These are representative sample records from Science.gov related to your search topic.
For comprehensive and current results, perform a real-time search at Science.gov.
1

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

NASA Astrophysics Data System (ADS)

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.

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

2014-05-01

2

Modeling maglev passenger compartment static magnetic fields from linear Halbach permanent-magnet arrays  

Microsoft Academic Search

Passenger compartment magnetic field levels in a low-speed magnetic levitation (maglev) vehicle that uses linear Halbach permanent-magnet arrays for both levitation and propulsion are computed through superposition of fields due to patches of magnetization charge at surfaces where the magnetization is discontinuous. End effects due to the finite lengths of the arrays lead to fields that decay much less rapidly

James F. Hoburg

2004-01-01

3

Halbach Magnetic Rotor Development  

NASA Technical Reports Server (NTRS)

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.

Gallo, Christopher A.

2008-01-01

4

Novel permanent magnet machines using Halbach cylinders  

Microsoft Academic Search

This paper describes various permanent magnet machines using Halbach cylinders (arrays), from using pre-magnetised anisotropic magnet segments having varying magnetisation orientations, to those moulded as bonded isotropic or anisotropic NdFeB ring magnets, which are subsequently impulse magnetised using a magnetisation fixture which produces a sinusoidal MMF distribution. Three possible magnetisation fixture designs are described. Various Halbach cylinder machine topologies are

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

2000-01-01

5

Position sensor for linear synchronous motors employing halbach arrays  

DOEpatents

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.

Post, Richard Freeman

2014-12-23

6

A two-pole Halbach permanent magnet guideway for high temperature superconducting Maglev vehicle  

Microsoft Academic Search

In order to improve the levitation performance of the high temperature superconducting (HTS) magnetic levitation (Maglev) vehicle, a two-pole Halbach array’s permanent magnet guideway (PMG) is proposed, which is called as Halbach PMG. The finite element method (FEM) calculations indicate that Halbach PMG has a wider high-field region than the present PMG of equal PM’s transverse section. The levitation force

H. Jing; J. Wang; S. Wang; L. Wang; L. Liu; J. Zheng; Z. Deng; G. Ma; Y. Zhang; J. Li

2007-01-01

7

Halbach array DC motor/generator  

DOEpatents

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.

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

1998-01-01

8

Halbach array DC motor/generator  

DOEpatents

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.

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

1998-01-06

9

Energy harvesting from electric power lines employing the Halbach arrays  

NASA Astrophysics Data System (ADS)

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.

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

2013-10-01

10

Optimal Halbach permanent magnet designs for maximally pulling and pushing nanoparticles  

E-print Network

Optimal Halbach permanent magnet designs for maximally pulling and pushing nanoparticles A. Sarwar Available online 19 September 2011 Keywords: Magnetic nanoparticle Targeted drug deliver Magnetic drug targeting Optimal permanent magnet Nano-particle trapping Pushing nanoparticle Halbach array design a b

Shapiro, Benjamin

11

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

NASA Technical Reports Server (NTRS)

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.

Thompson, William K.

2006-01-01

12

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

SciTech Connect

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.

NONE

1995-02-01

13

Torque Production in a Halbach Machine  

NASA Technical Reports Server (NTRS)

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.

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

2006-01-01

14

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

NASA Astrophysics Data System (ADS)

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.

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

2014-09-01

15

Magnetic arrays  

DOEpatents

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.

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

1997-05-20

16

Magnetic arrays  

SciTech Connect

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.

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

1997-05-20

17

Comparison of conventional and novel quadrupole drift tube magnets inspired by Klaus Halbach  

SciTech Connect

Quadrupole drift tube magnets for a heavy-ion linac provide a demanding application of magnet technology. A comparison is made of three different solutions to the problem of providing an adjustable high-field-strength quadrupole magnet in a small volume. A conventional tape-wound electromagnet quadrupole magnet (conventional) is compared with an adjustable permanent-magnet/iron quadrupole magnet (hybrid) and a laced permanent-magnet/iron/electromagnet (laced). Data is presented from magnets constructed for the SuperHILAC heavy-ion linear accelerator, and conclusions are drawn for various applications.

Feinberg, B. [Lawrence Berkeley Lab., CA (United States)

1995-02-01

18

Investigation on the Room Temperature Active Magnetic Regenerative Refrigerator with Permanent Magnet Array  

NASA Astrophysics Data System (ADS)

In this study, a room temperature active magnetic regenerative refrigerator is investigated experimentally as well as numerically. Gadolinium is selected as a magnetic refrigerant. A permanent magnet array, so called Halbach array, is employed to produce strong magnetic field. The AMR (Active Magnetic Regenerator) is reciprocated through the bore of the magnet array and produces cooling power. Helium is supplied by a helium compressor equipped with a rotary valve. Although the refrigeration effect is generated due to the pressure fluctuation of the helium flow, the enhancement of refrigeration by the magnetocaloric effect can be observed. One dimensional numerical simulation for the AMR is established. Measured mass flow rate, inlet temperature and pressure fluctuation are used as boundary conditions, and the calculated temperature distribution during the steady state is compared with the measured one. The model and the numerical simulation in this paper will be a useful tool for prediction of AMR's performance and investigation of the internal state of AMR.

Kim, Y.; Jeong, S.

2010-04-01

19

Metamaterial anisotropic flux concentrators and magnetic arrays  

E-print Network

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.

Bjørk, R; Bahl, C R H

2014-01-01

20

Coherent magnetic semiconductor nanodot arrays  

PubMed Central

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

2011-01-01

21

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)

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.

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

2012-10-01

22

Passive magnetic bearing system  

DOEpatents

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.

Post, Richard F.

2014-09-02

23

Design, optimization, and purity of permanent magnet helical wigglers for free-electron lasers  

NASA Astrophysics Data System (ADS)

A helical wiggler field can be produced inside a cylindrical waveguide by properly distributing and orienting an array of permanent magnets within an annular shell surrounding the waveguide. The design and optimization of such wigglers is considered herein, along with assessments of the strength and spectral purity achievable under practical constraints of equality and uniformly magnetized rare-earth cobalt magnets. Starting with the optimum continuum magnetization, a design is derived that differs from Halbach's primarily in that it includes axially directed components of magnetization. A comparison of the two approaches to helical wiggler design is made in terms of the field strength and purity each can achieve under similar constraints. The optimized design is shown to generate stronger and purer helical wiggler fields than Halbach's version for typical parameters. A modified design that uses many small magnets and does not fill the annular space is suggested and evaluated.

Diament, P.

1985-07-01

24

Investigation of magnetic interactions in large arrays of magnetic nanowires  

NASA Astrophysics Data System (ADS)

The magnetic interactions in large arrays of ordered magnetic nanowires with 12-48nm diameter and 55-95nm spacing were investigated using modified Henkel plots. The measurements for nanowire arrays ac demagnetized with the field applied parallel to the nanowire axis (the easy magnetization axis) indicate that the dominant interaction during the switching process is the magnetostatic coupling between the nanowires. Nevertheless, while the strength of the magnetostatic interactions increases with the magnetic moment associated with the nanowires, the increase is not linear with respect to the volume of the nanowires. Moreover, the dependence of the remanence curves on the field history suggests that even for magnetic nanowire systems with high geometric anisotropy, the magnetic pole structure of the nanowires can be complex. This conclusion is also supported by the field dependence of the initial magnetization curves.

Fodor, P. S.; Tsoi, G. M.; Wenger, L. E.

2008-04-01

25

The Inductrack Approach to Magnetic Levitation  

SciTech Connect

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.

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

2000-04-19

26

Phase combination for self-cancellation of magnetic force in undulators  

NASA Astrophysics Data System (ADS)

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.

Kinjo, Ryota; Tanaka, Takashi

2014-12-01

27

Self-organized magnetization in arrays of bistable nanowires  

Microsoft Academic Search

The study of arrays of magnetic nanowires is of interest for potential technological applications in perpendicular recording media. Magnetostatic interactions between individual nanowires play an important role in the magnetization process of the array. The objective of this work is to theoretically analyze the influence of the symmetry of the geometrical array. It is shown that magnetization reversal in an

J. Velazquez; M. Vazquez

2002-01-01

28

Studies of strong magnetic field produced by permanent magnet array for magnetic refrigeration  

NASA Astrophysics Data System (ADS)

The success of a room temperature magnetic refrigerator (RTMR) depends critically on two essential parts: a high magnetic field and a magnetic refrigerant material with large magnetocaloric effect. A carefully designed hollow cylindrical permanent magnet array (HCPMA) can be used to provide strong magnetic field in the cavity, the magnitude of the resulting static field can be even greater than the remanence magnetization of the magnets comprising a HCPMA. A thorough understanding of the magnetic field distribution will provide an invaluable insight into the design and optimization of HCPMA in the reciprocating and rotary RTMR systems. Here, we show a construction of a 16 piece HCPMA with realistic dimensions and we illustrate the mechanism of generating a high magnetic field in such device. We present an effective way to calculate the field distribution of a permanent magnet array with finite size and an unsymmetrical geometry. Furthermore, detailed numerical results of the magnetic field distribution and its dependence on device dimensions are presented.

Xu, X. N.; Lu, D. W.; Yuan, G. Q.; Han, Y. S.; Jin, X.

2004-06-01

29

Magnetic flux array for spontaneous magnetic reconnection experiments A. Kesich, J. Bonde, J. Egedal,a  

E-print Network

Magnetic flux array for spontaneous magnetic reconnection experiments A. Kesich, J. Bonde, J; published online 24 June 2008 Experimental investigation of reconnection in magnetized plasmas relies on accurate characterization of the evolving magnetic fields. In experimental configurations where the plasma

Egedal, Jan

30

Arrays of carbon nanoscrolls as deep subwavelength magnetic metamaterials  

NASA Astrophysics Data System (ADS)

We demonstrate theoretically that an array of carbon nanoscrolls acts as a hyperbolic magnetic metamaterial in the terahertz regime with genuine subwavelength operation corresponding to a wavelength-to-structure ratio of about 200. Due to the low sheet resistance of graphene, the electromagnetic losses in an array of carbon nanoscrolls are almost negligible, offering a very sharp magnetic resonance of extreme positive and negative values of the effective magnetic permeability. The latter property leads to superior imaging properties for arrays of carbon nanoscrolls which can operate as magnetic endoscopes in the terahertz range where magnetic materials are scarce. Our optical modeling is supplemented with ab initio density functional calculations of the self-winding of a single layer of graphene onto a carbon nanotube so as to form a carbon nanoscroll. The latter process is viewed as a means to realize ordered arrays of carbon nanoscrolls in the laboratory based on arrays of aligned carbon nanotubes which are now routinely fabricated.

Yannopapas, Vassilios; Tzavala, Marilena; Tsetseris, Leonidas

2013-10-01

31

Novel microwave properties and "memory effect" in magnetic nanowire array  

NASA Astrophysics Data System (ADS)

Ferromagnetic nanowire arrays embedded in insulating matrices have attracted great attention in recent years for their rich physics and potential as sensor and microwave applications. Magnetic nanowires made of 3d transitional metals or their alloys have the advantages of high saturation magnetizations, limited eddy current loss, and guaranteed microwave penetration due to nanometer size. The nanowire arrays can also have high ferromagnetic resonance (FMR) frequencies due to shape anisotropy. In this work, the following new phenomena of magnetic nanowire arrays are demonstrated and explained with a theoretical model. (1) A simple theoretical analysis indicates that high permeability is possible in nanowire arrays with the magnetocrystalline anisotropy comparable to the demagnetization energy and its easy axis perpendicular to the nanowire. With proper conditions, we have fabricated Co nanowire arrays with a crystalline easy axis perpendicular to the nanowire. For Co nanowire arrays with certain geometries, high permeability and low losses have been achieved. (2) Magnetic materials with tunable FMR are highly desirable in microwave devices. We demonstrate that the natural FMR of Ni90Fe10 nanowire array can be tuned continuously from 8.2 to 11.7 GHz by choosing different remanent state. Theoretical model based on dipolar interaction among nanowires has been developed to explain the observed phenomena. A double FMR feature caused by dipolar interaction in magnetic nanowire array was predicted and verified in Co nanowires. (3) A memory effect has also been demonstrated in magnetic nanowire arrays. The magnetic nanowire array has the ability to record the maximum magnetic field that the array has been exposed to after the field has been turned off. The origin of the memory effect is the strong magnetic dipole interaction among the nanowires. Based on the memory effect, a novel and extremely low cost EMP detection scheme is proposed. It has the potential to measure magnetic field pulses as high as a few hundred Oe without breaking down. In the proposed EMP detector, a magnetic field sensor is required to measure the surface field of the magnetic nanowire array. MgO based magnetic tunnel junction (MTJ) is one type of magnetic field sensors. We investigated the evolution of the magnetic transport properties as a function of short annealing time in MgO based MTJ junctions. It is found that the desired sensor behavior appears in samples annealed for 17 minutes. The result can be well fitted by using the superparamagnetism theory, suggesting the formation of superparamagnetic particles in the free layer during the high temperature annealing. The control of MTJ properties with annealing time is desirable in magnetic field sensor productions.

Kou, Xiaoming

2011-12-01

32

A magnetic microstirrer and array for microfluidic mixing  

Microsoft Academic Search

We report the development of a micromachined magnetic-bar micromixer for microscale fluid mixing in biological laboratory-on-a-chip applications. The mixer design is inspired by large scale magnetic bar mixers. A rotating magnetic field causes a single magnetic bar or an array of them to rotate rapidly within a fluid environment. A fabrication process of the magnetic bar mixer is developed. Results

Liang-Hsuan Lu; Kee Suk Ryu; Chang Liu

2002-01-01

33

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)

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.

Lu, Yiyun; Liu, Guoliang; Qin, Yujie

2014-10-01

34

Vectorial calibration of 3D magnetic field sensor arrays  

Microsoft Academic Search

The vectorial calibration of magnetic field sensor arrays along three axes is presented. In this context, a distinction must be made between the calibration of alignment errors between the 3D sensors and the calibration of orthogonality errors between the three axes of a 3D sensor. Alignment errors within the sensor array are determined by using a homogeneous vector field generated

M. P. Lassahn; G. Trenkler

1995-01-01

35

Magnetic properties of submicrometric antidot arrays in cobalt films  

NASA Astrophysics Data System (ADS)

Arrays of elliptical and square shaped submicrometric antidots were successfully prepared in a continuous cobalt layer using a technique combining electron beam lithography and ion beam etching. Their dynamic magnetic properties were investigated using Brillouin light scattering (BLS) spectroscopy. The BLS results are interpreted with the help of a semi quantitative model taking account of the demagnetizing field arising from the antidots array. In addition, we present magnetic force microscopy (MFM) images showing magnetic domains connecting each square antidot to its neighbours: this indicates that the antidots behave as pinning sites for domain walls through the whole patterned array. The MFM observations are compared to the magnetic topography calculated using the public OOMMF code.

Chérif, S.-M.; Roussigné, Y.; Moch, P.

2006-09-01

36

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

NASA Astrophysics Data System (ADS)

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.

Liu, Lu; Wang, Jiasu

2014-05-01

37

Selective actuation of arrays of carbon nanotubes using magnetic resonance.  

PubMed

We introduce the use of ferromagnetic resonance (FMR) to actuate mechanical resonances in as grown arrays of carbon nanotubes (CNTs) loaded with Ni particles (Ni-CNTs). This contactless method is closely related to the magnetic resonance force microscopy technique and provides spatial selectivity of actuation along the array. The Ni-CNT arrays are grown by chemical vapor deposition and are composed of homogeneous CNTs with uniform length (~600 nm) and almost equal diameter (~20 nm), which are loaded with Ni catalyst particles at their tips due to the tip growth mode. The vibrations of the Ni-CNTs are actuated by relying on the driving force that appears due to the FMR excited at about 2 GHz in the Ni particles (diameter ~100 nm). The Ni-CNT oscillations (frequency ~40 MHz) are detected mechanically by atomic force microscopy. The acquired oscillation images of the Ni-CNT uniform array reveal clear maxima in the spatial distribution of the oscillation amplitudes. We attribute these maxima to the "sensitive slices", i.e., the spatial regions of the Ni-CNT array where the FMR condition is met. Similar to magnetic resonance imaging, the sensitive slice is determined by the magnetic field gradient and moves along the Ni-CNT array as the applied magnetic field is ramped. Our excitation method does not require the presence of any additional microfabricated electrodes or coils near the CNTs and is particularly advantageous in cases where the traditional electrical actuation methods are not effective or cannot be implemented. The remote actuation can be effectively implemented also for arrays of other magnetic nanomechanical resonators. PMID:23742039

Volodin, Alexander; Santini, Claudia A; De Gendt, Stefan; Vereecken, Philippe M; Van Haesendonck, Chris

2013-07-23

38

Magnetic current loop array in a reflector antenna  

NASA Astrophysics Data System (ADS)

A magnetic current loop antenna array is designed, implemented, and measured. Radiation pattern, input impedance, and efficiency of the array are presented. The array is intended as a feed in a reflector antenna. Using a 360 mm solid dish, the overall gain of the reflector antenna is 24.6 dB at 9 GHz. The tolerance in placing the feed at the focal point of the dish is high. The present feed is low cost, self-supportive, robust, and easy to manufacture. It is an ideal substitute for the horn in a TVRO (television receive only) or VSAT (very small aperature terminal) antenna.

Yung, Edward K. N.; Lee, Wilson W. S.

1994-04-01

39

Optimizing colloidal dispersity of magnetic nanoparticles based on magnetic separation with magnetic nanowires array  

NASA Astrophysics Data System (ADS)

Based on sharp geometry of Ni nanowires, we developed a novel high-gradient magnetic separator that was composed of a nanowires array and a uniform magnetic field. When suspension of magnetic nanoparticles (MNPs) flowed through it, the relatively large nanoparticles or clusters were removed from the suspension so that the size distribution can be improved. The separation resulted from magnetic force so that extra molecules or solvents were unnecessary to add. The performance was proved by scanned electron microscopy characterization and dynamic light scattering measurement. The improvement in magnetic colloidal dispersivity is important for the biomedical application of MNPs. Our results may also play a role in microfluidic application and nanoparticle-based detection.

Sun, Jianfei; He, Miaomiao; Liu, Xuan; Gu, Ning

2014-09-01

40

Optimizing colloidal dispersity of magnetic nanoparticles based on magnetic separation with magnetic nanowires array  

NASA Astrophysics Data System (ADS)

Based on sharp geometry of Ni nanowires, we developed a novel high-gradient magnetic separator that was composed of a nanowires array and a uniform magnetic field. When suspension of magnetic nanoparticles (MNPs) flowed through it, the relatively large nanoparticles or clusters were removed from the suspension so that the size distribution can be improved. The separation resulted from magnetic force so that extra molecules or solvents were unnecessary to add. The performance was proved by scanned electron microscopy characterization and dynamic light scattering measurement. The improvement in magnetic colloidal dispersivity is important for the biomedical application of MNPs. Our results may also play a role in microfluidic application and nanoparticle-based detection.

Sun, Jianfei; He, Miaomiao; Liu, Xuan; Gu, Ning

2015-02-01

41

Single magnet levitation by repulsion using a planar coil array  

Microsoft Academic Search

This paper describes the controlled levitation of a single disk magnet above an array of cylindrical coils, using electromagnetic repulsion to generate actuation forces and torques from coil currents, and an optical motion tracking system to provide realtime position and orientation measurements for feedback control. Our method is to measure the electromagnetic forces and torques generated from a single cylindrical

Peter Berkelman; Michael Dzadovsky

2008-01-01

42

Electrochemical synthesis of highly ordered magnetic multilayered nanowire arrays  

NASA Astrophysics Data System (ADS)

Electrochemical deposition is a versatile technique that has been employed to synthesize various types of onedimensional nanostructures such as nanorods, nanotubes and nanowires to meet different requirements for applications. Magnetic nanowires in the form of multilayered structures, such as Co/Cu and permalloy (Ni80Fe20)/Cu, with ferromagnetic materials alternating with non-magnetic materials exhibit giant magnetoresistance (GMR) property that can be utilized in sensors and mass memory devices. This study focuses on the synthesis of highly ordered magnetic multilayered nanowire arrays using template-directed electrochemical deposition technique. The nanowires were electrodeposited within the nanopores of anodized alumina from sulphate baths via pulse potential technique. The structures and compositions of the wires were characterized using various microscopy and probe-based techniques. Magnetoresistance measurement was performed on the multilayered nanowire arrays.

Kok, Kuan-Ying; Ng, Inn-Khuan; Saidin, Nur Ubaidah; Zali, Nurazila Mat; Bustamam, Farah Khuwailah Ahmad; Shaari, Abdul Halim

2012-06-01

43

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

NASA Astrophysics Data System (ADS)

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.

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

2014-02-01

44

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

PubMed Central

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 field’s 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

Zablotskii, Vitalii; Dejneka, Alexandr; Kubinová, Šárka; Le-Roy, Damien; Dumas-Bouchiat, Frédéric; Givord, Dominique; Dempsey, Nora M.; Syková, Eva

2013-01-01

45

The Square Kilometre Array: A new probe of cosmic magnetism  

E-print Network

Magnetic fields are a fundamental part of many astrophysical phenomena, but the evolution, structure and origin of magnetic fields are still unresolved problems in physics and astrophysics. When and how were the first fields generated? Are present-day magnetic fields the result of standard dynamo action, or do they represent rapid or recent field amplification through other processes? What role do magnetic fields play in turbulence, cosmic ray acceleration and structure formation? I explain how the Square Kilometre Array (SKA), a next-generation radio telescope, can deliver stunning new data-sets that will address these currently unanswered issues. The foundation for these experiments will be an all-sky survey of rotation measures, in which Faraday rotation toward >10^7 background sources will provide a dense grid for probing magnetism in the Milky Way, nearby galaxies, and in distant galaxies, clusters and protogalaxies. Using these data, we can map out the evolution of magnetized structures from redshifts z > 3 to the present, can distinguish between different origins for seed magnetic fields in galaxies, and can develop a detailed model of the magnetic field geometry of the intergalactic medium and of the overall Universe. In addition, the SKA will certainly discover new magnetic phenomena beyond what we can currently predict or imagine.

Bryan M. Gaensler

2006-03-02

46

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

NASA Astrophysics Data System (ADS)

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.

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

2014-11-01

47

The Calibration of 3Axis Magnetic Sensor Array System for Tracking Wireless Capsule Endoscope  

Microsoft Academic Search

A magnetic localization and orientation system is proposed for tracking wireless capsule endoscope. This system uses a small magnet enclosed in the capsule to serve as excitation source. When the capsule moves, the magnet establishes a static magnetic field around. With the magnetic sensor array composed of Honeywell 3-axis magnetic sensors, HMC1053, the magnetic intensities in some pre-determined spatial points

Chao Hu; Max Q.-H. Meng; Mrinal Mandal

2006-01-01

48

Magnetic Sense Coil Array for the FAMU Spheromak  

NASA Astrophysics Data System (ADS)

First plasmas in the Florida A&M Spheromak are expected in 2012. Here we describe the design, construction, and calibration of a magnetic sense coil array that will provide measurements of the edge poloidal and toroidal magnetic field fluctuations in the spheromak. The electrostatically shielded coils are mounted flush with the inner edge of the vacuum chamber. Custom differential amplifiers, based on designs by the MST group at the University of Wisconsin-Madison, enable fluctuation measurements up to frequencies of 2 MHz.

Vandervort, Robert; Keesee, Amy; Lusk, Greg; Reynolds, Eric; Scime, Earl

2012-10-01

49

Domain configuration and magnetization switching in arrays of permalloy nanostripes  

NASA Astrophysics Data System (ADS)

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.

Iglesias-Freire, Ó.; Jaafar, M.; Pérez, L.; de Abril, O.; Vázquez, M.; Asenjo, A.

2014-04-01

50

Magnetic Fields with the Atacama Large Millimeter/Submillimeter Array  

NASA Astrophysics Data System (ADS)

The Atacama Large Millimeter/submillimeter Array (ALMA) is one of the largest radio telescopes and is located at 5, 000 m altitude in the Atacama desert in Chile. Its unprecedented sensitivity at extremely high angular and spectral resolution in the (sub-)millimetre wavelength regime, allows for countless advances in astrophysics. One of the areas in which ALMA can make unique contributions, is in that of the study of astrophysical magnetic fields. ALMA is expected to map the magnetic field geometry, and in some cases strength, in a large number of star forming regions, around evolved stars and planetary nebulae, and in nearby galaxies. This chapter provides examples of the amount of improvement ALMA offers the study of magnetic fields based on the current state-of-the-art and shortly introduces new tools that will be available to analyse (sub-)millimetre polarimetric observations.

Vlemmings, Wouter

51

Dependence of magnetization process on thickness of Permalloy antidot arrays  

SciTech Connect

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.

Merazzo, K. J.; Real, R. P. del; Asenjo, A.; Vazquez, M. [Instituto de Ciencia de Materiales de Madrid, Campus de Cantoblanco, 28049 Madrid (Spain)

2011-04-01

52

Magnetization reversal induced by irregular shape nanodots in square arrays  

NASA Astrophysics Data System (ADS)

Ni 80Fe 20 nanodots in square arrays of irregular shape (C 1h(m) and x-, y-translations symmetry) and circular shape (D 4h (4/mmm)) nanodots of the same area were fabricated under controlled exposure conditions by e-beam lithography, ion beam sputtering coating and further lift-off. The center-to-center nearest dot distances was 700 nm in all the measured arrays. An unpatterned film was fabricated in the same IBS batch for comparison purposes. Structures and magnetic properties were characterized using AFM, SEM and high-sensitivity focused magneto-optical Kerr effect (MOKE). The mechanism of the magnetization reversal of arrays is discussed in two different scenarios: vortex and single-domain. It has been shown that circular dots reverse only through vortex configuration whereas the irregular does either via single-domain and vortex configuration, depending of the dot size. Variable domain phases are confirmed by OOMMF (Object Oriented Micromagnetic Framework) micromagnetic simulations.

Redondo, C.; Sierra, B.; Moralejo, S.; Castano, F.

2010-07-01

53

Magnetocaloric effect: permanent magnet array for generation of high magnetic fields  

NASA Astrophysics Data System (ADS)

The magnetocaloric effect (MCE), the heating or cooling of magnetic materials in a magnetic field, is unusually large in the Gd_5(Si_xGe_1-x)4 alloy system. Normally the maximum in the MCE occurs at the Curie temperature (Tc) because the spin entropy change is a maximum. By suitable selection of the composition of this alloy system the Curie temperature can be changed over the range 25 K for x = 0 to 340 K for x =1, and the composition range around x = 0.5 exhibits the largest magnetocaloric effect. In order to increase the amount of heat exchanged the change in applied magnetic field should be as large as possible, and in this research values above 1.5 Tesla are suggested. We have studied a permanent magnet array based on NdFeB, which with a remanent magnetization of only 1.2 Tesla can still generate a magnetic flux density, or magnetic induction B of 2-3 Tesla. In order to generate the high magnetic induction in the absence of a power supply, a modified hollow cylindrical permanent magnet array (HCPMA) has been designed to produce the required strength of magnetic field. Soft magnetic materials including permalloy (NiFe) were used for focusing the magnetic field in the central region. The magnitude of the magnetic flux density at the center was about 2 Tesla. The magnitude and homogeneity of the magnetic field for this design are comparable with the conventional C-shaped yoke and HCPMA. This can be easily adapted for a low power rotary system in which the magnetocaloric material can be exposed alternately to high and low magnetic fields so that it can accept and reject heat from its surroundings.

Lee, Seong-Jae; Kenkel, John; Jiles, David

2002-03-01

54

Parallel RNA extraction using magnetic beads and a droplet array.  

PubMed

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

Shi, Xu; Chen, Chun-Hong; Gao, Weimin; Chao, Shih-Hui; Meldrum, Deirdre R

2015-02-01

55

High-resolution magnetic mapping using a SQUID magnetometer array  

SciTech Connect

This paper reports on a four-channel, high-resolution, Superconducting Quantum Interference Device (SQUID) magnetometer array used to map magnetic fields from various samples. Each SQUID has a 3 mm diameter pickup coil located 4.4 mm from the adjacent channel. The spacing between the cryogenic array and the room temperature sample is adjustable from 1.5 mm to 4.0 mm. We mapped the field from a 350 {mu}m diameter hole in an 11 cm {times} 15 cm {times} 60 {mu}m copper sheet that was carrying a current of 100 mA. Field shape and strength were compared with predictions from analytical and finite element models, which indicate that this technique should be able to detect an order of magnitude smaller flaws in flat plates.

Staton, D.J.; Ma, Y.P.; Sepulveda, N.G.; Wikswo, J.P. Jr. (Vanderbilt Univ., Nashville, TN (United States). Dept. of Physics and Astronomy)

1991-03-01

56

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

PubMed

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

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

2014-01-01

57

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

PubMed Central

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

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

2014-01-01

58

Development of a magnetic nanoparticle susceptibility magnitude imaging array.  

PubMed

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

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

2014-02-21

59

Development of a magnetic nanoparticle susceptibility magnitude imaging array  

NASA Astrophysics Data System (ADS)

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.

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

2014-02-01

60

A superconducting quadrupole magnet array for a heavy ion fusion driver  

SciTech Connect

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.

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

61

Graphene magnet realized by hydrogenated graphene nanopore arrays  

NASA Astrophysics Data System (ADS)

The so-called zigzag edge of graphenes theoretically has localized electrons due to the presence of flat energy bands near the Fermi level. The localized electron spins are strongly polarized, resulting in ferromagnetism. We fabricate graphenes with honeycomb-like arrays of hydrogen-terminated and low-defect hexagonal nanopores by a nonlithographic method using nanoporous alumina templates. We report large-magnitude room-temperature ferromagnetism caused by electron spins localizing at the zigzag nanopore edges. This promises to be a realization of rare-element free, controllable, transparent, flexible, and mono-atomic layer magnets and novel spintronic devices.

Tada, K.; Haruyama, J.; Yang, H. X.; Chshiev, M.; Matsui, T.; Fukuyama, H.

2011-10-01

62

How finite sample dimensions affect the reversal process of magnetic dot arrays  

NASA Astrophysics Data System (ADS)

We investigate the magnetization reversal of a magnetic dot array by means of magneto-optical Kerr effect and magnetic force microscopy measurements as well as micromagnetic simulations. We find that the finite dimensions of the dot array introduce a global configurational anisotropy that promotes state transitions first in dots near the sample boundaries. From there, the reversal process expands towards the sample body by means of collective magnetization processes originating in the magnetostatic coupling between the dots. These processes are characterized by transition avalanches and the formation of magnetization chains. These findings are important in the development of applications that rely on a robust control of dot magnetization states in dot arrays.

Van de Wiele, Ben; Fin, Samuele; Sarella, Anandakumar; Vavassori, Paolo; Bisero, Diego

2014-10-01

63

Preparation and magnetic properties of hard-magnetic (CoPt)/soft-magnetic (FeCo) composite nanocable array  

NASA Astrophysics Data System (ADS)

An array of hard-magnetic (CoPt)/soft-magnetic (FeCo) composite nanocable has been fabricated in the pores of porous anodic aluminum oxide templates: CoPt nanotubes were first prepared by high temperature chemical reduction method; FeCo alloy was then electrodeposited into the CoPt nanotubes. The morphology and structure of the nanocable array were characterized by scanning electron microscopy, transmission electron microscopy, and x-ray diffraction. The magnetic measurements showed that two apparent kinks appear in the hysteresis loop after the FeCo alloy was deposited into the CoPt nanotubes, which may be attributed to the hard-magnetic phase being partly or even completely decoupled from the soft-magnetic phase.

Zhou, D.; Zhu, M. G.; Zhou, M. G.; Guo, Z. H.; Li, W.

2011-04-01

64

Magnetic antenna excitation of whistler modes. II. Antenna arrays  

NASA Astrophysics Data System (ADS)

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.

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

2014-12-01

65

A Mobile Ferromagnetic Shape Detection Sensor Using a Hall Sensor Array and Magnetic Imaging  

PubMed Central

This paper presents a Mobile Hall Sensor Array system for the shape detection of ferromagnetic materials that are embedded in walls or floors. The operation of the Mobile Hall Sensor Array system is based on the principle of magnetic flux leakage to describe the shape of the ferromagnetic material. Two permanent magnets are used to generate the magnetic flux flow. The distribution of magnetic flux is perturbed as the ferromagnetic material is brought near the permanent magnets and the changes in magnetic flux distribution are detected by the 1-D array of the Hall sensor array setup. The process for magnetic imaging of the magnetic flux distribution is done by a signal processing unit before it displays the real time images using a netbook. A signal processing application software is developed for the 1-D Hall sensor array signal acquisition and processing to construct a 2-D array matrix. The processed 1-D Hall sensor array signals are later used to construct the magnetic image of ferromagnetic material based on the voltage signal and the magnetic flux distribution. The experimental results illustrate how the shape of specimens such as square, round and triangle shapes is determined through magnetic images based on the voltage signal and magnetic flux distribution of the specimen. In addition, the magnetic images of actual ferromagnetic objects are also illustrated to prove the functionality of Mobile Hall Sensor Array system for actual shape detection. The results prove that the Mobile Hall Sensor Array system is able to perform magnetic imaging in identifying various ferromagnetic materials. PMID:22346653

Misron, Norhisam; Shin, Ng Wei; Shafie, Suhaidi; Marhaban, Mohd Hamiruce; Mailah, Nashiren Farzilah

2011-01-01

66

Internal magnetic focusing in an array of ballistic cavities Peide D. Ye* and Seigo Tarucha  

E-print Network

Internal magnetic focusing in an array of ballistic cavities Peide D. Ye* and Seigo Tarucha NTT in an array of submicron circular cavities, fabricated by electron beam lithography and dry etching techniques. Pronounced magnetoresistance oscillations are observed that can be understood in terms of internal magnetic

Ye, Peide "Peter"

67

Application of Magnetic Circuit and Multiple-Coils Array in Induction Heating for Improving Localized Hyperthermia  

Microsoft Academic Search

? Abstract— Aiming the application of localized hyperthermia, a magnetic induction system with new approaches is proposed. The techniques in this system for improving the effectiveness of localized hyperthermia are that using magnetic circuit and the multiple-coil array instead of a giant coil for generating magnetic field. Specially, amorphous metal is adopted as the material of magnetic circuit. Detail design

Chi-Fang Huang; Xi-Zhang Lin; Yi-Ru Yang

2009-01-01

68

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

NASA Astrophysics Data System (ADS)

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.

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

2011-04-01

69

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

PubMed

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

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

2014-07-01

70

Orientation-dependent magnetic behavior in aligned nanoparticle arrays constructed by coaxial electrospinning  

NASA Astrophysics Data System (ADS)

A modified electrospinning process has been utilized to align magnetite (Fe3O4) nanoparticles inside highly oriented poly(ethylene oxide) nanofibers. The structural characterization of the fiber encapsulated nanoparticle arrays via electron microscopy has been detailed, and the magnetic behavior has been studied using vibrating sample magnetometry. The fiber encapsulated nanoparticle arrays exhibit orientation-dependent magnetic behavior with respect to the applied magnetic field. A strong anisotropy along orthogonal axes is obtained for aligned arrays and is manifested as a notable increase in the coercivity and remanence magnetization in the parallel field configuration. The magnetic behavior of isotropic fibers is also examined as a reference and no orientation dependence is observed. The results were found to corroborate theoretical predictions from the chain-of-spheres model. Such hybrid nanoparticle arrays may find relevance in applications requiring an orientation-dependent physical response and in the directional transfer of signals.

Sharma, Nikhil; Hassnain Jaffari, G.; Shah, S. Ismat; Pochan, Darrin J.

2010-02-01

71

CoCrPt antidot arrays with perpendicular magnetic anisotropy made on anodic alumina templates  

SciTech Connect

Ti(5 nm)/CoCrPt(5-20 nm) bilayers with perpendicular magnetic anisotropy were deposited by rf sputtering onto porous alumina films to form antidot arrays with period 105 nm and pore diameters ranging from 18 to 56 nm. The coercivities of the antidot arrays are greater than those of unpatterned films and show only a weak dependence on antidot diameter. Magnetic force microscopy of ac-demagnetized samples shows that the antidot arrays have domain sizes larger than the 105 nm period. The magnetic behavior is discussed in terms of domain wall pinning by the antidots.

Navas, D.; Ilievski, F.; Ross, C. A. [Department of Materials Science and Engineering, MIT, Cambridge, Massachusetts 02139 (United States)

2009-06-01

72

Local magnetization unit for GMR array based magnetic flux leakage inspection  

NASA Astrophysics Data System (ADS)

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.

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

2012-05-01

73

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

SciTech Connect

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."

