a commercial spacecraft. The application required a deployment mechanism design that was not only lightweight, but also could be produced and installed at the lowest possible cost. This paper covers design, test, and analysis of a mechanism that meets these requirements.

  10. Array for detecting microbes

    DOEpatents

    Andersen, Gary L.; DeSantis, Todd D.

    2014-07-08

    The present embodiments relate to an array system for detecting and identifying biomolecules and organisms. More specifically, the present embodiments relate to an array system comprising a microarray configured to simultaneously detect a plurality of organisms in a sample at a high confidence level.

  11. High density pixel array

    NASA Technical Reports Server (NTRS)

    Wiener-Avnear, Eliezer (Inventor); McFall, James Earl (Inventor)

    2004-01-01

    A pixel array device is fabricated by a laser micro-milling method under strict process control conditions. The device has an array of pixels bonded together with an adhesive filling the grooves between adjacent pixels. The array is fabricated by moving a substrate relative to a laser beam of predetermined intensity at a controlled, constant velocity along a predetermined path defining a set of grooves between adjacent pixels so that a predetermined laser flux per unit area is applied to the material, and repeating the movement for a plurality of passes of the laser beam until the grooves are ablated to a desired depth. The substrate is of an ultrasonic transducer material in one example for fabrication of a 2D ultrasonic phase array transducer. A substrate of phosphor material is used to fabricate an X-ray focal plane array detector.

  12. Multibeam Phased Array Antennas

    NASA Technical Reports Server (NTRS)

    Popovic, Zoya; Romisch, Stefania; Rondineau, Sebastien

    2004-01-01

    In this study, a new architecture for Ka-band multi-beam arrays was developed and demonstrated experimentally. The goal of the investigation was to demonstrate a new architecture that has the potential of reducing the cost as compared to standard expensive phased array technology. The goals of this specific part of the project, as stated in the yearly statement of work in the original proposal are: 1. Investigate bounds on performance of multi-beam lens arrays in terms of beamwidths, volume (size), isolation between beams, number of simultaneous beams, etc. 2. Design a small-scale array to demonstrate the principle. The array will be designed for operation around 3OGHz (Ka-band), with two 10-degree beamwidth beams. 3. Investigate most appropriate way to accomplish fine-tuning of the beam pointing within 5 degrees around the main beam pointing angle.

  13. Micromachined electrode array

    DOEpatents

    Okandan, Murat (Edgewood, NM); Wessendorf, Kurt O. (Albuquerque, NM)

    2007-12-11

    An electrode array is disclosed which has applications for neural stimulation and sensing. The electrode array, in certain embodiments, can include a plurality of electrodes each of which is flexibly attached to a common substrate using a plurality of springs to allow the electrodes to move independently. In other embodiments of the electrode array, the electrodes can be fixed to the substrate. The electrode array can be formed from a combination of bulk and surface micromachining, and can include electrode tips having an electroplated metal (e.g. platinum, iridium, gold or titanium) or a metal oxide (e.g. iridium oxide) for biocompatibility. The electrode array can be used to form a part of a neural prosthesis, and is particularly well adapted for use in an implantable retinal prosthesis.

  14. Microfabricated ion trap array

    DOEpatents

    Blain, Matthew G. (Albuquerque, NM); Fleming, James G. (Albuquerque, NM)

    2006-12-26

    A microfabricated ion trap array, comprising a plurality of ion traps having an inner radius of order one micron, can be fabricated using surface micromachining techniques and materials known to the integrated circuits manufacturing and microelectromechanical systems industries. Micromachining methods enable batch fabrication, reduced manufacturing costs, dimensional and positional precision, and monolithic integration of massive arrays of ion traps with microscale ion generation and detection devices. Massive arraying enables the microscale ion traps to retain the resolution, sensitivity, and mass range advantages necessary for high chemical selectivity. The reduced electrode voltage enables integration of the microfabricated ion trap array with on-chip circuit-based rf operation and detection electronics (i.e., cell phone electronics). Therefore, the full performance advantages of the microfabricated ion trap array can be realized in truly field portable, handheld microanalysis systems.

  15. Modifying Wire Array Z-pinch Ablation Structure and Implosion Dynamics Using Coiled Arrays

    SciTech Connect

    Hall, Gareth N.; Bland, Simon N.; Lebedev, Sergey V.; Chittenden, Jeremy P.; Palmer, James B. A.; Suzuki-Vidal, Francisco A.; Swadling, George F.; Niasse, Nicolas; Knapp, P. F.; Blesener, I. C.; McBride, R. D.; Chalenski, D. A.; Bell, K. S.; Greenly, J. B.; Blanchard, T.; Wilhelm, H.; Hammer, D. A.; Kusse, B. R.; Bott, Simon C.

    2009-01-21

    Coiled arrays, a cylindrical array in which each wire is formed into a helix, suppress the modulation of ablation at the fundamental wavelength. Outside the vicinity of the wire cores, ablation flow from coiled arrays is modulated at the coil wavelength and has a 2-stream structure in the r,{theta} plane. Within the vicinity of the helical wires, ablation is concentrated at positions with the greatest azimuthal displacement and plasma is axially transported from these positions such that the streams become aligned with sections of the coil furthest from the array axis. The GORGON MHD code accurately reproduces this observed ablation structure, which can be understood in terms of JxB forces that result from the interaction of the global magnetic field with a helical current path as well as additional current paths suggested by the simulations. With this ability to control where ablation streamers occur, large wavelength coils were constructed such that the breaks that form in the wires had sufficient axial separation to prevent perturbations in the implosion sheath from merging. This produces a new mode of implosion in which the global instability can be controlled and perturbations correlated between all wires in an array. For large wavelength 8-wire coiled arrays, this produced a dramatic increase in x-ray power, equalling that of a 32-wire straight array. These experiments were carried out on the MAGPIE generator (1 MA, 240 ns) at Imperial College, and the COBRA generator (1 MA, 100 ns) at Cornell University.

  16. Tailoring particle arrays by isotropic plasma etching: an approach towards percolated perpendicular media.

    PubMed

    Brombacher, Christoph; Saitner, Marc; Pfahler, Christian; Plettl, Alfred; Ziemann, Paul; Makarov, Denys; Assmann, Daniel; Siekman, Martin H; Abelmann, Leon; Albrecht, Manfred

    2009-03-11

    Plasma etching of densely packed arrays of polystyrene particles leads to arrays of spherical nanostructures with adjustable diameters while keeping the periodicity fixed. A linear dependence between diameter of the particles and etching time was observed for particles down to sizes of sub-50 nm. Subsequent deposition of Co/Pt multilayers with perpendicular magnetic anisotropy onto these patterns leads to an exchange-decoupled, single-domain magnetic nanostructure array surrounded by a continuous magnetic film. The magnetic reversal characteristic of the film-particle system is dominated by domain nucleation and domain wall pinning at the particle locations, creating a percolated perpendicular media system. PMID:19417519

  17. A Compact, Modular Superconducting Bolometer Array Package

    NASA Technical Reports Server (NTRS)

    Benford, Dominic J.

    2008-01-01

    We have designed a detector package to house a superconducting bolometer array, SQUID multiplexers, bias and integration circuitry, optical filtering, electrical connectors, and thermal/mechanical interfaces. This package has been used successfully in the GISMO 2mm camera, a 128-pixel camera operating at a base temperature of 270mK. Operation at lower temperatures is allowed by providing direct heat sinking to the SQUIDS and bias resistors, which generate the bulk of the dissipation in the package. Standard electrical connectors provide reliable contact while enabling quick installation and removal of the package. Careful design has gone into the compensation for differing thermal expansions, the need for heat sinking of the bolometer array, and the placement of magnetic shielding in critical areas. In this presentation, we detail the design and performance of this detector package and describe its scalability to 1280- pixel arrays in the near future.

  18. Metal Nanoparticle Arrays from Diblock Copolymer Templates

    NASA Astrophysics Data System (ADS)

    Sandstrom, Robert L.; Black, C. T.; Guarini, K. W.

    2002-03-01

    We use diblock copolymer thin film templates as masks for generating metal nanoparticle arrays composed of a wide variety of materials. The resulting nanoparticle diameters and nearest-neighbor separations can be controlled by varying polymer molecular weights, and in this experiment we present 20 nm diameter nanostructures on a 40 nm pitch. Our straightforward fabrication process consists of electron-beam deposition of metal into the template holes, followed by polymer dissolution to produce nanoparticle arrays over large wafer areas (up to 8 inch diameters). This procedure is analogous to the metal lift-off technique of standard photolithography, except the final structures are smaller than can be achieved with conventional means. We have demonstrated the flexibility of our process by producing metal nanoparticle arrays composed of Ti, Au, AuPd, and Co. We will present our current efforts aimed toward semiconductor and magnetic recording applications.