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

2008-03-27

74

Magnetic and transport properties of multilayer nanoscale antidot arrays C. C. Wang and A. O. Adeyeyea  

E-print Network

Magnetic and transport properties of multilayer nanoscale antidot arrays C. C. Wang and A. O to the interplay of different interlayer coupling mechanisms. The transport properties of the antidot arrays typically show a superposition of anisotropic and giant magnetoresistance effects, and the relative

Adeyeye, Adekunle

75

Spin-waves in cylindrical magnetic dot arrays with in-plane magnetization  

NASA Astrophysics Data System (ADS)

The discrete spectrum of dipole-exchange spin-wave modes of a tangentially magnetized cylindrical magnetic dot is calculated from the solution of the Landau-Lifshitz equation and the magnetostatic Maxwell equations in a cylindrical geometry. The general surface spin-pinning conditions at the radial dot boundary are considered. The main simplifying assumptions are: (i) the dot radius is much larger than the dot height; (ii) the distribution of the variable magnetization along the dot height is uniform. The approximate dispersion equation for spin-wave modes in a dot is obtained in a simple analytical form similar to the form of the dispersion equation in an infinite film. The quantization effect of the spin-wave frequencies appears due to the finite dot radius and is essential for submicron magnetic dots. The discrete spin-wave frequencies are calculated in a practically important case of the square array of permalloy cylindrical dots. The relative intensities of spin-wave modes, when observed by Brillouin light scattering, are considered. The role of interdot dipole-dipole coupling is discussed.

Guslienko, K. Yu.; Slavin, A. N.

2000-05-01

76

Magnetic interactions and reversal mechanisms in Co nanowire and nanotube arrays  

NASA Astrophysics Data System (ADS)

Ordered hexagonal arrays of Co nanowires (NWs) and nanotubes (NTs), with diameters between 40 and 65 nm, were prepared by potentiostatic electrodeposition into suitably modified nanoporous alumina templates. The geometrical parameters of the NW/NT arrays were tuned by the pore etching process and deposition conditions. The magnetic interactions between NWs/NTs with different diameters were studied using first-order reversal curves (FORCs). From a quantitative analysis of the FORC measurements, we are able to obtain the profiles of the magnetic interactions and the coercive field distributions. In both NW and NT arrays, the magnetic interactions were found to increase with the diameter of the NWs/NTs, exhibiting higher values for NW arrays. A comparative study of the magnetization reversal processes was also performed by analyzing the angular dependence of the coercivity and correlating the experimental data with theoretical calculations based on a simple analytical model. The magnetization in the NW arrays is found to reverse by the nucleation and propagation of a transverse-like domain wall; on the other hand, for the NT arrays a non-monotonic behavior occurs above a diameter of ˜50 nm, revealing a transition between the vortex and transverse reversal modes.

Proenca, M. P.; Sousa, C. T.; Escrig, J.; Ventura, J.; Vazquez, M.; Araujo, J. P.

2013-03-01

77

Magnetic Assembly of High-Density DNA Arrays for Genomic Analyses  

PubMed Central

A method for rapidly assembling high-density DNA arrays with near-perfect order is described. Photolithography is used to generate a wafer-scale array of microwells in a layer of photoresist on a chemically functionalized glass coverslip. The array is enclosed within a microfluidic device, and a suspension of superparamagnetic microbeads conjugated to DNA molecules is introduced into the chamber. A permanent magnet is used to direct the rapid assembly of the beads into the wells, with each well containing a single bead. These beads are immobilized on the glass surface via affinity binding, and excess beads can be recycled or washed away. Nonspecifically bound beads are removed by dissolving the photoresist. The result is a high-density array of beads with virtually no background. This method can be used to produce protein arrays for chip-based assays and DNA arrays for geno-typing or genome sequencing. PMID:18260655

Barbee, Kristopher D.; Huang, Xiaohua

2010-01-01

78

Circular sensor array and nonlinear analysis of homopolar magnetic bearings  

E-print Network

n-sensor array are operational. Sensor failures result in reduced synchronous amplitude and increased harmonic amplitudes after failure. These amplitudes are predicted using derived expressions and synchronous measurement error can be corrected using...

Wiesenborn, Robert Kyle

2007-04-25

79

Comparing artificial frustrated magnets: geometric effects in nanomagnet arrays  

Microsoft Academic Search

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

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

2009-01-01

80

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

NASA Technical Reports Server (NTRS)

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.

Groom, Nelson J.

1993-01-01

81

Dipolar Coupling Between Nanopillar Spin Valves and Magnetic Quantum Cellular Automata Arrays  

NASA Astrophysics Data System (ADS)

We experimentally demonstrate magnetostatic coupling between a nanopillar pseudo spin valve structure and a linear array of dipole-coupled permalloy nanomagnets. Using magnetic force microscopy, we study the interaction between the spin valve and the first element of the array, and present evidence that the nanomagnet couples with the hard layer of the spin valve for two spin valves with distinctly different composition. Our study includes a statistical analysis of antiferromagnetic order within the linear array and provides insights into the range of behavior that these arrays can display. These results bear directly on the design of magnetic quantum cellular automata (MQCA) logic devices, showing that multilayer devices can couple to simple nanomagnets. Redesigning the hard layer of the magnetoresistive devices would make them operational as an electronic input that will allow integration of MQCA networks in complex electronic circuitry.

Colci, Madalina; Johnson, Mark

2013-09-01

82

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

PubMed

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

Yan, Xinqiang; Zhang, Xiaoliang; Wei, Long; Xue, Rong

2014-04-01

83

Development of flexible array eddy current probes for complex geometries and inspection of magnetic parts using magnetic sensors  

NASA Astrophysics Data System (ADS)

Eddy Current Technique is a powerful method of inspection of metal parts. When size of flaws decreases, inspection areas become hardly accessible or material is magnetic, traditional winding coil probes are less efficient. Thanks to new CIVA simulation tools, we have designed and optimized advanced EC probes: flexible EC probe based on micro-coil arrays and EC probe with magnetic sensors, including specific electronics.

Marchand, B.; Decitre, J.-M.; Sergeeva-Chollet, N.; Skarlatos, A.

2013-01-01

84

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

NASA Astrophysics Data System (ADS)

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.

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

2008-08-01

85

Arrays  

NSDL National Science Digital Library

This interactive Flash applet helps students develop the concept of equal groups as a foundation for multiplication and division. The applet displays an array of dots, some of which are covered by a card. Student use the visible number of rows and columns to determine the total number of dots. Clicking on the card reveals the full array, and a voice announces the total.

2011-01-01

86

Visible broadband magnetic response from Ag chiral Z-shaped nanohole array  

E-print Network

We show that broadband magnetic response in visible range can be achieved through an Ag chiral Z-shaped nanohole array. The broadband effect is realized by incorporating multi-scaled inverted SRRs and metal/dielectric nanostrip antenna in one unit cell of only 260 nm square lattice, resulting in multiple excitations of magnetic resonances at different wavelengths. The collective modes show structure dependence and respond separately to LCP and RCP incident light. The Ag Z- and reverse-Z-shaped nanohole arrays have been experimentally realized by shadowing vapor deposition method which exhibit broadband transmission difference, in good agreement with numerical simulations.

Han, Chunrui

2015-01-01

87

Nanoparticle arrays: From magnetic response to coupled plasmon resonances  

NASA Astrophysics Data System (ADS)

We study optical properties of optomagnetic metamaterials consisting of regular arrays of single and double Au nanodots (nanopillars). Using a combination of data from variable angle spectroscopic ellipsometry, transmission, and reflection measurements, we identify localized plasmon resonances of gold nanodots and measure their dependence on dot size and substrate type. We demonstrate that arrays of Au nanopillars can support narrow collective plasmon resonances coupled to in-plane and out-of-plane localized plasmon resonances. The spectral positions of these plasmon modes are extracted from the angular dependence of the transmission and reflection spectra for two beam polarizations. We show that nanoarrays exhibit dramatically different optical response on conductive and nonconductive substrates and study its angular dependence. The optical response of nanoarrays is described well by coupled dipole approximation. The procedure for extracting optical constants of metamaterials based on ellipsometry is discussed and applied to our samples resulting in a calculated negative index of refraction for double-dot arrays at green light.

Kravets, V. G.; Schedin, F.; Pisano, G.; Thackray, B.; Thomas, P. A.; Grigorenko, A. N.

2014-09-01

88

Fast magnetic resonance spectroscopic imaging using RF coil arrays  

E-print Network

Conventional Magnetic Resonance Spectroscopic Imaging (MRSI) suffers from both low signal-to-noise (SNR), as well as long acquisition times. The development of high-fidelity gradient coils has opened opportunities for fast ...

Gagoski, Borjan Aleksandar

2006-01-01

89

Fabrication of ultra high density ferromagnetic column arrays by porous alumina template for magnetic recording media  

Microsoft Academic Search

In this paper, we succeeded in the fabrication of Co columns that had perpendicular anisotropy with density of 800 Gbit\\/inch2. The proposed method for realizing the high-density magnetic recording media is suitable for obtaining perpendicular anisotropy, since the anisotropy can be controlled by changing the aspect ratio of the magnetic columns. For realizing ferromagnetic column array with higher recording density,

T. Shimizu; K. Morimoto; M. Nagayanagi; Fujii Y; O. Yaegashi; G. R. Wu; H. Sakaue; T. Takahagi; S. Shingubara

2003-01-01

90

Magnetic properties of asymmetric antirectangular Ni80Fe20 arrays C. C. Wang, A. O. Adeyeye,a)  

E-print Network

Magnetic properties of asymmetric antirectangular Ni80Fe20 arrays C. C. Wang, A. O. Adeyeye; accepted 29 August 2003 The magnetic properties of antirectangular arrays (2 10 m2 ) embedded into 800 Ã? is not readily explained using the conventional anisotropic magnetoresistance effect. We attribute our results

Adeyeye, Adekunle

91

Direct observation of superconducting vortex clusters pinned by a periodic array of magnetic dots in ferromagnetic/superconducting hybrid structures  

E-print Network

Direct observation of superconducting vortex clusters pinned by a periodic array of magnetic dots flux quanta by a square array of 1- m-sized ferromagnetic dots in a magnetic-vortex state magnetoresistance measurements on the hybrid structures but suggest a modified picture of the pinning mechanism. DOI

Metlushko, Vitali

92

Design and Analysis of a Nested Halbach Permanent Magnet Magnetic Refrigerator  

E-print Network

with traditional vapor compression refrigerators. There are many reasons for this and questions remain cycle efficiencies can be large. Optimization of the device generates a number of areas for improvement

Victoria, University of

93

High frequency umbilical magnetic probe array for SSX wind tunnel  

NASA Astrophysics Data System (ADS)

The Swarthmore Spheromak Experiment (SSX) wind tunnel consists of a high velocity plume of magnetized plasma injected into a copper flux conserver with dimensions L = 1 m and R = 0.08 m (aspect ratio 10:1). The plasma spheromaks in this wind tunnel typically have densities on the order of 1 - 5 x10^15 cm-3 and flow speeds of 50 km/s. In the past, fluctuations and turbulence in the SSX plasma wind tunnel during magnetic reconnection have been examined by means of two high resolution (16 position at 0.46 cm spacing) radial magnetic probes. Results from the radial probes show high frequency magnetic fluctuations at the site of reconnection. Four more probes have been design to help detect magnetic fluctuations and reconnection activity along the axial direction of the wind tunnel. The four new probes have 8 positions at 0.95 cm spacing and have a flexible bellow in vacuum and a quartz jacket. The bellows act as an umbilical giving the probe excellent flexibility and versatility. The flexibility allows the probe to be bent so it lies along the axis of the flux conserver.

Werth, A. M.; Gray, T.; Brown, M. R.

2012-10-01

94

Tuning the extraordinary optical transmission through subwavelength hole array by applying a magnetic field  

Microsoft Academic Search

The transmission of light through a thin Ag film with a periodic subwavelength hole array can be influenced by the presence of the externally applied magnetic field H. Using a three-dimensional finite element method, we show that the spectral locations of the transmission peak resonances can be shifted by varying the mag- nitude and direction of the H. The transmission

Arvind Battula; Shaochen Chen; Yalin Lu; R. J. Knize; Kitt Reinhardt

2007-01-01

95

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

SciTech Connect

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.

Syed, Wasif [School of Applied and Engineering Physics, Cornell University, Ithaca, NY 14853 (United States); Laboratory of Plasma Studies, Cornell University, Ithaca, NY 14853 (United States); Blesener, Isaac; Hammer, David A. [School of Electrical and Computer Engineering, Cornell University, Ithaca, NY 14853 (United States); Laboratory of Plasma Studies, Cornell University, Ithaca, NY 14853 (United States); Lipson, Michal [School of Electrical and Computer Engineering, Cornell University, Ithaca, NY 14853 (United States)

2009-01-21

96

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

SciTech Connect

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.

Delgado-Aparicio, L.F.; Stutman, D.; Tritz, K.; Finkenthal, M.; Kaita, R.; Roquemore, L.; Johnson, D.; Majeski, R. [Johns Hopkins University, Department of Physics and Astronomy, Plasma Spectroscopy Group, Bloomberg Center 3400 N. Charles Street, Baltimore, Maryland 21218 (United States); Princeton University Plasma Physics Laboratory, P. O. Box 451, Princeton, New Jersey 08543 (United States)

2004-10-01

97

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

NASA Technical Reports Server (NTRS)

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.

Groom, Nelson J.; Britcher, Colin P.

1992-01-01

98

Synthesis and magnetic properties of large-area ferromagnetic cylindrical nanoshell and nanocup arrays  

NASA Astrophysics Data System (ADS)

Large-area arrays of magnetic Ni80Fe20 cylindrical nanoshells, nanocups, and perforated nanocups were synthesized using oblique deposition into topographical templates patterned using laser interference lithography. The geometry of the template and the tilt angle of the sample during deposition provide versatile control over the final geometry and dimension of nanostructures with thickness below 10 nm. Decreasing shell thickness led to a magnetization switching path between onion (bidomain) and reverse onion states, bypassing the vortex (flux-closed) state. The variation of magnetization reversal processes with geometry was characterized using vibrating sample magnetometry, and the results were in good agreement with micromagnetic simulations.

Wang, Z.; Shimon, G.; Liu, X.; Thompson, C. V.; Ross, C. A.; Choi, W. K.; Adeyeye, A. O.

2013-06-01

99

Synthesis and magnetic properties of Fe100-xMox alloy nanowire arrays  

NASA Astrophysics Data System (ADS)

The Fe100-xMox (13 <= x <= 25) alloy nanowire arrays are synthesized by electrodeposition of Fe2+ and Mo2+ with different ionic ratios into the anodic aluminum oxide templates. The crystals of Fe100-xMox alloy nanowires gradually change from polycrystalline phase to amorphous phase with the increase of the Mo content and the nanowires are of amorphous structure when the Mo content reaches 25 at%, which are revealed by the X-ray diffraction and the selected area electron diffraction patterns. As the Mo content increases, the magnetic hysteresis loops of Fe100-xMox alloy nanowires in parallel to the nanowire axis are not rectangular and the slopes of magnetic hysteresis loops increase. Those results indicate that the magnetostatic interactions between nanowires and the magnetocrystalline anisotropy both have significant influences on the magnetization reversal process of the nanowire arrays.

Gao, Hua; Gao, Da-Qiang; Xue, De-Sheng

2011-05-01

100

Robotic apparatuses, systems and methods  

NASA Technical Reports Server (NTRS)

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.

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

2004-01-01

101

Robotic apparatuses, systems and methods  

NASA Technical Reports Server (NTRS)

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.

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

2006-01-01

102

Magnetization reversal in an Fe film with an array of elliptical holes on a square lattice.  

SciTech Connect

The reversal mechanism for the magnetization in an Fe film with an array of elliptical holes is investigated using the diffracted magneto-optic Kerr effect (D-MOKE) technique. D-MOKE results are obtained as a function of temperature and the angle between the applied magnetic field and an ellipse axis. The transverse and longitudinal magnetization components and minor magnetization loops are also explored in order to understand the reversal process. The experimental results are interpreted using micromagnetic simulations. The simulations account for the strong angular dependence of the hysteresis loops and provide a detailed picture of how the local magnetization evolves during reversal. The actual reversal process occurs neither by coherent rotation of domains nor by clear domain-wall motion: domain smearing appears to be a more suitable description of the phenomenon.

Guedes, I.; Grimsditch, M.; Metlushko, V.; Vavassori, P.; Camley, R.; Ilic, B.; Neuzil, P.; Kumar, R.; Materials Science Division; Univ. Illinois at Chicago; Univ. di Ferrara; Univ. Colorado; Cornell Univ.; Inst. of Microelectronics

2003-01-01

103

Quantitative detection of DNA labeled with magnetic nanoparticles using arrays of MgO-based magnetic tunnel junction sensors  

NASA Astrophysics Data System (ADS)

We have demonstrated the detection of 2.5?M target DNA labeled with 16nm Fe3O4 nanoparticles (NPs) using arrays of magnetic tunnel junction sensors with (001)-oriented MgO barrier layers. A MTJ sensor bridge was designed to detect the presence of magnetic NPs bonded with target DNA. A raw signal of 72?V was obtained using complementary target DNA, as compared with a nonspecific bonding signal of 25?V from noncomplementary control DNA. Our results indicate that the current system's detection limit for analyte DNA is better than 100nM.

Shen, Weifeng; Schrag, Benaiah D.; Carter, Matthew J.; Xiao, Gang

2008-07-01

104

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

PubMed Central

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

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

2014-01-01

105

Quantitative imaging of stray fields and magnetization distributions in hard magnetic element arrays  

E-print Network

for combining MOIF imaging with magnetic force microscopy is demonstrated which allows for quantitative and magnetic force microscopy MFM 13,14 sense magnetic stray fields or stray field gradient distribu- tions the magnetization or the stray field distributions.2 The first concept is applied, e.g., in Kerr microscopy,3

Johansen, Tom Henning

106

A magnetic and magneto-optical investigation of Co-Pt alloy nanowire arrays.  

PubMed

We have investigated the magneto-optical properties of highly ordered Co-Pt alloy nanowire arrays embedded in anodic aluminum oxide templates. The magnetic field-dependent Stokes parameters, Faraday rotation angle and ellipticity were investigated by an in-house magneto-optical measurement system. The extracted hysteresis loops are broadly consistent with magnetic hysteresis loops obtained from the vibrating sample magnetometer. The maximum Faraday rotation angle and ellipticity of these samples were examined as a function of nanowire composition. With an increase of platinum content from 9 at.% to 86 at.% in the as-deposited nanowire arrays, the maximum Faraday rotation angle per length decreases linearly from 1.39 x 10(3) degrees/cm to 1.58 x 10(2) degrees/cm. The maximum ellipticity shows a similar behavior with the composition. These linear relationships suggest a dilution model for the magnetic moment in the alloy nanowires. Our results indicate that magneto-optical measurements comprise an effective and sensitive method for monitoring the behavior of AAO-based magnetic nanowire arrays. PMID:22629903

Zhang, Jun; Shen, Tiehan H; Jones, Grenville A; Jin, Yanxin; Wang, Hanbin; Wang, Hao

2012-02-01

107

Crystallographically driven magnetic behaviour of arrays of monocrystalline Co nanowires.  

PubMed

Cobalt nanowires, 40 nm in diameter and several micrometers long, have been grown by controlled electrodeposition into ordered anodic alumina templates. The hcp crystal symmetry is tuned by a suitable choice of the electrolyte pH (between 3.5 and 6.0) during growth. Systematic high resolution transmission electron microscopy imaging and analysis of the electron diffraction patterns reveals a dependence of crystal orientation from electrolyte pH. The tailored modification of the crystalline signature results in the reorientation of the magnetocrystalline anisotropy and increasing experimental coercivity and squareness with decreasing polar angle of the 'c' growth axis. Micromagnetic modeling of the demagnetization process and its angular dependence is in agreement with the experiment and allows us to establish the change in the character of the magnetization reversal: from quasi-curling to vortex domain wall propagation modes when the crystal 'c' axis tilts more than 75° in respect to the nanowire axis. PMID:25380279

Ivanov, Yu P; Trabada, D G; Chuvilin, A; Kosel, J; Chubykalo-Fesenko, O; Vázquez, M

2014-11-28

108

Stable Divergence Angles of a Magnetic Dipole Spiral Array  

NASA Astrophysics Data System (ADS)

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°).

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

109

High-resolution imaging of remanent state and magnetization reversal of superdomain structures in high-density cobalt antidot arrays  

NASA Astrophysics Data System (ADS)

Remanent state and magnetization reversal processes of a series of cobalt antidot arrays with a fixed hole diameter (d ? 55 nm) and an array periodicity (p) ranging between 95 and 524 nm were studied by in situ Lorentz microscopy (LM) as a function of the magnetic field. At remanence, defocused LM images showed the periodicity dependence of the magnetic states inside the lattice. A remarkable transition was observed in the type of domain structures as a function of p: for the large periodicities (p > 300 nm), conventional 90° and 180° domain walls were formed, whereas in small-period antidot arrays (p ? 160 nm) magnetic superdomain walls (SDWs) were nucleated to separate regions with different average magnetization direction, the so-called magnetic superdomains. In the SDW regime, a low-frequency Fourier filtering method was implemented to allow a quantitative analysis of the LM images by the transport of intensity equation method. In situ LM experiments under applied magnetic fields were performed to study the reversal magnetization process in a particular array (p = 160 nm), and clear differences were observed as a function of the magnetic field orientation. The switching process under magnetic fields parallel to the horizontal antidot rows occurs in two stages: the system first nucleates and propagates horizontal SDWs, parallel to the field. Then, at higher magnetic fields, vertical SDWs, perpendicular to the field, appear before saturation. When the magnetic field is applied at 45° with respect to the antidot rows, both horizontal and vertical SDWs are nucleated and propagated simultaneously. All the experiments were successfully correlated with micromagnetic simulations. The current study sheds new light on the magnetization reversal processes of antidot arrays and opens new possibilities of exploiting the potential of high-resolution in situ LM and new data analysis procedures to probe magnetization processes in nanomagnetism, particularly in periodic arrays of nanomagnets.

Rodríguez, L. A.; Magén, C.; Snoeck, E.; Gatel, C.; Castán-Guerrero, C.; Sesé, J.; García, L. M.; Herrero-Albillos, J.; Bartolomé, J.; Bartolomé, F.; Ibarra, M. R.

2014-09-01

110

High-resolution imaging of remanent state and magnetization reversal of superdomain structures in high-density cobalt antidot arrays.  

PubMed

Remanent state and magnetization reversal processes of a series of cobalt antidot arrays with a fixed hole diameter (d ? 55 nm) and an array periodicity (p) ranging between 95 and 524 nm were studied by in situ Lorentz microscopy (LM) as a function of the magnetic field. At remanence, defocused LM images showed the periodicity dependence of the magnetic states inside the lattice. A remarkable transition was observed in the type of domain structures as a function of p: for the large periodicities (p > 300 nm), conventional 90° and 180° domain walls were formed, whereas in small-period antidot arrays (p ? 160 nm) magnetic superdomain walls (SDWs) were nucleated to separate regions with different average magnetization direction, the so-called magnetic superdomains. In the SDW regime, a low-frequency Fourier filtering method was implemented to allow a quantitative analysis of the LM images by the transport of intensity equation method. In situ LM experiments under applied magnetic fields were performed to study the reversal magnetization process in a particular array (p = 160 nm), and clear differences were observed as a function of the magnetic field orientation. The switching process under magnetic fields parallel to the horizontal antidot rows occurs in two stages: the system first nucleates and propagates horizontal SDWs, parallel to the field. Then, at higher magnetic fields, vertical SDWs, perpendicular to the field, appear before saturation. When the magnetic field is applied at 45° with respect to the antidot rows, both horizontal and vertical SDWs are nucleated and propagated simultaneously. All the experiments were successfully correlated with micromagnetic simulations. The current study sheds new light on the magnetization reversal processes of antidot arrays and opens new possibilities of exploiting the potential of high-resolution in situ LM and new data analysis procedures to probe magnetization processes in nanomagnetism, particularly in periodic arrays of nanomagnets. PMID:25181396

Rodríguez, L A; Magén, C; Snoeck, E; Gatel, C; Castán-Guerrero, C; Sesé, J; García, L M; Herrero-Albillos, J; Bartolomé, J; Bartolomé, F; Ibarra, M R

2014-09-26

111

Construction of hysteresis loops of single domain elements and coupled permalloy ring arrays by magnetic force microscopy  

E-print Network

by magnetic force microscopy Xiaobin Zhua) and P. Gru¨tter Department of Physics, Center for the Physics particle array were studied by magnetic force microscopy MFM . For single domain permalloy particles: 10.1063/1.1540129 I. INTRODUCTION Magnetic force microscopy MFM is a powerful tool for studying

Grütter, Peter

112

Magnetic properties of Co/Pt nanoring arrays deposited on carbon nanotubes  

NASA Astrophysics Data System (ADS)

Multiple Co/Pt bilayers were deposited on vertically aligned carbon nanotubes on an anodic aluminum oxide template. The structural and the magnetic properties of the nanoring arrays were investigated by varying the number of Co/Pt bilayers in the ranges 3-10 in multilayers with a Ta(3.0 nm)/[Co(1.0 nm)/Pt(1.5 nm)]n/Ta(1.0 nm) structure. The thickness and diameter of the nanorings increased with increasing repeat number. Compared with Co/Pt films, the Co/Pt nanoring arrays showed a larger coercivity. However, the magnetostatic interactions between the nanorings became dominant in the reversal behavior and caused a nonsquare hysteresis loop. Giant magnetoresistance structures consisting of multiple Co/Pt bilayers and a thick Cu spacer exhibited magnetization curve that were in good agreement the summation of the moments of layers with varied bilayer repetition.

Yoon, Seungha; Ho Lee, Sang; Kwak, Wonyoung; Nam, Chunghee; Bae Kim, Won; Cho, B. K.

2014-05-01

113

Magnetic properties of Fe20 Ni80 antidots: Pore size and array disorder  

NASA Astrophysics Data System (ADS)

Magnetic properties of nanoscale Fe20Ni80 antidot arrays with different hole sizes prepared on top of nanoporous alumina membranes have been studied by means of magnetometry and micromagnetic simulations. The results show a significant increase of the coercivity as well as a reduction of the remanence of the antidot arrays, as compared with their parent continuous film, which depends on the hole size introduced in the Fe20Ni80 thin film. When the external field is applied parallel to the antidots, the reversal of magnetization is achieved by free-core vortex propagation, whereas when the external field is applied perpendicular to the antidots, the reversal occurs through a process other than the coherent rotation (a maze-like pattern). Besides, in-plane hysteresis loops varying the angle show that the degree of disorder in the sample breaks the expected hexagonal symmetry.

Palma, J. L.; Gallardo, C.; Spinu, L.; Vargas, J. M.; Dorneles, L. S.; Denardin, J. C.; Escrig, J.

2013-10-01

114

Enhanced magnetic response in a gold nanowire pair array through coupling with Bloch surface waves.  

PubMed

We numerically study the coupling of magnetic plasmon polaritons (MPPs) with Bloch surface waves (BSWs) in a system composed of a one-dimensional gold nanowire pair array lying on a periodic dielectric multilayer. At an appropriate period of the dielectric multilayer, maximum coupling takes place between the MPP and the BSW. It results in two branches of hybridized MPPs with a Rabi-type splitting as large as 125 meV. The maximal magnetic field intensity achieved in the center of nanowire pairs is enhanced greatly and an enhancement factor >1.5 is observed compared with that achieved by a nanowire pair array lying directly on a substrate. This has potential applications in nonlinear optics and near-field enhanced spectroscopy. PMID:21725429

Liu, Hai; Sun, Xiudong; Pei, Yanbo; Yao, Fengfeng; Jiang, Yongyuan

2011-07-01

115

Analysis of magnetic interaction in Ni nanowire array grown using electrodeposition process  

NASA Astrophysics Data System (ADS)

Simulation and comparison of magnetic properties were performed on three types of Ni nanowire arrays grown by electrodeposition using commercial nano channel alumina (NCA) templates with nominal pore sizes of 200, 100 and 20 nm. Experimental observations on the structural behaviour of the nanowires grown inside the pores of NCA templates show that the magnetic interaction depends on the effective pore diameter and the interpore distance. A numerical simulation model based on micromagnetic calculations using object-oriented micromagnetic computing framework (OOMMF) has been developed and reported experimental results on coercivity of Ni nanowires generally agreed with the simulated ones.

Rahman, I. Z.; Boboc, A.; Razeeb, K. M.; Rahman, M. A.

2005-04-01

116

Magnetic alignment of high-aspect ratio microwires into vertical arrays  

NASA Astrophysics Data System (ADS)

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.

Beardslee, Joseph

117

Facile synthesis, assembly, and immobilization of ordered arrays of monodisperse magnetic nanoparticles on silicon substrates.  

PubMed

This paper outlines the preparation of monodisperse MnFe(2)O(4) nanoparticles modified with omega-alkenyl moieties in a one-pot reaction, requiring no ligand-exchange step, followed by deposition of the resulting surfactant-coated nanoparticles onto a hydrogen-terminated silicon (111) wafer and covalent anchoring to the surface via UV-initiated bonding, creating a stable two-dimensional array of monodisperse magnetic nanoparticles. PMID:18931762

Leem, Gyu; Jamison, Andrew C; Zhang, Shishan; Litvinov, Dmitri; Lee, T Randall

2008-10-28

118

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

SciTech Connect

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.

Liu Yuhong; Maurer, David A.; Navratil, Gerald A.; Rivera, Nicholas [Department of Applied Physics and Applied Mathematics, Columbia University in the City of New York, New York, New York 10027 (United States)

2005-09-15

119

Magnetic properties of Fe20 Ni80 antidots: Pore size and array disorder J.L. Palma a,n  

E-print Network

20Ni80 antidot arrays with different hole sizes prepared on top of nanoporous alumina membranes have of antidots is based on the growth of a magnetic thin film on the top of the nanoporous alumina membranes

Spinu, Leonard

120

Finite size effects in the static and dynamic magnetic properties of FeNi wire array structures  

E-print Network

Finite size effects in the static and dynamic magnetic properties of FeNi wire array structures A and dynamic properties of FeNi wire arrays on GaAs 001 substrates. The wires were between 0.4 and 10 m wide- polar coupling can be introduced leading to changes in the field dependent magnetoresistance behavior.5

Adeyeye, Adekunle

121

MAGNETIC INDUCTION MAPPING IN TEM OF MICRO AND NANO PATTERNED CO/NI ARRAYS.  

SciTech Connect

Understanding magnetic structures and properties of patterned magnetic films at nanometer length-scale is the area of immense technological and fundamental scientific importance. The patterned magnetic films can be used for magnetic sensing . applications, magnetic recording, magnetoelectronics, microactuators and hybrid magneto-superconducting devices. The optimization of film properties is crucially dependent on the understanding of their magnetic properties, which in turn, become sensitive to the specific geometry and, hence, magnetic configurations of a given system when the elements diminish in size. Recent progress in the field of noninterferometric phase retrieval brings the ordinary Fresnel microscopy to a new quantitative level, capable of recovering both the amplitude and phase of the object from the experimental images [1,2], and thus induction mapping of small magnetic elements with known geometry ranging from micro- to few nanometers in size. The key concept behind this approach is the improvement of phase recovery algorithm derived from the transport-of-intensity (TIE) equation with a fast-solution via Fourier transform. A number of quantitative in-situ TEM magnetization experiments can be realized now with the help of magnetic-field calibrated microscope (see, for example [3]). To demonstrate the practical use of the new approach in TEM magnetic imaging with nanoscale resolution we have prepared several films directly on 3mm TEM-grids: (a) square-patterned magnetic films of Co islands with size of 6 pm (Fig. 1), and (b) nano-patterned arrays of Ni-nanodots (Fig.2) with lateral size about 40nm. The Co-films were prepared in UHV system by electron-beam evaporation of Co through an appropriate mask onto 30-nm-thick Si{sub 3}N{sub 4} membrane. The thickness of magnetic elements was approximately 40 nm as determined by EELS. The array of Ni-nanodots on a carbon membrane was prepared by electron-beam TEM-nanolithography followed by oblique angle deposition. Both types of the patterned arrays for Co and Ni films have been characterized by the TEM/ED methods. They were found to have a polycrystalline microstructure with the average crystallite size {approx}10 and 7 nm respectively. The Co films consisted of mixture of cubic and hcp phases. To experimentally check the sensitivity of TIE-recovered phase information to local magnetic configurations a set of in-focus and out-of-focus images was recorded on CCD (llarlk) during the in-situ magnetizing experiments in JEOL3000F microscope at different magnifications using the Gatan Imaging Filter (GIF) as function of applied field (H) and/or specimen tilt angle ({var_phi}) under constant external field. The results of the image processing (Figs.1-2), strongly suggest that TIE-phase retrieval method is a powerful tool suitable for local induction mapping B(x,y) of in-plane magnetization of magnetic elements down to few nanometers scale. The method is fast, robust, insensitive to noise, does not require the holographic equipment, and can be applied to a wide class of objects. The quantitative results can be obtained for films of known or uniform thickness.

VOLKOV,V.V.; ZHU,Y.; MALAC,M.; LAU,J.W.; SCHOFIELD,M.A.

2002-08-04

122

Studies on the magnetic reversal properties of cobalt anti-dot micropatterned arrays  

NASA Astrophysics Data System (ADS)

Large-area micropatterned arrays of cobalt anti-dots with different lattice symmetries (square and rhomboid geometry) and periodicities were fabricated by using the CMOS process. The surface morphology as well as the surface topography was checked by scanning electron microscopy and atomic force microscopy, and the magnetic properties were studied by MOKE and magnetic force microscopy (MFM). A systematic study on the magnetic-reversal mechanism, the in-plane anisotropy and the switching-field properties were carried out, together with the OOMMF simulations. It was found from the MOKE measurements that different lattice geometries induce different anisotropies with changes in the easy and the hard axes. In addition, the inclusion of non-magnetic holes in the uniform magnetic film, with modified lattice geometry and periodicity not only changes the domain configuration but also drastically affects the switching field. The MFM images in the remanent state show well-defined domain structures which are periodic in nature according to the lattice geometry. The observed change in the magnetic properties is closely related to the fact that the inclusion of non-magnetic vacancies hinders the domain wall motion, and to the geometrical variation giving rise to different anisotropy.

Deshpande, N. G.; Seo, M. S.; Jin, X. R.; Lee, S. J.; Lee, Y. P.; Rhee, J. Y.; Kim, K. W.

2010-03-01

123

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

NASA Astrophysics Data System (ADS)

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.

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

2012-04-01

124

Synthesis and magnetic characterization of Co-NiO-Ni core-shell nanotube arrays  

NASA Astrophysics Data System (ADS)

Well-aligned Ni and Co-NiO-Ni core-shell nanotube arrays with an average outer diameter of about 200 nm have been synthesized in a porous anodic aluminum oxide (AAO) template by the direct electro-deposition method. The result shows that the nanotubes were polycrystalline phase. Angular dependent coercivity Hc(?) indicates that the magnetization reversal mechanisms are mainly dominated by the "curling mode" for Ni nanotubes, while a transition from curling to transverse is observed in Co-NiO-Ni core-shell nanotubes at a large angle. A sharp increase in saturated magnetization (Ms) of Ni and Co-NiO-Ni core-shell nanotubes at 5 K was observed, due to dominance of the surface effect. Besides, the existed superparamagnetic nanoparticles also resulted in the increase of Ms for both cases. These structures have potential applications in the novel spintronics device, ultrasmall magnetic media, and other nanodevices.

Chen, J. Y.; Ahmad, N.; Shi, D. W.; Zhou, W. P.; Han, X. F.

2011-10-01

125

A Novel SNPs Detection Method Based on Gold Magnetic Nanoparticles Array and Single Base Extension  

PubMed Central

To fulfill the increasing need for large-scale genetic research, a high-throughput and automated SNPs genotyping method based on gold magnetic nanoparticles (GMNPs) array and dual-color single base extension has been designed. After amplification of DNA templates, biotinylated extension primers were captured by streptavidin coated gold magnetic nanoparticle (SA-GMNPs). Next a solid-phase, dual-color single base extension (SBE) reaction with the specific biotinylated primer was performed directly on the surface of the GMNPs. Finally, a “bead array” was fabricated by spotting GMNPs with fluorophore on a clean glass slide, and the genotype of each sample was discriminated by scanning the “bead array”. MTHFR gene C677T polymorphism of 320 individual samples were interrogated using this method, the signal/noise ratio for homozygous samples were over 12.33, while the signal/noise ratio for heterozygous samples was near 1. Compared with other dual-color hybridization based genotyping methods, the method described here gives a higher signal/noise ratio and SNP loci can be identified with a high level of confidence. This assay has the advantage of eliminating the need for background subtraction and direct analysis of the fluorescence values of the GMNPs to determine their genotypes without the necessary procedures for purification and complex reduction of PCR products. The application of this strategy to large-scale SNP studies simplifies the process, and reduces the labor required to produce highly sensitive results while improving the potential for automation. PMID:23139724

Li, Song; Liu, Hongna; Jia, Yingying; Deng, Yan; Zhang, Liming; Lu, Zhuoxuan; He, Nongyue

2012-01-01

126

Skew angle effects in shingled magnetic recording system with double/triple reader head array  

NASA Astrophysics Data System (ADS)

Shingled Magnetic Recording (SMR) is a scheme used to extend the life of the current perpendicular magnetic recording technology. SMR enables writing narrow tracks with a wide writer. Currently, SMR employs a single reader and will suffer inter-track interference (ITI) as the tracks become comparable in width to the reader. ITI can be mitigated by using narrower readers; however, narrower readers suffer from increased reader noise. Another approach to combat ITI is to process 2D readback and use ITI cancellation schemes to retrieve the data track. Multiple readbacks can be obtained either with a single reader and multiple revolutions or with a reader array. The former suffers from increased readback latency. In this work, we focus on the latter. When using a reader array, the skew angle poses major challenges. During writing, there is increased adjacent track erasure, and during readback the effective reader pitch varies and there is an increase in the 2D intersymbol interference caused by the rotated reader profile. In this work, we run micromagnetic simulations at different skew angles to train the grain flipping probability model, and then evaluate raw bit channel error rate performance at skew. In particular, we investigate the performance degradation caused by skewing of the 2 or 3 read head array for various read-head geometries.