  19. The Relationship of Magnetic Stiffness Between Single and Multiple YBCO Superconductors over Permanent Magnet Guideway

    NASA Astrophysics Data System (ADS)

    Lu, Yiyun; Lu, Bingjuan; Wang, Suyu

    2011-09-01

    For YBCO bulk levitating over a permanent magnet guideway (PMG), the magnetic stiffness is connected directly with the pinning properties of the measured sample. An experimental setup has been built to investigate the vertical and lateral magnetic stiffness of five high-temperature superconducting (HTS) bulk arrays over a PMG by two methods: the additive method, i.e., calculating the summation of the measured magnetic stiffness values of each HTS bulk in the array; the direct method, i.e., measuring directly the magnetic stiffness of the HTS bulk array. From the experimental results, it is found that the resultant magnetic stiffness of the HTS bulk array composing of multiple YBCO bulk is related with the magnetic stiffness of each individual single bulk, but the additive method does not predict the magnetic stiffness of the array very well because of the interaction between adjacent HTS bulk. The resultant magnetic stiffness of the HTS bulk array is less than the summation magnetic stiffness of each single HTS bulk. One numerical method is used to calculate the magnetic stiffness for comparing with experimental results. The results may be helpful to the design and optimization of the superconducting magnetic levitation system.

  20. Paramagnetic Meissner effect in Pb nanowire arrays

    NASA Astrophysics Data System (ADS)

    Yuan, Shijun; Ren, Liyuan; Li, Fashen

    2004-03-01

    The Meissner effect is one of the basic properties of superconductors. Recently, many experiments have shown that small-size superconducting samples may be paramagnetic in a weak magnetic field, the so-called paramagnetic Meissner effect (PME). In this paper, we report the observation of the PME in Pb nanowire arrays. We find that the signal of the PME increases with decreasing diameter of the nanowires. In a lead nanowire array of diameter about 40 nm, the oscillations of the PME are observed in field-cooling temperature-dependent magnetization M(T) curves. Surprisingly, the PME was also observed in zero-field-cooling M(T) curves. We conclude that the PME is in association with the metastable states in superconductors. The PME plays an important role only if the proportion of surface superconductors is sufficiently large.

  1. A submillimeter VLBI array

    NASA Astrophysics Data System (ADS)

    Weintroub, Jonathan

    2008-10-01

    A VLBI array operating at ? 1.3 mm and 0.8 mm is being designed using existing submillimeter telescopes as ad-hoc stations. Initial three station ? = 1.3 mm observations of SgrA* and other AGN have produced remarkable results, which are reported by Doeleman elsewhere in this proceedings. Future observations are planned with an enhanced array which has longer baselines, more stations, and greater sensitivity. At ? = 0.8 mm and on the long baselines, the array will have about a 20 ?as angular resolution which equals the diameter of the event horizon of the massive black hole in SgrA*. Candidate single dish facilities include the Arizona Radio Observatory Submillimeter Telescope (SMT) in Arizona, the Caltech Submillimeter Observatory (CSO) and the James Clerk Maxwell telescope (JCMT) in Hawaii, the Large Millimeter Telescope (LMT) in Mexico, ASTE and APEX in Chile, and the IRAM 30 m in Spain; interferometers include the Submillimeter Array (SMA) in Hawaii, the Combined Array for Research in Millimeter-wave Astronomy (CARMA) in California, IRAM PdB Interferometer in France, and the Atacama Large Millimeter Array (ALMA) in Chile. I will discuss the techniques we have developed for phasing interferometric arrays to act as single VLBI station. A strategy for detection of short (10s) time-scale source variability using VLBI closure phase will be described.

  2. Compound semiconductor SPAD arrays

    NASA Astrophysics Data System (ADS)

    Harmon, Eric S.; Naydenkov, Mikhail; Hyland, James T.

    2013-06-01

    Single photon avalanche diodes (SPADs) are revolutionizing ultra-sensitive photodetection applications, providing single photon sensitivity, high quantum efficiency and low dark noise at or near room temperature. When aggregated into arrays, these devices have demonstrated the ability to operate as photon number resolving detectors with wide dynamic range, or as single-photon imaging detectors. SPAD array performance has reached a point where replacing vacuum tube based MCP and PMT photodetectors for most applications is inevitable. Compound semiconductor SPAD arrays offer the unique proposition to tailor performance to match application specific wavelength, speed and radiation hardness requirements. We present a theoretical framework describing performance limits to compound semiconductor SPAD arrays and our latest experimental results detailing the performance of GaAs SPAD arrays. These devices achieve nanosecond rise and fall times, excellent photon number resolving capability, and low dark count rates. Single photon number resolving is demonstrated with 4% single photon detection efficiency at room temperature with dark count rates below 7 Mcps/mm2. Compound semiconductor SPAD arrays have the opportunity to provide orders of magnitude improvement in dark count rate and radiation hardness over silicon SPAD arrays, as well as the ability to detect wavelengths where silicon is blind.

  3. Ultralightweight solar array technology

    NASA Astrophysics Data System (ADS)

    Goldsmith, P.; Kurland, R.

    1982-06-01

    Flat fold array technology is described, and performance for a range of missions and power levels is predicted. The array employs large area flat panel flexible substrates. The solar cells are adhesively bonded to a thin Kapton substrate to form individual panel assemblies. Any number of these panel assemblies may be joined together to make a blanket assembly. A container assembly protects each blanket assembly when stowed, and a tension guide wire assembly controls the flexible blanket shape when fully extended. Blanket extension and retraction are achieved through a motor powered lightweight trilongeron coilable lattice mast assembly. Ground and zero gravity flight tests on prototype array assemblies are successful.

  4. Assembly of ordered microsphere arrays: Platforms for microarrays

    NASA Astrophysics Data System (ADS)

    Xu, Wanling

    Microarrays are powerful tools in gene expression assessment, protein profiling, and protein function screening, as well as cell and tissue analysis. With thousands of small array spots assembled in an ordered array, these small devices makes it possible to screen for multiple targets in a fast, parallel, high-throughput manner. The well-developed technology of DNA microarrays, also called DNA chips, has proved successful in all kinds of biological experiments, including the human genome-sequencing project. The development of protein arrays has lagged behind that of DNA arrays mainly because of the greater complexity of proteins. Some parts of the microarray technology can be transplanted into the realm of protein arrays, while others cannot. The challenges from the complexity of protein targets demand more robust and powerful devices. Traditional planar arrays, in which proteins bind directly to a planar surface, have a drawback in that some proteins will be denatured or cluster together after immobilization. Microsphere-based microarrays represent a more advanced strategy. The functional proteins are first attached to microspheres; these microspheres are then immobilized in arrays on a planar surface. In this dissertation, two approaches to assembling arrays of microspheres will be discussed. The hydrodynamic approach uses surface micromachining and Deep Reactive Ion Etching techniques to form an array of channels through a silicon wafer. By drawing fluid containing the microspheres through the channels they become trapped in the channels and thereby immobilized. In the magnetic approach, permalloy films are deposited on a silicon substrate and subsequently patterned to form magnetic attachment sites. An external magnetic field is then applied and the magnetic microspheres then assemble on these sites. Both devices are able to immobilize microspheres in an ordered array, as opposed to coarsely grouping them in array spots. The assembled arrays are robust in that they ensure a resolution rate of almost 100%. In addition, different patterns of array spots with various spacings and diameters can be fabricated to satisfy different requirements. Moreover, the devices are easy to clean and reuse, and the experimental set-ups are relatively simple and portable. All these features make them good platforms for all kinds of microarrays.

  5. Expandable LED array interconnect

    DOEpatents

    Yuan, Thomas Cheng-Hsin; Keller, Bernd

    2011-03-01

    A light emitting device that can function as an array element in an expandable array of such devices. The light emitting device comprises a substrate that has a top surface and a plurality of edges. Input and output terminals are mounted to the top surface of the substrate. Both terminals comprise a plurality of contact pads disposed proximate to the edges of the substrate, allowing for easy access to both terminals from multiple edges of the substrate. A lighting element is mounted to the top surface of the substrate. The lighting element is connected between the input and output terminals. The contact pads provide multiple access points to the terminals which allow for greater flexibility in design when the devices are used as array elements in an expandable array.

  6. Flexible retinal electrode array

    DOEpatents

    Okandan, Murat (Albuquerque, NM); Wessendorf, Kurt O. (Albuquerque, NM); Christenson, Todd R. (Albuquerque, NM)

    2006-10-24

    An electrode array which has applications for neural stimulation and sensing. The electrode array can include a large number of electrodes each of which is flexibly attached to a common substrate using a plurality of springs to allow the electrodes to move independently. The electrode array can be formed from a combination of bulk and surface micromachining, with electrode tips that can include an electroplated metal (e.g. platinum, iridium, gold or titanium) or a metal oxide (e.g. iridium oxide) for biocompatibility. The electrode array can be used to form a part of a neural prosthesis, and is particularly well adapted for use in an implantable retinal prosthesis where the electrodes can be tailored to provide a uniform gentle contact pressure with optional sensing of this contact pressure at one or more of the electrodes.

  7. Multi Sensor Array

    NASA Technical Reports Server (NTRS)

    Immer, Christopher; Voska, Ned (Technical Monitor)

    2002-01-01

    This paper presents viewgraphs on the Multi Sensor Array. The topics include: 1) MSA Algorithm; 2) Types of Sensors for the MSA; 3) How to test the MSA; 4) Monte Carlo Simulation; and 5) Accelerated Life Tests.

  8. Solar array cost reduction.

    NASA Technical Reports Server (NTRS)

    Bernatowicz, D. T.

    1972-01-01

    The costs regarding solar power systems are considered, giving attention to the total system cost index for the power system as a function of solar array area, and the recurring cost per square foot for the solar array versus the total area flight arrays built for each project. It is found that the costs decrease as production volume increases. Design standardization together with improvements in solar cell and array technology show promise of reducing costs. A long range program has been started to improve substantially the efficiency of silicon cells. Efficiencies approaching 20% are theoretically possible. One obstacle to cost reduction is that the volume of production required to satisfy the space program is not enough to justify a high degree of mechanization or automation.

  9. Random array grid collimator

    DOEpatents

    Fenimore, E.E.

    1980-08-22

    A hexagonally shaped quasi-random no-two-holes touching grid collimator. The quasi-random array grid collimator eliminates contamination from small angle off-axis rays by using a no-two-holes-touching pattern which simultaneously provides for a self-supporting array increasng throughput by elimination of a substrate. The presentation invention also provides maximum throughput using hexagonally shaped holes in a hexagonal lattice pattern for diffraction limited applications. Mosaicking is also disclosed for reducing fabrication effort.

  10. The NMR phased array.

    PubMed

    Roemer, P B; Edelstein, W A; Hayes, C E; Souza, S P; Mueller, O M

    1990-11-01

    We describe methods for simultaneously acquiring and subsequently combining data from a multitude of closely positioned NMR receiving coils. The approach is conceptually similar to phased array radar and ultrasound and hence we call our techniques the "NMR phased array." The NMR phased array offers the signal-to-noise ratio (SNR) and resolution of a small surface coil over fields-of-view (FOV) normally associated with body imaging with no increase in imaging time. The NMR phased array can be applied to both imaging and spectroscopy for all pulse sequences. The problematic interactions among nearby surface coils is eliminated (a) by overlapping adjacent coils to give zero mutual inductance, hence zero interaction, and (b) by attaching low input impedance preamplifiers to all coils, thus eliminating interference among next nearest and more distant neighbors. We derive an algorithm for combining the data from the phased array elements to yield an image with optimum SNR. Other techniques which are easier to implement at the cost of lower SNR are explored. Phased array imaging is demonstrated with high resolution (512 x 512, 48-cm FOV, and 32-cm FOV) spin-echo images of the thoracic and lumbar spine. Data were acquired from four-element linear spine arrays, the first made of 12-cm square coils and the second made of 8-cm square coils. When compared with images from a single 15 x 30-cm rectangular coil and identical imaging parameters, the phased array yields a 2X and 3X higher SNR at the depth of the spine (approximately 7 cm). PMID:2266841

  11. Adaptive processing array systems

    NASA Astrophysics Data System (ADS)

    Gabriel, William F.

    1992-01-01

    Adaptive array systems have undergone enormous growth and progress in the past two decades. Because this multidiscipline technology area is both complex and mathematics intensive, it often appears alien (and perhaps impractical) to the nonspecialist. To help bridge those gaps, this tutorial paper is limited to just three principal topic areas: sidelobe cancellers, fully adaptive arrays, and superresolution techniques. In each case, background material is included for perspective and clarity, and carefully selected references are provided. Recent developments are discussed briefly where appropriate.

  12. A Submillimeter VLBI Array

    NASA Astrophysics Data System (ADS)

    Weintroub, Jonathan; Primiani, R.; Moran, J.; Young, K.

    2009-01-01

    A VLBI array operating at 1.3 mm and 0.8 mm wavelengths is being built using existing submillimeter telescopes as ad-hoc stations. Initial three station 1.3 mm observations of SgrA* and other AGN have produced remarkable results reported by Doeleman et al. in Nature (Vol 445, p 78) and also at this meeting. For SgrA*, the intrinsic size (angular diameter) is found to be 37 microarcseconds, or less than four Schwartzschild radii. Future observations are planned with an enhanced array which has longer baselines, more stations, and greater sensitivity. At 0.8 mm and on the long baselines, the array will have a 20 microarcsecond angular resolution which equals the diameter of the event horizon of the massive black hole in SgrA*. Candidate single dish facilities include the Arizona Radio Observatory Submillimeter Telescope (ARO/SMT) in Arizona, the Caltech Submillimeter Observatory (CSO) and the James Clerk Maxwell telescope (JCMT) in Hawaii, the Large Millimeter Telescope (LMT) in Mexico, ASTE and APEX in Chile, and the IRAM 30 m in Spain; interferometers include the Submillimeter Array (SMA) in Hawaii, the Combined Array for Research in Millimeter-wave Astronomy (CARMA) in California, IRAM PdB Interferometer in France, and the Atacama Large Millimeter Array (ALMA) in Chile. We will discuss the challenges of converting existing submillimeter telescopes to act as VLBI stations at these short wavelengths. We will also describe techniques to improve the sensitivity of the array, which is crucial to discern the detailed structure of the source. In particular, we have developed a processor for phasing local interferometric arrays to contribute to VLBI observations with their full collecting area.

  13. SERS based immuno-microwell arrays for multiplexed detection of foodborne pathogenic bacteria

    NASA Astrophysics Data System (ADS)

    Sun, Jian; Hankus, Mikella E.; Cullum, Brian M.

    2009-05-01

    A novel surface enhanced Raman scattering (SERS)-based immuno-microwell array has been developed for multiplexed detection of foodborne pathogenic bacteria. The immuno-microwell array was prepared by immobilizing the optical addressable immunomagnetic beads (IMB) into the microwell array on one end of a fiber optic bundle. The IMBs, magnetic beads coated with specific antibody to specific bacteria, were used for immunomagnetic separation (IMS) of corresponding bacteria. The magnetic separation by the homemade magnetic separation system was evaluated in terms of the influences of several important parameters including the beads concentration, the sample volume and the separation time. IMS separation efficiency of the model bacteria E.coli O157:H7 was 63% in 3 minutes. The microwell array was fabricated on hydrofluoric acid etched end of a fiber optic bundle containing 30,000 fiber elements. After being coated with silver, the microwell array was used as a uniform SERS substrate with the relative standard deviation of the SERS enhancement across the microwell array < 2% and the enhancement factor as high as 2.18 x 107. The antibody modified microwell array was prepared for bacteria immobilization into the microwell array, which was characterized by a sandwich immunoassay. To demonstrate the potential of multiplexed SERS detection with the immuno-microwell array, the SERS spectra of different Raman dye labeled magnetic beads as well as mixtures were measured on the mircrowell array. In bead mixture, different beads were identified by the characteristic SERS bands of the corresponding Raman label.