Elidrissi, Moulay Rachid; Sann Chan, Kheong; Greaves, Simon; Kanai, Yasushi; Muraoka, Hiroaki

2014-05-01

127

2452 IEEE TRANSACTIONS ON PLASMA SCIENCE, VOL. 39, NO. 11, NOVEMBER 2011 Permanent-Magnet Helicon Discharge Array  

E-print Network

entail large and heavy electromagnets and their dc power supplies. Annular permanent magnets can produce helicon plasmas if used in the innovative way described here. An eight-tube array of such sources has been ionization efficiency, but they require a dc magnetic field, which normally would be an electromagnet large

Chen, Francis F.

128

IEEE TRANSACTIONS ON MAGNETICS, VOL. 37, NO. 4, JULY 2001 2067 Magnetoresistance Anisotropy of a Bi Antidot Array  

E-print Network

IEEE TRANSACTIONS ON MAGNETICS, VOL. 37, NO. 4, JULY 2001 2067 Magnetoresistance Anisotropy of a Bi, and D. J. Bergman Abstract--We have measured the magnetoresistance of a Bi an- tidot array film. The magnetoresistance exhibits a pronounced an- gular dependence on the direction of the magnetic field, e

Strelniker, Yakov M.

129

Magnetic properties of arrays of ``holes'' in Ni80Fe20films A. O. Adeyeye, J. A. C. Bland, and C. Daboo  

E-print Network

investigated the magnetization reversal and magnetoresistance behavior of a structure consisting of an arrayMagnetic properties of arrays of ``holes'' in Ni80Fe20films A. O. Adeyeye, J. A. C. Bland, and C for publication 9 April 1997 We have studied the magnetization reversal and magnetoresistance behavior

Adeyeye, Adekunle

130

Switching modes in easy and hard axis magnetic reversal in a self-assembled antidot array  

NASA Astrophysics Data System (ADS)

We study the reversal mechanisms in a self-assembled, hexagonally ordered Fe antidot array with a period of 200 nm and an antidot diameter of 100 nm which was prepared by polystyrene nanosphere lithography. Direction-dependent information in such a self-assembled sample is obtained by measuring the anisotropic magnetoresistance (AMR) through constrictions processed by focused ion beam milling in nearest neighbor and next nearest neighbor directions. We show that such an originally integral method can be used to investigate the strong in-plane anisotropy introduced by the antidot lattice. The easy and hard axis reversal mechanisms and corresponding AMR signals are modeled by micromagnetic simulations. Additional in-field magnetic force microscopy studies allow the correlation of microscopic switching to features in the integral AMR. We find that the easy axis of magnetization is connected to a distinct periodic magnetic domain pattern, which can be observed during the whole magnetization reversal. While this process is driven by nucleation and propagation of reversed domains, the hard axis reversal is characterized by a (stepwise) rotation of the magnetization via the antidot lattice’ easy axes.

Haering, Felix; Wiedwald, Ulf; Nothelfer, Steffen; Koslowski, Berndt; Ziemann, Paul; Lechner, Lorenz; Wallucks, Andreas; Lebecki, Kristof; Nowak, Ulrich; Gräfe, Joachim; Goering, Eberhard; Schütz, Gisela

2013-11-01

131

An investigation of the applicability of permanent magnet quadrupole arrays for high-power microwave tubes  

SciTech Connect

Magnetic quadrupoles have long been used in accelerator research for focusing high-energy particle beams. The advent of high-field, rare-earth permanent magnet materials has also spurred interest in permanent magnet quadrupoles (PMQ`s) since they are more lightweight and compact than their electromagnet counterparts and do not require power supplies or extraneous cooling. Here the authors study the potential use of closely-packed periodic permanent magnet quadrupoles for use in microwave tubes. In the most basic configuration, PMQ`s require four separate magnets in any given transverse plane, hence they are more expensive and complicated to assemble than conventional PPM stacks. Despite this fact, the stronger focusing available from PMQ`s may make them attractive for high-perveance beams, even at the low beam voltages generally of interest for compact slow-wave devices. Being iron-free systems, PMQ arrays may also lead to reductions in tube weight. The authors will compare and contrast PMQ and PPM stacks in terms of the beam focusing and beam quality that each provide and in terms of the comparative cost and difficulty of assembly. Results from two-dimensional beam envelope calculations and particle-in-cell simulations is discussed.

Booske, J.H.; Basten, M.A.; Louis, L.J.; Joe, J.; Scharer, J.E. [Univ. of Wisconsin, Madison, WI (United States). Dept. of Electrical and Computer Engineering

1996-12-31

132

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

SciTech Connect

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.

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

133

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

SciTech Connect

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.

Nikitin, Andrey G., E-mail: nikitin@cinam.univ-mrs.fr [Centre Interdisciplinaire de Nanoscience de Marseille” (CINaM, UPR 3118 CNRS), Aix-Marseille University, Campus de Luminy, Case 913, 13288 Marseille (France)

2014-02-10

134

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

NASA Technical Reports Server (NTRS)

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.

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

1994-01-01

135

Development of 3-D magnetic nano-arrays by electrodeposition into mesoporous silica.  

SciTech Connect

The development of periodic nanostructures fabricated by self-assembly of surfactants and block co-polymers has opened up the possibility of generating periodic magnetic nanostructures of types not accessible by self-assembly of nano-particles. The fabrication of mesoporous silica thin films around self-assembled block co-polymers is well established. Common structures for such films are SBA-15 which consists of hexagonal arrays of cylindrical pores and SBA-16 which has face centered arrays of spherical voids. These pores are connected by 1-2 nm thick flaws in the continuous silica phase producing an effectively continuous porous phase. After removal of the block co-polymer template, electrodeposition into the mesoporous silica thin films produces arrays of 5-10 nm diameter nano-wires and nano-particles. We have demonstrated that such materials can be fabricated on a wide range of metal substrates. Characterization by Scanning Electron Microscopies shows that the mesoporous silica is well ordered over micron scale areas. Grazing Incidence Small Angle X-ray Scattering (GISAXS) studies shows diffraction spots, consistent with the entire film being well ordered. GISAXS also shows that the mesoporous silica films survive removal of the template and electrodeposition of nickel and cobalt into the mesoporous silica films. Such films are of interest for their magnetic properties, as the nanophase and scale can be independently varied. Further, the presence of nanowires inside an insulator suggests that these films might also be of interest as the current confining element for Confined Current Path-Current Perpendicular to Plane GMR sensors.

Campbell, R.; Manning, J.; Bakker, M.G.; Li, X.; Lee, D.R.; Wang, J.; X-Ray Science Division; Univ. of Alabama

2006-01-01

136

Solid-State MultiSensor Array System for Real Time Imaging of Magnetic Fields and Ferrous Objects  

Microsoft Academic Search

In this paper the development of a solid-state sensors based system for real-time imaging of magnetic fields and ferrous objects is described. The system comprises 1089 magneto inductive solid state sensors arranged in a 2D array matrix of 33×33 files and columns, equally spaced in order to cover an approximate area of 300 by 300 mm. The sensor array is

D. Benitez; P. Gaydecki; S. Quek; V. Torres

2008-01-01

137

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

NASA Astrophysics Data System (ADS)

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.

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.

2013-02-01

138

Magnetization reversal and dynamics in non-interacting NiFe mesoscopic ring arrays  

NASA Astrophysics Data System (ADS)

The dynamics of magnetization (M) reversal and relaxation as a function of temperature (T) are reported in three non-interacting NiFe ring arrays having fixed ring outer diameter and varying widths. Additionally, the dependence of M(H) loop on the angle (?) between magnetic field (H) and the plane of the rings is addressed. The M(H) loops show a double step transition from onion state (OS) to vortex state (VS) at all temperatures (T = 3 to 300 K) and angles (? = 0 to 90°). The critical reversal fields HC1 (OS to VS) and HC2 (VS to OS) show a pronounced dependence on T, ring width, and ?. Estimation of the transverse and vortex domain wall energies reveals that the latter is favored in the OS. The OS is also the remanent state in the smallest rings and decays with the effective energy scale (U0/T) of 50 and 32 meV/K at 10 and 300 K, respectively. The robust in-plane anisotropy of magnetization of ring assemblies is established by scaling the M(H) with ?.

Kaur, M.; Husale, S.; Varandani, D.; Gupta, A.; Senguttuvan, T. D.; Mehta, B. R.; Budhani, R. C.

2014-04-01

139

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

NASA Astrophysics Data System (ADS)

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.

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

2012-02-01

140

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

PubMed Central

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

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

2014-01-01

141

Spectrum structure for a three-dimensional periodic array of quantum dots in a uniform magnetic field  

Microsoft Academic Search

By means of the operator extension theory, we construct an explicitly solvable model of a simple-cubic three-dimensional regimented array of quantum dots in the presence of a uniform magnetic field. The spectral properties of the model are studied. It is proved that for each magnetic flux the band is the image of the spectrum of the tight-binding operator under an

J. Bruening; V. V. Demidov; V. A. Geyler; A. V. Popov

2006-01-01

142

Spacing-dependent dipolar interactions in dendronized magnetic iron oxide nanoparticle 2D arrays and powders.  

PubMed

Self-assembly of nanoparticles (NPs) into tailored structures is a promising strategy for the production and design of materials with new functions. In this work, 2D arrays of iron oxide NPs with interparticle distances tuned by grafting fatty acids and dendritic molecules at the NPs surface have been obtained over large areas with high density using the Langmuir-Blodgett technique. The anchoring agent of molecules and the Janus structure of NPs are shown to be key parameters driving the deposition. Finally the influence of interparticle distance on the collective magnetic properties in powders and in monolayers is clearly demonstrated by DC and AC SQUID measurements. The blocking temperature T(B) increases as the interparticle distance decreases, which is consistent with the fact that dipolar interactions are responsible for this increase. Dipolar interactions are found to be stronger for particles assembled in thin films compared to powdered samples and may be described by using the Vogel Fulcher model. PMID:23306456

Fleutot, Solenne; Nealon, Gareth L; Pauly, Matthias; Pichon, Benoit P; Leuvrey, Cédric; Drillon, Marc; Gallani, Jean-Louis; Guillon, Daniel; Donnio, Bertrand; Begin-Colin, Sylvie

2013-02-21

143

An integrated and sensitive detection platform for biosensing application based on Fe@Au magnetic nanoparticles as bead array carries.  

PubMed

A sensitive and selective biosensor platform suited for SNP type using Fe@Au magnetic nanoparticles (GMNPs) to fabricate bead array is described. This new platform integrates the rapid binding kinetics of magnetic nanoparticles carriers, the multiplexing and encoding capabilities of chips, and tagged array. As a DNA sensor, the biotinylated single-stranded DNA was obtained by asymmetry PCR amplification, and then captured by GMNPs modified with streptavidin to form GMNP-ssDNA complexes without further purification. The complexes were immobilized on the slide to fabricate bead array through magnetic field. The bead array was hybridized with the corresponding allele-specific tag probes for each locus, and a pair of given universal detectors were applied to these markers analysis. Using bead array, all samples can be analyzed in one hybridization chamber which lowers the cost of the assay. Using universal tags, only a pair of universal dual-color probes labeled fluorophores was used for multiplex genotyping. Without the need of laborious and time-consuming elution, the experiment process was simple, reproducible and easy to handle. Two SNPs loci from 12 individual samples were discriminated using this platform and the results demonstrated that the expected scores and good discrimination were obtained between the two alleles from the two SNP loci. In summary, the integrated sensitive platform is adaptable and versatile, while offering a high-throughput capability needed for genome research and clinical applications. PMID:20728338

Liu, Hongna; Li, Song; Liu, Lishang; Tian, Lan; He, Nongyue

2010-12-15

144

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

PubMed Central

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 ? > 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

Jow, Uei-Ming; Ghovanloo, Maysam

2014-01-01

145

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

SciTech Connect

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.

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

1997-04-01

146

Theory of two-dimensional quantum-dot arrays in magnetic fields: Electronic structure and lateral quantum transport  

Microsoft Academic Search

A theory of the electronic structure and lateral quantum transport of finite ballistic two-dimensional arrays of coupled quantum dots in magnetic fields is formulated, based on a scattering-matrix approach. The quantum dots are connected to each other and to leads by constrictions with sufficiently strong transmission to suppress Coulomb blockade effects. The internal degrees of freedom of the quantum dots

George Kirczenow

1992-01-01

147

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

NASA Astrophysics Data System (ADS)

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.

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

2013-05-01

148

Enhanced Asymmetric Magnetization Reversal in Nanoscale Co/CoO Arrays: Competition between Exchange Bias and Magnetostatic Coupling  

NASA Astrophysics Data System (ADS)

Magnetization reversal was studied in square arrays of square Co/CoO dots with lateral size varying between 200 and 900nm. While reference nonpatterned Co/CoO films show the typical shift and increased width of the hysteresis loop due to exchange bias, the patterned samples reveal a pronounced size dependence. In particular, an anomaly appears in the upper branch of the magnetization cycle and becomes stronger as the dot size decreases. This anomaly, which is absent at room temperature in the patterned samples, can be understood in terms of a competition between magnetostatic interdot interaction and exchange anisotropy during the magnetic switching process.

Girgis, E.; Portugal, R. D.; Loosvelt, H.; van Bael, M. J.; Gordon, I.; Malfait, M.; Temst, K.; van Haesendonck, C.; Leunissen, L. H.; Jonckheere, R.

2003-10-01

149

Enhanced asymmetric magnetization reversal in nanoscale Co/CoO arrays: competition between exchange bias and magnetostatic coupling.  

PubMed

Magnetization reversal was studied in square arrays of square Co/CoO dots with lateral size varying between 200 and 900 nm. While reference nonpatterned Co/CoO films show the typical shift and increased width of the hysteresis loop due to exchange bias, the patterned samples reveal a pronounced size dependence. In particular, an anomaly appears in the upper branch of the magnetization cycle and becomes stronger as the dot size decreases. This anomaly, which is absent at room temperature in the patterned samples, can be understood in terms of a competition between magnetostatic interdot interaction and exchange anisotropy during the magnetic switching process. PMID:14611311

Girgis, E; Portugal, R D; Loosvelt, H; Van Bael, M J; Gordon, I; Malfait, M; Temst, K; Van Haesendonck, C; Leunissen, L H A; Jonckheere, R

2003-10-31

150

Graphoepitaxy of cylinder-forming block copolymers for use as templates to pattern magnetic metal dot arrays.  

PubMed

We report a method to fabricate high-quality patterned magnetic dot arrays using block copolymer lithography, metal deposition, and a dry lift-off technique. Long-range order of cylindrical domains oriented perpendicular to the substrate and in hexagonal arrays was induced in the block copolymer films by prepatterning the substrate with topographic features and chemically modifying the surface to exhibit neutral wetting behaviour towards the blocks of the copolymer. The uniformity of the domain size and row spacing of block copolymer templates created in this way was improved compared to those reported in previous studies that used graphoepitaxy of sphere-forming block copolymers. The pattern of block copolymer domains was transferred to a pattern of magnetic metal dots, demonstrating the potential of this technology for the fabrication of patterned magnetic recording media. PMID:21727448

Xiao, Shuaigang; Yang, Xiaomin; Edwards, Erik W; La, Young-Hye; Nealey, Paul F

2005-07-01

151

2556 IEEE TRANSACTIONS ON MAGNETICS, VOL. 38, NO. 5, SEPTEMBER 2002 Magnetic Properties of Lateral "Antidot" Arrays  

E-print Network

--Anisotropic magnetoresistance, antidot array, geometry-induced anisotropy, micromagnetic simulation. I. INTRODUCTION THERE has "Antidot" Arrays M. B. A. Jalil, Member, IEEE, S. L. A. Phoa, S. L. Tan, and A. O. Adeyeye, Member, IEEE array of square holes ("antidots"). In the submicron-size range, the presence of antidots significantly

Adeyeye, Adekunle

152

Magnetic property of a staggered-array undulator using a bulk high-temperature superconductor  

NASA Astrophysics Data System (ADS)

The magnetic field of a staggered-array undulator using a bulk high-temperature superconductor is calculated by analytical and numerical methods. Analytical formulas for the undulator field and the solenoid field required to generate the undulator field are derived from a simple two-dimensional model. The analytical calculation shows the degree of dependence of these fields on the undulator parameters, the generation of a high undulator field proportional to the critical current density of the bulk superconductor, and the good tunability of the undulator field over a wide range of values. The numerical calculation is performed in a three-dimensional geometry by two methods: the center field and energy minimization methods. The latter treats the current distribution inside the bulk, whereas the former neglects it as a natural extension of the analytical model. The calculation also reveals the dependence of the fields on the undulator parameters arising from the current distribution. From the comparison with experimental results, we find that the latter method reproduces the experimental results well, which indicates the importance of the current distribution inside the bulk. Therefore, we derive a semiempirical formula for the required solenoid field by modifying the analytical formula using the numerical results so as to include the effect of the current distribution. The semiempirical formula reproduces the numerical result with an error of 3%. Finally, we estimate the magnetic performance of the undulator as an example of using the formulas and values presented in this paper. The estimation shows that an undulator field twice as large as that of the present in-vacuum undulator but with an equal period and gap can be obtained at a temperature of approximately 20-40 K, and that deflection parameters (K values) of 1 and 2 can be achieved with periods of 5 and 10 mm at approximately 4-20 K.

Kinjo, Ryota; Mishima, Kenta; Choi, Yong-Woon; Omer, Mohamed; Yoshida, Kyohei; Negm, Hani; Torgasin, Konstantin; Shibata, Marie; Shimahashi, Kyohei; Imon, Hidekazu; Okumura, Kensuke; Inukai, Motoharu; Zen, Heishun; Kii, Toshiteru; Masuda, Kai; Nagasaki, Kazunobu; Ohgaki, Hideaki

2014-02-01

153

Microfluidic sorting and multimodal typing of cancer cells in self-assembled magnetic arrays  

PubMed Central

We propose a unique method for cell sorting, “Ephesia,” using columns of biofunctionalized superparamagnetic beads self-assembled in a microfluidic channel onto an array of magnetic traps prepared by microcontact printing. It combines the advantages of microfluidic cell sorting, notably the application of a well controlled, flow-activated interaction between cells and beads, and those of immunomagnetic sorting, notably the use of batch-prepared, well characterized antibody-bearing beads. On cell lines mixtures, we demonstrated a capture yield better than 94%, and the possibility to cultivate in situ the captured cells. A second series of experiments involved clinical samples—blood, pleural effusion, and fine needle aspirates— issued from healthy donors and patients with B-cell hematological malignant tumors (leukemia and lymphoma). The immunophenotype and morphology of B-lymphocytes were analyzed directly in the microfluidic chamber, and compared with conventional flow cytometry and visual cytology data, in a blind test. Immunophenotyping results using Ephesia were fully consistent with those obtained by flow cytometry. We obtained in situ high resolution confocal three-dimensional images of the cell nuclei, showing intranuclear details consistent with conventional cytological staining. Ephesia thus provides a powerful approach to cell capture and typing allowing fully automated high resolution and quantitative immunophenotyping and morphological analysis. It requires at least 10 times smaller sample volume and cell numbers than cytometry, potentially increasing the range of indications and the success rate of microbiopsy-based diagnosis, and reducing analysis time and cost. PMID:20679245

Saliba, Antoine-Emmanuel; Saias, Laure; Psychari, Eleni; Minc, Nicolas; Simon, Damien; Bidard, François-Clément; Mathiot, Claire; Pierga, Jean-Yves; Fraisier, Vincent; Salamero, Jean; Saada, Véronique; Farace, Françoise; Vielh, Philippe; Malaquin, Laurent; Viovy, Jean-Louis

2010-01-01

154

Enhancement of microbubble mediated gene delivery by simultaneous exposure to ultrasonic and magnetic fields.  

PubMed

It has been shown in previous studies that gene delivery can be enhanced by a variety of minimally-invasive techniques including: (1) exposure of cells to ultrasound in the presence of DNA and gas microbubbles and (2) exposure of cells to a magnetic field in the presence of DNA conjugated to magnetic nanoparticles. The aim of this work was to investigate whether it was possible to combine the advantages of both these techniques. It was found that transfection of Chinese hamster ovary cells by naked plasmid DNA was enhanced by combined exposure of the cells to ultrasound (10 s at 1 kHz pulse repetition frequency with 40 cycle 1 MHz sinusoidal pulses, 1 MPa peak to peak pressure) and a magnetic field (provided by five square cross-section N52 grade NdFeB magnets 25 x 10 x 10 mm with transversal magnetisation Br = 1.50 T arranged in a Halbach array), in the presence of one of two different microbubble/nanoparticle preparations. The first preparation consisted of phospholipid coated microbubbles mixed with micelles containing magnetic nanoparticles. The second consisted of microbubbles which were themselves magnetically active. These preparations were found to be more effective than either magnetic micelles or phospholipid coated microbubbles alone by a factor of 2.8 (total flux approximately 4 versus 1.4 x 10(6) photon/s) and the results were found to be statistically significant (p < 0.01). Two mechanisms are proposed to explain these observations: firstly, that the magnetic field facilitates close proximity between the cells and the microbubbles and hence increases the likelihood of transfection; second, that there is sensitisation of the cells, as a result of exposure to the magnetic field in the presence of the micelles, which increases their ability to be transfected upon exposure to ultrasound. Further work is in progress to determine which of these mechanisms is the most significant and the potential for other therapeutic applications. PMID:19282096

Stride, Eleanor; Porter, Colin; Prieto, Ana Garcia; Pankhurst, Quentin

2009-05-01

155

Enhanced synchronization in an array of spin torque nano oscillators in the presence of oscillating external magnetic field  

E-print Network

We demonstrate that the synchronization of an array of electrically coupled spin torque nano-oscillators (STNO) modelled by Landau-Lifshitz-Gilbert-Slonczewski (LLGS) equation can be enhanced appreciably in the presence of a common external microwave magnetic field. The applied microwave magnetic field stabilizes and enhances the regions of synchronization in the parameter space of our analysis, where the oscillators are exhibiting synchronized oscillations thereby emitting improved microwave power. To characterize the synchronized oscillations we have calculated the locking range in the domain of external source frequency.

B. Subash; V. K. Chandrasekar; M. Lakshmanan

2014-12-23

156

Enhanced magnetic performance of metal-organic nanowire arrays by FeCo/polypyrrole co-electrodeposition  

NASA Astrophysics Data System (ADS)

FeCo/polypyrrole (PPy) composite nanowire array, which shows enhanced magnetic remanence and coercivity along the nanowires, was fabricated by AC electrodeposition using anodic aluminum oxide templates. High resolution transmission electron microscopy shows that PPy grows on the surface of FeCo nanowires forming a coaxial nanowire structure, with a coating layer of about 4 nm. It suggests that the decreased dipolar interaction due to the reduced nanowire diameters is responsible for the enhancement of magnetic performance. The possible mechanism of this coating may be that PPy is inclined to nucleate along the pore wall of the templates.

Luo, X. J.; Xia, W. B.; Gao, J. L.; Zhang, S. Y.; Li, Y. L.; Tang, S. L.; Du, Y. W.

2013-05-01

157

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

PubMed

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

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

2014-01-01

158

Off-Axis Electron Holography of Magnetic Nanowires and Chains, Rings, and Planar Arrays of Magnetic Nanoparticles  

E-print Network

-dimensional arrays of naturally occurring magnetite crystals in minerals, and single crystalline Co nanowires passed through vacuum (or through a thin region of support film) with respect to a part of the same

Dunin-Borkowski, Rafal E.

159

Array magnetics modal analysis for the DIII-D tokamak based on localized time-series modelling  

NASA Astrophysics Data System (ADS)

Time-series analysis of magnetics data in tokamaks is typically done using block-based fast Fourier transform methods. This work presents the development and deployment of a new set of algorithms for magnetic probe array analysis. The method is based on an estimation technique known as stochastic subspace identification (SSI). Compared with the standard coherence approach or the direct singular value decomposition approach, the new technique exhibits several beneficial properties. For example, the SSI method does not require that frequencies are orthogonal with respect to the timeframe used in the analysis. Frequencies are obtained directly as parameters of localized time-series models. The parameters are extracted by solving small-scale eigenvalue problems. Applications include maximum-likelihood regularized eigenmode pattern estimation, detection of neoclassical tearing modes, including locked mode precursors, and automatic clustering of modes, and magnetics-pattern characterization of sawtooth pre- and postcursors, edge harmonic oscillations and fishbones.

Olofsson, K. E. J.; Hanson, J. M.; Shiraki, D.; Volpe, F. A.; Humphreys, D. A.; La Haye, R. J.; Lanctot, M. J.; Strait, E. J.; Welander, A. S.; Kolemen, E.; Okabayashi, M.

2014-09-01

160

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

NASA Astrophysics Data System (ADS)

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.

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

2013-06-01

161

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

Microsoft Academic Search

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

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

2010-01-01

162

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

PubMed Central

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

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

2014-01-01

163

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

NASA Astrophysics Data System (ADS)

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.

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

2014-09-01

164

Dynamics of Mass Transport and Magnetic Fields in Low-Wire-Number-Array Z Pinches  

SciTech Connect

The dynamics of mass transport were observed in a wire array implosion with multiframe laser probing. Plasma bubbles arise at breaks in the wires. Interferometry shows that the leading edge of the bubbles brings material to the axis of the array. The speed of this material was measured to be {>=}3x10{sup 7} cm/s during the wire array implosion. A shock was observed during the collision of the bubbles with the precursor. The Faraday effect indicates current flowing in breaks on the wires. The current switches from the imploding mass to the on-axis plasma column at the beginning of the x-ray pulse.

Ivanov, V. V.; Sotnikov, V. I.; Cowan, T. E.; Laca, P. J.; Astanovitskiy, A. L.; Haboub, A. [University of Nevada, Reno, 5625 Fox Ave, Reno, Nevada 89506 (United States); Sarkisov, G. S.; Jones, B.; Coverdale, C. A.; Deeney, C. [Sandia National Laboratories, Albuquerque, New Mexico 87110 (United States); Bland, S. N. [Blackett Laboratory, Imperial College, London SW7 2BZ (United Kingdom)

2006-09-22

165

Tracking the individual magnetic wires' switchings in ferromagnetic nanowire arrays using the first-order reversal curves (FORC) diagram method  

NASA Astrophysics Data System (ADS)

The complex hysteretic properties observed in structured ferromagnetic materials can be revealed with remarkable details in magnetization processes like the first-order reversal curves (FORC) - a characterization technique extensively used in recent years. The really fundamental problem in the analysis of experimental FORC diagrams is related to the possibility to link the hysteretic properties of real physical entities in a unique way with regions from the FORC distributions. Actually, what many scientists are often doing is to use a Preisach-type interpretation of FORC data without a proof for the accuracy of this procedure. In this paper we analyze in detail the relation between the switching events of physical entities given by the Preisach function and the FORC distribution in magnetic nanowire arrays with the aim to show the limits of the conventional interpretation of FORC data. For this type of sample we show how the real switching events are contributing to the experimental diagram. We present in a systematic manner the way in which the switchings of the physical wires are observed multiple times (both as positive or negative contributions). The multiplicity of switching occurrences is not the same for all the wires in the sample, being dependent on the wire intrinsic coercivity and its position in the array. In this manner one can track the switchings contributions of real magnetic wires on the FORC diagram.

Dobrot?, Costin-Ionu?; Stancu, Alexandru

2015-01-01

166

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

PubMed

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

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

2014-04-01

167

Development of a solid-state multi-sensor array camera for real time imaging of magnetic fields  

NASA Astrophysics Data System (ADS)

The development of a real-time magnetic field imaging camera based on solid-state sensors is described. The final laboratory comprises a 2D array of 33 x 33 solid state, tri-axial magneto-inductive sensors, and is located within a large current-carrying coil. This may be excited to produce either a steady or time-varying magnetic field. Outputs from several rows of sensors are routed to a sub-master controller and all sub-masters route to a master-controller responsible for data coordination and signal pre-processing. The data are finally streamed to a host computer via a USB interface and the image generated and displayed at a rate of several frames per second. Accurate image generation is predicated on a knowledge of the sensor response, magnetic field perturbations and the nature of the target respecting permeability and conductivity. To this end, the development of the instrumentation has been complemented by extensive numerical modelling of field distribution patterns using boundary element methods. Although it was originally intended for deployment in the nondestructive evaluation (NDE) of reinforced concrete, it was soon realised during the course of the work that the magnetic field imaging system had many potential applications, for example, in medicine, security screening, quality assurance (such as the food industry), other areas of nondestructive evaluation (NDE), designs associated with magnetic fields, teaching and research.

Benitez, D.; Gaydecki, P.; Quek, S.; Torres, V.

2007-07-01

168

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

NASA Astrophysics Data System (ADS)

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.

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

2014-04-01

169

Removing Strong Solar Array Disturbances and Telemetry Errors from DC Magnetic Field Measurements with a Dual Fluxgate Technique  

NASA Astrophysics Data System (ADS)

Due to a wrong wiring of the solar panels on a Double Star spacecraft, very large magnetic interferences (20- 30 nT) occurred in the magnetic field vector measure- ments. Furthermore, the shunting system of the space- craft solar power system caused sudden changes in the level of interferences. Finally the observations suffered from frequent telemetry errors causing random spikes in the data. With help of dual fluxgate measurements and signal processing technique, the data have been cleaned first from the spikes and then from the solar array dis- turbances to an accuracy of better than 0.5 nT for most of the time. This paper presents the basic steps of the cleaning procedures.

Laakso, H.; Klos, T.

2012-05-01

170

Measuring magnetism in the Milky Way with the Square Kilometre Array  

E-print Network

Magnetic fields in the Milky Way are present on a wide variety of sizes and strengths, influencing many processes in the Galactic ecosystem such as star formation, gas dynamics, jets, and evolution of supernova remnants or pulsar wind nebulae. Observation methods are complex and indirect; the most used of these are a grid of rotation measures of unresolved polarized extragalactic sources, and broadband polarimetry of diffuse emission. Current studies of magnetic fields in the Milky Way reveal a global spiral magnetic field with a significant turbulent component; the limited sample of magnetic field measurements in discrete objects such as supernova remnants and HII regions shows a wide variety in field configurations; a few detections of magnetic fields in Young Stellar Object jets have been published; and the magnetic field structure in the Galactic Center is still under debate. The SKA will unravel the 3D structure and configurations of magnetic fields in the Milky Way on sub-parsec to galaxy scales, includ...

Haverkorn, Marijke; Carretti, Ettore; Ferriere, Katia; Frick, Peter; Gaensler, Bryan; Heald, George; Johnston-Hollitt, Melanie; Jones, David; Landecker, Tom; Mao, Sui Ann; Noutsos, Aris; Oppermann, Niels; Reich, Wolfgang; Robishaw, Timothy; Scaife, Anna; Schnitzeler, Dominic; Stepanov, Rodion; Sun, Xiaohui; Taylor, Russ

2015-01-01

171

Josephson junction arrays as an experimental model for granular superconductors: influence of the McCumber parameter on their magnetic properties.  

NASA Astrophysics Data System (ADS)

We have measured the AC magnetic susceptibility of both shunted and unshunted two-dimensional Josephson junction arrays. Measurements were performed as a function of the temperature, T (1.5 K < T < 10 K), and the excitation magnetic field, h_AC (0.2 mOe < h_AC < 1000 mOe). In the unshunted arrays, the susceptibility is reentrant in temperature for high values of h_AC (F. M. Araujo-Moreira et al., Phys. Rev. Lett. \\underbar78), 4625, (1997).. Reentrance is not observed in shunted arrays, where the value of the McCumber parameter, ?_C, is very low compared to the value for unshunted arrays. These experimental findings are confirmed by numerical simulations of a simplified model based on a loop containing four junctions. The ?C dependence is consistent with the systematics of the paramagnetic Meissner effect in granular superconductors.

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

1998-03-01

172

Strongly Enhanced Pinning of Magnetic Vortices in Type-II Superconductors by Conformal Crystal Arrays  

NASA Astrophysics Data System (ADS)

Conformal crystals are nonuniform structures created by a conformal transformation of regular two-dimensional lattices. We show that gradient-driven vortices interacting with a conformal pinning array exhibit substantially stronger pinning effects over a much larger range of field than found for random or periodic pinning arrangements. The pinning enhancement is partially due to matching of the critical flux gradient with the pinning gradient, but the preservation of local ordering in the conformally transformed hexagonal lattice and the arching arrangement of the pinning also play crucial roles. Our results can be generalized to a wide class of gradient-driven interacting particle systems such as colloids on optical trap arrays.

Ray, D.; Olson Reichhardt, C. J.; Jankó, B.; Reichhardt, C.

2013-06-01

173

Structure and magnetic properties of three-dimensional (La,Sr)MnO3 nanofilms on ZnO nanorod arrays  

Microsoft Academic Search

Three-dimensional (3D) cubic perovskite (La,Sr)MnO3 (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.

Haiyong Gao; M. Staruch; Menka Jain; Pu-Xian Gao; Paresh Shimpi; Yanbing Guo; Wenjie Cai; Hui-Jan Lin

2011-01-01

174

A Multi-axis Compact Positioner with a 6-coil Platen Moving Over a Superimposed Halbach Magnet Matrix  

E-print Network

velocity in x is 10.50 cm/s and in y is 16.25 cm/s, respectively. The achieved acceleration in x is 43.75 cm/s^2 and in y is 95.59 cm/s^2, respectively. The achieved travel ranges are 15.24 cm in x, 20.32 cm in y, and 0.21 rad in the rotational motions...

Nguyen, Vu Huy

2012-07-16

175

Planar array of self-assembled GaxFe4-xN nanocrystals in GaN: magnetic anisotropy determined via ferromagnetic resonance.  

PubMed

The magnetic anisotropy of a planar array of GaxFe(4 - x)N nanocrystals (NCs) embedded in a GaN host is studied by ferromagnetic resonance. X-ray diffraction and transmission electron microscopy are employed to determine the phase and distribution of the nanocrystals. The magnetic anisotropy is found to be primarily uniaxial with the hard axis normal to the NCs plane and to have a comparably weak in-plane hexagonal symmetry. The origin of the magnetic anisotropy is discussed taking into consideration the morphology of the nanocrystals, the epitaxial relations, strain effects and magnetic coupling between the NCs. PMID:25201242

Grois, A; Devillers, T; Li, Tian; Bonanni, A

2014-10-01

176

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

NASA Technical Reports Server (NTRS)

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.

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

1988-01-01

177

Magnetic and magnetotransport properties of arrays of nanostructured antidots obtained by self-assembling polystyrene nanosphere lithography  

SciTech Connect

A well-ordered nanopatterned structure has been obtained in sputtered magnetic thin films by self-assembling of polystyrene nanospheres. Arrays of holes in Co, Ni, and Ni{sub 80}Fe{sub 20} films having a mean size ranging in the interval of 200-400 nm depending on the experimental condition have been prepared. Sample microstructure has been studied by scanning electron microscopy and atomic force microscopy. Room-temperature hysteresis loops have been measured in the parallel and perpendicular configuration (H{sub max}=20 kOe). Magnetoresistance (MR) measurements have been performed by means of a standard four-contact technique at several angles between the current and the magnetic field (H{sub max}=70 kOe) in the temperature interval of 4-200 K. An anisotropic MR effect has been observed in all compositions independent on the hole mean dimension. The role on magnetic and magnetotransport properties of either sample microstructure or composition has been studied in such patterned structures.

Tiberto, Paola; Boarino, Luca; Celegato, Federica; Coiesson, Marco; De Leo, Natascia; Vinai, Franco [INRIM, Strada delle Cacce 91, Torino I-10135 (Italy); Allia, Paolo [DISMIC, Politecnico di Torino, Corso Duca degli Abruzzi 24, Torino, 1-10129 (Italy)

2010-05-15

178

An automatic high-throughput single nucleotide polymorphism genotyping approach based on universal tagged arrays and magnetic nanoparticles.  

PubMed

Recent developments in highly parallel genome-wide studies are transforming the association of human health and diseases. In these studies, multiple SNP loci from large amount of samples need to be investigated to obtain a result with a high degree of confidence. Herein, we describe a novel, cost-effective and automated method for high-throughput single nucleotide polymorphisms (SNPs) genotyping based on universal tagged array and magnetic separation. By using two kinds of functionalized magnetic nanoparticles, the whole operation procedure including genome DNA extraction and SNP genotyping can be automatically performed by JANUS automated workstation (Perkin Elmer Inc.). Four different SNPs loci from 80 samples were scored using only one pair of universal dual-color probes, the phase of numerous SNPs can be automated assessed simultaneously. The results demonstrated that the expected scores and good discrimination were obtained between the two alleles from these four SNP loci. Due to adequately taking the advantages of high parallel read-out and intrinsically scalable properties of microarray, and the automated magnetic separation handling technology is highly adaptable fro multiplexing sample preparation and automated SNP analysis, also avoid the complex procedure including purification and concentration, the new strategy is high-throughput, simple, flexible, cost-effective, and will be very suitable for large-scale genotyping. PMID:23621030

Li, Song; Liu, Hongna; Jia, Yingying; Mou, Xianbo; Deng, Yan; Lin, Lin; Liu, Bin; He, Nongyue

2013-04-01

179

A 16-Channel Receive Array Insert for Magnetic Resonance Imaging of the Breast at 7T  

E-print Network

Breast cancer is the second leading cause of cancer death among females in the United States. Magnetic resonance imaging (MRI) has emerged as a powerful tool for detecting and evaluating the disease, with notable advantages over other modalities...

By, Samantha

2014-04-01

180

Origin of transverse magnetization in epitaxial Cu/Ni/Cu nanowire arrays  

E-print Network

The patterning-induced changes in the magnetic anisotropy and hysteresis of epitaxial (100)-oriented Cu/Ni(9, 10, 15 nm)/Cu planar nanowires have been quantified. When the Ni films are patterned into lines, strain relaxation ...

Ciria, M.

181

Chemical shift tensor determination using magnetically oriented microcrystal array (MOMA): 13C solid-state CP NMR without MAS.  

PubMed

Chemical shift tensors for the carboxyl and methyl carbons of L-alanine crystals were determined using a magnetically oriented microcrystal array (MOMA) prepared from a microcrystalline powder sample of L-alanine. A MOMA is a single-crystal-like composite in which microcrystals are aligned three-dimensionally in a matrix resin. The single-crystal rotation method was applied to the MOMA to determine the principal values and axes of the chemical shift tensors. The result showed good agreement with the literature data for the single crystal of L-alanine. This demonstrates that the present technique is a powerful tool for determining the chemical shift tensor of a crystal from a microcrystal powder sample. PMID:22975237

Kusumi, R; Kimura, F; Song, G; Kimura, T

2012-10-01

182

Vortex Pinning in Superconducting MoGe Films Containing Conformal Arrays of Nanoscale Holes and Magnetic Dots  

NASA Astrophysics Data System (ADS)

Recent numerical simulations by Ray et al. predict that a conformal pinning array can produce stronger vortex pinning effect than other pinning structures with an equivalent density of pinning sites [1]. Here we present experimental investigations on conformal pinning structures. Direct and conformal pinning arrays of triangular and square lattices were introduced into MoGe superconducting films using focused-ion-beam milling or electron-beam lithography. Transport measurements on critical currents and magnetoresistances were carried out on these samples to reveal the advantages of conformal pinnings. Effects of random pinnings with the same average density were also studied for comparison. Details on sample fabrications and effects of pinning types (holes versus magnetic dots) will be presented. Reference: [1] D. Ray, C.J. Olson Reichhardt, B. Janko, C. Reichhardt, arXiv:1210.1229 (2012) Work supported by the US DoE-BES funded Energy Frontier Research Center (YLW), and by Department of Energy, Office of Science, Office of Basic Energy Sciences (MLL, ZLX, LEO, RD, UW, WKK), under Contract No. DE-AC02-06CH11357

Wang, Y. L.; Latimer, M. L.; Xiao, Z. L.; Ocola, L. E.; Divan, R.; Welp, U.; Crabtree, G. W.; Kwok, W. K.

2013-03-01

183

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

SciTech Connect

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.

Gao Haiyong; Gao Puxian; Shimpi, Paresh; Guo Yanbing; Cai Wenjie; Lin Huijan [Institute of Materials Science, University of Connecticut, Storrs, Connecticut 06269-3136 (United States); Department of Chemical, Materials, and Biomolecular Engineering, University of Connecticut, Storrs, Connecticut 06269-3136 (United States); Staruch, M. [Department of Physics, University of Connecticut, Storrs, Connecticut 06269-3046 (United States); Jain, Menka [Institute of Materials Science, University of Connecticut, Storrs, Connecticut 06269-3136 (United States); Department of Physics, University of Connecticut, Storrs, Connecticut 06269-3046 (United States)

2011-03-21

184

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

NASA Technical Reports Server (NTRS)

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.

Groom, Nelson J.; Britcher, Colin P.

1991-01-01

185

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

NASA Technical Reports Server (NTRS)

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.

Alishahi, M. M.

1980-01-01

186

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

Microsoft Academic Search

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

S. Watson; C. H. Igney; O. Dössel; R. J. Williams; H. Griffiths

2005-01-01

187

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

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

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

2014-01-01

188

Nonuniform radiation damage in permanent magnet quadrupoles.  

PubMed

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

Danly, C R; Merrill, F E; Barlow, D; Mariam, F G

2014-08-01

189

Nonuniform radiation damage in permanent magnet quadrupoles  

NASA Astrophysics Data System (ADS)

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.

Danly, C. R.; Merrill, F. E.; Barlow, D.; Mariam, F. G.

2014-08-01

190

Tracking electron pathways with magnetic field: Aperiodic Aharonov-Bohm oscillations in coherent transport through a periodic array of quantum dots  

NASA Astrophysics Data System (ADS)

We study resonant tunneling through a periodic square array of quantum dots sandwiched between modulation-doped quantum wells. If a magnetic field is applied parallel to the quantum dot plane, the tunneling current exhibits a highly complex Aharonov-Bohm oscillation pattern due to the interference of multiple pathways traversed by a tunneling electron. Individual pathways associated with conductance beats can be enumerated by sweeping the magnetic field at various tilt angles. Remarkably, Aharonov-Bohm oscillations are aperiodic unless the magnetic field slope relative to the quantum dot lattice axes is a rational number.

Petrosyan, L. S.; Shahbazyan, T. V.

2015-01-01

191

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

SciTech Connect

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.

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

1995-06-01

192

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)

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.

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

193

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

PubMed

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

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

2014-01-01

194

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

PubMed Central

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

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

2014-01-01

195

Magnetization reversal of stripe arrays: comparison of PNR and MOKE results  

NASA Astrophysics Data System (ADS)

In order to minimize stray field energies, lateral structures often show a variety of domain configurations. A method which is very suitable for studying different remagnetization processes is polarized neutron reflectivity (PNR) because it can distinguish between reversal via coherent rotation or domain nucleation and wall movement. Furthermore, by applying PNR to lateral structures it is possible to perform measurements at Bragg peaks from the artificial periodicity and therefore filter out correlation effects between indivdiual magnetic units during reversal. We have studied the magnetization reversal of laterally structured CoFe films by PNR and compared the results to longitudinal MOKE measurements with the field applied in longitudinal and in transverse orientation [1]. In addition, Kerr-microscopy was used for visualizing the domain state at different field values. The parameters of the CoFe stripes were chosen such that a strong two-fold shape anisotropy is present in the polycrystalline stripes. By varying the width of the stripes the magnetic anisotropy can be changed. Consequently we observe more complex domain configurations for stripes with larger widths than for those with smaller widths. Neutron spin-flip scattering also indicates inhomogeneous stray fields most likely due to dipole-dipole interaction between the stripes. We acknowledge founding by DFG, SFB 491 and BMBF 032AE8BO [1] K. Theis-Bröhl, T. Schmitte, V. Leiner, H. Zabel, K. Rott, H. Brueckl, and J. McCord, Phys. Rev. B 67 (2003)

Zabel, Hartmut

2003-03-01

196

Effect of the cluster magnetization on the magnetotransport at low temperatures in ordered arrays of MnAs nanoclusters on (111)B GaAs  

NASA Astrophysics Data System (ADS)

The angle-dependent behavior of the magnetoresistance of ordered arrays of nanoclusters is studied. The arrays consist of single elongated MnAs nanoclusters, which were deposited on the (111)B GaAs substrate by selective-area metal-organic vapor phase epitaxy, which yields control of the position on the substrate as well as of the shape of the nanoclusters. Ferromagnetic resonance measurements were carried out in order to investigate the magnetic anisotropy of the nanoclusters, which is strongly determined by the cluster shape. Angle-dependent magnetotransport measurements were performed at T = 15 K. The magnetic field was rotated in three different geometries, one parallel and two perpendicular to the sample surface. At low magnetic fields the nanoclusters show nearly no influence on the transport through the matrix. However, at high magnetic fields the magnetization orientation of the nanoclusters affects the transport behavior of the sample due to the influence of the clusters’ dipolar field on the electronic states in the matrix. The experimental results obtained can be understood qualitatively by considering not only the transport properties of the GaAs matrix but also an average magnetization of the MnAs nanoclusters, whose orientation is determined by the magnetic anisotropy.

Elm, M. T.; Klar, P. J.; Ito, S.; Hara, S.; Krug von Nidda, H.-A.

2011-07-01

197

MFM and PEEM observation of micrometre-sized magnetic dot arrays fabricated by ion-microbeam irradiation in FeRh thin films  

PubMed Central

FeRh thin films were irradiated with a 10?MeV iodine ion microbeam to produce micrometre-scale ferromagnetic microstructures by modifying the local magnetic character from antiferromagnetism to ferromagnetism using ion-microbeam irradiation. Two-dimensional magnetic dot arrays of dimensions ?2?µm × 4?µm as well as 10?µm × 10?µm were successfully produced on the FeRh surface, which was confirmed by magnetic force microscopy (MFM). The results of photoemission electron microscopy (PEEM) combined with X-ray magnetic circular dichroism reveal that the easy axis of the magnetization of the ion-beam-irradiated ferromagnetism in the FeRh thin films lies in the film planes along the ?001? direction of the MgO substrates. PMID:22338683

Aikoh, K.; Tohki, A.; Matsui, T.; Iwase, A.; Satoh, T.; Takano, K.; Kohka, M.; Saitoh, Y.; Kamiya, T.; Ohkochi, T.; Kotsugi, M.; Nakamura, T.; Kinoshita, T.

2012-01-01

198

MFM and PEEM observation of micrometre-sized magnetic dot arrays fabricated by ion-microbeam irradiation in FeRh thin films.  

PubMed

FeRh thin films were irradiated with a 10 MeV iodine ion microbeam to produce micrometre-scale ferromagnetic microstructures by modifying the local magnetic character from antiferromagnetism to ferromagnetism using ion-microbeam irradiation. Two-dimensional magnetic dot arrays of dimensions ?2 µm × 4 µm as well as 10 µm × 10 µm were successfully produced on the FeRh surface, which was confirmed by magnetic force microscopy (MFM). The results of photoemission electron microscopy (PEEM) combined with X-ray magnetic circular dichroism reveal that the easy axis of the magnetization of the ion-beam-irradiated ferromagnetism in the FeRh thin films lies in the film planes along the <001> direction of the MgO substrates. PMID:22338683

Aikoh, K; Tohki, A; Matsui, T; Iwase, A; Satoh, T; Takano, K; Kohka, M; Saitoh, Y; Kamiya, T; Ohkochi, T; Kotsugi, M; Nakamura, T; Kinoshita, T

2012-03-01

199

Magnetic measurements using array of integrated Hall sensors on the CASTOR tokamak.  

PubMed

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

Duran, Ivan; Hronová, Olena; Stöckel, Jan; Sentkerestiová, Jana; Havlicek, Josef

2008-10-01

200

Anomalies in vortex lattice dynamics driven by induced ac currents in superconducting films with magnetic arrays of two-fold symmetry  

NASA Astrophysics Data System (ADS)

We study the dynamics of the vortex lattice driven by ac induced currents in the critical state regime, for T > 0.70 TC. The samples are superconducting films grown on top of two-fold symmetry array of magnetic dots. In these heterostructures, the induced ac currents flow parallel to the short and to the long side of the pinning array in different areas of the samples simultaneously. This behavior produces remarkable effects in the vortex lattice dynamics. First of all, periodic features are observed in the ac susceptibility versus applied magnetic field measurements which are related to matching effects between the vortex lattices and the magnetic array. However, the vortex lattice reconfiguration observed in magnetotransport experiments is absent. Some of these features are revealed as maxima instead of being minima, indicating higher mobility at certain matching fields. Competing unstable vortex configurations could lead to increase vortex mobility precluding the reconfiguration transition. At high temperatures, where the matching effects show up, the magnetic permeability of the dots is the mechanism that governs the JC(T) behavior. Moreover, the temperature dependence of the pinning force FP(T) shows a temperature crossover related to an unexpected enhancement in vortex mobility. Vortex–vortex interaction and the interplay between trapped and interstitial vortices are a hint to explain these phenomena.

Moreno, A. J.; Chiliotte, C. E.; Pasquini, G.; Bekeris, V.; Gomez, A.; del Valle, J.; Gonzalez, E. M.; Prieto, J. L.; Vicent, J. L.

2015-01-01

201

Magnetic properties of patterned arrays of exchange-biased IrMn/Co square dots  

NASA Astrophysics Data System (ADS)

Finite size effects on the exchange-bias properties of patterned antiferromagnetic/ferromagnetic (IrMn/Co) nanodots were investigated experimentally and by numerical simulations. Both the dot lateral dimension (200 × 200 nm2-50 × 50 nm2) and ferromagnetic layer thickness (2-25 nm) were varied. Two different behaviours were observed: single-shifted loops with coherent reversal for thin Co layers and double-shifted loops via a multidomain state during magnetization reversal for thicker Co. Atomistic simulations including magnetostatic interactions confirmed the existence of these two different regimes. MOKE measurements, focused on few dots, allowed a quantitative evaluation of dot-to-dot exchange-bias variability, which becomes particularly large in the regime of switching via multidomain state formation. This variability issue is of particular importance in the context of MRAM development and of magnetoresistive heads for hard-disk drives.

Vinai, G.; Moritz, J.; Gaudin, G.; Vogel, J.; Bonfim, M.; Lançon, F.; Prejbeanu, I. L.; Mackay, K.; Dieny, B.

2013-08-01

202

MgO-based magnetic tunnel junction sensors array for non-destructive testing applications  

NASA Astrophysics Data System (ADS)

A MgO-based magnetic tunnel junction (MTJ) sensor including 72 MTJs in series with 50 × 50 ?m2 was successfully microfabricated. Due to a two-step annealing strategy, a linear transfer curve was obtained. The tunneling magnetoresistance (TMR) value is as high as 159% and the sensitivity reaches 2.9%/Oe. The field detectivity exhibits the lowest value at 1 V bias current, attaining 1.76 nT/Hz0.5 and 170 pT/Hz0.5 for 10 Hz and 1 kHz, respectively. The results show that the sensor could be applied in non-destructive testing systems which are used for detecting small defects inside conductive materials.

Guo, D. W.; Cardoso, F. A.; Ferreira, R.; Paz, E.; Cardoso, S.; Freitas, P. P.

2014-05-01

203

Fault tolerant control of homopolar magnetic bearings and circular sensor arrays  

E-print Network

. .............................................18 2.5 Catcher Bearing Contact Model. ....................................................................21 2.6 Magnetic Suspension Control Scheme...........................................................23 2.7 3D FE Model of the Combo... ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? + ?? ? ? ? ? ? ?? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? + ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? + ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? = ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? + ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? gF F F F L L F F F F F L L F F F F F L L x x x I I x x x m I m I m r B d B d A d A d B dr A dr B dr A dr B c B c A c A c A c B cr A cr B cr A cr B b B b A b A b A b B br A br B br A br r r r r r pr pr r r r r r r tr r tr r 0 0 0 0 0 0 1 0 0 0 0 1 0 0...

Li, Ming-Hsiu

2006-04-12

204

Coronal temperature, density, and magnetic field maps of a solar acitve region using the Owens Valley Solar Array  

NASA Technical Reports Server (NTRS)

We present the first results of solar active region observations with the recently completed five-element Owens Valley Solar Array. On 1991 October 24, maps of Active Region AR 6891 were obtained at 22 frequencies from 1.2-7.0 GHz to provide brightness temperature spectra at each point. This is the first time that both high spatial and frequency-resolution brightness temperature spectra have been available over such a broad radio-frequency range. We find that over most of the region the spectra fall into one of the two well-defined categories: thermal free-free or thermal gyroresonance. In these cases, we use the spectra to deduce the spatial variation of physical parameters-electron temperature, column emission measure (intergral n(sup 2)(sub e) dl), and the coronal magnetic field strength-in and around the active region. Over a limited area of the region, the spectra resemble neither of the simple types, and alternative interpretations are required. The possibilties include the presence of fine structure that is unresolved at low frequencies; the presence of a small number of nonthermal electrons; or the presence of overlying, cooler 10(exp 6) K material which at low frequencies absorbs the hot (3 x 10(exp 6) K) thermal emission generated below.

Gary, Dale E.; Hurford, G. J.

1994-01-01

205

Magnetic behavior of as-deposited and annealed CoFe and CoFeCu nanowire arrays by ac-pulse electrodeposition  

NASA Astrophysics Data System (ADS)

CoFe and CoFeCu self-organized alloy nanowires were grown into anodic aluminum oxide template by potentiostatic mode of ac-pulse electrodeposition technique and subsequently annealed at 580 °C. The influence of bath composition, off-time between pulses and annealing treatment on the Cu content, microstructure and magnetic properties of CoFeCu nanowire arrays have been discussed. Increasing the off-time between pulses decreased the coercivity and saturation magnetization of the CoFeCu nanowires due to substitution of Co and Fe with Cu atoms which resulted in electroless process. Coercivity and squareness of the annealed samples increased due to improvement of samples crystallinity. Magnetic measurements showed high perpendicular magnetic anisotropy of the nanowires with easy axis parallel to nanowires axis. X-ray diffraction results indicated that annealed CoFeCu nanowires were polycrystalline with two distinct CoFe and Cu phases.

Ramazani, A.; Almasi-Kashi, M.; Golafshan, E.; Arefpour, M.

2014-09-01

206

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

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

García-Diego, Fernando-Juan; Sánchez-Quinche, Angel; Merello, Paloma; Beltrán, Pedro; Peris, Cristófol

2013-01-01

207

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)

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.

Jiang, C.; Müller-Petke, M.; Lin, J.; Yaramanci, U.

2015-02-01

208

Symmetry-Induced Giant Vortex State in a Superconducting Pb Film with a Fivefold Penrose Array of Magnetic Pinning Centers  

E-print Network

of flux lines in super- conducting thin films with aperiodic, fractal, or quasiperi- odic arrays the formation of one-dimensional channels for easy vortex flow, whereas the convolution of many build-in periods simulations of driven vortices inter- acting with a fivefold two-dimensional Penrose array of pinning sites

Moshchalkov, Victor V.

209

Organized Silica Microspheres Carrying Ferromagnetic Cobalt Nanoparticles as a Basis for Tip Arrays in Magnetic Force Microscopy  

E-print Network

in Magnetic Force Microscopy Sivarajan Ramesh,,§ Yair Cohen, Ruslan Prozorov, Kurikka V. P. M. Shafi, Doron to measure magnetic and atomic forces in nanodimensions.8,9 Magnetic force microscopy (MFM) involves in atomic force microscopy.8 The force derivative (F) for a pyramidal magnetic tip (of saturation

Prozorov, Ruslan

210

The reliability of the seismo-magnetic method derived from ULF/ELF observations by the South European Geomagnetic Array (SEGMA)  

NASA Astrophysics Data System (ADS)

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.

Schwingenschuh, Konrad; Prattes, Gustav; Eichelberger, Hans Ulrich; Magnes, Werner; Berghofer, Gerhard; Aydogar, Özer; Besser, Bruno P.; Boudjada, Mohammed; Stangl, Günter; Zhang, Tie Long; Wolbang, Daniel; Vellante, Massimo; Villante, Umberto; Rozhnoi, Alexander; Solovieva, Maria; Nenovski, Petko; Veztergom, Victor; Szendr?i, Judith

2013-04-01

211

Effect of AC Electrodeposition Conditions on Microstructure and Magnetic Properties of CoxNi1-x Nanowire Arrays Embedded in Anodic Aluminum Oxide Template  

NASA Astrophysics Data System (ADS)

CoxNi1-x alloy nanowire arrays were fabricated by ac electrodeposition technique into nanoporous alumina membranes. The effect of frequency, composition and electrolyte on the crystalline structure and magnetic properties of nanowire arrays were investigated. Different alloy nanowires were prepared with 50, 100, 200, 300, 400, 500, 800, and 1000 Hz deposition frequencies. Obtained results showed both the coercivity and squareness (parallel to the nanowires axis) weakly depend on the frequency and electrolyte. The coercivity initially decreased with increase in frequency then increased. This trend was more pronounced for Co-rich CoxNi1-x nanowires. A coercivity of 1560 Oe was obtained which may be due to the predomination of (002) direction at 1100 Hz deposition frequency.

Almasi Kashi, Mohammad; Ramazani, Abdolali; Akhshi, Nasrin; Sajad Esmaeily, Amir

2012-02-01

212

Determination of radial location of rotating magnetic islands by use of poloidal soft x-ray detector arrays in the STOR-M tokamak  

SciTech Connect

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.

Dreval, M. [Plasma Physics Laboratory, University of Saskatchewan, Saskatoon, SK S7N 5E2 (Canada); IPP NSC Kharkov Institute of Physics and Technology, Kharkiv (Ukraine); Xiao, C.; Elgriw, S.; Trembach, D.; Hirose, A. [Plasma Physics Laboratory, University of Saskatchewan, Saskatoon, SK S7N 5E2 (Canada); Wolfe, S. [Plasmionique, Brossard, Quebec, J4X 2S3 (Canada)

2011-05-15

213

Magnetic Nanopillars Fabricated Using Electron Beam Lithography  

E-print Network

. Characterized the arrays with magnetic force microscopy, revealing dipole interactions between the pillars. R E and etch uniform arrays of magnetic nanopillars. NANOFABFUTUREELECTRONICS Atomic force microscope and corresponding magnetic force microscope images of a nanopillar array. #12;

214

Nucleic acid delivery to magnetically-labeled cells in a 2D array and at the luminal surface of cell culture tube and their detection by MRI.  

PubMed

The magnetic labeling of living cells has become of major interest in the areas of cell therapy and tissue engineering. Magnetically labeled cells have been reported to allow increased and controlled seeding, tracking, and targeting of cells. In this work, we comprehensively characterize magnetic nanoparticles (MNPs) possessing a magnetite core of about 11 nm, and which are coated with the fluorinated surfactant F(CF2)nCH2CH2SCH2CH2C(O)OLi and 1,9-nonandithiol (NDT) for the nonspecific labeling of human pulmonary epithelial (H441) cells. We achieved a non-specific cell loading of 38 pg Fe/cell. In this work we combine magnetic cell labeling with subsequent genetic modification of the cells with non-viral transfection complexes associated with PEI-Mag2 magnetic nanoparticles upon gradient magnetic field application called magnetofection. The magnetic responsiveness and magnetic moment of the MNP-labeled cells and the magnetic transfection complexes were evaluated by measuring changes in the turbidity of prepared cells suspensions and complexes in a defined magnetic gradient field. The magnetic responsiveness of cells that were loaded with NDT-Mag1 MNPs (20-38 pg Fe/cell) was sufficient to engraft these labeled cells magnetically onto the luminal surface of a culture tube. This was achieved using a solenoid electromagnet that produced a radial magnetic field of 20-30 mT at the seeding area and an axial gradient field of approx. 4 T/m. The MNP-labeled cells were magnetofected in 2D arrays (well plates) and at the luminal surface of cell culture tube. The optimized magnetic pre-labeling of cells did not interfere with, or even increased, the efficiency of magnetofection in both culture systems without causing cell toxicity. Cell loading of 38 pg Fe/cell of NDT-Mag1 MNPs resulted in high transverse relaxivities r2*, thus allowing the MRI detection of cell concentrations that were equivalent to (or higher than) 1.2 microg Fe/ml. Multi-echo gradient echo imaging and R2* mapping detected as few as 1533 MNP-labeled H441 cells localized within a 50 microl fibrin clot and MNP-labeled cell monolayers that were engrafted on the luminal surface of a cell culture tube. Further loading of cells with MNPs did not increase either the magnetic responsiveness of the cells or the sensitivity of MR imaging. In summary, the NDT-Mag1 magnetic nanoparticles provided a high cell-loading efficiency, resulting in strong cell magnetic moments and a high sensitivity to MRI detection. The transfection ability of the labeled cells was also maintained, thereby increasing the magnetofection efficiency. PMID:20201231

Mykhaylyk, Olga; Steingötter, Andreas; Perea, Hector; Aigner, Joachim; Botnar, René; Plank, Christian

2009-12-01

215

Improvement in the microstructure and magnetic properties in arrays of dc pulse electrodeposited Co nanowires induced by Cu pre-plating  

NASA Astrophysics Data System (ADS)

Co nanowire arrays were pulse electrodeposited into nanoporous alumina templates via the dendrite pores of a thinned barrier layer formed by exponentially non-equilibrium anodization, either without or with Cu pre-plating. Electrolyte acidity (pH) dependence of the microstructure and magnetic properties of the prepared Co nanowires was investigated and compared. The process of Cu pre-plating prior to electrodeposition of Co nanowires along with an adjustment of the pH value was shown to significantly improve the magnetic properties of the Co nanowires and ultimately result in a high coercivity (about 3000 Oe) and squareness up to 98% at pH ? 5.7. The improvement of magnetic properties may be caused by the rotation of the hexagonal close packed c-axis of more crystal grains along with the wire axis, which supplements the shape anisotropy of the nanowires. The angular dependence of the coercivity (Hc(?)) of both types of prepared Co nanowires was also studied.

Ghaffari, M.; Ramazani, A.; Almasi Kashi, M.

2013-07-01

216

Structural and magnetic characterization of as-prepared and annealed FeCoCu nanowire arrays in ordered anodic aluminum oxide templates  

SciTech Connect

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.

Rodríguez-González, B., E-mail: jbenito@uvigo.es [CACTI, University of Vigo, E-36310 Vigo (Spain); International Iberian Nanotechnology Laboratory, INL. Av. Mestre J. Veiga, 4715-330 Braga (Portugal); Bran, C.; Warnatz, T.; Vazquez, M. [Institute of Materials Science of Madrid, CSIC, 28049 Madrid (Spain); Rivas, J. [International Iberian Nanotechnology Laboratory, INL. Av. Mestre J. Veiga, 4715-330 Braga (Portugal)

2014-04-07

217

Magnetic nanohole superlattices  

SciTech Connect

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.

Liu, Feng

2013-05-14

218

Optical, electronic, magnetic, and superconducting properties of quasiperiodic quantum dot arrays synthesized by a novel electrochemical technique  

NASA Astrophysics Data System (ADS)

Conventional nanosynthesis involves film growth followed by direct-write nanolithography. The last step has two major shortcomings in that (a) it causes material damage to the nanostructures and (b) it is always serial in nature whereby each wafer has to be patterned one at a time. The latter makes it impractical for large-scale commercial applications. To overcome these drawbacks, we have developed a novel and `gentle' electrochemical process for fabricating quantum dot arrays that allows parallel processing of millions of wafers. It causes minimal damage, is much cheaper than conventional nanolithography, and yet has the spatial resolution (approximately 1 nm) of state-of-the-art techniques. Semiconductor quantum dot arrays produced by this process show strong signatures of quantum confinement in their photoluminescence spectra. Superconducting quantum dots show a significant transition- temperature shift arising from an interplay of superconductivity with quantum confinement, while ferromagnetic quantum dots give rise to a novel giant magnetoresistance effect caused by remote spin-dependent scattering of electrons. These structures have also been characterized by a variety of analytical techniques--all of which attest to their high quality.

Bandyopadhyay, Supriyo; Miller, A. E.; Chandrasekhar, Meera

1995-04-01

219

Optimized design of a permanentmagnet tubular linear generator for wave energy conversion  

Microsoft Academic Search

A permanent magnet tubular linear generator (PMTLG) is presented for wave energy conversion due to its direct drive characteristics. Finite Element method is implemented to calculate and optimize the waveform of magnetic field along air-gap of PMTLG with Halbach array. The computational results are validated by experimental ones.

Haitao Yu; Bang Yuan; Hengshan Yang; Minqiang Hu; Lei Huang

2010-01-01

220

Influence of Y-doped induced defects on the optical and magnetic properties of ZnO nanorod arrays prepared by low-temperature hydrothermal process  

PubMed Central

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 90°C. 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

2012-01-01

221

Method and apparatus for control of a magnetic structure  

DOEpatents

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.

Challenger, Michael P. (Bothell, WA); Valla, Arthur S. (Bothell, WA)

1996-06-18

222

Amazing Arrays  

NSDL National Science Digital Library

This is a hands-on lesson for introducing and practicing building arrays to create models that represent the distributive property of multiplication, and then using those arrays to draw models of the equations they represent.

Edit, Format

2012-04-18

223

Nanocylinder arrays  

DOEpatents

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.

Tuominen, Mark (Shutesbury, MA); Schotter, Joerg (Bielefeld, DE); Thurn-Albrecht, Thomas (Freiburg, DE); Russell, Thomas P. (Amherst, MA)

2009-08-11

224

Magnetism  

NSDL National Science Digital Library

This webpage is part of the University Corporation for Atmospheric Research (UCAR) Windows to the Universe program. It describes the nature and configuration of magnetic fields, which are the result of moving electric charges, including how they cause magnetic objects to orient themselves along the direction of the magnetic force points, which are illustrated as lines. Magnetic field lines by convention point outwards at the north magnetic pole and inward at the south magnetic pole. The site features text, scientific illustrations and an animation. Text and vocabulary are selectable for the beginning, intermediate, or advanced reader.

Team, University C.

2007-12-12

225

Striped tape arrays  

NASA Technical Reports Server (NTRS)

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.

Drapeau, Ann L.; Katz, Randy H.

1992-01-01

226

Interference mode-locking of 2D magnetized colloids driven by dc and ac forces in periodic pinning arrays  

NASA Astrophysics Data System (ADS)

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.

Song, K. N.; Wang, H. L.; Ren, J.; Cao, Y. G.

2015-01-01

227

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)

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.

El-Ghussein, Fadi; Mastanduno, Michael A.; Jiang, Shudong; Pogue, Brian W.; Paulsen, Keith D.

2014-01-01

228

Hybrid photomultiplier tube and photodiode parallel detection array for wideband optical spectroscopy of the breast guided by magnetic resonance imaging  

PubMed Central

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

El-Ghussein, Fadi; Mastanduno, Michael A.; Jiang, Shudong; Pogue, Brian W.; Paulsen, Keith D.

2013-01-01

229

Magnetism  

NSDL National Science Digital Library

This radio broadcast discusses the history of magnetism from the time of its discovery by an apocryphal Greek sheperd until the late 16th century and the work of William Gilbert. There is also discussion of who pioneered the study of magnetism, what theories they constructed from its curious abilities, and how the power of the magnet was brought out of the realm of magic and into the service of science. The broadcast concludes with a discussion of why magnetism is still mysterious and how the modern search for the single magnetic pole, or magnetic monopole, could provide a fundamental unit of magnetism, essential for ultimate explanation. The broadcast is 41 minutes and 45 seconds in length.

230

Magnetic Cusp Configuration of the SPL Plasma Generator  

SciTech Connect

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.

Kronberger, Matthias; Chaudet, Elodie; Favre, Gilles; Lettry, Jacques; Kuechler, Detlef; Moyret, Pierre; Paoluzzi, Mauro; Prever-Loiri, Laurent; Schmitzer, Claus; Scrivens, Richard; Steyaert, Didier [CERN, 385 Route de Meyrin, 1211 Geneva (Switzerland)

2011-09-26

231

An experimental investigation of the improvement in the reception of TM (Transverse Magnetic)-polarized LF (Low-Frequency) waves with a two-element spaced array  

NASA Astrophysics Data System (ADS)

For this study, a 2-element spaced array antenna system was developed and tested. This array consisted of two well-spaced vertical loops combined with a microwave link. The array was tested to show improvements in signal-to-noise ratio over omnidirectional antennas, using received transmissions from an aircraft towing a long wire antenna. Gains in signal-to-noise ratio of up to 12.8 dB were demonstrated.

Tingley, F. M.; Kahler, R. C.

1984-05-01

232

Magnetism  

NSDL National Science Digital Library

This overview of magnetism provides a brief history prior to 1600 and continues with the work of William Gilbert, Hans Christian Oersted, and Andre-Marie Ampere in describing and exploring the magnetosphere and learning the role that electric current plays in producing magnetism. Magnetic field lines are then discussed, citing the work of Michael Faraday. The work of James Clerk Maxwell and Heinrich Hertz is mentioned in a discussion of the relationship of light waves and radio waves as part of the electromagnetic spectrum.

Stern, David

233

Adaptive arrays  

Microsoft Academic Search

A method for adaptively optimizing the signal-to-noise ratio of an array antenna is presented. Optimum element weights are derived for a prescribed environment and a given signal direction. The derivation is extended to the optimization of a \\

S. Applebaum

1976-01-01

234

Integration of spintronic interface for nanomagnetic arrays  

NASA Astrophysics Data System (ADS)

An experimental demonstration utilizing a spintronic input/output (I/O) interface for arrays of closely spaced nanomagnets is presented. The free layers of magnetic tunnel junctions (MTJs) form dipole coupled nanomagnet arrays which can be applied to different contexts including Magnetic Quantum Cellular Automata (MQCA) for logic applications and self-biased devices for field sensing applications. Dipole coupled nanomagnet arrays demonstrate adaptability to a variety of contexts due to the ability for tuning of magnetic response. Spintronics allows individual nanomagnets to be manipulated with spin transfer torque and monitored with magnetoresistance. This facilitates measurement of the magnetic coupling which is important for (yet to be demonstrated) data propagation reliability studies. In addition, the same magnetic coupling can be tuned to reduce coercivity for field sensing. Dipole coupled nanomagnet arrays have the potential to be thousands of times more energy efficient than CMOS technology for logic applications, and they also have the potential to form multi-axis field sensors.

Lyle, Andrew; Harms, Jonathan; Klein, Todd; Lentsch, August; Klemm, Angeline; Martens, Daniel; Wang, Jian-Ping

2011-12-01

235

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)

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.

Jang, Seok-Myeong; Park, Ji-Hoon; You, Dae-Joon; Choi, Sang-Ho

2009-04-01

236

Advanced superconducting gradiometer\\/Magnetometer arrays and a novel signal processing technique  

Microsoft Academic Search

Recent developments in superconducting magnetic gradiometer technology have led to the construction of advanced ultrasensitive gradiometer\\/magnetometer arrays. Details of construction techniques and data showing operational capabilities are presented. The most recent of the gradiometer\\/magnetometer arrays simultaneously measures five independent spatial gradients of the magnetic field and three vector components of the magnetic field. The measured signals from this array are

W. Wynn; C. Frahm; P. Carroll; R. Clark; J. Wellhoner; M. Wynn

1975-01-01

237

Electromagnetically Clean Solar Arrays  

NASA Technical Reports Server (NTRS)

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.

Stem, Theodore G.; Kenniston, Anthony E.

2008-01-01

238

Emerging protein array technologies for proteomics.  

PubMed

Numerous efforts have been made to understand fundamental biology of diseases based on gene expression. However, the relationship between gene expression and onset of disease 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. The authors 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 sensors are used to quantitatively measure the analytes of interest, which are labeled with magnetic nanoparticles. Similar to giant magnetoresistive sensors, 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, which have thousands of protein features directly expressed by nucleic acids on the array surface. The authors anticipate that these two emerging protein array platforms can be combined to produce synergistic benefits and open new applications in proteomics and clinical diagnostics. PMID:23414360

Lee, Jung-Rok; Magee, Dewey Mitchell; Gaster, Richard Samuel; LaBaer, Joshua; Wang, Shan X

2013-02-01

239

Emerging Protein Array Technologies for Proteomics  

PubMed Central

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

Lee, Jung-Rok; Magee, Dewey Mitchell; Gaster, Richard Samuel; LaBaer, Joshua; Wang, Shan X.