  14. Vortex circulation and polarity patterns in closely packed cap arrays

    NASA Astrophysics Data System (ADS)

    Streubel, Robert; Kronast, Florian; Reiche, Christopher F.; Mhl, Thomas; Wolter, Anja U. B.; Schmidt, Oliver G.; Makarov, Denys

    2016-01-01

    We studied curvature-driven modifications to the magnetostatic coupling of vortex circulation and polarity in soft-magnetic closely packed cap arrays. A phase diagram for the magnetic remanent/transition states at room temperature as a function of diameter and thickness was assembled. For specimens with vortex remanent state (40 nm-thick Permalloy on 330 nm spherical nanoparticles), both vortex circulation and polarity were visualized. Intercap coupling upon vortex nucleation leads to the formation of vortex circulation patterns in closely packed arrays. The remanent circulation pattern can be tailored choosing the direction of the applied magnetic field with respect to the symmetry axis of the hexagonal array. An even and random distribution of vortex polarity indicates the absence of any circulation-polarity coupling.

  15. Final Progress Report for the NASA Inductrack Model Rocket Launcher at the Lawrence Livermore National Laboratory

    SciTech Connect

    Tung, L S; Post, R F; Martinez-Frias, J

    2001-06-27

    The Inductrack magnetic levitation system, developed at the Lawrence Livermore National Laboratory, was studied for its possible use for launching rockets. Under NASA sponsorship, a small model system was constructed at the Laboratory to pursue key technical aspects of this proposed application. The Inductrack is a passive magnetic levitation system employing special arrays of high-field permanent magnets (Halbach arrays) on the levitating cradle, moving above a ''track'' consisting of a close-packed array of shorted coils with which are interleaved with special drive coils. Halbach arrays produce a strong spatially periodic magnetic field on the front surface of the arrays, while canceling the field on their back surface. Relative motion between the Halbach arrays and the track coils induces currents in those coils. These currents levitate the cradle by interacting with the horizontal component of the magnetic field. Pulsed currents in the drive coils, synchronized with the motion of the carrier, interact with the vertical component of the magnetic field to provide acceleration forces. Motional stability, including resistance to both vertical and lateral aerodynamic forces, is provided by having Halbach arrays that interact with both the upper and the lower sides of the track coils. At present, a 7.8 meter track composed of drive and levitation coils has been built and the electronic drive circuitry performs as designed. A 9 kg cradle that carries the Halbach array of permanent magnets has been built. A mechanical launcher is nearly complete which will provide an initial cradle velocity of 9 m/s into the electronic drive section. We have found that the drag forces from the levitation coils were higher than in our original design. However, measurements of drag force at velocities less than 1 m/s are exactly as predicted by theory. Provided here are recommended design changes to improve the track's performance so that a final velocity of 40 m/s can be achieved with the existing track. This project was designed and built as part of a Phase II contract that started in Feb. 1999 and ended in Sep. 2000 at a cost of $600K. A detailed budget on how this funding was spent is also included here.

  16. MEMS Microshutter Arrays for James Webb Space Telescope

    NASA Technical Reports Server (NTRS)

    Li, Mary J.; Beamesderfer, Michael; Babu, Sachi; Bajikar, Sateesh; Ewin, Audrey; Franz, Dave; Hess, Larry; Hu, Ron; Jhabvala, Murzy; Kelly, Dan; King, Todd; Kletetschkar, Gunther; Kutyrev, Alexander; Lynch, Barney; Moseley, Harvey; Mott, Brent; Oh, Lance; Rapchum, Dave; Ray, Chris; Sappington, Carol; Silverberg, Robert; Smith, Wayne; Snodgrass, Steve; Steptoe-Jackson, Rosalind; Valeriano

    2006-01-01

    MEMS microshutter arrays are being developed at NASA Goddard Space Flight Center for use as an aperture array for a Near-Infrared Spectrometer (NirSpec). The instruments will be carried on the James Webb Space Telescope (JWST), the next generation of space telescope after Hubble Space Telescope retires. The microshutter arrays are designed for the selective transmission of light with high efficiency and high contrast, Arrays are close-packed silicon nitride membranes with a pixel size of 100x200 microns. Individual shutters are patterned with a torsion flexure permitting shutters to open 90 degrees with a minimized mechanical stress concentration. Light shields are made on to each shutter for light leak prevention so to enhance optical contrast, Shutters are actuated magnetically, latched and addressed electrostatically. The shutter arrays are fabricated using MEMS technologies.

  17. Results from a prototype permanent magnet dipole-quadrupole hybrid for the PEP-II B-factory

    SciTech Connect

    Sullivan, M.; Bowden, G.; Ecklund, S.

    1997-06-01

    We describe the construction of a prototype hybrid permanent magnet dipole and quadrupole. The magnet consists of two concentric rings of Sm{sub 2}Co{sub 17} magnetic material 5 cm in length. The outer ring is made of 16 uniformly magnetized blocks assembled as a Halbach dipole and the inner ring has 32 blocks oriented in a similar fashion so as to generate a quadrupole field. The resultant superimposed field is an offset quadrupole field which allows us to center the field on the high-energy beam in the interaction region of the PEP-II B-factory. The dipole blocks are glued to the inside surface of an outer support collar and the quadrupole blocks are held in a fixture that allows radial adjustment of the blocks prior to potting the entire assembly with epoxy. An extensive computer model of the magnet has been made and from this model we developed a tuning algorithm that allowed us to greatly reduce the n=3 17 harmonics of the magnet.

  18. Transport of fast electrons in a nanowire array with collisional effects included

    NASA Astrophysics Data System (ADS)

    Li, Boyuan; Zhang, Zhimeng; Wang, Jian; Zhang, Bo; Zhao, Zongqing; Shan, Lianqiang; Zhou, Weimin; Cao, Lihua; Zhang, Baohan; Gu, Yuqiu

    2015-12-01

    The transport of picosecond laser generated fast electrons in a nanowire array is studied with two-dimensional particle-in-cell simulations. Our simulations show that a fast electron beam is initially guided and collimated by strong magnetic filaments in the array. Subsequently, after the decomposition of the structure of nanowire array due to plasma expansion, the beam is still collimated by the resistive magnetic field. An analytical model is established to give a criterion for long-term beam collimation in a nanowire array; it indicates that the nanowire cell should be wide enough to keep the beam collimated in picosecond scale.

  19. Detection of the spectra of multicharged ions with time resolution and the determination of the parameters of the hot component of the plasma in the case of the magnetic implosion of multiwire arrays

    NASA Astrophysics Data System (ADS)

    Anan'ev, S. S.; Dan'ko, S. A.; Kalinin, Yu. G.; Ye, Fan; Qin, Yi; Jiang, Shuqing; Xue, Feibiao; Li, Zhenghong; Yang, Jianlun; Xu, Rongkun

    2010-12-01

    The dynamics of the hot component of the plasma of imploding multiwire arrays has been analyzed using the time behavior of the X-ray spectral lines of multicharge ions. The spectra of H- and He-like aluminum ions with nanosecond time resolution have been detected using electron-optical chronography in experiments on the implosion of multiwire arrays by mega-ampere currents. The simultaneous appearance of the resonance lines of H- and He-like ions implies that the hot plasma whose electron temperature is higher than 0.5 keV has existed on the axis before the implosion of the main mass of the liner. The further dynamics of the intensity of the lines is primarily attributed to an increase in the mass of the emitting plasma.

  20. Design of a dual sensor probe array for internal field measurement in Versatile Experiment Spherical Torus.

    PubMed

    Jeong-hun, Yang; Chung, Kyoung-Jae; An, YoungHwa; Jung, Bong Ki; Jo, Jong Gab; Hwang, Y S

    2012-10-01

    A dual sensor probe array is designed and constructed for internal magnetic field measurement at Versatile Experiment Spherical Torus (VEST) at the Seoul National University. Simultaneous use of Hall sensors and chip inductors allows cross-calibration among the measurements and compensation for each other's weaknesses while their small sizes are expected to cause only mild plasma perturbations. Calibration of the dual sensor probe array, using a Helmholtz coil, shows good sensitivity for the magnetic field measurement of the VEST. Prior to Ohmic start-up, the magnetic field structure inside the vacuum chamber is measured by using the calibrated probe array. The dual sensor probe array is expected to be useful in analyzing the temporal magnetic field structure change during the magnetic reconnection and in reconstruction of the current profile during the discharge of the VEST device. PMID:23126895

  1. Design of a dual sensor probe array for internal field measurement in Versatile Experiment Spherical Torusa)

    NASA Astrophysics Data System (ADS)

    Jeong-hun, Yang; Chung, Kyoung-Jae; An, YoungHwa; Jung, Bong Ki; Jo, Jong Gab; Hwang, Y. S.