2014-01-01

240

Exchange bias in nanoscale antidot arrays D. Tripathy,1  

E-print Network

Exchange bias in nanoscale antidot arrays D. Tripathy,1 A. O. Adeyeye,1,a and N. Singh2 180Fe20 30 nm /Ir75Mn25 30 nm /Cu 2 nm multilayer antidot arrays. The antidot arrays exhibit to their technological applica- tions in magnetoresistive read heads and magnetic random access memories.6 The constant

Adeyeye, Adekunle

241

Conical wire array experiments on the zebra generator  

Microsoft Academic Search

Summary form only given. We present the results of recent conical wire array experiments on the Zebra generator. In this paper we will discuss the dynamics of conical wire array implosions, particularly the zippered implosion which results from the tapering of the array and the formation of a magnetic bubble near the small diameter electrode (the cathode). The implosion characteristics

D. J. Ampleford; B. Jones; C. A. Coverdale; C. A. Jennings; C. Deeney; P. D. LePell; V. L. Kantsyrev; V. V. Ivanov; A. S. Safronova; K. Williamson; G. Osborne; P. J. Laca; D. Fedin; N. Ouart; V. Nalajala; J. P. Chittenden

2006-01-01

242

Magnetic anisotropy of cobalt nanoparticle 2D arrays grown on corrugated MnF2(1 1 0) and CaF2(1 1 0) surfaces  

NASA Astrophysics Data System (ADS)

Cobalt nanoparticle 2D arrays with different effective thicknesses of cobalt layer (2 nm < deff < 10 nm) were grown by molecular beam epitaxy on CaF2(1 1 0)/Si(0 0 1) and MnF2(1 1 0)/CaF2(1 1 0)/Si(0 0 1) substrates with corrugated morphology of the surface. Surface morphology analysis showed that for effective thickness of cobalt layer deff = 5 nm the lateral dimensions of cobalt islands are about 5-10 nm and the distances between the islands differs in a half along and across the grooves. In both types of the heterostructures the shape of hysteresis loops measured by LMOKE depend on orientation of in-plane magnetic field relative to the direction of the grooves. The azimuthal dependence of coercive field Hc in Co/CaF2(1 1 0)/Si(0 0 1) structures corresponds to Stoner-Wohlfarth model's predictions, which takes into account the anisotropy of individual particles. In contrast to that, in Co/MnF2(1 1 0)/CaF2(1 1 0)/Si(0 0 1) structures these dependences are analogous to those predicted by the model based on account of magnetic-dipole interaction between particles which are placed in chains (chain-of-spheres-model). Possible explanations of the difference in magnetic anisotropy are suggested.

Baranov, D. A.; Krichevtsov, B. B.; Gastev, S. V.; Banschikov, A. G.; Fedorov, V. V.; Koshmak, K. V.; Suturin, S. M.; Sokolov, N. S.

2013-02-01

243

Magnetometer array for cusp and cleft studies observations of the spatial extent of broadband ULF magnetic pulsations at cusp\\/cleft latitudes  

Microsoft Academic Search

The authors have used magnetometer data from 10 locations in Arctic Canada and Greenland, covering over 5 hours in magnetic local time at magnetic latitudes from 75° to 79°, to characterize the dayside patterns of enhanced long-period ULF (10- to 600-s period) wave power at cusp\\/cleft latitudes. They conclude the following: (1) In agreement with earlier single-station studies, the authors

M. J. Engebretson; J. L. Alford; W. J. Hughes; E. Zesta; L. J. Cahill; R. L. Arnoldy; G. D. Reeves

1995-01-01

244

Coupling Between Waveguide-Fed Slot Arrays  

NASA Technical Reports Server (NTRS)

Coupling between two waveguide-fed planar slot arrays has been investigated using full-wave analysis. The analysis employs the method-of-moments solution to the pertinent coupled integral equations for the aperture electric field of all slots. In order to compute coupling between two arrays, the input port of the first array is excited with a TE(sub 10) mode wave while the second one is match-terminated. After solving the moment method matrix equations, the aperture fields of all slots are obtained and thereby the TE(sub 10) mode wave received at the input port of the second array is determined. Coupling between two arrays is the ratio of the wave amplitude arriving in the second array port to the incident wave amplitude at the first array port. The coupling mechanism has been studied as a function of spacing between arrays in different directions, e.g. the electric field plane, the magnetic field plane, and the diagonal plane. Computed coupling values are presented for different array geometries. This work is novel since it provides a good understanding of coupling between waveguide-fed slot arrays as a function of spacing and orientation for different aperture distributions and array architectures. This serves as a useful tool for antenna design engineers and system engineers.

Rengarajan, Sembiam

2011-01-01

245

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)

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.

Yamamoto, Shuu'ichirou; Shuto, Yusuke; Sugahara, Satoshi

2012-11-01

246

Tunable magnetic properties of arrays of Fe(1 1 0) nanowires grown on kinetically grooved W(1 1 0) self-organized templates  

NASA Astrophysics Data System (ADS)

We report a detailed magnetic study of a new type of self-organized nanowires discussed briefly previously [B. Borca et al., Appl. Phys. Lett. 90 (2007) 142507]. The templates, prepared on sapphire wafers in a kinetically limited regime, consist of uniaxially grooved W(1 1 0) surfaces, with a lateral period here tuned to 15 nm. Fe deposition leads to the formation of (1 1 0) 7 nm-wide wires located at the bottom of the grooves. The effect of capping layers (Mo, Pd, Au, Al) and underlayers (Mo, W) on the magnetic anisotropy of the wires was studied. Significant discrepancies with figures known for thin flat films are evidenced and discussed in terms of step anisotropy and strain-dependent surface anisotropy. Demagnetizing coefficients of cylinders with a triangular isosceles cross-section have also been calculated, to estimate the contribution of dipolar anisotropy. Finally, the dependence of magnetic anisotropy with the interface element was used to tune the blocking temperature of the wires, here from 50 to 200 K.

Borca, B.; Fruchart, O.; Kritsikis, E.; Cheynis, F.; Rousseau, A.; David, Ph.; Meyer, C.; Toussaint, J. C.

2010-01-01

247

Nanotube Array  

NASA Astrophysics Data System (ADS)

A TiO2 nanotube array was grown electrochemically by using single and mixed electrolyte/s with 20 V constant potential at room temperature. Anodization was carried out for 120 min using five different electrolytes, e.g., H3PO4, NH4F, HF, NH4F with H3PO4 and HF with H3PO4. Structural characterizations of the grown titania nanotubes were conducted by using x-ray diffraction and field emission scanning electron microscopy. Optical properties of the grown nanotubes were investigated through photoluminescence (PL) spectroscopy. In the case of the 4 M H3PO4 electrolyte, no perceptible growth of nanotubes was observed. The individual electrolytes of 0.3 M NH4F and 1 M HF resulted into the formation of the wall-connected nanotubes. In contrast, the mixed electrolytes comprising the strong (NH4F, HF) and weak (H3PO4) electrolytes have been found to be efficient for the growth of wall-separated titania nanotubes. The results of the PL spectroscopy have demonstrated that the free-standing nanotubes offer low PL intensity compared to its connected counterpart owing to the lower carrier recombination rate of free-standing nanotubes.

Hazra, A.; Dutta, K.; Bhowmik, B.; Manjuladevi, V.; Gupta, R. K.; Chattopadhyay, P. P.; Bhattacharyya, P.

2014-09-01

248

Nanolithographically defined magnetic structures and quantum magnetic disk (invited)  

E-print Network

, and are characterized using magnetic force microscopy. It has been demonstrated that manipulating the size, aspect ratioNanolithographically defined magnetic structures and quantum magnetic disk (invited) Stephen Y, University of Minnesota, Minneapolis, Minnesota 55455 Isolated and interactive arrays of magnetic

249

Development of a monolithic ferrite memory array  

NASA Technical Reports Server (NTRS)

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.

Heckler, C. H., Jr.; Bhiwandker, N. C.

1972-01-01

250

Design of 3x3 focusing array for heavy ion driver. Final report on CRADA  

SciTech Connect

This memo presents a design of a 3 x 3 quadrupole array for HIF. It contains 3 D magnetic field computations of the array build with racetrack coils with and without different shields. It is shown that it is possible to have a low error magnetic field in the cells and shield the stray fields to acceptable levels. The array design seems to be a practical solution to any size array for future multi-beam heavy ion fusion drivers.

Martovetsky, N N

2005-03-30

251

Investigation of ablation and implosion dynamics in linear wire arrays  

SciTech Connect

Ablation and implosion dynamics were investigated by optical probing in linear wire arrays of different geometry. Formation of ablation jets begins on the outermost wires. In the beginning of implosion plasma bubbles arise in breaks on the outer wires. Implosion bubbles move to the next wire in the array and hit the plasma column with the speed >250 km/s. Imploding plasma moves to the center of the array cascading from wire to wire. Configuration of magnetic fields in the linear array can be changed by variation of wire spacing. The regimes of ablation and implosion in the wire arrays are found to differ with different wire spacing.

Ivanov, V. V.; Sotnikov, V. I.; Haboub, A.; Sarkisov, G. E.; Presura, R.; Cowan, T. E. [University of Nevada, Reno, 5625 Fox Avenue, Reno, Nevada 89506 (United States); Ktech Corporation, Albuquerque, New Mexico 87123 (United States); University of Nevada, Reno, 5625 Fox Avenue, Reno, Nevada 89506 (United States)

2007-03-15

252

Parallel arrays of Josephson junctions for submillimeter local oscillators  

NASA Technical Reports Server (NTRS)

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.

Pance, Aleksandar; Wengler, Michael J.

1992-01-01

253

The Upgraded CARISMA Magnetometer Array in the THEMIS Era  

Microsoft Academic Search

This review describes the infrastructure and capabilities of the expanded and upgraded Canadian Array for Realtime InvestigationS\\u000a of Magnetic Activity (CARISMA) magnetometer array in the era of the THEMIS mission. Formerly operated as the Canadian Auroral\\u000a Network for the OPEN Program Unified Study (CANOPUS) magnetometer array until 2003, CARISMA capabilities have been extended\\u000a with the deployment of additional fluxgate magnetometer

I. R. Mann; D. K. Milling; I. J. Rae; L. G. Ozeke; A. Kale; Z. C. Kale; K. R. Murphy; A. Parent; M. Usanova; D. M. Pahud; E.-A. Lee; V. Amalraj; D. D. Wallis; V. Angelopoulos; K.-H. Glassmeier; C. T. Russell; H.-U. Auster; H. J. Singer

2008-01-01

254

Exploring Functional Connectivity Networks with Multichannel Brain Array Coils  

E-print Network

The use of multichannel array head coils in functional and structural magnetic resonance imaging (MRI) provides increased signal-to-noise ratio (SNR), higher sensitivity, and parallel imaging capabilities. However, their ...

Anteraper, Sheeba Arnold

255

A 4kb memory array for MRAM development  

E-print Network

The circuits for a A 4kb array of Magnetic Tunnel Junctions (MTJs) have been designed and fabricated in a 0:18¹m CMOS process with three levels of metal. Support circuitry for addressing, reading, writing, and test mode ...

Qazi, Masood

2007-01-01

256

Angular dependence of the magnetoresistance in nanoparticle arrays  

NASA Astrophysics Data System (ADS)

The interplay between the ferromagnetism and the charging effects strongly affects the electron transport through nanoparticle arrays when they are placed between two ferromagnetic electrodes with collinear magnetizations. There are oscillations in the current for the parallel orientation of magnetizations, and large values of the tunneling magnetoresistance (TMR). We analyze the transport properties in nanoparticle arrays for the case of noncollinear magnetizations. We show that the I-V and TMR curves strongly depend on the angle ? between the magnetization orientations of both electrodes. Large values of TMR are obtained for several values of ?.

Estévez, V.; Guslienko, K. Y.

2013-10-01

257

Effect of disorder on DNA electrophoresis in a microfluidic array of obstacles  

NASA Astrophysics Data System (ADS)

The size-based separation of electrophoresing DNA chains of varying lengths has been experimentally achieved in microfluidic obstacle arrays. The separation is actuated by the occurrence of size-dependent chain-obstacle collisions and the subsequent formation of hooked chain configurations in the array. We investigate the role played by disorder in array geometry in determining chain dynamics in the array. As a prototypical example of a disordered post array, we select a self-assembled array of magnetic colloids, wherein the degree of disorder may be varied by varying the magnetic field strength under which the array is generated. We employ Brownian dynamics simulations of chain electrophoresis in the array to compute the mobility, dispersivity, chain-obstacle collision probability, and mean chain stretch in the device, and demonstrate the link between the orientational order of the array and the resulting chain dynamics.

Mohan, Aruna; Doyle, Patrick S.

2007-10-01

258

Array to Multiply  

NSDL National Science Digital Library

In this lesson, students will understand the concept of arrays and will be able to create/draw an array for multiplication sentences. Engaging center game is used to help student with concrete visual representation of multiplication sentences.

2013-01-28

259

Innovative Electromagnetic Actuator Applied for High-Frequency Reciprocal Translation  

Microsoft Academic Search

A novel magnetically levitated linear actuator, mainly consisting of a Halbach magnetized moving-magnet armature, a cylindrical frame, a rod, and electromagnetic poles, is presented and analyzed for linear compressors applications. The Halbach magnetized armature naturally generates a periodically distributed magnetic field, which is interacted with that induced by the electromagnetic poles. Therefore, an axially reciprocating thrust force is induced that

Nan-Chyuan Tsai; Chao-Wen Chiang

2011-01-01

260

Demonstration of successful construction of linear arrays of Hall probes used to digitally image  

NASA Technical Reports Server (NTRS)

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.

1996-01-01

261

caArray - Browse  

Cancer.gov

Skip to Page Content Build 2.5.3_RC1 | Node: NCICB Welcome to caArray Browse Login Register About caArray What is caArray? Release Notes User Guide Global Quick Links National Cancer Institute (NCI) NCI Center for Biomedical Informatics and Information

262

Frequency diverse array radars  

Microsoft Academic Search

This paper presents a generalized structure for a frequency diverse array radar. In its simplest form, the frequency diverse array applies a linear phase progression across the aperture. This linear phase progression induces an electronic beam scan, as in a conventional phased array. When an additional linear frequency shift is applied across the elements, a new term is generated which

Paul Antonik; Michael C. Wicks; Hugh D. Griffiths; Christopher J. Baker

2006-01-01

263

The Square Kilometre Array  

NASA Astrophysics Data System (ADS)

The SKA is a global project to plan and construct the next-generation international radio telescope operating at metre to cm wavelengths. More than 50 institutes in 19 countries are involved in its development. The SKA will be an interferometric array with a collecting area of up to one million square metres and maximum baseline of at least 3000 km. The SKA reference design includes field-of-view expansion technology that will allow instantaneous imaging of up to several tens of degrees. The SKA is being designed to address fundamental questions in cosmology, physics and astronomy. The key science goals range from the epoch or re-ionization, dark energy, the formation and evolution of galaxies and large-scale structure, the origin and evolution of cosmic magnetism, strong-field tests of gravity and gravity wave detection, the cradle of life, and the search for extraterrestrial intelligence. The sensitivity, field-of-view and angular resolution of the SKA will make possible a program to create a multi-epoch data base of wide-angle relative astrometry to a few ?as precision for ~10,000,000 radio sources with S > 10 ?Jy.

Taylor, A. R.

2008-07-01

264

Thruster array thermal control  

NASA Technical Reports Server (NTRS)

This paper presents the results of a preliminary investigation of the thermal interactions between elements in the thruster array for a proposed Encke flyby mission. A clustered eight-thruster array was considered as the trial configuration in the current study. Electrically heated dummy thrusters were calibrated to represent the thruster thermal performance. The thermal behavior of the thruster array thermal mockup and the effects of thermal coating applications were investigated. Temperature measurements of the thruster array mockup were performed under various operational modes to substantiate the analytical results. A resultant analytical thermal network model was established to provide pertinent information for thruster array design tradeoff studies.

Wen, L.; Womack, J. R.

1973-01-01

265

Detection of weak magnetic signal for magnetic localization and orientation in capsule endoscope  

Microsoft Academic Search

A permanent magnet is embedded in the capsule endoscope to perform as an excitation source for tracking capsule's position and orientation, and a magnetic sensor array is built around the capsule to capture the signals from magnet. However, the magnet-field signal is weak and attenuates dramatically when the spatial distance between the magnet and the sensor increases. How to detect

Mao Li; Chao Hu; Shuang Song; Houde Dai; Max Q.-H. Meng

2009-01-01

266

Effect of contact geometry on the magnetoresistance response of Ni80Fe20 antidot array  

E-print Network

Effect of contact geometry on the magnetoresistance response of Ni80Fe20 antidot array C. C. Wang and sign of the magnetoresistance MR response in micron-size antirectangular array structures has been the various magnetic patterned structures, anti- dot arrays have received a lot of attention due

Adeyeye, Adekunle

267

VOLUME 77, NUMBER 11 P H Y S I C A L R E V I E W L E T T E R S 9 SEPTEMBER 1996 Magnetic Focusing of Composite Fermions through Arrays of Cavities  

E-print Network

of Composite Fermions through Arrays of Cavities J. H. Smet, D. Weiss, R. H. Blick, G. Lütjering, and K. von Festkörperphysik, D-79108 Freiburg, Germany (Received 9 February 1996) The magnetoresistance Rxx was investigated in arrays of abutted square cavities with lengths L ranging from 500 nm to 1.2 mm near filling factor n 1 2

Timme, Marc

268

Microwave detector response of the Josephson junction arrays  

SciTech Connect

This paper reports on microwave detector response {eta} for three types of superconducting structures:single edge-type Josephson junction, array of series connected junctions and array of RF series and DC parallel connected junctions investigated in the frequency range 35-120 GHz. Experimental dependence of {eta} vs biasing voltage is mainly determined by the interaction of junctions in array. The Selective response, that means narrow linewidth of Josephson radiation, has been observed for third type of superconducting structures in small magnetic field changing the phase shift between near placed junctions. These arrays have the advantage in coupling with the external microwave system.

Ovsyannikov, G.A.; Babayan, G.E. (Inst. of Radio Engineering and Electronics, Academy of Sciences, Moscow 103907 (SU)); Laptev, V.N.; Makhov, V.I. (Research Inst. of Physical Problems, Moscow 103460 (SU))

1991-03-01

269

Optimized Superconducting Quadrupole Arrays for Multiple Beam Transport  

SciTech Connect

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.

Meinke, Rainer, B.; Goodzeit, Carl, L.; Ball, Millicent, J.

2005-09-20

270

Intracavitary ultrasound phased arrays for thermal therapies  

NASA Astrophysics Data System (ADS)

Currently, the success of hyperthermia and thermal surgery treatments is limited by the technology used in the design and fabrication of clinical heating devices and the completeness of the thermometry systems used for guidance. For both hyperthermia and thermal surgery, electrically focused ultrasound generated by phased arrays provides a means of controlling localized energy deposition in body tissues. Intracavitary applicators can be used to bring the energy source close to a target volume, such as the prostate, thereby minimizing normal tissue damage. The work performed in this study was aimed at improving noninvasive prostate thermal therapies and utilized three research approaches: (1) Acoustic, thermal and optimization simulations, (2) Design and fabrication of multiple phased arrays, (3) Ex vivo and in vivo experimental testing of the heating capabilities of the phased arrays. As part of this study, a novel aperiodic phased array design was developed which resulted in a 30- 45% reduction in grating lobe levels when compared to conventional phased arrays. Measured acoustic fields generated by the constructed aperiodic arrays agreed closely with the fields predicted by the theoretical simulations and covered anatomically appropriate ranges. The power capabilities of these arrays were demonstrated to be sufficient for the purposes of hyperthermia and thermal surgery. The advantage of using phased arrays in place of fixed focus transducers was shown by demonstrating the ability of electronic scanning to increase the size of the necrosed tissue volume while providing a more uniform thermal dose, which can ultimately reduce patient treatment times. A theoretical study on the feasibility of MRI (magnetic resonance imaging) thermometry for noninvasive temperature feedback control was investigated as a means to improve transient and steady state temperature distributions achieved in hyperthermia treatments. MRI guided ex vivo and in vivo experiments demonstrated that the heating capabilities of the constructed phased arrays were adequate for hyperthermia and thermal surgery treatments. (Copies available exclusively from MIT Libraries, Rm. 14-0551, Cambridge, MA 02139-4307. Ph. 617-253-5668; Fax 617-253- 1690.)

Hutchinson, Erin

271

Microshutter Arrays for James Webb Space Telescope  

NASA Technical Reports Server (NTRS)

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

Li, Mary J.; Acuna, Nadine; Beamesderfer, Michael; Ewin, Audrey; Fettig, Rainer; Franz, Dave; Hess, Larry; Hu, Ron; Kelly, Dan; King, Todd

2004-01-01

272

Programmable Aperture with MEMS Microshutter Arrays  

NASA Technical Reports Server (NTRS)

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.

Moseley, Samuel; Li, Mary; Kutyrev, Alexander; Kletetschka, Gunther; Fettig, Rainer

2011-01-01

273

Levitated Duct Fan (LDF) Aircraft Auxiliary Generator  

NASA Technical Reports Server (NTRS)

This generator concept includes a novel stator and rotor architecture made from composite material with blades attached to the outer rotating shell of a ducted fan drum rotor, a non-contact support system between the stator and rotor using magnetic fields to provide levitation, and an integrated electromagnetic generation system. The magnetic suspension between the rotor and the stator suspends and supports the rotor within the stator housing using permanent magnets attached to the outer circumference of the drum rotor and passive levitation coils in the stator shell. The magnets are arranged in a Halbach array configuration.

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

2011-01-01

274

Testing Microshutter Arrays Using Commercial FPGA Hardware  

NASA Technical Reports Server (NTRS)

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.

Rapchun, David

2008-01-01

275

The Long Wavelength Array  

Microsoft Academic Search

Application of self-calibration techniques to low-frequency (< 150 MHz) radio interferometric data has enabled high-resolution, high sensitivity imaging at long wavelengths for the first time. We illustrate these advances using NRAO Very Large Array (VLA) 74 MHz images having sub-arcminute resolution and sub-Jansky sensitivity. The VLA 74 MHz breakthrough has inspired the Long Wavelength Array (LWA), a completely electronic array

N. E. Kassim; E. J. Polisensky; T. E. Clarke; B. C. Hicks; P. C. Crane; K. P. Stewart; P. S. Ray; K. W. Weiler; L. J. Rickard; T. J. W. Lazio; A. S. Cohen; M. E. Nord; W. C. Erickson; R. A. Perley

2005-01-01

276

The Long Wavelength Array  

Microsoft Academic Search

Sub-arcminute resolution and sub-Jy sensitivity below 100 MHz is now being obtained on a routine basis using self-calibration or field-based calibration techniques with the 74 MHz system on the NRAO Very Large Array (VLA). The VLA 74 MHz breakthrough has inspired an emerging suite of new low frequency instruments, including the Long Wavelength Array (LWA), an electronic array planned to

E. Polisensky; N. Kassim; T. J. W. Lazio; K. Weiler; P. Crane; P. Ray; K. Stewart; B. Hicks; A. Cohen; W. Peters; M. Nord; W. C. Erickson

2004-01-01

277

Focal plane array with modular pixel array components for scalability  

DOEpatents

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.

Kay, Randolph R; Campbell, David V; Shinde, Subhash L; Rienstra, Jeffrey L; Serkland, Darwin K; Holmes, Michael L

2014-12-09

278

Algorithms for Sorting Arrays  

NSDL National Science Digital Library

It is often necessary to have elements of an array sorted into ascending or descending order. There are several approaches or algorithms available for sorting unordered arrays. Choosing an appropriate algorithm may depend upon the situation, however, some well-known algorithms are just more efficient than others. Exercise 1 To move an element in an array, an algorithm must make sure that each element being moved is inserted into an empty location or it will overwrite the current element. Therefore, to swap two items in an array, one of the items must be moved to an empty location ...

Watts, Mrs.

2007-09-26

279

Modeling of soft magnetic composites  

Microsoft Academic Search

The electromagnetic properties of soft magnetic composites (SMCs) are studied based on a finite element model. In this approach, SMCs are modeled as an infinite array of hexagonal cylinders in two dimensions. Each cylinder is assumed to be saturable pure iron coated with a thin layer of binder or insulation. The array is excited by a current sheet or imposed

Yanhong Cui; G. B. Kliman

2004-01-01

280

Versatile microfluidic droplets array for bioanalysis.  

PubMed

We propose a novel method to obtain versatile droplets arrays on a regional hydrophilic chip that is fabricated by PDMS soft lithography and regional plasma treatment. It enables rapid liquid dispensation and droplets array formation just making the chip surface in contact with solution. By combining this chip with a special Christmas Tree structure, the droplets array with concentrations in gradient is generated. It possesses the greatly improved performance of convenience and versatility in bioscreening and biosensing. For example, high throughput condition screening of toxic tests of CdSe quantum dots on HL-60 cells are conducted and cell death rates are successfully counted quickly and efficiently. Furthermore, a rapid biosensing approach for cancer biomarkers carcinoma embryonic antigen (CEA) is developed via magnetic beads (MBs)-based sandwich immunoassay methods. PMID:25525675

Hu, Shan-Wen; Xu, Bi-Yi; Ye, Wei-Ke; Xia, Xing-Hua; Chen, Hong-Yuan; Xu, Jing-Juan

2015-01-14

281

A Compact, Modular Superconducting Bolometer Array Package  

NASA Technical Reports Server (NTRS)

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.

Benford, Dominic J.

2008-01-01

282

Journal of Magnetism and Magnetic Materials 188 (1998) L1--L7 Letter to the Editor  

E-print Network

of the magnetoresistance behavior in these non-interac- ting wire arrays as the wire width is reduced from 200 m to 0.3 m of a comprehensive study of the magnetic and magneto-transport properties in variable width wire arrays based on Ni ) in adjacent wires and then alternating them in an array, the coercivity can be `engineered'. Measurements were

Adeyeye, Adekunle

283

ISS Solar Array Management  

NASA Technical Reports Server (NTRS)

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.

Williams, James P.; Martin, Keith D.; Thomas, Justin R.; Caro, Samuel

2010-01-01

284

Array for detecting microbes  

SciTech Connect

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.

Andersen, Gary L.; DeSantis, Todd D.

2014-07-08

285

Telescope Array Experiment  

Microsoft Academic Search

The TA observatory is a hybrid detector system consisting of both a surface detector array as well as a set of fluorescence detectors. The observatory will measure the energy spectrum, anisotropy and composition of ultra-high energy cosmic rays. The surface detectors are being deployed and the array should be complete by the end of February, 2007. We will soon be

H. Kawai; S. Yoshida; H. Yoshii; K. Tanaka; F. Cohen; M. Fukushima; N. Hayashida; K. Hiyama; D. Ikeda; E. Kido; Y. Kondo; T. Nonaka; M. Ohnishi; H. Ohoka; S. Ozawa; H. Sagawa; N. Sakurai; T. Shibata; H. Shimodaira; M. Takeda; A. Taketa; M. Takita; H. Tokuno; R. Torii; S. Udo; Y. Yamakawa; H. Fujii; T. Matsuda; M. Tanaka; H. Yamaoka; K. Hibino; T. Benno; K. Doura; M. Chikawa; T. Nakamura; M. Teshima; K. Kadota; Y. Uchihori; K. Hayashi; Y. Hayashi; S. Kawakami; T. Matsuyama; M. Minamino; S. Ogio; A. Ohshima; T. Okuda; N. Shimizu; H. Tanaka; D. R. Bergman; G. Hughes; S. Stratton; G. B. Thomson; A. Endo; N. Inoue; S. Kawana; Y. Wada; K. Kasahara; R. Azuma; T. Iguchi; F. Kakimoto; S. Machida; K. Misumi; Y. Murano; Y. Tameda; Y. Tsunesada; J. Chiba; K. Miyata; T. Abu-Zayyad; J. W. Belz; R. Cady; Z. Cao; P. Huentemeyer; C. C. H. Jui; K. Martens; J. N. Matthews; M. Mostofa; J. D. Smith; P. Sokolsky; R. W. Springer; J. R. Thomas; S. B. Thomas; L. R. Wiencke; T. Doyle; M. J. Taylor; V. B. Wickwar; T. D. Wilkerson; K. Hashimoto; K. Honda; K. Ikuta; T. Ishii; T. Kanbe; T. Tomida

2008-01-01

286

Communications Satellites Using Arrays  

Microsoft Academic Search

Passive reflectors require large ground antennas and powers but permit use of unstabilized reflectors. Active systems, on the other hand, offer attractive performance through high directivity antennas but generally require stabilized vehicles. Further, the reliability of a satellite repeater amplifier is a critical factor. Automatic angle return arrays are investigated for both passive and active systems. These arrays, called Van

R. C. Hansen

1961-01-01

287

SOUTH AFRICA'S MEERKAT ARRAY  

E-print Network

SOUTH AFRICA'S MEERKAT ARRAY THE MEERKAT ARRAY, currently taking shape in South Africa's Karoo) is completed around 2024. Via MeerKAT, South Africa is playing a key role in design and technology developments for the SKA. Close to 100 young scientists and engineers are working on the MeerKAT project. Based

Jarrett, Thomas H.

288

Multibeam Phased Array Antennas  

NASA Technical Reports Server (NTRS)

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.

Popovic, Zoya; Romisch, Stefania; Rondineau, Sebastien

2004-01-01

289

Micromachined electrode array  

DOEpatents

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.

Okandan, Murat (Edgewood, NM); Wessendorf, Kurt O. (Albuquerque, NM)

2007-12-11

290

High density pixel array  

NASA Technical Reports Server (NTRS)

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.

Wiener-Avnear, Eliezer (Inventor); McFall, James Earl (Inventor)

2004-01-01

291

Microbial sensor cell arrays.  

PubMed

Motivated by the advantages endowed by high-throughput analysis, researchers have succeeded in incorporating multiple reporter cells into a single platform; the technology now allows the simultaneous scrutiny of a large collection of sensor strains. We review current aspects in cell array technology with emphasis on microbial sensor arrays. We consider various techniques for patterning live cells on solid surfaces, describe different array-based applications and devices, and highlight recent efforts for live cell storage. We review mathematical approaches for deciphering the data emanating from bioreporter collections, and discuss the future of single cell arrays. Innovative technologies for cell patterning, preservation and interpretation are continuously being developed; when they all mature, cell arrays may become an efficient analytical tool, in a scope resembling that of DNA microarray biochips. PMID:22176747

Melamed, Sahar; Elad, Tal; Belkin, Shimshon

2012-02-01

292

Amplitude steered array  

NASA Technical Reports Server (NTRS)

A spin stabilized satellite has an electronically despun antenna array comprising a multiplicity of peripheral antenna elements. A high gain energy beam is established by connecting a suitable fraction or array of the elements in phase. The beam is steered or caused to scan by switching elements in sequence into one end of the array as elements at the other end of the array are switched out. The switching transients normally associated with such steering are avoided by an amplitude control system. Instead of abruptly switching from one element to the next, a fixed value of power is gradually transferred from the element at the trailing edge of the array to the element next to the leading edge.

Dietrich, F. J.; Koloboff, G. J.; Martel, R. J.; Johnson, C. C. (inventors)

1974-01-01

293

Optical Magnetometer Array for Fetal Magnetocardiography  

E-print Network

We describe an array of spin-exchange relaxation free optical magnetometers designed for detection of fetal magnetocardiography (fMCG) signals. The individual magnetometers are configured with a small volume with intense optical pumping, surrounded by a large pump-free region. Spin-polarized atoms that diffuse out of the optical pumping region precess in the ambient magnetic field and are detected by a probe laser. Four such magnetometers, at the corners of a 7 cm square, are configured for gradiometry by feeding back the output of one magnetometer to a field coil to null uniform magnetic field noise at frequencies up to 200 Hz. Using this array, we present the first measurements of fMCG signals using an atomic magnetometer.

Wyllie, Robert; Wakai, Ronald T; Walker, Thad G

2012-01-01

294

Optical magnetometer array for fetal magnetocardiography  

NASA Astrophysics Data System (ADS)

We describe an array of spin-exchange relaxation free optical magnetometers designed for detection of fetal magnetocardiography (fMCG) signals. The individual magnetometers are configured with a small volume with intense optical pumping, surrounded by a large pump-free region. Spin-polarized atoms that diffuse out of the optical pumping region precess in the ambient magnetic field and are detected by a probe laser. Four such magnetometers, at the corners of a 7 cm square, are configured for gradiometry by feeding back the output of one magnetometer to a field coil to null uniform magnetic field noise at frequencies up to 200 Hz. Using this array, we present the first measurements of fMCG signals using an atomic magnetometer.

Wyllie, Robert; Kauer, Matthew; Wakai, Ronald T.; Walker, Thad G.

2012-06-01

295

Journal of Magnetism and Magnetic Materials 213 (2000) L1}L6 Letter to the Editor  

E-print Network

de"ned 25 nm thick Ni Fe wire arrays has been investigated using magnetoresistance (MRJournal of Magnetism and Magnetic Materials 213 (2000) L1}L6 Letter to the Editor Magnetoresistance) measurements. The structures consist of array of micron-size wires with inter-wire spacings in the range from

Adeyeye, Adekunle

296

A submillimeter VLBI array  

NASA Astrophysics Data System (ADS)

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.

Weintroub, Jonathan

2008-10-01

297

Thickness dependence of the levitation performance of double-layer high-temperature superconductor bulks above a magnetic rail  

NASA Astrophysics Data System (ADS)

A double-layer high-temperature superconductor (HTSC) arrangement was proposed and proved to be able to bring improvements to both levitation force and guidance force compared with present single-layer HTSC arrangement. To fully exploit the applied magnetic field by a magnetic rail, the thickness dependence of a double-layer HTSC arrangement on the levitation performance was further investigated in the paper. In this study, the lower-layer bulk was polished step by step to different thicknesses, and the upper-layer bulk with constant thickness was directly superimposed on the lower-layer one. The levitation force and the force relaxation of the double-layer HTSC arrangement were measured above a Halbach magnetic rail. Experimental result shows that a bigger levitation force and a less levitation force decay could be achieved by optimizing the thickness of the lower-layer bulk HTSC. This thickness optimization method could be applied together with former reported double-layer HTSC arrangement method with aligned growth sector boundaries pattern. This series of study on the optimized combination method do bring a significant improvement on the levitation performance of present HTS maglev systems.

Sun, R. X.; Zheng, J.; Liao, X. L.; Che, T.; Gou, Y. F.; He, D. B.; Deng, Z. G.

2014-10-01

298

The Geophysical Institute Magnetometer Array  

NASA Astrophysics Data System (ADS)

The Geophysical Institute Magnetometer Array (GIMA) consists of eight magnetometer stations distributed across Alaska spanning the auroral oval. Each station is equipped with a ring-core, fluxgate magnetometer, GPS clock and data logger. Data are returned from each station to the Geophysical Insitute, University of Alaska where it is verified, archived, and made available to the space science community. The GIMA web page, at http://magnet.gi.alaska.edu/, provides the data from five stations online in real-time. The GIMA web page also provides realtime data from four Russian magnetometer stations (NOK, Norilsk; PBK, Pebek; TIK, Tixie Bay; CCS, Cape Chelynskin). In addition, three other stations (operated by the USGS) in Alaska have online data available. The data set online spans the time period 1995 to the present. This presentation includes a review of the array, its capabilities (data collection parameters), the web site, and methods for acessing the data set. Interesting examples of the data will be used to illustrate the performance and capability of GIMA.

Heavner, M.

2005-12-01

299

Tunable Magnetic Properties of Heterogeneous Nanobrush: From Nanowire to Nanofilm  

PubMed Central

With a bottom-up assemble technology, heterogeneous magnetic nanobrushes, consisting of Co nanowire arrays and ferromagnetic Fe70Co30 nanofilm, have been fabricated using an anodic aluminum oxide template method combining with sputtering technology. Magnetic measurement suggests that the magnetic anisotropy of nanobrush depends on the thickness of Fe70Co30 layer, and its total anisotropy originates from the competition between the shape anisotropy of nanowire arrays and nanofilm. Micromagnetic simulation result indicates that the switching field of nanobrush is 1900 Oe, while that of nanowire array is 2700 Oe. These suggest that the nanobrush film can promote the magnetization reversal processes of nanowire arrays in nanobrush. PMID:20672098

2010-01-01

300

The Submillimeter Array  

NASA Astrophysics Data System (ADS)

The Submillimeter Array, a collaborative effort between the Smithsonian Institution and the Academia Sinica Institute of Astronomy and Astrophysics, was largely completed by November 2003, when scheduled science observations began. At that time the array consisted of eight six-meter diameter antennas equipped with receivers designed to operate in the atmospheric windows around 230, 345 and 650 GHz. During the past three years a number of improvements and upgrades have been made to the array which now performs nightly astronomical observations on a routine basis. These upgrades will be discussed as well as plans for short-term improvements.

Blundell, Raymond

301

MEMS Microshutter Arrays for James Webb Space Telescope  

NASA Technical Reports Server (NTRS)

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.

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

302

OncoArray Network  

Cancer.gov

The overall goal of the OncoArray Network is to gain new insight into the genetic architecture and mechanisms underlying breast, ovarian, prostate, colorectal, and lung cancers. The Network's major aim is to discover new cancer susceptibility variants.

303

Intelligent field emission arrays  

E-print Network

Field emission arrays (FEAs) have been studied extensively as potential electron sources for a number of vacuum microelectronic device applications. For most applications, temporal current stability and spatial current ...

Hong, Ching-yin, 1973-

2003-01-01

304

Multiplication Series: Number Arrays  

NSDL National Science Digital Library

This one-page article describes and illustrates how arrays can be used to represent many number concepts, including building multiplication facts, commutativity, parity (odd/even), and exploring factors, prime numbers, and square numbers.