    2012-10-01

    A dual sensor probe array is designed and constructed for internal magnetic field measurement at Versatile Experiment Spherical Torus (VEST) at the Seoul National University. Simultaneous use of Hall sensors and chip inductors allows cross-calibration among the measurements and compensation for each other's weaknesses while their small sizes are expected to cause only mild plasma perturbations. Calibration of the dual sensor probe array, using a Helmholtz coil, shows good sensitivity for the magnetic field measurement of the VEST. Prior to Ohmic start-up, the magnetic field structure inside the vacuum chamber is measured by using the calibrated probe array. The dual sensor probe array is expected to be useful in analyzing the temporal magnetic field structure change during the magnetic reconnection and in reconstruction of the current profile during the discharge of the VEST device.

  2. Composite arrays of superconducting microstrip line resonators

    SciTech Connect

    Mohebbi, H. R. Miao, G. X.; Benningshof, O. W. B.; Taminiau, I. A. J.; Cory, D. G.

    2014-03-07

    A novel design of an array of half-wave superconductive microstrip resonators is described. The resonator is intended to be useful for electron spin resonance studies of thin film samples at cryogenic temperatures. It achieves a high quality factor, has a small mode-volume, and creates a uniform magnetic field in a plane above the resonator. The device is made of thin film Niobium on sapphire wafer and is tested with a static magnetic field. Variation of Q-factor versus the magnetic field's strength at different temperatures is reported and is in a good agreement with simulation when the loss due to the vortices is included. Also, the power-dependence response of the resonator is shown in experiments and is verified by capturing the nonlinearity associated with the surface impedance of the superconducting film into the circuit model of the device.

  3. Solar array flight experiment

    NASA Technical Reports Server (NTRS)

    1986-01-01

    Emerging satellite designs require increasing amounts of electrical power to operate spacecraft instruments and to provide environments suitable for human habitation. In the past, electrical power was generated by covering rigid honeycomb panels with solar cells. This technology results in unacceptable weight and volume penalties when large amounts of power are required. To fill the need for large-area, lightweight solar arrays, a fabrication technique in which solar cells are attached to a copper printed circuit laminated to a plastic sheet was developed. The result is a flexible solar array with one-tenth the stowed volume and one-third the weight of comparably sized rigid arrays. An automated welding process developed to attack the cells to the printed circuit guarantees repeatable welds that are more tolerant of severe environments than conventional soldered connections. To demonstrate the flight readiness of this technology, the Solar Array Flight Experiment (SAFE) was developed and flown on the space shuttle Discovery in September 1984. The tests showed the modes and frequencies of the array to be very close to preflight predictions. Structural damping, however, was higher than anticipated. Electrical performance of the active solar panel was also tested. The flight performance and postflight data evaluation are described.

  4. Microelectronic electroporation array

    NASA Astrophysics Data System (ADS)

    Johnson, Lee J.; Shaffer, Kara J.; Skeath, Perry; Perkins, Frank K.; Pancrazio, Joseph; Scribner, Dean

    2004-06-01

    Gene Array technology has allowed for the study of gene binding by creating thousands of potential binding sites on a single device. A limitation of the current technology is that the effects of the gene and the gene-derived proteins cannot be studied in situ the same way, thousand site cell arrays are not readily available. We propose a new device structure to study the effects of gene modification on cells. This new array technology uses electroporation to target specific areas within a cell culture for transfection of genes. Electroporation arrays will allow high throughput analysis of gene effects on a given cell's response to a stress or a genes ability to restore normal cell function in disease modeling cells. Fluorescent imaging of dye labeled indicator molecules or cell viability will provide results indicating the most effective genes. The electroporation array consists of a microelectronic circuit, ancillary electronics, protecting electrode surface for cell culturing and a perfusion system for gene or drug delivery. The advantages of the current device are that there are 3200 sites for electroporation, all or any subsets of the electrodes can be activated. The cells are held in place by the electrode material. This technology could also be applied to high throughput screening of cell impermeant drugs.

  5. Folding of Nucleosome Arrays

    NASA Astrophysics Data System (ADS)

    Howell, Steven; Jimenez-Useche, Isabel; Andresen, Kurt; Yuan, Chongli; Qiu, Xiangyun

    2014-03-01

    Chromatin conformation and dynamics is central to gene functions including packaging, regulation, and repair. At the molecular level, the basic building block of chromatin is a nucleosome core particle (NCP) made of 147 base pairs (bp) of dsDNA wrapped around an octamer of histone proteins. These NCPs are connected by short 10-90 bps of linker DNA as beads on a string. Key factors determining the packaging of NCP arrays to form chromatin include ionic condition, linker DNA length, and epigenetic modifications, especially of the histone tails. We have investigated how the conformations of model tetra-NCP arrays are modulated by these factors using small angle x-ray scattering (SAXS). Here we present recent studies of the effects of ion (KCl and MgCl2), linker length, and histone modification (tail deletions) on NCP arrays. Our SAXS measurement makes it possible to learn about both the global compaction of NCP arrays and local inter-NCP spatial correlations within the same array.

  6. Imaging antenna arrays

    NASA Technical Reports Server (NTRS)

    Rutledge, D. B.; Muha, M. S.

    1982-01-01

    Many millimeter and far-infrared imaging systems are limited in sensitivity and speed because they depend on a single scanned element. Because of recent advances in planar detectors such as Schottky diodes, superconducting tunnel junctions, and microbolometers, an attractive approach to this problem is a planar antenna array with integrated detectors. A planar line antenna array and optical system for imaging has been developed. The significant advances are a 'reverse-microscope' optical configuration and a modified bow-tie antenna design. In the 'reverse-microscope' configuration, a lens is attached to the bottom of the substrate containing the antennas. Imaging is done through the substrate. This configuration eliminates the troublesome effects of substrate surface waves. The substrate lens has only a single refracting surface, making possible a virtually aplanatic system, with little spherical aberration or coma. The array is characterized by an optical transfer function that is easily measured. An array with 19 dB crosstalk levels between adjacent antennas has been tested and it was found that the array captured 50 percent of the available power. This imaging system was diffraction limited.

  7. Magnetic uniaxial wire medium

    NASA Astrophysics Data System (ADS)

    Morgado, Tiago A.; Costa, João T.; Silveirinha, Mário G.

    2016-02-01

    It is shown that a racemic array of helical-shaped metallic wires may have a dual electromagnetic response, such that for arbitrarily large wavelengths it concurrently supports two modes with hyperbolic- and elliptical-type dispersions. Importantly, one of the eigenwaves is nearly dispersionless and sees the metamaterial as a medium with extreme magnetic anisotropy. The metamaterial may thus behave as the magnetic analog of the conventional wire medium formed by a set of parallel straight metallic wires. It is demonstrated that the magnetic wire medium enables channeling the subwavelength details of transverse electric (TE) polarized waves.

  8. Pyroelectric detector arrays

    NASA Technical Reports Server (NTRS)

    Fripp, A. L.; Robertson, J. B.; Breckenridge, R. A. (inventors)

    1982-01-01

    A pryoelectric detector array and the method for making it are described. A series of holes formed through a silicon dioxide layer on the surface of a silicon substrate forms the mounting fixture for the pyroelectric detector array. A series of nontouching strips of indium are formed around the holes to make contact with the backside electrodes and form the output terminals for individual detectors. A pyroelectric detector strip with front and back electrodes, respectively, is mounted over the strip. Biasing resistors are formed on the surface of the silicon dioxide layer and connected to the strips. A metallized pad formed on the surface of the layer is connected to each of the biasing resistors and to the film to provide the ground for the pyroelectric detector array.

  9. Wireless Josephson Junction Arrays

    NASA Astrophysics Data System (ADS)

    Adams, Laura

    2015-03-01

    We report low temperature, microwave transmission measurements on a wireless two- dimensional network of Josephson junction arrays composed of superconductor-insulator -superconductor tunnel junctions. Unlike their biased counterparts, by removing all electrical contacts to the arrays and superfluous microwave components and interconnects in the transmission line, we observe new collective behavior in the transmission spectra. In particular we will show emergent behavior that systematically responds to changes in microwave power at fixed temperature. Likewise we will show the dynamic and collective response of the arrays while tuning the temperature at fixed microwave power. We discuss these spectra in terms of the Berezinskii-Kosterlitz-Thouless phase transition and Shapiro steps. We gratefully acknowledge the support Prof. Steven Anlage at the University of Maryland and Prof. Allen Goldman at the University of Minnesota. Physics and School of Engineering and Applied Sciences.

  10. Pyroelectric detector arrays

    NASA Technical Reports Server (NTRS)

    Fripp, A. L.; Robertson, J. B.; Breckenridge, R. (inventors)

    1982-01-01

    A pyroelectric detector array and the method for using it are described. A series of holes formed through a silicon dioxide layer on the surface of a silicon substrate forms the mounting fixture for the pyroelectric detector array. A series of nontouching strips of indium are formed around the holes to make contact with the backside electrodes and form the output terminals for individual detectors. A pyroelectric detector strip with front and back electrodes, respectively, is mounted over the strips. Biasing resistors are formed on the surface of the silicon dioxide layer and connected to the strips. A metallized pad formed on the surface of layer is connected to each of the biasing resistors and to the film to provide the ground for the pyroelectric detector array.

  11. Supersymmetric laser arrays

    NASA Astrophysics Data System (ADS)

    El-Ganainy, R.; Ge, Li; Khajavikhan, M.; Christodoulides, D. N.

    2015-09-01

    We introduce the concept of supersymmetric laser arrays that consist of a main optical lattice and its superpartner structure, and we investigate the onset of their lasing oscillations. Due to the coupling of the two constituent lattices, their degenerate optical modes form doublets, while the extra mode associated with unbroken supersymmetry forms a singlet state. Singlet lasing can be achieved for a wide range of design parameters, either by introducing stronger loss in the partner lattice or by pumping only the main array. Our findings suggest the possibility of building single-mode, high-power laser arrays and are also important for understanding light transport dynamics in multimode parity-time symmetric photonic structures.

  12. Electrostatically clean solar array

    NASA Technical Reports Server (NTRS)

    Stern, Theodore Garry (Inventor); Krumweide, Duane Eric (Inventor)

    2004-01-01

    Provided are methods of manufacturing an electrostatically clean solar array panel and the products resulting from the practice of these methods. The preferred method uses an array of solar cells, each with a coverglass where the method includes machining apertures into a flat, electrically conductive sheet so that each aperture is aligned with and undersized with respect to its matched coverglass sheet and thereby fashion a front side shield with apertures (FSA). The undersized portion about each aperture of the bottom side of the FSA shield is bonded to the topside portions nearest the edges of each aperture's matched coverglass. Edge clips are attached to the front side aperture shield edges with the edge clips electrically and mechanically connecting the tops of the coverglasses to the solar panel substrate. The FSA shield, edge clips and substrate edges are bonded so as to produce a conductively grounded electrostatically clean solar array panel.

  13. Magnetic ratchet for biotechnological applications

    NASA Astrophysics Data System (ADS)

    Auge, A.; Weddemann, A.; Wittbracht, F.; Htten, A.

    2009-05-01

    Transport and separation of magnetic beads are important in "lab on a chip" environments for biotechnological applications. One possible solution for this is the on-off ratchet concept. An asymmetric magnetic potential and Brownian motion of magnetic beads are required for such a ratchet. The asymmetric magnetic potential is achieved by combining an external magnetic field with a spatially periodic array of conducting lines. In this work finite element method simulations are carried out to design this asymmetric potential and to evaluate transport rates. Furthermore, experiments are carried out so as to compare to the simulation results.

  14. Design and numerical evaluation of a volume coil array for parallel MR imaging at ultrahigh fields

    PubMed Central

    Pang, Yong; Wong, Ernest W.H.; Yu, Baiying

    2014-01-01

    In this work, we propose and investigate a volume coil array design method using different types of birdcage coils for MR imaging. Unlike the conventional radiofrequency (RF) coil arrays of which the array elements are surface coils, the proposed volume coil array consists of a set of independent volume coils including a conventional birdcage coil, a transverse birdcage coil, and a helix birdcage coil. The magnetic fluxes of these three birdcage coils are intrinsically cancelled, yielding a highly decoupled volume coil array. In contrast to conventional non-array type volume coils, the volume coil array would be beneficial in improving MR signal-to-noise ratio (SNR) and also gain the capability of implementing parallel imaging. The volume coil array is evaluated at the ultrahigh field of 7T using FDTD numerical simulations, and the g-factor map at different acceleration rates was also calculated to investigate its parallel imaging performance. PMID:24649435

  15. Creating arrays by centrifugation.

    PubMed

    Jobs, Magnus; Howell, W Mathias; Brookes, Anthony J

    2002-06-01

    We describe afast, low-cost, and reliable way of creating arrays from sample molecules of interest present within microformatted sample vessels (such as 1536-well microplates). The principle involves simple centrifugal transfer of molecules of interest onto a solid planar or membrane surfaces placed over the initial sample vessel. Tools and procedures are presented that validate the robustness and precision of this facile solution to an otherwise difficult problem in modern molecular genetics. The availability of transferred DNA molecules for hybridization is also demonstrated. In conclusion, this "centrifugal-array" concept should help research studies to be applied on ever-greater scales with very simple machinery. PMID:12074163

  16. Solar array subsystems study

    NASA Technical Reports Server (NTRS)

    Richardson, P. W.; Miller, F. Q.; Badgley, M. B.

    1980-01-01

    The effects on life cycle costs of a number of technology areas are examined for a LEO, 500 kW solar array. A baseline system conceptual design is developed and the life cycle costs estimated in detail. The baseline system requirements and design technologies are then varied and their relationships to life cycle costs quantified. For example, the thermal characteristics of the baseline design are determined by the array materials and masses. The thermal characteristics in turn determine configuration, performance and hence life cycle cost.

  17. Array signal processing

    SciTech Connect

    Haykin, S.; Justice, J.H.; Owsley, N.L.; Yen, J.L.; Kak, A.C.

    1985-01-01

    This is the first book to be devoted completely to array signal processing, a subject that has become increasingly important in recent years. The book consists of six chapters. Chapter 1, which is introductory, reviews some basic concepts in wave propagation. The remaining five chapters deal with the theory and applications of array signal processing in (a) exploration seismology, (b) passive sonar, (c) radar, (d) radio astronomy, and (e) tomographic imaging. The various chapters of the book are self-contained. The book is written by a team of five active researchers, who are specialists in the individual fields covered by the pertinent chapters.

  18. Automated array assembly

    NASA Technical Reports Server (NTRS)

    Williams, B. F.

    1976-01-01

    Manufacturing techniques are evaluated using expenses based on experience and studying basic cost factors for each step to evaluate expenses from a first-principles point of view. A formal cost accounting procedure is developed which is used throughout the study for cost comparisons. The first test of this procedure is a comparison of its predicted costs for array module manufacturing with costs from a study which is based on experience factors. A manufacturing cost estimate for array modules of $10/W is based on present-day manufacturing techniques, expenses, and materials costs.

  19. Wire Array Photovoltaics

    NASA Astrophysics Data System (ADS)

    Turner-Evans, Dan

    Over the past five years, the cost of solar panels has dropped drastically and, in concert, the number of installed modules has risen exponentially. However, solar electricity is still more than twice as expensive as electricity from a natural gas plant. Fortunately, wire array solar cells have emerged as a promising technology for further lowering the cost of solar. Si wire array solar cells are formed with a unique, low cost growth method and use 100 times less material than conventional Si cells. The wires can be embedded in a transparent, flexible polymer to create a free-standing array that can be rolled up for easy installation in a variety of form factors. Furthermore, by incorporating multijunctions into the wire morphology, higher efficiencies can be achieved while taking advantage of the unique defect relaxation pathways afforded by the 3D wire geometry. The work in this thesis shepherded Si wires from undoped arrays to flexible, functional large area devices and laid the groundwork for multijunction wire array cells. Fabrication techniques were developed to turn intrinsic Si wires into full p-n junctions and the wires were passivated with a-Si:H and a-SiNx:H. Single wire devices yielded open circuit voltages of 600 mV and efficiencies of 9%. The arrays were then embedded in a polymer and contacted with a transparent, flexible, Ni nanoparticle and Ag nanowire top contact. The contact connected >99% of the wires in parallel and yielded flexible, substrate free solar cells featuring hundreds of thousands of wires. Building on the success of the Si wire arrays, GaP was epitaxially grown on the material to create heterostructures for photoelectrochemistry. These cells were limited by low absorption in the GaP due to its indirect bandgap, and poor current collection due to a diffusion length of only 80 nm. However, GaAsP on SiGe offers a superior combination of materials, and wire architectures based on these semiconductors were investigated for multijunction arrays. These devices offer potential efficiencies of 34%, as demonstrated through an analytical model and optoelectronic simulations. SiGe and Ge wires were fabricated via chemical-vapor deposition and reactive ion etching. GaAs was then grown on these substrates at the National Renewable Energy Lab and yielded ns lifetime components, as required for achieving high efficiency devices.