305

Flexible retinal electrode array  

DOEpatents

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.

Okandan, Murat (Albuquerque, NM); Wessendorf, Kurt O. (Albuquerque, NM); Christenson, Todd R. (Albuquerque, NM)

2006-10-24

306

Protein Functionalized Nanodiamond Arrays  

NASA Astrophysics Data System (ADS)

Various nanoscale elements are currently being explored for bio-applications, such as in bio-images, bio-detection, and bio-sensors. Among them, nanodiamonds possess remarkable features such as low bio-cytotoxicity, good optical property in fluorescent and Raman spectra, and good photostability for bio-applications. In this work, we devise techniques to position functionalized nanodiamonds on self-assembled monolayer (SAMs) arrays adsorbed on silicon and ITO substrates surface using electron beam lithography techniques. The nanodiamond arrays were functionalized with lysozyme to target a certain biomolecule or protein specifically. The optical properties of the nanodiamond-protein complex arrays were characterized by a high throughput confocal microscope. The synthesized nanodiamond-lysozyme complex arrays were found to still retain their functionality in interacting with E. coli.

Liu, Y. L.; Sun, K. W.

2010-06-01

307

Lunar Surface Arrays  

NASA Astrophysics Data System (ADS)

During the latter half of the 1980's, three concepts for low frequency arrays on the Moon were independently studied for NASA, leading to two workshops in 1990. Perhaps not surprisingly, when one considers the constraints, the concepts were all quite similar. Each consisted of tens to hundreds of dipoles deployed over tens of kilometers. Each element had asuperheterodyne receiver, a digitizer, and a data transmitter and antenna mast. Each team envisioned that the array would start small and grow with time. The main technical challenges were those of deploying the array on the Moon, and of correlating the data on the Moon or returning all the raw data to Earth. We review three lunar low-frequency array concepts and note possible alternative approaches to some of the concept features.

Kuiper, T. B. H.; Jones, D.

308

For publication in the Terrestrial, Atmospheric, and Oceanic Sciences, 1999 On two methods using magnetometer-array data for studying  

E-print Network

magnetometer-array data for studying magnetic pulsations P. J. Chi and C. T. Russell Institute of Geophysics-phase spectrum, ionospheric Hall currents, geomagnetic induction. Abstract Ground magnetometer data have been arrays of magnetometer stations have been established. However, the usage of magnetometer arrays

Chi, Pi-Jen "Peter"

309

A Submillimeter VLBI Array  

NASA Astrophysics Data System (ADS)

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.

Weintroub, Jonathan; Primiani, R.; Moran, J.; Young, K.

2009-01-01

310

The Submillimeter Array  

NASA Astrophysics Data System (ADS)

The Submillimeter Array, a collaborative project of the Smithsonian Astrophysical Observatory and the Academia Sinica Institute of Astronomy and Astrophysics, has begun operation on Mauna Kea in Hawaii. The array comprises a total of eight 6 m telescopes, which will cover the frequency range of 180-900 GHz. All eight telescopes have been deployed and are operational. First scientific results utilizing the three receiver bands at 230, 345, and 690 GHz have been obtained and are presented in the accompanying Letters.

Ho, Paul T. P.; Moran, James M.; Lo, Kwok Yung

2004-11-01

311

The Clark Lake array.  

NASA Technical Reports Server (NTRS)

A fully steerable array of 720 conical log spiral antennas nearing completion in southern California is described. It is capable of operation at any frequency between 15 and 130 MHz an instantaneous bandwidth of 3 MHz. The array is a pencil-beam instrument with a beam width proportional to the wavelength; it varies from 3 to 27 feet across the frequency range. It will soon be available for both solar and sidereal studies.

Erickson, W. C.

1973-01-01

312

Carbon nanotube array actuators  

NASA Astrophysics Data System (ADS)

Experimental investigations of highly vertically aligned carbon nanotubes (CNTs), also known as CNT-arrays, are the main focus of this paper. The free strain as result of an active material behavior is analyzed via a novel experimental setup. Previous test experiences of papers made of randomly oriented CNTs, also called Bucky-papers, reveal comparably low free strain. The anisotropy of aligned CNTs promises better performance. Via synthesis techniques like chemical vapor deposition (CVD) or plasma enhanced CVD (PECVD), highly aligned arrays of multi-walled carbon nanotubes (MWCNTs) are synthesized. Two different types of CNT-arrays are analyzed, morphologically first, and optically tested for their active characteristics afterwards. One type of the analyzed arrays features tube lengths of 750-2000 ?m with a large variety of diameters between 20 and 50 nm and a wave-like CNT-shape. The second type features a maximum, almost uniform, length of 12 ?m and a constant diameter of 50 nm. Different CNT-lengths and array types are tested due to their active behavior. As result of the presented tests, it is reported that the quality of orientation is the most decisive property for excellent active behavior. Due to their alignment, CNT-arrays feature the opportunity to clarify the actuation mechanism of architectures made of CNTs.

Geier, S.; Mahrholz, T.; Wierach, P.; Sinapius, M.

2013-09-01

313

Development of optical-based array devices using imaging fiber bundles: Optical tweezer arrays, nanoscale arrays, and microelectrode arrays  

Microsoft Academic Search

The work in this dissertation describes the development of imaging fiber-based array devices, specifically the fabrication and application of an optical tweezer array, a fiber-based nanoarray, and a nanotip array. With regards for the fabrication of an optical tweezer array, this thesis describes how fiber bundles have been used as a method to create multiple beams, which are used as

Jenny M. Tam

2005-01-01

314

Fabrication and characterization of nanostructured magnetic particles for applications in data storage  

E-print Network

Arrays of nanostructured magnetic particles ('nanomagnets') have potential applications in ultra-high-density data storage devices and dynamic magnetic memories, and are model systems for the study of magnetic phenomena ...

Farhoud, Maya S. (Maya Sami)

2001-01-01

315

Incipient magnetic rotation? A magnetic dipole band in 104Cd  

E-print Network

High spin states of the nucleus 104Cd have been studied using the Gammapshere array. The level scheme for 104Cd has been revised and evidence for a structure consisting of magnetic dipole transitions is presented. Shell model calculations, published previously, are invoked to support an interpretation of this structure as an incpient case of magnetic rotation where the transversal magnetic dipole moment is not strong enough to break the signature symmetry.

D. G. Jenkins; R. Wadsworth; J. A. Cameron; M. P. Carpenter; C. J. Chiara; R. M. Clark M. Devlin; P. Fallon; D. B. Fossan; I. M. Hibbert; R. V. F. Janssens; V. P. Janzen; R. Kruecken; D. R. LaFosse; G. J. Lane; T. Lauritsen; I. Y. Lee; A. O. Macchiavelli; C. M. Parry; D. G. Sarsantities; J. M. Sears; D. Seweryniak; J. F. Smith; K. Starosta; D. Ward; I. Wiedenhoever; A. N. Wilson; J. N. Wilson; S. Frauendorf

2000-07-05

316

Stability of discrete breathers in magnetic metamaterials  

E-print Network

Stability of discrete breathers in magnetic metamaterials Dmitry Pelinovsky1 and Vassilis Rothos2 1 describing magnetic metamaterials which consist of periodic arrays of split- ring resonators [4, 7]: ¨qn + V criterion to the multi-site breathers in magnetic metamaterials. 2 Formalism In what follows, we shall use

Pelinovsky, Dmitry

317

Composite arrays of superconducting microstrip line resonators  

SciTech Connect

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.

Mohebbi, H. R., E-mail: hmohebbi@uwaterloo.ca; Miao, G. X. [Institute for Quantum Computing, Waterloo, Ontario N2L 3G1 (Canada); Department of Electrical and Computer Engineering, University of Waterloo, Waterloo, Ontario N2L 3G1 (Canada); Benningshof, O. W. B. [Institute for Quantum Computing, Waterloo, Ontario N2L 3G1 (Canada); Department of Physics, University of Waterloo, Waterloo, Ontario N2L 3G1 (Canada); Taminiau, I. A. J. [Institute for Quantum Computing, Waterloo, Ontario N2L 3G1 (Canada); Cory, D. G. [Institute for Quantum Computing, Waterloo, Ontario N2L 3G1 (Canada); Perimeter Institute for Theoretical Physics, Waterloo, Ontario N2L 2Y5 (Canada); Department of Chemistry, University of Waterloo, Waterloo, Ontario N2L 3G1 (Canada)

2014-03-07

318

Solar array flight experiment  

NASA Technical Reports Server (NTRS)

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.

1986-01-01

319

Microbial Cell Arrays  

NASA Astrophysics Data System (ADS)

The coming of age of whole-cell biosensors, combined with the continuing advances in array technologies, has prepared the ground for the next step in the evolution of both disciplines - the whole cell array. In the present chapter, we highlight the state-of-the-art in the different disciplines essential for a functional bacterial array. These include the genetic engineering of the biological components, their immobilization in different polymers, technologies for live cell deposition and patterning on different types of solid surfaces, and cellular viability maintenance. Also reviewed are the types of signals emitted by the reporter cell arrays, some of the transduction methodologies for reading these signals, and the mathematical approaches proposed for their analysis. Finally, we review some of the potential applications for bacterial cell arrays, and list the future needs for their maturation: a richer arsenal of high-performance reporter strains, better methodologies for their incorporation into hardware platforms, design of appropriate detection circuits, the continuing development of dedicated algorithms for multiplex signal analysis, and - most importantly - enhanced long term maintenance of viability and activity on the fabricated biochips.

Elad, Tal; Lee, Jin Hyung; Gu, Man Bock; Belkin, Shimshon

320

GMR Biosensor Arrays: A System Perspective  

PubMed Central

Giant magnetoresistive biosensors are becoming more prevalent for sensitive, quantifiable biomolecular detection. However, in order for magnetic biosensing to become competitive with current optical protein microarray technology, there is a need to increase the number of sensors while maintaining the high sensitivity and fast readout time characteristic of smaller arrays (1 – 8 sensors). In this paper, we present a circuit architecture scalable for larger sensor arrays (64 individually addressable sensors) while maintaining a high readout rate (scanning the entire array in less than 4 seconds). The system utilizes both time domain multiplexing and frequency domain multiplexing in order to achieve this scan rate. For the implementation, we propose a new circuit architecture that does not use a classical Wheatstone bridge to measure the small change in resistance of the sensor. Instead, an architecture designed around a transimpedance amplifier is employed. A detailed analysis of this architecture including the noise, distortion, and potential sources of errors is presented, followed by a global optimization strategy for the entire system comprising the magnetic tags, sensors, and interface electronics. To demonstrate the sensitivity, quantifiable detection of two blindly spiked samples of unknown concentrations has been performed at concentrations below the limit of detection for the enzyme-linked immunosorbent assay. Lastly, the multipexability and reproducibility of the system was demonstrated by simultaneously monitoring sensors functionalized with three unique proteins at different concentrations in real-time. PMID:20207130

Hall, D. A.; Gaster, R. S.; Lin, T.; Osterfeld, S. J.; Han, S.; Murmann, B.; Wang, S. X.

2010-01-01

321

GMR biosensor arrays: a system perspective.  

PubMed

Giant magnetoresistive biosensors are becoming more prevalent for sensitive, quantifiable biomolecular detection. However, in order for magnetic biosensing to become competitive with current optical protein microarray technology, there is a need to increase the number of sensors while maintaining the high sensitivity and fast readout time characteristic of smaller arrays (1-8 sensors). In this paper, we present a circuit architecture scalable for larger sensor arrays (64 individually addressable sensors) while maintaining a high readout rate (scanning the entire array in less than 4s). The system utilizes both time domain multiplexing and frequency domain multiplexing in order to achieve this scan rate. For the implementation, we propose a new circuit architecture that does not use a classical Wheatstone bridge to measure the small change in resistance of the sensor. Instead, an architecture designed around a transimpedance amplifier is employed. A detailed analysis of this architecture including the noise, distortion, and potential sources of errors is presented, followed by a global optimization strategy for the entire system comprising the magnetic tags, sensors, and interface electronics. To demonstrate the sensitivity, quantifiable detection of two blindly spiked samples of unknown concentrations has been performed at concentrations below the limit of detection for the enzyme-linked immunosorbent assay. Lastly, the multiplexing capability and reproducibility of the system was demonstrated by simultaneously monitoring sensors functionalized with three unique proteins at different concentrations in real-time. PMID:20207130

Hall, D A; Gaster, R S; Lin, T; Osterfeld, S J; Han, S; Murmann, B; Wang, S X

2010-05-15

322

The Square Kilometre Array pulsar timing array  

NASA Astrophysics Data System (ADS)

The Square Kilometre Array (SKA) is envisioned as the meter- and centimeter-wavelength telescope of the 21st century, and gravitational wave studies via a pulsar timing array (PTA) form a key aspect of its science program. In its ultimate implementation, the SKA (phase 2) should enable the construction of a PTA consisting of as many as 100 spin-stable millisecond pulsars. The sensitivity of the SKA-PTA could approach gravitational wave strain amplitudes of 6 × 10-16 or better at fiducial gravitational wave frequencies of order 1 yr-1, at least an order of magnitude improvement in the gravitational wave strain amplitude that can be measured. Any nearby individual supermassive black hole binaries could be detected, and the existence of non-tensor modes can be tested. Beyond its PTA capabilities, the SKA will also enable a range of other tests of fundamental physics, such as tests of gravity in ultra-relativistic binaries and constraints on the nuclear equation of state.

Lazio, T. J. W.

2013-11-01

323

Status of The General Atomics Low Speed Urban Maglev Technology Development Program  

SciTech Connect

This paper presents the status of General Atomics Urban Maglev Program. The development provides an innovative approach for low speed transportation suitable for very challenging urban environments. Permanent magnets arranged in a 'Halbach' array configuration produce a relatively stiff magnetic suspension operating with an air gap of 25 mm. The project has progressed from design and prototype hardware testing, to the construction of a 120-meter full-scale test track, located in San Diego, California. Dynamic testing of the levitation, propulsion and guidance systems is being performed.

Gurol, S; Baldi, R; Bever, D; Post, R

2004-06-16

324

Electrostatically clean solar array  

NASA Technical Reports Server (NTRS)

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.

Stern, Theodore Garry (Inventor); Krumweide, Duane Eric (Inventor)

2004-01-01

325

Red microchip VECSEL array.  

PubMed

We report an InGaP/AlInGaP/GaAs microchip vertical-external-cavity surface emitting laser operating directly at red wavelengths and demonstrate its potential for array-format operation. Optical pumping with up to 3.3W at 532nm produced a maximum output power of 330mW at 675nm, in a single circularly-symmetric beam with M2<2. Simultaneous pumping with three separate input beams, generated using a diffractive optical element, achieved lasing from three discrete areas of the same chip. Output power of ~95mW per beam was obtained from this 3x1 array, each beam having a Gaussian intensity profile with M2<1.2. In a further development, a spatial light modulator allowed computer control over the orientation and separation of the pump beams, and hence dynamic control over the configuration of the VECSEL array. PMID:19498743

Hastie, Jennifer; Morton, Lynne; Calvez, Stephane; Dawson, Martin; Leinonen, Tomi; Pessa, Markus; Gibson, Graham; Padgett, Miles

2005-09-01

326

Status of UCLA Helical Permanent-Magnet Inverse Free Electron Laser  

SciTech Connect

A helical undulator, utilizing permanent-magnet of cylindrically symmetric (Halbach) geometry is being developed at UCLA's Neptune Facility. The initial prototype is a short 10 cm, 7 periods long helical undulator, designed to test the electron-photon coupling by observing the micro-bunching is currently being constructed. The Neptune IFEL facility utilizes a 15 MeV Photoinjector-generated electron beam of 0.5 nC interacting with CO{sub 2} of peak energy up to 100 J, estimated to have acceleration of 100 MeV/m. An Open Iris-Loaded Waveguide Structure (OILS) scheme which conserves laser mode size and wave fronts throughout the undulator, is utilized to avoid Gouy phase shift caused by focusing of the drive laser. Undulator design was tested by computer simulations Radia and Genesis 1.3. Coherent Transition Radiation and Coherent Cherenkov Radiation will be used for micro-bunching diagnostic. Currently permanent dipoles and their aluminum holders have been built, and the project is in its final state of assembly and undulator testing.

Knyazik, A.; Tikhoplav, R.; Frederico, J. T.; Affolter, M.; Rosenzweig, J. B. [Department of Physics and Astronomy, UCLA, Los Angeles, California 90095 (United States)

2009-01-22

327

Array signal processing  

SciTech Connect

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.

Haykin, S.; Justice, J.H.; Owsley, N.L.; Yen, J.L.; Kak, A.C.

1985-01-01

328

Cherenkov Telescope Array Sensitivity  

NASA Astrophysics Data System (ADS)

The Cherenkov Telescope Array (CTA) will provide unprecedented capabilities in the gamma-ray regime, from a few tens of GeV up to at least 100 TeV. The goal of CTA is to improve the sensitivity over the whole energy range covered by current ground-based telescopes by a factor of between 5 and 10, depending on the energy, to extend the range of energies observed, with significantly improved energy and angular resolution over previous instruments. Plans for the layout of the array and the estimated sensitivity, derived from Monte Carlo, will be presented.

Humensky, Brian; Grube, Jeff

2014-08-01

329

Wire Array Photovoltaics  

NASA Astrophysics Data System (ADS)

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.

Turner-Evans, Dan

330

Solar array subsystems study  

NASA Technical Reports Server (NTRS)

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.

Richardson, P. W.; Miller, F. Q.; Badgley, M. B.

1980-01-01

331

Magnetostatic interaction in FeCo nanowire arrays  

NASA Astrophysics Data System (ADS)

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.

Jia, Yijiao; Wang, Huanwen; Gao, Youhui; Chen, Peigeng; Lu, Jiadao; Han, Gang

2015-01-01

332

Flux avalanches in superconducting films with periodic arrays of holes.  

SciTech Connect

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.

Vlasko-Vlasov, V.; Welp, U.; Metlushko, V.; Crabtree, G. W.; Materials Science Division; Inst. of Solid State Physics RAS

2000-01-01

333

Spectrally narrowed external-cavity high-power stack of laser diode arrays  

PubMed Central

We describe an effective external cavity for narrowing the spectral linewidth of a multiarray stack of laser diode arrays. For a commercially available 279-W free-running five-array laser diode array operating at 60 A, we narrow the spectral linewidth to 0.40 nm at FWHM with 115 W of cw power output. This technique leads to the possibility of higher-efficiency, lower-cost production of hyperpolarized noble gases for magnetic resonance imaging. PMID:15981527

Zhu, H.; Ruset, I. C.; Hersman, F. W.

2005-01-01

334

Ferromagnetic resonance response of electron-beam patterned arrays of ferromagnetic nanoparticles  

NASA Astrophysics Data System (ADS)

We report on the fabrication and the dynamic magnetic properties of periodic permalloy dot arrays. Electron-beam lithography and e-gun evaporation have been used to make the arrays with the aspect ratio of 2 (dot diameter : 40 nm, height : 80 nm) and periods of 100 - 200 nm. The magnetic properties of the arrays and their interactions have been investigated by ferromagnetic resonance (FMR), magnetic force microscopy (MFM), and SQUID magnetometry. The measured FMR data show that the position and magnitude of resonant absorption peaks strongly depend on the angle between magnetic field and the lattice structure. The results of dot arrays with various kinds of structural parameters will be presented. Supported by Army Research Office, DAAD19-99-1-0334/P001

Jung, Sukkoo; Watkins, Byron; Feller, Jeffrey; Ketterson, John; Chandrasekhar, Venkat

2001-03-01

335

Wave modes of collective vortex gyration in dipolar-coupled-dot-array magnonic crystals  

PubMed Central

Lattice vibration modes are collective excitations in periodic arrays of atoms or molecules. These modes determine novel transport properties in solid crystals. Analogously, in periodical arrangements of magnetic vortex-state disks, collective vortex motions have been predicted. Here, we experimentally observe wave modes of collective vortex gyration in one-dimensional (1D) periodic arrays of magnetic disks using time-resolved scanning transmission x-ray microscopy. The observed modes are interpreted based on micromagnetic simulation and numerical calculation of coupled Thiele equations. Dispersion of the modes is found to be strongly affected by both vortex polarization and chirality ordering, as revealed by the explicit analytical form of 1D infinite arrays. A thorough understanding thereof is fundamental both for lattice vibrations and vortex dynamics, which we demonstrate for 1D magnonic crystals. Such magnetic disk arrays with vortex-state ordering, referred to as magnetic metastructure, offer potential implementation into information processing devices. PMID:23877284

Han, Dong-Soo; Vogel, Andreas; Jung, Hyunsung; Lee, Ki-Suk; Weigand, Markus; Stoll, Hermann; Schütz, Gisela; Fischer, Peter; Meier, Guido; Kim, Sang-Koog

2013-01-01

336

Automated inspection of surface breaking cracks using GMR sensor arrays  

SciTech Connect

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.

Pelkner, Matthias; Reimund, Verena; Erthner, Thomas; Panke, Nicolai; Kreutzbruck, Marc [BAM Federal Institute for Material Research and Testing, Unter den Eichen 87, 12205 Berlin (Germany)

2014-02-18

337

The breakdown of the fingerprinting of vortices by hysteresis loops in circular multilayer ring arrays  

E-print Network

arrays V. Rose,a X. M. Cheng, D. J. Keavney, and J. W. Freeland Advanced Photon Source, Argonne National magnetoresistive effect and takes ad- vantage of magnetic vortex states with controlled chirality within each FM characteristics. However, recent investigations of NiFe/Cu/Co dot arrays show that vortex formation in mul

Metlushko, Vitali

338

Brillouin scattering and diffracted magneto-optical Kerr effect from arrays of dots and antidots (invited)  

NASA Astrophysics Data System (ADS)

The magnetic properties of nanoarrays have been investigated using Brillouin scattering, magneto-optical Kerr effect (MOKE) and diffracted-MOKE (DMOKE) techniques. The anisotropies in negative arrays are found to be due to the shape of the holes and not due to the array itself. The DMOKE results allow us to extract the domain pattern at remanence.

Grimsditch, M.; Guedes, I.; Vavassori, P.; Metlushko, V.; Ilic, B.; Neuzil, P.; Kumar, R.

2001-06-01

339

64-Elements intraluminal ultrasound cylindrical phased array for transesophageal thermal ablation under fast MR temperature mapping  

E-print Network

thermal ablation under fast MR temperature mapping: An ex vivo study. Melodelima D.1 , Salomir R.1 the feasibility of using a cylindrical phased array for transoesophaeal thermal ablation under Magnetic Resonance the feasibility of thermal ablation using a phased array intraluminal ultrasound applicator and on line MR

Paris-Sud XI, Université de

340

Design of Linear Array Geometry for High Resolution Array Processing  

Microsoft Academic Search

The linear array is one of the most important types of multi-element sensor arrays, being extensively used in radar, sonar, telecommunications, radio astronomy and medical imaging systems. Traditionally, the array assumes uniform geometry with an inter-sensor spacing of ?\\/2, which limits resolvability because of the fixed aperture. Since the 1950's, much work has been done on designing nonuniform arrays with

Xinping Huang

1993-01-01

341

Analysis de arrays Introduction  

E-print Network

: involved in various diseases HIV acquisition and progression, Parkinson, Alzheimer, autoimmune diseases popul.): 1447 regions with CNV; 43% in more than one indiv.; at least 12 % of genome affected. High number changes and disease (From J. Fridlyand, "Introduction to Array CGH", 2004) (5 : 151) #12;Analysis

Díaz-Uriarte, Ramón

342

Cherenkov Telescope Array (CTA)  

NASA Astrophysics Data System (ADS)

Gamma-ray astronomy has a huge potential in astrophysics, particle physics and cosmology. CTA is an international initiative to build the next generation ground-based gamma-ray observatory. CTA will consist of two arrays for full sky coverage and will be operated as an open observatory. It will provide a deep insight into the high-energy universe.

Barres de Almeida, U.; de Gouveia Dal Pino, E. M.

2014-10-01

343

Array processors in chemistry  

SciTech Connect

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.

Ostlund, N.S.

1980-01-01

344

Basic Photovoltaic Array Sizing  

NSDL National Science Digital Library

This learning activity from the Advanced Technology Environmental and Energy Center (ATEEC) allows students to conduct a photovoltaic array sizing assessment. Users must download this resource for viewing, which requires a free log-in. There is no cost to download the item.

345

TRMM Solar Array Panels  

NASA Technical Reports Server (NTRS)

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.

1998-01-01

346

Arrays for space applications  

NASA Technical Reports Server (NTRS)

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.

Schuman, Harvey K.; Antonik, Paul; Malagisi, Carmen

1989-01-01

347

The Askaryan Radio Array  

NASA Astrophysics Data System (ADS)

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.

Hoffman, Kara D.

2013-01-01

348

Pulsar timing array  

NASA Astrophysics Data System (ADS)

Simultaneous timing of several pulsars distributed over the sky, so called Pulsar Timing Array (PTA), is used for a variety of metrological and astronomical applications. Three examples of PTA application are presented: link between celestial reference frames, ensemble pulsar time scale and detection of gravitational waves.

Rodin, Alexander E.

2010-11-01

349

Permanent Magnet Ecr Plasma Source With Magnetic Field Optimization  

DOEpatents

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.

Doughty, Frank C. (Plano, TX); Spencer, John E. (Plano, TX)

2000-12-19

350

Suspension array technology: evolution of the flat-array paradigm  

Microsoft Academic Search

Suspension arrays of microspheres analyzed using flow cytometry offer a new approach to multiplexed assays for large-scale screening applications. By optically encoding micron-sized polymer particles, suspension microarrays can be created to enable highly multiplexed analysis of complex samples. Each element in the array is comprised of a subpopulation of particles with distinct optical properties and each array element bears a

John P. Nolan; Larry A. Sklar

2002-01-01

351

Mutual coupling effects in antenna arrays, volume 1  

NASA Technical Reports Server (NTRS)

Mutual coupling between rectangular apertures in a finite antenna array, in an infinite ground plane, is analyzed using the vector potential approach. The method of moments is used to solve the equations that result from setting the tangential magnetic fields across each aperture equal. The approximation uses a set of vector potential model functions to solve for equivalent magnetic currents. A computer program was written to carry out this analysis and the resulting currents were used to determine the co- and cross-polarized far zone radiation patterns. Numerical results for various arrays using several modes in the approximation are presented. Results for one and two aperture arrays are compared against published data to check on the agreement of this model with previous work. Computer derived results are also compared against experimental results to test the accuracy of the model. These tests of the accuracy of the program showed that it yields valid data.

Collin, R. E.

1986-01-01

352

Large scale two-dimensional arrays of magnesium diboride superconducting quantum interference devices  

SciTech Connect

Magnetic field sensors based on two-dimensional arrays of superconducting quantum interference devices were constructed from magnesium diboride thin films. Each array contained over 30?000 Josephson junctions fabricated by ion damage of 30?nm weak links through an implant mask defined by nano-lithography. Current-biased devices exhibited very large voltage modulation as a function of magnetic field, with amplitudes as high as 8?mV.

Cybart, Shane A., E-mail: scybart@ucsd.edu; Dynes, R. C. [Department of Physics, University of California San Diego, La Jolla, California 92093 (United States); Materials Sciences Division, Lawrence Berkeley National Laboratory, Berkeley, California 94720 (United States); Wong, T. J.; Cho, E. Y. [Department of Physics, University of California San Diego, La Jolla, California 92093 (United States); Beeman, J. W. [Materials Sciences Division, Lawrence Berkeley National Laboratory, Berkeley, California 94720 (United States); Yung, C. S.; Moeckly, B. H. [Superconductor Technologies Inc., Santa Barbara, California 93111 (United States)

2014-05-05

353

Plasma-wave coupling and propagation using phased waveguide arrays  

Microsoft Academic Search

A study of the coupling and propagation of electron plasma waves excited by waveguide arrays is presented. The waves are generated in a low-temperature linear plasma column in a homogeneous magnetic field. As predicted from a theoretical model, efficient coupling to plasma waves can be obtained under appropriate conditions. These studies are of relevance to plasma heating in that the

S. Bernabel; W. M. Hooke; R. W. Motley; F. J. Paoloni; M. A. Heald; M. Brambilla

1977-01-01

354

Finite Element Analysis of Complex Antennas and Arrays  

Microsoft Academic Search

Various technical issues are addressed in the frequency- and time-domain finite element analysis of complex antennas and arrays that may consist of fine structures and composite materials. The paper starts with the finite element formulation of a generic antenna problem. Formulation for the modeling of general electrically and magnetically dispersive, lossy, and anisotropic materials in the time-domain finite element analysis

Jian-Ming Jin; Zheng Lou; Yu-Jia Li; Norma W. Riley; Douglas J. Riley

2008-01-01

355

Application of field emitter arrays to microwave power amplifiers  

Microsoft Academic Search

This paper describes the operation of a field emitter array (FEA) as the electron source of a traveling-wave tube (TWT) amplifier. Issues of beam control and focus at high current density and low magnetic field are addressed as well as issues relating to the inherent high emittance of the FEA beam and cathode protection from ion bombardment. Large signal, nonlinear

David R. Whaley; Bartley M. Gannon; Carl R. Smith; Carter M. Armstrong; Capp A. Spindt

2000-01-01

356

Supporting dynamic parallel object arrays  

Microsoft Academic Search

ABSTRACT We present efficient support for generalized arrays of parallel data driven objects. Array elements are regular C++ objects, and are scattered across the parallel machine. An individual element is addressed by its \\

Orion Sky Lawlor; Laxmikant V. Kalé

2003-01-01

357

Shielded Microstrip Array for 7T Human MR Imaging  

PubMed Central

The high-frequency transceiver array based on the microstrip transmission line design is a promising technique for ultrahigh field magnetic resonance imaging (MRI) signal excitation and reception. However, with the increase of radio-frequency (RF) channels, the size of the ground plane in each microstrip coil element is usually not sufficient to provide a perfect ground. Consequently, the transceiver array may suffer from cable resonance, lower Q-factors, and imaging quality degradations. In this paper, we present an approach to improving the performance of microstrip transceiver arrays by introducing RF shielding outside the microstrip array and the feeding coaxial cables. This improvement reduced interactions among cables, increased resonance stability, and Q-factors, and thus improved imaging quality. An experimental method was also introduced and utilized for quantitative measurement and evaluation of RF coil resonance stability or “cable resonance” behavior. PMID:19822470

Wu, Bing; Wang, Chunsheng; Kelley, Douglas A. C.; Xu, Duan; Vigneron, Daniel B.; Nelson, Sarah J.

2010-01-01

358

Spatially resolved single photon detection with a quantum sensor array  

PubMed Central

We propose a method of resolving a spatially coherent signal, which contains on average just a single photon, against the background of local noise at the same frequency. The method is based on detecting the signal simultaneously in several points more than a wavelength apart through the entangling interaction of the incoming photon with the quantum metamaterial sensor array. The interaction produces the spatially correlated quantum state of the sensor array, characterised by a collective observable (e.g., total magnetic moment), which is read out using a quantum nondemolition measurement. We show that the effects of local noise (e.g., fluctuations affecting the elements of the array) are suppressed relative to the signal from the spatially coherent field of the incoming photon as , where N is the number of array elements. The realisation of this approach in the microwave range would be especially useful and is within the reach of current experimental techniques. PMID:24322568

Zagoskin, A. M.; Wilson, R. D.; Everitt, M.; Savel'ev, S.; Gulevich, D. R.; Allen, J.; Dubrovich, V. K.; Il'ichev, E.

2013-01-01

359

Angle sensing with ferromagnetic nanowire arrays  

NASA Astrophysics Data System (ADS)

Hysteresis loops and Ferromagnetic Resonance (FMR) linewidths of Nickel ferromagnetic nanowire arrays are measured versus angle ?H between the applied magnetic field angle and the common nanowire axis. Using Preisach analysis, we extract from the hysteresis loop an interaction parameter ?i that strongly depends on ?H. Extending the analysis to FMR lineshapes, we deduce a strong dependence of the FMR field linewidth ?H on ?H through the interaction parameter ?i. Existence of a link between static (hysteresis) and dynamic (FMR) cases through ?H might be exploited in contactless absolute angle sensing devices that could compete with inductive, Hall, and magnetoresistive devices.

Tannous, C.; Gieraltowski, J.

2014-01-01

360

Flexible Transceiver Array for Ultrahigh Field Human MR Imaging  

PubMed Central

A flexible transceiver array, capable of multiple-purpose imaging applications in vivo at ultrahigh magnetic fields was designed, implemented and tested on a 7 T MR scanner. By alternately placing coil elements with primary and secondary harmonics, improved decoupling among coil elements was accomplished without requiring decoupling circuitry between resonant elements, which is commonly required in high frequency transceiver arrays in order to achieve sufficient element-isolation during RF excitation. This flexible array design is capable of maintaining the required decoupling among resonant elements in different array size and geometry, and is scalable in coil size and number of resonant elements (i.e. number of channels), yielding improved filling factors for various body parts with different geometry and size. To investigate design feasibility, flexibility, and array performance, a multi-channel, 16-element transceiver array was designed and constructed, and in vivo images of the human head, knee, and hand were acquired using a whole-body 7T MR system. 7T parallel imaging with GRAPPA performed using this flexible transceiver array was also presented. PMID:22246803

Wu, Bing; Zhang, Xiaoliang; Wang, Chunsheng; Li, Ye; Pang, Yong; Lu, Jonathan; Xu, Duan; Majumdar, Sharmila; Nelson, Sarah J.; Vigneron, Daniel B.

2012-01-01

361

Supporting dynamic parallel object arrays  

Microsoft Academic Search

We present efficient support for generalized arrays of parallel data driven objects. The “array elements” are scattered across a parallel machine. Each array element is an object that can be thought of as a virtual processor. The individual elements are addressed by their “index”, which can be an arbitrary object rather than a simple integer. For example, it can be

Orion Sky Lawlor; Laxmikant V. Kalé

2001-01-01

362

caArray - Experiment Details  

Cancer.gov

Skip to Page Content Build 2.5.3_RC1 | Node: NCICB Welcome to caArray Browse Login Register About caArray What is caArray? Release Notes User Guide Global Quick Links National Cancer Institute (NCI) NCI Center for Biomedical Informatics and Information

363

Thinned arrays using genetic algorithms  

Microsoft Academic Search

Large arrays are difficult to thin in order to obtain low sidelobes. Traditional statistical methods of aperiodic array synthesis fall far short of optimum configurations. Traditional optimization methods are not well suited for optimizing a large number of parameters or discrete parameters. This paper presents how to optimally thin an array using genetic algorithms. The genetic algorithm determines which elements

Randy L. Haupt

1994-01-01

364

Reflective array SAW narrowband filters  

Microsoft Academic Search

Experimental results are presented for a reflective-array SAW (surface acoustic wave) device that is optimized for narrowband filter applications. The filter consists of broadband input and output transducers with two weighted reflector arrays. Previous devices of this type have used reflective dot density and depth profile weighting for the reflective arrays. A unique implementation of this design technique for a

S. Gopani; R. B. Brown; J. H. Hines; B. H. Horine

1990-01-01

365

Tutorial: Performance and reliability in redundant disk arrays  

NASA Technical Reports Server (NTRS)

A disk array is a collection of physically small magnetic disks that is packaged as a single unit but operates in parallel. Disk arrays capitalize on the availability of small-diameter disks from a price-competitive market to provide the cost, volume, and capacity of current disk systems but many times their performance. Unfortunately, relative to current disk systems, the larger number of components in disk arrays leads to higher rates of failure. To tolerate failures, redundant disk arrays devote a fraction of their capacity to an encoding of their information. This redundant information enables the contents of a failed disk to be recovered from the contents of non-failed disks. The simplest and least expensive encoding for this redundancy, known as N+1 parity is highlighted. In addition to compensating for the higher failure rates of disk arrays, redundancy allows highly reliable secondary storage systems to be built much more cost-effectively than is now achieved in conventional duplicated disks. Disk arrays that combine redundancy with the parallelism of many small-diameter disks are often called Redundant Arrays of Inexpensive Disks (RAID). This combination promises improvements to both the performance and the reliability of secondary storage. For example, IBM's premier disk product, the IBM 3390, is compared to a redundant disk array constructed of 84 IBM 0661 3 1/2-inch disks. The redundant disk array has comparable or superior values for each of the metrics given and appears likely to cost less. In the first section of this tutorial, I explain how disk arrays exploit the emergence of high performance, small magnetic disks to provide cost-effective disk parallelism that combats the access and transfer gap problems. The flexibility of disk-array configurations benefits manufacturer and consumer alike. In contrast, I describe in this tutorial's second half how parallelism, achieved through increasing numbers of components, causes overall failure rates to rise. Redundant disk arrays overcome this threat to data reliability by ensuring that data remains available during and after component failures.

Gibson, Garth A.