  20. ALMA Extended Array

    NASA Astrophysics Data System (ADS)

    Kameno, S.; Nakai, N.; Honma, M.

    2013-10-01

    We propose to append five 12-m antennas within 300-km from ALMA to realize high angular resolution of < 1 mas and sensitivity to detect Tb < 1000 K. This ALMA extended array offers a new parameter space of Thermal universe with VLBI resolution. Proposed science case includes black-hole formation in sub-mm galaxies, mass accretion processes onto protostars, imaging stellar photospheres, distance measurements of stars, and so on. The array also functions as a part of sub-mm VLBI that targets black-hole imaging.

  1. Superconducting bulk magnets for magnetic levitation systems

    NASA Astrophysics Data System (ADS)

    Fujimoto, H.; Kamijo, H.

    2000-06-01

    The major applications of high-temperature superconductors have mostly been confined to products in the form of wires and thin films. However, recent developments show that rare-earth REBa 2Cu 3O 7- x and light rare-earth LREBa 2Cu 3O 7- x superconductors prepared by melt processes have a high critical-current density at 77 K and high magnetic fields. These superconductors will promote the application of bulk high-temperature superconductors in high magnetic fields; the superconducting bulk magnet for the Maglev train is one possible application. We investigated the possibility of using bulk magnets in the Maglev system, and examined flux-trapping characteristics of multi-superconducting bulks arranged in array.

  2. Experimental verification of the performance of the self-tunable loop-current array shielding module

    NASA Astrophysics Data System (ADS)

    Goleman, K.; Yamato, T.; Sasada, I.

    2006-04-01

    An active shielding module consisting of a self-tunable loop-current array is verified experimentally. Loop currents in the array are independently controlled by the magnetometer dedicated to each of them. Since magnetic field decays as 1/z3 along the distance z from the loop, the magnetic noise should be overcompensated at the location of the loop-current array to provide a good cancellation in the shielded area. In order to enable overcompensation in a stable feedback system, a small additional loop is combined to the magnetometer that reduces the magnetic direct coupling from the main loop current to the magnetometer. A feedback electronic circuit with a proportional-integral (PI) controller is combined with each of the array element to establish a stable canceling operation. An orthogonal fluxgate magnetometer is used to monitor incident magnetic noise. Shielding performance of an array consisting of nine loop currents arranged in a 3×3 grid was evaluated numerically and confirmed by experiments. Evaluation and measurements are done over the 1.5×1.5 m2 area 2 m in front of the array. The magnetic dipole disturbance source is placed 2 m further beyond the array. Attenuation of the magnetic field is calculated as 1/15. Experimental data show 1/10 attenuation.

  3. Synthesis Array Topology Metrics in Location Characterization

    NASA Astrophysics Data System (ADS)

    Shanmugha Sundaram, GA

    2015-08-01

    Towards addressing some of the fundamental mysteries in physics at the micro- and macro-cosm level, that form the Key Science Projects (KSPs) for the Square Kilometer Array (SKA; such as Probing the Dark Ages and the Epoch of Reionization in the course of an Evolving Universe; Galaxy Evolution, Cosmology, and Dark Energy; and the Origin and evolution of Cosmic Magnetism) a suitable interfacing of these goals has to be achieved with its optimally designed array configuration, by means of a critical evaluation of the radio imagingcapabilities and metrics. Of the two forerunner sites, viz. Australia and South Africa, where pioneering advancements to state-of-the-art in synthesis array radio astronomy instrumentation are being attempted in the form of pathfinders to the SKA, for its eventual deployment, a diversity of site-dependent topology and design metrics exists. Here, the particular discussion involves those KSPs that relate to galactic morphology and evolution, and explores their suitability as a scientific research goal from the prespective of the location-driven instrument design specification. Relative merits and adaptability with regard to either site shall be presented from invoking well-founded and established array-design and optimization principles designed into a customized software tool.

  4. A review of array radars

    NASA Astrophysics Data System (ADS)

    Brookner, E.

    1981-10-01

    Achievements in the area of array radars are illustrated by such activities as the operational deployment of the large high-power, high-range-resolution Cobra Dane; the operational deployment of two all-solid-state high-power, large UHF Pave Paws radars; and the development of the SAM multifunction Patriot radar. This paper reviews the following topics: array radars steered in azimuth and elevation by phase shifting (phase-phase steered arrays); arrays steered + or - 60 deg, limited scan arrays, hemispherical coverage, and omnidirectional coverage arrays; array radars steering electronically in only one dimension, either by frequency or by phase steering; and array radar antennas which use no electronic scanning but instead use array antennas for achieving low antenna sidelobes.

  5. Genetic Variation of BCL2 (rs2279115), NEIL2 (rs804270), LTA (rs909253), PSCA (rs2294008) and PLCE1 (rs3765524, rs10509670) Genes and Their Correlation to Gastric Cancer Risk Based on Universal Tagged Arrays and Fe3O4 Magnetic Nanoparticles.

    PubMed

    Mou, Xianbo; Li, Taotao; Wang, Jiuhai; Ali, Zeeshan; Zhang, Yuanying; Chen, Zhu; Deng, Yan; Li, Song; Su, Enben; Jia, Qiongying; He, Nongyue; Ni, Jian; Cui, Daxiang

    2015-11-01

    With the help of Fe3O4 nagnetic nanoparticles as a solid carrier and an excellent tool for separation, six SNP loci (rs2279115 of BCL2 gene, rs804270 of NEIL2 gene, rs909253 of LTA gene, rs2294008 of PSCA gene, rs3765524 and rs10509670 of PLCE1 gene) were selected to evaluate their relation to gastric cancer risk. Using two kinds of functionalized magnetic nanoparticles and universal tagged arrays, the whole operation procedure including genome DNA extraction and SNP genotyping was performed. All genotypes and allele frequencies were calculated in the cases and controls respectively to analyze their association with gastric cancer risk. Totally 200 pathological samples and 134 normal control subjects were collected. The results demonstrated that four SNP loci (rs2279115, rs804270, rs909253 and rs3765524) showed a potential association with gastric cancer risk, and the other two (rs2294008, rs10509670) possessed no difference/association among cases and controls. PMID:26554163

  6. Flux avalanches in superconducting films with periodic arrays of holes.

    SciTech Connect

    Vlasko-Vlasov, V.; Welp, U.; Metlushko, V.; Crabtree, G. W.; Materials Science Division; Inst. of Solid State Physics RAS

    2000-01-01

    The magnetic flux dynamics in Nb films with periodic hole arrays is studied magneto-optically. Flux motion in the shape of microavalanches along {l_brace}100{r_brace} and {l_brace}110{r_brace} directions of the hole lattice is observed. At lower temperatures anisotropic large scale thermo-magnetic avalanches dominate flux entry and exit. At T-T{sub c} critical-state-like field patterns periodically appear at fractions of the matching field.

  7. Magnetostatic interaction in FeCo nanowire arrays

    NASA Astrophysics Data System (ADS)

    Jia, Yijiao; Wang, Huanwen; Gao, Youhui; Chen, Peigeng; Lu, Jiadao; Han, Gang

    2015-01-01

    FexCo1-x alloy nanowire arrays are deposited by a dc electrochemical method with anodic aluminum oxide nanoporous templates. Effects of nanowire magnetic moment and interwire distance on the interwire magnetostatic interaction are studied in this paper. It is found that the interaction increases with increase of nanowire magnetic moment and/or decrease of interwire distance. An effective wire diameter is introduced to quantitatively analyze such inetraction. A Monte Carlo simulation is also carried out to calculate the experimental measurements.

  8. Arrays for space applications

    NASA Technical Reports Server (NTRS)

    Schuman, Harvey K.; Antonik, Paul; Malagisi, Carmen

    1989-01-01

    Concepts that were studied for application in space based radar (SBR) systems are presented. These antenna systems were for low earth orbit and require large fields of view (FOV). The systems included both space-fed and corporate-fed arrays.

  9. Antenna array research

    NASA Technical Reports Server (NTRS)

    Tai, C.

    1973-01-01

    Antenna array research on electromagnetic field problems in inhomogeneous media is presented along with characteristics of the Eaton lens. Comparisons are given of the radiation pattern and directivity of small Luneburg lens with a homogeneous lens. References and figure captions on radiation patterns are included.