1993-01-01

366

Spatial Determination of Magnetic Avalanche Ignition points  

Microsoft Academic Search

Using time-resolved measurements of local magnetization [1], we report studies of the propagation of magnetic avalanches (fast magnetization reversals) in Mn12-ac crystals triggered stochastically in response to a time-varying (swept) magnetic field. The spherical nature of the fronts produced by avalanches originating within the bulk is reflected in the time-of-arrival at an array of micro-Hall sensors placed on the surface

Reem Jaafar; S. McHugh; Yoko Suzuki; M. P. Sarachik; Y. Myasoedov; H. Shtrikman; E. Zeldov; R. Bagai; G. Christou

2007-01-01

367

Optically interconnected phased arrays  

NASA Technical Reports Server (NTRS)

Phased-array antennas are required for many future NASA missions. They will provide agile electronic beam forming for communications and tracking in the range of 1 to 100 GHz. Such phased arrays are expected to use several hundred GaAs monolithic integrated circuits (MMICs) as transmitting and receiving elements. However, the interconnections of these elements by conventional coaxial cables and waveguides add weight, reduce flexibility, and increase electrical interference. Alternative interconnections based on optical fibers, optical processing, and holography are under evaluation as possible solutions. In this paper, the current status of these techniques is described. Since high-frequency optical components such as photodetectors, lasers, and modulators are key elements in these interconnections, their performance and limitations are discussed.

Bhasin, Kul B.; Kunath, Richard R.

1988-01-01

368

Solid state neutron detector array  

DOEpatents

A neutron detector array is capable of measuring a wide range of neutron fluxes. The array includes multiple semiconductor neutron detectors. Each detector has a semiconductor active region that is resistant to radiation damage. In one embodiment, the array preferably has a relatively small size, making it possible to place the array in confined locations. The ability of the array to detect a wide range of neutron fluxes is highly advantageous for many applications such as detecting neutron flux during start up, ramp up and full power of nuclear reactors. 7 figs.

Seidel, J.G.; Ruddy, F.H.; Brandt, C.D.; Dulloo, A.R.; Lott, R.G.; Sirianni, E.; Wilson, R.O.

1999-08-17

369

Solid state neutron detector array  

DOEpatents

A neutron detector array is capable of measuring a wide range of neutron fluxes. The array includes multiple semiconductor neutron detectors. Each detector has a semiconductor active region that is resistant to radiation damage. In one embodiment, the array preferably has a relatively small size, making it possible to place the array in confined locations. The ability of the array to detect a wide range of neutron fluxes is highly advantageous for many applications such as detecting neutron flux during start up, ramp up and full power of nuclear reactors.

Seidel, John G. (Pittsburgh, PA); Ruddy, Frank H. (Monroeville, PA); Brandt, Charles D. (Mount Lebanon, PA); Dulloo, Abdul R. (Pittsburgh, PA); Lott, Randy G. (Pittsburgh, PA); Sirianni, Ernest (Monroeville, PA); Wilson, Randall O. (Greensburg, PA)

1999-01-01

370

The CHARA optical array  

NASA Astrophysics Data System (ADS)

The Center for High Angular Resolution Astronomy (CHARA) was established in the College of Arts and Sciences at Georgia State University in 1984 with the goals of designing, constructing, and then operating a facility for very high spatial resolution astronomy. The interest in such a facility grew out of the participants' decade of activity in speckle interferometry. Although speckle interferometry continues to provide important astrophysical measurements of a variety of objects, many pressing problems require resolution far beyond that which can be expected from single aperture telescopes. In early 1986, CHARA received a grant from the National Science Foundation which has permitted a detailed exploration of the feasibility of constructing a facility which will provide a hundred-fold increase in angular resolution over what is possible by speckle interferometry at the largest existing telescopes. The design concept for the CHARA Array was developed initially with the contractural collaboration of United Technologies Optical Systems, Inc., in West Palm Beach, Florida, an arrangement that expired in August 1987. In late November 1987, the Georgia Tech Research Institute joined with CHARA to continue and complete the design concept study. Very high-resolution imaging at optical wavelengths is clearly coming of age in astronomy. The CHARA Array and other related projects will be important and necessary milestones along the way toward the development of a major national facility for high-resolution imaging--a true optical counterpart to the Very Large Array. Ground-based arrays and their scientific output will lead to high resolution facilities in space and, ultimately, on the Moon.

McAlister, Harold A.

1992-11-01

371

Vertical comb array microactuators  

Microsoft Academic Search

A vertical actuator fabricated using a trench-refilled-with-polysilicon (TRiPs) process technology and employing an array of vertical oriented comb electrodes is presented. This actuator structure provides a linear drive to deflection characteristic and a large throw capability which are key features in many sensors, actuators and micromechanisms. The actuation principle and relevant theory is developed, including FastCap simulations for theoretical verification.

Arjun Selvakumar; Khalil Najafi

2003-01-01

372

The CHARA optical array  

NASA Technical Reports Server (NTRS)

The Center for High Angular Resolution Astronomy (CHARA) was established in the College of Arts and Sciences at Georgia State University in 1984 with the goals of designing, constructing, and then operating a facility for very high spatial resolution astronomy. The interest in such a facility grew out of the participants' decade of activity in speckle interferometry. Although speckle interferometry continues to provide important astrophysical measurements of a variety of objects, many pressing problems require resolution far beyond that which can be expected from single aperture telescopes. In early 1986, CHARA received a grant from the National Science Foundation which has permitted a detailed exploration of the feasibility of constructing a facility which will provide a hundred-fold increase in angular resolution over what is possible by speckle interferometry at the largest existing telescopes. The design concept for the CHARA Array was developed initially with the contractural collaboration of United Technologies Optical Systems, Inc., in West Palm Beach, Florida, an arrangement that expired in August 1987. In late November 1987, the Georgia Tech Research Institute joined with CHARA to continue and complete the design concept study. Very high-resolution imaging at optical wavelengths is clearly coming of age in astronomy. The CHARA Array and other related projects will be important and necessary milestones along the way toward the development of a major national facility for high-resolution imaging--a true optical counterpart to the Very Large Array. Ground-based arrays and their scientific output will lead to high resolution facilities in space and, ultimately, on the Moon.

Mcalister, Harold A.

1992-01-01

373

Array processor architecture  

NASA Technical Reports Server (NTRS)

A high speed parallel array data processing architecture fashioned under a computational envelope approach includes a data base memory for secondary storage of programs and data, and a plurality of memory modules interconnected to a plurality of processing modules by a connection network of the Omega gender. Programs and data are fed from the data base memory to the plurality of memory modules and from hence the programs are fed through the connection network to the array of processors (one copy of each program for each processor). Execution of the programs occur with the processors operating normally quite independently of each other in a multiprocessing fashion. For data dependent operations and other suitable operations, all processors are instructed to finish one given task or program branch before all are instructed to proceed in parallel processing fashion on the next instruction. Even when functioning in the parallel processing mode however, the processors are not locked-step but execute their own copy of the program individually unless or until another overall processor array synchronization instruction is issued.

Barnes, George H. (Inventor); Lundstrom, Stephen F. (Inventor); Shafer, Philip E. (Inventor)

1983-01-01

374

Mir Cooperative Solar Array  

NASA Technical Reports Server (NTRS)

The Mir Cooperative Solar Array (MCSA), produced jointly by the United States and Russia, was deployed on the Mir Russian space station on May 25, 1996. The MCSA is a photovoltaic electrical power system that can generate up to 6 kW. The power from the MCSA is needed to extend Mir's lifetime and to support experiments conducted there by visiting U.S. astronauts. The MCSA was brought to Mir via the Space Shuttle Atlantis on the STS-74 mission, launched November 12, 1995. This cooperative venture combined the best technology of both countries: the United States provided high-efficiency, lightweight photovoltaic panel modules, whereas Russia provided the array structure and deployment mechanism. Technology developed in the Space Station Freedom Program, and now being used in the International Space Station, was used to develop MCSA's photovoltaic panel. Performance data obtained from MCSA operation on Mir will help engineers better understand the performance of the photovoltaic panel modules in orbit. This information will be used to more accurately predict the performance of the International Space Station solar arrays. Managed by the NASA Lewis Research Center for NASA's International Space Station Program Office in Houston, Texas, the MCSA Project was completed on time and under budget despite a very aggressive schedule.

Skor, Mike; Hoffman, Dave J.

1997-01-01

375

Three-dimensional analysis of magnetometer array data  

NASA Technical Reports Server (NTRS)

A technique is developed for mapping magnetic variation fields in three dimensions using data from an array of magnetometers, based on the theory of optimal linear estimation. The technique is applied to data from the Scandinavian Magnetometer Array. Estimates of the spatial power spectra for the internal and external magnetic variations are derived, which in turn provide estimates of the spatial autocorrelation functions of the three magnetic variation components. Statistical errors involved in mapping the external and internal fields are quantified and displayed over the mapping region. Examples of field mapping and of separation into external and internal components are presented. A comparison between the three-dimensional field separation and a two-dimensional separation from a single chain of stations shows that significant differences can arise in the inferred internal component.

Richmond, A. D.; Baumjohann, W.

1984-01-01

376

Weld quality evaluation using a high temperature SQUID array  

SciTech Connect

This paper presents preliminary data for evaluating weld quality using high temperature SQUIDS. The SQUIDS are integrated into an instrument known as the SQUID Array Microscope, or SAMi. The array consists of ll SQUIDs evenly distributed over an 8.25 mm baseline. Welds are detected using SAMi by using an on board coil to induce eddy currents in a conducting sample and measuring the resulting magnetic fields. The concept is that the induced magnetic fields will differ in parts of varying weld quality. The data presented here was collected from three stainless steel parts using SAMi. Each part was either solid, included a good weld, or included a bad weld. The induced magnetic field's magnitude and phase relative to the induction signal were measured. For each sample considered, both the magnitude and phase data were measurably different than the other two samples. These results indicate that it is possible to use SAMi to evaluate weld quality.

Clark, D. D. (David D.); Espy, M. A. (Michelle A.); Kraus, Robert H., Jr.; Matlachov, A. N. (Andrei N.); Lamb, J. S. (Jessica S.)

2002-01-01

377

Magnetocardiography with a modular spin-exchange relaxation-free atomic magnetometer array  

NASA Astrophysics Data System (ADS)

We present a portable four-channel atomic magnetometer array operating in the spin-exchange relaxation-free regime. The magnetometer array has several design features intended to maximize its suitability for biomagnetic measurement, specifically foetal magnetocardiography, such as a compact modular design and fibre-coupled lasers. The modular design allows the independent positioning and orientation of each magnetometer. Using this array in a magnetically shielded room, we acquire adult magnetocadiograms. These measurements were taken with a 6-11 fT Hz-1/2 single-channel baseline sensitivity that is consistent with the independently measured noise level of the magnetically shielded room.

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

2012-05-01

378

Magnetocardiography with a modular spin-exchange relaxation-free atomic magnetometer array.  

PubMed

We present a portable four-channel atomic magnetometer array operating in the spin-exchange relaxation-free regime. The magnetometer array has several design features intended to maximize its suitability for biomagnetic measurement, specifically foetal magnetocardiography, such as a compact modular design and fibre-coupled lasers. The modular design allows the independent positioning and orientation of each magnetometer. Using this array in a magnetically shielded room, we acquire adult magnetocadiograms. These measurements were taken with a 6-11 fT Hz(-1/2) single-channel baseline sensitivity that is consistent with the independently measured noise level of the magnetically shielded room. PMID:22504066

Wyllie, R; Kauer, M; Smetana, G S; Wakai, R T; Walker, T G

2012-05-01

379

Field Directed Ordering in Magnetic Nanocrystal Structures  

NASA Astrophysics Data System (ADS)

Iron oxide nanocrystals (NCs) have been the focus of intense research owing to the observation of tunable magnetic properties which could lead to advances in many fields including magnetic storage devices and medicine. We have been targeting the use of iron oxide NCs as magnetoresistance (MR) based sensors using ordered NC arrays. In this work, we will present our efforts toward using external magnetic fields to induce intraparticle ordering in iron oxide NC drop cast films. We use x-ray diffraction to analyze effects of the external fields on the NC array structure, while using SQUID magnetometry to probe the effects of NC interactions on the magnetic properties of iron oxide NCs ranging from 5 - 20 nm in diameter. MR measurements suggest large changes in the MR ratio can be achieved using the directed ordering approach for NC arrays. Our work could provide new avenues towards the fabrication of new magnetic devices.

Lawson, Stuart; Meulenberg, Robert

2013-03-01

380

High-throughput magnetic flow sorting of human cells selected on the basis of magnetophoretic mobility  

NASA Astrophysics Data System (ADS)

We have shown the potential of a new method for optimizing the separation of human stem cell subsets from peripheral blood based on a novel cell labeling technique that leverages the capabilities of a new commercially available high speed magnetic cell sorting system (IKOTECH LLC, New Albany, IN). This new system sorts cells in a continuously flowing manner using a Quadrupole Magnetic cell Sorter (QMS). The sorting mechanism is based upon the magnetophoretic mobility of the cells, a property related to the relative binding distributions of magnetic particles per cell, as determined by the utilization of a Magnetic Cell Tracking Velocimeter (MCTV). KG-1 cells were competitively labeled with anti-CD34 magnetic beads and anti-CD34 FITC to obtain an optimal level of magnetophoretic mobility as visualized by the MCTV for high throughput sort recovery in the QMS. In QMS sorting, the concept of split-flow thin channel (SPLITT) separation technology is applied by having a sample stream enter a vertical annular flow channel near the channel's interior wall followed by another sheath flow entering near the exterior wall. The two flows are initially separated by a flow splitter. They pass through the bore of a Halbach permanent quadrupole magnet assembly, which draws magnetized cells outward and deflects them into a positive outflow, while negative cells continue straight out via the inner flow lamina. QMS sorts cells based upon their magnetophoretic mobility, or the velocity of a cell per unit ponderomotive force, the counterpart of fluorescence intensity in flow cytometry. The magnetophoretic mobility distribution of a cell population, measured by automated MCTV, is used as input data for the algorithmic control of sample, sheath, and outlet flow velocities of the QMS. In this study, the relative binding distributions of magnetic particles per cell were determined by MCTV using novel sorting and sizing algorithms. The resulting mobility histograms were used to set the QMS flow parameters so that desired cell populations could be selected on the basis of a mobility "window". The MCTV and the QMS are able to work together to provide good sort boundaries for cell populations that are mathematically defined as opposed to the traditional magnetic sort systems that solely rely on whether a cell is simply "magnetized" or not. One long-term application of this new high speed cell sorting system is to sterilely isolate large numbers of human stem cells directly from a donor's blood for subsequent manipulation in tissue culture for regenerative medicine within that same patient. This will eliminate the need for immune suppressive drugs in an autologous transplantation procedure.

Reece, Lisa M.; Sanders, Lehanna; Kennedy, David; Guernsey, Byron; Todd, Paul; Leary, James F.

2010-02-01

381

Size-dependent spin-wave frequency in ferromagnetic wire-array structures A. Ercole, A. O. Adeyeye, J. A. C. Bland, and D. G. Hasko  

E-print Network

a dramatic effect on the static magnetization behav- ior. Wire arrays are convenient for magnetoresistance MRSize-dependent spin-wave frequency in ferromagnetic wire-array structures A. Ercole, A. O. Adeyeye Kingdom Received 28 October 1997 Spin-wave frequency measurements in ferromagnetic FeNi wire-array

Adeyeye, Adekunle

382

Modeling high gradient magnetic separation from biological fluids.  

SciTech Connect

A proposed portable magnetic separator consists of an array of biocompatible capillary tubing and magnetizable wires immersed in an externally applied homogeneous magnetic field. While subject to the homogeneous magnetic field, the wires create high magnetic field gradients, which aid in the collection of blood-borne magnetic nanospheres from blood flow. In this study, a 3-D numerical model was created using COMSOL Multiphysics 3.2 software to determine the configuration of the wire-tubing array from two possible configurations, one being an array with rows alternating between wires and tubing, and the other being an array where wire and tubing alternate in two directions. The results demonstrated that the second configuration would actually capture more of the magnetic spheres. Experimental data obtained by our group support this numerical result.

Bockenfeld, D.; Chen, H.; Rempfer, D.; Kaminski, M. D.; Rosengart, A. J.; Chemical Engineering; Illinois Inst. of Tech.; Univ. of Chicago, Pritzker School of Medicine

2006-01-01

383

The Expanded Owens Valley Solar Array (EOVSA)  

NASA Astrophysics Data System (ADS)

The Expanded Owens Valley Solar Array (EOVSA) near Big Pine, CA is undergoing commissioning as a solar-dedicated microwave imaging array operating in the frequency range 2.5-18 GHz. The solar science to be addressed focuses on the 3D structure of the solar corona (magnetic field, temperature and density), and on the particle acceleration, transport and heating in solar flares. The project will support the scientific community by providing open data access and software tools for analysis and modeling of the data, to exploit synergies with on-going solar research in other wavelengths. The array consists of a total of 15 antennas, including the two 27-m antennas with He-cooled receivers for sensitive calibration, and thirteen 2.1-m antennas that each view the entire disk of the Sun. The system includes a completely new control system, broadband signal transmission, and high-speed digital signal processing, using new technology developed for the Frequency Agile Solar Radiotelescope (FASR). We present an overview of the instrument, the current status of commissioning activities, and some initial observations to assess performance.This research is supported by NSF grants AST-1312802, and NASA grants NNX11AB49G and NNX10AF27G to New Jersey Institute of Technology.

Gary, Dale E.; Hurford, Gordon J.; Nita, Gelu M.; White, Stephen M.; McTiernan, James; Fleishman, Gregory D.

2014-06-01

384

Magnetic force microscopy investigation of the magnetization reversal of permalloy particles at high temperatures  

NASA Astrophysics Data System (ADS)

The magnetization reversal of an array of permalloy particles formed by scanning probe lithography on the silicon dioxide surface has been investigated in the temperature range from room temperature to 800 K. Using scanning magnetic force microscopy and numerical calculations of the magnetic anisotropy field of a particle at different temperatures, it has been shown that an increase in the temperature leads to a decrease in the external magnetic field required to reverse the magnetization direction of the particle. From the obtained results, it has been concluded that the magnetization reversal of the studied particles is accompanied by the formation of an intermediate state with an inhomogeneous magnetization structure.

Nurgazizov, N. I.; Khanipov, T. F.; Bizyaev, D. A.; Bukharaev, A. A.; Chuklanov, A. P.

2014-09-01

385

Fabrication of Microshutter Arrays for James Webb Space Telescope  

NASA Technical Reports Server (NTRS)

Two-dimensional MEMS microshutter arrays are being developed at NASA Goddard Space Flight Center for use in the near-infrared region on the Next Generation Space Telescope (NGST). The microshutter arrays are designed for the selective transmission of light with high efficiency and high contrast. The NGST environment requires cryogenic operation at 45K. Microshutter arrays are fabricated out of silicon-oxide-insulated (SOI) silicon wafers. Arrays are close-packed silicon nitride membranes with a pixel size of 100x100 microns. 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 (RE) 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 frames 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.

Li, Mary J.; Zheng, Yun; Hess, Larry; Hu, Ron; Kelly, Dan; Lynch, Barney; Oh, Lance; Ray, Chris; Smith, Wayne; Babu, Sachi

2004-01-01

386

The Earth's Magnetic Field  

NSDL National Science Digital Library

This section of the Windows to the Universe website provides information and images about Earth's magnetic field (the magnetosphere), including detailed information about the aurora borealis, magnets, and solar wind. Windows to the Universe is a user-friendly learning system pertaining to the Earth and Space sciences. The objective of this project is to develop an innovative and engaging website that includes a rich array of documents, including images, movies, animations, and data sets that explore the Earth and Space sciences and the historical and cultural ties between science, exploration and the human experience. Links at the top of each page allow users to navigate between beginner, intermediate and advanced levels.

Johnson, Roberta

2000-07-01

387

The kilopixel array pathfinder project (KAPPa), a 16-pixel integrated heterodyne focal plane array: characterization of the single pixel prototype  

NASA Astrophysics Data System (ADS)

We report on the laboratory testing of KAPPa, a 16-pixel proof-of-concept array to enable the creation THz imaging spectrometer with ~1000 pixels. Creating an array an order of magnitude larger than the existing state of the art of 64 pixels requires a simple and robust design as well as improvements to mixer selection, testing, and assembly. Our testing employs a single pixel test bench where a novel 2D array architecture is tested. The minimum size of the footprint is dictated by the diameter of the drilled feedhorn aperture. In the adjoining detector block, a 6mm × 6mm footprint houses the SIS mixer, LNA, matching and bias networks, and permanent magnet. We present an initial characterization of the single pixel prototype using a computer controlled test bench to determine Y-factors for a parameter space of LO power, LO frequency, IF bandwidth, magnet field strength, and SIS bias voltage. To reduce the need to replace poorly preforming pixels that are already mounted in a large format array, we show techniques to improve SIS mixer selection prior to mounting in the detector block. The 2D integrated 16-pixel array design has been evolved as we investigate the properties of the single pixel prototype. Carful design of the prototype has allowed for rapid translation of single pixel design improvements to be easily incorporated into the 16-pixel model.

Wheeler, Caleb H.; Groppi, Christopher E.; Mani, Hamdi; McGarey, Patrick; Kuenzi, Linda; Weinreb, Sander; Russell, Damon S.; Kooi, Jacob W.; Lichtenberger, Arthur W.; Walker, Christopher K.; Kulesa, Craig

2014-07-01

388

Diode laser array  

NASA Technical Reports Server (NTRS)

A diode laser array comprises a substrate of a semiconductor material having first and second opposed surfaces. On the first surface is a plurality of spaced gain sections and a separate distributed Bragg reflector passive waveguide at each end of each gain section and optically connecting the gain sections. Each gain section includes a cavity therein wherein charge carriers are generated and recombine to generate light which is confined in the cavity. Also, the cavity, which is preferably a quantum well cavity, provides both a high differential gain and potentially large depth of loss modulation. Each waveguide has a wavelength which is preferably formed by an extension of the cavity of the gain sections and a grating. The grating has a period which provides a selective feedback of light into the gain sections to supporting lasing, which allows some of the light to be emitted from the waveguide normal to the surface of the substrate and which allows optical coupling of the gain sections. Also, the grating period provides an operating wavelength which is on the short wavelength side of the gain period of the gain sections required for laser oscillation. An RF pulse is applied so as to maximize the magnitude of the loss modulation and the differential gain in the gain sections. The array is operated by applying a DC bias to all the gain sections at a level just below the threshold of the gain sections to only one of the gain sections which raises the bias in all of the gain sections to a level that causes all of the gain sections to oscillate. Thus, a small bias can turn the array on and off.

Carlson, Nils W. (Inventor); Evans, Gary A. (Inventor); Kaiser, Charlie J. (Inventor)

1990-01-01

389

UAVSAR Phased Array Aperture  

NASA Technical Reports Server (NTRS)

This paper describes the development of a patch antenna array for an L-band repeat-pass interferometric synthetic aperture radar (InSAR) instrument that is to be flown on an unmanned aerial vehicle (UAV). The antenna operates at a center frequency of 1.2575 GHz and with a bandwidth of 80 MHz, consistent with a number of radar instruments that JPL has previously flown. The antenna is designed to radiate orthogonal linear polarizations in order to facilitate fully-polarimetric measurements. Beam-pointing requirements for repeat-pass SAR interferometry necessitate electronic scanning in azimuth over a range of -20degrees in order to compensate for aircraft yaw. Beam-steering is accomplished by transmit/receive (T/R) modules and a beamforming network implemented in a stripline circuit board. This paper, while providing an overview of phased array architecture, focuses on the electromagnetic design of the antenna tiles and associated interconnects. An important aspect of the design of this antenna is that it has an amplitude taper of 10dB in the elevation direction. This is to reduce multipath reflections from the wing that would otherwise be detrimental to interferometric radar measurements. This taper is provided by coupling networks in the interconnect circuits as opposed to attenuating the output of the T/R modules. Details are given of material choices and fabrication techniques that meet the demanding environmental conditions that the antenna must operate in. Predicted array performance is reported in terms of co-polarized and crosspolarized far-field antenna patterns, and also in terms of active reflection coefficient.

Chamberlain, Neil; Zawadzki, Mark; Sadowy, Greg; Oakes, Eric; Brown, Kyle; Hodges, Richard

2009-01-01

390

HTS ion damage Josephson junction technology for SQUID arrays  

NASA Astrophysics Data System (ADS)

The high temperature superconducting (HTS) Josephson Junction (JJ) ion damage technology we are developing is well suited for making large SQUID arrays. We have studied arrays of similar SQUIDs together with large SQIFs (Superconducting Quantum Interference Filter) with 2000 SQUIDs of different loop areas. Magnetic field sensitivity has been measured in both types of devices as a function of bias current and temperature. The effects of the barrier thickness (from 20 to 80 nm) and JJ length (2 or 5 ?m) on characteristics have been investigated.

Ouanani, S.; Kermorvant, J.; Crété, D.-G.; Lemaître, Y.; Mage, J.-C.; Marcilhac, B.; Bergeal, N.; Malnou, M.; Lesueur, J.; Mailly, D.; Ulysse, C.

2014-05-01

391

Zero-temperature spin-glass freezing in self-organized arrays of Co nanoparticles  

NASA Astrophysics Data System (ADS)

We study, by means of magnetic-susceptibility and magnetic-aging experiments, the nature of the glassy magnetic dynamics in arrays of Co nanoparticles, self-organized in N layers from N=1 (two-dimensional limit) up to N=20 (three-dimensional limit). We find no qualitative differences between the magnetic responses measured in these two limits, in spite of the fact that no spin-glass phase is expected above T=0 in two dimensions. More specifically, all the phenomena (critical slowing-down, flattening of the field-cooled magnetization below the blocking temperature and the magnetic memory induced by aging) that are usually associated with this phase look qualitatively the same for two-dimensional and three-dimensional arrays. The activated scaling law that is typical of systems undergoing a phase transition at zero temperature accounts well for the critical slowing-down of the dc and ac susceptibilities of all samples. Our data show also that dynamical magnetic correlations achieved by aging a nanoparticle array below its superparamagnetic blocking temperature extend mainly to nearest neighbors. Our experiments suggest that the glassy magnetic dynamics of these nanoparticle arrays is associated with a zero-temperature spin-glass transition.

López-Ruiz, R.; Luis, F.; Sesé, J.; Bartolomé, J.; Deranlot, C.; Petroff, F.

2010-03-01

392

The Submillimeter Array  

NASA Astrophysics Data System (ADS)

The submillimeter array, a collaboration between the Smithsonian Astrophysical Observatory and the Academia Sinica Institute of Astronomy and Astrophysics of Taiwan, is a pioneering radio-interferometer made up of eight 6-meter diameter antennas designed for high angular resolution astronomical observations of the cool universe throughout the major atmospheric windows from about 200 to 900 GHz. Each antenna houses a single cryostat, with an integrated cryocooler that can cool eight heterodyne receivers to 4 K. Four receiver bands are available: 180-250 GHz, 266-355 GHz, 320-420 GHz, and 600-700 GHz, and simultaneous observations are possible in any pair of high and low frequency receiver bands.

Blundell, Raymond

2007-07-01

393

Educational Cosmic Ray Arrays  

NASA Astrophysics Data System (ADS)

In the last decade a great deal of interest has arisen in using sparse arrays of cosmic ray detectors located at schools as a means of doing both outreach and physics research. This approach has the unique advantage of involving grade school students in an actual ongoing experiment, rather then a simple teaching exercise, while at the same time providing researchers with the basic infrastructure for installation of cosmic ray detectors. A survey is made of projects in North America and Europe and in particular the ALTA experiment at the University of Alberta which was the first experiment operating under this paradigm.

Soluk, R. A.

2006-04-01

394

Microhotplate gas sensor arrays  

NASA Astrophysics Data System (ADS)

In this work, micromachining and planar processing have been used to produce gas sensing devices with lower power consumption at lower cost. The small size brings new advantages for chemical selectivity as well: multi-element arrays whose time-varying signals can be interpreted using pattern recognition methods. The device platform is a `microhotplate,' consisting of a built-in heater, thermometer, and electrodes to probe the sensing films. Microhotplates are fabricated using CMOS-compatible technologies, enabling on-chip circuitry for multiplexing and signal amplification.

Cavicchi, Richard E.; Semancik, Stephen; Walton, Robin M.; Panchapakesan, Balaji; DeVoe, Don L.; Aquino-Class, Maria I.; Allen, James D.; Suehle, John S.

1999-11-01

395

Red microchip VECSEL array  

Microsoft Academic Search

We report an InGaP\\/AlInGaP\\/GaAs microchip vertical-external-cavity surface emitting laser operating directly at red wavelengths and demonstrate its potential for array-format operation. Optical pumping with up to 3.3W at 532nm produced a maximum output power of 330mW at 675nm, in a single circularly-symmetric beam with M2<2. Simultaneous pumping with three separate input beams, generated using a diffractive optical element, achieved lasing

Jennifer E. Hastie; Lynne G. Morton; Stephane Calvez; Martin D. Dawson; Tomi Leinonen; Markus Pessa; Graham Gibson; Miles J. Padgett

2005-01-01

396

Pulsar Timing Arrays  

NASA Astrophysics Data System (ADS)

In the last decade, the use of an ensemble of radio pulsars to constrain the characteristic strain caused by a stochastic gravitational wave background has advanced the cause of detection of very low frequency gravitational waves (GWs) significantly. This electromagnetic means of GW detection, called Pulsar Timing Array (PTA), is reviewed in this paper. The principle of operation of PTA, the current operating PTAs and their status are presented along with a discussion of the main challenges in the detection of GWs using PTA.

Joshi, Bhal Chandra

2013-01-01

397

Rotational magnetic induction tomography  

NASA Astrophysics Data System (ADS)

In magnetic induction tomography (MIT), an array of excitation coils is typically used to apply time-varying magnetic fields to induce eddy currents in the material to be studied. The magnetic fields from the eddy currents are then detected by an array of sensing coils to form an image of passive electromagnetic properties (i.e. conductivity, permittivity and permeability). Increasing the number of transmitters and receivers can provide a better image quality at the expense of a larger and more expensive MIT system. Instead of increasing the number of coils, this study investigates the possibility of rotating a single transmit-receive coil to image the electrical properties of the sample, by emulating an array of 200 transmit-receive coils by time-division multiplexing. Engineering details on the electromechanical design and development of a rotating MIT system are presented. The experimental results indicate that representative images of conductive samples can be obtained at 5 MHz by rotating a single transmit-receive coil.

Trakic, Adnan; Eskandarnia, Neda; Keong Li, Bing; Weber, Ewald; Wang, Hua; Crozier, Stuart

2012-02-01

398

Electrode array for neural stimulation  

DOEpatents

An electrode array for neural stimulation is disclosed which has particular applications for use in a retinal prosthesis. The electrode array can be formed as a hermetically-sealed two-part ceramic package which includes an electronic circuit such as a demultiplexer circuit encapsulated therein. A relatively large number (up to 1000 or more) of individually-addressable electrodes are provided on a curved surface of a ceramic base portion the electrode array, while a much smaller number of electrical connections are provided on a ceramic lid of the electrode array. The base and lid can be attached using a metal-to-metal seal formed by laser brazing. Electrical connections to the electrode array can be provided by a flexible ribbon cable which can also be used to secure the electrode array in place.

Wessendorf, Kurt O. (Albuquerque, NM); Okandan, Murat (Edgewood, NM); Stein, David J. (Albuquerque, NM); Yang, Pin (Albuquerque, NM); Cesarano, III, Joseph (Albuquerque, NM); Dellinger, Jennifer (Albuquerque, NM)

2011-08-16

399

STRUCTURE AND MAGNETIC FIELDS IN THE PRECESSING JET SYSTEM SS 433. III. EVOLUTION OF THE INTRINSIC BRIGHTNESS OF THE JETS FROM A DEEP MULTI-EPOCH VERY LARGE ARRAY CAMPAIGN  

SciTech Connect

We present a sequence of five deep observations of SS 433 made over the summer of 2007 using the Very Large Array in the A configuration at 5 and 8 GHz. In this paper, we study the brightness profiles of the jets and their time evolution. We also examine the spectral index distribution in the source. We find (as previously reported from the analysis of a single earlier image) that the profiles of the east and west jets are remarkably similar if projection and Doppler beaming are taken into account. The sequence of five images allows us to disentangle the evolution of brightness of individual pieces of jet from the variations of jet power originating at the core. We find that the brightness of each piece of the jet fades as an exponential function of age (or distance from the core), e{sup -}{tau}/{tau}{sup '}, where {tau} is the age at emission and {tau}' = 55.9 {+-} 1.7 days. This evolutionary model describes both the east and west jets equally well. There is also significant variation (by a factor of at least five) in jet power with birth epoch, with the east and west jets varying in synchrony. The lack of deceleration between the scale of the optical Balmer line emission (10{sup 15} cm) and that of the radio emission (10{sup 17} cm) requires that the jet material is much denser than its surroundings. We find that the density ratio must exceed 300:1.

Bell, Michael R.; Roberts, David H.; Wardle, John F. C., E-mail: mrbell@mpa-garching.mpg.de, E-mail: roberts@brandeis.edu, E-mail: wardle@brandeis.edu [Department of Physics, MS-057, Brandeis University, 415 South Street, Waltham, MA 02453 (United States)

2011-08-01

400

Phased array imaging on a 4.7T/33cm animal research system  

NASA Astrophysics Data System (ADS)

Although phased array technology has been standard on clinical magnetic resonance imaging (MRI) systems for many years, it is just now becoming available on small animal MRI systems. Bruker Instruments Ltd. has recently provided multiple rf channels on a 4.7T/33cm Avance, but further development was necessary to complete the phased array implementation. This work discusses the development of this other hardware, specifically the rf array coil, low impedance preamplifiers, excitation coil, and image combination algorithm. Comparison of the array coil to a quadrature coil indicates superior signal-to-noise ratio from the array. In vivo images of a cat spine acquired simultaneously from the individual channels of the array and a sum of squares combination are shown.

Beck, Barbara L.; Blackband, Stephen J.

2001-11-01

401

Electrodynamic Arrays Having Nanomaterial Electrodes  

NASA Technical Reports Server (NTRS)

An electrodynamic array of conductive nanomaterial electrodes and a method of making such an electrodynamic array. In one embodiment, a liquid solution containing nanomaterials is deposited as an array of conductive electrodes on a substrate, including rigid or flexible substrates such as fabrics, and opaque or transparent substrates. The nanomaterial electrodes may also be grown in situ. The nanomaterials may include carbon nanomaterials, other organic or inorganic nanomaterials or mixtures.

Trigwell, Steven (Inventor); Biris, Alexandru S. (Inventor); Calle, Carlos I. (Inventor)

2013-01-01

402

Active membrane phased array radar  

NASA Technical Reports Server (NTRS)

We have developed the first membrane-based active phased array in L-band (1.26GHz). The array uses membrane compatible Transmit/Receive (T/R) modules (membrane T/R) for each antenna element. We use phase shifters within each T/R module for electronic beam steering. We will discuss the T/R module design and integration with the membrane, We will also present transmit and receive beam-steering results for the array.

Moussessian, Alina; Del Castillo, Linda; Huang, John; Sadowy, Greg; Hoffman, James; Smith, Phil; Hatake, Toshiro; Derksen, Chuck; Lopez, Bernardo; Caro, Ed

2005-01-01

403

Solid state image sensing arrays  

NASA Technical Reports Server (NTRS)

The fabrication of a photodiode transistor image sensor array in silicon, and tests on individual elements of the array are described along with design for a scanning system for an image sensor array. The spectral response of p-n junctions was used as a technique for studying the optical-absorption edge in silicon. Heterojunction structures of Sb2S3- Si were fabricated and a system for measuring C-V curves on MOS structures was built.

Sadasiv, G.

1972-01-01

404

Finite size effect on spread of resonance frequencies in arrays of coupled vortices  

SciTech Connect

Dynamical properties of magnetic vortices in arrays of magnetostatically coupled ferromagnetic disks are studied by means of a broadband ferromagnetic-resonance (FMR) setup. Magnetic force microscopy and magnetic transmission soft X-ray microscopy are used to image the core polarizations and the chiralities which are both found to be randomly distributed. The resonance frequency of vortex-core motion strongly depends on the magnetostatic coupling between the disks. The parameter describing the relative broadening of the absorption peak observed in the FMR transmission spectra for a given normalized center-to-center distance between the elements is shown to depend on the size of the array.

Vogel, Andreas; Drews, André; Im, Mi-Young; Fischer, Peter; Meier, Guido

2011-01-25

405

Giant magnetoresistance in magnetic multilayered nanowires  

Microsoft Academic Search

Giant magnetoresistance (GMR) is observed in a new type of nanostructured material consisting of magnetic multilayered nanowires formed by electrodeposition into nanometer-sized pores of a template polymer membrane. The composition of these nanowires is modulated over nanometer length scales with distinct magnetic and nonmagnetic metallic layers. Magnetoresistance measurements with the current perpendicular to the layers were performed on the array

L. Piraux; J. M. George; J. F. Despres; C. Leroy; E. Ferain; R. Legras; K. Ounadjela; A. Fert

1994-01-01

406

The Askaryan radio array  

NASA Astrophysics Data System (ADS)

The Askar'yan Radio Array (ARA), a neutrino detector to be situated at the South Pole next to the IceCube detector, will be sensitive to ultrahigh-energy cosmic neutrinos above 0.1 EeV and will have the greatest sensitivity within the favored energy range from 0.1 EeV up to 10 EeV. Neutrinos of this energy are guaranteed by current observations of the GZK-cutoff by the HiRes and Pierre Auger Observatories. The detection method is based on Cherenkov emission by a neutrino induced cascade in the ice, coherent at radio wavelengths, which was predicted by Askar'yan in 1962 and verified in beam tests at SLAC in 2006. The detector is planned to consist of 37 stations with 16 antennas each, deployed at depths of up to 200 m under the ice surface. During the last two polar seasons (2010 - 2011, 2011 - 2012), a prototype station and a first detector station were successfully deployed and are taking data. These data have been and are currently being analyzed to study the ambient noise background and the radio frequency properties of the South Pole ice sheet. A worldwide collaboration is working on the planning, construction and data analysis of the detector array. This article will give a short report on the status of the ARA detector and show recent results from the recorded data.

Meures, Thomas; ARA Collaboration

2013-05-01

407

Integrated residential photovoltaic array development  

NASA Technical Reports Server (NTRS)

An advanced, universally-mountable, integrated residential photovoltaic array concept was defined based upon an in-depth formulation and evaluation of three candidate approaches which were synthesized from existing or proposed residential array concepts. The impact of module circuitry and process sequence is considered and technology gaps and performance drivers associated with residential photovoltaic array concepts are identified. The actual learning experience gained from the comparison of the problem areas of the hexagonal shingle design with the rectangular module design led to what is considered an advanced array concept. Building the laboratory mockup provided actual experience and the opportunity to uncover additional technology gaps.

Shepard, N. F., Jr.

1981-01-01

408

Nanoelectrode array for electrochemical analysis  

DOEpatents

A nanoelectrode array comprises a plurality of nanoelectrodes wherein the geometric dimensions of the electrode controls the electrochemical response, and the current density is independent of time. By combining a massive array of nanoelectrodes in parallel, the current signal can be amplified while still retaining the beneficial geometric advantages of nanoelectrodes. Such nanoelectrode arrays can be used in a sensor system for rapid, non-contaminating field analysis. For example, an array of suitably functionalized nanoelectrodes can be incorporated into a small, integrated sensor system that can identify many species rapidly and simultaneously under field conditions in high-resistivity water, without the need for chemical addition to increase conductivity.

Yelton, William G. (Sandia Park, NM); Siegal, Michael P. (Albuquerque, NM)

2009-12-01

409

Future directions for NICMOS arrays  

NASA Technical Reports Server (NTRS)

The Near Infrared Camera and Multi-Object Spectrometer (NICMOS) for the Hubble Space Telescope (HST) requires focal plane arrays of 256x256 pixels for both its cameras and its spectrometers. The new arrays, developed by the Rockwell Corporation for NICMOS, have 40 microns pixels of HgCdTe bump bonded to a switched MOSFET readout. Expected read noise and dark current for the arrays at 60 K are 30 e and 1 e/sec. respectively. The basis for these numbers is previous experience with 128x128 arrays.

Thompson, R.; Rieke, Marcia J.; Young, Erick T.; Mccarthy, D.; Rasche, Robert; Blessinger, Michael; Vural, Kadri; Kleinhans, William

1989-01-01

410

INVESTIGATION OF SIX ARRAY GEOMETRIES FOR FOCUSED ARRAY HYPERTHERMIA APPLICATIONS  

Microsoft Academic Search

The focusing properties of six array configurations in the form of square, square with interlaced elements, square ring, cross (+) shape, cross (X) shape, and square ring plus diagonals shape arrays are investigated. The performance parameters, such as field distribution in the focal region, size of the focal spot, depth of field, level of field at focal point, and sidelobe

K. H. Sayidmarie; A. M. Abdulkhaleq

2012-01-01

411

Scripps Orbit and Permanent Array Center: Permanent GPS Array Sites  

NSDL National Science Digital Library

This portal provides access to an extensive selection of Global Positioning Systems (GPS) arrays worldwide, totaling hundreds of sites. Each array link contains a listing of sites, a dynamic map, and contact information (when available). Data from the stations can be downloaded from an anonymous ftp site, and there are also links for data processing.

412

IEEE TRANSACTIONS ON MAGNETICS, VOL. 47, NO. 10, OCTOBER 2011 2951 Manipulation of the Excitation State of the Coupled  

E-print Network

. Index Terms--Anisotropic magnetoresistance, magnetic domains, magnetic resonance, spin; the static interaction between vortices in an array is, thus, negligibly small in the ground state. However- fore, the dynamic coupling in coupled pair or array of magnetic vortices causes a mode splitting, which

Otani, Yoshichika

413

Development of optical-based array devices using imaging fiber bundles: Optical tweezer arrays, nanoscale arrays, and microelectrode arrays  

NASA Astrophysics Data System (ADS)

The work in this dissertation describes the development of imaging fiber-based array devices, specifically the fabrication and application of an optical tweezer array, a fiber-based nanoarray, and a nanotip array. With regards for the fabrication of an optical tweezer array, this thesis describes how fiber bundles have been used as a method to create multiple beams, which are used as optical traps. By coupling a single beam into an imaging fiber bundle, the light energy is distributed across the face of the fiber bundle. Each illuminated individual fiber in the array propagates light to the distal face of the bundle, where light focusing elements at the end of each fiber focus the laser light and form optical traps. These optical traps are capable of capturing and arraying microspheres in parallel. The number of optical traps is determined by the number of fibers in the optical fiber bundle and is capable of creating a dense array (˜104 traps/mm2) of optical tweezers. This dissertation also describes the fabrication of fiber bundle-based nanoarrays with two different size formats---one with 700 nm array elements and one with 300 nm array elements. These arrays have an ultra-high packing density in that they contain 1 x 106 or 4.5 x 10 6 array elements/mm2. Current fiber bundle-based arrays have micron feature sizes and a high packing density, up to 5 x 10 4 fibers/mm2. These nanoarrays have feature sizes at least 4 times smaller than the micron-sized arrays used and contain up to 4.5 x 106 fibers/mm2. Nanofiber bundles were chemically etched to create nanowells into which sensors were deposited. The number of sensor elements in these arrays provides enough sensing positions such that they could be used to screen an entire genome while also moving towards the concept of a universal array. In addition, this high density of sensors allows for a large number of replicates, leading to an improvement in the signal to noise ratio. An improvement on creating nanoapertures that was originally developed by Paul Pantano, a former postdoctoral fellow in the Walt lab, is also discussed in this thesis. The original technique employed a mechanical puller that heated and pulled a fiber bundle, which was then polished and etched to create nanowells. Although effective, the technique was difficult to reproduce. (Abstract shortened by UMI.)

Tam, Jenny M.

414

Magnetic confinement of the superconducting condensate in superconductor-ferromagnet hybrid composites  

E-print Network

2007 The influence of an inhomogeneous magnetic field on the magnetoresistance of thin Al films, used with out-of-plane magnetization are explored: namely, i a plain film in a multidomain state and ii an array

Moshchalkov, Victor V.

415

Storage Schemes for Boundedly Extendible Arrays  

Microsoft Academic Search

The high costs of extendibility in array realizations can be reduced dramatically by placing a bound on how big the arrays of interest will grow. Whereas extendible array realizations require order of p · log p storage locations to store two-dimensional arrays having p or fewer positions, boundedly extendible array realizations (with a bound of p) can store these same

Arnold L. Rosenberg; Larry J. Stockmeyer

1977-01-01

416

Array diagrams and the Nial approach  

Microsoft Academic Search

The Nested Interactive Array Language, Nial, combines APL and LISP concepts and is based on the theory of nested rectangular arrays. Array theory provides a concise mathematical model of data capturing the essence of everyday data objects. Arrays are displayed by diagrams, which provide an easily comprehended way of communicating the rectangularity, nesting and content of arrays. A novel drawing

Fl. Schmidt; M. A. Jenkins

1982-01-01

417

Vortices in dense self-assembled hole arrays.  

SciTech Connect

We present a study of the upper critical field and pinning strength from the resistivity and magnetization of a Nb film containing a dense array of 45 nm diameter holes on a hexagonal lattice with a spacing of 101 nm. The holes were formed by self-assembly in anodic aluminum oxide (AAO) using an electrochemical procedure. Confinement effects and Little-Parks oscillations are seen above 6 K, and strong pinning with matching field effects is seen below 6 K. Above the first matching field interstitial vortices coexist with vortices trapped in the hole array. Pinning in the Nb films with hole arrays is enhanced by two orders of magnitude over that in continuous Nb films. At low temperature, flux avalanches are observed and imaged using the magneto-optical Faraday effect.

Crabtree, G. W.; Welp, U.; Xiao, Z. L.; Jiang, J. S.; Vlasko-Vlasov, V. K.; Bader, S. D.; Liang, J.; Chik, H.; Xu, J. M.

2002-10-09

418

The Submillimeter Array Project  

NASA Astrophysics Data System (ADS)

The Smithsonian Astrophysical Observatory and the Institute of Astronomy and Astrophysics of the Academia Sinica are building a submillimeter wavelength interferometer consisting of eight 6 meter antennas sited near the summit of Mauna Kea. Each antenna will be equipped with up to eight receivers covering 180 to 900 GHz, and the maximum angular resolution will vary from 0.1 to 0.4 arcseconds over the frequency range. A flexible correlator will accept two IF channels from each antenna of 2 GHz bandwidth. The first astronomical fringes between array antennas were obtained in October 1998 at the assembly facility in Westford, Massachusetts. Gradual deployment of antennas to Mauna Kea will begin in 1999.

Wilner, D. J.

1999-08-01

419

Diagnosable structured logic array  

NASA Technical Reports Server (NTRS)

A diagnosable structured logic array and associated process is provided. A base cell structure is provided comprising a logic unit comprising a plurality of input nodes, a plurality of selection nodes, and an output node, a plurality of switches coupled to the selection nodes, where the switches comprises a plurality of input lines, a selection line and an output line, a memory cell coupled to the output node, and a test address bus and a program control bus coupled to the plurality of input lines and the selection line of the plurality of switches. A state on each of the plurality of input nodes is verifiably loaded and read from the memory cell. A trusted memory block is provided. The associated process is provided for testing and verifying a plurality of truth table inputs of the logic unit.

Whitaker, Sterling (Inventor); Miles, Lowell (Inventor); Gambles, Jody (Inventor); Maki, Gary K. (Inventor)

2009-01-01

420

Light harvesting arrays  

DOEpatents

A light harvesting array useful for the manufacture of devices such as solar cells comprises: (a) a first substrate comprising a first electrode; and (b) a layer of light harvesting rods electrically coupled to the first electrode, each of the light harvesting rods comprising a polymer of Formula I: X.sup.1.paren open-st.X.sup.m+1).sub.m (I) wherein m is at least 1, and may be from two, three or four to 20 or more; X.sup.1 is a charge separation group (and preferably a porphyrinic macrocycle, which may be one ligand of a double-decker sandwich compound) having an excited-state of energy equal to or lower than that of X.sup.2, and X.sup.2 through X.sup.m+1 are chromophores (and again are preferably porphyrinic macrocycles).

Lindsey, Jonathan S. (Raleigh, NC)

2002-01-01

421

Lau array illuminator.  

PubMed

Spatial coherence can be created by appropriate spatial arrangements of incoherent point sources. Lau used a source of extended light and two amplitude gratings of identical periods, separated by the quarter Talbot distance, to provide coherent light. Because of the two successive amplitude gratings, most of the power is lost. By modifying the geometry of the second grating, I designed an array illuminator, providing several compression ratios and various topologies of the output plane, with significantly reduced losses. To further improve the power efficiency of the system, I used a longitudinal mirror system to collect the light rays that are lost in the initial Lau setup. Both one- and two-dimensional geometries are considered. PMID:15143813

Hamam, Habib

2004-05-10

422

Integrated semiconductor-magnetic random access memory system  

NASA Technical Reports Server (NTRS)

The present disclosure describes a non-volatile magnetic random access memory (RAM) system having a semiconductor control circuit and a magnetic array element. The integrated magnetic RAM system uses CMOS control circuit to read and write data magnetoresistively. The system provides a fast access, non-volatile, radiation hard, high density RAM for high speed computing.

Katti, Romney R. (Inventor); Blaes, Brent R. (Inventor)

2001-01-01

423

Illustrating Number Properties with Arrays  

NSDL National Science Digital Library

This brief article advocates the use of arrays to model the commutative and distributive properties as well as the inverse relationship between multiplication and division. The author explains how arrays also help children form mental pictures that support their memory and reasoning.

Way, Jenni

2002-10-01

424

Hubble Space Telescope Solar Array  

NASA Technical Reports Server (NTRS)

This is a view of a solar cell blanket deployed on a water table during the Solar Array deployment test. The Hubble Space Telescope (HST) Solar Arrays provide power to the spacecraft. The arrays are mounted on opposite sides of the HST, on the forward shell of the Support Systems Module. Each array stands on a 4-foot mast that supports a retractable wing of solar panels 40-feet (12.1-meters) long and 8.2-feet (2.5-meters) wide, in full extension. The arrays rotate so that the solar cells face the Sun as much as possible to harness the Sun's energy. The Space Telescope Operations Control Center at the Goddard Space Center operates the array, extending the panels and maneuvering the spacecraft to focus maximum sunlight on the arrays. The purpose of the HST, the most complex and sensitive optical telescope ever made, is to study the cosmos from a low-Earth orbit. By placing the telescope in space, astronomers are able to collect data that is free of the Earth's atmosphere. The HST Solar Array was designed by the European Space Agency and built by British Aerospace. The Marshall Space Flight Center had overall responsibility for design, development, and construction of the HST.

1985-01-01

425

High Voltage Space Solar Arrays  

NASA Technical Reports Server (NTRS)

Recent tests performed at the NASA Glenn Research Center and elsewhere have shown promise in the design and construction of high voltage (300-1000 V) solar arrays for space applications. Preliminary results and implications for solar array design will be discussed, with application to direct-drive electric propulsion and space solar power.

Ferguson, D. C.; Hillard, G. B.; Vayner, B. V.; Galofaro, J. T.; Lyons, Valerie (Technical Monitor)

2002-01-01

426

Array processing for wireless communications  

Microsoft Academic Search

By equipping the base stations of a wireless network with antenna arrays, it is possible to more fully exploit the spatial dimension in a wireless communication system. Multiple antennas can provide a processing gain to increase the base station range and improve coverage. Also, by exploiting the spatial selectivity of an antenna array, interference may be reduced which in turn

Björn Ottersten

1996-01-01

427

Magnetoresistance and magnetization of nanoengineered periodic magnetic composites  

NASA Astrophysics Data System (ADS)

Nanoengineered magnetic composites made of soft-hard magnetic materials and magnetic-conducting materials have shown a great interest in both applications and fundamental studies. In this study we fabricated magnetic composites with dimensions ranging from 15-100 nm. Samples were made in to two geometries; in one case magnetic dots in a conducting or magnetic matrix (dots-in-matrix) [1,2], while in the other case a stack of exchange-coupled long magnetic wires (multi-wire). We utilized diblock-copolymer lithography to fabricate ``dots-in-matrix'' samples and electron beam lithography and nanoimprint lithography to fabricate ``multi-wire'' samples. Magnetization and charge transport measurements in the 4.2-300 K temperature range were performed on these samples. We report a geometry dependent magnetic hysteresis and magnetoresistance for soft-hard magnetic composites and giant thermal hysteresis and an anomalous oscillatory magnetoresistance behavior for magnetic-conducting composites.[1] Singh et al. ``Realization of artificial Kondo lattices in nanostructured arrays,'' Phys. Rev. B 83, 014408 (2011).[2] Dickert et al. ``Anomalous magnetoresistance effect in nanoengineered material,'' (Submitted) arXiv:1209.0354

Thantirige, Rukshan; Dickert, Stefan; Singh, Deepak; Pradhan, Nihar; John, Jacob; Carter, Kenneth; Tuominen, Mark

2013-03-01

428

Competing anisotropies and temperature dependence of exchange bias in Co IrMn metallic wire arrays fabricated by nanoimprint lithography  

E-print Network

Competing anisotropies and temperature dependence of exchange bias in Co IrMn metallic wire arrays in the unpatterned film, was introduced in the wire arrays through wire patterning. The competing anisotropies were in magnetism.11 In this context, we report on the role of competing anisotropies and the temperature dependence

Krishnan, Kannan M.

429

Templated Assembly of Metal-Anion Arrays within Layered Hosts; Synthesis and Characterization of New Transition-Metal Oxyhalide Perovskites  

E-print Network

Templated Assembly of Metal-Anion Arrays within Layered Hosts; Synthesis and Characterization], superconductivity [12], ferroelectricity [13], colossal magnetoresistance [14-15] and magnetic transitions-anion arrays within receptive hosts and the formation of new mixed valence compounds. Additionally, we

Spinu, Leonard

430

Effect of disorder on DNA electrophoresis in a microfluidic array of obstacles Aruna Mohan and Patrick S. Doyle*  

E-print Network

,4 have em- ployed arrays comprising self-assembled columns of super- paramagnetic beads confined and Patrick S. Doyle* Department of Chemical Engineering, Massachusetts Institute of Technology, Cambridge electrophoretic separation in a self-assembled array of magnetic beads, the presence of dis- order in the obstacle

Doyle, Patrick S.

431

Permanent magnet edge-field quadrupole  

DOEpatents

Planar permanent magnet edge-field quadrupoles for use in particle accelerating machines and in insertion devices designed to generate spontaneous or coherent radiation from moving charged particles are disclosed. The invention comprises four magnetized rectangular pieces of permanent magnet material with substantially similar dimensions arranged into two planar arrays situated to generate a field with a substantially dominant quadrupole component in regions close to the device axis. 10 figs.

Tatchyn, R.O.

1997-01-21

432

Permanent magnet edge-field quadrupole  

DOEpatents

Planar permanent magnet edge-field quadrupoles for use in particle accelerating machines and in insertion devices designed to generate spontaneous or coherent radiation from moving charged particles are disclosed. The invention comprises four magnetized rectangular pieces of permanent magnet material with substantially similar dimensions arranged into two planar arrays situated to generate a field with a substantially dominant quadrupole component in regions close to the device axis.

Tatchyn, Roman O. (Mountain View, CA)

1997-01-01

433

Chunking of Large Multidimensional Arrays  

SciTech Connect

Data intensive scientific computations as well on-lineanalytical processing applications as are done on very large datasetsthat are modeled as k-dimensional arrays. The storage organization ofsuch arrays on disks is done by partitioning the large global array intofixed size hyper-rectangular sub-arrays called chunks or tiles that formthe units of data transfer between disk and memory. Typical queriesinvolve the retrieval of sub-arrays in a manner that accesses all chunksthat overlap the query results. An important metric of the storageefficiency is the expected number of chunks retrieved over all suchqueries. The question that immediately arises is "what shapes of arraychunks give the minimum expected number of chunks over a query workload?"In this paper we develop two probabilistic mathematical models of theproblem and provide exact solutions using steepest descent and geometricprogramming methods. Experimental results, using synthetic workloads onreal life data sets, show that our chunking is much more efficient thanthe existing approximate solutions.

Rotem, Doron; Otoo, Ekow J.; Seshadri, Sridhar

2007-02-28

434

Integrated residential photovoltaic array development  

NASA Technical Reports Server (NTRS)

Three basic module design concepts were analyzed with respect to both production and installation costs. The results of this evaluation were used to synthesize a fourth design which incorporates the best features of these initial concepts to produce a module/array design approach which offers the promise of a substantial reduction in the installed cost of a residential array. A unique waterproofing and mounting scheme was used to reduce the cost of installing an integral array while still maintaining a high probability that the installed array will be watertight for the design lifetime of the system. This recommended concept will also permit the array to be mounted as a direct or stand-off installation with no changes to the module design.

Shepard, N. F., Jr.

1981-01-01

435

Massively Parallel MRI Detector Arrays  

PubMed Central

Originally proposed as a method to increase sensitivity by extending the locally high-sensitivity of small surface coil elements to larger areas, the term parallel imaging now includes the use of array coils to perform image encoding. This methodology has impacted clinical imaging to the point where many examinations are performed with an array comprising multiple smaller surface coil elements as the detector of the MR signal. This article reviews the theoretical and experimental basis for the trend towards higher channel counts relying on insights gained from modeling and experimental studies as well as the theoretical analysis of the so-called “ultimate” SNR and g-factor. We also review the methods for optimally combining array data and changes in RF methodology needed to construct massively parallel MRI detector arrays and show some examples of state-of-the-art for highly accelerated imaging with the resulting highly parallel arrays. PMID:23453758

Keil, Boris; Wald, Lawrence L

2013-01-01

436

Loudspeaker line array educational demonstration.  

PubMed

This paper presents a physical demonstration of an audio-range line array used to teach interference of multiple sources in a classroom or laboratory exercise setting. Software has been developed that permits real-time control and steering of the array. The graphical interface permits a user to vary the frequency, the angular response by phase shading, and reduce sidelobes through amplitude shading. An inexpensive, eight-element loudspeaker array has been constructed to test the control program. Directivity measurements of this array in an anechoic chamber and in a large classroom are presented. These measurements have good agreement with theoretical directivity predictions, thereby allowing its use as a quantitative learning tool for advanced students as well as a qualitative demonstration of arrays in other settings. Portions of this paper are directed toward educators who may wish to implement a similar demonstration for their advanced undergraduate or graduate level course in acoustics. PMID:22423785

Anderson, Brian E; Moser, Brad; Gee, Kent L

2012-03-01

437

Nanoplasmonics of prime number arrays.  

PubMed

In this paper, we investigate the plasmonic near-field localization and the far-field scattering properties of non-periodic arrays of Ag nanoparticles generated by prime number sequences in two spatial dimensions. In particular, we demonstrate that the engineering of plasmonic arrays with large spectral flatness and particle density is necessary to achieve a high density of electromagnetic hot spots over a broader frequency range and a larger area compared to strongly coupled periodic and quasi-periodic structures. Finally, we study the far-field scattering properties of prime number arrays illuminated by plane waves and we discuss their angular scattering properties. The study of prime number arrays of metal nanoparticles provides a novel strategy to achieve broadband enhancement and localization of plasmonic fields for the engineering of nanoscale nano-antenna arrays and active plasmonic structures. PMID:20052140

Forestiere, Carlo; Walsh, Gary F; Miano, Giovanni; Dal Negro, Luca

2009-12-21

438

Micromagnetism of permalloy antidot arrays prepared from alumina templates.  

PubMed

Magnetic hysteresis processes of hexagonal arrays of permalloy antidots have been studied by means of micromagnetic simulations as a function of geometrical parameters. The ideal system shows a maximum of the coercive field as a function of the antidot diameter. The simulated magnetic behavior has been compared with experimental values for antidot arrays of permalloy prepared from alumina templates with thicknesses between 2 and 60 nm, showing a monotonic increase of the coercive field as a function of the antidot diameter. We show that the introduction into simulations of the combination of variable antidot diameters from bottom to top due to the fabrication process and, more importantly, large geometrical domains, which break the sample symmetry, solves the discrepancy between the simulations and the experiment. PMID:25380329

Gawronski, P; Merazzo, K J; Chubykalo-Fesenko, O; Del Real, R P; Vázquez, M

2014-11-28

439

Micromagnetism of permalloy antidot arrays prepared from alumina templates  

NASA Astrophysics Data System (ADS)

Magnetic hysteresis processes of hexagonal arrays of permalloy antidots have been studied by means of micromagnetic simulations as a function of geometrical parameters. The ideal system shows a maximum of the coercive field as a function of the antidot diameter. The simulated magnetic behavior has been compared with experimental values for antidot arrays of permalloy prepared from alumina templates with thicknesses between 2 and 60 nm, showing a monotonic increase of the coercive field as a function of the antidot diameter. We show that the introduction into simulations of the combination of variable antidot diameters from bottom to top due to the fabrication process and, more importantly, large geometrical domains, which break the sample symmetry, solves the discrepancy between the simulations and the experiment.

Gawronski, P.; Merazzo, K. J.; Chubykalo-Fesenko, O.; del Real, R. P.; Vázquez, M.

2014-11-01

440

Field induced Kosterlitz-Thouless transition in two-dimensional array of Nb-AlO-Nb Josephson junctions  

NASA Astrophysics Data System (ADS)

We present recent results on the magnetic field dependence of current-voltage characteristics (CVC) for an artificially prepared two-dimensional array of unshunted Nb-AlO x-Nb Josephson junctions. The results obtained from the measured CVC and critical current IC(T,H) differential magnetoresistance (DMR) R(T,H)=[ of the array are found to exhibit behavior compatible with field induced Kosterlitz-Thouless transition describing unbinding of vortex-antivortex pairs under applied magnetic field.

Sergeenkov, S.; Rivera, V. A. G.; Marega, E.; Araujo-Moreira, F. M.

2011-06-01

441

Sequential vortex hopping in an array of artificial pinning centers  

SciTech Connect

We use low-temperature magnetic force microscopy (MFM) to study the hopping motion of vortices in an array of artificial pinning centers (APCs). The array consists of nanoscale holes etched in a niobium thin film by Ar-ion sputtering through an anodic aluminum-oxide template. Variable-temperature magnetometry shows a transition temperature of 7.1 K and an enhancement of the magnetization up to the third matching field at 5 K. Using MFM with attractive and repulsive tip-vortex interaction, we measure the vortex-pinning strength and investigate the motion of individual vortices in the APC array. The depinning force for individual vortices at low field ranged from 0.7 to 1.2 pN. The motion of individual vortices was found to be reproducible and consistent with movement between adjacent holes in the film. The movements are repeatable but the sequence of hops depends on the scan direction. This asymmetry in the motion indicates nonuniform local pinning, a consequence of array disorder and hole-size variation.

Keay, J. C.

2010-02-24

442

A Compact, Modular Package for Superconducting Bolometer Arrays  

NASA Technical Reports Server (NTRS)

As bolometer arrays grow to ever-larger formats, packaging becomes a more critical engineering issue. We have designed a detector package to house a superconducting bolometer array, SQUID multiplexers, bias and filtering circuitry, and electrical connectors. The package includes an optical filter, magnetic shielding, and has well-defined thermal and mechanical interfaces. An early version of this package has been used successfully in the GISMO 2mm camera, a 128-pixel camera operating at a base temperature of 270mK. A more advanced package permits operation at lower temperatures 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. We describe how the design compensates for differing thermal expansions, allows heat sinking of the bolometer array, and features magnetic shielding in critical areas. We highlight the performance of this detector package and describe its scalability to 1280-pixel arrays in the near future.

Benford, D.

2008-01-01

443

Autoassembly Protein Arrays for Analyzing Antibody Cross-Reactivity  

PubMed Central

We report an autoassembly protein array capable of rapidly screening for aberrant antibody?antigen binding events. Our technique combines magnetic nanoparticle technology with proximity-based, magnetically responsive nanosensors for rapid (under 15 min) and high-density screening of antibody cross-reactivity at sensitivities down to 50 fM in a homogeneous assay. This method will enable the identification of the precise cause of aberrant or cross-reactive binding events in an easy-to-use, rapid, and high-throughput manner. PMID:20804215

2010-01-01

444

banner above paper title Defunctionalizing Push Arrays  

E-print Network

and Obsidian there are two different kinds of arrays, called Pull and Push arrays and in Repa there is a even that performs better. Pull- and Push arrays, that are present in Feldspar and Obsidian, provide

Svenningsson, Josef

445

Replica amplification of nucleic acid arrays  

DOEpatents

Disclosed are improved methods of making and using immobilized arrays of nucleic acids, particularly methods for producing replicas of such arrays. Included are methods for producing high density arrays of nucleic acids and replicas of such arrays, as well as methods for preserving the resolution of arrays through rounds of replication. Also included are methods which take advantage of the availability of replicas of arrays for increased sensitivity in detection of sequences on arrays. Improved methods of sequencing nucleic acids immobilized on arrays utilizing single copies of arrays and methods taking further advantage of the availability of replicas of arrays are disclosed. The improvements lead to higher fidelity and longer read lengths of sequences immobilized on arrays. Methods are also disclosed which improve the efficiency of multiplex PCR using arrays of immobilized nucleic acids.

Church, George M. (Brookline, MA); Mitra, Robi D. (Chestnut Hill, MA)

2010-08-31

446

Novel flux phases in superconductors with a periodic pinning array  

Microsoft Academic Search

Flux-line confinement by triangular and square regular arrays of microholes (“antidots”) has been studied in superconducting films (Pb, WGe) and multilayers (Pb\\/Ge). For relatively large antidots sharp cusp-like magnetization anomalies appear at the matching fields Hm. These anomalies are cuased by the formation of the multi-quanta vortex lattices at each subsequent Hm. The multi-quanta vortex lattices make possible a peacefull

V. V. Moshchalkov; M. Baert; E. Rosseel; V. V. Metlushko; M. J. Van Bael; Y. Bruynseraede

1997-01-01

447

Signals analysis of fluxgate array for wire rope defaults  

NASA Astrophysics Data System (ADS)

In order to detecting the magnetic leakage fields of the wire rope defaults, a transducer made up of the fluxgate array is designed, and a series of the characteristic values of wire rope defaults signals are defined. By processing the characteristic signals, the LF or LMA of wire rope are distinguished, and the default extent is estimated. The experiment results of the new method for detecting the wire rope faults are introduced.

Wei, Gu; Jianxin, Chu

2005-01-01

448

Design of a New Linear Magnetic Damper for Shock-Absorbing from Crash Accident of High Speed Vehicles  

Microsoft Academic Search

This paper proposes a new linear magnetic damper to absorb shock from the crash accident of high speed vehicles. The magnetic damper is composed of a copper plate, a yoke, and permanent magnets. The damping force is generated by the eddy current in the copper plate. Also, permanent magnets are aligned using Hallbach array to improve the damping force. Magnetic

Yongdae Kim; Heon Lee; Semyung Wang

2006-01-01

449

Transport of relativistic electron beams along wire arrays  

SciTech Connect

Theoretical prediction and particle simulations indicate that an array of longitudinal wires will allow electron beam propagation, without an external guiding magnetic field and above the drift tube limit, by providing a charge and current neutralizing background. This paper presents experimental tests of this transport concept by injecting a 60 ns, 18 kA pulse of 1.4 MeV electrons into an array of 1-m long wires with a 1 cm spacing, filling a hexagon with 8.7-cm average radius. Arrays were tested with wires of varying resistances and diameters ranging from 12 to 1.3 mil. Transport was tested with wires terminating on a common conducting beam collector and with wires terminating on individually insulated beam collectors. The data show good transport (up to 90% of injected current) without significant energy loss, for wire diameters 3 mil or less, while transport is cutoff after 10 ns when 12 mil wires are used. Particle simulations show that this cutoff is due to an instability fed by excess return current resulting from electron scattering by the wires. The arrays terminated on individually insulated beam collectors showed better transported beam profiles, with less pinching, than the arrays with a common conducting beam collector. Particle simulations also correlate well with this result and provide an understanding of the effect of scattering on transport and beam quality.

Richardson, R.A.; Denavit, J.; Di Capua, M.S.; Rambo, P.W. (University of California, Lawrence Livermore National Laboratory, Livermore, California 94550 (US))

1991-05-01

450

DC and RF Measurements of Serial Bi-SQUID Arrays  

E-print Network

SQUID arrays are promising candidates for low profile antennas and low noise amplifier applications. We present the integrated circuit designs and results of DC and RF measurements of the wideband serial arrays based on integration of linear bi-SQUID cells forming a Superconducting Quantum Interference Filter (bi-SQUID SQIF). Various configurations of serial arrays designs are described. The measured linearity, power gain, and noise temperature are analyzed and compared. The experimental results are matched to results of mathematical modeling. A serial bi-SQUID SQIF arrays are mounted into a coplanar waveguide (CPW) and symmetrically grounded to corresponding sides of CPW. The RF output comes out from the central common line, which is also used for DC biasing and forms a symmetrical balanced output. The signal and DC flux biasing line is designed as coplanar lines passed in parallel over each bi-SQUID cell in a bidirectional fashion concentrating magnetic flux inside of each cell. Serial bi-SQUID SQIF arrays ...

Prokopenko, G V; de Escobar, A Leese; Taylor, B; de Andrade, M C; Berggren, S; Longhini, P; Palacios, A; Nisenoff, M; Fagaly, R L

2012-01-01

451

AC losses in stacks and arrays of YBCO/hastelloy and monofilamentary Bi-2223/Ag tapes  

NASA Astrophysics Data System (ADS)

Formulae are presented for the eddy current AC power loss and the AC hysteresis loss of z-stacks and x-arrays made of metal-superconductor strips. The AC self-field case and the applied AC magnetic field case are examined for different stacking spacings of a z-stack and different lateral spacings of an x-array. The effect of different metal-to-superconductor width-ratios on the losses is investigated. Numerical values are given for the two losses in YBCO/hastelloy and in monofilamentary Bi-2223/Ag tapes. At 50 Hz, the eddy current loss in a z-stack or an x-array made of YBCO/hastelloy tapes is small compared to the hysteresis loss while in a z-stack or an x-array made of monofilamentary Bi-2223/Ag tapes, the eddy current loss contributes significantly at small current or small magnetic field amplitudes.

Müller, K.-H.

1999-01-01

452

Magnetocardiography with a modular spin-exchange relaxation free atomic magnetometer array  

E-print Network

We present a portable four-channel atomic magnetometer array operating in the spin exchange relaxation-free regime. The magnetometer array has several design features intended to maximize its suitability for biomagnetic measurement, specifically foetal magnetocardiography, such as a compact modular design, and fibre coupled lasers. The modular design allows the independent positioning and orientation of each magnetometer, in principle allowing for non-planar array geometries. Using this array in a magnetically shielded room, we acquire adult magnetocadiograms. These measurements were taken with a 6-11 fT Hz^(-1/2) single-channel baseline sensitivity that is consistent with the independently measured noise level of the magnetically shielded room.

Wyllie, R; Smetana, G; Wakai, R; Walker, T

2011-01-01

453

Ferromagnetism in Hydrogenated Graphene Nanopore Arrays  

NASA Astrophysics Data System (ADS)

Theoretically, the so-called zigzag edge of graphenes provides localized electrons due to the presence of flat energy bands near the Fermi level. Spin interaction makes the localized spins strongly polarized, yielding ferromagnetism. However, in most experimental studies, ferromagnetism has been observed in uncontrollable and complicated carbon-based systems. Here, we fabricate graphenes with honeycomblike arrays of hexagonal nanopores, which have a large ensemble of hydrogen-terminated and low-defect pore edges that are prepared by a nonlithographic method (nanoporous alumina templates). We observe large-magnitude ferromagnetism derived from electron spins localizing at the zigzag nanopore edges. This promises to be a realization of graphene magnets and novel spintronic devices.

Tada, K.; Haruyama, J.; Yang, H. X.; Chshiev, M.; Matsui, T.; Fukuyama, H.

2011-11-01

454

Ferromagnetism in hydrogenated graphene nanopore arrays.  

PubMed

Theoretically, the so-called zigzag edge of graphenes provides localized electrons due to the presence of flat energy bands near the Fermi level. Spin interaction makes the localized spins strongly polarized, yielding ferromagnetism. However, in most experimental studies, ferromagnetism has been observed in uncontrollable and complicated carbon-based systems. Here, we fabricate graphenes with honeycomblike arrays of hexagonal nanopores, which have a large ensemble of hydrogen-terminated and low-defect pore edges that are prepared by a nonlithographic method (nanoporous alumina templates). We observe large-magnitude ferromagnetism derived from electron spins localizing at the zigzag nanopore edges. This promises to be a realization of graphene magnets and novel spintronic devices. PMID:22181918

Tada, K; Haruyama, J; Yang, H X; Chshiev, M; Matsui, T; Fukuyama, H

2011-11-18

455

Vortex depinning in Josephson-junction arrays  

NASA Astrophysics Data System (ADS)

On the basis of a simple model we study the supercurrent-carrying capacity of a planar array of Josephson junctions. In particular we investigate the zero-temperature vortex-depinning current iBc, which is the largest supercurrent in an array containing one extra vortex on top of the ground-state vortex superlattice induced by an external magnetic field f. In the zero-field, f=0, case our results support the tilted-sinusoidal vortex-potential description of previous workers. However, in the fully frustrated, f=1/2 case, a more careful interpretation is required. We find that on the application of a transport current, the resulting vortex motion is not that of the extra vortex moving over a rigid field-induced vortex background. Rather, a vortex belonging to the checkerboard ground-state pattern first crosses over a junction into a neighboring ``empty'' plaquette. Then, the ``extra'' vortex moves to take its place. Our interpretation is based on a linear stability analysis, with the onset of vortex motion being associated with the vanishing of one eigenvalue of the stability matrix. Further applications of the method are suggested.

Dang, E. K. F.; Györffy, B. L.

1993-02-01

456

Particle sensor array  

NASA Technical Reports Server (NTRS)

A particle sensor array which in a preferred embodiment comprises a static random access memory having a plurality of ion-sensitive memory cells, ea