  10. Standard Transistor Arrays

    NASA Technical Reports Server (NTRS)

    Cox, G. W.; Carroll, B. D.; Pitts, E. R.; Wright, R. A.

    1983-01-01

    Standard Transistor Array (STAR) design system is semicustom approach to generating random-logic integrated MOS digital circuits. Primary program in STAR system is CAPSTAR, STAR Cell Arrangement Program. CAPSTAR is augmented by automatic routining program, Display program and library of logic cells.

  11. TRMM Solar Array Panels

    NASA Technical Reports Server (NTRS)

    1998-01-01

    This final report presents conclusions/recommendations concerning the TRMM Solar Array; deliverable list and schedule summary; waivers and deviations; as-shipped performance data, including flight panel verification matrix, panel output detail, shadow test summary, humidity test summary, reverse bias test panel; and finally, quality assurance summary.

  12. Array processors in chemistry

    SciTech Connect

    Ostlund, N.S.

    1980-01-01

    The field of attached scientific processors (''array processors'') is surveyed, and an attempt is made to indicate their present and possible future use in computational chemistry. The current commercial products from Floating Point Systems, Inc., Datawest Corporation, and CSP, Inc. are discussed.

  13. Automated array assembly

    NASA Technical Reports Server (NTRS)

    Daiello, R. V.

    1977-01-01

    A general technology assessment and manufacturing cost analysis was presented. A near-term (1982) factory design is described, and the results of an experimental production study for the large-scale production of flat-panel silicon and solar-cell arrays are detailed.

  14. The Askaryan Radio Array

    NASA Astrophysics Data System (ADS)

    Hoffman, Kara D.

    2013-01-01

    Ultra high energy cosmogenic neutrinos could be most efficiently detected in dense, radio frequency (RF) transparent media via the Askaryan effect. Building on the expertise gained by RICE, ANITA and IceCube's radio extension in the use of the Askaryan effect in cold Antarctic ice, we are currently developing an antenna array known as ARA (The Askaryan Radio Array) to be installed in boreholes extending 200 m below the surface of the ice near the geographic South Pole. The unprecedented scale of ARA, which will cover a fiducial area of ~ 100 square kilometers, was chosen to ensure the detection of the flux of neutrinos suggested by the observation of a drop in high energy cosmic ray flux consistent with the GZK cutoff by HiRes and the Pierre Auger Observatory. Funding to develop the instrumentation and install the first prototypes has been granted, and the first components of ARA were installed during the austral summer of 2010-2011. Within 3 years of commencing operation, the full ARA will exceed the sensitivity of any other instrument in the 0.1-10 EeV energy range by an order of magnitude. The primary goal of the ARA array is to establish the absolute cosmogenic neutrino flux through a modest number of events. This information would frame the performance requirements needed to expand the array in the future to measure a larger number of neutrinos with greater angular precision in order to study their spectrum and origins.

  15. Permanent Magnet Ecr Plasma Source With Magnetic Field Optimization

    DOEpatents

    Doughty, Frank C. (Plano, TX); Spencer, John E. (Plano, TX)

    2000-12-19

    In a plasma-producing device, an optimized magnet field for electron cyclotron resonance plasma generation is provided by a shaped pole piece. The shaped pole piece adjusts spacing between the magnet and the resonance zone, creates a convex or concave resonance zone, and decreases stray fields between the resonance zone and the workpiece. For a cylindrical permanent magnet, the pole piece includes a disk adjacent the magnet together with an annular cylindrical sidewall structure axially aligned with the magnet and extending from the base around the permanent magnet. The pole piece directs magnetic field lines into the resonance zone, moving the resonance zone further from the face of the magnet. Additional permanent magnets or magnet arrays may be utilized to control field contours on a local scale. Rather than a permeable material, the sidewall structure may be composed of an annular cylindrical magnetic material having a polarity opposite that of the permanent magnet, creating convex regions in the resonance zone. An annular disk-shaped recurve section at the end of the sidewall structure forms magnetic mirrors keeping the plasma off the pole piece. A recurve section composed of magnetic material having a radial polarity forms convex regions and/or magnetic mirrors within the resonance zone.

  16. Science with the Square Kilometre Array

    NASA Technical Reports Server (NTRS)

    Lazio, Joseph; Huynh, Minh

    2010-01-01

    The Square Kilometre Array (SKA) is the centimeter- and meter-wavelength telescope for the 21st Century. Its Key Science Projects are (a) The end of the Dark Ages, involving searches for an H i signature and the first metalrich systems; (b) Testing theories of gravitation using an array of pulsars to search for gravitational waves and relativistic binaries to probe the strong-field regime; (c) Observations of H i to a redshift z 2 from which to study the evolution of galaxies and dark energy. (d) Astrobiology including planetary formation within protoplanetary disks; and (c) The origin and evolution of cosmic magnetism, both within the Galaxy and in intergalactic space. The SKA will operate over the wavelength range of at least 1.2 cm to 4 m (70 MHz to 25 GHz), providing milliarcsecond resolution at the shortest wavelengths.

  17. Automated inspection of surface breaking cracks using GMR sensor arrays

    SciTech Connect

    Pelkner, Matthias; Reimund, Verena; Erthner, Thomas; Panke, Nicolai; Kreutzbruck, Marc

    2014-02-18

    We present a prototype for automated magnetic stray field testing of ferromagnetic roller bearings. For this purpose NDE-adapted GMR sensor arrays (giant magneto resistance) are used for the detection of surface breaking cracks. The sensors are miniaturized down to the lower ?m-regime to achieve adequate spatial resolution. In doing so, sensor arrays with up to 48 elements are used to inspect the bearing surface within a few seconds only. In contrast to magnetic particle inspection (MPI), where the global magnetization requires a further inspection step and succeeding demagnetization, the presented prototype only locally magnetize the surface area in the vicinity of the GMR Sensors. For the local magnetization, the applied sub-surface magnetic field was simulated and proofed for detecting flaws with a depth of a few 10 ?m. By multiplexing the sensor array with an adapted read out electronics we quasi simultaneously detect the normal field component of about 100?m above the surface. The detection of artificial notches with a depth of 40 ?m and more could be resolved with a SNR better than 20 dB. The presented testing facility is fast and provides a step towards automated testing of safety relevant steel components.

  18. The interaction field in arrays of ferromagnetic barcode nanowires

    NASA Astrophysics Data System (ADS)

    Clime, L.; Zhao, S. Y.; Chen, P.; Normandin, F.; Roberge, H.; Veres, T.

    2007-10-01

    A theoretical model and an experimental approach to the identification of the interaction field in ferromagnetic barcode nanowires are described and applied to electrodeposited Ni/Au cylindrical barcode arrays. Elementary hysteresis loops of individual magnetic segments in these barcode nanowires are considered as superpositions of fully irreversible and locally reversible magnetization processes, whose distributions of switching fields are experimentally identified by first order reversal curve measurements. Non-interacting major hysteresis loops of the arrays are computed as superpositions of several elementary loops by considering the distributions of switching fields as probability density functions. The interaction field is then computed from the condition that the geometric transformation of the experimental major hysteresis loop into the Preisach operative plane be well approximated by this non-interacting hysteresis loop. Experimental interaction field values are compared with those obtained by numerical micromagnetic computations and a very good agreement is obtained on extended Ni/Au barcode arrays. The simple and accurate phenomenological model for the interaction field in multisegmented ferromagnetic nanowire arrays proposed here provides an insight into the morphology of these magnetic nanomaterials, as quantitative information about individual nano-objects may be extracted from macroscopic measurements of their arrays.

  19. Detail of array structural elements through axis of array, looking ...

    Library of Congress Historic Buildings Survey, Historic Engineering Record, Historic Landscapes Survey

    Detail of array structural elements through axis of array, looking north-northeast - Over-the-Horizon Backscatter Radar Network, Columbia Falls Radar Site Receive Sector Two Antenna Array, At the end of Shadagee Ridge Road, Columbia Falls, Washington County, ME

  20. Multi-array borehole resistivity and induced polarization method with mathematical inversion of redundant data

    DOEpatents

    Ward, Stanley H.

    1989-01-01

    Multiple arrays of electric or magnetic transmitters and receivers are used in a borehole geophysical procedure to obtain a multiplicity of redundant data suitable for processing into a resistivity or induced polarization model of a subsurface region of the earth.